JP2009223156A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the occurrence of image-flowing in a short period of time without excessively consuming toner. <P>SOLUTION: The image forming apparatus has a refreshing mode to supply the toner from a developing apparatus to a photoreceptor during a non-image forming period. The refreshing mode comprises a base unit A set so that a large amount of toner is supplied, and a base unit B set so that a small amount of toner is supplied. In this case, the base unit means to rotate the photoreceptor for a predetermined period after applying the toner to the photoreceptor surface with a predetermined developing bias voltage in a predetermined developing bias period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

As charging means for uniformly charging the photosensitive member, those utilizing discharge are known. When the discharge is used, discharge products such as ozone and nitrogen oxide are generated along with the discharge.
In the charging roller method, discharge occurs only between the charging roller and the photoconductor, so that the amount of discharge products generated is smaller than that in the charging charger method.

  However, since the discharge concentrates in a narrow space between the charging roller and the photoconductor, the amount of discharge products adhering to the surface of the photoconductor increases. In particular, in the case of a charging roller to which an AC voltage is applied, this tendency is more remarkable because the number of discharges is increased. Since this discharge product is a hydrophilic substance, if the discharge product adheres to the surface of the photoreceptor, the electrical resistance of the surface of the photoreceptor may be reduced, and image flow may be caused in a high temperature and high humidity environment. In particular, when a photosensitive member that is difficult to remove the photosensitive layer, such as an amorphous silicon photosensitive member, is used, the image flow becomes remarkable.

  On the other hand, although the charging charger method generates a larger amount of discharge products than the charging roller method, the concentration of discharge in the space between the charging charger and the photoconductor is smaller than that of the charging roller method. The amount of discharge products adhering to the surface of the photoreceptor is reduced. However, the amount of discharge products adhering to the charger itself increases. In particular, when left in a high-temperature and high-humidity environment, the discharge product adhering to the charger itself tends to move to the opposing photoreceptor surface. For this reason, the image flow in a high temperature and high humidity environment is lighter than the charging roller method in most parts, but the image flow is severe in the part corresponding to the opposite part of the charging charger. It becomes easy.

  As described above, in the charging roller method, image flow is likely to occur in a portion corresponding to the entire area of the photoconductor. On the other hand, in the charging charger method, the image flow level is better than the charging roller in most regions. The portion corresponding to the charger-facing portion tends to cause a worse image flow than the charging roller.

  Therefore, as a measure for removing the discharge products attached to the surface of the photosensitive member and maintaining the image quality, by providing an elastic roller that contacts the photosensitive member and rotates with a rotational speed difference with respect to the photosensitive member, A method has been proposed in which the surface of the photoreceptor is polished to remove discharge products adhering to the surface of the photoreceptor (see Patent Document 1).

  However, it is difficult to always keep the surface of the photoconductor in the same state as a new one, and discharge products are gradually accumulated on the surface of the photoconductor. For this reason, when the image forming apparatus is turned off and left in a high temperature and high humidity environment for a long time, image flow occurs immediately after the image forming apparatus is turned on. In order to prevent the occurrence of this image flow, immediately after turning on the power of the image forming apparatus, toner adheres to the photoreceptor, and the toner is supplied to the cleaning unit to polish the surface of the photoreceptor. A method is employed in which discharge products and moisture adhering to the surface are removed (refresh mode), and then printing is performed.

  Note that Patent Documents 2 and 3 describe techniques for toner supply in the refresh mode. Further, Patent Document 4 describes a method of performing a refresh mode by determining the amount of discharge products accumulated on a photoconductor from the number of images and changing the amount of toner deposited on the photoconductor accordingly. ing.

Japanese Patent Laid-Open No. 10-312139 JP 7-234619 A JP 2005-208276 A Japanese Patent No. 3372880

  By the way, the water adhering to the surface of the photoreceptor reduces the polishing action of the toner. For this reason, it is preferable to quickly remove moisture by increasing the amount of toner supplied to the photoreceptor and causing the moisture adhering to the surface of the photoreceptor to adhere to the toner. On the other hand, in a photoconductor from which moisture on the surface of the photoconductor is almost removed, the amount of toner used for polishing for removing discharge products in the cleaning unit is limited even if the amount of toner supplied to the photoconductor is increased. Therefore, the polishing effect is not improved.

