JPS58155960A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To make it possible to control the diameter of ink dot by such an arrangement wherein a heater of which temperature can be adjusted is installed to a recording head which spouts ink droplets and the heater is arranged so that its set value of temperature can be varied to conform to the kind of a medium on which images are recorded. CONSTITUTION:A recording head 13 is equipped with a heater 12 for heating a part or all of an ink passage including a nozzle, and the temperature of ink detected by a temperature sensor 14 provided at the nozzle unit and fed back through a conversion amplifier 25 and compared by a comparator 26 with signals of a manual setting unit 31 and a reference temperature signal generator 24 and the temperature of ink is controlled through a heater drive unit 27. The operator causes a character and graphic generator in a recorder to generate a proper test pattern signal and applies the signal to a piezoelectric element 17 and visually inspects a test pattern 15 printed on a recording paper 19 by spouting ink droplets 10A and repeats printing of a test pattern by varying the setting of temperaures, and finally judges and determines an optimum nozzle temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly to an inkjet recording apparatus that can control the diameter of recorded dots.

Electric field control systems and charge control systems have long been known as inkjet recording devices, but these systems require means for forming ink droplets and means for controlling the ejection direction (deflection) of the character formation. and require expensive structures for security. On the other hand, as shown in Japanese Patent Publication No. 53-12138, K.

Inkjet recording is a method (hereinafter referred to as on-demand method) in which ink droplets are ejected from a nozzle by changing the volume of a pressure chamber each time an electric pulse is applied to a piezoelectric conversion electron of a recording head in response to an electrical signal for recording. The device is attracting attention in recent years. Japanese Patent Application Laid-Open No. 51-35231 is
This is a system in which a plurality of nozzles are mounted in one recording head. Figure 1 is a schematic diagram of this system. It is supplied to the pulse trap sensor 4. The pulse trap i14 branches into a plurality of pressure chambers 5 communicating with a plurality of nozzles 6 corresponding to the vertical pattern of the pulse trap i14. Further, a piezoelectric conversion electron 7 electrically connected to an electronic pulse generator 8 is adhered to a part of the wall of the pressure chamber 5. The piezoelectric conversion electron 7 is a suitable flexible plate that can be bent inward under pressure*S when it receives an electrical signal from the pulse generator 8, and is made of a piezoelectric tactile plate, for example, and is connected to the pressure chamber by a thin conductive electrode MK. Glued to the outside wall.

In this method, the electrical signal from the electronic pulse generator 8 causes the piezoelectric conversion electrons 7 to rapidly move inside the pressure chamber, and the resulting rapid decrease in the volume of the pressure chamber 5 and rise in pressure are caused by the The ink is ejected from the nozzle 6 as ink droplets W, and is caused to fly and reach the opposing recording 11e,
Record dot image II. Fig. m2 shows an inkjet recording apparatus having a specific configuration consisting of 7ilI nozzle arrays using the above-mentioned recording method.

By the way, in this type of recording head, the nozzle 6
The diameter of the ink droplets 10 ejected from the nozzle shape,
By adjusting the dimensions, the pulse voltage of the drive signal, the pulse length, etc. tv4, it becomes a constant value.

On the other hand, when the ink droplet 10 reaches the recording medium support 9 such as paper after being ejected from the nozzle 6, it penetrates into the support 9.
It is absorbed and forms dots (pixel points) of a certain size on the surface of the carrier. FIG. 3 is an example of recording on the iii* carrier by shifting four recording heads equipped with seven nozzles. Figure 3 (4) is a 7x5 standard dot matrix, Figure 113 (3) is a 7x5 compressed dot matrix,
Figure 113 (C) is an example of each print using a 7x9 dot matrix, but in order to obtain good print quality even from the same array of nozzles, it is desirable that each k be printed on the recording paper with the optimum dot diameter. I understand that. Characters, figures, etc. formed as a collection of ink dots on the surface of the general Kmll deity are subject to various restrictions Kf in terms of printing quality.
It must be formed to match.

In other words, in terms of readability and aesthetics of printed characters and figures, dot diameter, circularity, distribution, linearity due to mutual arrangement of dots, etc. should be within a certain appropriate value IIs. It must be formed as such.

