Image forming apparatus to which cartridge is attachable and including controller capable of determining whether cartridge is attached to image forming apparatus

An image forming apparatus includes a controller, a main body frame, a cartridge and a display. The cartridge includes a memory, a cartridge data terminal and a cartridge detection terminal. The controller includes a main body data terminal and a main body detection terminal. The main body data terminal is electrically connected to the cartridge data terminal. The main body detection terminal is electrically connected to the cartridge detection terminal in the case where the cartridge is attached to the main body frame. The controller is configured to perform determining whether the main body detection terminal and the cartridge detection terminal are electrically connected with each other. The controller is configured to perform displaying a determination result of the determining whether the main body detection terminal and the cartridge detection terminal are electrically connected with each other on the display.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2019-178765 filed Sep. 30, 2019. The entire content of the priority application is incorporated herein by reference.

TECHNICAL FIELD

BACKGROUND

An electro-photographic type image forming apparatus such as a laser printer and an LED printer is well known in the art. The image forming apparatus includes a drum cartridge and a toner cartridge. The drum cartridge includes a photosensitive drum. The toner cartridge includes a developing roller. The toner cartridge is attachable to and detachable from the drum cartridge. In a case where the toner cartridge is attached to the drum cartridge, the developing roller of the toner cartridge and the photosensitive drum of the drum cartridge are in contact with each other.

Further, there has been conventionally known a toner cartridge including a toner memory serving as a storage medium. The toner memory stores various information with respect to the toner cartridge. In recent years, the image forming apparatus handles not only information related to the toner cartridge, but also information related to the drum cartridge. Therefore, the drum cartridge is required to be provided with a drum memory serving as a storage medium for storing information related to the drum cartridge.

SUMMARY

There is such a conventional image forming apparatus that has both of a drum memory and a toner memory. In the conventional image forming apparatus, after a cover of the image forming apparatus is closed, a controller of the image forming apparatus determines whether communication with the drum memory is available. When the drum cartridge is not attached to the image forming apparatus, the controller determines that communication with the drum memory is not available. However, in the conventional image forming apparatus, when communication with the drum memory is not available, it cannot be determined whether the communication with the drum memory is not available because the drum cartridge is not attached to the image forming apparatus or because communication between the controller and the drum memory is disabled.

In view of the foregoing, it is an object of the present disclosure to provide a technology allowing determination of whether a cartridge is attached to an image forming apparatus and is established, without communication with the memory.

In order to attain the above and other objects, according to one aspect, the disclosure provides an image forming apparatus including a controller, a main body frame, a cartridge and a display. The cartridge is attachable to the main body frame. The cartridge includes a memory, a cartridge data terminal and a cartridge detection terminal. The memory stores information related to the cartridge. The cartridge data terminal is configured to communicate the information stored in the memory. The controller includes a main body data terminal and a main body detection terminal. The main body data terminal is electrically connected to the cartridge data terminal in a case where the cartridge is attached to the main body frame. The main body detection terminal is electrically connected to the cartridge detection terminal in the case where the cartridge is attached to the main body frame. The controller is configured to perform determining whether the main body detection terminal and the cartridge detection terminal are electrically connected with each other. The controller is configured to perform displaying a determination result of the determining whether the main body detection terminal and the cartridge detection terminal are electrically connected with each other on the display.

DETAILED DESCRIPTION

Hereinafter, an image forming apparatus100according to one embodiment of the present disclosure will be described with reference toFIGS. 1 through 8.

In the following description, an extending direction of a photosensitive drum will be referred to as a “first direction”. Further, a direction in which a plurality of photosensitive drums are arranged will be referred to as a “second direction”. The first direction and the second direction intersect with each other. Preferably, the first direction and the second direction are perpendicular to each other.

<1. Configuration of Image Forming Apparatus>

FIG. 1is a conceptual diagram of the image forming apparatus100. The image forming apparatus100is an electro-photographic printer. The image forming apparatus100may be a laser printer or a light emitting diode (LED) printer, for example. As illustrated inFIG. 1, the image forming apparatus100includes a main body frame101, a controller102, a display103, a cover108, a drum cartridge1, and a plurality of toner cartridges2.

The main body frame1has an insertion opening101a. The cover8is pivotally movable with respect to the main body frame101between a closed position and an open position. The closed position is a position where the cover108closes the insertion opening101a, and the open position is a position where the cover108opens the insertion opening101a. The image forming apparatus100includes a sensor109. The sensor109is configured to detect whether the cover108is pivoted from the open position to the closed position. When the sensor109detects that the cover108has pivoted from the open position to the closed position, a detection signal indicating that the cover has pivoted to the closed position is sent to the controller102.

Each of the plurality of toner cartridges2can be individually attached to the drum cartridge1. The drum cartridge1, to which the plurality of the toner cartridges2, are attached can be attached to the main body frame101through the insertion opening101a. The plurality of toner cartridges2store toner (developing agents) of respective colors such as cyan, magenta, yellow, and black, respectively. The image forming apparatus100is configured to form an image on a recording surface of a printing sheet with toner supplied from the plurality of toner cartridges2. Although the number of the toner cartridges2attachable to the drum cartridge1is four according to this embodiment, the number of toner cartridges2attachable to the drum cartridge1may be one, two, three, five or more.

The drum cartridge1includes a drum circuit board15and a drum memory151. The drum memory151is a storage medium, to which information can be written and from which information can be read. Each of the plurality of toner cartridges2includes a toner memory24. The toner memory24is a storage medium, to which information can be written and from which information can be read.

The controller102is positioned inside the main body frame101of the image forming apparatus100. The controller102includes, for example, a circuit board, a processor105such as a CPU, and a main body memory106serving as a storage medium. The controller102executes various processes by the processor105operating according to a program stored in the main body memory106. Specifically, the controller102executes a reading process to read information from the main body memory106and an operating process for operating the image forming apparatus100based on the information read by the reading process.

In a case where the plurality of toner cartridges2are attached to the drum cartridge1, the toner memory24of each toner cartridge2is electrically connected to the drum circuit board15. Further, in a case where the drum cartridge1attached with the toner cartridges2is mounted in the main body frame101, the controller102in the main body frame101and the drum circuit board15are electrically connected with each other. Accordingly, the toner memory24of each of plurality of toner cartridges2and the controller102are electrically connected with each other through the drum circuit board15.

The display103is, for example, a liquid crystal display or an organic EL display. The display103is configured to display various information with respect to the operation of the image forming apparatus100on a screen according to an instruction from the controller102.

