JPH06191057A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To perform printing free from density irregularity by providing a means detecting the printing densities of a plurality of recording heads, a means calculating the magnitude of difference of printing density between the respective recording heads and a correction means correcting the printing density difference between the heads. CONSTITUTION:The density of a printing surface is measured by a builtin light- emitting element and a photodetector measuring the quantity of the reflected light from the surface of paper. In a density adjusting mode, one recording paper for adjusting density is supplied and a built-in pattern for adjusting density is printed by a recording head 1a and a recording head 1b. Since the built-in pattern is printed so as to pass the arrangement position of a density sensor 10, the printing densities of the recording heads 1a, 1b are measured by feeding recording paper. The difference between the printing densities of both heads is calculated and, when there is density difference, the pulse width of the emission signal applied to the heads is changed to correct density difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for recording by ejecting ink droplets onto recording paper.

[0002]

2. Description of the Related Art Ink jet recording apparatuses can be classified into a serial type (serial printer) and a full line type depending on the type of head. Of these, serial printers that perform recording by scanning the recording head on the recording paper in the main scanning direction and the sub-scanning direction are widely used because the recording head is small and inexpensive. Further, in recent years, an ink jet cartridge in which a recording head unit and an ink tank are integrated has been developed to simplify the structure of a serial printer and improve maintainability.

The number of nozzles of the serial printer is selected in consideration of the printing speed and cost required by the apparatus. When high speed printing is required, a printing head with a large number of nozzles is used and a low speed printing apparatus is used. For this reason, a recording head with a small number of nozzles is used in consideration of cost. There is also a method of increasing the total number of nozzles by using a plurality of recording heads having a small number of nozzles without using a dedicated recording head for high speed recording. This is a very effective method in view of the difficulty in manufacturing a multi-nozzle recording head and the cost merit due to the mass production effect of a recording head having a small number of nozzles.

[0004]

However, since the size of the ejected liquid droplets differs slightly from head to head due to variations in head manufacturing, a plurality of recording heads causes a difference in print density, resulting in a striped print. There is a drawback that uneven density occurs.

Further, when a plurality of heads are arranged, when the recording heads are arranged in the main scanning direction (the direction perpendicular to the paper feed) as seen in an ordinary color printer, the carriage feed speed is doubled. That is, the liquid level in the ink tank sways due to an increase in acceleration, the main scanning distance increases due to an increase in the lateral width of the carriage portion, the drive motor becomes large, and the cost increases.

Therefore, an object of the present invention is to provide an ink jet recording apparatus which does not have such uneven printing density.

[0007]

In order to achieve such an object, an ink jet recording apparatus according to claim 1,
In an inkjet recording apparatus for performing recording by scanning a carriage member capable of mounting a plurality of recording heads in a main scanning direction and a sub-scanning direction relative to a recording sheet, a plurality of the recording heads arranged in series in a paper feeding direction. A recording head, a means for detecting the print densities of the plurality of recording heads, a means for calculating the magnitude of the difference in the print density between the print heads, and a print density difference between the heads based on the calculation result. The means for detecting the print density includes means for detecting whether or not a recording head is mounted, a storage battery for operating the detecting means when the power is cut off, and a detection result by the detecting means. A means to determine whether the head has been replaced,
It is characterized in that it has a printing means for printing a density judgment pattern on each recording head when it is judged that the head has been replaced, and a reading means for optically reading the printed judgment pattern.

An ink jet recording apparatus according to a second aspect is the ink jet recording apparatus according to the first aspect, wherein the plurality of recording heads are arranged at intervals of an integral multiple of a print width of each recording head. To do.

[0009]

According to the present invention, the plurality of recording heads arranged in series in the paper feed direction, the means for detecting the printing density of the plurality of recording heads, and the difference in the printing density between the recording heads. Since the means for calculating the size of the print density and the correction means for correcting the print density difference between the heads based on the calculation result are provided, it is possible to perform printing without unevenness in the print density.

