JP2012185332A - Transfer device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device that can efficiently eliminate static electricity from a transfer paper and obtain stable image quality with a small amount of transfer dust.SOLUTION: A transfer exit guide member 31 of a transfer exit guide plate 30 is provided with a destaticizing needle 32. When a transfer paper is transported on the transfer exit guide plate 30, an electric current flowing through the destaticizing needle 32 is measured by an ammeter 41, and an electric current value thereof is detected by a current detection circuit provided in a control circuit 40. A downstream side rotary member 33 having a plurality of downstream side eccentric cams 33b and an upstream side rotary member 34 having a plurality of upstream side eccentric cams 34b are provided under the transfer exit guide member 31 of the transfer exit guide plate 30. The downstream side rotary member 33 and the upstream side rotary member 34 are rotated by independently controlling the rotation of stepping motors connected to the respective rotary members by the control circuit 40 according to the detected electric current value, thereby changing the angle and height of the transfer exit guide member 31.

Description

  The present invention relates to a transfer device having a transfer outlet guide mechanism that is used in an image forming apparatus such as an electrophotographic printer, a facsimile machine, and a copier, and that transfers a transfer material after a toner image is transferred to a subsequent apparatus, And an image forming apparatus including the transfer device.

  Conventionally, an unstable toner image before being fixed by a fixing device on a transfer material (hereinafter referred to as transfer paper) after the electrostatic transfer of the toner image has been distorted by deformation or damage. Various transfer outlet guide mechanisms have been proposed to suppress this.

  For example, a configuration of a transfer outlet guide plate 30 which is a transfer outlet guide mechanism in a transfer belt type transfer device 20 as shown in FIG. The transfer device 20 electrostatically attracts the toner image formed on the photosensitive drum 1, which is a latent image carrier, onto the transfer belt 22 by electrostatic transfer onto the transfer paper at the transfer nip portion. It has a transport process for sending the transfer paper to the next process. A neutralization process is also provided for the purpose of positively neutralizing the charge on the transfer paper with the neutralization needle 32 which is a neutralization means provided on the transfer outlet guide plate 30 to prevent transfer dust.

  In the transfer process, a transfer bias is applied to the bias roller 26 by a high-voltage power source 27 to transfer the toner image onto the transfer paper. The transfer paper is conveyed by rotational driving of an endless transfer belt 22 that is hung between the driving roller 25 and the driven roller 24. The driving roller 25 and the driven roller 24 are used while being grounded. The transfer device 20 is covered from below by a casing 23 that is a cover.

  The transfer outlet guide plate 30 includes a grounded static elimination needle 32, a transfer outlet guide member 31, and a guide plate holder 37, and is fixed to the rear end portion of the casing 23. The transfer paper conveyed by the transfer belt 22 from the transfer nip portion toward the transfer outlet guide plate 30 is removed of static electricity on the transfer paper by the static elimination needle 32 on the transfer outlet guide member 31 and conveyed to the fixing inlet guide plate 53. Further, it is conveyed to a fixing nip portion of a fixing device (not shown). As described above, the charge transfer paper is discharged by the charge removal needle 32 provided on the transfer outlet guide plate 30, so that the unfixed transfer paper on which the toner image is transferred is conveyed in a charged state. Suppresses image distortion (hereinafter referred to as transfer dust).

  Patent Document 1 describes the configuration of a transfer outlet guide plate having the following configuration. A mechanism that allows the angle and height of the transfer exit guide plate provided with the static elimination member to be variable. The distance sensor provided on the transfer exit guide plate detects the paper lift and follows the paper. Change the angle and height of the plate to positively convey the transfer paper. By positively conveying the transfer paper in close contact, it is possible to keep the distance between the static elimination member and the transfer paper constant and suppress static elimination defects. In this way, by suppressing the discharge failure of the transfer paper, the transfer dust caused by the unfixed transfer paper on which the toner image has been transferred being conveyed in a charged state is prevented.

  However, when the transfer paper is conveyed to the subsequent fixing inlet guide plate 53 or the nip portion of the fixing device, the transfer paper is bent. In the configuration of the transfer device 20 as shown in FIG. 9, the transfer outlet guide plate 30 is fixed to the rear end portion of the casing 23, and the transfer outlet guide plate 30 cannot follow the above-described deflection. And the transfer paper cannot be kept at an appropriate distance. If the distance is not appropriate as described above, a portion that cannot be neutralized remains on the transfer paper, and a neutralization failure may occur. When the transfer paper in a state where the charge removal failure of the transfer paper has occurred is conveyed to the subsequent fixing inlet guide plate 53 or the nip portion of the fixing device, an image defect that transfer dust occurs occurs.

  Further, the toner image formed on the transfer paper is applied with a bias having a polarity opposite to that of the toner when the transfer paper is conveyed through the transfer nip portion, and the toner is electrostatically adsorbed on the transfer paper. For this reason, it is not transported to the position of the static elimination needle 32 provided on the transfer outlet guide plate 30, and the residual charge remains on the portion of the transfer paper that has not been neutralized. The portion of the transfer paper in which the residual charge remains in this manner easily sticks to the transfer outlet guide plate 30, and the transfer paper and the transfer outlet guide member 31 of the transfer outlet guide plate 30 are in close contact as shown in FIG. The contact area may increase. When the contact area increases, the surface potential of the transfer outlet guide member 31 increases due to frictional charging between the transfer outlet guide member 31 and the transfer paper, and is electrostatically attracted by abnormal discharge when the subsequent paper passes. The toner may move and transfer dust may occur.

