JP2001343807A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem engine type image forming device capable of securing image quality or improving productivity in compliance with user's need. SOLUTION: In this image forming unit, plural image forming units 1 (for example, 1a to 1d) are disposed in parallel along an intermediate transfer body 2 or the moving path of recording material 3, and each image forming unit 1 is equipped with an image carrier 4 carrying each color component image, then each color component image formed on the image carrier 4 of the image forming unit 1 is transferred to the recording material 3 directly or through the intermediate transfer body 2. In an image quality priority mode, image- forming is performed to satisfy relation Pc=n.S (n: integer or 1/integer) when it is assumed that the peripheral length of the image carrier 4 of the image forming unit 1 is S and the image-forming pitch of the image G is Pc, and in a productivity priority mode, image-forming is performed to satisfy relation Pm<Pc when it is assumed that the image-forming pitch of the image G is Pm.

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 copying machine or a printer, and more particularly to a method in which a plurality of image forming units are arranged in parallel along a moving path of an intermediate transfer member or a recording material. To an image forming apparatus of a so-called tandem engine type.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, for example, a plurality of image forming units (for example, adopting an electrophotographic system) are arranged in parallel with respect to an intermediate transfer belt extending in a horizontal direction, and each image forming unit is formed. A toner image of each color component is formed on an image carrier such as a photosensitive drum of the unit, and the toner images are sequentially transferred from the image forming units to the intermediate transfer belt. A so-called tandem engine type that performs batch transfer on paper is already known. It is also known that a transport belt for transporting paper is provided without using an intermediate transfer belt, and each color component toner image from each image forming unit is sequentially transferred to paper on the transport belt. ing.

However, in this type of tandem engine type image forming apparatus, even if the latent image writing timing of each color component image is accurately aligned for each image forming unit, a plurality of the same color images are printed. In the case of forming, there has been a technical problem that the color tone of the color image between the papers tends to vary.

Therefore, the applicant of the present application has previously described the dimensional relationship between the circumference S of the image carrier and the image forming pitch P in a so-called tandem engine type image forming apparatus by P = n · S
(N: integer or 1 / integer) has been proposed (see JP-A-11-84809). According to this, the image forming start position on the image carrier between each image forming unit is always synchronized beyond the job, so that the fluctuation component of the peripheral surface of the image carrier of each image forming unit is reduced. Since the density difference and color difference tendency of each color component image that occurs can be reproduced at the same position on the recording material, even when a plurality of the same images are formed, the color tone of the composite image of each color component image varies. As a result, it is possible to make the image quality equal to each other, thereby minimizing the variation in the image quality of each page and keeping the image quality always good.

[0005]

However, in the above-described image forming apparatus, since the image forming pitch is set in accordance with the circumference S of the image carrier, the size of the image (the size of the image carrier) is reduced. (The length in the circumferential direction), there is a technical problem that the waiting time until the start of the next image formation is lengthened and the productivity is reduced. In particular, when forming a single-color image such as a monochrome image, the variation in the hue of each page is not so noticeable, so that the productivity has been a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and is a tandem engine type image capable of ensuring image quality or improving productivity according to the needs of a user. A forming apparatus is provided.

Another object of the present invention is to provide a tandem engine type image forming apparatus capable of minimizing variations in image quality when forming a multicolor image and improving productivity when forming a single color image. .

[0008]

That is, according to the present invention, as shown in FIGS. 1A to 1C, a plurality of image forming units 1 are arranged along a moving path of an intermediate transfer member 2 or a recording material 3.
(For example, 1a to 1d) are arranged in parallel, each image forming unit 1 is provided with an image carrier 4 for carrying each color component image, and is formed on the image carrier 4 of each image forming unit 1. In the image forming apparatus which transfers the respective color component images to the recording material 3 via the intermediate transfer member 2 or directly, in the image quality priority mode, the peripheral length of the image carrier 4 of each image forming unit 1 is S, and the image G is When the image forming pitch is Pc, Pc =
An image is formed so as to satisfy the relationship of n · S (n: integer or 1 / integer). In the productivity priority mode, when the image formation pitch of the image G is Pm, the relationship of Pm <Pc is satisfied. Image formation.

