JP2022011570A - Fixing device and image forming apparatus - Google Patents

Abstract

To prevent the occurrence of AC banding.SOLUTION: A fixing device has: a rotating cylindrical film; a heater that includes a heat element (301) that generates heat upon energization and an insulator (304) that covers the heat element and is arranged inside the film; a slide member (605) that is arranged between the heater and the film and slid with an inner face of the film, the slide member having conductivity; a pressure member that is in pressure contact with the slide member with the film therebetween and forms a nip part with the slide member; and a conductive member that is connected with a ground potential through at least one impedance element (606). The fixing device heats to fix a toner image on a recording material to the recording material while sandwiching and conveying the recording material at the nip part. The slide member is electrically connected with the conductive member.SELECTED DRAWING: Figure 7

Description

The present invention relates to a fixing device used for an electrophotographic image forming apparatus and the like, and an image forming apparatus provided with the fixing device.

As a heat fixing type fixing device mounted on an electrophotographic printer or a copying machine, a heater having a heat generating resistor on a substrate made of ceramics or the like, a fixing film that moves while contacting the heater, and a fixing film are used. Some have a pressurizing roller facing the heater. The recording material that supports the unfixed toner image is heated while being sandwiched and conveyed by the nip portion (fixing nip portion) between the fixing film and the pressure roller, whereby the toner image on the recording material is heated and fixed to the recording material. Toner.

By the way, in the above-mentioned heat fixing type fixing device, a phenomenon called AC banding may occur when a recording material whose electric resistance is lowered by absorbing moisture by being left in a high temperature and high humidity environment for a long time is used. There is sex. When the recording material is sandwiched between the fixing nip parts while the toner image is being transferred, the AC voltage supplied from a commercial power source or the like to generate heat of the heater is transmitted to the transfer nip part via the recording material. It is superimposed on the DC voltage applied to the transfer member. In AC banding, the transfer current flowing between the transfer member and the image carrier fluctuates due to the waveform component of the AC voltage propagating through the recording material, causing uneven transferability, and as a result, the sub-scanning direction of the image. It means that an image defect of uneven shading appears in. Patent Document 1 proposes a technique of forming a conductive layer in the coated glass on the surface of a heater and grounding the conductive layer to reduce the influence of the AC voltage applied to the heating element on the transfer process. ..

Japanese Unexamined Patent Publication No. 2011-253072

The present invention is a further development of the above technique and provides a new configuration of a fixing device capable of suppressing the occurrence of AC banding.

One aspect of the present invention includes a rotating tubular film, a heat-generating resistor that generates heat by energization, and an insulator that covers the heat-generating resistor, and a heater arranged inside the film and the heater. A sliding member that is arranged between the film and the sliding member and slides on the inner surface of the film. It has a pressurizing member that forms a nip portion between the moving member and a conductive member that is connected to a ground potential via at least one impedance element, and the recording material is sandwiched and conveyed by the nip portion. It is a fixing device that heats a toner image on a recording material and fixes it to the recording material, wherein the sliding member is electrically connected to the conductive member. ..

According to the present invention, the occurrence of AC banding can be suppressed.

The schematic diagram of the image forming apparatus which concerns on Example 1. FIG. The schematic diagram for demonstrating the detail between transfer | fixation which concerns on a reference example. A cross-sectional view of a part of the fixing device according to the reference example. The equivalent circuit diagram of the image forming apparatus which concerns on a reference example. The figure which shows the voltage waveform in the transfer nip part which concerns on a reference example. FIG. 3 is a cross-sectional view of a part of the fixing device according to the first embodiment cut along the lateral direction. FIG. 3 is a cross-sectional view of a part of the fixing device according to the first embodiment cut along the longitudinal direction. The equivalent circuit diagram of the image forming apparatus which concerns on Example 1. FIG. FIG. 3 is a cross-sectional view of a part of the fixing device according to the second embodiment cut along the lateral direction. FIG. 3 is a cross-sectional view of a part of the fixing device according to the second embodiment cut along the longitudinal direction. The equivalent circuit diagram of the image forming apparatus which concerns on Example 2. FIG.

