Image forming apparatus

Abstract

An image forming apparatus has a fixing belt, a heating device, a switching element, a breaker, and a control section. The fixing belt is provided in a loopable manner and contacts a sheet on which a toner image is transferred. The heating device heats the fixing belt and heats the toner image via the heated fixing belt. The switching element supplies power supplied from a power source to the heating device. The breaker is connected between the power source and the switching element. The control section switches a state of the breaker to an off state if the state of the breaker is an on state and keeps the state of the breaker to the off state if the state of the breaker is the off state, in a case where the loop of the fixing belt is stopped.

Description

Technical Field

[0001] The embodiments described in this invention generally relate to image forming apparatus. Background Technology

[0002] Previously, image forming apparatuses were known to use a fixing device to fix a toner image onto a sheet. For example, the fixing device heats the toner image by contacting a heated fixing belt with the sheet, thus fixing the toner image onto the sheet on which the toner image has been transferred. Therefore, the fixing device includes a heating element for heating the fixing belt. The heating element is of the type that has a three-terminal bidirectional thyristor switch element provided in the power transmission path. Due to its characteristics, the three-terminal bidirectional thyristor switch element can sometimes cause the heating element to heat unintendedly due to noise from the power supply. Furthermore, the fixing device typically does not detect the temperature of the part heated by the heating element. Based on the above, image forming apparatuses with a fixing device of the type that has a three-terminal bidirectional thyristor switch element provided in the power transmission path are prone to unintended heating of the heating element due to noise from the power supply, thus potentially causing degradation of the fixing belt. Summary of the Invention

[0003] An image forming apparatus is characterized by comprising: a fixing belt arranged in a wraparound manner and in contact with a sheet on which a toner image has been transferred; a heating device for heating the fixing belt and heating the toner image via the heated fixing belt; a switching element for supplying power from a power source to the heating device; a circuit breaker connected between the power source and the switching element; and a control unit that, when the wrapping of the fixing belt stops, switches the state of the circuit breaker to an open state if the circuit breaker is in an on state, and maintains the state of the circuit breaker in an open state if the circuit breaker is in an open state. Attached Figure Description

[0004] Figure 1 This is a diagram illustrating an example of the structure of the image forming apparatus 1.

[0005] Figure 2 This is a hardware structure diagram of the image forming apparatus 1.

[0006] Figure 3 This is a front sectional view of the fixing device 30.

[0007] Figure 4 This is a structural diagram of the main part of the circuit diagram of heater unit 40.

[0008] Figure 5 This is a diagram illustrating an example of the flow of the first process in the processing performed by the control unit 6.

[0009] Figure 6 This is a diagram illustrating an example of the flow of the second process in the processing performed by the control unit 6. Detailed Implementation

[0010] Hereinafter, taking image forming apparatus 1 as an example, the image forming apparatus according to the embodiment will be described with reference to the accompanying drawings.

[0011] Figure 1 This is a diagram illustrating an example of the structure of the image forming apparatus 1.

[0012] The image forming apparatus 1 performs the process of forming an image on a sheet (paper) S.

[0013] The image forming apparatus 1 includes a housing 10, a scanner unit 2, an image forming unit 3, a sheet supply unit 4, a conveying unit 5, a paper discharge tray 7, a reversing unit 9, a control panel 8, and a control unit 6.

[0014] The housing 10 forms the shape of the image forming apparatus 1.

[0015] The scanner unit 2 reads the image information of the object to be copied as the brightness of light. The scanner unit 2 generates an image signal corresponding to the brightness of the read light. The scanner unit 2 outputs the generated image signal to the image forming unit 3.

[0016] The image forming unit 3 forms an output image using a recording agent such as a toner, based on an image signal received from the scanner unit 2 or an externally received image signal. Hereinafter, for ease of explanation, this output image will be referred to as a toner image. The image forming unit 3 transfers the formed toner image onto the surface of the sheet S. The image forming unit 3 heats and pressurizes the toner image transferred onto the surface of the sheet S, fixing the toner image onto the sheet S.

[0017] The sheet supply unit 4 supplies sheets S one by one to the transport unit 5 in conjunction with the image forming unit 3 forming the toner image. The sheet supply unit 4 includes a sheet receiving unit 20 and a pick-up roller 21.

[0018] The sheet storage section 20 stores sheets S of specified sizes and types.

[0019] Pick-up roller 21 picks up sheets S one by one from sheet receiving section 20. Pick-up roller 21 supplies the picked-up sheets S to conveying section 5.

[0020] The conveying unit 5 conveys the sheet S supplied by the sheet supply unit 4 to the image forming unit 3. The conveying unit 5 includes a conveying roller 23 and a positioning roller 24.

[0021] The conveying roller 23 conveys the sheet S supplied by the pick-up roller 21 to the positioning roller 24. The conveying roller 23 brings the leading edge of the sheet S in the conveying direction into contact with the roll gap N of the positioning roller 24.

[0022] The positioning roller 24 adjusts the position of the leading edge of the sheet S in the conveying direction by flexing the sheet S in the roller gap N. The positioning roller 24 conveys the sheet S according to the timing of the toner image transfer onto the sheet S by the image forming unit 3.

[0023] The image forming unit 3 will now be described in detail.

