JP6056152B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device that thermally fixes a developer image on a recording sheet.

  Conventionally, a fixing device having a heater that generates heat upon energization, a thermistor that detects the temperature of the heater, and a temperature at which control is performed to keep the heater temperature at a predetermined temperature by controlling energization (ON / OFF) to the heater. An image forming apparatus including a control unit is known (see Patent Document 1). The image forming apparatus disclosed in Patent Document 1 is configured to determine a failure when the temperature based on a signal from a thermistor within a certain period of time after power-on is lower than a threshold value.

Japanese Patent No. 3667055

  By the way, since the manner in which the temperature rises due to the heating of the heater varies depending on the environment where the image forming apparatus is installed, etc., in the configuration in which the failure is determined when the temperature based on the signal of the thermistor within a certain time is lower than the threshold value, There was a possibility that the error could not be judged properly. Specifically, for example, when the temperature of the installation environment is low, it takes time to increase the temperature, so the temperature based on the signal of the thermistor within a certain time may be lower than the threshold value even if there is no failure. In this case as well, there is a possibility of being determined as a failure.

  The present invention has been made in view of the above background, and an object thereof is to provide an image forming apparatus capable of appropriately determining an error.

In order to achieve the above object, an image forming apparatus of the present invention has a heat source, a fixing device that thermally fixes a developer image on a recording sheet, a temperature detection member that detects the temperature of the fixing device, and a heat source. And a control device for controlling the energization amount.
The control device includes a determination unit that determines whether the image forming apparatus is normal based on the temperature detected by the temperature detection member.
The determination unit acquires and stores the detected temperature as the first temperature before the first time elapses from when the energization to the heat source is started.
The determining means determines that the detected temperature is normal when the detected temperature reaches a predetermined temperature within the first time.
In addition, when the detected temperature does not reach the predetermined temperature within the first time, the determination unit acquires the detected temperature as the second temperature after the first time has elapsed, and the second temperature and the first temperature are acquired. When the temperature change amount based on the temperature is equal to or greater than a predetermined value, it is determined to be normal, and when the temperature change amount is less than the predetermined value, it is determined to be not normal.

  Since it takes time for the temperature around the temperature detection member to rise for a while after the energization of the heat source is started, there is a possibility that the detection temperature rise amount (temperature change amount) of the temperature detection member may vary. There is. Therefore, the determination means determines whether or not the detected temperature itself has reached a predetermined temperature until the first time has elapsed since the start of energization of the heat source, and the detected temperature has reached the predetermined temperature. In this case, it is determined that the image forming apparatus is normal.

  On the other hand, if the detected temperature does not reach the predetermined temperature within the first time period, this may be because, for example, the temperature of the installation environment is low, so it takes time to increase the temperature, a heat source or a temperature detecting member. In the first place, it is difficult to determine whether the temperature has risen due to a failure such as by the detected temperature alone within the first time. Therefore, the determination unit does not determine that the image forming apparatus is not normal within the first time, and the first temperature and the first time acquired after the first time elapses and before the first time elapses. It is determined whether or not the temperature change amount based on the second temperature acquired after the elapse is greater than or equal to a predetermined value.

When the temperature of the installation environment is low, the temperature rises over time because it takes a long time to rise. Therefore, the amount of temperature change is equal to or greater than a predetermined value, and the determination means is that the image forming apparatus is normal. It is determined that Further, when the heat source, the temperature detection member, or the like is out of order, the temperature does not rise, so the temperature change amount is less than a predetermined value, and the determination unit determines that the image forming apparatus is not normal.
As described above, according to the above configuration, whether or not the image forming apparatus is normal is determined using appropriate parameters within the first time and after the first time has elapsed. be able to.

In the above-described image forming apparatus, the determination unit can be configured to acquire the first temperature at the start of energization to the heat source.
In the present invention, the time of starting energization does not mean only the time of starting energization (simultaneously with the start of energization). That is, the start of energization may be a time slightly before the start of energization or a time slightly after the start of energization as long as the temperature at the start of energization can be substantially acquired. May be.

