JP2014178492A - Sheet conveying device, image forming apparatus, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveying device having a transfer member that transfers an image carried on an image carrier to a recording target medium such as a sheet, and can stabilize the speed of the recording target medium over time without the need to detect the speed itself of the recording target medium, so as to reduce or prevent a magnification error during the transfer; an image forming apparatus including the sheet conveying device, such as a copier and a printer; and an image forming method in such an image forming apparatus.SOLUTION: A sheet conveying device includes: a transfer member 64 that moves at an opposing part 57 arranged opposite to an image carrier 11 moving in an A1 direction, in a C1 direction extending along the A1 direction to pass a recording target medium S therethrough, so as to transfer an image on the image carrier 11 to the recording target medium S; and speed adjustment means 91 for adjusting the speed of movement at the opposing part 57 of at least one of the image carrier 11 and the transfer member 64 on the basis of a timing at which the recording target medium S is detected by detection units 21 and 22 that are arranged on the downstream side of the opposing part 57 in a direction of movement D1 of the recording target medium S at the opposing part 57 to detect the recording target medium S.

Description

  The present invention is provided in an image forming apparatus such as a copying machine, a facsimile, a printer, or a printing apparatus having a transfer member that transfers an image carried on an image carrier onto a recording medium such as paper, and has such a transfer member. The present invention relates to a sheet conveying apparatus, an image forming apparatus having the sheet conveying apparatus, and an image forming method in the image forming apparatus using the transfer member.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, facsimile machines, printers, and printing apparatuses having a transfer member such as a transfer roller that transfers an image carried on an image carrier such as an intermediate transfer body onto a recording medium such as paper. It is known (see, for example, [Patent Document 1]).

  Such an image forming apparatus is provided with such a transfer member and a paper transport device that transports a recording medium to which the image is transferred. The sheet conveying apparatus conveys the recording medium toward, for example, a fixing unit that fixes the image transferred to the recording medium to the recording medium.

  On the other hand, such an image forming apparatus has a sensor for detecting a jam that occurs when a recording medium is conveyed by each unit in the apparatus. Examples of the arrangement position of the sensor include a downstream side of the fixing unit in the conveyance direction of the recording medium (see, for example, [Patent Document 1]) and a conveyance path of the recording medium in the sheet conveyance device.

  By the way, in such an image forming apparatus, in order to transfer the image on the image carrier to the recording medium, the recording medium is passed through a transfer portion between the image carrier and the transfer member. There is a problem that a magnification error occurs when the speed when passing through the transfer portion is not a specified speed. For example, when a recording medium having a very low coefficient of friction is used, if the recording medium slips in the transfer portion and the passing speed becomes slow, the image on the image carrier is reduced in the moving direction of the recording medium. In this state, a magnification error that is transferred to the recording medium occurs.

  In other words, since there are various types of recording media and the friction coefficient is not constant, and the friction coefficient changes depending on the humidity of the environment even in the same recording medium, the passing speed of the recording medium in the transfer section is high. Indefinite, the transportability of the recording medium becomes unstable, and a magnification error may occur. The problem of magnification error at the time of transfer is a problem peculiar to the portion where the image is transferred, and cannot occur at the fixing portion.

As measures against this magnification error, the following can be considered.
-The transfer member is brought into contact with the image carrier at a high pressure in the transfer portion.-The friction coefficient of the surface of the transfer member is increased.-The speed of the recording medium that has passed through the transfer portion is detected.

  However, if the transfer member is brought into contact with the image carrier at a high pressure in the transfer section, the image carrier and the transfer member may be easily deteriorated, and the recording medium may be deteriorated over time due to this defect. It is conceivable that there is a problem that the transportability becomes unstable. Even if the friction coefficient of the surface of the transfer member is increased, it is considered that there is a problem that the friction coefficient of the surface of the transfer member decreases with time and the transportability of the recording medium becomes unstable. Further, it is considered that a sensor that detects the speed of the recording medium itself that has passed through the transfer portion is relatively expensive, resulting in a problem that causes an increase in the price of the apparatus.

  The present invention has a transfer member for transferring an image carried on an image carrier to a recording medium such as paper, and the speed of the recording medium is changed over time without detecting the speed of the recording medium itself. In a sheet conveying device that can stabilize and reduce or prevent a magnification error during transfer, an image forming apparatus such as a copying machine, a facsimile, a printer, and a printing apparatus having the sheet conveying device, and such an image forming apparatus. An object is to provide an image forming method.

  In order to achieve the above object, the present invention is arranged to face an image carrier that moves in a predetermined direction, and the same image is moved while moving in a direction along the predetermined direction at a facing portion that faces the image carrier. A transfer member that passes the recording medium between the carrier and transferring the image carried on the image carrier to the recording medium; and a moving part of the recording medium in the opposing portion. Based on a detection unit that is disposed downstream and detects the recording medium, and a timing at which the recording medium is detected by the detection unit, a moving speed in at least one of the facing parts of the image carrier and the transfer member And a speed adjusting means for adjusting the speed.

  The present invention is arranged to face an image carrier that moves in a predetermined direction, and moves between the image carrier and the image carrier while moving in a direction along the predetermined direction at a facing portion that faces the image carrier. A transfer member that passes the recording medium and transfers an image carried on the image carrier to the recording medium; and a recording member that is disposed downstream of the opposing portion in the moving direction of the recording medium in the opposing portion. A detection unit that detects the medium, and a speed adjustment unit that adjusts a moving speed in at least one of the facing portions of the image carrier and the transfer member based on a timing at which the recording medium is detected by the detection unit. Therefore, without detecting the speed of the recording medium itself, the speed of the recording medium can be stabilized over time, and a magnification error during transfer can be reduced or prevented. Image forming equipment It is possible to provide a.

1 is a schematic front view of an embodiment of an image forming apparatus to which the present invention is applied. FIG. 2 is a conceptual diagram for explaining that a recording medium conveyance speed at a facing portion is controlled by information detected by a detection unit provided in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a conceptual diagram for explaining that a conveyance speed of a recording medium in a facing portion is controlled by information detected when there are a plurality of detection units provided in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a conceptual diagram for explaining that a conveyance speed of a recording medium in a fixing unit is controlled by information detected by a detection unit provided in the image forming apparatus illustrated in FIG. 1.

  FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a color laser printer and can perform full color image formation. The image forming apparatus 100 may be other types of image forming apparatuses such as other types of printers, facsimile machines, copying machines, printing machines, and multifunction machines of copying machines and printers. The image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside.

  The image forming apparatus 100 forms an image using, as a recording medium that is a sheet-like recording medium, in addition to plain paper generally used for copying or the like, any of OHP sheets, cardboard, cardboard, and other thick paper, envelopes, and the like. It is possible. The image forming apparatus 100 is a single-sided image forming apparatus that can form an image on one side of a transfer sheet S that is a recording medium as a recording medium that is a recording medium, but can form an image on both sides of the transfer sheet S. A double-sided image forming apparatus may be used.

  The image forming apparatus 100 can form images as images corresponding to colors separated into yellow, magenta, cyan, and black, respectively, by forming toner on the photosensitive drums 20Y, 20M, 20C, and 20BK. A tandem structure in which the two are arranged in parallel is adopted.

  In this way, the image forming apparatus 100 carries a toner image, which is an image composed of toner as an image forming substance, on the photosensitive drums 20Y, 20M, 20C, and 20BK arranged in parallel so as to have a tandem structure. The tandem method is adopted. The photosensitive drums 20Y, 20M, 20C, and 20BK, which are photosensitive bodies that are latent image carriers, have a longitudinal direction in the direction perpendicular to the paper surface in FIG. 1, and extend in this direction.

