JP5707890B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  After the toner is transferred onto the recording paper by the transfer device, the recording paper on which the toner is placed is conveyed while being rubbed on the guide plate in order to be conveyed to the fixing device. At that time, the recording paper may float locally, causing a potential difference and disturbing the image.

(1) Conventionally, the recording paper has been neutralized with a static elimination needle or the like with a sharp tip to prevent the image disturbance. However, as a problem when using the static elimination needle, when the distance between the recording paper and the tip of the static elimination needle is too short, a discharge occurs between the tip of the static elimination needle and the recording paper, resulting in image distortion.

(2) a transfer belt that conveys the transfer paper fed so as to be in contact with the outer peripheral surface of the image carrier toward the fixing device, and a transfer paper guide mechanism provided between the transfer belt and the fixing device. The transfer paper guide mechanism comprises a transfer outlet side guide mechanism disposed on the transfer belt outlet side and a fixing inlet side guide mechanism disposed on the inlet side of the fixing device. There is an example in which a charge removal member is provided on the lower surface of the transfer surface of the transfer outlet guide mechanism, and the charge removal member faces an opening formed on the transfer surface (see, for example, Patent Document 1).

(3) A transfer belt that transfers image information held on the image carrier onto the transfer paper, electrostatically fixes the transfer paper, conveys it, driving means for driving the transfer belt, and charges on the transfer belt A transfer conveying apparatus provided with a charging means for providing a transfer, a transfer outlet guide plate for guiding the transfer paper immediately after the transfer paper is separated from the transfer belt, and a neutralizing needle for discharging the transfer paper in the middle of the transfer outlet guide plate There is an example in which the grounded electrode plate integrated with the transfer outlet guide plate is provided on the back side of the transfer surface of the transfer outlet guide plate (see, for example, Patent Document 2).

  However, in both cases (2) and (3), since the charge removal member is provided on the lower surface of the transfer surface of the transfer exit guide mechanism to remove the charge on the recording paper, the guide mechanism is affected by variations in paper stiffness and weight. The contact state changes, and the distance between the recording paper and the charge removal member also changes. For this reason, there is a concern that variations in the charge removal effect may occur depending on the recording paper type.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that prevents image disturbance caused by a charge removal member.

