JP2007156348A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of detecting the occurrence of jam at startup time for raising the temperature of a heating roller. <P>SOLUTION: The fixing device includes: the heating roller for fixing an unfixed toner image on a recording medium; a temperature sensor for detecting the temperature of the heating roller; a temperature control means for driving a heater, to raise the temperature of the heating roller up to a target temperature; and a jam detecting means for comparing a scheduled reaching temperature estimated that the temperature of the heating roller reaches at at least one timing in the temperature rising process of the heating roller with a measured temperature detected by a temperature detecting means, to detect the jam of the recording medium, based on the comparison result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes an unfixed toner image on a recording medium such as paper, and more particularly to a technique for detecting a jam in a recording medium that occurs in the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copying machines use a fixing device that heats an unfixed toner image by a heating roller and fixes it on a recording medium such as paper. In the fixing device, a jam of the recording medium may occur during the operation, and fixing of the unfixed toner image to the recording medium may not be performed.

2. Description of the Related Art Conventionally, as a fixing device that detects a jam, a fixing device that detects a jam based on a temperature detected by a temperature sensor used to control the temperature of a heating roller has been proposed (see Patent Document 1). For example, the fixing device described in Patent Document 1 includes a non-contact infrared temperature sensor disposed on the side of the heating roller as the temperature sensor. If the recording medium does not pass between the heating roller and the pressure roller and wraps around the surface of the heating roller and a jam occurs, the recording medium enters between the heating roller surface and the infrared temperature sensor. , The detected temperature decreases. The fixing device uses this fact to determine that a jam has occurred when the temperature detected by the infrared temperature sensor decreases and the amount of change exceeds a predetermined threshold.
Japanese Patent Publication No. 1-01586

  However, in the fixing device, it is sometimes necessary to detect a jam not only during the fixing operation but also when the heating roller is started up such as when the power is turned on. For example, when a jam occurs in the fixing operation and the printer is left as it is and enters a standby state, or when the recording medium is removed by the user but the power is turned off without being completely removed For example, a jam occurs before the fixing operation is resumed.

  However, in the fixing device described in Patent Document 1, a jam cannot be detected when the power is turned on again or when the operation state is changed from the standby state. In other words, when the fixing operation is started up, the temperature of the heating roller is originally low, so that the amount of change in temperature is small even when a jam occurs. For this reason, the change amount does not exceed the above-described threshold value, and a jam cannot be detected.

  One object of the present invention is to provide a fixing device that can detect the occurrence of a jam when the heating roller that raises the temperature of the heating roller is started up.

  In order to solve the above-described problems, a fixing device according to the present invention includes a heating roller that heats an unfixed toner image on a recording medium with the heat of the heater and fixes the image on the recording medium, and the heating roller. Temperature detection means for detecting the temperature of the heating roller, temperature control means for driving the heater to raise the temperature of the heating roller to a target temperature, and at least one timing in the process of temperature rise of the heating roller by the temperature control means A jam detection means for comparing the estimated temperature estimated to reach the temperature of the heating roller with the measured temperature detected by the temperature detection means, and detecting a jam of the recording medium based on the comparison result; Is provided.

  In the present invention, the jam detection means compares the estimated arrival temperature estimated to be reached by the heating roller at at least one timing in the process of temperature rise of the heating roller and the actually measured temperature detected by the temperature detection means, Jam is detected based on the comparison result. Therefore, according to the present invention, it is possible to detect the occurrence of a jam based on the difference between the actually measured temperature and the expected arrival temperature in the process of increasing the temperature of the heating roller, for example, at the time of starting the fixing device.

  In one aspect of the present invention, the jam detection unit further includes a nonvolatile storage unit that stores a jam occurrence history when a jam occurs in the operation of the fixing device before the temperature of the heating roller is increased by the temperature control unit. May detect a jam of the recording medium based on the comparison result when the jam occurrence history is held in the process of temperature rise of the heating roller by the temperature control means. In this aspect, the non-volatile storage means holds the jam occurrence history even when the power is turned off by the user and the power supply to the fixing device is stopped. Therefore, for example, when the temperature of the heating roller is raised again, such as when the power is turned on again, it can be detected whether or not the jam has been eliminated. Here, the non-volatile storage means may erase the jam occurrence history when the temperature of the heating roller reaches the target temperature by the temperature control means.