  The photosensitive drums 20Y, 20M, 20C, and 20BK are intermediate transfer belts that are configured as endless belts that are rotating bodies serving as image carriers provided in substantially the center of the main body 99 of the image forming apparatus 100. It is located on the outer peripheral surface side of the transfer belt 11, that is, on the image forming surface side. The photosensitive drums 20Y, 20M, 20C, and 20BK are arranged in this order from the upstream side in the A1 direction that is the moving direction of the endless belt-shaped transfer belt 11. The A1 direction is a counterclockwise direction in FIG. In each figure after FIG. 1, Y, M, C, and BK added after the numerals are the members for yellow, magenta, cyan, and black.

  Each of the photosensitive drums 20Y, 20M, 20C, and 20BK is an image forming unit 60Y that is an image forming unit for forming yellow (Y), magenta (M), cyan (C), and black (BK) images. It is provided in 60M, 60C and 60BK.

  The transfer belt 11 is rotatably supported by a frame (not shown) provided in the main body 99, and can move in the direction of arrow A1 while facing the respective photosensitive drums 20Y, 20M, 20C, and 20BK. Visible images, that is, toner images formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are respectively superimposed and transferred onto the transfer belt 11 that is an intermediate transfer member that moves in the direction of the arrow A1, and then as a recording material. The images are transferred onto the transfer paper S at once. Therefore, the image forming apparatus 100 is an intermediate transfer type, in other words, an indirect transfer type image forming apparatus. Therefore, the image forming apparatus 100 is a tandem indirect transfer type image forming apparatus.

  The lower portion of the transfer belt 11 faces the photosensitive drums 20Y, 20M, 20C, and 20BK, and the opposed portions transfer the toner images on the photosensitive drums 20Y, 20M, 20C, and 20BK. A primary transfer portion 58 for transferring to the transfer belt 11 is formed. In the transfer belt 11, a direction perpendicular to the paper surface in FIG. 1 is a width direction, and a direction perpendicular to this direction is an A1 direction.

  The superimposed transfer onto the transfer belt 11 is performed while shifting the timing from the upstream side toward the downstream side in the A1 direction in the process in which the transfer belt 11 moves in the A1 direction. This primary transfer is performed by a primary transfer roller 12Y as a primary transfer unit so that toner images formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are transferred to the same position on the transfer belt 11. , 12M, 12C, and 12BK. The primary transfer rollers 12Y, 12M, 12C, and 12BK are disposed at positions facing the photosensitive drums 20Y, 20M, 20C, and 20BK with the transfer belt 11 in between.

  The transfer belt 11 is a flexible multilayer in which the base layer is made of a material with low elongation, the surface of the base layer is covered with a material having good smoothness, and the base layer is overlapped with the coat layer. It is a structural member. Examples of the material of the base layer include a fluororesin, a PVDF sheet, and a polyimide resin. In this embodiment, polyimide is used. Examples of the material of the coat layer include a fluorine resin.

  Each of the transfer belts 11 has a detent guide (not shown) as a detent member at each edge thereof. The detent guide is arranged to prevent the transfer belt 11 from being biased in any of the width directions perpendicular to the paper surface in FIG. 1 corresponding to the main scanning direction when the transfer belt 11 rotates in the A1 direction. It is installed. The stopper guide is made of urethane rubber, but can be made of various rubber materials such as silicon rubber.

  The transfer belt 11 has a width corresponding to the A4-sized transfer sheet S in the width direction. Therefore, the image forming apparatus 100 can form an image on the transfer sheet S of A3 vertical size at the maximum.

The image forming apparatus 100 includes four image forming units 60Y, 60M, 60C, and 60BK as image forming means in the main body 99.
The image forming apparatus 100 is also an intermediate transfer belt unit as an intermediate transfer unit that is provided in the main body 99 so as to face the photosensitive drums 20Y, 20M, 20C, and 20BK, and includes the transfer belt 11. A transfer belt unit 10 is provided.
The image forming apparatus 100 also has a secondary transfer device 5 as a secondary transfer unit disposed in the main body 99 so as to face the transfer belt 11 on the right side of the transfer belt 11 in FIG.
The image forming apparatus 100 is also an exposure apparatus as a writing unit which is an optical writing unit as a latent image forming unit disposed in the main body 99 so as to face the lower side of the image forming units 60Y, 60M, 60C and 60BK. An optical scanning device 8 is provided.

The image forming apparatus 100 also serves as a paper feed cassette capable of stacking a large number of transfer sheets S conveyed toward the secondary transfer unit 57 between the transfer belt 11 and the secondary transfer apparatus 5 in the main body 99. A sheet feeding device 61 that is a sheet feeding tray is provided.
The image forming apparatus 100 also includes a registration roller pair 4 that feeds the transfer sheet S conveyed from the sheet feeding device 61 toward the secondary transfer unit 57 at a predetermined timing in the main body 99. .
The image forming apparatus 100 also has a sensor (not shown) in the main body 99 that detects that the leading edge of the transfer paper S has reached the registration roller pair 4.

The image forming apparatus 100 also includes a fixing device 6 as a roller fixing type fixing unit that is a fixing unit for fixing the toner image, that is, an unfixed toner image, onto the transfer sheet S on which the toner image is transferred. have.
The image forming apparatus 100 also includes a paper feed path 32 serving as a transfer medium transport path, which is a recording medium transport path provided with a transport roller 14 for transporting the transfer paper S fed from the sheet feeding device 61 in the main body 99. have.

The image forming apparatus 100 also serves as a discharge roller pair that is a discharge roller that discharges an image output product, which is a fixed transfer sheet S positioned at the end of the paper feed path 32, to the outside of the main body 99. A discharge roller 7 is provided.
The image forming apparatus 100 is also a guide that is a conveyance guide member serving as a guide member that guides the transfer sheet S disposed along the paper feed path 32 and passed through the secondary transfer unit 57 in the main body 99 to the fixing device 6. A member 67 is provided.

The image forming apparatus 100 also jams the transfer sheet S in the main body 99 at the downstream side of the secondary transfer unit 57 and the upstream side of the fixing device 6 in the transport direction D1 of the transfer sheet S in the paper feed path 32. Sensors 21 and 22 as jam detection sensors for detecting the above.
The image forming apparatus 100 is also disposed in the main body 99 above the transfer belt unit 10, and is filled with toner bottles 9Y, 9M, 9C, and 9BK filled with toner for supplying colors of yellow, cyan, magenta, and black. have.
The image forming apparatus 100 also has a paper discharge tray 17 as a paper discharge unit in the main body 99 on which the transfer paper S disposed on the upper side of the main body 99 and discharged to the outside of the main body 99 by the discharge roller 7 is stacked. ing.

The image forming apparatus 100 also has a drive device as a drive unit provided with a drive source such as a motor (not shown) that rotationally drives the photosensitive drums 20Y, 20M, 20C, and 20BK in the main body 99.
The image forming apparatus 100 also includes a control unit 91 as a control unit including a CPU, a memory, and the like (not shown) that controls the overall operation of the image forming apparatus 100 in the main body 99.

  The image forming apparatus 100 also functions as an input unit that includes a start switch or the like and that can input various types of information to the image forming apparatus 100, and also functions as a display unit that can display various types of information related to the image forming apparatus 100. An operation panel 92 is provided.

  The image forming units 60 </ b> Y, 60 </ b> M, 60 </ b> C, 60 </ b> BK, the transfer belt unit 10, the optical scanning device 8, and the fixing device 6 constitute an image forming unit located above the sheet feeding device 61.

In addition to the transfer belt 11, the transfer belt unit 10 includes primary transfer rollers 12Y, 12M, 12C, and 12BK as primary transfer bias rollers.
The transfer belt unit 10 also has a drive roller 72 as a drive member around which the transfer belt 11 is wound, a cleaning facing roller 74 as a stretch roller, and stretch rollers 75 and 33.
The transfer belt unit 10 also has a cleaning device 13 as a belt cleaning device that is disposed opposite to the transfer belt 11 and is an intermediate transfer member cleaning device that cleans the surface of the transfer belt 11.

