JP5448051B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus including a plurality of image forming units that respectively correspond to a plurality of colors including black and that form an image of a corresponding color on an image carrier included in the image forming apparatus (Patent Document 1, etc.) ).

  The image forming apparatus described in Patent Document 1 includes a direct transfer position for directly transferring a black image formed by a black image forming unit onto a recording medium, and a primary image from the remaining other color image forming units onto an intermediate transfer belt. There is a secondary transfer position where the transferred other color image is secondarily transferred from the intermediate transfer belt to the recording medium. The secondary transfer position is located upstream of the direct transfer position in the recording medium conveyance direction. Then, the recording medium transport device passes the recording medium through the secondary transfer position and the direct transfer position, the other color image transferred from the secondary transfer position onto the recording medium, and the recording medium from the direct transfer position. The black image transferred above is superimposed on the recording medium to form a full-color image on the recording medium. The recording medium on which the full-color image is formed is conveyed to a fixing device provided downstream in the recording medium conveyance direction from the direct transfer position, and the full-color image on the recording medium is fixed on the recording medium by the fixing device.

  The intermediate transfer belt is rotatably stretched by a plurality of roller members, and is rotationally driven by a driving roller that is one of the plurality of roller members. At the secondary transfer position, the drive roller and a secondary transfer roller facing the drive roller via an intermediate transfer belt are disposed. A secondary transfer nip is formed by the intermediate transfer belt and the secondary transfer roller coming into contact with each other at the secondary transfer position, and a recording medium is caused to enter the secondary transfer nip by a recording medium conveying device. The other color image transferred onto the intermediate transfer belt is secondarily transferred by a secondary transfer roller to which a transfer bias is applied to the surface of the recording medium in contact with the intermediate transfer belt at the secondary transfer nip. In addition, the secondary transfer roller can be brought into contact with and separated from the intermediate transfer belt by the contact / separation mechanism. When an image is formed on the recording medium only by the black image forming unit, the intermediate transfer is performed by the contact / separation mechanism. The secondary transfer roller is separated from the belt. As a result, the contact between the intermediate transfer belt and the recording medium transported between the intermediate transfer belt and the secondary transfer roller can be reduced, and the deterioration of the intermediate transfer belt can be suppressed and the life of the intermediate transfer belt can be extended. It is said that.

  The positional relationship between the secondary transfer position and the direct transfer position is set such that the recording medium is conveyed straight from the secondary transfer nip formed at the secondary transfer position to the direct transfer position. The Therefore, when the intermediate transfer belt and the secondary transfer roller are in contact, the recording medium that has passed through the secondary transfer nip can be conveyed straight to the direct transfer position.

  However, since the secondary transfer nip is not formed when the intermediate transfer belt and the secondary transfer roller are separated from each other, the recording medium passes through the gap formed between the intermediate transfer belt and the secondary transfer roller. Is conveyed to the direct transfer position.

  In the configuration in which the secondary transfer roller is in contact with and separated from the intermediate transfer belt, the secondary transfer roller faces the secondary transfer roller through the intermediate transfer belt depending on whether the secondary transfer roller and the intermediate transfer belt are in contact with each other or separated from each other. Do not change the position of the drive roller. That is, the drive roller is not displaced from the position where the drive roller is located when the intermediate transfer belt and the secondary transfer roller are in contact with each other to form the secondary transfer nip. Therefore, when the recording medium passes through a position where the front surface of the portion of the intermediate belt that is hung on the driving roller of the intermediate transfer belt is in contact with the recording medium, the intermediate transfer belt and the secondary transfer roller are When contacted, the recording medium passes through the same position as the position where the secondary transfer nip can be formed. Therefore, the recording medium can be conveyed straight to the direct transfer position. However, since the intermediate transfer belt easily deteriorates when the recording medium comes into contact with the intermediate transfer belt, it is not preferable that the recording medium pass through the contact position.

  Further, in the configuration in which the secondary transfer roller is brought into contact with and separated from the intermediate transfer belt, when the intermediate transfer belt and the secondary transfer roller are separated from each other, the intermediate transfer belt and the secondary transfer roller come into contact with each other and the secondary transfer nip. Is formed, the secondary transfer roller is displaced from the position where the secondary transfer roller is located. Therefore, when the recording medium passes through a position different from the contact position in the gap, the position shifted by the maximum displacement of the secondary transfer roller from the position where the secondary transfer nip can be formed. Will pass. Therefore, there arises a problem that the recording medium is hardly conveyed straight to the direct transfer position and paper jam is likely to occur.

  In the configuration in which the secondary transfer position is located downstream of the direct transfer position in the recording medium conveyance direction, a fixing device is disposed downstream of the secondary transfer position in the recording medium direction. Further, the positional relationship between the secondary transfer position and the fixing device is set such that the recording medium is conveyed straight from the secondary transfer nip to the fixing device.

  Even if the secondary transfer position is located downstream of the direct transfer position in the recording medium conveyance direction, the secondary transfer nip is formed when the recording medium passes through the contact position in the gap. The recording medium passes through the same position as the obtained position. Therefore, the recording medium can be conveyed straight to the fixing device. However, since the intermediate transfer belt easily deteriorates when the recording medium comes into contact with the intermediate transfer belt, it is not preferable that the recording medium pass through the contact position. Further, when the recording medium passes through the different positions in the gap, the recording medium passes through a position shifted by the maximum displacement of the secondary transfer roller from the position where the secondary transfer nip can be formed. become. Therefore, it is difficult for the recording medium to be conveyed straight to the fixing device, and a paper jam is likely to occur.

