JP2006159843A - Ink-jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a correction of the unevenness of the impact positions of inks due to the state of paper surface for a recorder. <P>SOLUTION: The distance between a recording head 1 and an opposite recording material 2 is detected by a sensor 5 between papers of a carriage 4 provided at the upstream of a printer. Based on this detected signal, the unevenness of the impact of the ink droplets between lines is corrected by adjusting the timing for heating a heater to deliver inks during printing without receiving the affection of printing in an outward-trip printing, a return-trip printing and a multi-pass printing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording apparatus that performs recording on a recording material in a non-contact manner, and more particularly to an ink jet recording apparatus having means for measuring the distance between a recording portion and a recording material.

  In recent years, as one of information output devices in word processors, personal computers, facsimiles, etc., there are recording devices such as printers that record information such as desired characters and images on a sheet-like recording material such as paper or film. It is popular.

  Various methods are known as recording methods of this recording apparatus, and as one of them, ink is ejected from a recording unit called a head onto a recording material such as paper, and the ink is landed on the recording material. There is an ink jet method in which recording is performed by forming dots on the top. This ink jet method is rapidly spreading because it has a high quietness because the recording portion does not come into contact with the recording material and is relatively easy to color.

  This ink jet printer is divided into a serial type ink jet printer and a full line type ink jet printer depending on the head structure. The serial type ink jet printer forms an image while scanning in the direction (main scanning direction) perpendicular to the conveyance direction of the recording paper, and after one or more scans are completed, the paper is moved in the main scanning direction. And the image is recorded on the next recording line. On the other hand, in a full-line type ink jet printer, nozzles are formed almost in the entire width direction of the paper, and printing is performed while transporting the paper without scanning the paper in the main scanning direction. The latter has the advantage that the recording speed is fast because one line in the width direction is formed at a time. On the other hand, the entire head becomes large because the head itself becomes large, and for high resolution recording. However, it is necessary to make the arrangement of the nozzles high density, and there is a problem that the manufacturing cost of the head becomes high. On the other hand, the former has an advantage that the cost of the apparatus is low because an image is recorded with a relatively small head, and most of current ink jet printers are serial ink jet printers.

  Since this serial type ink jet printer scans and records line by line as described above, if the position of the joint of the line is shifted, the image is disturbed between the lines and image unevenness occurs. In the case of inkjet printers that perform non-contact recording, the paper that has absorbed ink due to moisture contained in the ink tends to swell and undulate (hereinafter referred to as cockling), and the distance from the head can be kept constant by undulating the paper. Therefore, it is necessary to consider image unevenness because the joint position between lines is shifted. In addition, the platen for keeping the distance between the recording material paper and the head constant due to manufacturing variations, the distance between the recording material and the head cannot be kept constant over the entire recording area, and image unevenness occurs. It may occur.

The cockling tends to swell on plain paper such as copy paper, and does not swell so much on paper with a film or special coating. According to the experiment, when the ink shot amount was 19.3 nl / mm ² , an elongation of about 0.51% occurred in a certain copy paper. In general, as shown in FIG. 7, the sheet after recording is regulated in the surface direction by a spur 18 so that the swollen recording material 2 is placed on the platen 3 in the gap between the spurs 18 arranged at a predetermined interval in the main scanning direction. Displaces into a wavy state. According to the calculation, for example, when four cocklings occur at equal intervals in the longitudinal direction (210 mm) of A4 size paper, the surface direction of 0.5% of the paper stretches to approximately 1 in the direction perpendicular to the recording material surface. .2mm cockling occurs. The influence of the generated cockling appears when one line is recorded and then the next line is printed.

Conventionally, with respect to such problems, the distance between sheets facing the recording head is read by a sheet interval sensor mounted in front of the nozzle in the main scanning direction of the carriage, and the printing timing is controlled according to the value. A method for correcting printing variations is proposed. (For example, see Patent Document 1)
In addition, ink landing position deviation correction values are stored in the storage unit based on a plurality of values of the platen gap, which is the distance between the recording head and the platen (or called a gap), and in accordance with the platen gap during bidirectional printing. In addition, there has been proposed a method of correcting the landing position of ink by selecting and using an appropriate misregistration correction value. (For example, see Patent Document 2)
JP-A-11-240146 (page 11, FIG. 1) JP-A-16-122629 (page 14, FIG. 3)

  However, in the method disclosed in Japanese Patent Laid-Open No. 11-240146, a so-called inter-sheet sensor that measures the distance between the recording unit and the recording material is mounted in front of the nozzle in the main scanning direction of the carriage. In multi-pass printing in which printing is performed many times, the inter-sheet distance is read by the inter-sheet sensor on the printed sheet surface, and an accurate value cannot be read due to the influence of printing. In bi-directional printing, the paper interval sensor reads the distance between paper after printing in reverse printing, and an accurate value can be read only in forward printing. Further, in the printing in which the printing area covers the entire recording material, since the inter-sheet sensor is mounted in the main scanning direction of the carriage, the end value cannot be read unless the head is scanned outside the printing material.