[0024] The image forming unit 3 includes multiple image forming sections 25, a laser scanning unit 26, an intermediate transfer belt 27, a transfer section 28, and a fixing device 30.

[0025] The image forming unit 25 includes a photosensitive drum 25d. The image forming unit 25 forms a toner image on the photosensitive drum 25d that corresponds to an image signal received from the scanner unit 2 or an image signal received from an external source. Multiple image forming units 25Y, 25M, 25C, and 25K form toner images using yellow, magenta, cyan, and black toners, respectively.

[0026] A charge collector and a developer are arranged around the photosensitive drum 25d. The charge collector charges the surface of the photosensitive drum 25d. The developer contains a developer containing toners of yellow, magenta, cyan, and black. The developer develops the electrostatic latent image on the photosensitive drum 25d. As a result, a toner image is formed on the photosensitive drum 25d using the various colors of toner.

[0027] The laser scanning unit 26 exposes the charged photosensitive drum 25d by scanning laser L. The laser scanning unit 26 exposes the photosensitive drums 25d of different color image forming sections 25Y, 25M, 25C, and 25K using different lasers LY, LM, LC, and LK. Thus, the laser scanning unit 26 forms an electrostatic latent image on the photosensitive drum 25d.

[0028] The toner image on the surface of the photosensitive drum 25d is transferred onto the intermediate transfer belt 27 in one pass.

[0029] The transfer unit 28 transfers the toner image that was first transferred to the intermediate transfer belt 27 onto the surface of the sheet S at the secondary transfer position.

[0030] The fixing device 30 heats and pressurizes the toner image transferred onto the sheet S, fixing the toner image onto the sheet S.

[0031] The reversal unit 9 reverses the sheet S in order to form an image on the back side of the sheet S. The reversal unit 9 reverses the front and back sides of the sheet S discharged from the fixing device 30 by folding it back. The reversal unit 9 then conveys the reversed sheet S toward the positioning roller 24.

[0032] The paper tray 7 holds the sheet S with the image formed and discharged.

[0033] The control panel 8 is part of the input section where the operator inputs information for operating the image forming apparatus 1. The control panel 8 includes a touch panel, various physical keys, etc.

[0034] The control unit 6 controls each part of the image forming apparatus 1. Figure 1 The location of the control unit 6 shown is just one example; it could also be located in other places inside the image forming apparatus 1.

[0035] Figure 2 This is a hardware structure diagram of the image forming apparatus 1. The image forming apparatus 1 includes a CPU (Central Processing Unit) 91, a memory 92, an auxiliary storage device 93, etc., connected via a bus, and executes various programs. By executing various programs, the image forming apparatus 1 functions as a device including a scanner unit 2, an image forming unit 3, a sheet supply unit 4, a transport unit 5, a reversal unit 9, a control panel 8, and a communication unit 90.

[0036] CPU 91 functions as control unit 6 by executing various programs stored in memory 92 and auxiliary storage device 93. Control unit 6 controls the operation of each functional unit of image forming apparatus 1.

[0037] The auxiliary storage device 93 is constructed using storage devices such as magnetic hard disk devices and semiconductor storage devices. The auxiliary storage device 93 stores various types of information.

[0038] The communication unit 90 is configured to include a communication interface for connecting the device to an external device. The communication unit 90 communicates with the external device via the communication interface.

[0039] The fixing device 30 will now be described in detail.

[0040] Figure 3 This is a front sectional view of the fixing device 30. Figure 3 The three-dimensional coordinate system depicted in the middle represents Figure 3 The direction in the middle. For ease of explanation, the following will be... Figure 3 In the three-dimensional coordinate system depicted herein, the X-axis will be simply referred to as the X-axis. Furthermore, for ease of explanation, the positive direction of the X-axis will be referred to as the +x direction. Furthermore, for ease of explanation, the negative direction of the X-axis will be referred to as the -x direction. Furthermore, for ease of explanation, the following... Figure 3 In the three-dimensional coordinate system depicted herein, the Y-axis will be simply referred to as the Y-axis. Furthermore, for ease of explanation, the positive direction of the Y-axis will be referred to as the +y direction. Furthermore, for ease of explanation, the negative direction of the Y-axis will be referred to as the -y direction. Furthermore, for ease of explanation, the following... Figure 3In the three-dimensional coordinate system depicted herein, the Z-axis will be simply referred to as the Z-axis. Furthermore, for ease of explanation, the positive direction of the Z-axis will be referred to as the +z direction. Additionally, for ease of explanation, the negative direction of the Z-axis will be referred to as the -z direction.

[0041] The fixing unit 30 includes a pressure roller 30p and a film unit 30h.

[0042] A pressure roller 30p forms a gap N between itself and the film unit 30h. The pressure roller 30p applies pressure to the toner image on the sheet S that enters the gap N. The pressure roller 30p rotates and conveys the sheet S. The pressure roller 30p has a metal core 32, an elastic layer 33, and a release layer (not shown).

[0043] The metal core 32 is formed into a cylindrical shape from a metal material such as stainless steel. Both ends of the metal core 32 are supported axially to allow rotation. The metal core 32 is driven to rotate by a motor (not shown). The metal core 32 abuts against a cam component (not shown). The cam component rotates to bring the metal core 32 closer to and further away from the diaphragm unit 30h.

