JP2000218834A - Apparatus and method for driving ink jet printing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power loss of a transitor for driving a head. SOLUTION: A power supply circuit 1 outputs two kinds of different survice voltages Vs1, Vs2 and a drive waveform generating circuit outputs a signal containing drive waveforms different in shape and a driver circuit 102 supplies voltage to a piezoelectric vibrator 104 corresponding to this signal. A control part 3 selects a service voltage source proper corresponding to the shape of a drive waveform. By this constitution, the difference voltage (a difference between service voltage and the terminal voltage of the piezoelectric vibrator) applied across the collector and emitter of a charging transistor 102A at time of charge is reduced to reduce power loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus and a driving method for an ink jet print head which discharges ink droplets by driving a pressure generating element.

[0002]

2. Description of the Related Art In an ink jet printer, for example,
A predetermined voltage change is applied to a pressure generating element such as a piezoelectric vibrator to expand and contract, and an ink droplet is ejected by the pressure change accompanying the expansion and contraction. For example, a piezoelectric vibrator using PZT of the longitudinal vibration lateral effect type contracts when charged, and expands when discharged. When a flexural vibration type PZT is used, it expands when charged and expands and contracts when discharged. If one end of the piezoelectric vibrator is attached to the wall of the pressure generating chamber connected to the nozzle hole, a pressure change can be caused by expansion and contraction of the piezoelectric vibrator, and ink droplets can be ejected.

A driving device for a conventional ink jet print head will be described with reference to FIGS. 13 and 14. FIG.

FIG. 13A is a block diagram showing a main part of a driving device. The print head driving device includes a power supply circuit 100, a drive waveform generation circuit 101, a driver circuit 10
2, a switch circuit 103 and a piezoelectric vibrator 104 are included.

The power supply circuit 100 outputs a DC voltage Vs of, for example, about 42V. The drive waveform generation circuit 101
A driving waveform signal as shown in FIG. The drive waveform signal includes, for example, a relatively small trapezoidal drive waveform DS1 shown on the left side in the figure and a relatively large substantially trapezoidal drive waveform DS2 shown on the right side in the figure. More precisely, FIGS. 13B and 14 show the piezoelectric vibrator 104.
3 shows a change in the terminal voltage.

The first driving waveform DS1 is, for example, 10 V
Starting from the intermediate potential Vm of about
The voltage rises to H1, and after maintaining the maximum potential VH1 for a predetermined time, falls again to the intermediate potential Vm. The second drive waveform DS2 starts from the intermediate potential Vm and rises to the second maximum potential VH2 (VH2> VH1). After maintaining the maximum potential VH2 for a predetermined time, the minimum potential VL lower than the intermediate potential Vm Descend to Then, the second drive waveform DS2 returns to the intermediate potential Vm after holding the minimum potential VL for a predetermined time.

Since the maximum potential VH1 of the first drive waveform DS1 is relatively small, fine ink droplets can be ejected by charging / discharging the piezoelectric vibrator 104 in accordance with the first drive waveform DS1. On the other hand, since the second maximum potential VH2 is relatively large and a relatively steep discharge is performed, the use of the second drive waveform DS2 causes ejection of a larger ink droplet than the case of the first drive waveform DS1. Can be done.

The driver circuit 102 charges and discharges the piezoelectric vibrator 104 by operating the charging transistor 102A and the discharging transistor 102B according to the driving waveform signal from the driving waveform generating circuit 101. . The switch circuit 103 provided between the output side of the power supply circuit 100 and the driver circuit 102 operates on the basis of the grayscale data, so that the first drive waveform DS1,
One of the second drive waveforms DS2 is selected. For example, if a signal is input to the switch circuit 103 in synchronization with a period during which the first drive waveform DS1 is generated,
Charge and discharge according to the first drive waveform DS1 can be performed. Similarly, when a signal is input to the switch circuit 103 in accordance with the period during which the second drive waveform DS2 is generated, charging / discharging according to the second drive waveform DS2 can be performed. If the switch circuit 103 is kept closed, charging and discharging according to both the first drive waveform DS1 and the second drive waveform DS2 can be performed. Therefore,
For example, by adopting 2-bit data, there is no charge / discharge ([00]: gradation 1), only DS1 ([10]: gradation 2), only DS2 ([01] gradation 3), DS1 and D
The dot gradation can be performed in four stages of both S2 ([11]: gradation 4).

