Drum cartridge and image forming apparatus

Abstract

To provide a structure that can reduce the number of terminals in a drum cartridge having a drum memory mounted thereon.SOLUTION: A drum cartridge comprises: a frame to which toner cartridges can be attached; photoconductor drums; and drum circuit board 15. In a state where the toner cartridges are attached, the drum circuit board 15 relays information stored in toner memories included in the toner cartridges to an image forming apparatus.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a drum cartridge and an image forming apparatus.

Background Art

[0002] Conventionally, electrophotographic image forming apparatuses such as laser printers and LED printers are known. The image forming apparatus has a drum cartridge. The drum cartridge has a plurality of photosensitive drums. A plurality of toner cartridges are detachable from the drum cartridge. When a toner cartridge is attached to the drum cartridge, the developing roller of the toner cartridge contacts the photosensitive drum of the drum cartridge.

[0003] An image forming apparatus having a drum cartridge is described in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Also, conventionally, a toner cartridge having a toner memory as a storage medium is known. Various information regarding the toner cartridge is stored in the toner memory. In recent years, in an image forming apparatus, not only the toner cartridge but also a lot of information regarding the drum cartridge is handled. Therefore, it is required to mount a drum memory as a storage medium on the drum cartridge.

[0006] However, if toner memory is installed in the toner cartridge and drum memory is installed in the drum cartridge, the image forming apparatus will need terminals to electrically connect to the toner memory and terminals to electrically connect to the drum memory. This will require many terminals in the image forming apparatus.

[0007] The objective of the present invention is to provide a structure that allows drum memory to be mounted on a drum cartridge and reduces the number of terminals. [Means for solving the problem]

[0008] The present invention relates to a drum cartridge that can be mounted on an image forming apparatus, and is characterized by comprising: a frame on which a toner cartridge having a toner memory as a storage medium can be mounted; a photosensitive drum; a drum memory as a storage medium; and a drum circuit board that relays information stored in the toner memory to the image forming apparatus when the toner cartridge is mounted. [Effects of the Invention]

[0009] According to the present invention, the number of terminals can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This is a conceptual diagram of an image forming apparatus. [Figure 2] This is a perspective view of a drum cartridge. [Figure 3] This is a perspective view of a toner cartridge. [Figure 4] This is a perspective view of the first electrical terminal, the second electrical terminal, and the harness connecting them. [Figure 5] This is a perspective view of a toner cartridge. [Figure 6] This is a block diagram showing the electrical connections between the control unit, the drum circuit board, and the four toner circuit boards. [Figure 7]It is a flowchart showing the flow of processing after the drum cartridge is installed. [Figure 8] It is a flowchart showing the flow of the first determination process. [Figure 9] It is a flowchart showing the flow of the second determination process. [Figure 10] It is a flowchart showing the flow of the process of writing the main body information to the drum memory. [Figure 11] It is a flowchart showing the flow of the process of writing the toner information to the drum memory. [Figure 12] It is a flowchart showing the flow of the process of updating the rotation speed of the photosensitive drum. [Figure 13] It is a flowchart showing the flow of the process of updating the charging time of the photosensitive drum. [Figure 14] It is a flowchart showing the flow of the process of writing the error history to the drum memory. [Figure 15] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board in the second embodiment. [Figure 16] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board in the third embodiment. [Figure 17] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board in the fourth embodiment. [Figure 18] It is a flowchart showing the flow of the abnormality determination process in the fourth embodiment. [Figure 19] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board in the fifth embodiment. [Figure 20] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board in the sixth embodiment. [Figure 21] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board in the seventh embodiment. [Figure 22]It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board of the eighth embodiment. [Figure 23] It is a block diagram showing the electrical connection between the control unit, the drum circuit board, and the toner circuit board of the ninth embodiment.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] In the following description, the direction in which the rotation axis of the photosensitive drum extends is referred to as the "first direction". Also, the direction in which a plurality of photosensitive drums are arranged is referred to as the "second direction". The first direction and the second direction intersect (preferably orthogonally) with each other.

[0013] <1. First Embodiment> <1-1. Configuration of the Image Forming Apparatus> FIG. 1 is a conceptual diagram of an image forming apparatus 100. This image forming apparatus 100 is an electrophotographic printer. Examples of the image forming apparatus 100 include a laser printer or an LED printer. As shown in FIG. 1, the image forming apparatus 100 includes a main body casing 101, a control unit 102, a display 103, a drum cartridge 1, and a plurality of toner cartridges 2.

[0014] Multiple toner cartridges 2 can be individually mounted on the drum cartridge 1. The drum cartridge 1 with multiple toner cartridges 2 mounted can also be mounted on the main casing 101. Each of the multiple toner cartridges 2 contains toner (developer) of a different color (for example, cyan, magenta, yellow, and black). The image forming apparatus 100 forms an image on the recording surface of the printing paper using the toner supplied from the multiple toner cartridges 2. In this embodiment, the drum cartridge 1 is mounted on four toner cartridges 2. However, the number of toner cartridges 2 mounted on the drum cartridge 1 may be 1 to 3, or 5 or more.

[0015] The drum cartridge 1 includes a drum circuit board 15 and a drum memory 151. The drum memory 151 is a storage medium from which information can be read and written. Each of the toner cartridges 2 includes a toner circuit board 24 and a toner memory 241. The toner memory 241 is a storage medium from which information can be read and written.

[0016] The control unit 102 is located inside the main casing 101 of the image forming apparatus 100. The control unit 102 includes, for example, a circuit board, a processor 105 such as a CPU, and a main memory 106 which is a storage medium. The control unit 102 performs various processes in the image forming apparatus 100 by operating the processor 105 according to a program. Specifically, the control unit 102 performs a first read process to read information from the main memory 106, and an operation process to operate the image forming apparatus 100 based on the information read in the first read process.

[0017] When multiple toner cartridges 2 are mounted on the drum cartridge 1, the toner circuit board 24 of each toner cartridge 2 is electrically connected to the drum circuit board 15. Furthermore, when the drum cartridge 1 with the multiple toner cartridges 2 mounted is mounted on the main casing 101 of the image forming apparatus 100, the control unit 102 inside the main casing 101 is electrically connected to the drum circuit board 15. In other words, the toner circuit board 24 of each toner cartridge 2 and the control unit 102 are electrically connected via the drum circuit board 15.

[0018] The display 103 is, for example, a liquid crystal display or an organic EL display. The display 103 displays various information on the screen regarding the operation of the image forming apparatus 100 in accordance with commands from the control unit 102.

[0019] <1-2. About the Drum Cartridge Configuration> Next, we will describe the configuration of drum cartridge 1. Figures 2 and 3 are perspective views of drum cartridge 1.

[0020] As shown in Figures 2 and 3, the drum cartridge 1 has a plurality of photosensitive drums 11, a frame 12, a first electrical terminal 13, a plurality of second electrical terminals 14, and a drum circuit board 15. In this embodiment, there are four photosensitive drums 11. Also, there are four second electrical terminals 14.

[0021] The photosensitive drum 11 is a component for transferring toner supplied from the toner cartridge 2 to the printing paper. Multiple photosensitive drums 11 are arranged at intervals in a second direction. Each photosensitive drum 11 has a cylindrical outer surface extending in a first direction. The outer surface of the photosensitive drum 11 is covered with a photosensitive material. Each photosensitive drum 11 is also rotatable about a rotation axis extending in the first direction.

[0022] The frame 12 is a frame that holds multiple photosensitive drums 11. The frame 12 has multiple toner cartridge holders 121. The multiple toner cartridge holders 121 are arranged with spacing in the second direction. The toner cartridges 2 are mounted in the toner cartridge holders 121. Therefore, multiple toner cartridges 2 can be mounted in this frame 12. When the toner cartridges 2 are mounted in the toner cartridge holders 121, the outer surface of the photosensitive drum 11 and the outer surface of the developing roller 22 of the toner cartridge 2, which will be described later, come into contact.

[0023] Figure 4 is a perspective view of the first electrical terminal 13, the second electrical terminal 14, the drum circuit board 15, and the harnesses 16 and 17 connecting them.

[0024] The first electrical terminal 13 is a part that is electrically connected to a terminal provided inside the main casing 101 when the drum cartridge 1 is mounted in the main casing 101 of the image forming apparatus 100. The first electrical terminal 13 is fixed to the surface of the frame 12, for example. However, the first electrical terminal 13 may be immovable relative to the frame 12, or it may be slightly movable. The first electrical terminal 13 has a plurality of first terminals 131. Each first terminal 131 is an exposed conductor. Each first terminal 131 is electrically connected to a plurality of main body-side terminals 31 of the drum circuit board 15, which will be described later.

[0025] The second electrical terminal 14 is the part that is electrically connected to the terminal 242 of the toner circuit board 24, which will be described later, when the toner cartridge 2 is installed in the toner cartridge holder 121. The second electrical terminal 14 is provided for each toner cartridge holder 121. Each second electrical terminal 14 is located at the first end of the toner cartridge holder 121. Each second electrical terminal 14 is fixed to the surface of the frame 12, for example. However, the second electrical terminal 14 may be immovable relative to the frame 12, or it may be slightly movable. Each second electrical terminal 14 has a plurality of second terminals 141. Each second terminal 141 is an exposed conductor. Each second terminal 141 is electrically connected to a plurality of toner-side terminals 32 of the drum circuit board 15, which will be described later.

[0026] The drum circuit board 15 is a circuit board electrically connected to the first electrical terminal 13 and the second electrical terminal 14. The drum circuit board 15 is fixed to the surface of the frame 12, for example. As shown in Figure 4, the drum circuit board 15 and the first electrical terminal 13 are electrically connected via the first harness 16. The drum circuit board 15 and the second electrical terminal 14 are electrically connected via the second harness 17. For example, wire harnesses containing multiple conductors are used for the first harness 16 and the second harness 17.

[0027] As shown in Figure 4, the drum cartridge 1 has a drum memory 151, which is a storage medium. The drum memory 151 is located on the drum circuit board 15. Various information about the drum cartridge 1 is stored in the drum memory 151. For example, the drum memory 151 stores at least one of the following: information for identifying the drum cartridge 1 and information indicating the characteristics of the drum cartridge 1. The information for identifying the drum cartridge 1 includes, for example, at least one of the following: the manufacturing serial number of the drum cartridge 1 and an identification code indicating that it is a genuine product. The information indicating the characteristics of the drum cartridge 1 includes, for example, at least one of the following: the compatible model of the drum cartridge 1, the specifications of the drum cartridge 1, the lifespan of the photosensitive drum 11, the charging characteristics of the photosensitive drum 11, information indicating whether it is new or not, the rotation speed of the photosensitive drum 11, the charging time of the photosensitive drum 11, the number of printed pages, and the error history. Note that the drum memory 151 does not necessarily have to be located on the drum circuit board 15. Specifically, the drum memory 151 may be located on the surface of the frame 12.

[0028] The drum memory 151 has a first storage area for storing non-rewritable information and a second storage area for storing rewritable information. The first storage area can store at least one of the above-mentioned manufacturing serial number, identification code, compatible model, specifications, lifespan of the photosensitive drum 11, and charging characteristics of the photosensitive drum 11. The second storage area can store, for example, the usage status of the drum cartridge 1. The usage status of the drum cartridge 1 includes at least one of the above-mentioned information indicating whether it is new or not, the rotation speed of the photosensitive drum 11, the charging time of the photosensitive drum 11, the number of printed pages, and the error history.

[0029] Furthermore, the drum memory 151 can also store information about the toner cartridge 2. For example, the drum memory 151 can store the individual identification information of the toner cartridge 2 installed in the drum cartridge 1. This individual identification information is read from, for example, the toner memory 241 (described later) and written to the drum memory 151 of the drum circuit board 15. In this way, it is possible to distinguish whether the toner cartridge 2 installed in the drum cartridge 1 has been installed before or is being installed for the first time. However, the drum memory 151 does not necessarily have to be able to store information about the toner cartridge 2.

[0030] Furthermore, the drum memory 151 can store information about the usage history of the toner cartridge 2 installed in the drum cartridge 1. The usage history information of the toner cartridge 2 includes, for example, at least one of the following: the rotation speed of the developing roller 22, the amount of toner used, and the error history related to the toner cartridge 2. In this way, by storing the usage history information of the toner cartridge 2 in the drum memory 151, when a problem occurs, the problem can be analyzed simply by checking the drum memory 151, without having to check the toner memory 241 of each of the multiple toner cartridges 2 one by one. However, the drum memory 151 does not necessarily have to be able to store information about the usage history of the toner cartridge 2 installed in the drum cartridge 1.

[0031] <1-3. About the Toner Cartridge Configuration> Next, we will explain the configuration of toner cartridge 2. Below, we will describe the configuration of toner cartridge 2 when it is installed in drum cartridge 1, using the first and second directions described above.

[0032] Figure 5 is a perspective view of the toner cartridge 2. As shown in Figure 5, the toner cartridge 2 includes a casing 21, a developing roller 22, multiple gears, a coupling 231, a gear cover 232, a toner circuit board 24, and a toner memory 241.

[0033] The casing 21 is a housing capable of containing toner. The casing 21 extends in a first direction between a first outer surface 211 and a second outer surface 212. Inside the casing 21 is a storage chamber 213. The toner is housed in the storage chamber 213. The casing 21 also has an opening 214. The opening 214 is located at one end of the casing 21 in a third direction that intersects the first and second directions. The storage chamber 213 and the external space of the casing 21 are in communication through the opening 214.

[0034] The developing roller 22 is a roller that can rotate about a rotation axis extending in a first direction. The developing roller 22 is located at the opening 214 of the casing 21. That is, the developing roller 22 is located at one end of the casing 21 in a third direction. When the toner cartridge 2 is installed in the drum cartridge 1, the outer surface of the developing roller 22 contacts the outer surface of the photosensitive drum 11.

[0035] Toner is supplied from the storage chamber 213 to the outer surface of the photosensitive drum 11 via the developing roller 22. At this time, the toner carried on the outer surface of the developing roller 22 moves from the developing roller 22 to the photosensitive drum 11 in accordance with the electrostatic latent image formed on the outer surface of the photosensitive drum 11. As a result, the electrostatic latent image is made visible on the outer surface of the photosensitive drum 11.

[0036] Multiple gears, a coupling 231, and a gear cover 232 are located on the first outer surface 211 of the casing 21. The gear cover 232 is fixed to the first outer surface 211 of the casing 21, for example, by screws. At least some of the multiple gears are located between the first outer surface 211 of the casing 21 and the gear cover 232. The coupling 231 is exposed from the gear cover 232. When the drum cartridge 1 with the toner cartridge 2 installed is mounted in the image forming apparatus 100, the drive shaft of the image forming apparatus 100 is connected to the coupling 231. The rotation of the drive shaft is then transmitted to the developing roller 22 and the like via the coupling 231 and the multiple gears.

[0037] The toner circuit board 24 is held in a holder 25. In a first direction, the holder 25 is located between the first outer surface 211 of the casing 21 and the gear cover 232. However, the holder 25 may be located at other positions on the toner cartridge 2. It is also preferable that the holder 25 is movable in a second direction relative to the casing 21 and the gear cover 232.

[0038] The toner circuit board 24 has a plurality of terminals 242. Each terminal 242 is an exposed conductor. When the toner cartridge 2 is installed in the toner cartridge holder 121 of the drum cartridge 1, each terminal 242 of the toner circuit board 24 contacts a plurality of second terminals 141 of the second electrical terminal 14. In this embodiment, the toner circuit board 24 has four terminals 242. Also, the second electrical terminal 14 has four second terminals 141.