[0044] The elastic layer 33 is formed of an elastic material such as silicone rubber. The elastic layer 33 is formed on the outer peripheral surface of the metal core 32 with a certain thickness.

[0045] The release layer (not shown) is formed of resin materials such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). The release layer is formed on the outer peripheral surface of the elastic layer 33.

[0046] Using an ASKER-C hardness tester, the hardness of the outer circumferential surface of the pressure roller 30p is preferably 40° to 70° under a load of 9.8N. This ensures the area of ​​the roll gap N and the durability of the pressure roller 30p.

[0047] The pressure roller 30p can approach and move away from the film unit 30h via the rotation of the cam member. When the pressure roller 30p approaches the film unit 30h and is pressed by the pressure spring, a roller gap N is formed. On the other hand, if a paper jam occurs in the fixing device 30, the paper S can be removed by moving the pressure roller 30p away from the film unit 30h. By moving the pressure roller 30p away from the film unit 30h under a predetermined state, plastic deformation of the tubular film 35 caused by the pressure applied by the pressure roller 30p to the tubular film 35 can be prevented. This predetermined state is the state in which the tubular film 35 stops rotating (e.g., in a dormant state).

[0048] The pressure roller 30p rotates by a motor. When the pressure roller 30p rotates with the roll gap N formed, the tubular film 35 of the film unit 30h rotates passively. Hereinafter, for ease of explanation, the passive rotation of the tubular film 35 will be described as the rotation of the tubular film 35. The pressure roller 30p rotates with the sheet S positioned in the roll gap N, thereby conveying the sheet S in the conveying direction W.

[0049] The film unit 30h heats the toner image on the sheet S that enters the roll gap N. The film unit 30h includes a cylindrical film (cylindrical body) 35, a heater unit 40, a heater thermometer 62, a thermostat 68, and a film thermometer 64. In this embodiment, other components included in the film unit 30h, such as heat transfer components, are omitted from description.

[0050] The tubular film 35 is an example of a fixing belt. The tubular film 35 is formed in a tubular shape. From its inner circumference, the tubular film 35 sequentially comprises a base layer, an elastic layer, and a release layer. The base layer is formed into a tubular shape from a material such as nickel (Ni). The elastic layer is stacked on the outer circumferential surface of the base layer. The elastic layer is formed from an elastic material such as silicone rubber. The release layer is stacked on the outer circumferential surface of the elastic layer. The release layer is formed from a material such as PFA resin. The tubular film 35 is arranged in a manner that allows it to wrap around a predetermined axis. Therefore, the tubular film 35 wraps around the sheet S as the pressure roller 30p rotates. When the sheet S enters the roll gap N during this wrapping, the tubular film 35 contacts the sheet S at a predetermined contact position. Furthermore, the tubular film 35 is heated by the heater unit 40. Therefore, the tubular film 35 can heat the toner image of the sheet S that has entered the roll gap N.

[0051] The heater unit 40 is an example of a heating device. The heater unit 40 heats the fixing belt and heats the toner image on the sheet S via the heated tubular film 35.

[0052] The heater unit 40 is disposed inside the cylindrical diaphragm 35. A grease (not shown) is applied to the inner circumferential surface of the cylindrical diaphragm 35. The heater unit 40 contacts the inner circumferential surface of the cylindrical diaphragm 35 via the grease. If the heater unit 40 heats up, the viscosity of the grease decreases. This ensures the sliding properties of the heater unit 40 and the cylindrical diaphragm 35.

[0053] The heater thermometer 62 is, for example, a thermistor. The heater thermometer 62 measures the temperature of the heater unit 40.

[0054] The thermostat 68 is configured in the same way as the heater thermometer 62. The thermostat 68 cuts off the power to the heating element of the heater unit 40 when the measured temperature of the heater unit 40 exceeds the specified temperature.

[0055] like Figure 3As shown, a thin-film thermometer 64 is disposed inside the cylindrical thin film 35 and on the +x direction side of the heater unit 40. The thin-film thermometer 64 is in contact with the inner circumferential surface of the cylindrical thin film 35 to measure the temperature of the cylindrical thin film 35. Figure 3 As shown, the temperature of the cylindrical film 35 measured by the thin-film thermometer 64 is at a predetermined position that is in contact with the cylindrical film 35 and the sheet S, which is a position different from the position heated by the heater unit 40. Therefore, by measuring the temperature of the cylindrical film 35 within its surrounding area, the thin-film thermometer 64 can measure the temperature of the cylindrical film 35 with high precision.

[0056] Figure 4 This is a structural diagram of the main part of the circuit diagram of heater unit 40. Figure 4 Non-critical components such as connectors have been omitted. Figure 4 In the image, a bottom view of the heater unit 40 is shown. Figure 4 In this configuration, multiple contacts LN1 are electrically connected to each other via the transmission path. However, in... Figure 4 In order to prevent the diagram from becoming too complex, the transmission paths connecting multiple nodes LN1 to each other have been omitted. Figure 4 In this configuration, multiple contacts LN2 are electrically connected to each other via the transmission path. However, in... Figure 4 In order to prevent the diagram from becoming too complex, the transmission paths connecting multiple LN2 nodes to each other have been omitted. Figure 4 In this configuration, multiple contacts LN3 are electrically connected to each other via the transmission path. However, in... Figure 4 In order to prevent the diagram from becoming too complex, the transmission path connecting the multiple contacts LN3 to each other has been omitted. This is done without impairing the function of the image forming apparatus 1 described in the embodiment. Figure 4 The circuit diagram shown can be modified, replaced, or deleted in any way.

