JP2012093651A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of suppressing a recording body from being pulled downstream in a conveyance direction at a transfer nip and of positioning one side and other side of a guide member in a recording body width direction of the recording body at the optimum positions depending upon the amount of deflection even when there is a difference between the amount of deflection of one side and that of other side of the recording body in the recording body width direction of the recording body between the transfer nip and a fixing nip.SOLUTION: A front side of a guide member is moved to the optimum position depending upon the amount of deflection of a transfer paper by controlling a front side guide plate separation mechanism based on a detection result detected by a front side deflection amount detection sensor 65 disposed at a front side of a device. In addition to the above, an inner side of the guide member is moved to the optimum position depending upon the amount of deflection of the transfer paper by controlling an inner side guide plate separation mechanism 62 based on a detection result detected by an inner side deflection amount detection sensor disposed at an inner side of the device.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

  As a conventional image forming apparatus, a toner image on a toner image carrier such as a photosensitive member or an intermediate transfer member is transferred to a front surface of a transfer sheet while conveying the transfer sheet as a recording member at a transfer nip, and the toner image is transferred There is a type in which the transferred transfer paper is conveyed to a fixing nip, and the toner image on the transfer paper is fixed to the transfer paper while the transfer paper is conveyed in the fixing nip. If the transfer paper transport speed in the fixing nip is faster than the transfer paper transport speed in the transfer nip, the transfer paper is pulled downstream in the transport direction in the transfer nip, which may affect the image.

  Patent Document 1 describes an image forming apparatus in which the transfer paper conveyance speed at the transfer nip is higher than the transfer paper conveyance speed at the fixing nip. Thus, the transfer paper is not bent between the transfer nip and the fixing nip, and the transfer paper is not pulled downstream in the transport direction at the transfer nip, and it is possible to suppress the influence on the image.

  Further, in Patent Document 1, in order to control the bending direction of the transfer paper between the transfer nip and the fixing nip, the transfer paper is guided in contact with the back surface of the transfer paper disposed between the transfer nip and the fixing nip. The transfer paper transport member that transports the transfer paper in contact with the guide member or the back surface of the transfer paper is moved away from the back surface of the transfer paper after the leading edge of the transfer paper enters the fixing nip. Accordingly, a gap is formed on the back surface side of the transfer paper, and the deflection can escape from the back surface side of the transfer paper, so that the transfer paper can be bent to the back surface side of the transfer paper. Further, in Patent Document 1, the amount of movement of the guide member or transfer paper transport member in the direction away from the transfer paper is adjusted according to the amount of deflection of the transfer paper. Thereby, excessive adjustment can be suppressed and the drive time of the drive motor for moving the guide member can be shortened. Thereby, power consumption can be reduced.

However, the conveyance speed at the fixing nip may differ between the one side and the other side starting from the center in the transfer paper width direction, and the amount of deflection between the transfer nip and the fixing nip differs between one side and the other side in the transfer paper width direction. was there. The conveyance speed is different between one side and the other side in the transfer paper width direction for the following reasons. That is, the fixing nip includes a heating roller that includes a heat generating member inside and rotates with the transfer paper, and a pressure roller that contacts the fixing roller with a predetermined pressure and rotates. The pressure roller is pressed to the fixing roller side by the pressure unit, but the pressure applied to the fixing roller by the pressure roller differs on one side and the other side due to variations in the parts of the pressure unit There is. Thus, when the pressure applied to the fixing roller by the pressure roller is different between one side and the other side in the transfer paper width direction, the distance from the fixing nip to the rotation center of the pressure roller is one side and the other side in the transfer paper width direction. And different. As a result, the transfer paper conveyance speed in the fixing nip is different between the other side and the one side, and the amount of bending between the transfer nip and the fixing nip is different between the one side and the other side in the transfer paper width direction.
In addition, for example, when continuously printing images with a toner adhesion amount greatly different on one side and the other side with the center in the transfer paper width direction as a starting point, the transfer paper conveyance speed in the fixing nip is such that the transfer paper width direction on one side and the other side Different on the side. This is because the amount of heat taken away is different between the one side and the other side, and the temperature on the side where the toner adhesion amount on the transfer paper is small is higher than the temperature on the side where the toner adhesion amount on the transfer paper is large. As a result, the amount of thermal expansion on the higher temperature side is greater than the thermal expansion on the lower temperature side, and the transfer paper conveyance speed on the higher temperature side becomes the transfer on the lower temperature side. It becomes faster than the paper transport speed. As a result, the amount of deflection of the transfer paper differs between one side and the other side in the transfer paper width direction.

