JP2003200573A - Driving pulse generating circuit and ink jet recorder employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving pulse generating circuit, and an ink jet recorder employing it, in which a plurality of voltages can be generated continuously and stably through a simple arrangement. <P>SOLUTION: A Cockcroft-Walton type power supply circuit 411 is employed as a driving pulse supplying means and a pulse voltage being inputted to the power supply circuit 411 has variable pulse conditions. Furthermore, a circuit 415 for discharging a piezoelectric based on a reference potential is provided. Since a driving pulse generating circuit and an ink jet recorder having such an arrangement can generate a trapezoidal pulse driving voltage through a simple arrangement, the driving pulse does not rise nor fall abruptly and thereby heat generation loss can be suppressed in the peripheral circuit of the piezoelectric. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive pulse generation circuit used in an ink jet recording apparatus using a piezoelectric material whose volume changes by applying a drive pulse.

[0002]

2. Description of the Related Art A method of ejecting ink from an ink jet head for printing on a recording medium is basically to eject ink from the tip of a nozzle provided in the ink jet head. The nozzle is provided at the bottom of each of the channels arranged in the inkjet head. Specifically, the channel is pressurized for an extremely short time, and the ink in the pressurized channel is ejected as a single ink droplet from a thin nozzle at the bottom of the channel.

As a method of pressurizing the channel, there is known a method of generating pressure by using a piezoelectric body which is an electrostrictive element whose volume changes by applying a drive pulse.
That is, the channel is expanded / contracted by selectively applying the ejection drive pulse or the non-ejection drive pulse to the drive electrodes formed on both wall surfaces of the channel having a plurality of channels separated by the piezoelectric body. Then, the ink ejection operation is performed.

Incidentally, the waveform of the drive pulse is not a rectangular clock pulse, but a pulse having a rising portion (gradually rising period) and a falling portion (gradually falling period) of the voltage (hereinafter, It is preferable to use a trapezoidal pulse). This is because in the square-shaped pulse, the current flows to the drive electrode and the peripheral circuit in a concentrated manner when the pulse rises sharply and when it falls sharply, so that extra heat is generated by the resistance component of the common electrode and the peripheral circuit. . Here, if a trapezoidal pulse is applied, the rising and falling edges of the pulse are applied with a constant gradient. Therefore, the trapezoidal pulse does not cause a concentrated current flow as compared with the rectangular pulse,
It is possible to reduce heat loss of the drive electrode and its peripheral circuit.

As a method of generating the trapezoidal pulse, a plurality of kinds of voltages are prepared respectively, the pulse voltage is raised stepwise when the pulse is applied, and is lowered stepwise when the application is stopped. There is a way. In the case of an inkjet recording apparatus using a DC power source, a DC-DC converter is generally used to increase the voltage.

[0006]

However, one power supply circuit is required each time one type of voltage is generated. That is, the above-mentioned conventional method has a problem that a plurality of power supplies are required to generate a plurality of types of voltages, and the power supply circuit for implementing the method becomes complicated. On the other hand, in the case of an inkjet recording apparatus using a DC power supply, a DC-DC converter for generating a high voltage power supply is required, but the circuit itself of the DC-DC converter is composed of a capacitor, a resistor, a coil, a switching transistor and the like. Therefore, in this case as well, there has been a problem that the power supply circuit becomes complicated. As described above, if the circuit has a complicated structure, there is a problem that a large loss occurs in the power supplied to the power supply circuit.

The present invention has been made to solve the above problems, and an object thereof is a drive used in an ink jet recording apparatus for printing on a recording medium by utilizing the effect of electromechanical conversion in a piezoelectric body. It is an object of the present invention to provide a drive pulse generation circuit that makes it possible to continuously generate a plurality of stable voltages in a pulse generation circuit with a simple configuration, and an inkjet recording apparatus using the drive pulse generation circuit.

[0008]

In order to solve the above-mentioned problems, a drive pulse generation circuit according to the present invention is applied to an ink jet recording apparatus for printing on a recording medium by utilizing the effect of electromechanical conversion in a piezoelectric body. The drive pulse generation circuit used includes an input pulse generation means for generating an input pulse voltage, and a drive pulse supply means for generating a drive pulse voltage by inputting the input pulse voltage and supplying it to the piezoelectric body. A Cockcroft-Walton type power supply circuit is used as the drive pulse supply means, and the input pulse generation means is capable of changing the pulse condition of the input pulse voltage.

The Cockcroft-Walton type power supply circuit has a structure in which a combination of a rectifier and a capacitor is stacked in several stages. When an alternating current is applied, the voltage of the alternating current is cycled. Is a circuit that can generate a high voltage that is an integral multiple of the supplied voltage by stepping up the voltage.

The drive pulse generation circuit according to the present invention is adapted to input an arbitrary pulse train (input pulse) as an input pulse voltage to the Cockcroft-Walton type power supply circuit. Therefore, it is possible to transiently increase the output voltage of the Cockcroft-Walton type power supply circuit, and as a result, the drive pulse applied to the piezoelectric body can be output with the output waveform having the rising portion with a simple configuration. Can be

That is, according to the above arrangement, the Cockcroft-Walton type power supply circuit can output the input voltage of an arbitrary pulse train as a rising waveform having an arbitrary slope. Therefore, the drive pulse does not rise steeply, and heat loss in the peripheral circuit of the piezoelectric body can be suppressed.

The drive pulse generation circuit according to the present invention is characterized in that, in addition to the above-mentioned configuration, initialization discharge means for discharging the electric charge of the capacitor included in the Cockcroft-Walton type power supply circuit is further provided. There is.

According to the above construction, after the drive pulse voltage is raised by the Cockcroft-Walton type power supply circuit by the input of the input pulse voltage, the electric charge of the capacitor is discharged by the initialization discharge means, and the Cockcroft-Walton type power supply circuit is discharged. Can be initialized.

That is, in the above configuration, the initializing discharge means allows the capacitor to be in a state in which no electric charge is accumulated at the time when the input pulse voltage is newly input. Therefore, the Cockcroft-Walton type power supply circuit. Then, the drive pulse voltage can be reliably raised based on the newly input input pulse voltage. Therefore, the drive pulse voltage having the rising portion can be continuously generated, and accurate rising control can be performed even if the gradient of the rising portion is appropriately changed.

The drive pulse generating circuit according to the present invention is characterized in that, in addition to the above-mentioned structure, it further comprises piezoelectric discharge means for discharging the electric charge accumulated in the piezoelectric body based on the reference potential. There is.

According to the above structure, the piezoelectric discharge means discharges the electric charge accumulated in the piezoelectric body based on the reference potential. Therefore, if a target waveform having an arbitrary gradient is used as the reference potential, the drive voltage can be lowered with an arbitrary gradient. As a result, the above Cockcroft
By combining with a Walton type power supply circuit, the drive pulse applied to the piezoelectric body can be made into a trapezoidal output waveform having a rising portion and a falling portion with a simple configuration.

That is, according to the above configuration, the Cockcroft-Walton type power supply circuit and the piezoelectric discharge means can generate the drive voltage of the trapezoidal pulse.
Therefore, the drive pulse is not sharply raised or lowered, so that the heat generation loss in the peripheral circuit of the piezoelectric body can be further suppressed.

In addition to the above configuration, the drive pulse generating circuit according to the present invention is characterized in that the pulse condition changed in the input pulse generating means is the number of pulses, frequency or pulse width.

