JP3552469B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer, and more particularly, to an image forming apparatus such as a paper for transferring an unfixed toner image formed on an image carrier such as a photosensitive drum via an intermediate transfer drum. The present invention relates to an improvement in an image forming apparatus that transfers a recording material to a recording material.
[0002]
[Prior art]
2. Description of the Related Art As a multicolor image forming apparatus such as an electrophotographic copying machine or a laser printer, a developing device in which a plurality of toners of different colors are stored in an image carrier such as a photosensitive drum is arranged. The operation of transferring (primary transfer) to the intermediate transfer drum is repeated each time a color toner image of color is formed, and the color toner images of all colors are transferred to the intermediate transfer drum in a superimposed manner, and then collectively transferred to paper (secondary transfer). Transfer) to create a color print is known.
In this type of image forming apparatus, a non-contacting charge removing means and a sheet peeling assisting means such as a chute are provided on an intermediate transfer drum for removing electricity from a charged sheet downstream of the secondary transfer unit, and the sheet is peeled off. I was letting it. In many cases, a corotron is used as the static elimination means.
[0003]
[Problems to be solved by the invention]
By the way, it has been very difficult to remove charged paper (especially thin paper) without using the above-described peeling assisting means.
However, when the above-described peeling assisting means is used, particularly, in a situation where the resistance value of the paper is reduced in a high-temperature and high-humidity environment, the bias current necessary for the secondary transfer flows into the peeling assisting means. and Mai, the technical problem that the image quality defects due to bias leakage occurs was observed. Further, as long as corotron is used as the separation assisting means, ozone generation is inevitable. Further, an increase in cost due to the use of the separation assisting means is inevitable.
[0004]
The present invention has been made in order to solve the above technical problems, and it is intended to reliably peel off a recording material without using a peeling assisting means such as a corotron, and to use a peeling assisting means. An object of the present invention is to provide an image forming apparatus capable of effectively preventing various defects such as accompanying image quality defects.
[0005]
[Means for Solving the Problems]
That is , as shown in FIG. 1A, the basic structure of the present invention is to collectively transfer an intermediate transfer drum 1 for transferring and holding a toner image from an image carrier and a toner image on the intermediate transfer drum 1. In the image forming apparatus including the transfer roll 2 for transferring the recording medium 3 to the recording material 3, the intermediate transfer drum 1 is formed of a laminate including at least an elastic layer 1b on a base 1a, and the hardness of the transfer roll 2 is reduced. At least the hardness of the intermediate transfer drum 1 is set higher.
[0006]
In such technical means, the present invention is directed to a device provided with the intermediate transfer drum 1 and the transfer roll 2, and is usually used as a device for forming a color image. You may use it as a thing to do.
In the type of forming a color image, in a mode in which each color component image is sequentially transferred from the image carrier to the intermediate transfer drum 1, the image on the intermediate transfer drum 1 is not transferred at a time other than the secondary transfer step. Since the image passes through the next transfer site, it is necessary to design the image on the intermediate transfer drum 1 so as not to be destroyed by the transfer roll 2.
For example, the transfer roll 2 is constantly pressed against the intermediate transfer drum 1, but the transfer of the image on the intermediate transfer drum 1 to the transfer roll 2 side is avoided by cutting the transfer electric field in other than the secondary transfer process. Although no problem by equally appropriately selected to be, from the viewpoint of surely avoiding the destruction of the image on the intermediate transfer drum 1, pressing place the transfer roll 2 only the intermediate transfer drum 1 during the secondary transfer process Preferably, the transfer roll 2 is configured to be able to freely contact and separate from the intermediate transfer drum 1 so as to be able to do so.
These points are the same for the inventions of FIGS. 1B and 1C.
[0007]
Furthermore, in the present invention, it is preferable that the hardness of the entire lamination of the intermediate transfer drum 1 is 20 degrees or less in Asker C hardness.
Here, the limit value of the hardness of 20 degrees means a value necessary for obtaining an optimum nip shape, nip pressure and secondary transfer current in a transfer nip area between the transfer roll 2 and the transfer roller 2.
In addition, the fact that the hardness of the entire stack of the intermediate transfer drum 1 is 20 degrees or less in Asker C hardness means that, when focusing on the elastic layer 1b, the hardness of the elastic layer 1b is 15 degrees or less in Asker C hardness. It is equivalent.
