JPH10157102A - Ink jet recording device and head drive control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image quality from deteriorating by driving a device at the maximum drive frequency or less, and forming dots with a plurality of colors alternately and then scanning a carriage at least at a carriage speed when a dot pitch and the carriage speed satisfy a specific relationship when the head is driven at the maximum frequency. SOLUTION: When the minimum dot pitch corresponding to a resolution is set to Dp, a carriage speed for forming a dot with a dot pitch Dp is set to Vc when the minimum dot pitch corresponding to a resolution is driven at a maximum drive frequency fmax of a head, and then a relationship expressed by Dp=Vc×1/fmax is satisfied, a dot with at least two colors for a color to be printed is formed alternately at a dot pitch that is larger than the dot pitch Dp, thus reducing a real drive frequency (f), and scanning the carriage at a speed exceeding the carriage speed Vc when the relationship expressed by Dp=Vc×1/fmax is established. Also, by setting the carriage speed to Vc, a real drive frequency (f) is reduced, thus compensating for the decrease in the discharged amount of ink drop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus and a head drive control apparatus, and more particularly to an ink jet recording apparatus for printing high-quality images at high speed and a head drive control apparatus therefor.

[0002]

2. Description of the Related Art An ink jet recording apparatus has almost no vibration and noise during recording, and is particularly easy to colorize.
In addition to a printer that outputs data from a digital processing device such as a computer, it is also used for facsimile machines, copiers, and the like. This inkjet recording device
In response to a recording signal, an inkjet head equipped with a plurality of nozzles for ejecting ink droplets and an energy generating element such as an electromechanical transducer or a heating resistor provided for each nozzle is used as a recording head. By discharging ink droplets from a nozzle onto a recording medium (to which ink droplets adhere), high-speed, high-density, high-quality recording is performed.

In such an ink jet recording apparatus, it is required that the ink jet head can be driven at a high frequency in order to further increase the recording speed. However, as for the ejection characteristics of the ink jet head, the ink droplet ejection amount Mj tends to decrease due to the influence of the liquid surface vibration of the meniscus surface as the driving frequency increases. Further, when the environmental temperature of the ink jet head decreases, the fluid resistance increases because the ink viscosity increases, and the ink droplet ejection amount Mj decreases significantly. The dot diameter fluctuates due to such a decrease in the ink droplet ejection amount Mj, and the image quality is reduced.

Therefore, conventionally, as described in Japanese Patent Application Laid-Open No. 55-27210, a temperature detecting means for detecting an ambient temperature and a temperature detecting means for detecting a change in the environmental temperature of the ink jet head. An ink jet recording apparatus that changes the voltage level of a driving waveform for driving an ink jet head based on a detection result, or a method of generating a voltage pulse in a low temperature environment as described in JP-A-63-260452. 2. Description of the Related Art There is known a liquid jet recording apparatus provided with a drive voltage generating means for setting a fall time shorter than that at normal temperature.

[0005]

However, due to the structure of the ink jet head, the ratio of the ink droplet ejection amount Mj depending on the ink supply capacity increases as the driving frequency increases. Even if the voltage level of the drive waveform is changed in response to the environmental temperature change or the fall time of the voltage pulse is controlled, the decrease in the ink droplet ejection amount Mj cannot be suppressed.

There is a printing method called draft printing, which gives priority to printing speed over image quality. Usually, the moving speed of the carriage (carriage speed) is maintained while the driving frequency of the head is maintained. Since the dot arrangement density is high, the dot arrangement density (dot pitch Dp) is coarse, and the image quality is low.

[0007] The present invention has been made in view of the above points, and has as its object to prevent a decrease in image quality.

[0008]

According to a first aspect of the present invention, there is provided an ink jet recording apparatus in which one or a plurality of ink jet heads capable of ejecting ink droplets of a plurality of colors are mounted on a carriage. , The minimum dot pitch corresponding to the resolution is Dp, the maximum drive frequency of the inkjet head is fmax, and the speed of the carriage capable of forming dots at the dot pitch Dp when the inkjet head is driven at the maximum drive frequency fmax Is Vc, and Dp = Vc × 1 /
means for driving the inkjet head at a drive frequency equal to or lower than the maximum drive frequency fmax to alternately form dots of two or more colors, and scanning the carriage at a speed exceeding the carriage speed Vc when the relationship of fmax is satisfied. And means for causing this to occur.

According to a second aspect of the present invention, in the inkjet recording apparatus of the first aspect, black ink dots and composite black dots obtained by mixing yellow, magenta, and cyan inks are alternately formed, The carriage is scanned at twice the carriage speed Vc to perform monochrome printing.

According to a third aspect of the present invention, there is provided the ink jet recording apparatus according to the first aspect, wherein a single color black ink dot, a yellow ink dot,
Magenta ink dots, cyan ink dots,
Composite black dots formed by mixing yellow, magenta, and cyan inks are alternately formed, and the carriage is scanned at twice the carriage speed Vc to perform monochrome printing.

According to a fourth aspect of the present invention, there is provided the ink jet recording apparatus according to the first aspect, wherein a single color black ink dot, a yellow ink dot,
Magenta ink dots and cyan ink dots are alternately formed, and the carriage is scanned at a speed four times the scanning speed Vc of the carriage to perform monochrome printing.

According to a fifth aspect of the present invention, there is provided an ink jet recording apparatus in which one or a plurality of ink jet heads capable of discharging ink droplets of a plurality of colors are mounted on a carriage.
p, the maximum drive frequency of the inkjet head is fma
x, the inkjet head is driven at the maximum drive frequency fm
The speed of the carriage capable of forming dots at the dot pitch Dp when driven at ax is Vc, and Dp = Vc
Means for driving the inkjet head at a drive frequency equal to or lower than the maximum drive frequency fmax to alternately form dots of two or more colors when the relationship of × 1 / fmax is satisfied; Means for scanning at a speed.

According to a sixth aspect of the present invention, in the inkjet recording apparatus of the fifth aspect, the driving frequency of the inkjet head is set to a maximum driving frequency fma.
At a half of x or less, black ink dots and composite black dots obtained by mixing yellow, magenta, and cyan inks are alternately formed to perform monochrome printing.

According to a seventh aspect of the present invention, in the inkjet recording apparatus of the fifth aspect, the driving frequency of the inkjet head is set to a maximum driving frequency fma.
x or less of x, a single black ink dot, a yellow ink dot, a magenta ink dot, a cyan ink dot, and a composite black dot that is a mixture of yellow, magenta, and cyan inks Are alternately formed to perform monochrome printing.

According to an eighth aspect of the present invention, in the inkjet recording apparatus of the fifth aspect, the driving frequency of the inkjet head is set to a maximum driving frequency fma.
At a quarter of x or less, dots of a single color black ink, dots of a yellow ink, dots of a magenta ink, and dots of a cyan ink are alternately formed to perform monochrome printing.

According to a ninth aspect of the present invention, there is provided an ink jet recording apparatus according to any one of the fifth to eighth aspects, further comprising an environmental temperature means for detecting an environmental temperature of the ink jet head. Based on the above, dots of two or more colors are alternately formed only when the environmental temperature is equal to or lower than a predetermined temperature.

According to a tenth aspect of the present invention, there is provided the
10. The ink jet recording apparatus according to claim 9, further comprising means for changing a drive waveform applied to the ink jet head in accordance with a result of detecting the environmental temperature.

An ink jet recording apparatus according to claim 11 is
The ink jet recording apparatus according to any one of claims 5 to 10, wherein the permeability of the black ink used to the recording medium is lower than the permeability of the color ink to the recording medium.

