JP2010030161A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an inclination can not be detected only by printing a pattern and finding the distance between two patterns on a form for detecting the inclination of a carriage in the height direction. <P>SOLUTION: The image formation device includes the carriage 5 wherein a recording head 6 having nozzles for discharging a droplet is installed and scanned with movement in the main scan direction, a means for forming an inclination detecting pattern (dot Dp) for detecting the inclination of the carriage in the height direction against a form conveyance surface in the main scan direction, a reading sensor 30 which is installed in the carriage 5 and reads the dot Dp, and a means for detecting the inclination of the carriage 5 in the height direction by comparing the distance from a reference point of the carriage 5 in the main scan direction up to the point where the dot Dp is detected by the reading sensor 30 with a predetermined distance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a carriage on which a recording head for discharging droplets is mounted.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, a plotter, and a complex machine of these, for example, an ink jet recording apparatus using a recording head for discharging ink droplets is known. This ink jet recording apparatus means a sheet on which ink droplets are conveyed from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously), and a recording head A line type image using a serial type image forming apparatus that forms an image by ejecting droplets while moving in the main scanning direction, and a line type head that forms images by ejecting droplets without moving the recording head There is a forming device.

  In the present application, “image forming apparatus” means an apparatus that forms an image by ejecting ink onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, In addition, “image formation” not only applies an image having a meaning such as a character or a figure to a medium but also applies an image having no meaning such as a pattern to the medium (simply applying a droplet to the medium). It also means to land on. The “ink” is not limited to the ink, but is used as a general term for all liquids that can perform image formation, such as a recording liquid, a fixing processing liquid, and a liquid.

  In a serial type ink jet recording apparatus, a carriage on which a recording head is mounted is slidably guided by a main and subordinate guide member and moved and scanned in the main scanning direction. It is known that the carriage is inclined in the height direction with respect to the sheet conveyance surface. When such a tilt in the height direction of the carriage occurs, the distance (gap) between the nozzles having different positions in the main scanning direction and the sheet conveyance surface is different, and the flying distance from each nozzle is different. The image quality deteriorates because the position accuracy is lowered.

Therefore, for example, Patent Document 1 discloses a discharge pattern (position information) at the time of factory shipment and discharge for each number of prints set in advance in the user's use environment by a light receiving sensor fixed to a carriage that drives printing in the main scanning direction. A configuration is described in which a pattern is detected, the difference between these is calculated as a discharge accuracy difference (position shift) in the entire range of the carriage drive range, and the difference is adjusted at the discharge timing.
JP 2007-185870 A

In addition, regarding the gap variation between the carriage and the sheet conveyance surface, Patent Document 2 includes a means for measuring the distance between the print head and the recording medium for each scan to correct the droplet discharge timing. Japanese Patent Application Laid-Open No. H10-228688 discloses a method of correcting the droplet ejection timing by providing an adhesion position detection unit that detects in advance the adhesion position of the ink droplet on the recording medium when the ink droplet is ejected from the head at a predetermined timing. In this case, the distance between papers is measured by an optical paper distance sensor, and a correction value for a possible deviation amount is calculated from the obtained value to correct the droplet ejection timing.
JP 2007-044948 A JP 2000-233495 A JP 2003-334941 A

  However, in the configuration described in Patent Document 1 described above, the detection timing for reading the ejection pattern by the light receiving sensor is similarly shifted when the carriage tilts in the height direction due to secular change. An accurate difference from (initial position) cannot be obtained.

  That is, as shown in FIG. 23, when the patterns 1003a and 1003b formed on the paper 1002 (that is, on the same plane) are detected by the light receiving sensor 1001 mounted on the carriage 1000, the light receiving sensor 1001 is inclined (see FIG. 23). Even if (b)) is not tilted ((a) in the figure), the interval L is the same, so there is no difference from the initial value, and the tilt in the height direction of the carriage cannot be detected. .

