Image forming apparatus

Abstract

To prevent acquisition of outside temperature with low accuracy.SOLUTION: An image forming apparatus 1 comprises: a housing 10; a process unit 30 that forms a toner image on a sheet S; a fixing unit 40 that is arranged inside the housing 10, and fixes the toner image to the sheet S; a first temperature sensor 61 that detects the atmospheric temperature inside the housing 10; a second temperature sensor 63 that detects the temperature of the fixing unit 40; a fan 62 that exhausts air inside the housing 10; and a control unit 80 that acquires the temperature outside the housing 10 on the basis of a detection value from the first temperature sensor 61, a detection value from the second temperature sensor 63, and the operating time of the fan 62.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an image forming apparatus. The image forming apparatus of Patent Document 1 includes an internal temperature sensor, an external temperature calculation unit, a storage unit, a mode determination unit, and a clock unit. The internal temperature sensor detects an internal temperature, which is the temperature inside the apparatus body. The mode determination unit determines whether the current mode is a normal mode or a sleep mode. The storage unit stores correction data obtained by converting the difference between the internal temperature detected by the internal temperature sensor and the external temperature into data using the elapsed time from the start of each mode as a parameter. The clock unit estimates the elapsed time from the start of the mode determined by the mode determination unit to the current time. The external temperature calculation unit reads from the correction data a correction value for the current mode determined by the mode determination unit and for the time domain from the start of the mode measured by the clock unit to the current time, and obtains a temperature obtained by subtracting the correction value from the temperature detected by the internal temperature sensor as the external temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-79057 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the normal mode, the image forming apparatus receives various instructions from the user, and the operating conditions of the components of the image forming apparatus (such as the fixing unit) also vary depending on the contents of the instructions, and are not always the same. In contrast, the correction data stored in the storage unit is merely data that represents the difference between the internal temperature and the outside temperature when the components of the image forming apparatus reach a specific operating condition in the normal mode, with the elapsed time as a parameter. Therefore, if the actual operating conditions of the components of the image forming apparatus differ from the operating conditions assumed by the correction data, the correction value read from the correction data does not reflect the actual operating conditions of the image forming apparatus, and is an inaccurate value. As a result, there is a possibility that an outside temperature with low accuracy will be obtained.

[0005] An object of the present disclosure is to provide an image forming apparatus that can prevent low-accuracy acquisition of outside air temperature. [Means for solving the problem]

[0006] The image forming apparatus disclosed in this specification includes a housing, a process unit that forms a toner image on a sheet, a fixation unit disposed inside the housing that fixes the toner image to the sheet, a first temperature sensor that detects the ambient temperature inside the housing, a second temperature sensor that detects the temperature of the fixation unit, a fan that exhausts air from inside the housing, and a control unit that obtains the outside air temperature of the housing based on the detection value of the first temperature sensor, the detection value of the second temperature sensor, and the operating time of the fan.

[0007] Since the outside air temperature can be obtained by taking into account the operating status of the components of the image forming apparatus, such as the temperature of the fixing unit (the detection value of the second temperature sensor) and the operating time of the fan, it is possible to prevent obtaining an outside air temperature with low accuracy.

[0008] Conditions may be set for the control unit to acquire the outside air temperature of the housing, the conditions including a first condition that the continuous operation time of the fan is within a first predetermined time, and a second condition that the detection value of the first temperature sensor is equal to or greater than a value obtained by subtracting a first predetermined value from the detection value of the second temperature sensor.

[0009] By setting the operating time of the fan and the difference between the detection value of the first temperature sensor and the detection value of the second temperature sensor as conditions, it is possible to identify the conditions for the control unit to obtain the outside air temperature of the housing.

[0010] The control unit may be configured to acquire, when the first condition and the second condition are satisfied, a temperature based on a detection value of the first temperature sensor as the outside air temperature of the housing.

[0011] Even if the first condition is satisfied in an environment in which the fan operating time is short and the fixing unit can have a thermal effect on the first temperature sensor, the control unit can obtain the outside air temperature of the housing as long as the second condition is satisfied in a situation in which the first temperature sensor is not affected by the heat of the fixing unit due to the temperature difference between the first temperature sensor and the fixing unit.

[0012] The control unit may be configured to, when the first condition is not satisfied, acquire the detection value of the first temperature sensor as the outside air temperature of the housing, regardless of whether the second condition is satisfied or not.

[0013] When the first condition is not satisfied and the continuous operation time of the fan is longer than the first predetermined time, the fan can effectively ventilate the inside of the housing to bring outside air around the first temperature sensor, thereby allowing the control unit to obtain the outside air temperature of the housing regardless of the temperature of the fixing unit.

[0014] The control unit may be configured to operate the fan when power is applied to the fixing unit, and if the first condition and the second condition are satisfied, and the fan has operated continuously for more than a second predetermined time in the past and the time that has elapsed since the fan stopped operating is within a third predetermined time, acquire a value obtained by subtracting a second predetermined value from the detection value of the first temperature sensor as the outside air temperature of the housing.

[0015] If the fan has operated continuously for more than a second specified time in the past and the time that has elapsed since it stopped operating is within a third specified time, the accumulated heat generated by the fixing unit in the past remains inside the housing at the present, and the control unit can obtain the value obtained by subtracting a second specified value, which is the amount of accumulated heat, from the detection value of the first temperature sensor as the outside air temperature of the housing.

[0016] The control unit may be configured to operate the fan when power is applied to the fixing unit, and if the first condition and the second condition are satisfied, and the fan has operated continuously for more than a second predetermined time in the past, and the time that has elapsed since the fan stopped operating is longer than a third predetermined time, acquire the detection value of the first temperature sensor as the outside air temperature of the housing.

[0017] If the fan has operated continuously for more than a second specified time in the past and the time that has elapsed since it stopped operating is longer than a third specified time, it can be assumed that the heat accumulated in the housing due to the heat generated by the fixing unit in the past has been eliminated or reduced, and the control unit can acquire the detection value of the first temperature sensor as the outside air temperature of the housing.

