JP2012108323A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which comprises transfer means suppressing shape deformations of a conductive resin sheet as a transfer member no matter what usage conditions of the image forming apparatus are and is capable of suppressing image defects of vertical streaks generated by transfer unevenness in the longitudinal direction.SOLUTION: An image forming apparatus comprises transfer means 10 including a sheet transfer member 101 which presses, in order to transfer a toner image on an image carrier to a moving image reception member, the image reception member on the opposite side of the toner image transfer side. The transfer means 10 comprises support means 104 which supports the sheet transfer member 101 in such a manner that the sheet transfer member 101 can move in the longitudinal direction of the sheet transfer member 101 orthogonal to the upstream side and the downstream side in the image reception member movement direction and the movement direction of the image reception member, and regulation means 110-112 and 113-115 for regulating the movement of the sheet transfer member 101 after the movement of the image reception member.

Description

  The present invention generally relates to an electrophotographic image forming apparatus. In particular, in the present invention, in order to transfer a toner image formed on an image bearing member to an image receiving member such as a sheet or an intermediate transfer member, a sheet-like transfer member is installed on the back side of the image receiving member, and a voltage is applied to the transfer member. The present invention relates to an image forming apparatus that is configured to apply a pressing action.

  In an electrophotographic image forming apparatus, as a transfer member for transferring a toner image formed on an electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) as an image carrier to an image receiving member such as paper or an intermediate transfer member. A transfer roller having a conductive foam sponge body has been used. In recent years, further improvement in downsizing, low cost, and low power consumption of the apparatus is expected, and an image forming apparatus using a sheet-like member as a transfer member instead of the transfer roller has come to be seen.

  The prior art disclosed in Patent Document 1 will be described with reference to FIG.

  In this example, in order to transfer the toner image T formed on the photosensitive drum 201 onto the paper P, a resinous conductive resin sheet 206 is used as a transfer member. The sheet 206 is supported by fixing the conductive resin sheet end 203 to the support member 207. The other end of the conductive resin sheet 206 is a free end 204, and the leading end 205 of the sheet free end 204 is positioned downstream of the transfer position 200 in the rotational movement direction of the photosensitive drum 201. In contact with the photosensitive drum 201. A transfer voltage is applied to the conductive resin sheet 206 from the power source 202. The conductive resin sheet 206 is made of a resin material such as polyolefin having conductivity and elasticity, and can impart a uniform pressing action in the longitudinal direction of the photosensitive drum by the elasticity of the free end 204 of the conductive resin sheet 206. it can. Thereby, low cost can be realized by miniaturization and simplification.

In addition, by using a conductive resin sheet having an electric resistance of 10 ² to 10 ⁸ Ω and a low resistance, good transferability can be exhibited at a low voltage, and power consumption can be reduced.

JP-A-8-314294

  However, although the transfer means of the prior art realizes cost reduction by small size and simplicity and low power consumption by a low resistance conductive resin sheet, the conductive resin sheet may be deformed depending on use conditions, and due to uneven transfer in the longitudinal direction. It may cause vertical streak-like image defects.

  In the quadruple tandem type image forming apparatus shown in FIG. 1, the sheet-like transfer member according to the prior art shown in FIG. 11 is mounted as a primary transfer means for contacting a belt-like intermediate transfer member (intermediate transfer belt). In this case, we confirmed what kind of phenomenon occurred as a problem.

  One of the problems is that the conductive resin sheet free end on the downstream side in the rotational movement direction of the intermediate transfer belt is greatly undulated after the operating temperature of the image forming apparatus greatly fluctuates. FIG. 12 shows a state where the conductive resin sheet is undulated. When an image was printed on paper in this state, a vertical stripe-like image defect occurred on the image surface.

  The cause is that the conductive resin sheet expands / contracts according to the linear expansion coefficient of the conductive resin sheet due to fluctuations in the use temperature, while the conductive resin sheet end is fixed to the support member, while the conductive resin sheet free end is not It is mentioned that it is fixed.

  Specifically, if the use temperature changes greatly, the conductive resin sheet end cannot be expanded and contracted because it is fixed to the support, whereas the conductive resin sheet free end can expand and contract following the use temperature. . As described above, the degree of expansion / contraction of the conductive resin sheet is not uniform on the entire surface of the conductive resin sheet, thereby causing the free end of the conductive resin sheet to be wavy.

  As a second problem, when a large amount of paper is passed, a vertical streak-like image defect caused by transfer unevenness in the longitudinal direction may be caused. In particular, when a large amount of paper having a small width is passed, a vertical stripe-like image defect appears remarkably. Further, the central portion in the longitudinal direction of the free end of the conductive resin sheet was greatly waved.

  It is considered that this is mainly due to the fact that the end portion becomes larger than the central portion in the longitudinal direction in the tangential force in the rotational movement direction of the intermediate transfer belt generated between the conductive resin sheet and the intermediate transfer belt. The end portion of the conductive resin sheet is pulled strongly, and the end portion of the conductive resin sheet is stretched and creeped in the direction of rotational movement of the intermediate transfer belt. On the other hand, the tangential force at the center of the conductive resin sheet is low, and the conductive resin sheet itself is waved without being stretched in the direction of rotational movement of the intermediate transfer belt.

  The mechanism described above will be described in detail by taking as an example the case of passing a sheet having a small width.