  The present invention has been made in view of the above problems, and an object thereof is to accurately detect the inclination of the carriage in the height direction.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A carriage mounted with a recording head having nozzles for discharging liquid droplets and moved and scanned in the main scanning direction;
Pattern forming means for forming an inclination detection pattern for detecting an inclination of the carriage in the height direction with respect to the sheet conveyance surface in the main scanning direction;
Reading means mounted on the carriage for reading the inclination detection pattern;
Means for comparing the distance from the reference position in the main scanning direction of the carriage to the detection of the inclination detection pattern by the reading means with a predetermined distance, and detecting the inclination in the height direction of the carriage;
It was set as the structure equipped with.

  Here, it is possible to adopt a configuration in which the droplet discharge timing from the recording head is corrected according to the detection result of the inclination of the carriage in the height direction.

  Further, the droplet discharge timing can be corrected for each pixel of the print resolution, the droplet discharge timing can be corrected individually for the forward pass printing and the backward pass print, and the droplet discharge timing can be corrected for each nozzle.

  According to the image forming apparatus of the present invention, the distance from the reference position in the main scanning direction of the carriage to the detection of the inclination detection pattern by the reading unit is compared with the predetermined distance, and the height of the carriage is compared. Since the means for detecting the inclination is provided, the inclination in the height direction of the carriage can be accurately detected.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. An example of an ink jet recording apparatus as an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is an explanatory perspective view showing the entire configuration of the recording apparatus, FIG. 2 is an explanatory schematic plan view of a mechanism unit of the recording apparatus, and FIG. 3 is an explanatory schematic perspective view of the mechanism unit.

  The ink jet recording apparatus is a serial type ink jet recording apparatus, and includes a recording apparatus main body 1 and a support base 2 that supports the recording apparatus main body 1.

  Inside the recording apparatus main body 1, guide rods 3 and guide rails 4 are spanned on both side plates (not shown), and a carriage 5 can slide on these guide rods 3 and guide rails 4 in the direction of arrow A in FIG. Is held in.

  As shown in FIG. 2, the carriage 5 has eight recording heads 6k1 including liquid ejection heads that eject ink droplets of black (K), yellow (Y), magenta (M), and cyan (C). , 6k2, 6y1, 6y2, 6m1, 6m2, 6c1, and 6c2 (referred to as “recording head 6” when colors are not distinguished). The two recording heads for each color are arranged with their positions shifted in the main scanning direction and the direction orthogonal to the main scanning direction (paper feeding direction: sub-scanning direction).

  The main scanning mechanism that moves and scans the carriage 3 is disposed on one side in the main scanning direction, a driving pulley 12 that is rotationally driven by the driving motor 11, and on the other side in the main scanning direction. A driven pulley 13 and a belt member 14 wound around the drive pulley 12 and the driven pulley 13 are provided. The driven pulley 13 is tensioned outward by a tension spring 15 (in a direction away from the drive pulley 12).

  Here, the driving pulley 12 and the driven pulley 13 are arranged such that the pulley axial direction is located in a direction along the ink droplet ejection direction. The belt member 14 wound between the drive pulley 12 and the driven pulley 13 is composed of independent timing belts 14A and 14B made of two rubber toothed belts. 14A and 14B are arranged around the driving pulley 12 and the driven pulley 13 in this example without gaps in the pulley axis direction. In addition, these timing belts 14A and 14B are arranged on one side of the carriage 5 in a direction perpendicular to the main scanning direction by being partially fixed and held by a belt fixing portion 7 provided on the back side of the carriage 5, respectively. Has been.

  Further, as shown in FIG. 4, the carriage 5 includes a reflection type photosensor as a reading unit for reading an inclination detection pattern for detecting an inclination in the height direction of the carriage with respect to the sheet conveyance surface in the main scanning direction. A sensor 30 is provided.

