JP2006119279A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of thoroughly age¥ing an image bearing member in a short period of time, and removing extraneous matter such as a discharge product. <P>SOLUTION: A surface of a photoreceptor drum which is the image bearing member is rubbed and polished by a rubbing-polishing roller. The environmental temperature and environmental humidity are detected by a temperature sensor 18a and a humidity sensor 18b, respectively, and when a CPU 22 is set to a refresh mode, the photoreceptor drum and the rubbing-polishing roller are rotated, an image is formed on the photoreceptor drum while applying an electric field whose polarity is reverse to that in the case of transferring a toner image between the photoreceptor drum and a body to be subjected to transfer, and the rotation speed of the rubbing-polishing roller to the photoreceptor drum is changed on the basis of the environmental temperature and environmental humidity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine using an electrophotographic process, and more particularly to an image forming apparatus using an a-Si (amorphous silicon) photoreceptor.

  In general, in an image forming apparatus using an electrophotographic process, a discharge product is generated due to discharge when charging is performed by a corona charger, and the discharge product adheres to an image carrier such as a photosensitive drum. . In particular, in a high humidity environment, the discharge product takes in moisture in the atmosphere, resulting in a decrease in the resistance of the surface of the image carrier. As a result, a lateral flow of electric potential occurs at the edge portion of the electrostatic latent image formed on the surface of the image carrier, and a so-called image flow phenomenon occurs. The a-Si photosensitive member has higher hygroscopicity than OPC and other organic semiconductors. Therefore, the above-described image flow is likely to occur in an image carrier using the a-Si photosensitive member.

  In order to prevent such an image flow phenomenon, an abrasive is mixed into the toner, and a rubbing roller for rubbing and polishing the surface of the image carrier with the abrasive is provided to reduce the resistance of the image carrier surface. The component (that is, the discharge product) is removed. For example, when the image forming process is not performed, such as when the power is turned on or when returning from the energy saving mode, a surface potential is applied to the image carrier. Instead, there is a so-called solid (SOLID) image forming operation in which a large amount of toner is attached to the image carrier by performing a developing operation, and a refresh mode is provided in which the surface of the image carrier is rubbed and polished (see FIG. Patent Document 1).

  By the way, as described above, the decrease in resistance on the surface of the image carrier due to moisture absorption of the discharge product varies greatly depending on environmental conditions such as temperature and humidity. In the refresh mode in which solid image formation is always performed, the friction is irrelevant regardless of the environmental conditions. Since the polishing operation is performed, toner is unnecessarily consumed.

  In order to prevent such a problem, the solid image forming time, that is, the developing time is changed based on the temperature and humidity measured by the temperature and humidity sensor provided in the image forming apparatus, and then supplied to the rubbing polishing roller. There is an apparatus in which the amount of toner is changed to clean the image carrier (see Patent Document 2).

Japanese Patent Laid-Open No. 11-3014 JP 2002-14589 A

  By the way, both Patent Documents 1 and 2 have a problem that it takes time until image formation becomes possible because the refresh mode is performed when the power is turned on or when returning from the energy saving mode, which is troublesome for the user. Furthermore, in the image forming apparatus described in Patent Document 2, the solid image forming time is changed according to the temperature and humidity so that the toner is not consumed unnecessarily, but sufficient polishing is not performed. As a result, an image drift phenomenon may occur.

  As described above, in the image forming apparatuses described in Patent Documents 1 and 2, it is difficult to refresh the image carrier by performing aging of the image carrier in a short time, and further described in Patent Document 2. In the image forming apparatus, there is a problem that the image carrier cannot be sufficiently aged.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of sufficiently aging an image carrier in a short time in view of the problems of the prior art.

