JP2016017978A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can prevent unnecessary reduction of the life of an image carrier, and efficiently suppress cleaning failure to toner images for detection formed on the image carrier.SOLUTION: An image forming apparatus makes variable, on the basis of the cumulative number of fed sheets in which recording media are fed in the image forming apparatus, the number of times of passing in which after patch patterns B (toner images for detection) are detected by a photosensor 41 (detection means) and the patch patterns B reach the position of an intermediate transfer cleaning device (cleaning blade 10a), an intermediate transfer belt 8 (image carrier) is further moved to cause parts B' having patch patterns B formed thereon to pass through the position of the intermediate transfer cleaning device.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and in particular, a detection toner image is formed on the surface of an image carrier in addition to a transfer toner image, thereby The present invention relates to an image forming apparatus provided with a cleaning device for removing untransferred toner on a body.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, a cleaning apparatus for removing untransferred toner carried on the surface of an image carrier such as an intermediate transfer belt and a photosensitive drum is widely known. (For example, refer to Patent Document 1).

  In Patent Document 1, etc., the image forming apparatus is arranged side by side so that four photosensitive drums face an intermediate transfer belt (image carrier). On these four photosensitive drums, black (black), yellow, magenta, and cyan toner images are formed, respectively. Each color toner image formed on each photosensitive drum is transferred onto the intermediate transfer belt by a primary transfer roller installed so as to face the respective photosensitive drums via the intermediate transfer belt ( Primary transfer). Further, the toner images of a plurality of colors carried on the intermediate transfer belt are transferred onto a recording medium as a color image (transfer toner image) at a contact position between the intermediate transfer belt and the secondary transfer roller (transfer member). (Secondary transfer). At this time, the untransferred toner remaining on the intermediate transfer belt without being secondarily transferred onto the recording medium is removed by a cleaning device (cleaning blade) at a position downstream thereof.

  In such an image forming apparatus, a patch pattern (detection toner image) is formed on the surface of the intermediate transfer belt (image carrier) separately from the color image (transfer toner image), and the patch pattern is detected by a sensor. A technique for performing density correction and color misregistration correction of a color image based on the result detected by (detecting means) is widely used (see, for example, Patent Documents 2 and 3).

  On the other hand, Patent Document 4 discloses a “cleaning mode” in which the photosensitive drum and the transfer belt are idle-driven without applying a charging bias or a transfer bias in order to prevent toner filming from occurring on the transfer belt. A technique is disclosed that is executed every time the cumulative number of copies reaches a set value.

In the conventional image forming apparatus, the transfer toner image is not completely transferred to the recording medium by the transfer member, and a relatively small amount of untransferred toner remains on the image carrier, whereas the detection toner image is originally transferred. The toner image for detection is not sufficiently removed by the cleaning device because it is directly input to the cleaning device as untransferred toner in a state where it is carried on the image carrier without being transferred by the member. In some cases, a defect (referred to as “cleaning failure”) that passes through the position and remains on the surface of the image carrier may occur.
On the other hand, in order to prevent the occurrence of such a cleaning failure, the image carrier is idled (idle drive) after applying the technique of Patent Document 4 and detecting the detection toner image by the detection means. Thus, a measure for reliably removing the detection toner image by allowing the detection toner image to pass through the position of the cleaning device a plurality of times can be considered. However, if the image carrier is frequently idled, the life of the image carrier itself, a member in contact with the image carrier, a drive mechanism for driving the image carrier, and the like is shortened. Become.

  The present invention has been made to solve the above-described problems, and the cleaning failure for the detection toner image formed on the image carrier is efficiently performed without wastefully shortening the life of the image carrier. An object of the present invention is to provide an image forming apparatus that is inhibited by the above.

  An image forming apparatus according to a first aspect of the present invention includes an image carrier that travels in a predetermined direction, and a transfer that transfers a toner image carried on the surface of the image carrier to a recording medium as a transfer toner image. A member, a cleaning device that removes untransferred toner carried on the surface of the image carrier, and a toner image for transfer that is installed at a position upstream of the cleaning device in the running direction of the image carrier. A detection means for detecting a detection toner image formed on the surface of the image carrier, and after the detection toner image is detected by the detection means, the detection toner image is The number of passes through which the image carrier is further run after reaching the position of the apparatus and the portion where the detection toner image is formed passes through the position of the cleaning apparatus. Cumulative paper feed quantity of the recording medium is sheet passing or cumulative travel distance of the image bearing member, is to varying based on.

