JPH06297707A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To properly control an ink emitting amt. by expanding the volume of each pressure chamber to fill the pressure chamber with ink and contracting the volume of the pressure chamber to emit the ink from the pressure chamber and arbitrarily changing the expanding speed of the volume corresponding to the recording characteristics of a material to be recorded. CONSTITUTION:Many nozzles 1 are formed to a substrate 2. Pressure chambers 4, segment ink supply passages 5, a common ink chamber 6 and the communication port of an ink supply pipe 7 are respectively formed to the passage substrate 3 laminated to the substrate 2. Further, the pressure generating elements 10 arranged on a base substrate 8 are bonded to the bottom surface of the passage substrate 3. When a segment signal 25 and a common signal 26 are applied to the pressure generating elements 10 from a drive circuit 27, the volume of each of the pressure chambers 4 is reduced and the pressure in each of the pressure chambers is raised to emit ink from each nozzle. In this case, when the volume of each pressure chamber 4 is expanded and the pressure chamber 4 is filled with ink, the volume expanding speed of the pressure chamber 4 is arbitrarily changed corresponding to the recording characteristics of a material to be recorded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image of a printer or the like in which a pressure is generated in a pressure generating element by an electric signal, and the pressure causes an ink droplet to fly to form an ink image on a recording material such as recording paper. The present invention relates to a recording device, and more particularly, to an inkjet recording device.

[0002]

2. Description of the Related Art Ink jet recording apparatuses have the characteristics that they are non-impact, have low noise, and are capable of color output by using multicolor inks, and have become popular rapidly in recent years. In this inkjet recording device, a recording material or recording sheet having recording characteristics suitable for printing and printing, such as hygroscopicity or bleeding property, is designated as a recommended recording material. Had the problem that they were different. For example, even PPC paper is liable to bleed on recycled paper and has a larger dot diameter, and special paper has a different dot diameter depending on the type of coating material coated on the surface. Further, OHP sheets are less likely to bleed and have a smaller dot diameter. There was a tendency.

With respect to the above problem, for example, Japanese Patent Laid-Open No. 57-1
In Japanese Patent No. 38950, according to the recording characteristics of the recording material,
A technique has been devised in which the nozzle diameter is controlled by controlling the applied voltage, and the ink ejection amount is controlled. Also,
In JP-A-2-3327 and JP-A-4-33470, a means for detecting the bleeding rate of a recording material, or
A technique has been devised which has a means for identifying the type of recording material, changes the correction parameter according to the detection and identification results, and switches the masking coefficient at the time of color output.
Further, in Japanese Patent Laid-Open No. 3-248851, the dot diameter is changed by changing the gap between the inkjet head and the recording material according to the type of the recording material and controlling the speed at which the ink droplets adhere to the recording material. A technology for controlling the power source has been devised.

[0004]

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 57-138950, a plurality of control power supplies are used to control the ink ejection amount.
Alternatively, there is a problem that it is necessary to configure an amplifier circuit, which leads to an increase in cost, or that the number of controls is limited. Further, when the applied voltage is controlled and the nozzle diameter is changed, the ejection speed is changed along with the ink ejection amount, so that there is a problem in that the print quality is affected when both rows are driven. In addition, JP-A-2-3327 and JP-A-4-3327
In the technique disclosed in Japanese Patent Publication No. 33470, since it is impossible to control the dot diameter, it is impossible to completely cope with hygroscopicity and bleeding, especially in a low density portion, and further, it is applied to single color printing or the like. There was a problem that it could not be done. In the technique disclosed in Japanese Patent Application Laid-Open No. 3-248851, the speed at the time of adhesion is reduced by increasing the gap, but the flight stability of ink droplets is reduced, or the recording position accuracy on the recording material is reduced. There is a problem such as decrease.

The present invention solves these problems.
The purpose is to control the ink ejection volume at a low cost while maintaining a constant ink ejection speed without using multiple power supplies, etc., thereby obtaining a dot diameter that matches the recording characteristics of the recording material. The present invention provides an inkjet recording device capable of printing and printing on any recording material with excellent quality.

[0006]

An ink jet head recording apparatus of the present invention includes a nozzle for ejecting ink, a pressure chamber communicating with the nozzle, a pressure generating element for generating a pressure in the pressure chamber, and the pressure generating element. In an ink jet recording apparatus using an ink jet head having a voltage applying means for applying a voltage to a first stage, a first step of expanding the volume of the pressure chamber to fill the pressure chamber with ink and contracting the volume of the pressure chamber And a second step of ejecting ink, and the volume expansion rate of the pressure chamber in the first step is arbitrarily changed according to the recording characteristics of the recording material. .