  According to this, since the detected temperature considered to be the lowest before being heated by the heat source can be obtained as the first temperature, the temperature change amount can be calculated more accurately. Thereby, an error can be determined more appropriately.

In each of the image forming apparatuses described above, the determination unit can be configured to acquire the second temperature when the energization of the heat source is stopped.
In the present invention, the time when the energization is stopped does not mean only the time when the energization is stopped (at the same time as the energization is stopped). That is, the time when the power supply is stopped may be a time point a little before the power supply stop time or a time point a little after the power supply stop time as long as the temperature at the time of power supply stop can be substantially acquired. May be.

  According to this, since the detected temperature considered to be the highest when heated by the heat source can be acquired as the second temperature, the temperature change amount can be calculated more accurately. Thereby, an error can be determined more appropriately.

  In the image forming apparatus described above, the control device can be configured to stop energizing the heat source when the detected temperature reaches the target temperature. In the above-described image forming apparatus, the control device can be configured to stop energization of the heat source when the second time has elapsed from the start of energization of the heat source.

  According to these, an excessive temperature rise can be suppressed. Further, since unnecessary energization to the heat source can be suppressed, energy saving of the image forming apparatus can be achieved.

  In each of the image forming apparatuses described above, the determination unit is configured to execute a process of determining whether or not the image forming apparatus is normal when the power supply to the image forming apparatus is turned on and the first energization of the heat source is started. Can do.

  According to this, since the error determination of the present invention is executed whenever the power supply of the image forming apparatus is turned on and the first energization to the heat source is started, the error is appropriately determined when the image forming apparatus is turned on. can do.

  According to the present invention, it is possible to appropriately determine an error.

1 is a diagram illustrating a schematic configuration of a laser printer as an example of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows schematic structure of a fixing device and a control apparatus. It is a time chart (a)-(c) for explaining error judgment after power-on. It is a flowchart of control by a control apparatus.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the schematic configuration of the laser printer 1 and the fixing device 8 as an example of the image forming apparatus according to the present embodiment will be briefly described, and then the details of the laser printer 1 according to the characteristic part of the present invention will be described. A detailed configuration will be described.

  In the following description, the direction will be described with reference to the user who uses the laser printer 1. That is, the right side in FIG. 1 is “front”, the left side is “rear”, the front side is “left”, and the back side is “right”. Also, the vertical direction in FIG.

<Schematic configuration of laser printer and fixing device>
As shown in FIG. 1, a laser printer 1 includes a main body housing 2 that feeds a sheet S as an example of a recording sheet, an exposure device 4, and a toner image (developer) on the sheet S. A process cartridge 5 for transferring the image) and a fixing device 8 for fixing the toner image transferred onto the paper S by heat.

  The paper feed unit 3 is provided at a lower portion in the main body housing 2 and mainly includes a paper feed tray 31, a paper pressing plate 32, and a paper feed mechanism 33. The paper S stored in the paper feed tray 31 is moved upward by the paper pressing plate 32 and supplied toward the process cartridge 5 (between the photosensitive drum 61 and the transfer roller 63) by the paper feed mechanism 33.

  The exposure apparatus 4 is disposed in the upper part of the main body housing 2 and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, and the like that are not shown. In this exposure device 4, the surface of the photosensitive drum 61 is exposed by scanning the surface of the photosensitive drum 61 at high speed with laser light (see the chain line) based on the image data emitted from the laser light emitting unit.

  The process cartridge 5 is disposed below the exposure apparatus 4 and is detachably mounted on the main body housing 2 through an opening formed when the front cover 21 provided on the main body housing 2 is opened. Yes. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be detachably attached to the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner that contains toner (developer). The housing part 74 is mainly provided.

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 4, whereby an image is formed on the photosensitive drum 61. An electrostatic latent image based on the data is formed. Further, the toner in the toner container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer of a certain thickness on the developing roller 71. It is carried on.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 63 so that the toner image on the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 8 is disposed behind the process cartridge 5 and, as shown in FIG. 2, a fixing belt 81, a halogen lamp 82 as an example of a heat source, a nip plate 83, a reflecting plate 84, a backup roller 85, and the like. The stay 86 is mainly provided.

