JP2006347698A - Image forming device and conveyance position detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify the position of a recording medium being conveyed inside a device without providing a plurality of detecting sensors. <P>SOLUTION: The image forming device 1 is provided with a control part 10, feeding cassettes 440 to 442, detecting sensors 510 to 512, and a motor 502. Timing when paper is conveyed from the feeding cassettes 440 to 442 are detected by the detecting sensors 510 to 512. The control part 10 measures the conveying time of the paper based on the timing and monitors overload of the motor 502 upon conveying the paper. Based on the conveying time of the paper at the time of detecting the overload of the motor 502, the position in a conveyance passage 6 where the paper is stuck is specified. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for conveying a recording medium in an image forming apparatus that records an image on the recording medium. More specifically, the present invention relates to a technique for specifying the position of a recording medium to be conveyed.

  Conventionally, in an apparatus for recording an image at a predetermined position in the apparatus while conveying a sheet-like recording medium, an overload of a motor for conveying the recording medium is detected, and a jam (paper jam or the like is conveyed) An apparatus for detecting the occurrence of (abnormal) has been proposed. Such an apparatus is described in Patent Document 1, for example.

JP 11-059969 A

  However, the apparatus described in Patent Document 1 has a problem that the position of the recording medium in the apparatus cannot be specified unless a large number of detection sensors for detecting the recording medium are provided along the conveyance path. .

  For example, in the apparatus described in Patent Document 1, when a recording medium is jammed on the transport path in the apparatus (when a jam occurs), it is possible to detect this. However, the jammed recording medium must be removed by the operator. When the recording medium is to be removed, the operator needs to confirm by observing the inside of the apparatus where the recording medium is jammed, which is a burdensome operation for the operator. Furthermore, recently, an apparatus that can be observed only from the front side of the apparatus has appeared, called front access, and it is more difficult for an operator to find a recording medium in the apparatus.

  Therefore, the apparatus described in Patent Document 1 requires a large number of detection sensors in order to identify the position of the recording medium to be removed and inform the operator.

  The present invention has been made in view of the above problems, and an object of the present invention is to specify the position of a recording medium conveyed in the apparatus without providing a large number of detection sensors.

  In order to solve the above problems, an invention according to claim 1 is an image forming apparatus for forming an image on a recording medium, the conveying means for conveying the recording medium along the conveying path, and the passage of time from a predetermined time point. Position specifying that specifies the position of the recording medium on the transport path based on the time measuring means for measuring the time, the elapsed time measured by the time measuring means, and the transport speed of the recording medium by the transport means Means.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the invention, the predetermined time point includes a time point when the conveying unit starts conveying the recording medium.

  According to a third aspect of the invention, there is provided the image forming apparatus according to the first or second aspect of the invention, wherein the recording medium is detected by the conveying means at a predetermined position on the conveying path. And the predetermined time point includes a time point when the recording medium is detected by the medium detection means.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to third aspects, wherein the position of the recording medium specified by the position specifying unit is displayed on the transport path. The apparatus further comprises means.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to fourth aspects of the present invention, wherein when the conveying means is conveying the recording medium, the conveying means is overloaded. An abnormality monitoring means for monitoring is further provided, wherein the position specifying means specifies the position of the recording medium on the transport path when the overload is detected by the abnormality monitoring means.

  According to a sixth aspect of the present invention, there is provided a recording medium conveyance position detection method in an image forming apparatus, wherein (a) a conveyance unit conveys a recording medium along a conveyance path, and (b) from a predetermined time point. Measuring the elapsed time of the recording medium, and (c) identifying the position of the recording medium on the transport path based on the measured elapsed time and the transport speed of the transported recording medium. It is characterized by having.

  The invention of claim 7 is the transport position detecting method according to the invention of claim 6, wherein (d) when the transport means transports the recording medium, the overload of the transport means is monitored. The step (c) is a step of specifying the position of the recording medium on the transport path when the overload is detected in the step (d). And

  According to the first to seventh aspects of the present invention, for example, an optical sensor is not provided by specifying a position on the recording medium conveyance path based on the measured elapsed time and the recording medium conveyance speed. In addition, the position of the recording medium can be specified.

  According to the third aspect of the present invention, the position of the recording medium can be accurately determined even when the conveyance path is relatively long by detecting the recording medium conveyed by the conveyance means at a predetermined position on the conveyance path. Can be specified.

  According to the fourth aspect of the invention, by displaying the position on the transport path of the recording medium specified by the position specifying means, it is possible to easily inform the operator of the position on the transport path of the recording medium.

  According to the fifth and seventh aspects of the present invention, when the recording medium is conveyed, the position of the sheet to be removed can be specified by monitoring the overload of the conveying means, thereby reducing the burden on the operator. can do.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

<1. Embodiment>
FIG. 1 is a schematic view of an image forming apparatus 1 according to the present invention. FIG. 2 is a block diagram illustrating a connection state of each component of the image forming apparatus 1.

