JP2009015234A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, capable of more accurately ascertaining abnormal temperatures by controlling temperature based on a temperature gradation calculated from a change in the fixing temperature, even when the fixing temperature is higher than a set temperature. <P>SOLUTION: If temperature gradation, calculated by a temperature gradation calculating section, is smaller than a set temperature gradation, even when the temperature of a heating section is higher than that of the fixing temperature, the image forming apparatus does not determine that the temperature of the heating section is abnormal. Accordingly, the temperature of the heating section can be controlled through the control of a heat source by a control section so as to reach the fixing temperature. In addition, by calculating the temperature gradient, temperature can be decided as being abnormal, even if the temperature of the heating section has not reached the upper limit. Accordingly, the apparatus can ascertain abnormal temperature more accurately than in the conventional types and ensure high safety. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a fixing device for fixing a developer by heat, such as a printer, a facsimile machine, and a copying machine.

  Conventionally, there is an image forming apparatus in which an upper limit temperature and a lower limit temperature of a fixing temperature for thermally fixing a developer are set for each set temperature (see, for example, Patent Document 1). In this image forming apparatus, when the fixing temperature deviates from the upper limit temperature or the lower limit temperature, the temperature is abnormal and the process proceeds to an abnormal process.

Japanese Patent Laid-Open No. 05-006126

  In such an image forming apparatus, an upper limit temperature and a lower limit temperature are set for each set temperature. For this reason, even when there is no problem in safety, for example, when the user sets the medium incorrectly, the image forming apparatus may determine that the temperature is abnormal due to deviation from the set upper limit temperature or lower limit temperature. . Even in this case, there is a problem that the image forming apparatus shifts to an abnormal process and executes a process when an unnecessary abnormality occurs. Further, the image forming apparatus has a problem that the user's hand is frequently bothered when the user's operation is necessary for executing the processing when the abnormality occurs.

  In view of the above, the image forming apparatus of the present invention controls the temperature based on the temperature gradient calculated from the change in the fixing temperature even when the fixing temperature is higher than the set temperature. Accordingly, an object of the present invention is to provide an image forming apparatus that can more appropriately determine a temperature abnormality.

  The image forming apparatus of the present invention is an image forming apparatus for fixing a developer transferred by heating and pressing to a recording medium, and is heated by the heat source, a control unit for controlling the heat source, and the developer. A heating unit that heats the recording medium to which the image has been transferred, a pressurizing unit that is disposed opposite to the fixing unit and that sandwiches and presses the recording medium that passes between the heating unit and the heating object, and the heating unit A temperature detection unit that detects a temperature of the heating unit, and a temperature gradient calculation unit that calculates a temperature gradient of the heating unit detected by the temperature detection unit, wherein the control unit has a predetermined temperature that is determined in advance When the calculated temperature gradient is larger than the set temperature gradient based on a comparison result between the calculated temperature gradient calculated by the temperature gradient calculation unit and a preset temperature gradient set in advance by being detected by the temperature detection unit And controls so as to stop heating to the heating unit by the heat source.

  According to the image forming apparatus of the present invention, the temperature detection element detects the temperature of the heating unit heated by the heat source. Then, the temperature gradient calculation unit calculates a temperature gradient from the detected temperature. A control part performs temperature control of the heating part by a heat source from the comparison result of this calculated temperature gradient and a preset temperature gradient set in advance.

  In the image forming apparatus of the present invention, even when the temperature of the heating unit is higher than the fixing temperature, if the calculated temperature gradient calculated by the temperature gradient calculating unit is smaller than the set temperature gradient, the image forming apparatus can be determined to be abnormal. First, the temperature of the heating unit can be controlled to approach the fixing temperature by controlling the heat source by the control unit. Further, by calculating the temperature gradient, it is possible to determine that the temperature is abnormal even when the temperature of the heating unit does not reach the upper limit temperature. Therefore, it is possible to determine a temperature abnormality more appropriately than in the past, and to ensure high safety.

  The image forming apparatus of the present invention will be described below with reference to the drawings. The image forming apparatus of the present invention is not limited to the following description, and can be appropriately changed without departing from the gist of the present invention.

[Embodiment 1]
FIG. 1 is a diagram showing a configuration of an image forming apparatus of the present invention. As shown in FIG. 1, the image forming apparatus 1 includes a medium cassette 3, process units 11, 12, 13, and 14, a fixing unit 30, medium detection sensors 50 and 51, a medium passage sensor 52, and each roller. have. A sheet 2 as a recording medium is stored in the medium cassette 3.

  As shown in FIG. 1, the medium cassette 3 is a box-shaped member having an opening on the upper surface so that sheets 2 on which images are to be formed are deposited and at least the sheets 2 can be taken out. The medium cassette 3 is provided with a pickup roller 40 so as to contact the paper 2 in the medium cassette 3. By operating the pickup roller 40, the sheets 2 are separated one by one, drawn in the direction of the arrow 60, and supplied from the medium cassette 3 to the conveyance path.

  In the transport path from the medium cassette 3 to the process units 11, 12, 13, and 14, a pair of registration rollers 41 and 42, a medium detection sensor 50, and a pair of registration rollers 43 and 44 from the upstream side in the transport direction of the sheet 2 A medium detection sensor 51 is provided. The sheet 2 fed to the conveyance path by the pickup roller 40 is disposed in pressure contact with each other, and is conveyed in the direction of the arrow 61 by registration rollers 41 and 42 that sandwich the sheet 2 as a pair. When the paper 2 is transported by the registration rollers 41 and 42, the medium detection sensor 50, which is a mechanical sensor, is activated to detect the passage of the paper 2.

  Similarly, the sheet 2 is disposed in pressure contact with each other, and is conveyed in the direction of the arrow 62 by registration rollers 43 and 44 that sandwich the sheet 2 as a pair. When the sheet 2 is transported by the registration rollers 43 and 44, the medium detection sensor 51, which is a mechanical sensor, operates to detect the passage of the sheet 2. The transported paper 2 is transported to the process units 11, 12, 13, and 14 by the transport belt 20.

