Image forming apparatus

Abstract

The present invention provides an image forming apparatus capable of actively picking up paper whose behavior is unstable during transport. [Solution] The image forming apparatus comprises a transfer unit (e.g., an intermediate transfer belt 71) for transferring a toner image onto paper, a fixing unit (e.g., a fixing roller 31) for fixing the toner image onto the paper, a paper transport path 21 for transporting paper, and an adsorption unit 50 provided between the transfer unit and the fixing unit for electrostatically adsorbing the paper. The adsorption unit 50 moves in a direction away from the paper being transported between the transfer unit and the fixing unit.

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus including an adsorption unit that electrostatically adsorbs a sheet of paper.

Background Art

[0002] In an electrophotographic image forming apparatus, an image is formed on a sheet of paper conveyed through a paper conveyance path after undergoing processes such as transfer of a toner image and fixing by heating and pressurization. In such an image forming apparatus, the sheet of paper on which the toner image has been transferred is conveyed to a fixing unit while being separated from a transfer belt. At this time, the conveyance may become unstable due to the sheet sagging or the like, resulting in conveyance failure. Therefore, an image forming apparatus has been proposed that can stably convey a sheet of paper by guiding a thin or weak paper to the fixing unit (see, for example, Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] A conventional image forming apparatus includes a transfer unit that transfers a toner image onto a sheet (paper), a fixing unit provided above the transfer unit that fixes the toner image onto the sheet, and a guide member provided between the fixing unit and the transfer unit that guides the sheet to the fixing unit, and conveys the sheet toward the fixing unit while electrostatically adsorbing the sheet with the guide member.

[0005] Furthermore, conventional image forming apparatuses include a paper transport path through which paper is transported, a photoreceptor unit that supports a photoreceptor, a transfer roller that is pressed against the photoreceptor via the paper transport path, a transfer unit that supports the transfer roller, a paper guide provided between the photoreceptor unit and the fuser unit to guide the paper, and a support holder that supports the transfer unit and the paper guide. The support holder is movable to move the transfer unit and the paper guide away from the photoreceptor unit and the fuser unit.

[0006] In the image forming apparatus described above, the position of guide members and the like is fixed when transporting paper, so there is a possibility that the paper may not be able to be picked up if it moves too far away from the guide members.

[0007] This disclosure is made to solve the above-mentioned problems and aims to provide an image forming apparatus that can actively pick up paper whose behavior is unstable during transport. [Means for solving the problem]

[0008] The image forming apparatus according to this disclosure comprises a transfer unit for transferring a toner image onto paper, a fixing unit for fixing the toner image onto the paper, a paper transport path for transporting paper, and an adsorption unit provided between the transfer unit and the fixing unit for electrostatically adsorbing paper, wherein the adsorption unit moves in a direction toward and away from the paper being transported between the transfer unit and the fixing unit.

[0009] In the image forming apparatus according to this disclosure, the suction unit may be configured to move between a first position close to the paper transport path and a second position further away from it.

[0010] In the image forming apparatus according to this disclosure, the trajectory of the adsorption unit may be configured to intersect with the path taken by the paper being transported between the transfer unit and the fixing unit.

[0011] In the image forming apparatus according to this disclosure, when the leading edge of the paper approaches the suction part, the suction part, which is waiting at the first position, may be configured to move to the second position.

[0012] The image forming apparatus according to this disclosure includes a paper guide provided between the adsorption unit and the fixing unit for guiding the paper, and the second position may be configured to be closer to the paper guide than the first position.

[0013] The image forming apparatus according to this disclosure may be configured to include a paper detection unit provided along the paper transport path to the suction unit for detecting paper, and to calculate the timing at which the paper reaches the suction unit based on the detection result of the paper detection unit. [Effects of the Invention]

[0014] According to this disclosure, paper transport failures can be suppressed by moving the suction part to actively attract paper that behaves stably during transport. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] This is a schematic side view showing a portion of the paper transport path. [Figure 3] This is a schematic side view showing a portion of the paper transport path when the suction part is in the first position. [Figure 4] This is a schematic side view showing a portion of the paper transport path when the suction part is in the second position. [Modes for carrying out the invention]

[0016] The image forming apparatus according to the embodiment of this disclosure will be described below with reference to the drawings.

[0017] Figure 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure.

[0018] The image forming apparatus 100 is a multifunction device having a copy function, a scanner function, a facsimile function, and a printer function, and transmits the image of the document read by the image reading apparatus 130 to the outside, or forms the image of the document read by the image reading apparatus 130 or the image received from the outside in color or monochrome on a recording medium such as paper.

[0019] Above the image reading apparatus 130, a document conveying apparatus 110 supported to be openable and closable is provided. The document conveying apparatus 110 conveys one or a plurality of documents one by one in order. The image reading apparatus 130 reads the document placed on the document placing table 131 by scanning the scanning optical system, or reads the document conveyed by the document conveying apparatus 110 to generate image data.

