JP2966121B2 - Ink jet recording apparatus and ink refresh method for the apparatus - Google Patents

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 an ink refresh in a recording head for discharging ink.

[0002]

2. Description of the Related Art As one mode of refreshing ink in a recording head, an ejection recovery process is well known. These discharge the ink in the print head by pressurization or suction, or perform so-called idle discharge in which the ink is discharged at a site and timing not related to the recording, for example, so that the ink in the ink path or the like near the discharge port is formed. This is a process of discharging ink or the like that has increased in viscosity due to evaporation of water. As a result, non-ejection or ejection failure caused by the thickened ink or bubbles in the ink can be prevented.

[0003]

By the way, the evaporation of the ink moisture which causes the ink to thicken does not occur only in the ink path near the discharge port. This may occur in the entire ink in the recording head, such as a liquid chamber for storing the ink supplied to the ink path. The evaporation that occurs in such a part is relatively small in magnitude, and often does not lead to the occurrence of thickening that causes non-discharge and the like. However, evaporation of the ink moisture causes a relative increase in the dye concentration of the ink, and the concentration of the ink in the recording head changes depending on the degree of the evaporation.

[0004] Even if the degree of such a density change is relatively small, it may cause density unevenness which deteriorates the image quality of an image or the like recorded by these inks. Such density unevenness that occurs in a printed image or the like due to a change in the ink density becomes particularly noticeable in full-color printing in which printing is performed using inks of a plurality of colors.

As is apparent from the above, in order to simply prevent non-discharge or the like by discharging the thickened ink near the discharge port, it is sufficient to discharge at least the ink near the discharge port. The amount of ink discharged by ink suction and discharge can be relatively small. on the other hand,
In order to equalize the change in the density of the ink in the recording head, it is necessary to discharge substantially the entire ink in the recording head and refresh it with new ink, so that the discharge amount may be relatively large.

Therefore, in the conventional ejection recovery process, when the density change occurring in the ink in the recording head is taken into consideration, the amount of suction and the number of idle ejections increase, and the amount of ink consumed by the ejection recovery process increases. Was a problem.

SUMMARY OF THE INVENTION The present invention has been made based on the above-described viewpoint, and an object of the present invention is to reduce the amount of ink consumed due to the recovery of discharge due to idle discharge or ink suction. An object of the present invention is to provide a method of refreshing ink in a print head that can efficiently refresh ink and an ink jet printing apparatus that can execute the method.

[0008]

[Means for Solving the Problems] Therefore, in the present invention,
A plurality of ink discharge ports for discharging ink, an ink flow path corresponding to each of the discharge ports, and having an energy generating means for discharging ink, and a supply of ink to the plurality of ink flow paths. A common liquid chamber, an ink storage member storing ink to be supplied to the print head, and an ink supply system for supplying ink from the ink storage member to the print head. An ink refreshing method for an ink jet printing apparatus for performing printing by ejecting ink from the ink ejection port by applying energy to the ink in the printing head or the ink storage member or a part of the ink supply system. 1 discharge process, after the discharge, a suspend process for suspending the discharge of the ink for a predetermined time;
After the interruption, a second discharge process of discharging ink from the ink discharge port by applying energy to the ink in the recording head or the ink storage member or a part of the ink supply system again, At least one cycle of the processing including the first discharge, the interruption, and the second discharge is performed.
Also, a plurality of ink ejection ports for ejecting ink,
A recording head including an ink flow path corresponding to each of the discharge ports and having energy generating means for discharging ink, and a common liquid chamber for supplying ink to the plurality of ink flow paths; An ink storage member storing ink to be supplied to the head, an ink supply system for supplying ink from the ink storage member to the recording head,
In an ink refreshing method of an ink jet recording apparatus for performing recording by discharging ink, a convection generating process for generating a convection in the common liquid chamber, and after the convection generating process, the recording head or the ink storage member or the ink supply. And discharging the ink from the ink discharge port by applying energy to the ink in a part of the system.
Further, a plurality of ink discharge ports for discharging ink, an ink flow path having energy generating means for discharging ink corresponding to each of the discharge ports, and supplying ink to the plurality of ink flow paths. A common liquid chamber for
An ink jet recording apparatus comprising: a recording head comprising: an ink storage member that stores ink to be supplied to the recording head; and an ink supply system that supplies ink from the ink storage member to the recording head. In the recording apparatus, first energy action means for discharging ink from the ink ejection port 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 Interruption control means for interrupting the ejection of the ink for a predetermined time after the ejection by the action means; and after the interruption by the interruption control means, the ink is again applied to the recording head or the ink storage member or a part of the ink supply system. By applying energy, ink is discharged from the ink discharge port. A second energy application means for,
It is characterized by having.

In addition, a plurality of ink discharge ports for discharging ink, an ink flow path having energy generating means for supplying ink corresponding to each of the discharge ports, and a plurality of ink flow paths are provided. A print head comprising: a common liquid chamber for supplying ink; an ink storage member storing ink to be supplied to the print head; and an ink supply system for supplying ink from the ink storage member to the print head. In an ink jet recording apparatus that performs recording by discharging ink, the ink is discharged from the ink discharge port by applying energy to the ink in the recording head, the ink storage member, or a part of the ink supply system. Energy acting means, convection generating means for causing convection in the common liquid chamber, and convection generating means Thus after causing the convection,
Discharging means for discharging ink from the ink discharge port by applying the energy by the energy applying means.

