Image forming apparatus

Abstract

To provide an image forming apparatus that can prevent dew condensation on a surface of a photoconductor drum.SOLUTION: An image forming apparatus 1 comprises a main body housing 2, a photoconductor drum 41Y, a fixing unit 8, a fan 13, and a control unit 14. While printing is continued, the control unit 14 counts the cumulative number of printed pages N. The cumulative number of printed pages N is the accumulation of the number of pages printed by the image forming apparatus 1 within a first time. While printing is continued, when the cumulative number of printed pages N is less than a first number of pages N1, the control unit 14 rotates the fan 13 at a first speed. While printing is continued, when the cumulative number of printed pages N is equal to or more than the first number of pages N1, the control unit 14 rotates the fan 13 at a second speed. The second speed is faster than the first speed.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Conventionally, an image forming apparatus comprises a main housing, a photosensitive drum, a fixing unit, and a fan for exhausting air from inside the main housing.

[0003] For example, in Patent Document 1 below, when the temperature inside the main unit housing is lower than the ambient temperature, printing is performed with the fan stopped until the temperature difference between the ambient temperature and the photosensitive drum becomes sufficiently small, thereby suppressing condensation on the surface of the photosensitive drum. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-13015 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the image forming apparatus described in Patent Document 1, the printing paper is heated by the fixing unit, causing the moisture contained in the printing paper to evaporate and generate water vapor.

[0006] Therefore, when printing with the fan stopped, the relative humidity inside the printer's casing may rise excessively due to water vapor generated from the printing paper.

[0007] If the relative humidity inside the main unit's casing rises excessively, and the fan, which had been stopped, is then activated, the highly humid air inside the casing may come into contact with the surface of the photosensitive drum, potentially causing condensation on the drum's surface.

[0008] Therefore, the object of this disclosure is to provide an image forming apparatus that can suppress condensation on the surface of a photosensitive drum. [Means for solving the problem]

[0009] (1) The image forming apparatus disclosed herein comprises a main body housing, a photosensitive drum, a fuser unit, a fan, and a control unit. The main body housing has an exhaust port. The fuser unit fixes the toner transferred from the photosensitive drum to the sheet by heating. The fan generates an airflow directed toward the exhaust port.

[0010] The control unit counts the cumulative number of printed pages while printing is in progress. The cumulative number of printed pages is the total number of pages printed by the image forming apparatus.

[0011] If the cumulative number of printed pages is less than the first page count while printing is in progress, the control unit rotates the fan at the first speed.

[0012] The control unit rotates the fan at a second speed if the cumulative number of printed pages is equal to or greater than the first page count while printing is in progress. The second speed is faster than the first speed.

[0013] With this configuration, until the cumulative number of printed pages reaches the first page, the degree of increase in relative humidity inside the main unit enclosure due to water vapor generated by the printing process is low, so the fan rotation speed is suppressed to the first speed when the printing process is performed.

[0014] This prevents air near the fuser from being carried to the photosensitive drum by the airflow generated by the fan's rotation, while also suppressing the rise in relative humidity inside the main unit's casing.

[0015] Furthermore, while the fan's rotation speed is limited to the first speed, the fan's operating noise can be suppressed.

[0016] Then, after the cumulative number of printed pages reaches the first page, the relative humidity inside the main unit's casing may have increased due to the printing process, so the fan is set to rotate at a second speed, which is faster than the first speed.

[0017] This can suppress the excessive rise in the relative humidity inside the main body housing and suppress the dew condensation on the surface of the photosensitive drum.

[0018] (2) When the first hour has elapsed without executing the printing process, the control unit may set the cumulative printed page count to 0.

[0019] According to such a configuration, when the relative humidity inside the main body housing that has risen due to the printing process decreases because the first hour has elapsed without executing the printing process, the cumulative printed page count is set to 0.

[0020] This can suppress the rotation speed of the fan to the first speed again when the relative humidity inside the main body housing has decreased.

[0021] (3) When the cumulative printed page count reaches the first page count during a print job including a plurality of pages, the control unit may change the rotation speed of the fan from the first speed to the second speed during the print job.

[0022] According to such a configuration, even during a print job, if there is a possibility that the relative humidity inside the main body housing has become high due to the printing process, the fan can be rotated at a second speed faster than the first speed to suppress the excessive rise in the relative humidity inside the main body housing.

[0023] (4) The main body housing has an exhaust port on one outer wall in the first direction. The main body housing is configured to exhaust through the exhaust port by the fan. The image forming apparatus may further include a first sensor and a second sensor. The first sensor is located near one outer wall of the main body housing in the first direction. The first sensor can measure temperature and relative humidity. The second sensor can measure the temperature at a position closer to the photosensitive drum than the fixing unit on the other side of the main body housing in the first direction. The control unit processes the temperature measured by the first sensor as the first ambient temperature. The control unit estimates the second ambient temperature, which is the temperature around the photosensitive drum, based on the temperature measured by the second sensor.

[0024] (5) The control unit may set the fan speed based on the first ambient temperature when printing starts. The control unit may set the fan speed based on the second ambient temperature while printing continues.

[0025] (6) The image forming apparatus further comprises a developing unit. The developing unit has developing rollers. The developing unit is capable of supplying toner to a photosensitive drum. The second ambient temperature may be the temperature near the developing rollers.

[0026] (7) The developing unit may further include a layer thickness regulating blade. The layer thickness regulating blade regulates the thickness of the toner layer on the developing roller. The second ambient temperature may be the temperature of the layer thickness regulating blade.

[0027] (8) If the second ambient temperature is below the first temperature and the cumulative number of printed pages is less than the first number of pages, the control unit may rotate the fan at the first speed when executing the printing process. If the second ambient temperature is below the first temperature and the cumulative number of printed pages is equal to or greater than the first number of pages, the control unit may rotate the fan at the second speed when executing the printing process. If the second ambient temperature is equal to or greater than the first temperature, the control unit may rotate the fan at the second speed when executing the printing process.