[0008]
In the present invention , as shown in FIG. 1B, an intermediate transfer drum 1 for transferring and holding a toner image from an image carrier and a toner image on the intermediate transfer drum 1 are collectively recorded on a recording material 3. In the image forming apparatus, the intermediate transfer drum 1 is composed of a laminate including at least an elastic layer 1b on a substrate 1a, and the transfer roll 2 has a hardness of at least the intermediate transfer drum 1. The hardness is set to be higher than the hardness (corresponding to the basic configuration of the present invention), and the pressing direction m of the transfer roll 2 against the intermediate transfer drum 1 is determined by the center line L between the intermediate transfer drum 1 and the transfer roll 2. It is characterized by being displaced downstream in the transport direction.
[0009]
Further , as shown in FIG. 1C, another aspect of the present invention is to collectively transfer the toner image from the image carrier to the intermediate transfer drum 1 and the toner image on the intermediate transfer drum 1. In the image forming apparatus, the intermediate transfer drum 1 is formed of a laminate including at least an elastic layer 1b on a base 1a, and the transfer roll 2 has a hardness of at least The hardness of the intermediate transfer drum 1 is set higher than that of the intermediate transfer drum 1 (corresponding to the basic configuration of the present invention), and the transfer roll 2 is driven separately from the intermediate transfer drum 1 so that the peripheral speed v2 is higher than the peripheral speed v1 of the intermediate transfer drum 1. It is characterized by being. In the drawing, reference numeral 4 denotes a drive source of the transfer roll 2.
[0010]
1C, in the type in which the transfer roll 2 can be freely moved toward and away from the intermediate transfer drum 1, from the viewpoint of minimizing the load at the time of pressing the transfer roll 2, the transfer roll 2 Is preferably driven separately from the intermediate transfer drum 1, and is driven at least at a timing earlier than contact with the intermediate transfer drum 1.
[0011]
Next, the operation of the above technical means will be described.
In the basic configuration of the invention shown in FIG. 1 (a), the transfer roll 2 at the secondary transfer nip region bite into the intermediate transfer drum 1 having an elastic layer 1b, force separating the recording material 3 by the bite shape.
Further, in the invention shown in FIG. 1B, the transfer roll 2 bites into the intermediate transfer drum 1 having the elastic layer 1b in the secondary transfer nip area, and regulates the pressing direction of the transfer roll 2 so that the transfer is performed. The biting shape of the roll 2 is shifted to the downstream side in the transport direction of the recording material 3, and the recording material 3 is forcibly peeled off by the biting shape.
Further, in the invention shown in FIG. 1 (c), the transfer roll 2 bites into the intermediate transfer drum 1 having the elastic layer 1b in the secondary transfer nip area, and regulates the peripheral speed of the transfer roll 2 so that the transfer is performed. The biting shape of the roll 2 is shifted to the downstream side in the transport direction of the recording material 3, and the recording material 3 is forcibly peeled off by the biting shape.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings . The first embodiment shows an embodiment based on the basic configuration of the present invention (see FIG. 1A).
◎ Embodiment 1
FIG. 2 is a drawing schematically showing the overall configuration of a color image forming apparatus to which the present invention is applied.
The image forming apparatus 11 shown in FIG. 2 is configured as a color printer, and sequentially transfers (primary transfer) a photosensitive drum 12 for forming a toner image and a toner image formed on the photosensitive drum 12, and An intermediate transfer drum 13 that carries color toner images of different colors, a transfer roll 14 that collectively transfers the toner image on the intermediate transfer drum 13 onto a sheet 10, and a sheet transport system 15 that transports the sheet 10 are appropriately combined. It is a thing.

[0013]
In the present embodiment, the image forming apparatus 11 includes a writing device 17 for writing an electrostatic latent image by a laser beam around the photosensitive drum 12, a charger 18 for charging the photosensitive drum 12, A developing device 19 for developing an electrostatic latent image on the photosensitive drum 12 with a predetermined color toner and a cleaning device 20 for removing residual toner on the photosensitive drum 12 are arranged.
After the photosensitive drum 12 is uniformly charged by the discharge of the charger 18, the laser beam output from the writing device 17 is written via the mirror 21 to form an electrostatic latent image. The toner is supplied from the developing device 19 to the electrostatic latent image to be visualized as a toner image, and the toner image is transferred to the intermediate transfer drum 13.
The developing device 19 disposed with respect to the photosensitive drum 12 is provided with developing devices K (black), Y (yellow), M (magenta), and C (cyan) of four colors rotatably. Any one of the developing units is arranged to face the photosensitive drum 12 in accordance with the color information of the image input to the device 17, and one color toner is supplied from the selected developing unit, so that a specific color component is provided. Is formed so as to form a color toner image corresponding to.