  If a sheet having a small width is passed, a toner image is formed only at the center in the longitudinal direction of the intermediate transfer belt, and no toner image is present at the end in the longitudinal direction of the intermediate transfer belt. Since the toner image functions as a resistor, the effective current flowing through the photosensitive drum is larger at the end portion in the longitudinal direction than in the central portion in the longitudinal direction. Thereby, in the electrostatic attraction force generated between the intermediate transfer belt and the conductive resin sheet, the end portion in the longitudinal direction becomes larger. From the above, it is considered that the end portion is larger than the central portion in the longitudinal direction in the tangential force in the belt rotational movement direction generated between the conductive resin sheet and the intermediate transfer belt. In this verification, transfer control by constant voltage control is performed using a power source installed in the transfer means.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a transfer unit that suppresses deformation of the shape of a conductive resin sheet as a transfer member regardless of the use conditions of the image forming apparatus, and to suppress vertical streak-like image defects due to uneven transfer in the longitudinal direction. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention
An image carrier for carrying a toner image;
A transfer means having a sheet-like transfer member that acts on the opposite side of the image receiving member to the side on which the toner image is transferred in order to transfer the toner image of the image carrier to the moving image receiving member;
In an image forming apparatus having
The transfer means includes
Support means for supporting the sheet-like transfer member, the upstream and downstream sides in the moving direction of the image receiving member, and the longitudinal direction of the sheet-like transfer member orthogonal to the moving direction of the image receiving member A support means for movably supporting the sheet-like transfer member;
Restriction means for restricting movement of the sheet-like transfer member after the image receiving member has moved;
An image forming apparatus comprising:

  According to the present invention, it is possible to suppress the deformation of the shape of the sheet-like transfer member constituting the transfer means regardless of the use conditions of the image forming apparatus, and accordingly, the vertical stripe due to the transfer unevenness in the longitudinal direction of the sheet-like transfer member. Image defects can be suppressed

1 is a schematic sectional view of an image forming apparatus according to the present invention. 2 is a cross-sectional view of a primary transfer unit used in Examples 1, 2, and 3. FIG. 3 is a configuration diagram of a primary transfer unit used in Embodiment 1. FIG. It is a figure which shows the thermal expansion of the conductive resin sheet of Example 1. FIG. It is a figure which shows the movable amount of the conductive resin sheet of Example 1. FIG. 3 is an enlarged view showing a movable amount of a conductive resin sheet of Example 1. FIG. FIG. 6 is a configuration diagram of a primary transfer unit used in Embodiment 2. It is a figure which shows the movable amount of the conductive resin sheet of Example 2. FIG. FIG. 6 is a configuration diagram of a primary transfer unit used in Embodiment 3. It is a figure which shows the movable amount of the conductive resin sheet of Example 3. FIG. It is sectional drawing of the primary transfer means of a prior art. It is a figure which shows the mode of sheet corrugation of the primary transfer means of a prior art.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
First, an overall configuration of an embodiment of an image forming apparatus according to the present invention will be described with reference to FIG.

  Referring to FIG. 1, an image forming apparatus 100 according to the present embodiment is a four-tandem electrophotographic image forming apparatus. The image forming apparatus 100 includes first, second, third, and fourth image forming units Pa, Pb, Pc, and Pd that respectively form yellow, magenta, cyan, and black images as a plurality of image forming units. . In this embodiment, the configurations of the image forming portions Pa, Pb, Pc, and Pd are substantially the same except that the development colors are different.

  In the image forming apparatus 100 according to the present exemplary embodiment, a document reading apparatus connected to the image forming apparatus main body or a host device such as a personal computer is connected to the apparatus main body so that communication is possible. Therefore, in accordance with image information from the host device, four color full-color images of yellow (Y), magenta (M), cyan (C), and black (K) are recorded on a recording material (recording paper, plastic) using an electrophotographic method. Sheet, cloth, etc.).

  In the image forming apparatus 100 of this embodiment, a belt-like intermediate transfer member (hereinafter referred to as an “intermediate transfer belt”) 13 as an image receiving member moves in the direction of the arrow in the drawing and passes through each image forming unit. Each color image is superimposed on the intermediate transfer belt 13 in each image forming unit. Then, a recorded image is obtained by transferring the multiple toner images superimposed on the intermediate transfer belt 13 onto the recording material P.

  The image forming portion P (Pa to Pd) has a drum-shaped photosensitive member (photosensitive drum) 1 (1a to 1d) as an image carrier. On the outer periphery of the photosensitive drum 1 (1a to 1d), a charging device 2 (2a to 2d) as a charging unit, an exposure device (laser exposure optical system in this embodiment) 11 (11a to 11d) as an exposure unit, and development Developing units 8 (8a to 8d) as means are arranged. Further, a transfer device 10 (10a to 10d) as a primary transfer unit and a cleaning device 3 (3a to 3d) as a cleaning unit are provided on the outer periphery of the photosensitive drum 1 (1a to 1d). In this embodiment, the photosensitive drum 1, the charging device 2, the developing unit 8, and the cleaning device 3 are integrated into a cartridge 9 (9a to 9d).

  The intermediate transfer belt 13 as an intermediate transfer member is wound around a plurality of rollers 14 and 15 and rotates (rotates) in the direction indicated by the arrow. The transfer device 10 (10a to 10d) as the primary transfer unit is disposed at a position facing each photosensitive drum 1 (1a to 1d) with the intermediate transfer belt 13 interposed therebetween. In addition, a secondary transfer member 25 as a secondary transfer unit is provided at a position facing one roller 15 of the rollers around which the intermediate transfer belt 13 is wound.

  Further, the exposure, latent image, and primary transfer process in the image forming apparatus of this embodiment will be described.

  The first image forming portion Pa will be described. A drum-shaped electrophotographic photosensitive member as an image carrier, that is, the photosensitive drum 1a, is coated with a photoconductor made of an organic photosensitive member (OPC) on the outer peripheral surface of an aluminum cylinder. Configured. The photosensitive drum 1a has an outer diameter of 24 mm and is driven in the direction indicated by the arrow by a driving unit (not shown). Further, the photosensitive drum 1a is negatively charged by the charging roller 2a.