Hereinafter, exemplary embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration example of a laser beam printer (hereinafter referred to as a printer 118) as an image forming apparatus according to the first embodiment. The printer 118 performs a printing operation (also called an image forming operation or a paper passing operation) for forming an image on a recording material (also called a recording medium) based on image information input from an external information terminal via a network, for example. Execute. In addition to the single-function printer, the "image forming apparatus" includes a copying machine having a copying function and a multifunction device having a plurality of functions.

When the printing operation is started, the printer 118 picks up the recording materials 101 one by one from the feeding unit 116 by the feeding roller 102 and conveys them by the conveying rollers 103 and 104. When the transport of the recording material 101 is started, the passing of the front end and the rear end of the recording material 101 is detected by detecting the position of the paper passing detection flag 120 that swings in contact with the recording material 101 by an optical sensor or the like. Will be done. By detecting the tip of the recording material 101, the control unit of the printer 118 can determine the start timing of each electrophotographic process described below.

The process cartridge 109 is provided with a photosensitive drum 105 as an image carrier, a charging roller 106, and a developing roller 107, and a toner 108 as a developing agent is contained in the cartridge container. A high voltage is applied to the charging roller 106 at the start of the printing operation, and the surface of the photosensitive drum 105 is uniformly charged. Subsequently, the photosensitive drum 105 is irradiated with the laser beam 111 modulated based on the image information from the scanning optical device 110, and the image forming range is scanned and exposed, so that the charging pattern (electrostatic latent) corresponding to the image information is obtained. An image) is formed on the surface of the photosensitive drum 105. Due to the potential distribution on the surface of the photosensitive drum 105 and the high voltage applied to the developing roller 107, the toner carried on the developing roller 107 is transferred to the photosensitive drum 105, and the electrostatic latent image is developed to develop the toner image. It is visualized as.

The toner image formed on the surface of the photosensitive drum 105 is transferred to the recording material 101 by applying a high voltage to the transfer roller 112 as the transfer means. The recording material 1 to which the toner image is transferred is subjected to image fixing processing by a fixing device 125 including a heating device 113 and a pressurizing member 114. The recording material 101 that has passed through the fixing device 125 is discharged to the outside of the device by the discharge roller 115, and the image formation is completed. When continuously forming an image on a plurality of recording materials 101, it is possible to determine the transfer start timing of the next recording material 101 by detecting the rear end of the recording material 101 with the paper passing detection flag 120. Is. Further, the printer 118 is equipped with a fan 117. The fan 117 is provided to prevent the toner 108 from sticking in the process cartridge 109 due to the heat generated by the heating device 113, and to suppress heat generation of electrical components such as a power supply device.

The recording material 101 includes papers such as plain paper and cardboard, sheets with surface treatment such as plastic films, cloths, and coated papers, and sheets having a special shape such as envelopes and index papers, in size and material. A variety of different sheet materials can be used. Further, although the method of directly transferring the toner image from the photosensitive drum 105 to the recording material 101 is mentioned here, the method of transferring the toner image formed on the photoconductor to the recording material via an intermediate transfer body such as an intermediate transfer belt. The technique described below may be applied to the image forming apparatus.

Hereinafter, the details of the image forming apparatus of the reference example and the principle of AC banding generation will be described with reference to FIGS. 2 to 5. Most of the fixing device of the reference example and the fixing device according to the first embodiment have the same configuration.

(Details between transcription and fixation in the reference example)
First, the details from the transfer step to the fixing step in the image formation process will be described with reference to the schematic diagram of FIG. As described above, the toner image formed on the photosensitive drum 105 is transferred to the recording material 101 by the high voltage applied to the transfer roller 112. The transfer roller 112 is pressed against the photosensitive drum 105 to form a transfer nip Nt between the recording material 101 and the transfer roller 112. Further, a high DC voltage is applied to the transfer roller 112 by the transfer power supply 205. The high voltage (also referred to as transfer voltage) applied to the transfer roller 112 is a DC voltage having a polarity opposite to the normal charging polarity of the toner, which is a developer.