[0039] Furthermore, the toner cartridge 2 has a toner memory 241 (not shown in Figure 5; see Figure 6), which is a storage medium. The toner memory 241 is located on the toner circuit board 24. Various information about the toner cartridge 2 is stored in the toner memory 241. For example, the toner memory 241 stores at least one of the following: information for identifying the toner cartridge 2 and information indicating the characteristics of the toner cartridge 2. The information for identifying the toner cartridge 2 includes, for example, at least one of the manufacturing serial number of the toner cartridge 2 and an identification code indicating that it is a genuine product. The information indicating the characteristics of the toner cartridge 2 includes, for example, at least one of the following: compatible models of the toner cartridge 2, specifications of the toner cartridge 2, toner capacity, lifespan of the developer roller 22, information indicating whether it is new or not, rotation speed of the developer roller 22, number of printed pages, and error history. Note that the toner memory 241 does not necessarily have to be located on the toner circuit board 24. Specifically, the toner memory 241 may be located on the casing 21.

[0040] <1-4. About the Drum Circuit Board> Next, the more detailed configuration of the drum circuit board 15 will be described. Figure 6 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the toner circuit board 24. As shown in Figure 6, the drum circuit board 15 has a main unit side terminal 31, a toner side terminal 32, and a relay line 33.

[0041] <1-4-1. Regarding the terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. The main unit terminal 31 includes the main unit voltage terminal 31a, the main unit ground terminal 31b, the main unit clock terminal 31c, and the main unit signal terminal 31d. As shown in Figure 6, the number of main unit terminals 31 in this embodiment is multiple, specifically eight. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and five main unit signal terminals 31d. Also, there are multiple terminals 104 of the control unit 102, specifically eight.

[0042] The main unit voltage terminal 31a is electrically connected to the voltage terminal 104a of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0043] The main unit-side grounding terminal 31b is electrically connected to the grounding terminal 104b of the terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0044] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0045] The main unit-side signal terminal 31d is electrically connected to the signal terminal 104d of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15. In this embodiment, information is sent and received by serial communication. In this embodiment, there are five main unit-side signal terminals 31d, and there are five signal terminals 104d of the control unit 102. Each of the main unit-side signal terminals 31d is electrically connected to each of the signal terminals 104d when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100.

[0046] <1-4-2. Regarding the toner side terminals> The toner-side terminals 32 are electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminals 14 described above, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1. As a result, the drum circuit board 15 is electrically connected to the toner circuit board 24. As shown in Figure 6, the number of toner-side terminals 32 in this embodiment is 16.

[0047] Hereinafter, the four toner cartridges 2 installed in the drum cartridge 1 will be referred to as the first toner cartridge 2A, the second toner cartridge 2B, the third toner cartridge 2C, and the fourth toner cartridge 2D. The toner circuit board 24 of the first toner cartridge 2A will be referred to as the first toner circuit board 24A, the toner circuit board 24 of the second toner cartridge 2B will be referred to as the second toner circuit board 24B, the toner circuit board 24 of the third toner cartridge 2C will be referred to as the third toner circuit board 24C, and the toner circuit board 24 of the fourth toner cartridge 2D will be referred to as the fourth toner circuit board 24D.

[0048] The toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having four toner-side terminals 32, a third group 32C having four toner-side terminals 32, and a fourth group 32D having four toner-side terminals 32.

[0049] The toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0050] Each group's toner-side terminal 32 includes a toner-side voltage terminal 32a, a toner-side ground terminal 32b, a toner-side clock terminal 32c, and a toner-side signal terminal 32d.

[0051] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via a voltage relay line 33a, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminal 242a of terminal 242 on the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0052] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of terminal 242 on the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0053] The toner-side clock terminal 32c is electrically connected to the main unit-side clock terminal 31c via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminal 242c of terminal 242 on the toner circuit board 24. As a result, a clock signal is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15 at regular time intervals.

[0054] The toner-side signal terminal 32d is electrically connected to one of the main unit-side signal terminals 31d via a signal relay line 33d, which will be described later. The toner-side signal terminals 32d of the first group 32A, the second group 32B, the third group 32C, and the fourth group 32D are each electrically connected to different main unit-side signal terminals 31d. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminal 242d of terminal 242 on the toner circuit board 24. This makes it possible to send and receive signals indicating various information between the control unit 102 and the toner circuit board 24 via the drum circuit board 15.

[0055] <1-4-3. Regarding relay lines> The relay lines 33 include a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. As shown in Figure 6, there are multiple relay lines 33 in this embodiment, specifically eight. More specifically, there is one voltage relay line 33a, one ground relay line 33b, one clock relay line 33c, and five signal relay lines 33d.

[0056] One end of the voltage relay line 33a is electrically connected to the main unit voltage terminal 31a. The other end of the voltage relay line 33a branches into five. Specifically, the other end of the voltage relay line 33a includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. The fifth end of the voltage relay line 33a is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit voltage terminal 31a is supplied to the four toner-side voltage terminals 32a and the drum memory 151. By making the main unit voltage terminal 31a common in this way, the number of main unit terminals 31 can be reduced.

[0057] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into five. Specifically, the other end of the grounding relay wire 33b includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the ground voltage input to the main unit-side ground terminal 31b is supplied to the four toner-side ground terminals 32b and the drum memory 151. By making the main unit-side ground terminal 31b common in this way, the number of main unit-side terminals 31 can be reduced.

[0058] One end of the clock relay line 33c is electrically connected to the main unit clock terminal 31c. The other end of the clock relay line 33c branches into five. Specifically, the other end of the clock relay line 33c includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the first group 32A. The second end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the second group 32B. The third end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the third group 32C. The fourth end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the fourth group 32D. The fifth end of the clock relay line 33c is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the clock signal input to the main unit clock terminal 31c is supplied to the four toner-side clock terminals 32c and the drum memory 151. By making the main unit clock terminal 31c common in this way, the number of main unit terminals 31 can be reduced.

[0059] There are five signal relay lines 33d. One end of each signal relay line 33d is electrically connected to the main unit side signal terminal 31d. The other end of each signal relay line 33d includes a first end and a second end. The first end of each signal relay line 33d is electrically connected to the toner side signal terminal 32d. The second end of each signal relay line 33d is electrically connected to the drum memory 151. There are four first ends of each signal relay line 33d, and there is one second end of each signal relay line 33d. That is, the four main unit side signal terminals 31d and the four toner side signal terminals 32d are connected one-to-one by the signal relay lines 33d having the first ends. Also, one main unit side signal terminal 31d and the drum memory 151 are connected one-to-one by the signal relay line 33d having the second end.

[0060] <1-4-4. Information relay using drum circuit boards> In this manner, when the drum cartridge 1 with the toner cartridge 2 installed is mounted in the main casing 101 of the image forming apparatus 100, the control unit 102 and the toner circuit board 24 are electrically connected via the drum circuit board 15. Therefore, the drum circuit board 15 can relay information between the control unit 102 and the toner circuit board 24. For example, the drum circuit board 15 can acquire information stored in the toner memory 241 via the second harness 17 and the toner-side terminal 32, and output the acquired information to the control unit 102 via the main unit-side terminal 31 and the first harness 16. The drum circuit board 15 can also acquire information supplied from the control unit 102 via the first harness 16 and the main unit-side terminal 31, and output the acquired information to the toner circuit board 24 via the toner-side terminal 32 and the second harness 17.

[0061] Furthermore, as described in the second to ninth embodiments below, the drum cartridge 1 may include a multiplexer 34, a transistor array 35, a CPU 37, etc. The drum circuit board 15 may relay information between the control unit 102 and the toner circuit board 24 via the multiplexer 34, transistor array 35, and CPU 37.

[0062] In this way, by relaying the control unit 102 and the toner circuit board 24 via the drum circuit board 15, the number of terminals connected to the control unit 102 can be reduced compared to directly connecting the drum circuit board 15 and the toner circuit board 24 to each. For example, as shown in Figure 6, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 6, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 6, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 on the control unit 102.

[0063] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 6, the power supply voltage to be supplied to multiple toner circuit boards 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 6, the ground voltage to be supplied to multiple toner circuit boards 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 6, the clock signal to be supplied to multiple toner circuit boards 24 can be output from a single main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0064] <1-5. Processing after installing the drum cartridge> Next, we will explain the processing performed by the control unit 102 after the drum cartridge 1 has been installed in the main casing 101 of the image forming apparatus 100. Figure 7 is a flowchart showing the flow of this processing by the control unit 102.

[0065] When the drum cartridge 1 is installed in the main casing 101 of the image forming apparatus 100 and the front cover of the main casing 101 is closed, the control unit 102 first performs a first determination process (step S1). The first determination process is a process in which the control unit 102 determines whether or not it can communicate with the drum memory 151 and authenticates the drum memory.

[0066] Figure 8 is a flowchart showing the details of the first determination process. In the first determination process, first, the processor 105 of the control unit 102 transmits authentication information (second drum authentication information) to the main memory 106 (step S11) (third transmission process). For example, the processor 105 reads the authentication information (second drum authentication information) stored in a certain memory area of ​​the main memory 106. Then, the processor 105 transmits the read authentication information (second drum authentication information) to another area of ​​the main memory 106. After that, the processor 105 stores the authentication information (second drum authentication information) in another area of ​​the main memory 106. Then, the processor 105 receives a response value (third response value) from the main memory 106.

[0067] If the processor 105 does not receive a response value from the main memory 106, then communication between the processor 105 and the main memory 106 is invalid (step S12: no). In that case, the processor 105 outputs an error (step S13). Specifically, for example, the processor 105 reads the main communication error message information stored in the main memory 106. Then, the processor 105 displays the read main communication error message information on the display 103.

[0068] On the other hand, if the processor 105 receives a response value from the main memory 106, the communication between the processor 105 and the main memory 106 is valid (step S12: yes). In that case, the processor 105 sends authentication information (first drum authentication information) to the drum memory 151 (step S14) (first transmission process). For example, the processor 105 reads the authentication information stored in the main memory 106. Then, the processor 105 sends the read authentication information to the drum memory 151. After that, the processor 105 stores the authentication information in the drum memory 151. Then, the processor 105 receives a response value (first response value) from the drum memory 151 (first reception process).

[0069] If the processor 105 does not receive a response value from the drum memory 151, then communication between the processor 105 and the drum memory 151 is invalid (step S15: no). In that case, the processor 105 outputs an error (step S16) (first error output processing). Specifically, for example, the processor 105 reads the drum communication error message information stored in the main memory 106. Then, the processor 105 displays the read drum communication error message information on the display 103.

[0070] On the other hand, if the processor 105 receives a response value from the drum memory 151, the communication between the processor 105 and the drum memory 151 is valid (step S15: yes). In that case, the processor 105 then compares the response value from the main memory 106 (third response value) with the response value from the drum memory 151 (first response value) (step S17) (first comparison process). Specifically, the processor 105 determines whether the response value from the main memory 106 (third response value) and the response value from the drum memory 151 (first response value) match.

[0071] If the response value from the main memory 106 (third response value) and the response value from the drum memory 151 (first response value) do not match (step S18: no), the authentication of the drum memory 151 in the first determination process fails. In that case, the processor 105 outputs an error (step S19) (first error output process). Specifically, for example, the processor 105 reads the drum authentication error message information stored in the main memory 106. Then, the processor 105 displays the read drum authentication error message information on the display 103.

[0072] On the other hand, if the response value from the main memory 106 (third response value) and the response value from the drum memory 151 (first response value) match (step S18: yes), the authentication of the drum memory 151 in the first determination process is successful. In that case, the processor 105 proceeds to the process in step S2.

[0073] The control unit 102 may store a first predetermined value in the main memory 106. Then, in step S17 (first comparison process), the processor 105 may compare the response value from the drum memory 151 (first response value) with the first predetermined value. Specifically, the processor 105 may determine whether the response value from the drum memory 151 (first response value) and the first predetermined value match.

[0074] In that case, if the response value from the drum memory 151 does not match the first predetermined value, the authentication of the drum memory 151 fails. Therefore, the processor 105 outputs an error. Conversely, if the response value from the drum memory 151 matches the first predetermined value, the authentication of the drum memory 151 is successful. Therefore, the processor 105 proceeds to step S2.

[0075] Refer again to Figure 7. If the authentication of the drum memory 151 is successful, the processor 105 then reads the information stored in the drum memory 151 (step S2). The information read here includes, for example, at least one of the following: the manufacturing serial number of the drum cartridge 1, an identification code indicating that it is a genuine product, the compatible model of the drum cartridge 1, the specifications of the drum cartridge 1, the lifespan of the photosensitive drum 11, the charging characteristics of the photosensitive drum 11, information indicating whether it is new or not, the rotation speed of the photosensitive drum 11, the charging time of the photosensitive drum 11, the number of printed pages, and the error history.

[0076] Subsequently, the processor 105 determines whether the information read from the drum memory 151 is normal or not (step S3). Specifically, it determines whether the information read from the drum memory 151 meets predetermined conditions.

[0077] If the information read from the drum memory 151 is not normal, the information does not meet the predetermined conditions (step S4: no). In that case, the processor 105 outputs an error (step S5). Specifically, for example, the processor 105 reads the drum error message information stored in the main memory 106. Then, the processor 105 displays the read drum error message information on the display 103.

[0078] On the other hand, if the information read from the drum memory 151 is normal, the information meets the predetermined conditions (step S4: yes). In that case, the processor 105 performs a second determination process (step S6). The second determination process is a process in which the control unit 102 determines whether or not it can communicate with the toner memory 241 and authenticates the toner memory 241.

[0079] Figure 9 is a flowchart showing the details of the second determination process. In the second determination process, first, the processor 105 of the control unit 102 transmits authentication information (second toner authentication information) to the main memory 106 (step S61) (fourth transmission process). For example, the processor 105 transmits the authentication information stored in one memory area of ​​the main memory 106 to another area of ​​the main memory 106. After that, the processor 105 stores the authentication information in another area of ​​the main memory 106. Then, the processor 105 receives a response value (fourth response value) from the main memory 106.

[0080] If the processor 105 does not receive a response value from the main memory 106, then communication between the processor 105 and the main memory 106 is invalid (step S62: no). In that case, the processor 105 outputs an error (step S63). Specifically, for example, the processor 105 reads the main communication error message information stored in the main memory 106. Then, the processor 105 displays the read main communication error message information on the display 103.

[0081] On the other hand, if the processor 105 receives a response value from the main memory 106, the communication between the processor 105 and the main memory 106 is valid (step S62: yes). In that case, the processor 105 then sends authentication information (first toner authentication information) to the toner memory 241 (step S64) (second transmission process). For example, the processor 105 reads the authentication information stored in the main memory 106 and sends the read authentication information to the toner memory 241. After that, the processor 105 stores the authentication information in the toner memory 241. Then, the processor 105 receives a response value (second response value) from the toner memory 241 (second reception process).

[0082] If the processor 105 does not receive a response value from the drum memory 151, communication between the processor 105 and the toner memory 241 is invalid (step S65: no). In that case, the processor 105 outputs an error (step S66) (second error output processing). Specifically, for example, the processor 105 reads the toner communication error message information stored in the main memory 106. Then, the processor 105 displays the read toner communication error message information on the display 103.

[0083] On the other hand, if the processor 105 receives a response value from the drum memory 151, communication between the processor 105 and the toner memory 241 is valid (step S65: yes). In that case, the processor 105 then compares the response value from the main memory 106 (fourth response value) with the response value from the toner memory 241 (second response value) (step S67) (second comparison process). Specifically, the processor 105 determines whether the response value from the main memory 106 (fourth response value) and the response value from the toner memory 241 (second response value) match.

