JP5723831B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for detecting a recording medium in a conveyance path of the recording medium.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, as shown in Patent Documents 1 and 2 below, the timing for conveying a recording sheet to a transfer position of a toner image by a photosensitive drum and a transfer roller is adjusted, In order to correct the skew of the recording paper, the recording paper is temporarily stopped by a pair of registration rollers provided on the upstream side in the recording paper conveyance direction from the transfer position, and then the recording paper is moved to the transfer position. The technology that feeds paper secondly is adopted. In this case, a timing at which the recording paper reaches the registration roller pair is detected by a registration sensor disposed in the vicinity of the registration roller pair, and the control unit uses this timing to perform secondary paper feeding by the registration roller pair. Control the start timing.

  In a high-speed image forming apparatus with a high printing speed, recording is performed on the conveyance path by irradiating the recording paper conveyed on the conveyance path with light and receiving reflected light from the recording paper as the registration sensor. Many reflective sensors that detect the presence of paper are used. By using a reflective sensor as the resist sensor, unlike actuator sensors, the chattering of the actuator and the time loss required to return the posture of the actuator can be eliminated. Suitable for detection.

JP 2007-137618 A JP 2005-24705 A

  However, when an OHP sheet is used as the recording paper used for image formation, the OHP sheet is transparent, and the portion after the leading edge of the recording paper is likely to flutter. The reflected light is not sufficiently obtained in the portion after the leading edge, and there is a possibility that the timing at which the trailing edge of the recording paper arrives at the position where the reflective sensor is disposed may be erroneously detected. There is a problem in that the control unit erroneously displays a jam according to the recording sheet detection signal from the reflective sensor. In order to solve this problem, after the reflective sensor detects the leading edge of the OHP sheet, the control unit ignores the recording paper detection signal from the reflective sensor for a certain period of time, and after the certain period has elapsed, Control for detecting the trailing edge of the OHP sheet based on the paper detection signal is employed. However, in the case of a high-speed machine, since there is little tolerance in the detection time of the rear end of the OHP sheet, even if this detection method is used, the detection accuracy of the reflection type sensor having the defect due to the above factors still remains. May be erroneously detected.

  The present invention has been made to solve the above-described problem. Even in the case of a high-speed machine having a high printing speed, the present invention can accurately detect both the leading end and the trailing end of a recording medium, and in particular, recording paper. An object of the present invention is to prevent a situation in which a jam of a recording sheet is erroneously detected due to erroneous detection of the trailing edge of the recording sheet regardless of the type of recording sheet.

The invention according to claim 1 of the present invention includes a paper feeding unit that houses a recording medium and feeds the recording medium,
An image forming unit for forming an image by forming a toner image on the surface of the photosensitive drum and transferring the toner image to the recording medium;
A transport path for transporting the recording medium from the paper feed section toward the transfer position of the toner image to the recording medium by the image forming section; and the transfer position in the transport direction of the recording medium by the transport path And a registration roller that adjusts the timing at which the recording medium is conveyed to the transfer position, and a conveyance path that is upstream of the registration roller in the conveyance direction of the recording medium. A reflection type sensor that detects a medium; and an actuator sensor that is provided between the registration roller and the transfer position in the transport path and detects the recording medium transported toward the transfer position by the registration roller. A transport section;
A leading edge detection signal indicating that the leading edge of the recording medium output from the reflective sensor is detected as a jam of the recording medium conveyed by the conveying unit, and the recording medium output from the actuator sensor. A recording medium jam detection unit for detecting using a rear end detection signal indicating that the rear end has been detected;
A toner image to be transferred to the recording medium conveyed by the registration roller is formed on the surface of the photosensitive drum based on a leading end detection signal indicating that the leading end portion of the recording medium output from the actuator sensor is detected. And a control unit that controls the conveyance unit to stop conveyance of the recording medium when the recording medium jam detection unit detects a jam of the recording medium. is there.

  In the present invention, an actuator sensor that detects the recording medium conveyed to the transfer position by the registration roller is provided between the registration roller and the transfer position in the conveyance path, and the control unit is based on a tip detection signal from the actuator sensor. The timing for forming the toner image to be transferred to the recording medium on the surface of the photosensitive drum is adjusted, and the recording medium jam detection unit detects the jam of the recording medium by detecting the leading edge detection signal from the reflection sensor and the actuator. Detection is performed using a rear end detection signal from the sensor. That is, the present invention includes an actuator sensor for adjusting the timing of toner image formation on the surface of the photosensitive drum in accordance with the conveyance state of the recording medium after the secondary conveyance is started by the registration roller, and the actuator sensor outputs The detection signal of the recording paper is also used for jam detection of the recording medium, thereby improving the accuracy of jam detection.

  By performing jam detection in this way, even if the rear end portion of the recording medium conveyed at high speed on the conveyance path flutters and the detection accuracy of the rear end portion by the reflective sensor is lowered, the present invention In the case of a high-speed machine with a high printing speed, the actuator sensor detects the trailing edge of the recording medium and the jam detection unit detects the jam using the trailing edge detection signal from the actuator sensor. Thus, it is possible to accurately detect both the front end portion and the rear end portion of the recording medium, and in particular, it is possible to prevent a situation in which a jam of the recording paper is erroneously detected due to erroneous detection of the rear end portion of the recording paper.

  According to the present invention, it is possible to accurately detect the rear end portion of the conveyed recording medium, not only when the recording medium is plain paper but also when it is a transparent OHP sheet. Since the OHP sheet is transparent, the detection of the rear end portion of the OHP sheet tends to be inaccurate due to the above-mentioned fluttering, particularly in the detection by the reflection type sensor. Since the detection is performed by the actuator sensor, the trailing edge of the recording medium can be accurately detected even when the reflected light from the OHP sheet is insufficient and the fluttering overlaps. .

The invention according to claim 2 is the image forming apparatus according to claim 1, further comprising a type information acquisition unit that acquires type information of a recording medium used for the image formation,
When the type information indicating predetermined special paper is acquired in the type information acquisition unit, the control unit determines the interval in the transport direction between the recording media continuously transported by the transport unit, The distance is set longer than the distance between the reflective sensor and the actuator sensor in the transport direction.