In consideration of the fact that the deterioration of the image quality is not so noticeable when forming a single-color image, two or more image forming units 1 (for example, four of 1a to 1d) out of the plurality of image forming units 1 are considered. ) When forming a multi-color image, perform image formation in the image quality priority mode,
When a single color image is formed by using one image forming unit 1 (for example, 1d), it is preferable to form an image in the productivity priority mode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. FIG. 2 shows an embodiment of a tandem image forming apparatus (color laser printer) to which the present invention is applied. In the figure, a tandem image forming apparatus according to the present embodiment has an image forming unit 22 (specifically, 22Y) of four colors (yellow, magenta, cyan, and black in the present embodiment) in a main body housing 21. , 22M, 22C, and 22K) are arranged in the horizontal direction, and above the transfer unit 23 including the intermediate transfer belt 230 that is circulated and conveyed along the arrangement direction of the image forming units 22, is disposed. A supply cassette 24 for accommodating the paper P is provided below the housing 21, and a paper transport path 25 serving as a transport path for the paper P from the supply cassette 24 is vertically arranged.

In the present embodiment, each image forming unit 22 (specifically, 22Y, 22M, 22C, 22K)
Are, in order from the upstream in the circulation direction of the intermediate transfer belt 230,
These form toner images for yellow, magenta, cyan, and black, respectively.
, Each developing unit 33 and one common exposure unit 40. Here, the photoconductor unit 30
Is, for example, a photosensitive drum 31 and this photosensitive drum 31
(A charging roll in the present example) 32 for charging in advance
Cleaner 3 for removing residual toner on photoconductor drum 31
4 is integrated into a cartridge. Of these, the photosensitive drum 31 has a negatively charged photosensitive layer, and its diameter is φ30. The developing unit 33 develops the electrostatic latent image formed by exposure on the charged photosensitive drum 31 by the exposure unit 40 with a corresponding color toner (for example, negative polarity in the present embodiment). is there. Reference numeral 35 (specifically, 35Y, 35M, 35
C, 35K) are toner cartridges for replenishing the respective developing units 33 with the respective color component toners.

On the other hand, the exposure unit 40 includes, for example, four semiconductor lasers (not shown), one polygon mirror 42, an image forming lens (not shown), and each photoconductor unit 30 in a unit case 41. A mirror (not shown) is stored, the light from the semiconductor laser for each color component is deflected and scanned by the polygon mirror 42, and an optical image is formed on the corresponding exposure point on the photosensitive drum 31 via the imaging lens and the mirror. It is intended to lead.

In the present embodiment, the transfer unit 23 is, for example, an intermediate transfer belt 230 stretched between a pair of tension rolls (one of which is a drive roll) 231 and 232. A primary transfer device (primary transfer roll in this example) 51 is disposed on the back surface of the intermediate transfer belt 230 corresponding to the photosensitive drum 31. The primary transfer rolls 51 are each charged with a toner by a power source (not shown). By applying a voltage having a polarity opposite to the polarity, the toner image on the photosensitive drum 31 is electrostatically transferred to the intermediate transfer belt 230 side.

Further, a secondary transfer device 52 is disposed at a portion of the intermediate transfer belt 230 corresponding to the tension roll 232 on the downstream side of the most downstream image forming unit 22 K, and the primary transfer on the intermediate transfer belt 230 is performed. The image is secondarily transferred (collectively transferred) to the recording paper P. In the present embodiment, the secondary transfer device 52 includes a secondary transfer roll 521 that is disposed in pressure contact with the toner image bearing surface of the intermediate transfer belt 230.
And a backup roll (also used as a stretching roll 232 in this example) which is disposed on the back side of the intermediate transfer belt 230 and serves as a counter electrode of the secondary transfer roll 521.

In this embodiment, the intermediate transfer belt 2
Reference numeral 30 denotes a material in which a material for imparting conductivity such as carbon or an ionic conductive material is dispersed in a resin material such as polyimide, polycarbonate, or a fluorine-based resin, and has a resistance value of 10 ¹⁰ to
It is formed so as to be adjusted to about 10 ¹⁴ Ω · cm.

The primary transfer roll 51 is made by dispersing carbon in an elastic roll of urethane foam or the like, and has a resistance value of 10%.
^It is adjusted to about ⁶ to 10 ⁸ Ω · cm and formed into a size of φ18.

Further, the secondary transfer roll 521 is formed by injection molding a surface layer made of urethane resin on which carbon is also dispersed, on the outer periphery of an elastic roll made of urethane foam in which carbon is dispersed, and then a fluorine-based material. It has a three-layer structure of φ28 coated with a resin surface layer of 20 μm, and its resistance is adjusted to about 10 ⁷ to 10 ⁸ Ω · cm.