[0084] If the response value from the main memory 106 and the response value from the toner memory 241 do not match (step S68: no), the authentication of the toner memory 241 in the second determination process fails. In that case, the processor 105 outputs an error (step S69) (second error output process). Specifically, for example, the processor 105 reads the toner authentication error message information stored in the main memory 106. Then, the processor 105 displays the read toner authentication error message information on the display 103. The display 103 displays a message indicating an error.

[0085] On the other hand, if the response value from the main memory 106 and the response value from the toner memory 241 match (step S68: yes), the authentication of the toner memory 241 in the second determination process is successful. In that case, the processor 105 proceeds to the process in step S7.

[0086] The control unit 102 may store a second predetermined value in the main memory 106. Then, in step S67 (second comparison process), the processor 105 may compare the response value from the toner memory 241 (second response value) with the second predetermined value. Specifically, the processor 105 may determine whether the response value from the toner memory 241 (second response value) and the second predetermined value match.

[0087] In that case, if the response value from the toner memory 241 does not match the second predetermined value, the authentication of the toner memory 241 fails. Therefore, the processor 105 outputs an error. Conversely, if the response value from the toner memory 241 matches the second predetermined value, the authentication of the toner memory 241 is successful. Therefore, the processor 105 proceeds to step S7.

[0088] Refer again to Figure 7. If the authentication of the toner memory 241 is successful, the processor 105 then reads the information stored in the toner memory 241 (step S7). The information read here includes, for example, at least one of the following: the manufacturing serial number of the toner cartridge 2, an identification code indicating that it is a genuine product, the compatible model of the toner cartridge 2, the specifications of the toner cartridge 2, the toner capacity, the lifespan of the developer roller 22, information indicating whether it is new or not, the rotation speed of the developer roller 22, the number of printed pages, and the error history.

[0089] Subsequently, the processor 105 determines whether the information read from the toner memory 241 is normal or not (step S8). Specifically, it determines whether the information read from the toner memory 241 meets predetermined conditions.

[0090] If the information read from the toner memory 241 is not normal, the information does not meet the predetermined conditions (step S9: no). In that case, the processor 105 outputs an error (step S10). Specifically, for example, the processor 105 reads the toner error message information stored in the main memory 106. Then, the processor 105 displays the read toner error message information on the display 103.

[0091] On the other hand, if the information read from the toner memory 241 is normal, that information will meet the predetermined conditions (step S9: yes). In that case, the processor 105 will enter a standby state, waiting for a print command to be input.

[0092] Note that the processes in steps S6 to S10 are performed for each of the toner memories 241 of the multiple toner cartridges 2.

[0093] As described above, in this image forming apparatus 100, after the drum cartridge 1 is installed in the main casing 101, a first determination process (step S1) is performed on the drum memory 151, and then a second determination process (step S2) is performed on the toner memory 241. This allows for efficient performance of both the first determination process for the drum memory 151 and the second determination process for the toner memory 241.

[0094] In other words, in this image forming apparatus 100, the control unit 102 and the toner circuit board 24 are connected via the drum circuit board 15. Therefore, if the second judgment process is performed before the first judgment process, it will be unclear whether the problem lies in the communication between the control unit 102 and the drum circuit board 15, or between the drum circuit board 15 and the toner circuit board 24, if the result of the second judgment process is an error. For this reason, the first judgment process must also be performed to isolate the error. In contrast, as described above, if the first judgment process is performed before the second judgment process, if the result of the first judgment process is an error, the second judgment process will also inevitably result in an error, thus allowing the second judgment process to be omitted. This makes the first and second judgment processes more efficient by eliminating unnecessary judgment processes.

[0095] Furthermore, the processor 105 prioritizes outputting errors in step S16 or step S19 of the first determination process (first errors) over errors in step S66 or step S19 of the second determination process (second errors). Specifically, for example, the processor 105 displays a message indicating a first error on the display 103 before a message indicating a second error. In this way, the user of the image forming apparatus 100 can address communication failures with the drum circuit board 15 before communication failures with the toner circuit board 24. This allows for efficient error handling.

[0096] In other words, if the second error were output with priority over the first error, it would be unclear whether the second error was caused by a communication failure between the control unit 102 and the drum circuit board 15, or between the drum circuit board 15 and the toner circuit board 24. This could lead to wasted effort on the user's part. In contrast, if the first error is output with priority over the second error, as described above, the first error can be considered to be caused by a communication failure between the control unit 102 and the drum circuit board 15. Furthermore, if the second error is output without the first error being output, the second error can be considered to be caused by a communication failure between the drum circuit board 15 and the toner circuit board 24. Therefore, the user of the image forming apparatus 100 can appropriately determine which part needs to be addressed.

[0097] In the example above, the processor 105 executed the second determination process (step S6) after the first determination process (step S1). However, the processor 105 may execute the first and second determination processes in parallel and output the first error with priority over the second error. Specifically, the processor 105 may output the first error to the display before the second error, as in the example above. Alternatively, the processor 105 may output the first and second errors simultaneously and display the first error in a manner that is more visible than the second error. For example, the processor 105 may display the first error larger or darker than the second error.

[0098] Furthermore, in the above example, in the first and second determination processes, the control unit 102 received response information after transmitting authentication information. That is, in the first and second determination processes, the control unit 102 performed authentication through round-trip communication. However, the first and second determination processes may also be determination processes based on one-way communication.

[0099] <1-6. Writing main unit information to drum memory> Figure 10 is a flowchart showing an example of additional processing that can be added to the processing in Figure 7. In the example in Figure 10, if the information read from the drum memory 151 in step S4 is normal, the processor 105 first checks whether the information stored in the main memory 106 (hereinafter referred to as "main information") has been updated (step S101). If the main information has not been updated (step S101: no), the process proceeds directly to step S6.

[0100] On the other hand, if the main unit information has been updated (step S101: yes), the processor 105 writes the main unit information stored in the main unit memory 106 to the drum memory 151 (step S102). Specifically, the processor 105 performs a read operation to read the main unit information from the main unit memory 106 and a write operation to write the read main unit information to the drum memory 151.

[0101] The main unit information includes, for example, at least one of the following: information for identifying the image forming apparatus 100 and information indicating the characteristics of the image forming apparatus 100. The information for identifying the image forming apparatus 100 includes, for example, the manufacturing serial number of the image forming apparatus 100. The information indicating the characteristics of the image forming apparatus 100 includes, for example, at least one of the following: the model code of the image forming apparatus 100, the specifications of the image forming apparatus 100, the characteristics of the parts of the image forming apparatus 100, the usage history of the image forming apparatus 100, and the error history of the image forming apparatus 100.

[0102] In this way, by storing some of the information regarding the image forming apparatus 100 in the drum memory 151, the status of the image forming apparatus 100 can be determined based on the information stored in the drum memory 151. Therefore, when a malfunction occurs in the image forming apparatus 100, the manufacturer can recover only the drum memory 151 without recovering the image forming apparatus 100, and analyze the malfunction based on the main unit information stored in the drum memory 151.

[0103] <1-7. Writing toner information to drum memory> Figure 11 is a flowchart showing an example of a process that can be added to the process in Figure 7. In the example in Figure 11, if the information read from the toner memory 241 in step S9 is normal, the processor 105 first checks whether the information stored in the toner memory 241 (hereinafter referred to as "toner information") has been updated (step S201). If the toner information has not been updated (step S201: no), the processor enters a waiting state and waits for a print command to be input.

[0104] On the other hand, if the toner information has been updated (step S201: yes), the processor 105 writes the toner information stored in the toner memory 241 to the drum memory 151 (step S202). Specifically, the processor 105 performs a read operation to read the toner information from the toner memory 241 and a write operation to write the read toner information to the drum memory 151.

[0105] In step S201, the toner information of each of the four toner cartridges 2's toner memory 241 is checked to see if it has been updated. If the toner information has been updated in at least one toner memory 241, step S202 is executed. The toner information of all the toner memories 241 whose updates have been confirmed is then written to the drum memory 151.

[0106] The toner information includes, for example, at least one of the following: the manufacturing serial number of toner cartridge 2, an identification code indicating that it is a genuine product, the compatible models for toner cartridge 2, the specifications of toner cartridge 2, the toner capacity, the lifespan of the developer roller 22, information indicating whether it is new or not, the rotation speed of the developer roller 22, the number of printed pages, and the error history.

[0107] In this way, by storing some of the information about toner cartridge 2 in the drum memory 151, it is possible to know the information about toner cartridge 2 installed in drum cartridge 1 based on the information stored in the drum memory 151. Therefore, if a malfunction occurs in any of the drum cartridge 1 or the four toner cartridges 2, the manufacturer can recover only the drum memory 151 without having to recover all of the drum cartridge 1 and the four toner cartridges 2, and analyze the malfunction based on the toner information stored in the drum memory 151.

[0108] Furthermore, when a toner cartridge 2 is installed in drum cartridge 1, it is possible to determine whether that toner cartridge 2 has been installed in the past, based on the information stored in drum memory 151.

[0109] <1-8. Regarding the process of updating the drum rotation speed> As described above, the drum memory 151 can store the rotation count of the photosensitive drum 11. The rotation count of the photosensitive drum 11 is the cumulative number of rotations the photosensitive drum 11 has made since it began to be used. The rotation count of the photosensitive drum 11 stored in the drum memory 151 is updated as the printing process is executed in the image forming apparatus 100. The process of updating the rotation count of the photosensitive drum 11 will be explained below with reference to the flowchart in Figure 12.

[0110] The image forming apparatus 100 has a sensor (not shown) that detects the rotation of the photosensitive drum 11. The sensor outputs a detection signal for each rotation of the photosensitive drum 11. When the printing process is executed, the processor 105 of the control unit 102 first reads the rotation speed of the photosensitive drum 11 from the drum memory 151. Then, the processor 105 monitors for the presence or absence of a detection signal (step S301). If there is no detection signal (step S301: no), the processor 105 continues to monitor for a detection signal. When the photosensitive drum 11 has completed one rotation, a detection signal is output from the sensor (step S301: yes). Then, the processor 105 increments the rotation speed of the photosensitive drum 11 by one rotation (step S302).

[0111] Next, the processor 105 determines whether the difference between the rotational speed read from the drum memory 151 (the rotational speed after the last update) and the incremented rotational speed has reached a predetermined number of times (step S303). The predetermined number of times can be stored, for example, in the main memory 106. If the difference between the rotational speed after the last update and the incremented rotational speed is less than the predetermined number of times (step S303: no), the processor 105 continues to repeat the process in steps S301 to S303.

[0112] Eventually, when the difference between the rotation speed since the last update and the incremented rotation speed reaches a predetermined number of times (step S303: yes), the processor 105 writes the incremented rotation speed at that point to the drum memory 151. In other words, the processor 105 updates the rotation speed of the photosensitive drum 11 stored in the drum memory 151 (step S304).

[0113] The processor 105 then executes steps S301 to S304 for each of the four photosensitive drums 11.

[0114] In this way, by updating the rotation speed of the photosensitive drum 11 stored in the drum memory 151 at predetermined intervals, it becomes unnecessary to manage the rotation speed information of the photosensitive drum 11 in the main memory 106 of the image forming apparatus 100. Even if the drum cartridge 1 is swapped and used between multiple image forming apparatuses 100, the rotation speed of the photosensitive drum 11 can be appropriately managed for each drum cartridge 1. Therefore, the lifespan of the photosensitive drum 11 can be appropriately determined based on the rotation speed of the photosensitive drum 11 stored in the drum memory 151.

[0115] In particular, in the example shown in Figure 12, the rotation speed of the photosensitive drum 11 stored in the drum memory 151 is updated not after each rotation, but at predetermined intervals. This reduces the processing load on the processor 105. Therefore, delays in the printing process can be suppressed.

[0116] <1-9. Regarding the update process of the charging time> As described above, the drum memory 151 can store the charging time of the photosensitive drum 11. The charging time of the photosensitive drum 11 is the cumulative time that the photosensitive drum 11 has been charged by a charger (not shown) since the start of use of the photosensitive drum 11. The charging time of the photosensitive drum 11 stored in the drum memory 151 is updated as the printing process is executed in the image forming apparatus 100. The following describes the process of updating the charging time of the photosensitive drum 11 with reference to the flowchart in Figure 13.

[0117] When the printing process is executed, the processor 105 of the control unit 102 first reads the charging time of the photosensitive drum 11 from the drum memory 151. Then, the processor 105 monitors whether the photosensitive drum 11 is charged or not (step S401). If the drum memory 151 is not charged (step S401: no), the processor 105 continues to monitor whether the photosensitive drum 11 is charged or not. If the photosensitive drum 11 is charged (step S401: yes), the processor 105 measures the charging time of the photosensitive drum 11 (step S402). Then, it increments the charging time read from the drum memory 151 by the measured charging time.

[0118] Next, the processor 105 determines whether the difference between the charging time read from the drum memory 151 (charging time since the last update) and the incremented charging time has reached a predetermined time (step S403). The predetermined time can be stored, for example, in the main memory 106. If the difference between the charging time since the last update and the incremented charging time is less than the predetermined time (step S403: no), the processor 105 continues to repeat the process in steps S401 to S403.

[0119] Eventually, when the difference between the charging time since the last update and the incremented charging time reaches a predetermined time (step S403: yes), the processor 105 writes the incremented charging time at that point to the drum memory 151. In other words, the processor 105 updates the charging time of the photosensitive drum 11 stored in the drum memory 151 (step S404).

[0120] The processor 105 then executes steps S401 to S404 for each of the four photosensitive drums 11.

[0121] In this way, by updating the charge time of the photosensitive drum 11 stored in the drum memory 151 at predetermined intervals, it becomes unnecessary to manage the charge time information of the photosensitive drum 11 in the main memory 106 of the image forming apparatus 100. Even if the drum cartridge 1 is swapped and used between multiple image forming apparatuses 100, the charge time of the photosensitive drum 11 can be appropriately managed for each drum cartridge 1. Therefore, the lifespan of the photosensitive drum 11 can be appropriately determined based on the charge time of the photosensitive drum 11 stored in the drum memory 151.

[0122] In particular, in the example shown in Figure 13, the charging time of the photosensitive drum 11 stored in the drum memory 151 is updated at predetermined intervals rather than continuously. This reduces the processing load on the processor 105. Therefore, delays in the printing process can be suppressed.

[0123] <1-10. Handling of errors> As described above, the drum memory 151 can store an error history. The error history is written to the drum memory 151 when an error occurs in the drum cartridge 1. The process of writing this error history to the drum memory 151 will be explained below with reference to the flowchart in Figure 14.

[0124] In the following explanation, the four photosensitive drums 11 of the drum cartridge 1 will be referred to as the first photosensitive drum 11A, the second photosensitive drum 11B, the third photosensitive drum 11C, and the fourth photosensitive drum 11D.

[0125] During the printing process, the processor 105 of the control unit 102 constantly monitors for errors (step S501). Errors are detected by sensors inside the main casing 101 of the image forming apparatus 100. If no errors are detected (step S501: no), the processor 105 continues to monitor for errors.

[0126] If an error occurs (step S501: yes), the processor 105 first determines whether the error is related to the first photosensitive drum 11A (step S502). This determination is made, for example, by determining whether the sensor that detected the error is the sensor corresponding to the first photosensitive drum 11A. If the error is related to the first photosensitive drum 11A (step S502: yes), the processor 105 writes the error history to the first storage area of ​​the drum memory 151 (step S503). The error history includes, for example, at least one of the time the error occurred and the type of error.

