JP2000255135A - Dot printer equipped with function for detecting paper gap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dot printer capable of executing printing of high quality without depending on the size of a paper gap. SOLUTION: A printing head 10 is arranged so as to provide a gap with respect to a printing medium 200 and mounted on a carriage 11 to be reciprocally moved in a main scanning direction and the dot forming element formed to the leading end thereof forms a dot on the printing medium 200. A paper gap detecting means detecting the size of the gap between the printing head 10 and the printing medium is provided and the driving control part of the printing head 10 adds temporal offset to a timing signal corresponding to the detection result of the paper gap detecting means to drive the dot forming element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main scanning direction between a driving position of a dot forming element and a position of a dot formed on a printing medium by the driving due to a gap between a print head and a printing medium. Dot printer with paper gap detection function that can automatically correct misalignment
In particular, the present invention relates to the dot printer capable of performing high-quality printing without depending on the size of a paper gap.

[0002]

2. Description of the Related Art In recent years, an ink jet printer or a dot impact printer performs main scanning by a so-called BiD (bidy). That is, when an image is printed on a print medium, a dot forming element (a nozzle in the case of an ink jet printer, a pin in the case of a dot impact printer) is formed on the print head during the forward movement and the backward movement of the carriage. Driving).

In an ink jet printer or a dot impact printer, a gap (hereinafter, referred to as a gap) is formed between each dot forming element formed on a print head and a print medium.
And the dot forming element is driven while moving. For this reason, the position of the dot formed by the dot forming element is not the same as the driving position of the dot forming element, and is shifted from the driving position of the dot forming element.

[0004] Printing by UniD (Unidy),
That is, in printing in which the dot forming elements are driven only during the forward movement of the carriage, all the dots are shifted by the same distance in the main scanning direction, so that the printed image does not deteriorate due to the shift.

However, in the case of BiD, since the dot forming element is driven during both the forward movement and the backward movement of the carriage, the print image will be degraded unless the above-mentioned shift is taken care of. That is. Originally, an image printed during the forward movement of the carriage (hereinafter, referred to as a position that must match in position)
A position shift occurs between an image printed during the backward movement of the carriage (hereinafter, referred to as a “backward image”) and an image printed during the backward movement of the carriage, and the print result becomes unclear.

FIG. 5 shows a conventional dot printer. As shown in FIG. 5, the print head drive control unit 111 of the printer 110 does not add a time offset to the timing signal TS when the carriage 112 moves in the forward direction, and adjusts the timing when the carriage 112 moves in the backward direction. Each dot forming element 114 of the print head 113 is driven by adding a predetermined time offset to the signal TS (in FIG. 5, the signal to which the time offset has been added is denoted by TS ′). That is, when printing the return path image, the print head drive control unit 111 doubles the distance L between the drive position P1 of the dot forming element and the actual dot position P2 when printing the forward path image (that is, 2 ×). The dot forming element 114 is driven at a position apart from P1 by L).

The position detection of the print head 113 (that is, the position detection of the carriage 112 or the dot forming element 114) includes a linear scale 116 having slits formed at equal intervals, and an optical detecting section for optically detecting the number of passing slits. 115 is performed by the linear encoder unit. The carriage 112 is reciprocated by a pulse motor (not shown), and a pulse applied to the pulse motor and an output pulse from the optical detection unit 115 have a fixed timing relationship. Therefore, using the linear encoder unit, the timing signal given to the dot forming element 114 is calculated as [position accuracy of linear encoder] × N / [carriage speed].
(However, N can be changed and set with an accuracy of 2 or more positive integer) (in the present specification, the amount of this temporal change is referred to as “time offset”).

[0008]

By the way, in the conventional drive system shown in FIG. 5, the drive position of the dot forming element 114 due to the difference in the thickness of the print medium 200 (that is, the difference in the paper gap), and the drive Thus, the fluctuation of the distance from the dot position formed on the print medium 200 is not considered.

That is, in the conventional drive system, when printing on a print medium thinner than the print medium thickness set by the printer maker or when printing on a thick print medium, the forward image and the backward image are mainly used. There is a disadvantage that the image is deviated in the scanning direction and the print image is deteriorated.

In order to eliminate this inconvenience, it is possible to adopt a mechanical configuration in which the size of the paper gap is always constant even if the print medium thickness is different, but such a mechanical configuration is generally complicated. Therefore, there is a problem that the manufacturing cost increases and the number of components causes an increase in failure factors.