  In addition, the configuration described in Patent Document 1 is a configuration in which the transfer outlet guide plate conveyance surface and the transfer paper are always positively and closely conveyed in order to suppress static elimination defects. For this reason, as in the configuration shown in FIG. 9, the surface potential of the transfer outlet guide plate rises due to frictional charging, and the toner electrostatically adsorbed due to abnormal discharge moves when the subsequent paper passes. There is a possibility that an image defect occurs.

  As described above, in the conventional configuration, a study on an increase in the surface potential of the transfer outlet guide plate due to frictional charging between the transfer outlet guide plate and the transfer paper has not been performed. For this reason, for example, when a high-resistance paper type is passed or in a low-temperature and low-humidity environment, the transfer paper is likely to stick to the transfer outlet guide member, resulting in transfer dust caused by an increase in the surface potential of the transfer outlet guide plate. There was a case where an image defect occurred.

  The present invention has been made in view of the above problems, and its object is to suppress an increase in the surface potential of the transfer outlet guide mechanism without causing a failure in static elimination of the transfer material, and a stable image with less transfer dust. It is to provide a transfer device capable of obtaining quality.

In order to achieve the above-mentioned target, the transfer apparatus according to claim 1, wherein the transfer outlet has a charge eliminating means for removing the charge of the transfer material after electrostatically transferring the toner image on the image carrier to the transfer material. The transfer apparatus having a guide mechanism includes means for detecting the value of the current discharged by the charge removing unit and changing the angle and height of the transfer outlet guide mechanism in accordance with the detected value. Is.
Further, the transfer device according to claim 2 is the transfer device according to claim 1, wherein the type, size, basis weight, or combination of two or more of the types of paper selected before passing the paper is used. Accordingly, the amount of change in the angle and height of the transfer outlet guide mechanism is different.
Further, the transfer device according to claim 3 is the transfer device according to claim 1 or 2, wherein one of the type, size, and basis weight of the paper selected before passing the paper, or any two or more of them. Depending on the combination, the operation start timing for changing the angle and height of the transfer outlet guide mechanism is different.
According to a fourth aspect of the present invention, in the transfer device according to any one of the first to third aspects, the change of the angle and height of the transfer outlet guide mechanism can be controlled at an arbitrary timing during paper feeding. It is characterized by this.
An image forming apparatus according to a fifth aspect includes the transfer apparatus according to any one of the first to fourth aspects as a transfer apparatus.
The present invention changes the angle and height of the transfer outlet guide mechanism in accordance with the value of the current neutralized by the static eliminating means. Since the angle and height can be changed in this way, for example, the contact area between the transfer outlet guide mechanism and the transfer material can be adjusted as follows.
Here, if the contact area of the transfer material to the transfer outlet guide mechanism is appropriate, the transfer outlet guide mechanism in the initial state is horizontal, and the height of the upper surface is arranged upstream in the transfer material conveyance direction. It is assumed that they are arranged at the same height as the upper surface of the transfer conveying means. Further, the fixing inlet guide mechanism of the fixing device arranged on the downstream side in the transfer material conveyance direction is inclined so that the upstream side is the same height as the downstream end of the transfer outlet guide mechanism and the downstream side toward the fixing nip portion is higher. Are arranged. In addition, it is assumed that the charge removal means of the transfer outlet guide mechanism is provided near the downstream of the transfer outlet guide mechanism. When the transfer material transported on the transfer outlet guide mechanism arranged in this way is supported from below by the transfer outlet guide mechanism and the fixing inlet guide mechanism, the transfer outlet guide is located near the downstream end of the transfer outlet guide mechanism. It will be in a state somewhat separated from the mechanism. In this state, it is assumed that the distance between the charge eliminating unit and the transfer material is an appropriate distance.
When the transfer material transported on the transfer outlet guide mechanism configured in this way has an extremely low moisture content of the transfer material due to environmental changes, the transfer material is likely to stick to the transfer outlet guide mechanism, and the transfer material and the transfer material are transferred. The contact area with the outlet guide mechanism increases. When the contact area is increased in this manner, transfer dust due to frictional charging is likely to occur, and the transfer material is charged by frictional charging, and the current value that is neutralized by the neutralizing means increases.
Therefore, when the value of the current neutralized by the static elimination means becomes high, the height in the vicinity of the downstream side of the transfer outlet guide mechanism does not vary greatly, and the upstream side of the transfer outlet guide mechanism is lowered to provide an angle. The contact area can be reduced by separating the vicinity of the upstream side of the transfer outlet guide mechanism from the transfer material. By changing the angle and height in this way, the contact area between the transfer outlet guide mechanism and the transfer material is reduced while keeping the separation distance between the charge eliminating means and the transfer material at an appropriate distance.
Accordingly, the contact area between the transfer outlet guide mechanism and the transfer paper is reduced without causing the charge removal failure of the transfer material, and the frictional charge amount between the surface of the transfer outlet guide mechanism and the transfer paper is reduced. An increase in the surface potential of can be suppressed.

  The present invention can suppress an increase in the surface potential of the transfer outlet guide mechanism without causing a discharge failure of the transfer material, and therefore provides a transfer device that can obtain stable image quality with less transfer dust. it can.

