JP2010186026A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely control a threshold voltage for producing an electric discharge, with respect to a technique for discharging a previously set voltage in a part except a metallic member for guiding the conveyance of a recording material, when the value of a bias voltage for transferring an image comprising the powder of an electrified pigment to the recording material exceeds the predetermined voltage, in order to prevent the electric discharge to the metallic member from the rotating shaft of a rotating body to which the bias voltage is applied and/or the bearing of the rotating shaft. <P>SOLUTION: A transfer device includes: a shaft 104 supplying the bias voltage to a transfer roll 102; the bearing 105 supporting the shaft 104; and a metallic guide plate 111 guiding a paper conveyed toward the transfer roll 102, wherein discharge electrodes 113 and 114 are arranged away from each other on the way of the supply path of the bias voltage. At this time, an interval between the discharge electrodes 113 and 114 is set to a value at which the electric discharge is started between the discharge electrodes 113 and 114, before the electric discharge from the shaft 104 to the guide plate 111 is started. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer device and an image forming apparatus.

  In Patent Document 1, in a configuration including a grounded chute for guiding paper, a roll portion to which voltage is applied, and a shaft portion of the roll portion, the metal member is brought closer to the shaft portion than the chute. When the abnormally high voltage is applied to the shaft portion, a discharge is generated between the shaft portion and the metal member, and no discharge is generated between the shaft portion and the chute. Yes.

JP 2007-298906 A

  According to the present invention, the discharge from the rotating shaft of the rotating body to which a bias voltage for transferring charged powder onto the recording material and / or the bearing of the rotating shaft is applied to the metal member of the guide means for guiding the conveyance of the recording material is performed. In order to prevent this, when the bias voltage value exceeds a predetermined voltage, the threshold voltage that causes this discharge is controlled more precisely in the technique of discharging this voltage at a portion other than the metal member. With the goal.

  According to a first aspect of the present invention, there is provided a rotating body to which a bias voltage for transferring charged powder to a recording material is applied, a rotating shaft that supplies the bias voltage to the rotating body, a rotating shaft that contacts the rotating shaft, and the rotation A bias voltage supply member for supplying the bias voltage to the shaft; a first discharge electrode disposed in a conductive path from a power supply circuit for outputting the bias voltage to the bias voltage supply member; and the first discharge electrode. A second discharge electrode arranged at a predetermined distance and connected to a reference potential; and a guide means connected to the reference potential for guiding a recording material conveyed toward the rotating body. A transfer device comprising a metal member.

  According to a second aspect of the present invention, in the first or second aspect of the present invention, the first discharge electrode and the second discharge are more than a potential difference that causes a discharge between the rotating shaft and the metal member. It is characterized in that the potential difference that causes discharge between the electrode and the electrode is smaller.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the first discharge electrode and the second discharge electrode are shorter than the shortest distance between the rotating shaft and the metal member. The shortest distance between is smaller.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the bias voltage supply member is a bearing of the rotary shaft, and the bearing exerts a force on the bearing. One end of the spring to be applied is in contact, the other end of the spring is in contact with a supply electrode that supplies the bias voltage to the spring, and the first discharge electrode is the supply electrode, or The first discharge electrode is connected to the supply electrode.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the bias voltage supply member is a bearing of the rotating shaft, and the bearing is a metal member of the guide means. The distance between the first electrode and the second electrode does not change even if the bearing is moved with respect to the metal member of the guide means. And

  According to a sixth aspect of the present invention, there is provided a rotating body on which charged powder is formed, and a transfer device according to any one of the first to fifth aspects, wherein the powder is transferred from the rotating body to a transfer surface. An image forming apparatus including the image forming apparatus.

  According to the first aspect of the invention, the rotating shaft of the rotating body to which a bias voltage for transferring the charged powder to the recording material is applied and / or the guide means for guiding the conveyance of the recording material from the bearing of the rotating shaft. In order to prevent discharge to the metal member, a threshold voltage that causes this discharge in the technique of discharging this voltage at a portion other than the metal member when the value of the bias voltage exceeds a predetermined voltage. Can be controlled more precisely.

