JPH04147162A - Image forming device - Google Patents

Abstract

PURPOSE:To form images of high quality without staining the reverse side of a transfer material by sucking, carrying and conveying respective transfer materials, which are fed successively to a transfer material carrying means in the continuous operation of the image formation device, to the same position on the transfer carrying means at all times through the rotating operation of the transfer carrying means. CONSTITUTION:The center of a flow of the operation is on a CPU 501 and a main body operation sequence is indicated by a ROM 502. The operation, on the other hand, is timed by counting clock pulses, outputted by a transfer belt driving motor 505, by a counter 503 and referring the ROM 502 in order through the CPU 501 about the counted value. Paper distances corresponding to respective transfer material sizes are stored in part of the ROM 502 and the position of transfer materials sucked on a transfer belt is controlled to invariably the same position according to a transfer material and a number of copy that a user inputs with operation keys 504. Consequently, images of high quality can be formed without the reverse staining of the transfer materials.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to an image forming apparatus that forms a visualized image, that is, a toner image, on an image carrier and transfers the toner image to a transfer material. An electrophotographic or electrostatic recording method in which a transfer material is supported on a supporting means, and a toner image formed on an image bearing member such as a photosensitive drum or an insulating drum is transferred to the transfer material under the action of the transfer means. The present invention relates to an image forming apparatus that can be applied to type copying machines, printers, and the like.

In recent years, full-color electrophotographic copying machines have been widely used, and a typical four-drum type full-color electrophotographic copying machine is illustrated in FIG.

According to this example, the copying machine includes four image forming stations I, ①, ②, and IV. The first image forming station I has an electrophotographic photosensitive drum 1a as an image carrier which is rotatably supported and rotates in the direction of the arrow. A device 3a, a developing device 48, and the like are provided, and a toner image is formed on the photosensitive drum la. Further, the toner image is transferred to a transfer material P as described below, and the residual toner on the photosensitive drum 1a is removed by a cleaner 28a, and the photosensitive drum la is subjected to the next image forming process. The configurations of the other image forming stations ①, Il'l, and IV are exactly the same.

In order to carry and convey the transfer material P to each image forming station, a transfer belt 25 as a transfer material carrying means is provided passing through each image forming station and rotates in the direction of the arrow.

In other words, when the transfer material P, which is normally used as transfer paper, is fed from the paper feeding section to the transfer belt 25, the transfer material P is transferred to the adsorption charger 1.
9, it is attracted to the transfer belt 25. At this time, charges necessary for adsorption are injected into the transfer belt 25 by the grounded metal roller 20.

The transfer belt 25 rotates in the direction of the arrow L, and transfers the toner image formed by the first image forming station I to the charger 7a.
The image is transferred onto the transfer material P by using the method. Further, the toner images are sequentially transferred through the second, third, and fourth image forming stations, and the static charge L is removed by the charger 29, and the transfer material P is separated from the transfer belt 25. Ru. Finally, the toner image on the transfer material P is made into a permanently fixed image by the fixing device 18, and the operation ends.

The transfer belt 25 used here is a belt with a seamless structure.

FIG. 12 shows the operation sequence of the four-drum full-color electrophotographic copying machine of this example. This operation sequence is A
The figure shows the case where full-color copies are made continuously by horizontally feeding four sizes of transfer materials P, but the distance between the transferred transfer materials (hereinafter referred to as "inter-paper distance") is In addition, Table 1 shows the inter-paper distance for each transfer material size in the copying machine of this example, and it is constant 90 mm regardless of the size of the transfer material and the number of sheets in continuous operation.

Table 1 In this way, in conventional copying machines, by using a seamless transfer belt, the image forming operation, mainly the transfer process, can be performed under the same conditions at any location on the belt. It is configured to operate at the minimum distance between sheets that is not subject to restrictions on the operation of the main body, and at the same distance between sheets at all times even during continuous copying.

As a result, the number of copies is maximized, and when operating in the sequence shown in Figure 12, 28 copies/minute for A4 and 16 copies/min for A3.
．． Productivity of 5 pieces per minute was achieved.

The constraints due to the operation of the main body mentioned above include ■ Return time of the image reading unit after scanning, ■ Rotation of the feed roller of the paper feeder, etc., and rise time of stop operation, but the most dominant one is the above-mentioned ■ be. Since the return time in the above-mentioned (2) in this conventional example is 0.6 seconds, a slight margin is taken and the distance between the sheets is set to 90 mm.

