JP2005316085A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably prevent production of abnormal noise due to a cleaning blade when low density printing is continued in an image forming apparatus using a two-component developer. <P>SOLUTION: The image forming apparatus 10 has a developing device 11 provided with a developing roller 11d which carries the two-component developer comprising a magnetic carrier and a nonmagnetic toner with added external additives and develops an electrostatic latent image formed on a photoreceptor drum 13 with the nonmagnetic toner to form a toner image and screws 11b and 11c for conveying the two-component developer to the developing roller under stirring, and a cleaning member 15c which comes in contact with the photoreceptor drum and removes residual toner. When an average printing ratio of toner images is a stipulated value or below, in non-image-formation, the developing roller and the screws as well as the photoreceptor drum are driven, the developing device is replenished with the nonmagnetic toner as refreshing toner, and an electrostatic latent image region of a stipulated pattern is formed on the photoreceptor drum and developed by the developing device to form a toner region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and in particular, a two-component developer containing a magnetic carrier and toner (hereinafter simply referred to as a developer). The present invention relates to an image forming apparatus that performs image formation using the image forming apparatus.

  In general, in an image forming apparatus using a two-component developer containing toner and a magnetic carrier, toner is formed on an electrostatic latent image carrier such as a photosensitive drum from a developer carrier (developing roller). The electrostatic latent image is supplied to the electrostatic latent image to develop it into a toner image, and this toner image is transferred to a recording sheet to form an image. The residual toner remaining on the electrostatic latent image carrier is removed by a cleaning unit having a cleaning blade or the like.

  In the above-described image forming apparatus, for example, if low density printing is continuously performed, the amount of toner supplied from the developer carrier to the electrostatic latent image carrier is reduced, so that it remains on the electrostatic latent image carrier. Residual toner is also reduced. On the other hand, since the cleaning blade contacts the surface of the electrostatic latent image carrier and cleans the residual toner while rubbing the surface of the electrostatic latent image carrier, the residual toner on the electrostatic latent image carrier is reduced. That is, when the residual toner functioning as a lubricant is reduced, the frictional resistance between the electrostatic latent image carrier and the cleaning blade is increased, resulting in a problem that abnormal noise is generated from the cleaning blade.

  In order to prevent such problems, the operation sound of the cleaning blade is detected, and the detected sound is compared with the frequency and sound pressure of the abnormal sound stored in advance to determine whether there is an abnormality in the cleaning blade. If it is determined that there is an abnormality in the blade, a solid black toner image with a width equal to the blade width is formed during non-image formation between image formation and cleaning without transferring the toner image to the recording paper. Some of the toners sent to the blade and supplied to the cleaning blade reduce the frictional resistance between the electrostatic latent image carrier and the cleaning blade to prevent abnormal noise (so-called blade noise) (Patent Literature). 1).

  Further, the vibration of the cleaning blade is detected, the amplitude of the detected vibration is compared with a predetermined amplitude set in advance, and when the amplitude of the detected vibration is equal to or larger than the predetermined amplitude, the electrostatic latent image carrier is moved to the electrostatic latent image carrier. Vibration suppression control is performed to expose the specific pattern for vibration suppression, and the toner of the specific pattern adhered on the electrostatic latent image carrier is given to the cleaning blade, and the friction between the cleaning blade and the surface of the electrostatic latent image carrier There is one in which resistance is reduced (see Patent Document 2).

  When the main switch of the copying machine is turned on, the charging charger is turned on and the electrostatic latent image carrier is rotated to generate a charged region having a certain width on the surface of the electrostatic latent image carrier. When the electrostatic latent image carrier and the cleaning blade come into contact with each other by developing the area, toner is interposed at the contact portion between the cleaning blade and the electrostatic latent image carrier so as to reduce abnormal noise due to sliding contact. (See Patent Document 3).

