JP2009075224A - Belt unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt unit where belt deviation or meandering in an endless belt is appropriately prevented, and to provide an image forming apparatus equipped with the belt unit. <P>SOLUTION: The belt unit has a plurality of rolls and an endless belt tensioned and laid by the plurality of rolls and circularly moving in a predetermined moving direction, wherein the endless belt is formed so that at least one of two edges of the endless belt overhangs to be over the end of the roll. The belt unit is provided with a rib 131 extending along the overhanging edge, and is equipped with a pulley 111 rotating coaxially with one of the plurality of rolls and provided with a groove where the rib 131 is fit to regulate a relative position of the endless belt and the roll, then it is equipped with a cleaning part 140 for cleaning the rib 131. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a belt unit having a plurality of rolls and an endless belt that is stretched by the plurality of rolls and circulates in a predetermined movement direction, and an image forming apparatus including such a belt unit.

  2. Description of the Related Art Conventionally, as an image forming apparatus typified by an electrophotographic copying machine, a printer, or the like, for example, an intermediate transfer type color image forming apparatus using an intermediate transfer belt is widely known. In this color image forming apparatus, a plurality of color toner images are temporarily transferred so as to overlap each other at the same location on the intermediate transfer belt to form a multiple toner image, and then the multiple toner images on the intermediate transfer belt are transferred to a sheet. The multiple toner images transferred onto the paper are fixed by a fixing device to form a color image.

  In addition to such an intermediate transfer type color image forming apparatus, a direct transfer type color image forming apparatus using a paper conveying belt is also known. This color image forming apparatus forms a multiple toner image by transferring a plurality of color toner images so as to overlap each other at the same location on the paper carried and conveyed by the paper conveyance belt. A color image is formed by fixing.

  In these image forming apparatuses, an endless belt which is stretched by a plurality of rolls and circulates and moves in a predetermined moving direction is used as an intermediate transfer belt or a paper transport belt, and a belt unit configured by an endless belt and a plurality of rolls. Is provided. In such a belt unit, due to variations in the parallelism of the rotating shafts of a plurality of rolls that support the endless belt in a stretched manner, variations in the outer diameter of the roll, uneven tension due to a change in the circumferential length of the endless belt itself, etc. In some cases, the endless belt does not travel straight, but a so-called offset travel or meandering may occur along the axis of the roll. When such deviated running or meandering occurs, the transfer positions of the toner images of the respective colors that are transferred to the endless belt itself or transferred to the paper carried on the endless belt are shifted from each other, and the finally obtained color There is a risk that color shift, hue change, and the like occur in the image. Therefore, a technique has been proposed in which a rib that serves as a guide for regulating the relative position of the endless belt with respect to the roll when the endless belt travels is attached to the endless belt in order to prevent the endless belt from running or meandering. (For example, refer to Patent Document 1).

  FIG. 7 is a diagram illustrating an example in which the endless belt is prevented from running or meandering by a rib.

  FIG. 7 shows one roll 501 of a plurality of rolls constituting the belt unit and an endless belt 502. The endless belt 502 has a cross section parallel to the rotation shaft 501a of the roll 501. It is shown. When the roll 501 rotates in the direction of the arrow D31, the endless belt 502 follows the rotation and travels in the direction of the arrow D32 from the back to the front in the figure.

  The endless belt 502 shown in FIG. 7 has one of two edges protruding beyond the end of the roll 501, and a rib 503 extending along the edge on the inner periphery of the protruding portion. Is attached.

  The end of the roll 501 on the rib 503 side is provided with a pulley 504 that is attached to the rotating shaft 501a of the roll 501 and rotates coaxially with the roll 501 and has a groove on the circumferential surface. The groove has a bottom surface and two slopes, and the rib 503 is fitted into the groove.

  Further, by slightly shifting the drive roll shaft and the driven roll shaft from the completely parallel state, the endless belt 502 is intentionally tensioned in the direction of the arrow D33. . As a result, the endless belt 502 moves in the direction of the arrow D33 during traveling, and as shown in FIG. 7, a part of the side surface on the roll 501 side of the rib 503 is on the roll 501 side in the groove of the pulley 504. Touch the slope. Since the tension is always applied to the endless belt 502 during traveling, the contact state of the rib 503 with the slope of the pulley 504 is maintained.

In the example of FIG. 7, the endless belt 502 travels in a state where the rib 503 is in contact with the inclined surface of the pulley 504, so that the rib 503 serves as a guide, and the relative position of the endless belt 502 with respect to the roll 501 is regulated. Therefore, the run-off and meandering of the endless belt 502 are prevented.
JP 2005-92029 A

  By the way, in the image forming apparatus provided with the belt unit using the endless belt with ribs as described above, a problem that the ribs rise up the slopes of the grooves of the pulleys during traveling (hereinafter referred to as rib climbing). Is frequently occurring. When the ribs run up, the relative position of the endless belt with respect to the roll 501 deviates from the regulation, causing the one-sided running or meandering, and color misregistration in the color image occurs. In addition, the vibration generated in the endless belt when the rib is climbed cannot be ignored, and there is a possibility that the transfer to the endless belt itself or the transfer to the paper carried on the endless belt may be hindered by the vibration.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a belt unit in which an endless belt is appropriately prevented from running or meandering and an image forming apparatus including such a belt unit.

The belt unit of the present invention that achieves the above-described object provides:
In a belt unit having a plurality of rolls and an endless belt that is stretched by the plurality of rolls and circulates in a predetermined movement direction,
The endless belt has a rib extending on the inner circumference along at least one of two edges of the endless belt,
A groove that rotates coaxially with at least one of the plurality of rolls and that is integral with or separate from the roll and that regulates the relative position between the endless belt and the roll is provided by fitting the rib. Regulating members,
And a cleaning member for cleaning the rib.