  In the method disclosed in Japanese Patent Laid-Open No. 16-122629, correction values based on a plurality of platen gap values are determined before printing, and correction cannot be made for subtle variations in the paper surface state during printing.

(the purpose)
The present invention accurately determines the distance between a recording unit that ejects ink and a recording material such as paper on which the ink has landed to record an image even during any recording such as forward printing, return printing, or multi-pass printing. It is an object of the present invention to provide an ink jet recording apparatus that can measure the ink discharge timing and control the ink ejection timing.

  The above problem is that a sensor that measures the distance between the head and the paper is mounted on the carriage, and the mounting position is from the recording unit in the paper conveyance direction that can be accurately measured during any recording, such as forward printing, return printing, or multipass printing. Can also be realized by setting the upstream position.

  The ink jet recording apparatus of the present invention is equipped with a sensor for measuring the distance between a recording unit that ejects ink and a recording material on which the ink has landed and records an image, and the mounting position is always the position of the recording material. Since it is always performed on the paper immediately before printing without ink landing, the distance between the recording unit and the recording material can be accurately measured over the entire printing area without being affected by the swelling of the paper due to ink absorption even during recording. Can be measured, and ink ejection timing can be controlled more accurately.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a configuration of a printing unit of an inkjet printer. FIG. 2 is a view of the arrangement of the paper spacing sensors mounted on the carriage as viewed from the top of the printer.

  In FIG. 1, nozzles (not shown) for ejecting inks corresponding to the respective colors are provided in the recording head unit 1 and are arranged substantially in the sub-scanning direction (Y direction). When printing, bubbles are generated in the filled ink by overheating the internal heater of the recording head 1 at a specified timing, and ink is ejected from each nozzle. Reference numeral 2 denotes a sheet as a recording material. Reference numeral 3 denotes a platen for keeping the distance between the recording head 2 and the recording head 1 facing the reference value, and this reference value is the maximum value of the distance in the direction facing the recording head 1 and the recording material 2 surface.

  When image data is sent from a host such as a computer to the recording apparatus, the recording material 2 is sent in the sub-scanning direction (Y direction) shown in FIG. 1 by a transport mechanism (not shown) and fed to the printing position on the platen 3. Is done. When the recording material 2 is fed to a predetermined position, the carriage 4 scans the recording material 2 in the main scanning direction (X direction) via a belt by a drive motor, and performs printing on the recording material 2. When printing for one line is completed, the recording material 2 is conveyed for one line in the sub-scanning direction, and printing is performed sequentially. Here, an inter-sheet sensor 5 for detecting the distance between the recording head 1 and the recording material 2 is mounted on the carriage 4 upstream of the printer from the nozzle position mounted on the recording head 1 that ejects ink. . Further, positional information of the carriage 4 in the X direction is defined by reading a value of a linear encoder installed in parallel with the main scanning direction with respect to the carriage 4.

  As shown in FIG. 2, the inter-sheet sensor 5 is mounted upstream of the printer and parallel to the sub-scanning direction with respect to the nozzle position mounted on the recording head 1 that ejects ink. The sensor 5 sends a signal corresponding to the distance (hereinafter referred to as the inter-paper distance) from the recording material 2 orthogonal to the recording head 1 to the control unit described later in conjunction with the scanning of the carriage 4. As shown in FIG. 1, the inter-paper sensor 5 irradiates the recording material 2 with the laser beam L to detect reflected light, and outputs a DC signal whose level changes depending on the inter-paper distance.

  FIG. 3 is a block diagram of an embodiment of the present invention, and FIG. 4 is a timing diagram of signals at various parts in FIG. When the image data is transferred to the recording apparatus, the carriage 4 scans in the main scanning direction for printing. The position information of the carriage 4 is read by the linear encoder 7 and sent to the heat timing forming circuit 9 in the control unit 8 as a carriage position detection signal (see FIG. 4B). The heat timing circuit 9 generates a latch signal based on the position information of the carriage 4. The distance between the recording head 1 and the orthogonal recording material 2 is read by a paper gap sensor 5 and sent to the comparison circuit 10 in the control unit 8 as a paper gap detection signal. Here, when the distance between the sheets varies due to variations in cockling or platen manufacturing, the sheet spacing detection signal is not constant. In this state, the paper gap detection signal sent from the paper gap sensor 5 to the comparison circuit 10 is converted into a paper gap signal corresponding to the paper gap distance by several comparators shown in FIG.