  According to the present invention, it is possible to provide an image forming apparatus in which a cleaning failure with respect to a detection toner image formed on an image carrier can be efficiently suppressed without wastefully shortening the life of the image carrier or the like. it can.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows an image formation part. FIG. 5 is a schematic view showing a state in which a transfer toner image and a patch pattern are formed on the surface of an intermediate transfer belt along a running direction. It is a flowchart which shows the control performed at the time of adjustment mode using a patch pattern. 6 is a control table showing the relationship between the cumulative number of sheets passed and the ambient temperature and the number of idling of the intermediate transfer belt after the adjustment mode. 6 is a graph showing a change with time in surface roughness on the surface of an intermediate transfer belt. 6 is a graph showing a change with time of toner adhesion on the surface of an intermediate transfer belt. FIG. 10 is a schematic view showing a state in which a patch pattern is formed on the surface of an intermediate transfer belt as a modification, along a running direction.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the overall configuration and operation of the image forming apparatus 100 will be described.
As shown in FIG. 1, four toner containers 32Y, 32M, 32C, and 32K corresponding to the respective colors (yellow, magenta, cyan, and black) can be attached to and detached from the toner container accommodating portion 31 above the image forming apparatus 100. (Replaceable).
An intermediate transfer unit 15 is disposed below the toner container housing 31. Image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 (image carrier) of the intermediate transfer unit 15. .
Although illustration is omitted, toner replenishing devices are respectively disposed below the toner containers 32Y, 32M, 32C, and 32K. The toners stored in the toner containers 32Y, 32M, 32C, and 32K are respectively supplied (supplied) into the developing devices of the image forming units 6Y, 6M, 6C, and 6K by the toner replenishing device.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y (photosensitive member), a charging unit 4Y disposed around the photosensitive drum 1Y, a developing device 5Y (developing unit), A cleaning unit 2Y, a charge removal unit (not shown), and the like are included. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow toner image (image) is formed on the photosensitive drum 1Y. It will be.

  The other three image forming units 6M, 6C, and 6K have substantially the same configuration as that of the image forming unit 6Y corresponding to yellow except that the color of the toner used is different. A corresponding toner image (image) is formed. Hereinafter, description of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be described.

Referring to FIG. 2, the photosensitive drum 1Y is driven to rotate clockwise in FIG. 2 by a drive motor (not shown). The photoreceptor drum 1Y is a negatively chargeable organic photoreceptor having a photosensitive layer provided on a drum-like conductive support. Although not shown, the photosensitive drum 5 has an undercoat layer as an insulating layer, a charge generation layer as a photosensitive layer, and a charge transport layer sequentially laminated on a conductive support as a base layer.
Then, a predetermined charging bias is applied to the charging unit 4Y from a power supply unit (not shown), and the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (this is a charging process). The charging unit 4Y is a roller member formed by covering an outer periphery of a conductive metal core with a medium-resistance elastic layer, and is disposed so as to contact the photosensitive drum 1Y. The charging bias applied to the charging unit 4Y may be a direct current (DC) bias, an alternating current (AC) bias, or an alternating current (AC) bias superimposed on a direct current (DC) bias. It may be.
After that, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure unit 7 (see FIG. 1), and the electrostatic latent image corresponding to yellow by exposure scanning at this position. Is formed (this is an exposure step).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing device 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Specifically, referring to FIG. 2, a two-component developer G composed of toner and a carrier (magnetic carrier) is accommodated in the developing device 5Y. The developer G in the developing device 5Y is adjusted so that the toner concentration (the ratio of the toner in the developer G) detected by a magnetic sensor (not shown) is within a predetermined range. That is, according to the toner consumption in the developing device 5Y, the toner (replenishment toner) is replenished into the second developer transport unit 504Y by the toner replenishing device via the toner replenishing port 64Y.
The toner replenishing device is connected to the toner container 32Y shown in FIG. Although not shown, the toner replenishing device is stored in a driving unit that rotates and drives the toner container 32Y (toner bottle), a toner tank unit that stores toner discharged from the toner container 32Y, and a toner tank unit. A toner conveying section that conveys the toner toward the toner dropping path, and a toner dropping path that causes the toner conveyed by the toner conveying section to fall by its own weight toward the developing device 5Y (second developer conveying section 504Y). Has been.

Referring to FIG. 2, the toner (supplemented toner) replenished into the second developer conveying unit 504Y through the toner replenishing port 64Y is mixed with the developer G by the two conveying screws 505Y and 506Y. While being stirred, the first developer transport unit 503Y and the second developer transport unit 504Y separated by the partition member are circulated.
Thus, the toner in the developer G circulating in the circulation path is attracted to the carrier by frictional charging with the carrier and is carried together with the carrier on the developing roller 501Y having a plurality of magnetic poles formed around it. The developer G carried on the developing roller 501Y is conveyed as the developing roller 501Y rotates in the direction of the arrow, and reaches the position of the doctor blade 502Y. The developer G on the developing roller 501Y is regulated to an appropriate amount at this position, and then conveyed to a position facing the photosensitive drum 1Y (developing area). The toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field (developing electric field) formed in the developing area.
Here, the developer in the developing device 5Y is adjusted so that the toner ratio (toner concentration) in the developer is within a predetermined range. Specifically, according to the consumption of toner in the developing device 5Y, the toner stored in the toner bottle 32Y is supplied into the second developer transport unit 504Y by the toner supply device via the toner supply port 64Y.

Referring to FIG. 2, after the development process described above, the surface of photoreceptor drum 1Y reaches a position facing intermediate transfer belt 8 (intermediate transfer member) and first transfer roller 9Y (primary transfer member). At this position, the toner image on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 8 as an image carrier (this is a primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position (discharge generated on the photosensitive drum 1Y during discharge by the charging roller 4Y). The product and deposits such as toner additives such as silica added to the toner are also mechanically recovered by the cleaning blade 2a (this is a cleaning process).
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1Y is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, the laser beam L based on the image information is emitted from the exposure unit 7 disposed below the image forming unit onto the photosensitive drums of the image forming units 6M, 6C, and 6K. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the development process are primarily transferred while being superimposed on the intermediate transfer belt 8 (image carrier). Thus, a toner image is formed on the intermediate transfer belt 8 as a transfer toner image (color image).