The transfer belt unit 10 also has a drive system (not shown) provided with a motor 15 as a drive motor that is a drive source for rotating the drive roller 72.
The transfer belt unit 10 also has a power source as a first transfer bias applying unit (not shown) that applies a primary transfer bias independently to the primary transfer rollers 12Y, 12M, 12C, and 12BK.
The transfer belt unit 10 is also realized as a function of the controller 91, and is a first transfer bias controller that controls the application timing and magnitude of the primary transfer bias applied by the primary transfer rollers 12Y, 12M, 12C, and 12BK. have.

  The driving roller 72, the cleaning facing roller 74, and the stretching rollers 75 and 33 are support rollers that are wound around the transfer belt 11 so as to be able to be rotated and conveyed. The cleaning facing roller 74 and the stretching rollers 75 and 33 are driven rollers that rotate with the transfer belt 11 as a first rotating body as a rotating body that is rotationally driven by the driving roller 72. The drive roller 72 is rotationally driven with the target that the moving speed of the transfer belt 11 becomes V0 = 250 mm / s. Of the rollers 72, 74, 75, and 33 that are support rollers, not the roller 72 but any one of the rollers 74 and 33 is used as a driving roller, and the other roller is used as a driven roller. You may make it move to a direction.

  The primary transfer rollers 12Y, 12M, 12C, and 12BK press the transfer belt 11 from the back surface thereof toward the photosensitive drums 20Y, 20M, 20C, and 20BK to form primary transfer nips that are transfer nips. The primary transfer nip is formed at a portion of the transfer belt 11 that is stretched between the stretching rollers 75 and 33. The tension rollers 75 and 33 have a function of stabilizing the primary transfer nip.

  In each primary transfer nip, a primary transfer electric field is formed between the photosensitive drums 20Y, 20M, 20C, and 20BK and the primary transfer rollers 12Y, 12M, 12C, and 12BK due to the influence of the primary transfer bias. . The toner images of the respective colors formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are primarily transferred onto the transfer belt 11 due to the influence of the primary transfer electric field and nip pressure.

The drive roller 72 is in contact with a secondary transfer roller 64 provided as described later on the secondary transfer device 5 via the transfer belt 11, and is transferred between the transfer belt 11 and the secondary transfer roller 64. A secondary transfer portion 57 that is a nip portion as a secondary transfer nip as a nip is formed. Therefore, the driving roller 72 also serves as a counter roller as a secondary transfer counter roller. The drive roller 72 transfers the toner image on the transfer belt 11 that is secondarily transferred onto the transfer sheet S from the primary transfer portion 58 to the secondary transfer portion 57 in the secondary transfer portion 57 as a second transfer portion that is a transfer portion. The transfer belt 11 is driven to rotate by being rotated to convey the toner.
The cleaning counter roller 74 has a function as a tension roller as a pressure member that gives the transfer belt 11 a predetermined tension suitable for transfer.

  The cleaning device 13 is disposed to the left of the cleaning facing roller 74 and the stretching roller 75 in FIG. The cleaning device 13 includes a cleaning blade 76 disposed so as to contact the transfer belt 11 at a position facing the cleaning counter roller 74, and a case 77 in which the cleaning blade 76 is accommodated. The position facing the cleaning facing roller 74 is a position downstream of the secondary transfer unit 57 and upstream of the primary transfer unit 58 in the A1 direction.

The cleaning device 13 cleans the transfer belt 11 by scraping and removing foreign matters such as residual toner on the transfer belt 11 with a cleaning blade 76.
The transfer belt unit 10 can be integrally attached to and detached from the main body 99.

  The sheet feeding device 61 accommodates a plurality of transfer paper S in a state where a plurality of transfer papers S are stacked. The sheet feeding device 61 is arranged below the optical scanning device 8 at the lower part of the main body 99 in multiple stages, in this embodiment, in two stages. ing. The multi-stage sheet feeding device 61 forms a paper bank 31 as a paper feed unit serving as a paper feed table at the bottom of the main body 99.

The sheet feeding device 61 has a feeding roller 3 as a paper feeding roller pressed against the upper surface of the uppermost transfer paper S. The sheet feeding device 61 separates the uppermost transfer sheet S one by one and feeds it toward the registration roller pair 4 by rotating the feeding roller 3 counterclockwise at a predetermined timing. Then, it is guided to the paper feed path 32. In this respect, the feeding roller 3 also functions as a separation roller.
In addition to the conveying roller 14, the sheet feeding path 32 includes a registration roller pair 4 and a fixing device 6 that are located in the middle of the downstream side of the conveying roller 14 in the conveying direction of the transfer sheet S in this order. Yes.
The transfer sheet S delivered from the sheet feeding device 61 reaches the registration roller pair 4 through the sheet feeding path 32 and is abutted and stopped while being sandwiched between the rollers of the registration roller pair 4.

The registration roller pair 4 feeds the transfer sheet S to the secondary transfer unit 57 at a high speed Vr at a predetermined timing in accordance with the toner image formation timing by the image forming units 60Y, 60M, 60C, and 60BK. It is like that. In accordance with this, the rotational speed of the transfer belt 11, the rotational speeds of the photosensitive drums 20Y, 20M, 20C, and 20BK, the driving speed of the optical scanning device 8, and the like are performed at high speed, and image formation is performed at high speed. ing. Therefore, the image forming apparatus 100 is a so-called high speed machine.
The driving of the registration roller pair 4 at such timing is controlled by the control means 91. In this respect, the control means 91 functions as a resist paper feed control means.

  The optical scanning device 8 performs optical writing on the photosensitive drums 20Y, 20M, 20C, and 20BK along a direction perpendicular to the paper surface in FIG. Therefore, this direction is the main scanning direction, and this direction coincides with the width direction of the transfer belt 11.

The secondary transfer device 5 has a secondary transfer roller 64 disposed to face the transfer belt 11 at a position facing the drive roller 72.
The secondary transfer device 5 also serves as a drive motor that is a drive source that rotates the secondary transfer roller 64 in the C1 direction, which is the direction along the A1 direction, in the secondary transfer portion 57 that is a facing portion that faces the transfer belt 11. And a drive system (not shown) provided with the motor 16.
The secondary transfer device 5 also urges the secondary transfer roller 64 toward the drive roller 72 and a spring 18 which is a compression spring as a pressing member as a biasing member that presses against the transfer belt 11 in a pressure-contact manner. have.
The secondary transfer device 5 is also a power source that is a second transfer bias applying unit as a bias applying unit that applies a secondary transfer bias for transferring the toner image on the transfer belt 11 to the transfer sheet S to the secondary transfer roller 64. 19.

The secondary transfer device 5 also has secondary transfer speed control means as transfer speed control means that is realized as one function of the control means 91 and controls the motor 16 to change the rotation speed of the secondary transfer roller 64. ing.
The secondary transfer device 5 also includes a second transfer bias control unit that is realized as a function of the control unit 91 and controls the application timing and magnitude of the secondary transfer bias applied by the secondary transfer roller 64. .

The secondary transfer roller 64 transfers the toner image carried on the transfer belt 11 to the transfer sheet S by passing the transfer sheet S between the transfer belt 11 while rotating in the C1 direction in the secondary transfer unit 57. It is the transfer member which is a 2nd rotary body as a rotary body to perform.
The rotational speed of the secondary transfer roller 64, in other words, the moving speed of the peripheral surface of the secondary transfer roller 64 is driven with the target that the moving speed of the transfer belt 11 is 250 mm / s, except as described below. In addition, it is driven with the goal of V0 = 250 mm / s.

