JPH06317992A - Image forming device using intermediate transfer body - Google Patents

Abstract

PURPOSE:To prevent the degradation of image quality caused by the void state, etc., of a toner image at the time of transferring by setting the peripheral speed of an image carrier faster than that of an intermediate transfer body and making the speed difference between the peripheral speeds of the image carrier and the intermediate transfer body. CONSTITUTION:An intermediate transfer drum 2 is driven by an individual driving motor different from that of the photosensitive drum 1 and the peripheral speed V1 of the intermediate transfer drum 2 is set faster than the peripheral speed V2 of the photosensitive drum 1 by specific amounts (1-2%). Moreover, the peripheral speed of a bias roller 8 is equal to the peripheral speed V2 of the photosensitive drum 1. When the toner image T of the first color formed on the surface of the photosensitive drum 1 is transferred on the intermediate transfer drum 2 by a corona electrifier 14, the transferred toner image is slightly magnified in accordance with the speed ratio V1/V2, to be transferred and the thickness of toner is reduced by that, to increase the sticking force of the toner. After that, the toner image of the second color is formed on the photosensitive drum 1 and primarily transferred on the intermediate transfer drum 2 similarly and this process is repeated by a prescribed number.

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, and more particularly to an image forming apparatus using an intermediate transfer member.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, as a method of transferring a toner image formed on an image holding member such as a photosensitive drum onto a transfer material such as transfer paper At the same time as it is conveyed over the toner image on the body,
It is common to apply a charge from the back side of the transfer sheet to electrostatically attract the toner onto the transfer sheet. In particular, a transfer method in which the transfer sheet is temporarily supported on a transfer drum that is rotationally driven in synchronization with a photoconductor and a toner image is transferred onto the transfer sheet supported on the transfer drum is It is mainly used in color copiers because it allows direct multiple transfer of images.

Further, after the toner image on the photosensitive member is once primarily transferred onto an intermediate transfer member other than the transfer paper, the toner image newly transferred onto the intermediate transfer member is secondarily transferred onto the transfer paper to form a copy image. The method for obtaining the above is disclosed in JP-A No. 62-17757. In a color copying machine that performs multiple transfer in this manner, it is possible to suppress the occurrence of multiple transfer failure and color registration misalignment due to many factors such as the paper holding state, paper thickness and strain, and paper surface properties. It is known to have an effect. On the other hand, in a copying machine using a transfer drum, it is difficult to hold a thick and strong transfer paper on the transfer drum, and there is a problem that only a limited transfer paper can be used. However, with a color copying machine using an intermediate transfer member, black and white and color images can be obtained on the transfer paper regardless of the type of paper, and since it is not necessary to hold the paper on the transfer drum, paper feeding This has the advantage of simplifying the mechanism and reducing troubles such as paper jams.

In the case of a color electrophotographic apparatus using this intermediate transfer member, a light image decomposed for each different color component is individually exposed on the photosensitive member to form an electrostatic latent image for each color component, A color electron that obtains a color image by developing electrostatic latent images of the respective color components with developers of different colors to form individual visualized images, and superimposing and transferring the developed images on one transfer material. In a photographic device, an intermediate transfer member is provided between a photoconductor and a transfer material conveyance path, and the visible images of different colors individually formed on the photoconductor are once overlaid and transferred on the intermediate transfer member to form a composite image. Then, the composite image is transferred to the one transfer material.

FIG. 7 is a diagram showing a copying apparatus using a conventional intermediate transfer member. Reference numeral 100 denotes a photosensitive drum, and the surface of the photosensitive drum 100 has a primary charger (not shown),
The toner image T is formed by means of an electrophotographic process such as an image exposing means and a developing device. The toner image T formed on the surface of the photoconductor drum 100 is sent to the primary transfer position as the photoconductor drum 100 rotates.
Reference numeral 101 denotes an endless belt-shaped intermediate transfer member which is wound around a plurality of rolls, and the intermediate transfer member 101 is arranged so as to come into contact with or approach the surface of the photosensitive drum 100 at the primary transfer position. There is. 102 is an intermediate transfer member 1
A corona discharger for primary transfer disposed on the back side of the primary transfer position 01 for discharging the toner by applying a voltage having a polarity opposite to the charging polarity of the toner on the photosensitive drum 100. 10
3 is a transfer sheet 104 sent out from the sheet feeding tray 105
Is a bias roll for secondary transfer to which a transfer voltage having a polarity opposite to the toner charging polarity is applied. Reference numeral 106 denotes a feed roller that feeds the transfer paper 104 placed on the paper feed tray 105 toward the intermediate transfer body 101, and 107 denotes a peeling claw whose tip is provided so as to come into contact with and separate from the intermediate transfer body 101 at a peeling position. Reference numeral 108 denotes a conveyance belt that feeds the sheet peeled by the peeling claw 107 toward a fixing device (not shown).