[0057] The heater unit 40 includes a substrate (not shown), a first end heating element 40A mounted on the substrate, n central heating elements, and a second end heating element 40C. n can be any integer greater than or equal to 1. Figure 4 In this context, the n central heating elements are designated as central heating elements 40B1 to 40Bn. The first end heating element 40A, the n central heating elements, and the second end heating element 40C are examples of the heating elements of the heater unit 40 described above.

[0058] Three input terminals, 401, 402, and 403, are mounted on the base plate of the heater unit 40. Input terminal 401 is connected to contact L1. Input terminal 402 is connected to contact L2. Input terminal 403 is connected to contact L3.

[0059] Two heater thermometers 62 and two thermostats 68 are mounted on the base plate of heater unit 40. Figure 4 In the diagram, the two heater thermometers 62 are designated as heater thermometers 62A and 62B. Figure 4 In the diagram, the two thermostats 68 are referred to as thermostats 68A and 68B.

[0060] The substrate of the heater unit 40 is a generally rectangular substrate. A first end heating element 40A is mounted on one of the ends along the long side of the substrate of the heater unit 40, i.e., the first end. A second end heating element 40C is mounted on the other end along the long side of the substrate of the heater unit 40, i.e., the second end. Between the first end heating element 40A and the second end heating element 40C, n central heating elements are arranged from the first end heating element 40A side toward the second end heating element 40C side. These n central heating elements are arranged from the first end heating element 40A side toward the second end heating element 40C side in the order of central heating element 40B1, central heating element 40B2, ..., central heating element 40Bn.

[0061] Heater thermometer 62A is disposed, for example, within the range of the central heating element 40Bn. Heater thermometer 62B is disposed, for example, within the range of the second end heating element 40C. Heater thermometers 62A and 62B may also be disposed within the range of other heating elements provided in the heater unit 40.

[0062] Thermostat 68A is disposed within the area of ​​the first end heating element 40A. Thermostat 68B is disposed within the area of ​​the central heating element 40B2. Thermostats 68A and 68B may also be disposed within the areas of other heating elements provided in the heater unit 40.

[0063] One of the two terminals of thermostat 68A is connected to contact LN1 via a transmission path. The other of the two terminals of thermostat 68A is connected to one of the two terminals of thermostat 68B via a transmission path. The other of the two terminals of thermostat 68B is connected to one of the two terminals of heater thermometer 62A via a transmission path. The other of the two terminals of heater thermometer 62A is connected to one of the two terminals of heater thermometer 62B via a transmission path. The other of the two terminals of heater thermometer 62B is connected to the first end heating element 40A, n central heating elements, and the second end heating element 40C via transmission paths. Thus, power is supplied from input terminal 401 to thermostats 68A, 68B, and heater thermometers 62A, 62B. Additionally, power is supplied from input terminal 401 to the first end heating element 40A, n central heating elements, and the second end heating element 40C.

[0064] The terminal of the first end heating element 40A that is not connected to the heater thermometer 62B is connected to the contact LN2 via a transmission path. The terminal of the second end heating element 40C that is not connected to the heater thermometer 62B is connected to the contact LN2 via a transmission path. Thus, power is supplied from the input terminal 402 to the first end heating element 40A and the second end heating element 40C respectively.

[0065] The terminal of each of the n central heating elements that is not connected to the heater thermometer 62B is connected to the contact LN3 via a transmission path. Thus, power is supplied to each of the n central heating elements from the input terminal 403.

[0066] The input terminal 401 of the heater unit 40 is connected via a transmission path to the output terminal SC13 of the first switching circuit SC1. The input terminal 402 of the heater unit 40 is connected via a transmission path to the output terminal SC14 of the first switching circuit SC1. The input terminal 403 of the heater unit 40 is connected via a transmission path to the output terminal SC15 of the first switching circuit SC1. In addition to the three output terminals SC13 to SC15, the first switching circuit SC1 also has two input terminals SC11 and SC12.

[0067] The first switching circuit SC1 is a circuit that supplies a specified amount of power from the power source PS to the heater unit 40. The first switching circuit SC1 includes two switching elements: a first switching element T1 and a second switching element T2.

[0068] The first switching element T1 is, for example, a three-terminal bidirectional thyristor switching element. The first switching element T1 can also be a gate turn-off thyristor (GTO), an insulated gate bipolar transistor (IGBT), or the like to replace the three-terminal bidirectional thyristor switching element.

[0069] The second switching element T2 is, for example, a three-terminal bidirectional thyristor switching element. The second switching element T2 can also be a gate turn-off thyristor (GTO), an insulated gate bipolar transistor (IGBT), or the like to replace the three-terminal bidirectional thyristor switching element.

[0070] The first switching element T1 can be the same type of switching element as the second switching element T2, or it can be a different type of switching element than the second switching element T2. However, for reasons such as making control easier, the first switching element T1 is preferably the same type of switching element as the second switching element T2.