  Next, a scanning beam 12a modulated based on an image signal of the first color (yellow in the present embodiment 1) by an exposure unit 11a configured by a scanner unit or an LED array that scans laser light with a polygon mirror is generated. Irradiated onto the photosensitive drum 1a. Thereby, an electrostatic latent image of the first color is formed on the photosensitive drum 1a. When the electrostatic latent image formed on the photosensitive drum 1a reaches the developing sleeve 4a of the developing unit 8a, the electrostatic latent image is visualized by negative toner, and the first color (this embodiment) is displayed on the photosensitive drum 1a. In Example 1, a yellow toner image is formed.

  The toner 5a in the developing unit 8a is charged to the negative polarity by the developer applying blade 7a and applied to the developing sleeve 4a. Further, a negative voltage is supplied to the developing sleeve 4a from the high voltage power source 21a.

  Then, a voltage having a polarity opposite to that of the toner is supplied from the high voltage power source 22a to the primary transfer unit 10a, and the toner image (yellow in the first embodiment) on the photosensitive drum 1a is a belt-like intermediate transfer member serving as an image receiving member. That is, the image is transferred onto the intermediate transfer belt 13.

  Further, the primary transfer residual toner remaining on the photosensitive drum 1a without being transferred from the photosensitive drum 1a to the intermediate transfer belt 13 is collected by a cleaning device 3a provided with a cleaning blade in contact with the surface of the photosensitive drum.

  The above process is similarly performed in the second to fourth color magenta, cyan, and black image forming portions Pa, Pb, and Pc, and a plurality of color toner images are superimposed on the intermediate transfer belt 13. Since the image forming operations in the image forming units Pa, Pb, and Pc are the same as those in the first color, description thereof is omitted.

  Next, the secondary transfer process, the intermediate transfer belt cleaning, and the fixing process will be described.

  After the toners of a plurality of colors are transferred onto the intermediate transfer belt 13, a transfer material (hereinafter referred to as “paper”) P loaded on the transfer material cassette 16 is picked up by a paper feed roller 17 and is not shown. It is conveyed to the registration roller 18 by the conveyance roller. The registration roller 18 moves the sheet P to a contact portion formed by the intermediate transfer belt 13 and the secondary transfer roller 25, and the timing when the leading edge of the toner formed on the intermediate transfer belt 13 and the leading edge of the sheet coincide with each other. Send it out.

  Thereafter, a voltage having a polarity opposite to that of the toner is supplied from the high-voltage power source 26 to the secondary transfer roller 25, and the plurality of color toners on the intermediate transfer belt 13 are collectively transferred onto the sheet. Thereafter, the secondary transfer residual toner remaining on the intermediate transfer belt 13 is removed from the intermediate transfer belt 13 by the belt cleaning member 27.

  After the completion of the secondary transfer, the sheet P is moved to the fixing unit 19 and receives heat and pressure when passing through the fixing nip portion to fix the toner and form an image as a color image formed product (print, copy). It is discharged out of the device.

  Below, each component used in the present Example 1 is demonstrated.

The intermediate transfer belt 13 uses a general-purpose engineering plastic sheet having a thickness of 100 μm and a volume resistivity of 10 ¹¹ Ω · cm. The volume resistivity was measured using a Hiresta-UP (MCP-HT450) and UR measurement probe manufactured by Mitsubishi Chemical Corporation. The room temperature at the time of measurement was set to 23 ° C., the room humidity was set to 50%, and the applied voltage was 500 V and the measurement time was 10 sec.

  The intermediate transfer belt 13 is stretched on two rollers, a driving roller 15 and a tension roller 14, and the driving roller 15 is rotated in the direction of the arrow in the drawing by a motor (not shown), whereby the transfer belt 13 is shown in the drawing. Driven in the direction of the arrow.

The secondary transfer roller 25 is a nickel-plated steel rod having an outer diameter of 8 mm and an outer diameter of 18 mm covered with an NBR foam sponge body having a resistance value of 10 ⁸ Ω and a thickness of 5 mm. The secondary transfer roller 25 is brought into contact with the intermediate transfer belt 13 with a linear pressure of about 5 to 15 g / cm, and rotates at a substantially constant speed in the forward direction with respect to the moving direction of the intermediate transfer belt 13. It is arranged to do. The secondary transfer roller 25 is driven, and operates so as to follow the rotation of the driving roller 15 facing the secondary transfer roller 25.

  In this embodiment, the sheet moving speed of the image forming apparatus is 50 [mm / sec].

  The features of the first embodiment will be described below with reference to FIGS.

  FIG. 2 is a cross-sectional view of the primary transfer unit 10 used in the first embodiment. The primary transfer unit 10 includes a conductive resin sheet 101 that is a sheet-like transfer member, a sheet pressing elastic body 102, a sheet support member 104, a sheet cover member 103, and a pressing spring 105. The conductive resin sheet 101 is in contact with the intermediate transfer belt 13 so that the free end thereof is in the forward direction with respect to the moving direction of the intermediate transfer belt 13, and the toner image on the intermediate transfer belt 13 is transferred to the side. It acts on the opposite side (back side). In this embodiment, the toner image is slid in contact with the back surface of the intermediate transfer belt 13 at the transfer position T1 where the toner image is transferred. Primary transferability is ensured by applying a voltage to the conductive resin sheet 101 from the high-voltage power supply 22 (see FIG. 1).

In this example, as the conductive resin sheet 101, an ultrahigh molecular conductive polyethylene sheet (long length 220 × short 30 × thickness 0. 0) having a linear expansion coefficient of 17.0 (10 ⁻⁵ / ° C.) and a surface resistance of 10 (KΩ). 2 mm) is used. Further, urethane foam (long 222 × short 5 × thickness 5 mm) is used as the sheet pressing elastic body 102.

