JP6455034B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having an intermediate transfer belt. More specifically, the image forming apparatus has a cleaner member that removes foreign matters such as residual toner on the intermediate transfer belt, and the cleaner member also removes the filming material generated on the intermediate transfer belt. It is about.

  In an image forming apparatus using toner, a toner image formed on a photoreceptor is temporarily transferred to an intermediate transfer belt (primary transfer), and further transferred to an external output medium such as printing paper (second). (Next transfer) In an image forming apparatus having such an intermediate transfer belt, a cleaning unit for removing residual toner on the intermediate transfer belt is generally provided. This is because a certain amount of toner remains on the intermediate transfer belt even after the secondary transfer, and it is necessary to remove this residual toner before receiving the next primary transfer of a new toner image.

  Here, a film-like substance tends to be generated on the surface of the intermediate transfer belt by performing an image forming operation in a durable manner. This phenomenon is called filming, and the resulting film-like substance is called filming substance. The origin of the filming substance is a part of toner (external additive etc.) and paper powder, and these are fixed on the intermediate transfer belt to form a thin layer. When this filming material is generated, the resistance characteristic against the transfer current changes at that portion.

  On the other hand, filming does not always occur uniformly over the entire surface of the intermediate transfer belt. There is a tendency that filming is more likely to occur at a place where the toner image is not carried much than at a place where a large amount of toner image is carried. This is because, in a portion where the toner image is not carried so much, the action of scraping the filming material from the intermediate transfer belt by the cleaner member is weak. This is because the residual toner effectively has a polishing action to scrape the filming material from the intermediate transfer belt through the cleaner member. For this reason, the occurrence of filming has unevenness in the width direction of the intermediate transfer belt, which causes unevenness in image density.

  Therefore, it is necessary to remove the filming substance in the image forming apparatus. In the case of an image forming apparatus using a metal or rubber blade as the cleaner member, the filming substance removal performance can be enhanced by increasing the contact pressure of the blade to the intermediate transfer belt. However, this may damage the intermediate transfer belt or the blade itself may be worn. Therefore, in the image forming apparatus disclosed in Patent Document 1, a roller-shaped cleaner member is used, and a patch image is supplied onto the intermediate transfer belt during non-image formation. This aims to remove the filming material together with the toner supplied as a patch image from the intermediate transfer belt.

JP 2012-8191 A

  However, the above-described conventional technique has the following problems. That is, in the technique of Patent Document 1, there is a section where the filming material is not sufficiently removed in the width direction of the intermediate transfer belt. The reason for this is that, firstly, in the technique of Patent Document 1, the patch image is supplied only to the density reading position by the density sensor in the width direction of the intermediate transfer belt. Providing a large number of concentration sensors will alleviate this problem, but it will not completely resolve it. This is because even in an area that is determined to have high coverage by the density sensor and is not a patch image supply target, there may be a portion with low coverage if viewed in detail. In such a place, even if filming occurs, a patch image is not supplied. For this reason, the filming substance remains unremoved.

  On the other hand, it is also conceivable to supply a patch image not for each section but for the entire width direction of the intermediate transfer belt. In this way, the filming substance can be removed even at the above-mentioned places. However, the burden on the user is excessive. This is because the amount of toner consumed for removing the filming substance becomes so large that it cannot be neglected.

  The present invention has been made to solve the above-described problems of the prior art. In other words, the problem is that the image does not consume more toner than necessary, but effectively removes filming generated in the high coverage area, not to mention the low coverage area. It is to provide a forming apparatus.

An image forming apparatus according to an aspect of the present invention includes an intermediate transfer belt that is an annular belt-like member that carries a toner image and circulates in a circumferential direction, and creates the toner image and transfers the toner image to the intermediate transfer belt. An image forming apparatus having an image forming unit to be applied and a secondary transfer unit for transferring a toner image from an intermediate transfer belt to an external output medium, and forming an image downstream of the position of the secondary transfer unit on the intermediate transfer belt And a filming roller that is provided in contact with the toner image carrying surface upstream of the position of the part, and the filming removal operation for removing the filming material generated on the intermediate transfer belt and the foaming roller whose surface layer is composed of the foamed layer. A filming removal control unit that controls the intermediate transfer bell by the image forming unit with the transfer at the secondary transfer unit turned off during non-image formation. A patch supply unit for supplying a patch toner pattern in a partial range with respect to the upper width direction, and after supplying the patch toner pattern, the foaming roller is rotated in the first rotation state, and then in the second rotation state. A roller rotation control unit that rotates the roller rotation control unit, in the second rotation state, the absolute value of the speed ratio on the surface is 0.5 to 2 with respect to the circulation movement of the intermediate transfer belt in the second rotation state. with the 2.0 range and a Luca unter around, in a first rotational state, the speed difference on the outer peripheral surface on circulating movement of the intermediate transfer belt is small compared to when the second rotation state rotation The open area ratio of the cell wall surface in the foam layer is 50% or less.

