JP3663999B2 - Ink-jet printhead drive method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for driving an inkjet recording head that ejects ink droplets of different sizes from the same nozzle.
[0002]
[Prior art]
A technique that enables area gradation recording by ejecting ink droplets of different weights from the same nozzle is disclosed in, for example, two ejections within one recording cycle as described in JP-A-11-20165. Prepare a device drive signal with a pulse, select the first or second drive pulse, or both, and eject a small-diameter ink droplet by selecting a single pulse, or eject a large-diameter ink droplet by selecting both pulses There are some which perform multi-value conversion of three values or more, such as no discharge due to non-selection of a pulse. In this technique, the first and second pulses are designed by taking into account the behavior of the ink interface (meniscus) at the tip of the nozzle with respect to the timing from the end of the discharge signal of the first pulse to the start of the discharge signal of the second pulse. It is possible to increase the amount of ink ejected when both pulses are ejected simultaneously, compared to the sum of when ink is ejected independently, and the variable range of the recording dot diameter is expanded.
[0003]
More specifically, the driving signal for the pressure generating element includes a first driving pulse for discharging a first ink droplet from the plurality of nozzles and a second driving pulse for discharging a second ink droplet. The both pulses are each a pulse P1 for drawing the ink interface (meniscus) at the tip of the nozzle to the inside of the nozzle by expanding the pressure generating chamber, and the pressure in a state where the meniscus is drawn. A pulse P2 for forming and ejecting an ink droplet from the nozzle by abruptly contracting the generation chamber, and a natural vibration of the meniscus oscillated by the P1 and P2 after ink droplet ejection (the Helmholtz of the ink in the pressure generating chamber) At least a pulse P3 for damping the natural vibration by moving the meniscus in the opposite phase to the natural vibration of period Tc due to resonance) And are the first, second pulse is set to an intermediate potential equals its beginning and end.
[0004]
[Problems to be solved by the invention]
As described above, the potential difference between the first and second pulses is the same as the end and start potentials. Therefore, the potential difference sufficient for suppressing the meniscus residual vibration after the first dot discharge and the meniscus when discharging the second dot are eliminated. However, there is a problem that even if an attempt is made to individually set the potential difference that sufficiently performs the preliminary vibration, the potential difference is regulated by the intermediate potential.
The present invention has been made with the object of solving such problems, and provides a driving method capable of increasing the degree of freedom in forming a driving signal.
[0005]
[Means for Solving the Problems]
The present invention relates to a method of driving an ink jet recording head for causing ink droplets to be ejected from the nozzle openings by operating pressure generating elements provided corresponding to the plurality of nozzle openings. In the drive signal including the first drive pulse for ejecting the first ink droplet from the first drive pulse and the second drive pulse for ejecting the second ink droplet, the first pulse and the second pulse The gist is to make the substantial end potential of the first pulse and the substantial start potential of the second pulse independent by providing a gradual potential change process (timing adjustment signal) at the connection portion.
[0006]
The present invention provides a starting potential of an applied pulse that is conventionally constrained by the intermediate potential by providing a gentle charging / discharging pulse that does not intend the meniscus motion, in addition to the meniscus control pulses such as P1, P2, and P3. In this case, the control of the end potential is made possible in part.
[0007]
In the ink jet recording head, when ink droplets are ejected, abrupt pressure is generated in the pressure generating chamber, thereby generating vibration due to Helmholtz resonance of the fluid, which seems to depend on the rigidity and shape of the ink passage and the pressure generating chamber. . If the next discharge is performed in a state where the vibration is not sufficiently attenuated, a discharge defect such as a flight bend is caused. It is necessary to secure the vibration decay time and the time for the meniscus that has retreated to the inside of the nozzle after ejection to recover. Regarding the drive signal, in the drive signal having two pulses within one recording period, a certain amount of time is inevitably provided between the first pulse and the second pulse.
[0008]
The gist of the present invention is to use this time to provide a gentle charge / discharge pulse, but this “slow” is important. There are two problems with signals with steep potential gradients. One is that vibration of Helmholtz resonance occurs as described above. In order to prevent this oscillation, the time component of the timing adjustment signal is preferably set to a Helmholtz resonance period: about Tc or more. The second is that the meniscus moves in synchronism with the volume change of the pressure generating chamber due to the signal. Although the detailed mechanism will be described later, it is possible to suppress the synchronized movement of the meniscus by making the signal potential gradient as gentle as possible.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
1. Schematic configuration of printer
As shown in FIG. 4, the printer includes a mechanism for transporting paper P by a paper feed motor 23, a mechanism for reciprocating a carriage 31 in the axial direction of a platen 26 by a carriage motor 24, and a print head 28 mounted on the carriage 31. A control circuit 40 that controls the exchange of signals with the paper feed motor 23, the carriage motor 24, the print head 28, and the operation panel 32. The piezo element drive circuit 50 generates a drive signal for driving the piezo element in response to the above signal.