[0010]

According to the above construction, in the ink refreshing process such as the ejection recovery process and the ink replacement process in the recording head, the ink discharge process through the ejection port is performed by the energy generated by the energy acting means such as the ejection heater. As a result, an ink flow can be generated in the common liquid chamber of the recording head, and thereafter, the convection can be generated in the common liquid chamber by interrupting the discharge process, thereby uniformly mixing the ink in the common liquid chamber. Can be combined. Then, by discharging the ink again, the uniformly mixed ink can be discharged.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1A and 1B are explanatory views of a recording head for explaining the principle of the present invention. FIG.
FIG. 1A is a schematic diagram illustrating the flow of ink in a common liquid chamber and an ink path of a print head from above the print head, and FIG. 1B is a schematic cross-sectional view of the same portion of the print head as viewed from the side. It is.

1 (A) and 1 (B), the discharge port 1 is discharged from the common liquid chamber 113R by continuous discharge or suction.
When the ink is discharged through the liquid chamber 113R
The flow of ink as shown by the arrow in FIG.
When such an ink flow occurs, as shown by a hatched portion 113S in the figure according to the shape of the common liquid chamber 113R and an arrangement portion of the arrangement of the ejection ports 113J with respect to the liquid chamber 113R along with this flow. In many cases, a region where little ink flow occurs is formed. That is, this area 113
S may form a vortex in contact with the ink flow outside the region, but the ink flow due to such a vortex remains in the region without being mixed with the ink flow outside the region. Therefore,
It is difficult for the ink in the area 113S to be discharged to the outside of the recording head by idle discharge, suction, or the like.

On the other hand, when the ink discharge process due to idle discharge or suction is interrupted, convection occurs in the entire common liquid chamber 113R due to the influence of the vortex of the region 113S formed by the discharge process. In the case where the ink discharge process is performed by idle discharge, convection occurs in the common liquid chamber 113R due to heat of the discharge heater 112H that generates thermal energy for discharge. Due to these convections, the ink in the area 113S is mixed with the ink outside the area, and the common liquid chamber 113R
Will be distributed throughout.

Accordingly, if the discharge process is interrupted after performing idle discharge, ink suction, etc. for a predetermined time, the discharge process is performed by the discharge process in the common liquid chamber 113R during the interruption. If the ink in the area 113S, which is the area where the ink is discharged, is dispersed throughout the common liquid chamber 113R, and then the ink discharge processing is performed again,
Most of the ink staying in the inside is discharged from the ejection port 113J to the outside of the recording head by the ink flow generated by this processing, and the relatively high viscosity and concentration of the ink in the area 113S are reduced by mixing. On the other hand, according to the conventional discharge processing in which the discharge processing is not interrupted, once the area 113S is first formed by the discharge processing, this area continues to exist during this discharge. The remaining ink is not discharged out of the print head forever, and the ink density and the like are not reduced. For this reason, when the ink in the area 113S is mixed with other inks at the end of the discharge processing, and the ink is ejected during recording,
These inks are ejected and may adversely affect the image quality.

As is apparent from the above description, the provision of the interruption for a predetermined time in the discharge processing enables more rapid and effective ink refreshing, and the ink consumption accompanying the ink refreshing such as the discharge recovery processing. The amount can be reduced.

FIG. 2 is a schematic perspective view showing an example of an ink jet recording apparatus capable of performing the refresh processing shown in FIG. This apparatus uses a replaceable ink tank integrated recording head cartridge for black (Bk), cyan (C),
This is a full-color serial type printer provided for each of the four inks of magenta (M) and yellow (Y), and is used as a recording unit of a full-color copying machine as described later with reference to FIG. The head used in this printer has a resolution of 400 dpi, a driving frequency of 4 KHz, and has 128 ejection ports.

In FIG. 2, IJC is Y, M, C, Bk
And four recording head cartridges corresponding to the respective inks, in which a recording head and an ink tank storing ink for supplying ink to the recording head are integrally formed. Each recording head cartridge IJC is detachably mounted on the carriage by a configuration (not shown). Carriage 82
Are slidably engaged along the guide shaft 811 and
Drive belt 85 moved by a main scanning motor (not shown)
2 and a part of it. Thus, the recording head cartridge IJC can be moved for scanning along the guide shaft 811. Reference numerals 815, 816 and 817, 818 denote conveying rollers extending substantially parallel to the guide shaft 811 on the back side and the near side in the drawing of the recording area scanned by the recording head cartridge IJC. Transport rollers 815, 8
16 and 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 facing the surface of the recording head cartridge IJC on which the ejection port surface is disposed.

A recovery system unit is provided facing a movable area of the cartridge IJC adjacent to a recording area of the recording head cartridge IJC. This recovery system unit is used when performing the idle discharge or ink suction processing described with reference to FIG. 8300 in recovery units
Is a cap unit provided for each of a plurality of cartridges IJC having a recording head. The cap unit is slidable in the left and right direction in FIG. When the carriage 82 is at the home position, the carriage 82 is joined to the recording head and capped. In the recovery system unit, reference numeral 8401 denotes a blade as a wiping member.