Further, the voltage application means is a constant voltage, and the fall time or rise time of the voltage application voltage for driving the pressure generating element is variable according to the recording characteristics of the recording material. It is characterized by having means for changing the volume expansion rate of the pressure chamber in the first stage.

[0008]

The ink jet recording apparatus of the present invention can freely change only the ink ejection amount without changing the applied voltage and the ink ejection speed.
It is possible to provide an inkjet recording apparatus that can obtain a dot diameter that matches the recording characteristics of the recording material and that can print or print with excellent quality on any recording material at low cost.

[0009]

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

First, a drive embodiment will be described in which only the ink ejection amount is freely changed while the ink ejection speed is kept constant without changing the applied voltage.

FIG. 1 is a structural explanatory view of an ink jet head showing an embodiment of the present invention.

Reference numeral 2 shown in FIG. 1 is a nozzle forming substrate on which a plurality of nozzles 1 are formed. The opening area of the nozzle 1 and the thickness of the nozzle forming substrate 2 have a great influence on the ink ejection characteristics. The nozzle 1 can be formed with high precision by a precision pressing method, an electroforming method of nickel, an etching process of a silicon wafer, or the like. The flow path substrate 3 bonded to the nozzle forming substrate 2 is a member formed with the pressure chamber 4, the segment ink supply path 5, the common ink chamber 6, and the communication port of the ink supply pipe 7. When the flow path substrate 3 is bonded to the nozzle forming substrate 2, it is necessary to bond the nozzle 1 so that the nozzle 1 is located at the center of the pressure chamber 4 in order to enhance the ejection efficiency. The pressure chamber 4, the segment ink supply path 5, and the common ink chamber 6 thus formed are filled with ink.

The pressure generating elements 10 arranged on the base substrate 8 are bonded to the bottom surface of the flow path substrate 3 so as to correspond to the respective pressure chambers 4. The pressure generating element 10 shown in FIG.
When the segment signal 25 and the common signal 26 are applied from the drive circuit 27, the volume of the pressure chamber 4 is reduced and the pressure is increased, and ink is ejected from the nozzle 1.

2 (a) and 2 (b) are relationship diagrams showing the voltage waveform for driving the ink jet head and the displacement behavior of the pressure generating element.

FIG. 3A is an explanatory view showing a state where the volume of the pressure chamber is contracted, and FIG. 3B is an explanatory view showing a state where the volume of the pressure chamber is expanded. A meniscus 17 is formed in the nozzle 1 by the surface tension of the ink. Pressure generating element 10
When a voltage is applied, it expands in the displacement direction of arrow δ as shown in FIG. 3 (a), contracting the volume of the pressure chamber, while FIG. 3 (b) shows the state when no voltage is applied. As shown, the steady state is reached and the volume of the pressure chamber is relatively increased.

In FIG. 2A, the fall (discharge) time T1 and the rise (charge) time T2 of the voltage waveform 21 are shown.
Is smaller than the natural vibration period Ta of the pressure generating element,
The displacement behavior 22 of the pressure generating element 10 exhibits an excessive vibration behavior. In such a case, residual vibration occurs in the pressure chamber 4, and the meniscus 17 shown in FIG. 3 vibrates, which makes ink ejection unstable. However,
As shown in FIG. 2B, by setting the falling time T1 and the rising time T2 of the voltage waveform 21 applied to the pressure generating element 10 to be larger than the natural vibration cycle Ta of the pressure generating element 10, Since the generating element 10 does not exhibit excessive vibration behavior, the pressure chamber 4 and the meniscus 17 do not generate residual vibration, and ink ejection can be stably maintained.

Contrary to the pressure generating element 10 shown in FIG. 3,
A pressure generating element having a characteristic of contracting when a voltage is applied to expand the volume of the pressure chamber 4, while being in a steady state when a voltage is not applied and relatively contracting the volume of the pressure chamber 4. When 10 is used, the voltage waveform 21 and the displacement behavior 22 shown in FIG. 2 are inverted vertically, but the essential relationship between T1, T2 and Ta is the same, and T1, T2 ≧
By having the relationship of Ta, it is possible to stably maintain the ink ejection.

The natural vibration period Ta of the pressure generating element 10
Is expressed as in Equation 1.

[0019]

[Equation 1]

Here, L is the pressure generating element 10 shown in FIG.
In the displacement direction, ρ is the density of the pressure generating element 10, E is the Young's modulus of the pressure generating element 10, and λ is the frequency coefficient of the pressure generating element 10 which varies depending on the vibration mode. It is 1.875 in the pressure generating element 10 using the fixed longitudinal vibration.

