JP4596824B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus capable of forming double-sided images.

  2. Description of the Related Art Conventionally, an image forming apparatus capable of double-sided image formation is known. In this image forming apparatus, when image formation is performed on a first surface of a fed sheet, the sheet after image formation is formed. Is not discharged out of the apparatus, but is guided to the transport path by a pair of paper discharge rollers rotated in reverse, and further transported to a pair of registration rollers by a plurality of transport roller pairs. Inverted to two sides, image formation is performed on the second side of the paper, and after transfer and fixing, the paper is discharged out of the apparatus. Such double-sided image forming operation is described in Patent Document 1.

JP 07-115499 A

  However, according to such a method, during the reversing operation after the paper is detected by the paper discharge sensor, the paper is urgently stopped across, for example, the paper discharge roller pair and the conveyance roller pair, and then When the operation of the image forming apparatus is resumed, on the one hand, the discharge roller pair rotates forward to try to discharge the paper, and on the other hand, the transport roller pair rotates forward to try to convey the paper. As a result, the paper may be bent or torn.

  Therefore, the present invention solves such a problem, and an image forming apparatus capable of continuing to convey a recording material stopped between a paper discharge roller pair and a conveyance roller pair after the operation of the apparatus is resumed. An object is to provide a control method.

The image forming apparatus according to claim 1, an image forming unit that forms an image on a recording material, a paper discharge sensor that detects a recording material on which an image is formed by the image forming unit, and a leading edge of the recording material by the paper discharge sensor A timer for measuring the time from when the recording material is detected until the trailing edge of the recording material is detected, a paper discharge roller for discharging the recording material on which the image is formed, and a recording material on which the image is formed on the first surface the paper discharge rollers to form the images on the second surface, the image is formed on the first surface is switched to the reverse rotation to reverse the recording material from the forward rotation for discharging the recording material recorded in the image forming apparatus including a transfer control section for inverting the timber, wherein the transport control unit, when the recording material in which the sheet discharge roller image is formed on the first surface by reverse rotation Ru is inverted, the Measuring the time the recording material is being reversed and conveyed by a timer Started, the in the course of being inverted conveyed by sheet ejection rollers stops measurement of time by the timer and that Do the stop state, when resuming the conveyance of the recording material from the stopped state, the leading end of the recording material image on the first surface by the time the recording material from the time from the detection to the rear end is detected by subtracting the time being reverse conveyance has passed by reversely rotating said paper discharge roller is formed After the recording material is transported and the time from when the leading edge of the recording material is detected until the trailing edge is detected is subtracted from the time during which the recording material is transported in reverse, the paper discharge roller is moved forward. It is characterized by switching to rotation.

  Since the present invention is configured as described above, the recording material stopped between the paper discharge roller pair and the conveyance roller pair can be continuously conveyed after the operation of the apparatus is resumed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 shows a first embodiment of the present invention. This is an example of a color image forming apparatus, and its structure is shown in FIG.

  The color image forming apparatus 101 in FIG. 2 includes a cassette sheet supply unit 202b for storing paper 213, a multi-sheet supply tray 202a into which the paper 213 is manually fed by a user, and a paper 213 to the cassette sheet supply unit 202b and the multi-sheet supply. A sheet supply unit 219 for supplying from the tray 202a and an image forming unit 208 for performing image processing are provided.

  The image forming unit 218 uniformly charges the surfaces of the four photosensitive drums 215a, 215b, 215c, and 215d corresponding to each color of magenta, cyan, yellow, and black, and the photosensitive drums 215a, 215b, 215c, and 215d. Devices 217a, 217b, 217c, and 217d, and optical units 117a, 117b, 117c, and 117d as exposure means for irradiating a laser beam to form electrostatic latent images on the photosensitive drums 215a, 215b, 215c, and 215d, Developers 216 a, 216 b, 216 c, and 216 d that visualize the toner image by attaching toner to the electrostatic latent image, and a transfer roller 208 a as a transfer unit that transfers the toner image on the photosensitive drum 215 to the sheet 213, 208b, 208c, 208d and the like.

