JP2010079031A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, diagnosing whether a change-over state detecting switch for detecting the change-over state of pressurizing force to a fixing part by a pressure change-over mechanism is normal or not without any increase in number of parts. <P>SOLUTION: The image forming apparatus 100 includes: a fixing section 20 for heat fixing a paper sheet carrying toner in a nip between a heat roller 21 and a backup roller 22 pressurized by pressurizing mechanisms 23, 24; a pressure change-over mechanism 25 for switching the pressurizing force of the pressurizing mechanisms 23, 24 between high pressure and low pressure; a change-over state detecting switch 26 for detecting the change-over state of pressurizing force by the pressure change-over mechanism 25; a change-over state monitoring section 171 for monitoring the change-over state of pressurizing force by the pressure change-over mechanism 25 based on a temperature gradient in heating the heat roller 21; and a failure diagnosing section 172 for diagnosing whether the change-over state detecting switch 26 is normal or not based on the monitoring result of the change-over state monitoring section 171. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, a fixing unit that heat-fixes a sheet carrying toner on a nip between a heat roller pressurized by a pressure mechanism and a backup roller, and a pressure applied by the pressure mechanism is switched between high pressure and low pressure. The present invention relates to an image forming apparatus including a pressure switching mechanism.

  A heat roller type fixing device provided in an image forming apparatus that employs an electrophotographic system includes a heat roller that is heated to a predetermined temperature by a heater or the like inserted therein, and a backup roller that is pressed against the heat roller. Is done. The heat roller and the backup roller are pressurized by a pressure mechanism constituted by a coil spring or the like to form a nip for nipping and conveying the paper.

  The appropriate nip pressure varies depending on the paper type heated in the fixing unit. For example, an envelope or the like tends to wrinkle at a nip pressure corresponding to plain paper, and the nip pressure needs to be set low.

  In Patent Document 1, a recording material that supports an unfixed image by a heat roller and a backup roller is sandwiched and conveyed to perform fixing, and can be operated by the user and generates a normal nip pressure on the heat roller and the backup roller. An image forming apparatus having a fixing unit is described, which includes a lever that can be switched between a first position for switching and a second position for generating a nip pressure for special paper.

In the image forming apparatus described in Patent Document 1, the nip pressure generated in the heat roller and the backup roller can be switched according to the type of paper by operating the lever.
JP-A-6-337612

  In the image forming apparatus described in Patent Document 1, the position of the lever is confirmed to grasp the current nip pressure state. Therefore, a switching state detection switch for detecting the switching state of the pressure applied by the lever is provided, and the nip pressure state is displayed on a display unit such as a liquid crystal panel based on the detection result of the switching state detection switch. This improves the convenience of the image forming apparatus.

  Since the switching state detection switch is installed in the vicinity of the fixing unit, it may break down due to the influence of high heat generated from the fixing unit. The probability of the failure increases with time.

  If the switching state detection switch is not normal, by operating the lever according to the display, the nip pressure may be switched to an unsuitable nip pressure for the paper type, leading to unnecessary consumption of paper or toner. However, it is not preferable to newly install a part for diagnosing whether or not the switching state detection switch is normal, because it causes an increase in cost and may hinder downsizing of the device.

  In view of the above problems, an object of the present invention is to diagnose whether or not the switching state detection switch for detecting the switching state of the pressure applied to the fixing unit by the pressure switching mechanism is normal without adding parts. It is in providing a possible image forming apparatus.

  In order to achieve the above object, the first characteristic configuration of the image forming apparatus according to the present invention is the heat roller and the backup roller pressurized by the pressure mechanism as described in claim 1 of the claims. A fixing unit that heat-fixes the paper carrying the toner in the nip, a pressure switching mechanism that switches the pressure applied by the pressure mechanism to either high pressure or low pressure, and a switching state of the pressure applied by the pressure switching mechanism. A switching state detection switch that switches, a switching state monitoring unit that monitors the switching state of the applied pressure by the pressure switching mechanism based on a temperature gradient during heating of the heat roller, and the monitoring state based on the monitoring result by the switching state monitoring unit The fault diagnosis unit for diagnosing whether or not the switching state detection switch is normal is provided.

  When the pressure applied by the pressurizing mechanism is high and the nip pressure is high, the nip width becomes larger than when the pressure is low and the nip pressure is low, and the heat of the heat roller is deprived by the backup roller. Therefore, the temperature gradient during heating of the heat roller differs depending on whether the pressure applied by the pressurizing mechanism is high or low. That is, based on the temperature gradient, it is possible to grasp the switching state of the pressing force of the pressurizing mechanism by the pressure switching mechanism.

