Image forming apparatus and control method

Abstract

This invention aims to suppress contamination of the lens surface of the non-contact temperature sensing element, thereby enabling proper temperature detection by the non-contact temperature sensing element. [Solution] The image forming apparatus of the present invention comprises an image forming means, a fixing means, a duct disposed between the fixing means and the image forming means and having a non-contact temperature detection unit for detecting the temperature of the fixing means, an intake means provided at one end of the duct for supplying air into the duct, an exhaust means provided at the other end of the duct for discharging air from the duct, and a control means for controlling the operation of the intake means and the exhaust means. When the control means is supplying air into the duct, it drives the intake means before driving the exhaust means, and when it is stopping the supply of air into the duct, it stops the intake means after the exhaust means has stopped.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a control method, and can be applied to, for example, an image forming apparatus using an electrophotographic process.

Background Art

[0002] Patent Document 1 discloses an image forming apparatus that measures the temperature of a fixing device using a non-contact temperature detection element such as a thermopile.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the air near the fixing device contains floating substances such as paper dust, fixing toner, and water vapor contained in the paper medium. When the air flows, the floating substances may adhere to the lens of the non-contact temperature detection element. When floating substances adhere to the lens surface, there is a problem that the detection accuracy of the fixing device using the non-contact temperature detection element is affected.

[0005] Therefore, there is a need for an image forming apparatus and a control method that can suppress the contamination of the lens surface of the non-contact temperature detection element and perform appropriate temperature detection by the non-contact temperature detection element.

Means for Solving the Problems

[0006] To solve the above-mentioned problems, the first image forming apparatus of the present invention comprises: (1) an image forming means for forming a developer image on a medium; (2) a fixing means disposed downstream of the image forming means in the medium transport direction for fixing the developer image on the medium; (3) a duct disposed between the fixing means and the image forming means and having a non-contact temperature detection unit for detecting the temperature of the fixing means; (4) an intake means provided at one end of the duct for supplying air into the duct; (5) an exhaust means provided at the other end of the duct for discharging air from the duct; and (6) a control means for controlling the operation of the intake means and the exhaust means, wherein the control means drives the intake means before driving the exhaust means when supplying air into the duct, and stops the intake means after the exhaust means has stopped when stopping the supply of air into the duct.

[0007] The second aspect of the present invention relates to a control method for an image forming apparatus comprising: an image forming means for forming a developer image on a medium; a fixing means disposed downstream of the image forming means in the medium transport direction for fixing the developer image on the medium; a duct disposed between the fixing means and the image forming means and having a non-contact temperature detection unit for detecting the temperature of the fixing means; an intake means provided at one end of the duct for supplying air into the duct; an exhaust means provided at the other end of the duct for exhausting air from the duct; and a control means for controlling the operation of the intake means and the exhaust means, wherein the control means drives the exhaust means after driving the intake means, and stops the intake means after stopping the exhaust means. [Effects of the Invention]

[0008] According to the present invention, contamination of the lens surface of the non-contact temperature sensing element can be suppressed, enabling proper temperature detection by the non-contact temperature sensing element. [Brief explanation of the drawing]

[0009] [Figure 1] This is an internal configuration diagram showing the internal configuration of the image forming apparatus according to the first embodiment. [Figure 2] This is a configuration diagram showing the duct configuration according to the first embodiment. [Figure 3]This is a configuration diagram showing the configuration of the control system of the image forming apparatus according to the first embodiment. [Figure 4] This is a state transition diagram showing the operating states of the intake fan and exhaust fan in the first embodiment. [Figure 5] This is a flowchart showing the operation of transitioning to the fan ON state in the image forming apparatus of the first embodiment. [Figure 6] This is a flowchart showing the operation of transitioning to the fan OFF state in the image forming apparatus of the first embodiment. [Figure 7] This is a time chart showing the ON / OFF timing of the intake fan and exhaust fan in the first embodiment. [Figure 8] This is an explanatory diagram illustrating the airflow inside and around the duct when each fan is in operation according to the first embodiment. [Figure 9] This is a configuration diagram showing the duct configuration according to the second embodiment. [Figure 10] This is an explanatory diagram illustrating the airflow inside and around the duct when each fan is in operation according to the second embodiment. [Modes for carrying out the invention]

[0010] (A) First Embodiment In the following, a first embodiment of the image forming apparatus and control method according to the present invention will be described in detail with reference to the drawings.

[0011] (A-1) Configuration of the first embodiment Figure 1 is an internal configuration diagram showing the internal configuration of an image forming apparatus according to the first embodiment.

[0012] In FIG. 1, an image forming apparatus 101 according to the first embodiment includes a paper feed cassette 102, a registration roller 104, a pair of conveyance rollers 105, a photosensitive drum 106 (106K, 106Y, 106M, 106C), image forming units 111 (111K, 111Y, 111M, 111C), LED heads 112 (112K, 112Y, 112M, 112C), transfer rollers 113 (113K, 113Y, 113M, 113C), a transfer belt 114, a belt drive roller 115, a fixing device 116 as a fixing means, a pair of discharge rollers 120 and a pair of discharge rollers 121, a writing sensor 122, toner cartridges 123 (123K, 123Y, 123M, 123C) as developer storage units, an EXIT sensor 124, and a duct 125.

