JP5625658B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, a plurality of photosensitive members as an image carrier that carries an image on the surface, and a plurality of devices including various devices that perform image forming processing on the photosensitive member. A so-called tandem type in which image portions are arranged side by side is known. In this tandem type image forming apparatus, images on each photosensitive member are sequentially transferred to an intermediate transfer belt used as an intermediate transfer member by a primary transfer device, and then images on the intermediate transfer belt are transferred by a secondary transfer device. There are an intermediate transfer type that batch-transfers to a sheet, and a direct transfer type that sequentially transfers images on each photosensitive member to a sheet conveyed by a transfer belt or the like by a transfer device.

  Further, in the direct transfer type image forming apparatus using the conveying belt, in order to suppress the consumption and deterioration of the color toner and the wear of the color image photosensitive member during the formation of the monochrome image, FIG. As shown in FIG. 2, there is a belt belt 98 configured to be separable from the photoconductors 2Y, 2M, and 2C for color images other than black (see Patent Document 1 or 2). In this case, the plurality of transfer rollers 8Y, 8M, and 8C that are in contact with the color image photoreceptors 2Y, 2M, and 2C via the conveyance belt 98 are moved downward, so that the conveyance belt 98 is the color image photoreceptor. Separated from 2Y, 2M, 2C. As described above, by separating the conveyance belt 98, it is possible to stop the driving of the color image photoreceptors 2Y, 2M, and 2C that are not used during monochrome image formation, and the respective photoreceptors and the cleaning members that are in contact with them. It is possible to suppress the wear and the like and the deterioration of the color toner. Further, since the sheet can be conveyed without being brought into contact with the color image photoreceptors 2Y, 2M, and 2C, it is possible to prevent the photoreceptor from being worn by the contact with the sheet and the color toner from being attached (fogged) to the sheet. You can also

  However, in the configuration in which the transfer belts 8Y, 8M, 8C, and 8Bk are directly in contact with the photosensitive members 2Y, 2M, 2C, and 2Bk without the conveyance belt 98 as shown in FIG. If the transfer rollers 8Y, 8M, and 8C are moved downward and separated from the color image photoreceptors 2Y, 2M, and 2C as shown in FIG. There is a problem of disappearing. Therefore, in particular, a configuration that does not have such a conveyance belt requires a separate measure for suppressing deterioration of a color photoconductor that is not used when a monochrome image is formed.

  2. Description of the Related Art Conventionally, in a direct transfer type image forming apparatus that does not have a conveyance belt, two types of paper conveyance paths for color printing and monochrome printing are provided in order to suppress the wear and the like of a color photoconductor during monochrome image formation. Have been proposed (see Patent Document 3).

  Specifically, as shown in FIG. 6, a supply path A for supplying the paper P from the paper supply unit 6 to the black image photoreceptor 2Bk, and two transport paths B1 branched downstream in the supply direction. , B2 are arranged. Of the two transport paths B1 and B2, the transport path B1 on the upper side in the figure is a transport path for transporting the paper P so as to contact the color image photoreceptors 2Y, 2M, and 2C. The side transport path B2 is a transport path for transporting the paper P so as not to contact the color image photoreceptors 2Y, 2M, and 2C.

  When color image formation is performed in this image forming apparatus, the image on each of the photoreceptors 2Y, 2M, and 2C is transferred to the sheet P by conveying the sheet P via the upper conveyance path B1 in FIG. be able to. On the other hand, when performing monochrome image formation, the sheet P can be conveyed without contacting the photoreceptors 2Y, 2M, and 2C by conveying the sheet P via the lower conveyance path B2 in FIG. Therefore, it is possible to prevent the photoreceptors 2Y, 2M, and 2C from being worn out. Further, as shown in FIG. 6, the switching between the two transport paths B1 and B2 is a transport switching disposed so as to be swingable between the black image photoreceptor 2Bk and the yellow image photoreceptor 2Y. This is done by the member 99.

  However, since the conventional image forming apparatus shown in FIG. 6 has the conveyance switching member 99 disposed between the black image photoreceptor 2Bk and the yellow image photoreceptor 2Y, the black image photoreceptor. There is a problem that the distance between 2Bk and the photoreceptor 2Y for yellow image becomes wide, and the apparatus becomes large. Further, since the transfer switching member 99 is provided, there is a problem that the number of parts is increased and the cost is increased.

  Therefore, in view of such circumstances, the present invention can achieve downsizing and cost reduction, and at the time of image formation using a part of the image forming unit, the image forming unit not used for image formation is deteriorated. An object of the present invention is to provide an image forming apparatus that can be suppressed.

