JPS59133066A - Method of controlling quantity of ink drop - Google Patents

Abstract

For controlling the volume of ink droplets ejected from a drop on demand ink jet apparatus including a transducer (204) operable for producing a pressure disturbance within an associated ink chamber (200) for ejecting an ink droplet from an associated orifice (202), the transducer (204) is operated in an iterative manner for producing a plurality of successively equal or higher or lower amplitude pressure disturbances, or some combination thereof, within the ink chamber (200), for causing a plurality of successively equal or higher or lower velocity ink droplets, or some combination thereof, to be ejected from the orifice (202) of the ink jet apparatus, within a time period permitting the ink droplets to either merge in flight or upon striking a recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The field of the present invention relates to inkjet devices, and more particularly, the field of the present invention relates to inkjet devices, and more particularly, the amount of ink droplets ejected by the device;
or) relates to a method of operating an inkjet device to selectively control within a range the amount of ink impinging on a given point on a recording medium.

PRIOR ART The design of the actual inkjet device and the device that generates the required drop of ink is relatively new in the art. In conventional ink jet devices, the volume of each individual ink drop is a function of the shape of the ink jet device, the type of ink used, and the amount of pressure created within the ink chamber of the ink jet that causes the ink drop to be ejected from the associated orifice. Involved. Effective diameter and design of the orifice.

The volume and shape of the ink chamber associated with this orifice, the design of the transducer, and the manner in which the transducer is coupled to the ink chamber are all factors that determine the individual ink droplets ejected from the orifice. Typically, once the mechanical design of an inkjet device is fixed, control over the amount of ink drops ejected consists of varying the amplitude of the electrical pulses and thus the pressure applied to each transducer of the inkjet device. Yes, it can only be obtained within a narrow range.

DISCLOSURE OF THE INVENTION The present inventors have disclosed that a plurality of successively fast or slow or equal velocity ink drops, or a combination thereof'(i
l - the transducer of the inkjet such that the ink droplets are generated and ejected from the orifice of the inkjet in time to allow the ink droplets to coalesce in the air or impact the recording medium at the same point before impacting the recording medium; It has been found that by repeating the operation, it is possible to have a wide range of control over the thickness and tone of the print. This allows the amount of ink that impinges on the recording medium at a given point to be reduced by -l prior to impact.
fc is determined in part by the number of ink drops that coalesce at the point of impact.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention was discovered during the development of an improved method for operating the inkjet equipment shown in FIGS. 1-5. However, the inventor believes that the various embodiments of the invention illustrated in the drawings and described in the claims can be used in a wide range of inkjet devices, particularly jetting inkjet devices. There is.

However, the inkjet device described here is
It is for the purpose of illustration of the method of the invention and is not meant to be limiting. Also, only the basic mechanical features and operation of this device will be described in the following sections, and reference numerals used in previously made special mentions for details regarding this device will be referred to in the earlier application or to which they were patented. In order to facilitate reference to patent publications in such cases, the same ones used in these applications are used.

Referring to Figures 1 to 3, the inkjet device of the embodiment includes a chamber 200 that includes a transducer 204 for each jet in the array of jets (see Figure 3).
It has an orifice 202' (i7) for ejecting ink droplets in response to the pressurized state of the ink droplet.

Transducer 204 expands along its longitudinal axis and convergently expands into a second
(in the direction indicated by the arrow in the figure), the movement is
The signal can be transmitted to the chamber 200 by 06.

The coupling means 206 comprises a leg 207, a viscoelastic material 208 juxtaposed to the leg 207, and a diaphragm 210 preloaded into the position shown in FIGS. 1 and 2. .

Ink enters the chamber 2 from an unpressurized reservoir 212 via narrow inlet means formed by a narrow inlet opening 214.
00. The inlet opening 214 is a restriction plate 216117
': (see Figure 3).

As shown in FIG. 2, a reservoir 212 formed in the substrate 220 has a tapered end 212 guided into an inlet opening 214.
It has 22. As shown in FIG.
2 is supplied using a supply pipe 223 and an outlet pipe 225. Reservoir 212 is more flexible than diaphragm 210 . The diaphragm 210 communicates with the ink through a large opening 227 in the restriction plate 216 to fill the restriction plate 2.
16 is juxtaposed with the relief 229 portion of the plate member 226 yen.