  According to invention of Claim 2, before the discharge with respect to a metal member arises, discharge can be produced between the 1st electrode and the 2nd electrode.

  According to the third aspect of the present invention, it is possible to cause a discharge between the first electrode and the second electrode before the discharge to the metal member occurs.

  According to the invention described in claim 4, even if the bearing is moved by the repulsive force of the spring, a configuration is obtained in which the value of the discharge starting voltage between the first electrode and the second electrode is not affected. .

  According to the fifth aspect of the present invention, a configuration is obtained in which the value of the discharge starting voltage between the first electrode and the second electrode is not affected by the movement of the bearing.

It is a conceptual diagram of the transfer device using the invention. It is a conceptual diagram of the transfer device using the invention. It is a conceptual diagram of the transfer device using the invention. It is a conceptual diagram of the transfer device using the invention. It is a conceptual diagram which shows an example of a discharge electrode. 1 is a conceptual diagram illustrating an example of an image forming apparatus using the invention.

(1) First Embodiment FIG. 1 is a conceptual diagram illustrating an example of a transfer device according to an embodiment. FIG. 1 shows a transfer device 100. The transfer device 100 includes a photosensitive drum 101. In the state where the photosensitive drum 101 is rotating in the clockwise direction in the figure, the surface of the photosensitive drum 101 is partially exposed by being irradiated with laser light from a light source (not shown), and the latent image is exposed. Is formed. Toner where the latent image is formed is supplied with toner as pigment powder from a developing device (not shown), and a toner image is formed on the surface of the photosensitive drum 101.

A transfer roll 102 is disposed opposite to the photosensitive drum 101. The transfer roll 102 is made of cylindrical urethane containing carbon particles. The transfer roll 102 has a structure in which a metal shaft 104 is passed through the rotation center. In this example, the content of the carbon particles is adjusted so that the cylindrical urethane constituting the transfer roll 102 has a resistivity of 1 × 10 ⁸ to 1 × 10 ¹⁰ Ω · m. As shown in FIG. 1, the photosensitive drum 101 is slightly sunk into the transfer roll 102 (in this example, about 2 mm), and the transfer roll 102 is deformed accordingly.

The shaft 104 is supported in a rotatable state by a resin bearing 105. The bearing 105 has a resistance value capable of transmitting a bias voltage to the shaft 104 by mixing carbon particles so that the resistivity is 1 × 10 ⁸ to 1 × 10 ¹⁰ Ω · m. A groove for receiving the shaft 104 is formed in the bearing 105, and the shaft 104 is fitted into the groove in a rotatable state by utilizing the elastic deformation of the resin constituting the shaft.

  The bearing 105 is fitted into the concave portion 107 of the resin bearing support member 106 so as to be movable up and down in the figure, and is in a state of receiving the repulsive force of the spring 108 from the bottom of the concave portion 107. The transfer roll 102 is pressed toward the photosensitive drum 101 by the repulsive force of the spring 108. The bearing support member 106 is fixed to the housing 112 of the image forming apparatus in which the transfer device 100 is disposed. The housing 112 is made of resin.

  The spring 107 in a compressed state is made of metal, and a bias voltage is applied from an electrode 109 provided on the bottom surface of the recess 107. The electrode 109 is connected to the power supply circuit 110. The electrode 109 outputs a bias voltage. This bias voltage is, for example, about −3 to 8 kV with respect to the ground potential. The value of the bias voltage is determined by the type of toner used. The power supply circuit 110 is a switching power supply and includes a control circuit, a switching element, a transformer, a rectifier circuit, a voltage stabilization circuit, and a current stabilization circuit.

