JP2009145786A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus comprising a toner scatter detecting sensor constituted so as to not to produce defects, even if toner sticks thereto, with the passage of time, by the scattering of toner and which is capable of accurately determining the deterioration state due to the aging of developer as the progress situation of worsening of toner scatter. <P>SOLUTION: The image forming apparatus has a rotationally driven photoreceptor drum 10 which is rotated and driven, a developing apparatus 30 for developing an electrostatic latent image formed on the photoreceptor drum 10 by a two-component developer, and the toner scattering detecting sensor 100, provided near the developing apparatus 30. The toner scattering detecting sensor 100 detects the light irradiated from the developing apparatus 30 side, by receiving the light reflected from the photoreceptor drum 10 from a member near the developing apparatus or a developing apparatus member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using a two-component developer composed of a magnetic carrier and a nonmagnetic toner.

Generally, a toner image is formed by applying a two-component developer composed of toner and carrier to an electrostatic latent image formed electrostatically on the surface of an image carrier, and then the toner is applied to a transfer material such as paper. In an image forming apparatus that repeats the image transfer process, it is important that the toner always maintains a stable charge amount in order to obtain a high-quality image stably over a long period of time.
However, when a two-component developer is used, the repetition is received from a developer regulating member that is generally a plate-like blade provided to optimize the amount of developer on the developer carrier. Due to the stress, the external additive on the toner surface is buried in the toner or detached from the surface, or the toner component is fixed (spent) on the carrier surface.
When the external additive of the toner is buried or detached, and the external additive no longer exists on the toner surface, the non-electrostatic adhesion force between the toner and the carrier increases, and it adheres firmly to the carrier. Therefore, there is a problem that the developing ability as a developer lacks stability.
In addition, since the adhesion force between the toner and the carrier increases, the replacement with the newly supplied toner hardly occurs, the supplied toner cannot contact the carrier, or weakly charged by contact between the toners, It is transported to the development area while maintaining reverse charging. These weakly charged and reversely charged toners are not preferable because they are easily separated from the carrier and cause abnormal images such as image background stains and in-machine contamination due to toner scattering. Further, when transferring from a photosensitive member or an intermediate transfer material to paper, the transfer rate is lowered, so that there is a problem in that image graininess is reduced and solid images are made non-uniform and image quality is lowered.
The toner scattering is a phenomenon in which the toner having a low charge amount or charged in the reverse polarity is detached from the carrier in the magnetic brush that is raised due to the centrifugal force generated by the rotation of the developing sleeve and scattered outside the developing device.

In particular, when an image with a low image area ratio is repeatedly formed, the developer must repeatedly pass through the developer regulating member, and therefore, the toner surface additive is likely to be buried in the toner, causing a problem. There is a problem that is likely to occur. Also, if the toner component adheres to the carrier surface during repeated stresses, the charge imparting ability of the carrier to the toner will be reduced, so the toner will have a predetermined charge amount. This is not preferable because it becomes difficult to obtain and as a result causes image background contamination and toner scattering.
As a method for grasping the deterioration state of the developer as the amount of scattered toner, Patent Document 1 discloses an optical system comprising a light emitting unit that emits light and a light receiving unit that receives reflected light and converts it into an electrical signal in the vicinity of the developing device. There has been proposed a method in which a toner scattering detection sensor is provided and carrier or developer is appropriately replenished based on a signal from the detection sensor.
The toner scattering detection sensor proposed in Patent Document 1 includes a light emitting unit, a light receiving unit, and a lens provided in the vicinity of the developing device. When the toner scatters, the toner splattered from the developing device passes between the light emitting unit and the light receiving unit. At this time, the light emitted from the light emitting unit is reflected by the toner, and the reflected light is reflected by the light receiving unit. Is output in the form of being converted into an electrical signal.

