Image forming apparatus and fixing device mounting detection method

Abstract

To solve the problem in which a mounting state of a fixing device is difficult to be specified without preparing a special detection sensor in an image forming apparatus to which the fixing device is removably attached.SOLUTION: An image forming apparatus comprises: a fixing unit that is removably mounted in an image forming apparatus body; a side thermistor that is arranged on the fixing unit; a temperature detection section that detects a temperature of the fixing unit on the basis of temperature detection information of the side thermistor; a sub CPU that stores opening and closing information based on information of a cover opening sensor that detects opening and closing of a top cover; and a fixing unit mounting determination section that determines a mounting state of the fixing unit. The image forming apparatus determines that the side thermistor is disconnected When the temperature detection section does not normally detect the temperature, and determines that the fixing unit is not mounted when the top cover is open.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a method for detecting the installation of a fixing device in an image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a fixing device that is detachably provided in an image forming apparatus main body, and an image forming apparatus using the same have been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-88624 A (Page 8, FIG. 4) Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an image forming device with such a configuration, there was a problem that a dedicated sensor was required to detect the installation state of the fixing device, and even if a dedicated sensor was used, it became difficult to distinguish between a state in which the fixing device was not installed and a state in which the sensor was broken. [Means for solving the problem]

[0005] The image forming apparatus according to the present invention comprises: the fixing device is removably mounted on the image forming apparatus body and fixes a developer to a print medium by applying pressure and heat; a temperature sensor provided on the fixing device; a temperature detection unit that detects the temperature of the fixing device based on information from the temperature sensor; a cover opening / closing determination unit that determines whether a cover that opens and closes the image forming apparatus body is opened or closed based on information from an opening / closing sensor that detects the opening and closing of the cover when the fixing device is installed or removed and stores the opening / closing information; and an installation determination unit that determines the installation state of the fixing device in the image forming apparatus body, The mounting determination unit is characterized in that it performs a first determination process to determine whether the temperature detection unit is detecting the temperature of the fixing device normally, and if the temperature detection unit is not detecting the temperature normally, determines that the temperature sensor is disconnected if the cover is determined to be closed by the cover opening / closing determination unit, and determines that the fixing device is not mounted if the cover is determined to be open. Effect of the Invention

[0006] According to the present invention, it is possible to monitor whether the temperature detection of the fixing device is being performed normally and whether the cover is open or closed, and using the judgment results, it is possible to determine whether the temperature sensor itself is in a broken state or whether the fixing device is not yet installed, without adding a new sensor or circuit. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing a configuration of a main part of an image forming apparatus according to a first embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing the configuration of a fixing unit and a thermopile as viewed from the recording paper feed direction side. [Diagram 3] FIG. 2 is a block diagram of a main part of a control system of the image forming apparatus. [Figure 4] FIG. 1 is a circuit diagram showing the configuration of a side thermistor open check circuit. [Diagram 5] 10 is a graph showing the relationship between the temperature [°C] detected by the side thermistor and the AD value output by the A / D converter in the temperature detection unit. (a) shows the characteristics in the toner fixing actual use area (area enclosed by dotted line), and (b) shows the characteristics in the thermistor open check judgment area (area enclosed by dotted line). [Figure 6] 13 is a flowchart showing a flow of a thermistor determination process. [Figure 7] 13 is a flowchart showing a thermistor determination process with necessity determination, in which a necessity determination process is incorporated. [Figure 8]10 is a flowchart showing a flow of a cover open state storage process for determining whether or not the top cover is open. [Figure 9] 10 is a flowchart showing the flow of a fixing unit installation determination process for determining whether the side thermistor itself is in a disconnected state or whether the fixing unit is not installed. [Figure 10] 8 is a flowchart of a first modification of the thermistor determination process with necessity determination in the first embodiment shown in FIG. [Figure 11] 10 is a flowchart of a first modification of the fixing unit mounting determination process shown in FIG. 9 according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Embodiment 1 FIG. 1 is a diagram showing a configuration of a main part of an image forming apparatus 1 according to a first embodiment of the present invention.

