Fixing device and image forming apparatus

Abstract

To provide a fixing device and an image forming apparatus capable of reducing the number of terminals in a connector for connecting the fixing device and the image forming apparatus when a memory is mounted on the fixing device.SOLUTION: The fixing device 9 detachably mountable to the printer 1 includes the relay substrate 161 on which the memory 163 is mounted and to which the nip detecting sensor SE3 and the discharging sensor SE4 are connected. The relay board 161 relays the detection signal from the nip detection sensor SE3 and the clock signals of the memory 163 to the main body housing 2 of the printer 1 via the same first common terminals 253 and first fixing common terminals 260. Further, the relay board 161 relays the detection signal from the discharge sensor SE4 and the date signal of the memory 163 to the main body housing 2 of the printer 1 via the same second common terminals 254 and 262.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a fixing device that fixes a toner image formed on a sheet onto the sheet, and to an image forming apparatus in which the fixing device is detachable. [Background technology]

[0002] Conventionally, image forming apparatuses for forming a toner image on a sheet have been known, which heat the sheet on which the toner image has been formed to fix the image and perform printing. The sheet is generally heated by a fixing device heated by an energized heater, but the fixing device gradually deteriorates in print quality with continued use. Therefore, fixing devices are made detachable from the image forming apparatus via a connector, allowing them to be replaced at regular intervals.

[0003] The fixing device is equipped with various sensors for managing the state of the fixing device, such as a sensor for detecting the temperature of the fixing device, a sensor for detecting whether the heating roller and pressure roller are in pressure contact, and a sensor for detecting the passage of a sheet through the fixing device. The fixing device transmits signals from the various sensors to the image forming apparatus via connectors. As disclosed in JP 2021-113856 A, signals from these sensors are relayed once through a relay board provided in the fixing device, and then transmitted to a control unit on the image forming apparatus via the connected connector on the fixing device side and the connector on the image forming apparatus side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-113856 A (paragraphs 0035-0044, Figure 3) Summary of the Invention [Problem to be solved by the invention]

[0005] Increasing the number of terminals on the connector on the fixing device side increases costs and the size of the connector, so it is desirable to minimize the number of terminals on the connector of a fixing device that is detachable from an image forming apparatus. Also, if a memory is installed in the fixing device, the fixing device requires an additional terminal on the connector on the fixing device side to allow the image forming apparatus to access the memory. For this reason, technology to reduce the number of terminals on the connector on the fixing device side has been desired.

[0006] The present invention has been made to solve the above-mentioned problems in the conventional art, and aims to provide a fixing device and an image forming device that prevent an increase in the number of terminals in the connector that connects the fixing device and the image forming device when a memory is installed in the fixing device. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the fixing device of the present application is a fixing device that is detachable from an image forming device that forms a toner image on a sheet, and is characterized by comprising: a heating rotor that heats the sheet; a heater that heats the heating rotor; a pressure rotor that nips the sheet between the heating rotor and the pressure rotor; a first detection sensor for detecting the state of the fixing device; a fixing connector that is connected when attached to the image forming device, the fixing connector having a first fixing common terminal; a first common terminal connected to the first fixing common terminal; and a memory; and an relay board to which the first detection sensor is connected, which relays a first detection signal of the first detection sensor and a first memory signal of the memory to the image forming device via the first common terminal and the first fixing common terminal.

[0008] In addition, the image forming apparatus of the present application is an image forming apparatus in which the fixing device is detachable, and is characterized in that it comprises a main body connector connected to the fixing connector, the main body connector having a first main body common terminal connected to the first fixing common terminal, and a control board having a control unit connected to the main body connector, and the control unit is capable of receiving the first detection signal via the first common terminal, the first fixing common terminal, and the first main body common terminal, and is capable of sending and receiving the first memory signal via the first common terminal, the first fixing common terminal, and the first main body common terminal. [Effects of the Invention]

[0009] According to the fixing device of the present application having the above configuration, the relay board relays the first detection signal of the first detection sensor and the first memory signal for accessing the memory provided in the fixing device to the image forming device via the first common terminal and the first fixing common terminal, so it is possible to reduce the number of terminals of the fixing connector connecting the fixing device and the image forming device compared to when the first detection signal from the first detection sensor and the first memory signal for accessing the memory are relayed to the image forming device via separate terminals. Therefore, even if the fixing device is equipped with a memory, it is possible to prevent an increase in the number of terminals of the fixing connector connecting the fixing device and the image forming device. Furthermore, according to the image forming apparatus of the present application, the first detection signal of the first detection sensor and the first memory signal for accessing the memory of the fixing device are relayed to the image forming apparatus via the first fixing common terminal and the first main body common terminal between the attached fixing device and the image forming apparatus, so that the number of terminals of the fixing connector connecting the fixing device and the image forming apparatus can be reduced compared to when the first detection signal from the first detection sensor and the first memory signal for accessing the memory are relayed to the image forming apparatus via separate terminals. Therefore, even if the fixing device is equipped with a memory, it is possible to prevent an increase in the number of terminals of the fixing connector connecting the fixing device and the image forming apparatus. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating the configuration of a printer according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating the printer with the rear cover open. [Figure 3] FIG. 2 is a diagram illustrating a state in which the fixing device is removed from the printer. [Figure 4] FIG. 2 is a front view of the internal structure of the fixing device. [Figure 5] FIG. 2 is a rear view of the internal structure of the fixing device. [Figure 6] 10A and 10B are diagrams illustrating a pressure contact / separation mechanism. [Figure 7] FIG. 2 is a diagram showing the electrical configuration of the printer. [Figure 8] 3 is a diagram showing the electrical configuration of a relay board included in the fixing device according to the first embodiment. FIG. [Figure 9] 3 is a diagram showing the electrical configuration of a relay board included in the fixing device according to the first embodiment. FIG. [Figure 10] FIG. 2 is a diagram illustrating a clock signal output from an ASIC. [Figure 11] 4 is a flowchart of a printing process according to the first embodiment. [Figure 12] 10 is a flowchart of a printing process according to a second embodiment. [Figure 13] 10 is a flowchart of a printing process according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, first to third embodiments in which the image forming apparatus according to the present invention is embodied as a printer will be described with reference to the drawings.

[0012] First Embodiment First, the overall configuration of the printer 1 according to the first embodiment will be described. Fig. 1 shows a schematic configuration of the printer 1 according to the first embodiment. In the following description, the front-rear and up-down directions are as shown on the paper.

[0013] [Overall printer configuration]

[0014] The printer 1 according to the first embodiment is an electrophotographic color laser printer that forms a desired toner image on a sheet S. However, the printer 1 may also be a monochrome laser printer. The printer 1 includes a main body housing 2, a conveying unit 3, a processing unit 4, and a fixing device 9 that is detachable from the main body housing 2.

[0015] The main body housing 2 has a front cover 11, a rear cover 12, a supply tray 13, a discharge tray 22, a first transport path 25, a second transport path 26, and a third transport path 27. The front cover 11 is a cover that opens and closes a front opening 2A provided at the front of the main body housing 2, and is attached to the front surface of the main body housing 2 in an openable and closable manner. The rear cover 12 is a cover that opens and closes a rear opening 2B provided at the rear of the main body housing 2, and is attached to the rear surface of the main body housing 2 in an openable and closable manner. The supply tray 13 is detachably attached to the bottom of the main body housing 2. Sheets S are placed on the supply tray 13. The sheets S are standard-sized sheets such as A4 size. The sheets S are paper media such as plain paper or cardboard, but are not limited to these, and may also be transparencies. The discharge tray 22 is provided at the top of the main body housing 2, and sheets S on which images have been formed are placed on the discharge tray 22.

[0016] Furthermore, a multipurpose tray 14 is formed in a part of the front cover 11, and by tilting the multipurpose tray 14 toward the front, it is possible to manually insert a sheet S from the multipurpose tray 14. The printer 1 is capable of selectively printing not only on sheets S supplied from the supply tray 13, but also on sheets S inserted from the multipurpose tray 14.

[0017] The conveying section 3 has a pickup roller 33, a separation roller 34, a registration roller 35, a first conveying roller 36, a second conveying roller 37, a first switchback roller 38, a second switchback roller 39, a plurality of third conveying rollers 40, a flapper 30, and a main motor 201A (see FIG. 7). A part of the second conveying path 26 is formed by the rear cover 12 in the closed state.

[0018] The pickup roller 33 picks up the sheets S in the supply tray 13 that have been pushed upward by the sheet pressing plate 32, and transports them toward the first transport path 25. The separation roller 34 separates the sheets S picked up by the pickup roller 33 one by one.

[0019] Also, downstream of the pickup roller 33, there is provided a paper feed sensor 44 that detects the passage of a sheet S picked up from the supply tray 13 and fed to the conveying section 3, i.e., that the sheet S is being fed.

[0020] The registration rollers 35 are disposed upstream of the process unit 4 on the first transport path 25. The registration rollers 35 align the direction of the leading edge of the sheet S, and then transport the sheet S toward the process unit 4. The transport direction in which the registration rollers 35 transport the sheet is from the front to the rear.

[0021] Further, a pre-registration sensor 45 that detects the passage of the leading edge of the sheet S on the first transport path 25 is disposed upstream of the registration rollers 35 in the sheet transport direction. Similarly, a post-registration sensor 46 that detects the passage of the leading edge of the sheet S on the first transport path 25 is disposed downstream of the registration rollers 35 in the sheet transport direction. In addition to the above-mentioned paper feed sensor 44, the pre-registration sensor 45 and the post-registration sensor 46 each include an actuator that can rotate around a rotation axis and a photosensor (not shown), and when the actuator comes into contact with the sheet S passing through the first transport path 25 and falls, the photosensor located near the rotation axis of the actuator detects that the actuator has fallen, i.e., that the sheet S has passed.

[0022] The pre-registration sensor 45 is used to determine the timing of driving the registration roller 35 located downstream, and the post-registration sensor 46 is used to determine the timing of executing the image forming process in the process unit 4 located downstream.

[0023] When the conveying unit 3 conveys the sheet S outside the main body housing 2, if the rear cover 12 is closed, the sheet S conveyed from the process unit 4 is conveyed by the first conveying roller 36 and guided to the first conveying path 25 by the flapper 30 (30A). Thereafter, the conveying unit 3 conveys the sheet S guided to the first conveying path 25 by the second conveying roller 37 and the first switchback roller 38 and discharges the sheet S onto the discharge tray 22.

[0024] Furthermore, when the conveying unit 3 conveys the sheet S out of the main body housing 2 and the rear cover 12 is open, the sheet S conveyed from the process unit 4 is conveyed by the first conveying roller 36, guided rearward by the flapper 30 (30B) that has swung to the position shown by the imaginary line, and discharged through the rear opening 2B onto the open rear cover 12. The printer 1 is capable of forming an image on the sheet S even when the rear cover 12 is open, and the rear cover 12 is a cover that, when open, allows the sheet S on which an image has been formed to be discharged from the rear opening 2B.

[0025] Furthermore, when the conveying unit 3 conveys the sheet S conveyed from the process unit 4 again, the conveying unit 3 conveys the sheet S conveyed from the process unit 4 by the first conveying roller 36 and guides the sheet S to the first conveying path 25 or the second conveying path 26 by the flapper 30. When the conveying unit 3 guides the sheet S to the first conveying path 25, the conveying unit 3 conveys the sheet S in the first conveying path 25 to the third conveying path 27 by the second conveying roller 37 and the first switchback roller 38. When the conveying unit 3 guides the sheet S to the second conveying path 26, the conveying unit 3 conveys the sheet S in the second conveying path 26 to the third conveying path 27 by the second switchback roller 39.

[0026] The sheet S conveyed to the third conveying path 27 is supplied again to the processing unit 4 by the third conveying roller 40, the registration roller 35, etc. After that, an image is formed on the sheet S in the processing unit 4, and then the sheet S is discharged onto the discharge tray 22 by the conveying unit 3.

[0027] The conveying unit 3 also includes a separation pad 42 and a pickup feed roller 43 for separating and conveying the sheets S manually inserted from the multipurpose tray 14. The separation pad 42 and the pickup feed roller 43 separate the sheets S inserted from the multipurpose tray 14 one by one and convey them toward the process unit 4. The subsequent flow is the same as when the sheets are conveyed from the supply tray 13 described above.

[0028] The process unit 4 includes an exposure unit 5, a drum unit 6, four developing cartridges 7Y, 7M, 7C, and 7K, and a transfer unit 8. The process unit 4 has a function of forming a toner image on a sheet S.

[0029] The exposure unit 5 is disposed in the upper part of the main body housing 2, and includes a light source, a polygon mirror, a lens, a reflecting mirror, etc. (not shown). The exposure unit 5 exposes the surface of the photosensitive drum 61 by emitting a light beam indicated by a dashed dotted line onto the surface of the photosensitive drum 61.

[0030] The drum unit 6 is disposed between the supply tray 13 and the exposure unit 5 inside the main body housing 2, and includes four photosensitive drums 61, four chargers 62, a pinch roller 64, and a support frame 65 that supports the photosensitive drums 61 and other components. The drum unit 6 is detachable from the main body housing 2 through the front opening 2A when the front cover 11 is open. The pinch roller 64 faces the registration roller 35. The pinch roller 64 rotates following the rotation of the registration roller 35, and transports the sheet S together with the registration roller 35.