<2. Configuration of Drum Cartridge>

Next, the configuration of drum cartridge1will be described.FIGS. 2 and 3are perspective views of the drum cartridge1.

As illustrated inFIGS. 2 and 3, the drum cartridge1includes a plurality of photosensitive drums11, a drum frame12, a first connector13, a plurality of second connectors14and the drum circuit board15. In the present embodiment, the number of the photosensitive drums11is four, and the number of the plurality of second connectors14is four.

Each of the photosensitive drums11is configured to transfer toner supplied from the toner cartridge2to printing paper. The plurality of photosensitive drums11are arranged in the second direction at predetermined intervals therebetween. Each of the photosensitive drums11has a cylindrical outer peripheral surface extending in the first direction. The outer peripheral surface of the photosensitive drum11is covered with a photosensitive material. Further, each of the photosensitive drums11is rotatable about a rotation axis extending in the first direction.

The drum frame12is a frame body for holding the plurality of photosensitive drums11. The drum frame12includes a plurality of toner cartridge holders121. The plurality of toner cartridge holders121are arranged in the second direction at predetermined intervals therebetween. Each of the toner cartridge2is attachable to the corresponding toner cartridge holder121. Thus, the plurality of the toner cartridges are attachable to the drum frame12. When one of the toner cartridges2is attached to the toner cartridge holder121, the outer peripheral surface of the photosensitive drum11and an outer peripheral surface of the developing roller22provided in the toner cartridge2(described later) are in contact with each other.

FIG. 4is a perspective view illustrating the first connector13, the plurality of the second connectors14, the drum circuit board15and harnesses16and17for connecting the first connector13, the plurality of second connectors14and the drum circuit board15.

The first connector13is for being electrically connected to one or more terminals provided at the main body frame101when the drum cartridge1is attached to the main body frame101of the image forming apparatus100. The first connector13is, for example, fixed to a surface of the drum frame12. Incidentally, the first connector13may be immovable or slightly movable with respect to the drum frame12. The first connector13has a plurality of first terminals131. Each of the first terminals131is a conductor exposed on a surface of the drum frame12. Each of the first terminals131is electrically connected to a corresponding one of a plurality of main body side drum voltage terminals31(described later) of the drum circuit board15.

The plurality of second connectors14are for being electrically connected to terminals242of the toner memories24(described later) when the toner cartridges2are attached to the toner cartridge holders121. The plurality of second connectors14are provided for the toner cartridge holders121, respectively. Each of the second connectors14is located at an end of the corresponding toner cartridge holder121in the first direction. Further, each of the plurality of second connectors14is, for example, fixed to the surface of the drum frame12. Incidentally, the plurality of second connector14may be immovable or slightly movable with respect to the drum frame12. Each of the plurality of second connectors14has a plurality of second terminals141. Each of the second terminals141is a conductor exposed on the surface of the drum frame12. Each of the second terminals141is electrically connected to a corresponding one of a plurality of toner side drum voltage terminals32(described later) of the drum circuit board15.

The drum circuit board15is a circuit board electrically connected to the first connector13and the plurality of second connectors14. The drum circuit board15is, for example, fixed to the surface of the drum frame12. As illustrated inFIG. 4, the drum circuit board15is electrically connected with the first connector13through the first harness16. Further, the drum circuit board15is electrically connected with the plurality of second connectors14through the second harness17. Each of the first harness16and the second harness17is a wire harnesses including a plurality of conducting wires, for example.

Further, as illustrated inFIG. 4, the drum cartridge1includes the drum memory151serving as a storage medium. The drum memory151is provided on the drum circuit board15. Incidentally, the drum memory151may not be provided on the drum circuit board15. Specifically, the drum memory151may be provided at a surface of the drum frame12.

The drum memory151stores therein various information related to the drum cartridge1. For example, the drum memory151stores therein at least one of information identifying the drum cartridge1and information indicating the characteristics of the drum cartridge1. The information identifying the drum cartridge1includes, for example, at least one of: a manufacturing serial number of the drum cartridge1; and an identification code indicating that the drum cartridge1is a genuine product. The information indicating the characteristics of the drum cartridge1includes, for example, at least one of the following pieces of information: information indicating models of image forming apparatuses to which the drum cartridge1is attachable; a specification of the drum cartridge1; a service life of the photosensitive drum11; charging characteristics of the photosensitive drum11; information indicating whether the drum cartridge1is new; the total number of rotations by which the photosensitive drum11has been rotated; the total length of the charged times during which the photosensitive drum11has been charged; the total number of sheets that have been printed by the photosensitive drum11; and an error history of the drum cartridge1.

The drum memory151has a first storage area and a second storage area. The first storage area is an area for storing non-rewritable information. The second storage area is an area for storing rewritable information. The first storage area stores therein, for example, at least one of: the manufacturing serial number; the identification code; the information indicating models of image forming apparatuses to which the drum cartridge1is attachable; the specification; and the service life of the photosensitive drum11, all of which is described above. The second storage area stores therein, for example, information indicating usage status of the drum cartridge1. The information indicating the usage status of the drum cartridge1includes, for example, at least one of: the information indicating whether the drum cartridge1is new; the total number of rotations by which the photosensitive drum11has been rotated; the total length of charged times during which the photosensitive drum11has been charged; the total number of sheets that have been printed by the photosensitive drum11; and the error history of the drum cartridge1, all of which is described above.

<3. Configuration of Toner Cartridge>

Next, the configuration of the toner cartridge2will be described. In the following, the configuration of the toner cartridge2in the state where the toner cartridge2is attached to the drum cartridge1will be described using the above-described first direction and second direction.

FIG. 5is a perspective view of the toner cartridge2. As illustrated inFIG. 5, the toner cartridge2includes a casing21, a developing roller22, a plurality of gears, a coupling231, a gear cover232, the toner memory24, and a holder25.

The casing21is a housing configured to accommodate toner therein. The casing21extends in the first direction between a first outer surface211and a second outer surface212. A chamber213is formed inside the casing21. The chamber213stores the toner therein. Further, the casing2has an opening214. The opening214is positioned at one end of the casing21in a third direction which intersects both of the first direction and the second direction. The chamber213communicates with an outside of the casing21through the opening214.

The developing roller22is a roller rotatable about a rotation axis extending in the first direction. The developing roller22is positioned at the opening214of the casing21. That is, the developing roller22is positioned at one end of the casing21in the third direction. When the toner cartridge2is attached to the drum cartridge1, the outer peripheral surface of the developing roller22is in contact with the outer peripheral surface of the photosensitive drum11.

