JP4984483B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that determines the life of a unit that performs an operation of an electrophotographic process.

  In general, the life of each part in an image forming apparatus using an electrophotographic process is determined based on the number of printed sheets and the cumulative number of rotations of members. In this method, the difference in load on the image forming apparatus increases depending on the operating conditions of the image forming apparatus (for example, the black and white ratio of the print image, the size of the job, etc.) and the installation environment (temperature, humidity, etc.). The judgment may be wrong.

  In addition, as another method, a method of determining the life of an endless belt-like member based on whether or not a minute elastic wave vibration generated due to deformation and destruction of the endless belt-like member is detected (for example, see Patent Document 1). A method for determining the life of the cleaning roll according to the amount of deposits deposited on the cleaning roll (see, for example, Patent Document 2), and a method for determining the life of the photosensitive drum according to the surface resistance value of the photosensitive drum ( For example, see Patent Document 3).

Here, these methods are specialized for determining the lifetime of a specific member. However, even if the specific member itself does not reach the end of its life, it may affect image formation from the unit including the member. If a significant vibration is occurring, the unit should be determined to have a lifetime. However, until now, no method has been devised for determining the lifetime of a unit.
JP 2002-211952 A JP 2000-131989 JP 9-319271 A

  The present invention has been made in consideration of the above facts, and by always appropriately determining the life of a unit that performs an operation of an electrophotographic process and replacing the unit, a print image free from image quality defects is always output. With the goal.

The image forming apparatus according to claim 1 is an image forming apparatus in which a plurality of units that perform an image forming operation of an electrophotographic process can be replaced, and vibration detection means that detects vibrations generated in the units; When the maximum value of the amplitude of vibration detected by the vibration detection means exceeds a threshold, it is determined that the unit has reached the end of life by the life determination means for determining that the unit has reached the end of life. And notification means for notifying the replacement of the unit, wherein the life determination means stores a plurality of predetermined frequencies known in advance for each unit as a frequency at which banding is likely to occur, A predetermined frequency and a frequency of vibration generated in the unit are stored in association with each other, and the plurality of predetermined frequencies are selected from vibrations detected by the vibration detecting means. When the maximum value of the amplitude of any of the vibrations exceeds the threshold value of the amplitude set for each predetermined frequency, the unit stored in association with the predetermined frequency of the vibration has reached the end of its life It is characterized by determining .

  In the image forming apparatus according to the first aspect, the units that perform the image forming operation of the electrophotographic process, such as the photoconductor and the developing device, are replaceable, and it is determined by the life determination means that the unit has reached the end of its life. Then, the replacement of the unit is notified by the notification means.

  By the way, the life of the unit is determined by a method in which the vibration generated in the unit is detected by the vibration detecting means, and the life determining means determines whether or not the maximum amplitude of the detected vibration exceeds the threshold value. It has been broken.

  Here, when the gears and bearings in the unit are worn, a large vibration is generated with the worn gears and bearings as the vibration source, and the striped shading unevenness (so-called banding) exceeds the allowable value. Defects occur.

  Therefore, in the present invention, when a large vibration is generated from the unit, it is determined that the unit has reached the end of life, and the replacement of the unit is notified. As a result, a print image without image quality defects can always be output.

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect , wherein the vibration detecting unit is provided in the unit that performs an image forming operation of a color other than yellow.

  Here, yellow banding has low visibility and high tolerance. Therefore, in the image forming apparatus according to the fourth aspect, the vibration detection means is attached only to the unit that performs the image forming operation of colors other than yellow in consideration of the cost, and the life determination is performed only for the unit. .

  Since the present invention is configured as described above, it is possible to always output a print image free from image quality defects by appropriately determining the lifetime of the unit that performs the operation of the electrophotographic process and replacing the unit.

  A first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration of a laser beam printer 11 according to an embodiment of the present invention. The laser beam printer 11 forms an image on the recording paper P by applying a known electrophotographic process. The known electrophotographic process is formed on the photosensitive drum 12 through charging of the photosensitive drum 12, formation of an electrostatic latent image by exposure to the photosensitive drum 12, and development of the electrostatic latent image with toner. This is a series of processes for recording an image by transferring the toner image to the recording paper P and fixing the toner image on the recording paper P.

  The laser beam printer 11 is capable of forming a color image on the recording paper P using yellow, magenta, cyan, and black toners.

  As shown in FIG. 1, the laser beam printer 11 has a paper feeding unit 20 disposed at the bottom. The paper feed unit 20 is provided with a paper feed cassette 21 in which the recording paper P is accommodated.

  An image forming unit 30 is disposed above the paper feeding unit 20. The image forming unit 30 forms a color image on the recording paper P sent from the paper supply unit 20 by the known electrophotographic process described above.