  In the aspect of the invention, the jam detection unit may determine the scheduled temperature based on the first actual temperature detected by the temperature detection unit for a predetermined time from the detection of the first actual temperature. It is calculated as a temperature estimated that the temperature of the heating roller will reach after a lapse of time, and a second actually measured temperature detected after the lapse of the predetermined time is compared with the scheduled arrival temperature, and the recording medium is based on the comparison result The occurrence of a jam may be detected. Here, a failure detection unit that compares the first measured temperature with the second measured temperature and detects a failure of the fixing device based on the comparison result may be further provided. The apparatus further comprises a non-volatile storage unit that stores a jam occurrence history when a jam occurs in the operation of the fixing device before the temperature of the heating roller is increased by the temperature control unit. When the storage unit does not hold the jam occurrence history, the planned arrival temperature may be compared with the second actually measured temperature, and a failure of the fixing device may be detected based on the comparison result. This makes it possible to detect a failure of the fixing device in the process of increasing the temperature of the heating roller, for example, when the fixing device is activated.

  In order to solve the above-described problem, a control method according to the present invention is a method for controlling a fixing device that fixes an unfixed toner image on a recording medium. The heating method is provided in the fixing device by driving a heater. A temperature raising step for raising the temperature of the roller to a target temperature; a step for obtaining a predicted temperature that the temperature of the heating roller is estimated to reach at at least one timing in the temperature raising step; and at least a step in the temperature raising step. Detecting the temperature of the heating roller at one timing, comparing the detected temperature of the heating roller with the expected arrival temperature, and detecting a jam of the recording medium based on the comparison result; It is characterized by including.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 including a fixing device 10 according to an embodiment of the present invention.

  The image forming apparatus 1 is, for example, a copying machine, a printer, a facsimile, or the like, and fixes an unfixed toner image on a recording medium and an image forming mechanism 20 that forms an unfixed toner image on a recording medium such as paper. The fixing device 10 is included.

  The image forming mechanism 20 includes a photosensitive drum 22, a charging roller 23 disposed around the photosensitive drum 22, an optical scanning device 24, a developing device 25, a transfer roller 27, and a cleaning device 26. ing.

  The charging roller 23 uniformly charges the surface of the rotating photosensitive drum 22 with negative charges. The optical scanning device 24 irradiates the surface of the photosensitive drum 22 with a laser beam or LED (Light Emitting Diode) light of an image pattern to be output by the image forming apparatus 1, and electrostatic latent image on the surface of the photosensitive drum 22. Form. The developing device 25 attaches toner to the electrostatic latent image and forms a toner image corresponding to the image pattern on the surface of the photosensitive drum 22. The transfer roller 27 transfers the toner image to a recording medium such as a resinous sheet or paper, and forms an unfixed toner image on the recording medium. The recording medium on which the unfixed toner image is formed is conveyed to the fixing device 10. The cleaning device 26 removes residual toner, paper dust, and the like from the surface of the photosensitive drum 22. The recording medium before feeding is held in the feeding tray 4. The recording medium is transported from the paper feed tray 4 to the downstream side of the transport path (image forming mechanism 20 side) by a paper feed mechanism (not shown). When the image forming apparatus 1 has a copying function, it includes a scanner (not shown) that reads a document and generates image data.

  The fixing device 10 includes a heating roller 12, a pressure roller 13, a temperature sensor 14, and a control circuit 15. The pressure roller 13 is pressed against the heating roller 12 to form a nip portion through which the recording medium passes. The pressure roller 13 rotates together with the heating roller 12 when the fixing device 10 is operated, and conveys the recording medium to the downstream side of the conveyance path.

  The heating roller 12 includes a heater 11. During the operation of the fixing device 10, the heating roller 12 is heated to a temperature suitable for fixing the unfixed toner image on the recording medium by the heat of the heater 11, and the pressure roller is driven by driving a motor (not shown). 13 and the recording medium are rotated in the direction of conveying the recording medium to the downstream side of the conveying path. The recording medium is heated and pressurized when passing through the nip formed between the heating roller 12 and the pressure roller 13, and the unfixed toner image on the recording medium is fixed to the recording medium. The recording medium on which the toner image is fixed is transported along the transport path and discharged to the outside of the image forming apparatus 1.

  The heater 11 is controlled by the control circuit 15 to raise the temperature of the heating roller 12 until reaching a temperature suitable for fixing the unfixed toner image on the recording medium when the heating roller 12 is started up, and during the fixing operation, the heating roller 12 is heated. The surface temperature of 12 is maintained at a temperature suitable for the fixing.