The toner is supplied from the chamber213to the photosensitive drum11through the developing roller22. The toner carried on the outer surface of the developing roller22moves from the developing roller22to the photosensitive drum11according to the electrostatic latent image formed on the outer surface of the photosensitive drum11. As a result, the electrostatic latent image is developed into a visible image on the outer surface of the photosensitive drum11.

The plurality of gears, the coupling231and the gear cover232are positioned at the first outer surface211of the casing21. The gear cover232is fixed to the first outer surface211of the casing21with, for example, screws. At least one of the plurality of gears is positioned between the first outer surface211of the casing21and the gear cover232. The coupling231is exposed outside of the gear cover232. When the drum cartridge1attached with the toner cartridges2is attached to the main body frame101of the image forming apparatus100, drive shafts of the image forming apparatus100are connected to the couplings231of the toner cartridges2, and rotation of each drive shaft is transmitted to the developing roller22of the corresponding toner cartridge2through the coupling231and the plurality of gears of the corresponding toner cartridge2.

The toner memory24and the holder25are positioned between the first outer surface211of the casing21and the gear cover232in the first direction. The holder25holds the toner memory24. The holder25is movable relative to both of the casing21and the gear cover232in the second direction. Incidentally, the holder25may be fixed relative to both of the casing21and the gear cover232. Further, the toner memory24may be positioned at another position different from the position between the first outer surface211and the gear cover232. For example, the toner memory24may be positioned on a surface of the casing21.

The toner memory24has a plurality of terminals242. Each of the terminals242is a conductor exposed on a surface of the toner memory24. When the toner cartridge2is attached to the toner cartridge holder121of the drum cartridge1, the terminals242of the toner memory24are in contact with the second terminals141of the plurality of second connector14. In the present embodiment, the number of the terminals242of the toner memory24is four, and the number of the second terminals141of each second connector14is four.

The toner memory24stores therein various information related to the toner cartridge2. For example, the toner memory24stores therein at least one of information identifying the toner cartridge2and information indicating the characteristics of the toner cartridge2. The information identifying the toner cartridge2includes, for example, at least one of: a manufacturing serial number of the toner cartridge2; and an identification code indicating that the toner cartridge is a genuine product. The information indicating the characteristics of the toner cartridge2includes, for example, at least one of the following pieces of information: information indicating models of image forming apparatuses to which the toner cartridge2can be used; a specification of the toner cartridge2; a service life of the developing roller22; information indicating whether the toner cartridge2is new; the total number of rotations by which the developing roller22has been rotated; the total number of sheets that have been printed by the developing roller22; and an error history of the toner cartridge2.

Next, description will be made with respect to the terminals of the controller102.FIG. 6is a block diagram illustrating electrical connection between the controller102, the drum circuit board15, and the toner memories24. As illustrated inFIG. 6, the controller102has a plurality of main body terminals104. The plurality of main body terminals104include a main body voltage terminal104v, a main body ground terminal104g, a main body data terminal104d, a main body clock terminal104c, a main body detection terminal104s, and a main body interrupt terminal104i.

The main body voltage terminal104vis a terminal for supplying voltage to a main body side drum voltage terminal31v(described later) of the drum circuit board15. The controller102supplies a constant first voltage to the main body voltage terminal104vbased on power supplied from an outside of the controller102.

The main body ground terminal104gis a terminal for grounding a main body side drum ground terminal31g(described later) of the drum circuit board15. The voltage value of the main body ground terminal104gis a constant ground voltage lower than the first voltage.

The main body data terminal104dis a terminal for transmitting and receiving data between the controller102and the drum circuit board15. The main body data terminal104dis electrically connected to the processor105of the controller102.

The main body clock terminal104cis a terminal for supplying a clock signal having a constant period from the controller102to the drum circuit board15.

The main body detection terminal104sis a terminal for detecting whether the drum cartridge1is attached to the main body frame101. As illustrated inFIG. 6, the controller102has a voltage measurement circuit102afor measuring voltage at the main body detection terminal104s. Further, the controller102has a main body resistor107. The main body resistor107is an electric resistor. The main body resistor107has one end connected to the main body detection terminal104sand another end connected to the main body voltage terminal104v.

The main body interrupt terminal104iis a terminal for receiving an interrupt signal from a multiplexer34(described later). As illustrated inFIG. 6, the controller102has a signal detection circuit102bfor detecting the interrupt signal through the main body interrupt terminal104iwhen the main body interrupt terminal104ireceives the interrupt signal from the multiplexer34.

The following describes in detail the configuration of the drum circuit board15. In the example ofFIG. 6, the drum circuit board15has a plurality of main body side drum terminals31, a plurality of toner side drum terminals32, the multiplexer34, and a drum memory151. It should be noted that, as described above, the drum memory151may not be positioned on the drum circuit board15. Similarly, the multiplexer34may not be positioned on the drum circuit board15. For example, the multiplexer34and the drum memory151may be positioned on the surface of the drum frame12.

<5-1. Main Body Side Drum Terminal>

The plurality of main body side drum terminals31are electrically connected to the main body terminals104of the controller102through the above-described first connector13in the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. This allows the drum circuit board15and the controller102to be electrically connected with each other. The plurality of main body side drum terminals31include a main body side drum voltage terminal31v, a main body side drum ground terminal31g, a main body side drum data terminal31d, a main body side drum clock terminal31c, a drum detection terminal31s, and a drum interrupt terminal31i.

The main body side drum voltage terminal (cartridge voltage terminal)31vis electrically connected to the main body voltage terminal104vin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. This allows the first voltage to be supplied from the controller102to the main body side drum voltage terminal31vthrough the main body voltage terminal104v. As illustrated inFIG. 6, the main body side drum voltage terminal31vis electrically connected to the drum memory151.

The main body side drum ground terminal (cartridge ground terminal)31gis electrically connected to the main body ground terminal104gin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. This allows the main body side drum ground terminal31gto be grounded. That is, the voltage value of the main body side drum ground terminal31gis the ground voltage lower than the first voltage. As illustrated inFIG. 6, the main body side drum ground terminal31gis electrically connected to the drum memory151.

The main body side drum data terminal (cartridge data terminal)31dis electrically connected to the main body data terminal104din the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. This allows data to be transmitted and received between the controller102and the drum circuit board15. As illustrated inFIG. 6, the main body side drum data terminal31dis electrically connected to the multiplexer34and the drum memory151.