At least one of the drive roller 72 and the secondary transfer roller 64 is an elastic roller in which a portion supported by a respective rotation shaft (not shown) is formed of an elastic body such as rubber, and is in pressure contact with each other by a spring 18. By being in contact, they are in elastic contact with each other. Due to this elastic contact, the secondary transfer portion 57 is a nip portion having a width in the C1 direction.
The secondary transfer unit 57 forms a part of the paper feed path 32.

  The power source 19 applies a bias having a polarity opposite to the charging polarity of the toner constituting the toner image carried on the transfer belt 11 to the secondary transfer roller 64. Therefore, the secondary transfer roller 64 generates an attractive force with respect to the toner image carried on the transfer belt 11 by applying a bias from the power source 19, and electrostatically transfers the toner image onto the transfer paper S. In this respect, the secondary transfer roller 64 functions as an attractive roller. The secondary transfer unit 57 is a transfer position where the toner image on the transfer belt 11 that is an image carrier is transferred to the transfer paper S.

  Therefore, a secondary transfer electric field is formed between the transfer belt 11 and the secondary transfer roller 64 by the secondary transfer device 5 due to the influence of the secondary transfer bias in the secondary transfer portion 57. As a result, the toner image formed on the transfer belt 11 is secondarily transferred onto the transfer sheet S due to the influence of the secondary transfer electric field and nip pressure.

The application timing of the secondary transfer bias is shown in FIG. 2 after the control unit 91 functioning as the second transfer bias control unit drives the registration roller pair 4 by the control unit 91 functioning as the registration paper feed control unit. Thus, the control is performed so that the time Δt0 has elapsed.
As shown in the figure, during this time Δt0, the distance from the position where the leading edge of the transfer sheet S is stopped by the registration roller pair 4 to the center position in the C1 direction of the secondary transfer portion 57 is L0, and the registration roller pair 4 The transfer speed S of the transfer sheet S is expressed as follows.
Δt0 = L0 / Vr

  This time Δt0 is calculated by the control means 91. In this regard, the control unit 91 functions as a timing detection unit that detects the timing at which the leading edge of the transfer sheet S has passed through the secondary transfer unit 57 as the detection timing. In this embodiment, the control unit 91 functioning as a timing detection unit detects a detection timing at which the leading edge of the transfer sheet S has passed through the secondary transfer unit 57 as a timing at which the secondary transfer bias is applied by the power source 19. To do.

  However, the control unit 91 functioning as a timing detection unit detects a timing at which a position upstream of the secondary transfer unit 57 in the direction D1, for example, a position at which the leading edge of the transfer sheet S abuts against the registration roller pair 4 is passed. It may be detected as timing. This is because if the detection timing, which is the timing at which the registration roller pair 4 is driven, is detected, the above-described Δt0 is known, so that it is possible to estimate a passing speed V ′ described later. As the timing detection unit, a sensor or the like that detects that the leading edge of the transfer sheet S has passed the registration roller pair 4 may be used. As described above, the timing detection unit only needs to be able to detect the reference timing at which the passage speed V ′ can be calculated as the detection timing, and can be configured in various modes.

  The secondary transfer device 5 has a transport function for transporting the transfer sheet S after the transfer of the toner image in the secondary transfer unit 57 to the fixing device 6 by the rotation of the secondary transfer roller 64. The secondary transfer device 5 constitutes a paper transport device 30 together with the guide member 67 and the sensors 21 and 22. Note that the transfer belt unit 10, in particular, the transfer belt 11 and the driving roller 72 may also be elements constituting the sheet conveying device 30, and the registration roller pair 4 also constitutes the sheet conveying device 30 together with or instead of this. It may be an element. As described above, the configuration that contributes to the conveyance of the transfer paper S in the image forming apparatus 100 can be an element that constitutes the paper conveyance device 30.

  The sensors 21 and 22 installed between the transfer and fixing are both arranged on the downstream side of the secondary transfer unit 57 in the D1 direction. The sensors 21 and 22 are a first sensor and a first sensor, respectively, as a detection unit that optically detects the transfer paper S at the upstream and downstream end positions of the guide member 67 in the D1 direction. This is a second sensor which is a second detection unit. The guide member 67 is positioned between a plurality of, more specifically, the two sensors 21 and 22.

The sensor 21 is arranged so that the detection position of the leading edge of the transfer paper S is the next position. That is, the distance from the center position in the C1 direction of the secondary transfer portion 57 along the movement path of the transfer paper S in the paper feed path 32 corresponds to the length of the margin in the C1 direction on the leading end side of the transfer paper S. It arrange | positions so that it may become a position. Since the length of the margin is usually 20 to 30 mm, in this embodiment, the sensor 21 is arranged so that the distance is 20 mm.
A preferable arrangement position of the sensor 22 will be described later.

  Each of the sensors 21 and 22 emits light to a passing position of the transfer paper S in the paper feed path 32, and detects the transfer paper S by receiving light reflected by the transfer paper S among the emitted light. This is a sensor of the formula. For example, the sensors 21 and 22 may be of other types, which emit light to the passing position of the transfer paper S in the paper feed path 32 and detect that the emitted light is blocked by the transfer paper S. An optical sensor that detects the transfer sheet S may be used. The sensors 21 and 22 may also be contact sensors that detect the transfer sheet S by contacting the transfer sheet S.

  When the sensors 21 and 22 detect the transfer sheet S, as shown in FIG. 2, a signal indicating this is input to the control means 91, and the control means 91, based on the input timing of this signal, 22 recognizes the timing at which the transfer paper S, in particular, the leading edge of the transfer paper S is detected. In this regard, the control unit 91 functions as a detection timing recognition unit that recognizes the output times of the sensors 21 and 22 as such timings.

  The control unit 91 calculates and acquires the next time Δt using the timing at which the transfer sheet S is detected by the sensors 21 and 22 recognized by the control unit 91 functioning as the detection timing recognition unit. This time Δt is based on the timing when the power supply 19 is driven by the control means 91 functioning as the second transfer bias applying means and the secondary transfer bias is applied, that is, the detection timing described above, as shown in FIG. It was time to do. That is, the transfer sheet S is detected by the sensors 21 and 22 recognized by the control unit 91 functioning as the detection timing recognition unit from the detection timing, that is, the application transfer start time of the secondary transfer bias by the power source 19. Time to timing.

  As described above, Δt is a time difference between the detection timing and the timing at which the transfer sheet S is detected by the sensors 21 and 22 recognized by the control unit 91 functioning as the detection timing recognition unit. Therefore, Δt is the time that the leading edge of the transfer sheet S has moved from the center position of the secondary transfer portion 57 in the C1 direction to the position detected by the sensor 21 or the sensor 21.

  Since the positions of the sensors 21 and 22 in the direction D1 are different from each other, the time Δt is different between the sensors 21 and 22. As shown in FIG. 3, when the detection output of the transfer paper S by the sensor 21 is the paper detection output 1, and the detection output of the transfer paper S by the sensor 22 is the paper detection output 2, the time Δt for the sensor 21 is Δt1, The time Δt for the sensor 22 is Δt2. In terms of calculating and acquiring such times Δt, Δt1, and Δt2, the control unit 91 functions as a detection time acquisition unit, a first detection time acquisition unit, and a second detection time acquisition unit.

When the transfer speed of the transfer sheet S when Δt1 and Δt2 are calculated is v, the sensor 21, from the center position in the C1 direction of the secondary transfer unit 57 along the movement path of the transfer sheet S in the paper feed path 32, When the respective distances up to 22 are L1 and L2, the following relationship is established.
L1 / v = Δt1, L2 / v = Δt2

  The speed v ideally matches the rotational speed of the secondary transfer roller 64, in other words, the moving speed V0 of the peripheral surface of the secondary transfer roller 64, and is the above-mentioned 250 mm / s. However, for convenience of explanation, as will be described later, the passing speed at which the transfer sheet S should pass through the secondary transfer portion 57 should be obtained when the transfer belt 11 and the secondary transfer roller 64 are rotationally driven at V0 = 250 mm / s. Is a speed V′0.