According to a twelfth aspect of the present invention, there is provided a head drive control device for driving and controlling an ink jet head capable of discharging a plurality of color ink droplets mounted on a carriage, wherein the minimum dot pitch corresponding to the resolution is Dp,
The maximum drive frequency of the inkjet head is fmax,
The inkjet head is driven at the maximum drive frequency fmax
Vc is the speed of the carriage at which dots can be formed at the dot pitch Dp when driven by Dp, and Dp = Vc ×
When the relationship of 1 / fmax is satisfied, 2 for the color to be printed
Means are provided for alternately forming dots of the above colors at a dot pitch larger than the dot pitch Dp.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic plan view of a mechanism of an ink jet printing apparatus to which the present invention is applied, and FIG. 2 is a schematic side view of a mechanism of the printing apparatus.

In this ink jet recording apparatus, a carriage 4 is slidably mounted on a front guide 2 and a guide shaft 3 provided between left and right main scanning frames 1 and 1, and a yellow (Y) ), Magenta (M), cyan (C) and black (Bk), a recording head 5 composed of a plurality of ink jet heads for ejecting ink droplets, and an ink cartridge 6 of each color ink on the upper surface. Is detachably provided.

A main scanning motor 8 is attached to a substantially L-shaped stay 7 provided between the left and right main scanning frames 1 and 1, and a motor pulley 9 and a stay 7 mounted on a rotation shaft of the main scanning motor 8 are attached to the main scanning motor 8. A belt 11 is stretched between the attached side pulley 10 and the carriage 4 as shown in FIG.
Is fixed to the belt 11 by a belt clamp 12, and the main scanning motor 8 is rotated to drive the carriage 4 in FIG.
(The main scanning direction). The side pulley 10 is attached so as to be able to move slightly in the main scanning direction, and tension is applied to the belt 11 by a tension spring 13.

On the other hand, a platen 16 is rotatably mounted between the left and right sub-scanning frames 15, 15, and the transport roller 1 pressed against the peripheral surface of the platen 16 as shown in FIG.
7 and 18, and a paper pan 19 for guiding the paper along the peripheral surface of the platen 16. Then, the sheet feed tray 21 set at the lower front side of the recording apparatus
The paper 24, which is a recording medium loaded on the ascending tray 23 urged by the ascending spring 22, is fed out one by one by a paper feed roller 25 and a corner claw 26 of the paper feed tray 21, and is fed along a paper feed guide 27. The guide is guided to the peripheral surface of the platen 16.

A paper guide 28 serving as a paper guide is disposed near the paper exit of the platen 16 so as to face the carriage 4, and the paper 24 sent out from the platen 16 is pressed near the entrance of the paper guide 28. A paper press 29 is disposed, and a paper discharge roller 31 and a spur roller 3 for discharging the paper 24 to a paper discharge tray 30 near the exit.
2 are arranged.

Further, a sub-scanning motor 34 is mounted on a sub-frame 33 mounted on the main scanning frame 1 as shown in FIG. 1, and a motor gear 35 is mounted on a rotating shaft 34a of the sub-scanning motor 34 as shown in FIG. This motor gear 35
The idler gear 36 meshes with the idler gear 3
6 is engaged with a platen gear 38 attached to the end of the platen 16 to transmit the rotation of the sub-scanning motor 34 to the platen 16 and also to various rollers and rollers, so that the sub-scanning motor 34 , The platen 16 and various rollers and rollers rotate to convey the paper 24 on the paper guide 28 in the direction indicated by the arrow B (the sub-scanning direction).

With such a configuration, the recording head 5
While moving (carriage 4) in the main scanning direction and scanning,
The paper 24 is conveyed in the sub-scanning direction, and a desired color image is recorded on the paper 24 by ejecting ink droplets of a required color from nozzles of each inkjet head of the recording head 5.

Next, an example of an ink jet head constituting the recording head 5 will be described with reference to FIGS. FIG. 3 is an exploded perspective view of the inkjet head,
FIG. 4 is an enlarged sectional view of a main part of the head in a direction orthogonal to a channel direction (a nozzle arrangement direction), and FIG. 5 is an enlarged sectional view of a main part of the head in a channel direction.

In this ink-jet head, a plurality of piezoelectric elements 42, which are laminated piezoelectric elements, are joined and arranged in two rows on an insulating substrate 41 made of ceramic, glass epoxy resin, or the like. A frame 43 surrounding the periphery of the frame 42 is joined. Here, the piezoelectric element 4
Reference numeral 2 denotes alternately arranged drive units 44 serving as actuator elements and non-drive units 45 which simply fix and support the liquid chamber member. The upper surfaces of the multilayer piezoelectric element 42 and the frame 43 are positioned or ground on substantially the same plane.

A vibration plate 47 is joined to the upper surface of each of the piezoelectric elements 42 and the frame 43. The vibration plate 47 is formed of a diaphragm 48 serving as a displacement portion, a beam 49 connected to the non-driving portion 45, and a base 50 connected to the frame 43. The diaphragm 48 has an island shape which faces and connects to the driving portion 44. It is formed from a convex portion 51 and a thin film portion 52. The bonding between the substrate 41, the piezoelectric element 42, and the vibration plate 47 is performed by an adhesive 46.

A two-layer liquid chamber partition member 53 made of a photosensitive resin film or the like is provided on the vibration plate 47 by bonding.
A nozzle plate 55, which is a nozzle forming member in which a plurality of nozzles 54 are formed in two rows, is bonded to the liquid chamber partition member 53. The liquid chamber partition member 53 forms an upper partition 57 and a lower partition 58, respectively, and is located together with the vibration plate 47 and the nozzle plate 55 on the pressurized liquid chamber 59 facing the drive unit 44, on both sides of the pressurized liquid chamber 59, and the like. Common liquid chamber 60, pressurized liquid chamber 5
An ink supply path 61 which also serves as a fluid resistance portion communicating the common liquid chamber 60 with the common liquid chamber 60 is formed.

Here, as shown in FIG. 4 and FIG. 5, the piezoelectric element 42 has a PZT (= P
b (Zr · Ti) O ₃ ) 63 and internal electrodes 64 made of silver / palladium (AgPd) having a thickness of several μm / 1 layer are alternately laminated. The piezoelectric element has a thickness of 10 to 50 μm
The drive voltage can be reduced by using a multi-layer structure of / 1 layer. For example, an electric field strength of 1000 V / mm of the piezoelectric element can be obtained with a pulse voltage of 10 to 50 V. The material used for the piezoelectric element is not limited to the above,
BaTiO ₃ , PbT generally used as a piezoelectric element material
It is also possible to use a ferroelectric material such as TiO ₃ , (NaK) NbO ₃ , and other electromechanical transducers.

Each of the internal electrodes 64 of the piezoelectric element 42 has left and right end electrodes (external electrodes) 6 made of AgPd every other layer.
5,66. On the other hand, on the substrate 41, a pattern of a common electrode 67 for applying a driving waveform to the driving unit 44 is formed between the columns of the piezoelectric elements 42, and the driving unit 44 A pattern of an individual electrode 68 for providing a selection signal is provided. Then, the external electrode 65 of the driving unit 44 is connected to the conductive adhesive 7 such as a silver paste.
0 is connected to the common electrode 67, and the external electrode 66 is also connected to the individual electrode 68 via the conductive adhesive 70.

