JP3266069B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer type image forming apparatus having a transfer means for transferring a transferable image formed and carried on an image carrier to a transfer material.

More specifically, the present invention relates to an improvement in an image forming apparatus in which a transfer unit is a transfer unit of a contact transfer system.

[0003]

2. Description of the Related Art A transferable image of image information, which is generally a toner image, is formed on a surface of an image carrier by an appropriate image forming process, and the transferable image is transferred to a transfer material such as paper. 2. Description of the Related Art A transfer type image forming apparatus in which an image is fixed and output as an image formed product (copy, print) and an image carrier is repeatedly used for image formation has been widely used.

FIG. 4 is a schematic structural view of a typical example of such a transfer type image forming apparatus. The image forming apparatus of this embodiment is a copying machine or a printer using a transfer type electrophotographic process.

[0005] Reference numeral 10 denotes a drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) serving as an image bearing member.
Is rotated clockwise at a predetermined peripheral speed (process speed), and an image forming process of charging, image exposure, development, transfer, and cleaning is applied to the rotating photosensitive drum.

That is, the surface of the rotating photosensitive drum 10 is uniformly charged to a predetermined polarity and potential by the primary charger 11.

Next, image exposure 12 is performed on the charged surface by image exposure means (not shown) such as a document image projection exposure apparatus and an image-modulated laser beam scanning exposure apparatus as image information writing means. Then, the charged potential of the exposed light portion is attenuated, and an electrostatic latent image corresponding to the exposed image information is formed on the surface of the photosensitive drum.

The electrostatic latent image is sequentially visualized as a transferable toner image (developed image) by the developing device 13 at the developing site A.

The toner image is transferred to a transfer material 18 by a transfer means at a transfer portion T.

The transfer means in this embodiment is a contact transfer type transfer means using a roller-shaped contact transfer charger 16 (hereinafter referred to as a transfer roller).

The transfer roller 16 comprises, for example, a core metal and a medium-resistance elastic layer formed around the core metal.
A transfer portion T (transfer nip portion) is formed by pressing the photosensitive drum 10 with a predetermined pressing force against the elasticity of the elastic layer, and the photosensitive drum 10 is rotated in the forward direction with the rotation of the photosensitive drum 10. Rotates at a peripheral speed substantially the same as the rotational peripheral speed of

The transfer material 18 is fed from a feeding unit (not shown), and is fed to the transfer portion T at a timing adjusted by a registration roller 15 disposed in front of the transfer portion T.

That is, when the leading end of the toner image formed on the surface of the rotary photosensitive drum 10 reaches the transfer site T, the registration roller 15 is moved to the timing at which the leading end of the transfer material 18 just arrives at the transfer site T. Transfer material 18
To the transfer site T.

The transfer material 18 fed to the transfer site T has its surface in close contact with the rotating photosensitive drum 10 and is conveyed while nipping the transfer site T. Further, during a period from when the leading end of the transfer material 18 arrives at the transfer site T to when the rear end of the transfer material 18 exits the transfer site T, the core of the transfer roller 16 has a transfer bias power source 2.
From 0, a predetermined transfer bias is applied.

In the process in which the transfer material 18 is conveyed while nipping and transferring the transfer portion T, the toner image on the rotating photosensitive drum 10 is formed on the transfer material 18 by the transfer roller 16 as a contact transfer charger. The image is sequentially transferred by the action of the electric field and the pressing force at the transfer portion T.

When the transfer material 18 leaves the transfer portion T, it is separated from the surface of the rotating photosensitive drum 10 and transported to an image fixing device (not shown), and the transferred toner image is fixed as a permanently fixed image on the transfer material surface. The sheet is processed and discharged as an image formed product (copy, print).

After the transfer material is separated, the surface of the photosensitive drum 10 is cleaned by the cleaner 17 after removing contaminants such as residual toner and paper dust, and is repeatedly used for image formation.

