JP2002079668A - Ink jet recording apparatus, apparatus for controlling head driving, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image quality from decreasing because of using papers of different thicknesses. SOLUTION: A parameter of a driving waveform generated and outputted from a waveform generation circuit 84 according to the detected result of a platen gap sensor 16 which detects the thickness of the paper 10 is changed and applied to a recording head 6.

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, a head drive control apparatus, and a storage medium.

[0002]

2. Description of the Related Art In general, there is an image recording apparatus such as a printer, a facsimile, a copying apparatus, a plotter, or the like, in which an ink jet head for discharging ink droplets is mounted as a recording head. For example, in a serial scan type ink jet recording apparatus, a recording head is mounted on a carriage, and the head is moved in the main scanning direction while a paper (meaning that an ink droplet lands). A sheet or other material is conveyed in the sub-scanning direction, and ink droplets are ejected from a recording head according to an image to be recorded, and the ink droplets land on a sheet to record an image.

As described above, in an ink jet recording apparatus, an ink droplet ejected from a recording head flies and lands on a sheet to record (print, print) an image.
The image quality is greatly affected by the speed immediately before the ink droplet lands on the paper (this is called “ink droplet speed”).

[0004] Here, the ink droplet speed of the ink droplet ejected from the recording head becomes lower as the flying distance becomes longer and becomes higher as the flying distance becomes shorter, even if the speed at which it is ejected from the recording head is constant. If the ink droplet speed is too slow, the flying direction of the ink droplets is likely to be affected by random wind pressure or the like due to the movement of the carriage, so that the ink droplets cannot land at the target landing position and the image quality deteriorates. On the other hand, when the ink droplet speed is too high, the speed at which the ink droplet lands on the paper is too high, causing the ink droplets to rebound and scatter mist-like fine droplets. When the fine mist droplets adhere to the paper, the image quality is degraded. Further, when the mist-like fine droplets adhere to the nozzle surface of the recording head, the speed and the flying direction of the ejected ink droplets are affected, and the image quality is also deteriorated.

Therefore, in a conventional ink jet recording apparatus, as described in Japanese Patent Application Laid-Open No. Sho 60-262551, a recording head having a positioning portion provided on a head substrate is mounted on a carriage having a positioning portion. In some cases, the gap between the recording head and the sheet is kept constant when the gap between the carriage and the sheet does not fluctuate.

However, in the ink jet recording apparatus, various kinds of paper such as plain paper, OHP sheet, special paper (meaning either glossy paper or coated paper, or both) are used. Since the thickness is not constant, even if the distance between the recording head and the platen that conveys the paper is kept constant, the distance between the recording head and the paper, that is, the nozzle surface And the printing surface of the paper (this is called the "paper surface")
Will change.

Therefore, for example, Japanese Patent Application Laid-Open No. 62-242541
As described in Japanese Patent Application Laid-Open Publication No. H10-209, a driving unit for rotating a guide shaft around an axis provided at an eccentric position at both ends of a guide shaft for guiding a carriage is provided so that a recording head can advance and retreat with respect to a sheet. In some cases, the gap between the recording head and the platen can be adjusted in accordance with the type of paper to be used, so that the distance between the recording head and the surface of the paper can be kept constant.

[0008]

However, in order to adjust the distance between the recording head and the paper surface, it is not possible to provide, for example, a gap adjusting mechanism for moving the carriage or a gap adjusting mechanism for moving the platen on the back of the paper. , The mechanism becomes complicated and the cost increases. In this specification, the “platen” means a member facing the recording head, and includes all members called a platen roller, a guide, a print receiving member, and the like.

In addition, it is not convenient to operate the gap adjusting mechanism of the recording apparatus when selecting the paper type with a printer driver of a personal computer or the like as in the case of configuring a network. There are issues.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is applied to an ink jet recording apparatus having improved image quality at low cost, a head drive control apparatus having improved image quality at low cost, and to these apparatuses. It is an object of the present invention to provide a computer-readable recording medium.

[0011]

In order to solve the above problems, an ink jet recording apparatus according to the present invention changes the speed of ink droplets ejected from a recording head according to the distance between the recording head and a sheet. It is configured.

Here, it is preferable to change the parameters of the drive waveform applied to the recording head according to the distance between the recording head and the sheet. Further, it is preferable that a means for detecting the distance between the recording head and the sheet is provided.

[0013] The ink jet recording apparatus according to the present invention comprises:
In this configuration, the speed of ink droplets ejected from the recording head is changed according to the type of paper.

Here, it is preferable to change the parameters of the drive waveform applied to the recording head according to the type of paper. Further, it is preferable that the recording apparatus main body is provided with means for designating the type of paper. Further, it is preferable that the type of paper is designated by the host.

The parameters of the drive waveform can be changed by any one of the peak value, rise time constant, fall time constant, peak value and rise time constant, and pulse width of the drive waveform. Further, it is preferable to provide a unit for storing the distance information between the recording head and the sheet and the data of the drive waveform in a table. Further, it is preferable to include means for storing the sheet type information and the driving waveform data in a table. Furthermore, it is preferable that printing can be performed on both sides of the sheet.

The head drive control device according to the present invention is provided with means for changing a parameter of a drive waveform applied to the recording head in accordance with a distance between the recording head and a sheet.

The head drive control device according to the present invention is provided with means for changing the parameters of the drive waveform applied to the recording head according to the type of paper.

Here, the parameters of the driving waveform are changed by
This can be performed using any one of the peak value, rising time constant, falling time constant, peak value, rising time constant, and pulse width of the drive waveform. Further, it is preferable to provide a unit for storing the distance information between the recording head and the sheet and the data of the drive waveform in a table. Further, it is preferable to include means for storing the sheet type information and the driving waveform data in a table.

The storage medium according to the present invention has a configuration in which the type of paper and the data of the parameter of the drive waveform related to the ejection speed of the ink droplet are stored in association with each other.

Here, the type of paper is plain paper, special paper, O
It is preferably an HP sheet. Further, it is preferable that the data of the parameter of the drive waveform is one or more data of the peak value, the rising time constant, the falling time constant, and the pulse width.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of a main part of the recording apparatus.