An object of the present invention is to automatically correct a shift in the main scanning direction between a driving position of a dot forming element and a position of a dot formed on a print medium by the driving due to a paper gap. An object of the present invention is to provide a dot printer with a paper gap detection function capable of high quality printing.

[0012]

SUMMARY OF THE INVENTION The inventor of the present invention has proposed a print head in order to keep the forward image and the backward image from being misaligned in the main scanning direction even when the thickness of the print medium is different. Based on the belief that changing the timing of the drive pulse sent to the dot forming element based on the paper gap detection value will not require alteration or addition of the mechanical configuration and can also respond to changes in print medium thickness. The present invention has been made.

According to the present invention, a print head is disposed with a gap (ie, with a paper gap) between the print head and the print medium, and the print head is mounted on a carriage and reciprocates in the main scanning direction. In addition, the dot forming element formed at the tip is applied to a dot printer (such as an ink jet printer or a dot impact printer) that forms dots on the print medium.

The dot printer according to the present invention includes a paper gap detecting means for detecting the size of the gap between the print head and the print medium. Since the size of the paper gap is obtained by subtracting the print medium thickness from the known platen gap size, the paper gap detection means measures the print medium thickness mechanically to determine the size of the paper gap. May be detected.

Further, the paper gap detecting means may detect the size of the paper gap by using an optical means. Specifically, the paper gap detecting means can be constituted by an image sensor and an image processing means (usually, an appropriate processor provided in a printer). In this case, first, predetermined information having a different shape depending on the size of the paper gap (typically, a ruled line oriented in the sub-scanning direction or a figure such as a filled rectangle)
Is printed and read by an image sensor.

Then, the image processor analyzes the data on the predetermined information read by the image sensor, and detects the size of the paper gap (or the thickness of the print medium). Here, when a graphic is used as the predetermined information, the graphic includes, for example, an element formed when the carriage moves forward (hereinafter, referred to as an “outward graphic element”) and a form when the carriage moves backward. (Hereinafter, referred to as “return path graphic element”), which can be a predetermined graphic (that is, prepared by a printer maker or the like).
In this case, the size of the paper gap can be detected from the magnitude of the deviation between the outward graphic element and the return graphic element. The graphic may be a partial graphic when the user starts printing. In this case, for example, the image data of the partial graphic read by the image sensor corresponds to the partial graphic of the print data. The size of the paper gap can be detected by comparing with the image data to be processed.

The drive control unit of the print head adds this to the signal (timing signal) sent to the dot forming element in accordance with the detected value of the size of the paper gap by the image processing means.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) When a forward graphic element and a backward graphic element are printed without deviation,
The timing signal will be time optimized. Conversely, when the forward graphic element and the backward graphic element are printed with deviation, a timing error occurs in the timing signal (the degree of the error of the timing signal is different from the forward graphic element). The larger the deviation between the return graphic elements, the greater the deviation, and conversely, the smaller the deviation between the two graphic elements, the smaller.)

Therefore, the figures for paper gap detection are sequentially printed on a print medium with different values of the time offset, and the value of the time offset when the deviation between the forward graphic element and the backward graphic element is the smallest is optimized. Time offset value. That is, the image processing means obtains the number of pixels of the line in the case of a ruled line, the number of pixels or the area of a filled part in the case of a filled rectangle, etc., for the figure read by the sensor, The value of the time offset when a small number of paper gap detection figures are printed can be set as the optimal time offset value.

Therefore, by setting the time offset value in the drive control unit of the print head, it is possible to eliminate the deviation between the forward image and the backward image.

(2) There is a correlation between the size of the paper gap and the size of the deviation between the forward graphic element and the backward graphic element. The magnitude of the deviation between the forward graphic element and the backward graphic element depends on the size of the paper gap. Is determined. That is, if the magnitude of the deviation between the outward graphic element and the backward graphic element is known, the size of the paper gap at that time can be substantially detected.

Therefore, if the size of the paper gap and the value of the time offset corresponding to the size of the paper gap are stored in a table in advance, the size of the paper gap is calculated from the size of the deviation between the forward graphic element and the backward graphic element. Thus, an optimum time offset corresponding to the size of the paper gap can be obtained. The size of the deviation between the outward graphic element and the return graphic element can be obtained from the number of pixels of the line in the case of a ruled line, or the number of pixels or the area of the painted portion in the case of a painted rectangle or the like.