One end of each of the transducers 204 is slidably supported in the ID hole 224 of the leg 207 as shown in the figure, as shown in FIG. be done. The other end of each transducer 204 is flexibly attached to diblock 22817'3 by a flexible or resilient material 230, such as silicone rubber. A flexible resilient material 230 is disposed within groove 232 to provide support for the other end of transducer 204 (see FIG. 3). Electrical contact with the transducer 204 is made flexibly by a flexible printed circuit 234. Printed circuit 234 is electrically coupled to electrodes 260 of transducer 204 by suitable means, such as solder 236. The conductive pattern 238 is a printed circuit 234
formed on top.

Plate 226C (see FIGS. 1 and 3) has a hole 224 at the base of groove 237 that receives leg 207 of transducer 204, as described above.

The plate 226 has a glue septacle 230 for the heater sandwich 240, which includes a heating element 242 having a coil 244 and a retaining plate 24.
6, and a support plate 250 disposed immediately below the heater 240.
Equipped with. Groove 253 is for receiving a thermistor 252, which is used to monitor the temperature of heating element 242. The entire heater 240 is held within the −υ septacle of the cover plate 254 and the cover plate 226 .

As shown in FIG. 3, the various fc components of the inkjet device include a screw 256 extending upwardly through an aperture 257, a screw 258 extending downwardly through an aperture 259, and so on. The screws 258 are for holding the printed circuit board 234 in place on the entire board 228.The dashed lines in FIG. A263
Show i.

The connection section 263 connects the control section 261 to all inkjet devices in order to control the operation of the inkjet devices.

The control 261 selects the hot electrode 260 of the transducer 204 via the connection to the printed circuit 238 at the appropriate time fc 1 '! ' or more.

By applying a voltage, the selected transducer 204
An electric field is generated in a direction transverse to the longitudinal axis of the transducer 2
04(/'i) When the transducer 204 of the zero special foot, which contracts along its longitudinal axis, contracts due to pressure (see FIG. 5), the diaphragm 2 located below the legs 207 of the transducer 204
10 moves in the direction of the contracting transducer 204, thereby effectively expanding the entire volume of the connected chamber 200. When the volume of a particular chamber 200 is expanded in this way,
Negative pressure initially develops in the chamber, causing ink therein to flow away from the associated orifice 202 and directing ink from the reservoir 212 into the associated narrow inlet opening 21.
It flows into the room 200 yen via 4'Q. For a sufficient period of time, the ink supplied 111 completely fills the enlarged chamber and orifice, performing a "fill before dispensing" cycle. Immediately thereafter, the control unit 261 extracts all voltage control signals from a specific one or more of the selected converters 204, and connects the converter or converters 204 to a power source as shown in FIG. 3 times are executed to return the switch to the off state. 5 in January. The ringing signal (ends in a bow step υ) causes the transducer 204 to extend very slowly along its longitudinal axis, which causes the leg 207 of the transducer 204 to be transmitted through the viscoelastic material 208. They are pressed against the portions of the diaphragm 210 beneath them, causing a rapid contraction or reduction in the volume of the associated chamber or chambers 200. The decrease causes a pressure pulse or positive pressure fluctuation in the chamber 200, causing the ink drop to enter the orifice 2.
It is discharged from 02. Furthermore, as shown in Fig. 5,
When a given transducer 204 is pressurized, the transducer decreases in length and increases in thickness. But-j
The increase in speed has no bearing on the illustrated inkjet device; the variation in transducer length controls the action of the individual inkjet in the array. However, in this technique, by pressurizing the transducer for contraction along the longitudinal axis, additive stiffening of the transducer 204 is prevented and, in extreme cases, negative effects are avoided. is also prevented.

For purposes of explanation, it is assumed that the pulses shown in FIG. 6 are applied to one converter 2040 via the control unit 261. As shown, the first and second pulses 1.3 each have an exponential leading edge and a substantially linear trailing edge, each with a maximum amplitude of +V, ? +V2 Porto Ashi, widths are Tx and T2 respectively. It should be noted that the shape of the pulse 1.3 may be other than that shown here, depending on the particular inkjet device being driven and the particular application. In this example,
The maximum amplitude +V2 of pulse 3 is also larger than the maximum amplitude V1 of pulse l, and the falling time of the trailing edge of pulse 3 is shorter than the falling time of the trailing edge of pulse l. The degree of contraction of the selected transducer 204 is, within a certain range, directly related to the amplitude of the pulse applied to the transducer, such that the higher the amplitude, the greater the degree of contraction. Thus, at the end of a particular action or control pulse, the magnitude of the pressure fluctuation produced in the associated chamber 200 is directly related within a certain range to the magnitude of the control pulse already applied. Also, the larger the slope, ie, the shorter the fall time of the trailing edge of the control pulse, the faster the selected transducer 204 will expand or extend to rest at the end of the control pulse. Similarly, the greater the rate of expansion of transducer 204, the greater the magnitude of the associated pressure fluctuations that occur within fC chamber 200. Amplitude of pulse J, 3 +■1. +2 are each large enough to ensure ejection of an ink drop from the associated orifice 202 at the end of these pulses.