In this ink jet recording apparatus, a main guide rod 2 and a sub guide rod 3 are laid horizontally on a frame 1 in a substantially horizontal positional relationship, and the carriage 5 is moved by the main guide rod 2 and the sub guide rod 3 in the main scanning direction. Slidably supported.

The carriage 5 has four heads 6 for ejecting yellow (Y) ink, magenta (M) ink, cyan (C) ink, and black (Bk) ink, respectively. 6y ",
"6m", "6c", and "6k" are used. )
Also, the carriage 5 has four ink cartridges 7 for supplying inks of the respective colors to the heads 6 (the symbols of the ink cartridges of the respective colors are "7y", "7m", "7
c "and" 7k ". ) Is replaceable.

The head 6 is a piezo type in which an ink droplet is ejected by deforming and displacing a diaphragm forming the wall surface of the pressure chamber using an electromechanical transducer such as a piezoelectric element as a pressure generating means (driving means). , A bubble type in which a bubble is generated by ink film boiling using a heating resistor disposed in a pressurized chamber to discharge ink droplets, and a diaphragm (or a diaphragm that forms a wall of the pressurized chamber) An electrostatic type that discharges ink droplets by deforming and displacing the vibration plate with electrostatic force using an integrated electrode) and a counter electrode can be used.

The head 6 has three colors of light cyan, light magenta, and light yellow in addition to the four colors described above.
It is also possible to use a head of seven colors with additional colors. Further, as the head 6, instead of an independent head for each color, a multi-nozzle head having a nozzle for ejecting ink droplets of each color by one head may be used.

The carriage 5 is connected to a timing belt stretched between a driving pulley (drive timing pulley) rotated by a main scanning motor (not shown) and a driven pulley (idler pulley) to drive the main scanning motor. By controlling, the carriage 5 is moved and scanned in the main scanning direction.

The paper 10 set on the guide plate 8
Is taken in by a platen roller 13 rotated by a drive source (not shown) via a drive gear 11 and a sprocket gear 12, and is indicated by an arrow B by a peripheral surface of the platen roller 13 and a guide roller 14 and a pressure roller 15 pressed against the peripheral surface. It can be transported in any direction. The platen roller 13 has a knob 13a. A platen gap sensor 16 which is a thickness detection sensor for detecting the thickness of the paper 10 on the transport path of the paper 10
Has been arranged.

The platen gap sensor 16 has, for example, as shown in FIG. 3, a contact portion 20 which can contact the sheet 10 conveyed facing the peripheral surface of the platen roller 13 which is a conveying path. An arm 22 that swings with the support shaft 21 as a swing fulcrum according to the thickness of the arm 10;
A light sensor 24 that outputs a detection signal at a level corresponding to the displacement of the arm 22, that is, the thickness of the paper 10 when the light-shielding plate 23 provided at the other end of the sheet 2 moves in and out. Further, as the platen gap sensor 16, for example, a sensor that detects the thickness based on the difference in the reflection time of the laser light from the paper 10 and the conveyance path can be used.

In this ink jet recording apparatus, ink droplets are ejected from each of the recording heads 6 while moving the carriage 5 in the main scanning direction (the direction of arrow A), and an image for one line is formed on the paper 10. Is printed, and an image is recorded on the paper 10 while repeating the operation of transporting the paper 10 by one line in the sub-scanning direction (the direction of arrow B).

Next, an example of a piezo type ink jet head which can be used as the recording head 6 of the ink jet recording apparatus will be described with reference to FIGS. FIG. 4 is an explanatory sectional view of the head, and FIG.
It is a plane explanatory view showing in a transmission state.

In this ink jet head, a fluid resistance forming plate 32, a common ink flow path forming plate 33, and a nozzle plate 34 are sequentially laminated on a liquid chamber substrate 31 made of, for example, a single crystal silicon substrate and joined by an adhesive. , A plurality of nozzle holes 35, a plurality of liquid chambers 36 communicating with each nozzle hole 35, and a common ink flow path (common ink chamber) for supplying ink to the plurality of liquid chambers 36 via a fluid resistance portion 37. 38,
Nozzle communication passage 39 that communicates between nozzle hole 35 and liquid chamber 36
Etc. are formed.

Then, when forming a concave portion to become the liquid chamber 36 in the liquid chamber substrate 31 by anisotropic etching or the like, the etching of the liquid chamber 36 is performed by using an etching stop technique using a high-concentration P-type impurity diffusion layer such as boron. A vibration plate 40 forming a wall surface is also formed, and a laminated piezoelectric element 41
Are provided to constitute an actuator section (driving means).

In the ink jet head configured as described above, when a driving waveform is applied to the piezoelectric element 41, the piezoelectric element 41 is displaced in the stacking direction, and the diaphragm 40 is deformed and displaced toward the liquid chamber 36 and the liquid is displaced. The internal volume of the chamber 36 decreases, the pressure in the liquid chamber 36 increases, and ink droplets are ejected from the nozzle holes 35 through the nozzle communication passage 39.

Next, an example of an electrostatic ink jet head that can be used as the recording head 6 will be described with reference to FIGS. 6 is an explanatory sectional view of the head, and FIG. 7 is an explanatory plan view showing FIG. 6 in a transparent state.

The ink jet head includes a liquid chamber substrate 51 made of a single crystal silicon substrate or the like and a liquid chamber substrate 5
1, a lid member 52 provided above the liquid chamber substrate 51, an electrode substrate 53 provided below the liquid chamber substrate 51, and a nozzle plate 54 provided on the front side of the liquid chamber substrate 51 and the lid member 52.

By laminating the liquid chamber substrate 51, the lid member 52, and the electrode substrate 53, each nozzle hole 55 of the nozzle plate 54, a plurality of liquid chambers 56 communicating therewith, and each liquid chamber 56
And an ink flow path such as a common ink flow path (common ink chamber) 58 for supplying ink to the ink chamber via a fluid resistance portion 57, and a nozzle communication path 59 that connects the nozzle hole 55 and the liquid chamber 56. .