  In the present invention, when the recording medium transported for image formation is a predetermined special paper, the control unit determines the interval in the transport direction between the continuously transported recording media in the reflection direction and the actuator. Since the distance between the sensors is set to be longer than the distance between the sensors, the leading edge of the next recording medium that is subsequently conveyed is detected by the reflective sensor rather than the trailing edge of the recording medium that has been conveyed first is detected by the actuator sensor. The situation of being detected first does not occur.

  When a transparent OHP sheet is used as a recording medium for image formation, the interval between the recording sheets is set larger than that for plain paper in order to increase the detection accuracy by the reflection type sensor. In addition, the setting for increasing the paper interval is not a major factor for reducing the printing efficiency when an OHP sheet is used as a recording medium.

  The invention according to claim 3 is the image forming apparatus according to claim 2, wherein the recording medium jam detection unit receives the type information indicating plain paper in the type information acquisition unit. Is to obtain both the leading edge detection signal and the trailing edge detection signal from the reflective sensor and detect the jam of the recording medium using the leading edge detection signal and the trailing edge detection signal.

  According to the present invention, even when detection is performed by a reflection type sensor, when plain paper that maintains accuracy compared to special paper such as the OHP sheet is used as a recording medium for image formation, recording medium jam detection is performed. Since the head detects jamming of the recording medium using the leading edge detection signal and trailing edge detection signal obtained from the reflection type sensor, it eliminates chattering that is likely to occur by the actuator sensor and the time loss for returning the actuator, so that it It is possible to accurately detect a jam while conveying a recording sheet.

  According to the present invention, even in the case of a high-speed machine with a high printing speed, both the leading edge and the trailing edge of the recording medium are accurately detected, particularly due to erroneous detection of the trailing edge of the recording paper. A situation in which a jam of the recording paper is erroneously detected can be prevented regardless of the recording paper type.

1 is a side view illustrating a schematic mechanical configuration of an image forming apparatus according to an embodiment of the present disclosure. 1 is a block diagram illustrating an example of an electrical configuration of an image forming apparatus. FIG. 6 is a side view illustrating a configuration around a position where a registration roller pair is disposed in a conveyance path. 3 is a flowchart illustrating a first embodiment of operation control during image formation in the image forming apparatus. 3 is a flowchart illustrating a first embodiment of a recording paper jam detection process in the image forming apparatus. (A) is a diagram showing a recording paper detection signal output from a reflective sensor, (B) is a diagram showing a recording paper detection signal output from an actuator sensor, and (C) and (D) are from the actuator sensor when a jam occurs. It is a figure which shows the recording paper detection signal output. It is a figure which shows the recording paper detection signal output from a reflection type sensor, when the reflected light quantity which enters into a light-receiving part is unstable. 10 is a flowchart illustrating a second embodiment of operation control during image formation in the image forming apparatus. 10 is a flowchart illustrating a second embodiment of a recording paper jam detection process in the image forming apparatus.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing a schematic mechanical configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  As an image forming apparatus 1 according to an embodiment of the present invention, FIG. 1 shows an electrophotographic printer.

  An operation unit 47 is provided on the front upper portion of the image forming apparatus 1. The operation unit 47 includes a display unit 473 including an LCD (Liquid Crystal Display) or the like that displays the state of the image forming apparatus 1 and various messages to the operator. The operation unit 47 further includes operation keys 471 for setting the type and size of the recording paper used for image formation, the status of the image forming apparatus 1 (during job execution, jam (paper jam), etc. A lighting unit 472 made up of an LED (Light Emitting Diode) or the like that is turned on or off is provided in order to notify the occurrence of an error (e.g.

  A paper feeding unit 2 is disposed below the inside of the main body 10 of the image forming apparatus 1. The paper feed unit 2 has a detachable paper feed cassette 21 inside the main body 10. In the paper feed cassette 21, a plurality of recording papers P are stacked and stored. Further, the paper feed unit 2 includes a paper feed roller 22. The paper feed roller 22 is in contact with the uppermost recording paper P among the recording paper P stacked in the paper feeding cassette 21 and is rotationally driven by a rotational driving force supplied from a transport motor 34 (FIG. 2) described later. By the rotation driving of the paper feed roller 22, the recording paper P is picked up one by one in order from the highest one and is sent out from the paper feed cassette 21 to the transport path 3.

  The conveyance path 3 is provided from the paper supply unit 2 through the image forming unit 6 and the fixing unit 7 to the discharge tray 74, and guides the recording paper P from the paper supply unit 2 to the discharge tray 74. In the conveyance path 3, a separating roller pair 31, an intermediate roller 4, and a registration roller pair 5 (an example of a registration roller) are disposed on the upstream side of the image forming unit 6 in the conveyance direction of the recording paper P. Each of these rollers and roller pairs conveys the recording paper P received from the paper supply roller 22 toward the image forming unit 6 in the conveyance path 3.

  In addition, a manual feed tray 11 is provided on the front surface of the image forming apparatus 1 so that the side portion of the main body 10 can be freely opened and closed. A plurality of sheets of recording paper P can be placed on the manual feed tray 11 in the open state (the state shown in FIG. 1). A paper feed roller 111 is provided in the main body 10 at a position above the recording paper P placed on the manual feed tray 11. The conveyance path 3 is formed by being connected to the manual feed tray 11 and the paper feed roller 111, and a switching claw 32 is provided at a part where the conveyance path 3 is connected to the manual feed tray 11 and the paper feed roller 111. It has been. Whether the switching claw 32 rotates and changes its orientation so that the recording paper P guided to the position where the image forming unit 6 is disposed in the transport path 3 is the recording paper P transported from the paper feed cassette 21. The recording paper P conveyed from the manual feed tray 11 is switched.

  The intermediate roller 4 further transports the recording paper P that has been transported through the transport path 3 by the pair of rolling rollers 31 toward the registration roller pair 5 and the image forming unit 6.