As an image forming method, for example, a normal developing method in which a charged photosensitive member surface is exposed corresponding to a background portion of image information (background exposure method), and a portion other than the background portion is developed, There is a reversal development system in which exposure is performed corresponding to an image information section (image exposure system) and a non- exposed portion is developed, and these are used taking advantage of their respective characteristics.

As a transfer means for transferring a toner image as a transferable image on the photosensitive drum 10 side as an image carrier to a transfer material 18 such as paper, the transfer roller 16 is used as described above.
The transfer means of the contact transfer method using a contact transfer charger represented by (2) has become widespread, and compared with the transfer means using a corona charger and the like, the power supply capacity has been reduced, and the discharge product represented by ozone has been reduced. There are merits such as a small amount of generation.

In the case of such a contact transfer type transfer means, the following transfer problems generally occur easily.

That is, when the transfer means is "constant-current controlled", for example, when a small-size transfer material typified by a postcard is passed, a paper-passing area and a non-paper-passing area at the time of paper passing are determined. The transfer current easily flows in the non-sheet passing area due to the difference in the resistance of the transfer material, the amount of transfer charge applied to the back surface of the transfer material is reduced, and transfer failure such as transfer omission is likely to occur.

This phenomenon is more remarkable as the volume resistance of the transfer roller 16 which is a contact transfer charger is smaller. Therefore, the phenomenon can be improved by increasing the volume resistance of the transfer roller. Problems arise.

Therefore, there is a "constant voltage control" system in which a relatively large amount of transfer charge can be imparted to a small-size paper feed as compared to a large-size paper feed. This is generally output at a voltage value determined according to the volume resistance of the transfer roller, and it is possible to apply a relatively similar amount of transfer charge to large and small size transfer materials. , Has been adopted.

[0024]

However, problems at the time of transfer often occur due to an excessive or small amount of transfer charge applied to the back surface of the transfer material.

For example, a "drum memory" by transfer creates a memory on a photosensitive drum as an image carrier by causing a transfer charge to pass through a transfer material during paper passing due to excess, and forming a grayscale image when forming an image later. Conversely, when the amount is small, there is "transfer missing" which occurs because the toner is not sufficiently attracted to the transfer material.

In particular, in a method of forming a toner image on the surface of a photoconductor holding the same polarity as the toner, as represented by the reversal development system, the transfer polarity at the time of transfer is opposite to that of the surface of the photoconductor. Drum memory is more likely to occur than in the system.

These depend on a transfer charge amount, that is, roughly, a transfer current value at the time of transfer.

On the other hand, in the case of the constant voltage control, since the constant voltage value is usually set so as not to cause transfer omission even in a small size, the transfer charge amount of the transfer material tends to be excessive when the transfer material is large. . Therefore, in an environment and a configuration where a transfer failure is more likely to occur, good transfer cannot be performed on transfer materials of various sizes.

Accordingly, the present invention has been made to cope with such a situation. In a transfer type image forming apparatus in which the transfer unit is a contact transfer type transfer unit, the present invention is applicable to various paper passing sizes of a transfer material. It is another object of the present invention to provide an image forming apparatus capable of performing transfer with higher accuracy and constantly obtaining a high-quality image stably.