[0009] As shown in the figure, the image forming apparatus 1 is configured as an electrophotographic monochrome printer, and a paper feed tray 12 has recording paper 50 stacked therein as a recording medium, and is detachably attached to the lower part of the main body of the image forming apparatus 1. The pickup roller 15, together with a paper feed roller 16 and a separation roller 17 that are arranged in contact with each other as a pair, constitutes a paper feed section 25. The pickup roller 15 and the paper feed roller 16 are driven to rotate by a main motor 110 (FIG. 3), which will be described later, and the separation roller 17 generates torque in the counter-rotation direction by a torque generating means (not shown).

[0010] Therefore, the pickup roller 15 picks up the uppermost recording paper 50 that it comes into contact with from within the paper feed tray 12, and the paper feed roller 16 and separation roller 17 separate the recording papers 50 one by one and sequentially feed them onto the transport path, even when multiple sheets of recording paper 50 are pulled out at the same time, for example.

[0011] A pair of transport rollers 18 and a pair of registration rollers 19 are arranged in this order on the transport path downstream of paper feed section 25 in the transport direction of recording paper 50. The pair of transport rollers 18 transports recording paper 50 to the pair of registration rollers 19, which corrects skewed recording paper 50 by starting paper transport after the recording paper 50 comes into contact with the pair of registration rollers 19 based on the paper detection timing of entrance sensor 22, which detects the passage of recording paper 50, and sends the recording paper 50 to a nip portion between photoconductor drum 31 and transfer roller 38 of image forming unit 30, which rotates in the direction of the arrow.

[0012] The image forming unit 30 has a photoconductor drum 31 that carries a toner image, a charging roller 32, a developing roller 33, a supply roller 34, and a developing blade 35. The main body of the image forming unit 30 is further provided with a detachable toner cartridge 36 serving as a toner container.

[0013] A charging voltage is applied to the charging roller 32, which uniformly charges the surface of the photosensitive drum 31, and an electrostatic latent image is formed on the uniformly charged surface of the photosensitive drum 31 by light irradiation from the LED head 37. A developing voltage is applied to the developing roller 33, which causes toner to adhere to the electrostatic latent image formed on the surface of the photosensitive drum 31 to form a toner image, a supplying roller 34 is applied with a supplying voltage to supply toner to the developing roller 33, and a developing blade 35 regulates the thickness of the toner layer formed on the surface of the developing roller 33.

[0014] The transfer roller 38 is disposed opposite the photosensitive drum 31 so as to be in pressure contact with the photosensitive drum 31 to form a nip portion. When the recording paper 50 is fed into this nip portion, the toner development formed on the circumferential surface of the photosensitive drum 31 is transferred onto the paper surface by the transfer roller 38, to which a predetermined transfer voltage is applied, while the recording paper 50 passes through the nip portion between the photosensitive drum 31 and the transfer roller 38. The image forming unit 30 starts the process of forming the toner development on the circumferential surface of the photosensitive drum 31 based on the paper detection timing of the write start sensor 23, which detects the recording paper 50 after it has passed the pair of registration rollers 19.

[0015] The fixing unit 40 as a fixing device is removably mounted on the main body of the image forming apparatus 1, and includes a heat roller 41 and a backup roller 42, and as described below, when power is supplied to a heater 61 (FIG. 2) to heat the recording paper 50, the recording paper 50 is heated and pressurized to fuse the toner and perform fixing. As described above, for example, as with the fixing unit 40 of the image forming apparatus 1, with respect to each of the detachable or rotatable components, the portion excluding the component may be referred to as the device main body.

[0016] A thermopile 44, which is a non-contact temperature sensor, is used to control the heater 61 to keep the surface temperature of the heat roller 41 at a predetermined temperature. The thermopile 44 is installed inside a beam 43 to prevent the heat generated in the fixing unit 40 from being transmitted to the image forming unit 30. The recording paper 50, on which the toner has been fixed by heating and pressurizing in the fixing unit 40, is transported to a pair of discharge rollers 20, 21 and discharged outside the apparatus.

[0017] The discharge sensor 24 is a sensor that serves as a reference for detecting the completion of a series of image forming processes for one sheet of recording paper 50. The image forming apparatus 1 also includes a top cover 45 that can be opened and closed to replace the image forming unit 30, the toner cartridge 36, and the fixing unit 40, which are consumables, or to clear a paper jam, and the open / closed state of the top cover 45 is detected by a cover open sensor 46 that serves as an open / close sensor.