There is an example in which a bias roll is used instead of the corona discharger 102 as the primary transfer in the above-mentioned conventional example, but a detailed description is omitted. Similarly, as the secondary transfer means, instead of the bias roll 103. The description of an example using a corona discharger is also omitted.

Next, the operation of the copying machine using the intermediate transfer member having the above construction will be described. A toner image T is formed on the photosensitive drum 100 by the copy operation start signal, and
The intermediate transfer member 101 also moves at substantially the same speed as the peripheral speed of the photosensitive member, and the toner image T that has moved to the primary transfer position where the photosensitive drum 100 and the intermediate transfer member 101 are in contact with or close to each other is released from the primary transfer corona. By the action of the electric device 102, the intermediate transfer body 101 is electrostatically adsorbed and the primary transfer is performed. In the case of a color copying machine, this operation is performed 3 to 4 times according to each toner color. During this primary transfer operation, the bias roll 103 of the secondary transfer means is separated from the intermediate transfer member 101, and the transfer paper 104 is also on standby before the secondary transfer section. The transfer sheet 104 is sent to the secondary transfer position as the toner image after the primary transfer is moved to the secondary transfer position, and the bias roll 103 of the secondary transfer unit contacts the intermediate transfer member 101. The toner image T moved to the secondary transfer portion and the transfer paper 104 are sandwiched between the intermediate transfer body 101 and the secondary transfer bias roll 103 and undergo transfer, and the toner image is electrostatically adsorbed on the transfer paper 104. Then, the secondary transfer is executed. The transfer sheet 104 after the secondary transfer is sent to the fixing device by the conveyor belt 108 and fixed.

[0008]

However, the above-mentioned prior art has the following problems. That is, in the case of the above-mentioned conventional image forming apparatus, the toner image T formed on the photoconductor drum 100 is charged at the primary transfer position by the corona discharger 102, and the intermediate transfer member 101 is charged.
The toner images of the respective colors, which are transferred onto the intermediate transfer member 101 and sequentially transferred onto the intermediate transfer member 101, are transferred to the bias roll 10
It is configured to be transferred onto the transfer sheet 104 by the charging of 3.

By the way, in the case of the above image forming apparatus,
When the primary transfer is performed on the intermediate transfer member 101 by the charging of the corona discharger 102, there is a problem that the toner image on the intermediate transfer member 101 has a blank area.
That is, the toner image T formed on the photosensitive drum 100 is transferred onto the intermediate transfer member 101 by the charging of the corona discharger 102 at the primary transfer position. At that time, the toner image T is transferred onto the photosensitive drum 100. Formed toner image T
8, the edge portion of the toner image T mainly comes into contact with the surface of the intermediate transfer body 101, and the central portion of the toner image T tends to be separated from the surface of the intermediate transfer body 101. Therefore, when the toner image T formed on the photoconductor drum 100 is primarily transferred onto the intermediate transfer member 101 by the charging of the corona discharger 102, as shown in FIG. In particular, there is a problem that the white spots 110 occur at positions where straight images intersect.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to form a toner image at the time of transfer in an image forming apparatus using an intermediate transfer member. An object of the present invention is to provide an image forming apparatus using an intermediate transfer member capable of preventing deterioration of image quality due to a blank area or the like.

[0011]

The above-mentioned technical problems are as follows.
In the image forming apparatus using the intermediate transfer member according to the present invention,
In an image forming apparatus for forming an image by first transferring a developed image on an image carrier, which has been developed with charged toner, onto an intermediate transfer member and then secondarily transferring this from the intermediate transfer member onto a transfer material. This is achieved by setting the peripheral speed of the intermediate transfer member to be higher than the peripheral speed of the image bearing member so that the peripheral speeds of the image bearing member and the intermediate transfer member have a speed difference.

