JP2002103603A - Driving circuit of ink jet recording head, recorder having that circuit, and driving method of ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption by utilizing electric energy stored in a piezoelectric element by a driving voltage effectively. SOLUTION: Using a buffer circuit 3 outputting a voltage being applied to a piezoelectric element 5, and two capacitors C2 and C3 having capacitances larger than that of the piezoelectric element, operation of switches S2-S4 and the buffer circuit 3 is switched through a control circuit 7 such that the capacitors are connected in parallel and under a first state where the output therefrom is inputted to the buffer circuit 3, the capacitors are charged. Subsequently, the capacitors are connected in series and a switching is made to a second state where the output therefrom is inputted to the buffer circuit 3 and the piezoelectric element 5 is driven. A third state where signals passed through the buffer circuit 3 are inputted in parallel into the capacitors is thereby brought about and charges stored in the piezoelectric element 5 are stored in the capacitors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for driving an ink jet recording head, a recording apparatus having the circuit, and a method for driving an ink jet recording head. Driving of an ink jet recording head for discharging ink.

[0002]

2. Description of the Related Art As an information output device in, for example, a word processor, a personal computer, a facsimile, etc., there is a printer for recording desired information such as characters and images on a sheet-like recording medium such as paper or film.

[0003] Various types of printing methods are known for printers. However, ink-jet printing is possible because non-contact printing is possible on printing media such as paper, colorization is easy, and quietness is high. In recent years, the method has attracted special attention. As a configuration, a recording head that ejects ink according to desired recording information is mounted, and recording is performed while reciprocating scanning in a direction perpendicular to the feeding direction of a recording medium such as paper. Are generally widely used because they are inexpensive and easy to miniaturize.

As a driving principle of an ink jet recording head, a method utilizing energy generated by driving a piezoelectric element or a method utilizing bubble energy generated by locally heating ink by an electrothermal transducer. Etc. are known.

FIG. 2 is a diagram showing a general configuration of a driving circuit of an ink jet recording head utilizing energy generated by driving a piezoelectric element. In the figure, 1 is a power supply, C is a capacitor, 2 is a drive signal generation circuit, 3 is a buffer circuit, 4 is a switching element, 5 is a piezoelectric element, and the switching element 4 and the piezoelectric element 5 are provided inside the recording head IJH. Have been.

In such a circuit, the drive signal generation circuit 2
Circuit 3 by the pulse-like voltage generated by
Operates, and a voltage substantially equal to the power supply voltage is applied to the recording head IJH.
Supplied to At this time, a voltage is applied to the corresponding piezoelectric element 5 by selectively turning on the switching element 4.

[0007]

As a material for the piezoelectric element, barium titanate or the like is used. However, these materials have a high dielectric constant and a large capacitance of the piezoelectric element. Therefore, the piezoelectric element repeats charging and discharging each time a driving voltage is applied, and consumes power that is not used for discharging ink droplets.

This becomes more remarkable as the driving frequency is increased or the number of nozzles is increased, and the amount of electric power consumed in charging and discharging the piezoelectric element becomes considerable. For this reason, a method of using electric energy more effectively is desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an ink jet recording head capable of reducing power consumption by more effectively utilizing electric energy stored in a piezoelectric element by a driving voltage. It is an object of the present invention to provide a driving circuit, a recording apparatus having the circuit, and a method for driving an ink jet recording head.

[0010]

According to the present invention, there is provided a drive circuit for an ink jet recording head which achieves the above object, comprising: a driving circuit for driving an ink jet recording head for discharging ink droplets by using energy generated by driving a piezoelectric element; A circuit for outputting a voltage to be applied to the piezoelectric element, at least two capacitors having a capacitance larger than a capacitance of the piezoelectric element, and an output connected to the capacitor in parallel with the capacitor. A first state input to the circuit, a second state in which the capacitors are connected in series and the output thereof is input to the buffer circuit, and a signal passing through the buffer circuit is input in parallel to the capacitors A switching unit for switching between a third state and a charge state in the first state, and switching to the second state after charging the capacitor in the first state; Driven element, the third state in charge accumulated in the piezoelectric element so as to be accumulated in the capacitor, and a control means for controlling the operation of said switching means and said buffer circuitry.

The above object is also achieved by a recording apparatus having a driving circuit for the ink jet recording head.