In this specification, the conventional method in which the number of copies per time is prioritized L and the inter-paper distance is kept shortest and constant will be referred to as a "constant paper-interval mode" in this specification.

FIG. 13 is a diagram showing the position at which the transfer material P is attracted onto the transfer belt 25 whose total circumference length is 1600 mm when operating in the "constant paper spacing mode".
The transfer belt 25 is shown in an expanded form. Although Fig. 13 only shows up to the second cycle, if continuous copying is performed further, the third cycle, fourth cycle, etc. will continue under the condition that the paper distance a is constant. .

As can be seen from FIG. 13, the transfer material P attracted to the transfer belt 25 is not necessarily attracted in the second cycle to the position on the belt that was attracted in the first cycle, and in this example, the transfer material P is attracted to the transfer belt 25 in the first cycle. The transfer material of the second period is attracted to overlap the inter-paper area.

However, in the inter-paper area shown in the above conventional example, toner adheres for reasons to be described later, and back stains occur on the transfer material discharged after the second period in FIG. 13. There was a problem.

For example, the back side of the seventh sheet of transfer material P during continuous A4 full color copying according to the conventional example is stained in a band-like manner as shown by double diagonal lines in FIG. The dirt on the transfer belt 25 The toner itself is extremely small, with a reflection density of about 5%, but since it is band-shaped, the contrast between it and the white background becomes sharp, which significantly degrades the quality of the copy. It became.

In addition, in order to avoid such problems, when the length of the transfer belt 25 is L, the length of the transfer material P in the conveying direction is 1, and the distance between sheets is a, L/ (a-1 −42) =n
It is possible to determine L so that the relationship is (n; natural number), but since it is a mini-constant, the length of ρ is usually not one type, so it is realistic to always satisfy the above equation. It cannot be found within the length of the transfer belt 25.

Regarding the toner adhesion to the transfer belt 25 mentioned above, there are the following two main causes.

(1) Adhesion of floating toner From the developing device 4 (48 to 4d), in addition to the toner that adheres to the photosensitive drum 1 (1a to ld) during development or other times, the developing device installed in the developing device Some toner is scattered due to the influence of centrifugal force caused by the rotation of the developing sleeve 5 (58 to 5d) for carrying and conveying the toner. Further, although the cleaner 28 (288 to 28d) is originally intended to collect residual toner after transfer on the photosensitive drum 1, the toner peeled off from the photosensitive drum 1 is not completely collected in the cleaner container. A small amount will be dispersed into the air.

Scattered toner from the developing device 4 and the cleaner 28 falls onto the transfer belt 25, causing stains on the back side.

(2) Adhesion of fog toner Fog toner can be classified into the following two types.

■When the development operation is performed in the area corresponding to the paper gap (non-image area), toner with a small retained charge or with an opposite polarity charge may be contained in the developer. Because of this presence, some amount of development occurs even though it is a non-image area.

■If the development operation is stopped in the area corresponding to the paper gap,
The rotation of the developing sleeve 5 is stopped and started in the non-image area, and at that time, the movement of the developing sleeve 5 is the 14th rotation.
The result is as shown in Figure (a). Also, the toner remaining on the photosensitive drum 1 at this time is as shown in FIG. 14(b), and - toner stains caused by stopping and starting the rotation of the developing sleeve 5 while fishing on a boat are more serious than in case (2) above. There will be more.

Therefore, an object of the present invention is to control the position of the transfer material adsorbed onto the transfer belt or transfer drum so that it is always at the same position during continuous image forming operations, thereby preventing the back side of the transfer material from becoming stained. An object of the present invention is to provide an image forming apparatus capable of forming high-quality images.

・In order to The above object is achieved by an image forming apparatus according to the present invention.

To summarize, the present invention provides an image carrier on which a visible image is formed, a transfer material carrier provided adjacent to the image carrier and rotating while supporting a transfer material, and a transfer material carrier provided on the image carrier. In an image forming apparatus having a transfer means that operates to transfer a formed visible image to a transfer material carried by the transfer material carrying means, when the image forming apparatus is in continuous operation, the visible image is continuously transferred to the transfer material carrying means. The image forming apparatus is characterized in that each transfer material fed by the image forming apparatus is always suction-supported and conveyed at the same position on the transfer material carrying means through the rotational movement of the transfer material carrying means.

Preferably, when the total circumference of the transfer material carrying means is L and the length of the transfer material is ρ, the distance a between the transfer materials is L/(a+1!,) for each size of the transfer material. = n (n: natural number) is set so that L is satisfied, and during continuous operation of the image forming apparatus, this transfer material gap 871a is maintained during operation, and the transfer material carrying means is endlessly rotatable. Seamless belt or seamless drum.

