Image forming apparatus having a fixing unit and heating control method

An image processing apparatus includes a fixing unit including a heater and a fixing belt. The fixing belt is electrically connected between a first power source and a ground terminal. A controller is configured to control the heater to heat the fixing belt. The controller is further configured to determine whether a current is flowing through the fixing belt and, upon determining that a current is not flowing through the fixing belt, control the heater not to heat the fixing belt.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-165351, filed Sep. 11, 2019, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an image forming apparatus and a heating control method.

BACKGROUND

In a belt type or on-demand type fixing device, static electricity may be accumulated on a fixing belt because of its repeated sliding contact with sheets of paper and a heater element of the fixing device. When static electricity accumulates on the fixing belt, an electrostatic offset may occur, thereby deteriorating the quality of an output image formed on the sheet. To prevent the occurrence of such an electrostatic offset, a method has been developed to discharge the accumulated static electricity by connecting the fixing belt to a ground potential (hereinafter, referred to as “GND”). However, since the fixing belt rotates, the connection between the fixing belt and GND tends to be unstable or difficult to maintain continuously.

DETAILED DESCRIPTION

In general, according to one embodiment, an image forming apparatus capable of preventing quality deterioration of an image, and a heating control method are provided.

According to one embodiment, an image processing apparatus includes a fixing unit. The fixing unit includes a heater and a fixing belt. The fixing belt is electrically connected between a first power source and a ground terminal. A controller is configured to control the heater to heat the fixing belt. The controller is further configured to determine whether a current is flowing through the fixing belt and, upon determining that a current is not flowing through the fixing belt, control the heater not to heat the fixing belt.

Hereinafter, an image forming apparatus and a heating control method according to example embodiments will be described with reference to the drawings.

FIG. 1shows a configuration of an image forming apparatus1according to an embodiment. The image forming apparatus1is a multi function peripheral (MFP) device. The image forming apparatus1performs an image forming process and an image fixing process. The image forming process is a process of forming an image on a sheet. The image fixing process is a process of fixing the formed image onto the sheet. The sheet is, for example, a piece of paper on which characters, text, images, or the like can be formed. In general, any type of sheet can be used as long as the sheet can be handled by the image forming apparatus1. The image forming apparatus1can scan or read images on a sheet or document, generate digital data thereby, and generate an image file corresponding to an image on the sheet or document.

The image forming apparatus1includes an image reading unit10, a control panel20, an image forming unit30, a sheet storage unit40, a fixing device50, conveyor rollers61aand61b, paper discharge rollers62aand62b, and a control device70.

The image reading unit10reads an image formed on a sheet as bright and dark signals. For example, the image reading unit10reads (scans) an image printed on a sheet set on a document reading table or platen of the image forming apparatus1. The image reading unit10records the image data that is read/scanned. The recorded image data may be transmitted to another information processing apparatus via a network. The recorded image data may be used to form a corresponding image on another sheet with the image forming unit30.

The control panel20includes a display unit and an operation unit. The display unit is a display device, such as a liquid crystal display, an organic electro luminescence (EL) display, or the like. The display unit displays various types of information related to the image forming apparatus1according to a control signal of the control device70. The operation unit includes a plurality of buttons, keys, switches, or the like. The operation unit receives an input operation from a user. The operation unit outputs a signal according to an input operation performed by the user to the control device70. The display unit and the operation unit may be integrated into a touch-enabled display or the like.

The image forming unit30performs an image forming process. In the image forming process, the image forming unit30forms an image on a sheet based on image data generated by the image reading unit10or image data received through a network.

The image forming unit30includes a transfer belt31, an exposure unit32, a plurality of developing devices including developing devices33Y,33M,33C, and33K, and a plurality of photoconductive drums including photoconductive drums34Y,34M,34C, and34K, and a transfer unit35.

The transfer belt31is an intermediate transfer body. The transfer belt31rotates in a direction indicated by an arrow (depicted as the counterclockwise direction) according to rotation of a roller.