[0031] The developer cartridges 7Y, 7M, 7C, and 7K correspond to four colors: yellow (Y), magenta (M), cyan (C), and black (K), respectively, and are detachably mounted in the drum unit 6 in that order from the front to the rear of the printer 1. Each of the developer cartridges 7Y, 7M, 7C, and 7K includes a developer roller 71, a supply roller 72, and a toner storage section 73. Although the developer cartridges 7Y, 7M, 7C, and 7K differ in toner color, they are otherwise configured the same, and therefore, hereinafter, any one of them may be referred to as the developer cartridge 7.

[0032] The transfer unit 8 is disposed between the supply tray 13 and the drum unit 6 inside the main body housing 2, and includes a drive roller 81, a driven roller 82, a conveyor belt 83, and four transfer rollers 84. The conveyor belt 83 is stretched between the drive roller 81 and the driven roller 82, and its upper surface is in contact with the photosensitive drum 61. The four transfer rollers 84 are disposed inside the conveyor belt 83 so as to sandwich the conveyor belt 83 between themselves and the corresponding photosensitive drum 61.

[0033] The process unit 4 uniformly charges the surface of the photosensitive drum 61 using the charger 62, and exposes the surface of the photosensitive drum 61 using the exposure unit 5, thereby forming an electrostatic latent image on the surface of the photosensitive drum 61. The process unit 4 also supplies toner from a toner storage unit 73 to a supply roller 72, which then supplies the toner to the developing roller 71. The toner supplied to the developing roller 71 is carried on the developing roller 71 as the developing roller 71 rotates.

[0034] The process unit 4 supplies the toner carried on the development roller 71 to the electrostatic latent image formed on the photosensitive drum 61, thereby forming a toner image on the surface of the photosensitive drum 61. Thereafter, the process unit 4 transfers the toner image on the photosensitive drum 61 to the sheet S by transporting the sheet S supplied from the supply tray 13 by the transport unit 3 between the photosensitive drum 61 and the transport belt 83. Thus, the process unit 4 forms a toner image on the sheet S. Thereafter, the process unit 4 transports the sheet S to the fixing device 9.

[0035] When attached to the printer 1, the fixing device 9 is located behind the process unit 4 inside the main body housing 2. More specifically, the fixing device 9 is located between the closed rear cover 12 and the process unit 4. The fixing device 9 has a heating roller 91 that heats the sheet S and a pressure roller 92 that sandwiches the sheet S between the heating roller 91 and the pressure roller 92. The heating roller 91 is an example of a heating rotor. The pressure roller 92 is an example of a pressure rotor. In the first embodiment, the heating roller 91 has a heater 93 therein that heats the heating roller 91.

[0036] The fixing device 9 fixes the toner image formed on the sheet S to the sheet S by conveying the sheet S between the heating roller 91 and the pressure roller 92.

[0037] In addition, downstream of the fixing device 9 in the sheet conveying direction, there is also provided a discharge sensor SE4 that detects the passage of the sheet S that has passed between the heating roller 91 and the pressure roller 92, i.e., after the developer image has been fixed by the fixing device 9.

[0038] The printer 1 further includes a fixing fan 63 inside the main body housing 2. The fixing fan 63 is provided so as to exhaust air inside the main body housing 2 to the outside of the main body housing 2 when driven.

[0039] Meanwhile, the fixing device 9 is equipped with two fixing temperature sensors TH1 and TH2 for detecting the temperature of the heating roller 91. The fixing temperature sensors TH1 and TH2 are equipped with variable resistors whose resistance value changes depending on the temperature of the area to be detected, and are capable of outputting a signal corresponding to the temperature of the area to be detected. Here, fixing temperature sensors TH1 and TH2 are both arranged facing the heating roller 91 in a non-contact state, but each detects a different area. Fixing temperature sensor TH2 is a sensor for detecting the temperature of an area near the center of the heating roller 91. Fixing temperature sensor TH1 is a sensor for detecting the temperature of an area near the edge of the heating roller 91.

[0040] The fixing device 9 can be attached to and detached from the main body housing 2 through a rear opening 2B of the main body housing 2, which is opened by opening the rear cover 12. FIG. 2 shows the state in which the rear cover 12 is open. As shown in FIG. 2, the fixing device 9 includes a fixing housing 120, a fixed handle 130, and a lever 140. The fixed handles 130 are provided on both the left and right ends of the fixing housing 120, and the levers 140 are attached to the fixed handles 130.

[0041] 3, when the user holds each lever 140 and pulls each fixed handle 130 backward, the fixing device 9 can be detached from the main body housing 2. At this time, the fixing connector 160 provided on the fixing device 9 also detaches from the main body connector 150 provided on the main body housing 2. In other words, the fixing connector 160 and the main body connector 150 are connected when the fixing device 9 is attached to the main body housing 2, and are detached when the fixing device 9 is removed from the main body housing 2.

[0042] Although not shown, the main body housing 2 also has a fixed / unfixed detection switch 15 (see FIG. 7) at a location in contact with the fixing device 9 for detecting whether the fixing device 9 is attached to the main body housing 2. The fixed / unfixed detection switch 15 is turned on when the fixing device 9 is attached to the main body housing 2, and is turned off when the fixing device 9 is removed from the main body housing 2.

[0043] [Configuration of fixing device] Next, among the various components of the printer 1 described above, the fixing device 9, which is detachably attached to the main body housing 2 of the printer 1 and fixes the toner image on the sheet S, will be described in more detail with reference to the drawings. Figures 4 and 5 are views showing the internal structure of the fixing device 9 from the front and rear, respectively, with the outer housing wall covering the outside removed. In the following description, the front-to-back and up-to-down directions are as shown on the paper.

[0044] The fixing device 9 includes a heating roller 91 as an example of a heating member for heating the sheet S, a pressure roller 92 for sandwiching the sheet S between the heating roller 91, side frames 94A and 94B, a connecting frame 94C, and a pressure contact / separation mechanism 900.

[0045] The heating roller 91 extends in the longitudinal direction and rotates around its rotation axis. The heating roller 91 rotates by receiving the driving force of a main motor 201A provided in the printer 1. The heating roller 91 is a metal tube, and is heated by a heater 93 disposed inside. The heater 93 is, for example, a halogen heater.

[0046] In the following description, the longitudinal direction of the heating roller 91 will be simply referred to as the longitudinal direction. The longitudinal direction also refers to the direction of the rotation axis of the heating roller 91. The sheet S is transported from the front to the rear of the fixing device 9 and passes through the fixing device 9. After passing through the fixing device 9, the sheet S is transported on a first transport path 25 toward above the fixing device 9, as shown in FIG. 1.

[0047] The pressure roller 92 rotates following the rotation of the heat roller 91, and nips the sheet S between itself and the heat roller 91. The pressure roller 92 is made of an elastic member such as rubber.

[0048] The side frames 94A and 94B are located at both ends in the longitudinal direction of the heating roller 91 and the pressure roller 92. The side frames 94A and 94B support the heating roller 91 so that it can rotate.

[0049] The connecting frame 94C is a metal plate that extends in the longitudinal direction and connects the side frame 94A on one side in the longitudinal direction to the side frame 94B on the other side in the longitudinal direction.

[0050] The cam 97A is located adjacent to the side frame 94A and is rotatably supported relative to the side frame 94A. Similarly, the cam 97B is located adjacent to the side frame 94B and is rotatably supported relative to the side frame 94B. The cams 97A and 97B are connected to each other by a camshaft 98.

[0051] The pressure contact / separation mechanism 900 has arms 95A and 95B, springs 96A and 96B, and cams 97A and 97B. The pressure contact / separation mechanism 900 has a pressure contact state in which the heating roller 91 and the pressure roller 92 are pressed together, and a separated state in which the heating roller 91 and the pressure roller 92 are separated, and can switch between the pressure contact state and the separated state by moving at least one of the heating roller 91 and the pressure roller 92 relative to the other. In the pressure contact state, the pressure contact / separation mechanism 900 can adjust the nip pressure applied by the heating roller 91 and the pressure roller 92. In particular, in the first embodiment, the pressure contact / separation mechanism 900 switches between the pressure contact state and the separated state by moving the pressure roller 92 relative to the heating roller 91.

[0052] The following describes the pressure contact / separation mechanism 900 with reference to Fig. 6. Note that the operations of the arm 95A, spring 96A, and cam 97A in the side frame 94A are the same as the operations of the arm 95B, spring 96B, and cam 97B in the side frame 94B, so the following describes the operations of the arm 95A, spring 96A, and cam 97A in the side frame 94A as an example.

[0053] 6, the arm 95A has one end 110, the other end 111, a first portion 112, and a second portion 113. The arm 95A has one end 110 supported by the side frame 94A via a shaft 114 so as to be rotatable about the arm axis X1. The other end 111 has a cam follower 115. The cam follower 115 is capable of coming into contact with the cam 97A.

[0054] The first portion 112 and the second portion 113 are located between the one end 110 and the other end 111. The first portion 112 rotatably supports the pressure roller 92. The second portion 113 is a portion to which a spring 96A is connected. One end of the spring 96A is hooked to the second portion 113, and the other end of the spring 96A is hooked to the side frame 94A. The spring 96A biases the pressure roller 92 toward the heating roller 91 via the arm 95A.

[0055] The cam 97A is rotatably supported by the side frame 94A on one side in the longitudinal direction via a camshaft 98, and is rotatable about the cam axis X2. As shown in FIG. 6, the cam 97A has a distorted semicircular shape, and as it rotates, it comes into contact with the cam follower 115, causing the arm 95A to rotate about the arm axis X1. As the arm 95A rotates, the pressure roller 92 moves relative to the heating roller 91, switching between a pressure-contact state and a spaced state. The cam 97A is rotatable counterclockwise as shown in FIG. 6.

[0056] Here, the upper diagram in Fig. 6 shows a pressed state in which the heating roller 91 and the pressure roller 92 are pressed together. The lower diagram in Fig. 6 shows a separated state in which the heating roller 91 and the pressure roller 92 are separated. The middle diagram in Fig. 6 shows a state in the middle of transitioning from the pressed state to the separated state.

[0057] 4 and 5, continuing the description of the fixing device 9, the fixing device 9 further includes a cam gear 121 and a fixing gear 122. The cam gear 121 is fixed to one end of the camshaft 98 in the longitudinal direction. The cam gear 121 is connected to the cams 97A and 97B via the camshaft 98 and transmits driving force to the cams 97A and 97B. The cam gear 121 has a plurality of gear teeth 121A and a flange 121B extending from near the base of the gear teeth 121A to one side in the longitudinal direction. The flange 121B has a notch 121C for detecting the phase of the cam 97A.

[0058] The fixing gear 122 also has a plurality of gear teeth. The fixing gear 122 is fixed to one end of the heating roller 91 in the longitudinal direction. The fixing gear 122 is provided coaxially with the heating roller 91 and rotates integrally with the heating roller 91 around the rotation axis. The fixing gear 122 transmits driving force to the heating roller 91.

[0059] Furthermore, the fixing device 9 includes fixing temperature sensors TH1 and TH2 that detect the temperature of the heating roller 91, a nip detection sensor SE3, a discharge sensor SE4, a fixing connector 160, and a relay board 161. The fixing temperature sensors TH1 and TH2 are examples of temperature sensors, the nip detection sensor SE3 is an example of a first detection sensor, and the discharge sensor SE4 is an example of a second detection sensor.

[0060] The fixing temperature sensor TH1 is a sensor that detects the temperature of the heating roller 91, particularly in the area near the end. As shown in Fig. 4, the fixing temperature sensor TH1 is fixed to the connecting frame 94C with screws or the like at a position spaced above the heating roller 91 at the end in the longitudinal direction. The fixing temperature sensor TH1 is, for example, a thermistor.

[0061] On the other hand, the fixing temperature sensor TH2 is a sensor that detects the temperature of the heating roller 91, particularly in the region near the center. As shown in Fig. 4, the fixing temperature sensor TH2 is fixed to the connecting frame 94C with screws or the like at a position spaced above the heating roller 91 in the center in the longitudinal direction. The fixing temperature sensor TH2 is, for example, a thermistor.

[0062] Nip detection sensor SE3 is an optical sensor and includes a light-emitting element that emits light and a light-receiving element that receives light from the light-emitting element. The light-emitting element includes a light-emitting diode (described later) as a light-emitting element, and the light-receiving element includes a phototransistor Tr1 (see FIG. 9). When the pressure contact / separation mechanism 900 presses the heating roller 91 and the pressure roller 92 together as shown in the upper diagram of FIG. 6, the light from the light-emitting element is blocked by flange 121B of cam gear 121. On the other hand, when the pressure contact / separation mechanism 900 separates the heating roller 91 and the pressure roller 92 as shown in the lower diagram of FIG. 6, the light from the light-emitting element passes through notch 121C provided in flange 121B of cam gear 121, allowing the light-receiving element to receive the light without being blocked. As a result, as will be described later, the ASIC (an example of a control unit, an abbreviation for Application Specific Integrated Circuit) 210 mounted on the main board 200 is able to determine that the pressure-contact / separation mechanism 900 is in a separated state when the light-receiving unit receives light, and to determine that the pressure-contact / separation mechanism 900 is in a pressure-contact state when the light-receiving unit does not receive light.

