JP2006195003A - Image forming apparatus and its fixing bias output circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus which satisfies both of the improvement of tailing and the removal of the variation of transfer voltage by AC voltage, and its fixing bias output circuit. <P>SOLUTION: The image forming apparatus is equipped with a drum 1 for charging an image carrier, an exposure part for forming an electrostatic latent image on the drum 1, a developing part for developing the electrostatic latent image to be a toner image, a transfer part for transferring the toner image to recording material, and a fixing part for fixing the toner image on the recording material by holding and conveying the recording material between at least a heating member 100 and a pressure member 11 having an elastic layer and feeding AC voltage to the heating member. The fixing part is equipped with a bias voltage generation part 20 for applying bias voltage to the surface of at least either the heating member or the pressure member, and a conduction circuit for connecting the surface of the heating member or the pressure member with the bias voltage generation part. A capacitor 209 is inserted between the conduction circuit and grounding potential. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and a fixing bias output circuit thereof, for example, an image forming apparatus using an electrophotographic process such as a copying machine, a laser printer, and a facsimile machine, in particular, a charging unit for charging an image carrier, and the image carrier. An exposure unit that forms an electrostatic latent image thereon, a developing unit that develops the electrostatic latent image as a toner image, a transfer unit that transfers the toner image onto a recording material, and a toner image on the recording material A fixing means for fixing and fixing the toner image on the recording material by sandwiching and transporting the toner image between at least a heating member and a pressure member having an elastic layer, and realizing a heating function by supplying an AC voltage to the heating member The present invention relates to an image forming apparatus and a fixing bias output circuit thereof.

  In a fixing device in this type of image forming apparatus, in a high-temperature and high-humidity environment, when the moisture content of the recording material such as paper is high, the transfer charge supplied to the back surface of the recording material at the transfer portion is transmitted along the recording material. And the toner image transferred and formed on the recording material is easily lost.

  In addition, when the moisture content of the recording material is large, the amount of steam generated at the fixing nip where the heater and the pressure roller sandwich the recording material increases. Especially in the horizontal line image perpendicular to the conveyance direction of the recording material, steam called tailing is generated. The toner was scattered due to the pressure of.

  In addition, since the toner image holding force due to the transfer charge on the back surface of the recording material is weakened, the toner is not fixed to the recording material, and the toner adheres to the fixing film or the fixing roller. An image defect in which the adhered toner is fixed to the recording material after one rotation is likely to occur. In addition, toner adheres to the fixing film due to an offset phenomenon, and is transferred to a pressure roller pressed against the fixing film, which causes pressure roller contamination.

  Therefore, conventionally, in order to prevent image defects due to the generation of water vapor in the vicinity of the heating body, there is a method in which the fixing roller side is grounded and a voltage is applied to the electrode in contact with the recording material as disclosed in Patent Document 1, for example. Has been taken. Hereinafter, this voltage is referred to as a fixing bias.

On the other hand, the fixing device performs heat fixing with heat generated by power feeding to the resistance heating element. There are a method of using an AC voltage from a commercial power source as a power supply method and a method of using this AC voltage by rectifying and converting it to a DC voltage. Generally, the former, which does not require a rectifier circuit, can be configured at a lower cost.
Japanese Patent Laid-Open No. 08-272245

  By the way, in the method of applying the AC voltage to the resistance heating element, the glass coated with the resistance heating element acts as a capacitor on the equivalent circuit, so that the AC voltage is transmitted to the fixing nip portion through the fixing film. The On the other hand, when the moisture content of the recording material increases, the impedance of the recording material rapidly decreases. At this time, when the recording material is held between the transfer nip and the fixing nip composed of the photosensitive drum and the transfer roller at the same time, the AC voltage on the fixing nip is transmitted to the transfer nip through the recording material, and the transfer voltage on the transfer nip is changed. The fluctuation causes transfer unevenness, and as a result, appears as a striped pattern (density unevenness) in the main scanning direction of the image.