Further, the means for detecting the print density is a means for detecting the presence / absence of mounting of a recording head, a storage battery for operating the detecting means when the power is cut off, and a head replacement using the detection result of the detecting means. A means for determining the presence or absence of a print head, a printing means for printing a density determination pattern on each recording head when it is determined that the head has been replaced, and a reading means for optically reading the printed determination pattern. Therefore, the print density can be corrected only when the head is replaced, and the unnecessary judgment pattern can be prevented from being printed by detecting the unnecessary print density.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] FIG. 1 is a diagram showing an ink jet recording apparatus to which the present invention is applied. 1a in FIG.
Reference numerals 1b and 1b are recording heads, and in the present embodiment, two ink jet recording heads of a cartridge type, which are equipped with an ink tank and are replaced with new ones when the ink is exhausted, are mounted to accelerate the printing speed. A carriage member 2 holds the recording heads 1a and 1b with high precision and reciprocates in the main scanning direction, and is slidably held by the guide rod 11 and the abutting portion 2a. Reciprocation of the carriage member 2 is performed by a pulley 4 and a timing belt 3 driven by a motor (not shown). At this time, a print signal and power supplied to the recording heads 1a and 1b are incorporated in the carriage member 2. Is supplied from the electric circuit of the main body by the flexible cable 7 via the.

The recording paper 12 is fed from the lower side in the figure, bent horizontally by the paper feed roller 5 and the paper guide 6,
It is transported in the direction indicated by the arrow. The paper feed roller 5 and the paper discharge roller 9 are each driven by a drive system (not shown), and it is possible to convey the recording paper 12 with high accuracy in conjunction with the reciprocating movement of the carriage member 5 as needed. There is. Reference numeral 8 is a spur shaft, which is made of a highly water-repellent material, and is arranged with spurs 8a arranged so as to come into contact with the recording paper surface only at the circumferential portion formed in a blade shape to form unfixed ink immediately after printing. It has a structure that guides the recording paper without affecting the image even if it makes contact.

In this embodiment, the printing speed is increased by mounting two recording heads. When the printheads are arranged in the main scanning direction (the direction perpendicular to the paper feed direction) as seen in a normal color printer, the carriage feed speed must also be doubled, and the ink tank increases due to acceleration. This causes fluctuations in the internal liquid level, an increase in the main scanning distance due to an increase in the lateral width of the carriage portion, an increase in the size of the drive motor, and an increase in cost. In this embodiment, since the recording heads are arranged in two lines in the sub-scanning direction (direction parallel to the paper feeding direction), the above problem does not occur. However, the total width of the recording head in the sub-scanning direction is usually larger than the printing width for reasons such as the structure of the head and securing the capacity of the ink tank, so that the two heads cannot be connected completely. Therefore, in this example, the heads are separated by an integral multiple of the print width (7 times in this example) as shown in FIG. 2, print data is temporarily stored in the memory, and each print block is printed in every six skips. To create. That is, as shown in FIG. 3, first, the block A is printed, the recording paper is fed by twice the print width, and then B, then C are printed in alphabetical order to finally form a complete image. To do. Although there is an inefficient part where only one recording head can print at the beginning and the end of the recording paper, it is possible to reduce the printing time significantly compared to writing with one head as a whole.

Next, the head density adjusting method will be described. Inkjet heads may have different print densities due to variations in droplet size between heads due to manufacturing variations. Although the density difference is small, a serial printer having a plurality of heads has a problem that density discontinuity points are noticeable at the joint portion. In this example, this is dealt with by providing a correction function for automatically aligning the two head densities. In FIG. 1, a density sensor 10 measures the density of the printing surface by a built-in light emitting element and a light receiving element that measures the amount of light reflected from the paper surface. In the density adjustment mode, one sheet of recording paper for adjustment is fed, and the recording heads 1a and 1b print a built-in pattern for density adjustment. Since the built-in pattern is printed so as to pass the position where the density sensor 10 is installed, the recording head is conveyed to convey the recording head 1a and the recording head 1b.
Print density is measured. The difference between the print densities of the two heads is calculated, and if there is a density difference, the density difference is corrected by changing the pulse width of the ejection signal applied to the heads. Since the recording density correction means by changing the pulse width is well known, detailed description thereof will be omitted.

In this way, the unevenness due to the density difference between the heads is automatically removed, and good print quality can be obtained. However, this correction operation is a scan required when the head is replaced, but the head replacement is often performed when the apparatus is powered off, and it is difficult to know that the head has been actually replaced. It is possible to perform the correction operation automatically when the power of the device is turned on.
The recording paper for adjustment is wasted every N times, and the running cost increases. In this example, the recording head 1
By incorporating a means for detecting the presence / absence of a head by determining the presence or absence of a short pattern built in a and 1b by a circuit in the main body through the flexible cable 7 and a battery for operating this detecting means when the power is cut off, Even if the power is turned off, the head presence / absence is monitored, and the automatic correction operation is executed only when necessary. As a result, good print quality can be obtained without wasting recording paper.