On the other hand, there are two types of recording paper, which is the Ii* carrier for recording silver: one type is called absorbent paper, which allows ink to penetrate, and the other type is called non-absorbent paper, which allows ink to penetrate. Both types of recording paper come in many varieties due to differences in absorbency, and even if ink droplets of the same diameter come in contact with each other, the diameters of dots produced on the recording paper vary greatly between these types of recording paper.

For these reasons, the diameter of the ink dots 10 ejected from the nozzles 6 of the recording head 3 and the type of paper, etc. that is the mII carrier 9 are selected and assembled in such a way that a certain optimal dot diameter is obtained. For this reason, in conventional inkjet recording devices, optimal print quality can be obtained by providing a specified paper type or special paper for a certain recording head and special recording ink. I've guaranteed it. Conversely, if paper other than designated paper or special paper is used, the diameter of the ink dots recorded on the paper will be too large or too small, leading to a decrease in print quality.

However, as a user of a recording device, it is desired that stable print quality can always be obtained even if a general commercially available recording paper is freely selected and used.

While it is desired to print characters of a constant quality regardless of the type of paper, it is desirable to change the diameter of the dots on the recording paper depending on the type of characters to be printed and the type of recorded material to be obtained. It's heavy.

Accordingly, an object of the present invention is to provide an inkjet apparatus capable of controlling the diameter of dots formed on recording paper.

Still another object of the present invention is to provide an inkjet recording device capable of forming dots of various diameters on recording paper using a single recording head.

FIG. 4 is a diagram showing the characteristics of the ink used in the embodiment of the present invention. Figure 1114 (as shown in AJK,
When the temperature of the ink decreases, the viscosity of the ink tends to increase rapidly. Also, as shown in Figure 4 (B),
As the ink viscosity increases, the ink droplet diameter tends to decrease. There is a relationship between the diameter of the ink droplet and the diameter of the dot on the recording paper as shown in Figure 4 (C)K. Also,
In the figure, A indicates the characteristics of absorbent paper and N indicates the characteristics of non-absorbent paper.

From these, as shown in Figure 114 (D), if the nozzle temperature of the recording head is set low, the diameter of the ink droplets and, by extension, the diameter of the dots on the recording paper can be reduced, and conversely, if the nozzle temperature is set high, the dots can be reduced. The present invention provides an inkjet recording device that can obtain dots with a desired diameter by controlling and appropriately setting the nozzle temperature by utilizing such characteristics of ink. This is what we are trying to provide.

In addition, there are various kinds of ink generally used in inkjet recording devices, but as an embodiment of the present invention, the ink droplet diameter can be set at any time by changing the viscosity change due to the above-mentioned temperature control and has good jetting efficiency. An example of such an ink is an ink made of kerosene liquor, water, dye, or pigment.

Hereinafter, the details of the present invention will be explained based on Examples. Figure 5 shows an embodiment of a recording head 13 according to the present invention. Reference numeral 12 denotes a heater that heats part or all of the ink flow path including the nozzle; in the illustrated embodiment, the heater 12 heats the ink flow path that follows the pressure chamber and reaches the nozzle 16; For example, only the nozzle portion may be heated, or the ink flow path leading from the nozzle to the nozzle including the pressure chamber may be heated. Alternatively, the metal body of the ink ejecting head may be heated, but the method of heating is determined by the characteristics of the ink used and the structure of the recording head. 14 is a temperature sensor that detects the temperature of the nozzle portion. As the temperature sensor 14, in addition to temperature sensing elements such as thermostats, thermocouples, and varistors,
Even if the application is different from the original purpose, such as a semiconductor strain gauge or a semiconductor pressure sensor, it can be used as long as it has a large temperature coefficient. The heater may be electrically connected to the surface of the recording head by printing or etching, or may be a planar heating element or a constant temperature heating element. In addition, when using a constant temperature heating element, it is necessary to provide a plurality of elements each having a different point on each island. The heated heater is installed inside the nozzle as shown in Figure 6.
The recording head 13 may be installed directly in the rr flow path.
The nozzle portion may be constructed of a heating element such as a resistive conductor, and in this case, temperature control with extremely high response speed is possible. In the figure, numeral 51 represents a heating element, numeral 51 represents a protective layer, and numeral 51 represents a recording head component.