The exposure unit32is provided below the developing devices33Y,33M,33C, and33K facing the photoconductive drums34Y,34M,34C, and34K, respectively. The exposure unit32emits a laser beam toward a photoconductor layer on each of the photoconductive drums34Y,34M,34C, and34K. The exposure unit32is controlled to emit light based on the image data by the control device70. The exposure unit32emits the laser beam based on the image data, thereby a static electrical charge on the photoconductive layer of each of the photoconductive drums34Y,34M,34C, and34K disappears in areas corresponding to the exposure pattern. As a result, an electrostatic pattern is formed on the photoconductive layers of the photoconductive drums34Y,34M,34C, and34K. In other words, by the emission of the laser beam by the exposure unit32, an electrostatic latent image is formed on the photoconductive layers of the photoconductive drums34Y,34M,34C, and34K. In some examples, the exposure unit32may use light emitting diode (LED) light instead of a laser beam.

The developing devices33Y,33M,33C, and33K supply toner to the photoconductive drums34Y,34M,34C, and34K. For example, the developing device33Y develops the electrostatic latent image on the photoconductive layer of the photoconductive drum34Y with yellow (Y) toner. The developing device33M develops the electrostatic latent image on the photoconductive layer of the photoconductive drum34M with magenta (M) toner. The developing device33C develops the electrostatic latent image on the photoconductive layer of the photoconductive drum34C with cyan (C) toner. The developing device33K develops the electrostatic latent image on the photoconductive layer of the photoconductive drum33K with black (K) toner.

The developing devices33Y,33M,33C, and33K form toner images on the photoconductive drums34Y,34M,34C, and34K as visible images. The toner images formed on the photoconductive drums34Y,34M,34C, and34K are transferred onto the transfer belt31(primary transfer).

The transfer unit35includes a support roller35aand a secondary transfer roller35b. The transfer unit35transfers the toner image formed on the transfer belt31to the sheet at a secondary transfer location U. The secondary transfer location U is a location at which the support roller35aand the secondary transfer roller35bface each other with the transfer belt31interposed therebetween. The transfer unit35provides a transfer bias (controlled by a transfer current) to the transfer belt31. The transfer unit35transfers the toner image on the transfer belt31to the sheet using the transfer bias. The control device controls the transfer current used during this secondary transfer process.

The sheet storage unit40includes a single paper feed cassette or a plurality of paper feed cassettes. A paper feed cassette stores a sheet41of a predetermined size and a predetermined type. The paper feed cassette includes a pickup roller. The pickup roller picks up each sheet41from the paper feed cassette one by one. The pickup roller supplies the picked up sheet41to a conveyor unit80.

The fixing device50performs the image fixing process. In particular, the fixing device50fixes the toner image on the sheet41by applying heat and pressure to the sheet41.

The conveyor rollers61aand61bconvey the sheet41fed from the paper feed cassette to the image forming unit30. The conveyor rollers61aand61bface toward each other and form a nip.

The paper discharge rollers62aand62bdischarge the sheet41on which the image has been formed by the fixing device50to a discharging unit. The paper discharge rollers62aand62bface toward each other and form a nip.

The control device70controls each unit of the image forming apparatus1.

The conveyor unit80conveys the sheets41. The conveyor unit80provides a sheet conveyance path that includes a plurality of rollers disposed at various points along the sheet conveyance path. The sheet conveyance path is a path along which the sheet41is conveyed during the image forming processing or the like. The rollers rotate to convey the sheet41in response to the control of the control device70.

Hereinafter, a hardware configuration of the image forming apparatus1will be described.

FIG. 2is a hardware block diagram of the image forming apparatus1. The image forming apparatus1includes the image reading unit10, the control panel20, the image forming unit30, the sheet storage unit40, the control device70, an auxiliary storage device120, and a network interface130. The various units are connected to each other via a system bus2to enable data communication between the units and/or the control device70as necessary.

The image reading unit10, the control panel20, the image forming unit30, and the sheet storage unit40operate as described above, and thus repeated descriptions thereof are omitted.

The fixing device50includes a photocoupler501and a microcomputer502. In some examples, the microcomputer502may be included in or otherwise considered a part of the control device70. Alternatively, the function of the microcomputer502may be performed by a dedicated processor71or the like.