As described above, the piezoelectric vibrator 104 expands and contracts according to a change in the voltage supplied via the driver circuit 102. Pressure fluctuation occurs due to expansion and contraction of the piezoelectric vibrator 104, and ink droplets are ejected.

[0010]

According to the prior art, by appropriately selecting one or both of the drive waveforms DS1 and DS2, gradation control in units of one dot can be realized, and the print quality can be improved. Can be enhanced. However, in the related art, since a relatively high single voltage source of about 42 V is used, power loss in the driver circuit 102 is likely to increase. Therefore, the power consumption is increased and the amount of heat generated by the driver circuit 102 is increased, which may shorten the circuit life and the like.

As shown in FIG. 13C, each charging period C
A charging current flows through the charging transistor 102A through 1 to C3. Similarly, a discharge current flows through the discharge transistor 102B during each of the discharge periods D1 and D2. During charging, the supply voltage Vs and the voltage (VH) of the piezoelectric vibrator 104 are applied between the collector and the emitter of the charging transistor 102A.
1, VH2). At the time of discharging, a difference voltage between the voltage (VH1, VH2) of the piezoelectric vibrator 104 and the ground potential (0 V) is applied between the collector and the emitter of the discharging transistor 102B. Therefore, FIG.
As shown by hatched portions WD1 and WD2 in FIG. 4A, in each of the discharge periods D1 and D2, a power loss occurs due to the product of the differential voltage and the discharge current in the discharge transistor 102B. Similarly, as shown by hatched portions WC1 to WC3 in FIG. 14B, in each charging period C1 to C3, the charging transistor 1
Power loss occurs at 02A due to the product of the differential voltage and the charging current.

In recent years, the number of nozzles has been increased in order to increase the number of printable lines in one main scan and improve the printing speed. However, as the number of simultaneously driven nozzles increases, the head drive increases. The power loss of the entire circuit increases.
In particular, as shown in FIG. 13B, when a complicated driving waveform is applied to the piezoelectric vibrator 104 in order to perform dot gradation, charging may be performed only to a voltage value lower than the supply voltage. . Specifically, in the charging periods C1 and C3, only the maximum voltage VH1 that is significantly lower than the supply voltage Vs is charged, so that useless power loss occurs.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described various problems, and an object of the present invention is to provide a driving apparatus and a driving method for an ink jet print head capable of reducing power loss. .

[0014]

In order to achieve the above object, in the ink jet print head driving device according to the present invention, the voltage supply is controlled in accordance with the shape of the driving waveform signal.

That is, in the invention according to the first aspect, an ink-jet printhead driving device for ejecting ink droplets from each of the plurality of nozzles by operating pressure generating elements provided corresponding to each of the plurality of nozzles. A driving waveform signal generating means for generating a plurality of driving waveform signals having different shapes; and a waveform selecting means for selecting any one or a plurality of driving waveform signals among the driving waveform signals based on gradation data. Driving means for applying the supplied voltage to the pressure generating element in accordance with the drive waveform signal selected by the waveform selection means, and voltage supply to the drive means in accordance with the shape of the selected drive waveform signal And control means for variably controlling the control.

For example, when a voltage corresponding to a trapezoidal (including substantially trapezoidal) driving waveform signal is input to a pressure generating element such as a piezoelectric vibrator, the pressure generating element generates a pressure according to the shape of the driving waveform signal. In order to cause a change, this pressure change causes an ink droplet to be ejected from the nozzle. Therefore, by selecting the drive waveform signal, the size of the ink droplet, that is, the dot diameter can be adjusted. Here, the shape of the drive waveform signal indicates the shape and position of the entire signal. The position is
It means an initial voltage value or a reference voltage value. It should be noted that “the shape of the drive waveform signal” can be expressed as “specification of the drive waveform signal”. Depending on the shape of the drive waveform signal,
The difference between the terminal voltage of the pressure generating element and the supply voltage may increase. When the difference between the supply voltage and the terminal voltage of the pressure generating element increases, a power loss occurs during charging due to the product of the difference voltage applied to the driving means and the current flowing through the driving means. On the other hand, when the difference between the terminal voltage of the pressure generating element and the discharge potential (for example, the ground potential) to which the driving means is connected is large, power loss occurs during discharging. Therefore,
The control means controls power supply to the drive means in accordance with the shape of the drive waveform signal, thereby reducing power loss.