[0127] On the other hand, if the error that occurred is not related to the first photosensitive drum 11A (step S502: no), the processor 105 then determines whether the error is related to the second photosensitive drum 11B (step S504). This determination is made, for example, by whether the sensor that detected the error is the sensor corresponding to the second photosensitive drum 11B. If the error is related to the second photosensitive drum 11B (step S504: yes), the processor 105 writes the error history to a second storage area different from the first storage area of ​​the drum memory 151 (step S505). The error history includes, for example, at least one of the time the error occurred and the type of error.

[0128] On the other hand, if the error that occurred is not related to the second photosensitive drum 11B (step S504: no), the processor 105 then determines whether the error is related to the third photosensitive drum 11C (step S506). This determination is made, for example, by whether the sensor that detected the error is the sensor corresponding to the third photosensitive drum 11C. If the error is related to the third photosensitive drum 11C (step S506: yes), the processor 105 writes the error history to a third storage area of ​​the drum memory 151 that is different from the first and second storage areas (step S507). The error history includes, for example, at least one of the time the error occurred and the type of error.

[0129] On the other hand, if the error that occurred is not related to the third photosensitive drum 11C (step S506: no), the processor 105 then determines whether the error is related to the fourth photosensitive drum 11D (step S508). This determination is made, for example, by whether the sensor that detected the error is the sensor corresponding to the fourth photosensitive drum 11D. If the error is related to the fourth photosensitive drum 11D (step S508: yes), the processor 105 writes the error history to a fourth memory area of ​​the drum memory 151 that is different from the first to third memory areas (step S509). The error history includes, for example, at least one of the time the error occurred and the type of error.

[0130] <2. Second Embodiment> Figure 15 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the second embodiment. In the example of Figure 15, the drum cartridge 1 comprises the drum circuit board 15, the drum memory 151, and the multiplexer 34. The drum circuit board 15 has a main unit side terminal 31, a toner side terminal 32, and a relay line 33. The drum memory 151 and the multiplexer 34 are located on the drum circuit board 15. However, the drum memory 151 and the multiplexer 34 do not necessarily have to be located on the drum circuit board 15. Specifically, the drum memory 151 may be located on the surface of the frame 12.

[0131] <2-1. Regarding the terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 15, there are multiple main unit terminals 31 in this embodiment, specifically seven in number. Specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and four main unit signal terminals 31d.

[0132] The main unit voltage terminal 31a is electrically connected to the voltage terminal 104a of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0133] The main unit-side grounding terminal 31b is electrically connected to the grounding terminal 104b of the terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0134] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0135] The main unit signal terminal 31d is electrically connected to the signal terminal 104d of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0136] <2-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 15, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0137] The toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having four toner-side terminals 32, a third group 32C having four toner-side terminals 32, and a fourth group 32D having four toner-side terminals 32.

[0138] The toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0139] Each group's toner-side terminal 32 includes a toner-side voltage terminal 32a, a toner-side ground terminal 32b, a toner-side clock terminal 32c, and a toner-side signal terminal 32d.

[0140] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via a voltage relay line 33a, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminal 242a of terminal 242 on the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0141] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of terminal 242 on the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0142] The toner-side clock terminal 32c is electrically connected to the main unit-side clock terminal 31c via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminal 242c of terminal 242 on the toner circuit board 24. As a result, a clock signal is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15 at regular time intervals.

[0143] The toner-side signal terminal 32d is electrically connected to the multiplexer 34 via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminal 242d of terminal 242 of the toner circuit board 24.

[0144] <2-3. Regarding relay lines> As shown in Figure 15, the relay lines 33 in this embodiment include a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. Specifically, there is one voltage relay line 33a, one ground relay line 33b, one clock relay line 33c, and multiple signal relay lines 33d.

[0145] One end of the voltage relay line 33a is electrically connected to the main unit voltage terminal 31a. The other end of the voltage relay line 33a branches into five. Specifically, the other end of the voltage relay line 33a includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. The fifth end of the voltage relay line 33a is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit voltage terminal 31a is supplied to the four toner-side voltage terminals 32a and the drum memory 151. By making the main unit voltage terminal 31a common in this way, the number of main unit terminals 31 can be reduced.

[0146] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into five. Specifically, the other end of the grounding relay wire 33b includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the ground voltage input to the main unit-side ground terminal 31b is supplied to the four toner-side ground terminals 32b and the drum memory 151. By making the main unit-side ground terminal 31b common in this way, the number of main unit-side terminals 31 can be reduced.

[0147] One end of the clock relay line 33c is electrically connected to the main unit clock terminal 31c. The other end of the clock relay line 33c branches into five. Specifically, the other end of the clock relay line 33c includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the first group 32A. The second end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the second group 32B. The third end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the third group 32C. The fourth end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the fourth group 32D. The fifth end of the clock relay line 33c is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the clock signal input to the main unit clock terminal 31c is supplied to the four toner-side clock terminals 32c and the drum memory 151. By making the main unit clock terminal 31c common in this way, the number of main unit terminals 31 can be reduced.

[0148] The signal relay line 33d includes the main unit side signal relay line 331d, the toner side signal relay line 332d, and the drum signal line 333d. In this embodiment, there are multiple main unit side signal relay lines 331d, specifically four. There are also multiple toner side signal relay lines 332d, specifically four. There is one drum signal line 333d. Each main unit side signal relay line 331d electrically connects the main unit side signal terminal 31d to the multiplexer 34. Each toner side signal relay line 332d electrically connects the multiplexer 34 to the toner side signal terminal 32d. The drum signal line 333d electrically connects the multiplexer 34 to the drum memory 151.

[0149] <2-4. About Multiplexers> The multiplexer 34 is a switch circuit that switches the connection of signal lines. The main unit side signal terminal 31d has a main unit side address signal terminal and a main unit side data signal terminal. In this embodiment, there are four main unit side signal terminals 31d. Specifically, there are three main unit side address signal terminals and one main unit side data signal terminal.

[0150] The multiplexer 34 receives an address signal from the control unit 102 via the main unit-side address signal terminal. The address signal is a signal used to specify the communication destination. The multiplexer 34 switches communication to either the drum memory 151 or the toner-side signal terminal 32d according to the address signal received via the main unit-side address signal terminal.

[0151] Furthermore, the multiplexer 34 receives data signals from the control unit 102 via the main unit's data signal terminal. The data signals are signals indicating various information to be sent to the communication destination. The multiplexer 34 outputs the data signals received via the main unit's data signal terminal to the drum memory 151 or the toner-side signal terminal 32d.

[0152] In this way, by using the multiplexer 34, it is possible to switch between the drum memory 151 and the four toner memories 241 to be the communication destination, and output a data signal. Therefore, it is not necessary to provide a separate main unit signal terminal 31d for each of the drum memory 151 and the toner side signal terminal 32d. Consequently, the number of main unit signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0153] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 15 of this embodiment, only four signal terminals 31d on the main unit side are needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 15 of this embodiment, only four signal terminals 104d on the control unit 102 are needed.

[0154] <2-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 15, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 15, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 15, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0155] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 15, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 15, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 15, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0156] <3. Third Embodiment> Figure 16 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the third embodiment. In the example of Figure 16, the drum cartridge 1 comprises the drum circuit board 15, the drum memory 151, and the multiplexer 34. The drum circuit board 15 has a main unit side terminal 31, a toner side terminal 32, and a relay line 33. The drum memory 151 and the multiplexer 34 are located on the drum circuit board 15. However, the drum memory 151 and the multiplexer 34 do not necessarily have to be located on the drum circuit board 15. Specifically, the drum memory 151 may be located on the surface of the frame 12.

[0157] <3-1. Regarding the terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 16, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and one main unit signal terminal 31d.

[0158] The main unit voltage terminal 31a is electrically connected to the voltage terminal 104a of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0159] The main unit-side grounding terminal 31b is electrically connected to the grounding terminal 104b of the terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0160] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0161] The main unit signal terminal 31d is electrically connected to the signal terminal 104d of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0162] <3-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 16, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0163] The toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having four toner-side terminals 32, a third group 32C having four toner-side terminals 32, and a fourth group 32D having four toner-side terminals 32.

[0164] The toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0165] Each group's toner-side terminal 32 includes a toner-side voltage terminal 32a, a toner-side ground terminal 32b, a toner-side clock terminal 32c, and a toner-side signal terminal 32d.

[0166] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via a voltage relay line 33a, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminal 242a of terminal 242 on the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0167] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of terminal 242 on the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0168] The toner-side clock terminal 32c is electrically connected to the multiplexer 34 via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminal 242c of terminal 242 of the toner circuit board 24.

[0169] The toner-side signal terminal 32d is electrically connected to the multiplexer 34 via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminal 242d of terminal 242 of the toner circuit board 24.

[0170] <3-3. Regarding relay lines> As shown in Figure 16, the relay line 33 in this embodiment includes a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d.

[0171] One end of the voltage relay line 33a is electrically connected to the main unit voltage terminal 31a. The other end of the voltage relay line 33a branches into five. Specifically, the other end of the voltage relay line 33a includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. The fifth end of the voltage relay line 33a is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit voltage terminal 31a is supplied to the four toner-side voltage terminals 32a and the drum memory 151. By making the main unit voltage terminal 31a common in this way, the number of main unit terminals 31 can be reduced.

[0172] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into five. Specifically, the other end of the grounding relay wire 33b includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the ground voltage input to the main unit-side ground terminal 31b is supplied to the four toner-side ground terminals 32b and the drum memory 151. By making the main unit-side ground terminal 31b common in this way, the number of main unit-side terminals 31 can be reduced.

[0173] The clock relay line 33c includes the main unit-side clock relay line 331c, the toner-side clock relay line 332c, and the drum clock line 333c. In this embodiment, there is one main unit-side clock relay line 331c. There are multiple toner-side clock relay lines 332c, specifically four. There is one drum clock line 333c. The main unit-side clock relay line 331c electrically connects the main unit-side clock terminal 31c and the multiplexer 34. The toner-side clock relay lines 332c each electrically connect the multiplexer 34 and the toner-side clock terminal 32c. The drum clock line 333c electrically connects the multiplexer 34 and the drum memory 151.

[0174] The signal relay line 33d includes the main unit side signal relay line 331d, the toner side signal relay line 332d, and the drum signal line 333d. In this embodiment, there is one main unit side signal relay line 331d. There are multiple toner side signal relay lines 332d, specifically four. There is one drum signal line 333d. The main unit side signal relay line 331d electrically connects the main unit side signal terminal 31d to the multiplexer 34. The toner side signal relay lines 332d each electrically connect the multiplexer 34 to the toner side signal terminal 32d. The drum signal line 333d electrically connects the multiplexer 34 to the drum memory 151.

[0175] <3-4. About Multiplexers> The multiplexer 34 is a switch circuit that switches the connection of signal lines. The multiplexer 34 receives a clock signal from the control unit 102 via the main unit clock terminal 31c. The multiplexer 34 also supplies the obtained clock signal to each toner circuit board 24 via the toner-side clock terminal 32c, as well as to the drum memory 151. In other words, on this drum circuit board 15, the clock signal input to the main unit clock terminal 31c is supplied to the four toner-side clock terminals 32c and the drum memory 151. By commonizing the main unit clock terminal 31c in this way, the number of main unit terminals 31 can be reduced.

[0176] Furthermore, the multiplexer 34 receives an address signal and a data signal from the control unit 102 via the main unit-side signal terminal 31d. The address signal is a signal used to specify the communication destination. The data signal is a signal indicating various information to be sent to the communication destination. The multiplexer 34 switches communication to either the drum memory 151 or the toner-side signal terminal 32d according to the received address signal. The multiplexer 34 also outputs the received data signal to either the drum memory 151 or the toner-side signal terminal 32d.

[0177] In this way, by using the multiplexer 34, it is possible to switch between the drum memory 151 and the four toner memories 241 to be the communication destination and output a data signal. Therefore, it is not necessary to provide a separate main unit signal terminal 31d for each of the drum memory 151 and the four toner-side signal terminals 32d. Consequently, the number of main unit signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0178] In particular, the multiplexer 34 of this embodiment receives the address signal and the data signal via a single main unit-side signal terminal 31d. This allows for a further reduction in the number of main unit-side signal terminals 31d. Furthermore, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0179] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 16 of this embodiment, only one signal terminal 31d on the main unit side is needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 16 of this embodiment, only one signal terminal 104d on the control unit 102 is needed.

[0180] <3-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 16, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 16, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 16, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0181] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 16, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 16, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 16, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0182] <4. Fourth Embodiment> Figure 17 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the fourth embodiment. In the example of Figure 17, the drum cartridge 1 comprises the drum circuit board 15, the drum memory 151, and the multiplexer 34. The drum circuit board 15 has a plurality of main unit-side terminals 31, a plurality of toner-side terminals 32, and a plurality of relay lines 33. The drum memory 151 and the multiplexer 34 are located on the drum circuit board 15. Note that the drum memory 151 does not necessarily have to be located on the drum circuit board 15. Specifically, the drum memory 151 may be located on the surface of the frame 12.

[0183] <4-1. Regarding terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 17, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and one main unit signal terminal 31d.

[0184] The main unit voltage terminal 31a is electrically connected to the voltage terminal 104a of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0185] The main unit-side grounding terminal 31b is electrically connected to the grounding terminal 104b of the terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0186] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0187] The main unit signal terminal 31d is electrically connected to the signal terminal 104d of terminal 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0188] <4-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when four toner cartridges 2 are mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 17, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0189] The toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having four toner-side terminals 32, a third group 32C having four toner-side terminals 32, and a fourth group 32D having four toner-side terminals 32.

[0190] The toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0191] Each group's toner-side terminal 32 includes a toner-side voltage terminal 32a, a toner-side ground terminal 32b, a toner-side clock terminal 32c, and a toner-side signal terminal 32d.

[0192] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via a voltage relay line 33a, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminal 242a of terminal 242 on the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0193] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of terminal 242 on the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0194] The toner-side clock terminal 32c is electrically connected to the multiplexer 34 via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminal 242c of terminal 242 of the toner circuit board 24.

[0195] The toner-side signal terminal 32d is electrically connected to the multiplexer 34 via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminal 242d of terminal 242 of the toner circuit board 24.

[0196] <4-3. Regarding relay lines> As shown in Figure 17, the relay line 33 in this embodiment includes a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. Specifically, there is one voltage relay line 33a, one ground relay line 33b, multiple clock relay lines 33c, and multiple signal relay lines 33d.

[0197] One end of the voltage relay line 33a is electrically connected to the main unit voltage terminal 31a. The other end of the voltage relay line 33a branches into five. Specifically, the other end of the voltage relay line 33a includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the voltage relay line 33a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. The fifth end of the voltage relay line 33a is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit voltage terminal 31a is supplied to the four toner-side voltage terminals 32a and the drum memory 151. By making the main unit voltage terminal 31a common in this way, the number of main unit terminals 31 can be reduced.

[0198] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into five. Specifically, the other end of the grounding relay wire 33b includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the drum memory 151. Therefore, in the drum circuit board 15, the ground voltage input to the main unit-side ground terminal 31b is supplied to the four toner-side ground terminals 32b and the drum memory 151. By making the main unit-side ground terminal 31b common in this way, the number of main unit-side terminals 31 can be reduced.

[0199] The clock relay line 33c includes a main unit-side clock relay line 331c and a toner-side clock relay line 332c. In this embodiment, there is one main unit-side clock relay line 331c. There are multiple toner-side clock relay lines 332c, specifically four. One end of the main unit-side clock relay line 331c is electrically connected to the main unit-side clock terminal 31c. The other end of the main unit-side clock relay line 331c branches into two. Specifically, the other end of the main unit-side clock relay line 331c includes a first end and a second end. The first end of the main unit-side clock relay line 331c is electrically connected to the drum memory 151. The second end of the main unit-side clock relay line 331c is electrically connected to the multiplexer 34. The toner-side clock relay lines 332c each electrically connect the multiplexer 34 and the toner-side clock terminal 32c.