  An encoder sheet (also referred to as a linear scale or encoder scale) 21 for detecting the main scanning position of the carriage 5 is disposed along the main scanning direction of the carriage 5, and an encoder sensor 22 provided on the carriage 5. Thus, the encoder sheet 21 is read. Here, as shown in FIG. 5, the encoder sheet 21 is formed by alternately forming transparent portions 21a and black portions 21b at a predetermined pitch P (in the case of 600 dpi, 0.0423 [mm]).

  In the main scanning area of the carriage 5, in the recording area, the paper 10 is guided by the platen member 20 in a direction (sub-scanning direction: arrow B direction) perpendicular to the main scanning direction of the carriage 5 by a paper feed mechanism (not shown). Are intermittently conveyed. The platen member 20 is disposed on the carriage 5 so as to face the recording head 6 at least in the recording area along the main scanning area.

  In addition, a maintenance / recovery mechanism 8 that performs maintenance / recovery of the recording head 6 is disposed in one end side region of the main scanning region. Further, a main cartridge 9 containing ink of each color to be supplied to the recording head 6 is detachable from the recording apparatus main body 1 outside the carriage movement area in the main scanning direction or below the other end of the carriage movement area. Installed.

  In this ink jet recording apparatus, the carriage 5 is moved in the main scanning direction, and the recording head 6 is driven according to the image information while the paper 10 is intermittently fed in the sub scanning direction, thereby ejecting droplets. A required image is formed on 10.

Next, an outline of the control unit of the ink jet recording apparatus will be described with reference to a block diagram of FIG.
The control unit 100 includes a main calculation unit 101 that also serves as a pattern formation unit and an inclination detection unit according to the present invention that controls the entire recording apparatus, a head drive control unit 102 that controls the drive of the recording head 6, and a storage unit. 103, an externally writable program memory 104, a synchronization signal generator 105 that generates a clock with a cycle shorter than the pitch of the encoder sheet 21, and drive waveform data to be applied to the recording head 6 from the head drive controller 102. The stored drive waveform storage unit 106, the main scanning motor driving unit 107 that drives the main scanning motor 11, the sub-scanning motor driving unit 108 that drives the sub-scanning motor 16 for conveying the paper 10, and the inclination detection pattern A pattern generation unit 109 for generating the communication, a communication circuit 110 for communicating with the outside, and the like.

  The main processing unit 101 receives, via a cable or a network, print data from a host side such as an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, etc. To do. The RAM in the main control unit 101 is used as various buffers and work memories and stores various data, and the ROM stores various control routines executed by the CPU, font data and graphic functions, various procedures, and the like.

  The head drive control unit 102 includes a drive signal generation circuit that generates a drive waveform for driving the actuator means of the recording head 6 by A / D converting the drive waveform data stored in the drive waveform storage unit 106. The print data developed in the dot pattern data (bitmap data) from the control unit 101, the generated drive waveform, and the like are sent to a head driver (not shown) provided on the carriage 5 side for driving the recording head 6.

  The main calculation unit 101 gives predetermined inclination detection patterns for detecting the inclination of the carriage 5 in the height direction on the paper 10 by supplying the inclination detection pattern data from the pattern generation unit 109 to the head drive control unit 102. It is formed at the timing.

  The main calculation unit 101 detects the position of the carriage 5 in the main scanning direction based on the output signal of the encoder sensor 22 and controls the movement stop position of the carriage 5. Further, a reference position of the carriage 5 obtained from the encoder sensor 22 and a detection signal (reading signal) of a tilt detection pattern from the reading sensor 30 of the carriage 5 are inputted, and the main scanning direction of the carriage 5 is based on these detection signals. The droplet ejection timing from the recording head 6 is corrected by detecting the tilt in the height direction at the head and controlling the output timing of the drive waveform data from the drive waveform storage unit 106 according to the detected tilt in the height direction. Control.

Next, the droplet discharge timing correction processing by the control unit will be described with reference to the flowchart of FIG.
First, when it is detected that droplet discharge can be started from the nozzles of the recording head 6, it is determined whether or not it is set to perform position shift correction for correcting the droplet discharge timing in the main scanning direction, and when position shift correction is not performed, The process proceeds to a normal printing process after determining whether or not image formation preparation is complete.

