JP2015099269A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: when one of a plurality of heating elements printed on a substrate fails, image forming operation is prohibited until the substrate is replaced.SOLUTION: An image forming apparatus includes: a ceramic heater 111 having heating elements 111a, 111b printed on a first surface of a substrate 110, and heating elements 111c, 111d printed on a second surface of the substrate 110; a current detection circuit 33 which detects a failure of the heating elements 111a, 111b, 111c, or 111d; and a permission means CPU 101a which controls power to be supplied to the ceramic heater 111 on the basis of a result detected by a thermistor 104, and permits image formation on a recording material to be fixed by use of the heating elements 111c and 111d without using the heating elements 111a, 111b when a failure is detected in one of the heating elements 111a, 111b and no failure is detected in the heating elements 111c, 111d.

Description

  The present invention relates to a failure detection process of a fixing device for fixing a toner image on a recording material.

  An image forming apparatus employing an electrophotographic system forms a toner image by developing an electrostatic latent image corresponding to an original image using a developer containing toner. The toner image is transferred to a recording material such as paper, and fixed on the recording material by applying heat and pressure in a fixing device. For this reason, the image forming apparatus controls power supply to the heater so that the detection result of the temperature detection sensor provided in the fixing device becomes a predetermined temperature.

  In the image forming apparatus, if the heater of the fixing device or an electronic component that supplies electric power to the heater fails, the temperature of the heater may be excessively increased or a fixing failure may occur. Therefore, the image forming apparatus is provided with a configuration for detecting a failure of the fixing device. For example, if the sensor has a sensor for detecting the temperature of the heater, and the detected temperature when the power is supplied to any one of the plurality of heaters for a predetermined time does not exceed the threshold temperature, the heater failure is detected, There is one that prohibits the use of an image forming apparatus (Patent Document 1).

JP 2007-322883 A

  However, in the image forming apparatus described in Patent Document 1, when a failure of any one of the plurality of heaters is detected, the use of the image forming apparatus is used even though there is a heater that does not have a failure in the plurality of heaters. Was prohibited.

  Accordingly, an object of the present invention is to fix an image on a recording material that can be fixed using a non-failing heating element even if any of the heating elements fails in a fixing device having a plurality of heating elements. An object of the present invention is to provide an image forming apparatus that can permit formation.

  In order to solve the above-described problem, an image forming apparatus according to claim 1 includes an image forming unit that forms a toner image on a recording material, a substrate, a plurality of heating elements printed on the first surface of the substrate, At least one heating element printed on a second surface different from the first surface of the substrate, and heating the recording material on which the toner image is formed by the image forming means, Fixing means for fixing to a recording material; control means for controlling power to be supplied from a commercial power supply to the fixing means; the plurality of heating elements printed on the first surface of the substrate; and the second surface of the substrate. A failure detection means for detecting a failure of at least one heating element printed on the substrate, and a failure of any of the plurality of heating elements printed on the first surface of the substrate is detected by the failure detection means; and The substrate When no failure is detected in any of the heating elements printed on the two surfaces, the recording medium cannot fix the toner image without using the plurality of heating elements printed on the first surface of the substrate. Inhibiting image formation by the image forming means and fixing using a heating element printed on the second surface of the substrate without using the plurality of heating elements printed on the first surface of the substrate. Permission means for permitting image formation by the image forming means with respect to a possible recording material.

  According to the present invention, in a fixing device having a plurality of heating elements, even if any of the heating elements fails, image formation can be performed on a recording material that can be fixed using the heating element that has not failed. Can be allowed.

Schematic sectional view of the image forming apparatus Schematic sectional view of the fuser Diagram showing the heat distribution of the heating element Schematic diagram showing the configuration of an electric circuit that controls the power supplied to the fixing device Block diagram showing an electrical configuration related to fixing processing Flow chart of abnormality detection process Flow chart of abnormality detection process Flow chart of abnormality detection process

(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the image forming apparatus according to the present embodiment.

  An image forming apparatus 1 shown in FIG. 1 includes an image reading unit 1R and an image output unit 1P. The image reading unit 1R optically reads a document, converts it into an electrical signal (hereinafter referred to as a recorded image signal), and transmits it to the image output unit 1P. The image output unit 1P includes four image forming units 10a to 10d, an intermediate transfer belt 14, a cassette 18, and a fixing device 19. The image forming unit 10a forms a yellow toner image, the image forming unit 10b forms a magenta toner image, the image forming unit 10c forms a cyan toner image, and the image forming unit 10d forms a black toner image. To do.

  The image forming units 10a to 10d include photosensitive drums 11a to 11d, chargers 12a to 12d, developing units 13a to 13d, and laser scanner units 17a to 17d. The photosensitive drums 11a, 11b, 11c, and 11d function as a photoreceptor having a photosensitive layer on the surface.

  The chargers 12a, 12b, 12c, and 12d uniformly charge the surfaces of the photosensitive drums 11a, 11b, 11c, and 11d. The laser scanner units 17a, 17b, 17c, and 17d irradiate the photosensitive drums 11a, 11b, 11c, and 11d with light modulated according to the recording image signal transferred from the image reading unit 1R, via a mirror. . Thereby, electrostatic latent images of the respective color components are formed on the photosensitive drums 11a, 11b, 11c, and 11d.

  The developing devices 13a, 13b, 13c, and 13d develop the electrostatic latent images on the photosensitive drums 11a, 11b, 11c, and 11d using toner accumulated in the developing devices 13a, 13b, 13c, and 13d. To do. As a result, the toner images of the respective color components are carried on the photosensitive drums 11a, 11b, 11c, and 11d. That is, the image forming units 10a, 10b, 10c, and 10d function as an image forming unit that forms a toner image.

  The intermediate transfer belt 14 is an endless intermediate transfer member stretched by a plurality of rollers. The intermediate transfer belt 14 is conveyed in the direction of arrow T by the rotational driving of the roller. By transferring the toner images of the respective color components so as to overlap on the intermediate transfer belt 14, a full-color toner image is formed on the intermediate transfer belt 14. The toner remaining on the photosensitive drums 11a, 11b, 11c, and 11d without being transferred from the photosensitive drums 11a, 11b, 11c, and 11d to the intermediate transfer belt 14 is transferred by the drum cleaners 16a, 16b, 16c, and 16d. Removed.