[0200] The signal relay line 33d includes a main unit-side signal relay line 331d and a toner-side signal relay line 332d. In this embodiment, there is one main unit-side signal relay line 331d. There are multiple toner-side signal relay lines 332d, specifically four. One end of the main unit-side signal relay line 331d is electrically connected to the main unit-side signal terminal 31d. The other end of the main unit-side signal relay line 331d branches into two. Specifically, the other end of the main unit-side signal relay line 331d includes a first end and a second end. The first end of the main unit-side signal relay line 331d is electrically connected to the drum memory 151. The second end of the main unit-side signal relay line 331d is electrically connected to the multiplexer 34. The toner-side signal relay lines 332d each electrically connect the multiplexer 34 and the toner-side signal terminal 32d.

[0201] In other words, in this embodiment, the drum memory 151 is connected to the main unit clock terminal 31c without going through the multiplexer 34. Therefore, the drum memory 151 receives the clock signal input from the control unit 102 to the main unit clock terminal 31c without going through the multiplexer 34. Also, in this embodiment, the drum memory 151 is connected to the main unit signal terminal 31d without going through the multiplexer 34. Therefore, the drum memory 151 receives the data signal input from the control unit 102 to the main unit signal terminal 31d without going through the multiplexer 34.

[0202] <4-4. About Multiplexers> The multiplexer 34 is a switch circuit that switches the connection of signal lines. The multiplexer 34 receives a clock signal from the control unit 102 via the main unit clock terminal 31c. The multiplexer 34 also supplies the obtained clock signal to each toner circuit board 24 via the toner-side clock terminal 32c. In other words, in this drum circuit board 15, the clock signal input to the main unit clock terminal 31c is supplied to the four toner-side clock terminals 32c and the drum memory 151. By commonizing the main unit clock terminal 31c in this way, the number of main unit terminals 31 can be reduced.

[0203] Furthermore, the multiplexer 34 receives an address signal and a data signal from the control unit 102 via the main unit-side signal terminal 31d. The address signal is a signal used to specify the communication destination. The data signal is a signal indicating various information to be sent to the communication destination. In response to the received address signal, the multiplexer 34 switches the toner-side signal terminal 32d that will be the communication destination from among the four toner-side signal terminals 32d. The multiplexer 34 also outputs the received data signal to the toner-side signal terminal 32d that has been selected as the communication destination.

[0204] In this way, by using the multiplexer 34, it is possible to switch between the four toner memories 241 to select the toner memory 241 to communicate with and output a data signal. Therefore, it is not necessary to provide a separate main unit signal terminal 31d for each of the four toner-side signal terminals 32d. Consequently, the number of main unit signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0205] In particular, the multiplexer 34 of this embodiment receives the address signal and the data signal via a single main unit-side signal terminal 31d. This allows for a further reduction in the number of main unit-side signal terminals 31d. Furthermore, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0206] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 17 of this embodiment, only one signal terminal 31d on the main unit side is needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 17 of this embodiment, only one signal terminal 104d on the control unit 102 is needed.

[0207] <4-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 17, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 17, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 17, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0208] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 17, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 17, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 17, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0209] <4-6. Regarding the identification of abnormalities> In the third embodiment described above (Figure 16), if the control unit 102 transmits the authentication information described above to the drum memory 151 and there is no response from the drum memory 151, it is difficult to determine whether there is a problem with the drum memory 151 itself or with the communication path including the multiplexer 34.

[0210] However, in this embodiment, the drum memory 151 is connected to the main unit clock terminal 31c and the main unit signal terminal 31d without going through the multiplexer 34. That is, the main unit clock relay line 331c electrically connects the main unit clock terminal 31c to the multiplexer 34, and also electrically connects the main unit clock terminal 31c to the drum memory 151. In addition, the main unit signal relay line 331d electrically connects the main unit signal terminal 31d to the multiplexer 34, and also electrically connects the main unit signal terminal 31d to the drum memory 151.

[0211] This makes it easier to determine if an anomaly has occurred after the control unit 102 has sent authentication information to the drum memory 151. Figure 18 is a flowchart showing the procedure for determining an anomaly after the control unit 102 has sent authentication information to the drum memory 151.

[0212] In step S14 of Figure 8 described above, the processor 105 of the control unit 102 first determines whether or not there is a response from the drum memory 151 after sending authentication information to the drum memory 151 (step S601).

[0213] If there is a response from the drum memory 151 (step S601: yes), the processor 105 then determines whether or not there is a response from the multiplexer 34 (step S602).

[0214] If there is a response from the multiplexer 34 (step S602: yes), then both the drum memory 151 and the multiplexer 34 are functioning correctly (step S603). In this case, the processor 105 proceeds to the processing from step S17 onwards in Figure 8.

[0215] On the other hand, if there is no response from the multiplexer 34 in step S602 (step S602: no), the drum memory 151 is normal and the multiplexer 34 is abnormal. In this case, the processor 105 outputs an error (step S604). Specifically, for example, the processor 105 reads the drum communication path error message information stored in the main memory 106. Then, the processor 105 displays the read drum communication path error message information on the display 103.

[0216] Furthermore, if there is no response from the drum memory 151 in step S601 (step S601: no), the processor 105 then determines whether or not there is a response from the multiplexer 34 (step S605).

[0217] If there is a response from the multiplexer 34 (step S605: yes), the drum memory 151 is abnormal and the multiplexer 34 is normal. In this case, the processor 105 outputs an error (step S606). Specifically, for example, the processor 105 reads the drum memory error message information stored in the main memory 106. Then, the processor 105 displays the read drum memory error message information on the display 103.

[0218] On the other hand, if there is no response from the multiplexer 34 in step S605 (step S605: no), it is considered that both the drum memory 151 and the multiplexer 34 are malfunctioning, or that the drum cartridge 1 is not installed in the main casing 101 of the image forming apparatus 100. In this case, the processor 105 outputs an error (step S607). Since it is unlikely that the drum memory 151 and the multiplexer 34 will fail simultaneously, in step S607, for example, the processor 105 reads the drum cartridge installation error message information stored in the main memory 106. After that, the processor 105 displays the read drum cartridge installation error message information on the display 103.

[0219] <5. Fifth Embodiment> Figure 19 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the fifth embodiment. In the example of Figure 19, the drum cartridge 1 comprises a drum circuit board 15, a drum memory 151, a transistor array 35, and a general-purpose input / output port 36. The drum circuit board 15 has a plurality of main unit-side terminals 31, a plurality of toner-side terminals 32, and a plurality of relay lines 33. The drum memory 151, the transistor array 35, and the general-purpose input / output port 36 are located on the drum circuit board 15. Note that the drum memory 151 does not necessarily have to be located on the drum circuit board 15. Specifically, the drum memory 151 may be located on the surface of the frame 12.

[0220] <5-1. Regarding terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 19, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and one main unit signal terminal 31d.

[0221] The main unit voltage terminal 31a is electrically connected to the voltage terminals 104a of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0222] The main unit-side grounding terminal 31b is electrically connected to the grounding terminals 104b of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0223] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0224] The main unit-side signal terminal 31d is electrically connected to the signal terminals 104d of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0225] <5-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when four toner cartridges 2 are mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 19, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0226] The 16 toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having the other four toner-side terminals 32, a third group 32C having the other four toner-side terminals 32, and a fourth group 32D having the other four toner-side terminals 32.

[0227] The four toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0228] Each of the four toner-side terminals 32 in each group includes one toner-side voltage terminal 32a, one toner-side ground terminal 32b, one toner-side clock terminal 32c, and one toner-side signal terminal 32d.

[0229] The toner-side voltage terminal 32a is electrically connected to the transistor array 35 via a voltage relay line 33a, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminals 242a of the four terminals 242 of the toner circuit board 24.

[0230] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of the four terminals 242 of the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0231] The toner-side clock terminal 32c is electrically connected to the main unit-side clock terminal 31c via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminal 242c of the four terminals 242 of the toner circuit board 24. As a result, a clock signal is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15 at regular time intervals.

[0232] The toner-side signal terminal 32d is electrically connected to the main unit-side signal terminal 31d via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminal 242d of the four terminals 242 of the toner circuit board 24. This makes it possible to send and receive signals indicating various information between the control unit 102 and the toner circuit board 24 via the drum circuit board 15.

[0233] <5-3. Regarding relay lines> As shown in Figure 19, the relay line 33 in this embodiment includes a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. Specifically, there are multiple voltage relay lines 33a, one ground relay line 33b, one clock relay line 33c, and one signal relay line 33d.

[0234] The voltage relay line 33a includes the main unit-side voltage relay line 331a, the toner-side voltage relay line 332a, and the drum voltage line 333a. In this embodiment, there is one main unit-side voltage relay line 331a. There are multiple toner-side voltage relay lines 332a, specifically four. There is one drum voltage line 333a. One end of the main unit-side voltage relay line 331a is electrically connected to the main unit-side voltage terminal 31a. The other end of the main unit-side voltage relay line 331a branches into two. Specifically, the other end of the main unit-side voltage relay line 331a includes a first end and a second end. The first end of the main unit-side voltage relay line 331a is electrically connected to the transistor array 35. The second end of the main unit-side voltage relay line 331a is electrically connected to the general-purpose input / output port 36. The toner-side voltage relay lines 332a electrically connect the transistor array 35 and the toner-side voltage terminal 32a, respectively. The drum voltage line 333a electrically connects the transistor array 35 and the drum memory 151.

[0235] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into six. Specifically, the other end of the grounding relay wire 33b includes a first end, a second end, a third end, a fourth end, a fifth end, and a sixth terminal. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the drum memory 151. The sixth end of the grounding relay line 33b is electrically connected to the general-purpose input / output port 36. Therefore, on the drum circuit board 15, the grounding voltage input to the main unit-side grounding terminal 31b is supplied to the four toner-side grounding terminals 32b, the drum memory 151, and the general-purpose input / output port 36. In this way, by commonizing the main unit-side grounding terminal 31b, the number of main unit-side terminals 31 can be reduced.

[0236] One end of the clock relay line 33c is electrically connected to the main unit clock terminal 31c. The other end of the clock relay line 33c branches into six. Specifically, the other end of the clock relay line 33c includes a first end, a second end, a third end, a fourth end, a fifth end, and a sixth terminal. The first end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the first group 32A. The second end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the second group 32B. The third end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the third group 32C. The fourth end of the clock relay line 33c is electrically connected to the toner-side clock terminal 32c of the fourth group 32D. The fifth end of the clock relay line 33c is electrically connected to the drum memory 151. The sixth end of the clock relay line 33c is electrically connected to the general-purpose input / output port 36. Therefore, on the drum circuit board 15, the clock signal input to the main unit-side clock terminal 31c is supplied to the four toner-side clock terminals 32c, the drum memory 151, and the general-purpose input / output port 36. In this way, by commonizing the main unit-side clock terminal 31c, the number of main unit-side terminals 31 can be reduced.

[0237] One end of the signal relay line 33d is electrically connected to the main unit side signal terminal 31d. The other end of the signal relay line 33d branches into six. Specifically, the other end of the signal relay line 33d includes a first end, a second end, a third end, a fourth end, a fifth end, and a sixth terminal. The first end of the signal relay line 33d is electrically connected to the toner side signal terminal 32d of the first group 32A. The second end of the signal relay line 33d is electrically connected to the toner side signal terminal 32d of the second group 32B. The third end of the signal relay line 33d is electrically connected to the toner side signal terminal 32d of the third group 32C. The fourth end of the signal relay line 33c is electrically connected to the toner side signal terminal 32d of the fourth group 32D. The fifth end of the signal relay line 33d is electrically connected to the drum memory 151. The sixth end of the signal relay line 33d is electrically connected to the general-purpose input / output port 36. Therefore, on the drum circuit board 15, the signal input to the main unit side signal terminal 31d is supplied to the four toner side signal terminals 32d, the drum memory 151, and the general-purpose input / output port 36. In this way, by commonizing the main unit side signal terminal 31d, the number of main unit side terminals 31 can be reduced.

[0238] <5-4. About transistor arrays> The transistor array 35 is a switch circuit that switches the connections of voltage lines. The transistor array 35 receives power supply voltage from the control unit 102 via the main unit voltage terminal 31a. The transistor array 35 also receives address signals from the control unit 102 via the main unit signal terminal 31d and the general-purpose input / output port 36. The address signal is a signal used to specify the communication destination. In response to the received address signal, the transistor array 35 switches between the drum memory 151 and the four toner-side signal terminals 32d to select either the drum memory 151 or the toner-side signal terminal 32d as the communication destination. The transistor array 35 then supplies power supply voltage to the drum memory 151 or the toner-side signal terminal 32d selected as the communication destination.

[0239] In other words, the transistor array 35 supplies power voltage only to the drum memory 151 or toner memory 241 designated as the communication destination, among the drum memory 151 and the four toner memories 241. The drum memory 151 and the four toner memories 241 each receive data signals input from the signal terminal 242d only when power voltage is supplied. Therefore, the necessary data signals can be sent to the designated communication destination among the drum memory 151 and the four toner memories 241. In this way, it is not necessary to provide a separate main unit-side signal terminal 31d for each of the four toner-side signal terminals 32d. Therefore, the number of main unit-side signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0240] In particular, the drum circuit board 15 of this embodiment receives the address signal and the data signal via a single main unit-side signal terminal 31d. This allows for a further reduction in the number of main unit-side signal terminals 31d. Furthermore, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0241] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 19 of this embodiment, only one signal terminal 31d on the main unit side is needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 19 of this embodiment, only one signal terminal 104d on the control unit 102 is needed.

[0242] <5-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 19, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 19, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 19, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0243] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 19, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 19, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 19, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0244] <6. Sixth Embodiment> Figure 20 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the sixth embodiment. In the example of Figure 20, the drum cartridge 1 has a drum circuit board 15 and a CPU 37. The drum circuit board 15 has a plurality of main unit-side terminals 31, a plurality of toner-side terminals 32, and a plurality of relay lines 33. The CPU 37 is located on the drum circuit board 15.

[0245] <6-1. Regarding terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 20, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, and two main unit signal terminals 31d.

[0246] The main unit voltage terminal 31a is electrically connected to the voltage terminals 104a of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0247] The main unit-side grounding terminal 31b is electrically connected to the grounding terminals 104b of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0248] The two main unit-side signal terminals 31d are electrically connected to the signal terminals 104d of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0249] One of the two main unit-side signal terminals 31d is a transmit terminal. The other of the two main unit-side signal terminals 31d is a receive terminal. In this embodiment, information is transmitted and received using asynchronous serial communication. Therefore, a main unit-side clock terminal for receiving a clock signal is not required. This allows for a further reduction in the number of main unit-side terminals 31.

[0250] <6-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when four toner cartridges 2 are mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 20, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0251] The 16 toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having the other four toner-side terminals 32, a third group 32C having the other four toner-side terminals 32, and a fourth group 32D having the other four toner-side terminals 32.

[0252] The four toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0253] Each of the four toner-side terminals 32 in each group includes one toner-side voltage terminal 32a, one toner-side ground terminal 32b, and two toner-side signal terminals 32d.

[0254] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via the voltage relay line 33a, CPU 37, and power supply circuit 38, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminals 242a of the four terminals 242 of the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0255] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of the four terminals 242 of the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0256] The toner-side signal terminal 32d is electrically connected to the CPU 37 via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminals 242d of the four terminals 242 of the toner circuit board 24.

