JP2001113695A - Driving apparatus for ink-jet recording head and printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ease limits on a driving waveform to be supplied to driving elements in driving an ink-jet recording head. SOLUTION: The apparatus has a driving signal line for supplying a driving waveform, a first switch circuit which is connected between the driving signal line and a driving element and which can discharge charges stored in the driving element, a second switch circuit connected in parallel to the first switch circuit which can charge the driving element with charges, and a switch control circuit for supplying a first and a second switching signals to the first and second switch circuits respectively. A first rectifier circuit has a first switch and a first rectifying circuit connected in series. The first rectifying circuit is set so that a direction of a current from the driving element to the driving signal line becomes a forward direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device and a printing device for an ink jet recording head.

[0002]

2. Description of the Related Art In recent years, as an output device of a computer,
2. Description of the Related Art A color printer that discharges several colors of ink from a recording head has become widespread, and is widely used for printing an image processed by a computer or the like in multiple colors and multiple gradations. And
In order to realize multi-gradation printing, the weight of ink droplets ejected from nozzles of a recording head is controlled to control the size of ink dots formed on a print medium.

Conventionally, an ink-jet printer binarizes whether or not to form an ink dot, and expresses a halftone of a printed image by determining how many pixels in a given area have an ink dot. Was common.
However, recently, by forming a plurality of differently sized ink dots in one pixel using light and dark inks,
It is possible to express a halftone of a print image with more gradations.

For example, in an ink jet printer using a piezo element, in order to form ink dots having different sizes, it is necessary to control the meniscus (the surface shape of the ink at the nozzle opening) of the recording head or to control the ink. It is important to control the timing of drop ejection.
Therefore, in order to form a desired ink dot, a drive waveform for operating the piezo element of the recording head is changed according to the size of the ink dot to be formed. Then, by driving piezo elements provided corresponding to the plurality of nozzles of the recording head, ink droplets are ejected from the nozzles and printing is performed.

FIG. 19 is a block diagram showing a conventional driving device for an ink jet recording head. In FIG.
One piezo element 102 and its switch control circuit 10
4 is shown. The switch control circuit 104 generates a switching signal SW based on the print signal SI. The switch circuit 100 is turned on / off according to the switching signal SW, and the driving waveform C supplied to the piezo element 102
Turn OM on / off. Then, the piezo element 102 is driven according to the drive waveform COM, and ink droplets are ejected from the nozzles.

A piezo element has the property of a capacitor for storing electric charges. Therefore, when the drive voltage supplied to the piezo element changes from on to off, the charge stored up to that point is held, and the potential of the electrode of the piezo element (potential at point P in FIG. 19) is also considered to be held. Can be

[0007]

However, in reality, the piezo element discharges spontaneously, so that the electrode potential gradually decreases. FIG. 20 is an explanatory diagram illustrating a change in the electrode potential SEG of the piezo element due to ON / OFF of the switch circuit 100 in the conventional ink jet recording head driving device. When the switch circuit 100 is turned off from on, the electrode potential SEG of the piezo element 102 is spontaneously discharged.
Gradually descends. Then, when the switch circuit 100 is turned on again, the electrode potential SEG sharply increases. Conventionally, due to such a rapid rise of the electrode potential SEG, an ink droplet is erroneously ejected or an excessive current is applied to the piezo element 10.
There was a possibility of flowing to 2.

FIG. 21 is an explanatory diagram showing the timing of switching the switch circuit 100 from on to off and the electrode potential SEG during charging of the piezo element 102 with the drive waveform COM. As shown in the figure, if the timing of turning off the switch circuit 100 is shifted by Δt, the voltage supplied to the piezo element 102 is also shifted by ΔV. In FIG. 21,
Although only the timing of turning on and off the switch circuit during charging of the drive waveform COM to the piezo element is shown, the same occurs with the timing of turning on / off during charging and discharging.

In many cases, the driving waveform COM actually used has a time for charging and discharging the piezo element of 2 to 5 μs. On the other hand, the on / off time of the switch element is 1
There is variation within μs. for that reason,
If a switch is turned on / off during charging and discharging to supply a driving waveform, a driving waveform having a large voltage variation is supplied, which is not practical. That is, there is a problem that the drive waveform that can be actually supplied to the piezo element is limited to some extent.