JP 2006-3625 A

However, in the above-described toner scattering detection sensor system, the lens of the light emitting unit and the light receiving unit is contaminated due to toner adhesion over time due to toner scattering, and erroneously detects an actual toner scattering state. If this error is detected, the carrier or developer is appropriately replenished based on the output value of the toner scattering detection sensor, so that the carrier or developer is unnecessarily replenished.
In addition, the lens can be cleaned due to the toner adhering to the lens over time by the serviceman when the developer is replaced or when the maintenance of other units is performed. Since the gap between the light emitting portion and the light receiving portion is narrow, cleaning may be difficult or the cleaning may be forgotten. If the lens of the light emitting unit and the light receiving unit is not cleaned and the toner adheres to the lens, the toner is scattered even after the toner is not scattered after the toner is replaced with a new developer. The problem of false detection occurs.

Therefore, the present invention has been made in view of the above problems, and the problem is that the configuration of the toner scattering detection sensor is configured so that there is no problem even if toner adheres over time due to toner scattering. It is an object of the present invention to provide an image forming apparatus provided with a toner scattering detection sensor capable of accurately determining the deterioration state with time as the progress of toner scattering deterioration.
It is another object of the present invention to provide an image forming apparatus that facilitates cleaning of a toner scattering detection sensor by a service person during cleaning of a developing unit, and that can be reliably cleaned.

The features of the present invention, which is a means for solving the above problems, are listed below.
An image forming apparatus according to the present invention includes a rotating image carrier, a developing device that visualizes an electrostatic latent image formed on the image carrier with a two-component developer, and a toner scattering detection sensor in the vicinity of the developing device. In the image forming apparatus, the toner scattering detection sensor detects light irradiated from the developing device side by receiving reflected light from a member near the developing device or the developing device member and the image carrier. To do.
The image forming apparatus of the present invention further includes a toner recycling mechanism that collects toner remaining on the image carrier in the developing device, and is recycled to the developing device based on an output value of the toner scattering detection sensor. It is characterized by changing the amount of toner.
The image forming apparatus of the present invention further includes a charging device that charges the surface of the image carrier to a desired potential and a charging cleaning unit that cleans the charging device, based on the output value of the toner scattering detection sensor. The number of times of cleaning the charging device is changed.
In addition, the image forming apparatus of the present invention further outputs a developer replacement signal based on an output value of the toner scattering detection sensor.
In addition, the image forming apparatus of the present invention further outputs a signal for prohibiting the operation of the image forming apparatus based on an output value of the toner scattering detection sensor.

  With the image forming apparatus of the means to solve the above, it becomes possible to issue a developer replacement signal in a state in which the developer is effectively used for the maximum life, generation of abnormal images due to toner contamination in the machine, It is possible to prevent problems due to erroneous detection by other sensors such as a reflection density sensor, machine stoppage due to failure, and the like.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment of the present invention, and FIG. 2 is a partial plan view showing a part around a photoreceptor.
The copying machine includes a charging charger 20, an eraser 82, a developing device 30, a reflection density sensor 70 for detecting the reflection density of the surface of the photosensitive drum 10, a transfer charger 80, a separation charger 81, and a cleaning device around the photosensitive drum 10. 50. An optical writing device (not shown) is provided above the photosensitive drum 10.
At the time of image recording, the sheet is fed from a sheet feeding cassette (not shown), and is also conveyed to the lower side of the photosensitive drum 10 at a timing by a pair of registration rollers (not shown). The photosensitive drum 10 is rotationally driven by a driving device (not shown). At that time, the surface is uniformly charged by a charging charger 20, and an electrostatic latent image is formed by irradiating the surface with exposure L from an optical writing device. The
The charging charger 20 is provided with a wire cleaner mechanism 25 including a cleaner motor and a cleaner, and is operated in a timely manner to prevent abnormal images due to charging unevenness due to dirt on the charger wire 22. FIG. 3 is a schematic view showing the configuration of the wire cleaner mechanism. The k wire cleaner mechanism 25 slides with the cleaner member 26 from the end of the wire 22 of the charging charger 20 to the other end and cleans it.
The developing device 30 visualizes the electrostatic latent image thus formed on the surface of the photosensitive drum 10 with toner. This visible image is transferred by the transfer charger 80 onto the upper surface of the sheet conveyed to the lower side of the photosensitive drum 10. The sheet after image transfer is conveyed to a fixing device (not shown), and after the image is fixed, the sheet is discharged outside the apparatus. On the other hand, the toner remaining on the photosensitive drum 10 after the image transfer is scraped off by the blade 51 of the cleaning device 50 and collected at the bottom of the cleaning device 50. The developing device 30 includes a case 34 that includes a developing roller 31, a paddle 32, a stirring member 33, and the like, and a toner hopper 37 that is connected to an opening 35 provided at the upper end of the case 34. A toner supply roller 36 is provided in the opening 35.
In addition, a toner scattering detection sensor 100 is provided below the case 34 corresponding to the lower side of the developing roller 31.

