JPH0695536A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of smoothly conveying a storage medium, preventing deviation of images for storage and always forming images of high quality. CONSTITUTION:In an image forming device, provided with a drum-shaped latent image holder 6a, an electrostatic latent image formation means for forming an electrostatic latent image on the surface of the latent image holder 6a, a development means for forming a toner image on an electrostatic latent image surface by attaching a toner thereto, a transfer roller 6e for forming an image on a storage medium P by transferring the toner image onto the storage medium P, and a storage medium conveyance means for conveying the storage medium P to a transfer area, the latent image holder 6a and the transfer roller 6e are disposed opposite to each other via the storage medium P conveyed to the transfer area by the storage medium conveyance means, and the transfer roller 6e is disposed downstream of the latent image holder 6a along the direction in which the storage medium is conveyed.

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 an electrophotographic device or an electrostatic recording device.

[0002]

2. Description of the Related Art A plurality of image forming units are continuously arranged and a toner image formed for each image forming unit is
For example, there is known a color image forming apparatus that sequentially forms a color image by a transfer roller onto a recording medium conveyed by a transfer belt. FIG. 5 shows a main configuration of a color image forming apparatus of this type, that is, a required image is copied based on image information of each color from an image processing unit.
3 is a cross-sectional view showing the configuration of a color image forming unit for reproduction. The color image forming section is composed of, for example, an image forming unit 1 for yellow, an image forming unit 2 for magenta, an image forming unit 3 for cyan, and an image forming unit 4 for black.

Further, each of these image forming units 1,
The configurations of 2, 3, and 4 are all photoconductor drums (latent image bearing members) 1a, 2a, 3a, and 4a, and the photoconductor drums 1a, 2a, 3a, and 4a.
Charging means for uniformly charging the surface (for example, corona charger) 1b, 2b, 3b, 4b, the photosensitive drum 1a, 2a, 3a, 4a surface charged based on the image information from the image processing unit,
Electrostatic latent image forming means 1c, 2c, 3 for forming a required electrostatic latent image
c, 4c, developing means 1d, 2d, 3d, 4d for supplying toner to the electrostatic latent image surface to convert the electrostatic latent image into a toner image, and the toner image on a recording medium conveyed by the transfer belt 5. A configuration including transfer rollers 1e, 2e, 3e, 4e for transferring, and cleaning means 1f, 2f, 3f, 4f for removing transfer residual toner remaining from the transfer from the surface of the photosensitive drums 1a, 2a, 3a, 4a. Is made. That is, although the color toner to be used is different, a general image forming apparatus (unit) with a so-called cleaning means is continuously arranged (Japanese Patent Laid-Open No. 1-112267).

According to this color image forming apparatus, first, in the image forming unit 1, an electrostatic latent image of a yellow component color is formed on the surface of the photosensitive drum 1a, developed into a yellow toner image and transferred to a recording medium. . Then, in the image forming unit 2, an electrostatic latent image of magenta component color is formed on the surface of the photosensitive drum 2a, developed into a magenta toner image, and transferred in a layered manner onto a recording medium conveyed by the transfer belt 5. . Thereafter, after a required color image is copied and recorded through a similar process in sequence, the recording medium is separated from the surface of the transfer belt 5 by a separating device (not shown) and transferred to a fixing device (not shown). Will be established.

[0005]

However, in the case of the color image forming apparatus having the above configuration, there are the following problems in practical use. That is, in this type of image forming apparatus, the recording medium is supplied from the paper feed cassette onto the transfer belt,
The surface of the transfer belt (endless film) whose surface is charged by the charger is electrostatically attracted to the surface, and the transfer belt sequentially conveys the image to the image forming units. Next, the toner images formed on the photoconductor drum are sequentially transferred to the recording medium conveyed in this manner. At this time, the toner image is transferred to the transfer roller contacting the photoconductor drum via the transfer belt. Is an appropriate pressure is applied, and when the recording medium is inserted between the photosensitive drum and the transfer roller, the speed of the photosensitive drum fluctuates or the recording medium peels off the transfer belt. The medium may be misaligned, and when forming a color image, misalignment may occur between the toner images transferred by the image forming units. Therefore, it is often the case that a color image having a good image quality cannot be obtained, and there is a problem that reliability is poor.