  A recording material P is accommodated in the cassette 18. The recording material P is conveyed by adjusting the timing so that the toner image on the intermediate transfer belt 14 and the recording material P come into contact with each other. The transfer roller 15 transfers the toner image on the intermediate transfer belt 14 to the recording paper P by applying a transfer voltage while the toner image on the intermediate transfer belt 14 and the recording material P are in contact with each other. The toner remaining on the intermediate transfer belt 14 without being transferred from the intermediate transfer belt 14 to the recording material P is removed by a belt cleaner.

  The recording paper P on which the full-color toner image is transferred is heated by the fixing device 19. The toner image on the recording material P is fixed to the recording material P by the heat and pressure of the fixing device 19. Then, the recording material P on which the toner image is fixed is discharged to a discharge tray of the image forming apparatus 1 by a discharge roller.

  FIG. 2 is a schematic diagram showing the structure of the fixing device 19. The fixing device 19 includes a ceramic heater 111, a fixing film 201, a pressure roller 202, a stay 204, and a thermistor 104.

  The fixing film 201 is a cylindrical heat-resistant film material having a thickness of 40 to 100 [μm]. The pressure roller 202 is a roller in which a heat-resistant elastic layer 207 such as silicon rubber is provided on the outer periphery of the core metal 203.

  The stay 204 is a member having heat resistance and heat insulation, and presses the ceramic heater 111 against the pressure roller 202 via the fixing film 201. When the recording material P carrying the toner image passes through the fixing nip N, the toner image is fixed to the recording material P by the pressure acting on the fixing nip N and the heat generated by the ceramic heater 111. Is done.

  The pressure roller 202 is driven to rotate in the arrow B direction by the motor 112 (FIG. 5), so that the fixing film 201 is driven to rotate in the arrow C direction. An arrow A direction is a direction in which the recording material P is conveyed. That is, the fixing device 19 holds the recording material P in the fixing nip portion N and conveys the recording material P by the rotational driving of the pressure roller 202.

  The ceramic heater 111 has a substrate 110 (FIG. 3) whose longitudinal direction is a direction orthogonal to the conveyance direction in which the recording material P is conveyed by the rotation of the pressure roller 202 and the fixing film 201. Further, two heating elements are provided on the surface of the substrate 110 on the pressure roller 202 side (FIG. 3A) and on the surface of the substrate 110 opposite to the pressure roller 202 (FIG. 3B). 111a, 111b, 111c, and 111d are printed. Further, a thermistor 104 is provided at a substantially central portion of the ceramic heater 111 in the longitudinal direction of the substrate 110.

  FIG. 3A is a schematic view of a main part when the ceramic heater 111 is viewed from the pressure roller 202 side, and FIG. 3B is a main part when the ceramic heater 111 is viewed from the side opposite to the pressure roller 202. FIG. 3C is a heat generation distribution of the heating elements 111a to 111d.

  In the present embodiment, the recording material P is such that the central position of the recording material P in the direction orthogonal to the conveying direction in which the recording material P is conveyed passes through the reference position O of the fixing device 19 shown in FIG. P is conveyed.

  In the ceramic heater 111, heating elements 111a and 111b are formed on the first surface of the substrate 110, and heating elements 111c and 111d are formed on the second surface opposite to the first surface of the substrate 110. . The heating width of each heating element in the longitudinal direction of the substrate 110 has a relationship of heating element 111a> heating element 111b> heating element 111c> heating element 111d. Further, the heat generating width of the heat generating element 111a is wider than the width of the maximum size recording material that the image forming apparatus 1 can convey, and the heat generating width of the heat generating element 111d is the width of the minimum size recording material that can be conveyed by the image forming apparatus 1. Wider than.

  In this embodiment, for example, the heating element 111a is used for fixing a toner image on an A4 size or letter size recording material P, and the heating element 111d is used for recording a toner image on an A5 size or A4R size recording material P. Used for fixing.

  Further, the thickness of the substrate 110 of the ceramic heater 111 is determined by the distance between two adjacent heating elements (for example, the heating element 111a and the heating element 111b or the heating element 111c and the heating element 111d) formed on one surface. Too long. That is, the distance between two adjacent heating elements printed on the same surface is shorter than the distance between the first surface and the second surface of the ceramic heater 111.

  FIG. 4 is a schematic diagram showing a control circuit for supplying power to the ceramic heater 111. In the present embodiment, the AC power supply 32 converts the power supply voltage of the commercial power supply into an AC voltage of, for example, 24 [V] and 50 [Hz] and supplies it to the ceramic heater 111.

  In the ceramic heater 111, the heating element 111a and the heating element 111b are connected in parallel, and the heating element 111c and the heating element 111d are connected in parallel. The CPU 101a controls the power supplied to each of the heating elements 111a, 111b, 111c, and 111d by controlling the gate control type semiconductor switches 37, 38, 30, and 31, which will be described later, and the relays 35 and 36.

  When the CPU 101a turns on the relay 35, the AC power supply 32 can supply power to the heating elements 111a and 111b. When the CPU 101a turns off the relay 35, power is supplied from the AC power supply 32 to the heating elements 111a and 111b. It cannot be supplied.

  When the CPU 101a turns on the relay 36, the AC power supply 32 can supply power to the heating elements 111c and 111d. When the CPU 101a turns off the relay 36, power is supplied from the AC power supply 32 to the heating elements 111c and 111d. It cannot be supplied.

  The gate-controlled semiconductor switch 30 controls the power (power supply amount) supplied from the AC power source 32 to the heating element 111c based on a signal from the CPU 101a. Thereby, when the relay 36 is in the conductive state, the heating element 111c generates heat with a heat generation amount corresponding to the power supply amount.

  The gate-controlled semiconductor switch 31 controls the power (power supply amount) supplied from the AC power supply 32 to the heating element 111d based on a signal from the CPU 101a. Thereby, when the relay 36 is in a conductive state, the heating element 111d generates heat with a heat generation amount corresponding to the power supply amount.

