Image forming apparatus

Abstract

To provide a technique that enables a reduction of radiation noise generated when a low-voltage power supply board energizes a heating unit with AC voltage.SOLUTION: A printer 1 comprises: a fixing device 8 that has a fixing ground unit 80 that is connected to a heating unit 81 and a pressure roller 82; a low-voltage power supply unit 44 that has a low-voltage power supply board 110 that supplies AC voltage of an external commercial power supply 250 switched by a switching element 110F to a heater 90, and a power supply ground unit 44C that is connected to the ground of the external commercial power supply 250; and a main board 100 that has external connectors 130, 131 that allow connection to a PC 300 and a main board ground unit 107 that is connected to the power supply ground unit 44C, wherein ground terminals of the external connectors 130, 131 are connected to the main board ground unit 107. The fixing ground unit 80 is connected to the power supply ground unit 44C of the low-voltage power supply unit 44 without passing through the main board ground unit 107.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present application relates to an image forming apparatus including a fixing device that fixes a developer image formed on a sheet to the sheet.

Background Art

[0002] A fixing device that thermally fixes a developer image formed on a sheet is connected to the ground portion of an external commercial power supply via a sheet metal member. Patent Document 1 describes a fixing device configured to be grounded using leaf spring members provided on the left and right sides of the apparatus main body. On the other hand, there is also an image forming apparatus in which the ground portion of the fixing device is connected to the ground portion of the main board.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a conventional image forming apparatus in which the ground portion of the fixing device is connected to the ground portion of the main board, when an AC voltage is applied from the low-voltage power supply board to the heating portion via a heater harness, noise components generated by the large current flowing through the fixing device flow in the order of the main board ground portion, the ground terminal of the external connector of the main board, the ground of an external terminal such as a PC, the external commercial power supply, the ground wire of the power cable, and the power ground portion of the low-voltage power supply board. Therefore, there has been a problem that radiated noise is generated from the formed route.

[0005] An object of the present application is to provide a technique capable of reducing radiated noise generated when an AC voltage is applied from a low-voltage power supply board to a heating portion.

Means for Solving the Problems

[0006] To achieve the above object, the image forming apparatus of the present application includes a main body housing, an image forming unit that forms a developer image on a sheet, and a fixing device that thermally fixes the developer image formed on the sheet. The fixing device includes a heating unit having a heater, a pressurizing rotating body that presses the sheet against the heating unit, and a fixing ground unit connected to the heating unit and the pressurizing rotating body. The image forming apparatus further includes a low-voltage power supply board having a switching element that switches an AC voltage input from an external commercial power supply via a power cable, a power ground unit connected to the ground of the external commercial power supply via the power cable, a low-voltage power supply unit that supplies the AC voltage switched by the switching element to the heater, a control unit that controls the image forming unit and the switching element, an external connector that can be connected to an external terminal when a cable is connected, and a main board ground unit connected to the power ground unit of the low-voltage power supply unit. The image forming apparatus includes a main board to which the ground terminal of the external connector is connected to the main board ground unit. The fixing ground unit is connected to the power ground unit of the low-voltage power supply unit without passing through the main board ground unit.

[0007] In a configuration where the fixing ground unit is connected to the main board ground unit, when an AC voltage is applied from the low-voltage power supply board to the heating unit via a heater harness, noise components generated by a large current flowing through the fixing device flow in the order of the fixing ground unit, the main board ground unit, the ground terminal of the external connector of the main board, the ground of an external terminal such as a PC, the external commercial power supply, the ground wire of the power cable, and the power ground unit of the low-voltage power supply unit, and a route is formed that returns from the ground of the external commercial power supply to the power ground unit. Therefore, there is a problem that radiated noise is generated from the formed route.

[0008] Therefore, in the image forming apparatus of the present application, since the fixing ground unit is connected to the power ground unit without passing through the main board ground unit, the route returning from the fixing ground unit to the power ground unit via the external commercial power supply can be shortened, and thus the radiated noise from the formed route can be suppressed.

[0009] Further, the low-voltage power supply unit has an enclosure that covers the low-voltage power supply substrate, and the power supply ground unit is provided in the enclosure and is connected to the ground unit of the low-voltage power supply substrate, which is characterized in that.

[0010] The power supply ground unit is provided in the enclosure that covers the low-voltage power supply substrate. Since the distance between the power supply ground unit and the fixing ground unit can be shortened, the noise radiated on the route between the fixing ground unit and the power supply ground unit can be suppressed.

[0011] Further, the low-voltage power supply unit is disposed on one surface side of the main body housing, the main board is disposed on the other surface side of the main body housing, the fixing device is disposed so as to be parallel to the direction from one surface side to the other surface side, and includes a heater harness extending from the low-voltage power supply substrate. The AC voltage is supplied from the low-voltage power supply substrate to the heater via the heater harness. The end of the heater harness is connected to a position on one surface side of the fixing device, and the fixing ground unit is connected to the power supply ground unit of the low-voltage power supply unit, which is characterized in that.

[0012] Further, one surface of the main body housing is disposed opposite to the other surface of the main body housing. The low-voltage power supply unit is disposed such that the substrate surface of the low-voltage power supply substrate is parallel to one surface of the main body housing, and the main board is disposed such that its substrate surface is parallel to the other surface of the main body housing, which is characterized in that.

[0013] Since the distance between the fixing ground unit of the fixing device and the power supply ground unit of the low-voltage power supply unit disposed on one surface side can be shortened, the noise radiated on the route between the fixing ground unit and the power supply ground unit can be suppressed.

[0014] Further, the power supply ground unit of the low-voltage power supply unit is connected to the main board ground unit via a sheet metal member extending from one surface of the main body housing to the other surface, which is characterized in that.

[0015] Further, the image forming unit includes a photosensitive drum, a charger for charging the photosensitive drum, a developing unit for supplying a developer to an electrostatic latent image formed on the charged photosensitive drum to form a developer image, and a transfer member disposed opposite to the photosensitive drum for transferring the developer image to a sheet passing through a transfer nip portion between the photosensitive drum. The image forming apparatus further includes a high-voltage power supply board for applying a charging voltage to the charger and a transfer voltage to the transfer member respectively. The ground portion of the high-voltage power supply board is connected to a power ground portion provided in the enclosure, which is characterized in that.

