JP2007025010A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can be safely started without abnormal temperature rise of a heater when turning on an apparatus power source again, without increasing apparatus cost. <P>SOLUTION: When disconnection information of a thermistor 182 is recorded in an EEPROM 203 when a power source of a copying machine 1 is turned on, a fan 16 is driven for a first prescribed time in a self-diagnosis mode, and then disconnection of the thermistor 182 is detected while supplying power to a heater 181 for a second prescribed time with a low duty pattern, and a machine starting operation is started when disconnection of the thermistor 182 is not detected. In the case that the number of times of the self-diagnosis mode reaches a prescribed number when the power source is turned on again, the self-diagnosis mode is not executed, and it is displayed on an operation display part 13 that the thermistor 182 is disconnected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like, and more particularly to a technique for starting up an apparatus after detecting disconnection of a thermistor used for temperature detection of the apparatus parts.

  2. Description of the Related Art Conventionally, in an image forming apparatus, a thermistor that performs output in accordance with the temperature of an object to be measured has been used to detect the temperature of a fixing roller (heating roller) heated by a heater, for example.

  In an image forming apparatus having a thermistor whose analog / digital converted value (hereinafter referred to as AD value) becomes 0 when the thermistor is disconnected, the theory is that when the thermistor is detected when the apparatus is turned on. Specifically, it may be set so that it is determined that the thermistor is disconnected when the AD value becomes zero. However, in reality, even when the thermistor is disconnected, the AD value does not become zero, but fluctuates at a value close to zero. Moreover, since the AD value is close to 0 in a low temperature environment, it has not been possible to determine whether it is due to thermistor disconnection or the low temperature environment.

  In order to solve this problem, if the AD value of the thermistor does not change from a value close to 0 even if the heater is turned on for a predetermined time during the normal apparatus start-up operation performed after the apparatus power is turned on, the thermistor is disconnected. An image forming apparatus capable of making a determination and reporting a thermistor disconnection error is known.

  In the above image forming apparatus, even when the heater temperature is low after the apparatus power is turned on and the thermistor is disconnected, it is possible to detect the disconnection of the thermistor by turning on the heater for a predetermined time. Since the temperature does not become so high as to cause a malfunction in the device components (for example, the fixing roller (heating roller)), the danger to the device and the user due to the temperature rise is small.

  However, recently, it has been required to shorten the start-up time of the image forming apparatus. When the apparatus power is turned on, the heater is immediately turned on and the AD value of the thermistor does not change from a value near 0 for a predetermined time. In some cases, an image forming apparatus is known that can determine that the thermistor is disconnected and report a thermistor disconnection error. When the device power is turned on, the thermistor's AD value does not change from a value close to 0 while controlling the heater at a predetermined time duty ratio of 100%. An image forming apparatus capable of informing is known.

  However, even if the thermistor disconnection error is notified, if the user repeatedly turns off / on the apparatus power supply many times, the heater temperature rises without limit, which is extremely dangerous.

As prior art documents related to the solution of such problems, even if the apparatus power is turned off, the self-diagnosis data generated during the operation of the apparatus is retained, and the self-diagnosis data retained when the apparatus power is turned on again Accordingly, there has been disclosed and proposed an image forming apparatus capable of controlling the movement permission of the apparatus in accordance with the above and minimizing damage at the time of failure (see, for example, Patent Document 1 and Patent Document 2).
JP-A-8-52924 Japanese Patent Publication No. 7-73939

  Certainly, in the case of the image forming apparatuses disclosed in Patent Document 1 and Patent Document 2, when a disconnection of the thermistor is detected during operation of the apparatus, a flag corresponding to the result of the disconnection of the thermistor is displayed in the nonvolatile storage means. The heater is not energized when the device power is turned on again unless the flag is reset by a switch by a service person. Therefore, even if the device power is turned off and on many times by the user, the heater Temperature rise can be prevented.

