JP2002347245A - Inkjet printer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the number of pixels and to increase the speed of printing output without requiring a complicated circuit configuration. SOLUTION: A pressure chamber 20 partially having a vibrating plate 27 which is held at a constant potential and can be bent outward, and a pressure chamber 20
And a separate electrode 33 disposed opposite to each diaphragm with a gap 36 at a predetermined interval.
And a power supply for applying a voltage between the vibration plate 27 and the individual electrode 33, the semiconductor switch is connected to the individual electrode 33, and the conduction / non-conduction of the semiconductor switch is selectively switched. did. This modulates the waveform of the voltage applied between the diaphragm 27 and the individual electrode 33 by the power supply,
The voltage application / non-application between the electrode 7 and the individual electrode 33 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet printer.

[0002]

2. Description of the Related Art In recent years, an ink jet head has been installed because it has various advantages such as excellent silence, ability to cope with high-speed printing, and convenience by using easily available plain paper. Inkjet printers are widely used.

[0003] Among the ink jet printers, a so-called on-demand type ink jet printer that discharges only ink droplets necessary for printing does not consume ink unnecessarily and thus does not need to collect unnecessary ink. For this reason, the current printing method using an inkjet head is the mainstream.

[0004] The ink jet printer has, for example, a pressure chamber partially having a diaphragm that can be bent outward, a nozzle for communicating the pressure chamber with the outside, and a gap at a predetermined interval from each diaphragm. An ink jet head having individual electrodes opposed to each of the diaphragms, and applying a voltage output from a drive signal source between the diaphragm and the individual electrodes to generate an electrostatic force. There is a type in which ink droplets are ejected from nozzles by using a volume change in a pressure chamber caused by bending a diaphragm once outward in a pressure chamber by a force and then returning the diaphragm to an original position.

In order to eject ink droplets from the nozzles as described above, a trapezoidal pulse voltage is applied between the diaphragm and the individual electrodes (see FIG. 4).

[0006] In such an ink jet printer,
For example, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-214771, a charging circuit and a discharging circuit including a diaphragm and an individual electrode are provided. Is performed independently so that the waveform of the voltage applied between the diaphragm and the individual electrode is trapezoidal.

Further, as described above, in an ink jet head that discharges ink droplets by using electrostatic force,
For example, compared with an ink jet head that discharges ink droplets using a piezoelectric element or a heating element, less energy is required for printing, and power saving can be achieved.

[0008] In recent years, there has been a demand for higher definition of an image to be printed out. In order to increase the definition of an image to be printed out, it is necessary to increase the number of pixels.

As a method of multi-valued pixels, for example,
There is a method of modulating the diameter of each ink droplet. The diameter of the ink droplet can be modulated by changing the shape of the waveform of the voltage applied between the individual electrode and the diaphragm, and can be experimentally applied between the individual electrode and the diaphragm. It has been found that the shape of the waveform changes by independently adjusting the fall time of the applied voltage, the voltage peak value, or both the fall time and the voltage peak value.

As another method of multi-valued pixels, for example, there is a method of multi-valued pixels by modulating the number of dots per pixel.

[0011]

By the way, when the voltage peak value is changed, the change in the ink droplet diameter is smaller than when the fall time of the voltage applied between the individual electrode and the diaphragm is changed. The sensitivity is high, in other words, the control becomes difficult, and the adjustment in manufacturing becomes delicate, so that the cost in the manufacturing process is unavoidable.

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-214771, the voltage peak value of the voltage applied between the individual electrode and the diaphragm can be changed, but the fall time is changed. Can not.

In the method of multi-valued pixels by modulating the number of dots per pixel, a plurality of ink droplets are required for each pixel. It will be difficult.

As a countermeasure, in a conventional ink-jet printer, when the printing speed is increased by modulating the number of dots per pixel to make the pixels multi-valued, one ejection of ink droplets is performed. Since a circuit having a high processing speed capable of generating two pulses having a shorter cycle than the ejection cycle during the cycle is required, cost performance is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet printer capable of multi-valued pixels and high-speed printing without requiring a complicated circuit configuration.