In order to reduce the speed fluctuation of the photosensitive drum against such a problem, a motor having an extremely large torque is used as a drive source, and the position of the recording medium is detected by a sensor or the like to detect the motor. Although it is conceivable to attach a high-accuracy control device such as for controlling, it is not preferable because it causes an increase in size and cost of the image forming apparatus. Further, although a means for accurately adjusting the gap between the photosensitive drum and the transfer roller can be considered, there is a problem in that the operation is complicated.

The present invention has been made in consideration of the above circumstances, and provides an image forming apparatus capable of smoothly conveying a recording medium, suppressing positional deviation of a recorded image, and constantly forming a high quality image. With the goal.

[0008]

An image forming apparatus according to the present invention comprises a drum-shaped latent image carrier, electrostatic latent image forming means for forming an electrostatic latent image on the surface of the latent image carrier, and Developing means for forming a toner image by attaching toner to the electrostatic latent image surface,
An image forming apparatus comprising: a transfer roller that transfers the toner image onto a recording medium to form an image on the recording medium; and a recording medium conveying unit that conveys the recording medium to a transfer area. The transfer rollers are arranged to face each other with the recording medium conveyed to the transfer area by the recording medium conveying means, and the transfer rollers are arranged downstream of the latent image carrier along the conveying direction of the recording medium. It is characterized by being installed.

That is, the essence of the image forming apparatus of the present invention is that the drum-shaped latent image carrier and the transfer roller are arranged at asymmetrical positions with respect to the recording medium being conveyed.

[0010]

According to the image forming apparatus of the present invention having the above-described structure, the drum-shaped latent image carrier, for example, the transfer roller arranged to face the photosensitive drum is disposed between the photosensitive drum and the transfer roller. The recording medium is arranged and set on the downstream side of the photosensitive drum along the conveying direction of the recording medium. Therefore, at the moment when the recording medium conveying means, for example, the recording medium conveyed by the transfer belt comes into contact with the photoconductor drum, a sudden pressure is generated or abruptly applied between the photoconductor drum and the transfer roller. Is eliminated and reduced. Therefore, when a recording medium is inserted between the photoconductor drum and the transfer roller, the speed variation of the photoconductor drum caused by the torque variation caused by the insertion of the recording medium and the recording medium loaded on the photoconductor drum Easily avoids the phenomenon of peeling from the transfer belt that occurs at the moment of contact.
As a result, it is possible to form an image in which positional deviation is completely prevented.

[0011]

Embodiments of the present invention will be described below with reference to FIGS.

First, the point where the transfer roller is set and arranged on the downstream side of the drum-shaped latent image carrier, that is, the photosensitive drum, along the conveyance direction of the recording medium will be described. 2A and 2B are sectional views schematically showing the positional relationship between the photosensitive drum and the transfer roller in the image forming apparatus, and FIG. 2A is a conventional image forming apparatus and FIG. b) is the image forming apparatus of the present invention.

