JP6994124B2 - Heater and image forming device - Google Patents

Description

Embodiments of the present invention relate to heaters and image forming devices.

For example, as a heat source for a fixing portion mounted on an image forming apparatus, a planar heater provided with a plurality of heat generating resistors is used. In this planar heater, a plurality of heat generation resistors are arranged in the longitudinal direction. Therefore, the image forming apparatus can reduce the power consumption of the heat generating resistor in the region where the paper does not pass by generating heat only in the heat generating resistor in the region where the paper passes.
However, due to the arrangement of the plurality of heat generation resistors, the heat dissipation of the heat generation resistors at both ends in the longitudinal direction is large. Therefore, among the plurality of heat-generating resistors that generate heat, the heat-generating resistors at both ends in the longitudinal direction may have a lower temperature than the other adjacent heat-generating resistors.

Japanese Patent No. 5550263

An object to be solved by the present invention is to provide a heater and an image forming apparatus capable of suppressing a temperature drop of heat generation resistors at both ends in the longitudinal direction.

The heater of the embodiment has a plurality of heat generation resistors, a switch unit, a plurality of current paths, a switching unit, and a control unit. The plurality of heat generation resistors are arranged in the longitudinal direction. The switch unit is provided corresponding to each heat generation resistor, and controls the current flowing through the heat generation resistor by being switched to an on state or an off state. A plurality of current paths are provided corresponding to the heat generation resistors, and the current flows. Each of the current paths has a different resistance value. The switching unit switches to any of the current paths in the plurality of current paths. The control unit controls the on and off states of the switch unit and the operation of the switching unit.

The figure which shows the whole structure example of the image forming apparatus 1 of embodiment. The figure which shows an example of the schematic structure of the fixing part 70 in an embodiment. The figure which shows an example of the schematic structure of the heater 705 in an embodiment. The flowchart which shows the flow of the process of the control unit 100 in an embodiment. The figure which shows the modification of the schematic structure of the fixing part 70 in an embodiment.

Hereinafter, the heater of the embodiment will be described with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration example of the image forming apparatus 1 of the embodiment.
The image forming apparatus 1 is a multifunction device (MFP; Multi Function Peripheral) capable of forming a toner image on paper P. The paper P is, for example, a manuscript, paper on which characters, images, and the like are written. The paper P may be any material as long as it can be read by the image forming apparatus 1. The image forming apparatus 1 reads the image appearing on the paper P, generates digital data, and generates an image file.

The image forming apparatus 1 includes an image reading unit 10, a control panel 20, a printer unit 30, a paper accommodating unit 80, and a control unit 100. The printer unit 30 of the image forming apparatus 1 may be an apparatus for fixing a toner image or an inkjet type apparatus. In the present embodiment, the case where the printer unit 30 is a device for fixing a toner image will be described as an example. The image reading unit 10 reads the image information to be read as light and dark. The image reading unit 10 records the read image information. The recorded image information may be transmitted to another information processing device via a network. The recorded image information may be image-formed on the paper P by the printer unit 30.

The control panel 20 includes a display unit and an operation unit. The display unit is a display device such as a liquid crystal display and an organic EL (Electro Luminescence) display. The display unit displays various information about the image forming apparatus 1. The operation unit includes a plurality of buttons and the like. The operation unit accepts the user's operation. The operation unit outputs a signal corresponding to the operation performed by the user to the control unit of the image forming apparatus 1. The display unit and the operation unit may be configured as an integrated touch panel.

The printer unit 30 forms an image on the surface of the paper P based on the image data generated by the image reading unit 10. Further, the printer unit 30 may form an image on the surface of the paper P based on the image data transmitted by another information processing apparatus via the network. The printer unit 30 forms an image on the surface of the paper P, for example, with toner. The toner in the present embodiment includes a toner for a decolorizing recording agent (hereinafter referred to as “decoloring toner”) and a toner for a non-decolorizing recording agent (hereinafter referred to as “normal toner”). The usual toner is, for example, a toner such as yellow (Y), magenta (M), cyan (C), and black (K). The decolorizing toner is a colored toner like a normal toner, and is, for example, black. The decolorizing toner usually decolorizes at a temperature higher than the temperature at which the toner is fixed on the paper P. Here, decolorization means that an image formed of a color different from the base color of the paper P (including not only a chromatic color but also an achromatic color such as white and black) is visually invisible. .. The decolorization may be performed by a method other than the decolorization by heating.