Further, 8500 is a cap unit 83
Reference numeral 00 denotes a pump unit for sucking ink and the like from the discharge port of the recording head and the vicinity thereof via the print head. FIG. 3 shows a configuration example of a head cartridge mountable on a carriage of the ink jet recording apparatus shown in FIG. The cartridge according to the present embodiment has an ink tank unit IT and a head unit IJU integrally, and these are detachable from each other. Head unit I
A wiring connector 102 for receiving a signal for driving the ink ejection unit 101 of the JU and outputting a remaining ink amount detection signal is provided at a position in line with the head unit IJU and the ink tank unit IT. Therefore, in a posture which is taken when the cartridge is mounted on a carriage described later, the height H can be reduced and the thickness of the cartridge can be reduced. This makes it possible to reduce the size of the carriage when arranging the cartridges side by side as described above with reference to FIG.

When the head cartridge is mounted on the carriage, the knob 201 provided on the ink tank unit IT can be gripped and placed on the carriage with the ejection section 101 facing down. This knob 201
Engages with a lever provided on a carriage described later for performing the mounting operation of the cartridge. Then, at the time of mounting, the pins provided on the carriage side engage with the pin engaging portions 103 of the head unit IJU, and the head unit IJU is positioned.

In the head cartridge according to the present embodiment, an absorber 104 for wiping the surface of the ink discharge unit 101 and cleaning a member for cleaning the surface is arranged in parallel with the ink discharge unit 101. Further, an air communication port 203 for introducing air with ink consumption is provided substantially at the center of the ink tank unit IT.

FIG. 4 is an exploded perspective view of the head cartridge shown in FIG. The head cartridge according to the present example includes:
It is composed of a head unit IJU and an ink tank unit IT.
This will be described with reference to FIG.

Head Unit The base for mounting the components of the head unit IJU is a base plate 111 made of Al or the like, on which an element group for generating energy used for ink ejection is formed. Substrate 1
12 and a printed circuit board (PCB) 115 having wiring and the like 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 (discharge heater 112H shown in FIG. 1) that generates thermal energy that causes film boiling of the ink in response to energization. Hereinafter, this substrate 112 is referred to as a heater board.

The above-described wiring connector 102 is connected to the PCB 11
5, a drive signal from a control circuit (not shown) is received by the wiring connector 102, and the PCB 115
Is supplied to the heater board 112 via the. PCB11
Reference numeral 5 denotes a double-sided wiring board in this example, and further includes information unique to the head, for example, appropriate driving conditions for the electrothermal transducer,
A ROM-type IC 128 storing a D number, ink color information, driving condition correction data (head shading (HS) data), PWM control conditions, and the like, and a capacitor 12
9 are provided.

As shown in the figure, the IC 128 and the capacitor 129 are provided on the joint surface side of the PCB 115 with the base plate 111 and in the notch 11 of the base plate 111.
It is arranged at a position corresponding to 1A. by this,
If the height at the time of mounting the IC or the like is equal to or less than the thickness of the base plate 111, the IC or the like does not protrude from the surface when the PCB 115 and the base plate 111 are joined. Therefore, it is not necessary to consider a storage mode corresponding to the protrusion in the manufacturing process.

On the heater board 112, as shown in FIG. 1, a common liquid chamber (113R) for temporarily storing ink supplied from the ink tank unit IT side, and the liquid chamber and a discharge port (113J) are provided. A top plate 113 having a concave portion for forming a group of communicating liquid paths (113N) is arranged. The top plate 113 is integrally formed with a discharge port forming member (orifice plate) 113A in which ink discharge ports are formed. Reference numeral 114 denotes a pressing spring for forming the discharge unit 101 by bringing the top plate 113 and the heater board 112 into close contact with each other.

Reference numeral 116 denotes a head unit cover, which is an ink supply pipe 1 that enters the ink tank unit IT.
16A, an ink flow path 116B for communicating ink with the top plate-side ink introduction tube, and a base plate 111
Three pins 116C for three-point positioning or fixing to the
It is a member formed by integrally molding the pin engaging portion 103, the mounting portion of the absorber 104, and other necessary portions. A channel cover 117 is provided for the ink channel 116B. A filter 118 for removing bubbles and dust is provided at the tip of the ink supply pipe 116A, and an O-ring for preventing ink from leaking from the joint is provided.

In assembling the above head unit, the pins 111P projecting from the base plate are connected to the PCB.
Positioning is performed so as to be inserted into the through-hole 115P provided in 115, and both are fixed by bonding or the like. In fixing the two, precision is not so required. This is because the heater board 112 to be mounted on the base plate 111 with high accuracy is fixed separately from the PCB 115.

Next, the heater board 112 is precisely placed and fixed on the base plate 111, and necessary electrical connection with the PCB 115 is made. Then, the top plate 113 and the spring 114 are arranged, and after bonding and sealing are performed as necessary, positioning is performed by inserting three pins 116C protruding from the cover into the holes 111C of the base plate 111. Thereafter, the head unit is completed by thermally fusing these three pins 116C.

In the ink tank unit, in FIG.
1 is an ink container which forms the main body of the ink tank unit, 2
15 is an ink absorber for impregnating the ink, 216
Is an ink tank cover, 212 is an electrode pin for detecting the remaining amount of ink, and 213 and 214 are contact members for the pin 212.

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

The bottom side of the cylindrical portion 233 is opened in consideration of the ink filling step, and after filling, a cap 217 shown in FIG. 4 is attached and closed to the atmosphere. On the other hand, a spiral or meandering groove 235 is provided on the upper end surface in FIG. 4 (a spiral in the illustrated example), and a cylindrical portion 233 is formed at one end 235A of the groove (the center of the spiral groove in the illustrated example). There is an opening communicating with the internal space.
The other end 235 </ b> B of the groove is located at the position 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 an equal angle, 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 made through the atmosphere communication port 203, the spiral groove 233, the internal space of the cylindrical portion 233, and the groove 237. And the cylindrical part 2
The internal space of 33 functions as a buffer unit for preventing ink leakage due to vibration or swing. In addition, since there is the spiral groove 233 that lengthens the path to the atmosphere communication port 203, ink leakage is more effectively prevented.