  In the image forming apparatus according to the above aspect, the image forming apparatus creates a toner image and transfers the toner image onto the intermediate transfer belt. The toner image is transferred from the intermediate transfer belt to the external output medium by the secondary transfer unit, whereby an image is formed on the external output medium. Here, since filming material tends to be generated on the intermediate transfer belt as the image is formed, the filming removal operation controlled by the filming removal control unit is an operation different from the image forming operation. Done. In the filming removal operation, a patch toner pattern is supplied to a partial range in the width direction on the intermediate transfer belt by the image forming unit according to an instruction from the patch supply unit. Then, the roller rotation control unit sets the foaming roller in a first rotation state in which the speed difference on the outer peripheral surface with respect to the circulating movement of the intermediate transfer belt is small. As a result, the toner of the patch toner pattern passes through the secondary transfer portion and reaches the foaming roller while being carried on the intermediate transfer belt. Therefore, the toner is diffused in the width direction of the intermediate transfer belt by the foaming roller. As a result, a certain amount of toner is also present in the width direction area where the patch toner pattern is not supplied. Therefore, the roller rotation control unit causes the foaming roller to be in a second rotation state that is counter-rotating with respect to the circulating movement of the intermediate transfer belt. Here, since the opening ratio of the wall surface of the cell of the foam layer of the foam roller is low, most of the toner supplied to the foam roller does not enter the interior of the foam roller but stays near the surface. Therefore, the filming material generated on the intermediate transfer belt is effectively peeled off by the counter-rotating foaming roller and the polishing action of the toner existing there. The removal of the filming substance is also performed at a portion other than the width direction section where the patch toner pattern is supplied due to the above-described diffusion action.

  The roller rotation control unit in the image forming apparatus described above rotates the foaming roller in the first rotation state after the patch toner pattern is supplied from the image forming unit to the intermediate transfer belt. It is desirable that the process starts until reaching the place and continues until the time within the range of 0.5 to 5 seconds elapses after the patch toner pattern reaches the foam roller. By performing the first rotation state at such timing, the toner is surely diffused in the width direction.

  The image forming apparatus according to this aspect further includes a coverage rate calculation unit that calculates a coverage rate distribution by the toner image in the width direction of the intermediate transfer belt in image formation by the image forming unit, and the patch supply unit is determined in advance. When there is a section in the width direction having a coverage rate lower than a predetermined reference coverage rate at the patch supply timing, it is desirable that the patch toner pattern is supplied to a region including the section. As a result, the toner is preferentially supplied to the width direction section where the probability that the filming material is generated is high, and the filming material can be reliably removed.

  Further, it is desirable that the patch supply unit supplies the patch toner pattern only to a region in a section where the coverage rate is lower than the reference coverage rate over a predetermined reference width or more. In this way, it is possible to reliably supply the toner to the section where the filming substance is generated in a certain width while suppressing the consumption of the toner due to the formation of the patch toner pattern.

  In the image forming apparatus, the intermediate transfer belt is provided in contact with a position downstream of the secondary transfer portion and upstream of the image forming portion, and cleans the toner image carrying surface of the intermediate transfer belt. It is desirable that a plurality of cleaner members be provided, and at least the one located among the plurality of cleaner members at the most upstream position relative to the circulating movement of the intermediate transfer belt is a foaming roller. As a result, the foaming roller exhibits the filming removal function in the filming removal operation while performing other functions required for the cleaner member, such as removal of transfer residual toner during normal image formation, with other cleaner members. can do. In particular, at this time, the arrival of the patch toner pattern to the foaming roller is not disturbed by other cleaning members.

  In addition, when the intermediate transfer belt is an elastic belt having an elastic layer, it is significant to adopt this configuration. This is because elastic belts tend to produce filming substances more than belts that do not.

  According to this configuration, the image forming apparatus can effectively remove the filming generated in the high coverage area as well as the low coverage area without consuming toner more than necessary. Is provided.

1 is an overall configuration diagram of an image forming apparatus according to an embodiment. It is a perspective view explaining supply of the patch image for filming removal. It is a schematic diagram for demonstrating the relationship between the formed image and a patch image supply area | region. It is sectional drawing of the condition shown in FIG. It is sectional drawing explaining a 2nd mode. It is a perspective view explaining the 2nd mode. It is a table | surface which shows what was used as a filming removal member in an Example and a comparative example. It is a table | surface which shows the structure of an Example and a comparative example. It is a table | surface which shows the structure of an Example and a comparative example.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a tandem type full-color image forming apparatus. The image forming apparatus 1 of this embodiment is generally configured as shown in FIG. The image forming apparatus 1 in FIG. 1 has an intermediate transfer belt 2. The intermediate transfer belt 2 is an annular belt-like member that carries a toner image and circulates in the circumferential direction. The intermediate transfer belt 2 in FIG. 1 circulates in the clockwise direction in the drawing. The intermediate transfer belt 2 in this embodiment is a rubber belt.

  Four color image forming portions 3Y, 3M, 3C, and 3K are arranged along the lower side of the intermediate transfer belt 2 in FIG. Each of the image forming units 3Y, 3M, 3C, and 3K has a photoconductor 31, and forms a toner image on the photoconductor 31 and applies the toner image to the intermediate transfer belt 2. For this reason, a primary transfer roller 4 is provided on the back side of the intermediate transfer belt 2 for each photoconductor 31. The toner image on the photoreceptor 31 is transferred to the intermediate transfer belt 2 by the primary transfer roller 4. Hereinafter, the entire image forming units 3Y, 3M, 3C, and 3K may be collectively referred to as the image forming unit 3. In the image forming units 3Y, 3M, 3C, and 3K, a toner image is formed by a known electrophotographic process such as charging, exposure, and development.

