JP3057121B2 - 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 copying machine, a printer,
The present invention relates to an image forming apparatus using an electrophotographic method such as a facsimile, and more particularly, to an image forming apparatus having a carrier that carries a toner image and transports the toner to the next process.

[0002]

2. Description of the Related Art In a color image forming apparatus, a subtractive color mixing method is used.
It is necessary to form the primary color toner images on the transfer paper in a superimposed manner. Conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 52-73738, a toner image of each color component is formed on a photoreceptor in several times, and the toner image of each color component is formed once. 2. Description of the Related Art There is an image forming apparatus that forms a color image by sequentially transferring images on transfer paper.

For example, the image forming apparatus has a first carrier, a second carrier, and means for transferring a toner image on the first carrier onto the second carrier. An example of the image forming apparatus is one in which the body carries the toner image transferred from the first carrier and is rotated and conveyed to a process section for transferring the toner image to transfer paper.

In such a color image forming apparatus, the first
In order to make the transfer paper adhere to the photoreceptor several times as a carrier, a clamp mechanism that clamps the end of the transfer paper is provided, but the mechanism is very complicated,
The image cannot be transferred to the clamped portion of the transfer paper.

In view of this, a toner image for each color component is formed on the photoreceptor several times, and the toner image for each color component is transferred onto an intermediate transfer member as a second carrier that is driven to rotate. There is a technique in which a full-color toner image is formed by sequentially superposing and transferring the full-color toner image, and the full-color toner image is collectively transferred onto a transfer sheet.

In this technique, the toner remaining on the intermediate transfer member after image formation is cleaned by a cleaning device. The cleaning device includes, for example, a cleaning blade as a cleaning unit, and the cleaning blade is brought into contact with the intermediate transfer member to scrape and remove the remaining toner.

[0007]

However, the above technique has a problem in that after the residual toner is scraped off by the cleaning blade, the toner is scattered when the blade is released, and the inside of the apparatus becomes dirty.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus which prevents toner from scattering and does not cause toner contamination in the apparatus for a long time.

[0009]

In order to achieve the above object, the present invention is configured as follows. (1). A first carrier, a second carrier, and means for transferring a toner image on the first carrier onto the second carrier, wherein the second carrier is provided with the first carrier; The toner image transferred from the carrier is rotated and driven to convey the toner image to a step of transferring the toner image to recording paper. A cleaning member for removing the toner to be removed, the cleaning member is provided with a conductive member to which a bias voltage can be applied, and the cleaning member is attached to the conductive member immediately before the cleaning member is released from the second carrier. Apply a bias voltage of the opposite polarity to the charge polarity of the toner,
After the contact, the application of the bias voltage is stopped (claim 1). (2). A first carrier, a second carrier, and means for transferring a toner image on the first carrier onto the second carrier, wherein the second carrier is provided with the first carrier; The toner image transferred from the carrier is rotated and driven to convey the toner image to a step of transferring the toner image to recording paper. Cleaning means comprising an elastic blade for removing the toner to be removed is provided. The supporting member supporting the cleaning means is a conductive member capable of applying a bias voltage, and the surface of the supporting member is roughened. (Claim 2). (3). A first carrier, a second carrier, and means for transferring a toner image on the first carrier onto the second carrier, wherein the second carrier is provided with the first carrier; The toner image transferred from the carrier is rotated and driven to convey the toner image to a step of transferring the toner image to recording paper. Cleaning means for removing toner to be removed, a conductive member to which a bias voltage can be applied is attached to the cleaning means, and the conductive member is charged with toner immediately before the cleaning means is released from the second carrier. A bias voltage having a polarity opposite to the polarity is applied, the bias voltage is switched to a bias voltage having the same polarity as the charged polarity of the toner immediately before the contact, and the application is stopped after the contact.

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

The toner scattered when the blade is released is attracted to the conductive member by the bias voltage.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an image forming apparatus having a second carrier for carrying a toner image and conveying the toner image to the next step. Specifically, the second carrier carries the toner image transferred from the photoreceptor serving as the first image carrier, and is rotated to the step of transferring to the transfer target such as transfer paper. , And also includes other carriers that electrostatically carry and transport the carrier.