According to the above arrangement, the input pulse generating means generates the input pulse with the number of pulses, the frequency of the pulse, or the width of the pulse changed, and inputs the generated input pulse to the Cockcroft-Walton type power supply circuit, whereby the rising portion is generated. The slope of can be varied. That is, the output waveform can be controlled by changing any of the pulse conditions described above. Therefore, it becomes possible to obtain a more appropriate drive pulse according to various conditions, and it is possible to further suppress heat loss in the peripheral circuit of the piezoelectric body.

In addition to the above configuration, the drive pulse generating circuit according to the present invention is characterized in that the input pulse generating means changes the pulse condition by feeding back the drive pulse voltage.

According to the above arrangement, the input pulse generating means detects the drive pulse voltage and reflects it on the generation of the input pulse voltage. Therefore, it is possible to generate an input pulse according to the drive pulse, and it is possible to improve the accuracy of the drive pulse voltage as compared with the open loop type circuit.

The drive pulse generating circuit according to the present invention is characterized in that, in addition to the above configuration, it further comprises a regenerating means for recovering the electric charge accumulated in the piezoelectric body.

According to the above construction, the electric charge accumulated in the piezoelectric body can be recovered by the regenerating means and returned to the DC power source. Therefore, the electric energy for driving the piezoelectric body is effectively used, and the power consumption of the drive pulse generation circuit can be reduced.

The drive pulse generating circuit according to the present invention is characterized in that, in addition to the above configuration, an inductance element is further provided between the piezoelectric body and the regeneration means.

According to the above configuration, even when the slope of the rising portion or the falling portion of the drive pulse voltage is arbitrarily changed, it is possible to buffer the change in the potential due to the rising and falling. Therefore, even if a drive pulse voltage having a rising portion and a falling portion is applied to the piezoelectric body,
It is possible to suppress or prevent the loss that occurs at the time of application, and it is possible to further reduce the power consumption of the drive pulse generation circuit.

In addition to the above configuration, the drive pulse generation circuit according to the present invention has the number of stages of the Cockcroft-Walton type power supply circuit as n, and the individual capacitances of the capacitors included in the Cockcroft-Walton type power supply circuit. C
_{When C} and the electrostatic capacity of the piezoelectric body is C _P , the following relational expression C _P ≧ 4C _C / n is established.

According to the above structure, even if electric charge remains in the capacitor included in the Cockcroft-Walton type power supply circuit at the time of the previous driving, the electric charge can be absorbed by the piezoelectric body, and the Cockcroft is driven at each driving. -The Walton type power supply circuit can be initialized. Therefore, it becomes possible to reliably generate the predetermined drive pulse voltage even if the input pulse voltage which is different for each driving is used.

The ink jet recording apparatus according to the present invention is provided with the drive pulse generating circuit having the above-mentioned structure and the ink discharge nozzle using the piezoelectric material which changes its shape by the action of electric energy, and the drive pulse generating circuit outputs the signal. By applying a drive pulse to the piezoelectric body, ink is ejected by the action of pressure generated in the nozzle.

According to the above configuration, it is possible to generate a drive voltage of a pulse having at least a rising portion, preferably a trapezoidal pulse. Therefore, the drive pulse does not rise or fall steeply,
It is possible to suppress heat generation loss in the peripheral circuit of the piezoelectric body. In addition, the configuration of the drive pulse generation circuit can be simplified and the cost can be reduced. This makes it possible to provide an inkjet recording apparatus that operates reliably with a simple configuration.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The following will describe one embodiment of the present invention with reference to FIGS. 1 to 7.

An inkjet printer (inkjet recording apparatus) 1 according to an embodiment of the present invention is an apparatus for printing by ejecting ink on a sheet (recording medium) for image printing according to image data. Is.

First, the construction of the main part of the above ink jet printer is shown in a perspective view in FIG. 2 and in a perspective side view in FIG. The inkjet printer 1 includes a paper feed unit 2, a separation unit 3, a conveyance unit 4, a printing unit 5 and a discharge unit 6.

The paper feed section 2 is for feeding the paper P when printing is performed, and comprises a paper feed tray 7 and a pickup roller (not shown). When the printing is not performed, the function of storing the paper P is fulfilled.

The separating section 3 is for supplying the sheets P supplied from the sheet feeding section 2 to the printing section 5 one by one.
It comprises a paper feed roller 8 and a separating device 9. In the separating device 9, the friction between the pad portion (contact portion with the sheet) and the sheet is set to be larger than the friction between the sheets. Further, the paper feed roller 8 is set so that the friction between the paper feed roller 8 and the paper P is larger than the friction between the pad and the paper P and the friction between the paper P. Therefore, 2
Even if the sheet of paper P is sent to the separating unit 3, the paper P can be separated by the paper feed roller 8 and only the upper paper P can be sent to the transport unit 4.

The transporting section 4 is for transporting the sheets P supplied one by one from the separating section 3 to the printing section 5, and comprises a guide plate 10 and a roller pair 11. The roller pair 11 is a member that adjusts the conveyance of the paper P so that the ink is sprayed to an appropriate position on the paper P when the paper P is sent to the printing unit 5.

The printing unit 5 is for printing on the paper P supplied from the roller pair 11 of the transport unit 4, and is a carriage 14 having an ink jet head (ink ejection nozzle) 12 and an ink tank 13 mounted thereon. Carriage 14
A shaft 15 that slidably supports the carriage and a carriage are moved in a direction (main scanning direction, XY direction in FIG. 2) orthogonal to the conveyance direction of the paper P (sub scanning direction, Z direction in FIGS. 2 and 3). And a platen 17 that serves as a base for the paper P during printing. Here, the inkjet head 12 (hereinafter referred to as the head 12).
The structure of will be described. The head 12 ejects ink from the tip of a nozzle provided on the head 12. The nozzle is provided at the bottom of each of the channels arranged in the head 12. Specifically, the channel is pressurized for an extremely short time, and the ink in the pressurized channel is ejected as an ink droplet from a thin nozzle at the bottom of the channel. Next, the ink ejection operation will be described in detail. Since a piezoelectric material is used for the channel, the volume of the channel can be changed by applying a drive pulse to the channel, and thereby pressure is generated. That is, by selectively applying an ejection drive pulse or a non-ejection drive pulse to drive electrodes formed on both wall surfaces of the channel, a plurality of channels separated by the piezoelectric body are expanded / contracted to perform an ink ejection operation. I do.

The discharging section 6 is for discharging the printed paper P to the outside of the ink jet printer 1, and comprises an ink drying section (not shown), a discharging roller 18 and a discharging tray 19.

Next, the electric circuit of the ink jet printer 1 will be described with reference to the block diagram shown in FIG. As shown in FIG. 4, the electric circuit of the inkjet printer 1 includes a control unit 20, a head drive circuit 21, a carriage drive circuit 22, and a paper transport drive circuit 23.

The control unit 20 includes a CPU (Centra) not shown.
l Processing Unit) is a block that controls the operation of the inkjet printer 1 by performing calculations.
Memory 24, interface unit 25, image processing unit 2
6 and a drive system controller 27.

The memory 24 is a RAM (Random Access Mem).
memory) and a ROM (Read Only Memory). The RAM is mainly a storage means for temporarily storing the print data D, and the ROM is the inkjet printer 1.
It is a storage unit that stores the control program and various tables in advance.

The interface unit 25 receives a print command and print data D from the outside, and the image processing unit 2
6 and the drive system control unit 27. The image processing unit 26 is a block for performing various processes on the print data D input from the interface unit 25 and outputting the print data D to the head drive circuit 21. On the other hand, the drive system control unit 27 controls the drive system such as the carriage motor 28 and the paper transport motor 29 based on the print command and the print data D input from the interface unit 25. An output signal is derived to the carrier drive circuit 23.