[0016]

According to the first aspect of the present invention, there is provided an ink-jet printer comprising a pressure chamber partially including a vibrating plate which is held at a constant potential and is capable of flexing outwardly; A nozzle that communicates with each other, an individual electrode having a gap at a predetermined interval, opposed to each of the diaphragms, a power supply that applies a voltage between the diaphragm and the individual electrode, and a connection to the individual electrode. A semiconductor switch for selectively switching conduction / non-conduction of a voltage applied between the diaphragm and the individual electrode by the power supply.

Therefore, the diameter of the ink droplet can be modulated by modulating the waveform of the voltage applied between the diaphragm and the individual electrode by the power supply. Also, by selectively switching the conduction / non-conduction of the semiconductor switch,
Control of application / non-application of voltage between the diaphragm and the individual electrode can be speeded up.

According to a second aspect of the present invention, in the ink jet printer according to the first aspect, the semiconductor switch is a CMOS analog switch.

Therefore, by using a highly versatile CMOS analog switch as a semiconductor switch,
Cost performance can be improved. Further, since the CMOS analog switch can be easily integrated into an IC, it is possible to increase the number of channels.

According to a third aspect of the present invention, in the inkjet printer according to the first aspect, the semiconductor switch is a PMOS transistor, and the power supply applies a voltage higher than a potential of the diaphragm.

Therefore, PMO is used as a semiconductor switch.
By applying a voltage equal to or higher than the potential of the diaphragm between the diaphragm and the individual electrode using the S transistor, if the waveform of the voltage applied between the diaphragm and the individual electrode is different between the rise and fall It is possible to make it. This makes it possible to obtain the effect of the first aspect of the invention with a practically simple configuration.

According to a fourth aspect of the present invention, in the inkjet printer according to the first aspect, the semiconductor switch is an NMOS transistor, and the power supply applies a voltage equal to or lower than the potential of the diaphragm.

Therefore, NMO is used as a semiconductor switch.
By applying a voltage equal to or lower than the potential of the diaphragm between the diaphragm and the individual electrode using the S transistor, if the waveform of the voltage applied between the diaphragm and the individual electrode is different between the rising and the falling, It is possible to make it. This makes it possible to obtain the effect of the first aspect of the invention with a practically simple configuration.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. This embodiment is connected to a host machine such as a personal computer,
An application example to an ink jet printer that performs printing based on print data transmitted from a host machine will be described.

FIG. 1 is a vertical sectional side view schematically showing an ink jet printer according to a first embodiment of the present invention.
The casing 2 of the ink jet printer 1 has a paper feed port 4 in which a paper feed tray 3 for stacking and holding paper as a sheet-like recording material is mounted, a manual feed tray 5 for receiving paper feeding by manual feeding, and a printed paper tray. A paper discharge tray 6 from which paper is discharged is provided. In the paper feed port 4 and the manual feed tray 5, the paper to be stacked and held is stored in a paper transport path 7 described later.
A paper feed mechanism 8 for feeding paper to the paper is provided.

FIG. 1 shows a state in which the paper feed tray 3 is mounted on the paper feed port 4.

Although not shown, the casing 2 is provided with a power switch, various operation keys, a display for displaying an error message, and the like.

An upper cover 10 is provided on the upper surface of the casing 2 so as to be rotatable about the support shaft 9 in the direction away from the casing 2.

In the casing 2, a paper output port 6 or a manual feed tray 5 is connected to a paper output tray 6 via a printer unit 11.
The paper transport path 7 is formed. A transport mechanism 12 that transports the paper fed from the paper feed tray 3 or the manual feed tray 5 is provided in the paper transport path 7.

The printer unit 11 holds a carriage 13 which can reciprocate in a main scanning direction (a direction perpendicular to the paper of FIG. 1) by a motor (not shown), an ink jet head 14 mounted on the carriage 13, and ink to be supplied to the ink jet head 14. And the like.

During non-printing, the carriage 13 waits for printing at the end in the main scanning direction. Although it is a known technique, its illustration and description are omitted.
At the standby position, there is provided a reliability maintaining device that performs capping of the nozzle 16 of the inkjet head 14 to be described later, cleaning of the nozzle 16 and the vicinity of the nozzle 16, and the like.

FIG. 2 is a vertical sectional side view showing the ink jet head 14, and FIG. 3 is a vertical sectional front view thereof. The ink-jet head 14 includes substrates 17 and 1 joined in a stacked state.
8, the individual electrode substrate 19 is mainly configured.