[0018] The control unit may be configured not to acquire the outside air temperature of the housing when the first condition is satisfied but the second condition is not satisfied.

[0019] When the first condition is satisfied, the fan operating time is short, and when the second condition is not satisfied, the fixing unit is in a high temperature environment, and therefore the ambient temperature inside the housing and the actual outside air temperature of the housing differ significantly, the control unit does not acquire the detection value of the first temperature sensor as the outside air temperature of the housing, thereby effectively preventing the acquisition of an outside air temperature with low accuracy.

[0020] The control unit may be configured to include a memory unit that stores the outside air temperature of the housing, and the control unit performs processing to obtain the outside air temperature of the housing based on the conditions every time an update time shorter than the first predetermined time elapses, and when the latest outside air temperature of the housing is obtained, updates the outside air temperature stored in the memory unit to the latest outside air temperature, and does not update the outside air temperature stored in the memory unit unless the latest outside air temperature is obtained.

[0021] By performing a process for acquiring the outside air temperature of the housing every time the update time elapses, the outside air temperature stored in the memory unit can be continuously updated. Also, if the outside air temperature to be stored in the memory unit is not acquired, the control unit can perform various controls using the outside air temperature currently stored in the memory unit.

[0022] The control unit may be configured to control the fixing unit based on the acquired outside air temperature of the housing.

[0023] Since the fixing unit is affected by the outside temperature, it can operate stably by being controlled based on the obtained outside temperature.

[0024] The control unit may be configured to control the fixing unit so that the temperature of the fixing unit becomes a first predetermined target temperature when the outside air temperature of the housing is equal to or higher than a first predetermined outside air temperature, and to control the fixing unit so that the temperature of the fixing unit becomes a second predetermined target temperature higher than the first predetermined target temperature when the outside air temperature of the housing is lower than the first predetermined outside air temperature.

[0025] In a low-temperature environment where the outside air temperature of the housing is lower than a first predetermined outside air temperature, the control temperature of the fixing unit is increased to compensate for the heat absorbed by the fixing unit from the outside air, thereby stabilizing the fixability of the toner image.

[0026] The control unit may be configured to reduce a throughput of the fixing unit when the outside air temperature of the housing is lower than a second predetermined outside air temperature that is lower than the first predetermined outside air temperature.

[0027] In a low-temperature environment where the outside air temperature of the housing is lower than the second predetermined outside air temperature, the fixability of the toner image can be stabilized by lowering the throughput of the fixing unit.

[0028] The housing may be provided with an air intake port that communicates between the inside and outside of the housing, and the first temperature sensor may be disposed inside the housing and facing the air intake port.

[0029] By arranging the first temperature sensor opposite the air intake, outside air can be effectively sent to the first temperature sensor through the air intake, and the first temperature sensor can detect the outside air temperature with high accuracy.

[0030] The fixing unit may include a roller that feeds a sheet, and the fan and the first temperature sensor may be positioned on opposite sides of the fixing unit in a rotational axial direction of the roller.

[0031] By locating the fan and the first temperature sensor on opposite sides of the fixing unit, an air passage leading from the first temperature sensor to the fan can be formed. By disposing the fixing unit in the passage, the heat of the fixing unit can be sent to the fan through the passage, thereby reducing the effect of the heat of the fixing unit on the first temperature sensor.

[0032] The fixing unit may include a substrate and a heater having a resistive heating element disposed on the substrate, and the second temperature sensor may be configured to be in contact with the substrate.

[0033] The fan may be located between the rotation axis of the roller and the first temperature sensor when viewed in the direction of the rotation axis of the roller.

[0034] By positioning the fan between the rotation axis of the roller and the first temperature sensor as viewed in the direction of the rotation axis of the roller, the first temperature sensor is farther away from the fixing unit than the fan, and thus by separating the first temperature sensor from the fixing unit, the influence of heat from the fixing unit on the first temperature sensor can be reduced. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a perspective view of an image forming apparatus. [Diagram 2] FIG. 2 is a side view of the image forming apparatus. [Diagram 3] FIG. 3 is a central cross-sectional view showing an outline of the image forming apparatus. [Figure 4] Fig. 4(a) is a perspective view of the fixing unit, Fig. 4(b) is a cross-sectional view of the fixing unit, and Fig. 4(c) is a plan view showing the holder and the first temperature sensor. [Diagram 5] FIG. 5 is a perspective view showing the positional relationship between the fixing unit, the first temperature sensor, and the fan. [Figure 6] FIG. 6 is a block diagram showing the configuration of the image forming apparatus. [Figure 7] FIG. 7 is a flowchart showing a first example of the process of the control unit. [Figure 8] FIG. 8 is a flow diagram showing the acquisition process. [Figure 9] FIG. 9 shows the test results. [Figure 10] FIG. 10 is a flowchart showing a second example of the process of the control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical idea of ​​the present disclosure. Since each drawing is intended to conceptually explain the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for easy understanding. In each embodiment, each modified example, and in the drawings, the same or equivalent components are given the same reference symbols, and different components are given different reference symbols, and detailed descriptions of the components given the same reference symbols and descriptions of the effects associated therewith will not be repeated.

[0037] An image forming apparatus 1 according to an embodiment of the present invention will be described. The image forming apparatus 1 of this embodiment is a laser printer. In the following, the depth direction of the image forming apparatus 1 is defined as the front-rear direction, the width direction of the image forming apparatus 1 is defined as the left-right direction, and the height direction of the image forming apparatus 1 is defined as the up-down direction, defining the front-rear, up-down, left-right directions.

[0038] (1) Structure of the housing of the image forming device As shown in Figures 1 and 2, the image forming apparatus 1 includes a housing 10. The housing 10 is a hollow member having a substantially rectangular parallelepiped shape. The housing 10 includes a plurality of covers covering the top, bottom, left, right, front, and back. The space surrounded by the plurality of covers is defined as the interior of the housing 10. The plurality of covers include a first side cover 11, a second side cover 12, a top cover 13, and a front cover 14.