[0016] Further, the external connector is a USB connector to which a USB cable can be connected, which is characterized in that. Since the fixing ground portion is connected to the power ground portion without passing through the main board ground portion, when a USB cable is connected to the USB connector of the main board, the route from the fixing ground portion back to the power ground portion via the external commercial power supply can be shortened.

[0017] Further, the external connector is a LAN connector to which a LAN cable can be connected, which is characterized in that. Since the fixing ground portion is connected to the power ground portion without passing through the main board ground portion, when a LAN cable is connected to the LAN connector of the main board, the route from the fixing ground portion back to the power ground portion via the external commercial power supply can be shortened.

[0018] Further, the heater has a substrate and a resistive heating element to which an AC voltage is applied and formed on the substrate. The heating portion has an endless belt that rotates around the heater. The pressure rotating body forms a nip portion by sandwiching the belt between the heater. The pressure rotating body has a conductive shaft extending in the rotation axis direction of the pressure rotating body and an elastic layer covering the outer peripheral surface of the shaft. The fixing device further includes a grounding circuit connected to the heating portion and the pressure rotating body. The fixing ground portion is connected to the grounding circuit, which is characterized in that.

[0019] Further, the fixing device further includes a rectifying element in which the cathode is connected to the shaft of the pressure rotating body and the anode is connected to the belt of the heating unit. The grounding circuit has one end connected to the anode of the rectifying element and the other end connected to the ground. A capacitance element and a first resistance element are connected in series between the one end and the other end, and a second resistance element is connected in parallel to the capacitance element and the first resistance element. This is the gist of the invention.

[0020] Further, the heating unit further includes a heating rotating body heated by a heater. The pressure rotating body forms a nip portion with the heating rotating body, and the fixing ground portion is connected to the pressure rotating body. This is the gist of the invention.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present application will be described in detail with reference to the drawings.

[0023] FIG. 1 is a cross-sectional view showing a schematic configuration of a monochrome laser printer 1 according to an embodiment of the present application. The monochrome laser printer 1 is an example of an image forming apparatus. Hereinafter, the monochrome laser printer 1 will be abbreviated as the printer 1. In the following description, as shown in FIG. 1, the description will be based on the direction viewed from the user who uses the printer 1. That is, in FIG. 1, the right side is referred to as "front", the left side is referred to as "rear", the upper side is referred to as "upper", the lower side is referred to as "lower", the front side is referred to as "left", and the back side is referred to as "right".

[0024] As shown in FIG. 1, the printer 1 includes a main body housing 2, a sheet supply unit 3, a process unit PR, and a fixing device 8.

[0025] The sheet supply unit 3 is a mechanism for supplying the sheet S to the process unit PR, and is provided in the lower part of the main body housing 2. The sheet supply unit 3 includes a supply tray 31 for accommodating the sheet S, a sheet pressing plate 32, and a sheet supply mechanism 33. The sheet supply mechanism 33 includes a pickup roller 33A, a separation roller 33B, a first conveyance roller 33C, and a registration roller 33D. In the sheet supply unit 3, the sheet S in the supply tray 31 is brought close to the pickup roller 33A by the sheet pressing plate 32 and sent to the separation roller 33B by the pickup roller 33A. The sheet S is separated into single sheets by the separation roller 33B and conveyed by the first conveyance roller 33C. After aligning the positions of the leading ends of the sheets S, the registration roller 33D conveys the sheet S toward the process unit PR. Here, the direction in which the sheet S is conveyed is referred to as the conveyance direction, and the direction orthogonal to the conveyance direction in the plane of the sheet S is referred to as the width direction. Hereinafter, the width direction of the sheet S will be simply referred to as the "width direction".

[0026] The process unit PR has a function of forming a toner image on the sheet S supplied from the sheet supply unit 3. The process unit PR is a toner image forming unit. The process unit PR includes an exposure device 4 and a process cartridge 5.

[0027] The exposure device 4 is disposed at the upper part inside the main body housing 2 and includes a laser light source (not shown), a polygon mirror (shown with symbols omitted), a lens, a reflecting mirror, and the like. In the exposure device 4, laser light based on image data is emitted from the laser light source as shown by the dashed line and scanned on the surface of the photosensitive drum 61, thereby exposing the surface of the photosensitive drum 61.

[0028] The process cartridge 5 is disposed below the exposure device 4 and is detachable from the main body housing 2 through an opening formed when the front cover 21 provided on the main body housing 2 is opened. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

[0029] The drum unit 6 includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is detachable from the drum unit 6 and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, a toner storage portion 74 for storing toner which is dry toner, and an agitator 75.

[0030] In the process cartridge 5, after the surface of the photosensitive drum 61 is uniformly positively charged by the charger 62, it is exposed by the laser light from the exposure device 4, thereby forming an electrostatic latent image based on the image data on the photosensitive drum 61. Further, the toner in the toner storage portion 74 is supplied to the developing roller 71 through the supply roller 72 while being agitated by the agitator 75, and enters between the developing roller 71 and the layer thickness regulating blade 73 as the rotation of the developing roller 71 progresses and is carried on the developing roller 71 as a thin layer of a certain thickness.

[0031] The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized, and a toner image is formed on the photosensitive drum 61. Then, the sheet S supplied from the sheet supply unit 3 is conveyed through the transfer nip TN between the photosensitive drum 61 and the transfer roller 63, so that the toner image formed on the photosensitive drum 61 is transferred onto the sheet S.

[0032] The fixing device 8 fixes the toner image on the sheet S. The fixing device 8 includes a heating unit 81 and a pressure roller 82. One of the heating unit 81 and the pressure roller 82 is biased against the other by a biasing mechanism (not shown). In the fixing device 8, the sheet S onto which the toner image is transferred is conveyed between the heating unit 81 and the pressure roller 82, so that the toner image is thermally fixed on the sheet S. The sheet S on which the toner image is thermally fixed is discharged onto the discharge tray 22 by the second conveying roller 23 and the discharge roller 24. A fixing ground portion 80 is provided in the fixing device 8. The grounding of various electronic components mounted on the fixing device 8 is performed via the fixing ground portion 80. The detailed configuration of the fixing device 8 will be described later with reference to FIGS. 3 and 4.

