JP2016170183A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress a noise during sheet conveyance.SOLUTION: An image forming apparatus comprises: image forming means that forms a toner image on a recording medium; fixing means that applies heat and pressure with a pressure contact part to the recording material to which the toner image is transferred by the image forming means to fix the toner image to the recording medium; a conveyance path that is provided on the upstream side of the fixing means in the direction of conveyance of the recording medium; and curving means that is provided on the conveyance path, and curves recording medium in a curving direction of the pressure contact part with respect to the conveyance direction by pressing the recording medium with a first roll that drives the conveyed recording medium and a second roll that has a larger diameter than the first roll and has a contact part with the first roll deforming along the shape of the first roll.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus.

  It has a pair of rotating bodies pressed against each other with a nip portion, and guide means for guiding the paper so that the paper enters the nip portion of the rotating body, and the guide means is divided in the axial direction of the rotating body. There is known a fixing device having a fixed portion and a movable portion, and after the paper enters the nip portion of the rotating body, the movable portion is moved to press a part of the paper ( Patent Document 1).

JP 2006-267375 A

When the sheet conveyed to the fixing nip portion of the fixing device is curled to any side of the sheet, an impulse sound may be generated from the sheet at the fixing nip portion.
An object of the present invention is to provide an image forming apparatus capable of suppressing noise during paper conveyance.

In order to solve the above problem, an image forming apparatus according to claim 1,
Image forming means for forming a toner image on a recording medium;
Fixing means for fixing the toner image to the recording medium by heating and pressurizing the recording material, onto which the toner image has been transferred by the image forming means, at a press contact portion;
A conveyance path provided upstream of the fixing unit in the conveyance direction of the recording medium;
A bending means provided in the conveyance path, wherein the recording medium is bent in a bending direction of the press contact portion in the conveyance direction;
It is characterized by that.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
A first roll for driving the recording medium, the bending means;
The recording medium is sandwiched between the first roll and the recording medium is pressed against the first roll. The diameter of the recording medium is larger than that of the first roll, and the contact portion with the first roll is the first roll. A second roll deforming along the shape of
Pressing means for pressing the second roll and the first roll together,
It is characterized by that.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The pressing means acquires transport path information of the recording medium, and adjusts the amount of biting of the second roll relative to the first roll according to the transport path information;
It is characterized by that.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect,
The pressing unit acquires thickness information of the recording medium, acquires image density information of the toner image formed on the recording medium and environmental humidity information, and acquires the thickness information, the image density information, and According to the humidity information, adjust the amount of biting of the second roll with respect to the first roll,
It is characterized by that.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4,
The pressing means presses the first roll and the second roll through a cam;
It is characterized by that.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The bending means bends the tip of the recording medium;
It is characterized by that.

According to the first aspect of the present invention, noise during sheet conveyance can be suppressed as compared with the case where the recording medium does not have a bending unit that is bent in the bending direction of the pressure contact portion of the fixing unit in the conveyance direction. it can.
According to the second aspect of the present invention, the recording medium can be reliably bent.
According to the third aspect of the invention, the amount of bending can be adjusted according to the path of the recording medium being conveyed.
According to the fourth aspect of the present invention, the amount of curvature can be adjusted according to the thickness and image density of the recording medium being conveyed and the environmental humidity.
According to the fifth aspect of the invention, the amount of bending can be reliably adjusted.
According to the sixth aspect of the present invention, it is possible to give a curve to the necessary range of the recording medium.

2 is a schematic cross-sectional view showing an internal configuration of the image forming apparatus 1. FIG. 2 is a schematic diagram of an overall configuration of a sheet transport unit including a bending device 70 in the image forming apparatus 1. FIG. 3 is a schematic cross-sectional view illustrating a fixing nip portion N2 of the fixing device 60. FIG. FIG. 6 is a schematic diagram illustrating a state of a sheet P conveyed to a fixing nip portion N2. 3 is a schematic cross-sectional view of a bending device 70. FIG. FIG. 6 is a schematic diagram for explaining correction of a curled state of a sheet P in a bending device. 6 is a graph of measurement results of paper sound when the curl state of the leading end portion Pa of the paper P is changed.

