JP2006267146A - Transfer device and image forming apparatus using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device for preventing image defects such as image extension within an adjustment range of a prescribed amount of pressure-welding, and to inexpensively provide an image forming apparatus using it in a simple configuration. <P>SOLUTION: The transfer device 11 for transferring toner images onto a recording material 18 by inserting the recording material 18 into a nip part includes an intermediate transfer body 9 for forming the toner images, a transfer roll 12 arranged oppositely on the intermediate transfer body 9 for forming the nip part by subjecting the intermediate transfer body 9 to pressure welding, and an adjusting means for adjusting the pressure contact amount when forming the nip part. The transfer roll 12 comprises a shaft part 120 for forming a rotating shaft, and a single layer elastic layer part 125 formed on the outer periphery of the shaft part 120. When forming the nip part, a notch 125S directed from the outer periphery side to a rotating shaft center is formed, extended in a substantially axial direction in a deformation region of the elastic layer part 125. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transfer roll of an image forming apparatus using an electrophotographic system or an electrostatic transfer system such as a copying machine, a printer, a facsimile machine, or a multifunction machine of these, and more specifically, formed on an electrostatic latent image carrier. The present invention relates to a transfer device that transfers an image to a recording material via an intermediate transfer member and an image forming apparatus using the transfer device.

JP 2000-284555 A

  Conventionally, as a color image forming apparatus such as a color copying machine or a color printer to which an electrophotographic method is applied, a plurality of colors corresponding to each color such as yellow (Y), magenta (M), cyan (C), and black (BK) are used. An image forming unit is provided, and each color toner image sequentially formed on the photosensitive drum of each image forming unit is temporarily transferred onto the intermediate transfer member in a multiplex primary manner, and then transferred onto the intermediate transfer member in a multiplex manner. The toner image was secondarily transferred onto a recording material by a secondary transfer device, and then the toner image was heated and pressed to be fixed on the recording material to form a color image. There is a so-called intermediate transfer type image forming apparatus. The transfer device in the image forming apparatus using such an intermediate transfer member forms, for example, a transfer nip portion between a pair of rolls opposed to each other via an intermediate transfer belt as an intermediate transfer member. By inserting the recording material through the nip portion, the toner images are collectively transferred onto the recording material.

  In such a transfer apparatus, if a speed difference occurs between the recording material and the intermediate transfer member or the transfer roll at the transfer nip, an image defect such as image elongation occurs. The transfer roll disposed opposite to the intermediate transfer belt via the intermediate transfer belt is configured to be movable with respect to the opposed intermediate transfer belt and the backup roll, thereby reducing the amount of pressure contact at both axial ends when forming the nip portion. Adjustments have been made to reduce the speed difference between the two axial ends of the recording material, or to detect the pressure contact amount of the transfer roll and correct the recording material conveyance speed to prevent image defects such as image stretching. (For example, refer to Patent Document 1).

  For example, the image forming apparatus disclosed in Patent Document 1 detects an image on the secondary transfer roller transferred from the intermediate transfer belt by a sensor, detects the pressure contact amount of the secondary transfer roll, and uses this detection information. Based on this, the conveyance speed correction of the recording material and the pixel address position correction are performed to prevent the occurrence of image defects.

  By the way, at both ends in the axial direction of the transfer roll forming the transfer nip portion (hereinafter, one end side in the axial direction is also referred to as the In side and the other end side is also referred to as the Out side), When the difference occurs, the transfer roll is twisted. At this time, a torsional reaction force that depends on the roll hardness and the amount of twist acts on the transfer roll, and the roll torsional reaction force that depends on the amount of pressure contact on the In side and Out side of the transfer roll acts on the recording material. The speed difference between the In side and the Out side of the material can be eliminated. In other words, by adjusting the pressure contact amount of the transfer roll when forming the transfer nip on the In side and the Out side, respectively, the speed difference between the In side and the Out side of the recording material is eliminated, and image defects such as image stretching are prevented. On the other hand, if the amount of pressure contact is increased, transfer defects and the like are affected and the image quality is affected. Therefore, the range of the pressure contact amount that can be substantially adjusted is very narrow. .

  However, in the prior art disclosed in the above-mentioned patent document, even if a difference in speed occurs between the In side and the Out side of the recording material due to the difference in the pressure contact amount between the In side and the Out side of the transfer nip portion, The generated torsional reaction force is small, and within the predetermined pressure contact amount adjustment range, the speed difference between the In side and Out side of the recording material cannot be reduced, and the image parallelism cannot be maintained. It was.

  That is, there is a problem that it is difficult to prevent image defects such as image expansion within a predetermined pressure contact adjustment range that does not impair image quality.

  In view of the above-described problems of the prior art, the present invention provides a transfer device capable of preventing image defects such as image expansion within a predetermined pressure contact adjustment range, and image formation using the transfer device. An object of the present invention is to provide an apparatus with a simple configuration at low cost.