[0063] However, by adjusting the position of notch 121C in flange 121B, it is also possible to reverse the relationship between the light blocking state of nip detection sensor SE3 and the state of pressure contact / separation mechanism 900. That is, in the pressure contact state where heating roller 91 and pressure roller 92 are pressed together as shown in the upper diagram of Fig. 6, light from the light emitting unit can be received by passing through notch 121C, and in the separated state where heating roller 91 and pressure roller 92 are separated as shown in the lower diagram of Fig. 6, light from the light emitting unit can be blocked. In this case, ASIC 210 can determine that pressure contact / separation mechanism 900 is in the pressure contact state when the light receiving unit receives light, and can determine that pressure contact / separation mechanism 900 is in the separated state when the light receiving unit does not receive light.

[0064] The discharge sensor SE4 is a sensor that detects the sheet S that has passed through the nip position between the heating roller 91 and the pressure roller 92, i.e., after the developer image has been fixed by the fixing device 9. The discharge sensor SE4 includes an actuator that can rotate around a rotation axis and a photosensor. When the sheet S passes between the heating roller 91 and the pressure roller 92 and comes into contact with the roller, causing the actuator to tilt, the photosensor located near the rotation axis of the actuator detects that the actuator has tilted, i.e., that the sheet S has been discharged after the toner image has been fixed by the fixing device 9. More specifically, the photosensor includes a light-emitting element that emits light and a light-receiving element that receives light from the light-emitting element. The light-emitting element includes a light-emitting diode (described later) as a light-emitting element, and the light-receiving element includes a phototransistor Tr2 (see FIG. 9). When the sheet S has passed through the nip position and the actuator is tilted, the light from the light-emitting element is not blocked by the actuator and the light-receiving element can receive the light. On the other hand, when the sheet S is not at the nip position and the actuator is at the initial position, the light from the light-emitting unit is blocked by the actuator. As a result, as will be described later, the ASIC 210 of the printer 1 can determine that the sheet S has passed the nip position when the light-receiving unit receives light, and can determine that the sheet S is not at the nip position when the light-receiving unit does not receive light.

[0065] The fixing connector 160 has a plurality of terminals. When the fixing device 9 is attached to the main body housing 2 of the printer 1, the fixing connector 160 can be connected to the main body connector 150 (see FIG. 3) provided on the main body housing 2. The plurality of terminals of the fixing connector 160 are connected to corresponding terminals of the main body connector 150, respectively. The fixing connector 160 is located outside the side frame 94B in the longitudinal direction.

[0066] The relay board 161 relays signals from the fixing temperature sensors TH1 and TH2, the nip detection sensor SE3, and the discharge sensor SE4 to the fixing connector 160. The relay board 161 is provided with a plurality of connectors 162 for connecting to the respective sensors, and the connectors 162 are connected to the respective sensors by cables. The relay board 161 is also provided with a connector 162 for connecting to the fixing connector 160, and the connector 162 and the fixing connector 160 are also connected by cables.

[0067] Furthermore, the relay board 161 is equipped with a memory 163 for storing information about the fixing device 9, such as identification information and setting parameters of the fixing device, and information about the number of times the fixing device has been used and its lifespan. The relay board 161 has a signal line connected at one end to the memory 163, and relays data signals for reading and writing data and clock signals for synchronization with the control unit on the main body side of the printer 1 via the signal line. The data signals and clock signals are examples of memory signals.

[0068] The heater 93 provided in the heating roller 91 is also connected to the fixing connector 160 by a power cable. More specifically, the heater 93 is connected to the fixing connector 160 by a power cable via a thermostat (TM). The thermostat TM has a function of cutting off power when the temperature of the heating roller 91 exceeds the control range and becomes overheated.

[0069] When the fixing device 9 having the above configuration is attached to the main body housing 2 of the printer 1, the fixing connector 160 is connected to the main body connector 150. When the fixing connector 160 and the main body connector 150 are connected, temperature information detected by the fixing temperature sensors TH1 and TH2, the state of the pressure contact / separation mechanism 900 detected by the nip detection sensor SE3, sheet information detected by the discharge sensor SE4, and data signals for reading and writing data from the memory 163 can be transmitted to the control unit of the printer 1. Furthermore, a clock signal can be transmitted and received from the control unit of the printer 1 to the memory 163. When the fixing connector 160 and the main body connector 150 are connected, power can be supplied to the heater 93 from the power supply board of the main body housing 2. The power supply board is controlled by the ASIC 210 and supplies power to the heater 93 based on the temperature information detected by the fixing temperature sensors TH1 and TH2.

[0070] [Printer electrical configuration] Next, the electrical configuration of the printer 1 including the fixing device 9 will be described with reference to Fig. 7. Fig. 7 shows the electrical configuration of the printer 1 including the fixing device 9. Note that Fig. 7 mainly describes components necessary for explaining the first embodiment, and other components of the printer 1 are omitted.

[0071] As shown in FIG. 7, the main body housing 2 is provided with a main board 200, a main motor board 201, a high-voltage power supply board 202, and a low-voltage power supply board 203. The boards are connected to each other via harnesses. The main motor board 201 is equipped with a main motor 201A. When the main motor 201A is driven, the heating roller 91 of the fixing device 9 and the rollers of the conveying unit 3 rotate. The main board 200 is an example of a control board for the printer 1.

[0072] The high-voltage power supply board 202 supplies high voltages HV such as a development voltage and a charging voltage to the process unit 4. The high-voltage power supply board 202 has a high-voltage generation circuit 202C. The high-voltage generation circuit 202C generates a high voltage HV of, for example, about 1 kV based on a DC voltage, for example, DC 24 V, supplied from the low-voltage power supply board 203 via the main board 200, and supplies the high voltage HV to the process unit 4.

[0073] Furthermore, the main board 200 and the high-voltage power supply board 202 are connected via a first connection line CA1. The ASIC 210 mounted on the main board 200 controls the high-voltage power supply board 202, and therefore needs to send and receive control signals between the main board 200 and the high-voltage power supply board 202. The first connection line CA1 is for transmitting these control signals. Since there are multiple control signals, there are also multiple signal lines for transmitting these multiple control signals. Therefore, the first connection line CA1 is configured by a harness that bundles multiple signal lines.

[0074] The low-voltage power supply board 203 has an AC-DC conversion circuit 203C, which inputs an AC voltage supplied by a commercial power source, for example, AC 100 V, and converts this AC 100 V to a DC voltage, for example, DC 24 V, by the AC-DC conversion circuit 203C. The low-voltage power supply board 203 is connected to the main board 200 via a fourth connection line CA4, and outputs the generated DC 24 V to the main board 200.

[0075] The main board 200 has a DC-DC conversion circuit 211, which converts DC 24V from the low-voltage power supply board 203 to DC 3.3V by the DC-DC conversion circuit 211. This DC 3.3V is a voltage for driving various electronic components mounted on the main board 200. However, if there are electronic components that are driven by another DC voltage value, for example, DC 5V, multiple DC-DC conversion circuits may be provided to generate DC 5V or the like in addition to DC 3.3V.

[0076] Furthermore, the DC-DC conversion circuit 211 generates voltages of DC 3.3V and DC 1.8V to be input to the fixing device 9, in addition to the voltages for driving the various electronic components mounted on the main board 200. Regarding the DC 3.3V voltage, the DC-DC conversion circuit 211 generates ENG 3.3V, which is separate from the DC 3.3V voltage for driving the various electronic components mounted on the main board 200. The DC-DC conversion circuit 211 then supplies the ENG 3.3V and DC 1.8V voltages to the fixing device 9 via the main body connector 150. The main board 200 has a ground section GND, which serves as a reference potential when circuits such as the ASIC 210 operate, and is connected to a GND terminal, which is one of multiple terminals of the main body connector 150. The relay board 161 provided in the fixing device 9 uses these supplied voltages and ground potential to operate the fixing temperature sensors TH1 and TH2, nip detection sensor SE3, and discharge sensor SE4, and outputs signals from each sensor to the ASIC 210. Specifically, the fixing temperature sensor TH1, nip detection sensor SE3, and discharge sensor SE4 operate at ENG 3.3V, and the fixing temperature sensor TH2 operates at DC 1.8V.

[0077] Furthermore, when the printer 1 is in the "standby state," if it does not receive an image formation execution command or data related to image formation and a predetermined time has passed since it entered the "standby state," the power consumption state transitions from the "standby state" to the "sleep state." The "sleep state" is a mode in which the printer 1 consumes less power than the "standby state." For example, the display is turned off, the CPU clock is reduced, and the supply of the above-mentioned ENG 3.3V is stopped. However, DC 3.3V and DC 1.8V are continuously supplied. If the printer 1 receives an image formation execution command or data related to image formation in the "sleep state," it will return to the "standby state" and begin printing. The above-mentioned standby state is an example of a non-power-saving mode, and the sleep state is an example of a power-saving mode.

[0078] The low-voltage power supply board 203 is connected to the main body connector 150 via a third connection line CA3, and is connected to the inlet 204 via a fifth connection line CA5. The inlet 204 is used to input AC voltage supplied from a commercial power source. The AC voltage is, for example, AC 100 V. This AC voltage is also supplied to the fixing device 9 from the inlet 204 via the fifth connection line CA5, the low-voltage power supply board 203, the third connection line CA3, the main body connector 150, and the fixing connector 160. The AC voltage supplied to the fixing device 9 is also supplied to the heater 93 via a thermostat (TM).

[0079] The ASIC 210 mounted on the main board 200 has, for example, a CPU, memory, and input / output circuits (none of which are shown), and controls the entire printer 1, including the processing unit 4, by performing various arithmetic processing based on programs and data stored in the memory. The memory is an embedded memory, and may be configured by combining ROM, RAM, NVRAM, SSD, HDD, etc. It is used when various programs are executed.

[0080] In addition to the ASIC 210, the main board 200 is equipped with a motor drive circuit MD for driving the main motor 201A, an ON / OFF circuit 212 for switching whether or not to supply DC 24V to the high voltage generation circuit 202C of the high voltage power supply board 202, a detection circuit (DET) 213 for detecting whether the fixing presence / absence detection switch 15 for detecting whether or not the fixing device 9 is attached to the main body housing 2 is in the ON state or the OFF state, and the above-mentioned DC-DC conversion circuit 211.

[0081] The AC-DC conversion circuit 203C of the low-voltage power supply board 203 is connected to the DC-DC conversion circuit 211 via a power line PL. The power line PL connecting the AC-DC conversion circuit 203C and the DC-DC conversion circuit 211 is included in the fourth connection line CA4. The power line PL branches off at a branch point BP0 on the main board 200 before being input to the DC-DC conversion circuit 211, and extends therefrom, and is connected to the input side of the fixing presence / absence detection switch 15.

[0082] The output side of the fixed-fixing detection switch 15 is connected to the input side of the ON / OFF circuit 212 via the power line PL, and branches off at a first branch point BP1 on the power line PL located between the output side of the fixed-fixing detection switch 15 and the input side of the ON / OFF circuit 212 to be connected to the input side of the motor drive circuit MD. Furthermore, the output side of the fixed-fixing detection switch 15 branches off at a second branch point BP2 downstream of the first branch point BP1 on the power line PL located between the output side of the fixed-fixing detection switch 15 and the input side of the ON / OFF circuit 212 to be connected to the input side of the detection circuit 213.

[0083] The output side of the motor drive circuit MD is connected to the main motor 201A. The motor drive circuit MD is supplied with a voltage applied to a first branch point BP1 on the power line PL. Since the output voltage from the fixed-image detection switch 15 is applied to the first branch point BP1, when the fixed-image detection switch 15 is in the ON state, DC 24 V is applied, and when the fixed-image detection switch 15 is in the OFF state, 0 V is applied.

[0084] The motor drive circuit MD also receives a signal EN from the output port of the ASIC 210. The signal EN is a signal for enabling or disabling the motor drive circuit MD. For example, when the value of the signal EN is H, the motor drive circuit MD is enabled, and when the value of the signal EN is L, the motor drive circuit MD is disabled. However, even if the signal EN is H, the motor drive circuit MD does not operate unless DC 24V is applied to the motor drive circuit MD. In other words, when DC 24V is applied to the motor drive circuit MD and a signal EN of H is input, the motor drive circuit MD starts operating. When DC 24V is applied to the motor drive circuit MD and a signal EN of L is input, the motor drive circuit MD stops operating. Therefore, when 0V is applied to the motor drive circuit MD, the motor drive circuit MD stops operating regardless of the value of the signal EN. Note that a well-known method may be used as the method by which the motor drive circuit MD controls the main motor 201A, and therefore a description thereof will be omitted.

[0085] The output side of the ON / OFF circuit 212 is connected to the power supply voltage input side of the high-voltage generation circuit 202C of the high-voltage power supply board 202. A control signal is also input to the high-voltage generation circuit 202C from an output port (not shown) of the ASIC 210. The high-voltage generation circuit 202C has, for example, a boost circuit including a transformer and a transformer drive circuit, and as described above, boosts the input DC 24V based on the input control signal and supplies the generated high voltage HV, specifically, the charging voltage, the developing voltage, and the transfer voltage, to the process unit 4.

[0086] ASIC 210 outputs an HVEN signal to ON / OFF circuit 212. The HVEN signal is a signal for controlling ON / OFF circuit 212, and takes on either an ON (=H) or OFF (=L) value. When DC 24V is input from fixing presence / absence detection switch 15, ON / OFF circuit 212 switches whether or not to input DC 24V to high voltage generation circuit 202C according to the value of the HVEN signal output from ASIC 210.