[0071] exist Figure 4In the example shown, the input terminal SC11 of the first switching circuit SC1 is connected to the output terminal SC13 via a transmission path.

[0072] exist Figure 4 In the example shown, the input terminal SC12 of the first switching circuit SC1 is connected to the output terminal SC14 and the output terminal SC15 via two separate transmission paths.

[0073] exist Figure 4 In the example shown, a first switching element T1 is connected between the input terminal SC11 and the output terminal SC14. Specifically, the input terminal SC11 is connected to the input terminal of the first switching element T1. The output terminal of the first switching element T1 is connected to the output terminal SC14.

[0074] exist Figure 4 In the example shown, a second switching element T2 is connected between the input terminal SC11 and the output terminal SC15. Specifically, the input terminal SC11 is connected to the input terminal of the second switching element T2. The output terminal of the second switching element T2 is connected to the output terminal SC15.

[0075] The gate terminal of the first switching element T1 is connected to the CPU 91 of the control unit 6 via a transmission path not shown. That is, the control unit 6 inputs a signal to the gate terminal of the first switching element T1 to switch the state of the first switching element T1 to the ON state.

[0076] The gate terminal of the second switching element T2 is connected to the CPU 91 of the control unit 6 via a transmission path not shown. That is, the control unit 6 inputs a signal to the gate terminal of the second switching element T2 to switch the state of the second switching element T2 to the ON state.

[0077] The input terminal SC11 of the first switching circuit SC1 is connected to the output terminal SC23 of the second switching circuit SC2 via a transmission path. The input terminal SC12 of the first switching circuit SC1 is connected to the output terminal SC24 of the second switching circuit SC2 via a transmission path. In addition to the output terminals SC23 and SC24, the second switching circuit SC2 also has two input terminals SC21 and SC22.

[0078] like Figure 4 As shown, the second switching circuit SC2 is connected between the power supply PS and the first switching circuit SC1. The second switching circuit SC2 controls the supply of a predetermined power from the power supply PS to the first switching circuit SC1. Figure 4 In the example shown, the second switching circuit SC2 also removes noise from the specified power supplied by the power source PS.

[0079] The second switching circuit SC2 includes a circuit breaker SG, a fuse HS, a resistor R, and a filter FT. The second switching circuit SC2 can also be configured without the fuse HS, resistor R, and filter FT.

[0080] The input terminal SC21 of the second switching circuit SC2 is connected to one of the terminals of the fuse HS via a transmission path. The other terminal of the fuse HS is connected to the input terminal of the circuit breaker SG via a transmission path.

[0081] The circuit breaker SG is, for example, a relay switch. The circuit breaker SG can also be replaced by other switching elements such as field-effect transistors (FETs). The control terminals of the circuit breaker SG are connected to the CPU 91 of the control unit 6 via a transmission path not shown. That is, the control unit 6 inputs a signal to the control terminals of the circuit breaker SG to switch the state of the circuit breaker SG to the on or off state.

[0082] The output terminal of circuit breaker SG is connected via a transmission path to one of the terminals of resistor R and one of the two input terminals of filter FT. The other terminal of resistor R is connected via a transmission path to input terminal SC22 and the other of the two input terminals of filter FT. One of the two output terminals of filter FT is connected via a transmission path to output terminal SC23. The other of the two output terminals of filter FT is connected via a transmission path to output terminal SC24.

[0083] A filter FT is a filter that removes noise from a specified power supply provided by a power source PS. A filter FT can be any filter capable of removing noise from a specified power supply provided by PS.

[0084] The input terminal SC21 of the second switching circuit SC2 is connected to the power terminal PS1 of the power supply PS via a transmission path. The input terminal SC22 of the second switching circuit SC2 is connected to the power terminal PS2 of the power supply PS via a transmission path.

[0085] The power supply PS is an AC power source. The power supply PS only needs to be an AC power source; it can be any type of power source.

[0086] With the circuit structure described above, the heater unit 40 heats up some or all of the first end heating element 40A, n central heating elements, and second end heating element 40C according to the prescribed power supplied from the power source PS. Thus, the heater unit 40 can heat the cylindrical film 35 and, through the heated cylindrical film 35, heat the toner image.

[0087] When the first switching element T1, the second switching element T2, and the circuit breaker SG are in the first state, the heater unit 40 heats the cylindrical diaphragm 35. The first state is as follows: the circuit breaker SG is in the ON state and at least one of the first switching element T1 and the second switching element T2 is in the ON state.

[0088] When the first switching element T1, the second switching element T2, and the circuit breaker SG are in their second state, the heater unit 40 does not heat the cylindrical diaphragm 35. The second state is as follows: the circuit breaker SG is in the open state. In the second state, the first switching element T1 and the second switching element T2 can each be either in the on or off state.

[0089] However, when the circuit breaker SG is in the open state and at least one of the first switching element T1 and the second switching element T2 is in the closed state, the heater unit 40 may sometimes heat the cylindrical film 35 at unexpected times due to noise from the power supply PS. Therefore, the control unit 6 performs the switching control described below. As a result, the image forming apparatus 1 can suppress the situation where the heater unit 40 is unexpectedly heated due to noise from the power supply PS. As a result, the image forming apparatus 1 can suppress the deterioration of the cylindrical film 35.