[0028] (9) The control unit may rotate the fan at a third speed if the second ambient temperature is at or above the second temperature while printing is in progress. The second temperature is higher than the first temperature. The third speed is faster than the second speed.

[0029] (10) The control unit may rotate the fan at a fourth speed if the second ambient temperature is at or above the third temperature while printing is in progress. The third temperature is higher than the second temperature. The fourth speed is faster than the third speed.

[0030] (11) The control unit may set the fan rotation speed to the second speed or higher if the relative humidity measured by the first sensor is equal to or greater than a predetermined humidity when printing starts.

[0031] With this configuration, if the relative humidity measured by the first sensor is high, it may indicate that the relative humidity of the environment in which the image forming apparatus is installed is high, and that the humidity inside the main unit's casing is high even before the printing process is performed.

[0032] Therefore, regardless of the cumulative number of printed pages, the fan rotates at speed 2 or higher when the printing process is executed.

[0033] This makes it possible to suppress condensation on the surface of the photosensitive drum even when the relative humidity of the environment in which the image forming apparatus is installed is high.

[0034] (12) The control unit may set the fan rotation speed to the first speed or higher if, at the start of printing, the relative humidity measured by the first sensor is below a predetermined humidity and the second ambient temperature is below a predetermined temperature.

[0035] With this configuration, even if the relative humidity measured by the first sensor is low and the relative humidity of the environment in which the image forming apparatus is installed is low, if the second ambient temperature is low, the temperature of the photosensitive drum surface will be low, and there is a high possibility that condensation will form on the surface of the photosensitive drum.

[0036] Therefore, regardless of the cumulative number of printed pages, the fan rotates at speed 1 or higher when the printing process is executed.

[0037] This makes it possible to suppress condensation on the surface of the photosensitive drum even when the second ambient temperature is low.

[0038] (13) The first sensor and the second sensor may be thermistors. [Effects of the Invention]

[0039] According to the image forming apparatus of this disclosure, condensation on the surface of the photosensitive drum can be suppressed. [Brief explanation of the drawing]

[0040] [Figure 1] Figure 1 is a schematic diagram of the image forming apparatus. [Figure 2] Figure 2 is an explanatory diagram illustrating the arrangement of the first sensor, second sensor, fan, and control unit in the image forming apparatus shown in Figure 1. [Figure 3] Figure 3 is a perspective view of the main housing of the image forming apparatus shown in Figure 1. [Figure 4] Figure 4 is a block diagram illustrating the control of the image forming apparatus shown in Figure 1. [Figure 5] Figure 5 is a flowchart illustrating the control of the image forming apparatus shown in Figure 1. [Figure 6] Figure 6 is a flowchart illustrating the fan rotation speed settings at the start of printing, as shown in Figure 5. [Figure 7] Figure 7 is a flowchart illustrating the setting of the fan rotation speed while printing continues, as shown in Figure 5. [Figure 8] Figure 8 is a flowchart illustrating the fan control after printing is complete, as shown in Figure 5. [Figure 9] Figure 9 is a flowchart illustrating the setting of the fan rotation speed at the start of printing in the second embodiment. [Figure 10] Figure 10 is a flowchart illustrating the setting of the fan rotation speed during continuous printing in the second embodiment. [Figure 11] Figure 11 is a flowchart illustrating the setting of the fan rotation speed at the start of printing in the third embodiment. [Figure 12] Figure 12 is a flowchart illustrating the setting of the fan rotation speed during continuous printing in the reference configuration. [Modes for carrying out the invention]

[0041] 1. Outline of Image Forming Apparatus 1 Referring to Figure 1, the general layout of the image forming apparatus 1 will be described.

[0042] The image forming apparatus 1 comprises a main body housing 2, a sheet storage section 3, multiple drum units 4Y, 4M, 4C, 4K, multiple exposure heads 5Y, 5M, 5C, 5K, multiple developing units 6Y, 6M, 6C, 6K, a transfer device 7, a fixing unit 8, and a reading device 9.

[0043] 1.1 Main Unit 2 The main housing 2 houses the sheet storage section 3, drum units 4Y, 4M, 4C, 4K, exposure heads 5Y, 5M, 5C, 5K, developing units 6Y, 6M, 6C, 6K, transfer device 7, and fixing unit 8.

[0044] 1.2 Seat storage section 3 The sheet storage section 3 is capable of accommodating a sheet S. The sheet S is, for example, printing paper. The sheet S is transported toward the photosensitive drum 41Y of the drum unit 4Y.

[0045] 1.3 Drum Units 4Y, 4M, 4C, 4K The drum unit 4Y comprises a photosensitive drum 41Y and a charging device 42Y. In other words, the image forming apparatus 1 comprises a photosensitive drum 41Y.

[0046] The photosensitive drum 41Y has a cylindrical shape. The photosensitive drum 41Y extends in a first direction. The photosensitive drum 41Y is rotatable about axis A1. Axis A1 extends in a first direction.

[0047] The charging device 42Y charges the surface of the photosensitive drum 41Y. The charging device 42Y is a scorotron type charger. The charging device 42Y may also be a charging roller.

[0048] The drum units 4Y, 4M, 4C, and 4K are arranged in a second direction. The second direction intersects the first direction. Preferably, the second direction is perpendicular to the first direction. In the direction approaching the fixing section 8, the drum units 4Y, 4M, 4C, and 4K are arranged in the order of drum unit 4Y, drum unit 4M, drum unit 4C, and drum unit 4K. The description of drum units 4M, 4C, and 4K is the same as that of drum unit 4Y, so it is omitted.

[0049] 1.4 Exposure heads 5Y, 5M, 5C, 5K Exposure head 5Y exposes the surface of the photosensitive drum 41Y which has been charged by the charging device 42Y. Exposure head 5M exposes the surface of the photosensitive drum 41M which has been charged by the charging device 42M. Exposure head 5C exposes the surface of the photosensitive drum 41C which has been charged by the charging device 42C. Exposure head 5K exposes the surface of the photosensitive drum 41K which has been charged by the charging device 42K.

