JP2011118009A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transfer toner image held on the surface of an image holding member to a recording medium appropriately, even if the recording medium is considerably thick, when the toner image held on the surface of the image holding member is transferred to the recording medium by guiding the recording medium between the image holding member and a transfer roller. <P>SOLUTION: A recording medium S is guided between the surface of the image holding member 14 with a toner image held thereon and the transfer roller 17 with an elastic layer 17b formed along the periphery of a roller member 17a, and the toner image held on the surface of the image holding member is transferred to the recording medium. In this case, the amount of deformation of the recess of the elastic layer of the transfer roller in the thickness direction thereof when the thickest recording medium is guided between the surface of the image holding member and the transfer roller is set to &le;30% of the thickest recording medium. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a complex machine of these. In particular, an image holding member that moves while holding a toner image on the surface, a transfer roller having an elastic layer formed on the outer periphery of the roller member, and an elastic biasing means that presses the transfer roller against the surface of the image holding member. An image forming apparatus that guides a recording medium between a surface of an image holding member on which a toner image is held and a transfer roller, and transfers the toner image held on the surface of the image holding member to the recording medium. Even if the recording medium is thick, the toner image held on the surface of the image holding member is appropriately transferred to the recording medium.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a composite machine thereof, a toner image held on the surface of an image holding member such as a photosensitive drum or an intermediate transfer belt when forming a toner image on a recording medium Is transferred to a recording medium, and the toner image thus transferred is fixed on the recording medium.

  Here, when the toner image is transferred to the recording medium as described above, the transfer roller is pressed against the surface of the image holding member, and between the transfer roller and the surface of the image holding member holding the toner image. In addition, the recording medium is guided to the transfer roller, and an appropriate transfer bias voltage is applied to the transfer roller so that the toner image held on the surface of the image holding member is transferred to the recording medium.

  Further, in the image forming apparatus as described above, images are formed on various recording media.

  Here, when the recording medium is guided between the transfer roller and the surface of the image holding member on which the toner image is held, if the recording medium is thick, the recording medium is interposed between the transfer roller and the image holding member. There is a problem that the load at the time of entering temporarily increases, the moving speed of the image holding member changes, and the toner image on the surface of the image holding member cannot be properly transferred to the recording medium. In addition, in the intermediate transfer belt formed into an endless belt that is driven to rotate around the rotation roller, a deviation occurs between the intermediate transfer belt and the rotation roller, and the toner image on the surface of the image holding member is recorded. There is also a problem that it is impossible to transfer the image properly to the medium.

  Conventionally, as shown in Patent Document 1, a load applying roller is provided inside the intermediate transfer belt and a load facing roller is provided outside, and the intermediate transfer belt is sandwiched between the load applying roller and the load facing roller. Thus, there has been proposed a technique in which a load on the conveyance of the intermediate transfer belt is applied to reduce the speed fluctuation of the intermediate transfer belt.

  However, even in this case, when a recording medium having a large thickness enters between the transfer roller and an image holding member such as an intermediate transfer belt, the load is sufficiently suppressed from being temporarily increased. However, the moving speed of the image holding member etc. fluctuated and the toner image could not be properly transferred to the recording medium. Further, in the above case, a load applying roller and a load facing roller that sandwich the intermediate transfer belt are required, and the cost is high. In order to reduce the speed fluctuation, it is necessary to appropriately control the load on the conveyance of the intermediate transfer belt, and there is a problem that the control becomes difficult.

JP 2008-139749 A

  The present invention provides an image formation in which a recording medium is guided between a surface of an image holding member on which a toner image is held and a transfer roller, and the toner image held on the surface of the image holding member is transferred to the recording medium. An object of the present invention is to allow a toner image held on the surface of an image holding member to be appropriately transferred to a recording medium with a simple configuration even if the recording medium has a large thickness.

  In the present invention, in order to solve the above-described problems, an image holding member that moves while holding a toner image on the surface, a transfer roller having an elastic layer formed on the outer periphery of the roller member, and the transfer roller described above Elastic biasing means that presses against the surface of the image holding member, the recording medium is guided between the surface of the image holding member holding the toner image and the transfer roller, and held on the surface of the image holding member. In an image forming apparatus for transferring a toner image to a recording medium, a recording medium having a different thickness is guided between the surface of the image holding member and the transfer roller, and the toner image held on the surface of the image holding member is transferred to the recording medium. When the thickest recording medium is guided between the surface of the image holding member and the transfer roller, the amount of dent deformation in the thickness direction of the elastic layer of the transfer roller is 30% of the thickness of the thickest recording medium. less than Was to so that.