According to a second aspect of the present invention, the control means switches between a plurality of voltage sources in accordance with the shape of the selected drive waveform signal, so that the supply voltage to the drive means and the pressure generation The voltage supply to the driving means can be variably controlled so that the difference from the terminal voltage of the element is reduced.

For example, two types of voltage sources, one for a driving waveform signal having a large maximum voltage and one for a driving waveform signal having a small maximum voltage, are prepared in advance, and the voltage sources can be switched according to the selected driving waveform signal. If this is the case, it is possible to reduce the difference voltage applied to the driving means and reduce the power loss.

According to a third aspect of the present invention, the control means switches a plurality of voltage sources in accordance with the shape of the selected drive waveform signal, so that the discharge destination voltage of the drive means and the pressure generation The voltage supply to the driving means can be variably controlled so that the difference from the terminal voltage of the element is reduced.

A plurality of discharge voltage sources are prepared in accordance with the shape of the drive waveform signal, and the discharge voltage source is switched in accordance with the drive waveform signal to reduce the differential voltage applied to the drive means and reduce the power loss. Can be reduced.

According to a fourth aspect of the present invention, the control means switches between a plurality of supply voltage sources and a plurality of discharge destination voltage sources in accordance with the shape of the selected drive waveform signal, thereby controlling the drive. The voltage supply to the driving means is controlled such that the difference between the supply voltage to the means and the terminal voltage of the pressure generating element and the difference between the discharge destination voltage of the driving means and the terminal voltage of the pressure generating element are reduced. It can also be controlled.

Here, at least the following two types of voltage source switching methods can be adopted. In the first method, the voltage source is switched during a period in which the signal voltage of the drive waveform signal is constant, as in the invention according to claim 5. In the second method, the voltage source is switched during a period in which the signal voltage of the drive waveform signal is changing, as in the invention according to claim 6.

The switching timing of the voltage source may be detected by monitoring the clock signal as in the invention according to claim 7, or the signal voltage of the drive waveform signal may be detected as in the invention according to claim 8. May be detected by monitoring.

The plurality of voltage sources can be realized, for example, by using a power supply device having a plurality of voltage outputs. Alternatively, it can also be realized by adjusting the output voltage of a power supply device having a single voltage output as in the invention according to claim 10.

According to a thirteenth aspect of the present invention, in the driving apparatus for an ink jet type print head for ejecting ink droplets from each of the plurality of nozzles by operating a piezoelectric vibrator provided corresponding to each of the plurality of nozzles,
Drive waveform signal generating means for generating a plurality of trapezoidal drive waveform signals having different shapes, and waveform selecting means for selecting any one or a plurality of drive waveform signals among the respective drive waveform signals based on gradation data Driving means for applying the supplied voltage to the pressure generating element according to the driving waveform signal selected by the waveform selecting means, and supplying the driving voltage to the driving means according to the shape of the selected driving waveform signal Control means for controlling the difference between the supply voltage to the drive means and the terminal voltage of the pressure generating element by adjusting the voltage value, and the control means,
The initial voltage value at the start of charging the piezoelectric vibrator is V
1. When the supply voltage value is V2, when the terminal voltage value of the piezoelectric vibrator becomes (V2−V1) / 2, the supply voltage source is switched to the supply voltage source that outputs the voltage value V2. .

As a result, power loss during charging can be minimized in the drive waveform signal related to the supply voltage source having the voltage value V2.

The present invention can also be realized as a method of driving an ink jet print head.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, the same components as those described in the related art are denoted by the same reference numerals, and description thereof will be omitted.

