Fixing device and image forming apparatus

Abstract

To provide a fixing device and an image forming apparatus that can reduce the number of signal lines connecting the fixing device and the image forming apparatus to each other.SOLUTION: A fixing device 9 attachable / detachable to / from a printer 1, comprises: fixing temperature sensors TH1 to TH3 that detect a temperature of a heating roller 91; a nip detection sensor SE4 that detects a state of the fixing device 9; a fixing connector 160 that, when the fixing device 9 is mounted on a body housing 2 of the printer 1, is connected to a body connector 150 of the body housing 2; and a relay substrate 161 that relays signals from the fixing temperature sensors TH1 to TH3 and a signal from the nip detection sensor SE4 to the printer 1. In particular, the relay substrate relays the signal from the fixing temperature sensor TH3 and the signal from the nip detection sensor SE4 via a common terminal.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a fixing device for fixing a toner image transferred onto a sheet, and an image forming apparatus to which the fixing device is attached. [Background technology]

[0002] Conventionally, image forming apparatuses for printing images on sheets, which are print targets, have been known that heat the sheets onto which toner images have been transferred to fix the images, thereby printing. The sheet is typically heated by a fixing device that uses an energized heater. However, the fixing device gradually deteriorates in print quality with continued use. Therefore, fixing devices are made detachable from the image forming apparatus so that they can 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 and a sensor for detecting whether the fixing device is set in the image forming apparatus. As the fixing device is made detachable from the image forming apparatus, as disclosed in JP 2021-113856 A, signals from these sensors are relayed once by a relay board provided in the fixing device, and then transmitted to a control unit on the image forming apparatus via a connector on the fixing device side and a connector on the image forming apparatus side that are connected. [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] From the viewpoint of reducing costs and miniaturizing the device, it is preferable to reduce the number of signal lines (corresponding to the number of connector terminals) that transmit signals from the sensors provided in the fixing device to the image forming device, as disclosed in Patent Document 1. On the other hand, there is also a demand for detecting temperatures at more locations in the fixing device, but increasing the number of sensors for detecting temperature will increase the number of signal lines accordingly. Therefore, a technology for reducing the number of signal lines 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 make it possible to reduce the number of signal lines that transmit signals from a sensor provided in the fixing device to the image forming device, i.e., the number of signal lines that connect the fixing device and the image forming 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 has a main body connector and is detachable from an image forming device that forms an 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 temperature sensor that detects the temperature of the heating rotor; a detection sensor that detects the state of the fixing device; a fixing connector that connects to the main body connector when the fixing device is attached to the image forming device; and a relay board that has a common terminal connected to the fixing connector and is connected to each of the temperature sensor and the detection sensor, and that relays signals from the detection sensor and the temperature sensor to the image forming device via the common terminal.

[0008] Furthermore, a first image forming apparatus according to the present application is an image forming apparatus in which the fixing device described above is detachable, and is provided with a control board having a control unit capable of sending and receiving signals to and from the attached fixing device via the main body connector, the control unit being connected to the main body connector and capable of inputting signals from the common terminal, the pressure contact / separation mechanism being a mechanism in which, when in the pressure contact state, the gear of the pressure contact / separation mechanism shades the nip detection sensor, and when in the separated state, the gear of the pressure contact / separation mechanism does not shade the nip detection sensor, and the relay board is characterized in that, when the nip detection sensor is shaded, a voltage corresponding to the temperature detected by the temperature sensor is input from the common terminal to the control unit, and when the nip detection sensor is not shaded, a predetermined voltage is input from the common terminal to the control unit.

[0009] Furthermore, a second image forming apparatus according to the present application is an image forming apparatus in which the fixing device described above is detachable, and is provided with a control board having a control unit capable of sending and receiving signals to and from the attached fixing device via the main body connector, the control unit being connected to the main body connector and capable of inputting signals from the common terminal, the pressure contact / separation mechanism being a mechanism in which, when in the pressure contact state, the gear of the pressure contact / separation mechanism does not shade the nip detection sensor, and when in the separated state, the gear of the pressure contact / separation mechanism shades the nip detection sensor, and the relay board inputs a voltage corresponding to the temperature detected by the temperature sensor from the common terminal to the control unit when the nip detection sensor is not shaded, and inputs a predetermined voltage from the common terminal to the control unit when the nip detection sensor is shaded.

[0010] Furthermore, a third image forming apparatus according to the present application is an image forming apparatus in which the fixing device is detachable, wherein the non-passing area temperature sensor is a sensor for detecting the temperature of an area in which the sheet does not pass when forming an image on a sheet of a size narrower than a default size, and the apparatus is equipped with a control board having a control unit capable of sending and receiving signals between the attached fixing device via the main body connector, wherein the control board stores the temperature detected by the non-passing area temperature sensor in a memory and also stores the temperature detected by the passing area temperature sensor in the memory, and the control unit determines that a sheet of a size narrower than the default size is passing when the trend in temperature change detected by the non-passing area temperature sensor differs from the trend in temperature change detected by the passing area temperature sensor. [Effects of the Invention]

[0011] According to the fixing device of the present application having the above-described configuration, the relay board relays the signal from the detection sensor and the signal from the temperature sensor to the image forming device via a common terminal, which makes it possible to reduce the number of signal lines that transmit signals from the detection sensor and the temperature sensor provided in the fixing device to the image forming device, i.e., the number of signal lines that connect the fixing device and the image forming device, compared to the conventional case in which the signal from the detection sensor and the signal from the temperature sensor are connected to separate terminals and relayed to the image forming device. Furthermore, according to the first and second image forming devices of the present application, even if the relay board relays the signal from the detection sensor and the signal from the temperature sensor to the image forming device via a common terminal, it is possible to determine whether the device is in a pressed-contact state or a separated state, as well as the temperature detected by the temperature sensor, from the voltage value input to the control unit. In addition, according to the third image forming apparatus of the present application, by comparing the temperature change trends of the non-passing area temperature sensor and the passing area temperature sensor in the heating rotor of the fixing device, it is possible to determine whether the size of the sheet on which an image is to be formed is narrower than the default size, and it is possible to take action such as issuing a warning or canceling printing as necessary. [Brief explanation of the drawings]

[0012] [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 a fixing temperature sensor. [Figure 3] FIG. 2 is a diagram illustrating the printer with the rear cover open. [Figure 4] FIG. 2 is a diagram illustrating a state in which the fixing device is removed from the printer. [Figure 5] FIG. 2 is a front view of the internal structure of the fixing device. [Figure 6] FIG. 2 is a rear view of the internal structure of the fixing device. [Figure 7] 10A and 10B are diagrams illustrating a pressure contact / separation mechanism. [Figure 8] FIG. 2 is a diagram showing the electrical configuration of the printer. [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 an electrical configuration of a relay board included in the fixing device. [Figure 11] 4 is a diagram showing an analog voltage input to an ASIC via a common terminal in the first embodiment. FIG. [Figure 12] 4 is a flowchart of a temperature abnormality detection process according to the first embodiment. [Figure 13] 10 is a diagram showing the electrical configuration of a relay board included in a fixing device according to a second embodiment. FIG. [Figure 14] FIG. 10 is a diagram showing analog voltages input to an ASIC via a common terminal in the second embodiment. [Figure 15] FIG. 10 is a diagram showing the electrical configuration of a relay board included in the fixing device according to the third embodiment. [Figure 16] 11 is a diagram showing an analog voltage input to an ASIC via a common terminal in the third embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] 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.

[0015] [Overall printer configuration]

[0016] The printer 1 according to the first embodiment is an electrophotographic color laser printer that prints a desired image on a sheet S. However, the printer 1 may also be a monochrome laser printer. The printer 1 comprises a main body housing 2, a conveying unit 3, a processing unit 4, and a fixing device (fixing unit) 9 that is detachable from the main body housing 2.

[0017] 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.

