Image forming apparatus

Abstract

To provide an image reading apparatus capable of suppressing adhesion of toner to a guide part even when a recording medium is not conveyed.SOLUTION: The image forming apparatus 100 includes a photosensitive drum 210, a developing roller 310, a transfer roller 240, a guide portion 170, a receiving portion 400, and a moving portion 500. In the conveyance path 160 of the sheet P, the guide portion 170 is disposed at a position below the boundary portion B between the photosensitive drum 210 and the developing roller 310 and upstream of the nip portion 270 where the photosensitive drum 210 and the transfer roller 240 are in contact with each other, and guides the sheet P to the nip portion 270. The receiving portion 400 is located above the guide portion 170 and receives the toner falling from the boundary portion B to the conveyance path 160. The moving portion 500 moves the receiving portion 400 from a first position Ta on the transport path 160 to a second position Tb separated from the transport path 160.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] The image forming apparatus described in Patent Document 1 includes a photosensitive drum, a transfer roller, and a transfer entrance guide. The transfer entrance guide guides a recording medium into a transfer nip formed by the photosensitive drum and the transfer roller. The image forming apparatus described in Patent Document 1 changes the width direction length of the surface abutment portion of the transfer entrance guide depending on the width of the recording medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-71041 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the image forming apparatus described in Patent Document 1, when the recording medium is not being conveyed, the surface contact portion of the transfer entrance guide faces upward, and therefore, it is not possible to prevent toner from adhering to the surface contact portion.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide an image forming device that can suppress toner adhesion to the guide section even when a recording medium is not being transported. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a photosensitive drum, a developing roller, a transfer roller, a guide unit, a receiving unit, and a moving unit. A toner image is formed on the surface of the photosensitive drum. The developing roller applies toner for forming the toner image to the photosensitive drum. The transfer roller transfers the toner image formed on the photosensitive drum to a recording medium. The guide unit is disposed in a transport path for the recording medium below the boundary between the photosensitive drum and the developing roller and upstream of a nip where the photosensitive drum and the transfer roller contact each other, and guides the recording medium to the nip. The receiving unit is located above the guide unit and receives the toner that falls from the boundary into the transport path. The moving unit moves the receiving unit from a first position on the transport path to a second position away from the transport path. [Effects of the Invention]

[0007] According to the present invention, even when a recording medium is not being conveyed, it is possible to suppress toner from adhering to the guide portion. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating an image forming unit and a developing device according to the embodiment. [Figure 3] FIG. 2 is a perspective view showing a receiving portion and a moving portion according to the embodiment. [Figure 4] 10 is a diagram showing the receiving portion moved to a first position and its surrounding area. FIG. [Figure 5] 10 is a view showing the receiving portion moved to a second position and its surrounding area. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0010] An example of the configuration of an image forming apparatus 100 according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing the image forming apparatus 100 according to this embodiment. Figure 2 is a diagram showing an image forming section 200 and a developing device 300 according to this embodiment.

[0011] The image forming apparatus 100 is, for example, a copier, a printer, or a multifunction peripheral. The multifunction peripheral includes at least two of the following devices: a copier, a printer, and a facsimile.

[0012] As shown in Figures 1 and 2, the image forming apparatus 100 includes a sheet loading section 110, a conveying section 120, an image forming section 200, a fixing section 130, an ejection section 140, an image reading section 150, a conveying path 160, and a guide section 170.

[0013] In this embodiment, in image forming apparatus 100, the conveyance direction from image forming unit 200 toward discharge unit 140 is defined as the front, and the opposite direction is defined as the rear. The left side when image forming apparatus 100 is viewed from the rear is defined as the left side, and the opposite direction is defined as the right side. Furthermore, in the up-down direction perpendicular to the front-to-back and left-to-right directions of image forming apparatus 100, the side on which image reading unit 150 is located relative to image forming unit 200 is defined as the top, and the opposite direction is defined as the bottom. Note that these directions do not limit the orientation of image forming apparatus 100 of the present invention when in use.