The pattern portions of the common electrode 67 connected to the respective driving portions 44 are connected to each other by applying a conductive adhesive 70 in a hole 71 formed at the center of the frame 43. I have to. The common electrode 67 and the individual electrode 68 are respectively connected to the FPC cable 7.
2, 73 are connected. In addition, ink supply holes 75, 76, 77 for supplying ink supplied from the outside to the common liquid chamber 60 are provided in the substrate 41, the frame 43, and the vibration plate 47.
Are formed respectively.

The operation of the ink jet head configured as described above will be described. In this ink jet head, by applying a driving waveform (pulse voltage of 10 to 50 V) to the driving unit 44 in accordance with a recording signal, a displacement in the stacking direction occurs in the driving unit 44, and the vibration plate 47.
The pressurized liquid chamber 59 is pressurized through the diaphragm section 48 of the above and the pressure is increased, and ink droplets are ejected from the nozzle 54. At this time, ink flow also occurs in the direction of the ink supply path 61 leading from the pressurized liquid chamber 59 to the common liquid chamber 60.
By reducing the cross-sectional area of the ink supply path 61, the ink supply path 61 functions as a fluid resistance part, thereby reducing the flow of ink toward the common liquid chamber 60, thereby preventing a drop in ink ejection efficiency.

Then, with the end of the ink droplet ejection, the ink pressure in the pressurized liquid chamber 59 decreases, and a negative pressure is generated in the pressurized liquid chamber 59 due to the inertia of the ink flow and the discharge process of the drive pulse. To the ink filling process. At this time, the ink supplied from the ink tank flows into the common liquid chamber 60 and is filled from the common liquid chamber 60 into the pressurized liquid chamber 59 via the ink supply path 61. Then, when the vibration of the ink meniscus surface at the outlet of the nozzle 54 is attenuated and returned to the vicinity of the outlet of the nozzle 54 due to surface tension (refill) to reach a stable state, the next ink droplet ejection operation is started.

Next, a head drive control device according to the present invention in this ink jet recording apparatus will be described with reference to FIG. In the following description, the inkjet head is H, and the piezoelectric element serving as the driving unit is PZ.
T, the common electrode 67 uses Com, and the individual electrode 68 uses SEL. As described above, the recording head includes four heads for ejecting ink droplets of each color of yellow (Y), magenta (M), cyan (C), and black (Bk). A head that ejects ink droplets is a “Y head”, a head that ejects ink droplets of magenta (M) ink is an M head,
A head that ejects cyan (C) ink droplets is referred to as a C head, and a head that ejects black (Bk) ink droplets is referred to as a “Bk head”.

FIG. 6 is a block diagram showing an example of a head drive control device according to the present invention, FIG. 7 is a circuit diagram showing an example of a constant voltage drive circuit of a head drive section, and FIG. 8 is a waveform generation circuit of an identification voltage drive circuit. And FIG. 9 is a block diagram illustrating an example of a channel selection circuit of the head drive unit. Although only the Bk head drive unit is illustrated in detail in FIG.
The configurations of the head driving unit and the C head driving unit are the same as those of the Bk head driving unit.

The ink jet head H constituting the Bk head, the Y head, the M head, and the C head has a plurality of (m) nozzles for ejecting ink droplets (the number of nozzles is m = 64) as described above. It has 64 piezoelectric elements PZT, which are electromechanical transducers corresponding to each nozzle, one electrode of each piezoelectric element PZT is shared and used as a common electrode Com, and the other electrode is individually provided for each piezoelectric element PZT. To form an individual electrode (selection electrode) SEL.

On the other hand, a head drive control device for controlling the driving of the ink jet head H includes a Bk head drive unit 101, a Y head drive unit 102, and an M head drive unit 10.
3, a C head driving unit 104, and a control unit 105 that supplies control signals and the like to each of the head driving units 101 to 104. The control unit 105 is, for example, a microcomputer or the like that controls the entire inkjet recording apparatus. Can be configured.

The Bk head driving unit 101 includes a control unit 105
A waveform generation circuit 107 that receives a drive timing signal (pulse) STB from the controller and generates and outputs a drive waveform, and outputs the output of the waveform generation circuit 107 to the inkjet head H.
A constant voltage driving circuit 106 including a low impedance output circuit 108 for outputting to the common electrode Com of the
5, a channel (ch) selection circuit 10 that supplies selection signals Do1 to Do64 to the plurality of piezoelectric elements PZT of the inkjet head H based on the print data signal DI and the like from the printer 5.
9

The waveform generating circuit 10 of the constant voltage driving circuit 106
7 can be composed of, for example, a ROM, a D / A converter, or another pulse generation circuit and a waveform deformation circuit such as a calculus circuit, a clip circuit, or a clamp circuit. This waveform generation circuit 10
7 includes a drive timing signal generator 11 of the controller 105.
In addition to the drive timing signal STB that determines the timing for generating and outputting a drive waveform from 0, the Vp control signals SVp1 to SVp3 (Vp control signals SVp1 to SVp3) for adjusting and selecting the drive voltage (voltage value) Vp of the drive waveform from the Vp control signal generator 11. And / or tr control signals Str1 to Str3) for adjusting and selecting a rising time constant tr of a drive waveform to be described later are also input.

The low impedance output circuit 108
Is a buffer amplifier, SEPP (Single Ended Pu)
sh Pull) and the like. By using the low impedance output circuit 108, the output of the drive voltage waveform becomes a low impedance output to the piezoelectric element, and the waveform is not distorted due to the variation of the piezoelectric element and the difference in the number of drive channels.

The control unit 105 controls the drive timing signal ST
A drive timing signal generator 110 for generating and outputting B;
A Vp control signal generation unit 111 that generates and outputs Vp control signals SVp1 to SVp3, a pattern selection unit 112 that selects one of a single-color Bk pattern and a mixed-color Bk (Y + M + C) pattern as a Bk print pattern described below, A print signal generator 113 for outputting the print data signal DI, and a table 114 in which data defining the relationship between the ambient temperature, the Bk print pattern, and the drive voltage Vp of the drive waveform are provided.
Further, a detection signal from a temperature sensor 115 which is an environmental temperature detecting means for detecting an environmental temperature of the ink jet head is input to the control unit 105.

Here, an example of the waveform generating circuit and the low impedance output circuit in the constant voltage driving circuit 106 will be described with reference to FIG. The constant voltage drive circuit 106 connects an input terminal IN to which a drive timing pulse (drive timing signal) STB is supplied to a base of a transistor Tr1 via a buffer B and to a base of a transistor Tr2 via an inverter I, respectively. The power supply voltage Vpp is applied to the collector of the transistor Tr1, and the emitter of the transistor Tr2 is grounded.

A series circuit of a charging resistor Ra and a diode D1 is connected to the emitter of the transistor Tr1, and a series circuit of a discharging resistor Rb and a diode D2 is connected to the collector of the transistor Tr2.
Is connected to the anode side of the diode D2, a capacitor Ck is connected between this connection point a and the ground, and a time constant circuit at the time of charging with the charging resistor Ra and the capacitor Ck is formed by the discharging resistor Rb and the capacitor Ck. Constitutes a time constant circuit at the time of discharge. Further, the voltage Vout is applied to the connection point a via the diode Dk.

The connection point a is connected to the transistors Tr3 to Tr3.
The base of the transistor Tr3, which is the input side of the low impedance output circuit 104 composed of Tr6, and the transistor T
The common electrode Com of the inkjet head H is connected between the emitter of the transistor Tr5 and the collector of the transistor Tr6 on the output side.

