JPH0976496A - Ink jet head and ink jet print device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a print such as a favorable quality printing having neither uneven density not blur of dot nor missing of dot nor the like irrespective of the flow resistance and the driving frequency of an ink feeding system under the condition that the ink feeding system is fled from being influenced by pressure vibration. SOLUTION: The pressure vibration in an ink feeding system at the discharging of ink is detected with a pressure sensor 7 provided in a liquid chamber 3 so as to drive a piezoelectric element 6 provided in the liquid chamber 3 on the basis of the value of the detected pressure vibration in order to reduce the pressure vibration, resolution in preventing the print quality such as printing or the like from deteriorating due to poor discharging of ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head for ejecting ink droplets toward a recording medium for printing and an ink jet printing apparatus.

[0002]

2. Description of the Related Art Conventionally, a heater applies heat to ink to generate bubbles, and the pressure when the bubbles expand causes ink to be ejected from a discharge port of an inkjet head toward a recording medium for printing. Inkjet printing devices have been developed. For example, there is an inkjet print head as shown in FIG. Figure 2 (a)
2A is a cross-sectional view of the head, and FIG. 2B is a view on arrow S in FIG.

In FIG. 2, reference numeral 1 denotes an ink flow path which forms a nozzle. When the heater 2 is rapidly heated, the ink in the ink flow path 1 boils and bubbles are generated. The flow path 1 of the ink displaced by the bubbles is shown in FIG.
The ink is ejected from the ink ejection port on the left side of the center. Then, the ink in the common liquid chamber 3 is drawn toward the ink flow path 1 by the meniscus force at the ink ejection port and then returns to the original state. Reference numeral 4 denotes an ink supply path, which is connected to an ink tank (not shown) and supplies ink to the common liquid chamber 3. The print head of FIG. 2 is a serial print head, and the ink flow path 1 is formed in parallel in the horizontal direction (sub-scanning direction) for 64 nozzles as shown in FIG. The print head moves in a direction (main scanning direction) orthogonal to each other and scans a recording paper as a recording medium, thereby performing printing such as printing on the recording paper. Then, each time the print head completes one scan, the operation of moving the recording paper by 64 dots in the sub-scanning direction is repeated to perform printing such as printing on one recording paper.

In such an ink jet printing apparatus, it is known that pressure oscillation occurs in the ink supply system as ink is ejected from the ink ejection port. It is considered that this pressure oscillation is caused by ink ejection, because flow resistance in the ink supply system, inertial resistance in the ink tank (including the ink absorber), and bubbles in the ink become pressure oscillation elements.

As a concrete example, the pressure of the ink supply system will be measured using the print head of FIG. The print head of FIG. 3 is a prototype head having a pressure sensor 5 in the liquid chamber 3 of the print head of FIG. Using the print head of FIG. 3, for example, as shown in FIG. 8, when printing is performed by ejecting ink by 4 dots from the ink ejection ports of all 64 nozzles, the pressure sensor 5 in the liquid chamber 3 causes Figure 1
Pressure oscillations such as 0 are observed.

FIG. 5 is a pressure waveform diagram schematically showing the pressure vibration of FIG. 10, and FIG. 4 shows changes in the state of ink in the ink flow path 1 when the pressure vibration as shown in FIG. 5 occurs. It is a representation.

The effect of printing due to pressure vibration will be described below with reference to FIGS. 4 and 5. In FIG. 5, the pressure waveform is stable at time T1 before ink is ejected, and the ink flow path 1 is filled with ink as shown in FIG. 4A. Then, when the heater 2 is driven to generate heat by the drive pulse A of FIG. 5B and ink is ejected, the dot pattern of FIG. 8 is formed between the time point T1 and the time point T2, and FIG. ) The pressure oscillation shown in the pressure waveform occurs. After that, at time T2, the pressure of the ink supply system rises due to the pressure vibration, so that FIG.
As described above, the ink in the ink flow path 1 is in a state of protruding from the ejection port. At this time, when the drive pulse of D1 in FIG. 5B is applied, the dots in FIG. Dots larger than the normal dot d1 such as d2 are formed.