Here, the positional relationship between the secondary transfer position and the direct transfer position is limited to a case where the positional relationship is set such that the recording medium is conveyed straight from the secondary transfer nip to the direct transfer position. is not. Further, the positional relationship between the secondary transfer position and the fixing device is not limited to the case where the positional relationship is set such that the recording medium is conveyed straight from the secondary transfer nip to the fixing device.
That is, the positional relationship between the secondary transfer position and a predetermined position downstream of the secondary transfer position in the recording medium conveyance direction is that the recording medium is appropriately conveyed from the secondary transfer nip to the predetermined position. The positional relationship is set as follows. When the recording medium passes through the contact position in the gap, the recording medium passes through the same position as the position where the secondary transfer nip can be formed. Therefore, the recording medium can be appropriately conveyed to the predetermined position. However, since the intermediate transfer belt easily deteriorates when the recording medium comes into contact with the intermediate transfer belt, it is not preferable that the recording medium pass through the contact position. Further, when the recording medium passes through the different positions in the gap, the recording medium passes through a position shifted by the maximum displacement of the secondary transfer roller from the position where the secondary transfer nip can be formed. become. Therefore, it is difficult for the recording medium to be properly conveyed to the predetermined position, and a paper jam is likely to occur.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of reducing the occurrence of paper jam while reducing the contact between the intermediate transfer belt and the recording medium. It is.

In order to achieve the above object, the invention of claim 1 is directed to an intermediate transfer belt that is rotatably stretched around a plurality of roller members, and a first surface disposed opposite to the front surface of the intermediate transfer belt. One image carrier, first image forming means for forming an image on the first image carrier, and primary transfer of the image formed on the first image carrier onto the intermediate transfer belt The intermediate transfer belt and a secondary transfer nip formed by contacting the front surface of the intermediate transfer belt with the front surface of the intermediate transfer belt. A secondary transfer roller for secondary transfer of the image transferred on the belt onto the recording medium, a second image carrier provided on the upstream side or downstream side in the recording medium conveyance direction from the secondary transfer nip, Second image forming means for forming an image on the second image carrier, and on the second image carrier. An image forming apparatus comprising a direct transfer unit, the the formed image is transferred directly onto a recording medium, a first moving means for contacting and separating the intermediate transfer belt to the secondary transfer roller, the A second contact / separation unit for contacting and separating the intermediate transfer belt and the first image carrier, and the intermediate transfer belt and the first image carrier by the second contact / separation unit. Then, the intermediate transfer belt is separated from the secondary transfer roller by the first contact / separation means .
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the second transfer nip passes through a direct transfer position where an image is directly transferred from the second image carrier onto a recording medium. And a recording medium conveying belt that is rotatably stretched by a plurality of roller members, and the secondary transfer roller is connected to the intermediate transfer via the recording medium conveying belt. It is characterized by being in contact with the belt.
According to a third aspect of the present invention, in the image forming apparatus of the first aspect, when the intermediate transfer belt and the secondary transfer roller are separated from each other by the first contact / separation means, the first image carrier is provided. The drive of the body, the first image forming unit, the primary transfer unit, the plurality of roller members, and the intermediate transfer belt is stopped.
According to a fourth aspect of the present invention, in the image forming apparatus of the first, second, or third aspect, one of the plurality of roller members is connected to the secondary transfer roller at a secondary transfer position via the intermediate transfer belt. An opposing secondary transfer opposing roller, wherein the first contacting / separating means displaces the secondary transfer opposing roller in a direction away from the secondary transfer roller, and the intermediate transfer belt, the secondary transfer roller, Are separated from each other.
According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect , the intermediate transfer belt is rotatably stretched when the secondary transfer counter roller is displaced by the first contact / separation means. It has a mechanism for displacing at least one of the plurality of roller members other than the secondary transfer counter roller to suppress the occurrence of slack in the intermediate transfer belt.
According to a sixth aspect of the present invention, in the image forming apparatus of the fourth aspect , when the intermediate transfer belt and the first image carrier are separated by the second contact / separation means, the intermediate transfer belt When the secondary transfer counter roller is displaced by the first contact / separation means, the intermediate transfer belt is slackened by the secondary transfer counter roller and the support member. It has the mechanism which suppresses this, It is characterized by the above-mentioned.

  As described above, according to the present invention, there is an excellent effect that it is possible to make it difficult for paper jam to occur while reducing the contact between the intermediate transfer belt and the recording medium.

(A) Explanatory drawing in the case of displacing the whole intermediate transfer unit and separating an intermediate transfer belt from a photosensitive drum and a secondary transfer roller. (B) An explanatory view when the entire intermediate transfer unit is displaced and the intermediate transfer belt is brought into contact with the photosensitive drum and the secondary transfer roller. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. Explanatory drawing of an intermediate transfer unit and an image formation unit. FIG. 4 is a schematic diagram illustrating a state where an intermediate transfer belt and a secondary transfer roller are in contact with each other. FIG. 4 is a schematic diagram illustrating a state where an intermediate transfer belt and a secondary transfer roller are separated from each other. FIG. 3 is a schematic diagram when the primary transfer roller is displaced in a direction away from the photosensitive drum to separate the intermediate transfer belt from the photosensitive drum. FIG. 6 is a schematic diagram when the intermediate transfer belt and the secondary transfer roller are separated from each other while maintaining the positional relationship (geometric relationship) between the intermediate transfer unit and the photosensitive drum. FIG. 3 is a schematic configuration diagram of a contact / separation mechanism that contacts and separates the intermediate transfer belt and the secondary transfer roller while maintaining the positional relationship (geometric relationship) between the intermediate transfer unit and the photosensitive drum. FIG. 4 is a schematic diagram when a driving roller that supports an intermediate transfer belt is displaced in a direction away from the secondary transfer roller, and the intermediate transfer belt is separated from the secondary transfer roller. FIG. 6 is a schematic diagram when adjusting the tension of the intermediate transfer belt by the tension roller in accordance with the extension of the intermediate transfer belt when the drive roller is displaced to separate the intermediate transfer belt from the secondary transfer roller. FIG. 6 is a schematic diagram when a support member that supports the intermediate transfer belt when the intermediate transfer belt is separated from the photosensitive drum is disposed inside the loop of the intermediate transfer belt. FIG. 6 is a schematic diagram when the tension of the intermediate transfer belt is maintained by the driving roller and the support member after being separated from the secondary transfer roller. (A) Explanatory drawing when the intermediate transfer belt, the secondary transfer roller, and the photosensitive drum are separated. (B) Explanatory drawing when the intermediate transfer belt and the photosensitive drum are separated. (C) Explanatory drawing when the intermediate transfer belt is in contact with the secondary transfer roller and the photosensitive belt. (A) The schematic diagram which shows the state which the separation object and the drive roller separated. (B) The schematic diagram which shows the state which the separation object and the drive roller contacted.