  In FIG. 1, a secondary transfer roller 5 is disposed at a position downstream from the image forming unit 3 in the direction of circulation movement of the intermediate transfer belt 2. The secondary transfer roller 5 is for transferring the toner image on the intermediate transfer belt 2 to the printing paper S that is the final medium discharged outside the apparatus. That is, the intermediate transfer belt 2 moves from the position of the image forming unit 3 to the position of the secondary transfer roller 5 while carrying the toner image. The image forming apparatus 1 is also provided with a control unit 80. The control unit 80 controls each unit of the image forming apparatus 1. As a characteristic function of the control unit 80 as the present embodiment, there is an execution of a filming substance removing operation on the intermediate transfer belt 2 described later.

  A cleaning unit 9 is provided on the upper side of the intermediate transfer belt 2 in FIG. The position where the cleaning unit 9 is provided is a position downstream of the secondary transfer roller 5 and upstream of the image forming unit 3 in the direction of circulation movement of the intermediate transfer belt 2. The cleaning unit 9 is provided with a belt cleaner 6 and a foaming roller 7 on the upstream side thereof.

  The belt cleaner 6 is for removing residual toner on the intermediate transfer belt 2. The belt cleaner 6 is provided with two conductive brush rollers 61 arranged upstream and downstream. Both of the two conductive brush rollers 61 are arranged in contact with the toner image carrying surface of the intermediate transfer belt 2. These two conductive brush rollers 61 are biased in opposite directions. In this way, both the toner that maintains the original charging polarity and the toner whose polarity is reversed are removed from the transfer residual toner.

  The foaming roller 7 is for removing the above-mentioned filming substance generated on the intermediate transfer belt 2. For this reason, the foaming roller 7 is configured such that the cored bar 72 is covered with a foamed layer 71 formed of a polyurethane resin or other foamable resin. Further, the foaming roller 7 is arranged to bite into the toner image carrying surface of the intermediate transfer belt 2 to some extent. That is, the foaming roller 7 is arranged in a state of being pressed against the intermediate transfer belt 2. If the amount of biting of the foaming roller 7 with respect to the intermediate transfer belt 2 (the difference between the thickness of the foamed layer 71 in the free state and the minimum thickness in contact with the intermediate transfer belt 2) is too small, the filming material is removed. If the capacity is insufficient and is too large, an excessive load is applied from the intermediate transfer belt 2. For this reason, it is preferable that the amount of biting is within the range of 10% to 40% with respect to the thickness of the foamed layer 71 in the free state. Examples of the foamable resin constituting the foam layer 71 include silicone resins and rubber materials in addition to the above polyurethane resins.

The opening ratio of the cells (bubbles) in the foam layer 71 should be low. If the aperture ratio is too high, the filming substance removal performance is insufficient. This is because the cells are well connected to each other, so that the toner cannot be kept near the surface which is a contact position with the intermediate transfer belt 2. Preferably, the aperture ratio is 50% or less. The aperture ratio is a ratio obtained by the following expression with respect to the area S1 of the opening with the adjacent cell to the area S of the entire wall surface of the cell.
Opening ratio of cell wall surface (%) = (S1 / S) × 100

  For the areas S and S1, the area occupied by the wall surface and the area occupied by the opening on the enlarged cross-sectional photograph obtained by enlarging the cross section of the foam layer 71 with a microscope (an optical microscope or a scanning electron microscope) are used. That's fine. An open area ratio of 50% or less means that the cell structure of the foam layer 71 is a closed cell structure or a structure that is relatively close to the closed cell structure even if it is an open cell structure. It is. Thereby, the toner can be kept near the surface in the foam layer 71. For this reason, the removal performance of the filming substance by supplying the toner can be effectively exhibited.

  The cell diameter in the foam layer 71 is not particularly limited, but it is advantageous in the range of 50 μm to 1000 μm on average from the viewpoint of recoverability of the object to be cleaned. This is because an object to be cleaned that is smaller than the cell diameter is difficult to be collected by the foam layer 71, whereas if the cell diameter is too large, the wall surface of the cell is small. The thickness of the foam layer 71 is within a range of 5 mm to 30 mm in a normal apparatus configuration.

  The foamed resin used as the foamed layer 71 can be manufactured by either a mechanical floss method or a chemical foaming method, or a combination thereof. The opening ratio of polyurethane foam, generally called closed cell structure, manufactured by the mechanical floss method is about 1%, which is within the above-mentioned preferable range. The open area ratio of polyurethane foam, generally called an open cell structure, produced by a chemical foaming method is about 60%. Therefore, in this case, it is preferable to adjust and manufacture so that the aperture ratio is slightly lower.

  The foaming roller 7 is configured to peel off the filming material generated on the intermediate transfer belt 2 by being rotated with a speed difference with respect to the moving speed of the intermediate transfer belt 2. For this reason, the foaming roller 7 is provided with a rotation drive unit 8 that performs the rotation drive. Specifically, the rotation drive unit 8 is a motor. As a part of the filming substance removing operation, the control unit 80 controls the foaming roller 7 to rotate with a speed difference with respect to the intermediate transfer belt 2 as described above. A counter roller 73 is applied to the opposite side of the foaming roller 7 with the intermediate transfer belt 2 interposed therebetween. The counter roller 73 is always rotated by the circulating movement of the intermediate transfer belt 2.