1. First Embodiment A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a main part of the print head driving device.

The power supply circuit 1 according to the present embodiment includes two supply voltage sources Vs1 and Vs2. As shown in FIG. 2A, one supply voltage source Vs1 has a drive waveform DS1.
And the other supply voltage source Vs2 corresponds to the maximum potential VH2 of the drive waveform DS2. That is, each of the supply voltage sources Vs1 and Vs2 considers a voltage drop in the power supply path, a loss in the driver circuit 102, and the like.
It is set to be slightly higher than each of the maximum potentials VH1 and VH2. The output side of the power supply circuit 1 has a voltage switching circuit 2
The voltage switching circuit 2 switches to one of the supply voltage sources Vs1 and Vs2 according to a switching signal from the control unit 3. In the following description, the signs of Vs1 and Vs2 may be used even when indicating the value of the supply voltage.

The control section 3 as a "control means" outputs a switching signal to the voltage switching circuit 2 according to the drive waveform, thereby supplying a voltage corresponding to the drive waveform to the driver circuit 102.

Here, as a method for detecting the switching timing of the supply voltage source, at least one or both of the following two types can be adopted. The first method is to monitor a clock signal and switch the supply voltage source when a predetermined number of clocks have been counted, assuming that the switching time has come. The second method is to monitor a drive waveform signal or a voltage change of the pressure generating element 104, and switch the supply voltage source when the voltage reaches a predetermined voltage value.

The switching of the supply voltage source can be performed in association with the gradation data, or can be performed independently of the gradation data. In the former method, for example, when only the driving waveform DS1 is selected, the supply voltage source may be switched to Vs1, and the driving waveform DS1 may be selected.
It is not necessary to switch the supply voltage source in accordance with the occurrence period of 2. In the latter method, the supply voltage source is switched in accordance with the generation of the drive waveforms DS1 and DS2, regardless of the gradation data. When the switching of the supply voltage source is associated with the gradation data, the number of times of switching can be reduced, but the circuit structure becomes complicated. When the supply voltage source is switched irrespective of the gradation data, the number of times of switching is increased, but the circuit structure can be simplified. In the present invention, any of them may be adopted.

The control unit 3 according to the present embodiment is configured as shown in FIG.
As shown in (a), the driving waveform DS1 and the driving waveform DS2
The supply voltage source is switched during a period in which the signal voltage is not changing between. That is, in the initial state, the supply voltage source is set to Vs1, and the drive waveform DS
At a predetermined time point t1 after dropping from the maximum potential VH1 of 1 to the intermediate potential Vm, the supply voltage source is switched from Vs1 to Vs2. The supply voltage source is switched from Vs2 to Vs1 at a predetermined time t2 after the drive waveform DS2 has dropped from the maximum potential VH2 to the minimum potential VL.

Therefore, the first charging period C1 is performed under the supply voltage Vs1 close to the maximum potential VH1 as the target voltage, and the next charging period C2 is performed at the maximum potential VH as the target voltage.
2 is performed under a supply voltage Vs2 close to 2. Further, the next charging period C3 is performed under the supply voltage Vs1 relatively close to the intermediate voltage Vm which is the target voltage. As a result, in the charging periods C1 and C3, the difference voltage applied between the collector and the emitter of the charging transistor 102A decreases by (Vs2−Vs1), so that the hatched portion WC in FIG.
1a, the power loss during charging shown by WC3a is reduced.
Regarding the drive waveform DS2, the conventional supply voltages Vs and Vs
2 are substantially equal, there is no change in power loss during the charging period C2. Note that, as described above, the charging transistor 102
Since a difference voltage between the supply voltage and the terminal voltage of the piezoelectric vibrator 104 is applied between the collector and the emitter of A, the voltage change between the collector and the emitter is shown in FIG. It will be inverted.

According to the present embodiment configured as described above, a plurality of supply voltage sources Vs1, Vs2 prepared in advance are prepared.
Is appropriately switched according to the shape of the drive waveform signal by the control unit 3, so that the differential voltage applied to the charging transistor 102A can be reduced. Accordingly, power loss during charging can be reduced, and the amount of heat generated by the driver circuit 102 can be suppressed to improve circuit life, stability, and the like. In particular, in a print head that has a large number of nozzles such as 64 or 128 and is capable of dot gradation, the number of simultaneously driven nozzles is large, so that the effect of reducing power loss during charging is great.

2. Second Embodiment Next, FIG. 3 is a waveform diagram showing a method of switching a supply voltage according to a second embodiment. The feature of this embodiment lies in that the supply voltage source is switched during the change of the drive waveform signal (during the change of the terminal voltage of the piezoelectric vibrator). In the following embodiments, the same components as those described above are denoted by the same reference numerals, and description thereof will be omitted.