  Since Patent Document 1 moves the entire transfer sheet width direction of the guide member, as described above, if the deflection amount differs on one side and the other side, either one of the guide members in the width direction causes the deflection amount of the transfer sheet. There is a problem that it cannot be positioned at an optimal position according to the condition. If the amount of movement of the guide member is adjusted to the direction where the amount of bending is small, the side where the amount of bending is large cannot secure a sufficient space on the back side of the transfer paper, and the direction of bending cannot be controlled. As a result, the side with the larger amount of deflection is bent on the front side of the transfer paper, and the front side of the transfer paper faces the front side of the transfer paper between the transfer nip and the fixing nip. The toner image may be disturbed. Further, when the amount of movement of the guide member is adjusted to the one with the larger amount of deflection, the side with the smaller amount of deflection of the guide member is over-adjusted, and the drive time of the drive motor for moving the guide member is increased. It becomes longer and wastes power consumption.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress the recording body from being pulled downstream in the conveyance direction in the transfer nip, and to reduce the width of the recording medium between the transfer nip and the fixing nip. An image forming apparatus capable of positioning one side and the other side of the guide member in the recording member width direction at optimum positions according to the amount of deflection even when the amount of deflection of the recording member differs between the one side and the other side in the direction. Is to provide.

In order to achieve the above object, the invention of claim 1 is directed to a toner image carrier that carries a toner image, an image forming unit that forms a toner image on the toner image carrier, and the toner image carrier. A transfer member for forming a transfer nip for transferring the toner image on the toner image carrier onto the recording body while conveying the recording body, and a toner image on the recording body transferred by the transfer nip at the fixing nip. A fixing device that fixes the recording medium while conveying the recording medium, and a guide member that abuts the recording medium that has passed through the transfer nip on the side opposite to the toner image forming surface and guides the recording medium to the fixing nip. In the image forming apparatus in which the recording medium conveyance speed in the transfer nip is higher than the recording medium conveyance speed in the fixing nip, one side and the other side of the recording member width direction of the guide member are different from each other. It is characterized in that it has a capable of position configuration.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the first contact / separation means for contacting or separating one side of the guide member in the recording member width direction with respect to the recording member, and the recording of the guide member. The other side in the body width direction is disposed between the second contact / separation means for contacting / separating the recording medium and the transfer nip to the fixing nip, facing the toner image forming surface of the recording medium, and the toner image of the recording medium A first deflection amount detecting means for detecting a deflection amount on one side in the width direction of the recording body, which is provided on the recording body facing member which may come into contact with the forming surface; And detecting the second deflection amount detecting means by controlling the first contact / separation means based on the detection result of the second deflection amount detecting means and the detection result of the first deflection amount detecting means. And a control means for controlling the second contact / separation means based on the result. An image forming apparatus characterized by and.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the control means positions the one side and the other side of the guide member in the recording body width direction at the same position during non-image formation. The first contact / separation means and the second contact / separation means are controlled.
According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect of the present invention, there is provided a recording medium detection unit that detects that a leading end of the recording medium in the conveyance direction has entered the fixing nip, and the control unit includes: The recording body detection means performs contact / separation control of the guide member after detecting that the leading end of the recording body in the conveyance direction has entered the fixing nip.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the recording medium detecting means does not detect the trailing edge of the recording medium even if a predetermined time elapses after detecting the leading edge of the recording medium. In this case, it is determined that the conveyance error of the recording medium is detected.

According to the present invention, since the recording member width direction one side and the other side of the guide member can be positioned at different positions, even if the deflection amount differs between the recording body width direction one side and the other side, The guide member can be positioned at an optimal position corresponding to the amount of deflection on either the one side or the other side in the recording body width direction. As a result, it is possible to control the deflection between one side and the other side, between the transfer nip and the fixing nip. Further, excessive adjustment can be suppressed, and the drive time of a drive means such as a drive motor or a solenoid for moving the guide member can be minimized. Thereby, waste of power consumption can be suppressed.
Further, according to the present invention, the recording medium conveyance speed in the fixing nip is made slower than the recording medium conveyance speed in the transfer nip, so that the recording body is not pulled downstream in the conveyance direction in the transfer nip. It is possible to suppress problems such as image distortion. Thereby, a high quality image can be obtained.

1 is a configuration diagram showing a schematic configuration of an image forming apparatus according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating a secondary transfer nip and the surrounding configuration of the image forming apparatus. FIG. 4 is a diagram for explaining a transfer sheet conveyance state between a transfer nip and a fixing nip in a normal state. FIG. 3 is a schematic perspective view for explaining a transfer sheet conveyance state between a transfer nip and a fixing nip in a normal state. FIG. 3 is a schematic perspective view illustrating an example of a transfer sheet conveyance state between a transfer nip and a fixing nip when a speed difference occurs between the back side and the near side of the fixing nip. The figure explaining the conveyance state of the back side transfer paper in the example shown in FIG. The schematic block diagram which shows a back side guide plate contact-and-separation mechanism. The flowchart of contact / separation control for contacting / separating the back side of a guide member. (A) is a schematic block diagram when controlling so that a guide member may be spaced apart from transfer paper, (b) is a schematic block diagram when controlling so that a guide member may be moved to the transfer paper side.