[0014] A sheet P is placed on the sheet placement section 110. The sheet P is, for example, plain paper, recycled paper, thin paper, thick paper, coated paper, or an OHP (Overhead Projector) sheet. The sheet placement section 110 includes a cassette that can accommodate the sheet P. The conveying section 120 conveys the sheet P placed on the sheet placement section 110 toward the image forming section 200. The sheet P corresponds to, for example, a "recording medium."

[0015] The image forming unit 200 forms (prints) an image on a sheet P conveyed from the sheet loading unit 110 via the conveying unit 120. As shown in FIGS. 1 and 2 , the image forming unit 200 includes a photosensitive drum 210, a charging unit 220, an exposure unit 230, a developing device 300, a transfer roller 240, a cleaning member 250, and a charge removing unit 260.

[0016] The charging unit 220 uniformly charges the surface of the photosensitive drum 210. The exposure unit 230 irradiates the surface of the photosensitive drum 210 with light based on image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 210. The image data is, for example, image data generated by the image reading unit 150, image data stored in a storage unit (not shown), or image data received from an external device via a network (not shown).

[0017] The developing device 300 deposits toner onto the electrostatic latent image on the photosensitive drum 210 to form a toner image on the surface of the photosensitive drum 210 .

[0018] The transfer roller 240 transfers the toner image onto the sheet P. The transfer roller 240 is disposed below the photosensitive drum 210. The transfer roller 240 comes into contact with the photosensitive drum 210 to form a nip portion 270. Note that the transfer roller 240 is not limited to a roller. It may also be a transfer device having a transfer function.

[0019] The cleaning member 250 removes toner remaining on the surface of the photosensitive drum 210. The charge removing unit 260 removes residual charges from the surface of the photosensitive drum 210.

[0020] The sheet P onto which the toner image has been transferred in the image forming unit 200 is transported toward the fixing unit 130. The fixing unit 130 applies heat and pressure to the sheet P to fix the toner image onto the sheet P. The fixing unit 130 has a fixing roller 131 and a pressure roller 132.

[0021] Fixing roller 131 is heated by an electrically-heated heating element that generates heat when energized. Pressure roller 132 is disposed opposite to fixing roller 131. The circumferential surface of pressure roller 132 is in contact with the circumferential surface of fixing roller 131 in a pressed state.

[0022] The sheet P with the fixed toner image is transported through the transport path 160 toward the discharge section 140. The discharge section 140 includes a pair of discharge rollers and a discharge tray. The pair of discharge rollers discharge the sheet P onto the discharge tray. In this manner, an image is printed on the sheet P.

[0023] The image reading unit 150 reads an image of a document and generates image data. The read image data is stored in a storage unit. The conveying path 160 forms a part of the conveying unit 120. The conveying path 160 includes an input path for conveying the sheet P to the nip portion 270 and an output path for conveying the sheet P from the nip portion 270.

[0024] The guide section 170 guides the sheet P to the nip section 270. The guide section 170 is disposed midway along the transport path 160. The guide section 170 guides the sheet P being transported along the transport path 160 to the nip section 270. The guide section 170 is disposed at a position upstream of the nip section 270 where the photosensitive drum 210 and the transfer roller 240 come into contact with each other.

[0025] The guide section 170 has a cross section formed in a substantially arc shape. Specifically, the front portion (downstream portion) of the guide section 170 is positioned at a height that decreases toward the front. The rear portion (upstream portion) of the guide section 170 is positioned at a height that decreases toward the rear. As a result, the guide section 170 places the sheet P on an upper portion and sends the sheet P toward the nip section 270. The left-right length of the guide section 170 is the same as the left-right length of the conveying path 160, for example.

[0026] As shown in FIG. 2, the developing device 300 includes a developing roller 310 as a toner carrier, a toner charging member (not shown), a container (not shown), a toner supply roller 330, and a casing 340.