  The registration roller pair 5 is provided on the upstream side of the transfer position N of the toner image by the image forming unit 6 with respect to the conveyance direction of the recording paper P in the conveyance path 3. The registration roller pair 5 is rotated and stopped by an engine control unit 9 to be described later, and the timing (arrival timing) at which the recording paper P held in the nip portion of the registration roller pair 5 is conveyed to the transfer position N is set. adjust.

  In the conveyance path 3, a reflective sensor 101 is provided as a registration sensor at a position upstream of the registration roller pair 5 and downstream of the intermediate roller 4 in the conveyance direction of the recording paper P. Yes. The reflective sensor 101 is, for example, an optical sensor, and detects the recording paper P that is upstream and in the vicinity of the registration roller pair 5 in the conveyance direction of the recording paper P.

  An actuator sensor 102 is provided at a position upstream of the transfer position N of the image forming unit 6 and downstream of the registration roller pair 5 in the conveyance direction of the recording paper P. The actuator sensor 102 detects the recording paper P conveyed toward the transfer position N by the registration roller pair 5.

  For example, the recording paper detection signal output from the reflective sensor 101, that is, the leading edge detection signal indicating that the leading edge portion of the recording paper P has been detected is used to measure the timing of the rotational driving start of the registration roller pair 5. . A recording paper detection signal (a leading edge detection signal indicating that the leading edge of the recording paper P has been detected) output from the actuator sensor 102 is a timing for starting the formation of a toner image on the surface of the photosensitive drum 61 by the image forming unit 6. Used to measure

  The image forming unit 6 includes a photosensitive drum 61 that rotates at a predetermined speed and carries a toner image. A charging unit 62 disposed on the top of the photoconductive drum 61 charges the surface of the photoconductive drum 61 almost uniformly at a constant potential. An exposure unit 63 is provided on the downstream side of the charging unit 62 in the rotation direction of the surface of the photosensitive drum 61. The exposure unit 63 irradiates the photosensitive drum 61 with a laser beam L based on image data sent from the computer 20 (FIG. 2) or the like connected to the image forming apparatus 1 via a network, thereby exposing the electrostatic latent image. Formed on the surface of the body drum 61.

  A developing unit 64 is provided on the downstream side of the exposure unit 63 in the rotation direction of the surface of the photosensitive drum 61. The developing unit 64 supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 61 to form a toner image. Further, a transfer roller 65 is disposed below the photosensitive drum 61. A transfer bias for transferring a toner image is applied to the transfer roller 65, and the transfer roller 65 is formed on the surface of the photosensitive drum 61 with respect to the recording paper P that has entered the transfer position N that is a nip portion with the photosensitive drum 61. The toner image is transferred.

  A fixing unit 7 is provided on the downstream side in the transport direction of the recording paper P from the transfer position N of the image forming unit 6. The fixing unit 7 includes a heating roller 72 that incorporates a heating element 71 and a pressure roller 73 that presses against the heating roller 72 to form a nip. When the recording paper P carrying the unfixed toner image after the transfer enters the nip portion of the fixing unit 7 by the heating roller 72 and the pressure roller 73, the toner is heated and pressed by the two rollers. The toner of the image is melted and fixed on the recording paper P. The recording paper P after the toner image is fixed is sent upward through the discharge conveyance path 7b, and the recording paper P is moved to the top of the main body by the conveyance roller pair 75 and the discharge roller pair 76 provided in the discharge conveyance path 7b. It is discharged to a discharge tray 74 arranged at the top.

  Next, the electrical configuration of the image forming apparatus 1 will be described. FIG. 2 is a block diagram illustrating an example of an electrical configuration of the image forming apparatus 1.

  As shown in FIG. 2, the image forming apparatus 1 includes a control unit 8 inside. The control unit 8 controls the overall operation of the image forming apparatus 1. The control unit 8 includes a CPU 81, an image processing unit 82, and the like. The control unit 8 is connected to the storage unit 83. The storage unit 83 is a combination of nonvolatile and volatile storage devices such as ROM, RAM, and flash ROM. For example, the storage unit 83 stores a control program, control data, and the like for the image forming apparatus 1. The CPU 81 is a central processing unit, and controls and calculates each unit of the image forming apparatus 1 based on a control program and setting data stored in the storage unit 83.

  The image processing unit 82 is a circuit including an ASIC, an image processing RAM, and the like. The image processing unit 82 performs various image processing such as enlargement, reduction, density conversion, data format conversion, and the like on the image data in accordance with the setting. The image processing unit 82 sends the image data after the image processing to the exposure unit 63. The exposure unit 63 receives this image data, performs scanning and exposure, and forms an electrostatic latent image on the photosensitive drum 61.

  The control unit 8 is connected to the operation unit 47. The control unit 8 accepts an instruction input by an operation of the operation key 471 by the operator on the operation unit 47. Further, the control unit 8 controls display by the display unit 473 of the operation unit 47 and lighting by the lighting unit 472. For example, when an error such as a jam occurs, the control unit 8 turns on the lighting unit 472 and causes the display unit 473 to display a message indicating that an error has occurred.

  The control unit 8 is connected to the interface unit 84. The interface unit 84 is a communication interface for communicating with a computer 20 (for example, a personal computer or a server) that is a transmission source of print data including image data to be printed and setting data for printing via a network or a cable. It is. The image forming apparatus 1 performs printing based on image data and setting data from the computer 20 input to the interface unit 84. The setting data received by the interface unit 84 includes type information indicating the recording paper type (type of plain paper, OHP sheet, etc.) of the recording paper P used for image formation, size information specifying the paper size, and the like. The control unit 8 (which is an example of a type information acquisition unit) receives the setting data from the computer 20 via the interface unit 84, thereby acquiring the type information of the recording paper P used for printing. The size information may be acquired by an operation of the operation key 471 of the operation unit 47 by the operator and the control unit 8 accepting the input size information. The control unit 8 shares the acquired type information of the recording paper P with the engine control unit 9.

