JP3284502B2 - Ink jet recording device - 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 having a nozzle opening and a recording head for discharging ink droplets from the nozzle opening.

[0002]

2. Description of the Related Art An ink jet recording apparatus has relatively low noise during printing and can form small dots at a high density. For this reason, they are used in many printings including color printing these days.

[0003] Such an ink jet recording apparatus is
An ink jet recording head that receives supply of ink from an ink cartridge, and a paper feeding unit that moves recording paper relatively to the recording head, while moving the recording head on the carriage in the width direction of the recording paper. Recording (printing) is performed by discharging ink droplets onto the recording paper. A print head that can eject black, yellow, cyan, and magenta color inks is mounted on the carriage.Full-color printing is possible by changing the ejection ratio of each ink in addition to text printing using black ink. ing.

The ink jet recording head performs printing by discharging ink pressurized in a pressure generating chamber from a nozzle as ink droplets onto recording paper. Therefore, printing failure may occur due to an increase in ink viscosity due to evaporation of the ink solvent component from the nozzle opening and solidification of the ink. Also, due to the adhesion of dust and air bubbles,
Poor printing can occur.

[0005] For this reason, the ink jet recording apparatus is provided with a capping means for sealing the nozzle openings of the recording head during non-printing, and a cleaning device for cleaning the nozzle plate if necessary.

The capping means functions as a lid for preventing the ink from drying at the nozzle openings when printing is stopped. Further, when the nozzle opening is clogged in cooperation with the suction pump, the nozzle plate is brought into close contact with the capping means, and the ink is suctioned from the nozzle opening by the negative pressure from the suction pump, thereby opening the nozzle opening. It also has a function of eliminating clogging due to ink solidification and ink ejection failure due to air bubbles entering the ink flow path.

[0007] Forcible suction and discharge processing of ink for eliminating clogging of the recording head and mixing of air bubbles into the ink flow path is usually called a cleaning operation. This processing operation is executed when printing is restarted after a long period of suspension of the apparatus, or when the user operates, for example, a cleaning switch in order to eliminate the deterioration of the quality of the recorded image.

After the ink droplets are discharged by negative pressure,
A wiping operation of the head surface is performed by a wiping member made of an elastic plate such as rubber.

[0009] A function is also provided for forcibly ejecting ink droplets by applying a drive signal unrelated to printing to the recording head. This is commonly called a flushing operation.
This processing operation is performed for the purpose of recovering an irregular meniscus near the nozzle opening of the recording head due to wiping or the like after the cleaning operation. In addition, the process is performed for the purpose of discharging and discharging the mixed color ink flowing backward from the nozzle by wiping. Further, the process is executed at regular intervals for the purpose of preventing clogging due to thickening of the ink in the nozzle opening having a small ejection amount of the ink droplet during printing.

[0010]

By the way, the above-described ink jet type recording apparatus is equipped with a recording head having a structure shown in FIG. 10, for example. That is, FIG. 10 is a sectional view showing the configuration of one flow path of the recording head 5. As shown in FIG. 10, in an actual multi-nozzle type print head, nozzle rows in which channels and nozzles are formed in rows are arranged in parallel.

In the figure, reference numeral 5a is a diaphragm. A lower electrode 5b is formed on the surface of the diaphragm 5a.
A piezoelectric element 5 made of PZT or the like is provided on the surface of the lower electrode 5b.
c is arranged. An upper electrode 5d is arranged on the surface of the piezoelectric element 5c. For this reason, the piezoelectric element 5c is driven to expand and contract by the drive signals supplied to the upper and lower electrodes,
Along with this, the diaphragm 5a is driven vertically in the figure.

A spacer 5e is arranged on the lower surface side of the diaphragm 5a. The spacer 5e has a concave portion forming a cavity (pressure generating chamber) 5f on the lower surface side of the vibration plate 5a on which the piezoelectric element 5c is arranged.

An ink supply port forming substrate 5g is disposed on the lower surface side of the spacer 5e. An ink supply port 5h is formed in the substrate 5g so as to communicate with the cavity 5f.

On the lower surface side of the ink supply port forming substrate 5g, a spacer 5i is arranged. Spacer 5i
Have a common ink chamber, that is, a concave portion forming a reservoir 5j.

A nozzle plate 5m having a nozzle opening 5k is arranged on the lower surface of the spacer 5i. In addition, the ink supply port forming substrate 5g and the spacer 5i are provided with an opening for forming a nozzle communication path 5n that linearly connects the cavity 5f and the nozzle opening 5k. The spacer 5e, the ink supply port forming substrate 5g, the spacer 5i, and the like are integrally joined to each other via an adhesive layer.

As described above, the diaphragm 5a vibrates in the vertical direction in the figure due to the expansion and contraction of the piezoelectric element 5c. In this case, when power is supplied to the piezoelectric element 5c, the diaphragm 5a moves downward. At this time, the ink in the cavity 5f is pressurized and pushed out through the nozzle communication path 5n, and is ejected as an ink droplet from the nozzle opening 5k. Also, the piezoelectric element 5c
Is discharged, the diaphragm 5a returns to the original state.
As a result, the cavity 5f expands, and the ink in the reservoir 5j forming the common ink chamber is taken into the cavity 5f via the ink supply port 5h, and is supplied to the cavity 5f as ink for the next printing. .