The liquid chamber substrate 51 is formed on the wall of the liquid chamber 56 by an etching stop technique using a high-concentration P-type impurity diffusion layer such as boron when forming a concave portion serving as the liquid chamber 56 by anisotropic etching or the like. Is also formed. Then, a concave portion 61 is formed in a portion of the electrode substrate 53 such as a thermal oxide film formed on the substrate 53, and an electrode 62 facing the diaphragm 60 is provided in the concave portion 61, and the electrode 62 and the diaphragm 60 An actuator unit (driving means) that deforms and displaces the diaphragm 60 by electrostatic force is configured. Note that an insulating film 63 made of an oxide film or the like for preventing dielectric breakdown and short circuit is formed on the surface of the electrode 62.

The lid member 52 has an ink supply path 58.
And an ink supply port 65 for supplying ink from the ink cartridge to the common ink flow path 58.

Here, the liquid chamber substrate 51 and the electrode substrate 53 are bonded by a bonding method such as direct bonding, anodic bonding, or eutectic bonding, and the liquid chamber substrate 51 and the lid member 52 are bonded by an adhesive, The plate 54 is also bonded with an adhesive.

In this ink jet head, by applying a drive waveform between the diaphragm 60 and the electrode 62, the diaphragm 60 is deformed and displaced toward the electrode 62 by electrostatic force, and the drive waveform is turned off from this state. As a result, the diaphragm 60 is returned and deformed, and the volume / pressure in the liquid chamber 56 changes, so that ink droplets are ejected from the nozzle holes 55.

Next, a control section of the ink jet recording apparatus will be described with reference to FIG. Control unit 80
Is an arithmetic processing unit (hereinafter, referred to as a “CPU”) 8 such as a microcomputer that controls the entire recording apparatus.
1, a ROM 82 storing required fixed information, an R used as a working memory and an image memory for storing data obtained by processing image data transferred from the host.
AM 83 and a waveform generation circuit 84 for generating and outputting a drive waveform
, A head drive circuit 85, drivers 86, 87, 88
, Detection signal buffers 89 and 90, and A / D converter 91
Etc. are provided. Illustration of I / O ports and the like is omitted.

Here, the CPU 81 inputs various kinds of information such as image data and information indicating the paper type from the printer driver 101 of the host 100 via a cable or a network such as the Internet or a LAN. Also, various instruction information such as information indicating the paper type and reliability recovery instruction information is input from the operation panel 92 provided in the recording apparatus.
That is, means for designating the paper type is provided in the main body of the recording apparatus by a key of the operation panel 92 or a menu selection method.

The CPU 81 receives a detection signal from a detector 93 for detecting a model mounted on the carriage 5 via a detection signal buffer 89. A detection signal from an ink end / near sensor, a paper presence / absence sensor for detecting the start and end of the paper via the detection signal buffer 89,
Signals from various sensors such as a home position sensor that detects the home position (reference position) of the carriage 5 are also taken in.

Further, the CPU 81 takes in the conversion result from the A / D converter 91 for A / D converting the paper thickness detection signal input from the platen gap sensor 16 via the detection signal buffer 90, and calculates the conversion result from the paper thickness. Recording head 6
Is obtained between the nozzle surface and the paper surface (print surface) (this is defined as a “platen gap”), and drive waveform data corresponding to the platen gap is obtained by the waveform generation circuit 8.
Give to 4.

The waveform generation circuit 84 includes a D / A converter and the like, and converts the drive waveform data supplied from the CPU 81 into a D / A signal.
By performing A-conversion or the like, a drive waveform having a required peak value, pulse width, rising time constant, and falling time constant is generated and output. The waveform generating circuit 84 and the CPU 81 constitute a means for changing the parameters of the drive waveform. Here, the peak value of the drive waveform can be changed by changing the voltage applied to the D / A converter. Also, D / A
The rise time constant of the drive waveform can be changed by changing the charging time constant by combining the converter and the integration circuit, and the falling time of the drive waveform can be changed by changing the discharge time constant. The time constant can be changed.

The head drive circuit 85 converts the drive waveform from the waveform generation circuit 84 into the heads 6y, 6m, 6
c, 6k. The driver 86 drives a main scanning motor 94 for moving the carriage 5 in accordance with drive data given from the CPU 81, and the driver 87
Roller 13 according to drive data given from
The sub-scanning motor 95 is rotated to rotate.

A driver 88 drives a maintenance mechanism motor 9 for driving a head reliability maintenance / recovery mechanism (not shown in FIG. 1) in accordance with drive data supplied from the CPU 81.
6 is driven. The reliability maintenance / recovery mechanism is a mechanism to improve the reliability of the head and always maintain the print quality.
It mainly comprises an ink suction pump, a cleaning wiper, a cap for preventing the head surface from drying and the like.

Next, another example of the waveform generating circuit 84 will be described with reference to FIGS. First, FIG.
Is connected to an input terminal IN to which a drive timing pulse MM from the CPU 81 is applied, via a buffer B, to the base of a transistor Tr1 and via an inverter I to a base of a transistor Tr2, respectively. The power supply voltage Vpp is applied to the collector of 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.

The connection point a is connected to the transistors Tr3 to Tr3.
A transistor Tr connected between the base of the transistor Tr3 and the base of the transistor Tr4 on the input side of the low-impedance output circuit composed of Tr6 and serving as the output side
A driving waveform P obtained between the emitter of the transistor 5 and the collector of the transistor Tr6 is output.

On the other hand, the voltage Vout output from the voltage output terminal Vout of the three-terminal regulator 110 is connected to the diode Dk.
Is supplied to the connection point a. By supplying a constant voltage source to the voltage input terminal Vin, the three-terminal regulator 110 controls the resistance R1a connected between the adjustment terminal adj and the voltage output terminal Vout, and the resistance selection circuit 111 connected between the adjustment terminal adj and the ground. A voltage corresponding to the resistance value R2 is output from the voltage output terminal Vout, and the output voltage Vout
Is determined by, for example, Vout = 1.25 × (1 + R2 / R1).