The substrate 17 and the individual electrode substrate 19, or
The substrate 17 and the individual electrode substrate 19 are joined by direct joining at a high temperature of 100 ° C. or eutectic joining in which a binder such as gold is interposed at each boundary surface.

The substrate 17 is joined to the substrate 18 to form a pressure recess 21 forming a pressure chamber 20, a reservoir recess 23 forming a reservoir 22, a nozzle recess 24 forming a nozzle 16, and an orifice 25. An orifice recess 26 to be formed is formed. Pressure recess 21
The diaphragm 27 is provided at the bottom of the. The nozzle recess 24 communicates the end face of the substrate 17 with the pressure recess 21 and is formed to be narrower and shallower than the pressure recess 21 and the reservoir recess 23. The orifice recess 26
The pressure concave portion 21 and the reservoir concave portion 23 are communicated with each other, and are formed to be narrower and shallower than the pressure concave portion 21 and the reservoir concave portion 23.

The substrate 17 of this embodiment is formed by performing anisotropic etching on P-type silicon. At the time of anisotropic etching, high-concentration boron is doped into a portion to be the vibration plate 27 so as to lower the etching rate. Thereby, it is possible to obtain the vibration plate 27 in which the dimensional accuracy of the plate thickness is well maintained.

The substrate 17 is provided with a common electrode 28 for applying a ground potential (grounding) to the substrate 17 and maintaining the diaphragm 27 at a constant potential. The common electrode 28 of the present embodiment is formed by sintering (thermal diffusion) a metal such as aluminum sputtered on the surface of the substrate 17. Thereby, the common electrode 2
8 between the substrate 8 and the substrate 17 and the substrate 1
7 and the common electrode 28 can be in ohmic contact.

The ink supply hole 2 penetrating the substrate 18 in the thickness direction is provided at a position facing the reservoir concave portion 23 of the substrate 18.
9 are formed. A connection pipe 30 to which a tube (not shown) communicating with the ink cartridge 15 is connected is connected to the ink supply hole 29.

The individual electrode substrate 19 joined to the substrate 17 on the side opposite to the substrate 18 is formed by sequentially joining a substrate layer 31, a dielectric layer 32, and individual electrodes 33.
In the present embodiment, the individual electrode substrate 19 is formed of P-type silicon, but the material for forming the individual electrode substrate 19 is not limited to this. Any material that can withstand the heat applied to the substrate 19 may be used.

The substrate layer 31 is formed of the same type of P-type silicon as the substrate 17. Dielectric layer 3 of substrate layer 31
The substrate layer electrode extraction portion 34 is connected to the end face opposite to 2. The surface of the substrate layer electrode extraction portion 34 is
9 is formed by sintering (thermal diffusion) a metal such as aluminum sputtered on the surface of the substrate 9.

The dielectric layer 32 is a layer of an oxide film that covers one end surface of the substrate layer 31. The dielectric layer 32 is formed by isotropic etching so that a bonding portion 35 bonded to the substrate 17 projects into the substrate 17 side. As a result, when the substrate 17 and the bonding portion 35 of the dielectric layer 32 are bonded, a gap 36 having a predetermined interval is formed between the substrate 17 and the individual electrode 33. This gap 36
Forms a gas layer 37 described later, and is set to 0.2 μm in the present embodiment.

The individual electrodes 33 are formed on the substrate 17 and the dielectric layer 32.
Are provided so as to face each of the vibration plates 27 in a state where they are joined. The individual electrode 33 is connected to a drive circuit 38 described later, and a voltage is appropriately applied by the operation of the drive circuit 38. Individual electrode 3 of the present embodiment
3 is for TiN formed on the surface of the dielectric layer 32,
It is formed by performing a patterning process with a pattern facing each of the vibration plates 27.

The gap 36 formed between the vibration plate 27 and the individual electrode 33 is closed by a sealant 39 provided between the substrate 17 and the individual electrode substrate 19, and is isolated from the outside. A gas layer 37 is formed. Sealant 3
9 is an adhesive formed of, for example, an epoxy resin or the like.