  The image forming apparatus 1 is provided with an engine control unit 9 for controlling parts related to image formation (engine unit 90, for example, paper feeding unit 2, conveyance unit 30, image forming unit 6, fixing unit 7). Yes. The engine control unit 9 includes an engine CPU 91, a memory 92, a timer unit 93, and a recording medium jam detection unit 94.

  The engine CPU 91 is an arithmetic processing device that performs calculations and processing based on programs and data in the memory 92. The memory 92 is a ROM or RAM that stores control programs and data related to image formation. The timer 93 measures the time related to control. It is also possible to measure the time with the engine CPU 91 without providing the time measuring unit 93. The recording medium jam detection unit 94 detects a jam of the recording paper P in the conveyance path 3 based on a recording paper detection signal obtained from the reflective sensor 101 and the actuator sensor 102.

  The engine control unit 9 controls the operation of each unit of the engine unit 90 by the engine CPU 91 based on a control program and control data related to printing in the memory 92 so that image formation is appropriately performed. The control unit 8 and the engine control unit 9 in the present embodiment are examples of the control unit in the claims. In the present embodiment, an example is shown in which an engine control unit 9 that controls a part that performs image formation is provided separately from the control unit 8, but the engine control unit 9 and the control unit 8 are integrated and controlled. The unit 8 may execute the function and processing of the engine control unit 9.

  The conveyance unit 30 includes a conveyance path 3, a reflection type sensor 101, an actuator sensor 102, a conveyance motor 34, a registration roller electromagnetic clutch 51, an intermediate roller electromagnetic clutch 41, and a rotation driving force from the conveyance motor 34. , The sheet feeding rollers 22 and 111, the rolling roller pair 31, the intermediate roller 4, the registration roller pair 5, the conveyance roller pair 75, and the discharge roller pair 76.

  The reflective sensor 101 and the actuator sensor 102 are driven under the control of the engine control unit 9 and output the above-described recording paper detection signal to the engine control unit 9.

  The conveyance unit 30 includes a conveyance motor 34, a registration roller electromagnetic clutch 51, and an intermediate roller electromagnetic clutch 41.

  The transport motor 34 is a drive source that supplies rotational driving force to the paper feed rollers 22, 111, the separating roller pair 31, the intermediate roller 4, the registration roller pair 5, the transport roller pair 75, and the discharge roller pair 76. The engine control unit 9 rotates the transport motor 34 such that each pair of rollers such as the registration roller pair 5 and the intermediate roller 4 rotates at a predetermined speed.

  The registration roller electromagnetic clutch 51 switches whether the driving force is transmitted from the transport motor 34 to the registration roller pair 5 and controls the rotation of the registration roller pair 5. When rotating the registration roller pair 5, the engine control unit 9 turns the registration roller electromagnetic clutch 51 into a state of transmitting the driving force (ON state) while rotating the transport motor 34. Thereby, the registration roller pair 5 rotates.

  On the other hand, when stopping the registration roller pair 5, the engine control unit 9 stops the conveyance motor 34 or sets the registration roller electromagnetic clutch 51 to a state where the driving force is not transmitted (off state). As a result, the registration roller pair 5 is stopped.

  The intermediate roller electromagnetic clutch 41 switches the transmission (on) or non-transmission (off) of the driving force from the transport motor 34 to the intermediate roller 4 and controls the rotation of the intermediate roller 4. When rotating the intermediate roller 4, the engine control unit 9 turns on the intermediate roller electromagnetic clutch 41 while rotating the transport motor 34. Thereby, the intermediate roller 4 rotates. On the other hand, when stopping the intermediate roller 4, the engine control unit 9 stops the transport motor 34 or turns off the intermediate roller electromagnetic clutch 41. Thereby, the intermediate roller 4 stops.

  Next, the configuration of the reflective sensor 101 and the actuator sensor 102 will be described. FIG. 3 is a side view illustrating a configuration around the position where the registration roller pair 5 is disposed in the conveyance path 3.

  In the conveyance path 3, a reflective sensor 101 is provided at a position upstream of the registration roller pair 5 and downstream of the intermediate roller 4 in the conveyance direction of the recording paper P. As a registration sensor, the reflective sensor 101 detects the recording paper P that is upstream and in the vicinity of the registration roller pair 5 in the conveyance direction of the recording paper P.

  An actuator sensor 102 is provided at a position upstream of the transfer position N of the image forming unit 6 and downstream of the registration roller pair 5 in the conveyance direction of the recording paper P. The actuator sensor 102 detects the recording paper P conveyed toward the transfer position N by the registration roller pair 5.

  The reflective sensor 101 is, for example, an optical sensor. The reflective sensor 101 includes an LED (Light Emitting Diode) and the like, and a light emitting unit 101a that irradiates light toward the conveyance path 3, and a light emitting unit 101a that includes a photodiode and the like and is reflected by the recording paper P. A light receiving unit 101b that receives the reflected light of the light.

  At the position where the reflective sensor 101 is disposed, in a state where the recording paper P does not pass through the disposed position, the reflected light of the light emitted from the light emitting unit 101a is transmitted to the light receiving unit S2b due to the absence of the recording paper P. Is not received. On the other hand, when the recording paper P passes through the arrangement position of the reflective sensor 101, the light emitted from the light emitting unit 101a is reflected by the recording paper P, and the light receiving unit 101b receives the reflected light.

  The reflective sensor 101 switches the output level (output voltage value) of the recording paper detection signal in accordance with whether the reflected light is received or not received by the light receiving unit 101b. For example, when the light receiving unit 101 b does not receive reflected light, the reflective sensor 101 outputs an off signal (Low signal) as a recording paper detection signal to the recording medium jam detection unit 94. At the time of the light reception, the reflective sensor 101 outputs, for example, an ON signal (High signal) as a recording paper detection signal to the recording medium jam detection unit 94. The recording medium jam detection unit 94 responds to a change in the state of the signal output from the reflective sensor 101 (for example, based on either High or Low, change from High to Low, change from Low to High). Then, the presence or absence of the recording paper P at the position where the reflective sensor 101 is disposed, and the arrival and passage of the leading edge and the trailing edge of the recording paper P are detected.