The fixing belt 81 is an endless (cylindrical) belt having heat resistance and flexibility, and both ends thereof are guided to rotate by guide members (not shown).
The halogen lamp 82 is a heater that heats the toner transferred onto the paper S by heating the nip plate 83 and the fixing belt 81 by generating heat when energized, and is disposed inside the fixing belt 81.

  The nip plate 83 is a plate-like member that receives radiant heat from the halogen lamp 82, and is disposed so as to be in sliding contact with the inner surface of the fixing belt 81. The nip plate 83 is formed of, for example, an aluminum plate having a high thermal conductivity in order to transmit the radiant heat received from the halogen lamp 82 to the toner on the paper S via the fixing belt 81. Note that a lubricant (not shown) such as heat-resistant fluorine grease is held between the nip plate 83 and the fixing belt 81 to reduce friction between the nip plate 83 and the rotating fixing belt 81. Yes.

  The reflection plate 84 is a member that reflects the radiant heat from the halogen lamp 82 toward the nip plate 83, and is disposed so as to surround the halogen lamp 82 inside the fixing belt 81. The reflection plate 84 is formed by bending an aluminum plate or the like into a substantially U shape in cross section, for example, having a high reflectance of infrared rays and far infrared rays.

  The backup roller 85 is a roller that conveys the paper S to and from the fixing belt 81 and pressurizes the toner transferred onto the S, and is disposed below the nip plate 83 with the fixing belt 81 interposed therebetween. The backup roller 85 is rotationally driven by a driving force transmitted from a motor (not shown) provided in the main body housing 2, and the fixing belt 81 is caused by a frictional force with the fixing belt 81 (or the paper S) at this time. Is driven to rotate.

  The stay 86 is a member that secures the rigidity of the nip plate 83 to which a load is applied from the backup roller 85 by supporting the nip plate 83 via the reflection plate 84, and is disposed so as to cover the reflection plate 84. The stay 86 has relatively high rigidity, for example, is formed by bending a steel plate or the like.

  In the fixing device 8, the sheet S on which the toner image is transferred is conveyed between the heated fixing belt 81 and the backup roller 85, so that the toner image (toner) is heated on the sheet S by heat and pressure. It is fixed. As shown in FIG. 1, the paper S on which the toner image is thermally fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

<Detailed configuration of laser printer>
Next, a detailed configuration of the laser printer 1 according to the characteristic part of the present invention will be described.
The laser printer 1 further includes a thermistor 87 as an example of a temperature detection member and a control device 10.

  The thermistor 87 is a member that detects the temperature of the fixing device 8, and is disposed inside the fixing belt 81 of the fixing device 8. More specifically, the thermistor 87 is disposed so that the temperature detection surface faces the nip plate 83 heated by the halogen lamp 82, and detects the temperature of the nip plate 83 as the temperature of the fixing device 8. A detection signal of the thermistor 87 (hereinafter referred to as detection temperature) is output to the control device 10.

  The control device 10 is a device that controls the amount of current supplied to the halogen lamp 82, and is disposed at an appropriate position in the main body housing 2. The control device 10 includes a CPU, a RAM, a ROM, an input / output interface (not shown), and the like, and performs control by performing each arithmetic processing based on the temperature detected by the thermistor 87 or a preset program. Run.

  An example of the control of the energization amount to the halogen lamp 82 by the control device 10 will be briefly described. The control device 10 determines the duty ratio based on the difference between the detected temperature of the thermistor 87 and a preset target temperature. The energization (ON or OFF) to the halogen lamp 82 is controlled based on the duty ratio. In this embodiment, the duty ratio may be set to a predetermined fixed value in the initial error determination operation after power-on described later. Further, the control device 10 is configured so that the target temperature can be set as appropriate according to the operation mode of the laser printer 1. Therefore, for example, the target temperature during the printing operation in which the toner image is transferred and thermally fixed on the paper S is different from the target temperature during the initial error determination operation after the power is turned on.