[0010] Such a problem is not limited to a piezo element, but is a problem common to driving elements generally having a property as a capacitor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to alleviate restrictions on a drive waveform supplied to a drive element in driving an ink jet recording head.

[0012]

Means for Solving the Problems and Their Functions / Effects To solve at least a part of the above-mentioned problems, the present invention provides:
A drive signal line for supplying a drive waveform, a first switch circuit connected between the drive signal line and the drive element, and capable of discharging the charge stored in the drive element; A second switch circuit connected in parallel with the first switch circuit and capable of charging the drive element, and supplying first and second switching signals to the first and second switch circuits, respectively. And a switch control circuit. The first switch circuit has a first switch and a first rectifier circuit connected in series to each other, and the first rectifier circuit controls a direction of a current from the drive element to the drive signal line. It is installed so as to be forward.

In this circuit configuration, the first switch circuit functions as a circuit for discharging the driving element, and the second switch circuit functions as a circuit for charging the driving element. Therefore, by appropriately turning on / off the first switch circuit and the second switch circuit based on the first switching signal and the second switching signal, respectively, it is possible to limit the drive waveform supplied to the drive element. Can be eased.

The second switch circuit has a second switch and a second rectifier circuit connected in series to each other, and the second rectifier circuit connects the drive signal line to the drive element. It can be installed so that the direction of the current is forward.

With such a circuit configuration as well, the first switch circuit functions as a circuit for discharging the drive element, and the second switch circuit functions as a circuit for charging the drive element. Therefore, the first switch circuit and the second switch circuit
By appropriately performing on / off control of the switch circuit based on the first switching signal and the second switching signal, the restriction on the drive waveform supplied to the drive element can be relaxed.

The present invention further comprises a third switch circuit connected between the drive signal line and the drive element in parallel with the first and second switch circuits and capable of charging and discharging the drive element. As such, the switch control circuit may supply the third switching signal to the third switch circuit.

Since the third switch circuit is not provided with a rectifier circuit, when the third switch is turned on,
The drive waveform can be supplied to the drive element without passing through the rectifier circuit. Therefore, it is possible to supply a more preferable drive waveform to the drive element.

The switch control circuit generates the first switching signal such that the timing of switching the first switch from off to on is set in a section where the voltage level of the drive waveform is equal to or higher than the electrode potential of the drive element. Along with
It is preferable that the second switching signal is generated such that the timing for switching the second switch from off to on is set within a section where the voltage level of the drive waveform is equal to or lower than the electrode voltage of the drive element. By doing so, it is possible to prevent a sudden change in the electrode potential of the driving element.

Further, the drive waveform has a portion where the rate of change of the voltage level is substantially zero, and the switch control circuit determines the timing at which the first and second switches are turned on / off by the voltage of the drive waveform. Preferably, the first and second switching signals are generated so as to be set within a section where the level change rate is substantially zero.

By doing so, even if the on / off timing of the first and second switch circuits is slightly shifted, the drive waveform supplied to the drive elements can be made the same, and the electrode of each drive element can be made the same. The potential can be controlled.

It should be noted that the present invention can be realized in various forms such as a driving device of an ink jet recording head and a printing device.

[0022]

Embodiments of the present invention will be described below in the following order based on examples. A. First Embodiment of Recording Head Drive Device: C. Second embodiment of recording head driving device: C. Third Embodiment of Recording Head Driving Device Overall configuration of printing device:

A. FIG. 1 is a block diagram showing the configuration of a drive unit according to a first embodiment of the present invention. The driving device includes a first switch circuit 60, a first diode 61, a second switch circuit 62, a second diode 64, and a piezo element 66.
And a switch control circuit 70. One electrode of the piezo element 66 is grounded, and the other electrode is connected to the first diode 61 and the second diode 64 in parallel. The first switch circuit 60 is connected in series with the first diode 61, and the first diode 61 is connected so that current flows only from the piezo element 66 to the drive signal line 30. Further, the second switch circuit 62 is connected in series with the second diode 64, and the second diode 64 is connected so that current flows only from the drive signal line 30 to the piezo element 66 side. . These two sets of switch circuits and diodes are connected in parallel. The positional relationship between the switch circuits and the diodes in each set may be reversed from that shown in the figure.