  In the present invention, the inventor found the fact that the cause of the running of the rib in the belt unit of the type using the endless belt with the rib is an unnecessary material such as toner attached to the rib. The present invention has been made based on this fact. The belt unit of the present invention is a type of belt unit using an endless belt with a rib. However, according to the belt unit of the present invention, the rib is cleaned by the cleaning member. Unnecessary items contributing to the problem are reliably removed. As a result, according to the belt unit of the present invention, the climbing of the ribs can be effectively suppressed, and the endless running and meandering of the endless belt can be appropriately prevented.

Here, in the belt unit of the present invention,
“The cleaning member cleans the rib by being pressed against the rib,
A form of “having a retracting mechanism for bringing the cleaning member into and out of contact with the rib” is a preferable form.

  In the belt unit of this preferred form, as a cleaning method for the rib, a method of pressing the cleaning member, which is effective for removing unnecessary materials, is employed. Here, while this method is an effective cleaning method, it has a problem that a load may be applied to an object to be cleaned. According to the belt unit of this preferred embodiment, the belt unit is provided with a retract mechanism that contacts and separates the cleaning member from the rib, so that, for example, operation such as suppressing the pressing against the rib to a minimum is possible. Thus, the rib can be effectively cleaned while suppressing the load on the rib.

In the belt unit of the present invention,
The form “the cleaning member cleans at least the side surface of the roll side of the rib” is a typical form.

The belt unit of the present invention is
It may be in the form of “the cleaning member is a brush”,
It may be in the form of “the cleaning member is a pad”.

  The cleaning member in these forms is suitable for cleaning by a method such as pressing against a cleaning object, and an effective cleaning effect can be obtained.

The image forming apparatus of the present invention that achieves the above-described object
In the process of forming a toner image and finally transferring and fixing the toner image on a sheet of paper to form an image on the sheet, a plurality of rolls and a predetermined movement direction stretched by the plurality of rolls In an image forming apparatus using a belt unit having an endless belt that circulates and moves,
This belt unit
The endless belt has a rib extending on the inner circumference along at least one of two edges of the endless belt,
A groove that rotates coaxially with at least one of the plurality of rolls and that is integral with or separate from the roll and that regulates the relative position between the endless belt and the roll is provided by fitting the rib. Regulating members,
And a cleaning member for cleaning the rib.

  According to the image forming apparatus of the present invention, the climbing of the ribs is effectively suppressed, and the endless running and meandering of the endless belt can be appropriately prevented.

Here, in the image forming apparatus of the present invention,
“The cleaning member cleans the rib by being pressed against the rib,
A retract mechanism for contacting and separating the cleaning member with respect to the rib;
A recognition unit for recognizing the amount of toner forming the toner image;
When the amount of toner recognized by the recognizing unit is within a predetermined range, the cleaning member is moved away from the rib by the retract mechanism, and the amount of toner is outside the predetermined range. The retraction mechanism is provided with a control unit for bringing the cleaning member into contact with the rib.

  Here, “recognizing the amount of toner” mentioned above may be to predict the amount of toner based on an image to be formed by this image forming apparatus, and is actually used for image formation. Alternatively, the toner amount may be measured, or the toner amount itself may be transmitted in an information format by a user operation or the like.

  In general, in an image forming apparatus, if the amount of toner that forms a toner image is too large, the toner is likely to scatter in the apparatus, while if the amount of toner that forms a toner image is too small, the toner image is formed. There is a high risk that the supporting carrier will be scattered in the apparatus. In these cases, there is an increased possibility that unnecessary materials will adhere to the ribs, and the ribs will rise. According to this preferred embodiment of the image forming apparatus, by appropriately setting the predetermined range, it is possible to perform operations such as cleaning the rib when the risk of scattering of toner or carrier in the apparatus increases. By such an operation, it is possible to effectively clean the rib while suppressing the load on the rib.

In the image forming apparatus of the present invention,
“This image forming apparatus forms a toner image using a toner containing at least a binder resin having a number average molecular weight of 2500 to 20000 and a colorant,”
“This image forming apparatus forms a toner image using a toner containing at least a binder resin having a softening point of 60 ° C. or higher and 120 ° C. or lower and a colorant,”
“This image forming apparatus forms a toner image using a toner containing a wax having a melting point of 40 ° C. or higher and 150 ° C. or lower”,
A form in which “this image forming apparatus forms a toner image using a toner having a volume average diameter of 4 μm or more and 15 μm or less” is a preferable form.

  According to these preferred embodiments of the image forming apparatus, the ribs are cleaned even if the above-mentioned toner that works on the image quality of the toner image, but easily adheres to the ribs, easily causes the ribs to rise. Therefore, the boarding is avoided. As a result, while the toner image with good image quality is formed, it is possible to appropriately prevent the endless belt from running or meandering.

  Note that the image forming apparatus of the present invention is only shown here as a basic form and a characteristic form of the image forming apparatus, but this is only for avoiding duplication. Includes not only the above-described form but also various forms corresponding to the above-described forms of the belt unit.

  As described above, according to the present invention, it is possible to obtain a belt unit in which an offset endless running or meandering in an endless belt is appropriately prevented, and an image forming apparatus including such a belt unit.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

  The image forming apparatus 1 shown in FIG. 1 corresponds to an embodiment of the image forming apparatus according to the present invention, and is a direct transfer type color image forming apparatus using a sheet conveying belt, and includes a driving roll 110 and a driven roll 120. A belt unit 100 using a sheet conveying belt 130 that is stretched between two rolls and circulates and moves in the direction of an arrow D12 is provided. The paper P drawn from a paper tray (not shown) is carried on the surface of the paper transport belt 130 and transported.