As shown in FIG. 2, the toner hopper 37 has a horizontally long box shape, and a toner replenishing port 42 and a toner recovery port 40 are arranged in parallel on the upper surface near one end in the longitudinal direction, and is appropriately supported near the toner replenishing port 42. A toner bottle 41 is attached, and a toner conveying screw 39 is accommodated from the toner replenishing port 42 to the lower side of the toner recovery port 40. An agitator 38 is provided in the toner hopper 37 in parallel with the toner conveying screw 39.
Further, the developing device 30 is connected to a toner conveying device 60 for conveying the used toner collected by the cleaning device 50 to the toner hopper 37. In the toner transport device 60, one end of a transport pipe 61 is connected to the cleaning device 50, and the other end of the transport pipe 61 is connected to the toner recovery port 40 of the toner hopper 37. A conveying screw 53 is provided at the bottom of the cleaning device 50, and a conveying screw 62 is rotatably provided within the conveying pipe 61. Therefore, during image recording, a driving force from a driving source (not shown) is transmitted to the conveying screw 53 and the conveying screw 62 to rotate, and the collected toner collected by the cleaning device 50 is conveyed by the conveying screws 53 and 62 to collect the toner. It can always be fed into the toner hopper 37 from the mouth 40. That is, the toner scraped off by the cleaning blade 51 of the cleaning device 50 at the time of image recording is transported through the cleaning device 50 to the front of the drawing sheet by the transport screw 53 and collected by the transport screw 62 to the toner hopper 37. Further, new toner from the toner bottle 41 is conveyed to the back of the toner hopper 37 by the conveying screw 39.
The drive motor 43 of the toner replenishing roller 36 is connected to the CPU 72 of the microcomputer 71 for calculation control by the driver 44 and is driven and controlled.
This is an A / D converter 73 for converting the analog detection output from the reflection density sensor 70 into a digital value, and is connected so as to input the output value of the converted reflection density sensor 70 to the CPU 72. The microcomputer 71 includes a RAM 74 and a ROM 75.

Further, the drum motor 63 rotationally drives the photosensitive drum 10, and the conveyance screw 62 and the drum motor 63 can be connected / released by a clutch 64.
FIG. 4 is a schematic diagram illustrating a state in which waste toner is conveyed from the cleaning device to the developing device. The waste toner bottle 52 is connected to collect waste toner from the cleaning device 50. When the clutch 64 of the transport screw 62 for the recycled toner T is turned on, the recycled toner T is transported as shown in FIG. 4A, so that the recycled toner hardly falls into the waste toner bottle 52. When the clutch 64 is turned off, the recycled toner T accumulates as shown in FIG. 4B, so that the waste toner naturally falls into the waste toner bottle 52. As a result, all the waste toner is not supplied to the developing device 30, and in particular, the recycled toner can be transported to either the developing device 30 or the waste toner bottle 52 when the transport screw 62 is in the stopped state. I have to.