In the present embodiment, the secondary transfer roll 521 is grounded, and a bias having the same polarity as the charged polarity of the toner is applied to the backup roll (stretch roll 232). Furthermore, the intermediate transfer belt 23
A belt cleaner 53 is disposed on the upstream side of the most upstream image forming unit 22Y of the intermediate transfer belt 230.
The upper residual toner is removed.

The supply cassette 24 is provided with a nudger roll 61 for picking up the paper P. Immediately after the nudger roll 61, a separating mechanism 62 composed of a feed roll for separating and sending out the paper P and a retard roll is provided. It is arranged. Further, on the downstream side of the separating mechanism 62, the takeaway roll 63 and the paper P
A registration roll (registration roll) 64 is provided, which is temporarily stopped in a state where it is nipped and then supplied to the secondary transfer portion at a predetermined timing. On the other hand, a fixing device 65 is provided in the paper transport path 25 located downstream of the secondary transfer portion, and a first discharge roll 66 and a second discharge roll 67 for discharging recording paper are provided downstream of the fixing device 65.
Is provided, and the discharged paper P is stored in a storage tray 68 formed on an upper portion of the main body housing 21.

Reference numeral 71 denotes a takeaway sensor provided between the separation mechanism 62 and the takeaway roll 63, reference numeral 72 denotes a registration sensor provided immediately before the registration roll 64, and reference numeral 73 denotes a first discharge roll 66 and a second discharge roll. Discharge roll 6
7 is a discharge sensor provided between the discharge sensor 7 and the discharge sensor 7.

Next, an image forming process of the tandem type image forming apparatus according to the present embodiment will be described. In the tandem image forming apparatus shown in FIG. 2, when a print start switch (not shown) or an image output device such as a personal computer is turned on, an image forming process is executed. Now, for example, 1
7 "(inch) size paper P (279.4 × 431.
8 mm), an attempt is made to create a continuous plurality of full-color images, and image formation is performed in the image quality priority mode. Each image forming unit 22 (22Y, 22M, 22C, 22
K), each color component toner image is formed, and the intermediate transfer belt 2
The respective color component toner images are sequentially transferred onto the intermediate transfer belt 230 in a multiplex manner, and the full-color image (multiple transfer image) on the intermediate transfer belt 230 is collectively transferred onto the paper P. At this time, the intermediate transfer belt 2
The full-color image Gc of each page on page 30 is shown in FIG.
As shown in FIG.
It is sequentially formed at a dimension interval six times the circumference S of one.

FIG. 4 is a timing diagram of the paper transport system when a color image is created. still,
In the figure, reference numeral Ps indicates the leading end of the paper P, and reference numeral Pe indicates the trailing end of the paper P. At the time of forming a color image, the timing of feeding the sheet P from the registration roll 64 is determined in accordance with the timing at which the full-color image Gc reaches the secondary transfer device 52 (secondary transfer position). It is set to the same length as Pc.

As described above, when forming a full-color image,
Since the image forming units 22Y, 22M, 22C, and 22K are used, the image forming pitch Pc is set to an integral multiple of the circumferential length S of the photosensitive drum, so that the photosensitive drum 31 of each image forming unit 22 has Since the density difference and color difference tendency of each color component image generated due to the fluctuation component of the peripheral surface can be reproduced at the same position on the paper P, even when a plurality of the same full-color images are formed, each color component It is possible to equalize the shades of the composite images of the images without variation, and accordingly, it is possible to minimize the variation in the full-color image quality of each page and to keep the full-color image quality good at all times.

On the other hand, when attempting to create a plurality of continuous monochrome images (monochrome black images) on the same 17 ″ (inch) size paper, image formation is performed in the productivity priority mode. Each image forming unit 22 Among them, a black component toner image is formed by the black image forming unit 22 </ b> K, is primarily transferred onto the intermediate transfer belt 230,
The monochrome image on 30 is secondarily transferred to paper P. At this time, the monochrome image G of each page on the intermediate transfer belt 230
m is, for example, as shown in FIG. 3B, the image forming pitch Pm is irrelevant to the circumference S of the photosensitive drum 31, and is more than the image forming pitch Pc for forming the same size full-color image. Are sequentially formed at short dimensional intervals.