[0087] The output side of the detection circuit 213 is connected to an input port (not shown) of the ASIC 210. When the detection signal from the detection circuit 213 is L, the ASIC 210 determines that the fixing presence / absence detection switch 15 is in the ON state, and when the detection signal from the detection circuit 213 is H, the ASIC 210 determines that the fixing presence / absence detection switch 15 is in the OFF state.

[0088] Additionally, the input port of the ASIC 210 is connected to the output side of a rear cover open / close detection switch 16 that detects the opening and closing of the rear cover 12. The rear cover open / close detection switch 16 is provided near the rear cover 12 and outputs a rear cover open / close signal that indicates a value according to the opening and closing of the rear cover 12. The ASIC 210 can determine whether the rear cover 12 is open or closed by checking the value of this rear cover open / close signal.

[0089] Furthermore, the input port of the ASIC 210 is also connected to the output side of each of the sensors, namely, the paper feed sensor 44, the pre-registration sensor 45, and the post-registration sensor 46, which are arranged on the first transport path 25. The ASIC 210 can determine the transport status of the sheet S on the first transport path 25 by checking the values ​​of signals input from the paper feed sensor 44, the pre-registration sensor 45, and the post-registration sensor 46 as well as the discharge sensor SE4 of the fixing device 9.

[0090] The main board 200 is connected to the high-voltage power supply board 202 via a connector 200A on the main board 200 side, a first connection line CA1, and a connector 202A on the high-voltage power supply board 202 side. The high-voltage power supply board 202 is connected to the main connector 150 via a connector 202B on the high-voltage power supply board 202 side and a second connection line CA2.

[0091] As described above, the main body housing 2 includes the inlet 204, and the AC voltage supplied from the inlet 204 is input to the low-voltage power supply board 203 via the connector 203A on the low-voltage power supply board 203 side. The low-voltage power supply board 203 is connected to the main body connector 150 via the connector 203B on the low-voltage power supply board 203 side and the third connection line CA3.

[0092] Furthermore, when the fixing device 9 is attached to the main body housing 2 of the printer 1, the main body connector 150 is connected to the fixing connector 160. The fixing connector 160 is connected to the relay board 161 provided in the fixing device 9 via the connector 161A on the relay board 161 side. As described above, the fixing device 9 is equipped with the heater 93. An AC voltage, for example, AC 100 V, input from the inlet 204 is supplied to the heater 93 via the low-voltage power supply board 203, the third connection line CA3, the main body connector 150, and the fixing connector 160.

[0093] The heater 93 is heated by the AC 100V supplied in this manner. When AC 100V is supplied to the heater 93, the ASIC 210 controls the heating temperature of the heater 93 by controlling the on / off timing of the AC 100V supplied to the heater 93. To control this heating temperature, the fixing temperature sensors TH1 and TH2 are provided as described above. The fixing temperature sensors TH1 and TH2 are each composed of two sensors as shown in FIG. 4.

[0094] The fixing temperature sensor TH1, which detects the temperature of the end of the heat roller 91, receives ENG 3.3V from the relay board 161 and operates at this ENG 3.3V. Meanwhile, the fixing temperature sensor TH2, which detects the temperature of the center of the heat roller 91, receives DC 1.8V and operates at this DC 1.8V. The reason for using different operating voltages for the fixing temperature sensors TH1 and TH2 is to enable temperature detection by at least one of the fixing temperature sensors even if the power line is disconnected or the DC-DC conversion circuit 211 is broken, as described above. Furthermore, when the printer 1 transitions to the sleep mode, the supply of ENG 3.3V is stopped, while the supply of DC 1.8V is maintained, as described above. This allows some fixing temperature sensor TH2 to operate even when the printer transitions to the sleep mode.

[0095] Then, in order for the ASIC 210 of the main board 200 to control the heating temperature of the heater 93, signals THM1 and THM2 output by the fixing temperature sensors TH1 and TH2, respectively, are transmitted from the fixing device 9 to the main board 200. More specifically, the signals THM1 and THM2 are transmitted to the main board 200 via the relay board 161, the fixing connector 160, the main body connector 150, the second connection line CA2, the high-voltage power supply board 202, and the first connection line CA1. The ASIC 210 of the main board 200 controls the on / off timing of the AC 100 V supplied to the heater 93 based on the signals THM1 and THM2 from the fixing temperature sensors TH1 and TH2. In addition to the detection signals from the fixing temperature sensors TH1 and TH2, the fixing device 9 also transmits detection signals from the nip detection sensor SE3 and the discharge sensor SE4 to the main board 200.

[0096] [Electrical configuration of relay board] Next, the electrical configuration of the printer 1 described above, particularly the electrical configuration of the relay board 161 provided in the fixing device 9, will be described in more detail using Figures 8 and 9. Figures 8 and 9 show only the relay board 161 provided in the fixing device 9 and the associated electrical configuration of the printer 1.

[0097] First, referring to FIG. 8, the fixing temperature sensor TH1 (see FIG. 4) of the fixing device 9 will be described. The fixing temperature sensor TH1 has a variable resistor R2 whose resistance value changes depending on the temperature of the object to be detected. One end of the variable resistor R2 of the fixing temperature sensor TH1 is connected to the ENG 3.3V power supply of the relay board 161, and the other end is connected to a terminal of the fixing connector 160 via a signal line. The relay board 161 relays a signal from the fixing temperature sensor TH1 to the main board 200 via a dedicated temperature sensor output terminal 251. On the main board 200 side, one end of the resistor R1 having a predetermined resistance value is connected to a terminal of the ASIC 210 connected to the temperature sensor output terminal 251 and receiving the signal from the fixing temperature sensor TH1, and the other end of the resistor R1 is connected to the ground GND of the main board 200. On the other hand, the ASIC 210 includes an AD conversion circuit unit 210A. As a result, for the fixing temperature sensor TH1, an analog voltage obtained by dividing ENG3.3V by the variable resistor R2 and resistor R1 is input to the AD conversion circuit unit 210A of the ASIC 210. More specifically, for the fixing temperature sensor TH1, an analog voltage obtained by dividing ENG3.3V by the variable resistor R2 and resistor R1 is input to the AD conversion circuit unit 210A of the ASIC 210. Then, the ASIC 210 identifies the temperature detected by the fixing temperature sensor TH1 based on the digital value converted by the AD conversion circuit unit 210A. An analog voltage signal of the following equation (1) is input to the AD conversion circuit section 210A. Vin=3.3V×R1 / (variable R2+R1) (1) As described above, the variable resistor R2 varies with the change in the detected temperature, and the analog voltage Vin changes.

[0098] Next, referring to FIG. 8, the fixing temperature sensor TH2 (a sensor that detects the temperature of a region near the center of the heating roller 91; see FIG. 4) of the fixing device 9 will be described. The fixing temperature sensor TH2 has a variable resistor R2 whose resistance value changes depending on the detected temperature. One end of the variable resistor R2 of the fixing temperature sensor TH2 is connected to a DC 1.8V power supply provided on the relay board 161, and the other end is connected to a terminal of the fixing connector 160 via a signal line. The relay board 161 relays a signal from the fixing temperature sensor TH2 to the main board 200 via a dedicated temperature sensor output terminal 252. On the main board 200 side, one end of a resistor R1 having a predetermined resistance value is connected to a terminal of the ASIC 210 that is connected to the temperature sensor output terminal 252 and receives the signal from the fixing temperature sensor TH2, and the other end of the resistor R1 is connected to the ground GND of the main board 200. On the other hand, the ASIC 210 includes an AD conversion circuit unit 210B. As a result, for the fixing temperature sensor TH2, an analog voltage obtained by dividing 1.8V by the variable resistor R2 and resistor R1 is input to the AD conversion circuit unit 210B of the ASIC 210. More specifically, for the fixing temperature sensor TH2, an analog voltage obtained by dividing 1.8V by the variable resistor R2 and resistor R1 is input to the AD conversion circuit unit 210B of the ASIC 210. Then, the ASIC 210 identifies the temperature detected by the fixing temperature sensor TH2 based on the digital value converted by the AD conversion circuit unit 210B. The AD conversion circuit section 210B receives an analog voltage of the following equation (2). Vin=1.8V×R1 / (variable R2+R1) (2) As described above, the variable resistor R2 varies with the change in the detected temperature, and the analog voltage Vin changes.

[0099] As described above, the fixing temperature sensors TH1 and TH2 are provided with the resistor R1 on the main board 200 side and connected to the ground GND, so the analog voltage Vin has a potential based on the ground GND of the main board 200, not the relay board 161. This prevents ground deviation when analog-to-digital conversion is performed in the AD conversion circuit units 210A and 210B, making it possible to detect temperatures more accurately.

[0100] The voltages of the power supply of ENG 3.3V and DC 1.8V provided in the relay board 161 are generated in the DC-DC conversion circuit 211 of the main board 200 and supplied to the fixing device 9 via the main body connector 150 (see FIG. 7).

[0101] Next, referring to FIG. 9 , the nip detection sensor SE3, the discharge sensor SE4, and the memory 163 provided in the fixing device 9 will be described. The nip detection sensor SE3 has a light-emitting diode and a phototransistor Tr1, and the discharge sensor SE4 has a light-emitting diode and a phototransistor Tr2. The memory 163 is a storage medium that stores information about the fixing device 9, such as its identification information, setting parameters, number of uses, and lifespan. The memory 163 has a CLK terminal and a DATA terminal, to which a first memory connection line L1 and a second memory connection line L2 are connected as signal lines. The relay board 161 relays data signals for reading data and clock signals for synchronization between the memory 163 and the ASIC 210 on the main board 200 via these signal lines. The memory 163 is also connected to a ground GND and a power supply. The phototransistor Tr1 is an example of a first switching unit, and the phototransistor Tr2 is an example of a second switching unit.

[0102] First, the nip detection sensor SE3 and the memory 163 will be mainly described. To reduce the number of terminals in the fixing connector 160 and the main connector 150, the signal lines for the detection signal from the nip detection sensor SE3 and the clock signal from the memory 163 are unified into a single common signal line. Specifically, the relay substrate 161 has a first wiring L3, one end of which is connected to the first common terminal 253, and a first memory connection wiring L1, one end of which is connected to the CLK terminal of the memory 163. The other end of the first wiring L3 is connected to the nip detection sensor SE3, and the other end of the first memory connection wiring L1 is connected to the first wiring L3. The fixing connector 160 also has a first fixing common terminal 260, and the first common terminal 253 and the first fixing common terminal 260 are connected to each other by a signal line. As a result, the relay substrate 161 relays the signal from the nip detection sensor SE3 and the clock signal from the memory 163 to the main substrate 200 via the same first common terminal 253 and first fixing common terminal 260.

[0103] Meanwhile, the main body connector 150 on the main board 200 side has a first main body common terminal 261 connected to the first fixing common terminal 260. Furthermore, the first main body common terminal 261 and the first control terminal 255 of the ASIC 210 are connected to each other by a signal line. That is, the first control terminal 255 is connected to the first common terminal 253 via the first fixing common terminal 260 and the first main body common terminal 261. The main board 200 also has a predetermined resistor R3, one end of which is connected to the first control terminal 255 of the ASIC 210 to which a signal from the nip detection sensor SE3 and a clock signal from the memory 163 are input, and the other end of which is connected to a DC 3.3 V power supply provided on the main board 200. That is, the first wiring L3 is also connected to a DC 3.3 V power supply via the main board connector 150 and the fixing connector 160. The emitter of phototransistor Tr1 is connected to the ground GND of relay substrate 161, and the collector is connected to first common terminal 253 via first wiring L3. The DC 3.3V power supply provided on main substrate 200 is an example of a first power supply unit. The ground GND of relay substrate 161 is an example of a board ground unit, and phototransistor Tr1 switches the connection between ground GND and first common terminal 253 as follows depending on the state of fixing device 9, more specifically, the detection result of nip detection sensor SE3.

[0104] As described above, when the pressure contact / separation mechanism 900 of the fixing device 9 is in a pressure contact state in which the heating roller 91 and the pressure roller 92 are in pressure contact as shown in the upper diagram of FIG. 6, light from the light-emitting diode (LED) is blocked by the flange 121B of the cam gear 121 and does not enter the phototransistor Tr1. When the phototransistor Tr1 is in an off state in which no light enters, the ground portion GND of the relay substrate 161 and the first common terminal 253 are disconnected. Because no current flows from the 3.3V DC power supply of the main substrate 200 to the collector and emitter of the phototransistor Tr1, the voltage input to the first control terminal 255 of the ASIC 210 is 3.3V minus the current I (= 0) × R3, i.e., 3.3V. As a result, during the pressure contact state, 3.3V is input to the first control terminal 255 of the ASIC 210 from the 3.3V DC power supply of the main substrate 200.

[0105] On the other hand, as described above, when the pressure contact / separation mechanism 900 of the fixing device 9 is in the separated state in which the heating roller 91 and the pressure roller 92 are separated as shown in the lower diagram of FIG. 6, light from the light-emitting diode is input to the phototransistor Tr1 without being blocked by the flange 121B of the cam gear 121. When the phototransistor Tr1 is in the ON state in which light is input to the phototransistor Tr1, the ground portion GND of the relay board 161 and the first common terminal 253 are connected. Current flows from the DC 3.3V power supply provided on the main board 200 to the collector and emitter of the phototransistor Tr1, which has a resistance of 0. The voltage input to the first control terminal 255 of the ASIC 210 is 3.3V minus the current I × R3. However, the resistance value of the resistor R3 is preset so that the voltage input to the first control terminal 255 is 0V. As a result, 0V is input to the first control terminal 255 of the ASIC 210 during the separated state.