  A discharge electrode 113 is connected to the wiring connecting the electrode 109 and the power supply circuit 110. The discharge electrode 113 is exposed on the side surface of the bearing support member 106. A discharge electrode 114 is arranged with a space in opposition to the discharge electrode 113. The discharge electrode 114 has a pointed shape on the side facing the discharge electrode 113 so that discharge between the discharge electrode 113 and the discharge electrode 113 is likely to occur. The discharge electrode 114 is fixed to the housing 112 and connected to a ground potential serving as a reference potential.

  On the upstream side of the contact portion between the photosensitive drum 101 and the transfer roll 104 (the upstream side considered in the paper conveyance direction), a metal guide plate (chute that functions as a guide member) 111 as a guide unit is disposed. ing. The guide plate 111 is connected to a reference potential (ground potential) to prevent unintentional charging of the paper. In the figure, the guide plate 111 is directly grounded, but may be grounded via a resistor or a varistor. In addition, the guide plate 111 is made of a resin guide member instead of a metal guide plate (chute that functions as a guide member), and a metal is provided in a part of the resin guide member. The resin may protrude from a part of the metal guide member.

  The distance d between the discharge electrode 113 and the discharge electrode 114 is set so that the discharge between the shaft 104 and / or the bearing 105 and the guide plate 111 starts when the potential with respect to the ground of the electrode 109 is increased. The distance at which discharge starts between the discharge electrode 113 and the discharge electrode 114 is set. The distance d is determined experimentally, but is set to a value of 60 to 90% as a guide for the shortest distance between the shaft 104 and / or the bearing 105 and the guide plate 111.

(Example of dimension d)
In the following description, the power supply circuit 110 outputs a negative potential in consideration of the potential with respect to the ground. The maximum rated value of the absolute value is 5 kV, and when this value exceeds 8 kV, the shaft 104 and the guide plate A case will be described in which there is a possibility that electric discharge occurs between the bearing 111 and the bearing 105 and the guide plate 111. In this case, the value of the abnormal high voltage is a value exceeding 6.5 kV in terms of an absolute value. An abnormally high voltage is a voltage whose absolute value of the output of the power supply circuit 110 is larger than a value that guarantees the normal operation of the transfer apparatus 100 (a value that naturally allows a certain margin) (described below). In the example, it means a potential difference of 6.5 kV or more.

(basic action)
First, an outline of basic operations of the fixing device 100 will be described. The sheet is supplied from the right direction in FIG. 1, slides on the guide plate 111, and is conveyed toward a contact portion of the photosensitive drum 101 with the transfer roll 102. The sheet is sandwiched between the photosensitive drum 101 and the transfer roll 102, whereby the toner image on the photosensitive drum 101 is transferred onto the sheet.

  At this time, a negative bias voltage is applied to the transfer roll 102 from the power supply circuit 110. By this bias voltage, an electric force that presses the charged toner (charged pigment powder) constituting the toner image to the sheet side acts, and the above-described transfer is promoted.

(Operation when abnormally high voltage occurs)
An example of operation when an abnormally high voltage is output from the power supply circuit 110 will be described. A case is assumed where an abnormally high voltage is output from the power supply circuit 110 due to a failure or malfunction of a device constituting the power supply circuit 110.

  In this case, before the discharge between the shaft 104 and the guide plate 111 or between the bearing 105 and the guide plate 111 occurs, the discharge electrode 113 and the discharge electrode 114 are set to have a lower discharge start voltage. A discharge occurs. For this reason, a phenomenon in which electric discharge occurs between the shaft 104 and the guide plate 111 or between the bearing 105 and the guide plate 111 is suppressed.

(Superiority)
In the above-described technology for generating an intentional discharge using the discharge electrode when an abnormally high voltage is generated, the potential difference at the start of discharge (in order to control the stability of the operation of the device and the damage to parts) It is desirable to be able to set the threshold value precisely. For example, if there is a variation in the threshold value in the configuration using the discharge electrode for each product, the potential difference at the start of discharge between the discharge electrodes is low in some products and high in some products. In the former case, in the normal operating range, the possibility of occurrence of discharge using the discharge electrode increases, and the possibility that normal operation is hindered increases. In the latter case, before the function of bypassing the abnormally high voltage functions normally, the possibility that electric discharge occurs between the shaft 104 and the guide plate 111 or between the bearing 105 and the guide plate 111 increases.