  The temperature sensor 14 is a non-contact infrared temperature sensor that is spaced apart from the surface of the heating roller 12 and detects infrared rays emitted from the surface of the heating roller 12. The temperature sensor 14 outputs a voltage corresponding to the amount of infrared radiation, that is, the surface temperature, to the control circuit 15. The control device 15 detects the surface temperature at a predetermined cycle based on the input voltage.

  The control circuit 15 is connected to the heater 11 and the temperature sensor 14 and controls the heater 11 based on the surface temperature of the heating roller 12 detected by the temperature sensor 14. The control circuit 15 may be a circuit that controls the entire image forming apparatus 1.

  FIG. 2 is a configuration block diagram of the control circuit 15. The control circuit 15 includes a control unit 16, a storage unit 17, an operation unit 18, and a display unit 19.

  The control unit 16 includes, for example, a CPU (Central Processing Unit), and executes a program stored in the storage unit 17. Details of specific processing executed by the control unit 16 will be described later in detail.

  The storage unit 17 includes, for example, a ROM (Read Only Memory) that is a nonvolatile storage medium, a flash memory, a hard disk, and a RAM (Random Access Memory) that is a volatile storage medium. . The storage unit 17 stores a program executed by the control unit 16 and also functions as a work memory for the control unit 16. In the present embodiment, when a jam occurs in the fixing operation, the non-volatile storage medium of the storage unit 17 stores a jam occurrence history, and the jam occurs even when the image forming apparatus 1 is turned off. The history is retained. The jam occurrence history will be described in detail later.

  The operation unit 18 is, for example, an operation button or a touch panel, and outputs a user operation content to the control unit 16.

  The display unit 19 is a display, for example, and presents information to the user in accordance with instructions input from the control unit 16. In this embodiment, when a jam occurs in the fixing device 10, a message notifying that a jam has occurred is displayed.

  Here, processing executed by the control unit 16 will be described. The control unit 16 executes processing for controlling the heater 11 so that the surface temperature of the heating roller 12 becomes a temperature suitable for fixing unfixed toner (hereinafter referred to as a target temperature) during the fixing operation. The processing performed by the control unit 16 during the fixing operation is, for example, processing for controlling the heater 11 on / off.

  In the process of turning on / off the heater 11, the control unit 16 detects the surface temperature of the heating roller 12 at a predetermined cycle based on the voltage input from the temperature sensor 14, and the surface temperature of the heating roller 12 is set to the target temperature. When higher, the heater 11 is turned off. Thereafter, when the surface temperature becomes lower than the target temperature, the control unit 16 turns on the heater 11 again. The controller 16 keeps the surface temperature of the heating roller 12 at the target temperature by repeatedly turning the heater 11 on and off during the fixing operation. If the user does not give an instruction to form an image and the fixing operation by the fixing device 10 is not executed for a predetermined time or longer, the control unit 16 maintains the surface temperature of the heating roller 12 at a temperature lower than the target temperature, and the fixing device. 10 may be shifted from the operating state to the standby state.

  In addition, the control unit 16 executes processing for detecting a jam in the recording medium. The processing for detecting a jam during the fixing operation is performed as follows, for example.

  When a jam occurs, as shown in FIG. 3A, the recording medium enters between the heating roller 12 and the temperature sensor 14, and the recording medium blocks the infrared rays emitted from the heating roller 12. As shown in FIG. 3B, when the recording medium comes into contact with the heating roller 12 and absorbs the heat of the heating roller 12, the temperature detected by the temperature sensor 14 decreases. Therefore, the control unit 16 detects a jam based on the temperature detected by the temperature sensor 14. For example, the control unit 16 temporarily stores the surface temperature of the heating roller 12 detected at a predetermined cycle in the storage unit 17. Then, when the surface temperature detected at the next detection is lower than the temperature detected last time and the amount of change exceeds a preset threshold, it is determined that the recording medium has jammed. At this time, the control unit 16 displays a message notifying that a jam has occurred on the display unit 19, and stores a jam occurrence history in a nonvolatile storage medium of the storage unit 17.

  Note that the method of detecting a jam in the fixing operation is not limited to this. For example, the fixing device 10 includes a recording medium detection sensor that detects the passage of the recording medium on the upstream side and the downstream side of the nip portion formed between the pressure roller 13 and the heating roller 12. Then, after the upstream recording medium detection sensor detects the passage of the recording medium, the control unit 16 detects a jam in the fixing device 10 when the downstream recording medium detection sensor does not detect the passage of the recording medium for a certain time. Jam occurrence history may be stored in a non-volatile storage medium in the storage unit 17 by determining that it has occurred.