The fixing device 6 includes a heater 66 that is a heating roller heater as a heating source serving as a heating unit, and a heating roller 62 that is a hollow metal roller having the heater 66 therein.
The fixing device 6 also includes a pressure roller 69 that is a hollow roller that is in pressure contact with the heating roller 62 and forms a fixing nip 70 as a nip portion that is a pressure contact portion with the heating roller 62.

The fixing device 6 also has a drive system (not shown) provided with a motor 63 as a drive motor that is a drive source for rotationally driving the heating roller 62.
The fixing device 6 is a compression spring (not shown) which is a pressing member as a pressing member that urges the pressing roller 69 toward the heating roller 62 and presses and contacts the heating roller 62 in a pressing manner. It has a spring.

The fixing device 6 also has a fixing case 65 as a casing that surrounds and includes the above-described configuration provided in the fixing device 6 so that the configuration cannot be directly touched by an operator.
The fixing device 6 also includes a fixing speed control unit that is implemented as a function of the control unit 91 and that controls the rotational speed of the heating roller 62 by the motor 63, in other words, to change the conveyance speed of the transfer sheet S in the fixing nip 70. ing.

  The fixing case 65 is provided with a guide member 68 that is a conveyance guide member serving as a guide member that is disposed along the paper feed path 32 and guides the transfer sheet S guided to the fixing device 6 by the guide member 67 to the fixing nip 70. Have. The sensor 22 optically detects the transfer sheet S at the upstream end position of the guide member 68 in the direction D1, in other words, immediately before the transfer sheet S enters the fixing device 6.

  The fixing device 6 passes the transfer paper S carrying a toner image between the fixing nips 70 so that the toner image carried on the transfer paper S is applied to the surface of the transfer paper S by the action of heat and pressure. It has become established.

  In such a fixing process, the rotational speed V3 of the heating roller 62 and the pressure roller 69, in other words, the moving speed V3 of the peripheral surface of the heating roller 62 and the pressure roller 69 is 1-2% slower than the moving speed of the transfer belt 11. Driven with the goal of becoming. This is because the speed of the transfer sheet S passing through the fixing nip 70 is slower than the rotation speed of the secondary transfer roller 64, thereby forming the deflection of the transfer sheet S between the secondary transfer portion 57 and the fixing nip 70. This is to stabilize the conveyance of the transfer sheet S at the fixing nip 70 and perform good fixing. Therefore, the transfer sheet S is conveyed while being in contact with the guide member 67 and the guide member 68, and the posture in the conveyance process is maintained. Even when the posture of the transfer sheet S is maintained in this way, the conveyance of the transfer sheet S in the fixing nip 70 is stabilized and good fixing is performed.

  The yellow, cyan, magenta, and black toners in the toner bottles 9Y, 9M, 9C, and 9BK are polymerized toners in which the wax component is uniformly dispersed therein. Less precipitation to the outside. The toners of the respective colors are supplied to the developing devices 80Y, 80M, 80C, and 80BK provided as follows in the image forming units 60Y, 60M, 60C, and 60BK by a predetermined supply amount through a conveyance path (not shown). .

  As shown in FIG. 1, the image forming units 60Y, 60M, 60C, and 60BK have the same configuration. The image forming units 60Y, 60M, 60C, and 60BK are arranged in the following order around the photosensitive drums 20Y, 20M, 20C, and 20BK along the rotation direction B1 that is clockwise in FIG. Is provided. Primary transfer rollers 12Y, 12M, 12C, and 12BK, cleaning devices 71Y, 71M, 71C, and 71BK as cleaning units, and neutralizing devices 78Y, 78M, 78C, and 78BK as neutralizing units are provided. Further, charging devices 79Y, 79M, 79C, and 79BK as charging means for performing AC charging and developing devices 80Y, 80M, 80C, and 80BK as developing means for performing development with a two-component developer are provided. Further, the toner density and line position of the reference toner images formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are detected at the time of process control that is in the adjustment mode, and the toner density and line position deviation correction are performed. The image detection sensor (not shown) is provided.

  Each of the image forming units 60Y, 60M, 60C, and 60BK can be pulled out from the main body 99 along a guide rail (not shown) fixed to the main body 99, and can be pushed into the main body 99. In this way, the image forming units 60Y, 60M, 60C, and 60BK are process cartridges that are detachably installed on the main body 99, respectively. When the image forming units 60Y, 60M, 60C, and 60BK as process cartridges are pushed into the main body 99, they are loaded and positioned at predetermined positions suitable for image formation. Making a process cartridge in this way is very preferable because it can be handled as a replacement part, so that the maintainability is remarkably improved. In addition, since the life of each part, which is an element of the process cartridge, is equal, unnecessary replacement is prevented and suppressed, and the structure is further preferable.

  In the image forming apparatus 100 having such a configuration, when a signal to form a color image is input and the start switch is pressed, the following operation is started. That is, an image forming job that is a print job including image information corresponding to a full-color image that is a desired image to be formed by the control unit 91 is stored and held in the memory, and the next operation is also started. That is, the drive roller 72 is driven, the transfer belt 11, the cleaning counter roller 74, and the stretching rollers 75 and 33 are driven to rotate, and the photosensitive drums 20Y, 20M, 20C, and 20BK are rotationally driven in the B1 direction.

  As the photosensitive drums 20Y, 20M, 20C, and 20BK are rotated in the B1 direction, their surfaces are uniformly charged to a predetermined polarity by the charging devices 79Y, 79M, 79C, and 79BK, respectively. The photosensitive drums 20Y, 20M, 20C, and 20BK are respectively exposed to electrostatic latent images corresponding to yellow, magenta, cyan, and black by exposure scanning or irradiation of light-modulated laser light from the optical scanning device 8. A latent image is formed by the image. The laser beam irradiation is an upward irradiation in the main scanning direction substantially coincident with the direction perpendicular to the paper surface of FIG. Then, the electrostatic latent images are developed on the photosensitive drums 20Y, 20M, 20C, and 20BK with toners of yellow, magenta, cyan, and black, respectively, by the developing devices 80Y, 80M, 80C, and 80BK. As a result, single-color images composed of magenta, cyan, and black toner images are formed on the photosensitive drums 20Y, 20M, 20C, and 20BK, respectively.

  The controller 91 separates the image information stored in the memory into color information of each color of yellow, magenta, cyan, and black when driving the optical scanning device 8 to form an electrostatic latent image corresponding to each color. . Then, the control unit 91 drives the optical scanning device 8 based on each color image information which is monochromatic image information separated into each color.

  The yellow, magenta, cyan, and black toner images obtained by visual development are developed from the yellow toner image located on the most upstream side in the A1 direction, from the magenta toner image, the cyan toner image, and the black toner image. In order, it is transferred sequentially. This transfer is performed by primary transfer to the same position on the transfer belt 11 rotating in the A1 direction by the primary transfer bias formed by the primary transfer rollers 12Y, 12M, 12C, and 12BK. By this primary transfer, a composite color image which is a full-color toner image is formed and carried on the transfer belt 11.

  On the other hand, when a signal indicating that a color image should be formed is input, one of the sheet feeding devices 61 provided in the paper bank 31 is selected, and a feeding roller provided in the selected sheet feeding device 61 is selected. 3 rotates to feed out the transfer paper S. At this time, the paper feed roller 3 separates the uppermost transfer paper S among the transfer papers S stacked on the sheet feeding device 61 one by one and feeds them to the paper feed path 32. The transfer sheet S thus fed into the paper feed path 32 is further transported by a transport roller (not shown), and stops in a state of being abutted against the registration roller pair 4.