  However, in the image forming apparatuses disclosed in Patent Document 1 and Patent Document 2, when the flag corresponding to the result of the disconnection of the thermistor stored in the nonvolatile storage means is reset by the switch by the serviceman, when the apparatus is turned on If the thermistor is not normally repaired by the serviceman, the heater temperature will be correct if the thermistor is not normally repaired. If the heater is controlled without being measured for a long time, the heater may become abnormally hot, which is very dangerous. Even if the serviceman intends to repair the disconnection, thermistors in other locations may be disconnected or the AD value itself may be incorrect. If the heater is controlled without being measured for a long time, the heater may become abnormally hot, which is very dangerous. For this reason, there is room for improvement with respect to heater control when the apparatus power is turned on. In addition, since the image forming apparatuses disclosed in Patent Document 1 and Patent Document 2 need to be newly provided with a switch, the apparatus cost increases.

  SUMMARY OF THE INVENTION In view of the above-described problems, the present invention provides an image forming apparatus capable of safely starting an apparatus without causing an abnormally high temperature when the apparatus power is turned on again without increasing the apparatus cost. With the goal.

  In order to achieve the above object, an image forming apparatus according to the present invention is provided in one or a plurality of apparatus parts, and is provided in a heater for heating the apparatus parts, the apparatus parts, and the temperature of the apparatus parts. A thermistor that performs output in accordance with the power supply, a fan for cooling the heater, a power supply means for supplying power to the heater, a disconnection detection means for detecting disconnection of the thermistor, and the start-up completion of the apparatus And a memory control unit for storing information on disconnection of the thermistor in a nonvolatile memory when the disconnection of the thermistor is detected by the disconnection detection unit. When the disconnection information of the thermistor is stored in the memory, as a self-diagnosis, the fan is driven for a first predetermined time, and then for a second predetermined time. Self-diagnosis control means for causing the disconnection detection means to detect disconnection of the thermistor while supplying power to the heater at a predetermined duty ratio to the power supply means, and disconnection of the thermistor by the disconnection detection means during the self-diagnosis. If not detected, the control means is configured to shift to the startup operation of the apparatus. With such a configuration, the apparatus can be safely started even when the apparatus power supply is repeatedly turned off and on. In addition, since it is possible to start up the apparatus safely without adding a new switch, it is possible to prevent an increase in apparatus cost.

  The image forming apparatus having the above configuration includes a display unit for displaying predetermined information, and the memory control unit detects the disconnection of the thermistor by the disconnection detection unit during the self-diagnosis. In the case, the number of self-diagnosis is accumulated and stored in the nonvolatile memory, and the control means is configured such that the number of self-diagnosis stored in the nonvolatile memory is a predetermined number of times when the apparatus is turned on. In the case where it reaches, the self-diagnosis control means does not perform the self-diagnosis, but displays that the thermistor is disconnected on the display unit. With such a configuration, it is possible to notify the user of the disconnection of the thermistor without increasing the temperature of the heater even when the apparatus power supply is repeatedly turned OFF / ON.

  As described above, the image forming apparatus according to the present invention can safely start up the apparatus without increasing the apparatus cost.

  Hereinafter, a case where the present invention is applied to a copying machine will be described as an example. In the present embodiment, a case where a thermistor and a heater are provided in the fixing roller (heating roller) of the copying machine according to the present invention will be described as an example. FIG. 1 is a block diagram showing the configuration of the main part of a copying machine according to the present invention, and FIG. 2 is a longitudinal sectional view schematically showing the structure of the main part of the copying machine according to the present invention.

  As shown in both figures, the copier 1 of this embodiment includes a central processing unit 10 (hereinafter referred to as a CPU [Central Processing Unit] 10) that controls the operation of the entire apparatus, and a document transport that automatically transports a document. Unit 11, a document take-in unit 12 that takes in a document transported from document transport unit 11 and generates image data, and an operation display unit 13 that includes operation means (such as a numeric keypad or touch panel) and display means (such as a liquid crystal display). An image forming unit 15 that forms a toner image on a sheet based on image data, a sheet conveying unit 14 that conveys the sheet to the image forming unit 15 and discharges the sheet from the apparatus, and an image forming unit 15. The fixing unit 18 for fixing the toner image formed on the sheet to the sheet, the power switch 17 for turning on / off the apparatus power, the heater 181 and the thermistor 182 to be described later are cooled. The analog output input from the fan 16 and the thermistor 182 is converted to digital, and a digital value (hereinafter referred to as an AD value) is input to the CPU 10 (hereinafter referred to as an A / D unit 19). And a memory unit 20 used for the work area, and various control programs, storage of disconnection information of the thermistor 182 and the number of times of the self-diagnosis mode, and the like.