[0014]
The first transfer for transferring the toner image on the photosensitive drum 12 to the intermediate transfer drum 13 is performed by applying a bias having a polarity opposite to that of the toner to the base 31 (see FIG. 3) of the intermediate transfer drum 13.
This operation is repeated a plurality of times to form toner images of a plurality of colors on the intermediate transfer drum 13. The second transfer for transferring the toner image superimposed on the intermediate transfer drum 13 onto the sheet 10 is performed by applying a bias having a polarity opposite to that of the toner to the transfer roll 14.
In the present embodiment, the transfer roll 14 is supported so as to be able to freely contact and separate from the intermediate transfer drum 13 by a contact and separation mechanism (not shown), and transfers the toner image on the intermediate transfer drum 13 to the paper 10. Only in this case, the toner image is pressed toward the intermediate transfer drum 13 and exerts an effect of transferring a toner image to the paper 10 by applying a transfer bias.
[0015]
A cleaning device 22 is disposed downstream of the transfer roll 14 and upstream of the primary transfer portion with respect to the intermediate transfer drum 13. 13 is to be cleaned. Therefore, the cleaning device 22 is not pressed against the intermediate transfer drum 13 at all times, and is illustrated with respect to the intermediate transfer drum 13 so that the cleaning is performed in synchronization with the operation of transferring the toner image onto the paper 10. Supported via an external retract mechanism. The cleaning device 22 is configured to be able to contact the intermediate transfer drum 13 in a state where the cleaning device 22 is synchronized with a transfer roll 14 for transferring a toner image from the intermediate transfer drum 13 to the sheet 10. By using the control means, the control of each mechanism can be simplified.
[0016]
Further, in the present embodiment, the paper transport system 15 arranges a paper feed tray 25 at the lower portion of the apparatus main body, and transports the paper 10 by using a paper feed roller 26 disposed with respect to the paper feed tray 25. It constitutes means for sending out toward the road 24. Further, a paper aligning device (not shown) is arranged between a paper feed unit (paper feed roller 26) from the paper feed tray 25 and the image transfer unit, and the image transfer unit is aligned with the paper 10. , And transports the paper 10 in synchronization with the speed of the intermediate transfer drum 13 during the image transfer operation. Then, the toner image is transferred from the intermediate transfer drum 13 while the paper 10 is transported along the paper transport path 24, and the color print fixed through the fixing device 27 is discharged to a discharge tray (not shown). I have to.
[0017]
Next, the intermediate transfer drum 13 and the transfer roll 14 used in the present embodiment will be described in detail.
The intermediate transfer drum 13 to place in correspondence to the photosensitive drum 12, especially as shown in FIG. 3, on a substrate 31, by dispersing carbon or ion ¹⁰ 5 ^{to 10 12} Omega, preferably ¹⁰ 5 ^{to 10 10} the elastic layer 32 which is the resistance adjusted to about Omega provided, to disperse the carbon with ¹⁰ 5 ^{to 10 12} Omega, preferably at ¹⁰ 5 ^{to 10 10} Omega about the resistance adjusted belt layer 33 provided thereon, further belt If necessary, a coating layer 34 such as fluorine is provided on the layer 33.
[0018]
In the present embodiment, for example, a foamed urethane layer is used as the elastic layer 32, urethane rubber is used as the belt layer 33, and a fluorine coat is used as the coat layer 34.
Here, the overall resistance value of the laminate is about 10 ⁵ to 10 ¹² Ω, and preferably about 10 ⁵ to 10 ¹⁰ Ω. Further, the hardness of the entire lamination is 20 degrees or less in Asker C hardness, preferably 10 to 15 degrees. In the present embodiment, it is confirmed that the hardness of the elastic layer 32 itself is 15 degrees or less in Asker C hardness in order for the hardness of the entire layer to be 20 degrees or less in Asker C hardness.
[0019]
The requirement that the hardness of the entire laminate be 20 degrees or less in Asker C hardness has been confirmed by the following experiment.
That is, as shown in FIG. 5A, for example, the transfer roll 14 is pressed against the intermediate transfer drum 13 with a constant pressing force (for example, a load on one side is 1.5 kg) to change the hardness of the intermediate transfer drum 13. When the maximum current value for peeling was measured, it was experimentally found that the optimum current value was 5 to 10 μA, and in consideration of the fact that the peeling became worse as the current value was increased, With a margin, it was confirmed that the peeling hardness was 20 degrees or less even when a current value was applied to 15 to 20 μA.