  Furthermore, in order to reduce tailing, it is effective to take measures to lower the output impedance of the fixing bias, that is, the resistance value of the discharge resistance. However, since this discharge resistance is one of the leakage paths of the transfer voltage, The transfer voltage is lowered. When the DC component of the transfer voltage is reduced, the AC voltage transmitted from the fixing nip is more emphasized, and strong transfer unevenness is caused.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image forming apparatus and a fixing bias output circuit thereof that achieve both improvement of tailing and removal of transfer voltage fluctuation due to AC voltage. To do.

  The present invention is an image forming apparatus having the following configuration.

  (1) Charging means for charging the image carrier, exposure means for forming an electrostatic latent image on the image carrier, developing means for developing the electrostatic latent image as a toner image, and recording the toner image Transfer means for transferring onto the material; and fixing means for fixing the toner image on the recording material by sandwiching and conveying the recording material between at least a heating member and a pressure member having an elastic layer, In the image forming apparatus including a fixing unit that supplies an AC voltage to the member, the fixing unit generates a bias voltage for applying a bias voltage to at least one surface of the heating member or the pressure member, and A conductive means for connecting the surface of the heating member or the pressure member and the bias voltage generating means, and a capacitive element is inserted between the conductive means and the ground potential, Can be removed AC voltage variation component to be transferred to the transfer nip, it is possible to eliminate the density unevenness. .

  (2) A resistance element is further inserted in series with the capacitive element between the conductive means and the ground potential, and an AC voltage fluctuation component transmitted from the commercial power source to the transfer nip is removed. In addition to eliminating the density unevenness, the apparatus can be protected even when a surge voltage such as a lightning strike enters the commercial power supply. .

  (3) The capacitive element and / or the resistive element is provided on a generating circuit board that provides the bias electricity generating means, and no additional member is required, so that an inexpensive configuration can be achieved. Even in a mechanical configuration, a simpler configuration can be achieved.

  As described above, according to the present invention, in a system including a heating member for fixing a toner image on a recording material or a means for applying a bias voltage to at least one of the pressing members, the heating member or the pressing member By inserting a capacitor or resistor in the conductive path that connects the bias voltage to the bias voltage, it is possible to remove disturbance of the AC voltage component transmitted from the commercial power supply to the transfer nip, and the moisture absorption that is left under high humidity Even in the case of low impedance paper such as paper, there is an effect that sufficient image quality can be easily realized at low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Schematic configuration example of image forming apparatus>
FIG. 8 is a schematic configuration diagram of an electrophotographic laser beam printer (hereinafter referred to as LBP) which is an example of an image forming apparatus to which the fixing bias output circuit of the present embodiment is applied.

  In FIG. 8, reference numeral 1 denotes an organic photosensitive drum (hereinafter abbreviated as a photosensitive drum) as an image carrier having an organic photosensitive layer formed on the surface thereof, and is driven to rotate in the arrow direction X. 2 is a charging roller for uniformly charging the surface of the photosensitive drum 1 in a negative polarity, 3 is a laser scanner unit for performing laser exposure with intensity modulation according to image data, and 4 is a negative polarity one-component toner. Is a developing device that visualizes an electrostatic latent image, and performs so-called reversal development that develops the exposed portion. 5 is a transfer roller for transferring the toner image onto the recording material P, 6 is a charge eliminating needle for separating the recording material from the photosensitive drum 1, and 7 is for cleaning the toner remaining on the photosensitive drum 1 after the transfer process. It is a cleaner.

  The recording material P to which the toner image has been transferred is sent through a conveyance guide 8 to a fixing device including a heater unit 10, a pressure roller 11, a fixing inlet guide 9, a paper discharge guide 12, a paper discharge roller 13, and the like. The toner image is heated and fixed by being nipped and conveyed by the heater unit 10 and the pressure roller 11.

  In the present embodiment, the paper discharge roller 13 is made of conductive rubber, and the cored bar 13a is grounded. Therefore, when a fixing bias is applied to the fixing film, which will be described later, and the recording material P is nipped and conveyed by both the fixing film, the pressure roller 11 and the paper discharge roller 13, the bias power is supplied to the ground via the recording material P. An energization path Y is formed.