  In addition to controlling the operation of the entire apparatus, the CPU 10 performs control related to restarting of the apparatus after detection of thermistor disconnection, which will be described in detail later. Further, the CPU 10 includes a disconnection detection unit that detects disconnection of the thermistor, a memory control unit that controls a nonvolatile memory (in this embodiment, an EEPROM), a self-diagnosis control unit that performs control when performing a self-diagnosis, and , To play the role.

  The paper transport unit 14 includes a plurality of (three in this embodiment) paper storage units 141 a to 141 c serving as a paper supply source to the image forming unit 15, and the paper storage units 141 a to 141 c to the image forming unit 15. A sheet feeding unit 142 serving as a common sheet conveyance path and a discharge roller 143 that discharges printed sheets out of the apparatus are provided.

  In addition, the paper feed unit 142 includes a plurality of paper feed rollers 142b including a pair of rollers that carry paper from each of the paper storage units 141a to 141c to the registration rollers 142a, and a front end of the paper that has been conveyed from the paper feed roller 142b. And a registration roller 142 a that conveys the sheet to the image forming unit 15 in accordance with the operation of the image forming unit 15.

  As shown in FIG. 2, the image forming unit 15 uniformly charges the photosensitive drum 151 of the latent image carrier on which the toner image is formed on the drum surface based on the image data, and the surface of the photosensitive drum 151 to a predetermined potential. A charging unit 154 for irradiating a laser beam based on image data, an exposure unit 153 for forming an electrostatic latent image on the surface of the photosensitive drum 151, and a toner image from the electrostatic latent image on the surface of the photosensitive drum 151. A developing device 152 formed on the surface of the drum 151, a transfer roller 157 for electrostatically transferring a toner image formed on the surface of the photosensitive drum 151 to the conveyed paper, and a toner remaining on the surface of the photosensitive drum 151 And a static eliminator 155 for neutralizing the surface of the photosensitive drum 151.

  As shown in FIGS. 1 and 2, the fixing unit 18 is provided on the outer periphery of a rotation shaft (not shown) of a fixing roller 183 (that is, a heating roller) described later, a heater 181 that heats the fixing roller 183, and a heater A fixing roller 183 that is heated to a temperature optimum for fixing the toner image on the paper by 181, contacts a pressure roller 184 described later, and heats and presses the paper conveyed from the image forming unit 15, and fixing A pressure roller 184 that is in contact with the roller 183 and presses the sheet conveyed from the image forming unit 15 and a fixing roller 183. The analog output corresponding to the temperature of the fixing roller 183 is A / A. A thermistor 182 that inputs to the D section 19.

  As shown in FIG. 1, the memory unit 20 includes a ROM [Read Only Memory] 201 in which various control programs and various thresholds are stored, a RAM [Random Access Memory] 202 used as a work area, and a disconnection of the thermistor 182. And an EEPROM [Electronically Erasable and Programmable Read Only Memory] 203, which is a rewritable nonvolatile memory used for storing information related to the above and the number of times I of a self-diagnosis mode to be described later.

