JP6398898B2 - Intermediate transfer unit and image forming apparatus having the same - Google Patents

Description

  The present invention includes an endless intermediate transfer belt that rotates in a predetermined direction, and sequentially transfers toner images onto a recording medium at a time after the toner images are sequentially superimposed on the intermediate transfer belt by a plurality of image forming units. The present invention relates to a unit and an image forming apparatus including the unit.

  2. Description of the Related Art Conventionally, an endless intermediate transfer belt that rotates in a predetermined direction and a plurality of image forming units provided along the intermediate transfer belt are provided, and toner images of each color are formed on the intermediate transfer belt by the image forming units. There is known an intermediate transfer type image forming apparatus in which the images are sequentially superimposed and then transferred onto a recording medium at once.

  Such an intermediate transfer type image forming apparatus includes an intermediate transfer unit including an intermediate transfer belt. The intermediate transfer unit has a plurality of primary transfer members that face the photosensitive drums of the respective colors via the intermediate transfer belt, and is formed on the photosensitive drum by applying a predetermined primary transfer bias to each primary transfer member. The toner image is primarily transferred onto the intermediate transfer belt.

  For example, in Patent Document 1, a plurality of unit-side bias terminals that supply primary transfer biases to a plurality of primary transfer members are arranged along the attaching / detaching direction of the intermediate transfer unit so as to fit in a space formed by recessing the intermediate transfer belt inward. An image forming apparatus arranged in a row is disclosed.

  Patent Document 2 discloses an endless belt (intermediate transfer belt), a contact member (primary transfer roller) that contacts the endless belt on the inner peripheral surface side of the endless belt, and a current supply that contacts the outer peripheral surface of the endless belt. An intermediate transfer unit comprising: a member; a facing member facing the current supply member via an endless belt; a voltage maintaining element connected to the contact member and the facing member; and a contact portion connected to the voltage maintaining element. The voltage maintaining element is grounded when the contact portion and the apparatus main body come into contact with each other when the intermediate transfer unit is attached to the apparatus main body, and current flows from the current supply member to the voltage maintaining element through the endless belt and the opposing member. A forming apparatus is disclosed.

JP 2010-49095 A JP 2013-231947 A

  Incidentally, when a primary transfer bias is applied to a plurality of primary transfer members from one high-voltage power supply, a resistor for adjusting the amount of current flowing in a bias circuit connecting the high-voltage power supply and each primary transfer member is disposed. This resistor is mounted on the substrate and assembled into an assembly so that the assembly work of the image forming apparatus becomes easy, and there is no need to provide a separate space for arranging the resistor. It is common to be implemented.

  However, when a resistor is mounted on a high voltage substrate, it is difficult to replace only the resistor on the substrate, and the entire substrate needs to be replaced. Further, since the high voltage substrate is mounted in the image forming apparatus main body, the work of removing the high voltage substrate becomes complicated. Therefore, there is a problem that it is difficult to easily change the current value flowing from the high-voltage power source to each primary transfer member.

  In view of the above problems, the present invention includes an intermediate transfer unit that can easily adjust the amount of current flowing through each primary transfer member when a primary transfer bias is applied from a high-voltage power source to a plurality of primary transfer members. An object is to provide an image forming apparatus.

  In order to achieve the above object, the first configuration of the present invention includes an intermediate transfer belt, a driving roller, a tension roller, a plurality of primary transfer members, a support frame, a primary transfer contact terminal, and a power supply line. And an intermediate transfer unit that is detachable from the image forming apparatus main body. The intermediate transfer belt is endless and moves along a plurality of image forming units. The drive roller rotates the intermediate transfer belt. The tension roller rotates following the intermediate transfer belt and applies a predetermined tension to the intermediate transfer belt. The plurality of primary transfer members are arranged to face the image carrier disposed in each image forming unit with the intermediate transfer belt interposed therebetween, and transfer the toner image formed on the image carrier onto the intermediate transfer belt. The support frame supports the drive roller, the tension roller, and the primary transfer member. The primary transfer contact terminal is in contact with the terminal of the high-voltage board on the image forming apparatus main body side. The power supply line branches from the primary transfer contact terminal and applies a primary transfer bias to each primary transfer member. The resistor adjusts the value of the current flowing through each primary transfer member, and is mounted at a connection portion between the power supply line and each primary transfer member.

