JP2007293217A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing a sheet material from stopping at the fixing nip of a fixing unit if conveyance of sheets one overlapping the other occurs, thereby improving usability for a jam removal, and capable of stopping a conveying operation in a shortest time if paper is caught by a projection or the like on a conveying path, thereby avoiding an abnormal state of the image forming apparatus. <P>SOLUTION: If a feed paper sensor 7 can not detect the trailing end of a sheet material 2 after detecting the leading end of the sheet material 2 and in the case where a fixing paper ejection sensor 16 and a full detection sensor 17 have detected the presence of sheet of paper, a CPU 13 determines that the sheets one overlapping the other have been conveyed, and then the CPU 13 stops the conveying operation after the fixing paper ejection sensor 16 detects the training end of the sheet material 2. In the case where the fixing paper ejection sensor 16 and full detection sensor 17 detect the empty of paper, the CPU 13 determines that a sheet is caught on the sheet material conveying path 5, and the CPU 13 immediately stops the conveying operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a laser beam printer.

  FIG. 8 is a diagram for explaining a technique related to a conventional image forming apparatus.

  The sheet material 2 loaded in the sheet feeding cassette 1 is fed by a cassette feeding roller 3, fed by a feeding roller 4 onto a sheet material feeding path 5 in an image forming apparatus such as a printer, and fed by a feeding sensor 7. Image timing and the positions of the front and rear ends of the sheet material 2 are detected. Further, the leading edge of the sheet material 2 is aligned by the sheet feed sensor 7 with the registration roller 6, and the sheet material 2 is conveyed to the transfer roller 8 and the photosensitive drum 9. The latent image written on the photosensitive drum 9 by the laser scanner 15 is transferred to the sheet material 2 by the transfer roller 8 and the photosensitive drum 9. Then, the toner is conveyed to the pressure roller 10, the fixing film 11, and the ceramic heater 11-a, which is a fixing device 18 for fixing the toner to the sheet material 2, and is pressed and fixed. 19 is discharged. The CPU 13 controls the heater drive circuit 14 to control the temperature of the ceramic heater 11-a.

  3 is a schematic perspective view of the fixing device 18, in which 11-c is a fixing heater support stay, 11-a is a ceramic heater, 10 is a pressure roller, 11-d is a fixing nip portion, and 11 is fixing. It is a film.

  Further, the CPU 13 detects the leading edge and the trailing edge of the sheet material 2 (hereinafter referred to as a sheet) by the sheet feeding sensor 7 and detects the length of the sheet from the detected timing of the leading edge and the trailing edge of the sheet. Then, the timing for driving a paper feed solenoid (not shown) for driving the cassette paper feed roller 3 is adjusted based on the length of the paper.

  4A is a timing chart showing ON / OFF of the paper feed solenoid, and FIG. 4B is a timing chart showing ON / OFF of the paper feed sensor 7. In FIG. 4, the leading edge of the paper reaches the paper feed sensor 7 after the paper feed time Tp after the first paper feed is started (301) (302). After the CPU 13 detects the trailing edge of the paper with the paper feed sensor 7, the CPU 13 starts feeding the second paper (303). The interval between the first and second sheets is the paper feed time Tp, and the leading edge of the second sheet reaches the paper feed sensor 7 (304). The CPU 13 detects the rear edge of the second sheet (305) and then feeds the third sheet. The leading edge of the third sheet reaches the sheet feed sensor 7 at 306.

  Here, for example, when a double feed of sheets occurs as shown in FIG. 5 when the second sheet is fed (405, 408), the amount of the double feed is a constant jam margin as shown in FIG. When the time Tm is exceeded, it is determined that a conveyance failure jam (hereinafter referred to as a paper conveyance jam). In FIG. 6, this is a paper feed stay jam detection. When it is determined that the paper conveyance jam has occurred, immediate conveyance is stopped in order to prevent the user from becoming an unclearable paper conveyance jam if the conveyance is further continued.