  On the other hand, when the misalignment correction execution setting is set, it is determined whether or not the sheet passing number has reached a predetermined set number for starting the misalignment correction operation. After determining whether image formation preparation is complete, the process proceeds to normal printing.

  Further, when the number of sheets to be passed reaches the set number for starting the misalignment correction operation, an inclination detection pattern (hereinafter referred to as “specific printing pattern”) is printed.

  This specific print pattern is printed in advance in the storage unit 103 from the main calculation unit 101 to the pattern generation unit 109 or from an inclination detection pattern (hereinafter referred to as “specification” acquired from the outside via the communication circuit 101). The specific print pattern generation method is instructed based on the information related to the generation method of “print pattern”), and the required specific print pattern data is transferred to the head drive control unit 102.

  At the same time, the recording head stored in the drive waveform storage unit 106 according to the print resolution and environmental temperature, which is stored in the program memory 104 in advance or taken in from the outside via the communication circuit 101 and is the current target. 6 driving waveform is selected and transferred to the head driving control unit 102.

  As a result, the specific print pattern data necessary for printing the specific print pattern and various control signals necessary for driving the recording head 6 are transferred from the head drive control unit 102 to the driver on the recording head 6 side. The drive control of the motor 11 and the sub-scanning motor 16 is performed, the carriage 5 is moved and scanned in the main scanning direction, the paper 10 is conveyed in the sub-scanning direction, and a specific print pattern is printed on the paper 10.

  Thereafter, the main operation unit 101 performs main scanning of the carriage 5 to read a specific print pattern printed on the paper 10 by the reading sensor 30, and while reading the specific print pattern, the carriage 5 at each pixel position. Is calculated by a predetermined calculation method, which will be described later, and information on the inclination in the height direction of the carriage for each pixel (hereinafter simply referred to as “carriage inclination”) is stored in the storage unit 103.

Then, using the carriage tilt information for each pixel stored in the storage unit 103, a correction value for the droplet ejection timing for each pixel is calculated by a method described later, and the head drive control unit 102 uses the detected position of the encoder sheet 21 as a reference. The predetermined droplet discharge timing is corrected by a correction value corresponding to the carriage tilt, and the droplet discharge timing is reset.

  In this case, in this recording apparatus, as shown in FIGS. 8 and 9, the droplet discharge is performed for a predetermined time (from the synchronization signal generator 105) determined for the nozzle on the basis of the output signal (encoder detection timing) from the encoder sensor 22. The time point after the elapse is used as the droplet discharge timing (print timing).

  When bidirectional printing is performed, the droplet discharge timings are individually reset in the forward path (FIG. 8) and the backward path (FIG. 9), and the number of forward pixels is Tf1 to Tfn, and the number of backward pixels is Tb1 to Tbn. The droplet discharge timing is stored and held. In this example, the case where the inclination of the carriage 5 is the same with respect to the carriage traveling direction in the forward path and the return path is shown, but the case where the inclination of the carriage 5 does not change between the forward path and the return path (for example, the return path is also shown in FIG. There is also a case of moving in a posture).

  In addition, when dot formation and sensing (reading by the sensor 30) are performed in real time (same path), only one shift between the forward path and the backward path can be detected, but by performing dot formation and sensing through different paths. The deviation between the forward path and the return path can be detected.

  Further, when printing a specific print pattern, as shown in FIG. 10A, when printing on the paper 10 is overlapped by printing of adjacent pixels (when overlapping like dots D1, D2, and D3). As shown in FIG. 10B, printing is performed as a specific print pattern in which dots are separated in the sub-scanning direction, or the amount of droplets is small as shown in FIG. By printing a specific print pattern using a drive waveform for ejecting small droplets, a situation in which detection is not possible for each pixel is avoided.