  In the conventional image forming apparatus, the amount of toner supplied to the surface of the photoreceptor is always set constant during the refresh operation. Therefore, when a large amount of toner is set in order to quickly remove the water adhering to the surface of the photoconductor, the water adhering to the surface of the photoconductor can be efficiently removed, but the discharge product can be removed. Therefore, since the amount of toner used for polishing is limited, the polishing effect is not enhanced and excessive toner is consumed wastefully.

  On the other hand, when the toner supply amount is set to be small so as not to waste toner in the polishing for removing the discharge product, the amount of toner used for the polishing for removing the discharge product is appropriate. The amount of water adhering to the surface of the photosensitive member is not sufficient in order to quickly remove it, and the start-up time from when the image forming apparatus is turned on until it becomes ready for printing becomes longer. Become.

  Therefore, a main object of the present invention is to provide an image forming apparatus that can suppress the occurrence of image flow in a short time without excessive consumption of toner.

  The invention according to claim 1 is a photoconductor, a developing device that visualizes an electrostatic latent image formed on the surface of the photoconductor with toner, and a cleaning device that contacts the photoconductor surface and cleans the photoconductor surface. The image forming apparatus includes a refresh mode in which toner is supplied to the photosensitive member by a developing device during non-image formation, and the refresh mode includes a basic unit A in which a large amount of toner is supplied and An image forming apparatus comprising a basic unit B in which a toner supply amount is set to be small. Here, the basic unit means that after the toner is adhered to the surface of the photoconductor with a predetermined development bias voltage and development bias time, the photoconductor is rotated for a predetermined time.

  According to the first aspect of the present invention, first, toner is supplied to the entire surface of the photosensitive member in the basic unit A having a large toner supply amount, and most of the water adhering to the photosensitive member surface is quickly removed by a sufficient amount of toner. . Thereafter, in the basic unit B in which the toner supply amount is set to be small, discharge products adhering to the surface of the photosensitive member are efficiently removed with a minimum amount of toner.

  The invention according to claim 2 is an invention dependent on the invention according to claim 1, comprising a sensor for detecting the in-machine temperature, the outside temperature, and the outside humidity of the image forming apparatus, and based on the detection value of the sensor. An image forming apparatus that determines execution of a refresh mode.

  If the external environment is not hot and humid when the image forming apparatus is turned on, the discharge product absorbs less water and it is difficult to place an image flow due to the discharge product, so there is no need to perform the refresh mode. According to the second aspect of the present invention, unnecessary operations are omitted by determining whether or not to perform the refresh mode based on the detection values of the sensors that detect the in-machine temperature, the outside temperature, and the outside humidity of the image forming apparatus. Thus, the start-up time of the image forming apparatus is shortened.

  The invention according to claim 3 is an invention dependent on the invention according to claim 1 or claim 2, wherein the development bias time of the basic unit A is set to be longer than the time required for one rotation of the photoreceptor. An image forming apparatus is characterized.

  According to the third aspect of the present invention, since the developing bias time of the basic unit A is set to be longer than the time required for one rotation of the photosensitive member, the toner is reliably supplied to the entire surface of the photosensitive member. Moisture can be reliably removed.

  The invention according to claim 4 is an invention dependent on the invention according to any one of claims 1 to 3, wherein the cleaning device includes a cleaning blade and a cleaning roller. Device.

  In the invention of claim 4, since the cleaning device includes the cleaning blade and the cleaning roller, it is possible to reliably remove moisture and discharge products adhering to the surface of the photoreceptor.

  The invention according to claim 5 is an image forming apparatus according to any one of claims 1 to 4, wherein the toner contains abrasive particles.

  The toner used to perform the refresh mode has a reduced polishing ability when discharge products and moisture adhere to it. In the invention of claim 5, since the toner contains the abrasive particles, it is possible to suppress a decrease in the polishing ability of the toner.

  A sixth aspect of the present invention is an image forming apparatus according to the first to fifth aspects of the present invention, wherein the photoconductor is made of amorphous silicon.