[0020] The image forming apparatus 100 is provided with a photosensitive drum 2, a charger 3, a developing device 4, a drum cleaning device 5, an intermediate transfer belt device 7, a secondary transfer roller 11, an optical scanning device 12, a fixing unit, a paper feeding unit 18, and the like.

[0021] In the image forming apparatus 100, image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black) is handled. The image forming apparatus 100 is provided with four photosensitive drums 2, chargers 3, developing devices 4, and drum cleaning devices 5 for forming four types of toner images, and each is associated with black, cyan, magenta, and yellow, respectively, to constitute four image stations Pa, Pb, Pc, and Pd.

[0022] The charger 3 uniformly charges the surface of the photoreceptor drum 2 to a predetermined potential. The light scanning device 12 exposes the surface of the photoreceptor drum 2 to form an electrostatic latent image. The developing device 4 develops the electrostatic latent image on the surface of the photoreceptor drum 2 to form a toner image on the surface of the photoreceptor drum 2. The drum cleaning device 5 removes and recovers residual toner from the surface of the photoreceptor drum 2. Through the above series of operations, toner images of each color are formed on the surface of each photoreceptor drum 2.

[0023] The intermediate transfer belt device 7 comprises intermediate transfer rollers 6, an endless intermediate transfer belt 71, an intermediate transfer drive roller 72, an intermediate transfer driven roller 73, and a cleaning device 9. Four intermediate transfer rollers 6 are provided inside the intermediate transfer belt 71 to form four different toner images corresponding to each color. The intermediate transfer rollers 6 transfer the toner images of each color formed on the surface of the photoreceptor drum 2 to the circulating intermediate transfer belt 71.

[0024] The intermediate transfer belt 71 is stretched over the intermediate transfer drive roller 72 and the intermediate transfer driven roller 73. In the image forming apparatus 100, the toner images of each color formed on the surface of each photoreceptor drum 2 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 71. The cleaning device 9 removes and collects waste toner that remains on the surface of the intermediate transfer belt 71 without being transferred to the paper.

[0025] The secondary transfer roller 11 grips the paper that has been transported through the paper transport path 21 between itself and the intermediate transfer belt 71 at the transfer nip section. The secondary transfer roller 11 is in contact with the intermediate transfer drive roller 72 so as to sandwich the intermediate transfer belt 71. As the paper passes through the transfer nip section, the toner image on the surface of the intermediate transfer belt 71 is transferred to the paper and it is then transported to the fuser section.

[0026] In the image forming apparatus 100, the transfer section is composed of a photoreceptor drum 2, a charger 3, a developing device 4, a drum cleaning device 5, an intermediate transfer belt device 7, and a secondary transfer roller 11, and the toner image is transferred to the paper in the transfer nip section described above.

[0027] The image forming apparatus 100 includes a fixing section comprising a fixing roller 31 and a pressure roller 32 that rotate around an axis. The fixing section inserts the paper on which the toner image has been transferred into the nip between the fixing roller 31 and the pressure roller 32, heats and pressurizes it, and fixes the toner image to the paper.

[0028] The paper feeding unit 18 is equipped with a paper feeding cassette for loading recording media (paper) used for image formation and is located below the optical scanning device 12. The paper is pulled out of the paper feeding unit 18 by the pickup roller 16 and transported to the paper transport path 21. The paper transported to the paper transport path 21 passes through the transfer nip section and other nip sections and is discharged to the output tray 19 by the discharge roller pair 17.

[0029] The paper transport path 21 is equipped with a registration roller 14 and a pair of discharge rollers 17. The registration roller 14 transports the paper at a speed equal to the process speed at which the image is formed on the paper. The registration roller 14 is located between the paper feed section 18 and the secondary transfer roller 11 and adjusts the timing of paper transport so that the toner image is transferred to the paper by the secondary transfer roller 11. For example, the registration roller 14 holds the transported paper and waits (stops temporarily), then starts transporting the paper at a constant speed in synchronization with the secondary transfer roller 11.

[0030] When image formation is to be performed on the back side of the paper as well as the front side, the paper transport direction is changed by the discharge roller pair 17 and the paper is transported to the inversion transport path 22. In the inversion transport path 22, the paper is guided to the registration roller 14 with its front and back sides reversed by the inversion transport roller 15. The image forming apparatus 100 forms an image on the back side of the paper guided to the registration roller 14 in the same way as the front side and discharges it to the output tray 19.