  Next, the document copying operation in the copying machine 1 configured as described above will be described. In the document copying operation of the copying machine 1 of this embodiment, when a document is first transported from the document transport unit 11 to the document capture unit 12, the document capture unit 12 captures the document and generates image data. Is done. The generated image data is temporarily stored in the memory unit 20, read again, and sent to the image forming unit 15. Subsequently, the image forming unit 15 starts image forming processing, and an electrostatic latent image is formed on the surface of the photosensitive drum 151 uniformly charged to a predetermined potential by the charger 154 by the exposure unit 153 based on the image data. Made. Subsequently, a toner image is formed on the surface of the photosensitive drum 151 from the electrostatic latent image by the developing device 152. The toner image formed on the surface of the photosensitive drum 151 is transferred by the transfer roller 157 to the sheet conveyed by the sheet feeding unit 142 from any one of the sheet storage units 141a to 141c.

  Thereafter, the sheet carrying the unfixed toner image is sent to the fixing unit 18, heated and pressed by the fixing unit 18 to fix the toner image on the sheet, and then discharged by the discharge roller 143. Further, after the toner remaining on the surface of the photosensitive drum 151 is removed by the cleaning unit 156, the surface of the photosensitive drum 151 is neutralized by the static eliminator 156. A solid line arrow in FIG. 2 indicates a sheet conveyance path.

  Further, in the copying machine 1 of the present embodiment, the control of the heater 181 provided in the fixing roller 183 is performed as follows after the apparatus startup is completed. In the copying machine 1 of this embodiment, an analog output from the thermistor 182 is input to the A / D unit 19 and converted into a digital value (AD value). An AD value is input from the A / D unit 19 to the CPU 10. Based on the AD value and the control program stored in the ROM 201, the CPU 10 supplies duty-controlled power to the heater 181 from the power supply unit (not shown) so that the fixing roller 183 has an appropriate temperature. Such control is repeated to control the heater 181 provided in the fixing roller 183 so that the fixing roller 183 has an appropriate temperature.

  At this time, although the power is supplied to the heater 181 from the power supply unit (not shown), the CPU 10 sets the AD value of the thermistor 182 for a predetermined time (for example, 1 second) to a predetermined threshold (for example, 5). ), It is determined that the thermistor 182 is disconnected, and the flag of the preset storage area of the EEPROM 203 is set from “0” to “1”. The flag “1” set in the EEPROM 203 corresponds to the disconnection information of the thermistor 182. When the CPU 10 determines that the AD value of the thermistor 182 is larger than a predetermined threshold (for example, 5), it is determined that the thermistor 182 is not disconnected, and the preset storage area of the EEPROM 203 is determined. The flag remains “0”.

  The copying machine 1 according to the present embodiment is characterized by disconnection detection control of the thermistor 182 that is performed so that the heater 181 does not reach an abnormally high temperature when the apparatus power is turned on. Therefore, in the following, with reference to the flowchart of FIG. 3, a detailed description will be given of disconnection detection control of the thermistor 182 that is performed so that the heater 181 does not reach an abnormally high temperature when the apparatus is turned on in the copying machine 1 of the present embodiment. I do.

  In the copying machine 1 of the present embodiment, when the power switch 17 is pressed and the apparatus power is turned on in step S3-1, the thermistor disconnection has previously occurred in the EEPROM 203 by the CPU 10 in step S3-2. It is checked whether or not the flag “1” indicating this is set. When it is determined by the CPU 10 that the flag “1” indicating that the thermistor has been disconnected previously is set in the EEPROM 203 (S3-2 YES), the process proceeds to step S3-3. On the other hand, if the CPU 10 determines that the flag “1” indicating that the thermistor has been disconnected has not been previously set in the EEPROM 203 (NO in S3-2), the CPU 10 determines in step S3-4. Normal startup operation is performed. If the fixing roller 183 needs to be heated in the normal start-up operation of the copying machine 1 performed in step S3-4, the heater 181 is controlled by the CPU 10 in the later-described step S3-9. Electric power is supplied from an electric power supply unit (not shown) with a duty pattern (for example, duty 100%) having a longer ON time than.

  Subsequently, in step S3-3, the AD value input to the CPU 10 is compared with a predetermined threshold value (for example, 5) stored in the ROM 201 in order to determine whether the AD value is near 0. When the CPU 10 determines that the AD value is not less than a predetermined threshold (for example, 5) (S3-3 NO), the flag stored in the EEPROM 203 is changed from “1” to “1” in step S3-5. After being cleared to "0", a normal startup operation of the copying machine 1 is performed in step S3-4.