Hereinafter, a description will be given based on an embodiment in which the second carrier is an intermediate transfer belt. FIG. 2 is a schematic configuration diagram of the color copying apparatus according to the present invention, and FIG. 3 is an enlarged configuration around the photosensitive member and the intermediate transfer belt.

In FIG. 2, a color image reading apparatus (hereinafter, referred to as a color scanner) 1 converts an image of a document 3 through an illumination lamp 4, mirror groups 5-1, 5-2, 5-3 and a lens 6. An image is formed on a photoelectric conversion element, for example, a color sensor 7 using a CCD. Then, the color image information of the original is read for each color separation light of, for example, blue (hereinafter, referred to as B), green (hereinafter, referred to as G), and red (hereinafter, referred to as R), and is converted into electrical image information. .

Then, based on the color separation image signal intensity levels of B, G, and R obtained by the color scanner 1,
A color conversion process is performed by an image processing unit (not shown), and color image data of black (hereinafter, referred to as BK), cyan (hereinafter, referred to as C), magenta (hereinafter, referred to as M), and yellow (hereinafter, referred to as Y) are obtained. obtain.

This is converted into a color image recording device (hereinafter referred to as a color printer) 2 by BK, BK,
Visualization of C, M, and Y is performed, and these are superimposed to form a four-color full-color image.

Next, an outline of the color printer 2 will be described with reference to FIGS. The writing optical unit 8 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the original image, and electrostatically writes on the photosensitive drum 9 as a first latent image carrier. Form a latent image.

The photosensitive drum 9 rotates in a counterclockwise direction as indicated by an arrow. Around the photosensitive drum 9, a photosensitive member cleaning unit (including a pre-cleaning static eliminator) 10, a static elimination lamp 11, a charger 12, a potential Sensor 13, BK developing device 14, C developing device 15, M developing device 16, Y developing device 17,
A development density pattern detector 18, an intermediate transfer belt 19 as a second carrier, and the like are arranged.

Each developing device has a developing sleeve (14-1, 15-1, 16-1, 17-1) which rotates so that a developer faces the photosensitive drum 9 in order to develop an electrostatic latent image.
And a developing paddle that rotates to pump up and agitate the developer, and a sensor for detecting the toner concentration of the developer.

Order of developing operation (color image forming order)
Will be described below using examples of BK, C, M, and Y. However, the image forming order is not limited to this.

When the copying operation is started, reading of BK image data is started at a predetermined timing by the color scanner 1, and based on this image data, light writing / latent image formation by laser light is started (hereinafter referred to as BK image). The electrostatic latent image based on the data is called a BK latent image, and the same applies to C, M, and Y).

In order to enable development from the leading end of the BK latent image, the developing sleeve 14-1 starts rotating before the leading end of the latent image reaches the developing position of the BK developing unit 14 to transfer the BK latent image to the B position.
Develop with K toner. Thereafter, the developing operation of the BK latent image area is continued, but when the rear end of the BK latent image passes the BK developing position, the developing operation is disabled. This is completed at least before the leading end of the C latent image based on the next C image data arrives.

Next, the BK toner image formed on the photosensitive drum 9 is transferred onto the surface of the intermediate transfer belt 19 which is driven at the same speed as the photosensitive drum 9 (hereinafter, from the photosensitive member to the intermediate transfer belt). Is referred to as a belt transfer).

The belt transfer is performed by applying a predetermined bias voltage to the transfer bias roller 20 while the photosensitive drum 9 and the intermediate transfer belt 19 are in contact with each other.

The intermediate transfer belt 19 includes a photosensitive drum 9
The toner images of BK, C, M, and Y which are sequentially formed are sequentially aligned on the same surface to form a four-color superimposed belt transfer image, and thereafter, collective transfer is performed on transfer paper. The configuration and operation of the intermediate transfer belt unit will be described later.

