JPH04255360A - Ink jet recording apparatus and method for refreshing ink of the apparatus - Google Patents

Abstract

PURPOSE:To reduce the amount of ink consumed by the ink refreshing processing of an ink jet recording head. CONSTITUTION:When first ink discharge processing is carried out through emitting orifices 113J by the energy generated by an energy acting means such as an emission heater 112H in the ink refreshing processing such as emission recovery processing or ink replacing processing in a recording head, an ink stream is generated in the common liquid chamber 113R or the recording head and, during the interruption of the first discharge processing, a convection is generated in the common liquid chamber 113R to uniformly mix the ink in the common liquid chamber 113R. Thereafter, by again performing second ink discharge, the uniformly mixed ink is discharged.

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 more particularly to ink refreshing in a recording head for ejecting ink.

0002

2. Description of the Related Art Ejection recovery processing is well known as one type of ink refresh processing in a recording head. These can be used to remove ink from the ink path near the ejection ports by discharging the ink inside the print head by applying pressure or suction, or by performing so-called idle ejection, in which ink is ejected at a location and timing that is not involved in printing. This is a process for discharging ink, etc. that has thickened due to evaporation of water. Thereby, non-ejection or ejection failure caused by thickened ink or air bubbles in the ink can be prevented.

0003

[Problems to be Solved by the Invention] Incidentally, the evaporation of ink moisture that causes ink viscosity does not occur only in the ink path near the ejection port, but also in the entire ink path and A liquid chamber for storing ink supplied to this ink path may also be formed throughout the ink in the recording head. The degree of evaporation that occurs in such areas is relatively small, so in many cases it does not lead to thickening that causes non-discharge or the like. However, the evaporation of ink water causes a relative increase in the dye density of the ink, and the density of the ink in the recording head changes depending on the degree of this evaporation.

[0004] Even if such density changes are relatively small, they may cause density unevenness that deteriorates the image quality of images recorded with these inks. Density unevenness that occurs in recorded images due to such changes in ink density is particularly noticeable in full-color printing in which printing is performed using inks of a plurality of colors.

As is clear from the above, when simply preventing ejection failure by discharging the thickened ink near the ejection port, it is sufficient that at least the ink near the ejection port is ejected. The amount of ink discharged due to ink suction and ejection can be relatively small. on the other hand,
In order to equalize density changes that occur in the ink within the print head, it is necessary to discharge almost all of the ink within the print head and refresh it with new ink, so the amount of discharge may be relatively large.

Therefore, in conventional ejection recovery processing, when considering the density change that occurs in the ink in the recording head, the amount of suction and the number of blank ejections increase, resulting in a large amount of ink consumption associated with the ejection recovery processing. There was a problem with becoming something.

The present invention has been made based on the above-mentioned viewpoint, and its purpose is to reduce the amount of ink consumed due to ejection recovery due to dry ejection or ink suction, and to reduce the amount of ink consumed in the recording head. An object of the present invention is to provide a method for refreshing ink in a recording head that can efficiently refresh ink, and an inkjet recording apparatus that can carry out the method.

[0008]

[Means for solving the problem] To this end, in the present invention,
A recording head for discharging ink, an ink storage member storing ink to be supplied to the recording head, and an ink supply system for supplying ink from the ink storage member to the recording head, In an ink refresh method for an inkjet recording apparatus that performs recording, ink is discharged from an ink ejection port of the recording head by applying energy to the ink in the recording head, the ink storage member, or a part of the ink supply system. First discharge treatment, after the discharge,
An interruption process that interrupts ink discharge for a predetermined period of time; after the interruption, ink is removed from the ink ejection port by applying energy to the ink again in the recording head, the ink storage member, or a part of the ink supply system; a second discharge process for discharging the first discharge;
The present invention is characterized in that the process consisting of the above-mentioned interruption process and the above-mentioned second discharge process is executed for at least one cycle.

[0009] The apparatus also includes a recording head for discharging ink, an ink storage member storing ink to be supplied to the recording head, and an ink supply system for supplying ink from the ink storage member to the recording head, In an inkjet recording apparatus that performs recording by discharging ink, ink is discharged from an ink discharge port of the recording head by applying energy to the ink in the recording head, the ink storage member, or a part of the ink supply system. a first energy applying means for causing the first energy to act;
an interruption control means for interrupting ink ejection for a predetermined period of time after ejection by the energy applying means; and second energy application means for discharging ink from the ink ejection port by applying energy to the ink discharge port.

0010

[Operation] According to the above configuration, in the ink refresh process such as the ejection recovery process or the ink replacement process in the recording head, the first ink ejection process via the ejection port is performed using the energy generated by the energy applying means such as the ejection heater. When this is performed, an ink flow occurs in the common liquid chamber of the recording head, and thereafter, while this first discharge process is interrupted, convection occurs in the common liquid chamber and the ink in the common liquid chamber is mixed uniformly. Thereafter, by performing the second ink discharge again, this uniformly mixed ink is discharged.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1A and 1B are explanatory diagrams of a recording head for explaining the principle of the present invention. Figure 1 (A
) is a schematic diagram showing the flow of ink in the common liquid chamber and ink path of the recording head from above the recording head, and FIG. 1(B) is a schematic cross-sectional view of the same portion of the recording head viewed from the side. .