FIG. 5 is a timing diagram of the paper transport system when a monochrome image is created. When a monochrome image is formed, the feeding timing of the sheet P from the registration roll 64 is determined in accordance with the timing at which the monochrome image Gm reaches the secondary transfer device 52 (secondary transfer position). P
Set to the same length as m. Therefore, the sending pitch Ppm at the time of monochrome image formation is set shorter than the sending pitch Ppc at the time of full color image formation.

As described above, when forming a monochrome image, only the image forming unit 22K is used, so that the photosensitive drums 31 of the other image forming units 22Y, 22M and 22C are used.
There is almost no need to consider the density difference and color difference tendency of each color component toner image generated due to the fluctuation component of the peripheral surface of the photosensitive drum 31. Therefore, the image forming pitch Pm is independent of the circumferential length S of the photosensitive drum 31. Is not adversely affected by the setting of, the productivity can be improved as compared with the case of forming a full-color image.

In the present embodiment, the image forming pitch Pc at the time of full-color image formation is set to 6 times the circumference S of the photosensitive drum 31.
Although the number is multiplied, it changes depending on the size of the full-color image to be formed and the size of the circumference S of the photosensitive drum 31, and may be set to an integral multiple or (1 / integer) multiple.

In this embodiment, an image forming mode (image quality priority mode) that emphasizes image quality when forming a full-color image is an image forming mode (productivity priority mode) that emphasizes productivity when forming a monochrome image (single color image). Mode) is automatically selected, but the present invention is not limited to this, and the user may be able to select it.

[0029]

As described above, according to the present invention,
In a so-called tandem engine type image forming apparatus, the dimensional relationship between the circumference S of the image carrier and the image forming pitch Pc is represented by Pc.
= N · S (n: integer or 1 / integer), and an image quality priority mode for performing image formation at an image formation pitch Pm shorter than the image formation pitch Pc. Therefore, image quality can be ensured or productivity can be improved according to the needs of the user.

In the present invention, when a multicolor image is formed by using two or more image forming units among a plurality of image forming units, image formation is performed in the image quality priority mode, and one image forming unit is used. When forming a single-color image by using the unit, if the image formation is performed in the productivity priority mode, it is possible to minimize variations in image quality when forming a multi-color image, and when forming a single-color image. Productivity can be improved.

[Brief description of the drawings]

1A is an explanatory diagram illustrating a schematic configuration example of an image forming apparatus according to the present invention, FIG. 1B is an explanatory diagram illustrating a relationship between a circumference of an image carrier and an image forming pitch in an image quality priority mode,
FIG. 4C is an explanatory diagram showing a relationship between the circumference of the image carrier and the image forming pitch in the productivity priority mode.

FIG. 2 is an explanatory diagram illustrating an outline of an image forming apparatus according to the embodiment;

3A is an explanatory diagram illustrating an image forming state when forming a full-color image, and FIG. 3B is an explanatory diagram illustrating an image forming state when forming a monochrome image.

FIG. 4 is a timing diagram relating to paper supply timing and image formation timing during full-color image formation.

FIG. 5 is a timing diagram related to a sheet supply timing and an image formation timing during monochrome image formation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming unit, 2 ... Intermediate transfer body, 3 ... Recording material,
4. Image carrier, S: circumference of image carrier, Pc: image formation pitch in image quality priority mode, Pm: image formation pitch in productivity priority mode

Claims (2)

[Claims] A plurality of image forming units arranged in parallel along a moving path of an intermediate transfer body or a recording material, each image forming unit including an image carrier for carrying each color component image; In an image forming apparatus that transfers each color component image formed on the image carrier of each image forming unit to a recording material via an intermediate transfer body or directly, in the image quality priority mode, the image carrier of each image forming unit is When the circumference is S and the image forming pitch is Pc,
An image is formed so as to satisfy the relationship of Pc = n · S (n: an integer or 1 / integer). In the productivity priority mode, when the image forming pitch of the image is Pm, the relationship of Pm <Pc is satisfied. Image forming apparatus for performing image formation as described above. 2. The image forming apparatus according to claim 1, wherein when forming a multicolor image using two or more image forming units among the plurality of image forming units, the image forming apparatus operates in the image quality priority mode. An image forming apparatus, wherein an image is formed and an image is formed in the productivity priority mode when a single color image is formed using one image forming unit.