JP2010155345A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a positional accuracy of an image formed on a paper sheet. <P>SOLUTION: In an image forming device which includes a first conveying mechanism 13 for conveying the paper sheet by a predetermined timing to the downstream side, a second conveying mechanism 15 for receiving the paper sheet conveyed by the first conveying mechanism 13 and conveying it to the further downstream side, and an image forming section 16 for forming the image on the paper sheet conveyed by the second conveying mechanism 13, the first distance information is acquired by a first distance information acquiring part 13d until a predetermined time point after a front end of the paper sheet reaches the second conveying mechanism 15, and the second distance information is acquired by a second distance information acquiring part 15d after the predetermined time point. A starting timing of image formation on the paper sheet by the image forming section 16 is controlled on the basis of the acquired first and second distance information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, a sheet is conveyed by a first conveying mechanism, a sheet conveyed by the first conveying mechanism is conveyed by a second conveying mechanism, and an image is applied to the sheet conveyed by the second conveying mechanism. The present invention relates to an image forming apparatus for forming the image.

  Conventionally, paper fed from a paper feed tray is transported by a registration roller, the paper transported by the registration roller is received by a transport belt, and ink is ejected onto the paper by an ink head while transporting the paper by the transport belt. Various ink jet printers have been proposed that form images.

  In the ink jet printer as described above, in order to form an image at an appropriate position on the paper, it is necessary to appropriately control the timing of starting ink ejection from the ink head to the paper.

  For example, in the ink jet printer described in Patent Document 1, a double feed sensor disposed upstream of the transport path and a reflective top edge sensor disposed in the vicinity of the ink head downstream of the transport path. A trigger is acquired based on the signal, and the ink ejection start timing is controlled based on the trigger.

Specifically, the pulse signal of the encoder provided on the platen roller of the conveyor belt is counted from the time when the paper is detected by the double feed sensor, and when the count number is within a predetermined range, the paper is detected by the top edge sensor. If it is detected, the detection information is used as a trigger, and if it is not detected by the top edge sensor within the predetermined range, a timing signal is generated when the count reaches a predetermined value. The timing signal is used as a trigger.
JP 2006-231620 A

  However, in the method described in Patent Document 1, when the reflectance of the paper decreases due to the type of paper, the paper may not be detected normally by the top edge sensor. In that case, as described above, the timing signal generated when the count of the pulse signal from when the paper is detected by the double feed sensor reaches a predetermined value is used as a trigger. When the paper is detected by the sensor, the paper is transported by the registration roller, and at the time when ink ejection is started on the paper, the paper is transported by the transport belt, and the transport mechanism is different.

  In many cases, the conveyance speed of the registration roller and the platen roller of the conveyance belt are not the same, and the registration roller conveys the sheet until the sheet reaches the conveyance belt. Further, since the timing at which the double feed sensor detects the paper is immediately after the paper starts to be transported from the registration roller, the transport speed is unstable. Further, the conveyance rate of the registration rollers varies depending on various conditions such as the type of paper and mechanical factors. Considering the above situation, just counting the pulse signal of the encoder provided on the platen roller of the conveyor belt as in the method described in Patent Document 1, the count number accurately determines the conveyance distance of the paper. It is not shown, and the position of the sheet cannot be detected accurately, and the position accuracy of the image formed on the sheet is lowered.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of improving the positional accuracy of an image formed on a sheet.

  The image forming apparatus according to the present invention receives a first transport mechanism that transports a sheet downstream at a predetermined timing, and a second transport that receives the sheet transported by the first transport mechanism and transports the sheet further downstream. 1st distance information according to the conveyance distance of the paper by a 1st conveyance mechanism in the image forming apparatus provided with the mechanism and the image formation part which forms an image with respect to the paper conveyed by the 2nd conveyance mechanism A first distance information acquisition unit that acquires the second distance information acquisition unit that acquires second distance information according to the conveyance distance of the sheet by the second conveyance mechanism, and the leading edge of the sheet is the second conveyance The first distance information is acquired until a predetermined time after reaching the mechanism, the second distance information is acquired after the predetermined time, and the acquired first distance information and second distance information are acquired. Based on the above, image formation on paper by the image forming unit Characterized in that an image forming control unit for controlling the start timing.