[0039] The first side cover 11 and the second side cover 12 are disposed at an interval in the left-right direction. The second side cover 12 is disposed to the right of the first side cover 11. Top cover 13 is provided from the upper part of the first side cover 11 to the upper part of the second side cover 12. The front cover 14 is rotatably supported between the front part of the first side cover 11 and the second side cover 12, and opens and closes the front part of the housing 10.

[0040] The housing 10 includes a first frame 15a and a second frame 15b. The first frame 15a is disposed facing the first side cover 11 from the left side. The second frame 15b is disposed facing the second side cover 12 from the right side.

[0041] The housing 10 is provided with an intake port 18 and an exhaust port 19. Each of the intake port 18 and the exhaust port 19 passes between the inside of the housing 10 and the outside of the housing 10. The intake port 18 is disposed in the front part and toward the upper part of the first side cover 11. The exhaust port 19 is disposed in the front-rear central part and toward the upper part of the second side cover 12.

[0042] (2) Internal structure of the case As shown in FIG. 3, the image forming apparatus 1 includes a paper feed section 20, a process section 30, a fixing unit 40, and a paper discharge section 50.

[0043] The paper feed section 20 includes a paper feed tray 21, a paper feed mechanism 22, a conveying roller pair 23, and a registration roller pair 24. The paper feed tray 21 stores sheets S. The paper feed tray 21 includes a pressure plate 21a that supports the sheets S from below. The paper feed mechanism 22 includes a paper feed roller 22a, a separation roller 22b, and a separation pad 22c. The paper feed roller 22a feeds the sheets S stored in the paper feed tray 21. The separation roller 22b separates the sheets S sent out by the paper feed roller 22a one by one between the separation pad 22c and the paper feed roller 22a. The separated sheets S are transported toward the process section 30 by the conveying roller pair 23 and the registration roller pair 24.

[0044] The process section 30 forms a toner image on a sheet S. The process section 30 includes a process cartridge 31 that transfers the toner image onto the surface of the sheet S, and an exposure unit 32 that exposes the surface of a photosensitive drum 31c in the process cartridge 31 to light.

[0045] With the front cover 14 open, the process cartridge 31 can be attached to and detached from a cartridge attachment position P inside the housing 10. The process cartridge 31 includes a developer accommodating chamber 31a, a developing roller 31b, a photosensitive drum 31c, a transfer roller 31d, and a charger 31e.

[0046] The developer storage chamber 31a stores toner that serves as the developer. The developing roller 31b carries toner that is supplied from the developer storage chamber 31a and positively charged by a supply roller (not shown). The surface of the photosensitive drum 31c is uniformly charged by the charger 31e and then exposed by the exposure unit 32. The exposed portion of the photosensitive drum 31c has a lower potential than the other portions, and an electrostatic latent image based on the image data is formed on the photosensitive drum 31c. Positively charged toner is supplied from the developing roller 31b to the surface of the photosensitive drum 31c on which the electrostatic latent image has been formed, thereby visualizing the electrostatic latent image into a toner image.

[0047] With a transfer bias applied to the surface of the transfer roller 31d, the sheet S is conveyed while being sandwiched between the photosensitive drum 31c on which the toner image is formed and the transfer roller 31d, whereby the toner image formed on the surface of the photosensitive drum 31c is transferred to the surface of the sheet S.

[0048] The fixing unit 40 applies heat and pressure to the sheet S onto which the toner image has been transferred, thereby fixing the toner image to the sheet S. The fixing unit 40 is disposed inside the housing 10. A detailed description of the fixing unit 40 will be given later.

[0049] The paper discharge section 50 includes a paper discharge roller pair 51 and a paper discharge tray 52. ​​The paper discharge roller pair 51 conveys the sheet S conveyed from the fixing unit 40 to the paper discharge tray 52. ​​The paper discharge tray 52 is provided on the top cover 13.

[0050] The image forming apparatus 1 may have a re-conveying path R and a roller pair 25 that conveys the sheet S along the re-conveying path P. The re-conveying path P and the roller pair 25 cause the image forming apparatus 1 to perform double-sided printing by conveying the sheet S that has passed through the process unit 30 and the fixing device 40 back to the process unit 30.

[0051] The image forming apparatus 1 includes a paper discharge sensor 60. The paper discharge sensor 60 is disposed between the fixing unit 40 and the pair of paper discharge rollers 51 in the conveying direction of the sheet S. The paper discharge sensor 60 can detect the sheet S that has passed through the fixing unit 40.

[0052] As shown in FIG. 1 and FIG. 2, the image forming apparatus 1 includes a first temperature sensor 61, a fan 62, and a fan 62. The first temperature sensor 61 detects the temperature inside the housing 10. The first temperature sensor 61 is, for example, a thermistor. The first temperature sensor 61 is disposed inside the housing 10 and is installed on the first frame 15a. The first temperature sensor 61 is disposed inside the air intake 18 and is disposed opposite the air intake 18. The fan 62 has a driving source such as a motor and exhausts air inside the housing 10. The fan 62 is disposed inside the housing 10 and is installed on the second frame 15b. The fan 62 is disposed inside the exhaust port 19 and is disposed opposite the exhaust port 19. As shown by the arrow A in FIG. 1, when the fan 62 rotates, the air inside the housing 10 is sent to the outside of the housing 10 through the exhaust port 19. As a result, as shown by the arrow B in FIG. 1, the air outside the housing 10 is sent to the inside of the housing 10 through the air intake 18. As a result, the inside of the housing 10 is ventilated.

[0053] (3) Fixing unit An example of the configuration of the fixing unit 40 will be described.

[0054] As shown in FIGS. 4(a) to 4(c), the fixing unit 40 includes a heater 41, a belt 42, a holder 43, a pressure port 44, and a stay 45.

[0055] The heater 41 is a heat source and is a plate-like member extending in the longitudinal direction of the fixing unit 40. The heater 41 has a substrate 41A and a resistance heating element 41B. The substrate 41A is in the form of a plate extending along the longitudinal direction of the fixing unit 40. The resistance heating element 41B is provided on the substrate 41A along the longitudinal direction of the fixing unit 40.