1 is an overall schematic diagram of a copier according to an embodiment. 1 is a schematic explanatory diagram of a transfer device according to Embodiment 1. FIG. Explanatory drawing of a transfer exit guide plate. Explanatory drawing of the structure which changes an angle and height. Explanatory drawing of the transfer exit guide member (a) which provided the static elimination means, and an angle and height change means (b). Explanatory drawing of the relationship between the detected electric current value and the step angle of a stepping motor. Explanatory drawing of the example of an initial state of a transfer exit guide plate. Explanatory drawing of the transfer exit guide plate at the time of controlling to reduce the contact area of a transfer exit guide plate and transfer paper. Explanatory drawing of the structure which provided the conventional transfer exit guide plate fixedly. Explanatory drawing of the contact state of the conventional transfer exit guide plate and transfer paper.

  Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter simply referred to as a copying machine) as an image forming apparatus will be described with reference to examples. First, an outline of the copying machine of this embodiment will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of a copying machine according to the present embodiment.

  As shown in FIG. 1, the copying machine includes a photosensitive drum 1 as a latent image carrier in an apparatus main body 100. Around the photosensitive drum 1, image forming devices such as a charging device 2, a developing device 3, a transfer device 20, a cleaning device 4, and a charge eliminating device 5 are disposed. A fixing device 50 is disposed on the left side of the cleaning device 4 in the drawing. A document reading device 300 is provided on the upper portion of the apparatus main body 100. Further, an automatic document feeder 8 is attached to the document reader 300 so as to be openable and closable so as to cover the contact glass 7 installed on the upper surface thereof. On the other hand, a double-sided unit 67 is disposed below the apparatus main body 100. The apparatus main body 100 is placed on a paper feed table 200. In the paper feed table 200, a plurality of paper feed cassettes 60 are provided in multiple stages. Each paper feed cassette 60 is provided with a paper feed roller 61 corresponding thereto. Each paper feed roller 61 conveys transfer paper or the like, which is a transfer medium fed out from the corresponding paper feed cassette 60, to the conveyance path 62.

  Next, the copying operation of this copying machine will be described. First, the copy document is set on the automatic document feeder 8 or on the contact glass 7. After the setting, when a start switch (not shown) on the operation screen is pressed, the image information of the set original is read by the original reading device 300 in units of pixels. In response to this document reading operation, the transfer paper in the paper feed cassette 60 selected in advance is transported to the transport path 62 by the rotation of the corresponding paper feed roller 61. The transfer paper transported to the transport path 62 is abutted against the registration roller 64 via the paper feed path 63 and is temporarily stopped. The temporarily stopped transfer paper is fed below the photosensitive drum 1 as the registration roller 64 rotates at a predetermined timing in accordance with the rotation of the photosensitive drum 1.

  In response to the document reading operation, the photosensitive drum 1 rotates in a predetermined direction. As the photosensitive drum 1 rotates, the surface of the photosensitive drum 1 is first uniformly charged by the charging device 2. Next, a laser beam L corresponding to the image information of the document read by the document reading device 300 is irradiated to the surface of the photosensitive drum 1 by the laser writing device 6. As a result, an electrostatic latent image corresponding to the original image is formed on the surface of the photosensitive drum 1. This electrostatic latent image is converted into a visible image (toner image) by toner in the developer supplied from the developing device 3. The toner image formed on the photosensitive drum 1 is transferred by the transfer device 20 onto the transfer paper fed below the photosensitive drum 1 by the rotation of the registration roller 64. In this toner image transfer process, toner remaining on the surface of the photosensitive drum 1 without being transferred onto the transfer paper is removed from the surface of the photosensitive drum 1 by the cleaning device 4. Further, the charge remaining on the surface of the photosensitive drum 1 after the transfer process is neutralized by the neutralization device 5.

  The transfer paper on which the toner image has been transferred in the transfer process is conveyed to the fixing device 50 by the transfer device 20. The fixing device 50 fixes the toner image transferred in the transfer process onto the transfer paper. The transfer paper on which the toner image has been fixed passes through a paper discharge path 65 and is discharged onto a paper discharge tray (not shown) outside the apparatus. Here, when the toner image is also formed on the back surface of the sheet on which the toner image is fixed, the transfer paper after the toner image is formed on one side passes through the reverse path 66 and is sent to the duplex unit 67. It is. The transfer sheet sent to the duplex unit 67 is turned upside down and sent to the registration roller 64 and temporarily stopped. The transfer paper with the front and back sides reversed is transferred to and fixed on the back side of the toner image, as in the case of copying on one side, and then discharged onto a discharge tray outside the apparatus through a discharge path 65. .

  Next, the transfer device 20 which is a characteristic part of the present embodiment will be described with reference to examples.

Example 1
First, Example 1 which is a first example of the present embodiment will be described with reference to the drawings. 2 is a schematic explanatory view of the transfer device 20 according to the present embodiment, FIG. 3 is an explanatory view of a transfer outlet guide plate, and FIG. FIG. 5 is an explanatory diagram of the transfer outlet guide member (a) provided with the charge eliminating means and the angle and height changing means (b). FIG. 6 is a graph showing the relationship between the detected current value and the step angle of the stepping motor. It is explanatory drawing. 7 is an explanatory diagram of an example of an initial state of the transfer outlet guide plate, and FIG. 8 is an explanatory diagram of the transfer outlet guide plate when control is performed so as to reduce the contact area between the transfer outlet guide plate and the transfer paper. is there.