A method of driving an ink jet recording head that achieves the above object is a method of driving an ink jet recording head that discharges ink droplets by using energy generated by driving a piezoelectric element. A buffer circuit for outputting a voltage to be applied to the piezoelectric element, and at least two capacitors having a capacitance larger than the capacitance of the piezoelectric element, and connecting the capacitors in parallel and outputting the output to the buffer circuit. After charging the capacitor in the first state, the capacitor is connected in series, the output is switched to the second state in which the output is input to the buffer circuit, the piezoelectric element is driven, and the signal passing through the buffer circuit is output. Is stored in the capacitor as a third state in which the electric charge stored in the piezoelectric element is input in parallel to the capacitor. Is the way, it switches the operation of the connection and the buffer circuit of the capacitor.

That is, a buffer circuit for outputting a voltage to be applied to a piezoelectric element when driving an ink jet recording head for ejecting ink droplets by using energy generated by driving the piezoelectric element, At least two capacitors having a capacitance larger than the capacitance are prepared, the capacitors are connected in parallel, the capacitors are charged in a first state in which the output is input to the buffer circuit, and then the capacitors are connected in series. The piezoelectric element is driven by switching to a second state in which the output is input to the buffer circuit. In a third state in which the signal passed through the buffer circuit is input in parallel to the capacitor, the electric charge accumulated in the piezoelectric element is changed to the capacitor. Switches the connection of the capacitor and the operation of the buffer circuit so that the data is accumulated in the buffer circuit.

According to this, a pump-up circuit using at least two capacitors is formed to drive the piezoelectric element with a voltage twice as high as the charged voltage, and the electric charge accumulated in the piezoelectric element during driving is reduced. Since it can be returned to the capacitor, electric energy can be effectively used, and power consumption for driving the recording head can be reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

In the embodiment described below, a printer is described as an example of a recording apparatus using an ink jet recording method.

In this specification, "recording" (sometimes referred to as "printing") refers not only to the formation of significant information such as characters and figures, but also to the perception of humans irrespective of significance or insignificance. Regardless of whether or not the image has been exposed so as to be able to perform the process, the case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or a case where the medium is processed is also described.

The "recording medium" is not limited to paper used in a general recording apparatus, but is widely applicable to ink, such as cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. Things are also represented.

Further, “ink” (sometimes referred to as “liquid”) is to be interpreted as widely as the definition of “recording (printing)”, and by being applied on a recording medium, A liquid that can be used for forming an image, a pattern, a pattern, or the like, processing a recording medium, or processing ink (for example, coagulating or insolubilizing a colorant in ink applied to the recording medium) is used.

First, a description will be given of a recording apparatus to which the driving circuit for an ink jet recording head according to the present invention is applied.

<Schematic Description of Apparatus Main Body> FIG. 9 is an external perspective view showing the outline of the configuration of an ink jet printer IJRA as a typical embodiment to which the driving circuit of the ink jet recording head of the present invention is applied.

Referring to FIG. 9, a spiral groove 500 of a lead screw 5005 which rotates through driving force transmission gears 5009 to 5011 in conjunction with forward and reverse rotation of a driving motor 5013.
The carriage HC engaged with the carriage 4 has a pin (not shown), and is supported by the guide rail 5003 to reciprocate in the directions of arrows a and b. The print head I is provided on the carriage HC.
An integrated ink jet cartridge IJC containing a JH and an ink tank IT is mounted.

Reference numeral 5002 denotes a paper holding plate, and a carriage H
The recording paper P is pressed against the platen 5000 over the moving direction of C. Reference numerals 5007 and 5008 denote photocouplers, which are home position detectors for confirming the presence of the carriage lever 5006 in this region and switching the rotation direction of the motor 5013.

Reference numeral 5016 denotes a member for supporting a cap member 5022 for capping the front surface of the recording head IJH.
Reference numeral 15 denotes a suction device that suctions the inside of the cap, and performs suction recovery of the recording head through the opening 5023 in the cap. 5
Reference numeral 017 denotes a cleaning blade. Reference numeral 5019 denotes a member which allows the blade to move in the front-rear direction. These members are supported by a main body support plate 5018. It goes without saying that the blade is not limited to this form and a known cleaning blade can be applied to this example.

Reference numeral 5021 denotes a lever for starting suction for recovery from suction, and a cam 5020 which engages with the carriage.
The driving force from the driving motor is controlled by a known transmission mechanism such as clutch switching.

The capping, cleaning, and suction recovery are configured so that desired operations can be performed at the corresponding positions by the action of the lead screw 5005 when the carriage comes to the area on the home position side. If a desired operation is performed at the timing, any of the embodiments can be applied.