  Here, when the thickest recording medium is guided between the surface of the image holding member and the transfer roller as described above, the amount of dent deformation in the thickness direction of the elastic layer of the transfer roller is that of the thickest recording medium. When the thickness is 30% or less, the pressing force for pressing the transfer roller against the surface of the image holding member can be adjusted by the elastic biasing means.

  The image holding member is not particularly limited as long as the image holding member moves while holding the toner image on the surface. However, the image holding member is an endless belt-like image holding member that is driven to rotate across a plurality of rotating rollers. The rotating roller and the transfer roller are made to face each other through the image holding member.

  An elastic biasing member such as a spring member can be used as the elastic biasing unit that presses the transfer roller against the surface of the image holding member. Further, in adjusting the pressing force by the elastic urging means so that the amount of dent deformation in the thickness direction of the elastic layer of the transfer roller is 30% or less with respect to the thickness of the thickest recording medium as described above, For example, one end portion of a rotating arm that rotates around a fulcrum is attached to each end portion of a spring member provided along the transfer roller, and the above-described transfer roller is provided by the other end portion of the rotating arm. Can be pressed against the surface of the image holding member.

  Here, in the image forming apparatus of the present invention, the thickness of the recording medium guided between the surface of the image holding member holding the toner image and the transfer roller is not particularly limited, but the toner held on the surface of the image holding member This is effective when an image is appropriately transferred to a recording medium having a thickness of 0.3 mm or more.

  In the image forming apparatus of the present invention, the recording medium is guided between the surface of the image holding member holding the toner image and the transfer roller having the elastic layer formed on the outer periphery of the roller member, and the surface of the image holding member. When transferring the held toner image to the recording medium, the thickness of the elastic layer of the transfer roller is deformed when the thickest recording medium is guided between the surface of the image holding member and the transfer roller as described above. The amount was adjusted to 30% or less with respect to the thickness of the thickest recording medium. For this reason, even when a recording medium having a large thickness enters between the transfer roller and the image holding member, the amount of dent deformation in the thickness direction of the elastic layer of the transfer roller decreases, and the load temporarily increases. It will be sufficiently suppressed.

  As a result, even when a thick recording medium having a thickness of 0.3 mm or more is guided between the transfer roller and the image holding member, and the toner image held on the surface of the image holding member is transferred to the recording medium, Fluctuations in the moving speed of the image holding member are suppressed, and the toner image is appropriately transferred to a thick recording medium. In particular, when an endless belt-like image holding member that is spanned between a plurality of rotating rollers and driven to rotate is used and the rotating roller and the transfer roller are opposed to each other through the image holding member, thick recording is performed. When the medium enters between the transfer roller and the image holding member, a load applied to the image holding member is reduced, and a shift between the image holding member and the rotating roller is prevented, The toner image on the surface of the image holding member is appropriately transferred to a thick recording medium.

  Further, when the pressing force of the transfer roller that presses against the surface of the image holding member is adjusted by the elastic biasing means, the end portions on both sides of the spring member provided along the transfer roller are respectively rotated around the fulcrum. A recording medium guided between the transfer roller and the image holding member by attaching one end of the rotating arm and pressing the transfer roller against the surface of the image holding member by the other end of the rotating arm. The rotating arm is rotated according to the thickness of the image, and the pressing force of the transfer roller against the surface of the image holding member is appropriately adjusted, so that the amount of dent deformation in the thickness direction of the elastic layer of the transfer roller is appropriately controlled. Will come to be.

