JP2000098683A - Multicolor image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multicolor image forming device which is capable of preventing the occurrence of cleaning blade peeling and cleaning defects and stably maintaining high cleaning performance for a long period of time. SOLUTION: This multicolor image forming device has a traveling photosensitive drum (image carrying body) 2, a transfer drum (recording material carrying body) 5 which comes into contact with this photosensitive drum 2, a primary electrostatic charger (electrostatic charging member) 3 which has a conductive substrate facing the photosensitive drum via this transfer drum 5, a cleaning blade 7a which removes the toners remaining on the photoreceptor drum 2 by coming into contact with the photosensitive drum 2 and multicolor developing devices 4 (4Y, 4C, 4M, 4K) by each of colors which house the toners containing external additives of >=0.5 μm in size themselves having a polishing effect. In such a case, the device is provided with an external additive replenishing member for replenishing the developing devices 4 (4Y, 4C, 4M, 4K) with the external additives in addition to toner supplying members for supplying the toners.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art By repeating a process of supplying toner to an electrostatic latent image electrostatically formed on the surface of an image carrier to form a toner image, and transferring the toner image to a transfer material such as paper. In a known image forming apparatus for forming an image, it is difficult to transfer all the toner from the image carrier to the transfer material at the time of transfer, and it is inevitable that some toner remains on the image carrier. For this reason, it is necessary to sufficiently clean the residual toner every time transfer is performed, and various cleaning means have been conventionally proposed. However, cleaning means formed of a cleaning blade made of an elastic material such as urethane rubber is used. When the sharp edge is seen in the direction of travel of the image carrier and the residual toner is scraped by pressing against the surface of the image carrier downstream of the transfer site, the structure is simple, compact, and cost effective. Has been widely used since it is advantageous.

Further, with respect to an image carrier in which Teflon or the like is dispersed for surface hardening of an organic photoreceptor or the like, the friction between the image carrier and the cleaning blade is suppressed and the charging property is smoothed for the purpose of improving the cleaning property. It is well known that the surface of the image carrier is roughened along the circumferential direction in the early stage of the image carrier in order to achieve this.

However, there is a problem that the surface of the image carrier is shaved because the cleaning blade always contacts the image carrier during image formation. In particular, when the toner has a small particle size (for example, 8 μm or less), it is necessary to increase the hardness of the urethane rubber so that cleaning failure does not occur. When the high-hardness cleaning blade is brought into contact with the image carrier for a long time, the image carrier becomes smoother than the initial state, thereby increasing the frictional force between the image carrier and the cleaning blade. There is a possibility that the cleaning blade will become more worn out due to being turned over or slippery, or the vibration of the cleaning blade will be increased, and cleaning failure will be likely to occur.

Therefore, in order to prevent the cleaning blade from turning up and chattering, a toner having a small particle size (for example, 8 μm or less) having a polishing effect of 0.5 μm is used.
m or more external additives are externally added, and the surface of the image carrier is polished by the polishing action of the external additives.

[0006]

However, an electric current is applied to a charging member having a conductive substrate opposed to the image carrier via the recording material carrier so that a visible image on the image carrier is formed on the recording material. At the time of transfer, an external additive of 0.5 μm or more externally added to a toner having a small particle diameter (for example, 8 μm or less) also has polarity. The agent easily remains on the image carrier. Then, in the case of a multi-color image forming apparatus, the amount of the external additive remaining on the image carrier differs for each color, resulting in a difference in cleaning performance for each color.

[0007] When the amount of the external additive becomes large, not only the surface of the image carrier is polished but also damaged, and the external additive easily adheres to the image carrier, resulting in deterioration of image quality. I will.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object thereof is to prevent the occurrence of turning over of a cleaning blade and poor cleaning and to stably maintain high cleaning performance for a long period of time. An object of the present invention is to provide a multicolor image forming apparatus.

[0009]

In order to achieve the above-mentioned object, the invention according to claim 1 comprises a moving image carrier, a recording material carrier in contact with the image carrier, and a recording material carrier. A charging member having a conductive substrate opposed thereto, a cleaning blade for contacting the image carrier and removing toner remaining on the image carrier, and having a size of 0.5 μm or more having a polishing effect by itself. In a multicolor image forming apparatus having a developing device for each color of multicolor containing a toner containing an external additive, an external additive for supplying an external additive to the developing device in addition to a toner supply member for supplying the toner. It is characterized in that an agent supply member is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, development, transfer and cleaning are performed for each color so that the charge amount of the charging member to the transfer of the conductive substrate is made different depending on the color. It is characterized by having done.

