JP4632936B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that detects the leading end of a recording medium and conveys the recording medium to a predetermined printing position based on the detection result.

  As various image forming apparatuses such as printers, facsimiles, copying machines, plotters, printer / fax / copier multifunction machines, etc., recording heads (printing heads) constituted by droplet discharging heads that discharge recording liquid (for example, ink) droplets are used. ) Is mounted on a carriage, and the carriage is also referred to as a recording medium (hereinafter referred to as “paper”, but the material is not limited to paper, and the recording medium, recording paper, transfer material, printing material, printing medium, etc.) In addition, serial scanning is performed in a direction orthogonal to the conveyance direction), and the recording medium is intermittently conveyed according to the recording width, and the image is recorded on the recording medium by alternately repeating conveyance and recording. There is a serial type image forming apparatus that forms (recording, printing, printing, and printing are also used synonymously). There is also a line type image forming apparatus provided with a line type head.

In such an image forming apparatus, the paper sensor that detects (detects) the leading edge of the paper mounted on the carriage detects that the leading edge of the paper has arrived, and the predetermined paper is printed on the basis of the detected paper leading edge position. There is something that is transported to a position.
JP 2004-237893 A

  In this case, the leading edge detection position may be shifted for each apparatus due to a shift in the assembly position of the paper sensor or a detection error of the sensor itself, and printing may not be performed at the intended position. Therefore, it is necessary to adjust the leading edge detection position by the paper sensor.

In Patent Document 2, in order to perform registration adjustment so that the printing positions of the forward path and the backward path can be accurately positioned in the vertical direction in the scanning direction of the recording head, not only the landing positions of the forward path and the next backward path but also the backward path The adjustment value is determined by paying attention to the landing position of the next forward path.
JP-A-2005-219320

Further, in Patent Document 3, the displacement of the print position of each head is determined based on the detection data from the print position detecting means for detecting the print position of each head, and the position of each head is corrected based on the displacement data between the heads. And a head moving means.
JP 05-301353 A

  As described above, in an image forming apparatus including a recording head that discharges droplets, it is necessary that the nozzle of the recording head and the sheet detecting unit that detects the leading edge of the sheet have a predetermined positional relationship. Since the distance between the nozzles of the recording head and the paper detection means varies due to the mounting variation of the means, it is necessary to align the nozzles of the recording head and the paper detection means.

  On the other hand, the image forming apparatus is required to improve the printing speed. For this purpose, during continuous printing, the distance between the preceding paper and the following paper (hereinafter referred to as “paper gap”) is as narrow as possible. For example, in the configuration in which the paper sensor is mounted on the carriage, when printing a plurality of pages by continuous printing, the preceding paper is scanned after the last scan. Since the carriage moves to a predetermined position for detecting the leading edge of the paper, and the leading edge detection operation of the following paper is started, it takes time to detect the leading edge of the following paper. Loss will occur and the gap between the sheets cannot be kept below a certain level. As a result, there arises a problem that a limit in relation to the detection of the leading edge of the paper also occurs in improving the printing speed.

  Therefore, for example, separately from the paper detection means mounted on the carriage, a separate paper detection means is arranged on the upstream side of the paper conveyance direction with respect to the paper detection means, and the leading edge of the paper is detected by a plurality of paper detection means. Can be considered.

  However, when a plurality of paper detection means for detecting the leading edge of the paper is provided as described above, it is necessary to perform adjustment operations such as printing a test pattern and inputting an adjustment value as described above for each paper detection means. As a result, there is a problem that the tip detection position adjustment becomes troublesome.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus that simplifies the tip detection position adjustment work when a plurality of recording medium detection units are provided.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
In an image forming apparatus in which a recording head is mounted on a carriage and a recording medium is conveyed in a direction perpendicular to the scanning direction of the carriage to form an image on the recording medium.
First detection means for detecting the recording medium mounted on the carriage;
A second detection means arranged on the upstream side in the recording medium conveyance direction relative to the first detection means for detecting the recording medium;
Means for storing a distance between the first detection means and the second detection means;
Storage means for storing a test pattern for correcting the leading end detection position of the recording medium;
Based on the result of alignment of the relationship between the first detection means designated when the stored test pattern is printed out and the nozzle position of the recording head and the stored distance, the second detection And a means for correcting the relationship between the means and the nozzle position of the recording head .

