JP2003215867A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which prevents soil on a base during supply of toner while minimizing soil on the base, which is caused by positive electrification, and degradation in the properties of following the base, and obtains a stable image. <P>SOLUTION: Photosensors 15A and 15B are arranged on the left and right sides of a transfer belt 3 in the direction in which paper is passed. When toner is supplied, the level of soil on the base is detected. Based upon a difference between the detection values of the photosensors 15A and 15B, the potential of the base is altered in order to decrease a quantity of reversely electrified toner which is used for development. Alternatively, the maximum quantity of toner to be supplied is decreased to minimize soil on the base, which is caused by positive electrification, or to minimize degradation in the properties of following the base. This prevents the base from being soiled during the supply of toner. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrostatic copying machine, a printer or a facsimile machine.

[0002]

2. Description of the Related Art In a two-component developing type printer or copying machine, in order to obtain stable image quality in image formation, it is necessary to stabilize the toner charge amount and toner concentration of the developer. Is desirable. A photo sensor or the like is used to adjust the charge amount, and a magnetic sensor or the like is used to stabilize the toner concentration. Particularly in a color printer or a copying machine, unlike a black-and-white monochromatic machine, there are many occasions in which a high-area image is continuously formed, and therefore control is often performed at a high toner density (high carrier coverage).

However, the higher the toner concentration, the larger the amount of toner covering the carrier (higher carrier coverage), and the less chance that newly supplied toner comes into contact with the carrier. As a result, defective charging or charging between toner particles is performed and the toner particles become oppositely charged, and scumming is likely to occur during replenishment. In particular, when the humidity is low, the charge amount becomes high and the bond between the toner and the carrier becomes strong, and in order to maintain the image density, the toner density becomes higher than in the normal environment.
Soil easily occurs when replenishing.

In view of the above-mentioned conventional problems, the present invention is
By detecting the background stain level during replenishment, the development amount of the oppositely charged toner amount can be reduced by changing the background potential,
By reducing the maximum replenishment amount, it is possible to eliminate the occurrence of background stains during replenishment while suppressing the occurrence of positively charged background stains and the deterioration of solid followability, and to obtain a stable image. The purpose is to provide.

[0005]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention uses a two-component developing agent containing a toner and a carrier, and uses a biaxial developing stirring member. A developing device used is provided, an optical sensor is arranged at an end of the developing device on which the replenishment toner appears on the developing sleeve, and means for adjusting image forming conditions according to an output value of the optical sensor is provided. It is characterized in that the toner is replenished at a predetermined replenishment time, and the image forming condition is adjusted by the difference between the output values of the optical sensor before and after the toner replenishment.

In order to achieve the above object, the image forming apparatus according to the second aspect of the present invention is the image forming apparatus according to the first aspect, in which two or more photosensors are arranged at the left and right ends of the image area. Is characterized by.

In order to achieve the above object, the image forming apparatus according to the third aspect of the present invention is the image forming apparatus according to the second aspect, wherein the two or more photosensors perform both image density correction and color misregistration correction. Is characterized by.

In order to achieve the above object, the image forming apparatus according to the fourth aspect is the image forming apparatus according to any one of the first to third aspects, in which the presence or absence of toner replenishment is determined based on the difference between the photosensor output values. It is characterized by adjusting the skin potential.

In order to achieve the above object, the image forming apparatus according to the fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, in which it is determined whether toner is replenished or not based on the difference between the photosensor output values. It is characterized by adjusting the maximum replenishment time.

In order to achieve the above object, an image forming apparatus according to the sixth aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, in which it is determined whether toner is replenished or not based on the difference between the photosensor output values. Then, the toner replacement mode is executed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a target 2 of the present invention.
FIG. 2 is a schematic cross-sectional view showing an image forming apparatus provided with a plurality of component developing devices, and FIG. 2 is an enlarged cross-sectional view showing the photosensitive member and the vicinity of the developing device of the image forming apparatus shown in FIG. The image forming apparatus shown is a 4-drum full color electrophotographic system,
The apparatus main body 1 is provided with four cylindrical photosensitive drums 2A, 2B, 2C, and 2D that are latent image carriers, and are arranged so as to contact the upper surface of the transfer belt 3 in FIG. is there.