  According to the sixth aspect of the present invention, a good image can be provided in the long term even with an image forming apparatus using an amorphous silicon photoconductor that is liable to cause image flow.

  According to the image forming apparatus of the present invention, first, in the basic unit A in which the toner supply amount is set to be large, most of the water adhering to the surface of the photoconductor is quickly removed with a sufficient amount of toner, and then the toner supply amount is In the basic unit B set to be small, discharge products adhering to the surface of the photoreceptor are removed with a minimum amount of toner. As a result, it is possible to obtain an image forming apparatus that can suppress the occurrence of image flow in a short time without excessive consumption of toner.

  The above-described object, other objects, features, and advantages of the present invention will become more apparent from the following description of the best mode for carrying out the invention with reference to the drawings.

  FIG. 1 is a schematic diagram showing an example of an image forming apparatus (color laser printer) according to the present invention.

  In the lower part of the main body of the image forming apparatus 1, a paper feed unit 2 such as a paper feed cassette that accommodates a stack of stacked paper is provided. At one end portion of the paper feeding unit 2, a separation feeding unit 3 for feeding the stacked paper P one by one from the uppermost paper is provided.

  Above the paper feed unit 2, a conveyance path 5 is formed that extends substantially horizontally from the main body right side surface portion to the main body left side surface portion and further extends upward to the paper discharge tray 4 formed on the upper surface of the main body. A separating / feeding means 3, a conveying roller pair 6, a secondary transfer roller 7, a fixing roller pair 8, conveying roller pairs 9 and 10, and a discharge roller pair 11 are arranged in this order along the conveying path 5 from the upstream side. .

  An endless annular intermediate transfer belt 12 is rotatably disposed above the horizontal conveyance path 5. The intermediate transfer belt 12 is suspended from a driving roller 13, a driven roller 14, a tension roller 15 and a primary transfer roller 16, and the driving roller 13 is rotated and driven together with the rollers 14, 15, 16 in FIG. As shown by the arrow, it is rotated clockwise. The driving roller 13 is in contact with the secondary transfer roller 7 via the intermediate transfer belt 12, and a cleaning blade 17 is driven downstream of the contact portion (secondary transfer region) in the rotation direction of the intermediate transfer belt 12. 13 is in contact with the intermediate transfer belt 12 so as to be in pressure contact therewith. The primary transfer roller 16 is in contact with a photosensitive drum 18 which is an electrostatic latent image carrier via the intermediate transfer belt 12. The photosensitive drum 18 is made of amorphous silicon or the like.

  The photosensitive drum 18 is rotated counterclockwise by a driving device (not shown), and a charging roller 19, which is a contact charger, a developing unit 20, a primary transfer roller 16, a cleaning roller 21, and a cleaning blade are sequentially arranged along the rotation direction. 22 is disposed. The charging roller 19 abuts on the upper portion of the photosensitive drum 18 and rotates following the rotation of the photosensitive drum 18. On the opposite side of the charging roller 19 that is in contact with the photosensitive drum 18, a conductive brush roller 23 that is a charger cleaning member is disposed in contact with the charging roller 19 in the longitudinal direction. A laser optical unit 24 using a known optical system is disposed above the developing unit 20.

  The developing unit 20 has a substantially cylindrical shape as a whole, and is supported rotatably at both ends thereof. The interior of the developing unit 20 is divided into four rooms by a cross-shaped partition wall 20a, which corresponds to yellow (Y), magenta (M), cyan (C), and black (K) toners. Thus, four developing units 25Y, 25M, 25C, and 25K are configured. In addition, arrangement | positioning of the image development apparatus to illustrate is an example, Comprising: It is not limited to this.

  Each of the developing devices 25Y, 25M, 25C, and 25K includes developing rollers 26, 27, 28, and 29 that are individually driven to rotate. Further, a drive unit is connected to the developing unit 20 via a clutch (not shown), and by driving the drive unit, the developing unit 20 rotates to select a developing roller of any developing unit. For example, the developing operation is performed by being disposed opposite to the photosensitive drum 18.

