JP5397592B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine thereof, and in particular, conveys a recording medium in contact with an image carrier such as an intermediate transfer belt, a photosensitive drum, or a photosensitive belt. The present invention relates to an image forming apparatus provided with a transfer member such as a secondary transfer roller, a transfer roller, and a transfer belt that transfers a toner image carried on an image carrier to a recording medium.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, a toner image carried on an image carrier such as an intermediate transfer belt is transferred to a recording medium by a transfer member that forms a nip portion in contact with the image carrier. Techniques are known (see, for example, Patent Documents 1 to 3).

In the image forming apparatus in Patent Document 1 or the like, four photosensitive drums are arranged side by side so as to face the intermediate transfer belt. On these four photosensitive drums, black (black), yellow, magenta, and cyan toner images are formed, respectively. Then, the toner images of the respective colors formed on the respective photoconductive drums are transferred onto the intermediate transfer belt in an overlapping manner. Further, the toner images of a plurality of colors carried on the intermediate transfer belt are transferred onto a recording medium as a color image at a contact position between the intermediate transfer belt and the secondary transfer roller (transfer member).
In such an image forming apparatus, in order to transfer the toner image on the image carrier onto the recording medium without expansion or contraction in the transport direction, it is necessary to keep the traveling speed of the image carrier and the transfer member constant. is there. In such an image forming apparatus, there is a case where a cleaning blade is brought into contact with the transfer member in order to clean deposits adhering to the transfer member. In such a case, since the load for driving the transfer member becomes relatively large, the transfer member is not driven by the frictional force caused by the contact with the image carrier, but the image carrier is driven. In addition to the driving means, it is necessary to provide driving means for driving the transfer member independently.

  On the other hand, in Patent Document 2 and the like, the detection result of the temperature detecting means for detecting the temperature in the image forming apparatus and the driving of the transfer conveyance belt are set for the purpose of making the traveling speed of the transfer conveyance belt (transfer member) constant. A technique is disclosed in which the roller diameter of the driving roller is calculated from the linear expansion coefficient of the roller to control the output of the driving means of the transfer conveyance belt.

JP 2004-61882 A JP 2006-71983 A JP 2002-268297 A

  When a conventional image forming apparatus is provided with a drive unit that drives a transfer member in addition to a drive unit that drives an image carrier, variations in the accuracy of parts of the image carrier and the transfer member (for example, the secondary transfer roller) Variation in the diameter of the roller, the thickness of the intermediate transfer belt, etc.), and the temperature and humidity change depending on the use environment of the apparatus, resulting in changes in the shape of the image carrier or transfer member (for example, the roller diameter of the secondary transfer roller). , The change in the thickness of the intermediate transfer belt, etc.), resulting in a difference in surface speed (linear speed difference) between the two members at the nip portion between the image carrier and the transfer member. . In such a case, a large frictional load is generated at the nip portion between the image carrier and the transfer member, and due to variations in the running speed of the image carrier, the color shift of the toner image transferred onto the image carrier is shifted. This causes a problem that the toner image is generated or the toner image transferred onto the recording medium expands or contracts in the transport direction. Furthermore, a large frictional load is generated in the nip portion between the image carrier and the transfer member, and the image carrier and the transfer member are worn out and deteriorated, or driving means (such as a gear and a drive motor) for driving them. It will also wear out.

  The present invention has been made in order to solve the above-described problems. In addition to the change in the use environment of the apparatus, even if there is a variation in the accuracy of the parts, the image carrier and the transfer member An object of the present invention is to provide an image forming apparatus in which the surface speed difference between both members does not occur in the nip portion.

An image forming apparatus according to a first aspect of the present invention includes an image carrier that carries a toner image and travels in a predetermined direction, and a nip portion that contacts the image carrier and a recording medium is conveyed. A transfer member that forms and travels in a predetermined direction and transfers a toner image carried on the image carrier to a recording medium; first drive means that transmits a driving force to the image carrier; and the transfer A second driving means configured to transmit a driving force to the member and to block the transmission of the driving force; an abutting member that abuts on and away from the transfer member; and a nip portion When the recording medium is not conveyed, the abutting member is separated from the transfer member and abuts against the image carrier in a state where transmission of the driving force to the transfer member by the second driving unit is blocked. The traveling speed of the transfer member Speed detection means for detecting the contact or indirectly, and when the recording medium is conveyed to the nip portion, and when the driving force is transmitted to the transfer member by the second driving means, The traveling speed of the transfer member is controlled based on the detection result detected by the speed detecting means.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the recording medium is conveyed to the nip portion, and the transfer member is moved to the transfer member by the second driving unit. When the driving force is transmitted, the traveling speed of the transfer member is controlled so as to travel at the traveling speed detected by the speed detecting means.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the thickness of the recording medium conveyed to the nip portion is detected directly or indirectly. A detection result detected by the speed detection means when the recording medium is transported to the nip portion when the recording medium is transported to the transfer member by the second driving means. And the traveling speed of the transfer member based on the detection result detected by the thickness detecting means.