[0018] Furthermore, a multipurpose tray (manual feed tray) 14 is formed in a part of the front cover 11, and by tilting the multipurpose tray 14 forward, 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. Also, by inserting sheets S from the multipurpose tray 14, it is possible to print on sheets S of sizes other than the default size (e.g., A4) placed on the supply tray 13, and it is also possible to print on sheets S of, for example, B5 size or postcard size, which are narrower than the default size.

[0019] 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. 8). A part of the second conveying path 26 is formed by the rear cover 12 in the closed state.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] On the other hand, the process unit 4 has a function of forming an image on the sheet S and transfers a toner image onto the sheet S. 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 (heating rotator) 91 that heats the sheet S, and a pressure roller (pressure rotator) 92 that nips the sheet S between the heating roller 91 and the pressure roller 92. In the first embodiment, the heating roller 91 has a heater 93 therein that heats the heating roller 91. As will be described later, the fixing device 9 also has a pressure contact / separation mechanism that switches the heating roller 91 and the pressure roller 92 between a pressure contact state and a spaced state. The internal structure of the fixing device 9 will be described in detail later.

[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. Thereafter, the process unit 4 transports the sheet S to the fixing device 9.

[0035] The fixing device 9 fixes the toner image transferred onto the sheet S to the sheet S by transporting the sheet S between the heating roller 91 and the pressure roller 92 (fixes the toner image formed on the sheet S) to form an image on the sheet S.

[0036] In addition, downstream of the fixing device 9 in the sheet conveying direction, there is also provided a discharge sensor SE5 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.

[0037] 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.

[0038] Meanwhile, the fixing device 9 is equipped with three fixing temperature sensors TH1 to TH3 for detecting the temperature of the fixing device 9 (more specifically, the heating roller 91). The fixing temperature sensors TH1 to TH3 are equipped with variable resistors whose resistance values ​​change depending on the detected temperature, and are capable of outputting a signal corresponding to the detected temperature. As shown in FIG. 2, the fixing temperature sensors TH1 to TH3 are all arranged facing the heating roller 91 in a non-contact state, but each detects a different area. Fixing temperature sensor TH2 detects the temperature of an area near the center of the heating roller 91, fixing temperature sensor TH1 detects the temperature of an area near the end of the heating roller 91, and fixing temperature sensor TH3 detects the temperature of an area near the end opposite to fixing temperature sensor TH1.

[0039] As described above, the printer 1 can print on sheets S of sizes other than the default size (A4) placed on the supply tray 13 by inserting a sheet S from the multipurpose tray 14. As shown in FIG. 2 , when printing on a sheet S of the default size, the sheet S passes between the heating roller 91 and the pressure roller 92 across almost the entire width of the heating roller 91. When printing on a sheet S narrower than the default size, the sheet S passes between the heating roller 91 and the pressure roller 92, moving closer to one end (the fixing temperature sensor TH1 side). That is, when printing on a sheet S narrower than the default size, the fixing temperature sensor TH3 serves as a sensor (non-passing area temperature sensor) for detecting the temperature of an area where the sheet S does not pass. Meanwhile, the fixing temperature sensors TH1 and TH2 serve as sensors (passing area temperature sensors) for detecting the temperature of an area where the sheet S passes, even when printing on a sheet S narrower than the default size. When printing is performed on a sheet S of a predetermined size, all of the fixing temperature sensors TH1 to TH3 function as sensors for detecting the temperature of the area through which the sheet S passes.

[0040] In the first embodiment, three fixing temperature sensors TH1 to TH3 are provided to detect the temperature of the heating roller 91, but the number of fixing temperature sensors does not necessarily have to be three and may be two or four or more. In the first embodiment, the number of fixing temperature sensors TH1 to TH3 is three, which is more than conventional, but as will be described later, a signal from a nip detection sensor that detects the positional relationship between the heating roller 91 and the pressure roller 92 and a signal from the fixing temperature sensor TH3 are output to the main body housing 2 side via a common terminal, so it is possible to reduce the number of signal lines connecting the fixing device 9 and the main body housing 2.

[0041] 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. 3 shows the state in which the rear cover 12 is open. As shown in Fig. 3, 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.

[0042] 4, 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.

[0043] Although not shown, the main body housing 2 also has a fixed / unfixed detection switch 15 (see FIG. 8) 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.

[0044] [Configuration of fixing device] Next, among the 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 5 and 6 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.

[0045] The fixing device 9 includes a heating roller (heating rotor) 91 as an example of a heating member that heats the sheet S, a pressure roller (pressure rotor) 92 that nips the sheet S between the heating roller 91, side frames 94A, 94B, a connecting frame 94C, arms 95A, 95B, springs 96A, 96B, and cams 97A, 97B.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] The arms 95A, 95B, springs 96A, 96B, and cams 97A, 97B constitute a pressure contact / separation mechanism that can switch between a pressure contact state in which the heating roller 91 and the pressure roller 92 are pressed together (nipped) and a separated state in which the heating roller 91 and the pressure roller 92 are separated. The pressure change mechanism 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 (for the pressure contact state, the nip pressure can also be adjusted). Particularly in the first embodiment, the pressure contact / separation mechanism switches between the pressure contact state and the separated state by moving the pressure roller 92 relative to the heating roller 91.

[0053] The pressure contact / separation mechanism will be described below with reference to Fig. 7. Note that the operations of arm 95A, spring 96A, and cam 97A in side frame 94A are the same as those of arm 95B, spring 96B, and cam 97B in side frame 94B, so the operations of arm 95A, spring 96A, and cam 97A in side frame 94A will be described below as an example.

[0054] 7, 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.

[0055] 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.

[0056] 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 around the cam axis X2. As shown in FIG. 7, 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 around 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. 7.

[0057] Here, the upper diagram in Fig. 7 shows a pressed state in which heating roller 91 and pressure roller 92 are pressed together. The lower diagram in Fig. 7 shows a separated state in which heating roller 91 and pressure roller 92 are separated from each other. The middle diagram in Fig. 7 shows a state in the middle of transitioning from the pressed state to the separated state.

[0058] 5 and 6, 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.

[0059] 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.

[0060] Furthermore, the fixing device 9 includes a nip detection sensor SE4, a discharge sensor SE5, a fixing connector 160, and a relay board 161 in addition to the fixing temperature sensors TH1 to TH3 (FIG. 2) that detect the temperature of the heating roller 91 described above.

[0061] Nip detection sensor SE4 is a sensor that detects the phase of cam 97A. More specifically, nip detection sensor SE4 is an optical sensor that includes a light-emitting element that emits light and a light-receiving element that receives the 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 Tr (see FIG. 10). When the heating roller 91 and the pressure roller 92 are in a pressed-contact state as shown in the upper diagram of FIG. 7, the light from the light-emitting element is blocked by a gear (specifically, flange 121B of cam gear 121) of the pressure contact / separation mechanism. On the other hand, when the heating roller 91 and the pressure roller 92 are in a separated state as shown in the lower diagram of FIG. 7, the light from the light-emitting element passes through a 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 control unit of the printer 1 can determine that the pressure-contact / separation mechanism is in the separated state when the phototransistor Tr in the light-receiving unit receives light, and can determine that the pressure-contact / separation mechanism is in the pressed state when the phototransistor Tr in the light-receiving unit does not receive light.

[0062] 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 SE4 and the state of the pressure contact / separation mechanism. That is, in the pressure contact state where heat roller 91 and pressure roller 92 are pressed together as shown in the upper diagram of FIG. 7, light from the light-emitting unit can be received by passing through notch 121C, and in the separated state where heat roller 91 and pressure roller 92 are separated as shown in the lower diagram of FIG. 7, light from the light-emitting unit can be blocked. In this case, the control unit of printer 1 can determine that the pressure contact / separation mechanism is in the pressure contact state when phototransistor Tr in the light-receiving unit receives light, and can determine that the pressure contact / separation mechanism is in the separated state when phototransistor Tr in the light-receiving unit does not receive light.