<Description of Control Structure> Next, a control structure for executing the recording control of the above-described apparatus will be described.

FIG. 10 shows an ink jet printer IJRA.
FIG. 3 is a block diagram showing a configuration of a control circuit of FIG. In the figure showing a control circuit, 1700 is an interface for inputting a recording signal, 1701 is an MPU, 1702 is an MPU 1
ROM 701 for storing a control program to be executed by 701
A DRAM 703 stores various data (such as the recording signal and recording data supplied to the head). 17
A gate array (GA) 04 controls supply of print data to the print head IJH, and also controls data transfer between the interface 1700, the MPU 1701, and the RAM 1703. Reference numeral 1710 denotes a carrier motor for transporting the recording head IJH, and reference numeral 1709 denotes a transport motor for transporting the recording paper. Reference numeral 1705 denotes a head driver for driving the recording head, and reference numerals 1706 and 1707 denote motor drivers for driving the transport motor 1709 and the carrier motor 1710, respectively.

The operation of the above control configuration will be described. When a recording signal is input to the interface 1700, the gate array 1
The recording signal is converted into recording data for printing between the 704 and the MPU 1701. And the motor driver 1
The printheads 706 and 1707 are driven, and the printhead is driven according to the print data sent to the head driver 1705 to perform printing.

Here, the control program executed by the MPU 1701 is stored in the ROM 1702.
An erasable / writable storage medium such as an EEPROM may be further added so that the host computer connected to the inkjet printer IJRA can change the control program.

<Explanation of Ink Cartridge> As described above, the ink tank IT and the recording head IJH are formed integrally and are exchangeable ink cartridge IJC.
However, the ink tank IT and the recording head IJH may be configured to be separable so that only the ink tank IT can be replaced when the ink runs out.

FIG. 11 is an external perspective view showing the structure of an ink cartridge IJC in which an ink tank and a head can be separated. In the ink cartridge IJC, as shown in FIG. 11, the ink tank IT and the recording head IJH can be separated at the position of the boundary line K. Ink cartridge IJ
C is provided with an electrode (not shown) for receiving an electric signal supplied from the carriage HC when it is mounted on the carriage HC, and the electric signal drives the recording head IJH as described above. Then, the ink is ejected.

In FIG. 11, reference numeral 500 denotes an ink ejection port array. The ink tank IT is provided with a fibrous or porous ink absorber for holding ink.

[Embodiment] FIG. 1 is a circuit diagram showing a configuration of an embodiment of a drive circuit of an ink jet recording head of the present invention applied to the above ink jet printer. This driving circuit corresponds to the head driver 1705 in the block diagram of FIG.

In FIG. 1, reference numeral 1 denotes a power supply for supplying electric power for driving the piezoelectric element, and S1 to S4 denote semiconductor switches such as FETs for switching a circuit configuration. C1 is a capacitor for stabilizing the power supply voltage, and C2 and C3 are capacitors for accumulating electric charges for driving the piezoelectric elements, and have a capacity sufficiently larger than the total capacitance of the piezoelectric elements included in the recording head. Use each. Reference numeral 2 denotes a drive signal generation circuit that generates a pulse signal for driving the piezoelectric element according to the drive control signal, and reference numeral 3 denotes a buffer circuit for driving the piezoelectric element.

Reference numeral 4 denotes a semiconductor switch for selectively applying a drive voltage to each piezoelectric element according to recording data.
Reference numeral 5 denotes a piezoelectric element such as barium titanate that expands / contracts a pressure chamber provided in the recording head and discharges ink droplets.

The semiconductor switch 4 and the piezoelectric element 5 are provided in the recording head IJH corresponding to each nozzle. The piezoelectric element 5 of the present embodiment is configured such that when the applied voltage increases, the volume of the pressure chamber decreases, and ink droplets are ejected from the corresponding nozzle.

Reference numeral 6 denotes a comparator for detecting a drive voltage and comparing the detected value with a predetermined value. Reference numeral 7 denotes a control circuit for switching S2 to S4 according to a drive waveform control signal and an output signal of the comparison circuit 6.

FIG. 3 is a graph showing an example of a drive waveform output from the buffer circuit 3 and applied to the piezoelectric element 5 in this embodiment. The voltage V1 in the figure is equal to the voltage value output from the power supply 1, and V2 is twice the voltage of V1. Va and Vb are voltages set as thresholds of the comparator 6 for switching S2 to S4, and are set to voltages slightly lower and slightly higher than V1, respectively.