In the conventional image forming apparatus, as shown in FIG.
As shown in, the photosensitive drum 1a and the transfer roller 1e are arranged at symmetrical positions with respect to the transfer belt 5a, and
The distance between the axis of the photosensitive drum 1a and the roller axis of the transfer roller 1e is set to be slightly smaller than a value obtained by adding the thickness of the transfer belt 5a to the radius of the photosensitive drum 1a and the radius of the transfer roller 1e. Therefore, when the recording medium P is conveyed, the recording medium P on the transfer belt 5a is inserted between the photoconductor drum 1a and the transfer roller 1e, and the transfer roller 1e is deformed, whereby the photoconductor drum 1a is deformed. A pressure is generated between the recording medium P and the recording medium P and is conveyed. Moreover, at this time, the recording medium P such as paper is surely conveyed and the photosensitive drum
It is necessary to efficiently transfer the toner image formed on the recording medium P onto the recording medium P. For this reason, the photoconductor drum 1a and the recording medium P are in close contact, and the transfer electric field is applied sufficiently and stably. Are required at the same time. That is, when the photoconductor drum 1a and the recording medium P are in close contact with each other, an electric field is uniformly applied, and by appropriately selecting the rubber hardness of the transfer roller 1e, the contact width with the photoconductor drum 1a also becomes constant. The electric field will be applied more stably. However, in this case, when the recording medium P is inserted, in order to efficiently transfer the toner image, the transfer roller 1e and the photosensitive drum 1a are in a state where sufficient pressure is applied between them.
When the position of 1e is set, a large torque is applied to the photosensitive drum 1a, which causes speed fluctuation. On the other hand, in the case of the image forming apparatus of the present invention, as shown in FIG. 2 (b), when the recording medium P on the transfer belt 10a comes into contact with the photosensitive drum 6a, the recording medium is directly below the photosensitive drum 6a. Since there is nothing that hinders the deformation of the P and the transfer belt 10a, the recording medium P is smoothly transported, and the photosensitive drum 6a, the recording medium P, the transfer belt 10a, and the transfer roller 6e are not enough. It is guided to the transfer area which is contacted under pressure. Therefore, when the recording medium P contacts the photoconductor drum 6a, a large torque is not applied to the photoconductor drum 6a, and the speed fluctuation of the photoconductor drum 6a is also eliminated.

In such an image forming apparatus of the present invention, the position where the transfer roller 6e is arranged is such that the photosensitive drum 6a, the recording medium P, the transfer belt 10a and the transfer roller 6e are sufficiently pressed in the transfer area. Within the range in which the recording medium P can be brought into contact with the recording medium P, it can be appropriately set on the downstream side of the photosensitive drum 6a with respect to the transport direction of the recording medium P. In addition, the axial distance h [mm] between the drum shaft of the photoconductor drum 6a and the roller shaft of the transfer roller 6e is φ ₁ [mm] for the photoconductor drum 6a and φ ₂ [mm for the transfer roller 6e. ], Thickness D of transfer belt 10a [mm], thickness T of recording medium P [m]
when the m], is set so as to satisfy _{(φ 1/2 + φ 2} /2) ≦ h ≦ (φ 1/2 + φ 2/2 + D + T) relational expression.

Next, the structure of the image forming apparatus according to the present invention will be described.

FIG. 1 is a sectional view showing a structural example of a main part (image forming part) of a color image forming apparatus according to the present invention.
In this image forming apparatus, first, the recording medium P is taken out from the paper feed cassette (not shown) and the registration roller is used.
Recording medium P by P _1, P ₂ is guided to on the transfer belt 10a. The transfer belt 10a is provided with a charging roller 10e and a driven roller 10c for applying an electric charge to the recording medium P and adsorbing the recording medium P on the transfer belt 10a. Here, as shown in FIG. 1, the charging roller 10e is arranged closer to the developing unit than the driven roller 10c, and the recording medium P
Is supplied onto the transfer belt 10a, the transfer belt 10a is first contacted and then the charging roller 10e is contacted. On the contrary, the charging roller 10
The e may be arranged closer to the paper feed cassette than the driven roller 10c.