  The belt unit 100 corresponds to an embodiment of the belt unit of the present invention, and controls the operations of the two rolls 110 and 120, the paper transport belt 130, a cleaning unit 140 described later, and the cleaning unit 140. The control unit 150 is provided. Here, each of the rolls 110 and 120 and the sheet conveying belt 130 correspond to an example of a roll and an endless belt according to the present invention, respectively. The control unit 150 corresponds to an example of serving as a recognition unit and a control unit according to the present invention. The belt unit 100 will be described in detail later.

  The image forming apparatus 1 includes four toner image forming units that are arranged adjacent to the belt unit 100 and form toner images of each color of K (black), C (cyan), M (magenta), and Y (yellow). 20k, 20c, 20m, and 20y are provided. Each color toner image forming unit includes photosensitive drums 21k, 21c, 21m, and 21y that rotate in the direction of arrow D11, charging rolls 22k, 22c, 22m, and 22y that uniformly charge the surface of each photosensitive drum, Cleaning rolls 23k, 23c, 23m, and 23y for cleaning each charging roll, and electrostatic latent image formation for forming an electrostatic latent image on each photosensitive drum by irradiating the charged photosensitive drum with laser light L The devices 24k, 24c, 24m, and 24y, and developing agents including toners of various colors and carriers are accommodated, and the electrostatic latent images on the respective photosensitive drums are developed through predetermined developing rolls 25k_1, 25c_1, 25m_1, and 25y_1. And developing devices 25k, 25c, 25m, and 25y that form toner images of the respective colors, and the toner images formed on the photosensitive drums are transferred to the paper P. Because of the transfer roll 26k, 26c, 26m, and includes a 26y, a cleaning blade 27k for removing residual toner remaining on the photosensitive drum after the transfer, 27c, 27m, and 27y. The formation and transfer of the toner images in the toner image forming units of the respective colors are performed at a timing such that the toner images of the respective colors are transferred onto the same position on the paper P transported by the paper transport belt 130. Thus, a multiple toner image in which the toner images of these colors are superimposed on the paper P is formed.

  In this embodiment, a developer containing a binder resin and a colorant, which will be described below, and a toner having toner base particles to which a wax described later is added, a carrier, and the like is used.

  First, the binder resin is not specified in the present embodiment, but is preferably made of the following materials and has the following characteristics.

  As the binder resin material, polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, Known materials such as polyethylene, polypropylene, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax can be used. Of these, styrene-acrylic copolymers and polyesters are preferred.

  The number average molecular weight (Mn) of the binder resin is preferably 2500 or more and 20000 or less, and more preferably 4000 or more and 15000 or less. When the number average molecular weight (Mn) is less than 2500, it is difficult to adjust the charge amount. As a result, it tends to adhere to the groove and easily rise on the rib, and it is difficult to obtain image strength after fixing. In addition, uneven thin-line melting may occur during fixing. On the other hand, when the number average molecular weight (Mn) exceeds 20000, coarse particles are generated, and the adjustment of the charge amount tends to be difficult. As a result, it tends to adhere to the groove and easily rise on the rib, and the lowest fixing. The temperature may rise. The weight average molecular weight (Mw) of the binder resin is preferably 9000 or more and 90000 or less, and more preferably 12000 or more and 60000 or less. When the weight average molecular weight (Mw) is less than 9000, it is difficult to obtain the image strength after fixing as in Mn, and uneven thin-line melting may occur during fixing, while the weight average molecular weight (Mw) is 90000. If it exceeds 1, the minimum fixing temperature rises, and there may be a problem that the toner is not easily pulverized in the manufacture of the toner (particularly, the production by the kneading pulverization method).

  Furthermore, the softening point (Tm) of the binder resin is preferably 60 ° C. or higher and 120 ° C. or lower, and more preferably 80 ° C. or higher and 100 ° C. or lower. When the softening point (Tm) is less than 60 ° C., it is difficult to remove the toner attached to the grooves, and the ribs are likely to rise. On the other hand, if the softening point (Tm) exceeds 120 ° C., the fixing temperature may increase. The glass transition point (Tg) of the binder resin is preferably 45 ° C. or higher and 70 ° C. or lower, and more preferably 50 ° C. or higher and 60 ° C. or lower. When the glass transition point (Tg) is less than 45 ° C., the toner may be easily blocked by heat. On the other hand, when the glass transition point (Tg) exceeds 70 ° C., the fixing temperature may be increased. is there.

  In the present embodiment, when the toner is manufactured, the molecular weight (Mn, Mw) of the binder resin is measured using Tosoh GPC: HLC8120GPC. The softening point (Tm) is measured using a flow tester: CFT500C manufactured by Shimadzu Corporation. Further, the glass transition point (Tg) is measured using DSC: DSC60 manufactured by Shimadzu Corporation.

  Next, examples of the colorant include known organic or inorganic pigments.

  In addition, it is preferable to add wax to the toner base particles because it does not require oil supply to the fixing device and is preferable in terms of space saving. In this embodiment, the toner having toner base particles to which the wax is added is also used. It is used. As this wax, although not specified in the present embodiment, synthetic wax such as polyolefin wax, oxidized polyolefin wax, and Fischer-Tropsch wax, petroleum wax, mineral wax, animal and plant wax and the like can be used alone or in combination. The melting point of the wax is preferably from 40 ° C. to 150 ° C., particularly preferably from 50 ° C. to 120 ° C.

  In addition to the wax, a charge control agent may be added to the toner base particles. As the charge control agent, those conventionally used in developers can be used, but metal salts of benzoic acid, metal salts of salicylic acid, alkyl salicylic acid used in powder toners for Xerography (registered trademark). Metal salts, metal salts of catechol, metal-containing bisazo dyes, tetraphenylborate derivatives, quaternary ammonium salts, compounds selected from the group consisting of alkylpyridinium salts, resin-type charge control agents containing polar groups, and these A suitable combination of these can be preferably used.