In this example, the control device70includes the processor71, a read only memory (ROM)72, and a random access memory (RAM)73. The processor71is, for example, a central processing unit (CPU). The processor71performs various processes by loading a program from the ROM72onto the RAM73and then executing the program.

The ROM72stores a program to be executed by the processor71. The RAM73temporarily stores data used by each unit of the image forming apparatus1. The RAM73may also store digital data generated by the image reading unit10. The RAM73may temporarily store a print job and a print job log or the like.

The auxiliary storage device120is, for example, a hard disk or a solid state drive (SSD), and stores various types of data. The various types of data are, for example, digital data, such as image data, a print job, a print job log, and the like.

The network interface130transmits and receives data to or from another apparatus. Here, in this example, the other apparatus is an information processing apparatus, such as a personal computer, a tablet terminal, a smart phone, or the like. The network interface130operates as an input interface to receive data or instruction transmitted from the other apparatus. The instruction transmitted from the other apparatus can be a print execution instruction. The network interface130operates as an output interface to transmit data to the other apparatus as needed.

Hereinafter, a configuration of the fixing device50will be described.

FIG. 3is a front cross-sectional view of the fixing device50. The fixing device50includes a pressurizing roller530pand a film unit530h.

The pressurizing roller530pforms a nip N with the film unit530h. The pressurizing roller530ppresses the toner image on the sheet when the sheet enters the nip N. The pressurizing roller530protates and conveys the sheet. The pressurizing roller530pincludes a cored bar532, an elastic layer533, and a release layer (not separately depicted).

As described above, the pressurizing roller530pis capable of pressing a surface of a cylindrical film535and is rotatable.

The cored bar532is formed in a cylindrical shape by a metal material such as stainless steel or the like. Both end portions of the cored bar532in an axial direction are rotatably supported. The cored bar532is driven by a motor to rotate. The cored bar532contacts, for example, a cam member. The cam member rotates such that the cored bar532will approach and be separated from the film unit530haccording to the cam member position.

The elastic layer533is formed of an elastic material such as silicone rubber or the like. The elastic layer533is formed on an outer peripheral surface of the cored bar532in a uniform thickness.

The release layer is formed of a resin material such as a poly[tetrafluoroethylene-co-perfluoro (alkyl vinyl ether)] copolymer or the like (referred to as a PFA resin in this context). The release layer is formed on an outer peripheral surface of the elastic layer533.

Hardness of an outer peripheral surface of the pressurizing roller530pmay be 40° to 70° with respect to a load of 9.8 N measured by an ASKER-C hardness tester. Accordingly, the area of the nip N and the durability of the pressurizing roller530pare secured.

The pressurizing roller530pcan approach and be separated from the film unit530hvia rotation of the cam member. The nip N is formed when the pressurizing roller530pis brought close to the film unit530hand pressed by a spring element or the like. However, if a sheet jam occurs at the fixing device50, the jammed sheet may be removed by separating the pressurizing roller530pfrom the film unit530hby rotation of the cam member. Plastic deformation of the cylindrical film535is prevented by separating the pressurizing roller530pfrom the film unit530hwhen the cylindrical film535is not rotating, e.g., during a sleep state.

The pressurizing roller530pis rotated by a motor. When the pressurizing roller530pis rotated while the nip N is formed, the cylindrical film535of the film unit530his driven and rotated. The pressurizing roller530protates and conveys a sheet in a conveying direction W through the nip N.

The film unit530hheats a toner image on the sheet that has entered the nip N. The film unit530hincludes the cylindrical film535, a heater55, a heat transfer member549, a support member536, a stay538, a heater thermometer562, a thermostat568, and a thermistor58.

The cylindrical film535is formed in a cylindrical shape. The cylindrical film535includes a base layer, an elastic layer, and a release layer arranged sequentially from an inner peripheral side. The base layer is formed in a cylindrical shape of a material such as nickel (Ni). The elastic layer is stacked on an outer peripheral surface of the base layer. The elastic layer is formed of an elastic material such as silicone rubber or the like. The release layer is stacked on an outer peripheral surface of the elastic layer. The release layer is formed of a material such as PFA resin or the like.