[0063] The discharge sensor SE5 is a sensor that detects 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. The discharge sensor SE5 includes an actuator that can rotate around a rotation axis and a photosensor, and when the sheet S passes between the heating roller 91 and the pressure roller 92 and comes into contact with the roller 92, causing the actuator to fall, the photosensor located near the rotation axis of the actuator detects that the actuator has fallen, i.e., that the sheet S has been discharged after the developer image has been fixed by the fixing device 9.

[0064] On the other hand, 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 a main body connector 150 (see FIG. 4) provided on the main body housing 2. The fixing connector 160 is located outside the side frame 94B in the longitudinal direction.

[0065] The relay board 161 relays signals from the fixing temperature sensors TH1 to TH3, the nip detection sensor SE4, and the discharge sensor SE5 to the fixing connector 160. The relay board 161 has a plurality of connectors (terminals) 162 for connecting to the respective sensors, and the connectors 162 are connected to the respective sensors by cables. The relay board 161 also has a connector 162 for connecting to the fixing connector 160, and the connector 162 and the fixing connector 160 are similarly connected by cables. Here, in the first embodiment, the relay board 161 basically has a connector 162 for connecting the sensors, one for each sensor. However, in order to reduce the number of terminals of the fixing connector 160 and the main body connector 150, the relay board 161 is configured to output the respective signal lines of the fixing temperature sensor TH3 and the nip detection sensor SE4 to the fixing connector 160 as a single common signal line. This will be described in detail later.

[0066] 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.

[0067] 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 to TH3, the state of the pressure contact / separation mechanism detected by the nip detection sensor SE4, and sheet information detected by the discharge sensor SE5 can be transmitted to the control unit of the printer 1. 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 control unit and supplies power to the heater 93 based on the temperature information detected by the fixing temperature sensors TH1 to TH3.

[0068] [Printer electrical configuration] Next, the electrical configuration of the printer 1 including the fixing device 9 will be described with reference to Fig. 8. Fig. 8 shows the electrical configuration of the printer 1 including the fixing device 9. Note that Fig. 8 mainly describes components necessary for explaining the first embodiment, and other components of the printer 1 are omitted.

[0069] As shown in Fig. 8, the main body housing 2 is provided with a main board (control 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. A main motor 201A is mounted on the main motor board 201. When the main motor 201A is driven, the heating roller 91 of the fixing device 9 and the rollers of the conveying section 3 rotate.

[0070] 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.

[0071] Furthermore, the main board 200 and the high-voltage power supply board 202 are connected via a first connection line CA1. An ASIC (control unit, an abbreviation for Application Specific Integrated Circuit) 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.

[0072] 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.

[0073] The main board 200 has a DC-DC conversion circuit 211, which converts DC 24V from the low-voltage power supply board 203 to, for example, 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.

[0074] 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. These generated voltages of DC 3.3V and DC 1.8V are supplied to the fixing device 9 via the main body connector 150 together with the ground potential. Then, as will be described later, the relay board 161 provided in the fixing device 9 uses these supplied voltages and the ground potential to operate the fixing temperature sensors TH1 to TH3, the nip detection sensor SE4, and the discharge sensor SE5, and outputs signals from each sensor to the ASIC 210.

[0075] 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 for inputting AC voltage (AC 100V) supplied from a commercial power source, and 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 voltage supplied to the fixing device 9 is also supplied to the heater 93 described above via a thermostat (TM).

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 to TH3 are provided as described above. The fixing temperature sensors TH1 to TH3 are made up of three sensors as shown in FIG. 2. The fixing temperature sensors TH1 to TH3 are arranged in positions where they can detect the temperatures of the left end, center, and right end of the heating roller 91, which is long in the left-right direction.

[0090] Here, the fixing temperature sensors TH1 and TH3, which detect the temperatures at both ends of the heat roller 91, are supplied with DC 3.3V from the relay board 161, and operate at this DC 3.3V. Meanwhile, the fixing temperature sensor TH2, which detects the temperature at the center of the heat roller 91, is supplied with DC 1.8V, and operates at this DC 1.8V. The fixing temperature sensors TH1 to TH3 operate at different operating voltages in this way to ensure that at least one fixing temperature sensor can detect temperature even if the power line is disconnected or the DC-DC conversion circuit 211 is damaged, preventing the supply of either DC 3.3V or DC 1.8V. Furthermore, when the printer 1 transitions to the sleep mode, the supply of ENG 3.3V is stopped, but the supply of DC 1.8V is maintained, as described above. This allows some fixing temperature sensors TH2 to operate even when the printer transitions to the sleep mode. The details of the operation of the fixing temperature sensors TH1 to TH3 on the relay board 161 will be described later.

[0091] When the printer 1 is in the "standby state (non-power saving mode)" and 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 (power saving mode)." The "sleep state" is a mode that consumes less power than the "standby state," and, for example, the display is turned off, the CPU clock is slowed down, and the supply of DC 3.3V is also stopped as described above. When the printer 1 receives an image formation execution command or data related to image formation in the "sleep state," it returns to the "standby state" and starts printing.

[0092] Then, in order for the ASIC 210 of the main board 200 to control the heating temperature of the heater 93, signals THM1 to THM3 related to the temperatures detected by the fixing temperature sensors TH1 to TH3, respectively, i.e., signals THM1 to THM3 detected within the fixing device 9, are transmitted from the fixing device 9 to the main board 200. More specifically, the signals THM1 to THM3 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 to THM3 from the fixing temperature sensors TH1 to TH3. In addition to the detection signals from the fixing temperature sensors TH1 to TH3, the fixing device 9 also transmits detection signals from the nip detection sensor SE4 and the discharge sensor SE5 to the main board 200.

[0093] [Electrical configuration of relay board] 9 and 10, 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. Figures 9 and 10 show only the relay board 161 provided in the fixing device 9 and the associated electrical configuration of the printer 1.

[0094] First, referring to FIG. 9, the fixing temperature sensor TH1 (a sensor for detecting the temperature of an area on one end of the heating roller 91; see FIG. 2) 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 detected temperature. One end of the variable resistor R2 of the fixing temperature sensor TH1 is connected to a DC 3.3V 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 TH1 to the main board 200 via a dedicated 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 output terminal 251 and receiving the signal from the fixing temperature sensor TH1. The other end of the resistor R1 is connected to the ground GND of the main board 200 (for example, 0 V, but a reference potential other than 0 V may be used; the same applies below). 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 3.3V 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 3.3V 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. The AD conversion circuit section 210A receives an analog voltage (signal) of the following equation (1). 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.

[0095] Next, referring to FIG. 9, the fixing temperature sensor TH2 (a sensor that detects the temperature of a region near the center of the heating roller 91; see FIG. 2) 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 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 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.

[0096] 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.

[0097] Furthermore, the DC 3.3V and DC 1.8V power supply voltages 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 together with the ground potential (see FIG. 8). As described above, when the operation mode of the printer 1 transitions to the "sleep state (power saving mode)", the supply of DC 3.3V is stopped, but the supply of DC 1.8V is maintained. Therefore, in the sleep state, temperature detection by the fixing temperature sensor TH1 is no longer possible, but temperature detection by the fixing temperature sensor TH2 can continue.

[0098] 10, the fixing temperature sensor TH3 (a sensor that detects the temperature of the region on the other end side of the heating roller 91, see FIG. 2) and the nip detection sensor SE4 provided in the fixing device 9 will be described. The fixing temperature sensor TH3 has a variable resistor R2 whose resistance value changes depending on the detected temperature. On the other hand, the nip detection sensor SE4 has a light emitting diode and a phototransistor Tr.