  Further, the volume average diameter of the toner is not specified in this embodiment, but is preferably 4 μm or more and 15 μm or less, and more preferably 5 μm or more and 10 μm or less. When the volume average diameter is less than 4 μm, not only the fluidity of the toner is deteriorated, but also it becomes difficult to provide sufficient charging ability from the carrier, and therefore, adhesion to the rib 131 is likely to occur. When the volume average diameter exceeds 15 μm, the effect of improving the reproducibility, gradation, and graininess of fine dots becomes poor.

  The image forming apparatus 1 according to the present embodiment fixes a multiple toner image formed on a sheet P conveyed by a sheet conveying belt 130 using a developer in which the toner and the carrier are mixed as described above. 30. The fixing device 30 fixes the multiple toner image onto the paper P, thereby completing a color image.

  The image forming apparatus 1 of the present embodiment is generally configured as described above.

  Next, details of the belt unit 100 will be described.

  FIG. 2 is a view of the belt unit 100 of FIG.

  In FIG. 2, components other than the belt unit 100 in the image forming apparatus 1 are omitted for easy viewing of the drawing.

  First, the material of the paper conveyance belt 130 and the rib 131 will be described.

  Examples of the material of the paper conveying belt 130 include polyamideimide resin, polyester resin, polyimide resin, polyurethane resin, polyamide resin, and fluorine resin. The belt body may or may not have a joint. The thickness of the belt body is usually preferably about 20 μm to 200 μm. In this embodiment, a belt satisfying 80 ± 5 μm within the belt surface is prepared. As an example of the belt body, in the case of an intermediate transfer belt and a transfer conveyance belt in an image forming apparatus using an electrophotographic method, a semiconductive belt made of a polyimide resin containing a conductive agent is used. As a material of the paper conveying belt 130, for example, Toyobo Viromax (registered trademark) HR-20NN / 40NN can be suitably used as a polyamideimide resin.

  In addition, when used as a transfer / conveying belt, carbon black, aluminum, copper alloy, graphite, aluminum, copper as a conductive filler as necessary to control the surface resistivity in the range of 9 logΩ / sq to 14 logΩ / sq. A metal or alloy such as an alloy, zinc oxide, kalim titanate, tin oxide, metal oxide such as tin oxide-indium oxide or tin oxide-antimony oxide composite oxide, or a conductive polymer such as polyaniline alone or 2 Used in combination of more than one species. Among these, carbon black is preferable as the conductive filler in terms of cost. Moreover, processing aids, such as a dispersing agent and a lubricant, can be added as needed.

  Here, the surface resistivity was measured in an environment of 22 ° C. and 55% RH using a Hiresta (registered trademark) UPMCP-450 UR probe manufactured by Dia Instruments Co., Ltd., and measured according to JISK6911. 24 points (3 places in the width direction × 8 places in the circumferential direction) of the belt were measured, and the average value was taken as the surface resistivity of the belt.

  In this embodiment, a belt satisfying an average surface resistivity of 12 ± 1 logΩ / sq is used.

  As a material of the rib 131, an elastic body having an appropriate hardness such as polyurethane, polyurethane rubber, silicone rubber, polyester elastomer, neoprene rubber, chloroprene rubber, nitrile rubber, or the like can be used. Among these, polyurethane rubber and silicone rubber are particularly preferable in consideration of electrical insulation, moisture resistance, solvent resistance, ozone resistance, heat resistance, and wear resistance. In this embodiment, urethane rubber is used.

  There are two methods for bonding the rib 131 and the paper transport belt 130, such as a method of applying an elastic adhesive between the rib and the belt, and a method of inserting and bonding a heat-sensitive adhesive sheet.

  The elastic adhesive used is an adhesive whose durometer hardness after the curing reaction is in the range of A30 / S to A50 / S, and is Super X (registered) based on an acrylic-modified silicone polymer manufactured by Cemedine Co., Ltd. (Trademark) No8008, Syflex (registered trademark) 100 mainly composed of a specially modified silicon polymer manufactured by Konishi Co., Ltd. can be used.

  In the present embodiment, Super X (registered trademark) No. 8008 mainly composed of an acrylic-modified silicone polymer manufactured by Cemedine Co., Ltd. was preferably used because of its adhesive strength with the belt base material.

  Further, the heat-sensitive adhesive sheet is not particularly limited as long as it has excellent adhesiveness with the paper conveyance belt 130 and the rib 131 used. For example, an adhesive mainly composed of a resin material such as an acrylic resin, a silicon resin, a urethane resin, a natural or synthetic rubber resin, or a synthetic resin resin such as vinyl chloride / vinyl acetate copolymer can be used. Specific examples thereof include polyester adhesive sheets GM-913 and GM-920 manufactured by Toyobo Co., Ltd., and polyester adhesive sheets D3600 manufactured by Sony Chemical Corporation. From the adhesive strength with the belt substrate, a polyester-based adhesive sheet D3600 manufactured by Sony Chemical Co., Ltd. and a polyester-based adhesive sheet GM-920 manufactured by Toyobo Co., Ltd. are preferable materials.

  A method for attaching the rib 131 to the paper conveying belt 130 is not particularly limited. Generally, in the case of adhesion using a heat-sensitive adhesive sheet, the heat-sensitive adhesive sheet is attached to the rib 131 by heating and pressing. After being attached, the release paper is peeled off, and then applied to the paper transport belt 130 by heating and pressing. Further, in the case of adhesion by a layer made of an elastic adhesive, the elastic sheet is applied to the rib 131, and then the sheet conveying belt 130 is integrated by being pressed and adhered to the sheet conveying belt 130. To do.

  In addition, it is important to bond without bubbles, and usually use a method such as bonding with a hand roller, rubber roller, press, etc., bonding under reduced pressure, bonding under pressure, etc. Can do. Further, the surface of the rib 131 or the surface of the paper conveying belt 130 may be improved in adhesion by performing corona treatment, primer treatment, aging, or the like.