Further, by providing a plurality of grooves 237 at an equal angle on the side surface of the cylindrical portion 233 located substantially at the center of the ink tank as in the present embodiment, the absorber 215 located around the same can be provided. It is possible to secure a uniform state of balance with the atmosphere and prevent local concentration of ink in the absorber. This can also ensure smooth ink supply to the absorber compression area (around the supply port 231) described later.

Note that the groove 237 extends below the center of the thickness of the container and is provided over a range completely including the range A where the supply port 231 exists. In addition, it is formed in a range in which the position of the remaining amount detection pin 212 is also taken into consideration, thereby ensuring a uniform ink presence state or air communication state around the pin existing portion, and improving the accuracy of the remaining amount detection. be able to.

The ink impregnating absorber 215 according to this embodiment is provided with a hole 215A for receiving the insertion of the cylindrical portion 233. By arranging the tubular portion 233 in the hole 215A, the absorber 215 is not compressed by the tubular portion 233, and no ink remains in the compressed portion where the negative pressure is high. On the other hand, the absorber 21 according to the present example
Reference numeral 5 is a shape in which the portion located at the supply port 231 is slightly swelled 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). Thus, when the absorber 215 is stored in the ink tank unit, the expanded portion is in a compressed state, so that the absorber 215 has a high negative pressure at that portion, and thus supplies ink smoothly. Mouth 23
It can be introduced to one side.

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

Here, reference numeral 800 denotes a controller constituting a main control unit, for example, a CPU 801 in the form of a microcomputer for executing processing described later in FIG. 10, a program corresponding to the procedure, and a pulse width modulation described later. , A ROM 803 storing fixed data such as a heat pulse voltage value, a pulse width, and the like, and a RAM 805 provided with an area for developing image data, a work area, and the like. The controller 800 further has a timer 807 for measuring a non-recording time or the like. Reference numeral 810 denotes a host device serving as a supply source of image data (in this example, a reader unit for image reading). The image data and other commands and status signals are transmitted through an interface (I / F) 8.
12 to and from the controller.

Reference numeral 820 denotes a command from the operator such as a power switch 822, a copy switch 824 for instructing the start of recording (copying), and a large recovery switch 826 for instructing activation of a large recovery which is one mode of the ejection recovery process. This is a switch group that receives an input. Reference numeral 830 denotes a sensor group for detecting a device state, such as 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 a pump position.

Reference numeral 840 denotes a head driver for driving the electrothermal transducer of the printhead according to print data and the like. Part of the head driver is a temperature control heater 30A,
It is also used to drive 30B. Further, the temperature detection values from the temperature sensors 20A and 20B are
Enter 00. 850 is a main scanning motor for moving the carriage 82 in the main scanning direction, and 852 is its driver. A sub-scanning motor 860 is used to convey (sub-scan) a recording medium.

There are various known methods of driving the electrothermal transducer (ejection heater) at the time of ejection in the above-described ink jet recording apparatus, that is, the form of the drive signal applied to the electrothermal transducer. Typical examples thereof include a single-pulse electric signal and a double-pulse (division pulse) drive signal capable of relatively controlling the amount of ink droplets to be ejected. In addition, the present applicant has proposed a method in which the initial pulse width of the double pulse is modulated to control the amount of ejected ink droplets in accordance with the head temperature, thereby suppressing the density unevenness of a recorded image.

The idle discharge according to the principle of the present invention described with reference to FIG. 1 may be performed by any of the drive signals applied to the electrothermal transducer to generate the discharge. Since the droplet volume can be controlled more finely, this is one of the most suitable driving signals for suppressing the ink consumption accompanying the ink refresh of the recording head.

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

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

In FIG. 6, V _OP is the drive voltage, P ₁ is the pulse width of the first pulse (hereinafter, referred to as preheat pulse) of a plurality of divided heat pulses, P ₂ is the interval time, and P ₃ is the second. It is a pulse width of a pulse (hereinafter, referred to as a main heat pulse). T ₁ , T ₂ , and T ₃ indicate times for determining P ₁ , P ₂ , and P ₃ . The drive voltage V _OP is one of the values indicating electric energy required for the electric heat conversion element to which the voltage is applied to generate heat energy in the ink in the ink liquid path formed by the heater board and the top plate. The value is determined by the area, resistance value, film structure, and liquid path structure of the recording head of the electrothermal transducer. The divided pulse width modulation driving method includes P ₁ , P ₂ ,
And is to be given sequentially pulse width of P _3, the pre-heat pulse is mainly a pulse for controlling the ink temperature in the liquid path, have an important role in the discharge amount control of this embodiment I load . The preheat pulse width is set to a value that does not cause a bubbling phenomenon in the ink due to the thermal energy generated by the electrothermal converter when applied.

The interval time is provided to provide a predetermined time interval so that the pre-heat pulse and the main heat pulse do not interfere with each other, and to make the temperature distribution of the ink in the ink liquid path uniform. The main heat pulse is caused to foam in the ink in the liquid passage is for discharging ink from the discharge port, the area of the width P ₃ is an electrothermal transducer, resistance, film structure and the recording head It is determined by the structure of the ink liquid path.