That is, in the present embodiment, as shown in FIG. 3A, (1) the supply voltage source Vs1 is set as an initial state, and (2) a predetermined voltage during the charging period C2 of the driving waveform DS2. At time t1a, the supply voltage source is switched from Vs1 to Vs2. (3) Then, as in the above embodiment, the supply voltage source is switched from Vs2 to Vs1 at a predetermined time t2 during the period of maintaining the minimum voltage VL.

Accordingly, as shown in FIG. 3B, the power losses WC1a and WC3a in the charging periods C1 and C3.
Is the same as in the first embodiment. However, in the charging period C2, since the supply voltage source is switched in the middle, the voltage loss WC2b (t) when the supply voltage source is Vs1
1b-t1a) and power loss WC2c (between t1a-t1c) when the supply voltage source is Vs2. The sum of these power losses WC2b and WC2c is smaller than the power loss WC2a in the first embodiment. Since the use period of the lower supply voltage source Vs1 is long (t1a> t
1) This is because the differential voltage applied to the charging transistor 102A can be reduced accordingly.

In this embodiment configured as described above,
The same effects as in the first embodiment can be obtained. In addition, in the present embodiment, since the supply voltage source is switched during the change of the drive waveform signal, the use period of the supply voltage source can be extended, and the power loss can be further reduced.

Here, the condition for minimizing the power loss during the charging period C2 will be considered together with FIG. As shown in FIG. 4A, the power loss during the charging period C2 of the driving waveform DS2 is equivalent to the area indicated by the hatched portions WC2b and WC2c, and the condition for minimizing the area of these hatched portions is the charging period C2.
2 is a condition for minimizing the power loss. Therefore, a condition for maximizing the area of the blank rectangular portion BS may be obtained.

FIG. 4B is a geometrical representation of a power loss portion during the charging period C2. FIG.
The oblique line shown by the thick line in (b) can be expressed as V = -at + b. Assuming that the voltage related to the square portion BS is Vx and the time is tx, Vx can be obtained as Vx = −a · tx + b (Equation 1), and the area S (BS) of the square portion BS
Can be obtained as S (BS) = tx · Vx (Equation 2). By rearranging Equation 1 for tx and substituting it into Equation 2, S (BS) = − (Vx−b) / a · Vx (Equation 3) is obtained. By rearranging the third equation, S (BS) = − (1−a) · {(Vx−b / 2)} 2 + b {2/4} (Equation 4) is obtained. The condition where Equation 4 takes the maximum value is when Vx = b / 2 (Equation 5). Here, since the gradient a indicates the gradient of the charging characteristic, if the charging current value is Ichg and the piezo capacitance of the piezoelectric vibrator 104 is C, a = Ichg / C. On the other hand, since the initial voltage value at the start of charging is Vm and the supply voltage value is Vs2, b = Vs2−Vm. Therefore, to minimize power loss, Vx = (Vs2-Vm)
It suffices to control the voltage supply so as to satisfy / 2 (Equation 6). That is, the value of the supply voltage source Vs1 may be set so as to satisfy Expression 6, or the time tx may be set.

3. Third Embodiment FIG. 5 is a block diagram showing a third embodiment. The feature of the present embodiment lies in that the output voltage of the power supply circuit 11 is variably controlled. That is, although the power supply circuit 11 has a single output terminal, the voltage value to be output is variably controlled in response to a switching signal from the control unit 3. For example, a plurality of reference voltages are prepared in the power supply circuit 11 and the output voltage value can be variably controlled by switching the reference voltage to be used according to the switching signal from the control unit 3. In the present embodiment configured as described above, the same effect as in each of the above-described embodiments can be obtained.

4. Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS. A feature of the present embodiment is that a plurality of discharge destination voltage sources are prepared, and the discharge destination voltage sources are switched according to the shape of the drive waveform signal.

That is, in the print head driving device according to the present embodiment, the discharge transistor 102B is not grounded to the same ground potential as the piezoelectric vibrator 104,
It is connected to the discharge destination voltage circuit 21 via the discharge destination switching circuit 22. As shown in FIG. 7A, the discharge destination voltage circuit 21 includes a discharge destination voltage source Vg1 having a voltage value equal to the ground potential and a discharge destination voltage source Vg2 having a voltage value slightly lower than the intermediate potential Vm. Have.