Here, a capacitive actuator section 40 is formed by the vibration plate 27, the individual electrodes 33, and the gas layer 37. Although details will be described later, the actuator unit 4
A drive signal source 41 as a power supply for applying a voltage between the diaphragm 27 and the individual electrode 33 is connected to 0 (see FIG. 6). Although not shown and described because it is a known technique, the drive signal source 41 has a built-in microcomputer,
The waveform of the output voltage can be arbitrarily modulated.

On the surface of the individual electrode 33, a protective layer 42 for covering the surface of the individual electrode 33 is provided. The protective layer 42 is formed of silicon dioxide formed on the surface of the individual electrode 33.
It is formed by patterning (SiO ₂ ). Accordingly, it is possible to prevent the individual electrodes 33 from being damaged due to the contact of the flexed diaphragm 27 during printing.

In such an ink jet printer 1, at the time of printing, the voltage output from the drive signal source 41 is selectively applied to the individual electrodes 33 of the ink jet head 14 by the drive circuit 38. When a voltage is applied to the individual electrode 33, an electrostatic force is generated between the individual electrode 33 to which the voltage is applied and the diaphragm 27 facing the individual electrode 33, and opposes the individual electrode 33 to which the voltage is applied. The vibration plate 27 bends outward from the pressure chamber 20. Diaphragm 27
Bends outwardly of the pressure chamber 20 so that the pressure chamber 20
The volume inside the pressure chamber 20 increases, and a negative pressure is generated in the pressure chamber 20 due to the increase in the volume inside the pressure chamber 20. By this negative pressure, ink is supplied from the ink cartridge 15 into the pressure chamber 20 via the ink supply hole 29 and the tube. When the application of the voltage to the individual electrode 33 is stopped after a certain period of time,
The flexed diaphragm 27 suddenly returns to its initial position by its own restoring force. As a result, the volume in the pressure chamber 20 that has increased due to the bending of the vibration plate 27 sharply decreases, and the ink supplied into the pressure chamber 20 is pressurized and the ink droplets are ejected from the nozzle 16. .

At the time of discharging the ink droplets described above, between the vibration plate 27 and the individual electrodes 33, as shown in FIG.
A trapezoidal pulse voltage is applied. Specifically, the trapezoidal pulse voltage means that when voltage application is started, the voltage gradually rises from the same ground potential as the potential of the diaphragm 27 to the voltage peak value Vh with a rise time tr, and the voltage peak value Vh When the application of the voltage to the individual electrode 33 is stopped after a lapse of a certain period of time, the voltage has a waveform that gradually falls from the voltage peak value Vh to the ground potential with a fall time tf.

FIG. 5 shows the ejection volume v of the ink droplet.
FIG. 6 is a correlation diagram showing a relationship between the time and the fall time tf. When the fall time tf is between the time t0 and the time t1,
The ejection volume v of the ink droplet ejected from the nozzle 16 to the outside is constant. This time t1 is determined by the response speed of the pressure chamber 20, and thereafter this time t1 is referred to as the response time t.
One. When the fall time tf is longer than the response time t1, the ejection volume v of the ink droplet ejected from the nozzle 16 to the outside is determined according to the fall time tf, and decreases as the fall time tf becomes longer. When the fall time tf becomes longer than a predetermined time, the ejection volume v becomes zero.

Although not particularly shown, it has been found from another experiment that the fall time tf is shorter than the time t2 in order to control the ejection volume of the ink droplets well. This time t2 is referred to as a discharge limit time t2.

By controlling the voltage value applied between the vibration plate 27 and the individual electrode 33 so that the fall time tf is between the response time t1 and the ejection limit time t2, the ink droplet is controlled. Can be modulated.

In the present embodiment, a drive signal source 41 for outputting a voltage applied between the diaphragm 27 and the individual electrode 33
Since it is possible to arbitrarily modulate the waveform of the voltage output by drive control of the microcomputer, it is possible to accurately modulate the diameter of the ink droplet. by this,
The pixels can be multi-valued, and the printed and printed image can be enhanced.

FIG. 6 is a block diagram schematically showing a drive circuit 38 included in the ink jet printer 1 and the electrical connections of the components that are driven and controlled by the drive circuit 38. The drive circuit 38 includes an actuator unit 40
And a complementary metal oxide semiconductor (CMOS) as a semiconductor switch connected to the actuator section 40.
An on-ductor analog switch 43 and an analog switch control circuit 44 for controlling the driving of the CMOS analog switch 43 are provided.