  The image forming apparatus 1 includes a control unit 10, a communication unit 20, a scanner unit 30, and a printer unit 40. By providing these configurations, the image forming apparatus 1 is configured as a multifunction machine having functions such as a printing apparatus, a copying machine, and a FAX apparatus. In the following description, the image forming apparatus 1 will be described using an example in which paper (paper) is used as a recording medium. However, the recording medium of the present invention is not limited to “paper”, and may be, for example, “plate”. There may be.

  The control unit 10 is provided inside the image forming apparatus 1, and is used as an MPU 100 that performs predetermined calculations by operating according to a program, a flash memory 101 that mainly stores a program, and a working area of the MPU 100. RAM 102 and image memory 103 in which image data is stored. The RAM 102 also stores user data and the like in the image forming apparatus 1 and is backed up by a battery so that the stored contents are not erased. Further, the flash memory 101 may be substituted by a read-only ROM, for example.

  Moreover, the control part 10 is provided with the function to measure time based on a clock signal (reset signal), and can measure the elapsed time from a predetermined timing. Such a timer function may be realized separately by hardware.

  Further, the control unit 10 includes an operation panel 104 for an operator to input instructions, a codec 105 that is dedicated hardware for executing predetermined data conversion processing (data compression and the like), and a display unit that displays various data. 106.

  The operation panel 104 corresponds to various buttons arranged on the panel, but a mouse or a keyboard may be separately connected. In other words, any operation panel 104 may be employed as long as an operator instruction can be input to the image forming apparatus 1.

  The codec 105 is dedicated hardware that mainly compresses and decompresses image data. For example, if the image data is stored in the image memory 103 in the bitmap format, the amount of data becomes enormous. Therefore, in the image forming apparatus 1, the image data is compressed by the codec 105 and then stored in the image memory 103.

  When printing the image data on paper, the compressed image data is read from the image memory 103, decompressed, and output to the printer image processing circuit 400. In the image forming apparatus 1 according to the present embodiment, the image data may be data read by the scanner unit 30, for example, data received by the communication unit 20 via a network (so-called FAX data or print data). Etc.).

  The display unit 106 is a touch panel type liquid crystal display, and displays various data on the screen to the operator in accordance with a control signal from the MPU 100. Although details will be described later, the position of the sheet in the image forming apparatus 1 is displayed on the display unit 106. As a result, for example, when the paper is jammed during conveyance, the operator can easily confirm the position where the jam has occurred, so that the paper can be removed.

  The display unit 106 may be capable of inputting various instructions by an operator touching the screen. In that case, the display unit 106 has a part of the function of the operation panel 104.

  The communication unit 20 includes an NCU 200 that controls communication with the network, and a modem 201 that performs A / D conversion of data and the like. With such a configuration, the communication unit 20 realizes data communication, FAX communication, and the like between the image forming apparatus 1 and another apparatus connected to the network. Note that the network connected to the communication unit 20 includes a public line network, a FAX communication network, a packet communication network, a LAN, the Internet, and the like.

  The scanner unit 30 includes a scanner mechanism control unit 300, a motor driver 301, a motor 302, a CCD 303, and a scanner image processing circuit 304.

  The scanner mechanism control unit 300 controls the motor 302 via the motor driver 301. The motor 302 conveys the document to the reading position of the CCD 303 by rotating a conveyance roller (not shown). That is, the motor 302 conveys the document to the reading position of the CCD 303.

  The CCD 303 optically reads an image recorded on a document and transmits an electrical signal to the scanner image processing circuit 304. The scanner image processing circuit 304 generates image data based on an input signal from the CCD 303 and stores it in the image memory 103.

  The printer unit 40 includes a printer image processing circuit 400, a transfer unit 42, and a fixing unit 43 as a configuration for printing (recording) an image on a sheet.

  The printer image processing circuit 400 performs predetermined processing on the image data expanded by the codec 105 and outputs the processed image data to the LED print head 420 as shown in FIG. That is, the printer image processing circuit 400 functions as hardware for high-speed processing of image data for each pixel.

  The transfer unit 42 includes an LED print head 420, a photosensitive drum 421, a developing roller 422, and a transfer roller 423.

  The LED print head 420 sensitizes the cylindrical surface of the photosensitive drum 421 by blinking an LED (not shown) in accordance with an electric signal input from the printer image processing circuit 400. In this way, the LED print head 420 forms an electrostatic latent image on the cylindrical surface of the photosensitive drum 421.

  The photosensitive drum 421 is a cylindrical member in which a layer of a photosensitive material is formed on a cylindrical surface, and is configured to rotate around a cylindrical axis by a driving mechanism (not shown). The developing roller 422 develops the electrostatic latent image formed on the photosensitive drum 421. Further, the transfer roller 423 transfers toner to the paper based on the developed visible image.

  With such a configuration, the transfer unit 42 has a function of transferring the toner to the printing surface of the paper in accordance with the image pattern.