  In the sheet conveying belt 130 constituting the belt unit 100, the left edge in the figure protrudes beyond the ends of the two rolls, and the protruding edge is on the inner circumference of the edge. A rib 131 is attached. The rib 131 has a constant width RW and thickness RT. In addition, when the rib 131 is affixed over the entire inner circumference of the paper transport belt 130, a portion that slightly snakes out cannot be obtained because the rib 131 cannot be completely parallel to the edge of the paper transport belt 130. In the present embodiment, the straightness RS, which is the shift amount to the roll side shown in the drawing, of the rib 131 is equal to or less than a predetermined dimension determined by design. The rib 131 corresponds to an example of the rib according to the present invention.

  Further, at the end of the drive roll 110 of the two rolls on the rib 131 side, a groove 111a is attached to the rotating shaft 110a of the drive roll 110 and rotates coaxially with the drive roll 110 on the peripheral surface. A provided pulley 111 is provided. The groove 111a has a bottom surface and two inclined surfaces, and the rib 131 is fitted into the groove 111a. The pulley 111 corresponds to an example of a regulating member according to the present invention, and the groove 111a provided in the pulley 111 corresponds to an example of a groove according to the present invention.

  Further, in this belt unit 100, the left end portion in the drawing of the rotation shaft 120a of the driven roll 120 is slightly shifted in the direction of the arrow D13 from the back of the drawing to the front with respect to the right end portion. As a result, the sheet conveying belt 130 is slightly twisted, and a tension in the direction of the arrow D14 is applied during traveling. As a result, the sheet conveying belt 130 moves in the direction of the arrow D14, and a part of the side surface of the rib 131 on the drive roll 110 side comes into contact with the slope of the groove 111a of the pulley 111 on the drive roll 110 side. Since the tension is always applied to the sheet conveying belt 130 during traveling, the contact state of the rib 131 with the slope of the pulley 111 is maintained. In this belt unit 100, the rib 131 functions as a guide by running in a state where the end of the rib 131 is in contact with the inclined surface of the groove 111 a of the pulley 111 as described above, and the relative of the paper transport belt 130 to the drive roll 110. Since the position is regulated, it is possible to prevent the paper transport belt 130 from running or meandering.

  Here, the floating material such as floating toner or floating carrier generated at the time of transfer may adhere to the rib 131. As described above, the mechanism that causes the rib 131 to act as a guide during travel is effective in preventing the paper transport belt 130 from being offset. However, if an unnecessary object such as toner adheres to the rib 131, friction between the inclined surface with which the rib 131 is in contact with the rib 131 in the groove 111a of the pulley 111 and the rib 131 is increased. There is a possibility that a problem (striking of the ribs) occurs in which the slope of the groove 111a slides up. In the present embodiment, a cleaning unit 140 that cleans the ribs 131 is provided in order to effectively suppress the occurrence of the ribs.

  Details of the cleaning unit 140 will be described below.

  FIG. 3 is a perspective view showing details of the cleaning unit 140.

  The cleaning unit 140 includes a brush 141 that is pressed against a portion of the rib 131 that contacts the inclined surface of the groove 111a of the pulley 111 while rotating, and a rotating shaft 141a of the brush 141, and a rib 131 indicated by an arrow D15 in the drawing. The spring 142 biased in the direction away from the direction and the direction indicated by the arrow D16 in the figure rotate to apply a force in the direction opposite to the biasing force of the spring 142 to the rotating shaft 141a of the brush 141, and the arrow D17 indicates And a cam 143 that releases the force on the rotating shaft 141a by rotating in the direction. Here, the brush 141 corresponds to an example of the cleaning member according to the present invention, and the combination of the spring 142 and the cam 143 corresponds to an example of the retract mechanism according to the present invention.

  The cleaning unit 140 is fixed to a frame (not shown) that is immovable with respect to the paper conveying belt 130, and an arrow indicates a portion of the rib 141 that contacts the inclined surface of the groove 111 a of the pulley 111 by the movement of the cam 143. As indicated by D18, the brush 141 is pressed or released. The movement of the cam 143 is controlled by the control unit 150 shown in FIG. 1 according to the amount of toner for forming toner images on the photosensitive drums 21k, 21c, 21m, and 21y. When the paper transport belt 130 circulates in a state where the brush 141 is pressed against the rib 141, the rib 141 is cleaned by the brush 141. As a result, unnecessary materials on the ribs 141 that cause the ribs to be lifted are removed, and the ribs are effectively prevented from being lifted. It will be.

  Further, in the present embodiment, the brush type cleaning unit 140 illustrated in FIG. 3 is illustrated, but the cleaning unit referred to in the present invention is not limited to the brush type, and may be, for example, another type as follows. Also good.

  FIG. 4 is a diagram showing another type of cleaning unit.

  This different type of cleaning unit 140 ′ is different from the cleaning unit 140 of this embodiment shown in FIG. 2 in that a brush 141 made of urethane foam is provided instead of the brush 141. In FIG. 4, components equivalent to those of the cleaning unit 140 in FIG. 2 are denoted by the same reference numerals as in FIG. 2. The pad 141 'corresponds to an example of the cleaning member referred to in the present invention.

  In this other type of cleaning section 140 ′, the rib 131 is cleaned by a urethane foam pad 141 ′. Also in this different type of cleaning unit 140 ′, the cam 143 moves in the same manner as the cleaning unit 140 of the present embodiment, in order to form a toner image on the photosensitive drums 21k, 21c, 21m, and 21y. It is controlled according to the amount.

  FIG. 5 is a diagram illustrating control with respect to the movement of the cam 143 in accordance with the amount of toner forming a toner image in the cleaning unit 140 of the present embodiment.

  FIG. 5 shows a graph G1 that schematically shows the relationship between the degree of unwanted material adhering to the rib 131 and the amount of toner that forms a toner image. In this graph G1, the horizontal axis represents the toner density indicating the amount of toner that forms a toner image, and the vertical axis represents the amount of dirt indicating the degree of unwanted material adhering to the rib 131. The line L which shows is described. As can be seen from this line L, the amount of dirt increases when the toner density is too high and conversely when the toner density is too low.