  The failure diagnosis unit diagnoses that the switching state detection switch is normal when the monitoring result by the switching state monitoring unit and the detection result by the switching state detection switch match. It can be diagnosed as malfunctioning.

  As described in claim 2, the second characteristic configuration is the same as the first characteristic configuration described above, in addition to the pressure detected by the switching state detection switch when the print start switch is operated. If the switching state corresponds to the paper type set by the paper setting unit, the heat roller is heated to operate the switching state monitoring unit, and the failure diagnosis unit diagnoses that the switching state detection switch is normal. A printing control unit that starts printing when the printing is performed.

  When the switching state of the pressing force detected by the switching state detection switch corresponds to the paper type set in the paper setting unit, the operator who operates the print start switch performs printing with the pressing force corresponding to the paper type. I think it will be done. However, if the switching state detection switch is out of order, printing according to the operator's intention is not performed. Therefore, when printing can be performed according to the operator's intention, the print control unit starts printing.

  According to the third feature configuration, as described in claim 3, in addition to the second feature configuration described above, the print control unit is configured such that the switching state detection switch has failed by the failure diagnosis unit. When it is diagnosed and the switching state monitoring unit monitors that the applied pressure is switched to the low pressure side, printing is started.

  There is a low possibility that the paper will be wrinkled when the pressure is switched to the low pressure side. Therefore, even if the switching state detection switch is out of order, the print control unit can perform printing without wrinkles while preventing a decrease in productivity.

  According to the fourth feature configuration, as described in claim 4, in addition to the second feature configuration described above, the print control unit is configured such that the switching state detection switch is failed by the failure diagnosis unit. When the diagnosis is performed and the switching state monitoring unit monitors that the pressing force is switched to the high pressure side, and the switching state of the pressing force corresponds to the paper type set by the paper setting unit The point is to start printing.

  It is important for the operator to perform intended printing. If the switching state of the pressure detected by the switching state detection switch corresponds to the paper type set in the paper setting unit, the switching state detection switch Even if it is diagnosed that there is a failure, it is preferable to start printing.

  As described above, according to the present invention, it is possible to diagnose whether or not the switching state detection switch for detecting the switching state of the pressure applied to the fixing unit by the pressure switching mechanism is normal without adding parts. An image forming apparatus can be provided.

  In the following, an embodiment of an image forming apparatus employing the present invention will be described using a printer employing an electrophotographic system.

  As shown in FIG. 1, the printer 100 forms a toner image based on an operation unit 11 that is a man-machine interface and image data input via a network or the like, and transfers the toner image onto a conveyed sheet. The image forming unit 12 to be transported, the paper transporting unit 13 to transport the paper from the paper cassette 14, and the fixing for fixing the toner image on the paper by sandwiching and transporting the paper carrying the toner image formed by the image forming unit 12 A unit 20 is provided, and each unit is centrally controlled by the system control unit 17.

  The operation unit 11 includes a display unit such as a liquid crystal panel and a plurality of hardware keys such as a start key 110 that is a print start switch for instructing start of printing. The image forming unit 12 includes a photoconductor, a charging device arranged around the photoconductor, an exposure device, a developing device, and the like.

  As shown in FIG. 2, the fixing unit 20 includes a heat roller 21 and a backup roller 22 that are pressed by the pressure mechanisms 23 and 24 to form a nip, and pressure applied by the pressure mechanisms 23 and 24 is high or low. There are provided a pressure switching mechanism 25 for switching to either one and a switching state detection switch 26 for detecting the switching state of the applied pressure by the pressure switching mechanism 25.

  A heater 21 a such as a halogen lamp is inserted in the axial center of the heat roller 21. Further, a thermistor 21b is installed so as to contact the surface of the heat roller 21, and the temperature of the heat roller 21 is detected by the thermistor 21b. The backup roller 22 is pressed by the pressure mechanisms 23 and 24 and is pressed against the heat roller 21.

  The pressure mechanism 23 is configured by a spring, and the pressure mechanism 24 is configured by a pressure lever. The pressurizing mechanisms 23 and 24 are arranged symmetrically on the front side and the back side of the printer 100 with the front of FIG. 2 as the front side.

  Each spring 23 has one end fixed to the casing of the printer 100 and the other end fixed to the corresponding pressure lever 24, and each spring 23 is applied in the direction in which the nip pressure between the heat roller 21 and the backup roller 22 increases. The pressure lever 24 is pressed and urged. Each pressure lever 24 swings around a support shaft 24a. Further, the concave portion provided at the bottom corresponding to the shape of the bearing portion 22a of the backup roller 22 is in contact with the bearing portion 22a.