  A paper discharge tray 40 from which the recording paper P is discharged is disposed obliquely below the image forming unit 30, and a transport unit 100 is provided on the left side of the paper discharge tray 40. The transport unit 100 transports the recording paper P on which an image has been formed by the image forming unit 30 to the paper discharge tray 40 and discharges it.

  Next, an outline of the configuration of the image forming unit 30 and an outline of a process for forming a color image on the recording paper P will be described.

  As shown in FIG. 1, in the image forming unit 30, four photosensitive drums 12 are rotatably arranged in the order of yellow, magenta, cyan, and black from the right side in the drawing. Each photosensitive drum 12 is rotated in the direction of arrow K by a motor (not shown).

  A charger 14 is disposed above each photoconductor drum 12, and a charging bias Vc is applied to the charger 14 to charge the surface of the photoconductor drum 12 to a predetermined potential. After charging, exposure is performed by light emitted from an exposure head 16 disposed above the photosensitive drum 12, and a latent image corresponding to image information is formed on the surface of the photosensitive drum 12. Each color toner charged to a predetermined polarity is carried on the developing roller 19 of each color developing unit 18. The latent image formed on the surface of each photosensitive drum 12 is developed by applying a developing bias Vd to the developing roller 19 and becomes a toner image of each color.

  The toner images of the respective colors respectively formed on the four photosensitive drums 12 are transferred by the first transfer roller 15 onto the intermediate transfer belt 13 disposed below the photosensitive drums 12, and are then transferred onto the intermediate transfer belt 13. To be a full-color toner image.

  On the other hand, the recording paper P stored in the paper feed cassette 21 is sent out by the pickup roller 26 and sent to the image forming unit 30 by the transport roller 28.

  The recording paper P sent to the image forming unit 30 is sent to a nip portion between the second transfer roller 32 and the intermediate transfer roller 34 by a registration roller 68 at a predetermined timing, and a full-color toner image is transferred to the recording paper P. The The toner image is transferred to the surface of the recording paper P on the intermediate transfer roller 34 side.

  The recording paper P on which the full-color toner image is transferred is sent to the fixing device 36. The fixing device 36 fixes the toner image on the recording paper P with heat and pressure. The recording paper P on which the toner image is fixed is discharged to the paper discharge tray 40 by the discharge roller 42.

  On the other hand, the toner image is not completely transferred to the intermediate transfer belt 13 and the recording paper P, and a part thereof remains as residual toner on the photosensitive drum 12 and the intermediate transfer belt 13. This residual toner is removed by the cleaning device 44 on the photosensitive drum 12 or the cleaning device 38 on the intermediate transfer belt.

  Here, in the laser beam printer 11 of this embodiment, the photosensitive drum 12 that performs the operation of the electrophotographic process, the charger 14, the exposure head 16, the developing unit 18, the transfer unit 23 including the intermediate transfer belt 13, and the cleaning device 44. The life of the developer 18 as a unit that affects the operation of the electrophotographic process is determined by the occurrence of vibration due to the deterioration of the components. It has come to be. Hereinafter, a configuration for determining the lifetime of the developing unit 18 as a unit will be described.

  As shown in FIG. 1, an acceleration sensor 50 serving as a vibration detection unit is installed in the M, C, and K developing devices 18. Each acceleration sensor 50 is connected to a life determination unit 51 (see FIG. 2). The life determination unit 51 is provided with a low-pass filter 52, an FFT (Fast Fourier Transform) analyzer 54, a comparator 56, and a CPU 58 (both see FIG. 2).

  Each acceleration sensor 50 is connected to the FFT analyzer 54 via a low-pass filter 52, and the time waveform output from each acceleration sensor 50 is subjected to low-pass filter processing by the low-pass filter 52. Here, only the low frequency band that can be reproduced by the electrophotographic process passes. Then, the time waveform of the frequency that has passed through the low-pass filter 54 is input to the FFT analyzer 54. Then, the FFT analyzer 54 performs an FFT process and extracts only a specific frequency from the time waveform.

  By the way, when the gear wears, the meshing state of the gears that mesh with each other fluctuates, and the rotational variation of the gears that mesh with each other occurs to generate vibration. Further, when the bearing is worn, the support state of the rotating shaft supported by the bearing becomes unstable and vibration is generated. The generated vibration resonates with the mirror of the exposure head 16 and the scanning speed of the laser beam in the sub-scanning direction fluctuates, and the photosensitive drum 12 vibrates in the sub-scanning direction, thereby The pixel position is changed on the drum 12. Further, the developing roller 19 and the photosensitive drum 12 are vibrated and the gap between the developing roller 19 and the photosensitive drum 12 is changed, so that the dot diameter is changed on the photosensitive drum 12. As a result, banding occurs, resulting in image quality defects.