  In the image forming apparatus of the present invention, a thickness information detection unit that detects information according to the thickness of the paper is further provided between the first transport mechanism and the second transport mechanism, and image formation control is performed. The image forming start timing can be corrected based on the information corresponding to the thickness.

  Further, a paper detection unit for detecting paper is further provided between the first transport mechanism and the second transport mechanism, and the image formation control unit is configured to perform image formation based on the timing when the paper is detected by the paper detection unit. It is possible to correct the start timing.

  Further, a temperature measurement unit that measures the environmental temperature may be further provided, and the image formation control unit may correct the image formation start timing based on the environmental temperature measured by the temperature measurement unit.

  In addition, a back tension measurement unit that measures the back tension applied to the sheet when the sheet is conveyed by the first conveyance mechanism is further provided, and the image formation control unit is configured to be based on the back tension measured by the back tension measurement unit. Thus, the start timing of image formation can be corrected.

  In addition, a temporal change information acquisition unit that acquires information related to the temporal change of the first transport mechanism is further provided, and the image formation control unit is configured to perform image formation based on the information related to the temporal change measured by the temporal change information acquisition unit. The start timing can be corrected.

  Further, the thickness information detection unit can be used to detect double feeding of paper.

  Further, the paper detection unit can be used to detect double feeding of paper.

  Moreover, the encoder provided in the 1st conveyance mechanism can be used as a 1st distance information acquisition part.

  Further, an encoder provided in the second transport mechanism can be used as the second distance information acquisition unit.

  Further, the image forming unit has an ink head for discharging ink onto a sheet, and the image formation control unit controls the start timing of ink discharge from the ink head as the start timing of image formation. Can do.

  According to the image forming apparatus of the present invention, the first distance information is acquired until a predetermined time after the time when the leading edge of the paper reaches the second transport mechanism, and the second distance information is acquired after the predetermined time. And the start timing of image formation on the sheet by the image forming unit is controlled based on the acquired first distance information and second distance information, so that more accurate position information of the sheet And the positional accuracy of the image formed on the paper can be improved.

  In the image forming apparatus of the present invention, a thickness information detection unit for detecting information corresponding to the thickness of the sheet is further provided between the first transport mechanism and the second transport mechanism, When the image formation start timing is corrected based on the corresponding information, information corresponding to the thickness of the sheet can be acquired as information representing the conveyance rate of the first conveyance mechanism. Image formation can be started at a timing that also takes into account the conveyance rate of the first conveyance mechanism, and the positional accuracy of the image can be further improved.

  In addition, a paper detection unit that detects paper is further provided between the first transport mechanism and the second transport mechanism, and the image formation start timing is corrected based on the timing at which the paper is detected by the paper detection unit. In this case, since the information indicating the conveyance rate of the first conveyance mechanism can be acquired based on the detection timing of the sheet from the time when the conveyance of the sheet is started by the first conveyance mechanism, the first Image formation can be started at a timing that also takes into consideration the conveyance rate of one conveyance mechanism, and the positional accuracy of the image can be further improved.

  In addition, when a temperature measurement unit that measures the environmental temperature is further provided and the start timing of image formation is corrected based on the environmental temperature measured by the temperature measurement unit, the first transport mechanism is determined depending on the environmental temperature. Even if the transport rate changes, image formation can be started at a timing that also takes into account the change in the transport rate of the first transport mechanism, so that the positional accuracy of the image can be further improved.

  In addition, a back tension measurement unit that measures the back tension applied to the sheet when the sheet is conveyed by the first conveyance mechanism is further provided, and image formation is started based on the back tension measured by the back tension measurement unit. When the timing is corrected, even if the back tension is applied to the sheet due to roller load or friction on the upstream side of the first transport mechanism, the transport rate of the first transport mechanism may change. Since the image formation can be started at a timing that also takes into account the change in the conveyance rate of the first conveyance mechanism, the position accuracy of the image can be further improved.