In order to achieve the object, the present invention has the following configuration.
(1): a transfer device for passing a recording paper between a transfer roller disposed opposite to an image carrier on which a toner image is carried, and transferring the toner image on the image carrier to the recording paper; a fixing device for fixing the toner image through the recording sheet between the fixing roller and the pressure roller, the image type forming apparatus having a guide along the transport path for transporting the recording paper to the fixing device from the transfer device ,
The guide is divided into a guide on the transfer device side and a guide on the fixing device side, and both guides are covered at a joint portion of the guides so as to intersect the guides, and the recording paper is conveyed to the intersecting portion. Provide a metal member with an opening to be a path,
The metal member is all of the ridge portion and the corner portion R shape,
The volume resistance of the guide on the transfer device side is set lower than the volume resistance of the guide on the fixing device side . For example, the metal member has a plate shape, and an opening is formed so as not to block the conveyance path. The flat portion has no protrusion and the corner portion is rounded so as not to induce discharge. R shape. The conveyance path is divided into two parts, the volume resistance of the conveyance path on the transfer device side is low resistance compared to the latter, and the volume resistance of the conveyance path on the fixing device side is high resistance compared to the former, and the conveyance paths are connected. By placing a metal member that does not have a caddy part so that it has a large conveyance path and surrounds the periphery, the recording paper becomes a static elimination needle compared to the case where a conventional static elimination needle with a sharp tip is used. Without disturbing the image due to the discharge that occurs when approaching, and covering the periphery of the conveyance path with a metal member without cadence, the entire recording paper is gradually discharged to prevent the image disturbance.
(2): In the image forming apparatus described in (1), the metal member is grounded. By grounding the metal member to the ground, there is a path for releasing the charge of the recording paper, and the charge is removed more strongly than (1).
(3): In the image forming apparatus described in (1), a current having a polarity opposite to that of the toner is applied to the metal member. By applying a bias having a polarity opposite to that of the toner to the metal member, it is possible to remove electricity more strongly than in (2).
(4): In the image forming apparatus described in any one of (1) to (3), the downstream end of the sheet passing downstream of the guide on the fixing device side is an intersection of the fixing roller and the pressure roller. The image carrier is located on the side of the image carrier with respect to the tangent line passing through. From the tangent line at the intersection of the fixing roller and pressure roller, the downstream end of the fixing device side of the guide is on the transfer belt side, so that the recording paper can always be pressed against the guide on the fixing device side. The image is prevented from being disturbed by the potential difference generated by floating from the surface (the potential of the floating portion is high, and the potential difference is generated because the portion in contact with the guide is low), and the actions (1) to (3) are prevented. Has an effect advantage.
(5): In the image forming apparatus described in any one of (1) to (3), the leading end of the sheet passing downstream side of the guide on the transfer device side is an intersection of the image carrier and the transfer roller. The image carrier is located on the side of the image carrier with respect to the tangent line passing through. From the tangent to the intersection of the intermediate transfer belt and the paper transfer roller, the downstream end of the guide on the transfer device side is on the transfer belt side so that the recording paper is always pressed against the guide on the transfer device side. Image disturbance due to a potential difference generated by floating from the guide is prevented in advance, and the effects of claims 1 to 3 are also provided.
(6): In the image forming apparatus described in any one of (1) to (3), the linear velocity of the fixing device is made slower than the linear velocity of the transfer device. Since the linear velocity of the fixing device is slower than the linear velocity of the transfer device, the recording paper can always be pressed against both the conveyance path on the transfer device side and the conveyance path on the fixing device side. Image disturbance due to a potential difference generated by floating from the road is prevented in advance, and the effects of claims 1 to 3 are also provided.
(7): In the image forming apparatus described in any one of (1) to (6), the volume resistance of the guide on the transfer device side is set to 4 × 10 ¹ Ω · cm or less. The recording paper charged by the transfer device can be slightly neutralized on the transfer device side, and has a powerful neutralizing effect in addition to the metal sheet.
(8): In the image forming apparatus described in any one of (1) to (6), the volume resistance of the guide on the fixing device side is set to 10 ¹⁴ to 10 ¹⁹ Ω · cm. The guide on the fixing device side is easily frictionally charged with the recording paper. After the charge removal, the recording paper is brought into close contact with the guide to prevent image disturbance due to the potential difference, and the conveyance state of the recording paper is stabilized and the recording at the fixing unit is performed. Paper wrinkles can also be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the image forming apparatus which prevented the image disorder resulting from a static elimination member beforehand can be provided.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus. It is the perspective view which showed the arrangement | positioning aspect of a guide and a metal member. FIG. 3 is a schematic configuration diagram illustrating an enlarged arrangement configuration of guides on the fixing device side. FIG. 4 is a schematic configuration diagram illustrating an enlarged arrangement configuration of guides on a transfer device side.

[Example of overall configuration of image forming apparatus]
An embodiment of an image forming apparatus to which the present invention is applied will be described with reference to FIG. In the following embodiments, an electrophotographic image forming apparatus capable of forming a full-color image is illustrated. The full-color image forming apparatus according to this example is an image forming station corresponding to image forming apparatuses 10Y (yellow), 10C (cyan), 10M (magenta), and 10K (black) for four colors which are image carrier units. And an optical unit 20, an intermediate transfer body unit 30, a paper feed unit 40, a fixing unit 50, and the like as exposure means capable of irradiating a laser beam.