The main body side drum clock terminal31cis electrically connected to the main body clock terminal104cin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. This allows a clock signal to be supplied from the controller102to the drum circuit board15at a constant time interval. As illustrated inFIG. 6, the main body side drum clock terminal31cis electrically connected to the multiplexer34and the drum memory151.

The drum detection terminal (cartridge detection terminal)31sis electrically connected to the main body detection terminal104sin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. As illustrated inFIG. 6, the drum circuit board15has a first drum resistor (cartridge resistor)331. The first drum resistor331is an electric resistor. The first drum resistor331has one end of the first drum resistor331connected to the drum detection terminal31sand another end connected to the main body side drum ground terminal31g.

The drum interrupt terminal31iis electrically connected to the main body interrupt terminal104iin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. As illustrated inFIG. 6, the drum interrupt terminal31iis electrically connected to an interrupt output port342(described later) of the multiplexer34.

The plurality of toner side drum terminals32are electrically connected to the toner memories24of the toner cartridges2through the above-described plurality of second connectors14in the state where the toner cartridges2are attached to the drum frame12of the drum cartridge1. This allows the drum circuit board15and the toner memories24to be electrically connected with each other.

Hereinafter, four toner cartridges2to be attached to the drum cartridge1are referred to as a first toner cartridge2A, a second toner cartridge2B, a third toner cartridge2C, and a fourth toner cartridge2D. The toner memory24for the first toner cartridge2A is referred to as a first toner memory24A, the toner memory24for the second toner cartridge2B is referred to as a second toner memory24B, the toner memory24for the third toner cartridge2C is referred to as a third toner memory24C, and the toner memory24for the fourth toner cartridge2D is referred to as a fourth toner memory24D.

As illustrated inFIG. 6, each toner memory24has a toner voltage terminal242v, a toner ground terminal242g, a toner data terminal242d, and a toner clock terminal242c. Further, each toner memory24has a toner resistor243. The toner resistor243is an electric resistor. The toner resistor243has one end connected to the toner voltage terminal242vand another end connected to the toner data terminal242d.

The plurality of toner side drum terminals32include a first group32A having four toner side drum terminals32, a second group32B having four toner side drum terminals32, a third group32C having four toner side drum terminals32, and a fourth group32D having four toner side drum terminals32.

The toner side drum terminals32of the first group32A are electrically connected to the first toner memory24A in the state where the first toner cartridge2A is attached to the drum frame12of the drum cartridge1. The toner side drum terminals32of the second group32B are electrically connected to the second toner memory24B in the state where the second toner cartridge2B is attached to the drum frame12of the drum cartridge1. The toner side drum terminals32of the third group32C are electrically connected to the third toner memory24C in the state where the third toner cartridge2C is attached to the drum frame12of the drum cartridge1. The toner side drum terminals32of the fourth group32D are electrically connected to the fourth toner memory24D in the state where the fourth toner cartridge2D is attached to the drum frame12of the drum cartridge1.

The toner side drum terminals32of each group include a toner side drum voltage terminal32v, a toner side drum ground terminal32g, a toner side drum data terminal32d, and a toner side drum clock terminal32c.

The toner side drum voltage terminal32vof each group is electrically connected to the main body side drum voltage terminal31v. In the state where one toner cartridge2is attached to the drum frame12of the drum cartridge1, the toner side drum voltage terminal32vof the corresponding group is electrically connected to the toner voltage terminal242vof the toner memory24in the toner cartridge2. This allows the first voltage to be supplied from the controller102to the toner memory24through the drum circuit board15.

The toner side drum ground terminal32gof each group is electrically connected to the main body side drum ground terminal31g. In the state where one toner cartridge2is attached to the drum frame12of the drum cartridge1, the toner side drum ground terminal32gof the corresponding group is electrically connected to the toner ground terminal242gof the toner memory24in the toner cartridge2. This allows the toner ground terminal242gto be grounded.

The toner side drum data terminal32dof each group is electrically connected to the multiplexer34. In the state where one toner cartridge2is attached to the drum frame12of the drum cartridge1, the toner side drum data terminal32dof the corresponding group is electrically connected to the toner data terminal242dof the toner memory24in the toner cartridge2.

As illustrated inFIG. 6, the drum circuit board15has a second drum resistor332. The second drum resistor332is an electric resistor. The second drum resistor has one end connected to the toner side drum data terminal32dand the multiplexer34, and another end connected to both of the main body side drum ground terminal31gand the toner side drum ground terminal32g.

The toner side drum clock terminal32cof each group is electrically connected to the multiplexer34. In the state where one toner cartridge2is attached to the drum frame12of the drum cartridge1, the corresponding toner side drum clock terminal32cis electrically connected to the toner clock terminal242cof the toner memory24.

The toner memory24may have such a configuration, in which the toner resistor243and an E2PROM, in which information can be written in serial communication and from which information can be read in serial communication, are mounted on a small substrate. In this case, the toner voltage terminal242v, toner ground terminal242g, toner data terminal242d, and toner clock terminal242cwhich are mounted on the small substrate are connected to the E2PROM, and the toner voltage terminal242vand toner data terminal242dwhich are mounted on the small substrate are connected to the toner resistor243.

The multiplexer34is a switch circuit for switching among the toner memories24to select one of the toner memories24as a communication destination. The multiplexer34receives a clock signal from the controller102through the main body side drum clock terminal31c. Further, the multiplexer34supplies the input clock signal to the toner memories24through the toner side drum clock terminals32c.

Further, the multiplexer34receives an address signal and a data signal from the controller102through the main body side drum data terminal31d. The address signal is a signal for designating the toner memory24of a communication destination. The data signal is a signal indicating various information items to be transmitted to the toner memory24of a communication destination. The multiplexer34selects one of the four toner side drum data terminals32daccording to the received address signal. Then, the multiplexer34outputs the received data signal to the toner memory24through the selected toner side drum data terminal32d.

That is, the multiplexer34can switch data transmission and/or reception among data transmission and/or reception for the first toner memory24A, data transmission and/or reception for the second toner memory24B, data transmission and/or reception for the third toner memory24C, and data transmission and/or reception for the fourth toner memory24D.

The multiplexer34has four interrupt input ports341and one interrupt output port342so as to allow the controller102to execute interrupt processing. The four interrupt input ports341are in one to one correspondence with the four groups32A,32B,23C, and32D. Each interrupt input port341is connected to the toner side drum data terminal32dand the second drum resistor332in the corresponding group. The interrupt output port342is connected to the drum interrupt terminal31i.