[0013] Note that the part composed of the image forming unit 111 and the transfer belt 114 is also collectively referred to as an "image forming means".

[0014] The image forming apparatus 101 is a color printer that employs an electrophotographic process for forming a color image using developers (for example, toner) of K = black, Y = yellow, M = magenta, and C = cyan.

[0015] Inside the image forming apparatus 101, a substantially S-shaped conveyance path is provided. The paper feed cassette 102 side is the upstream side of the conveyance path, and the discharge roller 121 side is the downstream side of the conveyance path.

[0016] Members (components) distinguished by toner color are suffixed with "K, Y, M, C" at the end of the reference numeral. When describing members (components) regardless of toner color, for ease of explanation, the description is made by omitting "K, Y, M, C" as in "image forming unit 111".

[0017] The paper feed cassette 102 holds a printing medium (for example, paper) P. The printing medium P fed out by the hopping roller 103 is corrected for skew by the registration roller 104 and then sent to the transfer belt 114 by the conveyance roller 105 at a predetermined timing.

[0018] The image forming unit 111 is equipped with a photosensitive drum 106 inside and is positioned opposite the transfer belt 114. For example, the image forming units 111K, 111Y, 111M, and 111C are arranged in the order from the upstream to the downstream side of the transport path. However, the arrangement order of the image forming units 111 is not limited to this.

[0019] The transfer belt 114 includes a transfer roller 113 and a belt drive roller 115. The transfer belt 114 transports the printing medium P to the image forming unit 111, and the toner image generated on the photoreceptor drum 106 by the transfer roller 113 is transferred to one surface of the printing medium P. In this way, the image forming unit 111, the LED head 112, and the toner cartridge 123 form a toner image on one surface of the printing medium P.

[0020] The fixing device 116 is a fixing means that heats and pressurizes the printing medium P, on which a toner image has been formed on one surface, to fuse the toner to one surface of the printing medium P and fix the image.

[0021] The fuser unit 116 comprises a fuser belt 117 having a heater 119 inside, and a backup roller 118. The fuser belt 117 is heated when power is supplied to the heater 119. The printing medium P, which has been heated and pressurized toner fixed in the fuser unit 116, is discharged outside the unit by passing through the discharge roller 120 and discharge roller 121.

[0022] Here, the write-out sensor 122 is a sensor that detects the presence or absence of the printing medium P. The detection signal from the write-out sensor 122 serves as a reference for the exposure timing of the LED head 112 and the timing for applying high voltage to the transfer roller 113.

[0023] Furthermore, the EXIT sensor 124 is also a sensor that detects the presence or absence of the printing medium P. The detection signal from the EXIT sensor 124 serves as a criterion for determining whether or not a series of image forming processes for the printing medium P has been completed.

[0024] The duct 125 is installed to prevent heat generated in the fixing device 116 from being conducted to the image forming unit 111. The duct 125 has a duct body (frame), a ventilation section surrounded by the duct body (frame), and a non-contact temperature sensing element 126 such as a thermopile provided in the ventilation section.

[0025] For example, the duct 125 is positioned inside the image forming apparatus 101, downstream of the image forming unit 111 and upstream of the fixing device 116. The duct body of the duct 125 is, for example, a frame with a rectangular cross-section, and both ends of it engage with the side walls of the image forming apparatus 101. In other words, the duct 125 is arranged to extend in the left-right direction (Y-axis direction) of the image forming apparatus 101. Note that the structure of the duct 125 is not limited to that shown in Figure 1.

[0026] The duct 125 has a detection window 201 (see Figure 2) as an opening facing the fixing device 116, and the fixing device 116 also has an opening 116A facing the duct 125. Through the holes (openings) in the duct 125 and the fixing device 116, the non-contact temperature sensing element 126 measures the temperature of the fixing belt 117. The non-contact temperature sensing element 126 provides the detected temperature to the fixing control unit 302 (see Figure 3), and the fixing control unit 302 controls the temperature of the heater 119 of the fixing belt 117.

[0027] The duct 125 is equipped with two fans 127, which are installed at each end of the duct 125. Of the two fans 127, one is an intake fan (hereinafter also referred to as the "intake means") 127A that draws air into the duct 125, and the other is an exhaust fan (hereinafter also referred to as the "exhaust means") 127B that expels the air inside the duct 125 to the outside. In Figure 1, since the two fans 127 are in overlapping positions, the intake fan 127A and the exhaust fan 127B are collectively referred to as fan 127.

[0028] Figure 2 is a configuration diagram showing the configuration of the duct 125 according to the first embodiment.