[0010]
The mechanism for reciprocating the carriage 31 in the axial direction of the platen 26 is an endless drive belt between the carriage motor 24 and a slide shaft 34 that is laid in parallel with the axis of the platen 26 and slidably holds the carriage 31. A pulley 38 that stretches 36, a position detection sensor 39 that detects the origin position of the carriage 31, and the like.
[0011]
A black ink cartridge 71 and a color ink cartridge 72 can be mounted on the carriage 31. A total of six ink ejection heads 61 to 66 are formed on the print head 28 below the carriage 31, and an introduction pipe 67 (see FIG. 5) that guides ink from the ink tank to each color head at the bottom of the carriage 31. 5) is erected. When the cartridge for black ink and color ink 72 is mounted on the carriage 31 from above, an introduction tube 67 is inserted into a connection hole provided in each cartridge, and ink can be supplied from each ink cartridge to the ejection heads 61 to 66. It becomes.
[0012]
Ink ejection from the inkjet nozzles Nz in the ink ejection heads 61 to 66 is controlled by the control circuit 40 and the piezo element driving circuit 50. The internal configuration of the control circuit 40 is shown in FIG. As shown in the figure, inside the control circuit 40 is an interface (hereinafter referred to as I / F) 43 for receiving print data including multi-value gradation information from a computer, a RAM 44 for storing various data, and various types of data. ROM 45 that stores a routine program for data processing, a control unit 46 including a CPU, an oscillation circuit 47, and a drive signal generation circuit 48 that generates a drive signal to each piezo element of the print head 28 described later. And an I / F 49 for transmitting print data and drive signals developed into dot pattern data to the paper feed motor 23, carriage motor 24, and piezo element drive circuit 50.
[0013]
In the present embodiment, print data that has been ternarized by the printer driver is sent from the computer. The control circuit 40 stores the print data in the reception buffer 44A, and then the nozzle array of the print head. It is sufficient that the data is once expanded in the output buffer 44C according to the arrangement of the data, and this is output by meeting the I / F 49. On the other hand, if the data transmitted from the computer is non-multivalued print data, the printer 22 may perform ternarization processing in the control circuit 40. In this case, the print data is stored in the reception buffer 44A inside the recording apparatus via the I / F 43. After the command analysis is performed on the recording data stored in the reception buffer 44A, it is sent to the intermediate buffer 44B. In the intermediate buffer 44B, the recording data in the intermediate format converted into the intermediate code by the control unit 46 is held, and the process for adding the print position, modification type, size, font address, etc. of each character is controlled. This is executed by the unit 46. Next, the control unit 46 analyzes the recording data in the intermediate buffer 44B, performs ternarization according to the gradation information, and develops and stores the dot pattern data in the output buffer 44C.
[0014]
In any case, the ternary dot pattern is developed and stored in the output buffer 44C. As will be described later, since the print head has 48 nozzles for each color, after preparing dot pattern data corresponding to one scan of the head in the output buffer 44C, this dot pattern data is stored in the I / F 49. Output via. As will be described later, the print data developed as dot pattern data is composed of, for example, 2 bits as gradation data for each nozzle, with “00” having no dots and “10” forming a small dot, “11” corresponds to large dot formation. The data configuration and dot formation will be described later.
[0015]
2. Ink ejection mechanism
A mechanism for ejecting ink and forming dots will be described. FIG. 7 is an explanatory diagram showing a schematic configuration of the ink ejection head 28, and FIG. 8 is a schematic diagram showing how ink is ejected by expansion and contraction of the piezo element PE. When the ink cartridges 71 and 72 are mounted on the carriage 31, the ink in the ink cartridge is sucked out through the introduction pipe 67 using the capillary phenomenon as shown in FIG. The head 28 is led to each color head 61 to 66.
[0016]
As will be described later, the heads 61 to 66 of each color are provided with 48 nozzles Nz for each color, and each nozzle is one of electrostrictive elements as a pressure generating element and is responsive. Excellent piezo element PE is arranged. As shown in FIG. 8A, the piezo element PE is installed at a position in contact with the ink passage 68 that guides ink to the nozzle Nz. As is well known, the piezo element PE is an element that transforms electro-mechanical energy at an extremely high speed because the crystal structure is distorted by application of a voltage. In this embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE contracts for the voltage application time, as shown in FIG. One side wall of the ink passage 68 is deformed. As a result, the volume of the ink passage 68 contracts in accordance with the contraction of the piezo element PE, and the ink corresponding to the contraction becomes particles Ip and is ejected from the tip of the nozzle Nz at high speed. Printing is performed by the ink particles Ip landing on the paper P mounted on the platen 26.