When the ground voltage is supplied to at least one of the four interrupt input ports341, the multiplexer34outputs a first interrupt signal from the interrupt output port342. On the other hand, when a second voltage higher than the ground voltage and lower than the first voltage is supplied to all the four interrupt input ports341, the multiplexer34outputs a second interrupt signal from the interrupt output port342. The first interrupt signal is a voltage signal. The second interrupt signal is also a voltage signal, but the value of the voltage of the second interrupt signal is different from that of the voltage of the first interrupt signal.

<5-4. Relay of Information by Drum Circuit Board>

In the state where the drum cartridge1attached with the toner cartridges2is attached to the main body frame101of the image forming apparatus100, the controller102and the toner memories24are electrically connected with each other through the drum circuit board15. With this configuration, the drum circuit board15can relay information between the controller102and the toner memories24. For example, the controller102can read information stored in the toner memories24through the second harness17, the drum circuit board15, and the first harness16. Further, the controller102can write data in the toner memory24through the first harness16, the drum circuit board15, and the second harness17.

<6. Detection of Presence/Absence of Drum Cartridge>

Next, referring to the flow chart illustrated inFIG. 7, description will be made with the respect to a process in which the controller102of the image forming apparatus100determines whether the drum cartridge1is attached to the main body frame101.

The controller102of the image forming apparatus100determines whether power is switched from OFF to ON or whether the cover108is moved from the open position to the closed position in a power-ON state (S11). The controller102determines that the cover108is moved from the open position to the closed position based on a detection signal from the sensor109.

When the controller102determines that power is switched from OFF to ON or that the cover108is moved from the open position to the closed position in the power-ON state (S11; yes), the voltage measurement circuit102aof the controller102measures the voltage value of the main body detection terminal104s.

It is noted that in a case where the drum cartridge1is not attached to the main body frame101, no current flows through the main body resistor107. Thus, the voltage at the main body detection terminal104shas the same potential with the potential of the first voltage at the main body voltage terminal104v, which is connected to the main body detection terminal104sthrough the main body resistor107.

On the other hand, in a case where the drum cartridge1is attached to the main body frame101, current flows from the main body voltage terminal104vtoward the main body ground terminal104gthrough: the main body resistor107; main body detection terminal104s; drum detection terminal31s; first drum resistor331; and main body side drum ground terminal31g. Thus, the voltage at the main body detection terminal104s, which is positioned between the main body resistor107and the first drum resistor331, becomes a second voltage that is lower than the first voltage and higher than the ground voltage.

Accordingly, the controller102determines whether the voltage at the main body detection terminal104smeasured by the voltage measurement circuit102ais the first voltage or the second voltage (S12, first determination process). When determining that the voltage at the main body detection terminal104sis the first voltage (S12: no), the controller102determines that the main body detection terminal104sand the drum detection terminal31sare not connected with each other (S13). That is, the controller102determines that the drum cartridge1is not attached to the main body frame101.

Then, the controller102instructs the display103to display the result of the first determination process (S14, first display control processing). Specifically, the controller102instructs the display103to display a message indicating that the drum cartridge1is not attached to the main body frame101.

On the other hand, when determining that the voltage at the main body detection terminal104smeasured by the voltage measurement circuit102ais the second voltage (S12: yes), the controller102determines that the main body detection terminal104sand the drum detection terminal31sare connected with each other (step S15). That is, the controller102determines that the drum cartridge1is attached to the main body frame101.

Then, the controller102instructs the display103to display the result of the first determination process (S16, first display control process). Specifically, the controller102instructs the display103to display a message indicating that the drum cartridge1is attached to the main body frame101.

When determining in the first determination process that the main body detection terminal104sand the drum detection terminal31sare connected with each other, the controller102determines, after the first display control process, whether the controller is able to communicate with the information stored in the drum memory151(S17, second determination process). That is, the controller102determines whether the controller102is able to communicate with the information stored in the drum memory151through the main body data terminal104dand the main body side drum data terminal31d.

In the second determination process, the controller102transmits authentication information to the drum memory151, for example. Then, when the controller102receives a response value from the drum memory151, the controller102determines that the controller102is able to communicate with the information stored in the drum memory151. On the other hand, when the controller102does not receive a response value from the drum memory151, the controller102determines that the controller102is unable to communicate with the information stored in the drum memory151.

When determining that the controller102is unable to communicate with the information stored in the drum memory151(S17: no), the controller102instructs the display103to display a determination result indicating that the controller102is unable to communicate with the information stored in the drum memory151(S18, second display control process). Specifically, the controller102instructs the display103to display a message indicating that the controller102is unable to communicate with information stored in the drum memory151.

On the other hand, when determining that the controller is able to communicate with the information stored in the drum memory151(S17: yes), the controller102reads the information stored in the drum memory151through the main body side drum data terminal31dand the main body data terminal104d(S19). Specifically, the controller102reads, from the drum memory151, at least one of information identifying the drum cartridge1and information indicating characteristics of the drum cartridge1.

As described above, in the first determination process, the controller102of the image forming apparatus100can determine whether the main body detection terminal104sand the drum detection terminal31sare connected with each other based on a voltage at the main body detection terminal104s. Further, in the first determination process, the controller102can determine whether the drum cartridge1is attached to the main body frame101based on whether the main body detection terminal104sand the drum detection terminal31sare connected with each other. Thus, the controller102can determine whether the drum cartridge1is attached to the main body frame101without communicating with the drum memory151.

<7. Detection of Presence/Absence of Toner Cartridge>

Next, referring to the flow chart illustrated inFIG. 8, description will be made with the respect to a process in which the controller102of the image forming apparatus100determines whether the toner cartridge2is attached to the drum frame12.

The controller102of the image forming apparatus100determines whether power is switched from OFF to ON or whether the cover108is moved from the open position to the closed position in the power-ON state (S21). The controller102determines that the cover108is moved from the open position to the closed position based on a detection signal from the sensor109.

When the controller102determines that power is switched from OFF to ON or that the cover108is moved from the open position to the closed position in the power-ON state (S21: yes), the signal detection circuit102bof the controller102detects an interrupt signal received by the main body interrupt terminal104i.

Here, a case where the toner cartridge2is not attached to the corresponding toner cartridge holder121of the drum frame12and a case where the toner cartridge2is attached to the corresponding toner cartridge holder121will be considered.