[0018] 1, the X direction is the conveying direction (direction of arrow A) when the recording paper 50 passes through the pressure contact portion between the photosensitive drum 31 and the transfer roller 38, the Y direction is the direction of the rotation axis of the photosensitive drum 31, and the Z direction is the direction perpendicular to both axes. In this case, the Z direction is set to be approximately vertical.

[0019] FIG. 2 is a diagram showing the essential configuration of the fixing unit 40 and the thermopile 44 as viewed from the paper feed direction side of the recording paper 50. As shown in FIG.

[0020] As shown in the figure, inside the fixing unit 40, a heat roller 41 as a heating member and a backup roller 42 as a pressure member are disposed opposite to each other so as to sandwich the recording paper 50 conveyed from the transfer roller 38, forming a nip portion. By passing the recording paper 50 through this nip portion, the toner development transferred onto the recording paper 50 and adhering thereto by weak electrostatic force is fixed onto the recording paper 50 by heating with the heat roller 41 and pressure with the backup roller 42. The heat roller 41 is driven to rotate in the direction of the arrow by a main motor 110 (FIG. 3) described later, and the backup roller 42 rotates following the rotation of the heat roller 41. Although the backup roller 42 is driven here, the backup roller 42 may also be directly driven to rotate like the heat roller 41.

[0021] The heat roller 41 is equipped with a heater 61 (such as a halogen heater) inside, and a raw tube made of an aluminum alloy or the like is coated with a fluororesin such as PFA (perfluoroalkoxyalkane) to ensure release properties and prevent the recording paper 50 from wrapping around it.

[0022] Backup roller 42 has a rubber layer on an aluminum alloy or stainless steel tube, which is compressed by pressure to form a specified nip width with heat roller 41 and ensure contact time between passing recording paper 50 and heat roller 41. The rubber layer is either coated with a fluororesin such as PFA as with heat roller 41, or covered with a tube such as PFA and bonded.

[0023] Thermopile 44 is mounted on the main body of image forming apparatus 1, and detects the temperature at the longitudinal center of heat roller 41. Heater 61 is temperature controlled so that the temperature detected by thermopile 44 becomes a target temperature. Side thermistor 62 as a temperature sensor is disposed outside (non-paper passing portion) of paper passing area W of maximum width 210 mm through which image forming apparatus 1 can pass paper, and monitors the non-paper passing portion of heat roller 41 so that it does not exceed its heat resistance temperature during printing operation.

[0024] FIG. 3 is a block diagram of a main portion of a control system of the image forming apparatus 1. As shown in FIG. The printer control unit 101 is connected to a display unit 107 for informing the user of the status of the device, an LED head 37, a high-voltage power supply unit 108 which is a circuit for generating the high voltage to be applied to the image forming unit 30 and the transfer roller 38, a discharge motor 109 which drives each of the drive side rollers of the discharge roller pair 20, 21, the entrance sensor 22, the writing sensor 23, the discharge sensor 24, the cover open sensor 46, a main motor 110, a thermopile 44, a side thermistor 62 in the fixing unit 40, and a low-voltage power supply unit 111 which serves as a heater drive circuit.

[0025] In addition, the main motor 110 rotates and drives each of the driving rollers of the pickup roller 15, the paper feed roller 16, the pair of conveying rollers 18 and the pair of registration rollers 19, each of the rotating members such as the photosensitive drum 31 of the image forming unit 30, and the heat roller 41 of the fixing unit 40 via a rotation transmission system.

[0026] Printer control unit 101 includes, as components related to the present invention, a fixing unit installation determination unit 102 as an installation determination unit, a sub-CPU 103 as a cover open / close determination unit having a memory unit 104, a temperature detection unit 105 for fixing unit 40, and a heater control unit 106. Temperature detection unit 105 includes an analog-to-digital converter (hereinafter referred to as an A / D converter) that converts the temperature detected by thermopile 44 and side thermistor 62 into a detection voltage of a digital value.