The switch control circuit 70 generates first and second switching signals SW1 and SW2 according to the print signal SI, and supplies them to the first switch circuit 60 and the second switch circuit 62, respectively. .

FIGS. 2 to 6 show the drive waveform COM and the electrode potential SEG of the piezo element 66 by the on / off control of the first switch circuit 60 and the second switch circuit 62 (FIG. 1). FIG. 9 is an explanatory diagram showing an example of a change in the potential at point P). As shown in FIG. 2, the drive waveform COM in one pixel section T rises at a finite non-negative finite change rate in the sections T1a, T1b, T1c, and T1d. In the sections T2a, T2b, and T2c, the voltage level falls at a non-positive finite change rate. here,
"Rise at a non-negative, finite rate of change" refers to a gradual rise such that the rate of change is zero or a finite positive value, rather than a step-like rise where the rate of change is nearly infinite. Means In addition, "falling at a non-positive finite change rate" does not mean a step-like drop at which the change rate becomes almost infinite, but a gradual drop such that the change rate takes 0 or a finite negative value. It means to do.
The boundary of each section has a portion where the rate of change of the voltage level is almost zero.

In the example of FIG. 2, all the sections T1a to T1
At d, the two switch circuits 60 and 62 are both on. In this case, when the voltage level of the drive waveform COM rises, the piezo element 66 is charged via the second diode 64. When the voltage level of the drive waveform COM decreases, the piezo element 66 is discharged via the first diode 61. Accordingly, the electrode potential SEG of the piezo element 66 is equal to the drive waveform C in all the sections.
It changes with the change of OM.

In the example of FIG. 3, the first switch circuit 60
Is off in the section T1a to T1b, and the section T2
It is on from b to T1d. On the other hand, the second switch circuit 62 is off in the sections T1a and T2a,
It is on in the sections T1b to T1d. In this case, when the two switch circuits 60 and 62 are turned off at the time when the initial change rate of the voltage level in the section T1a is almost 0,
The electrode potential SEG of the piezo element 66 gradually decreases due to spontaneous discharge. In the section T1b, the second switch circuit 6
2 is turned on, but at the beginning of the section T1b, the voltage level of the drive waveform COM is higher than the electrode potential S of the piezo element 66.
Since it is lower than EG, a reverse voltage is applied to the second diode 64 and no current flows. Then, the driving waveform CO
M rises, and the electrode potential S of the piezo element 66 increases.
When the voltage level of the drive waveform COM is higher than that of EG, a forward voltage is applied to the second diode 64, so that the electrode potential SEG of the piezo element 66 becomes higher than the drive waveform COM.
It rises with the voltage change of. Since the two switch circuits 60 and 62 are both ON after the section T2b, the electrode potential SEG of the piezo element 66 becomes equal to the drive waveform CO.
It changes with the change of M. In addition, since a sufficient time elapses from the time when the second switch circuit 62 is turned on to the time when the forward voltage is applied to the second diode 64, the time when the second switch circuit 62 is turned on is 1-2 μs. , The same drive waveform COM is supplied to the piezo element 66.

In the conventional circuit shown in FIG. 19, when the switch circuit 100 changes from off to on, the electrode potential SEG of the piezo element 102 instantaneously rises as shown in FIG. On the other hand, in the case of FIG. 3, the electrode potential SEG of the piezo element 66 gradually rises according to the waveform of the drive waveform COM in the section T1b. As a result,
It is possible to prevent an ink droplet from being ejected by mistake and an excessive current from flowing to the piezo element.

In the example of FIG. 4, the first switch circuit 60
Is off in all the sections T1a to T1d.
On the other hand, the second switch circuit 62 operates in the sections T1a to T2c.
At the time T1d, and is on at the section T1d.
In this case, the same operation as when the second switch circuit 62 is switched from off to on in FIG. 3 is performed, and the electrode potential SEG of the piezo element 66 gradually rises.