The paper storage unit 80 includes a plurality of paper cassettes 80A, 80B, and 80C. Each of the paper cassettes 80A, 80B, and 80C stores a predetermined size and type of paper P, respectively. In this embodiment, the paper feed cassettes 80A, 80B, and 80C are set as follows. The new paper P is housed in the paper cassette 80A. Here, the new paper P represents a paper P that has never been used for printing. The paper cassette 80B contains the decolorized paper P. The paper cassette 80C contains the paper P used as the backing paper. The settings of the paper cassettes 80A, 80B, and 80C can be changed as appropriate. Further, in the following description, the paper cassette 80A will be referred to as a normal paper cassette, and the paper cassettes 80B and 80C will be described as a reused paper cassette. Each paper cassette 80A, 80B and 80C includes pickup rollers 81A, 81B and 81C, respectively. Each pickup roller 81A, 81B and 81C takes out one sheet of paper P from each of the paper feed cassettes 80A, 80B and 80C. The pickup rollers 81A, 81B and 81C supply the taken-out paper P to the transport unit 50.

The transport unit 50 transports the paper P in the printer unit 30 and the paper storage unit 80. The transport unit 50 includes a paper feed roller 52A, a paper feed roller 52B, a paper feed roller 52C, a transport roller 53, and a resist roller 54. The paper feed rollers 52A, 52B and 52C convey the paper P supplied by the pickup rollers 81A, 81B and 81C to the resist roller 54. The resist roller 54 conveys the paper P to the transfer unit 55 side according to the timing at which the transfer unit 55 of the printer unit 30, which will be described later, transfers the toner image onto the surface of the paper P. The resist roller 54 aligns the tip of the paper P fed by the transport roller 53 with the nip N, and then transports the paper P to the transfer unit 55 side.

Next, the detailed configuration of the printer unit 30 will be described. The printer unit 30 includes a developing unit 31, an exposure unit 38, an intermediate transfer belt 39, a transfer unit 55, an inversion unit 60, and a fixing unit 70. In the present embodiment, the developing unit 31 has a number corresponding to the toner to be handled. Hereinafter, the developing unit corresponding to the yellow (Y) toner will be referred to as a developing unit 31Y, and the developing unit corresponding to the magenta (M) toner will be referred to as a developing unit 31M. Further, the developing unit corresponding to the cyan (C) toner is referred to as a developing unit 31C, and the developing unit corresponding to the black (K) toner is referred to as a developing unit 31K. Further, the developing unit corresponding to the decolorizing toner is referred to as a developing unit 31D.

Each developing unit 31 (31Y, 31M, 31C, 31K, 31D) supplies the developing agent contained in the developing agent accommodating unit to the photoconductor drum. The developer accommodating unit is a container for accommodating the developer. The developer is a mixture of a carrier composed of magnetic fine particles and each toner. When the developer is agitated, the toner is triboelectrically charged. As a result, the toner adheres to the surface of the carrier due to the electrostatic force. A first mixer, a second mixer, a developing roller, and a temperature / humidity sensor are arranged inside the developer accommodating portion. The first mixer and the second mixer stir the developer. The first mixer and the second mixer carry the developer. The second mixer is located below the developing roller. The second mixer supplies the developer contained in the developer accommodating portion to the surface of the developing roller. The temperature / humidity sensor detects the temperature and humidity inside the developer accommodating unit as the state of the printer unit 30.

The photoconductor drum has a photoconductor layer on the surface. The photoconductor drum is rotated clockwise by the drive of the developing motor. A developing unit 31, a charging unit, a static elimination unit, a cleaning unit, and a transfer roller are arranged around the photoconductor drum.
The charged portion uniformly charges the surface (photoreceptor layer) of the photoconductor drum. For example, the charging portion charges the surface of the photoconductor drum (photoreceptor layer) negatively. As a result, a toner image is formed on the surface of the photoconductor drum (photoreceptor layer) according to the electrostatic latent image.