[0027] Heater control unit 106 controls the temperature of heater 61 inside fixing unit 40 so that the temperature detected by thermopile 44 becomes a predetermined temperature. The output of side thermistor 62 is also input to fixing unit installation determination unit 102 and is used for detecting the installation of fixing unit 40. In the energy saving mode, printer control unit 101 is in a state where only sub-CPU 103 is energized, and in the energy saving mode, sub-CPU 103 stores in memory unit 104 the open / closed state, i.e., whether or not top cover 45 is opened.

[0028] 4 is a circuit diagram showing the configuration of a disconnection check (open check) circuit for side thermistor 62. In the drawing, only side thermistor 62 is located inside fixing unit 40, and the rest are configured inside printer control unit 101.

[0029] As shown in the figure, a power supply of 3.3 V is applied to one terminal of the side thermistor 62, and the other terminal is connected to the + input terminal of an operational amplifier 155. A thermistor read range switching signal S1 is applied to the gate of the FET 152, and the drain of the FET 152 is connected to the + input terminal of the operational amplifier 155 via a resistor 153 (10 kΩ in this case) and is also connected to the source of the FET 152 via a resistor 154 (330 kΩ in this case), with the source potential set to 0 V (ground potential). The - input terminal of the operational amplifier 155 is directly connected to the output terminal and operates as a voltage follower, and the output terminal is connected to the signal input section of the temperature detection section 105.

[0030] The potential at point A, which is the potential at the + input terminal of operational amplifier 155, is impedance converted by a voltage follower formed by operational amplifier 155, and then input to temperature detection unit 105. Here, the thermistor read range switching signal S1 is normally set to a high "H" level, and is set to a low "L" level during a thermistor open check.

[0031] Therefore, if the resistance value between points A and B is the detected resistance value, when the thermistor read range switching signal S1 is at the “H” level, FET 152 is shorted, so the detected resistance value is the resistance value of resistor 153, and when the thermistor read range switching signal S1 is at the “L” level, FET 152 is open, so the detected resistance value is the total resistance value of resistors 153 and 154.

[0032] Therefore, the potential at point A, which is the potential at the + input terminal of operational amplifier 155, is a voltage value obtained by dividing the power supply potential of 3.3 V by the resistance value of side thermistor 62, an element whose resistance value changes depending on temperature, and the detected resistance value, and changes depending on the temperature of the fixing unit 40 (heat roller 41) based on the heat generated by heater 61.

[0033] Here, the thermistor used as side thermistor 62 is an element whose resistance changes with temperature, but since the characteristic is not completely linear with respect to temperature, the region in which linearity can be ensured (where precision can be achieved) is changed by changing the detection resistance value.

[0034] 5 is a graph showing the relationship between the detected temperature [°C] detected by side thermistor 62 and the AD value (digital value) [0 to 1023] output by the A / D converter provided in temperature detection unit 105. FIG. 5(a) shows the characteristics of the toner fixing actual use range (area enclosed by dotted line), which is the high temperature range set during normal use, and FIG. 5(b) shows the characteristics of the thermistor open check judgment range (area enclosed by dotted line) set during a thermistor open check. Hereinafter, the toner fixing actual use range may be referred to as the high temperature range, and the thermistor open check judgment range may be referred to as the low temperature range.

[0035] As shown in Figure 5(a), under normal circumstances, a linear characteristic is obtained in the high temperature range of detection temperature from approximately 130[°C] to 180°C[°C], and as shown in Figure 5(b), during a thermistor open check, the thermistor read range switching signal S1 is switched so that a linear characteristic is obtained in the low temperature range of detection temperature from approximately -25[°C] to -5°C[°C].

[0036] That is, when accuracy is desired in the high temperature range, the thermistor read range switching signal S1 is set to "H" level, the detection resistance value is the resistance value of resistor 153, and the temperature detection sensitivity is lowered, and when accuracy is desired in the low temperature range, the thermistor read range switching signal S1 is set to "L" level, and the detection resistance value is the total resistance value of resistors 153 and 154, and the temperature detection sensitivity is increased. Here, the resistance value of resistor 153 is set to 10 kΩ, and the resistance value of resistor 154 is set to 330 kΩ to adjust the high temperature range and low temperature range. Note that increasing the temperature detection sensitivity corresponds to the second temperature reading sensitivity, and decreasing the temperature detection sensitivity corresponds to the first temperature reading sensitivity.