[0050] 1.5 Developing Units 6Y, 6M, 6C, 6K The developing unit 6Y is capable of supplying toner to the photosensitive drum 41Y. More specifically, the developing unit 6Y supplies toner onto the surface of the photosensitive drum 41Y that has been exposed by the exposure head 5Y. The developing unit 6Y comprises a developing housing 61Y, a developing roller 62Y, and a layer thickness regulating blade 63Y.

[0051] The developing unit 61Y can accommodate toner.

[0052] The developing roller 62Y is capable of supplying toner from the developing housing 61Y to the surface of the photosensitive drum 41Y. The developing roller 62Y is in contact with the photosensitive drum 41Y. The developing roller 62Y may be separated from the photosensitive drum 41Y by a predetermined distance. The developing roller 62Y has a cylindrical shape. The developing roller 62Y extends in a first direction. The developing roller 62Y is rotatable about axis A2. Axis A2 extends in a first direction.

[0053] The layer thickness regulating blade 63Y regulates the toner layer thickness on the developing roller 62Y.

[0054] The explanation for developing units 6M, 6C, and 6K is the same as for developing unit 6Y, so it will be omitted.

[0055] 1.6 Transfer device 7 The transfer device 7 has a belt 71 and a plurality of transfer rollers 72Y, 72M, 72C, and 72K.

[0056] The belt 71 transports the sheet S from the sheet storage section 3 toward the fixing section 8. The belt 71 is in contact with the photosensitive drums 41Y, 41M, 41C, and 41K.

[0057] The transfer roller 72Y transfers the toner on the photosensitive drum 41Y to the sheet S being transported by the belt 71. The transfer roller 72M transfers the toner on the photosensitive drum 41M to the sheet S being transported by the belt 71. The transfer roller 72C transfers the toner on the photosensitive drum 41C to the sheet S being transported by the belt 71. The transfer roller 72K transfers the toner on the photosensitive drum 41K to the sheet S being transported by the belt 71.

[0058] 1.7 Fixing section 8 The fuser unit 8 heats and pressurizes the sheet S onto which the toner has been transferred. The fuser unit 8 fixes the toner transferred to the sheet S from the photosensitive drums 41Y, 41M, 41C, and 41K to the sheet S by heating. Specifically, the fuser unit 8 has a heating roller 81, a heater 82, and a pressurizing roller 83. When the sheet S passes between the heating roller 81 and the pressurizing roller 83, the heating roller 81 heats the sheet S. The heater 82 is located inside the heating roller 81. The heater 82 heats the heating roller 81. When the sheet S passes between the heating roller 81 and the pressurizing roller 83, the pressurizing roller 83 pressurizes the sheet S toward the heating roller 81. The sheet S that has passed through the fuser unit 8 is discharged between the main body housing 2 and the reader 9.

[0059] 1.8 Reader 9 The reading device 9 is capable of reading the image of the original document. The reading device 9 is located on top of the main housing 2. Because the reading device 9 is located on top of the main housing 2, the image forming apparatus 1 has a structure in which moisture tends to accumulate inside the main housing 2. Note that the image forming apparatus 1 does not necessarily have to be equipped with the reading device 9.

[0060] 2. Details of Image Forming Apparatus 1 Next, the details of the image forming apparatus 1 will be described with reference to Figures 2 to 4.

[0061] As shown in Figure 2, the image forming apparatus 1 further comprises a first sensor 11, a second sensor 12, a fan 13, and a control unit 14.

[0062] 2.1 Details of Main Unit Casing 2 The main unit housing 2 comprises a main unit frame 21 and a main unit cover 22.

[0063] 2.1.1 Main frame 21 The main frame 21 supports the drum units 4Y, 4M, 4C, 4K, the transfer device 7, and the fixing unit 8. The main frame 21 has two side plates 211A, 211B and two frames 212A, 212B.

[0064] The side plate 211A is located at one end of the main housing 2 in the first direction. The side plate 211A extends in the second direction and in the vertical direction. The side plate 211A is a sheet metal made of, for example, iron or stainless steel.

[0065] The side plate 211B is located at the other end of the main housing 2 in the first direction. The side plate 211B is located away from the side plate 211A in the first direction. The side plate 211B extends in the second direction and in the vertical direction. The side plate 211B is a sheet metal made of, for example, iron or stainless steel.

[0066] Frame 212A is located between side plates 211A and 211B in a first direction. Frame 212A extends in a second direction and in the vertical direction. Frame 212A is, for example, a molded resin product. Frame 212A is attached to side plate 211A.

[0067] Frame 212B is located between side plates 211A and 211B in a first direction. Frame 212B is located away from frame 212A in a first direction. Frame 212B extends in a second direction and in the vertical direction. Frame 212B is, for example, a molded resin product. Frame 212B is attached to side plate 211B.

[0068] The drum units 4Y, 4M, 4C, 4K, the transfer device 7, and the fixing unit 8 are located between frame 212A and frame 212B in the first direction. The drum units 4Y, 4M, 4C, 4K, the transfer device 7, and the fixing unit 8 are supported by frame 212A and frame 212B.

[0069] 2.1.2 Main body cover 22 The main body cover 22 constitutes the exterior of the image forming apparatus 1. The main body cover 22 covers the main body frame 21. In a first direction, the main body cover 22 has one outer wall 22A and the other outer wall 22B.

[0070] The outer wall 22A is located at one end of the main body cover 22 in the first direction. In the first direction, the outer wall 22A is located on the opposite side of the side plate 211B from the side plate 211A. The outer wall 22A covers the side plate 211A. The outer wall 22A extends in the vertical direction and in the second direction. As shown in Figure 3, the outer wall 22A has an exhaust port 23. In other words, the main body housing 2 has an exhaust port 23 on one of the outer walls 22A in the first direction. As a result, the main body housing 2 is configured to exhaust air through the exhaust port 23 by the fan 13. The outer wall 22A also has a ventilation port 221. The ventilation port 221 is configured to allow the area around the first sensor 11, which will be described later, to ventilate with the outside air.