[0257] One of the two toner-side signal terminals 32d of the four toner-side terminals 32 in each group is a transmit terminal. The other of the two toner-side signal terminals 32d of the four toner-side terminals 32 in each group is a receive terminal. As described above, in this embodiment, information is transmitted and received by asynchronous serial communication. Therefore, a toner-side clock terminal for outputting a clock signal is not required.

[0258] <6-3. Regarding relay lines> As shown in Figure 20, the relay line 33 in this embodiment includes a voltage relay line 33a, a ground relay line 33b, and a signal relay line 33d. Specifically, there are multiple voltage relay lines 33a, one ground relay line 33b, multiple clock relay lines 33c, and multiple signal relay lines 33d.

[0259] The voltage relay line 33a includes a main unit-side voltage relay line 331a and a toner-side voltage relay line 332a. In this embodiment, there is one main unit-side voltage relay line 331a. There is also one toner-side voltage relay line 332a. One end of the main unit-side voltage relay line 331a is electrically connected to the main unit-side voltage terminal 31a. The other end of the main unit-side voltage relay line 331a branches into two. Specifically, the other end of the main unit-side voltage relay line 331a includes a first end and a second end. The first end of the main unit-side voltage relay line 331a is electrically connected to the CPU 37. The second end of the main unit-side voltage relay line 331a is electrically connected to the power supply circuit 38. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit-side voltage terminal 31a is supplied to the CPU 37 and the power supply circuit 38.

[0260] The CPU 37 and the power supply circuit 38 are electrically connected. Also, one end of the toner-side voltage relay line 332a is electrically connected to the power supply circuit 38. The other end of the toner-side voltage relay line 332a branches into four. Specifically, the other end of the toner-side voltage relay line 332a includes a first end, a second end, a third end, and a fourth end. The first end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. Therefore, in the drum circuit board 15, the power supply voltage output from the power supply circuit 38 is supplied to the four toner-side voltage terminals 32a.

[0261] One end of the ground relay line 33b is electrically connected to the main body side ground terminal 31b. The other end of the ground relay line 33b branches into five. Specifically, the other end of the ground relay line 33b includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the ground relay line 33b is electrically connected to the toner side ground terminal 32b of the first group 32A. The second end of the ground relay line 33b is electrically connected to the toner side ground terminal 32b of the second group 32B. The third end of the ground relay line 33b is electrically connected to the toner side ground terminal 32b of the third group 32C. The fourth end of the ground relay line 33b is electrically connected to the toner side ground terminal 32b of the fourth group 32D. The fifth end of the ground relay line 33b is electrically connected to the CPU 37. Therefore, in the drum circuit board 15, the ground voltage input to the main body side ground terminal 31b is supplied to the four toner side ground terminals 32b and the CPU 37. Thus, by sharing the main body side ground terminal 31b, the number of main body side terminals 31 can be reduced.

[0262] The signal relay line 33d includes a main body side signal relay line 331d and a toner side signal relay line 332d. The number of the main body side signal relay lines 331d in the present embodiment is plural, specifically two. The number of the toner side signal relay lines 332d is plural, specifically eight. One end of the main body side signal relay line 331d is electrically connected to the main body side signal terminal 31d. The other end of the main body side signal relay line 331d is electrically connected to the CPU 37. One end of the toner side signal relay line 332d is electrically connected to the CPU 37. The other end of the toner side signal relay line 332d is electrically connected to the toner side signal terminal 32d.

[0263] <6-4. About the CPU> The CPU (Central Processing Unit) 37 is a processor that switches the connection of signal lines according to a program. In the present embodiment, the CPU 37 and the drum memory 151 are integrated as a single chip. However, the CPU 37 and the drum memory 151 may be separate. A program readable by the CPU 37 is stored in the drum memory (memory) 151. The program may already be stored in the drum memory 151 at the time of shipment of the drum cartridge 1 as a product. Alternatively, the program may be stored in the main body memory 106 of the image forming apparatus 100 and read from the main body memory 106 and stored in the drum memory 151 when the power of the image forming apparatus 100 is turned on.

[0264] The CPU 37 receives a data signal from the control unit 102 via the main body side signal terminal 31d. The data signal is a signal indicating various information to be sent to the communication destination. Also, the CPU 37 switches the drum memory 151 or the toner side signal terminal 32d serving as the communication destination among the drum memory 151 and the four toner side signal terminals 32d according to the program read from the drum memory 151. Further, the CPU 37 outputs the received data signal to the drum memory 151 or the toner side signal terminal 32d selected as the communication destination.

[0265] In this way, by using the CPU 37, the drum memory 151 or the toner memory 241 serving as the communication destination can be switched from among the drum memory 151 and the four toner memories 241, and the data signal can be output. For this reason, it is not necessary to separately prepare the main body side signal terminal 3ld for each of the drum memory 151 and the four toner side signal terminals 32d. Therefore, the number of the main body side signal terminals 31d can be reduced. Also, the number of the signal terminals 104d of the control unit 102 can be reduced.

[0266] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 20 of this embodiment, only two signal terminals 31d on the main unit side are needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 20 of this embodiment, only two signal terminals 104d on the control unit 102 are needed.

[0267] <6-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 20, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 20, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b.

[0268] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 20, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 20, the ground voltage to be supplied to the four toner circuit boards 24 can be output from a single main unit ground terminal 31b.

[0269] <7. Seventh Embodiment> Figure 21 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the seventh embodiment. In the example of Figure 21, the drum cartridge 1 has a drum circuit board 15, a multiplexer 34, and a CPU 37. The drum circuit board 15 has a plurality of main unit-side terminals 31, a plurality of toner-side terminals 32, and a plurality of relay lines 33. The multiplexer 34 and CPU 37 are located on the drum circuit board 15.

[0270] <7-1. Regarding terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 21, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and one main unit signal terminal 31d.

[0271] The main unit voltage terminal 31a is electrically connected to the voltage terminals 104a of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0272] The main unit-side grounding terminal 31b is electrically connected to the grounding terminals 104b of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0273] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0274] The main unit-side signal terminal 31d is electrically connected to the signal terminals 104d of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0275] <7-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when four toner cartridges 2 are mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 21, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0276] The 16 toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having the other four toner-side terminals 32, a third group 32C having the other four toner-side terminals 32, and a fourth group 32D having the other four toner-side terminals 32.

[0277] The four toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0278] Each of the four toner-side terminals 32 in each group includes one toner-side voltage terminal 32a, one toner-side ground terminal 32b, one toner-side clock terminal 32c, and one toner-side signal terminal 32d.

[0279] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via the voltage relay line 33a, CPU 37, and power supply circuit 38, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminals 242a of the four terminals 242 of the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0280] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of the four terminals 242 of the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0281] The toner-side clock terminal 32c is electrically connected to the multiplexer 34 via a clock relay line 33c, which will be described later. Also, in a state where the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminal 242c of the four terminals 242 of the toner circuit board 24.

[0282] The toner-side signal terminal 32d is electrically connected to the multiplexer 34 via a signal relay line 33d, which will be described later. Also, in a state where the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminal 242d of the four terminals 242 of the toner circuit board 24.

[0283] <7-3. About the relay line> As shown in FIG. 21, the relay line 33 of the present embodiment includes a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. Specifically, the number of voltage relay lines 33a is plural, the number of ground relay lines 33b is one, the number of clock relay lines 33c is plural, and the number of signal relay lines 33d is plural.

[0284] The voltage relay line 33a includes a main body-side voltage relay line 331a and a toner-side voltage relay line 332a. The number of the main body-side voltage relay lines 331a in the present embodiment is one. The number of the toner-side voltage relay lines 332a is one. One end of the main body-side voltage relay line 331a is electrically connected to the main body-side voltage terminal 31a. The other end of the main body-side voltage relay line 331a branches into two. Specifically, the other end of the main body-side voltage relay line 331a includes a first end and a second end. The first end of the main body-side voltage relay line 331a is electrically connected to the CPU 37. The second end of the main body-side voltage relay line 331a is electrically connected to the power supply circuit 38. Therefore, in the drum circuit board 15, the power supply voltage input to the main body-side voltage terminal 31a is supplied to the CPU 37 and the power supply circuit 38.

[0285] The CPU 37 and the power supply circuit 38 are electrically connected. Also, one end of the toner-side voltage relay line 332a is electrically connected to the power supply circuit 38. The other end of the toner-side voltage relay line 332a branches into five. Specifically, the other end of the toner-side voltage relay line 332a includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. The fifth end of the toner-side voltage relay line 332a is electrically connected to the multiplexer 34. Therefore, on the drum circuit board 15, the power supply voltage output from the power supply circuit 38 is supplied to the four toner-side voltage terminals 32a and the multiplexer 34.

[0286] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into six. Specifically, the other end of the grounding relay wire 33b includes the first end, the second end, the third end, the fourth end, the fifth end, and the sixth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the CPU 37. The sixth end of the grounding relay line 33b is electrically connected to the multiplexer 34. Therefore, on the drum circuit board 15, the grounding voltage input to the main unit side grounding terminal 31b is supplied to the four toner side grounding terminals 32b, the CPU 37, and the multiplexer 34. In this way, by commonizing the main unit side grounding terminal 31b, the number of main unit side terminals 31 can be reduced.

[0287] The clock relay line 33c includes a main unit-side clock relay line 331c and a toner-side clock relay line 332c. In this embodiment, there is one main unit-side clock relay line 331c. There are multiple toner-side clock relay lines 332c, specifically four. One end of the main unit-side clock relay line 331c is electrically connected to the main unit-side clock terminal 31c. The other end of the main unit-side clock relay line 331c is electrically connected to the CPU 37. One end of the toner-side clock relay line 332c is electrically connected to the multiplexer 34. The other end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c.

[0288] The signal relay line 33d includes a main unit-side signal relay line 331d and a toner-side signal relay line 332d. In this embodiment, there is one main unit-side signal relay line 331d. There are multiple toner-side signal relay lines 332d, specifically four. One end of the main unit-side signal relay line 331d is electrically connected to the main unit-side signal terminal 31d. The other end of the main unit-side signal relay line 331d is electrically connected to the CPU 37. One end of the toner-side signal relay line 332d is electrically connected to the multiplexer 34. The other end of the toner-side signal relay line 332d is electrically connected to the toner-side signal terminal 32d.

[0289] The CPU 37 and the multiplexer 34 are electrically connected.

[0290] <7-4. About CPUs and Multiplexers> The CPU (Central Processing Unit) 37 is a processor that outputs address signals according to a program. In this embodiment, the CPU 37 and the drum memory 151 are integrated as a single chip. However, the CPU 37 and the drum memory 151 may be separate components. The drum memory 151 stores a program that can be read by the CPU 37. The program may already be stored in the drum memory 151 when the drum cartridge 1 is shipped as a product. Alternatively, the program may be stored in the main memory 106 of the image forming apparatus 100, and when the power to the image forming apparatus 100 is turned on, it may be read from the main memory 106 and stored in the drum memory 151.

[0291] The CPU 37 receives data signals from the control unit 102 via the main unit's signal terminal 31d. The CPU 37 also transmits the received data signals to the multiplexer 34. The data signals are signals indicating various information to be sent to the communication destination. The CPU 37 also generates address signals according to the program read from the drum memory 151. The CPU 37 then transmits the generated address signals to the multiplexer 34. The address signals are signals used to specify the communication destination.

[0292] The multiplexer 34 is a switch circuit that switches the connection of signal lines. The multiplexer 34 receives an address signal from the CPU 37. Then, according to the received address signal, the multiplexer 34 switches the toner-side signal terminal 32d that will be the communication destination among the four toner-side signal terminals 32d. In other words, the multiplexer 34 is controlled by the CPU 37. The multiplexer 34 also receives a data signal from the CPU 37. Then, the multiplexer 34 outputs the received data signal to the toner-side signal terminal 32d designated as the communication destination.

[0293] In this way, by using the CPU 37 and the multiplexer 34, it is possible to switch between the four toner memories 241 to select the toner memory 241 to communicate with and output a data signal. Therefore, it is not necessary to provide a separate main unit signal terminal 31d for each of the four toner-side signal terminals 32d. Consequently, the number of main unit signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0294] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 21 of this embodiment, only one signal terminal 31d on the main unit side is needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 21 of this embodiment, only one signal terminal 104d on the control unit 102 is needed.

[0295] <7-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 21, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 21, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 21, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0296] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 21, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 21, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 21, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0297] <8. Eighth Embodiment> Figure 22 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the eighth embodiment. In the example of Figure 22, the drum cartridge 1 has a drum circuit board 15, a transistor array 35, and a CPU 37. The drum circuit board 15 has a plurality of main body-side terminals 31, a plurality of toner-side terminals 32, and a plurality of relay lines 33. The transistor array 35 and the CPU 37 are located on the drum circuit board 15.

[0298] <8-1. Regarding terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 22, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and one main unit signal terminal 31d.

[0299] The main unit voltage terminal 31a is electrically connected to the voltage terminals 104a of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0300] The main unit-side grounding terminal 31b is electrically connected to the grounding terminals 104b of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0301] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0302] The main unit-side signal terminal 31d is electrically connected to the signal terminals 104d of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0303] <8-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when four toner cartridges 2 are mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 22, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0304] The 16 toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having the other four toner-side terminals 32, a third group 32C having the other four toner-side terminals 32, and a fourth group 32D having the other four toner-side terminals 32.

[0305] The four toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0306] Each of the four toner-side terminals 32 in each group includes one toner-side voltage terminal 32a, one toner-side ground terminal 32b, one toner-side clock terminal 32c, and one toner-side signal terminal 32d.

[0307] The toner-side voltage terminal 32a is electrically connected to the transistor array 35 via a voltage relay line 33a, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminals 242a of the four terminals 242 of the toner circuit board 24.

[0308] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of the four terminals 242 of the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0309] The toner-side clock terminal 32c is electrically connected to the CPU 37 via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminals 242c of the four terminals 242 of the toner circuit board 24.

[0310] The toner-side signal terminal 32d is electrically connected to the CPU 37 via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminals 242d of the four terminals 242 of the toner circuit board 24. This makes it possible to send and receive signals indicating various information between the control unit 102 and the toner circuit board 24 via the drum circuit board 15.

[0311] <8-3. Regarding relay lines> As shown in Figure 22, the relay line 33 in this embodiment includes a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. Specifically, there are multiple voltage relay lines 33a, one ground relay line 33b, multiple clock relay lines 33c, and multiple signal relay lines 33d.

[0312] The voltage relay line 33a includes a main unit-side voltage relay line 331a and a toner-side voltage relay line 332a. In this embodiment, there is one main unit-side voltage relay line 331a. There are multiple toner-side voltage relay lines 332a, specifically four. One end of the main unit-side voltage relay line 331a is electrically connected to the main unit-side voltage terminal 31a. The other end of the main unit-side voltage relay line 331a branches into two. Specifically, the other end of the main unit-side voltage relay line 331a includes a first end and a second end. The first end of the main unit-side voltage relay line 331a is electrically connected to the CPU 37. The second end of the main unit-side voltage relay line 331a is electrically connected to the transistor array 35. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit-side voltage terminal 31a is supplied to the CPU 37 and the transistor array 35. One end of the toner-side voltage relay line 332a is electrically connected to the transistor array 35. The other end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a. The CPU 37 and the transistor array 35 are also electrically connected.

[0313] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into six. Specifically, the other end of the grounding relay wire 33b includes the first end, the second end, the third end, the fourth end, the fifth end, and the sixth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the CPU 37. The sixth end of the grounding relay line 33b is electrically connected to the transistor array 35. Therefore, on the drum circuit board 15, the grounding voltage input to the main unit-side grounding terminal 31b is supplied to the four toner-side grounding terminals 32b, the CPU 37, and the transistor array 35. In this way, by commonizing the main unit-side grounding terminal 31b, the number of main unit-side terminals 31 can be reduced.