  The gate-controlled semiconductor switch 37 controls the power (power supply amount) supplied from the AC power source 32 to the heating element 111a based on a signal from the CPU 101a. As a result, when the relay 35 is in the conductive state, the heating element 111a generates heat with a heat generation amount corresponding to the power supply amount.

  The gate-controlled semiconductor switch 38 controls the power (power supply amount) supplied from the AC power supply 32 to the heating element 111b based on a signal from the CPU 101a. As a result, when the relay 35 is in the conductive state, the heating element 111b generates heat with a heat generation amount corresponding to the power supply amount.

  The current detection circuit 33 detects the current that flows from the AC power supply 32 to the heating elements 111a, 111b, 111c, and 111d, and outputs the detection result to the CPU 101a. That is, the current detection circuit 33 functions as a current detection unit that detects a current flowing through each of the heating elements 111a, 111b, 111c, and 111d.

  In the present embodiment, the CPU 101a individually supplies power to each of the heating elements 111a, 111b, 111c, and 111d, and breaks down the heating element whose current value detected by the current detection circuit 33 is not within the predetermined range. Detected as a heating element.

  FIG. 5 is a block diagram showing an electrical configuration relating to the fixing process of the image forming apparatus 1. The CPU 101a is a control circuit that controls each unit in order to perform a fixing process for fixing the toner image on the recording material P. The ROM 101b stores a control program for controlling various processes executed by the fixing device 19. The RAM 101c is a system work memory used for the CPU 101a to execute a control program. Since the thermistor 104 has been described with reference to FIG. Furthermore, since the current detection circuit 33, the relays 35 and 36, and the gate control type semiconductor switches 30, 31, 37, and 38 are also illustrated in FIG. 4, description thereof is omitted here.

  The operation unit 102 is a numeric keypad for inputting the number of copies, a copy magnification, and the like, a copy button for starting image formation, a setting button for setting the number of copies, the paper type and size of the recording material P, and various types of the image forming apparatus 1. A liquid crystal screen capable of displaying guidance for assisting scanning is provided. An image or message for notifying the user of the state of the image forming apparatus 1 is displayed on the liquid crystal screen. The liquid crystal screen, for example, notifies that the image forming apparatus 1 is forming an image or notifies the image forming apparatus 1 that an error such as a jam has occurred.

  An analog-digital conversion circuit 103 (hereinafter referred to as A / D 103) converts a voltage value based on the resistance value of the thermistor 104 into a digital signal. Here, the thermistor 104 changes the resistance value according to the temperature of the ceramic heater 111. The CPU 101 a detects the temperature of the ceramic heater 111 based on the digital signal output from the thermistor 104 and converted by the A / D 103.

  Then, the CPU 101a inputs the gate controlled semiconductor switches 30, 31, 37, and 38 so that the temperature of the ceramic heater 111 detected by the thermistor 104 becomes the target temperature corresponding to the paper type of the recording material P. The input signal to be determined is determined.

  Note that the CPU 101a determines the heating elements 111a, 111b, 111c, and 111d to which power is to be supplied based on the size of the recording material P. That is, the CPU 101a determines the heat generation width of the ceramic heater 111 based on the size of the recording material P, and also determines the heat generating elements 111a, 111b, 111c, and 111d of the ceramic heater 111 suitable for this heat generation width. For example, if the recording material P is A4 plain paper, the CPU 101a selects the heating element 111a and controls the relay 35 to be in a conductive state, thereby permitting power supply to the heating element 111a.

  Note that the size of the recording material P and the paper type information may be acquired by the CPU 101a based on information input by the user using the operation unit 102, and image data transferred from an external PC (not shown) is stored in the CPU 101a. May be obtained by analyzing.

  The motor 112 rotates the pressure roller 202 (FIG. 2). The CPU 101a inputs an ON signal to the motor control circuit 107 after a signal for starting image formation is input. In response to the ON signal being input, the motor control circuit 107 drives the motor 112 to rotate at the target rotation speed so that the rotation speed of the pressure roller 202 becomes the target rotation speed. Further, the motor control circuit 107 may be configured to vary the target rotation speed according to the paper type. For example, in a paper type such as thick paper having a basis weight larger than that of plain paper, the rotation speed slower than that of the pressure roller 202 when the fixing device 19 fixes the toner image on the plain paper is set. Also good.

  In the present embodiment, a plurality of heating elements 111a, 111b, 111c, and 111d are formed on the first surface and the second surface of the ceramic heater 111. When the surface of the ceramic heater 111 is cracked due to the influence of temperature change, a plurality of heating elements printed on the cracked surface may be short-circuited. Further, since the resistance value of the heating element printed on the cracked surface changes, it becomes impossible to control the power supply to the heating element with high accuracy, so the temperature of the ceramic heater 111 is set to the target temperature. May be out of control.

  In the conventional image forming apparatus, the use of the image forming apparatus 1 is prohibited when a crack occurs. However, in the present embodiment, the fixing process can be performed by a heating element printed on the surface where no crack is generated. If so, the image forming apparatus 1 is configured to continue image formation.

  Hereinafter, failure detection processing for detecting failures of the heating elements 111a, 111b, 111c, and 111d and notifying the size of the recording material P on which the toner image can be fixed by the fixing device 19 will be described with reference to FIG. 6, FIG. 7, and FIG. I will explain. The failure detection process is executed by the CPU 101a shown in FIG. 5 reading out a program stored in the ROM 101b.

  In the present embodiment, when the main power supply of the image forming apparatus 1 is turned on, the CPU 101a executes a failure detection process. When the time during which the image forming apparatus 1 does not form an image reaches a predetermined time, or when the user selects the failure detection processing mode using the operation unit 102, the CPU 101a executes the failure detection processing. It may be a configuration.

  When the failure detection process is executed, the CPU 101a first controls the relay 35 to a conductive state and controls the relay 36 to a non-conductive state in order to determine whether an abnormality has occurred in the heating element 111a (S101). ). As a result, power can be supplied from the AC power source 32 to the heating element 111a and the heating element 111b.