Therefore, according to the present invention, since the external additive replenishing member for replenishing the external additive to the developing device is provided, the external additive replenishing amount is controlled by the color and the external additive is cleaned by the color. By keeping the reaching amount to the blade constant, it is possible to prevent the turning of the cleaning blade and the occurrence of cleaning failure, and to stably maintain high cleaning performance over a long period of time, and to increase the friction between the image carrier and the cleaning blade. In addition, the torque of the image carrier can be prevented from increasing.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a view showing the configuration of a full-color copying machine according to the present invention. A photosensitive drum 2 as an image carrier is rotatably supported in the main body of the full-color copying machine in a direction indicated by an arrow. The image forming means described below is disposed around the periphery.

The image of the original 25 to be copied is projected by a lens 26 onto an image sensor 27 such as a CCD. The image sensor 27 separates the image of the document 25 into a number of pixels and generates a photoelectric conversion signal corresponding to the density of each pixel. The photoelectric conversion signal output from the image sensor 27 is sent to an analog image signal processing circuit 28, where the signal is converted into a pixel image signal having an output level corresponding to the density of the pixel, and pulse width modulation is performed. The signal is sent to the circuit 29.

The laser drive pulse output from the pulse width modulation circuit 29 is supplied to a semiconductor laser 30 to cause the semiconductor laser 30 to emit light for a time corresponding to the pulse width. Therefore, the semiconductor laser 30 is driven for a longer period of time for the high-density pixels, and is driven for a shorter period of time for the low-density pixels. For this reason, the photosensitive drum 2 is exposed to a high-density pixel in a longer range in the main scanning direction by an optical system described later, and to a low-density pixel in a shorter range in the main scanning direction. That is, the dot size of the electrostatic latent image differs according to the density of the pixel.

Accordingly, it goes without saying that the toner consumption for the high density pixels is larger than that for the low density pixels. In FIG. 4D, the electrostatic latent images of the low, medium and high density pixels are indicated by L, M and H, respectively.

The laser beam 30a emitted from the semiconductor laser 30 is swept by the rotating polygon mirror 31,
A spot image is formed on the photosensitive drum 2 by a lens 32 such as an f / θ lens and a fixed mirror 33 that directs the laser beam 30 a in the direction of the photosensitive drum 2. In this manner, the laser beam 30a scans the photosensitive drum 2 in a direction substantially parallel to the rotation axis of the photosensitive drum 2 (main scanning direction), and
An electrostatic latent image is formed thereon.

The photosensitive drum 2 has Amosphas silicon, selenium, OPC, etc. on its surface and rotates in the direction of the arrow.
Is charged uniformly. Thereafter, the photosensitive drum 2 is exposed and scanned by a laser beam 30a modulated according to the image information signal, and an electrostatic latent image corresponding to the image information signal is formed on the photosensitive drum 2. This electrostatic latent image is
The developing device 4 (4Y, 4C, 4B, 4K) using a two-component developer in which toner particles and carrier particles are mixed is reversely developed to form a visible image (toner image).
Here, the reversal development is a development method in which a toner charged to the same polarity as the latent image is attached to a region of the photoconductor exposed to light, and the toner is visualized.

The above-mentioned electrostatic latent image is stored in each color developing device 4 (4Y, 4Y).
C, 4M, and 4K) to give a developer (toner) and visualize it as a visible image (toner image).

The developing device 4 stores four color toners of magenta, cyan, yellow and black separately.
Developing devices 4M, 4C, 4Y, and 4K, and the desired developing devices (4M, 4C, 4Y, and 4K)
The electrostatic latent image formed on the photosensitive drum 2 is developed by being brought into contact with and separated from the outer peripheral surface of the photosensitive drum 2 and is visualized as a toner image. Then, the toner image formed on the photosensitive drum 2 is transferred to a transfer material P which is a recording material carried on a transfer device (hereinafter, referred to as a transfer drum) 5 described below and conveyed in the direction of the arrow.

The toner remaining on the photosensitive drum 2 after the transfer of the toner image is removed and collected by a cleaning device 7 disposed downstream in the drum rotation direction.

A transfer sheet 8 is adhered to the outer peripheral surface of the transfer drum 5, and a transfer material suction means for holding the transfer material P on the transfer sheet 8 by suction is provided inside the transfer sheet. The transfer material suction means includes a suction charger 9 for applying a charge having a characteristic opposite to that of the toner image on the photosensitive drum 2 to the opposite side of the transfer sheet 8 and a conductive roller 10 provided outside the transfer drum 5. ing. The conductive roller 10 is grounded. The conductive roller 10 serves as an opposite electrode of the attraction charger 9 and has a function of injecting charges into the transfer material P to electrostatically attract the transfer material P to the transfer sheet 8. Fulfill.