  This conversion will be described with reference to FIG. As shown in FIG. 4, the comparison circuit 10 includes N (N is arbitrarily set) comparators 10.1, 10.2,. N and the adder 16. The reference voltage differs step by step for each comparator 10 (Vref1, Vref2,..., VrefN), and the comparison according to the paper surface state is made by comparing the inter-sheet detection signal from the inter-sheet sensor 5 in each comparator 10. Calculate the signal. The comparison signals calculated by the N comparators 10 are combined by the adder circuit 16 to generate a paper interval signal (see FIG. 4A). The generated inter-sheet signal is converted into digital data n by the A / D converter 11.

  The converted digital data n becomes n = 0 when the inter-paper distance is maximum (reference value), and n gradually increases to N (the number of comparators) as the distance decreases. The value of n varies depending on the displacement information that is the difference between the distance between the recording material 2 facing the recording head 1 and the distance (reference value) between the recording head 1 and the platen 3. Here, the timing promoting circuit 12 (promoting here means that the heater driving timing is advanced) is generated by using the value of n as a latch signal generated in accordance with the detection signal from the encoder 7 as shown in FIG. ), The heater drive timing signal is generated by advancing to N stages by time T-nt (n = 0, 1, 2... N).

  FIG. 6 shows the configuration of the timing acceleration circuit 12. The signals from the N timing promoting circuits 12 are selected by the analog switch 17 with respect to the input latch signal, and the latch signal is advanced by a predetermined time to be output to the heater drive circuit 13. Here, the analog switch 17 is configured to uniquely select one of the latch signals based on the input digital data n.

  As described above, the heater drive timing signal is the time obtained by adding the variable decay time −nt (n = 0, 1, 2,... N) corresponding to the inter-paper signal to the constant delay time T. This is a signal obtained by advancing the encoder detection signal. Further, the heater driving circuit 13 drives the recording head 1 in accordance with the recording data I / F 14 input from the recording data I / F 14 to the data transfer circuit 15, and the head driving is performed in synchronization with the heater driving timing signal.

  As described above, by changing the ejection timing of the ink droplets according to the inter-paper distance between the recording material 2 facing the recording head 1, the deviation of the ink landing position due to variations in cockling and platen manufacturing is corrected. Ink can be landed on the position. For example, as shown in FIG. 1, ink droplets that are ejected when the carriage 4 scans in the main scanning direction and land on the original position a according to the trajectory T are caused by variations in cockling or platen manufacturing, and thus the recording material 2. Can be landed on the ideal landing position a ′ by the above timing correction. Therefore, the landing position of the ink in the main scanning direction on the surface of the recording material 2 is always corrected, and an image with little dot deviation can be obtained regardless of the state of the paper.

  Here, since the paper gap sensor 5 is mounted on the upstream side of the printer with respect to the nozzles mounted on the recording head 1 as described above, not only single-pass printing but also printing is performed many times without conveying the paper. Even in multi-pass printing, the paper surface state immediately before printing can always be detected and the landing position can be corrected without being affected by printing.

  Even when bidirectional printing is performed, the paper gap sensor 5 is mounted on the upstream side of the printer with respect to the nozzles mounted on the recording head 1, so that it is not affected by printing and is always immediately before printing. It is possible to detect a change in the state of the paper surface due to the cockling of the ink, and it is possible to land an ink droplet at an ideal landing position.

  Further, as shown in FIG. 2, the inter-sheet sensor 5 is mounted on the nozzle mounted on the recording head 1 in parallel on the sub-scanning line, so that the print area 6 extends to the end of the recording material 2. Even when printing is performed without margins, it is possible to detect the state of the paper immediately before printing without affecting the printing operation, and it is possible to correct the landing position over the entire printing region 6.

  In the above embodiment, the displacement information is generated on the recording device side. However, the various types of displacement information are generated from the recording data in a host computer connected to the outside, and the generated recording information is combined with the recording data. You may make it supply to a recording device.

  In addition, the present invention is provided with means (for example, an electrothermal converter, a laser beam, etc.) for generating thermal energy as energy used for performing ink ejection, particularly in the ink jet recording system, and the thermal energy. As a result, an excellent effect can be obtained in a recording head and a recording apparatus of a type that causes a change in the state of ink. This is because such a system can achieve high recording density and high definition.

