JP3387272B2 - Color image forming equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming method in which a single color toner image formed on each of a plurality of image carriers is sequentially transferred onto a transfer material conveyed by a transfer material conveying body to form a color image. It relates to the device.

[0002]

2. Description of the Related Art In recent years, a predetermined monochromatic toner image is formed on a plurality of image forming members such as photoconductors by an electrophotographic method, and a transfer material such as a transfer paper is formed in an endless belt shape or a drum shape. A color configured to obtain a color image by being adsorbed to the transferred transfer material carrier and sent to the transfer position of each image forming body, and transferred and fixed so that the toner images are sequentially superposed on the transfer material. Many image forming apparatuses have been proposed.

For example, in Japanese Patent Laid-Open No. 4-166957, four drum-shaped photoconductors each provided with an electrophotographic image forming process means are used, and the photoconductor drums are respectively placed near the transfer positions of the photoconductor drums. An endless belt-shaped recording material supporting member is arranged so as to rotate, and a plurality of pressing means for pressing the recording material conveying belt toward the photosensitive drum to contact the drum surface are transferred. The color image forming apparatus is shown in position.

In this color image forming apparatus, a plurality of pressing means as transfer assisting members are all turned on (pressing operation) immediately before transferring the toner image on the photosensitive drum of the first color, while the final color toner is pressed. Immediately after the transfer of the image on the photosensitive drum is completed, all are turned off (press release operation)
Is set to. Then, by turning on / off the pressing means at such timing,
The time during which the pressing unit pushes up the recording material conveying belt is kept to a minimum, and wear of the photosensitive drum, the recording material conveying belt, and the pressing unit is prevented.

[0005]

However, in the above-mentioned color image forming apparatus, the cause is vibrations generated when the pressing means is turned on and off with respect to the recording material conveying belt, and a braking action due to frictional resistance. There is a big problem that defective image quality occurs.

Therefore, an object of the present invention is to provide, as a color image forming apparatus having the above-mentioned structure, a color image forming apparatus capable of preventing a defective image quality which occurs due to the on / off operation of the pressing means. To provide.

[0007]

SUMMARY OF THE INVENTION A color image forming apparatus according to the present invention comprises a plurality of image carriers on which a monochromatic toner image is formed, and a transfer material carrier which is arranged close to the transfer positions of the respective image carriers. And a plurality of pressing means for pressing the transfer material conveying body toward the image carrier at each transfer position to bring it into contact with the image carrier, a pressing operation by the plurality of pressing means is performed. The first color latent image writing process is sequentially executed, and the pressing operation by each pressing unit is canceled after the final color transfer process is completed.

The above-mentioned pressing means is provided one for each image carrier, and, for example, a pressing member for contacting and pressing the transfer material carrying member and a transfer member by moving the pressing member up and down are transferred. The material transporting carrier can be constituted by a contacting / separating mechanism capable of urging the carrier toward the image carrier or releasing the urging.

The pressing operation by the plurality of pressing means is sequentially performed with a time lag, and the pressing operation by the pressing means for the final color is always completed before the start of the latent image writing process for the first color. I'll do it. Moreover, the pressing operation by the plurality of pressing means is released after the transfer process on the image carrier of the final color is completed. The release operation is
It may be carried out simultaneously or sequentially for all the pressing means, but it is desirable to carry out sequentially with a time difference.
When the pressing operation by the pressing unit and the release thereof are sequentially performed, in each case, the pressing unit for the first color is started and the pressing unit for the final color is performed. Therefore, it is necessary to set the timing such that the pressing operation and the releasing operation thereof by the plurality of pressing means are not performed at least while the latent image writing is started or the transfer process is not completed on any of the image carriers. Good.

Further, in the present invention, the image bearing member is composed of a photosensitive member or a dielectric member capable of forming a latent image by an electrophotographic system or an electrostatic recording system, and its form is drum-like or belt-like. Either may be used. The transfer material conveying body is for adsorbing and holding a transfer material formed of recording paper or the like for transferring a monochromatic toner image formed on the image bearing body and conveying it to a transfer position or the like. It has a drum shape. In the case of a belt-shaped transfer material carrier, it is desirable to use a seamless belt.

The image forming apparatus according to the present invention can form a full-color image as well as a black-and-white image and a mono-color image by including a plurality of image carriers independent of each other. Further, this image forming apparatus can be mainly applied to a color copying machine, a color printer or the like.