1 is a schematic explanatory view showing an image forming apparatus according to an embodiment of the present invention. It is a schematic side view of the transfer roller used in the image forming apparatus of the above embodiment. In the image forming apparatus of the above embodiment, a partial plan view illustrating a state in which the transfer roller is pressed against the surface of the intermediate transfer belt at a position facing one rotation roller by the elastic biasing unit. In the image forming apparatus of the above-described embodiment, (A) is a partial side view illustrating a state before the recording medium is guided between the intermediate transfer belt and the transfer roller, and (B) is an intermediate transfer belt and the transfer roller. FIG. 5 is a partial side view illustrating a state where a recording sheet having a thickness of T is guided between the two and the elastic layer of the transfer roller is deformed. In the experimental example, a thick recording sheet is obtained by elastically urging and pressing the transfer roller against the intermediate transfer belt by four types of spring members having spring constants of 0.17, 1.0, 1.3, and 2.1. In the experimental example in which the toner is guided between the transfer roller and the intermediate transfer belt, the spring constant of the spring member, the concave deformation rate of the elastic layer in the thickness direction of the transfer roller, and the rotation roller that rotationally drives the intermediate transfer belt It is the figure which showed the relationship with the maximum variation | change_quantity of a torque. In the above experimental example, when a spring member having a spring constant of 1.0 is used, it is a diagram illustrating a change in torque in a rotating roller that rotationally drives an intermediate transfer belt. In the above experimental example, when a spring member having a spring constant of 2.1 is used, it is a diagram illustrating a change in torque in a rotating roller that rotationally drives an intermediate transfer belt. In the image forming apparatus of the above-described embodiment, it is a partial explanatory view showing a modified example of the elastic urging means for pressing the transfer roller against the surface of the intermediate transfer belt.

  Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the image forming apparatus according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  In the image forming apparatus according to this embodiment, as shown in FIG. 1, four developing devices 13 each containing a developer are provided corresponding to the four photosensitive drums 10. In this developer, black, yellow, magenta, and cyan toners are used with different toner colors.

  In this image forming apparatus, the respective photosensitive drums 10 are rotated so that the surface of each photosensitive drum 10 is charged by the charging device 11, and the photosensitive drums 10 thus charged are charged. The latent image forming device 12 performs exposure according to the image formation information, and forms an electrostatic latent image on the surface of each photosensitive drum 10.

  Next, toner of a predetermined color is supplied from the corresponding developing device 13 to the electrostatic latent image on each photosensitive drum 10 and developed on each photosensitive drum 10 on which the electrostatic latent image is thus formed. Thus, a toner image of each color is formed on the surface of each photoconductive drum 10.

  Further, each of the primary drums is opposed to each of the photosensitive drums 10 via an intermediate transfer belt (image holding member) 14 in the form of an endless belt that is driven to rotate around a plurality of rotating rollers 14a. A transfer roller 15 is provided.

  Then, the toner images of the respective colors formed on the respective photosensitive drums 10 as described above are primarily transferred sequentially to the surface of the intermediate transfer belt 14 by the respective primary transfer rollers 15, and this intermediate transfer belt 14. A full-color toner image is formed on the surface of the toner. On the other hand, residues such as toner remaining on the surface of each photosensitive drum 10 without being transferred to the intermediate transfer belt 14 are removed by the first cleaning device 16.

  Further, a transfer roller 17 having an elastic layer 17b formed on the outer periphery of a roller member 17a as shown in FIGS. 1 and 2 is provided at a position facing the one rotation roller 14a over which the intermediate transfer belt 14 is bridged. The surface of the intermediate transfer belt 14 is pressed by an elastic biasing means (not shown).

  The recording sheet (recording medium) S accommodated in the lower part of the image forming apparatus is guided between the intermediate transfer belt 14 and the transfer roller 17 and formed on the surface of the intermediate transfer belt 14 as described above. The full color toner image is guided to the position of the transfer roller 17, and the full color toner image formed on the intermediate transfer belt 14 is transferred onto the recording sheet S by the transfer roller 17.

  Thereafter, the recording sheet S on which the full-color toner image is transferred is guided to the fixing device 18, and the transferred full-color toner image is fixed on the recording sheet S, and then the recording on which the full-color toner image is fixed in this way. The sheet S is discharged. On the other hand, the toner and other residues remaining on the intermediate transfer belt 14 without being transferred to the recording sheet S are removed from the intermediate transfer belt 14 by the second cleaning device 19.

  Here, in the embodiment shown in FIG. 3, when the transfer roller 17 is pressed against the surface of the intermediate transfer belt 14 by the elastic biasing means at the position facing the one rotating roller 14 a as described above, in the embodiment shown in FIG. As means 20, a spring member 21 is attached to each bearing member 17 d provided on each shaft 17 c extending from the transfer roller 17 on both sides, and the bearing member 17 d is directed toward the intermediate transfer belt 14 by the spring member 21. The transfer roller 17 is pressed against the surface of the intermediate transfer belt 14 by being elastically biased.

