JP2006137049A - Printing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speed up the nozzle clogging detection process for a printing head. <P>SOLUTION: A plurality of check marks are printed while reciprocating the printing head by a carriage 28, and the check marks are read by a photo-sensor 41 on the carriage to detect the nozzle clogging in the printer. A controller 60 stores the level of a signal string which is read by the photo-sensor 41 in the outward trip in a memory 61, and judges the level of the signal string which has been stored in the memory 61. In addition, the controller 60 stores the level of the signal string which has been read by the photo-sensor 41 in the return trip in the memory 61, and judges the level of the signal string stored in the memory 61 in the same manner as the outward trip in the opposite order from the reading order of the photo-sensor 41. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for performing check pattern detection at high speed by a sensor provided in a head.

2. Description of the Related Art Conventionally, in an inkjet printer or the like, a printer that prints a predetermined check pattern on a printing paper, reads the printed check pattern using an optical sensor or the like, and automatically detects clogging of nozzles of a print head is known. (For example, patent document 1). In this case, the optical sensor is mounted on the carriage together with the print head and the like, and the determination is performed by scanning the check pattern on the printing paper by moving the carriage.
JP-A-9-19397

  However, in the conventional automatic detection of nozzle clogging, when scanning the printing paper while moving the carriage, the scanning direction is limited to one direction. For this reason, since the scanning is not performed when the carriage is moving in the reverse direction, this time is wasted.

  Therefore, an object of the present invention is to speed up the process of detecting a check pattern by a sensor provided in a print head.

  A printing apparatus according to an embodiment of the present invention is a printing apparatus that prints a plurality of check patterns while reciprocating a print head with a carriage, and detects the check patterns with a reading sensor on the carriage. The level of the signal string read by the sensor in the forward path is stored in the storage means, the forward path determination means for determining the level of the signal string stored in the storage means, and the level of the signal string read by the reading sensor in the backward path Return path determination means for storing the signal in the storage means and determining the level of the signal sequence stored in the storage means by performing the same process as in the forward path in the reverse order to the order read by the reading sensor. Prepare.

  In a preferred embodiment, the return path determination means corrects the position of the level of the signal sequence by an offset value corresponding to a positional deviation that occurs when reading in the return path, and then determines in the same manner as in the forward path. You may do it.

  Hereinafter, a color inkjet printer (hereinafter referred to as “printer”) as a printing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing the main configuration of the printer 20 according to the present embodiment. The printer 20 is driven by a paper stacker 22, a conveyance roller 24 that is driven by a motor (not shown) and conveys printing paper P as a printing medium, a platen plate 26, a carriage 28, a carriage motor 30, and a carriage motor 30. The traction belt 32 and a guide rail 34 for guiding the carriage 28 are provided. Further, the carriage 28 has a print head 36 having a large number of nozzles as an ink discharge section arranged along the transport direction (hereinafter also referred to as sub-scanning direction) of the print paper P, and determines whether ink is discharged or not. The optical sensor 41 as a determination means to perform and a linear encoder 29 for reading the code plate 33 are mounted. Further, a rotary encoder 25 is provided on the shaft of the transport roller 24, and the transport amount of the printing paper P is controlled based on the output of the rotary encoder 25. For this reason, the position of the carriage 28 in a direction substantially orthogonal to the conveyance direction of the printing paper (hereinafter also referred to as the main scanning direction) is detected by the linear encoder 29, and the position of the printing paper P is detected by the rotary encoder 25. It is possible. That is, the printer 20 is configured to accurately recognize the relative position between the carriage 28 and the printing paper P based on the output signals of the encoders 25 and 29.

  The printing paper P is fed from a paper stacker 22 by a paper feeding roller (not shown), conveyed by a conveying roller 24, and sent on the surface of the platen plate 26 in the sub scanning direction SS. The carriage 28 is pulled by a pulling belt 32 driven by a carriage motor 30 and moves in the main scanning direction MS along the guide rail 34. The main scanning direction MS and the sub-scanning direction SS are almost orthogonal.

  FIG. 2 is a diagram illustrating the arrangement of the nozzles and the optical sensor 41 when the print head 36 is viewed from above. The print head 36 includes a light black ink nozzle row KL for discharging light black ink, a light magenta ink nozzle row ML for discharging light magenta ink, and a light cyan ink nozzle for discharging light cyan ink. A line CL, a photo black ink nozzle line KP for discharging black ink mainly used for printing natural images, a dark black ink nozzle line KD for discharging dark black ink, and a dark cyan ink are discharged. There are provided a dark cyan ink nozzle row CD for discharging, a dark magenta ink nozzle row MD for discharging dark magenta ink, and a yellow ink nozzle row YD for discharging yellow ink. In this example, the first nozzle # 1 is arranged on the downstream side in the conveyance direction of the printing paper P.