[0012]

According to the present invention, the pressing operation and the releasing operation thereof by the plurality of pressing means are not performed while the latent image writing is started or the transfer step is not completed on at least one of the image carriers. Therefore, the vibrations and the like generated by the respective operations do not adversely affect the image formation on the image carrier and the transfer of the image. Moreover, since the pressing operation by the pressing means is sequentially performed with a time difference,
The pressing action does not adversely affect the image formation and the transfer of the image due to the braking action generated between the transfer material transport body and the instantaneous deflection of the transport body. In particular, when this pressing operation is performed at the same time, the driving power is concentrated and excessively consumed due to the operation, which may cause a malfunction of the entire device due to a voltage drop. There is no such concern in the invention.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 and 2 show an embodiment of the present invention. FIG. 1 is a schematic configuration diagram showing a main part of a color image forming apparatus, and FIG. 2 is an enlarged view showing a pressing means and its peripheral part. Is.

This color image forming apparatus rotates in the direction of the arrow and is a photosensitive drum 1k, 1y, 1 as an image carrier.
m, 1c. These four photosensitive drums 1k,
Similarly, a charger 2, a laser scanning type image exposure device 3, a developing device 4, a pre-transfer charger 5, a transfer device 6, a cleaning device 7, etc. are arranged around 1y, 1m and 1c, respectively. Therefore, each photosensitive drum 1 (k, y, m,
Monochromatic toner images of k (black), y (yellow), m (magenta), and c (cyan) are formed on c).

For example, when the color image forming apparatus is configured as a digital color copying machine, a color image reading device reads a document set on a document table (not shown), and the read signal is digital image processed by the image signal processing means. It can be converted into a signal and temporarily stored in a memory, and toner images of respective colors can be formed based on the stored digital image signals of four colors (k, y, m, c). That is, the image exposure devices 3k, 3k are supplied in accordance with the digital image signals of the respective colors input from the image signal processing means.
y, 3m, 3c are respectively driven, and chargers 2k, 2y,
Photoreceptor drum 1k uniformly charged by 2m and 2c,
An electrostatic latent image is written in each of 1y, 1m and 1c. Then, the respective electrostatic latent images are developed by the developing devices 4k, 4y, 4m and 4c containing the toners of the respective colors (k, y, m, c) to form the toner images of the respective colors. When the color image forming apparatus is configured as a device such as a printer, toner images of respective colors may be formed based on an image signal input to the image signal processing unit from the outside or the like.

Further, in this color image forming apparatus, the transfer material transfer consisting of a seamless belt is carried out so as not to be in contact with the lower side which is the transfer position of the above-mentioned four photosensitive drums 1k, 1y, 1m and 1c. The belts 10 are arranged close to each other. The transfer material conveying belt 10 is stretched around a driving roll 11, a peeling roll 12, a tension roll 13, an idler roll 14, etc., and is rotated in the arrow direction. Further, the transfer material conveying belt 10
Each transfer device 6 disposed on the opposite side of each photoconductor drum 1
Transfer baffles 8 as pressing means are provided on the front sides of k, 6y, 6m, and 6c. Further, around the transfer material conveying belt 10, in order to separate the transfer material P to be fed, an adsorption charger 15 for adsorbing the transfer material P onto the belt, an adsorption roll 16, and the transfer material P from the belt 10. Peeling claw 17, a fixing device 18 for fixing an unfixed toner image on the transfer material P, a static eliminator 19 for discharging the belt 10, and a cleaning device 20 for removing residual deposits on the belt 10. Is provided. And
On the transfer material conveying belt 10, a plurality of transfer materials P can be sucked and held in respective holding areas and simultaneously transferred.

As shown in FIG. 2, the transfer baffle 8 has a flexible pressing member 80, and a supporting member 8 for supporting the pressing member 80, which rotates about a support shaft 81.
2 and a retract mechanism 83 that rotates the support member 82 in the directions of arrows P and Q by a predetermined amount, and the main parts thereof are configured. The pressing operation by the transfer baffle 8 is performed by rotating the support member 82 in the arrow P direction by the retract operation of the retract mechanism 83 and pressing the transfer material conveying belt 10 slightly by the tip of the pressing member 80. Done. As a result, the belt 10 comes into contact with the surface of the photosensitive drum 1. On the other hand, the pressing operation by the transfer baffle 8 is released by rotating the support member 82 in the direction of the arrow Q by the retract mechanism 83 and separating the tip end portion of the pressing member 80 from the inner surface of the belt 10.
As a result, the belt 10 is brought into non-contact with the photoconductor drum 1. The on / off operation timing of the transfer baffle 8 will be described later.