  The original operation of the image forming apparatus 1 is, of course, image formation on the printing paper S. That is, while the intermediate transfer belt 2 is circulated, a toner image is formed by the image forming unit 3 and transferred to the intermediate transfer belt 2, and the toner image is transferred to the printing paper S by the secondary transfer roller 5. Removal of the transfer residual toner on the intermediate transfer belt 2 after passing through the secondary transfer roller 5 is performed by a belt cleaner 6. Note that image data necessary for forming a toner image in the image forming unit 3 is supplied from the control unit 80.

The filming substance removing operation, which is a characteristic operation of the present invention in the image forming apparatus 1, will be described below. The filming substance removing operation is performed at a time other than image formation. The contents are divided into the following three. This will be sequentially described below.
1. 1. Supply of the patch image 10 onto the intermediate transfer belt 2 2. Driving the foaming roller 7 in the first mode Driving the foaming roller 7 in the second mode

  First, the supply of the patch image of “1.” will be described. The patch image is a toner image that is not intended for transfer onto the printing paper S. Normally, the patch image 10 is formed for toner supply to the foaming roller 7 as shown in FIG. 2, although it is formed for density adjustment and alignment adjustment between colors.

  That is, FIG. 2 shows the patch image 10 supplied on the intermediate transfer belt 2. This is formed by the image forming unit 3 and transferred onto the intermediate transfer belt 2 separately from the purpose of transfer to the printing paper S. When the patch image 10 is supplied, the transfer bias of the secondary transfer roller 5 is turned off. In FIG. 2, a toner reservoir 11 on the front side of the foaming roller 7 is also depicted. The foaming roller 7 in FIG. 2 is in a stopped state in a first mode, which will be described later, and the toner reservoir 11 is where the toner of the patch image 10 is retained by being blocked by the stopped foaming roller 7. is there. Although both the patch image 10 and the toner reservoir 11 are depicted in FIG. 2, the toner reservoir 11 and another patch image 10 need not exist at the same time. .

  FIG. 2 also shows that the patch image 10 is supplied only to an area where a filming substance (hereinafter simply referred to as filming) 12 is generated in the width direction of the intermediate transfer belt 2. . This point will be described. In order to supply the patch image as shown in FIG. 2, it is only necessary to estimate an area where the filming 12 is generated in the width direction of the intermediate transfer belt 2. This estimation is possible based on image data of past image formation.

  For example, it is assumed that a large number of image formations as shown in FIG. In the example shown in FIG. 3, the Y solid pattern 13 and the K solid pattern 16 exist near both ends in the width direction of the intermediate transfer belt 2, and the M solid pattern 14 and the C solid pattern 15 exist just inside them. . A complete blank area 17 exists between the M solid pattern 14 and the C solid pattern 15 (near the center in the width direction of the intermediate transfer belt 2). If only such image formation is performed continuously, the average coverage in the regions P and R near the both ends in the width direction of the intermediate transfer belt 2 in FIG. 3 is very high. . On the other hand, in the area Q in the center in the width direction, the average coverage in the area is almost zero.

  In the image forming apparatus 1, when there is an area where the average coverage in the past image formation is lower than a predetermined threshold as in the area Q of FIG. decide. This is because there is a high possibility that filming 12 is generated in that region. The supply of the patch image 10 shown in FIG. 2 corresponds to an example of such a case. Here, the difference in color in the formed image (Y, M, C, K) may be ignored in calculating the coverage.

  If FIG. 3 is viewed in detail, it can be seen that even within the regions P and R, there are portions with low coverage. A narrow gap between the Y solid pattern 13 and the M solid pattern 14 and a narrow gap between the C solid pattern 15 and the K solid pattern 16. Although it is considered that the filming 12 is also generated in these places (see FIG. 2), the patch image 10 is not supplied to the places. For this reason, the image forming apparatus 1 sets a minimum reference width for determining that the patch image 10 is supplied. That is, when there is a region where the average coverage is lower than the above-described threshold over a width equal to or greater than the minimum reference width, it is determined that the patch image 10 is supplied to that region. As the minimum reference width, for example, an appropriate ratio such as 1/5 or 1/8 of the entire width or the sheet passing width of the intermediate transfer belt 2 may be determined. Alternatively, instead of setting the minimum reference width, it is also possible to fix the method of dividing the region with respect to the width direction of the intermediate transfer belt 2 (that is, the method of dividing the regions P, Q, and R in FIG. 3). You can do the same, but that's fine.

  Although the patch image 10 itself is not supplied to the thin filming areas in the areas P and R, the toner is diffused by “2. Driving the foaming roller 7 in the first mode” described later. . In FIG. 3, there is a blank portion on the outer side of the Y solid pattern 13 and the K solid pattern 16. The coverage is also low in this part, but this part is usually outside the sheet passing range of the printing paper S and can be ignored. Further, the color of the toner used as the patch image 10 is not particularly limited. Any one of Y, M, C, and K may be fixedly designated as the color for the patch image 10. Alternatively, the color with the oldest toner bottle exchange may be determined as the color for the patch image 10 each time. If there is still another determination method, that may be used. Further, the length of the supplied patch image 10 with respect to the circulating movement direction of the intermediate transfer belt 2 may be determined in advance so that the toner amount becomes an amount necessary for removing the filming 12.