  According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the third aspect, wherein the recording medium is conveyed to the nip portion and is transferred to the transfer member by the second driving unit. When the driving force is transmitted, the traveling speed of the transfer member is such that when the recording medium is thick, the traveling speed is lower than when the recording medium is thin, based on the traveling speed detected by the speed detecting means. Is to control.

An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the contact member is a cleaning blade for cleaning the surface of the transfer member. Is.

An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, wherein the speed detection means detects the traveling speed of the transfer member in the apparatus. This is not performed when the recording medium is being conveyed.

According to a seventh aspect of the present invention, an image forming apparatus according to any one of the first to sixth aspects further comprises a detecting means for detecting temperature or / and humidity in the apparatus, and the speed is increased. Detection of the traveling speed of the transfer member by the detecting means is not performed when the detection value detected by the detecting means is within a predetermined range.

An image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to any one of the first to seventh aspects, wherein a load applied to the second driving unit is directly applied when the transfer member is driven. Load detecting means for automatically or indirectly detecting the travel speed of the transfer member by the speed detecting means is not performed when the value detected by the load detecting means is within a predetermined range.

An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to any one of the first to eighth aspects, wherein the transfer member can be moved toward and away from the image carrier. It is configured.

  In the present invention, when the recording medium is not conveyed to the nip portion, the traveling speed of the transfer member is detected by the speed detection means in a state where transmission of the driving force to the transfer member is interrupted, and the recording medium is conveyed to the nip portion. When the driving force is transmitted to the transfer member, the traveling speed of the transfer member is controlled based on the detection result detected by the speed detection means. Thereby, in addition to the change in the environment of use of the apparatus, even when there is a variation in component accuracy, there is no difference in surface speed between both members in the nip portion between the image carrier and the transfer member. An image forming apparatus can be provided.

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

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a block diagram showing a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing an image forming unit thereof. FIG. 3 is a configuration diagram showing the vicinity of the intermediate transfer belt and the secondary transfer roller.
First, the configuration and operation of the entire image forming apparatus will be described.
As shown in FIG. 1, an intermediate transfer belt device 15 is installed in the center of the image forming apparatus main body 100. Further, image forming units 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 of the intermediate transfer belt device 15. Further, a secondary transfer roller 19 (transfer member) is disposed so as to face the intermediate transfer belt 8 of the intermediate transfer belt device 15.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y, a charging unit 4Y disposed around the photosensitive drum 1Y, a developing unit 5Y, a cleaning unit 2Y, and a static eliminating unit (non-static unit). Etc.). Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y.

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

Referring to FIG. 2, the photosensitive drum 1Y is driven to rotate counterclockwise in FIG. 2 by a drive motor (not shown). Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (a charging process).
Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure unit 7, and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (in the exposure process). is there.).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing portion 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 and the transfer roller 9Y (primary transfer roller), and the toner image on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 8 at this position. Transferred (primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position is collected in the cleaning unit 2Y by the cleaning blade 2a (cleaning). Process.)
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, a laser beam L based on image information is irradiated from the exposure unit 7 disposed above the image forming unit onto the photosensitive drums 1M, 1C, and 1K of the image forming units 6M, 6C, and 6K. Is done. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 serving as an image carrier onto which the toner images of the respective colors are transferred in a superimposed manner reaches a contact position (nip portion) with the secondary transfer roller 19 serving as a transfer member. At this position, the secondary transfer counter roller 12B sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a nip portion (secondary transfer nip). Then, a high voltage (secondary transfer bias) opposite to the polarity of the toner is applied to the secondary transfer roller 19. As a result, the color toner image formed on the intermediate transfer belt 8 is transferred onto the recording medium P such as transfer paper conveyed to the position of the secondary transfer nip (secondary transfer step). . At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.
Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning unit 10. At this position, the untransferred toner on the intermediate transfer belt 8 is removed.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

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

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged out of the apparatus by a pair of discharge rollers (not shown). The transferred P discharged from the apparatus by the pair of paper discharge rollers is sequentially stacked on the stack unit as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration and operation of the developing unit in the image forming unit will be described in more detail with reference to FIG.
The developing unit 5Y includes a developing roller 51Y that faces the photosensitive drum 1Y, a doctor blade 52Y that faces the developing roller 51Y, two transport screws 55Y disposed in the developer containing unit, and an opening in the developer containing unit. A toner replenishment path 43Y that communicates with each other via a toner density, a density detection sensor 56Y that detects a toner density in the developer, and the like. The developing roller 51Y includes a magnet fixed inside, a sleeve rotating around the magnet, and the like. In the developer accommodating portion, a two-component developer composed of a carrier and toner is accommodated.

The developing unit 5Y configured as described above operates as follows.
The sleeve of the developing roller 51Y rotates in the direction of the arrow in FIG. The developer carried on the developing roller 51Y by the magnetic field formed by the magnet moves on the developing roller 51Y as the sleeve rotates. Here, the developer in the developing device 5Y is adjusted so that the toner ratio (toner concentration) in the developer is within a predetermined range.
Thereafter, the toner replenished in the developer accommodating portion circulates through the two separated developer accommodating portions while being mixed and stirred together with the developer by the two conveying screws 55Y (movement in the direction perpendicular to the paper surface of FIG. 2). .) The toner in the developer is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller 51Y together with the carrier by the magnetic force formed on the developing roller 51Y.