[0027] The toner contained in the container is supplied to the developing roller 310 by the toner supply roller 330. The developing roller 310 is configured to support the toner supplied by the toner supply roller 330. The developing roller 310 applies toner for forming a toner image to the photosensitive drum 210. The developing roller 310 is disposed behind the photosensitive drum 210. A boundary B between the developing roller 310 and the photosensitive drum 210 is located above the guide portion 170. In other words, the guide portion 170 is disposed below the boundary B. In this embodiment, the boundary B refers to the area between the photosensitive drum 210 and the developing roller 310, particularly the peripheral area including the area where they are closest to each other. The developing roller 310 includes, for example, a shaft, a magnet roll 320, and a cylindrical sleeve.

[0028] The magnet roll 320 is fixed to the shaft and positioned within the sleeve. The magnet roll 320 has magnetic poles at least on its surface. Examples of the magnetic poles of the magnet roll 320 include north and south poles based on permanent magnets. The sleeve is positioned on the surface of the developing roller 310 and is supported so as to be rotatable around the shaft. More specifically, the shaft and sleeve are connected so that the sleeve can rotate around the non-rotating magnet roll 320.

[0029] The casing 340 houses a portion of the developing roller 310 and the toner supply roller 330. A partition section 180 is disposed below the casing 340. The partition section 180 divides the interior of the image forming apparatus 100 into a lower region where the transport path 160 is disposed and an upper region where the developing device 300 is disposed.

[0030] Toner is supplied to a storage section of the developing device 300 from a toner container (not shown) that is detachable from the image forming apparatus 100. The toner in the storage section is supplied to the developing roller 310 by a toner supply roller 330. The toner is attracted to the sleeve of the developing roller 310 by the magnetic force of the magnet roll 320 and is carried on the surface of the sleeve of the developing roller 310. The toner carried on the surface of the sleeve is charged by friction with the toner charging member. If the toner is a positively charged toner, the positively charged toner is charged to a positive polarity by friction. If the toner is a negatively charged toner, the negatively charged toner is charged to a negative polarity by friction.

[0031] The charged toner is supplied to the photosensitive drum 210 by the rotation of the sleeve of the developing roller 310. As a result, the toner adheres to the electrostatic latent image formed on the photosensitive layer of the photosensitive drum 210, thereby forming a toner image on the photosensitive layer. In this way, the electrostatic latent image formed on the surface of the photosensitive drum 210 is developed.

[0032] Next, the toner image on the photosensitive layer of photosensitive drum 210 is transferred to sheet P. Thereafter, fixing unit 130 heats and pressurizes the toner to fix it to sheet P. As a result, an image is formed on sheet P. After the image is formed, cleaning member 250 (see FIG. 1) removes toner remaining on the surface of photosensitive drum 210.

[0033] The image forming apparatus 100 will be further described with reference to Figures 3 to 5. Figure 3 is a perspective view showing the receiving section 400 and the moving section 500 according to this embodiment. Figure 4 is a view showing the receiving section 400 moved to the first position Ta and its surrounding area. Figure 5 is a view showing the receiving section 400 moved to the second position Tb and its surrounding area. The image forming apparatus 100 further includes the receiving section 400 and the moving section 500.

[0034] 2, receiving section 400 is disposed below boundary section B and above guide section 170 on transport path 160. As a result, receiving section 400 receives toner that falls from boundary section B onto transport path 160.

[0035] As shown in FIGS. 3 to 5 , the moving unit 500 moves the receiving unit 400. Specifically, the moving unit 500 moves the receiving unit 400 from a first position Ta on the conveying path 160 to a second position Tb away from the conveying path 160. Because the guide unit 170 is located below the boundary portion B, the guide unit 170 corresponds to a part of the conveying path 160 onto which the toner falls. In other words, when the receiving unit 400 moves to the first position Ta, the receiving unit 400 receives the toner that falls onto the guide unit 170. Furthermore, when the receiving unit 400 moves to the second position Tb, the receiving unit 400 moves away from the conveying path 160 (the guide unit 170) and allows the sheet P to pass through. Therefore, when the sheet P is not being conveyed, the receiving unit 400 can receive the toner that falls onto the guide unit 170 by moving the receiving unit 400 to the first position Ta. Therefore, even when the sheet P is not being transported, it is possible to prevent toner from adhering to the guide section 170. Here, the first position Ta corresponds to a position in contact with the transport path 160 or a position slightly separated from the guide section 170. The second position Tb corresponds to a position spaced a predetermined distance above the guide section 170. The predetermined distance is a distance that allows the sheet P to pass forward.