Here, the second sensing means and said first detection means said configuration used depending on the type of the recording medium, the second detecting means and said first detecting means is off in the configuration used depending on the printing mode.

The distance between the first detecting means and the second detecting means is off in the configuration using the actual measurement value and the theoretical value.

According to the image forming apparatus of the present invention, the first detection unit that detects the recording medium mounted on the carriage, and the recording medium that is disposed upstream of the first detection unit in the recording medium conveyance direction is detected. Second detection means; means for storing the distance between the first detection means and the second detection means; storage means for storing a test pattern for correcting the leading end detection position of the recording medium; and the stored test pattern The relationship between the second detection means and the nozzle position of the recording head based on the alignment result of the relationship between the first detection means designated when printing and the nozzle position of the recording head and the stored distance Therefore, it is not necessary to adjust the tip detection position for all of the plurality of detection means, and the tip detection position adjustment operation is simplified.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory perspective view of the image forming apparatus as an example of the image forming apparatus according to the present invention as viewed from the front side.
The image forming apparatus includes an apparatus main body 1, a paper feed tray 2 for loading paper loaded in the apparatus main body 1, and a sheet on which an image is recorded (formed) by being detachably mounted on the apparatus main body 1. A paper discharge tray 3 for stocking is provided. Further, a cartridge loading for loading an ink cartridge that protrudes from the front surface to the front side of the apparatus main body 1 and is lower than the upper surface is provided at one end side of the front surface of the apparatus main body 1 (side of the paper supply / discharge tray section). The cartridge loading unit 4 has an operation / display unit 5 provided with operation buttons and a display.

  The cartridge loading unit 4 includes a plurality of recording liquid cartridges that contain recording liquids (inks) of different colors, for example, black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink. Ink cartridges 10k, 10c, 10m, and 10y (referred to as “ink cartridge 10” when colors are not distinguished) are inserted from the front side to the rear side of the apparatus main body 1 and can be loaded. A front cover (cartridge cover) 6 that is opened when the ink cartridge 10 is attached or detached is provided on the front side of the unit 4 so as to be openable and closable.

  Further, the operation / display unit 5 has the remaining amounts of the ink cartridges 10k, 10c, 10m, and 10y of each color at the arrangement positions corresponding to the mounting positions (arrangement positions) of the ink cartridges 10k, 10c, 10m, and 10y of the respective colors. The remaining amount display portions 11k, 11c, 11m, and 11y for each color for displaying the near end and the end are arranged. Further, the operation / display unit 5 is also provided with a power button 12, a paper feed / print resume button 13, and a cancel button 14. By means of the operation sequence or combination of the buttons 12 to 14 of the operation / display unit 5, it is possible to select and designate means for instructing print output of the tip position adjustment test pattern according to the present invention and the tip position adjustment value.

Next, the mechanism of the image forming apparatus will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram for explaining the overall configuration of the mechanism unit, and FIG. 3 is a plan view for explaining a main part of the mechanism unit.
A carriage 23 is slidably held in a main scanning direction by a guide rod 21 and a stay 22 that are horizontally mounted between left and right side plates (not shown), and is slidable between a driving pulley 25 and a driven pulley 26 by a main scanning motor 24. 3 moves and scans in the direction indicated by the arrow (carriage scanning direction: main scanning direction) in FIG.

  The carriage 23 has recording heads 31k, 31c, 31m, and 31y (distinguishable) composed of droplet ejection heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). Otherwise, it is referred to as “recording head 31”.) A nozzle row in which nozzles for ejecting a plurality of droplets are arranged in a direction intersecting the main scanning direction with the ink droplet ejection direction facing downward.