The resistor selection circuit 111 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. V from
p control signals SVp1 to SVp3 are applied to transistors Q1 to Q
By inputting to each of the three bases, the output voltage Vout of the three-terminal regulator 110 can be changed at up to eight levels.

In this circuit, when the drive timing signal MM is input to the input terminal IN and the "H" level is input to the inverter buffer IB, the inverter buffer IB outputs a voltage level lower than the power supply voltage Vpp. The transistor Tr1 is turned on, the inverter I becomes "L", and the transistor Tr2 is turned off. Therefore, the charging of the capacitor Ck is started at a charging time constant determined by the charging resistor Ra and the capacitor Ck by the power supply voltage Vpp. .

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 + V
This voltage is clipped to the level d), and this voltage becomes the maximum value (Vp = Vout + Vd) of the drive voltage Vp of the drive waveform P.

When the drive timing signal MM is no longer input to the input terminal IN and the "L" level is input to the inverter buffer IB, the inverter buffer IB
Becomes the power supply voltage Vpp and the transistor Tr1 is turned off. On the other hand, the output of the inverter I is inverted with respect to the output of the inverter buffer B.
At the same time as the transistor 1 is turned off, the transistor Tr2 is turned on, and the capacitor Ck charged to the voltage Vp with the discharge time constant determined by the discharge resistor Rb and the capacitor Ck is discharged.

Therefore, in this circuit, the peak value (voltage value) of the drive voltage Vp of the drive waveform P can be changed by changing the output voltage Vout of the three-terminal regulator 110.

Next, the waveform generation circuit 84 shown in FIG.
In the waveform generation circuit 84 of FIG. 9, the tr control circuit 1 that changes the rising time constant tr of the drive waveform P by changing the charging resistance Ra connected in series with the diode D1.
12 is provided.

The tr control circuit 112 includes a diode D
1 is connected in series with a parallel circuit of charging resistors Ra1, Ra2, Ra3, and these charging resistors Ra1, Ra2, Ra3
The switching transistors Tr11, Tr12 and Tr13 are connected between the power supply voltage Vpp and the power supply voltage Vpp.

Then, the transistors Tr11, Tr1
2 and Tr13 are connected to inverter buffers IB1, IB2 and IB3, respectively, and these inverter buffers IB1, IB2 and IB3 are connected to gate circuits G1 and G3, respectively.
2, a drive timing signal MM is input via G3.
Each of these gate circuits G1, G2, G3 is a CPU
When the tr control signals Str1 to Str3 from “81” are “H”, the circuit is opened to output the drive timing signal MM to the buffers B1, B2, and B3.

Accordingly, the CPU 81 sets the drive timing signal MM to “H” and sets any of the 3-bit tr control signals Str1, Str2, and Str3 to “H”, thereby setting the tr control signals Str1, Str2, S
The buffers B1, B2, and B3 selected by tr3 output a voltage level lower than the power supply voltage Vpp, and one of the corresponding transistors Tr11, Tr12, and Tr13 is turned on, and the selected resistors Ra1 to Ra are turned on.
The capacitor Ck is charged with a start-up time constant tr determined by any one of No. 3 and the capacitor Ck.

Thus, the peak value and the rise time constant tr of the drive voltage Vp of the drive waveform P can be changed.

Next, an example of the head drive circuit 85 will be described with reference to FIG. The head drive circuit (driver IC) 85 receives a print signal (serial data) SD, a shift clock CLK, a latch signal LAT, and the like from the CPU 81. This head drive circuit 8
Reference numeral 5 denotes a shift register 115 for inputting a serial clock CLK from the CPU 81 and serial data SD which is a print signal, and a register value of the shift register 115 to C
A latch circuit 116 that latches with a latch signal LAT from the PU 81, a level conversion circuit 117 that changes the output value of the latch circuit 116, and a level conversion circuit 117
Switch array 11 whose on / off is controlled by the switch
8 The analog switch array 118 has m recording heads 6 (the number of nozzles is m).
And analog switches AS1 to ASm connected to the above actuator units (such as the above-described piezoelectric elements or electrodes).

Then, a print signal (serial data) is supplied to the shift register circuit 115 in accordance with the shift clock CLK.
The latch circuit 116 latches the print signal SD in the shift register circuit 115 in accordance with the latch signal LAT, and inputs the latched print signal SD to the level conversion circuit 117. The level conversion circuit 117 controls the analog switch ASm connected to each actuator according to the content of the data.
(M = 1 to m) is turned on / off.

This analog switch ASm (m = 1 to
m) includes an amplifier (AMP) 119 from the waveform generation circuit 84.
The drive waveform P is supplied to the actuator section of the head 6 when the analog switch ASm (m = 1 to m) is turned on.

Next, the operation of the ink jet recording apparatus thus configured will be described with reference to FIGS. First, a platen gap G (see FIG. 2), which is an ink droplet speed when an ink droplet ejected from the recording head 6 lands on the paper 10 and a distance from the nozzle surface of the recording head 6 to the surface (print surface) of the paper 10. Figure 1)
This will be described with reference to FIG.

FIG. 9 shows the relationship between the ink droplet speed and the platen gap, and shows that the ink droplet speed decreases as the platen gap G increases. That is, the ink droplets fly out of the nozzle surface at a high speed, but the ink droplet speed decreases as the distance from the nozzle surface increases.

Next, the relationship between the ink droplet speed and the image quality will be described with reference to FIG. In the drawing, the ink droplet speed is higher as going to the right, and the image quality is higher as going up. Here, when the ink droplet speed is divided into the A region, the B region, and the C region, the ink droplet speed is low (low).
The case is the area A, and as the speed of the ink drops increases, the area becomes the area B of the high image quality area.
Area. The region having the best image quality is the B region, and the A and C regions have lower image quality than the B region.