For example, the developing unit 31Y develops an electrostatic latent image on the surface (photoreceptor layer) of the photoconductor drum with yellow (Y) toner. Further, the developing unit 31M develops an electrostatic latent image on the surface (photoreceptor layer) of the photoconductor drum with magenta (M) toner. Further, the developing unit 31C develops an electrostatic latent image on the surface (photoreceptor layer) of the photoconductor drum with cyan (C) toner. Further, the developing unit 31K develops an electrostatic latent image on the surface (photoreceptor layer) of the photoconductor drum with black (K) toner. Further, the developing unit 31D develops an electrostatic latent image on the surface (photoreceptor layer) of the photoconductor drum with a decolorizing toner.

The cleaning unit removes untransferred toner and the like on the surface of the photoconductor drum by scraping it off. The cleaning unit removes the toner on the surface of the photoconductor drum after the toner image is transferred from the photoconductor drum onto the intermediate transfer belt 39. The toner removed by the cleaning unit is collected in a waste toner tank and discarded.

The static eliminator faces the photoconductor drum that has passed through the cleaning unit. The static eliminator irradiates the surface of the photoconductor drum with light. As a result, the non-uniform charge of the photoconductor layer is made uniform. That is, the photoconductor layer is statically eliminated.
The transfer roller faces the photoconductor drum with the intermediate transfer belt 39 interposed therebetween. The transfer roller abuts on the surface of the photoconductor drum with the intermediate transfer belt 39 interposed therebetween. The transfer roller transfers (primary transfer) the toner image on the surface of the photoconductor drum onto the intermediate transfer belt 39.

The exposure unit 38 is provided at a position facing the photoconductor drum of each of the developing units 31Y, 31M, 31C, 31K, and 31D. The exposure unit 38 irradiates the surface (photoreceptor layer) of the photoconductor drums of the developing units 31Y, 31M, 31C, 31K, and 31D with laser light. The exposure unit 38 is controlled to emit light based on the image data by the control of the control unit 100. The exposure unit 38 irradiates the laser beam based on the image data. As a result, the negative charge on the surface (photoreceptor layer) of the photoconductor drum of each developing unit 31Y, 31M, 31C, 31K, 31D disappears. As a result, an electrostatic pattern is formed on the surface of the photoconductor drum (photoreceptor layer) at the position irradiated with the laser beam. That is, an electrostatic latent image is formed on the surface (photoreceptor layer) of the photoconductor drum by irradiation of the laser beam by the exposure unit 38. The exposure unit 38 may use LED (Light Emitting Diode) light instead of the laser light.

The reversing unit 60 reverses the paper P discharged from the fixing unit 70 by switchback. The reversing unit 60 conveys the reversed paper P to the front of the resist roller 54 again. The inversion unit 60 inverts the paper P in order to form a toner image on the back surface of the paper P that has been fixed.

The fixing unit 70 applies heat and pressure to the paper P under the control of the control unit 100. The fixing unit 70 fixes the toner image transferred to the paper P by the heat and pressure.
Hereinafter, as the printing type, the case of printing with normal toner is described as normal printing, and the case of printing with decolorizing toner is described as eco-printing.

FIG. 2 is a diagram showing an example of the schematic configuration of the fixing portion 70 in the present embodiment.
As shown in FIG. 2, the fixing portion 70 includes a fixing belt 701, a press roller 702, a belt transport roller 703, a tension roller 704, and a heater 705.

The fixing belt 701 is an endless belt. The fixing belt 701 is provided with an elastic layer on the surface. The fixing belt 701 faces the press roller 702.
The press roller 702 has an elastic layer on its surface. The press roller 702 is rotatably supported along the rotation direction t shown in FIG.
The fixing belt 701 and the press roller 702 have a width larger than the maximum paper width (width in the transport orthogonal direction of the paper P) that the image forming apparatus 1 can pass through.
The fixing belt 701 is pressed against the surface of the press roller 702. The contact portion between the fixing belt 701 and the press roller 702 forms a fixing nip. The fixing nip is longer than the maximum paper width that can be passed. The width of the fixing nip in the transport direction A of the paper P is set to a predetermined width. The predetermined width is a width that can supply the amount of heat for heat-fixing the toner image transferred to the paper P.

