JPH04170558A - Picture forming device - Google Patents

Abstract

PURPOSE:To obtain a good picture stably over a long period by supplying a toner by an amount in accordance with a proportion of areas of a picture location to a non-picture location in a picture region to a sensitive material. CONSTITUTION:A light receiving element 14 is arranged in a position, after a toner image is formed by a developing machine 4, to read a light/dark pattern by irradiating a surface of a sensitive material and to feed a signal of the pattern to a control unit 15, and bias voltage in accordance with the signal is applied to a conductive roller 17, arranged in a cleaner, to transfer a toner, adhering to the conductive roller, to the sensitive material. In a toner amount transferred to the sensitive material, the applied voltage of a bias power supply 16 is controlled by the control unit 15 in a manner wherein the larger is a light/dark region of the light/dark pattern of a picture in a sensitive material surface, detected by the light receiving element 14, the larger the toner amount is increased. In this way, a good picture is obtained stably over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine and a printer thereof.

(Prior art and problems to be solved) After uniformly charging the surface of an image carrier to form an electrostatic latent image and then a toner image, the toner image is transferred to a transfer material such as paper. In a well-known image forming apparatus including a step, a means for uniformly charging a photoreceptor serving as an image carrier;
A corona charger is used as a transfer means for transferring a toner image onto a transfer material, a means for separating a transfer material from an image carrier, etc. It has a simple structure, is advantageous in terms of cost, and can perform relatively stable charging. As is well known, it has been widely used in practice.

This type of corona charger usually has a configuration in which a charged wire is stretched inside a conductive shield case with a hollow-shaped cross section, and a high voltage is applied to the charged wire to generate a discharge. Since this method utilizes charging by ionized corona ions in the surrounding gas due to discharge from the charged wire to the surrounding shield case, it is inevitable that large amounts of ozone and nitrogen oxides will be generated when the gas is ionized. These substances may adhere to the photosensitive layer of the image carrier and promote its deterioration, or they may adhere and further absorb moisture, lowering the resistance of the photosensitive layer and causing electrostatic latent images and, therefore, deterioration of the image quality of toner images. there were.

To deal with this situation, it has been proposed to install a fan to exhaust and remove ozone and nitrides, or to raise the temperature of the photoreceptor using a heater to prevent the resistance from decreasing due to moisture absorption. has been done.

However, the substances that adhere to the photoreceptor and absorb moisture, causing deterioration of image quality, are not limited to those mentioned above. On the other hand, it may adhere to the photoreceptor and further absorb moisture, causing image disturbances, and such a situation cannot be dealt with by the above-mentioned means.

In particular, if you are using transfer paper that contains a large amount of talc, and the machine is left unattended until the next day or longer by turning off the power switch and unplugging it after copying is complete, the exhaust fan should be Since the heater that heats the photoreceptor is not operating, the electrostatic latent image tends to be disturbed due to the generation and accumulation of foreign substances as mentioned above. Such image disturbances are especially likely to occur in areas with a small image ratio. noticeable.

The present invention was made in view of this situation, and it supplies sufficient toner to the image carrier surface corresponding to the portion with a small image ratio, thereby grinding the image carrier surface and removing talc. The above-mentioned foreign matter, including precipitates such as
Grinding is performed with an amount of toner according to the image ratio and image configuration, so that the amount of grinding is made as uniform as possible over the entire image forming surface, so that images can be stably obtained over a long period of time. The object of the present invention is to provide a forming device.

(2) Structure of the invention (technical means for solving the problem, its effect) In order to achieve the above object, the present invention provides a method for forming a transferable toner image on a photoreceptor, transferring it to a transfer material, and then In an image forming apparatus configured to remove residual toner remaining on the body with a cleaning blade, the image forming apparatus is provided with means for supplying an amount of toner to a photoreceptor according to the ratio of the area of an image area to a non-image area in an image area. It is characterized by:

With this configuration, it is possible to apply enough toner to grind the surface of the photoreceptor even in areas with a small image ratio, thereby preventing foreign matter from adhering to the photoreceptor and deterioration of image quality due to this. can be effectively prevented.

(Description of Embodiments) FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention.
A photoreceptor 1 that rotates in a direction is uniformly charged by a negative charger 2, and this charged surface is irradiated with an image signal such as a slit exposure or an image-modulated laser beam to create a static i
A latent image is formed.