[0056] The substrate 41A is made of, for example, a ceramic material, and two resistance heating elements 41B are formed in parallel to each other on one surface of the substrate 41A by, for example, print patterning. In addition, wiring and terminals for supplying power to the resistance heating elements 41B are also provided on the substrate 41A.

[0057] The belt 42 is an endless belt that includes an inner circumferential surface 42A that contacts the heater 41 and rotates around the heater 41. The belt 42 is a cylindrical member with a low heat capacity. The belt 42 is made of a single-layer or composite-layer film that has heat resistance, releasability, strength, durability, and the like.

[0058] The holder 43 is a member that supports the heater 41 and rotates and holds the belt 42, and is made of a resin material having heat resistance and insulating properties. The holder 43 has a support surface 43A that supports the heater 41. The support surface 43A supports the heater 41, facing the surface of the heater 41 opposite to the resistance heating element 41B. The heater 41 has a surface on which the resistance heating element 41B is provided. The surface of the belt 42 faces the inner circumferential surface 42A of the belt 42.

[0059] The pressure nozzle 44 forms a nip portion N by sandwiching the belt 42 between itself and the surface of the heater 41. Both ends of the pressure nozzle 44 are supported by a pair of side frames via bearings. The pressure nozzle 44 is rotated by a drive source such as a motor included in the image forming apparatus 1, and the belt 42 rotates in accordance with the rotation of the pressure nozzle 44. When the pressure nozzle 44 rotates, the sheet S is heated and pressurized in the nip portion N while being fed. The sheet S to which the toner image has been transferred by the process unit 30 is heated and pressurized in the nip portion N, so that the toner image is fixed to the sheet S.

[0060] The stay 45 is a member for increasing the rigidity of the holder 43, and is disposed on the opposite side to the support surface 43A of the holder 43. When the rigidity of the holder 43 is high, the stay 45 can be omitted.

[0061] The image forming apparatus 1 includes a second temperature sensor 63. The second temperature sensor 63 detects the temperature of the fixing unit 40. In this embodiment, the second temperature sensor 63 includes a first sensor 63a and a second sensor 63b. As shown in FIG. 4C, each of the first sensor 63a and the second sensor 63b is provided to face the rear surface 43B of the holder 43 opposite to the support surface 43A. Holes 43C and 43D are formed in the rear surface 43B of the holder 43. The first sensor 63a contacts the rear surface of the substrate 41A through the hole 43C. The second sensor 63b contacts the rear surface of the substrate 41A through the hole 43D.

[0062] (4) Positional relationship between the fixing unit, the first temperature sensor, and the fan 5, the fan 62 and the first temperature sensor 61 are located on opposite sides of the fixing device 40 in terms of the position in the rotation axis direction of the pressure port-ruler 44. The rotation axis direction is the direction in which the rotation axis 44a of the pressure port-ruler 44 extends, which is the left-right direction in this embodiment. In this embodiment, in terms of the left-right position, the fan 62 is located on the right side of the fixing device 40, and the first temperature sensor 61 is located on the left side.

[0063] When viewed in the direction of the rotation axis of the pressurizing port-ruler 44 (left-right direction), the fan 62 is located between the rotation axis 44a of the pressurizing port-ruler 44 and the first temperature sensor 61. In this embodiment, the fan 62 is an axial fan having a rotation axis 62a in a direction (left-right direction) perpendicular to the second side cover 12, and when viewed in the direction of the rotation axis of the pressurizing port-ruler 44, among the pressurizing port-ruler 44, the first temperature sensor 61, and the fan 62, the first temperature sensor 61 is located at the frontmost position, the rotation axis 44a of the pressurizing port-ruler 44 is located at the rearmost position, and the rotation axis 62a of the fan 62 is located in the center between the front and rear.

[0064] (5) Other configurations of the image forming apparatus As shown in FIG. 6, the image forming apparatus 1 includes a storage unit 70 and a control unit 80.

[0065] The storage unit 70 includes a main storage device (e.g., a semiconductor memory) such as a Read Only Memory (ROM) and a Random Access Memory (RAM), and may further include a non-volatile auxiliary storage device such as a Non-Volatile Memory (NVM). The storage unit 70 stores various computer programs executed by the control unit 80.

[0066] The storage unit 70 stores the outside air temperature of the housing 10. More specifically, the outside air temperature of the housing 10 stored in the storage unit 70 is not the actual outside air temperature of the housing 10, but an estimated value of the outside air temperature of the housing 10. The control unit 80 controls the fixing unit 40 based on the outside air temperature stored in the storage unit 70.

[0067] The control unit 80 includes an ASIC (Application Specific Integrated Circuit). The control unit 80 may include a processor such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The control unit 80 controls each element of the image forming apparatus 1 by executing a computer program stored in the storage unit 70.

[0068] As shown in FIG. 1, FIG. 3 and FIG. 6, when performing a printing operation in which an image is formed on a sheet S by the process unit 30 and the image is fixed on the sheet S by the fixing unit 40, the control unit 80 energizes the fixing unit 40 to raise the temperature of the fixing unit 40 to a predetermined target temperature. The printing operation includes not only a case in which an image is formed and fixed on a single sheet S, but also a case in which an image is continuously formed and fixed on a plurality of sheets S. During the printing operation, the control unit 80 feeds back the temperature detected by the second temperature sensor 63 and controls the energization of the fixing unit 40 so that the fixing unit 40 reaches a predetermined target temperature. In this embodiment, when the control unit 80 energizes the fixing unit 40, it operates (rotates) the fan 62. As a result, during the printing operation, the heater 41 of the fixing unit 40 generates heat inside the housing 10 by energizing the fixing unit 40, but the heat inside the housing 10 is discharged to the outside of the housing 10 by continuously operating (rotating) the fan 62. When the printing operation is completed, the control unit 80 stops the power supply to the fixing unit 40, and further stops the fan 62.