[0031] A manual feed tray 150 is mounted on the front of the image forming apparatus 100 so as to be openable and closable, and an open / close door 160 is mounted on the rear of the image forming apparatus 100 so as to be open / closable. Paper loaded in the open manual feed tray 150 is supplied to the manual feed transport path 23 near the front. The manual feed transport path 23 merges with the paper transport path 21 near the rear just before the registration roller 14, and the paper is transported to the registration roller 14 by the manual feed transport roller 13 located in the manual feed transport path 23. When the open / close door 160 is opened, the reversing transport path 22 is exposed, and jammed paper and other materials can be collected.

[0032] The paper feed unit 18 is located below the manual feed transport path 23 and is configured to be removable to the outside through the front of the device 101. When the paper feed unit 18 is removed, a space is created below the manual feed transport path 23.

[0033] Next, the structure of a part of the paper transport path 21, specifically the transfer section (particularly around the secondary transfer roller 11) and the vicinity of the fixing section, will be described with reference to Figure 2.

[0034] Figure 2 is a schematic side view showing a portion of the paper transport path.

[0035] Figure 2 schematically shows the portion of the paper transport path 21 from the registration roller 14 to the fixing section (fixing roller 31 and pressure roller 32). As described above, in the paper transport path 21, the intermediate transfer drive roller 72 and the secondary transfer roller 11 are arranged downstream of the registration roller 14 along the paper transport direction. In the transfer section, the surface of the paper transported in the paper transport path 21 faces the intermediate transfer drive roller 72 and the intermediate transfer belt 71, and the back surface faces the secondary transfer roller 11. In the fixing section, the surface faces the fixing roller 31, and the back surface faces the pressure roller 32.

[0036] Between the transfer section and the fixing section, a transfer-side paper guide 41, a suction section 50, and a fixing-side paper guide 42 (an example of a paper guide) are provided along the paper transport path 21. The transfer-side paper guide 41, the suction section 50, and the fixing-side paper guide 42 are positioned on the side facing the back surface of the paper.

[0037] The transfer-side paper guide 41 and the fixing-side paper guide 42 are part of the housing that constitutes the main body of the device, and serve as walls separating the inside of the main body of the device from the paper transport path 21. The transfer-side paper guide 41 is located near the secondary transfer roller 11, and the fixing-side paper guide 42 is located near the pressure roller 32.

[0038] The suction part 50 is an electrostatic plate charged with a polarity opposite to that of the paper, and electrostatically attracts the paper. The suction part 50 is positioned between the transfer-side paper guide 41 and the fixing-side paper guide 42 in the paper transport direction. The suction part 50 may partially overlap with the transfer-side paper guide 41 and the fixing-side paper guide 42, and this can be avoided by cutting out parts of them to prevent interference.

[0039] The paper transport path 21 between the transfer unit and the fixing unit has a gap slightly wider than the thickness of the paper, allowing the paper to move in the thickness direction. Figure 2 shows two examples of paths the paper takes between the transfer unit and the fixing unit: a first path Ka and a second path Kb. The first path Ka is the path that travels the shortest possible distance between the transfer unit and the fixing unit. On the other hand, the second path Kb is a curved path that protrudes further towards the back side of the paper than the first path Ka, and is longer than the first path Ka. The transfer-side paper guide 41 and the fixing-side paper guide 42 described above are positioned along the second path Kb, with a small gap between them and the first path Ka.

[0040] As described above, in the paper transport path 21, there is room for the paper to move, so the path taken during transport sometimes differs depending on the part of the paper. For example, one end of the paper in the width direction may follow the first path Ka, and the other end in the width direction may follow the second path Kb. In this case, the distance traveled from the transfer unit to the fixing unit differs depending on the part, which sometimes resulted in the paper being transported at an angle and causing transport problems. In contrast, in this embodiment, the behavior of the transported paper is stabilized by moving the suction unit 50 that electrostatically attracts the paper.

[0041] The suction unit 50 is connected to a drive source (not shown), such as a solenoid or a motor, and moves in a direction toward or toward the paper being transported between the transfer unit and the fixing unit. Specifically, the suction unit 50 is configured to move between a first position close to the paper transport path 21 and a second position further away, where the paper transport path 21 corresponds to the first path Ka. Figure 2 shows the state in which the suction unit 50 is in the second position, and the end of the suction unit 50 facing the paper transport path 21 (the left end in Figure 2) is positioned along the second path Kb.

[0042] Next, the movement of the adsorption unit 50 will be explained with reference to Figures 3 and 4.

[0043] Figure 3 is a schematic side view showing a portion of the paper transport path when the suction part is in the first position.

[0044] The image forming apparatus 100 has a paper detection unit that detects the paper P, located along the paper transport path 21, between the paper and the suction unit 50. In this embodiment, the paper detection unit is a registration roller 14, and it detects the timing to resume transporting the paper P that has been left waiting. The image forming apparatus 100 calculates the timing at which the paper P reaches the suction unit 50 based on the detection result of the paper detection unit, the timing at which the registration roller 14 transports the paper, and the transport speed of the paper P by the various rollers. Note that the paper detection unit is not limited to a registration roller 14, but may be various sensors provided along the paper transport path 21.