  Therefore, in order to solve such problems, the present invention provides an image carrier, a charger for charging the image carrier, an exposure device that exposes the image carrier to form an electrostatic latent image, and the image A developing device that develops the electrostatic latent image formed on the carrier with toner to form a toner image, and the toner image is transferred by a transfer electric field applied between the image carrier and the transfer member. In an image forming apparatus for performing a transfer process for transferring to a body, a rubbing polishing roller for rubbing and polishing the surface of the image carrier, and a temperature / humidity detecting means for detecting temperature / humidity in the environment and outputting a temperature / humidity detection signal In the refresh mode in which the toner is applied to the rubbing and polishing roller without passing through the transfer process and the image bearing member is rubbed and polished, the image bearing member and the rubbing and polishing roller are driven to rotate to carry the image bearing When a toner image is transferred between the body and the transfer target The developing device is controlled with a polar electric field applied to form an image on the image carrier, and the rotational speed of the rubbing polishing roller relative to the image carrier is changed based on the temperature and humidity detection signal. And a control means.

  In the present invention, the control means increases the rotation speed of the rubbing polishing roller with respect to the image carrier as the temperature and humidity indicated by the temperature and humidity detection signal increases. Further, the control means makes the rotation speed of the rubbing polishing roller in the refresh mode higher than the rotation speed of the rubbing polishing roller in the image forming step. The image carrier is, for example, an amorphous silicon photoreceptor, and the charger is, for example, a corona charger.

  As described above, when the image forming apparatus according to the present invention is in the refresh mode, the image carrier and the rubbing polishing roller are rotationally driven to transfer the toner image between the image carrier and the transfer target. An image is formed on the image carrier with an electric field of reverse polarity applied, and the rotation speed of the rubbing polishing roller with respect to the image carrier is changed based on the temperature / humidity detection signal. Accordingly, the discharge product adhering to the surface of the image carrier and absorbing moisture can be removed.As a result, even in a high temperature and high humidity environment, the image carrier is sufficiently aged in a short time to attach the discharge product and the like. The kimono can be removed from the surface of the image carrier, and the image flow phenomenon does not occur.

  In the present invention, as the temperature and humidity indicated by the temperature and humidity detection signal is increased, the rotational speed of the rubbing polishing roller with respect to the image carrier is increased. There is an effect that it is possible to satisfactorily remove deposits such as discharge products adsorbed on the image carrier by absorbing moisture in a humid environment.

  In the present invention, the rotation speed of the rubbing polishing roller in the refresh mode is set higher than the rotation speed of the rubbing polishing roller in the image forming process, that is, the rotation speed of the rubbing polishing roller in the image forming process is refreshed. Since the rotational speed of the rubbing polishing roller is lower than that in the mode, the driving load of the rubbing polishing roller is not increased in the image forming process, and image defects such as image jitter do not occur.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  Referring to FIG. 1, FIG. 1 is a diagram showing a color image forming apparatus which is an example of an image forming apparatus according to the present invention. Here, a color image forming apparatus will be described, but the present invention is only a color image forming apparatus. It can also be applied to a monochrome image forming apparatus. In FIG. 1, the illustrated image forming apparatus includes an a-Si photosensitive drum 1 as an image carrier, an optical scanning unit 2, a corona charger 3, and color developing devices 4 to 7 (for example, yellow (Y), magenta (M ), Cyan (C), black (BK) developing device), a sheet conveying device 9 using an endless belt, and a cleaning unit 10 for cleaning the photosensitive drum 1. A friction polishing roller 15 and a blade 17 are provided.

  An intermediate transfer drum 12 that is a transfer target is in contact with the photosensitive drum 1, and residual toner on the intermediate transfer drum 12 is cleaned by a cleaning unit 11. Further, a secondary transfer roller 13 is disposed in contact with the intermediate transfer drum 12, and a fixing device 14 is disposed downstream of the nip portion between the secondary transfer roller 13 and the intermediate transfer drum 12. Further, a temperature sensor 18a and a humidity sensor 18b for measuring the temperature and humidity inside the apparatus are disposed in the image forming apparatus.