[0071] As shown in Figure 2, the outer wall 22B is located at the other end of the main housing 2 in the first direction. The outer wall 22B is located away from the outer wall 22A in the first direction. The outer wall 22B is located on the opposite side of the side plate 211A from the side plate 211B in the first direction. The outer wall 22B covers the side plate 211B. The outer wall 22B extends in the vertical direction and in the second direction.

[0072] 2.2 First Sensor 11 The first sensor 11 is located near one outer wall 22A of the main housing 2 in the first direction. The first sensor 11 is located between the outer wall 22A and the side plate 211A in the first direction. The first sensor 11 is positioned close to the ventilation opening 221 in the second direction. The first sensor 11 is also located on one side in the first direction with respect to drum unit 4Y (see Figure 1), which is the drum unit furthest from the fixing unit 8 among the multiple drum units 4Y, 4M, 4C, 4K. The first sensor 11 is located away from the fixing unit 8 in the second direction. The first sensor 11 is located further from the fixing unit 8 than the second sensor 12 in the second direction. In other words, the distance between the first sensor 11 and the fixing unit 8 in the second direction is longer than the distance between the second sensor 12 and the fixing unit 8 in the second direction. The first sensor 11 is capable of measuring temperature and relative humidity. The first sensor 11 is a thermistor.

[0073] 2.3 Second Sensor 12 The second sensor 12 is located on the other side of the main housing 2 in the first direction. More specifically, the second sensor 12 is located near the other outer wall 22B of the main housing 2 in the first direction. By positioning the second sensor 12 away from the fan 13, it is less affected by the airflow generated by the fan 13. The second sensor 12 is located between the outer wall 22B and the side plate 211B in the first direction. The second sensor 12 is located on the other side of the drum unit 4M in the first direction. The second sensor 12 is located away from the fixing unit 8 in the second direction. The second sensor 12 can measure the temperature at a position closer to the photosensitive drum 41M (see Figure 1) than to the fixing unit 8. The second sensor 12 is a thermistor.

[0074] 2.4 Fan 13 The fan 13 generates an airflow within the main housing 2 toward the exhaust port 23. In the first direction, the fan 13 is located near one of the outer walls 22A of the main housing 2. In the first direction, the fan 13 is located between the outer wall 22A and the fixing part 8. The fan 13 is positioned opposite the exhaust port 23 (see Figure 3).

[0075] 2.5 Control Unit 14 The control unit 14 is located between the outer wall 22B and the side plate 211B in the first direction. As shown in Figure 4, the control unit 14 is electrically connected to the first sensor 11, the second sensor 12, and the fan 13. The control unit 14 is a control circuit board. The control unit 14 has a processor and memory. For example, the processor is a CPU. The memory may be volatile memory or non-volatile memory. For example, RAM and ROM are examples of memory.

[0076] The control unit 14 processes the temperature measured by the first sensor 11 as the first ambient temperature T1. The first ambient temperature T1 refers to the simulated temperature outside the main body housing 2 when the image forming apparatus 1 is in standby mode. As described above, the first sensor 11 is located inside the main body housing 2, but it is located away from the fixing unit 8 and near the ventilation opening 221 of the outer wall 22A. Therefore, when the image forming apparatus 1 is in standby mode, the temperature measured by the first sensor 11 can be considered as the temperature outside the main body housing 2.

[0077] The control unit 14 estimates the second ambient temperature T2 based on the temperature measured by the second sensor 12. The second ambient temperature T2 is the temperature around the photosensitive drum 41Y, 41M, 41C, 41K. More specifically, the second ambient temperature T2 is the temperature near the developing roller 62Y, 62M, 62C, 62K. Even more specifically, the second ambient temperature T2 is the temperature of the layer thickness regulating blade 63Y, 63M, 63C, 63K.

[0078] The control unit 14 calculates the second ambient temperature T2 using the following formula.

[0079] Formula for calculating the second ambient temperature T2: Second ambient temperature T2 = a × log(temperature measured by the second sensor 12) 2 +b × log(temperature measured by the second sensor 12) + c In formula (1), a, b, and c are coefficients obtained by multiple regression analysis of experimental values.

[0080] 3. Control of the image forming apparatus 1 Next, the control of the image forming apparatus 1 will be explained with reference to Figures 5 to 8.

[0081] 3.1 Setting the fan speed at the start of printing As shown in Figure 5, when the control unit 14 receives a print command including a print job, it sets the rotation speed of the fan 13 at the start of printing (S1).

[0082] As shown in Figure 6, when printing starts, the control unit 14 sets the rotation speed of the fan 13 based on at least one of the first ambient temperature T1 and the relative humidity H1 measured by the first sensor 11.

[0083] More specifically, at the start of printing, if the first ambient temperature T1 is less than a predetermined temperature T (S11:NO) and the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S12:NO), the control unit 14 sets the rotation speed of the fan 13 to a first speed (S13).

[0084] The specified temperature T is, for example, 32°C. The specified humidity H is, for example, 60%.

[0085] On the other hand, at the start of printing, if the first ambient temperature T1 is less than a predetermined temperature T (S11: NO) and the relative humidity H1 measured by the first sensor 11 is greater than or equal to a predetermined humidity H (S12: YES), the control unit 14 sets the rotation speed of the fan 13 to the second speed (S14). The second speed is faster than the first speed. In other words, at the start of printing, if the first ambient temperature T1 is less than a predetermined temperature T (S11: NO) and the relative humidity H1 measured by the first sensor 11 is greater than or equal to a predetermined humidity H (S12: YES), the control unit 14 sets the rotation speed of the fan 13 to the first speed or higher.

[0086] If the relative humidity H1 measured by the first sensor 11 is equal to or greater than a predetermined humidity H, it is possible that the humidity of the environment in which the image forming apparatus 1 is installed (ambient humidity) is high, and that the humidity inside the main unit housing 2 is high even before the printing process is performed.

[0087] Therefore, before printing starts, the control unit 14 sets the rotation speed of the fan 13 to the first speed or higher.

[0088] This allows the fan 13 to rotate at a speed of 1 or higher from the start of printing, suppressing condensation on the surface of the photosensitive drums 41Y, 41M, 41C, and 41K even when the ambient humidity is high.