  In order to achieve the above object, a transfer device of the present invention forms an intermediate transfer member on which a toner image is formed and a nip portion that is disposed opposite to the intermediate transfer member and presses the intermediate transfer member. A transfer apparatus that includes a transfer roll and an adjusting unit that adjusts a pressure contact amount when the nip portion is formed, and passes a recording material through the nip portion to transfer a toner image onto the recording material. The transfer roll includes a shaft portion that forms a rotating shaft and a single-layer elastic layer portion formed on the outer periphery of the shaft portion, and is formed in a deformation region of the elastic layer portion when the nip portion is formed. Is characterized in that a cut from its outer peripheral side toward the center of the rotation axis extends so as to extend substantially in the axial direction.

  Here, the single-layer elastic layer refers to an elastic layer formed of a single material having the same mechanical properties and electrical properties.

  Further, the pressure contact amount refers to the amount of biting (elastic deformation amount) of the transfer roll with respect to the intermediate transfer member when the nip portion is formed.

  In the transfer device of the present invention configured as described above, the transfer roll includes a shaft portion that forms a rotating shaft and a single-layer elastic layer portion formed on the outer periphery of the shaft portion, and forms a nip portion. In the deformation region of the elastic layer portion, a cut from the outer peripheral side toward the center of the rotation axis is formed so as to extend substantially in the axial direction, so that the image quality is limited. Within the adjustment range of the pressure contact amount of the transfer roll, a sufficient torsional reaction force can be generated on the transfer roll to reduce the speed difference between the widthwise ends of the recording material, thereby preventing image defects such as image elongation. The transfer roll can be provided at a low cost with a simple configuration.

  The elastic layer portion may have Asker C hardness of 50 degrees or more.

  Here, the Asker C hardness refers to the hardness when measured with an Asker C type hardness tester in accordance with the Japan Rubber Association standard SRIS 0101.

  In this case, since the elastic layer portion has an Asker C hardness of 50 degrees or more, a sufficient torsional reaction force is generated in the transfer roll within the adjustment range where the pressure contact amount is limited, and the image parallelism is maintained. It is possible to realize the hardness of the transfer roll that can be used.

  Further, the depth of the cut may be half or more of the thickness of the elastic layer portion.

  In this case, since the depth of cut is more than half of the thickness of the elastic layer portion, a sufficient twisting reaction force is generated on the transfer roll within the adjustment range where the amount of press contact is limited, thereby improving the image parallelism. The cut of the elastic layer part that can be maintained can be realized.

  In addition, the transfer device of the present invention includes an intermediate transfer member on which a toner image is formed, a transfer roll that is disposed to face the intermediate transfer member and forms a nip portion by pressing the intermediate transfer member, and the nip. Adjusting means for adjusting the amount of pressure contact when forming the portion, and a transfer device for transferring the toner image onto the recording material by inserting a recording material through the nip portion, And an elastic layer portion formed on the outer periphery of the shaft portion, wherein the elastic layer portion has a low hardness coarse material region and a high hardness dense material region alternately in the circumferential direction. And the cross-sectional area of the low hardness region in the deformation region of the elastic layer portion when forming the nip portion and perpendicular to the rotation axis of the transfer roll is the high hardness region. It is characterized by being larger than the cross-sectional area That.

  Here, the low hardness region refers to an Asker C hardness of 10 degrees or less, and the high hardness region refers to an Asker C hardness of 40 to 100 degrees or less.

  When configured in this manner, the transfer roll includes a shaft portion that forms a rotation axis and an elastic layer portion formed on the outer periphery of the shaft portion, and the elastic layer portion has a low hardness coarse material region. And a dense material region having high hardness are alternately formed in the circumferential direction, and are within the deformation region of the elastic layer portion when forming the nip portion, and are low in a cross section perpendicular to the rotation axis of the transfer roll. Since the cross-sectional area of the hardness region is larger than that of the high-hardness region, sufficient torsional reaction force is generated in the transfer roll within the limited adjustment range of the pressure contact amount of the transfer roll in order to maintain image quality. Thus, a transfer roll capable of reducing the speed difference between the end portions in the width direction of the recording material and preventing image defects such as image elongation can be provided at a low cost with a simple configuration.

  In the above, the adjusting means controls the pressure contact amount of the transfer roll so that the parallelism becomes zero according to the ambient temperature and humidity based on the relationship between the temperature and humidity obtained in advance and the parallelism inclination. May be.

  Here, the parallelism inclination refers to a numerical value defined by {(difference between lengths of parallel lines formed in the conveyance direction at both ends of the recording material) / roll biting amount}.