The invention of claim 1 is arranged in parallel along a recording medium supply unit for supplying a recording medium, a recording medium conveying means for conveying the supplied recording medium, and a conveying path for conveying the recording medium, In an image forming apparatus comprising a plurality of image forming units for forming an image on a recording medium to be conveyed, for supplying the recording medium to the upstreammost image forming unit connected to the upstream end of the conveying path in the conveying direction A first supply path; and a second supply path for supplying a recording medium to the image forming unit different from the uppermost image forming unit that merges in the middle of the transport path, and the recording medium supply unit Is configured to be movable, and the supply position for supplying the recording medium from the recording medium supply unit can be arranged so as to selectively correspond to the upstream end in the supply direction of the first supply path and the second supply path. Configure and detect the position of the recording medium supply unit Includes a location detection means, based on the position of the recording medium supply unit detected by said position detecting means, which is constituted so as to determine the image formation mode.

Since the image forming apparatus includes the first supply path and the second supply path, a conveyance path that allows the recording medium to pass through all the image forming units, and a conveyance path that allows the recording medium to pass only through some of the image forming units. And can be selected. Specifically, when the recording medium is supplied via the first supply path, the recording medium is supplied to the most upstream image forming unit. In this case, all the recordings from the most upstream to the most downstream are made. A recording medium is supplied to the image portion. On the other hand, when the recording medium is supplied via the second supply path, the recording medium is supplied from the imaging unit to which the recording medium is supplied to the downstream imaging unit. Is not supplied with a recording medium. Therefore, when image formation in the upstream image forming unit is not required, by selecting the second supply path, unnecessary driving of the upstream image forming unit and unnecessary contact with the recording medium are performed. This can be avoided, and deterioration of the image forming unit can be suppressed. In addition, since the second supply path is arranged so as to merge in the middle of the transport path, recording from the second supply path to the transport path is possible without providing a transport switching member for switching the transport path. It is possible to guide the medium.
Further, by moving the recording medium supply unit and arranging the supply position of the recording medium supply unit selectively corresponding to the upstream ends in the supply direction of the first supply path and the second supply path, The recording medium can be selectively sent from the recording medium supply unit to both supply paths. Thereby, it is not necessary to provide a plurality of recording medium supply units corresponding to the respective supply paths, and the size and cost can be reduced.
In addition, by detecting the position of the recording medium supply unit by the position detection means, the recording medium supply unit is improperly arranged, so that the recording medium is not supplied properly, and the recording medium is jammed or jammed. Occurrence can be prevented in advance. Further, the image forming mode is determined on the basis of the position of the recording medium supply unit detected by the position detecting unit, thereby arranging the recording medium supply unit (selecting the supply path) and selecting the image forming mode. It is possible to prevent the occurrence of a printing error due to the mismatch.

The invention of claim 2 is provided in parallel along a recording medium supply unit for supplying a recording medium, a recording medium conveying means for conveying the supplied recording medium, and a conveying path for conveying the recording medium, In an image forming apparatus comprising a plurality of image forming units for forming an image on a recording medium to be conveyed, for supplying the recording medium to the upstreammost image forming unit connected to the upstream end of the conveying path in the conveying direction A first supply path; and a second supply path for supplying a recording medium to the image forming unit different from the uppermost image forming unit that merges in the middle of the transport path, and the recording medium supply unit was configured to be movable each recording medium, the recording medium supply unit is moved by the recording medium, a supply position for supplying the recording medium from the recording medium supply unit, away from each other in the moving direction of the recording medium supply unit It arranged the first supply path Wherein the feed direction upstream end of the second supply path is obtained by arrangement configured to be able to selectively correspond.

  One recording medium is provided by moving the recording medium supply unit so that the supply position of the recording medium supply unit is selectively associated with the upstream end of the first supply path and the second supply path in the supply direction. The recording medium can be selectively sent out from the supply unit to both supply paths. Thereby, it is not necessary to provide a plurality of recording medium supply units corresponding to the respective supply paths, and the size and cost can be reduced.

  Further, when the recording medium supply unit is configured to be movable, at least one of the first supply path and the second supply path can be formed shorter than when the recording medium supply unit is fixed. For this reason, the printing time can be shortened. In addition, when the recording medium supply unit is fixed, the upstream ends in the supply direction of both the first supply path and the second supply path must be arranged at the same position. Although a member is required, if the recording medium supply unit is configured to be movable, the conveyance switching member is not necessary, and the number of parts can be reduced.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect of the present invention, the image forming apparatus further includes a position detection unit that detects the position of the recording medium supply unit.

  In this case, since the position of the recording medium supply unit can be detected by the position detection means, the recording medium supply failure due to improper arrangement of the recording medium supply unit, the resulting recording medium clogging or jamming, etc. Occurrence of problems can be prevented in advance.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the image forming mode is determined based on the position of the recording medium supply unit detected by the position detecting means.

  By configuring the image forming mode to be determined based on the position of the recording medium supplying unit detected by the position detecting means, the disagreement between the arrangement of the recording medium supplying unit (selection of the supply path) and the selection of the image forming mode. It is possible to prevent the occurrence of printing mistakes due to.

  A fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, further comprising driving means for independently driving and stopping the plurality of image forming units.