In FIGS. 1A and 1B, the discharge port 1 is discharged from the common liquid chamber 113R by continuous discharge or suction.
When discharging ink via 13J, the liquid chamber 113R
Ink flows as shown by the arrow in the figure. When such ink flow occurs, as shown by the shaded area 113S in the figure, depending on the shape of the common liquid chamber 113R and the location of the arrangement of the ejection ports 113J with respect to the liquid chamber 113R. In many cases, areas are formed where almost no ink flow occurs. That is, this area 113
In S, a vortex may be generated by coming into contact with an ink flow outside the area, but the ink flow due to such a vortex is not mixed with the ink flow outside the area and remains within the area. Accordingly,
It is difficult to discharge the ink within the area 113S to the outside of the recording head due to idle ejection, suction, or the like.

On the other hand, when the ink discharge process due to idle ejection or suction is interrupted, convection is generated throughout the common liquid chamber 113R due to the influence of the vortex in the area 113S formed by this discharge process. Furthermore, when ink discharge processing is performed by idle discharge, convection is also generated within the common liquid chamber 113R by the heat of the discharge heater 112H that generates thermal energy for discharge. Due to these convection, the ink in the area 113S is mixed with the ink outside the area, and the common liquid chamber 113R is mixed with the ink in the area 113S.
will be distributed throughout the interior.

Therefore, if the ink discharging process is interrupted after performing the ink discharging process by idle ejection, ink suction, etc. for a predetermined period of time, the ink formed by the discharging process in the common liquid chamber 113R is discontinued. If the ink in the area 113S is dispersed throughout the common liquid chamber 113R, and then the ink discharge process is performed again, the ink in the area 113S, which is the area where the ink is discharged, is dispersed throughout the common liquid chamber 113R.
Most of the ink that had stayed in the region 113S is discharged out of the print head from the ejection port 113J by the ink flow generated by this process, and the relatively high viscosity and concentration of the ink in the region 113S is reduced by mixing. On the other hand, according to the conventional discharge process that does not interrupt the discharge process, once the region 113S is formed at the beginning of the discharge process, this region continues to exist during the discharge. The remaining ink will not be discharged outside the recording head forever, and its ink density will not be lowered. Therefore, after the ejection process ends, the ink that was in the area 113S mixes with other inks, and when ink is ejected during recording, these inks may be ejected and adversely affect image quality. there were.

As is clear from the above, by providing a predetermined period of interruption in the ejection process, it is possible to perform ink refresh more quickly and effectively, and the ink consumption associated with ink refresh, such as ejection recovery process, can be performed more quickly and effectively. The amount can be reduced.

FIG. 2 is a schematic perspective view showing an example of an inkjet recording apparatus capable of carrying out the refresh process shown in FIG. This device has replaceable ink tank integrated print head cartridges for black (Bk) and cyan (C).
, magenta (M), yellow (Y) This is a full-color serial type printer that is equipped for each of the four color inks, and is used as a recording section of a full-color copying machine as will be described later with reference to FIG. The head used in this printer is
It has a resolution of 400 dpi, a driving frequency of 4 KHz, and 128 ejection ports.

In FIG. 2, IJC is Y, M, C, Bk
There are four print head cartridges corresponding to each type of ink, and the print head and an ink tank storing ink to supply ink to the print head are integrally formed. Each recording head cartridge IJC is detachably attached to the carriage by a structure not shown. carriage 82
is slidably engaged along the guide shaft 811, and
Drive belt 85 moved by a main scanning motor (not shown)
Connect with part of 2. This allows the recording head cartridge IJC to move for scanning along the guide shaft 811. 815, 816 and 817, 818 are conveyance rollers extending substantially parallel to the guide shaft 811 on the back side and the front side in the figure of the recording area scanned by the recording head cartridge IJC. Conveyance rollers 815, 8
16, 817, and 818 are driven by a sub-scanning motor (not shown) to convey the recording medium P. The transported recording medium P forms a recording surface that faces the surface on which the ejection port surface of the recording head cartridge IJC is disposed.

A recovery system unit is provided facing a movable area of the cartridge IJC adjacent to the recording area by the recording head cartridge IJC. This recovery system unit is used when performing the idle ejection or ink suction process described in FIG. 1. 8300 for recovery units
A cap unit is provided corresponding to a plurality of cartridges IJC each having a recording head, and can be slid in the left and right directions in the figure as the carriage 82 moves, and can be moved up and down in the vertical direction. When the carriage 82 is at the home position, it is joined to the recording head section and capped. Further, in the recovery system unit, 8401 is a blade serving as a wiping member.

Furthermore, 8500 is a cap unit 83.
This is a pump unit for sucking ink, etc. from the ejection port of the print head and its vicinity via the ejection port 00. FIG. 3 shows an example of the configuration of a head cartridge that can be mounted on the carriage of the inkjet recording apparatus shown in FIG. The cartridge according to this example integrally includes an ink tank unit IT and a head unit IJU, and these can be attached to and detached from each other. head unit I
A wiring connector 102 for receiving signals for driving the ink ejection section 101 of the JU and for outputting a remaining ink amount detection signal is provided at a position parallel to the head unit IJU and the ink tank unit IT. Therefore, in the posture taken when this cartridge is loaded into a carriage, which will be described later, the height H can be reduced, and the thickness of the cartridge can be reduced. This allows the carriage to be made smaller when the cartridges are arranged side by side as described above with reference to FIG.

When mounting the head cartridge on the carriage, the head cartridge can be placed on the carriage by grasping the knob 201 provided on the ink tank unit IT with the ejection section 101 facing downward. This knob 201
engages with a lever provided on the carriage, which will be described later, for performing a cartridge mounting operation. When the head unit IJU is attached, a pin provided on the carriage side engages with a pin engaging portion 103 of the head unit IJU, and the head unit IJU is positioned.