  The charger 217 and the developing unit 216 are sequentially arranged around the photosensitive drum 215 in accordance with the rotation direction of the photosensitive drum 215. Here, the photosensitive drum 215, the charger 217, and the developing unit 216 are integrally formed as a cartridge to form process cartridges 206a, 206b, 206c, and 206d.

  The sheet 213 supplied by the sheet supply unit 219 is conveyed from the upstream side (downward in the figure) to the downstream side (upward in the figure) in the sheet conveyance direction. During this time, the sheet 213 is appropriately detected by the registration sensor 110, the pre-fixing sensor 111, and the paper discharge sensor 112 disposed along the conveyance path 201.

  Each image forming process of the image forming unit 218 operates in synchronization with the timing at which the sheet 213 is detected by the registration sensor 110, the pre-fixing sensor 111, and the paper discharge sensor 112, and the process cartridge 206 performs magenta, The toner images of the respective colors are sequentially superimposed and transferred onto the paper 213 in the order of cyan, yellow, and black. Thereafter, the color toner image superimposed and transferred onto the sheet 213 is heated and pressed by the fixing unit 214 and melted and fixed on the first surface of the sheet 213, and the fixed sheet 213 is discharged to the discharge tray 210.

  If an image is also formed on the second side of the sheet 213, the sheet 213 is reversed from the first side to the second side, and therefore, synchronized with the timing when the trailing edge of the sheet 213 is detected by the paper discharge sensor 112. Then, the paper discharge roller pair 209 is rotated in the reverse direction to guide the paper 213 to the transport path, and the paper 213 guided to the transport path is transported through the transport path by the transport rollers 211a, 211b, and 211c, and again the image forming unit Then, the sheet 213 is reversed from the first surface to the second surface.

  The color toner image formed by the image forming unit 208 is transferred to the second surface of the paper 213, and the color toner image transferred onto the paper 213 is melted and fixed by the fixing device 214. The paper 213 after fixing is discharged to the discharge tray. It is discharged to 210.

  Referring to FIG. 1, the same parts as those in FIG. 2 are denoted by the same reference numerals. The color image forming apparatus 101 is connected to the host computer 104 directly or via a network. Image formation data created by the host computer 104 is received by the controller 103 and converted into an image signal. The controller 103 inquires of the control unit 102 about the state, confirms that the image formation is possible, and then issues an instruction to start image formation to the control unit 102. Upon receiving the image formation start instruction, the control unit 102 is connected to the conveyance control unit 105, the fixing drive control unit 106, the optical units 117a, 117b, 117c, and 117d, the drum drive control unit 108, and the paper feed control unit. 107 to start image formation preparation such as starting each load.

  The control unit 102 includes a first timer 102f, a second timer 102s, a third timer 102t, and a volatile memory 102m. The first timer 102f, the second timer 102s, and the third timer 102t The timer values of the first timer 102f, the second timer 102s, and the third timer 102t are stored in the memory 102m, and read / write to the memory 102 is controlled.

  The conveyance control unit 105 drives and controls the conveyance motor 113 according to the control of the control unit 102, thereby controlling the driving of the transfer rollers 208a, 208b, 208c, and 208d and the conveyance rollers 211a, 211b, and 211c. The fixing drive control unit 106 controls driving of the fixing device 214 and the discharge roller pair 209 by driving the fixing motor 114. The paper feed controller 107 controls the drive of the paper feed pickup rollers 203 a and 203 b, the paper feed transport rollers 204 a and 204 b, and the registration roller 205 by driving the paper feed motor 115. The drum drive control unit 108 controls the driving of the process cartridges 206a, 206b, 206c, and 206d by driving the drum motors 116a, 116b, 116c, and 116d.