[0045] Figure 3 shows the state in which the suction unit 50 is in the first position, with the end of the suction unit 50 facing the paper transport path 21 positioned along the first path Ka. When transporting paper P, the suction unit 50 moves to wait in the first position before the leading edge of the paper P (paper leading edge Pa) arrives. When paper P passes through the transfer section, the paper leading edge Pa is attracted to the suction unit 50 in the first position, and paper P becomes electrostatically attached to the suction unit 50. With paper P electrostatically attached, the suction unit 50 moves to the second position, as shown in Figure 4, which will be described later.

[0046] As described above, by moving the suction unit 50 to actively attract the paper P, whose behavior is unstable during transport, transport failures of the paper P can be suppressed. Furthermore, since the suction unit 50 moves toward and away from the paper transport path 21, the transported paper P can be reliably attracted. In addition, by calculating the timing of the paper P's arrival, the suction unit 50 can be moved appropriately.

[0047] Figure 4 is a schematic side view showing a portion of the paper transport path when the suction part is in the second position.

[0048] In Figure 4, the suction part 50 has moved in the direction of arrow F compared to Figure 3, showing the state where the suction part 50 is in the second position. When the suction part 50 moves to the second position while electrostatically adsorbing the paper P, the paper P is guided to follow the second path Kb. In this way, the suction part 50 can guide the paper P to the appropriate path by moving while adsorbing the leading edge of the paper P. Note that the direction in which the suction part 50 moves is not limited to the direction of arrow F, but can also move in the opposite direction to arrow F.

[0049] As shown in Figures 3 and 4, the trajectory of the suction unit 50 as it moves between the first and second positions intersects with the path taken by the paper being transported between the transfer unit and the fixing unit. As shown in Figure 3, at the first position, the suction unit 50 is positioned so as to protrude from the path taken by the paper P (second path Kb), making it easier to pick up the floating paper P.

[0050] As shown in Figures 3 and 4, comparing the positions where the suction part 50 is located, the second position is closer to the fixing-side paper guide 42 than the first position. When following the second path Kb, the leading edge Pa of the paper, having passed through the suction part 50, comes onto the fixing-side paper guide 42 as close as possible, thus mitigating the impact when it comes into contact with the fixing-side paper guide 42. In this way, the paper P moves to a position close to the fixing-side paper guide 42 while being attracted to it, allowing for smooth guidance of the paper P.

[0051] With respect to the suction part 50, the force that attracts the paper P increases as the area facing the paper P widens, but even when separated from the paper P, it acts to pull the approaching paper P towards it. Therefore, the timing of the movement of the suction part 50 from the first position to the second position can be adjusted as appropriate, and the leading edge Pa of the paper does not need to be in contact with the suction part 50 when the suction part 50 starts to move.

[0052] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of symbols]

[0053] 11. Secondary transfer roller (part of the transfer section) 14. Registration roller (an example of a paper detection unit) 21 Paper transport path 31 Fixing roller (part of the fixing section) 32 Pressure roller (part of the fixing section) 41 Transfer side paper guide 42 Fuser side paper guide 50 Adsorption part 71 Intermediate transfer belt (part of the transfer section) 72 Intermediate transfer drive roller (part of the transfer section) 100 Image forming apparatus

Claims

1. A transfer unit that transfers the toner image onto the paper, A fixing unit for fixing the aforementioned toner image onto the paper, A paper transport path for transporting paper, An image forming apparatus comprising an adsorption unit provided between the transfer unit and the fixing unit for electrostatically adsorbing paper, The adsorption unit moves in a direction away from the paper being transported between the transfer unit and the fixing unit. An image forming apparatus characterized by the following.

2. An image forming apparatus according to claim 1, The suction part moves between a first position close to the paper transport path and a second position further away from it. An image forming apparatus characterized by the following.

3. An image forming apparatus according to claim 2, The trajectory of the adsorption unit intersects with the path taken by the paper being transported between the transfer unit and the fixing unit. An image forming apparatus characterized by the following.

4. An image forming apparatus according to claim 2, When the leading edge of the paper approaches the suction part, the suction part, which is waiting in the first position, moves to the second position. An image forming apparatus characterized by the following.

5. An image forming apparatus according to claim 4, A paper guide is provided between the adsorption part and the fixing part to guide the paper, The second position is closer to the paper guide than the first position. An image forming apparatus characterized by the following.

6. An image forming apparatus according to claim 1, It is provided along the paper transport path up to the aforementioned suction section and includes a paper detection unit for detecting paper, Based on the detection result of the paper detection unit, the timing at which the paper reaches the suction unit is calculated. An image forming apparatus characterized by the following.

Images