JP2002323803A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the deterioration of color toner and also preventing the turn-up of a cleaning blade caused by the winding of the cleaning blade into an endless belt as an image forming device having a developing device equipped with at least a black developing unit and a color developing unit. SOLUTION: In the case of forming a toner image for preventing the turn-up of the cleaning blade, whether a copying mode is a black monochrome mode or not is judged (step 1). When judging that it is the black monochrome mode, a line image for preventing the turn-up of the blade is formed at a non-image part after finishing a copying job by a 1st developing unit 1 (black developing unit) (step 2). On the other hand, in a mode other than the black monochrome mode at the step 1, that is, in a red monochrome mode and a two-color mode, a solid image for preventing the turn-up of the blade is formed at the non-image part after finishing the copying job by a 2nd developing unit 2 (red developing unit) (step 3).

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 a copying machine, a facsimile, and a printer.
An image with a transfer device configured to hold and convey the transfer material with an endless belt to transfer the toner image on the image carrier to the transfer material, and to clean the toner attached to the endless belt after separation of the transfer material with a cleaning blade. The present invention relates to a forming apparatus.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a facsimile, and a printer, a toner image developed on a photoconductor is transferred to a transfer material, and the transferred transfer material is separated from the photoconductor. A transfer device using a transfer belt is known as a device for transporting the toner to a fixing device.

The transfer belt of the transfer device is an endless, medium-resistance belt running body made of an elastic member such as a rubber-based material. The transfer belt is supported by a plurality of rollers such as a driving roller and a driven roller and faces the photosensitive member. Be placed. At the time of transfer, a transfer belt holding the transfer material is brought into contact with the photoreceptor, and the transfer material is nipped and conveyed at a nip portion with the photoreceptor, and a high voltage is applied to a bias applying means disposed on the back side of the transfer belt. As a result, the toner image on the photoreceptor is transferred to the transfer material, and the transfer material after the transfer is separated from the photoreceptor and transported to the fixing unit. Further, the transfer device is provided with a cleaning blade for removing toner and paper dust attached to the surface of the transfer belt after the transfer material is separated.

In a copying machine or the like equipped with the above-described transfer device, if a large number of copies having a small image area are taken or a large number of blank copies are taken erroneously, there is no toner adhered to the transfer belt, and The toner on the edge of the cleaning blade that is in contact is also eliminated. For this reason, the friction coefficient μ between the transfer belt and the cleaning blade is increased, the rubbing resistance is increased, the transfer speed of the transfer belt is changed, synchronization is lost, and the edge of the cleaning blade is caught on the belt surface, and the cleaning is performed. The edge of the blade may be turned up. When the blade is turned over, it causes the occurrence of cleaning failure, the back contamination of the transfer material, the scattering of toner, and the damage of the transfer belt.

Therefore, for example, in Japanese Patent Publication No. 7-74929, in order to prevent the cleaning blade from turning up,
An image forming apparatus that forms a linear or horizontal toner image between papers of a photoconductor, transfers the toner image to a transfer belt, and supplies the toner image to an edge portion of the cleaning blade (a portion in contact with the transfer belt). Is disclosed. According to this image forming apparatus, the toner is held between the transfer belt and the cleaning blade to act as a lubricant, the friction coefficient μ between the transfer belt and the cleaning blade is reduced, and the transfer speed of the transfer belt is kept constant. , And the occurrence of curling of the cleaning blade can be prevented. Further, Japanese Patent Application Laid-Open No. 11-45035 discloses that, in consideration of the effects of toner characteristics and development conditions when forming a toner image for prevention of curling or the like, prevention of curling due to winding of a cleaning blade onto a transfer belt, There is disclosed an image forming apparatus capable of achieving both prevention of transfer material back surface contamination.

Conventionally, as a developing method of an image forming apparatus, a one-component developing method using a toner as a developer and a two-component developing method using a toner and a carrier as a developer are known. In the two-component developing method, the life of the developer is determined by the deterioration of the characteristics of the carrier. Therefore, it is necessary to replace the developer when the characteristics of the carrier deteriorate.
On the other hand, the one-component developing method has a feature that a stable image can be obtained by replenishing the toner even when the toner is exhausted. Also, since it is not necessary to stir the toner and the carrier and perform triboelectric charging as in the two-component developing method,
There is also a feature that a stirring mechanism is not required and the size and cost of the apparatus can be reduced as compared with the two-component developing system.