That is, in this case, only one paper gap detecting graphic (consisting of a forward graphic element and a backward graphic element) is printed on a print medium, and a time offset corresponding to the size of the paper gap is calculated. By setting based on the above-described table, it is possible to eliminate the deviation between the outward image and the backward image.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A printer 1 includes a carriage 11 on which a print head 10 is mounted, a medium transport mechanism 121 for flexibly transporting a print medium 200 in a sub-scanning direction, a transport controller 122 for controlling the same, and a carriage 11. Drive mechanism 131 for reciprocating the print head in the main scanning direction, a carriage drive control unit 132 for controlling the carriage drive mechanism 131, and an image sensor unit 14 fixedly disposed on the transport destination side of the print head 10. Further, the printer 1 includes an image processing unit 1 for inputting a signal from the image sensor unit 14.
5. Print head drive control unit 16 that drives nozzles 101 (dot forming elements in the present invention) formed in print head 10, RAM 171 and EEPROM 172
, An encoder unit 18 including a linear scale 181 and an optical detection unit 182, and a processing unit 19, and further include a platen 110 formed below the print head 10.

The medium transport mechanism 121 includes a pulse motor 12
11, a transport control unit 122 including a transport roller 1212 and the like.
Sends a conveyance pulse MTP to the pulse motor 1211 of the medium conveyance mechanism 121 to convey the print medium 200 in the sub-scanning direction in a furrow.

The carriage driving mechanism 131 includes a pulse motor 1311, a timing belt 1312, and the like. The carriage drive control unit 132 sends a carriage drive pulse CDP to the pulse motor 1311 of the carriage drive mechanism 131 to reciprocate the carriage 11 at a constant speed in the print area while the conveyance of the print medium 200 is stopped.

The image sensor section 14 includes an optical reading element (CCD) 141 and a reading light source (LED) 14.
Consists of two. In FIG. 1, the image sensor unit 14 is provided at the center of the reciprocating movement area of the carriage 11 and on the side to which the print medium 200 is transported. FIG. 2 shows a positional relationship between the print head 10 and the image sensor unit 14 in the sub-scanning direction. In FIG. 1, the image sensor unit 14
Is provided only for paper gap detection.
Of course, when a well-known scanner / printer is used, the image reading means provided in the scanner is replaced with the image reading means shown in FIG.
Can be used as the image sensor unit 14.

The image processing means 15 converts the signal from the optical reading element 141 into image data IMD and stores it in the RAM 171. The image processing means 15 reads out the image data IMD from the RAM 171 and can perform image analysis described later. . Here, the image processing hand throw 15 and the above-mentioned image sensor unit 14 constitute a paper gap detecting means in the present invention.

The print head drive control unit 16 includes a timing signal generation circuit 161 and a timing change unit 162.
including. In the normal print mode, the print data PD stored in the RAM 171 is sent to the timing signal generation circuit 161. In the paper gap detection mode, the data on the paper gap detection graphic stored in the EEPROM 172 is replaced with the timing signal. It is sent to the generation circuit 161. Timing signal generation circuit 161
Is a timing signal TS for driving the nozzle 101
Generate The signal generated by the timing signal generation circuit 161 is temporally changed by the timing changing means 162. The timing signal generation circuit 161 can output an accurate timing signal obtained by subdividing one cycle of the signal output by the optical detection unit 182 of the encoder unit 18. The timing change unit 162 can make a temporal change to the timing signal TS generated by the timing signal generation circuit 161 (that is, set the time offset TOS) with the accuracy.

The EEPROM 172 has a printer BIO
Paper gap detection program PDP and test print program TP for paper gap detection together with S
P is stored. At the time of paper gap detection, the processing device 19 can activate the test print program TPP to send a print command of a graphic for paper gap detection to the print head drive control unit 16. PD
By calling P, the paper gap PG can be detected.

The processing device 19 functions as a controller for the entire printer system. In FIG.
The transport control unit 122, the carriage drive control unit 132, and the print head drive control unit 16 are configured separately from the processing device 19. However, the processing device 19 performs some or all of the functions of the control units. Can also. In FIG. 1, the image processing unit 15 is also configured separately from the processing device 19, but the processing device 19 can also perform some or all of the functions of the image processing method 15.

Hereinafter, two specific examples of the dot printer of FIG. 1 will be described.