On the photosensitive drum 9 side, the C step is performed after the BK step. At a predetermined timing, reading of C image data by the color scanner 1 starts.
The latent image C is carried by the writing of the laser beam based on the image data.

The C developing device 15 moves the developing position relative to the developing position.
After the rear end of the previous BK latent image has passed and before the leading end of the C latent image has arrived, the rotation of the developing sleeve 15-1 is started and C
The latent image is developed with C toner.

Thereafter, the development of the C latent image area is continued, but when the trailing end of the latent image has passed, the development is disabled as in the case of the BK developing device. This is also completed before the leading end of the next M latent image arrives.

Incidentally, for each of the steps M and Y,
The operations of reading image data, forming a latent image, and developing are the same as those in the above-described steps BK and C, and thus description thereof is omitted.

Next, the intermediate transfer belt unit will be described. The intermediate transfer belt unit 19 includes the driving roller 2
1. The transfer bias roller 20 is stretched around the transfer bias roller 20 and the driven roller group, and is driven and controlled by a drive motor (not shown) as described later.

As shown in FIG. 3, the belt cleaning unit 22 includes a brush roller 22-1, a blade 22-2 as a cleaning means, and a contact / separation mechanism 22- which brings the outer blade into and out of contact with the intermediate transfer belt. After the first color BK image is transferred to the belt, the second, third, and fourth colors are separated from the belt surface by the contact / separation mechanism 22-3 during the belt transfer. .

The paper transfer unit 23 includes a paper transfer bias roller 23-1, a roller cleaning blade 23-
2, and a mechanism 23-3 for contacting and separating from the belt.

The bias roller 23-1 is usually
Although it is separated from the surface of the intermediate transfer belt 19, when the four-color superimposed images formed on the surface of the intermediate transfer belt 19 are collectively transferred to transfer paper, they are pressed by the contact / separation mechanism 23-3 in a timely manner. A predetermined bias voltage is applied to the roller 23-1 to perform transfer to paper.

The transfer paper 24 is fed by a feed roller 25 and a registration roller 26 at the timing when the leading end of the four-color superimposed image on the intermediate transfer belt surface reaches the paper transfer position.

The manner of movement of the intermediate transfer belt 19 is as follows.
After the belt transfer of the BK toner image of the color has been completed to the rear end, the following three methods are conceivable. One of these methods or one of these methods or the copy speed depending on the copy size is used. , Operated by a combination of efficient methods.

(1). Constant speed forward system. After the belt transfer of the BK toner image, the forward movement continues at a constant speed.

[0042] Then, B on the surface of the intermediate transfer belt 19
When the leading end position of the K image reaches the belt transfer position of the contact portion with the photosensitive drum 9 again,
So that the tip of the next C toner image is exactly at that position,
Images are formed at appropriate timing.

. After that, M, Y
Proceeding to an image process, a four-color superimposed belt transfer image is obtained.

[0044] Following the Y toner image belt transfer step for the fourth color, the four-color superimposed toner image on the belt surface is collectively transferred to the transfer paper 24 as described above while moving forward.

(2). Skip forward movement method. When the belt transfer of the BK toner image is completed, the intermediate transfer belt 19 is separated from the surface of the photosensitive drum 9 and skipped at a high speed in the forward movement direction. Thereafter, the intermediate transfer belt 19 is brought into contact with the photosensitive drum 9 again.

[0046] Then, B on the surface of the intermediate transfer belt 19
When the leading end position of the K image reaches the transfer position of the intermediate transfer belt again, the image is formed on the photosensitive drum 9 side at a timing such that the leading end portion of the next C toner image just comes to that position. . As a result, the C image is belt-transferred while being accurately aligned with the BK image.

[0047] After that, M, Y
Proceeding to an image process, a four-color superimposed belt transfer image is obtained.

[0048] Subsequent to the belt transfer process of the Y toner image of the fourth color, the four-color image on the belt 19 is
The color superimposed toner images are collectively transferred to the transfer paper 24.

(3). Reciprocating (quick return) method When the belt transfer of the BK toner image is completed, the intermediate transfer belt 19 is separated from the photosensitive drum 9 surface, and
At the same time, the forward movement is stopped and a high-speed return is made in the reverse direction.