Next, the present invention will be described in more detail with reference to the drawings with reference to embodiments and specific examples. However, the present invention is not limited to these embodiments and specific examples.
Also, in the description using the following drawings, it should be noted that the drawings are schematic and the ratio of each dimension and the like are different from the actual ones, and are necessary for the description for easy understanding. Illustrations other than the members are omitted as appropriate.

(1) Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a longitudinal sectional view showing the internal configuration of the image forming apparatus 1.
Hereinafter, the overall configuration and operation of the image forming apparatus 1 will be described with reference to the drawings.

  The image forming apparatus 1 includes a control device 10, a paper feeding device 20, a photosensitive unit 30, a developing device 40, a transfer device 50, and a fixing device 60. On the upper surface (Z direction) of the image forming apparatus 1, a discharge tray T for discharging and storing the paper P on which an image is recorded is formed.

The control device 10 includes a controller 11 that controls the operation of the image forming apparatus 1, an image processing unit 12 that is controlled by the controller 11, a power supply device 13, and the like. The power supply device 13 applies a voltage to the photoconductor unit 30, the developing device 40, the transfer device 50, and the like.
The image processing unit 12 converts print information input from an external information transmission apparatus (for example, a personal computer) into image information for forming a latent image, and outputs a drive signal to the exposure apparatus LH at a preset timing. To do.

The image forming apparatus 1 is provided with a temperature / humidity sensor ST1 that detects the temperature and humidity in the machine as an environment in a machine that does not receive direct radiant heat from the fixing device 60 that generates heat, the power supply device 13, or the like.
The controller 11 acquires the value detected by the temperature / humidity sensor ST1, the image density information included in the image information output from the image processing unit 12, the presence / absence of double-sided printing included in the print information, and the paper attribute information, and the power supply device The voltage applied from 13 is controlled, and the pressing force of the bending device 70 described later is controlled.

At the bottom of the image forming apparatus 1, a paper feeding device 20 on which a large number of recording media P are stacked is provided. The paper P whose position in the width direction is determined by a regulating plate (not shown) is 1 from the top. Each sheet is pulled forward (-X direction) by the sheet drawer 22.
The paper P drawn from the paper drawer 22 is transported to the nip portion of the registration roller pair 23 through the first paper transport path S1 provided with the bending device 70.

  The photoconductor unit 30 includes a photoconductor drum 31 that is provided in parallel above the sheet feeding device 20 (Z direction) and is driven to rotate. Yellow (Y), magenta (M), cyan (C), and black (K) toner images are formed on the respective photosensitive drums 31 by the respective developing devices 40.

  Each color toner image formed on the photosensitive drum 31 of each photosensitive unit 30 is sequentially electrostatically transferred (primary transfer) onto the intermediate transfer belt 51 of the transfer device 50 to form a superimposed toner image in which the respective color toners are superimposed. Is done. The superimposed toner image on the intermediate transfer belt 51 is sent out from the registration roller pair 23 and is collectively transferred by the secondary transfer roller 52 onto the paper P guided by the conveyance guide S1a.

In the fixing device 60, a fixing nip portion N <b> 2 (fixing region) is formed by a pressure contact region between the pair of fixing belts 61 and the pressure roller 62.
The paper P onto which the toner images are collectively transferred in the transfer device 50 is conveyed to the fixing nip portion N2 of the fixing device 60 through the conveyance guide 53 in a state where the toner images are not fixed, and a pair of the fixing belt 61 and the pressure roller By 62, the toner image is fixed by the action of pressure bonding and heating.

  The paper P on which the fixing toner image is formed is discharged and accommodated from the discharge roller pair 69 to the discharge tray portion T on the upper surface of the image forming apparatus 1. Further, in the case of duplex printing, the discharge roller pair 69 is driven reversely and is transported from the reverse transport path S2 to the registration roller pair 23 via the bending device 70 to form an image on the back surface.