In these specific examples, the paper gap detection figure is a painted rectangular figure, but is not limited to this.

[First Specific Example] When the test print program TPP is started, the processing device 19 sends a print command for the paper gap detection graphic PDF to the print head drive control unit 16. In this print command, the timing change means 162 sequentially sets a plurality of (9 in this specific example) time offsets TOS in the timing signal TS, the timing signal generation circuit 161 generates the timing modulation signal TMS, and the print head 10 represents nine timing modulation signals T
Based on MS, same figure PDF for paper gap detection
Each of which contains a sequence.

The graphic PDF for paper gap detection includes a forward graphic element PDFA and a backward graphic element PDFB.
When the timing modulation signal TMS conforms to the size of the paper gap PG, that is, when the time offset TO
If the setting of S is appropriate, the forward path graphic element PDFA
No deviation occurs between the return path graphic element PDFB and the return path graphic element PDFB. On the other hand, when the timing modulation signal TMS does not conform to the size of the paper gap PG, that is, when the setting of the time offset TOS is too large or too small, the forward graphic element PDFA and the backward graphic element PDFB. And no deviation occurs between them.

FIG. 3 shows examples of nine paper gap detection figures PDF1 to PDF9. In this specific example, the forward path graphic element PIDFA and the return path graphic element PDFB must be printed at exactly the same position and in the same size when the timing modulation signal conforms to the size of the paper gap. In FIG. 3, the forward path graphic element is indicated by a dotted line, the return path graphic element is indicated by a solid line, and a state in which the forward path graphic element and the return path graphic element are printed at the same position in PDF4 is shown. In this embodiment, the processing device 19 controls the transport control unit 12 during one reciprocation of the carriage.
2 does not cause the medium transport mechanism 121 to perform the transport operation.

Next, the processing device 19 outputs a paper gap detection command PDI to the image sensor unit 14.
In this detection command PDI, the optical reading element 141 reads the printed figures PDF1 to PDF9 for paper gap detection, stores each read data in the RAM 171, and the image processing means 15 expands the data in the RAM 171 into the memory space. A sequence for detecting the area of each of the paper gap detection figures PDF1 to PDF9 is included.

The image processing means 15 calculates the filled area of the paper gap detection figures PDF1 to PDF9,
A process for specifying a figure having the smallest filling area among these is performed. Information relating to this processing result, for example, information such as the order of the time offset when a figure having the smallest filling area is printed, is sent to the processing device 19.
Passed to. The processing device 19 sets the time offset TOS when printing the paper gap detection graphic (PDF4 in FIG. 3) having the smallest filling area in the timing changing means 162.

The print head drive control unit 16 includes a RAM
From step 171, print data such as graphics is called. The timing signal generation circuit 161 sends a timing modulation signal TMS based on the time offset TOS set in the timing changing means 162 to the nozzle 101 of the print head 10 to perform printing.

In the first specific example, nine paper gap detecting graphics PDF1 to PDF9 are printed on the print medium 200, but only one paper gap detecting graphic is printed as shown in the second specific example. It is also possible to print on the print medium 200 and detect the paper gap PG based on this.

[Second Specific Example] In the second specific example, as the value of the time offset increases, the forward path graphic element PDF
Each graphic element PDFA, P is set so that the deviation between A and the return path graphic element PDFB becomes large or small.
DFB is defined.

In this case, two lookup tables LUT1 and LU as illustrated in FIGS. 4A and 4B are used.
T2 is stored in the EEPROM 172.

As shown in FIG. 4A, the first look-up table LUT1 has a paper gap detection graphic PD at a predetermined (reference) time offset TOS.
The relationship between the deviation between the outward graphic element PDFA and the backward graphic element PDFB when F0 is printed and the size of the paper gap PG at this time are tabulated. In addition, the second lookup table LUT2 includes FIG.
As shown in (B), the size of the paper gap PG,
The relationship between the time offset TOS and the value of the time offset TOS that matches the size of the paper gap PG is tabulated.

The processing device 19 activates the test print program TPP and sends a print command for the paper gap detection graphic PDF to the print head drive control unit 16. In this print command, the timing change means 162 sets a specific time offset TOS in the timing signal TS, the timing signal generation circuit 161 generates a timing modulation signal TMS, and the print head 10 A sequence for printing two paper gap detection figures PDF0 is included.