  Then, the CPU 101a supplies predetermined power to the heating element 111a by the gate control type semiconductor switch 37 and prohibits power supply to the heating element 111b by the gate control type semiconductor switch 38 (S102). Thereby, CPU101a supplies electric power only to the heat generating body 111a (S103).

  Next, the CPU 101a acquires the detection result of the current value flowing through the heating element 111a detected by the current detection circuit 33 (S104), and determines whether or not the current flowing through the heating element 111a is an abnormal value. (S105). In step S105, the CPU 101a determines whether or not the value of the current flowing through the heating element 111a detected by the current detection circuit 33 is within a predetermined range. Then, the CPU 101a determines that the heating element 111a is normal if the current value is within a predetermined range, and determines that the heating element 111a is abnormal if the current value is not within the predetermined range. .

  In step S104, the CPU 101a controls the gate-controlled semiconductor switch 37 to sample the current value after a predetermined time has elapsed after supplying predetermined power to the heating element 111a. This is because the current value flowing through the heating element 111a after the gate-controlled semiconductor switch 37 supplies predetermined power to the heating element 111a is a current value (target current) corresponding to the resistance value of the heating element 111a and the voltage of the AC power supply 32 This is because it takes a little time to reach (value). Therefore, in this embodiment, the time (predetermined time) required for the current value flowing through the heating element 111a to reach the target current value after the predetermined power is supplied to the heating element 111a by the gate-controlled semiconductor switch 37 is set. The current value is not sampled until it has elapsed.

  Further, the resistance values of the heating elements 111a, 111b, 111c, and 111d are designed so that the current value detected by the current detection circuit 33 falls within a predetermined range when a predetermined power is supplied. .

  If the detected current of the current detection circuit 33 is not within the predetermined range in step S105, the CPU 101a determines that the heating element 111a is abnormal. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate control type semiconductor switches 30, 31, 37, and 38 (S106). Further, the CPU 101a controls the relay 35 to a non-conduction state (S107). As a result, the CPU 101a stops power supply to the heating element 111a (S108).

  According to the present embodiment, since it is determined whether or not the heating element 111a is abnormal based on the current value flowing through the heating element 111a, the heating element 111a is abnormal based on the temperature of the heating element 111a using a thermistor. It is possible to reduce the time required for determining an abnormality rather than determining whether or not. This is because the time when the current detection circuit 33 detects the current value flowing through the heating element 111a as in this embodiment is detected by the temperature detection sensor such as a thermistor as in the method of Patent Document 1. This is because it is shorter than time.

  Furthermore, according to the present embodiment, since the time for detecting the current value flowing through the heating element 111a is short (for example, 0.5 seconds or less), even if the heating element 111a has failed, Overheating of the fixing device 19 and the fixing device 19 can be suppressed during the detection process.

  Here, if the detection current of the current detection circuit 33 is not within the predetermined range in step S105, the first surface of the ceramic heater 111 on which the heating element 111a and the heating element 111b are printed has been damaged. there is a possibility. When the first surface of the ceramic heater 111 is damaged and the heating element 111a and the heating element 111b are short-circuited, the resistance values of the heating elements 111a and 111b change, and an excessive temperature rise or fixing failure of the fixing device 19 occurs. It can happen. Therefore, when the abnormality of the heating element 111a is detected, the CPU 101a prohibits execution of the fixing process using the first surface of the ceramic heater 111 on which the heating elements 111a and 111b are printed.

  When the first surface of the ceramic heater 111 is damaged, the CPU 101a does not determine the abnormality of the heat generating element 111b printed on the same surface as the heat generating element 111a, but on a surface different from the surface on which the heat generating element 111a is printed. It is determined whether or not an abnormality has occurred in the printed heating element 111c.

  The CPU 101a controls the relay 35 to a non-conduction state and controls the relay 36 to a conduction state in order to determine whether or not an abnormality has occurred in the heating element 111c (S109). As a result, power can be supplied from the AC power source 32 to the heating element 111c and the heating element 111d.

  Then, the CPU 101a supplies predetermined power to the heating element 111c by the gate-controlled semiconductor switch 30, and prohibits power supply to the heating element 111d by the gate-controlled semiconductor switch 31 (S110). Thereby, CPU101a supplies electric power only to the heat generating body 111c (S111).

  Next, the CPU 101a acquires the value of the current flowing through the heating element 111c detected by the current detection circuit 33 (S112), and determines whether or not the current flowing through the heating element 111c is an abnormal value (S113). The method of sampling the current value in step S112 is the same method as in step S104 described above, and a description thereof is omitted here.

  In step S113, the CPU 101a determines whether or not the value of the current flowing through the heating element 111c detected by the current detection circuit 33 is within a predetermined range. Then, the CPU 101a determines that the heating element 111c is normal if the current value is within a predetermined range, and determines that the heating element 111c is abnormal if the current value is not within the predetermined range. .

  If the detected current of the current detection circuit 33 is not within the predetermined range in step S113, the CPU 101a determines that the heating element 111c is abnormal. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate control type semiconductor switches 30, 31, 37, and 38 (S114). Further, the CPU 101a controls the relay 36 to be in a non-conductive state (S115). As a result, the CPU 101a stops power supply to the heating element 111c (S116).

  Here, when an abnormality is detected in the heating element 111c in step S113, there is a possibility that damage such as a crack has occurred on the second surface of the ceramic heater 111 on which the heating element 111c and the heating element 111d are printed. . When the second surface of the ceramic heater 111 is damaged and the heating element 111c and the heating element 111d are short-circuited, the resistance values of the heating elements 111c and 111d change, and the fixing device 19 is overheated or defectively fixed. It can happen.

  For this reason, any one of the plurality of heating elements provided on the first surface of the ceramic heater 111 is damaged, and any one of the heating elements provided on the second surface of the ceramic heater 111 is damaged. If YES, the CPU 101a selects the image formation prohibition mode (S117). The image formation prohibition mode is a mode for prohibiting the fixing operation of the fixing device 19 and the execution of the image forming operation by the image output unit 1P. In step S117, if at least one of the heat generating elements 111a or 111b is determined to be abnormal and the heat generating element 111c is determined to be abnormal, the CPU 101a shifts to the image formation prohibition mode.