[0089] Furthermore, if the first ambient temperature T1 is above a predetermined temperature T at the start of printing (S11: YES), the control unit 14 sets the rotation speed of the fan 13 to the third speed (S15). The third speed is faster than the second speed.

[0090] 3.2 Counting the cumulative number of printed pages Next, as shown in Figure 5, the control unit 14 executes the printing process based on the print command. When executing the printing process, the control unit 14 rotates the fan 13 at the set rotation speed.

[0091] While printing continues, the control unit 14 counts the cumulative number of printed pages N each time a page is printed (S2, S3). The cumulative number of printed pages N is the cumulative number of pages printed by the image forming apparatus 1.

[0092] 3.3 Setting the rotation speed of fan 13 while printing is in progress Next, while printing continues, the control unit 14 sets the rotation speed of the fan 13 each time a page is printed (S4).

[0093] As shown in Figure 7, the control unit 14 sets the rotation speed of the fan 13 based on at least one of the second ambient temperature T2, the relative humidity H1 measured by the first sensor 11, and the cumulative number of printed pages N while printing is in progress.

[0094] When the image forming apparatus 1 is in standby mode, relative humidity H1 represents the ambient humidity. On the other hand, when the image forming apparatus 1 is printing, the relative humidity inside the main housing 2 increases due to the water vapor generated by printing. Therefore, when the image forming apparatus 1 is printing, relative humidity H1 can be considered as the relative humidity inside the main housing 2 during printing. The first sensor 11 is located on the same side as the fan 13 in the first direction. Therefore, the first sensor 11 is easily affected by the airflow generated by the fan 13, and can detect changes in humidity inside the main housing 2 earlier compared to when it is located on the opposite side of the fan 13 in the first direction.

[0095] In more detail, if, while printing is in progress, the second ambient temperature T2 is less than the first temperature T1 (S21:NO, S22:NO, S23:NO), the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S24:NO), and the cumulative number of printed pages N is less than the first number of pages N1 (S25:NO), the control unit 14 sets the rotation speed of the fan 13 to the first speed (S26). In other words, if, while printing is in progress, the second ambient temperature T2 is less than the first temperature T1 (S21:NO, S22:NO, S23:NO), the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S24:NO), and the cumulative number of printed pages N is less than the first number of pages (S25:NO), the control unit 14 rotates the fan 13 at the first speed when executing the printing process.

[0096] The first temperature T1 is, for example, 31°C. The second temperature T2 is higher than the first temperature T1. The second temperature T2 is, for example, 36°C. The third temperature T3 is higher than the second temperature T2. The third temperature T3 is, for example, 39°C. The first number of pages N1 is, for example, 60 pages.

[0097] Until the cumulative number of printed pages N reaches the first page count N1, the degree of increase in relative humidity inside the main unit enclosure 2 due to water vapor generated by the printing process is low, so when the printing process is executed, the rotation speed of the fan 13 is suppressed to the first speed.

[0098] This prevents the air near the fixing unit 8 from being carried to the photosensitive drums 41Y, 41M, 41C, and 41K by the airflow generated by the rotation of the fan 13, while also suppressing the rise in relative humidity inside the main unit housing 2.

[0099] Furthermore, while the rotation speed of fan 13 is suppressed to the first speed, the operating noise of fan 13 can be suppressed.

[0100] On the other hand, while printing continues, if the second ambient temperature T2 is less than the first temperature T1 (S21:NO, S22:NO, S23:NO), the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S24:NO), and the cumulative number of printed pages N is equal to or greater than the first number of pages N1 (S25:YES), the control unit 14 sets the rotation speed of the fan 13 to the second speed (S27). In other words, while printing continues, if the second ambient temperature T2 is less than the first temperature T1 (S21:NO, S22:NO, S23:NO), the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S24:NO), and the cumulative number of printed pages N is equal to or greater than the first number of pages N1 (S25:YES), the control unit 14 rotates the fan 13 at the second speed.

[0101] Furthermore, if the cumulative number of printed pages N reaches the first page count N1 during a print job that includes multiple pages, the control unit 14 changes the rotation speed of the fan 13 from the first speed to the second speed during the print job.

[0102] After the cumulative number of printed pages N reaches the first page count N1, the relative humidity inside the main unit casing 2 may have increased due to the printing process, so the fan 13 is rotated at a second speed, which is faster than the first speed.

[0103] This prevents the relative humidity inside the main unit housing 2 from rising excessively, thereby suppressing condensation on the surface of the photosensitive drum 41Y.

[0104] Furthermore, if, while printing is in progress, the second ambient temperature T2 is less than the first temperature T1 (S21: NO, S22: NO, S23: NO), and the relative humidity H1 measured by the first sensor 11 is equal to or greater than the predetermined humidity H (S24: YES), the control unit 14 also sets the rotation speed of the fan 13 to the second speed (S27).

[0105] Furthermore, if the second ambient temperature T2 is greater than or equal to the first temperature T1 and less than the second temperature T2 while printing is in progress (S21: NO, S22: NO, S23: YES), the control unit 14 also sets the rotation speed of the fan 13 to the second speed (S27). In other words, if the second ambient temperature T2 is greater than or equal to the first temperature T1 and less than the second temperature T2 while printing is in progress (S21: NO, S22: NO, S23: YES), the control unit 14 rotates the fan 13 at the second speed.

[0106] Furthermore, if the second ambient temperature T2 is greater than or equal to the second temperature T2 and less than the third temperature T3 while printing is in progress (S21: NO, S22: YES), the control unit 14 sets the rotation speed of the fan 13 to the third speed (S28). In other words, if the second ambient temperature T2 is greater than or equal to the second temperature T2 and less than the third temperature T3 while printing is in progress (S21: NO, S22: YES), the control unit 14 rotates the fan 13 at the third speed.