In the head cartridge according to this example, an absorber 104 for cleaning a member that wipes the surface of the ink ejecting section 101 to clean it is juxtaposed to the ink ejecting section 101. Further, an atmosphere communication port 203 through which air is introduced as ink is consumed is provided approximately at the center of the ink tank unit IT.

FIG. 4 is an exploded perspective view of the head cartridge shown in FIG. 3. The head cartridge according to this example is
It consists of a head unit IJU and an ink tank unit IT, and the detailed configuration of these units is as follows.
This will be explained using this figure and the like.

Head unit The standard for mounting the components of the head unit IJU is a base plate 111 made of Al or the like, on which a group of elements for generating energy used for ink ejection is formed. Board 1
12 and a printed circuit board (PCB) 115 having wiring etc. for supplying power to the element,
These are connected by wire bonding or the like. The substrate 112 is provided with an electrothermal conversion element (ejection heater 112H shown in FIG. 1) that generates thermal energy that causes film boiling in ink in response to energization. In the following, this substrate 112 will be referred to as a heater board.

The wiring connector 102 described above is connected to the PCB 11.
A drive signal from a control circuit (not shown) is received by the wiring connector 102 and connected to the PCB 115.
is supplied to the heater board 112 via. PCB11
5 is a double-sided wiring board in this example, and further contains information specific to the head, such as appropriate driving conditions for the electrothermal transducer, I
ROM-format IC 128 and capacitor 12 that store D number, ink color information, drive condition correction data (head shading (HS) data), PWM control conditions, etc.
9 are arranged.

As shown in the figure, the IC 128 and the capacitor 129 are placed on the side of the PCB 115 that is connected to the base plate 111 and in the notch 11 of the base plate 111.
It is placed at a position corresponding to 1A. by this,
If the height of the IC etc. when mounted is equal to or less than the thickness of the base plate 111, the IC etc. will not protrude from the surface when the PCB 115 and the base plate 111 are bonded. Therefore, there is no need to consider the storage mode corresponding to these protrusions in the manufacturing process.

As shown in FIG. 1, on the heater board 112, there is a common liquid chamber (113R) for temporarily storing ink supplied from the ink tank unit IT side, and a common liquid chamber (113R) that connects the liquid chamber and a discharge port (113J). A top plate 113 having a recessed portion for forming a group of communicating liquid channels (113N) is arranged. Further, an ejection port forming member (orifice plate) 113A having an ink ejection port formed therein is integrally formed on the top plate 113. Reference numeral 114 denotes a pressing spring for constructing the discharge section 101 by bringing the top plate 113 and the heater board 112 into close contact.

Reference numeral 116 denotes a head unit cover, which covers the ink supply pipe section 1 that enters the ink tank unit IT.
16A, an ink flow path 116B for ink communication between this and the ink introduction pipe section on the top plate side, and a base plate 111
Three pins 116C for three-point positioning or fixing,
This is a member formed by integrally molding the pin engaging part 103, the attachment part of the absorber 104, and other necessary parts. A channel lid 117 is arranged for the ink channel 116B. Further, a filter 118 for removing air bubbles and dust is provided at the tip of the ink supply pipe 116A, and
An O-ring is provided to prevent ink from leaking from the joint.

When assembling the above head unit, the pin 111P protruding from the base plate must be connected to the PCB.
115 so as to be inserted into the through hole 115P, and the two are fixed by adhesive or the like. In fixing both of them, precision is not required so much. This is because the heater board 112, which should be mounted with high precision on the base plate 111, is fixed separately from the PCB 115.

Next, the heater board 112 is placed and fixed on the base plate 111 with high precision, and the necessary electrical connections with the PCB 115 are made. After arranging the top plate 113 and the springs 114 and performing adhesion and sealing as necessary, three pins 116C protruding from the cover are inserted into the holes 111C of the base plate 111 for positioning. Thereafter, the head unit is completed by heat-sealing these three pins 116C.

Ink tank unit 21 in FIG.
1 is an ink container forming the main body of the ink tank unit; 2
15 is an ink absorber for impregnating ink, 216
212 is an ink tank lid, 212 is an electrode pin for detecting the remaining amount of ink, and 213 and 214 are contact members related to the pin 212.

The ink container 211 generally has pins 212,
It integrally includes a portion 220 for attaching the contact members 213 and 214 and the above-described head unit IJU, a supply port 231 for receiving the entry of the ink supply pipe portion 116A, and a knob 201, and also has a portion 220 on the bottom side in FIG. It has a hollow cylindrical portion 233 that is erected approximately at the center thereof. Such an ink container can be formed by integral molding of resin.

The bottom side of the cylindrical portion 233 is open in consideration of the ink filling process, and after filling, a cap 217 shown in FIG. 4 is attached to close it off from the atmosphere. On the other hand, in FIG. 4, a spiral or meandering groove 235 is provided on the upper end surface (in the illustrated example, a spiral groove), and at one end 235A of the groove (in the illustrated example, the center of the spiral groove), a cylindrical portion 235 is provided. An aperture is provided that leads to the internal space of. Further, the other end 235B of the groove is located at a portion of the atmosphere communication port 203 provided in the tank lid 216.

A plurality of (four in the illustrated example) grooves 237 are provided on the side surface of the cylindrical portion 233 at equal angles and communicate with the internal space of the cylindrical portion 233 . As a result, communication between the inside of the ink tank unit and the atmosphere is established through the atmosphere communication port 203, the spiral groove 233, the internal space of the cylindrical portion 233, and the inside of the ink tank unit.
This is through the groove 237. And the cylindrical part 233
The internal space functions as a buffer section to prevent ink leakage due to vibration or rocking. In addition, atmospheric communication port 2
Since the spiral groove 233 that lengthens the path leading to 03 exists, ink leakage is more effectively prevented.