  Next, an image forming operation by the image forming apparatus 1 having the above configuration will be described. First, when the photosensitive drum 18 is rotationally driven, the charging roller 19 is driven to rotate, and the surface 18a of the photosensitive drum 18 is uniformly charged. Based on the input image signal, the laser optical unit 24 operates to irradiate the charged photosensitive drum 18 with the laser light L, and an electrostatic latent image is formed on the surface 18a of the photosensitive drum 18. The The electrostatic latent image formed in this way is applied with toner from the developing rollers 26, 27, 28, and 29 to which the predetermined developing bias voltage is applied by the developing unit 20, and is developed as a toner image. . In the present embodiment, the photosensitive drum 18 is charged and the electrostatic latent image formed by exposure is developed as a “printing mode” with respect to a “refresh mode” described later.

  In the case of monochrome image formation, only the developing roller 29 of the developing unit 25K is disposed opposite to the photosensitive drum 18 on which the electrostatic latent image is formed to form a black toner image on the surface 18a of the photosensitive drum 18. In the case of color image formation, the developing unit 20 is rotated by driving the driving unit, and the developing rollers 26, 27, 28, and 29 of the four developing units 25Y, 25M, 25C, and 25K are sequentially and selectively exposed. A toner image of each color is formed on the surface 18 a of the photosensitive drum 18 so as to face the photosensitive drum 18.

  The toner image formed on the surface 18 a of the photosensitive drum 18 in this way is primarily transferred onto the intermediate transfer belt 12 that rotates clockwise by the primary transfer roller 16. That is, in the case of monochrome image formation, a black toner image formed on the surface 18a of the photosensitive drum 18 is transferred onto the intermediate transfer belt 12 rotated by the primary transfer roller 16 to form a monochrome image. In the case of color image formation, the toner images of the respective colors formed on the surface 18a of the photosensitive drum 18 are transferred onto the intermediate transfer belt 12 that is sequentially rotated by the primary transfer roller 16, and these are superimposed to form a color image. To do. In the case of color image formation, the cleaning blade 17 is separated from the intermediate transfer belt 12 during the primary transfer operation.

  Then, in a predetermined secondary transfer region, the secondary transfer roller 7 feeds the paper P fed from the paper feed unit 2 by the separation feeding unit 3 and further transported along the transport path 5 by the transport roller pair 6. The monochrome image or color image on the intermediate transfer belt 12 is secondarily transferred at once.

  In this way, the paper P on which the monochrome image or color image is transferred is transported in the substantially horizontal direction on the transport path 5, and the toner image on the paper P is heated and fixed by the fixing roller pair 8. After fixing, the paper P is changed in the transport direction upward at the downstream portion of the transport roller pair 9, further transported on the transport path 5 by the transport roller pair 10, and finally onto the paper discharge tray 4 by the paper discharge roller pair 11. The paper is ejected.

  The untransferred toner that is not primarily transferred and remains on the photosensitive drum 18 is removed by the cleaning roller 21 and the cleaning blade 22. Untransferred toner that has not been secondarily transferred and remains on the intermediate transfer belt 12 is removed by the cleaning blade 17. The removed toner is conveyed to a waste bottle (not shown) by a toner collecting device such as a collecting screw.

  The photosensitive drum 18 has a photosensitive layer made of amorphous silicon, has an outer diameter of 28 to 32 mm, and is driven to rotate at a linear speed of 140 to 160 mm / second.

  The cleaning roller 21 is an elastic roller having an outer diameter of 10 to 14 mm in which foaming synthetic rubber or plastic is formed on a shaft core having an outer diameter of 6 to 10 mm. The cleaning roller 21 is pressed against the photosensitive drum 18 and is driven in a direction opposite to the rotational direction of the photosensitive drum 18 at a speed approximately 0.7 times that of the photosensitive drum 18. Therefore, the action of polishing the surface of the photosensitive drum 18 is caused not only by the cleaning blade 22 but also by the cleaning roller 21. The synthetic rubber or plastic to be used is preferably an elastic soft rubber or soft plastic, such as a synthetic rubber such as butadiene rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), or a material such as thermoplastic elastomer. Used. Since the cleaning blade 22 and the cleaning roller 21 are provided, moisture and discharge products adhering to the surface of the photosensitive drum 18 can be reliably removed.