[0107] Furthermore, if the second ambient temperature T2 is equal to or higher than the third temperature T3 while printing is in progress (S21:YES), the control unit 14 sets the rotation speed of the fan 13 to the fourth speed (S29). In other words, if the second ambient temperature T2 is equal to or higher than the third temperature T3 while printing is in progress (S21:YES), the control unit 14 rotates the fan 13 at the fourth speed. The fourth speed is faster than the third speed.

[0108] By gradually increasing the rotation speed of the fan 13 in response to the rise in the second ambient temperature T2, the operating noise of the fan 13 can be suppressed while cooling the inside of the main unit enclosure 2 as needed.

[0109] As shown in Figure 5, the control unit 14 repeatedly performs the following actions for each page printed (S2): counting the cumulative number of printed pages N (S3) and setting the rotation speed of the fan 13 (S4), until the print job is completed (S5:NO).

[0110] 3.4 Fan control after print job completion Next, if the print job is completed (S5:YES), the control unit 14 starts measuring the time (S6) and starts fan control after the print job is completed (S7).

[0111] As shown in Figure 7, in the fan control after the completion of a print job, if the second ambient temperature T2 is equal to or greater than the third temperature T3 within a predetermined time after the completion of the print job (S31:NO) (S32:NO), the control unit 14 rotates the fan 13 at a first speed (S33).

[0112] The prescribed time is, for example, 20 minutes.

[0113] On the other hand, if the second ambient temperature T2 falls below the second ambient temperature T2 within a predetermined time after the print job is completed (S31: NO) (S32: YES, S34: YES), the control unit 14 stops the fan 13 (S35).

[0114] Furthermore, if the second ambient temperature T2 becomes less than the third temperature T3 and greater than or equal to the second temperature T2 within a predetermined time after the completion of the print job (S31: NO), the control unit 14 maintains the rotation speed of the fan 13 at the first speed.

[0115] Furthermore, if a predetermined time has elapsed since the completion of the print job (S31: YES), the control unit 14 stops the fan 13 (S35).

[0116] Next, as shown in Figure 5, if one hour has elapsed since the completion of the print job (S8:YES), the control unit 14 resets the cumulative number of printed pages N to 0 (S9). In other words, if one hour has elapsed without executing a print process (S8:YES), the control unit 14 resets the cumulative number of printed pages to 0 (S9).

[0117] The first hour is set to a sufficient amount of time to reduce the relative humidity inside the main unit enclosure 2. For example, the first hour is 2 hours.

[0118] If the first hour elapses without printing (S8:YES), the cumulative number of printed pages is reduced to 0, which allows the relative humidity inside the main unit enclosure 2 to decrease, and the rotation speed of the fan 13 can be reduced back to the first speed.

[0119] Furthermore, if the control unit 14 receives a new print command before the first hour has elapsed since the completion of the print job (S8: NO) (S10: YES), it resets the rotation speed of the fan 13 at the start of printing (S1).

[0120] Furthermore, if it is before the first hour has elapsed since the completion of the print job (S8:NO) and no new print command has been received (S10:NO), the control unit 14 continues the fan control after the completion of the print job (S7).

[0121] 4. Effects (1) According to the image forming apparatus 1, as shown in Figure 7, during continuous printing, until the cumulative number of printed pages N reaches the first number of pages N1 (S25:YES), the degree of increase in relative humidity inside the main body housing 2 due to water vapor generated by the printing process is low, so the rotation speed of the fan 13 is suppressed to the first speed (S26).

[0122] This suppresses the airflow generated by the rotation of the fan 13 from carrying air near the fixing unit 8 to the photosensitive drums 41Y, 41M, 41C, and 41K, while also suppressing the rise in relative humidity inside the main unit housing 2.

[0123] Furthermore, while the rotation speed of fan 13 is suppressed to the first speed, the operating noise of fan 13 can be suppressed.

[0124] On the other hand, if the cumulative number of printed pages N is equal to or greater than the first number of pages N1 while printing is in progress (S25: YES), the control unit 14 rotates the fan 13 at a second speed that is faster than the first speed (S27).

[0125] In other words, after the cumulative number of printed pages N reaches the first page count N1, the relative humidity inside the main unit casing 2 may increase due to the printing process, so the fan 13 is rotated at a second speed, which is faster than the first speed.

[0126] This prevents the relative humidity inside the main unit 2 from rising excessively, thereby suppressing condensation on the surfaces of the photosensitive drums 41Y, 41M, 41C, and 41K.

[0127] (2) According to the image forming apparatus 1, as shown in Figure 5, if the first time has elapsed without performing the printing process (S8: YES), the control unit 14 sets the cumulative number of printed pages N to 0 (S9).

[0128] In other words, the cumulative number of printed pages is reset to 0 when the relative humidity inside the main unit 2, which increased due to the printing process, decreases after 1 hour has passed without performing any printing.

[0129] This allows the rotation speed of the fan 13 to be reduced back to the first speed once the relative humidity inside the main unit 2 has decreased.

[0130] (3) According to the image forming apparatus 1, as shown in Figure 7, if the cumulative number of printed pages N reaches the first number of pages N1 in the middle of a print job that includes multiple pages (S25: YES), the control unit 14 changes the rotation speed of the fan 13 from the first speed to the second speed in the middle of the print job.

[0131] This allows the fan 13 to rotate at a second speed, which is faster than the first speed, to prevent the relative humidity inside the main unit 2 from rising excessively, even during a print job, if the printing process may be causing the relative humidity inside the main unit 2 to increase.

[0132] (4) According to the image forming apparatus 1, as shown in Figure 7, if the second ambient temperature T2 is equal to or greater than the first temperature T1 during printing (S23: YES), the control unit 14 rotates the fan 13 at the second speed (S25).

[0133] Furthermore, if the second ambient temperature T2 is greater than or equal to the second temperature T2 while printing is in progress (S22: YES), the control unit 14 rotates the fan 13 at the third speed (S28). The second temperature T2 is higher than the first temperature T1. The third speed is faster than the second speed.

[0134] Furthermore, if the second ambient temperature T2 is higher than or equal to the third temperature T3 while printing is in progress (S21: YES), the control unit 14 rotates the fan 13 at the fourth speed (S29). The third temperature T3 is higher than the second temperature T2. The fourth speed is faster than the third speed.