[0099] Furthermore, in order to reduce the number of terminals of the fixing connector 160 and the main connector 150, the relay board 161 unifies the signal lines of the fixing temperature sensor TH3 and the nip detection sensor SE4 into a single common signal line. Specifically, the relay board 161 relays the signal from the fixing temperature sensor TH3 and the signal from the nip detection sensor SE4 to the main board 200 via a common terminal 253. Meanwhile, the main board 200 has a predetermined resistor (first resistor) R3, one end of which is connected to a terminal of the ASIC 210 connected to the common terminal 253 and to which signals from the fixing temperature sensor TH3 and the nip detection sensor SE4 are input, and the other end of which is connected to a DC 1.8V power supply provided on the main board 200. The relay board 161 also has a combined resistor made up of a variable resistor R2 and a predetermined resistor (second resistor) R4 connected in series to the variable resistor R2. One end of the combined resistor is connected to the ground GND of the relay board 161, and the other end of the combined resistor is connected to the common terminal 253. The phototransistor Tr is connected in parallel with the combined resistor, the emitter is connected to the ground portion GND of the relay substrate 161 , and the collector is connected to the common terminal 253 .

[0100] As described above, when the pressure contact / separation mechanism 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. 7, the light from the light-emitting diode (LED) is blocked by the flange 121B of the cam gear 121 and does not enter the phototransistor Tr. When the phototransistor Tr is in an off state in which no light is entered, no current flows from the collector to the emitter of the phototransistor Tr. Instead, current flows from the 1.8V DC power supply on the main board 200 to the ground GND via resistor R3, variable resistor R2, and resistor R4. Meanwhile, the ASIC 210 includes an AD conversion circuit 210C. As a result, for the fixing temperature sensor TH3, an analog voltage obtained by dividing 1.8V by the combined resistor and resistor R3 is input to the AD conversion circuit 210C of the ASIC 210 during the pressure contact state. More specifically, the fixing temperature sensor TH3 divides 1.8V into an analog voltage using a combined resistor and resistor R3, and inputs the resulting voltage to the AD conversion circuit unit 210C of the ASIC 210. The ASIC 210 then identifies the temperature detected by the fixing temperature sensor TH3 using the digital value converted by the AD conversion circuit unit 210C. The AD conversion circuit section 210C receives an analog voltage of the following equation (3): Vin = 1.8V × (variable R2 + R4) / (variable R2 + R4 + R3) (3) As described above, the variable resistor R2 varies with the change in the detected temperature, and the analog voltage Vin changes.

[0101] On the other hand, as described above, when the pressure contact / separation mechanism 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. 7, light from the light-emitting diode is input to the phototransistor Tr without being blocked by the flange 121B of the cam gear 121. Then, when light is input to the phototransistor Tr in the ON state, current flows only to the collector and emitter sides of the phototransistor Tr, whose resistance is considered to be zero, from the DC 1.8V power supply provided on the main board 200, and current basically does not flow to resistor R3, variable resistor R2, or resistor R4. As a result, when the resistance of the signal line and phototransistor Tr is considered to be zero for the fixing temperature sensor TH3 during the separated state, an analog voltage of the following equation (4) is input to the AD conversion circuit unit 210C (assuming the potential of the ground unit GND is 0V). Vin=1.8V-(R3×I)=0V···(4) As described above, regardless of the detected temperature, the analog voltage Vin is a fixed voltage.

[0102] As a result, as shown in FIG. 11, when the phototransistor Tr is off, Vin≠0V is input to the ASIC 210, making it possible to detect that the heating roller 91 and the pressure roller 92 are in a pressed-contact state. More specifically, when Vin is in the range from Vin_min (=1.8V×(R4 / (R3+R4))) to Vin_max (=1.8V), the ASIC 210 can detect that the heating roller is nipped by the pressure roller. Meanwhile, the ASIC 210 can also detect the temperature of the fixing temperature sensor TH3 based on the value of the analog voltage Vin. That is, even if the fixing temperature sensor TH3 and the nip detection sensor SE4 are connected and relayed through a common terminal, it is possible to detect whether the pressure contact / separation mechanism is in a pressed or separated state while also detecting the temperature of the fixing temperature sensor TH3.

[0103] On the other hand, when the phototransistor Tr is on, Vin = 0V is input to the ASIC 210, and when Vin reaches 0V, it is possible to detect that the heating roller 91 and pressure roller 92 are in a separated state. While the pressure contact / separation mechanism is in the separated state, the fixing temperature sensor TH3 cannot detect the temperature. However, the fixing temperature sensors TH1 and TH2 can still detect the temperature of the heating roller 91, so temperature control of the heater 93 can be performed without any problems. As will be described later, the temperature detected by the fixing temperature sensor TH3 is used to detect temperature abnormalities that occur when printing sheets narrower than the default size. However, even if the temperature cannot be detected in the separated state, the above determination can be made as long as the temperature can be detected in the pressure contact state. Therefore, the inability of the fixing temperature sensor TH3 to detect the temperature in the separated state is not a major disadvantage.

[0104] [Control processing by the control unit] Next, among the various control processes executed by the ASIC 210 of the printer 1 having the above configuration, the process of detecting an abnormal temperature of the fixing device 9 will be described with reference to Fig. 12. Fig. 12 is a flowchart illustrating the main process executed after the printer 1 is powered on, particularly the process related to detecting an abnormal temperature of the fixing device 9. Note that each process shown in the flowchart in Fig. 12 below is stored in a memory provided in the printer 1 and is executed by the ASIC 210 (controller).

[0105] First, in step (hereinafter abbreviated as S) 1, the ASIC 210 starts the printing process in accordance with a print command. The print command is transmitted, for example, via a network interface provided in the printer 1 from a PC or the like connected by wire or wirelessly, along with image data to be printed. Alternatively, the printing process can be started by receiving an image formation execution command at a user interface provided in the printer 1. When printing starts, as shown in FIG. 7, the cams 97A and 97B in the fixing device 9 rotate, moving the pressure roller 92 relative to the heating roller 91 to switch from a separated state to a pressed state. In addition to driving the process unit 4 and the main motor 201A, the ASIC 210 also controls the on / off timing of the 100V AC power supplied to the heater 93 based on signals THM1 to THM3 from the fixing temperature sensors TH1 to TH3.

[0106] Next, in S2, the ASIC 210 acquires the temperature detected by the fixing temperature sensor TH1, whose detection area is near one end of the heating roller 91, and the temperature detected by the fixing temperature sensor TH3, whose detection area is near the other end of the heating roller 91, as shown in FIG. 2. Specifically, the temperature detected by the fixing temperature sensor TH1 is identified by converting the analog voltage Vin input to the AD conversion circuit unit 210A (FIG. 9), and the temperature detected by the fixing temperature sensor TH3 is identified by converting the analog voltage Vin input to the AD conversion circuit unit 210C (FIG. 10). The details of temperature detection by the fixing temperature sensors TH1 and TH3 have already been described using FIGS. 9 and 10, so a detailed description is omitted. Furthermore, as mentioned above, the fixing temperature sensor TH3 cannot detect the temperature while the pressure contact / separation mechanism is in the separated state. Therefore, the processing from S2 onward is basically performed only when printing has started and the pressure contact / separation mechanism is in the pressed state.

[0107] Then, in S3, ASIC210 compares the difference between the detected temperature E1' of the fixing temperature sensor TH1 detected last time and the detected temperature E1 of the fixing temperature sensor TH1 detected this time with the difference between the detected temperature E3' of the fixing temperature sensor TH3 detected last time and the detected temperature E3 of the fixing temperature sensor TH3 detected this time, and determines whether the following equation (5) holds. (E1´-E1)×α>(E3´-E3)···(5) Here, α is a predetermined coefficient that is set appropriately. Meanwhile, E1′ and E3′ are stored in memory in S5, which will be described later.

[0108] 2, the size of the sheet S to be printed on in the printer 1 is not limited to the default size (A4) supplied from the supply tray 13; by inserting a sheet S from the multipurpose tray 14, it is also possible to print on a sheet S of a size other than the default size (e.g., A4) placed on the supply tray 13. As shown in FIG. 2, when a sheet S of the default size is printed, the sheet S passes between the heat roller 91 and the pressure roller 92 over almost the entire width of the heat roller 91, whereas when a sheet S narrower than the default size is printed, the sheet S passes between the heat roller 91 and the pressure roller 92, moving closer to one end (the fixing temperature sensor TH1 side). In other words, when printing on a sheet S of a size narrower than the default size, the fixing temperature sensor TH3 serves as a sensor for detecting the temperature in an area where the sheet S does not pass.