Furthermore, by providing a plurality of grooves 237 at equal angles on the side surface of the cylindrical portion 233 located approximately at the center of the ink tank as in this example, the absorber 215 located around the grooves 237 can be It is possible to ensure a uniform balance with the atmosphere and prevent local concentration of ink within the absorber. This also ensures smooth ink supply to the absorber compression area (around the supply port 231), which will be described later.

The groove 237 extends below the center of the thickness of the container and is provided over a range that completely encompasses the range A where the supply port 231 exists. In addition, it is formed in a range that takes into consideration the position of the remaining amount detection pin 212, thereby ensuring an even ink presence state or an atmosphere communication state around the area where the pin is present, and improving the accuracy of remaining amount detection. be able to.

The ink-impregnated absorber 215 according to this example is provided with a hole 215A through which the cylindrical portion 233 is inserted. By locating the cylindrical portion 233 in this hole 215A, the absorber 215 is not compressed by the cylindrical portion 233, and no ink remains in the compressed portion where the negative pressure is high. On the other hand, the absorber 215 according to this example
The portion located at the supply port 231 has a slightly swollen shape with respect to the shape of the space formed by the ink tank lid 216 and the ink container 211 (indicated by a dashed line in FIG. 4). As a result, when the absorber 215 is housed in the ink tank unit, the swollen part is in a compressed state, so the absorber 215 has a high negative pressure in that part, and therefore ink can be smoothly supplied. Mouth 231
This means that it can be introduced to the side.

FIG. 5 is a block diagram showing an example of the configuration of a control system in the inkjet recording apparatus.

Here, 800 is a controller serving as a main control unit, which includes a CPU 801 in the form of a microcomputer, for example, which executes the processing described later in FIG. The image forming apparatus includes a ROM 803 that stores fixed data such as heat pulse voltage values, pulse widths, and other fixed data, and a RAM 805 that has an area for developing image data, a work area, and the like. The controller 800 further includes a timer 807 for measuring non-recording time and the like. Reference numeral 810 denotes a host device (in this example, a reader unit for image reading) that serves as a source of image data, and image data, commands, status signals, etc. are sent to an interface (I/F) 8.
The data is transmitted to and received from the controller via 12.

Reference numeral 820 indicates commands by the operator, such as a power switch 822, a copy switch 824 for commanding the start of recording (copying), and a large recovery switch 826 for commanding the start of large recovery, which is one aspect of ejection recovery processing. A group of switches that accept input. 830 is a group of sensors for detecting the device state, including a sensor 832 for detecting the position of the carriage 82 such as a home position and a start position, and a sensor 834 including a leaf switch and used for detecting the pump position.

Reference numeral 840 denotes a head driver for driving the electrothermal transducer of the recording head in accordance with recording data and the like. Also, a part of the head driver is equipped with temperature control heaters 30A, 3
It is also used to drive 0B. Furthermore, the temperature detection values from the temperature sensors 20A and 20B are sent to the controller 80.
Enter 0. 850 is a main scanning motor for moving the carriage 82 in the main scanning direction, and 852 is its driver. 860 is a sub-scanning motor, which is used to transport (sub-scan) the recording medium.

Various methods are known for driving the electrothermal transducer (ejection heater) during ejection in the above-mentioned inkjet recording apparatus, that is, various modes of driving signals applied to the electrothermal transducer. Typical examples include a single-pulse electric signal and a double-pulse (divided pulse) drive signal that can control the amount of ejected ink droplets relatively well. Furthermore, the applicant has proposed a method in which the amount of ejected ink droplets is controlled in accordance with the head temperature by modulating the initial pulse width of this double pulse, thereby suppressing density unevenness in a recorded image.

The idle ejection according to the principle of the present invention explained in FIG. Since the droplet volume can be controlled more precisely, it is one of the most suitable drive signals for suppressing ink consumption associated with ink refresh of the print head.

The pulse width modulation of this divided (double) pulse and the ejection amount control thereby will be briefly described below.

FIG. 6 is a diagram for explaining divided pulses according to an embodiment of the present invention.

In FIG. 6, VOP is the drive voltage, P1
is the pulse width of the first pulse (hereinafter referred to as preheat pulse) of the plurality of divided heat pulses, P2 is the interval time, and P3 is the pulse width of the second pulse (hereinafter referred to as main heat pulse). T1,T
2 and T3 indicate the time for determining P1, P2, and P3. The drive voltage VOP is one of the values that indicates the electrical energy necessary for the electrothermal converter to which this voltage is applied to generate thermal energy in the ink in the ink liquid path composed of the heater board and the top plate. The value is determined by the area of the electrothermal transducer, the resistance value, the film structure, and the liquid path structure of the recording head. The divided pulse width modulation driving method sequentially applies pulses with widths of P1, P2, and P3, and the preheat pulse is a pulse mainly used to control the ink temperature in the liquid path, and the ejection in this embodiment It plays an important role in controlling quantity. The width of this preheat pulse is set to a value that does not cause bubbling in the ink due to thermal energy generated by the electrothermal transducer upon application of the preheat pulse.

The interval time is provided to provide a certain time interval so that the preheat pulse and the main heat pulse do not interfere with each other, and to equalize the temperature distribution of the ink in the ink liquid path. The main heat pulse causes bubbles in the ink in the liquid path and causes the ink to be ejected from the ejection port, and its width P3 depends on the area of the electrothermal converter, resistance value, film structure, and ink of the recording head. Determined by the structure of the liquid path.