The peripheral speed difference between the image bearing member and the intermediate transfer member is set to, for example, 1 to 10%.

[0013]

In the present invention, the peripheral speed of the intermediate transfer member is set higher than the peripheral speed of the image carrier so that the peripheral speeds of the image carrier and the intermediate transfer member have a speed difference. When the toner image is transferred from the image carrier onto the intermediate transfer member, the peripheral speed of the intermediate transfer member is faster than the peripheral speed of the image carrier, so the toner image transferred onto the intermediate transfer member is Is enlarged along the rotation direction of the toner, the thickness of the toner is thinned accordingly, the amount of toner that directly contacts the surface of the intermediate transfer body increases, and the adhesive force of the toner to the intermediate transfer body increases. , The transfer efficiency is improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 1 shows an embodiment of an image forming apparatus using the intermediate transfer member according to the present invention.

In FIG. 1, 1 is a photosensitive drum,
On the surface of the photoconductor drum 1, a toner image T in black and white or in colors such as cyan, magenta, yellow and black is formed by a well-known electrophotographic process (not shown). 2 is a photoconductor drum 1 at a predetermined transfer position.
An intermediate transfer drum as an intermediate transfer member arranged so as to come into contact with the surface of the sheet, 3 is a feed roller for feeding the transfer sheet 5 placed on the sheet feed tray 4 toward the intermediate transfer drum 2, and 6 is a peeling position. , A peeling claw whose front end is provided so as to be able to come in contact with and separate from the intermediate transfer drum 2, and 8 is a toner image T transferred onto the intermediate transfer drum 2 on the transfer paper 5.
Bias roller for next transfer, 9 is a conveyor belt for feeding the transfer sheet 5 peeled by the peeling claw 6 toward the fixing device 10, and 14 is a primary transfer disposed inside the intermediate transfer drum 2 at a transfer position. Is a reference position sensor for detecting the reference position of the intermediate transfer drum 2.

As shown in FIG. 2, the intermediate transfer drum 2 includes a hollow drum 11 made of metal or the like, an insulating layer 12 made of polycarbonate or the like provided on the outer periphery of the hollow drum 11, and an insulating layer 12 on the insulating layer 12. And the intermediate layer 13 provided in a laminated state. The intermediate layer 13
Contains an appropriate amount of an antistatic agent such as carbon black in various materials such as fluorine-based synthetic resins such as polycarbonate and PVDF, and has a volume resistivity of 10 ⁸ to 10 ¹⁵ Ω.
Formed by a material adjusted to be / cm,
Its thickness is set to 0.05 to 0.2 mm.

The bias roller 8 for the secondary transfer is also used.
As for the JIS hardness of 50 to 70 on the surface of the metal cored bar
The surface hardness of the bias roller 8 for secondary transfer is set higher than that of the surface of the intermediate transfer drum 2. for that reason,
When the toner image is transferred from the intermediate transfer drum 2 onto the transfer sheet 5, the transfer sheet 5 is conveyed in a state of being sandwiched by the pressure contact portion between the intermediate transfer drum 2 and the bias roller 8 for secondary transfer. Is adapted to rotate along the surface of the secondary transfer bias roller 8 having a high surface hardness and prevent the transfer paper 5 from being caught in the intermediate transfer drum 2 side.

By the way, in this embodiment, the intermediate transfer drum 2 is rotationally driven by an original drive motor different from the photosensitive drum 1, and the rotational speed V ₁ (peripheral speed) of the intermediate transfer drum 2 is reduced. Speed) is the photoconductor drum 1
The rotational speed V ₂ (peripheral speed) is set by a predetermined amount (1-2%).

The intermediate transfer drum 2 may be rotationally driven in accordance with the rotation of the photosensitive drum 1 instead of being rotationally driven by an original drive motor. In this case, by changing the ratio of the gear that transmits the rotational force of the photosensitive drum 1 to the intermediate transfer drum 2, or by setting the outer diameter of the intermediate transfer drum 2 larger than that of the photosensitive drum 1, the intermediate transfer is performed. The rotation speed of the drum 2 can be set to be higher than the rotation speed of the photosensitive drum 1 by a predetermined amount.