[0029] As illustrated in Figure 2, an intake fan 127A is installed at one end of the duct 125, and an exhaust fan 127B is installed at the other end, so that the air inside the duct 125 flows from the intake fan 127A side to the exhaust fan 127B side.

[0030] Furthermore, the non-contact temperature sensing element 126 is installed inside the duct 125 near the detection window 201 and detects the temperature of the fixing device 116 through the detection window 201.

[0031] The air surrounding the fuser unit 116 contains suspended particles such as paper dust, fuser toner, and water vapor contained in the paper media. If these suspended particles adhere to the lens of the non-contact temperature sensing element 126, the detected temperature may drop.

[0032] Therefore, conventionally, in order to prevent airborne particles from adhering to the lens of the non-contact temperature sensing element 126, the non-contact temperature sensing element 126 is installed inside the duct 125, and the size of the detection window 201 is made approximately the same as the size of the non-contact temperature sensing element 126, thereby preventing airborne particles from entering the duct 125. Even so, airborne particles can still adhere to the lens.

[0033] Therefore, in this embodiment, the airflow within the duct 125 is controlled by controlling the operation of the intake fan 127A and the exhaust fan 127B to suppress the entry of airborne particles. The method for controlling the operation of the intake fan 127A and the exhaust fan 127B will be described in detail in the operation section.

[0034] Figure 3 is a configuration diagram showing the control system of the image forming apparatus 101 according to the first embodiment.

[0035] In Figure 3, the image forming apparatus 101 includes, as a control system, a print control unit 301, a fuser control unit 302, a fan control unit 303 connected to the intake fan 127A and the exhaust fan 127B, a paper feed motor 304, a belt motor 305, an ID motor 306, a fuser motor 307, an LED head 112, and a high-voltage unit 308.

[0036] The print control unit 301 is connected to the fuser control unit 302, fan control unit 303, paper feed motor 304, belt motor 305, ID motor 306, fuser motor 307, LED head 112, and high voltage unit 308, and controls these components.

[0037] Furthermore, the print control unit 301 acquires the temperature of the fuser unit 116 detected by a non-contact temperature sensing element 126 such as a thermopile, and issues a fan drive command to the fan control unit 303.

[0038] For example, when the power is turned on, or when the temperature detected by the non-contact temperature sensing element 126 rises above the first temperature (threshold), the heat generated by the fixing device 116 increases. To suppress the transfer of heat to the image forming unit 111, the print control unit 301 issues a command to the fan control unit 303 to turn on the fan, causing air to circulate through the duct 125. By circulating air through the duct 125 in this way, the transfer of heat to the image forming unit 111 can be suppressed.

[0039] For example, if the power is turned off, or if the temperature detected by the non-contact temperature sensing element 126 is high, but the fan is operated and the detected temperature subsequently falls below the first temperature (threshold), the print control unit 301 issues a command to the fan control unit 303 to turn off the fan, thereby stopping the airflow into the duct 125.

[0040] The fuser control unit 302 controls the fuser device 116 to a target temperature according to printing conditions such as paper thickness and paper width.

[0041] The fan control unit 303 controls the operation (ON) and stopping (OFF) of the intake fan 127A and the exhaust fan 127B under the control of the printing control unit 301. For example, the printing control unit 301 issues commands to the fan control unit 303 to turn the intake fan 127A and the exhaust fan 127B ON and OFF, and the fan control unit 303 operates the intake fan 127A and the exhaust fan 127B ON and OFF according to these commands.

[0042] For example, when the fan control unit 303 blows air into the duct 125, it drives (turns on) the intake fan 127A before driving (turns on) the exhaust fan 127B, and when it stops the airflow into the duct 125, it stops (turns off) the intake fan 127A after the exhaust fan 127B has stopped (turned off).

[0043] When the fan operation is controlled in this manner, the operation of the intake fan 127A and the exhaust fan 127B when they start or stop running will be as follows.

[0044] For example, when air is being passed through the duct 125, the intake fan 127A starts operating first when the intake fan 127A and exhaust fan 127B start operating, and when the air is being passed through the duct 125 to stop, the exhaust fan 127 stops first when the intake fan 127A and exhaust fan 127B stop operating.

[0045] The paper feed motor 304 is a stepping motor or DC motor for feeding and transporting the printing medium P.

[0046] The belt motor 305 is a stepping motor or DC motor for driving the transfer belt 114.

[0047] The ID motor 306 is a DC motor for driving the image forming unit 111.

[0048] The fixing motor 307 is a DC motor for driving the fixing device 116 and the discharge rollers 120 and 121. For example, the rotational drive of the fixing device 116 is achieved by reducing the driving force of the fixing motor 307 via a gear train and then transmitting it to the backup roller 118.

[0049] The LED head 112 exposes the surface of the charged photoreceptor drum.

[0050] The high-voltage unit 308 is a circuit that generates a high voltage for charging and developing in the image forming unit 111 and for transfer in the transfer belt 114.