FIG. 7 is a diagram showing the dependence of the ejection amount on the preheat pulse. In the figure, V0 is P1 = 0 [μs
ec], and this value is determined by the head structure. Incidentally, V0 in this example is the environmental temperature TR.
= 25°C, V0 = 18.0 [ng/dot].

As shown by the curve a in FIG. 7, the discharge amount Vd increases as the pulse width P1 of the preheat pulse increases.
The pulse width P1 increases linearly from 0 to P1LMT, and in a range where the pulse width P1 is larger than P1LMT, the change loses linearity, and reaches a maximum value when it is saturated at the pulse width P1MAX.

In this way, the pulse width P1LM shows that the change in the discharge amount Vd with respect to the change in the pulse width P1 is linear.
The range up to T is effective as a range in which the ejection amount can be easily controlled by changing the pulse width P1. Incidentally, in this example shown by curve a, P1LMT=1.87
(μs), and the discharge amount at this time is VLMT = 24
．． It was 0 [ng/dot]. In addition, the pulse width P1MAX when the discharge amount Vd reaches the saturated state is P1MAX
X=2.1 [μs], and the discharge amount VMAx at this time
=25.5 [ng/dot].

[0051] When the pulse width is larger than P1MAX, the ejection amount Vd is smaller than VMAX. This phenomenon occurs when a preheat pulse with a pulse width in the above range is applied, causing minute bubbles (just before film boiling) on the electrothermal converter, and before the bubbles disappear, the next main heat pulse is applied. The microbubbles disturb the foaming caused by the main heat pulse, thereby reducing the ejection amount. This region is called a pre-foaming region, and in this region, it is difficult to control the ejection amount using the preheat pulse.

[0052] P1 = 0 to P1LMT [μs
] If we define the slope of the straight line that shows the relationship between the discharge amount and the pulse width in the range as the preheat pulse dependence coefficient, then the preheat pulse dependence coefficient is:

[0053]

[Math 1]

[0054] This coefficient KP is determined by the head structure, driving conditions, ink physical properties, etc., regardless of temperature. That is, curves b and c in FIG. 7 show the case of other print heads, and it can be seen that the ejection characteristics change if the print heads are different. In this way, if the recording head is different, the upper limit value P1LMT of the preheat pulse P1 will be different.
As will be described later, an upper limit value P1LMT is determined for each recording head to control the ejection amount. Incidentally, in the recording head and ink shown by curve a of this example, KP = 3.2.
09 [ng/μsec·dot].

That is, another factor that determines the ejection amount of an inkjet recording head is the temperature of the recording head (ink temperature).

FIG. 8 is a diagram showing the temperature dependence of the discharge amount. As shown in the curve a of FIG. 8, the ejection amount V
d increases linearly. If we define the slope of this straight line as the temperature dependence coefficient, then the temperature dependence coefficient:

[0057]

[Math 2]

[0058] This coefficient KT is determined by the structure of the head, the physical properties of the ink, etc., regardless of the driving conditions. In FIG. 8, curves b and c also show the case of other recording heads. Incidentally, in the recording head of this embodiment, KT = 0.3[
ng/°C·dot].

As is clear from the explanations regarding FIGS. 7 and 8, when ejecting is performed by driving the electrothermal transducer with divided pulses, the amount of ink droplets to be ejected is equal to that of the first pulse in the divided pulses. Varies depending on the width, and
Generally, the amount of ejected ink droplets also varies depending on the ink temperature at that time, that is, the environmental temperature. Therefore, when recording, by modulating the initial pulse width of the divided pulses according to the environmental temperature, it is possible to keep the amount of ejected ink droplets constant and prevent density unevenness in the recorded image. It can be done. FIG. 9 shows the width P of the first pulse of the divided pulses.
This shows the modulation of 1. As shown in FIG. 9, one of the drive signals 1 to 11 is selected depending on the detected environmental temperature.

When performing idle ejection according to the embodiment of the present invention, it is effective to use the above-described pulse width modulation of the divided pulses. In other words, in the case of dry ejection, there is no requirement to make the amount of ejected ink droplets uniform, so it is necessary to minimize the total amount of ink consumed due to dry ejection while generating heat to effectively generate convection. The pulse width can be modulated so that it can be generated depending on the environmental temperature at that time.

FIG. 10 is a flowchart showing the processing procedure when performing ejection recovery processing due to empty ejection as an embodiment of the present invention. This processing procedure is started when the copying machine is powered on, and is performed in parallel with various processes related to warming up in the copying machine.

[0062] When this process is started, step S101
Then, the time ta during which ejection is not performed, including the time when the power is off, is read from a predetermined register. This time ta is measured based on the above-mentioned timer 807, and the same applies to each time shown below. next,
The time ta detected in step S103 is also a predetermined time td
Determine whether it is greater than or not. This predetermined time td
is set according to the time required for the influence of evaporation of ink water in the print head to reach the common liquid chamber and change the ink concentration. For example, in step S103 where 24 hours etc. ta is the predetermined time t
If a is greater than a, a dry discharge operation is initiated according to an embodiment of the present invention. That is, in step S105, idle ejection is started, and in step S107, idle ejection is performed until it is determined that the predetermined time tj1 has elapsed. After the idle discharge for this time tj1, the time ts is ejected in steps S109 and S111.
The idle discharge is interrupted for a period of time, and steps S113 and S1 are performed again.
At step 15, idle ejection is simultaneously performed for a time tj2, and the present processing procedure ends.

[0063] The number of times empty ejection is performed is not limited to two with an interruption as described above, but two empty ejections with an interruption as shown in the following experimental examples are considered to be one cycle. may be performed for multiple cycles.