  As for the typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, the thermal energy is generated in the electrothermal transducer, and the recording head This is effective because film boiling occurs on the heat acting surface of the liquid, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, since the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve discharge of a liquid (ink) having particularly excellent responsiveness. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (straight liquid channel or right-angle liquid channel) of the discharge port, the liquid channel, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting part The configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which is disposed in a bending region, are also included in the present invention. In addition, for a plurality of electrothermal transducers, Japanese Patent Application Laid-Open No. Sho 59-123670 that discloses a configuration in which a common slit is used as a discharge portion of the electrothermal transducer or an aperture that absorbs pressure waves of thermal energy is provided. The effect of the present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 59-138461 which discloses a configuration corresponding to the discharge unit. That is, whatever the form of the recording head is, according to the present invention, recording can be performed reliably and efficiently.

  Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by the recording apparatus. As such a recording head, either a configuration satisfying the length by a combination of a plurality of recording heads or a configuration as a single recording head formed integrally may be used.

  In addition, even the serial type as shown in the above example can be connected to the main body of the recording head or attached to the main body of the device so that electrical connection with the main body of the device and ink supply from the main body are possible. The present invention is also effective when a replaceable chip type recording head or a cartridge type recording head in which an ink tank is integrally provided in the recording head itself is used.

  In addition, it is preferable to add a recording head ejection recovery means, a preliminary auxiliary means, and the like as the configuration of the recording apparatus of the present invention, since the effects of the present invention can be further stabilized. Specifically, heating is performed using a capping unit, a cleaning unit, a pressurizing or suction unit, an electrothermal transducer, a heating element different from this, or a combination thereof. Examples include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

  Also, regarding the type or number of recording heads to be mounted, for example, a plurality of recording heads are provided corresponding to a plurality of inks having different recording colors and densities, in addition to one provided corresponding to a single color ink. May be used. That is, for example, as a recording mode of the recording apparatus, not only a recording mode of only a mainstream color such as black, but also a recording head may be configured integrally or by a combination of a plurality of different colors, Alternatively, the present invention is extremely effective for an apparatus having at least one of full-color recording modes by color mixing.

  In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, ink that is solidified at room temperature or lower and that softens or liquefies at room temperature may be used. In the ink jet method, the temperature of the ink itself is generally adjusted within a range of 30 ° C. or higher and 70 ° C. or lower to control the temperature of the ink so that it is in the stable discharge range. A liquid material may be used. In addition, it is solidified and heated in an untreated state in order to actively prevent the temperature rise caused by thermal energy from being used as the energy for changing the state of the ink from the solid state to the liquid state, or to prevent the ink from evaporating. You may use the ink which liquefies by. In any case, by applying thermal energy according to the application of thermal energy according to the recording signal, the ink is liquefied and liquid ink is ejected, or when it reaches the recording medium, it already starts to solidify. The present invention can also be applied to the case of using ink having the property of being liquefied for the first time. The ink in such a case is in a state of being held as a liquid or a solid in a porous sheet recess or through-hole as described in JP-A-54-56847 or JP-A-60-71260. Alternatively, the electrothermal converter may be opposed to the electrothermal converter. In the present invention, the most effective one for each of the above-described inks is to execute the above-described film boiling method.

  In addition, the ink jet recording apparatus according to the present invention may be used as an image output terminal of an information processing device such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. The thing etc. may be sufficient.

It is a figure which shows the structure of embodiment of this invention. It is the figure which showed the element structure of embodiment from the printer upper surface. It is a block diagram which shows embodiment. It is a block diagram of a comparison addition circuit. FIG. 4 is a timing chart showing signals at various parts in FIG. 3. It is a block diagram of a timing promotion circuit. It is explanatory drawing of a cock ring.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording head 2 Recording material 3 Platen 4 Carriage 5 Paper gap sensor 6 Print area 7 Carriage encoder 8 Control part 9 Heat timing formation circuit 10 10.1, 10.2, 10. N Comparison circuit 11 A / D converter 12 Timing acceleration circuit 13 Heater drive circuit 14 Recording data I / F
15 Data Transfer Circuit 16 Adder Circuit 17 Analog Switch 18 Spur

Claims (2)

  In a recording apparatus that performs recording in a non-contact manner on a recording material using a recording unit that ejects ink, the recording material conveyed in the sub-scanning direction facing the recording unit that reciprocates in the main scanning direction; An ink jet recording apparatus comprising: a sensor for measuring the distance of the ink, and means for controlling an ink discharge timing from the recording unit based on the distance information output from the sensor during recording.   The sensor is installed at a position where the distance between the recording material and the recording unit immediately before the recording unit discharges ink to the recording material can be measured, and is reciprocated in the same manner as the recording unit during recording. 2. The ink jet recording apparatus according to claim 1, wherein the distance can be measured over the entire region of the recording member in the main scanning direction.

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