  Reference numeral 90 denotes a CPU for controlling the operation of the LBP according to the present embodiment, and based on outputs from the top sensor 18, the discharge sensor 19, and the like that control communication with external devices and detect the front and rear end positions of the recording material. Controls energization of motor, laser, high voltage and heater.

  In the present embodiment, a DC bias output from a primary charging high voltage output circuit (bias power supply) 20 is induced to the surface of the fixing film via a discharge resistor 26.

  In the fixing device, heat fixing is performed by applying an AC voltage from the commercial power source 213 to the resistance heating element on the heater 212. At this time, the application timing and application time are controlled by turning ON / OFF the switch element 302 by the CPU 90. The glass coating the heater 212 is electrically regarded as a capacitor, and the capacitance value in this embodiment is about several hundred pF. Accordingly, the AC voltage of the commercial power source 213 is transmitted from the resistance heating element through the coating glass to the fixing nip portion where the heater and the pressure roller sandwich the recording material.

(Configuration example of main part of fixing device)
FIG. 9 is a diagram illustrating a main part of the fixing device of the present embodiment.

  Reference numeral 212 denotes a ceramic heater in which a resistance heating element made of a silver alloy is printed on an alumina substrate, a glass coating is applied to the resistance heating element surface, and a thermistor 155, an electrode (not shown), and the like are arranged. 130 is a film guide and heater holder made of a heat-resistant resin such as a liquid crystal polymer, and 100 is a cylindrical base film surface having a thickness of 30 to 80 μm and an inner diameter of φ24 mm in which a heat conductive filler is dispersed in polyimide resin, and is electrically conductive to fluororesin. A primer layer with a carbon dispersion of 1 × 10E5 Ω · cm or less and a thickness of 2 to 10 μm is formed, and a resistance imparting a conductivity imparting substance to a fluororesin is further formed on the primer layer with a resistance of 1 × 10E7 Ω · cm The fixing film has a three-layer structure in which a release layer having a thickness of 1 to 10E13 Ω · cm and a thickness of 5 to 20 μm is formed. Reference numeral 170 denotes a reinforcing sheet metal for preventing the heater unit (heating member) 10 including the heater 150, the film 100, the film guide 130, and the like from causing unnecessary deformation due to the pressure contact with the pressure roller (pressure member) 11. Is a discharge resistor that connects the high-voltage bias power supply 20 and the film 100.

('Tail image' phenomenon and countermeasures)
A toner scattering phenomenon called “tail image” will be described with reference to FIG.

  In the figure, the temperature of the fixing nip N formed by the pressure contact between the heater unit 10 and the pressure roller 11 is controlled to a temperature of about 150 ° C. to 200 ° C., and the moisture contained in the recording material P during the sheet passing. Always evaporate and vapor 60 is generated. Due to the vapor pressure, a part T of the unfixed toner image on the upstream side from the fixing nip portion N is blown off to the downstream side in the conveyance direction of the recording material, whereby the trailing image is generated.

  The fixing bias applied by the bias power source 20 via the discharge resistor 26 is applied to improve an image defect called “tailing”, and an outline of the operation of the fixing bias will be described below. To do.

  FIG. 11 is an example of an equivalent circuit when the recording material P onto which the toner image is transferred enters the fixing nip portion N when a DC bias having the same polarity as the toner is applied to the surface of the fixing film. Note that the same reference numerals as those in FIGS. 8 to 10 denote the same functional components.

  Reference numeral 102 denotes a conductive primer layer of the fixing film 100 described with reference to FIG. 9, a DC bias of −600 V is applied from the bias power source 20, and reference numeral 103 denotes a release layer described with reference to FIG. The bias is applied to the conductive primer layer 102 by bringing a power supply member such as a conductive brush or a conductive rubber ring (not shown) into contact with the conductive primer layer 102.