[0109] As described above, the heating roller 91 is heated by an internal heater 93, but some of the heat is lost by the sheet S passing through during printing. Therefore, the printer 1 controls the temperature of the heater 93 in advance, anticipating a temperature drop due to the passage of the sheet S. However, when printing on a sheet S narrower than the default size, the temperature is not lowered by the sheet S in areas where the sheet S does not pass. Therefore, even if the same temperature control as when printing on a sheet S of the default size is performed, the temperature may become higher than expected on the device side, and printing must be stopped before it exceeds the allowable range. Therefore, in S3, if the trend in temperature change detected by the fixing temperature sensor TH3 differs from the trend in temperature change detected by the fixing temperature sensor TH1—more specifically, if the temperature rise of the fixing temperature sensor TH3 is significantly greater than the temperature rise of the fixing temperature sensor TH1—it is predicted that a temperature abnormality has occurred in the fixing device 9 due to the passage of a sheet S narrower than the default size.

[0110] If the condition of S3 is not met, that is, if it is determined that no temperature abnormality has occurred in the fixing device 9 (S3: NO), after waiting for a predetermined time (e.g., 100 ms) (S4), the currently detected temperature E1 of the fixing temperature sensor TH1 is stored in memory as E1'. Similarly, the currently detected temperature E3 of the fixing temperature sensor TH3 is stored in memory as E3' (S5).

[0111] Thereafter, in S6, the ASIC 210 determines whether the printing process according to the print command has been completed.

[0112] If it is determined that the printing process according to the print command has been completed (S6: YES), the program ends. On the other hand, if it is determined that the printing process according to the print command has not been completed (S6: NO), the program returns to S2 and continues to detect abnormal temperatures in the fixing device 9.

[0113] On the other hand, if the condition of S3 is satisfied, that is, if it is determined that a temperature abnormality has occurred in the fixing device 9 due to the passage of a sheet S of a size narrower than the default size (S3: YES), the printing process is forcibly terminated (S7) to prevent any further temperature rise in the fixing device 9. However, it is also possible to issue only a warning and continue the printing process.

[0114] As described above in detail, the fixing device 9 according to the first embodiment is a fixing device 9 that is detachable from the printer 1, and includes a heating roller 91 that heats the sheet S, a heater 93 that heats the heating roller 91, a pressure roller 92 that nips the sheet S between the heating roller 91 and the pressure roller 92, fixing temperature sensors TH1 to TH3 that detect the temperature of the heating roller 91, a nip detection sensor SE4 that detects the state of the fixing device 9, a fixing connector 160 that connects to a main body 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, and a relay board 161 that relays signals from the fixing temperature sensors TH1 to TH3 and a signal from the nip detection sensor SE4 to the printer 1. In particular, the signals from the fixing temperature sensor TH3 and the nip detection sensor SE4 are relayed via a common terminal 253, which makes it possible to reduce the number of signal lines that transmit signals from the sensors in the fixing device 9 to the main body housing 2 of the printer 1, i.e., the number of signal lines that connect the fixing device 9 and the main body housing 2 of the printer 1, compared to conventional fixing devices. The fixing device 9 also includes temperature sensors, including a fixing temperature sensor TH3 for detecting the temperature of the area of ​​the heating roller 91 where the sheet S does not pass, and fixing temperature sensors TH1 and TH2 for detecting the temperature of the area of ​​the heating roller 91 where the sheet S passes. The relay board 161 relays signals from the nip detection sensor SE4 and the fixing temperature sensor TH3 to the printer 1 via a common terminal 253, and relays signals from the fixing temperature sensors TH1 and TH2 to the printer 1 via output terminals 251 and 252. This allows the temperatures of the heating roller 91 to be detected, particularly in the area where the sheet passes and the area where the sheet does not pass. This makes it possible to detect temperature abnormalities, particularly in the area where the sheet does not pass. Furthermore, by sharing a signal line between some of the temperature sensors and the nip detection sensor SE4, even if a temperature detection condition occurs where it is difficult to detect the temperature, the other temperature sensors can continue to detect the temperature, allowing for appropriate temperature control of the heating roller. In addition, the printer 1 is further provided with a pressure-contact / separation mechanism that can switch between 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 the nip detection sensor SE4 is a sensor that can detect whether the roller is in a pressure-contact state or a separated state. This makes it possible to reduce the number of signal lines connecting the fixing device 9 and the main body housing 2 of the printer 1 while enabling the nip detection sensor SE4 to detect the pressure-contact state and the separated state. The printer 1 also includes a main board 200 having an ASIC 210 that can send and receive signals to and from the fixing device 9 via the main connector 150. The ASIC 210 is connected to the main connector 150 and can input signals from a common terminal 253. The pressure-contact / separation mechanism is a mechanism that, when in a pressure-contact state, the gear of the pressure-contact / separation mechanism shields the nip detection sensor SE4 from light, and when in a separated state, the gear of the pressure-contact / separation mechanism does not shield the nip detection sensor SE4 from light. When the nip detection sensor SE4 is shielded from light, the relay board 161 inputs a voltage corresponding to the temperature detected by the fixing temperature sensor TH3 from the common terminal 253 to the ASIC 210. When the nip detection sensor SE4 is not shielded from light, the relay board 161 inputs a predetermined voltage from the common terminal 253 to the ASIC 210. Therefore, the ASIC 210 can determine whether the pressure-contact / separation mechanism is in a pressure-contact state or a separated state based on the input voltage. Furthermore, when in the pressure-contact state, the input voltage can detect the temperature of the fixing temperature sensor TH3. In addition, the fixing temperature sensor TH3 has a variable resistor R2 whose resistance value changes depending on the detected temperature, and the nip detection sensor SE4 has a light-emitting diode and a phototransistor. When in a pressed-contact state, light from the light-emitting diode is not input to the phototransistor, but when in a separated state, light from the light-emitting diode is input to the phototransistor. The ASIC 210 has a terminal connected to the common terminal 253. The main board 200 has a first resistor R3 having one end connected to the terminal and the other end connected to the power supply of the main board 200. The relay board 161 has a composite resistor consisting of a variable resistor R2 and a second resistor R4 connected in series to the variable resistor R2. One end of the composite resistor is connected to the ground GND of the relay board 161 and the other end of the composite resistor is connected to the common terminal 253. The phototransistor is connected in parallel with the composite resistor. The emitter of the phototransistor is connected to the ground GND of the relay board 161, and the collector of the phototransistor is connected to the common terminal 253. As a result, when the phototransistor is off, a voltage other than 0V is input to the ASIC 210, making it possible to detect that the heating roller 91 and the pressure roller 92 are in a pressed-contact state. On the other hand, when the phototransistor is on, 0V is input to the ASIC 210, making it possible to detect that the heating roller 91 and the pressure roller 92 are in a separated state when the input voltage reaches 0V. The ASIC 210 can also detect the temperature of the fixing temperature sensor TH3 based on the input voltage value. In other words, even if the fixing temperature sensor TH3 and the nip detection sensor SE4 are connected and relayed through a common terminal, it is possible to detect whether the pressure contact / separation mechanism is in a pressed-contact state or a separated state while also detecting the temperature of the fixing temperature sensor TH3. In addition, the fixing temperature sensor TH3 is a sensor for detecting the temperature in an area where the sheet S does not pass when forming an image on a sheet narrower than the default size, and is equipped with a main board 200 having an ASIC 210 that can send and receive signals via the main body connector 150 between the fixing device 9 attached to the main body housing 2 of the printer 1, and the main board 200 stores the temperature detected by the fixing temperature sensor TH3 in memory, and also stores the temperature detected by the fixing temperature sensor TH1 in memory, and the ASIC 210 determines that a sheet narrower than the default size is passing if the temperature change trend detected by the fixing temperature sensor TH3 is different from the temperature change trend detected by the fixing temperature sensor TH1 (S7).Therefore, it is possible to prevent temperature abnormalities from occurring in the area of ​​the heating roller 91 where the sheet S does not pass when printing on a sheet S that is narrower than the default size.