  The process units 11, 12, 13, and 14 are electrophotographic process units corresponding to toners as four color developers of cyan (C), magenta (M), yellow (Y), and black (K), respectively. . Each process unit includes a photosensitive drum, a charging roller for charging the surface of the photosensitive drum, an LED head that exposes the photosensitive drum based on input image data to form an electrostatic latent image, and a surface of the photosensitive drum. A developing roller that develops the formed electrostatic latent image with toner, a developing blade that uniformly regulates the toner layer formed on the surface of the developing roller, a sponge roller that supplies toner to the developing roller, and a toner of each color And a toner cartridge for containing the toner. The process units 11, 12, 13, and 14 generate cyan, magenta, yellow, and black toner images.

  Below the process units 11, 12, 13, and 14, there are provided transfer rollers 21, 22, 23, and 24 that transfer the toner image developed on the photosensitive drum onto the sheet 2 conveyed by the conveyance belt 20. Yes. The sheet 2 that has been transported through the transport path is transported in the direction of the arrow 63 by the transport belt 20 by the high voltage applied to each of the transfer rollers 21, 22, 23, and 24, while being processed in the process units 11, 12, 13. , 14 is transferred. The sheet 2 on which the toner image is transferred is conveyed to the fixing unit 30 by the conveyance belt 20.

  FIG. 2 is a diagram illustrating the structure of the fixing unit 30. As shown in FIG. 2, the fixing unit 30 is in pressure contact with a heater 104 as a heat source typified by, for example, a halogen lamp, a heating roller 46 as a heating unit provided in the heater 104, and the heating roller 46. A pressure roller 45 as a pressure unit that presses the sheet 2 so as to be sandwiched between the heating roller 46 and a temperature detection element 31 such as a thermistor for measuring the temperature of the surface of the heating roller 46. It is comprised by. The sheet 2 conveyed by the conveying belt 20 passes between the heating roller 46 heated by the heater 104 and the pressure roller 45, so that the toner on the sheet 2 is heat-pressed.

  The temperature detection element 31 is provided in the vicinity of the heating roller 46 in a non-contact manner, and detects the surface temperature of the heating roller 46. FIG. 3 is a diagram illustrating the arrangement position of the temperature detection element. When the sheet 2 is conveyed to the fixing unit 30 and passes between the heating roller 46 and the pressure roller 45, the area of the heating roller 46 and the pressure roller 45 that contacts the sheet 2 is defined as a medium passing area. This medium passage area changes depending on the size. For example, as shown in FIG. 3, when an A6 size sheet as the minimum sheet is conveyed, the minimum sheet width of 105 mm is the medium passage area. The temperature detecting element 31 is provided above the minimum sheet width as the medium passing area in order to measure the surface temperature of the medium passing area of the heating roller 46.

  The sheet 2 having the fixed toner image is conveyed in the direction of the arrow 64 as the heating roller 46 and the pressure roller 45 rotate. When the paper 2 is conveyed to the downstream side of the fixing unit 30 by the heating roller 46 and the pressure roller 45, the medium passage sensor 52 is activated and the passage of the paper 2 is detected.

  In the present embodiment, the fixing unit 30 is mainly composed of the heating roller 46 and the pressure roller 45. However, a fixing unit in which two endless belts each having a built-in heater are pressed against each other may be used as the fixing unit. Good.

  The paper 2 on which the toner image is fixed by the fixing unit 30 is disposed in pressure contact with each other, and is conveyed in the direction of the arrow 65 by the discharge rollers 47 and 48 that sandwich the paper 2 as a pair. That is, the sheet 2 is discharged to the outside of the image forming apparatus 1 by the discharge rollers 47 and 48.

  FIG. 4 is a block diagram of the image forming apparatus. The image forming apparatus 1 includes a control unit 106, a heater control unit 112 as a heat source control unit, a motor drive control unit 113, a motor 114, a temperature detection unit 115, an operation panel control unit 117, and an operation panel 118. , A display unit 119, a medium passage sensor 121, a temperature gradient calculation unit 122, and a connection connector 130.

  The control unit 106 includes an external interface 111, a CPU (central processing unit) 107, a ROM (Read Only Memory) 108, a memory 109, a timer 110, a host interface (hereinafter referred to as a host I / F) 150, Built in. The control unit 106 performs overall control of the entire image forming apparatus 1.

  The external interface 111 is an interface between the control unit 106, the heater control unit 112, the motor drive control unit 113, and the operation panel control unit 117, and transmits a command from the control unit 106 to control each member. The external interface 111 also receives signals from the temperature detection unit 115, the temperature comparison unit 124, the temperature gradient calculation unit 122, the gradient comparison unit 125, and the medium passage sensor 52.

  The CPU 107 executes various types of programs stored in the ROM 108 while using the memory 109, thereby enabling the control unit 106 to control each member. The ROM 108 is a non-volatile storage component, and stores a program executed by the CPU 107 and setting data. The memory 109 stores values to be compared with temperatures and temperature gradients described later. The memory 109 temporarily stores and reads programs and setting data executed by the CPU 107.

  The timer 110 measures time. The time measured by the timer 110 is used when calculating the calculated temperature gradient. The host I / F 150 is an interface used for connection with the host computer 151 and receives print data transmitted from the connected host computer 151. The connection between the image forming apparatus 1 and the host computer 151 via the host I / F 150 may be wired or wireless.

  The temperature detection unit 115 detects the temperature based on the output from the temperature detection element 31 that measures the surface temperature of the heating roller 46 via the connection connector 130, and inputs the detected temperature to the control unit 106. In the present invention, the target temperature Ttg (° C.) is the target temperature of the surface of the heating roller 46 as the fixing temperature, and the upper limit temperature Tu (° C.) is the upper limit of the surface temperature of the heating roller 46. A temperature arbitrarily set to determine whether or not to calculate the calculated temperature gradient is set as a predetermined temperature Tc (° C.). These temperatures have a relationship of Tu> Tc> Ttg. The target temperature Ttg, the upper limit temperature Tu, and the predetermined temperature Tc are stored in the memory 109. The temperature comparison unit 124 compares the preset target temperature Ttg, upper limit temperature Tu, and predetermined temperature Tc with the temperature of the surface of the heating roller 46 detected by the temperature detection unit 115, and transmits the comparison result to the control unit 106. To do.