FIG. 7 is a diagram showing the dependency of the ejection amount on the preheat pulse. In FIG. 7, V ₀ is P ₁ = 0 [μs
c], and this value is determined by the head structure. Incidentally, V ₀ in this embodiment is the environmental temperature T _R = 25.
In the case of ° C., V ₀ = 18.0 [ng / dot].

[0049] As indicated by the curve a in FIG. 7, in accordance with an increase in the pulse width P ₁ of the pre-heat pulse, the ejection amount V _d is increased with a linearity from Pasuru width P ₁ is 0 to P _1LMT In the range where the pulse width P ₁ is larger than P _1LMT , the change loses linearity and saturates and becomes maximum at the pulse width P _1MAX .

[0050] Thus, the range of variation of the ejection amount V _d relative to the change in the pulse width P ₁ until the pulse width P _1LMT showing the linearity is easily control the discharge amount by changing the pulse width P ₁ It is effective as a range that can be performed. _Incidentally , in this embodiment shown by the curve a, P _1LMT = 1.87 (μs), and the discharge amount at this time is V _LMT = 24.0 [ng / do].
t]. The pulse width P _1MAX when the discharge amount V _d is saturated is P _1MAX = 2.1 [μs],
The discharge amount V _{MAX at} this time was 25.5 [ng / dot].

[0051] When the pulse width is greater than the P _1MAX, the discharge amount V _d is smaller than V _MAX. This phenomenon is that when a preheat pulse having a pulse width in the above range is applied, fine bubbling (a state immediately before film boiling) occurs on the electrothermal transducer, and the next main heat pulse is generated before the bubble disappears. The ejection rate is reduced by the applied micro bubbles, which disturb the bubbling by the main heat pulse. This region is called a pre-foaming region, and in this region, it becomes difficult to control the discharge amount via a preheat pulse.

If the slope of a straight line indicating the relationship between the discharge amount and the pulse width in the range of P ₁ = 0 to P _1LMT [μs] shown in FIG. 7 is defined as the preheat pulse dependence coefficient, the preheat pulse dependence coefficient is:

[0053]

(Equation 1)

Is as follows. This coefficient K _P is determined by the head structure, driving conditions, physical properties of the ink, and the like irrespective of the temperature. That is, curves b and c in FIG. 7 show the case of another print head, and it can be seen that the ejection characteristics change when the print head is different. As described above, since the upper limit value _P1LMT of the preheat pulse P1 is different when the printheads are different, the discharge amount control is performed by setting the upper limit value _P1LMT for each printhead as described later. Incidentally, in the recording head and the ink indicated by the curve a in the present embodiment, K _P = 3.209 [ng / ng].
μsec · dot].

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

FIG. 8 is a diagram showing the temperature dependence of the discharge amount. As shown in curve a of Figure 8, the ejection amount V _d relative to the increase in environmental temperature T _R of the recording head (= head temperature T _H) increases linearly. If the slope of this line is defined as a temperature-dependent coefficient, the temperature-dependent coefficient:

[0057]

(Equation 2)

Is as follows. This coefficient K _T does not depend on the driving conditions, but is determined by the structure of the head, the physical properties of the ink, and the like. FIG.
Also, curves b and c show the cases of other recording heads.
Incidentally, in the recording head of this embodiment, K _T = 0.3 [n]
g / ° C. · dot].

As is clear from the description with reference to FIGS. 7 and 8, when the electrothermal transducer is driven by the divided pulse to perform ejection, the amount of the ejected ink droplet is determined by the first pulse of the divided pulse. Depending on the width,
Generally, the amount of ejected ink droplets differs depending on the ink temperature at that time, that is, the environmental temperature. Therefore, when printing, by modulating the initial pulse width of the divided pulse according to the environmental temperature, the amount of ink droplets to be ejected is kept constant so that the density unevenness does not occur in the printed image. Can be FIG. 9 shows the width P of the first pulse of the divided pulse.
₁ shows the state of modulation. As shown in FIG. 9, one of the drive signals 1 to 11 is selected according to the detected environmental temperature.

When performing idle discharge according to the embodiment of the present invention, it is effective to use the pulse width modulation of the divided pulse described above. That is, in the case of idle discharge, since there is no request to make the amount of the discharged ink droplets uniform, the heat for effectively generating convection is minimized while minimizing the total amount of ink consumption accompanying the idle discharge. The pulse width can be modulated so that it can be generated according to the environmental temperature at that time.

FIG. 10 is a flowchart showing a processing procedure in the case of performing the ejection recovery processing by idle ejection as one embodiment of the present invention. This processing procedure is started when the power of the copier is turned on, and is performed in parallel with each process related to warm-up in the copier.

When this processing 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. The time t _a is intended to be measured in accordance with the timer 807 described above, the same applies to the time indicated below. Then, time detected in step S103 t _a also determines whether or not larger than the predetermined time t _d. The predetermined time t _d is for the influence of the evaporation of the ink moisture in the recording head is set according to the time to reach the changing up the common liquid chamber and ink density, for example, is set for 24 hours, etc. in step S103, the time t _a be a larger than the predetermined time t _a, the idle discharge operation according to an embodiment of the present invention is initiated. That is, idle discharge is started in step S105, and idle discharge is performed until it is determined in step S107 that the predetermined time t _j1 has elapsed. After the idle ejection for the time t _{j1, the} idle ejection is interrupted for the time t _{s in} steps S109 and S111, and again in the steps S113 and S115 simultaneously for the time t _j2.
The idle discharge is performed during this period, and the processing procedure ends.