A tension roller 704 and two belt transfer rollers 703 are arranged inside the fixing belt 701. The fixing belt 701 is stretched from the inside by a tension roller 704 and two belt transport rollers 703.
The tension roller 704 presses the inside of the fixing belt 701. The tension roller 704 applies tension to the fixing belt 701.

The belt transport roller 703 is rotationally driven counterclockwise (see arrow s) shown by a drive motor (not shown). When the belt transport roller 703 rotates, the fixing belt 701 is rotationally driven in the counterclockwise direction shown by the arrow B.

The heater 705 heats the paper P through the fixing belt 701 at the fixing nip. For example, the heater 705 is formed in a plate shape. The heater 705 is provided with a heat generating portion on one surface in the plate thickness direction. The heat generating portion of the heater 705 contacts the inside of the fixing belt 701 on the back side of the fixing nip. The heater 705 is arranged so that its longitudinal direction is along the longitudinal direction of the fixing nip.

The heat generated in the heat generating portion of the heater 705 is thermally conducted in the thickness direction of the fixing belt 701. The heat that is heat-conducted to the fixing belt 701 is also heat-conducted to the press roller 702 at the fixing nip site. As the paper P passes through the fixing nip, the paper P is heated at the fixing nip.
The heater 705 heats the fixing nip only via the fixing belt 701. Therefore, in the fixing portion 70, the temperature responsiveness of the fixing nip is superior to that of the heating method using radiation such as a halogen lamp. For example, the heater 705 is a ceramic heater.

FIG. 3 is a diagram showing an example of a schematic configuration of the heater 705 in the present embodiment.
As shown in FIG. 3, the heater 705 includes a base material 801 and a plurality of heat generation resistors 802 (802a to 802 g), a first electrode 803, a plurality of second electrodes 804 (804a to 804 g), and a switch unit 810 (810a to 810a to). 810 g), current paths L1 and L2, and a switching unit 820 (820a to 820 g).

The heat generation resistors 802a to 802g are arranged in the longitudinal direction on the base material 801. The first electrode 803 is connected to one of the heat generation resistors 802a to 802g in the lateral direction. A second electrode 804 is connected to the other side of the heat generation resistors 802a to 802g in the lateral direction. In the present embodiment, the first electrode 803 is a common electrode and the second electrode 804 is an individual electrode. That is, the first electrode 803 is connected to one of the heat generating resistors 802a to 802g in the lateral direction. The second electrode 804 includes a second electrode 804a to 804 g. The second electrodes 804a to 804g are connected to the other side of the heat generation resistors 802a to 802g in the lateral direction, respectively. The first electrode 803 is connected to one output terminal of the AC power supply 900.

The switch portion 810 is provided in each heat generation resistor 802a to 802g. The switch unit 810 individually controls the current flowing through the heat generation resistors 802a to 802g by being switched to the on state or the off state. For example, the switch unit 810 includes terminals H1 and H2. When the switch unit 810 is in the ON state, the terminal H1 and the terminal H2 are electrically connected. In this embodiment, the terminal H1 is connected to the second electrode 804. For example, the switch unit 810 shifts from the off state to the on state when the control signal is output from the control unit 100.

The current paths L1 and L2 are provided in each heat generation resistor 802a to 802g. In the present embodiment, the case where the heater 705 includes two current paths L1 and L2 will be described, but the present invention is not limited to this, and a plurality of current paths may be provided.
The current paths L1 and L2 have different resistance values from each other. For example, the current path L2 includes a resistor R, and has a higher resistance value than the current path L1. Therefore, the value of the current flowing through the current path L2 is lower than that of the current path L1.