[0037] In the above configuration, a method for detecting the mounting of the fixing unit 40 according to the present invention will be described.

[0038] The installation detection of the fixing unit 40 is made based on a comprehensive judgment result of a thermistor judgment process, which judges whether or not the fixing unit 40 is in an open state based on the detection temperature detected using the side thermistor 62, and the stored contents of a cover open state storage process, which judges and stores the open / closed state of the top cover 45.

[0039] The open state here refers to a state in which a disconnection has occurred between point G and point H on the side thermistor 62 side in Figure 4, where the side thermistor 62 itself is defective (disconnected) or the fixing unit 40 is not installed, and hereinafter may be referred to as the open state of the temperature detection system.

[0040] First, the thermistor determination process performed by the fixing unit mounting determination section 102 will be described with reference to the flowchart shown in Fig. 6. Fig. 6 is a flowchart showing the flow of the thermistor determination process. Note that this thermistor determination process is performed in step S404 in the fixing unit mounting determination process (see Fig. 9) described later.

[0041] When the process starts, the thermistor read range switching signal S1 is changed from "H" level to "L" level to switch the read range from the high range to the low range (step S101), and after waiting (for example, 20 ms) for the temperature detection signal (for example, the voltage value at point P) to stabilize, the temperature detection value (AD value) of the side thermistor 62 detected sequentially by the temperature detection unit 105 is read, for example, five times every 5 ms (step S103).

[0042] The thermistor read range switching signal S1 is changed from "L" level to "H" level to change the read range back from the low temperature range to the high temperature range (step S104), and the read values ​​read in step S103 are averaged (step S105). Note that instead of simple averaging, processing to remove signal noise may be performed, such as averaging three out of five readings excluding the top and bottom.

[0043] Next, the average value obtained in step S105 is compared with a predetermined open determination threshold (step S106). The open determination threshold as the second threshold at this time is preferably set to an extremely low temperature value, such as -20°C (AD value of 110 to 120). That is, the detected temperature in a normal state may drop to around 0°C, while in an open state, the AD value is close to 0 and the detected temperature is much lower than -20°C, so the threshold here is set to -20°C.

[0044] If the average value is higher than the open judgment threshold (step S106, Yes), the side thermistor 62 is determined to be not in an open state. If the average value is equal to or lower than the open judgment threshold (step S106, No), the processes from step S101 to step S106 are repeated a maximum Max number of times (step S108, No). If the average value is still equal to or lower than the open judgment threshold even after the Max number of times (e.g., 3 times) (step S108, Yes), the side thermistor 62 is determined to be in an open state, and the flow ends.

[0045] Therefore, if it is determined that the side thermistor 62 is in an open state, this indicates that the side thermistor 62 itself is defective (disconnected) or that the fixing unit 40 is not installed, whereas if it is determined that the side thermistor 62 is not in an open state, this indicates that the fixing unit 40 is installed and that the side thermistor 62 is in a normal state.

[0046] The above-mentioned thermistor determination process usually takes about 300 ms. In recent years, the FPOT (First Print Out Time) required for image forming devices such as printers is only a few seconds, so it is better to shorten it even by about 300 ms. Note that FPOT here is the time required from when the print data starts to be received from the host until the first sheet of recording paper 50 is discharged outside the image forming device 1.

[0047] Therefore, before actually entering the thermistor determination process, it is desirable to incorporate a necessity determination process that skips the thermistor determination process when it is not necessary to execute the thermistor determination process. Fig. 7 is a flowchart showing the thermistor determination process with necessity determination that incorporates this necessity determination process and is performed by the fixing unit implementation determination section 102, and the thermistor determination process with necessity determination will be described based on this flowchart.

[0048] When the process starts, the temperature detection value (AD value) is read (step S201) while the thermistor read range switching signal S1 is at the "H" level and the read range is set to the high temperature range. If the temperature detection value read here is within a predetermined temperature range, for example, between 40°C and 180°C here (step S202, Yes), the flow ends without performing the thermistor determination process. If it is not within the range (step S202, No), the thermistor determination process shown in Figure 6 is executed (step S203).

[0049] Here, in step S202, it is determined whether the read temperature detection value is within a predetermined temperature range, but it may be determined whether the temperature detection value is equal to or higher than the lower limit (40° C.) of the temperature range. The lower limit (40° C.) of the predetermined temperature range corresponds to a first threshold value.