  In addition, a temporal change information acquisition unit that acquires information related to the temporal change of the first transport mechanism is further provided, and the start timing of image formation is corrected based on the information related to the temporal change measured by the temporal change information acquisition unit. In this case, even if the first transport mechanism changes over time and the transport rate of the first transport mechanism changes, image formation is started at a timing that also takes into account the change in the transport rate of the first transport mechanism. Therefore, the position accuracy of the image can be further improved.

  Further, when the thickness information detection unit is used to detect double feeding of paper, it is not necessary to further provide a double feeding sensor, so that cost can be reduced and the apparatus can be downsized.

  Further, when the paper detection unit is used to detect double feeding of paper, it is not necessary to further provide a double feeding sensor, so that the cost can be reduced and the apparatus can be downsized.

  Hereinafter, an inkjet printer using an embodiment of an image forming apparatus of the present invention will be described in detail with reference to the drawings. The present invention is characterized by the timing of ink ejection in the ink jet printer described below. First, the schematic configuration of the ink jet printer will be described. FIG. 1 is a schematic configuration diagram of the ink jet printer.

  As shown in FIG. 1, the inkjet printer 1 includes a paper feed tray 11 on which paper 2 is stacked, and a sheet of paper 2 stacked on the paper feed tray 11 from the top one by one with a pickup roller. A primary paper feed roller section 12 that feeds toward the roller section 13, a registration roller section 13 that abuts the paper 2 sent out by the primary paper feed roller section 12 and conveys the paper further downstream at a predetermined timing; A sheet conveying belt unit 15 that receives the sheet 2 conveyed by the registration roller unit 13 and conveys the sheet 2 toward the image forming unit 16 on the downstream side, and is installed between the registration roller unit 13 and the sheet conveying belt unit 15. A multi-feed sensor 14, an image forming unit 16 for forming an image by ejecting ink onto a sheet conveyed by a sheet conveying belt unit 15, and the entire apparatus. And a control unit 17.

  The primary paper feed roller unit 12 includes two series of rubber rollers 12a and 12b and a first paper feed drive motor (not shown). The rubber rollers 12a and 12b are fed in the paper transport direction (paper surface) by the first paper feed drive motor. Although it rotates from the left to the right), at the time when the sheet is conveyed by the registration roller unit 13, the structure rotates with the movement of the sheet (one-way).

  The upstream rubber roller 12a is pressed against the uppermost sheet 2 loaded on the sheet feed table 11 with a predetermined pressure, and flows the sheet downstream with the frictional force thereof. The rubber roller 12b on the downstream side is configured to sandwich the paper with the separating plate 12c. Even if a plurality of sheets are supplied, the separating plate 12c is fixed and made of a material that can obtain a frictional force larger than the frictional force between the sheets. Therefore, the sheet closer to the separating plate 12c loses its conveying force. Only the sheet close to the rubber roller 12b is conveyed downstream.

  The registration roller unit 13 includes a pair of transport rollers 13a and 13b configured to sandwich (nip) a sheet, and a second paper feed drive motor 13c that drives the transport roller pair. Unlike the primary paper feed roller unit 12, the registration roller unit 13 has a structure capable of accurately controlling the amount of paper transport. The registration roller unit 13 intermittently operates for each paper sheet and feeds the paper to the paper transport belt unit 15 with good timing. It can be sent.

  The second paper feed drive motor 13c of the registration roller unit 13 is a servo motor. The second paper feed drive motor 13c is provided with an encoder 13d. The encoder 13d outputs a pulse signal according to the rotation of the second paper feed drive motor 13c. The pulse signal output from the encoder 13d is output to the control unit 17, and the control unit 17 outputs a speed control signal to the second paper feed drive motor 13c based on the count number of the pulse signal. The pulse signal output from the encoder 13d is input to the image formation control unit 17a of the control unit 17. The image formation control unit 17a counts the input pulse signal, and the count number is used as the registration roller unit 13. Is acquired as the first distance information corresponding to the transport distance of the paper 2. That is, the encoder 13d is used to control the second paper feed drive motor 13c and is used to acquire first distance information corresponding to the conveyance distance of the paper 2 by the registration roller unit 13. .