  A sheet is conveyed from the transfer unit 42 to the fixing unit 43. As described above, the toner is transferred to the sheet conveyed to the fixing unit 43 by the transfer unit 42. The fixing unit 43 melts the toner on the paper transported by heating and welds it to the paper by pressure. Thus, the fixing unit 43 has a function of fixing the toner to the paper.

  In addition, the printer unit 40 includes a paper feed unit 44 and a discharge unit 45. The sheet feeding unit 44 includes sheet feeding cassettes 440 to 442, and sheets for recording images are set in the sheet feeding cassettes 440 to 442, respectively. Papers of different sizes and colors are set in the paper feed cassettes 440 to 442. Of course, the same type of paper may be set. The discharge unit 45 is a mechanism for finally discharging the sheet after the image is recorded out of the apparatus.

  The number of paper feed cassettes provided in the paper feed unit 44 is not limited to three. Further, instead of automatically feeding paper from the paper feed cassettes 440 to 442, for example, a configuration (manual feed) in which an operator manually feeds the image forming apparatus 1 onto a tray may be employed.

  Further, the printer unit 40 includes a transport unit 50 for transporting a sheet on which an image is recorded by the image forming apparatus 1 along the transport path 6.

  The transport unit 50 includes a print mechanism control circuit 500, a motor driver 501, and a motor 502. The transport unit 50 includes a plurality of pickup rollers 503 to 505, a plurality of transport rollers 506 to 509, and a plurality of detection sensors 510 to 514 along the transport path 6. With such a configuration, the transport unit 50 transports the paper from the paper feed unit 44 to the discharge unit 45.

  The print mechanism control circuit 500 controls the rotation of the motor 502 via the motor driver 501 while transmitting and receiving control signals to and from the MPU 100. Further, overload of the motor 502 is monitored via the motor driver 501, and when this is detected, the MPU 100 is notified of the detection result. More specifically, the value of the current supplied to the motor 502 is monitored, and it is determined that an overload is detected when the current value rises above a predetermined value (set value).

  The print mechanism control circuit 500 controls the rotation of the pickup rollers 503 to 505. Further, the detection result of the paper is transmitted to the MPU 100 according to the output of the detection sensors 510 to 514.

  The motor 502 generates a driving force for conveying the paper. The driving force generated by the motor 502 is transmitted to the transport rollers 506 to 509 via various link members. The motor 502 is an electric motor that is rotated by being supplied with electric power from a power source (not shown), and has a characteristic that the current value increases when torque is increased due to overload. Therefore, if the rotation of the transport rollers 506 to 509 is hindered due to a paper jam or the like, the current value of the motor 502 increases, and the print mechanism control circuit 500 can detect the occurrence of a jam.

  The pickup rollers 503 to 505 are provided corresponding to the paper feed cassettes 440 to 442, respectively, and have a function of taking out paper from each of the paper feed cassettes 440 to 442 by rotation. For example, when the pickup roller 503 rotates once, one sheet in the sheet feeding cassette 440 is sent out toward the transport path 6. In other words, depending on which of the pick-up rollers 503 to 505 is selected by the print mechanism control circuit 500, it is determined from which of the paper feed cassettes 440 to 442 the sheet is fed.

  The conveyance rollers 506 to 509 are rollers to which the driving force generated by the motor 502 is transmitted, and are provided along the conveyance path 6. In the image forming apparatus 1, the paper is transported along the transport path 6 by transporting the paper by the transport rollers 506 to 509.

  In the present embodiment, the transport rollers 506 and 507 are disposed in the paper feed unit 44, and the transport roller 508 is disposed in the main body 2 and on the front side of the transfer unit 42. Further, the transport roller 509 is disposed in the discharge unit 45.

  For convenience of illustration, in FIG. 1, four (four pairs) transport rollers 506 to 509 are shown with the same size, but the number of transport rollers is not limited to this, and the same It is not limited to the size and shape.

  The detection sensors 510 to 514 are optical sensors that emit light in a predetermined direction and are turned on when the light is blocked to detect the presence of an object (paper). The detection sensors 510 to 514 are arranged at predetermined positions along the conveyance path 6 and transmit the detection result (ON / OFF state) to the print mechanism control circuit 500. As a result, the image forming apparatus 1 can detect a sheet at a location where the detection sensors 510 to 514 are disposed. Therefore, it is possible to detect whether or not the transported paper has passed the place where each of the detection sensors 510 to 514 is disposed, and the timing of the passage.

  In the present embodiment, the detection sensor 510 is disposed in the vicinity of the outlet of the paper feed cassette 442 in order to detect that the paper is carried out from the paper feed cassette 442. Similarly, the detection sensors 511 and 512 are arranged near the outlets of the paper feed cassettes 441 and 440, respectively. The detection sensor 513 is disposed in front of the transfer unit 42 in the main body 2, and mainly detects that the sheet is conveyed to the transfer unit 42. Further, the detection sensor 514 is disposed in the vicinity of the exit of the fixing unit 43 and mainly detects that the sheet is carried out of the fixing unit 43.