[0314] The clock relay line 33c includes the main unit-side clock relay line 331c and the toner-side clock relay line 332c. In this embodiment, there is one main unit-side clock relay line 331c. There is also one toner-side clock relay line 332c. One end of the main unit-side clock relay line 331c is electrically connected to the main unit-side clock terminal 31c. The other end of the main unit-side clock relay line 331c is electrically connected to the CPU 37. One end of the toner-side clock relay line 332c is electrically connected to the CPU 37. The other end of the toner-side clock relay line 332c branches into four. Specifically, the other end of the toner-side clock relay line 332c includes a first end, a second end, a third end, and a fourth end. The first end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the first group 32A. The second end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the second group 32B. The third end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the third group 32C. The fourth end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the fourth group 32D. Therefore, on the drum circuit board 15, the clock signal input to the main unit-side clock terminal 31c is supplied to the four toner-side clock terminals 32c via the CPU 37. In this way, by commonizing the main unit-side clock terminal 31c, the number of main unit-side terminals 31 can be reduced.

[0315] The signal relay line 33d includes the main unit side signal relay line 331d and the toner side signal relay line 332d. In this embodiment, there is one main unit side signal relay line 331d. There is one toner side signal relay line 332d. One end of the main unit side signal relay line 331d is electrically connected to the main unit side signal terminal 31d. The other end of the main unit side signal relay line 331d is electrically connected to the CPU 37. One end of the toner side signal relay line 332d is electrically connected to the CPU 37. The other end of the toner side signal relay line 332d branches into four. Specifically, the other end of the toner side signal relay line 332d includes a first end, a second end, a third end, and a fourth end. The first end of the toner side signal relay line 332d is electrically connected to the toner side signal terminal 32d of the first group 32A. The second end of the toner-side signal relay line 332d is electrically connected to the toner-side signal terminal 32d of the second group 32B. The third end of the toner-side signal relay line 332d is electrically connected to the toner-side signal terminal 32d of the third group 32C. The fourth end of the toner-side signal relay line 332d is electrically connected to the toner-side signal terminal 32d of the fourth group 32D. Therefore, on the drum circuit board 15, a signal input to one main unit-side signal terminal 31d is supplied to four toner-side signal terminals 32d via the CPU 37. In this way, by commonizing the main unit-side signal terminal 31d, the number of main unit-side terminals 31 can be reduced.

[0316] <8-4. About CPUs and Transistor Arrays> The CPU (Central Processing Unit) 37 is a processor that outputs address signals according to a program. In this embodiment, the CPU 37 and the drum memory 151 are integrated as a single chip. However, the CPU 37 and the drum memory 151 may be separate components. The drum memory 151 stores a program that can be read by the CPU 37. The program may already be stored in the drum memory 151 when the drum cartridge 1 is shipped as a product. Alternatively, the program may be stored in the main memory 106 of the image forming apparatus 100, and when the power to the image forming apparatus 100 is turned on, it may be read from the main memory 106 and stored in the drum memory 151.

[0317] The CPU 37 receives data signals from the control unit 102 via the main unit-side signal terminal 31d. The CPU 37 also transmits the received data signals to the four toner-side signal terminals 32d. The data signals are signals that indicate various information to be sent to the communication destination. The CPU 37 also generates address signals according to the program read from the drum memory 151. The CPU 37 then transmits the generated address signals to the transistor array 35. The address signals are signals used to specify the communication destination.

[0318] The transistor array 35 is a switch circuit that switches the connections of voltage lines. The transistor array 35 receives power supply voltage from the control unit 102 via the main unit voltage terminal 31a. The transistor array 35 also receives an address signal from the CPU 37. In response to the received address signal, the transistor array 35 switches the toner-side signal terminal 32d that will be the communication destination among the four toner-side signal terminals 32d. The transistor array 35 then supplies power supply voltage to the toner-side signal terminal 32d that has been selected as the communication destination.

[0319] In other words, the transistor array 35 supplies power voltage only to the toner memory 241 designated as the communication destination among the four toner memories 241. Each of the four toner memories 241 receives data signals transmitted from the CPU 37 only when power voltage is supplied. Therefore, the necessary data signals can be sent to the designated communication destination among the four toner memories 241. In this way, it is not necessary to provide a separate main unit-side signal terminal 31d for each of the four toner-side signal terminals 32d. Therefore, the number of main unit-side signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0320] In particular, the drum circuit board 15 of this embodiment receives the address signal and the data signal via a single main unit-side signal terminal 31d. This allows for a further reduction in the number of main unit-side signal terminals 31d. Furthermore, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0321] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 22 of this embodiment, only one signal terminal 31d on the main unit side is needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 22 of this embodiment, only one signal terminal 104d on the control unit 102 is needed.

[0322] <8-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 22, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 22, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 22, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0323] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 22, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 22, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 22, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0324] <9. Ninth Embodiment> Figure 23 is a block diagram showing the electrical connections between the control unit 102, the drum circuit board 15, and the four toner circuit boards 24 of the ninth embodiment. In the example of Figure 23, the drum cartridge 1 has a drum circuit board 15, a multiplexer 34, and a CPU 37. The drum circuit board 15 has a plurality of main unit-side terminals 31, a plurality of toner-side terminals 32, a plurality of relay lines 33, a multiplexer 34, and a CPU 37. The multiplexer 34 and CPU 37 are located on the drum circuit board 15.

[0325] <9-1. Regarding terminals on the main unit> The main unit terminal 31 is electrically connected to the terminal 104 of the control unit 102 via the first electrical terminal 13 described above when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This electrically connects the drum circuit board 15 and the control unit 102. As shown in Figure 23, there are multiple main unit terminals 31 in this embodiment, specifically four. More specifically, there is one main unit voltage terminal 31a, one main unit ground terminal 31b, one main unit clock terminal 31c, and one main unit signal terminal 31d.

[0326] The main unit voltage terminal 31a is electrically connected to the voltage terminals 104a of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies power voltage to the drum circuit board 15.

[0327] The main unit-side grounding terminal 31b is electrically connected to the grounding terminals 104b of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, a grounding voltage is supplied from the control unit 102 to the drum circuit board 15.

[0328] The clock terminal 31c on the main unit side is electrically connected to the clock terminal 104c of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. As a result, the control unit 102 supplies a clock signal to the drum circuit board 15 at regular time intervals.

[0329] The main unit-side signal terminal 31d is electrically connected to the signal terminals 104d of the multiple terminals 104 of the control unit 102 when the drum cartridge 1 is mounted in the main unit casing 101 of the image forming apparatus 100. This makes it possible to send and receive signals indicating various information between the control unit 102 and the drum circuit board 15.

[0330] <9-2. Regarding the toner side terminals> The toner-side terminal 32 is electrically connected to the toner circuit board 24 of the toner cartridge 2 via the second electrical terminal 14 described above, when four toner cartridges 2 are mounted on the frame 12 of the drum cartridge 1. This electrically connects the drum circuit board 15 and the toner circuit board 24. As shown in Figure 23, the number of toner-side terminals 32 in this embodiment is multiple, specifically 16.

[0331] The 16 toner-side terminals 32 include a first group 32A having four toner-side terminals 32, a second group 32B having the other four toner-side terminals 32, a third group 32C having the other four toner-side terminals 32, and a fourth group 32D having the other four toner-side terminals 32.

[0332] The four toner-side terminals 32 of the first group 32A are electrically connected to the first toner circuit board 24A when the first toner cartridge 2A is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the second group 32B are electrically connected to the second toner circuit board 24B when the second toner cartridge 2B is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the third group 32C are electrically connected to the third toner circuit board 24C when the third toner cartridge 2C is mounted on the frame 12 of the drum cartridge 1. The four toner-side terminals 32 of the fourth group 32D are electrically connected to the fourth toner circuit board 24D when the fourth toner cartridge 2D is mounted on the frame 12 of the drum cartridge 1.

[0333] Each of the four toner-side terminals 32 in each group includes one toner-side voltage terminal 32a, one toner-side ground terminal 32b, one toner-side clock terminal 32c, and one toner-side signal terminal 32d.

[0334] The toner-side voltage terminal 32a is electrically connected to the main unit-side voltage terminal 31a via the voltage relay line 33a, CPU 37, and power supply circuit 38, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side voltage terminal 32a is electrically connected to the voltage terminals 242a of the four terminals 242 of the toner circuit board 24. As a result, power voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0335] The toner-side grounding terminal 32b is electrically connected to the main unit-side grounding terminal 31b via a grounding relay line 33b, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side grounding terminal 32b is electrically connected to the grounding terminal 242b of the four terminals 242 of the toner circuit board 24. As a result, a grounding voltage is supplied from the control unit 102 to the toner circuit board 24 via the drum circuit board 15.

[0336] The toner-side clock terminal 32c is electrically connected to the CPU 37 via a clock relay line 33c, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side clock terminal 32c is electrically connected to the clock terminals 242c of the four terminals 242 of the toner circuit board 24.

[0337] The toner-side signal terminal 32d is electrically connected to the multiplexer 34 via a signal relay line 33d, which will be described later. Furthermore, when the toner cartridge 2 is mounted on the frame 12 of the drum cartridge 1, the toner-side signal terminal 32d is electrically connected to the signal terminals 242d of the four terminals 242 of the toner circuit board 24.

[0338] <9-3. Regarding relay lines> As shown in Figure 23, the relay line 33 in this embodiment includes a voltage relay line 33a, a ground relay line 33b, a clock relay line 33c, and a signal relay line 33d. Specifically, there are multiple voltage relay lines 33a, one ground relay line 33b, multiple clock relay lines 33c, and multiple signal relay lines 33d.

[0339] The voltage relay line 33a includes a main unit-side voltage relay line 331a and a toner-side voltage relay line 332a. In this embodiment, there is one main unit-side voltage relay line 331a. There is also one toner-side voltage relay line 332a. One end of the main unit-side voltage relay line 331a is electrically connected to the main unit-side voltage terminal 31a. The other end of the main unit-side voltage relay line 331a branches into two. Specifically, the other end of the main unit-side voltage relay line 331a includes a first end and a second end. The first end of the main unit-side voltage relay line 331a is electrically connected to the CPU 37. The second end of the main unit-side voltage relay line 331a is electrically connected to the power supply circuit 38. Therefore, in the drum circuit board 15, the power supply voltage input to the main unit-side voltage terminal 31a is supplied to the CPU 37 and the power supply circuit 38.

[0340] The CPU 37 and the power supply circuit 38 are electrically connected. Also, one end of the toner-side voltage relay line 332a is electrically connected to the power supply circuit 38. The other end of the toner-side voltage relay line 332a branches into five. Specifically, the other end of the toner-side voltage relay line 332a includes a first end, a second end, a third end, a fourth end, and a fifth end. The first end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the first group 32A. The second end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the second group 32B. The third end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the third group 32C. The fourth end of the toner-side voltage relay line 332a is electrically connected to the toner-side voltage terminal 32a of the fourth group 32D. The fifth end of the toner-side voltage relay line 332a is electrically connected to the multiplexer 34. Therefore, on the drum circuit board 15, the power supply voltage output from the power supply circuit 38 is supplied to the four toner-side voltage terminals 32a and the multiplexer 34.

[0341] One end of the grounding relay wire 33b is electrically connected to the main unit side grounding terminal 31b. The other end of the grounding relay wire 33b branches into six. Specifically, the other end of the grounding relay wire 33b includes the first end, the second end, the third end, the fourth end, the fifth end, and the sixth end. The first end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the first group 32A. The second end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the second group 32B. The third end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the third group 32C. The fourth end of the grounding relay wire 33b is electrically connected to the toner side grounding terminal 32b of the fourth group 32D. The fifth end of the grounding relay wire 33b is electrically connected to the CPU 37. The sixth end of the grounding relay line 33b is electrically connected to the multiplexer 34. Therefore, on the drum circuit board 15, the grounding voltage input to the main unit side grounding terminal 31b is supplied to the four toner side grounding terminals 32b, the CPU 37, and the multiplexer 34. In this way, by commonizing the main unit side grounding terminal 31b, the number of main unit side terminals 31 can be reduced.

[0342] The clock relay line 33c includes the main unit-side clock relay line 331c and the toner-side clock relay line 332c. In this embodiment, there is one main unit-side clock relay line 331c. There is also one toner-side clock relay line 332c. One end of the main unit-side clock relay line 331c is electrically connected to the main unit-side clock terminal 31c. The other end of the main unit-side clock relay line 331c is electrically connected to the CPU 37. One end of the toner-side clock relay line 332c is electrically connected to the CPU 37. The other end of the toner-side clock relay line 332c branches into four. Specifically, the other end of the toner-side clock relay line 332c includes a first end, a second end, a third end, and a fourth end. The first end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the first group 32A. The second end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the second group 32B. The third end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the third group 32C. The fourth end of the toner-side clock relay line 332c is electrically connected to the toner-side clock terminal 32c of the fourth group 32D. Therefore, on the drum circuit board 15, the clock signal output from the CPU 37 is supplied to the four toner-side clock terminals 32c.

[0343] The signal relay line 33d includes a main unit-side signal relay line 331d and a toner-side signal relay line 332d. In this embodiment, there is one main unit-side signal relay line 331d. There are multiple toner-side signal relay lines 332d, specifically four. One end of the main unit-side signal relay line 331d is electrically connected to the main unit-side signal terminal 31d. The other end of the main unit-side signal relay line 331d is electrically connected to the CPU 37. One end of the toner-side signal relay line 332d is electrically connected to the multiplexer 34. The other end of the toner-side signal relay line 332d is electrically connected to the toner-side signal terminal 32d.

[0344] The CPU 37 and the multiplexer 34 are electrically connected.

[0345] <9-4. About CPUs and Multiplexers> The CPU (Central Processing Unit) 37 is a processor that outputs address signals according to a program. In this embodiment, the CPU 37 and the drum memory 151 are integrated as a single chip. However, the CPU 37 and the drum memory 151 may be separate components. The drum memory 151 stores a program that can be read by the CPU 37. The program may already be stored in the drum memory 151 when the drum cartridge 1 is shipped as a product. Alternatively, the program may be stored in the main memory 106 of the image forming apparatus 100, and when the power to the image forming apparatus 100 is turned on, it may be read from the main memory 106 and stored in the drum memory 151.

[0346] The CPU 37 receives data signals from the control unit 102 via the main unit's signal terminal 31d. The CPU 37 also transmits the received data signals to the multiplexer 34. The data signals are signals indicating various information to be sent to the communication destination. The CPU 37 also generates address signals according to the program read from the drum memory 151. The CPU 37 then transmits the generated address signals to the multiplexer 34. The address signals are signals used to specify the communication destination.

[0347] The multiplexer 34 is a switch circuit that switches the connection of signal lines. The multiplexer 34 receives an address signal from the CPU 37. Then, according to the received address signal, the multiplexer 34 switches the toner-side signal terminal 32d that will be the communication destination among the four toner-side signal terminals 32d. In other words, the multiplexer 34 is controlled by the CPU 37. The multiplexer 34 also receives a data signal from the CPU 37. Then, the multiplexer 34 outputs the received data signal to the toner-side signal terminal 32d designated as the communication destination.