  The hardness of the cleaning roller 21 is preferably in the range of 30 to 60 degrees in terms of ASKER-C hardness. If the hardness is less than 30 degrees, the contact area between the cleaning roller 21 and the photosensitive drum 18 becomes large, and jitter noise tends to appear. When the hardness exceeds 60 degrees, the contact state with the photosensitive drum 18 becomes non-uniform, and the surface polishing of the photosensitive drum 18 tends to be uneven. From the viewpoint of suppressing jitter noise and from the viewpoint of toner retention on the surface of the cleaning roller 21, a foam roller is desirable. The ASKER-C hardness can be measured using, for example, an Asker-C hardness meter manufactured by Molecular Instruments Co., Ltd.

  The cleaning roller 21 is applied with a pressing force against the photosensitive drum 18 by two springs having a pressing force of 4 to 8 N from both ends thereof. If the pressure contact force is too strong, jitter noise becomes remarkable, and if the pressure contact force is too weak, the polishing action is lost.

  The toner used in this embodiment contains an abrasive. When the discharge product or moisture adheres to the toner used for carrying out the refresh mode, the polishing ability is reduced. However, since the toner contains an abrasive, the reduction in the polishing ability of the toner can be suppressed. The abrasive is not particularly limited, and examples thereof include titanium oxide, strontium titanate, cerium oxide, and alumina oxide. The abrasive is preferably added in an amount of 0.5 to 5.0% by mass with respect to the toner. When the addition amount is less than 0.5% by mass, the surface of the photosensitive drum 18 is insufficiently polished, and the hygroscopic discharge products adhering to the surface of the photosensitive drum 18 cannot be sufficiently removed. Occurs, resulting in an image defect. On the other hand, if the addition amount exceeds 5.0% by mass, the color of the printed matter becomes turbid or the fluidity of the toner is extremely deteriorated. The abrasive preferably has an average particle size of 0.01 to 1 μm. As a result, the effect of polishing the surface of the photosensitive drum 18 by the cleaning roller 21 via the transfer residual toner is increased, so that the discharge product can be effectively removed. In the present embodiment, a toner in which a part of titanium oxide is added as an abrasive to each color toner is used.

  Next, the operation in the refresh mode by the image forming apparatus 1 will be described. In the refresh mode, the photosensitive drum 18 is not charged and black toner is attached to the photosensitive drum 18 by applying a developing bias (bias development) to the black developing device 25K. Then, by applying a reverse bias in the primary transfer, most of the black toner adhering on the photosensitive drum 18 reaches the cleaning roller 21 and the cleaning blade 22, thereby polishing the surface of the photosensitive drum 18. The control device 30 (see FIG. 1) switches between the refresh mode and the print mode, controls the applied bias in the refresh mode, and controls the rotation of the photosensitive drum 18.

  As shown in FIG. 2, the refresh mode has a basic unit of rotating the photosensitive drum 18 for a certain period of time after black toner is attached to the photosensitive drum 18 by bias development, and this basic unit is repeated. Has been. This basic unit is composed of a basic unit A in which the toner supply amount is set large and a basic unit B in which the toner supply amount is set small.

As for the developing bias voltage, for example, when positively charged toner is used with respect to the potential of the photosensitive drum 18, the DC voltage Vdc is preferably +50 to 200V, and the AC voltage is preferably superimposed on this. As the AC voltage, V _PP (peak AC bias) is preferably 0.5 to 2.0 kV and the frequency f is 2 to 4 kHz. The amount of toner adhering to the photosensitive drum 18 varies depending on the development bias voltage and the development bias time.

  In the basic unit A, it is desirable that the development bias time is set to be longer than the time required for one rotation (one rotation) of the photosensitive drum 18. By setting in this way, the toner is reliably supplied to the entire surface of the photosensitive drum 18, so that most of the water adhering to the surface of the photosensitive drum 18 can be reliably removed by the toner.

  On the other hand, in the basic unit B, it is desirable to set the developing bias time to the time required for the photosensitive drum 18 to take 1/20 to 1/2 rotation. If the developing bias time is too short, the amount of toner that contributes to polishing is too small, and the effect of suppressing discharge products and moisture adhering to the surface of the photosensitive drum 18 by polishing the surface of the photosensitive drum 18 is lost. If the development bias time is too long, only toner that does not contribute to polishing increases.