[0033] Next, the electrical configuration of the printer 1 will be described with reference to FIG. 2. As shown in FIG. 2, the printer 1 further includes a control unit 101, a ROM 102, a RAM 103, a non-volatile memory 104, a pre-registration sensor SE1, a post-registration sensor SE2, a discharge sensor SE3, a LAN connector 130, and a USB connector 131. The control unit 101, the ROM 102, the RAM 103, and the non-volatile memory 104 are mounted on the main board 100. Further, a main board ground portion 107 is provided on the main board 100. The main board ground portion 107 is a member that serves as the reference potential for the circuit operation of the mounted components such as the control unit 101 and the ROM 102.

[0034] The control unit 101 is composed of, for example, an ASIC, and performs overall control of each part of the printer 1. The control unit 101 is equipped with a LAN I / F 105 for data exchange with an external device connected to the LAN connector 130, for example, a PC 300 (see FIG. 6), via a LAN cable 230, and a USB I / F 106 for data exchange with an external device connected to the USB connector 131, for example, a PC 300 (see FIG. 6), via a USB cable 231. The LAN connector 130 is provided with a ground terminal 130B. The ground terminal 130B and the LAN I / F 105 are connected via a ground wire 130A. The LAN I / F 105 is electrically connected to the main board ground part 107. The main board ground part 107 is a member that serves as the reference potential for the circuit operation of the LAN I / F 105. Similarly, the USB connector 131 is also provided with a ground terminal 131B, and the ground terminal 131B and the USB I / F 106 are connected via a ground wire 131A. The main board ground part 107 is a member that serves as the reference potential for the circuit operation of the USB I / F 106.

[0035] In addition, the control unit 101 is electrically connected to a ROM 102, a RAM 103, a non-volatile memory 104, a main motor 108, a pre-registration sensor SE1, a post-registration sensor SE2, a fixing device 8, a low-voltage power supply unit 44, and a high-voltage power supply board 112.

[0036] The ROM 102 stores various control programs for controlling the printer 1, various settings, and the like.

[0037] The RAM 103 is used as a work area from which various control programs are read, and a storage area for temporarily storing image data included in a print job. The control unit 101 controls each part of the printer 1 while storing the processing results in the RAM 103 or the non-volatile memory 104 according to the control programs read from the ROM 102 and the signals output from various sensors.

[0038] The low-voltage power supply unit 44 includes a box-shaped metal enclosure 44A (see FIG. 5) and a low-voltage power supply board 110. The low-voltage power supply unit 44 has the low-voltage power supply board 110 inside the enclosure 44A.

[0039] The main body housing 2 is provided with an inlet 200. The inlet 200 is for inputting an AC voltage (for example, AC100V) supplied by an external commercial power supply. A power cable 210 having a power plug P is connected to the inlet 200. The power plug P consists of three terminals including an earth terminal, and the power cable 210 consists of three cores: a live-side cable PCL, a neutral-side cable PCN, and an earth cable EC. Then, the live-side cable PCL and the neutral-side cable PCN are connected to the connector 110A of the low-voltage power supply board 110 via the inlet 200. Also, the earth cable EC is connected to a power ground portion 44C provided in the enclosure 44A via the inlet 200. The power ground portion 44C is connected to the ground portion 110C of the low-voltage power supply unit 44 via the enclosure 44A and a metal leg 44B (see FIG. 5).

[0040] By connecting the earth cable EC to the power ground portion 44C, the ground portion 110C of the low-voltage power supply board 110 is grounded. The detailed configuration of the low-voltage power supply unit 44 will be described later with reference to FIG. 5.

[0041] The live-side terminal T11 of the connector 110A is connected to the live-side terminal T21 of the connector 110B via a relay 110E, and the neutral-side terminal T12 of the connector 110A is connected to the neutral-side terminal T22 of the connector 110B via a switching element 110F. Then, the live-side terminal T21 of the connector 110B is connected to one power supply terminal PT1 of the heater 90, and the neutral-side terminal T22 of the connector 110B is connected to the other power supply terminal PT2 of the heater 90.

[0042] The control unit 101 outputs a control signal toward the low-voltage power supply board 110. The relay 110E is for turning on / off the AC100V input. The control unit 101 performs on / off control of the relay 110E by the control signal. The switching element 110F is an element including, for example, a triac or the like. The control unit 101 controls the switching element 110F by the control signal. The control unit 101 performs phase control and frequency control of AC100V by the control signal, and adjusts the amount of power supplied to the heater 90.

[0043] Also, an AC-DC conversion circuit 110D is provided on the low-voltage power supply board 110. The AC100V input to the connector 110B of the low-voltage power supply board 110 is also input to the AC-DC conversion circuit 110D (not shown), and the AC-DC conversion circuit 110D converts the AC100V into a DC voltage, for example, DC24V. The low-voltage power supply board 110 outputs the converted DC24V to the main board 100 and the high-voltage power supply board 112.

[0044] The high-voltage power supply board 112 boosts the DC24V from the low-voltage power supply board 110 to generate a high voltage. A charging voltage application circuit 112A, a developing voltage application circuit 112B, and a transfer voltage application circuit 112C are provided on the high-voltage power supply board 112. The charging voltage application circuit 112A applies a positive-polarity charging voltage to the charger 62. The charging voltage is, for example, from 5kV to 8kV. The developing voltage application circuit 112B applies a positive-polarity developing voltage to the developing roller 71. The developing voltage is, for example, from 300V to 500V.

[0045] The transfer voltage application circuit 112C applies a transfer voltage to the transfer roller 63. The control unit 101 controls the transfer voltage using the transfer voltage application circuit 112C so that the current flowing through the transfer roller 63 becomes a predetermined current value. At this time, the transfer voltage is a negative-polarity voltage and has a value of about minus (-) several thousand volts.

[0046] The high-voltage power supply board 112 is further provided with a ground portion 112D that serves as the reference potential for the circuit operations of mounted components such as the charging voltage application circuit 112A, the developing voltage application circuit 112B, and the transfer voltage application circuit 112C. The ground portion 112D of the high-voltage power supply board 112 is a member that serves as the reference potential for the circuit operations of mounted components such as the charging voltage application circuit 112A.

[0047] The main motor 108 transmits a driving force to the roller group 35, the pressure roller 82, and the photosensitive drum 61. The roller group 35 includes a pickup roller 33A, a first conveyance roller 33C, a registration roller 33D, a developing roller 71, a second conveyance roller 23, a discharge roller 24, and the like. When the control unit 101 drives the main motor 108, a driving force is transmitted to the roller group 35, the pressure roller 82, and the photosensitive drum 61. Then, the roller group 35, the pressure roller 82, and the photosensitive drum 61 rotate in a direction to convey the sheet S in the conveyance direction.