[0090] The following describes the processing performed by the control unit 6.

[0091] Figure 5 This diagram illustrates an example of the flow of the first process performed by the control unit 6. The first process involves switching the state of the circuit breaker SG from closed to open when the circumduction of the cylindrical diaphragm 35 has stopped and the circuit breaker SG is in the closed state. The second process involves maintaining the state of the circuit breaker SG in the open state when the circumduction of the cylindrical diaphragm 35 has stopped and the circuit breaker SG is in the open state. The control unit 6 performs this process repeatedly, for example, during the startup of the image forming apparatus 1. Figure 5 The flowchart shown illustrates the processing.

[0092] The control unit 6 determines whether the cylindrical film 35 is wound (ACT101). For example, if the motor that rotates the pressure roller 30p is not driven, the control unit 6 determines that the cylindrical film 35, which is wound according to the rotation of the pressure roller 30p, is not wound. For example, if the motor that rotates the pressure roller 30p is driven, the control unit 6 determines that the cylindrical film 35, which is wound according to the rotation of the pressure roller 30p, is wound. The control unit 6 may also be configured to determine whether the cylindrical film 35 is wound using other methods such as using a sensor.

[0093] If the control unit 6 determines that the cylindrical film 35 is wrapped (ACT101-Yes), it switches to ACT101 and determines again whether the cylindrical film 35 is wrapped.

[0094] On the other hand, if the control unit 6 determines that the cylindrical diaphragm 35 is not wrapped (ACT101 - Yes), it determines whether the circuit breaker SG is in the open state (ACT102). Figure 5 In the code, the action of ACT102 is indicated by "Circuit breaker disconnected?".

[0095] If the control unit 6 determines that the circuit breaker SG is in the open state (ACT102-Yes), it switches to ACT101 and determines again whether the cylindrical diaphragm 35 is wrapped.

[0096] On the other hand, if the control unit 6 determines that the circuit breaker SG is not in the open state (ACT102 - No), it switches the state of the circuit breaker SG to the open state (ACT103). Figure 5 In this process, the action of ACT103 is indicated by "circuit breaker tripped". After the action of ACT103 is performed, the control unit 6 moves to ACT101 to determine again whether the cylindrical diaphragm 35 is wrapped.

[0097] As described above, when the rotation of the cylindrical diaphragm 35 stops and the circuit breaker SG is in the ON state, the image forming apparatus 1 switches the state of the circuit breaker SG to the OFF state. Furthermore, when the rotation of the cylindrical diaphragm 35 stops and the circuit breaker SG is in the OFF state, the image forming apparatus 1 maintains the state of the circuit breaker SG in the OFF state. Therefore, the image forming apparatus 1 can suppress the situation where the heater unit 40 is unexpectedly heated due to noise from the power supply PS. As a result, the image forming apparatus 1 can suppress the deterioration of the cylindrical diaphragm 35.

[0098] Figure 6This diagram illustrates an example of the flow of the second process performed by the control unit 6. For ease of explanation, at least one of the first switching element T1 and the second switching element T2 will be referred to as switching element TO. For ease of explanation, both the first switching element T1 and the second switching element T2 will be referred to as switching element TA. The second process is the process of not switching the state of the circuit breaker SG when the state of the switching element TO is in the ON state. The second process is the process of keeping the state of the circuit breaker SG in the OFF state without heating the cylindrical diaphragm 35 by the heater unit 40. The second process is the process of performing the 21st process described below when the heater unit 40 starts heating the cylindrical diaphragm 35. The 21st process is the process of switching the state of the circuit breaker SG to the ON state after the state of the circuit breaker SG is switched while the state of the switching element TA is in the OFF state, and then switching the state of the switching element TO to the ON state. The second process is the process of performing the 22nd process described below when the heater unit 40 stops heating the cylindrical diaphragm 35. The 22nd process is to switch the state of the switching element TA to the open state and then switch the state of the circuit breaker SG to the open state. The second process is to switch the state of the circuit breaker SG to the closed state based on the start of the encirclement of the cylindrical diaphragm 35. The control unit 6 repeatedly performs this process, for example, during the startup of the image forming apparatus 1. Figure 6 The flowchart shown illustrates the processing.

[0099] The control unit 6 determines whether to heat the cylindrical film 35 (ACT201). For example, if the control unit 6 receives an operation to start forming an image on the sheet S, it determines that the cylindrical film 35 should be heated. For example, if the control unit 6 does not receive an operation to start forming an image on the sheet S, it determines that the cylindrical film 35 should not be heated. The control unit 6 may also determine whether to heat the cylindrical film 35 using other methods.

[0100] If the control unit 6 determines that heating of the cylindrical diaphragm 35 is not permitted (ACT201 - No), it determines whether the state of the switching element TA is open (ACT208). Figure 6 In the code, the action of ACT208 is indicated by "Switch off?".

[0101] If the control unit 6 determines that the state of the switching element TA is in the off state (ACT208-Yes), it proceeds to step S201 and determines again whether to heat the cylindrical film 35.

[0102] On the other hand, if the control unit 6 determines that the state of the switching element TA is not open (ACT208 - No), it switches the state of the switching element TA to open (ACT209). Figure 6 In the code, "switch off" is used to indicate the processing of ACT209.