  According to the first configuration of the present invention, the resistor can be replaced in a state where the intermediate transfer unit is removed from the image forming apparatus main body. Compared with the configuration in which the resistor is mounted on the high-voltage board side, Replacement work is facilitated. Therefore, an optimal primary transfer bias according to the characteristics of the primary transfer member can be applied by exchanging the resistors in accordance with variations in characteristics of the primary transfer member, and transfer properties can be improved. In addition, the intermediate transfer unit can be shared with a plurality of types of image forming apparatuses having different specifications of the image carrier and the primary transfer member, and the cost can be reduced by sharing parts.

FIG. 2 is a schematic diagram showing an internal configuration of an image forming apparatus 100 including an intermediate transfer unit 30 according to the present invention. Enlarged view of the vicinity of the image forming unit Pd in FIG. A perspective view of an intermediate transfer unit 30 according to an embodiment of the present invention mounted on the image forming apparatus 100. 3 is a perspective view showing a state where the intermediate transfer belt 8 is removed from the intermediate transfer unit 30 shown in FIG. Side view of intermediate transfer unit 30 viewed from the front side of image forming apparatus 100 Enlarged view around the transfer contact terminal portion 37 in FIG. Enlarged view around the charging contact terminal 39 in FIG. Side view around transfer contact terminal 37 A plan view of the left side frame 33b of the intermediate transfer unit 30 as viewed from the inside. The top view of the resistor 43 attached inside the left side frame 33b Partial sectional view of the vicinity of the resistor 43 connected to the primary transfer roller 6a of the intermediate transfer unit 30

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a configuration of an image forming apparatus 100 provided with an intermediate transfer unit 30 of the present invention, and FIG. 2 is an enlarged view of the vicinity of an image forming portion Pd in FIG.

  The image forming apparatus 100 of FIG. 1 has the following configuration. In the main body of the image forming apparatus 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the transport direction (left side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and cyan, magenta, and yellow are respectively performed by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  These image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c and 1d which carry visible images (toner images) of the respective colors, and are further illustrated by a driving means (not shown). In FIG. 1, an intermediate transfer belt 8 that rotates counterclockwise is provided adjacent to each of the image forming portions Pa to Pd. The toner images formed on the photosensitive drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 8 that moves while being in contact with the photosensitive drums 1a to 1d. As an example, the image is transferred onto the transfer paper P at one time, and further fixed on the transfer paper P in the fixing unit 13, and then discharged from the main body of the image forming apparatus 100. While the photosensitive drums 1a to 1d are rotated in the clockwise direction in FIG. 1, an image forming process for the photosensitive drums 1a to 1d is executed.

  The transfer paper P onto which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the main body of the image forming apparatus 100, and is conveyed to the secondary transfer roller 9 via the paper feed roller 12a and the registration roller pair 12b. . A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a (seamless) belt having no seam is mainly used.

  Next, the image forming units Pa to Pd will be described. Around and below the photosensitive drums 1a to 1d arranged to be rotatable, chargers 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d, and image information to each of the photosensitive drums 1a to 1d. The exposure unit 5 for exposing the toner, the developing units 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d are removed. Cleaning devices 7a, 7b, 7c and 7d are provided.

  Hereinafter, the image forming unit Pd will be described in detail with reference to FIG. 2, but the description is omitted because the image forming units Pa to Pc have basically the same configuration. As shown in FIG. 2, a charger 2d, a developing unit 3d, and a cleaning device 7d are disposed around the photosensitive drum 1d along the drum rotation direction (clockwise direction in FIG. 1). A primary transfer roller 6d is disposed across the surface. Further, a belt cleaning unit 19 including a belt cleaning blade 19a for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed on the downstream side in the rotation direction of the intermediate transfer belt 8 with respect to the photosensitive drum 1d.

  The charger 2d has a charging roller 22 that contacts the photosensitive drum 1d and applies a charging bias to the drum surface, and a charging cleaning roller 23 for cleaning the charging roller 22. The developing unit 3d includes two agitating and conveying screws 24, a magnetic roller 25, and a developing roller 26, and a developing bias having the same polarity (positive) as that of toner is applied to the developing roller 26 on the drum surface. Let the toner fly.

  The cleaning device 7 d includes a rubbing roller 27, a cleaning blade 28, and a recovery screw 29. The rubbing roller 27 is pressed against the photosensitive drum 1d with a predetermined pressure, and is driven to rotate in the same direction on the contact surface with the photosensitive drum 1d by a driving means (not shown). The speed is controlled faster than the peripheral speed of 1d (1.2 times here). Examples of the rubbing roller 27 include a structure in which a foam layer made of EPDM rubber and having an Asker C hardness of 55 ° is formed as a roller body around a metal shaft. The material of the roller body is not limited to EPDM rubber, but may be a rubber or foamed rubber body of another material, and those having an Asker C hardness of 10 to 90 ° are preferably used.