In the case where the toner cartridge2is not attached to the corresponding toner cartridge holder121, the toner voltage terminal242vof the toner cartridge2is not connected to the toner side drum voltage terminal32vof the drum circuit board15and, similarly, the toner ground terminal242gof the toner cartridge2is not connected to the toner side drum ground terminal32gof the drum circuit board15, and the toner data terminal242dof the toner cartridge2is not connected to the toner side drum data terminal32dof the drum circuit board15. Therefore, no current flows through the second drum resistor332connected to the toner side drum data terminal32d. Thus, the voltage at the toner side drum data terminal32dbecomes the same potential as the potential of the ground voltage at the main body side drum ground terminal31g, which is connected to the toner side drum data terminal32dthrough the second drum resistor332. The ground voltage at the toner side drum data terminal32dis input to the interrupt input port341of the multiplexer34.

On the other hand, in the case where the toner cartridge2is attached to the toner cartridge holder121, the toner voltage terminal242vof the toner cartridge2is connected to the toner side drum voltage terminal32vof the drum circuit board15. The toner ground terminal242gof the toner cartridge2is connected to the toner side drum ground terminal32gof the drum circuit board15. The toner data terminal242dof the toner cartridge2is connected to the toner side drum data terminal32dof the drum circuit board15. Therefore, current flows from the main body voltage terminal104vtoward the main body ground terminal104gthrough: the main body side drum voltage terminal31v; toner side drum voltage terminal32v; toner voltage terminal242v; toner resistor243; toner data terminal242d; toner side drum data terminal32d; second drum resistor332; and main body side drum ground terminal31g. Thus, the voltage at the toner side drum data terminal32d, which is positioned between the toner resistor243and the second drum resistor332, becomes the second voltage that is lower than the first voltage and higher than the ground voltage. The second voltage at the toner side drum data terminal32dis input to the interrupt input port341of the multiplexer34. In other words, the first voltage supplied from the main body voltage terminal104vis dropped by the toner resistor243to become the second voltage, which in turn is input to the interrupt input port341of the multiplexer34.

Thus, when at least one of the four toner cartridge holders121is attached with no toner cartridge2, the ground voltage is input to at least one of the four interrupt input ports341of the multiplexer34. In this case, the multiplexer34outputs the first interrupt signal from the interrupt output port342to the main body interrupt terminal104ithrough the drum interrupt terminal31i.

On the other hand, when all the four toner cartridge holders121are attached with the toner cartridges2, the second voltage is input to all the four interrupt input ports341of the multiplexer34. In this case, the multiplexer34outputs the second interrupt signal, whose voltage value is different from that of the first interrupt signal, from the interrupt output port342to the main body interrupt terminal104ithrough the drum interrupt terminal31i.

Accordingly, the controller102determines whether the interrupt signal detected by the signal detection circuit102bis the first interrupt signal or second interrupt signal (S22, third determination process). In other words, the controller102determines whether the main body voltage terminal104vand the toner voltage terminal242vare electrically connected with each other via the main body side drum voltage terminal31vand the toner side drum voltage terminal32v. When determining that the interrupt signal detected by the signal detection circuit102bis the first interrupt signal (S22: no), the controller102determines that at least one of the toner cartridge holders121in the drum frame12is attached with no toner cartridge2(S23).

Then, the controller102instructs the display103to display the result of the third determination process (S24, third display control process). Specifically, the controller102instructs the display103to display a message (first error message) indicating that at least one toner cartridge holder121of the drum frame12is attached with no toner cartridge2.

On the other hand, when determining, in the third determination process, that the interrupt signal detected by the signal detection circuit102bis the second interrupt signal (S22: yes), the controller102determines that all the toner cartridge holders121of the drum frame12are attached with the toner cartridges2(S25).

Then, the controller102instructs the display103to display the result of the third determination process (S26, third display control process). Specifically, the controller102instructs the display103to display a message indicating that all the toner cartridge holders121of the drum frame12are attached with the toner cartridges2.

When determining, in the third determination process, that all the toner cartridge holders121of the drum frame12are attached with the toner cartridges2, the controller102determines, after the third display control process, whether the controller102is able to communicate with the information stored in all of the four toner memories24(S27, fourth determination process). That is, the controller102determines whether the controller102is able to communicate with information stored in the toner memories24through the drum circuit board15.

In the fourth determination process, the controller102transmits authentication information to each of the four toner memories24, for example. Then, when the controller102receives a response value from each of the four toner memories24, the controller102determines that the controller102is able to communicate with the information stored in each of the four toner memories24. On the other hand, when the controller102receives no response value from at least one toner memory24, the controller102determines that the controller102is unable to communicate with the information stored in the at least one toner memory24.

When determining that the controller102is unable to communicate with the information stored in the at least one toner memory24(S27: no), the controller102instructs the display103to display a determination result indicating that the controller102is unable to communicate with the information stored in at least one toner memory24(S28, fourth display control process). Specifically, the controller102instructs the display103to display a message (second error message) indicating that the controller102is unable to communicate with information stored in at least one toner memory24.

On the other hand, when determining that the controller102is able to communicate with the information stored in all of the four toner memories24(S27: yes), the controller102reads information stored in each of the four toner memories24through the drum circuit board15(S29). Specifically, the controller102reads, from the toner memory24of each toner cartridge2, at least one of information for identifying the toner cartridge2and information indicating characteristics of the toner cartridge2.

As described above, in the third determination process, the controller102of the image forming apparatus100determines that the toner cartridge2is not attached to the toner cartridge holder121of the drum frame12when the second voltage is not supplied to the interrupt input port341of the multiplexer34through the toner memory24in the state where the interrupt input port341of the multiplexer34is electrically connected to the main body ground terminal104g. Further, in the third determination process, the controller102determines that the toner cartridge2is attached to the toner cartridge holder121of the drum frame12when the second voltage is supplied to the interrupt input port341of the multiplexer34through the toner memory24.

Thus, the controller102can determine whether the toner cartridge2is attached to the drum frame12without transmitting and receiving data with the toner memory24.

Further, in the image forming apparatus100, the multiplexer34outputs the first interrupt signal to the controller102when the second voltage is not supplied to the interrupt input port341of the multiplexer34through the toner memory24in the state where the interrupt input port341of the multiplexer34is electrically connected to the main body ground terminal104g. Further, in the image forming apparatus100, the multiplexer34outputs the second interrupt signal to the controller102when the second voltage is supplied to the interrupt input port341of the multiplexer34through the toner memory24.