  FIG. 3 shows the configuration of the primary transfer means 10 in the first embodiment. The assembly procedure and the dimensions of each component will be described with reference to FIG.

  As shown in FIG. 3 (a), the conductive resin sheet 101 includes a conductive resin sheet 101 at both ends and a central portion in a direction orthogonal to the moving direction of the intermediate transfer belt 13 of the conductive resin sheet 101 (ie, the longitudinal direction). End holes 110 and 112 and a central hole 111 are provided. The end holes 110 and 112 are 10 × longitudinal 2 mm, and the central hole 111 is 10 × longitudinal 4 mm. The distance 1 between the end holes 110 and 112 and the center hole 111 is 90 (mm), and each hole end (upper end in FIG. 3A) is shown by a dotted line (1) shown in FIG. Aligned along.

  The sheet support member 104 has protrusion ends 113 and 115 and a protrusion center 114 (long 8 × short 1.5 mm) so as to correspond to the end holes 110 and 112 and the center hole 111 of the conductive resin sheet 101, respectively. Is provided. The distance m between the protrusions is set to 92 (mm), and the end surfaces of the protrusions (the upper end surface in FIG. 3A) are aligned along the dotted line (2) shown in FIG. The protrusions 113, 115, and 114 at the end and center of the sheet support member 104 are inserted into the end and center holes 110, 112, and 111 of the conductive resin sheet 101, and support members that support the conductive resin sheet 101. Constitute. Although details will be described later, the holes 110 to 112 of the conductive resin sheet 101 and the protrusions 113 to 115 of the sheet support member 104 are upstream and downstream in the moving direction of the intermediate transfer belt 13 of the conductive resin sheet 101. A restricting means for restricting movement to is configured.

  The seat cover member 103 is provided with end holes 116 and 118 and a center hole 117 (long 10 × short 2 mm) corresponding to the protrusion ends 113 and 115 and the protrusion center 114, respectively. The distance n between the holes is 90 (mm), and the hole ends (upper ends in FIG. 3A) are aligned along the dotted line (3) shown in FIG.

  As shown in FIG. 3B, the protrusion ends 113 and 115 and the protrusion center 114 of the sheet support member 104 are inserted into the end holes 110 and 112 and the center hole 111 of the conductive resin sheet 101, respectively. At this time, in the short direction, a movable range of 0.5 mm is provided between the end of the protrusion and the end hole, and a movable range of 2.5 mm is provided between the center of the protrusion and the central hole. Further, the movable range between the protrusion and the hole in the longitudinal direction is 2.0 (mm) for both the end and the center. If the intermediate transfer belt 13 rotates, the conductive resin sheet 101 can move to the downstream side in the rotational movement direction of the intermediate transfer belt 13 by the movable range. Therefore, the end portion and the central portion of the conductive resin sheet 101 can move to the downstream side in the rotational movement direction of the intermediate transfer belt 13 by 0.5 mm and 2.5 mm, respectively.

  As described above, the rotational movement of the intermediate transfer belt 13 causes the conductive resin sheet 101 to start moving downstream in the rotational movement direction, and the movement of the conductive resin sheet is restricted by the protrusions of the sheet support member 104 and stops. . The distance traveled from when the conductive resin sheet starts to move until the movement stops is defined as “sheet movable amount”.

  Next, as shown in FIG. 3C, the protrusion ends 113 and 115 and the protrusion center 114 of the sheet support member 104 are inserted into the end holes 116 and 118 and the center hole 117 of the sheet cover member 103, respectively. . Then, the end portion of the seat cover member 103 is screwed, and the seat cover member 103 and the seat support member 104 are fixed. In addition, the conductive resin sheet 101 is not crimped by this fixing.

  Finally, as shown in FIG. 3D, the sheet pressing elastic body 102 is bonded and fixed to the sheet supporting member 104 to complete the primary transfer unit 10.

  The characteristics of the first embodiment are briefly summarized as follows. That is, the conductive resin sheet 101 is movable because it is not fixed by adhesion, pressure bonding, or the like. Further, by making the movable range formed by the protrusions of the sheet supporting member 104 and the hole of the conductive resin sheet 101 different between the end portion and the central portion, the sheet movable amount in the longitudinal central portion is made larger than the longitudinal end portion. ing.

  The operation of the first embodiment will be described with reference to FIGS.

  FIG. 4E shows the primary transfer unit 10 with the sheet cover member 103 removed. In the first embodiment, the conductive resin sheet 101 is not fixed by adhesion, pressing, or the like, and thereby a movable range is formed by the protruding portion of the sheet support member 104 and the hole of the conductive resin sheet 101. These movable ranges are 0.5 to 2.5 (mm) in the short direction and 2.0 (mm) in the longitudinal direction, as described above.

On the other hand, the conductive resin sheet 101 used in Example 1 has a linear expansion coefficient of 17.0 (10 ⁻⁵ / ° C.), a longitudinal direction of 220 (mm), and a lateral direction of 30 (mm). From this, when the use temperature changes by 1 ° C., the conductive resin sheet 101 expands and contracts by about 0.0374 (mm) in the longitudinal direction and by about 0.0051 (mm) in the lateral direction.

  If the use temperature rises by 25 ° C., the conductive resin sheet 101 expands by about 0.935 (mm) in the longitudinal direction and by about 0.128 (mm) in the short direction. The movable range is larger than the expansion amount, and the conductive resin sheet 101 can expand in accordance with a linear expansion coefficient without the sheet support member 104 protrusions inhibiting the expansion of the conductive resin sheet 101. 4 (f) and 4 (g) are enlarged views of the state of the center hole 111 and the sheet support member 104 protrusion center 114 of the conductive resin sheet 101 before and after the use temperature change described above.