  Next, the first mode of “2.” will be described. The first mode is a rotation state of the foaming roller 7 for diffusing the toner supplied on the intermediate transfer belt 2 as the patch image 10 in the width direction of the intermediate transfer belt 2. In this first mode, the foaming roller 7 is stopped or rotated at a low rotational speed. In the case of rotation, counter rotation or width rotation may be performed with respect to the circulating movement of the intermediate transfer belt 2. Specifically, the ratio θ (= V2 / V1) of the speed V2 of the surface of the foaming roller 7 to the circulating movement speed V1 of the intermediate transfer belt 2 may be 0.5 or less in absolute value. This is because the slower the rotation speed of the foaming roller 7, the more advantageous is that the toner in the toner reservoir 11 can be continued without leaking downstream. The best is a stop. Hereinafter, the rotation state of the foaming roller 7 in the first mode is assumed to be stopped. Actually, the foaming roller 7 shown in FIG. 2 is in the first mode.

  The patch image 10 supplied onto the intermediate transfer belt 2 in “1.” moves along with the circulation movement of the intermediate transfer belt 2. When the patch image 10 passes through the secondary transfer roller 5 (now off) due to this movement, the foam roller 7 that is most upstream in the cleaning unit 9 is first encountered next. In the first mode, since the foaming roller 7 is in a stopped state, the patch image 10 cannot pass through the foaming roller 7, and is blocked there and becomes a toner reservoir 11 (FIG. 4). As described above with reference to FIG. 2, the toner reservoir 11 and a different patch image 10 do not have to exist at the same time.

  As shown in FIG. 2, most of the toner in the toner reservoir 11 is present in the central portion of the intermediate transfer belt 2 in the width direction. This is because the toner is originally supplied to the area as the patch image 10. However, a certain amount of toner comes as a patch image 10 in that region. This is because the secondary transfer roller 5 is off and toner is not taken on the printing paper S. For this reason, the toner overflows in the area, and therefore the toner spreads outward in the width direction from the area. This is toner diffusion. Due to this diffusion, a certain amount of toner is distributed to the area where the patch image 10 is not supplied (areas P and R in FIG. 3) at the position before the foaming roller 7.

  What is necessary is just to perform as follows about the period which makes the rotation state of the foaming roller 7 the 1st mode. First, the beginning of the first mode may be somewhere after the patch image 10 is formed and before the patch image 10 reaches the foaming roller 7 at the latest. The best is to start the first mode at the same time that the top of the patch image 10 reaches the foaming roller 7.

  The end of the first mode may be determined so that the toner diffusion in the toner reservoir 11 extends over the entire width direction of the intermediate transfer belt 2. Specifically, in the case of the intermediate transfer belt 2 having a width on the premise of a normal office-size printing paper, the diffusion time may be in the range of about 0.5 seconds to 5 seconds. Therefore, it is preferable that the end of the first mode is when the diffusion time has elapsed since the rear end of the patch image 10 has reached the foaming roller 7.

  When the first mode ends, the second mode of “3.” is performed next. The second mode is a rotation state of the foaming roller 7 for peeling off the filming 12 generated on the intermediate transfer belt 2 by the foaming roller 7. In the second mode, the foaming roller 7 is rotated in the counter direction with respect to the circulating movement of the intermediate transfer belt 2 as shown in FIG. The rotation speed is preferably such that the value of the speed ratio θ is within a range of −2.0 to −0.5 (a negative sign indicates that the counter is rotated). That is, the absolute value of the speed ratio θ is preferably in the range of 0.5 to 2.0. If the speed ratio θ is a small value in absolute value, the rotational speed of the foaming roller 7 is slow, and the filming 12 stripping effect is low. On the other hand, when the absolute value of the speed ratio θ is large, the stripping effect is high, but the load applied to the foaming roller 7 becomes excessive and the life thereof is shortened.

Since the rotational speed of the foaming roller 7 is determined as described above, when the speed difference of the surface of the foaming roller 7 relative to the circulating intermediate transfer belt 2 is considered as an absolute value, the aforementioned speed V1, Using V2,
| V1 | + | V2 |
It is expressed. From the range of the speed ratio θ, this is in the range of 1.5 to 3 times | V1 |. On the other hand, this speed difference in the first mode is within the range of 0.5 to 1.5 times of | V1 | (same as | V1 | when the foaming roller 7 is stopped). Therefore, this speed difference is always greater in the second mode than in the first mode. Conversely, the rotational speed of the foaming roller in the first mode is determined so that this speed difference is smaller than that in the second mode. This is due to the difference in purpose between the first mode and the second mode. This is because in the first mode, it is required to diffuse the toner while accumulating on the foaming roller 7, whereas in the second mode, the scraping ability of the filming 12 is required.

  In the second mode, as shown in FIG. 6, the filming 12 is removed with respect to the entire width direction of the intermediate transfer belt 2. This is because the toner is diffused in the entire width direction of the intermediate transfer belt 2 by the previous first mode. For this reason, all three filming 12 seen on the upstream side (lower left side in the figure) in FIG. 6 have disappeared on the downstream side (upper right side in the figure) from the foaming roller 7. The portion of the wide filming 12 at the center in the width direction of the intermediate transfer belt 2 is the portion where the patch image 10 was originally supplied. For this reason, toner in the toner reservoir 11 is abundant in this portion. Therefore, even the wide filming 12 is removed without any problem. A thin filming 12 portion in the width direction of the intermediate transfer belt 2 and slightly closer to the end is a portion where the patch image 10 was not originally supplied. However, there is still a certain amount of toner in this area. This is because the diffusion of toner in the first mode has reached. Therefore, the thin filming 12 is sufficiently scraped off by the foaming roller 7.