  Then, the heater control unit 112 controls on / off of the heater 104 via the connection connector 130 based on the output from the temperature detection unit 115. The temperature gradient calculation unit 122 calculates a calculated temperature gradient based on the time information of the timer 110, the information in the memory 109, and the temperature detected by the temperature detection unit 115. The gradient comparison unit 125 receives the calculated temperature gradient calculated by the temperature gradient calculation unit 122, compares the value of the predetermined temperature gradient stored in the memory 109 in advance with the calculated temperature gradient, and compares the comparison result. This is transmitted to the control unit 106.

  The motor drive control unit 113 drives the motor 114 based on outputs from the heater control unit 112 and the control unit 106. The motor 114 drives various rollers of the image forming apparatus based on the control of the motor drive control unit 113. As a result, the sheet 2 is conveyed, and the toner image is transferred and fixed.

  The display unit 119 displays information related to the image forming apparatus 1 with a display mechanism represented by, for example, an LCD (Liquid Crystal Display). The display unit 119 may be mounted with a light emitting component typified by an LED (Light Emitting Diode). The operation panel 118 is a panel for operating the image forming apparatus 1 and includes, for example, a plurality of key switches. The operation panel control unit 117 controls the operation panel 118 to display information related to the image forming apparatus 1 based on the output from the control unit 106. In addition, the operation panel control unit 117 transmits information input on the operation panel 118 to the control unit 106.

  As shown in FIGS. 1 and 5, the medium passage sensor 52 is disposed on the downstream side in the transport direction of the sheet 2 on which the toner 123 of the heating roller 46 and the pressure roller 45 is transferred. The medium passage sensor 52 detects whether or not the sheet 2 exists on the sensor, and transmits the detection result to the control unit 106. The medium passage sensor 52 may be a sensor that can be detected by mechanical movement or a sensor that can be detected by optical reflection or transmission of light.

  FIG. 6 is a processing block diagram illustrating processing in the image forming apparatus described in the first embodiment. First, the temperature detection unit 115 detects the temperature of the surface of the heating roller 46 based on the output from the temperature detection element 31. And the temperature detection part 115 outputs the temperature which is the detection result to the control part 106, the temperature gradient calculation part 122, and the temperature comparison part.

  The temperature gradient calculation unit 122 calculates a calculated temperature gradient from information in the memory 109 and the timer 110. The temperature gradient calculation unit 122 outputs the calculated value of the calculated temperature gradient to the gradient comparison unit 125. The gradient comparison unit 125 compares a predetermined set temperature gradient value stored in advance in the memory 109 with the calculated calculated temperature gradient value. Then, the gradient comparison unit 125 outputs the comparison result to the control unit 106.

  The temperature comparison unit 124 compares a preset temperature with the temperature of the heating roller 46 detected by the temperature detection unit 115. Then, the temperature comparison unit 124 outputs the comparison result to the control unit 106.

  The control unit 106 controls the heater control unit 112 and the operation panel control unit 117 based on the comparison result output from the gradient comparison unit 125. The heater control unit 112 controls on / off of the heater 104 when the control of the control unit 106 is input. The operation panel control unit 117 controls the operation panel 118 and the display unit 119 when the control of the control unit 106 is input. Further, operation panel control unit 117 outputs information input on operation panel 118 to control unit 106.

  The motor drive control unit 113 controls driving and stopping of the motor 114 when the control of the control unit 106 is input. The medium passage sensor 52 detects whether or not the sheet 2 has passed through the heating roller 46 and the pressure roller 45 and outputs the result to the control unit 106. The timer 110 not only outputs time information to the temperature gradient calculation unit 122 but also outputs time information to the control unit 106.

  Hereinafter, the operation of the image forming apparatus 1 of the present invention described in the first embodiment will be described separately at the start of printing and at the end of printing. First, at the start of printing, as shown in FIG. 9, the image forming apparatus 1 is in a standby state in step S001. At this time, the heater control unit 112 controls the heater 104 so that the surface temperature of the heating roller 46 approaches the preset target temperature Ttg.

  Specifically, first, the surface temperature of the heating roller 46 is detected by the temperature detection unit 115 based on the output of the temperature detection element 31. The temperature comparison unit 124 compares the detected surface temperature with the target temperature Ttg stored in the memory 109 and outputs the comparison result to the control unit 106. Based on the comparison result, the control unit 106 turns the heater control unit 112 on when the surface temperature of the heating roller 46 is lower than Ttg and turns off when the surface temperature of the heating roller 46 is higher than Ttg. 104 is controlled.

  While the control unit 106 controls the surface temperature of the heating roller 46 with the heater control unit 112, the temperature comparison unit 124 detects the surface temperature of the heating roller 46, the target temperature Ttg and the upper limit temperature stored in the memory 109. The Tu and the predetermined temperature Tc are compared, and the comparison result is output to the control unit 106. Then, the control unit 106 determines how the surface temperature of the heating roller 46 is related to the target temperature Ttg, the upper limit temperature Tu, and the predetermined temperature Tc stored in the memory 109 based on the input comparison result. judge. The heater control unit 112 controls the heater 104 based on this determination result.

  In step S002, the image forming apparatus 1 determines whether print data has been received from the host computer 151 connected by the host I / F 150. If not received, the standby state described as step S001 is maintained, and the printer waits until print data is received.

  When print data is received via the host I / F in step S002, the control unit 106 starts printing in step S003. The motor drive control unit 113 drives the motor 114 under the control of the control unit 106 to rotate the heating roller 46 and the pressure roller 45.

  When the motor 114 is driven, the image forming apparatus 1 performs continuous printing in step S004, and printing is performed based on the print data received from the host computer 151. The continuous printing indicates that printing is continuously performed at a predetermined medium interval.