JP 2003-295707 A (paragraph (0021) to paragraph (0023), FIG. 4) JP-A-8-171315 (Pages 2 to 4, FIGS. 1 to 5) Japanese Patent Laid-Open No. 10-91049 (pages 2 to 3, FIGS. 1 to 3)

  By the way, an external additive (fine particles) such as silica is externally added to the toner, and when the toner is supplied to the cleaning blade as described above, the external additive acts between the cleaning blade and the electrostatic latent image carrier. It plays a role in reducing frictional resistance. On the other hand, in an image forming apparatus using a two-component developer, toner (T) / carrier (C) is maintained at a predetermined ratio (for example, 5 wt% to 8 wt%), and is supplied from a toner supply container. The toner thus supplied is supplied to the developer carrying member while being agitated with the two-component developer in the developing device. At this time, the toner is rubbed with the carrier to be charged, but a phenomenon occurs in which the external additive is embedded in the toner during the rub. In a state where low density printing is continued, the toner consumption is small, so that the toner staying in the developing device for a long time increases, and the ratio of the toner embedded with the external additive increases.

  Even if such a toner is supplied to the cleaning blade, the external additive is embedded, so it is difficult to reduce the frictional resistance between the cleaning blade and the electrostatic latent image carrier, and the abnormal noise is not solved. Will be wasted.

  In both of Patent Documents 1 to 3 described above, although toner is supplied to the cleaning blade to reduce the frictional resistance between the cleaning blade and the electrostatic latent image carrier, image formation using a two-component developer is performed. In the apparatus, there is a problem that it is difficult to reduce the abnormal noise of the cleaning blade by reducing the frictional resistance between the cleaning blade and the electrostatic latent image carrier when low density printing continues.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus that can reliably eliminate abnormal noise of a cleaning member (cleaning blade) when low-density printing continues using a two-component developer. And

  In order to solve the above-described problems, the present invention provides an electrostatic latent image formed on an electrostatic latent image carrier carrying a two-component developer having toner added with at least a magnetic carrier and an external additive. A developing device including a developer carrying member that is developed with the toner to form a toner image and a conveying unit that conveys the two-component developer to the developer carrying member while stirring; An image forming apparatus having a cleaning member that contacts and removes residual toner remaining on the electrostatic latent image carrier, and a determination unit that determines whether an average print rate of the toner image is equal to or less than a specified value; When the determination unit determines that the average printing rate is equal to or less than a specified value, the electrostatic latent image carrier is driven during non-image formation, and the developer carrier and the conveyance unit are driven to supply toner to the developing device. As refresh toner An image forming unit that forms an electrostatic latent image region having a predetermined pattern on the electrostatic latent image carrier and develops the electrostatic latent image region into a toner region by the developing device; And the toner region is moved to the position of the cleaning member in accordance with the driving of the electrostatic latent image carrier.

  In the present invention, after a predetermined time elapses after the drive control means starts supplying the refresh toner, the image forming means forms the electrostatic latent image region and develops it on the developer carrier. Apply a bias. The predetermined time is at least the time from when the refresh toner is replenished to when the refresh toner is agitated and conveyed by the conveying means and reaches the developer carrier, and the amount of the refresh toner is It is preferable that the amount of toner for developing the electrostatic latent image area is substantially equal.

  As described above, the image forming apparatus according to the present invention determines whether or not the average print rate of the toner image is equal to or less than the specified value, and determines that the average print rate is equal to or less than the specified value. The electrostatic latent image area having a predetermined pattern on the electrostatic latent image carrier is driven by driving the electrostatic latent image carrier and driving the developer carrier and the conveying means to replenish the developing device with toner as refresh toner. The electrostatic latent image area is developed by the developing device to become a toner area, and the toner area is moved to the position of the cleaning member in accordance with the driving of the electrostatic latent image carrier, so that the external additive is buried. The toner containing the refreshing toner that is not contained is given to the cleaning member, and the role as a lubricant can be satisfactorily exhibited. As a result, abnormal noise in the cleaning member can be reliably eliminated. There is a cormorant effect.

  In the present invention, after the refresh toner supply is started, at least after the refresh toner is replenished, the time when the refresh toner is agitated and conveyed by the conveying means and reaches the developer carrying member passes. Since a developing bias is applied to the developer carrying member, refresh toner can be reliably applied to the electrostatic latent image region. Further, if a predetermined pattern is defined so that the amount of refresh toner is substantially equal to the amount of toner for developing the electrostatic latent image area, the toner is supplied to the cleaning member, and then the carrier in the developing device. The toner-to-toner ratio does not change.