  The number of optical sensors included in the image forming apparatus 1 is not limited to five, and the arrangement position is not limited to the position shown in FIG.

  3 to 8 are flowcharts showing the operation of the image forming apparatus 1 in the present embodiment. 3 to 8 mainly show processing related to the sheet transport operation among the operations of the image forming apparatus 1. Hereinafter, an example in which the transport unit 50 transports the sheets stored in the paper feed cassette 442 will be described.

  In the image forming apparatus 1, first, the rotation of the motor 502 is started (step S11). As described above, the image forming apparatus 1 conveys a sheet on which an image is recorded by the driving force of the motor 502. When step S11 is executed, the driving force of the motor 502 is transmitted to the transport rollers 506 to 509 via a link member (belt, gear train, etc.), and these start to rotate.

  Next, the timer T1 is started to start time measurement (timekeeping) (step S12), and rotation of the pickup roller 505 is started (step S13). The timer T1 is a function realized by the MPU 100 of the control unit 10 and is a timer for measuring the rotation duration time of the pickup roller 505. That is, the MPU 100 measures the time from the time (predetermined time) when the pickup roller 505 starts to rotate. The pickup roller 505 starts rotating when a control signal output from the print mechanism control circuit 500 is given to a solenoid (not shown) provided correspondingly.

  When step S13 is executed, the MPU 100 monitors step S14 while monitoring the number of rotations of the pickup roller 505 (step S14), the expiration of the timer T1 (step S16), and the detection result of the detection sensor 510 (step S17). Or repeat S17.

  When it is detected that the pickup roller 505 has made one rotation (Yes in step S14), the MPU 100 regards that the driving operation for sending out the paper in the paper feed cassette 442 has been completed, and causes the print mechanism control circuit 500 to rotate the pickup roller 505. Is stopped (step S15). However, the MPU 100 continues to monitor the timer T1 and the detection sensor 510 even after executing step S15.

  If the detection sensor 510 does not sense the leading edge of the paper before the predetermined time has elapsed since the time measurement by the timer T1 is started (when the leading edge of the paper is not turned on), the timer T1 expires (Yes in step S16).

  If the pickup roller 505 operates normally, the paper in the paper feed cassette 442 is sent out to the transport path 6 within a predetermined time after the pickup roller 505 starts rotating. In this case, the leading edge of the fed paper is detected by the detection sensor 510. Accordingly, when the timer T1 expires without the detection sensor 510 detecting the paper, the MPU 100 cannot pick up the paper normally by the pickup roller 505, and the paper feed unit 44 (paper feed cassette 442). Therefore, it is determined that the paper could not be supplied normally.

  That is, if the MPU 100 determines Yes in step S16, the print mechanism control circuit 500 stops the rotation of the motor 502 and the pickup roller 505 (step S18). Further, the position of the paper causing the jam is specified to be the paper feed cassette 442 (in the paper feed unit 44), displayed on the display unit 106 (step S19), and the process is terminated.

  As described above, in the image forming apparatus 1, it is possible to determine whether or not the sheet has reached the monitoring position of the detection sensor 510 by arranging the detection sensor 510 along the conveyance path 6. Thereby, even when the pickup roller 505 is rotated, when the sheet is not conveyed on the conveyance path 6, the position where the sheet is jammed (the position where the jam occurs) is accurately displayed on the display unit 106. be able to. Therefore, the operator can easily know the position of the sheet, and the burden on the operator in the restoration work can be reduced.

  Note that the “predetermined time” for determining that the timer T1 has timed out is measured in advance during normal times, and a predetermined value is set. In the following description, the same applies to the timers T2 to T6 and the predetermined values Th1 to Th3. If step S15 is executed before step S18 is executed, only the process of stopping the motor 502 is executed in step S18.

  On the other hand, if the detection sensor 510 senses the paper (becomes ON state) before the timer T1 expires (Yes in step S17), the MPU 100 normally sends the leading edge of the paper to the transport path 6. The timer T2 is started (FIG. 4: Step S21). The timer T2 is a timer for measuring the time required to take out the paper from the paper feed cassette 442.

  When the time measurement by the timer T2 is started, the MPU 100 monitors the number of rotations of the pickup roller 505 (step S22), the detection result of the detection sensor 510 (step S24), and the expiration of the timer T2 (step S25). Meanwhile, steps S22 to S25 are repeated.

  When the MPU 100 detects that the pickup roller 505 has rotated once (Yes in step S22), it is considered that the driving operation for sending out the paper in the paper feed cassette 442 is completed, and the pickup mechanism 505 rotates the pickup roller 505. Is stopped (step S23). However, even after executing step S23, the MPU 100 continues to monitor the timer T2 and the detection sensor 510. If step S15 has already been performed, steps S22 and S23 may be skipped.

