JPS63137245A - Toner scattering detector for image forming machine - Google Patents

Abstract

PURPOSE:To prevent scattering of a toner by detecting the situation of toner sticking to the non-image forming part of the image area on the surface of a drum,, which causes toner scattering, by a reflex optical sensor to raise a predictive alarm. CONSTITUTION:If the light reflectivity is reduced by toner sticking to the non- image forming part on the drum and the quantity of incident light on a photo transistor TR 29 of a toner scattering detector is smaller than a prescribed value, the TR 29 is turned off. As the result, a collector potential V1 is raised and the output of a comparator 32 goes to the high level. Thus, toner sticking to the non-image forming part on the drum is detected. Since the toner is more replenished according as the toner is gradually accumulated on the non-image forming part after the start of sticking and the toner consumption is increased, toner scattering is caused by the occurrence of electrification defect of the toner or the like. Consequently, toner sticking to the non-image forming part on the drum is detected to quickly detect toner scattering in the foreboding stage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for detecting scattering of developing toner in an image forming machine such as an electrophotographic copying machine.

(Prior Art) In image forming machines, such as electrophotographic copying machines (described below using this example), toner scattering from the developing device occurs over time or due to various causes such as poor developing bias. do. If this toner scattering occurs, the inside of the machine becomes dirty, and the toner adheres to various elements inside the machine, harming the functions of each element and reducing copy image quality, so it is important to detect this toner scattering as early as possible. It is necessary to take measures such as cleaning and cleaning.

Conventionally, as a countermeasure to this problem, as shown in Japanese Patent Laid-Open No. 57-40270, a detector (light-receiving element) such as a phototransistor that receives the light from the static elimination lamp through a filter is installed below the developing device. When the filter or the detector itself becomes contaminated due to toner scattering, the detector detects an abnormality (toner scattering) based on the decrease in incident light m, and indicates the abnormality by lighting a lamp, etc.Toner scattering A detection device was proposed.

However, according to this conventional device, the detection function does not work until it detects that toner scattering actually occurs, or in other words, the detection function does not work until after toner scattering has occurred. Copy image quality deterioration has occurred and is progressing, and at this point detection will be delayed.

For this reason, there are drawbacks such as recovery processing being time-consuming.

(Object of the Invention) Therefore, the present invention provides a toner scattering detection device for an image forming machine that can detect toner scattering at its precursor stage and issue an advance warning of toner scattering.

(Structure of the Invention) The present invention develops an electrostatic latent image formed on the surface of a rotating photoreceptor into a toner image using a developing device, transfers this toner image onto copy paper using a transfer device, and then cleans the image. In an image forming machine configured to remove residual toner by a device, at a position facing an image area on the surface of the photoconductor downstream of the developing device in the rotational direction of the photoconductor and upstream of the cleaning device. , a reflective optical sensor is provided, which includes a light projecting element that irradiates light to a non-image forming area within the image area, and a light receiving element that receives reflected light from the non-image forming area; It is equipped with an abnormality display means for displaying an abnormality based on the output from the sensor.

In this configuration, since toner adhesion to the non-image forming area of the photoreceptor leads to an increase in toner consumption - toner charging failure -> toner scattering, it is possible to detect whether or not toner is adhering to this non-image forming area. , toner scattering can be detected at its precursor stage.

(Example) An example of the present invention will be described with reference to the drawings. In this embodiment, an electrophotographic copying machine is taken as an example of an application target (image forming machine).

FIG. 1 shows the overall configuration of this copying machine, and FIG. 2 shows a portion of the same. In both figures, reference numeral 1 denotes a housing of a copying machine. In the housing 1, a contact glass 2 on which a document is placed and a document presser 3 are arranged on the upper part, and a document irradiation lamp 4 and a reflector plate 5 are arranged inside the housing 1. , mirrors 6a, 6b,
6c, 6d and a lens assembly 7 are provided to constitute an optical system. 8 is a timing switch that detects the start of exposure (the leading edge of the document) by this optical system.

Around the photoreceptor drum (hereinafter simply referred to as drum) 9, which receives light from the optical system and forms an electrostatic latent image,
In order in the direction of rotation of the drum shown by the arrow in the figure, there is a main charging device 10 including a corona discharger, an eraser 11, a developing device 12 that develops the electrostatic latent image on the drum 9 into a toner image, and a toner image that is transferred to a copy paper. A transfer device 13 for transferring the transferred copy paper from the drum 9, a separating device 14 for separating the transferred copy paper from the drum 9, a cleaning device 15 for removing residual toner etc. from the drum 9, a discharge lamp 16, etc. are arranged. 17 is a copy paper cassette, and the copy paper fed out from this cassette 17 by a paper feed roller 18 is transferred to the transfer device 13 by a paper feed conveyance mechanism 20 equipped with registration rollers 19, 19 as shown by the chain line arrow in FIG. After being sent and transferred, minutes + tmV device 14
, the conveyor belt assembly 21, and the fixing device W122, and are discharged by the discharge rollers 23 and 24, and are stacked and accommodated on the paper discharge tray 25. Reference numeral 26 in FIG. 1 is a pre-registration switch provided facing the registration rollers 19, and this switch 26 detects that the copy sheet has arrived at the registration rollers 19, that is, that the next sheet has been fed.