FIG. 5 is a cross-sectional view of a toner scattering detection sensor provided in the vicinity of the developing device.
FIG. 6 is a front view of the toner scattering detection sensor viewed from the photosensitive drum side.
The toner scattering detection sensor 100 includes a light emitting unit 101 configured by an LED light source, a transparent plate 102, a light receiving unit 103 configured by a phototransistor, and the like, and a case 104 surrounding the light emitting unit 101 and the light receiving unit 103.
The developer deteriorated with time increases the amount of weakly charged and reversely charged toner in the developer, and toner scattering worsens. The toner 105 scattered from the developing device 30 adheres to and accumulates on the transparent plate 102 of the toner scattering detection sensor 100 disposed in the vicinity of the developing roller 31.
The toner scattering detection sensor 100 performs detection at a timing before or after image creation, and the light emitted from the light emitting unit 101 passes through the transparent plate 102 and is reflected by the background portion of the photosensitive drum 10. The reflected light passes through the transparent plate 102 again, is read by the light receiving unit 103, and is output in a form converted into an electric signal.

FIG. 7 shows a detection result of toner scattering by the toner scattering detection sensor 100. When the deterioration of the developer has not progressed relatively, the amount of toner scattered from the developing device is small, and therefore the amount of toner deposited and deposited on the transparent plate 102 is small. In this case, since the light irradiated from the light emitting unit 101 is less blocked by the toner deposited on the transparent plate 102, the amount of light returning to the light receiving unit 103 is increased.
On the other hand, when the deterioration of the developer progresses, the amount of light irradiated from the light emitting unit 101 is blocked by the toner deposited on the transparent plate 102 and returns to the light receiving unit 103. The amount of light decreases.
Due to the deterioration of the toner scattering with time, the level of the output value of the toner scattering detection sensor 100 proceeds from L1 → L2 → L3 → L4. For example, if the level of the normal use range is up to L3 and the output of the toner scattering detection sensor 100 falls below L3, a developer replacement signal is output.
Although the display of the replacement signal is not shown, it is configured to be displayed on a display panel (operation panel) provided in the image forming apparatus.

トナー飛散の進行状況を検知して、リサイクルトナーを使用する割合を決めることができるので、早期にリサイクルトナーの使用を抑制しなくてもよく、最大限にリサイクルトナーの利用ができるという効果がある。 Further, when the developer is continuously used without replacing the developer and the level of the output value reaches L4, it is judged that the deterioration of the developer has reached the limit, and if the toner is continuously used as it is, the toner scattering further increases. Therefore, it is preferable to issue a signal for prohibiting the operation of the image forming apparatus and stop the image forming operation of the main body so as not to increase damage.
Here, another operation example performed based on the output value of the toner scattering detection sensor 100 will be described. In general, in an image forming apparatus capable of toner recycling, agglomerated toner having paper dust as a core adheres to a developer regulating member (not shown) in the developing device 30 over time, leading to an insufficient amount of developer pumped up, resulting in an image. Problems such as missing and toner scattering occur. In addition, toner scattering with the progress of developer deterioration also proceeds at the same time.
Therefore, as the level of the output value of the toner scattering detection sensor 100 advances from L1 → L2 → L3, as an example, the clutch of the recycled toner conveying screw 62 is stepwise to prevent the toner scattering deterioration from progressing. The ratio of the time to turn on the clutch 64 is decreased in the ratio of the time to turn on the 64 and the time to turn off the 64. Table 1 shows an example of a change in the amount of recycled toner based on the output value of the toner scattering detection sensor. As shown in Table 1, as the developer deteriorates, the ratio of using the recycled toner is decreased.

Since it is possible to detect the progress of toner scattering and determine the proportion of recycled toner to be used, there is no need to suppress the use of recycled toner at an early stage, and the use of recycled toner is maximized. .