  As an ink jet head constituting the recording head 31, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. It is possible to use a shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like provided as pressure generating means for generating a pressure for discharging a droplet. In addition, the inkjet head has a configuration in which a plurality of nozzle rows are arranged and a plurality of nozzle rows are arranged, and droplets of the same color are ejected from each nozzle row. Also good.

  The carriage 23 is equipped with a sub tank 32 for each color for supplying each color ink to the recording head 31. Each color sub-tank 32 is supplementarily supplied with ink of each color from the ink cartridge 10 of each color mounted in the cartridge loading unit 4 via the ink supply tube of each color.

  On the other hand, as a sheet feeding unit that is a feeding unit for feeding the sheets 42 stacked on the sheet stacking unit (pressure plate) 41 of the sheet feeding tray 2, the sheets 42 are separated and fed one by one from the sheet stacking unit 41. A half paddle (feed roller) 43 and a separation pad 44 made of a material having a large friction coefficient are provided opposite to the half-moon roller (sheet feed roller) 43, and the separation pad 44 is urged toward the sheet feed roller 43 side.

  In order to feed the sheet 42 fed from the sheet feeding unit to the lower side of the recording head 31, a guide member 45 for guiding the sheet 42, a counter roller 46, a transport guide member 47, and a tip pressure roller. A pressing member 48 having a (pressing roller) 49, and a conveying belt 51 that is a conveying means for electrostatically attracting the fed paper 42 and conveying it at a position facing the recording head 31. .

  The transport belt 51 is an endless belt, and is configured to wrap around the transport roller 52 and the tension roller 53 and circulate in the belt transport direction (sub-scanning direction). This transport belt 51 is, for example, a surface layer that is a sheet adsorbing surface formed of a pure resin material having a thickness of about 40 μm that is not subjected to resistance control, such as ETFE pure material, and resistance control by carbon with the same material as this surface layer. And a back layer (medium resistance layer, ground layer).

  A charging roller 56 is provided as charging means for charging the surface of the conveyor belt 51. The charging roller 56 is disposed so as to come into contact with the surface layer of the conveyor belt 51 and to be rotated by the rotation of the conveyor belt 51, and applies a predetermined pressing force to both ends of the shaft as a pressing force. In addition, a guide member 57 is disposed on the back side of the conveyance belt 51 so as to correspond to a printing area by the recording head 31.

  The conveyance belt 51 rotates in the belt conveyance direction (sub-scanning direction) in FIG. 3 when the conveyance roller 52 is rotationally driven by the sub-scanning motor 58 via the drive belt 59 and the pulley 60.

  Further, as a paper discharge unit for discharging the paper 42 recorded by the recording head 31, a separation claw 61 for separating the paper 42 from the conveyance belt 51, a paper discharge roller 62, and a paper discharge roller 63 are provided. The paper discharge tray 3 is provided below the paper discharge roller 62.

  A duplex unit 71 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 71 takes in the paper 42 returned by the reverse rotation of the conveyance belt 51, reverses it, and feeds it again between the counter roller 46 and the conveyance belt 51. The upper surface of the duplex unit 71 is a manual feed tray 72.

  Further, as shown in FIG. 3, a maintenance / recovery mechanism 81 including a recovery means for maintaining and recovering the nozzle state of the recording head 31 is arranged in the non-printing area on one side of the carriage 23 in the scanning direction. Yes.

  The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a to 82d (hereinafter referred to as “caps 82” when not distinguished from each other) for capping the nozzle surfaces of the recording head 31, and nozzle surfaces. A wiper blade 83 that is a blade member for wiping the ink, and an empty discharge receiver 84 that receives liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid. ing. Here, the cap 82a is a sucking and moisturizing cap (hereinafter referred to as "suction cap"), and the other caps 82b to 82d are moisturizing caps.

  Further, in the non-printing area on the other side of the carriage 23 in the scanning direction, there is an empty space for receiving a liquid droplet when performing an empty discharge for discharging a liquid droplet that does not contribute to recording in order to discharge the recording liquid thickened during recording or the like. A discharge receiver 88 is arranged, and the idle discharge receiver 88 is provided with openings 89 a to 89 d along the nozzle row direction of the recording head 31.