[0069] (6) Acquisition process by the control unit A description will now be given of the acquisition process performed by the control unit 80. The acquisition process is a process performed by the control unit 80 to acquire the outside air temperature.

[0070] As shown in FIG. 7, in step S1, the image forming apparatus 1 is turned on.

[0071] In step S2, if the image forming apparatus 1 is powered off (Yes in step S2), the process ends. If the image forming apparatus 1 is not powered off (No in step S2), the process proceeds to step S3.

[0072] In step S3, the control unit 80 determines whether an update time has elapsed since the acquisition process was completed. If multiple acquisition processes have been performed in the past, the control unit 80 determines whether an update time has elapsed since the most recent acquisition process among the multiple acquisition processes was completed.

[0073] If the update time has elapsed since the acquisition process was completed (Yes in step S3), the process proceeds to step S4. If the update time has not elapsed since the acquisition process was completed (No in step S3), the process proceeds to step S2.

[0074] In step S4, the control unit 80 performs an acquisition process. When the acquisition process ends, the process proceeds to step S2.

[0075] In this embodiment, the update time is one minute, and the acquisition process is performed every minute.

[0076] The acquisition process (step S4 in FIG. 7) will now be described.

[0077] As shown in FIG. 8, in step S4a, it is determined whether or not all of the first condition, the second condition, and the third condition are satisfied.

[0078] The first condition indicates a condition that the continuous operation time of the fan 62 is within a first predetermined time. The continuous operation time of the fan 62 is, for example, a continuous power supply time to the drive source of the fan 62, and the control unit The count is made by dividing the first predetermined time by 80. The first predetermined time is, for example, 5 minutes. Within the first predetermined time, 0 minutes, i.e., the fan 62 is stopped, is also included. Compared to the first predetermined time, the update time (step S3 in FIG. 7) is shorter.

[0079] In addition, when the fan 62 is operated while power is being applied to the fixing device 40, in the first condition, the continuous operation time of the fan 62 may be read as the continuous power supply time to the fixing device 40. The continuous power supply time to the fixing device 40 is the time during which power supply is controlled so that the fixing device 40 reaches a predetermined target temperature.

[0080] The second condition indicates a condition in which the detection value of the first temperature sensor 61 is equal to or greater than a value obtained by subtracting a first predetermined value from the detection value of the second temperature sensor 63.

[0081] The first predetermined value of the second condition is set to prevent the outside air temperature of the storage unit 70 from being updated due to a misjudgment that the atmosphere inside the housing 10 is not cooled due to detection errors of the first temperature sensor 61 and the second temperature sensor 63. The first predetermined value is, for example, the sum of the maximum detection errors of the first temperature sensor 61 and the second temperature sensor 63. In this embodiment, the detection error of the first temperature sensor 61 is ±2°C, and the detection error of the second temperature sensor 63 is ±6°C, so the first predetermined value is 8°C. Furthermore, by setting the first predetermined value, it is possible to obtain the outside air temperature even when the fixing unit 40 has residual heat sufficient to update the outside air temperature.

[0082] The detection value of the second temperature sensor 63 will be described. In this embodiment, the second temperature sensor 63 is composed of a plurality of sensors, including a first sensor 63a and a second sensor 63b (see FIG. 4(c)). When the second temperature sensor 63 is composed of a plurality of sensors, the detection value of the second temperature sensor 63 is the detection value of at least one of the plurality of sensors (in this embodiment, the detection value of at least one of the first sensor 63a and the second sensor 63b). When the second temperature sensor 63 is composed of a plurality of sensors, the detection value of the second temperature sensor 63 may be the average value of the detection values ​​of the plurality of sensors (in this embodiment, the average value of the detection value of the first sensor 63a and the detection value of the second sensor 63b). Also, unlike this embodiment, when the second temperature sensor 63 provided in the fixing unit 40 is composed of one sensor, the detection value of the second temperature sensor 63 is the detection value of the one sensor.

[0083] The third condition indicates a condition that the fan 62 has operated continuously for a second predetermined time or more in the past, and the time that has elapsed since the fan 62 stopped operating is within a third predetermined time. The second predetermined time is, for example, 3 minutes. The third predetermined time is, for example, 4.5 hours. When the fan 62 has previously ended its continuous operation for the second predetermined time or more, the control unit 80 starts counting the time, and determines whether the third predetermined time has elapsed at present (at the time of determining whether the third condition is satisfied). Note that, in the case where the fan 62 is operated while power is being applied to the fixing unit 40, in the third condition, the fact that the fan 62 has operated continuously for the second predetermined time or more may be interpreted as the fixing unit 40 being continuously powered for the second predetermined time or more.

[0084] If all of the first, second, and third conditions are not satisfied (No in step S4a), the process proceeds to step S4b. If all of the first, second, and third conditions are satisfied (Yes in step S4a), the process proceeds to step S4f.

[0085] In step S4b, if the first condition is not satisfied (Yes in step S4b), the process proceeds to step S4c. If the second condition is satisfied (Yes in step S4b), the process proceeds to step S4c.

[0086] If the first condition is satisfied and the second condition is not satisfied (No in step S4b), The process proceeds to step S4e.

[0087] In step S4c, the control unit 80 acquires the detection value of the first temperature sensor 61 as the outside air temperature. In detail, the control unit 80 acquires the detection value of the first temperature sensor 61 as the outside air temperature when the first condition is not satisfied, and also acquires the detection value of the first temperature sensor 61 as the outside air temperature when the second condition is not satisfied.

[0088] In step S4d, when the control unit 80 acquires the outside air temperature (the detection value of the first temperature sensor 61), it stores the acquired outside air temperature, which is the latest outside air temperature, in the memory unit 70. As a result, the outside air temperature stored in the memory unit 70 is updated to the latest outside air temperature. When the outside air temperature in the memory unit 70 is updated, the acquisition process ends, and the process proceeds to step S2 (see FIG. 7).

[0089] In step S4e, the control unit 80 does not acquire the outside air temperature. As a result, the acquisition process ends without updating the outside air temperature stored in the storage unit 70, and the process proceeds to step S2 (see FIG. 7).