Next, when ink is ejected by the drive pulse B shown in FIG. 5C, the pressure vibration shown in FIG. 5A is generated as in the case described above. Then, at time T3, the pressure of the ink supply system is lowered due to the pressure vibration, so that the ink in the ink flow path 1 is retracted toward the liquid chamber 3 as shown in FIG. 4C. At this time, if the drive pulse of D2 in FIG. 5C is applied,
The dot d3 in FIG. 5E is smaller than the normal dot d1.

Further, as shown in FIG. 9, for example, an operation of ejecting ink by 4 dots from the ink ejection ports of all 64 nozzles and then pausing the ejection of ink from all the ink ejection ports of 64 nozzles by 4 dots. When printing is repeated, the pressure vibration is increased and becomes large, and there is a possibility that ink may drip from the ejection port or ink may not be ejected.

As described above, the pressure vibration causes a change in the ink ejection amount, density unevenness due to defective ink ejection, so-called tooth chipping, etc., and deteriorates print quality.

Conventionally, in order to prevent such pressure oscillation, the flow resistance in the ink supply passage 4 is increased or the liquid chamber 3
By devising the shape of (1) so that the pressure vibration does not reach the ink flow path 1, or the driving frequency of the heater 2 does not overlap with the frequency of the pressure vibration, no problem occurs in printing.

[0012]

However, when the flow resistance in the ink supply path 4 is increased, the time from the ejection of ink until the ink is refilled in the ink flow path 1 (refill cycle). Becomes large and the drive frequency of the heater 2 cannot be increased. Also, when the liquid chamber 3 becomes large due to the increase in the number of nozzles, the liquid chamber 3
The shape of can't be changed easily. Further, in order to prevent the drive frequency and the frequency of the pressure vibration from overlapping with each other, it may be necessary to fix the drive frequency to a certain constant value, which is an obstacle to speeding up printing.

The object of the present invention is to avoid the influence of pressure vibration of the ink supply system regardless of the flow resistance and drive frequency of the ink supply system, and to provide good image quality without uneven density, blurred dots, or missing dots. An object of the present invention is to provide an inkjet head and an inkjet printing apparatus that can realize printing such as printing.

[0014]

An ink jet head of the present invention is an ink jet head capable of ejecting ink supplied from an ink supply system into an ink introducing part from an ink ejection port, wherein the ink introducing part is provided in the ink introducing part. It is characterized by comprising a pressure adjusting means capable of adjusting the pressure of the ink in the ink introducing portion so as to damp the pressure fluctuation.

A first embodiment of the inkjet printing apparatus of the present invention is an inkjet printing apparatus for printing on a print medium using an inkjet head capable of ejecting ink, and the inkjet head of the present invention is provided as the inkjet head. ,
It is characterized by comprising a control means for controlling the pressure adjusting means in accordance with a pressure fluctuation in the ink introducing portion due to the ejection of ink from the ejection port.

A second aspect of the ink jet printing apparatus of the present invention is an ink jet printing apparatus for printing on a print medium using an ink jet head capable of ejecting ink. The ink jet head includes a detection unit that detects the pressure of ink and outputs a detection signal for controlling the pressure adjustment unit, and a control unit that controls the pressure adjustment unit based on the detection signal of the detection unit. It is characterized by being prepared.

According to the present invention, the pressure vibration of the ink supply system is reduced, and the defective ejection of ink due to the pressure vibration is prevented.

Further, by detecting the pressure to be reduced, the pressure vibration of the ink supply system can be accurately read and the pressure vibration can be surely reduced regardless of the print pattern such as printing. .

