JPH0391782A - Deteriorated toner removing device - Google Patents

Abstract

PURPOSE:To positively remove deteriorated toner which causes fogging from a developing device by developing in a non-image part, outside of an area where recording or copying is performed originally, in a fogging state. CONSTITUTION:When the power source of an electronic copying machine is turned on, the deteriorated toner removing device controls a motor driving circuit 26 and a high-voltage control circuit 28 and actuates them. When a main motor 27 begins to be driven, the high-voltage power source 29 is actuated. At time T2, a developing bias applied to the magnet roll 33 of the developing device is set to a potential V2 and at the same time, a magnet roll 33 begins to be rotated under the control of a clutch 32. The fogging density by the developing bias V2 is detected by a density sensor 25 and when the density is larger than a reference value, namely, the amount of deteriorated toner is large, a developing bias V2 for removing the toner is applied continuously to the magnet roll 33 to perform the removing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention is applicable to image processing in which an electrostatic latent image is formed and developed on a photoreceptor, such as in electronic copying machines, certain types of printers, or facsimile machines. The present invention relates to devices, and particularly to a deteriorated toner removing device for removing toner that is nearing the end of its life or has deteriorated and is present in the developing device of these image processing devices.

``Prior Art'' In image processing devices such as electronic copying machines, printers and facsimile machines that record using photoreceptors, two-part developer consisting of toner and carrier, or a so-called developer that combines these functions into one, is used. An electrostatic latent image is developed using a particulate developer as a carrier resistor.

Taking a two-step developer as an example, the toner is charged to a predetermined polarity by contacting the carrier, and is electrostatically attracted to the electrostatic latent image on the photoreceptor. However, these characteristics of the developer do not change forever, and the charging performance deteriorates with use.

Here, deterioration in chargeability refers to the occurrence of low charge or an increase in toner that is charged to the opposite polarity. If such deteriorated toner increases, fogging will occur in low-density areas and non-image areas of the image, impairing the quality of the image.

"Problem to be Solved by the Invention" As is well known, in a developing device such as an electronic copying machine, 100% of the toner supplied to the area where the electrostatic latent image is formed is
It is not something that is consumed in that area. Most of the toner remains within the developing device without being attracted to the electrostatic latent image, circulates within the device again, and is used for later development. For this reason, in the developing device, due to internal circulation, the amount of toner with deteriorated chargeability gradually increases and is piled up in M piles.

Therefore, even if new developer is partially contained in the developing device, the overall developing characteristics deteriorate, and a situation has arisen in which the toner in the developing device must be completely replaced when its life reaches the end.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a deteriorated toner removing device that can efficiently remove such deteriorated toner from inside a developing device.

"Means for Solving the Problem" The present invention includes a non-image area charging means for charging a predetermined area other than the area where image information is to be formed on the photoconductor, and (11) charging by the non-image area charging means. The deteriorated toner removing device is provided with a fogging potential setting means for setting a potential so that fogging occurs in the developed area during development.

That is, in the present invention, development is performed in a fogged state in a non-image area outside the area where recording or copying is originally performed, and the deteriorated toner that has caused the fogging is actively removed from the developing device.

"Principle of the Invention" Before proceeding to the description of the embodiments, the relationship between non-image areas and fogging will be described.

FIG. 2 shows the potentials and the ratios of these charges when the new developer is charged. In the case of the new developer shown in this example, all of the developer is charged to the + (plus) side, and the areas where the potential is particularly low or particularly high are relatively reduced.

FIG. 3 shows similar characteristics of a deteriorated developer. The developer in this example is intended to be developed into a positive charge, but as it ages and deteriorates, a portion of the developer becomes charged in a negative direction as shown by region 1l. Further, even if the toner is charged in the + direction, a large amount of toner exists in areas where the potential is low as shown in area 12.

FIG. 4 shows nine potential shapes in the case of a negative phenomenon. Here, the potential VIIXG is the potential of the non-image area (background area of the image) on the photoreceptor, and is, for example, about +IOOOV.

The potential Vi is the potential of the image portion, and is, for example, about +100V. The potential V+ is a developing bias applied to a magnet roll (not shown) of the developing device during normal recording, and is, for example, a potential of about +600V to +700V.

Under such a potential profile, the toner particles (2), which are positively charged to a normal degree in FIG. 2 or 3, are attracted to the potential VI of the image area. The difference between the developing bias V and the potential VBkG of the non-image area is called the cleaning field C, F, and if this potential difference is large to some extent as in this example, a low potential will appear at the location of the potential V of the non-image area. Charged and deteriorated toner such as toner charged to a weakly opposite polarity (areas 11 and 12 in Fig. 3) are difficult to adhere to.In other words, in normal development, the developing bias is set to potential V1 to prevent fogging in non-image areas. is prevented.