The states of the switches S2 to S4 change as shown in FIG. 4 according to the respective periods T1 to T3 in FIG. FIGS. 5 to 7 are circuit diagrams schematically showing the driving circuit when the switches S2 to S4 are in the state shown in FIG. 4 during the periods T1 to T3, respectively. Hereinafter, the operation of the present embodiment will be described with reference to these drawings.

First, during standby, the switches S2 to S4 are set to the positions shown in FIG.
The connection state of the drive circuit is as shown in FIG. 5, and the voltage applied to the piezoelectric element 5 is V3 which is almost close to the ground voltage.

When S1 is turned on in the circuit state shown in FIG. 5, power supply voltage V1 is applied to capacitors C2 and C3. In this state, at the time point t1 when the charging of C2 and C3 is completed, the switch S1 is first turned off to disconnect the power supply in order to start the driving of the piezoelectric element.
Is operated to start applying a voltage to the piezoelectric element.

When the comparator 6 detects that the applied voltage has risen and has exceeded the threshold voltage Va, the switches S2 to S4 are brought into the state shown by T2 in FIG. The connection state switches as shown in FIG. At this time, since C2 and C3 are connected in series, the voltage output from the buffer circuit 3 changes at time t1.
As a result, the voltage rises to a voltage V4 near V2 which is almost twice V1.
At this time, the piezoelectric element to which the voltage is applied reduces the volume of the pressure chamber, and ink droplets are ejected from the corresponding nozzle.

After a lapse of a predetermined time, the switches S2 to S4 are set to the state indicated by T3 in FIG. 4 according to the switching signal from the control circuit 7, and the connection state is switched as shown in FIG. Accordingly, the voltage output from the buffer circuit 3 decreases with time from the time point t2. At this time, the electric charges stored in each piezoelectric element 5 are charged into the capacitors C2 and C3 via the buffer circuit 3.

During this time, charging and discharging are performed between the capacitors C2 and C3 and the piezoelectric element 5, and by setting the capacitance of the capacitor sufficiently larger than the total capacitance of the piezoelectric element 5, the voltage of the capacitor is reduced. There is almost no fluctuation.

When the comparator 6 detects that the output voltage of the buffer circuit 3 has become lower than Vb, the switches S2 to S4 are brought into the state shown by T1 in FIG. The state switches as shown in FIG. As a result, the voltage applied to the piezoelectric element 5 further decreases, and returns to the original voltage V3 at time t3. In this period T1, the electric charge released from the piezoelectric element 5 is not returned to the capacitor.

Thereafter, the switch S1 is turned on again, and the capacitors C2 and C3 are charged by the power supply 1 to prepare for the next drive. The piezoelectric element 5 is driven by repeating the above operation.

In the above operation, the timing for switching on / off of the switch S1 may be near t0 and t3 in FIG. 3, respectively.
3 may be turned off when the battery 3 is sufficiently charged, and may be turned on until the drive voltage drops to V3.

As described above, according to the present embodiment,
By switching the connection state of the two capacitors C2 and C3, the piezoelectric element can be driven with a voltage approximately twice the power supply voltage, and the electric charge accumulated in the piezoelectric element at the time of driving is transferred to the capacitor again. It is possible to reduce the power consumption when driving the recording head by returning and effectively using the electric energy.

[Modification] In the above embodiment, the connection state of the circuit is switched from the state shown in FIG. 5 to the state shown in FIG. 6 during the period from T1 to T2 when the voltage applied to the piezoelectric element is rising. However, in this case, if the switching time is not shortened, the waveform may be disturbed at the time of switching, which may affect the ejection.

In order to prevent this, the waveform of the drive voltage of the piezoelectric element 5 may be as shown in FIG. In this case, the connection state of the circuit is switched from the state of FIG. 5 to the state of FIG. 6 when the drive voltage is V6, which is the lowest. With this configuration, in the state where the driving voltage is the lowest, the piezoelectric element is in a state where the pressure chamber is expanded and the ink is being drawn, so that even if the driving waveform is slightly disturbed, the influence is small.

However, in this case, it is necessary to rapidly increase the drive voltage from the lowest voltage V6 to the highest voltage V7, so that the use efficiency of electric energy is lower than in the above-described embodiment.

[Other Embodiments] In addition to the printer exemplified in the above embodiment, the present invention is applied to a line printer using a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus. It can also be applied. In this case, the configuration of the recording head may be either a configuration that satisfies the length by combining a plurality of recording heads, or a configuration as a single recording head that is integrally formed.