[0135] By gradually increasing the rotation speed of the fan 13 in response to the rise in the second ambient temperature T2, the operating noise of the fan 13 can be suppressed while cooling the inside of the main unit enclosure 2 as needed.

[0136] (5) According to the image forming apparatus 1, as shown in Figure 6, when the relative humidity H1 measured by the first sensor 11 at the start of printing is equal to or greater than a predetermined humidity H (S12: YES), the control unit 14 rotates the fan 13 at the second speed (S14).

[0137] With this configuration, if the relative humidity H1 measured by the first sensor 11 is high, the relative humidity of the environment in which the image forming apparatus 1 is installed is high, and there is a possibility that the humidity inside the main unit housing 2 is high even before the printing process is performed.

[0138] Therefore, at the start of printing, the fan 13 is rotated at the second speed.

[0139] This makes it possible to suppress condensation on the surfaces of the photosensitive drums 41Y, 41M, 41C, and 41K, even when the relative humidity of the environment in which the image forming apparatus 1 is installed is high.

[0140] 5. Second Embodiment Next, a second embodiment will be described with reference to Figures 9 and 10. In the second embodiment, the same reference numerals are used for components and processes as in the first embodiment described above, and their descriptions are omitted.

[0141] As shown in Figure 9, in the second embodiment, when setting the rotation speed of the fan 13 at the start of printing (S1), the control unit 14 does not drive the fan 13 at the start of printing (S41) if the first ambient temperature T1 is less than a predetermined temperature T and the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S11: NO, S12: NO).

[0142] This further reduces the noise from the fan 13 when printing starts.

[0143] Furthermore, as shown in Figure 10, the control unit 14 sets the rotation speed of the fan 13 based on at least one of the following while printing is in progress: the first ambient temperature T1, the second ambient temperature T2, the relative humidity H1 measured by the first sensor 11, and the cumulative number of printed pages N.

[0144] In more detail, the control unit 14 does not drive the fan 13 (S53) if the first ambient temperature T1 is less than a predetermined temperature T (S51: NO), the second ambient temperature T2 is less than the first ambient temperature T1 (S21: NO, S22: NO, S23: NO), the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S24: NO), and the cumulative number of printed pages N is less than the first number of pages N1 (S52: NO).

[0145] In the second embodiment, the first number of pages N1 is, for example, 120 pages.

[0146] In the second embodiment, the control unit 14 sets the rotation speed of the fan 13 to the third speed if the first ambient temperature T1 is equal to or greater than a predetermined temperature T (S51: YES) and the second ambient temperature T2 is less than the fourth temperature T4 (S54: NO).

[0147] The fourth temperature T4 is higher than the third temperature T3. The fourth temperature T4 is, for example, 41.5°C.

[0148] On the other hand, if the first ambient temperature T1 is above a predetermined temperature T (S51:YES) and the second ambient temperature T2 is above a fourth temperature T4 (S54:YES), the control unit 14 sets the rotation speed of the fan 13 to the fourth speed.

[0149] In the second embodiment, the same effects and advantages as those of the first embodiment described above can be obtained.

[0150] 6. Third Embodiment Next, a third embodiment will be described with reference to Figure 11. In the third embodiment, the same reference numerals are used for components and processes as in the first embodiment described above, and their descriptions are omitted.

[0151] In the third embodiment, when setting the rotation speed of the fan 13 at the start of printing (S1), the first ambient temperature T1 is less than a predetermined temperature T (S11:NO), the relative humidity H1 measured by the first sensor 11 is less than a predetermined humidity H (S12:NO), and the first ambient temperature T1 is less than a second predetermined temperature T 10If the value is less than (S61: NO), the control unit 14 sets the rotation speed of the fan 13 to the third speed (S62).

[0152] In the third embodiment, the predetermined humidity H is, for example, 55%. The second predetermined temperature T 10 For example, this is 20℃.

[0153] At the start of printing, even if the relative humidity H1 measured by the first sensor 11 is low (S12:NO), if the first ambient temperature T1 is low (S61:NO), the surface temperature of the photosensitive drum 41Y, 41M, 41C, 41K is low, and there is a high possibility that condensation will form on the surface of the photosensitive drum 41Y, 41M, 41C, 41K.

[0154] Therefore, when printing starts, the fan 13 is rotated at speed 1 or higher.

[0155] This makes it possible to suppress condensation on the surfaces of the photosensitive drums 41Y, 41M, 41C, and 41K even when the temperature of the installation environment of the image forming apparatus 1 is low.

[0156] On the other hand, at the start of printing, the first ambient temperature T1 is less than the predetermined temperature T (S11:NO), the relative humidity H1 measured by the first sensor 11 is less than the predetermined humidity H (S12:NO), and the first ambient temperature T1 is less than the second predetermined temperature T 10 If the above conditions are met (S61: YES), the control unit 14 sets the rotation speed of the fan 13 to the second speed (S63).

[0157] Furthermore, at the start of printing, if the first ambient temperature T1 is less than a predetermined temperature T (S11: NO) and the relative humidity H1 measured by the first sensor 11 is equal to or greater than a predetermined humidity H (S12: YES), the control unit 14 sets the rotation speed of the fan 13 to the fourth speed (S64).

[0158] Furthermore, if the first ambient temperature T1 is above a predetermined temperature T at the start of printing (S11: YES), the control unit 14 also sets the rotation speed of the fan 13 to the fourth speed (S64).

[0159] Even in the third embodiment, the same operational effects as those of the first embodiment can be obtained.

[0160] 7. Reference embodiment Next, a reference embodiment will be described with reference to FIG. 12. In the reference embodiment, the same members and processes as those in the above-described first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0161] In the reference embodiment, during printing, the control unit 14 sets the rotational speed of the fan 13 based on at least one of the second ambient temperature T2 and the relative humidity H1 measured by the first sensor 11.