  Accordingly, it is important to precisely set the potential difference (threshold value) at the start of discharge between the electrodes for discharge. The potential difference at the start of discharge between the discharge electrodes is determined by the dimension of the interval d. Therefore, it is important to control d precisely. Generally, the discharge start voltage between electrodes sandwiching air can be estimated to be about 1 kV per mm. Therefore, when a discharge is intentionally generated in a portion that fluctuates in mm, an error in kV is inevitable. In other words, when it is necessary to control the discharge start voltage with a deviation of 1 kV or less, the accuracy of the position of the member that causes discharge is required to be 1 mm or less.

  In the example shown in FIG. 1, the discharge electrode 113 and the discharge electrode 114 are fixed to a fixed member that does not move (does not move). That is, the discharge electrode 113 is fixed to the bearing support member 106, and the discharge electrode 114 is fixed to the housing 112. The bearing support member 106 is fixed to the housing 112. For this reason, the value of d can be precisely determined with an accuracy of mm or less, and the deviation of the value of d for each product can be reduced.

(Modification 1)
FIG. 2 is a conceptual diagram illustrating an example of the transfer device according to the embodiment. FIG. 2 shows the transfer device 120. Portions of the transfer device 120 that are the same as those in FIG. 1 are the same as those described with reference to FIG.

  In the transfer device 120 illustrated in FIG. 2, the wiring from the electrode 109 is connected to the electrode 121 provided in the housing 112. The electrode 121 has a planar shape and is connected to a wiring from the output of the power supply circuit 110. Further, the discharge electrode 122 is disposed opposite to the electrode 121 at a predetermined interval. The discharge electrode 122 is connected to the ground potential and has a pointed tip that faces the electrode 121. Further, the discharge electrode 122 is fixed to the housing 112 via a support member 123.

  In this example, the electrode 121 also functions as a discharge electrode paired with the discharge electrode 122. When the absolute value of the voltage applied to the electrode 121 from the power supply circuit 110 is increased, the distance between the electrode 121 and the discharge electrode 122 is between the shaft 104 and the guide plate 111 or between the bearing 105 and the guide plate. The value is such that a discharge occurs between the electrode 121 and the discharge electrode 122 before the discharge occurs between the electrode 111 and the discharge electrode 122. The setting of the distance between the electrode 121 and the discharge electrode 122 is the same as in FIG.

  Also in the example shown in FIG. 2, the electrode 121 and the discharge electrode 122 are fixed to a non-moving member, so that the distance between them can be set precisely. For this reason, the potential difference at which discharge starts can be set accurately.

(Modification 2)
FIG. 3 is a conceptual diagram illustrating an example of the transfer device according to the embodiment. FIG. 3 shows the transfer device 130. Parts of the transfer device 130 having the same reference numerals as those in FIG. 1 are the same as those described with reference to FIG.

  In the transfer device 130 shown in FIG. 3, a sealed space 131 is provided under the electrode 109 disposed on the bottom surface of the concave portion 107 of the bearing support member 106, and the discharge electrode 132 is fixed thereto. The discharge electrode 132 is opposed to the back surface of the electrode 109 on the side in contact with the spring 108 with a predetermined interval. Further, the side of the discharge electrode 132 facing the electrode 109 has a sharp shape. The setting of the distance between the discharge electrode 132 and the electrode 109 is the same as in FIG.