  Further, in the present embodiment, in step S117, the CPU 101a shifts to the image formation prohibition mode, and an abnormality has occurred in the fixing device 19 on the liquid crystal screen of the operation unit 102, and the ceramic heater 111 needs to be replaced. Message is displayed. When it is determined that at least one of the heating elements 111a or 111b is abnormal and the heating element 111c is abnormal, the operation unit 102 notifies the abnormality of the fixing device 19.

  On the other hand, if the detected current of the current detection circuit 33 is within the predetermined range in step S105, the CPU 101a determines that the heating element 111a is not abnormal. Next, the CPU 101a determines whether or not the heating element 111b has failed.

  When the CPU 101a detects a failure of the heating element 111b, the gate control type semiconductor switch 38 supplies predetermined power to the heating element 111b and the gate control type semiconductor switch 37 prohibits power supply to the heating element 111a ( S118). As a result, the CPU 101a stops the power supply to the heating element 111a and supplies power only to the heating element 111b (S119).

  Next, the CPU 101a acquires the detection result of the current value flowing through the heating element 111b detected by the current detection circuit 33 (S120), and determines whether or not the current flowing through the heating element 111b is an abnormal value. (S121). The method of sampling the current value in step S120 is the same method as in step S104 described above, and a description thereof is omitted here.

  In step S121, the CPU 101a determines whether or not the value of the current flowing through the heating element 111b detected by the current detection circuit 33 is within a predetermined range. Then, the CPU 101a determines that the heating element 111b is normal if the current value is within a predetermined range, and determines that the heating element 111b is abnormal if the current value is not within the predetermined range. .

  If the detected current of the current detection circuit 33 is not within the predetermined range in step S121, the CPU 101a determines that the heating element 111c is abnormal. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate-controlled semiconductor switches 30, 31, 37, and 38 (S122). Further, the CPU 101a controls the relay 35 to a non-conduction state (S123). As a result, the CPU 101a stops power supply to the heating element 111b (S124).

  On the other hand, if the detected current of the current detection circuit 33 is not within the predetermined range in step S121, the CPU 101a determines that the heating element 111b has failed. In the present embodiment, even when a failure of the heating element 111b is detected, the fixing process using the first surface of the ceramic heater 111 on which the heating elements 111a and 111b are printed is not executed. In this embodiment, when a failure of the heating element 111b is detected, the process proceeds to step S109 described above, and whether or not an abnormality has occurred in the heating element 111c printed on a different surface from the surface on which the heating element 111b is printed. Determine whether.

  If the detected current of the current detection circuit 33 is within the predetermined range in step S113, the CPU 101a determines that the heating element 111c is not abnormal. Next, the CPU 101a determines whether or not the heating element 111d has failed.

  When the CPU 101a detects a failure of the heating element 111d, the gate control type semiconductor switch 31 supplies predetermined power to the heating element 111d, and the gate control type semiconductor switch 30 prohibits power supply to the heating element and 111c. (S125). As a result, the CPU 101a stops the power supply to the heating element 111c and supplies power only to the heating element 111d (S127).

  Next, the CPU 101a acquires the detection result of the current value flowing through the heating element 111d detected by the current detection circuit 33 (S127), and determines whether or not the current flowing through the heating element 111d is an abnormal value ( S128). The method of sampling the current value in step S127 is the same method as in step S104 described above, and a description thereof is omitted here.

  In step S128, the CPU 101a determines whether or not the value of the current flowing through the heating element 111d detected by the current detection circuit 33 is within a predetermined range. Then, the CPU 101a determines that the heating element 111d is normal if the current value is within a predetermined range, and determines that the heating element 111d is abnormal if the current value is not within the predetermined range. .

  If the detected current of the current detection circuit 33 is not within the predetermined range in step S128, the CPU 101a determines that the heating element 111d is abnormal. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate-controlled semiconductor switches 30, 31, 37, and 38 (S129). Further, the CPU 101a controls the relay 36 to be in a non-conductive state (S130). Thereby, the CPU 101a stops the power supply to the heating element 111d (S131).

  On the other hand, if the detected current of the current detection circuit 33 is not within the predetermined range in step S128, the CPU 101a determines that the heating element 111d has failed. In the present embodiment, even when a failure of the heating element 111d is detected, the fixing process using the second surface of the ceramic heater 111 on which the heating elements 111c and 111d are printed is not executed.

  For this reason, any one of the plurality of heating elements provided on the first surface of the ceramic heater 111 is damaged, and any one of the heating elements provided on the second surface of the ceramic heater 111 is damaged. If yes, the CPU 101a selects the image formation prohibition mode (S132). The image formation prohibition mode is the same mode as the image formation prohibition mode in step S117 described above.

  In step S132, if at least one of the heat generating elements 111a and 111b is determined to be abnormal and the heat generating element 111d is determined to be abnormal, the CPU 101a shifts to the image formation prohibition mode.

  Further, in the present embodiment, in step S132, the CPU 101a shifts to the image formation prohibition mode, and an abnormality has occurred in the fixing device 19 on the liquid crystal screen of the operation unit 102, and the ceramic heater 111 needs to be replaced. Message is displayed. When it is determined that at least one of the heating elements 111a or 111b is abnormal and the heating element 111d is abnormal, the operation unit 102 notifies the abnormality of the fixing device 19.

  If the detected current of the current detection circuit 33 is within the predetermined range in step S128, the CPU 101a determines that no abnormality has occurred in the heating element 111d. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate-controlled semiconductor switches 30, 31, 37, and 38 (S133). As a result, the CPU 101a stops supplying power to the heating element 111d (S134).

  The CPU 101a selects the paper type restriction mode when the heat generating elements 111a and 111b are out of order and the fixing process to a paper type having a size equal to or smaller than the heat generating width of the heat generating elements 111c and 111d can be performed ( S135). The paper type restriction mode in step S135 is a mode that permits image formation of the image output unit 1P on the recording material P having a size equal to or smaller than the heat generation width of the heating elements 111c and 111d.