In FIG. 4, the potential V2 is set closer to the potential V B K G of the non-image area than the potential V1, for example, 900 V or +1000 V, which is the same as the potential of the non-image area.
It is a value of about . When the developing bias is changed to the potential V2 instead of the potential V1, the cleaning field C. as the difference between the developing bias V2 and the potential VellG of the non-image area. F, decreases. Accordingly, the potentials of the non-image area V, lX. Toner particles with low charge and weakly reversed polarity (regions 11 and 12 in FIG. 3) are likely to adhere to these areas, causing fogging in these areas.

In the present invention, fogging is actively generated in the non-image area by, for example, changing the developing bias from the potential V1 to the potential V2 as in this example.

At this time, the deteriorated toner that has accumulated and adsorbed onto the photoreceptor is actively removed by cleaning.

Note that when the developing bias is raised from the potential V to the potential V2, the potential of the image portion becomes V. becomes relatively low, and the normally positively charged toner particles (2) are more likely to be attracted to the image area. Therefore, in order to prevent the occurrence of "fogging" in the image area due to this, setting the developing bias to potential V2 is limited only to the non-image area, and in the image area, development /, a
The bias voltage is set to the normal potential V.

"Example" Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 schematically shows the circuit structure of a deteriorated toner removing device in an electronic copying machine as an embodiment of the present invention. This deteriorated toner removing device includes a CPU (central processing unit) 21. This CPU 21 is connected to the following units through a bus 22 such as a data path, and performs general control of an electronic copying machine in addition to removing deteriorated toner.

<i) ROM2 3: A read-only memory that stores various programs for control.

(ii>RAM2 4 : Random access memory for temporarily storing various data for control.

(iii) Density sensor 25: This is an optical sensor that is disposed facing the surface of a photoreceptor drum (not shown) and optically measures the density of toner adhered thereto.

(iv) Motor drive circuit 26: This is a circuit that controls the drive of the main motor 27.

(v) High voltage control circuit 28: This is a circuit that controls the output of the high voltage power supply 29.

(vi) Clutch control circuit 31: Turns on/off the rotation of the magnet roll 33 of the developing device by connecting the clutch 32.
This is a circuit for turning off. A developing bias of potential V1 or V2 is applied to the magnet roll 33 from the high voltage power supply 29.

FIG. 5 shows the control operation of the deteriorated toner removing device of this embodiment, and FIG. 6 shows the operation timing of each part of the device under this control.

When the electronic copying machine is powered on, the deteriorated toner removing device controls the motor drive circuit 26 and high voltage control circuit 28 shown in FIG. 1 to start them (step 2 in FIG. 5). FIG. 6a shows that at this time T1 the main motor 27
This shows that the high-voltage power supply 29 has started to be driven at the same timing.

After a short time t1 has elapsed from time T1 (step ■; Y), at this time T2, the developing noise applied to the magnet roll 33 of the developing device is set to the potential v2, and at the same time, the magnet roll 33 is turned off by the control of the clutch 32. Rotation begins (Stenop■).6th
Figure C shows that the developing bias is set to potential ■2 at time T2, and Figure d shows that the rotation of the magnet roll 33 is started at this time.

After this, when the time t2 for the photosensitive drum to rotate to a certain extent has elapsed (step ■), the developing bias v2
The density sensor 25 starts detecting the density of "fogging" caused by this (step (2)).

Then, when this density D is larger than the reference value D1,
That is, when the amount of deteriorated toner is large (Y), the developing bias V2 is set to the magnetic roll 3 to remove it.
3 is continuously applied, and its removal operation is performed.

On the other hand, when the density D becomes equal to or smaller than the reference value D after a certain amount of time has passed (step ■; N), all work for removing deteriorated toner is completed at that time T3. (end).

"Modification" (First Modification) FIG. 7 shows the operation timing of the deteriorated toner removing device in the first modification of the present invention. In this modification, the main motor 27 and the high voltage power supply 29 are started at time T when a start button (not shown) of the electronic copying machine is pressed (FIG. 7aSb). Then, a little later time T
, the developing bias applied to the magnet roll 33 of the developing device is set to the potential v2 (FIG. 7C), and at the same time, the rotation of the magnet roll 33 is started under the control of the clutch 32 (FIG. 7D). The developing bias v2 continues for a predetermined deteriorated toner removal period, and then at time T6
Then, the developing bias is changed to the normal potential V.

In this state, copies 41-1 to 41-N are performed on each copy sheet as shown in FIG. 7e. After the final copying 41-N is completed, the developing bias is changed from the potential VI again to the potential V2 for causing fogging at time T7. Then, in this state, the deteriorated toner is removed. The work of removing the deteriorated toner is carried out for a predetermined period of time, and all operations of the photosensitive drum and the like end at time T thereafter.