The next KIIT cabinet is a configuration diagram showing an embodiment of the present invention. 6゜13 is a recording head mounted with a heater ut-* for implementing the present invention,
Possibly driven. 19, for example, the Kiyoroshigen was introduced,
When the nozzle temperature reaches a predetermined setting value by the heater 12, the recording device selectively applies a small drop of 10 mm of ink from the nozzle 16 to the required tie ink while driving the recording paper 19 and the brass head (■). The ink is ejected to record a predetermined print on the recording paper 19 in the form of an ink matrix. (See Figure 3) At this time, the size of the ink dots depends on the ink absorbency and moisture content of the recording paper 19, the physical properties of the ink, and the chemical reaction that occurs when the ink touches the recording paper 19. is determined, and becomes a constant value.

In addition, the shape of the ink dot is #3! Although it is shown as a circle in J, if you observe it closely, it may turn out to be quite irregular in shape, especially depending on the properties of the recording paper, resulting in a deterioration in print quality. The size of the ink dots differs from K in terms of the size of the characters, the arrangement method of the constituent elements of the dot dot box, the number of arrangements, etc., and the best printing quality can be obtained than with K if the size of the ink dots is set to an appropriate value.

Below, FIG. 7 will be explained in detail.

The operator of the recording device visually observes the print quality y recorded by inkjet on the recording paper 19, and inputs an appropriate value from the manual setting section 31K in order to adjust the % nozzle temperature so as to obtain the optimum ink dot size. It is something to do. That is, a suitable test pattern signal 1 is generated from a character/figure generator (not shown) in the brass distribution device, and this image signal is applied to the piezoelectric transducer 9, thereby causing an ink droplet 1 o from the nozzle.
A test pattern 15 is printed on the recording paper 19. Once a series of test patterns have been printed in this way, change the nozzle temperature setting and print the test pattern again. Repeat step 1.2 to print each test pattern corresponding to each nozzle temperature setting. Create a table. The operator looks at this test pattern table, judges and determines the nozzle Δ and temperature suitable for this recording paper 11K,
This is input through the manual setting section 31K. In addition,
In the figure, 24 is a reference signal generator, 2S is a conversion amplifier, 1 is a comparator, 27 x 8 heater driver, and 2 is a piezoelectric conversion element drive circuit.

Further, in this embodiment, after the inkjet diameter is manually determined as described above, it is also possible to automatically control the temperature of one nozzle so that the inkjet diameter becomes the optimum dot F diameter.

Next, FIG. 1118 is a configuration diagram showing a different embodiment of the present invention. When the power of the recording device is turned on and the nozzle temperature reaches a predetermined value by the heater 12, the recording device drives the printing paper 19 and the recording head 13v to emit ink droplets from the nozzle 16 at the required timing. A predetermined dot test pattern 15 is ejected onto the recording paper 19.
Record. The recording paper 19 is further moved upward, and the dot test pattern 15 on the recording paper reaches the vicinity of the iIm reading section 4.

The dots constituting the dot test pattern 15f1 on the recording paper are irradiated by a light source 21, and a single dot part and its surroundings are enlarged through an optical system, and the size and density of the dots are read by an image reading section 'ZIK'. . As the image reading section n, a photodiode, a phototransistor, a photomultiplier, a phototube, a photoreflector, or the like can be used. The image information signal input from the image reading unit n is transferred to the image information processing unit. At the Art Rin Processing Department School, we compare the signal when there is a dot in the field of view of the artist and the signal when there is no dot, and also based on the changes in the signal when the dot enters and exits the field of view. The dot sit+* diameter is calculated, and the nozzle setting temperature required to make the diameter and concentration of the met dots optimal (f) is calculated.

Based on the calculated nozzle set temperature, the first reference temperature signal generating section generates a signal corresponding to the optimum temperature value and sends it to the comparator. On the other hand, the output signal of the nozzle temperature sensor t-14 is sent via the conversion amplifier 5 as a signal indicating the current temperature of the nozzle.
, and the comparator sends it to . The comparator 26 compares the above two temperature signals and drives the heater W via the heater drive 1127 to control the nozzle temperature so as to obtain the optimum dot diameter and concentration.