  In accordance with the timing at which the composite color image superimposed on the transfer belt 11 moves to the secondary transfer portion 57 as the transfer belt 11 rotates in the A1 direction, in other words, the sheet feeding timing is measured, and the registration roller pair 4 Rotates. As a result, the transfer sheet S is sent to the secondary transfer unit 57, where the composite color image is brought into close contact with the transfer sheet S sent to the secondary transfer unit 57, and the secondary transfer bias and nip pressure. As a result, the image is secondarily transferred and recorded on the transfer paper S all at once.

  Since the transfer sheet S is conveyed by the secondary transfer device 5, more specifically, conveyed by the rotation of the secondary transfer roller 64 and sent to the fixing device 6. It is detected in the time of about Δt1 and Δt2. However, if the transfer sheet S is jammed or jammed between the registration roller pair 4 and the secondary transfer unit 57 or between the secondary transfer unit 57 and the detection position of the sensor 21 or sensor 22, the transfer sheet S is not detected. .

Therefore, in the following case, the image forming apparatus 100 determines that the jam of the transfer sheet S has occurred, and displays the fact that the jam has occurred on the operation panel 92 functioning as a display unit.
When the control unit 91 that functions as the first detection time acquisition unit calculates Δt′1 that allows sufficient time for the above-described Δt1, the control unit 91 that functions as the second detection time acquisition unit Thus, when Δt′2 is calculated with sufficient time for Δt2 described above, this determination is made by the control means 91. In this regard, the control unit 91 functions as a jam occurrence determination unit.

  If the jam does not occur, the transfer paper S passes through the fixing nip 70 between the heating roller 62 and the pressure roller 69 in the fixing device 6, and the toner of the transferred transfer image is supported by the action of heat and pressure. Is melted to fix the composite color image.

  The transfer sheet S on which the composite color image has been fixed, which has passed through the fixing device 6, is discharged out of the main body 99 through the discharge roller 7 and stacked on the discharge tray 17 at the top of the main body 99.

  Photoreceptor drums 20Y, 20M, 20C, and 20BK have transfer residual toner that is residual toner remaining after transfer removed from the surface by cleaning devices 71Y, 71M, 71C, and 71BK. Further, the photosensitive drums 20Y, 20M, 20C, and 20BK are neutralized by the neutralization devices 78Y, 78M, 78C, and 78BK, the surface potential is initialized, and used for the next charging by the charging devices 79Y, 79M, 79C, and 79BK. Is done.

  The transfer belt 11 that has passed the secondary transfer portion 57 after the secondary transfer is cleaned by removing the transfer residual toner remaining on the surface after the transfer by the cleaning blade 76 provided in the cleaning device 13, and the next transfer. Prepare for.

  When the toner image on the transfer belt 11 is transferred to the transfer paper S when performing image formation in this way, the transfer paper S is passed through the secondary transfer portion 57 as described above. If the speed of the transfer sheet S at that time is not a prescribed speed, a magnification error occurs. For example, when the coefficient of friction of the transfer sheet S is very low, slippage occurs between the transfer sheet S and the secondary transfer roller 64 in the secondary transfer unit 57, and the transfer speed of the transfer sheet S becomes slow. Then, it takes time to pass through the secondary transfer unit 57, and a magnification error occurs in a mode in which the image on the transfer belt 11 is transferred to the transfer sheet S in a state of being reduced in the D1 direction.

There are various types of transfer paper S, and as described above, there are various recording media on which image formation is possible with the image forming apparatus 100, and the friction coefficient is not constant. In addition, the friction coefficient varies depending on environmental humidity and the like even on the same recording medium. Therefore, since the transportability of the transfer sheet S by the secondary transfer roller 64 can be unstable, the speed of passing through the secondary transfer unit 57 can change and a magnification error can occur.
Therefore, in the image forming apparatus 100, the sensor 21 and the sensor 22 for detecting a jam are also used as a countermeasure for the magnification error.

  Specifically, based on the timing when the leading edge of the transfer sheet S is detected by the sensors 21 and 22, at least one of the transfer belt 11 and the secondary transfer roller 64, in this embodiment, 2 of the secondary transfer roller 64. The moving speed, that is, the rotational speed in the next transfer portion 57 is adjusted. This is because adjusting the rotational speed of the transfer belt 11 also requires speed adjustment of the photosensitive drums 20Y, 20M, 20C, 20BK, and the like.

This adjustment will be described more specifically.
First, the control unit 91 uses the Δt1 and Δt2 acquired by the control unit 91 functioning as the first detection time acquisition unit and the second detection time acquisition unit, and the transfer sheet S passing through the secondary transfer unit 57. The speed V ′, which is the passing speed of the vehicle, is calculated and acquired in an estimated manner. In this respect, the control means 91 functions as a speed estimation means and a speed acquisition means, and can strictly estimate the speed V ′. The speed V ′, which is the estimated value, is calculated from the center position in the C1 direction of the secondary transfer portion 57 along the movement path of the transfer sheet S in the sheet feed path 32 to the sensors 21 and 22, respectively. Distances L1 and L2. The speed V ′ is obtained as speed V′1 = L1 / Δt1 when Δt1 and L1 are used, and is obtained as speed V′2 = L2 / Δt2 when Δt2 and L2 are used. Note that the times Δt1 and Δt2 when the speeds V′1 and V′2 are obtained are smaller than the above-described times Δt′1 and Δt′2.

  Next, the obtained speeds V′1 and V′2 are compared with the ideal speed of the transfer sheet S passing through the secondary transfer portion 57, in other words, the speed V′0 which is a specified value, and these are inconsistent. In this case, the following control is performed by the control unit 91 functioning as a secondary transfer speed control unit. That is, the control unit 91 functioning as the secondary transfer speed control unit matches the rotation speed of the secondary transfer roller 64 by the motor 16 with the target speed V′0 to which the speeds V′1 and V′2 are applied. To control. In this regard, the control unit 91 that functions as a secondary transfer speed control unit functions as a speed adjustment unit.

  The control unit 91 that functions as a speed adjustment unit uses the speed V ′ (= V′1 or V′2) acquired by the control unit 91 that functions as a speed acquisition unit, and sets the rotation speed of the secondary transfer roller 64 to a speed. The motor 16 is controlled with the goal of V = V0 + (V′0−V ′). When V′0 = V0, the speed V = 2V0−V ′.

  As described above, the control unit 91 functioning as the speed adjustment unit is configured to control the motor 16 based on Δt1 and Δt2 acquired by the control unit 91 functioning as the first detection time acquisition unit and the second detection time acquisition unit. The drive is controlled and the speed V is adjusted.

  Here, the speed V1 obtained as the speed V when the speed V'1 is used may be different from the speed V2 obtained as the speed V when the speed V'2 is used. As this reason, the following reason is mentioned, for example. That is, the speed V′1 obtained using the sensor 21 is the speed before the transfer paper S comes into contact with the guide member 67, but the speed V′2 obtained using the sensor 22 is the speed V′2 obtained by using the sensor 22. This is because the speed is obtained in contact with the member 67 and receiving the friction of the guide member 67. The sensor 22 is used in anticipation of speed fluctuation due to the frictional force of the guide member 67. Therefore, when such speed fluctuations can be ignored, the sensor 22 may be omitted, and the detection unit may be configured by a single sensor 21.

  When V′1 ≠ V′2, the speed V1 is used from when the leading edge of the transfer paper S is detected by the sensor 21 until it is detected by the sensor 22, and after the leading edge of the transfer paper S is detected by the sensor 22. Uses speed V2.