  In step S135, since the CPU 101a has already detected a failure of the heating element 111a or 111b, the fixing process using the heating elements 111a and 111b printed on the first surface of the ceramic heater 111 cannot be performed. However, the fixing process using the second surface of the ceramic heater 111 on which the heating elements 111c and 111d are printed can be executed.

  In the present embodiment, the CPU 101a shifts to a paper type restriction mode in which a fixing operation can be performed with the size of the recording material P on which a toner image is formed being restricted. Specifically, in this paper type restriction mode, for example, the image output unit 1P is prohibited from forming a toner image on an A4 size or letter size recording material P, and for an A5 size recording material P or the like. Mode in which a toner image can be formed.

  Further, the CPU 101a displays a message on the liquid crystal screen of the operation unit 102 that the toner image can be formed on the A5 size recording material P or the like, although the fixing device 19 is abnormal.

  In step S121, if the current detected by the current detection circuit 33 is within a predetermined range, the CPU 101a determines that no abnormality has occurred in the heating element 111b. Then, the CPU 101a determines whether or not the heating element 111c has failed.

  When detecting the failure of the heating element 111c, the CPU 101a controls the relay 35 to the non-conductive state and controls the relay 36 to the conductive state (S136). As a result, power can be supplied from the AC power source 32 to the heating element 111c and the heating element 111d.

  Then, the CPU 101a supplies predetermined power to the heating element 111c by the gate-controlled semiconductor switch 30, and prohibits power supply to the heating element 111d by the gate-controlled semiconductor switch 31 (S137). As a result, the CPU 101a supplies power only to the heating element 111c (S138).

  Next, the CPU 101a acquires the detection result of the current value flowing through the heating element 111c detected by the current detection circuit 33 (S139), and determines whether or not the current flowing through the heating element 111c has an abnormal value ( S140). The method of sampling the current value in step S139 is the same method as in step S104 described above, and thus description thereof is omitted here.

  In step S140, the CPU 101a determines whether or not the value of the current flowing through the heating element 111c detected by the current detection circuit 33 is within a predetermined range. Then, the CPU 101a determines that the heating element 111c is normal if the current value is within a predetermined range, and determines that the heating element 111c is abnormal if the current value is not within the predetermined range. .

  In step S140, if the current detected by the current detection circuit 33 is not within the predetermined range, the CPU 101a determines that the heating element 111c is abnormal. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate-controlled semiconductor switches 30, 31, 37, and 38 (S141). Further, the CPU 101a controls the relay 36 to be in a non-conductive state (S142). Thereby, the CPU 101a stops the power supply to the heating element 111c (S143).

  Here, if the detected current of the current detection circuit 33 is not within the predetermined range in step S140, the second surface of the ceramic heater 111 is damaged, and the resistance values of the heating elements 111c and 111d change, and the fixing device. 19 overheating and poor fixing may occur. Therefore, when the abnormality of the heating element 111c is detected, the CPU 101a prohibits execution of the fixing process using the second surface of the ceramic heater on which the heating elements 111c and 111d are printed.

  At this time, in the CPU 101a, the heating element 111c printed on the second surface of the ceramic heater 111 is out of order, but the size of the heating elements 111a and 111b printed on the first surface of the ceramic heater 111 is less than the heating width. Is determined to be feasible. That is, since the heat generation width of the heat generating elements 111a and 111b is wider than the heat generation width of the heat generating element 111c, the toner image can be fixed on the recording material P of A4 size or letter size. Therefore, the CPU 101a can form a toner image on the recording material P having a size that allows the image forming apparatus 1 to form an image on the liquid crystal screen of the operation unit 102, which is abnormal in the fixing device 19. Is displayed (S144), the failure detection process is terminated. At this time, the heat generating width of the heat generating elements 111a and 111b is wider than the heat generating width of the heat generating elements 111c and 111d, so that it is possible to form an image on all paper types that the image forming apparatus 1 can convey.

  On the other hand, if the detected current of the current detection circuit 33 is within the predetermined range in step S140, the CPU 101a determines that there is no abnormality in the heating element 111c. Then, the CPU 101a determines whether or not the heating element 111d has failed.

  When detecting a failure of the heating element 111d, the CPU 101a supplies predetermined power to the heating element 111d by the gate-controlled semiconductor switch 31 and prohibits power supply to the heating element 111c by the gate-controlled semiconductor switch 30 ( S145). As a result, the CPU 101a stops the power supply to the heating element 111c and supplies power only to the heating element 111d (S146).

  Next, the CPU 101a acquires the detection result of the current value flowing through the heating element 111d detected by the current detection circuit 33 (S147), and determines whether or not the current flowing through the heating element 111d is an abnormal value ( S148). Since the method of sampling the current value in step S147 is the same method as in step S104 described above, description thereof is omitted here.

  In step S148, the CPU 101a determines whether or not the current value flowing through the heating element 111d detected by the current detection circuit 33 is within a predetermined range. Then, the CPU 101a determines that the heating element 111d is normal if the current value is within a predetermined range, and determines that the heating element 111d is abnormal if the current value is not within the predetermined range. .

  In step S148, if the current detected by the current detection circuit 33 is not within the predetermined range, the CPU 101a determines that the heating element 111d is abnormal. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by the gate-controlled semiconductor switches 30, 31, 37, and 38 (S149). Further, the CPU 101a controls the relay 36 to be in a non-conductive state (S150). Thereby, the CPU 101a stops the power supply to the heating element 111d (S151).

  Here, if the current flowing through the heating element 111d is an abnormal value in step S148, the CPU 101a determines that the heating element 111d is out of order. If the current flowing through the heating element 111d is not within the predetermined range, the CPU 101a prohibits execution of the fixing process using the second surface of the ceramic heater 111 on which the heating element 111c and the heating element 111d are printed.