  Further, the carriage 33 is provided with a first sheet sensor 91 which is a first detection means including a reflection type photosensor for detecting the leading end of the sheet 42 to be conveyed. Further, a second detection comprising a reflective photosensor for detecting the leading edge of the paper 42 at a position facing the conveyance roller 52 on the upstream side of the pressing roller 49, which is upstream of the first paper sensor 91 in the paper conveyance direction. A second paper sensor 92 as a means is arranged. Note that the first and second paper sensors 91 and 92 are not limited to reflective sensors, and transmissive sensors, physical switches, and the like can also be used.

  The second sheet sensor 92 is preferably as close to the first sheet sensor 91 as possible in terms of detection accuracy. However, in consideration of the fact that the movement of the carriage 23 should not be hindered and the installation space, this image forming apparatus is used. Then, although it arrange | positions in the upstream vicinity of the pressing roller 49, it is not restricted to this. However, in order to perform detection in a state where the sheet 42 is stably conveyed, the position facing the conveying roller 52 is preferable. It is also possible to use a conveying means that does not use a conveying belt (for example, a conveying means using a conveying roller).

  In the ink jet recording apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feeding tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and the transport belt 51 and the counter roller 46, and the leading end is guided by the conveying guide 37 and pressed against the conveying belt 51 by the tip pressing roller 49, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately and repeatedly applied to the charging roller 56 from an AC bias supply unit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 51 alternates, that is, a loop In the sub-scanning direction, which is the direction, plus and minus are alternately charged in a band shape with a predetermined width. When the paper 42 is fed onto the conveyance belt 51 charged alternately with plus and minus, the paper 42 is attracted to the conveyance belt 51, and the paper 42 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 51.

  Therefore, by driving the recording head 31 according to the image signal while moving the carriage 23, ink droplets are ejected onto the stopped paper 42 to record one line, and after the paper 42 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 42 has reached the recording area, the recording operation is finished and the paper 42 is discharged onto the paper discharge tray 3.

  During printing (recording) standby, the carriage 23 is moved to the maintenance / recovery mechanism 81 side, the recording head 31 is capped by the cap 82, and the nozzles are kept in a wet state to prevent ejection failure due to ink drying. . Further, the recording liquid is sucked from the nozzle by a suction pump (not shown) with the recording head 31 capped by the cap 82 (referred to as “nozzle suction” or “head suction”), and the thickened recording liquid and bubbles are discharged. Perform recovery action. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 31 is maintained.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.
The control unit controls the entire image forming apparatus, and includes a main control unit 301 composed of a microcomputer that also serves as a control unit and a storage unit for controlling the tip position according to the present invention, and a microcomputer that controls printing. And a print control unit 302 configured as described above.

  Then, the main control unit 301 uses the main scanning motor 24 and the sub-scanning motor 58 as described above in order to form an image on the paper 42 based on the print processing information input from the communication circuit 300. Drive control is performed via the drive circuit 303 and the sub-scanning motor 304, and control such as sending print data to the print control unit 302 is performed. The internal ROM of the control unit 301 stores and holds in advance a tip position adjustment pattern related to tip position adjustment according to the present invention.

  The main control unit 301 receives a detection signal from a carriage position detection circuit 305 that detects the position of the carriage 23, and the main control unit 301 controls the movement position and movement speed of the carriage 23 based on the detection signal. To do. The carriage position detection circuit 305 detects the position of the carriage 23 by, for example, reading and counting the number of slits of an encoder sheet arranged in the scanning direction of the carriage 23 with a photosensor mounted on the carriage 23. The main scanning motor drive circuit 303 rotates the main scanning motor 24 according to the carriage movement amount input from the main control unit 301 to move the carriage 23 to a predetermined position at a predetermined speed.