  When the CPU 10 determines that the AD value is less than a predetermined threshold (for example, 5) in step S3-3 (S3-3 YES), the CPU 10 performs self-diagnostic mode in step S3-6. Is started, and the number I of continuous self-diagnosis modes (described later) stored in the EEPROM 203 is compared with a predetermined threshold (for example, 3 times) stored in the ROM 201. When the CPU 10 determines that the number of times I is not less than a predetermined threshold (for example, 3 times) (NO in S3-6), power is not supplied to the heater 181 and the self-diagnosis mode is not performed. In step S3-7, the CPU 10 displays a disconnection error of the thermistor 182 on the operation display unit 13.

  In step S3-6, when the CPU 10 determines that the self-diagnosis mode is started and the number I of continuous executions of the self-diagnosis mode described later is less than a predetermined threshold (for example, 3 times). (S3-6 YES), in step S3-8, the CPU 16 drives the fan 16 at full speed for a first predetermined time (for example, 30 seconds). This is because the heater 181 and the fixing roller 183 become hot when the apparatus is turned on last time, and the thermistor 182 may not be able to accurately detect the temperature of the fixing roller 183. The temperature is decreasing. In addition, since the temperature of the heater 181 and the fixing roller 183 is decreased by driving the fan 16, the safety of the apparatus when the apparatus power is turned on can be improved.

  Subsequently, in step S3-9, the power supply unit (not shown) is controlled by the CPU 10 and the heater 181 is switched from the power supply unit (not shown) to the heater 181 so that the ON time is shorter than that during the fixing process (normal time). Then, electric power is supplied in a low duty pattern (duty ratio), and control of the heater 181 is started.

  Subsequently, in step S3-10, the CPU 10 detects the disconnection of the thermistor 182 while supplying power to the heater 181 with a low duty pattern (duty ratio) for a second predetermined time (for example, 5 seconds). Thus, the AD value is sampled. At this time, in step S3-10, the heater 181 is controlled using a duty pattern (duty ratio) lower than normal, and there is no danger that the temperature of the heater 181 and the fixing roller 183 will rise excessively. The predetermined time is set longer than the time for detecting disconnection of the thermistor 182 after the start-up of the apparatus is completed.

  Subsequently, in step S3-11, the CPU 10 compares the AD value sampled in step S3-10 with a predetermined threshold value (for example, 5), and the AD value is less than the predetermined threshold value (for example, 5). In this case, it is determined that the thermistor 182 has been repaired and has not been disconnected (S3-11 NO), and since the thermistor 182 has been repaired and has not been disconnected in step S3-12, the CPU 10 stores the flag stored in the EEPROM 203. Is cleared from “1” to “0”.

  Subsequently, in step S3-13, the CPU 10 initializes (sets to 0) the number of times of self-diagnosis mode I, and the self-diagnosis mode is terminated. In step S3-4, the normal startup of the copying machine 1 is completed. The raising operation is performed.

  In step S3-11, the CPU 10 compares the AD value sampled in step S3-10 with a predetermined threshold (for example, 5), and the AD value is less than the predetermined threshold (for example, 5). The thermistor 182 is determined to be disconnected (YES in S3-11), and the CPU 10 increments the number I of the self-diagnosis mode by 1 and stores it in the EEPROM 203 in step S3-14. In step S3-7, the CPU 10 displays a disconnection error of the thermistor 182 on the operation display unit 13, and the self-diagnosis mode ends.

  As described above, in the copying machine 1 of the present embodiment, the thermistor 182 is completely repaired when the disconnection of the thermistor 182 is detected after the apparatus startup is completed and the power switch 17 is turned OFF / ON. Unless it is determined that the power is not supplied to the heater 181 with a normal duty pattern (duty ratio) with a long ON time, the power switch 17 is repeatedly turned OFF / ON. However, the copying machine 1 can be started up safely. In addition, since the copying machine 1 according to the present embodiment can safely start up the apparatus without adding a new switch, it is possible to prevent an increase in apparatus cost.