[0115] Second Embodiment Next, a printer and a fixing device according to a second embodiment will be described with reference to Figures 13 and 14. In the following description, the same reference numerals as those in the configuration of the printer 1 and fixing device 9 according to the first embodiment shown in Figures 1 to 12 indicate the same or equivalent parts as those in the configuration of the printer 1 and fixing device 9 according to the first embodiment.

[0116] 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 fixing device 9 according to the first embodiment are different in electrical configuration, particularly with respect to the fixing temperature sensor TH3 (a sensor that detects the temperature of the area on the other end side of the heating roller 91, see FIG. 2) and the nip detection sensor SE4 shown in FIG. 10.

[0117] 13, the fixing temperature sensor TH3 and the nip detection sensor SE4 included in the fixing device 9 according to the second embodiment will be described. The fixing temperature sensor TH3 has a variable resistor R2 whose resistance value changes depending on the detected temperature. On the other hand, the nip detection sensor SE4 has a light-emitting diode and a phototransistor Tr.

[0118] As in the first embodiment, the relay board 161 combines the signal lines of the fixing temperature sensor TH3 and the nip detection sensor SE4 into a single common signal line to reduce the number of terminals of the fixing connector 160 and the main connector 150. Specifically, the relay board 161 relays signals from the fixing temperature sensor TH3 and the nip detection sensor SE4 to the main board 200 via a common terminal 253. The relay board 161 also has a composite resistor consisting of a variable resistor R2 and a predetermined resistor (first resistor) R1 connected in series with the variable resistor R2. The relay board 161 also has a predetermined resistor (second resistor) R3, one end of which is connected to the collector of the phototransistor Tr and the other end of which is connected to the common terminal 253. One end of the composite resistor is connected to a DC 1.8V power supply provided in the relay board 161, and the other end of the composite resistor is connected to the common terminal 253. The phototransistor Tr has an emitter connected to the ground GND of the relay board 161, and a collector connected to the common terminal 253 via a resistor R3.

[0119] In the second embodiment, the position of notch 121C in flange 121B is adjusted, so that the relationship between the light blocking state of nip detection sensor SE4 and the state of the pressure contact / separation mechanism is reversed from that in the first embodiment. That is, in the pressure contact state where heating roller 91 and pressure roller 92 are in pressure contact as shown in the upper diagram of Fig. 7, light from the light emitting unit can be received by passing through notch 121C, and in the separation state where heating roller 91 and pressure roller 92 are separated as shown in the lower diagram of Fig. 7, the light from the light emitting unit is blocked.

[0120] Therefore, when the pressure contact / separation mechanism 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. 7 , light from the light-emitting diode (LED) is input to the phototransistor Tr without being blocked by the flange 121B of the cam gear 121. When the phototransistor Tr is in an ON state, current flows from the 1.8V DC power supply of the relay board 161 to the collector and emitter of the phototransistor Tr, i.e., through resistor R1, variable resistor R2, and resistor R3. Meanwhile, the ASIC 210 includes an AD conversion circuit 210C. As a result, for the fixing temperature sensor TH3, an analog voltage obtained by dividing 1.8V by the combined resistor and resistor R3 is input to the AD conversion circuit 210C of the ASIC 210 during the pressure contact state. More specifically, for the fixing temperature sensor TH3, an analog voltage obtained by dividing 1.8V by the combined resistor and resistor R3 is input to the AD conversion circuit 210C of the ASIC 210. The ASIC 210 then identifies the temperature detected by the fixing temperature sensor TH3 based on the digital value converted by the AD conversion circuit unit 210C. The AD conversion circuit section 210C receives an analog voltage of the following equation (6): Vin=1.8V×(R3 / (variable R2+R1+R3)) (6) As described above, the variable resistor R2 varies with the change in the detected temperature, and the analog voltage Vin changes.

[0121] On the other hand, as described above, when the pressure contact / separation mechanism 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. 7, the light from the light emitting diode is blocked by the flange 121B of the cam gear 121 and is not input to the phototransistor Tr. In the OFF state in which no light is input to the phototransistor Tr, no current flows from the collector to the emitter of the phototransistor Tr, i.e., no current flows through resistor R1, variable resistor R2, or resistor R3. As a result, no voltage drop occurs in the fixing temperature sensor TH3 during the separated state, and an analog voltage of 1.8 V, the same voltage as the DC 1.8 V power supply provided in the relay board 161, is input. As described above, regardless of the detected temperature, the analog voltage Vin is a fixed voltage.

[0122] As a result, when the phototransistor Tr is on as shown in FIG. 14, Vin≠1.8V is input to the ASIC 210, making it possible to detect that the heating roller 91 and the pressure roller 92 are in a pressed-contact state. More specifically, when Vin is in the range from Vin_min (=0V) to Vin_max (=1.8V×(R3 / (R1+R3))), the ASIC 210 can detect that the heating roller is in a pressed-contact state (nipped) with the pressure roller. Meanwhile, the ASIC 210 can also detect the temperature of the fixing temperature sensor TH3 based on the value of the analog voltage Vin. That is, even if the fixing temperature sensor TH3 and the nip detection sensor SE4 are connected and relayed through a common terminal, it is possible to detect whether the pressure contact / separation mechanism is in a pressed-contact state or a separated state while also detecting the temperature of the fixing temperature sensor TH3.

[0123] On the other hand, when the phototransistor Tr is off, Vin = 1.8V is input to the ASIC 210, and when Vin reaches 1.8V, it is possible to detect that the heating roller 91 and pressure roller 92 are separated. While the pressure contact / separation mechanism is in the separated state, the fixing temperature sensor TH3 cannot detect the temperature. However, the fixing temperature sensors TH1 and TH2 can still detect the temperature of the heating roller 91, so the temperature control of the heater 93 can be performed without any problems. As explained in FIG. 12, the temperature detected by the fixing temperature sensor TH3 is used to detect temperature abnormalities that occur when printing sheets narrower than the default size. However, even if the temperature cannot be detected in the separated state, the above determination can be made as long as the temperature can be detected in the pressure contact state. Therefore, the inability of the fixing temperature sensor TH3 to detect the temperature in the separated state is not a major disadvantage.

[0124] As described above in detail, the printer according to the second embodiment includes a main board 200 having an ASIC 210 that can send and receive signals to and from the fixing device 9 via the main body connector 150. The ASIC 210 is connected to the main body connector 150 and can input signals from the common terminal 253. The pressure-contact / separation mechanism is a mechanism in which, when in a pressure-contact state, the gear of the pressure-contact / separation mechanism does not shield the nip detection sensor SE4 from light, and when in a separated state, the gear of the pressure-contact / separation mechanism shields the nip detection sensor SE4 from light. When the nip detection sensor SE4 is not shielded from light, the relay board 161 inputs a voltage corresponding to the temperature detected by the fixing temperature sensor TH3 from the common terminal 253 to the ASIC 210. When the nip detection sensor SE4 is not shielded from light, the relay board 161 inputs a predetermined voltage from the common terminal 253 to the ASIC 210. Therefore, the ASIC 210 can determine whether the pressure-contact / separation mechanism is in a pressure-contact state or a separated state based on the input voltage. Furthermore, when in a pressure-contact state, the input voltage can detect the temperature of the fixing temperature sensor TH3. Furthermore, fixing temperature sensor TH3 has variable resistor R2 whose resistance value changes depending on the detected temperature. Nip detection sensor SE4 has a light-emitting diode and a phototransistor. In the pressed state, light from the light-emitting diode is input to the phototransistor. In the separated state, light from the light-emitting diode is not input to the phototransistor. Intermediate board 161 has a composite resistor consisting of variable resistor R2 and a first resistor R1 connected in series to variable resistor R2, and a second resistor R3. One end of the composite resistor is connected to the power supply of intermediate board 161, and the other end of the composite resistor is connected to common terminal 253. The phototransistor has an emitter connected to the ground GND of intermediate board 161 and a collector connected to common terminal 253 via second resistor R3. As a result, when the phototransistor is on, voltages other than the power supply voltage of intermediate board 161 are input to ASIC 210, making it possible to detect that heating roller 91 and pressure roller 92 are in a pressed-contact state. On the other hand, when the phototransistor is off, the voltage of the power supply of the relay board 161 is input to the ASIC 210, and when the input voltage reaches the value of the power supply voltage of the relay board 161, it is possible to detect that the heating roller 91 and the pressure roller 92 are in a separated state. The ASIC 210 can also detect the temperature of the fixing temperature sensor TH3 based on the input voltage value. In other words, even if the fixing temperature sensor TH3 and the nip detection sensor SE4 are connected and relayed through a single common terminal, it is possible to detect whether the pressure contact / separation mechanism is in the pressed state or the separated state while also detecting the temperature of the fixing temperature sensor TH3.