In addition to these dry ejections, in order to promote convection in the common liquid chamber as explained in the principle of the present invention, the ink in the head may be heated by a sub-heater during the interruption of the dry ejection. Alternatively, the ink in the head may be heated by applying a drive signal to the ejection heater to the extent that the ink is not ejected.

Furthermore, in the explanation so far, the ink discharge process is performed by dry discharge or ink suction, but it is also possible to discharge ink from the discharge port by pressurizing the inside of the head through the ink tank or part of the ink supply system. Alternatively, ink may be discharged by a combination of these methods. For example, during the first discharge after an interruption, the ink is discharged by suction or pressure;
After the interruption, ink may be discharged by idle ejection.

Each of the experimental examples shown below uses the discharge treatment based on the principle of the present invention that has been explained so far. Also, as a comparative example, a case where ink discharge processing is performed by a conventional method is shown. In the comparative example and each experimental example, Figure 3
Remove the head cartridge shown in the printer from the printer.
After allowing the ink to stand for a day to promote evaporation of ink water through the ejection ports, various discharge treatments were performed.

(Comparative Example) In a comparative example, dry ejection was performed using a conventional method without any interruption time. Incidentally, during this idle ejection, ink droplets due to the idle ejection are deposited on the paper in the same manner as during printing in order to observe the density change due to the idle ejection. This also applies to the empty discharge in each of the following experimental examples. Dry discharge is performed at the maximum driving frequency of 4KH from all multiple nozzles.
Discharge was performed at Z for 1 second. FIG. 11 shows the density change on the paper at that time. If printing was continued in this state, density unevenness occurred at the beginning of printing as shown in FIG. 11.

(Experimental Example 1) According to the processing procedure shown in FIG. 10, 0.0.
Discharge was performed for 5 seconds, then idle discharge was interrupted for 0.5 seconds, and then discharge was performed again for 0.5 seconds at 4KHZ. FIG. 12 shows the measurement of the density printed on paper by this ejection. As is clear from this figure, the density difference was alleviated by the second dry ejection, and density unevenness became extremely slight even when printing was performed.

(Experimental Example 2) Ejection was performed for 0.25 seconds at the maximum driving frequency of 4 KHz from all the plurality of ejection ports. Next, the dry discharge was interrupted for 0.25 seconds, and then the discharge was made again for 0.25 seconds at 4KHZ, and then the dry discharge was interrupted for 0.25 seconds. Then, the above-described cycle was repeated once again, and the total idle ejection time was set to 1 second. FIG. 13 shows the results of these dry ejections performed on paper and the measured densities. In the image printed after this, density unevenness does not occur as shown in FIG. 13.

As can be seen from the results of Comparative Example and Experimental Examples 1 and 2, instead of continuously performing the same number of blank discharges, a certain period of non-discharge time (interruption) was performed between a series of blank discharges. By providing this, it is possible to effectively remove ink that has increased in viscosity or density within the head and refresh it with new ink. Note that if the duration of continuous ejection in one empty ejection is short, the flow velocity and temperature rise in the liquid chamber will be small, so the above-mentioned effect will be reduced.

By the way, in each of the above experimental examples, 4KHZ
Although the explanation was given using the driving frequency of
Z, 1KHZ may be used, but if the frequency is too low, the ink flow velocity will be low and the thermal effect will be small, so the effect of causing convection in the liquid chamber will be reduced, which is not preferable.

(Experimental Example 3) In Experimental Example 3, unlike Examples 1 and 2, the driving frequency was changed for each of the multiple dry ejections, and the head temperature was not raised too high by driving at a relatively low frequency during the final dry ejection. I tried not to. That is, when dry ejection is performed as in Experimental Examples 1 and 2, the head temperature becomes somewhat high immediately after the dry ejection operation ends. For this reason, it takes time for the head temperature to reach the normal recording temperature, and the start of printing may be delayed.

Specifically, 4KHZ discharge for 0.5 seconds,
Dry ejection was performed three times with interruptions while gradually lowering the drive frequency: 0.5 second interruption, 2 KHZ ejection for 0.5 seconds, 0.5 second interruption, and 1 KHZ ejection for 1 second.

That is, first, by high-duty ejection of 4KHZ, the ink flow in the liquid chamber is made high speed, and a large convection is generated, and the high-duty printing causes convection due to the effect of increasing the temperature of the ink in the liquid chamber. Wait until the ink in the liquid chamber is evenly stirred during ejection. Waiting for this time also has the effect of reducing the viscosity of the thickened ink. Then 2KHZ, 1K
By gradually lowering the drive duty for ejection with HZ, the temperature inside the head can be stabilized by the effect of heat dissipation due to ink ejection.

(Experimental Example 4) Out of the 128 outlets, the first to 64th outlets eject at 4KHZ for 0.5 seconds, the 65th to 128th do not emit during that time, and then Conversely, the fluid was not discharged from the 1st to 64th discharge ports, but was discharged at 4 KHz for 0.5 seconds from the 65th to 128th discharge ports. and,
This idle discharge was then repeated for one cycle. Even with this ejection method, density unevenness could be effectively eliminated, as shown in FIG. 15.

In the above-mentioned Experimental Examples 1 to 4, a method for refreshing ink in a recording head and a configuration thereof were explained using an ejection recovery process due to a dry ejection as an example. However, the aspect of ink refresh that updates the ink in the print head and ink supply system is not limited to the ejection recovery process; for example, the ink refresh method and its configuration according to the present invention can also be applied to replacing ink in the print head. can do.