In the example of FIG. 5, the first switch circuit 60
Is off in the section T1a to T1b, and the section T2
It is on from b to T1d. On the other hand, the second switch circuit 62 is on in the sections T1a, T1b to T1d, and is off in the section T2a. In this case, the electrode potential SEG of the piezo element 66 changes in accordance with the change in the drive waveform COM in the section T1a, and when the change rate of the initial voltage level in the section T2a is substantially zero, the second electrode potential SEG changes to the second level.
When the switch circuit 62 is turned off, it gradually falls due to spontaneous discharge. At this time, since the driving waveforms at the end of the section T1a and the initial period of the section T2a are flat (there is no voltage fluctuation), the same driving waveform COM is applied to the piezo element 66 even if the time during which the second switch circuit 62 is turned off varies. Supplied to Then, in the section T1b, the second switch circuit 62 is turned on again. However, in the early part of the section T1b, the voltage level of the drive waveform COM is higher than the piezo element 66.
, The reverse voltage is applied to the second diode 64, and no current flows. Thereafter, when the voltage level of the drive waveform COM rises and the voltage level of the drive waveform COM becomes higher than the electrode potential SEG of the piezo element 66, a forward voltage is applied to the second diode 64. The electrode potential SEG of the driving waveform C
It rises with the voltage change of OM. After section T2b,
Since the two switch circuits 60 and 62 are both turned on, the electrode potential SEG of the piezo element 66 changes with a change in the drive waveform COM.

In the example of FIG. 6, the first switch circuit 60
Is off in the section T1a, and the sections T2a to T1
On at d. On the other hand, the second switch circuit 62
Is off in the sections T1a to T2a, and
It is on from b to T1d. In this case, the section T1a
At the point when the rate of change of the initial voltage level
When the two switch circuits 60 and 62 are turned off, the electrode potential SEG of the piezo element 66 gradually decreases due to spontaneous discharge. When the first switch circuit 60 is turned on in the section T2a, the voltage level of the drive waveform COM is higher than the electrode potential SEG of the piezo element 66 at the beginning of the section T2a. Voltage is applied and no current flows. Thereafter, when the voltage level of the drive waveform COM falls and becomes lower than the electrode potential SEG of the piezo element 66, a forward voltage is applied to the first diode 61. Therefore, the electrode potential SEG of the piezo element 66 becomes It descends with changes. In addition, since a sufficient time elapses from the time when the first switch circuit 60 is turned on to the time when the forward voltage is applied to the first diode 61, the time when the first switch circuit 60 is turned on is 1-2 μs. The same driving waveform COM is applied to the piezo element 6 even if the variation of
6. Since the two switch circuits 60 and 62 are both turned on after the section T1b,
The electrode potential SEG of the piezo element 66 changes with a change in the drive waveform COM.

As shown in FIGS. 2 to 6, by performing on / off control of the first switch circuit 60 and the second switch circuit 62, a part of the drive waveform COM is selectively piezo-electrically driven. It can be supplied to the element 66. Further, when the supply of the drive waveform COM to the piezo element 66 is interrupted and then restarted, the switching of the switch circuits 60 and 62 to the ON state is performed when the rate of change of the drive waveform COM is substantially zero. The electrode voltage SE of the piezo element 66 even if the timing varies.
G can be prevented from changing suddenly. That is, by controlling the on / off timing of the first switch circuit 60 and the second switch circuit 62, it is possible to suppress a sudden change in the electrode potential SEG of the piezo element 66 and to apply various drive waveforms to the piezo element 66. Can be supplied to

B. Second Embodiment of Recording Head Driving Device: FIG. 7 is a block diagram showing a configuration of a driving device according to a second embodiment of the present invention. In this drive device, a third switch circuit 65 is provided between the drive signal line 30 and the piezo element 66 of the drive device of the first embodiment, and includes a first switch circuit 60 and a first diode 61; And the second diode 64 are connected in parallel. The third switch circuit 65 has a switch control circuit 70
Is connected. The switch control circuit 70 includes three switching signals SW1, SW2,
SW3, and each of the three switch circuits 60,
62, 65.