  The developer carried on the developing roller 51Y is conveyed in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52Y. The developer on the developing roller 51Y is conveyed to a position facing the photosensitive drum 1Y (development area) after the developer amount is made appropriate at this position. The toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field formed in the development area. Thereafter, the developer remaining on the developing roller 51Y reaches the upper portion of the developer accommodating portion as the sleeve rotates, and is detached from the developing roller 51Y at this position.

Next, the intermediate transfer belt device 15 will be described in more detail with reference to FIG.
As shown in FIG. 3, the intermediate transfer belt device 15 includes an intermediate transfer belt 8 as an image carrier, four primary transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12A, a secondary transfer counter roller 12B, a tension. The roller 12C, the correction roller 12D, the intermediate transfer cleaning unit 10, and the like. The intermediate transfer belt 8 (image carrier) is stretched and supported by a plurality of roller members 12A to 12D, and is moved endlessly in the direction of the arrow in FIG. 3 by the rotational drive of one roller member (drive roller) 12A. The

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

In the first embodiment, the intermediate transfer belt 8 as an image carrier is made of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), or the like. It is composed of a single layer or a plurality of layers, and a conductive material such as carbon black is dispersed. The intermediate transfer belt 8 is adjusted so that the volume resistivity is in the range of 10 ⁷ to 10 ¹² Ωcm and the surface resistivity on the back side of the belt is in the range of 10 ⁸ to 10 ¹² Ωcm. The intermediate transfer belt 8 is set to have a thickness in the range of 80 to 100 μm. In the first embodiment, the thickness of the intermediate transfer belt 8 is set to 90 μm. The peripheral length of the intermediate transfer belt 8 is set to 2197.5 mm.
If necessary, a release layer can be coated on the surface of the intermediate transfer belt 8. At that time, materials used for the coating are ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four A fluororesin such as fluorinated ethylene-hexafluoropropylene copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.
Further, as a method for manufacturing the intermediate transfer belt 8, there are a casting method, a centrifugal molding method, and the like, and a step of polishing the surface is performed as necessary.

The four primary transfer rollers 9Y, 9M, 9C, and 9K are configured to separate the intermediate transfer belt 8 from the photosensitive drums 1Y, 1M, 1C, and 1K.
Specifically, among the four primary transfer rollers 9Y, 9M, 9C, and 9K, the three primary transfer rollers 9Y, 9M, and 9C for color are integrally held in a housing (not shown). It is configured to be movable integrally in the vertical direction. Further, the black primary transfer roller 9K is configured to be movable up and down independently. Then, the four primary transfer rollers 9Y, 9M, 9C, and 9K move to the positions indicated by broken lines in FIG. 3, so that the intermediate transfer belt 8 is separated from the photosensitive drums 1Y, 1M, 1C, and 1K (broken line positions). To move to.). The operation of separating the intermediate transfer belt 8 from the photosensitive drums 1Y, 1M, 1C, and 1K is performed to reduce wear deterioration of the intermediate transfer belt 8, and is mainly performed during non-image formation. . Note that the black primary transfer roller 9K is configured to be movable in the vertical direction independently when the monochrome image is formed, the three primary transfer rollers 9Y, 9M, and 9C for color are moved downward. This is because the photosensitive drums 1Y, 1M, and 1C for use are separated from the intermediate transfer belt 8.

The drive roller 12A is rotationally driven by a first drive motor 71 as first drive means connected to the shaft portion. As a result, the intermediate transfer belt 8 travels in a predetermined traveling direction (clockwise in FIG. 3).
The secondary transfer counter roller 12B is in contact with the secondary transfer roller 19 (transfer member) via an intermediate transfer belt 8 as an image carrier. The tension roller 12 </ b> C is in contact with the outer peripheral surface of the intermediate transfer belt 8. An intermediate transfer cleaning unit 10 (cleaning blade) is installed between the secondary transfer counter roller 12B and the tension roller 12C.
Based on the displacement (displacement amount) of the intermediate transfer belt 8 detected by a meandering detection sensor (not shown), the correction roller 12D has one end as a fixed end and the other end moves in the vertical direction ( The rotation axis is inclined). Thereby, the displacement (meandering) of the intermediate transfer belt 8 in the width direction is corrected.

Further, the secondary transfer roller 19 as a transfer member moves so as to be in contact with and away from the intermediate transfer belt 8 (secondary transfer counter roller 12B) by a contact / separation mechanism (not shown) of the transfer device 30 (not shown). The movement is in the direction of the arrow.) The secondary transfer roller 19 is a coating made of a rubber material such as NBR (nitrile rubber) on the core metal, a rubber layer having a hardness (JIS-A) of about 53 degrees, and a high resistance resin material having a layer thickness of about 15 μm. The layers are sequentially stacked.
Further, the secondary transfer roller 19 as a transfer member is a second drive unit provided separately from the first drive motor 71 (first drive unit) that transmits the driving force to the intermediate transfer belt 8 (drive roller 12A). A driving force is transmitted by the second driving motor 72 and is rotated counterclockwise in FIG. The driving force of the second drive motor 72 is input to the shaft portion of the secondary transfer roller 19 via the electromagnetic clutch 73, a gear train, a timing belt, a pulley, and the like. In the first embodiment, transmission of the driving force from the second drive motor 72 to the secondary transfer roller 19 can be cut off by the off operation of the electromagnetic clutch 73.