[0106] As a result, in a state where it is necessary to detect the state of the fixing device 9, such as when the fixing device 9 is performing a fixing process, the ASIC 210 can detect whether the pressure contact / separation mechanism 900 is in a pressed state or a separated state, based on the voltage input to the first control terminal 255 from the power supply of the main board 200. Specifically, when the phototransistor Tr1 is off, 3.3 V (≠ 0 V) ​​is input to the ASIC 210, so it is possible to detect that the heating roller 91 and the pressure roller 92 are in a pressed state. On the other hand, when the phototransistor Tr1 is on, 0 V is input to the ASIC 210, so when the input voltage reaches 0 V, it is possible to detect that the heating roller 91 and the pressure roller 92 are in a separated state.

[0107] 9, the ASIC 210 includes a ground GND connected to the first control terminal 255, and an internal switch 257 that switches the connection between the first control terminal 255 and the ground GND. When the pressure contact / separation mechanism 900 is in the pressure contact state, i.e., when a voltage of 3.3 V is input to the first control terminal 255 of the ASIC 210, the internal switch 257 of the ASIC 210 is alternately turned on and off, which repeatedly switches between a connected state and a disconnected state between the first control terminal 255 and the ground GND. As a result, it is possible to repeatedly output a High signal of 3.3 V and a Low signal of 0 V from the ASIC 210 to the CLK terminal of the memory 163, as shown in FIG. 10. These High and Low signals serve as clock signals and serve as a reference when the ASIC 210 reads data from the memory 163. Furthermore, the internal switch 257 of the ASIC 210 is basically in an off state when it is necessary to detect the state of the fixing device 9, such as during image formation, i.e., when detection is performed by the nip detection sensor SE3, the first control terminal 255 and the ground section GND are in a disconnected state.

[0108] As described above, when it is necessary to detect the state of the fixing device 9, the state of the fixing device 9 is detected using the nip detection sensor SE3. However, there are other states in which it is not necessary to detect the state of the fixing device 9, such as (a) a state before receiving an instruction to form an image on the sheet S from the process unit 4, (b) a state after image formation on the sheet S is completed, and (c) a state in which the sheet S is present on the conveyance path upstream of the nip position of the fixing device 9 even during image formation. Therefore, in such states, the ASIC 210 can transmit and receive a clock signal from the memory 163 via the first wiring L3 or the first common terminal 253, instead of transmitting and receiving a detection signal from the nip detection sensor SE3. Specifically, when it is not necessary to detect the state of the fixing device 9 and an instruction to read data from the memory 163 has been received, the function of the corresponding pin of the ASIC 210 is switched from inputting sensor information to I2C (Inter-Integrated Circuit). Then, by repeatedly turning on and off the internal switch 257, a clock signal for synchronization is transmitted from the ASIC 210 to the memory 163 via the first control terminal 255, the first main body common terminal 261 of the main body connector 150, and the first fuser common terminal 260 and first common terminal 253 of the fuser connector 160. That is, when it is necessary to detect the state of the fuser device 9, the nip detection sensor SE3 detects the state of the fuser device 9, while when it is not necessary to detect the state of the fuser device 9, the clock signal can be transmitted to the memory using the same signal line and connector terminal. While the nip detection sensor SE3 cannot perform detection while the clock signal is being transmitted, this does not pose a major problem because it is not necessary to detect the state of the fuser device 9. As a result, there is no need to provide dedicated signal lines and connector terminals for accessing the memory 163, and by sharing the signal lines and connector terminals of existing sensors, it is possible to reduce the number of terminals of the fuser connector 160 and the main body connector 150.

[0109] However, when the pressure contact / separation mechanism 900 is in the separated state, that is, when a voltage of 0 V is input to the first control terminal 255 of the ASIC 210, even if the internal switch 257 of the ASIC 210 is turned on and off, the voltage remains at 0 V and therefore no clock signal can be output. Therefore, the ASIC 210 particularly sets the pressure contact / separation mechanism 900 to the pressed state, and when the phototransistor Tr1 disconnects the ground part GND from the first common terminal 253, the clock signal from the memory 163 is transmitted from the first common terminal 253.

[0110] Next, the discharge sensor SE4 and the memory 163 will be mainly described. In order to reduce the number of terminals of the fixing connector 160 and the main body connector 150, the relay board 161 unifies the signal lines for the detection signal of the discharge sensor SE4 and the data signal of the memory 163 into a single common signal line. Specifically, the relay board 161 has a second wiring L4, one end of which is connected to the second common terminal 254, and a second memory connection wiring L2, one end of which is connected to the DATA terminal of the memory 163. The discharge sensor SE4 is connected to the other end of the second wiring L4, and the other end of the second memory connection wiring L2 is connected to the second wiring L4. The fixing connector 160 also has a second fixing common terminal 262, and the second common terminal 254 and the second fixing common terminal 262 are connected to each other by a signal line. As a result, the relay board 161 relays the signal from the discharge sensor SE4 and the data signal of the memory 163 to the main board 200 via the same second common terminal 254 and second fixing common terminal 262.

[0111] Meanwhile, the main body connector 150 on the main board 200 side has a second main body common terminal 263 connected to the second fixing common terminal 262. Furthermore, the second main body common terminal 263 and the second control terminal 256 of the ASIC 210 are connected to each other by a signal line. That is, the second control terminal 256 is connected to the second common terminal 254 via the second fixing common terminal 262 and the second main body common terminal 263. The main board 200 also has a predetermined resistor R4 whose one end is connected to the second control terminal 256 of the ASIC 210, through which a signal from the discharge sensor SE4 and a data signal from the memory 163 are input and output, and whose other end is connected to a DC 3.3V power supply provided on the main board 200. That is, the second wiring L4 is also connected to a DC 3.3V power supply via the main board connector 150 and the fixing connector 160. The phototransistor Tr2 has an emitter connected to the ground GND of the relay substrate 161 and a collector connected to the second common terminal 254 via the second wiring L4. The DC 3.3V power supply provided in the main substrate 200 is an example of a second power supply unit. The ground GND of the relay substrate 161 is an example of a substrate ground unit, and the phototransistor Tr2 switches the connection between the ground GND and the second common terminal 254 as follows, depending on whether or not the sheet S has passed through the nip position, more specifically, the detection result of the discharge sensor SE4.

[0112] As described above, when the sheet S passes through the nip between the heating roller 91 and the pressure roller 92, the light from the discharge sensor SE4 of the fixing device 9 is input to the phototransistor Tr2 without being blocked by the actuator. When the phototransistor Tr2 is in the ON state, where light is input to the phototransistor Tr2, the ground GND of the relay board 161 and the second common terminal 254 are connected. A current flows from the DC 3.3V power supply provided on the main board 200 to the collector and emitter of the phototransistor Tr2, whose resistance is considered to be zero. The voltage input to the second control terminal 256 of the ASIC 210 is 3.3V minus the current I × R4. However, the resistance of the resistor R4 is preset so that the voltage input to the second control terminal 256 is 0V. As a result, while the sheet S is passing through the nip between the heating roller 91 and the pressure roller 92, 0V is input to the second control terminal 256 of the ASIC 210.

[0113] On the other hand, as described above, when the sheet S is not present at the nip position between the heating roller 91 and the pressure roller 92, the discharge sensor SE4 of the fixing device 9 blocks light from the light-emitting diode (LED) by the actuator and does not input it to the phototransistor Tr2. When the phototransistor Tr2 is in the off state, where no light is input, the ground GND of the relay board 161 is disconnected from the second common terminal 254. Because no current flows from the DC 3.3V power supply of the main board 200 to the collector and emitter of the phototransistor Tr2, the voltage input to the second control terminal 256 of the ASIC 210 is 3.3V minus the current I (=0) × R4, i.e., 3.3V. As a result, while the sheet S is not present at the nip position between the heating roller 91 and the pressure roller 92, 3.3V is input to the second control terminal 256 of the ASIC 210 from the DC 3.3V power supply of the main board 200.

[0114] As a result, in a state where it is necessary to detect the state of the fixing device 9, such as when the fixing device 9 is performing a fixing process, the ASIC 210 can detect whether or not a sheet has passed through the nip position based on the voltage input to the second control terminal 256 from the power supply of the main board 200. Specifically, when the phototransistor Tr2 is on, 0 V is input to the ASIC 210, and therefore, when the input voltage reaches 0 V, it can be detected that the sheet S is passing through the nip position between the heating roller 91 and the pressure roller 92. On the other hand, when the phototransistor Tr2 is off, 3.3 V (≠ 0 V) ​​is input to the ASIC 210, and therefore, it can be detected that the sheet S is not present in the nip position between the heating roller 91 and the pressure roller 92.

[0115] As described above, the discharge sensor SE4 is used to detect whether the sheet S has passed through the nip position of the fixing device 9. However, for example, (a) a state before the process unit 4 receives an instruction to form an image on the sheet S, (b) a state after image formation on the sheet S is completed, or (c) a state in which the sheet S is present upstream of the nip position of the fixing device 9 on the conveyance path even during image formation, are states in which it is not necessary to detect whether the sheet S has passed through the nip position of the fixing device 9. Therefore, in such states, the ASIC 210 can transmit and receive data signals from the memory 163 via the second wiring L4 and the second common terminal 254, instead of transmitting and receiving detection signals from the discharge sensor SE4. Specifically, when the ASIC 210 receives an instruction to read data from the memory 163 and there is no need to detect whether the sheet S has passed through the nip position of the fixing device 9, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from inputting sensor information to I2C (Inter-Integrated Circuit). Then, a data signal is transmitted from the memory 163 to the ASIC 210 via the second common terminal 254, the second fixing common terminal 262 of the fixing connector 160, the second main body common terminal 263 of the main body connector 150, and the second control terminal 256. On the other hand, when an instruction to update the memory 163 is received, a data signal is transmitted from the ASIC 210 to the memory 163 via the second control terminal 256, the main body connector 150, the fixing connector 160, and the second common terminal 254. That is, when it is necessary to detect whether the sheet S has passed through the nip position of the fixing device 9, the discharge sensor SE4 performs detection, and when it is not necessary to detect whether the sheet S has passed through the nip position of the fixing device 9, the same signal line and connector terminal can be used to transmit and receive data signals between the ASIC 210 and the memory 163. While data transmission and reception is being performed, the discharge sensor SE4 cannot perform detection, but this does not pose a major problem because it is not necessary to detect whether the sheet S has passed through the nip position of the fixing device 9.As a result, there is no need to provide dedicated signal lines or connector terminals for accessing memory 163, and by sharing the signal lines and connector terminals of existing sensors, it is possible to reduce the number of terminals of the fixing connector 160 and the main body connector 150.

[0116] [Control processing by the control unit] Next, of the various control processes executed by the ASIC 210 of the printer 1 having the above configuration, a print process for forming an image on a sheet S will be described with reference to FIG. 11. In the first embodiment, an example will be described in which, when forming an image on a sheet S, the memory 163 of the fixing device 9 is accessed before receiving an instruction to form an image on the sheet S. FIG. 11 is a flowchart illustrating the main process executed after the printer 1 is powered on, particularly the print process executed to form an image. Note that each process shown in the flowchart in FIG. 11 below is stored in a memory provided in the printer 1 and is executed by the ASIC 210.

[0117] First, in step (hereinafter abbreviated as S) 1, the ASIC 210 determines whether or not there has been a command to access the memory 163 of the fixing device 9. The command to access the memory 163 is executed, for example, immediately after the main power of the printer 1 is turned on, immediately after the fixing device 9 is attached to the main body housing 2 of the printer 1, i.e., immediately after the fixing unit is replaced, etc.

[0118] If it is determined that there is an access command to the memory 163 of the fixing device 9 (S1: YES), the process proceeds to S2. On the other hand, if it is determined that there is no access command to the memory 163 of the fixing device 9 (S1: NO), the process proceeds to S8.

[0119] In S2, ASIC 210 drives main motor 201A and turns on the electromagnetic clutch to drive pressure contact / separation mechanism 900 of fixing device 9, and in particular moves pressure roller 92 relative to heating roller 91, thereby transitioning from a separated state in which heating roller 91 and pressure roller 92 are separated to a pressed state in which heating roller 91 and pressure roller 92 are in pressure contact (FIG. 6). ASIC 210 receives a detection signal from nip detection sensor SE3. Note that the initial state is the separated state.

[0120] Thereafter, in S3, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from input of sensor information to I2C. Note that while switching to I2C, the ASIC 210 cannot receive detection signals from the nip detection sensor SE3 and the discharge sensor SE4.