  As shown in FIG. 2, the transfer device 20 of this embodiment includes a photosensitive drum 1 as a latent image carrier, a transfer belt 22 as transfer / conveying means stretched around a driving roller 25 and a driven roller 24, and the like. Thus, a transfer nip portion is formed. Further, on the downstream side of the transfer belt 22 in the transfer paper conveyance direction, a transfer outlet guide mechanism that neutralizes the transfer sheet electrostatically attracted to the transfer belt 22 and guides it to the fixing inlet guide plate 53 of the fixing device 50 on the downstream side. The transfer exit guide plate 30 is provided. The transfer device 20 is covered from below by a casing 23 that is a cover.

  The process of the transfer device 20 includes a transfer process, a transport process, and a static elimination process. In the transfer process, a bias image having a polarity opposite to that of the toner is applied to the back surface of the transfer belt 22 in the transfer nip portion from the high voltage power source 27 via the bias roller 26, and the toner image adsorbed to the latent image on the photosensitive drum 1. Is transferred onto the transfer paper. In the transporting process, the transfer sheet electrostatically attracted to the transfer belt 22 is sent to the fixing device 50 (not shown in FIG. 2) via the transfer outlet guide plate 30 and the fixing inlet guide plate 53. In the static elimination step, the static elimination needle 32 which is a static elimination means provided on the transfer outlet guide plate 30 neutralizes the transfer sheet electrostatically attracted to the transfer belt 22 and charged.

The transfer outlet guide plate 30 relating to the transport process and the charge eliminating process is mainly composed of the following. They are a static elimination needle 32, a transfer outlet guide member 31, a means for changing the angle and height of the transfer outlet guide member 31 (hereinafter referred to as angle / height changing means), and a guide plate holder 37 for supporting them.
The static elimination needle 32 is grounded via an ammeter 41 that is a means for detecting a current value flowing through the static elimination needle 32. Then, residual charge is removed from the transfer paper conveyed by the transfer belt 22 from the transfer nip portion toward the transfer outlet guide plate 30 by the static elimination needle 32 held by the transfer outlet guide member 31. The static elimination needle 32 removes the residual charge on the transfer paper, so that the toner is scattered due to the movement of the charge when entering the fixing inlet guide plate 53 and the fixing nip (not shown), and the scattered toner is transferred to the transfer paper. It plays a role in preventing the occurrence of abnormal images such as dirt on the transfer paper that adheres. Further, the angle / height changing means of the transfer outlet guide member 31 controls the contact area between the surface of the transfer outlet guide member 31 and the transfer paper in accordance with the value obtained by detecting the current discharged by the charge removal needle 32. .

  The control according to the value detected by the static elimination needle 32 detects the value of the current flowing through the static elimination needle 32, and from the control circuit 40 according to the detected current value, the drive source of the angle / height changing means This is done by issuing an operation command. The current value is detected by measuring the current flowing through the static elimination needle 32 with an ammeter 41 and detecting it with a current detection circuit (detailed explanation is omitted) provided in the control circuit 40. The control circuit 40 includes the current detection circuit, a controller (CTL) that sends a pulse signal, and a driver that supplies power.

  The control circuit 40 controls the angle / height changing means of the transfer outlet guide plate 30 in accordance with the detected current value, so that the contact area between the transfer paper and the transfer outlet guide member 31 can be reduced without causing a discharge failure. Can be reduced. By reducing the contact area between the transfer paper and the transfer outlet guide member 31, the influence of frictional charging between the surface of the transfer outlet guide member 31 and the transfer paper is reduced, and transfer dust caused by this frictional charging is suppressed. Is possible.

  As shown in FIG. 3, the change in the angle and height of the transfer outlet guide member 31 by the angle / height changing means of the transfer outlet guide plate 30 is performed on the back side (lower side in FIG. 3) of the transfer outlet guide member 31. This is done by providing these rotating members and rotating them. Specifically, as shown in FIG. 4, guides provided on the vertical side plates of the guide plate holder 37, respectively, at substantially the center of both vertical end surfaces parallel to the transfer paper conveyance direction of the transfer outlet guide member 31. A protrusion 38 that slides on the inner peripheral surface of the elongated hole is provided. The transfer outlet guide member 31 has a rotation center that is perpendicular to the transfer sheet conveyance direction and has a horizontal rotation center, and has a downstream rotation member 33 on the downstream side in the transfer sheet conveyance direction and an upstream rotation member 34 on the upstream side. It is provided at an appropriate position on the back side of the guide member 31. Then, by rotating each rotation member perpendicular to the transfer paper conveyance direction on the back side of the transfer outlet guide member 31 and pressing the surface on the back side of the transfer outlet guide member 31 from below, the angle and height of the transfer outlet guide member 31 are increased. Has changed.