  In the CPU 101a, the heating element 111d printed on the second surface of the ceramic heater 111 is out of order, but the paper type is not larger than the heating width of the heating elements 111a and 111b printed on the first surface of the ceramic heater 111. It is determined that the fixing process can be performed. That is, since the heat generation width of the heat generating elements 111a and 111b is wider than the heat generation width of the heat generating element 111d, the toner image can be fixed on the recording material P of A4 size or letter size. Therefore, the CPU 101a can form a toner image on the recording material P having a size that allows the image forming apparatus 1 to form an image on the liquid crystal screen of the operation unit 102, which is abnormal in the fixing device 19. Is displayed (S144), the failure detection process is terminated. At this time, the heat generating width of the heat generating elements 111a and 111b is wider than the heat generating width of the heat generating elements 111c and 111d, so that it is possible to form an image on all paper types that the image forming apparatus 1 can convey.

  However, when a toner image is continuously fixed on a recording material whose width in the direction orthogonal to the conveying direction of the A5 size recording material P or the like is smaller than the heat generation width of the heating elements 111a and 111b, the heat generation width and the recording material P There is a possibility that the temperature of the end region that does not contact will overheat. For this reason, in the present embodiment, when the heating elements 111a and 111b are normal and the heating elements 111c and 111d are out of order, the mode is shifted to a mode in which the productivity of fixing processing by the fixing device 19 is reduced. It was.

  If the current value detected by the current detection circuit 33 in step S148 is within a predetermined range, it is determined that no abnormality has occurred in the heating element 111d. That is, in step S153, the CPU 101a determines that the heating elements 111a, 111b, 111c, and 111d have not failed. Then, the CPU 101a stops the power supply to the heating elements 111a, 111b, 111c, and 111d by all the gate-controlled semiconductor switches 30, 31, 37, and 38 (S153). As a result, the CPU 101a stops energizing the heating element 111d (S154), and then ends the failure detection process.

  According to the present embodiment, if any failure of the plurality of heating elements printed on one surface of the substrate 110 is detected and the heating element printed on the other surface is not broken, the failure has occurred. It is possible to permit image formation on a recording material that can be fixed by a heating element that is not malfunctioning without using the heating element.

  Further, the ceramic heater 111 of the present embodiment has a configuration in which the heating element 111a and the heating element 111b are printed on the first surface of the substrate 110, and the heating element 111c and the heating element 111d are printed on the second surface of the substrate 110. ing. That is, the heating width of all the heating elements printed on the first surface of the substrate 110 is shorter than the heating width of all the heating elements printed on the second surface of the substrate 110. However, the heating width of the heating element printed on the first surface and the second surface of the substrate 110 is not limited to this configuration. For example, the heating element 111a having the longest heating width and the heating element 111d having the shortest heating width may be printed on the first surface of the substrate 110.

  In the present embodiment, the heat generation distribution of the heating elements 111 a, 111 b, 111 c, and 111 d printed on the substrate 110 generates heat in the area that contacts the recording material P of the minimum size that can be conveyed by the image forming apparatus 1. Designed to be However, the heat generation distribution of the heat generating element is not limited to this configuration. For example, a heat generating element having a heat generation distribution in which the temperature of the end region increases in the direction orthogonal to the transport direction is printed on the first surface of the substrate 110. It may be a configured. Further, the first surface of the substrate 110 may be configured such that a heating element having a heat generation distribution in which the temperature of the central portion increases in a direction orthogonal to the transport direction is printed.

  In the present embodiment, two heating elements are printed on the first surface and the second surface of the substrate 110, respectively. However, the heat generated on the first surface and the second surface of the substrate 110 is printed. The number of bodies is not limited to this configuration. For example, two heating elements may be printed on the first surface of the substrate 110, and one heating element may be printed on the second surface of the substrate 110. For example, the first surface of the substrate 110 may be printed. Alternatively, three or more heating elements may be printed, and two heating elements may be printed on the second surface of the substrate 110.

  Here, a failure detection process of the ceramic heater 111 in which the three heating elements 111α, 111β, and 111γ are printed on the first surface of the substrate 110 and the two heating elements 111θ and 111η are printed on the second surface will be described. . First, the CPU 101a supplies predetermined power to any one of the heating elements (for example, 111α) printed on the first surface of the substrate 110, and the current detected by the current detection circuit 33 is within a predetermined range. It is determined whether or not. If the current detected by the current detection circuit 33 is within a predetermined range, predetermined power is supplied to another heating element (for example, 111β) printed on the first surface, and the current detected by the current detection circuit 33 is It is determined whether it is within a predetermined range.

  For example, when the heating element 111β is out of order, the current detected by the current detection circuit 33 is not within a predetermined range. Then, the CPU 101a supplies predetermined power to the heating element 111θ printed on the second surface without determining the failure of the heating element 111γ printed on the first surface, and the current detected by the current detection circuit 33. Is determined to be within a predetermined range.

  For example, when it is determined that the heating elements 111θ and 111η are not out of order, the CPU 101a permits the image output unit 1P to form an image on the recording material P having a size equal to or less than the heating width of the heating elements 111θ and 111η. Select the paper type restriction mode. In this paper type restriction mode, the toner image is fixed on the recording material P using only the heating elements 111θ and 111η without using the heating elements 111α, 111β, and 111γ.

  On the other hand, when the heating element 111θ also fails, the CPU 101a selects the image formation prohibition mode without determining the failure of the heating element 111η printed on the second surface.

  As described above, even in a configuration in which three or more heating elements are printed on the first surface of the substrate 110 and two heating elements are printed on the second surface of the substrate 110, the paper type that can form an image is selected. The image formation can be continued by selecting.

  In the embodiment, the size of the recording material P that can be fixed is determined by using the surface of the ceramic heater 111 on which a non-failing heating element is printed. However, in the present invention, the size of the recording material P is determined. The configuration to be determined is not limited. For example, when fixing a toner image on special paper having a larger basis weight than a prescribed basis weight, a configuration in which power is supplied to a plurality of heating elements printed on one surface of the ceramic heater 111 is conceivable. In such a configuration, the paper type of the recording material P that can be fixed without using the printed surface of the heating element in which a failure is detected may be determined. According to this configuration, if any failure of the plurality of heating elements printed on one surface of the substrate 110 is detected, and if any of the heating elements printed on the other surface is not broken, the failure has occurred. Without using the heating element, it is possible to determine the paper type of the recording material that can be fixed by the heating element that is not malfunctioning.