  Further, the main control unit 301 receives a detection signal from a conveyance amount detection circuit 306 that detects the movement amount of the conveyance belt 51, and the main control unit 301 moves the movement amount and movement speed of the conveyance belt 51 based on the detection signal. To control. The conveyance amount detection circuit 306 detects the conveyance amount by, for example, reading and counting the number of slits of the rotary encoder sheet attached to the rotation shaft of the conveyance roller 52 with a photo sensor. The sub-scanning motor driving circuit 304 rotates the sub-scanning motor 58 in accordance with the conveyance amount input from the main control unit 301 to rotate the conveyance roller 52 to move the conveyance belt 51 to a predetermined position at a predetermined speed. Move with.

  The main control unit 301 rotates the sheet feeding roller 43 once by giving a sheet feeding roller driving command to the sheet feeding roller driving circuit 307. The main control unit 301 rotationally drives a motor (not shown) of the maintenance / recovery mechanism 81 via the maintenance / recovery mechanism drive motor drive circuit 308, thereby raising and lowering the cap 82, raising and lowering the wiper blade 83, and driving a suction pump (not shown). And so on.

  Further, the main control unit 301 inputs the detection signals from the first paper sensor 91 and the second paper sensor 92 described above, detects the leading end position of the paper 42 from both or one of the detection signals, The conveyance of the paper 42 to the printing position (image formation area by the recording head 31) is controlled according to the detection result. Further, control for adjusting the leading edge detection position by the first paper sensor 91 and the second paper sensor 92 is also performed.

  Further, the main control unit 301 takes in information stored in the non-volatile memory 316 provided in each ink cartridge 10 attached to the cartridge loading unit 4 through the cartridge communication circuit 314, performs necessary processing, and It is stored and held in a non-volatile memory (for example, EEPROM) 315 which is a main body storage means.

  Further, the main control unit 301 receives a detection signal from an environmental sensor 313 that detects environmental temperature and environmental humidity.

  The print control unit 302 generates pressure for discharging droplets of the recording head 31 based on the signal from the main control unit 301 and the carriage position and conveyance amount from the carriage position detection circuit 305 and the conveyance amount detection circuit 306. Data for driving the means is generated, and the above-mentioned image data is transferred to the head drive circuit 310 as serial data, and the transfer clock and latch signal necessary for transferring the image data and confirming the transfer, drop control, etc. In addition to outputting a signal (mask signal) etc. to the head drive circuit 310, it comprises a D / A converter, a voltage amplifier, a current amplifier, etc. for D / A converting the pattern data of the drive signal stored in the ROM. Drive waveform generation means and drive waveform selection means to be given to the head driver, one drive pulse (drive signal) or a plurality of drive parameters. Scan to generate a composed drive waveform (drive signal) to the head drive circuit 310.

  The head drive circuit 310 selectively selects a drive signal constituting a drive waveform supplied from the print control unit 302 based on image data corresponding to one row of the print head 31 that is input serially. The recording head 31 is driven by applying it to a driving element (for example, a piezoelectric element as described above) that generates energy for discharging the ink. At this time, by selecting a driving pulse constituting the driving waveform, for example, dots having different sizes such as large droplets (large dots), medium droplets (medium dots), and small droplets (small dots) can be distinguished. it can.

Next, processing in the print start position adjustment mode for adjusting the paper leading edge detection position in the image forming apparatus will be described with reference to FIG.
When adjusting the paper leading edge detection position for the image forming apparatus, the user operates a predetermined key from the operation / display unit 5 as described above or a personal computer (not shown) connected to the image forming apparatus. Using a user interface screen of a host device such as a computer, an instruction to start execution of the print start position adjustment mode for adjusting the paper leading edge detection position is given.

  When the execution start of the print start position adjustment mode is instructed, the leading edge detection position adjustment pattern (test pattern) stored and held in the internal ROM is printed out. At this time, the driving of the paper feed roller 43 is started to feed the paper 42 for printing the test pattern. After the second paper sensor 92 detects the leading edge of the paper, the first paper sensor 91 detects the leading edge of the paper. The distance until the detection is detected by the transport amount detection circuit 306, and the measured value of the distance between the second paper sensor 92 and the first paper sensor 91 is stored and held. The distance at this time can be obtained from the difference between the count values obtained by the count values of the encoder sensors of the carry amount detection circuit 306 when the second and first paper sensors 91 and 92 detect the leading edge of the paper. it can.