A downstream rotary member 33 and an upstream rotary member 34 as shown in FIG. 5B are provided in parallel below the transfer outlet guide member 31 shown in FIG.
The downstream rotation member 33 includes a downstream shaft 33a and a plurality of downstream eccentric cams 33b attached to the downstream shaft 33a. The plurality of downstream eccentric cams 33b press the transfer outlet guide member 31 from the back side as the downstream shaft 33a rotates. Similarly, the upstream rotation member 34 includes an upstream shaft 34a and a plurality of upstream eccentric cams 34b attached to the upstream shaft 34a. The plurality of upstream eccentric cams 34b press the transfer outlet guide member 31 from the back side as the downstream shaft 33a rotates. Here, each rotating member is rotationally driven by a steering motor (STM) whose rotation is controlled by the control circuit 40 in accordance with the detected current value. Specifically, the downstream rotating member 33 is rotationally driven by the rotation control of the downstream stepping motor 35 connected to one end of the downstream shaft 33a by the control circuit 40. Similarly, the upstream rotating member 34 is also rotationally driven by the rotation control of the upstream stepping motor 36 connected to one end of the upstream shaft 34 a by the control circuit 40. In this way, by controlling the rotation of the stepping motors connected to each rotating member independently by the control circuit 40, it is possible to finely control the change in the angle and height of the transfer outlet guide member 31. Become.

  Although the number of eccentric cams attached to each shaft is not determined, in order to incline the angle of the transfer outlet guide plate 30 in the main scanning direction without deviation, the eccentric cam having a width of about 10 mm. It is desirable to arrange 6 to 10 at regular intervals. Moreover, it is desirable to use polyacetal (POM) that is highly durable and excellent in insulation as the material of each eccentric cam.

  Further, as shown in FIGS. 3 and 5A, the static elimination needle 32 is placed in the static elimination opening provided in the transfer outlet guide member 31, and the top end thereof from the surface of the transfer outlet guide member 31 facing the transfer paper. A plurality are provided at the same interval so as to be slightly lower. In the configuration of this embodiment, the static elimination needle 32 has a tip that is approximately 2 mm below the surface of the transfer outlet guide member 31, a diameter of φ = 0.5 to 1.0 mm, a spacing of approximately 2 mm, and a material of stainless steel. Met. The neutralizing needle 32 grounds the current of the neutralized transfer paper, which is attached between the center of the transfer paper conveyance direction on the back surface of the transfer outlet guide member 31 and the horizontal surface of the guide plate holder 37, to the housing and releases it. A tension spring 39 also serving as a ground wire is connected. By providing the tension spring 39, the transfer outlet guide member 31 can flexibly follow the movement of the downstream eccentric cam 33b and the upstream eccentric cam 34b.

  The control circuit 40 controls the rotation according to the current value detected by the downstream stepping motor 35 and the upstream stepping motor 36 of the angle / height changing means configured as described above, so that the transfer outlet guide member 31 The angle and height can be changed.

  Each stepping motor can be rotationally controlled with high accuracy by pulse input. Taking advantage of this characteristic, the angle / height changing means of this embodiment can be adjusted in multiple stages. As a result, the angle and height of the transfer outlet guide member 31 can be freely changed, and it is possible to cope with various paper types, sizes, and paper passing environments. As the type of stepping motor, it is desirable to use a five-phase stepping motor capable of positioning with a high accuracy with a basic step angle of 0.72 deg.

  Here, the relationship between the detected current value and the step angle of the stepping motor will be described using the downstream stepping motor 35 as an example with reference to FIG. In the current detection circuit provided in the control circuit 40, the static elimination current value per transfer sheet measured by the ammeter 41 is constantly detected. As shown in FIG. 6, when the detected current value reaches the operation start level, a pulse signal is output from the controller in the control circuit 40, and the downstream stepping motor 35 rotates. The rotation of the downstream stepping motor 35 increases the height of the contact position of the downstream eccentric cam 33b that contacts the back side of the transfer outlet guide member 31, and increases the angle of the transfer outlet guide member 31. Control is possible. In addition, since the rotation control of the upstream stepping motor 36 is also performed in conjunction with the rotation control of the downstream stepping motor 35, the angle of the transfer outlet guide member 31 and the height thereof can be finely changed.

  For example, when the transfer paper sticks to the transfer outlet guide member 31 and the detected current value reaches the operation start level, the initial state angle and height shown in FIG. The angle and height of the transfer outlet guide member 31 are changed to the state. Here, in the example of the initial state shown in FIG. 7, the downstream eccentric cam 33 b and the upstream eccentric cam 34 b have two line segments that connect the rotation axes in a cross section perpendicular to the rotation axis of each shaft. Each eccentric cam is rotated in the shape of a letter C symmetrical to the bisector. Since each eccentric cam rotates in a C-shape symmetrical with respect to the bisector connecting the rotation axes, the transfer outlet guide member 31 is in a horizontal state. Further, the state shown in FIG. 8 is the transfer paper conveyance direction of the transfer outlet guide member 31 in which the downstream eccentric cam 33b and the upstream eccentric cam 34b are rotated counterclockwise by a predetermined angle from the initial state. The downstream side is high and the upstream side is low.

  By changing the angle and height of the transfer outlet guide member 31 in this way, the transfer outlet guide is maintained while keeping the distance between the tip of the static elimination needle 32 and the transferred transfer paper within a suitable range of charge removal. The contact area between the member 31 and the transfer paper can be reduced. Therefore, it is possible to reduce the contact area between the surface of the transfer outlet guide member 31 of the transfer outlet guide plate 30 serving as the transfer outlet guide mechanism and the transfer paper, without causing a charge removal failure of the transfer paper. Since the contact area can be reduced, the triboelectric charge amount between the transfer outlet guide member 31 and the transfer paper can be reduced, and an increase in the surface potential of the transfer outlet guide member 31 can be suppressed. Therefore, in the transfer apparatus 20 of the present embodiment, it is possible to suppress an increase in the surface potential of the transfer outlet guide member 31 without causing a discharge failure of the transfer paper, so that the transfer paper can be discharged efficiently. Stable image quality with little transfer dust is obtained.