[0020]
It is preferable that the transfer roll 14 that can be brought into contact with and separated from the intermediate transfer drum 13 is at least harder than the intermediate transfer drum 13 and has less distortion when pressed. In this embodiment, a SUS metal roll is used. The pressing force is 1.5 kg or more on one side, preferably 2.0 kg or more. The drive is driven by the intermediate transfer drum 13 when pressed.
[0021]
Here, the requirement that the pressing force of the transfer roll 14 be 1.5 kg or more, preferably 2.0 kg or more on one side has been confirmed by the following experiment.
That is, as shown in FIG. 5B, for example, a maximum peeling force is applied to the intermediate transfer drum 13 having a constant hardness (Asker C hardness of 15 degrees) while changing the pressing force of the transfer roll 14 according to the present embodiment. When the current value was measured, it was confirmed that the pressing force of the transfer roll 14 to be peeled off was 1.5 kg or more on one side even when the current value was applied to 15 to 20 μA with a margin.
[0022]
Therefore, in the second transfer portion of the present embodiment, as shown in FIG. 4, the transfer roll 14 is formed so as to bite into the soft intermediate transfer drum 13 side. When a sheet (not shown) enters such a transfer nip area, even the sheet 10 such as a thin sheet is stably forcibly peeled in the direction of the arrow in the figure. You.
Therefore, according to the present embodiment, by setting the Asker C hardness of the stack of the intermediate transfer drum 13 to 20 degrees or less and making the hardness of the transfer roll 14 harder (higher) than that of the intermediate transfer drum 13, thin paper is impossible. It was confirmed that the film could be peeled off without any problem.
[0023]
◎ Embodiment 2
FIG. 6A is an explanatory diagram illustrating a main part of the image forming apparatus according to the second embodiment.
In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but the direction in which the transfer roll 14 is pressed against the intermediate transfer drum 13 is different from that of the first embodiment. Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.
That is, in the first embodiment, as shown in FIG. 6B, the pressing direction (moving direction) m of the transfer roll 14 against the intermediate transfer drum 13 is directed to the center O of the intermediate transfer drum 13. ing.
On the other hand, in the present embodiment, as shown in FIG. 7 in particular, the pressing direction (moving direction) m of the transfer roll 14 against the intermediate transfer drum 13 is different from that between the intermediate transfer drum 13 and the transfer roll 14 at the time of separation. A line L2 parallel to L1 passing through the center of the transfer roll 14 when the transfer roll 14 is pressed is defined by a gap δ with respect to L1. It is eccentric. The pressing direction m is defined so as to move downstream from the center line between the intermediate transfer drum 13 and the transfer roll 14 when pressed against the intermediate transfer drum 13 and does not face the center O of the intermediate transfer drum. It is set as follows.
[0024]
Therefore, in the present embodiment, the shape of the transfer nip between the intermediate transfer drum 13 and the transfer roll 14 is smaller than that of the first embodiment, As a result, the discharge direction of the paper from the paper discharge unit side of the transfer nip area is set to a direction further away from the intermediate transfer drum 13, and the paper is further discharged compared to the first embodiment. Peeling performance is improved.
[0025]
◎ Embodiment 3
FIG. 8 is an explanatory diagram illustrating a main part of the image forming apparatus according to the third embodiment.
In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the second embodiment, but the driving method of the transfer roll 14 is different from that of the second embodiment. Note that components similar to those of the second embodiment are denoted by the same reference numerals as those of the first embodiment, and a detailed description thereof will be omitted.
That is, in the second embodiment, the transfer roll 14 is driven by the intermediate transfer drum 13.
On the other hand, in the present embodiment, the transfer roll 14 is driven to rotate by a separate drive source 40, and the drive source 40 transmits the transfer roll 14 at least earlier than when the transfer roll 14 is pressed against the intermediate transfer drum 13. Is pressed while rotating.
Further, in the present embodiment, the drive source 40 can variably set the rotation speed of the transfer roll 14, and is set, for example, to be a speed v2 slightly higher than the rotation speed v1 of the intermediate transfer drum 13. Things.
[0026]
By doing so, the shape of the transfer nip between the intermediate transfer drum 13 and the transfer roll 14 is smaller than that of the second embodiment, as shown in FIG. Accordingly, the direction in which the paper is discharged from the paper discharge unit side of the transfer nip area is set to a direction further away from the intermediate transfer drum 13, and the paper peeling performance is further improved compared to the second embodiment. but improved, thin paper peeling also becomes easy.