DESCRIPTION OF SYMBOLS 10a Image formation part 10b Image formation part 10c Image formation part 10d Image formation part 30 Gate control type semiconductor switch 31 Gate control type semiconductor switch 33 Current detection circuit 37 Gate control type semiconductor switch 38 Gate control type semiconductor switch 101a CPU
104 Thermistor 110 Substrate 111 Ceramic Heater 111a Heating Element 111b Heating Element 111c Heating Element 111d Heating Element

Claims (17)

Image forming means for forming a toner image on a recording material;
A substrate, a plurality of heating elements printed on the first surface of the substrate, and at least one heating element printed on a second surface different from the first surface of the substrate; Fixing means for fixing the toner image to the recording material by heating the recording material on which the toner image is formed;
Control means for controlling power to be supplied from a commercial power source to the fixing means;
Failure detection means for detecting a failure of the plurality of heating elements printed on the first surface of the substrate and at least one heating element printed on the second surface of the substrate;
Failure of any of the plurality of heating elements printed on the first surface of the substrate is detected by the failure detection means, and failure of any of the heating elements printed on the second surface of the substrate is detected. If not detected, the image forming means prohibits image formation on the recording material that cannot fix the toner image without using the plurality of heating elements printed on the first surface of the substrate, and An image formed by the image forming unit on a recording material that can be fixed using the heating element printed on the second surface of the substrate without using the plurality of heating elements printed on the first surface of the substrate. An image forming apparatus comprising: permission means for permitting formation. The permission unit includes a determination unit that determines a paper type of a recording material that can be fixed using a heating element printed on the second surface of the substrate,
The image forming apparatus according to claim 1, wherein the permission unit permits image formation by the image forming unit to the recording material of the paper type determined by the determination unit. The fixing unit fixes the toner image on the recording material while conveying the recording material;
The permission unit determines a width of a recording material that can be fixed using a heating element printed on the second surface of the substrate in a direction orthogonal to a conveyance direction in which the fixing unit conveys the recording material. Having a decision part,
The image forming apparatus according to claim 1, wherein the permission unit permits image formation by the image forming unit with respect to a recording material having a width equal to or less than the width determined by the determination unit.   The permission unit is configured such that no failure is detected in any of the plurality of heating elements printed on the first surface of the substrate by the failure detection unit, and the at least printed on the second surface of the substrate. Recording that can be fixed using a heating element printed on the first surface of the substrate without using a heating element printed on the second surface of the substrate when a failure of one heating element is detected 4. The image forming apparatus according to claim 1, wherein image formation by the image forming unit is permitted for a material.   The image forming unit forms the toner image on the recording material permitted by the permission unit, and enters a restriction mode in which the formation of the toner image is prohibited on the recording material not permitted by the permission unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled.   6. The image according to claim 1, further comprising an informing unit for informing a malfunction of the fixing unit when the malfunctioning heating element is detected by the malfunction detecting unit. Forming equipment.   The image forming apparatus according to claim 6, wherein the notification unit further reports a fixable recording material using a heating element in which no failure is detected by the failure detection unit.   7. The informing means further informs that an image can be formed on a recording material that can be fixed using a heating element in which no failure is detected by the failure detecting means. Image forming apparatus. The failure detection means detects a current flowing through the plurality of heating elements printed on the first surface of the substrate and the at least one heating element printed on the second surface of the substrate. Having a detector,
The failure detection means supplies power to each of the plurality of heating elements printed on the first surface of the substrate and each of the at least one heating element printed on the second surface of the substrate. The image forming apparatus according to any one of claims 1 to 8, wherein when the current is detected, a heating element that cannot detect a current is detected by the current detection unit. The failure detection means detects a current flowing through the plurality of heating elements printed on the first surface of the substrate and the at least one heating element printed on the second surface of the substrate. Having a detector,
The failure detection means supplies power to each of the plurality of heating elements printed on the first surface of the substrate and each of the at least one heating element printed on the second surface of the substrate. 9. The image forming apparatus according to claim 1, wherein a heating element whose current detected by the current detection unit is not within a predetermined range when detected is detected. 10. The failure detection means detects a failure of each of the plurality of heating elements by supplying power to each of the plurality of heating elements printed on the first surface of the substrate,
The failure detecting means detects a failure of any one of the plurality of heating elements printed on the first surface of the substrate before other heating elements included in the plurality of heating elements. The method of claim 10, further comprising determining whether the at least one heating element has failed by supplying power to the at least one heating element printed on the second surface of the substrate. Image forming apparatus.   The plurality of heating elements printed on the first surface and the at least one heating element printed on the second surface are widths of regions in which the recording material is heated in a conveyance direction in which the recording material is conveyed The image forming apparatus according to claim 1, wherein the image forming apparatuses are different from each other. The fixing unit fixes the toner image on the recording material while conveying the recording material;
The plurality of heating elements printed on the first surface includes a first heating element and a second heating element,
The region where the first heating element heats the recording material in the direction orthogonal to the conveying direction in which the fixing unit conveys the recording material is the second heating element in the direction orthogonal to the conveying direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is different from a region where the material is heated.   The width of the region in which the first heating element heats the recording material in the direction orthogonal to the conveyance direction is the width in the direction orthogonal to the conveyance direction of the region in which the second heating element heats the recording material. The image forming apparatus according to claim 13, wherein the image forming apparatus is wider.   The area in which the first heating element heats the recording material and the area in which the second heating element heats the recording material do not overlap in a direction orthogonal to the transport direction. The image forming apparatus according to 13. The plurality of heating elements printed on the first surface includes a first heating element and a second heating element,
The distance between the first heating element and the second heating element is shorter than the distance between the first surface and the second surface, according to any one of claims 1 to 15. Image forming apparatus.   The permission unit includes any one of the plurality of heating elements printed on the first surface of the substrate by the failure detection unit, and the at least one heating element printed on the second surface of the substrate. 17. The image forming apparatus according to claim 1, wherein when an image failure is detected, image formation by the image forming unit is prohibited.

Images