  Rd is a resistance from the bias power source 20 to the discharge resistor 26, Re represents a contact resistance between the power supply member and the conductive primer layer, and a resistance to the vicinity of the fixing nip N of the conductive primer layer 102, Rf Represents the resistance of the release layer. In the vicinity Pn of the fixing nip portion N (region between the release layer and the pressure roller), the recording material P such as paper is heated and water vapor is generated. Compared with other resistors connected in series, it is negligibly small, and can be regarded as equipotential in the Pn region. Since the moisture content of the paper after passing through the fixing nip portion N decreases and the temperature increases, the resistance value cannot be ignored, and the resistance to the paper discharge roller 13 that is a ground electrode is represented by Rg. Further, the contact resistance of the paper discharge roller 13 as the ground electrode with the recording material P and the resistance to the ground E are represented by Rh.

  In FIG. 11, −600 V is applied from the bias power supply 20, and the surface potential that appears on the surface of the fixing film 100 from −400 to −550 V due to the voltage drop due to the resistor Rd and the discharge resistor 26. When a current I flows from the conductive primer layer 102 of the fixing film 100 through the release layer 103, the recording material P, and the paper discharge roller 13 which is a ground electrode, between the conductive primer layer 102 and the equipotential portion Pn of the recording material P. An electric field Ef is generated. As a result, since the toner has a negative charge, the restraining force Ft acts on the recording material P, and particularly in the vicinity of the fixing nip N, the toner is strongly restrained by the recording material P, and the tailing, offset, scattering, etc. Image defects are greatly improved. When the voltage value of the bias power source 20 is constant, the strength of the electric field Ef increases as the resistance value of the discharge resistor 26 decreases, improving the improvement effect.

  However, when the resistance value of the discharge resistor 26 is reduced, when the recording material P is gripped by both the transfer portion and the fixing portion, the transfer current transmitted through the recording material P causes the fixing film 100 and the discharge resistor 26 to pass. Since it tends to flow out through, a transfer voltage (DC voltage) at a transfer nip portion (Nt in FIG. 1 described later) is lowered, resulting in problems such as a decrease in density and whiteout. Therefore, the resistance value of the discharge resistor 26 is limited by these conditions.

<First Configuration Example of Image Forming Apparatus of Present Embodiment>
FIG. 1 is a diagram showing an outline of the fixing bias output circuit of the present embodiment and its discharge resistance. In the present embodiment, the bias power source 20 is branched from the primary charging output circuit.

  In FIG. 1, the discharge resistor 26 includes two resistors 207 and 208, and a bias is applied to the fixing film through these resistors. The bias power source 20 is connected to the commercial power source 213 through the discharge resistors 207 and 208, the fixing film 100, and the heater 212. Therefore, in order to satisfy safety standards (IEC 60950 1999 etc.), it is necessary to provide reinforced insulation in these paths. In the present embodiment, the voltage value applied to the fixing film is about −600 V, and the maximum peak value of the commercial power supply is 240 × √2 = 340 V. Therefore, the maximum operating voltage is 940V. IEC 60950 requires basic insulation and additional insulation with a dielectric breakdown voltage of 2343 V for an operating voltage of 950 V.

  In this embodiment, resistors having a withstand voltage of 2343 V or more are used for 207 and 208. According to IEC 60950: 1999 “2.2.8.2”, in this embodiment, two resistors having a withstand voltage of 2343 V or more per resistor are connected in series to form double insulation of basic insulation and additional insulation. You can do that. Further, the resistance values of 207 and 208 need to be the same nominal resistance value according to the provision of the same paragraph. In this embodiment, the resistance values of 207 and 208 are each 20 MΩ.

Here, regarding the resistance value of the recording material P, when recycled paper is used, the volume resistivity may decrease to about 2 × 10 ⁸ Ω · cm under high humidity. When converted to A4 size paper (length 297 mm × width 210 mm) having a thickness of 0.1 mm, the resistance value is approximately 300 MΩ. In this embodiment, since the distance between the fixing nip N and the transfer nip Nt is 120 mm, the resistance value therebetween is approximately 120 MΩ. Compared to this, the resistance value is at least two orders of magnitude greater under non-humidity.

  FIG. 2 shows each resistance value in a humid environment that exists between the transfer power supply 300 (+1 kVdc) and the bias circuit 20 (−600 Vdc).