[0017]
Although the principle of ink droplet ejection using a piezo element has been described with reference to schematic diagrams, details of an ink ejection mechanism using an actual piezo element PE are shown in FIG. FIG. 7 is a cross-sectional view showing an example of the mechanical cross-sectional structure of the recording heads 61-66. As shown in the figure, this head is mainly composed of an actuator unit 121 and a flow path unit 122. The actuator unit 121 includes a piezo element PE, a first lid member 130, a second lid member 136, a spacer 135, and the like. The first lid member 130 is composed of a zirconia thin plate having a thickness of about 6 μm, and a piezoelectric element PE is fixed to the surface of the first lid member 130 so as to face a pressure generation chamber 132 described later. A drive electrode 134 made of a flexible metal layer is formed.
[0018]
Here, the piezoelectric element PE forms a flexural vibration type actuator with the first lid member 130. The piezo element PE is deformed in a direction to shrink the volume of the pressure generating chamber 132 to which charge is added, and expands to expand the volume of the pressure generating chamber 132 based on the discharge of the added charge. Deform.
[0019]
The spacer 135 provided at the lower portion of the first lid member 130 is configured by forming a through hole in a ceramic plate such as zirconia having a thickness suitable for forming the pressure generating chamber 132, for example, 100 μm. Both surfaces are sealed by a second lid member 136 and a first lid member 130, which will be described later, to form the pressure generating chamber 132 described above.
[0020]
Like the spacer 135, the second lid member 136 fixed to the other end of the spacer 135 is made of ceramic such as zirconia. The second lid member 136 is provided with two communication holes 138 and 139 that form an ink flow path with the pressure generation chamber 132. The communication hole 138 connects an ink supply port 137 to be described later and the pressure generation chamber 132, and the communication hole 139 connects the nozzle opening Nz and the other end of the pressure generation chamber 132.
[0021]
These members 130, 135, and 136 are grouped as an actuator unit 121 without using an adhesive by forming a clay-like ceramic material into a predetermined shape, laminating them, and firing them.
[0022]
Next, the flow path unit 122 will be described. The flow path unit 122 includes an ink supply port forming substrate 140, an ink chamber forming substrate 143, a nozzle plate 145, and the like. The ink supply port forming substrate 140 also serves as a fixed substrate for the actuator unit 121 and is provided with an ink supply port 137 on one end side of the pressure generating chamber 132 side and a nozzle opening Nz on the other end side of the pressure generating chamber 132. ing. The ink supply port 137 is designed to be sufficiently small compared to the ink chamber 141 and the pressure generation chamber 132 that are common to the nozzles and function as an orifice.
[0023]
The ink chamber forming substrate 143 is a member whose other surface is sealed by the nozzle plate 145 and forms the ink chamber 141 together with the ink supply port forming substrate 140, and the nozzle communication hole 144 connected to the nozzle opening 123 is provided. It has been. The ink chamber 141 is connected to an ink flow path (not shown) connected to the ink cartridges 71 and 72 so that ink flows from an ink tank (not shown).
[0024]
The ink supply port forming substrate 140, the ink chamber forming substrate 143, and the nozzle plate 145 are fixed by adhesive layers 146 and 147 such as a heat-welding film and an adhesive between them. It is composed.
[0025]
The flow path unit 122 and the actuator unit 121 described above are fixed by an adhesive layer 148 such as a heat-welded film or an adhesive, and constitute the recording heads 61 to 66.
[0026]
With the above configuration, when a voltage is applied between the drive electrodes 131 and 134 of the piezo element PE to add a charge, the piezo element PE contracts and the volume of the pressure generating chamber 132 decreases, and conversely, the charge is discharged. The piezo element PE extends and the volume of the pressure generating chamber 132 increases. When the pressure generating chamber 132 expands, the pressure in the pressure generating chamber 132 decreases and ink flows from the common ink chamber 141 into the pressure generating chamber 132. When electric charge is added to the piezo element PE, the volume of the pressure generating chamber 132 is reduced, the pressure in the pressure generating chamber 132 increases in a short time, and the ink in the pressure generating chamber 132 is ejected to the outside through the nozzle opening Nz. Is done. At this time, the ink droplet Ip is ejected to the outside.