[0050] Therefore, in this thermistor determination process with necessity determination, if it is determined in step S202 that the side thermistor 62 can normally detect the temperature of the heat roller 41 heated by the heating control of the heater 61 of the fixing unit 40, it is determined at that stage that the fixing unit 40 is attached and the side thermistor 62 is in a normal state. This eliminates the need to execute the thermistor determination process at unnecessary times.

[0051] Next, a cover open state storage process performed by the sub-CPU 103 as a cover open / close determination unit will be described with reference to the flowchart shown in Fig. 8. Fig. 8 is a flowchart showing the flow of the cover open state storage process for determining whether or not the top cover 45 is open.

[0052] This flow starts when the main power supply of the image forming apparatus 1 is turned on, and the cover open memory value in the memory unit 104 is set to "Yes" (step S301). As a result, if the main power supply of the image forming apparatus 1 is turned off (if the power supply is unplugged or there is a power outage), the cover open memory value is latched to the "Yes" state the next time the main power supply is turned on.

[0053] Next, the cover open sensor 46 monitors whether the top cover 45 is closed (step S203, No), and when it detects that the top cover 45 is closed (step S302, Yes), the device initialization process is executed (step S303). Note that the device initialization process here refers to various error checks, consumables status checks, etc.

[0054] If the initial process has ended normally (step S304, Yes), the cover open stored value in storage unit 104 is set to "No" (step S305), and the cover open sensor 46 then monitors whether top cover 45 is open (step S306, No). If it detects that top cover 45 is open (step S306, Yes), the cover open stored value in storage unit 104 is set to "Yes" (step S307), and the process transitions to step S302, where the open / closed state of top cover 45 is monitored while the main power of image forming apparatus 1 is on.

[0055] If the device initialization process in step S303 does not end normally (step S304, No), an "error" message is displayed on the display unit 107 and the cover open state storage process ends.

[0056] Therefore, in the cover open state storage process, the open / closed state of the top cover 45 is monitored while the main power supply of the image forming apparatus 1 is on. Then, when the power supply is turned on or while the top cover 45 is open, the cover open storage value "Yes" is stored, and when the top cover 45 is closed, the device initialization process is executed, and when the device initialization process is normally completed, the cover open storage value "No" is stored. However, if the device initialization process is not normally completed, an "error" message is displayed on the display unit 107, and the cover open state storage process is terminated.

[0057] Next, a fixing unit installation determination process performed by the fixing unit installation determination section 102 to determine whether the side thermistor 62 itself is in a disconnected state or whether the fixing unit 40 is not installed will be described with reference to the flowchart shown in Fig. 9. Fig. 9 is a flowchart showing the flow of the fixing unit installation determination process.

[0058] Here, the cover open state storage process comprehensively judges the cover open memory value that is constantly stored and updated in the memory section 104 of the sub-CPU 103 and the result of the above-mentioned thermistor judgment process to determine the mounting of the fixing unit 40 and each state of the side thermistor 62.

[0059] The fixing unit mounting determination process is executed when the image forming apparatus 1 is turned on, when printing starts, and when the apparatus is initialized when the top cover is closed (various error checks, consumables status checks, etc.).

[0060] When the process starts, first, the cover open storage value stored in the storage unit 104 of the sub CPU 103 is read (step S401), and a process is performed to determine whether or not it is necessary to perform thermistor determination process (step S402). The process here corresponds to the processes in steps S201 and S202 of the above-mentioned thermistor determination process with necessity determination (see FIG. 7).

[0061] If the determination in step S402 is that thermistor determination processing is not required (corresponding to step S202, Yes) (step S403, No), this means that with the fixing unit 40 installed, the side thermistor 62 is correctly detecting the heating temperature of the heater 61, and the processing is terminated.

[0062] If it is determined in step S402 that the thermistor determination process is necessary (corresponding to No in step S202) (Yes in step S403), the thermistor determination process described in FIG. 6 is executed (step S404).

[0063] If the determination in step S404 is that the printer is not in an open state (corresponding to step S107) (step S405, No), this means that the fixing unit 40 is installed and the side thermistor 62 is properly detecting the heating temperature of the heater 61, and the process is terminated.