  The optical sensor 41 mounted on the carriage 28 is disposed on the downstream side in the transport direction from the first nozzle # 1 of the yellow ink nozzle row YD located on the most anti-home position side of the print head 36 and on the anti-home position side. . In this example, for example, it is provided at a position of 8.58 mm downstream of the first nozzle in the transport direction and 51.75 mm on the non-home position side.

  FIG. 3 is an explanatory diagram showing a mechanism of operation of the optical sensor 41 in the embodiment of the present invention. FIG. 3A shows an example in which the light emitting unit is provided at a position perpendicular to the printing paper as a printing medium. FIG. 3B is a diagram illustrating an example in which the light emitting unit is provided at a position where light is emitted obliquely with respect to the printing paper surface.

  The optical sensor 41 for determining whether or not ink is ejected from the nozzles includes, for example, a light emitting unit 41a and a light receiving unit 41b as shown in FIG. In the present embodiment, the light receiving unit 41b is an example in which one light receiving unit for mainly receiving the diffuse reflection component of the reflected light is provided. However, in addition to this, the regular reflection component of the reflected light is mainly provided. It is good also as a structure which provided another light-receiving part for light-receiving.

  The light emitting unit 41a is a light projecting unit that emits light toward the printing paper. That is, at the time of ink ejection determination, light is emitted toward the area of the printing paper on which a printing pattern having a printing block formed corresponding to each nozzle with ink ejected from the nozzle is to be printed. It will be. In the present embodiment, the spot 10 is set so that one printing block BL of the printing pattern is included in an area (hereinafter referred to as a spot) irradiated with printing paper by the light emitted from the light emitting unit 41a. Has been. Details of the print pattern will be described later.

  The light emitter may be a light emitting diode, a laser diode, an incandescent bulb, or the like. The color of the illuminant is preferably a color that is complementary to the color of the determination target print image such as a print pattern. For example, a red light emitter is used to detect a cyan print image, a green light emitter is used to detect a magenta print image, and a blue light emitter is used to detect a yellow print image. Good. If the color of the illuminant and the color of the printed image have a complementary relationship, the level of the output signal can be significantly increased as compared to the case where the color is not so.

  Therefore, in order to obtain a stable output for a printed image of any color, it is preferable to use a white light emitter as much as possible.

  The light receiving part 41b is a photoelectric conversion means for receiving the reflected light reflected from the print pattern. A photodiode, a phototransistor, or the like is preferable as the light receiving element. Preferably, a light receiving element having good sensitivity characteristics with respect to visible light is preferable.

  It is desirable that the position of the light receiving part 41b for mainly receiving the diffuse reflection component is not in the position of regular reflection with respect to the light emitting part 41a as shown in FIG. 3, and the light emitting part 41a as shown in FIG. The light receiving portion 41b may be attached at a position perpendicular to the paper surface, and the light receiving portion 41b may be attached obliquely to the paper surface. As shown in FIG. 3B, the light emitting portion 41a is attached obliquely to the paper surface, and the light receiving portion 41b is attached to the paper surface. You may attach vertically. In particular, in printing media having a coating layer on the surface, such as glossy printing paper, most of the incident light is regularly reflected by the coating layer on the surface, but the positions of regular reflection between the light emitting part 41a and the light receiving part 41b are reflected. If it is not attached, the color of the printing block under the coating layer can be reliably determined.

  And the light emitted from the light emission part 41a is reflected by the printing paper on which the printing block was printed, and the diffuse reflection component of the reflected light reaches the light receiving part 41b. The light receiving unit 41b outputs an output signal corresponding to the amount of received light. If this output signal is smaller than a preset threshold value, it is determined that the ink has been normally ejected from the nozzle that should form the print block irradiated with the light emitted from the light emitting section 41a, and the output signal is output. When it is larger than the threshold value, it is determined that ink is not ejected from the nozzle.