  In the figure, R207 and R208 are the resistance values of the discharge resistors 207 and 208, Rt is the total value of the resistance value of the transfer roller 5 and the output impedance of the transfer power supply 300, and Rp is the length between the transfer nip Nt and the fixing nip N. The resistance value of the recording material P is shown. Nt and N indicate positions on the equivalent circuit corresponding to the transfer nip and the fixing nip, respectively.

  2A is an example when the recording material P does not absorb moisture, and FIG. 2B is an example when the recording material P absorbs moisture. From this figure, it is understood that the transfer voltage on the transfer nip Nt is lower in the moisture absorbent paper than in the case where the moisture absorbent paper is non-absorbent paper. Even when the transfer voltage is lowered using these moisture-absorbing papers, the image density defined as the specification is designed to be maintained.

  However, as shown in FIG. 3, when the transfer voltage is subject to fluctuations in the alternating current component, it is much lower than the minimum transfer voltage, so that periodic density unevenness depending on the commercial power supply frequency occurs or is not transferred at all. White spots occur periodically.

  In order to improve this, in this embodiment, a capacitor 209 is inserted into a conductive path for supplying a bias to the fixing film 100 as shown in FIG.

  Hereinafter, the effect of the capacitor 209 and the required capacitance value will be described with reference to FIG.

  P0 indicates the position of the glass coating portion of the heater 212, P1 indicates the position of the fixing nip N, P3 indicates the position of the transfer nip Nt, and P3 indicates the position of the output portion of the transfer power supply 300. FIG. 4 shows an equivalent circuit in these positional relationships. C 1 represents a capacitor capacity component value formed by the glass coating of the heater 212. In this embodiment, it is about 200 pF to 400 pF, and 250 pF is described as an example. C3 represents the output capacitance of the transfer power supply 300 and the stray capacitance of the ground potential, and is estimated to be about several pF to several tens pF. Here, 10 pF is described as an example. The AC voltage transmitted from the commercial power source 213 through the glass coating of the heater 212 passes through the recording material P and reaches the transfer nip Nt (position P2 in FIG. 4). Accordingly, the amplitude of the AC voltage at the position P2 is determined by the ratio of the combined impedance (complex impedance) Z0 of C1 and Rp and the combined impedance Z2 of Rt and C3. Here, these combined impedances are determined as follows.

Here, f is a commercial power supply frequency (60 Hz is used as a calculation example), j represents a complex number, and j ² = −1. The absolute value of the combined impedance of Z0 and Z2 is determined as follows:

  When Z0 and Z2 are calculated based on these equations, when the recording material P in FIG. 4A does not absorb moisture, the AC voltage at the P2 position is 300 / 10300≈0.03 of the AC voltage at the P0 position. It turns out that it attenuates to 3%. Similarly, when the recording material P in FIG. 4B absorbs moisture, the attenuation rate is about 70%, and it can be seen that a very large AC voltage is transmitted to the transfer nip Nt. Consider the case where the capacitor C2 is inserted between the fixing nip N (P1) and the ground potential as shown in FIG. As C2, as an example, a maximum value of 10,000 pF was used as a capacitance value that was easily available at low cost among high-pressure ceramic capacitors. If the complex impedance of C2 is Z4, the complex impedance of C1 is Z1, and the combined impedance from P1 to P3 is Z3, each is determined as follows.

  The absolute values of these combined impedances are determined as follows:

Using these equations, Z4 = 0.3 MΩ, Z1 = 10 MΩ, and Z3 = 380 MΩ are calculated. Since Z4 is very small compared to Z3, the combined impedance of Z3 and Z4 can be regarded as approximately 0.3 MΩ. Therefore, the AC voltage attenuation rate at the fixing nip N (P1) is about 3%, and the AC voltage attenuation rate at the transfer nip Nt (P2) is about 2% based on the ratio of Rp and Z2. That is, even when moisture-absorbing paper is used, the attenuation rate is about the same as when dry paper is used, indicating that fluctuations in transfer voltage due to AC voltage can be removed.
When printing was actually performed with 10000 pF inserted, it was confirmed that density unevenness was eliminated.