  A cleaning blade 28 is fixed in contact with the photosensitive drum 1d on the surface of the photosensitive drum 1d downstream of the contact surface with the rubbing roller 27 in the rotation direction. As the cleaning blade 28, for example, a polyurethane rubber blade having a JIS hardness of 78 ° is used, and is attached at a predetermined angle with respect to the tangential direction of the photosensitive member at the contact point. It should be noted that the material, hardness and dimensions of the cleaning blade 28, the amount of biting into the photosensitive drum 1d, the pressure contact force, and the like are appropriately set according to the specifications of the photosensitive drum 1d.

  Residual toner removed from the surface of the photosensitive drum 1d by the rubbing roller 27 and the cleaning blade 28 is discharged to the outside of the cleaning device 7d as the recovery screw 29 rotates, and is conveyed to a toner recovery container (not shown). Stored. As the toner used in the present invention, silica, titanium oxide, strontium titanate, alumina or the like is embedded in the toner particle surface as an abrasive and held so as to partially protrude on the surface. Those that are electrostatically attached to the surface are used.

  Next, an image forming procedure in the image forming apparatus 100 will be described. When the start of image formation is input by the user, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d. Next, the exposure unit 5 irradiates the surfaces of the photosensitive drums 1a to 1d with light, and electrostatic latent images corresponding to image signals are formed on the photosensitive drums 1a to 1d. Each of the developing units 3a to 3d is filled with a predetermined amount of cyan, magenta, yellow, and black toner stored in the toner containers 4a to 4d by a replenishing device (not shown). The toner is supplied onto the photosensitive drums 1a to 1d by the developing units 3a to 3d and electrostatically attached, whereby a toner image corresponding to the electrostatic latent image formed by exposure from the exposure unit 4 is formed. It is formed.

  The primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and cyan, magenta, yellow, and yellow on the photosensitive drums 1a to 1d. A black toner image is primarily transferred onto the intermediate transfer belt 8. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning devices 7a to 7d in preparation for the subsequent formation of a new electrostatic latent image.

  When the intermediate transfer belt 8 starts to rotate counterclockwise as the drive roller 11 is rotated by a drive motor (not shown), the transfer paper P is adjacent to the intermediate transfer belt 8 from the registration roller 12b at a predetermined timing. It is conveyed to the provided secondary transfer roller 9 and a full-color image is transferred onto the transfer paper P. The transfer paper P onto which the toner image has been transferred passes through the paper transport path 18 and is transported to the fixing unit 13. The toner remaining on the surface of the intermediate transfer belt 8 is removed by the belt cleaning unit 19.

  The transfer paper P conveyed to the fixing unit 13 is heated and pressed by the fixing roller pair 13a to fix the toner image on the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image is formed is distributed in the transport direction by the branching portion 14 that branches in a plurality of directions. When an image is formed on only one side of the transfer paper P, it is discharged as it is onto the discharge tray 17 by the discharge roller 15.

  On the other hand, when images are formed on both sides of the transfer paper P, a part of the transfer paper P that has passed through the fixing unit 13 is once protruded from the discharge roller 15 to the outside of the image forming apparatus 100. Thereafter, the transfer paper P is distributed to the reverse conveyance path 20 by the branching section 14 by rotating the discharge roller 15 in the reverse direction, and is re-conveyed to the secondary transfer roller 9 with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 8 is transferred by the secondary transfer roller 9 to the surface of the transfer paper P where the image is not formed and conveyed to the fixing unit 13 to fix the toner image. , And discharged to the discharge tray 17.

  3 is a perspective view of the intermediate transfer unit 30 mounted on the image forming apparatus 100, FIG. 4 is a perspective view showing a state in which the intermediate transfer belt 8 is removed from the intermediate transfer unit 30 of FIG. 3, and FIG. 2 is a side view of a transfer unit 30. FIG. 3 and 4 show a state in which the intermediate transfer unit 30 is viewed from the left back side in FIG. 1, and FIG. 5 shows the intermediate transfer unit 30 on the front side of the image forming apparatus 100 (the front side in FIG. 1). ). As shown in FIGS. 3 to 5, the intermediate transfer unit 30 contacts the intermediate transfer belt 8 that is stretched between the tension roller 10 and the drive roller 11, and the photosensitive drums 1 a to 1 d via the intermediate transfer belt 8. Primary transfer rollers 6a to 6d. The intermediate transfer unit 30 can be inserted into and pulled out from the side surface (right side in FIG. 1) of the image forming apparatus 100 in the horizontal direction (arrow AA ′ direction in FIG. 3) with respect to the image forming apparatus 100 main body.