  When the image formation preparation is completed, the control unit 102 issues a paper feed instruction to the paper feed control unit 107, so that the sheet 213 is started to be fed by the sheet supply unit 219. At this time, the control unit 102 changes to the image forming state and notifies the controller 103 that the image forming state has changed. When the front end of the fed paper 213 is detected by the registration sensor 110, the control unit 102 sends an image formation start signal to the controller 103 after a predetermined time. The controller 103 that has received the image formation start signal outputs an image signal in synchronization with the image formation start signal.

  The image signal output from the controller 103 is modulated into an on / off signal of a laser beam by the optical units 117a to 117d and is exposed on the photosensitive drum 215.

  As the paper 213 is transported on the transport path 201, the image forming unit 218 is controlled to form a color image on the paper 213. When the image forming process ends normally, and the trailing edge of the sheet 213 is detected by the paper discharge sensor 112, the control unit 102 determines that the image forming has ended normally, and confirms that the image forming state is again possible. Notify the controller 103.

  In the above-described double-sided image forming operation, after the sheet 213 is guided to the conveyance path 201, it is necessary to return the rotation direction of the discharge roller pair 209 to the normal rotation in preparation for the next sheet conveyance. The timing for returning the rotation direction of the paper discharge roller pair 209 to the normal rotation is determined based on the time for which the paper 213 passes through the paper discharge sensor 112.

  FIG. 3 is a flowchart illustrating a control procedure by the conveyance control unit 105 when guiding a sheet to the conveyance path 201. Wait until the leading edge of the paper 213 is detected by the paper discharge sensor 112 (S301). When the leading edge of the paper 213 is detected by the paper discharge sensor 112, the first timer 102f is cleared and the increment of the first timer 102f is started. The process waits until the trailing edge of the paper 213 is detected by the paper discharge sensor 112 (S303). When the trailing edge of the sheet 213 is detected by the paper discharge sensor 112, the increment of the first timer 102f is stopped (S304), the decrement of the first timer 102f is started (S305), and the pair of paper discharge rollers 209 is rotated in reverse.

  When the conveyance of the sheet 213 is not stopped due to a jam or the like (S306), the process waits until the first timer 102f becomes 0 (S307), and when the first timer 102f becomes 0, the discharge roller Return pair 209 to forward rotation. On the other hand, when the conveyance of the sheet 213 is stopped due to a jam or the like, the driving of the discharge roller 209 and the conveyance rollers 211a, 211b, and 211c is stopped (S308), and the decremented first timer 102f is stopped. The value is stored in the memory 102m (S309), and the first timer 102f is stopped.

  Thereafter, the process waits until the operation can be resumed (S310). When the user can resume the operation by processing a jam or the like, the sheet 213 remaining on the conveyance path 201 is detected (S311).

  FIG. 4 is a flowchart showing in more detail step S311 of FIG. First, the decrement of the second timer 102s is started (S401). If the paper is transported to any position on the transport path 201, the second timer 102 s will receive the paper from the registration sensor 110, the pre-fixing sensor 111, or the paper discharge sensor 112. The time that is surely detected by any one of the sensors is set. Specifically, the distance between the sensors provided along the conveyance path 201, that is, the distance between the sensors with the longest distance between the sensors is set. A time obtained by dividing by the paper conveyance speed and adding a predetermined margin is set. Then, it is determined whether or not the remaining time stored in the memory 102m is 0 (S402). When it is determined that the remaining time is 0, all of the transport rollers 211a, 211b, and 211c are rotated forward (S403).

  On the other hand, if it is determined that the remaining time is not 0, the paper discharge roller pair 209 is rotated in the reverse direction (S404), the transport rollers 211a, 211b, and 211c are all rotated in the forward direction (S405), and the third timer 102t is The remaining time stored in the memory 102m is set (S406), and the decrement of the third timer 102t is started (S407). The registration sensor 110, the pre-fixing sensor 111, and the paper discharge sensor 112 on the conveyance path 201 are monitored (S408), and while the paper is not detected by these sensors, the second timer 102s is waited until it becomes zero. (S410).

  Meanwhile, when the third timer 102t becomes 0 (S411), the paper discharge roller pair 209 is rotated forward. When the second timer 102s reaches 0, the second timer 102s and the third timer 102t are stopped (S412), and the transport rollers 211a, 211b, and 211c are stopped (S413), and the image formation is enabled (S414). ).