[0051] (A-2) Operation of the first embodiment Next, the operation of the control method for the intake fan 127A and exhaust fan 127B of the duct 125 in the image forming apparatus 101 of the first embodiment will be described with reference to the drawings.

[0052] Figure 4 is a state transition diagram showing the operating states of the intake fan 127A and the exhaust fan 127B in the first embodiment.

[0053] Figure 4 shows the states of the four fans 127 (intake fan 127A and exhaust fan 127B) as shown in states A to D, and explains the transition from one state to another.

[0054] The print control unit 301 sends fan ON and fan OFF requests to the fan control unit 303, and the fan control unit 303 controls the operation of the intake fan 127A and the exhaust fan 127B.

[0055] "State A" is the fan OFF state. In "State A" (fan OFF state), the intake fan 127A is OFF and the exhaust fan 127B is OFF.

[0056] "State B" is the exhaust OnDelay state. In the exhaust OnDelay state of "State B", the intake fan 127A is ON and the exhaust fan 127B is OFF.

[0057] "State C" means the fan is ON. In "State C," the intake fan 127A is ON and the exhaust fan 127B is ON.

[0058] "State D" is the intake OffDelay state. In the intake OffDelay state of "State D," the intake fan is ON and the exhaust fan is OFF.

[0059] When a request is received from the print control unit 301 while in any of the above states, "State A," "State B," "State C," or "State D," the state transitions as follows.

[0060] When a fan is requested to be turned ON while in "State A: Fan OFF state," the system transitions to "State B: Exhaust OnDelay state." In other words, the intake fan 127A turns from OFF to ON, but the exhaust fan 127B remains OFF.

[0061] If a fan OFF request is received while in "State B: Exhaust OnDelay State," the system transitions to "State A: Fan OFF State." In other words, the intake fan 127A goes from ON to OFF, but even in this case, the exhaust fan 127B remains OFF.

[0062] When the predetermined exhaust OnDelay time has elapsed while in "State B: Exhaust OnDelay State," the system transitions to "State C: Fan ON State."

[0063] If a fan OFF request is received while "State C: Fan ON," the system transitions to "State D: Intake Off Delay." In other words, the intake fan 127A remains ON, while the exhaust fan 127B changes from ON to OFF.

[0064] When a fan ON request is received while in "State D: Intake Off Delay State," the state transitions to "State C: Fan ON State." In other words, the intake fan 127A remains ON, while the exhaust fan 127B changes from OFF to ON.

[0065] When the predetermined intake off delay time has elapsed while in "State D: Intake Off Delay State," the system transitions to "State A: Fan Off State."

[0066] Here, "exhaust OnDelay time" refers to the delay time between turning on the intake fan 127A and turning on the exhaust fan 127B when transitioning to the fan ON state.

[0067] Furthermore, "Intake Off Delay Time" refers to the delay time between turning off the exhaust fan 127B and turning off the intake fan 127A when transitioning to the fan OFF state.

[0068] The "exhaust OnDelay time" and "intake OffDelay time" are determined by the shape of the duct 125 and the specifications of the intake fan 127A and exhaust fan 127B.

[0069] For example, the cross-sectional area of ​​duct 125 is 1200 mm². 2 The length is 300 mm, the diameter of the intake fan 127A is 40 mm, and the diameter of the exhaust fan 127B is 80 mm. In this case, when both the "exhaust OnDelay time" and the "intake OffDelay time" are set to, for example, 1.0 second, the objective of the present invention is fully achieved. That is, the air flowing between the detection windows 201 of the duct 125 can be directed from the duct 125 towards the fixing device 116, so that the lens surface of the non-contact temperature sensing element 126 does not become dirty.

[0070] However, the values ​​of "exhaust OnDelay time" and "intake OffDelay time" are not limited to these values, as long as it is possible to prevent air from flowing into the duct 125 from the vicinity of the fixing device 116.

[0071] The value of "Exhaust OnDelay Time" can be the time from when the intake fan 127A turns ON until the fan starts rotating stably, and the value of "Intake OffDelay Time" should preferably be the time from when the exhaust fan 127B turns OFF until the fan stops.

[0072] In other words, the start timing of the ON operation (or OFF operation) of the intake fan 127A and the exhaust fan 127B should not be the same, nor should their start timings be reversed.

[0073] The values ​​for "exhaust OnDelay time" and "intake OffDelay time" can be the same or different, and depending on the volume of the duct 125, they can be, for example, between 0.1 seconds and several seconds.

[0074] Figure 5 is a flowchart showing the operation to transition to the fan ON state in the image forming apparatus 101 of the first embodiment.

[0075] [S501] The fan control unit 303 checks the command received from the print control unit 301 (S501). If it is a fan ON command (S501 / Yes), processing proceeds to S502; otherwise, it remains at S501.

[0076] [S502] If the command to turn the fan ON is issued, the fan control unit 303 turns on the intake fan 127A (S502).

[0077] [S503] The fan control unit 303 checks the command received from the print control unit 301 (S503). If it is a fan OFF command (S503 / Yes), the process proceeds to S504. If it is not a fan OFF command (S503 / No), the process proceeds to S505.