  Usually, L1 <L2 and the detection accuracy of the speed V ′ is higher for V′2, and the speed V′0 is originally defined as the speed of the transfer sheet S that should enter the fixing nip 70. This is because. Therefore, when transferring to the next transfer sheet S, the speed V2 is used from the beginning.

  On the other hand, the speed V′1 is a speed detected by the influence of slippage between the transfer sheet S and the secondary transfer roller 64 before the transfer sheet S is brought into contact with the guide member 67 to cause a speed fluctuation. In order to estimate the conveyance speed once before such speed fluctuation occurs. Therefore, the speed V <b> 1 is used from when the leading edge of the transfer sheet S is detected by the sensor 21 until it is detected by the sensor 22. As described above, the sensor 21 is arranged such that the distance from the secondary transfer portion 57 is a position corresponding to the length of the margin on the leading end side of the transfer sheet S. In the sense of detecting the speed of the transfer sheet S, it is particularly preferable that the transfer sheet S is disposed at the next position. That is, among the plurality of detection units, the sensor 21 on the most upstream side in the D1 direction detects the transfer paper S on the front side, in other words, on the upstream side in the D1 direction from the landing point where the leading edge of the transfer paper S contacts the guide member 67. It is preferable to arrange | position.

  As described above, by using the plurality of sensors 21 and 22 as the detection unit, the speed V ′ of the transfer sheet S can be acquired according to the speed fluctuation factor of the transfer sheet S. However, as described above, the sensor 22 may be omitted and the sensor 21 may be used, and the sensor 21 also detects the speed before the transfer paper S receives the contact with the guide member 67 and the speed fluctuation occurs. If it is unnecessary to do so, the sensor 22 may be used.

  Since the speed V′0 is defined as the speed of the leading edge of the transfer sheet S that should enter the fixing nip 70, the position where the sensor 22 is disposed is preferably closer to the fixing nip 70. Considering that the transfer sheet S abuts not only the guide member 67 but also the guide member 68, the sensor 22 is arranged to detect the transfer sheet S at the end position on the downstream side of the guide member 68 in the D1 direction. It is preferable that Therefore, at least the sensor 22 on the most downstream side in the D1 direction among the plurality of detection units may be provided in the fixing device 6.

  The first transfer sheet S is conveyed by the secondary transfer roller 64 that is driven to rotate at the speed V 0 until the leading edge is detected by the sensor 21, and the speed when the leading edge is detected by the sensor 21. If V′0 ≠ V′1, the speed is changed while passing through the secondary transfer portion 57. That is, while passing through the secondary transfer portion 57, the transfer sheet S is conveyed by the secondary transfer roller 64 that is driven to rotate at the speed V1. However, since the sensor 21 is disposed such that the distance from the secondary transfer portion 57 corresponds to the length of the margin on the leading end side of the transfer paper S, the transfer belt is not affected even when such a shift occurs. The transfer of the toner image from 11 is started after such a shift. Therefore, the transfer magnification does not change during the transfer due to the shift.

  Similarly, the first transfer sheet S is conveyed by the secondary transfer roller 64 that is rotationally driven at the speed V <b> 1 until the leading edge is detected by the sensor 22, and the speed when the leading edge is detected by the sensor 22. If V′1 ≠ V′2, the speed is changed while passing through the secondary transfer portion 57. That is, the transfer sheet S is conveyed by the secondary transfer roller 64 that is rotationally driven at the speed V2 while passing through the secondary transfer portion 57. However, even if V′1 ≠ V′2, the difference between these speeds is not so large. Therefore, even if such a shift occurs, the change in transfer magnification during transfer is small due to such a shift. It can be ignored.

  By adjusting the speed V as described above, the image forming apparatus 100 is caused by instability of the transfer of the transfer paper S by the secondary transfer roller 64 caused by the friction coefficient of the transfer paper S being different. Measures are taken against transfer magnification error in the next transfer portion 57. Therefore, it is possible to reduce the transfer pressure of the secondary transfer portion 57 set by the spring 18 and reduce the friction coefficient of the surface of the secondary transfer roller 64. Therefore, it is possible to stabilize the passage speed of the transfer sheet S of the secondary transfer unit 57 over time, to reduce or prevent a magnification error, and to extend the lifetime of the secondary transfer roller 64, the transfer belt 11, and the like. The service life of the image forming apparatus 100 can be extended. Further, by using the sensors 21 and 22 that are jam detection sensors for adjusting the speed V, it is not necessary to detect the transfer speed of the transfer sheet S, and the speed V is adjusted without increasing the number of parts. It is possible to avoid an increase in price due to the adjustment of the speed V.

Further, in the image forming apparatus 100, based on the time Δt acquired by the control unit 91 functioning as the detection time acquisition unit, the transfer speed S of the transfer sheet S in the fixing nip 70 and the speed V3 of the fixing device 6 are also determined. Adjusted.
In this case, the control unit 91 that functions as the detection time acquisition unit uses the timing recognized by the control unit 91 that functions as the detection timing recognition unit and the transfer sheet S is not detected by the sensors 21 and 22 to use the next time. Δt3 is calculated and acquired. In this regard, the control unit 91 functions as a third detection time acquisition unit.
As shown in FIG. 4, the time Δt <b> 3 is a time from when the rear end of the transfer sheet S is not detected by the sensor 21 until it is not detected by the sensor 22. That is, Δt3 is a time difference between the timing at which the transfer sheet S is no longer detected by the sensor 21 and the timing at which the transfer sheet S is no longer detected by the sensor 22, which is recognized by the control unit 91 functioning as a detection timing recognition unit.

  The transport speed V′3 of the transfer sheet S when Δt3 is calculated is the control means 91 when the distance from the sensor 21 to the sensor 22 along the movement path of the transfer sheet S in the sheet feed path 32 is L3. Thus, V′t3 = L3 / Δt3 is calculated and acquired in an estimated manner. In this respect, the control unit 91 functions as a fixing speed estimation unit and a fixing speed acquisition unit.

  Next, the acquired speed V′3 is compared with the ideal speed of the transfer sheet S passing through the fixing nip 70, in other words, the speed V′t that is a specified value, and if these do not match, the fixing speed control is performed. The following control is performed by the control means 91 functioning as a means. That is, the control unit 91 functioning as a fixing speed control unit controls the rotation speed of the heating roller 62 by the motor 63 so that the speed V′3 coincides with the target speed V′t. In this regard, the control unit 91 that functions as a fixing speed control unit functions as a fixing speed adjustment unit.

  The control means 91 functioning as the fixing speed adjusting means uses the speed V′3 acquired by the control means 91 functioning as the fixing speed acquisition means, and changes the rotation speed of the heating roller 62 to the speed Vt = V3 + (V′t−V). The motor 63 is controlled with the goal of '3). When V't = V3, the speed Vt = 2V3-V'3.

  In the fixing device 6, the transfer speed of the transfer sheet S in the fixing nip 70 changes due to the following reasons. When the amount of change is large, the stability of the transfer sheet S is reduced, and the transfer sheet S Problems such as wrinkles can occur. This is because the transfer sheet S may slip in the fixing nip 70 and the peripheral surfaces of the heating roller 62 and the pressure roller 69 move in the fixing nip 70 due to thermal expansion of the heating roller 62 and the pressure roller 69. For example, the speed changes.

  However, by controlling the speed at which the transfer paper S passes through the fixing nip 70 as described above, measures against wrinkles of the transfer paper S caused by instability of conveyance of the transfer paper S in the fixing nip 70 are taken. Therefore, good fixing is performed and high-quality image formation is performed. In addition, by using the sensors 21 and 22 that are jam detection sensors for adjusting the speed Vt, it is not necessary to detect the transfer speed of the transfer sheet S, and the speed Vt is adjusted without increasing the number of parts. Therefore, it is possible to avoid the occurrence of high price for adjusting the speed Vt.