The head drive circuit 21 is a circuit for driving the head 12, and the carriage drive circuit 22.
Is a circuit for driving the timing belt 10,
The paper transport drive circuit 23 is a circuit for driving the paper feed roller 8 and the discharge roller 16 for transporting the paper P.

In the above structure, the ink jet printer 1 prints by the following operation. First,
The control unit 20 makes a print request to the inkjet printer 1 based on a print command and print data D from the outside. The inkjet printer 1 that received the print request
The sheet P on the paper feed tray 7 is carried out from the paper feed unit 2 to the separation unit 3 by a pickup roller (not shown).

Next, the carried-out sheet P passes through the separating section 3 by the sheet feeding roller 8 and is sent to the conveying section 4.
In the transport unit 4, the sheet P is transported between the head 1 and the platen 17 by the roller pair 11.

In the printing section 5, ink is sprayed from the ink nozzles of the head 12 onto the paper P on the platen 13 in accordance with the image information. Specifically,
First, the carriage 14 moves in the main scanning direction. Along with this, the head 12 discharges the ink in the ink tank 13 onto the sheet P, which has been stopped on the platen 17, in accordance with the print data. In this way, the main scanning by the head 12 is performed. Then, the control unit 20 controls the head 12
An image is formed on the paper P by transporting the paper P by a predetermined pitch in the sub-scanning direction each time the main scanning of one line is completed.

The printed paper P passes through an ink drying section (not shown) and is discharged by the discharge roller 18 to the discharge tray 1.
It is discharged to 9. After that, the paper P is provided to the user as a printed matter.

Next, the head drive circuit 21 and the drive pulse generation circuit 4 for supplying power to the head drive circuit 21.
The configuration of 0 will be described based on FIGS. 1 and 5.

As shown in FIG. 1, drive pulse generating circuit 40 in the present embodiment includes at least two circuit configurations of rising waveform generating circuit 410 and falling waveform generating circuit 420.

The rising waveform generating circuit 410 is, as shown in FIG. 1, a Cockcroft-Walton type power supply circuit 411 (hereinafter abbreviated as Cockcroft circuit 411).
An initialization discharge circuit 412 connected to the Cockcroft circuit 411, a voltage application switch 413 connected between the Cockcroft circuit 411 and the initialization discharge circuit 412 and the head drive circuit 21, and a Cockcroft circuit 4
11 and the input pulse generation circuit 414 shown in FIG.

On the other hand, the falling waveform generating circuit 420
Includes a piezoelectric discharge circuit 415 connected to the rising waveform generation circuit 410 via the head drive circuit 21, and a regenerative circuit 416 connected to the piezoelectric discharge circuit 415.

As shown in FIG. 1, the head drive circuit 21 includes a piezoelectric body selection switch (switch) 31 as an analog switch, a piezoelectric body 32, a drive electrode 33, and a resistor 34. The piezoelectric body selection switch 31 is an analog switch for selecting the piezoelectric body 32 to which the drive pulse output from the Cockcroft circuit 411 is applied. The piezoelectric body 32 forms each channel for ejecting ink and separates each channel. The drive electrode 33 is provided on each piezoelectric body 32 and is an electrode for applying a drive pulse to each piezoelectric body 32. That is, the drive pulse is selectively applied to the piezoelectric body 32 via the drive electrode 33 by the piezoelectric body selection switch 31, and ink is ejected from the channel formed by the selected piezoelectric body 32.

In the actual head drive circuit 21, the piezoelectric switch 31, the piezoelectric body 32, the drive electrode 33, and the resistor 34 are actually provided by the number of nozzles of the head 12.
However, in the present embodiment, only one combination of the piezoelectric body switch 31, the piezoelectric body 32, the drive electrode 33, and the resistor 34 is described for convenience of explanation.

The rising waveform generating circuit 410 and the falling waveform circuit 420 serve as a power source for generating the driving pulse, and both are characteristic parts of the present embodiment.

In the present embodiment, the waveform of the drive pulse generated by the rising waveform generation circuit 410 is not a square pulse, but the lowermost stage of FIG. 6 in order to reduce the heat loss of the drive electrode 33 and its peripheral circuits. As shown in the waveform of the drive pulse voltage V _PZT , the pulse is a pulse (hereinafter referred to as a trapezoidal pulse) in which the voltage rises (rises) and falls (falls) in a stepwise manner. The rising waveform generation circuit 410 is a means for forming a rising portion of the trapezoidal pulse (a gradually rising period), and the falling waveform generation circuit 420 is a falling portion of the trapezoidal pulse (gradual falling). Period).

First, the rising waveform generation circuit 410 will be described.

The Cockcroft circuit 41 included in the rising waveform generating circuit 410 is, for example, as shown in FIG. 1, a combination of a rectifier (diode in this case) 43 and a capacitor 44 which are stacked in several stages to provide a stable high voltage. In the present invention, as shown in FIG. 1, the initialization discharge circuit 42 is connected in parallel at the lowermost stage and the uppermost stage. The Cockcroft circuit 41 can generate a stable high voltage by stepwise increasing the voltage charged in the capacitor 44 each time the power source is electrically switched.

Now, for the operation of the Cockcroft circuit 41,
The basic circuit shown in FIG. 7 (Cockcroft circuit 6
0) will be described. In addition, this embodiment shown in FIG.
The Cockcroft circuit 41 has two rectifiers 43
It has a configuration in which the combination with the capacitor 44 is stacked in four stages.
However, in FIG.
With a configuration in which the combination of the sink and the condenser is stacked in three stages
The amplitude V as the input power supply _0p-pAC power supply (commercial AC power
Source) 61 is used.

The Cockcroft circuit 60 shown in FIG.
A configuration of repeated combination of rectifier D and the capacitor C of each individual in three stages, where shall enter voltage ± V _0/2 from one of the AC power supply 61 for each cycle.

[0059] First, in the AC input amplitude V _0p-p, the first negative half cycle, the AC power source 61 is -V _0/2
Is input, the capacitor C1 is connected to V via the rectifier D1.
It is charged to _0/2. Subsequent positive half cycle, when the AC source 61 to enter the + V _0/2, the input voltage is superimposed with electric charge charged in the capacitor C1. That is,
The negative terminal of the capacitor C1 is charged to + V _0/2, the positive terminal is charged to + V _0. With this,
The capacitor C4 is charged so as to converge to + V ₀ via the rectifier D2.

[0060] Further, the second period of the negative half cycle, when the AC power source 61 to input -V _0/2, the input voltage is superimposed with the electric charge charged in the capacitor C4. That is, the minus terminal of the capacitor C4 is charged to + V _0/2, the positive terminal is charged to + V _0. here,
Since the positive terminal of the capacitor C1 becomes the reference potential, the capacitor C2 is charged so as to converge to + V ₀ via the rectifier D3. Therefore, the capacitor C2 has V ₀
Will be charged. Further, the second round of positive half cycle, when the AC source 61 to enter the + V _0/2, the input voltage is superimposed on a charge V ₀ which is charged in the capacitor C2. That is, the minus terminal of the capacitor C2 is charged to + V _0/2, the positive terminal is charged to + V _0. Accordingly, the capacitor C5 is connected to the rectifier D
It is charged via 4 to converge to + V ₀ .

Then, in the negative half cycle of the third cycle,
AC power supply 61 is -V₀ Input / 2, input voltage
Overlaps with the electric charge charged in the capacitor C5. You
That is, the negative terminal of the capacitor C5 is + V₀ To / 2
Charged and the positive terminal is + 3V ₀ It is charged to / 2. This
Then, the positive terminal of the capacitor C2 becomes the reference potential.
Therefore, the capacitor C3 is + 3V via the rectifier D3.₀ /
It is charged so as to converge to 2. In this way,
In the Crocroft circuit 60, ± V in 1 cycle₀ / 2
By inputting pressure, during the nth positive cycle,
N · (V₀ / 2) charge convergence
Can be made.