The toner image transferred onto the recording material 101 is conveyed to the right in FIG. 2 and reaches the fixing device 125. The heating device 113 of the fixing device 125 is composed of a heater 202, a sliding plate 203, a film 204, and a holding member 306 (see FIG. 3) that holds them. The pressurizing member 114 of the fixing device 125 is pressed against the heating device 113, and forms a fixing nip Nf between the recording material 101 and the pressurizing member 114.

A commercial power supply 201 and a control circuit 206 are connected to the heater 202. The heater 202 is driven by an AC voltage supplied from the commercial power source 201 to generate heat. The CPU 207 operates the control circuit 206 based on the temperature result of the temperature detecting element provided in the heating device 113, and controls the energization / shutoff of the heater 202 to keep the heating device 113 at a predetermined temperature. Take control. The temperature detecting element is, for example, a thermistor arranged between the heater 202 and the holding member 306.

The film 204 is made of a flexible and heat-resistant material formed into a tubular shape. For example, the film 204 is made of polyimide as a main material, and by adding a high thermal conductive filler made of conductive carbon, the thermal conductivity is improved and the film is conductive. Those with sex can be used. As the film 204, a film formed of an insulating resin material or a metal formed in a thin film form can also be used.

As shown in the figure, the recording material 101 is sandwiched between both the transfer nip Nt and the fixing nip Nf during the printing operation. In this state, the transfer power supply 205 and the fixing nip Nf are electrically connected to each other via the impedance of the recording material 101.

(Cross-sectional configuration of the fixing device according to the reference example)
Next, the cross-sectional configuration of the fixing device in the reference example will be described with reference to FIG. In the following description, the axial directions of X, Y, and Z are the same as those shown in FIG. 1 with respect to the shape of the members, the positional relationship between the members, and the like. That is, the longitudinal direction of the fixing nip Nf (the direction perpendicular to the transport direction of the recording material in the fixing nip Nf, the main scanning direction at the time of image formation) is defined as the "X-axis direction". Further, the directions perpendicular to each other in the plane perpendicular to the X-axis direction are defined as the Y-axis direction and the Z-axis direction.

FIG. 3 is a view of a cross section (short cross section) of the fixing device 125 according to a reference example cut in a virtual plane (YZ plane) perpendicular to the X-axis direction as viewed from the X-axis direction. In the heater 202, a heat generating resistor 301 that generates heat by energization and a conductor (not shown) for applying a voltage to the heat generating resistor 301 are arranged in the X-axis direction on a thin plate-shaped substrate 302 that is elongated in the X-axis direction. The formed one is used. The substrate 302 includes one using a ceramic material such as alumina and one using a metal material such as stainless steel. Hereinafter, the direction along the main surface of the substrate 302 and perpendicular to the longitudinal direction (X-axis direction) is referred to as the lateral direction of the heater 202.

In the region where the heat generation resistor 301 is formed when the substrate 302 is viewed in the thickness direction, the surface of the substrate 302 is coated with the coated glass 303, and the heat generation resistor 301 is formed on the coated glass 303. .. The coated glass 303 functions as an insulating layer that insulates the substrate 302 and the heat generation resistor 301 to which the commercial power supply voltage is applied. Further, the coated glass 304 is further coated on the heat generation resistor 301. The coated glass 304 is an insulator that insulates the heat generation resistor 301 and the conductive sliding plate 203, and also functions as a protective layer that protects the heat generation resistor 301. The coated glasses 303 and 304 may be formed by using an insulating material other than glass.

The holding member 306 holds the heater 202 and the sliding plate 203, and holds the film 204 rotatably inside the film 204. The sliding plate 203, which is a sliding member of this embodiment, is arranged between the heater 202 and the film 204 in a state of being held by the holding member 306 and in contact with the inner surface of the film 204. Therefore, the film 204 can rotate while sliding on the sliding plate 203 on the inner surface (inner peripheral surface).

The sliding plate 203 is arranged for soaking the heat of the heater 202 in the X-axis direction (longitudinal direction) (uniformizing the temperature distribution) and improving the sliding durability with the film 204, and is formed of, for example, a metal material. .. The heat-resistant film 204 slides while being consolidated by the pressure member 114 having an elastic layer on the exposed surface of the sliding plate 203. As the pressurizing member 114, for example, a roller member having a heat-resistant and elastic elastic layer such as silicon rubber formed on the outer peripheral portion of a metal columnar core metal can be used.