[0064] If it is determined in step S404 that the side thermistor 62 is in an open state (corresponding to step S109) (Yes in step S405), this indicates that the side thermistor 62 itself is defective or that the fixing unit 40 is not mounted.

[0065] For this reason, the sub-CPU 103 reads out the cover open stored value from the storage section 104, and if the cover open stored value is "absent", i.e., the top cover 45 is closed (step S406, Yes), it is determined that the side thermistor 62 itself is open (defective) (step S407), and if the cover open stored value is "present", i.e., the top cover 45 is open (step S406, No), it is determined that the fixing unit 40 is not attached (step S408). Note that the process from step S404 onwards corresponds to the first determination process.

[0066] If the cover open memory value is determined to be "none" in step S406, this means that the device initialization process, which does not terminate normally unless the fixing unit 40 is installed, has terminated normally, so in step S407, it is determined that the side thermistor 62 itself is open (disconnected) with the fixing unit 40 installed.

[0067] Furthermore, if the cover open memory value is determined to be "present" in step S406, it is possible that the fixing unit 40 has been removed, or that "although it appears to be attached, a connector misfit occurred between the fixing unit 40 and the main body of the image forming apparatus 1 when it was inserted or removed", so it is determined that "the fixing unit is not installed" when the thermistor is detected to be open. Note that step S401 corresponds to the first step, steps S404 and S405 correspond to the second step, and steps S406 to S408 correspond to the third step.

[0068] Here, cases where it is determined to be in an open state include a defect (disconnection) in side thermistor 62 itself, not only when fixing unit 40 is not installed, but also when the connector between fixing unit 40 and the main body of image forming apparatus 1 is not properly fitted. Taking this situation into consideration, when it is determined that the fixing unit is not installed (step S408), it is desirable to display a message on display unit 107 that prompts the user to take action, such as "Please check that the fixing unit is set correctly."

[0069] Variation 1. 10 is a flowchart of Variation 1 of the thermistor determination process with necessity determination in the first embodiment shown in FIG. 7, and FIG. 11 is a flowchart of Variation 1 of the fixing unit mounting determination process in the first embodiment shown in FIG.

[0070] As shown in FIG. 2, in the fixing unit 40 of the present embodiment 1, an example is shown in which one side thermistor 62 is arranged facing one end of the heat roller 41 as an internal temperature sensor, but in the variant example 1 here, multiple thermistors are arranged, for example, facing both ends and the center of the heat roller 41.

[0071] In this case, in the thermistor determination process with necessity determination of the first modified example, it is determined whether or not all of the multiple thermistors serving as temperature sensors are within a predetermined temperature range, as is carried out in step 502 of the flowchart in Fig. 10. The other processes in steps S501 and S503 are exactly the same as the processes in steps S201 and S203 in the flowchart in Fig. 7 described above, and therefore description thereof will be omitted here.

[0072] Similarly, in the fixing unit mounting determination process of Modification 1, it is determined whether all of the multiple thermistors serving as all temperature sensors are open, as is performed in step S605 of the flowchart in Fig. 11. The other processes in steps S601 to S604 and steps S606 to S608 are exactly the same as the processes in steps S401 to S404 and steps S406 to S408 in the flowchart in Fig. 9, and therefore description thereof will be omitted here.

[0073] However, in the case of Modification 1, a check is made on multiple temperature sensors (thermistors) to see if they are open, but the probability that all thermistors are defective is extremely low, so when it is determined that all are open (S605, Yes), it is highly likely that the fixing unit 40 is not yet attached. Therefore, the effect of the processing of Modification 1, which performs steps S606 and onwards, is modest.