  In the copying machine 1 according to the present embodiment, when the CPU 10 determines in step S3-6 that the number of times I is not less than a predetermined threshold (for example, 3 times) (NO in S3-6), the heater 181 is used. In step S3-7, the CPU 10 displays a disconnection error of the thermistor 182 on the operation display unit 13 without power supply to the power supply, and the device power OFF / Even if ON is repeated, the self-diagnosis mode is not performed. Therefore, the temperature of the heater 181 does not rise, and the user can be notified of the disconnection of the thermistor 182.

  In the above embodiment, the case where the thermistor 182 and the heater 181 are provided in the fixing roller 183 has been described as an example. However, the mounting position and number of the thermistor and heater are limited to the configuration of the present invention. Instead, the thermistor and heater may be provided in other device parts that require temperature control, and the same control as in the above embodiment may be performed.

  In the above embodiment, the copying machine 1 has been described as an example. However, the configuration of the present invention is not limited to this, and can be widely applied to image forming apparatuses such as printers and facsimiles. Is possible.

  The configuration of the present invention can be variously modified within the scope of the present invention in addition to the above embodiment.

  The present invention can be widely applied to image forming apparatuses such as printers and facsimiles in addition to copying machines, and is a technique useful for starting up a safe apparatus after detecting the disconnection of the thermistor.

FIG. 2 is a block diagram showing a main configuration of a copier according to the present invention. These are the longitudinal cross-sectional views which show typically the principal part structure of the copying machine which concerns on this invention. These are flowcharts of the self-diagnosis mode when the power is turned on in the copying machine of the present embodiment.

Explanation of symbols

1 Copier 10 Central processing unit (CPU)
DESCRIPTION OF SYMBOLS 11 Document conveyance part 12 Document taking-in part 13 Operation display part 14 Paper conveyance part 141a-141c Paper storage part 142 Paper feed part 142a Registration roller 142b Paper feed roller 143 Ejection roller 15 Image formation part 151 Photosensitive drum 152 Developer 153 Exposure unit 154 Charger 155 Static eliminator 156 Cleaning unit 157 Transfer roller 16 Fan 17 Power switch 18 Fixing unit 181 Heater 182 Thermistor 183 Fixing roller 184 Pressure roller 19 Analog / digital conversion unit (A / D unit)
20 Memory part 201 ROM
202 RAM
203 EEPROM

Claims (2)

A heater that is provided in one or a plurality of apparatus parts and that heats the apparatus parts, a thermistor that is provided in the apparatus parts and that outputs in accordance with the temperature of the apparatus parts, and a fan that cools the heater And a power supply means for supplying power to the heater, a disconnection detection means for detecting disconnection of the thermistor, and when the disconnection of the thermistor is detected by the disconnection detection means after the start-up of the apparatus is completed. An image forming apparatus having memory control means for storing disconnection information of the thermistor in a non-volatile memory,
When the disconnection information of the thermistor is stored in the nonvolatile memory at the time of power-on of the device, as a self-diagnosis, after driving the fan for a first predetermined time, for a second predetermined time, Self-diagnosis control means for causing the disconnection detection means to detect disconnection of the thermistor while supplying power to the heater at a predetermined duty ratio to the power supply means, and disconnection of the thermistor by the disconnection detection means during the self-diagnosis. An image forming apparatus comprising: a control unit that shifts to a startup operation of the apparatus when the image is not detected. A display unit for displaying predetermined information;
When the disconnection of the thermistor is detected by the disconnection detection means during the self-diagnosis, the memory control means accumulates and stores the number of times of the self-diagnosis in the nonvolatile memory,
The control means causes the self-diagnosis control means to perform the self-diagnosis when the number of self-diagnosis stored in the nonvolatile memory reaches a predetermined number when the apparatus is turned on. The image forming apparatus according to claim 1, wherein the display unit displays the fact that the thermistor is disconnected.

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