[0090] In step S4f, the control unit 80 acquires a correction value as the outside air temperature. The correction value is a value obtained by subtracting a second predetermined value from the detection value of the first temperature sensor 61. The second predetermined value is, for example, 2°C.

[0091] In step S4g, when the control unit 80 acquires the outside air temperature (correction value), it stores the acquired outside air temperature, which is the latest outside air temperature, in the memory unit 70. As a result, the outside air temperature stored in the memory unit 70 is updated to the latest outside air temperature. When the outside air temperature in the memory unit 70 is updated, the acquisition process ends, and the process proceeds to step S2 (see FIG. 7).

[0092] (7) Test results 9 shows the relationship between time and the temperature difference. The temperature difference is a value obtained by subtracting the actual outside air temperature of the housing 10 from the detection value of the first temperature sensor 61 (ambient temperature inside the housing 10).

[0093] The graph shown in Fig. 9 was obtained by a test conducted by the inventor of the present application. In the test, 12 printing operations were performed with a 10-minute interval between each printing operation. In the test, the fan 62 was operated continuously for 3 minutes or more in each of the 12 printing operations. In the test, the image forming apparatus 1 was kept stopped after the 12th printing operation was completed.

[0094] In Figure 9, point A1 indicates the time when the first printing operation starts, point B1 indicates the time when the first printing operation ends, point A2 indicates the time when the second printing operation starts, point B2 indicates the time when the second printing operation ends, point A3 indicates the time when the seventh printing operation starts, point B3 indicates the time when the seventh printing operation ends, point A4 indicates the time when the twelfth printing operation starts, and point B4 indicates the time when the twelfth printing operation ends.

[0095] As shown by points A1 to A4, when the printing operation is started, the heater 41 of the fixing unit 40 generates heat by energizing the fixing unit 40, but the fan 62 operates continuously to ventilate the inside of the housing 10. As a result, ventilation by the fan 62 progresses over time, and the temperature difference becomes smaller.

[0096] As shown by points B1 to B4, when the printing operation is completed, power supply to the fixing unit 40 is stopped, but the fan 62 is also stopped, suppressing ventilation inside the housing 10. As a result, the residual heat of the fixing unit 40 causes the ambient temperature inside the housing 10 to rise over time, and the temperature difference becomes large.

[0097] As shown by point B4, when the 12th printing operation is completed, the residual heat of the fixing unit 40 causes the ambient temperature inside the housing 10 to rise over time, increasing the temperature difference. After a certain amount of time has passed (the point shown by point A5 in FIG. 9), natural ventilation begins to occur inside the housing 10, and the fixing unit 40 itself also cools naturally, gradually decreasing the ambient temperature inside the housing 10. As a result, from the point shown by point A5, the temperature difference gradually decreases over time.

[0098] When a third predetermined time (4.5 hours in this embodiment) has elapsed as shown at point B5 from the time when the final printing operation (the 12th printing operation) is completed as shown at point B4, the temperature difference becomes about 1.5°C, which is the same as the temperature difference when sufficient ventilation is being performed by the fan 62. After the time shown at point B5, the temperature difference becomes small enough that the detection value of the first temperature sensor 61 can be regarded as the same as the actual outside air temperature of the housing 10.

[0099] (8) Why is the value detected by the first temperature sensor taken as the outside air temperature? The reason why the control unit 80 acquires the detection value of the first temperature sensor 61 as the outside air temperature in step S4c as shown in FIG. 8 will be described.

[0100] (8-1) First reason In step S4c, if the first condition is not satisfied, the control unit 80 acquires the detection value of the first temperature sensor 61 as the outside air temperature.

[0101] When the first condition is not satisfied, that is, when the continuous operation time of the fan 62 is longer than the first predetermined time, ventilation inside the housing 10 by the fan 62 progresses to a certain extent, so that the temperature difference becomes small enough that the detection value of the first temperature sensor 61 can be regarded as the actual outside air temperature of the housing 10. (See the change in temperature difference when moving from point A2 to point B2 in FIG. 9, the change in temperature difference when moving from point A3 to point B3 in FIG. 9, etc.). Therefore, when the first condition is not satisfied, the control unit 80 acquires the detection value of the first temperature sensor 61 as the outside air temperature.

[0102] (8-2) Second reason In step S4c, if the second condition is satisfied, the control unit 80 acquires the detection value of the first temperature sensor 61 as the outside air temperature. In step S4c, if the second condition is satisfied, more specifically, it indicates a case where the second condition is satisfied but the third condition is not satisfied.

[0103] (8-2-1) When the second condition is met When the second condition is satisfied, that is, when the detection value of the first temperature sensor 61 is equal to or greater than the detection value of the second temperature sensor 63 minus the first predetermined value, the temperature of the fixing unit 40 (the detection value of the second temperature sensor 63) becomes close to the atmospheric temperature inside the housing 10. This indicates that the fixing unit 40 is cold enough not to affect the detection value of the first temperature sensor 61.

[0104] (8-2-2) When the third condition is not met If the third condition is not satisfied, i.e., if the time that has elapsed since the fan 62 stopped operating continuously for more than the second predetermined time is longer than the third predetermined time, the temperature difference becomes smaller, as shown at point B5 in FIG. 9 and after.

[0105] (8-2-3) Summary of the second reason Therefore, in step S4c, if the second condition is satisfied but the third condition is not satisfied, the fixing unit 40 is cold and the temperature difference is small. This does not lead to a situation in which the deviation between the detection value of the first temperature sensor 61 (ambient temperature inside the housing 10) and the actual outside air temperature of the housing 10 is accelerated, so the control unit 80 obtains the detection value of the first temperature sensor 61 as the outside air temperature.

[0106] (9) Why is the outside temperature not recorded? As shown in FIG. 8, in step S4e, if the first condition is satisfied but the second condition is not satisfied, the reason why the control unit 80 does not acquire the outside air temperature will be described.