FIGS. 8 to 12 show a piezo element by the on / off control of the drive waveform COM, the first switch circuit 60, the second switch circuit 62, and the third switch circuit 65 in the second embodiment. The electrode potential SEG at 66 (P in FIG. 7)
FIG. 9 is an explanatory diagram illustrating an example of a change in (potential at a point). Drive waveform C
OM is the same as in the first embodiment.

In the example of FIG. 8, all the sections T1a to T1
At d, the three switch circuits 60, 62, 65 are on. In this case, in all sections, the electrode potential SEG of the piezo element 66 changes according to the change of the drive waveform COM. The first and second switch circuits 60, 6
2 is turned off in all the sections T1a to T1d, the same operation is performed.

In the circuit of the second embodiment, since no diode is connected to the third switch circuit 65, when the third switch circuit 65 is in the ON state, the driving waveform is transmitted through the third switch circuit 65. COM is supplied to the piezo element 66 as it is. Therefore, a more preferable drive waveform can be supplied to the piezo element 66 as compared with the circuit of the first embodiment.

In the example of FIG. 9, the first and second switch circuits 60 and 62 are turned on / off at the same timing as in the example shown in FIG. Further, the third switch circuit 65 is off in the sections T1a to T1b, and is turned off in the sections T2b to T2b.
It is on at 1d. In this case, when the second switch circuit 62 is switched from off to on in the section T1b, the electrode potential SE of the piezo element 66 is increased as in the example of FIG.
G changes with the voltage change of the drive waveform COM. After the section T2b, after the third switch 65 is turned on, the same operation is performed even if the first and second switch circuits 60 and 62 are turned off.

In the example of FIG. 10, the first and second switch circuits 60 and 62 are turned on / off at the same timing as in the example shown in FIG. Further, the third switch circuit 65 includes:
It is off in all the sections T1a to T1d. In this case, when the second switch circuit 62 switches from off to on in the section T1d, the electrode potential SEG of the piezo element 66 changes with the voltage change of the drive waveform COM, as in the example of FIG.

In the example of FIG. 11, the first and second switch circuits 60 and 62 are turned on / off at the same timing as in the example shown in FIG. Further, the third switch circuit 65 includes:
It is on in the sections T1a, T2b to T1d and off in the sections T2a, T1b. In this case, the electrode potential SEG of the piezo element 66 changes as in the example of FIG. Note that when the third switch circuit 65 in the sections T1a and T2b and thereafter is in the ON state, the same operation is performed even if the first and second switch circuits 60 and 62 are turned off.

In the example of FIG. 12, the first and second switch circuits 60 and 62 are turned on / off at the same timing as in the example shown in FIG. Further, the third switch circuit 65 includes:
It is off in the sections T1a and T2a, and the sections T1b to
It is on at T1d. In this case, the piezo element 66
The electrode potential SEG changes in the same manner as in the example of FIG. In addition,
After the section T1b, after the third switch 65 is turned on, the same operation is performed even if the first and second switch circuits 60 and 62 are turned off.

As described above, also in the second embodiment, by performing on / off control of the first switch circuit 60 and the second switch circuit 62, a part of the drive waveform COM can be selectively changed to the piezo element. 66. When the supply of the drive waveform COM to the piezo element 66 is interrupted and restarted, the switch circuits 60 and 62
Is switched to the ON state when the change rate of the drive waveform COM is substantially zero, so that the electrode voltage SEG of the piezo element 66 can be prevented from suddenly changing even if the timing varies. That is,
First switch circuit 60 and second switch circuit 62
By controlling the on / off timing of the piezo element 66, it is possible to supply a variety of drive waveforms to the piezo element 66 while suppressing a sudden change in the electrode potential SEG of the piezo element 66.

C. Third Embodiment of Recording Head Driving Device: FIG. 13 is a block diagram showing a configuration of a driving device according to a third embodiment of the present invention. This driving device is the same as the recording head driving device of the first embodiment except that the second diode 64 is omitted.

FIG. 14 shows a driving waveform C in the third embodiment.
FIG. 14 is an explanatory diagram showing an example of a change in the electrode potential SEG (potential at point P in FIG. 13) of the piezo element 66 due to ON / OFF control of the OM, the first switch circuit 60, and the second switch circuit 62. The drive waveform COM is the same as in the first embodiment.