[0348] In this way, by using the CPU 37 and the multiplexer 34, it is possible to switch between the four toner memories 241 to select the toner memory 241 to communicate with and output a data signal. Therefore, it is not necessary to provide a separate main unit signal terminal 31d for each of the four toner-side signal terminals 32d. Consequently, the number of main unit signal terminals 31d can be reduced. In addition, the number of signal terminals 104d of the control unit 102 can also be reduced.

[0349] Specifically, in the example shown in Figure 6 of the first embodiment, five signal terminals 31d on the main unit side were required, whereas in the example shown in Figure 23 of this embodiment, only one signal terminal 31d on the main unit side is needed. Also, in the example shown in Figure 6 of the first embodiment, five signal terminals 104d on the control unit 102 were required, whereas in the example shown in Figure 23 of this embodiment, only one signal terminal 104d on the control unit 102 is needed.

[0350] <9-5. Information relay using drum circuit boards> In this embodiment as well, the control unit 102 and the toner circuit board 24 are relayed by the drum circuit board 15. Therefore, the number of terminals can be reduced compared to when the drum circuit board 15 and the toner circuit board 24 are directly connected to the control unit 102. For example, as shown in Figure 23, the power supply voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit voltage terminal 31a. Also, as shown in Figure 23, the ground voltage to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit ground terminal 31b. Furthermore, as shown in Figure 23, the clock signal to be supplied to the drum memory 151 of the drum circuit board 15 and the toner memory 241 of the toner circuit board 24 can be output from a single main unit clock terminal 31c. This reduces the number of terminals 104 of the control unit 102.

[0351] In particular, as in this embodiment, when there are multiple toner circuit boards 24, the number of terminals can be further reduced by relaying the control unit 102 and the multiple toner circuit boards 24 via the drum circuit board 15. For example, as shown in Figure 23, the power supply voltage to be supplied to the four toner circuit boards 24 can be output from one main unit voltage terminal 31a. Also, as shown in Figure 23, the ground voltage to be supplied to the four toner circuit boards 24 can be output from one main unit ground terminal 31b. Furthermore, as shown in Figure 23, the clock signal to be supplied to the four toner circuit boards 24 can be output from one main unit clock terminal 31c. This further reduces the number of terminals 104 of the control unit 102.

[0352] <10. Variation> Although the first to ninth embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

[0353] The structures, circuit configurations, and processing procedures in each of the above embodiments are merely illustrative. Various elements appearing in each of the above embodiments may be replaced with other known elements without departing from the spirit of the present invention. Furthermore, various elements appearing in each of the above embodiments may be combined as appropriate without creating any inconsistencies. [Explanation of symbols]

[0354] 1 Drum Cartridge 2.2A~2D Toner Cartridge 11, 11A~11D Photosensitive drum 12 frames 13. First electrical terminal 14. Second electrical terminal 15 Drum circuit board 16,17 Wire harness 21 Casing 22 Developing roller 23 Gear section 24, 24A~24D Toner Circuit Board 25 holder 31 Main unit side terminal 31a Main unit voltage terminal 31b Body side ground terminal 31c Main unit clock terminal 31d Main unit signal terminal 32 Toner side terminal 32a Toner-side voltage terminal 32b Toner-side grounding terminal 32c toner-side clock terminal 32d Toner-side signal terminal 33 relay lines 33a Voltage relay line 33b Grounding relay line 33c clock relay cable 33d signal relay line 34 Multiplexer 35 Transistor Array 36 General-purpose input / output ports 37 CPU 38 Power circuit 100 Image forming apparatus 101 Main casing 102 Control Unit 103 displays 104 terminals 104a voltage terminal 104b Ground terminal 104c clock terminal 104d signal terminal 121 Toner Cartridge Holder 131 1st terminal 141 2nd terminal 151 Drum Memory 241 Toner Memory 242 terminals 242a Voltage terminal 242b Ground terminal 242c clock terminal 242d signal terminal 331a Main unit voltage relay line 331c Main unit clock relay cable 331d Main unit side signal relay line 332a Toner-side voltage relay line 332c Toner-side clock relay cable 332d Toner-side signal relay line 333a Drum voltage line 333c Drum Clock Line 333d Drum signal line

Claims

1. A drum cartridge that can be attached to the main casing of an image forming apparatus, A frame on which a first toner cartridge having a first toner memory as a storage medium and a second toner cartridge having a second toner memory as a storage medium can be mounted, Photosensitive drum and The storage medium is drum memory, With the first toner cartridge and the second toner cartridge installed, a drum circuit board relays the information stored in the first toner memory and the second toner memory to the control unit of the image forming apparatus, With the drum cartridge, in which the first toner cartridge and the second toner cartridge are installed, mounted in the main casing, a first electrical terminal is electrically connected to the control unit and relays the information stored in the first toner memory, the second toner memory, and the drum memory to the control unit. With the first toner cartridge and the second toner cartridge mounted on the frame, each of the plurality of toner cartridges has a plurality of second electrical terminals that can be electrically connected to the toner memory, Equipped with, The drum circuit board is Multiple terminals on the main body side that are electrically connected to the first electrical terminal, Multiple toner-side terminals electrically connected to the multiple second electrical terminals, Multiple relay lines connecting the terminal on the main unit side and the terminal on the toner side, A drum cartridge characterized by having the following features.

2. A drum cartridge according to claim 1, A drum cartridge characterized in that the first electrical terminal and the main body terminal are connected via a conductor.

3. A drum cartridge according to claim 2, The aforementioned multiple terminals on the main unit side are, The voltage terminal on the main unit side is electrically connectable to the voltage terminal of the image forming apparatus, The grounding terminal on the main unit side is electrically connectable to the grounding terminal of the image forming apparatus, Includes, The aforementioned multiple toner-side terminals are, The toner-side voltage terminals are electrically connectable to the voltage terminals of the aforementioned toner memory, The toner-side grounding terminal is electrically connectable to the grounding terminal of the toner memory, Includes, The aforementioned multiple relay lines are A voltage relay line connecting the main unit voltage terminal and the toner voltage terminal, A grounding relay wire connecting the main unit-side grounding terminal and the toner-side grounding terminal, A drum cartridge characterized by containing [the following].

4. A drum cartridge according to claim 3, The aforementioned multiple toner-side terminals are, The first toner cartridge has a first toner-side voltage terminal that is electrically connectable to the first voltage terminal of the first toner circuit board, The second toner side voltage terminal, which is electrically connectable to the second voltage terminal of the second toner circuit board of the second toner cartridge, The first toner cartridge has a first toner-side grounding terminal that is electrically connectable to the first grounding terminal of the first toner circuit board, The second toner cartridge has a second toner-side grounding terminal that is electrically connectable to the second grounding terminal of the second toner circuit board, It has, The aforementioned voltage relay line connects the main unit voltage terminal, the first toner voltage terminal, and the second toner voltage terminal. The drum cartridge is characterized in that the grounding relay line connects the main body side grounding terminal, the first toner side grounding terminal, and the second toner side grounding terminal.

5. A drum cartridge according to claim 1, A drum cartridge characterized in that the second electrical terminal and the toner-side terminal are connected via a conductor.

6. A drum cartridge according to claim 5, The aforementioned multiple terminals on the main unit side are, The voltage terminal on the main unit side is electrically connectable to the voltage terminal of the image forming apparatus, The grounding terminal on the main unit side is electrically connectable to the grounding terminal of the image forming apparatus, Includes, The aforementioned multiple toner-side terminals are, The toner-side voltage terminals are electrically connectable to the voltage terminals of the toner circuit board of the aforementioned toner cartridge, The toner side grounding terminal is electrically connectable to the grounding terminal of the toner circuit board, Includes, The aforementioned multiple relay lines are A voltage relay line connecting the main unit voltage terminal and the toner voltage terminal, A grounding relay wire connecting the main unit-side grounding terminal and the toner-side grounding terminal, A drum cartridge characterized by containing [the following].

7. A drum cartridge according to claim 5 or claim 6, The drum circuit board is characterized in that, with the drum cartridge mounted in the main body casing of the image forming apparatus, it outputs information stored in the toner memory, which is input via the toner-side terminal, to the control unit of the image forming apparatus via the main body-side terminal.

8. A drum cartridge according to claim 2, A switch circuit that, in accordance with the address signal obtained from the main unit terminal, switches the toner terminal to which communication will be received from one of the multiple toner terminals to another toner terminal. A drum cartridge characterized by having the following features.

9. A drum cartridge according to claim 8, The aforementioned multiple terminals on the main unit side are, Main unit side signal terminal that can be electrically connected to the signal terminal of the image forming apparatus. Includes, The aforementioned multiple toner-side terminals are, Toner-side signal terminals that can be electrically connected to the signal terminals of the aforementioned toner memory Includes, The aforementioned switch circuit is characterized in that, in accordance with the address signal obtained from the main unit side signal terminal, it switches the toner side signal terminal to which communication will be received from one of the plurality of toner side signal terminals to another toner side signal terminal.

10. A drum cartridge according to claim 9, The aforementioned relay line is A signal relay line on the main unit side connects the signal terminal on the main unit side and the switch circuit, A toner-side signal relay line connecting the toner-side signal terminal and the switch circuit, A drum cartridge characterized by containing [the following].

11. A drum cartridge according to any one of claims 8 to 10, The aforementioned switch circuit is a drum cartridge characterized by being a multiplexer.

12. A drum cartridge according to claim 8, The aforementioned multiple terminals on the main unit side are, The voltage terminal on the main unit that can be electrically connected to the voltage terminal of the image forming apparatus. Includes, The aforementioned multiple toner-side terminals are, The toner-side voltage terminals are electrically connectable to the voltage terminals of the aforementioned toner memory. Includes, The aforementioned switch circuit is characterized in that, in accordance with the address signal obtained from the main unit terminal, it switches one of the plurality of toner-side voltage terminals to which the voltage input from the main unit terminal is supplied to another toner-side voltage terminal, thus providing a drum cartridge.

13. A drum cartridge according to claim 12, The aforementioned relay line is A main unit voltage relay line connects the main unit voltage terminal and the switch circuit, A toner-side voltage relay line connecting the toner-side voltage terminal and the switch circuit, A drum cartridge characterized by containing [the following].

14. A drum cartridge according to claim 12 or claim 13, The aforementioned switch circuit is a transistor array, characterized in that it is a drum cartridge.

15. A drum cartridge according to any one of claims 8 to 14, The drum cartridge is characterized in that the switch circuit switches the communication destination from one of the plurality of toner-side terminals and the drum memory to another toner-side terminal, from the toner-side terminal to the drum memory, or from the drum memory to the toner-side terminal, in accordance with the address signal obtained from the main unit-side terminal.

16. A drum cartridge according to claim 15, The drum circuit board is Drum signal line connecting the switch circuit and the drum memory A drum cartridge characterized by having the following features.

17. A drum cartridge according to claim 15, The aforementioned relay line connects the main unit terminal to the switch circuit and also connects the main unit terminal to the drum memory, characterized in that it is a drum cartridge.

18. A drum cartridge according to claim 2, Processor It has, The drum cartridge is characterized in that the processor switches the toner terminal to which communication is to be toned, from one of the plurality of toner terminals to another, or controls a switch circuit to switch the toner terminal to which communication is toned, according to a program stored in the drum memory.

19. A drum cartridge according to claim 18, The drum cartridge is characterized in that the processor switches the toner terminal to which communication will be received, from one of the plurality of toner terminals to another, according to a program stored in the drum memory.

20. A drum cartridge according to claim 18, The drum cartridge is characterized in that the processor controls a switch circuit that switches the toner terminal to which communication will be received from one of the plurality of toner terminals to another toner terminal, according to a program stored in the drum memory.

21. A drum cartridge according to any one of claims 18 to 20, The drum cartridge is characterized in that the processor is located on the drum circuit board.

22. A drum cartridge according to claim 1, A drum cartridge characterized in that the drum memory stores information for identifying the drum cartridge.

23. A drum cartridge according to any one of claims 1 to 22, A drum cartridge characterized in that the drum memory stores information indicating the characteristics of the drum cartridge.

24. A drum cartridge according to any one of claims 1 to 23, The drum cartridge is characterized in that the drum memory is capable of storing individual identification information stored in the toner memory of the toner cartridge installed in the drum cartridge.

25. A drum cartridge according to any one of claims 1 to 24, The drum memory is characterized in that it can store information about the usage history of the toner cartridge.

26. A drum cartridge according to any one of claims 1 to 25, The aforementioned drum memory is A first memory area that stores information that cannot be rewritten, A second memory area that stores rewritable information, A drum cartridge characterized by having the following features.

27. A drum cartridge according to claim 26, The drum cartridge is characterized in that the second memory area is capable of storing the usage status of the drum cartridge.

28. A drum cartridge according to claim 27, The drum cartridge is characterized in that the aforementioned usage conditions include the rotation speed of the photosensitive drum.

29. A drum cartridge according to claim 27 or claim 28, The drum cartridge is characterized in that the usage conditions include the charging time of the photosensitive drum.

30. A drum cartridge according to any one of claims 1 to 29, The drum memory is located on the drum circuit board, characterized in that it is a drum cartridge.

31. An image forming apparatus comprising a drum cartridge according to any one of claims 1 to 30, An image forming apparatus characterized in that the toner memory stores information for identifying the toner cartridge.

32. An image forming apparatus comprising a drum cartridge according to any one of claims 1 to 31, An image forming apparatus characterized in that the toner memory stores information indicating the characteristics of the toner cartridge.

33. The drum cartridge according to claim 1, Control unit and An image forming apparatus comprising, The image forming apparatus is characterized in that the drum circuit board relays the information stored in the toner memory to the control unit.

34. An image forming apparatus according to claim 33, The control unit, A first read process that reads information from the drum memory, Based on the information read out by the first reading process, an operation process is performed to operate the image forming apparatus, An image forming apparatus characterized by its ability to perform the following.

35. An image forming apparatus according to claim 34, The control unit, A second reading process which reads information from the toner memory of the toner cartridge, A write process is performed to write the information read in the second read process to the drum memory, An image forming apparatus characterized by its ability to perform the following.

36. The drum cartridge according to claim 1, Control unit and An image forming apparatus comprising, The control unit, A first determination process to determine whether or not communication with the drum memory is possible, A second determination process to determine whether or not communication with the toner memory is possible, A first error output process that outputs the first error that occurred in the first determination process, A second error output process that outputs the second error that occurred in the second determination process, It is possible to do this, The image forming apparatus is characterized in that the second error output processing is performed after the first error output processing.

37. An image forming apparatus according to claim 36, The image forming apparatus is characterized in that the second determination process is performed after the first determination process.

38. An image forming apparatus according to claim 36, The image forming apparatus is characterized in that the second determination process is performed in parallel with the first determination process.

39. An image forming apparatus according to any one of claims 36 to 38, The control unit, In the first determination process, authentication information is sent to the drum memory, and it is determined whether the response value matches a predetermined value. The image forming apparatus is characterized in that, in the second determination process, authentication information is transmitted to the toner memory and it is determined whether the response value matches a predetermined value.

40. An image forming apparatus according to any one of claims 36 to 38, It also has internal memory as a storage medium, The control unit, In the first determination process, authentication information is transmitted to the main unit memory and the drum memory, and it is determined whether the response value from the main unit memory and the response value from the drum memory match. The image forming apparatus is characterized in that, in the second determination process, authentication information is transmitted to the main unit memory and the toner memory, and it is determined whether the response value from the main unit memory and the response value from the toner memory match.

41. An image forming apparatus according to any one of claims 36 to 39, Display capable of showing information Furthermore, The image forming apparatus is characterized in that the display shows the first error output in the first error output processing.

42. An image forming apparatus according to any one of claims 36 to 41, It also features a display capable of showing information, The image forming apparatus is characterized in that the display shows the second error output in the second error output processing.

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