[0121] Next, in S4, the ASIC 210 starts accessing the memory 163 of the fixing device 9. Specifically, to perform synchronization, a clock signal is transmitted from the ASIC 210 to the memory 163 via the first control terminal 255, the first main body common terminal 261 of the main body connector 150, the first fixing common terminal 260 of the fixing connector 160, and the first common terminal 253. Then, while performing synchronization based on the clock signal, data is read from the memory 163, and a data signal is transmitted from the memory 163 to the ASIC 210 via the second common terminal 254, the second fixing common terminal 262 of the fixing connector 160, the second main body common terminal 263 of the main body connector 150, and the second control terminal 256. Note that in S4, the pressure contact / separation mechanism 900 is in the pressure contact state, and therefore, as described above, the clock signal can be output by repeatedly turning on and off the internal switch 257 (FIG. 10). Furthermore, access to memory 163 in S4 is a state prior to receiving an instruction to form an image on sheet S for the process unit 4, and so is a state in which there is basically no need to detect the state of the fixing device 9. Therefore, there is basically no problem even if transmission and reception of detection signals from nip detection sensor SE3 and discharge sensor SE4 are temporarily stopped and instead transmission and reception of clock signals and data signals from memory 163 are performed. Note that transmission and reception of clock signals and data signals may be performed simultaneously, or one of them may be performed first.

[0122] The information read from memory 163 in S4 includes, for example, serial information of the fixing device 9, and information about the number of uses so far and the number of uses remaining, which is the lifespan of the fixing device 9. The read information is used, for example, to authenticate whether the fixing device 9 is a product compatible with the printer 1, to notify when it is time to replace the fixing device 9, etc.

[0123] Thereafter, in S5, the ASIC 210 determines whether or not to stop accessing the memory 163 of the fixing device 9, that is, whether or not reading of the necessary information has been completed.

[0124] If it is determined that the access to the memory 163 of the fixing device 9 is to be stopped (S5: YES), the process proceeds to S6. On the other hand, if it is determined that the access to the memory 163 of the fixing device 9 is not to be stopped (S5: NO), the access to the memory 163 continues.

[0125] In S6, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from I2C to input of sensor information. As a result, the ASIC 210 becomes able to receive detection signals from the nip detection sensor SE3 and the discharge sensor SE4, and can subsequently detect the state of the fixing device 9 when it is necessary to detect the state of the fixing device 9.

[0126] Next, in S7, the ASIC 210 drives the main motor 201A and turns off the electromagnetic clutch to drive the pressure contact / separation mechanism 900 of the fixing device 9 described above, and in particular moves the pressure roller 92 relative to the heating roller 91, thereby transitioning from a pressure contact state in which the heating roller 91 and the pressure roller 92 are pressed together to a separated state in which the heating roller 91 and the pressure roller 92 are separated (Figure 6).

[0127] Thereafter, in S8, the ASIC 210 determines whether a print command has been received. The print command is transmitted, for example, from a PC or the like connected via a wired or wireless connection via a network interface provided in the printer 1, along with image data to be printed. Alternatively, the print process can be started by receiving an image formation execution command at a user interface provided in the printer 1.

[0128] If it is determined that a print command has been received (S8: YES), the image formation process is executed (S9). Specifically, in the image formation process, the ASIC 210 first drives the process unit 4 and the main motor 201A, and controls the heater 93 based on signals from the fixing temperature sensors TH1 and TH2. Then, the pressure / separation mechanism 900 switches from the separation state to the pressure / separation state, picks up the sheet S in the supply tray 13, transports it toward the transport unit 3, and starts image formation on the sheet S after the post-registration sensor 46 detects the leading edge of the sheet S. Image data to be printed is received from an external device, such as a PC, via a network interface, along with a print command. The surface of the photosensitive drum 61 is exposed to light by a laser unit, forming an electrostatic latent image based on the image data. The developing roller 71 then supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 61, thereby forming a toner image on the surface of the photosensitive drum 61. The transfer roller 84 then transports the sheet S between itself and the photosensitive drum 61, thereby transferring the toner image formed on the surface of the photosensitive drum 61 to the sheet S as it passes through the transfer nip. In this way, an image is formed on the sheet S. Thereafter, the toner image formed on the sheet S by the process unit 4 is fixed to the sheet S using the fixing device 9. When the discharge sensor SE4 detects the leading edge of the sheet S that has passed through the nip position between the heating roller 91 and pressure roller 92 of the fixing device 9, the first conveying roller 36, the second conveying roller 37, and the first switchback roller 38 are driven to rotate forward, thereby conveying the sheet S on the first conveying path 25 in the conveying direction. The sheet S is then discharged onto the discharge tray 22, completing the image forming process.

[0129] On the other hand, if it is determined that a print command has not been received (S8: YES), the process returns to S1.

[0130] As described in detail above, the fixing device 9 of the first embodiment is a fixing device 9 that can be attached to and detached from a printer 1 that forms an image on a sheet S, and includes a heating roller 91 that heats the sheet S, a pressure roller 92 that nips the sheet S between the heating roller 91, fixing temperature sensors TH1 and TH2 that detect the temperature of the heating roller 91, a nip detection sensor SE3 and a discharge sensor SE4 that detect the state of the fixing device 9, a fixing connector 160 that connects to a main connector 150 that the main body housing 2 has when the fixing device 9 is attached to the main body housing 2 of the printer 1, temperature sensor output terminals 251 and 252 that are connected to the fixing connector 160, and a relay board 161 to which the fixing temperature sensors TH1 and TH2, the nip detection sensor SE3 and the discharge sensor SE4 are respectively connected. The relay board 161 relays temperature detection signals from the fixing temperature sensors TH1 and TH2 to the main body housing 2 of the printer 1 via the temperature sensor output terminals 251 and 252, and relays the detection signal from the nip detection sensor SE3 and the clock signal from the memory 163 to the main body housing 2 of the printer 1 via the first common terminal 253 and the first fixing common terminal 260. This prevents an increase in the number of terminals of the fixing connector connecting the fixing device 9 to the main body housing 2 of the printer 1, even when the fixing device 9 is equipped with the memory 163. Furthermore, the relay board 161 relays the detection signal from the discharge sensor SE4 and the data signal from the memory 163 to the main body housing 2 of the printer 1 via the second common terminal 254. This prevents an increase in the number of terminals of the fixing connector connecting the fixing device 9 to the main body housing 2 of the printer 1, even when the fixing device 9 is equipped with the memory 163. In addition, the relay substrate 161 has a first wiring L3 having one end connected to the first common terminal 253 and a first memory connection wiring L1 having one end connected to the memory 163, and the nip detection sensor SE3 has the other end connected to the first wiring L3, and the other end of the first memory connection wiring L1 is connected to the first wiring L3, so that the wiring for transmitting and receiving the detection signal of the nip detection sensor SE3 and the wiring for accessing the memory can be shared. In addition, the relay board 161 has a second wiring L4 having one end connected to the second common terminal 254 and a second memory connection wiring L2 having one end connected to the memory 163, and the discharge sensor SE4 has the other end of the second wiring L4 connected to it, and the other end of the second memory connection wiring L2 connected to the second wiring L4, so that it is possible to share the wiring for transmitting and receiving the detection signal of the discharge sensor SE4 and the wiring for accessing the memory. In addition, the relay board 161 has a ground section GND, and the nip detection sensor SE3 has a phototransistor Tr1 to which the other end of the first wiring L3 is connected and which switches the connection between the ground section GND and the first common terminal 253 depending on the detection result of the state of the fixing device 9. The relay board 161 outputs a detection signal of the nip detection sensor SE3 from the first common terminal 253 depending on the switching of the phototransistor Tr1, and when the phototransistor Tr1 disconnects the ground section GND from the first common terminal 253, the relay board 161 transmits and receives a clock signal of the memory 163 from the first common terminal 253. Therefore, it is possible to transmit and receive a clock signal to and from the memory 163, especially when the phototransistor Tr1 is off. The printer 1 also includes a main body connector 150 connected to the fixing connector 160, and a main board 200 having an ASIC 210 connected to the main body connector 150. The ASIC 210 can receive detection signals from the nip detection sensor SE3 via the first common terminal 253, the first fixing common terminal 260, and the first main body common terminal 261, and transmits and receives clock signals from the memory 163 via the first common terminal 253, the fixing connector 160, and the main body connector 150. This makes it possible to reduce the number of terminals of the fixing connector connecting the fixing device 9 and the main body housing 2 of the printer 1 compared to conventional methods. The relay board 161 of the fixing device 9 has a first wiring L3 connected at one end to the first common terminal 253, a first memory connection wiring L1 connected at one end to the memory 163, and a ground portion GND. The nip detection sensor SE3 has a phototransistor Tr1 to which the other end of the first wiring L3 is connected and which switches between connection and non-connection of the ground portion GND and the first common terminal 253 depending on the state of the fixing device 9. The ASIC 210 has a first control terminal 255 connected to the first common terminal 253 via the fixing connector 160 and the main body connector 150, and is required to detect the state of the fixing device 9. When the state of the fixing device 9 needs to be detected, the state of the fixing device 9 is detected based on the voltage input to the first control terminal 255 in response to the switching of the phototransistor Tr1 of the nip detection sensor SE3, and when there is no need to detect the state of the fixing device 9, the clock signal of the memory 163 is transmitted and received from the first control terminal 255. Therefore, when there is a need to detect the state of the fixing device 9, the state of the fixing device 9 can be detected by the nip detection sensor SE3, while when there is no need to detect the state of the fixing device 9, the memory 163 can be accessed using the same terminal as the nip detection sensor SE3. Furthermore, when there is no need to detect the state of the fixing device 9, the ASIC 210 outputs a clock signal to be sent to the memory 163 via the first fixing common terminal 260, the first main body common terminal 261, and the first common terminal 253 to the memory 163, thereby making it possible to reduce the number of connector terminals connecting the fixing device 9 and the main body housing 2 of the printer 1 compared to conventional methods. Furthermore, when there is no need to detect the state of the fixing device 9, the ASIC 210 receives a data signal for reading data from the memory 163 from the second control terminal 256 via the second common terminal 254, the second fixing common terminal 262 and the second main body common terminal 263, thereby making it possible to reduce the number of terminals of the fixing connector connecting the fixing device 9 and the main body housing 2 of the printer 1 compared to conventional methods. In particular, it is possible to share the connector terminal for transmitting and receiving the detection signal of the discharge sensor SE4, which detects whether or not a sheet has passed through the nip position between the heating roller 91 and the pressure roller 92, and the connector terminal for accessing the memory. Furthermore, the ASIC 210 is provided with a ground section GND connected to the first control terminal 255, and an internal switch 257 that switches the connection between the first control terminal 255 and the ground section GND. When the pressure contact / separation mechanism 900 is in a pressure contact state, i.e., when a voltage of 3.3V is input to the first control terminal 255 of the ASIC 210, the internal switch 257 of the ASIC 210 is alternately turned on and off, thereby repeatedly connecting and disconnecting the first control terminal 255 and the ground section GND, and it becomes possible to repeatedly output High and Low signals consisting of 3.3V and 0V from the ASIC 210 to the CLK terminal of the memory 163, i.e., to output a clock signal. In addition, the state in which there is no need to detect the state of the fixing device 9 is the state prior to receiving an instruction to form an image on the sheet S to the process unit 4, and when there is an instruction to read data from the memory 163, a clock signal is sent from the first control terminal 255 and a data signal is received from the second control terminal 256.Therefore, when there is a need to detect the state of the fixing device 9, the state of the fixing device 9 can be detected by the nip detection sensor SE3 and the discharge sensor SE4, while when there is no need to detect the state of the fixing device 9, access to the memory 163 becomes possible.

[0131] Second Embodiment Next, a printer and a fixing device according to a second embodiment will be described with reference to Fig. 12. In the following description, the same reference numerals as those in the configuration of the printer 1 and the fixing device 9 according to the first embodiment shown in Figs. 1 to 11 indicate the same or equivalent parts as those in the configuration of the printer 1 and the fixing device 9 according to the first embodiment.

[0132] The schematic configuration of the printer and fixing device according to the second embodiment is almost the same as that of the printer 1 and fixing device 9 according to the first embodiment. In addition, the various control processes are also almost the same as those of the printer 1 and fixing device 9 according to the first embodiment. However, the printer 1 and the fixing device 9 according to the first embodiment are different from each other, particularly with respect to the timing of accessing the memory 163 in the printing process shown in FIG.

[0133] Among the various control processes executed by the ASIC 210 of the printer 1 according to the second embodiment, a print process for forming an image on a sheet S will be described below with reference to FIG. 12. In the second embodiment, an example will be described in which, when forming an image on a sheet S, the memory 163 of the fixing device 9 is accessed after image formation on the sheet S is completed. FIG. 12 is a flowchart illustrating the main process executed after the printer 1 is turned on, particularly the print process executed after a print command is received. The print command is transmitted, for example, via a network interface provided in the printer 1 from a PC or the like connected via a wired or wireless connection, along with image data to be printed. Alternatively, the print process can be initiated by receiving an image formation execution command via a user interface provided in the printer 1. The processes shown in the flowchart in FIG. 12 below are stored in the memory provided in the printer 1 and are executed by the ASIC 210.

[0134] First, in S11, the ASIC 210 turns on the heater 93 and controls the heater 93 so that the heating roller 91 reaches the target temperature while monitoring the temperatures detected by the fixing temperature sensors TH1 and TH2.

[0135] Next, in S12, the ASIC 210 drives the main motor 201A to rotate in the forward direction. When the main motor 201A is driven in the forward direction, the output of the main motor 201A transmits driving force to each of the rollers, namely, the pickup roller 33, the separation roller 34, the registration roller 35, the pressure roller 92, the first conveyance roller 36, the second conveyance roller 37, and the first switchback roller 38. However, the registration roller 35 does not start rotating simultaneously with the other rollers, and the timing at which it starts rotating is determined by the timing at which the pre-registration sensor 45 detects the sheet S in order to align the direction of the leading edge of the sheet S. Each roller rotates to convey the sheet S in the conveyance direction.