  Hereinafter, an embodiment when the present invention is applied to an image forming apparatus will be described. FIG. 1 is a configuration diagram showing a schematic configuration of the image forming apparatus. The central portion of the image forming apparatus includes image stations 15Y, 15C, 15M, and 15K for forming toner images of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). ing. Hereinafter, the subscripts Y, C, M, and K of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively. Each of the image stations 15Y, 15C, 15M, and 15Bk includes an optical unit 8 as a latent image forming unit that can irradiate the drum-shaped photoconductors 20Y, 20C, 20M, and 20Bk with laser light. Above the image station 15, an intermediate transfer unit 10 serving as a transfer unit including the intermediate transfer belt 11 is provided. Further, a fixing unit 6 is provided as fixing means for fixing the toner image transferred to the intermediate transfer belt 11 to the transfer paper 2. In addition, toner bottles 9Y, 9C, 9M, and 9Bk that store toner of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) are loaded on the upper portion of the image forming apparatus.

  Since the image stations 15Y, 15C, 15M, and 15Bk have the same structure, the K-color image station 15Bk will be described. It is a block diagram which shows the internal structure of the image station 15Bk of Bk color. The image station 15Bk includes a photoconductor 20Bk that is a latent image carrier, a charging device 30Bk that is a charging unit that charges the photoconductor 20Bk to a predetermined potential, a developing device 50Bk that is a developing unit that develops a latent image formed on the photoconductor 20Bk, A cleaning device 40Bk for cleaning residual toner on the photoconductor 20Bk is provided. Further, the image station 15Bk may be provided with a charge removing unit that removes the surface of the photoconductor 20Bk that has passed through the cleaning device 40Bk, if necessary. Further, a recycling unit that returns the toner removed by the cleaning device 40Bk to the developing device 50Bk may be provided.

  The image station 15Bk is configured as a process cartridge that integrally supports the photoconductor 20Bk, the charging device 30Bk, the developing device 50Bk, and the cleaning device 40Bk, and is detachable from the apparatus main body. Thus, the user can replace the photoconductor 20Bk, the developing device 50Bk, the charging device 30Bk, and the cleaning device 40Bk in the form of a cartridge.

  As shown in FIG. 1, the intermediate transfer unit 10 serving as a transfer unit transfers toner images formed on the intermediate transfer belt 11 and the photoconductors 20Y, 20C, 20M, and 20Bk stretched around a plurality of rollers onto the intermediate transfer belt 11. Primary transfer rollers 12Y, 12C, 12M, and 12Bk. These parts are integrally supported by the intermediate transfer belt case 14. Further, the intermediate transfer unit 10 includes a secondary transfer roller 5 that transfers the toner image transferred onto the intermediate transfer belt 11 onto the transfer paper 2 that is a transfer target, and an intermediate transfer belt 11 that is not transferred onto the transfer paper 2. A belt cleaning device 13 for cleaning the transfer residual toner is provided.

  A transfer sheet 2 as a recording medium in the sheet cassette 1 is fed to an intermediate transfer belt 11 as a toner image carrier and a secondary transfer roller 5 as a transfer member by a sheet feed roller 3 disposed in the vicinity of the sheet cassette 1. Is conveyed to the secondary transfer section. In the transfer sheet conveyance path between the sheet feeding roller 3 and the secondary transfer roller 5, a registration roller pair 4 is arranged for timing the feeding of the fed transfer sheet 2 to the secondary transfer unit.

  The fixing unit 6 serving as fixing means performs fixing by applying heat and pressure to the toner image transferred onto the transfer paper 2. The heating in the fixing unit 6 is usually preferably 80 ° C to 200 ° C. Then, the transfer sheet 2 having been fixed is discharged out of the apparatus by the discharge roller pair 7. The fixing unit 6 includes a pressure roller 6a and a fixing roller 6b provided with a heat source therein, and the pressure roller 6a contacts the fixing roller 6b to form a fixing nip. The configuration of the fixing unit 6 is not particularly limited and can be appropriately selected according to the purpose. For example, a fixing belt may be used instead of the fixing roller 6b. In this image forming apparatus, the toner on the transfer paper 2 is fixed by heating and pressing, but the toner image on the transfer paper 2 may be fixed on the transfer paper 2 by other methods.

