JP2017072824A - Transfer device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device that can maintain a satisfactory state of peeling of a sheet from an image carrier, and an image forming apparatus including the transfer device.SOLUTION: A transfer device (secondary transfer device 60) comprises a transfer roller (secondary transfer roller 62), a peeling electrode 64, and a protective member 65. The transfer roller transfers a toner image formed on an image carrier to a sheet at a transfer position. The peeling electrode 64 is arranged on the downstream of the transfer position to which the sheet is conveyed and includes a plurality of needle electrodes 641. The protection member 65 is arranged on the transfer roller side with respect to the peeling electrode 64 and overlapped with the peeling electrode 64. The protective member 65 has a notch part 651 provided as a recess at a position facing at least one of the plurality of needle electrodes 641.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a transfer device that transfers a toner image formed on an image carrier onto a sheet, and an image forming apparatus including the transfer device.

  In the image forming apparatus, the toner image formed on the photosensitive drum is transferred to a sheet, or the toner image formed on the photosensitive drum is primarily transferred to an intermediate transfer belt, and the toner image is transferred from the intermediate transfer belt to the sheet. There is something that is secondary transferred. The sheet on which the toner image is transferred is conveyed to the fixing device via the transfer position of the toner image. At this time, the sheet is likely to be drawn toward an image carrier such as a photosensitive member or an intermediate transfer belt by an electrostatic force generated on the sheet. For this reason, conventionally, a technique has been proposed in which the paper on which the toner image is transferred is peeled off from the image carrier.

  As an example, a technique has been proposed in which an electric field is generated on the opposite side of the image carrier from the paper, thereby electrically peeling the paper. In this technique, for example, a sawtooth electrode employed in the corona charging device described in Patent Document 1 is used.

JP-A-10-90974

  However, in the sawtooth electrode, the tip of each sawtooth is sharply pointed. For this reason, there is a possibility that the saw-tooth electrode may be deformed when the paper touches the saw-tooth electrode during conveyance of the paper, and when the user or serviceman touches the saw-tooth electrode during maintenance. If the sawtooth electrode is deformed, the formation of an electric field for peeling the paper may be hindered. If the formation of the electric field is insufficient, the paper is wound around the image carrier before being conveyed to the fixing device, causing a paper jam.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a transfer device and an image forming apparatus capable of maintaining a good state with respect to the separation of a sheet from an image carrier.

  The transfer device according to the present invention includes a transfer roller, a peeling electrode, and a protective member. The transfer roller transfers the toner image formed on the image carrier onto the paper at the transfer position. The peeling electrode is arranged on the downstream side of the transfer position where the paper is conveyed and has a plurality of needle-like electrodes. The protective member is disposed on the transfer roller side with respect to the peeling electrode, and is overlapped with the peeling electrode. The protective member has a notch in a position facing at least one of the plurality of needle-like electrodes. ing.

  According to the above transfer device, a voltage is applied to the peeling electrode so that the peeling electrode has a polarity opposite to the charging polarity of the paper, whereby a concentrated electric field starting from the tip of the needle electrode peels the paper. Formed as a peeling electric field. And in the said transfer apparatus, the notch part is recessedly provided in the protection member in the position facing at least 1 needle-shaped electrode. For this reason, the acicular electrode corresponding to the notch does not overlap with the protective member, and therefore, the peeling electric field formed with the tip of the acicular electrode as the starting point can be efficiently applied to the paper.

  In addition, while the protective member is stacked on the peeling electrode, the notch portion is partially provided at a position facing the acicular electrode, so that the acicular electrode corresponding to the notch portion does not overlap the protective member, It is protected by the edge of the protective member constituting the notch. Therefore, it is difficult for the paper or the user to contact the tip of the needle electrode.

  In the above-described transfer device, the protection member has a tip edge that protrudes from the tip of each of the plurality of needle-like electrodes. According to this configuration, when the protective member is viewed from the peeling electrode side, the tip of the needle-like electrode is located inside the notch. Therefore, the tip of the needle electrode can be protected from contact with paper or a user.