Furthermore, in the present embodiment, the transfer roller 14 is small speed fluctuation of the intermediate transfer drum 13 due to the load at the time of pressing the intermediate transfer drum 13, correspondingly, stable and good images are acquired.
[0027]
【The invention's effect】
As described above, according to the present invention, by devising the hardness relationship between the intermediate transfer drum and the transfer roll, the pressing direction of the transfer roll, and the driving method, a separation assisting unit such as a corotron is not required in the secondary transfer unit. With such a configuration, excellent effects are obtained as compared with the following conventional devices.
{Circle around (1)} Even without the conventional peeling assisting means, a stable and good image can be obtained without deteriorating the paper peeling performance.
{Circle around (2)} Since the conventional separation assisting means such as corotron is not required, the generation of ozone as in the conventional case can be minimized. No good image is obtained.
{Circle around (3)} Since the conventional peeling assisting means is unnecessary, there is no cost for the peeling assisting means and the accompanying accessories, so that the cost is greatly reduced.
(4) By setting the hardness of the intermediate transfer drum to be soft and the hardness of the transfer roll to be higher than that, there is no nip failure in the secondary transfer part and stress concentration in the transfer nip area. Is less likely to occur in the image, and a stable and good image is obtained accordingly.
[Brief description of the drawings]
FIGS. 1A to 1C are explanatory diagrams showing an outline of an image forming apparatus according to the present invention.
FIG. 2 is an explanatory diagram illustrating an outline of a first embodiment of an image forming apparatus to which the present invention has been applied.
FIG. 3 is an explanatory diagram showing details of an intermediate transfer drum used in the first embodiment.
FIG. 4 is an enlarged explanatory diagram of a secondary transfer area according to the first embodiment.
5A is a graph showing the relationship between the hardness of the intermediate transfer drum and the secondary transfer current value, and FIG. 5B shows the relationship between the one-sided load of the transfer roll pressing force and the secondary transfer current value. FIG.
FIG. 6A is an explanatory diagram illustrating a main part of the image forming apparatus according to the second embodiment, and FIG. 6B is an explanatory diagram illustrating a main part of the image forming apparatus according to the first embodiment.
FIG. 7 is an enlarged explanatory diagram of a secondary transfer area according to the second embodiment.
FIG. 8 is an explanatory diagram illustrating a main part of an image forming apparatus according to a third embodiment;
FIG. 9 is an enlarged explanatory diagram of a secondary transfer area according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer drum, 1a ... Substrate, 1b ... Elastic layer, 2 ... Transfer roll, 3 ... Recording material, 4 ... Drive source

Claims (3)

An intermediate transfer drum (1) for transferring and holding a toner image from an image carrier, and a transfer roll (2) for transferring the toner image on the intermediate transfer drum (1) to a recording material (3) at a time In the image forming apparatus comprising:
The intermediate transfer drum (1) is formed of a laminate including at least an elastic layer (1b) on a substrate (1a), and the hardness of the transfer roll (2) is set to be at least higher than the hardness of the intermediate transfer drum (1). Yes,
The pressing direction (m) of the transfer roll (2) against the intermediate transfer drum (1) is downstream of the center line (L) between the intermediate transfer drum (1) and the transfer roll (2) in the transport direction of the recording material (3). An image forming apparatus characterized in that the image forming apparatus is deviated from the image forming apparatus. An intermediate transfer drum (1) for transferring and holding a toner image from an image carrier, and a transfer roll (2) for transferring the toner image on the intermediate transfer drum (1) to a recording material (3) at a time In the image forming apparatus comprising:
The intermediate transfer drum (1) is formed of a laminate including at least an elastic layer (1b) on a substrate (1a), and the hardness of the transfer roll (2) is set to be at least higher than the hardness of the intermediate transfer drum (1). Yes,
An image forming apparatus, wherein the transfer roll (2) is driven separately from the intermediate transfer drum (1) and has a peripheral speed higher than the peripheral speed of the intermediate transfer drum (1). The image forming apparatus according to claim 2 , wherein the transfer roll (2) is freely movable toward and away from the intermediate transfer drum (1).
An image forming apparatus characterized in that the transfer roll (2) is driven separately from the intermediate transfer drum (1), and is driven at least at a timing earlier than contact with the intermediate transfer drum (1).

Images