J1 discharge 1 Next, the image forming apparatus according to the present invention will be described in more detail based on an embodiment.
The present invention is assumed to be embodied in the four-drum full-color electrophotographic copying machine described in connection with FIG. Therefore, a description of the structure of the full-color electrophotographic copying machine and the boat fishing operation will be omitted.

FIG. 1 shows the operation sequence when continuous copying is performed using A3 size transfer material in this embodiment.

As can be understood from FIG. 1, according to the present invention, the distance between the sheets is increased from the first period to the second period, and the transfer material P is transferred during the first period even during the second period. The transfer belt 25 is configured to be attracted to the same position on the transfer belt 25.

Table 2 shows the length of the transfer material and the paper distance when continuous copying is made of the transfer material P of each size. At the same time as with the conventional device, the circumferential length of the transfer belt 250 is calculated as 1600 mm. ing.

Table 2 FIG. 2 is a diagram showing at which position the transfer material P is attracted on the transfer belt 25 when the present embodiment is operated, and shows the transfer belt 25 in an expanded form.

The operational control aspect of the copying machine according to this embodiment is shown in an operational block diagram in FIG. According to this embodiment, the center of the operation flow is in the CPU 501, and the main body operation sequence is R.
Indicated by OM (Read Only Memory) 502. In addition, regarding the components of each part within the main body, the CPU 50
1, a DC controller 506, a D/A converter (not shown), an I10 port, and various parts such as a pickup roller, registration roller, drum motor, etc. in the paper feeding device related to paper feeding operation, Sends commands to high-voltage power supplies, etc.

On the other hand, the timing of the operation is such that the pulse clock output by the transfer belt drive motor (pulse motor) 505 is integrated L by the counter 503, and the value is sequentially sent to the CPU 501.
This is done by referring to the ROM 502 via the ROM 502.

In addition, a part of the ROM 502 stores the paper distance corresponding to each transfer material size shown in Table 2. Achieve "adsorption mode". In this specification, the term "same position suction mode" refers to a mode in which control is performed so that the position of the transfer material suctioned onto the transfer belt is always at the same position during continuous copying.

FIG. 4 shows an operation sequence when A4 size continuous copying is performed according to another embodiment of the present invention.

In the first embodiment described above, in order to achieve the "same position suction mode", the paper distance when moving from the first cycle to the second cycle, that is, A
In 4 mode, the 5th and 6th, 10th and 11th...
・This method achieves the objective of the present invention, which is to prevent stains on the back side, but the transfer material is not ejected at regular intervals, which creates an unnatural feeling for the user. It is possible to give

Therefore, in this embodiment, by changing the paper distance depending on the size of the transfer material, both fixed time interval and "same position suction mode" are achieved.

Now, assuming that the length of the transfer belt is L, the paper distance is a, and the length of the transfer material is 2, in this embodiment, L/(a + β) = n
The paper distance a is determined according to the size of the transfer material so that (n; natural number) holds.

Table 3 shows the paper gap 811a for each size of transfer material, and the calculation was made assuming that the transfer belt circumference was 1600 mm.

Table 3 Figure 5 shows the transfer belt 2 when operated according to this embodiment.
5 is a diagram showing where the transfer material P is attracted onto the transfer belt 5, and shows the transfer belt 25 in an unfolded form. The paper distance a is longer (from 90 mm to 110 mm) compared to the conventional technology, but the "same position suction mode" has been achieved.
Moreover, the distance a between each paper is constant, and by continuous copying operation,
The transfer material is discharged at regular time intervals.

When the operation sequence is performed based only on the pulse clock signal sent from the belt drive motor 505 as in Examples 1 and 2, the maximum number of pulse clocks output is ±0.5. Since there is an error of about 10%, it is not suitable in cases where particularly strict control accuracy is required or where the number of sheets that can be set by the user at a time is large.

FIG. 6 shows an outline of the apparatus of this embodiment. According to this embodiment, a light shielding plate 30 is provided on the transfer belt 25, and the home position of the transfer belt 25 is detected every cycle by a photosensor 506 on the main body. Then, the count of the pulse clock sent from the belt drive motor 505 is reset and corrected every cycle.