  In the example shown in FIG. 3 as well, the electrode 109 and the discharge electrode 132 are fixed to a non-moving member, so that the distance between them can be set precisely. For this reason, the potential difference at which discharge starts can be set accurately. Further, since the space 131 is hermetically sealed, it is possible to prevent a situation in which the discharge electrode is touched unintentionally and the setting of the discharge start voltage is changed during replacement of other components. Further, since the space 131 is sealed, the influence of dust, toner powder, and humidity on the value of the discharge start voltage can be reduced. For this reason, the stability of the set value of the discharge start voltage can be enhanced.

(Modification 3)
FIG. 4 is a conceptual diagram illustrating an example of the transfer device according to the embodiment. FIG. 4 shows the transfer device 140. Parts of the transfer device 140 having the same reference numerals as those in FIG. 1 are the same as those described with reference to FIG.

  In the transfer device 140, a discharge electrode 141 is connected to the guide plate 111. The discharge electrode 141 is fixed to the bearing support member 106 by a fixing member 142. A discharge electrode 144 is disposed on the side surface of the bearing support member 106 facing the discharge electrode 141. The discharge electrode 144 is connected to an electrode 143 formed at the edge portion of the recess 107 of the bearing support member 106. The electrode 143 contacts the bearing 105 attached to the recess 105.

  According to this configuration, the discharge electrode 141 is connected to the ground potential via the guide plate 111, and the discharge electrode 144 is connected to the output of the power supply circuit 110 via the electrode 143, the bearing 105, the spring 108, and the electrode 109. Is done. Here, the setting of the distance between the discharge electrode 141 and the discharge electrode 144 is the same as in the case of FIG.

  When the power supply circuit 110 outputs an abnormally high voltage, the discharge electrode 141 and the discharge are discharged before the discharge between the shaft 104 and the guide plate 111 or the discharge between the bearing 105 and the guide plate 111 is started. Discharge occurs between the electrode 144 and the electrode 144. Thereby, the discharge between the shaft 104 and the guide plate 111 or the discharge between the bearing 105 and the guide plate 111 is suppressed.

(Modification 4)
In the configuration shown in FIG. 4, an electrode that contacts the rotating shaft 104 while being elastically deformed may be arranged, and this electrode may be connected to the discharge electrode 144.

(Other)
In the example shown in FIGS. 1 to 4, the rotating body indicated by reference numeral 101 is a photosensitive drum, but the present invention is applied to a type in which a transfer belt is adopted as a rotating body facing the transfer roll 102. Is also possible. In this case, the toner image is primarily transferred to the transfer belt, and the sheet is sandwiched between the transfer belt and the transfer roll 102, whereby the toner image on the transfer belt is secondarily transferred to the sheet.

  FIG. 5 is a conceptual diagram showing an example of a discharge electrode portion. FIG. 1 shows a configuration in which the discharge electrodes 151 and 152 are opposed to each other and separated by a predetermined size, and the periphery thereof is covered with a cylindrical cover 153 to form a sealed space. In this example, the discharge electrode 151 has a planar shape, and has a rod-like structure in which the discharge electrode 152 has a protruding shape pointed toward the discharge electrode 151. Reference numerals 154 and 155 denote lead wires from the respective discharge electrodes.

  In the structure shown in FIG. 5, since the discharge space is sealed, inconvenience that the discharge electrode is unintentionally touched and the electrode interval of the discharge electrode is changed in the replacement operation of other components is avoided. Further, since the discharge space is sealed, the influence of dust, toner powder, and humidity on the discharge start voltage can be reduced. For this reason, the stability of the set value of the discharge start voltage can be enhanced. The configuration shown in FIG. 5 can be applied to the configurations shown in FIGS. 1, 2, and 4, for example.

  In the plurality of examples described above, both discharge electrodes may have a sharp protruding structure. Further, when a protruding structure is adopted, a plurality of protruding portions may be arranged. One of the discharge electrodes may be a wiring pattern, a metal part used for power feeding, or the like as long as the part is energized with a power supply voltage.