[0048] The pre-registration sensor SE1 is a sensor that is disposed upstream of the registration roller 33D in the conveyance path 40 and detects the passage of the sheet S. As the pre-registration sensor SE1, a sensor having an actuator that swings when the sheet S abuts, an optical sensor, or the like can be used. The pre-registration sensor SE1 outputs an on signal when the sheet S is passing and an off signal when the sheet S is not passing. The detection signal from the pre-registration sensor SE1 is output to the control unit 101.

[0049] The post-registration sensor SE2 is a sensor that is disposed upstream of the fixing device 8 in the conveyance path 40, specifically, between the registration roller 33D and the transfer roller 63, and detects the passage of the sheet S. The post-registration sensor SE2 has the same configuration as the pre-registration sensor SE1. The detection signal from the post-registration sensor SE2 is output to the control unit 101.

[0050] The discharge sensor SE3 is disposed between the nip portion NP and the second conveying roller 23 in the conveying path 40, and detects the passage of the sheet S. The discharge sensor SE3 has the same configuration as the pre-registration sensor SE1. The detection signal from the discharge sensor SE3 is output to the control unit 101.

[0051] FIG. 3 shows a schematic configuration of the fixing device 8. As shown in FIG. 3(a), the fixing device 8 includes a heating unit 81, a pressure roller 82 as an example of a pressure rotating body, a diode 85 as a rectifying element, a static eliminator brush 83, and a grounding circuit 87. One of the heating unit 81 and the pressure roller 82 is biased against the other by a biasing mechanism (not shown) as described above.

[0052] The heating unit 81 includes a heater 90, a belt 81A, a holder 81B, and a stay 81C. The heater 90 is a flat heater that heats the sheet S via the belt 81A, and is supported by the holder 81B. The structure of the heater 90 will be described later with reference to FIG. 4.

[0053] The holder 81B is made of, for example, resin, and contacts the inner peripheral surface 81A1 of the belt 81A to guide the belt 81A. The stay 81C is a member that supports the holder 81B, and is formed by bending a plate material having higher rigidity than the holder 81B, such as a steel plate, into a U-shaped cross section.

[0054] The belt 81A is an endless belt having heat resistance and flexibility, and is made of metal or resin. The heater 90, the holder 81B, and the stay 81C are disposed inside the belt 81A, and the belt 81A is configured to rotate around the heater 90 and the holder 81B. The inner peripheral surface 81A1 of the belt 81A contacts the heater 90, and the outer peripheral surface 81A2 of the belt 81A contacts the pressure roller 82 or the sheet S.

[0055] As shown in Fig. 3(b), the pressing roller 82 has a columnar shaft 82A and a cylindrical roller portion 82B. The shaft 82A is made of, for example, metal. The roller portion 82B, which is an example of an elastic layer, is an elastic layer that covers a part of the shaft 82A and is made of, for example, rubber. The pressing roller 82 forms a nip portion NP (see Fig. 3(a)) for heating and pressing the sheet S by sandwiching the belt 81A between itself and the heater 90.

[0056] The cathode of the diode 85 is connected to the shaft 82A of the pressing roller 82 via the first sheet metal member PL1. The anode of the diode 85 is connected to one terminal T1 of the grounding circuit 87 via the second sheet metal member PL2.

[0057] The static eliminator brush 83 is for eliminating static electricity from the belt 81A and is composed of a brush portion 83A made of a plurality of conductive fibers. And, as shown in Fig. 3(b), the brush portion 83A contacts the surface of the longitudinal end of the belt 81A. One end 83B, which is on the side opposite to the brush portion 83A of the static eliminator brush 83, is connected to the second sheet metal member PL2 via the third sheet metal member PL3. One end 83B of the static eliminator brush 83 is connected to one terminal T1 of the grounding circuit 87 via the third sheet metal member PL3 and the second sheet metal member PL2. Note that the first to third sheet metal members PL1 to PL3 are not limited to sheet metal members and may be conductive wires.

[0058] The grounding circuit 87 is a circuit for grounding (earthing) the belt 81A, which is the heating portion 81, and the pressing roller 82. The grounding circuit 87 has two terminals T1 and T2. One terminal T1 is connected to the anode of the diode 85 via the second sheet metal member PL2 as described above, and the other terminal T2 is connected to the fixing ground portion 80.

[0059] The fixing ground portion 80 is electrically connected to the power supply ground portion 44C via a sheet metal member 45A, which will be described later, and a box-shaped metal enclosure 44A. Therefore, the fixing ground portion 80 is grounded (earthed), and the other terminal T2 of the grounding circuit 87 is grounded (earthed).

[0060] The grounding circuit 87 is configured by connecting a capacitor C and a first resistor R1 in series between one terminal T1 and the other terminal T2, and connecting a second resistor R2 in parallel therewith. The resistance value of the first resistor R1 is, for example, a value in the range of 1 kΩ to 1000 kΩ, and the resistance value of the second resistor R2 is, for example, a value in the range of 10 MΩ to 100 MΩ. Depending on the size of the first resistor R1 or the second resistor element, the voltage generated between the terminal T1 and the fixing ground portion 80 becomes a value close to 0V.

[0061] When the amount of charge flowing toward the grounding circuit 87 temporarily increases, it flows to the fixing ground portion 80 via the capacitor C and the first resistor R1. In the case of the charge constantly flowing toward the grounding circuit 87, the charge does not flow through the capacitor C, and the charge flows to the second resistor R2 having a larger resistance value than the first resistor R1.

[0062] The belt 81A is connected to the grounding circuit 87 via the static eliminator brush 83, so that the surface potential of the belt 81A becomes substantially 0V. The pressure roller 82 is connected to the grounding circuit 87 via the diode 85, and the cathode of the diode 85 is connected to the pressure roller 82. Depending on the connection direction of the diode 85 and the value of the reverse breakdown voltage of the diode 85, the surface potential of the pressure roller 82 is shifted by the reverse breakdown voltage of the diode 85 from the potential of the fixing ground portion 80 and becomes about several hundred V negative (minus).