The above detection method is clearly illustrated in FIGS. 7(a) and 7(b). FIG. 7(a) is a partial plan view of the transfer belt 25, and FIG. 7(b) is a partial sectional view. In this embodiment, an optical detection method using a photosensor is used as the detection means, but the detection method is not limited to this, and other methods such as an electric method or a magnetic method may be used. Needless to say, it's a good thing.

FIG. 8 is an operational block diagram according to this embodiment. Pulse clocks sent from the belt drive motor 505 are integrated and counted by a counter 503 and sent to the CPtJ 501. A certain number of pulse clocks When the count is counted, it is determined that the transfer belt 25 has made one rotation L. For example, in the case of the first embodiment, it is determined that the second cycle has started, and the operation is continued, but in the case of this embodiment, it reaches X. . When the home position is detected by the sensor 506, regardless of whether it has not been reached, the counter 503 is reset and the count becomes 0'', and it is determined that the second cycle has begun, and the operation begins.

According to this embodiment, it is possible to achieve a "same position suction mode" that is even more accurate than embodiments 1 and 2.

In explaining each of the above embodiments, a four-drum type full-color electrophotographic copying machine using a transfer belt 25 has been explained as an example, but the present invention is not limited thereto.

For example, a four-drum full color copying machine using a seamless transfer drum 25 as shown in FIG. 9, or a seamless transfer drum 2 as shown in FIG.
The invention can also be suitably implemented in a one-drum type full-color copying machine using a 5".

Furthermore, although not shown here, the present invention is not limited to color copying machines, but can be applied to black and white copying machines, printers, etc. without any loss of effectiveness.

l Anal protrusion 1 The image forming apparatus according to the present invention configured as described above includes:
During continuous image formation, the position of the transfer material adsorbed onto the seamlessly formed transfer belt or transfer drum is controlled so that it is always in the same position, resulting in high-quality images without stains on the back of the transfer material. It is possible to achieve the effect that image formation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an operation sequence of a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram showing the suction position of the transfer material on the transfer belt in Example 1. FIG. 3 is an operational block diagram of the first embodiment. FIG. 4 is a diagram showing the operation sequence of the second embodiment of the image forming apparatus according to the present invention. FIG. 5 is a diagram showing the suction position of the transfer material on the transfer belt in Example 2. FIG. 6 is an apparatus configuration diagram of a four-drum type full-color electrophotographic copying machine according to a third embodiment of the image forming apparatus according to the present invention. FIG. 7 is a diagram showing a home position detection method according to the third embodiment. FIG. 8 is an operational block diagram of the third embodiment. FIG. 9 is an apparatus configuration diagram of a four-drum seamless transfer drum full-color electrophotographic copying machine that can embody the present invention. FIG. 10 is an apparatus configuration diagram of a one-drum seamless transfer drum full-color electrophotographic copying machine that can embody the present invention. FIG. 11 is an apparatus configuration diagram of a conventional four-drum type full-color electrophotographic copying machine to which Embodiment 1 of the present invention is applied. FIG. 12 is a diagram showing the operation sequence of the conventional device. FIG. 13 is a diagram showing the suction position of the transfer material on the transfer belt of the conventional device. FIG. 14 is a diagram illustrating stains on the back side of a transfer material in a conventional apparatus. 1 (la to 1d): Image carrier 25.25'25'': Transfer material carrying means 7 (7a to 7
d): Transfer means Fig. 2 Fig. 5 Fig. 1 period 2nd period Fig. 9 Fig. 10 Fig. 16 Fig. 1 internal period 2nd internal period Fig. 14 (a) (b)

Claims (1)

[Scope of Claims] 1) An image carrier on which a visible image is formed, a transfer material carrier provided adjacent to the image carrier and rotating while carrying a transfer material, and an image carrier on the image carrier. an image forming apparatus comprising: a transfer means that operates to transfer a visible image formed on a transfer material to a transfer material carried by the transfer material carrying means;
During continuous operation of the image forming apparatus, each transfer material that is continuously fed to the transfer material carrying means is always adsorbed and held at the same position on the transfer material carrying means through the rotational movement of the transfer material carrying means. An image forming apparatus characterized in that the image forming apparatus is transported by 2) When the total circumference of the transfer material carrying means is L and the length of the transfer material is l, the distance a between the transfer materials is as follows for each size of the transfer material: L/(a+l)=n( 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is set so that the following relationship (n: natural number) holds true, and the image forming apparatus operates while maintaining the distance a between the transfer materials during continuous operation of the image forming apparatus. 3) The image forming apparatus according to claim 1 or 2, wherein the transfer material carrying means is an endlessly rotating seamless belt or a seamless drum.