  Here, referring to FIG. 1, the intermediate transfer unit 15 includes an intermediate transfer belt 8 as an image carrier, four primary transfer rollers 9Y, 9M, 9C, and 9K as secondary transfer members. The roller 12, the first tension roller 13, the second tension roller 14, the intermediate transfer cleaning device 10 as a cleaning device, and the like. The intermediate transfer belt 8 is stretched and supported by a plurality of roller members 12 to 14 and is endlessly moved in the direction of the arrow in FIG. 1 by the rotational drive of one roller member 12 (secondary transfer opposing roller).

Four primary transfer rollers 9Y, 9M, 9C, and 9K (primary transfer members) sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K to form primary transfer nips. doing. A primary transfer bias having a polarity opposite to the polarity of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the arrow direction (predetermined direction) and sequentially passes through the primary transfer nips of the primary transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images (transfer toner images) of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 onto which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19 as a transfer member (secondary transfer member). At this position, the secondary transfer counter roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. Then, a secondary transfer bias having a polarity opposite to the toner polarity is applied to the secondary transfer roller 19 (or a secondary transfer bias having the same polarity as the toner polarity is applied to the secondary transfer counter roller 12. May be.) As a result, the transfer toner image carried on the intermediate transfer belt 8 is transferred onto the recording medium P such as transfer paper conveyed to the position of the secondary transfer nip (secondary transfer step). That is, the secondary transfer roller 19 (or the secondary transfer counter roller 12) transfers the toner image carried on the surface of the intermediate transfer belt 8 as an image carrier to the recording medium P as a transfer toner image. Is functioning as
The secondary transfer roller 19 as a transfer member has an elastic layer (conductive rubber layer) having a rubber hardness of about 48 to 58 Hs formed of a rubber material such as urethane rubber on a cored bar made of an iron-based material. Roller member.

At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8 that has passed the position of the secondary transfer nip. Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning device 10 after passing through the position of the photo sensor 41 (detection means). At this position, deposits such as untransferred toner on the intermediate transfer belt 8 are collected. That is, the intermediate transfer cleaning device 10 functions as a cleaning device that removes untransferred toner carried on the surface of the intermediate transfer belt 8 as an image carrier.
Specifically, the intermediate transfer cleaning device 10 as a cleaning device is a cleaning that removes deposits (mainly untransferred toner) that are in contact with the surface of the intermediate transfer belt 8 and adhere to the surface of the intermediate transfer belt 8. A blade 10a (intermediate transfer cleaning blade) is installed. The cleaning blade 10a is obtained by holding a plate-like blade body made of a rubber material such as urethane rubber, hydrin rubber, silicone rubber, fluorine rubber or the like on a holding plate, and has a predetermined angle and a predetermined pressure on the surface of the intermediate transfer belt 8. It is in contact. As a result, the untransferred toner (including the untransferred toner of the transfer toner image and a patch pattern as a detection toner image to be described later) adhering to the intermediate transfer belt 8 is mechanically scraped and intermediate transfer is performed. It is collected in the cleaning device 10.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from a paper feeding unit 26 disposed below the apparatus main body 100 via a paper feeding roller 27, a registration roller pair 28, and the like. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P conveyed to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 (timing roller pair) whose rotation driving has been stopped. Then, the registration roller pair 28 is rotationally driven in time with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip portion. Thus, a desired transfer toner image (color image) is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image has been transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20 (fixing device). Here, the fixing unit 20 includes a fixing roller 21 in which a heater (heat source) is provided, a pressure roller 22 for forming a fixing nip where the recording medium P is conveyed in pressure contact with the fixing roller 21, and the like. is set up. At this fixing nip position, the color image (transfer toner image) transferred onto the surface of the recording medium P is fixed on the recording medium P by heat and pressure generated by the fixing roller 21 and the pressure roller 22. The
Thereafter, the recording medium P is discharged to the outside of the apparatus through the rollers of the discharge roller pair 29. The recording media P discharged to the outside of the apparatus by the discharge roller pair 29 are sequentially stacked on the stack unit 30 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

In this embodiment, the intermediate transfer belt 8 as an image carrier is a belt member having a single layer structure in which a conductive material such as carbon black is dispersed in PAI (polyamideimide). The intermediate transfer belt 8 has a belt peripheral length of about 963.8 mm, an arithmetic average roughness Ra of the belt surface measured by JIS-B0601-2001 of about 0.016 μm, and a maximum height Rz of about 0.166 μm. The volume resistivity is set to about 10 ⁷ to 10 ¹² Ωcm, and the thickness is set to about 80 to 100 μm. Thus, by using a single-layer structure formed of PAI (polyamideimide) as the intermediate transfer belt 8, it is relatively inexpensive and can improve the durability of the belt. As will be described with reference to FIG. 7 and the like, the patch pattern B (detection toner image) is likely to be poorly cleaned, so that the application of the present invention is particularly useful.