Hereinafter, a first embodiment in which the present invention is applied to a color laser printer (hereinafter simply referred to as a printer) which is an electrophotographic image forming apparatus will be described.
FIG. 2 is a schematic configuration diagram illustrating the printer according to the embodiment. In the figure, the printer includes a printer unit.

  The printer unit includes four image forming units 1Y, 1M, 1C, and 1K for forming yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K) toner images. As shown in FIG. 3, the intermediate transfer unit 6 of the printer unit is horizontally arranged by a driving roller 8, a tension roller 15, and three primary transfer rollers 26Y, 26M, and 26C arranged inside the belt loop. The intermediate transfer belt 12 is stretched in an extending posture. The tension roller 15 is pivotally supported so that the tension is applied to the intermediate transfer belt 12 by being biased by a spring 61 from the inner side to the outer side of the intermediate transfer belt. The intermediate transfer belt 12 as an image carrier is moved endlessly in the counterclockwise direction in the drawing by the rotational driving of the driving roller 8. The three image forming units 1Y, 1M, 1C are arranged so as to be arranged along the stretched surface of the intermediate transfer belt 12.

  The image forming units 1Y, 1M, 1C, and 1K each include a photosensitive drum 11Y, 11M, 11C, and 11K, a charging device (not shown), a developing device (not shown), and a drum cleaning device (not shown). As a common holding body. The charging device uniformly charges the peripheral surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K, which are rotationally driven by a driving unit (not shown), in the dark with a polarity opposite to the charging polarity of the toner. As shown in FIG. 3, the image forming units 1Y, 1M, and 1C are integrated as an image forming unit 5. The image forming units 1Y, 1M, and 1C can be attached to and detached from the image forming unit 5, respectively. It is configured.

  Optical writing units 2Y, 2M, 2C, and 2K are disposed above the image forming units 1Y, 1M, and 1C and on the left side of the image forming unit 1K. Color image information sent from an external personal computer (not shown) is decomposed into Y, M, C, and K information by an image processing unit (not shown) and then processed in the printer unit. The optical writing unit 2 drives Y, M, C, and K light sources (not shown) by a well-known technique based on Y, M, C, and K color-separated image information. Write light for K is generated. Then, the peripheral surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K uniformly charged by the charging device are scanned with Y, M, C, and K writing light. Thereby, electrostatic latent images for Y, M, C, and K are formed on the peripheral surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K. Examples of the light source for the writing light include laser diodes and LEDs.

  The electrostatic latent images formed on the peripheral surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K are developed by a developing device that employs a well-known two-component developing system that uses a two-component developer composed of toner and carrier. Y, M, C, K toner images are obtained. Note that a developing device that employs a well-known one-component developing method using a one-component developer made of toner may be used.

  Of the four photosensitive drums, the photosensitive drums 11Y, 11M, and 11C are in contact with the intermediate transfer belt 12 to form primary transfer nips for Y, M, and C. Further, primary transfer rollers 26Y, 26M, and 26C that press the intermediate transfer belt 12 toward the photosensitive drums 11Y, 11M, and 11C are disposed inside the loop of the intermediate transfer belt 12. A primary transfer bias is applied to each of the primary transfer rollers 26Y, 26M, and 26C, whereby a transfer electric field is formed in the primary transfer nip for Y, M, and C. The Y, M, and C toner images formed on the peripheral surfaces of the photosensitive drums 11Y, 11M, and 11C are formed on the intermediate transfer belt 12 at the primary transfer nip for Y, M, and C by the action of a transfer electric field and nip pressure. The image is transferred while being superimposed on the surface (outer surface of the loop). As a result, a three-color superimposed toner image is formed on the front surface of the intermediate transfer belt 12.

  A direct transfer unit 7 is disposed on the right side of the intermediate transfer belt 12 in the drawing. The direct transfer unit 7 has an endless direct transfer belt 13. The direct transfer belt 13 is stretched in a vertically long posture by the secondary transfer roller 9, the drive roller 14, the tension roller 16, and the K transfer roller 36 </ b> K. Can be moved endlessly. The tension roller 16 is pivotally supported so as to swing, and is directly biased by the spring 62 from the inner side to the outer side of the transfer belt so as to directly apply tension to the transfer belt 13. Further, a portion where the direct transfer belt 13 is wound around the secondary transfer roller 9 is brought into contact with a portion where the intermediate transfer belt 12 is driven around the driving roller 8 to form a secondary transfer nip. A secondary transfer bias is applied to the secondary transfer roller 9, thereby forming a transfer electric field in the secondary transfer nip. Further, the direct transfer belt 13 is placed in contact with the K transfer roller 36K so as to abut the K photoconductor drum 11K, thereby forming a K direct transfer nip. Similarly to the primary transfer rollers 26Y, 26M, and 26C, a transfer bias is also applied to the transfer roller 36K, thereby forming a transfer electric field in the direct transfer nip for K.

  A first paper feed cassette 3 and a second paper feed cassette 4 are disposed below the housing of the printer unit so as to overlap in the vertical direction. These paper feed cassettes send out the recording paper P accommodated therein to the paper transport path. The fed recording paper P abuts against a registration roller pair 111 disposed in a paper conveyance path extending in the vertical direction in the printer unit and the skew is corrected, and then sandwiched between the rollers of the registration roller pair 111. . Then, the sheet is further sent upward by the registration roller pair 111 at a predetermined timing.