However, the above-mentioned one-component developing system has the above-mentioned excellent features, but has the following disadvantages. There is no problem when the image ratio of the original is high, but when the original image has a low image ratio, the amount of toner used is extremely small, so that the same toner stays on the developing sleeve or the supply roller for a long time. There is a problem that causes deterioration of characteristics of the. In particular, when a color toner is used as a one-component developer, the used image ratio is further reduced, so that the deterioration of the toner characteristics is further promoted. Specifically, the following problems occur due to the deterioration of the toner characteristics. The first problem is that the image density is reduced because the toner staying on the developing roller and the supply roller for a long time is used. This is a problem that occurs because the electrostatic attraction of the toner to the developing roller is increased and the toner is hardly developed. The second problem is that when a magnetic toner is used, the consumption of the magnetic toner is small, so that it takes a considerable amount of time to reach the toner end, and the same toner is stirred for a long period of time. Deterioration becomes severe. As a result, the image density is further reduced. In addition, when a non-magnetic toner is used, when a new non-magnetic toner is replenished at the end of the toner, a new problem occurs by mixing the toner having the deteriorated characteristics with the toner having not deteriorated. . More specifically, the deteriorated residual toner and the new toner are frictionally charged with each other, the residual toner is reversely charged, and the new toner is normally charged. As a result, the toner particles are electrostatically attracted to each other, and exist as a toner mass having a strong reverse charge. In the case of the reversal developing method, the strongly oppositely charged toner mass adheres to the non-image area on the photoconductor. Then, in the transfer, the charge of the opposite polarity is charged up on the transfer paper, so that only the normally charged new toner is transferred onto the transfer paper. This is called replenishment background soiling.

Therefore, for example, in Japanese Patent No. 2737009, characteristics relating to the amount of toner consumption (for example, the density of the pattern portion on the photosensitive drum, the potential of the photosensitive drum, the frequency of the signal of the remaining amount detecting means, etc.) are detected. There is disclosed an image forming apparatus that forcibly consumes toner in a non-image area of a photosensitive drum when it is detected that the consumption amount is small. According to this image forming apparatus, it is possible to prevent the characteristic deterioration of the toner, particularly the characteristic deterioration of the one-component developer toner.

[0009]

However, in the image forming apparatus described in Japanese Patent No. 2737009, when a color toner is used as a one-component developer, a one-point use method is generally used. Deterioration cannot be prevented. In addition, since the toner is forcibly consumed when it is detected that the consumption amount is small, a large amount of toner is discarded. In addition, non-image areas during copying (paper space, etc.)
Further, since the toner is forcibly attached, the toner on the photosensitive drum becomes untransferred toner, and a large amount of toner enters the cleaning section at the same time, which may cause a cleaning failure.

Further, the invention disclosed in Japanese Patent Application Laid-Open No. 11-45035 discloses an invention for forming a toner image for preventing the cleaning blade from being turned up, for example, a developing device having a black developing device and a one-component color developing device. When the present invention is applied to an image forming apparatus having a toner image, forming the toner image with a color toner rather than a black toner is more advantageous for cleaning. This is because the average particle size of the color toner (for example, 11.5 μm for the red toner) is generally smaller than the average particle size of the black toner (for example, 6.8 μm).
This is because, since m) is larger, the color toner hardly slips through the sliding contact portion between the transfer belt and the cleaning blade, and is thus favorably cleaned. However, when a toner image for preventing the cleaning blade from being twisted or the like is formed in a certain cycle using only the one-component color developing device, the one-component color developing device is frequently used, and the toner image is consumed in forming the toner image. Since the amount is small, there is a problem that the one-component color toner is easily deteriorated. In addition, even when an image is formed using only a black developing device, since the one-component color developing device is operated to form the toner image, there is a problem that the time until the apparatus stops is long. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus having at least a developing device having a black developing device and a color developing device, in which the deterioration of color toner is prevented. To prevent
It is an object of the present invention to provide an image forming apparatus capable of preventing a cleaning blade from being turned up by being wound around an endless belt.