[0036] In this embodiment, when the sheet P is not being conveyed on the conveying path 160, the receiving portion 400 approaches the guiding portion 170 and at least partially covers the upper portion of the guiding portion 170, thereby preventing the guiding portion 170 from being exposed. When the sheet P is being conveyed on the conveying path 160, the receiving portion 400 moves upward away from the guiding portion 170. This ensures a space between the receiving portion 400 and the guiding portion 170 through which the sheet P can pass, and the guiding portion 170 guides the sheet P to the nip portion 270. Moreover, because the receiving portion 400 moves upward and rearward, it is possible to avoid interference between the receiving portion 400 and the photosensitive drum 210.

[0037] The receiving portion 400 extends in a left-right direction that intersects with the conveying direction of the sheet P. Specifically, the guide portion 170 extends from one left-right end side to the other left-right end side of the conveying path 160. As a result, the guide portion 170 is covered by the receiving portion 400 from one left-right end side to the other left-right end side, which further reduces adhesion of toner to the guide portion 170. The left-right direction corresponds to, for example, the "first direction."

[0038] The receiving portion 400 has a generally U-shaped cross section. The receiving portion 400 has a bottom wall portion 410, a front wall portion 420, and a rear wall portion 430. The bottom wall portion 410 faces the guide portion 170. The bottom wall portion 410 is configured in a generally rectangular plate shape. The front wall portion 420 protrudes upward from the front end portion of the bottom wall portion 410. A sponge portion 440 is provided at the upper end portion of the front wall portion 420, extending from one end side to the other end side in the left-right direction. The rear wall portion 430 protrudes upward from the rear end portion of the bottom wall portion 410. In other words, the receiving portion 400 has a recessed portion 450 that is open upward. This prevents toner from falling from the receiving portion 400 to the guide portion 170, even if toner accumulates on the bottom wall portion 410.

[0039] When the receiving portion 400 moves to the second position Tb, the toner accumulated in the recess 450 or the toner falling from the boundary portion B may pass between the casing 340 and the receiving portion 400 and scatter into an upper region above the partition portion 180. Therefore, in this embodiment, the third contact portion 350 is provided.

[0040] The third contact portion 350 blocks the movement of toner from the upstream side to the downstream side of the third contact portion 350. The third contact portion 350 is located above the receiving portion 400. The third contact portion 350 is disposed at the lower part of the front end portion of the casing 340. A storage portion is formed at the lower part of the front end portion of the casing 340, and the third contact portion 350 is stored in this storage portion. When the receiving portion 400 moves to the second position Tb, the third contact portion 350 abuts from above against the receiving portion 400 (bottom wall portion 410) located at the second position Tb. The third contact portion 350 separates the recessed portion 450 into a front region and a rear region. This prevents toner from scattering through the recessed portion 450 of the receiving portion 400 into an upper region above the partition portion 180 during transport of the sheet P.

[0041] 3 to 5, the moving part 500 will be further described. As shown in FIGS. 3 to 5, the moving part 500 has a main body shaft part 510, a first contact part 520, a second contact part 530, a first transmission part 540, and a second transmission part 550.

[0042] The main body shaft 510 extends in a transverse direction (left-right direction) that intersects with the front-rear direction. The main body shaft 510 is configured to be rotatable about its axis.