Now, as described above, each photosensitive drum 1
The monochromatic toner images of the respective colors formed on k, 1y, 1m, and 1c are adjusted by the pre-transfer charger 5 to the optimum charging state for transfer, if necessary, and then subjected to the action of the transfer device 6. The transfer material P is successively superposed and transferred onto the transfer material P that is adsorbed and conveyed by the transfer material conveyance belt 10. That is,
The transfer material P is conveyed by the belt 10 so that each photosensitive drum 1 is transferred.
By passing the transfer positions of k, 1y, 1m, and 1c in contact with the belt 10 in this order, the toner images are transferred so as to be superposed. The transfer material P on which the multi-color toner images have been formed after the transfer process on the photoconductor drum 1c is completed.
Is peeled from the belt 10 by the peeling pawl 17 and sent to the fixing device 18, where it is subjected to a fixing process and then discharged to the outside of the machine.

After the transfer process is completed, each photoconductor drum is cleaned by the cleaning device 7 to remove the charge, and then the image forming process as described above is continuously repeated or waits for the next image forming process. To do. On the other hand, the transfer material conveying belt 10 after the transfer material P is peeled off is discharged by the charge eliminator 19 and then cleaned by the cleaning device 20.

By the way, in such an image forming apparatus, when vibrations or the like generated during the on / off operation of the transfer baffle 8 are transmitted to the photosensitive drum 1 during the latent image formation by the image exposure apparatus 3, for example, the photosensitive drum 1 is exposed. A slight displacement of the body drum 1 causes a shift in the irradiation position of the exposure light 3a, which causes poor image quality.

Therefore, in this embodiment, the transfer baffle 8 is set to be turned on / off at the following timing. FIG. 3 is a timing chart for explaining the on / off operation timing. The on / off operation timing shown in FIG. 3 is a basic setting content when one full-color image is printed. Note that, in FIG. 3 (the same applies to FIGS. 4 and 5), the charts regarding the formation and transfer of the toner images of the second color (y) and the third color (m) are omitted.

First, the transfer baffles 7k, 7y, 7m,
As shown in FIG. 3, the on-operation (pressing operation) of 7c is performed in this order (k, y, m, before the time S at which the latent image writing by the image exposure device 3k for the first color (k) is started.
It is designed to be performed in c). Also, each transfer baffle 7
The off operation (press release operation) of k, 7y, 7m, and 7c is
The process is performed in this order (k, y, m, c) after time E when the transfer process (operation of the transfer device 6c) for the final color (c) is completed. In this embodiment, both the ON operation and the OFF operation are sequentially performed with a shift of about 100 msec. As a result, temporary and excessive power consumption in the apparatus does not occur, and it is possible to avoid problems such as defective image formation due to voltage drop.

When a full-color image is continuously printed, on / off operation timing of the transfer baffle 8 is set as shown in FIGS. FIG. 4 is a timing chart in the case where two full-color images are continuously printed on two transfer materials (that is, two transfer materials P are continuously adsorbed to the front and rear holding areas on the conveyor belt 10) and printed. FIG. 5 shows two transfer materials P that intermittently feed a full-color image (that is, two transfer materials P in a holding area before and after the holding area on the conveyance belt 10 is opened by one or more sheets). The timing chart at the time of printing after making each adsorb | suck is shown.

As shown in FIG. 4, the transfer material 2 is continuously fed.
When printing continuously on one sheet,
When the writing of the latent image of the first color (k) of the first sheet is started
Point S ₁Before k, y, m, c
It is set, but for the off operation it is not the first one but two
Time point E when the transfer process of the final color (c) of the eye is completed₂After
Is set in order of k, y, m, and c.
That is, when the transfer process for the final color (c) of the first sheet is completed
Point E₁Then, writing the latent image of the first color (k) on the second sheet
Already started (S₂) Therefore, the occurrence of poor image quality, etc.
At this point (E₁) Transfer baffle 7
It should not be turned off.

On the other hand, as shown in FIG. 5, when printing is continuously performed on two sheets of transfer material that are intermittently fed, when the transfer step for the final color (c) of the first sheet is completed, the time point E ₁ and the second color (K)
If there is a certain amount of free time T ₀ between the time point S _{2 at} which the latent image writing is started and the time point after the time point E ₁ , the off operation is performed once in the order of k, y, m, and c. It is set so that the ON operation is performed again in the order of k, y, m, and c before S ₂ . That is, when there is a vacant time T ₀ between the end time E ₁ of the transfer process of the first color of the first sheet and the start time S ₂ of the latent image writing of the second color, the transfer baffle 8 is turned off / on positively. It is desirable to carry out the operation so as to minimize unnecessary contact time between the conveyor belt 10 and the photosensitive drum 1. As a result, it is possible to prevent transfer baffle abrasion due to rubbing against the conveyor belt 10 and transfer of fixing oil or the like adhering to the conveyor belt 10 to the photosensitive drum 1 side. In the case of continuous printing in such an intermittent state, as a matter of course, the first ON operation is sequentially performed before the first color latent image writing start time S ₁ of the first sheet, and the final Off operation is 2
It is set so as to be sequentially performed after the time point E _{2 at} which the color transfer process ends.