Further, in this embodiment, the rotation speed V ₂ (peripheral speed) of the bias roller 8 is set to a speed equal to the rotational speed V ₂ of the photosensitive drum 1 (circumferential speed).

With the above-mentioned structure, the image forming apparatus using the intermediate transfer member according to this embodiment is as follows.
It is designed to prevent a blank area of the toner image from occurring during the primary transfer. That is, in the image forming apparatus, as shown in FIG. 1, a color toner image T of the first color (for example, cyan color) is formed on the surface of the photosensitive drum 1 by a well-known electrophotographic process (not shown).
The toner image T formed on the surface of the photosensitive drum 1 is
It is transferred onto the intermediate transfer drum 2 by the charging of the corona charger 14 for primary transfer.

At this time, the rotation speed V ₁ of the intermediate transfer drum 2 is set to be higher than the rotation speed V ₂ of the photosensitive drum 1 by a predetermined amount (1-2%). Therefore, the toner image T formed on the surface of the photoconductor drum ₁ has a speed ratio V ₁ / V ₁ between the rotation speed V ₂ of the photoconductor drum 1 and the rotation speed V 1 of the intermediate transfer drum 2 as shown in FIG. Depending on V ₂ ,
The image is transferred onto the intermediate transfer drum 2 in a slightly expanded state. Therefore, since the toner image T transferred onto the intermediate transfer drum 2 has a small thickness, the area of the toner directly transferred onto the intermediate transfer drum 2 increases and the adhesive force to the intermediate transfer drum 2 increases. And the transferability is improved. Further, since the toner carrying amount per unit area of the intermediate transfer drum 2 is reduced, the transfer efficiency is increased. As a result, when the primary transfer is performed from the photoconductor drum 1 onto the intermediate transfer drum 2, it is possible to reliably prevent the occurrence of a blank area of the toner image.

Thereafter, a second color toner image T is formed on the photosensitive drum 1, and the second color toner image T is formed.
Is primarily transferred onto the intermediate transfer drum 2 in the same manner as described above. Then, this process is repeated until the transfer of the predetermined number of color toner images T is completed.

At this time, the alignment of the toner image T on the intermediate transfer drum 2 is performed by detecting the reference position of the intermediate transfer drum 2 by the reference position sensor 15 and synchronizing it with the rotation of the photosensitive drum 1. .

When the primary transfer of the toner images T of all colors onto the intermediate transfer drum 2 is completed, the transfer sheet 5 placed on the paper feed tray 4 is rotated. The toner image T, which is sent out by the feed roller 3 in synchronism and transferred onto the intermediate transfer drum 2, is nipped and conveyed by the intermediate transfer drum 2 and the bias roller 8 for secondary transfer which is in pressure contact with the intermediate transfer drum 2 and is transferred. Secondary transfer is performed by pressure.

[0027] At this time, the rotational speed V ₂ of the bias roller 8 for the secondary transfer, the intermediate transfer drum 2 rotation speed V ₁
The toner image T carried on the intermediate transfer drum 2 is, as shown in FIG. 4, set to be slower than the above and is set to be equal to the rotation speed V ₂ of the photosensitive drum 1.
Depending on the speed ratio V ₂ / V ₁ of the rotational speeds of the intermediate transfer drum 2 and the bias roller 8 for secondary transfer, the size is slightly reduced and becomes the same size as that formed on the photosensitive drum 1. It is transferred onto the transfer paper 5 in the closed state. Therefore, also in this secondary transfer, the toner image T is surely transferred onto the transfer paper 5 without causing white spots of the toner.

The bias roller 8 for the secondary transfer is used.
Has a surface hardness higher than that of the surface of the intermediate transfer drum 2. Therefore, when the toner image is transferred from the intermediate transfer drum 2 onto the transfer sheet 5, the intermediate transfer drum 2 and the secondary transfer are transferred. The transfer sheet 5 conveyed in a state of being sandwiched by the pressure contact portion with the bias roller 8 for secondary transfer is rotated along the surface of the bias roller 8 for secondary transfer having high surface hardness, and the intermediate transfer drum 2 side. The transfer sheet 5 is prevented from being caught in the sheet.