The CMOS analog switch 43 is an NMO
S (N-channel MOS) transistor 45 and PMOS (P-chan
nel MOS) transistor 46 and a complementary metal oxide semiconductor.

The individual electrodes 33 of the actuator section 40 are connected to the CMOS analog switch 43.
On the opposite side of the CMOS analog switch 43 from the actuator section 40, the drive signal source 4 for outputting a voltage to be applied to the actuator section 40 via an NMOS transistor 45 and a PMOS transistor 46.
1 is connected.

The CMOS analog switch 43 of the present embodiment applies the potential output from the drive signal source 41 to the gate terminal of the NMOS transistor 45 under the control of the analog switch control circuit 44, and connects the gate terminal of the PMOS transistor 46 to the gate terminal. By setting it to the ground potential (grounding), it is made conductive. The CMOS analog switch 43 applies the potential output from the drive signal source 41 to the gate terminal of the PMOS transistor 46 under the control of the analog switch control circuit 44, and sets the gate terminal of the NMOS transistor 45 to the ground potential (earth). ) To make a non-conductive state.

The NMOS transistor 45 and the PMOS in the CMOS analog switch 43 of the present embodiment
The transistor 46 is provided so that the resistance of the CMOS analog switch 43 in the closed state is negligibly small compared to the impedance of the inkjet head 14.
The channel length is set to be sufficiently long. Thereby, C
The potential of the individual electrode 33 when the MOS analog switch 43 is conductive can be made substantially equal to the potential of the drive signal source 41.

The analog switch control circuit 44 includes a plurality of PMOS transistors 44a, 44b, 44c, 44
d. Each transistor is supplied with power supplies p1, p2, etc. so as to enable operation. P
MOS transistors 44a, 44b and 44c, 44d
Forms a logic circuit NOT, and operates 45 and 46 according to the print data.

For the analog switch control circuit 44,
When the print data of "ejection" is input, the PMOS transistor 44a is turned off. As a result, the ground potential is applied to the gate terminal of the PMOS transistor 46 by the operation of the logic circuit NOT, and the NMOS transistor 4
The gate terminal 5 is supplied with a potential from the drive signal source 41.

On the other hand, when "non-ejection" print data is input to the analog switch control circuit 44, the PMO
The S transistor 44a is turned on, the ground potential is applied to the gate terminal of the PMOS transistor 44b,
The potential from the drive signal source 41 is applied to the gate terminal of the OS transistor 46.

FIG. 7 shows the output timing of print data,
5 is a timing chart showing a relationship between a waveform of a voltage output from a drive signal source 41 and a waveform of a voltage applied between a diaphragm 27 and an individual electrode 33 of an actuator unit 40.

When the transmitted print data is “ejection”, the analog switch control circuit 44
The analog switch 43 is turned on.

As a result, the voltage + V output from the drive signal source 41 is applied to the gate terminal of the NMOS transistor 45, and the gate terminal of the PMOS transistor 46 is set to the ground potential. Thus, a voltage is applied between the diaphragm 27 and the individual electrode 33.

Here, the voltage output from the drive signal source 41 is controlled by the analog switch control circuit 44 and the diaphragm 27 and the individual electrode 33 are driven via the CMOS analog switch 43 having a high response speed of conduction / non-conduction. , The speed of modulation of the number of dots per pixel can be increased without having to provide a complicated circuit configuration. Thus, multi-valued pixels can be achieved, and high definition of an image can be achieved.

At this time, the output timing of the voltage from the drive signal source 41 is adjusted to the conduction / non-conduction state transition time of the CMOS analog switch 43 by the switching control of the analog switch control circuit 44 from the output of the print data. The voltage output from the drive signal source 41 is
7 and the individual electrodes 33 can be applied better.

On the other hand, if the transmitted print data is “non-discharge”
, The analog switch control circuit 44
The CMOS analog switch 43 is turned off.