  The tension roller 10, the driving roller 11, and the primary transfer rollers 6 a to 6 d are supported by the roller support frame 31. The roller support frame 31 includes a first support frame 31a and a second support frame 31b. The first support frame 31a and the second support frame 31b are rotatably connected at a rotation fulcrum 31c.

  The tension roller 10 is supported on the end portion (left end portion in FIG. 5) opposite to the rotation fulcrum 31c of the first support frame 31a. Further, primary transfer rollers 6a and 6b are supported in order from the tension roller 10 between the tension roller 10 and the rotation fulcrum 31c. The driving roller 11 is supported on the end portion (the right end portion in FIG. 5) of the second support frame 31b opposite to the rotation fulcrum 33c. Further, primary transfer rollers 6c and 6d are supported in order from the rotation fulcrum 31c side between the driving roller 11 and the rotation fulcrum 31c, and the belt of the belt cleaning unit 19 is obliquely above the primary transfer roller 6d. A counter roller 32 facing the cleaning blade 19a (see FIG. 2) is supported.

  A right side frame 33a and a left side frame 33b are mounted on the right side (front side in FIG. 1) and the left side (back side in FIG. 1) of the roller support frame 31, respectively. Development contact terminals 35a to 35d for electrically connecting a high voltage substrate (not shown) and the development units 3a to 3d (see FIG. 1) are provided on the upper surface of the right side frame 33a. When the intermediate transfer unit 30 is inserted to a predetermined position in the main body of the image forming apparatus 100, a terminal (not shown) on the high voltage substrate side and the developing contact terminal portion 35 come into contact with each other, and the developing bias to the developing units 3a to 3d is reduced. Application is possible.

  Further, on the upper surface of the left side frame 33b, a transfer contact terminal portion 37 for electrically connecting the high-voltage substrate, the primary transfer rollers 6a to 6d, and the secondary transfer roller 9 (see FIG. 1), and the high-voltage substrate and the charging member. A charging contact terminal portion 39 for electrically connecting the devices 2a to 2d is provided. When the intermediate transfer unit 30 is inserted to a predetermined position in the main body of the image forming apparatus 100, the terminals 41a to 41g (see FIGS. 6 and 7) on the high voltage substrate side, the transfer contact terminal portion 37, and the charging contact terminal portion 39 are in contact with each other. In addition, bias can be applied to the primary transfer rollers 6a to 6d, the secondary transfer roller 9, and the chargers 2a to 2d.

  6 is an enlarged view around the transfer contact terminal portion 37 in FIG. 3 (inside the broken line circle S1 in FIG. 3), and FIG. 7 is an enlarged view around the charged contact terminal portion 39 in FIG. 3 (in the broken line circle S2 in FIG. 3). 8 and 8 are side views of the periphery of the transfer contact terminal portion 37. FIG.

  As shown in FIGS. 6 and 8, the transfer contact terminal portion 37 applies a primary transfer bias to the primary transfer rollers 6a to 6c facing the cyan, magenta, and yellow image forming portions Pa to Pc (see FIG. 1). The color transfer contact terminal 37a to be applied, the black transfer contact terminal 37b to apply the primary transfer bias to the primary transfer roller 6d facing the black image forming portion Pd (see FIG. 1), and the secondary transfer bias to the secondary transfer roller 9. Including a secondary transfer contact terminal 37c for applying a guide rib and guide ribs 40a to 40d.

  The color transfer contact terminal 37a and the secondary transfer contact terminal 37c are formed in a concave shape on the upper surfaces of the guide ribs 40a and 40d, respectively, and the black transfer contact terminal 37b is formed in a window shape on the side surface of the guide rib 40c. Note that the terminal 41b that contacts the black transfer contact terminal 37b is provided on a dedicated high-voltage substrate that is different from the terminal 41a that contacts the color transfer contact terminal 37a.