Return is to B on the intermediate transfer belt 19 surface.
The leading end position of the K image passes through the position equivalent to the belt transfer in the reverse direction, and after moving a predetermined distance, stops and enters the standby state.

[0051] Next, when the leading end of the C toner image on the photosensitive drum 9 reaches a predetermined position before the belt transfer position, the intermediate transfer belt 19 is started again in the forward movement direction. Further, the intermediate transfer belt 19 is started again in the forward movement direction.

Further, the intermediate transfer belt 19 is brought into contact with the surface of the photosensitive drum 9 again. Also in this case, the C image is transferred to the intermediate transfer belt 19 under the condition that the C image is exactly overlapped with the BK image on the belt.

[0053] After that, M, Y
Proceeding to an image process, a four-color superimposed belt transfer image is obtained.

[0054] Subsequent to the belt transfer process of the Y toner image of the fourth color, the toner image moves forward at the same speed without returning, and the four-color superimposed toner image on the surface of the intermediate transfer belt 19 is collectively transferred to the transfer paper 24.

The transfer paper 24 onto which the four-color superimposed toner image has been collectively transferred from the intermediate transfer belt surface is transferred to the paper transport unit 2.
7, the toner image is fused and fixed by a fixing roller 28-1 and a pressure roller 28-2 controlled to a predetermined temperature, and discharged to a copy tray 29.
Get a full color copy.

The photosensitive drum 9 after the belt transfer is
The surface is cleaned by the photoconductor cleaning unit 10, and the charge is uniformly removed by the charge removing lamp 11. Further, the intermediate transfer belt 19 after transferring the toner image onto the transfer paper 24 is pressed again by the belt cleaning unit 22 by the contact / separation mechanism 22-3 to clean the surface.

At the time of repeat copying, the operation of the color scanner 1 and the image formation on the photosensitive drum 9 are performed at a predetermined timing following the Y (fourth color) image process of the first sheet. (1st color) Proceed to the image process.

In the intermediate transfer belt 19, following the batch transfer process of the first four-color superimposed image onto transfer paper,
The second sheet of the BK toner image is transferred to the belt in a region where the surface is cleaned by the belt cleaning unit 22. After that, the operation is the same as that of the first sheet.

The transfer paper cassettes 30, 31, 32,
Transfer papers of various sizes are stored in 33, and the paper is fed and conveyed toward the registration rollers 26 at a timing from a storage cassette of the size paper designated by an operation panel (not shown). When manually feeding paper for an overhead projector, thick paper, or the like, a manual paper feed tray 34 is used.

The above description has been given of the copy mode for obtaining four full-color images.
In the case of the color copy mode, the same operation as described above is performed for the designated color and the number of times.

In the case of the single-color copying mode, only the developing unit for the color is set in the developing state until the predetermined number of sheets is completed, and the intermediate transfer belt 19 is kept in contact with the surface of the photosensitive drum 9 while the developing unit is in the developing state. Driving at a constant speed in the forward direction,
The belt cleaning unit 22 also includes the intermediate transfer belt 19.
The copy operation is performed while keeping contact with.

When a color image is formed on the intermediate transfer belt 19, it is necessary to release the blade 22-2 as the cleaning means from the intermediate transfer belt 19. The toner remaining on the belt after transfer to the transfer paper is scraped off by a blade, but the scraped toner floats in the space inside the cleaning unit.

Here, when the blade 22-2 is released,
The floating toner scatters outside the unit, particularly, on the downstream side of the blade 22-2. If the scattered toner adheres to the transfer belt again, it appears as a stain on the copy image.

In order to collect toner scattered when the blade 22-2 is released from the intermediate transfer belt 19 by switching a switch of the power supply means 50 as shown in FIG. A bias voltage having a polarity opposite to the charged polarity of the toner is applied to the blade holder 39.

Although the bias voltage may be constantly applied, it is preferable to stop the application at the time of blade contact and start the application immediately before the blade is released from the viewpoint of power consumption (FIG. 4A).