Next, the developing unit in this image forming apparatus includes, for example, a yellow cleanerless image forming unit 6, a magenta cleanerless image forming unit 7, a cyan cleanerless image forming unit 8, and a black cleanerless image forming unit 8. It is composed of a cleanerless image forming unit 9. Each of these cleanerless image forming units 6, 7, 8 and 9 is a drum-shaped latent image carrier, that is, a photosensitive drum (for example, OPC photosensitive drum) 6a, 7a, 8a, 9a, Photoconductor drums 6a, 7a, 8a, 9a
Charging means (for example, corona charger) 6b, 7b, 8b, 9b for uniformly charging the surface, and a photosensitive drum charged based on image information from a separately provided image processing unit (not shown) Electrostatic latent image forming means (print heads) 6c, 7c, 8c, 9c for forming a desired electrostatic latent image on the surfaces 6a, 7a, 8a, 9a, and one-component non-magnetic toner, for example, on the electrostatic latent image surfaces. Supplying means 6d, 7d, 8d, 9d for developing the electrostatic latent image into a toner image,
Transfer means 6f, 7f, 8f, 9f including transfer rollers (electric field means) 6e, 7e, 8e, 9e for transferring the toner image onto the recording medium P,
After transferring the toner image to the recording medium P, the photoconductor drums 6a, 7
Discharge lamps (light emitters) 6g, 7g, 8g, 9g for erasing the electric charges remaining on the surfaces a, 8a, 9a, and the untransferred toner remaining after the transfer are dispersed on the surfaces of the photosensitive drums 6a, 7a, 8a, 9a. Of the transfer residual toner, which contributes to uniform charging by the charging means 6b, 7b, 8b, 9b and promotes the cleaning action by the developing means 6d, 7d, 8d, 9d.
It is configured with 6h, 7h, 8h, and 9h. That is,
Although different colored toners are used, so-called cleanerless image forming apparatuses (units) 6, 7, 8 and 9 are continuously arranged.

Further, 10 is a recording medium for transferring the toner image.
The transfer roller 6e, which is a recording medium carrying means for carrying P,
A transparent endless film-shaped transfer belt formed of a dielectric or a resistor having a resistance value of 10 ⁹ Ω · cm or more, which constitutes the transfer means 6f, 7f, 8f, 9f in cooperation with 7e, 8e, 9e. 10a
, A driving roller 10b and a driven roller 10c that make the transfer belt 10a run endlessly, and a running transfer belt 10a.
Belt cleaner 10d for cleaning surfaces, transfer belt
10a and a charging roller 10e that charges the recording medium P. Then, on the transfer belt 10a forming a part of the recording medium conveying means 10, the recording medium P is supplied from the registration rollers P ₁ and P ₂ in conjunction with image formation, and then the recording medium P is conveyed. While the transfer roller 6
By e, 7e, 8e, and 9e, a required transfer electric field is formed in each transfer area to sequentially perform transfer.
Here, as described above, the transfer rollers 6e, 7e, 8e, 9e
Are arranged on the downstream side of the photosensitive drums 6a, 7a, 8a, 9a in the transport direction of the recording medium P. Further, it is preferable that the transfer rollers 6e, 7e, 8e, 9e are composed of a conductive elastic roller having an elastic layer and a conductive layer.

FIG. 3 shows such transfer rollers 6e, 7e, 8
The configuration of e and 9e is shown in perspective with a part cut away. That is, the illustrated transfer roller 6e has, for example, a conductive layer 6e having a resistance value of 10 ⁹ Ω · cm or more, preferably 10 ¹¹ Ω · cm or more, which is composed of a resin or elastomer-based binder and a conductive filler at least on the outer peripheral surface. ′ And having an elastic layer 6e ″ made of oil-resistant rubber having a hardness of 40 degrees or less, preferably 30 degrees or less as measured by JIS K6301 A type hardness tester inside the conductive layer 6e ′. The oil-resistant rubber forming the elastic layer 6e ″ is as follows.
For example, EPDM, urethane, silicone, chloroprene,
NBR and the like can be mentioned, and a system in which a conductive filler is dispersed therein to make it conductive may be used within a range that does not impair the hardness described above. Further, as a material used for forming the conductive layer 6e ', a solvent-soluble binder such as a commercially available conductive urethane-based paint or a conductive acrylic-based paint, in which a conductive filler such as conductive carbon is dispersed, Alternatively, a conductive resin or the like can be used. In FIG. 3, m is an elastic layer
The metal shaft 6e ″ and the conductive layer 6e ′ are formed on the peripheral surface, and a required voltage is applied to the metal shaft m.