  As shown in FIG. 7, the charging contact terminal portion 39 applies a charging bias to the chargers 2a to 2d (see FIG. 1) disposed in the cyan, magenta, yellow, and black image forming portions Pa to Pd. Charging contact terminals 39a to 39d and guide ribs 40e to 40h are included. The charging contact terminals 39a to 39d are formed in concave shapes on the upper surfaces of the guide ribs 40e to 40h, respectively.

  When the intermediate transfer unit 30 is inserted in the direction of arrow A in FIG. 3 with respect to the main body of the image forming apparatus 100, the guide ribs 40a to 40h slide along a guide rail (not shown) on the main body of the image forming apparatus 100. The intermediate transfer unit 30 is inserted into the image forming apparatus 100 while maintaining a horizontal state without being inclined in the horizontal direction and the vertical direction with respect to the insertion direction.

  When the intermediate transfer unit 30 is inserted to a predetermined position, the terminals 41a to 41c of the high voltage board mounted on the main body side of the image forming apparatus 100 become the color transfer contact terminal 37a, the black transfer contact terminal 37b, and the secondary transfer contact terminal 37c, respectively. It becomes possible to apply a transfer bias to the primary transfer rollers 6a to 6d and the secondary transfer roller 9 in contact with each other. Similarly, the terminals 41d to 41g of the high-voltage board come into contact with the charging contact terminals 39a to 39d, respectively, and the charging bias can be applied to the chargers 2a to 2d.

  Although not described in detail here, when the intermediate transfer unit 30 is inserted into the main body of the image forming apparatus 100, the terminals (not shown) of the high-voltage board come into contact with the development contact terminals 35a to 35d (see FIG. 5) for development. It is also possible to apply a developing bias to the units 3a to 3d.

  FIG. 9 is a plan view of the left side frame 33b of the intermediate transfer unit 30 as viewed from the inside. Inside the left side frame 33b, a resistor 43 for adjusting the current value flowing through the primary transfer rollers 6a to 6c facing the cyan, magenta, and yellow image forming portions Pa to Pc is disposed. As described above, since the primary transfer bias is applied to the primary transfer roller 6d facing the black image forming portion Pd from a dedicated high-voltage substrate different from the primary transfer rollers 6a to 6c, primary transfer is performed. A resistor 43 for adjusting the value of the current flowing through the roller 6d is mounted on the high voltage substrate.

  FIG. 10 is a plan view of the resistor 43 attached to the inside of the left side frame 33b. The resistor 43 used in the present embodiment is a resistor (high Meg resistor) having a resistance value in units of mega ohms, and includes a resistor main body 43a in which an electric resistance element is built, and two protruding from the resistor main body 43a. Lead 43b. The resistor body 43a displays a resistance value by a color code or a numerical value.

  FIG. 11 is a partial cross-sectional view of the vicinity of the resistor 43 connected to the primary transfer roller 6a of the intermediate transfer unit 30 (cross-sectional view taken along the line XX ′ in FIG. 9). The attachment structure of the resistor 43 will be described with reference to FIG. The same applies to the mounting structure of the resistor 43 (the center and right resistor 43 in FIG. 9) connected to the primary transfer rollers 6b and 6c.

  As shown in FIG. 11, the two leads 43b of the resistor 43 are pressed against the inner surface of the left side frame 33b by one ends of the contact springs 47a and 47b. An annular spring receiving groove 45 (see FIG. 9) for receiving the end portions of the first contact spring 47a and the second contact spring 47b is formed on the inner surface of the left side frame 33b. The displacement of the contact spring 47b is prevented. The other end of the first contact spring 47a is in contact with the power supply line 50 extending from the color transfer contact terminal 37a, and the other end of the second contact spring 47b rotatably supports the rotating shaft 51 of the primary transfer roller 6a. In contact with the metal bearing 53.

  With this configuration, the color transfer contact terminal 37a and the rotary shaft 51 of the primary transfer rollers 6a to 6c are electrically connected. A current value flowing from the high-voltage substrate to each primary transfer roller 6a-6c is adjusted by a resistor 43 connected between the color transfer contact terminal 37a and the primary transfer rollers 6a-6c, and each primary transfer roller 6a-6c is adjusted. An appropriate primary transfer bias is applied.