[0019]

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

FIG. 1 is a schematic sectional view of a print head in an ink jet printing apparatus of the present invention. The print head of FIG. 1 is similar to the conventional one described above.
In the figure, 1 is an ink flow path forming a nozzle, 2 is a heater, 3 is a common liquid chamber for supplying ink to a plurality of ink flow paths 1, and 4 is an ink supply path connected to an ink tank. . The common liquid chamber 3 constitutes an ink introducing section to which ink is supplied from the ink supply system. 6
Is a piezoelectric element as pressure adjusting means driven to damp the pressure vibration, and 7 is a pressure sensor for reading the pressure vibration.

First, the pressure vibration in question and the operation of the piezoelectric element 6 for preventing the pressure vibration in this embodiment will be described with reference to FIG.

Pressure oscillation occurs when ink is ejected from all nozzles of the recording head and a large amount of ink is supplied. For example, when a large amount of ink is continuously ejected from the ink flow path 1 of FIG. 1, a large amount of ink in the ink tank is supplied through the ink supply path 4, so the pressure of the ink supply system becomes low. . At this time, as described later, by driving the piezoelectric element 6 to expand inward of the liquid chamber 3, the volume of the liquid chamber 3 is reduced and the pressure drop is eliminated. In FIG. 1, H1 is the amount of expansion of the piezoelectric element 6 inward of the liquid chamber 3, and the inner surface 6a of the piezoelectric element 6 is displaced from the normal reference position P0 to the expansion position P1 so that The volume is reduced and pressure drop is avoided. 6a 'indicates the inner surface of the piezoelectric element 6 at the expanded position P1, and the expansion amount H1 of the piezoelectric element 6 is controlled to an amount according to the pressure in the liquid chamber 3 as described later.

Next, when the ejection of the ink is suddenly stopped, the supply of the ink from the ink tank is suddenly stopped, so that the pressure of the ink supply system is increased by the inertial force of the ink. At this time, as described later, by driving the piezoelectric element 6 so as to contract to the outside of the liquid chamber 3, the volume of the liquid chamber 3 increases and the pressure rise is eliminated. In FIG. 1, H
2 is the amount of contraction of the piezoelectric element 6 to the outside of the liquid chamber 3, and when the inner surface of the piezoelectric element 6 is displaced from the reference position P0 to the contracted position P2, the volume inside the liquid chamber 3 increases and the pressure increases. Rise is avoided. 6a ″ indicates the inner surface of the piezoelectric element 6 at the contracted position P2, and the contracted amount H2 of the piezoelectric element 6 is controlled to an amount according to the pressure in the liquid chamber 3 as described later.

FIG. 6 is a block diagram of a drive circuit for driving and controlling the recording head, and FIG. 7 is a conceptual diagram of pressure control of the ink supply system according to this embodiment. Next, the drive control operation will be described with reference to FIGS. 1, 6 and 7.

First, image data such as printing is stored in the image memory 8 of the recording device from the host computer. When printing such as printing is started, the image data is sent to the head drive unit 11, and the pressure sensor 7 causes the liquid chamber 3 to move.
The detection of the pressure oscillation inside is started. The detection voltage of the pressure sensor 7 corresponding to the pressure in the liquid chamber 3 is set to an appropriate voltage for driving the piezoelectric element 6 by the inverting amplifier circuit 9 to attenuate the pressure vibration in the liquid chamber 3 as described above. Inverted, amplified and converted. Then, the piezoelectric element driver 10 drives the piezoelectric element 6 by the converted voltage. As described above, the piezoelectric element 6 is expanded and driven so that the inner surface 6a thereof is displaced to the position of 6a 'in FIG. 1 when the pressure of the ink supply system is high, while the inner surface 6a thereof is driven when the pressure is small.
Is contracted and driven so as to be displaced to the position of 6a ″ in FIG.