On the other hand, regarding the optimum positional relationship between the photosensitive drums 6a, 7a, 8a, 9a and the transfer rollers 6e, 7e, 8e, 9e,
It is appropriately set in consideration of the contact width between the recording medium P and the photoconductor drums 6a, 7a, 8a, 9a. The optimum value of a typical electrophotographic printer is as follows.
FIG. 4 is a schematic cross-sectional view schematically showing a transfer area in the image forming apparatus. In this cross-sectional view, the diameter of the photosensitive drum 6a is φ ₁ [mm], and the conventional image as shown in FIG. The contact point between the photosensitive drum 6a and the transfer roller 6e in the forming apparatus is A, and the contact point between the photosensitive drum 6a and the transfer roller 6e in the image forming apparatus of the present invention is B, as shown in FIG. 2B.
Set the length of the photosensitive drum 6a surface from point A to point B to l [m
m] and point A−OB− (where O is the center axis of the photoconductor drum 6a) is θ [rad], the transfer belt 10a
The length of the contact portion between the surface of the photosensitive drum 6a and the photosensitive drum 6a, in other words, the contact width l [mm] between the recording medium P and the photosensitive drum 6a.
Is expressed by the following equation.

Contact length l = φ ₁ π (θ / 2π) Here, the photosensitive drum 6a used in a typical printer.
When the diameter φ ₁ is 30 mm and the optimum value of the contact width l is 2 to 6 mm, the optimum value range of θ is 0.1 to 0.4 rad. Therefore, θ is 0.1 ~
0.4 rad su. If the photoconductor drum 6a and the transfer drum 6e are arranged in a positional relationship, the toner image can be efficiently recorded on the recording medium P.
In addition to being able to be transferred to, it is possible to reduce the occurrence of reverse transfer. The diameter of the transfer roller 6e is preferably about 1/4 to 2/3 of the diameter of the photosensitive drum 6a.
When the diameter of 6a is extremely small, for example, 20 mm or less, it is preferable to use the transfer roller 6e having a diameter larger than the above range. The reason is that if the metal shaft m that constitutes the transfer roller 6e maintains a thickness that does not curve extremely in the longitudinal direction, the elastic layer 6e ″ becomes thin, and as a result, the required contact width, This is because a uniform pressure cannot be obtained.

While adopting such a configuration, in the image forming apparatus according to the present invention, a charge eliminating lamp (light emission) is provided on the inner side of the transfer belt 10a forming a part of the recording medium conveying means 10 as shown in FIG. Body) 6g, 7g, 8g, 9g are arranged. In this way, the transfer belt 10a is made transparent, and the photosensitive drums 6a, 7a, 8 are provided inside the traveling transfer belt 10a.
Static erasing lamps 6g, 7g, 8 for erasing charges after transfer on surfaces a and 9a
By arranging g and 9g, residual charge can be erased while promoting compactness. That is, by skillfully utilizing the space in the area of the recording medium transporting means 10, the surfaces of the photoconductor drums 6a, 7a, 8a, 9a are electrically cleaned, and the contribution to the high quality of image formation is continuously achieved. . In FIG. 1, 12 is a fixing unit for fixing the toner image transferred on the recording medium P to the recording medium P, and 13 is a partition between the cleanerless image forming units 6, 7, 8 and 9.

The construction and functions of the developing means 6d, 7d, 8d, 9d in the cleanerless image forming units 6, 7, 8, 9 will be described below. The photosensitive drums 6a, 7a,
Roller-type toner carrier 6d ₁ , 7d ₁ , 7d ₁ , 9d ₁ , which bears the toner layer on the peripheral surfaces arranged to face 8a, 9a, the toner carrier 6d ₁ , 7d ₁ , 7d ₁ , 9d ₁ surface Toner supply members 6d ₂ , 7d ₂ , 8d ₂ for supplying toner to. 9d _2, wherein the toner carrying member _{6d 1, 7d 1, 7d 1} , 9d toner layer regulating blade 6d ₃ for regulating the thickness of the toner layer carried on the peripheral surface of the _1, 7d _3, 8d
₃ , 9d ₃ , toner carrier 6d ₁ , 7d ₁ , 7 after toner is supplied to the electrostatic latent image surface of the photoconductor drums 6a, 7a, 8a, 9a
Toner collecting blade 6d that collects toner on d ₁ and 9d _{1
It is provided with 4} , 7d ₄ , 8d ₄ , 9d ₄ , and toner storage tanks 6d ₅ , 7d ₅ , 8d ₅ , 9d ₅ for storing toner while mounting these.