In this constant voltage drive circuit 106, when drive timing pulse STB is input to input terminal IN and "H" level is input to buffer B, buffer B outputs a voltage level lower than power supply voltage Vpp. As a result, the transistor Tr1 is turned on, the inverter I becomes "L" and the transistor Tr2 is turned off, so that charging of the capacitor Ck starts at a charging time constant determined by the charging resistor Ra and the capacitor Ck by the power supply voltage Vpp. Is done.

At this time, the diode Dk is connected to the connection point a.
Since the voltage Vout is applied via the (drop voltage Vd), the charging voltage of the capacitor Ck does not rise to the power supply voltage Vpp, and the voltage (Vout +
Vd) and the drive voltage V
It becomes the maximum value of p (Vp = Vout + Vd).

When the drive timing pulse STB is not inputted to the input terminal IN and the "L" level is inputted to the buffer B, the output of the buffer B becomes the power supply voltage Vpp.
As a result, the transistor Tr1 is turned off, while the output of the inverter I is inverted with respect to the output of the buffer B. Therefore, the transistor Tr1 is turned off and the transistor Tr2 is turned on at the same time. The discharging of the capacitor Ck charged to the voltage Vp with the determined discharging time constant starts.

Therefore, by changing the voltage Vout applied to the waveform generating circuit 107 of the constant voltage driving circuit 106, the driving voltage Vp of the driving waveform can be variably controlled.

The circuit configuration of the Vout generator for generating and outputting the voltage Vout that defines the drive voltage Vp will be described with reference to FIGS. This voltage Vou
The t generation unit includes a three-terminal regulator 121 and a resistance selection circuit 122. By supplying a constant voltage source to the voltage input terminal Vin, the three-terminal regulator 121 supplies a resistance R1a connected between the adjustment terminal adj and the voltage output terminal Vout and a resistance R1a of the resistance selection circuit 122 connected between the adjustment terminal adj and the ground. A voltage corresponding to the value R2 is output from the voltage output terminal Vout. For example, LM317T (trade name) manufactured by National Semiconductor can be used.
Therefore, the output voltage Vout from the three-terminal regulator 121 is, for example, Vout = 1.25 × (1 + R2 /
R1).

The resistor selection circuit 122 is constituted by connecting in series a parallel circuit of a resistor Rs, a resistor Rp, and resistors R21 to R23 selected by switching transistors Q1 to Q3. For example, SN740 manufactured by Texas Instruments
6 (product name) or the like. The resistance selection circuit 122 includes the Vp of the control unit 105 described above.
Vp control signals SVp1 to SVp from control signal generator 111
Vp3 is input to the bases of the transistors Q1 to Q3, respectively.

Therefore, while supplying the power supply voltage Vpp to the three-terminal regulator 121, the Vp control signal generator 1
By applying the 11-bit to 3-bit Vp control signals SVp1 to SVp3 to the resistor selection circuit 122, the output voltage Vout of the three-terminal regulator 121 can be changed at a maximum of eight different levels. By inputting as the voltage Vout of the voltage driving circuit 106, the driving voltage Vp of the driving waveform can be set to a predetermined value.

The different voltage Vout is generated, for example, by using a voltage dividing circuit in which a resistor and a parallel circuit of a variable resistor and a capacitor are connected in series, and the voltage across the capacitor is output as the voltage Vout. Thus, it is also possible to change the variable resistance.

Next, the channel selection circuit 109 will be described with reference to FIG. This channel selection circuit 10
Reference numeral 9 denotes a 64-bit shift register 126 having the same number of bits or more as the number m of nozzles (here, m = 64) for taking in the serial input SI with the clock CLK, and a latch signal / Latch with LAT (note that the sign “/” means inversion) 6
A gate circuit group 128 composed of a 4-bit latch circuit 127 and a gate circuit G corresponding to each piezoelectric element PZT having one input of the output of the latch circuit 127 and the other input of the drive timing signal / STB via the NOT circuit NG. When,
It has a transistor array 129 made up of transistors Q that are turned on / off by the output of each gate circuit G and a diode array 130 made up of diodes D connected to each transistor Q, corresponding to each piezoelectric element PZT.

Then, the print data signal DI input as the serial input SI is taken into the shift register 126 in response to the clock signal CLK, and the latch circuit 127 outputs the latch signal / LAT to the shift register 12 at that time.
6 is latched, the required gate circuit G is opened by the drive timing signal / STB from the control unit 105, and the transistor Q is turned on, thereby selecting the selection signal Don (n
= 1 to 64) and outputs the low impedance output circuit 108
Is applied to the piezoelectric element PZT for driving.

Next, the operation of the head drive control device configured as described above will be described with reference to FIGS.
First, the background of the present invention will be described. General driving frequency f of the inkjet head (driving waveform period 1 /
FIG. 10 shows the relationship between f) and the ink droplet ejection amount Mj. Here, the upper limit of the drive frequency f at which the normal drive is possible is up to a frequency (maximum drive frequency) fmax at which the ink droplet ejection amount Mj does not change. At this time, if the moving speed of the carriage (carriage speed) is Vc, Vc * 1
An image is formed at a dot pitch of / fmax = Dp (* in the formula is a multiplication symbol). That is, if the minimum dot pitch corresponding to the resolution is Dp, the maximum drive frequency of the inkjet head is fmax, and the speed of the carriage capable of forming dots at the dot pitch Dp when the inkjet head is driven at the maximum drive frequency fmax is Vc, Dp = V
The relationship of c × 1 / fmax is established.

Therefore, in order to keep the dot pitch Dp constant and keep the carriage speed higher than the carriage speed Vc, the drive frequency f of the ink jet head must be higher than the maximum drive frequency fmax. However, when the driving frequency f of the head is increased to the maximum driving frequency fmax or higher, the dots become larger with the fluctuation of the ink droplet ejection amount Mj at the time of 100% printing (a state in which ink droplets are ejected in each cycle of the driving waveform). Or become smaller.

For example, if scanning is performed at twice the carriage speed Vc, the head must be driven at a driving frequency f twice (= 2 * fmax) the maximum driving frequency fmax in order to keep the dot pitch Dp constant. Therefore, the period of the driving waveform at this time is 1 / (2 * fma, as shown in FIG.
x).

In this case, when monochrome printing is performed with a Bk head (the nozzle arrangement direction is the sub-scanning direction) as shown in FIG. 12A, 50% printing (drive waveform) is performed as shown in FIG. ), The driving frequency f is substantially 2 * fmax * 1/2.
= Fmax, which is the same as driving at the maximum drive frequency fmax, so that the ink droplet ejection amount Mj does not fluctuate.

However, when monochrome printing is performed with the Bk head (the nozzle arrangement direction is the sub-scanning direction) as shown in FIG.
In the case of% printing, the drive frequency f is 2 * fmax, and the drive is performed at twice the maximum drive frequency fmax (period of 1/2 * fmax). As shown in FIG. Since the amount Mj decreases, white streaks occur.

Incidentally, such an ink droplet ejection amount Mj
As described above, the change in the ink droplets originally shifts to the next ink droplet ejection operation after the meniscus after the ink ejection is in a steady state. However, due to the drive frequency or the fluid resistance of the ink, While the meniscus does not fall into the steady state, the next drive pulse (drive waveform) causes ejection of ink droplets. Especially,
If the fluid resistance is large, as in the case where the ink viscosity is high, the ability to supply ink to the liquid chamber is reduced, and the ink droplet ejection amount Mj is significantly reduced. In other words, the fluctuation of the ink droplet ejection amount Mj largely depends on the ink supply capability to the liquid chamber determined by the physical properties of the ink and the liquid chamber structure.