That is, as shown in FIG.
The ink droplet I ejected from the nozzle hole 35 (simplified and illustrated in the examples of FIGS. 4 and 5 described above) flies toward the paper 10 and collides (landing) with the paper surface of the paper 10. Here, the region A shown in FIG. 13 is a case where the ink speed is low, and FIG. 14 is a case where the paper 10 is located at a position where the platen gap is large. At this time, the ink drops I
Since the speed immediately before colliding with zero is low, it is impossible to land at a target location due to random wind pressure or the like generated when the carriage 5 scans, so that the image quality is deteriorated as shown in FIG.

Region C in FIG. 13 shows the case where the ink droplet speed is high, and FIG. 14 shows the case where the paper 10 is located at a position where the platen gap is small. At this time, the ink droplet I lands on the target position of the paper 10 because the ink droplet speed is high. However, when the ink droplet speed is too high, the mist ink droplet Ia rebounds and floats from the paper 10 and re-adheres to the paper 10. The printing surface, or adheres to the nozzle surface of the head to affect the ejection speed and ejection direction of the ink droplet I,
As shown in FIG. 13, the image quality is reduced.

As described above, when the image quality is affected by the platen gap G, the image quality is affected because the platen gap G changes depending on the type of the sheet such as the thickness.

Therefore, in the present invention, the platen gap G
The speed of the ink droplets ejected from the recording head 6 is changed in accordance with the condition (2) so that the speed of the ink droplets when landing on the sheet surface is substantially constant. The speed of the ink droplets ejected from the recording head 6 can be changed by changing the driving waveform applied to the recording head 6.

That is, as shown in FIG. 15, when the nozzle surface is at the position a and the platen is at the position e, the position of the sheet surface becomes thicker according to the thickness of the sheet when the sheet 10 is inserted. The position changes to position c and position b. Therefore, the platen gap G, which is the distance between the recording head 6 and the paper surface, becomes shorter as the thickness of the paper used increases.

Therefore, assuming that the print quality guaranteed area is the area B, when the paper is thin and the paper surface is between positions de, the ink droplet ejection speed (the speed of the ink droplet immediately after leaving the nozzle surface) ) So that Vj becomes the speed Vj1,
The ink droplet speed is set to fall within the region B. When the thickness of the sheet is an intermediate thickness and the sheet surface is between the positions c and d, the ejection speed Vj of the ink droplet is changed to the speed Vj2 (Vj2 <Vj).
1) so that the ink droplet speed falls within the region B. Furthermore, the thickness of the paper is so large that the paper surface is at position b.
-C, the ejection speed Vj of the ink droplets becomes V
j3 (Vj3 <Vj2) so that the ink droplet speed falls in the B region.

As described above, by changing the ejection speed of the ink droplets in accordance with the platen gap, the ink droplet speed is set in the region B where the image quality can be guaranteed.
High quality images can be recorded even if the platen gap changes.

In this case, in order to change the ink droplet discharge speed Vj, the parameters of the drive waveform applied to the recording head 6 may be changed. As shown in FIG. 16, the parameters of the drive waveform include the drive voltage Vp and the pulse width P.
w, rise time constant tr, fall time constant tf, and drive cycle f.

When a piezo-type ink jet head as described with reference to FIGS. 4 and 5 is used as a recording head and ink droplets are ejected by displacement of the piezoelectric element in the extension direction, as shown in FIG. As the drive voltage Vp is increased, the ink droplet ejection speed Vj is also increased.
As shown in FIG. 18, the driving voltages Vp1, Vp2, Vp3 (Vp1>Vp2> Vp3) according to the platen gap G.
It is sufficient to apply the driving waveform of

As shown in FIG. 19, the longer the rising time constant tr of the drive waveform, the longer the ink droplet ejection speed Vj
Becomes slower, so that the rising time constants tr1, tr2, tr3 according to the platen gap G as shown in FIG.
A drive waveform of (tr3>tr2> tr1) may be applied. Further, as shown in FIG. 21, the driving voltage Vp and the rising time constant tr can be changed in combination.

Next, when the diaphragm 50 is driven by a contact driving method in which the diaphragm 50 is brought into contact with the electrode 56 using an electrostatic ink jet head as described in FIGS. 6 and 7 as a recording head, a pulse voltage is applied. When the vibration plate 50 is attracted and a negative pressure is generated in the pressurizing chamber 46 and the pressure oscillates at the natural frequency of the pressurizing chamber 46, the pressure at the time of pulse fall is lower than that at the time of pulse rise. Since the residual pressure vibration and the restoring pressure are superimposed, as shown in FIG. 22, a difference occurs in the ink droplet ejection characteristics depending on the pulse width of the applied pulse voltage.

Accordingly, as shown in FIG. 23, the pulse widths Pw1, Pw1
What is necessary is just to apply the drive waveform of w2 and Pw3.
Note that the magnitude relationship between the pulse widths Pw1, Pw2, and Pw3 cannot be unambiguously determined by the set pulse width as can be seen from FIG. Further, since the ink droplet ejection speed Vj also decreases by reducing the restoration speed of the diaphragm 10, the ink droplet ejection speed Vj can also be changed by changing the fall time constant tf.

Further, in the case where a bubble type ink jet head having a heating resistor and generating bubbles by film boiling to discharge ink droplets is used, similarly to the case of the piezo type ink jet head, the drive voltage Vp or / p of the drive waveform is used. By changing the rising time constant tr, the ink droplet ejection speed Vj can be changed.

The drive control of the head executed by the control unit 80 will be described with reference to FIG. First, a first example of head drive control will be described with reference to FIG. Here, the platen gap G is calculated based on the detection signal from the platen gap sensor 16, and the drive waveform is changed according to the calculation result.

That is, the control unit drives a paper feed roller (not shown) to feed the paper 10, and at this time, converts the detection signal from the platen gap sensor 16 from A / D converter 91 to data from the A / D converter 91. Then, the thickness of the sheet 10 and the predetermined nozzle surface of the recording head 6 and the platen roller 1
Then, a platen gap G is calculated based on the gap between the platen gap G.