  It should be noted that the main arithmetic unit 101 detects the specific print pattern this time based on information notified in advance or written in the storage unit 103 by the communication circuit 101 (for example, for each pixel). Or whether it is performed at several points in the main scanning direction), and the required inclination detection operation is performed.

Next, setting of a specific print pattern generated by the pattern generation unit will be described with reference to FIG.
The setting of a specific print pattern used for detecting the inclination of the carriage as the specific print pattern is stored in the storage unit 103 in advance, or taken in from the outside by the communication circuit 110 and similarly stored in the storage unit 103.

Here, as the setting information of the specific print pattern, a pattern of the minimum unit of repetition is set.
For the main scanning direction, the print pattern start position: Pms1, the print pattern end position Pme1, the number of continuous prints in the main scan: Nm1, the interval until the next continuous print: Nmd1, the main scan pattern repeat count : Pmr is set.

  These set values need to be set for the number of lines of the minimum unit pattern to be repeated in the sub-scanning direction for each main scanning line (if the minimum unit of the specific print pattern is n lines, 1 to n minutes are set. necessary).

  For the sub-scanning direction, the start position for starting the specific print pattern: Pss, the end position for ending the specific print pattern: Pse, the interval until the next continuous printing: Nsd, and the main scan pattern repetition count Psr1 are set. .

  As a result, as shown in FIG. 11, a necessary specific print pattern can be generated.

Next, an outline of the detection of the inclination in the height direction of the carriage in the present invention will be described with reference to FIG.
First, as shown in FIG. 12A, with the position in the main scanning direction of the carriage 5 detected by the encoder sensor 22 as a reference position, a predetermined distance L0 from the reference position (as will be described later, the clock signal from the synchronization signal generator 105). The dot Dp constituting the specific print pattern is printed at the position corresponding to the count value. When the carriage 5 is not inclined in the height direction as shown in FIG. 12A, the distance from the reference position to the dot Dp is the distance L0.

  On the other hand, as shown in FIG. 12B, when the carriage 5 is inclined in the direction in which the front side in the carriage movement direction becomes higher, droplet discharge is performed at a distance L0 from the reference position to form dots Dp. In this case, the position at which the dot Dp is formed due to the inclination of the carriage 5 is at a distance L2 (L2> 10) with respect to the reference position.

  On the other hand, as shown in FIG. 12C, when the carriage 5 is tilted in the direction in which the rear side in the carriage movement direction becomes higher, droplets are ejected from the reference position at a distance L0 to form dots Dp. The position at which the dot Dp is formed due to the inclination of 5 is the position of the distance L1 (L1 <10) with respect to the reference position.

  Therefore, by comparing the distance from the reference position to the dot Dp when the reading sensor 30 detects the dot Dp with the distance L0 (initial value) when the carriage 5 is not inclined, the direction of inclination of the carriage 5 and The inclination angle (inclination) θ can be detected.

  In this way, the distance until the specific print pattern is detected based on the reference position of the carriage 5 is measured, and the difference from the distance (initial value) when there is no inclination is obtained to detect the inclination of the carriage 5. be able to.

  That is, only measuring the distance between two dots of the specific print pattern is a measurement of the relative position. Therefore, when the carriage 5 is inclined, the reading sensor 30 is also inclined, and as a result, the distance between the two dots is not changed. On the other hand, in the present invention, since the reference position is fixed, the inclination of the carriage 5 can be detected by measuring the distance from the reference position to the dots of the specific print pattern. The fixed reference position means that the reference position is fixed when calculating the initial value. For example, when calculating the inclination for each pixel as described later, The reference position may be changed.

  Hereinafter, the carriage tilt detection method will be described in detail with reference to FIG. Note that the droplet velocity Vjet [mm / s] discharged from the recording head 6 is extremely higher than the moving velocity (carriage velocity) V [mm / s] of the carriage 5.