In the example of FIG. 14, the first and second switch circuits 60 and 62 are turned on / off at the same timing as in the example shown in FIG. In this case, the electrode potential SEG of the piezo element 66 changes as in the example of FIG. That is, the section T
When the two switch circuits 60 and 62 are turned off at the time when the initial rate of change of the voltage level of 1a is almost 0, the electrode potential SEG of the piezo element 66 gradually decreases due to spontaneous discharge. When the first switch circuit 60 is turned on in the section T2a, the drive waveform COM is initially provided in the section T2a.
Is higher than the electrode potential SEG of the piezo element 66, a reverse voltage is applied to the first diode 61, and no current flows. Thereafter, when the voltage level of the drive waveform COM falls and becomes lower than the electrode potential SEG of the piezo element 66, a forward voltage is applied to the first diode 61. Therefore, the electrode potential SEG of the piezo element 66 becomes It descends with changes. Further, after the first switch circuit 60 is turned on, the first diode 61
Time elapses before the forward voltage is applied to the first switch circuit 60.
The same drive waveform COM is supplied to the piezo element 66 even if a variation of μs occurs. Then, after the section T1b, 2
Since the two switch circuits 60 and 62 are both turned on, the electrode potential SEG of the piezo element 66 has the drive waveform C
It changes with the change of OM. Note that after the section T1b,
After the second switch 62 is turned on, the same operation is performed even if the first switch circuit 60 is turned off.

As described above, by performing on / off control of the first switch circuit 60 and the second switch circuit 62, a part of the drive waveform COM can be selectively supplied to the piezo element 66. it can. Also, the piezo element 6
When the supply of the drive waveform COM to the control circuit 6 is interrupted and then resumed, the timing of switching the switch circuits 60 and 62 to the ON state is set at a time when the rate of change of the drive waveform COM is almost 0, so that the timing varies. , The sudden change in the electrode voltage SEG of the piezo element 66 can be prevented. That is, the first switch circuit 60
By controlling the on / off timing of the second switch circuit 62, it is possible to supply a variety of drive waveforms to the piezo element 66 while suppressing a sudden change in the electrode potential SEG of the piezo element 66. .

D. Overall Configuration of Printing Apparatus: FIG. 15 is a block diagram showing the overall configuration of a printing apparatus as one embodiment of the present invention. As shown in FIG. 15, the printing apparatus includes a computer 90, a control circuit 40, a paper feed motor 23,
A carriage motor 24 for performing main scanning and a recording head 50
And

In the computer 90, an application program operates under a predetermined operating system. The operating system incorporates a video driver and a printer driver, and displays an image on a display and performs various image processing.

The control circuit 40 includes an interface 41 for receiving a print signal and the like from a computer 90, a RAM 42 for storing various data, a ROM 43 for storing various data processing routines and the like, an oscillation circuit 44,
A control unit 45 including a CPU and the like;
And an interface 47 for sending print signals and drive signals to the paper feed motor 23, the carriage motor 24, and the recording head 50.

The RAM 42 is used as a receiving buffer 42A, an intermediate buffer 42B or an output buffer 42C. The print signal from the computer 90 is stored in the reception buffer 42A via the interface 41.
This data is converted into an intermediate code and stored in an intermediate buffer 4.
2B. Then, necessary processing is performed by the control unit 45 with reference to font data, graphic functions, and the like in the ROM 43, dot pattern data is developed, and stored in the output buffer 42C. The dot pattern data is sent to the recording head 50 via the interface 47.
Sent to

FIG. 16 is a block diagram showing an electrical configuration of the recording head 50 corresponding to the first embodiment shown in FIG. The recording head 50 includes a plurality of shift registers 51A to 51N corresponding to the number of nozzles, a plurality of logic circuits 52A to 52N, and a plurality of level shifters 53A to 53N.
A plurality of first switch circuits 54A to 54N; a plurality of first diodes 55A to 55N; a plurality of second switch circuits 56A to 56N; a plurality of second diodes 57A to 57N; Piezo elements 58A to 58N
And The print signal SI is supplied to the shift register 51A in synchronization with the clock signal CLK from the oscillation circuit 44.
To 51N. This print signal SI is latched in the logic circuits 52A to 52N in synchronization with the latch signal LAT, and is converted into two switching signals SW1 and SW2 in each logic circuit. These switching signals SW1 and SW2 are amplified by the level shifters 53A to 53N, and supplied to the first switch circuits 54A to 54N and the second switch circuits 56A to 56N, respectively.