[0012]

In order to achieve the above object, a first aspect of the present invention is a latent image forming means for forming an electrostatic latent image on an image carrier, and a latent image on the image carrier. And a developing device for developing the toner image with toner, and holding the transfer material on an endless belt whose surface moves endlessly, transferring the toner image on the image carrier to the transfer material, and transferring the transferred transfer material. A transfer device configured to convey the toner adhered to the endless belt after separation of the transfer material by the endless belt and to clean the toner adhered to the endless belt with a cleaning blade. In an image forming apparatus, a toner image is formed on a non-image portion of the image carrier by a latent image forming means and a developing device, and the toner image is transferred to the endless belt and supplied to a sliding contact portion of the cleaning blade. A first developing device containing a black toner; And at least two developing devices and the second developing device accommodating a color toner, the black monochrome mode,
A control unit configured to have an image mode such as a color monochromatic mode and a multicolor mode, and forming a toner image for preventing the turning of the cleaning blade or the like by using a developing device used for a developing operation in each image mode; It is characterized by the following.

In this image forming apparatus, a toner image for preventing the cleaning blade from being twisted or the like is formed by using a developing device which has been subjected to a developing operation in each image mode. More specifically,
When a black monochrome image is formed, the toner image is formed using the first developing device, and when a monochrome monochrome image is formed, the toner image is formed using the second developing device. When an image in the multi-color mode is formed, the toner image is formed using one of the first and second developing devices. Thus, the frequency of use of the second developing device can be reduced as compared with the case where the toner image is formed only by the second developing device containing the color toner which is advantageous for cleaning. Therefore, the stress applied to the color toner of the second developing device can be reduced to suppress the deterioration, and a stable image can be obtained. Further, when the image is formed in the black monochrome mode, the second developing device does not operate, so that the stop time of the apparatus can be shortened as compared with the case where the toner image is formed only by the second developing device. Power consumption can be reduced.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the first developing device is used to form a toner image for preventing the cleaning blade from being turned up, and the second developing device is used for forming the toner image. The control means controls the image forming so that the image forming areas of the toner image for preventing the turning of the cleaning blade are different from each other when forming the toner image for preventing the turning of the cleaning blade by using the image forming apparatus. It is characterized by the following.

The average particle size of the black toner contained in the first developing device is, for example, 6.8 μm. When the red toner is used as the color toner contained in the second developing device, the average particle size is, for example, 11. 5 μm. As described above, the cleaning of the endless belt by the cleaning blade is more advantageous for the red toner having a larger particle diameter than the black toner. For this reason, a black image of a small area, for example, a line image is formed with the black toner of the first developing device which is disadvantageous for cleaning, and the cleaning load by the cleaning blade is reduced to prevent poor cleaning of the endless belt. As a result, back contamination of the transfer material can be prevented. On the other hand, the red toner of the second developing unit, which is advantageous for cleaning, forms a solid image having a large area, for example, and increases the consumption of the red toner to prevent the deterioration of the toner. Thereby, a stable image can be obtained in the color (red) single-color mode or the multi-color mode. In addition, even if a solid image having a large area is formed with red toner, cleaning is easy, and therefore, the back contamination of the transfer material does not occur.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the control means forms the toner image for preventing the cleaning blade from being turned up based on the average particle size of the toner used. It is characterized in that control for changing the area is performed.

In this image forming apparatus, in the case of a black toner having a small average particle size, for example, in the case of a black toner, the image forming area is reduced to maintain the cleaning property of the endless belt by the cleaning blade. On the other hand, in the case of, for example, a red toner having a large average particle diameter, the image forming area is increased to increase the toner consumption and prevent the toner from being deteriorated.

According to a fourth aspect of the present invention, there is provided the image forming apparatus of the first aspect, further comprising a counting device for counting the number of images formed on the transfer material by using the second developing device. In accordance with the accumulated count by the counting device after the developing device reaches the toner end and replenishes the toner, the control means controls the toner image for preventing the turning of the cleaning blade formed by the second developing device. It is characterized in that control for sequentially increasing the image forming area is performed.

In this image forming apparatus, the number of images formed by the second developing device is counted by the counting device after the second developing device reaches the toner end and replenishes the toner. The number of formed images is known, and the deterioration state of the toner can be determined from the accumulated number of images. The toner is more deteriorated when the number of accumulated images is small than when the number is large. Then, for example, the image forming area when the accumulated image formation number is small (for example, less than 2,000 sheets) is larger than when it is large (for example, 2,000 sheets or more). As a result, the consumption amount of the deteriorated toner is increased, and the number of images formed with the deteriorated toner can be reduced by quickly ending the toner. The deteriorated toner has a large toner cohesion degree, so that even if the image forming area is increased, the load on cleaning is small and there is no problem.