Thus, when the first interrupt signal is output from the multiplexer34, the controller102can determine that the toner cartridge2is not attached to the toner cartridge holder121of the drum frame12. On the other hand, when the second interrupt signal is output from the multiplexer34, the controller102can determine that the toner cartridge2is attached to the toner cartridge holder121of the drum frame12.

Further, the controller102of the image forming apparatus100determines that at least one toner cartridge holder121of the drum frame12is attached with no toner cartridge2when the second voltage is not supplied to the interrupt input port341of the multiplexer34through at least one of the plurality of toner memories24in the state where the interrupt input port341of the multiplexer34is electrically connected to the main body ground terminal104g. Further, the controller102determines that all the toner cartridge holders121of the drum frame12are attached with the toner cartridges2when the second voltages are supplied to all the plurality of interrupt input ports341of the multiplexer34through the toner memories24. As described above, the controller102can determine whether all the toner cartridge holders121of the drum frame12are attached with the toner cartridges2.

Further, the controller102of the image forming apparatus100instructs the display103to display messages such that the contents of the messages are different in the case where the toner cartridge holder121is attached with no toner cartridge2and in the case where the controller102is unable to communicate with the toner memory24of the toner cartridge2attached to the toner cartridge holder121. This allows the controller to display an error state in more detail.

While the one embodiment has been described above, the present disclosure is not limited to the above-described embodiment. Hereinafter, various modifications will be described focusing on differences from the above-described embodiment.

FIG. 9is a block diagram illustrating electrical connection between the controller102, the drum circuit board15, and the toner memory24according to a first modification. The first modification differs from the above embodiment in the manner how the main body resistor107and the first drum resistor331are connected to other components.

The main body resistor107according to the first modification is configured such that the main body resistor107has one end connected to the main body detection terminal104sand another end connected to the main body ground terminal104g. The first drum resistor331according to the first modification is configured such that the drum resistor331has one end connected to the drum detection terminal31sand another end connected to the main body side drum voltage terminal31v.

When the drum cartridge1is not attached to the main body frame101, no current flows through the main body resistor107. Thus, the voltage at the main body detection terminal104shas the same potential as the potential of the ground voltage at the main body ground terminal104g, which is connected to the main body detection terminal104sthrough the main body resistor107.

On the other hand, when the drum cartridge1is attached to the main body frame101, current flows from the main body voltage terminal104vtoward the main body ground terminal104gthrough: the main body side drum voltage terminal31v; first drum resistor331; drum detection terminal31s; main body detection terminal104s; and main body resistor107. Thus, the voltage at the main body detection terminal104s, which is positioned between the first drum resistor331and the main body resistor107, becomes the second voltage that is lower than the first voltage and higher than the ground voltage.

In the first determination process, the controller102determines whether the voltage at the main body detection terminal104smeasured by the voltage measurement circuit102ais the ground voltage or second voltage. When determining that the voltage at the main body detection terminal104sis the ground voltage, the controller102determines that the main body detection terminal104sand the drum detection terminal31sare not connected with each other. That is, the controller102determines that the drum cartridge1is not attached to the main body frame101.

On the other hand, when determining, in the first determination process, that the voltage at the main body detection terminal104sis the second voltage, the controller102determines that the main body detection terminal104sand the drum detection terminal31sare connected with each other. That is, the controller102determines that the drum cartridge1is attached to the main body frame101.

In this first modification as well as the above-described embodiment, the controller102can determine whether the drum cartridge1is attached to the main body frame101based on the voltage at the main body detection terminal104s. Thus, the controller102can determine whether the drum cartridge1is attached to the main body frame101without exchanging data with the drum memory151.

FIG. 10is a block diagram illustrating electrical connection between the controller102, the drum circuit board15, and the toner memories24according to a second modification. The second modification differs from the above-described embodiment in that a thermistor331tis used as the first drum resistor331.

The thermistor331tis a temperature sensor including an electric resistor. The resistance value of the thermistor331tchanges according to the temperature. The thermistor331thas one end connected to the drum detection terminal31sand another end connected to the main body side drum ground terminal31g. Thus, the controller102can determine whether the drum cartridge1is attached to the main body frame101by performing the first determination process in the same manner as in the above-described embodiment.

Further, in this second modification, the resistance value of the thermistor331tchanges according to the temperature. Thus, when the drum cartridge1is attached to the main body frame101, the value of the second voltage at the main body detection terminal104salso changes according to the temperature. This allows the controller102to detect the temperature inside the main body frame101based on the value of the second voltage measured by the voltage measurement circuit102a.

In the second modification, the thermistor331tserves both as the first drum resistor331and the temperature sensor. This eliminates the need to separately provide the first drum resistor331and the temperature sensor, allowing reduction in the number of components in the drum circuit board15.

FIG. 11is a block diagram illustrating electrical connection between the controller102, the drum circuit board15, and one toner memory24according to a third modification. The third modification differs from the above-described embodiment in the following respects: the number of the toner cartridges2that can be attached to the drum frame12is one; the controller102has a second main body resistor107t, a second main body detection terminal104t, and a second voltage measurement circuit102t; the drum circuit board15has a main body side drum detection terminal31tand a toner side drum detection terminal32t; and the toner memory24has a toner detection terminal242t.

The second main body resistor107thas one end connected to the second main body detection terminal104tand another end connected to the main body voltage terminal104v. The main body side drum detection terminal31tis electrically connected to the second main body detection terminal104tin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. The toner side drum detection terminal32tis electrically connected to the main body side drum detection terminal31t. The toner detection terminal (cartridge detection terminal)242tis electrically connected to the toner side drum detection terminal32tin the state where the toner cartridge2is attached to the drum frame12. The toner resistor243(cartridge resistor) has one end connected to the toner detection terminal242tand another end connected to the toner ground terminal242g. The second voltage measurement circuit102tcan measure the voltage at the second main body detection terminal104t.

When the toner cartridge2is not attached to the drum frame12, no current flows through the second main body resistor107t. Thus, the voltage at the second main body detection terminal104thas the same potential as the first voltage at the main body voltage terminal104v, which is connected to the main body detection terminal104tthrough the main body resistor107.