  The recording paper P delivered from the registration roller pair 111 sequentially passes through the K direct transfer nip and the Y, M, and C secondary transfer nips formed in the paper conveyance path. When the recording paper P passes through the K direct transfer nip, the K toner image on the peripheral surface of the photosensitive drum 11K is transferred onto the recording paper P under the action of a transfer electric field or nip pressure. Further, after that, when the recording paper P passes through the secondary transfer nip, three colors (Y, M, C) on the intermediate transfer belt 12 with respect to the K toner image transferred onto the recording paper P. The superimposed toner image is batch-transferred collectively under the action of a transfer electric field or nip pressure. As a result, a full-color image that is a four-color superimposed toner image of Y, M, C, and K is formed on the surface of the recording paper P.

  Transfer residual toner adhering to the surface of the photosensitive drums 11Y, 1M, 1C, and 1K after passing through the primary transfer nip for Y, M, and C and the direct transfer nip for K is removed by the drum cleaning device. Is done. The drum cleaning device for Y, M, C, and K may be a system that scrapes off toner with a cleaning blade, a system that scrapes off toner with a fur brush roller, or a magnetic brush cleaning system. It may be used.

  Above the secondary transfer nip, a fixing device 10 is provided that forms a fixing nip by contact between a heating roller and a pressure roller. The recording paper P that has passed through the secondary transfer nip is sent to a fixing nip in the fixing device 10 and subjected to a fixing process for fixing a full-color image on the recording paper P by heat and pressure. The positional relationship between the secondary transfer nip and the fixing nip of the fixing device 10 is set such that the recording paper P is conveyed straight from the secondary transfer nip to the fixing device 10. Thereafter, the recording paper P passes through the paper discharge path, passes through the paper discharge roller pair 30, and is discharged and stacked on a paper discharge tray 31 provided on the upper surface of the printer unit housing.

  In this printer, in the monochrome mode for forming a monochrome image, the K photoconductor drum 11K is optically scanned by the optical writing unit 2K based on monochrome image data sent from an external personal computer (not shown). The electrostatic latent image for K formed thereby is developed into a K toner image by the developing device for K. The K toner image is directly transferred onto the recording paper P by the K direct transfer nip and then fixed on the recording paper P by the fixing device 10.

  The image forming units 1Y, 1M, 1C (photosensitive drums 11Y, 11M) are driven by useless driving by forming a monochrome image with the driving of the image forming units 1Y, 1M, 1C and the intermediate transfer belt 12 stopped. , 11C) and the intermediate transfer belt 12 can be avoided, and the life can be extended.

  In the monochrome mode, since the K toner image is directly transferred from the image forming unit 1K to the recording paper P sent from the registration roller pair 111 and sent to the K direct transfer nip by the direct transfer belt 13, the image forming unit 1Y, In addition to M and C, the image forming unit 1K is also arranged along the stretched surface of the intermediate transfer belt 12, and the K toner image is transferred onto the recording paper P via the intermediate transfer belt 12 at the secondary transfer nip. High-speed printing can be realized as compared with the configuration in which the image is transferred to the printer.

[Configuration example 1]
In the printer of this embodiment, as shown in FIGS. 4 and 5, the intermediate transfer belt 12 is brought into contact with and separated from the secondary transfer roller 9 via the direct transfer belt 13, and the secondary transfer roller in the monochrome mode. 9, the intermediate transfer belt 12 is separated. In this configuration, since the secondary transfer roller 9 and the recording paper P are conveyed while being in contact with each other via the direct transfer belt 13, even if the intermediate transfer belt 12 is separated from the secondary transfer roller 9, the direct transfer belt 13. Therefore, the behavior of the recording paper P between the transfer belt 13 and the fixing device 10 can be stabilized without changing the transporting posture of the recording paper P carried and transported. For this reason, it is possible to suppress paper jams and the occurrence of wrinkles and image disturbance on the recording paper P after being discharged from the fixing device 10. Further, by separating the intermediate transfer belt 12 from the secondary transfer roller 9, the recording paper P carried and conveyed directly on the transfer belt 13 does not come into contact with the intermediate transfer belt 12, so that the intermediate transfer belt 12 is deteriorated. Thus, the life of the intermediate transfer belt 12 can be extended.

  In the monochrome mode, when the intermediate transfer unit 6 is separated from the secondary transfer roller 9, the entire intermediate transfer unit 6 is separated from the photosensitive drums 11Y, 11M, and 11C as shown in FIGS. It is possible to prevent the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C from deteriorating due to the friction between the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C.

  FIG. 1 shows a contact / separation mechanism for contacting / separating the intermediate transfer unit 6 with respect to the photosensitive drums 11Y, 11M, 11C and the secondary transfer roller 9. 1A shows a case where the intermediate transfer unit 6 is separated from the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9, and FIG. 1B shows that the intermediate transfer unit 6 is separated from the photosensitive drums 11Y, 11Y, 11Y, and 11D. 11M, 11C, and the secondary transfer roller 9.

  When the intermediate transfer unit 6 is separated from the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9, the motor 70 is rotated and the gear 72 is rotated clockwise in FIG. Then, the cam 73 is pushed down around the fulcrum 73a along with the rotation of the gear 72, and the arm 74 is rotated around the fulcrum 74a along with the displacement of the cam 73 and lowered by its own weight. The arm 74 is linked to the other arm 75 via the link mechanism 76, and all the arms move in the same manner. The arms 74 and 75 and the intermediate transfer unit 6 are connected to each other, and the intermediate transfer unit 6 is lowered by its own weight in accordance with the displacement of the arms 74 and 75. As a result, the intermediate transfer unit 6 is separated from the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9.