[0107] When the first condition is satisfied, the continuous operation time of the fan 62 is short, and ventilation by the fan 62 is not sufficient, contrary to the case where the first condition is satisfied. When the second condition is not satisfied, the temperature of the fixing unit 40 is high, contrary to the case where the second condition is satisfied. Therefore, when the first condition is satisfied but the second condition is not satisfied, ventilation by the fan 62 is not sufficient inside the housing 10, and the fixing unit 40 is at a high temperature, so that the detection value of the first temperature sensor 61 (ambient temperature inside the housing 10) is significantly higher than the actual outside air temperature of the housing 10. As a result, if the detection value of the first temperature sensor 61 is acquired as the outside air temperature in this state, the outside air temperature acquired will be low in accuracy, and therefore the control unit 80 does not acquire the outside air temperature.

[0108] (10) Reasons for obtaining correction values As shown in FIG. 8, in step S4a, when all of the first condition, the second condition, and the third condition are satisfied, the reason why the control unit 80 acquires a correction value (a value obtained by subtracting a second predetermined value from the detection value of the first temperature sensor 61) as the outside air temperature will be explained.

[0109] When all of the first, second, and third conditions are satisfied, the second condition is satisfied so that the fixing unit 40 is cooled, but the third condition is satisfied so that the accumulated heat generated by the past heat generation of the fixing unit 40 remains inside the housing 10 at present (see the temperature difference in the period between points B4 and B5 in FIG. 9), and the first condition is satisfied so that ventilation by the fan 62 is not performed sufficiently. As a result, it can be estimated that the detection value of the first sensor is higher than the actual outside air temperature of the housing 10 by the amount of the accumulated heat. As a result, the control unit 80 acquires a correction value (a value obtained by subtracting the second predetermined value, which is the amount of the accumulated heat, from the detection value of the first temperature sensor 61) as the outside air temperature, rather than the detection value itself of the first temperature sensor 61.

[0110] (11) Fuser control process in the control unit The fixing unit control process in which the control unit 80 controls the fixing unit 40 based on the outside air temperature stored in the storage unit 70 will be described.

[0111] As shown in FIG. 10, in step S10, the image forming apparatus 1 is turned on.

[0112] In step S11, the control unit 80 determines whether or not electricity is being applied to the fixing unit 40. If electricity is being applied to the fixing unit 40 (Yes in step S11), the process proceeds to step S12. If electricity is not being applied to the fixing unit 40 (No in step S11), the process proceeds to step S17.

[0113] In step S12, the control unit 80 operates the fan 62.

[0114] In step S13, the control unit 80 determines whether the outside air temperature stored in the memory unit 70 is equal to or higher than a first predetermined temperature. The first predetermined temperature is, for example, 15° C. If the outside air temperature stored in the memory unit 70 is equal to or higher than the first predetermined temperature (Yes in step S13), the process proceeds to step S14. If the outside air temperature stored in the memory unit 70 is not equal to or higher than the first predetermined temperature (No in step S13), the process proceeds to step S18.

[0115] In step S14, the control unit 80 controls the heater 41 of the fixing unit 40 so that the temperature of the fixing unit 40 becomes a predetermined first target temperature. The first target temperature is, for example, 190° C. .

[0116] In step S15, the control unit 80 determines whether or not power supply to the fixing unit 40 has been stopped. If power supply to the fixing unit 40 has been stopped (Yes in step S15), the process proceeds to step S16. If power supply to the fixing unit 40 has not been stopped (No in step S15), the process proceeds to step S13.

[0117] In step S16, the control unit 80 stops the fan 62.

[0118] In step S17, if the image forming apparatus 1 is powered off (Yes in step S17), the process ends. If the image forming apparatus 1 is not powered off (No in step S17), the process proceeds to step S11.

[0119] In step S18, the control unit 80 determines whether the outside air temperature stored in the memory unit 70 is equal to or higher than a second predetermined temperature. The second predetermined temperature is a temperature lower than the first predetermined temperature. The second predetermined temperature is, for example, 5°C. If the outside air temperature stored in the memory unit 70 is equal to or higher than the second predetermined temperature (Yes in step S18), the process proceeds to step S19. If the outside air temperature stored in the memory unit 70 is not equal to or higher than the second predetermined temperature (No in step S19), the process proceeds to step S20.

[0120] In step S19, the control unit 80 controls the heater 41 of the fixing unit 40 so that the temperature of the fixing unit 40 becomes a predetermined second target temperature. The second target temperature is a temperature higher than the first predetermined target temperature. The second target temperature is, for example, 195° C. Next, the process proceeds to step S15.

[0121] In step S20, the control unit 80 controls the heater 41 of the fixing unit 40 so that the temperature of the fixing unit 40 becomes a predetermined second target temperature. Furthermore, the control unit 80 reduces the throughput of the fixing unit 40. In this case, for example, during a printing operation, the number of sheets S passing through the fixing unit 40 per unit time is reduced (e.g., halved) by reducing the conveying speed of the sheets S or increasing the interval between the multiple sheets S conveyed without reducing the conveying speed of the sheets S. Next, the process proceeds to step S15.

[0122] (12) Effects As described above, the control unit 80 obtains the outside air temperature of the housing 10 based on the detection value of the first temperature sensor 61 that detects the atmospheric temperature inside the housing 10, the detection value of the second temperature sensor 63 that detects the temperature of the fixing unit 40, and the operating time of the fan 62 that exhausts the air inside the housing 10. This makes it possible to obtain the outside air temperature taking into consideration the operating conditions of the components of the image forming apparatus 1, such as the temperature of the fixing unit 40 (detection value of the second temperature sensor 63) and the operating time of the fan 62, thereby making it possible to prevent obtaining an outside air temperature with low accuracy.

[0123] Although the embodiments and modifications have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims (for example, (A) to (E) below). Furthermore, the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0124] (A) In this embodiment, when the printing operation is completed, the control unit 80 stops the supply of electricity to the fixing unit 40. However, the present invention is not limited to this. When the printing operation is completed, the control unit 80 may supply electricity to the fixing unit 40 so that the temperature of the fixing unit 40 becomes lower than the temperature during the printing operation, and may stop the supply of electricity to the fixing unit 40 after a predetermined time has elapsed since the end of the printing operation. In this case, the control unit 80 may stop the supply of electricity to the fixing unit 40 by turning on the fan 62. Stop the rotation.