  Next, an image forming process (image forming method) for obtaining a color image in the image forming apparatus having the above configuration will be described. In the image forming process, the surface of each of the photoconductors 20Y, 20C, 20M, and 20Bk is charged to a predetermined potential. The surface of each charged photoconductor 20Y, 20C, 20M, and 20Bk is exposed based on the image data, and each photoconductor is exposed. It has a latent image forming step of forming a latent image on the surface of 20Y, 20C, 20M, and 20Bk. Further, the image forming apparatus includes a developing process in which toner is supplied from the developing rollers of the developing devices 50Y, 50C, 50M, and 50Bk to the latent images on the photoconductors 20Y, 20C, 20M, and 20Bk to visualize the latent images. The image forming apparatus includes a transfer process for transferring the visible image on the surface of each photoconductor to the transfer paper 2 and a fixing process for fixing the visible image on the transfer paper 2 onto the transfer paper. This will be specifically described below.

  First, in each of the image stations 15Y, 15C, 15M, and 15K, the photoconductor 20 is uniformly charged by the charging device 30. Thereafter, the optical unit 8 scans and exposes the laser beam based on the image information to form a latent image on the surface of the photoconductor 20. The latent image on the photoconductor 20 is developed with each color toner carried on the developing roller of the developing device 50 to be visualized as a toner image. The toner image on the photoconductor 20 is sequentially transferred onto the transfer belt 11 that is rotated counterclockwise by the action of each primary transfer roller 12. The image forming operation of each color at this time is shifted in timing from the upstream side toward the downstream side in the moving direction of the intermediate transfer belt 11 so that the toner image is transferred to the same position on the intermediate transfer belt 11. Executed. The surface of the photoreceptor 20 after the primary transfer is finished is cleaned by the cleaning device 40 and is prepared for the next image formation.

  On the other hand, the transfer paper 2 in the paper feed cassette 1 is transported by a paper feed roller 3 disposed in the vicinity of the paper feed cassette 1, and is transported to a secondary transfer section by a registration roller pair 4 at a predetermined timing. . In the secondary transfer portion, the toner image formed on the intermediate transfer belt 11 is transferred to the transfer paper 2. The transfer paper 2 onto which the toner image has been transferred passes through the fixing unit 6 to be fixed, and is discharged out of the apparatus by a discharge roller 7. Similar to the photoconductor 20, the untransferred toner remaining on the transfer belt 11 is cleaned by a belt cleaning device 13 that contacts the intermediate transfer belt 11. Further, a predetermined amount of toner filled in the toner bottle 9 is supplied to each developing device 50 through a conveyance path (not shown) according to necessity.

Next, a characteristic configuration of the printer will be described. FIG. 2 is an enlarged configuration diagram illustrating the secondary transfer nip and the surrounding configuration of the image forming apparatus according to the embodiment.
As shown in the figure, the surface has an endless movement, and has a secondary transfer roller 5 that forms a transfer nip Nt that is a secondary transfer nip that transfers a toner image onto the transfer paper 2 facing the intermediate transfer belt 11. ing. The secondary transfer roller 5 is pressed toward the counter roller 51 by a secondary transfer pressure spring 56. The intermediate transfer belt 11 rotates in the direction of arrow A in the figure. In addition, the image forming apparatus includes a fixing unit 6 that fixes the toner image on the transfer sheet 2 that is a recording medium on which the toner image is transferred at the transfer nip Nt, at the fixing nip Nf. Further, a guide member 63 that contacts the back surface of the transfer paper 2 that has passed through the transfer nip Nt and guides the conveyance direction toward the fixing nip Nf is provided.

  An attachment portion 54 provided at the end of the guide member 63 on the secondary transfer roller side is rotatably attached to the shaft 55 of the secondary transfer roller 5. A sheet member 63a is attached to the guide surface of the guide member 63 for guiding the transfer paper 2 by, for example, a double-sided tape. The sheet member 63a is made of, for example, a material that, when frictionally charged with the transfer paper 2, charges the transfer paper to the polarity of the secondary transfer bias, that is, the polarity opposite to the charge polarity of the toner on the transfer paper. As a result, while the transfer paper moves to the fixing nip Nf, the charge of the toner opposite to the polarity of the toner on the transfer paper 2 increases due to frictional charging with the sheet member 63a, thereby improving the toner holding function on the transfer paper. it can. As a result, it is possible to suppress toner from being scattered on the fixing roller 6b when entering the fixing nip, and to prevent forward dust.

  In the present embodiment, the transfer speed of the transfer paper 2 at the transfer nip Nt is higher than the transfer speed of the transfer paper 2 at the fixing nip Nf. As a result, the transfer paper 2 is conveyed in a bent state as shown in FIG. 3 between the transfer nip and the fixing nip, and the transfer paper 2 is suppressed from being pulled in the conveyance direction at the transfer nip Nt. , Image disturbance can be suppressed.

  When the speed difference between the transfer nip Nt and the fixing nip Nf has a predetermined relationship, as shown in FIGS. 3 and 4, the transfer paper 2 has a front surface (toner image forming surface) in the vicinity of the transfer paper conveyance path. The transfer paper 2 is bent toward the front side in a region where there is no opposing member (region B in FIG. 3). Therefore, the front surface side of the transfer paper 2 is conveyed to the fixing nip Nf without touching anywhere.