  The actuator sensor 102 is, for example, a mechanical switch. The actuator sensor 102 includes an actuator 1021 that rotates when pressed by the recording paper P, and outputs an ON signal that indicates the presence of the recording paper P when the contact is closed by the rotation of the actuator due to the pressing. If it is not received, the actuator does not rotate, and when the contact is not closed, an off signal indicating the absence of the recording paper P is output.

  The actuator 1021 of the actuator sensor 102 maintains the posture shown by the solid line in FIG. 3 without being pressed by the recording paper P when the recording paper P has not reached the position where the actuator sensor 102 is disposed. When the actuator 1021 is in the posture, the contact in the actuator sensor 102 is in an open state. On the other hand, when the recording paper P reaches the position where the actuator sensor 102 is disposed and the actuator 1021 is pressed by the recording paper P, the actuator 1021 rotates and changes its posture as shown by a broken line in FIG. . The contact in the actuator sensor 102 is configured to be closed when the actuator 1021 is in the posture.

  The actuator sensor 102 outputs an ON signal (High signal) as a recording paper detection signal indicating that the recording paper P has been detected when the contact is in the closed state, and recording is performed when the contact is in the open state. An off signal (Low signal) is output as a recording paper detection signal indicating that the paper P is not detected.

  The recording medium jam detecting unit 94 detects the presence of the recording paper P at the position where the actuator sensor 102 is disposed in the same manner as in the case of the reflective sensor 101 in response to a change in the state of the recording paper detection signal output from the actuator sensor 102. Alternatively, the absence and the arrival and passage of the leading edge and trailing edge of the recording paper P are detected.

  Next, a first embodiment of operation control during image formation in the image forming apparatus 1 will be described. FIG. 4 is a flowchart illustrating a first embodiment of operation control during image formation in the image forming apparatus 1.

  The image forming operation is started by the control unit 8 and the engine control unit 9 when receiving a print job from the computer 20 connected to the network, for example. At the time of this image forming operation, first, the engine control unit 9 picks up the recording paper P stored in the paper feed cassette 21 one by one by the paper feed roller 22 and feeds the recording paper P to the conveyance path 3. The recording paper P is conveyed toward the image forming unit 2 by the intermediate roller 4 (S1). In the case of continuous printing in which image formation is continuously performed on a plurality of recording sheets P, the engine control unit 9 uses the pair of rolling rollers 31 and the intermediate roller 4 toward the image forming unit 2 to form a plurality of recording sheets P. Are conveyed continuously.

  The engine control unit 9 uses the timing at which the recording paper P is started to be transported to the transport path 3 by the paper feed roller 22, and the predetermined time from the timing (by the roller pair 31, the intermediate roller 4, and the resist roller pair 5). The toner image on the surface of the photosensitive drum 61 is transferred to the recording paper P after the passage (determined based on the recording paper conveyance speed and the distance between the paper feeding unit 2 and the toner image transfer position N). Thus, the toner image formation start timing by the image forming unit 6 of the toner image to be transferred onto the recording paper P is set.

  A recording paper detection signal indicating that the recording paper P started to be conveyed reaches the position where the reflective sensor 101 as the registration sensor is disposed and the reflective sensor 101 has detected the leading end of the recording paper P. Is output to the engine control unit 9 (YES in S2), the time measuring unit 93 starts measuring the time elapsed since the reception of the front end detection signal (S3).

  When the elapsed time is counted by the time measuring unit 93 (YES in S4), the engine control unit 9 turns on the registration roller electromagnetic clutch 51 to transmit the rotational power of the transport motor 34 to the registration roller pair 5. The registration roller pair 5 is rotationally driven (S5).

  This waiting time is the time t1 from the start of conveyance of the recording paper P from the paper supply unit 2 to the set start timing of toner image formation, and the conveyance of the recording paper P from the paper supply unit 2. When the time t3 that is a difference obtained by subtracting the time t2 from the start to the time when the leading edge of the recording paper P is detected by the reflective sensor 101 is smaller than a predetermined time tf, the time from the specified time tf A time t4 that is a difference obtained by subtracting t3 is set as the waiting time. The specified time tf is a time required for the leading edge of the recording paper P to reach the transfer position N from the registration roller pair 5 by conveyance by the registration roller pair 5.

  That is, the engine control unit 9 uses the reception timing of the leading edge detection signal from the reflective sensor 101 to appropriately set the timing at which the leading edge of the recording paper P reaches the toner image transfer position N of the image forming unit 6. Adjust the timing.

  After the engine control unit 9 starts transporting the recording paper P toward the transfer position N of the image forming unit 2 by the registration roller pair 5, the actuator sensor 102 is downstream of the registration roller pair 5 in the recording paper transport direction. When the leading edge of the recording paper P is detected and the engine control unit 9 receives a leading edge detection signal as a recording paper detection signal indicating that the leading edge of the recording paper P has been detected from the actuator sensor 102 (YES in S6). The engine control unit 9 adjusts the toner image formation start timing on the photosensitive drum 61 by the image forming unit 6 using the reception timing of the leading edge detection signal. In the present embodiment, the engine control unit 9 causes the image forming unit 6 to start forming a toner image on the surface of the photosensitive drum 61 when receiving the tip detection signal from the actuator sensor 102 (YES in S6, S7). ).

  The engine control unit 9 uses the registration roller pair 5 to transfer the recording paper P to the toner image transfer position N of the image forming unit 6, that is, the recording paper P conveyed between the photosensitive drum 61 and the transfer roller 65. The toner image on the surface of the photosensitive drum 61 is transferred by the transfer roller 65 (S8). Similarly, the processing of S2 to S8 is performed on each recording sheet P that is continuously conveyed between the photosensitive drum 61 and the transfer roller 65, and the toner images on the photosensitive drum 61 are sequentially transferred. Is done.

  The engine control unit 9 causes the recording paper P, on which image formation in the image forming unit 6 has been completed, to pass through the fixing unit 7 and then is discharged onto the discharge tray 74 by the transport roller pair 75 and the discharge roller pair 76.