  Accordingly, when the recording medium is supplied via the second supply path, it is possible to stop driving the image forming unit that does not perform image formation. Accordingly, unnecessary driving of the image forming unit can be prevented, and drive deterioration of the image forming unit can be suppressed and energy saving can be achieved.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a common driving unit that applies a driving force to the plurality of image forming units, and the respective image forming units from the driving unit. Switching means for independently switching between transmission and interruption of the driving force to the unit.

  In this case, when the recording medium is supplied via the second supply path, the drive transmission to the image forming unit that does not perform image formation can be interrupted to stop the drive. Thereby, similarly to the above, unnecessary driving of the image forming unit can be prevented, and drive deterioration of the image forming unit can be suppressed and energy saving can be achieved. Further, in this case, since the driving means of the image forming unit can be configured by a common driving means, it is possible to reduce the size and cost as compared with the case where separate driving means are provided.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the second supply path is disposed on the opposite side of the image forming unit across the transport path. It is a thing.

  By disposing the second supply path on the side opposite to the image forming unit across the transport path, the second supply path can be disposed at a place where there is a margin in the space. Miniaturization can be achieved.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the recording medium is guided to the image forming unit to which the recording medium is supplied via the second supply path. And a guide member for both the recording medium supplied via the first supply path and the recording medium supplied via the second supply path. It is composed.

  Since the guide member serves as both the guide member for the recording medium supplied via the first supply path and the recording medium supplied via the second supply path, the recording medium can be conveyed without increasing the number of parts. Can be secured.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the posture of the recording medium that has been supplied to the first supply path and the second supply path, respectively. And a registration means for feeding out the recording medium in time with the image formed by the image forming unit.

  By providing the registration means in both the first supply path and the second supply path, it is possible to correct the orientation of the recording medium and adjust the conveyance timing in each supply path, and to improve the quality of the printed image. Will be able to keep on.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the drive means of the registration means respectively disposed in the first supply path and the second supply path is a common drive means. is there.

  By using the driving means of the resist means arranged in each supply path as a common driving means, it is possible to reduce the size and cost.

  The invention according to claim 11 is the image forming apparatus according to any one of claims 1 to 10, wherein the plurality of image forming units include an image forming unit that forms a black image and a plurality of image forming units that form a color image. An image forming unit that forms the black image on the most downstream side, and supplies a recording medium to the image forming unit that forms the black image via the second supply path; It is composed.

  In this case, when the second supply path is selected, the recording medium is supplied only to the image forming unit that forms the black image, and the recording medium is not supplied to the image forming unit that forms the color image. This can avoid unnecessary driving of the image forming unit for forming a color image and unnecessary contact with the recording medium when forming a monochrome image generally frequently used, and suppresses deterioration of the image forming unit. Can do.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, each of the plurality of image forming units includes at least an image carrier that carries an image on a surface thereof. A plurality of transfer means for transferring the image on the carrier to the recording medium are arranged in direct contact with each image carrier and are configured to function as the recording medium conveying means.

  As described above, the image forming apparatus according to the present invention includes the first supply path and the second supply path, thereby conveying the recording medium through all of the image forming units, and a part of the image forming units. Therefore, it is possible to avoid the contact of the recording medium with the image carrier that does not perform image formation even if the transfer unit is not brought into and out of contact with the image carrier. For this reason, there is no problem of a decrease in transportability due to the transfer unit being separated from the image carrier, so that stable transport of the recording medium can be realized.

  According to the present invention, since the recording medium can be guided from the second supply path to the transport path without providing the transport switching member for switching the transport path, the cost of providing the transport switching member can be reduced. It is possible to prevent an increase and an increase in the space between the image forming units due to securing the installation space for the conveyance switching member, and it is possible to realize a reduction in size and cost.

1 is a schematic configuration diagram of a direct transfer type tandem type image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of the stopper for making a paper feeding cassette stand still. It is a schematic block diagram of a position detection means. FIG. 10 is a diagram for explaining the movement of the sheet feeding cassette and the operation of the contact member. FIG. 10 is a schematic configuration diagram of a conventional image forming apparatus configured to be able to contact and separate a conveyance belt with respect to a photoconductor. It is a schematic block diagram of the conventional image forming apparatus which has two branched conveyance paths.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

  FIG. 1 is a schematic configuration diagram of a direct transfer type tandem type image forming apparatus according to an embodiment of the present invention. However, the configuration of the present invention is not limited to the image forming apparatus shown in FIG. 1, and can also be applied to other copiers, printers, facsimiles, or multifunction peripherals thereof.

  In the image forming apparatus 100 shown in FIG. 1, four process units 1Y, 1M, 1C, and 1Bk as image forming units are detachably attached to the image forming apparatus main body 101. Each process unit 1Y, 1M, 1C, 1Bk contains toners of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. Other than that, the configuration is the same.