  Further, by mounting the resistor 43 on the intermediate transfer unit 30 side, the resistor 43 can be replaced while the intermediate transfer unit 30 is pulled out from the image forming apparatus 100, so that the resistor 43 is mounted on the high voltage substrate side. In comparison, the replacement work of the resistor 43 is facilitated. Further, since the resistor 43 is attached by sandwiching the two leads 43b of the resistor 43 between the first contact spring 47a, the second contact spring 47b, and the left side frame 33b, a member for fixing the resistor 43 is unnecessary. The replacement work can be further simplified. Accordingly, by exchanging the resistor 43 in accordance with variations in the characteristics of the primary transfer rollers 6a to 6c, an optimum primary transfer bias corresponding to the characteristics of the primary transfer rollers 6a to 6c can be applied, and transfer performance can be improved. Can be improved.

  Further, by replacing the resistor 43 mounted on the intermediate transfer unit 30, the intermediate transfer unit 30 can be used for a plurality of types of image forming apparatuses 100 having different specifications of the photosensitive drums 1a to 1c and the primary transfer rollers 6a to 6c. The image forming apparatus 100 can be reduced in cost by sharing parts.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the intermediate transfer unit 30 of the above embodiment, three resistors 43 connected to the primary transfer rollers 6a to 6c are mounted on the intermediate transfer unit 30, but four resistors connected to the primary transfer rollers 6a to 6d. All the resistors 43 can be mounted on the intermediate transfer unit 30.

  The present invention is not limited to the tandem type color printer shown in FIG. 1, but can be applied to various image forming apparatuses using an intermediate transfer unit, such as a color copying machine, a color complex machine, and a facsimile.

  The present invention can be used in an intermediate transfer unit that sequentially superimposes toner images formed by a plurality of image forming units on an intermediate transfer belt by primary transfer and then performs secondary transfer onto a recording medium. By utilizing the present invention, an intermediate transfer unit capable of easily adjusting the amount of current flowing to each primary transfer member when a primary transfer bias is applied to a plurality of primary transfer members from a high-voltage power supply, and an image forming apparatus including the intermediate transfer unit Can be provided.

Pa to Pd Image forming units 6a to 6d Primary transfer roller (primary transfer member)
8 Intermediate transfer belt 9 Secondary transfer roller 10 Tension roller 11 Drive roller 19 Belt cleaning unit 30 Intermediate transfer unit 31 Roller support frame (support frame)
33a Right side frame (support frame)
33b Left side frame (support frame)
37 Transfer contact terminal portion 37a Color transfer contact terminal (primary transfer contact terminal)
37b Black transfer contact terminal 37c Secondary transfer contact terminal 40a-40h Guide rib 41a-41g Terminal (high voltage substrate)
43 resistor 43a resistor body 43b lead 47a first contact spring 47b second contact spring 50 power supply line 51 rotating shaft 53 bearing portion 100 image forming apparatus

Claims (4)

An endless intermediate transfer belt that moves along a plurality of image forming units;
A driving roller for rotating the intermediate transfer belt;
A tension roller that rotates following the intermediate transfer belt and applies a predetermined tension to the intermediate transfer belt;
A plurality of primary transfer members disposed opposite to the image carriers disposed in the respective image forming units with the intermediate transfer belt interposed therebetween, and transferring a toner image formed on the image carrier onto the intermediate transfer belt; ,
A support frame that supports the drive roller, the tension roller, and the primary transfer member;
In an intermediate transfer unit that is detachable from the image forming apparatus main body,
A primary transfer contact terminal that contacts a terminal of the high-voltage substrate on the image forming apparatus main body side;
A power supply line that branches from the primary transfer contact terminal and applies a primary transfer bias to each primary transfer member;
Is provided,
A resistor for adjusting a current value flowing through each primary transfer member is mounted on a connection portion between the power supply line and each primary transfer member,
The resistor has a resistor body and two leads protruding from the resistor body,
The two leads, and the one end of the first contact spring which is electrically connected to the power supply line, and one end of the second contact spring electrically connected to said primary transfer member, the support frame The resistor is detachably held on the support frame by being sandwiched between
Wherein the first contact spring and the second contact spring is pressed against the one end the supporting frame a spring, wherein the support frame in a state sandwiched the lead first contact spring and the second the intermediate transfer unit, characterized in that the annular spring receiving groove for receiving the one end of the contact spring are formed. The primary transfer member is a primary transfer roller having a metal rotation shaft, and the other end of the second contact spring is an axial direction of a metal bearing portion that rotatably supports the rotation shaft of the primary transfer roller. The intermediate transfer unit according to claim 1, wherein the intermediate transfer unit is in contact with an outer surface .   The intermediate transfer unit according to claim 1, wherein the resistor has a resistance value in units of mega ohms.   An image forming apparatus comprising the intermediate transfer unit according to claim 1.