Then, a process of selecting a driving waveform based on the obtained platen gap G is performed. For example, according to the relationship between the gap and the ink droplet speed described with reference to FIG. A drive waveform for ejecting ink droplets at the ejection speed Vj1 is selected, and when the platen gap G is “medium”, the ink droplet ejection speed Vj is selected.
The drive waveform for ejecting ink droplets is selected in Step 2, and when the platen gap G is "small", the drive waveform for ejecting ink droplets at the ink droplet ejection speed Vj3 is selected.

Thus, when the head is driven, the CPU 81
Is supplied to the waveform generation circuit 84, the waveform generation circuit 84 outputs a drive voltage Vp corresponding to the platen gap G, a rise time constant tr,
The driving waveform having the falling time constant tf is applied to the head driving circuit 8.
5, and the recording head 6 is driven.

Therefore, when the thickness of the sheet 10 changes and the platen gap G changes due to a change in the type of the sheet 10 to be used, the ejection speed of the ink droplet changes accordingly, and (Ink drop speed) becomes substantially constant, and the image quality can be improved.

Next, a second example of head drive control will be described with reference to FIG. Here, the change of the parameter of the drive waveform according to the platen gap G is associated with the print mode. That is, the control unit drives a paper feed roller (not shown) to feed the paper 10, fetches print mode data, determines whether the high quality print mode is selected, and determines whether the high quality print mode is selected. The platen gap G in the same manner as in the first example.
, One of the driving waveforms for ejecting ink droplets at the ink droplet ejection speeds Vj1, Vj2, and Vj3 is selected. When the mode is not the high quality mode, the driving waveform for ejecting ink droplets at the ink droplet ejection speed Vj1 is selected.

As described above, by selecting whether or not to change the drive waveform in accordance with the print mode, the processing when print quality is not required is simplified.

In each of the above examples, the platen gap G is calculated based on the thickness of the paper. However, the detection data of the thickness of the paper is used as it is as the data indicating the platen gap (in this case, the thickness is large). Then, the gap becomes smaller.), And the drive waveform can be selected according to the thickness detection data.

Next, a third example of head drive control will be described with reference to FIG. Here, the control unit fetches the gap information and drives the ink droplets at the ink droplet discharge speeds Vj1, Vj2, and Vj3 according to the platen gap G in the same manner as in the first example in accordance with the gap information. 5 is selected.

In this case, the gap information, for example, “large gap”, “medium gap”, “small gap” can be input from the operation panel 92 of the printing apparatus main body, or is transferred from the printer driver 101 on the host 100 side. To do. As described above, the gap can be specified, and the drive waveform is changed and selected according to the specified gap, thereby simplifying the processing and the configuration. However, in this case, a gap designation operation is required. For example, when a high-quality print mode is designated on the printer driver 101 side, if the gap is also designated, the operability is significantly reduced. Absent.

Next, a fourth example of head drive control will be described with reference to FIG. Here, the control unit fetches the paper type information and discharges ink droplets at the ink droplet discharge speeds Vj1, Vj2, and Vj3 according to the platen gap G in the same manner as in the first example according to the paper type information. Select one of the drive waveforms. The input of the paper type information is performed from the operation panel 92 of the printing apparatus main body or transferred from the printer driver 101 of the host 100. Further, by providing means for detecting the type of the fed paper 10, the paper type information can be obtained.

That is, the paper 10 is classified into types such as plain paper, special paper such as coated paper and glossy paper, and OHP sheets. Generally, the thickness is about 0.1 mm for plain paper and 0 for special paper. .15mm thickness, OHP sheet is 0.1mm
It is about 2 to 0.3 mm thick. Therefore, when the paper 10 is plain paper, a drive waveform for discharging ink droplets at the ink droplet discharge speed Vj1 is selected, and when the paper 10 is dedicated paper, a drive waveform for discharging ink droplets at the ink droplet discharge speed Vj2 is selected.
In the case of an HP sheet, a drive waveform for ejecting ink droplets at the ink droplet ejection speed Vj3 is selected.

As described above, by changing the parameters of the drive waveform according to the type of the paper 10, the accuracy is slightly lower than in the case where the platen gap G is detected. High quality images can be maintained even when a change in G occurs.

Next, another embodiment of the head drive control device according to the present invention will be described with reference to FIG. In this control unit, a table is prepared by associating the data of the paper thickness corresponding to the platen gap G with the data of the drive waveform parameters (drive voltage Vp, rise time constant tr, fall time constant tf, pulse width Pw, etc.). A drive waveform table 97 is provided. The conversion result of the A / D converter 91 for A / D converting the detection signal of the platen gap sensor 16 is provided to the drive waveform table 97, and drive waveform data is generated from the drive waveform table 97. The signal is supplied to the circuit 84.

The drive waveform table 97 can be configured to be stored and held in various storage means such as a nonvolatile memory. The drive waveform table may be a table corresponding to the type of paper.

As described above, by providing the drive waveform table 97 in which the platen gap information or the paper type information and the drive waveform data are tabulated, the CPU 81
The processing on the side can be simplified, and the processing speed can be improved.

Next, referring to FIG. 29, an example of an ink jet head capable of changing the ink droplet speed will be described as still another embodiment of the present invention. This ink jet head is the same as the piezo type ink jet head described with reference to FIGS. 3 and 4 except that the piezoelectric element 42 can be driven and controlled separately from the piezoelectric element 41 and has a different displacement amount in the stacking direction with respect to the same driving voltage as the piezoelectric element 41. It is provided.

In this ink jet head, the amount of displacement of the vibration plate depends on the amount of displacement of the piezoelectric element 41 and / or the piezoelectric element 42 in the extension direction. When this is applied only to the piezoelectric element 41, when applied only to the piezoelectric element 42,
When the voltage is applied to both the piezoelectric element 41 and the piezoelectric element 42, the displacement amount in the elongation direction as a whole is different. Therefore, the ejection speed of the ink droplet can be changed by selecting the piezoelectric element to be applied even with the same drive waveform, and the ink droplet speed is made substantially constant (within the range in which print quality can be guaranteed) regardless of the change in the gap. be able to.