As described above, Ta can be relatively easily determined from the shape and the physical constant of the pressure generating element 10, and T1 and T2
In addition, stable ejection of ink becomes possible by setting Ta larger than Ta.

FIG. 4 is a relationship diagram showing the behavior of the voltage waveform 21, the volume change behavior 23 in the pressure chamber, and the meniscus level 24 when the ink jet recording apparatus of the present invention is driven.

FIG. 5 is a partially enlarged view of the ink jet head for explaining the embodiment of the present invention. In FIG. 5, the pressure generating element 10 shown in FIGS. 1 and 3 is shown as a more specific laminated piezoelectric element 20. This laminated piezoelectric element 20 is composed of a segment electrode 15, a piezoelectric material layer 13, and a common electrode 16, and expands in the laminating direction by applying a voltage (d33 effect) and contracts in the laminating direction and orthogonal direction (d31 effect). ) Has characteristics.

The basic driving method of the ink jet recording apparatus using the d33 effect will be described below with reference to FIGS.

Time t0 to t1 is a steady state. As shown in FIG. 4, since the voltage level is Vh in this state, the laminated piezoelectric element 20 shown in FIG. 5 exhibits the deformation behavior as shown by the broken line A, and the volume change 2 of the pressure chamber 4
3 is a state in which the volume of the pressure chamber 4 is relatively contracted C
At level 0. The meniscus level 24 shown in FIG. 4 is maintained at a steady level M0 held by the surface tension of the ink.

The time t1 to t2 is the first step of the driving method of the present ink jet recording apparatus. As shown in FIG. 4, in this state, the voltage waveform 21 is discharged to the level shown by VL at the fall time T1, and the volume change 2 of the pressure chamber 4
3 changes to the level of C1, expands the volume of the pressure chamber 4, and reduces the pressure in the pressure chamber 4. At this time, the meniscus 17 is drawn toward the inside of the pressure chamber 4 to the meniscus level 24 shown in FIG. 4 up to the level shown by M1.

Times t2 to t3 are the second step of the driving method of the ink jet recording apparatus. As shown in FIG. 4, in this state, the voltage waveform 21 is maintained at the level indicated by VL, and therefore the volume change 23 of the pressure chamber 4 is also maintained at the level of C1 which is the state in which the volume of the pressure chamber is expanded. It At this time, an inertial flow of ink in the direction of the nozzle 1 is generated in the pressure chamber 4, and the meniscus 17 has a steady level M.
I try to return to 0.

Times t3 to t4 are the third step of the driving method of the present ink jet recording apparatus. As shown in FIG. 4, in this state, the voltage waveform 21 is charged to the level shown by Vh again at the rising time T2, and the pressure chamber 4
The volume change 23 of the pressure chamber 4 is changed to the level of C0.
Since the volume of the ink is contracted and the pressure in the pressure chamber 4 is increased, the meniscus 17 is strongly pushed out in the ink ejection direction, and the ink droplets fly. The amount of ink discharged at this time corresponds approximately to the area of the hatched portion S shown in FIG.

As described above, the basic driving method of the ink jet recording apparatus is constituted by the three steps of time t1 to t4.

However, in the first step and the third step, as shown by the broken line 31 in FIG. 4, the falling time T1 and the rising time T2 of the voltage waveform are the natural vibration period Tc of the ink in which the pressure chamber is filled. If less than
An oscillatory behavior like the volume change of the pressure chamber 4 shown by the broken line 33 is generated, and the meniscus level is disturbed as shown by the broken line 34, which becomes a factor to make the ink ejection unstable. That is, as shown in the voltage waveform 21 shown in FIG. 4, T1, T2 ≧
In the case of the relationship of Tc, it is possible to stably maintain the ejection of ink and achieve high printing quality.

Regarding the method of driving the ink jet head using the d31 effect, only the voltage waveform 21 shown in FIG. 4 is inverted up and down, but the essential relationship between T1, T2 and Tc is that when the d33 effect is used. Similarly, T1, T2 ≧ T
High print quality can be realized by having the relationship of c.

The natural vibration period Tc of the ink filled in the pressure chamber 4 is expressed by the equation (2).

[0033]

[Equation 2]

Here, Mn is the inertance of the nozzle 1,
Mi is the inertance of the ink supply path, Ci is the ink compliance, and Cc is the pressure chamber 4 compliance.

Further, Mn, Mi, Ci and Cc are defined by the equations 3 to 6 as follows.