The heater55includes a substrate55aand a heating layer55b. In the present disclosure, an x direction, a y direction, and a z direction are defined as follows. The y direction is a longitudinal direction of the substrate55a. The y direction is parallel to a width direction and the rotation axis of the cylindrical film535. The x direction is a lateral direction of the substrate55aand thus is perpendicular to the y direction. The z direction is a normal direction of the substrate55aand perpendicular to the x and y directions. A configuration of the heater55will be described later.

As shown inFIG. 3, a straight line CL connecting an axis pc of the pressurizing roller530pand an axis hc of the film unit530his defined. A center541cof the substrate55ain the x direction is arranged in a +x direction with respect to the straight line CL. Since the substrate55aextends in the +x direction of the nip N with respect to the substrate55b, the temperature of the edge in the +x direction of the substrate55btends to be lower, which helps a sheet passing through the nip N in separating from the film unit530h.

A center545cof the heating layer55bin the x direction is located on the straight line CL. The heating layer55bis entirely included in an area of the nip N and is present at the center of the nip N. Accordingly, heat distribution in the nip N is substantially uniform, and thus the sheet passing through the nip N is uniformly heated.

As shown inFIG. 3, the heater55is arranged inside the cylindrical film535. A lubricant is applied on an inner peripheral surface of the cylindrical film535. The heater55contacts the inner peripheral surface of the cylindrical film535via the lubricant. When the heater55generates heat, the viscosity of the lubricant will be decreased. Accordingly, the sliding property between the heater55and the cylindrical film535is improved by the heating.

As described above, the cylindrical film535is a thin film, which slides along a surface of the heater55while contacting the surface.

The heat transfer member549is formed of a metal material having high thermal conductivity, such as copper or the like. An outer shape of the heat transfer member549is similar to an outer shape of the substrate55aof the heater55. The heat transfer member549contacts a surface of the heater55.

The support member536is formed of a resin material, such as liquid crystal polymer or the like. The support member536is arranged to cover the upper (z direction) surface side inFIG. 3of the heater55and both sides in the x direction. The support member536supports the heater55through the heat transfer member549. Round chamfers are formed on both end portions of the support member536in the x direction. The support member536supports the inner peripheral surface of the cylindrical film535at both end portions of the heater55in the x direction.

When the sheet passing through the fixing device50is heated, a temperature distribution occurs in the heater55according to a size of the sheet. When the temperature of the heater55is locally increased, the temperature may exceed a heat-tolerance temperature of the support member536formed of the resin material. The heat transfer member549averages (mediates) the temperature distribution along the heater55. Accordingly, the heat resistance of the support member536can be secured even if certain local temperatures at points along the length of the heater55are higher than the heat-tolerance temperature of the support member536.

The stay538shown inFIG. 3is formed of a bent steel plate material or the like. A cross section of the stay538perpendicular to the y direction is formed in a U shape. The stay538is mounted on the above (z direction) support member536. The support member536is positioned at the ends of the U-shaped opening so as to close the U-shaped opening of the stay538. The stay538extends in the y direction. Both end portions of the stay538in the y direction are fixed to a housing or the like of the image forming apparatus1. Accordingly, the film unit530his physically supported by the image forming apparatus1. The stay538improves rigidity of the film unit530hto limit bending or flexing. A flange (not shown) for restricting movement of the cylindrical film535in the y direction is mounted near both end portions of the stay538in the y direction.

The heater thermometer562is arranged on the upper (z direction) surface side of the heater55with the heat transfer member549disposed therebetween. For example, the heater thermometer562is a thermistor. The heater thermometer562is mounted on and supported by a surface of the support member536. A temperature sensitive element of the heater thermometer562contacts the heat transfer member549through a hole penetrating the support member536in the z direction. The heater thermometer562measures the temperature of the heater55via the heat transfer member549.

The thermostat568is arranged on the heater55similarly to the heater thermometer562. The thermostat568blocks a current flowing to the heating layer55bwhen the temperature of the heater55detected via the heat transfer member549exceeds a predetermined temperature.

The thermistor58(also referred to as a film thermometer) is arranged inside the cylindrical film535as shown inFIG. 3. The thermistor58contacts the inner peripheral surface of the cylindrical film535and measures the temperature of the cylindrical film535.