  Here, the frequency of vibration generated in the developing device 18 is known in advance by experiments or the like and stored in the CPU 58. Of the frequencies stored in the CPU 58, a frequency at which banding is likely to occur (for example, the same frequency as the natural frequency of the exposure head 16 or the photosensitive drum 12 or the gear meshing frequency) is known in advance by experiments or the like. This frequency is extracted by the FFT analyzer 54.

  A comparator 56 and a CPU 58 are connected to the FFT analyzer 54. The comparator 56 stores a threshold value of the maximum value of the vibration amplitude of the frequency extracted by the FFT analyzer 54, and outputs the comparison result.

  Here, the amplitude value of vibration when banding exceeding the allowable value occurs is known by experiment or the like for each frequency, and this amplitude value is stored in the comparator 56 as a threshold value.

  A CPU 58 is connected to the comparator 56. The CPU 58 determines the lifetime of the developing unit 18 as a unit according to the comparison result output from the comparator 56 and outputs the determination result. Here, when the maximum value of the vibration amplitude of the frequency extracted by the FFT analyzer 54 exceeds the threshold value, the CPU 58 determines that the developing unit 18 has reached the lifetime as a unit.

  The CPU 58 includes a display panel control unit 62 (see FIG. 2) for controlling the display panel 60 (see FIG. 2) and a warning buzzer control unit 66 (for controlling on / off of the warning buzzer 64 (see FIG. 2)). Are connected). When the CPU 58 determines that the developing unit 18 has reached the end of its life as a unit, the display panel control unit 62 causes the display panel 60 to display a warning display for notifying the replacement time of the developing unit 18, and a warning buzzer. The controller 66 turns on the warning buzzer 64.

  After that, when the developing unit 18 is replaced with a new one, a large vibration that causes banding exceeding the allowable value from the new developing unit 18 does not occur, so that the warning display is not displayed on the display panel 60 and the warning buzzer is displayed. 64 is not activated.

  As described above, in the present embodiment, whether or not the vibration that causes banding to exceed the allowable value is generated from the M, C, and K color developing devices 18 that are units that perform the operation of the electrophotographic process, The life of the developing unit 18 is determined. As a result, a print image without banding exceeding the allowable value can always be output.

  Here, the banding of Y color has low visibility and high tolerance. For this reason, in this embodiment, considering the cost, the acceleration sensor 50 is not attached to the Y-color developing device 18 so that the life of the Y-color developing device 18 is not determined.

  In the present embodiment, the acceleration sensor 50 is provided only in the developing device 18. However, if there is another unit that generates vibrations that cause banding and other image defects, the acceleration is also applied to the unit. It is desirable to attach the sensor 50 and determine the life of the unit in the same manner as the developing unit 18.

  Further, in the present embodiment, vibrations having a frequency at which banding is likely to occur are extracted from a time waveform including vibrations having a number of frequencies, and it is determined whether or not the amplitude exceeds a threshold value for each extracted frequency. Instead of every time, it may be determined whether the amplitude of the time waveform exceeds a threshold value.

  In the present embodiment, extraction of a specific frequency from the time waveform is performed using FFT calculation, but it may be performed using a band pass filter or a notch filter. In addition, a configuration performed by a CPU including all functions of a low-pass filter, an FFT analyzer, and a comparator is also applicable.

  Further, in the present embodiment, an acceleration sensor is used as the vibration detection means, but other means may be used as long as it can detect vibration generated in the unit.

It is a figure which shows schematic structure of the laser beam printer of this embodiment. It is a block diagram which shows schematic structure of the electric system of the laser beam printer of this embodiment.

Explanation of symbols

11 Laser beam printer (image forming device)
18 Developer (unit)
50 Acceleration sensor (vibration detection means)
51 Life judging section (life judging means)
60 Display panel (notification means)
64 Warning buzzer (notification means)

Claims (2)

An image forming apparatus in which a plurality of units that perform an image forming operation of an electrophotographic process can be replaced,
Vibration detecting means for detecting vibration generated in the unit;
Life determination means for determining that the unit has reached the end of its life when the maximum value of the amplitude of vibration detected by the vibration detection means exceeds a threshold;
When the life determining means determines that the unit has reached the end of its life, a notifying means for notifying the replacement of the unit;
Have
The life determination means includes
As a frequency at which banding is likely to occur, a plurality of predetermined frequencies that are known in advance for each unit are stored,
Storing the predetermined frequency and the frequency of vibration generated in the unit in association with each other;
When the vibrations of the plurality of predetermined frequencies are extracted from the vibrations detected by the vibration detection unit, and the maximum value of any amplitude of the vibrations exceeds an amplitude threshold set for each predetermined frequency, An image forming apparatus comprising: determining that a unit stored in association with a predetermined frequency of the vibration has reached the end of its life . The image forming apparatus according to claim 1, wherein the vibration detecting unit is provided in the unit that performs an image forming operation of a color other than yellow.

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