The concept of pressure control of the ink supply system by the piezoelectric element 6 will be described with reference to FIG. The pressure vibration of the ink supply system is detected by the pressure sensor 7 as a detection voltage, and the inverting amplifier circuit 9
To the piezoelectric element 6 by the inverting amplifier circuit 9, and the detected voltage is converted to a piezoelectric element drive voltage by the inverting amplifier circuit 9.
Is driven, the pressure vibration of the ink supply system is attenuated. That is, by driving the piezoelectric element 6 according to the detection result of the pressure vibration, the pressure of the ink supply system is feedback-controlled to attenuate the pressure vibration.

Here, the gain A of the inverting amplifier circuit 9 in FIG.
Is an important factor, and if the driving amount of the piezoelectric element 6 is too small, the pressure vibration is not attenuated, and if it is too large, the pressure vibration may oscillate greatly. There is a nature. Regarding the setting of the gain A, for example, at the development stage of the recording head, the gain A may be adjusted and the optimum condition may be found while performing printing as shown in FIG. When the gain A differs depending on the recording head, for example, the head can be extracted for each manufacturing lot during the manufacturing process of the recording head to adjust the gain A.

As described above, by driving the piezoelectric element 6, it is possible to damp the pressure vibration of the ink supply system and prevent deterioration of print quality such as printing due to the pressure vibration.

FIG. 11 is a schematic perspective view showing a main part of an ink jet printing apparatus according to an embodiment of the present invention.

In FIG. 11, the print head 51 is
For example, 64 ink ejection ports (not shown) are provided in the conveying direction of the recording paper 57 on the surface facing the recording paper 57 as a print medium. In addition, the print head 51 has this 6
An ink flow path (not shown) is provided so as to communicate with each of the four ink ejection ports.
An electrothermal converter that generates thermal energy for ejecting ink is formed on a substrate that constitutes the print head 1. The electrothermal converter generates heat by an electric pulse applied according to drive data, which causes film boiling in the ink, and the ink is ejected from the ink ejection port as bubbles are generated by the film boiling. Let A common liquid chamber that is commonly communicated with the ink channels is provided in each ink channel, and the ink stored therein is supplied to the ink channels according to the ejection operation in each ink channel.

The carriage 52 carries the print head 51 and slidably engages with a pair of guide rails 53 extending parallel to the recording surface of the recording paper 57. As a result, the print head 51 can move along the guide rail 53, and recording is performed by ejecting ink toward the recording surface at a predetermined timing in accordance with this movement. After the above movement, the recording paper 57 is conveyed by a predetermined amount in the direction of the arrow in the figure, and the above movement is performed again to perform recording. By repeating such an operation, the recording paper 57
Then, record sequentially.

The above-mentioned conveyance of the recording paper 57 is carried out by a pair of conveying rollers 54 arranged above and below the recording surface.
And 55 are rotated. Further, a platen 56 for maintaining the flatness of the recording surface is provided on the back side of the recording surface of the recording paper 57.

The movement of the carriage 52 described above is
For example, a belt (not shown) attached thereto can be driven by a motor, and rotation of the transport rollers 54 and 55 can be similarly performed by transmitting the rotation of the motor to them.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for performing ink ejection, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of 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,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
It is effective because bubbles can be formed inside. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. It is more preferable to make this drive signal into a pulse shape because bubbles can be immediately and appropriately grown and contracted, so that liquid (ink) ejection 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 ejection port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned respective 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.

Further, 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 which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus or the electrical connection to the main body of the apparatus and the ink from the main body of the apparatus by being mounted on the main body of the apparatus. 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 ejection recovery means of the recording head, preliminary auxiliary means and the like since the effects of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

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 from the solid state of the ink 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 heat energy such as ink that is liquefied by applying heat 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 the 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 transmitting / receiving function. It may be a form or the like.

[0043]

As described above, according to the present invention,
By driving the pressure adjusting means such as a piezoelectric element, the pressure vibration of the ink supply system can be attenuated, and the deterioration of print quality such as printing due to the influence of the pressure vibration can be prevented.