In the fixing nip Nf, a temperature deviation may occur in the transfer paper width direction, and the transfer paper conveyance speed in the fixing nip Nf may be different between the one side and the other side. For example, when the transfer paper 2 having a toner image formed on one side in the width direction of the transfer paper is continuously printed, a temperature difference occurs between one side and the other side of the transfer paper 2. Further, in an apparatus that conveys one side in the width direction, after continuously printing a sheet having a short width, the temperature on one side in the width direction is lower than that on the other side. Thus, when a difference occurs between the temperature on one side in the width direction and the temperature on the other side, the thermal expansion amount of the pressure roller 6a that is rotationally driven by the drive motor differs between the one side and the other side. As a result, the distance from the fixing nip Nf to the center of rotation of the pressure roller 6a differs between the one side and the other side, and the transfer paper conveyance speed at the fixing nip Nf differs between the one side and the other side.
In addition, rotation shafts (not shown) provided at both ends of the pressure roller 6a are pressed toward the fixing roller 6b by pressure springs (not shown) as pressure units. However, there may be a difference between the pressurizing force on one side and the pressurizing force on the other side due to variations in parts of the pressure spring. As a result of the difference in the applied pressure, the distance from the fixing nip Nf to the pressure roller 6a differs between the one side and the other side, and the transfer paper conveyance speed at the fixing nip Nf differs between the one side and the other side.

FIG. 5 is a perspective view for explaining the bending of the transfer paper 2 when the transfer paper conveyance speed V2 on the back side in the fixing nip Nf is slower than the transfer paper conveyance speed V1 on the near side.
As shown in FIG. 4, when the transfer paper 2 is transported at the same target transport speed as the transfer paper transport speed V2 on the back side in the fixing nip Nf and the transfer paper transport speed V1 on the near side, At the target position, bending that is curved toward the front surface side of the transfer sheet in a direction orthogonal to the transfer sheet conveyance direction is possible.
On the other hand, as shown in FIG. 5, if the rear transfer paper transport speed V2 in the fixing nip Nf is different from the front transfer paper transport speed V1, the above-described deflection is in a direction perpendicular to the transfer paper transport direction. As a result, the position of either one of the deflections (the back side in FIG. 5) approaches the fixing nip Nf side and deviates from the target area (area B in FIG. 3). As described above, when the position of the deflection is closer to the fixing nip side than the target area, as shown in FIG. 6, the front surface (toner image) of the transfer paper 2 arranged in the vicinity of the transfer paper transport path is shown. There is a possibility of coming into contact with a facing member (the receiving surface 64 in the drawing shown in FIG. 6) facing the forming surface. Thus, if the front surface of the transfer paper 2 comes into contact with the member, the toner image formed on the front surface of the transfer paper 2 is disturbed, resulting in a problem that the image quality deteriorates. End up.

  Therefore, as in the image forming apparatus described in Patent Document 1, it may be considered that the entire guide member 63 is greatly separated from the transfer paper 2 when the leading edge of the transfer paper 2 enters the fixing nip Nf. Thus, by separating, a space is formed on the back surface side of the transfer paper 2, the transfer paper 2 can be bent toward the back surface side, and the transfer paper can be prevented from being bent toward the front surface side. it can. As a result, the front surface of the transfer paper is disposed between the transfer nip and the fixing nip and is prevented from coming into contact with a member (the receiving surface 64 in the present embodiment) facing the front surface of the transfer paper. Can do. However, in order not to bend the transfer paper to the front surface side, the entire guide member 63 needs to be largely separated from the transfer paper 2, and a large space for moving the guide member 63 in the apparatus is secured. There is a need to. Further, since the amount of movement of the guide member 63 increases, there is a problem that power consumption increases.

  Therefore, in the present embodiment, even if the transfer paper is bent to the front surface side, the front surface of the transfer paper 2 is prevented from coming into contact with a member disposed between the transfer nip and the fixing nip. Specific description will be given below.

  As shown in FIG. 2, the fixing device side of the guide member 63 is pressed to the transfer paper conveyance path side by the compression spring 58, and the abutting protrusions 63 b provided at both ends in the width direction of the guide member 63 are It is in contact with a receiving surface 64 provided in the fixing unit 6. In addition, on the front side and the back side of the receiving surface 64, a deflection amount detection sensor 65 is provided as a deflection amount detection unit. A laser displacement meter can be used as the deflection amount detection sensor 65. By measuring the distance between the laser displacement meter and the transfer paper 2, the amount of deflection of the transfer paper 2 at the location facing the receiving surface 64 can be measured. That is, it can be measured that the closer the distance between the laser displacement meter and the transfer paper 2 is, the larger the amount of deflection on the front surface side of the transfer paper 2 is.