(2) Configuration and Operation of the Paper Conveying Unit FIG. 2 is a schematic diagram of the overall configuration of the paper conveying unit including the bending device 70 in the image forming apparatus 1, and FIG. 3 is a schematic cross-sectional view illustrating the fixing nip portion N2 of the fixing device 60. FIG. 4 is a schematic diagram illustrating the state of the paper P conveyed to the fixing nip portion N2, and FIG. 5 is a schematic cross-sectional view of the bending device.
Hereinafter, the configuration of the sheet conveyance unit and the sheet bending action of the image forming apparatus 1 will be described with reference to the drawings.

(2.1) Configuration of the Paper Conveying Unit As shown in FIG. 2, the paper conveying unit in the image forming apparatus 1 includes the paper drawing unit 22, the first paper conveying path S1, the bending device 70, the secondary transfer roller 52, and the conveying. It includes a guide 53, a fixing device 60, and a reverse conveyance path S2.

Just above the front end side of the paper cassette 21 is provided a nudger roller 22a that contacts the front end side of the upper surface of the paper P and feeds the paper P from the paper cassette 21. A feed roller 22b is provided downstream of the nudger roller 22a in the sheet conveying direction.
Below the feed roller 22b, a retard roller (separation roller) 22c is arranged to face the feed roller 22b, and the feed roller 22b and the retard roller 22c form a pair to separate and overlap the paper P. P is fed sheet by sheet (see arrow R1 in FIG. 2).

  A first paper transport path S1 is provided on the downstream side of the feed roller 22b in the paper transport direction to guide the paper P sent out from the feed roller 22b to the registration roller pair 23, and on the upstream side of the registration roller pair 23 in the paper transport direction. A bending device 70 is disposed as a bending means.

  The sheet P that has passed through the nip portion N1 of the bending device 70 is guided to the conveyance guide S1a of the first sheet conveyance path S1 and conveyed to the registration roller pair 23. The toner P held on the intermediate transfer belt 51 by the secondary transfer portion TR formed by the secondary transfer roller 52 and the intermediate transfer belt 51 in a state where the paper P conveyed to the registration roller pair 23 forms a loop and is aligned. The image is transferred at once.

The sheet P on which the toner images are collectively transferred by the secondary transfer unit TR is guided to the back surface of the sheet by the conveyance guide 53 and is conveyed to the fixing nip N2 of the fixing device 60. The fixing device 60 includes an IH (Induction Heating) heater 80, a fixing belt 61 that fixes the toner image by electromagnetic induction heating by the IH heater 80, and a pressure having an elastic body layer 62 a disposed so as to face the fixing belt 61. A roller 62 is provided.
On the inner peripheral side of the fixing belt 61, there is provided a pressing pad 63 that is pressed from the pressure roller 62 through the fixing belt 61 to form the fixing nip portion N2.

In the fixing device 60 having such a configuration, the surface of the fixing belt 61 and the surface of the pressure roller 62 are pressed against each other, so that the surface of the fixing belt 61 is subjected to an application by a load received from the pressure roller 62 at the fixing nip portion N2. The pressure roller 62 is deformed so as to substantially follow the arc shape of the surface. That is, as shown in FIG. 3, the pressure roller 62 bites into the fixing belt 61.
At this time, the elastic layer 62a of the pressure roller 62 is not deformed because the hardness of the elastic layer 62a is based on the hardness of the pressure pad 63 that receives the pressing force of the pressure roller 62 on the inner peripheral side of the fixing belt 61. Also because it is expensive.

As shown in FIG. 4, the paper P conveyed to the fixing nip N2 of the fixing device 60 has its leading end Pa curled to one side of the paper P depending on the case of single-sided printing or double-sided printing. There may be.
Further, even in the case of single-sided printing, the leading end Pa curls toward one of the surfaces in a state where it is fed by the feed roller 22b from the state loaded on the paper cassette 21 according to the environmental humidity. There may be.
Further, it is known that the paper P on which the toner image on the surface is fixed by the fixing device 60 also changes its curl state depending on the image density representing the ratio of the toner image adhesion area on the paper to the area of the paper P.

  When the leading end portion Pa of the paper P conveyed to the fixing nip portion N2 of the fixing device 60 is curled to any surface side of the paper P, the impact is removed from the paper P when entering the fixing nip portion N2. Paper sound (impulse sound) may occur.