[0074] As described above, according to the fixing device installation detection method of this embodiment, it is possible to determine whether the side thermistor 62 itself acting as a temperature sensor is in a disconnected state or whether the fixing unit 40 is not installed, by using the determination results of the open state of the temperature detection system and the open / closed state of the top cover 45, without adding any new sensors or circuits. [Industrial Applicability]

[0075] The present invention can be used in image forming apparatuses (such as copying machines, facsimiles, printers, and multi-function machines) that form images on media by using an electrophotographic system. [Explanation of symbols]

[0076] 1 image forming apparatus, 12 paper feed tray, 15 pickup roller, 16 paper feed roller, 17 separation roller, 18 conveying roller pair, 19 registration roller pair, 20 discharge roller pair, 21 discharge roller pair, 22 entrance sensor, 23 writing sensor, 24 discharge sensor, 25 paper feed section, 30 image forming unit, 31 photosensitive drum, 32 charging roller, 33 developing roller, 34 supply roller, 35 developing blade, 36 toner cartridge, 37 LED head, 38 transfer roller, 40 fixing unit, 41 heat roller, 42 backup roller, 43 beam, 44 thermopile, 45 top cover, 46 cover open sensor, 50 recording paper, 61 heater, 62 side thermistor, 101 printer control section, 102 fixing unit implementation determination section, 103 sub-CPU, 104 memory section, 105 temperature detection section, 106 heater control section, 107 display section, 108 high voltage power supply unit, 109 discharge motor, 110 main motor, 111 low voltage power supply unit, 152 FET, 153 resistor, 154 resistor, 155 operational amplifier.

Claims

1. a fixing device that is detachably mounted on the image forming apparatus body and fixes the developer onto the print medium by applying pressure and heat; a temperature sensor provided in the fixing device; a temperature detection unit that detects the temperature of the fixing device based on information from the temperature sensor; a cover open / close determination unit that determines whether a cover for opening and closing the image forming apparatus body is open or closed based on information from an open / close sensor that detects whether the cover is open or closed when the fixing device is attached or detached, and stores the open / close information; a mounting determination unit that determines a mounting state of the fixing device in the main body of the image forming apparatus; Equipped with The image forming apparatus is characterized in that the installation determination unit performs a first determination process to determine whether the temperature detection unit is detecting the temperature of the fixing device normally, and if the temperature detection unit is not detecting the temperature normally, determines that the temperature sensor is disconnected if the cover is determined to be closed by the cover opening / closing determination unit, and determines that the fixing device is not installed if the cover is determined to be open.

2. 2. The image forming apparatus according to claim 1, wherein the mounting determination section does not perform the first determination process when the temperature detected by the temperature detection section is equal to or higher than a first threshold value.

3. 2. The image forming apparatus according to claim 1, wherein the mounting determination section does not perform the first determination process when the temperature detected by the temperature detection section is within a predetermined range having a first threshold as a lower limit.

4. 3. The image forming apparatus according to claim 2, wherein the mounting determination unit determines that the temperature detection unit is not detecting the temperature of the fixing device normally when the detected temperature of the temperature detection unit is equal to or lower than a second threshold value that is lower than the first threshold value.

5. 3. The image forming apparatus according to claim 1, wherein the cover open / close determining unit determines that the cover is closed when the cover is closed and an initial process for the apparatus is normally completed.

6. 6. The image forming apparatus according to claim 5, wherein the apparatus initial processing includes an error check and a consumables status check of the apparatus.

7. 5. The image forming apparatus according to claim 4, wherein the temperature detection unit has a second temperature reading sensitivity when reading the detected temperature to be compared with the second threshold value that is higher than a first temperature reading sensitivity when reading the detected temperature to be compared with the first threshold value.

8. 3. The image forming apparatus according to claim 1, wherein the temperature sensor is disposed in the vicinity of a heating member of the fixing device.

9. 3. The image forming apparatus according to claim 1, wherein the temperature sensor is disposed in a main body of the fixing device.

10. A method for detecting whether a fixing device is mounted in an image forming apparatus, comprising: a first step of determining an open / closed state of a cover for opening and closing the main body of the image forming apparatus; a second step of determining whether a temperature detected based on a temperature sensor provided in the fixing device is normally detected; a third step of determining that the temperature sensor is disconnected if the cover is determined to be in a closed state in the first step when it is determined that the detected temperature is not normally detected in the second step, and determining that the fixing device is not installed if the cover is determined to be in an open state in the first step; 13. A fixing device mounting detection method comprising:

11. 11. The mounting detection method for a fixing device according to claim 10, further comprising: determining whether the detected temperature is equal to or higher than a first threshold value following the first step; and if the detected temperature is equal to or higher than the first threshold value, not performing the second step and the third step.

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