That is, in this modification, when the operator presses the start button to start the copying operation, the deteriorated toner is removed for a predetermined period of time before and after the actual copying. Moreover, in this modification, a relatively short period immediately after the start button is pressed, during which "breaking-in" of the photoreceptor drum is normally performed, is used as the first half period for removing deteriorated toner. Therefore, when the operator presses the start button? This does not significantly increase the time it takes to get the first copy.

(Second Modification) FIG. 8, which corresponds to FIG. 7, shows the operation timing of the deteriorated toner removing device in the second modification of the present invention. This modified example is applied to an electronic copying machine that uses cut paper, but like the embodiment and the first modified example, it can also be applied to an image processing device such as a laser printer that uses cut paper. can.

In this second modification, the developing bias is set to the potential V2 in a time period when copying 41 is not performed between cut sheets, such as the period from time Tl (l to time T), and copying 4l
The potential is set to V during the time period in which the all copies 4
All operations of the photoreceptor drum, etc., end at time T1■ after step 1 is performed. As described above, in this modification, the developing bias is switched between consecutive copies or consecutive prints, and the deteriorated toner is removed in the state of potential V2.

Although the embodiments and modifications have been described above on the premise of negative development, positive development may also be performed in image processing apparatuses such as copying machines and printers that have optical systems such as lasers and light emitting diodes.

FIG. 9 is for explaining the removal of deteriorated toner when this positive development is performed. The same symbols as in FIG. 4 are used in this figure as well. When positive development is performed, the size of the cleaning field can be controlled not only by controlling the developing bias but also by the size of irradiation from a laser, a light emitting diode, or the like. In other words, the potential VllXG of the non-image area is changed to the potential VBKl in the normal case.
By lowering the irradiation level than l+-1, it is possible to set the potential vaI (a-.), which is seven orders of magnitude closer to the developing bias VD, narrowing the cleaning field and setting it in a state where fogging is likely to occur. In order to achieve this, for example, when modulating the laser beam, the laser beam irradiation may be made relatively strong only during the period when the deteriorated toner is removed.

In the case of bright development, it is possible to control the power related to the amount of light in a shorter time than with the development bias which requires time for switching. Therefore, high-speed switching is possible even between continuous copying or continuous printing as in the second modified example. As a result, it becomes possible to remove deteriorated toner even in high-speed copying machines, high-speed printers, and the like. Further, even in a bright development system using a conventional exposure lens, the same control as described above is possible by controlling the intensity of the exposure amount.

In addition, although the photoreceptor drum was explained in the embodiment, the present invention can also be applied to the case of removing deteriorated toner in a developing device that develops an electrostatic latent image on another photoreceptor such as a photoreceptor belt. Of course it can be done.

"Effects of the Invention" As explained above, in the present invention, a predetermined area other than the area where image information is to be formed on the photoreceptor is charged,
Since this charged area is developed with fog generated, if this type of development is performed at the start of copying or recording, it will not only be possible to prevent fog, but also cause the device to stop for a while. If the charge level of the developer has dropped during the process, fogging of the initial print can be prevented and the charge level of the developer can be increased.

Further, according to the present invention, since deteriorated toner is removed by generating fog on the photoreceptor, even non-image areas of the photoreceptor may be actively covered with toner particles, and these toners may be exposed to the cleaning blade. Functions as a cleaning aid. That is, it is possible to produce an effect of extending the life of the cleaning blade that removes toner particles.

[Brief explanation of drawings]

FIGS. 1 to 6 are for explaining one embodiment of the present invention, of which FIG. Figure 2 is a characteristic diagram showing the potentials and charge rates when new developer is charged, Figure 3 is a characteristic diagram showing similar characteristics of deteriorated developer, and Figure 4 is for negative development. FIG. 5 is a flowchart showing the control operation of the deteriorated toner removing device, and FIG. 6 is a timing chart showing the operation timing of each part of the device. , FIG. 7 is a timing diagram showing the operation timing of the deteriorated toner removing device in the first modification of the present invention, and FIG. 8 is a timing diagram showing the operation timing of the deteriorated toner removing device in the second modification of the invention. The timing diagram, FIG. 9, is an explanatory diagram showing the principle of removing deteriorated toner when blur development is performed. 21...CPU, 23...ROM
, 24...RAM, 25...Density sensor, 28...High voltage control circuit, vsuc,...Potential of non-image area, V1...
...Potential of image area, VI SV2, V+, ...Development bias.

Claims (1)

[Scope of Claims] Non-image area charging means for charging a predetermined area other than the area where image information is to be formed on the photoreceptor; What is claimed is: 1. A deteriorated toner removing device comprising: a deterioration toner removing device comprising: a deterioration toner potential setting means for setting a potential to cause fogging to occur;