  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 partially showing an example of an image forming apparatus according to Embodiment 1 of the present invention, and this image forming apparatus 10 includes a developing unit 11 and a drum unit 12. The drum unit 12 includes a photosensitive drum (for example, an a-Si photosensitive drum) 13 that is an electrostatic latent image carrier, a charger 14, and a cleaning unit 15. A charger 14, an exposure device 16, and a cleaning unit 15 are disposed around the photosensitive drum 13, and the surface of the photosensitive drum 13 is uniformly charged by the charger 14 when image formation is performed. Thereafter, the photosensitive drum 13 is exposed by the exposure device 16 according to the image data, and an electrostatic latent image is formed on the photosensitive drum 13. The electrostatic latent image is developed by the developing unit 11 to form a toner image on the photosensitive drum 13.

  The toner image on the photosensitive drum 13 is transferred to, for example, a recording sheet, and then the recording sheet is sent to a fixing unit (not shown), where the toner image on the recording sheet is fixed, The paper is discharged to a paper discharge tray (not shown). Residual toner remaining on the photosensitive drum 13 after the transfer is removed by the cleaning unit 15.

  As shown in FIG. 1, the cleaning unit 15 has a unit housing 15 a, a cleaning roller 15 b is rotatably disposed on the unit housing 15 a, and further, the unit housing is located downstream in the rotation direction of the photosensitive drum 13. A cleaning blade (cleaning member) 15c is attached to 15a. The cleaning roller 15 b and the cleaning blade 15 c are in contact with the photosensitive drum 13.

  The residual toner on the photosensitive drum 12 is removed by the cleaning roller 15b, and the residual toner is further removed by the cleaning blade 15c. The residual toner is conveyed to the toner disposal path (not shown) by the cleaning screw 15d. Then, it is discarded into a waste toner container (not shown) through the toner disposal path.

  The developing unit 11 has a developing container 11a, and a two-component developer (an external additive is added to the toner in the two-component developer) is stored in the developing container 11a. First and second screw bodies (conveying means) 11b and 11c are arranged in the developing container 11a, and the two-component developer is charged while being stirred by these screw bodies 11b and 11c. The toner is supplied to a developing roller (developer carrier) 11d facing the body drum 13 with a predetermined gap. A layer thickness regulating blade 11e is provided facing the developing roller 11d, and the developer layer on the developing roller 11d is regulated by the layer thickness regulating blade 11e.

  A toner container 17 is attached to the upper end of the developing container 11a, and toner is supplied from the toner container 17 to the developing container 11a through a toner supply port 17a. In the vicinity of the toner supply port 17 a, a toner supply roller 17 b is disposed in the toner container 17, and a stirring member 17 c is disposed in the toner container 17. Then, the toner density in the developing container 11a is detected by a toner density sensor (not shown), and the toner replenishing roller 17b is driven in accordance with the detected toner density, so that the toner is replenished to the developing container 11a through the toner replenishing port 17a. The T / C is maintained within a predetermined range.

  Referring to FIG. 2, FIG. 2 is a perspective view showing the developing unit 11 and the drum unit 12 in a separated state. The developing unit 11 and the boss receiving part 121 formed on the drum unit 12 develop the developing unit 11 and the drum unit 12. The unit 11 and the drum unit 12 are engaged, and the state shown in FIG. 1 is obtained. Note that, by driving the first and second screw bodies 11b and 11c (FIG. 1), the two-component developer in the developing container 11a is stirred while being conveyed in the direction indicated by the solid line arrow in FIG. .

  By the way, in the above-described image forming apparatus, when low density printing is continued, the toner consumption is small, so that the toner staying in the developing container 11a for a long time increases, and the external additive is buried as described above. The percentage of toner increases. Even if such toner is supplied to the cleaning unit 15 side, the external additive is embedded, so it is difficult to reduce the frictional resistance between the cleaning blade 15c and the photosensitive drum 13, and the cleaning blade 15c is abnormal. Sound will be generated. This is confirmed by the occurrence of abnormal noise from the cleaning blade when 1300 sheets are printed intermittently with an average printing ratio of 0.8%. Therefore, the average printing ratio of 1000 sheets has a threshold of 1.0%. It was.