  First, in this recording apparatus, as shown in FIG. 13, on the carriage 5, the encoder sensor 22 and the nozzle 6n of the recording head 6 are physically different positions with respect to the main scanning direction (an upper assembly constant). A). Similarly, the reading sensor 30 and the nozzle 6n of the recording head 6 are disposed at physically different positions (assumed to be an assembly constant B) in the main scanning direction. Therefore, when the carriage 5 is tilted in the height direction, the direction of droplets ejected from the nozzles 6n changes by an angle θ according to the tilt θ of the carriage 5, as shown in FIG.

  Accordingly, the print timing will be described with reference to FIG. Here, the slit pattern (transparent portion 21a) of the nth encoder sheet 21 corresponding to the number of target print pixels shown in FIG. 5A is read by the encoder sensor 22, and the output signal of the encoder sensor 22 shown in FIG. Is detected by the clock clk from the synchronizing signal generator 105 shown in FIG. 5B, and the timing trigger is generated with the position shown in FIG. Timing of (n1 + a) when an offset value n1 [clk] taking into account the physical distance (constant A) between the encoder sensor 22 and the nozzle 6n from the encoder detection position and a predetermined value a [clk] are further passed therefrom. A droplet is ejected to print a dot D.

  The offset value at this time, that is, the number of clocks n1 [clk] corresponding to the time difference between the encoder and the nozzle, is the encoder sensor-nozzle distance A [mm], the carriage speed V “mm / s”, and the internal clock frequency M [MHz]. ], When the time t [s] from the input of the encoder signal to the nozzle position is obtained, the following equations (1) to (3) are obtained.

  Next, the detection timing of the specific print pattern will be described with reference to FIG. As described above, when the dot Dp constituting the specific print pattern is printed at the print timing of the nth pixel, if the carriage 5 is not inclined, as shown in FIG. Becomes a signal that rises while the dot Dp is detected, and includes a droplet discharge timing (n1 + a), a clock number n2 [clk] corresponding to the time difference between the nozzle and the reading sensor, and a clock number n3 [clk] corresponding to the nozzle radius. Considering this, the dot Dp is detected at the timing when the count value of the clock number n4 is reached from the encoder detection position of the nth pixel.

  In other words, there is a physical deviation in assembly between the reading sensor 30 and the nozzle 6n on the carriage 5, and it is detected late with respect to the nozzle 6n, so the number of clocks corresponding to the time difference between the nozzle and the reading sensor. n2 [clk], the number of clocks corresponding to the nozzle radius n3 [clk], the nozzle-read sensor distance B [mm], the dot radius D [mm], the carriage speed V [mm / s], the internal clock frequency M When [MHz] is the time t [s] from the input of the encoder signal to the nozzle position, the following equations (4) to (7) are obtained.

  Here, in order to perform more accurate detection, the number of clocks corresponding to the radius is assumed to be the number of clocks n3 [clk], considering that the diameter of the print dot Dp is also taken into consideration. .

  Therefore, the clock number n4 [clk] corresponding to the detection timing of the dot Dp corresponding to the nth pixel is “n4 = a + n1 + n2−n3” [clk].

  In this case, the clock numbers n1 and n2 are converted into encoder pulse (encoder output signal) count values, and the number of clocks corresponding to the print timing from the detection timing of the absolute position pattern of the encoder sheet 21 at the position corresponding to the offset. It is also possible to count a [clk] and the number of clocks n3 [clk] corresponding to the pixel radius.

  Here, when the carriage 5 is tilted, the reading sensor 30 is moved up and down (see FIG. 14) by the sensor position of the reading sensor 30 due to the tilt of the carriage 5 even when printing is performed for the nth pixel at the above-described printing timing. The timing for detecting the dot Dp is shifted. Therefore, when the carriage 5 is not yet tilted at the time of factory shipment or the like, printing is performed over an appropriate printing region, the detection timing of the detection is stored as an initial value, and during the actual droplet discharge timing correction operation, By detecting how much and how much the actual timing detected for the initial printing timing in the traveling direction with respect to the initial value is deviated, the inclination of the carriage 5 and its direction can be detected.