[0078] [S504] If the command to turn off the fan is issued, the fan control unit 303 turns off the intake fan 127A (S504).

[0079] [S505] Unless a fan OFF command is issued, the fan control unit 303 determines whether or not the pre-set exhaust OnDelay time has elapsed (S505).

[0080] If the exhaust OnDelay time has not elapsed (S505 / No), the process returns to S503 and waits until the exhaust OnDelay time has elapsed.

[0081] On the other hand, once the exhaust OnDelay time has elapsed (S505 / Yes), the process proceeds to S506.

[0082] [S506] Once the exhaust OnDelay time has elapsed, the fan control unit 303 turns on the intake fan 127A (S506).

[0083] Figure 6 is a flowchart showing the operation to transition to the fan OFF state in the image forming apparatus 101 of the first embodiment.

[0084] [S601] The fan control unit 303 checks the command received from the print control unit 301 (S601). If it is a fan OFF command (S601 / Yes), processing proceeds to S602; otherwise, it remains at S601 (S601 / No).

[0085] [S602] If the command to turn off the fan is issued, the fan control unit 303 turns off the exhaust fan 127B (S602).

[0086] [S603] The fan control unit 303 checks the command received from the print control unit 301 (S603). If it is a fan ON command (S603 / Yes), processing proceeds to S604. If it is not a fan ON command (S603 / No), processing proceeds to S605.

[0087] [S604] If the command to turn the fan ON is issued, the fan control unit 303 turns on the exhaust fan 127B (S604).

[0088] [S605] If the fan is not turned ON, the fan control unit 303 determines whether the pre-set intake OffDelay time has elapsed (S605).

[0089] If the intake OffDelay time has not elapsed (S605 / No), the process returns to S603 and waits until the intake OffDelay time has elapsed.

[0090] On the other hand, once the intake OffDelay time has elapsed (S605 / Yes), the process proceeds to S606.

[0091] [S606] Once the intake OffDelay time has elapsed, the fan control unit 303 turns off the intake fan 127A (S606).

[0092] Figure 7 is a time chart showing the ON / OFF timing of the intake fan 127A and exhaust fan 127B in the first embodiment. In the example in Figure 7, the time chart shows the fan being turned ON and then OFF.

[0093] In Figure 7, when the fan is OFF and the print control unit 301 issues a fan ON command, the intake fan 127A turns ON first, and after the exhaust ON Delay time has elapsed, the exhaust fan 127B turns ON.

[0094] Furthermore, if a fan OFF command is issued from the print control unit 301 while the fan is ON, the exhaust fan 127B will turn OFF first, and after the intake OFF Delay time has elapsed, the intake fan 127A will turn OFF.

[0095] Figure 8 is an explanatory diagram illustrating the airflow inside and around the duct 125 when each fan is in operation according to the first embodiment.

[0096] In Figures 8(a) to 8(c), arrow "801" indicates the airflow drawn into duct 125 from the outside by the intake fan 127A. Arrow "802" indicates the airflow discharged from duct 125 to the outside by the exhaust fan 127B. Arrow "803" indicates the airflow through duct 125 from intake fan 127A towards exhaust fan 127B. Arrow "804" indicates the airflow from intake fan 127A towards detection window 201 opened in duct 125. Arrow "805" indicates the airflow from detection window 201 towards exhaust fan 127B. Arrow "806" indicates the airflow from detection window 201 to area 808 outside duct 125. Arrow "809" indicates the airflow from area 808 outside duct 125 to detection window 201.

[0097] Region "807" represents the spatial area near the detection window 201 inside the duct 125, and region "808" represents the area near the detection window 201 outside the duct 125. The atmospheric pressure in region 807 is expressed as atmospheric pressure "P807," and the atmospheric pressure in region 808 is expressed as atmospheric pressure "P808."

[0098] First, Figure 8(c) will be used to explain the airflow when airborne particles adhere to the lens of the non-contact temperature sensing element 126.

[0099] Figure 8(c) shows the airflow inside and around the duct 125 when the intake fan 127A is OFF and the exhaust fan 127B is ON.

[0100] The air "802" discharged by the exhaust fan 127B is formed by the air "803" supplied from the intake fan 127A, which is in the OFF state, and the air "805" supplied from the detection window 201. In other words, although the intake fan 127A is OFF, the exhaust fan 127B takes in the air "803" from the intake fan 127A side and the air "805" from the detection window 201 side, and the exhaust fan 127B exhausts the air inside the duct 125.

[0101] At this time, the amount of air "803" flowing from the intake fan 127A (the amount of air flowing) becomes less compared to the amount of air "803" in FIG. 8(a).

[0102] Here, when an air flow "805" occurs from the detection window 201 to the exhaust fan 127B, the magnitude relationship between the air pressure "P807" and the air pressure "P808" becomes "P807 < P808", and the air pressure in the region "808" becomes higher than the air pressure in the region "807".