  If the detection sensor 510 does not detect the passage of the sheet until a predetermined time has elapsed since the time measurement by the timer T2 is started, the timer T2 expires (Yes in step S25).

  If the transport unit 50 is operating normally, the trailing edge of the paper passes through the detection sensor 510 within a predetermined time, and the detection sensor 510 is turned off. Therefore, by monitoring the timing when the detection sensor 510 is turned off, it can be detected that the sheet has passed the position where the detection sensor 510 is disposed. However, when the timer T2 expires without the detection sensor 510 detecting the passage of the paper, the MPU 100 detects that the paper is near the exit of the paper feed cassette 442 (position where the pickup roller 505 or the detection sensor 510 is disposed). Consider it clogged.

  Therefore, when it is determined Yes in step S25, the printing mechanism control circuit 500 stops the rotation of the motor 502 and the pickup roller 505 (step S26). Further, the position of the paper causing the jam is specified as the position of the pickup roller 505, and is displayed on the display unit 106 (step S27), and the process ends.

  As described above, in the image forming apparatus 1, it is possible to determine whether the sheet has passed the monitoring position of the detection sensor 510 by arranging the detection sensor 510 along the conveyance path 6. Thereby, even when the pickup roller 505 is rotated, when the sheet is not conveyed on the conveyance path 6, the position where the sheet is jammed can be accurately displayed on the display unit 106. Therefore, the operator can easily know the position of the sheet, and the burden on the operator in the restoration work can be reduced.

  If steps S15 and S23 are executed before step S26 is executed, only the process for stopping the motor 502 is executed in step S26.

  On the other hand, when the detection sensor 510 is in an OFF state and the passage of the sheet is sensed by the time when the timer T2 expires (Yes in step S24), the MPU 100 has successfully sent the sheet onto the conveyance path 6 ( It is determined that the carry-out processing from the paper feed cassette 442 has ended, and the timer T3 is started (FIG. 5: Step S31). Note that the timer T3 is a timer that measures the time from when the paper conveyance is started.

  When the time measurement by the timer T3 is started, the MPU 100 monitors the detection result of the detection sensor 513 (step S32), the overload of the motor 502 (step S33), and the expiration of the timer T3 (step S39). S32, S33, and S39 are repeated.

  When the current value of the motor 502 increases and an overload of the motor 502 is detected (Yes in step S33), the MPU 100 gives a control signal to the print mechanism control circuit 500 to stop the rotation of the motor 502. In response to this control signal, the printing mechanism control circuit 500 stops the rotation of the motor 502 via the motor driver 501 (step S34).

  Further, the time measurement by the timer T3 is stopped (step S35), the value of the timer T3 at the time of the stop is obtained, and it is compared and determined whether or not this value is equal to or less than a predetermined value Th1 (step S36). The predetermined value Th1 is a value that is set by measuring in advance the time from when the sheet passes the position where the detection sensor 510 is disposed until it is conveyed into the main body 2.

  If the value of the timer T3 is equal to or less than the predetermined value Th1 (Yes in step S36), the MPU 100 determines that the sheet has not yet reached the main body 2 and remains in the paper feed unit 44. That is, in this case, the MPU 100 identifies the paper position as the paper feed path in the paper feed unit 44, displays it on the display unit 106 (step S37), and ends the process.

  Specifically, as an example in which step S <b> 37 is executed, a case where paper is entangled with the transport rollers 506 and 507 can be considered. The case where the paper becomes tangled with the transport rollers 506 and 507 is a case where a jam occurs at a position relatively close to the detection sensor 510, and therefore the value of the timer T3 is equal to or less than the predetermined value Th1. .

  On the other hand, if the value of the timer T3 is larger than the predetermined value Th1, it is determined that the paper has already reached the main body 2. That is, in this case, the MPU 100 specifies the paper position as the paper feed path in the main body 2 and displays it on the display unit 106 (step S38), and ends the process.

  Specifically, as an example in which step S38 is executed, a case where the sheet is entangled with the conveyance roller 508 can be considered. This is because the value of the timer T3 exceeds the predetermined value Th1 until the overload of the motor 502 is detected when the paper becomes tangled with the conveyance roller 508 relatively far from the detection sensor 510.

  In the image forming apparatus 1, as shown in step S36, the position of the sheet is specified only by the value of the timer T3. The principle that enables such position specification will be briefly described. In the transport unit 50 of the image forming apparatus 1, the transport speed of the paper is determined in advance. If the transport unit 50 is operating normally, at least the same type of paper is transported at approximately the same transport speed (each paper being transported). The speed distribution on the transport path 6 is substantially equal and is not necessarily constant speed transport). That is, since the predetermined value Th1 is a value set according to the conveyance speed of the conveyance unit 50, in practice, step S36 determines the position of the sheet based on the value of the timer T3 and the conveyance speed of the conveyance unit 50. This is equivalent to specifying.