  In the above transfer device, the protective member is preferably provided with a plurality of notches in a region facing at least a part of the conveyed paper. According to this configuration, it is possible to provide a plurality of notches in a region facing the side edge of the paper that is likely to be wound around the image carrier. Thereby, the needle-shaped electrode exposed by the notch can be concentrated on the area facing the side edge of the paper. Therefore, the peeling electric field can be concentrated on the side edge of the paper, and as a result, the paper can be peeled more efficiently from the image carrier. A plurality of notches may be provided in a region facing the center of the sheet. As a result, the entire sheet is easily peeled off, and as a result, the paper discharge direction from the transfer position can be stabilized.

  In the transfer device, the protection member may be provided with a first region where a notch is provided, and a second region where the protection member overlaps the entire two or more continuous needle-like electrodes. As an example, the first region is provided with a notch at a position facing every other one of the plurality of needle electrodes.

  An image forming apparatus according to the present invention includes an image forming unit that forms a toner image on an image carrier, and the transfer device that is applied to transfer a toner image formed on the image carrier to a sheet. According to this configuration, it is possible to efficiently peel the sheet conveyed via the transfer position from the image carrier against an electrostatic force that tends to be drawn toward the image carrier. In the transfer device, the tip of the needle-like electrode can be protected from contact with paper or a user.

  In the image forming apparatus, it is preferable that the shortest distance from the tip of the needle electrode to the transfer roller in the transfer device is smaller than the shortest distance from the tip of the needle electrode to the image carrier. According to this configuration, a new electric field (second peeling electric field) can be generated between the tip of the needle electrode and the transfer roller, and as a result, at a position closer to the secondary transfer position. A peeling electric field can be applied to the paper. Therefore, it is possible to more efficiently peel the sheet from the image carrier.

  According to the present invention, it is possible to maintain a good state with respect to the separation of the sheet from the image carrier.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment. FIG. 3 is a perspective view showing a secondary transfer device provided in the image forming apparatus. (A) The expansion perspective view which showed the principal part of the secondary transfer apparatus, (B) The expansion perspective view which showed the said principal part, omitting the paper guide part. (A) The top view which showed the peeling electrode with which a secondary transfer apparatus is equipped, and a protection member, (B) It is sectional drawing which follows the IVB-IVB line | wire shown by FIG. 4 (A). It is explanatory drawing about the electric field which arises in the vicinity of the application of the voltage to each part, and the secondary transfer position. It is explanatory drawing about the electric field produced in the vicinity of a secondary transfer position in 3rd Embodiment. It is the top view which showed other examples of the peeling electrode and the protection member as 4th Embodiment.

[1] First Embodiment [1-1] Outline of Image Forming Apparatus As shown in FIG. 1, the image forming apparatus includes an image reading unit 10, an image forming unit 20, a paper feeding unit 30, and paper discharge. Unit 40. The image reading unit 10 reads an image of a document and generates image data from the read image. The image forming unit 20 performs printing on a sheet supplied from the sheet feeding unit 30 by performing an image forming process based on the image data. The printed paper is discharged to the paper discharge unit 40.

  In the image forming apparatus, a conveyance path 33 for conveying the paper supplied from the paper supply unit 30 to the paper discharge unit 40 is formed. Specifically, the conveyance path 33 extends from the paper feed unit 30 to the paper discharge unit 40 via a secondary transfer position and a fixing position described later. The image forming apparatus may be provided with other conveyance paths used for various purposes such as a conveyance path for double-sided printing.

  The image forming unit 20 includes four image forming stations 21 to 24, an exposure unit 3, an intermediate transfer device 50, a secondary transfer device 60, and a fixing device 70. The image forming stations 21 to 24 are arranged in a line in the circumferential direction of the intermediate transfer belt 51 and form toner images of four colors of black, cyan, magenta, and yellow based on the image data.

  Each of the image forming stations 21 to 24 includes a photosensitive drum 1, a charger 2, a developing device 4, an intermediate roller 5, and a cleaner unit 6. The photosensitive drum 1 is an electrostatic latent image carrier, and rotates in a predetermined direction when a driving force is transmitted from a driving source (not shown). The charger 2 charges the peripheral surface of the photosensitive drum 1 so as to have a predetermined potential. The exposure unit 3 irradiates the respective photosensitive drums 1 of the image forming stations 21 to 24 with laser beams modulated based on image data in the respective colors of four colors (black, cyan, magenta, and yellow). . Thereby, an electrostatic latent image based on the image data of the corresponding hue is formed on the peripheral surface of each photosensitive drum 1. The toner is supplied from the developing device 4 to the peripheral surface, whereby the electrostatic latent image is visualized and a toner image is formed.