  In the above-described image forming apparatus, first, the cleaning unit 11 and the secondary transfer roller 13 are retracted to the retracted position by a retracting device (not shown), and a high voltage of, for example, +300 V is supplied to the photosensitive drum 1. The intermediate transfer drum 12 is grounded. The photosensitive drum 1 is rotated in the direction indicated by the solid arrow by a drum driving motor (not shown in FIG. 1), and the photosensitive drum 1 is indicated by a solid arrow by the drum driving motor (not shown in FIG. 1). When the surface of the photosensitive drum 1 is charged to, for example, about +800 V by the charger 3 and the photosensitive drum 1 is exposed with an image corresponding to each color by the optical scanning unit 2, the portion exposed to light The (exposed portion) remains at + 300V, and the portion not exposed to light (unexposed portion) remains at + 800V.

  Then, the developing rollers 4a to 7a of the developing devices 4 to 7 are rotationally driven by developing roller driving motors (not shown in FIG. 1), respectively, and the developing rollers of the developing devices corresponding to the developing devices 4 to 7 ( When a development bias is applied to a development bias application unit (not shown in FIG. 1) and development is performed, toner adheres to the exposure unit and a toner image is formed on the photosensitive drum 1. . The toner image moves from the photosensitive drum 1 to the intermediate transfer drum 12 that is at the ground potential at the nip portion where the photosensitive drum 1 and the intermediate transfer drum 12 are in contact, and primary transfer is performed.

  When the toner images of all colors are primarily transferred to the intermediate transfer drum 12, the cleaning unit 11 and the secondary transfer roller 13 are brought into contact with the intermediate transfer drum 12 by the above-described retracting device and transferred to the secondary transfer roller 13. Voltage is applied, the recording medium 8 is conveyed from a paper feed cassette (not shown) to the nip portion between the secondary transfer roller 13 and the intermediate transfer drum 12, and the toner image on the intermediate transfer drum 12 is transferred to the recording medium. Secondary transfer to 8. Thereafter, the recording medium 8 is discharged by being heated and pressurized by the fixing device 14.

  During this time, the cleaning unit 10 uses the residual toner remaining without being transferred from the photosensitive drum 1 to the intermediate transfer drum 12, and is first rubbed by a rubbing roller drive motor (not shown in FIG. 1). The surface of the photosensitive drum 1 is rubbed and polished by the rubbing polishing roller 15, and the remaining toner is scraped off from the surface of the photosensitive drum 1 by the blade 17 to clean the photosensitive drum 1. On the other hand, the residual toner remaining without being transferred from the intermediate transfer drum 12 to the recording medium 8 is cleaned by the cleaning unit 11.

  By the way, as described above, the a-Si photosensitive drum 1 in the high-temperature and high-humidity environment is caused by the moisture absorption of the discharge product and the high hygroscopicity of the a-Si photosensitive drum itself. Moisture is taken into discharge products and the surface resistance of the photosensitive drum 1 is reduced. When such a decrease in surface resistance occurs, image flow tends to occur.

  Here, referring to FIG. 2, the drum driving motor 23, the developing roller driving motor 24, the developing bias applying unit 25, and the rubbing roller driving motor 26 are controlled by a control unit (CPU) 22. A temperature sensor 18a and a humidity sensor 18b are connected to the CPU 22 via the A / D conversion unit 21, and as described later, a temperature detection signal output from the temperature sensor 18a and a humidity detection signal output from the humidity sensor 18b. The drum drive motor 23 and the rubbing roller drive motor 26 are driven and controlled based on the above.

  Although not shown, the CPU 22 is provided with a memory, in which a rubbing roller drive motor rotation speed correction table (hereinafter simply referred to as a correction table) is stored, and the CPU 22 refers to the correction table. The rotation ratio between the rubbing roller driving motor 26 and the drum driving motor 23 (that is, the peripheral speed (linear speed) ratio between the photosensitive drum 1 and the rubbing polishing roller 15) is controlled.