Hereinafter, the configuration and operation related to the “adjustment mode” executed in the present embodiment will be described in detail.
Referring to FIGS. 1 and 3, in image forming apparatus 100 in the present embodiment, photosensor 41 (optical sensor) as a detection unit is located from the positions of image forming units 6Y, 6M, 6C, and 6K. Accordingly, the intermediate transfer belt 8 (image carrier) is positioned upstream of the cleaning device 10 in the running direction of the intermediate transfer belt 8 (image carrier), and the intermediate transfer belt 8 (image carrier) is located with respect to the secondary transfer roller 19 (transfer member). It is installed at a position downstream in the traveling direction.
The photosensor 41 is a patch pattern as a detection toner image formed on the surface of the intermediate transfer belt 8 separately from the transfer toner image A (a normal toner image secondarily transferred to the recording medium P). It functions as a detecting means for detecting B. Specifically, the photosensor 41 as a detecting means is a sensor composed of a light emitting element and a light receiving element, and the light emitted from the light emitting element is reflected by the patch pattern B carried on the intermediate transfer belt 8 and received. Based on the amount of light input to the element, the image density of the patch pattern B formed in a single color is detected, or the color shift of the patch pattern B formed by overlapping a plurality of colors is detected. Based on the detection result detected by the photosensor 41, the image forming conditions (charging bias, developing bias, exposure timing, exposure output, etc.) in the image forming units 6Y, 6M, 6C, and 6K are adjusted. Thus, color image density correction and color misregistration correction are performed (this series of control is referred to as “adjustment mode”).

This adjustment mode is performed mainly during non-image formation and during a warm-up operation immediately after the main power is turned on. That is, the patch pattern B (detection toner image) is formed on the surface of the intermediate transfer belt 8 at a timing different from the timing at which the transfer toner image A is formed on the surface of the intermediate transfer belt 8.
In FIG. 3, in order to facilitate understanding of the positional relationship between the transfer toner image A (ordinary toner image) and the patch pattern B (detection toner image) on the intermediate transfer belt 8, both A and B are used. Is shown on the intermediate transfer belt 8.
In FIG. 3, in order to clarify the relationship with the image area W (maximum image area), a transfer toner image A (normal toner image) formed as an output image on the recording medium P is a solid image. Although illustrated, the transfer toner image A does not have to be formed on the entire surface of the image area W, and may be formed partially within the image area W.

Referring to FIG. 3, in the present embodiment, the width direction (the vertical direction in FIG. 1 and the left-right direction in FIG. 3) in which transfer toner image A is formed on intermediate transfer belt 8 (image carrier). The patch pattern B (detection toner image) is formed outside the image area W in the direction perpendicular to the running direction indicated by the black arrow in FIG.
The secondary transfer roller 19 (transfer member) is installed in a range in the width direction where the patch pattern B (detection toner image) cannot be transferred to the recording medium P. That is, the roller portion of the secondary transfer roller 19 (the portion in contact with the intermediate transfer belt 8) is a range slightly larger than the image region W so as to include the image region W and has a width including the patch pattern B. It is formed in a range not including the range of directions.
In addition, the cleaning blade 10a (intermediate transfer cleaning blade) is formed in a range including the image region W and a region outside the region (non-image region) and in the width direction including the patch pattern B. .
Further, the intermediate transfer belt 8 and the photosensitive drums 1Y, 1M, 1C, and 1K and the primary transfer rollers 9Y, 9M, 9C, and 9K reach the range in the width direction including the patch pattern B as in the cleaning blade 10a. Is formed.

In this embodiment, at the time of warming up (non-image formation), the photosensitive drums 1Y, 1M, 1C are subjected to the image forming process (charging / exposure / development process) described above with reference to FIGS. A patch pattern B is formed in a non-image area on 1K. Then, in the primary transfer process, the patch pattern B is primarily transferred to the intermediate transfer belt 8, and the patch pattern B that has passed through the position of the secondary transfer roller 19 as it is is detected by the photosensor 41 (detection means). The patch pattern B that has passed through the position of the photo sensor 41 then reaches the position of the cleaning blade 10a (intermediate transfer cleaning device 10) and is removed from the intermediate transfer belt 8.
On the other hand, when the patch pattern B is detected by the photosensor 41, based on the detection result, the image density of the toner image formed on each of the photosensitive drums 1Y, 1M, 1C, and 1K becomes a target adjustment value. The image forming conditions (development bias, charging bias, exposure output, etc.) are adjusted as appropriate, and the image forming conditions prevent color deviation from occurring in the color image formed on the intermediate transfer belt 8 in an overlapping manner. (The exposure timings on the four photosensitive drums 1Y, 1M, 1C, and 1K, etc.) are adjusted as appropriate. Then, after such an adjustment mode is completed, the normal image forming process (printing operation) described above with reference to FIGS. 1 and 2 is performed.
For the mode of the patch pattern B formed on the surface of the intermediate transfer belt 8 and the adjustment control of the image forming conditions using the patch pattern B, known ones (for example, see Patent Documents 2 and 3) are used. be able to.