  The double feed sensor 14 detects information corresponding to the thickness of the paper 2 in the process of being conveyed downstream by the registration roller unit 13, and outputs the thickness information to the control unit 17. In the present embodiment, as the double feed sensor 14, a transmissive optical sensor in which a projector 14 a and a light receiver 14 b are arranged to face each other via a conveyance path of the paper 2 is used. A signal corresponding to the intensity of the light received by the light receiver 14 b is output from the double feed sensor 14 to the control unit 17. Then, the control unit 17 determines based on the signal output from the double feed sensor 14 whether the paper is being double fed. The signal output from the double feed sensor 14 is input to the image formation control unit 17a of the control unit 17, and the image formation control unit 17a uses the signal output from the double feed sensor 14 as a trigger as an encoder. The count of the pulse signal output from 13d is started.

  The sheet conveying belt unit 15 includes a conveying belt 15a that conveys the sheet 2, a conveying roller 15b that conveys the conveying belt 15a, a drive motor 15c that rotates the conveying roller 15b, and an encoder 15d that is provided on the conveying roller 15b. . After the sheet 2 conveyed from the registration roller unit 13 is attracted or electrostatically attracted to the conveyance belt 15a, the sheet 2 is conveyed while maintaining a constant speed, and the image is formed in the image forming unit 16. The paper 2 is conveyed to a downstream paper discharge section (not shown).

  The encoder 15d outputs a pulse signal according to the rotation of the transport roller 15b. The pulse signal output from the encoder 15d is output to the control unit 17, and the control unit 17 outputs a speed control signal to the drive motor 15c based on the count number of the pulse signal. The pulse signal output from the encoder 15d is input to the image formation control unit 17a of the control unit 17, and the image formation control unit 17a counts the input pulse signal, and the count number is used as the paper conveyance belt unit. 15 is acquired as second distance information corresponding to the conveyance distance of the sheet 2 by 15. Further, the image formation control unit 17a outputs a print pulse signal to the image forming unit 16 based on the input pulse signal. The image forming unit 16 ejects ink based on the print pulse signal.

  That is, the encoder 15d is used to control the drive motor 15c, and is used to acquire the second distance information and the print pulse signal corresponding to the transport distance of the paper 2 by the paper transport belt unit 15. is there.

  The image forming unit 16 is provided in a non-contact state above the transport surface and includes a line head that selectively ejects ink toward the paper 2. In the present embodiment, in order to form a full-color image, four color line heads of K (black), C (cyan), M (magenta), and Y (yellow) are provided.

  As described above, the control unit 17 controls the entire apparatus, and particularly includes an image formation control unit 17a for controlling image formation. The image forming control unit 17a discharges ink discharged from the image forming unit 16 onto the paper 2 based on pulse signals output from the encoder 13d of the registration roller unit 13 and the encoder 15d of the paper transport belt unit 15. Is to control. The control method will be described in detail later.

  Next, the operation of the ink jet printer of this embodiment will be described.

  First, in response to an input of a print instruction, the paper feed tray 11 is raised to a position where the uppermost portion of the stacked paper comes into pressure contact with the rubber roller 12 a of the primary paper feed roller unit 12. Then, the conveyance speed of the conveyance belt 15a of the sheet conveyance belt unit 15 is set to a specified value, and other control setup necessary for sheet conveyance is performed.

  Then, the control unit 17 activates the primary paper feed drive motor of the primary paper feed roller unit 12 with a predetermined acceleration. The primary paper feed roller unit 12 starts conveying the uppermost paper 2 of the paper feed table 11. After the transport speed of the primary paper feed roller unit 12 reaches a preset speed, the paper 2 is transported while maintaining that speed.

  Then, after the leading edge of the sheet 2 conveyed by the primary paper feed roller unit 12 is abutted between the conveyance roller 13a and the conveyance roller 13b of the registration roller unit 13, and after a predetermined amount of slack is secured, the primary The rubber rollers 12a and 12b of the paper feed roller unit 12 are stopped.

  Then, after the conveyance of the sheet 2 by the primary sheet feeding roller unit 12 is stopped, the registration roller unit 13 starts to be activated after a predetermined period.