  Here, when the toner density is too high, the amount of dirt increases because the toner image is formed on each of the photosensitive drums 21k, 21c, 21m, and 21y in the image forming apparatus 1 of FIG. This is because if the amount of toner is too large, there is a high possibility that the toner will scatter in the apparatus. In addition, the amount of dirt increases when the toner concentration is too low because the amount of toner that forms a toner image is too small and the carrier that assists in forming the toner image is more likely to scatter in the apparatus. . In these cases, there is an increased possibility that the rib 131 rides up due to an unnecessary object attached to the rib 131. Therefore, in the present embodiment, the control unit 150 in FIG. 1 calculates the toner density from the image data representing the image to be formed, and the toner density is a threshold value on the high density side where the possibility of toner scattering exceeds a predetermined value. When it is higher than DH or when it is lower than the threshold DL on the low concentration side where the possibility of carrier scattering is higher than a predetermined level, the cam 143 shown in FIG. 3 is rotated in the direction indicated by the arrow D16 to make the brush 141 rib. Press against 131. On the other hand, when the calculated toner density is within the range of the low density side threshold DL or more and the high density side threshold DH or less, the control unit 150 of FIG. 1 moves the cam 143 shown in FIG. The brush 141 is moved away from the rib 131 by rotating in the direction indicated by D17.

  Here, the cleaning method of pressing the cleaning member is an effective cleaning method, but has a problem that a load may be applied to the rib 131 to be cleaned. However, according to the control described above by the control unit 150 of FIG. 1, the pressing against the rib 131 is suppressed to the minimum necessary, and the load on the rib 131 can be suppressed and cleaning can be performed effectively. As a result, the running of the ribs 131 is effectively suppressed, and it is possible to appropriately prevent the paper transport belt 130 from running off and meandering.

  As described above, according to the image forming apparatus 1 of the first embodiment of the present invention, the running of the rib 131 as a guide for the travel of the paper transport belt 130 can be suppressed. And meandering can be prevented appropriately.

  Next, a second embodiment of the present invention will be described.

  The second embodiment is different from the first embodiment in that the image forming apparatus is an intermediate transfer system.

  FIG. 6 is a schematic view showing an image forming apparatus according to the second embodiment of the present invention.

  The image forming apparatus 2 shown in FIG. 6 corresponds to an embodiment of the image forming apparatus of the present invention, and is an intermediate transfer type color image forming apparatus using an intermediate transfer belt, and includes a drive roll 210 and two driven rolls 220. , 230 and a belt unit 200 that uses an intermediate transfer belt 240 that circulates and moves in the direction of an arrow D22.

  In the image forming apparatus 2, four toner image forming units 40 k, 40 c, 40 m, and 40 y that form toner images of colors K, C, M, and Y are disposed adjacent to the belt unit 200. Each color toner image forming unit includes photosensitive drums 41k, 41c, 41m, and 41y that rotate in the direction of arrow D21, charging rolls 42k, 42c, 42m, and 42y that uniformly charge the surface of each photosensitive drum, Cleaning rolls 43k, 43c, 43m, and 43y for cleaning each charging roll, and electrostatic latent image formation for forming an electrostatic latent image on each photosensitive drum by irradiating the charged photosensitive drum with laser light L The devices 44k, 44c, 44m, and 44y, and developing agents including toners and carriers of the respective colors are accommodated, and electrostatic latent images on the respective photosensitive drums are developed through predetermined developing rolls 45k_1, 45c_1, 45m_1, and 45y_1. Developing units 45k, 45c, 45m, and 45y that form toner images of the respective colors, and toner images formed on the photosensitive drums are transferred to intermediate transfer bells. The primary transfer roll 46k for transferring 240 comprises 46c, 46m, and 46y, the cleaning blade 47k for removing residual toner remaining on the photosensitive drum after the transfer, 47c, 47m, and 47y. The formation and transfer of the toner images in the toner image forming units of the respective colors are performed at a timing such that the toner images of the respective colors are transferred to the same place on the intermediate transfer belt 240, thereby the intermediate transfer belt 240. A multi-toner image in which the toner images of these colors are superimposed on each other is formed.

  In the present embodiment, the same developer as the toner in the first embodiment described above is used.

  Further, in the image forming apparatus 2, the secondary transfer roll 50 is disposed at a position facing the lower driven roll 230 in the belt unit 200 on the lower side in the drawing with the intermediate transfer belt 240 interposed therebetween. A nip portion is formed by sandwiching the intermediate transfer belt 240 by these two rollers. When the paper P is inserted into the nip at the timing when the multiple toner image on the intermediate transfer belt 240 reaches the nip, the multiple toner image is transferred to the paper P. Further, the image forming apparatus 2 includes a fixing device 60 that fixes the multiple toner image formed on the paper P. The multiple toner image is fixed on the paper P by the fixing device 60 to complete a color image. .

  Here, in the second embodiment, a mechanism equivalent to the mechanism including the rib 131 that functions as a guide for traveling of the sheet conveying belt 140 and the pulley 111 having the groove into which the rib 131 fits in the first embodiment described above is an intermediate. It is provided in order to prevent the transfer belt 240 from running offset and meandering. A cleaning unit 250 equivalent to the cleaning unit 140 in the first embodiment and the cleaning unit 250 are used to clean the ribs included in the mechanism for preventing the intermediate transfer belt 240 from being offset. The belt unit 200 is provided with a controller 260 that controls the movement of the cam. Since the mechanism including the rib and the pulley, the cleaning unit 250, and the control unit 260 are the same as those provided in the first embodiment, detailed description thereof is omitted.