Hereinafter, the characteristic configuration and operation of image forming apparatus 100 according to the present embodiment will be described in detail.
As described above, in the present embodiment, the “adjustment mode” is executed mainly during warm-up. At this time, in this embodiment, after the patch pattern B (detection toner image) is detected by the photo sensor 41 (detection means), the patch pattern B reaches the position of the intermediate transfer cleaning device 10 (cleaning blade 10a). After that, the image forming apparatus 100 records the number of passes (the number of repasses) in which the intermediate transfer belt 8 further travels (idle) and passes the portion B ′ where the patch pattern B is formed at the position of the intermediate transfer cleaning device 10. This is variable based on the cumulative number of sheets to which the medium P is passed (cumulative print number).

That is, in any case, the patch pattern B formed on the intermediate transfer belt 8 in the adjustment mode is once cleaned by passing through the position of the cleaning blade 10a. Thus, the number of idling of the intermediate transfer belt 8 is controlled so as to vary the number of times that the cleaning process is performed after passing the position of the cleaning blade 10a (the number of times of passage).
Here, the “number of idle rotations” of the intermediate transfer belt 8 is the number of times that the intermediate transfer belt 8 travels (idls) further continuously by the control of the drive motor by the control unit 90 after the adjustment mode ends. One idling is equivalent to the running of the intermediate transfer belt 8 for one round. In the present embodiment, when the adjustment mode ends, the portion B ′ where the patch pattern B has been formed is positioned downstream from the intermediate transfer cleaning device 10 by 0.7 to 0.9 laps. It has become. Therefore, referring to FIG. 5, the number of idling times is zero when the portion B ′ where the patch pattern B is formed after the adjustment mode is converted into the number of times of passing through the position of the intermediate transfer cleaning device 10 again. (The cleaning process for the patch pattern B is performed only once). Similarly, the number of idling 0.4 times in FIG. 5 is equivalent to the number of times of passing 1 time (cleaning process 2 times), and the number of times of idling 1.4 times is equivalent to the number of times of passing 2 times (cleaning process 3 times). 2.4 times corresponds to 3 passes (4 cleanings).
Hereinafter, in the present embodiment, the control for additionally performing the idling of the intermediate transfer belt 8 to perform the cleaning process of the patch pattern B will be appropriately referred to as a “cleaning mode”.

As described above, the number of times that the patch pattern B is subjected to the cleaning process according to the cumulative number of sheets to be passed varies depending on the frequency of use of the intermediate transfer belt 8, and the cleaning process is performed once. This is because the patch pattern B cannot be sufficiently removed by simply performing, and the patch pattern B ′ may remain on the intermediate transfer belt 8 after cleaning.
Specifically, as shown in FIG. 6, in the initial stage when the intermediate transfer belt 8 is close to a new one, the arithmetic average roughness Ra and the maximum height Rz of the belt surface are both low and the belt surface is relatively smooth. When the intermediate transfer belt 8 is used to some extent (mid-term), the arithmetic average roughness Ra and the maximum height Rz of the belt surface are both high, and the belt surface is not relatively smooth. Therefore, as shown in FIG. 7, the toner adhesion to the intermediate transfer belt 8 is stronger at the initial stage than at the time (medium period), and the cleaning of the patch pattern B is likely to occur. Therefore, in the initial stage, control is performed so that the number of times of cleaning processing (number of times of passage) is larger than that of time (medium term). In particular, when the arithmetic average roughness Ra is 0.02 or less and the maximum height Rz is 0.2 or less, a cleaning failure in which the patch pattern B slips through the cleaning blade 10a is likely to occur. Further, the inventors of the present application have confirmed through experiments that such a phenomenon becomes significant in the intermediate transfer belt 8 having a single layer structure of polyamideimide.
Further, when the intermediate transfer belt 8 is further used, the cleaning blade 10a and the intermediate transfer belt 8 are also worn due to the sliding contact with the cleaning blade 10a. . For this reason, the control is performed so that the number of cleaning processes (the number of times of passage) is increased again when shifting from the middle stage to the final stage over time. Even when a roller member such as a cleaning brush is used in place of the cleaning blade 10a, almost the same phenomenon occurs. Therefore, it is preferable to perform the cleaning mode in the same manner.

  Specifically, with reference to FIG. 5, in the present embodiment, the number of passes (the number of idling) increases until the cumulative number of sheets passed reaches zero from the first threshold (20,000 sheets (20k sheets)), Until the cumulative number of sheets passed exceeds the first threshold and reaches the second threshold (200,000 sheets (200k sheets)), the number of passes (idling number) decreases, and after the cumulative number of sheets passes the second threshold The drive motor that drives the intermediate transfer belt 8 is controlled by the control unit 90 so that the number of passes increases again.

By performing such control, the cleaning of the patch pattern B is uniformly performed when the adjustment mode is performed (when the patch pattern B is formed) regardless of whether it is initial or elapsed or whether the cumulative number of sheets has passed. The intermediate transfer belt 8 itself, members such as the cleaning blade 10a that contacts the intermediate transfer belt 8, and the intermediate transfer belt 8 are driven as compared with the case where the number of times of processing (the idling speed of the intermediate transfer belt 8) is increased. It is possible to reduce a problem that the life of the drive mechanism is shortened. That is, the defective cleaning of the patch pattern B formed on the intermediate transfer belt 8 is efficiently suppressed without wastefully shortening the life of the intermediate transfer belt 8 or the like.
In the present embodiment, as described above with reference to FIG. 3 and the like, the patch pattern B is formed in the non-image area, and therefore, compared to the case where the patch pattern B is formed in the image area W. The patch pattern B that has undergone cleaning failure is not directly transferred onto the recording medium P, and an abnormal image (cleaning failure image) is not output. However, if the poorly cleaned toner formed in the non-image area of the intermediate transfer belt 8 is left as it is, the toner will eventually adhere to the intermediate transfer belt 8, and the photoreceptor drum 1Y, 1M, 1C, 1K and the cleaning blade 10a will be damaged. In such a case, the subsequent adjustment mode (image density correction or color misregistration correction) is not accurately performed, which affects the output image. Therefore, application of the present invention is useful.