To the photosensitive drums 2A to 2D, developing devices 4A to 4D having different colors of toner to be used are provided so as to correspond to each other. The developing devices 4A to 4D hold a colored toner corresponding to the image data color-separated by the developer, and apply a bias to perform development 2
It is a component developing device.

A writing unit 5 for exposing color-separated image data is arranged above the photosensitive drums 2A to 2D, and a double-sided unit 6 is arranged below the photosensitive drums 2A to 2D. 7 in the figure
Is a charging roller for charging the photosensitive drums 2A to 2D, 8
Is a fixing device that fixes the image on the transfer paper on which the image is transferred.

Each of the photoconductor drums 2A to 2D has the same structure such as a cleaning device for removing the transfer residual toner,
The photoconductor drum 2A forms an image corresponding to magenta color, the photoconductor drum 2B forms an image corresponding to cyan color, the photoconductor drum 2C forms an image corresponding to yellow color, and the photoconductor drum 2D forms It forms images corresponding to black color, and they are arranged in a row at intervals in the transport direction of the transfer paper.The toner images are transferred to the transferred transfer paper at each transfer position. Form a permanent, full-color image.

The developing devices 4A to 4D also have the same structure, and the developing roller 9 in close proximity to or in sliding contact with the photosensitive drums 2A to 2D and the two parallel stirring and conveying screws 10A and 1A.
0B and only the color of the toner used is different. The developing device 4A is magenta, the developing device 4B is cyan, and the developing device 4 is
C is for yellow, and the developing device 4D is for toner of different colors such as black. In detail, inside the developing casing 11 having openings formed toward the photoconductor drums 2A to 2D, a developer partially exposed from the openings and carrying a developer composed of toner and a magnetic carrier on the surface thereof. A developing roller 9 made of a non-magnetic material as a carrier, in which a magnet roller as a magnetic field generating means is fixedly arranged, and a developer regulation for regulating the amount of the developer carried and carried on the developing roller 9. The doctor 12 is provided as a member. Reference numeral 13 in the figure denotes a magnetic permeability sensor (hereinafter referred to as T sensor).

Further, the developing devices 4A to 4D of this embodiment are
As shown in FIG. 3, the toner is replenished from the opening 14 on the right side in the sheet passing direction and conveyed to the left side in the drawing by the stirring and conveying screw 10B on the side opposite to the developing roller 9, and on the developing roller 9, the replenishment toner is supplied from the left side. It will be developed.

In this image forming apparatus, when the image forming operation is started, each of the photosensitive drums 2A to 2D rotates in the clockwise direction in FIG. 1, and a voltage is applied between the photosensitive drums 2A to 2D and the charging roller 7. The surface is uniformly charged by. Then, the writing unit 6 irradiates the charging surface of each of the photoconductor drums 2A to 2D with a laser beam corresponding to an image of each color, and a latent image corresponding to each color is formed thereon. The latent images reach the positions of the developing devices 4A to 4D as the photoconductor drums 2A to 2D rotate, and are developed by magenta, cyan, yellow, and black toners to become toner images of respective colors.

While the transfer paper P is being attracted to the transfer belt 3 and conveyed, the yellow, magenta, cyan, and black toner images are sequentially transferred to the upper surface in FIG. 1, and the photosensitive drum 2D is transferred. When it passes through, a full-color toner image in which four colors are superposed is formed. On the transfer paper P on which the image is formed, heat and pressure are applied by the fixing device 8 to melt and fix the toner image, and then the paper is discharged.