  Specifically, each of the process units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2Y, 2M, 2C, and 2Bk as an image carrier that carries an image on the surface, and a photoreceptor 2Y, 2M, 2C, and Charge rollers 3Y, 3M, 3C, 3Bk as charging means for charging the surface of 2Bk, and developing devices 4Y, 4M as developing means for visualizing the electrostatic latent images on the photoreceptors 2Y, 2M, 2C, 2Bk , 4C, 4Bk, and cleaning means (not shown) for cleaning the surfaces of the photoreceptors 2Y, 2M, 2C, 2Bk.

  Each of the photoconductors 2Y, 2M, 2C, and 2Bk is rotated at a linear speed of 60 mm / s counterclockwise by a driving device (not shown). Each charging roller 3Y, 3M, 3C, 3Bk is in contact with the surface of the photoreceptor 2Y, 2M, 2C, 2Bk, and the charging roller 3Y, 3M, 3C, 3Bk is rotated by the rotation of the photoreceptor 2Y, 2M, 2C, 2Bk. Is driven to rotate. Further, the charging rollers 3Y, 3M, 3C, and 3Bk are configured to be applied with DC or a bias in which AC is superimposed on DC by a high voltage power source (not shown). Each of the developing devices 4Y, 4M, 4C, and 4Bk is a one-component contact type developing device in which one-component toner as a developer is initially stored. Each developing device 4Y, 4M, 4C, 4Bk is configured to be supplied with a predetermined developing bias from a high voltage power source (not shown).

  In the image forming apparatus main body 101, an exposure device 5 serving as an exposure unit that exposes the surface of each of the photoreceptors 2Y, 2M, 2C, and 2Bk, and a paper feeding unit 6 serving as a recording medium supply unit that supplies a recording medium. And four transfer rollers 8Y, 8M, 8C, and 8Bk as transfer means for transferring the toner images on the photoreceptors 2Y, 2M, 2C, and 2Bk onto the recording medium, and fixing the toner images transferred to the recording medium. A fixing device 9 or the like is provided as a fixing unit to be used.

  The exposure device 5 is configured to irradiate each of the photoreceptors 2Y, 2M, 2C, and 2Bk with laser light corresponding to image information. As this exposure apparatus 5, a laser beam scanner using a laser diode or the like can be used.

  The paper supply unit 6 includes a paper supply cassette 7 as a recording medium storage unit that stores the recording medium P, and a paper supply roller 10 as a recording medium supply unit that supplies the recording medium stored in the paper supply cassette 7. Is provided. Here, the recording medium P accommodated in the paper feed cassette 7 includes not only plain paper generally used for copying and the like, but also OHP sheets, thick paper such as cards and postcards, envelopes, and the like. In this embodiment, as a mechanism for supplying the recording medium P from other than the paper supply unit 6, a manual feed tray 14 and a paper feed roller 15 for supplying the recording medium P from the manual feed tray 14 are provided on the image forming apparatus main body 101. It is arranged on the side wall.

The transfer rollers 8Y, 8M, 8C, and 8Bk are disposed in contact with the photoreceptors 2Y, 2M, 2C, and 2Bk, respectively. Further, a predetermined transfer bias is applied to each of the transfer rollers 8Y, 8M, 8C, and 8Bk from a high-voltage power source that is independent of each color (not shown). As the transfer rollers 8Y, 8M, 8C, and 8Bk, a conductive sponge roller, a conductive solid roller, or the like can be used. In the case of a conductive sponge roller, for example, it is configured by covering a metal core such as SUS with an elastic body adjusted to a resistance value of 10 ⁴ to 10 ¹³ Ω with a conductive material. As materials for the transfer rollers 8Y, 8M, 8C, and 8Bk, ion conductive rollers (urethane + carbon dispersion, NBR, hydrin), electronic conductive type rollers (EPDM), and the like are used, and generally Asker C hardness 35 The one having an angle of 60 ° is used. The transfer rollers 8Y, 8M, 8C, and 8Bk are rotationally driven by a drive motor (not shown), and also serve as a recording medium transport unit that transports the recording medium. Here, the recording medium is conveyed from the yellow image photoreceptor 2Y toward the black image photoreceptor 2Bk.

  On the upstream side in the recording medium conveyance direction of the contact portions between the photoconductors 2Y, 2M, 2C, and 2Bk and the transfer rollers 8Y, 8M, 8C, and 8Bk, there are a plurality of guides for guiding the recording medium to the contact portions. Guide members 12a to 12e are provided. Each guide member 12a-12e is comprised with the electroconductive material like a SUS board, for example. Further, when the guide members 12a to 12e are made of a conductive material, the guide members 12a to 12e are prevented from accumulating charges in the guide members 12a to 12e when the recording medium is rubbed against the guide members 12a to 12e. Is preferably connected to the ground of the image forming apparatus main body 101 and held at the same potential. Thereby, it is possible to prevent the electric charges accumulated in the guide members 12a to 12e from adversely affecting the images formed by the image forming units 1Y, 1M, 1C, and 1BK and the images transferred to the recording medium. .