  Referring also to FIG. 3, when the photosensitive drum refresh mode (hereinafter simply referred to as refresh mode) is entered (in this refresh mode, for example, the main switch is turned on and the fixing temperature is lower than a predetermined temperature (for example, 120 ° C.)). 2, although not shown in Fig. 2, the fixing temperature is input to the CPU 22. Further, the user may operate the operation panel to perform the refresh mode. For example, when image flow occurs when image formation is performed, the user operates the operation panel to enter the refresh mode), and a drum refresh operation trigger is generated. The CPU 22 reads the temperature detection signal and the humidity detection signal from the temperature sensor 18a and the humidity sensor 18b, respectively (step S1). .

  Then, the CPU 22 refers to the correction table and determines the rotation speed of the rubbing roller drive motor 15 based on the temperature detection signal and the humidity detection signal (step S2). FIG. 4 is a diagram showing an example of the correction table. In the correction table, temperature is set on the horizontal axis and humidity is set on the vertical axis. In the temperature / humidity region indicated by S1, the linear speed ratio of the rubbing polishing roller 15 to the photosensitive drum 15 is 1.2. In the temperature / humidity region indicated by S2, the anti-photosensitive drum of the rubbing polishing roller 15 is opposed to the photosensitive drum. The linear speed ratio is 1.6. In the temperature / humidity region indicated by S3, the linear speed ratio of the rubbing and polishing roller 15 to the photosensitive drum is 2.0. Thus, as the temperature and humidity increase, the linear speed ratio of the rubbing polishing roller 15 to the photosensitive drum is increased.

  The CPU 22 rotates the rubbing roller drive motor 26 in the temperature and humidity region S1 so that the number of rotations of the rubbing polishing roller 15 is 1.2 × photosensitive drum rotation number × reduction ratio (rpm). (The CPU 22 controls the drum drive motor 23 so that the rotation speed of the photosensitive drum 1 can be known from the rotation speed of the drum drive motor 23). Similarly, in the temperature / humidity region S2, the CPU 22 rubs the rubbing roller drive motor 26 so that the number of rotations of the rubbing polishing roller 15 is 1.6 × photosensitive drum rotation number × reduction ratio (rpm). In the temperature and humidity region S3, the rubbing roller drive motor 26 is set so that the number of revolutions of the rubbing polishing roller 15 is 2.0 × photosensitive drum rotation number × reduction ratio (rpm). Is determined (step S2).

  After determining the rotation speed of the rubbing roller drive motor 26 as described above, the CPU 22 starts a drum refresh operation (step S3). When the drum refresh operation is started, the CPU 22 controls the developing bias application unit 25 without applying a high voltage to the photosensitive drum 1, that is, with the high voltage turned off, for example, the photosensitive drum. The developing bias is applied for a predetermined time only to the developing device on the most downstream side in the rotation direction, that is, the black (BK) developing device 7. At this time, a voltage having the same polarity as the toner (+300 V, +600 V with respect to the ground) is applied to the intermediate transfer drum 12 with reference to the potential (300 V) of the photosensitive drum 1.

  The color image forming apparatus consumes the largest amount of black (BK) toner. For this reason, the toner amount that can be accommodated in a black toner container (not shown) can be accommodated more than other colors. Further, when black is developed first, other colors become cloudy, and therefore, the black developing device 7 is usually disposed on the most downstream side in the rotation direction of the photosensitive drum 1. Therefore, if an abrasive having a polishing effect is added to the black toner used in the developing device 7 arranged at the most downstream side and the discharge product is cleaned as described later, this occurs when other colors are used. There is no imbalance in toner consumption.

  Note that not only the black toner but also the toner of other colors may be added with an abrasive, and the discharge product may be cleaned with the toner added with the abrasive. Furthermore, the developing devices 4 to 7 may be appropriately selected so that the same amount of toner is consumed when the photosensitive drum 1 is cleaned by adding an abrasive to all color toners. .