As a result, the voltage + V output from the drive signal source 41 is applied to the gate terminal of the PMOS transistor 46, and the gate terminal of the NMOS transistor 45 is set to the ground potential. As a result, no voltage is applied between the diaphragm 27 and the individual electrode 33,
Of the ink droplets from the nozzles 16.

In addition, by using the CMOS analog switch 43, which is highly versatile and easy to implement as an IC, as a semiconductor switch, it is possible to improve cost performance and increase the number of channels without complicating the circuit. Can be.

Next, a second embodiment of the present invention will be described with reference to FIGS. The present embodiment is applied to an ink-jet printer that performs printing without modulating the diameter of ink droplets, and is provided with only a PMOS transistor instead of the CMOS analog switch 43. Note that the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 8 is a block diagram showing a part of a drive circuit provided in an ink jet printer according to a second embodiment of the present invention. In the drive circuit 47 of the present embodiment, the conduction / connection between the drive signal source 41 and the actuator section 40 is established.
A non-conductive PMOS transistor 50 having a high response speed is provided as a semiconductor switch.

FIG. 9 is a correlation diagram showing the relationship between the voltage and the resistance between BB at both ends of the PMOS transistor 50 when the PMOS transistor 50 is conducting. If the resistance between B and B when the PMOS transistor 50 is in the conductive state is the ON resistance, then B-B
The voltage of the PMOS transistor 50 and the ON resistance between them are in inverse proportion.

The ON resistance of the PMOS transistor 50 is
When the voltage rises due to the application of a voltage between B and B, the time constant represented by the ON resistance and the capacitance of the actuator unit 40 is changed by the diaphragm 27 and the individual electrode 3.
3 is set so as to be equal to the time constant at the rise time tr (see FIG. 6) in the target waveform of the voltage applied between the first and third waveforms.

The time constant represented by the ON resistance and the capacitance of the actuator section 40 varies with the ON resistance of the PMOS transistor 50 when the voltage falls due to the stop of the application of the voltage between B and B. Board 27
It is set to be equal to the time constant of the fall time tf (see FIG. 6) in the target waveform of the voltage applied between the voltage and the individual electrode 33.

Specifically, the O of the PMOS transistor 50
The N resistance is determined by the PMOS transistor 50 by experiments or the like.
The above-described PMOS transistor 50 is realized by adjusting the channel length and the width of the transistor to obtain an optimum value.

FIG. 10 is a timing chart showing the relationship between the output timing of print data, the waveform of the voltage output from the drive signal source 41, and the waveform of the voltage applied between the diaphragm 27 and the individual electrode 33. It is a chart.

In this embodiment, after the print data is output, the analog switch control circuit 44 controls the PMOS
The waveform of the voltage output from the drive signal source 41 is a rectangular wave after the transition time when the conduction / non-conduction state of the transistor 50 is switched has elapsed.

When the transmitted print data is “discharge”, the analog switch control circuit 44
The transistor 50 is turned on, the voltage output from the drive signal source 41 is applied to the gate terminal of the PMOS transistor 50, and a voltage is applied between the diaphragm 27 and the individual electrode 33.

At this time, since the PMOS transistor 50 whose ON resistance value is adjusted as described above is used, even when the voltage output from the drive signal source 41 is a rectangular wave, the diaphragm 27 and the individual electrodes 33 are used. , A voltage having an ideal waveform can be applied.

As a result, the diameter of the ink droplet can be controlled to a constant size without using a special drive signal source 41, and it is possible to speed up the modulation of the number of dots per pixel without having to provide a complicated circuit configuration. Can be achieved.
Thus, multi-valued pixels can be achieved, and high definition of an image can be achieved.

In this embodiment, the PMOS transistor 50 is used. However, the present invention is not limited to this.
Instead of the MOS transistor 50, an NMOS transistor (see FIG. 6) may be used.

Although not specifically shown, even when an NMOS transistor is used, the NMOS transistor may be used at the time of rising and falling of the voltage due to the application of a voltage equal to or lower than the potential of the diaphragm 27 to both ends of the NMOS transistor. The respective time constants represented by the ON resistance of the transistor and the capacitance of the actuator section 40 are optimized by adjusting the channel length and width.