  When the intermediate transfer unit 6 is brought into contact with the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9, the motor 70 is rotated and the gear 72 is rotated counterclockwise through the gear 71 in the drawing. Then, the cam 73 is pushed up around the fulcrum 73a along with the rotation of the gear 72, and the arm 74 is turned around the fulcrum 74a and pushed up along with the displacement of the cam 73. Since the arms 74 and 75 are linked via the link mechanism 76 as described above, all the arms move in the same manner, and the intermediate transfer unit 6 connected to the arms 74 and 75 is pushed up. As a result, the intermediate transfer unit 6 comes into contact with the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9.

  Since the contact / separation operation of the intermediate transfer unit 6 is an arc orbit, at the time of separation, the intermediate transfer belt 12 is separated from the secondary transfer roller 9 after the intermediate transfer belt 12 is separated from the photosensitive drums 11Y, 11M, and 11C. At the time of contact, the intermediate transfer belt 12 is brought into contact with the secondary transfer roller 9, and then the intermediate transfer belt 12 is brought into contact with the photosensitive drums 11Y, 11M, and 11C. Therefore, the contact / separation operation can be performed without damaging the photosensitive drums 11Y, 11M, and 11C. Further, since the intermediate transfer belt 12 can be brought into and out of contact with the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9 by one contact / separation mechanism, the intermediate transfer belt 12 is attached using a separate contact / separation mechanism. The number of parts can be reduced and the cost can be reduced as compared with the configuration in which the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9 are brought into contact with and separated from each other.

  Further, as shown in FIG. 6, the primary transfer rollers 26Y, 26M, and 26C are displaced away from the photosensitive drums 11Y, 11M, and 11C, and the intermediate transfer belt 12 is separated from the photosensitive drums 11Y, 11M, and 11C. A simple configuration may be used. In this case, unlike the case where the entire intermediate transfer unit 6 as shown in FIG. 5 is separated from the photosensitive drums 11Y, 11M, and 11C, a space-saving configuration is possible.

[Configuration example 2]
In this configuration example, as shown in FIG. 7, the intermediate transfer belt 12 and the secondary transfer roller 9 are maintained while maintaining the positional relationship (geometric relationship) between the intermediate transfer unit 6 and the photosensitive drums 11Y, 11M, and 11C. Detach the contact. By maintaining the positional relationship (geometric relationship) between the intermediate transfer unit 6 and the photosensitive drums 11Y, 11M, and 11C as in this configuration example, the intermediate transfer belt 12 and the secondary transfer roller 9 are brought into contact with and separated from each other. Deterioration of the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C due to both rubbing can be suppressed.

  FIG. 8 shows a contact / separation mechanism for contacting / separating the intermediate transfer belt 12 and the secondary transfer roller 9 while maintaining the positional relationship (geometric relationship) between the intermediate transfer unit 6 and the photosensitive drums 11Y, 11M, and 11C. .

  When the intermediate transfer belt 12 is separated from the secondary transfer roller 9, the motor 80 is rotated and the gear 82 is rotated clockwise through the gear 81 in the drawing. As the gear rotates, the cam 83 rotates around the fulcrum 83a in the clockwise direction in the drawing, and the link mechanism 86 to which the arms 84 and 85 are connected is attached to the spring mounting base 88 in the image forming apparatus main body. The spring 87 is pushed back. When the link mechanism 86 is pushed back by the spring 87 in this way, the arms 84 and 85 connected to the link mechanism 86 rotate around the fulcrums 84a and 85a counterclockwise in the drawing. The arms 84 and 85 are connected to the image forming unit 5 and the intermediate transfer unit 6, and the image forming unit 5 and the intermediate transfer unit 6 are displaced in the direction of arrow A in the drawing as the arms 74 and 75 rotate. As a result, the intermediate transfer belt 12 is separated from the secondary transfer roller 9 while maintaining the geometric relationship between the image forming unit 5 and the intermediate transfer unit 6.

  When the intermediate transfer belt 12 is brought into contact with the secondary transfer roller 9, the motor 80 is rotated and the gear 82 is rotated counterclockwise through the gear 81. Then, along with the rotation of the gear 82, the cam 83 rotates about the fulcrum 83a counterclockwise in the figure, and the link mechanism 86 to which the arms 84 and 85 are connected is connected to the spring 87 attached to the spring mounting base 88. Is pushed out against the biasing force from the spring 87. Thus, when the link mechanism 86 is pushed out against the urging force from the spring 87, the arms 84 and 85 connected to the link mechanism 86 rotate around the fulcrum 84a and the fulcrum 85a in the clockwise direction in the drawing. Since the arms 84 and 85 are connected to the image forming unit 5 and the intermediate transfer unit 6, the image forming unit 5 and the intermediate transfer unit 6 are displaced in the direction of arrow B in the drawing in accordance with the rotation of the arms 74 and 75. To do. As a result, the intermediate transfer unit 6 contacts the secondary transfer roller 9 while maintaining the geometric relationship between the image forming unit 5 and the intermediate transfer unit 6.

  Since the intermediate transfer belt 12 contacts and separates from the secondary transfer roller 9 while maintaining the geometric relationship (positional relationship) between the image forming unit 5 and the intermediate transfer unit 6, the intermediate transfer belt 12 and the photosensitive drum 11Y are brought into contact with and separated from each other. , 11M, 11C can be prevented from rubbing against each other.

[Configuration example 3]
In this configuration example, as shown in FIG. 9, the driving roller 8 that supports the intermediate transfer belt 12 is displaced away from the secondary transfer roller 9, and the intermediate transfer belt 12 is separated from the secondary transfer roller 9. Yes. Accordingly, the intermediate transfer belt 12 can be separated from the secondary transfer roller 9 by displacing the drive roller 8 without moving the entire intermediate transfer unit 6.