In addition to the cartridge-type recording head in which the ink tank is provided integrally with the recording head itself described in the above embodiment, the recording head is electrically connected to the apparatus main body by being mounted on the apparatus main body. A replaceable chip-type recording head, which enables a simple connection and supply of ink from the apparatus main body, may be used.

Further, it is preferable to add recovery means for the printhead, preliminary auxiliary means, and the like to the configuration of the printing apparatus described above, since the printing operation can be further stabilized. Specifically, there are a capping unit, a cleaning unit, a pressurizing or suctioning unit, or a combination thereof for the recording head. It is also effective to provide a preliminary ejection mode for performing ejection that is different from printing, in order to perform stable printing.

Further, the recording mode of the recording apparatus is not limited to a recording mode of only a mainstream color such as black, and may be a single recording head or a combination of plural recording heads. Alternatively, the apparatus may be provided with at least one of full colors by color mixture.

Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus composed of one device (for example, a copying machine, a facsimile, etc.) Device).

Another object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiment is recorded to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. It is needless to say that the present invention can also be achieved by a CPU or an MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. Also,
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the operating system (OS) running on the computer based on the instructions of the program code.
It goes without saying that a case where the functions of the above-described embodiments are implemented by performing some or all of the actual processing, and the processing performs the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. Needless to say, the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0060]

As described above, according to the present invention, a pump-up circuit using at least two capacitors is formed to drive a piezoelectric element with a voltage twice as high as a charged voltage. Since the electric charge accumulated in the piezoelectric element can be returned to the capacitor, the electric energy can be effectively used, and the power consumption when driving the recording head can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a configuration of an embodiment of a drive circuit of an inkjet recording head according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a driving circuit of a conventional inkjet recording head.

FIG. 3 is a graph showing an example of a driving waveform of the circuit of FIG. 1;

FIG. 4 is a diagram showing states of switches S2 to S4 in each period.

FIG. 5 is a diagram illustrating a connection state of a circuit during a period T1.

FIG. 6 is a diagram illustrating a connection state of a circuit in a period T2.

FIG. 7 is a diagram illustrating a connection state of a circuit in a period T3.

FIG. 8 is a graph showing another example of the driving waveform of the circuit of FIG. 1;

FIG. 9 is a diagram illustrating an appearance of a printer according to a preferred embodiment of the present invention.

FIG. 10 is a block diagram illustrating a control configuration of the printer in FIG. 9;

FIG. 11 is a view showing an ink jet cartridge of the printer in FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply 2 Drive signal generation circuit 3 Buffer circuit 4 Switch 5 Piezoelectric element 6 Comparator 7 Control circuit C1-C3 Capacitor S1-S4 Switch

Claims (6)

[Claims] 1. A driving circuit for an ink jet recording head for discharging ink droplets using energy generated by driving a piezoelectric element, wherein: a buffer circuit for outputting a voltage to be applied to the piezoelectric element; A first state in which the capacitors are connected in parallel and the output of which is input to the buffer circuit, and the capacitor is connected in series and the output is The second input to the buffer circuit
And a switching means for switching between a third state in which a signal passed through the buffer circuit is input in parallel to the capacitor; and a second state after charging the capacitor in the first state. Switch to drive the piezoelectric element,
A drive circuit for controlling the operation of the switching means and the buffer circuit so that the electric charge accumulated in the piezoelectric element in the state described above is accumulated in the capacitor. . 2. The drive circuit according to claim 1, wherein the control unit controls the switching state of the switching unit according to an output voltage of the buffer circuit. 3. The driving circuit according to claim 1, wherein the switching unit includes a semiconductor switching element. 4. A recording apparatus comprising the ink jet recording head drive circuit according to claim 1. Description: 5. A method for driving an ink jet recording head for discharging ink droplets by using energy generated by driving a piezoelectric element, comprising: a buffer circuit for outputting a voltage to be applied to the piezoelectric element; After preparing at least two capacitors having a capacitance larger than the capacitance of the element, connecting the capacitors in parallel and charging the capacitors in a first state in which the output is input to the buffer circuit, A third state in which a capacitor is connected in series and its output is switched to a second state in which the output is input to the buffer circuit to drive the piezoelectric element, and a signal passed through the buffer circuit is input in parallel to the capacitor. Connecting the capacitor and the buffer circuit so that the electric charge accumulated in the piezoelectric element is accumulated in the capacitor. The driving method of ink jet recording head is characterized in that switches the operation. 6. The method according to claim 5, wherein a connection state of the capacitor is switched according to an output voltage of the buffer circuit.