[0030]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) In an image forming apparatus having a transfer means for transferring a transferable image formed and carried on an image carrier to a transfer material, the transfer means forms a transfer portion in contact with the image carrier. A contact transfer type transfer unit having a contact transfer charger for applying a transfer charge to the transfer material passed through the transfer portion and transferring a transferable image on the image carrier side to the transfer material side,
A constant current control unit that outputs a predetermined current value to the contact transfer charger; and a constant voltage control unit that outputs a predetermined voltage value. Te, constant current control said transfer means is capable of switching to either the constant voltage control, the predetermined current value and the predetermined voltage value, the surface treatment changing stiffness of the transfer material, the release property
The image forming apparatus is switchable in accordance with at least one of the information. That is, the transfer unit is switched to either constant current control or constant voltage control in accordance with the size of the transferred transfer material. More specifically, when the size of the transferred transfer material is equal to or larger than a predetermined size. In some cases, by switching the transfer means to constant current control, more precise control can be performed for transfer problems that often depend on the transfer current value, and the size of the transfer material to be passed is set to a predetermined value. By switching to the constant voltage control when the size is smaller than the predetermined size, a constant amount of transfer charge can be imparted even to a small-sized transfer material, and a high-quality image can always be stably obtained. Then, the device that performs the constant current control and the constant voltage control use divide transfer control in accordance with the transfer material size, a predetermined current value and a predetermined voltage value, the surface treatment changing stiffness of the transfer material, the release property By making the switching possible in accordance with at least one of the information, it is possible to perform the transfer in accordance with the characteristics of the transfer material.

[0032]

[0033]

(2) The transfer unit is switched to constant current control when the size of the transferred transfer material is equal to or larger than a predetermined size, and is switched to constant voltage control when the size of the transfer material is smaller than the predetermined size. The image forming apparatus according to (1 ) .

[0035]

[0036]

(3) Charging means for uniformly charging the image carrier, image information writing means for forming an electrostatic latent image of image information on the charged image carrier, and static electricity formed on the image carrier. the latent image has a developing means for visualizing imaging, characterized in that the transferable image on the image bearing member is formed (1) or
The image forming apparatus according to (2) .

(4) The image forming apparatus according to (3) , wherein the electrostatic latent image is visualized by reversal development.

(5) The transferable image formed and carried on the image carrier is a toner image (1) to (4).
The image forming apparatus according to any one of the above.

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (FIG. 1) FIG. 1 is a schematic structural diagram of an image forming apparatus according to the present embodiment.

The structure of the image forming apparatus of this embodiment is substantially the same as that of the above-described image forming apparatus shown in FIG. 4, and thus the same reference numerals are given to the same components and portions, and the description thereof will not be repeated.

In the image forming apparatus of this embodiment, the polarity of the charging process by the primary charger 11 of the photosensitive drum 10 as the image carrier is negative.

The toner development of the electrostatic latent image formed on the surface of the photosensitive drum 10 by the developing unit 13 is a reversal development method using negative polarity toner (negative toner).

The polarity of the transfer bias is positive.

The paper passing speed of the transfer material is 105 mm / s.

The maximum paper passing size is A4 horizontal paper passing width (297 m).
m), and the minimum paper passing size is a postcard length (equivalent to 105 mm).

Transfer Roller 16 as Contact Transfer Charger
Was 315 mm in length.

Reference numerals 21, 22, and 23 denote constant current power supply, constant voltage power supply, and transfer switching control means for the transfer roller 16.

Either constant current control or constant voltage control of the transfer means is selected by the transfer switching control means 23, and the constant current power supply 21 (constant power supply) is supplied to the transfer roller 16 during the transfer of the transfer material at the transfer portion T. A transfer bias is applied from a current control) or a constant voltage power supply 22 (a constant voltage control).

In this embodiment, the transfer switching control means 2
Selection switching between the constant current control and the constant voltage control of the transfer unit 3 is performed according to the size of the transfer material 18 passed through the apparatus. The input of the paper passing size of the transfer material 18 is input by the user, and the transfer switching control unit 23 outputs the output of the transfer bias to the transfer roller 16 based on the input. The paper passing size of the transfer material 18 is B5 horizontal paper passing width (257 m
m) or more, the constant current control output by the constant current power supply 21. When the paper passing size of the transfer material 18 is smaller than the B5 horizontal paper passing width, the output is switched to the constant voltage control output by the constant voltage power supply 22.

During constant current control, output control was performed with a control value of 9 μA.