With such a pressure structure, the sliding plate 203 and the pressure member 114 are pressed against each other via the film 204, and a fixing nip Nf is formed between the sliding plate 203 and the pressure member 114. When the recording material 101 on which the unfixed toner image is formed is carried into the fixing nip Nf, the heat of the heat generating resistor 301 is transferred to the toner image on the recording material 101 via the sliding plate 203 and the film 204. Granted to 101. As a result, the toner melts, and then the toner cools and hardens, so that a fixed image fixed on the surface of the recording material 101 can be obtained.

Here, as shown as a virtual capacitor (broken line) in FIG. 3, the heat generation resistor 301 and the substrate 302, and the heat generation resistor 301 and the sliding plate 203 are capacitively coupled. Cg1 represents a capacitive component formed between the heat generation resistor 301 and the sliding plate 203 via the coated glass 304. Cg2 represents a capacitive component formed between the heat generation resistor 301 and the substrate 302 via the coated glass 303.

(Equivalent circuit of reference example)
FIG. 4 shows an equivalent circuit diagram electrically equivalent to an image forming apparatus in which a recording material 101 is sandwiched between a transfer nip Nt and a fixing nip Nf in a reference example. The transfer nip voltage VNt is applied to the transfer nip Nt by transmitting the DC voltage generated by the transfer power supply 205 via the impedance 401 of the transfer roller 112.

To the fixing nip Nf, the AC voltage of the commercial power supply 201 applied to the heat generation resistor 301 is transmitted to the sliding plate 203 via the capacitance Cg1 of the coated glass 304, and is applied from the sliding plate 203 as the fixing nip voltage VNf. The Rukoto. At this time, the transfer nip voltage VNt is affected by the fixing nip voltage VNf due to the impedance of the recording material 101. In a high humidity environment, the recording material 101 absorbs moisture and the impedance decreases. When the recording material 101 is sandwiched between both the transfer nip Nt and the fixing nip Nf in a state where the impedance is lowered, the fixing nip voltage VNf is superimposed on the transfer nip voltage VNt.

FIG. 5 is a diagram showing the measurement result of the voltage value at the transfer nip Nt. The period T1 in FIG. 5 is a period from when the tip of the recording material P rushes into the transfer nip Nt to when the tip of the recording material P rushes into the fixing nip Nf. The period T2 is a period after the tip of the recording material P has entered the fixing nip Nf and before the rear end of the recording material P has passed through the transfer nip Nt. As described above, when the vibrating fixing nip voltage VNf is superimposed on the transfer nip voltage VNt, the current (transfer current) flowing from the transfer nip Nt to the photosensitive drum 105 periodically vibrates at the commercial power frequency during the period T2. .. When the amplitude of such a transfer current becomes larger than the allowable range, density unevenness appears in the transferred toner image at intervals corresponding to the power frequency cycle of the commercial power supply 201. Such a phenomenon in which image density unevenness occurs at intervals corresponding to the power frequency cycle of the commercial power supply 201 is called AC banding.

(Cross-sectional configuration of the fixing device according to the first embodiment)
In order to deal with AC banding, in this embodiment, as shown in FIGS. 6 and 7, a configuration in which the sliding plate 605 is grounded via at least one impedance element is adopted. The "impedance element" is a general term for, for example, a resistor, a capacitor (capacitor), an inductor, or a combination thereof. In this embodiment, a resistor is used as the impedance element. Hereinafter, the elements having the same reference numerals as those of the reference example are assumed to have the same configuration and operation as those of the reference example, and the parts different from the reference example will be mainly described.

As shown in FIG. 6, the heater 202 of the present embodiment has a heat-generating resistor 301 that generates heat by energization and a conductivity for applying a voltage to the heat-generating resistor 301 on a thin plate-shaped substrate 602 elongated in the X-axis direction. A body (not shown) formed in the X-axis direction is used. The substrate 602 includes a substrate 602 using a ceramic material such as alumina and a substrate 602 using a metal material such as stainless steel. In this embodiment, a substrate 602 using a metal material will be described as an example.