  Further, the sheet P on which the toner images are collectively transferred by the secondary transfer unit TR is conveyed to the fixing nip N2 of the fixing device 60 while being guided by the conveyance guide 53 on the back surface of the sheet. Is difficult to be restrained, and there is a possibility that image defects such as white spots in the image, band-like density unevenness called smear, and paper wrinkles may occur.

(2.2) Bending Device As shown in FIG. 5A, the bending device 70 has a sheet P between the metal first roll 71 that drives the conveyed sheet P and the first roll 71. A second roll 72 that presses the paper P against the first roll 71 with the sheet sandwiched therebetween is paired.
The second roll 72 is trapezoidal than the first roll 71, and a roll made of an elastic body whose nip portion N <b> 1 (see FIG. 5B) with the first roll 71 is deformed along the shape of the first roll 71. It is.

The second roll 72 is instructed by a cam mechanism 73 as pressing means. The cam mechanism 73 includes a cam receiving member 73A and a rotating cam 73B. The second roll 72 is supported by the cam receiving member 73A so that the shaft portion 72a is rotatable. The cam receiving member 73A has one end 73Aa at the rotating shaft portion. It is rotatably supported by the apparatus main body around 73Ac.
The other end 73Ab of the cam receiving member 73A receives a pressing force according to the rotation angle of the rotating cam 73B that receives the driving force (see R2 in FIG. 5B), and the cam receiving member 73A rotates (see FIG. 5B). (See R3 in FIG. 5B).

  As shown in FIG. 5B, the bending device 70 changes the amount of biting of the second roll 72 into the first roll 71 by the rotation of the cam receiving member 74 according to the rotation angle of the rotary cam 75. Thus, the amount of bending of the recording medium conveyed while being sandwiched by the nip portion N1 is changed.

(3) Operation of Curving Device FIG. 6 is a schematic diagram for explaining the correction of the curled state of the paper P in the curving device 70, and FIG. 7 shows the measurement result of the paper sound when the curled state of the leading end portion Pa of the paper P is changed. It is a graph of.
Hereinafter, the operation and action of the bending device 70 will be described with reference to the drawings.

  The image forming apparatus 1 according to the present embodiment acquires transport path information and thickness information of the paper P, image density information of a toner image formed on the paper P, and environmental humidity information, and transport path information and thickness information. The amount of biting of the second roll 72 relative to the first roll 71 is adjusted according to the image density information and the humidity information.

  Here, in the image forming apparatus 1, the curl amount of the leading edge Pa of the paper P conveyed to the nip portion N <b> 1 of the bending device 70 depends on whether it is single-sided printing or double-sided printing, including upper curl and down curl directions. It is predicted in advance according to the distinction, paper attribute information such as paper quality and basis weight of the paper P to be used, image density information and environmental humidity information in the case of duplex printing.

  Corresponding to the predicted curl amount, in a state where the paper P is fed from the bending device 70, the leading end portion Pa of the paper P is pressed so as to curl in the bending direction of the fixing nip portion N2 in the fixing device 60. That is, the paper P is corrected so as to be in an upper curl state with respect to the conveyance direction to the fixing nip portion N2.

  Specifically, as shown in FIG. 6, the rotating cam 73B is rotated by a motor (not shown) so that the leading end Pa of the paper P becomes an upper curl corresponding to the predicted curl direction and curl amount. As a result, the rotation cam 73B rotates to a predetermined rotation angle, whereby the cam receiving member 73A is rotationally displaced to a predetermined position.

  Along with the rotational displacement of the cam receiving member 73A, the large-diameter second roll 72 comes into contact with the metal first roll 71 with a predetermined amount of biting, and the second roll 72 is driven accordingly. As a result, the curl direction and the curl amount of the paper P are corrected so as to be in an upper curl state with a predetermined curl amount.

The fixing nip formed by deforming the sheet P, which has been corrected so as to be in an upper curl state with respect to the conveyance direction of the sheet P to the fixing nip portion N2, substantially along the arc shape of the surface of the pressure roller 62. When entering the portion N2, the leading end portion Pa of the paper P enters in accordance with the curvature direction of the pressure roller 62, and the behavior change of the paper P in the secondary transfer portion TR from the conveyance guide 53 of the paper P changes. It is suppressed.
As a result, a shocking paper sound (impulse sound) generated from the paper P is suppressed, and the occurrence of image defects such as white spots, smears, and paper wrinkles is suppressed.