The drive waveform COM from the drive waveform generation circuit 46 is input to the input sides of the first switch circuits 54A to 54N and the second switch circuits 56A to 56N, and the outputs of the first switch circuits 54A to 54N. On the output side of the second switch circuits 56A to 56N via the first diodes 55A to 55N.
Piezo elements 58A to 58N are connected via 57N. First diodes 55A to 55N are connected in series to the first switch circuits 54A to 54N such that the drive waveform COM side is in the forward direction from the piezo elements 58A to 58N side. Also, the second switch circuits 56A to 56A
N represents the piezo elements 58A to 58 from the drive waveform COM side.
The second diodes 57A to 57A-5
7N are connected in series.

The first switch circuits 54A to 54N
Correspond to the first switch circuit 60 shown in FIG. 1, and each of the second switch circuits 56A to 56N corresponds to the second switch circuit 62 shown in FIG.
Also, one set of the illustrated shift register, logic circuit, and level shifter (for example, 51A, 52A, 53A)
Corresponds to the switch control circuit 70 of FIG.

FIG. 17 is a block diagram showing an electrical configuration of a recording head 50 corresponding to the second embodiment shown in FIG. The circuit of FIG. 17 has a configuration in which a plurality of third switch circuits 59A to 59N are added to the circuit of FIG. 16, and the rest is the same as the circuit of FIG.

FIG. 18 is a block diagram showing an electrical configuration of a recording head 50 corresponding to the third embodiment shown in FIG. The circuit of FIG. 18 has a configuration in which a plurality of second diodes 57A to 57N are removed from the circuit of FIG. 16, and the rest is the same as the circuit shown in FIG.

As is well known, a piezo element is an element that distorts the crystal structure due to the application of a voltage and converts electro-mechanical energy at an extremely high speed. When the driving waveform COM is supplied to the piezo elements 58A to 58N, the piezo elements 58A to 58N are deformed accordingly, and the wall of the ink chamber is also deformed. This controls the ejection of ink droplets from the nozzles. Printing is performed by the ejected ink droplets adhering to the print medium. The piezo element may be operated in any one of a so-called flexural vibration mode and a longitudinal vibration mode.

E. Modifications: Several embodiments of the present invention have been described above, but the present invention is not limited to such embodiments at all, and may be implemented in various modes without departing from the scope of the invention. Implementation is possible. For example, the following modifications are possible.

In the above embodiment, the on / off control is performed in a section where the rate of change of the voltage level of the drive waveform COM is almost 0 in consideration of the on / off timing of the switch. On the other hand, the on / off control may be performed in a section in which the voltage level changes at a finite change rate without considering the on / off timing shift of the switch. By doing so, it is possible to supply more various drive waveforms to the piezo element.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a driving device of an ink jet recording head as a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the operation of the first embodiment.

FIG. 3 is an explanatory diagram showing the operation of the first embodiment.

FIG. 4 is an explanatory diagram showing the operation of the first embodiment.

FIG. 5 is an explanatory diagram showing the operation of the first embodiment.

FIG. 6 is an explanatory diagram showing the operation of the first embodiment.

FIG. 7 is a block diagram showing a driving device of an ink jet recording head according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing the operation of the second embodiment.

FIG. 9 is an explanatory diagram showing the operation of the second embodiment.

FIG. 10 is an explanatory diagram showing the operation of the second embodiment.

FIG. 11 is an explanatory diagram showing the operation of the second embodiment.

FIG. 12 is an explanatory diagram showing the operation of the second embodiment.

FIG. 13 is a block diagram showing a driving device of an ink jet recording head as a third embodiment of the present invention.

FIG. 14 is an explanatory diagram showing the operation of the third embodiment.

FIG. 15 is a block diagram illustrating an overall configuration of a printing apparatus as one embodiment of the present invention.