  In this way, the filming is satisfactorily removed by performing the three steps “1.”, “2.”, “3.” in this order. Note that the duration of the second mode may be determined such as for one circulation or two revolutions of the intermediate transfer belt 2. In addition, as a trigger for executing this filming substance removal operation, a triggering event may be determined in advance. For example, for example, immediately after the image forming apparatus 1 is turned on or immediately after the power switch is turned off, every predetermined number of image forming sheets (for example, every 500 sheets or every 1000 sheets) can be considered.

  Furthermore, the coverage calculated from the image data of the past image formation can also be used as a trigger for the filming substance removal operation. That is, for each image formation, the coverage at a predetermined number of past image formations is calculated for each position in the width direction. As a result, if the threshold and the minimum reference width described with reference to FIGS. 2 and 3 are satisfied, the removal operation is executed. This is referred to as “coverage rate measurement” in the description of the test examples described later. In any case, the supply area of the patch image 10 may be determined based on the coverage state in the image formation of a predetermined number of sheets in the latest past at that time (also every 500 sheets or every 1000 sheets, for example).

  Further, the rotation mode of the foaming roller 7 during normal image formation is not particularly limited. The intermediate transfer belt 2 may be driven following the circular movement, or may be the same as the first mode or the second mode. However, driven is preferable in the sense of reducing an extra load on the foaming roller 7. Furthermore, when the foaming roller 7 is stopped in the first mode, it is preferable that the phase angle when the foaming roller 7 is stopped is not the same every time. If the same position is brought into contact with the intermediate transfer belt 2 every time in the first mode, the deterioration of the foamed layer 71 proceeds only at that point. This is because the original life of the foaming roller 7 cannot be exhibited.

  Note that the above-described filming removal operation is naturally performed under the control of the control unit 80. That is, the control unit 80 also has a function as a patch supply unit and a function as a roller rotation control unit. In particular, the supply of the patch image 10 is performed by instructing the image forming unit 3 from the control unit 80. The operation of the rotation state of the foaming roller 7 in the first mode or the second mode is performed by controlling the rotation driving unit 8 by the control unit 80.

  Next, the effect confirmation test conducted by the present inventors will be described. In this test, a bizhub C554 type machine manufactured by Konica Minolta was used as the base machine, and the cleaner was modified as appropriate, and the required control function was incorporated into the test machine. With this testing machine, continuous printing for 100,000 sheets of image formation on A4 size paper (landscape) was performed, and it was confirmed whether filming could be suppressed. The image to be formed was as shown in FIG. For this reason, the supply area of the patch image 10 is as shown in FIG.

  The foaming roller 7 used in this test or a comparative example thereof is listed in the table of FIG. Among these, “brush” is a brush roller. Further, “SUM24G” which is a material of “metal roller” is a kind of sulfur and sulfur composite free-cutting steel. FIG. 8 shows a list of configurations of the example and the comparative example. Items that require special explanation in the item names in the table of FIG. 8 will be described.

Filming removal member: This is a column indicating which one of the foaming roller 7 or the comparison example in the table of FIG. 7 is used.

Arrangement: The above-mentioned “filming removal member” is arranged on either the upstream side or the downstream side with respect to other cleaning members (the belt cleaner 6 in the example of FIG. 1) in the entire cleaning unit 9. It is a column indicating whether or not.

Rotation state: The numerical value after “Counter” or “With” is the absolute value of the speed ratio θ described above. The speed (V1) of the circulating movement of the intermediate transfer belt 2 was fixed at 250 mm / s in both examples and comparative examples.

Coverage rate measurement: This column indicates whether the coverage rate calculation result is used as a trigger for the filming removal operation. In the example in which this column is “present”, the coverage ratios at 11 measurement points arranged uniformly over the entire width direction of the intermediate transfer belt 2 were counted based on the past 500 image data. Then, when there is a measurement point where the coverage is less than 1%, the continuous printing is interrupted at that time, and control for executing the filming removal operation is performed. In the case of “None” in this column, the above-described control is not applied, and the continuous printing is interrupted for every 5000 sheets of image formation, and the filming removal operation is executed.

Bias application: A column indicating whether or not a bias application has been performed on the “filming removal member”. In the example of “Yes” in this column, a bias is applied so that the “filming removal member” becomes +500 V with respect to the intermediate transfer belt 2 in the second mode.

  The reasons why Comparative Example 1 to Comparative Example 12 in the table of FIG. 8 are not examples but comparative examples are as follows.

Comparative Example 1: “Arrangement” is not upstream but downstream.
Comparative Examples 2 to 4: The rotation state in the second mode is not a counter but a stop.
Comparative example 5: The rotation state in the second mode is not a counter but a width.
Comparative Example 6: Although the rotation state in the second mode is a counter, the θ value exceeds 2.0.
Comparative Example 7: “Filming removing member” is not a single bubble but a brush.
Comparative Example 8: “Filming removing member” is not a single bubble but a metal roller.
Comparative Example 9: “Filming removing member” is not a single bubble but a pad.
Comparative Example 10: “Filming removing member” is not a single bubble but a continuous bubble.
Comparative Examples 11 and 12: “Patch Image” is “None” instead of “Yes”.