  The pressure switching mechanism 25 is installed so that the pressure applied by the pressure mechanisms 23 and 24 can be switched according to the paper type so that the paper to be heated and fixed by the fixing unit 20 is not wrinkled. It consists of a lever of the mold. Two pressure switching mechanisms 25 are provided corresponding to the pressure levers 24, and are arranged symmetrically on the front side of the printer 100 (the front side in FIG. 1 is the front side of the printer) and the back side. Has been.

  One end of each presses against the bottom of each pressure lever 24. When the other end is operated upward, the pressure lever 24 swings downward due to the pressure from the spring 23, and the pressure mechanisms 23, 24 apply pressure. Switch the pressure to the high pressure side. When the other end is operated downward, the pressure lever 24 swings upward by pressing from the other end, and the pressure applied by the pressure mechanisms 23 and 24 is switched to the low pressure side.

  An operation method of the pressure switching mechanism 25 when switching the pressurizing force by the pressurizing mechanisms 23 and 24 will be described. First, the cover 18 is opened and the fixing unit 20 is pulled out to the cover 18 side. When the paper to be heat-fixed by the fixing unit 20 is a special paper such as an envelope that tends to be wrinkled by the high pressure side pressure, the pressure switching mechanism 25 is operated to switch the pressure to the low pressure side. When it is plain paper that does not easily wrinkle even with a high-pressure side pressure, the pressure switching mechanism 25 is operated to switch the pressure to the high-pressure side. After switching the pressing force, the fixing unit 20 is returned to the original position, and the cover 18 is closed.

  The switching state detection switch 26 is a micro switch, and is switched on and off in response to pressing from the bottom of the pressure switching mechanism 25 on the other end side. In the present embodiment, the pressure switching mechanism 25 is turned on when the applied pressure switching state is on the high pressure side and turned off when the pressure switching mechanism 25 is on the low pressure side.

  The system control unit 17 is a board having a microcomputer including a CPU, a ROM storing a CPU operation program, and a RAM as a work area of the CPU.

  As shown in FIG. 3, the system control unit 17 switches the applied pressure switching state by the pressure switching mechanism 25 based on the print control unit 170 that controls the printing operation of the printer 100 and the temperature gradient when the heat roller 21 is heated. A switching state monitoring unit 171 for monitoring and a failure diagnosis unit 172 for diagnosing whether or not the switching state detection switch 26 is normal based on a monitoring result by the switching state monitoring unit 171 are provided.

  In addition, a paper setting unit 173 that sets a paper type based on data related to a paper type used for printing the image data, which is input together with image data from a computer terminal (not shown) connected via a network, and a switching state An informing unit 174 is provided for informing that the switching state of the applied pressure by the pressure switching mechanism 25 detected by the detection switch 26 does not correspond to the paper type set by the paper setting unit 173. Each unit is a functional block embodied in the system control unit 17 by the CPU executing an operation program.

  The switching state monitor unit 171 stores a graph showing a temperature gradient during heating of the heat roller 21 corresponding to when the pressure switching mechanism 25 is on the high pressure side and the low pressure side. For example, FIG. 4A is an example of a graph showing a temperature gradient when the pressure switching state by the pressure switching mechanism 25 is on the high pressure side, and FIG. It is an example of the graph which shows a temperature gradient when a state is a low voltage | pressure side.

  Based on the temperature of the heat roller 21 detected by the thermistor 21b when the heat roller 21 is heated, the switching state monitor unit 171 obtains a graph indicating the temperature gradient of the heat roller 21 during the heating. And the said graph and the memorize | stored graph are compared, the switching state of the applied pressure by the pressure switching mechanism 25 is monitored, and a monitoring result is output.

  For example, a graph stored when the shape of each graph or the slope of a tangent at a predetermined point in time for each graph (for example, after the elapse of a predetermined time since the heater 21a is turned on or when the inflection point temperature is reached) matches or approximates A monitor result indicating that the pressure is switched to the corresponding pressure is output.

  On / off of the switching state detection switch 26 is input to the failure diagnosis unit 172. When the monitoring by the switching state monitoring unit 171 shows that the switching state detection switch 26 is on, a monitoring result indicating that the switching state of the applied pressure by the pressure switching mechanism 25 is the high pressure side is obtained, or the switching state detection switch When the monitoring result that the switching state of the applied pressure by the pressure switching mechanism 25 is the low pressure side is obtained when the switch 26 is off, the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is normal, The diagnosis result is output.