  When configured in this way, the adjusting means presses the transfer roll so that the parallelism becomes zero according to the ambient temperature and humidity based on the relationship between the temperature and humidity determined in advance. Since the amount is controlled, more precise control of the parallelism of the recording material can be performed according to environmental conditions.

  Note that the present invention is not limited to the transfer device described above, but also targets an image forming apparatus including such a transfer device.

  According to the present invention, in order to maintain the image quality, within the limited adjustment range of the pressure contact amount of the transfer roll, the speed difference between the end portions in the width direction of the recording material is reduced, and image defects such as image elongation are reduced. A transfer device that can be prevented can be realized with a simple configuration at low cost.

<First embodiment>

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, an example of an image forming apparatus to which the developing device according to the present invention can be applied will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a tandem type color image forming apparatus 100 according to the present invention.

  In this image forming apparatus 100, color image information sent from an image reading device (not shown), a personal computer, an image data input device or the like is input, and image processing is performed on the input image information. Is called.

  In FIG. 1, 1Y, 1M, 1C, and 1K are electrophotographic image forming units that form toner images of yellow, magenta, cyan, and black, respectively, and are endless intermediate transfer stretched by a plurality of stretch rolls. 1Y, 1M, 1C, and 1K are arranged in series in the order in which the belt 9 travels.

  The image forming units 1Y, 1M, 1C, and 1K according to the present embodiment adopt an electrophotographic system, for example, and are so-called tandem type full-color image forming units. Specifically, the color image forming units 1Y to 1K of four colors (in this embodiment, Y (yellow), M (magenta), C (cyan), K (black)) are arranged in the horizontal direction (right in the figure). The intermediate transfer belt 9 is circulated and conveyed in a predetermined direction (in this example, clockwise in the figure) along the arrangement direction of the image forming units 1Y to 1K. Further, color toner cartridges 10Y to 10K corresponding to the respective image forming units 1Y to 1K are disposed above them.

  Each of the image forming units 1Y to 1K includes, for example, photosensitive drums 2Y to 2K, which are electrostatic latent image carriers that form and carry toner images of the respective components, and around the photosensitive drums 2Y to 2K. The chargers 3Y to 3K for charging the photosensitive drums 2Y to 2K, the laser scanning devices 4Y to 4K for writing the electrostatic latent images on the photosensitive drums 2Y to 2K, and the toner of each component are accommodated. Developing devices 5Y to 5K that visualize electrostatic latent images on the photosensitive drums 2Y to 2K, and each component toner image on the photosensitive drums 2Y to 2K are transferred onto the intermediate transfer belt 9, for example, a transfer roll. Electrophotographic devices such as primary transfer devices 6Y to 6K, cleaners 7Y to 7K for cleaning residual toner on the photosensitive drums 2Y to 2K, and static eliminators 8Y to 8K are provided.

  The intermediate transfer belt 9 is circulated and conveyed by being stretched around a plurality of stretching rolls, and the electrostatic latent image carriers 2Y, 2M corresponding to the electrophotographic image forming units 1Y, 1M, 1C, 1K. , 2C, 2K are respectively inserted between the primary transfer means 6Y, 6M, 6C, 6K arranged opposite to each other.

In addition, the intermediate transfer belt in the present embodiment is a material containing a suitable amount of carbon black or the like as a conductive agent in resins such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate, acrylic, vinyl chloride, or various rubbers. A material having a thickness of about 0.1 mm and a volume resistivity of 10 ⁶ to 10 ¹⁴ Ω · cm is used.

  Further, the secondary transfer device 11 in the present embodiment includes a backup roll 13 that stretches the intermediate transfer belt 9 and a secondary transfer roll 12 that is disposed to face the backup roll 13.

Here, the transfer roll 12 is formed of a foamed urethane rubber having a volume resistivity of 10 ⁴ to 10 ⁶ Ω · cm, and the transfer roll 12 has a volume resistivity and a material density (foaming rate) of the transfer roll 12. The hardness is adjusted. Reference numeral 14 denotes a cleaner for cleaning the intermediate transfer belt 9.

  Next, an image forming operation on the intermediate transfer belt 9 in the image forming apparatus configured as described above will be described using the image forming unit 1Y that forms a yellow toner image as a representative example.

  First, the surface of the photosensitive drum 2Y is uniformly charged by the uniform charger 3Y. Next, image exposure corresponding to the yellow image is performed by the exposure device 4Y, and an electrostatic latent image corresponding to the yellow image is formed on the surface of the photosensitive drum 2Y.

  The electrostatic latent image corresponding to the yellow image is converted into a yellow toner image by the developing device 5Y, and is transferred onto the intermediate transfer belt 9 by the pressing force and electrostatic attraction force of the primary transfer roll 6Y constituting a part of the primary transfer means. The The yellow toner remaining on the photosensitive drum 2Y after the transfer is scraped off by the cleaning device 7Y. The surface of the photosensitive drum 2Y is neutralized by the neutralization device 8Y and then charged again by the uniform charger 3Y for the next image forming cycle.