  In this way, a solid image is formed on the photosensitive drum 11, but a voltage having the same polarity as that of the toner having a polarity opposite to that at the time of transfer is applied to the intermediate transfer drum 12 with reference to the photosensitive drum 1. The solid image reaches the rubbing and polishing roller 15 of the cleaning unit 10 without being transferred to the intermediate transfer drum 1 side. Then, the rubbing polishing roller 15 rubs and polishes the surface of the photosensitive drum 1 with an abrasive contained in the toner, and cleans discharge products and other adhering substances adhering to the surface of the photosensitive drum 1. Remove.

  At this time, as described above, the rotational speed of the rubbing polishing roller 15 is set according to the environmental temperature and humidity, and the rotational speed of the rubbing polishing roller 15 is larger than the rotational speed of the photosensitive drum 1. The rubbing property of the surface of the photosensitive drum by the rubbing and polishing roller 15 is improved, and deposits such as discharge products can be satisfactorily removed by rubbing. Since the rotational speed of the rubbing polishing roller 15 becomes higher than the rotational speed of the photosensitive drum 1 as the temperature and humidity increase, the rubbing by the rubbing polishing roller 15 occurs at high temperature and high humidity. In addition, the surface of the photosensitive drum can be aged in a short time to remove deposits such as discharge products.

  In any case, when the rotational speed of the rubbing polishing roller 15 is changed according to the environmental temperature and humidity as described above, that is, in the refresh mode, the rotational speed of the rubbing polishing roller 15 is The rotational speed of the rubbing polishing roller 15 at the time of formation is increased (in the refresh mode, the peripheral speed ratio between the rubbing polishing roller 15 and the photosensitive drum 1 is made larger than that at the time of image formation). The CPU 22, the drum drive motor 23, the development roller drive motor 24, the development bias application unit 25, and the rubbing roller drive motor 26 function as control means.

  When the refresh operation is completed in this way, the CPU 22 performs control to apply a high voltage to the photosensitive drum 1 and applies an electric potential having the same polarity as that of the toner based on the photosensitive drum 1 to the intermediate transfer drum 12. Stop and return to the ground potential to return to the normal image forming process. When returning to the normal image forming process, as a result of removing the deposits such as discharge products as described above, even if the environmental temperature and humidity rise, moisture remains on the surface of the photosensitive drum 1. There is no adhesion and no image drift phenomenon occurs.

  By the way, when the image forming apparatus is left for 24 hours and the refresh operation as described above is performed, the peripheral speed ratio between the rubbing polishing roller 15 and the photosensitive drum 1 is changed to change the peripheral speed ratio and the refresh operation time ( The refresh operation time is the time required to remove deposits such as discharge products on the photosensitive drum 1 to such an extent that the image flow phenomenon does not occur). Results were obtained. In FIG. 5, a straight line A is a straight line showing the relationship between the peripheral speed ratio at a temperature of 30 ° C. and a humidity of 80% and the refresh time, and a straight line B is a peripheral speed ratio and a refresh time at a temperature of 30 ° C. and a humidity of 70% The straight line C indicating the relationship between the peripheral speed ratio and the refresh time when the temperature is 30 ° C. and the humidity is 60% is a straight line. Here, the time from when the main switch is turned on until the fixing device warms up and image formation becomes possible, that is, the time during which the refresh operation can be performed is defined as the refresh operation time threshold Th. The refresh operation time threshold value Th is, for example, 80 seconds.

  As apparent from FIG. 5, in the straight line A, when the peripheral speed ratio becomes 2.0, the refresh operation time becomes 80 seconds or less, and in the straight line B, the refresh operation time becomes when the peripheral speed ratio becomes 1.6. 80 seconds or less. In addition, in the straight line C, it can be seen that when the peripheral speed ratio is 1.2, the refresh operation time is 80 seconds or less. Thus, it can be seen that when the peripheral speed ratio is increased as the temperature and humidity become higher, the photosensitive drum 1 can be aged in a short time, and deposits such as discharge products can be removed well in a short time. Increasing the peripheral speed ratio inevitably increases the driving load of the rubbing polishing roller 15. Therefore, increasing the peripheral speed ratio during image formation may cause image defects such as image jitter. It is desirable to increase the peripheral speed ratio only at this time. FIG. 5 is an example, and the peripheral speed ratio between the rubbing polishing roller 15 and the photosensitive drum 1 needs to be set differently depending on the length of the refresh operation time threshold Th that can perform the refresh operation.