  When the drive roller 8 is displaced and the intermediate transfer belt 12 is separated from the secondary transfer roller 9, there is a possibility that the photosensitive drums 11 </ b> Y, 11 </ b> M, 11 </ b> C and the intermediate transfer belt 12 are rubbed due to the extension of the intermediate transfer belt 12. Therefore, as shown in FIG. 9, the primary transfer rollers 26Y, 26M, and 26C are displaced away from the photosensitive drums 11Y, 11M, and 11C to separate the intermediate transfer belt 12 from the photosensitive drums 11Y, 11M, and 11C. Thus, it is possible to prevent the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C from being deteriorated due to the friction between the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C.

  Further, as shown in FIG. 10, the tension roller 15 causes the intermediate transfer belt 12 to be extended by the extension of the intermediate transfer belt 12 when the drive roller 8 is displaced to separate the intermediate transfer belt 12 from the secondary transfer roller 9. By adjusting the tension and maintaining a desired stretched state, the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11D are caused by the friction between the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C as described above. 11C degradation can be prevented.

  If there is no space for stretching the intermediate transfer belt 12 by the tension roller 15, the primary transfer rollers 26Y, 26M, and 26C are placed inside the loop of the intermediate transfer belt 12 as shown in FIGS. A support member 18 that supports the intermediate transfer belt 12 when the intermediate transfer belt 12 is moved away from the drums 11Y, 11M, and 11C and separated from the photosensitive drums 11Y, 11M, and 11C is disposed. Thus, as shown in FIG. 12, the tension of the intermediate transfer belt 12 can be maintained by the drive roller 8 and the support member 18 after being separated from the secondary transfer roller 9.

  In FIG. 13, the driving roller 8 that supports the intermediate transfer belt 12 is displaced so that the intermediate transfer belt 12 is brought into contact with and separated from the secondary transfer roller 9, and the primary transfer rollers 26Y, 26M, and 26C are displaced, thereby causing the photosensitive drum to move. A contact / separation mechanism for contacting and separating the intermediate transfer belt 12 with respect to 11Y, 11M, 11C is shown. 13A shows the case where the intermediate transfer belt 12, the secondary transfer roller 9, and the photosensitive drums 11Y, 11M, and 11C are separated from each other. FIG. 13B shows the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M. 11C are separated from each other, and FIG. 13C shows the case where the intermediate transfer belt 12, the secondary transfer roller 9, and the photosensitive drums 11Y, 11M, and 11C are in contact with each other.

  In the case where the intermediate transfer unit 6 is separated from the secondary transfer roller 9, the slide table 93 is shown in the figure via a pinion gear 91 attached to the motor 90 by rotating the motor 90 and a rack gear 92 formed on the slide table 93. Move horizontally in the direction of arrow C. Along with the movement of the slide table 93, the joint 94 that connects the slide table 93 and the drive roller 8 rotates clockwise in the drawing around the fulcrum 94a. The drive roller 8 is separated from a secondary transfer roller (not shown) by the rotation of the joint 94. Even after the drive roller 8 is separated from the secondary transfer roller, the slide table 93 further moves horizontally in the direction of arrow C in the figure, but the drive roller 8 does not move because the joint 94 has play. Further, the frames 95Y, 95M, and 95C guided in the vertical direction of the image forming apparatus main body by the guide members 96Y, 96M, and 96C ride on the convex portions 93aY, 93aM, and 93aC of the slide base 93, so that the springs 97Y, 97M, The primary transfer rollers 26Y, 26M, and 26C are pushed upward by the urging force from 97C, and the primary transfer rollers 26Y, 26M, and 26C and a photosensitive drum (not shown) are in contact with each other through an intermediate transfer belt (not shown). The primary transfer rollers 26Y, 26M, and 26C pushed up in this way are moved from the projections 93aY, 93aM, and 93aC to the upper surface of the slide table 93 by moving the slide table 93 in the direction of arrow C in the figure. By moving to 93bY, 93bM, and 93bC, the springs 97Y, 97M, and 97C are not pushed up by the urging force and fall downward. As described above, the primary transfer rollers 26Y, 26M, and 26C are lowered, whereby the intermediate transfer belt can be separated from the photosensitive drum.

  When the intermediate transfer unit 6 is brought into contact with the secondary transfer roller 9, the motor 90 is rotated and the slide table 93 is moved horizontally in the direction of arrow D in the figure via the pinion gear 91 and the rack gear 92. Along with the movement of the slide table 93, the joint 94 rotates counterclockwise in the figure around the fulcrum 94a. Due to the rotation of the joint 94, the driving roller 8 comes into contact with a secondary transfer roller (not shown). Even after the drive roller 8 comes into contact with the secondary transfer roller, the slide table 93 further moves horizontally in the direction of arrow D in the figure, but the drive roller 8 does not move because the joint 94 has play. Further, the pieces 95Y, 95M, and 95C move from the upper surfaces 93bY, 93bM, and 93bC of the slide table 93 onto the convex portions 93aY, 93aM, and 93aC of the slide table 93 by the movement of the slide table 93 in the arrow D direction in the drawing. The primary transfer rollers 26Y, 26M, and 26C are pushed up by the biasing force from the springs 97Y, 97M, and 97C. By thus pushing up the primary transfer rollers 26Y, 26M, and 26C, the intermediate transfer belt can be brought into contact with the photosensitive drum.

  Further, by providing play in the joint 94, the timing at which the primary transfer rollers 26Y, 26M, and 26C are displaced to bring the intermediate transfer belt 12 into and out of contact with the photosensitive drums 11Y, 11M, and 11C, and the drive roller 8 are displaced. Thus, the timing at which the intermediate transfer belt 12 is brought into contact with and separated from the secondary transfer roller 9 is shifted. That is, as described above, the intermediate transfer belt 12 is separated from the photosensitive drums 11Y, 11M, and 11C at the time of separation, and then the intermediate transfer belt 12 is separated from the secondary transfer roller 9. After the intermediate transfer belt 12 is brought into contact with the next transfer roller 9, the intermediate transfer belt 12 is brought into contact with the photosensitive drums 11Y, 11M, and 11C. Further, since the intermediate transfer belt 12 can be brought into and out of contact with the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9 by one contact / separation mechanism, the intermediate transfer belt 12 is attached using a separate contact / separation mechanism. The number of parts can be reduced and the cost can be reduced as compared with the configuration in which the photosensitive drums 11Y, 11M, and 11C and the secondary transfer roller 9 are brought into contact with and separated from each other.