  In the present embodiment, the number of cleaning processes for the patch pattern B in the adjustment mode (the number of idle rotations of the intermediate transfer belt 8) is determined by determining the initial, elapsed time (medium period), and elapsed time (final period) based on the cumulative number of sheets passed. ) Was variably controlled. On the other hand, the number of cleaning processes for the patch pattern B in the adjustment mode (intermediate transfer) is determined by judging the initial, elapsed time (intermediate period), and elapsed time (final period) based on the accumulated travel distance of the intermediate transfer belt 8 (image carrier). The idling speed of the belt 8 can be variably controlled. Specifically, if the traveling speed of the intermediate transfer belt 8 is always constant, the variable control in the adjustment mode described above can be performed based on the drive time of the drive motor that drives the intermediate transfer belt 8.

Further, as shown in FIG. 1, the image forming apparatus 100 according to the present embodiment is provided with a temperature sensor 85 as temperature detecting means for detecting the ambient temperature (outside air temperature).
Then, referring to FIG. 5, when the temperature detected by temperature sensor 85 (temperature detection means) is low, the number of passes (the number of idling) is larger than when the temperature detected by temperature sensor 85 is high. It is controlled to become. That is, based on the ambient temperature, the number of cleaning processes for the patch pattern B in the adjustment mode (the idling speed of the intermediate transfer belt 8) is variably controlled.
Such control is performed even when the surface property of the intermediate transfer belt 8 is the same, and when the ambient temperature is high, defective cleaning of the patch pattern B hardly occurs, and when the ambient temperature is low, the patch is used. This is because defective cleaning of the pattern B is likely to occur. This is considered to be caused by the fact that the hardness of the cleaning blade 10a made of a rubber material changes with temperature.
By performing such control, when the adjustment mode is performed regardless of the ambient temperature (when the patch pattern B is formed), the number of times of cleaning processing for the patch pattern B (idle rotation of the intermediate transfer belt 8) is performed. As compared with the case of performing the number), the defective cleaning of the patch pattern B formed on the intermediate transfer belt 8 can be efficiently suppressed without wastefully shortening the life of the intermediate transfer belt 8 or the like.

Hereinafter, with reference to FIGS. 4 and 5, an example of variable control of the number of cleaning processes (the idling speed of the intermediate transfer belt 8) for the patch pattern B in the adjustment mode based on the cumulative number of sheets to be passed and the ambient temperature will be described. explain.
Referring to FIG. 4, when the adjustment mode is started in accordance with the warm-up operation of image forming apparatus 100 (step S1), patch pattern B is formed on intermediate transfer belt 8 through the image forming process described above. (Step S2). Then, the patch pattern B is detected by the photosensor 41, and image forming condition adjustment control is performed based on the detection result (step S3). At the same time, the accumulated sheet number is detected by a counter (built in the control unit 90) that counts the accumulated sheet number, and the ambient temperature is detected by the temperature sensor 85 (step S4).
Then, the detected information about the cumulative number of sheets to be passed and the temperature are collated with the control table shown in FIG. 5 stored in advance in the memory (ROM) by the CPU of the control unit 90 and added after the adjustment mode is completed. The number of idling times X (number of passes) of the intermediate transfer belt 8 to be performed is determined (step S5). Then, it is determined whether or not the number of idling X determined in step S5 is greater than zero (step S6). If it is greater than zero, a “cleaning mode” is set in which the intermediate transfer belt 8 is further idled by the determined number of idling. If it is zero (step S7), if it is zero, the “cleaning mode” is not executed and this flow is ended (step S8).

  For example, if it is detected in steps S4 to S5 that the ambient temperature is less than 10 ° C. and the cumulative number of sheets to be passed is 20,000 sheets (20k sheets) or less, the control table shown in FIG. The number of times is determined to be 1.4 times (one pass number), and the intermediate transfer belt 8 is idly driven accordingly. In steps S4 to S5, the ambient temperature is in the range of 10 ° C. to 25 ° C., and the cumulative number of sheets passed is in the range of 20,000 (20k) to 200,000 (200k). If it is detected, it is determined from the control table shown in FIG. 5 that the number of idling is zero (the number of passes is zero), and the intermediate transfer belt 8 is immediately driven without performing idling of the intermediate transfer belt 8 after the adjustment mode. Will stop driving.