The switching unit 820 (820a to 820g) is provided on each heat generation resistor 802a to 802g. The switching unit 820 switches to either current path in the current paths L1 and L2. For example, the switching unit 820 is a three-way switch. However, the three-way switch is an example of the switching unit 820. The switching unit 820 may be something other than a three-way switch. Hereinafter, a case where the switching unit 820 is a three-way switch will be described. For example, the switching unit 820 includes a common terminal C, a first terminal T1 and a second terminal T2. The common terminal C is connected to the other output terminal of the AC power supply 900. The first terminal T1 is connected to the terminal H2 of the switch unit 810. The second terminal T2 is connected to the terminal H2 of the switch unit 810 via the resistor R.
For example, the switching unit 820 connects the common terminal C and the first terminal T1 when the switching signal is output from the control unit 100. As a result, the current path L1 is formed, and the AC current output from the AC power supply 900 flows in the order of the heat generation resistor 802, the switch unit 810, and the switching unit 820.

The switching unit 820 connects the common terminal C and the second terminal T2 when the switching signal is not output from the control unit 100. As a result, the current path L2 is formed, and the AC current output from the AC power supply 900 flows in the order of the heat generation resistor 802, the switch unit 810, the resistance R, and the switching unit 820.

The control unit 100 controls the heating of the heater 705. For example, the control unit 100 detects the size of the paper P on which the toner image is formed and determines the required heating width. Then, the control unit 100 selects a plurality of heat generation resistors 802 corresponding to the required heating width, and causes a current output from the AC power supply 900 to flow through the selected heat generation resistors 802. As a result, the toner image is fixed on the paper P. However, the control unit 100 makes the current flowing through the heat generation resistors 802 at both ends in the longitudinal direction higher than that of the other heat generation resistors 802 among the plurality of selected heat generation resistors 802. As a result, the control unit 100 suppresses the temperature drop of the heat generation resistors 802 at both ends in the longitudinal direction.

For example, when the heat generating resistors 802a to 802g are selected based on the size of the paper P, the control unit 100 outputs a switching signal to the switching unit 820a and the switching unit 820g. When the switching unit 820a and the switching unit 820g acquire the switching signal from the control unit 100, the switching unit 820a switches from the current path L2 to the current path L1. As a result, the current value flowing through the heat generation resistor 802a and the heat generation resistor 802g is higher than that of the other heat generation resistors 802b to 802f.

The control unit 100 controls PWM (Pulse Width Modulation) between the on state and the off state of the switch unit 810. For example, the control unit 100 switches the switch unit 810 to an on state or an off state at a timing corresponding to the zero crossing point of the alternating current output from the alternating current power supply 900. For example, it is assumed that the heat generation resistors 802a to 802g are selected based on the size of the paper P. In that case, the control unit 100 makes the detail ratio of the switch units 810a and 810g higher than that of the switch units 810b to 810f.

When the frequency of the AC current output from the AC power supply 900 is 50 Hz, the zero cross period of the AC current is 10 msec. Therefore, when the switch unit 810 is PWM-controlled at a detail ratio of 60%, the control unit 100 causes an alternating current to flow through the heat generation resistor 802 for 60 msec during 1 sec.

Hereinafter, the duty ratio of the switch unit 810 corresponding to the heat generation resistors 802 at both ends may be referred to as a first duty ratio. Further, the duty ratio of the switch unit 810 other than the switch unit 810 corresponding to the heat generating resistors 802 at both ends may be referred to as a second duty ratio.

For example, the first duty ratio and the second duty ratio are determined by the constraint conditions of the paper P such as the size, thickness, and material of the paper P. The control unit 100 may store in its own device a table associated with the constraint conditions and the first duty ratio and the second duty ratio in advance. The control unit 100 may acquire the first duty ratio and the second duty ratio corresponding to the detected constraint condition of the paper P from the table. The table may be pre-generated experimentally. The first duty ratio and the second duty ratio may be determined by the outside air temperature.

FIG. 4 is a flowchart showing a processing flow of the control unit 100 in the present embodiment. Note that FIG. 4 describes the processing of the control unit 100 with respect to the heater 705.
The control unit 100 detects the size of the paper P (ACT101). The control unit 100 selects a heat generation region corresponding to the detected size of the paper P. That is, the control unit 100 selects a plurality of heat generation resistors 802 corresponding to the detected size of the paper P (ACT102). In the following description, a case where the heat generation resistors 802b to 802f are selected as the plurality of heat generation resistors 802 corresponding to the size of the paper P will be described. The control unit 100 outputs a switching signal to the switching units 820b and 820f corresponding to the heat generation resistors 802b and 802f at both ends in the longitudinal direction (ACT103).