[0103] Next, control unit 6 remains on standby until a predetermined second time elapses (ACT210). The predetermined second time is, for example, 50 milliseconds. The predetermined second time can be shorter than 50 milliseconds or longer than 50 milliseconds.

[0104] If the control unit 6 determines that a predetermined second time has elapsed (ACT210 - Yes), it switches the state of circuit breaker SG to the open state (ACT211). Figure 6 In this process, the action of ACT211 is indicated by "circuit breaker tripped". After the action of ACT211 is performed, the control unit 6 moves to ACT201 to determine again whether to heat the cylindrical diaphragm 35.

[0105] On the other hand, when the control unit 6 determines that the tubular film 35 is to be heated (ACT201 - Yes), it controls the motor that rotates the pressure roller 30p, causing the pressure roller 30p to rotate. As a result, the control unit 6 causes the tubular film 35 to begin to rotate (ACT202).

[0106] Next, the control unit 6 determines whether the state of the switching element TA is open (ACT203). Figure 6 In the code, the action of ACT203 is indicated by "Switch off?".

[0107] When the control unit 6 determines that the switching element TA is in the open state (ACT203 - Yes), it switches the circuit breaker SG to the closed state (ACT205). Figure 6 In the text, the processing of ACT205 is indicated by "circuit breaker connected".

[0108] On the other hand, if the control unit 6 determines that the state of the switching element TA is not open (ACT203 - No), it switches the state of the switching element TA to open (ACT204). Figure 6 In this context, the processing of ACT204 is indicated by "switch off". After the processing of ACT204 is completed, control unit 6 moves on to ACT205.

[0109] After processing ACT205, control unit 6 remains in standby mode until a predetermined first time elapses (ACT206). The predetermined first time is, for example, 50 milliseconds. The predetermined first time can be shorter or longer than 50 milliseconds. The predetermined first time can be the same as or different from a predetermined second time.

[0110] If the control unit 6 determines that a predetermined first time has elapsed (ACT206 - Yes), it switches the state of the switching element TO to the ON state (ACT207). Figure 6 In this context, the processing of ACT207 is indicated by "switch on". After the processing of ACT207 is completed, control unit 6 transfers to ACT201.

[0111] Here, the process flow of ACT201→ACT202→ACT203→ACT204→ACT205→ACT206→ACT207→ACT201 is, for example, the process of starting the heating of the cylindrical film 35. That is, when the image forming apparatus 1 starts heating the cylindrical film 35 with the heater unit 40, it performs the 21st process as described above. As described above, the 21st process is as follows: after switching the state of the circuit breaker SG to the on state while keeping the state of the switching element TA in the off state, the state of the switching element TO is switched to the on state. As a result, the image forming apparatus 1 can suppress the shortening of the lifespan of the circuit breaker SG.

[0112] The processing flow of ACT201→ACT202→ACT203→ACT204→ACT205→ACT206→ACT207→ACT201 is, for example, the process of starting the winding of the cylindrical film 35. That is, the image forming apparatus 1 switches the state of the circuit breaker SG to the on state according to the start of the winding of the cylindrical film 35. As a result, the image forming apparatus 1 can more reliably suppress the degradation of the cylindrical film 35 caused by unintended heating due to noise from the power supply PS.

[0113] The process of ACT201→ACT208→ACT201 is, for example, a process in which the heating of the cylindrical film 35 by the heater unit 40 is not performed. That is, the image forming apparatus 1 keeps the circuit breaker SG in the open state without heating the cylindrical film 35 by the heater unit 40.

[0114] The process flow of ACT201→ACT208→ACT209→ACT210→ACT211→ACT201 is, for example, the process of ending the heating of the cylindrical film 35. That is, when the image forming apparatus 1 ends the heating of the cylindrical film 35 by the heater unit 40, it performs the 22nd process as described above. As described above, the 22nd process is the process of switching the state of the switching element TA to the open state and then switching the state of the circuit breaker SG to the open state. As a result, the image forming apparatus 1 can suppress the shortening of the lifespan of the circuit breaker SG.

[0115] Furthermore, when the switching element TO is in the ON state, Figure 6 The flowchart shown also demonstrates a process that does not involve switching the state of the circuit breaker SG. Therefore, the image forming apparatus 1 can suppress the shortening of the lifespan of the circuit breaker SG.

[0116] It should be noted that the image forming apparatus 1 may also have a structure in which either the first switching element T1 or the second switching element T2 is included in the first switching circuit SC1. In this case, in the image forming apparatus 1, the heating of the first end heating element 40A, the n central heating elements, and the second end heating element 40C is controlled by either the first switching element T1 or the second switching element T2.

[0117] As described above, the image forming apparatus (image forming apparatus 1 in this example) includes a fixing belt (a cylindrical film 35 in this example), a heating device (a heater unit 40 in this example), a switching element (a switching element TO in this example), a circuit breaker (a circuit breaker SG in this example), and a control unit (control unit 6 in this example). The fixing belt is arranged in a wraparound manner and contacts a sheet (sheet S in this example) on which a toner image has been transferred. The heating device heats the fixing belt and heats the toner image via the heated fixing belt. The switching element supplies power from the power supply to the heating device. The circuit breaker is connected between the power supply and the switching element. When the wrapping of the fixing belt stops, if the circuit breaker is in the on state, the control unit switches the state of the circuit breaker to the off state. When the wrapping of the fixing belt stops, if the circuit breaker is in the off state, the control unit keeps the state of the circuit breaker in the off state. Thus, the image forming apparatus can suppress unintended heating of the heating device due to noise from the power supply.