The number of times of idle discharge is not limited to two with the interruption as described above, and two idle discharges with interruption as one cycle as in each of the following experimental examples are taken as one cycle. May be performed in a plurality of cycles.

In order to promote convection in the common liquid chamber as described in the principle of the present invention in addition to these idle discharges, the ink in the head is heated by the sub-heater during the idle discharge interruption. Alternatively, the ink in the head may be heated by applying a drive signal that does not cause ejection to the ejection heater.

Further, in the above description, the ink discharge processing is performed by idle discharge or ink suction. However, the inside of the head is pressurized through the ink tank or a part of the ink supply system to discharge the ink from the discharge port. May be performed, or ink may be discharged by a combination of these. For example, at the first discharge after an interruption, ink is discharged by suction or pressure,
After the interruption, the ink may be discharged by idle discharge.

Each of the following experimental examples uses the above-described discharge processing according to the principle of the present invention.
In addition, as a comparative example, a case where an ink discharging process is performed by a conventional method is shown. In the comparative example and each experimental example, FIG.
1 Remove the head cartridge shown in
Each discharge process was performed after allowing the ink to evaporate through the discharge port after leaving it to stand for a day.

(Comparative Example) In the comparative example, idle discharge was performed by a conventional method without interruption time. In addition, at the time of this idle discharge, ink droplets due to the idle discharge are made to adhere to the paper, as in the case of printing, in order to check the density change due to the idle discharge. This is the same for idle discharge in the following experimental examples. Empty discharge is 4K of the maximum drive frequency from multiple nozzles
Discharged at _HZ for 1 second. FIG. 11 shows the density change on the paper at that time. If printing was performed as it was, density unevenness occurred at the beginning of the printing as shown in FIG.

[0068] In 4KH _Z of the maximum driving frequency of a plurality of all the ejection openings in accordance with the processing procedure shown in Experimental Example 1 FIG. 10 0.
5 seconds discharge no rows, interrupted then spit 0.5 seconds, followed discharged again 0.5 seconds 4KH _Z. FIG. 12 shows the density measured on paper by this ejection. As is clear from this figure, the density difference was alleviated by the second idle discharge, and the density unevenness became very small even when printing was performed.

[0069] it was carried out 0.25 seconds discharge in 4KH _Z maximum drive frequency from (Experiment 2) multiple full discharge ports. Then suspended idle discharge 0.25 seconds and then interrupted again 4KH _Z and then at 0.25 seconds spit ejected 0.25 seconds. Then, the above-described cycle was performed again, and the total time of the idle discharge was set to 1 second. These idle discharges are performed on the paper, and the density of the paper is measured, as shown in FIG. In the image printed thereafter, density unevenness does not occur as shown in FIG.

As can be seen from the results of the comparative example and the experimental examples 1 and 2, the non-discharge time (interruption) for a certain period of time is not continuously performed even with the same number of idle discharges. By providing the ink, the ink having increased viscosity and density in the head can be effectively removed and refreshed with new ink. Note that if the time of continuous ejection in one empty ejection is short, the above effects are reduced because the flow velocity in the liquid chamber and the temperature rise are small.

By the way, in the above experimental examples have been described in the driving frequency of 4KH _Z, if it is possible to produce a certain flow rate in the common liquid chamber, less 2KH
_Z, but it may be 1 kH _Z, so when is a low frequency, the flow rate of the ink is small, undesirably effect to cause convection in the liquid chamber for thermal effects also small decreases.

(Experimental Example 3) In Experimental Example 3, unlike Embodiments 1 and 2, the driving frequency of each of the multiple idle discharges was changed, and the final idle discharge was driven at a relatively low frequency to raise the head temperature too high. I did not do it. That is, when the idle discharge is performed as in Experimental Examples 1 and 2, the head temperature slightly increases immediately after the end of the idle discharge operation. For this reason, it takes time until the head temperature during normal recording is reached, and printing may be delayed.

Specifically, 4 KHz _Z discharge is performed for 0.5 second,
0.5 seconds interruption, 2KH _Z ejecting 0.5 seconds, 0.5 seconds interrupt, performing three air ejection placed interruptions gradually lowering the driving frequency to refer to 1 kH _Z discharge 1 second, and Was.

[0074] That is, the first high-duty ejection of 4KH _Z, then the flow of ink in the liquid chamber at high speed,
Generates large convection, and causes convection due to the effect of increasing the temperature of the ink in the liquid chamber due to high duty printing,
Wait for the ink in the liquid chamber to be uniformly stirred during non-ejection. Waiting for this time also has the effect of reducing the viscosity of the thickened ink. Then 2KH _Z, 1KH _Z
By gradually lowering the drive duty for ejection, the temperature inside the head can be stabilized by the effect of heat radiation by ink ejection.

[0075] Experimental Example 4 of the 128 ejection openings, firstly, discharged 0.5 seconds from the discharge port from first to 64th in 4KH _Z, from 65 th to 128 th not ejected during which then reverse without discharged from the 64th discharge port from the first, was discharged from the discharge port from the 65 th to 128 th in 0.5 seconds 4KH _Z. This idle discharge was continuously repeated for one cycle. Even with this discharge method, as shown in FIG. 15, it was possible to effectively eliminate density unevenness.