  From the above, even if the use temperature fluctuates greatly, the occurrence of undulation of the conductive resin sheet 101 can be suppressed.

  Next, the sheet movable amount of the first embodiment will be described with reference to FIGS. FIG. 5 (h) shows the primary transfer means 10 before the intermediate transfer belt 13 rotates and FIG. 5 (i) shows the primary transfer means 10 during the intermediate transfer belt 13 rotational movement from two viewpoints, that is, a perspective view and a front view. ing. Note that the seat cover member 103 is not shown for easy understanding. 6 (j) shows an enlarged view of the hole of the conductive resin sheet 101 and the protrusion of the sheet support member 104 during the rotational movement of the intermediate transfer belt 13 before the rotational movement of the intermediate transfer belt 13. In FIG. As shown.

  A movable region in which the conductive resin sheet 101 can move downstream in the rotational movement direction of the intermediate transfer belt 13 is indicated by regions o, p, and q in FIG. Regions o, p, and q are 0.5, 2.5, and 0.5 (mm), respectively.

  As shown in FIG. 6 (k), when the intermediate transfer belt 13 rotates, a tangential force acts downstream in the intermediate transfer belt rotational movement direction, and the conductive resin sheet 101 moves downstream in the intermediate transfer belt 13 rotational movement direction. That is, the end portion and the central portion of the conductive resin sheet 101 can move to the downstream side in the rotational movement direction of the intermediate transfer belt 13 by movable regions o, p, q (0.5, 2.5, 0.5 mm), respectively. is there. Therefore, the sheet movable amount at the end portion is 0.5 mm, and the sheet movable amount at the central portion is 2.5 mm. Thereby, as shown in FIG.8 (i), the downstream end of the conductive resin sheet 101 is extended so that a circular arc may be drawn.

  From the above, if a small amount of small-size paper is passed through a large amount, the tangential force at the end becomes larger than that at the center, and the end of the conductive resin sheet 101 is stretched in the belt rotational movement direction and is easily creeped. Even if it becomes a condition, a problem does not occur. That is, also in this case, since the central portion of the conductive resin sheet 101 is always stretched in the rotational movement direction of the intermediate transfer belt 13, it is possible to prevent the conductive resin sheet 101 from wavy.

  Next, in order to confirm the effect of the first embodiment, the following test was performed in comparison with the conventional technique. The transfer means shown in FIG. 11 was used as a conventional technique. Further, as in the case of Example 1, an ultra high molecular weight conductive polyethylene sheet was used for the sheet member 206 of the transfer means, and the sheet member 206 and the sheet support member 207 were bonded and fixed with a double-sided tape.

(1) After changing the installation environment of the image forming apparatus, it was confirmed whether or not an image defect occurred.
Specifically, the installation environment of the image forming apparatus was changed from room temperature / humidity (25 ° C./25%) to room temperature / humidity (50 ° C./50%) and left for 24 hours. After that, in a room temperature / humidity (50 ° C./50%) environment, blue (cyan and magenta) as secondary colors is printed on one surface of A4 paper (Canon CS-814), and the vertical color due to transfer unevenness in the longitudinal direction is printed. The presence or absence of streak-like image defects was confirmed.

(2) The presence or absence of image defects was confirmed when a large amount of small-size paper was passed.
Specifically, every 5000 sheets of B5 paper (Canon CS-814) is intermittently passed, and blue (cyan and magenta), which is a secondary color, is printed on one side of A4 paper (Canon CS-814). A vertical streak-like image defect due to uneven transfer in the longitudinal direction was confirmed.

  In the transfer means of Example 1, in any of the tests (1) and (2), a vertical stripe-like image defect due to uneven transfer in the longitudinal direction does not occur, and a good image can be output. It was.

  On the other hand, in the transfer means using the prior art, in both the tests (1) and (2), as shown in FIG. 12, the sheet member is greatly undulated and the vertical streak-like image is caused by the transfer unevenness in the longitudinal direction. A defect occurred.

  As described above, according to the first embodiment, the conductive resin sheet used as the transfer means is attached to the sheet support member by non-adhesion and non-pressure bonding, and the sheet movable amount at the central portion in the longitudinal direction of the conductive resin sheet is set. It is set as the structure made larger than the sheet | seat longitudinal direction edge part. With this configuration, it is possible to provide a transfer unit configuration that suppresses deformation of the sheet shape regardless of the use conditions of the image forming apparatus, and it is possible to suppress vertical streak-like image defects due to transfer unevenness in the longitudinal direction.

  Even if the sheet hole shape and the protrusions are different from the first embodiment such as a round shape, an elliptical shape, and a square shape, the same effect can be obtained even if the number of sheet holes and the number of protrusions are large. Needless to say, the detailed description is omitted.

Example 2
Next, a second embodiment of the present invention will be described.

  The second embodiment is also the image forming apparatus shown in FIG. 1 described in the first embodiment. Therefore, for the detailed description of the image forming operation of the image forming apparatus, the used member, etc., the description of the first embodiment is used, and the description thereof is omitted here.

  The features of the second embodiment will be described below with reference to FIG.

  7A and 7D show the main components of the primary transfer unit 10 and the completed state of the primary transfer unit 10 of the second embodiment. Differences from the first embodiment will be described with reference to FIGS. 7A and 7D, and important dimensions of each component will be described. In addition, since each component material, an assembly method, etc. are equivalent to Example 1, description is abbreviate | omitted.

  7A, the difference from Example 1 is that the end holes 120, 122 and the central hole 121 of the conductive resin sheet 101 have the same dimensions, and the sheet support member 104 in the short direction. The protrusion ends 123 and 125 provided on the protrusion and the protrusion center 124 are not aligned. Details will be described below.