  Next, a first embodiment of recording paper jam detection processing in the image forming apparatus 1 will be described. FIG. 5 is a flowchart showing a first embodiment of a recording paper jam detection process in the image forming apparatus 1. 6A is a diagram showing a recording paper detection signal output from the reflective sensor 101, FIG. 6B is a diagram showing a recording paper detection signal output from the actuator sensor 102, and FIGS. 6C and 6D are jam occurrences. 4 is a diagram illustrating a recording paper detection signal that is sometimes output from an actuator sensor 102. FIG. Note that the recording paper jam detection process is performed in parallel with the above-described operation control during image formation.

  At the time of image formation execution, as described above, after the engine control unit 9 starts conveying the recording paper P stored in the paper feed cassette 21 toward the image forming unit 6 (S11), the reflective sensor 101 is When a leading edge detection signal indicating that the leading edge of the recording paper P has been detected is output to the engine control unit 9 (YES in S12), the timer 93 starts to count the time elapsed since the leading edge detection signal was received. (S13). The timekeeping by the timekeeping unit 93 may be performed in conjunction with the timekeeping of S3 in FIG. 4 or may be performed separately from the timekeeping of S3 in FIG.

  The recording medium jam detection unit 94 of the engine control unit 9 as a recording sheet detection signal indicating that the trailing edge of the recording sheet P has been detected from the actuator sensor 102 during a predetermined time period measured by the timing unit 93. It waits for the rear end detection signal to be output (NO in S14, S17). During this predetermined time, after the leading end of the recording paper P being conveyed reaches the arrangement position of the reflective sensor 101 in the conveying path 3, the trailing edge of the recording paper P is the actuator sensor. This is the time required to reach the position 102. For example, for this predetermined time, the distance in the recording sheet conveyance direction (for example, 297 mm in the case of A4 size) indicated by the sheet size of the recording sheet P applied to the current image formation is recorded by the conveyance unit 30. It is calculated by dividing by the conveyance speed of P.

  Here, when the recording medium jam detection unit 94 receives the rear end detection signal from the actuator sensor 102 before the elapsed time of the predetermined time is measured by the time measuring unit 93 (NO in S14), YES in S17. ), The process ends without determining that the recording paper jam has occurred. Thereafter, the processes of S12 to S17 are repeated for all the recording sheets P until the image formation by the image forming unit 6 is completed.

  On the other hand, if the recording medium jam detection unit 94 does not receive the rear end detection signal from the actuator sensor 102 even when the predetermined time has elapsed by the time measuring unit 93 (NO in S17, YES in S14), In order to indicate that the trailing edge of the recording paper P has not arrived at the position where the actuator sensor 102 has been disposed even after an appropriate time has elapsed, the recording medium jam detection unit 94 causes the recording paper P to jam. (S15). After the jam detection, the engine control unit 9 stops the image formation by the image forming unit 6 and the conveyance operation of the recording paper P by the conveyance unit 30 (S16). Thereafter, the image forming apparatus 1 enters a standby mode in which the operator waits for the jam to be cleared.

  For example, when a plurality of recording sheets P are continuously conveyed and no jam occurs in the conveying path 3, the recording medium detection signal from the reflective sensor 101 in the recording medium jam detection unit 94 is as follows. FIG. 6A shows the result. That is, the recording paper P exists at the position where the reflective sensor 101 is disposed, the light reflected by the recording paper P of the light emitted from the light emitting unit 101 a is received by the light receiving unit 101 b, and a high signal is received from the reflective sensor 101. An output H (high) period T1 (time t11) and a period from when the recording sheet P passes to the next recording sheet P being conveyed to the position where the reflective sensor 101 is disposed, that is, the light receiving unit. An L (low) period T2 (time t12) in which 101b cannot receive the reflected light and a Low signal is output periodically occurs. The time t11 is a value determined according to the length of the recording paper P in the conveyance direction and the conveyance speed of the recording paper P.

  The reception state of the recording paper detection signal from the actuator sensor 102 by the recording medium jam detection unit 94 is as shown in FIG. 6B when a jam does not occur in the conveyance path 3. That is, when the recording paper P reaches the position where the actuator sensor 102 is disposed, the front end of the recording paper P is pressed by the recording paper P and rotated to close the contact, and the high signal is output H (high). ) Period T3 (time t13) and a period from when the recording sheet P passes the position where the actuator sensor 102 is disposed to the next recording sheet P is conveyed to the position where the actuator sensor 102 is disposed, that is, recording. The paper P does not press the actuator 1021, the contact is opened, and an L period T4 (time t14) in which a Low signal is output periodically occurs. The time t13 is determined according to the length in the conveyance direction of the recording paper P and the conveyance speed of the recording paper P.

  In this case, the recording medium jam detection unit 94 receives the leading edge detection signal (the rising edge E1 shown in FIG. 6A) from the reflective sensor 101, and then the trailing edge detection signal (FIG. 6) by the actuator sensor 102. When the time t15 measured by the time measuring unit 93 until the time when the falling edge E2) shown in (B) is received is within the predetermined time, it is determined that no jam has occurred. .

  On the other hand, when a jam occurs, the recording paper P stays at the position where the actuator sensor 102 is disposed for the time t13 or more. For example, as shown in FIG. A signal of H (high) for a period equal to or greater than t13 is continuously output to the recording medium jam detection unit 94. If a jam occurs when the leading edge of the recording paper P has not reached the position where the actuator sensor 102 is disposed, for example, as shown in FIG. Only the low signal is output to the recording medium jam detection unit 94.

  When the recording medium jam detection unit 94 receives the recording paper detection signal shown in FIGS. 6C and 6D from the actuator sensor 102, the timer 93 counts the predetermined time. Since the trailing edge detection signal has not been received from the actuator sensor 102 by the time, the recording medium jam detection unit 94 determines that a jam has occurred.