The effect obtained by setting the off / on operation timing of the transfer baffle 8 as described above is particularly effective with respect to the region side of the transfer material conveying belt 10 which is on the downstream side in the rotation direction of the driving roll 11 as in this embodiment. This is more remarkably obtained in a color image forming apparatus having a configuration in which a plurality of photosensitive drums are arranged side by side.

This is because the transfer material conveying belt 10 is generally related to the driving force transmitting action of the driving rolls.
The drive roll rotating direction upstream side (in this example, the static eliminator 19
To equal the belt area to be side) which is arranged from becoming relatively taut during rotation, drive roll rotation direction downstream side a region (side where the photosensitive drum or the like is high) the upstream It becomes slightly slack compared to the area. Therefore, in the downstream side region of the transfer material transport belt 10 in a slightly slack state, the slack is promoted when the transfer baffle 8 is turned on / off, and the belt behavior is likely to change.
As a result, there is a high possibility that image quality will be poor. From this, the photoconductor drum is connected to the transfer material conveying belt 1
In the apparatus arranged in the downstream region of 0, it is extremely effective to turn on / off the transfer baffle at the timing as described above from the viewpoint of preventing the occurrence of defective image quality.

[0029]

As described above, in the color image forming apparatus of the present invention, the pressing operation by the plurality of pressing means and the releasing operation thereof are performed at the timings as described above, so that they occur at the respective operations. It is possible to reliably prevent defective image quality caused by such vibrations and braking action. In addition, since the pressing operations are sequentially performed with a time lag, the image quality is deteriorated due to the behavior variation of the transfer material transport body which is likely to occur when the pressing operations are simultaneously performed, and the operation is excessive. At the same time, it is possible to prevent image quality defects and the like caused by voltage drop due to excessive power consumption.

In the case where the pressing operation and the releasing operation by the plurality of pressing means are sequentially performed in the order from the pressing means for the first color to the pressing means for the final color, Compared with the case where the order is reversed (from the last color side to the first color), it is possible to more reliably prevent the behavior variation of the transfer material transporter that may occur due to each operation. Further, in particular, by performing the releasing operation sequentially in the order as described above, when the transfer material after the transfer of the final color is slightly separated from the transfer position (of the pressing means), the pressing means of the final color is pressed. Since the releasing operation is performed, it is possible to avoid the problem that the unfixed toner image transferred onto the transfer material is disturbed by the vibration or the like generated during the releasing operation. Therefore, in the case of the above, it is possible to more surely obtain the above-described effect of preventing the image quality defect and the like.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing a pressing unit (transfer baffle) of FIG. 1 and its peripheral configuration.

FIG. 3 is a timing chart showing a basic example of on / off operation timing of a pressing unit.

FIG. 4 is a timing chart showing an irregular example of the on / off operation timing of the pressing means.

FIG. 5 is a timing chart showing another irregular example of the on / off operation timing of the pressing means.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 8 ... Pressing means, 10 ... Transfer material conveying body.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Hayashi 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (72) Inventor Junichiro Samejima, 2274 Hongo, Ebina City, Kanagawa Prefecture Within Fuji Xerox Co., Ltd. (72) Inventor Ryoichi Tsuruoka 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (56) Reference JP-A-4-134369 (JP, A) JP-A-6-110339 (JP, A) JP-A-6-102776 (JP, A) JP 62-127770 (JP, A) JP 64-59258 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/01-15 / 01 117

Claims (3)

(57) [Claims] And 1. A monochromatic plurality of image bearing members on which a toner image is formed of a transfer material transport belt you rotate disposed close over the transfer position thereof the image carriers, the transfer material transport
Is pressed toward the image carrier-side belt at each transfer position and a plurality of pressing means for contacting the image bearing member, said plurality
The image carrier is driven by a drive roller that rotates the transfer material transport belt.
Of the conveyor belt in the downstream side in the rotation direction of the conveyor belt.
In the mounted color image forming apparatus, the pressing operation by the plurality of pressing means is sequentially performed before the start step of writing the latent image of the first color, and the pressing operation by each pressing means is canceled after the transfer step of the final color is completed. A color image forming apparatus characterized in that. 2. The apparatus according to claim 1, wherein the pressing operation by the plurality of pressing means is sequentially performed in order from the pressing means for the first color to the pressing means for the last color. Characteristic color image forming apparatus. 3. The apparatus according to claim 1 or 2, wherein the pressing operation by the plurality of pressing means is released in order from the pressing means for the first color to the pressing means for the last color. A color image forming apparatus characterized by the above.