  Here, in the image forming apparatus using the two-component developer, blade friction reduction control is performed as follows in order to prevent abnormal noise (blade squeal) generated by the cleaning blade 15c.

  Referring to FIG. 3, when printing is completed in image forming apparatus 10 (that is, when non-image formation is being performed: step S1), a control device (not shown) determines a predetermined number of sheets (for example, based on image data). In step S2, it is determined whether the average print rate PT of the immediately preceding 1000 sheets is equal to or less than a predetermined threshold value (for example, 1%). If PT> 1%, the control device places the image forming apparatus 10 in a standby state (step S3).

  On the other hand, if PT ≦ 1%, the control device determines that the frictional resistance between the photosensitive drum 13 and the cleaning blade 15c is high, and sets the photosensitive drum motor (not shown) and the developing motor (not shown). Turned on (step S4), rotationally drives the photosensitive drum 13, and rotationally drives the developing roller 11d and the screw bodies 11b and 11c. Further, the control device supplies a toner replenishing motor (not shown) for a predetermined time (this predetermined time is used to replenish the developing container 11 with refresh toner necessary to prevent the abnormal noise from being generated from the cleaning blade. The toner supply roller 17b is driven to supply toner from the toner container 17 to the developing container 11a (hereinafter, the supplied toner is referred to as refresh toner).

  Thereafter, when a predetermined time elapses, the control device turns on the charger 14 and applies a developing bias to the developing roller 11d (charging and developing bias on: step S6). This predetermined time is the time required for the refresh toner replenished from the toner replenishing port 17a to reach the developing roller 11d. For example, the two-component developer is driven by the screw bodies 11b and 11c in the direction shown in FIG. When the time required for the two-component developer to make a round in the developing container 11a when being agitated and conveyed is about 90 seconds, the predetermined time is about 90 seconds. The predetermined time is the time after the start of refresh toner supply.

  The control device controls the exposure device 16 to form a belt-like electrostatic latent image on the photosensitive drum 13 (band-like latent image formation: step S7). As a result, a belt-like solid toner image is formed on the photosensitive drum 13. At this time, since the refresh toner has reached the developing roller 11d by the screw bodies 11b and 11c, even if there is toner that has been continuously accumulated in the developing container 11a for a long time with low density printing, Such toners have a high charge amount due to agitation with a magnetic carrier for a long time and are strongly attracted to the carrier, so they are difficult to develop. Therefore, a refresh toner with a short agitation time and a low charge amount is preferred. Is supplied to the photosensitive drum 13. Then, without performing the transfer, the belt-like toner image is supplied to the cleaning unit 15 side, and the belt-like toner image containing the refresh toner (that is, the toner not having the external additive embedded therein) functions as a lubricant, The frictional resistance between the photosensitive drum 13 and the cleaning blade 15c is reduced, so that no abnormal noise is generated.

  Thereafter, the control device turns off the charger 14 and the developing bias (step S8), further turns off the drum motor and the developing motor (step S9), and puts the image forming apparatus 10 in a standby state. When the toner replenishing motor is turned on for a predetermined time, the amount of refresh toner replenished from the toner container 17 to the developing container 11a and the amount of toner consumed in the belt-shaped electrostatic latent image area (that is, the belt-shaped electrostatic If the toner amount required to develop the latent image is substantially the same, the T / C after the cleaning blade friction reduction control is hardly changed. In other words, the belt-shaped exposure pattern is defined so that the amount of toner replenished in a predetermined time and the amount of toner required to develop the belt-shaped electrostatic latent image region are substantially the same.

  Referring to FIG. 4, in FIG. 4, the same steps as those described in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 4, when printing is completed in the image forming apparatus 10 in step S <b> 1, the control apparatus determines in step S <b> 2 a predetermined threshold value (for example, the average print rate PT for a predetermined number of sheets (for example, 1000 sheets immediately before)). 1%) or less is determined. If PT ≦ 1%, cleaning blade friction reduction control (steps S4 to S9) is performed.