[0118] Alternatively, in an image forming apparatus, the switching element can also be a three-terminal bidirectional thyristor switching element.

[0119] Alternatively, in an image forming apparatus, the circuit breaker can also be a relay switch.

[0120] Alternatively, the control unit can be configured such that the circuit breaker does not switch its state when the switching element is in the ON state.

[0121] Alternatively, the control unit can be configured to keep the circuit breaker in the open state when the heating device does not heat the fixing belt.

[0122] Alternatively, the control unit can be configured such that, when the heating device starts heating the fixing belt, after switching the state of the circuit breaker to the on state while keeping the state of the switching element in the off state, the state of the switching element is switched to the on state.

[0123] Alternatively, the control unit may be configured such that, when the heating device starts heating the fixing belt, the state of the circuit breaker is switched to the on state while the state of the switching element is kept in the off state, and after a predetermined first time has elapsed since the state of the circuit breaker was switched to the on state, the state of the switching element is switched to the on state.

[0124] Alternatively, the control unit can be configured such that, when the heating device stops heating the fixing belt, after switching the state of the switching element to the open state, the circuit breaker is switched to the open state.

[0125] Alternatively, the control unit may be configured to switch the state of the switching element to the open state when the heating device stops heating the fixing belt, and switch the state of the circuit breaker to the open state after a predetermined second time has elapsed since the switching element was switched to the open state.

[0126] Alternatively, the control unit can be configured to switch the circuit breaker to the on state based on the start of the fixing belt's rotation.

[0127] It should be noted that a program for implementing the functions of any component in the apparatus described above (e.g., image forming apparatus 1) can also be recorded on a computer-readable recording medium, and the computer system can read and execute the program. It should be noted that the term "computer system" here includes hardware such as an operating system (OS) and peripheral devices. Furthermore, "computer-readable recording medium" refers to removable media such as floppy disks, optical disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into the computer system. In addition, "computer-readable recording medium" also includes media that retain programs for a certain period of time, such as volatile memory (RAM), which is installed inside a computer system acting as a server or client when transmitting programs via networks such as the Internet or communication lines such as telephone lines.

[0128] Furthermore, the aforementioned program can also be transmitted from a computer system storing the program in a storage device or similar device to another computer system via a transmission medium or through transmission waves in the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium that has the function of transmitting information, such as a network (communication network) like the Internet or a communication line (communication line) like a telephone line.

[0129] In addition, the above-described program can also be used to implement a portion of the functions described above. Furthermore, the above-described program can also be a program that can achieve the above functions by combining with programs already recorded in the computer system, a so-called differential file (differential program).

[0130] While several embodiments have been described, these embodiments are merely illustrative and not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and likewise within the scope of the invention as described in the claims and its equivalents.

Claims

1. An image forming apparatus, characterized in that, have: The fixing belt is set in a way that allows it to wrap around the sheet and come into contact with the toner image transferred onto it; A heating device heats the fixing belt and then heats the toner image via the heated fixing belt; A switching element supplies power from a power source to the heating device; A circuit breaker, connected between the power supply and the switching element; and The control unit determines whether the fixing tape is wound. If it determines that the winding of the fixing tape has stopped, it determines whether the circuit breaker is in an open state. If the circuit breaker is in an on state, it switches the circuit breaker to an open state; if the circuit breaker is in an open state, it keeps the circuit breaker in an open state. When the fixing tape is not heated using the heating device, the control unit keeps the circuit breaker in the open state. When the control unit starts heating the fixing belt by the heating device, it switches the state of the circuit breaker to the on state while keeping the switching element in the off state, and then switches the state of the switching element to the on state. When the heating device stops heating the fixing belt, the control unit switches the state of the circuit breaker to the open state after switching the state of the switching element to the open state.

2. The image forming apparatus according to claim 1, characterized in that, The switching element is a three-terminal bidirectional thyristor switching element.

3. The image forming apparatus according to claim 1, characterized in that, The circuit breaker is a relay switch.

4. The image forming apparatus according to claim 1, characterized in that, The control unit does not switch the state of the circuit breaker when the state of the switching element is on.

5. The image forming apparatus according to claim 1, characterized in that, When the heating device starts heating the fixing belt, the control unit switches the state of the circuit breaker to the on state while keeping the state of the switching element in the off state. After a predetermined first time has elapsed since the state of the circuit breaker was switched to the on state, the control unit switches the state of the switching element to the on state.

6. The image forming apparatus according to claim 1, characterized in that, When the heating device stops heating the fixing belt, the control unit switches the state of the switching element to the open state, and after a predetermined second time has elapsed since the state of the switching element was switched to the open state, switches the state of the circuit breaker to the open state.

7. The image forming apparatus according to claim 1, characterized in that, The control unit switches the circuit breaker to the ON state based on the start of the fixing tape's winding.

Images