  The control device 10 energizes the halogen lamp 82 when the temperature detected by the thermistor 87 reaches the target temperature set according to the operation mode (for example, the target temperature TPth shown in FIGS. 3A and 3B). Is stopped (OFF) (see times t2 and t4). Further, as shown in FIG. 3C, the control device 10 energizes the halogen lamp 82 when a time-out time TM2 as a second time elapses from the start of energization to the halogen lamp 82 (time t1). It is configured to stop (see time t5). The control device 10 also determines that the rear cover 25 is opened based on a signal from a sensor (not shown) that detects opening / closing of the rear cover 25 (see FIG. 1) while the halogen lamp 82 is energized. It is comprised so that the electricity supply to 82 may be stopped.

The control apparatus 10 has the determination means 11 as a function part relevant to this invention.
The determination unit 11 has a function of determining whether or not the laser printer 1, specifically, the fixing device 8 (both the halogen lamp 82 and the thermistor 87) is normal based on the temperature detected by the thermistor 87. Yes.

  Specifically, as shown in FIGS. 3A to 3C, the determination unit 11 is turned on when the laser printer 1 is turned on (time t0) and the first energization of the halogen lamp 82 is started ( At time t1), the detected temperature of the thermistor 87 at this time is acquired and stored as the first temperature TP1.

  Then, as shown in FIG. 3A, the determination means 11 has a predetermined temperature detected by the thermistor 87 within the first time TM1 (between times t1 and t3) from when the energization to the halogen lamp 82 is started. When the target temperature TPth (target temperature at the time of initial error determination operation after power-on) is reached as an example of the temperature, it is determined that the fixing device 8 is normal (time t2).

  On the other hand, as shown in FIGS. 3B and 3C, when the temperature detected by the thermistor 87 does not reach the target temperature TPth within the first time TM1, the determination means 11 performs the first time TM1. Specifically, after the elapse of time, when the energization of the halogen lamp 82 is stopped (time t4 or t5), the detected temperature of the thermistor 87 at this time is acquired as the second temperature TP2.

  Thereafter, the determination unit 11 sets in advance a temperature change amount based on the second temperature TP2 and the first temperature TP1, for example, a difference (absolute value) between the second temperature TP2 and the first temperature TP1. It is determined whether or not it is equal to or greater than a predetermined value. Then, as shown in FIG. 3B, when the difference (temperature change amount) between the second temperature TP2 and the first temperature TP1 is equal to or greater than a predetermined value, the determination unit 11 determines that the fixing device 8 is normal. When the difference between the second temperature TP2 and the first temperature TP1 is less than a predetermined value as shown in FIG. 3C, the determination unit 11 determines that the fixing device 8 is not normal. Is determined.

  When the determination unit 11 determines that the fixing device 8 is normal, the control device 10 controls the amount of current supplied to the halogen lamp 82 so that the temperature of the fixing device 8 (nip plate 83) is higher than that during the printing operation. A standby mode (control for preparing for printing operation) is executed to keep the temperature at a predetermined low temperature. Note that energization of the halogen lamp 82 is not completely stopped in the standby mode because the lubricant held between the nip plate 83 and the fixing belt 81 is heated to input image data. This is to shorten the transition time from the standby mode to the printing operation.

  When the determination unit 11 determines that the fixing device 8 is not normal, the control device 10 informs the user that the fixing device 8 is not normal through a liquid crystal display (not shown) provided in the laser printer 1 (for example, And information for prompting replacement of the fixing device 8). Note that, when the determination unit 11 determines that the fixing device 8 is not normal, the control device 10 may execute an error determination for specifying a failure location or the like separately from the present invention.

  Next, control by the control device 10, mainly determination processing by the determination unit 11, will be described in detail using the flowchart shown in FIG. 4 (also refer to FIG. 3 as appropriate).