  In the present embodiment, a mode in which a fixing bias is applied to the conductive primer layer 102 of the fixing film 100 has been described, but the present invention is also effective in a mode in which the fixing bias is applied from the pressure roller 11.

  As described above, according to this embodiment, the AC voltage fluctuation component transmitted from the commercial power supply to the transfer nip is removed by inserting the capacitor in the conductive path of the fixing bias applied to the fixing roller or the fixing film. And density unevenness can be eliminated.

<Second Configuration Example of Image Forming Apparatus of Present Embodiment>
In the first configuration example 1, the configuration in which the capacitor is added to the conductive path of the fixing bias has been described. In the second configuration example, a configuration in which a resistor is further added in series will be described.

  When only a capacitor is inserted as in the first configuration example, as shown in FIG. 4C, the impedance between the commercial power supply and the ground potential is the sum of Z1 and Z4, but Z1 >> Z4. Therefore, it can be regarded approximately as Z1. Here, when a common mode surge is generated in the commercial power source due to lightning or the like, the surge voltage is applied to Z1, that is, the glass coating of the heater 212. When a surge protection circuit is provided or when the pressure resistance of the glass coating is high, there is no problem, but when there is no protection circuit and the pressure resistance of the glass coating is low, the glass coating is destroyed. In order to prevent breakdown even when a lightning surge voltage (± 4 kV, pulse width 50 us) as specified in the international standard IEC61000-4-5 is applied, the voltage applied to the glass coating is a breakdown voltage (in the second configuration example, (It shall be 1.5 kV) or less. In order to solve this, in the present embodiment, a case where a resistor 301 and a capacitor 209 are inserted in series between the conductive path of the fixing bias and the ground potential as shown in FIG. 5 or FIG. 6 will be described. When the transient characteristics of the voltage applied to the glass coating during lightning surge application are simulated by a computer, the voltage applied to the glass coating is calculated to be 1.5 kV or less when the resistance 301 is about 500 kΩ or more.

  However, when the resistance value of the resistor 301 increases, the effect of eliminating the density unevenness decreases. FIG. 7 shows an equivalent circuit when 1 MΩ is inserted as the resistor 301. The impedance Z4 is 1.04 MΩ, and the attenuation rate of the AC voltage at P1 is about 9%. Further, the attenuation rate at P2 is about 7%. When image printing was performed under these conditions, it was possible to obtain the same image quality as when the recording material P that did not absorb moisture shown in FIG. When R301 is further increased to 5 MΩ and 10 MΩ for printing, density unevenness gradually occurs. Accordingly, by setting the resistance value of the resistor 301 and the combined impedance of the capacitor C2 to be not more than one tenth of the impedance of the glass coating of the heater 212, the effect of the present invention can be sufficiently obtained.

  From the above, even when the pressure resistance of the glass coating is low, the AC voltage fluctuation transmitted from the commercial power supply to the transfer nip can be obtained by inserting a capacitor and resistor in series in the conductive path of the fixing bias applied to the fixing roller or fixing film. The components can be removed to eliminate density unevenness, and the device can be protected even when a surge voltage such as a lightning strike enters the commercial power supply.

<Third Configuration Example of Image Forming Apparatus of This Embodiment>
In the first configuration example and the second configuration example, the capacitor 209 and the resistor 301 are provided in a conductive path connecting the surface of the fixing film 100 or the pressure roller 11 and the bias power source 20. As a means for realizing it, a separate contact, a capacitor, and a member for holding the resistor 301 are required.

  Although not shown in the third configuration example, the capacitor 209 and the resistor 301 are mounted on a substrate on which the circuit of the bias power supply 20 is mounted.

  Thereby, since an additional member is not required, it becomes possible to set it as an inexpensive structure. Even in a mechanical configuration, a simpler configuration can be achieved.