  The rotation time of the photosensitive drum 18 is preferably 5 to 40 seconds in the basic unit A and 5 to 40 seconds in the basic unit B. If the rotation time of the photosensitive drum 18 is too short, the water absorption effect and the polishing effect on the surface of the photosensitive drum 18 by the toner cannot be sufficiently exhibited. If the rotation time of the photoconductor drum 18 is too long, the amount of toner interposed between the cleaning roller 21 and the photoconductor drum 18 is reduced, and the amount of intervening toner becomes non-uniform in the direction of the rotation axis, resulting in a polishing action. Unevenness occurs.

  In addition, discharge products and moisture adhere to the toner used for polishing, and the toner's polishing ability decreases with this adhesion. As a result of optimization, in the basic unit A, it is preferable that the development bias voltage Vdc is 50 to 150 V, the development bias time is 600 to 800 milliseconds, and the rotation time of the photosensitive drum 18 is 8 to 12 seconds. It turned out to be preferable. In the basic unit B, it is found that the development bias voltage Vdc is preferably 100 to 150 V, the development bias time is preferably 110 to 130 milliseconds, and the rotation time of the photosensitive drum 18 is preferably 8 to 12 seconds. It was. By frequently feeding a small amount of toner having a high polishing power little by little, the polishing ability of the surface of the photosensitive drum 18 can be enhanced.

  As described above, in the refresh mode by the image forming apparatus 1, first, toner is supplied to the entire surface of the photosensitive drum 18 in the basic unit A in which a large amount of toner is set, and the photosensitive drum 18 is supplied with a sufficient amount of toner. Most of the water adhering to the surface can be removed quickly. Thereafter, in the basic unit B in which the toner supply amount is set to be small, the discharge product adhering to the surface of the photosensitive drum 18 with the minimum necessary amount of toner can be efficiently removed.

  Further, the image forming apparatus 1 includes a sensor 32 (see FIG. 1) that detects an environmental temperature (in-machine temperature) and an environmental humidity (in-machine humidity). For example, the environmental temperature is 26 ° C. or higher and the environmental humidity is 70%. In the above-described case and when it is determined that the in-machine temperature is low, the refresh mode is performed. On the other hand, when the external environment is not high temperature and high humidity when the image forming apparatus 1 is turned on, the discharge product absorbs little water and the image flow due to the discharge product is difficult to place, so the refresh operation is omitted and the image forming apparatus 1 is omitted. Reduce startup time. The in-machine temperature may be determined based on the detection result obtained by providing the in-machine temperature sensor 33, or may be substituted by the thermistor temperature provided in the fixing device. In the present embodiment, it is determined that the in-machine temperature is low when the thermistor temperature is less than 100 ° C. Further, when an image flow occurs due to an unexpected situation, for example, when the surface of the photosensitive drum 18 is condensed due to a sudden change in the environment where the image forming apparatus is placed, the user can operate from the operation panel of the image forming apparatus 1. It is desirable that the refresh mode can be selected.

  The image forming apparatus 1 was used to evaluate image flow. The photosensitive drum 18 has a photosensitive layer made of amorphous silicon, an outer diameter of 30 mm, and was driven to rotate at a linear speed of 151 mm / sec. The cleaning roller 21 is an elastic roller having an outer diameter of 12 mm in which foamed EPDM is formed on a shaft core having an outer diameter of 8 mm, presses the photosensitive drum 18 with two springs having a pressing force of 6 N, and the linear velocity is 105 mm. / Sec. The hardness of the cleaning roller 21 was 50 degrees in terms of ASKER-C hardness.

  The image forming apparatus 1 is placed in an environment having a temperature of 23 ° C. and a relative humidity of 50% (hereinafter referred to as a normal environment), and forms a total of 10,000 color images with a color printing rate of 3%. 18 discharge products were intentionally generated on the surface. After the 10,000 color images were formed, the image forming apparatus 1 was left off for 12 hours in an environment having a temperature of 30 ° C. and a relative humidity of 80% (hereinafter referred to as a high-temperature and high-humidity environment) with the power supply off. After being left, the power of the image forming apparatus 1 was turned on, and a refresh operation was performed to enable printing.