Further, in this embodiment, as shown in FIG. 4, photosensors 15A and 15B are arranged on the left side and the right side of the transfer belt 3 in the sheet passing direction (indicated by an arrow in the figure), respectively. The photo sensor 15A and the photo sensor 15B on the right side can adjust the left and right color misregistration. Appropriate adjustment methods may be used for the color misregistration correction and the image density correction using the two photo sensors.

The toner density in the developing devices 4A to 4D is consumed by the image data and is kept substantially constant by replenishing the toner according to the image area and the detection value of the T sensor 13 in the developing device. Further, the process control (on the photoconductor drums 2A to 2D or on the transfer belt 3) is performed once for 10 sheets (the number of sheets may be about 5 to 200 sheets depending on the aim).
A plurality of halftone and solid patterns P formed above
The target value, the charging potential, and the light amount of the T sensor 13 are set according to a mode in which k to Py are detected by the photosensors 15A and 15B, converted into the adhesion amount, and set so that the target adhesion amount is obtained.

Unlike a monochrome monochromatic machine, a color printer or a copying machine has many opportunities to continuously form a high-area image, so that it is necessary to control the toner with a high toner density (high carrier coverage). The table shown in FIG. 5 collectively shows carrier coverage rates for full-color printers and black-and-white printers.

FIGS. 6 and 7 show the mechanism of background stain during toner replenishment. In FIG. 7, the replenishment toner A on the sleeve is shown to be reversely charged, and the toner B is shown to be normally charged. The higher the toner concentration, the greater the amount of toner that covers the carrier, and the less the chance that newly supplied toner will come into contact with the carrier. As a result, poor charging and charging between toner particles are performed, resulting in reversely charged toner,
Soil easily occurs when replenishing. In the full-color image forming apparatus, in the case of the tandem system (4 drum 4 development), the development of the color not forming the image and the photoconductor may also rotate, and the toner in the developer may not rotate. Since the additive is embedded, the charge amount of the replenishment toner is likely to be different. Further, when the humidity is low, the charge amount becomes high, so that the bond between the toner and the carrier becomes strong, and in order to maintain the image density, the toner density becomes higher than in the normal environment, and the background stain is likely to occur at the time of replenishment.

FIG. 8 shows the relationship between the regular background stain and the background stain at the time of replenishment with respect to the background potential between the tape transfer ID on the drum (background stain on the drum). The background stain when replenishing toner is an oppositely charged background stain, which decreases when the background potential is narrowed.
There is a concern that regular scumming may occur (weakly charged toner may cause scumming).

9 and 10 show changes in the photosensor output value (Vsg) with respect to time when the toner supply amount is changed. In either case, when the toner supply amount is reduced, the background stain level at the time of supply is improved. However, the replenishment time followed by all A3 solids (forming a solid image on the entire surface of A3 size paper) is 1500 milliseconds, and when the replenishment time is short, the followability of the image area deteriorates. The total amount of toner consumed for A3 is 29.7 cm ² × 42.0 cm ² × 0.60 mg / c
m ² and the replenishment time is a value calculated as a replenishment amount of 0.50 mg / millisecond.

Note that FIG. 9 shows the case where one photosensor detects background dirt at the time of replenishment, FIG. 10 shows the case where two photosensors detect it, and FIG. 10 shows the left and right photosensors 1.
Difference between output values of 5A and 15B (VsgB-VsgA = ΔV
It is detected from sg).

FIG. 11 shows the relationship between the photosensor output value and the toner adhesion amount (hereinafter referred to as M / A), and FIG. 12 shows the relationship between the photosensor output and the background stain rank. In this example, the background stain rank is set to 3.5 or higher.