In addition to the heater thermometer562and the thermistor58, the image forming apparatus1may further include an environmental thermometer for measuring surrounding temperatures or the like. In general, the environmental thermometer measures a temperature around the mounted location thereof. The environmental thermometer may be mounted on any location in the vicinity of the fixing device50. In this context, the vicinity of the fixing device50is any location where the environmental thermometer is able to measure an environment temperature of the space in which the fixing device50is located. The environmental thermometer may be mounted on, for example, a housing located outside the film unit530h.

FIG. 4is a diagram showing a configuration of the heater55.

As shown inFIG. 4, the heater55includes four layers including a glass layer55c, the heating layer55b, a glass layer55d, and the substrate55astacked in this order on an inner surface of a fixing belt53.

The substrate55ais formed of a metal material such as stainless steel or the like, or a ceramic material such as aluminum nitride or the like. The substrate55ais formed in an elongated rectangular plate shape. The substrate55ais arranged inside the cylindrical film535. The substrate55aextends in a longitudinal direction parallel to an axial direction of the cylindrical film535.

The heating layer55bis formed of, for example, a silver palladium alloy or the like. An outer shape of the heating layer55bhas a rectangular shape, the longitudinal direction of which corresponds to the y direction and the lateral direction of which corresponds to the x direction.

Hereinafter, a mechanism for detecting whether the fixing belt53included in the fixing device50of the image forming apparatus1is connected to GND.

FIG. 5is a schematic diagram showing the mechanism for detecting whether the fixing belt53of the current embodiment is connected to GND.

As shown inFIG. 5, the photocoupler501and the microcomputer502are used as the mechanism for detecting whether the fixing belt53is connected to GND. Alternatively, instead of the photocoupler501, for example, another insulating type detection element, such as a current transformer, may be used as the insulated detection element. In other words, any element may be used instead of the photocoupler501as long as a current flowing on a primary circuit side is detectable on a secondary circuit side in a non-contact (insulated) manner.

As shown inFIG. 5, the photocoupler501includes a light emitting diode501aand a light receiving element501b. An anode of the light emitting diode501ais connected to a power source of a primary circuit. A cathode of the light emitting diode501ais connected to the fixing belt53. The fixing belt53is connected to GND. An anode of the light receiving element501bis connected to a power source of a secondary circuit. A cathode of the light receiving element501bis connected to the microcomputer502and GND.

According to such a configuration, when the fixing belt53is connected to GND, the light emitting diode501aemits light because a current flows from the power source on the primary circuit through the light emitting diode501ato GND. When light emitted by the light emitting diode501ais being received by the light receiving element501b, the light receiving element501bpasses a current from the power source of the secondary circuit to GND. When detecting a current passing through the light receiving element501b, the microcomputer502outputs, to the control device70, a notification indicating normality (a normal state). If current does not pass through the light receiving element501b(that is, no light is detected from the light emitting diode501a) a notification indicating abnormality (an abnormal state) is output from the microcomputer502to the control device70.

The control device70obtains the notification output from the microcomputer502. When the notification indicating the normal state is obtained, the control device70determines that the fixing belt53is connected to GND. When it is determined that the fixing belt53is connected to GND (normal state), the control device70starts rotation (or maintains rotation) of the fixing belt53and starts a heating process (or maintains a heating process) by the heater55.

FIG. 6shows a case in which the fixing belt53is not connected to GND. As shown inFIG. 6, when connection between the fixing belt53and GND is disconnected due to, for example, a wiring disconnection, the current from the power source at the primary circuit does not flow through the light emitting diode501a. As a result, the light emitting diode501adoes not emit light. When the light is not received from the light emitting diode501a, a current from the power source of the secondary circuit will not flow through the light receiving element501b. Upon detecting that the current is not flowing through the light receiving element501b, the microcomputer502outputs a notification indicating the abnormal state to the control device70.

Upon obtaining the notification indicating the abnormal state, the control device70determines that the fixing belt53is not connected to GND (abnormal state). When it is determined that the fixing belt53is not connected to GND, the control device70stops the rotation (or will not start the rotation) of the fixing belt53and stops the heating process (or will not start the heating process) by the heater55.