  Each of the image forming apparatuses 10Y, 10C, 10M, and 10K has the same structure. Each of the image forming apparatuses 10Y, 10C, 10M, and 10K has a photosensitive drum 12 as an image carrier, and a charging device 13 that charges the photosensitive drum as a process unit that operates on the photosensitive drum. A cleaning device 14 for removing the developer remaining on the photosensitive drum 14 is integrally formed, and a developing device 15 for developing a latent image formed on the photosensitive drum is connected to the cleaning device 14. Each image forming device is configured to be detachable from the image forming apparatus main body in the opening / closing direction of the opening / closing face plate (to be described later) (rotational axis direction of the photoreceptor).

  The intermediate transfer body unit 30 includes a transfer belt 31 as a transfer medium (intermediate transfer body), primary transfer rollers 35 (four) for transferring the toner images formed on the respective photosensitive drums 12 to the transfer belt 31, and a transfer belt. A secondary transfer roller 36 that further transfers the toner image transferred onto the recording paper P to the recording paper P is provided.

  The paper feed unit 40 operates the arm 48 installed inside the paper feed cassette 41 by a lift motor (not shown) to raise the tray bottom plate 47, thereby bringing the bundle of recording paper P into contact with the calling roller 42. By rotating the calling roller 42, the bundle of recording papers P is shifted downstream, the uppermost sheet is separated by the paper feeding roller 43 and the reverse roller 44, and conveyed to the secondary transfer region by the conveying roller 45 and the registration roller 46. To do.

  The fixing unit 50 constituting the fixing device includes a fixing roller 51 and a pressure roller 52, and performs fixing by applying heat and pressure to the toner image on the recording paper P.

  In the above-described configuration, first, in the image forming device 10Y for the first color, yellow, the photosensitive drum 12 is uniformly charged by the charging device 13, and then a latent image is formed by the laser light emitted from the optical unit 20. The latent image is developed by the developing device 15 to form a toner image.

  The transfer belt 31 is supported by support rollers 31a, 31b, 31c and a tension roller 31d and is driven to rotate counterclockwise. A primary transfer roller 35 is disposed on the transfer belt 31 stretched substantially linearly between the support roller 31b and the tension roller 31d so as to face the respective photosensitive drums 12 from the inside. The yellow toner image carried on the photosensitive drum 12 is primarily transferred onto the transfer belt 31 by the bias applied by the primary transfer roller 35.

  A secondary transfer roller 36 is opposed to the support roller 31c with the transfer belt 31 therebetween, and the support roller 31c and the secondary transfer roller 36 constitute a transfer device 37 for secondary transfer.

  After completion of the primary transfer, the photosensitive drum 12 is cleaned by the cleaning device 14 to prepare for the next image formation. The residual toner collected by the cleaning device 14 is stored in a waste toner collection bottle (not shown) installed in the direction of taking out the image forming device (the direction of the rotation axis of the photosensitive drum). The waste toner collection bottle is detachable from the main body of the image forming apparatus so that it can be replaced when it is full.

  Following the yellow toner image carried on the transfer belt 31, a similar image forming process is performed in each of the image forming apparatuses 10C, 10M, and 10K for C, M, and K to form toner images of the respective colors. The yellow toner image formed earlier is transferred onto the transfer belt 31 in sequence.

  On the other hand, the recording paper P is conveyed from the paper feed cassette 41 to the secondary transfer region between the support roller 31c and the transfer belt 31, and is transferred onto the transfer belt 31 by the function of the secondary transfer roller 36 to which a transfer bias is applied. The toner image formed in an overlapping manner is transferred onto the recording paper P.

  In this manner, the transfer device 37 transfers the recording paper P between the secondary transfer roller 36 disposed opposite to the transfer belt (image carrier) 31 on which the toner image is carried. The toner image on the belt 31 is transferred to recording paper.

  The recording paper P to which the toner image has been transferred is conveyed to the fixing unit 50, where the toner image is fixed at the nip portion between the fixing roller 51 and the pressure roller 52 of the fixing unit 50, and the discharge tray 55 is discharged by the discharge roller 55. The paper is discharged.

  In order to supply new toner to the image forming apparatuses 10Y, 10C, 10M, and 10K, the toner bottles 57Y, 57C, 57M, and 57K are rotated, and the toner is conveyed through a pipe (not shown).