[0063] FIG. 4 shows a schematic configuration of the heater 90. FIG. 4(a) is a plan view of the heater 90, and FIG. 4(b) is a cross-sectional view taken along the A-A arrow in FIG. 3(b). As shown in FIG. 4(a), the heater 90 includes a substrate 91, a resistance heating element 92 composed of a first resistance heating element 92A and a second resistance heating element 92B, conductive wires 93A to 93C, and power supply terminals PT1 and PT2.

[0064] The substrate 91 is made of an elongated rectangular plate of ceramic with aluminum oxide as the material. On the surface 91A of the substrate 91, a linear first resistance heating element 92A and a second resistance heating element 92B are formed in parallel, for example, by printing copper paste. The first resistance heating element 92A and the second resistance heating element 92B each extend in the longitudinal direction of the substrate 91, which is parallel to the axial direction of the roller portion 82B, and are formed apart from each other in the short direction perpendicular to the longitudinal direction. The lengths of the first resistance heating element 92A and the second resistance heating element 92B in the longitudinal direction are longer than the length in the width direction of the sheet S.

[0065] One end 92A1 of the first resistance heating element 92A is connected to the power supply terminal PT1 via the conducting wire 93A, and one end 92B1 of the second resistance heating element 92B is connected to the power supply terminal PT2 via the conducting wire 93B. Then, the other end 92A2 of the first resistance heating element 92A and the other end 92B2 of the second resistance heating element 92B are connected via a U-shaped conducting wire 93C. The power supply terminals PT1 and PT2 are for inputting AC100V. When AC100V is input from the power supply terminals PT1 and PT2, the first resistance heating element 92A and the second resistance heating element 92B generate heat. Incidentally, the first resistance heating element 92A and the second resistance heating element 92B are sealed by the glass material 94.

[0066] Two thermistors TH1 and TH2 are provided in contact with the back surface 91B of the substrate 91. One thermistor TH1 is provided in contact with approximately the center in the longitudinal direction of the back surface 91B of the substrate 91, and the other thermistor TH2 is provided in contact with the vicinity of one end in the longitudinal direction of the back surface 91B of the substrate 91 (see Fig. 3(b)). The thermistors TH1 and TH2 detect the temperature of the heater 90 and output it to the control unit 101 as a temperature signal. The control unit 101 controls the temperature of the heater 90 to reach the target temperature based on the temperature signals from the thermistors TH1 and TH2. Incidentally, the number of the thermistors TH1 and TH2 is not limited to two, and may be one or three or more.

[0067] The heater 90 is supported by the holder 81B such that its surface 91A faces the inner peripheral surface 81A1 of the belt 81A (see Fig. 3(a)).

[0068] FIG. 5 schematically shows the internal configuration of the printer 1. As shown in FIG. 5, the printer 1 includes a first resin frame 49A and a second resin frame 49B inside the main body housing 2. The first resin frame 49A is disposed at a position close to the right side wall 2A of the main body housing 2, and the second resin frame 49B is disposed at a position close to the left side wall 2B of the main body housing 2.

[0069] Inside the first and second resin frames 49A and 49B, a process unit PR and a fixing device 8 are disposed. Both the process unit PR and the fixing device 8 are disposed parallel to the direction from the right side wall 2A to the left side wall 2B.

[0070] Outside the first resin frame 49A and at the rear part inside the main body housing 2, a low-voltage power supply unit 44 is installed. The low-voltage power supply unit 44 includes a box-shaped metal enclosure 44A that covers a low-voltage power supply board 110. The low-voltage power supply board 110 is fixed, for example, to metal legs 44B provided inside the enclosure 44A so that its board surface is parallel to the right side wall 2A. The ground portion 110C of the low-voltage power supply board 110 is at the four corners of the board surface of the low-voltage power supply board 110. The ground portions 110C of the low-voltage power supply board 110 at the four corners are fixed to the metal legs 44B with screws.

[0071] A power supply ground portion 44C is provided on the rear side wall of the enclosure 44A, and a ground cable EC of a power cable 210 is connected to the power supply ground portion 44C. The ground portion 110C of the low-voltage power supply board 110 is grounded by being connected to the power supply ground portion 44C of the low-voltage power supply unit 44 via the legs 44B and the enclosure 44A.

[0072] The low-voltage power supply board 110 and the fixing device 8 are connected via a heater harness HH extending from a connector 110B (see FIG. 2) of the low-voltage power supply board 110. And the end HH1 of the heater harness HH is connected to a position on the right side wall 2A side of the fixing device 8.

[0073] A sheet metal member 45A for connecting the fixing ground portion 80 and the enclosure 44A is provided. The fixing ground portion 80 is connected to the power supply ground portion 44C via the sheet metal member 45A and the enclosure 44A. As a result, the fixing ground portion 80 is grounded, and the other terminal T2 of the ground circuit 87 connected to the fixing ground portion 80 is also grounded.

[0074] Also, a high-voltage power supply board 112 is installed outside the first resin frame 49A and at the front part inside the main body housing 2. The ground portion 112D of the high-voltage power supply board 112 is screwed to a metal plate 45B at the corner of the board surface. The ground portion 112D of the high-voltage power supply board 112 and the enclosure 44A of the low-voltage power supply unit 44 are connected via the plate 45B. The ground portion 112D of the high-voltage power supply board 112 is connected to the power supply ground portion 44C via the plate 45B and the enclosure 44A.

[0075] Furthermore, the first resin frame 49A is also formed with bearings (not shown) for receiving the right side of the rotating shafts of the photosensitive drum 61 and transfer roller 63 (not shown in FIG. 5) of the process unit PR, and bearings (not shown) for receiving the right side of the shaft 82A of the pressure roller 82.

[0076] The second resin frame 49B is also formed with bearings for receiving the left side of the rotating shaft of the photosensitive drum 61 and receiving the drum drive gear shaft 50 with a drive gear, and bearings for receiving the left side of the shaft 82A of the pressure roller 82 and receiving the fixing drive gear shaft 51 with a drive gear.

[0077] Outside the second resin frame 49B, from the front part to the rear part inside the main body housing 2, a metal gear plate 42 is installed. The main motor 108 is installed on the surface 42A of the gear plate 42, that is, the surface facing the left side wall 2B of the main body housing 2, and a plurality of drive gears (not shown) are installed on the back surface 42B of the gear plate 42. The control unit 101 controls the drive of the main motor 108 to rotate the rotation shaft 108A of the main motor 108, and drives the drive gears to rotate the drum drive gear shaft 50, the fixing drive gear shaft 51, etc.