  When a multicolor image is formed, an image forming process similar to the above is performed at the timing in consideration of the relative position difference between the electrophotographic image forming units 1Y, 1M, 1C, and 1K. This is also performed in the photographic image forming units 1M, 1C, and 1K, and a full color toner image is formed on the intermediate transfer belt 9.

  The full-color toner image formed on the intermediate transfer belt 9 is pressed against the backup roll 13 supporting the intermediate transfer belt 9 on the recording material 18 conveyed to the secondary transfer position at a predetermined timing. The secondary transfer roll 12 is transferred by the pressing force and electrostatic attraction force.

  A predetermined size of the recording material 18 is fed from a paper feed cassette 17 as a recording material storage unit disposed in the lower part of the image forming apparatus 100 by a paper feed roll 17a. The fed recording material 18 is conveyed to a secondary transfer position of the intermediate transfer belt 9 by a plurality of conveyance rolls 19 and registration rolls 20 at a predetermined timing. Then, as described above, the full-color toner image is collectively transferred from the intermediate transfer belt 9 to the recording material 18 by the secondary transfer device 11 including the backup roll 13 and the secondary transfer roll 12. .

  The recording material 18 onto which the full color toner image has been transferred from the intermediate transfer belt 9 is separated from the intermediate transfer belt 9 and then conveyed to a fixing device 15 disposed downstream of the secondary transfer device 11. The fixing device 15 fixes the toner image on the recording material 18 with heat and pressure. The recording material 18 fixed in the fixing device 15 is then discharged onto the paper discharge tray 25 by the discharge rolls 21 and 22.

  Further, the residual toner on the intermediate transfer belt 9 that could not be transferred onto the recording material 18 by the secondary transfer device 11 is conveyed to the intermediate transfer body cleaning device 14 as it is adhered on the intermediate transfer belt 9, and is cleaned. 14 is removed from the intermediate transfer belt 9 to prepare for the next image formation.

  The image forming apparatus according to the present invention is not limited to the above-described tandem type image forming apparatus. For example, a so-called rotary type image forming apparatus in which each color developing unit is collectively accommodated in a rotating body. In addition, the present invention can also be applied to an image forming apparatus using a drum-shaped intermediate transfer body instead of the intermediate transfer belt.

  Next, the configuration of the transfer device 11 according to the present embodiment will be described with reference to FIGS. Here, FIG. 2 is a schematic diagram showing the amount of pressure contact of the transfer roll 12 with respect to the backup roll 13 (hereinafter also referred to as the amount of biting), and FIG. 3 is a schematic diagram for explaining parallelism. In FIG. 2, for the sake of clarity, the intermediate transfer belt 9 is omitted, and the backup roll 13 and the transfer roll 12 are shown in the vertical direction in the figure.

  As shown in FIG. 2, in the transfer device 11 according to the present invention, the transfer roll 12 is formed so as to be movable in the arrow direction in the figure with respect to the backup roll 13. That is, the transfer roll 12 is formed so as to be movable with respect to the backup roll 13 by a known adjustment mechanism (not shown), and the amount of biting into the backup roll 13 is set at both axial ends (in this example, in the figure). , In side and Out side).

  Specifically, for example, as schematically shown in FIG. 3, sample line images Lout and Lin are formed on the In side and Out side on the recording material 18, and the respective line lengths are set to the In side and Out side, respectively. This is detected by a position detection sensor (not shown) provided in the vicinity of the conveyance path, and parallelism is calculated from the detection result.

  Here, the degree of parallelism ΔL means a difference in line length between the Out side and the In side of the line image in the drawing, that is, ΔL (mm) = Lout line length (mm) −Lin line length (mm). And

  Then, the amount of biting of the transfer roll 12 such that the parallelism is zero is calculated from this parallelism ΔL and a predetermined parallelism inclination determined by the configuration of the transfer roll 12, and based on this calculation result, The transfer roll 12 is moved by a known adjusting mechanism so as to realize a predetermined biting amount (pressure contact amount) with respect to the backup roll 13.

  As described above, in the transfer device 11 according to the present embodiment, the adjusting means adjusts the amount of biting on the In side and Out side of the transfer roll 12 with respect to the backup roll 13 based on the detection result of the position detection sensor. Thus, the velocity difference at both axial end portions (In side, Out side) of the recording material 18 is adjusted, and the image parallelism is maintained (parallelism is set to zero).