[0043] The first contact portion 520 contacts the sheet P being transported forward. For example, a plurality of first contact portions 520 may be provided. Each first contact portion 520 is fixed to the circumferential surface of the main body shaft portion 510 and extends radially outward from the main body shaft portion 510. The first contact portion 520 falls forward when it contacts the front end of the sheet P being transported. The first contact portion 520 rotates the main body shaft portion 510 around its axis in the X1 direction.

[0044] The first transmission part 540 rotates in synchronization with the rotation of the main body shaft part 510. The first transmission part 540 has a disk shape. However, the first transmission part 540 is not limited to a disk shape. The first transmission part 540 may be a gear. The first transmission part 540 is fixed to one side end of the main body shaft part 510.

[0045] The second transmission part 550 abuts against the first transmission part 540 and rotates in synchronization with the rotation of the first transmission part 540. The second transmission part 550 is formed in a shape corresponding to the shape of the first transmission part 540. The second transmission part 550 is supported rotatably relative to the image forming apparatus 100.

[0046] The second contact portion 530 contacts the receiving portion 400 (bottom wall portion 410) from below. The second contact portion 530 is fixed to the second transmission portion 550 and extends radially outward from the second transmission portion 550. The tip portion (radially outer end portion) of the second contact portion 530 contacts the bottom wall portion 410 of the receiving portion 400. In other words, the second contact portion 530 rotates in synchronization with the rotation of the main body shaft portion 510 to contact the receiving portion 400 and move the receiving portion 400 from the first position Ta to the second position Tb. This allows the moving portion 500 to convert the conveying force for conveying the sheet P into a moving force for moving the receiving portion 400 from the first position Ta to the second position Tb.

[0047] The moving unit 500 further includes a biasing unit 560. Specifically, the biasing unit 560 is a compression spring wound around the circumferential surface of the main body shaft 510. One end of the biasing unit 560 is fixed to the image forming apparatus 100, and the other end of the biasing unit 560 is fixed to the main body shaft 510. The biasing unit 560 biases the main body shaft 510 to rotate in the X1 direction. In other words, the biasing unit 560 moves the receiving unit 400 from the second position Tb to the first position Ta. This prevents toner from adhering to the guide unit 170 when the sheet P is not being transported on the transport path 160.

[0048] When the sheet P is not being conveyed on the conveying path 160, the biasing portion 560 biases the main body shaft portion 510, causing the first transmission portion 540 to rotate in the Y1 direction. In synchronization with this, the second transmission portion 550 rotates in the Y2 direction, causing the second contact portion 530 to move the receiving portion 400 from the second position Tb to the first position Ta (see FIG. 4). When the sheet P is being conveyed on the conveying path 160, the sheet P contacts the first contact portion 520, causing the first transmission portion 540 to rotate in the X1 direction. In synchronization with this, the second transmission portion 550 rotates in the X2 direction, causing the second contact portion 530 to move the receiving portion 400 from the first position Ta to the second position Tb (see FIG. 5).

[0049] When the receiving portion 400 moves from the first position Ta to the second position Tb, the second contact portion 530 moves from a front lower position to a rear upper position. Therefore, when the receiving portion 400 moves from the first position Ta to the second position Tb, the second contact portion 530 moves the receiving portion 400 toward the upstream side in the transport direction. This makes it possible to avoid interference between the receiving portion 400 and the photosensitive drum 210.

[0050] The embodiments of the present invention have been described above with reference to the drawings (FIGS. 1 to 5). However, the present invention is not limited to the above-described embodiments and can be embodied in various forms without departing from the spirit of the present invention. The drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, etc. of each component shown in the drawings may differ from the actual components due to the convenience of creating the drawings. Furthermore, the materials, shapes, dimensions, etc. of each component shown in the above-described embodiments are merely examples and are not particularly limited, and various modifications are possible within a range that does not substantially depart from the effects of the present invention.