[0027]
By the way, the ink existing in the flow path to the nozzle Nz of the print head 28 for ink jet recording configured as described above causes a vibration phenomenon as a fluid in accordance with a change in the pressure in the pressure generating chamber 132. There are at least two types of natural vibrations in this vibration. One is vibration with a relatively long period in which a meniscus which is an ink interface reciprocates after ejecting ink droplets. This is called natural vibration (period Tm). The other is a vibration called Helmholtz resonance generated in the fluid due to the presence of the pressure generation chamber 132, and is a vibration having a relatively short period (period Tc) as compared with the natural vibration.
[0028]
3. Outline of large and small dot formation
The 48 nozzles Nz of each color provided in the printer of this embodiment have the same inner diameter. Two types of dots having different diameters can be formed using the nozzle Nz. This principle will be described.
[0029]
FIG. 9 is an explanatory diagram schematically showing the relationship between the drive waveform of the nozzle Nz and the ejected ink Ip when the ink is ejected. The drive waveform indicated by a broken line in FIG. 9A is a waveform when a normal dot is ejected. When an appropriate voltage is applied to the piezo element PE in the section d1, the piezo element PE is deformed in the direction of increasing the volume of the pressure generating chamber 132. Therefore, as shown in the state A in FIG. Then, the nozzle Nz is recessed. On the other hand, when an appropriate voltage is suddenly applied as shown in the section d2 using the driving waveform shown by the solid line in FIG. 9A, the meniscus Me becomes as shown in FIG. 9B in the state a in FIG. 9B. Compared to the state A of the above, it becomes a state that is greatly indented.
[0030]
The meniscus shape varies depending on the pulse waveform of an appropriate voltage applied to the piezo element PE for the following reason. The piezoelectric element is deformed according to the pulse shape of the applied voltage, and when the volume of the pressure generating chamber 132 increases, if the change is very slow, the volume of the pressure generating chamber 132 increases. The ink is supplied from the common ink chamber 141, and the meniscus hardly changes. On the other hand, when the expansion and contraction of the piezo element PE is performed in a short time and the volume of the pressure generating chamber 132 changes rapidly, the supply of ink from the ink chamber 141 is limited by the ink supply port 137, so that it is in time. Therefore, the meniscus is affected by the change in the volume of the pressure generating chamber 132. When the change in the voltage applied to the piezo element PE is slow, the meniscus retraction is small, and when the change in the applied voltage is abrupt, the meniscus retraction is large depending on the balance of the ink supply. Yes.
[0031]
Next, when an appropriate voltage is applied to the piezo element after the meniscus is retracted (section d3 in FIG. 9A), ink is ejected based on the principle described above with reference to FIG. At this time, from the state where the meniscus is not dented so much (in FIG. 9B, state A), large ink droplets are ejected as shown in FIGS. 9B and 9C, and the meniscus is greatly dented (see FIG. 9). 9 (B) from state a), small ink droplets are ejected as shown in states b and c of FIG. 9 (B).
[0032]
The change rate of the applied voltage also affects the discharge speed. When the voltage change, that is, the volume change of the pressure generating chamber is abrupt, the meniscus motion associated therewith becomes faster and the discharge speed increases. This can also be said in the case where the meniscus is drawn into the nozzle by the discharge signal. In this case, the discharge speed is increased due to the reaction of the drawing.
[0033]
When the voltage change rate in the sections d1 and d2 in FIG. 9A is large, the ink droplets are small and fast. For example, when the voltage change rate in the section d3 in FIG. 9A is large, the ink droplet is large and fast. In the design of the drive signal, an ink droplet having a required size and speed is obtained by a balance between the magnitudes of these two signals (potential gradient).
[0034]
4). Piezo element drive circuit
In this embodiment, based on such a relationship between the driving waveform and the dot diameter, a driving waveform for forming a small dot with a small dot diameter and a driving waveform for forming a large dot with a large dot diameter are used. (See FIG. 10) The manner of formation of large and small ink droplets due to the difference in the drive signal will be described later together with the details of the generation of the drive signal.
[0035]
First, a configuration for generating a drive signal having the waveform shown in FIG. 10 will be described. The drive signal shown in FIG. 10 is generated by the piezo element drive circuit 50. FIG. 11 is a block diagram showing the internal configuration of this piezo element driving circuit. As shown in the figure, in the piezo element driving circuit 50, a memory 51 that receives and stores a signal from the control circuit 40, a latch 52 that reads and temporarily holds the contents of the memory 51, and a latch 52 An adder 53 that adds the output and the output of another latch 54 described later, a D / A converter 56 that converts the output of the latch 54 into analog data, and a voltage amplitude for driving the converted analog signal to drive the piezo element PE And a current amplifying unit 58 for supplying a current corresponding to the amplified voltage signal. Here, the memory 51 is determined by a predetermined parameter that determines the waveform of the drive signal. As shown in FIG. 11, the piezo element driving circuit 50 receives clock signals 1, 2, 3, data signals 0 to 3 and a reset signal from the control circuit 40.