  In FIG. 5, 401, 403, 405, and 408 are timings for starting paper feeding, 402, 404, and 407 are timings for detecting the leading edge of the paper by the paper feed sensor 7, and 403 and 406 are trailing edges of the paper. Is the timing to detect. Reference numeral 409 indicates that there is no gap between the third and fourth sheets, and a paper transport jam has occurred (in the drawing, it is simply referred to as a jam occurrence). In 410, the sheet feeding jam is generated in 409, the sheet feeding solenoid is not turned on, the fifth sheet is not fed, and the sheet feeding time Tp0 is shorter than the sheet feeding time Tp. . Reference numeral 411 indicates that the paper feed sensor 7 is maintained in the ON state due to the occurrence of double feed. In addition, since double feed occurs after the second sheet, the inter-paper time T3 is shorter than the inter-paper time T2. Note that since double feed occurs after the second sheet is fed, the maximum throughput is obtained after 404.

In FIG. 6, reference numerals 501 and 503 denote timings for starting paper feeding, and reference numerals 502 and 504 denote timings for detecting the leading edge of the paper by the paper feed sensor 7. Reference numeral 505 indicates that the trailing edge of the sheet could not be detected, and reference numeral 506 indicates that the trailing edge of the sheet could not be detected when the jam margin time Tm has elapsed, and a paper feed staying jam was detected.
JP 09-124173 A

  However, in the above-described configuration, when such a double feed occurs, it is determined that a paper transport jam has occurred, and the paper transport is immediately stopped. Therefore, the paper often stops at the fixing nip portion 11-d. When the paper is jammed in the fixing nip portion 11-d and stopped due to the paper conveyance jam, the user needs to perform the jam processing. However, a large pressure is applied to the fixing nip portion 11-d to secure the fixing property. Therefore, it is difficult for the user to handle the jam. In order to reduce this pressure, there is a configuration in which a user operates a pressure release lever to release pressure during jam processing. However, the method in which the user manually releases the pressure is inconvenient for the user, and the fixing device 18 has a problem in trying to remove the paper that caused the paper conveyance jam while forgetting the release operation. There was a risk of giving. There are also image forming apparatuses that incorporate a mechanism that automatically releases pressure by opening the door. However, the addition of this mechanism may increase the cost and result in a higher apparatus cost for the user. there were.

  In addition, when the paper transport jam occurs, if the transport is not stopped immediately, an unclearable paper transport jam that is difficult for the user to jam may occur.

  The present invention has been made paying attention to the above points, and when double feeding occurs, the sheet material is prevented from stopping at the fixing nip portion of the fixing device, and the usability of the jam processing is improved. An object of the present invention is to provide an image forming apparatus that can perform the above-described process. It is another object of the present invention to provide an image forming apparatus capable of stopping a conveying operation in the shortest time and avoiding a problem with the image forming apparatus when a catch on a protrusion on the conveying path occurs.

  In order to solve the above-described problems, an image forming apparatus of the present invention has the following configuration and performs the following control.

  (1) In an image forming apparatus that forms an image on a recording material, a first sensor unit that detects the conveyed recording material, a heating fixing unit that heat-fixes the developer on the recording material, and a heating fixing unit Second sensor means arranged on the downstream side for detecting the recording material, third sensor means arranged on the downstream side from the second sensor means for detecting the recording material, and control for controlling the conveying operation of the recording material And when the trailing edge of the recording material is not detected after a predetermined time from the detection of the leading edge of the recording material by the first sensor means, the control means includes the second sensor means and the third sensor means. An image forming apparatus characterized in that the timing for outputting the conveyance failure jam of the recording material is controlled in accordance with a detection result of the sensor means.

  According to the present invention, it is possible to improve the usability of the jam processing when the paper is stopped by the fixing device when a conveyance failure jam due to double feeding occurs. In addition, if it is determined that the paper jam has occurred when the paper is caught on the protrusion on the conveyance path, the jam can be stopped in the shortest time, and the trouble of the image forming apparatus in such a case can be avoided. can do.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

(First embodiment)
1 and 2 are diagrams illustrating an embodiment of the present invention.