In the above-described Experimental Examples 1 to 4, the method of refreshing the ink in the print head and the configuration for refreshing the ink in the recording head using the example of the ejection recovery processing by the idle ejection have been described. However, the mode of the ink refresh for updating the ink of the recording head and the ink supply system is not limited to the ejection recovery processing. For example, the ink refresh method and the configuration according to the present invention are also applied to the exchange of the ink in the recording head. can do.

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

Some printers using such a recording head can perform multicolor printing by replacing the ink tank with another ink. However, in such a configuration, it is necessary to completely eliminate the ink in the recording head and the ink supply system when replacing the ink tank, and to prevent the deterioration of the image quality caused by mixing with the ink of another color.

In this case, a suction operation or the like is performed to replace the ink in the recording head or the like. The flow of the ink in the ink path due to the suction operation, particularly, the ink flow in the common liquid chamber is shown in FIG. There is a part where the flow is poor and the ink is not easily replaced.

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

Here, idle discharge may be performed instead of the suction operation. However, in the case of replacement of the ink tank or the like, bubbles may stagnate at the junction between the head and the ink tank. For the discharging operation, a suction operation is preferable, and then the discharging operation with interruption may be performed by idle discharge. (Others) In addition, the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for performing ink ejection, particularly in an ink jet recording method. The present invention brings about an excellent effect in a print head and a printing apparatus of a type in which a change in the state of ink is caused by energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44,558 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, 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 on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

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

It is preferable to add recovery means for the print head, preliminary auxiliary means, and the like provided as a configuration of the printing apparatus in the present invention since the effects of the present invention can be further stabilized. . If these are specifically mentioned, capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof, Performing a preliminary ejection mode in which ejection is performed separately from printing is also effective for performing stable printing.

The types and the number of recording heads to be mounted are not limited to those provided only for one color ink, and for a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to the printing mode of only the mainstream color such as black, but may be any of integrally forming the printing head or a combination of a plurality of printing heads. The present invention is also extremely effective for an apparatus provided with at least one of full colors by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or below and which softens or liquefies at room temperature, or an ink jet system In general, the temperature of the ink itself is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Anything can be used. In addition, the temperature rise due to thermal energy can be positively prevented by using it as energy for changing the state of the ink from a solid state to a liquid state, or ink that solidifies in a standing state to prevent evaporation of the ink can be used. In any case, the ink is liquefied by the application of the thermal energy according to the recording signal, and the ink is liquefied, and the liquid ink is discharged. The present invention is also applicable to a case where an ink that liquefies for the first time by energy is used. In such a case, the ink is disclosed in JP-A-54-56847 or JP-A-60
As described in JP-A-71260, a configuration may be adopted in which a liquid or solid substance is held in a concave portion or through hole of a porous sheet and opposed to an electrothermal converter. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

Further, the form of the ink jet recording apparatus of the present invention is not limited to those used as image output terminals of information processing equipment such as computers, copying apparatuses combined with readers and the like, and facsimile apparatuses having a transmission / reception function. It may take a form.

[0090]

As is apparent from the above description, according to the present invention, in the ink refreshing process such as the ejection recovery process or the ink replacement process in the recording head, the ejection is performed by the energy generated by the energy acting means such as the ejection heater. By performing the ink discharging process through the outlet, it is possible to cause a flow of ink in the common liquid chamber of the recording head, and thereafter, by interrupting the discharging process, convection can be generated in the common liquid chamber. In addition, the ink in the common liquid chamber can be uniformly mixed. And
Thereafter, by discharging the ink again, the uniformly mixed ink can be discharged.

As a result, the ink in the head liquid chamber can be effectively refreshed, the amount of ink discharged such as the number of idle discharges can be reduced, and the consumption of ink can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory views for explaining the operation of the present invention. FIG.

FIG. 2 is a schematic perspective view illustrating an example of an ink jet recording apparatus that performs an ink refresh method according to the present invention.

FIG. 3 is a perspective view of a recording head and an ink tank integrated type head cartridge mounted on the ink jet recording apparatus shown in FIG. 2;

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

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

FIG. 6 is a waveform diagram showing a drive signal at the time of ink ejection used in the ink jet recording apparatus shown in FIG.

FIG. 7 is a perspective view illustrating a relationship between a pulse width of a driving signal and an ink ejection amount illustrated in FIG. 6;

FIG. 8 is a diagram illustrating a relationship between a recording head temperature (environmental temperature) and an ink ejection amount.

FIG. 9 is a waveform chart for explaining a mode of pulse width modulation of the drive signal shown in FIG. 6;

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

FIG. 11 is a diagram illustrating an effect of a comparative example with respect to an experimental example of idle discharge to which the present invention is applied.

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

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

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

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

[Explanation of symbols]

 112H Electrothermal converter (ejection 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 (18)