[0036]
FIG. 12 is an explanatory diagram showing how the waveform of the drive signal is determined by the configuration of the piezo element drive circuit 50 described above. Prior to the generation of the drive signal, several data signals indicating the slew rate of the drive signal and the address signal of the data signal from the control circuit 40 are synchronized with the clock signal 1 and the piezo element drive circuit 50. Is output to the memory 51. Although the data signal has only one bit, as shown in FIG. 13, data is exchanged by serial transfer using the clock signal 1 as a synchronization signal. That is, when a predetermined slew rate is transferred from the control circuit 40, first, a multi-bit data signal is output in synchronization with the clock signal 1, and then the address for storing this data is synchronized with the clock signal 2. Output as address signals 0-3. The memory 51 reads the address signal at the timing when the clock signal 2 is output, and writes the received data to the address. Since the address signal is a total of 4 bits from 0 to 3, a maximum of 16 types of slew rates can be stored in the memory 51. Note that the most significant bit of data is used as a code.
[0037]
After the setting of the slew rate for each address A, B,... Is completed, when the address B is output to the address signals 0 to 3, the first clock signal 2 causes the slew rate corresponding to the address B to be first. Is held by the latch 52. In this state, when the clock signal 3 is next output, a value obtained by adding the output of the first latch 52 to the output of the second latch 54 is held in the second latch 54. That is, as shown in FIG. 12, once the slew rate corresponding to the address signal is selected, every time the clock signal 3 is received thereafter, the output of the second latch 54 increases or decreases according to the slew rate. The slew rate stored in the address B has a value corresponding to the voltage increase by the voltage ΔV1 per unit time ΔT. Whether to increase or decrease is determined by the sign of the data stored at each address.
[0038]
In the example shown in FIG. 12, the address A stores a value 0 as the slew rate, that is, a value when the voltage is maintained. Therefore, when the address A is validated by the clock signal 2, the waveform of the drive signal is maintained in a state where there is no increase / decrease, that is, a flat state. Further, the address C stores a slew rate corresponding to the voltage per unit time ΔT being decreased by ΔV2. Therefore, after the address C becomes valid by the clock signal 2, the voltage gradually decreases by this voltage ΔV2.
[0039]
By simply outputting the address signal and the clock signal 2 from the control circuit 40 by the method as described above, the waveform of the drive signal can be freely controlled.
[0040]
5. Outline Description
Regarding the drive signal in the embodiment, each constituting pulse and its role will be described with reference to FIG. The drive signal is roughly composed of a first pulse and a second pulse in a recording cycle corresponding to one recording pixel. Here, in order to simplify the description, it is assumed that the timing adjustment signal is a potential holding signal.
[0041]
The first pulse starts from the intermediate potential Vm (T11), and the signal T12 is applied. At this time, the piezo element PE bends in the direction of reducing the volume of the pressure generating chamber 132, and a positive pressure is generated in the pressure generating chamber. As a result, the meniscus rises from the nozzle opening 123. The potential gradient during this period is set to be gentle (more than Tc) so as not to eject ink and not to excite Helmholtz resonance (period Tc). While the hold pulse T13 is applied, the meniscus that rises with the charging pulse T12 starts to move back into the nozzle opening 123 due to vibration of the period Tm due to the surface tension of the ink. When the discharge pulse T14 is applied, the piezo element PE bends in the direction in which the pressure generating chamber 132 is expanded, and a negative pressure is generated in the pressure generating chamber. The movement of the meniscus into the nozzle opening 123 due to the negative pressure is superimposed on the vibration of the above period Tm, and the meniscus is largely drawn into the nozzle opening 123.
[0042]
In this way, by applying the discharge pulse T14 at the timing when the meniscus moves toward the inside of the nozzle opening 123, the meniscus can be largely drawn into the nozzle opening 123 even with a relatively small potential difference of the discharge pulse T14. When the charging pulse T16 is applied from the state in which the meniscus is drawn, a positive pressure is generated in the pressure generating chamber 132, the meniscus rises from the nozzle opening 132, and is ejected as an ink droplet. As described above, since the meniscus is ejected from a state in which it is drawn largely from the nozzle opening, the ink droplet becomes small.