In this embodiment, unlike the reference example, the sliding plate 605 and the substrate 602 are brought into contact with each other so as to be in a state of being electrically conductive. The substrate 602 is wider than the range of the coated glass 303 because the contact portion with the sliding plate 605 is provided. In other words, the range of formation of the insulating layer is limited to a part of the surface of the substrate 602. Since the sliding plate 605 of this embodiment is connected to the substrate 602, it has a U-shape (square C-shape) in the cross section (short cross section) seen in the X-axis direction. That is, in the sliding plate 605, the extending portions 605b and 605c extend from both ends of the surface 605a (the surface extending in the transport direction of the recording material in the fixing nip Nf) in contact with the inner surface of the film 204 in the direction away from the fixing nip Nf. Shape. Then, the extending portions 605b and 605c come into contact with the substrate 602 exposed outside the range of the coated glass 303, so that the sliding plate 605 and the substrate 602 are electrically connected. Since the substrate 602 is made of a metal material, the substrate 602 and the sliding plate 605 are electrically equipotential.

The connection configuration between the sliding plate 605 and the substrate 602 described above is an example, and for example, the protrusion provided on the substrate 602 may be brought into contact with the flat plate-shaped sliding plate 605. The extending portions 605b and 605c that come into contact with the substrate 602 may be provided over the entire area of the sliding plate 605 in the X-axis direction, or may be provided only in a part of the sliding plate 605 in the X-axis direction. Further, the means for electrically connecting the sliding plate 605 and the substrate 602 is not limited to the configuration in which the sliding plate 605 and the substrate 602 are brought into contact with each other in the short cross section.

FIG. 7 is a view of a cross section (longitudinal cross section) obtained by cutting a part of the fixing device 125 of this embodiment in a virtual plane (XZ plane) along the X-axis direction in the Y-axis direction, and is a grounding of the substrate 602. The configuration is shown. The conductor 701 is in contact with the end surface 602a of the substrate 602 in the X-axis direction (longitudinal direction). Since the end surface 602a of the substrate 602 is cut after firing the heat generation resistors 301 and the coated glasses 303 and 304, the insulating coating on the surface seen in stainless steel or the like is thin. Therefore, it is easy to secure an electrical connection with the conductor 701. The conductor 701 is preferably a metal member having a spring property (for example, a plate shape or a coil shape).

The conductor 701 is connected to one end of the resistor 606. The other end of the resistor 606 is connected to a grounded conductor 702, such as the metal frame of the fixing device 125 fixed to the body frame of the printer 118. As a method of connecting the conductors 701 and 702 and the resistor 606, for example, it is preferable to provide a notch in the conductors 701 and 702 to sandwich the terminal of the resistor 606, or to fix the conductors 606 with screws or the like to conduct the conductors. With these configurations, the substrate 602 is electrically connected to the ground potential via the resistor 606.

(Equivalent circuit of Example 1)
FIG. 8 shows an equivalent circuit diagram when the configuration of the first embodiment shown in FIGS. 6 and 7 is adopted. Unlike the case of the reference example shown in FIG. 5, the sliding plate 605 and the substrate 602 are connected and have the same electrical potential. Then, a current can be flowed in and out from the sliding plate 605 via the substrate 602 and the resistor 606. Therefore, the AC voltage applied from the heat generation resistor 301 to the heat generation resistor 301 via Cg1, which is a capacitive component of the coated glass 304, is less likely to affect the fixing nip Nf.

It is preferable to use a resistor 606 having a resistance value lower than that when the recording material 101 absorbs moisture. For example, if the impedance of the recording material 101 that has absorbed moisture is about 100 MΩ, it may be several MΩ to several tens of MΩ. As a result, even if the impedance of the recording material 101 is lowered due to the influence of moisture absorption, the influence of being superimposed on the transfer nip voltage VNt can be reduced, and the occurrence of AC banding can be suppressed.