  Further, since the hardness of the transfer roll 12 slightly changes depending on the ambient temperature and humidity, a temperature and humidity sensor is provided, and the relationship between the ambient temperature and humidity and the parallelism inclination of the transfer roll 12 is obtained in advance. Based on the relational expression or the relational table, the amount of biting of the transfer roll 12 may be controlled by the adjusting means so that the parallelism becomes zero according to the ambient temperature and humidity. As a result, it is possible to control the speed of the recording material with higher accuracy and to control the parallelism more precisely according to the surrounding environmental conditions.

  Next, the relationship between the amount of biting and the parallelism in the transfer device 11 configured as described above will be described with reference to FIG.

  In general, even when the movement amount (pressure contact amount) of the transfer roll 12 is controlled using the adjustment mechanism as described above, it may be difficult to control the speed of the recording material 18 only by controlling the amount of biting.

  For example, if the amount of biting is increased, the pressure contact force at the nip portion becomes excessive, and the image quality is affected. Specifically, a transfer defect such as adhesion of an unfixed toner image on the recording material 18 to the intermediate transfer belt 9 occurs. In particular, when high-quality images are formed, the influence of image defects due to such transfer defects is increased.

  Therefore, in order to maintain the parallelism by controlling the speed of the recording material 18 without impairing the image quality, the allowable adjustment range Ra in which the amount of biting can be controlled is generally narrow as shown in FIG. For example, about ± 0.5 mm).

  In order to eliminate the speed difference between the In side and the Out side of the recording material 18 within the limited adjustment range Ra, that is, to make the parallelism zero, the parallelism determined by the configuration of the transfer roll 12 is used. It is necessary to increase the absolute value of the slope of.

That is, when the relationship between the parallelism and the amount of biting has an inclination as shown by the straight line L _{0 in} the figure, the point P ₀ where the parallelism is zero is outside the allowable range Ra. Since the image quality is deteriorated, it is necessary to realize the relationship (straight line L ₁ ) between the parallelism and the amount of biting that has the point P ₁ where the parallelism becomes zero within the allowable range Ra.

  On the other hand, when the transfer roll 12 is made of, for example, a low-hardness material, the torsion amount is large but the rigidity is small. The reaction force is not transmitted from the In side to the Out side, and the speed of the recording material is not adjusted sufficiently. That is, since the ratio of the change in parallelism to the change in the amount of biting is small, the absolute value of the inclination of parallelism cannot be increased.

  On the other hand, when the transfer roll 12 is made of, for example, a high-hardness material, the rigidity is large but the torsion amount is small. Similarly, the absolute value of the inclination of the parallelism cannot be increased, and the recording material The speed is not adjusted sufficiently.

  Therefore, in the transfer device 11 according to the present invention, the elastic layer portion of the transfer roll 12 is configured to have a predetermined configuration, so that the roll hardness and the twist amount are determined within the adjustment range Ra where the amount of biting is limited. The predetermined roll reaction force is generated, thereby realizing a predetermined parallelism inclination and eliminating the speed difference between the In side and the Out side of the recording material 18, that is, making the parallelism zero. A transfer device 11 that can be used is realized.

  Below, the structure of the transfer roll 12 which concerns on this Embodiment is demonstrated with reference to FIG.

  As shown in FIG. 5, the transfer roll 12 according to the present embodiment is formed of a shaft portion 120 that forms a rotating shaft, and a single-layer elastic layer portion 125 that is formed around the shaft portion 120. Yes. Thus, the cost can be reduced by forming the transfer roll 12 with the single elastic layer portion 125.

  Furthermore, the transfer roll 12 in the present embodiment is formed with radial cuts 125 </ b> S extending from the outer peripheral side of the elastic layer portion 125 toward the rotation center of the shaft portion 120 and extending substantially in the axial direction.

  In the present embodiment, 16 incisions 125S are formed radially from the outer periphery to the shaft portion 120 at predetermined angular intervals in the circumferential direction from the outer periphery of the elastic layer portion 125 toward the center of rotation.

Note that the interval, quantity, and the like of the cuts 125S are not limited to the above-described 16 locations, and at least one cut 125S exists in the deformation region of the elastic layer portion 125 when the nip portion is formed. What is necessary is just to be formed. For example, as schematically shown in FIG. 6, both end portions N ₀ along the conveyance direction of the recording material in the transfer nip region between the transfer roll 12, the intermediate transfer belt 9, and the backup roll 13. , N ₁ to the rotation center of the transfer roll 12, Re ₀ , Re ₁ , the outer periphery Re ₂ of the elastic layer portion 125 extending to the nip region, and the outer periphery Re ₃ of the shaft portion 120. In the cross-sectional area Re having a shape, it is preferable that at least one notch 125S exists.

  The results of a comparative evaluation with a single-layer transfer roll having a conventional configuration using the transfer roll 12 according to this embodiment formed as described above are shown as Example 1.