[0136] Thereafter, in S13, the ASIC 210 determines whether the temperature of the heating roller 91 has reached the target temperature T based on the temperatures detected by the fixing temperature sensors TH1 and TH2.

[0137] If it is determined that the heating roller 91 has reached the target temperature T (S13: YES), the process motor is driven (S14). As a result, the photosensitive drum 61 and the developing roller 71 provided in the process unit 4 rotate. If it is determined that the target temperature T has not been reached (S13: NO), the process waits.

[0138] Next, in S15, the ASIC 210 drives the main motor 201A and turns on the electromagnetic clutch to drive the pressure contact / separation mechanism 900 of the fixing device 9, and in particular moves the pressure roller 92 relative to the heat roller 91, thereby transitioning from a separated state in which the heat roller 91 and the pressure roller 92 are separated to a pressed state in which the heat roller 91 and the pressure roller 92 are in pressure contact (FIG. 6). Note that the initial state is the separated state.

[0139] Thereafter, in S16, the ASIC 210 executes image formation processing. Specifically, in the image formation processing, the sheet S in the supply tray 13 is picked up and transported toward the transport unit 3. After the post-registration sensor 46 detects the leading edge of the sheet S, image formation on the sheet S begins. Image data to be printed is received along with a print instruction from an external device, such as a PC, via a network interface. The surface of the photosensitive drum 61 is exposed to light by a laser unit, forming an electrostatic latent image based on the image data. The developing roller 71 supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 61, thereby forming a toner image on the surface of the photosensitive drum 61. The transfer roller 84 then transports the sheet S between itself and the photosensitive drum 61, transferring the toner image formed on the surface of the photosensitive drum 61 to the sheet S passing through the transfer nip. In this manner, image formation on the sheet S is completed. The toner image formed on the sheet S by the process unit 4 is then fixed to the sheet S using the fixing device 9. Then, when the discharge sensor SE4 detects the leading edge of the sheet S that has passed through the nip position between the heating roller 91 and the pressure roller 92 of the fixing device 9, the first conveying roller 36, the second conveying roller 37, and the first switchback roller 38 are driven to rotate forward, and the sheet S on the first conveying path 25 is conveyed in the conveying direction. Then, the sheet S is finally discharged onto the discharge tray 22.

[0140] Next, in S17, after image formation is started in S16, the ASIC 210 determines whether a predetermined time has elapsed since the post-registration sensor 46 detected the leading edge of the sheet S. The predetermined time that serves as the determination criterion in S17 is the time required for the entire sheet S to pass through the process unit 4 after the post-registration sensor 46 detects the leading edge of the sheet S.

[0141] If it is determined that a predetermined time has elapsed since the post-registration sensor 46 detected the leading edge of the sheet S (S17: YES), it is assumed that image formation on the sheet S by the process unit 4 has been completed, so the drive of the process motor is stopped and the image formation process is terminated (S18). On the other hand, if it is determined that the predetermined time has not elapsed since the post-registration sensor 46 detected the leading edge of the sheet S (S17: NO), image formation on the sheet S by the process unit 4 continues.

[0142] Next, in S19, the ASIC 210 determines whether a predetermined time has elapsed since the discharge sensor SE4 switched from ON to OFF, that is, since the trailing edge of the sheet S passed through the nip position between the heating roller 91 and the pressure roller 92. The predetermined time that serves as the determination criterion in S19 is the time required from when the discharge sensor SE4 detects the passage of the trailing edge of the sheet S until the sheet S is discharged onto the discharge tray 22.

[0143] If it is determined that a predetermined time has elapsed since the discharge sensor SE4 was switched from ON to OFF (S19: YES), the heater 93 and the main motor 201A are turned off (S20). However, the pressure contact / separation mechanism 900 is not shifted to the separation state. On the other hand, if it is determined that the predetermined time has not elapsed since the discharge sensor SE4 was switched from ON to OFF (S19: NO), the conveyance of the sheet S on which the image has been formed continues.

[0144] Thereafter, in S21, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from sensor information input to I2C in accordance with an access command to the memory 163 of the fixing device 9. The access command to the memory 163 of the fixing device 9 may be executed every time image formation on the sheet S is completed, or may be executed only under specific conditions, for example, when image formation on the sheet S is completed after printing every 10 sheets. The processes of S21 to S25 are performed only when there is an access command to the memory 163 of the fixing device 9.

[0145] Next, in S22, the ASIC 210 starts accessing the memory 163 of the fixing device 9. Specifically, to perform synchronization, a clock signal is transmitted from the ASIC 210 to the memory 163 via the first control terminal 255, the first main body common terminal 261 of the main body connector 150, the first fixing common terminal 260 of the fixing connector 160, and the first common terminal 253. Then, while performing synchronization based on the clock signal, data is read from the memory 163, and a data signal is transmitted from the memory 163 to the ASIC 210 via the second common terminal 254, the second fixing common terminal 262 of the fixing connector 160, the second main body common terminal 263 of the main body connector 150, and the second control terminal 256. Note that in S22, the pressure contact / separation mechanism 900 is in the pressure contact state, and therefore, as described above, the clock signal can be output by repeatedly turning on and off the internal switch 257 (FIG. 10). Furthermore, the memory 163 is accessed in S22 after image formation on the sheet S for the process unit 4 has been completed, so there is basically no need to detect the state of the fixing device 9. Therefore, even if the transmission and reception of detection signals from the nip detection sensor SE3 and the discharge sensor SE4 are temporarily stopped and instead the memory 163 transmits and receives clock signals and data signals, no problem will occur. The transmission and reception of the clock signal and the data signal may be performed simultaneously, or one of them may be performed first.

[0146] The information read from memory 163 in S22 includes, for example, information relating to the lifespan of fixing device 9, such as the number of uses up to now and the number of uses remaining. Furthermore, the lifespan of fixing device 9 is updated, for example, by counting up the number of printed sheets or counting down the number of uses remaining. When updating, a data signal is sent from ASIC 210 to memory 163 to update the data.

[0147] Thereafter, in S23, the ASIC 210 determines whether a predetermined time has elapsed since the start of access to the memory 163 of the fixing device 9, that is, whether the time required to complete reading of necessary information and updating of data has elapsed.

[0148] If it is determined that a predetermined time has elapsed since the start of access to the memory 163 of the fixing device 9 (S23: YES), the access to the memory is stopped (S24). On the other hand, if it is determined that the predetermined time has not elapsed since the start of access to the memory 163 of the fixing device 9 (S23: NO), the access to the memory 163 continues.

[0149] Thereafter, in S25, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from I2C to sensor reading, which enables the ASIC 210 to receive detection signals from the nip detection sensor SE3 and the discharge sensor SE4, and subsequently enables the ASIC 210 to detect the state of the fixing device 9 when it is necessary to detect the state of the fixing device 9.

[0150] Next, in S26, ASIC 210 drives main motor 201A and turns off the electromagnetic clutch to drive pressure contact / separation mechanism 900 of fixing device 9, and in particular moves pressure roller 92 relative to heat roller 91, thereby transitioning from a pressure contact state in which heat roller 91 and pressure roller 92 are in pressure contact to a separation state in which heat roller 91 and pressure roller 92 are separated (FIG. 6). Then, main motor 201A is stopped.

[0151] As described above in detail, the fixing device 9 according to the second embodiment defines the state after the image formation on the sheet S is completed as a state in which it is not necessary to detect the state of the fixing device 9. Then, in response to an instruction to read data from the memory 163, a clock signal is sent from the first control terminal 255 and a data signal is received from the second control terminal 256. Therefore, when it is necessary to detect the state of the fixing device 9, the state of the fixing device 9 can be detected by the nip detection sensor SE3 and the discharge sensor SE4, while when it is not necessary to detect the state of the fixing device 9, it is possible to access the memory 163.

[0152] Third Embodiment Next, a printer and a fixing device according to a third embodiment will be described with reference to Fig. 13. In the following description, the same reference numerals as those in the configuration of the printer 1 and the fixing device 9 according to the first embodiment shown in Figs. 1 to 11 indicate the same or equivalent parts as those in the configuration of the printer 1 and the fixing device 9 according to the first embodiment.

[0153] The schematic configuration of the printer and fixing device according to the third embodiment is almost the same as that of the printer 1 and fixing device 9 according to the first embodiment. In addition, the various control processes are also almost the same as those of the printer 1 and fixing device 9 according to the first embodiment. However, the printer 1 and the fixing device 9 according to the first embodiment are different from each other, particularly with respect to the timing of accessing the memory 163 in the printing process shown in FIG.

[0154] Among the various processes executed by the ASIC 210 of the printer 1 according to the third embodiment, a print process for forming an image on a sheet S will be described below with reference to FIG. 13. In the third embodiment, an example will be described in which the memory 163 of the fixing device 9 is accessed during image formation on the sheet S. FIG. 13 is a flowchart illustrating the main process executed after the printer 1 is turned on, particularly the print process executed after a print command is received. The print command is transmitted, for example, via a network interface provided in the printer 1 from a PC or the like connected via a wired or wireless connection, along with image data to be printed. Alternatively, the print process can be initiated by receiving an image formation execution command via a user interface provided in the printer 1. The processes shown in the flowchart in FIG. 13 below are stored in the memory provided in the printer 1 and are executed by the ASIC 210.

[0155] First, in S31, the ASIC 210 turns on the heater 93 and controls the heater 93 so that the heating roller 91 reaches the target temperature while monitoring the temperatures detected by the fixing temperature sensors TH1 and TH2.

[0156] Next, in S32, the ASIC 210 drives the main motor 201A to rotate in the forward direction. When the main motor 201A is driven in the forward direction, the output of the main motor 201A transmits driving force to each of the rollers, namely, the pickup roller 33, the separation roller 34, the registration roller 35, the pressure roller 92, the first conveyance roller 36, the second conveyance roller 37, and the first switchback roller 38. However, the registration roller 35 does not start rotating simultaneously with the other rollers, and the timing at which it starts rotating is determined by the timing at which the pre-registration sensor 45 detects the sheet S in order to align the direction of the leading edge of the sheet S. Each roller rotates to convey the sheet S in the conveyance direction.

[0157] Thereafter, in S33, the ASIC 210 determines whether the temperature of the heating roller 91 has reached the target temperature T based on the temperatures detected by the fixing temperature sensors TH1 and TH2.

[0158] If it is determined that the heating roller 91 has reached the target temperature T (S33: YES), the process motor is driven (S34). As a result, the photosensitive drum 61 and the developing roller 71 provided in the process unit 4 rotate. If it is determined that the target temperature T has not been reached (S33: NO), the process waits.

[0159] Next, in S35, the ASIC 210 drives the main motor 201A and turns on the electromagnetic clutch to drive the pressure contact / separation mechanism 900 of the fixing device 9, and in particular moves the pressure roller 92 relative to the heat roller 91, thereby transitioning from a separated state in which the heat roller 91 and the pressure roller 92 are separated to a pressed state in which the heat roller 91 and the pressure roller 92 are in pressure contact (FIG. 6). Note that the initial state is the separated state.

[0160] Thereafter, in S36, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from sensor information input to I2C in accordance with the access command to the memory 163 of the fixing device 9. The access command to the memory 163 of the fixing device 9 may be executed every time image formation on the sheet S is started, or may be executed only under specific conditions, for example, when image formation on the sheet S is started every time 10 sheets are printed. The processes of S36, S37, and S39 to S41 are performed only when there is an access command to the memory 163 of the fixing device 9.

[0161] Next, in S37, the ASIC 210 starts accessing the memory 163 of the fixing device 9. Specifically, to perform synchronization, a clock signal is transmitted from the ASIC 210 to the memory 163 via the first control terminal 255, the first main body common terminal 261 of the main body connector 150, the first fixing common terminal 260 of the fixing connector 160, and the first common terminal 253. Then, while performing synchronization based on the clock signal, data is read from the memory 163, and a data signal is transmitted from the memory 163 to the ASIC 210 via the second common terminal 254, the second fixing common terminal 262 of the fixing connector 160, the second main body common terminal 263 of the main body connector 150, and the second control terminal 256. The ASIC 210 can output a clock signal (FIG. 10). Furthermore, the memory 163 is accessed in S37 at the timing when an image is formed on the sheet S in the process unit 4, but this is before the sheet is detected by the discharge sensor SE4, i.e., before the sheet reaches the fixing device 9, so there is basically no need to detect the state of the fixing device 9. Therefore, there is basically no problem even if the transmission and reception of the detection signals from the nip detection sensor SE3 and the discharge sensor SE4 are temporarily stopped and instead the transmission and reception of the clock signal and data signal of the memory 163 is performed. The transmission and reception of the clock signal and the data signal may be performed simultaneously, or one of them may be performed first.

[0162] The information read from the memory 163 in S37 is, for example, information relating to the setting parameters of the fixing device 9. The ASIC 210 can then control the fixing device 9 based on the information relating to the setting parameters of the fixing device 9 that has been read.