  Next, the operation of the image forming apparatus 1 at the end of printing will be described. As illustrated in FIGS. 10 and 11, the image forming apparatus 1 performs the continuous printing described in step S <b> 003 described above in step S <b> 101. At this time, the heater control unit 112 controls the heating roller 46 to approach the target temperature Ttg based on the comparison result between the surface temperature of the heating roller 46 and the target temperature Ttg by the temperature comparison unit 124. Further, since it is in a continuous printing state, the motor drive control unit 113 controls the motor 114 to rotate at a constant speed.

  Then, the control unit 106 monitors the signal from the medium passage sensor 52, and determines whether or not the final sheet 2 has passed in step S102. At this time, the control unit 106 monitors whether or not the sheet 2 has passed at a predetermined medium interval by a signal from the medium passage sensor 52, and determines that the state in which the paper 2 has not passed at the predetermined medium interval is the final. Assuming that the paper 2 has passed, the end of continuous printing is determined.

  In step S102, when the final sheet 2 has not passed, the control unit 106 continues the continuous printing described in step S101 until the continuous printing ends because the continuous printing is being performed. If the final sheet 2 has passed in step S102, printing is terminated in step S103. Then, the control unit 106 controls the motor drive control unit 113 to stop the motor 114, and the motor drive control unit 113 stops the motor 114 based on this control in step S104.

  FIG. 7 shows the relationship between the temperature transition of the heater and signals output from the motor drive control unit, the heater control unit, and the medium passage sensor. Here, the target temperature Ttg during printing and the predetermined temperature Tc maintain a relationship of Tc> Ttg, and the upper limit temperature Tu and the predetermined temperature maintain a relationship of Tu> Tc. As shown in FIG. 7, the surface temperature of the heating roller 46 rapidly increases so as to approach the upper limit temperature Tu from the target temperature Ttg at the time A when the continuous printing ends. This is called an overshoot of the heating roller 46. This overshoot keeps the balance between the heat from the heater 104 and the heat absorbed by the passing paper 2 under the control of the heater 104 by the heater control unit 112 until time A during continuous printing. Although stable near the temperature Ttg, heat absorption by the paper 2 is eliminated when the motor 114 is stopped, and heat generated by the heater 104 before time A is released.

  After stopping the motor 114 in step S104, the control unit 106 determines in step S105 whether or not the surface temperature of the heating roller 46 detected by the temperature detection unit 115 has reached the predetermined temperature Tc due to the above-described overshoot. . At this time, the temperature comparison unit 124 compares the value of the surface temperature of the heating roller 46 output from the temperature detection unit 115 with the value of the predetermined temperature Tc stored in the memory 109 in advance. Then, the temperature comparison unit 124 outputs the comparison result to the control unit 106, and the control unit 106 determines whether or not the surface temperature of the heating roller 46 has reached the predetermined temperature Tc based on the comparison result.

  In step S305, when the surface temperature of the heating roller 46 does not reach the predetermined temperature Tc, the temperature comparison unit 124 compares the surface temperature of the heating roller 46 with the target temperature Ttg and outputs the comparison result to the control unit 106. . Based on the comparison result, the controller 106 determines whether or not the surface temperature of the heating roller 46 has reached the target temperature Ttg in step S111. When the surface temperature of the heating roller 46 reaches the target temperature Ttg, the surface temperature of the heating roller 46 is close to the target temperature Ttg. Therefore, the process proceeds to step S112 and enters the standby state described in step S001. 46 temperature control is performed.

  In step S111, when the surface temperature of the heating roller 46 has not reached the target temperature Ttg, the process proceeds to step S105, and steps S105 to S111 are repeated.

  In step S105, when the surface temperature of the heating roller 46 reaches the predetermined temperature Tc, the control unit 106 sets the timing at which the surface temperature of the heating roller 46 reaches the predetermined temperature Tc as time t1, and the timer 110 sets the time t1 as a base point. In step S106, the process waits for n seconds from time t1.

  After the elapse of n seconds, the temperature gradient calculation unit 122 calculates a temperature gradient ΔTr (° C./second) based on the surface temperature of the heating roller 46 detected by the temperature detection unit 115 in step S107. This temperature gradient ΔTr is (the surface temperature of the heating roller when n seconds have elapsed—the surface temperature of the heating roller when time t1) / n (Expression 1) or (the surface temperature of the heating roller when n seconds have elapsed) − (N-1) surface temperature of the heating roller with the passage of seconds) / n (n-1) (Equation 2). Hereinafter, the calculated temperature gradient ΔTr is referred to as a calculated temperature gradient.

  The temperature gradient calculation unit 122 stores or reads the temperature data in the memory 109, reads the time data from the timer 110, and calculates the calculated temperature gradient ΔTr using the above formula 1 or formula 2. The calculated temperature gradient ΔTr is output to the gradient comparison unit 125.

  After calculating the calculated temperature gradient ΔTr, the gradient comparison unit 125 reads a predetermined set temperature gradient ΔTa previously stored in the memory 109 and compares the input calculated temperature gradient ΔTr with the set temperature gradient ΔTa. Then, the gradient comparison unit 125 outputs the comparison result to the control unit 106. In step S108, the control unit 106 determines whether or not the calculated temperature gradient ΔTr calculated is greater than a predetermined set temperature gradient ΔTa (ΔTr> ΔTa) based on the comparison result input from the gradient comparison unit. .

  If ΔTr ≦ ΔTa in step S108, the control unit 106 determines that the surface temperature of the heating roller 46 does not reach the upper limit temperature Tu and determines that the surface temperature is normal. This is because during the overshoot, the heater 104 is off, so that the heat of the heating roller 46 is only dissipated. Therefore, it is clear that the surface temperature of the heating roller 46 decreases, and the calculated calculated temperature gradient ΔTr becomes a small value as time passes. That is, if ΔTr ≦ ΔTa in step S108, the temperature of the heating roller 46 decreases, and the calculated temperature gradient ΔTr becomes a small value as time passes. For this reason, the set temperature gradient ΔTa is obtained by experiments so as to be a value that does not reach the upper limit temperature Tu.