  As specific contents of the comparative evaluation, first, using a single-layer transfer roll 12C having a conventional configuration as shown in FIG. 7A, the hardness of the elastic layer portion 125 is Asker C hardness of 10 It was formed so as to be degrees, 30 degrees, 50 degrees, and 70 degrees, and the relationship (inclination of parallelism) between the parallelism and the amount of biting in each hardness was measured and calculated. The measurement results are shown in FIG.

  The outer diameter of each of the transfer rolls 12 and 12C was φ28 (mm), and the thickness of the elastic layer portion 125 was 10 (mm).

  As shown in FIG. 7B, when the hardness of the elastic layer portion 125 is changed (10 degrees to 70 degrees) using a single-layer transfer roll 12C having a conventional configuration, first, a low hardness region is obtained. In (10 degrees), the parallelism inclination was about 0.2, which was a numerical value deviating from the target value 2.4.

  This is because the roll reaction force, which depends on the product of roll hardness and twist amount, is high in the low hardness region (10 degrees or less in Asker C), but the roll hardness is low and the predetermined twist reaction force. This is because the ratio of the change in parallelism to the change in the amount of biting is small, and the absolute value of the inclination of the parallelism is also small.

  Next, in the medium hardness region (30 degrees), the parallelism inclination was about −0.1, which was also a numerical value far from the target value 2.4.

  This is because although the roll hardness is slightly higher than in the low hardness region (10 or less in Asker C), the amount of twist becomes small, and eventually only the torsional reaction force similar to that in the low hardness region can be obtained. It is.

  Furthermore, in the high hardness region (50 degrees, 70 degrees), the parallelism inclination was about -0.9, -1.2, and none of the target values -2.4 could be achieved.

  This is because although the roll hardness is high, the amount of twist is small and a predetermined twist reaction force cannot be obtained.

  As a result, when the transfer roll 12C having the conventional configuration is used, the parallelism inclination tends to increase as the hardness of the elastic layer portion 125 is increased. It is understood that the desired torsional reaction force (−2.4 or less) cannot be obtained for the reason.

  Next, using the transfer roll according to the present embodiment (see FIG. 5), the elastic layer portion 125 is formed to have an Asker C hardness of 10 degrees, 30 degrees, 50 degrees, and 70 degrees. Thus, the relationship between the parallelism and the amount of biting in each hardness (inclination of parallelism) was measured and calculated. The measurement results are shown in FIG.

  As understood from FIG. 8, when the transfer roll 12 according to the present embodiment is used, the single-layer roll having a conventional configuration in which the absolute value of the parallelism inclination is not cut at any hardness. It turns out that it is increasing compared with 12C. Furthermore, it can be seen that as the hardness of the elastic layer portion 125 of the transfer roll 12 itself increases, the inclination of the parallelism is closer to the target value. In particular, when the hardness of the transfer roll 12 is 50 degrees or more in Asker C hardness, the inclination of the parallelism is about −2.7, and it is understood that the target value of −2.4 or less is achieved. Is done.

  As described above, according to the transfer roll 12 according to the present embodiment, it is possible to increase the inclination of the parallelism with respect to the transfer roll 12C having the conventional configuration without cutting, and in particular, the Asker C hardness is 50 degrees or more. When the elastic layer portion 125 is formed as described above, a sufficient torsional reaction force can be generated in the transfer roll 12 within the adjustment range Ra of the predetermined amount of biting so that the parallelism can be made zero, and the recording material 18 It was verified that sufficient speed control and parallelism control were possible.

  Further, when the transfer performance was evaluated using the transfer roll 12 according to the present embodiment having such a cut 125S, it was confirmed that there was no large transfer electric field disturbance and no transfer failure due to the presence of the cut 125S. did it. This is considered to suppress the disturbance of the transfer electric field because the recording material 18 having a high resistance is interposed between the backup roll 13 and the transfer roll 12 when transferring to the recording material 18. It is done.

It should be noted that the cutting depth of the radial cutting 125S in the present embodiment is not less than half of its thickness from the outer peripheral side of the elastic layer portion 125 toward the rotation center of the shaft portion 120, thereby achieving a desired effect. It was also confirmed that it was obtained.
<Second Embodiment>

  Next, a second embodiment of the transfer roll according to the present invention will be described with reference to FIG.

  The transfer roll 12A in the present embodiment is obtained by changing the configuration of the elastic layer portion of the transfer roll 12 in the previous embodiment, and members similar to those in the previous embodiment are denoted by the same reference numerals. A description thereof will be omitted. The image forming apparatus to which the transfer roll according to the present embodiment is applied is also the same as that of the previous embodiment, and a description thereof will be omitted. Here, FIG. 9 is a diagram schematically showing a hardness configuration of the elastic layer portion in a cross section orthogonal to the rotation axis.