Next, the outline of the developing / simultaneous cleaning in the cleanerless image forming units 6, 7, 8 and 9 will be described. When an electrostatic latent image is formed on the surface of the photoconductor drums 6a, 7a, 8a, 9a by the electrostatic latent image forming means 6c, 7c, 8c, 9c, it exists in a charged portion (that is, an unexposed portion or a non-image portion). The transfer residual toner is charged by charging means 6b, 7b,
Since it is positively charged by 8b and 9b, the toner carrying members 6d ₁ , 7d ₁ , 7d ₁ and 9d ₁ to the photosensitive drums 6a, 7a and 8d.
An electric field that suppresses the transfer of the toner to the a and 9a surfaces, that is, the potential of the charged portion and the toner carrier 6d ₁ , 7d ₁ , 7d ₁ ,
By the electric field due to the potential difference from the potential of 9d ₁ , the toner is transferred to the toner carrier 6d ₁ , 7d ₁ , 7d ₁ , 9d ₁ . At the same time, the transfer residual toner existing in the non-charged portion, that is, the exposed portion or the image portion, receives a force from the toner carrier 6d ₁ , 7d ₁ , 7d ₁ , 9d ₁ toward the photosensitive drums 6a, 7a, 8a, 9a, It remains on the surfaces of the photoconductor drums 6a, 7a, 8a, 9a. New toner is transferred from the toner carriers 6d ₁ , 7d ₁ , 7d ₁ , 9d ₁ to this non-charged portion, and cleaning is performed at the same time as development.

On the other hand, in the transfer means 6f, 7f, 8f, 9f, the transfer rollers 6e, 7e, 8e, 9e forming the transfer means 6f, 7f, 8f, 9f and the dielectric material forming the transfer belt 10a. Alternatively, by a concerted action with the resistor, a required transfer electric field is easily and surely formed in the transfer region, and transfer is efficiently performed. That is, the photosensitive drums 6a, 7a, 8
The toner image formed on the surfaces a and 9a is transferred to the recording medium P without a large amount of toner particles forming the toner image remaining on the surfaces of the photoconductor drums 6a, 7a, 8a and 9a. Moreover,
In this transfer, when the recording medium P on the transfer belt 10a comes into contact with the photosensitive drums 6a, 7a, 8a, 9a, the transfer belt 10a is deformed just below the photosensitive drums 6a, 7a, 8a, 9a. Since the recording medium P is smoothly conveyed because there is no obstruction, the photosensitive drums 6a, 7a, 8a, 9a,
Recording medium P, transfer belt 10a and transfer rollers 6e, 7e,
8e, 9e It is guided to the transfer area that contacts. Therefore, when the recording medium P contacts the photosensitive drums 6a, 7a, 8a, 9a,
A large torque is not applied to the photoconductor drums 6a, 7a, 8a, 9a, and the speed fluctuations of the photoconductor drums 6a, 7a, 8a, 9a are eliminated, but the peeling phenomenon of the recording medium P from the transfer belt 10a occurs. The resulting positional shift of the image can be easily prevented or suppressed. Further, as described above, the transfer is efficiently performed, and the transfer residual toner after the transfer is significantly reduced.
In combination with the suppression of the positive image generation due to the development / simultaneous cleaning in the developing means 6d, 7d, 8d, 9d, it becomes possible to form a clear high quality color image. Moreover,
After transferring the toner image onto the recording medium P, the photosensitive drum 6a,
The surfaces 7a, 8a and 9a are illuminated by the static elimination lamps (light emitters) 6g, 7g, 8g and 9g via the transfer belt 10a, so that the accumulated charges are easily erased. That is, the surfaces of the photoconductor drums 6a, 7a, 8a, 9a are cleaned electrically, and are used for charging (charging) by the charging means 6b, 7b, 8b, 9b for forming the next image. Therefore, the influence of the electric charge applied in the previous image formation is completely removed, the possibility that a positive image or the like is generated is eliminated, and high-quality image formation is repeated.