[0163] Thereafter, in S38, the ASIC 210 executes image formation processing in parallel with accessing the memory 163. Specifically, in the image formation processing, the sheet S in the supply tray 13 is picked up and transported toward the transport unit 3. After the post-registration sensor 46 detects the leading edge of the sheet S, image formation on the sheet S begins. Image data to be printed is received along with a print instruction from an external device, such as a PC, via a network interface. The surface of the photosensitive drum 61 is exposed to light by a laser unit, forming an electrostatic latent image based on the image data. The developing roller 71 supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 61, thereby forming a toner image on the surface of the photosensitive drum 61. The transfer roller 84 then transports the sheet S between itself and the photosensitive drum 61, transferring the toner image formed on the surface of the photosensitive drum 61 to the sheet S passing through the transfer nip. In this manner, image formation on the sheet S is completed. The toner image formed on the sheet S by the process unit 4 is then fixed to the sheet S using the fixing device 9. Then, when the discharge sensor SE4 detects the leading edge of the sheet S that has passed through the nip position between the heating roller 91 and the pressure roller 92 of the fixing device 9, the first conveying roller 36, the second conveying roller 37, and the first switchback roller 38 are driven to rotate forward, and the sheet S on the first conveying path 25 is conveyed in the conveying direction. Then, the sheet S is finally discharged onto the discharge tray 22.

[0164] Next, in S39, after image formation is started in S38, the ASIC 210 determines whether a predetermined time has elapsed since the post-registration sensor 46 detected the leading edge of the sheet S. The predetermined time that serves as the determination criterion in S39 is a time that is shorter than the time from when the post-registration sensor 46 detects the leading edge of the sheet S until the sheet S passes through the process unit 4 and the leading edge of the sheet S reaches the fixing device 9, and is longer than the time required to complete reading of necessary information from the memory 163 and updating of data.

[0165] If it is determined that a predetermined time has elapsed since the post-registration sensor 46 detected the leading edge of the sheet S (S39: YES), access to the memory is stopped (S40). On the other hand, if it is determined that the predetermined time has not elapsed since the post-registration sensor 46 detected the leading edge of the sheet S (S39: NO), access to the memory 163 continues.

[0166] Thereafter, in S41, the ASIC 210 switches the function of the corresponding pin of the ASIC 210 from I2C to sensor reading. As a result, the ASIC 210 becomes able to receive detection signals from the nip detection sensor SE3 and the discharge sensor SE4, and can subsequently detect the state of the fixing device 9 when it is necessary to detect the state of the fixing device 9.

[0167] Next, in S42, after image formation is started in S16, the ASIC 210 determines whether a predetermined time has elapsed since the post-registration sensor 46 detected the passage of the trailing edge of the sheet S. The predetermined time that serves as the determination criterion in S42 is the time required for the entire sheet S to pass through the process unit 4 after the post-registration sensor 46 detects the passage of the trailing edge of the sheet S.

[0168] If it is determined that a predetermined time has elapsed since the post-registration sensor 46 detected the passage of the trailing edge of the sheet S (S42: YES), it is assumed that image formation on the sheet S by the process unit 4 has been completed, so the drive of the process motor is stopped and the image formation process is terminated (S43). On the other hand, if it is determined that the predetermined time has not elapsed since the post-registration sensor 46 detected the passage of the trailing edge of the sheet S (S42: NO), image formation on the sheet S by the process unit 4 continues.

[0169] Next, in S44, the ASIC 210 determines whether a predetermined time has elapsed since the discharge sensor SE4 switched from ON to OFF, that is, since the trailing edge of the sheet S passed through the nip position between the heating roller 91 and the pressure roller 92. The predetermined time that serves as the determination criterion in S44 is the time required from when the discharge sensor SE4 detects the passage of the trailing edge of the sheet S until the sheet S is discharged onto the discharge tray 22.

[0170] If it is determined that a predetermined time has elapsed since the discharge sensor SE4 was switched from ON to OFF (S44: YES), the heater 93 and the main motor 201A are turned off (S45). On the other hand, if it is determined that the predetermined time has not elapsed since the discharge sensor SE4 was switched from ON to OFF (S44: NO), the conveyance of the sheet S on which the image has been formed continues.

[0171] Next, in S46, the ASIC 210 drives the main motor 201A and turns off the electromagnetic clutch to drive the pressure contact / separation mechanism 900 of the fixing device 9 described above, and in particular moves the pressure roller 92 relative to the heating roller 91, thereby transitioning from a pressure contact state in which the heating roller 91 and the pressure roller 92 are pressed together to a separated state in which the heating roller 91 and the pressure roller 92 are separated (Figure 6).

[0172] As described above in detail, the fixing device 9 according to the third embodiment defines a state in which it is not necessary to detect the state of the fixing device 9 as a state after receiving an instruction to form an image on a sheet and the pressure contact / separation mechanism 900 switches from the separation state to the pressure contact state, but before the sheet S is detected by the discharge sensor SE4. In response to an instruction to read data from the memory 163, a clock signal is transmitted from the first control terminal 255 and a data signal is received from the second control terminal 256. Therefore, when it is necessary to detect the state of the fixing device 9, the state of the fixing device 9 can be detected by the nip detection sensor SE3 and the discharge sensor SE4, while when it is not necessary to detect the state of the fixing device 9, access to the memory 163 is possible.

[0173] The present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications are possible within the scope of the present invention. For example, in the above embodiment, in order to reduce the number of terminals of the fixing connector 160 and the main body connector 150, the relay board 161 shares the signal lines for the detection signal of the nip detection sensor SE3 and the clock signal of the memory 163 as one common signal line, and shares the signal lines for the detection signal of the discharge sensor SE4 and the data signal of the memory 163 as one common signal line, but it is also possible to share the signal line for only one of the nip detection sensor SE3 and the discharge sensor SE4 with the signal line for the memory 163. Also, it is also possible to share the signal lines for the detection signal of the discharge sensor SE4 and the clock signal of the memory 163 as one common signal line, and share the signal lines for the detection signal of the nip detection sensor SE3 and the data signal of the memory 163 as one common signal line.

[0174] Furthermore, in the above embodiment, the printer 1 has been described as an example of an image forming apparatus, but it may also be, for example, a copy machine, a facsimile machine, or a multifunction machine having a printer function and a scanner function. [Explanation of symbols]

[0175] 1...printer (image forming apparatus), 2...main body housing, 9...fixing device, 91...heating roller, 92...pressure roller, 150...main body connector, 160...fixing connector, 161...relay board, 163...memory, 200...main board (control board), 210...ASIC (control unit), 253...first common terminal, 254...second common terminal, 255...first control terminal, 256...second control terminal, 257...internal switch, 260...first fixing common terminal, 261...first main body common terminal, 262...second fixing common terminal, 263...second main body common terminal, 900...pressure contact / separation mechanism, TH1, TH2...fixing temperature sensor, SE3...nip detection sensor, SE4...discharge sensor, S...sheet

Claims

1. A fixing device that is detachable from an image forming apparatus that forms a toner image on a sheet, a heating rotor that heats the sheet; a heater that heats the heating rotor; a pressure rotating body that nips the sheet between itself and the heating rotating body; a first detection sensor for detecting a state of the fixing device; a fixing connector that is connected when attached to the image forming apparatus and has a first fixing common terminal; a relay board having a first common terminal connected to the first fixing common terminal and a memory, the relay board having the first detection sensor connected thereto, and relaying a first detection signal of the first detection sensor and a first memory signal of the memory to the image forming apparatus via the first common terminal and the first fixing common terminal; A fixing device comprising:

2. the relay substrate has a first wiring having one end connected to the first common terminal and a first memory connection wiring having one end connected to the memory; The first detection sensor is connected to the other end of the first wiring, the other end of the first memory connection wiring is connected to the first wiring; 2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image on the toner image.

3. the relay board has a board ground portion, the first detection sensor has a first switching section to which the other end of the first wiring is connected and which switches between connection and non-connection of the substrate ground section and the first common terminal in accordance with a detection result of the state of the fixing device; The relay substrate is outputting the first detection signal from the first common terminal in response to switching of the first switching unit; a first memory signal of the memory is transmitted and received through the first common terminal in a state in which the first switching unit disconnects the substrate ground unit from the first common terminal; 3. The fixing device according to claim 2.

4. 10. An image forming apparatus in which the fixing device according to claim 1 is detachable, a main body connector connected to the fixing connector, the main body connector having a first main body common terminal connected to the first fixing common terminal; a control board having a control unit connected to the main body connector, The control unit the first detection signal can be received via the first common terminal, the first fixing common terminal, and the first main body common terminal; the first memory signal can be transmitted and received via the first common terminal, the first fixing common terminal, and the first main body common terminal; An image forming apparatus characterized by:

5. In the fixing device, the relay substrate includes a first wiring having one end connected to the first common terminal, a first memory connection wiring having one end connected to the memory, and a substrate ground portion; the first detection sensor has a first switching section to which the other end of the first wiring is connected and which switches between connection and non-connection of the substrate ground section and the first common terminal depending on the state of the fixing device; The control unit a first control terminal connected to the first common terminal via the first fixing common terminal and the first main body common terminal, and detecting the state of the fixing device based on a voltage input to the first control terminal in response to switching of the first switching unit of the first detection sensor when it is necessary to detect the state of the fixing device, and transmitting and receiving the first memory signal from the first control terminal when it is not necessary to detect the state of the fixing device; 5. The image forming apparatus according to claim 4.

6. the first memory signal is a data signal for the control unit to read data from the memory, The control unit receiving the first memory signal from the first control terminal via the first common terminal, the first fixing common terminal, and the first main body common terminal when there is no need to detect the state of the fixing device; 6. The image forming apparatus according to claim 5.

7. 7. The image forming apparatus according to claim 6, wherein the first detection sensor is a discharge sensor for detecting whether or not the sheet has passed through a nip position between the heating rotator and the pressure rotator.

8. the first memory signal is a clock signal output from the control board to the memory, The control board outputting the first memory signal to the memory via the main body connector, the first fixing common terminal, and the first main body common terminal when there is no need to detect the state of the fixing device; 6. The image forming apparatus according to claim 5.

9. the fixing device, a pressure contact / separation mechanism that can switch between a pressure contact state in which the heating rotator and the pressure rotator are in pressure contact with each other and a separation state in which the heating rotator and the pressure rotator are separated from each other, the first detection sensor is a nip detection sensor for detecting whether the pressure-contact state or the separation state is in, and when the pressure-contact state is in, the first switching unit causes the board ground portion and the first common terminal to be in a disconnected state, and when the separation state is in, the first switching unit causes the board ground portion and the first common terminal to be in a connected state; The control unit a ground section, a first control terminal, and an internal switch section that switches between connection and non-connection between the ground section, The control board a first power supply unit connected to the first wiring; The control unit When it is necessary to detect the state of the fixing device, the internal switch unit disconnects the first control terminal from the ground unit, and then detects whether the fixing device is in the pressure-contact state or the separated state based on a voltage input from the first power supply unit to the first control terminal; When there is no need to detect the state of the fixing device and the fixing device is in the pressure contact state, the first memory signal is output to the memory by repeatedly connecting or disconnecting the first control terminal and the ground portion using the internal switch portion.

9. The image forming apparatus according to claim 8.

10. Further, a second detection sensor is provided which is a discharge sensor for detecting whether or not the sheet has passed through a nip position between the heating rotary member and the pressure rotary member, The relay substrate is a second common terminal connected to the fixing connector, a second wiring having one end connected to the second common terminal, and a second memory connection wiring having one end connected to the memory, relaying a second detection signal from the second detection sensor and a second memory signal from the memory to the image forming apparatus via the second common terminal; The second detection sensor is a second switching unit that switches between connection and disconnection of the board ground unit and the second common terminal depending on whether a sheet has passed through the nip position; the control unit has a second control terminal, The control board a second power supply unit connected to the second wiring; the second memory signal is a data signal for the control unit to read data from the memory, The control unit When it is necessary to detect the state of the fixing device, it detects whether or not a sheet has passed through the nip position based on the voltage input from the second power supply unit to the second control terminal, and when it is not necessary to detect the state of the fixing device and the fixing device is in the pressure contact state, it receives the second memory signal from the second control terminal via the second common terminal, the fixing connector, and the main body connector.

10. The image forming apparatus according to claim 9.

11. an image forming unit that forms a toner image on a sheet; The control unit The state in which it is not necessary to detect the state of the fixing device is a state prior to receiving an instruction to the image forming unit to form a toner image on a sheet, and when an instruction to read data from the memory is received, the first memory signal is transmitted from the first control terminal and the second memory signal is received from the second control terminal.

11. The image forming apparatus according to claim 10.

12. an image forming unit that forms a toner image on a sheet; The control unit The state in which it is not necessary to detect the state of the fixing device is a state after the toner image formation on the sheet is completed, and when an instruction to read the data in the memory is given, the first memory signal is transmitted from the first control terminal and the second memory signal is received from the second control terminal.

11. The image forming apparatus according to claim 10.

13. an image forming unit that forms a toner image on a sheet; The control unit receiving an instruction to form a toner image on the sheet, and transmitting the first memory signal from the first control terminal and receiving the second memory signal from the second control terminal after the pressure contact / separation mechanism has switched from the separation state to the pressure contact state and before the sheet is detected by the discharge sensor; 11. The image forming apparatus according to claim 10.

14. a temperature sensor for detecting the temperature of the heating rotor; The relay substrate is a temperature sensor output terminal connected to the fixing connector, the temperature sensor being connected thereto, and a temperature detection signal of the temperature sensor being relayed to the image forming apparatus via the temperature sensor output terminal; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

Images