The outline of the operation of controlling the diameter of ink droplets based on the present invention has been specifically explained above using a preferred embodiment. Note that the above-described printing and control operations for controlling the ink droplet diameter are performed not only when the power is turned on to the recording device, but also during normal printing operations, so that the recording paper 19 may be affected by changes in the external environment, etc. It is possible to respond to changes in characteristics. That is, even if the paper quality of the recording paper gradually changes or suddenly changes during continuous printing, it is easier to deal with it by performing the above control operation.

Note that this control operation can be printed out using i! ii) A more appropriate dot diameter can be obtained by not only performing the series of operations of performing temperature processing and correcting the temperature set value only once, but also repeating this series of operations again at the temperature after the reset. It is possible to obtain.

It goes without saying that this control operation is performed every time a new recording paper 19 is loaded.

In addition, if the recording head is designed to be able to run outside the normal printing area for characters, figures, etc., and into the left or right margin of the recording paper, the above test pattern for controlling the ink droplet diameter can be used. Printing may be performed in the margin area.

In the embodiment shown in FIG. 8, the reading section 4 is a single channel receiver such as a photodiode.
I! However, in other embodiments, an element having a multi-channel light receiving section such as a photodiode array, CCD1, vidicon camera tube, etc. may be used.

In this case, the image processing unit 23 can perform control so that the effective area of the dot, for example, the area of the portion of one dot (K) where the reflection hardness is 0.6 or more, becomes constant y.

Further, another example will be shown. This eliminates the need to print a test pattern by jetting ink droplets to control the diameter of ink droplets. In this case, a bar code indicating the type of recording paper or an optimum nozzle temperature predetermined for the type and a unique code 15 is placed at a predetermined location on the edge of the recording surface of the recording paper 19.
This means that the tape is printed or perforated in advance. The embodiment will be explained again using the 8th WJK. ii*Reading Department 4
When the code such as the bar code and the drilling technique are read, the image processing unit determines the optimum nozzle temperature according to the conversion table stored in advance based on that information, and generates a reference temperature signal. A signal corresponding to the optimum nozzle temperature value is generated from the device and sent to the ratio l1l) 26. A comparator processes this signal and a signal obtained from the output of the temperature sensor 14 via a conversion amplifier δ.

The heater 9 is driven by a heater drive unit n to obtain a constant optimum nozzle temperature. Furthermore, tree example K OI,
Of course, it is possible to set any nozzle temperature, that is, any dot diameter, from the manual setting section 31K.

Next, another embodiment of the present invention will be described.

The relationship between the nozzle degree and the ink droplet diameter at the bottom of the ink droplet shape in the recording head 13 is as explained in Figure 4 above. It has been confirmed that not only changing the ink droplet diameter λ, but also changing the velocity of the ink droplet ejected from the nozzle. This causes a number of errors when printing on both sides, that is, when the recording head prints both when running to the left and when running to the right. Normally, considering the time required for the ink droplets to fly from the nozzles of the recording head 13 to the recording paper 19, dots are formed at predetermined positions regardless of whether the ink is running to the left or to the right. The ejection timing of one ink droplet is adjusted and set in advance.

However, as mentioned above, the speed of the ink droplet changes as the nozzle temperature changes, so at a certain nozzle temperature, the ejection timing of the ink droplet must be set so that there is no dot shift even during bidirectional printing. Even if the nozzle temperature is changed by carrying out the present invention, in bidirectional printing, the recording paper 19
The positions of the dots formed on the top will be different, which will impair the print quality.1 For example, when printing a vertically long straight line in a tabulation table, etc., by dividing it into two-way prints, the resulting straight line will be meandering. It's become a thing and it's heavy.

Embodiment 1 of the present invention shown in the ms diagram is constructed in order to prevent these drawbacks, and is characterized by the provision of a delay circuit section 411. In FIG. It is activated in response to a signal from the department and causes 10 mm of ink droplets to be ejected from the nozzle 16. In addition, the delay circuit 41 is used to control the generation of the drive signal sent from the drive circuit section 42 to the piezoelectric conversion electronics 17. That is, the driving circuit section 41 determines an appropriate delay amount for the drive signal based on the signal obtained from the reference temperature generator, based on the predetermined conversion table or conversion formula, and thereby determines the appropriate delay amount for the drive signal. This delays the generation of drive signals from the circuit department. The drive circuit section is set in advance to generate a drive signal corresponding to the minimum delay time. In this case, the delay circuit 1141 determines the optimal delay amount for the recording head and recording paper currently in use based on the reference temperature signal coming from the reference temperature generation ROM, and adjusts the Klitter accordingly.
[-The generation of drive signals from the circuit department is delayed. In this way, even if the nozzle set temperature is adjusted as the recording paper 19 is changed and the ejection speed of the ink droplets changes, the recording sickle device in this embodiment allows the recording head 13 to move to the left,
Dots can always be formed correctly at predetermined positions regardless of whether the vehicle is running to the right.