  In the above-described first embodiment, the color image forming apparatus has been described. Similarly, in the monochrome image forming apparatus, in the refresh mode, the peripheral speed ratio between the rubbing polishing roller and the photosensitive drum is increased to increase the photosensitive drum. If the surface of 1 is rubbed and polished, the image flow phenomenon will not occur. In the case of a monochrome image forming apparatus, a recording sheet is a transfer target.

  In the refresh mode, the photosensitive drum and the rubbing polishing roller are driven to rotate, and an electric field having a polarity opposite to that in the case of transferring the toner image between the photosensitive drum and the transfer target (for example, an intermediate transfer drum) is applied. In this state, an image is formed on the photosensitive drum, and the rotation speed of the rubbing polishing roller with respect to the photosensitive drum is changed based on the temperature / humidity detection signal. As a result of being able to remove the discharge product adhering to and adsorbing moisture, it can be applied to, for example, an image forming apparatus using a corona charger as a charger.

It is a figure which shows an example of the image forming apparatus by Example 1 of this invention. FIG. 2 is a block diagram illustrating an example of a control drive system used in the image forming apparatus illustrated in FIG. 1. 3 is a flowchart for explaining a control operation in a refresh mode in the image forming apparatus shown in FIG. It is a figure which shows an example of the correction table memorize | stored in CPU shown in FIG. It is a figure which shows the relationship between the refresh operation time and circumferential speed ratio at the time of changing the circumferential speed ratio of a photoconductive drum and a rubbing polishing roller by the difference in temperature / humidity environment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 a-Si photosensitive drum 2 Optical scanning unit 3 Corona charger 4-7 Developing apparatus 9 Paper conveyance apparatus 10,11 Cleaning unit 12 Intermediate transfer drum 14 Fixing device 15 Rub grinding roller 17 Blade 18a Temperature sensor 18b Humidity sensor 21 A / D conversion unit 22 Control unit (CPU)
23 Drum drive motor 24 Development roller drive motor 25 Development bias application unit 26 Rub roller drive motor

Claims (5)

An image carrier, a charger that charges the image carrier, an exposure device that exposes the image carrier to form an electrostatic latent image, and an electrostatic latent image formed on the image carrier as a toner An image forming apparatus that performs a transfer process of transferring the toner image to a transfer object by a transfer electric field applied between the image carrier and the transfer object.
A rubbing and polishing roller for rubbing and polishing the surface of the image carrier;
Temperature and humidity detection means for detecting temperature and humidity in the environment and outputting a temperature and humidity detection signal;
In the refresh mode in which the toner is applied to the rubbing and polishing roller without passing through the transfer step and the image carrier is rubbed and polished, the image carrier and the rubbing and polishing roller are driven to rotate, and the image carrier and The developing device is controlled to form an image on the image carrier while an electric field having a reverse polarity is applied to the case where a toner image is transferred between the transfer materials, and the rubbing against the image carrier is performed. An image forming apparatus comprising: a control unit that changes a rotational speed of the polishing roller based on the temperature and humidity detection signal.   2. The image forming apparatus according to claim 1, wherein the controller increases the rotational speed of the rubbing polishing roller with respect to the image carrier as the temperature and humidity indicated by the temperature and humidity detection signal increases. apparatus.   3. The image forming apparatus according to claim 2, wherein the control unit is configured to make a rotation speed of the rubbing polishing roller in the refresh mode higher than a rotation speed of the rubbing polishing roller in the image forming step. apparatus.   2. The image forming apparatus according to claim 1, wherein the image carrier is an amorphous silicon photoconductor.   The image forming apparatus according to claim 1, wherein the charger is a corona charger.

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