13 to 18 are flowcharts showing the operation of the above-described embodiment apparatus according to the present invention. Figure 1
The flowchart of 3 shows the basic operation of the background stain detection mode during replenishment when the number of photosensors is one or more. When there are two or more photosensors, only the photosensor on the side of the replenishment toner (photosensor 15A in FIG. 4) is used for detection. After the operation is started, the developer is sufficiently agitated for about 7 to 30 seconds (step 1) to make a background-free state (toner-free state), and then the photosensor output value Vsg.
Is adjusted to 4.0V (step 2). Then, toner is replenished at an arbitrary toner replenishment time α millisecond (step 3), and it is determined whether or not the photosensor output value (Vsg1) is larger than 3.7, which is a background stain rank of 3.5 or less (step 3). 4) When it is 3.7 or less, it is judged that there is background stain at the time of replenishment (step 5), and the image forming condition is changed (step 6). Here, the supply time α millisecond is the maximum supply time,
In this example, all A3 solids are set to 1500 milliseconds.
If the photosensor output value (Vsg1) is larger than 3.7, it is determined that there is no background stain during replenishment (step 7), and the image forming conditions are not changed (step 8). In the case of this flowchart, color determination is arbitrary.

The flowchart of FIG. 14 shows the basic operation in the replenishment background stain detection mode when two or more photosensors are used. Both the photosensors 15A and 15B of FIG. 4 are used. After the operation is started, the toner is replenished at an arbitrary toner replenishment time α millisecond (step 1), and the photo sensor 15
The output values (VsgA, VsgB) of A and 15B are read (step 2). Basically, the output value (VsgA) of the photosensor 15A detects the background stain at the time of replenishment, but when the developing roller 9 is the center, the output value (VsgB) of the photosensor 15B on the side where the replenishment toner is far is compared. Since the output value of the photo sensor 15B is not affected by the background stain at the time of replenishment, it is not necessary to sufficiently stir the developer, and there is no background stain. When the development stirring time is not required, the photosensor output value is adjusted to 4.0V (Vsg). Ground pollution rank 3.
Photosensor 15B and photosensor 15A that are 5 or less
It is judged whether the difference VsgB-VsgA between the output values is larger than 0.3 (step 3), and when it is 0.3 or less, it is judged that there is background stain during replenishment (step 4), and the image forming condition is changed. (Step 5). When it is 0.3 or more, it is judged that there is no background stain at the time of replenishment (step 6), and the image forming condition is not changed (step 7). Here again, the replenishment time α millisecond is the maximum replenishment time, and in this example, it is 1500 milliseconds that all A3 solids follow. Also in the case of this flowchart, the color judgment is arbitrary.

The flow chart of FIG. 15 shows the operation when the background potential is changed when there is background dirt during replenishment.
Although it is almost the same as the flowchart in FIG. 13, the maximum toner replenishment time is determined in step 6 (step 6
a) If the replenishment time is 600 milliseconds or longer, the operation is reduced by 300 milliseconds (step 6b). The effect is as shown in FIG.

The flow chart of FIG. 16 shows the operation when the maximum replenishment time is changed when there is background dirt during replenishment. Although it is almost the same as the flowchart in FIG. 13, the magnitude of the background bias is determined in step 6 (step 6
a) If the background bias is 150 V or more, the operation is lowered by 20 V (step 6b). The effect is as shown in FIG.

The flow chart of FIG. 17 shows the operation for replacing the toner in the agent when the background stain is present during replenishment. This is also almost the same as the flowchart of FIG. 13, but when there is background stain during replenishment (step 5), the toner in the agent is replaced (step 6).