By the way, if the resistor 606 is directly connected to the sliding plate 605 and is to be grounded, it is necessary to provide some kind of connection portion. In such a case, it is necessary to provide a shape for connection, but since the sliding plate 605 has a role of transferring heat from the heater 202 to the recording material 101, the heat transfer efficiency due to the increase in heat capacity as the parts become larger. There is a risk that the heat distribution will deteriorate and the balance (uniformity) of the heat distribution will be lost. Further, since the sliding plate 605 is arranged between the heater 202 and the film 204, it may be difficult to provide a connecting portion on the sliding plate 605. On the other hand, the substrate 602 is held by the holding member 306, and it is relatively easy to contact the substrate 602 from the surface on the non-coated glass side (the surface different from the surface facing the fixing nip Nf). Therefore, in this embodiment, the above-mentioned arrangement concern is solved by connecting the sliding plate 605 to the resistor 606 via the metal substrate 602.

As another method for dealing with AC banding, as in Patent Document 1, a conductive layer is formed in the glass coating of the heater, and the conductive layer is grounded. However, since the conductive layer is formed in the glass coating, the number of manufacturing processes increases, and the unit price of the heater parts increases. Further, since the contact portion with the conductive layer is formed on the heater, there is a concern that the amount of heat generated in the longitudinal direction may be uneven and the substrate area may increase. On the other hand, in this embodiment, these concerns are solved by grounding the conductive sliding plate 605.

(Modification example)
In the first embodiment described above, the conductor 701 is brought into contact with the end surface 602a in the X-axis direction (longitudinal direction) of the substrate 602 to be connected to the resistor 606, but is opposed to another side surface of the substrate 602 (for example, the fixing nip Nf). The conductor 701 may be brought into contact with the surface opposite to the surface to be used. Further, an opening may be provided in the coated glasses 303 and 304 on the substrate 602 so that the protrusion provided on the sliding plate 605 comes into contact with the substrate 602 through the opening.

Further, in the first embodiment, the sliding plate 605 is connected to the resistor 606 via the metal substrate 602 in consideration of the reason for arrangement, but the increase in heat capacity is within the permissible range even if the connecting portion is provided. When it fits, the sliding plate 605 may be connected to the ground potential without passing through the substrate 602. In that case, the substrate 602 may be formed of an insulating material such as ceramic. Further, even when connecting to the resistor 606 via the substrate 602, for example, the main body of the substrate 602 may be formed of an insulating material, and a conductive layer such as a metal thin film may be formed on the surface of the main body.

As the second embodiment, an embodiment in which the details of the grounding configuration are different from those of the first embodiment will be described with reference to FIGS. 9 to 11. Hereinafter, the elements having the same reference numerals as those in the first embodiment shall have substantially the same configuration and operation as those in the first embodiment, and the parts different from the first embodiment will be mainly described.

(Cross-sectional configuration of the fixing device according to the second embodiment)
FIG. 9 shows a cross-sectional view of the fixing device 125 according to the present embodiment. The heating device 113 of the fixing device 125 includes a heater 808, a sliding plate 805, a heat equalizing member 807, a film 204, and a holding member 806 for holding the heater 808. The heater 808 has a heat-generating resistor 801 that generates heat by energization and a conductor (not shown) for applying a voltage to the heat-generating resistor 801 on a thin plate-shaped substrate 802 that is elongated in the X-axis direction in the X-axis direction. The formed one is used. In this embodiment, a substrate 802 using a ceramic material such as alumina will be described as an example.

The surface of the substrate 802 is coated with coated glass 804 in the region where the heat generation resistor 801 is formed when the substrate 802 is viewed in the thickness direction. The coated glass 804 functions as an insulating layer that insulates the heat generation resistor 801 to which the commercial power supply voltage is applied and the conductive sliding plate 203, and also as a protective layer that protects the heat generation resistor 801.

The heat equalizing member 807 has a function of equalizing the temperature distribution in the longitudinal direction of the fixing nip Nf. The heat equalizing member 807 is a plate-shaped member using a high thermal conductive material such as aluminum, and is arranged between the heater 808 and the holding member 806. The heat equalizing member 807 aims to raise the temperature of the non-paper-passing region (the region outside the paper-passing region, which is the region through which the recording material passes during the printing operation in the X-axis direction), and to improve the unevenness of the detected temperature. It is a highly thermally conductive conductive material arranged in. As the heat soaking member 807, for example, a member extending in the X-axis direction over a range substantially the same as or including the heat generation resistor 801 in the X-axis direction can be used.