  Further, the control unit 16 performs a process of increasing the surface temperature of the heating roller 12 to the target temperature when the heating roller 12 is started up, such as when the power is turned on or when the fixing device 10 is shifted from the standby state to the operating state, and a fixing operation. And a process of confirming whether or not the jam that occurred in the above is resolved.

  Here, the process at the time of starting which the control part 16 performs is demonstrated. FIG. 4 is a flowchart illustrating an example of processing executed by the control unit 16 at startup.

  When the power of the image forming apparatus 1 is turned on or the operation unit 18 is operated by the user to instruct to form an image on a recording medium such as paper, the control unit 16 turns on the heater 11 and turns on the heating roller 12. While the temperature rise is started (S101), the storage unit 17 is accessed to determine whether or not a jam occurrence history is held in the nonvolatile storage medium (S102). Here, when the jam occurrence history is not held, the control unit 16 detects the surface temperature of the heating roller 12 based on the voltage input from the temperature sensor 14 (S103), and the surface temperature is the target temperature. It is determined whether or not Tp has been reached (S104). When the surface temperature reaches the target temperature Tp, the temperature rise of the heating roller 12 by the heater 11 is finished, and the process at the time of start-up is finished. When the surface temperature does not reach the target temperature Tp, the process of detecting the surface temperature at a predetermined cycle and determining whether or not the target temperature Tp has been reached is continued until the surface temperature reaches the target temperature Tp. .

  On the other hand, if the jam occurrence history is held in S102, that is, if a jam has occurred in the fixing operation before starting up the heating roller 12, it is confirmed whether or not the jam has been eliminated. Execute the process. In the process of confirming the removal of the jam, the control unit 16 estimates a temperature at which the surface temperature should reach at a predetermined timing in the process of the temperature rise of the heating roller 12 (hereinafter referred to as a planned arrival temperature Ta). Then, when the surface temperature actually measured by the temperature sensor 14 at the predetermined timing is lower than the scheduled temperature Ta, it is determined that the jam has not yet been resolved, and the process at the time of starting up the heating roller 12 is finished. .

  Specifically, after determining that the jam occurrence history is held in S102, the control unit 16 detects the surface temperature of the heating roller 12 (hereinafter referred to as a first actually measured temperature) (S105).

  After that, the control unit 16 calculates the estimated temperature Ta as a temperature estimated to reach the surface temperature of the heating roller 12 after a predetermined time Ct has elapsed from the time when the first measured temperature T1 is detected (S106). The predetermined time Ct may be the same time as the period in which the control unit 16 detects the surface temperature of the heating roller 12 during the fixing operation, or may be a time longer than the period. The calculation of the scheduled arrival temperature Ta by the control unit 16 is performed as follows, for example.

  The storage unit 17 holds in advance a change amount ΔT of the surface temperature that rises during the predetermined time Ct due to the heat of the heater 11. The control unit 16 acquires the change amount ΔT, adds the change amount ΔT to the first actually measured temperature T1, and sets the obtained value as the expected arrival temperature Ta. This change amount ΔT may be a fixed value, for example, or may be a value set in association with the environmental temperature or the surface temperature of the heating roller 12.

  When the change amount ΔT is a value set in association with the environmental temperature and the surface temperature of the heating roller 12, the storage unit 17 is a temperature that associates the change amount ΔT with the environmental temperature Te and the surface temperature T of the heating roller 12, for example. An environmental temperature sensor (for example, a thermistor or a temperature sensitive diode) that holds the change amount table and detects the environmental temperature Te is provided inside the image forming apparatus 1. FIG. 6 is a diagram illustrating an example of a temperature change amount table. In this temperature change amount table, the environmental temperature Te is shown in the top row, the surface temperature T of the heating roller 12 is shown in the leftmost column, and the change amount ΔT is associated with each environmental temperature Te and the surface temperature T. Is set. The control unit 16 detects the environmental temperature Te based on the voltage input from the environmental temperature sensor when calculating the expected arrival temperature Ta, and refers to the temperature change amount table to refer to the environmental temperature Te and the first actually measured temperature. A change amount ΔT is acquired based on T1. Then, the estimated change temperature Ta is calculated by adding the obtained variation ΔT to the first actually measured temperature T1.