Note that the control table shown in FIG. 5 is an example, and the control table related to the cleaning mode is not limited to this, and the number of paper sheets (number of thresholds) or the number of temperatures (number of thresholds). ) Can be further subdivided (increased) or simplified (decreased).
Further, specific setting values related to the cleaning mode such as the number of sheets to be passed, the temperature threshold itself, the number of thresholds, the number of idling (passing times), and the like can be obtained from the operation panel 80 of the image forming apparatus 100 (see FIG. 1). It can also be configured so that it can be changed to an arbitrary set value. For example, the “idling speed” in the control table shown in FIG. 5 can be set to an arbitrary value in the range of 0.1 to 3 times. As a result, it is possible to control the optimum cleaning mode according to the state even when there is a variation in characteristics between apparatuses or when the maintenance of the intermediate transfer unit 15 is performed before the end of its service life. become.

Here, in the present embodiment, after the patch pattern B (detection toner image) is detected by the photosensor 41 (detection means), and after the image forming conditions are adjusted based on the detection result ( When the intermediate transfer belt 8 further travels (after the adjustment mode) (in the cleaning mode), a charging bias is applied to the plurality of charging portions (4Y) that respectively charge the plurality of photosensitive drums 1Y, 1M, 1C, and 1K. The primary transfer bias is controlled not to be applied to the primary transfer rollers 9Y, 9M, 9C, and 9K (primary transfer members). That is, when the cleaning mode is executed and the intermediate transfer belt 8 is idled, both the charging bias and the primary transfer bias are turned off.
By performing such control, the patch pattern B ′ remaining on the intermediate transfer belt 8 is electrostatically moved and attached to the photosensitive drums 1Y, 1M, 1C, and 1K during the cleaning mode, and the photosensitive drum 1Y. It is possible to reduce a problem that filming due to toner occurs in 1M, 1C, and 1K.

In the present embodiment, the patch pattern B (detection toner image) is formed on the surface of the intermediate transfer belt 8 at a timing different from the timing at which the transfer toner image A is formed on the surface of the intermediate transfer belt 8. did.
In contrast, in the present embodiment, since the patch pattern B is formed in the non-image area, the same timing as the timing at which the transfer toner image A is formed on the surface of the intermediate transfer belt 8 is used. Thus, the patch pattern B can be formed on the surface of the intermediate transfer belt 8. In such a case, after a series of transfer processes for the transfer toner image A on the intermediate transfer belt 8 is completed (after the image forming operation is completed), the patch pattern B based on the number of sheets to be passed and the temperature is applied. By performing the cleaning mode with the bottom of the book aligned so that the number of cleaning processes is equivalent to that of the present embodiment, the same effect as that of the present embodiment can be obtained.

In the present embodiment, the patch pattern B (detection toner image) outside the region (non-image region) with respect to the image region W in the width direction where the transfer toner image A is formed on the intermediate transfer belt 8 (image carrier). ) Is formed.
On the other hand, as shown in FIG. 8, the patch pattern B (in the image area W) in the area (image area W) with respect to the image area W in the width direction where the transfer toner image A is formed on the intermediate transfer belt 8 (image carrier). A detection toner image) may be formed. In that case, the secondary transfer roller 19 (transfer member) can maintain the state in which the patch pattern B is carried on the intermediate transfer belt 8 at least at the timing when the patch pattern B passes through the position (secondary member). A bias having a polarity different from the secondary transfer bias (which is a transfer bias in a normal secondary transfer process) is applied so as not to move toward the transfer roller 19.
Even in such a case, in the adjustment mode in the warm-up operation, the variable control (cleaning mode) of the number of cleaning processes for the patch pattern B based on the number of sheets to be passed and the temperature is performed in the same manner as in the present embodiment. By doing so, an effect similar to that of the present embodiment can be obtained. In particular, when the patch pattern B is formed in the image area W, there is a possibility that the defective patch pattern B is transferred onto the recording medium P and an abnormal image (defective cleaning image) is output. Therefore, by applying the present invention, such a problem can be prevented. Further, when the patch pattern B is formed in the image region W, the size in the width direction of the intermediate transfer belt 8, the cleaning blade 10a, the photosensitive drums 1Y, 1M, 1C, and 1K can be reduced, so that the image formation is performed. The apparatus 100 can be reduced in size as a whole.

  As described above, in this embodiment, after the patch pattern B (detection toner image) is detected by the photosensor 41 (detection unit), the patch pattern B is transferred to the intermediate transfer cleaning device 10 (cleaning blade 10a). After reaching the position, the image forming apparatus 100 records the number of times the intermediate transfer belt 8 (image carrier) further travels and passes the portion B ′ where the patch pattern B is formed at the position of the intermediate transfer cleaning device 10. It is variable based on the cumulative number of sheets through which the medium P is passed. Accordingly, it is possible to efficiently prevent a cleaning failure with respect to the patch pattern B formed on the intermediate transfer belt 8 without wastefully shortening the life of the intermediate transfer belt 8 or the like.

In this embodiment, the color image forming apparatus 100 using the intermediate transfer belt 8 as an image carrier, the secondary transfer roller 19 as a transfer member, and the intermediate transfer cleaning device 10 as a cleaning device is used. The present invention was applied. In contrast, an image forming apparatus using another image carrier, a transfer member, or a cleaning device (for example, a photosensitive drum is used as an image carrier, a transfer roller is used as a transfer member, and a photoconductor is used as a cleaning device. The present invention can also be applied to a monochrome image forming apparatus in which a drum cleaning device is used.
In such a case, the same effect as in the present embodiment can be obtained.