FIG. 7 is a schematic configuration diagram showing the back guide plate contacting / separating mechanism.
As shown in FIG. 7, the back guide plate contact / separation mechanism as the first contact / separation means drives the back cam 62 that contacts the fixing nip side of the back end of the guide member 63 and the back cam 62. And a rear motor 66 as a driving source. A control unit 67 as a control unit is connected to the back motor 66. Although not shown, the front side guide plate 63 has a front side guide plate contact / separation mechanism as a second contact / separation means having the same configuration as the back side guide plate contact / separation mechanism. . That is, the front guide plate contacting / separating mechanism has a front cam (not shown) that contacts the fixing nip side of the front end of the guide member 63 and a front motor (not shown) that drives the front cam. is doing.

  Further, the guide member 63 is formed of a member that can be elastically deformed to some extent.

  The control unit 67 controls the rotation angle of the front cam (not shown) based on the detection result of the deflection amount detection sensor 65 provided on the front side, so that the front side of the guide member 63 is placed on the transfer paper 2. Adjustment is performed according to the amount of deflection on the front side. Further, by controlling the rotation angle of the back cam 62 based on the detection result of the bending amount detection sensor 65 provided on the back side, the back side of the guide member 63 is set to the back side bending amount of the transfer paper 2. Adjustments are made according to

FIG. 8 is a flowchart of contact / separation control for contacting / separating the back side of the guide member 63.
When a transfer paper detection sensor (not shown), which is a recording medium detection means provided near the fixing nip Nf, detects the leading edge of the transfer paper 2, contact / separation control is started. The control unit 67 monitors whether or not the amount of deflection of the transfer sheet 2 at the position where the back side deflection amount detection sensor 65 is disposed is equal to or greater than a threshold value (S1). When the amount of deflection is equal to or greater than the threshold value (YES in S1), the portion of the transfer paper 2 that is bent toward the front side is the portion where the deflection amount detection sensor 65 is disposed (the receiving surface 64 is disposed). The front surface of the transfer paper 2 may be in contact with the receiving surface 64. Therefore, in this case, the control unit 67 performs a separation operation for separating the back side of the guide member 63 from the transfer paper 2 (S2). Specifically, the back side drive motor 66 is driven to rotate the back side cam 62. When the back cam 62 is rotated, the fixing nip side of the back end of the guide member 63 is pushed away from the transfer paper 2 by the back cam 62. As a result, against the pressure force of the compression spring 58, the fixing nip Nf side on the back side of the guide member 63 moves in a direction away from the transfer paper with the shaft 55 of the secondary transfer roller 5 as a fulcrum. As a result, a space is created on the back side of the transfer paper on the back side. Therefore, for example, as shown in FIG. 6, the amount of bending of the portion of the transfer paper that has been in contact with the guide member 63 and bent on the back surface side increases, and the amount of bending on the front surface side of the transfer paper 2 decreases. Become. As a result, the back side front surface of the transfer paper 2 is separated from the back side deflection amount detection sensor 65, and the back side front surface of the transfer paper 2 is prevented from contacting the receiving surface 64. be able to. When a transfer paper detection sensor (not shown) detects the trailing edge of the transfer paper and detects that the trailing edge of the transfer paper 2 has entered the fixing nip (YES in S3), the control unit 67 The drive motor is driven, the back cam 62 is rotated, and the back side of the guide member 63 is moved to the initial position (S6).
On the other hand, even if a predetermined time has elapsed after the transfer paper detection sensor (not shown) provided in the vicinity of the fixing nip Nf detects the leading edge of the transfer paper, the transfer paper detection sensor (not shown) has passed through the rear edge of the transfer paper. If this is not detected (YES in S4), it is determined that a conveyance failure has occurred, the conveyance is stopped (S5), and the back side of the guide member 63 is moved to the initial position (S6).

  Also on the front side of the guide member 63, the same control as in FIG. 8 is performed to perform contact / separation control on the front side of the guide member. That is, the amount of deflection on the front side of the transfer paper is detected by the amount of deflection sensor on the near side. When the amount of deflection on the front side of the transfer paper is equal to or larger than the threshold value, the front side of the transfer paper 2 may come into contact with the receiving surface 64, so that the front side of the guide member 63 is removed from the transfer paper. Control is performed so as to be separated. As a result, the front surface of the transfer paper 2 can be prevented from coming into contact with the receiving surface 64, and the toner image formed on the front side of the transfer paper 2 can be prevented from being disturbed. it can. In addition, after the rear end of the transfer sheet 2 enters the fixing nip Nf, the guide member 63 is returned to the initial position, so that the back side and the near side of the guide member 63 are at the initial position during non-image formation. Can be positioned. As a result, the guide member 63 can be prevented from being left for a long time in a twisted state, and the plastic deformation of the guide member 63 can be prevented.