For example, a case where the present invention is applied to an inkjet recording apparatus using one recording head and having a replaceable cartridge type ink tank for storing ink to be supplied to the recording head will be described below.

[0078] Some printers using such a recording head are configured to be able to print in multiple colors by replacing the ink tank with another type of ink. However, in such a configuration, when replacing the ink tank, it is necessary to completely remove ink from within the recording head and from the ink supply system to prevent deterioration in image quality caused by mixing with ink of other colors.

In this case, in order to replace the ink in the recording head etc., a suction operation etc. will be performed, but the flow of ink in the ink path, especially in the common liquid chamber, due to the suction operation is as shown in FIG. There are some areas where the ink flow is poor and the ink cannot be easily replaced.

On the other hand, by performing the suction operation with an interruption period according to the present invention, the common liquid chamber is refreshed relatively well.

Here, it is possible to perform a dry ejection instead of a suction operation, but when replacing the ink tank, air bubbles may accumulate at the joint between the head and the ink tank, so the first ink As for the ejection operation, a suction operation is preferable, and after that, an interrupted ejection operation may be performed by dry ejection. (Others) Note that, in particular, in the inkjet recording method, the present invention includes a means (for example, an electrothermal converter, a laser beam, etc.) for generating thermal energy as the energy used for ejecting ink, and This provides excellent effects in recording heads and recording apparatuses that use energy to cause changes in the state of ink. This is because such a system can achieve higher recording density and higher definition.

For its typical configuration and principle, see, for example, US Pat. Nos. 4,723,129 and 4,740.
Preferably, it is carried out using the basic principles disclosed in the '796 specification. This method is the so-called on-demand type.
It is applicable to both continuous types, but in particular, in the case of on-demand type, it is applicable to the electrothermal converter placed corresponding to the sheet holding the liquid (ink) or the liquid path. , by applying at least one drive signal that corresponds to recorded information and provides a rapid temperature rise exceeding nucleate boiling, the electrothermal transducer generates thermal energy to produce film boiling on the thermally active surface of the recording head. liquid (ink) that corresponds one-to-one to this drive signal.
This is effective because it can form air bubbles inside. The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection opening to form at least one droplet. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, making it possible to eject liquid (ink) with particularly excellent responsiveness. This pulse-shaped drive signal is described in US Pat. No. 4,463,359 and US Pat.
345262 are suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

[0083] In addition to the configuration of the recording head that is a combination of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44 disclose a configuration in which a heat acting part is arranged in a bending region.
A configuration using the specification of No. 59600 is also included in the present invention. In addition, JP-A-59-123670 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal converters, and a hole that absorbs pressure waves of thermal energy is disclosed. The effects of the present invention are also effective even with a configuration based on Japanese Patent Application Laid-open No. 138461/1985 which discloses a configuration corresponding to the discharge section. That is, regardless of the form of the recording head, according to the present invention, recording can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by a recording apparatus. Such a recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally.

In addition, even in the case of a serial type as in the above example, the recording head is fixed to the main body of the apparatus, or by being attached to the main body of the apparatus, electrical connection with the main body of the apparatus and ink flow from the main body of the apparatus are possible. The present invention is also effective when using a replaceable chip-type recording head that can be supplied with ink or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself.

Further, it is preferable to add a recovery means for the recording head, a preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus to the present invention, because the effects of the present invention can be further stabilized. . Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

[0087] Regarding the type and number of recording heads mounted, for example, in addition to a single head that corresponds to a single color ink, there are also systems that correspond to a plurality of inks of different recording colors and densities. A plurality of them may be provided. That is, for example, the recording mode of the recording apparatus is not limited to a recording mode for only a mainstream color such as black, but may also be a recording mode in which the recording head is configured integrally or in a combination of multiple colors, The present invention is also extremely effective for devices equipped with at least one full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid, but ink that solidifies at room temperature or lower, softens or liquefies at room temperature, or inkjet method. In general, the temperature of the ink itself is adjusted within the range of 30°C to 70°C to keep the viscosity of the ink within the stable ejection range. Any eggplant is fine. In addition, the temperature increase caused by thermal energy can be actively prevented by using the energy to change the state of the ink from a solid state to a liquid state, or ink that solidifies when left standing is used to prevent ink evaporation. In any case, the ink is liquefied by applying thermal energy in accordance with the recording signal, and the liquid ink is ejected, or the ink has already begun to solidify by the time it reaches the recording medium. The present invention is also applicable when using ink that is liquefied only by energy. The ink used in such cases is disclosed in Japanese Patent Application Laid-Open No. 54-56847 or Japanese Patent Application Laid-Open No. 60-1989.
As described in Japanese Patent No. 71260, the material may be held in a liquid or solid state in a porous sheet recess or through-hole and face an electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

In addition, the inkjet recording apparatus of the present invention may be used as an image output terminal for information processing equipment such as a computer, a copying machine combined with a reader, or a facsimile machine having a transmitting and receiving function. It may also take a form.

[0090]

As is clear from the above description, according to the present invention, during ink refresh processing such as ejection recovery processing and ink replacement processing in a recording head, ejection is improved by energy generated by an energy applying means such as an ejection heater. When the first ink discharge process via the outlet is performed, an ink flow occurs in the common liquid chamber of the recording head, and thereafter, while this first discharge process is interrupted, convection occurs in the common liquid chamber and the common liquid chamber The ink is mixed evenly. Then again the second
By performing ink discharge, this uniformly mixed ink is discharged.

As a result, the ink in the head liquid chamber can be effectively refreshed, the amount of discharged ink such as the number of blank ejections can be reduced, and the amount of ink consumed can be reduced.