The control unit 100 acquires the first duty ratio and the second duty ratio corresponding to the constraint condition of the paper P from the table stored in the storage unit of the own device (ACT104). The first duty ratio is a higher value than the second duty ratio. The control unit 100 outputs a control signal of the first detail ratio to the switch units 810b and 810f. The control unit 100 outputs a control signal of the second detail ratio to the switch units 810c to 810e (ACT105).

According to the heater 705 of at least one embodiment described above, it is possible to suppress a temperature drop of the heat generation resistor 802 at both ends in the longitudinal direction. Further, the heater 705 can adjust the current flowing through the heat generation resistor 802 at both ends in the longitudinal direction while keeping the thickness of the resistance film of the heat generation resistor 802 uniform.

Further, in the above-described embodiment, the heater 705 may be configured to include the control unit 100.

Further, in the above-described embodiment, the case where the fixing portion 70 includes the endless-shaped rotating body shown in FIG. 2 has been described as an example, but the present invention is not limited to this. For example, the fixing portion 70 may include an endless rotating body shown in FIG.
FIG. 5 is a diagram showing a modified example of the schematic configuration of the fixing portion 70 in the present embodiment.
The fixing portion 70A of this modification includes a fixing belt 1001, a film guide 1002, a press roller 1003, and a heater 705.

The fixing belt 1001 is an endless belt. The fixing belt 1001 is supported by the film guide 16. Then, the fixing belt 1001 orbits around the heater 705 in accordance with the rotation of the lower press roller 1003. That is, the fixing belt 1001 receives power from the rotational power of the press roller 1003 and orbits around the heater 705. On the other hand, the fixing belt 701 orbits around the heater 705 while being constantly applied with tension by the belt transport roller 703 and the tension roller 704.

The function of the control unit 100 in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, a "computer-readable recording medium" is a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line, and dynamically holds the program for a short period of time. It may also include a program that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or a client in that case. Further, the above program may be for realizing a part of the above-mentioned functions, and may be further realized for realizing the above-mentioned functions in combination with a program already recorded in the computer system.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 ... Image forming apparatus, 20 ... Control panel, 30 ... Printer unit, 31 (31Y, 31C, 31M, 31K, 31D) ... Development unit, 38 ... Exposure unit, 39 ... Intermediate transfer belt, 50 ... Conveyance unit, 52A, 52B, 52C ... Paper feed roller, 53 ... Conveyor roller, 54 ... Resist roller, 55 ... Transfer unit, 60 ... Inversion unit, 70 ... Fixing unit, Heater 705, 100 ... Control unit

Claims (4)

With multiple heat-generating resistors arranged in the longitudinal direction,
A switch unit provided corresponding to each of the heat-generating resistors and controlling the current flowing through the heat-generating resistor by being switched to an on state or an off state.
A plurality of current paths provided corresponding to the heat generation resistors and through which the current flows, and
A switching unit that switches to any of the current paths in the plurality of current paths, and
A control unit that controls the on and off states of the switch unit and the operation of the switching unit,
Equipped with
Each of the current paths is a heater with a different resistance value. The heater according to claim 1, wherein the switching unit switches the path of the current flowing through the heat-generating resistors at both ends to the current path having a low resistance value among the heat-generating resistors. The heater according to claim 1 or 2, wherein the control unit controls the switch unit to an on state or an off state at a timing corresponding to the zero crossing point of the current. A printer unit that forms an image on paper,
A plurality of heat-generating resistors arranged in the longitudinal direction to heat the paper, and
A switch unit provided on each heat generation resistor and controlling the current flowing through the heat generation resistor by being switched to an on state or an off state.
A plurality of current paths provided corresponding to the heat generation resistors and through which the current flows, and
A switching unit that switches to any of the current paths in the plurality of current paths, and
A control unit that controls the on and off states of the switch unit and the operation of the switching unit,
Equipped with
Each of the current paths is an image forming apparatus having a different resistance value.

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