  In the case where some trouble occurs in the reflective sensor 101, a situation in which the recording paper P is not accurately detected may occur. For example, when the fluttering of the recording paper P being conveyed is large, it is assumed that the leading edge of the recording paper P has relatively small fluttering, so that the light receiving unit 101b of the reflective sensor 101 sufficiently reflects the reflected light of the recording paper P. Although the light can be received, the amount of reflected light entering the light receiving unit 101b is not stable in the portion after the leading end where the flicker is relatively large, and there may be a time period during which the reflected light from the recording paper P cannot be received sufficiently. . FIG. 7 is a diagram illustrating a recording sheet detection signal output from the reflective sensor when the amount of reflected light entering the light receiving unit 101b is unstable. For example, as shown in FIG. 7, even if the recording paper P is present and a high signal should be output, a signal such as a low signal is generated and a signal output from the reflective sensor 101 is generated. The waveform may be distorted. In this case, since a plurality of Low signals may be received before the predetermined time elapses, the recording paper is detected based on the recording paper detection signal from the light receiving unit 101b of the reflective sensor 101. When the rear end of P is detected, the recording medium jam detection unit 94 may not accurately detect the presence or absence of a jam.

  However, in the present embodiment, as described above, the recording medium jam detection unit 94 uses the rear end detection signal from the actuator sensor 102 to detect the rear end of the recording paper P. It can be detected accurately. Even if the recording paper P is fluttered as described above, the pressure applied to the actuator 1021 by the recording paper P is reliably released by the passage of the recording paper P. Therefore, according to the actuator sensor 102, the recording paper can be accurately detected. This is because the rear end portion of P is detected.

  In addition, when the trailing edge detection signal from the actuator sensor 102 is used, since the adverse effect on the recording sheet detection signal due to the flapping of the recording sheet P is extremely small, the recording medium jam detection is performed before the predetermined time has elapsed. Even if the unit 94 receives the High signal, the rear end detection signal is highly reliable. For this reason, according to the jam detection according to the present embodiment, even when the recording paper P having a size different from the size of the recording paper P indicated by the setting data (different length in the transport direction) is transported, the recording paper is accurately detected. The leading edge and the trailing edge of P can be detected to perform jam detection with high accuracy. Note that the situation in which the recording paper P having a size different from the size of the recording paper P indicated by the setting data is conveyed to the manual feed tray 11 by a different size from the recording paper size indicated by the setting data. This may occur when the recording paper P is placed and used for image formation.

  As described above, in this embodiment, after secondary conveyance of the recording paper P to the transfer position N by the registration roller pair 5 is started, toner image formation on the surface of the photosensitive drum 61 corresponding to the conveyance state of the recording paper P is performed. The trailing edge detection signal output from the actuator sensor 102 for timing adjustment is also used for jam detection of the recording paper P, thereby improving the accuracy of jam detection.

  By performing the jam detection in this way, even if the rear end portion of the recording medium P conveyed at high speed on the conveyance path flutters and the detection accuracy of the rear end portion by the reflective sensor is lowered, In the present invention, the rear end portion of the recording medium P is detected by the actuator sensor 102, and the recording medium jam detection unit 94 detects the jam using the rear end detection signal from the actuator sensor 102. Therefore, the printing speed is high. Even in the case of a printing machine, both the leading edge and the trailing edge of the recording medium P are accurately detected, and in particular, the recording paper jam is erroneously detected due to the erroneous detection of the trailing edge of the recording paper P. Can be prevented.

  According to this embodiment, not only when the recording paper P is plain paper, but also when the recording paper P is a transparent OHP sheet, it is possible to accurately detect the rear end portion of the recording paper P being conveyed. Since the OHP sheet is transparent, detection of the rear end portion of the OHP sheet is likely to be inaccurate due to the above-mentioned fluttering, particularly in the detection by the reflective sensor 101. Since the detection of the edge is performed by the actuator sensor 102, the trailing edge of the recording paper P is accurately detected even when the reflected light from the OHP sheet is insufficient and the flickering overlaps. Can be detected.

  In this way, since the recording medium jam detection unit 94 detects a jam using the trailing edge detection signal output from the actuator sensor 102, the leading edge of the recording paper P is used even in the case of a high-speed machine with a high printing speed. It is possible to accurately detect both the front and rear end portions, and in particular, it is possible to prevent a situation in which a jam of the recording paper is erroneously detected due to erroneous detection of the rear end portion of the recording paper P.

  Next, a second embodiment of operation control during image formation in the image forming apparatus 1 will be described. FIG. 8 is a flowchart illustrating a second embodiment of operation control during image formation in the image forming apparatus 1. Note that the description of the same processing as in the first embodiment is omitted.

  In the second embodiment, the engine control unit 9 adjusts the interval (interval) between the recording sheets P during continuous printing according to the type of the recording sheet P that is set.

  When the engine control unit 9 receives a print job from the computer 20 connected to the network, the engine control unit 9 acquires the recording sheet type of the recording sheet P used for the current image formation from the type information included in the setting data of the print job. (S21). If the acquired recording sheet type indicates an OHP sheet (YES in S22), the engine control unit 9 sets the distance between the recording sheets P during continuous printing as the distance for the OHP sheet (S23). On the other hand, when the acquired size information indicates plain paper (NO in S22), the engine control unit 9 sets the distance between the recording papers P during continuous printing to the distance for plain paper (S32). The OHP sheet is an example of predetermined special paper.

  Since the OHP sheet is transparent, depending on the reflective sensor 101, the reflected light from the recording paper P is less than in the case of plain paper. For this reason, the engine control unit 9 sets the gap between the OHP sheets to be larger than the gap between the plain papers in order to increase the accuracy in detecting the leading edge of the recording paper P by the reflective sensor 101. The gap between the OHP sheets is set according to the accuracy of the reflective sensor 101, but the engine control unit 9 determines whether the gap between the OHP sheets is the reflective sensor 101 in the conveyance direction of the recording paper P and A distance longer than the distance between the actuator sensors 102 is set.

  On the other hand, in the case of plain paper, there is no problem as in the case of the OHP sheet. Therefore, the gap between plain papers is set smaller than that in the case of OHP sheets. The space between the plain papers is preferably set as small as possible according to the accuracy of the reflective sensor 101.