  After calculating the expected arrival temperature Ta in S106, the control unit 16 again sets the surface temperature of the heating roller 12 (hereinafter referred to as the second measured temperature T2) after a predetermined time Ct has elapsed from the time when the first measured temperature T1 is detected. ) Is detected (S107).

  Then, the control unit 16 determines whether or not the second actually measured temperature T2 is higher than the scheduled arrival temperature Ta (S108). When a jam has occurred, the recording medium enters between the temperature sensor 14 and the heating roller 12 as shown in FIG. 3A, or the recording medium moves as shown in FIG. It is in contact with the surface of the heating roller 12. Therefore, the second measured temperature detected by the control unit 16 when a jam has occurred is a value lower than the surface temperature that should be detected when the jam has not occurred, that is, the expected arrival temperature Ta. Therefore, in the determination of S108, when the second actually measured temperature T2 is lower than the scheduled arrival temperature Ta, the control unit 16 determines that the jam of the recording medium has not yet been resolved (S109). Then, a message notifying that a jam has occurred is displayed on the display unit 19 (S110), and the heater 11 is turned off and the process at the time of starting is ended.

  On the other hand, as a result of the comparison in S108, when the second actually measured temperature T2 is higher than the scheduled arrival temperature Ta, the control unit 16 determines whether or not the second actually measured temperature T2 is higher than the target temperature Tp (S111). ). Here, when the second measured temperature T2 is higher than the target temperature Tp, the control unit 16 determines that the jam has been resolved and the surface temperature has reached a temperature suitable for fixing, and the storage unit 17 is erased (S112), the process at the time of starting up the heating roller 12 is terminated, and the process during the fixing operation described above, that is, the surface temperature of the heating roller 12 is set to the target temperature Tp. The process to maintain is started.

  If the result of determination in S111 is that the second measured temperature T2 is lower than the target temperature Tp, the process returns to S105, where the first measured temperature T1 is detected again based on the voltage of the temperature sensor 14, and then the heating roller 12 The subsequent processing is repeated until the surface temperature reaches the target temperature Tp or a jam is detected.

  As described above, according to the fixing device 10, when the heating roller 12 is started up, the expected arrival temperature Ta is calculated as the temperature to be reached in the process of the temperature increase of the heating roller 12, and the expected arrival temperature Ta and the temperature sensor are calculated. 14 is compared with the surface temperature detected, and it is determined whether or not the jam that occurred before start-up has been resolved.

  In the process of starting the heating roller 12 described above, the control unit 16 compares the first measured temperature with the second measured temperature, and detects a failure of the heater 11 based on the comparison result. May be.

  Specifically, as shown in the flowchart of FIG. 5, after detecting the second measured temperature T2 in S107, the control unit 16 compares the first measured temperature T1 with the second measured temperature T2. (S113). As a result of the comparison, when the second actually measured temperature T2 is lower than the first actually measured temperature T1, the surface temperature of the heating roller 12 is lowered despite the heater 11 being turned on. There may be a failure. Therefore, in this case, the control unit 16 may display a message notifying the failure of the heater 11 on the display unit 19 (S114), and the processing at the time of starting up the heating roller 12 may be terminated.

  Further, the process of detecting the failure of the heater 11 when the heating roller 12 is started up is that jam occurs in the fixing operation before the storage roller 17 holds the jam occurrence history, that is, before the heating roller 12 is started up. Even if not, it may be executed.

  For example, as shown in the flowchart of FIG. 5, even when it is determined in S102 that the storage unit 17 does not hold the jam occurrence history, the control unit 16 detects the first measured temperature T1 ( In step S115, the amount of change ΔT is added to the first actually measured temperature T1 to calculate the scheduled arrival temperature Ta (S116). Then, after a predetermined time Ct has elapsed from the time point at which the first measured temperature T1 was detected, the second measured temperature T2 is detected (S117), and the planned arrival temperature Ta is compared with the second measured temperature T2 ( S118). If the heater 11 is turned on and the second actually measured temperature T2 does not reach the expected temperature Ta even though the jam has not occurred, the heater 11 may be broken. Therefore, when the second actually measured temperature T2 is lower than the planned arrival temperature Ta, the control unit 16 determines that the heater 11 has failed, and displays a message notifying the failure of the heater 11 on the display unit 19 ( S114), the process at the time of starting up the heating roller 12 may be terminated.