  As described above, the image forming apparatus 1 according to the present embodiment uses the elapsed time (timer T3 value) measured by the MPU 100 and the sheet conveyance speed by the conveyance unit 50 on the sheet conveyance path 6. By specifying the position, it is not necessary to provide an optical sensor in the meantime (in the embodiment, from the detection sensor 510 to the detection sensor 513).

  In other words, in the image forming apparatus 1, if the moment when the paper is carried out from the paper feed cassettes 440 to 442 (time measurement start timing of the timer T <b> 3) can be determined, the overload of the motor 502 is monitored to thereby carry the paper conveyance path 6. The upper position can be specified.

  In the case where the conveyance speed is different for each sheet, a method of simply comparing with the predetermined value Th1 cannot be used as in step S36. In such a case, based on the value of the timer T3 and the conveyance speed of the conveyance unit 50 (for example, it can be obtained from the rotation speed of each conveyance roller 506 to 509), the conveyance distance of the paper between them is calculated. To do. Then, the position advanced by the calculated transport distance from the position where the detection sensor 510 is disposed may be specified as the “sheet position”.

  In addition, the image forming apparatus 1 specifies the position of the sheet by an overload applied to the transport rollers 506 to 509 instead of the optical sensor (detection sensors 510 to 514). Therefore, in order to improve the positional accuracy of the specified paper, it is necessary to dispose a relatively large number of conveying rollers 506 to 509 (narrow intervals) on the conveying path 6.

  However, since the transport rollers 506 to 509 are rollers to which the driving force for transporting the paper is transmitted, the transport rollers 506 to 509 are transported at a distance interval equal to or less than the length of the paper regardless of whether or not the paper is specified for the position of the paper. It is a mechanism arranged on the path 6. That is, also in the conventional apparatus, a number of mechanisms corresponding to the transport rollers 506 to 509 are arranged on the transport path as compared with the optical sensor. Therefore, the image forming apparatus 1 does not need to increase the number of conveying rollers 506 to 509 as compared with the conventional apparatus, and does not increase the manufacturing cost of the apparatus.

  If the transport unit 50 is operating normally, the leading edge of the paper reaches the position where the detection sensor 513 is disposed within a predetermined time, and the detection sensor 513 is turned on. That is, it should be detected by the detection sensor 513 within a predetermined time that the sheet has been conveyed to the position where the detection sensor 513 is disposed. Nevertheless, when the timer T3 expires without the detection sensor 513 sensing the paper, the MPU 100 moves from the position where the detection sensor 510 is disposed to the position where the detection sensor 513 is disposed. It is assumed that the sheet is jammed in the sheet feeding path (on the conveyance path 6).

  Therefore, if it is determined Yes in step S39, the printing mechanism control circuit 500 stops the rotation of the motor 502 in response to the control signal from the MPU 100 (step S40). Further, the position of the paper causing the jam is specified as the above-mentioned paper feed path, displayed on the display unit 106 (step S41), and the process is terminated.

  In the image forming apparatus 1, when the paper is jammed, an overload of the motor 502 is not always observed. For example, even when the paper is jammed, the motor 502 is not overloaded as long as the transport rollers 506 to 509 slip and continue to idle.

  However, in the image forming apparatus 1, it is determined whether or not the sheet that has passed the position where the detection sensor 510 is disposed has reached the position where the detection sensor 513 is disposed within a predetermined period of time by the timer T3. Can be monitored. That is, when the paper does not reach the predetermined position within the predetermined time, the abnormality of the transport unit 50 can be detected even when no overload is observed in the motor 502. Therefore, it is possible to notify the operator that an abnormality has occurred. However, in this case, it is not possible to specify whether it is in the paper feed unit 44 or the main body 2 as in steps S37 and S38.

  On the other hand, before the timer T3 expires, the detection sensor 513 is turned on, and when the detection sensor 513 senses the leading edge of the paper (Yes in step S32), the MPU 100 starts the timer T4 (FIG. 6: Step S51). The timer T4 is a timer that measures the time from when the sheet reaches the detection sensor 513.

  Each process of steps S51 to S61 shown in FIG. 6 is almost the same as each process of steps S31 to S41 shown in FIG.

  When the time measurement by the timer T4 is started, the MPU 100 monitors the detection result of the detection sensor 514 (step S52), the overload of the motor 502 (step S53), and the expiration of the timer T4 (step S59). S52, S53, and S59 are repeated.

  If an overload of the motor 502 is detected (Yes in step S53), the print mechanism control circuit 500 stops the rotation of the motor 502 via the motor driver 501 (step S54).

  Further, the MPU 100 stops the time measurement by the timer T4 (step S55), acquires the value of the timer T4 when stopped, and compares and determines whether or not this value is equal to or less than a predetermined value Th2 (step S56). . The predetermined value Th2 is a value that is set by measuring in advance the time from when the sheet reaches the position where the detection sensor 513 is disposed until it is conveyed into the fixing unit 43.