  FIG. 9 shows a list of test results for each of the examples and comparative examples of FIG. Details of each test item in the table of FIG. 9 are as follows.

Filming: A column indicating the evaluation results of the filming occurrence state on the intermediate transfer belt 2 after completion of printing durability. Specifically, a high coverage region (regions P and R in FIG. 3) and a low coverage region (same region Q) were visually observed and evaluated as follows.
OO: The difference between the high coverage area and the low coverage area cannot be recognized.
○○: Although it is not obvious at first glance, the difference between the high coverage area and the low coverage area can be recognized if you observe closely.
○: Within the high coverage area, the image portion (position where the Y solid pattern 13, the M solid pattern 14, the C solid pattern 15 and the K solid pattern 16 are formed) and the non-image portion (the Y solid pattern 13 and the M solid pattern 14). And a slight difference between the C solid pattern 15 and the K solid pattern 16).
X: Remarkable difference between the image portion and the non-image portion is recognized within the high coverage area.

Filming removal member durability: This is a column showing the evaluation results of the damage state of the “filming removal member” after completion of printing. Specifically, the surface of the “filming removal member” (the surface of the contact surface to the intermediate transfer belt 2 for the pad) is observed visually and with a digital microscope (Keyence VHF-500F type machine) Evaluation was performed as follows.
OO: No damage is seen at all.
○○: Although it is not obvious at first glance, damage can be recognized if observed closely.
○: Damage is recognized, but does not affect image quality.
X: Damaged to an extent that affects the image quality.

Comprehensive evaluation: An evaluation result obtained by combining the results of the above two items.
◯: When the above two items are both ◯ or more.
X: When one of the above two items has x.

  From FIG. 9, all of Examples 1 to 16 were good results. Among them, in particular, in Example 15, the “coverage rate measurement” is set to “none”, but the result is still good. From this, it can be seen that it is not always necessary to trigger the removal operation of the filming substance by measuring the coverage rate, and it is only necessary to perform the removal operation periodically for each determined number of sheets. However, when Example 15 is compared with Example 1 in which the conditions are the same except for the presence / absence of coverage rate measurement, Example 1 has one more o in the “filming” evaluation item. From this, it can be said that it is better to trigger by measuring the coverage rate.

  In the sixteenth embodiment, the “bias application” is only “present”. However, when Example 16 is compared with Example 1 in which the conditions are the same except for the presence or absence of bias application, the evaluation results are exactly the same. From this, it can be seen that from the viewpoint of filming removal performance, bias application is unnecessary, but even if applied, there is no harmful effect.

  On the other hand, in Comparative Examples 1-12, all the results were not good. In particular, the “filming” item itself was bad, and the filming 12 was not sufficiently removed. Moreover, the item “Filming removal member durability” was not good depending on the comparative example. The following outlines the reasons why the results of each comparative example were not good.

Comparative Example 1: It is considered that the toner of the patch image 10 did not sufficiently reach the foaming roller 7 because the “arrangement” is not upstream but downstream. For this reason, it is considered that the foaming roller 7 was performing the removal operation in a state where there was not enough toner. In other words, it can be said that the foaming roller 7 needs to be arranged at the most upstream as compared with other members in the cleaning unit 9. Otherwise, the toner of the patch image 10 is eaten by another cleaning member and does not reach the foaming roller 7.

Comparative Examples 2 to 4: It is considered that the filming 12 was not sufficiently peeled off by the foaming roller 7 in the second mode because the rotation state in the second mode was not a counter but stopped. In addition, the comparative example 2 which stopped the foaming roller 7 also in the first mode was not good in durability of the foaming roller 7. This is considered to be because the same location in the foaming roller 7 continued to contact the intermediate transfer belt 2 and the location was locally degraded.

Comparative Example 5: It is considered that the filming 12 was not sufficiently peeled off by the foaming roller 7 in the second mode because the rotation state in the second mode was not a counter but a width.

Comparative Example 6: Since the θ value in the rotation state in the second mode exceeds 2.0, it is considered that the deterioration of the foaming roller 7 progressed early and was no longer used at an early stage. . This means that the rotational speed of the counter rotation of the foaming roller 7 is too fast and the load on the foamed layer 71 is excessive. In fact, in this comparative example, “filming removal member durability” is also “x”.

Comparative Examples 7 to 9: Since the “filming removal member” is not a single bubble but a brush, a metal roller or a pad, it was originally not a member suitable for scraping the filming 12 from the intermediate transfer belt 2. Conceivable. In particular, it is considered that the pad of Comparative Example 9 that is always in a stopped state and receives friction from the intermediate transfer belt 2 has been damaged early due to the same reason as in Comparative Example 2 above.

Comparative Example 10: Since the “filming removing member” is not a single bubble but a continuous bubble, it is considered that the toner supplied as the patch image 10 could not be retained near the surface of the foaming roller 7. For this reason, it is considered that substantially no toner is present at the position where the intermediate transfer belt 2 and the foaming roller 7 rub against each other, and the filming 12 has not been sufficiently removed.

Comparative Examples 11 and 12: Since the “patch image” is “not” instead of “present”, it is considered that the foaming roller 7 was in the second mode with almost no toner. In this case, it is considered that the foaming roller 7 was not able to remove the filming 12 sufficiently.