In this copying machine, a position downstream of the developing device 12 in the drum rotational direction, that is, between the developing device W112 and the transfer device 13, is located at or near the center of the drum surface in the drum axial direction (regardless of the copy size). A reflective optical sensor 27 is provided facing the portion through which the copy paper always passes during transfer. This optical sensor 27 includes a light emitting diode 28 as a light projecting element that illuminates a non-image forming area within an image area (an area excluding areas where no image is always formed at both ends of the drum axis) on the drum surface; It consists of a photodiode 1 and a transistor 29 as a light-receiving element that receives reflected light from a non-image forming area. Adhesion of toner to the image forming area is detected. The configuration of this detection circuit is shown in FIG.

The phototransistor 29 of the optical sensor 27 has an emitter that is grounded and a collector that is connected to a power supply bus line 31 via a resistor 30, and the collector potential of this phototransistor 29 is V1.
is applied to one input terminal of comparator 32. The other input terminal of this comparator 32 is connected to a resistor 33 and a variable resistor 34.
, a slider potential V2 of a variable resistor 34 in a voltage dividing circuit consisting of a resistor 35 is input as a reference potential, and a comparator 32 compares this reference potential (2) with the collector potential (2).

In this configuration, when toner is not attached to the non-image forming area in the drum image area (including cases where the amount is so small that it does not cause a problem even if it is attached), the light to this non-image forming area is Since the reflectance is high and the amount of light incident on the phototransistor 29 is large, the phototransistor 29 becomes conductive. Therefore, since the collector potential 1 is low at this time, the output from the comparator 32 is at L level. On the other hand, the light reflectance decreases due to the toner being placed on the non-image forming area of the drum, and the phototransistor 2
When the amount of light incident on the transistor 9 decreases to a predetermined amount or less, the transistor 29 is turned off, so that the collector potential V1 becomes high and the output of the comparator 32 becomes 1 level. In this way, toner adhesion to the non-image forming portion of the drum is detected.

This non-image forming area of the drum is an area to which toner should not originally adhere, and when toner begins to adhere to this non-image forming area due to various causes such as the passage of time or poor developing bias described above, this gradually As toner is accumulated and toner consumption m increases, toner replenishment increases, resulting in toner charging failure, and
Cleaning device 1 prevents toner from adhering to non-image forming areas.
Toner scattering occurs due to the poor cleaning caused by No. 5. Therefore, by detecting toner adhesion to the non-image forming portion of the drum as described above, it is possible to detect toner scattering as soon as it becomes a sign.

The output of the comparator 32 is input to a lamp circuit (not shown) and a drive section for copying operation, and the 11 outputs from the comparator 32 turn on the lamp and issue a toner scattering warning. The system stops working,
Copy operation is canceled.

FIG. 3 shows a block configuration of such a control system. Reference numeral 36 denotes an 1IItI1 section, into which the detection signal from the sensor 27, the switch signals from the pre-registration switch 26 and the timing switch 8 are input. The control unit 36 processes each of these signals and issues a driving command to the driving unit 37, and based on this driving command, the driving unit 37
However, the main motor 38 and the optical system motor 3 for driving the optical system
9. Activate the registration clutch 40 for the registration roller 19 and the paper feed clutch 41 for the paper feed roller 18. Further, the above-mentioned lamp display section for toner scattering advance warning is incorporated into the operation section 42 in which various operation elements such as a print key are arranged so as to be easily visible to the operator.

Next, the overall operation of the copying machine including toner scattering detection will be explained with reference to the flowchart shown in FIG.

First, in step S1, it is determined whether or not a start signal has been issued by operating a print key or the like, and when copying starts, the main motor 38 is driven (step 82) and the paper feed clutch 41 is turned on. (
Step 83). As a result, the paper feeding operation by the paper feeding roller 18, that is, the primary paper feeding is started, and whether or not the copy paper has reached the registration rollers 19 is determined in step S4 by whether or not the pre-registration switch 26 is on. .

When this switch 26 is turned on, the counter 1 is set (step S5), and the copy paper is held at the entrance of the registration roller 19 for a predetermined period of time. After undergoing so-called skew correction, time-up is determined in step S6. Then, in step S7, the paper feed clutch 41 is turned off. Next, the optical system motor 39 is driven to start the operation of the optical system (step Sa), the timing switch 8 is turned on to determine the document leading edge position (step Se), and the registration clutch 40 is turned on (step Sa). Sm),
The copy paper is transported toward the transfer device 13, that is, secondary paper feeding is performed. Then, when the pre-registration switch 26 is turned off (step 511), the optical system returns to its original position (step 512), and the counter 2 is set in step S13.