In this embodiment, as shown in FIG.
A Cockcroft circuit 411 having a configuration in which a combination of individual rectifiers 43 and capacitors 44 is stacked in several stages is applied, and when an AC voltage of ± V _co / 2 is input to the Cockcroft circuit 41, the output terminal of the uppermost stage is applied. Can obtain an output voltage of 4V _co .

Here, in the present invention, the input voltage V _co input to the input terminal 46 of the Cockcroft circuit 411 is a pulse voltage (referred to as the input pulse voltage V _in ). Therefore, the power supply means included in the drive pulse generation circuit 40 according to the present invention is the input pulse generation circuit 414 shown in FIG. This input pulse generation circuit 414
Makes it possible to change the pulse condition of the input pulse voltage V _in . Therefore, in the present invention, the Cockcroft circuit 4
11 is used as a drive pulse supply means, and in the Cockcroft circuit 411, the input pulse voltage V _in is input by appropriately changing the pulse condition from the input pulse generation circuit 414, and thus the drive pulse voltage V _PZT having a waveform having a rising portion is input. Is generated and supplied to the piezoelectric body 32.

Drive pulse generation circuit 40 according to the present invention
Inputs an arbitrary pulse train (input pulse) generated by the input pulse generation circuit 414 as the input pulse voltage V _in to the Cockcroft circuit 411. Moreover, the input pulse generation circuit 414 can change the pulse condition based on a predetermined condition.

Therefore, the output voltage of the Cockcroft circuit 411 can be transiently increased and applied as a drive pulse having a rising portion to the piezoelectric body 32, and the slope of the rising portion of the drive pulse voltage V _PZT can be changed. it can. Therefore, it is possible to obtain a more appropriate drive pulse according to various conditions, and it is possible to suppress heat loss in the peripheral circuit of the piezoelectric body 32.

In the present invention, the input pulse generation circuit 41
The pulse conditions that can be changed in No. 4 are not particularly limited, but preferably include the number of pulses, frequency or pulse width. In this embodiment, an example of changing the number of pulses will be described.

Input pulse generation circuit in the present embodiment
As shown in FIG. 5A, the reference numeral 414 denotes a comparator (Fig.
Medium CMP) 441, AND gate 442, capacitor 4
43, resistors 444, 445, 446, 447, 448
Input pulse voltage V_inThe number of pulses in
It is like this. Specifically, the comparator 441
Reference potential V from the positive input terminal_refBut on the minus side
Drive voltage V from the power terminal _PZTIs being input
It Resistors 444 and 445 are connected to the negative input terminal.
Has been continued.

The output terminal of the comparator 441 is AND
It is connected to one of the input terminals of the gate 442. AN
The clock signal CK is applied from the other input terminal of the D gate 442. The AND gate 442 also receives the input timing signal SW1 of the voltage application switch 413 (the uppermost signal in FIG. 6). AND gate 442
The output terminal of is connected to the capacitor 443, is grounded via the resistor 446, and is connected to the DC power supply V _cc via the resistor 447. The capacitor 443 is grounded via the resistor 448 and connected to the input terminal 46 of the Cockcroft circuit 411 via the terminal 47. With this configuration, the number of pulses can be changed as described later.

The detailed functions and actions of the pulse generation circuit 414 in the present embodiment will be described together with the overall operation description of the drive pulse generation circuit 40 in the present embodiment.

Rising waveform generation circuit 4 in the present invention
10 is provided with an initialization discharge circuit 412 that discharges the charges of the capacitors 44 ... Included in the Cockcroft circuit 411. The initialization discharge circuit 412 includes a switch 421, an NPN type transistor 422, a resistor 423.
424, the base of the transistor 422 is connected to the 5V line (line in the figure) via the resistor 423 and the switch 421.
The collector of 22 is connected to the uppermost output terminal of the Cockcroft circuit 411 via the resistor 424, and the emitter is connected to the lowermost stage.

In the initialization discharge circuit 412, the input pulse voltage V _in is input from the input pulse generation circuit 414,
After the drive pulse voltage V _PZT is raised by the Cockcroft circuit 411, the switch 421 is turned on to discharge the electric charge of the capacitors 44 ... And the Cockcroft circuit 41.
4 can be initialized. Therefore, when the input pulse voltage V _in is newly input from the input pulse generation circuit 414, the Cockcroft circuit 411 reliably outputs the drive pulse voltage V _PZT based on the newly input input pulse voltage V _in. Can be launched. therefore,
The drive pulse voltage V _PZT having the rising portion can be continuously generated, and accurate rising control can be performed even if the gradient of the rising portion is appropriately changed.

The drive pulse voltage V _PZT output from the Cockcroft circuit 411 is applied to the piezoelectric body 32 of the head drive circuit 21, and its application control is performed by the voltage application switch 413. Voltage application switch 413
Is a switch 431, a MOSFET-P type transistor 432, a Schottky type rectifier (diode) 43.
It is composed of 3. The gate of the transistor 432 is connected to the switch 431, the drain is connected to the Cockcroft circuit 411 (and the initialization discharge circuit 412), and the source is connected to the anode of the rectifier 433.

The switch 431 of the voltage application switch 413 is turned on / off by the input timing signal SW1 shown in the uppermost stage of FIG. 6, and the cathode of the rectifier 433 is connected to the head drive circuit 21. Therefore, based on the input timing signal SW1, the transistor 432 applies the drive pulse voltage V _PZT from the Cockcroft circuit 411 to the head drive circuit 21.

Next, the falling waveform generation circuit 420 will be described.

The piezoelectric discharge circuit 415 included in the falling waveform generation circuit 420, based on the reference potential V _ref ,
The electric charge accumulated in the piezoelectric body 32 is discharged. In the present embodiment, as shown in FIG. 1, the comparator 451 and the PNP
Type transistor 452, PNP type transistor 45
3 and resistors 454, 455, 456, and 457. The base of the transistor 452 is connected to the resistor 454, the collector is connected to the resistors 455 and 456 and the negative input terminal of the comparator 451, and the emitter is grounded. The base of the transistor 453 is connected to the resistor 457, the emitter is connected to the head drive circuit 21 and the resistor 456, and the collector is connected to the regeneration circuit 416 described later. The transistor 453 is connected to the output terminal of the comparator via the resistor 457.

Switch in voltage application switch 413
As the transistor 431 is turned on, the transistor 452
Driving the piezoelectric body 32 to the minus input terminal of the generator 451
Voltage V_PZT Enter. In the comparator 451, the
Input terminal to the reference potential V _ref Has been entered,
Dynamic voltage V_PZT And reference potential V_ref And are compared. Standard electricity
Rank V_ref Drive voltage V_PZT The higher the
Transistor 4 connected to the output terminal of the data 451
At 53, the electric charge of the piezoelectric body 32 is discharged from the head drive circuit 21.
To discharge.

[0077] Therefore, in the piezoelectric discharge circuit 415, as shown in the second stage from the top in FIG. 6, the reference potential V _ref
If a target waveform having an arbitrary gradient is used as the input, this target waveform is input to the comparator 451, and chopping is performed by the transistor 452 so that the gradient is in accordance with this input value, the drive pulse voltage V _PZT can be set to an arbitrary gradient. You can stop at. As a result, by combining with the Cockcroft circuit 411, the drive pulse applied to the piezoelectric body 32 can be made into a trapezoidal pulse having a rising portion and a falling portion (V _PZT at the bottom of FIG. 6).