  In step S108, if ΔTr ≦ ΔTa, the gradient comparison unit 125 continues to compare the calculated temperature gradient ΔTr with the stored predetermined temperature gradient ΔTa, and sends the result to the control unit 106. Output. In step S118, the control unit 106 determines whether ΔTr is a positive value and whether the relationship of ΔTr ≦ ΔTa continues indefinitely based on the result.

  In step S118, when ΔTr is a positive value and the relationship ΔTr ≦ ΔTa does not continue indefinitely, the process proceeds to step S111. On the other hand, when ΔTr is a positive value and the relationship ΔTr ≦ ΔTa continues in step S118, the temperature comparison unit 124 determines the surface temperature of the heating roller 46 and the upper limit stored in the memory 109. The temperature Tu is compared, and the comparison result is output to the control unit 106. In step S116, the control unit 106 determines whether the surface temperature of the heating roller 46 is higher than the upper limit temperature Tu based on the comparison result input from the temperature comparison unit 124.

  In step S116, when the surface temperature of the heating roller 46 is equal to or lower than the upper limit temperature Tu, the temperature comparison unit 124 compares the surface temperature of the heating roller 46 with a predetermined temperature Tc stored in the memory 109, and compares the comparison. The result is output to the control unit 106. In step S117, the control unit 106 determines whether or not the surface temperature of the heating roller 46 is higher than a predetermined temperature Tc based on the comparison result input from the temperature comparison unit 124.

  In step S117, when the surface temperature of the heating roller 46 is equal to or lower than the predetermined temperature Tc, the process proceeds to step S111. On the other hand, when the surface temperature of the heating roller 46 is higher than the predetermined temperature Tc in step S117, the process proceeds to step S116, and it is compared again whether or not the surface temperature of the heating roller 46 exceeds the upper limit temperature Tu.

  If ΔTr> ΔTa in step S108, or if the surface temperature of the heating roller 46 is higher than the upper limit temperature Tu in step S116, the control unit 106 determines that there is an abnormality. If the control unit 106 determines that there is an abnormality, in step S109, the heater control unit 112 is controlled to forcibly turn off the heater 104.

  Then, the control unit 106 controls the operation panel control unit 117 and causes the display unit 119 to display that there is an abnormality in step S110. After displaying the abnormality on the display unit 119, the control unit 106 waits until a recovery process is input in step S113. This restoration process is input from the operation panel control unit 117 via the operation panel 118. This restoration process may be a user operation for starting the initial process or an apparatus power on / off.

  After the restoration process is input, the temperature comparison unit 124 compares the surface temperature of the heating roller 46 with the target temperature Ttg and outputs the comparison result to the control unit 106. In step S114, the control unit 106 determines whether the surface temperature of the heating roller 46 is lower than the target temperature Ttg based on the comparison result input from the temperature comparison unit 124.

  In step S114, when the surface temperature of the heating roller 46 is equal to or higher than the target temperature Ttg, the control unit 106 does not accept the recovery process, returns to step S113, and causes the display unit 119 to display an abnormality.

  In step S114, when the surface temperature of the heating roller 46 is lower than the target temperature Ttg, the control unit 106 receives a recovery process in step S115, and proceeds to step S112.

  FIG. 8 is linked to FIG. 7 and shows the temperature gradient of the surface temperature of the heating roller with respect to the time axis. In the case of FIGS. 7 and 8, the normal or abnormal timing due to the temperature gradient in step S108 is after n seconds from the time t1. Since the calculated temperature gradient ΔTr calculated at this time is higher than the predetermined set temperature gradient ΔTa, the heater 104 is forcibly turned off by the heater control unit 112 by the control unit 106. In this case, as shown in FIG. 7, the surface temperature of the heating roller 46 does not exceed the upper limit temperature Tu. That is, even if the upper limit temperature Tu is not exceeded, the surface temperature abnormality of the heating roller 46 can be detected by the temperature gradient.

  As described above, according to the image forming apparatus 1 of the first embodiment, when the calculated temperature gradient ΔTr calculated at a predetermined timing is equal to or less than the predetermined set temperature gradient ΔTa, the temperature does not become abnormal, and the operation by the user Can be controlled by the controller 106 so that the surface temperature of the heating roller 46 approaches the target temperature Ttg. Therefore, the operation at the time of abnormality processing becomes unnecessary. Further, by calculating the calculated temperature gradient ΔTr at a predetermined timing, it can be determined that the temperature is abnormal even when the surface temperature of the heating roller 46 has not reached the upper limit temperature Tu. Therefore, it is possible to determine a temperature abnormality more appropriately than in the past, and to ensure high safety.

[Embodiment 2]
In the image forming apparatus 1 described in the second embodiment, the time during which the temperature gradient continues is considered in the determination of the temperature abnormality. Hereinafter, the image forming apparatus 1 described in the second embodiment will be described, but the description of the same items as those in the first embodiment will be omitted.

  The image forming apparatus 1 described in the second embodiment is similar to the processing block diagram illustrated in FIG. 12 in that the image forming apparatus 1 described in the first embodiment has a duration measuring unit 131, a timer 134, and a continuation. A time comparison unit 132 is added.

  As in the first embodiment, the duration measurement unit 131 measures the time during which the calculated temperature gradient ΔTr calculated by the temperature gradient calculation unit 122 is higher than the set temperature gradient ΔTa as the duration. Part. The duration measurement unit 131 receives a temperature gradient comparison result from the gradient comparison unit 125. At this time, the duration measuring unit 131 measures the duration from the time counted by the timer 134. This timer 134 is substantially the same as the timer 110.

  The duration comparison unit 132 is input with the duration measured by the duration measurement unit 131 and compares a predetermined set time stored in advance in the memory 109 with the input duration. Then, the duration comparison unit 132 outputs the comparison result to the control unit 106.

  Hereinafter, the operation of the image forming apparatus 1 of the present invention described in the second embodiment will be described separately at the start of printing and at the end of printing. First, at the start of printing, as shown in FIG. 15, the image forming apparatus 1 is in a standby state in step S201. At this time, the heater control unit 112 controls the heater 104 so that the surface temperature of the heating roller 46 approaches the preset target temperature Ttg.