When this latent image arrives at the development site where the developing device 4 exists, toner is supplied from the developing device 4 and is electrostatically attracted to the latent image to form a toner image.

When the toner image reaches the transfer site where the photoreceptor 1 and the transfer/separation charger 6 are formed facing each other, the transfer material is conveyed from the conveyance path 5 to the transfer site in time with this,
At the same time, a transfer bias is applied to the transfer charger, and the toner image on the photoreceptor side is transferred to the transfer material by the action of the electric field formed thereby.

Thereafter, the transfer material is discharged from the transfer site via the conveyance path 9 and the fixing device 8 to the outside.

At the transfer site, some toner that has not been transferred to the transfer material reaches the position of the cleaner 7 as the photoreceptor 1 rotates and is removed by the cleaning blade 7a, and the residual charge is further erased by the pre-exposure lamp 12. , the photoreceptor 1 enters the next image forming process and becomes stuck.

In the illustrated apparatus, a light-receiving element 14 is disposed at a position after a toner image is formed by the developing device 4, and the light-receiving element 14 is irradiated onto the surface of the photoreceptor to read its brightness and darkness pattern, and the signal is output. A conductive roller 17 that sends a bias voltage to the cleaner according to the signal sent to the control device 15.
is applied to transfer the toner adhering to the conductive roller to the photoreceptor.

At this time, the amount of toner transferred to the photoreceptor is
The control device 15 controls the applied voltage of the bias power supply 16 so that the larger the bright region of the bright and dark pattern of the image on the photoreceptor surface detected by the toner, the more the amount of toner increases.

As the light receiving element, one that irradiates light onto the part to be measured and measures the amount of reflected light is suitable.For example, an LED array with a wavelength of 550 to 570 nm is used as a light source, and the amount of reflected light is converted to a photoelectric conversion element or a photodetector. Convert it to voltage using a sensor such as a diode.

The reading pixel density of the sensor can be used as appropriate, ranging from a coarse precision of obtaining an integral value of a bright part over the entire image area to a fine precision of a pixel density of 4 to 16 pixels.

The control device integrates the voltage conversion values of the brightness and darkness patterns of the image measured as described above to calculate the area of the bright area. The power supply 16 is controlled so as to output a bias to the extent that a toner image of the density is formed.

This bias power source is preferably one in which alternating current is superimposed on direct current, so that the alternating current conditions used for the developing device 4 can be used as is, and a peak-to-peak voltage Vpp of 1000 V or more is suitable, and 1300 to 1500 V is preferable. , the frequency is 800
~2000Hz, preferably 1400-1800Hz is optimal.

Of course, it is also possible to use only direct current or alternating current.

FIG. 2 is a timing chart showing the timing of bias application to the conductive roller.

As shown in the figure, primary charging, image exposure, and development bias are applied, and the image on the photoreceptor is read by the light-receiving element 14.Then, the image is transferred to the transfer material as usual by applying the transfer bias to the transfer charger. Ru.

In this case, the transfer charger continues discharging for a time t2 that is approximately the same as or longer than the transfer time t1 even after the transfer is completed, and charges the photoreceptor surface, and during this time t2, the conductive roller 1
7 to form a solid black image.

The time t2 is based on the value read by the light receiving element 14,
Furthermore, the length is increased or decreased depending on the abrasion characteristics of the photoreceptor and the amount of hard particles such as magnetite contained in the toner.

Figure 3 shows the integral value of the amount of light received by the light receiving element 14 and the conductive roller 1.
7 is a graph showing the relationship between bias application times in No. 7.

When the image area on the photoreceptor is large and the amount of light reflected by the light receiving element 14 is small, when the integral value of the amount of received light in FIG. 3 is a, the bias application time to the conductive roller 17 is t; A solid black image is formed on the photoreceptor with a length corresponding to .

When the image area on the photoreceptor is small and the integral value of the amount of received light is b, the bias application time to the conductive roller 17 is t, and a solid black image with a length corresponding to this is formed. is naturally thicker than the image length.

Note that this bias application time can of course be adjusted depending on conditions such as transfer.

With this configuration, 1. Depending on the form of the toner image formed on the photoreceptor, an appropriate amount of toner is supplied to the photoreceptor in the area leading to the cleaner according to the toner image, and thereby the photoreceptor is Therefore, it is possible to effectively remove paper dust, nitrogen oxides, and talc with an amount of toner suitable for various image forming modes.