  As shown in FIG. 4, when the laser printer 1 is turned on by the user (time t0), the control device 10 starts energizing the halogen lamp 82 (S11, time t1). The detected temperature of the thermistor 87 is acquired and stored as the first temperature TP1 (S12). Thereafter, the control device 10 determines whether or not the detected temperature TP of the thermistor 87 has reached the target temperature TPth (target temperature in the initial error determination operation after power-on) (S13).

  As shown in FIG. 3A, when the fixing device 8 is normal and the temperature of the installation environment of the laser printer 1 is not extremely low, the detection temperature TP of the thermistor 87 is short (within the first time TM1). ) Reaches the target temperature TPth (S13, Yes), the control device 10 determines that the fixing device 8 is normal (S18), and ends the processing (determination processing) of the flowchart shown in FIG. Although not shown in FIG. 4, the control device 10 stops energization (OFF) of the halogen lamp 82 when the temperature detected by the thermistor 87 reaches the target temperature TPth (time t <b> 2). The first time TM1 here is about 5 to 7 seconds as an example.

  On the other hand, as shown in FIG. 3B, when the fixing device 8 is normal but the temperature of the installation environment of the laser printer 1 is extremely low, the temperature detected by the thermistor 87 is unlikely to rise. As shown in FIG. 3C, when the fixing device 8 (at least one of the halogen lamp 82 and the thermistor 87) has failed, the detection temperature of the thermistor 87 does not increase. The target temperature TPth is not reached within one time TM1 (S13, No). In this case, the control device 10 determines whether or not the first time TM1 has elapsed (S14). Note that the control device 10 repeatedly executes the processes of steps S13 and S14 until the first time TM1 elapses.

  When the first time TM1 has elapsed (S14, Yes), the control device 10 determines whether or not the energization to the halogen lamp 82 is stopped (S15), and the energization to the halogen lamp 82 is stopped ( (S15, Yes), the detected temperature of the thermistor 87 at this time is acquired as the second temperature TP2 (S16). Thereafter, the control device 10 determines whether or not the difference (TP2−TP1) between the second temperature TP2 and the first temperature TP1 is equal to or greater than a predetermined value C (S17).

  As shown in FIG. 3B, when the detected temperature of the thermistor 87 is difficult to rise, the detected temperature of the thermistor 87 becomes the target temperature TPth after a certain period of time, so the difference (TP2−TP1) is a predetermined value. C or more (S17, Yes). In this case, the control device 10 determines that the fixing device 8 is normal (S18), and ends the determination process. On the other hand, as shown in FIG. 3C, when the fixing device 8 is out of order and the temperature detected by the thermistor 87 does not rise, the difference (TP2-TP1) is less than the predetermined value C (No in S17). . In this case, the control device 10 determines that the fixing device 8 is not normal (error) (S19), and ends the determination process.

  4, when the rear cover 25 (see FIG. 1) is opened and the energization of the halogen lamp 82 is stopped during the processing of the flowchart illustrated in FIG. 4, the control device 10 causes the halogen lamp 82 to be closed after the rear cover 25 is closed. Is started (S11), and the process of step S12 is executed (resumed).

According to the above, the following effects can be obtained in the present embodiment.
Since it takes time for the temperature around the thermistor 87 (nip plate 83) to rise for a while after the energization of the halogen lamp 82 is started, the detection temperature of the thermistor 87 is increased (temperature change amount). Variations can occur. Therefore, the determination unit 11 determines that the fixing device 8 is normal during the first time TM1 when the detected temperature itself reaches the target temperature TPth.

  On the other hand, if the detected temperature does not reach the target temperature TPth within the first time TM1, this is because the temperature of the installation environment shown in FIG. It is difficult to determine whether the temperature has risen due to the failure of the fixing device 8 shown in 3 (c) only by the detected temperature within the first time TM1. Therefore, the determination unit 11 does not determine that the fixing device 8 is not normal within the first time TM1, and after the first time TM1 has elapsed, the difference between the second temperature TP2 and the first temperature TP1 ( It is determined whether or not (temperature change amount) is equal to or greater than a predetermined value.