The flow chart of FIG. 18 shows the operation in the toner replacement mode. After stirring all colors of the developer (step 1) and determining the execution color (step 2),
The consumption mode is entered (step 3), the consumption pattern (halftone image) is developed on the photosensitive drum corresponding to the execution color, and the pattern on the photosensitive drum is transferred onto the transfer belt 3 and consumed (step 4). ). After the toner is consumed, the toner is agitated, the toner concentration (TC) of the developer is read (step 5), and the toner is consumed up to the toner end level.
The output value Vt of the T sensor 13 is the target T sensor 1
3 output upper limit value (toner end level) Vref + 1.
It is continuously detected three times that the voltage is 2 V or more, or it is determined whether or not the output value of the T sensor 13 does not reach the toner end level even after repeating 100 times (step 6). The upper limit value of the output value Vt of the target T sensor 13 is set to Vref.
Although it is set to + 1.2V, + 1.2V is arbitrary. When the toner end level is not consumed in the judgment of step 6, development and stirring are repeated (step 4,
5). After reaching the toner end level, as a post-processing step, the transfer belt is thoroughly cleaned (step 7), and after the cleaning is completed, the toner is replenished by the same operation as the toner end recovery (step 8), and the toner density is increased. Set (TC) to the target value. However, if the T sensor value does not reach the toner end level even after repeating 100 times, it is considered to be abnormal, and the post-processing step and the recovery are started (steps 9 and 10).

Although frequent occurrences of these operations can prevent the occurrence of background stains during replenishment, the problems such as machine unusability for 10 to 20 minutes and insufficient toner yield can be performed with a minimum number of times.

The developing conditions in the image forming apparatus to which the present invention is applied are shown below. <Mechanical Conditions> -Gap between developing roller 9 and photosensitive drums 2A to 2D (hereinafter GP): 0.4 to 0.6 mm-Gap between developing roller 9 and doctor 12 (hereinafter GD):
0.4-0.6 mm Diameter 18φ of developing roller 9 Linear velocity of photosensitive drums 2A-2D 60-250 mm / sec Linear velocity ratio of developing roller to linear velocity of photosensitive drum 1.
1 to 1.8 <Developer> Carrier: Ferrite, average diameter 50 to 70 μm Toner: Polyol resin, polyester resin, average particle diameter 6 to 7 μm, additive amount 0.5 to 2.0 wt%,
Carrier coverage rate 30-80%, charge amount (Q / M) 10
30 μC / g

[0035]

As described above, the image forming apparatus according to the present invention is a biaxial developing and stirring member, and has a photosensor at the end of the developing sleeve where the replenishment toner is mixed with the developer and appears on the developing sleeve. By detecting the background stain level during replenishment, the development amount of the reversely charged toner can be reduced by changing the background potential, and the maximum replenishment amount can be reduced to minimize the occurrence of positively charged background stain and the deterioration of solid followability. It is possible to prevent the occurrence of background stains during replenishment while suppressing the amount to the limit, and obtain a stable image. Further, since the replacement of the toner in the developer can be suppressed to the minimum time, the toner combined with the carrier is effectively refreshed, and the difference in the charge amount distribution with the replenishment toner is eliminated, so that the scumming at the time of replenishment is prevented. A stable image can be obtained without any occurrence.

As described above, the image forming apparatus according to the second aspect uses the two or more photosensors and compares the output values of the two photosensors to obtain the detection effect in addition to the common effect. This has the effect of shortening the time.

As described above, the image forming apparatus according to the third aspect uses the photosensor for color misregistration correction, so that in addition to the common effects described above, a new cost does not occur, and replenishment background stains occur. Is effective.

As described above, the image forming apparatus according to a fourth aspect of the present invention detects replenishment background stains by using a photosensor so that the replenishment background stains read by the photosensor are below a certain level. By adjusting the background potential, in addition to the above-mentioned common effects, there is an effect that the background stain can be prevented before supply of an image before the image is formed on the transfer paper by reflecting the development conditions.

As described above, the image forming apparatus according to a fifth aspect of the present invention detects replenishment background stains by using a photosensor, and ensures that the replenishment background stains read by the photosensors are below a certain level. By limiting the maximum supply time,
In addition to the common effects described above, there is an effect that scumming at the time of replenishment can be prevented.

As described above, the image forming apparatus according to a sixth aspect of the present invention detects replenishment background stains by using a photosensor, and when the replenishment background stains read by the photosensor are above a certain level, toner is supplied. By performing the replacement mode,
In addition to the common effects described above, the time for the toner replacement mode can be shortened and the effects can be secured.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an image forming apparatus including a plurality of two-component developing devices to which the present invention is applied.