  As described above, in the present embodiment, the deflection amount detection sensor 65 is provided on the opposing member (the receiving surface 64 in the present embodiment) that may be in contact with the front surface of the transfer paper 2. When the amount of deflection on the front surface side exceeds a threshold value and the front surface of the transfer paper 2 approaches the receiving surface 64 by a threshold value or more, the guide member 63 is controlled so as to be separated. The front surface can be moved away from the surface 64. Thereby, even if the transfer paper 2 bends to the front surface side, it is possible to suppress the front surface of the transfer paper 2 from coming into contact with the receiving surface 64. As a result, as in the image forming apparatus described in Patent Document 1, the transfer paper is prevented from being bent to the front surface side, so that the front surface of the transfer paper 2 between the transfer nip and the fixing nip The amount of movement of the guide member 63 can be reduced as compared with the case where the front surface of the transfer paper is not brought into contact with the opposing member. Therefore, compared with the image forming apparatus described in Patent Document 1, the space in which the guide member moves can be narrowed. As a result, the apparatus can be made compact.

  Further, by performing the separating operation of the guide member 63 independently on the back side and the front side of the guide member 63, for example, as shown in FIG. When the surface side is bent at the target position, the front side is not separated, and only the back side of the guide member 63 is separated, so that the movement of the guide member 63 is minimized. be able to. Thereby, useless power consumption can be suppressed.

  Further, since the separation control of the guide member 63 is performed after the leading edge of the transfer paper 2 enters the fixing nip Nf, the guide member 63 can guide the leading edge of the transfer paper 2 to the fixing nip Nf. The leading edge of the transfer paper 2 can be made to enter the fixing nip Nf satisfactorily.

  Further, for example, the initial position of the cam is set to the position shown in FIG. 7, the back side deflection amount detection sensor detects the back side deflection amount, and the front side deflection amount detection sensor sets the front side deflection amount of the transfer paper. Detect. Then, as shown in FIG. 9A, the side with the larger amount of deflection is controlled to move the guide member 63 away from the transfer paper 2, and the side with the smaller amount of deflection is as shown in FIG. 9B. Alternatively, the guide member 63 may be controlled to move to the transfer paper side. By controlling in this way, it is possible to shift the position of the front surface side of the transfer paper 2 to the region B shown in FIG.

  In the present embodiment, the guide member 63 is contacted and separated by using the cam mechanism. However, for example, the guide member 63 is pushed to the side away from the transfer sheet by using a solenoid to guide the guide member 63. May be moved away from the transfer paper.

As described above, according to the image forming apparatus of the present embodiment, the intermediate transfer belt 11 that is a toner image carrier that carries a toner image, and the image forming means that forms a toner image on the intermediate transfer belt 11 (each image station 15Y, 15C, 15M, 15Bk, optical unit 8, primary transfer rollers 12Y, 12C, 12M, 12Bk, and the like) and the transfer paper 2 as a recording medium facing the intermediate transfer belt 11 while being transferred onto the transfer paper 2 The toner image on the transfer paper transferred at the transfer nip is fixed to the transfer paper 2 while the transfer paper 2 is conveyed at the fixing nip. A guide for guiding the transfer paper to the fixing nip by contacting the fixing unit 6 as a fixing device and the toner image forming surface of the transfer paper that has passed through the transfer nip. And a timber 63, is faster than the transfer sheet conveyance speed transfer sheet conveyance speed in the transfer nip in the fixing nip. As a result, the recording medium conveyance speed in the fixing nip is made slower than the recording medium conveyance speed in the transfer nip, so that the recording body is not pulled downstream in the conveyance direction in the transfer nip, and the image is disturbed in the transfer nip. Problems can be suppressed. Thereby, a high quality image can be obtained.
Further, according to the image forming apparatus of the present embodiment, the guide member 63 is configured such that one side and the other side of the transfer paper width direction can be positioned at different positions. As a result, even if the amount of bending differs on one side and the other side in the transfer paper width direction, the guide member can be positioned at an optimum position corresponding to the amount of bending. As a result, excessive adjustment can be suppressed and wasteful power consumption can be suppressed.