The constant voltage control is performed when the transfer roller 1
6, the voltage applied at the time of the constant current of 9 μA was measured, the constant voltage value at the time of paper feeding was determined based on the detected voltage value, and output control was performed (this constant voltage control was performed by ATVC control (Au).
to Transfer Voltage Contr
ol)).

By adopting the configuration of this embodiment, good transfer is obtained in both cases of large-size paper passing of B5 horizontal paper or more and small-size paper less than B5 horizontal paper. Sex was obtained.

In this embodiment, the paper passing size of the transfer material is input by the user. However, the present invention is not limited to this. For example, the size detection result of the paper passing transfer material from the transfer material size detecting means such as a sensor may be used. At this time, the switching of the constant current control or the constant voltage control of the transfer unit by the transfer switching control unit 23 may be performed. Of course, the maximum sheet passing size, the minimum sheet passing size, the length of the transfer roller, the transfer material reference width for selecting and switching between the constant current control and the constant voltage control of the image forming apparatus are not limited to the present embodiment. It is. For example, the transfer material reference width of the selection switching between the constant current control and the constant voltage control may be changed based on the volume resistance value of the transfer roller 16 to be used, and for example, the identification of typical postcards and envelopes of small size paper. The control may be switched according to the size of the transfer material.

In the present embodiment, the transfer material passing speed of the image forming apparatus is 105 mm / s, the constant current control value is 9 μA, and the constant voltage control is ATVC control. However, the present invention is not limited to this. , Of course.

As described above, in the transfer roller system,
By executing constant current control for large-size transfer materials and constant-voltage control for small-size transfer materials, in the case of large-size transfer materials, in general, in the case of transfer failures that are current-dependent (transfer charge amount-dependent), Optimum control is performed. In the case of a small-sized transfer material, almost optimal transfer charge can be applied by constant voltage control, and satisfactory transfer can be performed for both large and small-sized transfer materials. That is, it is possible to improve the accuracy of the transfer control in the transfer roller system, and to perform optimal control corresponding to a transfer material having a large size and a small size. The corresponding width of small size transfer material can be reduced, and the constant voltage control value is
By being able to adapt to smaller size transfer materials,
In general, it is possible to prevent and reduce transfer defects depending on current.

<Reference Example> (FIG. 2) FIG. 2 is a schematic structural diagram of an image forming apparatus according to a reference example .

The image forming apparatus of this embodiment is different from the image forming apparatus of the first embodiment in that a humidity sensor 24
To switch between constant current control values during constant current control and / or constant voltage control values during constant voltage control based on the detected humidity data of the humidity sensor 24, and Thus, it is possible to obtain better transferability corresponding to the above.

The other configuration, specifications, control conditions, and the like of the image forming apparatus are the same as those of the image forming apparatus of the first embodiment, so that the description will not be repeated.

The switching control means 23 comprises a humidity sensor 24
Of the constant current control value during the constant current control, and / or the switching of the constant voltage control value during the constant voltage control based on the detected humidity data.

In this embodiment , the humidity is less than 45%,
The constant current control value at the time of the constant current control was switched to 11 μA, 8 μA, and 6 μA in three stages of less than and more than three stages, respectively. Also, at the time of constant voltage control, the constant voltage control value was switched in accordance with three equations for the output conversion of the ATVC control.

By adopting the structure of the present embodiment , the transfer material 18 having a low resistance is generally used even when the transfer material 18 having a low resistance by absorbing moisture is used. A transfer material tends to require a larger amount of transfer charge, and in the case of a low resistance, a higher transfer voltage causes the transfer material to penetrate the transfer material from the back surface of the transfer material and affect the charge polarity of the toner. From the tendency, an optimal transfer charge amount can be given to the transfer material.

By doing so, more environmentally friendly,
Stable and good image formation can be performed.

In the present embodiment , the result of the moisture absorption and the resistance value of the transfer material 18 are measured based on the detection result of the humidity sensor 24, and the constant current control value and the constant voltage control You can switch the value.