  Specifically, first, the surface temperature of the heating roller 46 is detected by the temperature detection unit 115 based on the output of the temperature detection element 31. The temperature comparison unit 124 compares the detected surface temperature with the target temperature Ttg stored in the memory 109 and outputs the comparison result to the control unit 106. Based on the comparison result, the control unit 106 turns the heater control unit 112 on when the surface temperature of the heating roller 46 is lower than Ttg and turns off when the surface temperature of the heating roller 46 is higher than Ttg. 104 is controlled.

  While the control unit 106 controls the surface temperature of the heating roller 46 with the heater control unit 112, the temperature comparison unit 124 detects the surface temperature of the heating roller 46, the target temperature Ttg and the upper limit temperature stored in the memory 109. The Tu and the predetermined temperature Tc are compared, and the comparison result is output to the control unit 106. Then, the control unit 106 determines how the surface temperature of the heating roller 46 is related to the target temperature Ttg, the upper limit temperature Tu, and the predetermined temperature Tc stored in the memory 109 based on the input comparison result. judge. The heater control unit 112 controls the heater 104 based on this determination result.

  In step S <b> 202, the image forming apparatus 1 determines whether print data has been received from the host computer 151 connected by the host I / F 150. If not received, the standby state described as step S201 is maintained, and the printer waits until print data is received.

  When print data is received via the host I / F in step S202, the control unit 106 starts printing in step S203. The motor drive control unit 113 drives the motor 114 under the control of the control unit 106 to rotate the heating roller 46 and the pressure roller 45.

  When the motor 114 is driven, the image forming apparatus 1 performs continuous printing in step S204, and printing is performed based on the print data received from the host computer 151. The continuous printing indicates that printing is continuously performed at a predetermined medium interval.

  Next, the operation of the image forming apparatus 1 at the end of printing will be described. As shown in FIGS. 16 to 18, the image forming apparatus 1 performs the continuous printing described in step S <b> 203 described above in step S <b> 301. At this time, the heater control unit 112 controls the heating roller 46 to approach the target temperature Ttg based on the comparison result between the surface temperature of the heating roller 46 and the target temperature Ttg by the temperature comparison unit 124. Further, since it is in a continuous printing state, the motor drive control unit 113 controls the motor 114 to rotate at a constant speed.

  Then, the control unit 106 monitors the signal from the medium passage sensor 52, and determines whether or not the final sheet 2 has passed in step S302. At this time, the control unit 106 monitors whether or not the sheet 2 has passed at a predetermined medium interval by a signal from the medium passage sensor 52, and determines that the state in which the paper 2 has not passed at the predetermined medium interval is the final. Assuming that the paper 2 has passed, the end of continuous printing is determined.

  In step S302, when the final sheet 2 has not passed, the control unit 106 continues the continuous printing described in step S301 until the continuous printing ends because the continuous printing is being performed. If the final sheet 2 has passed in step S302, printing is terminated in step S303. Then, the control unit 106 controls the motor drive control unit 113 to stop the motor 114, and the motor drive control unit 113 stops the motor 114 based on this control in step S304.

  FIG. 13 shows the relationship between the temperature transition of the heater and signals output from the motor drive unit control unit, heater control unit, and medium passage sensor. Here, the target temperature Ttg during printing and the predetermined temperature Tc maintain a relationship of Tc> Ttg, and the upper limit temperature Tu and the predetermined temperature maintain a relationship of Tu> Tc. As shown in FIG. 13, the surface temperature of the heating roller 46 suddenly rises from the target temperature Ttg to the upper limit temperature Tu and overshoots at the time A when the continuous printing ends.

  After stopping the motor 114 in step S304, the control unit 106 determines in step S305 whether or not the surface temperature of the heating roller 46 detected by the temperature detection unit 115 has reached the predetermined temperature Tc due to the above-described overshoot. . At this time, the temperature comparison unit 124 compares the value of the surface temperature of the heating roller 46 output from the temperature detection unit 115 with the value of the predetermined temperature Tc stored in the memory 109 in advance. Then, the temperature comparison unit 124 outputs the comparison result to the control unit 106, and the control unit 106 determines whether or not the surface temperature of the heating roller 46 has reached the predetermined temperature Tc based on the comparison result.

  In step S305, when the surface temperature of the heating roller 46 does not reach the predetermined temperature Tc, the temperature comparison unit 124 compares the surface temperature of the heating roller 46 with the target temperature Ttg and outputs the comparison result to the control unit 106. . Based on the comparison result, the control unit 106 determines whether or not the surface temperature of the heating roller 46 has reached the target temperature Ttg in step S312. When the surface temperature of the heating roller 46 reaches the target temperature Ttg, the surface temperature of the heating roller 46 is close to the target temperature Ttg. Therefore, the process proceeds to step S313 and enters the standby state described in step S201, and the heating roller 46 temperature control is performed.

  If the surface temperature of the heating roller 46 has not reached the target temperature Ttg in step S312, the process proceeds to step S305, and steps S305 to S312 are repeated.

  In step S305, when the surface temperature of the heating roller 46 reaches the predetermined temperature Tc, the control unit 106 controls the temperature gradient calculation unit 122, and the temperature gradient calculation unit 122 is detected by the temperature detection unit 115 in step S306. Based on the surface temperature of the heated roller 46, a temperature gradient ΔTr (° C./second) is calculated. This calculated temperature gradient ΔTr is derived from the change in the surface temperature of the heating roller 46 from n−1 seconds to n seconds after the time t1 when the surface temperature of the heating roller 46 reaches the predetermined temperature Tc (heating for n seconds). Roller surface temperature- (n-1) seconds of heating roller surface temperature) / (n- (n-1)) (Expression 3).

  The temperature gradient calculation unit 122 stores or reads the temperature data in the memory 109, reads the time data from the timer 110, and calculates the calculated temperature gradient ΔTr using the above-described equation 3. The calculated temperature gradient ΔTr is output to the gradient comparison unit 125.