  The test pattern printed out at this time is a chart as shown in FIG. 6, for example. When this chart is printed, theoretically, the distance a1 between the leading edge of the sheet and the upper line 501a and the distance a2 between the trailing edge of the sheet and the lower line 501b are equal.

  However, actually, in the schematic diagram of FIG. 7, the detection position (detection position) by the nozzle 31n1 on the most upstream side in the paper conveyance direction of the recording head 31 (this is referred to as “first nozzle”) and the first paper sensor 91. For example, when the first paper sensor 91 is displaced in the direction of the paper feed start position (upstream side in the paper conveyance direction) due to a deviation or the like when the first paper sensor is attached, the distance a1 from the front end of the paper to the upper line 501a. Becomes shorter, and the distance a2 from the rear end of the sheet to the lower line 501b becomes longer.

  This deviation amount, that is, the adjustment value of the first paper sensor 91 is the deviation between the upper line and the lower line when the above-described test chart (test pattern) is folded so that the leading edge and trailing edge of the printed paper are aligned. The user can judge visually from the amount.

  Therefore, the user inputs an adjustment value of the first paper sensor 91 (adjustment value of the paper leading edge detection position by the first paper sensor 91) based on this visual result. Here, the user uses the operation / display unit 5 of the image forming apparatus or the UI screen of the host to select an adjustment value (a numerical value itself or a number corresponding to a predetermined adjustment value, for example) may be selected. input.

  In this way, the adjustment value of the first paper sensor 91 input (given) is stored in the internal RAM of the main control unit 301 or a nonvolatile memory such as the EEPROM 315.

  Thereafter, using the supplied adjustment value of the first sheet sensor 91, the adjustment value of the sheet leading edge detection position by the second sheet sensor 92 is calculated, and the calculated adjustment value of the second sheet sensor 92 is calculated by the main control unit 301. The data is stored in an internal RAM or a nonvolatile memory such as an EEPROM 315.

  Then, although not shown, printing is performed by adjusting the print start position using the adjustment value stored for the paper leading edge detection position by the first paper sensor 91 and the second paper sensor 92 thereafter. Become.

Therefore, calculation of the adjustment value of the paper leading edge detection position by the second paper sensor 92 will be described.
First, the adjusted position of the paper leading edge detection position of the first paper sensor 91 is calculated. This position is based on the position of the first nozzle 31n1, and the position after adjustment of the leading edge detection position by the first sheet sensor 91 is Nd, the theoretical value of the sheet leading edge detection position by the first sheet sensor 91 is N, and the internal memory When the stored adjustment value of the leading edge detection position by the first paper sensor 91 is R1, the position Nd after the leading edge detection position is adjusted by the first paper sensor 91 is calculated by the following equation (1).

  When the adjustment value is positive, the position of the paper sensor is shifted from the theoretical value upstream in the paper transport direction (feed start direction). When the adjustment value is negative, the paper sensor is downstream (exhaust). This indicates that the position of the sheet sensor is shifted in the (paper direction).

  Further, as shown in FIG. 6, the theoretical value of the distance from the first nozzle 31n1 to the paper leading edge detection position by the second paper sensor 92 is X, the first paper sensor 91 and the first paper sensor 91 measured at the time of the test pattern printing output described above. When the measured value of the distance to the second paper sensor 91 is Sd and the adjustment value of the leading edge detection position by the second paper sensor 92 is R2, the adjustment value R2 of the second paper sensor 92 is expressed by the following equation (2). Is calculated by

  Here, (X−N) is a theoretical value of the interval (distance) from the paper leading edge detection position by the first paper sensor 91 to the paper leading edge detection position by the second paper sensor 92.

  As described above, in this image forming apparatus, the first and second paper sensors that detect the leading edge of the sheet at different positions on the upstream side and the downstream side in the sheet conveying direction, and the adjustment value of the leading edge detection position by the first sheet sensor. Since the leading edge detection position is adjusted by the second sheet sensor, it is not necessary to adjust the leading edge detection position for the second sheet sensor, and the leading edge detection position adjustment work is simplified.