  As shown in FIG. 7A, the conductive resin sheet 101 is provided with end holes 120 and 122 and a central hole 121 (long 10 × short 4 mm) having the same dimensions. The distance l between the end holes 120 and 122 and the center hole 121 is 90 (mm), and each hole end (upper end in FIG. 7A) is shown by a dotted line (1) shown in FIG. Aligned along.

  The sheet supporting member 104 has protrusion ends 123 and 125 and a protrusion center 124 (long 8 × short 1.5 mm) so as to correspond to the end holes 120 and 122 and the central hole 121 of the conductive resin sheet 101, respectively. The distance m between the protrusions is set to 92 (mm). Further, the end faces (upper end faces in FIG. 7 (a)) of the protrusion ends 123 and 125 are aligned along the dotted line (2 ′) shown in FIG. 7 (a), and along the dotted line (2). The end surface (the upper end surface in FIG. 7A) of the projection center 124 is aligned. The distance between the dotted line (2) and the dotted line (2 ') was 1.5 mm. That is, in FIG. 7A, the protrusion center 124 is located above the protrusion ends 123 and 125.

  The seat cover member 103 is provided with end holes 126 and 128 corresponding to the protrusion ends 123 and 125 and the protrusion center 124, respectively, and a center hole 127 (long 10 × short 2 mm). n is 90 (mm). Further, the end surfaces of the end holes 126 and 128 (upper end surface in FIG. 7A) are aligned along the dotted line (3 ′) shown in FIG. 7, and the central hole is aligned along the dotted line (3). 127 end faces (upper end face in FIG. 7A) are aligned. The distance between the dotted line (3) and the dotted line (3 ') was 1.5 mm. That is, in FIG. 7A, the central hole 127 is located above the end holes 126 and 128.

  That is, when the hole of the conductive resin sheet 101 is inserted into the protrusion of the sheet support member 104, a movable range of 2.5 mm is provided between the protrusion and the hole in the short direction. The movable range between the protrusion and the hole in the longitudinal direction is 2.0 (mm) for both the end and the center.

  The operation of the second embodiment will be described with reference to FIGS.

  In the second embodiment, the conductive resin sheet 101 is not fixed by adhesion, pressing, or the like, so that a movable range is formed by the protrusions of the sheet support member 104 and the holes of the conductive resin sheet 101. These movable ranges are 2.5 (mm) in the lateral direction and 2.0 (mm) in the longitudinal direction, as described above.

On the other hand, the conductive resin sheet 101 used in Example 2 has a linear expansion coefficient of 17.0 (10 ⁻⁵ / ° C.), a longitudinal direction of 220 (mm), and a lateral direction of 30 (mm). From this, when the use temperature changes by 1 ° C., the conductive resin sheet 101 expands and contracts by about 0.0374 (mm) in the longitudinal direction and by about 0.0051 (mm) in the lateral direction.

  If the use temperature rises by 25 ° C., the conductive resin sheet 101 expands by about 0.935 (mm) in the longitudinal direction and by about 0.128 (mm) in the short direction.

  That is, according to the second embodiment, the above-described movable range is set to be larger than the expansion amount, and the protruding portion of the sheet support member 104 does not hinder the expansion of the conductive resin sheet 101, and the conductive resin. The sheet 101 can expand according to the linear expansion coefficient. The state of the central hole 121 of the conductive resin sheet 101 and the central part 124 of the sheet support member 104 before and after the change in the use temperature is enlarged and shown in FIGS.

  From the above, even if the use temperature fluctuates greatly, the occurrence of undulation of the conductive resin sheet 101 can be suppressed.

  Next, the sheet movable amount of the second embodiment will be described with reference to FIG. Note that the definition of the sheet movable amount has been described in the first embodiment, and a description thereof is omitted here.

  FIG. 8 (h) shows the primary transfer means 10 before the intermediate transfer belt 13 is rotationally moved, and FIG. 8 (i) shows the primary transfer means 10 during the rotational movement of the intermediate transfer belt 13, and the sheet cover member 103 is not shown. Absent. Further, FIG. 8 (j) shows an enlarged view of the hole of the conductive resin sheet 101 and the protrusion of the sheet support member 104 during the rotational movement of the intermediate transfer belt 13 before the rotational movement of the intermediate transfer belt 13 and FIG. 6 (k). As shown.

  As shown in FIG. 8 (j), since the protruding portion of the sheet supporting member 104 has a different installation position in the short direction between the end portion and the central portion, the center of the conductive resin sheet 101 is provided only on the end surface of the protruding portion 124 of the sheet supporting member 104. Part holes are caught. At this time, the movable ranges o, p, and q shown in FIG. 8 (j) are 1.0, 2.5, and 1.0 (mm), respectively.

  8K, when the intermediate transfer belt 13 rotates, a tangential force acts on the downstream side in the rotational movement direction of the intermediate transfer belt, and the conductive resin sheet 101 moves downstream in the rotational movement direction of the intermediate transfer belt 13. That is, the end portion and the center portion of the conductive resin sheet 101 can move to the downstream side in the rotational movement direction of the intermediate transfer belt 13 by movable regions o, p, q (1.0, 2.5, 1.0 mm), respectively. It becomes. Accordingly, the sheet movable amount at the end portion is 1.0 mm, and the sheet movable amount at the central portion is 2.5 mm. As a result, as shown in FIG. 8I, the downstream end of the conductive resin sheet 101 is stretched to draw an arc.

  From the above, if a small amount of small-size paper is passed through a large amount, the tangential force at the end becomes larger than that at the center, and the end of the conductive resin sheet 101 is stretched in the belt rotational movement direction and is easily creeped. Even if it becomes a condition, there is no problem. That is, also in this case, since the central portion of the conductive resin sheet 101 is always stretched in the rotational movement direction of the intermediate transfer belt 13, the occurrence of undulations in the conductive resin sheet 101 can be suppressed.