[Embodiment 2] In this embodiment, as a recording head,
Although the ink jet cartridge integrated with the ink tank is used, an ink jet recording apparatus of a type in which the ink tank is fixed to the main body and ink is supplied to the head by a tube may be used. Furthermore, although the case where the number of heads is 2 has been described, it goes without saying that the same effect can be obtained by increasing the number of heads to 3, or 4.

Although the density sensor is fixed to the main body in the first embodiment, it is possible to fix the density sensor to the carriage member by providing a signal line for the sensor on the flex. In this case, the density data can be read by printing the density adjustment pattern on any part of the recording paper.For example, by printing a certain pattern at the end of the recording paper and reading this, the density of the head In addition to the detection of the difference, it is possible to confirm that printing has been completed and that there is ink remaining.

(Others) The present invention is particularly provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, even in the ink jet recording system. The present invention brings about excellent effects in a recording head and a recording apparatus of the type in which the state of ink is changed by the heat energy. This is because such a system can achieve high density recording and high definition recording.

Regarding the typical structure and principle thereof, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal in a one-to-one correspondence
It is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, the liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, US Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The structure using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in JP-A-59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the apparatus main body or the electrical connection with the apparatus main body and the ink from the apparatus main body by being attached to the apparatus main body The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add an ejection recovery means of the recording head, a preliminary auxiliary means and the like because the effect of the present invention can be further stabilized. Specifically, heating is performed by using a capping unit, a cleaning unit, a pressure or suction unit for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but it may be either the recording head is integrally formed or a plurality of combinations may be used. The present invention is also extremely effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet system, it is common to control the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change of the ink from the solid state to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying thermal energy such as ink that is liquefied by applying thermal energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as a form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. It may be a form or the like.

[0027]

As is apparent from the above, according to the ink jet recording apparatus of the present invention, the print densities of the plurality of recording heads arranged in series in the paper feeding direction are detected, and the printing between the recording heads is performed. Since the magnitude of the density difference is calculated and the print density difference between the heads is corrected based on the calculation result, it is possible to perform high-quality printing in which density unevenness between the heads is not noticeable.

Further, the print density is detected by activating a detection means for detecting the presence / absence of mounting of a recording head with a storage battery when the power is cut off, and using the detection result to determine the presence / absence of replacement of the head. When the judgment is made, each recording head is made to print the density judgment pattern, and the judgment pattern is optically read to be read, so that it is possible to correct the print density only when the head is replaced, It is possible to prevent unnecessary judgment patterns from being printed by detecting unnecessary print density.

[Brief description of drawings]

FIG. 1 is a diagram showing a recording apparatus embodying the present invention.

FIG. 2 is a diagram showing an arrangement of recording heads.

FIG. 3 is a diagram showing a recording order of print blocks.

[Explanation of symbols]

 1a, 1b Recording head 2 Carriage member 3 Timing belt 7 Flex 10 Density sensor 12 Recording paper

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Claims (5)

[Claims] 1. A carriage member, on which a plurality of recording heads for ejecting ink are arranged and mounted in a sub-scanning direction, the carriage member being arranged in a main scanning direction and a sub-scanning direction relative to a recording medium. In an inkjet recording apparatus for performing recording by scanning, a unit for detecting print densities of the plurality of recording heads, a unit for calculating a difference in print densities between the recording heads, and based on the calculation result. An inkjet recording apparatus comprising: a correction unit that corrects a print density difference between heads. 2. A carriage member on which a plurality of recording heads for ejecting ink are arranged and mounted in the sub-scanning direction,
An ink jet recording apparatus for performing recording by scanning the carriage member relatively in a main scanning direction and a sub scanning direction with respect to a recording medium, a unit for detecting print density of the plurality of recording heads, and a unit between the recording heads. An ink jet recording apparatus comprising: a unit for calculating a difference in print density and a correction unit for correcting a print density difference between heads based on the calculation result. 3. A means for detecting the print density, a means for detecting whether or not a recording head is mounted, a storage battery for operating the detecting means when the power is cut off, and a head replacement using the detection result of the detecting means. A means for determining the presence / absence of a print head, a printing means for printing a density determination pattern on each recording head when it is determined that the head has been replaced, and a reading means for optically reading the printed determination pattern. The inkjet recording apparatus according to claim 1 or 2, further comprising: 4. The ink jet recording apparatus according to claim 1, wherein the arrangement interval of the plurality of recording heads is an integral multiple of the print width of each recording head. 5. The plurality of recording heads each generate a bubble in the ink by utilizing thermal energy, and eject the ink as the bubble is generated. The inkjet recording device according to item 1.