  Here, the tip speed of the sheet 2 from the start of the registration roller unit 13 to the start of ink ejection by the image forming unit 16 is shown in FIG. As shown in FIG. 2, first, after the second paper feed drive motor 13c of the registration roller unit 13 is accelerated at a predetermined acceleration and reaches a predetermined speed, the speed is maintained. When the registration roller unit 13 transports the sheet at a predetermined speed for a predetermined period, the sheet 2 is detected by the double feed sensor 14.

  Then, the signal acquired by the double feed sensor 14 is output to the control unit 17, and it is determined whether or not the double feed is performed in the control unit 17. The second sheet feeding drive motor 13c is stopped, and the conveyance of the sheet 2 by the registration roller unit 13 is stopped.

  On the other hand, when the control unit 17 determines that the double feed is not performed, the conveyance of the paper 2 by the registration roller unit 13 is continued, and the paper is detected by the double feed sensor 14 in the image formation control unit 17a. The counting of the pulse signal output from the encoder 13d of the registration roller unit 13 is started from the time (t1 in FIG. 2).

  After the sheet 2 is conveyed by the registration roller unit 13 at a constant speed, the second paper feed drive motor 13c of the registration roller unit 13 is decelerated at a predetermined acceleration. The paper is conveyed while maintaining

  When the leading edge of the sheet 2 conveyed by the registration roller unit 13 reaches the sheet conveyance belt unit 15, the image formation control unit 17a holds the count Pr of the pulse signal of the encoder 13d counted so far. The counting of the pulse signal output from the encoder 15d of the paper transport belt unit 15 is started. That is, the image formation control unit 17 a switches from counting the pulse signal of the encoder 13 d of the registration roller unit 13 to counting of the pulse signal of the encoder 15 d of the paper transport belt unit 15. In the present embodiment, the counting target is switched as described above when the leading edge of the sheet 2 reaches the position Pa shown in FIG. 1 (t2 in FIG. 2). In addition, the time from time t1 to time t2 in FIG. 2 is set in advance according to the configuration of the apparatus. In the present embodiment, the count target is switched when the leading edge of the sheet 2 reaches the position Pa shown in FIG. 1, but this position is not limited to Pa, and the leading edge of the sheet is the sheet conveying belt. If it is after the time of reaching the part 15, it may be appropriately shifted.

  After the count target is switched by the image formation control unit 17a as described above, the paper 2 is conveyed toward the image forming unit 16 by the paper conveyance belt unit 15. It is assumed that the conveyance speed of the paper conveyance belt unit 15 is set to be slower than the conveyance speed of the registration roller unit 13.

  Then, the image formation control unit 17a adds the count number of the pulse signal output from the encoder 15d to the count number Pr, and starts the ink discharge when the added count number becomes Pr + Pb (t3 in FIG. 2). Get as a trigger. Then, based on the trigger, a control signal is output to the image forming unit 16, and the image forming unit 16 starts ink ejection by the line head based on the input control signal and starts image formation. In the present embodiment, it is assumed that the count number corresponding to the transport distance from Pa to the trigger position T shown in FIG.

  Then, the sheet 2 is continuously conveyed to the downstream side by the sheet conveying belt unit 15, and the image formation control unit 17 a is configured so that each line head of the image forming unit 16 is based on the pulse signal output from the encoder 15 d of the sheet conveying belt unit 15. A control signal is output to each line head, and each line head forms an image on the sheet 2 by ejecting ink at an appropriate timing based on the input control signal.

  In the description of the above embodiment, the image forming control unit 17a starts counting the pulse signals of the encoder 13d of the registration roller unit 13 from the time when the detection information of the sheet 2 from the double feed sensor 14 is received. However, this is for obtaining a more accurate ink ejection trigger, and is not limited to this. For example, the pulse signal count of the encoder 13d is started from the time when the registration roller unit 13 starts transporting the paper 2. You may make it do.

  In the inkjet printer 1 of the above embodiment, the detection information of the paper 2 output from the double feed sensor 14 is used as a trigger for starting the counting of the pulse signal of the encoder 13d, but the double feed of the paper 2 is detected. In such a case, a paper leading edge detection sensor for detecting the leading edge of the paper may be provided instead of the double feed sensor, and the detection information of the paper leading edge detection sensor may be used as a trigger. As the paper leading edge detection sensor, a transmissive optical sensor may be used, or a reflective optical sensor may be used.