  Next, in order to confirm the effect of Example 2, tests (1) and (2) described in Example 1 were performed.

  In the transfer means of Example 2, in both the tests (1) and (2), no vertical streak-like image defect due to transfer unevenness in the longitudinal direction occurred, and a good image could be output. .

  As described above, according to the second embodiment, the conductive resin sheet used as the transfer unit is attached to the sheet support member by non-adhesion and non-pressure bonding, and the sheet movable amount at the central portion in the longitudinal direction of the conductive resin sheet is set. It is set as the structure made larger than the sheet | seat longitudinal direction edge part. With this configuration, it is possible to provide a transfer unit configuration that suppresses deformation of the sheet shape regardless of the use conditions of the image forming apparatus, and it is possible to suppress vertical streak-like image defects due to transfer unevenness in the longitudinal direction.

  Even if the sheet hole shape and the protrusions are different from the second embodiment such as a round shape, an elliptical shape, and a square shape, the same effect can be obtained even if the number of sheet holes and the number of protrusions are large. Needless to say, the detailed description is omitted.

Example 3
Next, a third embodiment of the present invention will be described.

  The third embodiment is also the image forming apparatus shown in FIG. 1 described in the first embodiment. Therefore, for the detailed description of the image forming operation of the image forming apparatus, the used member, etc., the description of the first embodiment is used, and the description thereof is omitted here.

  The features of the third embodiment will be described below with reference to FIG.

  FIGS. 9A and 9D show the main components of the primary transfer unit 10 and the completed state of the primary transfer unit 10 according to the third embodiment. Differences from the first embodiment will be described with reference to FIGS. 9A and 9D, and important dimensions of each part will be described. In addition, since each component material, an assembly method, etc. are equivalent to Example 1, description is abbreviate | omitted.

  9A, the difference from Example 1 is that the end holes 130 and 132 and the central hole 131 of the conductive resin sheet 101 have the same dimensions, and the sheet support member 104 is provided. This is that the projection end 133, 135 and the projection center 134 have different dimensions in the short direction. Details will be described below.

  As shown in FIG. 9A, the conductive resin sheet 101 is provided with end holes 130 and 132 and a central hole 131 (long 10 × short 4 mm) having the same dimensions. Then, the distance l between the end holes 130 and 132 and the center hole 131 is 90 (mm), and the end of each hole is in FIG. 9A, and the upper edge is in the dotted line (1) shown in FIG. Aligned along.

  The sheet support member 104 includes protrusion ends 133 and 135 (longitudinal 8 × short side 3.0 mm) and protrusion central portions so as to correspond to the end holes 130 and 132 and the central hole 131 of the conductive resin sheet 101, respectively. 134 (long 8 × short 1.5 mm) is provided. The distance m between the protrusions is set to 92 (mm). Further, the end faces of the protrusion ends 133 and 135 and the protrusion center 134 (upper end face in FIG. 9A) are aligned along the dotted line (2) shown in FIG.

  The seat cover member 103 is provided with end holes 136 and 138 and a center hole 137 (long 10 × short 4 mm) corresponding to the protrusion ends 133 and 135 and the protrusion center 134, respectively. n is 90 (mm). Further, the end faces of the end holes 136 and 138 and the center hole 137 (upper end face in FIG. 9A) are aligned along the dotted line (3) shown in FIG.

  That is, when the conductive resin sheet 101 hole is inserted into the protrusion of the sheet support member 104, a 1.0 mm movable range is provided between the protrusion end and the end hole in the short side direction, A movable range of 2.5 mm is provided between the partial holes. The movable range between the protrusion and the hole in the longitudinal direction is 2.0 (mm) for both the end and the center.

  The operation of the third embodiment will be described with reference to FIGS.

  In the third embodiment, the conductive resin sheet 101 is not fixed by adhesion, pressing, or the like, and thereby a movable range is formed by the protruding portion of the sheet support member 104 and the hole of the conductive resin sheet 101. These movable ranges are 1.0 to 2.5 (mm) in the short direction and 2.0 (mm) in the longitudinal direction, as described above.

On the other hand, the conductive resin sheet 101 used in Example 3 has a linear expansion coefficient of 17.0 (10 ⁻⁵ / ° C.), a longitudinal direction of 220 (mm), and a lateral direction of 30 (mm). From this, when the use temperature changes by 1 ° C., the conductive resin sheet 101 expands and contracts by about 0.0374 (mm) in the longitudinal direction and by about 0.0051 (mm) in the lateral direction.

  If the use temperature rises by 25 ° C., the conductive resin sheet 101 expands by about 0.935 (mm) in the longitudinal direction and by about 0.138 (mm) in the short direction.

  That is, according to the third embodiment, the above-described movable range is set to be larger than the expansion amount, and the conductive resin does not hinder the protrusion of the sheet support member 104 from expanding the conductive resin sheet 101. The sheet 101 can expand according to the linear expansion coefficient. 9 (f) and 9 (g) are enlarged views of the state of the center hole 131 and the sheet support member 104 protrusion center 134 of the conductive resin sheet 101 before and after the use temperature change described above.

  From the above, even if the use temperature fluctuates greatly, the occurrence of undulation of the conductive resin sheet 101 can be suppressed.

  Next, the sheet movable amount of the third embodiment will be described with reference to FIG. Note that the definition of the sheet movable amount has been described in the first embodiment, and a description thereof is omitted here.

  10 (h) shows the primary transfer means 10 before the intermediate transfer belt 13 is rotationally moved, and FIG. 10 (i) shows the primary transfer means 10 during the rotational movement of the intermediate transfer belt 13, and the sheet cover member 103 is not shown. Absent. FIG. 10 (j) shows an enlarged view of the hole of the conductive resin sheet 101 and the protrusion of the sheet support member 104 during the rotational movement of the intermediate transfer belt 13 before the rotational movement of the intermediate transfer belt 13. In FIG. As shown.