  In addition, in the image forming apparatus main body 101, two supply paths, a first supply path A1 and a second supply path A2, for supplying the recording medium P from the paper supply unit 6 are arranged. The first supply path A1 is connected to the upstream end in the transport direction of the transport path B that transports the recording medium P, and the recording medium P passes through the first supply path A1 to the image forming unit 1Y for yellow image. It comes to be supplied. On the other hand, the second supply path A2 joins the conveyance path B between the image forming section 1C for cyan image and the image forming section 1Bk for black image, and recording is performed via the second supply path A2. The medium P is supplied to the black image forming unit 1Bk. In each of the supply paths A1 and A2, registration roller pairs 11 and 13 are provided as registration means for correcting the posture of the recording medium P and adjusting the conveyance timing. Each of the guide members 12d and 12e disposed between the black image transfer roller 8Bk and the cyan image transfer roller 8C is either the first supply path A1 or the second supply path A2. The recording medium P supplied through the supply path can also be guided.

  The paper feed cassette 7 provided in the paper feed unit 6 is configured to be reciprocally movable in the horizontal direction by a position variable mechanism (not shown). As a result, the paper feed cassette 7 can be switched between a state disposed at a position indicated by a solid line and a state disposed at a position indicated by a one-dot chain line. In the state where the paper feed cassette 7 is disposed at the position indicated by the solid line in the drawing, the supply position (or the position where the paper feed roller 10 is disposed) Q for supplying the recording medium P from the paper feed cassette 7 is the first. In the state where the paper feed cassette 7 is disposed at the position indicated by the one-dot chain line in the drawing in correspondence with the upstream end of the supply path A1 in the supply direction, the supply position Q is the supply direction of the second supply path A2. It is arranged corresponding to the upstream end. That is, the recording medium P can be sent out by selecting one of the first supply path A1 and the second supply path A2 by moving the paper feed cassette 7 in the horizontal direction.

  The position variable mechanism for moving the paper feed cassette 7 includes, for example, a lever for operating the paper feed cassette 7, a sensor for detecting the position of the paper feed cassette 7, and a lock mechanism for restricting the movement of the paper feed cassette 12. Yes. In the present embodiment, as shown in FIG. 2, the position variable mechanism includes stoppers 13a and 13b for stopping the sheet feeding cassette 7 at respective positions. As shown in FIG. 1, the paper feed roller 10 is also configured to be movable together with the paper feed cassette 7.

Further, in order to detect the position of the paper feed cassette 7, the image forming apparatus main body 101 is provided with position detection means including a contact member 16 that can come into contact with the paper feed cassette 7.
As shown in FIG. 3, the position detection means includes a contact member 16 and a transmission type sensor 17. The transmissive sensor 17 includes a light emitting unit 17a that emits light and a light receiving unit 17b that receives light emitted from the light emitting unit 17a. The contact member 16 is rotatably attached to the support shaft 18, and the optical path of the transmission sensor 17 is blocked by the contact member 16 when the contact member 16 rotates about the support shaft 18. It is possible to switch between the normal state and the transparent state.

  As shown in FIG. 4A, when the paper feed cassette 7 is disposed corresponding to the first supply path A <b> 1, the contact member 16 is in contact with the paper feed cassette 7. In this case, the optical path of the transmissive sensor 17 shown in FIG. 3 is in a transmissive state, and a detection signal is generated. On the other hand, as shown in FIG. 4B, when the paper feed cassette 7 is disposed corresponding to the second supply path A2, the contact member 16 does not come into contact with the paper feed cassette 7, The tip of the contact member 16 swings downward. Thereby, the optical path of the transmission type sensor 17 shown in FIG. 3 is interrupted, and the detection signal is stopped. As described above, the position of the paper feed cassette 7 is detected based on the presence or absence of the detection signal.

  It is also possible to generate and stop the detection signal by reversing the blocking and transmission of the optical path accompanying the rotation of the contact member 16. Further, the position detection means is not limited to this configuration. For example, a terminal is provided for each of the paper feed cassette 7 and the sensor, and the position of the paper feed cassette 7 is detected by detecting the presence or absence of electrical continuity due to the contact and separation of these terminals as the paper feed cassette 7 moves. You may make it do.

  In addition, the image forming apparatus according to the present embodiment has a color image forming mode that uses all the image forming units 1Y, 1M, 1C, and 1Bk and a monochrome image forming mode that uses only the image forming unit 1Bk for black images. It is configured to be selectable. The selection of the image forming mode is controlled so as to be determined based on the position of the paper feed cassette 7 detected by the position detecting means.