  The image forming apparatus 2 according to the second embodiment of the present invention can suppress the climbing of the ribs similarly to the image forming apparatus 1 according to the first embodiment described above. Can be prevented.

  In the above description, a brush type cleaning unit and a pad type cleaning unit using a foamed urethane pad are illustrated as an example of the cleaning unit in the present invention. However, the present invention is not limited thereto. The cleaning unit of the present invention may be, for example, a non-woven fabric type that cleans the inner surface of the pulley groove with a non-woven fabric.

In the above description, as an example of a recognition unit according to the present invention, a control unit that also serves as an example of a control unit according to the present invention that recognizes the amount of toner by calculating toner density from image data representing an image to be formed. Although 150 is illustrated, the present invention is not limited to this. The recognition unit referred to in the present invention may recognize, for example, the amount of toner by measuring the amount of toner actually used for image formation. May be used to recognize the amount of toner.
(Example)
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

  First, evaluation methods for Examples and Comparative Examples will be described.

  For this evaluation, a halftone dot pattern (also called a screen) is used as a test image.

  FIG. 8 is an enlarged view of a test image (halftone) used in Examples and Comparative Examples.

  The halftone which is the test image TG is an image in which 45 ° oblique lines are arranged in parallel at a predetermined interval. Here, during the transfer of the test image to the paper, if a problem such as the above-described rib climbing occurs, the paper transport belt is shifted or meandered, and the transfer position shift (registration) of the parallel lines is caused. Arise.

  FIG. 9 is a diagram illustrating an example of a registration error.

  Part (a) of FIG. 9 schematically shows image omission due to instantaneous speed UP as an example of a registration error, and Part (b) shows toner image concentration due to instantaneous speed reduction as an example of registration error. Part (c) schematically shows toner image misalignment due to lateral play as an example of misregistration.

  In this evaluation method, after outputting 50,000 predetermined images, the amount of registration d in each image in which 30 test images GT were continuously output was measured, and the maximum value thereof was calculated as an evaluation value.

Hereinafter, individual examples and comparative examples will be described.
[Example 1]
In Example 1, the direct transfer type image forming apparatus of the first embodiment described above is employed, and a brush is used as the cleaning member.

  The brush has a fiber material made of propylene, a fiber thickness of 10 denier, and a bundle of 120 conductive filaments having a fiber bundle of 120 mm, and is planted at a bundle density of 125 bundles / inch 2 on a rotating shaft with a diameter of 4 mm. The brush is shaped so that the diameter of the outermost edge of the brush is 10 mm.

  A pulley with an angle of 80 ° was used.

  FIG. 10 is a diagram illustrating the angle of the pulley.

  Part (a) in FIG. 10 shows a pulley P1 having an angle of 50 °, and part (b) in FIG. 9 shows a pulley P2 having an angle of 80 °. As described above, in Example 1, the pulley P2 having an angle of 80 ° is used. The pulley P1 having an angle of 50 ° is used in other examples and comparative examples described later.

  In the first embodiment, the cleaning of the cleaning member is not performed, and the rib is constantly cleaned.

  In such a configuration, after outputting 50,000 predetermined images, the registration amount d in each image in which 30 consecutive test images were output was measured, and the maximum value thereof was calculated as an evaluation value. The evaluation results will be described below.

  FIG. 11 is a table listing the conditions of Examples and Comparative Examples and the result of registration.

  In Table T1 shown in FIG. 11, examples are shown in the upper part, and comparative examples are shown in the lower part. As for the embodiments, the apparatus type of the image forming apparatus of each embodiment including the above-described embodiment 1, the angle of the employed pulley, the type of the cleaning member, whether or not the retract control is performed, and the amount of registration are shown. . For the comparative example, the apparatus type of the image forming apparatus, the angle of the employed pulley, and the amount of registration are shown.

For Example 1, the amount of registration was 60 μm.
[Example 2]
In Example 2, the intermediate transfer type image forming apparatus of the second embodiment described above is employed, and a brush is used as the cleaning member.

  The brush uses the same cleaning member as in the first embodiment.

  A pulley with an angle of 80 ° was used.

  Rib cleaning is always performed without retract control of the cleaning member.

After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 70 μm.
[Example 3]
In Example 3, the direct transfer type image forming apparatus of the first embodiment described above is employed, and a brush is used as the cleaning member.

  The brush uses the same cleaning member as in the first embodiment.

  A pulley with an angle of 80 ° was used.

  When the cleaning control of the cleaning member is higher than the threshold value DH on the high density side where the possibility of toner scattering is higher than a predetermined value, or when it is lower than the threshold value DL on the low density side where the possibility of carrier scattering is higher than a predetermined value. Only contact was made and cleaning was carried out.

After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 50 μm.
[Example 4]
In Example 4, the direct transfer type image forming apparatus of the first embodiment described above is employed, and a brush is used as the cleaning member.

  The brush uses the same cleaning member as in the first embodiment.

  A pulley having an angle of 50 ° shown in Part (a) of FIG. 10 was used.

  When the cleaning control of the cleaning member is higher than the threshold value DH on the high density side where the possibility of toner scattering is higher than a predetermined value, or when it is lower than the threshold value DL on the low density side where the possibility of carrier scattering is higher than a predetermined value. Only contact was made and cleaning was carried out.

After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 60 μm.
[Example 5]
In Example 5, the direct transfer type image forming apparatus of the first embodiment described above is employed, and a pad is used as the cleaning member.

  The pad is urethane foam with a foam density of 50 pieces / 25 mm, the size is 10 mm × 10 mm, the thickness is 5 mm, and is in contact with the rib centering on the rib inner end face.

  A pulley with an angle of 50 ° was used.

  When the cleaning control of the cleaning member is higher than the threshold value DH on the high density side where the possibility of toner scattering is higher than a predetermined value, or when it is lower than the threshold value DL on the low density side where the possibility of carrier scattering is higher than a predetermined value. Only contact was made and cleaning was carried out.