[0080]

According to the ink jet printer of the first aspect of the present invention, a pressure chamber partially having a diaphragm kept at a constant potential and capable of flexing outwardly is communicated with the pressure chamber and the outside. Nozzle, an individual electrode disposed opposite to each diaphragm with a predetermined gap, a power source for applying a voltage between the diaphragm and the individual electrode, and a diaphragm connected to the individual electrode and powered by the power source. A semiconductor switch that selectively switches between conduction and non-conduction of a voltage applied to the individual electrode, wherein a power supply modulates a waveform of a voltage applied between the diaphragm and the individual electrode to form an ink droplet. By modulating the diameter of the pixel, it is possible to achieve multi-valued pixels, and it is possible to increase the definition of a printed image. In addition, by controlling the application / non-application of a voltage between the diaphragm and the individual electrode by selectively switching the conduction / non-conduction of the semiconductor switch, it is not necessary to provide a complicated circuit configuration and the number of pixels can be increased. It is possible to increase the speed at the time of modulating the number of dots per pixel for achieving a value.

According to the second aspect of the present invention, in the ink jet printer according to the first aspect, a CMOS analog switch which has high versatility and is easily integrated into a semiconductor is used as a semiconductor switch, thereby improving cost performance. In addition, it is possible to increase the number of channels without complicating the circuit.

According to the third aspect of the present invention, in the ink jet printer according to the first aspect, a voltage higher than the potential of the diaphragm is applied between the diaphragm and the individual electrode by using a PMOS transistor as a semiconductor switch. This makes it possible to make the waveform of the voltage applied between the diaphragm and the individual electrode different between the rise and fall, so that the effect of the invention described in claim 1 can be obtained with a practically simple configuration. Can be.

According to the fourth aspect of the present invention, in the ink jet printer according to the first aspect, a voltage equal to or lower than the potential of the diaphragm is applied between the diaphragm and the individual electrode by using an NMOS transistor as a semiconductor switch. This makes it possible to make the waveform of the voltage applied between the diaphragm and the individual electrode different between the rise and fall, so that the effect of the invention described in claim 1 can be obtained with a practically simple configuration. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view schematically showing an ink jet printer according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing an ink jet head.

FIG. 3 is a longitudinal sectional front view thereof.

FIG. 4 is an explanatory diagram illustrating an example of a waveform of a voltage output from a drive signal source.

FIG. 5 shows a discharge volume v of ink droplets and a fall time tf.
FIG. 6 is a correlation diagram showing a relationship with the following.

FIG. 6 is a block diagram schematically showing a drive circuit and an electrical connection of each unit driven and controlled by the drive circuit.

FIG. 7 is a timing chart showing a relationship between print data output timing, a voltage waveform output from a drive signal source, and a voltage waveform applied between a diaphragm and an individual electrode of an actuator unit. .

FIG. 8 is a block diagram illustrating a part of a drive circuit included in an inkjet printer according to a second embodiment of the present invention.

FIG. 9 is a correlation diagram showing a relationship between a voltage and a resistance between BB of the PMOS transistor when the PMOS transistor is in a conductive state.

FIG. 10 is a timing chart showing a relationship among print data output timing, a voltage waveform output from a drive signal source, and a voltage waveform applied between a diaphragm and an individual electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ink jet printer 16 Nozzle 20 Pressure chamber 27 Vibration plate 33 Individual electrode 41 Power supply 43 Semiconductor switch, CMOS analog switch 50 Semiconductor switch, PMOS transistor

Claims (4)

[Claims] A pressure chamber partially including a diaphragm that is held at a constant potential and can bend outwardly; a nozzle that communicates the pressure chamber with the outside; and a gap having a predetermined interval. An individual electrode opposed to each diaphragm; a power source for applying a voltage between the diaphragm and the individual electrode; and a power source connected to the individual electrode and connected between the diaphragm and the individual electrode by the power source. And a semiconductor switch that selectively switches between conduction and non-conduction of a voltage applied to the inkjet printer. 2. The ink jet printer according to claim 1, wherein said semiconductor switch is a CMOS analog switch. 3. The ink jet printer according to claim 1, wherein said semiconductor switch is a PMOS transistor, and said power supply applies a voltage higher than a potential of said diaphragm. 4. The ink jet printer according to claim 1, wherein said semiconductor switch is an NMOS transistor, and said power supply applies a voltage lower than a potential of said diaphragm.