[0125] Third Embodiment Next, a printer and a fixing device according to a third embodiment will be described with reference to Figures 15 and 16. In the following description, the same reference numerals as those in the configuration of the printer 1 and fixing device 9 according to the first embodiment shown in Figures 1 to 12 indicate the same or equivalent parts as those in the configuration of the printer 1 and fixing device 9 according to the first embodiment.

[0126] 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 fixing device 9 according to the first embodiment are different in electrical configuration, particularly with respect to the fixing temperature sensor TH3 (a sensor that detects the temperature of the area on the other end side of the heating roller 91, see FIG. 2) and the nip detection sensor SE4 shown in FIG. 10.

[0127] 15, the fixing temperature sensor TH3 and the nip detection sensor SE4 of the fixing device 9 according to the third embodiment will be described. The fixing temperature sensor TH3 has a variable resistor R2 whose resistance value changes depending on the detected temperature. On the other hand, the nip detection sensor SE4 has a light-emitting diode and a phototransistor Tr.

[0128] As in the first embodiment, relay board 161 combines the signal lines of fixing temperature sensor TH3 and nip detection sensor SE4 into a single common signal line to reduce the number of terminals of fixing connector 160 and main connector 150. Specifically, relay board 161 relays signals from fixing temperature sensor TH3 and nip detection sensor SE4 to main board 200 via common terminal 253. Meanwhile, relay board 161 has a predetermined resistor (first resistor) R1 connected at one end to a terminal of ASIC 210 connected to common terminal 253 and receiving signals from fixing temperature sensor TH3 and nip detection sensor SE4, and connected at the other end to a DC 1.8V power supply provided on main board 200. Relay board 161 also has a composite resistor consisting of variable resistor R2 and predetermined resistor (second resistor) R3 connected in series to variable resistor R2. Furthermore, there is also provided a predetermined resistor (third resistor) R4, one end of which is connected to the collector of the phototransistor Tr and the other end of which is connected to the common terminal 253. One end of the combined resistor is connected to the ground portion GND of the relay substrate 161, and the other end of the combined resistor is connected to the common terminal 253. The phototransistor Tr and resistor R4 are connected in parallel with the combined resistor, the emitter is connected to the ground portion GND of the relay substrate 161, and the collector is connected to the common terminal 253.

[0129] When the pressure contact / separation mechanism 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. 7 , the light from the light-emitting diode is blocked by the flange 121B of the cam gear 121 and does not enter the phototransistor Tr. When the phototransistor Tr is in an off state in which no light is entered, no current flows from the collector to the emitter of the phototransistor Tr. Instead, current flows from the 1.8V DC power supply on the main board 200 to the ground GND via resistor R1, variable resistor R2, and resistor R3. Meanwhile, the ASIC 210 includes an AD conversion circuit 210C. As a result, for the fixing temperature sensor TH3, an analog voltage obtained by dividing 1.8V by the combined resistor and resistor R1 is input to the AD conversion circuit 210C of the ASIC 210 during the pressure contact state. More specifically, the fixing temperature sensor TH3 inputs an analog voltage obtained by dividing 1.8V by a combined resistor and resistor R1 to the AD conversion circuit unit 210C of the ASIC 210. Then, the ASIC 210 identifies the temperature detected by the fixing temperature sensor TH3 based on the digital value converted by the AD conversion circuit unit 210C. The AD conversion circuit section 210C receives an analog voltage of the following equation (7): Vin=1.8V×(variable R2+R3) / (variable R2+R1+R3) (7) As described above, the variable resistor R2 varies with the change in the detected temperature, and the analog voltage Vin changes.

[0130] On the other hand, as described above, when the pressure contact / separation mechanism 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. 7, light from the light-emitting diode is input to the phototransistor Tr without being blocked by the flange 121B of the cam gear 121. When the phototransistor Tr is in the ON state, current flows from the 1.8V DC power supply on the main board 200 to the collector and emitter of the phototransistor Tr. That is, current flows from the 1.8V DC power supply to the ground GND via resistor R1, variable resistor R2, and resistor R3, and also flows to the ground GND via resistor R1, resistor R4, and the phototransistor Tr. On the other hand, the ASIC 210 includes an AD conversion circuit 210C. As a result, during the separated state, an analog voltage obtained by dividing 1.8V by a parallel resistor (the combined resistor and the parallel resistance of resistor R4) and resistor R1 is input to the AD conversion circuit 210C of the ASIC 210 for the fixing temperature sensor TH3. More specifically, the fixing temperature sensor TH3 divides 1.8V into an analog voltage using a parallel resistor and resistor R1, and inputs the divided analog voltage to the AD conversion circuit unit 210C of the ASIC 210. The ASIC 210 then identifies the temperature detected by the fixing temperature sensor TH3 using the digital value converted by the AD conversion circuit unit 210C. The AD conversion circuit section 210C receives analog voltages of the following equations (8) and (9). Vin=1.8V×(Rh / (R1+Rh)) (8) 1 / Rh=1 / R4+1 / (R2+R3) (9) As described above, the variable resistor R2 varies with the change in the detected temperature, and the analog voltage Vin changes.

[0131] As a result, as shown in FIG. 16 , the range of the voltage value Vin input to the ASIC 210 differs depending on whether the phototransistor Tr is off or on. Therefore, it is possible to detect whether the heating roller 91 and the pressure roller 92 are in a pressed-contact state or a separated state from the input voltage value of Vin. More specifically, the ASIC 210 can detect that the heating roller is in a pressed-contact state (nipped) with the pressure roller when Vin is between Vin_min (=1.8V×(R3 / (R1+R3))) and Vin_max (=1.8V). Meanwhile, the ASIC 210 can also detect the temperature of the fixing temperature sensor TH3 based on the value of the analog voltage Vin. That is, even if the fixing temperature sensor TH3 and the nip detection sensor SE4 are connected and relayed through a common terminal, it is possible to detect whether the pressure contact / separation mechanism is in a pressed-contact state or a separated state while also detecting the temperature of the fixing temperature sensor TH3.

[0132] On the other hand, when Vin is in the range of Vin_min (=1.8V×(Rh / (R1+Rh)), 1 / Rh=1 / R4+1 / R3) to Vin_max (=1.8V×(R4 / (R1+R4))), the ASIC 210 can detect that the heating roller 91 and the pressure roller 92 are in a separated state. In the third embodiment, the temperature of the fixing temperature sensor TH3 can be detected even when the pressure contact / separation mechanism is in the separated state.