[Configuration example corresponding to claims]
In FIG. 1, conventionally, a series of guides for guiding the recording paper P is provided along the conveyance path of the recording paper P from the transfer device 37 to the fixing unit 50. On the other hand, in the present invention, the conventional continuous guide is divided into two guides, a guide 101 on the transfer device 37 side and a guide 102 on the fixing device 50 side. In this example, the guides 101 and 102 have a plate shape, but are not limited thereto.

  Furthermore, it has the structure which has the metal member 100 in the aspect which cross | intersects these guides at the joint part of these guides 101 and guides 102. FIG. In this example, the metal member 100 has a plate shape, but is not limited thereto.

Such division structure, the secondary transfer roller 36 is transferred the toner image electrostatically by, and charged recording sheet P is brought from the left side of the guide 101 in FIG. 1, 3 and 4, each of the left surface of the guide 102 The toner image is conveyed into the nip between the fixing roller 51 and the pressure roller 52 while being rubbed with the toner, and the toner image is fixed on the recording paper.

  The guide 101 and the guide 102 are electrically insulated from the metal member 100. Thereby, when the recording paper P comes into contact with the guide, the toner dust generated by the paper transfer current flowing through the recording paper P can be suppressed.

  As shown in FIG. 2, the metal member 100 has a plate shape having dimensions of width W and depth D, and the metal member 100 has an opening 100a having a width W1 that allows the recording paper P to pass therethrough. Has been. The guides 101 and 102 have substantially the same width dimension in phase with the width W1, and are supported by the main body of the fixing unit 50 or the main body of an image forming apparatus (not shown). The metal member 100 is similarly supported.

  The metal member 100 is arranged in such a manner as to intersect these guides at the joint portion between the guide 101 and the guide 102. The guide 101 has an arrangement size relationship that can be completely projected on the metal member 100, and the guide 101 cannot be seen from the guide 102 side by being hidden by the metal member 100. That is, the metal member 100 covers the guide 101. Similarly, the guide 102 has an arrangement size relationship that can be completely projected onto the metal member 100, and the guide 102 cannot be seen from the guide 101 side by being hidden by the metal member 100. That is, the metal member 100 covers the guide 102. Thus, since the metal member 100 has a larger outer size than the recording paper P and the guides 101 and 102 that pass through the opening 100a, the entire metal member 100 can be neutralized until reaching both sides and the width direction of the recording paper P.

  The metal member 100 does not have a corner. All the ridge lines and corners have R-shaped metal members. For example, the metal member has a plate shape and the opening 100a is formed so as not to block the conveyance path, but the flat portion has no protrusion so as not to induce discharge from the recording paper P, and The corner has a rounded R shape.

For example, by setting the volume resistance of the guide 101 on the transfer device side to 4 × 10 ¹ Ω · cm or less, the recording paper P charged by the transfer device 37 can be slightly discharged on the transfer device side, and the metal In addition to the plate 101, it is possible to provide an image forming apparatus having a strong charge eliminating effect.

Further, by setting the volume resistance of the guide 102 on the fixing device side to 10 ¹⁴ to 10 ¹⁹ Ω · cm, the guide 102 is easily charged by friction with the recording paper P. The recording paper P is brought into close contact to prevent image disturbance due to a potential difference, and the conveyance state of the recording paper P can be stabilized to prevent the recording paper from being wrinkled in the fixing unit.

  As a result, the volume resistance of the guide 101 on the transfer device side is lower than the volume resistance of the guide 102 on the fixing device side. Further, since the tip is not sharpened like the static elimination needle or is not extremely close to the recording paper, image disturbance due to discharge due to rapid static elimination can be prevented.

  By grounding the metal member 100 to the ground, the charge of the recording paper P is allowed to flow to the ground of the machine body, or by applying a bias of a reverse polarity to the toner (for example, a positive polarity if the toner is negatively charged). Can be adjusted.