The falling waveform generating circuit 420 includes:
Further, a regenerative circuit 416 for collecting the electric charge accumulated in the piezoelectric body 32 is provided. In the present embodiment, as shown in FIG. 1, it is composed of an inductance element 461, a rectifier (diode) 462, and an electrolytic capacitor 463.

Specifically, the transistor 453 of the piezoelectric discharge circuit 415 is provided on one side of the inductance element 461.
And a 5 V line and an electrolytic capacitor 463 are connected to the other. The inductance element 46 is provided on one side of the electrolytic capacitor 463.
The 1.5V line is connected, and the other side is connected to the rectifier 462 and grounded. The rectifier 462 has an anode connected to the electrolytic capacitor 463 and a cathode connected to the inductance element 461 (and the piezoelectric body discharge circuit 415).
An electric current flows from 61 to the electrolytic capacitor.

Therefore, in the regeneration circuit 416, the electric charge of the piezoelectric body 32 discharged by the piezoelectric body discharge circuit 415 can be collected in the electrolytic capacitor 463. The collected charges can be returned to the DC power supply _Vcc .
Therefore, the electric energy for driving the piezoelectric body 32 is effectively used, and the power consumption of the drive pulse generation circuit 40 can be reduced.

Moreover, the inductance element 461 is
Can be regarded as being provided between the piezoelectric body 32 and the regenerative circuit 416, so that the slope of the rising portion or the falling portion of the drive pulse voltage V _PZT applied to the piezoelectric body 32 can be arbitrarily changed. Even in the case, the change in the electric potential due to the rise / fall can be buffered and smoothed. Therefore, it is possible to suppress or prevent the loss that occurs when the drive pulse voltage V _PZT is applied, and it is possible to further reduce the power consumption of the drive pulse generation circuit 40.

If a resistor is used in place of the inductance element 461, the electric charge collected will be lost due to heat generation of the resistor, which is not preferable from the viewpoint of low power consumption. In addition, the inductance element 4
When the transistor 453 and the electrolytic capacitor 463 are directly connected without providing 61, it is possible to recover the charge without loss, but since a surge current flows,
Depending on the situation, the transistor 453 and the electrolytic capacitor 463 may be damaged, which is not preferable.

Next, based on the timing chart shown in FIG. 6, the drive pulse generation circuit 40 in the present embodiment.
The overall operation of the above will be described. In FIG. 6, time is the horizontal axis,
With the magnitude of the potential as the vertical axis, the input timing signal SW1, the reference potential V _ref , the input pulse voltage V _in , the discharge pulse signal Q and the discharge signal DCH used in the drive pulse generation circuit 40 in the present embodiment, The relationship between the output voltage V _CP output from the Cockcroft circuit 411 and the drive pulse voltage V _PZT is shown.

First, the switch 431 of the voltage application switch 413 is turned on based on the uppermost input timing signal SW1. At the same time as this turning on, the input pulse generation circuit 4
14 generates an input pulse as shown in the third stage of FIG. 6, for example, and inputs it to the Cockcroft circuit 411. At the same time, as shown in the fifth row of FIG. 6, the discharge signal DCH is stopped, and the discharge of the piezoelectric body 32 by the piezoelectric body discharge circuit 415 is stopped. Therefore, the Cockcroft circuit 41
1 output voltage V _out (driving pulse voltage V
_PZT ) is surely applied to the piezoelectric body 32.

Here, in the input pulse generation circuit 414 shown in FIG. 5A, the target waveform prepared in advance, that is, the reference potential V _ref and the drive pulse voltage V _PZT shown in the second stage of FIG. It is input to 441 and these are compared. Reference potential V _{re f} is the driving pulse voltage V _PZT
AND gate 442 has clock signal C
Output K. An input pulse is generated based on the clock signal CK and input to the Cockcroft circuit 411.

Here, the change in the number of pulses by the input pulse generation circuit 414 will be described. The basic operation of the Cockcroft circuit 411 is to raise the voltage by the peak voltage of the alternating current in one cycle of the alternating current. Therefore, when the number of pulses is changed as the input pulse condition, as shown in FIG. 5B, if the reference potential V _ref is not reached, one pulse of the input pulse voltage V _in is output and the reference potential V _{ref is} output. If it is above, the pulse of the input pulse voltage V _in at that time is thinned out. As a result, the frequency of a constant pulse width at the time of turning on can be changed, and the drive pulse voltage V _PZT can be changed. Note that FIG.
The change in the drive pulse voltage V _PZT in (b) is actually smooth, but is shown as a large step for convenience of explanation.

Then, the output potential V _CP output from the Cockcroft circuit 411 rises so as to have a predetermined gradient as shown in the second stage from the bottom in FIG. Then, when the generation / input of the input pulse is stopped, the rising is stopped and becomes constant, and further, the output potential V _CP is lowered by turning off the input timing signal SW1,
The drive voltage input to the piezoelectric body 32, that is, the drive pulse voltage V _PZT (output voltage V _out ) is maintained at a constant value.

That is, in the present embodiment, the input pulse generation circuit 414 changes the number of pulses (that is, pulse condition) by feeding back the drive pulse voltage V _PZT for driving the piezoelectric body 32. It is possible. Therefore, the drive pulse voltage V _PZT is detected and reflected _in the generation of the input pulse voltage V _in , and the accuracy of the drive pulse voltage V _PZT can be improved as compared with the open loop type circuit.

After that, for the transistor 453,
By inputting the pulse signal Q shown in the 4th stage of 6,
Reference potential V input to the palette 451_ref Along the gradient of
Drive pulse voltage V_PZT Is chopped.
As a result, the drive pulse voltage V _PZT Is the reference potential V_ref No
As it goes down from a certain voltage value. As a result, the trapezoid
Pulse is formed.

As described above, in the drive pulse generation circuit and the ink jet recording apparatus according to the present invention, the drive voltage of the trapezoidal pulse can be generated by the Cockcroft-Walton type power supply circuit and the piezoelectric discharge circuit. Therefore, the drive pulse is not sharply raised or lowered, so that the heat generation loss in the peripheral circuit of the piezoelectric body can be further suppressed.

Further, since the input pulse generation circuit can change the pulse condition, it is possible to change the slope of the rising portion. That is, it becomes possible to control the output waveform by the input pulse in which the pulse condition is changed. Therefore, it becomes possible to obtain a more appropriate drive pulse according to various conditions, and it is possible to further suppress heat loss in the peripheral circuit of the piezoelectric body.

The above-described present embodiment does not limit the scope of the present invention, and various modifications can be made within the scope of the present invention. Therefore, the configuration of each circuit is
It goes without saying that the configuration is not limited to that shown in FIG. 1 and FIG.

[Second Embodiment] The following will describe another embodiment of the present invention in reference to FIG.
For convenience of explanation, members having the same functions as those used in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the first embodiment, the capacitance of the capacitor in the Cockcroft circuit 411 is not particularly limited, but in the present embodiment, the capacitance of the capacitor with respect to the capacitance of the piezoelectric body 32 should be defined. Thus, the Cockcroft circuit 411 is made easier to initialize.

That is, in the drive pulse generating circuit 40 according to the present embodiment and the ink jet recording apparatus 1 including the same, the number of stages of the Cockcroft circuit 411 included in the rising waveform generating circuit 410 is n, and the cockcroft circuit 411 is included. When the individual capacitance of the capacitor 44 is C _C and the capacitance of the piezoelectric body 32 included in the head drive circuit 21 is C _P , the following relational expression (1) C _P ≧ 4C _C / n.・ ・ (1) is established.