[0133] As described above in detail, the printer according to the third embodiment includes a variable resistor R2 whose resistance value changes depending on the detected temperature, a nip detection sensor SE4 includes a light-emitting diode and a phototransistor, and when in the pressed-contact state, light from the light-emitting diode is not input to the phototransistor, but when in the separated state, light from the light-emitting diode is input to the phototransistor, an ASIC 210 includes a terminal connected to a common terminal 253, a main board 200 includes a first resistor R1 having one end connected to the terminal and the other end connected to a power supply for the main board 200, an interconnect board 161 includes a composite resistor consisting of a variable resistor R2 and a second resistor R3 connected in series with the variable resistor R2, and a third resistor R4, one end of the composite resistor is connected to the ground GND of the interconnect board 161 and the other end of the composite resistor is connected to the common terminal 253, a phototransistor is connected in parallel with the composite resistor, an emitter of the phototransistor is connected to the ground GND of the interconnect board 161, and a collector of the phototransistor is connected to the common terminal 253 via the third resistor R4. As a result, the range of the voltage value input to ASIC 210 differs depending on whether the phototransistor is off or on, so it is possible to detect from the input voltage value of Vin whether the heating roller 91 and pressure roller 92 are in a pressed-contact state or a separated state. Furthermore, ASIC 210 can also detect the temperature of fixing temperature sensor TH3 based on the input voltage value. That is, even if fixing temperature sensor TH3 and nip detection sensor SE4 are connected and relayed through a single common terminal, it is possible to detect the temperature of fixing temperature sensor TH3 while also detecting whether the pressure contact / separation mechanism is in a pressed-contact state or a separated state.

[0134] 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, three fixing temperature sensors TH1 to TH3 are provided to detect the temperature of the heating roller 91, but the number of fixing temperature sensors does not necessarily have to be three and may be two or four or more. Also, the signal from fixing temperature sensor TH3 and the signal from nip detection sensor SE4 are output to the main body housing 2 side via the common terminal 253, but the signal from fixing temperature sensor TH1 or fixing temperature sensor TH2 and the signal from nip detection sensor SE4 may also be output to the main body housing 2 side via the common terminal 253.

[0135] In addition, in the above embodiment, the temperature change trend of the fixing temperature sensor TH1 is compared with the temperature change trend of the fixing temperature sensor TH3 in the processing of S3, but the temperature change trend of the fixing temperature sensor TH2 may also be compared with the temperature change trend of the fixing temperature sensor TH3.

[0136] 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]

[0137] 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, 200... main board (control board), 210... ASIC (control unit), TH1 to TH3... fixing temperature sensor, SE4... nip detection sensor, SE5... discharge sensor, S... sheet

Claims

1. A fixing device that has a main body connector and is detachable from an image forming apparatus that forms an 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 temperature sensor for detecting the temperature of the heating rotor; a detection sensor for detecting a state of the fixing device; a fixing connector that is connected to the main body connector when the fixing device is attached to the image forming apparatus; a relay board having a common terminal connected to the fixing connector and connected to each of the temperature sensor and the detection sensor, the relay board relaying signals from the detection sensor and the temperature sensor to the image forming apparatus via the common terminal; A fixing device comprising:

2. The temperature sensor a non-passage area temperature sensor for detecting the temperature of an area of ​​the heating rotary body where the sheet does not pass; a passage area temperature sensor for detecting the temperature of an area of ​​the heating rotor through which the sheet passes, The relay substrate is It further has an output terminal, relaying a signal from the detection sensor and a signal from the non-passage area temperature sensor to the image forming apparatus via the common terminal; relaying a signal from the passing area temperature sensor to the image forming apparatus via the output terminal; 2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

3. 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, 2. The fixing device according to claim 1, wherein the detection sensor is a nip detection sensor capable of detecting whether the fixing device is in the pressure contact state or the separated state.

4. 4. An image forming apparatus in which the fixing device according to claim 3 is detachable, a control board having a control unit capable of transmitting and receiving signals to and from the attached fixing device via the main body connector; the control unit is connected to the main body connector and is capable of receiving a signal from the common terminal; The pressure contact / separation mechanism includes: When the pressing state is established, the gear of the pressing / separating mechanism shields the nip detection sensor from light. a mechanism in which, when in the separated state, a gear of the pressure contact / separation mechanism does not shield the nip detection sensor from light, An image forming apparatus characterized in that, when the nip detection sensor is shielded from light, the relay board inputs a voltage corresponding to the temperature detected by the temperature sensor from the common terminal to the control unit, and when the nip detection sensor is not shielded from light, it inputs a predetermined voltage from the common terminal to the control unit.

5. the temperature sensor has a variable resistor whose resistance value changes depending on the detected temperature, the nip detection sensor has a light emitting diode and a phototransistor, and in the pressed state, light from the light emitting diode is not input to the phototransistor, and in the separated state, light from the light emitting diode is input to the phototransistor; the control unit has a terminal connected to the common terminal, the control board has a first resistor having one end connected to the terminal and the other end connected to a power supply of the control board; The relay substrate is a combined resistor consisting of the variable resistor and a second resistor connected in series to the variable resistor; one end of the combined resistor is connected to the ground portion of the relay substrate, and the other end of the combined resistor is connected to the common terminal; 5. The image forming apparatus according to claim 4, wherein the phototransistor is connected in parallel with the combined resistor, the emitter of the phototransistor is connected to the ground portion of the relay substrate, and the collector of the phototransistor is connected to the common terminal.

6. the temperature sensor has a variable resistor whose resistance value changes depending on the detected temperature, the nip detection sensor has a light emitting diode and a phototransistor, and in the pressed state, light from the light emitting diode is not input to the phototransistor, and in the separated state, light from the light emitting diode is input to the phototransistor; the control unit has a terminal connected to the common terminal, the control board has a first resistor having one end connected to the terminal and the other end connected to a power supply of the control board; The relay substrate is a combined resistor consisting of the variable resistor and a second resistor connected in series to the variable resistor, and a third resistor; one end of the combined resistor is connected to the ground portion of the relay substrate, and the other end of the combined resistor is connected to the common terminal; 5. The image forming apparatus according to claim 4, wherein the phototransistor is connected in parallel with the combined resistor, the emitter of the phototransistor is connected to the ground portion of the relay substrate, and the collector of the phototransistor is connected to the common terminal via the third resistor.

7. 4. An image forming apparatus in which the fixing device according to claim 3 is detachable, a control board having a control unit capable of transmitting and receiving signals to and from the attached fixing device via the main body connector; the control unit is connected to the main body connector and is capable of receiving a signal from the common terminal; The pressure contact / separation mechanism includes: When the pressing state is established, the gear of the pressing / separating mechanism does not block the light from the nip detection sensor, a mechanism for blocking light from the nip detection sensor when the pressing / separating mechanism is in the separated state, An image forming apparatus characterized in that the relay board inputs a voltage corresponding to the temperature detected by the temperature sensor from the common terminal to the control unit when the nip detection sensor is not shaded, and inputs a predetermined voltage from the common terminal to the control unit when the nip detection sensor is shaded.

8. the temperature sensor has a variable resistor whose resistance value changes depending on the detected temperature, the nip detection sensor has a light emitting diode and a phototransistor, and in the pressed state, light from the light emitting diode is input to the phototransistor, and in the separated state, light from the light emitting diode is not input to the phototransistor; The relay substrate is a combined resistor consisting of the variable resistor and a first resistor connected in series to the variable resistor, and a second resistor; one end of the combined resistor is connected to a power supply of the relay board, and the other end of the combined resistor is connected to the common terminal; 8. The image forming apparatus according to claim 7, wherein the emitter of the phototransistor is connected to the ground portion of the relay substrate, and the collector of the phototransistor is connected to the common terminal via the second resistor.

9. 3. An image forming apparatus in which the fixing device according to claim 2 is detachable, the non-passage area temperature sensor is a sensor for detecting the temperature of an area where the sheet does not pass when forming an image on a sheet having a size narrower than a predetermined size, a control board having a control unit capable of transmitting and receiving signals to and from the attached fixing device via the main body connector; The control board storing the temperature detected by the non-passage area temperature sensor in a memory, and storing the temperature detected by the pass-through area temperature sensor in the memory; The control unit An image forming apparatus characterized in that, when the temperature change trend detected by the non-passing area temperature sensor differs from the temperature change trend detected by the passing area temperature sensor, it is determined that a sheet of a size narrower than a predetermined size is passing through.

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