  Further, in this embodiment, the angle and height of the transfer outlet guide member 31 are changed according to the current value to be neutralized, and each stepping motor is turned on when the current flowing through the static elimination needle 32 does not reach the operation start level. Control without rotation is possible. That is, when the current flowing through the static elimination needle 32 does not reach the operation start level and there is a low possibility of occurrence of transfer dust, control without changing the angle and height of the transfer outlet guide member 31 can be performed. Therefore, in the transfer device 20 of the present embodiment, it is possible to suppress the risk of occurrence of a conveyance failure such as a paper jam due to a change in the transfer path (conveyance path) of the transfer paper due to the movement of the transfer outlet guide member 31.

(Example 2)
Next, Example 2 which is a second example of the present embodiment will be described. The transfer device 20 of this embodiment is different from the transfer device 20 of Embodiment 1 only in the following points. In the transfer outlet guide plate 30 of the transfer device 20 of the present embodiment, the transfer outlet guide member is selected according to any one of the type, size, basis weight, or combination of two or more of the sheets selected before passing the paper. The difference is that the angle 31 and the amount of change in height are made different. Since other points relating to the configuration and operation are the same as those of the transfer device 20 of the first embodiment described above, the same points will be omitted as appropriate.

  In the transfer device 20 of the present embodiment, the angle and height of the transfer outlet guide member 31 are independent of each other by the control circuit 40 of the downstream stepping motor 35 and the upstream stepping motor 36 as in the transfer device 20 of the first embodiment. The rotation control is performed. In the present embodiment, the advantages of the independent rotation control by the control circuit 40 are utilized more than in the first embodiment. Specifically, the angle and height of the transfer outlet guide member 31 are arbitrarily changed according to the type, size, basis weight, or combination of any two or more of the sheets selected before passing. The amount of change to be made was changed.

  For example, in general, a thick paper having a high basis weight or a transfer paper having a paper type of OHP or the like has a high specific resistance, so that the value of the current flowing through the static elimination needle 32 is relatively higher than that of plain paper. Become. However, since the rigidity is high (the stiffness is strong), in the configuration in which the angle and height of the transfer outlet guide member 31 are changed based only on the detected current value, the distance between the charge removal needle 32 and the transfer paper tends to increase. . Further, when the angle of the transfer outlet guide member 31 is increased, the transfer paper conveyance angle is increased, and the risk of occurrence of a conveyance failure such as a jam or a wrinkle due to a collision when the fixing roller enters is increased. For this reason, it is desirable to set the angle change amount lower than that of plain paper for thick paper or transfer paper whose paper type is OHP or the like.

  In addition, in the case of transfer paper such as OHP, the specific resistance is high and the charge amount of the transfer paper increases, so that the force of sticking to the transfer outlet guide member 31 is stronger than that of plain paper. Moreover, since the rigidity is high, the contact force when contacting the transfer outlet guide member 31 is also increased, and the risk of transfer dust due to frictional charging between the transfer outlet guide member 31 and the transfer paper is further increased.

  For these reasons, in the configuration in which the angle and height of the transfer outlet guide member 31 are changed based only on the detected current value, it is necessary to perform control more suitable for plain paper that is used more frequently than thick paper or OHP. Absent. For this reason, when a paper type having a high specific resistance such as thick paper or OHP and having a high rigidity is passed, the margin for suppressing generation of transfer dust is lower than when passing a plain paper or the like. End up. Conventionally, there has been no transfer exit guide mechanism that achieves both image quality and transportability at the same level between plain paper and paper types with high specific resistance such as thick paper and OHP and high rigidity.

  Even if the types of paper are the same, the amount of deflection when being conveyed on the transfer outlet guide plate 30 may differ depending on the paper size, and the distance between the static elimination needle 32 and the transfer paper will also differ. For this reason, in the configuration in which the angle and height of the transfer outlet guide member 31 are changed based only on the detected current value, it is necessary to perform control that is more suitable for the frequently used paper size than for the less frequently used paper size. I don't get it. For this reason, for example, a transfer sheet having a low use frequency, such as a long size paper, has a lower margin for suppressing generation of transfer dust than when a transfer sheet having a high use frequency is passed. End up.

  Therefore, in the transfer device 20 of the present embodiment, the transfer outlet guide member 31 is arbitrarily selected according to any one of the type, size, basis weight, or combination of two or more of the sheets selected before passing. The amount of change for changing the angle and height is varied. By configuring in this way, the amount of change in the angle and height of the transfer outlet guide member 31 can be optimized for the transfer paper to be passed, and the margin of transfer dust is improved without deteriorating the transport quality. Can be made. For example, even when a transfer sheet having a higher specific resistance and higher rigidity than that of plain paper and a thick transfer sheet is passed, the angle and height of the transfer outlet guide member 31 according to the transfer sheet to be passed. Can be changed. Therefore, even when a transfer sheet having high specific resistance and high rigidity is passed, the margin of transfer dust can be improved without deteriorating the transport quality.