As described above, according to the present embodiment, the intermediate transfer belt 12 that is rotatably stretched around the plurality of roller members, and the first image carrier disposed to face the front surface of the intermediate transfer belt 12. A first image forming unit that forms an image on the first image carrier, and a primary transfer unit that primarily transfers the image formed on the first image carrier onto the intermediate transfer belt 12. A secondary transfer nip that is formed by the transfer rollers 26Y, 26M, and 26C and the front surface of the intermediate transfer belt 12 facing each other and formed by contacting the front surface of the intermediate transfer belt 12 and itself. A secondary transfer roller 9 for secondary transfer of an image transferred on the intermediate transfer belt 12 onto a recording sheet as a recording medium, and a second transfer roller provided upstream or downstream of the secondary transfer nip in the recording sheet conveyance direction. Form an image on the second image carrier and the second image carrier In the image forming apparatus including the second image forming unit and the transfer roller 36K which is a direct transfer unit for directly transferring the image formed on the second image carrier onto the recording paper, the secondary transfer roller 9 A contact / separation mechanism that is a contact / separation means for contacting / separating the intermediate transfer belt 12 with respect to the intermediate transfer belt 12, and a second contact / separation mechanism for contacting / separating the intermediate transfer belt 12 and the first image carrier, After the intermediate transfer belt 12 and the first image carrier are separated from each other by the second contact / separation mechanism, the intermediate transfer belt 12 is separated from the secondary transfer roller 9 by the contact / separation mechanism . According to this embodiment, the intermediate transfer belt 12 is brought into contact with and separated from the secondary transfer roller 9 by the contact and separation mechanism. Accordingly, the intermediate transfer belt 12 is separated from the secondary transfer roller 9 by the contact / separation mechanism, so that the intermediate transfer belt 12 is moved from the recording medium conveyance path when the intermediate transfer belt 12 is in contact with the secondary transfer roller 9. Can be evacuated. Therefore, it recording paper that is being conveyed to the opposing portion between the intermediate transfer belt 12 and the secondary transfer roller 9 is hard to contact with the intermediate transfer belt 12, wear of the intermediate transfer belt 12 is suppressed gills of the intermediate transfer belt 12 life Can be extended. In the configuration in which the intermediate transfer belt 12 is brought into contact with and separated from the secondary transfer roller 9, the position of the secondary transfer roller 9 is different depending on whether the secondary transfer roller 9 and the intermediate transfer belt 12 are in contact with each other or separated from each other. Do not change. Therefore, when the intermediate transfer belt 12 is separated from the secondary transfer roller 9 by the contact / separation mechanism and the recording paper is conveyed, if the recording paper passes through a position where the secondary transfer roller 9 and the recording paper are in contact with each other, the intermediate transfer is performed. When the belt 12 and the secondary transfer roller 9 are in contact with each other, the recording paper passes through the same position where the secondary transfer nip can be formed. Therefore, paper jams can be made less likely to occur because the recording paper can be transported along the same recording paper transport path as when the intermediate transfer belt 12 and the secondary transfer roller 9 are in contact with each other.
Further, after the intermediate transfer belt 12 and the first image carrier are separated by the second contact / separation mechanism, the intermediate transfer belt 12 is separated from the secondary transfer roller 9 by the contact / separation means. When the transfer belt 12 and the secondary transfer roller 9 are separated from each other, the intermediate transfer belt 12 and the first image carrier are rubbed against each other to prevent the intermediate transfer belt 12 and the first image carrier from being worn. can do.
According to the present embodiment, the recording paper is carried and conveyed so as to pass through the direct transfer position where the image is directly transferred from the second image carrier onto the recording paper and the secondary transfer nip. A direct transfer belt 13 which is a recording medium conveyance belt stretched around a plurality of roller members in a rotatable manner is provided, and the secondary transfer roller 9 is in contact with the intermediate transfer belt 12 via the direct transfer belt 13. As a result, fluctuations in the recording paper conveyance path between the direct transfer position and the secondary transfer nip are suppressed, and the recording paper can be stably conveyed between the direct transfer position and the secondary transfer nip.
Further, according to the present embodiment, when the intermediate transfer belt 12 and the secondary transfer roller 9 are separated by the contact / separation mechanism, the first image carrier, the first image forming unit, the primary transfer roller 26, By stopping the driving of the plurality of roller members and the intermediate transfer belt 12, the wear of the first image carrier, the intermediate transfer belt 12, and the like can be suppressed, and the life can be extended .
Also, according to this embodiment, the driving roller one of the plurality of roller members is also a secondary transfer counter roller facing the secondary transfer roller 9 at the secondary transfer position via the intermediate transfer belt 12 8 The contact / separation mechanism displaces the intermediate transfer belt 12 and the secondary transfer roller 9 by displacing the driving roller 8 in a direction away from the secondary transfer roller 9. Accordingly, it is possible to reduce the number of objects to be separated and reduce the energy required for the separation. Further, it is possible to save the space in the image forming apparatus main body as compared with the case where the entire intermediate transfer unit 6 is displaced.
Further, according to the present embodiment, at least one roller other than the drive roller 8 among the plurality of roller members that rotatably stretch the intermediate transfer belt 12 when the drive roller 8 is displaced by the contact / separation mechanism. By having a mechanism for displacing the tension roller 15 as a member to prevent the intermediate transfer belt 12 from slackening, the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, and 11C rub against each other. 12 and the photosensitive drums 11Y, 11M, and 11C can be prevented from being deteriorated.
Further, according to the present embodiment, the support member 18 that supports the intermediate transfer belt 12 when the intermediate transfer belt 12 and the first image carrier are separated by the second contact / separation mechanism, When the drive roller 8 is displaced by the contact / separation mechanism, the intermediate transfer belt 12 and the photoconductor drum 11Y are provided with a mechanism that suppresses slack in the intermediate transfer belt 12 caused by the drive roller 8 and the support member 18. , 11M, 11C can be prevented from deteriorating the intermediate transfer belt 12 and the photosensitive drums 11Y, 11M, 11C.