ワイヤクリーナの動作は一般的には、電源ＯＮ時のウオームアップ時間中に行ったり、所定の枚数以上のコピー後のジョブエンド後に自動的に実行される。
ワイヤクリーナの動作時は、ジョブが停止するので、不必要にワイヤクリーナの動作を行うとコピー生産性が低下してしまう問題がある。
トナー飛散の進行状況を検知して、効果的なタイミングにてワイヤクリーナの動作を行うことができるので、コピー生産性の低下を最小限に押さえながら、帯電ムラによる異常画像を防止できるという効果がある。 Further, in order to prevent an abnormal image due to uneven charging due to dirt on the wire of the charger 20 due to toner scattering, for example, the level of the output value of the toner scattering detection sensor 100 proceeds from L1 → L2 → L3. Table 2 is an example of a change in the operation interval of the wire cleaner of the charging charger 20 based on the output value of the toner scattering detection sensor 100. As shown in Table 2, the operation interval of the wire cleaner is shortened.

The operation of the wire cleaner is generally performed during a warm-up time when the power is turned on or automatically after a job end after a predetermined number of copies or more.
Since the job is stopped during the operation of the wire cleaner, if the wire cleaner is operated unnecessarily, there is a problem that the copy productivity is lowered.
The progress of toner scattering can be detected and the wire cleaner can be operated at an effective timing, so that it is possible to prevent abnormal images due to uneven charging while minimizing the reduction in copy productivity. is there.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a partial plan view of an image forming apparatus according to an embodiment of the present invention. It is the schematic which shows the structure of a wire cleaner. FIG. 6 is a schematic diagram illustrating a state in which waste toner is conveyed from a cleaning device to a developing device. FIG. 3 is an enlarged cross-sectional view of a toner scattering detection sensor provided in the vicinity of a developing device according to an embodiment of the present invention. FIG. 3 is a front view of the toner scattering detection sensor according to the embodiment of the present invention as viewed from the photosensitive drum side. 6 is a detection result of toner scattering by a toner scattering detection sensor according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Photoconductor drum 20 Charger charger 21 Charger main body 22 Wire 25 Wire cleaner 26 Cleaner member 30 Developing device 31 Developing roller 32 Paddle 33 Stirring member 34 Case 35 Opening 36 Toner supply roller 37 Toner hopper 38 Agitator 39 Toner conveying screw 40 Toner Collection Port 41 Toner Bottle 42 Toner Replenishment Port 43 Toner Supply Roller Drive Motor 44 Drive Motor Driver 50 Cleaning Device 51 Cleaning Blade 52 Waste Toner Bottle 53 Conveying Screw 60 Toner Conveying Device 61 Conveying Pipe 62 Conveying Screw 63 Drum Motor 64 Clutch 70 Reflection density sensor 71 Microcomputer 72 CPU
73 A / D converter 74 Microcomputer RAM
75 Microcomputer ROM
80 Transfer Charger 81 Separation Charger 82 Eraser 100 Toner Scattering Detection Sensor 101 Light Emitting Unit 102 Transparent Plate 103 Light Receiving Unit 104 Case T Toner

Claims (5)

An image carrier that is driven to rotate;
A developing device that visualizes the electrostatic latent image formed on the image carrier with a two-component developer;
In an image forming apparatus having a toner scattering detection sensor in the vicinity of a developing device,
The toner scattering detection sensor detects light irradiated from the developing device side by receiving reflected light from a member near the developing device or a developing device member and an image carrier. The image forming apparatus includes a toner recycling mechanism that collects toner remaining on the image carrier in a developing device;
The image forming apparatus according to claim 1, wherein the amount of recycled toner collected by the developing device is changed based on an output value of the toner scattering detection sensor. The image forming apparatus includes a charging device that charges the surface of the image carrier to a desired potential, and a charge cleaning unit that cleans the charging device.
The image forming apparatus according to claim 1, wherein the number of times the charging device is cleaned is changed based on an output value of the toner scattering detection sensor. The image forming apparatus according to claim 1, wherein the image forming apparatus outputs a developer replacement signal based on an output value of the toner scattering detection sensor. The image forming apparatus according to claim 1, wherein the image forming apparatus outputs a signal for prohibiting operation of the image forming apparatus based on an output value of the toner scattering detection sensor. .

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