  The intermediate transfer device 50 includes an intermediate transfer belt 51 (corresponding to an “image carrier” recited in the claims), a drive roller 52 that drives the intermediate transfer belt 51, and the intermediate transfer belt 51 together with the drive roller 52. And a support roller 53 to support. The drive roller 52 and the support roller 53 are arranged in parallel to each other, and the intermediate transfer belt 51 is stretched around these rollers in a loop shape. Specifically, the intermediate transfer belt 51 is stretched around the drive roller 52 and the support roller 53 so that the outer peripheral surface sequentially faces the respective photosensitive drums 1 of the image forming stations 21 to 24 during the rotation.

  Intermediate rollers 5 are disposed at positions facing the photosensitive drum 1 with the intermediate transfer belt 51 interposed therebetween. When a toner image is transferred (primary transfer) from each of the four photosensitive drums 1 to the intermediate transfer belt 51, the intermediate roller 5 has a polarity opposite to that of the toner charging polarity (minus in this embodiment) (in this embodiment). (Plus) primary transfer bias is applied. At this time, constant voltage control is performed. The toner images are sequentially transferred to the intermediate transfer belt 51 at the primary transfer positions facing the four photosensitive drums 1, so that the four color toner images are superimposed on the outer peripheral surface of the intermediate transfer belt 51. A full color toner image is formed (primary transfer).

  The toner image formed on the outer peripheral surface of the intermediate transfer belt 51 is conveyed to a secondary transfer position where the toner image is transferred to the sheet by the secondary transfer device 60 by the rotation of the intermediate transfer belt 51. In the present embodiment, the secondary transfer roller 62 provided in the secondary transfer device 60 is disposed at a position facing the driving roller 52 via the intermediate transfer belt 51, and a predetermined pressure is applied to the outer peripheral surface of the intermediate transfer belt 51. It is in pressure contact. The secondary transfer position is a position on the driving roller 52 in the circulation path of the intermediate transfer belt 51. The secondary transfer roller 62 is grounded via a conductive bearing or contact electrode (not shown) connected to the core part (shaft part) (see FIG. 5). Details of the secondary transfer device 60 will be described later.

  When a toner image is transferred (secondary transfer) from the intermediate transfer belt 51 to a sheet, a secondary transfer bias V1 having the same polarity as the toner charging polarity (minus in this embodiment) is applied to the driving roller 52 (FIG. 5). 5). At this time, by performing constant current control, the secondary transfer current flows from the secondary transfer roller 62 to the drive roller 52 via the paper and the intermediate transfer belt 51. As a result, the full-color toner image carried on the outer peripheral surface of the intermediate transfer belt 51 is transferred onto the sheet at the secondary transfer position. The toner remaining on the intermediate transfer belt 51 after the secondary transfer is collected by a cleaning unit 54 (see FIG. 1).

  The sheet on which the toner image is transferred is conveyed to the fixing device 70. The fixing device 70 includes a heating roller 71, a fixing belt 72 heated by the heating roller 71, and a pressure roller 73 pressed against the fixing belt 72 at a fixing position. The sheet passes through the fixing position, and the toner image is firmly fixed on the sheet by heating and pressing.

  In such an image forming apparatus, the sheet passing through the secondary transfer position has a polarity opposite to the charging polarity of the toner (secondary transfer current flowing from the secondary transfer roller 62 to the drive roller 52 via the sheet). In this embodiment, the toner is charged positively and is easily attracted toward the intermediate transfer belt 51. For this reason, if no countermeasure is taken, the sheet is wound around the intermediate transfer belt 51 before being conveyed to the fixing device 70, which causes a sheet jam. Therefore, in the present embodiment, the secondary transfer device 60 is configured as follows.