[0051] (1) As described with reference to FIGS. 1 to 5, in the above embodiment, an example was shown in which receiving portion 400 has recess 450 in its upper portion, but this is not limited thereto. Receiving portion 400 only needs to receive toner that falls from boundary portion B between developing roller 310 and photosensitive drum 210, and may simply be a plate material. Furthermore, while an example was shown in which receiving portion 400 has only a storage function for storing the received toner, it may also have a discharge function for discharging the accumulated toner to the outside of image forming apparatus 100 in addition to the storage function.

[0052] (2) As described with reference to FIGS. 1 to 5, in the above embodiment, the receiving portion 400 moves from the first position Ta to the second position Tb, which is higher than the first position Ta. However, this is not limiting. The receiving portion 400 only needs to be able to move between a position that covers the guide portion 170 so that toner does not adhere to the guide portion 170 and another position. In this case, the receiving portion 400 may move from the first position Ta, which is located above the guide portion 170, to the second position Tb, which is horizontally spaced apart.

[0053] (3) As described with reference to Figures 1 to 5, in the above embodiment, the disk-shaped first transmission part 540 and the disk-shaped second transmission part 550 come into contact with each other to directly transmit the driving force that moves the receiving part 400. However, this is not limiting. The first transmission part 540 and the second transmission part 550 may be formed of meshable gears. Furthermore, the first transmission part 540 and the second transmission part 550 may be spaced apart and connected to each other by an endless belt.

[0054] (4) As described with reference to Figures 1 to 5, in the above embodiment, the bottom wall 410 and the third contact portion 350 are spaced apart when the receiving portion 400 is in the first position Ta, and the bottom wall 410 and the third contact portion 350 are in contact when the receiving portion 400 is in the second position Tb. However, this is not limiting. The third contact portion 350 may be configured to be movable up and down, so that the receiving portion 400 is always in contact with the third contact portion 350 from the first position Ta to the second position Tb. In this case, for example, a space is formed in the casing 340 that allows the third contact portion 350 to move. [Industrial Applicability]

[0055] The present invention can be used in the field of image forming devices. [Explanation of symbols]

[0056] 100: Image forming device 160: Transport route 170: Information department 210: Photosensitive drum 240: Transfer roller 270: Nip section 310: Developing roller 350: Third contact part 400: Receiving part 450: Recess 500: Moving section 510: Main body shaft 520: 1st contact part 530: Second contact part 560: biasing part B: Boundary P: Sheet (recording medium) Ta: 1st position Tb: 2nd position

Claims

1. a photosensitive drum on whose surface a toner image is formed; a developing roller that deposits toner for forming the toner image onto the photosensitive drum; a transfer roller that transfers the toner image formed on the photosensitive drum onto a recording medium; a guide section that is disposed in a conveyance path of the recording medium below a boundary between the photosensitive drum and the developing roller and upstream of a nip section where the photosensitive drum and the transfer roller come into contact with each other, and that guides the recording medium to the nip section; a receiving portion located above the guide portion and configured to receive the toner falling from the boundary portion into the transport path; a moving unit that moves the receiving unit from a first position on the conveying path to a second position away from the conveying path; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1 , wherein the receiving portion extends in a direction intersecting the conveying direction of the recording medium.

3. The image forming apparatus according to claim 2 , wherein the receiving portion has a recessed portion that is open upward.

4. The moving unit is a main body shaft portion extending in the intersecting direction and rotatable about an axis; a first contact portion that contacts the recording medium being conveyed, thereby rotating the main body shaft portion about the axis; a second abutment portion that rotates in synchronization with the rotation of the main body shaft portion to abut against the receiving portion and move the receiving portion from the first position to the second position; The image forming apparatus according to claim 2 , further comprising:

5. The image forming apparatus according to claim 4 , wherein the second contact portion moves the receiving portion toward the upstream side in the transport direction when moving the receiving portion from the first position to the second position.

6. The moving portion further includes a biasing portion, The image forming apparatus according to claim 4 , wherein the biasing portion moves the receiving portion from the second position to the first position.

7. Further provided is a third contact portion located above the receiving portion, The image forming apparatus according to claim 1 , wherein the third contact portion contacts the receiving portion located at the second position.

Images