[0078] Outside the second resin frame 49B, a metal main plate 43 is installed at the rear part inside the main body housing 2. And the main board 100 is installed on the main plate 43. There are main board ground parts 107 at the four corners of the board surface of the main board 100. The main board ground parts 107 of the main board 100 and the main plate 43 are connected by a conductive member 45E such as a metal screw. Also, the main plate 43 and the gear plate 42 are connected via a sheet metal member 45D. Further, the gear plate 42 and the plate 45B are connected by a sheet metal member 45C arranged in the left - right direction across the main body housing 2 from the gear plate 42 side to the plate 45B side.

[0079] In this way, the ground of the external commercial power supply 250 (see FIG. 6) is connected to the fixing ground part 80 of the fixing device 8 via the earth cable EC of the power cable 210, the power ground part 44C of the low - voltage power supply part 44, and the enclosure 44A. Also, the ground of the external commercial power supply 250 is connected to the main board ground part 107 of the main board 100 via the earth cable EC of the power cable 210, the power ground part 44C of the low - voltage power supply part 44, the enclosure 44A, the plate 45B, the sheet metal member 45C, the gear plate 42, the sheet metal member 45D, the main plate 43, and the conductive member 45E.

[0080] As described with reference to FIG. 5, in the embodiment of the present invention, the fixing ground portion 80 is directly connected to the power supply ground portion 44C via the sheet metal member 45A and the box-shaped metal enclosure 44A. The fixing ground portion 80 is characterized in that it is directly connected to the power supply ground portion 44C without passing through the main board 100. To explain the effects in the embodiment of the present invention, FIG. 6, which is a comparative example, will be described.

[0081] In the printer 1' as a comparative example in FIG. 6, the fixing ground portion 80 is connected to the gear plate 42 via the sheet metal member 45F. The printer 1' as a comparative example in FIG. 6 differs from the printer 1 of the present embodiment in FIG. 5 in that the sheet metal member 45A is connected to the enclosure 44A. Further, FIG. 6 shows a state where the printer 1' as a comparative example is connected to the external commercial power supply 250 by the power cable 210, the LAN connector 130 (or the USB connector 131) of the printer 1 is connected to the PC 300 by the LAN cable 230 (or the USB cable 231), and the PC 300 is connected to the external commercial power supply 250 by the power cable 220.

[0082] In the printer 1' as a comparative example, when an AC voltage is applied from the low-voltage power supply board 110 to the heating unit 81 via the heater harness HH, the noise component generated by the large current flowing through the fixing device 8 flows into the fixing ground portion 80. The noise component flowing into the fixing ground portion 80 of the printer 1' passes through the sheet metal member 45F, the gear plate 42, the sheet metal member 45D, the main plate 43, the conductive members 45E such as screws, the main board 100, the ground terminal 130B (or the ground terminal 131B) of the LAN connector 130, the LAN cable 230 (or the USB cable 231), the PC 300, and the power cable 220 in sequence and flows into the ground of the external commercial power supply 250.

[0083] When the noise component passes through the routes of the main board 100, the LAN cable 230, the PC 300, and the power cable 220 from the fixing ground portion 80, radiated noise is generated from the routes while passing through them. The noise component passing through the ground of the external commercial power supply 250 returns to the power ground portion 44C via the power cable 210. In particular, there is a problem that radiated noise is generated at grounding locations such as the power ground portion 44C and the ground portion 110C of the low-voltage power supply board 110. In the case of the printer 1' of the comparative example as shown in FIG. 6, separate measures against radiated noise such as arranging noise countermeasure components such as ferrite cores at various locations were necessary.

[0084] FIG. 7 shows a state where the printer 1 of the present embodiment is connected to the external commercial power supply 250 by the power cable 210, the LAN connector 130 (or the USB connector 131) of the printer 1 is connected to the PC 300 by the LAN cable 230 (or the USB cable 231), and the PC 300 is connected to the external commercial power supply 250 by the power cable 220.

[0085] In the case of the printer 1 of the present embodiment, when an AC voltage is applied from the low-voltage power supply board 110 to the heating unit 81 via the heater harness HH, the noise component flowing through the fixing ground portion 80 of the printer 1 flows through the sheet metal member 45A, the enclosure 44A, the power ground portion 44C, and the earth cable EC to the ground of the external commercial power supply 250. In the case of the present embodiment of FIG. 7, the route returning from the fixing ground portion 80 to the power ground portion 44C via the ground of the external commercial power supply 250 is shorter than the route in the case of the comparative example of FIG. 6. Therefore, in the case of the present embodiment of FIG. 7, the generation of radiated noise on the route can be suppressed compared to the case of the comparative example of FIG. 6. As a result, in the case of the printer 1 of the present embodiment, noise countermeasure components such as ferrite cores are not required at various locations, and the manufacturing cost of the entire printer 1 can be reduced.

[0086] FIG. 8 shows a schematic configuration of a fixing device 8' having a configuration different from that of the fixing device 8 in FIG. 3. The fixing device 8' in FIG. 7 is different from the fixing device 8 in that a heating roller 88 is employed instead of the heating unit 81 of the fixing device 8.

[0087] As shown in FIG. 8, a heater 89 is installed inside the heating roller 88. The heater 89 is, for example, a halogen heater and heats the heating roller 88. In the fixing device 8' of FIG. 7, the shaft 82A is connected to the fixing ground portion 80. As a result, the shaft 82A is connected to the ground of the external commercial power supply 250 via the fixing ground portion 80, the sheet metal member 45A, the plate 45B, the power supply ground portion 44C, and the ground cable EC. As a result, the fixing ground portion 80 is grounded.