In this embodiment, various recording media S having different thicknesses are guided between the intermediate transfer belt 14 and the transfer roller 17, and a toner image formed on the intermediate transfer belt 14 is recorded by the transfer roller 17. In transferring to the sheet S, the spring constant of the spring member 21 is set appropriately. Then, by appropriately setting the spring constant in the spring member 21 as described above, the transfer before the recording sheet S is guided between the intermediate transfer belt 14 and the transfer roller 17 as shown in FIG. The thickness of the elastic layer 17b of the roller 17 is x ₀ , and the elasticity of the transfer roller 17 when the thickest recording sheet S is guided between the intermediate transfer belt 14 and the transfer roller 17 as shown in FIG. the thickness of the layer 17b in the case of the _{x 1,} the elastic layer 17b of the thickness direction dent deformation amount Δx of the transfer roller 17 ₍₌ x 0 -x ₁₎ is, with respect to the thickness T of the thickest recording sheet S of the 30% or less.

  In this way, when the amount of dent deformation Δx in the thickness direction of the elastic layer 17b of the transfer roller 17 is 30% or less with respect to the thickness T of the thickest recording sheet S, the elastic layer 17b of the transfer roller 17 is. The elastic repulsive force due to the deformation of the intermediate transfer belt is weakened, the load applied to the intermediate transfer belt 14 is reduced, the torque in the rotating roller 14a for rotating the intermediate transfer belt 14 is suppressed, and the movement of the intermediate transfer belt 14 is suppressed. Variations in speed and the like are prevented, and deviations between the intermediate transfer belt 14 and the rotating roller 14a are also suppressed. As a result, even when the thick recording sheet S is used, the toner image is appropriately transferred from the intermediate transfer belt 14 to the recording sheet S by the transfer roller 17.

Here, as an experimental example, a commercially available copying machine (manufactured by Konica Minolta: Bizhub C353) was used, and a thick recording sheet having a basis weight of 420 g / m ² and a thickness of 0.47 mm was used as described above. Four types of spring members having spring constants of 0.17, 1.0, 1.3, and 2.1 were used as the spring members that elastically urge and press the transfer roller against the intermediate transfer belt.

  Then, the recording sheet is guided between the transfer roller pressed by each spring member and the intermediate transfer belt, and a deformation amount Δx in the thickness direction of the elastic layer in the transfer roller pressed by each spring member is obtained. The ratio of the dent deformation amount Δx of the elastic layer to the thickness of the recording sheet (the dent deformation rate) is calculated, and the maximum amount of torque fluctuation in the rotating roller for rotating the intermediate transfer belt is obtained. Is shown in FIG. FIG. 6 shows torque fluctuations in the rotating roller when a spring member having a spring constant of 1.0 is used, and FIG. 7 shows torque fluctuations in the rotating roller when a spring member having a spring constant of 2.1 is used. It was.

  As a result, the smaller the spring constant of the spring member that elastically urges and presses the transfer roller against the intermediate transfer belt, the smaller the deformation rate of the recess in the thickness direction of the elastic layer of the transfer roller, and the intermediate transfer belt is driven to rotate. When the maximum amount of torque fluctuation in the rotating roller is small and the deformation ratio of the elastic layer in the thickness direction of the transfer roller becomes 30% or less, the maximum amount of torque fluctuation in the rotating roller that rotationally drives the intermediate transfer belt is 1. It was less than 50 N · m.

Next, using the four types of spring members having spring constants of 0.17, 1.0, 1.3, and 2.1 as described above, the transfer roller is elastically biased against the intermediate transfer belt and pressed. Each of the ladder pattern images formed on the intermediate transfer belt was transferred to a thick recording sheet having a basis weight of 420 g / m ² and a thickness of 0.47 mm to form a ladder pattern image on each recording sheet. Then, the ladder pattern image formed on each recording sheet in this way is compared with the limit sample of the ladder pattern image. If the ladder pattern image is clearer than the limit sample, ○, the ladder pattern image than the limit sample Is shown in Table 1 below.

  As a result, when a spring member having a spring constant of 0.17 or 1.0 was used and the dent deformation rate in the thickness direction of the elastic layer of the transfer roller was 30% or less, Even when a thick recording sheet is used, the ladder pattern image is appropriately transferred.