  When the monitoring result that the switching state of the applied pressure by the pressure switching mechanism 25 is the low pressure side is obtained when the switching state detection switch 26 is on, or when the switching state detection switch 26 is off, the pressure switching is performed. When a monitoring result is obtained that the switching state of the pressurizing force by the mechanism 25 is on the high pressure side, the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 has failed, and outputs the diagnosis result.

  The notification unit 174 includes table data indicating the relationship between the paper type and the pressurizing force by the pressurizing mechanisms 23 and 24, and based on the table data, the pressurizing force of the pressure switching mechanism 25 detected by the switch state detection switch 26. It is determined whether or not the switching state corresponds to the paper type set by the paper setting unit 173. When not corresponding, the corresponding computer terminal and the display unit provided in the operation unit 11 are informed so as to prompt the operation of the pressure switching mechanism 25.

  In addition, when the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is malfunctioning, the notification unit 174 displays the diagnosis result on the display unit included in the operation unit 11.

  When image data is input, the print control unit 170 corresponds to the switching state of the applied pressure by the pressure switching mechanism 25 and the sheet type set by the sheet setting unit 173 based on the detection result of the switching state detection switch 26. If it is “corresponding”, printing is started.

  Specifically, the print control unit 170 drives the motor 3 installed in each unit. Based on the temperature detected by the thermistor 21b, the heater 21a is on / off controlled so that the heat roller 21 reaches a predetermined temperature, and the heat roller 21 is heated.

  The motor 3 includes a motor that is provided in the image forming unit 12 and drives a photosensitive member, a motor that is provided in the paper conveyance unit 13 and that drives various rollers and a conveyance belt, and a heat roller 21 that is provided in the fixing unit 20. For example, a motor to be driven.

  Then, when the heat roller 21 reaches a predetermined temperature, the print control unit 17 forms a toner image in the image forming unit 12 based on the input image data, and uses the paper of the paper type set by the paper setting unit 173. The paper is transported from the cassette 14 by the paper transport unit 13 and the toner image is transferred onto the paper. The sheet carrying the toner image is nipped and conveyed at the nip between the heat roller 21 and the backup roller 22 constituting the fixing unit 20, and the toner image is heated and fixed on the sheet. The paper on which the toner image is fixed by the fixing unit 20 is discharged by the paper discharge roller 16.

  The print control unit 170 waits for an operation of the start key 110 when the detection result of the switching state detection switch 26 is “not compatible”.

  When the start state 110 is operated, the print control unit 170 determines that the heating roller detects that the switching state of the pressing force detected by the switching state detection switch 26 corresponds to the sheet type set by the sheet setting unit 173. 21 is heated to operate the switching state monitor unit 171, and printing is started when the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is normal.

  When the print control unit 170 is diagnosed by the failure diagnosis unit 174 that the switching state detection switch 26 has failed and is monitored by the switching state monitor unit 171 that the applied pressure has been switched to the low pressure side, Start printing.

  The print control unit 170 is diagnosed by the failure diagnosis unit 174 that the switching state detection switch 26 has failed, and is monitored by the switching state monitor unit 171 that the applied pressure has been switched to the high pressure side. If the switching state of the pressing force corresponds to the paper type set by the paper setting unit 173, printing is started.

  The print control unit 170 is diagnosed by the failure diagnosis unit 174 that the switching state detection switch 26 has failed, and is monitored by the switching state monitor unit 171 that the applied pressure has been switched to the high pressure side. When the pressing force switching state does not correspond to the paper type set by the paper setting unit 173, the operation of the start key 110 is awaited again. At this time, the notification unit 174 notifies that the switching state detection switch 26 has failed.

  The print control by the print control unit 170 will be described using the flowchart shown in FIG.

  When image data is input to the printer 100 (S 1), the print control unit 170 determines the switching state of the applied pressure by the pressure switching mechanism 25 and the sheet type set by the sheet setting unit 173 from the detection result of the switching state detection switch 26. It is determined whether or not. When “corresponding” (S2), printing is started (S3).

  When “not supported”, the notification unit 174 notifies that “not supported” (S4).

  If there is no operation of the start key 110 (S5) and a print cancel operation is performed on the operation unit 11 (S6), the print control unit 170 does not perform printing.

  When the start key 110 is operated, the print controller 170 determines whether or not the switching state of the applied pressure by the pressure switching mechanism 25 corresponds to the sheet type set by the sheet setting unit 173 based on the detection result of the switching state detection switch 26. Determine again. When “not supported” (S7), the print control unit 170 starts printing (S3). This is because there is no change in the operator's intention with respect to the switching state of the pressure applied by the pressure switching mechanism 25, and printing intended by the operator is performed.