[0088] As described above, the printer 1 of the present embodiment includes a main body housing 2, a process unit PR that forms a toner image on a sheet S, and a fixing device 8 that thermally fixes the toner image formed on the sheet S. The fixing device 8 includes a heating unit 81 having a heater 90, a pressure roller 82 that presses the sheet S against the heating unit 81, and a fixing ground portion 80 connected to the heating unit 81 and the pressure roller 82. The printer 1 also includes a low-voltage power supply board 110 having a switching element 110F that switches an AC voltage input from the external commercial power supply 250 via a power cable 210, a power supply ground portion 44C connected to the ground of the external commercial power supply 250 via the power cable 210, a low-voltage power supply unit 44 that supplies the AC voltage switched by the switching element 110F to the heater 90, a control unit 101 that controls the process unit PR and the switching element 110F, external connectors 130 and 131 that can be connected to a PC 300 when cables 230 and 231 are connected, a main board ground portion 107 connected to the power supply ground portion 44C of the low-voltage power supply unit 44, and a main board 100 in which the ground terminals of the external connectors 130 and 131 are connected to the main board ground portion 107. The fixing ground portion 80 is connected to the power supply ground portion 44C of the low-voltage power supply unit 44 without passing through the main board ground portion 107.

[0089] In the configuration where the fixing ground portion 80 is connected to the main board ground portion 107, when an AC voltage is applied from the low-voltage power supply board 110 to the heating portion 81 via the heater harness HH, the noise components generated by the large current flowing through the fixing device 8 flow in the order of the main board ground portion 107, the ground terminals of the external connectors 130 and 131 of the main board 100, the ground of an external terminal such as a PC, the external commercial power supply 250, the ground cable EC of the power cable 210, and the ground portion 110C of the low-voltage power supply board 110, and a route is formed that returns from the ground of the external commercial power supply 250 to the power supply ground portion 44C. Therefore, there is a problem that radiated noise is generated on the formed route, and particularly, radiated noise is generated at the grounding locations such as the power supply ground portion 44C.

[0090] Therefore, in the printer 1 of the present application, since the fixing ground portion 80 is connected to the power supply ground portion 44C without passing through the main board ground portion 107, the route from the fixing ground portion 80 back to the power supply ground portion 44C via the external commercial power supply 250 can be made shorter than in the case of the comparative example as described above, so that the radiated noise generated on the route can be suppressed.

[0091] Further, the low-voltage power supply portion 44 has an enclosure 44A that covers the low-voltage power supply board 110, and the power supply ground portion 44C is provided in the enclosure 44A and is connected to the ground portion 110C of the low-voltage power supply board 110. The power supply ground portion 44C is provided in an enclosure that covers the low-voltage power supply board 110. Since the distance between the power supply ground portion 44C and the fixing ground portion 80 can be shortened, the radiated noise generated on the route between the fixing ground portion 80 and the power supply ground portion 44C can be suppressed.

[0092] Further, the low-voltage power supply unit 44 is disposed on the right side wall 2A side of the main body housing 2, the main board 100 is disposed on the left side wall 2B side of the main body housing 2, the fixing device 8 is disposed parallel to the direction from the right side wall 2A side to the left side wall 2B side, and includes a heater harness HH extending from the low-voltage power supply board 110. An alternating voltage is supplied from the low-voltage power supply board 110 to the heater 90 via the heater harness HH. The end HH1 of the heater harness HH is connected to a position on the right side wall 2A side of the fixing device 8, and the fixing ground portion 80 is connected to the power supply ground portion 44C of the low-voltage power supply unit 44.

[0093] Further, the right side wall 2A of the main body housing 2 is disposed opposite to the left side wall 2B of the main body housing 2. The low-voltage power supply unit 44 is disposed such that the board surface of the low-voltage power supply board 110 is parallel to the right side wall 2A of the main body housing 2, and the main board 100 is disposed such that its board surface is parallel to the left side wall 2B of the main body housing 2.

[0094] Further, the power supply ground portion 44C of the low-voltage power supply unit 44 is connected to the main board ground portion 107 via a sheet metal member 45C extending from the right side wall 2A to the left side wall 2B of the main body housing 2.

[0095] Further, the process unit PR includes a photosensitive drum 61, a charger 62 for charging the photosensitive drum 61, a developing roller 71 for supplying toner to the electrostatic latent image formed on the charged photosensitive drum 61 to form a toner image, and a transfer roller 63 disposed opposite to the photosensitive drum 61 for transferring the toner image to a sheet S passing through a transfer nip TN between the photosensitive drum 61 and the transfer roller 63. The printer 1 further includes a high-voltage power supply board 112 for applying a charging voltage to the charger 62 and a transfer voltage to the transfer roller 63 respectively. The ground portion 112D of the high-voltage power supply board 112 is connected to the power supply ground portion 44C provided in the enclosure 44A.

[0096] Further, the external connector is a USB connector 131 to which a USB cable 231 can be connected, and is characterized in that. Since the fixing ground portion 80 is connected to the power ground portion 44C without passing through the main board ground portion 107, when the USB cable 231 is connected to the USB connector 131 of the main board 100, the route from the fixing ground portion 80 back to the power ground portion 44C via the external commercial power supply 250 can be shortened.

[0097] Further, the external connector is a LAN connector 130 to which a LAN cable 230 can be connected, and is characterized in that. Since the fixing ground portion 80 is connected to the power ground portion 44C without passing through the main board ground portion 107, when the LAN cable 230 is connected to the LAN connector 130 of the main board 100, the route from the fixing ground portion 80 back to the power ground portion 44C via the external commercial power supply 250 can be shortened.

[0098] Further, the heater 90 includes a substrate 91 and a resistive heating element 92 formed on the substrate 91 to which an alternating voltage is applied. The heating unit 81 includes an endless belt 81A that rotates around the heater 90. The pressure roller 82 forms a nip portion NP by sandwiching the belt 81A with the heater 90, and includes a conductive shaft 82A extending in the rotational axis direction of the pressure roller 82 and a roller portion 82B covering the outer peripheral surface of the shaft 82A. The fixing device 8 further includes a grounding circuit 87 connected to the heating unit 81 and the pressure roller 82, and the fixing ground portion 80 is connected to the grounding circuit 87, and is characterized in that.

[0099] Further, the fixing device 8 further includes a diode 85 having a cathode connected to the shaft 82A of the pressure roller 82 and an anode connected to the belt 81A of the heating unit 81. The grounding circuit 87 includes one end T1 connected to the anode of the diode 85 and the other end T2 connected to the ground. A capacitor C and a first resistor R1 are connected in series between the one end T1 and the other end T2, and a second resistor R2 is connected in parallel to the capacitor C and the first resistor R1, and is characterized in that.