The control section 23 controls the discharge destination of the driver circuit 102 by outputting a switching signal to the discharge destination switching circuit 22 at a predetermined timing. As shown in FIG. 7A, the control unit 23 sets the discharge destination voltage source to Vg2 in the discharge period D1 falling to the intermediate potential Vm, and sets the discharge destination voltage source to Vg1 in the discharge period D2 falling to the minimum potential VL. The discharge destination voltage source is switched so that That is, in the initial state, the voltage is set to the discharge destination voltage source Vg2 and the driving waveform D
At a predetermined time point t3 during the period when S2 maintains the maximum potential VH2, the discharge destination voltage source is switched from Vg2 to Vg1. Next, at a predetermined time point t4 after returning from the minimum potential VL to the intermediate potential Vm, the discharge destination voltage source is switched from Vg1 to Vg2. As described in the above embodiment, the switching timing can be detected by monitoring the number of clocks and the signal voltage.

In the present embodiment configured as above,
As shown by a shaded portion WD1a in FIG. 7B, during the discharge period D1, the discharge transistor 102B is set to the intermediate potential Vm.
To connect to the discharge destination voltage source Vg2 having a voltage value close to
(Vg2−Vg1) the discharge transistor 102
The differential voltage applied between the collector and the emitter of B can be reduced, and power loss can be reduced. Note that there is no change in the power loss during the discharge period D2.

5. Fifth Embodiment Next, a fifth embodiment of the present invention will be described with reference to FIG. This embodiment is characterized in that three types of discharge destination voltage sources are used and the voltage source is switched during the change of the signal voltage.

As shown in FIG. 8A, in this embodiment, a new discharge destination voltage source Vg3 is provided in addition to the above-described discharge destination voltage sources Vg1 and Vg2. The voltage value of the discharge destination voltage source Vg3 can be set to, for example, approximately half the difference between the maximum potential VH2 and the minimum potential VL. The control unit 23 initially sets the discharge destination voltage source to Vg2, and switches the discharge destination voltage source from Vg2 to Vg3 at a predetermined time t3 when the drive waveform DS2 maintains the maximum potential VH2. Next, the control unit 23 determines at a predetermined time t during the discharge period D2.
At 5, the discharge destination voltage source is switched from Vg3 to Vg1.
Finally, the control unit 23 changes the minimum potential VL to the intermediate potential Vm.
At a predetermined time point t4 after returning to Vg1.
To Vg2.

In this embodiment having the above-described structure, the power loss during the discharge period D1 can be reduced, as in the fourth embodiment. In addition, in the present embodiment, two types of discharge destination voltage sources Vg during discharge period D2.
1 and Vg3, the discharge destination voltage source Vg
3, the difference voltage during the period (t5-t3) connected to the power supply 3 can be further reduced, and the power loss WD during the same period can be reduced.
2b can be significantly reduced. Therefore, the power loss in the discharge period D2 can be reduced more than the power loss WD2a in the above embodiment (WD2a>
WD2b + WD2c).

6. Sixth Embodiment Next, FIG. 9 is a block diagram of a print head driving device according to a sixth embodiment. The features of this embodiment are:
As in the third embodiment, the discharge destination voltage circuit 3
The point is that the value of the voltage source 1 is variably controlled. That is, although the present discharge destination voltage circuit 31 has a single input terminal,
The value of the voltage source is variably controlled according to the switching signal from the control unit 23. In this embodiment configured as described above, the same effects as in the above-described fourth and fifth embodiments can be obtained.

7. Seventh Embodiment Next, FIG. 10 is a block diagram of a print head driving device according to a seventh embodiment. The feature of the present embodiment is that each charging period C1 is controlled according to the drive waveforms DS1 and DS2.
Of the supply voltage source and the respective discharge periods D1, D3
2 in that both the switching of the discharge destination voltage source are performed.

That is, the control device 41 has a function of controlling the switching of the supply voltage source and a function of controlling the switching of the discharge destination voltage source. The voltage source is controlled at a predetermined timing in accordance with the drive waveform signal. Is switched. In the present embodiment configured as described above, power loss can be reduced in both the charging period and the discharging period.