The operation of the image forming apparatus will be described below with reference to FIG.
In the case of forming a color image, first, the paper feed cassette 7 is disposed at the left position in the drawing. As a result, the contact member 16 comes into contact with the paper feed cassette 7 and is detected, and the color image forming mode is selected.
When the image forming operation is started, the photosensitive members 2Y, 2M, 2C, and 2Bk are rotated counterclockwise in the drawing by a driving device (not shown), and the charging rollers 3Y, 3M, and 3C are driven by a high-voltage power source (not shown). , 3Bk is applied with a predetermined bias, the surfaces of the photoreceptors 2Y, 2M, 2C, 2Bk are uniformly charged with a predetermined polarity. Next, a laser beam is irradiated from the exposure device 5 onto the surface of each of the charged photoconductors 2Y, 2M, 2C, and 2Bk to form an electrostatic latent image. At this time, the image information to be exposed on each of the photoreceptors 2Y, 2M, 2C, and 2Bk is single-color image information obtained by separating a desired color image into color information of yellow, magenta, cyan, and black. The toner is supplied to the electrostatic latent images formed on the photoreceptors 2Y, 2M, 2C, and 2Bk in this way by the developing devices 4Y, 4M, 4C, and 4Bk, so that the electrostatic latent images are converted into toner images. Visualized (visualized).

  When the image forming operation is started, the recording medium P accommodated in the paper feed cassette 7 or the recording medium P placed on the manual feed tray 14 is sent out by the paper feed roller 10 or 15. The recording medium P sent out from the paper feed cassette 7 by the paper feed roller 10 contacts the registration roller pair 11 through the first supply path A1 and is temporarily stopped, and the posture is corrected here. When the recording medium P is sent out from the manual feed tray 14, it contacts the registration roller pair 11 through the supply path from the manual feed tray 14, and the posture of the recording medium P is similarly corrected. Thereafter, the driving of the registration roller pair 11 is resumed at a predetermined timing, and the recording medium P is sent to the conveyance path B.

  The recording medium P has a transfer nip between the photoconductors 1Y, 1M, 1C, and 1Bk and the transfer rollers 8Y, 8M, 8C, and 8Bk, a photoconductor 1Y for yellow images, a photoconductor 1M for magenta images, The cyan image photoreceptor 1C and the black image photoreceptor 1BK pass in this order. At this time, a predetermined transfer bias (+400 to +1000 V) is applied to each transfer roller 8Y, 8M, 8C, 8Bk from a high voltage power source (not shown), and a transfer electric field is formed in each transfer nip. Thus, when the recording medium P sequentially passes through the transfer nips, the toner images on the photoconductors 2Y, 2M, 2C, and 2Bk are transferred so as to overlap the recording medium P in the order of yellow, magenta, cyan, and black. Is done. Thus, a color image is carried on the recording medium P.

  Further, the toner remaining on each of the photoconductors 2Y, 2M, 2C, and 2Bk is removed by a cleaning device (not shown) to prepare for the next image formation. Thereafter, the recording medium P onto which the toner image has been transferred is conveyed to the fixing device 9, where the recording medium P is heated and pressurized to fix the toner image, and then the recording medium P is discharged out of the apparatus. .

Next, when forming a monochrome image, the paper feed cassette 7 is moved to the right side of the figure and disposed at a position indicated by a one-dot chain line. As a result, the contact member 16 is not in contact with the paper feed cassette 7, and the monochrome image forming mode is selected.
In this case, when the image forming operation is started, a toner image is formed only on the black image photoreceptor 2Bk through the same process as described above. In addition, the recording medium P is sent out from the paper feed cassette 7 to the second supply path A2, and the recording medium P comes into contact with the registration roller pair 13 disposed in the second supply path A2 and is temporarily stopped. Is corrected. Thereafter, the driving of the registration roller pair 13 is resumed at a predetermined timing, and the recording medium P enters the transfer nip between the black image photosensitive member 2Bk and the transfer roller 8Bk in contact with the recording medium P via the second supply path A2. Supplied. When the recording medium P passes through the transfer nip, the toner image on the black image photoreceptor 2Bk is formed by a transfer electric field formed by applying a predetermined transfer bias to the black image transfer roller 8Bk. The image is transferred onto the recording medium P, and a monochrome image is carried on the recording medium P.

  After that, the recording medium P onto which the toner image has been transferred is fixed by the fixing device 9 and discharged outside the apparatus in the same manner as described above. Further, the toner remaining on the black image photoreceptor 2Bk is removed by a cleaning device (not shown) to prepare for the next image formation.

  As described above, in the image forming apparatus of the present embodiment, when monochrome image formation is performed, the recording medium P is supplied to the black image forming unit 1Bk via the second supply path A2. Therefore, at this time, the recording medium P does not come into contact with the photoconductors 2Y, 2M, and 2C for color images that are not used for image formation. For this reason, the photoconductors 2Y, 2M, and 2C are unnecessarily brought into contact with the photoconductors 2Y, 2M, and 2C for color images, and the color toner adheres to the recording medium P (fogging). Etc. can be prevented.

  In the present embodiment, the driving means for the photosensitive members 2Y, 2M, 2C, and 2Bk of the respective colors are configured by separate motors so that the driving and stopping of the photosensitive members 2Y, 2M, 2C, and 2Bk can be performed independently. I have to. For this reason, it is possible to stop the driving of the color image photoreceptors 2Y, 2M, and 2C during monochrome image formation. Thereby, unnecessary driving of the photoconductors 2Y, 2M, and 2C for color images can be prevented to save energy, and color toner is deteriorated, both members are worn due to the cleaning member sliding on the photoconductor, and the like. Can be suppressed.