In the present embodiment , switching is performed in three stages according to the detection result of the humidity sensor, but it may be performed in two stages or in multiple stages.

Further, it is needless to say that the present invention is not limited to the constant current value and the like used in the present embodiment .

<Second Embodiment> In the above-mentioned reference example, the control value is switched by detecting the degree of moisture absorption as a characteristic of the transfer material. However, other characteristics that contribute to the transfer characteristics, such as thickness, rigidity, Material, processing,
Surface treatment, based on one or more of the information such as the size, may also be subjected to the control value switching.

In general, in the case of a thick transfer material, a relatively large transfer current (transfer charge) tends to be required, and a higher transfer voltage tends to be required in order to uniformly apply the transfer charge. . Also, the higher the rigidity, the more likely the hollow phenomenon that often occurs in a character image, for example, tends to occur. Similarly, for the material of the transfer material and the processing, the optimum transfer charge and voltage are different due to the difference in volume resistance and the like. Also, for example, if the releasability is good, the void in the character is likely to occur due to the good releasability. Transfer charge and voltage are different. By performing transfer control in consideration of such characteristics, it is possible to cope with a wider range of transfer materials.

<Third Embodiment> The main configuration of the image forming apparatus of the present embodiment is the same as that of the image forming apparatus of the first embodiment.

In this embodiment, when the volume resistance value of the transfer roller 16 as a contact transfer charger is less than a predetermined resistance, the switching of the transfer bias depending on the paper passing size of the transfer material is controlled. This is performed only when a transfer roller having resistance is used.

In this embodiment, the transfer roller 1
6, the voltage applied at the time of the constant current of 9 μA was measured, and based on the detected voltage value, the constant voltage output control was performed at the time of paper passing when the voltage was lower than the predetermined detection voltage.

Generally, the volume resistance of the transfer roller changes depending on the degree of durability and the environment. Therefore, by enabling the constant voltage control based on the transfer material passing size when the volume resistance is less than a certain volume resistance, for example, the calculation time for calculating the constant current value for the constant voltage control is reduced, and as a result, the photosensitive member Drum 10
, The damage to the photosensitive drum can be reduced, and the durability of the photosensitive drum can be improved.

With such a configuration, good transfer can be easily performed, and the life of the image forming apparatus, particularly, the photosensitive drum can be extended.

<Fourth Embodiment> (FIG. 3) FIG. 3 is a schematic structural diagram of an image forming apparatus according to this embodiment.

In the image forming apparatus of this embodiment, a multi-stage cassette paper feeding unit 25 is used as a transfer material feeding unit to the transfer site T.
And a manual feed unit 25a.

The other constructions, specifications, control conditions, and the like of the image forming apparatus are the same as those of the image forming apparatus of the first embodiment, and the description thereof will not be repeated.

In this embodiment, constant current control of transfer bias and constant voltage control of transfer bias are performed based on information on whether paper is fed from the cassette paper feed unit 25 or paper is fed from the manual paper feed unit 25a. Perform a switch.

In the case of the apparatus according to the present embodiment, when the manual paper feeding means 25a, which often feeds transfer materials of relatively various sizes and materials, is designated to feed the paper, the control is switched to the constant voltage control correspondingly.

By adopting the configuration of this embodiment, it is possible to effectively cope with large and small-sized transfer materials with a relatively simple configuration, and to perform good image formation.

In this embodiment, the manual paper feeder 25a
Is specified by specifying the paper feeding means, but it goes without saying that any paper feeding means may be supported.

As described above, in the transfer roller system,
Executing constant voltage control during the transfer of a transfer material from a specific paper supply unit (feeding unit) makes it possible to optimize a large-size transfer material in a transfer defect that generally depends on current (transfer charge amount). In the case of a small-sized transfer material, almost optimal transfer charge can be applied by constant voltage control, and satisfactory transfer can be performed for both large and small-sized transfer materials. That is, it is possible to improve the accuracy of the transfer control in the transfer roller system, and to perform optimal control corresponding to a transfer material having a large size and a small size. Since the corresponding width of the small-size transfer material can be reduced and the constant voltage control value can be adapted to the small-size transfer material as compared with the related art, it is possible to generally prevent or reduce a transfer defect depending on current.