The relational expression (1) will be specifically described. As shown in FIG. 8A, the Cockcroft circuit 41
1, a grounded power source 62, an input side capacitor 63 connected to the power source 62, and an input side capacitor 63.
It is replaced with a simplified model consisting of the output side capacitor 64 which is connected to and grounded.

In this case, the input side capacitor 63 is connected to the input side (input terminal 46 in the Cockcroft circuit 411).
The output side capacitor 64 corresponds to the output side (head drive circuit 21 side) of the Cockcroft circuit 411 (see FIG. 1A). In (a), it corresponds to the capacitor 44) connected in series on the right side and the piezoelectric body 32 included in the head drive circuit 21. Therefore, the capacitance C _S of the input side capacitor 63 is a series combination of the capacitance C _C of the input side capacitor 44, and the capacitance C _P ′ of the output side capacitor 64 is the static capacitance of the output side capacitor 44. The capacitance C _C and the capacitance C _P of the piezoelectric body 32 are combined in series.

Therefore, the peak value of the input pulse is set to V _OP ,
When the initial charge of the input side capacitor 63 is V _CO , the piezoelectric body 3
When the initial charge of 2 is V _PO , the capacitor 44 is charged in the negative cycle, and the charging current flowing into the piezoelectric body 32 in the positive cycle to which the initial charge is given is a function I (t) of time t. , The following equation (2) is established.

[0099]

[Equation 1] However, in the above formula (2), assuming that the number of stages of the Cockcroft circuit 411 is n, C _S = C _C / n and C _P '
= C _P + C _S.

Here, the charging voltage of the piezoelectric body 32 is set to
the function V of t_C(t), this V _C(t) is the above formula
From (2), it is obtained as the following equation (3).

[0101]

[Equation 2] Furthermore, from the above formula (3), at the start of charging the piezoelectric body 32,
Alternatively, immediately after the start of charging, the charging voltage V _{C of the} piezoelectric body 32
The relationship of the following equation (4) is established between (t) and the electrostatic capacitance C _S of the input side capacitor 63 and the electrostatic capacitance C _P ′ of the output side capacitor 64.

[0102]

[Equation 3] The relationship of the above formula (4) is as shown in FIG. 8B, in which the piezoelectric body 3 with respect to the electrostatic capacitance C _S of the input side capacitor 63.
The normalized capacitance C _P / C _S that is the ratio of the capacitance C _P of 2 is taken as the horizontal axis, and the capacitance C _S of the input side capacitor 63 and the capacitance C _P 'of the output side capacitor 64 are Sum C _S +
It is represented by a graph with the normalized voltage C _S / (C _S + C _P ) which is the ratio of the capacitance C _S to C _P 'as the vertical axis.

As described above, since C _S = C _C / n, the normalized capacity C _P / C _S = C _P / (C _C /
n). Therefore, as shown in FIG. 8B, in the Cockcroft circuit 411, as the capacitance C _P of the piezoelectric body 32 as a load or the number of stages n of the Cockcroft circuit 411 increases, one cycle of input pulse The charging voltage will decrease. However, it can be seen that when the normalized capacity C _P / C _S = 4 is exceeded, the rate of decrease decreases. Therefore, in the Cockcroft circuit 411, the conditions for realizing efficient charging,
Alternatively, the above relational expression (1) can be obtained as a condition for ensuring a wide charge dynamic range.

Thus, the capacitance C of the capacitor 44 is
_{If the} above relational expression (1) is established between C and the electrostatic capacitance C _P of the piezoelectric body 32, even if the electric charge remains in the capacitor 44 of the Cockcroft circuit 411 during the previous driving, the electric charge is It becomes possible for the piezoelectric body 32 to absorb, and the Cockcroft circuit 411 can be initialized every time it is driven. Therefore, it becomes possible to reliably generate the predetermined drive pulse voltage V _PZT even when the input pulse voltage V _in which is different for each driving is used. In addition, the first embodiment
The initialization can be made more reliable by combining with the initialization discharge circuit 412 in FIG.

The number of stages n of the Cockcroft circuit 411 is n.
If the voltage is low, a high voltage value can be obtained by applying it once.
2 is applied, but the number of stages n is large and the capacitor 44
If the capacitance is smaller than that of the piezoelectric body 32, the voltage value applied to the piezoelectric body 32 can be suppressed to a low value by one application. Therefore, it is very preferable that the number of stages n of the Cockcroft circuit 411 is 4 or more.

[Third Embodiment] The following will describe still another embodiment of the present invention with reference to FIGS. 9 and 10. For convenience of explanation, the first embodiment
Alternatively, members having the same functions as the members used in 2 are given the same member numbers, and the description thereof will be omitted.

In the first embodiment, the input pulse generation circuit 414 can change the number of pulses as the pulse condition, but in the present embodiment, the frequency or the pulse width can be changed as the pulse condition.

Specifically, as shown in FIG. 9A, the input pulse generation circuit 417 in the present embodiment includes an error amplifier 471 and a pulse width modulator (PWM in the figure) 47.
2, buffer 473, capacitor 474, resistor 475
It is composed of 476/477/478/479.

The reference potential V _ref is input from the plus side input terminal of the error amplifier 471, and the drive pulse voltage V _PZT is input from the minus side input terminal. Resistors 474 and 475 are connected to the negative side input terminal. The output terminal of the error amplifier 471 is the pulse width modulator 4
The pulse width modulator 472, which is connected to 72, modulates the pulse width so that the pulse width is widened based on the input of the clock signal CK when a positive error occurs in the error amplifier 471.

The output terminal of the pulse width modulator 472 is connected to the buffer 473, and the input timing signal SW1 of the voltage application switch 413 (see FIG. 6) is connected to the buffer 473.
Signal of the uppermost stage) is also input. The output terminal of the buffer 473 is connected to the capacitor 474, and
It is grounded via a resistor 477 and is connected to a DC power supply V _cc via a resistor 478. The capacitor 474 is a resistor 47
It is grounded via 9 and is connected to the input terminal 46 of the Cockcroft circuit 411 via a terminal 47.

Alternatively, as shown in FIG. 10A, the input pulse generation circuit 418 according to the present embodiment includes an error amplifier 481 and a variable frequency oscillator (VFO in the figure) 48.
2, buffer 483, capacitor 484, resistor 485
It may be composed of 486/487/488/489.

The reference potential V _ref is inputted from the plus side input terminal of the error amplifier 481, and the drive pulse voltage V _PZT is inputted from the minus side input terminal. Resistors 484 and 485 are connected to the negative input terminal. The output terminal of the error amplifier 471 is the pulse width modulator 4
72 is connected to the variable frequency oscillator 482,
When a positive error occurs in the error amplifier 481, the frequency is increased based on the input of the clock signal CK to oscillate so as to follow the rising of charging.

The output terminal of the variable frequency oscillator 482 is connected to the buffer 483, and the input timing signal SW1 (the uppermost signal in FIG. 6) of the voltage application switch 413 is also input to the buffer 483. The output terminal of the buffer 483 is connected to the capacitor 484, grounded via the resistor 487, and connected to the DC power supply V _cc via the resistor 488. The capacitor 484 is grounded via the resistor 489 and connected to the input terminal 46 of the Cockcroft circuit 411 via the terminal 47.

The input pulse generation circuit 417 changes the pulse width so that the input pulse generation circuit 4 is changed.
18 is an output voltage V by changing the frequency.
_out i.e. it is possible to change the rising slope and reaches a voltage of the driving pulse voltage V _PZT.

The input pulse generation circuits 417 and 41
The change of the pulse condition by 8 will be described. As described in the first embodiment, the basic operation of the Cockcroft circuit 411 is to raise the voltage by the peak voltage of the alternating current in one cycle of the alternating current.