[0103] Therefore, the air flow "809" near the detection window 201 is in the direction from the fixing device 116 into the duct 125. Then, air containing floating substances such as paper dust, unfixed toner, and water vapor generated in the fixing device 116 flows into the duct 125 and adheres to the lens surface of the non-contact temperature detection element 126. This causes a decrease in the detection accuracy of the non-contact temperature detection element 126.

[0104] This embodiment prevents the air flow flowing in through the detection window 201 described in FIG. 8(c). Hereinafter, it will be described using FIGS. 8(a) and 8(b).

[0105] FIG. 8(a) is a diagram showing the air flow inside and around the duct 125 when both the intake fan 127A and the exhaust fan 127B are in the ON state (fan ON state).

[0106] Most of the air "801" taken in by the intake fan 127A is recovered by the exhaust fan 127B, and an air flow "803" from the intake fan 127A toward the exhaust fan 127B occurs.

[0107] A portion of the air "801" taken in by the intake fan 127A becomes air "804" directed toward the detection window 201. At this time, the relationship between the atmospheric pressure "P807" in region "807" and the atmospheric pressure "P808" in region "808" is "P807 > P808", meaning that the atmospheric pressure in region "807" is greater than the atmospheric pressure in region "808". Therefore, as indicated by the arrow "806" showing the airflow between the detection windows 201, an airflow is generated from inside the duct 125 toward the fixing device 116.

[0108] Thus, when the fan is ON, an airflow is generated as indicated by the arrow "806," which prevents the lens of the non-contact temperature sensing element 126 from becoming dirty.

[0109] Figure 8(b) shows the airflow inside and around the duct 125 when the intake fan 127A is ON and the exhaust fan 127B is OFF.

[0110] The air "801" drawn in by the intake fan 127A is divided into air "803" that goes towards the exhaust fan 127B and air "804" that goes towards the detection window 201.

[0111] At this time, since the exhaust fan 127B is OFF, the amount of air "803" (i.e., the amount of air flowing) from the intake fan 127A to the exhaust fan 127B is less than the amount of air flowing indicated by arrow "803" in Figure 8(a).

[0112] At this time, the amount of airflow "804" blown from the intake fan 127A to the detection window 201 increases, so the relationship between the atmospheric pressure "P807" in region 807 and the atmospheric pressure "P808" in region 808 becomes "P807 > P808", meaning that the atmospheric pressure in region "807" is greater than the atmospheric pressure in region "808". As a result, an airflow is generated from inside the duct 125 toward the fixing device 116, as indicated by the arrow "806" showing the airflow between the detection windows 201.

[0113] Even in this state, the airflow indicated by arrow "806" is generated, which prevents the lens of the non-contact temperature sensing element 126 from becoming dirty.

[0114] (A-3) Effects of the first embodiment As described above, according to the first embodiment, it is possible to prevent a situation in which the intake fan 127A is turned OFF and the exhaust fan 127B is turned ON, so that the air flowing between the detection windows of the duct is always directed from the duct towards the fuser.

[0115] This prevents the lens surface from becoming dirty due to airflow from the fuser being received by the non-contact temperature sensing element, and the resulting deterioration of detection accuracy.

[0116] (B) Second Embodiment Next, a second embodiment of the image forming apparatus and image forming method according to the present invention will be described in detail with reference to the drawings.

[0117] (B-1) Configuration of the second embodiment The configuration and control system of the image forming apparatus of the second embodiment are basically the same as those of the image forming apparatus 101 of the first embodiment, so the second embodiment will also be explained using Figures 1 and 3.

[0118] The difference from the first embodiment lies in the configuration inside the duct 125, so this explanation will focus on the configuration inside the duct 125.

[0119] Figure 9 is a configuration diagram showing the configuration of the duct 125 according to the second embodiment.

[0120] Similar to the first embodiment, an intake fan 127A is installed at one end of the duct 125, and an exhaust fan 127B is installed at the other end, and the air inside the duct 125 flows from the intake fan 127A side to the exhaust fan 127B side.

[0121] Furthermore, similar to the first embodiment, the non-contact temperature sensing element 126 is provided in the duct 125 near the detection window 201 and detects the temperature of the fixing device 116 through the detection window 201.

[0122] A partition 900 is provided inside the duct 125 to separate the detection window 201 and the non-contact temperature detection element 126. The partition 900 has a partition wall 901 provided between the exhaust fan 127B and the detection window 201 (or the non-contact temperature detection element 126), and a bottom wall 902 extending from one end (for example, the lower end) of the partition wall 901 toward the intake fan 127A along the longitudinal direction (Y-axis direction) of the duct 125.

[0123] Here, various methods can be applied to attach the partition 900, but for example, it can be attached by fitting the partition 900 into the inner wall of the duct 125. For example, the partition wall 901 and the bottom wall 902 can be formed integrally, and the partition wall 901 can be attached to the upper inner wall of the duct 125.