Next, an embodiment in which the driving waveform data is stored in the printer driver on the host side will be described with reference to FIG. In this case, the printer driver 10
The data of the driving waveform is stored as 1 in association with the paper type. The printer driver 101 includes a CD-ROM,
It is downloaded via the Internet in addition to a storage medium such as an FD.

That is, as described above, the thickness of the paper is generally determined by a special paper such as plain paper, coated paper, glossy paper, or the like.
Since it is determined by the type of the HP sheet or the like, the parameters of the drive waveform according to the platen gap corresponding to the selected paper are also determined.

Therefore, the printer driver 101 provides the paper type, for example, the above-mentioned plain paper, dedicated paper, and OHP sheet, and the parameters of the drive waveform (parameters (drive voltage Vp, rising time constant tr, (Fall time constant tf, pulse width Pw, etc.).

Then, as shown in FIG. 30, when the mode using plain paper is selected as the print mode,
In the case of plain paper, the drive waveform data for ejecting ink droplets at the ink droplet ejection speed Vj1 is transferred. When the mode using the special paper is selected, the drive waveform data for ejecting ink droplets at the ink droplet ejection speed Vj2 is transferred. Select and OHP
When a mode using a sheet is selected, data of a driving waveform for ejecting ink droplets at the ink droplet ejection speed Vj3 is transferred.

On the recording device side, the printer driver 101
By generating and outputting a drive waveform based on the drive waveform data transferred from the printer, ink droplets are ejected at an ink droplet speed corresponding to the paper type. As described above, when associating the paper type with the data of the driving waveform related to the ink droplet speed, the load on the control unit of the printing apparatus main body is reduced as compared with the case where the printing apparatus main body is used.

[0104]

As described above, according to the ink jet recording apparatus of the present invention, the speed of the ink droplet ejected from the recording head is changed according to the distance between the recording head and the paper. , The image quality can be maintained even when the paper thickness changes, the mechanism becomes simple,
Costs are also reduced.

Here, by changing the parameters of the drive waveform applied to the recording head according to the distance between the recording head and the paper, the speed of the ink droplet can be changed with a simple configuration. Further, by providing a means for detecting the distance between the recording head and the sheet, the distance between the recording head and the sheet can be accurately obtained.

According to the ink jet recording apparatus of the present invention, since the speed of the ink droplets ejected from the recording head is changed according to the type of paper, the image quality is maintained even if the thickness of the paper changes. Simplification of the mechanism and cost reduction.

Here, by changing the parameters of the drive waveform applied to the recording head in accordance with the type of paper, the speed of the ink droplet can be changed with a simple configuration. Further, since the recording apparatus main body is provided with means for designating the type of paper, the type can be designated at the time of paper setting. Further, by specifying the paper type from the host side, the operability when using the recording device via the network is improved.

The parameters of the drive waveform can be changed by using any one of the peak value, rising time constant, falling time constant, peak value and rising time constant, and pulse width of the drive waveform. , An appropriate driving waveform can be applied.

Further, by providing means for storing the information on the distance between the recording head and the sheet and the data of the drive waveform in the form of a table, the processing speed of the control unit is improved. Further, the provision of the means for storing the sheet type information and the driving waveform data in a table form improves the processing speed of the control unit. Furthermore, by enabling printing on both sides of a sheet, double-sided printing can be performed with high image quality.

According to the head drive control device of the present invention, the means for changing the parameters of the drive waveform applied to the recording head according to the distance between the recording head and the sheet are provided, so Even when the thickness of the sheet changes, the recording apparatus using the sheet can perform the recording while maintaining the image quality, so that the mechanism of the recording apparatus is simplified and the cost is reduced.

According to the head drive control device of the present invention, since the means for changing the parameters of the drive waveform applied to the recording head in accordance with the type of paper is provided, the recording device using paper having different thicknesses is used. Even if the thickness of the paper changes, recording can be performed while maintaining the image quality, the mechanism of the recording apparatus is simplified, and the cost is reduced.

Here, the parameters of the driving waveform are changed by
An appropriate drive waveform can be applied to the actuator section of the recording head by performing any one of the peak value, rise time constant, fall time constant, peak value and rise time constant, and pulse width of the drive waveform. . Can be. Further, it is preferable to provide a unit for storing the distance information between the recording head and the sheet and the data of the drive waveform in a table. Further, it is preferable to include means for storing the sheet type information and the driving waveform data in a table.

According to the storage medium of the present invention, since the type of the paper and the data of the parameter of the drive waveform related to the ejection speed of the ink droplet are stored in association with each other, the type of the paper to be used is determined. The parameters of the drive waveform are transferred to the recording device, and the recording device that uses paper with different thicknesses can be recorded while maintaining the image quality even if the thickness of the paper changes. And cost is reduced.

Here, the type of paper is plain paper, special paper, O
By using the HP sheet, it is possible to drive the recording head with a drive waveform that can maintain image quality corresponding to a normally used sheet. Since the parameter data of the drive waveform is one or more of the peak value, the rise time constant, the fall time constant, and the pulse width, an appropriate drive waveform according to the recording head of the recording apparatus is selected. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic perspective explanatory view of a mechanism section of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory side sectional view of the recording apparatus.

FIG. 3 is an explanatory diagram showing an example of a platen gap sensor of the recording apparatus.

FIG. 4 is an explanatory cross-sectional view in the longitudinal direction of a liquid chamber, showing an example of an ink jet head constituting a recording head of the recording apparatus.

FIG. 5 is an explanatory cross-sectional view of the inkjet head in a lateral direction of a liquid chamber.

FIG. 6 is an explanatory cross-sectional view in the longitudinal direction of a liquid chamber showing another example of an ink jet head constituting a recording head of the recording apparatus.

FIG. 7 is an explanatory cross-sectional view of the ink jet head in a lateral direction of a liquid chamber.

FIG. 8 is a block diagram illustrating an outline of a control unit of the recording apparatus.

FIG. 9 is a block diagram illustrating another example of the waveform generation circuit of the control unit.