  Further, the amount of change in the angle and height of the transfer outlet guide member 31 can be optimized for the transfer paper to be passed, and friction between the bent transfer paper and the transfer outlet guide member 31 can be reduced. . And then. By reducing rubbing between the bent transfer paper and the transfer outlet guide member 31, an increase in the surface potential of the transfer outlet guide member 31 can be suppressed, and the risk of occurrence of transfer dust can be further reduced. For example, even for the same type of paper, a long size paper increases the conveyance angle, reduces the friction between the transfer paper due to paper deflection and the transfer outlet guide member 31, and increases the surface potential of the transfer outlet guide member 31. And the risk of occurrence of transfer dust can be reduced.

  Here, the amount of change in the rotation angle of each stepping motor corresponding to any one of the type, size, and basis weight of the paper, or a combination of two or more of them is obtained in advance by an experiment or the like, and the control circuit 40 Is stored in a storage unit (not shown).

(Example 3)
Next, Example 3 which is a third example of the present embodiment will be described. The transfer device 20 of the present embodiment is different from the transfer device 20 of Embodiments 1 and 2 only in the following points. In the transfer outlet guide plate 30 of the transfer device 20 of the present embodiment, the transfer outlet guide member is selected according to any one of the type, size, basis weight, or combination of two or more of the sheets selected before passing the paper. The operation start timing for changing the angle and height of 31 is different. Since other points relating to the configuration and operation are the same as those of the transfer device 20 of the first and second embodiments, the same points will be omitted as appropriate.

  The transfer paper conveyed on the transfer outlet guide plate 30 differs in the total amount of current flowing through the static elimination needle 32 depending on the type, size, and basis weight of the paper to be passed. For this reason, the configuration in which the angle and height of the transfer outlet guide member 31 are changed based only on the detected current value is more suitable for the type, size, and basis weight of the frequently used paper than for the less frequently used paper. Control must be done. For example, even if the paper type and basis weight are the same, if the transfer paper to be passed is a small size paper, the total amount of current flowing through the static elimination needle 32 is small, and at the same operation start timing as the frequently used paper size, Increased risk of transcription dust generation.

  Further, the specific resistance varies depending on the type and basis weight of the paper, and the amount of charge held on the transfer paper also varies. For this reason, in the configuration in which the angle and height of the transfer outlet guide member 31 are changed based only on the detected current value, the type of the specific resistance sheet having the higher use frequency, the basis weight, than the specific resistance sheet having the lower use frequency. Control that is more appropriate to the amount must be performed. For example, even if the paper type and size are the same, the higher the basis weight of the transfer paper to be passed, the higher the specific resistance and the higher the amount of charge held on the transfer paper. At the same operation start timing as the basis weight, the risk of occurrence of transfer dust increases. Even when the paper size and basis weight are the same, the amount of charge held on the transfer paper is also increased when the specific resistance is high, such as when the type of paper to be passed is OHP. At the same operation start timing as plain paper having a low specific resistance, the risk of occurrence of transfer dust increases.

  Therefore, in this embodiment, the angle and height of the transfer outlet guide member 31 are changed in accordance with any of the type, size, basis weight, or combination of two or more selected sheets before passing. The operation start timing is changed. With this configuration, the operation start timing can be set according to the transfer paper to be passed, and the risk of occurrence of transfer dust can be further reduced. For example, even if the type of paper to be passed and the basis weight are the same, if the transfer paper is a small size paper, the current detection reference value that triggers the start of operation is lowered, and the timing for changing the angle and height is set. By accelerating, the risk of occurrence of transfer dust can be further reduced. Even if the paper type and size are the same, the higher the basis weight of the transfer paper to be passed, the lower the current detection reference value that triggers the start of operation, and the earlier the timing for changing the angle and height. Thus, the risk of occurrence of transfer dust can be reduced. In addition, even if the paper size and basis weight are the same, the higher the specific resistance of the type of paper to be passed, the lower the current detection reference value that triggers the operation start, and the timing for changing the angle and height. By speeding up, the risk of occurrence of transfer dust can be further reduced.

  Further, in the transfer device 20 of the copying machine of the present embodiment described above, the change of the angle and height of the transfer outlet guide member 31 by the angle / height changing means of the transfer outlet guide plate 30 which is a transfer outlet guide mechanism is generally performed. It can be performed at any timing in the paper. That is, the angle / height changing means of the transfer outlet guide plate 30 can be operated during paper passing by detecting the current with the static elimination needle 32 in addition to the time of paper selection before paper passing. There is no limitation on the operation timing. As a result, the risk of occurrence of transfer dust can be reduced without stopping the paper passing operation of the copying machine as the image forming apparatus and reducing the productivity. Further, even when transfer sheets of different paper types are alternately passed, it is possible to transfer the transfer paper at the optimum angle and height of the transfer outlet guide member 31 according to the paper type.

  Here, the disturbance of the toner image due to the vertical movement when the transfer paper is conveyed on the transfer outlet guide member 31 is often changed by the angle / height changing means of the transfer outlet guide plate 30 in an initial state. Most likely to occur when changing to. Therefore, in order to suppress the disturbance of the toner image due to the vertical movement when the transfer sheet is conveyed on the transfer outlet guide member 31, the timing for changing to the initial state is performed at the timing between the transfer sheets to be conveyed. It is desirable. In particular, in a configuration in which the type, size, and basis weight of the paper can be selected before the paper is passed, the angle and height of the transfer outlet guide member 31 are set at a timing when the transfer paper does not pass over the transfer outlet guide member 31. Then, the amount of subsequent change can be reduced. Accordingly, it is possible to further suppress the disturbance of the toner image due to the vertical movement when the transfer paper is conveyed on the transfer outlet guide member 31, and to reduce the time required for changing the angle and height of the transfer outlet guide member 31. .