FIG. 7 shows the sheet sound when the image forming apparatus 1 enters the fixing nip portion N2 by using the sheet P in which the curling state of the leading end portion Pa of the sheet P is changed by changing the amount of biting of the bending device 70. It is the graph which showed the average value of 5 times which measured.
As shown in FIG. 7, when the curl state of the leading end portion Pa of the paper P is almost not curled (A), the curl state of the leading end Pa of the paper P is in the upper curl state (B). As a result, the peak sound pressure level as a sound was low.

  On the other hand, when the curled state of the leading end portion Pa of the paper P is the down curled state (C), the curled state of the leading end portion Pa of the paper P is almost absent (A), and the curled state of the leading end portion Pa of the paper P is the upper curl. In any state (B), the peak sound pressure level as the paper sound was high.

  In the state where the leading edge Pa of the paper P is hardly curled (A) and the curled state of the leading edge Pa of the paper P is the upper curled state (B), the occurrence of image defects was not recognized. When the curled state of the tip end portion Pa of the P is in the down curled state (C), smear may occur.

As described above, the image forming apparatus 1 according to the present embodiment includes, as the bending device 70, the first roll 71 that drives the conveyed paper P, the first roll 71 having a larger diameter than the first roll 71. The second roll 72 is deformed along the shape of the first roll 71, and the cam mechanism 73 adjusts the amount of biting by pressing the second roll 72 against the first roll 71.
The cam mechanism 73 determines the amount of biting of the second roll 72 with respect to the first roll 71 according to the conveyance path information of the paper P, thickness information, image density information of the toner image formed on the paper P, and environmental humidity information. Adjustment is made so that the curl direction and the curl amount of the paper P are in an upper curl state with a predetermined curl amount.

  As a result, when the paper P enters the fixing nip portion N2 of the fixing device 60, the leading end portion Pa of the paper P enters in the direction of the curvature of the pressure roller 62, and the paper P conveyance guide 53 To the secondary transfer section TR, the change in the behavior of the paper P is suppressed, the paper sound (impulse sound) generated from the paper P is suppressed, and the occurrence of image defects such as white spots, smears, paper wrinkles, etc. is suppressed. Is done.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 10 ... Control apparatus 20 ... Paper feed apparatus 30 ... Photoconductor unit 40 ... Developing apparatus 50 ... Transfer apparatus 51 ... Intermediate transfer belt 52 ... Secondary transfer roller 53 ... Conveying guide 60 ... Fixing device 61 ... Fixing belt 62 ... Pressure roller 63 ... Press pad 70 ... Bending device 71 ... First roll 72 .... Second roll 73 ... Cam mechanism P ... Paper N1 ... Nip part N2 ... Fixing nip part

Claims (6)

Image forming means for forming a toner image on a recording medium;
Fixing means for fixing the toner image to the recording medium by heating and pressurizing the recording material, onto which the toner image has been transferred by the image forming means, at a press contact portion;
A conveyance path provided upstream of the fixing unit in the conveyance direction of the recording medium;
A bending means provided in the conveyance path, wherein the recording medium is bent in a bending direction of the press contact portion in the conveyance direction;
An image forming apparatus. A first roll for driving the recording medium, the bending means;
The recording medium is sandwiched between the first roll and the recording medium is pressed against the first roll. The diameter of the recording medium is larger than that of the first roll, and the contact portion with the first roll is the first roll. A second roll deforming along the shape of
Pressing means for pressing the second roll and the first roll together,
The image forming apparatus according to claim 1. The pressing means acquires transport path information of the recording medium, and adjusts the amount of biting of the second roll relative to the first roll according to the transport path information;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The pressing unit acquires thickness information of the recording medium, acquires image density information of the toner image formed on the recording medium and environmental humidity information, and acquires the thickness information, the image density information, and According to the humidity information, adjust the amount of biting of the second roll with respect to the first roll,
The image forming apparatus according to claim 3.
Place. The pressing means presses the first roll and the second roll through a cam;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The bending means bends the tip of the recording medium;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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