  If the temperature of the installation environment is low, the temperature will eventually increase, so that the difference becomes equal to or greater than a predetermined value, and the determination unit 11 determines that the fixing device 8 is normal. If the fixing device 8 has failed, the temperature does not increase, so the difference becomes less than a predetermined value, and the determination unit 11 determines that the fixing device 8 is not normal.

  As described above, the determination unit 11 determines whether or not the fixing device 8 is normal using appropriate parameters (detected temperature or temperature change amount) within the first time TM1 and after the first time TM1 has elapsed. Therefore, it is possible to appropriately determine an error.

  In the present embodiment, the determination unit 11 obtains the first temperature TP1 at the start of energization of the halogen lamp 82. Therefore, the detection temperature considered to be the lowest before being heated by the halogen lamp 82 is set to the first temperature TP1. Can be obtained as Thereby, since the difference with 2nd temperature TP2 can be calculated more correctly, an error can be determined more appropriately.

  In addition, since the determination unit 11 acquires the second temperature TP2 when the energization of the halogen lamp 82 is stopped, the detection unit 11 acquires the detected temperature that is considered to be the highest when heated by the halogen lamp 82 as the second temperature TP2. Can do. Thereby, since the difference between the second temperature TP2 and the first temperature TP1 can be calculated more accurately, an error can be determined more appropriately.

  Further, the determination means 11 always executes the error determination described above when the laser printer 1 is turned on and the first energization of the halogen lamp 82 is started. Therefore, when the laser printer 1 is turned on. An error can be determined appropriately.

  Further, since the control device 10 stops energization of the halogen lamp 82 when the detected temperature reaches the target temperature or when the timeout time TM2 has elapsed from the start of energization of the halogen lamp 82, the fixing belt 81 ( Excessive temperature rise in the nip portion between the nip plate 83) and the backup roller 85 can be suppressed. Further, since unnecessary energization to the halogen lamp 82 can be suppressed, energy saving of the laser printer 1 can be achieved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the embodiment, the determination unit 11 is configured to acquire the first temperature at the start of energization of the halogen lamp 82, but the present invention is not limited to this. Explaining with reference to FIG. 3, the determination means starts the energization of the halogen lamp 82 before the elapse of the first time TM1, for example, when the laser printer 1 is turned on (time t0). The first temperature may be obtained when a predetermined time shorter than the first time TM1 elapses from time (time t1). Moreover, in the said embodiment, although the determination means 11 was comprised so that the 2nd temperature might be acquired at the time of the electricity supply stop to the halogen lamp 82, this invention is not limited to this. Referring to FIG. 3, after the first time TM <b> 1 has elapsed, the determination means, for example, when the predetermined time has elapsed from the time when the first time TM <b> 1 has elapsed, regardless of whether the halogen lamp 82 is turned on or off. The temperature of 2 may be acquired.

  In the embodiment, the difference between the second temperature and the first temperature is exemplified as the temperature change amount based on the second temperature and the first temperature. However, the present invention is not limited to this, for example, the first temperature The amount of temperature change based on the second temperature and the first temperature may be a ratio between the second temperature and the first temperature. Further, the temperature change amount is the rate of temperature increase calculated based on the second temperature value and the first temperature value, and the time when the second temperature and the first temperature are acquired (shown in FIG. 3). Or the slope of the temperature graph).

  In the embodiment, the predetermined temperature and the target temperature TPth (target temperature at the time of initial error determination operation after power-on) are the same value. However, the present invention is not limited to this, for example, the predetermined temperature and The value may be different from the target temperature.

  In the embodiment described above, in order to shorten the transition time from the standby mode to the printing operation, the energization to the halogen lamp 82 is not stopped (the energization is continued) in the standby mode. The invention is not limited to this. For example, referring to FIG. 2, if the nip plate 83 can be quickly heated by the halogen lamp 82, the energization to the halogen lamp 82 (heat source) is stopped in the standby mode. Also good.