According to a fifth aspect of the present invention, in the image forming apparatus of the first aspect, there is provided a counting device for counting the number of images formed using the cleaning blade, and the use of the cleaning blade by the counting device. When the cumulative number of image formations from the start exceeds a predetermined count, the control means controls the image forming of the toner image by using a developing device containing a toner having a large average particle diameter among the developing devices. Is performed.

In this image forming apparatus, the state of wear of the edge portion of the cleaning blade can be predicted by counting the accumulated number of formed images after the use of the cleaning blade by the counting device. When the edge portion of the cleaning blade is worn, for example, black toner having a small average particle diameter passes through the sliding contact portion with the endless belt, making cleaning difficult. For this reason, when a predetermined cumulative number of images has been formed since the start of use of the cleaning blade, the above-described toner image is formed only with, for example, a color toner having a large average particle size, so that the load on cleaning can be reduced. It is possible to prevent the transfer material from being stained on the back side, which is caused by poor cleaning.

The invention of claim 6 is the invention of claims 1, 2, 3, 4
Alternatively, in the image forming apparatus according to the fifth aspect, a one-component color toner is used as the color toner stored in the second developing device.

The one-component developing system has a disadvantage that the developing device can be reduced in size and cost, but it is liable to be deteriorated particularly in a color toner which is not frequently used. In this image forming apparatus, the frequency of use of the second developing device can be reduced as compared with the case where the toner image is formed only by the second developing device containing the one-component color toner. Therefore, it is possible to reduce the stress applied to the one-component color toner of the second developing device and suppress the deterioration. Further, a solid image having a large area, for example, a solid image can be formed with the one-component color toner of the second developing device, and the consumption of the one-component color toner can be increased to prevent deterioration of the toner.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to an embodiment of the present invention, which is an example of an image forming apparatus of a two-color simultaneous image forming system used as an image forming unit or a printer of a digital copying machine. In FIG. 1, the image forming apparatus irradiates a drum-shaped photoreceptor 4, a first charging device 5 disposed therearound, and write light L1 from a first optical writing device (not shown). 1st optical writing section, 1st
A developing device 1, a second charging device 6, a second optical writing unit irradiated with writing light L2 from a second optical writing device (not shown),
The image forming apparatus includes a developing device 2, a transfer device 3 of a contact transfer type using a transfer belt, a cleaning device 7, a charge removing device 8, and the like. It should be noted that illustrations of a paper feed unit that feeds the transfer paper S to the transfer unit, a paper feed mechanism such as a registration roller, a fixing device provided downstream of the transfer device 3, and the like are omitted.

The first charging device 5, the first optical writing device (not shown), and the first developing device 1 are for forming a black image, for example.
The first optical writing device includes a laser diode (LD), an optical deflector, an imaging lens system, a mirror, and the like. The laser diode emits light in response to a black image signal from an image processing unit (not shown). The writing light L1 is scanned on the photosensitive member 4 charged by the first charging device 5 to write an electrostatic latent image of a black image, and the latent image of the black image is subjected to a first development using, for example, a two-component developer. The image is developed with the black toner of the apparatus 1. The second charging device 6, the second optical writing device (not shown), and the second developing device 2 are for forming a color image of one color such as red or blue,
The second charging device 6 charges the photoconductor 4 after the black image is formed, and the second optical writing device is a writing device using a laser beam similar to the first optical writing device (or a writing device including an LED array or the like). ), The laser diode emits light in response to a color image signal such as red or blue from an image processing unit (not shown),
The writing light L2 is scanned on the photoconductor 4 to write an electrostatic latent image corresponding to a color image such as red or blue, and the latent image of the color image is converted into a second developing device 2 using, for example, a one-component developer. Developed with the color toner.

The black and color toner images formed on the photoreceptor 4 are supplied from a paper supply unit (not shown) and transferred to a transfer nip between the transfer belt 31 of the transfer device 3 and the photoreceptor 4 via a registration roller. The image is transferred onto the transfer sheet S conveyed to the copy unit.
Then, the residual toner is removed from the photoconductor 4 after the transfer of the toner image by the cleaning device 7, and the charge is removed by the charge removing device 8.