In the present embodiment, the photo sensor 41 (detecting means) is positioned upstream of the cleaning device 10 in the traveling direction of the intermediate transfer belt 8 and is intermediate to the secondary transfer roller 19. It was installed at a position downstream in the traveling direction. However, the photo sensor 41 (detection means) is located upstream of the cleaning device 10 in the running direction of the intermediate transfer belt 8, and the intermediate transfer belt 8 is positioned relative to the image forming units 1Y, 1M, 1C, and 1K. It is only necessary to be installed at a position downstream in the traveling direction. For example, the intermediate transfer belt 8 is located upstream of the secondary transfer roller 19 in the traveling direction, and is located at the image forming units 1Y, 1M, 1C, and 1K. On the other hand, the intermediate transfer belt 8 can be installed at a position downstream of the running direction.
In such a case, the same effect as in the present embodiment can be obtained.

In the present embodiment, the intermediate transfer belt 8 having a PAI single-layer structure is used. As the intermediate transfer belt 8, PI (polyimide), PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene) are used. Copolymer), PC (polycarbonate), etc. may be formed in a single layer or a plurality of layers, and a conductive material such as carbon black dispersed therein may be used.
Furthermore, a release layer can be coated on the surface of the intermediate transfer belt 8 as necessary. At that time, materials used for the coating are ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four A fluororesin such as fluorinated ethylene-hexafluoropropylene copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.
Moreover, as a manufacturing method of the intermediate transfer belt 8, a casting method, a centrifugal molding method, or the like can be used, and a step of polishing the surface can be performed as necessary.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1Y, 1M, 1C, 1K photosensitive drum,
8 Intermediate transfer belt (image carrier),
9Y, 9M, 9C, 9K primary transfer roller (primary transfer member),
10 Intermediate transfer cleaning device (cleaning device),
10a Cleaning blade (intermediate transfer cleaning blade),
12 Secondary transfer counter roller,
19 Secondary transfer roller (transfer member, secondary transfer member),
41 Photosensor (detection means),
80 operation panel (operation means),
85 Temperature sensor (temperature detection means),
90 control unit (CPU),
100 image forming apparatus (image forming apparatus main body), P recording medium,
A transfer toner image (normal toner image),
B, B 'patch pattern (detection toner image), W image area.

JP 2013-228653 A JP 2006-47605 A JP 2000-184198 A Japanese Patent Laid-Open No. 10-221978

Claims (8)

An image carrier that travels in a predetermined direction;
A transfer member for transferring a toner image carried on the surface of the image carrier to a recording medium as a transfer toner image;
A cleaning device for removing untransferred toner carried on the surface of the image carrier;
A detecting unit which is installed at a position upstream of the image carrier in the running direction with respect to the cleaning device and detects a detection toner image formed on the surface of the image carrier separately from the transfer toner image; ,
With
After the detection toner image is detected by the detection means, after the detection toner image reaches the position of the cleaning device, the image carrier is further driven to move to the position of the cleaning device. The number of times of passage through the portion where the image is formed is variable based on the cumulative number of sheets through which the recording medium is passed by the image forming apparatus or the cumulative travel distance of the image carrier. Image forming apparatus.   The number of passages increases until the cumulative sheet passing number or the cumulative traveling distance reaches the first threshold value from zero, and the cumulative sheet passing number or the cumulative traveling distance exceeds the first threshold value and reaches the second threshold value. 2. The control is performed so that the number of passages decreases until the number of passes, and the number of passages increases again after the cumulative number of sheets passed or the cumulative travel distance exceeds the second threshold. The image forming apparatus described. Equipped with a temperature detection means for detecting the ambient temperature,
The control is performed such that when the temperature detected by the temperature detection means is low, the number of times of passage is increased compared to when the temperature detected by the temperature detection means is high. The image forming apparatus according to claim 2. The detection means is installed at a position downstream of the transfer member in the running direction of the image carrier,
The detection toner image is formed on the surface of the image carrier at a timing different from the timing at which the transfer toner image is formed on the surface of the image carrier. Item 4. The image forming apparatus according to Item 3. The detection toner image is formed outside an area with respect to the image area in the width direction where the transfer toner image is formed on the image carrier,
The image forming apparatus according to claim 1, wherein the transfer member is installed in a range in a width direction in which the detection toner image cannot be transferred to a recording medium. The detection toner image is formed in an area with respect to an image area in a width direction in which the transfer toner image is formed on the image carrier.
The transfer member is applied with a bias having a polarity different from the transfer bias so that the detection toner image can be held on the image carrier at least at the timing when the detection toner image passes through the transfer member. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The image carrier is an intermediate transfer belt made of polyamideimide,
The image forming apparatus according to claim 1, wherein the transfer member is a secondary transfer roller or / and a secondary transfer counter roller as a secondary transfer member. A plurality of photosensitive drums arranged side by side so as to face the intermediate transfer belt;
A plurality of primary transfer members installed to face the plurality of photosensitive drums via the intermediate transfer belt;
With
The plurality of photosensitive drums after the detection toner image is detected by the detection means and after the image forming conditions are adjusted based on the detection result, when the image carrier is further run. The control is performed so that a charging bias is not applied to a plurality of charging portions that respectively charge the plurality of primary transfer members, and a control is performed so that a primary transfer bias is not applied to the plurality of primary transfer members. Image forming apparatus.

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