  As described in detail above, according to the present embodiment, the foaming roller 7 made of a foamed resin having a single foam structure is disposed at the upstream position in the cleaning unit 9. Then, the patch image 10 is partially supplied onto the intermediate transfer belt, and the first mode in which the toner is diffused in the width direction by the foaming roller 7, and the filming on the intermediate transfer belt is performed by rotating the foaming roller 7 counter. And the second mode in which 12 is peeled off. Thus, the image forming apparatus 1 is realized in which the filming 12 generated on the intermediate transfer belt 2 is effectively removed so that the density unevenness of the image does not occur.

  In particular, since the foaming roller 7 comes into contact with the intermediate transfer belt 2 first after the secondary transfer roller 5, the toner of the patch image 10 reliably reaches the foaming roller 7. For this reason, high filming removal performance is exhibited. Further, the supply area of the patch image 10 is limited to an area with low coverage. For this reason, an excessive amount of toner is not consumed for the filming removal operation. Nevertheless, the filming 12 that occurs locally in the high coverage area can also be removed. This is because the toner of the patch image 10 is accumulated in front of the foaming roller 7 and diffused in the width direction by setting the foaming roller 7 to the first mode prior to the second mode. In addition, the material of the foam layer of the foam roller 7 is a single-foam type foam resin, so that the toner of the patch image 10 that has reached the foam roller 7 stays in the vicinity of the contact position between the intermediate transfer belt 2 and the foam roller 7. To be placed. This ensures that the filming removal performance is exhibited.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the configuration of the cleaning unit 9 is not limited to that shown in FIG. In the present invention, the belt cleaner 6 is not provided in the cleaning unit 9 but only the foaming roller 7 is provided. This is because even in this configuration, the foaming roller 7 is in contact with the intermediate transfer belt 2 first after the secondary transfer roller 5. Further, when the belt cleaner 6 exists on the downstream side of the foaming roller 7, the member that contacts the intermediate transfer belt 2 in the belt cleaner 6 may be the same as the foaming roller 7.

  Further, the area for supplying the patch image 10 may be a slightly wider area than the area determined as the low coverage area. Further, the intermediate transfer belt 2 is not limited to a rubber belt but may be a resin belt. However, since the rubber belt having an elastic layer tends to cause filming 12, the significance of applying the present invention is greater.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Intermediate transfer belt 3Y etc. Image formation part 4 Primary transfer roller 5 Secondary transfer roller 6 Belt cleaner 7 Foam roller 10 Patch image 71 Foam layer 80 Control part Q Low coverage area

Claims (6)

An intermediate transfer belt that is an annular belt-like member that carries a toner image and circulates in the circumferential direction, an image forming unit that creates a toner image and applies the toner image to the intermediate transfer belt by transfer, and the intermediate transfer belt In an image forming apparatus having a secondary transfer unit for transferring a toner image from a belt to an external output medium,
A foaming roller provided on the intermediate transfer belt in contact with the toner image carrying surface at a position downstream of the secondary transfer portion and upstream of the image forming portion; ,
A filming removal control unit for performing a filming removal operation for removing the filming material generated on the intermediate transfer belt,
The filming removal control unit
A patch supply unit that supplies a patch toner pattern to a partial range in the width direction on the intermediate transfer belt by the image forming unit in a state where transfer at the secondary transfer unit is turned off during non-image formation When,
A roller rotation control unit that rotates the foaming roller in a first rotation state and then rotates in a second rotation state after supplying the patch toner pattern;
The roller rotation control unit, the foam roller,
Wherein in the second rotation state, with respect to the circulating movement of the intermediate transfer belt, the absolute value of the velocity ratio at the surface is to Luke Unter around a in the range of 0.5 to 2.0,
In the first rotation state, the rotational difference on the outer peripheral surface with respect to the circulating movement of the intermediate transfer belt is smaller than that in the second rotation state.
An image forming apparatus, wherein an opening ratio of a cell wall surface in the foam layer is 50% or less. The image forming apparatus according to claim 1, wherein the roller rotation control unit is
Rotating the foaming roller in the first rotation state;
Starting from when the patch toner pattern is supplied from the image forming unit to the intermediate transfer belt until the patch toner pattern reaches the foam roller,
An image forming apparatus, wherein the patch toner pattern continues until a time within a range of 0.5 to 5 seconds elapses after the patch toner pattern reaches the foaming roller. The image forming apparatus according to claim 1, wherein:
A coverage rate calculating unit for calculating a coverage rate distribution by a toner image in the width direction of the intermediate transfer belt in image formation by the image forming unit;
The patch supply unit supplies a patch toner pattern to a region including the section when a width direction section having a coverage ratio lower than a predetermined reference coverage ratio exists at a predetermined patch supply timing. An image forming apparatus. The image forming apparatus according to claim 3, wherein the patch supply unit includes:
The image forming apparatus, wherein the patch toner pattern is supplied only to an area in a section where the coverage rate is lower than the reference coverage rate over a predetermined reference width or more. The image forming apparatus according to any one of claims 1 to 4, wherein:
A plurality of cleaner members for cleaning a toner image carrying surface of the intermediate transfer belt provided in contact with a position downstream of the secondary transfer portion and upstream of the image forming portion of the intermediate transfer belt. Have
Among the plurality of cleaner members, at least the one located most upstream with respect to the circulating movement of the intermediate transfer belt is the foaming roller. In the image forming apparatus according to any one of claims 1 to 5,
The image forming apparatus, wherein the intermediate transfer belt is an elastic belt having an elastic layer.

Images