  If the value of the timer T4 is equal to or less than the predetermined value Th2 (Yes in step S56), the MPU 100 determines that the sheet has not yet reached the fixing unit 43 and remains in the transfer unit. In other words, in this case, the MPU 100 specifies the position of the sheet as the inside of the transfer unit 42, displays it on the display unit 106 (step S57), and ends the process.

  Specifically, an example in which step S57 is executed is when the transfer roller 423 is jammed. In this case, since the paper is jammed at a position relatively close to the detection sensor 513, the value of the timer T4 is equal to or less than the predetermined value Th2.

  On the other hand, if the value of the timer T4 is larger than the predetermined value Th2, it is determined that the sheet has already reached the fixing unit 43. That is, in this case, the MPU 100 specifies the position of the sheet as the inside of the fixing unit 43, displays it on the display unit 106 (step S58), and ends the process.

  Specifically, an example in which step S58 is executed is when the paper in the roller in the fixing unit 43 is jammed. In this case, since the paper is jammed at a position relatively far from the detection sensor 513, the value of the timer T4 exceeds the predetermined value Th2.

  If the transport unit 50 is operating normally, the leading edge of the paper reaches the position where the detection sensor 514 is disposed within a predetermined time, so that the detection sensor 514 is turned on. That is, it should be detected by the detection sensor 514 within a predetermined time that the sheet has been conveyed to the position where the detection sensor 514 is disposed. Nevertheless, when the timer T4 expires without the detection sensor 514 sensing the paper, the MPU 100 moves from the position where the detection sensor 513 is disposed to the position where the detection sensor 514 is disposed. It is assumed that the paper is jammed in between.

  Therefore, when it is determined Yes in step S59, the MPU 100 causes the printing mechanism control circuit 500 to stop the rotation of the motor 502 (step S60). Further, the position of the paper causing the jam is identified as the transfer unit 42 or the fixing unit 43, and displayed on the display unit 106 (step S61), and the process is terminated.

  On the other hand, when the detection sensor 514 is turned on before the timer T4 expires and the detection sensor 514 senses the leading edge of the paper (Yes in Step S52), the MPU 100 starts the timer T5 (FIG. 7: Step S71). Note that the timer T5 is a timer that measures the time from the time when the sheet is unloaded from the fixing unit 43.

  Since each process of step S71 thru | or S81 shown in FIG. 7 is substantially the same as each process of step S31 thru | or S41 shown in FIG. 5 already demonstrated, it demonstrates easily, abbreviate | omitting suitably.

  When the time measurement by the timer T5 is started, the MPU 100 monitors the detection result of the detection sensor 514 (step S72), the overload of the motor 502 (step S73), and the expiration of the timer T5 (step S79). S72, S73, and S79 are repeated.

  If an overload of the motor 502 is detected (Yes in step S73), the print mechanism control circuit 500 stops the rotation of the motor 502 via the motor driver 501 (step S74).

  Further, the MPU 100 stops the time measurement by the timer T5 (step S75), obtains the value of the timer T5 when it is stopped, and compares and determines whether or not this value is equal to or less than a predetermined value Th3 (step S76). The predetermined value Th3 is a value set by measuring in advance the time from when the leading edge of the paper reaches the position where the detection sensor 514 is disposed until the trailing edge of the paper is unloaded from the fixing unit 43. It is.

  If the value of the timer T5 is equal to or less than the predetermined value Th3 (Yes in step S76), the MPU 100 determines that the sheet still remains in the fixing unit 43. That is, in this case, the MPU 100 identifies the position of the sheet as the inside of the fixing unit 43, displays it on the display unit 106 (step S77), and ends the process.

  On the other hand, if the value of the timer T5 is larger than the predetermined value Th3, it is determined that the sheet has already been carried out from the fixing unit 43 (the rear end of the sheet has come out of the fixing unit 43). That is, in this case, the MPU 100 specifies the position of the sheet as the inside of the discharge unit 45, displays it on the display unit 106 (step S78), and ends the process.

  If the transport unit 50 is operating normally, the sheet passes through the position where the detection sensor 514 is disposed within a predetermined time, so that the detection sensor 514 is turned off. That is, the fact that the paper has passed the detection sensor 514 should be sensed by the detection sensor 514 within a predetermined time. Nevertheless, when the timer T5 expires without the detection sensor 514 detecting the passage of the paper, the MPU 100 considers that the paper is jammed at the position where the detection sensor 514 is disposed. However, in this case, since it cannot be determined whether the leading edge of the sheet is on the detection sensor 514 or the trailing edge, it is not possible to specify whether the sheet has already been carried out of the fixing unit 43. Can not.

  That is, when it is determined Yes in step S79, the MPU 100 causes the print mechanism control circuit 500 to stop the rotation of the motor 502 (step S80). Further, the position of the paper causing the jam is specified as either the fixing unit 43 or the discharge unit 45, and is displayed on the display unit 106 (step S81), and the process is terminated.