  In the above description, the scheduled arrival temperature Ta is calculated by adding the change amount ΔT to the first actually measured temperature T1, but the scheduled arrival temperature Ta is, for example, the start of processing when the heating roller 12 is started up. The scheduled arrival temperature Ta may be set in advance in association with the elapsed time from the time, and stored in the storage unit 17. In this case, the control unit 16 accesses the storage unit 17 to acquire the planned reaching temperature Ta instead of calculating the planned reaching temperature Ta in S106.

  Further, when detecting the surface temperature of the heating roller 12, the control unit 16 determines whether or not the voltage input from the temperature sensor 14 is between a predetermined lower limit value and an upper limit value. When the upper limit value is exceeded, it is determined that the temperature sensor 14 has failed, a message for notifying the failure of the temperature sensor 14 is displayed on the display unit 19, and processing when the heating roller 12 is started up May be terminated.

1 is a schematic cross-sectional view of an image forming apparatus including a fixing device according to an embodiment of the present invention. It is a functional block diagram of the image forming apparatus. FIG. 6 is a diagram illustrating a state in which a jam of a recording medium has occurred in the fixing device. It is a flowchart figure which shows the example of the process at the time of starting of a heating roller. It is a flowchart figure which shows the other example of the process at the time of starting of a heating roller. It is a figure which shows the example of a temperature variation table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing apparatus, 4 Paper feed tray, 10 Fixing apparatus, 11 Heater, 12 Heating roller, 13 Pressure roller, 14 Temperature sensor, 15 Control circuit, 16 Control part, 17 Storage part, 18 Operation part, 19 Display part, 20 image forming mechanism, 22 photosensitive drum, 23 charging roller, 24 light scanning device, 25 developing device, 26 cleaning device, 27 transfer roller.

Claims (7)

A heating roller that includes a heater and heats the unfixed toner image on the recording medium with the heat of the heater to fix the image on the recording medium;
Temperature detecting means for detecting the temperature of the heating roller;
Temperature control means for driving the heater to raise the temperature of the heating roller to a target temperature;
Comparing the estimated arrival temperature estimated to reach the temperature of the heating roller at at least one timing in the process of temperature increase of the heating roller by the temperature control means and the actual temperature detected by the temperature detection means, Jam detecting means for detecting jam of the recording medium based on the comparison result;
A fixing device comprising: The fixing device according to claim 1,
Non-volatile storage means for storing a jam occurrence history when a jam occurs in the operation of the fixing device before the temperature increase of the heating roller by the temperature control means,
The jam detection means detects a jam of the recording medium based on the comparison result when the jam occurrence history is held in the process of temperature rise of the heating roller by the temperature control means.
A fixing device. The fixing device according to claim 2,
The nonvolatile storage means erases the jam occurrence history when the temperature of the heating roller reaches the target temperature by the temperature control means.
A fixing device. The fixing device according to any one of claims 1 to 3,
The jam detecting means is configured to reach the scheduled temperature based on the first measured temperature detected by the temperature detecting means, when the temperature of the heating roller reaches a predetermined time after the first measured temperature is detected. Then, the temperature is calculated as an estimated temperature, the second measured temperature detected after the predetermined time has passed is compared with the scheduled arrival temperature, and the occurrence of a jam in the recording medium is detected based on the comparison result.
A fixing device. The fixing device according to claim 4,
A failure detection means for comparing the first measured temperature with the second measured temperature and detecting a failure of the fixing device based on the comparison result;
A fixing device. In the fixing device according to claim 4 or 5,
Non-volatile storage means for storing a jam occurrence history when a jam occurs in the operation of the fixing device before the temperature increase of the heating roller by the temperature control means,
The failure detection unit compares the scheduled arrival temperature and the second actually measured temperature when the nonvolatile storage unit does not hold the jam occurrence history, and based on the comparison result, the fixing device Detect failure of the
A fixing device. A method for controlling a fixing device for fixing an unfixed toner image on a recording medium, comprising:
A temperature raising step of driving a heater to raise the temperature of a heating roller provided in the fixing device to a target temperature;
Obtaining a scheduled temperature estimated to reach the temperature of the heating roller at at least one timing in the temperature raising step;
Detecting the temperature of the heating roller at at least one timing in the temperature raising step;
Comparing the detected temperature of the heating roller and the expected temperature, and detecting a jam of the recording medium based on the comparison result;
A method comprising the steps of:

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