FIG. 2 is an enlarged cross-sectional view showing the vicinity of a photoconductor and a developing device of the image forming apparatus shown in FIG.

3 is a cross-sectional view showing in detail a developing device of the image forming apparatus shown in FIG.

4 is a conceptual perspective view showing the arrangement of photosensors on the transfer belt of the image forming apparatus shown in FIG.

FIG. 5 is a diagram showing carrier coverage rates of a full-color printer and a monochrome printer.

FIG. 6 is a diagram showing a distribution of a charge amount as a mechanism of background stain when replenishing toner.

FIG. 7 is a diagram showing a model of stain generation as a mechanism of background stain during toner supply.

FIG. 8 is a diagram showing a relationship between a regular ground stain and a background stain at the time of replenishment with respect to a background potential between a tape transfer ID on a drum (ground stain on a drum).

FIG. 9 is a diagram showing a transition of a photosensor output value (Vsg) with respect to time when the toner supply amount is changed.

FIG. 10 is a diagram showing changes in the photosensor output value difference (ΔVsg) with respect to time when the toner supply amount is changed.

FIG. 11 is a photo sensor output value and a toner adhesion amount (hereinafter referred to as M
It is a figure which shows the relationship with / A).

FIG. 12 is a diagram showing a relationship between a photosensor output and a background stain rank.

FIG. 13 is a diagram showing a basic operation in a replenishment background stain detection mode when one or more photosensors are provided.

FIG. 14 is a diagram showing a basic operation in a replenishment background stain detection mode when two or more photosensors are provided.

FIG. 15 is a diagram showing an operation when the background potential is changed when there is background contamination during replenishment.

FIG. 16 is a diagram showing an operation when the maximum replenishment time is changed when there is soiling during replenishment.

FIG. 17 is a diagram showing an operation for replacing the toner in the agent when there is background stain during replenishment.

FIG. 18 is a diagram showing an operation in a toner replacement mode in a developer.

[Explanation of symbols]

1 device body 2A-2D photoconductor drum 3 Transfer belt 4A-4D developing device 5 writing unit 6 duplex unit 7 charging roller 8 fixing device 9 Development roller 10A, 10B Agitating and conveying screw 11 Development casing 12 Doctor 13 Permeability sensor (T sensor) 15A, 15B Photo sensor

Continued front page    F-term (reference) 2H027 DA09 DD07 DE02 DE07 DE10                       EA01 EA04 EA05 EA06 EA18                       EB04 EC03 EC06 EC10 EC15                       EC20 FA10 FB07                 2H030 AA01 AB02 AD02 AD16 BB34                       BB38 BB42                 2H077 AD06 DA05 DA10 DA62 DB02                       DB08 DB25 EA03 GA13

Claims (6)

[Claims] 1. A developing device using a two-component developer containing a toner and a carrier and using a biaxial developing stirring member,
An optical sensor is arranged at the end of the developing device where the replenishment toner appears on the developing sleeve, and means for adjusting the image forming condition according to the output value of the optical sensor is provided. The image forming apparatus is characterized in that the image forming condition is adjusted based on the difference between the output values of the optical sensor before and after the toner replenishment. 2. The image forming apparatus according to claim 1, wherein two or more photosensors are arranged at left and right ends of an image area. 3. The image forming apparatus according to claim 2, wherein the two or more photo sensors perform both image density correction and color misregistration correction. 4. The image forming apparatus according to claim 1, wherein the background potential is adjusted by determining the presence or absence of toner replenishment based on the difference between the photosensor output values. 5. The image forming apparatus according to claim 1, wherein the maximum replenishment time is adjusted by determining the presence or absence of toner replenishment based on the difference between the photosensor output values. 6. The image forming apparatus according to claim 1, wherein the toner replacement mode is executed by determining the presence or absence of toner replenishment based on the difference between the photosensor output values.