  In the image forming apparatus according to the present embodiment, as a contact / separation mechanism for displacing the intermediate transfer belt 12 with respect to the secondary transfer roller 9 by displacing the driving roller 8 of the intermediate transfer belt or the entire intermediate transfer unit 6, FIG. It is also possible to use the contact / separation mechanism shown in FIG. 14A shows a state in which the separation target 25 and the driving roller 8 are separated from each other, and FIG. 14B shows a state in which the separation target 25 and the driving roller 8 are in contact with each other. In this contact / separation mechanism, the rotation of the input gear 21 is transmitted to the gear 22, the cam 23 is rotated in accordance with the rotation of the gear 22, and the arm 24 connected to the cam 23 is moved by the rotation of the cam 23, whereby the separation target 25. Is separated from the drive roller 8 of the intermediate belt. The separation target 25 is the drive roller 8 of the intermediate transfer belt 12, the intermediate transfer unit 6, or the like.

  The distance for separating the intermediate transfer belt 12 from the secondary transfer roller 9 and the photosensitive drums 11Y, 11M, and 11C may be about 2 mm. Further, the intermediate transfer belt 12 may be brought into contact with and separated from the secondary transfer roller 9 and the photosensitive drums 11Y, 11M, and 11C at the same time.

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Optical writing unit 3 Paper feed cassette 4 Paper feed cassette 5 Image forming unit 6 Intermediate transfer unit 7 Direct transfer unit 8 Drive roller 9 Secondary transfer roller 10 Fixing device 11 Photosensitive drum 12 Intermediate transfer belt 13 Direct Transfer belt 14 Drive roller 15 Tension roller 16 Tension roller 18 Support member 21 Input gear 22 Gear 23 Cam 24 Arm 25 Separation target 26 Primary transfer roller 30 Paper discharge roller pair 31 Paper discharge tray 36 Transfer roller 61 Spring 62 Spring 70 Motor 71 Gear 72 gear 73 cam 74 arm 74a fulcrum 75 arm 75a fulcrum 76 link mechanism 80 motor 81 gear 82 gear 83 cam 83a fulcrum 84 arm 84a fulcrum 85 arm 85a fulcrum 86 link mechanism 87 88 spring mount 90 motor 91 pinion gear 92 a rack gear 93 sliding base 93a protrusion 93b upper surface 94 fitting 94a fulcrum 95 piece 96 guide member 97 spring 111 registration roller pair

JP 2004-205943 A

Claims (6)

An intermediate transfer belt rotatably stretched around a plurality of roller members;
A first image carrier disposed opposite to the front surface of the intermediate transfer belt;
First image forming means for forming an image on the first image carrier;
Primary transfer means for primarily transferring an image formed on the first image carrier onto the intermediate transfer belt;
The intermediate transfer belt was transferred onto the intermediate transfer belt at a secondary transfer nip formed by being opposed to the front surface of the intermediate transfer belt and formed by contacting the front surface of the intermediate transfer belt with itself. A secondary transfer roller for secondary transfer of an image onto a recording medium;
A second image carrier provided upstream or downstream of the secondary transfer nip in the recording medium conveyance direction;
Second image forming means for forming an image on the second image carrier;
Direct transfer means for directly transferring an image formed on the second image carrier onto a recording medium;
In an image forming apparatus comprising:
A first moving means for contacting and separating the intermediate transfer belt to the secondary transfer roller,
A second contact / separation means for contacting and separating the intermediate transfer belt and the first image carrier;
The intermediate transfer belt and the first image carrier are separated from each other by the second contact / separation unit, and then the intermediate transfer belt is separated from the secondary transfer roller by the first contact / separation unit. An image forming apparatus. The image forming apparatus according to claim 1.
A plurality of roller members rotatably capable of carrying and transporting the recording medium so as to pass through the direct transfer position where the image is directly transferred from the second image carrier onto the recording medium and the secondary transfer nip. A recording medium transport belt stretched by
The image forming apparatus, wherein the secondary transfer roller is in contact with the intermediate transfer belt via the recording medium conveying belt. The image forming apparatus according to claim 1.
When the intermediate transfer belt and the secondary transfer roller are separated by the first contact / separation means, the first image carrier, the first image forming means, the primary transfer means, and the plurality of An image forming apparatus, wherein driving of the roller member and the intermediate transfer belt is stopped. The image forming apparatus according to claim 1, 2 or 3.
One of the plurality of roller members is a secondary transfer opposing roller that faces the secondary transfer roller at a secondary transfer position via the intermediate transfer belt,
The first contact / separation means displaces the secondary transfer counter roller in a direction away from the secondary transfer roller to separate the intermediate transfer belt from the secondary transfer roller. apparatus. The image forming apparatus according to claim 4 .
At least one of the plurality of roller members other than the secondary transfer counter roller that rotatably stretches the intermediate transfer belt when the secondary transfer counter roller is displaced by the first contact / separation means. An image forming apparatus having a mechanism for suppressing the slack of the intermediate transfer belt by displacing the intermediate transfer belt. The image forming apparatus according to claim 4 .
A support member that supports the intermediate transfer belt when the intermediate transfer belt and the first image carrier are separated by the second contact / separation unit;
A mechanism that suppresses the occurrence of slack in the intermediate transfer belt by the secondary transfer counter roller and the support member when the secondary transfer counter roller is displaced by the first contact / separation unit; An image forming apparatus.

Images