[0036]

[Equation 3]

Here, ρ is the ink density, and S (x) is shown in FIG.
The cross-sectional area of the nozzle in the thickness X of the nozzle forming substrate 2 shown in FIG.

[0038]

[Equation 4]

Here, ρ is the density of the ink, and S (l) is shown in FIG.
The cross-sectional area of the supply path at the ink supply path length l shown in
Is a proportional constant considering an unsteady solution determined by the shape of the supply path, and n is the number of supply paths for the nozzle (2 in this embodiment).

[0040]

[Equation 5]

Here, v is the volume of the pressure chamber 4, ρ is the density of ink, and c is the speed of sound of ink.

[0042]

[Equation 6]

Here, ΔV is the deformation volume of the pressure chamber per unit pressure, and P0 is the unit pressure.

As the natural vibration period Tc of the ink thus determined is smaller, the ink ejection interval is narrowed,
High-speed printing is possible.

Further, the base substrate 8 shown in FIG. 5 is ideally a rigid body, and specifically, it is desirable that the acoustic impedance (Young's modulus × specific gravity) is large. Therefore,
As shown in FIG. 5, one end of the laminated piezoelectric element 20 is held on the base substrate 8 having a Young's modulus and a specific gravity equal to or higher than the Young's modulus and the specific gravity of the laminated piezoelectric element 20, so that the pressure is increased with respect to the pressure chamber 4. The pressure can be efficiently transmitted.

FIG. 6 is a characteristic diagram of the ink discharge speed 50 and the ink discharge amount 60 with respect to the fall time (discharge time) T1 for explaining the driving method of the ink jet recording apparatus according to the embodiment of the present invention.

FIG. 7 is an enlarged photograph of the ink droplet flight form with respect to the fall time (discharge time) T1 for explaining the driving method of the ink jet recording apparatus according to the embodiment of the present invention. It should be noted that this enlarged photograph is taken in a state in which a certain time has elapsed since the voltage was applied to the laminated piezoelectric element 20.

The fall time (discharge time) T1 is the minimum T
Although it is premised that it is larger than a, by changing only T1 as in the area I shown in FIG. 6, it is possible to change only the ink ejection amount 60 without changing the ink ejection speed 50.

Specifically, as shown in FIG. 7, the fall time T1 changes from 8 (μs) to 20 (μs), and the expansion speed of the pressure chamber 4 is changed to change the ink ejection speed 50. It is possible to increase or decrease only the ink ejection amount without performing the above. The ink ejection speed 50 is rather correlated with the volumetric contraction speed of the pressure chamber 4, and the volumetric expansion speed of the pressure chamber 4 is the amount of ink supplied to the pressure chamber 4 (inertial flow amount).
It has been confirmed experimentally that there is a correlation. Assuming that the dot diameter transferred onto the recording material is proportional to the cube root of the ink ejection amount, the dot diameter can be changed twice by changing the ink amount eight times, for example. The feature of the ink jet recording apparatus of the present invention is to positively utilize such a phenomenon to control the ink ejection amount without changing the applied voltage generated by the drive circuit.

Next, a means for grasping the recording characteristics of the recording material will be described. As means, for example, a test print of an isolated dot is performed outside the image recording area of the recording material prior to image formation, and the dot diameter is illuminated by an issuing element provided in the apparatus, and a light receiving element array such as a CCD sensor is used. It can be dealt with by measuring.

Further, for example, the recording material is replenished in the recording device,
Before printing, as shown in FIGS. 8A to 8C, a plurality of solid patterns having different dot diameters are printed by the above-described driving method, and a suitable dot diameter is obtained. It is also possible to set by the user. Specifically, the unit length Y per resolution of the recording device
On the other hand, when the dot diameter 28 is small as shown in (a),
It is not preferable because defective coating occurs in a solid pattern. Further, if the dot diameter 28 is too large as in (c), it leads to poor quality of ink due to poor ink drying, especially in solid patterns, and thickening of characters and the like. It is preferable that the coating defect is eliminated as in the state of (b).

Further, it is also possible to record the condition in which the dot diameter suitable for each recording material is recorded in advance in the recording device and set by the user.