  In addition to the secondary transfer roller 19, the holding member 36 of the transfer device 30 holds a cleaning blade 61 as a cleaning unit, a lubricant supply brush 62, a charge eliminating needle 63, and a paper dust removing brush 64. The cleaning blade 61 is a plate-like member made of a rubber material, and abuts against the secondary transfer roller 19 to mechanically remove deposits such as toner adhering to the surface of the secondary transfer roller 19. The paper dust removing brush 64 is a brush roller in which brush bristles are wound on a core metal, and is attached to the surface of the secondary transfer roller 19 by sliding contact with the secondary transfer roller 19 and deposits such as paper dust. Remove. The static elimination needle 63 is disposed at a position facing the secondary transfer roller 19 and applies a predetermined voltage to neutralize the charge charged on the surface of the secondary transfer roller 19. The lubricant supply brush 62 is in sliding contact with the solid lubricant urged by the spring and the secondary transfer roller 19, and supplies the lubricant scraped from the solid lubricant onto the secondary transfer roller 19. The lubricant supplied onto the secondary transfer roller 19 is also supplied to the intermediate transfer belt 8 and the wear resistance of the intermediate transfer belt 8 and the secondary transfer roller 19 is improved.

Normally, the secondary transfer roller 19 is pressed against the secondary transfer counter roller 12B via the intermediate transfer belt 8 by the pressure mechanism of the transfer device 30 (the state shown in FIG. 3).
The transfer device 30 is provided with a contact / separation mechanism together with a pressure mechanism. The contact / separation mechanism of the transfer device 30 functions as a manual contact / separation mechanism for manually contacting / separating the secondary transfer roller 19 that is in pressure contact with the intermediate transfer belt 8 (secondary transfer opposing roller 12B), and the apparatus main body. Based on the control of 100, it also functions as an automatic contact / separation mechanism for automatically contacting / separating the secondary transfer roller 19 to / from the intermediate transfer belt 8 (secondary transfer counter roller 12B). The automatic contact / separation mechanism is controlled so that the secondary transfer roller 19 is separated from the intermediate transfer belt 8 when the secondary transfer process is not performed. The automatic contact / separation mechanism performs secondary transfer to the intermediate transfer belt 8 without separating the secondary transfer roller 19 from the intermediate transfer belt 8 when detection by a rotation speed detection sensor 74 described later is performed. The roller 19 is controlled to contact. The manual contact / separation mechanism is operated by a user, a serviceman, or the like when the power of the apparatus main body 100 is shut off and when the secondary transfer roller 19 needs to be manually separated (contacted / separated). .

Although not shown, the pressure mechanism (contact / separation mechanism) of the transfer device 30 includes a holding member 36 that holds the secondary transfer roller 19, a pressure plate, a manual cam, an automatic cam, a first spring, a second spring, and the like. It consists of The pressure plate is configured to rotate together with the holding member 36 that holds the secondary transfer roller 19. The holding member that holds the secondary transfer roller 19 is formed in a substantially box shape. In addition to the secondary transfer roller 19, a cleaning blade 61, a lubricant supply brush 62, a charge eliminating needle 63, a paper dust removing brush 64, and the like. Holding. Further, the holding member 36 includes a second driving means (including a driving motor 72, an electromagnetic clutch 73, a gear train, a timing belt, a pulley, etc.) for transmitting a driving force to the secondary transfer roller 19. A rotation speed detection sensor 74 as speed detection means for detecting the rotation speed (running speed) of the secondary transfer roller 19 and a guide plate for guiding the recording medium P to the secondary transfer nip are also provided.
Although not shown in the drawings, the rotational speed detection sensor 74 as a speed detection means optically detects the marking formed radially on the detection plate installed on the shaft portion of the secondary transfer roller 19 with a photo sensor. Thus, the encoder obtains the rotational speed of the secondary transfer roller 19 from the detection cycle. As a result, the traveling speed of the secondary transfer roller 19 is indirectly detected.

The characteristic configuration and operation of the image forming apparatus according to the first embodiment will be described in detail below.
The transfer device 30 according to the first embodiment includes a rotation speed detection sensor (speed detection) that detects the rotation speed (running speed) of the secondary transfer roller 19 (transfer member) in contact with the intermediate transfer belt 8 (image carrier). Means) are installed. Then, when the recording medium P is not conveyed to the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 (at a timing when a normal image forming process is not performed), power is supplied to the electromagnetic clutch 73. The rotation of the secondary transfer roller 19 by the rotation speed detection sensor 74 (speed detection means) in a state where the transmission of the driving force to the secondary transfer roller 19 by the second drive motor 72 (second drive means) is cut off. Number detection is performed. As described above, the rotation speed of the secondary transfer roller 19 detected by the rotation speed detection sensor 74 with the electromagnetic clutch 73 turned off in a state where the secondary transfer roller 19 is in contact with the intermediate transfer belt 8 is the first The rotational speed of the secondary transfer roller 19 that rotates at a constant speed (the linear velocity at the nip portion is equal) with the intermediate transfer belt 8 by the frictional force with the intermediate transfer belt 8 driven by the drive motor 71. is there.
When the recording medium P is conveyed to the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 (at a timing when a normal image forming process is performed), electric power is supplied to the electromagnetic clutch 73. A driving force is transmitted to the secondary transfer roller 19 by the second drive motor 72 (second drive means), and the rotational speed (running) of the secondary transfer roller 19 is determined based on the detection result detected by the rotational speed detection sensor 74. Speed). Specifically, the rotation speed (running speed) of the secondary transfer roller 19 described above is controlled such that the secondary transfer roller 19 is driven at the rotation speed detected by the rotation speed detection sensor 74. To do.