The transfer device 3 includes an endless, medium-resistance transfer belt 31 disposed opposite the photosensitive member 4, and a transfer belt 3.
1, a driving roller 33 and a driven roller 34, a bias applying roller 35 disposed on the back side of the transfer belt 31 for applying a transfer bias, and a cleaning blade 32 for cleaning the surface of the transfer belt 31. , And a contact / separation mechanism 3 for moving the transfer belt 31 toward and away from the photoconductor 4
6 (contacting / separating levers and driving means such as a solenoid or a cam for driving the contacting / separating levers). The transfer belt 31 is rotated in the direction indicated by an arrow in the figure in accordance with the transfer of the transfer paper S from a registration roller (not shown), and the transfer belt 31 is moved by the contact / separation mechanism 36 by a signal from a control unit (not shown). The transfer paper S is pushed up and comes into contact with the photoconductor 4 and is opposed to the photoconductor 4 at a position facing the photoconductor 4.
A transfer nip portion having a width capable of transporting the photosensitive drum 4 while contacting the photosensitive drum 4 is formed. When the transfer paper S enters the transfer nip portion, a transfer bias is applied by a transfer bias roller 35, and a charge having a polarity opposite to that of the toner on the photoconductor 4 is applied to the transfer belt 31 to form a toner image. Transfer is performed.

The transfer paper S that has passed through the transfer nip portion is electrostatically attracted and conveyed in accordance with the movement of the transfer belt 31, and the drive roller 33 separates the curvature. The driving roller 3
The transfer paper S separated from the transfer belt 31 in 3 is conveyed to a fixing device (not shown), and the toner on the transfer paper S is heated and
It is fixed on the transfer paper S by pressure or the like. On the other hand, the transfer paper S
The transfer belt 31 on which image transfer and separation have been completed is rubbed on the surface by a cleaning blade 32 made of polyurethane rubber or the like, so that residual toner and paper dust adhering to the surface of the transfer belt 31 are removed.

Since the transfer belt 31 is made of a medium-resistance rubber member, when the coefficient of friction with the cleaning blade 32 also made of a rubber member (polyurethane rubber) increases, the edge of the cleaning blade 32 is attached to the transfer belt 31. The phenomenon that the edge portion is turned up is generated (hereinafter, referred to as “blade turning up”). When the blade is turned over, a cleaning failure occurs, and at the same time, the transfer belt 31 is damaged, resulting in a transfer failure. In order to prevent such blade turning, a toner image for preventing blade turning is formed in a non-image portion, and the toner image is transferred to the transfer belt 31.
A method is used in which an appropriate amount of toner is provided to the cleaning blade 32 and the friction coefficient is reduced using the toner as a lubricant.
The transfer belt 31 can be more easily cleaned by the cleaning blade 32 if the toner image for preventing the turning of the cleaning blade is formed with red toner having an average particle diameter smaller than that of the black toner. However, when the toner image is formed using only the red toner of the second developing device 2, the second developing device 2
There is a problem that the red toner is liable to be deteriorated because the frequency of use of the toner increases and the consumption of the toner image is small. In particular, since the second developing device 2 is a one-component developing system, the red toner is more likely to deteriorate. Further, even when a black monochromatic image is formed using only the first developing device 1, the second developing device 2 is operated to form the toner image. Problem.

[Embodiment 1] Therefore, the image forming apparatus according to the present embodiment forms a toner image for preventing the turning of the cleaning blade by using a developing device used for a developing operation in each image mode. did. FIG. 2 is a flowchart for determining whether to form the toner image for preventing the turning of the cleaning blade or the like using black toner or red toner. FIG. 3A is a timing chart when the toner image is formed with black toner, and FIG. 3B is a timing chart when the toner image is formed with red toner.

In FIG. 2, it is determined whether or not the copy mode is the black monochrome mode (step 1). In the case of the black monochromatic mode, the first developing device 1 (black developing device) forms a line image for preventing the blade from being turned over in the non-image portion after the end of the copy job at the timing shown in FIG. Step 2). On the other hand, in step 1, a mode other than the black monochromatic mode,
That is, in the monochromatic red mode and the two-color mode, the second developing device 2
At the timing shown in FIG. 3B, a solid image for preventing the blade from being turned is formed at the timing shown in FIG. 3B by the (red developing device) (Step 3).