  After calculating the calculated temperature gradient ΔTr, the gradient comparison unit 125 reads a predetermined set temperature gradient ΔTa previously stored in the memory 109 and compares the input calculated temperature gradient ΔTr with the set temperature gradient ΔTa. Then, the gradient comparison unit 125 outputs the comparison result to the control unit 106. In step S307, the control unit 106 determines whether or not the calculated temperature gradient ΔTr calculated is larger than a predetermined set temperature gradient ΔTa (ΔTr> ΔTa) based on the comparison result input from the gradient comparison unit. .

  If ΔTr ≦ ΔTa in step S307, the control unit 106 determines that the surface temperature of the heating roller 46 does not reach the upper limit temperature Tu, and determines that it is normal. As in the first embodiment, it is clear that the surface temperature of the heating roller 46 decreases, and the calculated calculated temperature gradient ΔTr becomes a small value as time passes. That is, if ΔTr ≦ ΔTa in step S307, the temperature of the heating roller 46 decreases, and the calculated temperature gradient ΔTr becomes a small value as time passes.

  In step S307, if ΔTr ≦ ΔTa, the gradient comparison unit 125 continues to compare the calculated temperature gradient ΔTr with the stored predetermined temperature gradient ΔTa, and the result is sent to the control unit 106. Output. In step S321, the control unit 106 determines whether ΔTr is a positive value based on the result and whether the relationship of ΔTr ≦ ΔTa continues indefinitely.

  If ΔTr is a positive value in step S321 and the relationship ΔTr ≦ ΔTa does not continue indefinitely, the process proceeds to step S312. On the other hand, when ΔTr is a positive value and the relationship ΔTr ≦ ΔTa continues in step S321, the temperature comparison unit 124 determines the surface temperature of the heating roller 46 and the upper limit stored in the memory 109. The temperature Tu is compared, and the comparison result is output to the control unit 106. In step S319, the control unit 106 determines whether or not the surface temperature of the heating roller 46 is higher than the upper limit temperature Tu based on the comparison result input from the temperature comparison unit 124.

  In step S319, when the surface temperature of the heating roller 46 is equal to or lower than the upper limit temperature Tu, the temperature comparison unit 124 compares the surface temperature of the heating roller 46 with the predetermined temperature Tc stored in the memory 109, and compares the comparison. The result is output to the control unit 106. In step S320, the control unit 106 determines whether or not the surface temperature of the heating roller 46 is higher than the predetermined temperature Tc based on the comparison result input from the temperature comparison unit 124.

  If the surface temperature of the heating roller 46 is equal to or lower than the predetermined temperature Tc in step S320, the process proceeds to step S312. On the other hand, if the surface temperature of the heating roller 46 is higher than the predetermined temperature Tc in step S320, the process proceeds to step S319, and it is compared again whether or not the surface temperature of the heating roller 46 exceeds the upper limit temperature Tu.

  In step S307, if ΔTr> ΔTa, the control unit 106 determines that there is an abnormality. If the control unit 106 determines that there is an abnormality, in step S308, the duration measurement unit 131 uses the timer 134 to start measuring the duration of the state ΔTr> ΔTa.

  Then, the duration measuring unit 131 integrates the count of the timer 134 in step S309. At this time, the duration measuring unit 131 sets the accumulated count as the duration m. The duration measuring unit 131 that has thus measured the duration m outputs the value of the duration m to the duration comparing unit 132.

  When the value of the duration m is input, the duration comparison unit 132 compares the duration m with the set time S stored in the memory 109 and outputs the comparison result to the control unit 106. In step S <b> 310, the control unit 106 determines whether the duration m in the state of ΔTr> ΔTa is greater than the predetermined set time S (m> S) based on the comparison result input from the duration comparison unit 132. Judge whether or not.

  In step S310, when m ≦ S, the control unit 106 controls the gradient comparison unit 125, and causes the gradient comparison unit 125 to compare the calculated temperature gradient ΔTr with the set temperature gradient ΔTa again. Then, the gradient comparison unit 125 outputs the comparison result to the control unit 106. In step S311, based on the comparison result input from the gradient comparison unit, the control unit 106 determines whether the calculated calculated temperature gradient ΔTr is greater than a predetermined set temperature gradient ΔTa (ΔTr> ΔTa). .

  If ΔTr ≦ ΔTa in step S311, the process proceeds to step S321 and the above-described processing is performed. On the other hand, if ΔTr> ΔTa in step S311, the duration measurement unit 131 proceeds to step S309 and repeats the processing shown in steps S307 to S310 again.

  If m> S in step S310, or if the surface temperature of the heating roller 46 is higher than the upper limit temperature Tu in step S319, the control unit 106 determines that there is an abnormality. If the controller 106 determines that there is an abnormality, in step S314, the heater controller 112 is controlled to forcibly turn off the heater 104.

  Then, the control unit 106 controls the operation panel control unit 117 and causes the display unit 119 to display that there is an abnormality in step S315. After displaying the abnormality on the display unit 119, the control unit 106 waits until a recovery process is input in step S316. This restoration process is input from the operation panel control unit 117 via the operation panel 118. This restoration process may be a user operation for starting the initial process or an apparatus power on / off.

  After the restoration process is input, the temperature comparison unit 124 compares the surface temperature of the heating roller 46 with the target temperature Ttg and outputs the comparison result to the control unit 106. In step S317, the control unit 106 determines whether the surface temperature of the heating roller 46 is lower than the target temperature Ttg based on the comparison result input from the temperature comparison unit 124.

  In step S317, if the surface temperature of the heating roller 46 is equal to or higher than the target temperature Ttg, the control unit 106 does not accept the recovery process, returns to step S316, and causes the display unit 119 to display an abnormality.

  In step S317, when the surface temperature of the heating roller 46 is lower than the target temperature Ttg, the control unit 106 accepts a recovery process in step S318, and proceeds to step S313.