[1-2] Secondary Transfer Device As shown in FIGS. 2 to 3B, the secondary transfer device 60 includes a frame 63, a peeling electrode 64, in addition to the secondary transfer roller 62 described above. The protective member 65 and the paper guide part 67 are further provided.

  The frame 63 is a member for unitizing the components of the secondary transfer device 60, and the secondary transfer roller 62 is pivotally supported by the frame 63. Further, a protective member 65 and a paper guide portion 67 are fixed to the frame 63, and the protective member 65 and the paper guide portion 67 are sequentially arranged on the downstream side of the secondary transfer position where the paper is conveyed. The frame 63 is formed using various resins suitable for molding, such as polycarbonate / ABS resin. Further, at least one of the protection member 65 and the paper guide portion 67 may be formed integrally with the frame 63.

  The peeling electrode 64 is disposed on the downstream side of the secondary transfer position, and is held on the surface of the protective member 65 opposite to the secondary transfer roller 62. The peeling electrode 64 includes a base portion 640 and a plurality of needle-like electrodes 641 protruding from the base portion 640 (see FIG. 3B). Specifically, the base portion 640 is held by the protective member 65 in a state in which the extending direction is along the rotation axis of the secondary transfer roller 62 (a state in which the base portion 640 is aligned with the longitudinal direction of the secondary transfer roller 62). Has been. The plurality of needle-like electrodes 641 are provided on the edge 640a of the base portion 640 on the sheet conveyance path 33 side (intermediate transfer belt 51 side), and project from the edge 640a toward the conveyance path 33 (FIG. 4 (A) and FIG. 5).

  In the present embodiment, the base portion 640 has a length approximately the same as the length of the secondary transfer roller 62, and a plurality of needle-like electrodes 641 are spaced at a predetermined interval over the entire edge 640 a of the base portion 640. It is arranged. The length L of the needle electrode 641 is preferably about 1.5 mm to 2 mm. By setting the length L within such a range, the tip of the needle electrode 641 can be moved away from the base portion 640. This makes it easier for the electric field to concentrate on the tip of the needle electrode 641.

  A connection electrode plate 642 is electrically connected to the base portion 640 of the peeling electrode 64 (see FIG. 3B). The connection electrode plate 642 is connected to a coil 643 that is a contact terminal. Then, the coil 643 and the connection electrode plate 642 are connected to the peeling electrode 64 by connecting the coil 643 to a high-voltage power supply for electrodes (not shown) installed in the image forming apparatus via a connection terminal (not shown). The predetermined voltage V2 (in this embodiment, about −2 kV to −3 kV) is applied through constant voltage control (see FIG. 5).

  The protective member 65 is positioned on the secondary transfer roller 62 side with respect to the peeling electrode 64 and is superimposed on the peeling electrode 64. Specifically, the protection member 65 has a leading edge 65a located on the conveyance path 33 side, and the leading edge 65a protrudes toward the conveyance path 33 from any of the plurality of needle-like electrodes 641. (See FIGS. 4A to 5).

  As shown in FIGS. 4A and 4B, the protective member 65 has a notch 651 recessed at each position facing the alternate needle-like electrode 641. Specifically, the notch 651 has a shape in which a part of the leading edge 65a of the protection member 65 is recessed in a U shape. Therefore, when the protective member 65 is viewed from the peeling electrode 64 side, the tip of the needle electrode 641 corresponding to the notch 651 is located inside the notch 651. In addition, it is preferable that the opening width W of the notch part 651 in the front-end | tip edge 65a is about 1-2 mm, and it is more preferable that it is about 1 mm. The shape of the notch 651 is not limited to a U shape, and can be deformed into various shapes such as a V shape and a square groove shape.

  According to the configuration of the first embodiment, a constant voltage is applied to the peeling electrode 64 so that the peeling electrode 64 has a polarity opposite to the charging polarity of the paper (plus in this embodiment). Thereby, a concentrated electric field starting from the tip of the needle electrode 641 is formed as a peeling electric field E1 for peeling the paper (see FIG. 5). In the secondary transfer device 60, a notch 651 is recessed in the protective member 65 at a position facing the needle electrode 641. For this reason, the acicular electrode 641 corresponding to the notch 651 does not overlap the protective member 65, and therefore, the peeling electric field E1 formed with the tip of the acicular electrode 641 as the starting point can be efficiently applied to the sheet. it can. Therefore, the sheet conveyed via the secondary transfer position can be efficiently peeled from the intermediate transfer belt 51 against an electrostatic force that tends to draw the sheet toward the intermediate transfer belt 51 (image carrier). it can.