In the case of the pulse generation circuit 417, the pulse width is changed. Therefore, as shown in FIG. 9B, in the input pulse generation circuit 417, the charging time according to the reference potential V _ref is set shorter than the charging time to the peak (that is, the pulse of the input pulse voltage V _in ). Change the width). As a result, the drive pulse voltage V _PZT that rises in one cycle including the discharging time is controlled to a voltage smaller than the peak, and the drive pulse voltage V _PZT is changed.

On the other hand, in the case of the pulse generation circuit 418,
Change the frequency. Therefore, the Cockcroft circuit 41
According to the basic operation of No. 1, as shown in FIG. 10B, by changing the frequency of the input pulse voltage V _{in to} a frequency that matches the slope of the reference potential V _ref , the drive pulse voltage V in
Change _PZT . 9B and 10B, the change of the drive pulse voltage V _PZT is actually smooth, but is shown as a large step for convenience of explanation.

Therefore, the output waveform can be controlled by changing any of the pulse conditions (number of pulses (first embodiment), frequency, and pulse width) in the input pulse voltage. Therefore, it becomes possible to obtain a more appropriate drive pulse according to various conditions, and it is possible to further suppress heat loss in the peripheral circuit of the piezoelectric body.

A Cockcroft-Walton type power supply circuit is known as a technique for increasing the voltage, and as an example in which this Cockcroft-Walton type power supply circuit is used as a high-voltage power supply for an ink jet head, Japanese Patent Laid-Open No. 2000-2000 is used.
Japanese Patent Publication No. 127409 discloses a recording device using an electro-sensitive movable medium. The above-mentioned publication uses a Cockcroft-Walton type power supply circuit for a high-voltage power supply circuit of an ink jet recording apparatus using an electro-sensitive operation medium, and outputs one high voltage from one Cockcroft-Walton type power supply circuit. I am letting you.

On the other hand, in the ink jet recording apparatus according to the present invention, first, a Cockcroft-Walton type power supply circuit is used as a power supply circuit of the ink jet recording apparatus using a piezoelectric body whose volume changes by applying a driving pulse. In addition, in order to form a trapezoidal pulse, by applying an input pulse to the Cockcroft-Walton type power supply circuit so that the pulse condition can be changed, a rising portion is formed and a piezoelectric body is formed. A big difference is that the discharge means is used to form the falling portion.

According to the above arrangement, since the Cockcroft-Walton type power supply circuit is applied to the power supply circuit of the ink jet recording apparatus using the piezoelectric material, it is possible to transiently use the output of the Cockcroft-Walton type power supply circuit. Thus, it is possible to efficiently take out while gradually increasing the voltage (reached voltage) that is an integral multiple of the specific voltage. Further, since this Cockcroft-Walton type power supply circuit is used in combination with the piezoelectric discharging means, it is possible to gradually decrease the voltage which is an integral multiple of the specific voltage.

Moreover, the voltage rise and the ultimate voltage value can be easily realized only by changing the pulse condition of the input pulse voltage, and the voltage drop is also realized by the chopping by the transistor and the smoothing of the inductance element. can do. Further, even if the input of the voltage drop is analog, since the voltage is low and the current is low, it can be easily created by integrating digital oscillation.

Conventionally, a DC-DC converter has been used to extract a voltage higher than a specific voltage. DC
Since the DC converter is composed of a capacitor, a resistor, a coil, and a switching transistor and has a complicated circuit, the power loss tends to increase. on the other hand,
The Cockcroft-Walton type power supply circuit used in the present invention basically has a very simple configuration including a capacitor and a rectifier, so that power loss can be suppressed as compared with a DC-DC converter.

Further, according to the above structure, in the power supply circuit of the ink jet recording apparatus which requires a plurality of voltages, the power supply circuit has a very simple circuit structure.

That is, conventionally, in order to generate a plurality of specific voltages, it is necessary to prepare a plurality of power supply circuits unique to each. As a result, the power supply circuit of the inkjet recording apparatus has become very complicated. On the other hand, with the above configuration, since a plurality of voltages can be taken out from a single power supply circuit, the power supply circuit has a very simple circuit configuration.

Further, the drive pulse generating circuit according to the present invention is composed of a simple diode without using an analog switch which is an active element. Therefore, as compared with a charge pump used for driving a liquid crystal having a small load capacity, it can be suitably used for high-speed discharge driving of a piezoelectric body having a large capacity load such as driving an inkjet head. In particular, the drive pulse generation circuit according to the present invention is
It is suitable for applying a pulsed large load current, and is also suitable for avoiding an output tap by parallel / parallel switching when a charge pump is used.

In particular, when the Cockcroft-Walton type power supply circuit is used, the first advantage is that by changing the pulse conditions such as the number of pulses, frequency and pulse width,
The point is that the ultimate voltage can be changed subtly. In the charge pump, the voltage can be changed only at each originally set stage unless a separate adjusting circuit is provided. Moreover, when the voltage is changed, the number of stages is changed.

A second advantage is that the Cockcroft-Walton type power supply circuit can generate a higher voltage than the power supply. If a Cockcroft-Walton type power supply circuit is used, a high drive voltage can be generated while the power supply remains low, but a charge pump cannot generate a drive voltage higher than the power supply voltage. Therefore, the present invention using the Cockcroft-Walton type power supply circuit can be preferably used in an inkjet recording apparatus.

The present invention is not limited to the above-described embodiments, but various modifications can be made within the scope of the claims, and the technical means disclosed in the different embodiments, respectively. It goes without saying that the embodiments obtained by appropriately combining the above are also included in the technical scope of the present invention.

[0130]

As described above, the drive pulse generating circuit according to the present invention includes the input pulse generating means for generating the input pulse voltage, and the drive pulse voltage generated by the input of the input pulse voltage to the piezoelectric body. A driving pulse supply means for supplying the driving pulse, and a Cockcroft-Walton type power supply circuit is used as the driving pulse supply means, and the input pulse generating means allows the pulse condition of the input pulse voltage to be changed. is there.

Therefore, in the above configuration, the Cockcroft-Walton type power supply circuit can output the input voltage of an arbitrary pulse train as a rising waveform having an arbitrary slope. Therefore, the drive pulse does not rise steeply, so that it is possible to suppress the heat generation loss in the peripheral circuit of the piezoelectric body.

The drive pulse generating circuit according to the present invention is, in addition to the above configuration, further provided with an initializing discharge means for discharging the electric charge of the capacitor included in the Cockcroft-Walton type power supply circuit.

Therefore, in the above structure, the initializing discharge means allows the capacitor to be in a state in which no electric charge is accumulated at the time when the input pulse voltage is newly input. Therefore, the Cockcroft-Walton type In the power supply circuit, the drive pulse voltage can be reliably raised based on the newly input input pulse voltage.
Therefore, it is possible to continuously generate the drive pulse voltage having the rising portion, and it is possible to accurately perform the rising control even if the gradient of the rising portion is appropriately changed.

The drive pulse generating circuit according to the present invention is, in addition to the above configuration, further provided with a piezoelectric discharge means for discharging the electric charge accumulated in the piezoelectric body based on the reference potential.

Therefore, in the above configuration, the drive voltage of the trapezoidal pulse can be generated by combining with the Cockcroft-Walton type power supply circuit. for that reason,
Since the drive pulse is not steeply raised or lowered, it is possible to further suppress the heat generation loss in the peripheral circuit of the piezoelectric body.

In addition to the above configuration, the drive pulse generating circuit according to the present invention has a configuration in which the pulse condition changed in the input pulse generating means is the number of pulses, frequency or pulse width.

Therefore, in the above configuration, the output waveform can be controlled by changing any of the pulse conditions. Therefore, it is possible to obtain a more appropriate drive pulse according to various conditions, and it is possible to further suppress heat loss in the peripheral circuit of the piezoelectric body.