More specifically, information on the rotational speed of the secondary transfer roller 19 detected by the rotational speed detection sensor 74 when the recording medium P is not passing (when not printing) is the rotational speed due to rotation. It is sent to the CPU of the control unit 75. Then, when the recording medium P is passed (printed), the control unit 75 drives the second drive motor 72 (the second transfer motor 72) so that the secondary transfer roller 19 is rotationally driven by the rotational speed detected by the rotational speed detection sensor 74. This is a variable speed motor.
In the CPU of the control unit 75, a rotation speed N1 of the secondary transfer roller 19 that is a default value (standard value) is set in advance. The rotation speed N1 of this default value does not cause variations in the accuracy of parts such as the secondary transfer roller 19 and the same speed as that of the intermediate transfer belt 8 at the nip portion when the use environment of the apparatus is normal temperature and humidity. Therefore, the rotation speed of the secondary transfer roller 19 is optimal. Further, due to variations in the accuracy of parts such as the secondary transfer roller 19 and the use environment of the apparatus being high temperature and high humidity, the roller diameter of the secondary transfer roller 19 has become larger than the intended one. In this case, the rotation speed N2 of the secondary transfer roller 19 detected by the rotation speed detection sensor 74 in the state of rotation with the intermediate transfer belt 8 becomes smaller than the default rotation speed N1, and is 2 when the sheet is passed thereafter. The next transfer roller 19 is rotationally driven by the second drive motor 72 at a rotational speed N2 (variably controlled rotational speed). On the other hand, the roller diameter of the secondary transfer roller 19 becomes smaller than the target due to variations in the accuracy of the components of the secondary transfer roller 19 and the like, and the use environment of the apparatus is low temperature and low humidity. In the case of jamming, the rotational speed N3 of the secondary transfer roller 19 detected by the rotational speed detection sensor 74 in the state of being rotated with the intermediate transfer belt 8 becomes larger than the default rotational speed N1, and the subsequent sheet passing is performed. Sometimes, the secondary transfer roller 19 is rotationally driven by the second drive motor 72 at the rotational speed N3 (variably controlled rotational speed).

  With such a configuration and operation, both the members 8 at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 even when there is a variation in component accuracy in addition to changes in the usage environment of the apparatus. , 19 can suppress a problem that a surface speed difference occurs. Accordingly, a large frictional load is not generated at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19, and a problem that color misregistration occurs in the toner image transferred and superimposed on the intermediate transfer belt 8 or on the recording medium P The problem that the toner image transferred to the belt expands and contracts in the transport direction and the problem that the intermediate transfer belt 8, the secondary transfer roller 19 and the driving means for driving them are worn out are reduced.

As described above, the rotation number detection sensor 74 (speed detection means) does not detect the rotation number of the secondary transfer roller 19 when the recording medium P is being conveyed in the apparatus. In other words, the rotation speed of the secondary transfer roller 19 is detected by the rotation speed detection sensor 74 when the recording medium P is not passing (when not printing). Specifically, the secondary transfer by the rotation speed detection sensor 74 is performed immediately after the main switch (main power supply) of the apparatus main body 100 is turned on, at the time of pre-operation immediately before the start of printing, or at the time of adjustment for adjusting printing conditions. The number of rotations of the roller 19 is detected. As a result, the above-described effects can be obtained without lowering the output image productivity during normal paper feeding (printing).
In the first embodiment, the traveling speed of the secondary transfer roller 19 is detected by the rotation speed detection sensor 74 (encoder). However, the method of detecting the traveling speed of the secondary transfer roller 19 is not limited to this. Absent.

Here, the image forming apparatus 100 according to the first embodiment detects the thickness (paper thickness) of the recording medium P conveyed to the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19. A paper thickness sensor 76 is installed as a means. The paper thickness sensor 76 (thickness detection means) can be a photo sensor that detects the distance between the rollers of the registration roller pair 28 in a state where the recording medium P is sandwiched.
Then, when the recording medium P is conveyed to the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 (at the timing when the normal image forming process is performed), the electromagnetic clutch 73 is supplied with electric power and the first. The driving force is transmitted to the secondary transfer roller 19 by the two-drive motor 72 (second drive means), the detection result detected by the rotation speed detection sensor 74 and the paper thickness sensor 76 (thickness detection means). The number of rotations (traveling speed) of the secondary transfer roller 19 is controlled on the basis of the detection result detected in step S2. Specifically, the above-described control of the rotational speed (traveling speed) of the secondary transfer roller 19 is based on the rotational speed detected by the rotational speed detection sensor 74 when the recording medium P is thicker than when it is thin. The rotational speed of the secondary transfer roller 19 is controlled so that the secondary transfer roller 19 travels at a low traveling speed.