  Here, in the ink jet printer 1 of the above-described embodiment, the pulse signal of the encoder 13d of the registration roller unit 13 and the pulse signal of the encoder 15d of the paper transport belt unit 15 are obtained by switching, and based on these added values. By controlling the ink ejection start timing, image formation with higher positional accuracy is performed. This is based on the premise that the registration roller unit 13 has a good sheet conveyance rate.

  For example, when the conveyance rate is poor due to slippage in the conveyance rollers 13a and 13b of the registration roller unit 13, the conveyance speed at the leading edge of the sheet 2 is as indicated by the dotted line in FIG. Originally, the sheet 2 is detected by the double feed sensor 14 at time t1, but the sheet 2 is detected by the double feed sensor 14 at time t1 ′ later than time t1. Even after the sheet 2 is detected by the double feed sensor 14, the conveyance speed of the sheet 2 by the registration roller unit 13 is slowed down. Therefore, it is assumed that the image forming control unit 17a switches the pulse signal to be counted with a good conveyance rate. If it is performed based on the preset count number Pr, the pulse signal to be counted is switched before the leading edge of the sheet 2 still reaches the sheet conveying belt unit 15, and the position accuracy of the image formation is changed. Will fall.

  Therefore, for example, in the image formation control unit 17a, the conveyance rate of the registration roller unit 13 is acquired, the count correction value Pr ′ corresponding to the conveyance rate is acquired, and the count correction value Pr ′ is added to the count number Pr. The pulse signal to be counted may be switched based on the added value Pr + Pr ′. That is, the image forming control unit 17a starts counting the pulse signal of the encoder 13d from the time t1 ′ when the paper is detected by the double feed sensor 14, and when the count reaches Pr + Pr ′ (time in FIG. 3). t2 ′), the pulse signal to be counted may be switched from the pulse signal of the encoder 13d to the pulse signal of the encoder 15d.

  For the count correction value Pr ′ corresponding to the conveyance rate, for example, the transmission amount of the sheet 2 is calculated based on the light intensity signal detected by the double feed sensor 14, and the conveyance rate is calculated based on the transmission amount. And the count correction value Pr ′ may be acquired based on the conveyance rate. The relationship between the light intensity signal and the transmission amount, the relationship between the transmission amount and the conveyance rate, and the relationship between the conveyance rate and the count correction value Pr ′ may be set in advance using a mathematical formula, or set using a table or the like. You may make it do. Note that the relationship between the transmission amount and the conveyance rate is such that the smaller the transmission amount, that is, the thicker the sheet 2, the lower the conveyance rate. The relationship between the conveyance rate and the count correction value Pr ′ is that the count correction value Pr ′ increases as the conveyance rate decreases.

  Further, as a method of obtaining the conveyance rate of the registration roller unit 13, for example, a time point t1 detected by the multi-feed sensor 14 with a delay due to slippage in the registration roller unit 13 from the time when the conveyance of the sheet by the registration roller unit 13 is started. The conveyance rate may be acquired based on the time until '(see FIG. 3) and the distance between the registration roller unit 13 and the double feed sensor 14.

  Further, since the conveyance rate of the registration roller unit 13 changes due to expansion of the conveyance rollers 13a, 13b and the like depending on the environmental temperature, a temperature sensor 18 for further measuring the environmental temperature is further provided (see FIG. 1). The count correction value Pr ′ may be calculated based on the environmental temperature detected by the above. In this case, the lower the environmental temperature, the worse the conveyance rate, so the count correction value Pr 'may be increased.

  Further, the conveyance rate of the registration roller unit 13 depends on the back tension applied to the paper 2 due to the roller load and friction on the conveyance path upstream of the registration roller unit 13, changes with time of the conveyance rollers 13 a and 13 b of the registration roller unit 13, and the like. Also changes. Therefore, the back tension applied to the paper 2 may be measured, and the count correction value Pr ′ may be calculated based on the measured back tension. Alternatively, the elapsed time from the manufacture of the apparatus may be measured, and the elapsed time may be calculated based on the elapsed time. The count correction value Pr ′ may be calculated. In the above description, the elapsed time is acquired as information related to the temporal change of the registration roller unit 13, but the present invention is not limited to this, and other information may be used as long as the information is related to the temporal change. Further, the back tension applied to the paper 2 can be indirectly measured, for example, by measuring the value of the current flowing through the second paper feed drive motor 13c or the first paper feed drive motor.