As described above, the transfer device 20 according to the copying machine of the present embodiment can provide the following operations and effects. The angle / height changing means of the transfer outlet guide plate 30 can be controlled by the control circuit 40 according to the current value neutralized by the static elimination needle 32. Since the angle / height changing means can be controlled in this way, for example, when the current value neutralized by the static elimination needle 32 is high, the distance between the static elimination needle 32 and the transfer paper is maintained at an appropriate distance, and the transfer outlet Adjustment can be made to reduce the contact area between the guide member 31 and the transfer paper. Therefore, the contact area between the transfer outlet guide member 31 and the transfer paper is reduced without causing a discharge failure of the transfer paper, the amount of frictional charge between the surface of the transfer outlet guide member 31 and the transfer paper is reduced, and the transfer outlet guide. An increase in the surface potential of the member 31 can be suppressed. Therefore, since the increase in the surface potential of the transfer outlet guide member 31 can be suppressed without causing a transfer paper discharge failure, the transfer paper can be discharged efficiently, and stable image quality with less transfer dust can be achieved. The resulting transfer device 20 can be provided.
Further, the transfer device 20 according to the copying machine of the present embodiment can provide the following operations and effects. Because the amount of change in the angle and height of the transfer outlet guide member 31 is arbitrarily changed according to the type, size, basis weight, or combination of any two or more of the sheets selected before the sheet is passed. , It can be optimized for the transfer paper to be passed. Therefore, it is possible to improve the margin of transfer dust without deteriorating the transport quality. Further, the amount of change in the angle and height of the transfer outlet guide member 31 can be optimized for the transfer paper to be passed, and friction between the bent transfer paper and the transfer outlet guide member 31 can be reduced. . Further, by reducing the friction between the bent transfer paper and the transfer outlet guide member 31, an increase in the surface potential of the transfer outlet guide member 31 can be suppressed, and the risk of occurrence of transfer dust can be reduced.
Further, the transfer device 20 according to the copying machine of the present embodiment can provide the following operations and effects. The operation start timing for changing the angle and height of the transfer outlet guide member 31 is made different depending on the type, size, basis weight, or combination of any two or more of the sheets selected before the sheet is passed. be able to. Thus, the operation start timing according to the transfer paper to be passed can be obtained. By starting the operation according to the transfer paper to be passed, the risk of occurrence of transfer dust can be further reduced.
Further, the transfer device 20 according to the copying machine of the present embodiment can provide the following operations and effects. The angle / height changing means of the transfer outlet guide plate 30 can be operated during paper passing by detecting the current with the static elimination needle 32 in addition to the paper selection before paper passing, and particularly the operation during paper passing. The timing does not matter. As a result, the risk of occurrence of transfer dust can be reduced without stopping the paper passing operation of the copying machine as the image forming apparatus and reducing the productivity. Further, even when transfer sheets of different paper types are alternately passed, it is possible to transfer the transfer paper at the optimum angle and height of the transfer outlet guide member 31 according to the paper type.
Further, in the copying machine of the present embodiment, by providing any one of the transfer devices 20 described above, the same operational effects as the provided transfer device 20 can be obtained.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Developing device 4 Cleaning device 5 Static elimination device 20 Transfer device 22 Transfer belt 23 Casing 24 Driven roller 25 Drive roller 26 Bias roller 27 High voltage power supply 30 Transfer outlet guide plate 31 Transfer outlet guide member 32 Static elimination needle 33 Downstream rotating member 33a Downstream shaft 33b Downstream eccentric cam 34 Upstream rotating member 34a Upstream shaft 34b Upstream eccentric cam 35 Downstream stepping motor 36 Upstream stepping motor 37 Guide plate holder 38 Protrusion 39 Tension spring 40 Control circuit 41 Ammeter 50 Fixing device 53 Fixing inlet guide plate 100 Device main body

JP 2008-197587 A

Claims (5)

In a transfer apparatus provided with a transfer outlet guide mechanism having a charge eliminating means for removing the charge of the transfer material after electrostatically transferring the toner image on the image carrier to the transfer material,
A transfer apparatus comprising: means for detecting the value of the current discharged by the charge removing means and changing the angle and height of the transfer outlet guide mechanism in accordance with the detected value. The transfer device according to claim 1,
The amount of change in the angle and height of the transfer outlet guide mechanism differs depending on the type, size, basis weight, or combination of any two or more of the papers selected before passing. Transfer device. In the transfer device according to claim 1 or 2,
The operation start timing for changing the angle and height of the transfer outlet guide mechanism differs depending on the type, size, basis weight, or combination of any two or more selected before passing the paper. The transfer device. In the transfer device according to any one of claims 1 to 3,
A transfer apparatus characterized in that an angle and a height change of a transfer outlet guide mechanism can be controlled at an arbitrary timing during sheet passing.   An image forming apparatus comprising the transfer device according to claim 1 as a transfer device.

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