Also, in this embodiment, the second embodiment
Transfer material characteristics that contribute to transfer characteristics, such asIf thick
, Rigidity, material, processing, surface treatment, etc.
Constant current control value during constant current control based on multiple pieces of information
Switching or constant voltage control value cutoff during constant voltage control
You can change it.

By adopting such a configuration, it is a matter of course that good transfer can be performed corresponding to transfer materials having various characteristics.

Also, in this embodiment, as in the third embodiment, it is possible to switch over at a predetermined volume resistance value based on the volume resistance of the transfer roller 16.

<Others> 1) The image carrier 10 is not limited to an electrophotographic photosensitive member, but may be an electrostatic recording dielectric, a magnetic recording magnetic material, or the like, and forms a transferable image on the image carrier. The principle and process are arbitrary.

Further, the present invention is not limited to the drum type, but may be any type such as a belt type, a web type, and a sheet type.

2) The contact transfer charger 16 is not limited to the roller type, but may be of a belt type or a combination of a belt and an electrode blade.

3) The transfer material may be an intermediate transfer member such as an intermediate transfer drum or the same belt.

[0094]

As described above, according to the present invention,
Transfer means Der transfer means is a contact transfer scheme is, the transfer material rhino
Transfer system that uses constant current control and constant voltage control depending on the
For a transfer type image forming apparatus that performs control, it is possible to provide an image forming apparatus that can perform transfer with higher accuracy even in various paper passing sizes of a transfer material and that can always obtain a high-quality image stably. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic configuration model diagram of an image forming apparatus according to a reference example .

FIG. 3 is a schematic diagram illustrating a configuration of an image forming apparatus according to a fourth embodiment.

FIG. 4 is a schematic configuration model diagram of an example of a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 image carrier (photosensitive drum) 11 primary charger 12 image exposure 13 developing device 15 resist roller 16 contact transfer charger (transfer roller) 17 cleaner 18 transfer material 20 transfer bias power supply 21 constant current power supply 22 constant voltage power supply 23 switching Control means 24 Humidity sensor

Claims (5)

(57) [Claims] 1. An image forming apparatus having a transfer means for transferring a transferable image formed and carried on an image carrier to a transfer material, wherein the transfer means forms a transfer portion in contact with the image carrier.
A contact transfer type transfer means having a contact transfer charger for applying a transfer charge to the transfer material passed through the transfer portion and transferring a transferable image on the image carrier side to the transfer material side; A constant current control means for outputting a predetermined current value to the container, and a constant voltage control means for outputting a predetermined voltage value to the container. constant current control means is switchable to either the constant voltage control, the predetermined current value and the predetermined voltage value, the transfer material
Stiffness, the image forming apparatus, characterized in that the switchable in response to at least one of information of the surface treatment changing the release properties. 2. The method according to claim 1, wherein the transfer means is switched to constant current control when the size of the transferred transfer material is equal to or larger than a predetermined size, and is switched to constant voltage control when the size of the transfer material is smaller than the predetermined size. Item 2. The image forming apparatus according to Item 1 . A charging means for uniformly charging the wherein image carrier,
The image carrier has image information writing means for forming an electrostatic latent image of image information on a charged image carrier, and developing means for visualizing the electrostatic latent image formed on the image carrier. the image forming apparatus according to claim 1 or 2, characterized in that the transfer image is formed. 4. The image forming apparatus according to claim 3 , wherein the electrostatic latent image is visualized by reversal development. Transferable image 5. was formed and held on the image carrier by the image forming apparatus according to any one of claims 1 to 4, characterized in that a toner image.