It should be noted that those skilled in the art can make various additions and changes within the scope of the present invention described in each embodiment. For example, instead of using a single driving waveform signal including the driving waveforms DS1 and DS2, FIG.
As shown in (a), drive waveform generating circuits 51 and 52 for respectively generating the drive waveforms DS1 and DS2 are provided, and the selecting circuit 53 is configured to select the drive waveform generating circuit based on gradation data. Can also.

Further, as shown in FIG. 11B, the voltage sources are not limited to two or three types of voltage sources, and Vsn, Vsn + 1, Vsn
sn + 2,. . . As described above, more voltage sources can be prepared and switched appropriately.

Further, as shown in FIG. 12A, a switch circuit 61 for selecting a drive waveform signal based on gradation data includes a drive waveform generation circuit 101 and a driver circuit 102.
Can be provided between the driver circuit 102 and the piezoelectric vibrator 104 as shown in FIG.

[0057]

As described above, according to the apparatus and method for driving an ink jet print head according to the present invention, the voltage supply to the driving means is controlled according to the shape of the driving waveform signal. Can be reduced. Therefore, power loss in the driving means can be reduced, and power consumption, circuit life, and circuit stability can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main part of a print head driving device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing a relationship between a change in a terminal voltage of a piezoelectric vibrator (a signal voltage of a drive waveform signal; the same applies hereinafter) and a power loss during charging.

FIG. 3 is a waveform diagram showing a relationship between a change in terminal voltage of a piezoelectric vibrator and a power loss during charging according to a second embodiment of the present invention.

4A and 4B show a method of switching a supply voltage source so that power loss is minimized. FIG. 4A is a waveform diagram illustrating power loss during a charging period C2, and FIG. 4B is a diagram illustrating the power loss minimized. FIG. 9 is an explanatory diagram for obtaining a condition to be performed.

FIG. 5 is a block diagram showing a main part of a print head driving device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a main part of a print head driving device according to a fourth embodiment of the present invention.

FIG. 7 is a waveform diagram showing a relationship between a terminal voltage of a piezoelectric vibrator and a power loss during discharging.

FIG. 8 is a waveform chart showing a relationship between a terminal voltage change of a piezoelectric vibrator and a power loss at the time of discharging according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram illustrating a main part of a print head driving device according to a sixth embodiment of the present invention.

FIG. 10 is a block diagram showing a main part of a print head driving device according to a seventh embodiment of the present invention.

FIG. 11A relates to a modification of the present invention, and FIG.
And FIG. 13B is an explanatory diagram showing a second modified example.

FIG. 12A relates to a modification of the present invention, and FIG.
And (b) is a block diagram showing a fourth modification.

FIG. 13A is a block diagram showing a main part of a print head driving device according to the related art;
(B) is a waveform diagram showing a change in terminal voltage of the piezoelectric vibrator,
FIG. 3C is an explanatory diagram showing the relationship between the discharge current and the charge current of the piezoelectric vibrator.

14 (a) is a waveform diagram showing power loss during discharging, and FIG. 14 (b) is a waveform diagram showing power loss during charging.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 power supply circuit 2 voltage switching circuit 3 control unit 11 power supply circuit 21 discharge destination voltage circuit 22 discharge destination switching circuit 23 control unit 31 discharge destination voltage circuit 41 control unit 51 drive waveform generation circuit 52 drive waveform generation circuit 53 selection circuit 61 switch circuit Reference Signs List 101 drive waveform generation circuit 102 driver circuit 102A charging transistor 102B discharging transistor 103 switch circuit 104 piezoelectric vibrator Vs supply voltage source Vg discharge destination voltage source

Claims (15)