A transfer charger 11 for applying a charge of the opposite polarity to the toner to the transfer sheet 8 is provided at a position in the transfer drum 5 corresponding to the pressure contact position with the photosensitive drum 2.

Further, inside and outside the transfer drum 5, a pair of AC corona dischargers 12, 13 opposed to each other with the transfer sheet 8 interposed therebetween are provided in order to weaken the attraction force of the transfer material P after the image transfer to the transfer sheet 8. Have been. And these A
A separation claw 14 is provided on the downstream side in the rotation direction of the transfer drum 5 with respect to the C corona dischargers 12 and 13. Also, the AC corona discharger 1 is adjacent to the outer AC corona discharger 13.
The AC corona discharger 15 performs an AC corona discharge in order to prevent image disturbance due to peeling discharge generated when the transfer material P and the transfer sheet 8 are separated.

On the other hand, the transfer material P stored in the cassette 16
Is 1 from the highest one by the pickup roller 17.
The sheet is fed one by one, and is conveyed in synchronism with the toner image formed on the photosensitive drum 2 by the pair of registration rollers 18.
The transfer material P conveyed to the transfer drum 5 is adsorbed and held on the transfer sheet 8 attached to the outer peripheral surface of the transfer drum 5 when passing between the conductive roller 10 and the attraction charger 9, and is conveyed. The toner image on the photosensitive drum 2 is transferred onto the transfer material P by the transfer charger 11 at the pressure contact portion between the transfer drum 5 and the photosensitive drum 2. The transfer material P on which the toner image has been transferred is conveyed while being carried on the transfer drum 5, and its adsorbing force is weakened when passing through the AC corona dischargers 12, 13. It is separated from the transfer sheet 8.

The transfer material P separated from the transfer drum 5 is
The toner image is conveyed to the downstream side by the conveyance belt 19 and passes through the fixing roller 20 and the pressure roller 21 to be heated and fixed by the toner image. Then, at the time of one-sided image formation, the transfer material P on which the toner image is fixed is discharged to the discharge tray 23 outside the apparatus by the discharge roller pair 22. When forming a double-sided image, the transfer material P on which the toner image has been fixed is temporarily stored in a double-sided cassette 24 in the apparatus by the discharge roller pair 22.

At the time of double-sided image formation, the transfer material P primarily stored in the double-sided cassette 24 is again fed one by one from the uppermost one by the double-sided cassette pickup roller.
The image forming operation is repeated to form an image on the back surface of the transfer material P.

By the way, in this embodiment, when a transfer current for transferring from the photosensitive drum 2 is applied during transfer, the charging potential on the transfer sheet 8 rises, and this is repeated for each color, as shown in FIG. 2 from the first color
The charging potential on the transfer sheet 8 increases for the third color, the third color from the second color, and the fourth color from the third color. Therefore, the force for electrically attracting the toner from the photosensitive drum 2 onto the transfer material P is different.

FIG. 3 shows the surface condition of the transfer sheet 8 and the transfer material P.

As shown in FIG. 3, in this embodiment, the negatively charged toner on the photosensitive drum 2 is transferred onto the transfer material P. However, in the case of a positive charge (that is, the same polarity as the transfer), the toner is more likely to remain on the photosensitive drum 2. That is, 0.5 μm having the same polishing effect as that of the transfer contained in the waste toner according to the transfer order.
The above external additives differ.

In this embodiment, an abrasive replenishing member for replenishing the abrasive is provided in order to keep the amount of the external additive in the transfer residual toner reaching the cleaning device 7 irrespective of the transfer order. The abrasive is supplied from the abrasive replenishing member to the developing devices 4Y, 4C,
4M and 4K are supplied from the toner supply port.

First, as can be seen from FIGS. 2 and 3, the external additive having the same polarity as that of the transfer and having the same polarity as that of the photosensitive drum becomes the second color from the first color and the third color from the second color. 2 is hardly left on the cleaning device 7, and as a result, the amount of the external additive that reaches the cleaning device 7 differs, and the content of the first color is the largest, followed by the second color, the third color, and so on.

Therefore, the external additives are supplied such that the content of the external additives in the residual toner that reaches the cleaning device 7 for each color is made constant with the toner consumption of each color.