As a result, it is not necessary to increase the flow resistance of ink, to devise the shape of the head, or to lower the drive frequency in order to prevent pressure vibration, and simplify the design of the ink supply system of the head. In addition, the printing speed such as printing can be increased by increasing the driving frequency.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an inkjet head in an inkjet printing apparatus of the present invention.

FIG. 2 is a schematic configuration diagram of an inkjet head in a conventional inkjet printing apparatus.

3 is a cross-sectional view of a schematic configuration in the case where the inkjet head of FIG. 2 is provided with a pressure sensor for measuring pressure vibration.

4 is a cross-sectional view of a main part for explaining a change in ink due to pressure vibration of the inkjet head of FIG.

5 is a timing chart for explaining a relationship between a pressure vibration waveform, a drive pulse, and a recording dot in the inkjet head of FIG.

FIG. 6 is a block configuration diagram of a drive circuit of an inkjet head in the inkjet printing apparatus of the present invention.

FIG. 7 is a conceptual diagram of a pressure control system in the inkjet printing apparatus of the present invention.

FIG. 8 is a schematic diagram of print dots for explaining an example of a drive pattern in which pressure vibration occurs in a conventional inkjet head.

FIG. 9 is a schematic diagram of print dots for explaining another example of a drive pattern in which pressure vibration occurs in a conventional inkjet head.

10 is an explanatory diagram of an observed pressure waveform of the liquid chamber when the drive pattern of FIG. 8 is executed.

FIG. 11 is a schematic perspective view of a main part of the inkjet printing apparatus of the present invention.

[Explanation of symbols]

 1 Ink flow path 2 Heater 3 Liquid chamber 4 Ink supply path 5 Pressure sensor 6 Piezoelectric element 7 Pressure sensor 8 Image memory 9 Inversion amplification circuit 10 Piezoelectric element driver 11 Head drive unit

Claims (9)

[Claims] 1. An ink jet head capable of ejecting ink supplied from an ink supply system into an ink introducing section from an ink ejection port, wherein the ink introducing section is provided in the ink introducing section so as to attenuate pressure fluctuations in the ink introducing section. An ink jet head, comprising a pressure adjusting means capable of adjusting the pressure of the ink. 2. The ink introducing section has a liquid chamber communicating with a plurality of the ink ejection ports, and the pressure adjusting means is capable of adjusting the pressure of ink in the liquid chamber. Item 2. The inkjet head according to Item 1. 3. The ink jet head according to claim 2, wherein the pressure adjusting means is capable of adjusting the volume of the liquid chamber. 4. The ink jet head according to claim 2, wherein the pressure adjusting unit has a piezoelectric element capable of displacement control inward or outward of the liquid chamber. 5. The detecting means for detecting the pressure of the ink in the ink introducing portion and outputting a detection signal for controlling the pressure adjusting means, according to any one of claims 1 to 4. Inkjet head. 6. The ink jet head according to claim 1, wherein the ink jet head has an electrothermal conversion element that generates heat energy that causes film boiling in the ink, as energy used for ejecting the ink. The inkjet head according to any one of claims. 7. An inkjet printing apparatus for printing on a print medium using an inkjet head capable of ejecting ink, comprising the inkjet head according to claim 1 as the inkjet head, and An ink jet printing apparatus comprising: a control unit that controls the pressure adjusting unit according to a pressure fluctuation in the ink introducing unit due to the ejection of ink from an outlet. 8. An inkjet printing apparatus for printing on a print medium by using an inkjet head capable of ejecting ink, wherein the inkjet head has the inkjet head according to claim 5, and the detection signal of the detection means is provided. An ink jet printing apparatus comprising a control means for controlling the pressure adjusting means based on the above. 9. The ink jet head according to claim 7, wherein the ink jet head has an electrothermal conversion element that generates heat energy that causes film boiling in the ink, as energy used for ejecting the ink. The inkjet printing apparatus described.