  More specifically, information on the rotational speed of the secondary transfer roller 19 detected by the rotational speed detection sensor 74 when the recording medium P is not passing (when not printing) is the rotational speed due to rotation. It is sent to the CPU of the control unit 75. Further, information on the thickness of the recording medium P detected by the paper thickness sensor 76 (thickness detection means) is also sent to the CPU of the control unit 75. Then, the second transfer motor 72 (rotation) is performed by the control unit 75 so that the secondary transfer roller 19 is rotationally driven by the rotational speed detected by the rotational speed detection sensor 74 when the recording medium P is passed (printing). This is a number variable type motor), but the number of rotations is corrected based on the detection result detected by the paper thickness sensor 76. This is because when the thick recording medium P is passed, the speed when passing the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 is higher than when the thin recording medium P is passed. It is because it is easy to become.

  In the image forming apparatus 100 according to the first embodiment, when using 60 gsm paper, which is the thinnest type of the recording medium P, on the basis of specifications, when using the recording medium P thicker than 60 gsm paper, the thickness thereof is used. Accordingly, the rotation speed of the secondary transfer roller 19 is corrected so as to be reduced. For example, when 300 gsm paper, which is the type of the thickest recording medium P, is used according to the specifications, the secondary transfer roller 19 is rotationally driven at a rotational speed that is 0.4% slower than the rotational speed when 60 gsm paper is used. When the rotational speed of the secondary transfer roller 19 detected by the rotational speed detection sensor 74 is N3, the final thickness is detected when the thickness of the recording medium P detected by the paper thickness sensor 76 is equivalent to that of 60 gsm paper. The rotational speed of the secondary transfer roller 19 controlled to N2 remains N3, and when the thickness of the recording medium P detected by the paper thickness sensor 76 is equivalent to that of 300 gsm paper, the secondary transfer finally controlled is controlled. The rotation speed of the roller 19 is N3 × 99.6%.

In addition to the case where the use environment of the apparatus changes and the variation in component accuracy occurs due to such a configuration and operation, even when various recording media P having different thicknesses are used, the intermediate transfer belt 8 and the secondary transfer belt 8 are used. It is possible to suppress a problem that a difference in surface speed occurs between the members 8 and 19 at the nip portion with the transfer roller 19 and to optimize the speed of the recording medium P passing through the nip portion between the both members 8 and 19. . Accordingly, a large frictional load is not generated at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19, and a problem that color misregistration occurs in the toner image transferred and superimposed on the intermediate transfer belt 8 or on the recording medium P The problem that the toner image transferred to the belt expands and contracts in the transport direction and the problem that the intermediate transfer belt 8, the secondary transfer roller 19 and the driving means for driving them are worn out are reduced.
In the first embodiment, the paper thickness sensor 76 that directly detects the thickness of the recording medium P is used as the thickness detection unit that detects the thickness (paper thickness) of the recording medium P. It is also possible to indirectly detect the thickness of the recording medium P based on input information related to the type of the recording medium P input to an operation unit (not shown) of the image forming apparatus 100.

  As described above, in the first embodiment, when the recording medium P is not conveyed to the nip portion between the intermediate transfer belt 8 (image carrier) and the secondary transfer roller 19 (transfer member), the secondary transfer roller 19. When the rotational speed (running speed) of the secondary transfer roller 19 is detected by the rotational speed detection sensor 74 (speed detection means) with the transmission of the driving force to the recording medium P being conveyed to the nip portion. The rotational speed of the secondary transfer roller 19 is controlled based on the detection result detected by the rotational speed detection sensor 74 when the driving force is transmitted to the secondary transfer roller 19. As a result, in addition to changes in the use environment of the apparatus, even if there is a variation in component accuracy, the surface speeds of both members 8 and 19 at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 are detected. It is possible to suppress problems that cause differences.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 4 is a configuration diagram showing the vicinity of the intermediate transfer belt 8 and the secondary transfer roller 19 in the second embodiment. FIG. 5 is a flowchart showing a part of the control performed in the image forming apparatus of FIG.
In the image forming apparatus according to the second embodiment, a cleaning blade 61 that is in contact with the secondary transfer roller 19 is configured to be able to contact and separate, and a detection unit 77 that detects temperature and humidity in the apparatus is installed. This is different from that of the first embodiment in that load detecting means 78 for detecting the load applied to the second motor 72 is installed.