Here, each of the developing units 4Y, 4C, 4M, 4K
Is detected by detecting the amount of toner when toner is replenished from the toner replenishing tank to the developing devices 4Y, 4C, 4M, and 4K based on the detected density of the developer by a density detection sensor (not shown). The detection of the toner amount is performed by installing a rotary encoder or the like on a transport screw for replenishment and detecting the rotation amount of the transport screw. In this embodiment, as shown in FIG. 1, a video counter 49 is provided in the main body of the image forming apparatus to accumulate the image amount (image ratio) of the image formed based on the image information signal (image signal). This video counter 4
9 was used to construct a toner consumption detecting device.

The output signal of the pulse width modulation circuit 29 is A
The clock pulse (pulse shown in FIG. 4B) from the clock pulse oscillator 48 is supplied to one input of the ND gate 47 and the other input of the AND gate 47. Accordingly, as shown in FIG. 4C, the AND gate 47 supplies a number of clock pulses corresponding to the respective pulse widths of the laser drive pulses S, I, and W, that is, a number of clock pulses corresponding to the density of each pixel. Is output. The number of clock pulses is integrated by the counter 49 for each image, and the video count is calculated (A4 maximum video count is 3707 × 10 ⁶ ).

The pulse integration signal C1 (video count number) for each pixel from the counter 49 is used to form the developing device 4 (4
Y, 4C, 4M, 4K).

Therefore, this video count number is stored in the CPU 5
0 and stored in the RAM 51. And
When the video count of the next image information signal is calculated, the stored video count is integrated. CP
U50 stores the toner consumption of each color when supplying the external additive in the form of a video count number.
Reference numeral 50 compares the reference value K1 of the video count number with the integrated value, and when K becomes larger than K1, supplies the external additive itself having a polishing effect. FIG. 5 is a flowchart showing the above processing procedure.

Assuming that the supply amount of the external additive having the same polarity as the transfer and having the polishing effect itself is S, S1, S2, S3, S4 for each color in the transfer order with respect to a certain toner consumption reference value K1.
Are set, and these amounts S1 to S4 differ depending on the prescription of the external additive and the value of the transfer. In the present embodiment, S1 <S
2 <S3 <S4.

As described above, by controlling the replenishment amount of the abrasive by the color and keeping the amount of the abrasive reaching the cleaning blade 7a by the color, occurrence of turning over of the cleaning blade 7a and occurrence of cleaning failure are prevented. At the same time, the friction between the photosensitive drum 2 and the cleaning blade 7a and the increase in the torque of the photosensitive drum 2 itself can be prevented, and this state can be maintained for a long period of time. Can be secured.

[0040]

As is apparent from the above description, according to the present invention, since the external additive replenishing member for replenishing the external additive to the developing device is provided, the external additive replenishing amount is controlled by the color. By keeping the amount of the external additive reaching the cleaning blade by color constant, it is possible to prevent the turning of the cleaning blade and the occurrence of poor cleaning, and to stably maintain high cleaning performance over a long period of time.
It is possible to prevent the friction between the image carrier and the cleaning blade from increasing and the torque of the image carrier from increasing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a multicolor image forming apparatus (full color copying machine) according to the present invention.

FIG. 2 is a diagram illustrating a change in a charging potential of a transfer material.

FIG. 3 is a diagram illustrating a state of a transfer material and a surface of a transfer sheet.

FIG. 4 is a diagram illustrating a method of counting density information of an image information signal with a video counter.

FIG. 5 is a flowchart showing a control procedure of a supply amount of an external additive.

[Explanation of symbols]

 Reference Signs List 2 photosensitive drum (image carrier) 3 primary charger (charging member) 4 developing device 5 transfer drum (recording material carrier) 7 cleaning device 7a cleaning blade 11 transfer charger 48 clock pulse oscillator 49 counter 50 CPU 51 RAM P Transfer material (recording material)

Claims (2)

[Claims] An image bearing member that runs, a recording material bearing member that contacts the image bearing member, a charging member that has a conductive substrate opposed to the recording material bearing member via the recording material bearing member, and contacts the image bearing member. A cleaning blade for removing toner remaining on the image carrier in contact with the cleaning blade;
In a multicolor image forming apparatus having a developing device for each color of multicolor containing a toner containing an external additive of μm or more, in addition to a toner supply member for supplying toner, an external additive is supplied to the developing device. A multicolor image forming apparatus provided with an external additive replenishing member. 2. The multicolor image forming apparatus according to claim 1, wherein development, transfer, and cleaning are performed for each color, and a charge amount of the charging member to transfer to the conductive substrate is changed depending on the color.