[0125] (B) A modified example of the fixing device 40 will be described. The modified example of the fixing device 40 includes a pressure roller and a heating roller with a halogen heater disposed therein. The pressure roller rotates while sandwiching the sheet S between the pressure roller and the heating roller and pressing the sheet S against the heating roller. As a result, the sheet S is fed while the toner image transferred to the sheet S is fixed to the sheet S by the heat of the halogen heater. The second temperature sensor 63 is disposed opposite the heating roller without contacting it, and detects the temperature of the heating roller. The heat source of the fixing device 40 is not limited to a halogen heater or a ceramic heater, and may be, for example, a carbon heater that utilizes heat generated by a resistor, an IH heater that performs induction heating, or the like.

[0126] (C) The first temperature sensor 61 and the second temperature sensor 63 are not limited to thermistors, and may be other elements capable of detecting temperature, such as thermocouples and semiconductor temperature sensors.

[0127] (D) In ​​this embodiment, the process unit 30 forms a black and white toner image on the sheet. However, the present invention is not limited to this. The process unit 30 may use toners of multiple colors to form a color toner image on the sheet. In this case, the process unit 30 may be a tandem type device using multiple photosensitive drums, or a rotary type device using a single photosensitive drum.

[0128] (E) The image forming apparatus 1 may further include at least one of a copy function, a scan function, a FAX function, and an ADF function (automatic document feeder function).

[0129] The descriptions "first," "second," "third," etc. mentioned above are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words. [Explanation of symbols]

[0130] 1. Image forming device 10. Chassis 30 Process Section 40 Fixing unit 61 First temperature sensor 62 Fans 63 Second temperature sensor 80 Control section S Seat

Claims

1. A housing and a process section for forming a toner image on a sheet; a fuser disposed inside the housing and configured to fuse the toner image onto the sheet; A first temperature sensor that detects an atmospheric temperature inside the housing; a second temperature sensor for detecting a temperature of the fixing unit; A fan that exhausts air from inside the housing; a control unit that acquires an outside air temperature of the housing based on a detection value of the first temperature sensor, a detection value of the second temperature sensor, and an operating time of the fan; An image forming apparatus comprising:

2. A condition is set for the control unit to acquire the outside air temperature of the housing; The condition is A first condition is that the continuous operation time of the fan is within a first predetermined time; a second condition that the detection value of the first temperature sensor is equal to or greater than a value obtained by subtracting a first predetermined value from the detection value of the second temperature sensor; The image forming apparatus of claim 1 .

3. The image forming apparatus according to claim 2 , wherein the control unit is configured to obtain, when the first condition and the second condition are satisfied, a temperature based on a detection value of the first temperature sensor as an outside air temperature of the housing.

4. The image forming apparatus according to claim 2 , wherein the control unit, when the first condition is not satisfied, acquires the detection value of the first temperature sensor as the outside air temperature of the housing, regardless of whether the second condition is satisfied.

5. The control unit is operating the fan while the fixing unit is energized; 4. The image forming apparatus of claim 3, wherein when the first condition and the second condition are satisfied, and the fan has operated continuously for more than a second predetermined time in the past and the time that has elapsed since the fan stopped operating is within a third predetermined time, a value obtained by subtracting a second predetermined value from the detection value of the first temperature sensor is obtained as the outside air temperature of the housing.

6. The control unit is operating the fan while the fixing unit is energized; 4. An image forming apparatus as described in claim 3, wherein when the first condition and the second condition are satisfied, and the fan has operated continuously for more than a second predetermined time in the past and the time that has elapsed since the fan stopped operating is longer than a third predetermined time, the detection value of the first temperature sensor is obtained as the outside air temperature of the housing.

7. The image forming apparatus according to claim 2 , wherein the control unit does not acquire the outside air temperature of the housing when the first condition is satisfied but the second condition is not satisfied.

8. A storage unit that stores an outside air temperature of the housing, The control unit is performing a process for acquiring the outside air temperature of the housing based on the condition every time an update time shorter than the first predetermined time has elapsed; When the latest outside air temperature of the housing is acquired, the outside air temperature stored in the storage unit is updated to the latest outside air temperature; The image forming apparatus according to claim 2 , wherein the outside air temperature stored in the storage unit is not updated unless the latest outside air temperature is acquired.

9. The image forming apparatus according to claim 1 , wherein the control unit controls the fixing unit based on the acquired outside air temperature of the housing.

10. The control unit is When the outside air temperature of the housing is equal to or higher than a first predetermined outside air temperature, the fixing unit is controlled so that the temperature of the fixing unit becomes a first predetermined target temperature; 10. The image forming apparatus according to claim 9, wherein when the outside air temperature of the housing is lower than the first predetermined outside air temperature, the fixing unit is controlled so that the temperature of the fixing unit becomes a second predetermined target temperature that is higher than the first predetermined target temperature.

11. The control unit is The image forming apparatus according to claim 10 , wherein when the outside air temperature of the housing is lower than a second predetermined outside air temperature that is lower than the first predetermined outside air temperature, a throughput of the fixing unit is reduced.

12. The housing has an intake port that communicates between the inside and the outside of the housing, The image forming apparatus according to claim 1 , wherein the first temperature sensor is disposed inside the housing and opposed to the intake port.

13. The fixing device includes a roller for feeding a sheet.

9. The image forming apparatus according to claim 1, wherein the fan and the first temperature sensor are located on opposite sides of the fixing unit with respect to a rotation axis direction of the roller.

14. the fixing unit includes a substrate and a heater having a resistive heating element disposed on the substrate; The image forming apparatus according to claim 1 , wherein the second temperature sensor is in contact with the substrate.

15. 14. The image forming apparatus according to claim 13, wherein the fan is located between the rotation axis of the roller and the first temperature sensor when viewed in the direction of the rotation axis of the roller.

Images