According to such a configuration, it can be reliably detected whether the fixing belt53is connected to GND, and when the fixing belt53is not connected to GND, operations of the fixing belt53and heater55are definitely stopped. In the aforementioned embodiments, the microcomputer502outputs the notification indicating the abnormal state when the current is not flowing through the light receiving element501b, but the present disclosure is not limited thereto. For example, the microcomputer502may output the notification indicating an abnormal state when the current level of the current flowing through the light receiving element501bis less than or equal to some predetermined threshold value or the like.

Hereinafter, an operation of a mechanism for detecting whether the fixing belt53is connected to GND will be described.

FIG. 7is a flowchart of operations of the image forming apparatus1.

The microcomputer502detects a current state (ACT001). When detecting that the current is flowing, the microcomputer502outputs a notification indicating the normal state to the control device70. On the other hand, when detecting that the current is not flowing, the microcomputer outputs a notification indicating the abnormal state to the control device70. The control device70receives the notification output from the microcomputer502.

Upon receiving a notification indicating the abnormal state, the control device70determines that the fixing belt is not connected to GND. Upon determining that the fixing belt53is not connected to GND (No in ACT002), the control device70stops (or will not permit the start of) the rotation of the fixing belt53and the heating process by the heater55(ACT003). Thus, the operations of the image forming apparatus1shown in the flowchart ofFIG. 7end.

On the other hand, upon determining that the fixing belt53is connected to GND (Yes in ACT002), the control device70starts the rotation of the fixing belt53and the heating process by the heater55(ACT004).

Then, after a predetermined time increment (for example, one second) elapses (Yes in ACT005), the microcomputer502detects the current state again (ACT006). Upon detecting that the current is not flowing, the microcomputer502outputs a notification indicating the abnormal state to the control device70. The control device70receives the notification output from the microcomputer502.

Upon receiving the notification indicating the abnormal state, the control device70determines that the fixing belt53is not connected to GND. Upon determining that the fixing belt53is not connected to GND (No in ACT007), the control device70stops the rotation of the fixing belt53and the heating process by the heater55(ACT003). Then, the operations of the image forming apparatus1shown in the flowchart ofFIG. 7end.

On the other hand, when detecting that the current is flowing, the microcomputer502outputs a notification indicating the normal state to the control device70. The control device70receives the notification output from the microcomputer502. Upon receiving the notification indicating the normal state, the control device70determines that the fixing belt53is connected to GND. Upon determining that the fixing belt53is connected to GND (Yes in ACT007), the control device70continues to rotate the fixing belt53and perform the heating process by the heater55. Thereafter, after another predetermined time increment (for example, one second) elapses (Yes in ACT005), the microcomputer502detects the current state again (ACT006). The subsequent operations are the same as described above.

Modified Example

In some instances, the fixing belt53may become an electrically active part due to, for example, malfunction of the heater55or breakage of the glass layer55cor55d. When the fixing belt53becomes an electrically active part, a current may flow from the power source of the primary circuit into the fixing belt53even if the intended connection of the fixing belt53to GND is disconnected. In this case, the light emitting diode501aof the photocoupler501may erroneously emit light.

If the light emitting diode501aerroneously emits light, the light receiving element501breceives the light emitted by the light emitting diode501aand will thus still allow a current to flow from the power source on the secondary circuit to GND through the light receiving element501b. Upon detecting the current, the microcomputer502could output a notification indicating the normal state to the control device70. Based upon this notification indicating the normal state, the control device70would erroneously determine that the fixing belt53is still properly connected to GND. Accordingly, despite the fixing belt53not being connected to GND, the rotation of the fixing belt53and the heating process by the heater55might still be performed or attempted.

In the present example, it is assumed that the heater55is a heater that performs a heating process by cycling between an on state and an off state to achieve the desired heating level. In such a case, the microcomputer502can be configured, for example, to detect the current state only when the heater55is in an off state of the heating process. This can prevent the erroneous operation described above since no current is separately being provided to the heater55during the off state.

Another example of the operation of the mechanism for detecting whether the fixing belt53is connected to GND will be described.