  As shown in FIG. 3, the downstream end 102a of the sheet passing through the guide 102 on the fixing device side is a dimension value Δ1, for example, from the tangent line 60 passing through the intersection point Q1 of the fixing roller 51 and the pressure roller 52. By being on the 31st side, the recording paper P is always pressed against the guide 102 on the fixing device side, and the potential difference generated when the recording paper P floats from the guide 102 (the potential of the floating portion increases, and the guide 102 Image disturbance due to the potential difference occurring because the portion in contact with is low. The tendency of the recording paper P to press against the guide 102 on the fixing device side is reinforced when the opening 100a is on the opposite side of the transfer belt 31 from the tangent line 60 as in this example.

  As shown in FIG. 4, the paper passing downstream tip 101a of the guide 101 is closer to the transfer belt side than the tangent 61 of the intersection Q2 between the transfer belt 31 and the secondary transfer roller 36. Thus, the recording paper P is always pressed against the guide 101, and image disturbance due to a potential difference generated by floating from the guide 101 can be prevented in advance.

  By making the linear velocity of the fixing device 50 slower than the linear velocity of the transfer device 37, the recording paper P is pressed against the guide 101 and the guide 102, and the potential difference generated by floating from the guides 101 and 102 (the floating portion of the floating portion). Image disturbance due to a high potential and a potential difference due to a low portion in contact with the guide can be prevented in advance.

10Y, 10C, 10M, 10K Image forming device 12 Photosensitive drum 13 Charging device 14 Cleaning device 15 Developing device 20 Optical unit 30 Intermediate transfer member unit 31 Transfer belt 31a, 31b, 31c Support roller 31d Tension roller 35 Primary transfer roller 36 Second Next transfer roller 37 Transfer device 40 Paper feed unit 42 Calling roller 43 Paper feed roller 44 Reverse roller 45 Transport roller 46 Registration roller 47 Tray bottom plate 48 Arm 50 Fixing unit 51 Fixing roller 52 Pressure roller 55 Paper discharge roller 56 Paper discharge tray 57Y , 57C, 57M, 57K Toner bottle 60 Tangent 100 Metal member 100a Opening 101 Transfer device side guide 102 Fixing device side guide P Recording paper Q1, Q2 Intersection point W, W1 Width Δ1, Δ2 Dimension value

JP 2002-268301 A Japanese Patent Laid-Open No. 2002-156834

Claims (8)

The recording paper is passed between a transfer roller disposed opposite to the image carrier on which the toner image is carried, and a transfer device for transferring the toner image on the image carrier to the recording paper, a fixing roller, in the image type forming apparatus having a guide along the conveying path for conveying a fixing device for fixing, the recording paper fixing device from said transfer device said toner image through the recording sheet between the pressure roller,
The guide is divided into a guide on the transfer device side and a guide on the fixing device side, and both guides are covered at a joint portion of the guides so as to intersect the guides, and the recording paper is conveyed to the intersecting portion. Provide a metal member with an opening to be a path,
The metal member is all of the ridge portion and the corner portion R shape,
An image forming apparatus , wherein the volume resistance of the guide on the transfer device side is lower than the volume resistance of the guide on the fixing device side .   2. The image forming apparatus according to claim 1, wherein the metal member is grounded. 2. The image forming apparatus according to claim 1, wherein a bias having a polarity opposite to that of toner is applied to the metal member. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein a downstream end portion of the guide on the fixing device side is closer to the image carrier than a tangent line passing through an intersection of the fixing roller and the pressure roller. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein a leading end portion of the guide on the transfer device side on the downstream side is closer to the image carrier than a tangent line passing through an intersection of the image carrier and the transfer roller. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein a linear velocity of the fixing device is made slower than a linear velocity of the transfer device. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus, wherein the volume resistance of the guide on the transfer device side is 4 × 10 ¹ Ω · cm or less. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus, wherein a volume resistance of a guide on the fixing device side is set to 10 ¹⁴ to 10 ¹⁹ Ω · cm.

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