On the other hand, when the toner cartridge2is attached to the drum frame12, current flows from the main body voltage terminal104vtoward the main body ground terminal104gthrough: the second main body resistor107t; second main body detection terminal104t; main body side drum detection terminal31t; toner side drum detection terminal32t; toner detection terminal242t; toner resistor243; toner ground terminal242g; toner side drum ground terminal32g; and main body side drum ground terminal31g. Thus, the voltage at the second main body detection terminal104t, which is positioned between the second main body resistor107tand the toner resistor243, is the second voltage that is lower than the first voltage and higher than the ground voltage.

In the third determination process, the controller102determines whether the voltage at the second main body detection terminal104tmeasured by the second voltage measurement circuit102tis the first voltage or second voltage. That is, the controller102determines, in S22, whether the voltage at the second main body detection terminal104tmeasured by the second voltage measurement circuit102tis the first voltage or second voltage. In other words, the controller102determines whether the main body detection terminal104tand the toner detection terminal242tare electrically connected with each other via the main body side drum detection terminal31tand the toner side drum detection terminal32t. When determining that the voltage at the second main body detection terminal104tis the first voltage, the controller102determines that the toner side drum detection terminal32tand the toner detection terminal242tare not connected with each other. That is, the controller102determines that the toner cartridge2is not attached to the drum frame12.

On the other hand, when determining, in the third determination process, that the voltage at the second main body detection terminal104tmeasured by the second voltage measurement circuit102tis the second voltage, the controller102determines that the toner side drum detection terminal32tand the toner detection terminal242tare connected with each other. That is, the controller102determines that the toner cartridge2is attached to the drum frame12.

As described above, in the third determination process, the controller102of the image forming apparatus100can determine whether the toner side drum detection terminal32tand the toner detection terminal242tare connected with each other based on the amount of the voltage at the second main body detection terminal104t. Further, in the third determination process, the controller102can determine whether the toner cartridge2is attached to the drum frame12based on whether the toner side drum detection terminal32tand the toner detection terminal242tare connected with each other. Thus, the controller102can determine whether the toner cartridge2is attached to the drum frame12without communicating with the toner memory24.

FIG. 12is a block diagram illustrating electrical connection between the controller102, the drum circuit board15, and the toner memories24according to a fourth modification. In FIG.12, showing of the data terminals and clock terminals is omitted. The fourth modification differs from the above-described embodiment in the following respects: the controller102has a second main body resistor107t, a second main body detection terminal104t, and a second voltage measurement circuit102t; the drum circuit board15has a main body side drum detection terminal31t, four toner side drum detection terminals32t, and four third drum resistors333; and each of the toner memories24has a toner detection terminal242t.

The resistor107thas one end connected to the second main body detection terminal104tand another end connected to the main body voltage terminal104v. The main body side drum detection terminal3it is electrically connected to the second main body detection terminal104tin the state where the drum cartridge1is attached to the main body frame101of the image forming apparatus100. The four third drum resistors333are connected in parallel. One end of each of the four third drum resistors333is connected to the main body side drum detection terminal31t, and the other end thereof is connected to the corresponding toner side drum detection terminal32t. In each toner memory, the toner detection terminal (cartridge detection terminal)242tis electrically connected to the toner side drum detection terminal32tin the state where the toner cartridge2is attached to the drum frame12. Further, the toner detection terminal242tis electrically connected to the toner ground terminal242g. The second voltage measurement circuit102tcan measure the voltage at the second main body detection terminal104t.

When no toner cartridge2is attached to the drum frame12, no current flows through the second main body resistor107t. Thus, the voltage at the second main body detection terminal104thas the same potential as the first voltage at the main body voltage terminal104v, which is connected to the second main body detection terminal104tthrough the main body resistor107.

On the other hand, when at least one toner cartridge2is attached to the drum frame12, current flows from the main body voltage terminal104vtoward the main body ground terminal104gthrough: the second main body resistor107t; second main body detection terminal104t; main body side drum detection terminal3it; one of the third drum resistors333that is connected to the toner memory24of the attached toner cartridge2; toner side drum detection terminal32t; toner detection terminal242t; toner ground terminal242g; toner side drum ground terminal32g; and main body side drum ground terminal31g. Thus, the voltage at the second main body detection terminal104t, which is positioned between the second main body resistor107tand the third drum resistor333, becomes the second voltage that is lower than the first voltage and higher than the ground voltage.

In the fourth modification, resistance values of the four third drum resistors333differ from one another. Further, resultant resistance values of parallel combinations of any two, three or four of the four third drum resistors333differ from one another. With such a configuration, the voltage value of the second voltage changes depending on a combination of the third drum resistors333, through which current flows.

In the third determination process, the controller102determines whether the voltage at the second main body detection terminal104tmeasured by the second voltage measurement circuit102tis the first voltage or second voltage. That is, the controller102determines, in S22, whether the voltage at the second main body detection terminal104tmeasured by the second voltage measurement circuit102tis the first voltage or second voltage. In other words, the controller102determines whether the main body detection terminal104tand the toner detection terminal242tare electrically connected with each other via the main body side drum detection terminal31tand the toner side drum detection terminal32t. When determining that the voltage at the second main body detection terminal104tis the first voltage, the controller102determines that none of the toner side drum detection terminals32tof the drum circuit board15are connected with the toner detection terminal242t. That is, the controller102determines that the drum frames12is attached with no toner cartridges2.

On the other hand, when determining, in the third determination process, that the voltage at the second main body detection terminal104tmeasured by the second voltage measurement circuit102tis the second voltage, the controller102determines that at least one of the toner side drum detection terminals32tof the drum circuit board15is connected with the toner detection terminal242t. That is, the controller102determines that at least one toner cartridge2is attached to the drum frame12.

In this case, the controller102further determines a combination of the attached toner cartridges2based on the voltage value of the second voltage. Specifically, the correspondence relationship between a plurality of combinations of the toner cartridges2to be attached and voltage values of the second voltage are previously stored in the main body memory106of the controller102. The controller102determines, in the third determination process, a combination of the attached toner cartridges2based on the voltage value of the second voltage measured by the second voltage measurement circuit102tand the correspondence relationship read from the main body memory106.

The structures, the circuit configurations and processing procedures in the above-described embodiments and modifications are merely examples. Various elements appearing in the above-described embodiments and modifications may be replaced with other known elements without departing from the scope of the disclosure. Further, various elements appearing in the above-described embodiments and modifications may be appropriately combined within a range in which inconsistency does not occur.

While the description has been made in detail with reference to the specific embodiment, it would be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the disclosure.

For example, the first drum resistor331in the first modification (FIG. 9) may be replaced with a thermistor331tas in the second modification (FIG. 10).