  As shown in FIG. 10J, the protrusions of the sheet support member 104 have different dimensions in the short direction at the end and the center. At this time, the movable regions o, p, and q shown in FIG. 10 (j) are 1.0, 2.5, and 1.0 (mm), respectively.

  Next, as shown in FIG. 10K, when the intermediate transfer belt 13 rotates, a tangential force acts downstream in the intermediate transfer belt rotational movement direction, and the conductive resin sheet 101 moves downstream in the intermediate transfer belt 13 rotational movement direction. That is, the end portion and the central portion of the conductive resin sheet 101 can be moved to the downstream side in the rotational movement direction of the intermediate transfer belt 13 by the movable regions o, p, q (1.0, 2.5, 1.0 mm), respectively. Become. Accordingly, the sheet movable amount at the end portion is 1.0 mm, and the sheet movable amount at the central portion is 2.5 mm. Accordingly, as shown in FIG. 10I, the downstream end of the conductive resin sheet 101 is stretched so as to draw an arc.

  From the above, if a small amount of small-size paper is passed through a large amount, the tangential force at the end becomes larger than that at the center, and the end of the conductive resin sheet 101 is stretched in the belt rotational movement direction and is easily creeped. Even if it becomes a condition, a problem does not occur. That is, in this case, since the central portion of the conductive resin sheet 101 is always stretched in the rotational movement direction of the intermediate transfer belt 13, the occurrence of undulations in the conductive resin sheet 101 can be suppressed.

  Next, in order to confirm the effect of the third embodiment, the tests (1) and (2) described in the first embodiment were performed.

  In the transfer means of Example 3, in any of the tests (1) and (2), a vertical stripe-like image defect due to uneven transfer in the longitudinal direction does not occur, and a good image can be output. It was.

As described above, according to the third embodiment, the conductive resin sheet used as the transfer means is attached to the sheet supporting member by non-adhesion and non-pressure bonding, and the sheet movable amount at the central portion in the longitudinal direction of the conductive resin sheet is set. It is set as the structure made larger than the sheet | seat longitudinal direction edge part. As a result, it is possible to provide a transfer unit configuration that suppresses deformation of the sheet shape regardless of the use conditions of the image forming apparatus, and to suppress vertical streak-like image defects due to uneven transfer in the longitudinal direction. Even if the shape is different from the third embodiment such as a round shape, an elliptical shape, a square shape, etc., it is needless to say that the same effect can be obtained even if the number of sheet holes and the number of protrusions are large. Therefore, detailed description is omitted.

  In each of the above embodiments, the toner image on the photosensitive drum 1 is temporarily transferred to the intermediate transfer belt 13 as an image receiving member, and then the toner image on the intermediate transfer belt 13 is transferred to the recording paper P. It was described as being a forming device. The present invention is not limited to the image forming apparatus having this configuration. The present invention is equally applicable to an image forming apparatus that transfers a toner image on the photosensitive drum 1 directly to a recording paper P as an image receiving member or a recording paper P as an image receiving member conveyed by a transfer material conveying belt or the like. Applicable. Of course, the present invention is not limited to a color image forming apparatus, and can be similarly applied to a monochrome image forming apparatus. Since the configuration of such an image forming apparatus is well known to those skilled in the art, further detailed description is omitted.

1 (1a to 1d) Photosensitive drum (image carrier)
2 (2a to 2d) Charging roller (charging means)
8 (8a to 8d) Developing unit 10 (10a to 10d) Primary transfer means 11 (11a to 11d) Exposure means 13 Intermediate transfer belt (intermediate transfer member, image receiving member)
25 Secondary transfer means 27 Cleaning means 101 Conductive resin sheet (sheet-like transfer member)
102 sheet pressing elastic body 103 sheet cover member 104 sheet supporting member (supporting means)
105 Pressing spring 110, 111, 112 Conductive resin sheet hole (regulating means)
113, 114, 115 Sheet support member protrusion (support, regulating means)
116, 117, 118 Seat cover member hole

Claims (3)

An image carrier for carrying a toner image;
A transfer means having a sheet-like transfer member that acts on the opposite side of the image receiving member to the side on which the toner image is transferred in order to transfer the toner image of the image carrier to the moving image receiving member;
In an image forming apparatus having
The transfer means includes
Support means for supporting the sheet-like transfer member, the upstream and downstream sides in the moving direction of the image receiving member, and the longitudinal direction of the sheet-like transfer member orthogonal to the moving direction of the image receiving member A support means for movably supporting the sheet-like transfer member;
Restriction means for restricting movement of the sheet-like transfer member after the image receiving member has moved;
An image forming apparatus comprising:   After the image receiving member moves, the sheet-like transfer member starts to move downstream in the moving direction of the image-receiving member, and then the restricting means for restricting the movement of the sheet-like transfer member causes the sheet-like transfer member to move. When the distance moved downstream in the moving direction of the image receiving member of the sheet-like transfer member before the movement is stopped is a sheet movable amount, the sheet at the center in the longitudinal direction of the sheet-like transfer member The image forming apparatus according to claim 1, wherein the movable amount is larger than the sheet movable amount at an end portion in a longitudinal direction of the sheet-like transfer member. The regulating means has a plurality of sheet holes formed in the longitudinal direction of the sheet-like transfer member, and a plurality of supports formed in the supporting means and inserted into the sheet holes,
The position of the sheet hole is moved downstream in the moving direction of the image receiving member by the movement of the image receiving member, and the movement of the sheet hole is restricted by the support. The image forming apparatus described in 1.

Images