FIG. 9 is a partial explanatory view of a drive circuit for explaining the ink jet recording apparatus according to the embodiment of the present invention.
Tr1 to Tr3 are transistors that control the magnitude of the fall time (discharge time) T1. When Tr0 is ON and Tr1 to Tr4 are all OFF, the current Ic1 flows and the current flows through the laminated piezoelectric element 20. At this time, the laminated piezoelectric element 20 is charged with a rising time (charging time) T2 determined by the capacitance value of the resistance element R0 and the laminated piezoelectric element 20. Then Tr0
When is turned off and any of Tr1 to Tr4 is turned on, a current Ic2 flows, and the electric charge charged in the laminated piezoelectric element 20 is discharged. ON-OFF of Tr1 to Tr4
The control is based on the recording characteristic result of the recording material described above.
It is determined by the pressure chamber volume expansion speed variable circuit 29.
Specifically, R1 to R4 are resistance elements having the same characteristics, and
If the fall time T1 is 4 when only r1 is ON and Tr2, Tr3, and Tr4 are OFF, Tr1 and Tr
If only 2 is turned ON, the fall time T1 becomes 2. If all Tr1 to Tr4 are turned ON, the fall time T1 becomes 1. With such a drive circuit, the fall time T1 can be easily set.

As described above, by freely changing the volume expansion speed of the pressure chamber according to the recording characteristics of the recording material, only the ink discharge amount can be freely changed without changing the applied voltage and the ink discharge speed. Although the inkjet recording apparatus that can obtain the dot diameter that matches the recording characteristics of the recording material has been described, the present inkjet recording apparatus can be applied to color recording as well as single color recording.

[0055]

As is apparent from the above description, the ink jet recording apparatus of the present invention can change the volume expansion speed of the pressure chamber in the first stage arbitrarily according to the recording characteristics of the recording material. By freely changing only the ink ejection amount without changing the applied voltage and the ink ejection speed, a dot diameter that matches the recording characteristics of the recording material can be obtained, and excellent quality can be obtained for any recording material. This has the effect of providing an inkjet recording device capable of printing and printing at low cost.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a main part of a head of an inkjet recording apparatus of the present invention.

FIG. 2 is a relationship diagram showing a voltage waveform for driving a head of the inkjet recording apparatus of the present invention and a displacement behavior of a pressure generating element.

FIG. 3A is a state in which the volume of the pressure chamber is contracted in the head of the ink jet recording apparatus of the present invention, and FIG.
FIG. 6 is an explanatory diagram showing a state where the volume of the pressure chamber is expanding.

FIG. 4 is a relationship diagram showing a voltage waveform for driving the head of the ink jet recording apparatus of the present invention, volume change behavior in the pressure chamber, and meniscus behavior.

FIG. 5 is an enlarged view of a main part of the head showing an embodiment of the present invention.

FIG. 6 is a fall time (discharge time) T for explaining a first inkjet head driving method according to an embodiment of the present invention.
FIG. 3 is a characteristic diagram of ink ejection speed and ink ejection amount for No. 1;

FIG. 7 is a fall time (discharge time) T for explaining a first inkjet head driving method according to an embodiment of the present invention.
FIG. 3 is an enlarged photograph of an ink droplet flying form for No. 1;

FIGS. 8A to 8C are schematic diagrams illustrating a dot transfer state in the embodiment of the present invention.

FIG. 9 is a partial explanatory diagram of a drive circuit illustrating an inkjet head drive method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle 2 Nozzle formation substrate 3 Flow path substrate 4 Pressure chamber 8 Base substrate 10 Pressure generating element 20 Multilayer piezoelectric element

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

FIG. 7 is a model showing how ink droplets fly with respect to the fall time (discharge time) T1 for explaining the driving method of the inkjet recording apparatus according to the embodiment of the present invention.
It is a Dell diagram . Incidentally, this figure shows the state where a predetermined time has elapsed since a voltage is applied to the laminated piezoelectric element 20.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

FIG. 7 is a fall time (discharge time) for explaining a first inkjet head driving method according to an embodiment of the present invention.
FIG. 6 is a model diagram showing a flight form of an ink droplet with respect to T1.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (2)

[Claims] 1. An ink jet head having a nozzle for ejecting ink, a pressure chamber communicating with the nozzle, a pressure generating element for generating a pressure in the pressure chamber, and a voltage applying unit for applying a voltage to the pressure generating element. The inkjet recording apparatus to be used has a first step of expanding the volume of the pressure chamber to fill the pressure chamber with ink, and a second step of contracting the volume of the pressure chamber to eject ink. An ink jet recording apparatus, wherein the volume expansion rate of the pressure chamber in the first stage is arbitrarily changed according to the recording characteristics of the recording material. 2. The voltage applying means is a constant voltage, and the fall time or rise time of the voltage applied voltage for driving the pressure generating element is variable according to the recording characteristics of the recording material. 2. The ink jet recording apparatus according to claim 1, further comprising means for changing the volume expansion rate of the pressure chamber in the first stage.