  At this time, the optical sensor 41 is configured so that, for example, the output of the light receiving unit 41b that has received light reflected by a predetermined printing sheet that has not been printed at all or a printing pattern of each color has a predetermined value. The amount of light emitted from the light emitting portion 41a is adjusted by the light amount control means controlled by the above, or the output of the light receiving portion 41b is adjusted by the output control means. FIG. 4 is a diagram showing individual differences of optical sensors in a white light emitter. Even if it is a white illuminant, there are individual differences, and here, the output value when a printed pattern printed with each ink color using a white LED with a yellow tendency and a white LED with a blue tendency is shown. Yes. As shown in the figure, the two light emitters have different output values, particularly when irradiated with yellow, cyan, and magenta print patterns. For this reason, the light emitter is adjusted by adjusting the output of the light receiving unit using the actually mounted optical sensor and the print pattern actually printed on the print medium used for printing. It is possible to prevent misjudgment that may occur due to individual differences, print medium differences, ink color differences, and the like.

  Next, a check pattern for detecting nozzle clogging will be described. The check pattern 200 includes a plurality of blocks 210 as shown in FIG. The printer 20 prints this check pattern 200 on the printing paper P. At this time, each block 210 performs printing using a predetermined nozzle. Therefore, when a certain nozzle is clogged, the block 210 corresponding to the nozzle is not printed. For this reason, after the printer 20 prints the check pattern 200, the optical sensor 41 reads the check pattern 200, and when an unprinted block 210 is detected, the clogging of the nozzle corresponding to the block 210 can be detected. .

  In the present embodiment, first, after the check pattern 200 is printed on the print paper P, the print paper P is rewound, the check pattern 200 is read by the optical sensor 41, and based on the level of the signal sequence output as a result, Check for nozzle clogging.

  FIG. 6 is a functional block diagram related to the nozzle clogging determination performed by the printer 20 according to this embodiment. That is, the printer 20 includes a controller 60 that performs control of the carriage motor 30 and the optical sensor 41 and determination of nozzle clogging, and a memory 61 that stores an output value of the optical sensor 41 and the like.

  The controller 60 controls the carriage motor 30 to drive the carriage 28. At this time, the controller 60 controls the optical sensor 41 to read the check pattern 200. Further, the controller 60 receives the output value of the signal sequence and the output value of the linear encoder 29 based on the result read by the optical sensor 41 as described above. Further, the controller 60 controls the carry motor 31 to rotate the carry roller 24 so as to feed and rewind the printing paper P.

  Here, the carriage 28 is reciprocated in the main scanning direction by the carriage motor 30. Then, in the forward path of the reciprocating motion of the carriage 28 (from left to right in FIG. 5), the optical sensor 41 reads the line on which the block 210 in the first row is printed. Then, a signal sequence based on the image read by the optical sensor 41 is output to the controller 60. Further, in the return path of the carriage 28 in the reciprocating motion (from right to left in FIG. 5), the optical sensor 41 reads the line on which the block 210 in the second row is printed and outputs a signal string to the controller 60. Similarly, for the third and subsequent rows, the optical sensor 41 reads the check pattern on the forward path and the return path, respectively.

  Each time the carriage 28 moves, the linear encoder 29 reads the code plate 33 and outputs information indicating the position in the main scanning direction.

  Based on the output of the linear encoder 29, the controller 60 stores a value indicating a signal level, which is an output value of the optical sensor 41, in the memory 61. For example, the address of the memory 61 and the output value of the linear encoder 29 are associated in advance. Then, the output value of the optical sensor 41 is stored at an address determined by the output value of the linear encoder 29. For example, in the example of FIG. 7A, since the output of the linear encoder 29 in the forward path increases from 0 to 180, the memory addresses 1000 to 1180 are stored in order. On the other hand, in the case of the return path, since the output of the linear encoder decreases from 180 to 0, it is stored in memory addresses 1180 to 1000 in FIG. That is, the sensor output values are stored in the memory in the reverse order to that in the forward path.

  At this time, in the case of a return path, registration may be made at an address shifted by a predetermined offset value. Thereby, it is possible to correct the deviation of the output of the linear encoder 29 that occurs between the forward path and the backward path. This offset value is due to, for example, the position on the printing paper in the main scanning direction in which the optical sensor 41 starts reading in the forward path and the backward path, depending on the mounting position of the optical sensor 41. This is a fixed value unique to the printing apparatus. Therefore, the offset value is determined in advance at the time of factory shipment.

  Next, the procedure of the print head nozzle clogging detection process in this embodiment will be described with reference to the flowchart of FIG. First, the printing apparatus 20 prints the check pattern 200 on the printing paper P, and rewinds the printing paper P on which the check pattern 200 is printed to the top (S11). Then, the controller 60 controls the carriage motor 30 to drive the carriage 28. Here, in the forward path, the optical sensor 41 on the carriage 28 reads the check pattern 200 and sends the output value to the controller. At this time, the output value of the linear encoder 29 on the carriage 28 is simultaneously output to the controller. (S12). Then, the controller 60 stores the output value of the optical sensor 41 in the memory 61 associated with the output value of the linear encoder 29 (S13). That is, here, the output value of the optical sensor 41 is stored in order from the address 1000.