[0043]
The discharge pulse T18 is a discharge pulse for suppressing an increase in vibration amplitude due to Helmholtz resonance of the meniscus excited by the discharge pulse T14 and the charge pulse T16, and at the timing when the natural vibration of the period Tc goes to the outlet of the nozzle opening 123, A discharge pulse is applied to direct the meniscus toward the inside of the nozzle, which is the reverse direction. This timing is set according to the time of T17. As a result, the natural vibration of the period Tc is attenuated quickly. T18 ends at the intermediate potential Vm, and the first pulse ends at the intermediate potential.
[0044]
Next, the second pulse will be described. The second pulse also starts from the intermediate potential Vm (T19). Next, a negative pressure is generated in the pressure generating chamber 132 by the discharge pulse T 21, and the meniscus is drawn into the nozzle opening 123. This discharge pulse T21 is set to have a smaller potential difference than the discharge pulse T14 of the first pulse, and the amount of meniscus pull-in is also smaller than that of the first pulse. When the charging pulse T23 is applied in this state, a positive pressure is generated in the pressure generating chamber 132, the meniscus rises from the nozzle opening 123, and is ejected as ink droplets. Since the meniscus pull-in amount before ejection is smaller than that in the first pulse, the size of the ejected ink droplet is smaller than that in the first pulse. The last discharge pulse of T25 is a discharge pulse for suppressing oscillation due to Helmholtz resonance of the meniscus excited by T21 and T23, and plays the same role as T18 in the first pulse. T25 ends at the intermediate potential Vm, and the second pulse ends at the intermediate potential.
[0045]
The above is a case where only one of the first and second pulses is selected alone in one recording cycle. Next, a case where both pulses are selected and ejection is continuously performed in one recording cycle will be described with reference to FIG. After the ejection by the first pulse, the meniscus largely recedes from the nozzle opening 123 (700), and then starts to return toward the nozzle opening 123 due to the surface tension of the meniscus. Eventually, the meniscus reaching the aperture surface (701) starts to vibrate with the natural oscillation period Tm and rises to the outside of the aperture surface (while the hold pulse T19 without potential change is applied). The discharge pulse T21 of the second pulse is applied around time 702 and acts to draw the meniscus into the nozzle by the negative pressure of the pressure generating chamber 132, but is canceled by the rising movement of the meniscus due to natural vibration. Further, since the original meniscus displacement also protrudes outward from the nozzle, the meniscus pull-in remains small as a result. Here, ink droplets are ejected by the charging pulse T23, but the formed ink droplets are larger than when ejected by the second pulse alone. As described above, the ink droplet is enlarged by the timing of the natural vibration induced by the ejection by the first pulse and the ejection by the second pulse. Specifically, the time from the end of the first pulse to the second pulse first signal T21 is about 3/8 of the meniscus return time TR + natural vibration period Tm.
[0046]
6). Example 1 of the present invention
FIG. 1 shows an embodiment of a driving method according to the present invention in the form of a driving signal, which is characterized by the residual vibration at the end of the first pulse, more specifically after ink droplet ejection. The signal S17 that suppresses the continuation of the end potential is lower than the intermediate potential Vm by ΔV and continues for more than twice the period Tc of the Helmholtz resonance oscillation, and then causes movement in the meniscus until the application start potential of the second pulse. The signal SC2 that rises to the intermediate potential Vm with a potential gradient not to be generated is applied.
[0047]
In the first pulse, a large meniscus is drawn by the signals S11 to S13, and a small-diameter ink droplet is ejected by applying an ejection signal S15 from the lowest potential VL to V2, and then an intermediate potential from the potential V2 via the potential holding signal S16. By applying the signal S17 from Vm to a potential V3 that is lower by ΔV, residual vibration after ejection is suppressed, and the first ink droplet formation is completed.
[0048]
After the ejection by the first pulse is completed, while waiting for attenuation of the residual vibration of the meniscus and recovery of the meniscus to the nozzle opening, recovery from the potential V3 to the intermediate potential Vm is performed by the timing adjustment signal SC2. Since the potential gradient of the signal SC2 is set sufficiently gradual, ink inflow due to a change in the volume of the pressure generation chamber is performed from the common ink chamber 141, and Helmholtz resonance is not excited. As a result, potential recovery can be performed without causing meniscus motion, but conversely, a design in which meniscus motion is intentionally caused by this signal may be performed. In this embodiment, the application time of SC2 is set to be twice or more of Tc.
[0049]
The second pulse starts from the intermediate potential Vm, the pull-in signal S21 is applied to the potential V5, a large-diameter ink droplet is ejected by the ejection signal S23 through S22, and the second ink droplet is ejected by the residual vibration suppression signal S25 through S24. Formation is complete.