FIG. 16 is a block diagram illustrating an electrical configuration of the recording head according to the first embodiment.

FIG. 17 is a block diagram illustrating an electrical configuration of a recording head according to a second embodiment.

FIG. 18 is a block diagram illustrating an electrical configuration of a recording head according to a third embodiment.

FIG. 19 is a block diagram showing a conventional driving device for an ink jet recording head.

FIG. 20 is an explanatory diagram showing a change in electrode potential of a piezo element due to ON / OFF of a switch circuit in a conventional ink jet recording head driving device.

FIG. 21 is an explanatory diagram showing the timing of switching the switch circuit from on to off and the electrode potential SEG during charging of the drive waveform COM to the piezo element.

[Explanation of symbols]

 23 ... Paper feed motor 24 ... Carriage motor 30 ... Drive signal line 40 ... Control circuit 41 ... Interface 42 ... RAM 42A ... Reception buffer 42B ... Intermediate buffer 42C ... Output buffer 43 ... ROM 44 ... Oscillation circuit 45 ... Control unit 46 ... Drive Waveform generation circuit 50 Print heads 51A-51N Shift registers 52A-52N Logic circuits 53A-53N Level shifters 54A-54N Switch circuits 55A-55N Diodes 56A-56N Switch circuits 57A-57N Diodes 58A-58N Piezo elements 59A to 59N Switch circuit 60 Switch circuit 61 Diode 62 Switch circuit 64 Diode 65 Switch circuit 66 Piezo element 70 Switch control circuit 90 Computer 100 Switch times Road 102: Piezo element 104: Switch control circuit 110: Drive signal line

Claims (6)

[Claims] An ink droplet is ejected from a nozzle by driving a driving element provided corresponding to a plurality of nozzles using a driving waveform generated based on a print signal of an image to be printed. A drive device for an ink jet recording head, comprising: a drive signal line for supplying the drive waveform; a drive signal line connected between the drive signal line and the drive element; and a charge stored in the drive element. A first switch circuit capable of discharging, and connected in parallel with the first switch circuit,
A second switch circuit capable of charging the drive element with electric charge, and a switch control circuit for supplying first and second switching signals to the first and second switch circuits, respectively. The first switch circuit has a first switch and a first rectifier circuit connected in series to each other, and the first rectifier circuit is configured to control a direction of a current from the drive element to the drive signal line. A driving device for an ink jet type recording head, which is installed so that is directed in the forward direction. 2. The driving device for an ink jet recording head according to claim 1, wherein the second switch circuit has a second switch and a second rectifier circuit connected in series to each other. The driving device for an ink jet type recording head, wherein the second rectifier circuit is provided so that a direction of a current from the driving signal line to the driving element is a forward direction. 3. The driving device for an ink jet recording head according to claim 2, further comprising: a first switching circuit connected in parallel with the first and second switching circuits between the driving signal line and the driving element. And a third switch circuit capable of charging and discharging the drive element, wherein the switch control circuit supplies a third switching signal to the third switch circuit. 4. The driving apparatus for an ink jet recording head according to claim 1, wherein the switch control circuit sets a timing at which the first switch is switched from off to on by the drive waveform. The first switching signal is generated so that the voltage level of the drive signal is set to be equal to or higher than the electrode voltage of the drive element, and the timing of switching the second switch from off to on is determined by the voltage level of the drive waveform. Generating the second switching signal so that the second switching signal is set within an interval equal to or lower than the electrode potential of the driving element. 5. The driving apparatus for an ink jet recording head according to claim 1, wherein the drive waveform has a portion where a rate of change in a voltage level is substantially zero, and wherein the switch control is performed. The circuit sets the first and second switching signals such that a timing for switching on / off of the first and second switches is set within a section in which a change rate of a voltage level of the drive waveform is substantially zero. An inkjet recording head drive device that generates 6. A printing apparatus for recording an image on a print medium by discharging ink droplets, comprising: a plurality of nozzles for discharging ink droplets; and a plurality of nozzles provided corresponding to the plurality of nozzles. A printing device, comprising: a recording head having the following driving elements: and the driving device for an ink jet recording head according to claim 1.