  In the embodiment, the determination process of the present invention is executed when the laser printer 1 is turned on and the first energization of the halogen lamp 82 is started. However, the present invention is not limited to this. . For example, in an image forming apparatus configured to stop energization of the heat source in the standby mode, the determination process of the present invention may be executed every time energization of the heat source is started.

  In the embodiment, the thermistor 87 (temperature detection member) is provided so as to detect the temperature of the nip plate 83 as the temperature of the fixing device 8, but the present invention is not limited to this. For example, referring to FIG. 2, the temperature detection member is arranged with the temperature detection surface facing the fixing belt 81, the backup roller 85, etc., so that the temperature of the fixing device 8 is set as the fixing belt 81 or the backup belt. It may be provided so as to detect the temperature of the roller 85 or the like.

  The configuration of the fixing device 8 shown in the embodiment is an example, and the present invention is not limited to the configuration of the embodiment. For example, in the above-described embodiment, the fixing device 8 includes the fixing belt 81. However, the fixing device 8 is not limited thereto, and includes, for example, a circular metal roller (a so-called heating roller) instead of the fixing belt. It may be a configuration. Moreover, in the said embodiment, although the halogen lamp 82 (halogen heater) was illustrated as a heat source, it is not limited to this, For example, a carbon heater, IH heater, a ceramic heater, etc. may be sufficient.

  In the embodiment, the laser printer 1 that forms a monochrome image is exemplified as the image forming apparatus. However, the present invention is not limited to this, and may be a printer that forms a color image, for example. The image forming apparatus is not limited to a printer, and may be, for example, a copier or a multi-function machine including a document reading apparatus such as a flat bed scanner.

  In the embodiment, the paper S such as so-called plain paper or postcard is shown as an example of the recording sheet. However, the present invention is not limited to this, and may be, for example, an OHP sheet.

DESCRIPTION OF SYMBOLS 1 Laser printer 8 Fixing apparatus 10 Control apparatus 11 Determination means 82 Halogen lamp 87 Thermistor S Paper

Claims (6)

A fixing device having a heat source and thermally fixing the developer image on the recording sheet;
A temperature detection member for detecting the temperature of the fixing device;
A control device for controlling the amount of current supplied to the heat source,
The control device is a determination unit that determines whether or not the image forming apparatus is normal based on a temperature detected by the temperature detection member, executes a first determination process, and further performs the first determination process. It has a determination means for executing the second determination process according to the determination result,
The determination means includes
When energization to the heat source is started, the detected temperature is acquired and stored as a first temperature,
In the first determination process, when the detected temperature reaches a predetermined temperature within the first time, it is determined that the detected temperature is normal, and the detected temperature does not reach the predetermined temperature within the first time. Shifts to the second determination process,
In the second determination process, the detected temperature is set to the predetermined time after the first time elapses and when the energization of the heat source is started until the second time longer than the first time elapses. When the temperature reaches, the predetermined temperature is acquired as the second temperature, and when the temperature change amount based on the second temperature and the first temperature is equal to or greater than the predetermined value, it is determined that the temperature is normal. When the second time has elapsed without the detected temperature reaching the predetermined temperature, the detected temperature when the second time has elapsed is acquired as the second temperature, and the second temperature When the temperature change amount based on the temperature and the first temperature is equal to or greater than a predetermined value, it is determined to be normal, and when the temperature change amount is less than the predetermined value, it is determined to be not normal. An image forming apparatus. The image forming apparatus according to claim 1, wherein the determination unit acquires the first temperature when energization of the heat source is started. The image forming apparatus according to claim 1, wherein the determination unit acquires the second temperature when the energization of the heat source is stopped. The image forming apparatus according to claim 3, wherein the control device stops energization of the heat source when the detected temperature reaches a target temperature. 5. The image forming apparatus according to claim 3, wherein the control device stops energization to the heat source when a second time has elapsed from the start of energization to the heat source. 6. 2. The process according to claim 1, wherein the determination unit executes a process of determining whether or not the image forming apparatus is normal when power is turned on and the first energization of the heat source is started. The image forming apparatus according to claim 5.

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