According to the color image forming apparatus having the above structure,
First, the required electrostatic latent image pattern is formed on the surface of the photoconductor drum 6a by the image information corresponding to the yellow image, and the developing / simultaneous cleaning is performed by the developing unit 6d at the next stage according to the above-described action principle. A toner image corresponding to the electrostatic latent image pattern is formed on the surface of the photosensitive drum 6a. The toner image thus formed is transferred from the surface of the photosensitive drum 6a to the recording medium P that is synchronously conveyed by the transfer unit 6f. After this transfer, the surface of the photosensitive drum 6a is
Irradiated by the static elimination lamp 6g, the charge is removed, and the transfer residual toner dispersing means 6h disperse the transfer residual toner almost uniformly, and the surface of the photoconductor drum 6a is made uniform to correspond to the yellow image again. The electrostatic latent image pattern formation, development, and simultaneous cleaning are repeated.

On the other hand, the recording medium P on which the yellow image has been transferred is conveyed to the next magenta cleanerless image forming unit 7 side, and the operation or operation is performed in the same manner as in the yellow cleanerless image forming unit 6. By the operation, the required magenta images are transferred in layers on the recording medium P to which the yellow image has been transferred. Less than,
In the cleanerless image forming unit 8 for cyan and the cleanerless image forming unit 9 for black, toner images of the corresponding color images are transferred and transferred, and then fixed by the fixing unit 12 to obtain a desired color image. Is obtained.

Each cleanerless image forming unit 6,
In the image forming process of 7, 8 and 9, so-called cleaning means is not provided separately, but the developing means 6d, 7d,
By the development and simultaneous cleaning by 8d and 9d, the transfer residual toner on the surface of the photoconductor drums 6a, 7a, 8a and 9a can be easily and surely removed, so that the color mixture of the toner images of the respective colors can be eliminated and the image can be sharpened. A (sharp) and high-quality color image is always formed.

In the color image forming apparatus having the above structure, all the image forming units are cleaner-less image forming units 6, 7, 8 and 9, but in the present invention, these are provided with a dedicated cleaning means. It may be an image forming unit. For example, the image forming unit located on the most upstream side in the conveyance direction of the recording medium P may be the yellow cleanerless image forming unit 6, and the other may be an image forming unit with a dedicated cleaning unit.
In this case, the effect of color mixing can be avoided more effectively. Alternatively, the image forming unit located on the most downstream side in the conveying direction of the recording medium P is the cleaner-less image forming unit 8 for black, and the other is an image forming unit with a dedicated cleaning unit (or a dedicated cleaning unit). Image forming unit and a cleanerless image forming unit), and in this configuration, the toner storage tank 9d ₅ of the black cleanerless image forming unit 9 is used for forming a single color image by keeping a relatively large capacity. You can The image forming unit located on the most downstream side in the transport direction of the recording medium P is an image forming unit with a cleaning unit for yellow or an image forming unit with a cleaning unit for cyan, and the others are cleanerless image forming units. Also, even in the case of this configuration, the influence of color mixture can be more effectively avoided.

In any case, in the above-mentioned color image forming apparatus, the arrangement and position of each image forming unit are appropriately selected and set in consideration of proper use (whether it is a single color or color) or the characteristics of the toner used. However, from the viewpoint of downsizing the color image forming apparatus as described above, it is desirable to dispose at least one cleanerless image forming unit.

Further, in the above configuration example, the case of a color image forming apparatus in which a plurality of image forming units are continuously arranged is illustrated, but according to the present invention, the same applies to a single color image forming apparatus having a transfer roller. It is possible to obtain an image that is accurately positioned with respect to the recording timing of the image signal. Further, in the present invention, the position of the static elimination lamp for erasing the residual charges on the surface of the photosensitive drum is not limited to the inside of the transfer belt, and the transfer belt forming a part of the recording medium conveying means is removed. For example, the recording medium conveying means may be constituted by only the conveying rollers.