After that, the transfer paper 5 on which the toner image T has been transferred is separated from the intermediate transfer drum 2 by the separation claw 6 and is conveyed to the fixing device 10 by the conveying belt 9 where the fixing process is performed and the outside of the device. And the image forming process is completed.

Next, in order to confirm the effect of the image forming apparatus according to the above-mentioned embodiment, the present inventors prototyped the apparatus as shown in FIG. 1 and measured the speed of the photosensitive drum 1 and the intermediate transfer drum 2. An experiment was conducted by changing the ratio and examining the occurrence state of white spots in the toner during the primary transfer.

FIG. 5 shows the results of the above experiment.
In the figure, ◯ indicates a state in which no white spots have occurred (good), Δ indicates a state in which no white spots have occurred (practical), and x indicates a state in which white spots have occurred. As is clear from this figure, the speed ratio between the photosensitive drum 1 and the intermediate transfer drum 2 is set to 1
Although it is possible to reliably prevent the occurrence of white spots by setting it to 12%, if the speed ratio between the photoconductor drum 1 and the intermediate transfer drum 2 is set too large, the distortion due to the deviation of the toner image T becomes large. Therefore, 1 to 1
By setting it to 0%, it is possible to form a good image while preventing white spots in the toner.

FIG. 6 shows an image forming apparatus using an intermediate transfer member according to another embodiment of the present invention. In this embodiment, the intermediate transfer member is not a drum-shaped one but a belt-shaped intermediate one. A transfer body is used. That is, in this embodiment, at the transfer position of the photosensitive drum 1, the endless belt-shaped intermediate transfer belt 20 is arranged so as to be circulated and movable by the four rollers 21 to 24 so as to come into contact with the surface of the photosensitive drum 1. Has been done.

The intermediate transfer belt 20 is basically similar to the intermediate transfer drum 2 of the above-described embodiment in that the conductive layer 11 made of a flexible material and the polycarbonate provided on the outer periphery of the conductive layer 11 are formed. And an intermediate layer 13 provided on the insulating layer 12 in a laminated state.

In this embodiment, the intermediate transfer belt 20 is rotated and driven by a unique drive motor different from the photosensitive drum 1, and the rotation speed V ₁ (circulation) of the intermediate transfer belt 20 is reduced. The speed is set to be higher than the rotation speed V ₂ (peripheral speed) of the photosensitive drum 1 by a predetermined amount (1 to 2%).

Further, in this embodiment, the rotation speed V ₂ (peripheral speed) of the bias roller 8 is set to a speed equal to the rotational speed V ₂ of the photosensitive drum 1 (circumferential speed).

The other structure and operation are the same as those of the above-mentioned embodiment, and the explanation thereof will be omitted.

[0037]

The present invention has the above-described structure and operation, and provides an image forming apparatus using an intermediate transfer member.
It is possible to provide an image forming apparatus using an intermediate transfer member capable of preventing deterioration of image quality due to a blank area of a toner image during transfer.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an image forming apparatus using an intermediate transfer member according to the present invention.

FIG. 2 is a cross-sectional view of the intermediate transfer drum of FIG. 1 taken along the line AA ′.

FIG. 3 is a schematic diagram showing a transfer state of a toner image.

FIG. 4 is a schematic diagram showing a transfer state of a toner image.

FIG. 5 is a chart showing experimental results.

FIG. 6 is a block diagram showing another embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional image forming apparatus.

FIG. 8 is a schematic diagram showing a transfer state of a toner image.

FIG. 9 is a schematic diagram showing a white spot occurrence state.

[Explanation of symbols]

1 photoconductor drum, 2 intermediate transfer drum, 5 transfer paper, T toner image.

Claims (2)

[Claims] 1. An image is formed by first transferring a developed image on an image carrier, which has been developed with charged toner, onto an intermediate transfer member, and then secondarily transferring this from the intermediate transfer member onto a transfer material. In the image forming apparatus described above, the peripheral speed of the intermediate transfer member is set to be higher than the peripheral speed of the image carrier, and the peripheral speeds of the image carrier and the intermediate transfer member have a difference in speed. Image forming apparatus using the body. 2. The image formation using the intermediate transfer member according to claim 1, wherein the speed difference between the peripheral speeds of the image carrier and the intermediate transfer member is set to 1 to 10%. apparatus.