  In FIG. 1, a sheet material 2 (corresponding to a recording material) stacked in a sheet feeding cassette 1 is fed by a cassette sheet feeding roller 3, and a sheet material conveying path 5 in an image forming apparatus such as a printer is conveyed by a conveying roller 4. It is transported up. The sheet timing sensor 7 (corresponding to the first sensor means) detects the image timing and the positions of the leading and trailing edges of the sheet material 2. Further, the leading edge of the sheet material 2 is aligned by the sheet feed sensor 7 with the registration roller 6, and the sheet material 2 is conveyed to the transfer roller 8 and the photosensitive drum 9. The sheet material 2 to which the toner (corresponding to the developing material) is transferred by the transfer roller 8 and the photosensitive drum 9 is conveyed to a fixing device 18 (corresponding to a heating fixing unit) for fixing the toner to the sheet material 2 and is pressed. After fixing, the paper is discharged by a paper discharge roller 12. The fixing device 18 includes a pressure roller 10, a fixing film 11, a ceramic heater 11-a, and the like, details of which will be described later. Here, the temperature of the ceramic heater 11-a is detected by the thermistor 11-b and transmitted to the CPU 13 (corresponding to the control means). The CPU 13 controls the power applied to the ceramic heater 11-a via the heater drive circuit 14 so that the temperature of the thermistor 11-b becomes a desired constant temperature.

  Reference numeral 16 denotes a fixing paper discharge sensor (corresponding to the second sensor means) for detecting the presence or absence of the sheet material 2 after pressure fixing, and the signal is turned ON when the sheet material 2 passes. Reference numeral 17 denotes a full load detection sensor (corresponding to the third sensor means) that detects whether or not the sheet material 2 loaded on the paper discharge tray 19 is full, and the signal is turned ON when the sheet material 2 passes.

  FIG. 2 is a flowchart for explaining processing when a paper conveyance jam (corresponding to a conveyance failure jam) according to this embodiment occurs.

  In FIG. 2, upon receiving a print instruction, printing is started (step S101) and paper feeding is started (step S102). After that, when the leading edge of the sheet material 2 (hereinafter referred to as paper) is detected by the paper feed sensor 7, the paper feed staying jam detection timer determines a predetermined value determined from the paper length T1 and the jam margin time Tm (see FIG. 6). A value (corresponding to a certain time) is set (step S103). This paper feed staying jam detection timer counts down with time and finally stops at zero. After the leading edge of the paper reaches the paper feed sensor 7, it is checked whether the paper feed jamming detection timer is 0 (step S104).

  If the paper feed staying jam detection timer is not 0 in step S104, it is checked whether the trailing edge of the paper has passed through the paper feed sensor 7 (step S105). If the paper feed sensor 7 has not been removed, the process starts again from step S104. If it has passed through the paper feed sensor 7, it is checked whether or not printing has been completed (step S106). If the printing is finished, the printing operation is finished (step S107). If the next printing is not finished, the process returns to step S102.

  If it is determined in step S104 that the paper feed staying jam detection timer is 0, it is checked whether the fixed paper discharge sensor 16 has paper (step S108). If the fixing paper discharge sensor 16 has paper, the full load detection sensor 17 is checked (step S109). If the full-load detection sensor 17 has paper, the printer waits until the fixing paper discharge sensor 16 detects the trailing edge of the paper (step S110), and then displays a paper feed jam and stops (step S111). . On the other hand, if the fixing paper discharge sensor 16 or the full load detection sensor 17 is out of paper in step S108 or step S109, a paper feed stay jam is immediately displayed and stopped (step S111).

  The display of the paper feed stay jam is executed by outputting a signal indicating the paper feed stay jam from the CPU 13 to a display unit (not shown).

(Second embodiment)
FIG. 7 is a flowchart illustrating processing when a paper conveyance jam occurs according to this embodiment.

  In the second embodiment, as shown in FIG. 7, in response to a print instruction, printing is started (step S701) and paper feeding is started (step S702). Thereafter, when the paper feed sensor 7 detects the leading edge of the paper, a predetermined value determined from the paper length T1 and the jam margin time Tm is set in the paper feed jam detection timer (step S703). This paper feed staying jam detection timer counts down with time and finally stops at zero. After the leading edge of the paper reaches the paper feed sensor 7, it is checked whether the paper feed staying jam detection timer is 0 (step S704).

  If the paper feed staying jam detection timer is not 0 in step S704, it is checked whether the trailing edge of the paper has passed through the paper feed sensor 7 (step S705). If the paper feed sensor 7 has not been removed, the process starts again from step S704. If the paper feed sensor 7 has been removed, it is checked whether or not printing has been completed (step S706). If the printing is finished, the printing operation is finished (step S707). If the next printing is not finished, the process returns to step S702.