  On the other hand, when the detection sensor 514 is turned off before the timer T5 expires and the detection sensor 514 senses the passage of the paper (Yes in step S72), the MPU 100 starts the timer T6 (FIG. 8: Step S91). The timer T6 is a timer for determining the timing for stopping the transport operation by the transport unit 50.

  When the time measurement by the timer T6 is started, the MPU 100 repeats steps S92 and S95 while monitoring overload of the motor 502 (step S92) and expiration of the timer T6 (step S95).

  If an overload of the motor 502 is detected (Yes in step S92), the print mechanism control circuit 500 stops the rotation of the motor 502 (step S93). In this case, since the paper has already passed the detection sensor 514, it can be determined that a jam has occurred in the transport roller 509, for example. Therefore, the MPU 100 specifies the position of the sheet as the inside of the discharge unit 45, displays it on the display unit 106 (step S94), and ends the process.

  On the other hand, when the timer T6 expires (Yes in step S95), the MPU 100 regards that the conveyance of the sheet by the conveyance unit 50 has been completed normally, stops monitoring the overload of the motor 502, and print mechanism control circuit. The rotation of the motor 502 is stopped by 500 (step S96), and the process is terminated.

  As described above, in the image forming apparatus 1, the position of the paper is specified by measuring the time from the time when the paper conveyance is started to the time when the overload of the motor 502 is detected by the timer T3. Can do. Therefore, the position of the paper can be specified with high accuracy without increasing the number of optical sensors.

  Note that the image forming apparatus 1 according to the present embodiment is configured to accurately identify the position of the sheet by the detection sensors 510 to 514. In other words, the detection sensors 510 to 514 are provided to complement the position detection process, but the detection sensors 510 to 514 are not essential mechanisms. For example, the position of the sheet can be specified by measuring the time from when the rotation of the pickup rollers 503 to 505 is started until when the overload of the motor 502 is detected.

<2. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, the operator may be notified of the position of the jammed paper by voice guidance.

  In the above embodiment, the paper position is displayed only when there is an abnormality such as a paper jam (when a jam occurs), but the paper is being conveyed even in a normal state. May be displayed sequentially.

  In the image forming apparatus 1, the sheet is conveyed by one motor 502, but the conveyance rollers 506 to 509 may be driven by a plurality of motors.

1 is a schematic view of an image forming apparatus according to the present invention. 2 is a block diagram illustrating a connection state of each component of the image forming apparatus. FIG. 3 is a flowchart showing the operation of the image forming apparatus. 3 is a flowchart showing the operation of the image forming apparatus. 3 is a flowchart showing the operation of the image forming apparatus. 3 is a flowchart showing the operation of the image forming apparatus. 3 is a flowchart showing the operation of the image forming apparatus. 3 is a flowchart showing the operation of the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Control part 100 MPU
DESCRIPTION OF SYMBOLS 104 Operation panel 106 Display part 2 Main body 40 Printer part 42 Transfer part 420 Print head 43 Fixing part 44 Paper feed part 50 Conveyance part 500 Print mechanism control circuit 501 Motor driver 502 Motor 506, 507, 508, 509 Conveyance roller 510,511, 512, 513, 514 Detection sensor 6 Transport path

Claims (7)

An image forming apparatus for forming an image on a recording medium,
Transport means for transporting the recording medium along the transport path;
A time measuring means for measuring the elapsed time from a predetermined time point;
Position specifying means for specifying the position of the recording medium on the transport path based on the elapsed time measured by the time measuring means and the transport speed of the recording medium by the transport means;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the predetermined time includes a time when the transport unit starts transporting the recording medium. The image forming apparatus according to claim 1, wherein:
A medium detecting unit for detecting the recording medium conveyed by the conveying unit at a predetermined position on the conveying path;
The image forming apparatus according to claim 1, wherein the predetermined time includes a time when the recording medium is detected by the medium detection unit. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, further comprising: a display unit configured to display a position on the transport path of the recording medium specified by the position specifying unit. The image forming apparatus according to any one of claims 1 to 4,
An abnormality monitoring means for monitoring an overload of the conveying means when the conveying means is conveying the recording medium;
The image forming apparatus, wherein the position specifying unit specifies a position of the recording medium on the conveyance path when the overload is detected by the abnormality monitoring unit. A method for detecting a conveyance position of a recording medium in an image forming apparatus,
(a) transporting the recording medium along a transport path by a transport means;
(b) measuring the elapsed time from a predetermined time point;
(c) identifying the position of the recording medium on the transport path based on the measured time elapsed and the transport speed of the transported recording medium;
A transport position detecting method characterized by comprising: It is a conveyance position detection method of Claim 6, Comprising:
(d) further comprising the step of monitoring an overload of the conveying means when the conveying means is conveying the recording medium;
The step (c) is a step of specifying the position of the recording medium on the conveyance path when the overload is detected in the step (d).

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