  If the sheet is detected by any of the registration sensor 110, the pre-fixing sensor 111, and the sheet discharge sensor 112 before the second timer 102s reaches 0, the second timer 102s and the third timer 102s The timer 102t is stopped (S415) and all the transport rollers 211a, 211b, and 211c are stopped (S416), and at the same time, the value of the third timer 102t is stored in the memory 102m (S417).

  If a sheet is detected at a position where the sheet can be forcibly discharged, forced discharge is performed (S418). On the other hand, if the paper is detected at a position where the paper cannot be forcibly discharged, for example, at the pre-fixing sensor 111 or the paper discharge sensor 112, the fact that a jam has occurred is displayed on the display panel 118 (S419). Encourage jam handling.

  FIG. 5 is a flowchart showing step S418 of FIG. 4 in more detail. First, the decrement of the second timer 102s is started (S501). Regardless of the position of the sheet 213 in the conveyance path 201, the second timer 102s can reliably convey the sheet outside the color image forming apparatus by driving the conveyance rollers 211a, 211b, and 211c. More specifically, the discharge time is set. Specifically, the length in the longitudinal direction of the maximum size of paper that can be passed is added to the longest transport distance in the transport path 201, and the obtained value is the transport speed. A time obtained by dividing and adding a predetermined margin is set.

  It is determined whether or not the remaining time stored in the memory 102m is 0 (S502). When it is determined that the remaining time of the memory 102m is 0, all the transport rollers 211a, 211b, and 211c are rotated forward (S503). On the other hand, when it is determined that the remaining time of the memory 102m is not 0, the paper discharge roller pair 209 is rotated in the reverse direction (S504), and the transport rollers 211a, 211b, and 211c are all rotated in the forward direction (S505). The remaining time is set in the third timer 102t (S506), and the decrement of the third timer 102t is started (S507). Wait until the second timer 102s becomes 0 (S510). In the meantime, when the third timer 102t becomes 0 (S511), the paper discharge roller pair 209 is rotated forward.

  When the second timer 102s reaches 0, the second timer 102s and the third timer 102t are stopped (S512), and all of the transport rollers 211a, 211b, and 211c are stopped (S513), and an image formable state is set (S514). .

  The application of the residual paper detection and forced discharge method described above is not limited to the color image forming apparatus having the structure shown in FIG. 2, but can be applied to other types of image forming apparatuses.

  In this embodiment, the example in which the memory 102m is used has been described. However, a nonvolatile memory can be used instead of the memory 102m. When a non-volatile memory is used, even when the color image forming apparatus is turned off, the contents of the non-volatile memory are retained without being erased. After that, even if the power is turned off, the remaining paper detection and forced paper discharge operation will be started when the power is turned on next time, thereby reliably detecting the stopped paper in the color image forming apparatus. And can be discharged.

<Second Embodiment>
This embodiment is different from the first embodiment in that a transport speed corresponding to the type of paper can be selected from a plurality of transport speeds. For example, in the case of normal office paper, image formation is performed at a normal speed, but in the case of glossy paper, the temperature of the fixing device 214 is set to a lower temperature than that of office paper and the conveyance speed is reduced to half. As a speed, the image with higher gloss was realized.

  FIG. 6 is a flowchart illustrating a control procedure by the transport control unit 105 when guiding a sheet to the transport path. The process waits until the discharge sensor 112 detects the leading edge of the sheet 213 (S601). When the leading edge of the sheet 213 is detected, the first timer 102f is cleared and the increment of the first timer 102f is started (S602). Then, it waits until the trailing edge of the paper 213 is detected by the paper discharge sensor 112 (S603). When the trailing edge of the paper 213 is detected by the paper discharge sensor 112, the increment of the first timer 102f is stopped (S604). The decrement of the 1 timer 102f is started (S605).