  Incidentally, when the frictional resistance between the cleaning blade 15c and the photosensitive drum 13 increases, the torque of the drum motor also increases (that is, the frictional resistance and the drum motor torque are in a proportional relationship). Therefore, in this case, the drum motor torque when abnormal noise is generated in the cleaning blade 15c is measured in advance by experiment, and a torque threshold is set according to the measurement result. Monitor (for example, the drum motor torque is proportional to the value of the current flowing through the drum motor, so the drum motor torque is monitored by detecting this current value). If PT> 1%, the control device compares the drum motor torque T with the torque threshold value Ts in step S10 to determine whether the drum motor torque is high. When it is determined that the drum torque is high, the control device performs cleaning blade friction reduction control (steps S4 to S9).

  In this way, whether or not the frictional resistance is large is determined based on both the printing rate and the drum torque, and if one of them is not satisfied, the cleaning blade friction reduction control is performed. In addition, it is possible to prevent abnormal noise such as blade noise.

  As is apparent from the above description, the control device collectively functions as a determination unit, a drive control unit, and an image forming unit. As described above, instead of forming an electrostatic latent image, control for turning off charging by the same charger 14 may be performed.

  When it is determined whether or not the average print rate of the toner image is equal to or less than a specified value, and it is determined that the average print rate is equal to or less than the specified value, the electrostatic latent image carrier is driven during non-image formation and the developer carrier And driving the conveying means to replenish the developing device with toner as refresh toner, forming an electrostatic latent image region of a predetermined pattern on the electrostatic latent image carrier, and developing the electrostatic latent image region by the developing device. Since the toner area is developed, the toner containing the refresh toner is given to the cleaning member, so that the role as a lubricant can be satisfactorily exhibited. As a result, an image using a two-component developer is obtained. The present invention can be applied to prevent the generation of abnormal noise of the cleaning member in the forming apparatus.

It is sectional drawing which shows partially Example 1 of the image forming apparatus by this invention. FIG. 2 is a perspective view showing a drum unit and a developing unit separately in the image forming apparatus shown in FIG. 1. 3 is a flowchart illustrating an example of cleaning blade friction reduction control in the image forming apparatus illustrated in FIG. 1. 6 is a flowchart illustrating another example of cleaning blade friction reduction control in the image forming apparatus illustrated in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Developing unit 11a Developing container 11b, 11c Screw body 11d Developing roller 11e Layer thickness regulating blade 12 Drum unit 13 Photosensitive drum 14 Charger 15 Cleaning unit 15b Cleaning roller 15c Cleaning blade 15d Cleaning screw 16 Exposure unit 17 Toner container 17a Toner supply port 17b Toner supply roller

Claims (4)

Developing a two-component developer having toner added with at least a magnetic carrier and an external additive, and developing the electrostatic latent image formed on the electrostatic latent image carrier with the toner to form a toner image A developing device comprising: a developer carrying member; and a conveying unit that conveys the two-component developer to the developer carrying member while stirring; and the electrostatic latent image carrying member contacting the electrostatic latent image carrying member. An image forming apparatus having a cleaning member for removing residual toner remaining in
Determining means for determining whether an average printing rate of the toner image is equal to or less than a specified value;
When the determination means determines that the average printing rate is equal to or less than a specified value, the electrostatic latent image carrier is driven during non-image formation, and the developer carrier and the conveyance unit are driven to perform the development. Drive control means for supplying toner as refresh toner to the apparatus;
Image forming means for forming an electrostatic latent image area having a predetermined pattern on the electrostatic latent image carrier and developing the electrostatic latent image area by the developing device to form a toner area;
An image forming apparatus, wherein the toner region is moved to the position of the cleaning member in accordance with driving of the electrostatic latent image carrier.   After a predetermined time elapses after the drive control means starts supplying the refresh toner, the image forming means forms the electrostatic latent image area and applies a developing bias to the developer carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   3. The predetermined time is a time from when at least the refresh toner is replenished until the refresh toner is agitated and conveyed by the conveying means and reaches the developer carrying member. Image forming apparatus.   The image forming apparatus according to claim 3, wherein the amount of the refresh toner is substantially equal to a toner amount for developing the electrostatic latent image area.

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