  Further, the notch 651 is partially provided at a position facing the needle electrode 641 while the protection member 65 is overlapped on the peeling electrode 64, so that the needle electrode 641 corresponding to the notch 651 is protected by the protection member 65. Even if they do not overlap with each other, they are protected by the edge of the protective member 65 constituting the notch 651. Specifically, when the protective member 65 is viewed from the peeling electrode 64 side, the tip of the needle electrode 641 corresponding to the notch 651 is positioned inside the notch 651 (see FIG. 4A). Therefore, the tip of the needle-like electrode 641 can be protected from contact with paper or a user. As a result, the needle electrode 641 is prevented from being deformed, and a good state can be maintained with respect to the separation of the sheet from the intermediate transfer belt 51 (image carrier).

[2] Second Embodiment As shown in FIG. 3B, in the protective member 65, a region where every other notch 651 is provided with respect to the needle-like electrode 641 is defined as a first region R1. The first region R1 is not limited to occupying the entire region in the longitudinal direction of the protective member 65, and the following second region R2 different from the first region R1 may be further provided. That is, in the second region R2, the protective member 65 is not provided with the notch portion 651, and the protective member 65 overlaps the entire two or more continuous needle electrodes 641. Therefore, in the second region R2, the needle electrode 641 does not protrude from the protection member 65, and therefore the tip of the needle electrode 641 is protected by the protection member 65, while the concentrated electric field formed at the tip of the needle electrode 641 is protected. The effect on the paper is suppressed.

  A plurality of second regions R2 may be provided in the longitudinal direction of the protective member 65, and the width in the longitudinal direction may be changed as appropriate. Then, by appropriately changing at least one of the change in the arrangement of the first region R1 and the second region R2 and the change in the width of the second region R2 in the longitudinal direction of the protection member 65, the length of the protection member 65 is increased. The distribution of the peeling electric field E1 in the direction can be set to a desired distribution (a distribution in which a desired strength is formed). Thereby, it is possible to provide one or a plurality of places (a place where the peeling electric field E1 is large) as a starting point of peeling at an appropriate place in the longitudinal direction of the protective member 65. Therefore, it is possible to maintain a better state with respect to the separation of the sheet from the intermediate transfer belt 51 (image carrier).

  Accordingly, the following preferred embodiment can be considered. In other words, in the protection member 65, a region facing both side edges of the sheet that is likely to be wound around the intermediate transfer belt 51 can be defined as the first region R1, and the other region can be defined as the second region R2. Further, the first region R1 may be provided in a plurality of regions corresponding to both end portions of various sizes of sheets so as to correspond to various sizes of sheets passing through the conveyance path 33. Furthermore, the first region R <b> 1 may be provided also in the central region in the longitudinal direction of the protective member 65 (region facing the central portion of the sheet). As a result, the entire sheet can be easily peeled off, and as a result, the paper discharge direction from the secondary transfer position can be stabilized.

  According to the configuration of the second embodiment, the needle-like electrode 641 exposed by the notch 651 is located in the region (first region R1) facing both side edges of the sheet that is likely to be wound around the intermediate transfer belt 51. Since they are provided in a concentrated manner, the peeling electric field E1 can be concentrated on both side edges of the paper. Therefore, the sheet can be peeled from the intermediate transfer belt 51 more efficiently.

[3] Third Embodiment As shown in FIG. 6, it is preferable that the needle-like electrode 641 of the peeling electrode 64 is disposed close to the secondary transfer roller 62. Specifically, in the peeling electrode 64, the shortest distance L1 from the tip of the needle electrode 641 to the secondary transfer roller 62 is preferably smaller than the shortest distance L2 from the tip of the needle electrode 641 to the drive roller 52.