  As shown in FIG. 9, in the transfer roll 12A according to the present embodiment, in the cross section orthogonal to the rotation shaft 120, the elastic layer portion 125 has a sparse material region (low hardness region) 125a and a dense material region (high Hardness region) 125b, and the low hardness region 125a and the high hardness region 125b are alternately formed along the circumferential direction.

  Specifically, in the deformation region of the elastic layer portion 125 when forming the nip portion with the backup roll 13 via the intermediate transfer belt 9, the low hardness region 125 a and the high hardness in the cross section orthogonal to the rotation shaft 120. The region 125b exists, and the cross-sectional area Sa of the low hardness region 125a in the cross section is formed to be larger than the cross-sectional area Sb of the high hardness region.

  In the present embodiment, the hardness of the low hardness region 125a is 5 degrees in Asker C hardness, and the hardness of the high hardness region 125b is 50 degrees in Asker C hardness. Furthermore, in the present embodiment, the ratio of the cross-sectional area Sa of the low-hardness region and the cross-sectional area Sb of the high-hardness region is formed to be 75:25, and the high-hardness region Sb with respect to the rotating shaft 120 is formed. Thus, they were formed radially in eight directions at equal angular intervals.

In addition, the shape, quantity, and the like of the low hardness region 125a and the high hardness region 125b are not limited to the eight radial directions described above, but in the deformation region of the elastic layer portion 125 when forming the nip portion, The low hardness region 125a and the high hardness region 125b exist, and the cross-sectional area Sa of the low-hardness region 125a is larger than the cross-sectional area Sb of the high-hardness region 125b in a cross section orthogonal to the rotation axis 120. It only has to be done. For example, as schematically shown in FIG. 6, both end portions N ₀ along the conveyance direction of the recording material in the transfer nip region between the transfer roll 12, the intermediate transfer belt 9, and the backup roll 13. , N ₁ to the rotation center of the transfer roll 12, Re ₀ , Re ₁ , the outer periphery Re ₂ of the elastic layer portion 125 extending to the nip region, and the outer periphery Re ₃ of the shaft portion 120. In the cross-sectional area Re having a shape, the low-hardness area 125a and the high-hardness area 125b exist, and the cross-sectional area Sa of the low-hardness area 125a is larger than the cross-sectional area Sb of the high-hardness area 125b. It is preferable.

  The results of a comparative evaluation with a transfer roll having another configuration using the transfer roll 12A according to the present embodiment configured as described above are shown as Example 2.

Specifically, in addition to the transfer roll 12A according to the present embodiment (see FIG. 9), the content of the comparative evaluation is a transfer roll 12A ₁ as a modified example of the present embodiment, and the transfer rolls 12A ₂ and 12A as comparative examples. ₃ was created as follows, and the relationship between each parallelism and the amount of biting (inclination of parallelism) was measured and calculated.
Transfer roll 12A ₁ (Modification): The ratio of the cross-sectional area Sa of the low hardness region 125a in the cross section orthogonal to the rotation axis 120 to the cross-sectional area Sb of the high hardness region 125b is 75:25 (the transfer roll 12A and The same), the high hardness region 125b was formed so as to be spot-like scattered in the circumferential direction at equal angular intervals with respect to the rotation center (see FIG. 10).
Transfer roll 12A ₂ (comparative example): Low hardness regions 125a and high hardness regions 125b were alternately formed along the radial direction in a cross section orthogonal to the rotation axis 120 (see FIG. 11).
Transfer roll 12A ₃ (comparative example): formed so that the cross-sectional area Sa of the low hardness region 125a in the cross section orthogonal to the rotation shaft 120 is smaller than the cross-sectional area Sb of the high hardness region 125b (see FIG. 12). .

The outer diameters of the transfer rolls 12A, 12A ₁ , 12A ₂ , 12A ₃ were all φ28 (mm), and the thickness of the elastic layer portion 125 was 10 (mm).

The results of measuring the parallelism of each transfer roll using such transfer rolls 12A, 12A ₁ , 12A ₂ , 12A ₃ are shown in FIG. 13 and FIG. Here, FIG. 13 is a diagram showing the results of measurement of the transfer roll 12A and the transfer roll 12A _1, FIG. 14 is a diagram showing the results of measurement of the transfer roll 12A ₂ and the transfer roller 12A _3.

As understood from FIG. 13, in the patterns (transfer rolls 12A and 12A ₁ ) formed so that the cross-sectional area Sa of the low-hardness region 125a is larger than the cross-sectional area Sb of the high-hardness region 125b, parallelism is used. It can be seen that the slope of is within the target value of −2.4.

On the other hand, in the pattern (transfer roll 12A ₂ ) in which the low hardness regions 125a and the high hardness regions 125b are alternately formed in the radial direction, the parallelism inclination is about −0.5, and the target value (−2.4). It can be seen that the following cannot be achieved.