  Further, as means for independently driving and stopping the photosensitive members 2Y, 2M, 2C, and 2Bk of the respective colors, driving transmission and interruption from the driving means to the photosensitive members 2Y, 2M, 2C, and 2Bk are switched independently. It is also possible to use switching means such as a clutch. In addition, in this case, since the driving means for each of the photoconductors 2Y, 2M, 2C, and 2Bk can be configured by a common driving means, the size and cost can be reduced as compared with the case where separate driving means are provided. .

  In addition, the paper feed cassette 7 and the paper feed roller 10 are configured so as to be selectively arranged to correspond to one of the first supply path A1 and the second supply path A2 by the position variable mechanism. The recording medium P can be selectively sent to both the supply paths A1 and A2 by the paper feed cassette 7 and the paper feed roller 10. For this reason, it is not necessary to provide a plurality of paper feed cassettes 7 and paper feed rollers 10 corresponding to the respective supply paths A1 and A2, and a reduction in size and cost can be achieved.

  If the upstream ends in the supply direction of both the first supply path A1 and the second supply path A2 are arranged at the same position, the positions of the paper feed cassette 7 and the paper feed roller 10 are fixed. Even so, it is possible to supply the recording medium P to both the supply paths A1 and A2. However, in this case, it is necessary to provide a conveyance switching member for selecting one of the two supply paths A1 and A2 and guiding the recording medium P at the supply position Q of the paper feed cassette 7. Further, for example, when the paper feed cassette 7 is fixed at the left side position (the position indicated by the solid line) in FIG. 1, if the second supply path A2 is disposed from the supply position Q at that position, compared to the present embodiment. As a result, the second supply path A2 becomes longer. On the other hand, when the paper feed cassette 7 and the paper feed roller 10 are configured to be movable as in the present embodiment, at least one of the first supply path A1 and the second supply path A2 may be formed short. In addition, since the conveyance switching member is unnecessary, it is possible to reduce the printing time and the number of parts.

  In this embodiment, since the position of the paper feed cassette 7 can be detected by the position detection means, the paper feed failure of the recording medium P due to improper arrangement of the paper feed cassette 7 is accompanied by this. It is possible to prevent the occurrence of problems such as clogging of the recording medium P and jamming. Further, since the image forming mode is determined based on the position of the paper feed cassette 7 detected by the position detecting means, the arrangement of the paper feed cassette 7 (selection of the supply path) and the image forming mode (color) It is possible to prevent the occurrence of a printing error due to a mismatch with the image formation mode or the monochrome image formation mode.

  In addition, since the registration roller pairs 11 and 13 are provided in both the first supply path A1 and the second supply path A2, the posture correction of the recording medium P and the conveyance timing are adjusted in each of the supply paths A1 and A2. Adjustments can be made and the quality of the printed image can be kept good. Further, by using the driving means for the registration roller pairs 11 and 13 arranged in the supply paths A1 and A2 as a common driving means, it is possible to reduce the size and cost.

  The guide members 12d and 12e disposed between the black image transfer roller 8Bk and the cyan image transfer roller 8C are connected to the recording medium P supplied via the first supply path A1. Since both of the guide members of the recording medium P supplied via the second supply path A2 are used, the transportability of the recording medium P can be ensured without increasing the number of parts.

  Further, as shown in FIG. 1, in the present embodiment, the second supply path A2 is located at a place where the space on the side opposite to the image forming units 1Y, 1M, 1C, and 1Bk has a margin with respect to the transport path B. It is arranged. Thereby, further downsizing of the entire apparatus is achieved.

  In addition, since the second supply path A2 is arranged so as to merge in the middle of the transport path B, the transport from the second supply path A2 can be performed without providing a transport switching member for switching the transport path. It is possible to guide the recording medium P to the route B.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention. In the above-described embodiment, the black image forming unit 1Bk is arranged on the most downstream side, and the recording medium P can be supplied to the black image forming unit 1Bk through the second supply path A2. Although the color image forming units 1Y, 1M, and 1C are prevented from being deteriorated at the time of formation, the arrangement order of the image forming units 1Y, 1M, 1C, and 1Bk for each color is not limited to that shown in FIG. In addition, the second supply path A2 is not limited to the case where the recording medium is supplied to the most downstream image forming unit, but the upstream side (however, the most upstream image forming unit It is also possible to configure so that the recording medium can be supplied to the image forming unit. Further, a plurality of supply paths for supplying the recording medium to an image forming unit different from the most upstream image forming unit may be provided.