  The controller 60 sequentially reads the output value of the optical sensor 41 stored in the memory 61, that is, the signal level read by the optical sensor 41 from the address 1000, and executes a process for detecting nozzle clogging (S14). .

  Next, after the transport roller 24 is driven and the printing paper P is sent to a position where the block 210 in the second row can be read, the controller 60 sends a check pattern to the optical sensor 41 in the return path for returning the carriage 28 to the home position. And the output values of the optical sensor 41 and the linear encoder 29 are acquired (S15). The controller 60 corrects the output value of the linear encoder 29 with the offset value, and stores the output value of the optical sensor 41 in the memory 61 at the address determined by the corrected output value (S16). That is, at this time, the output value read by the optical sensor 41 is stored in the memory 61 in the reverse order to that in the forward path.

  The controller 60 reads the signal level output from the optical sensor 41 stored in the memory 61 in order from the address 1000 in the same processing procedure as in the forward path, and determines nozzle clogging (S17). Here, in step S16, since the signal sequence is stored in the memory 61 so as to be in the same order as in the forward path, it can be determined in step S17 using substantially the same algorithm as in step S14.

  Then, the above process is repeated for all rows of the check pattern (S18).

  As a result, the check pattern can be read in both the forward path and the backward path to determine nozzle clogging. Further, by determining the data read by the optical sensor 41 in the return path in the reverse order of the read order, it can be processed using substantially the same algorithm as in the forward path.

  The above-described embodiments of the present invention are examples for explaining the present invention, and are not intended to limit the scope of the present invention only to those embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

  For example, in the case of the return path, the output value of the optical sensor 41 is stored in the memory 61 in the reverse order to that in the case of the outbound path, but this is not necessarily limited thereto. For example, the data may be stored in the memory 61 in the same order as in the forward path, and read in the reverse order when the controller 60 reads from the memory 61. Alternatively, the memory area for storing the forward path data and the memory area for storing the return path data may be different areas.

  In the above embodiment, the check pattern reading for detecting clogging of nozzles and the determination based on the read signal have been described. In addition, for example, a check pattern with a shifted Bi-D value is printed, It is also possible to apply the automatic Bi-D adjustment in which the printed check pattern is read and the best one among them is selected as the Bi-D value.

1 is a schematic perspective view showing a main configuration of a color inkjet printer 20 in an embodiment of the present invention. The figure which shows arrangement | positioning of the nozzle and optical sensor at the time of seeing the print head 36 from upper direction. (A) is explanatory drawing which shows the structure of a light emission part in the example which equipped the light emission part in embodiment of this invention in the position perpendicular | vertical with respect to the printing paper as a printing medium, (b) is a printing paper surface. Explanatory drawing which shows the structure of a light emission part in the example provided in the position light-emitted diagonally with respect to. The figure which shows the individual difference of the optical sensor in a white light-emitting body. FIG. 4 is a diagram illustrating an example of a check pattern 200 and movement of the carriage 28 when the optical sensor 41 reads the check pattern 200. 3 is a functional block diagram relating to nozzle clogging determination of the printer 20. FIG. The figure explaining the order which stores the output value of the optical sensor 41 in the memory 61. FIG. 6 is a flowchart illustrating a procedure of a print head nozzle clogging detection process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Printer, 22 ... Paper stacker, 24 ... Conveyance roller, 25 ... Rotary encoder, 26 ... Platen board, 28 ... Carriage, 29 ... Linear encoder, 30 ... Carriage motor, 31 ... Conveyance motor, 36 ... Print head, 41 ... Optical sensor, 60 ... controller, 61 ... memory.

Claims (2)

A printing apparatus that prints a plurality of check patterns while reciprocating a print head with a carriage, and detects the check patterns with a reading sensor on the carriage,
Storing the level of the signal sequence read by the reading sensor in the outward path in a storage unit, and determining the level of the signal sequence stored in the storage unit;
The level of the signal sequence read by the reading sensor in the return path is stored in the storage unit, and the level of the signal sequence stored in the storage unit is in the reverse order to the order read by the reading sensor, A printing apparatus comprising return path determination means for performing determination by performing similar processing.   The return path determination means corrects the position of the level of the signal sequence by an offset value corresponding to a positional deviation that occurs during reading in the return path, and then determines in the same manner as in the forward path. Item 2. The printing apparatus according to Item 1.

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