[0124] In this example, the partition 900 is fitted into the inner wall of the duct 125, and although it can guide most of the airflow, the space between the detection window 201 and the exhaust fan 127B is not completely sealed. In other words, the area around the partition 901 attached to the upper inner wall of the duct 125 is not completely sealed, and there is a very small gap.

[0125] (B-2) Operation of the second embodiment Next, the operation of the control method for the intake fan 127A and exhaust fan 127B of the duct 125 in the image forming apparatus 101 of the second embodiment will be described with reference to the drawings.

[0126] Since the fan control method in the image forming apparatus 101 of the second embodiment is basically the same as that of the first embodiment, Figures 4 to 7 can also be used in the second embodiment.

[0127] Hereinafter, with reference to FIG. 10, the air flow in and around the duct 125 in the driving state of each fan according to the second embodiment will be described.

[0128] FIG. 10(c) is a diagram showing the air flow in and around the duct 125 in a state where the intake fan 127A is OFF and the exhaust fan 127B is ON.

[0129] Here, the structure inside the duct 125 is provided with a partition 900 so that the air taken in from the intake fan 127A flows more toward the non-contact temperature detection element 126 and the detection window 201.

[0130] As described above, this partition 900 is installed in a form that fits into the inner wall of the duct 125.

[0131] Therefore, the vicinity of the partition wall 901 provided between the detection window 201 and the exhaust fan 127B is not completely sealed. As shown in FIG. 10(c), when the intake fan 127A is OFF and the exhaust fan 127B is ON, air "805" flowing from the detection window 201 toward the exhaust fan 127B is generated through the gap near the partition wall 901.

[0132] Thus, when the exhaust fan 127B exhausts the air inside the duct 125, not only the air "803" flowing from the OFF intake fan 127A to the exhaust fan 127B but also the air "805" flowing from the detection window 201 toward the exhaust fan 127B through a slight gap near the partition wall 901 exists.

[0133] At this time, due to the generation of the air flow "805" from the detection window 201 to the exhaust fan 127B, the magnitude relationship between the air pressure "P807" in the region 807 and the air pressure "P808" in the region 808 becomes "P807 < P808", and the air pressure in the region "808" is greater than the air pressure in the region "807".

[0134] Therefore, an air flow from the fixing device 116 toward the duct 125 occurs, as indicated by the arrow "809" showing the air flow between the detection windows 201.

[0135] As a result, air containing suspended matter such as paper dust, unfixed toner, and water vapor generated in the fixing unit 116 flows into the duct 125 and adheres to the lens surface of the non-contact temperature sensing element 126. This causes a decrease in the detection accuracy of the non-contact temperature sensing element 126.

[0136] Therefore, the second embodiment uses the fan control method described in Figures 4 to 7 to prevent the flow of air entering through the detection window 201 described in Figure 10(c).

[0137] The following explanation will be given using Figures 10(a) and 10(b).

[0138] Figure 10(a) shows the airflow inside and around the duct 125 when both the intake fan 127A and the exhaust fan 127B are ON (fan ON state).

[0139] Most of the air "801" taken in by the intake fan 127A is collected by the exhaust fan 127B, creating an airflow "803" from the intake fan 127A towards the exhaust fan 127B.

[0140] A portion of the air "801" taken in by the intake fan 127A becomes air "804" directed toward the detection window 201. At this time, the relationship between the atmospheric pressure "P807" in region "807" and the atmospheric pressure "P808" in region "808" is "P807 > P808", meaning that the atmospheric pressure in region "807" is greater than the atmospheric pressure in region "808". Therefore, as indicated by the arrow "806" showing the airflow between the detection windows 201, an airflow is generated from inside the duct 125 toward the fixing device 116.

[0141] Although an airflow may also occur from the detection window 201 towards the exhaust fan 127B through the partition wall 901, the amount of air "804" flowing from the intake fan 127A towards the detection window 201 is overwhelmingly larger, so the airflow will be as shown by arrow "806".

[0142] Thus, when the fan is ON, an airflow is generated as indicated by the arrow "806," which prevents the lens of the non-contact temperature sensing element 126 from becoming dirty.

[0143] Figure 10(b) shows the airflow inside and around the duct 125 when the intake fan 127A is ON and the exhaust fan 127B is OFF.

[0144] The air "801" drawn in by the intake fan 127A is divided into air "803" that goes towards the exhaust fan 127B and air "804" that goes towards the detection window 201.

[0145] At this time, since the exhaust fan 127B is OFF, the amount of air "803" (i.e., the amount of air flowing) from the intake fan 127A to the exhaust fan 127B is less than the amount of air flowing indicated by arrow "803" in Figure 8(a).

[0146] At this time, the amount of airflow "804" blown from the intake fan 127A to the detection window 201 increases, so the relationship between the atmospheric pressure "P807" in region 807 and the atmospheric pressure "P808" in region 808 becomes "P807 > P808", meaning that the atmospheric pressure in region "807" is greater than the atmospheric pressure in region "808". As a result, an airflow is generated from inside the duct 125 toward the fixing device 116, as indicated by the arrow "806" showing the airflow between the detection windows 201.