  When “corresponding” (S7), the print controller 170 activates the switching state monitor 171 (S8). When the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is normal (S9), printing is started (S3).

  Even when the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 has failed (S9), the switching state of the applied pressure by the pressure switching mechanism 25 is determined by the monitoring result by the switching state monitoring unit 171. If it is “low pressure side” (S10), printing is started (S3).

  Further, even if the switching state of the applied pressure by the pressure switching mechanism 25 is “high pressure side” in the monitoring result by the switching state monitoring unit 171 (S10), the monitoring result corresponds to the paper type set by the paper setting unit 173. When printing is in progress (S11), printing is started (S3).

  When the monitoring result by the switching state monitor unit 171 and the paper type set by the paper setting unit 173 do not correspond (S11), the notification unit 174 notifies that the switching state detection switch 26 has failed (S12), and prints. The controller 170 waits for the operation of the start key 110 again.

  Another embodiment will be described below.

  In the above-described embodiment, the print control unit 170 may start printing even when the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 has failed. May not start. That is, printing may be started only when the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is normal.

  In the above-described embodiment, when the image data is input from the computer terminal, the switching state of the applied pressure by the pressure switching mechanism 25 detected by the pressure state detection switch 26 corresponds to the sheet type set by the sheet setting unit 173. In this case, the print control unit 170 starts printing, but the present invention is not limited to this.

  When the image data is input, the switching state monitor unit 171 may be operated, and the print control unit 170 may start printing based on the diagnosis result for the switching state detection switch 26 by the failure diagnosis unit 172.

  For example, printing may be started when the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is normal. When the failure diagnosis unit 172 diagnoses that the switching state detection switch 26 is normal, the predetermined diagnosis described in the above embodiment is performed. Printing may be started if the conditions are met.

  In the above-described embodiment, the printer 100 to which the present invention is applied has been described as an example. However, the present invention adopts an electrophotographic method and a copying machine or a fax machine including a heat roller fixing unit in addition to the printer. It can be applied to any image forming apparatus.

  For example, when the present invention is applied to a copying machine in which image data is read by a scanner and copying of the image data is started when the start key is operated, the start key may be used as a print start switch.

  Note that each of the above-described embodiments is merely an example of the present invention, and the scope of the present invention is not limited by the description. The specific configuration of each part is appropriately selected within the scope of the effects of the present invention. It goes without saying that changes can be designed.

Illustration of printer Illustration of fixing unit Explanatory diagram of functional blocks related to the present invention provided in the system control unit (A) is explanatory drawing of temperature gradient when applied pressure is high pressure, (b) is explanatory drawing of temperature gradient when applied pressure is low pressure. A flowchart for explaining the operation of the print control unit

Explanation of symbols

20: fixing unit 25: pressure switching mechanism 26: pressure state detection switch 110: print start switch (start key)
170: Print control unit 171: Switching state monitor unit 172: Failure diagnosis unit 173: Paper setting unit

Claims (4)

  A fixing unit that heat-fixes the paper carrying the toner at the nip between the heat roller pressurized by the pressure mechanism and the backup roller, and a pressure switching mechanism that switches the pressure applied by the pressure mechanism to either high pressure or low pressure. A switching state detection switch for detecting a switching state of the applied pressure by the pressure switching mechanism, and a switching state monitoring unit for monitoring the switching state of the applied pressure by the pressure switching mechanism based on a temperature gradient during heating of the heat roller; An image forming apparatus comprising a failure diagnosis unit that diagnoses whether or not the switching state detection switch is normal based on a monitoring result by the switching state monitoring unit.   When the print activation switch is operated, if the switching state of the pressure detected by the switching state detection switch corresponds to the paper type set in the paper setting unit, the heat roller is heated to switch the state. The image forming apparatus according to claim 1, further comprising: a print control unit that operates a monitor unit and starts printing when the failure diagnosis unit diagnoses that the switching state detection switch is normal.   When the print control unit is diagnosed by the failure diagnosis unit that the switching state detection switch has failed and is monitored by the switching state monitor unit that the applied pressure is switched to the low pressure side, The image forming apparatus according to claim 2, wherein printing is started.   When the print control unit is diagnosed by the failure diagnosis unit that the switching state detection switch has failed and is monitored by the switching state monitor unit that the applied pressure has been switched to the high pressure side. 3. The image forming apparatus according to claim 2, wherein printing is started when the switching state of the pressing force corresponds to the paper type set by the paper setting unit.

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