[0032]

As described above, according to the image forming apparatus of the present invention, the photoconductor that is generated when the recording medium is inserted between the photoconductor drum (electrostatic latent image carrier) and the transfer roller. Since it is possible to easily prevent the positional deviation of the image caused by the fluctuation of the drum speed or the temporary separation of the recording medium from the transfer belt, it is possible to always form a high quality image.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main configuration of an image forming apparatus according to the present invention.

2A and 2B schematically show a positional relationship between a photosensitive drum and a transfer roller in an image forming apparatus, FIG. 2A is a sectional view of a conventional image forming apparatus, and FIG. FIG. 3 is a cross-sectional view of an image forming apparatus.

FIG. 3 is a partially cutaway perspective view showing a configuration example of a transfer roller included in the image forming apparatus according to the present invention.

FIG. 4 is a schematic sectional view schematically showing a transfer region in the image forming apparatus.

FIG. 5 is a cross-sectional view showing a main part configuration of a conventional color image forming apparatus.

[Explanation of symbols]

1, 2, 3, 4 ... Image forming units 1a, 2a, 3a, 4
a, 6a, 7a, 8a, 9a ... Photosensitive drums 1b, 2b, 3b, 4
b, 6b, 7b, 8b, 9b ... Charging means 1c, 2c, 3c, 4c, 6
c, 7c, 8c, 9c ... Electrostatic latent image forming means 1d, 2d, 3d, 4
d, 6d, 7d, 8d, 9d ... Developing means 1e, 2e, 3e, 4e, 6
e, 7e, 8e, 9e ... Transfer rollers 1f, 2f, 3f, 4f ... Cleaning means 6f, 7f, 8f, 9f ... Transfer means 1g, 2
g, 3g, 4g, 6g, 7g, 8g, 9g ... Static elimination lamps 6h, 7h, 8
h, 9h ... Means for dispersing transfer residual toner 1h, 2h, 3h, 4
h, 13 ... Partitioner between cleanerless image forming units
6, 7, 8, 9 ... Cleanerless image forming unit 6d
₁ , 7d ₁ , 8d ₁ , 9d ₁ ... Toner carrier 6d ₂ , 7d ₂ , 8d ₂ , 9d ₂ ... Toner supply body 6d ₃ , 7
_{d 3, 8d 3, 9d 3} ... toner layer regulating blade 6d _4, 7d
₄ , 8d ₄ , 9d ₄ ... Toner collecting blades 6d ₅ , 7d ₅ ,
8d ₅ , 9d ₅ ... Toner storage tank 5, 10 ... Recording medium conveying means
5a, 10a ... Transfer belt 10b ... Driving roller 1
0c ... driven roller 10d ... belt cleaner 10e ... charging roller 6e ′ ... conductive layer 6e ″ ... elastic layer m
... metal shaft P ... recording medium P _1, P ₂ ... registration rollers 12 ... fixing unit

Front Page Continuation (72) Inventor Kenichi Mori 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research Institute Co., Ltd. Incorporated company Toshiba Research Institute (72) Inventor Norihiro Osugi 6-78 Minamimachi, Mishima City, Shizuoka Prefecture

Claims (1)

[Claims] 1. A drum-shaped latent image carrier, an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the latent image carrier, and toner attached to the surface of the electrostatic latent image to form a toner image. An image forming apparatus comprising: a developing unit that forms a toner image; a transfer roller that transfers the toner image to a recording medium to form an image on the recording medium; and a recording medium conveying unit that conveys the recording medium to a transfer area. The latent image carrier and the transfer roller are arranged to face each other with the recording medium conveyed to the transfer area by the recording medium conveying unit, and the transfer roller conveys the latent image along the conveyance direction of the recording medium. An image forming apparatus, which is arranged downstream of a body.