FIG. 8is a flowchart of operations of the image forming apparatus1. Operations from ACT101to ACT104shown inFIG. 8are substantially the same as the operations from ACT001to ACT004described in conjunction withFIG. 7, and thus separate descriptions thereof are omitted.

After the operation of ACT104, after a predetermined time increment (for example, one second) elapses (Yes in ACT105), the microcomputer502(or the control device70) detects a state of the heating process by the heater55(ACT106). When the heater55is an on state (No in ACT107), the microcomputer502does not detect the current application state.

When the state of the heating process by the heater55is an off state (Yes in ACT107), the microcomputer602detects the current application state again (ACT108). Upon detecting that the current is not flowing, the microcomputer502outputs the notification indicating the abnormal state to the control device70. The control device70receives the notification output from the microcomputer502.

Upon receiving the notification indicating the abnormal state, the control device70determines that the fixing belt53is not connected to GND. Upon determining that the fixing belt53is not connected to GND (No in ACT109), the control device70stops the rotation of the fixing belt53and the heating process by the heater55(ACT103). As such, the operations of the image forming apparatus1shown in the flowchart ofFIG. 8end.

On the other hand, upon detecting that the current is flowing, the microcomputer502outputs the notification indicating the normal state to the control device70. The control device70receives the notification output from the microcomputer502. Upon receiving the notification indicating the normal state, the control device70determines that the fixing belt53is connected to GND. Upon determining that the fixing belt53is connected to GND (Yes in ACT109), the control device70continues to rotate the fixing belt53and perform the heating process by the heater55. Thereafter, after the predetermined time increment (for example, one second) elapses (Yes in ACT105), the microcomputer502again detects the state of the heating process by the heater55(ACT106). The subsequent operations are the same as described above.

As described above, the image forming apparatus1according to the above embodiments includes the fixing device50and the control device70. The fixing device50includes the heater55and the fixing belt53. The fixing belt53contacts each of the heater55and a member (for example, the thermistor58) that is not in contact with the heater55. The fixing belt53is heated by the heater55. The control device70determines whether the fixing belt53is connected to GND. When it is determined that the fixing belt53is not connected, the control device70stops the heating process by the heater55.

With the above configuration, the image forming apparatus1may detect whether the fixing belt53is connected to GND. Accordingly, the image forming apparatus1may stop the heating by the heater55when the fixing belt53is not connected to GND.

As described above, in a belt type or on-demand type fixing device, static electricity may be accumulated on the fixing belt. When the static electricity is accumulated on the fixing belt, an electrostatic offset may occur and the quality of an output image may deteriorate. However, in the image forming apparatus1according to the aforementioned embodiments, static electricity may be discharged by connecting the fixing belt53to GND. Furthermore, since the image forming apparatus1may stop the fixing device50when it is detected that the fixing belt53is not connected to GND, accumulation of static electricity on the fixing belt53can be prevented. As a result, occurrence of an electrostatic offset can be prevented.

As described above, since occurrence of an electrostatic offset is prevented, deterioration of the quality of an output image is prevented.

The image forming apparatus1stops a current flowing to the heater55when it is detected that the fixing belt53is not connected to GND. As a result, an unintended change in the distance between the heater55and the fixing belt53can be prevented.

Various functions of the image forming apparatus1in the above-described embodiments may be implemented by a computer executing a software program. In such a case, the program for implementing the function (or functions) can be recorded on a non-transitory computer readable recording medium and the function is be performed by a computer system that reads and executes the program recorded on the recording medium. Here, a “computer system” includes hardware, such as one or more processors, one or more peripheral devices, or the like. The computer system may function according to an operating system thereon. In this context, a “computer readable recording medium” denotes a portable medium, such as a flexible disk, a magneto-optical disk, ROM, CD-ROM, or the like, or a storage device such as a hard disk or the like built in the computer system. The “computer readable recording medium” may be implemented as a cloud-based storage solution and/or server and the relevant program may be transmitted via a communication link, such as a network like the Internet, or a telephone line. The relevant program for implementing a function or functions described above, may perform the function in combination with another program or programs already recorded on the computer system, such as an operating system of the computer system.