In addition, in this embodiment, since the characteristic that the ejection speed of the ink ROM differs depending on the nozzle temperature depending on the nozzle temperature, the delay time of the drive signal generation is changed as follows.
It is configured so that each nozzle can be controlled independently.

In the above-mentioned embodiment, the generation of the drive signal is delayed so that tK dots are always formed at a predetermined time. The voltage or rise time constant of the drive signal may be controlled so that the ejection mode of the ink droplets is constant regardless of the nozzle temperature.

It is also possible to control the ejection speed of the ink droplets by changing the ink pressure in the recording head 13, and also by changing the frequency, pulse width, or falling time constant of the drive signal, or by changing the ink pressure in the recording head 13. By controlling the traveling speed of the head 13, etc., the scope of application of the present invention can be further expanded.

As mentioned above, when the actual v4v is implemented, it becomes unnecessary to specify the recording paper, which was previously essential for the inkjet recording sickle 1111, and the user of the recording sickle device can select the recording paper with a good λ. It has become possible to use it freely. At this time, the recording paper is automatically identified by the recording device, and automatic correction is also possible to maintain the best print quality.

Figure 2 is a schematic cross-sectional view of a recording head in a conventional on-demand type inkjet recording apparatus.

FIGS. 3A and 3B are examples of ink dot matrices printed on recording paper.

Sheet 4 Figures (A), CB), (CJ, (1 is a diagram showing the characteristics of ink necessary for implementing the present invention, Figure 5 is a schematic diagram of the recording head in which the present invention is implemented, 96 The figures are a top view of the nozzle part of the recording head implemented according to the present invention, an IET diagram,
FIGS. 8 and 1119 are configuration diagrams of a recording sickle device embodying the present invention.

! ...Ink tank 3...Recording head 6.16...Nozzle 7.17...
・Piezoelectric conversion electron 8.18...Electronic pulse generator 9.19...Image carrier (recording paper, etc.) 10,
IQ&... Ink droplet 12... Heater 13... Recording head, 14...
・Temperature sensor = 15...Te, strike pattern
Addition: Optical system 4: Light source 4
・・・・・・Image reading section...Image processing section...Reference temperature signal generation section 5...Conversion amplifier 26 °---Comparator τ ...Heater drive unit 31...Manual setting department...Drive circuit 1152...
Heating element fee - Yoshimi Kuwahara Figure 1 ¥52 figure - 10%J) e'-(0
) CD) Figure 5 Figure 6

Claims (6)

[Claims] (1) An inkjet recording apparatus characterized by being provided with a recording head K for ejecting ink droplets and a temperature-controllable heater to heat part or all of the ink flow path including the nozzles of the recording head. (2) In the recording apparatus according to claim S, paragraph 1, the setting value of the temperature of the jet nozzle of the recording head can be changed depending on the type sK of the recording sickle iii* carrier. An inkjet recording device that uses mold as a mold. (3) An inkjet recording device according to claim 11E2, characterized in that the inkjet recording device is equipped with a device for printing a test pattern or the like at 4 temperatures gK on the image carrier. (4) In the recording device according to claim 1113, when detecting and recognizing the result of false printing,
An inkjet recording device characterized by controlling the temperature of an ejection nozzle of a placement head. (5) In the recording device according to claim 112, detecting a code determined for each type of scissor carrier, which is formed in advance on the carrier by printing or perforation. An inkjet recording apparatus characterized by controlling the temperature of an ejection nozzle of a recording head. (6) In the recording apparatus according to any one of Claims S, Items 1 to 5, a signal is applied to a piezoelectric transducer for ejecting droplets in response to the temperature of the ejection nozzle of the print head. tie, voltage, pulse time constant, pulse length,
Frequency or ink pressure inside the recording head, etc.
An inkjet printer IIka1, characterized in that it is configured such that at least one or more of the inkjet printers can be controlled.