Here, as a method for compensating for the decrease in the ink droplet ejection amount Mj, for example, it is conceivable to increase the drive voltage Vp of the drive waveform, and as shown in FIG.
Is increased, the ink droplet ejection amount Mj can be increased accordingly when the drive frequency f = fmax. However, at the time of high frequency driving, that is, f = 2 * f
When driving at the driving frequency of max, the ink droplet ejection amount Mj hardly increases even if the driving voltage Vp is increased.

Therefore, in order to increase the ink droplet ejection amount Mj at the time of high frequency driving, the ink viscosity must be lowered or
It is conceivable to increase the ink supply capacity by reducing the fluid resistance value of the fluid resistance part due to the liquid chamber structure. However, if the physical properties of the ink are changed to reduce the viscosity of the ink, the image quality may be significantly deteriorated. Also, if the fluid resistance value of the liquid chamber is reduced, the liquid chamber and the common liquid chamber become large, which leads to an increase in the size of the head.

Therefore, in the head drive control device according to the present invention, the minimum dot pitch corresponding to the resolution is set to D
p, the maximum drive frequency of the inkjet head is fma
x, the inkjet head is driven at the maximum drive frequency fm
The speed of the carriage capable of forming dots at the dot pitch Dp when driven at ax is Vc, and Dp = Vc
A means is provided for alternately forming dots of two or more colors at a dot pitch larger than the dot pitch Dp when the relationship of × 1 / fmax is satisfied.

Thus, when the relationship of Dp = Vc × 1 / fmax is established, the substantial driving frequency f is reduced, and the carriage is moved at the carriage speed when the relationship of Dp = Vc × 1 / fmax is established. Scanning can be performed at a speed exceeding Vc, or a substantial reduction in the driving frequency f as the carriage speed Vc can compensate for a decrease in the ink droplet ejection amount Mj.

That is, as shown in FIG. 15A, in this ink jet recording apparatus, a Y head for discharging Y ink, an M head for discharging M ink, a C head for discharging C ink, and a Bk ink for discharging A recording head composed of Bk heads (each having a plurality of nozzles in the sub-scanning direction) is provided, and the carriage 4 on which the recording head is mounted is scanned at twice the carriage speed Vc (2 * Vc).

Here, when monochrome printing is performed (the color to be printed is black), dots of a single color Bk ink by a Bk head (hereinafter simply referred to as “Bk dots”. The same applies to other colors. ) And composite (mixed color) Bk dots (mixed color Bk dots) that mix each of the Y, M, and C inks to form black are alternately formed at a dot pitch (2 * Dp) larger than the dot pitch Dp. .

That is, when the Bk dots and the mixed color Bk dots are formed alternately, even if the carriage speed is set to twice the carriage speed Vc, the Bk dots formed by the respective heads and the mixed color Bk dots are formed. Each pitch only needs to satisfy the relationship of 2 * Dp = 2 * Vc * 1 / fmax, and the driving frequency f of each head is twice the maximum driving frequency fmax because the carriage speed is doubled. 2 * fmax), it is only necessary to drive at the maximum drive frequency fmax, so that the ink droplet ejection amount Mj does not decrease and no white streak occurs even when 100% printing is performed. Will be.

The number of colors to be printed may be two or more. For example, as shown in FIG. 16, when performing monochrome printing, Bk dots, Y dots, M dots, C dots, Bk dots alternately, that is, mixed color Bk dots,
Even if the Bk dots, Y dots, Bk dots, C dots, Bk dots, and M dots are alternately formed in this order (not limited to this order), even if the carriage speed is doubled, driving is performed at the maximum driving frequency fmax. Thus, the dot pitch Dp can be obtained.

Further, as shown in FIG.
Y dots, M dots, and C dots can be alternately formed. In this case, although the black (Bk) density is lower than the patterns of FIGS. 15 and 16, the pitch of dots formed by each head is 4 * Dp = 4 * Vc * 1 / (f
max), the carriage speed Vc can be quadrupled.

Here, since the substantial driving frequency of the head can be reduced, the case where the carriage is scanned at the carriage speed Vc or higher while driving the head at the maximum driving frequency fmax is described. On the other hand, the head can be driven at a reduced drive frequency f while scanning the carriage at the carriage speed Vc.

That is, even when the inkjet head is driven at the maximum drive frequency fmax and the carriage is scanning at the carriage speed Vc, if the environmental temperature of the inkjet head changes, the physical properties of the ink also change.
In particular, in a low-temperature environment, the ink viscosity increases, so that the fluid resistance increases. As a result, as shown by the broken line in FIG.

Therefore, in such a case as well, FIG.
As described with reference to FIGS. 5 to 17, by alternately forming dots of Bk, Y, M, C, and mixed color Bk (Y + M + C), the substantial drive frequency of each head can be reduced to １ ／ or Since it can be reduced to ４, it is possible to correct a decrease in the ink droplet ejection amount Mj. Further, since the drive frequency is lowered, the adjustment of the drive voltage is also performed, so that the ink droplet ejection amount Mj can be more effectively corrected.

In order to perform the above-described head drive control, the head drive control device according to the present invention includes a table 114 as shown in FIG. This table 1
14, the ambient temperature (° C.) and B
Data indicating the relationship between the k print pattern and the drive voltage Vp (V) is stored in a table. As the Bk printing pattern, as described above, a single color pattern that forms Bk dots using only Bk ink, and a mixed color with Yk dots (Y + M + C)
Dots are alternately formed, or Bk dots and color (Y, M, C) dots are alternately formed, or Bk dots, mixed color Bk dots, and color (Y, M, C) dots are alternately formed. The color mixture pattern to be formed is set.

Therefore, the Vp control signal generating section 111 of the control section 105 sets the driving voltage Vp corresponding to the detected environmental temperature from the table 114 based on the environmental temperature of the ink jet head (recording head) detected by the temperature sensor 115. 3-bit Vp control signals SVp1 to SVp
3 is read and output to the constant voltage drive circuits 106 of the head drive units 101 to 104. Thereby, as described in FIG. 8 described above, the voltage Vout corresponding to the 3-bit Vp control signals SVp1 to SVp3 is output from the voltage Vout generation unit.
Out is generated and output, and the drive voltage Vp of the drive waveform is variably set to a drive voltage value with respect to the ambient temperature, thereby preventing a drop in the ink droplet ejection amount Mj.

On the other hand, the pattern selection unit 112 of the control unit 105
Selects a mixed color pattern or a single color pattern as the Bk printing pattern based on the detected environmental temperature. Based on the selection result, the print signal generation unit 113 determines whether the selected Bk printing pattern is a mixed color pattern. The shift register shown in FIG. 9 which configures each channel selection circuit 109 of the head driving units 101 to 104 so that the printing is performed by any one of the printing patterns of FIGS. When the selected Bk printing pattern is a single-color pattern, a print data signal DI such that printing is performed using only Bk dots is output to the channel selection circuit 109 of the head driving unit 101. .

Thus, the Bk head alone, the Bk head, the Y head, the M head, and the C head are driven in accordance with the selected Bk printing pattern, and when a mixed color Bk pattern is used, two color dots (single color Bk) are used. Dots and mixed color Bk dots) are alternately formed, and when the environmental temperature is low, printing is performed by substantially lowering the driving frequency f to increase the ink droplet ejection amount Mj to secure a required dot diameter. I do.