Referring to FIG. 7, assume that pulse l is applied to a selected one of transducers 204. Referring to FIG. When the pulse l ends,
A typical ink drop 5 is ejected from the associated oriSwiss 202. Assume that pulse 3 is applied to the selected transducer 204 when pulse l has substantially ended. Immediately after the end of pulse 3, a second ink drop 7 is ejected from the associated orifice 202, as shown for example in FIG.

The amplitude of pulse 3 is greater than pulse l, and pulse 3
Since the fall time of the pulse l is shorter than the pulse l, the ink drop 7 has a substantially greater velocity than the airborne ink drop 5. As mentioned above, pulse l.

Even if the fall times of pulse 3 are equal, as long as the amplitude of pulse 3 is larger than that of pulse 1, or even if these amplitudes are equal, the fall time of pulse 3 is smaller than that of pulse 1, then The velocity of the ink droplet 7 is also greater than that of the ink droplet 5. Therefore, the amplitude control of the control pulse,
Alternatively, control of the trailing edge fall time of the control pulse, or a combination of the two, may be used to e.g. By appropriately controlling the parameters, the velocity of the second ink drop 7 can be adjusted such that the ink drop 7 catches up with the ink drop 5 while each ink drop is in the air, causing the ink drops 5,7 to move as shown in FIG. They are made large enough to cause them to all begin to coalesce into one another. Assuming sufficient airborne time, the ink droplets 5 and 7 will coalesce into an ink droplet shape as shown in FIG. 10, prior to the combined ink droplets hitting the recording medium. Alternatively, the relative velocity of the ink drops (successively fast or slow) and the movement of the recording medium cause the ink drops to strike the recording medium at the same point without coalescing while being carried through the air. You can do this and get the same result. Thus, the size of the ink drop, and therefore the amount of ink, that strikes the recording medium at a particular point is substantially increased relative to using only a single ink drop, and such control of the amount of ink allows you to directly control thick printing.

Pulse 1 used by the inventor in conducting the experiment.
Typical values for parameters 3 are 28 volts and 30 volts for +■1°+v2, respectively, pulse width T,
, T2 each one of 60 microseconds, pulse 1,
The fall times were 2 microseconds and 1 microsecond for 3, respectively. In this example, the viscosity of the ink was 12 centipoise. For the particular inkjet device operated by the inventor, the mechanical diameter of the ink drop 5 is 1.8 mm, the second ink drop 7 is 2.2 mm, and the combined ink drop 9 is The diameter of the other ink droplets, that is, S-, which was 4.0 mm, is, as mentioned above, pulse], 3
can be obtained within a certain range through control of the amplitude and fall time.

Within certain limits, the size of ink droplets ejected from an inkjet device is controlled by adjusting the amplitude and fall time of control pulses applied to the inkjet device. The extent of control over the size, or amount, of the final ink droplets that strike the recording medium can be achieved through other embodiments of the present invention that coalesce a number of ink droplets flying through the air or at the point of impacting the recording medium. Substantially expanded.

In FIG. 11, the pulse l 1 , 13 (D amplitude
■□, +■2 are each shown to be equal (eg, typically 30 volts). In this example, the trailing edge of pulse ii has a fall time of about 10 microseconds, while the trailing edge of pulse 13 has a fall time of about 1 microsecond. Therefore, an ink drop produced by the action of pulse jl on a selected transducer 204 will also have a substantially lower velocity than a subsequent ink drop produced by the action of pulse 13 on transducer 204. Has speed. Therefore, pulse 1
Only the fall time control is used to control the overall velocity of the ink drops produced by the application of 93. In this embodiment, it is assumed that the second ejected high-speed ink droplet merges with the first ejected ink droplet while in the air or at the point where it hits the recording medium, as described above.

In FIG. 12, the third control or firing pulse 15
is added following the end of pulse 13. In one experiment with a given inkjet device, the inventors determined that, for example, the amplitude of the pulses 11°13.15 were all 30 volts 2 added to the DVl.