  According to the configuration of the third embodiment, a new electric field (second peeling electric field different from the peeling electric field E1 described in the first embodiment) is formed between the tip of the needle electrode 641 and the secondary transfer roller 62. E2) can be generated, and as a result, the peeling electric field E2 can be applied to the sheet at a position closer to the secondary transfer position. Therefore, the sheet can be peeled from the intermediate transfer belt 51 more efficiently.

[4] Fourth Embodiment As shown in FIG. 7, the protection member 65 may be provided with a plurality of notches 651 corresponding to the plurality of needle-like electrodes 641 one by one. According to this configuration, the concentrated electric field (peeling electric field E1) generated at the tip of each of the plurality of needle-like electrodes 641 can be efficiently applied to the paper without being wasted.

  The configuration of the protective member 65 is not limited to the configuration described in the above embodiment, and may be modified to various configurations in which a notch 651 is recessed at a position facing at least one of the plurality of needle-like electrodes 641. it can.

[5] Fifth Embodiment In the configuration of each part of the image forming apparatus described in the above embodiment, the secondary transfer device 60 further includes a secondary transfer belt interposed between the intermediate transfer belt 51 and the secondary transfer roller 62. The present invention can also be applied to a provided image forming apparatus. In this case, in the secondary transfer device 60, the peeling electrode 64 is provided on the inner surface side of the secondary transfer belt (the side opposite to the paper conveyance path 33). Also in this configuration, the peeling electric field E1 generated at the tip of the needle electrode 641 included in the peeling electrode 64 can be applied to the paper.

  Further, the configuration of each part of the image forming apparatus described in the above embodiment is also applied to the case where the sheet is efficiently peeled from the photosensitive drum 1 in the image forming apparatus that transfers the toner image to the sheet at the primary transfer position. Can do.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Further, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charger 3 Exposure unit 4 Developer 5 Intermediate roller 6 Cleaner unit 10 Image reading part 20 Image formation part 21, 22, 23, 24 Image formation station 30 Paper feed part 33 Conveyance path 40 Paper discharge part 50 Intermediate Transfer device 51 Intermediate transfer belt 52 Drive roller 53 Support roller 54 Cleaning unit 60 Secondary transfer device 62 Secondary transfer roller 63 Frame 64 Peeling electrode 65 Protection member 65a Tip edge 67 Paper guide unit 70 Fixing device 71 Heating roller 72 Fixing belt 73 Pressure roller 640 Base portion 640a Edge 641 Needle electrode 642 Connection electrode plate 643 Coil 651 Notch E1, E2 Stripping electric field L Length L1, L2 Shortest distance R1 First region R2 Second region V1 Secondary transfer bias V2 Predetermined Voltage W Opening width

Claims (7)

A transfer roller for transferring a toner image formed on the image carrier to a sheet at a transfer position;
A separation electrode disposed on the downstream side of the transfer position where the paper is conveyed, and having a plurality of needle-shaped electrodes;
A protective member disposed on the transfer roller side with respect to the peeling electrode and overlaid on the peeling electrode;
With
The transfer device, wherein the protective member has a notch recessed at a position facing at least one of the plurality of needle-like electrodes.   2. The transfer device according to claim 1, wherein the protection member has a leading end edge protruding from a leading end of each of the plurality of needle-like electrodes.   The transfer device according to claim 1, wherein the protection member is provided with a plurality of the cutout portions in a region facing at least a part of the sheet to be conveyed.   The said protection member is provided with the 1st area | region in which the said notch part was provided, and the 2nd area | region where the protection member overlapped the whole two or more continuous acicular electrodes, The 1-3 area | region is provided. The transfer device according to any one of the above.   5. The transfer device according to claim 4, wherein in the first region, the notch is provided at a position facing every other one of the plurality of needle-like electrodes. 6. An image forming unit for forming a toner image on the image carrier;
The transfer device according to claim 1, wherein the transfer device is applied to transfer of the toner image formed on the image carrier to a sheet.
An image forming apparatus.   The image forming apparatus according to claim 6, wherein a shortest distance from the tip of the needle electrode to the transfer roller in the transfer device is smaller than a shortest distance from the tip of the needle electrode to the image carrier.

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