By setting the counter 2, the timing at which the rear end of the toner image formed on the drum surface passes the optical sensor 27 is measured (step S%), and the optical sensor 27 detects toner adhesion to the non-image forming portion of the drum surface. will be carried out.

At this time, if the optical sensor 27 does not detect any abnormality (toner adhesion), the process advances from step 815 to step S16, where the registration clutch 40 is turned off and the rotation of the registration rollers 19 is stopped. After that, it is determined in step Sv whether or not to perform continuous copying. If the answer is No, the main motor 38 is turned off (step 518) and the process returns to step S1. If YES, the process returns to step S3 and the paper feed clutch is turned on. The operations from then on are repeated.

On the other hand, when the optical sensor 27 detects toner adhesion on the non-image forming area and outputs an abnormal output in step Ss, a stop signal is sent from the control section 36 to the drive section 37 in FIG. 3, and the operation of the drive system is stopped. Stop and abort copying (step 81g)
becomes. At the same time, an alarm lamp built into the operating section 42 lights up to issue an advance warning of toner scattering (step 820). This allows the user to know that toner scattering occurs at a premonitory stage, so that toner scattering can be prevented by taking appropriate measures at this point. After the recovery process, whether or not to reset based on the operation of the reset button etc. (whether r4 is always resolved or not)
is determined in step S21, and if YES, step S1
The copy operation can be resumed by returning to .

Note that the optical sensor 27 mainly detects toner adhesion to the non-image forming portion of the drum surface as described above.
The same effect as described above also occurs when toner falls off the surface of the developing device 12 or the drum and adheres to the optical sensor 27 for some reason.

By the way, since toner scattering has an important effect on image formation, it is desirable to stop the copying operation at the same time as the abnormality is detected as described above, but in the case of this device, since the precursor stage of toner scattering is detected Since there is plenty of time until actual toner scattering, the flow may be configured such that only an abnormality is displayed at the time of abnormality detection, and the copying operation continues as is.

In addition, in the above description, the optical sensor 27 is placed facing near the center of the drum surface in the axial direction, and detects toner adhesion to the non-image forming area on the rear end side of the toner image near the center of the image area. However, it is also possible to detect an abnormality in a non-image forming part in the width direction - side part of both I& areas. In this case, since the widthwise position of the non-image forming portion changes depending on the copy size, it is sufficient to arrange a plurality of optical sensors according to the copy size and to extract a detection signal from one of them. Furthermore, since toner adhesion to the non-image forming area clearly appears immediately after development, the optical sensor 27 detects the presence of the toner in the non-image forming area as in the above embodiment. It is most desirable to place the optical sensor 27 between the transfer device 12 and the transfer device 13, but if the optical sensor 27 is placed downstream of the transfer device RFI 13 in the drum rotation direction and upstream of the cleaning device M5. However, it is possible to detect toner adhesion to non-image forming areas.

(Effects of the Invention) As described above, the present invention uses a reflective optical sensor to detect a situation that leads to toner scattering, such as toner adhesion to a non-image forming area in the image area of the drum surface, and issues an advance warning. It is possible to detect toner scattering at an early stage, rather than after it actually occurs, as was the case in the past, making early treatment possible, preventing toner scattering, and facilitating recovery processing. It will come true.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of an electrophotographic copying machine incorporating a detection device 4 according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of the same, and FIG. Block diagram shown,
FIG. 4 is a block diagram of the detection circuit, and FIG. 5 is a flowchart for explaining the copy operation. 9... Photosensitive drum, 12... Developing device, 13...
・Transfer device, 15...Cleaning device, 27...
Optical sensor, 28... A light emitting diode as a light emitting element of the optical sensor, 28... A phototransistor as a light receiving element. Patent applicant Agent: Sanda Kogyo Co., Ltd.
Patent Attorney Etsushi Kotani Patent Attorney Chief 1) 1 Patent Attorney Yasuo Itaya Figure 2

Claims (1)

[Claims] 1. The electrostatic latent image formed on the surface of the rotating photoreceptor is developed into a toner image by a developing device, and after this toner image is transferred to copy paper by a transfer device, the remaining toner is removed by a cleaning device. In an image forming machine configured to remove the image, a portion of the image area within the image area is placed at a position facing the image area of the photoreceptor surface downstream of the developing device in the rotational direction of the photoreceptor and upstream of the cleaning device. A reflective photosensor is provided, which includes a light projecting element that irradiates light onto a non-image forming area, and a light receiving element that receives reflected light from the non-image forming area. 1. A toner scattering detection device for an image forming machine, characterized in that the toner scattering detection device for an image forming machine is provided with an abnormality display means for displaying an abnormality when the image forming machine is detected.