  In this case, the leading end detection by the second sheet sensor based on the adjustment value of the leading end detection position by the first sheet sensor specified when the leading end detection position adjustment test pattern is printed out and the interval between the first and second sheet sensors. By calculating the position adjustment value of the position, the position adjustment value of the leading edge detection position by the second sheet sensor can be obtained with a simple configuration. In this case, it is possible to calculate a position adjustment value with higher accuracy by using the difference between the theoretical value and the actual measurement value as the distance between the first paper sensor and the second paper sensor.

Next, a first example of printing processing using the first paper sensor and the second paper sensor in this image forming apparatus will be described with reference to FIG.
Here, after the paper 42 is fed, it is determined whether or not the printing mode is the high speed mode. If the printing mode is not the high speed mode, the first paper sensor 91 of the carriage 23 is used to detect the leading edge of the paper. If the high-speed mode is set, the paper leading edge is detected using the second paper sensor 92 upstream of the first paper sensor 91.

  Then, the paper is transported by the transport belt 51, the leading edge of the paper 42 to be transported is detected using the set first paper sensor 91 or the second paper sensor 92, and the image data writing start position (first scan position) is detected. ), The paper 42 is conveyed, and it is determined whether or not the timing for feeding the next paper 42 is reached. When the timing for feeding the next paper 42 is reached, the feeding of the paper 42 for the next page is started. If the timing of feeding the next sheet 42 is not reached, a printing process for forming an image on the sheet 42 of the current page is performed, and the conveyance and printing of the sheet 42 are repeated until printing on the sheet 42 of the current page is completed.

  Then, it is checked whether it is the last page or not, and it is determined whether or not printing for all the pages is completed. Printing for each page is repeated until the last page is reached, and when the last page is reached, the last page is discharged. The printing process ends.

  That is, when continuous printing is performed, the paper 42 is continuously fed with a predetermined interval between papers, and at the timing when the last scan image formation of the preceding page (preceding paper) is completed, the predetermined paper is used. The next page (following paper) is being conveyed at intervals. At this time, the carriage 3 is moved to a predetermined paper front end detection position (a predetermined position for detecting the front end of the paper 42) to detect the front end of the next page, but the carriage 23 is moved to a predetermined paper front end detection position. The next page sheet is conveyed by the conveyor belt 51 while the sheet is being conveyed. Therefore, depending on the conveyance speed of the paper 42, the leading edge of the next page paper passes under the carriage 23 before the carriage 23 arrives at the paper leading edge detection position. The leading edge of the page paper may not be detected.

  Therefore, in this image forming apparatus, when the printing mode is high-speed printing, the leading edge of the sheet can be reliably detected by detecting the leading edge of the sheet using the second sheet sensor 92.

Next, a second example of printing processing using the first paper sensor and the second paper sensor in this image forming apparatus will be described with reference to FIG.
Here, whether to detect the leading edge of the sheet by the first sheet sensor 91 or to detect the leading edge of the sheet by the second sheet sensor 92 is selected according to the type of the sheet. For example, as shown in FIG. 9, the space between plain papers for which higher speed printing is required is reduced (here, 40 mm). On the other hand, by reducing the space between papers, double feeding or continuous feeding is performed. Other paper types such as glossy paper and OHP, which increase the risk, have a margin between papers (here, 60 mm).

  When the conveyance speed is constant, the time between the end of the preceding sheet and the leading edge of the next page passing the sheet leading edge detection position by the first sheet sensor 91 after the last scanning of the preceding sheet is shortened (decreases) between the sheets. Becomes shorter. For this reason, when the sheet interval is less than or equal to a predetermined value, the leading edge of the next page may pass under the carriage 23 before the carriage 23 arrives at the leading edge detection position.