(57) [Claims] A plurality of ink ejections for ejecting ink.
Ejects ink corresponding to the outlet and each of the discharge ports
An ink flow path having energy generating means for
A common liquid chamber for supplying ink to a number of said ink flow paths
And a recording head comprising: an ink storage member that stores 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 ink refreshing method for an ink jet recording apparatus to be performed, a first discharge process of discharging ink from the ink discharge port by applying energy to the ink in the recording head or the ink storage member or a part of the ink supply system, After the ejection, an interruption process for interrupting the ejection of the ink for a predetermined time. After the interruption, the ink is applied again to the recording head or the ink storage member or a part of the ink supply system by applying energy to the ink. A second discharging process for discharging the ink from the discharge port. An ink refreshing method comprising executing at least one cycle of a process including the first discharging, the interruption, and the second discharging. 2. The recording apparatus according to claim 1, wherein the first discharging process includes
Suction through the discharge port or the ink storage member
Or pressurized energy through a part of the ink supply system.
The ink on the ink
The second discharge process is performed by discharging the recording head.
Energy generated by energy generation means for
Ink to discharge ink.
2. The ink refresh method according to claim 1, wherein:
Law. 3. The recording head according to claim 1 , wherein:
Increasing the temperature of the ink in the ink
Item 3. The ink refreshing method according to item 1 or 2. 4. A method according to claim 1, wherein a part of said plurality of ink ejection ports is provided.
The ink ejection port is the first or the other ink ejection port.
Discharge of ink is suspended during the second discharge process
During the interruption process, the ink discharging process is performed.
4. The method according to claim 1, wherein
3. The ink refreshing method according to item 1. 5. A plurality of ink discharges for discharging ink.
Ejects ink corresponding to the outlet and each of the discharge ports
An ink flow path having energy generating means for
A common liquid chamber for supplying ink to a number of said ink flow paths
And an ink storage unit storing ink to be supplied to the print head.
Material and ink from the ink storage member to the recording head.
Ink supply system for printing by ejecting ink.
A convection generating process for generating convection in the common liquid chamber; and after the convection generating process, the recording head or the ink.
In the storage member or a part of the ink supply system,
The ink by applying energy to the ink.
A discharging process for discharging the ink from the discharge port . 6. The method according to claim 1, wherein each of the discharging processes includes an operation of the recording head.
Energy generated by energy generation means acts on ink
Discharges ink by causing
The ink refresh method according to claim 1 or 5, wherein 7. Each of the discharging processes is performed before the recording head.
Suction through the discharge, or the ink storage member or
Energy by pressurization through a part of the ink supply system
Ejects ink by acting on the ink
The ink cliff according to claim 1 or 5, wherein
Resh method. 8. The recording head during the convection generation processing.
Characterized by increasing the temperature of the ink in the ink
The ink refresh method according to claim 5. 9. The recording head according to claim 1, wherein the recording head ejects ink.
Thermal energy generation as a means of generating energy
9. A method according to claim 1, further comprising means.
An ink refreshing method according to any one of the preceding claims. 10. The method according to claim 10 , wherein the thermal energy is supplied during the interruption.
The recording using heat energy generated by the generating means;
The feature is to raise the temperature of the ink in the head
The ink refreshing method according to claim 9, wherein: 11. A plurality of inks for discharging ink.
Ink is ejected corresponding to each ejection port and each ejection port
An ink flow path having energy generating means for performing
Common liquid for supplying ink to a plurality of the ink flow paths
Head, and an ink storage unit storing ink to be supplied to the print head
Material and ink from the ink storage member to the recording head.
Ink supply system for printing by ejecting ink.
In the recording apparatus, the recording head or the ink storage member or the ink
Energy to the ink in a part of the ink supply system.
To discharge ink from the ink discharge port.
A first energy action means to be discharged and a predetermined time after the discharge by the first energy action means.
Control means for interrupting the discharge of ink, and after the interruption by the interrupt control means, the recording head and the recording head are again stopped.
Or a part of the ink storage member or the ink supply system
By applying energy to the ink in
To discharge ink from the ink ejection port.
An ink jet recording apparatus comprising: the Energy action means. 12. The first and second energy action means.
Is the energy generated by the energy generating means of the recording head.
Drain ink by applying energy to ink.
12. The ink jet printer according to claim 11, wherein
Jet recorder. 13. The first and second energy action means.
Is suction through the discharge port of the recording head, or
Via a part of the ink storage member or the ink supply system
To apply the energy of the applied pressure to the ink
12. The method according to claim 11, wherein the ink is discharged.
3. The ink jet recording apparatus according to claim 1. 14. The apparatus according to claim 14, wherein the first energy action means is
Suction through the discharge port of the recording head, or
Pressurization through the ink storage member or a part of the ink supply system
Energy by acting on the ink
And the second energy action means comprises:
Energy generation means for ejection in the print head
By applying the generated energy to the ink
12. The method according to claim 11, wherein the ink is discharged.
Inkjet recording device. 15. During the interruption by the interruption control means,
Heating to raise the temperature of ink in the recording head
12. The method according to claim 11, further comprising:
15. The ink jet recording apparatus according to 14. 16. A plurality of inks for discharging ink
Supplying ink corresponding to the discharge port and each of the discharge ports
An ink flow path having energy generating means for performing
Common liquid for supplying ink to a plurality of the ink flow paths
Head, and an ink storage unit storing ink to be supplied to the print head
Material and ink from the ink storage member to the recording head.
Ink supply system for printing by ejecting ink.
In the recording apparatus, the recording head or the ink storage member or the ink
Energy to the ink in a part of the ink supply system.
To discharge ink from the ink discharge port.
Energy action means for emitting , convection generating means for generating convection in the common liquid chamber, and after the convection is generated by the convection generating means ,
Applying the energy by means of energy action
Discharging ink from the ink discharge port
And an ejection unit . 17. The recording head for ejecting ink.
Heat energy as a means of generating energy for
17. The method according to claim 11, further comprising: means for producing.
The inkjet recording device according to any one of the above. 18. The method according to claim 17 , wherein the thermal energy is supplied during the interruption.
The recording using heat energy generated by the generating means;
The feature is to raise the temperature of the ink in the head
The inkjet recording apparatus according to claim 17, wherein