As described above, in this embodiment, an example has been described in which the drive voltage Vp of the drive waveform is variably controlled in accordance with the environmental temperature. However, the rising time constant tr of the drive waveform is variably controlled, or the drive waveform Vp is controlled. By variably controlling both the drive voltage Vp and the rise time constant tr, the ink droplet discharge speed Vj and the discharge amount Mj can be more finely controlled.
Image quality can be further improved.

Here, a circuit example of the constant voltage driving circuit capable of varying the rising time constant tr of the driving waveform will be described with reference to FIG. This constant voltage driving circuit is different from the constant voltage driving circuit shown in FIG. 7 in that the charging resistors Ra1, Ra2, Ra are connected in series with the diode D1.
3 are connected in parallel, and these charging resistors Ra1, Ra
2, Ra3 and the power supply voltage Vpp, switching transistors Tr11, Tr12, Tr13 are connected respectively.

Then, the transistors Tr11, Tr1
2 and Tr13 have buffers B1 and B
2 and B3, and these buffers B1, B2 and B3
, A drive timing pulse STB is input via gate circuits G1, G2, and G3. These gate circuits G1, G
2 and G3 are tr control signals S from the control unit 105, respectively.
When tr1, Str2, and Str3 are "H", they are opened and drive timing pulses STB are supplied to buffers B1 and B2.
2 and B3.

Therefore, the control unit 105 sets the drive timing pulse STB to “H” and sets the 3-bit tr
By setting any of the control signals Str1, Str2, and Str3 to "H", the tr control signals Str1, St2
Buffers B1, B2, B3 selected by r2, Str3
Outputs a voltage level lower than the power supply voltage Vpp, and the corresponding transistors Tr11, Tr12, Tr
13 is turned on, and the selected resistor Ra
The capacitor Ck is charged with a start-up time constant tr determined by any one of 1 to Ra3 and the capacitor Ck.

Therefore, a maximum of 8
Since the capacitor Ck can be charged with various types of start-up time constants tr, the start-up time constants tr
It is possible to select and generate and output three types of drive waveforms of 1, tr2 and tr3.

In this case, the drive voltage Vp of the drive waveform
May be fixed or may be varied using the circuit shown in FIG. 8 described above. If the voltage Vout is varied, a plurality of different start-up time constants tr and drive voltages Vp may be used. A drive waveform can be selectively generated and output.

Next, another embodiment of the present invention will be described with reference to FIG. 6 and FIGS. In this embodiment, the above-described single-color Bk pattern and mixed-color Bk pattern are selected according to the type of Bk ink to be used. That is, in general, when trying to increase the character quality or solid density of Bk (black), a non-permeable B
k ink may be used. On the other hand, as the color ink, when a non-penetrable ink is used, bleeding between colors becomes large, so that a permeable ink is used. Therefore, when a non-permeable ink is used for the Bk ink and a permeable ink is used for the color ink, the viscosity of the Bk ink is higher than the viscosity of the color ink. Dot diameter may not be obtained.

Therefore, a pattern selection signal from the host or a pattern selection signal by a switch or menu selection system provided in the ink jet recording apparatus main body is supplied to the print signal generation unit 113 of the control unit 105 shown in FIG.
The print signal generator 113 selects a single color pattern or a mixed color pattern as a Bk printing pattern according to the input pattern selection signal.

The print signal generator 113 outputs the Bk signal as shown in FIGS.
Dots and mixed color (Y + M + C) dots are formed alternately (FIG. 2
0) Alternatively, Bk dots and color (Y, M, C) dots are alternately formed (FIG. 22), or Bk dots, mixed color Bk dots, and color (Y, M, C) dots are alternately formed. (FIG. 21) The print data signal DI is transmitted to the head driving units 101 to 10 so that printing is performed with the mixed color pattern.
4 is output to each channel selection circuit 109.

As described above, by alternately forming Bk dots and Y, M, C, and mixed color Bk (Y + M + C) dots in accordance with the physical properties of the ink, the driving frequency is substantially reduced from fmax to 1/2. *
fmax or ＊* fmax, and it is possible to prevent a decrease in the ink droplet ejection amount Mj of Bk dots. Further, similarly to the above-described embodiment, if the drive voltage Vp is adjusted according to the environmental temperature, the dot diameter can be more accurately aligned.

Next, still another embodiment of the present invention will be described with reference to FIG. FIG. 23 is a main block diagram showing a control unit of the ink jet recording apparatus. In this embodiment, there are two printing modes, a high-speed printing mode and a high-quality printing mode. Therefore, the control unit 140 includes a print mode selection unit 141 that selects one of the high-speed print mode and the high-quality print mode, and a motor drive that controls a main scan motor drive circuit 142 that drives the main scan motor 8. The print data signal D is sent to the control unit 143 and the channel selection circuit of each head.
A print signal generator 144 for sending I, a table 145
And

The print mode selection section 141 selects a print mode based on a switch provided in the main body of the recording apparatus or a mode selection signal based on a menu selection method. The motor drive control unit 143 controls the main scanning motor drive circuit 142 at a scanning speed according to the print mode selected by the print mode selection unit 141.
The drive of the main scanning motor 8 is controlled via the controller to scan the carriage 4.

The print signal generator 144 outputs a print data signal DI for forming a single color Bk dot in accordance with the print mode selected by the print mode selector 141, or a single color Bk dot and a mixed color Bk dot as shown in FIG. Are generated and output. Table 145
In FIG. 24, a print mode, a Bk print pattern,
Data indicating the relationship between the carriage speed and the execution drive frequency is stored.

The operation of this embodiment thus configured will be described. First, 600 dpi (Dp = 42.3 μm) at the maximum drive frequency fmax = 16 kHz of the head
In order to output an image having a resolution of Vc, the carriage speed Vc becomes Vc = 677 mm / s (this is referred to as "high quality mode"). Here, when performing monochrome printing, B
If printing is performed using only k ink, the carriage speed V
When c is doubled (Vc = 1354 mm / s), the relationship of Dp = Vc * 1 / fmax holds as described above, so that the driving frequency f of the inkjet head is set to twice the maximum driving frequency fmax ( f = 2 * fmax = 32 kHz) to obtain an image of 600 dpi, or set the driving frequency f to the maximum driving frequency fmax (= 16 kHz) and set 3
Either to obtain an image of 00 dpi (Dp = 84.6 μm) must be selected.

However, when the driving frequency f of the head is 2 * f
When max is set to 32 kHz, the image density is reduced due to a decrease in the ink droplet ejection amount Mj, white stripes and density unevenness are generated, and the resolution is reduced to 300 dpi (dot pitch is set to 2 * Dp). In the case of (2), since the dot diameter twice or more is required and the ink droplet ejection amount Mj does not follow, the image quality is remarkably deteriorated in any case.

Therefore, in this embodiment, the maximum drive frequency fmax of the head is 16 kHz, and the speed of the carriage is 2 *.
Vc = 1354 mm / s, resolution 600 dpi (Dp = 42.
In the high-speed print mode in which an image is output at 3 μm), printing is performed using the above-described mixed color pattern.

That is, when the high-speed printing mode is designated as the printing mode, the printing mode selection unit 141 selects the high-speed printing mode, and the motor drive control unit 143 determines from the table 145 that the carriage speed is twice Vc = 1354.
The driving of the main scanning motor 8 is controlled via the main scanning motor driving circuit 142 so that the speed becomes mm / s. On the other hand, the print signal generation unit 144 sends print data to the channel selection circuit of each head drive unit so that Bk dots and mixed color Bk (Y + M + C) dots are alternately formed as shown in FIG. Signal D
Outputs I. At this time, the maximum driving frequency f of the head is f
max = 16 kHz, the ink droplet ejection amount M
j does not decrease and required image quality can be ensured.