Since the first developing device 1 contains black toner having an average particle size of 6.8 μm, it is disadvantageous for the cleaning blade 32 to clean the transfer belt 31. Therefore, it is advantageous for the cleaning property that the toner image for preventing the blade from turning is as small as possible.
The blade turnover prevention image is a line image. Although the amount of toner input to the cleaning blade 32 is small because it is a line image, it is sufficient as a lubricant for the blade. On the other hand, the second developing device 2 contains red toner having an average particle size of 11.5 μm, which is advantageous for cleaning. However, the second developing device 2
Since the red toner is a non-magnetic one-component toner, if the number of copies until the toner end detection is activated is large, stress is applied to the toner for a long period of time, so that there is a disadvantage that the characteristics of the toner tend to deteriorate. Therefore, it is desirable to use the second developing device 2 as little as possible. The present embodiment is characterized in that a toner image for curling prevention is created by the second developing device 2 only when the second developing device 2 is used, and an image is formed by a solid image or a halftone image. Cleaning blade 32
Although the amount of toner input to the toner increases, the average toner particle diameter of the red toner is as large as 11.5 μm, so that there is no problem in cleaning performance. Further, since the curling prevention toner image is created with a solid image or a halftone image, the consumption amount of the red toner increases, and the deteriorated toner can be used effectively.
As a result, a stable red image is obtained.

Embodiment 2 Next, another embodiment 2 will be described. FIG. 4 is a block diagram of the second embodiment. Also,
FIG. 5 is a flowchart of the image formation of the toner image for preventing the curl. In the second embodiment, as shown in FIG. 4, a counting device for counting the number of red image copies is provided. Then, the mechanism detects the toner end of the red toner, detects that new toner has been put into the second developing device 2, resets the accumulated number of counts, and starts a new count.

Then, in the flowchart of FIG.
When red copying is performed, the number of accumulated copies of the red image is counted (step 1), and the operation is divided into the following three operations depending on the number of accumulated copies (step 2).
If it is less than the specified value 1 (step 3), it is determined whether the toner end has been reached (step 4). If the toner end has been reached, the accumulated count number is reset (step 5).
A blade turning prevention toner image is formed under the image forming condition 1 of the blade turning prevention solid image (step 6), and the copying is completed. If the toner end has not come in step 4, a toner image for preventing the blade from being turned up is formed under image forming condition 1.
(Step 6), and the copying is completed.

On the other hand, if it is determined in step 2 that the cumulative number of copies is equal to or more than the specified value 1 and less than 2 (step 7), it is determined whether or not the toner end is in the meantime (step 8). In this case, the accumulated count number is reset at that time (step 9), and the creation of the blade turn-prevention toner image is created under the imaging condition 1 (step 1).
0), end the copy. If the toner end has not been reached in step 8, a blade turn-prevention toner image is created under the image forming condition 2 (step 11), and the copy ends.

If the cumulative number of copies is equal to or more than the specified value 2 (step 12) in step 2 above, it is determined whether or not the toner end has been reached (step 13). The number of sheets is reset (step 14), and a toner image for preventing blade turn-up is created under image forming condition 1 (step 15), and copying is completed. If the toner end has not come in step 13, the creation of the toner image for preventing the blade from being turned up is performed according to the image forming condition 3.
(Step 16), and the copying is terminated. It should be noted that when the second developing device 2 is used to form a curling prevention toner image of the cleaning blade 32, the specified value 1
Table 1 shows the relationship between 2 and the imaging conditions 1 to 3.

[Table 1]

Referring to the timing chart of FIG. 3B, the second developing device 2 forms a solid image for prevention of turning over, and
As the write operation time of the LD becomes longer, the second charger, the second developing device, and the transfer bias application time are naturally extended.

In the case of the second embodiment, the conditions for forming a solid image for preventing the curling of the cleaning blade 32 are changed according to the cumulative number of copies (from the end of toner) of the second developing device 2. The amount of toner consumption is changed to prevent toner deterioration. As a result, a stable image can be obtained for the image created by the second developing device 2.