Referring to FIG. 4, in the transfer device 30 according to the second embodiment, a cleaning blade 61 as an abutting member that abuts on the secondary transfer roller 19 moves so as to come into contact with and separate from the secondary transfer roller 19. It is configured as follows. Although not shown, the cleaning blade 61 (contact member) is urged in a direction to contact the secondary transfer roller 19 by a pressure spring. In addition, a solenoid that rotates the cleaning blade 61 is installed at a position (a position indicated by a broken line in FIG. 4) that cancels the urging force of the pressure spring and moves away from the secondary transfer roller 19.
Then, when the rotational speed of the secondary transfer roller 19 is detected by the rotational speed detection sensor 74 (speed detection means), the cleaning blade 61 is separated from the secondary transfer roller 19.
As a result, the rotational speed of the secondary transfer roller 19 is detected by the rotational speed detection sensor 74 in a state in which the sliding resistance of the secondary transfer roller 19 is reduced, so that the secondary rotating around the intermediate transfer belt 8 is performed. The detection accuracy of the number of rotations of the transfer roller 19 is improved, and a problem that a difference in surface speed between the members 8 and 19 at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 is further suppressed.
In the second embodiment, only the cleaning blade 61 that contacts the secondary transfer roller 19 is configured to be able to contact and separate, and the rotational speed detection sensor 74 uses the rotation speed detection sensor 74 in a state where the cleaning blade 61 is separated from the secondary transfer roller 19. Rotational speed was detected. On the other hand, the lubricant supply brush 62 and the paper dust removing brush 64 that are in contact with the secondary transfer roller 19 are also configured to be able to come into contact with and separate from each other. The number of rotations can be detected by 74.

  In the second embodiment, a temperature sensor / humidity sensor 77 is installed as detection means for detecting the temperature / humidity in the image forming apparatus 100. The rotation speed of the secondary transfer roller 19 is not detected by the rotation speed detection sensor 74 (speed detection means) when the detection value detected by the temperature sensor / humidity sensor 77 (detection means) is within a predetermined range. So that it is controlled. This is because when the temperature and humidity in the image forming apparatus 100 are close to room temperature humidity, there is little change in the roller diameter of the secondary transfer roller 19 and the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19. This is because the difference in surface speed generated between the members 8 and 19 is relatively small. By performing such control by the temperature sensor / humidity sensor 77, the rotational speed detection sensor 74 detects the rotational speed of the secondary transfer roller 19, and the control of the rotational speed of the secondary transfer roller 19 based on the detection result. Can be performed at the minimum frequency required. Therefore, by repeating the detection and control of the rotational speed described above, the problem that the durability of the intermediate transfer belt 8, the secondary transfer roller 19, and the driving means for driving them is lowered is reduced.

In the second embodiment, a torque detection sensor 78 as a load detection unit that directly detects a load applied to the second drive motor 72 when the secondary transfer roller 19 is driven by the second drive motor 72 is provided. It is installed. The torque detection sensor 78 (load detection means) is a current detector that detects the magnitude of the current value supplied to the second drive motor 72. In the second embodiment, the torque detection sensor 78 that directly detects the motor load is used as the load detection unit that detects the load applied to the second drive motor 72. However, the load applied to the second drive motor 72 is not limited. It is also possible to use load detecting means for detecting indirectly.
The rotation speed detection sensor 74 (speed detection means) does not detect the rotation speed of the secondary transfer roller 19 when the value detected by the torque detection sensor 78 (load detection means) is within a predetermined range. I have control. This is because, when the load of the second drive motor 72 detected by the torque detection sensor 78 is small, the surface speed difference generated between the members 8 and 19 at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19. Is considered to be small. By performing such control by the torque detection sensor 78, detection of the rotation speed of the secondary transfer roller 19 by the rotation speed detection sensor 74 and control of the rotation speed of the secondary transfer roller 19 based on the detection result are performed. It can be done as often as necessary. Therefore, by repeating the detection and control of the rotational speed described above, the problem that the durability of the intermediate transfer belt 8, the secondary transfer roller 19, and the driving means for driving them is lowered is reduced.

FIG. 5 is a flowchart showing the control by the torque detection sensor 78 described above.
First, when the load F of the second drive motor 72 is detected by the torque detection sensor 78 (steps S1 and S2), it is determined whether or not the value F is within a predetermined range (A1 ≦ F ≦ A2) (step S1). S3). As a result, when the load F of the second drive motor 72 is within a predetermined range (A1 ≦ F ≦ A2), it is assumed that the surface speed difference at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 is small. The flow is terminated without controlling the rotational speed of the secondary transfer roller 19 (step S7).
On the other hand, if the load F of the second drive motor 72 is outside the predetermined range (A1> F or F> A2) in step S3, the intermediate transfer belt 8 and the secondary transfer roller 19 First, the electromagnetic clutch 73 is turned off to interrupt the drive of the secondary transfer roller 19 by the second drive motor 72 (step S4). Thereafter, the rotational speed of the secondary transfer roller 19 is detected by the rotational speed detection sensor 74 (step S5), and the rotational speed of the secondary transfer roller 19 is controlled and the electromagnetic clutch 73 is connected based on the detection result (step S5). Step S6), the flow after step S2 is repeated.

  As described above, also in the second embodiment, similarly to the first embodiment, the recording medium P is located at the nip portion between the intermediate transfer belt 8 (image carrier) and the secondary transfer roller 19 (transfer member). The rotational speed (traveling speed) of the secondary transfer roller 19 is detected by the rotational speed detection sensor 74 (speed detection means) in a state in which the transmission of the driving force to the secondary transfer roller 19 is interrupted when not being conveyed. The rotational speed of the secondary transfer roller 19 is controlled based on the detection result detected by the rotational speed detection sensor 74 when the recording medium P is conveyed to the secondary transfer roller 19 and the driving force is transmitted to the secondary transfer roller 19. doing. As a result, in addition to changes in the use environment of the apparatus, even if there is a variation in component accuracy, the surface speeds of both members 8 and 19 at the nip portion between the intermediate transfer belt 8 and the secondary transfer roller 19 are detected. It is possible to suppress problems that cause differences.