Further, the maximum driving frequency fmax of the head = 8
To output an image with a resolution of 600 dpi (Dp = 42.3 μm) at kHz, the carriage speed Vc becomes Vc
= 338.5 mm / s (this is referred to as “high quality mode”). At this time, if the dots are alternately formed as shown in FIG. 16 by using the above-described head drive control device, the carriage speed is kept at 4 with fmax = 8 kHz.
High-speed printing can be performed with the double Vc = 1354 mm / s.

The configuration and drive waveform of the head drive section are as follows.
The drive waveform is not limited to the one in the above-described embodiment, as long as ink droplets can be stably ejected, and the drive waveform may be any shape such as a triangular waveform and a Sin (sine) waveform. Also, in the case of a head structure in which ink droplets are ejected when the drive waveform falls (the polarization direction of the piezoelectric element is a positive voltage), such as when the displacement of the piezoelectric element in the d31 direction is used as the energy generating means of the ink jet head. Is the start time constant tr
Instead, the fall time constant tf may be controlled. Further, instead of an electromechanical transducer such as a piezoelectric element, an electrothermal transducer can be used as an energy generating element.

[0098]

As described above, according to the ink jet recording apparatus of the first aspect, when the relationship of Dp = Vc × 1 / fmax is satisfied, the ink jet head is driven at a driving frequency equal to or lower than the maximum driving frequency fmax. Since means for alternately forming dots of two or more colors and means for scanning the carriage at a speed exceeding the carriage speed Vc are provided, high-speed printing is performed without deteriorating image quality while maintaining a desired dot diameter. be able to.

According to the ink jet recording apparatus of claim 2, in the ink jet recording apparatus of claim 1,
A black ink dot and a composite black dot in which yellow, magenta and cyan inks are mixed are alternately formed, and the carriage is moved at a carriage speed V.
Since monochrome printing is performed by scanning at twice the speed of c, monochrome printing can be performed at high speed without deteriorating image quality while maintaining a desired dot diameter.

According to the ink jet recording apparatus of claim 3, in the ink jet recording apparatus of claim 1,
Monochrome black ink dots, yellow ink dots, magenta ink dots, cyan ink dots, and composite black dots obtained by mixing the yellow, magenta, and cyan inks are alternately formed, and the carriage is formed. Since the monochrome printing is performed by scanning at twice the carriage speed Vc, high-speed printing of a monochrome image can be performed without deteriorating image quality while maintaining a desired dot diameter.

According to the ink jet recording apparatus of claim 4, in the ink jet recording apparatus of claim 1,
Monochromatic black ink dots, yellow ink dots, magenta ink dots, and cyan ink dots are alternately formed, and the carriage is scanned at a speed four times the scanning speed Vc of the carriage to print a monochrome image. Therefore, it is possible to print a monochrome image at a higher speed without deteriorating the image quality while maintaining a desired dot diameter. .

According to the fifth aspect of the present invention, when the relationship of Dp = Vc × 1 / fmax is satisfied, the inkjet head is driven at a drive frequency equal to or lower than the maximum drive frequency fmax to alternate the dots of two or more colors. And a means for scanning the carriage at a speed equal to or lower than the carriage speed Vc, so that the ink supply can be followed even if the physical properties of the ink and the environmental temperature change, to obtain a desired ink droplet ejection amount Mj. And a decrease in image quality can be prevented.

According to the ink jet recording apparatus of claim 6, in the ink jet recording apparatus of claim 5,
The driving frequency of the inkjet head is set to the highest driving frequency f.
Since the black ink dots and the composite black dots obtained by mixing the yellow, magenta, and cyan inks are alternately formed at a half or less of max to perform monochrome printing, the ink physical properties and Even if the environmental temperature changes, the desired ink droplet ejection amount Mj can be obtained by following the ink supply, and a decrease in the image quality of the monochrome image can be prevented.

According to the ink jet recording apparatus of claim 7, in the ink jet recording apparatus of claim 5,
The driving frequency of the inkjet head is set to the highest driving frequency f.
Set to not more than 1/2 of max, a composite black dot obtained by mixing single-color black ink dots, yellow ink dots, magenta ink dots, cyan ink dots, and yellow, magenta, and cyan inks Are formed alternately, and monochrome printing is performed. Therefore, even if the physical properties of the ink and the environmental temperature change, the ink supply can be followed to obtain a desired ink droplet ejection amount Mj. Quality deterioration can be prevented.

According to the ink jet recording apparatus of claim 8, in the ink jet recording apparatus of claim 5,
The driving frequency of the inkjet head is set to the highest driving frequency f.
Since the single-color black ink dot, the yellow ink dot, the magenta ink dot, and the cyan ink dot are alternately formed at １ ／ or less of max to perform monochrome printing. Even if the physical properties and the environmental temperature change, the desired ink droplet ejection amount Mj can be obtained by following the ink supply, and the deterioration of the image quality of the monochrome image can be prevented.

According to the ninth aspect of the present invention, in the inkjet recording apparatus of any one of the fifth to eighth aspects, the environmental temperature of the inkjet head is detected, and the environmental temperature is determined in advance based on the detection result. In this configuration, dots of two or more colors are alternately formed only when the temperature is equal to or lower than the predetermined temperature. Therefore, even if the environmental temperature changes, ink supply can be followed to obtain a desired ink droplet ejection amount Mj. The image quality of the image can be prevented from deteriorating.

According to the ink jet recording apparatus of the tenth aspect, the ink jet recording apparatus of the ninth aspect is provided with the means for changing the drive waveform applied to the ink jet head in accordance with the detection result of the environmental temperature. The driving waveform can be adjusted with the driving frequency to be adjusted, the ink droplet ejection amount Mj can be corrected with high accuracy, and an image with high image quality can be obtained.

According to the ink jet recording apparatus of claim 11, in the ink jet recording apparatus of any of claims 5 to 10, the permeability of the used black ink to the recording medium is more than the permeability of the color ink to the recording medium. Since the configuration is low, a desired dot diameter can be formed by high-frequency driving even when non-permeable black ink is used, and a high-quality image can be obtained.

According to the head drive control device of the twelfth aspect, in the head drive control device for driving and controlling the ink jet head mounted on the carriage and capable of discharging ink droplets of a plurality of colors, Dp = Vc × 1 / fmax When the relationship is satisfied, a means for alternately forming dots of two or more colors at a dot pitch larger than the dot pitch Dp with respect to the color to be printed is provided, so that the drive frequency is maintained and the desired resolution is maintained. It is possible to perform high-speed printing by increasing the carriage speed while maintaining the carriage speed, or to obtain a desired image quality in which the ink droplet ejection amount Mj is corrected by lowering the drive frequency while maintaining the carriage speed.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a mechanism of an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is a schematic side view of a mechanism section of the recording apparatus.

FIG. 3 is an exploded perspective view of an ink jet head constituting a recording head of the recording apparatus.

FIG. 4 is an explanatory sectional view of the inkjet head.

FIG. 5 is an explanatory cross-sectional view of the inkjet head in a direction orthogonal to FIG. 4;

FIG. 6 is a block diagram of a head drive control device according to the present invention.

FIG. 7 is a circuit diagram showing an example of a constant voltage driving circuit of the head driving unit in FIG. 6;

FIG. 8 is a block diagram illustrating an example of a voltage Vout generation unit included in a waveform generation circuit of the identification voltage drive circuit.