  For example, when the carriage 5 is inclined in the direction in which the rear side in the traveling direction becomes higher, as shown in FIG. 17, the dot Dp is printed at the position shown by the broken line with respect to the dot Dp shown by the solid line corresponding to the initial value. The number of clocks n4 ′ [clk] when ′ is detected is larger than the initial number of clocks n4 [clk] (detected at a timing later than the initial position).

  Further, when the carriage 5 is inclined in the direction in which the front side in the traveling direction becomes higher, as shown in FIG. 18, the dot Dp is printed at the position shown by the broken line with respect to the dot Dp shown by the solid line corresponding to the initial value. The number of clocks n4 ′ [clk] when ′ is detected is smaller than the initial number of clocks n4 [clk] (detected at a timing earlier than the initial position).

  At this time, as shown in FIG. 19, the inclination θ of the carriage 5 is expressed by the following (7) and (7) due to the assembling relationship between the position of the nozzle 6 n and the sensor position of the reading sensor 30 and the detection timing deviation due to the inclination of the carriage 5. It is obtained by the equation (8).

  In this way, by comparing the distance from the reference position in the main scanning direction of the carriage to the detection of the inclination detection pattern by the reading unit with a predetermined distance, the inclination in the height direction of the carriage is detected. Even when an inclination detection pattern is printed on the same plane, the inclination of the carriage in the height direction can be accurately detected.

  Next, correction of droplet discharge timing will be described. The droplet velocity Vjet [mm / s] is sufficiently larger than the carriage velocity V [mm / s], and the influence of the velocity component in the parallel direction on the droplet drop is negligible.

  As shown in FIG. 20, since the height h [mm] is shifted according to the direction of the inclination of the carriage 5, the height deviation h ′ [mm] of the nozzle 6n due to the inclination is the left inclination. Time (when the detection timing of the first dot print is n4 ′ <n4) is expressed by equation (10), and when it is tilted right (when the detection timing of the first dot print is n4 ′> n4) (11 ) Respectively.

  Based on the droplet discharge speed Vjet [mm / s] and the previously calculated inclination θ of the carriage 5, the time t when the droplet reaches the print target (paper 10) can be calculated from the equation (12). Further, from the time t, the droplet velocity Vjet [mm / s] and the previously calculated inclination 5 of the carriage 5, the landing position deviation amount Δx corresponding to the inclination θ of the carriage 5 can be calculated as shown in the equation (13). .

  If printing is performed by shifting the printing timing (droplet ejection timing) by the landing position deviation amount Δx, that is, by shifting the timing by the timing adjustment time Δt1 obtained by the equation (14), the printing is adjusted to the target landing position. It becomes possible.

  Here, this adjustment time Δt1 can be expressed by equation (15). In order to adjust this time, the print timing is originally measured at the timing of the clock CLK of the synchronization signal generation unit 105 from the rising edge of the encoder. Therefore, when converted into the number of clocks of the synchronization signal (clock), the number of clocks nt1 for counting the adjustment time Δt1 is obtained by the equations (16) and (17), and the print timing is controlled by the number of clocks nt1. By doing so, the print position due to the carriage tilt can be corrected.

  Further, as shown in FIG. 21, it can be seen that an error occurs with respect to the time when the print timing is originally measured in consideration of the distance corresponding to the assembly position due to the inclination of the carriage 5.

  The print timing error corresponding to this can be detected by detecting the inclination θ of the carriage, and can be corrected by adjusting the timing corresponding to the number of clocks nt2 obtained by the equations (18) to (22).

  Therefore, the correction timing based on the inclination of the carriage 5 may be corrected to the initial timing by nt1 + nt2 [clk].

Next, the case where there are a plurality of nozzles will be described with reference to FIG.
Even when the number of nozzles increases, the main calculation unit 101 performs the landing position deviation correction operation by tilting the carriage 5 in the height direction for any nozzle and detects the tilt angle θ. After that, as shown in FIG. 20, the correction value is calculated by using the distance between the encoder sensor 22 and the reading sensor 30 (the assembly upper constants A1 to A4 and B1 to B4) for each nozzle 6nk, 6ny, 6nm, and 6nc. Then, the droplet ejection timing (print timing) for each pixel of each nozzle is corrected.