V2. and + are all equal to 30 volts), pulses li, 13, and 15 have exponential fall times of 10 microseconds, 5 microseconds, and 1 microsecond, respectively, and pulse widths of 60 microseconds each. , 40 microseconds, and 30 microseconds. When applied to a selected transducer 204 of a given inkjet device, pulse 1iidix of ink drops are ejected;
Pulse 3 causes all of the second ink droplets to be ejected at a higher velocity than the ml ink droplets, and pulse 15 causes a third ink droplet to be ejected at a similarly high velocity, so that all of these ink droplets are recorded. The relative speed is such that they coalesce in the air before hitting the medium. In this way, the size of ink droplets in an inkjet system can be adjusted.
ζ By virtue of this, a wide range of control can be obtained. the distance from the recording medium to the selected inkjet orifice 202;
Depending on the relative speed of movement of the recording medium and/or the inkjet head, and the design of the particular inkjet device, a large number of ink drops may be ejected at rather high speeds to allow them to coalesce in the air or at the point of impact. It is possible to greatly control the size of ink droplets from one printing position to another recording medium.

Note that in fact, after the end of the special firing pulse, the ink droplets
It is not expelled immediately. For example, when pulse 1.3 of FIG. 6 is applied to the transducer 204 of the inkjet device used in our experiments, ink drop 5 is ejected 4 microseconds after the end of pulse l, and Ink droplet 2 is ejected 3 microseconds after the end of pulse 3.

The velocity of the first ink droplet was measured to be 3.5 meters per second, and the velocity of the second ink droplet was 5.0 meters per second.

With full reference to FIG. 13, the illustrated combination of waveforms causes the interjet device to eject two ink droplets that coalesce at a common point of impact on the print media) with a diameter of 5. .3 to 5.6 mm (0,
It produces a dot pattern that varies from 135 to 0142 millimeters) and prints the size of a kana shiku. Typically, T,
, T2. T, and T4 are each 80,
4.18, and 6 microsecond tare), pulse 17.1
The amplitude of pulse 9 was 110 volts and the amplitude of pulse 21 was 73 volts.
Dot patterns of various sizes can be printed on OCOPY).

Paper type and ink composition affect the size of the dot pattern in a given use. Typically, the pulse 17°19
1'=jJ is 9 microseconds and 1 microsecond, respectively.
0 microseconds. Under the above conditions, immediately after the end of pulse 17, the first ink drop in the range of 8-10 meters per second is generated. The combination of pulses i9 and 21 also causes a second ink droplet to be generated approximately 2 microseconds after the end of pulse 19.

Although the pulse 21 is not of sufficient amplitude to generate a third drop, it exits the ink jet orifice as quickly as possible without the second drop t1 pulse 21 acting. Also, pulse 21 (C) allows the inkjet device to operate at a gastric frequency, reducing the problem of ink droplets in the orifice. The velocity of cs'M is typically 6-8 meters per second. Slowing down the velocity of the second ink drop with respect to the first ink drop
In this example, this is achieved by the presence of pulse 21.
By increasing the amplitude of pulse 19, the velocity of the second ink drop is increased. Furthermore, by changing the delay time T2 between the end of pulse 17 and the start of pulse 19, the thickness of the print can be adjusted within a certain circle.

By requiring only pulse 17 to activate the two ink cartridges in Figure ν14, a dot pattern with a diameter in the range of 3.3 to 35 mm (1,084 to 0.089 mm) is obtained. The diameter of such a dot pattern is such that a combination of pulses 17°, 19, and 21 times is used to fully operate an inkjet printer, resulting in printing with a fairly thin thickness.

Referring to Figure fA15, pulse 1 as shown in Figure 5
The combination of 7.21 operates the inkjet to produce ink drops having diameters in the range of 2.9 to 3.0 millimeters (0.074 to 0.076 millimeters). This combination allows for very thin printing.

By using various combinations of the waveforms of Figures 13, 14, and 15, the desired shading can be obtained. Such shading is known as the -7 tone. Note that the first
3, the second ink droplet has a lower velocity than the first ink droplet, but the ink droplets coalesce at a common point of impact on the print media.

As already mentioned, the relative velocities of the ink drops, the head 2 of the inkjet and the recording medium cause the two ink drops to impinge on the recording medium at substantially the same point, thereby producing a dot pattern of a predetermined size. unite at that point so as to cause

Therefore, the waveform used to drive an inkjet device is designed to produce ink drops that are produced in succession, as long as the timing of the system allows the drops to impinge on the recording medium at substantially the same point. Provide successively faster or slower speeds or a combination of these. In this way, one or more ink drops can be selected arbitrarily to print a dot pattern of a desired thickness at a certain point on the recording medium.