(2) Second Embodiment An example of an image forming apparatus using the present invention will be described. FIG. 6 is a conceptual diagram showing an example of an image forming apparatus using the invention. FIG. 6 shows the image forming apparatus 10. The image forming apparatus 10 includes a paper storage device 11. The sheet storage device 11 stores a plurality of sheets. The paper stored in the paper storage device 11 is pulled out to the transport path 12 by a transport roll (not shown) and sent to the transfer device 13.

  The transfer device 13 has the same configuration as the transfer device 100 shown in FIG. FIG. 6 shows a cleaning roll 31, a charging device 32, a laser beam irradiation device 33 and a developing device 34 for performing photosensitivity, which are not shown in FIG. 1.

  The cleaning roll 31 removes unnecessary toner remaining on the surface of the photosensitive drum 101. The charging device 32 charges the surface of the photosensitive drum 101 to a negative potential. The laser light irradiation device 33 irradiates the photoconductive drum 101 with laser light that serves as drawing light for forming a latent image on the surface of the photoconductive drum 101. The laser beam irradiation device 33 includes an optical system that scans and irradiates laser light and a laser beam generator. The developing device 34 includes a container that stores toner, and a toner supply roll 34 a that supplies toner to the photosensitive drum 101.

  Transfer devices 14 to 16 are sequentially arranged on the downstream side of the transfer device 13. The transfer devices 14 to 16 have the same configuration as the transfer device 13. In this example, the CMYK four-color basic toner images are sequentially transferred onto the paper in the transfer devices 13 to 16. Here, C is cyan, M is magenta, Y is yellow, and K is black.

  In the transfer devices 13 to 16, the paper on which the toner images of the respective basic colors are formed is sent to the fixing device 17. The fixing device 17 includes a heating roll 18 having a built-in heater and a pressure roll 19, and heat and pressure are applied with a sheet sandwiched between both rolls. As a result, the unfixed toner image on the paper is fixed on the paper, and a fixed image is obtained. The paper for which the fixing process has been completed is discharged onto the paper discharge surface 20.

  The present invention can be applied to a transfer device of an image forming apparatus.

  DESCRIPTION OF SYMBOLS 101 Photosensitive drum, 102 ... Transfer roll, 104 ... Shaft, 105 ... Bearing, 106 ... Bearing support member, 107 ... Recessed part, 108 ... Spring, 109 ... Electrode, 110 ... Power supply circuit, 111 ... Guide plate.

Claims (6)

A rotating body to which a bias voltage is applied to transfer the charged powder to the recording material;
A rotating shaft for supplying the bias voltage to the rotating body;
A bias voltage supply member that contacts the rotating shaft and supplies the bias voltage to the rotating shaft;
A first discharge electrode disposed in a conductive path from a power supply circuit that outputs the bias voltage to the bias voltage supply member;
A second discharge electrode disposed at a predetermined distance from the first discharge electrode and connected to a reference potential;
A transfer device comprising: a metal member that is connected to the reference potential and guides a recording material conveyed toward the rotating body.   The potential difference in which discharge occurs between the first discharge electrode and the second discharge electrode is smaller than the potential difference in which discharge occurs between the rotating shaft and the metal member. 2. The transfer apparatus according to 1.   The shortest distance between the first discharge electrode and the second discharge electrode is smaller than the shortest distance between the rotating shaft and the metal member. The transfer apparatus described. The bias voltage supply member is a bearing of the rotary shaft;
One end of a spring that applies force to the bearing is in contact with the bearing,
The other end of the spring is in contact with a supply electrode that supplies the bias voltage to the spring,
The transfer device according to claim 1, wherein the first discharge electrode is the supply electrode, or the first discharge electrode is connected to the supply electrode. . The bias voltage supply member is a bearing of the rotary shaft;
The bearing is movable relative to the metal member of the guide means;
The distance between the first electrode and the second electrode does not change even if the bearing is moved with respect to the metal member of the guide means. The transfer apparatus described. A rotating body on which charged powder is formed;
An image forming apparatus comprising: the transfer device according to claim 1, wherein the powder is transferred from the rotating body to a transfer surface.

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