[0050]
According to this embodiment, V2 can be set low because the offset of ΔV from the intermediate potential Vm is performed as the end potential of S17, and as a result, the ejected ink droplets can be reduced by applying a small ejection signal S15 of the first pulse. can do. In addition, this offset allows the intermediate potential Vm, which is the starting potential of the second pulse pull-in signal, to be set high, and as a result, by applying a large second pulse pull-in signal S21, the discharge speed is increased and the discharge stability is increased. The landing accuracy can be improved.
[0051]
7. Embodiment 2 of the present invention
FIG. 2 shows an embodiment of the drive method of the present invention in the form of a drive signal waveform. In this embodiment, after the first pulse ends at the intermediate potential Vm, the residual vibration of the meniscus is attenuated. While waiting for recovery of the meniscus to the nozzle opening, the timing adjustment signal SC2 causes the intermediate potential Vm to drop to a potential V4 that is lower than Vm by ΔV ′. As in the first embodiment, since the potential gradient of the signal SC2 is set to be sufficiently gradual, ink inflow due to a change in the volume of the pressure generating chamber is almost from the common ink chamber 141, and excitation of Helmholtz resonance also occurs. Absent. As a result, potential recovery can be performed without causing meniscus motion. In this embodiment, the application time of SC2 is set to be twice or more of Tc.
[0052]
The pull-in signal S21 ′ of the second pulse is applied from the potential V4 to V5, and through S22 ′, the ejection signal S23 ′ is applied from the potential V5 to the maximum potential V6 ′, thereby ejecting a large diameter ink droplet. The formation of the second ink droplet is completed by applying the residual vibration suppression signal S25 'through the potential V6 to the intermediate potential Vm.
[0053]
In the second embodiment, compared with the first embodiment, the ink droplet diameter formed by the second pulse is intended to be larger. Since the starting potential of the pull-in signal S21 ′ is offset by ΔV lower than the intermediate potential, the signal S23 ′ is greatly applied without unnecessarily increasing the final potential of the discharge signal S23 ′ and the highest potential V6 ′. Ink droplets can be enlarged. On the other hand, when the conventional driving method as shown by the broken line, that is, when the start potential of the second pulse is the intermediate potential Vm, the maximum potential V7 ′ of the signal for ink droplet ejection becomes high, and the driving circuit The electronic parts constituting the circuit require high pressure resistance, which increases the cost. Furthermore, the potential difference between the potential V7 ′ and the intermediate potential becomes large, and the signal S25 ′ for suppressing the meniscus residual vibration after ink droplet ejection may be excessively suppressed, that is, cause reverse oscillation, leading to unstable ejection.
[0054]
8). Embodiment 3 of the present invention
FIG. 3 shows an embodiment of the drive method of the present invention in the form of a drive signal waveform. The drive signal of the first embodiment is the first precharge pulse S11 and the subsequent potential holding pulse. The difference is that there is no pulse corresponding to S12. S13 '' changes from a high intermediate potential to V1 '' and pulls in the meniscus.S14 '' is followed by S15 '' and small diameter ink droplets are ejected.S16 '' is followed by S17 ''. The residual vibration is suppressed to V3 ″ exceeding the intermediate potential by ΔV, and the first pulse is completed by recovering to the intermediate potential by SC2 ″. In the second pulse that follows, by setting the pull-in signal S21 ″ before ejection to be smaller than S13 ″ and the ejection signal S23 ″ to be larger than S15 ″, an ink droplet having a diameter larger than that of the first ink droplet is set. Forming. In this embodiment, by setting the intermediate potential high, the preliminary pulse before S13 ″ is omitted, and the drive frequency is increased.
[0055]
As mentioned above, although the Example of this invention was described, this invention is not limited to these Examples at all, In the range which does not change the summary of this invention, it can implement in a various aspect. For example, in the above-described embodiment, the piezoelectric element employs a flexural vibrator type PZT, but may be a longitudinal vibration effect type PZT or a stacked type PZT. However, in this case, charging and discharging are interchanged with respect to the flexible vibrator type PZT. Further, the pressure generating element is not limited to a piezo element, and other displacement elements such as a magnetostrictive element may be used.
[Brief description of the drawings]
FIG. 1 is a waveform diagram of a drive signal showing a first embodiment of the drive method of the present invention.
FIG. 2 is a waveform diagram of drive signals showing a second embodiment of the drive method of the present invention.
FIG. 3 is a waveform diagram of a drive signal showing a third embodiment of the drive method of the present invention.
FIG. 4 is an explanatory diagram showing an internal configuration of a printer with a driving system as a center.
FIG. 5 is a configuration diagram showing a schematic configuration around an introduction pipe of a print head.