In the second specific example, the forward graphic element PDFA and the backward graphic element P
It is printed with a certain deviation from the DFB.

Next, the processing unit 19 outputs a paper gap detection command to the image sensor unit 14. In this detection command, the optical reading element 141 reads the printed figure PDF0 for paper gap detection and refers to the first lookup table LUT1 to obtain the size of the paper gap from the area of the figure PDF0 for paper gap detection. A sequence for determining an optimum value of the time offset from the size of the paper gap with reference to the second lookup table LUT2.

Look-up tables LUT1 and LU
The information about the optimum value of the time offset for the print medium 200 obtained from T2 is
9 passed. The processing device 19 sets this time offset in the timing changing means 162.

The print head drive control unit 16 includes a RAM
From step 171, print data such as graphics is called. The timing signal generation circuit 161 sends a timing modulation signal TMS based on the time offset set in the timing changing means 162 to the nozzle 101 of the print head 10 to perform printing.

According to the present invention, the paper gap detecting graphic can be printed in the leading margin. As in the first specific example, even when about nine paper gap detection figures are printed continuously, they can be accommodated within a width of 5 to 10 mm. In the second specific example, , 1
It is possible to fit within a width of mm. Therefore, the print medium 200 used for paper gap detection is used.
Even if this is used as it is as a print medium for normal printing, in most cases, it will not be annoying.

Further, in each of the above specific examples, the area of the painted figure as the paper gap detecting figure is measured as the measured area to determine the area to be painted over. However, even when ruled lines are used as the paper gap detecting figure, the first concrete example is used. The technique used in the examples can be applied as it is. When a ruled line is used as the paper gap detection graphic, the same paper gap detection as in the first and second specific examples is performed by using the ruled line interval as a measurement amount instead of the dip area. Can be.

As described above, the size of the paper gap for the print medium 200 is determined, and the optimal time offset is automatically set, so that high-quality printing is realized.

[0052]

According to the present invention, for a print medium having an arbitrary thickness, the hardware is not changed at all times.
Since an appropriate time offset can be automatically set for the timing signal, it is possible to eliminate a positional shift between the forward image and the backward image.

[Brief description of the drawings]

FIG. 1 is a schematic view of an ink jet printer showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional relationship between a print head and an image sensor unit in FIG. 1;

FIG. 3 is a diagram illustrating an example of a paper gap detection graphic used in the first specific example;

FIG. 4A is a diagram showing a first lookup table used in a second specific example, and FIG. 4B is a diagram showing a second lookup table also used in the second specific example.

FIG. 5 is a diagram showing a conventional BiD type printer.

[Explanation of symbols]

 Reference Signs List 1 printer 10 print head 11 carriage 14 image sensor unit 15 image processing means 16 print head drive control unit 17 storage device 18 encoder unit 19 processing device 101 nozzle 110 platen 121 medium transport mechanism 122 transport control unit 131 carriage drive mechanism 132 carriage drive control Unit 141 Optical reading element 142 Reading light source 161 Timing signal generation circuit 162 Timing changing unit 171 RAM 172 EEPROM 181 Linear scale 182 Optical detection unit 200 Print medium 1211 Pulse motor 1212 Transport roller 1311 Pulse motor 1312 Timing belt

Claims (4)

[Claims] A print head is disposed with a gap between the print head and a print medium.
A dot printer mounted on a carriage and reciprocating in the main scanning direction, and a dot forming element formed at the tip of the dot printer forms dots on the print medium, the size of the gap between the print head and the print medium being determined. Comprising a paper gap detecting means for detecting, the drive control unit of the print head, according to the detection result of the paper gap detecting means, to drive the dot forming element by adding a time offset to the timing signal,
A dot printer with a paper gap detection function. 2. An image sensor for optically reading predetermined information printed by the print head, and a size of a gap between the print head and a print medium based on a read result of the image sensor. 2. A dot printer with a paper gap detection function according to claim 1, further comprising: an image processing means for determining. 3. The paper gap detecting graphic according to claim 3, wherein the predetermined information has a shape different depending on a size of a gap between a print head and a print medium, and the paper gap detecting graphic is used when the carriage moves forward. 3. The dot printer with a paper gap detection function according to claim 2, wherein the dot printer comprises a graphic element formed and a graphic element formed when moving backward. 4. The dot printer with a paper gap detection function according to claim 3, wherein the graphic element is a ruled line or a solid graphic in the main scanning direction.