Here, as shown as a virtual capacitor (broken line) in FIG. 9, the heat generation resistor 801 and the sliding plate 805, and the resistance temperature detector 801 and the resistance temperature member 807 are capacitively coupled. Cg3 represents a capacitive component formed between the heat generation resistor 801 and the sliding plate 805 via the coated glass 804. Cc represents a capacitive component formed between the heat generation resistor 801 and the heat soaking member 807 via the substrate 802.

In this embodiment, the width of the heat equalizing member 807 is wider than the width of the substrate 802 with respect to the lateral direction of the substrate 802, and the sliding plate 805 is configured as the heat equalizing member via both sides of the substrate 802 in the lateral direction. It is in contact with 807. In other words, the sliding plate 805 has a U-shape (square C-shape) in the cross section (short cross section) seen in the X-axis direction in order to connect to the heat soaking member 807. That is, in the sliding plate 805, the extending portions 805b and 805c extend from both ends of the surface 805a (the surface extending in the transport direction of the recording material in the fixing nip Nf) in contact with the inner surface of the film 204 in the direction away from the fixing nip Nf. Shape. Then, the extending portions 805b and 805c are in contact with the heat equalizing member 807, so that the sliding plate 805 and the heat equalizing member 807 are electrically connected to each other. Since the heat equalizing member 807 is made of a conductive material, the heat equalizing member 807 and the sliding plate 805 are electrically at the same potential.

FIG. 10 is a view of a cross section (longitudinal cross section) obtained by cutting a part of the fixing device 125 of this embodiment in a virtual plane (XZ plane) along the X-axis direction in the Y-axis direction, and is a view of the heat equalizing member 807. Shows the grounding configuration of. The surface 807a of the heat equalizing member 807 on the side opposite to the contact surface (the surface on the fixing nip Nf side) with the substrate 802 is in contact with the conductor 1001 held by the holding member 806. The conductor 1001 is preferably a metal member having a spring property. The conductor 1001 is in contact with the heat equalizing member 807 at one end, and the other end is exposed to the outside of the holding member 806. With the above configuration, it is possible to secure a conduction path for grounding the sliding plate 805 inside the holding member 806, and it is possible to reduce the size.

In this embodiment, a capacitive impedance 1003 (capacitor) is used as the impedance element. The conductor 1001 is connected to one end of the capacitive impedance 1003. The other end of the capacitive impedance 1003 is connected to a grounded conductor 1002, such as the frame of the fixing device 125 fixed to the main body frame of the printer 118. As a method of connecting the conductors 1001 and 1002 and the capacitive impedance 1003, for example, it is preferable to provide a notch in the conductors 1001 and 1002 to sandwich the terminal of the capacitive impedance 1003 or to fix the conductor 1003 with a screw or the like to conduct the conductor. With these configurations, the heat soaking member 807 is electrically connected to the ground potential via the capacitive impedance 1003.

(Equivalent circuit of Example 2)
FIG. 11 shows an equivalent circuit diagram when the configuration of the second embodiment shown in FIGS. 9 and 10 is adopted. Unlike the case of the reference example shown in FIG. 5, the sliding plate 805 and the heat equalizing member 807 are connected and have the same potential electrically. Then, a current can flow in and out from the sliding plate 805 via the heat equalizing member 807 and the capacitive impedance 1003. Therefore, the AC voltage applied from the heat generation resistor 801 to the heat generation resistor 801 via Cg3, which is a capacitive component of the coated glass 804, is less likely to affect the fixing nip Nf.

The capacitive impedance 1003 makes the impedance at the commercial power frequency lower than the resistance value when the recording material 101 absorbs moisture. For example, assuming that the commercial power supply frequency is 50 Hz and the impedance of the recording material 101 is 100 MΩ, the capacitive impedance 1003 may be about several hundred pF. In addition, in the case of capacitive impedance, since it has frequency characteristics, the influence on each power supply should be selected so that it has a high impedance for the DC voltage of the transfer power supply 205 and a low impedance for the commercial power supply 201. Is possible.