FIG. 6 is a block diagram showing an embodiment of the control device of the printer.
FIG. 7 is a cross-sectional view showing an embodiment of a recording head.
FIGS. 8A and 8B are explanatory views showing the principle of ejecting ink droplets by expansion and contraction of a piezo element, respectively.
FIGS. 9A and 9B are schematic diagrams showing the relationship between the drive signal applied to the piezo element and the movement of the meniscus, respectively.
FIG. 10 is an explanatory diagram illustrating each waveform of a drive signal.
FIG. 11 is a block diagram illustrating an embodiment of a piezo element driving circuit.
FIG. 12 is an explanatory diagram showing a process of generating a drive pulse.
FIG. 13 is a timing chart of each signal when a slew rate is set in a memory using a data signal.
FIG. 14 is a diagram showing an example of meniscus displacement when ink is ejected by a single drive pulse.
[Explanation of symbols]
22 ... Printer
23 ... Paper feed motor
24 ... Carriage motor
26 ... Platen
28… Ink ejection head
31 ... carriage
32 ... Control panel
34 ... Sliding shaft
36 ... Drive belt
38 ... pulley
39… Position detection sensor
40 ... Control circuit
43 ... I / F
44 ... RAM
44A ... Receive buffer
44B ... Intermediate buffer
44C ... Output buffer
45 ... ROM
46 ... Control unit
47. Oscillator circuit
48 ... Drive signal generation circuit
49 ... I / F
50 ... Piezo element drive circuit
51 ... Memory
52 ... First latch
53 ... Adder
54… Second latch
55… Level shifter
56 ... D / A converter
57… Voltage amplifier
58… Current amplifier
61-66 ... Ink ejection head
67… Introduction pipe
68 ... Ink passage
71,72… Ink cartridge
121 ... Actuator unit
122… Channel unit
123… Nozzle opening
130: First lid member
132… Pressure generation chamber
134 ... Drive electrode
135 ... Spacer
136 ... second lid member
137… Ink supply port
138,139… Communication hole
140 ... Ink supply port forming substrate
141… Ink chamber
143 ... Ink chamber forming substrate
144 ... Nozzle communication hole
145 ... Nozzle plate
146,147,148… Adhesive layer

Claims (5)

A first signal for drawing the meniscus from the nozzle opening toward the pressure generation chamber, a second signal for holding the final potential of the first signal, and a third for ejecting ink droplets by abrupt pressurization of the pressure generation chamber A signal, a fourth signal that holds the final potential of the third signal, and a fifth signal that suppresses meniscus residual vibration after ink droplet ejection in a direction opposite to the third signal from the potential of the fourth signal. A first pulse and a second pulse provided;
An intermediate potential that is applied to a potential between the fifth signal final potential of the first pulse and the second pulse first signal start potential, and equal to the first pulse start potential and the second pulse end potential, and a potential exceeding the intermediate potential. And a timing adjustment signal having a potential gradient that varies between and does not cause substantial movement of the meniscus,
An ink jet recording head that selects one of a non-printing state in which no pulse is selected, dot formation by the first pulse, dot formation by the second pulse, and dot formation by combining two types of ink droplets by both pulses in one recording cycle. Driving method. A first signal for drawing the meniscus from the nozzle opening toward the pressure generation chamber, a second signal for holding the final potential of the first signal, and a third for ejecting ink droplets by abrupt pressurization of the pressure generation chamber A signal, a fourth signal that holds the final potential of the third signal, and a fifth signal that suppresses meniscus residual vibration after ink droplet ejection in a direction opposite to the third signal from the potential of the fourth signal. A first pulse and a second pulse provided;
An intermediate potential that is applied to a potential between the fifth signal final potential of the first pulse and the second pulse first signal start potential and that is equal to the first pulse start potential and the second pulse end potential and lower than the intermediate potential And a timing adjustment signal having a potential gradient that does not cause substantial movement in the meniscus,
An ink jet recording head that selects one of a non-printing state in which no pulse is selected, dot formation by the first pulse, dot formation by the second pulse, and dot formation by combining two types of ink droplets by both pulses in one recording cycle. Driving method.   The ink jet recording head driving method according to claim 2, wherein the timing adjustment signal changes from a potential lower than the intermediate potential to an intermediate potential.   The ink jet recording head driving method according to claim 2, wherein the timing adjustment signal changes from the intermediate potential to a potential lower than the intermediate potential.   5. The method of driving an ink jet recording head according to claim 3, wherein the timing adjustment signal has a natural vibration period Tc or more due to Helmholtz resonance in the pressure generating chamber.

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