After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 40 μm.
[Comparative Example 1]
The comparative example 1 employs the direct transfer type image forming apparatus of the first embodiment described above, and has no cleaning member. A pulley with an angle of 80 ° was used.

After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 160 μm.
[Comparative Example 2]
The comparative example 2 employs the intermediate transfer type image forming apparatus of the first embodiment described above, and has no cleaning member. A pulley with an angle of 80 ° was used.

After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 160 μm.
[Comparative Example 3]
Comparative Example 3 employs the direct transfer type image forming apparatus of the first embodiment described above, and has no cleaning member. A pulley with an angle of 50 ° was used.

  After the output of 50,000 predetermined images, the registration amount d in each image in which 30 test images are output continuously is measured, and the maximum value thereof is calculated as an evaluation value. As a result, the registration amount is as shown in FIG. Was 130 μm.

1 is a schematic diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a view of the belt unit 100 of FIG. 1 as viewed from the direction of an arrow C. FIG. 5 is a perspective view showing details of a cleaning unit 140. It is a figure which shows another type of cleaning part. FIG. 6 is a diagram illustrating control on the movement of a cam 143 according to the amount of toner forming a toner image in the cleaning unit 140 of the present embodiment. It is a schematic diagram showing an image forming apparatus according to a second embodiment of the present invention. It is a figure which shows the example which prevents the offset running and meandering in an endless belt with a rib. It is the enlarged view of the test image (halftone) used by the Example and the comparative example. It is a figure which shows the example of a registration gap. It is a figure explaining the angle of a pulley. It is the table | surface which listed the conditions of the Example and the comparative example, and the result of a registration gap.

Explanation of symbols

1, 2 Image forming apparatus 20k, 20c, 20m, 20y, 40k, 40c, 40m, 40y Toner image forming unit 21k, 21c, 21m, 21y, 41k, 41c, 41m, 41y Photosensitive drums 22k, 22c, 22m, 22y , 42k, 42c, 42m, 42y Charging roll 23k, 23c, 23m, 23y, 43k, 43c, 43m, 43y Cleaning roll 24k, 24c, 24m, 24y, 44k, 44c, 44m, 44y Electrostatic latent image forming device 25k, 25c, 25m, 25y, 45k, 45c, 45m, 45y Developer 25k_1, 25c_1, 25m_1, 25y_1, 45k_1, 45c_1, 45m_1, 45y_1 Developing rolls 26k, 26c, 26m, 26y Transfer rolls 27k, 27c, 27m, 27y, 47k 47c, 47m, 47y Cleaning blade 30, 60 Fixing device 46k, 46c, 46m, 46y Primary transfer roll 50 Secondary transfer roll 100, 200 Belt unit 110, 210 Drive roll 110a Rotating shaft 111 Pulley 111a Groove 120, 220, 230 Follower roll 130 Paper transport belt 131 Rib 140,250 Cleaning unit 140 'Another type of cleaning unit 141 Brush 141' Pad 141a Rotating shaft 142 Spring 143 Cam 150, 260 Control unit 240 Intermediate transfer belt 501 Roll 501a Rotating shaft 502 Endless belt 503 rib

Claims (11)

In a belt unit having a plurality of rolls and an endless belt that is stretched by the plurality of rolls and circulates in a predetermined movement direction,
The endless belt has a rib extending on the inner circumference along at least one edge of two edges of the endless belt,
A groove that rotates coaxially with at least one of the plurality of rolls and that is integral with or separate from the roll and that regulates the relative position between the endless belt and the roll by fitting the rib is provided. Regulating members,
A belt unit comprising: a cleaning member for cleaning the rib. The cleaning member cleans the rib by being pressed against the rib,
The belt unit according to claim 1, further comprising a retract mechanism that contacts and separates the cleaning member with respect to the rib.   The belt unit according to claim 1, wherein the cleaning member cleans at least a side surface of the rib on the roll side.   The belt unit according to claim 1, wherein the cleaning member is a brush.   The belt unit according to claim 1, wherein the cleaning member is a pad. In the process of forming an image on the paper by forming a toner image and finally transferring and fixing the toner image on the paper, a plurality of rolls and a predetermined moving direction stretched by the plurality of rolls In an image forming apparatus using a belt unit having an endless belt that circulates and moves,
The belt unit
The endless belt has a rib extending on the inner circumference along at least one edge of two edges of the endless belt,
A groove that rotates coaxially with at least one of the plurality of rolls and that is integral with or separate from the roll and that regulates the relative position between the endless belt and the roll by fitting the rib is provided. Regulating members,
An image forming apparatus comprising a cleaning member for cleaning the rib. The cleaning member cleans the rib by being pressed against the rib,
A retract mechanism for contacting and separating the cleaning member with respect to the rib;
A recognition unit for recognizing the amount of toner forming the toner image;
When the amount of toner recognized by the recognizing unit is within a predetermined range, the retraction mechanism moves the cleaning member away from the rib, and the amount of toner is outside the predetermined range. The image forming apparatus according to claim 6, further comprising a control unit that causes the cleaning mechanism to abut the rib on the retract mechanism.   8. The image according to claim 7, wherein the image forming apparatus forms a toner image using a toner containing at least a binder resin having a number average molecular weight of 2500 to 20000 and a colorant. Forming equipment.   The image forming apparatus forms a toner image using a toner containing at least a binder resin having a softening point of 60 ° C. or higher and 120 ° C. or lower and a colorant. The image forming apparatus according to the description.   10. The image forming apparatus according to claim 7, wherein the image forming apparatus forms a toner image using a toner containing a wax having a melting point of 40 ° C. or higher and 150 ° C. or lower. Image forming apparatus.   The image forming apparatus according to claim 7, wherein the image forming apparatus forms a toner image using toner having a volume average diameter of 4 μm to 15 μm.

Images