  FIG. 14 is linked with FIG. 13 and shows the temperature gradient of the surface temperature of the heating roller with respect to the time axis. In the case of FIGS. 13 and 14, the duration m during which the calculated temperature gradient ΔTr exceeds the predetermined set temperature gradient ΔTa after the surface temperature of the heating roller 46 exceeds the predetermined temperature Tc is longer than the predetermined set time S. It has become. That is, it shows that the state of ΔTr> ΔTa continues longer than the preset time S. At this time, the heater 104 is forcibly turned off by the heater control unit 112 by the control unit 106. In this case, as shown in FIG. 13, the surface temperature of the heating roller 46 does not exceed the upper limit temperature Tu. That is, even if the upper limit temperature Tu is not exceeded, the surface temperature abnormality of the heating roller 46 can be detected by the temperature gradient.

  As described above, according to the image forming apparatus 1 of the second embodiment, even when the calculated temperature gradient ΔTr calculated at a predetermined timing is larger than the predetermined set temperature gradient ΔTa, this state is set in advance. When the time is shorter than the time S, the temperature does not become abnormal. Even if a temperature rise that lasts for a time shorter than the set time S occurs, the temperature rise is instantaneous, so it is clear that the surface temperature of the heating roller 46 immediately decreases. . Therefore, in the image forming apparatus 1 according to the second embodiment, the control unit 106 can control the surface temperature of the heating roller 46 so as to approach the target temperature Ttg without requiring any user operation. Therefore, in addition to the effects described in the first embodiment, the number of operations during abnormal processing is smaller than in the case of the image forming apparatus of the first embodiment.

  The image forming apparatus 1 of the present invention has been exemplified for the printing apparatus, but can also be used for an MFP apparatus, a facsimile apparatus, and a copying apparatus.

1 is a diagram illustrating a configuration of an image forming apparatus of the present invention. FIG. 3 is a diagram illustrating a structure of a fixing unit mounted on the image forming apparatus of the present invention. It is a figure explaining the installation position of the temperature detection element installed in the image forming apparatus of this invention. It is a block diagram of the image acquisition and forming apparatus of the present invention. FIG. 5 is a diagram illustrating a sheet conveyance direction in the vicinity of the fixing unit of the present invention. FIG. 2 is a processing block diagram of the image forming apparatus of the present invention described in the first embodiment. FIG. 3 is a diagram showing transition of the surface temperature of the heating roller of the image forming apparatus of the present invention described in the first embodiment. FIG. 3 is a diagram illustrating a transition of a temperature gradient of a surface temperature of a heating roller of the image forming apparatus of the present invention described in the first embodiment. FIG. 3 is a diagram showing a processing flow at the start of printing in the image forming apparatus of the present invention described in the first embodiment. FIG. 3 is a diagram illustrating a processing flow at the end of printing in the image forming apparatus of the present invention described in the first embodiment. FIG. 3 is a diagram illustrating a processing flow at the end of printing in the image forming apparatus of the present invention described in the first embodiment. 6 is a processing block diagram of an image forming apparatus of the present invention described in Embodiment 2. FIG. FIG. 6 is a diagram showing a transition of the surface temperature of the heating roller of the image forming apparatus of the present invention described in the second embodiment. FIG. 6 is a diagram illustrating a transition of a temperature gradient of a surface temperature of a heating roller of an image forming apparatus of the present invention described in a second embodiment. FIG. 10 is a diagram showing a processing flow at the start of printing in the image forming apparatus of the present invention described in the second embodiment. FIG. 6 is a diagram showing a processing flow at the end of printing in the image forming apparatus of the present invention described in the second embodiment. FIG. 6 is a diagram showing a processing flow at the end of printing in the image forming apparatus of the present invention described in the second embodiment. FIG. 6 is a diagram showing a processing flow at the end of printing in the image forming apparatus of the present invention described in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper 3 Media cassette 11, 12, 13, 14 Process unit 20 Conveyor belt 21, 22, 23, 24 Transfer roller 30 Fixing unit 31 Temperature detection element 40 Pickup roller 41, 42, 43, 44 Registration roller 45 Pressure roller 46 Heating roller 47, 48 Discharging roller 50, 51 Medium detection sensor 52 Medium passage sensor 104 Heater 106 Control unit 107 CPU
108 ROM
109 Memory 110 Timer 111 External interface 112 Heater control unit 113 Motor drive control unit 114 Motor 115 Temperature detection unit 117 Operation panel control unit 118 Operation panel 119 Display unit 121 Medium passage sensor 122 Temperature gradient calculation unit 123 Toner 124 Temperature comparison unit 125 Gradient Comparison unit 130 Connector 131 Duration measurement unit 132 Duration comparison unit 134 Timer 150 Host I / F
151 Host computer

Claims (5)

An image forming apparatus for fixing a developer transferred by heating and pressing to a recording medium,
A heat source,
A control unit for controlling the heat source;
A heating unit that heats the recording medium heated by the heat source and having the developer transferred thereon;
A pressure unit that is disposed opposite to the fixing unit and sandwiches and presses the recording medium that passes between the fixing unit and the heating object;
A temperature detection unit for detecting the temperature of the heating unit;
A temperature gradient calculation unit that calculates a temperature gradient of the heating unit detected by the temperature detection unit;
The control unit detects a predetermined temperature determined in advance by the temperature detection unit, and based on a comparison result between the calculated temperature gradient calculated by the temperature gradient calculation unit and a preset temperature gradient set in advance, When the calculated temperature gradient is larger than the set temperature gradient, the image forming apparatus is controlled to stop heating the heating unit by the heat source. A time measurement unit that measures a time during which the calculated temperature gradient is continuously larger than the set temperature gradient;
The control unit compares the duration measured by the time measurement unit with a preset set time, the calculated temperature gradient is larger than the set temperature gradient, and the duration is shorter than the set time. 2. The image forming apparatus according to claim 1, wherein when the length is long, control is performed so that heating of the heating unit by the heat source is stopped.   The image forming apparatus according to claim 1, further comprising a display unit that displays that the image forming apparatus is abnormal when the calculated temperature gradient is larger than the set temperature gradient.   3. A display unit that displays that the image forming apparatus is abnormal when the calculated temperature gradient is larger than the set temperature gradient and the duration is longer than the set time. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the temperature detection unit is disposed in a medium passing region of the heating unit through which the recording medium passes.