In addition to the above configuration, the drive pulse generating circuit according to the present invention has a configuration in which the input pulse generating means changes the pulse condition by feeding back the drive pulse voltage.

Therefore, in the above configuration, the input pulse generating means detects the drive pulse voltage and reflects it on the generation of the input pulse voltage. Therefore, it is possible to generate an input pulse corresponding to the drive pulse, and it is possible to improve the accuracy of the drive pulse voltage as compared with the open loop type circuit.

The drive pulse generating circuit according to the present invention has a structure which, in addition to the above structure, further includes a regenerating means for recovering the charges accumulated in the piezoelectric body.

Therefore, in the above-mentioned structure, the electric charge accumulated in the piezoelectric body can be recovered by the regenerating means and returned to the DC power source. Therefore, the electric energy for driving the piezoelectric body is effectively used, and it is possible to reduce the power consumption of the drive pulse generation circuit.

The drive pulse generating circuit according to the present invention has a structure in which an inductance element is further provided between the piezoelectric body and the regeneration means in addition to the above structure.

Therefore, in the above configuration, even if the slope of the rising portion or the falling portion of the drive pulse voltage is arbitrarily changed, it is possible to buffer the change in the potential due to the rise and the fall. Therefore, it is possible to suppress or prevent the loss that occurs at the time of application, and it is possible to further reduce the power consumption of the drive pulse generation circuit.

In the drive pulse generating circuit according to the present invention, in addition to the above configuration, the number of stages of the Cockcroft-Walton type power supply circuit is n, and the individual capacitances of the capacitors included in the Cockcroft-Walton type power supply circuit are set. C
_{When C} and the electrostatic capacity of the piezoelectric body is C _P , the following relational expression C _P ≧ 4C _C / n is established.

Therefore, in the above configuration, even when the electric charge remains in the capacitor included in the Cockcroft-Walton type power supply circuit at the time of the previous driving, the electric charge can be absorbed by the piezoelectric body, and it is possible to drive each time the driving is performed. The Cockcroft-Walton type power supply circuit can be initialized.
Therefore, it is possible to reliably generate the predetermined drive pulse voltage even if the input pulse voltage that is different for each driving is used.

As described above, the ink jet recording apparatus according to the present invention includes the drive pulse generating circuit having the above-described structure,
An ink discharge nozzle using a piezoelectric body that changes its shape by the action of electric energy, and by applying a drive pulse output from the drive pulse generation circuit to the piezoelectric body, the action of pressure generated in the nozzle The ink is ejected by means of.

Therefore, with the above configuration, it is possible to generate a drive voltage of a pulse having at least a rising portion, preferably a trapezoidal pulse. Therefore, the drive pulse does not rise or fall sharply, and heat loss in the peripheral circuit of the piezoelectric body can be suppressed. In addition, the configuration of the drive pulse generation circuit can be simplified and the cost can be reduced. by this,
It is possible to provide an inkjet recording device that operates reliably with a simple configuration.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a drive pulse generation circuit according to the present invention.

FIG. 2 is a perspective view showing an ink jet recording apparatus in which the drive pulse generating circuit shown in FIG. 1 is incorporated.

FIG. 3 is a perspective side view showing an inkjet recording apparatus in which the drive pulse generation circuit shown in FIG. 1 is incorporated.

FIG. 4 is a block diagram showing a circuit configuration in the inkjet recording apparatus shown in FIGS. 2 and 3.

5A is a circuit diagram showing an example of an input pulse generation circuit included in the drive pulse generation circuit shown in FIG.
(B) is a graph which shows typically the change of the drive pulse voltage by the input pulse generation circuit shown in (a).

6 is an input timing signal, a reference potential, an input voltage, a discharge pulse signal and a discharge signal used in the drive pulse generation circuit shown in FIG. 1, an output voltage and a drive pulse output from a Cockcroft-Walton type power supply circuit. It is a timing chart which shows the relationship of a voltage.

7 is a circuit diagram showing a commercial AC power supply and a Cockcroft-Walton type power supply circuit used in the drive pulse generation circuit shown in FIG.

8A is a circuit diagram showing a case where the Cockcroft-Walton type power supply circuit is replaced with a simplified model in the drive pulse generation circuit shown in FIG. 1, and FIG.
Is the Cockcroft /
7 is a graph showing a relationship between a normalized voltage and a normalized capacity of a Walton power supply circuit.

9A is a circuit diagram showing another example of the input pulse generation circuit shown in FIG. 5A, and FIG. 9B is a circuit diagram showing a driving pulse voltage by the input pulse generation circuit shown in FIG. It is a graph which shows change typically.

10A is a circuit diagram showing still another example of the input pulse generation circuit shown in FIG. 5A, and FIG.
6 is a graph schematically showing a change in drive pulse voltage by the input pulse generation circuit shown in (a).

[Description of Reference Signs] 1 inkjet printer (inkjet recording device) 12 inkjet head (ink ejection nozzle) 21 head drive circuit 32 piezoelectric body 40 drive pulse generation circuit 44 capacitor 60 Cockcroft-Walton type power supply circuit 61 AC power supply (commercial AC power supply) 410 rising waveform generation circuit (rising waveform generation means) 411 Cockcroft-Walton type power supply circuit (driving pulse supply means) 412 initialization discharge circuit (initialization discharge means) 414 input pulse generation circuit (input pulse generation means) 415 piezoelectric discharge Circuit (piezoelectric discharge means) 416 Regeneration circuit (regeneration means) 461 Inductance element

Claims (9)

[Claims] 1. A drive pulse generating circuit used in an ink jet recording apparatus for printing on a recording medium by utilizing the effect of electromechanical conversion in a piezoelectric body, and input pulse generating means for generating an input pulse voltage, and the input pulse. Drive pulse supply means for generating a drive pulse voltage by inputting a voltage and supplying it to the piezoelectric body. As the drive pulse supply means, a Cockcroft-Walton type power supply circuit is used and the input pulse generation means. The drive pulse generation circuit is characterized in that the pulse condition of the input pulse voltage can be changed. 2. The initialization discharge means for discharging the electric charge of the capacitor included in the Cockcroft-Walton type power supply circuit is further provided.
The drive pulse generation circuit according to. 3. The drive pulse generation circuit according to claim 1, further comprising piezoelectric discharge means for discharging charges accumulated in the piezoelectric body based on a reference potential. 4. The pulse condition is number of pulses, frequency or pulse width.
The drive pulse generation circuit according to. 5. The drive pulse generation circuit according to claim 1, wherein the input pulse generation means changes the pulse condition by feeding back the drive pulse voltage. . 6. The drive pulse generation circuit according to claim 1, further comprising a regeneration means for recovering the electric charge accumulated in the piezoelectric body. 7. Further, between the piezoelectric body and the regeneration means,
7. The drive pulse generation circuit according to claim 6, further comprising an inductance element. 8. The number of stages of the Cockcroft-Walton type power supply circuit is n, the capacitance of each capacitor included in the Cockcroft-Walton type power supply circuit is C _C, and the capacitance of the piezoelectric body is C _P The drive pulse generating circuit according to claim 1, wherein the following relational expression C _P ≧ 4C _C / n is satisfied. 9. A drive pulse generation circuit comprising: the drive pulse generation circuit according to any one of claims 1 to 8; and an ink ejection nozzle using a piezoelectric body that changes its shape by the action of electric energy. An ink jet recording apparatus, characterized in that the ink is ejected by the action of the pressure generated in the nozzle by applying a drive pulse output by the piezoelectric body to the piezoelectric body.