FIG. 10 is a block diagram illustrating still another example of the waveform generation circuit of the control unit.

FIG. 11 is a block diagram illustrating an example of a head drive circuit of the control unit.

FIG. 12 is an explanatory diagram for explaining a relationship between a platen gap and an ink droplet speed;

FIG. 13 is an explanatory diagram for explaining a relationship between an ink droplet speed and print quality;

FIG. 14 is an explanatory diagram for explaining a relationship between an ink droplet speed and print quality;

FIG. 15 is an explanatory diagram for explaining the principle of the present invention;

FIG. 16 is an explanatory diagram provided for describing parameters of a driving waveform.

FIG. 17 is an explanatory diagram for explaining a relationship between a driving voltage of a driving waveform and an ink droplet speed;

FIG. 18 is an explanatory diagram for explaining a change in drive voltage of a drive waveform;

FIG. 19 is an explanatory diagram for explaining a relationship between a rising time constant of a driving waveform and an ink droplet speed;

FIG. 20 is an explanatory diagram for explaining a change in a rising time constant of a driving waveform;

FIG. 21 is an explanatory diagram for explaining a change in a drive waveform and a rise time constant of a drive waveform;

FIG. 22 is an explanatory diagram for explaining a relationship between a pulse width and an ink droplet ejection speed in the electrostatic inkjet head.

FIG. 23 is an explanatory diagram provided for describing a pulse width of a driving waveform.

FIG. 24 is a flowchart illustrating an example of a drive waveform changing process performed by a control unit of the recording apparatus.

FIG. 25 is a flowchart illustrating another example of the drive waveform changing process performed by the control unit of the recording apparatus.

FIG. 26 is a flowchart illustrating yet another example of the drive waveform changing process performed by the control unit of the recording apparatus.

FIG. 27 is a flowchart illustrating yet another example of the drive waveform changing process performed by the control unit of the recording apparatus.

FIG. 28 is a block diagram illustrating an outline of another example of the control unit of the recording apparatus.

FIG. 29 is an explanatory cross-sectional view in a liquid chamber longitudinal direction illustrating still another example of the ink jet head of the recording apparatus.

FIG. 30 is a flowchart illustrating an example of processing of a printer driver.

[Description of Symbols] 5: carriage, 6: recording head, 7: ink cartridge, 10: paper, 13: platen roller, 16: platen gap sensor, 41: piezoelectric element, 60: diaphragm
62: electrode, 84: waveform generation circuit, 85: head drive circuit, 91: A / D converter, 92: operation panel, 101:
Printer driver.

Claims (27)

[Claims] 1. An ink jet recording apparatus having a recording head for discharging ink droplets, wherein the speed of ink droplets discharged from the recording head is changed according to the distance between the recording head and paper. Inkjet recording device. 2. An ink jet recording apparatus according to claim 1, wherein parameters of a drive waveform applied to said recording head are changed according to a distance between said recording head and a sheet. . 3. An ink jet recording apparatus according to claim 1, further comprising means for detecting a distance between said recording head and a sheet. 4. An ink jet recording apparatus equipped with a recording head for discharging ink droplets, wherein the speed of ink droplets discharged from the recording head is changed according to the type of the paper. 5. The ink jet recording apparatus according to claim 4, wherein a parameter of a driving waveform applied to the recording head is changed according to a type of the sheet. 6. The ink jet recording apparatus according to claim 4, wherein said recording apparatus main body is provided with means for designating a type of said sheet. 7. The ink jet recording apparatus according to claim 4, wherein the type of the paper is designated by a host. 8. The ink jet recording apparatus according to claim 2, wherein a peak value of the driving waveform is changed. 9. The ink jet recording apparatus according to claim 2, wherein a rising time constant of the driving waveform is changed. 10. The ink jet recording apparatus according to claim 2, wherein a fall time constant of the drive waveform is changed. 11. The ink jet recording apparatus according to claim 2, wherein a peak value and a rise time constant of the driving waveform are changed. 12. The ink jet recording apparatus according to claim 2, wherein a pulse width of the driving waveform is changed. 13. The ink-jet recording apparatus according to claim 2, further comprising: means for storing distance information between the recording head and a sheet and data of the driving waveform in a table. Ink jet recording device. 14. The ink-jet recording apparatus according to claim 5, further comprising means for storing said sheet type information and said drive waveform data in a table. 15. The ink jet recording apparatus according to claim 1, wherein printing is possible on both sides of the sheet. 16. A head drive control device for controlling the driving of a recording head for discharging ink droplets, wherein a means for changing a parameter of a driving waveform applied to the recording head according to a distance between the recording head and a sheet. A head drive control device comprising: 17. A head drive control device for controlling the driving of a recording head for ejecting ink droplets, comprising: means for changing a parameter of a driving waveform applied to the recording head in accordance with a type of the sheet. Characteristic head drive control device. 18. The head drive control device according to claim 16, wherein a peak value of the drive waveform is changed. 19. The head drive control device according to claim 16, wherein a rising time constant of the drive waveform is changed. 20. The head drive control device according to claim 16, wherein a fall time constant of the drive waveform is changed. 21. The head drive control device according to claim 16, wherein a peak value and a rise time constant of the drive waveform are changed. 22. The head drive control device according to claim 16, wherein a pulse width of the drive waveform is changed. 23. The head drive control device according to claim 16, further comprising means for tabulating and storing the distance between the recording head and a sheet and the data of the drive waveform. Head drive control device. 24. The head drive control device according to claim 17, further comprising means for tabulating and storing the paper type and the drive waveform data. 25. A computer-readable storage medium storing a printer driver for driving and controlling an ink-jet recording apparatus, in which data of driving waveform parameters relating to the type of paper and the ejection speed of ink droplets are stored in association with each other. A storage medium characterized by the following. 26. The storage medium according to claim 25, wherein the type of the paper is a plain paper, a special paper, or an OHP sheet. 27. The storage medium according to claim 25, wherein the data of the parameter of the drive waveform is one or more data of a peak value, a rising time constant, a falling time constant, and a pulse width. Characteristic storage medium.