  If the paper conveyance is not stopped due to a jam or the like (S606), the process waits until the first timer 102f becomes 0 (S607). On the other hand, when the conveyance of the sheet is stopped due to a jam or the like, the driving of the discharge roller 209 and the conveyance rollers 211a, 211b, and 211c is stopped (S608), and the decremented first timer 102f is used. Is converted into a remaining transport distance that can be transported with this value (S609), the remaining transport distance is stored in the memory 102m (S610), and the first timer 102f is stopped.

  Thereafter, the process waits until the operation can be resumed (S611). When the user can resume the operation by processing a jam or the like, the sheet remaining on the conveyance path 201 is detected (S612).

  FIG. 7 is a flowchart showing step S612 of FIG. 6 in more detail. First, the decrement of the second timer 102s is started (S701). Regardless of the position on the conveyance path 201 where the sheet 213 is stopped, the second timer 102s drives the conveyance rollers 211a, 211b, and 211c at a normal speed, thereby causing the registration sensor 110, the pre-fixing sensor 111, Alternatively, a time that can be reliably detected by any one of the paper discharge sensors 112 is set.

  It is determined whether the remaining conveyance distance stored in the memory 102m is 0 (S702). If it is determined that the remaining transport distance is 0, all of the transport rollers 211a, 211b, and 211c are rotated forward at normal speed (S703). On the other hand, if it is determined that the remaining transport distance is not 0, the paper discharge roller pair 209 is reversely rotated at the normal speed (S704), and the transport rollers 211a, 211b, and 211c are all normally rotated at the normal speed (S705). Then, the remaining transport distance in the memory 102m is converted into a transport time at normal speed (S706), set in the third timer 102t (S707), and decrementing the third timer 102t is started (S708).

  The registration sensor 110, the pre-fixing sensor 111, and the paper discharge sensor 112 on the conveyance path 201 are monitored (S709), and while the paper is not detected by these sensors, the second timer 102s waits until it becomes zero. (S710). In the meantime, when the third timer 102t becomes 0 (S711), the paper discharge roller pair 209 is rotated forward at normal speed. When the second timer 102s reaches 0, the second timer 102s and the third timer 102t are stopped (S712), and all the transport rollers 211a, 211b, and 211c are stopped (S713), and an image can be formed (S714). .

  If the paper is detected by any of the registration sensor 110, the pre-fixing sensor 111, and the paper discharge sensor 112 before the second timer 102s reaches 0, the second timer 102s and the third timer 102t are set. In addition to stopping (S715), all of the transport rollers 211a, 211b, and 211c are stopped (S716). At the same time, the current remaining time of the decremented third timer 102t is converted into the remaining transport distance that can transport the paper in this remaining time (S717), and the obtained remaining transport distance is stored in the memory 102m (S102). S718).

  If the sheet is detected at a position where it can be forcibly ejected, the sheet is forcibly ejected (S719). On the other hand, if the paper is detected at a position where it cannot be forcibly ejected, the fact that a jam has occurred is displayed on the display panel 118 (S720), and the user is prompted to perform jam processing.

  FIG. 8 is a flowchart showing in more detail step S719 of FIG. First, the decrement of the second timer 102s is started (S801). Regardless of the position on the transport path 201 where the sheet 213 is stopped, the second timer 102s can reliably move the transport rollers 211a, 211b, and 211c out of the color image forming apparatus by driving at normal speed. The time that can be discharged is set. It is determined whether the remaining conveyance distance in the memory 102m is 0 (S802). When it is determined that the remaining transport distance is 0, all of the transport rollers 211a, 211b, and 211c are normally rotated at normal speed (S803). On the other hand, if it is determined that the remaining transport distance is not 0, the paper discharge roller pair 209 is rotated in reverse at normal speed (S804), and the transport rollers 211a, 211b, and 211c are all rotated forward at normal speed (S805). Then, the remaining transport distance in the memory 102m is converted into the remaining transport time at the normal speed (S806), the obtained remaining transport time is set in the third timer 102t (S807), and the decrement of the third timer 102t is started. (S808).