Further, the surface of the blade holder 39 is roughened, so that the toner trapped on the surface of the holder can be hardly dropped.

As another example of the present invention, it is conceivable that a bias voltage having a polarity opposite to that of the toner is applied immediately before the blade is released, and a bias voltage having the same polarity as the toner is applied immediately before the contact (FIG. 4). (B)).

Accordingly, when the amount of toner trapped on the blade holder becomes excessive, the toner repels the toner downstream of the contact portion of the blade due to the electrostatic repulsion between the holder and the toner and the impact force at the time of contact. Drops and adheres on the belt.

In this case, as shown in FIG. 5, the next image forming area starts from the start of the blade contact, and the circumference of the intermediate transfer belt is larger than the circumference of the maximum usable transfer paper. The toner T adheres to the non-image area when the next image is generated, that is, before the front end of the next image area and after the rear end of the image area.

Therefore, no stain is generated by the toner falling on the copy image. The toner attached on the belt is removed by the next cleaning operation.

[0071]

According to the present invention, it is possible to provide an image forming apparatus which prevents scattering of toner and does not cause toner contamination in the apparatus for a long time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a cleaning unit according to the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of a color copying machine according to the present invention.

FIG. 3 is an enlarged view illustrating a periphery of a photoconductor and an intermediate transfer belt of FIG. 2;

FIG. 4 is a diagram illustrating the relationship between the contact / separation of the blade and the application timing of the bias voltage.

FIG. 5 is an explanatory diagram of an intermediate transfer belt.

[Explanation of symbols]

 19 Intermediate transfer belt (as an intermediate transfer member) 22-2 Blade (as a cleaning unit) 39 Blade holder (as a conductive member)

Continuation of the front page (56) References JP-A-2-282776 (JP, A) JP-A-58-76875 (JP, A) JP-A-60-22176 (JP, A) JP-A-49-62137 (JP, A) JP-A-60-87382 (JP, A) JP-A-57-64279 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/14-13/18 G03G 15/14-15/14 101 G03G 15/16-15/16 103 G03G 15/18-15/18 101 G03G 21/10-21/12 G03G 21/00 370-540 G03G 21/14

Claims (3)

(57) [Claims] A first carrier, a second carrier, and means for transferring a toner image on the first carrier onto the second carrier; An image forming apparatus configured to carry the toner image transferred from the first carrier to the process unit for transferring the toner image to a recording sheet by being rotationally driven; A cleaning means for removing the toner remaining on the carrier, a conductive member capable of applying a bias voltage is attached to the cleaning means, and immediately before the cleaning means is released from the second carrier, An image forming apparatus comprising: applying a bias voltage having a polarity opposite to a polarity of toner charged to the conductive member; and stopping the application of the bias voltage after the contact. 2. The image forming apparatus according to claim 1, further comprising a first carrier, a second carrier, and a unit for transferring a toner image on the first carrier onto the second carrier. An image forming apparatus configured to carry the toner image transferred from the first carrier to the process unit for transferring the toner image to a recording sheet by being rotationally driven; A cleaning means comprising an elastic blade for removing the toner remaining on the carrier, and a supporting member for supporting the cleaning means being a conductive member capable of applying a bias voltage, and a surface of the supporting member being An image forming apparatus having been subjected to a surface roughening process. 3. A second carrier comprising a first carrier, a second carrier, and means for transferring a toner image on the first carrier onto the second carrier. An image forming apparatus configured to carry the toner image transferred from the first carrier to the process unit for transferring the toner image to a recording sheet by being rotationally driven; A cleaning means for removing toner remaining on the carrier, and a conductive member to which a bias voltage can be applied is attached to the cleaning means, and the cleaning means is provided immediately before the cleaning means is released from the second carrier. Image forming characterized in that a bias voltage having a polarity opposite to the toner charging polarity is applied to a member, a bias voltage is switched to a bias voltage having the same polarity as the toner charging polarity immediately before the contact, and the application is stopped after the contact. Dress .