  In the above-described embodiment, when the transfer roller 17 is pressed against the surface of the intermediate transfer belt 14 by the elastic biasing means 20, each bearing provided on each shaft 17 c extended on both sides of the transfer roller 17. The members 17d are elastically urged toward the intermediate transfer belt 14 by the spring members 21, respectively, so that the transfer roller 17 is pressed against the surface of the intermediate transfer belt 14. The elastic urging means 20 is as described above. It is not limited to.

  For example, as shown in FIG. 8, the spring member 23 is held by the holding member 22 provided along the axial direction of the transfer roller 17, and the both ends of the spring member 23 are rotated around the fulcrum 24 a respectively. Attaching one end of the rotating arm 24 to be moved, and holding each bearing member 17d provided on each shaft 17c extending from the transfer roller 17 on both sides to the other end of the rotating arm 24, One end side of the rotating arms 24 on both sides is urged outward by the spring member 23, and thereby each bearing member 17d held at the other end of each rotating arm 24 that rotates about the fulcrum 24a. The transfer roller 17 can be pressed against the surface of the intermediate transfer belt 14 by being elastically biased toward the intermediate transfer belt 14. In this way, even if the spring member 23 is lengthened, the spring member 23 is prevented from being bent and corresponds to the thickness of the recording sheet S guided between the transfer roller 17 and the intermediate transfer belt 14. Each of the rotating arms 24 is rotated against the spring member 23, and the pressing force of the transfer roller 17 against the surface of the intermediate transfer belt 14 is appropriately adjusted, so that the elastic layer 17b of the transfer roller 17 in the thickness direction is adjusted. The amount of dent deformation can be appropriately controlled.

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 11 Charging apparatus 12 Latent image forming apparatus 13 Developing apparatus 14 Intermediate transfer belt (image holding member)
14a Rotating roller 14 Primary transfer device 15 Primary transfer roller 16 First cleaning device 17 Transfer roller 17a Roller member 17b Elastic layer 17c Shaft 17d Bearing member 18 Fixing device 19 Second cleaning device 20 Elastic biasing means 21 Spring member 22 Holding member 23 Spring member 24 Rotating arm 24a Support point S Recording sheet (recording medium)
T Recording sheet thickness

Claims (6)

  An image holding member that moves while holding a toner image on the surface, a transfer roller having an elastic layer formed on the outer periphery of the roller member, and an elastic biasing means that presses the transfer roller against the surface of the image holding member. In the image forming apparatus, the recording medium is guided between the surface of the image holding member on which the toner image is held and the transfer roller, and the toner image held on the surface of the image holding member is transferred to the recording medium. When a different recording medium is guided between the surface of the image holding member and the transfer roller to transfer the toner image held on the surface of the image holding member to the recording medium, the thickest recording medium is transferred to the surface of the image holding member. An image forming apparatus characterized in that a deformation amount of a concave portion in a thickness direction of an elastic layer of a transfer roller when guided between the rollers is 30% or less with respect to a thickness of the thickest recording medium.   2. The image forming apparatus according to claim 1, wherein the elastic recording member adjusts a pressing force for pressing the transfer roller against the surface of the image holding member by the elastic urging unit, whereby the thickest recording medium is formed on the surface of the image holding member and the transfer roller. An image forming apparatus in which the amount of deformation in the thickness direction of the elastic layer of the transfer roller when it is guided between the two is 30% or less with respect to the thickness of the thickest recording medium.   3. The image forming apparatus according to claim 1 or 2, wherein an endless belt-shaped image holding member is spanned between a plurality of rotating rollers and driven to rotate, and the rotating roller and the transfer roller are passed through the image holding member. And an image forming apparatus characterized by facing each other.   4. The image forming apparatus according to claim 1, wherein the thickest recording medium has a thickness of 0.3 mm or more.   5. The image forming apparatus according to claim 1, wherein a spring member is used as the elastic urging unit.   6. The image forming apparatus according to claim 1, wherein the elastic urging means is pivoted around the fulcrum at the ends of both sides of the spring member provided along the transfer roller. An image forming apparatus, wherein one end of an arm is attached and the transfer roller is pressed against the surface of the image holding member by the other end of the rotating arm.

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