1 is a diagram illustrating a first configuration example of an image forming apparatus according to an embodiment. FIG. 6 is an equivalent circuit diagram for explaining a decrease in transfer voltage when moisture absorbent paper is used. It is a figure for demonstrating the problem which it is going to solve by this embodiment. It is an equivalent circuit diagram explaining the effect obtained by the first configuration example. It is a figure explaining one example of the 2nd example of composition of the image forming device of this embodiment. It is a figure explaining other examples of the 2nd example of composition of an image forming device of this embodiment. It is an equivalent circuit diagram explaining the effect acquired by the 2nd example of composition. 1 is a diagram illustrating an overall configuration of an image forming apparatus. FIG. 2 is a diagram illustrating a configuration of a fixing device applied to the image forming apparatus. It is a figure for demonstrating the "tailing" which is the conventional subject. It is a conceptual diagram of the general countermeasure with respect to the "tailing" which is the conventional subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic photosensitive drum 2 Charging member 10 Heater unit 11 Pressure roller 13 Paper discharge roller 33 Static elimination brush 20 High voltage power supply for primary charging 26 Discharge resistance 50 Fixing roller 90 CPU
DESCRIPTION OF SYMBOLS 100 Fixing film 102 Primer layer of fixing film 103 Release layer 130 of film 130 Film guide 155 Thermistor 170 Reinforcement sheet metal 207,208 Discharge resistance 209 High voltage capacitor 212 Heater 213 Commercial power supply 300 Transfer power supply 301 Resistance

Claims (9)

Charging means for charging the image carrier;
Exposure means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image as a toner image;
Transfer means for transferring the toner image onto a recording material;
Fixing means for fixing the toner image on the recording material by sandwiching and transporting the recording material between at least a heating member and a pressure member having an elastic layer, wherein the heating member is supplied with an AC voltage. An image forming apparatus comprising:
The fixing means;
Bias voltage generating means for applying a bias voltage to at least one surface of the heating member or the pressure member;
A conductive means for connecting the surface of the heating member or the pressure member and the bias voltage generating means;
An image forming apparatus, wherein a capacitive element is inserted between the conductive means and a ground potential.   The capacitance value of the capacitive element is selected such that the attenuation rate of the AC voltage at the transfer nip is the same as that when dry paper is used when moisture-absorbing paper is used. The image forming apparatus according to 1.   When the total value of the resistance value of the transfer roller and the output impedance of the transfer power source is 150 MΩ, and the resistance value of the recording material having a high moisture content in the length between the transfer nip and the fixing nip is 120 MΩ, the capacitive element is The image forming apparatus according to claim 2, wherein the image forming apparatus is a high-voltage ceramic capacitor of approximately 10,000 pF.   The image forming apparatus according to claim 1, wherein a resistance element is further inserted in series with the capacitive element between the conductive means and a ground potential.   5. The image forming apparatus according to claim 4, wherein a resistance value of the resistance element is selected such that a voltage applied to the glass coating is equal to or lower than a withstand voltage so as not to be destroyed even when a lightning surge voltage is applied. .   When the total value of the resistance value of the transfer roller and the output impedance of the transfer power source is 150 MΩ, and the resistance value of the recording material having a high moisture content in the length between the transfer nip and the fixing nip is 120 MΩ, the resistance element is 6. The image forming apparatus according to claim 5, wherein the resistance is approximately 1 MΩ.   5. The image forming apparatus according to claim 1, wherein the capacitive element and / or the resistive element is provided on a generation circuit board that provides the bias electricity generation unit. Charging means for charging the image carrier;
Exposure means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image as a toner image;
Transfer means for transferring the toner image onto a recording material;
Fixing means for fixing the toner image on the recording material by sandwiching and conveying the recording material between at least a heating member and a pressure member having an elastic layer, wherein the heating member is supplied with an AC voltage. A fixing bias output circuit for applying a bias voltage to at least one surface of the heating member or the pressure member in an image forming apparatus comprising:
A fixing bias output circuit, wherein a capacitive element is inserted between a conductive means for connecting a surface of the heating member or the pressure member and a bias voltage generating means and a ground potential.   9. The fixing bias output circuit according to claim 8, wherein a resistance element is further inserted in series with the capacitive element between the conductive means and the ground potential.

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