  The basic unit A of the refresh mode was set to a development bias voltage Vdc of 70 V, a development bias time of 650 milliseconds, and a rotation time of the photosensitive drum 18 of 10 seconds. The basic unit B was set to a development bias voltage Vdc of 120 V, a development bias time of 120 milliseconds, and a rotation time of the photosensitive drum 18 of 10 seconds. Since the bias voltage Vdc of the basic unit A is set to about half of the bias voltage Vdc of the basic unit B, the toner amount per unit area on the photosensitive drum 18 of the basic unit A is about half of the basic unit B. . After this refresh operation, a character image was printed. The printed state was visually confirmed and image flow evaluation was performed. Operating conditions and evaluation results are shown in Table 1.

The image flow was evaluated in three ranks.
Rank A: Little character flow is observed.
Rank B: An acceptable level with a slight character flow.
Rank C: The character flow is bad.

  “Refresh mode total toner consumption” in Table 1 is a relative comparison value of the total toner consumption in each example. In the basic unit B, the toner consumption at a developing bias time of 100 milliseconds was calculated as “1”.

(Example 1 to Example 4)
In Example 1, the basic unit A in which the toner supply amount was set large was performed once, and then the basic unit B in which the toner supply amount was set small was repeated 12 times. In Example 2, after the basic unit A was carried out once, the basic unit B was repeated 10 times. In Example 3, after repeating the basic unit A once, the basic unit B was repeated 8 times. In Example 4, after repeating the basic unit A twice, the basic unit B was repeated 6 times.

  In Example 1, there was no character flow, and the rank was A. Furthermore, in Examples 2 to 4, the flow of characters was good and rank A or B. Therefore, Example 1-Example 4 made comprehensive evaluation (circle).

(Comparative Examples 1 to 3)
In Comparative Example 1, the basic unit A in which the toner supply amount was set large was not implemented, and only the basic unit B in which the toner supply amount was set small was repeated 12 times. In Comparative Example 2, the basic unit A was not carried out, and the basic unit B was repeated 15 times. In Comparative Example 3, the basic unit A was not carried out, and the basic unit B was repeated 18 times.

  In Comparative Example 1, the flow of characters was so bad that it was rank C. In Comparative Examples 2 and 3, although the character flow was good and rank A or B, the total time required for the refresh mode was longer than that of Examples 1 to 4, and the total amount of toner consumed in the refresh mode Also, the amount was larger than those in Examples 1 to 4. Therefore, in Comparative Examples 1 to 3, the overall evaluation is x.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is carried out within the range of the summary.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. 6 is a graph showing a refresh operation of the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Intermediate transfer body 18 Photosensitive drum 21 Cleaning roller 22 Cleaning blade 25Y, 25M, 25C, 25K Developer 30 Controller 32 Temperature / humidity sensor 33 Temperature sensor

Claims (6)

Image forming apparatus comprising: a photosensitive member; a developing device that visualizes an electrostatic latent image formed on the surface of the photosensitive member with toner; and a cleaning device that contacts the photosensitive member surface to clean the photosensitive member surface. A device,
In non-image formation, the developing device has a refresh mode in which toner is supplied to the photoreceptor, and the refresh mode has a basic unit A in which the toner supply amount is set large and a basic unit in which the toner supply amount is set small. An image forming apparatus comprising: B.   The image according to claim 1, further comprising: a sensor that detects an in-machine temperature, an outside temperature, and an outside humidity of the image forming apparatus, wherein the refresh mode is determined based on a detection value of the sensor. Forming equipment.   3. The image forming apparatus according to claim 1, wherein a bias development time of the basic unit A is set to be equal to or longer than a time required for one rotation of the photosensitive member.   The image forming apparatus according to claim 1, wherein the cleaning device includes a cleaning blade and a cleaning roller.   The image forming apparatus according to claim 1, wherein the toner contains abrasive particles.   The image forming apparatus according to claim 1, wherein the photosensitive member is made of amorphous silicon.

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