Further, in the pattern (transfer roll 12A ₃ ) formed so that the cross-sectional area Sa of the low-hardness area 125a is smaller than the cross-sectional area Sb of the high-hardness area 125b, the parallelism inclination is about −1.1. It can be seen that the value (below -2.4) cannot be achieved.

From the above, the transfer roll 12A of the present embodiment, according to the 12A _1, as with the previous embodiment, it is possible to increase the slope of the parallelism, in the adjustment range of the predetermined amount of bite, It was verified that a sufficient torsional reaction force was generated on the transfer roll 12 to make the parallelism zero, and that sufficient speed control and parallelism control on the recording material 18 were possible.

1 is a schematic configuration diagram illustrating an image forming apparatus according to the present invention. It is a figure which shows typically the amount of biting of the transfer roll which concerns on this invention. It is a schematic diagram explaining the parallelism which concerns on this invention. It is a schematic diagram explaining the relationship between the parallelism and the amount of biting according to the present invention. It is sectional drawing which shows the structure of the transfer roll which concerns on 1st embodiment of this invention. It is a schematic diagram which shows simply the elastic deformation area | region which concerns on this invention. It is sectional drawing (a) which shows the structure of the single layer roll of a conventional structure, and the figure (b) which shows the measurement result about the relationship between a parallelism inclination at the time of using this single layer roll, and roll hardness. It is a figure which shows the measurement result about the relationship between a parallelism inclination at the time of using the transfer roll which concerns on 1st embodiment of this invention, and roll hardness. It is sectional drawing which shows the structure of the transfer roll which concerns on 2nd embodiment of this invention. It is sectional drawing which shows the structure of the modification of the transfer roll which concerns on 2nd embodiment of this invention. It is sectional drawing which shows the structure of the transfer roll which concerns on a comparative example. It is sectional drawing which shows the structure of the transfer roll which concerns on a comparative example. It is a figure which shows the measurement result about the relationship between the parallelism inclination at the time of using the transfer roll which concerns on 2nd embodiment of this invention, and the transfer roll which concerns on a modification, and roll hardness. It is a figure which shows the measurement result about the relationship between a parallelism inclination at the time of using the transfer roll which concerns on the comparative example of this invention, and roll hardness.

Explanation of symbols

  1Y-1K: color image forming unit, 2Y-2K: photosensitive drum, 3Y-3K: charger, 4Y-4K: exposure device, 5Y-5K: developing device, 6Y-6K: primary transfer device, 7Y-7K: Cleaner, 8Y-8K: neutralization device, 9: intermediate transfer belt, 10Y-10K: color toner cartridge, 11: secondary transfer device, 12, 12A: secondary transfer roll, 13: backup roll, 15: fixing device, 18 : Recording material, 100: Image forming apparatus, 120: Shaft portion, 125: Elastic layer portion, 125S: Cut, 125a: Low hardness region, 125b: High hardness region

Claims (6)

An intermediate transfer member on which a toner image is formed, a transfer roll that is disposed opposite to the intermediate transfer member and presses the intermediate transfer member to form a nip portion, and a pressure contact amount when the nip portion is formed. And a transfer device for transferring a toner image onto the recording material by inserting a recording material into the nip portion,
The transfer roll includes a shaft portion that forms a rotating shaft, and a single-layer elastic layer portion formed on the outer periphery of the shaft portion,
In the deformation region of the elastic layer portion when the nip portion is formed, a cut from the outer peripheral side toward the rotation axis center is formed so as to extend substantially in the axial direction. Transfer device.   The transfer device according to claim 1, wherein the elastic layer portion has an Asker C hardness of 50 degrees or more.   The transfer device according to claim 1, wherein a depth of the cut is at least half of a thickness of the elastic layer portion. An intermediate transfer member on which a toner image is formed, a transfer roll that is disposed opposite to the intermediate transfer member and presses the intermediate transfer member to form a nip portion, and a pressure contact amount when the nip portion is formed. And a transfer device for transferring a toner image onto the recording material by inserting a recording material into the nip portion,
The transfer roll includes a shaft portion that forms a rotating shaft, and an elastic layer portion formed on the outer periphery of the shaft portion,
In the elastic layer portion, a low-hardness coarse material region and a high-hardness dense material region are alternately formed in the circumferential direction, and within the deformation region of the elastic layer portion when the nip portion is formed. The transfer device is characterized in that the cross-sectional area of the low hardness region in the cross section perpendicular to the rotation axis of the transfer roll is larger than the cross-sectional area of the high hardness region.   The adjusting means controls the pressure contact amount of the transfer roll based on the relationship between the temperature and humidity obtained in advance and the parallelism inclination so that the parallelism becomes zero according to the ambient temperature and humidity. The transfer apparatus according to claim 1, wherein the transfer apparatus is characterized in that:   An image forming apparatus comprising the transfer device according to claim 1.

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