Third Embodiment Next, a third embodiment will be described. In the third embodiment, the cumulative number of used cleaning blades 32 is counted, and it is detected that the number of used cleaning blades is larger than a predetermined value. It is characterized by the following.
Since the cleaning blade 32 is in rubber-to-rubber friction with the transfer belt 31, the cleaning blade 3
2 easily wears, which is disadvantageous for cleaning performance. When the cleaning blade 32 is in a new state, the blade edge surface is firm, so that the first developing device (black developing device)
Even if black toner having an average particle diameter of 6.8 μm is input, cleaning is possible. However, when about 10,000 sheets of A4 size are used, the edge surface becomes rough, and cleaning of the black toner becomes difficult. Therefore, when it is detected that the cleaning blade 32 corresponding to A4 or more than 10,000 sheets is used, the image formation of the blade turning prevention toner image is performed only by the second developing device (red developing device) 2 so that the average particle size is reduced. 1
The 1.5 μm red toner is to be cleaned, and the cleaning property is advantageous.

FIG. 6 is a flowchart for explaining the operation of the third embodiment. The cumulative number of used cleaning blades 32 is counted (step 1), and the specified value 1 (A
It is determined whether or not the number has exceeded (equivalent to 10,000 sheets) (step 2). If the value does not exceed the specified value 1, a blade turn-prevention toner image is created in each developing unit in each image mode (step 3). In other words, the first developing device (black developing device) 1 is used in the black monochromatic mode, and the second developing device (red developing device) 2 is used in the monochromatic red mode and the two-color mode to prevent the blade from turning. Create a toner image.

If the value exceeds the specified value 1 in step 2,
The formation of the blade turn-up preventing toner image is performed only by the second developing device (red developing device) 2 (step 4). If the cumulative number of sheets used exceeds the specified value 2 (20,000 sheets corresponding to A4) (step 5), and if the cleaning blade 32 has been replaced (step 6), the cumulative counter is reset (step 7). ), End copying. On the other hand, if the cleaning blade 32 has not been replaced in step 6, the replacement time of the cleaning blade 32 is displayed on an operation panel or the like (not shown), and the toner image for preventing the blade from being turned is formed by the second developing device (red developing device). ) 2 only (step 8), and the copy is terminated. Also in the case of the third embodiment, similarly to the above-described second embodiment, the image formation conditions of the curl prevention toner image can be changed by the accumulated number of copies of the second developing device (red developing device) 2.

In each of the above-described embodiments, an example has been described in which the present invention is applied to an image forming apparatus which includes two developing units, a black developing unit and a red developing unit, for one photosensitive member and simultaneously forms two colors. Of course, the present invention can be applied to an image forming apparatus having three or four developing units for one photosensitive member. Further, the present invention can be applied to a tandem type image forming apparatus provided with a developing device for each of a plurality of photoconductors.

[0043]

According to the first to sixth aspects of the present invention, compared with the case where the toner image for preventing the turning of the cleaning blade is formed only by the second developing device containing the color toner which is advantageous for cleaning, the second developing device is used. The use frequency of the developing device can be reduced. Therefore, the stress applied to the color toner of the second developing device can be reduced to suppress the deterioration, and there is an excellent effect that a stable image can be obtained. Further, when the image is formed in the black monochrome mode, the second developing device does not operate, so that the stop time of the apparatus can be shortened as compared with the case where the toner image is formed only by the second developing device. There is also an excellent effect that power consumption can be reduced.

In particular, in the second and third aspects of the present invention,
When the first developing device (black toner having an average particle diameter of 6.8 μm) is used, the image formation of the toner image is reduced (for example, a line image) to reduce the cleaning load, and the transfer material due to the cleaning failure of the endless belt is reduced. There is an excellent effect that back dirt can be prevented. When the second developing device (red toner having an average particle diameter of 11.5 μm) is used, the area for forming the toner image for preventing the blade from turning (for example, a solid image) is increased so that toner consumption is accelerated. Therefore, there is an excellent effect that a stable image can be obtained.

In particular, according to the invention of claim 4, the counting device for counting the number of images formed using the second developing device (for example, red toner) is used. The state can be determined.
Then, depending on the number of image formations determined to be in a less deteriorated state and the number of image formations determined to be in an advanced state, if the creation area of the blade turn-prevention toner image formed using color toner is different. Can be made. In a state where toner deterioration has progressed, the image forming area can be increased to increase the toner consumption, and the number of images formed with the deteriorated toner as the toner end can be reduced quickly.