  After setting the sheet interval according to the recording sheet type, S24 to S31, which are the same processes as S1 to S8 of the first embodiment, are performed.

  Further, as the jam detection process performed in parallel with the image formation control according to the second embodiment, any one of the jam detection process according to the first embodiment described above and the jam detection process according to the second embodiment described later. Is also applicable.

  In the above description, only two types of OHP sheet and plain paper are described as recording paper types. However, the engine control unit 9 further sets different paper intervals according to other recording paper types. It is good.

  According to the image forming control according to the second embodiment, when the recording paper P transported for image formation is an OHP sheet, the engine control unit 9 records the above-described recording between the continuously transported OHP sheets. In order to set the interval in the transport direction of the paper P to a distance longer than the distance between the reflective sensor 101 and the actuator sensor 102, the actuator sensor 102 detects the rear end portion of the recording paper P transported first. In addition, the situation in which the leading end portion of the next recording paper P to be subsequently conveyed is detected first by the reflective sensor 101 does not occur.

  When a transparent OHP sheet is used as the recording paper P, the interval between the recording papers P is larger than that of plain paper in order to increase the detection accuracy of the leading end of the recording paper P by the reflective sensor 101. Therefore, the setting for increasing the paper gap as described above does not become a major factor for reducing the printing efficiency when the OHP sheet is used as the recording paper P.

  Next, a second embodiment of the recording paper jam detection process in the image forming apparatus 1 will be described. FIG. 9 is a flowchart illustrating a second embodiment of the recording paper jam detection process in the image forming apparatus 1. Note that the description of the same processing as in the first embodiment is omitted.

  In the second embodiment, when the acquired recording paper type is plain paper (NO in S41), the leading edge detection signal from the reflective sensor 101 is used for the leading edge of the recording paper P. (S50) As for the rear end portion of the recording paper P, the rear end detection signal (E3 shown in FIG. 6A) indicating that the rear end portion is detected from the reflective sensor 101 is used (S52, S53). ), Jam detection is performed (S46). Note that jam detection is performed in the same manner as in the first embodiment except that the trailing edge detection signal from the reflective sensor 101 is used to detect the trailing edge of the recording paper P.

  On the other hand, when the acquired type of the recording paper P is an OHP seed (YES in S41), the recording medium jam detecting unit 94 is a reflection type for the leading end of the recording paper P as in the first embodiment. A recording paper detection signal indicating that the leading edge of the recording paper P has been detected from the sensor 101 is used (S43), and the trailing edge of the recording paper P is detected from the actuator sensor 102 for the trailing edge of the recording paper P. Jam detection is carried out (S46) using a recording paper detection signal indicating that this has occurred (S45, S48).

  According to the second embodiment, even when detection is performed by the reflective sensor 101, plain paper that maintains accuracy in the detection result compared to special paper such as an OHP sheet is used as the recording paper P for image formation. When used, the recording medium jam detection unit 94 detects the jam of the recording paper P by using the leading edge detection signal and the trailing edge detection signal obtained from the reflective sensor 101, so that the chattering that is likely to occur by the actuator sensor 102 is detected. In addition, it is possible to detect a jam with high accuracy while transporting the recording paper at high speed while omitting the time loss for returning the actuator 1021.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above-described embodiment, an example in which the image forming apparatus according to the present invention is a printer has been described. However, the image forming apparatus according to the present invention is not limited to this, and other types such as a copier, a facsimile machine, and a multi-function machine can be used. It may be an image forming apparatus.

  The configurations and processes shown in the above embodiments using FIGS. 1 to 9 are only one embodiment of the present invention, and are not intended to limit the present invention to the configurations and processes.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed part 3 Conveyance path 4 Intermediate roller 5 Registration roller pair 6 Image forming part 7 Fixing part 8 Control part 9 Engine control part 30 Conveyance part 61 Photosensitive drum 65 Transfer roller 94 Recording medium jam detection part 47 Operation Unit 471 operation key 472 lighting unit 473 display unit 101 reflection type sensor 101a light emitting unit 101b light receiving unit 102 actuator sensor 1021 actuator P recording paper

Claims (3)

A paper feeding unit that houses the recording medium and feeds the recording medium;
An image forming unit for forming an image by forming a toner image on the surface of the photosensitive drum and transferring the toner image to the recording medium;
A transport path for transporting the recording medium from the paper feed section toward the transfer position of the toner image to the recording medium by the image forming section; and the transfer position in the transport direction of the recording medium by the transport path And a registration roller that adjusts the timing at which the recording medium is conveyed to the transfer position, and a conveyance path that is upstream of the registration roller in the conveyance direction of the recording medium. A reflection type sensor that detects a medium; and an actuator sensor that is provided between the registration roller and the transfer position in the transport path and detects the recording medium transported toward the transfer position by the registration roller. A transport section;
A leading edge detection signal indicating that the leading edge of the recording medium output from the reflective sensor is detected as a jam of the recording medium conveyed by the conveying unit, and the recording medium output from the actuator sensor. A recording medium jam detection unit for detecting using a rear end detection signal indicating that the rear end has been detected;
A toner image to be transferred to the recording medium conveyed by the registration roller is formed on the surface of the photosensitive drum based on a leading end detection signal indicating that the leading end portion of the recording medium output from the actuator sensor has been detected. And a control unit that controls the conveyance unit to stop conveying the recording medium when a jam of the recording medium is detected by the recording medium jam detection unit. A type information acquisition unit for acquiring type information of a recording medium used for the image formation;
When the type information indicating predetermined special paper is acquired in the type information acquisition unit, the control unit determines the interval in the transport direction between the recording media continuously transported by the transport unit, The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be longer than a distance between the reflective sensor and the actuator sensor in a transport direction.   The recording medium jam detection unit obtains both the leading edge detection signal and the trailing edge detection signal from the reflective sensor when the classification information indicating the plain paper is acquired in the classification information acquisition unit, The image forming apparatus according to claim 2, wherein a jam of the recording medium is detected using a leading edge detection signal and a trailing edge detection signal.