[0147] Even in this state, an airflow may still occur from the detection window 201 towards the exhaust fan 127B through the partition wall 901. However, even in this case, since the intake fan 127A is ON, the amount of air "804" (the amount of air flowing) from the intake fan 127A towards the detection window 201 is overwhelmingly large, so the airflow will be as shown by the arrow "806".

[0148] Even in this state, the airflow indicated by arrow "806" is generated, which prevents the lens of the non-contact temperature sensing element 126 from becoming dirty.

[0149] (B-3) Effects of the second embodiment As described above, according to the second embodiment, it is possible to prevent a situation in which the intake fan 127A is turned OFF and the exhaust fan 127B is turned ON, so that the air flowing between the detection windows of the duct is always directed from the duct towards the fuser. This prevents the lens surface from becoming dirty due to the non-contact temperature sensing element receiving airflow from the fuser, and the resulting deterioration of detection accuracy.

[0150] (C) Other embodiments Although various modified embodiments were mentioned in the first and second embodiments described above, the present invention can also be applied to the following modified embodiments.

[0151] (C-1) The present invention can also be applied to electrophotographic printers, copiers, facsimile machines, or multifunction printers that combine multiple of these functions.

[0152] (C-2) The sizes of the intake fan 127A and the exhaust fan 127B can be set according to the size (volume) of the duct 125, but in the first and second embodiments described above, the size of the exhaust fan 127B is larger than the size of the intake fan 127A.

[0153] For example, the exhaust fan 127B may be twice the size of the intake fan 127A (for example, twice the diameter), and the exhaust fan 127B may be used not only for exhausting air from within the duct 125 but also for exhausting air from the surrounding space outside the duct 125 (especially the space between the fixing device 116 and the duct 125). [Explanation of symbols]

[0154] 101...Image forming apparatus, 102...Paper feed cassette, 103...Hopping roller, 104...Registration roller, 105...Conveyor roller, 106...Photoconductor drum, 111 (111C, 111K, 111M, 111Y)...Image forming unit, 112...LED head, 113...Transfer roller, 114...Transfer belt, 115...Belt-driven roller, 116...Fuser, 116A...Opening, 117...Fuser belt, 118...Backup roller, 119...Heater, 120...Ejection roller, 121...Ejection roller, 122...Write sensor, 123...Toner cartridge, 124...EXIT sensor 125...Duct, 126...Non-contact temperature sensing element, 127...Fan, 127A...Intake fan, 127B...Exhaust fan, 201...Sensing window, 301...Print control unit, 302...Fusing control unit, 303...Fan control unit, 304...Paper feed motor, 305...Belt motor, 306...ID motor, 307...Fusing motor, 308...High voltage unit, 900...Partition section, 901...Partition wall, 902...Bottom wall.

Claims

1. Image forming means for forming a developer image on a medium, A fixing means is disposed downstream of the image forming means in the medium transport direction and fixes the developer image onto the medium, A duct disposed between the fixing means and the image forming means, having a non-contact temperature detection unit for detecting the temperature of the fixing means, An intake means is provided at one end of the duct to supply air into the duct, An exhaust means is provided at the other end of the duct for discharging the air inside the duct, Control means for controlling the operation of the intake means and the exhaust means Equipped with, The control means, When air is passed through the duct, the intake means is driven before the exhaust means is driven. When stopping the airflow into the duct, the intake means is stopped after the exhaust means is stopped. An image forming apparatus characterized by the following features.

2. The duct has a detection window at a position corresponding to the fixing means, The non-contact temperature detection unit is disposed within the duct and measures the temperature of the fixing means through the detection window. The duct has a partition inside which the detection window and the non-contact temperature detection unit are separated. The image forming apparatus according to feature 1.

3. The control means, When air is passed through the duct, after the intake means is driven, and after a first time has elapsed, the exhaust means is driven. When stopping the airflow into the duct, the intake means is stopped after a second period of time has elapsed following the stopping of the exhaust means. The image forming apparatus according to feature 1.

4. When air is passed through the duct, the intake means starts to operate first when the intake means and exhaust means start to operate. When stopping the airflow into the duct, the exhaust means starts to stop first when the intake means and the exhaust means stop operating. The image forming apparatus according to feature 1.

5. Image forming means for forming a developer image on a medium, A fixing means is disposed downstream of the image forming means in the medium transport direction and fixes the developer image onto the medium, A duct disposed between the fixing means and the image forming means, having a non-contact temperature detection unit for detecting the temperature of the fixing means, An intake means is provided at one end of the duct to supply air into the duct, An exhaust means is provided at the other end of the duct for discharging the air inside the duct, Control means for controlling the operation of the intake means and the exhaust means A control method for an image forming apparatus comprising, The control means is After driving the intake means, the discharge means is driven, The intake means is stopped after the discharge means is stopped. A control method characterized by the following:

Images