The heat equalizing member 807 may be grounded via a circuit in which a resistor and a capacitive impedance are connected in series as in the first embodiment. As a result, even if the impedance of the recording material 101 is lowered due to the influence of moisture absorption, the influence of being superimposed on the transfer nip voltage VNt can be reduced, and the occurrence of image unevenness can be further suppressed.

(Modification example)
Not limited to the metal heater substrate described in the first embodiment and the heat equalizing member 807 described in the second embodiment, the sliding member may be grounded via another conductive member included in the fixing device. For example, when a metal stay fixed to the frame of the fixing device is provided as a reinforcing member for reinforcing the holding members 306 and 806 in the first and second embodiments, the sliding member is connected to this stay to form the stay. It may be grounded via an impedance element.

Further, in Examples 1 and 2, a plate-shaped sliding plate is exemplified as an example of the sliding member, but even a sheet-shaped member having thinner and more flexibility (for example, a sheet material of iron alloy or aluminum) may be used. good. Further, in Examples 1 and 2, a simple configuration in which the heater is connected to a commercial power source is adopted, but the configuration of this technology can be applied even in a configuration in which the heater is supplied with power from an AC power source different from the commercial power source to generate heat. be.

(Other embodiments)
Although the techniques according to the present disclosure have been described above by way of examples, the embodiments given here are merely examples. That is, the dimensions, materials, shapes, arrangements, operation modes, etc. of the components described in the embodiments should be appropriately changed depending on the conditions to which the present technology is applied, and are described in the claims. The contents given should not be construed as being limited to the embodiment.

114: Pressurizing member / 125: Fixing device / 202,808: Heater / 203,605,805: Sliding member (sliding plate) / 204: Film / 301: Heat generation resistor / 302,802: Substrate / 304, 804: Insulator / 606: Impedance element, Resistor / 807: Conductive member, Heat soaking member / 1003: Impedance element, Capacitor

Claims (10)

A rotating tubular film and
A heater arranged inside the film, including a heat-generating resistor that generates heat by energization and an insulator that covers the heat-generating resistor.
A sliding member that is arranged between the heater and the film and slides on the inner surface of the film, and has a conductive sliding member.
A pressure member that is pressed against the sliding member with the film sandwiched between them to form a nip portion between the sliding member and the sliding member.
A conductive member connected to a ground potential via at least one impedance element,
A fixing device that heats the toner image on the recording material and fixes it to the recording material while sandwiching and transporting the recording material between the nip portions.
The sliding member is electrically connected to the conductive member.
A fixing device characterized by that. The heater further includes a plate-shaped substrate made of metal and an insulating layer formed of an insulating material on the substrate, and the heat generation resistor is provided on the insulating layer.
The fixing device according to claim 1. The conductive member is the substrate.
The fixing device according to claim 2, wherein the fixing device is characterized by the above. The heater further includes a plate-shaped substrate made of an insulating material, and the heat generation resistor is provided on the substrate.
The fixing device according to claim 1. The conductive member is provided on the side opposite to the surface of the heater in contact with the sliding member with respect to the heater, and is a heat equalizing member for making the temperature distribution in the longitudinal direction of the nip portion uniform.
The fixing device according to claim 1. The conductive member is a reinforcing member that reinforces the fixing device.
The fixing device according to claim 1. The at least one impedance element comprises a resistor.
The fixing device according to any one of claims 1 to 6, wherein the fixing device is characterized by the above. The at least one impedance element comprises a capacitor.
The fixing device according to any one of claims 1 to 7, wherein the fixing device is characterized by the above. The at least one impedance element comprises a resistor and a capacitor connected in series.
The fixing device according to any one of claims 1 to 6, wherein the fixing device is characterized by the above. With a rotating image carrier,
A transfer means for transferring a toner image supported on the surface of the image carrier to a recording material by applying a transfer voltage.
The fixing device according to any one of claims 1 to 9, wherein the toner image transferred to the recording material by the transfer means is fixed to the recording material.
An image forming apparatus comprising.

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