  Even when there is a nozzle in front of the printing direction from the position of the encoder sensor 22 (encoder position), it is sufficient to perform printing quickly by giving the corresponding distance as an offset value of the encoder value. On the other hand, when the nozzle is arranged at the rear, it is sufficient to perform the printing slowly with the distance corresponding to the offset value of the encoder value.

  In the above embodiment, the distance is processed by the clock count value, but the distance can also be processed by time.

1 is an explanatory perspective view illustrating an overall configuration of an example of an ink jet recording apparatus according to the present invention. It is a typical plane explanatory view of a mechanism part similarly. It is an outline perspective explanatory view of the mechanism part similarly. It is front explanatory drawing similarly used for description of the reading sensor of a carriage. It is explanatory drawing similarly used for description of an encoder sheet. It is a block explanatory view explaining the outline of a control part similarly. FIG. 6 is a flowchart for explaining the carriage tilt detection and the droplet discharge timing correction processing. It is explanatory drawing with which it uses for description of the setting of the droplet discharge timing in an outward path. It is explanatory drawing with which it uses for description of the setting of the droplet discharge timing in a return path. It is explanatory drawing with which it uses for description of the printing method of a specific printing pattern. It is explanatory drawing with which explanation of the setting of a specific printing pattern is provided. It is explanatory drawing with which it uses for description of the outline | summary of the carriage inclination detection in this invention. It is explanatory drawing with which it uses for description of arrangement | positioning of an encoder sensor, a nozzle, and a reading sensor. It is explanatory drawing with which it uses for description similarly when a carriage inclines. It is explanatory drawing with which it uses for description of printing timing. It is explanatory drawing with which it uses for description of the printing timing and detection timing of a specific printing pattern when there is no inclination of a carriage. It is explanatory drawing with which it uses for description of the detection timing of the specific printing pattern when a carriage inclines. FIG. 18 is an explanatory diagram for explaining the detection timing of a specific print pattern when the carriage is tilted in the opposite direction to FIG. 17. FIG. 6 is an explanatory diagram for explaining an assembling relationship between a nozzle position and a sensor position of a reading sensor and a shift in detection timing due to a tilt of a carriage. It is explanatory drawing with which it uses for description of droplet discharge timing. It is explanatory drawing with which it uses for description of droplet discharge timing. It is explanatory drawing with which it uses for description when the number of nozzles increases. It is explanatory drawing with which it uses for description that inclination detection cannot be performed in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Recording apparatus main body 2 ... Support stand 5 ... Carriage 6k1, 6k2, 6y1, 6y2, 6m1, 6m2, 6c1, 6c2 ... Recording head 7 ... Belt fixing part 10 ... Paper 20 ... Platen member 30 ... Read sensor

Claims (5)

A carriage mounted with a recording head having nozzles for discharging liquid droplets and moved and scanned in the main scanning direction;
Pattern forming means for forming an inclination detection pattern for detecting an inclination of the carriage in the height direction with respect to the sheet conveyance surface in the main scanning direction;
Reading means mounted on the carriage for reading the inclination detection pattern;
Means for comparing the distance from the reference position in the main scanning direction of the carriage to the detection of the inclination detection pattern by the reading means with a predetermined distance, and detecting the inclination in the height direction of the carriage;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein a droplet discharge timing from the recording head is corrected in accordance with a detection result of an inclination in the height direction of the carriage.   The image forming apparatus according to claim 2, wherein the droplet discharge timing is corrected for each pixel of the print resolution.   4. The image forming apparatus according to claim 2, wherein the droplet discharge timing is individually corrected at the time of forward printing and at the time of backward printing.   5. The image forming apparatus according to claim 2, wherein the droplet discharge timing is corrected for each nozzle.

Images