[Claims] 1. An ink-jet printhead driving device for ejecting ink droplets from each nozzle by operating a pressure generating element provided corresponding to each of the plurality of nozzles, wherein a plurality of driving units having different shapes are provided. A drive waveform signal generating means for generating a waveform signal; a waveform selecting means for selecting any one or a plurality of drive waveform signals among the drive waveform signals based on grayscale data; A drive unit that applies the pressure to the pressure generating element according to the drive waveform signal selected by the selection unit; and a control unit that controls voltage supply to the drive unit according to the shape of the selected drive waveform signal. A drive device for an ink-jet printhead, characterized in that: 2. The method according to claim 1, wherein the control unit switches a plurality of voltage sources according to a shape of the selected drive waveform signal so that a difference between a supply voltage to the drive unit and a terminal voltage of the pressure generating element is determined. 2. The driving apparatus for an ink jet print head according to claim 1, wherein a voltage supply to said driving means is controlled so as to reduce the voltage. 3. The control means switches between a plurality of voltage sources according to the shape of the selected drive waveform signal, so that a difference between a discharge destination voltage of the drive means and a terminal voltage of the pressure generating element is determined. 2. The driving apparatus for an ink jet print head according to claim 1, wherein a voltage supply to said driving means is controlled so as to reduce the voltage. 4. The control means switches between a plurality of supply voltage sources and a plurality of discharge destination voltage sources in accordance with the shape of the selected drive waveform signal, whereby the supply voltage to the drive means and the pressure 2. The voltage supply to the drive unit according to claim 1, wherein a difference between a terminal voltage of the generation unit and a difference between a discharge destination voltage of the drive unit and a terminal voltage of the pressure generation unit are reduced. 3. Drive unit for inkjet print head. 5. The switching of the voltage source is performed during a period when the signal voltage of the drive waveform signal is constant.
A driving device for an ink jet print head according to claim 4. 6. The switching of the voltage source is performed during a period when the signal voltage of the drive waveform signal is changing.
A driving device for an ink jet print head according to claim 4. 7. The driving device for an ink jet print head according to claim 5, wherein the switching of the voltage source is performed by monitoring a clock signal. 8. The driving apparatus for an ink jet print head according to claim 5, wherein the voltage source is switched by monitoring a signal voltage of the driving waveform signal. 9. The driving device for an ink jet print head according to claim 2, wherein the plurality of voltage sources are obtained by using a power supply device having a plurality of voltage outputs. 10. The driving device for an ink jet print head according to claim 2, wherein the plurality of voltage sources are obtained by adjusting an output voltage of a power supply device having a single voltage output. . 11. The driving apparatus according to claim 1, wherein the drive waveform signal has a trapezoidal portion. 12. The driving device for an ink-jet printhead according to claim 1, wherein the pressure generating element is a piezoelectric vibrator. 13. A driving apparatus for an ink jet print head for ejecting ink droplets from each of said plurality of nozzles by operating a piezoelectric vibrator provided corresponding to each of said plurality of nozzles. Driving waveform signal generating means for generating a trapezoidal driving waveform signal; waveform selecting means for selecting any one or a plurality of driving waveform signals among the driving waveform signals based on gradation data; supplied voltage Means for applying to the pressure generating element according to the drive waveform signal selected by the waveform selection means, and adjusting the voltage value supplied to the drive means according to the shape of the selected drive waveform signal. Control means for controlling so as to reduce the difference between the supply voltage to the drive means and the terminal voltage of the pressure generating element. Control means, an initial voltage value at the time of starting charging to the piezoelectric vibrator V1, when the supply voltage value was set to V2,
When the terminal voltage value of the piezoelectric vibrator becomes (V2−V1) / 2, the driving apparatus is switched to a supply voltage source that outputs the voltage value V2. 14. A method of driving an ink jet print head for ejecting ink droplets from each of said plurality of nozzles by operating a pressure generating element provided corresponding to each of said plurality of nozzles. One or a plurality of drive waveform signals corresponding to the gradation data are selected from the waveform signals, and a supply voltage source according to the shape of the selected drive waveform signal is selected from a plurality of supply voltage sources prepared in advance. A voltage corresponding to the drive waveform signal is supplied to the pressure generating element by switching to (i). 15. A method of driving an ink-jet print head for ejecting ink droplets from each of said plurality of nozzles by actuating pressure generating elements provided corresponding to each of said plurality of nozzles. One or a plurality of drive waveform signals corresponding to the gradation data are selected from the waveform signals, and a discharge destination corresponding to the shape of the selected drive waveform signal is selected from a plurality of discharge destination voltage sources prepared in advance. A method for driving an ink jet print head, characterized in that a voltage according to the drive waveform signal is supplied to the pressure generating element by switching to a voltage source.