  In the case of the configuration of the present invention, since the contact of the recording medium with the color image photosensitive member can be avoided without moving the transfer roller away from the photosensitive member, the above-described transfer roller is used as the photosensitive member. There is no problem of a decrease in transportability due to separation from the center. For this reason, the configuration of the present invention is particularly suitable in terms of ensuring stable transportability in the configuration having no transport belt as shown in FIG. 1, but if the second supply path can be secured, the transport belt can be used. The configuration of the present invention can also be applied to the used image forming apparatus.

  As described above, according to the present invention, the second supply path for supplying the recording medium to the image forming unit different from the most upstream image forming unit is arranged so as to merge in the middle of the transport path. Therefore, the recording medium can be guided from the second supply path to the transport path without providing a transport switching member for switching the transport path. In the conventional configuration shown in FIG. 6, the conveyance path of the recording medium is branched toward the downstream, so the conveyance switching member 99 has to be disposed at the branch position. Since the conveyance path and the supply path of the medium are configured to merge toward the downstream, it is not necessary to dispose the conveyance switching member 99. For this reason, the image forming apparatus of the present invention can prevent an increase in cost due to the provision of the conveyance switching member, and an increase in space between the respective image forming units by securing an installation space for the conveyance switching member. Miniaturization and cost reduction can be realized.

1Y to 1Bk process unit (imaging part)
2Y-2Bk photoconductor (image carrier)
6 Paper feed unit (recording medium supply unit)
8Y-8Bk transfer roller (transfer means)
11 Registration roller pair (registration means)
12a to 12e Guide member 13 Registration roller pair (registration means)
A1 First supply path A2 Second supply path B Transport path P Recording medium

JP 2001-27852 A JP-A-11-95619 JP 2004-70152 A

Claims (12)

A recording medium supply unit that supplies the recording medium, a recording medium conveying unit that conveys the supplied recording medium, and a conveyance path for conveying the recording medium are arranged side by side, and an image is recorded on the conveyed recording medium. In an image forming apparatus comprising a plurality of image forming units for forming
The first supply path connected to the upstream end of the transport path in the transport direction for supplying a recording medium to the uppermost image forming section, and the uppermost image forming section joined together in the transport path. A second supply path for supplying the recording medium to the different image forming units ;
The recording medium supply unit is configured to be movable, and the supply position for supplying the recording medium from the recording medium supply unit selectively corresponds to the upstream end in the supply direction of the first supply path and the second supply path. Configured to be arranged,
A position detecting means for detecting the position of the recording medium supply unit;
An image forming apparatus configured to determine an image forming mode based on a position of the recording medium supply unit detected by the position detecting unit . A recording medium supply unit that supplies the recording medium, a recording medium conveying unit that conveys the supplied recording medium, and a conveyance path for conveying the recording medium are arranged side by side, and an image is recorded on the conveyed recording medium. In an image forming apparatus comprising a plurality of image forming units for forming
The first supply path connected to the upstream end of the transport path in the transport direction for supplying a recording medium to the uppermost image forming section, and the uppermost image forming section joined together in the transport path. A second supply path for supplying the recording medium to the different image forming units;
The recording medium supply unit is configured to be movable for each recording medium , the recording medium supply unit is moved for each recording medium, and a supply position for supplying the recording medium from the recording medium supply unit is moved to the recording medium supply unit. An image forming apparatus , wherein the first supply path and the second supply path, which are arranged apart from each other in a direction, can be arranged so as to selectively correspond to upstream ends of the supply direction.   The image forming apparatus according to claim 2, further comprising a position detection unit that detects a position of the recording medium supply unit.   The image forming apparatus according to claim 3, wherein the image forming mode is determined based on a position of the recording medium supply unit detected by the position detecting unit.   5. The image forming apparatus according to claim 1, further comprising a driving unit configured to independently drive and stop the plurality of image forming units.   5. A common driving unit that applies a driving force to the plurality of image forming units, and a switching unit that independently switches transmission and interruption of the driving force from the driving unit to the image forming units. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, wherein the second supply path is disposed on the opposite side of the image forming unit with the conveyance path interposed therebetween.   A guide member for guiding the recording medium is provided in the image forming unit to which the recording medium is supplied via the second supply path, and the guide member is supplied via the first supply path. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to serve as both a guide member for a medium and a recording medium supplied via the second supply path.   Registration means for correcting the posture of the recording medium supplied to each of the first supply path and the second supply path and sending the recording medium in time with the image formed by the image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed.   The image forming apparatus according to claim 9, wherein a driving unit of the registration unit disposed in each of the first supply path and the second supply path is a common driving unit.   The plurality of image forming units includes an image forming unit that forms a black image and a plurality of image forming units that form a color image, and the image forming unit that forms the black image is disposed on the most downstream side, and The image forming apparatus according to claim 1, wherein a recording medium is supplied to the image forming unit that forms a black image via the second supply path.   Each of the plurality of image forming units includes at least an image carrier that carries an image on the surface, and a plurality of transfer units that transfer an image on the image carrier to a recording medium are in direct contact with the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to function as the recording medium conveying unit.

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