  If the paper feed staying jam detection timer is 0 in step S704, it is checked whether the fixing paper discharge sensor 16 has paper (step S708). If the fixing paper discharge sensor 16 has paper, the full load detection sensor 17 is checked (step S709). When the full load detection sensor 17 has paper, the maximum jam extension time timer Tx is set. In Tx, even when the maximum paper size (corresponding to the maximum recording material length L) is double fed, the trailing edge of the second double fed paper can pass through the fixing paper discharge sensor 16. A value (corresponding to a time determined from the maximum recording material length L) is set (step S710). If Tx is not 0 (step S711), the process waits until the fixed paper discharge sensor 16 detects the trailing edge of the paper (step S712), and then stops displaying the paper feed stay jam (step S713). . On the other hand, if the fixing paper discharge sensor 16 or the full load detection sensor 17 is out of paper in step S708 or step S709, the paper feed stay jam is immediately displayed and stopped (step S713). When the maximum paper jam extension time timer Tx reaches 0 while waiting for the fixing paper discharge sensor 16 to detect the trailing edge of the paper (step S712), a paper feed jam is displayed at that time. Stop (step S713).

  As in the first embodiment, the display of the paper feed stay jam is executed by outputting a signal indicating the paper feed stay jam from the CPU 13 to a display unit (not shown).

  When the distance between the paper feed sensor 7 and the fixing paper discharge sensor 16 is A, the distance between the paper feed sensor 7 and the full load detection sensor 17 is B, and the maximum paper size L is L, the maximum paper size L is A <L. <B relationship shall be satisfied.

Cross-sectional view of an image forming apparatus according to the present invention Flowchart for explaining processing when a paper transport jam occurs according to the first embodiment 1 is a schematic perspective view of a fixing device according to an image forming apparatus of the present invention. (A) Timing chart showing ON / OFF of paper feed solenoid, (b) Timing chart showing ON / OFF of paper feed sensor In the timing chart when double feed occurs, (a) a timing chart showing ON / OFF of a paper feed solenoid, (b) a timing chart showing ON / OFF of a paper feed sensor FIG. 6 is a timing chart for explaining the timing of detection of jammed paper jam, (a) a timing chart showing ON / OFF of a paper feed solenoid, and (b) a timing chart showing ON / OFF of a paper feed sensor. Flowchart for explaining processing at the time of occurrence of paper conveyance jam according to the second embodiment Cross-sectional view of a conventional image forming apparatus

Explanation of symbols

1 Paper cassette 2 Sheet material (equivalent to recording material)
3 Cassette paper feed roller 4 Transport roller 5 Sheet material transport path 6 Registration roller 7 Paper feed sensor (corresponding to first sensor means)
8 Transfer roller 9 Photosensitive drum 10 Pressure roller 11 Fixing film 11-a Ceramic heater 11-b Thermistor 11-c Fixing heater support stay 11-d Fixing nip portion 12 Paper discharge roller 13 CPU (corresponding to control means)
14 heater driving circuit 15 scanner unit 16 fixing paper discharge sensor (corresponding to second sensor means)
17 Full load detection sensor (equivalent to third sensor means)
18 Fixing device (equivalent to heat fixing means)
19 Discharge tray

Claims (3)

In an image forming apparatus for forming an image on a recording material,
First sensor means for detecting the recording material being conveyed, heat fixing means for heat fixing the recording material to the recording material, and second sensor means for detecting the recording material disposed downstream of the heat fixing means And third sensor means disposed downstream of the second sensor means for detecting the recording material, and control means for controlling the conveying operation of the recording material,
When the trailing edge of the recording material is not detected after a predetermined time from the detection of the leading edge of the recording material by the first sensor means, the control means uses the detection results of the second sensor means and the third sensor means. In response, the image forming apparatus controls the timing of outputting the conveyance failure jam of the recording material. The image forming apparatus according to claim 1.
When the trailing edge of the recording material is not detected, the control means determines the conveyance failure jam when both the detection results of the second sensor means and the third sensor means indicate that the recording material is present. Is obtained from the time determined based on the maximum recording material length L that the image forming apparatus can pass through or the time until the trailing edge of the recording material is detected by the second sensor means. An image forming apparatus. The image forming apparatus according to claim 2.
The relationship between the distance A between the first sensor means and the second sensor means, the distance B between the first sensor means and the third sensor means, and the length L of the maximum recording material Is an image forming apparatus, wherein A <L <B.