In particular, in the fifth aspect of the present invention, since a device for counting the number of image formations in which the cleaning blade has been used is provided, the wear of the edge of the cleaning blade can be predicted. Before it becomes difficult, a curling prevention toner image can be formed using only a color toner that is advantageous for cleaning properties. Thereby, excellent cleaning can be performed by the cleaning blade, and there is an excellent effect that it is possible to prevent back contamination of the transfer material caused by poor cleaning of the endless belt.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart of forming a toner image for preventing a turning of a cleaning blade according to the first embodiment.

FIG. 3A is a timing chart of forming a toner image for preventing a turning of a cleaning blade by a first developing device (black developing device). (B) is a timing chart of toner image formation for preventing the turning of the cleaning blade by the second developing device (red developing device).

FIG. 4 is a block diagram illustrating a configuration provided with a red copy number counting device according to a second embodiment.

FIG. 5 is a flowchart of toner image formation for preventing a cleaning blade from being turned up according to the second embodiment.

FIG. 6 is a flowchart of toner image formation for preventing a cleaning blade from turning according to a third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st developing device (toner image forming means for curling prevention etc.) 2 2nd developing device (toner image forming means for curling etc. prevention) 3 transfer device 4 photoreceptor 5 1st charging device 6 2nd charging device 20 development Roller 21 Blade for regulating layer thickness 23 Toner supply roller 31 Transfer belt 32 Cleaning blade for transfer belt 33 Drive roller 34 Follower roller 35 Transfer bias applying roller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G03G 15/16 G03G 15/16 21/00 370 21/00 370 376 376 384 384 384 21/10 318 F term ( Reference) 2H027 DA45 DE07 ED08 ED24 ED28 EE07 FA28 FA35 2H030 AD01 AD03 AD07 AD16 BB02 BB23 BB32 BB44 BB46 BB63 2H134 GA05 GB02 GB05 HD17 KG04 KH15 KJ02 2H200 GA23 GA34 GA46 GA47 GA50 GA51 GB01B12B22 J02H02 J02H02 LB09 LB13 LB35 MA03 MA20 MB02

Claims (6)

[Claims] 1. A latent image forming means for forming an electrostatic latent image on an image carrier, a developing device for developing the latent image on the image carrier with toner to make the image visible, and a surface endlessly moving. The transfer material is held on an endless belt, the toner image on the image carrier is transferred to the transfer material, and the transferred transfer material is conveyed to a fixing unit by the endless belt, and the endless belt after the transfer material is separated is transferred. A transfer device configured to clean toner adhered to the belt with a cleaning blade, and a toner image formed on a non-image portion of the image carrier by the latent image forming means and the developing device in order to prevent the cleaning blade from being turned up. And an image forming apparatus for transferring the toner image to the endless belt and supplying the toner image to a sliding portion of the cleaning blade, wherein the developing device includes a first developing device containing black toner and a color developing device. At least two developments with a second developing device And a toner image for preventing the turning of the cleaning blade by using a developing device configured to have image modes such as a black monochromatic mode, a color monochromatic mode, and a multicolor mode, and subjected to a developing operation in each image mode. An image forming apparatus comprising control means for forming an image. 2. The image forming apparatus according to claim 1, wherein the first developing device forms the toner image for preventing the turning of the cleaning blade and the cleaning blade using the second developing device. In the case of forming a toner image for preventing curling or the like, the control means performs control for forming the cleaning blade with different image forming areas for the toner image for preventing curling or the like. Forming equipment. 3. The image forming apparatus according to claim 1, wherein the control means controls the image forming area of the toner image for preventing the turning of the cleaning blade or the like based on the average particle size of the toner used. And an image forming apparatus. 4. An image forming apparatus according to claim 1, further comprising a counting device for counting the number of images formed on the transfer material by using said second developing device, wherein said second developing device has a toner end. The control means sequentially changes the image forming area of the toner image for preventing the turning of the cleaning blade formed by the second developing device in accordance with the accumulated count number by the counting device after the toner is replenished. An image forming apparatus that performs control to increase the size. 5. The image forming apparatus according to claim 1, further comprising a counting device for counting the number of image formed by using said cleaning blade, wherein the accumulated image from the start of use of said cleaning blade by said counting device. When the number of sheets formed exceeds a predetermined count, the control means performs control for forming the toner image using a developing device containing a toner having a large average particle diameter among the developing devices. Image forming apparatus. 6. The image forming apparatus according to claim 1, wherein a one-component color toner is used as the color toner stored in said second developing device.