FIG. 9 is a block diagram illustrating an example of a channel selection circuit of the head driving unit in FIG. 6;

FIG. 10 is a diagram illustrating a relationship between a driving frequency and an ink droplet ejection amount Mj in an inkjet head.

FIG. 11 is a waveform chart for explaining a drive waveform at a drive frequency f = 2 * fmax.

FIG. 12 is an explanatory diagram for explaining the dot density in the case of 50% printing at a drive frequency f = 2 * fmax.

FIG. 13 is an explanatory diagram for explaining dot density in the case of 100% printing at a drive frequency f = 2 * fmax.

FIG. 14 shows a drive voltage Vp and an ink droplet ejection amount M of a drive waveform.
Diagram for explaining the relationship between j and fmax

FIG. 15 is an explanatory diagram illustrating an example of alternate printing of single-color Bk dots and mixed-color Bk dots for explaining one embodiment of the present invention;

FIG. 16 is an explanatory diagram illustrating an example of alternate printing of single-color Bk dots, Y dots, M dots, C dots, and mixed-color Bk dots.

FIG. 17 is an explanatory diagram illustrating an example of alternate printing of Bk dots, Y dots, M dots, and C dots of a single color.

FIG. 18 is an explanatory diagram of a table used for describing the head drive control device.

19 is a circuit diagram showing another example of the constant voltage drive circuit of the head drive unit in FIG.

FIG. 20 shows a single color Bk for explaining another embodiment of the present invention.
Explanatory diagram for explaining an example of alternate printing of dots and mixed color Bk dots

FIG. 21 is an explanatory diagram illustrating an example of alternate printing of single-color Bk dots, Y dots, M dots, C dots, and mixed-color Bk dots.

FIG. 22 is an explanatory diagram illustrating an example of alternate printing of Bk dots, Y dots, M dots, and C dots of a single color.

FIG. 23 is a main part block diagram for explaining still another embodiment of the present invention.

FIG. 24 is an explanatory diagram of a table used for describing the embodiment.

[Explanation of symbols]

4 ... carriage, 5 ... recording head, 16 ... platen, 3
4 ... Sub-scanning motor, 42 ... Piezoelectric element, 44 ... Drive section, 5
4 ... Nozzle, 59 ... Pressurized liquid chamber, 101 ... Bk head drive unit, 102 ... Y head drive unit, 103 ... M head drive unit, 104 ... C head drive unit, 105 ... Control unit, 106
... constant voltage drive circuit, 107 ... waveform generation circuit, 107 ... low impedance output circuit, 108 ... channel selection circuit, 110 ... drive timing signal generator, 111 ... Vp
Control signal generation unit, 112: pattern selection unit, 113: print signal generation unit, 114: table, 115: temperature sensor,
141: print mode selection unit, 143: motor drive control unit, 144: print signal generation unit, 145: table.

Claims (12)

[Claims] 1. An ink jet recording apparatus in which one or a plurality of ink jet heads capable of ejecting ink droplets of a plurality of colors are mounted on a carriage, the minimum dot pitch corresponding to the resolution is Dp, and the maximum drive frequency of the ink jet head is fmax. When the inkjet head is driven at the maximum drive frequency fmax, the speed of the carriage capable of forming dots at the dot pitch Dp is V
c, and when the relationship of Dp = Vc × 1 / fmax is satisfied,
The inkjet head is driven at the maximum drive frequency fmax
An ink jet recording apparatus comprising: means for driving at the following driving frequencies to alternately form dots of two or more colors; and means for scanning the carriage at a speed exceeding the carriage speed Vc. 2. The ink jet recording apparatus according to claim 1, wherein black ink dots and composite black dots obtained by mixing yellow, magenta, and cyan inks are alternately formed, and the carriage is moved at the carriage speed. An ink jet recording apparatus for performing monochrome printing by scanning at twice the speed of Vc. 3. The ink jet recording apparatus according to claim 1, wherein a single-color black ink dot, a yellow ink dot, a magenta ink dot, a cyan ink dot, and yellow, magenta, and cyan inks. And a composite black dot formed by alternately mixing a plurality of black dots, and scanning the carriage at twice the carriage speed Vc to perform monochrome printing. 4. The ink jet recording apparatus according to claim 1, wherein dots of a monochromatic black ink, dots of a yellow ink, dots of a magenta ink, and dots of a cyan ink are alternately formed, and the carriage is formed. An ink jet recording apparatus for performing monochrome printing by scanning at a speed four times the scanning speed Vc of the carriage. 5. In an ink jet recording apparatus in which one or a plurality of ink jet heads capable of ejecting ink drops of a plurality of colors are mounted on a carriage, the minimum dot pitch corresponding to the resolution is Dp, and the maximum drive frequency of the ink jet head is fmax. When the inkjet head is driven at the maximum drive frequency fmax, the speed of the carriage capable of forming dots at the dot pitch Dp is V
c, and when the relationship of Dp = Vc × 1 / fmax is satisfied,
The inkjet head is driven at the maximum drive frequency fmax
An ink jet recording apparatus comprising: means for driving at the following driving frequencies to alternately form dots of two or more colors; and means for scanning the carriage at a speed equal to or lower than the carriage speed Vc. 6. The ink jet recording apparatus according to claim 5, wherein the driving frequency of the ink jet head is set to a half or less of a maximum driving frequency fmax, and the black ink dots and the yellow, magenta, and cyan inks are used. An ink jet recording apparatus characterized in that mixed color composite black dots are alternately formed to perform monochrome printing. 7. The ink jet recording apparatus according to claim 5, wherein the driving frequency of the ink jet head is set to not more than の of the maximum driving frequency fmax, and the black ink dot, the yellow ink dot, and the magenta ink are used. An ink-jet recording apparatus for alternately forming dots of a black ink, dots of a cyan ink, and composite black dots in which yellow, magenta, and cyan inks are mixed to perform monochrome printing. 8. The ink jet recording apparatus according to claim 5, wherein the driving frequency of the ink jet head is set to 1/4 or less of the maximum driving frequency fmax, and the black ink dot, the yellow ink dot, and the magenta ink are used. An ink jet recording apparatus which performs monochrome printing by alternately forming dots of cyan ink and dots of cyan ink. 9. An ink jet recording apparatus according to claim 5, further comprising an environmental temperature means for detecting an environmental temperature of said inkjet head, wherein said environmental temperature is detected based on a detection result of said environmental temperature detecting means. Wherein two or more color dots are alternately formed only when the temperature is equal to or lower than a predetermined temperature. 10. The ink jet recording apparatus according to claim 9, further comprising means for changing a drive waveform applied to said ink jet head in accordance with a result of detecting said environmental temperature. 11. An ink jet recording apparatus according to claim 5, wherein the black ink used has a lower permeability to a recording medium than the color ink penetrates to the recording medium. Recording device. 12. A head drive control device for driving and controlling an ink jet head capable of discharging ink droplets of a plurality of colors mounted on a carriage, wherein a minimum dot pitch corresponding to resolution is Dp, and a maximum drive frequency of the ink jet head is fmax, the speed of the carriage capable of forming dots at the dot pitch Dp when the inkjet head is driven at the maximum drive frequency fmax is V
c, and when the relationship of Dp = Vc × 1 / fmax is satisfied,
A head drive control device comprising means for alternately forming dots of two or more colors at a dot pitch larger than a dot pitch Dp for a color to be printed.