  Therefore, after feeding the paper 42, it is determined whether or not the paper 42 is plain paper. At this time, if the paper 42 is not plain paper, the first paper sensor 91 of the carriage 23 is set to detect the leading edge of the paper. If the paper 42 is plain paper, the first paper sensor 91 is used. A setting is made to detect the leading edge of the sheet using the second sheet sensor 92 on the upstream side.

  Then, the paper is transported by the transport belt 51, the leading edge of the paper 42 to be transported is detected using the set first paper sensor 91 or the second paper sensor 92, and the image data writing start position (first scan position) is detected. ), The paper 42 is conveyed, and it is determined whether or not the timing for feeding the next paper 42 is reached. When the timing for feeding the next paper 42 is reached, the feeding of the paper 42 for the next page is started. If the timing of feeding the next sheet 42 is not reached, a printing process for forming an image on the sheet 42 of the current page is performed, and the conveyance and printing of the sheet 42 are repeated until printing on the sheet 42 of the current page is completed.

  Then, it is checked whether it is the last page or not, and it is determined whether or not printing for all the pages is completed. Printing for each page is repeated until the last page is reached, and when the last page is reached, the last page is discharged. The printing process ends.

  As described above, the first paper sensor or the second paper sensor detects the leading edge of the paper according to the type of paper to be printed, so that when the plurality of pages are continuously printed, the space between the papers becomes narrow and the first paper sensor. Even when the leading edge is not detected in time, the leading edge can be detected by the second sheet sensor, so that the printing speed can be improved and stable image formation can be performed while accurately detecting the leading edge of the sheet.

  In this example, the sheet interval is used as the print mode condition for switching between the first sheet sensor and the second sheet sensor as the detection means for detecting the leading edge of the sheet. However, the type of sheet to be used, the sheet thickness, the resistance value, and single-sided printing. / The first paper sensor 91 and the second paper 92 can be switched and used as a paper sensor for detecting the leading edge using conditions such as the presence / absence of double-sided printing and the paper size.

  In the above example, the first paper sensor or the second paper sensor is used from the detection of the leading edge of the paper on the first page, but the first paper sensor may be used only on the first page. .

1 is a perspective view illustrating an example of an image forming apparatus according to the present invention as viewed from the front side. 2 is a configuration diagram illustrating an outline of a mechanism unit of the image forming apparatus. FIG. It is principal part plane explanatory drawing of the mechanism part. FIG. 2 is a block explanatory diagram illustrating an overview of a control unit of the image forming apparatus. It is a flowchart with which it uses for description of the paper front end detection position adjustment operation | movement of the control part. It is explanatory drawing which shows an example of a test pattern. FIG. 10 is an explanatory diagram for explaining calculation of an adjustment value of a leading end detection position of a second paper sensor. It is a flowchart which shows an example of a printing process. It is a flowchart which shows the other example of a printing process. FIG. 10 is an explanatory diagram for explaining FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Ink cartridge 23 ... Carriage 31 ... Recording head 51 ... Conveying belt 91 ... 1st paper sensor 92 ... 2nd paper sensor 301 ... Main control part

Claims (4)

In an image forming apparatus in which a recording head is mounted on a carriage and a recording medium is conveyed in a direction perpendicular to the scanning direction of the carriage to form an image on the recording medium.
First detection means for detecting the recording medium mounted on the carriage;
A second detection means arranged on the upstream side in the recording medium conveyance direction relative to the first detection means for detecting the recording medium;
Means for storing a distance between the first detection means and the second detection means;
Storage means for storing a test pattern for correcting the leading end detection position of the recording medium;
Based on the result of alignment of the relationship between the first detection means designated when the stored test pattern is printed out and the nozzle position of the recording head and the stored distance, the second detection An image forming apparatus comprising: means for correcting a relationship between the means and a nozzle position of the recording head . The image forming apparatus according to claim 1, wherein the first detection unit and the second detection unit are selectively used according to a type of the recording medium. The image forming apparatus according to claim 1, wherein the first detection unit and the second detection unit are selectively used according to a print mode. Distance between the second detecting means and said first detecting means An apparatus according to claim 1 which comprises using the actual measurement value and the theoretical value

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