  It waits until the second timer 102s becomes 0 (S809). In the meantime, when the third timer 102t becomes 0 (S810), the paper discharge roller pair 209 is rotated forward at normal speed. When the second timer 102s reaches 0, the second timer 102s and the third timer 102t are stopped (S811), and all the transport rollers 211a, 211b, and 211c are stopped (S812), and an image can be formed (S813). .

  As described above, since a plurality of transport speeds are selected and the remaining paper is detected and forcibly discharged, the paper stopped on the transport path can be reliably detected and discharged in the shortest time.

It is a block diagram which shows the 1st Embodiment of this invention. 1 is a cross-sectional view illustrating a structure of a color image forming apparatus according to a first embodiment. 6 is a flowchart illustrating a control procedure by a conveyance control unit 105 when guiding a sheet to a conveyance path. It is a flowchart which shows step S311 of FIG. 3 in detail. 5 is a flowchart showing step S418 of FIG. 4 in more detail. 6 is a flowchart illustrating a control procedure by a conveyance control unit 105 when guiding a sheet to a conveyance path. It is a flowchart which shows step S612 of FIG. 6 in detail. It is a flowchart which shows step S719 of FIG. 7 in detail.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Color image forming apparatus 102 Control part 102f 1st timer 102m Memory 102s 2nd timer 102t 3rd timer 103 Controller 104 Host computer 105 Conveyance control part 106 Fixing device drive control part 107 Paper feed control part 108 Drum drive control part 109 Cover opening / closing Detection sensor 110 Registration sensor 111 Pre-fixing sensor 112 Paper discharge sensor 113 Conveyance motor 114 Fixing motor 115 Paper feed motor 118 Display panel 201 Conveyance path 205 Registration roller 209 Paper discharge roller 210 Discharge tray 211a, 211b, 211c Conveyance roller 213 Paper 214 Fixing 215a, 215b, 215c, 215d Photosensitive drum 216a, 216b, 216c, 216d Developer 217a, 217b, 217c, 217d Charger

Claims (3)

Image forming means for forming an image on a recording material;
A paper discharge sensor for detecting a recording material on which an image is formed by the image forming means;
A timer that measures the time from when the leading edge of the recording material is detected by the paper discharge sensor to when the trailing edge of the recording material is detected;
A paper discharge roller for discharging the recording material on which the image is formed;
The paper discharge rollers to form the images on the second surface of the recording material on which the image is formed on the first surface, the reverse rotation to reverse the recording material from the forward rotation for discharging the recording material A transfer control unit that switches and reverses the recording material on which the image is formed on the first surface;
The transfer control unit, the recording material on which the image is formed on the first surface Ru is inverted by the sheet discharge rollers are reversely rotated, the recording material to start measuring the time being inverted conveyed by said timer the in the course of being inverted conveyed by the paper discharge roller and that Do the stopped state to stop the time measurement by the timer, when to resume the conveyance of the recording material from the stopped state, the leading end of the recording material is detected recording medium recording material from time to the trailing edge is detected that the image on the first surface are reversed to the paper discharge rollers until the time obtained by subtracting the time being reverse conveyance has passed is formed from When the recording material is subtracted from the time from when the leading edge of the recording material is detected until the trailing edge is detected, the paper discharge roller is rotated forward. An image characterized by switching Forming apparatus. The recording material transport speed when forming an image on the recording material by the image forming means can be switched between a first speed and a second speed that is slower than the first speed,
The conveyance control unit conveys the recording material from a time obtained by subtracting a time during which the recording material is reversely conveyed from a time from when the leading edge of the recording material is detected to when the trailing edge is detected, and a conveying speed of the recording material. The image forming apparatus according to claim 1, wherein a distance is obtained, and a rotation time of the paper discharge roller and the conveyance roller is determined based on the obtained conveyance distance and the first speed.   The image forming apparatus according to claim 1, wherein the stopped state is a state in which the conveyance of the recording material is urgently stopped when an abnormality occurs in the image forming apparatus.

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