[0100] Further, the heating unit has a heating roller 88 heated by a heater 89, the pressure roller 82 forms a nip portion with the heating roller 88, and the fixing ground portion 80 is connected to the pressure roller 82, which is characterized by this.

[0101] Note that the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit thereof.

[0102] (1) In the above embodiment, the scorotron type charger has been described as an example of the charger 62, but the charger 62 may be a charging roller.

[0103] (2) In the above embodiment, the monochrome laser printer 1 has been described as an example of the image forming apparatus, but it is not limited thereto, and a color laser printer may be used.

Explanation of reference numerals

[0104] 1…Monochrome laser printer (image forming apparatus), 2…Main body housing, 2A…Right side wall (one surface), 2B…Left side wall (the other surface), 8…Fixing device, 44…Low voltage power supply unit, 44C…Power supply ground unit, 49A…First resin frame, 49B…Second resin frame, 61…Photoconductor drum, 62…Charging device, 63…Transfer roller (transfer member), 71…Developing roller (developer), 80…Fixing ground unit, 81…Heating unit, 81A…Belt, 81B…Holder, 81C…Stay, 82…Pressing roller (pressing rotating body), 82A…Shaft, 82B…Roller part (elastic layer), 83…Static eliminator brush, 85…Diode (rectifying element), 87…Grounding circuit, 88…Heating roller (heating rotating body), 89, 90…Heater, 91…Substrate, 92…Resistive heating element, 92A…First resistive heating element, 92B…Second resistive heating element, 100…Main substrate, 101…Control unit, 107…Main substrate ground unit, 110…Low voltage power supply substrate, 110C…Ground unit, 110F…Switching element, 112…High voltage power supply substrate, 112D…Ground unit, 130…LAN connector, 131…USB connector, 210, 220…Power cable, 230…LAN cable, 231…USB cable, 250…External commercial power supply, 300…PC (external terminal), C…Capacitor (capacitance element), EC…Grounding cable, HH…Heater harness, NP…Nip part, PR…Process unit (image forming unit), R1…First resistor (first resistive element), R2…Second resistor (second resistive element), S…Sheet, TH1, TH2…Thermistor, TN…Transfer nip (transfer nip part).

Claims

1. A main body housing, an image forming unit that forms a developer image on a sheet, a fixing device that thermally fixes the developer image formed on the sheet, the fixing device including a heating unit having a heater, a pressing rotator that presses the sheet against the heating unit, and a fixing ground unit connected to the heating unit and the pressing rotator, a low-voltage power supply board having a switching element that switches an AC voltage input from an external commercial power supply via a power cable, and a power ground unit connected to the ground of the external commercial power supply via the power cable, the low-voltage power supply unit supplying the AC voltage switched by the switching element to the heater, a control unit that controls the image forming unit and the switching element, an external connector that can be connected to an external terminal when a cable is connected, and a main board ground unit connected to the power ground unit of the low-voltage power supply unit, a main board having a ground terminal of the external connector connected to the main board ground unit, characterized in that the fixing ground unit is connected to the power ground unit of the low-voltage power supply unit without passing through the main board ground unit, of an image forming apparatus.

2. the low-voltage power supply unit has an enclosure that covers the low-voltage power supply board, the power ground unit is provided in the enclosure and is connected to the ground unit of the low-voltage power supply board, of the image forming apparatus according to claim 1.

3. the low-voltage power supply unit is disposed on one surface side of the main body housing, the main board is disposed on the other surface side of the main body housing, the fixing device is disposed parallel to a direction from the one surface side to the other surface side, including a heater harness extending from the low-voltage power supply board, the AC voltage is supplied from the low-voltage power supply board to the heater via the heater harness, a terminal end of the heater harness is connected to a position on the one surface side of the fixing device, the fixing ground unit is connected to the power ground unit of the low-voltage power supply unit, of the image forming apparatus according to claim 1.

4. the one surface of the main body housing is disposed opposite to the other surface of the main body housing, the low-voltage power supply unit is disposed such that a board surface of the low-voltage power supply board is parallel to the one surface of the main body housing, The main substrate is arranged such that its substrate surface is parallel to the other surface of the main body housing. The image forming apparatus according to claim 3, characterized by the above.

5. The power supply ground portion of the low-voltage power supply unit is connected to the main substrate ground portion via a sheet metal member extending from one surface of the main body housing to the other surface. The image forming apparatus according to claim 4, characterized by the above.

6. The image forming unit has a photosensitive drum, a charger for charging the photosensitive drum, a developing device for supplying a developer to an electrostatic latent image formed on the charged photosensitive drum to form a developer image, a transfer member arranged to face the photosensitive drum and transferring the developer image to a sheet passing through a transfer nip portion between the photosensitive drum and the transfer member, and has The image forming apparatus further includes a high-voltage power supply substrate for applying a charging voltage to the charger and a transfer voltage to the transfer member respectively. The ground portion of the high-voltage power supply substrate is connected to the power supply ground portion provided in the enclosure. The image forming apparatus according to claim 2, characterized by the above.

7. The external connector is a USB connector to which a USB cable can be connected. The image forming apparatus according to claim 1, characterized by the above.

8. The external connector is a LAN connector to which a LAN cable can be connected. The image forming apparatus according to claim 1, characterized by the above.

9. The heater has a substrate and a resistive heating element to which an alternating voltage is applied and formed on the substrate. The heating portion has an endless belt that rotates around the heater. The pressure rotating body forms a nip portion by sandwiching the belt with the heater, has a conductive shaft extending in the rotational axis direction of the pressure rotating body, and an elastic layer covering the outer peripheral surface of the shaft. The fixing device further has a grounding circuit connected to the heating portion and the pressure rotating body. The fixing ground portion is connected to the grounding circuit. The image forming apparatus according to claim 1, characterized by the above.

10. The fixing device further has a rectifying element with its cathode connected to the shaft of the pressure rotating body and its anode connected to the belt of the heating portion. The grounding circuit has one end connected to the anode of the rectifying element and the other end connected to ground. A capacitor element and a first resistor element are connected in series between the one end and the other end, and a second resistor element is connected in parallel to the capacitor element and the first resistor element. The image forming apparatus according to claim 9, characterized in that.

11. The heating unit includes a heated rotating body heated by the heater. The pressure rotating body forms a nip portion with the heated rotating body. The fixing ground portion is connected to the pressure rotating body. The image forming apparatus according to claim 1, characterized in that.

Images