In the above case, the application time of the bias applied to the conductive roller 17 was changed depending on the size of the image area on the photoreceptor, but the amount of toner applied to the photoreceptor at the position after transfer was changed. As a means of adjustment, as shown on the vertical axis on the right side of FIG. 3, as the amount of image toner on the photoreceptor decreases and the amount of light received by the light receiving element increases, a bias is applied to the conductive port 17. By varying the bias while keeping the time constant, i.e., by increasing the contrast potential relative to the photoreceptor surface potential so that more toner is deposited on the roller, results similar to those of the previous embodiment can be obtained. .

FIG. 4 is a schematic side view of an image forming apparatus showing another embodiment, and FIG. 5 is a timing chart of the same as above, in which parts corresponding to those of the apparatus shown in FIG. 1 are given the same reference numerals. are shown, and their explanation will be omitted unless necessary.

- The charging of the surface of the photoreceptor by the wide charger 2 takes approximately twice the length of the image, that is, the time shown in the figure (t3+t
Discharge only a).

Thereafter, a toner image is formed on the surface of the photoconductor 1, and its bright and dark pattern is detected by the light receiving element 14. This result is sent to the control device 15a, and the light emitting element 11, which consists of an LED array, etc. As a result, an inverted latent image is formed on the charged surface of the photoreceptor 1.

This latent image is developed by the developing device 4, and this toner image reaches the cleaner 7 without being transferred by the transfer charger.

With this configuration, the toner is conveyed to the cleaner, and the toner is also supplied to the area on the photoreceptor where no toner exists, which corresponds to the white background area of the image, thereby effectively performing a grinding action on the surface of the photoreceptor. Foreign substances such as talc can be removed.

FIG. 6 shows still another embodiment, and the seventh section is its timing chart.

In the -order charging, as shown in the figure (ts+j,), discharge is performed for a time corresponding to approximately twice the image length.

Digital image exposure, such as a laser beam, is then performed to form a latent image.

Immediately after performing the exposure for a time T corresponding to the image length, the controller 15b connects the power source 13b to perform the inversion exposure of the above-mentioned image exposure.

Thereafter, development and transfer is carried out in the usual manner, and a bias is applied to the conductive roller 17 of the cleaner 7 to form a reverse image of the normal image, which reaches the cleaning blade.

With this configuration, it is possible to directly invert the digital exposure signal to form an inverted image.
The configuration is simple, and since the toner in the cleaner can be reused and applied to the blade edge portion, no extra toner is consumed (which is convenient).

(3) As described in detail, according to the present invention, even in the case of an image with a small image ratio and a large amount of white background, this condition is detected and the toner is applied to the photoreceptor before reaching the cleaning blade. Because it is possible to apply sufficient toner to the blade,
Talc and other foreign substances deposited from the paper used as the transfer material can be effectively removed from the photoreceptor, which has a remarkable effect on obtaining high-quality images.

Furthermore, since new toner is not used to supply the necessary toner to the cleaning blade, toner that has been collected in the cleaner can be used, which is advantageous in terms of running costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a timing chart showing the same operation as above, FIG. 3 is a graph showing the relationship between the amount of received light and control conditions, and FIG. A schematic side view of an image forming apparatus showing another embodiment of the present invention; FIG. 5 is a timing chart showing the same operation as above; FIG. 6 is a schematic side view of an image forming apparatus showing still another embodiment; The figure is a timing chart showing the same operation as above. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 2...-wide charger, 4...Developer, 6...Transfer charger, 7...Cleaner, 12...
Pre-exposure device, 15.15a, 15b---control device, 1
6.16a116b...Bias power supply. Figure 1 Figure 2 Figure 3 Receipt its1 Figure 4 Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) In an image forming apparatus configured to form a transferable toner image on a photoconductor and transfer it to a transfer material, residual toner remaining on the photoconductor is removed by a cleaning blade, the image in the image area is An image forming apparatus comprising means for supplying an amount of toner to a photoreceptor according to the area ratio of the area and the non-image area. (2) The image forming apparatus according to claim 1, wherein after forming an image on the photoreceptor, a reversed image of the image is formed, and this reversed image is applied to the photoreceptor for cleaning. (3) In an image forming apparatus equipped with a cleaning device that forms a transferable toner image on a photoconductor and removes residual toner remaining on the photoconductor after transferring the image to a transfer material, the cleaning device includes: An image forming apparatus that has means for performing development using toner collected in a cleaning device.