  Further, the back side guide plate contacting / separating mechanism, which is a first contact / separation means for contacting / separating one side of the guide member 63 in the transfer sheet width direction with respect to the transfer sheet, and the transfer sheet width direction other side of the guide member 63 Is disposed between the front guide plate contacting / separating mechanism as the second contacting / separating means for contacting and separating from the transfer nip to the fixing nip, and is opposed to the toner image forming surface of the recording medium to form the toner image on the recording medium. A back side deflection amount detection sensor as a first deflection amount detection means provided on the receiving surface 64 that is a member that may be in contact with the surface and detects a deflection amount on one side in the recording body width direction; And a near-side deflection amount detection sensor as a second deflection amount detection means for detecting the deflection amount on the other side in the width direction of the transfer sheet. Then, the control unit, which is a control unit, controls to move the guide member on one side in the transfer paper width direction in the direction of separating based on the detection result of the back side deflection amount detection sensor, and the detection by the front side deflection amount detection sensor. Based on the result, control is performed so that the guide member 63 on the other side in the width direction of the transfer sheet is moved in the separating direction. Thereby, even if the transfer paper is bent to the front surface side, the front surface of the transfer paper can be prevented from coming into contact with the receiving surface 64. Thereby, image disturbance can be suppressed and a high-quality image can be obtained. In addition, the amount of movement of the guide member can be reduced and power consumption can be reduced as compared with the case where the guide member is separated from the transfer paper so as not to bend the transfer paper to the front side. In addition, the apparatus can be made compact.

  In addition, when the image is not formed, the control unit performs control so that one side and the other side of the guide member in the width direction of the recording member on the fixing nip side are positioned at the same position, so that the guide member is left twisted for a long time. Can be prevented, and plastic deformation of the guide member can be suppressed.

  Also, it has a transfer paper detection sensor as a recording medium detection means for detecting that the transfer paper conveyance direction tip has entered the fixing nip, and the control unit fixes the transfer paper detection sensor and the transfer paper conveyance direction tip. After detecting that it has entered the nip, the guide member is controlled to be separated. As a result, the leading edge of the transfer paper can be guided to the fixing nip by the guide member, and the leading edge of the transfer paper can smoothly enter the fixing nip.

  Further, when the transfer paper detection sensor does not detect the trailing edge of the transfer paper even after a predetermined time has elapsed after detecting the leading edge of the transfer paper, it is determined that the transfer paper is abnormal, thereby determining the transfer paper lyrics. Jam detection can be performed using the leading edge detection sensor, and the cost of the apparatus can be reduced compared to the case where a jam detection sensor is used separately from the transfer paper detection sensor.

2: transfer paper 5: secondary transfer roller 6: fixing unit 6a: pressure roller 6b: fixing roller 8: optical unit 11: intermediate transfer belt 12: primary transfer roller 15: image station 51: counter roller 54: attachment unit 56 : Secondary transfer pressure spring 58: compression spring 62: back side cam 63: guide member 63a: sheet member 63b: abutment protrusion 64: receiving surface 65: deflection amount detection sensor 66: back side motor 67: control unit Nf: Fixing nip Nt: transfer nip

Japanese Patent No. 3617269

Claims (5)

A toner image carrier for carrying a toner image;
Image forming means for forming a toner image on the toner image carrier;
A transfer member for forming a transfer nip for transferring the toner image on the toner image carrier on the recording body while conveying the recording body facing the toner image carrier;
A fixing device for fixing the toner image on the recording body transferred at the transfer nip to the recording body while conveying the recording body at the fixing nip;
A guide member that contacts the opposite side of the toner image forming surface of the recording body that has passed through the transfer nip and guides the recording body to the fixing nip;
In the image forming apparatus in which the recording material conveyance speed in the transfer nip is faster than the recording material conveyance speed in the fixing nip,
An image forming apparatus characterized in that the recording member width direction one side and the other side of the guide member can be positioned at different positions. The image forming apparatus according to claim 1.
First contact / separation means for contacting and separating one side of the guide member in the recording body width direction with respect to the recording body;
A second contacting / separating means for contacting and separating the other side of the guide member in the recording body width direction with respect to the recording body;
It is arranged between the transfer nip and the fixing nip, and is provided on a recording member facing member that faces the toner image forming surface of the recording member and may come into contact with the toner image forming surface of the recording member. First deflection amount detecting means for detecting a deflection amount on the side;
A second deflection amount detecting means provided on the recording member facing member for detecting the deflection amount on the other side in the recording body width direction;
Control means for controlling the first contact / separation means based on the detection result of the first deflection amount detection means, and for controlling the second contact / separation means based on the detection result of the second deflection amount detection means; An image forming apparatus comprising: The image forming apparatus according to claim 2.
The control means controls the first contact / separation means and the second contact / separation means so that the one side and the other side of the recording member width direction of the guide member are positioned at the same position at the time of non-image formation. Image forming apparatus. The image forming apparatus according to claim 2 or 3,
A recording medium detection means for detecting that the leading end of the recording medium in the conveying direction has entered the fixing nip;
The image forming apparatus according to claim 1, wherein the control unit performs contact / separation control of the guide member after the recording body detection unit detects that the leading end of the recording body in the conveyance direction has entered the fixing nip. The image forming apparatus according to claim 4.
If the recording medium detecting means does not detect the trailing edge of the recording medium even after a predetermined time has elapsed after detecting the leading edge of the recording medium, it is determined that the recording medium is abnormally conveyed. apparatus.

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