  In each of the above embodiments, the intermediate transfer belt 8 on which toner images of a plurality of colors are carried in an overlapping manner is used as an image carrier, and the secondary transfer roller 19 that secondarily transfers the toner image onto the recording medium P is used as a transfer member. The present invention is applied to the image forming apparatus. However, the application of the present invention is not limited to this. For example, a toner image carried on an image carrier such as a photoreceptor drum or a photoreceptor belt is transferred onto a recording medium by a transfer member such as a transfer roller or a transfer belt. The present invention can also be applied to an image forming apparatus and the like for transferring. Even in this case, when the recording medium is not conveyed to the nip portion between the image carrier and the transfer member, the speed detection means detects the traveling speed of the transfer member in a state where the transmission of the driving force to the transfer member is interrupted. And controlling the traveling speed of the transfer member based on the detection result detected by the speed detection means when the recording medium is conveyed to the nip portion and the driving force is transmitted to the transfer member. The same effect as in each embodiment can be obtained.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is sectional drawing which shows an image formation part. FIG. 3 is a configuration diagram illustrating the vicinity of an intermediate transfer belt and a secondary transfer roller. It is a block diagram which shows the vicinity of the intermediate transfer belt and the secondary transfer roller in Embodiment 2 of this invention. 5 is a flowchart showing control performed by the image forming apparatus of FIG.

Explanation of symbols

8 Intermediate transfer belt (image carrier),
12A driving roller,
12B secondary transfer counter roller,
19 Secondary transfer roller (transfer member),
30 Transfer device,
61 Cleaning blade (contact member),
71 1st drive motor (1st drive means),
72 second drive motor (second drive means),
73 electromagnetic clutch,
74 Rotational speed detection sensor (speed detection means),
75 control unit,
76 Paper thickness sensor (thickness detection means),
77 Temperature sensor / humidity sensor (detection means)
78 Torque detection sensor (load detection means),
100 Image forming apparatus main body (apparatus main body).

Claims (9)

An image carrier that carries a toner image and travels in a predetermined direction;
A transfer member that abuts against the image carrier to form a nip portion where the recording medium is conveyed, and travels in a predetermined direction to transfer the toner image carried on the image carrier to the recording medium;
First driving means for transmitting a driving force to the image carrier;
Second driving means configured to transmit a driving force to the transfer member and to be able to block the transmission of the driving force;
An abutting member that abuts against the transfer member so as to be able to come into contact with and separate from,
When the recording medium is not conveyed to the nip portion, the image bearing member is separated from the transfer member so that transmission of the driving force to the transfer member by the second driving unit is blocked. Speed detecting means for directly or indirectly detecting the traveling speed of the transfer member that contacts the body;
With
When the recording medium is conveyed to the nip portion and when the driving force is transmitted to the transfer member by the second driving unit, the transfer member is moved based on the detection result detected by the speed detecting unit. An image forming apparatus that controls a traveling speed.   When the recording medium is conveyed to the nip portion and when the driving force is transmitted to the transfer member by the second driving unit, the recording medium is traveled at the traveling speed detected by the speed detecting unit. The image forming apparatus according to claim 1, wherein a traveling speed of the transfer member is controlled. A thickness detecting means for directly or indirectly detecting the thickness of the recording medium conveyed to the nip portion;
When the recording medium is conveyed to the nip portion and when the driving force is transmitted to the transfer member by the second driving unit, the detection result detected by the speed detecting unit and the thickness detecting unit The image forming apparatus according to claim 1, wherein the traveling speed of the transfer member is controlled based on the detected detection result.   When the recording medium is conveyed to the nip portion and when the second driving unit transmits the driving force to the transfer member, the recording medium is based on the traveling speed detected by the speed detecting unit. 4. The image forming apparatus according to claim 3, wherein when the thickness of the transfer member is large, the traveling speed of the transfer member is controlled so that the traveling speed is smaller than when the thickness is small. The image forming apparatus according to claim 1, wherein the contact member is a cleaning blade that cleans a surface of the transfer member. 6. The image forming apparatus according to claim 1, wherein the speed detection unit does not detect the traveling speed of the transfer member when a recording medium is conveyed in the apparatus. A detecting means for detecting temperature or / and humidity in the apparatus;
The detection of the running speed of the transfer member by the speed detection unit is not performed when the detection value detected by the detection unit is within a predetermined range. Image forming apparatus. A load detecting means for directly or indirectly detecting a load applied to the second driving means when driving the transfer member;
The detection of the traveling speed of the transfer member by the speed detection unit is not performed when the value detected by the load detection unit is within a predetermined range. Image forming apparatus. The image forming apparatus according to claim 1, wherein the transfer member is configured to be able to contact and separate relative to the image carrier.

Images