[0162] In setting the rotational speed of the fan 13 during printing (S1), when the second ambient temperature T2 is less than the predetermined temperature T 11 (S71: NO), the relative humidity H1 measured by the first sensor 11 is less than the predetermined humidity H (S72: NO), and the second ambient temperature T2 is less than the predetermined temperature T 12 (S73: NO), the rotational speed of the fan 13 is set to the third speed (S74).

[0163] The predetermined temperature T 11 is, for example, 36°C. The predetermined humidity H in the reference embodiment is, for example, 55%. The predetermined temperature T 12 is, for example, 20°C.

[0164] On the other hand, when the second ambient temperature T2 is less than the predetermined temperature T 11 (S71: NO), the relative humidity H1 measured by the first sensor 11 is less than the predetermined humidity H (S72: NO), and the second ambient temperature T2 is greater than or equal to the predetermined temperature T 12 (S73: YES), the rotational speed of the fan 13 is set to the second speed (S75).

[0165] Also, when the second ambient temperature T2 is less than the predetermined temperature T 11 (S71: NO) and the relative humidity H1 measured by the first sensor 11 is greater than or equal to the predetermined humidity H (S72: YES), the rotational speed of the fan 13 is set to the fourth speed (S76).

[0166] The control unit 14 determines when the second ambient temperature T2 is a predetermined temperature T 11 If the above conditions are met (S71:NO), the rotation speed of fan 13 is set to the fourth speed (S76). [Explanation of symbols]

[0167] 1. Image forming apparatus 2 Main unit 4 Photosensitive drum 6. Developing Unit 8 Fixing section 11. First Sensor 12. Second Sensor 13 Fans 14 Control Unit 22A Exterior Wall 23 Exhaust vent 62 Developing Roller N: Cumulative number of printed pages N1 Page number T1 Primary ambient temperature T Predetermined temperature T2 Second ambient temperature T1 1st temperature T2 second temperature T3 third temperature H1 Relative humidity H Specified humidity

Claims

1. A main body housing having an exhaust port on one outer wall in a first direction, Photosensitive drum and A fixing unit that fixes the toner transferred from the photosensitive drum to the sheet by heating, A first sensor located near one of the outer walls of the main body housing in the first direction, capable of measuring temperature and relative humidity, A second sensor capable of measuring the temperature at a position closer to the photosensitive drum than the fixing unit on the other side of the main housing in the first direction, A fan that generates an airflow toward the exhaust port, Control unit and Equipped with, The main housing is configured to exhaust air through the exhaust port by the fan, The control unit, The temperature measured by the first sensor is processed as the first ambient temperature. Based on the temperature measured by the second sensor, the second ambient temperature, which is the temperature around the photosensitive drum, is estimated. The control unit, while printing continues, The cumulative number of printed pages, which is the sum of the number of pages printed by the image forming apparatus, is counted. If the cumulative number of printed pages is less than the first number of pages, the fan is rotated at the first speed. An image forming apparatus that, when the cumulative number of printed pages is equal to or greater than the first number of pages, rotates the fan at a second speed faster than the first speed.

2. A main body housing having an exhaust port, Photosensitive drum and The toner transferred from the photosensitive drum to the sheet is fixed to the sheet by heating. The attachment part, A fan that generates an airflow toward the exhaust port, Control unit and Equipped with, The control unit, while printing continues, The cumulative number of printed pages, which is the sum of the number of pages printed by the image forming apparatus, is counted. If the cumulative number of printed pages is less than the first number of pages, the fan rotates at the first speed. Let, If the cumulative number of printed pages is equal to or greater than the first number of pages, the fan is set to the first speed Rotate at a second speed faster than 1 degree, The control unit, An image forming apparatus that, if a first hour has elapsed without performing a printing process, resets the cumulative number of printed pages to zero.

3. The control unit, The image forming apparatus according to claim 1 or 2, wherein if the cumulative number of printed pages reaches the first number of pages during a print job that includes multiple pages, the rotation speed of the fan is changed from the first speed to the second speed during the print job.

4. The control unit is The image forming apparatus according to claim 1, wherein if a first time elapses without performing a printing process, the cumulative number of printed pages is set to 0.

5. The control unit, When printing starts, the fan's rotation speed is set based on the first ambient temperature. The image forming apparatus according to claim 1, wherein the rotation speed of the fan is set based on the second ambient temperature while printing is in progress.

6. The image forming apparatus is The system further comprises a developing unit having a developing roller and capable of supplying toner to the photosensitive drum, The image forming apparatus according to claim 1, wherein the second ambient temperature is the temperature near the developing roller.

7. The developing unit further includes a thickness regulating blade for regulating the thickness of the toner layer on the developing roller, The image forming apparatus according to claim 6, wherein the second ambient temperature is the temperature of the layer thickness regulating blade.

8. The control unit, while printing continues, If the second ambient temperature is less than the first temperature and the cumulative number of printed pages is less than the first number of pages, the fan is rotated at the first speed. If the second ambient temperature is less than the first temperature and the cumulative number of printed pages is equal to or greater than the first number of pages, the fan is rotated at the second speed. The image forming apparatus according to any one of claims 1, 5 to 7, wherein the fan is rotated at a second speed when the second ambient temperature is equal to or greater than the first temperature.

9. The control unit, while printing continues, The image forming apparatus according to claim 8, wherein if the second ambient temperature is higher than the first temperature, the fan is rotated at a third speed faster than the second speed.

10. The control unit, while printing continues, The image forming apparatus according to claim 9, wherein if the second ambient temperature is higher than the second temperature (a third temperature or higher), the fan is rotated at a fourth speed faster than the third speed.

11. The control unit, at the start of printing, The image forming apparatus according to claim 1, wherein if the relative humidity measured by the first sensor is equal to or greater than a predetermined humidity, the rotation speed of the fan is set to the second speed or greater.

12. The control unit, at the start of printing, The image forming apparatus according to claim 11, wherein if the relative humidity measured by the first sensor is less than the predetermined humidity and the first ambient temperature is less than the predetermined temperature, the rotation speed of the fan is set to the first speed or higher.

13. The image forming apparatus according to claim 1, wherein the first sensor and the second sensor are thermistors.

Images