  In the above embodiment, the image forming apparatus of the present invention is applied to an ink jet printer. However, the image forming apparatus is not limited to an ink jet printer, and may be any print engine that requires non-contact and highly accurate alignment. You may apply.

1 is a schematic configuration diagram of an ink jet printer using an embodiment of an image forming apparatus of the present invention. The figure which shows the front-end | tip speed | velocity | rate of the sheet | seat from the start start of a registration roller part to the start of ink discharge by an image formation part The figure which shows the front-end | tip speed | velocity | rate of the sheet | seat from the starting start of a registration roller part to the start of ink discharge by an image forming part in the case where the conveyance rate of a registration roller part is good

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Paper feed stand 12 Primary paper feed roller part 12a Rubber roller 12b Rubber roller 13 Registration roller part 13a Carry roller 13b Carry roller 13c Second paper feed drive motor 13d Encoder 14 Double feed sensor 14a Light projector 14b Light receiver 15 Paper carry belt part 15a Carry Belt 15b Conveying roller 15c Drive motor 15d Encoder 15d Encoder 16 Image forming unit 17 Control unit 17a Image forming control unit 18 Temperature sensor

Claims (11)

A first transport mechanism that transports the paper downstream at a predetermined timing; a second transport mechanism that receives the paper transported by the first transport mechanism and transports the paper further downstream; and a second transport An image forming apparatus including an image forming unit that forms an image on a sheet conveyed by a mechanism.
A first distance information acquisition unit that acquires first distance information according to a conveyance distance of the paper by the first conveyance mechanism;
A second distance information acquisition unit that acquires second distance information according to a conveyance distance of the paper by the second conveyance mechanism;
The first distance information is acquired until a predetermined time after the time when the leading edge of the paper reaches the second transport mechanism, the second distance information is acquired after the predetermined time, and the acquisition is performed. An image forming apparatus comprising: an image forming control unit configured to control a start timing of image formation on the paper by the image forming unit based on the first distance information and the second distance information. . A thickness information detection unit configured to detect information according to the thickness of the paper between the first transport mechanism and the second transport mechanism;
The image forming apparatus according to claim 1, wherein the image forming control unit corrects a start timing of the image forming based on information corresponding to the thickness. A paper detection unit for detecting the paper between the first transport mechanism and the second transport mechanism;
The image forming apparatus according to claim 1, wherein the image formation control unit corrects the start timing of the image formation based on a timing when the paper is detected by the paper detection unit. It is further equipped with a temperature measurement unit that measures the environmental temperature,
The image according to any one of claims 1 to 3, wherein the image formation control unit corrects a start timing of the image formation based on an environmental temperature measured by the temperature measurement unit. Forming equipment. A back tension measuring unit that measures a back tension applied to the paper when the paper is being transported by the first transport mechanism;
The said image formation control part correct | amends the start timing of the said image formation based on the back tension measured by the said back tension measurement part, The any one of Claim 1 to 4 characterized by the above-mentioned. Image forming apparatus. A temporal change information acquisition unit for acquiring information on the temporal change of the first transport mechanism;
6. The image forming control unit according to claim 1, wherein the image forming control unit corrects a start timing of the image formation based on information on a change over time measured by the time change information acquisition unit. The image forming apparatus according to Item.   The image forming apparatus according to claim 2, wherein the thickness information detection unit is used to detect double feeding of the paper.   The image forming apparatus according to claim 3, wherein the paper detection unit is used to detect double feeding of the paper.   The image forming apparatus according to claim 1, wherein the first distance information acquisition unit is an encoder provided in the first transport mechanism.   The image forming apparatus according to claim 1, wherein the second distance information acquisition unit is an encoder provided in the second transport mechanism. The image forming unit includes an ink head that ejects ink onto the paper;
The image forming apparatus according to claim 1, wherein the image forming control unit controls a start timing of ink ejection from the ink head as a start timing of the image formation.

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