The control unit 261 is configured, for example, by a logical operation circuit, a microprocessor programmed to obtain the necessary control functions, or a combination of the two. In addition, the Wave Chick model l 7 was manufactured by Wave Chick Company of Sun Diego, California.
A Wavetek Model 75 waveform generator was used by the inventor to obtain the waveforms shown in Figures @6,11°12.13,14,15.

In a practical system, the control section 261 is designed to obtain the necessary waveforms and functions for each particular use, as already mentioned. Having shown and described a particular embodiment of the method of the present invention for operating an inkjet device that increases the range of control over the amount of ink that impinges on a recording medium at a given point, i.e. the diameter of the ink droplets, the claims Other embodiments within the scope described herein will occur to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an inkjet device, FIG. 2 is an enlarged view of a part of the cross section shown in FIG. 1, and FIG. 3 includes the embodiment shown in FIGS. 1 and 2. FIG. 4, an exploded perspective view of the inkjet device, shows the transducer in an unpressurized state;
FIG. 5 is a partial cross-sectional view of the transducer of FIG. 4 in a pressurized state; FIG. 6 is a partial cross-sectional view of the transducer shown in FIGS. 1 and 83; FIG. An example electrical pulse waveform diagram. Fig. 7 is a perspective view showing an ink droplet ejected from an orifice, and Fig. 8 shows an ink droplet that has already been ejected and is still in the air.
FIG. 3 is a perspective view showing ink droplets simultaneously ejected from Oriswiss. Figure 9 is a perspective view showing the coalescence of two ink drops in mid-air; Figure 10 is a perspective view showing all of the typical ink droplets formed after a number of ink drops have coalesced prior to impacting the recording medium. Figure 11 is a graph showing the waveform of an electrical pulse in another embodiment of the present invention, Figure 12 is a graph showing the waveform of an electrical pulse in yet another embodiment of the present invention. Figures 14 and 15 are graphs showing waveforms of other embodiments of the present invention. Note that the same reference numerals in each figure indicate the same or corresponding parts. 5.7 Ink droplets, 200... chambers,
202... Orifice, 204... Converter. Patent applicant Exxon Research and Engineering Company Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Kyosuke Nakayama Patent attorney Akira Yamaguchi Masaya Nishiyama

Claims (1)

[Claims] 1. In order to eject ink droplets from the orisuis,
The ink was ejected from an inkjet device containing transducer means operative to create pressure fluctuations within the ink chamber. A method for controlling the volume of ink droplets, the method comprising: repeatedly activating the transducer means to create a plurality of successive pressure fluctuations in the ink chamber; generating one or a combination of ink droplets of slow or equal velocity to be ejected from the oriSwiss while in the air or in time to allow the plurality of ink droplets to coalesce at the point of impact on the recording medium; A method of controlling the amount of ink droplets that perform a process. 2. said transducer means is responsive to an electrical pulse for producing a pressure fluctuation within said ink chamber, the magnitude of the pressure fluctuation being directly proportional to the slope of the trailing edge of said electrical pulse, said step further comprising: , one of successive greater or lesser or equal trailing edge slopes,! 2. A method as claimed in claim 1, including the step of applying to said transducer means successive electrical pulses having at least one of the following: or some combination thereof. 3. A method as claimed in claim 2, including the step of shaping said electrical pulse to have an exponential leading edge. 4. The control method according to claim 2 or 3, comprising the step of forming the trailing edge of the electrical pulse to be exponential. 5. To obtain the necessary velocity of the ink droplet. and adjusting the amplitude of each of said electrical pulses, wherein the magnitude of the pressure fluctuations produced by said transducer means is directly proportional to the amplitude of each of said electrical pulses. The control method described in Section 4. 6. The control method according to claim 2 or 3, comprising the step of shaping the trailing edge of the electrical pulse into a substantially straight line. 7. 7. A method as claimed in claim 6, including the step of adjusting the amplitude of said electrical pulses, wherein the magnitude of said pressure fluctuation is each directly proportional to the amplitude of said pulse. 8. Immediately following the predetermined one of the electrical pulses, the step includes the step of generating a second pulse immediately after the predetermined one of the electrical pulses to terminate the ink drop associated with the predetermined one of the electrical pulses from the orifice sooner; 6. A control method according to claim 5, in which the ink droplets finish earlier than in the absence of the second pulse. 9. The control method according to claim 8, further comprising the step of controlling the delay time between the successive electrical pulses in order to control the thickness of printing.