  The sensors 21 and 22 which are jam detection sensors are also used for detecting a jam of the transfer sheet S in the fixing nip 70 or the like. When such a jam occurs, the transfer paper S is continuously detected by the sensor 21 or the sensor 22, and thus the above-described Δt3 is not acquired or even if acquired, the value is much larger than usual, for example, Δt′3. Therefore, in the image forming apparatus 100, when Δt′3 that allows sufficient time for Δt3 is calculated by the control unit 91 that functions as the third detection time acquisition unit, the jam of the transfer sheet S is fixed to the fixing device 6. It is judged that it occurred in the vicinity. Then, the control unit 91 displays this on the operation panel 92 that functions as a display unit. Such a determination is made by the control means 91. In this respect, the control unit 91 functions as a fixing jam occurrence determination unit. Note that the time Δt3 when the speed V′3 is obtained is smaller than the time Δt′3 described above.

  In the present embodiment, the control means 91 is disposed in a non-volatile memory and / or a volatile memory so as to face the transfer belt 11 that is the image carrier that moves in the A1 direction described above, and the transfer belt 11. A transfer sheet S, which is a recording medium, passes between the transfer belt 11 while being moved in the direction along the A1 direction in the secondary transfer portion 57, which is a facing portion facing the transfer belt 11, and is carried on the transfer belt 11. And a secondary transfer roller 64 that is a transfer member that transfers the toner image, which is a current image, to the transfer paper S, and a downstream side of the secondary transfer portion 57 in the moving direction D1 of the transfer paper S in the secondary transfer portion 57. Based on the sensors 21 and 22 that are detection units for detecting the transfer sheet S, and the timing at which the transfer sheet S is detected by the sensors 21 and 22, the transfer belt 11 and the secondary transfer roller 64 are reduced. In order to execute a sheet conveying method for conveying a recording medium and an image forming method for forming an image using a control means 91 functioning as a speed adjusting means for adjusting the moving speed in at least one secondary transfer portion 57. The sheet conveying program and the image forming program are stored. In this respect, the control unit 91 or the non-volatile memory and / or the volatile memory functions as a sheet conveyance program storage unit and an image forming program storage unit. Such a sheet conveying program and an image forming program can be stored not only in a nonvolatile memory and / or a volatile memory provided in the control unit 91 but also in the following storage medium. That is, a semiconductor medium (for example, RAM, nonvolatile memory, etc.), an optical medium (for example, DVD, MO, MD, CD-R, etc.), a magnetic medium (for example, hard disk, magnetic tape, flexible disk, etc.) and other storage media Can be memorized. Such a memory and other storage media constitute a computer-readable recording medium that stores the paper transport program and the image forming program when the paper transport program and the image forming program are stored.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

For example, when a plurality of detection units are provided, the number may be three or more instead of two.
In various configurations described below, for example, in a configuration in which an image on a photoconductor is directly transferred to a recording medium, the photoconductor corresponds to an image carrier, and a member that performs primary transfer corresponds to a transfer member. Will be.

  Even if the image forming apparatus to which the present invention is applied is a tandem type, it is possible to adopt a direct transfer system instead of the indirect transfer system described above. Further, the present invention is not a so-called tandem image forming apparatus, so that a color image is obtained by sequentially forming toner images of respective colors on a single photosensitive drum (image carrier) and sequentially superimposing the respective color toner images. The present invention can be similarly applied to a one-drum type image forming apparatus. The present invention is also applicable to a system using an intermediate transfer member (image carrier) that develops a toner image of each color on an image carrier such as a sheet-like organic photoreceptor, but separates the color overlay itself. It is possible to apply. The present invention can be similarly applied to image forming apparatuses such as a system using a plurality of intermediate transfer bodies (image carriers) and a system using intermediate color toner.

  In addition, in recent years, in accordance with demands from the market, color image forming apparatuses, such as color copiers and color printers, have increased in number, but image forming apparatuses can only form monocolor images. It may be.

  The developer as an image forming material used in such an image forming apparatus is not limited to a two-component developer, but may be a one-component developer, and the image forming material may be another one that requires fixing. May be.

The image forming apparatus may not be a copier, a printer, and a facsimile machine, but may be a single unit thereof, or may be a multi-function machine of another combination such as a copier and printer. .
The image forming apparatus may be a printing apparatus. The image forming apparatus is not limited to a high speed machine.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

DESCRIPTION OF SYMBOLS 11 Image carrier 19 Bias application means 21, 22 Several detection part 30 Paper conveyance apparatus 57 Opposing part 64 Transfer member 67 Guide member located between several detection parts 70 Fixing part 91 Speed adjustment means, speed acquisition means, timing Detection unit 100 Image forming apparatus A1 Predetermined direction C1 Direction along predetermined direction D1 Direction of movement of recording medium in opposite part S Recording medium

JP 2008-225069 A

Claims (9)

It is arranged opposite to an image carrier that moves in a predetermined direction, and passes a recording medium between the image carrier and the image carrier while moving in a direction along the predetermined direction at a facing portion that faces the image carrier. A transfer member for transferring the image carried on the image carrier to the recording medium;
A detection unit that is disposed on the downstream side of the opposing part in the moving direction of the recording medium in the opposing part and detects the recording medium;
A sheet conveying apparatus comprising: a speed adjusting unit that adjusts a moving speed of at least one of the image bearing member and the transfer member on the facing portion based on a timing when the recording medium is detected by the detecting unit. In the paper conveyance device according to claim 1,
Based on the timing, the recording medium has speed acquisition means for acquiring a passing speed at which the recording medium passes through the facing portion;
The sheet conveying apparatus, wherein the speed adjusting unit adjusts the moving speed based on the passing speed acquired by the speed acquiring unit. In the paper conveyance device according to claim 1 or 2,
A timing detection unit that detects a timing at which a recording medium passes through a position upstream of the opposing part or the opposing part in the moving direction;
The speed adjusting means adjusts the moving speed based on a time difference between a detection timing detected by the timing detection unit and a timing when a recording medium is detected by the detection unit. . In the paper conveying apparatus of Claim 3,
Bias applying means is provided for applying a transfer bias at the opposing portion for transferring the image carried on the image carrier to the recording medium when the recording medium passes through the opposing portion. And
The paper conveyance device, wherein the timing detection unit detects a timing at which the transfer bias is applied by the bias applying unit as the detection timing. In the paper conveyance device according to any one of claims 1 to 4,
A plurality of the detection units in the moving direction;
The sheet conveying apparatus, wherein the speed adjusting unit adjusts the moving speed based on a time difference between timings when the recording medium is detected by two detecting units included in the plurality of detecting units. In the paper conveyance device according to claim 5,
A sheet conveying apparatus comprising: a guide member that guides movement of a recording medium that is located between the plurality of detection units and that has passed through the facing unit. In the paper conveyance device according to claim 5 or 6,
Based on the time difference, the transport speed of the recording medium in the fixing unit that fixes the image transferred to the recording medium when the recording medium that has passed through the facing section passes and passes through the facing section. The sheet conveying device is characterized by being adjusted.   An image forming apparatus comprising: the sheet conveying device according to claim 1; and the image carrier. An image carrier that moves in a predetermined direction;
The image-bearing member is disposed so as to face the image carrier, and the recording medium is passed between the image carrier and moving in the direction along the predetermined direction at the opposite portion facing the image carrier. A transfer member for transferring an image carried on the body to the recording medium;
A detection unit that is disposed on the downstream side of the opposing part in the moving direction of the recording medium in the opposing part and detects the recording medium;
Based on the timing when the recording medium is detected by the detection unit, an image is formed by using a speed adjusting unit that adjusts a moving speed in at least one of the facing parts of the image carrier and the transfer member. Forming method.

Images