[Brief explanation of the drawing]

FIGS. 1A and 1B are explanatory diagrams for explaining the action of the present invention, respectively.

FIG. 2 is a schematic perspective view showing an example of an inkjet recording apparatus that implements an ink refresh method according to the present invention.

3 is a perspective view of a recording head and ink tank integrated head cartridge installed in the inkjet recording apparatus shown in FIG. 2; FIG.

4 is an exploded perspective view of the head cartridge shown in FIG. 3. FIG.

5 is a block diagram showing a control configuration of the inkjet recording apparatus shown in FIG. 2. FIG.

6 is a waveform diagram showing drive signals used in ink jetting in the inkjet recording apparatus shown in FIG. 2; FIG.

7 is a perspective view showing the relationship between the pulse width of the drive signal shown in FIG. 6 and the amount of ink ejection.

FIG. 8 is a diagram showing the relationship between print head temperature (environmental temperature) and ink ejection amount.

9 is a waveform diagram for explaining an aspect of pulse width modulation of the drive signal shown in FIG. 6. FIG.

FIG. 10 is a flowchart showing an example of a processing procedure when performing idle ejection according to an embodiment of the present invention.

FIG. 11 is a diagram showing the effect of a comparative example on an experimental example of dry discharge to which the present invention is applied.

FIG. 12 is a diagram showing the effect of a first experimental example of dry discharge to which the present invention is applied.

FIG. 13 is a diagram showing the effect of a second experimental example of dry discharge to which the present invention is applied.

FIG. 14 is a diagram showing the effect of a third experimental example of dry discharge to which the present invention is applied.

FIG. 15 is a diagram showing the effect of a fourth experimental example of dry discharge to which the present invention is applied.

[Explanation of symbols]

112H Electrothermal converter (discharge heater) 113j
Discharge port 113N Ink path 113R Common liquid chamber 113S Area 800 Controller 801 CPU 803 ROM 805 RAM 807 Timer 8300 Cap unit 8500 Pump unit

Claims (14)

[Claims] Claim 1: A recording head for ejecting ink;
Ink refreshing of an inkjet recording apparatus that performs recording by ejecting ink, comprising an ink storage member storing ink to be supplied to the recording head, and an ink supply system for supplying ink from the ink storage member to the recording head. In the method, a first discharge process of discharging ink from an ink ejection port of the recording head by applying energy to the ink in the recording head, the ink storage member, or a part of the ink supply system; after the discharge; , an interruption process that interrupts ink discharge for a predetermined period of time, and after the interruption, ink is removed from the ink ejection port by applying energy to the ink again in the recording head, the ink storage member, or a part of the ink supply system. a second ejection process for ejecting the ink, the ink refreshing method comprising executing at least one cycle of each process of the first ejection, the interruption, and the second ejection. 2. The first and second discharge processes are characterized in that the ink is discharged by applying energy generated by an energy generating means for discharge in the recording head to the ink. Ink refresh method described. 3. The first and second discharge processes apply energy to the ink by suction through the ejection ports of the recording head or by pressurization through the ink storage member or a part of the ink supply system. 2. The ink refreshing method according to claim 1, wherein the ink is discharged by applying the action to the ink. 4. The first discharge process includes applying energy to the ink by suction through the ejection ports of the recording head or by pressurization through the ink storage member or a part of the ink supply system. 2. The second discharge process is characterized in that the ink is discharged by applying energy generated by an energy generating means for discharge in the recording head to the ink. How to refresh ink. 5. The ink refresh method according to claim 1, further comprising increasing the temperature of ink in the recording head during the interruption process. 6. The ink refreshing method according to claim 1, wherein the recording head has thermal energy generating means as a means for generating energy for ejecting ink. 7. The ink refresh method according to claim 6, wherein during the interruption process, the temperature of the ink in the recording head is increased using thermal energy generated by the thermal energy generating means. . 8. A recording head for ejecting ink;
An inkjet recording apparatus that performs recording by discharging ink, comprising an ink storage member storing ink to be supplied to the recording head and an ink supply system for supplying ink from the ink storage member to the recording head. a first energy application means for discharging ink from an ink ejection port of the recording head by applying energy to the ink in the recording head, the ink storage member, or a part of the ink supply system; and the first energy application means an interruption control means for interrupting the ink ejection for a predetermined period of time after the ink ejection; An inkjet recording apparatus comprising: a second energy applying means that discharges ink from the ink ejection port by applying the second energy. 9. The first and second energy application means discharge the ink by applying energy generated by the energy generation means for ejection in the recording head to the ink. 8. The inkjet recording device according to 8. 10. The first and second energy applying means apply energy to ink by suction through the ejection ports of the recording head or by applying pressure through the ink storage member or a part of the ink supply system. 9. The inkjet recording apparatus according to claim 8, wherein the ink is discharged by acting on the inkjet recording apparatus. 11. The first energy application means applies energy to the ink by suction through the ejection port of the recording head or by pressurization through the ink storage member or a part of the ink supply system. 9. The inkjet recording apparatus according to claim 8, wherein the second energy application means discharges the ink by applying energy generated by an energy generation means for ejection in the recording head to the ink. . 12. The inkjet recording apparatus according to claim 8, further comprising heating means for increasing the temperature of the ink in the recording head during the interruption by the interruption control means. . 13. Claims 8 to 12, wherein the recording head has thermal energy generating means as means for generating energy for ejecting ink.
The inkjet recording device according to any one of the above. 14. The apparatus according to claim 13, wherein during the interruption by the interruption control means, the temperature of the ink in the recording head is increased by using thermal energy generated by the thermal energy generation means. Inkjet recording device.