Due to the contraction of the cavity 5f by the piezoelectric element 5c, the cavity 5f is moved from the reservoir 5j.
While f is supplied with ink, ink droplets are ejected from the nozzle opening 5k through the cavity 5f and the nozzle communication path 5n.

FIGS. 11 (a) and 11 (b) show the operation of ink droplets when ink droplets are ejected during a flushing operation in the recording head having the above-described configuration.

In the conventional control mode, FIG.
As shown in FIG.
From the nozzle opening 5k, a main droplet M of ink and subsequently a columnar ink are ejected. As shown in FIG. 11B, a part of the columnar ejection ink following the main droplet M is formed by a plurality of minute ink droplets S (also referred to as satellite droplets. )
Becomes

The microdroplets S shown in FIG. 11B usually have a slow speed and an extremely small weight, and are in a state of being easily floated. For this reason, the fine droplet S becomes mist ink (mist) and contaminates the inside of the printing apparatus, or is discharged outside through an opening hole (for example, an exhaust hole of a cooling fan) provided in the printing apparatus to clean the periphery of the apparatus. Or pollute.

In particular, in a recording apparatus in which the second flushing area is arranged on the opposite side of the capping means with respect to the printing area, the flushing amount that can be discharged into the capping means is usually restricted, and the second flushing area is limited. On the other hand, a large amount of flushing needs to be performed.

In particular, as shown in FIG. 12, an opening hole 13 is formed in a member (paper guide member) 8 facing the nozzle opening 5k of the recording head 5 as a second flushing area, and an absorbing material is formed on the bottom side thereof. In the case where the recording head 14 is provided, the distance from the nozzle forming surface of the recording head 5 to the absorbent 14 for receiving the flushed ink is relatively large, about several tens mm.

As described above, when there is a relatively large distance from the nozzle forming surface of the recording head 5 to the absorbing material 14, the minute droplet S is applied to the absorbing material 14 arranged on the bottom side of the opening 13. Before reaching, float as indicated by the arrow,
The problem of contaminating the surroundings occurs. In particular, in a recent printing apparatus in which the amount of each ink droplet is controlled as small as possible in order to realize high image quality, the problem appears more remarkably.

Further, the ink droplets discharged from the nozzle openings are considerably charged, and can be accelerated by the static electricity generated in the driving section in the recording apparatus.

Further, the ejected ink droplets can be accelerated by an airflow from an exhaust fan arranged to suppress a rise in temperature in the apparatus.

The present invention has been made in view of the above-mentioned problems, and provides an ink jet recording apparatus capable of effectively suppressing the generation of mist and floating fine droplets during a flushing operation. Accordingly, it is an object of the present invention to provide an ink jet recording apparatus that does not contaminate the inside and outside of the apparatus.

[0027]

SUMMARY OF THE INVENTION The present invention provides a drive signal supply unit for generating a flushing drive signal, a recording head having a nozzle opening, and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Wherein the flushing drive signal is a signal such that the ink droplets ejected from the nozzle openings are only the main ink droplets.

The flushing drive signal of the present invention uses only ink droplets ejected from the nozzle openings as main ink droplets and does not generate microdroplets, so that contamination due to the generation of microdroplets can be prevented.

Such a flushing drive signal is usually a periodic signal for flushing efficiency. In particular,
When the unit cycle waveform has a trapezoidal waveform including a continuous first slope, a potential maintaining section, and a second slope, the duration of the trapezoidal waveform, the slope of the first slope, in addition to the frequency of the drive signal. The degree, the magnitude of the potential of the potential maintaining unit, and the degree of inclination of the second inclined part can be controlled as variable parameters.

More specifically, when the slope of the first slope is gentle and the slope of the second slope is steep, the frequency of the drive signal, the duration of the trapezoidal waveform, and the magnitude of the potential of the potential maintaining unit This is preferable because the allowable setting range becomes large.

Further, the present invention includes a drive signal supply unit for generating a flushing drive signal, a recording head having a nozzle opening, and ejecting ink droplets from the nozzle opening based on the flushing drive signal, The above-mentioned flushing drive signal is a signal such that the momentum of each of the ejected ink droplets is equal to or more than a predetermined value.

The flushing drive signal according to the present invention is used to set the momentum of the ink droplet ejected from the nozzle opening to a predetermined value or more. Contamination due to scattering can be prevented.

Such a flushing drive signal is usually a periodic signal because of the efficiency of flushing. In particular,
When the unit cycle waveform has a trapezoidal waveform including a continuous first slope, a potential maintaining section, and a second slope, the duration of the trapezoidal waveform, the slope of the first slope, in addition to the frequency of the drive signal. The degree, the magnitude of the potential of the potential maintaining unit, and the degree of inclination of the second inclined part can be controlled as variable parameters.

Further, the present invention includes a drive signal supply unit for generating a flushing drive signal, a recording head having a nozzle opening, and discharging ink droplets from the nozzle opening based on the flushing drive signal, The flushing drive signal causes the ink droplet to be ejected intermittently and continuously from the nozzle opening, and the ejected ink droplet has a main ink droplet and a minute droplet ejected after the main ink droplet. Is a signal that combines with a subsequent main ink droplet within a predetermined distance range.

The flushing drive signal of the present invention combines the microdroplets ejected from the nozzle openings with the subsequent main ink drops, so that contamination due to the scattering of the microdroplets can be prevented.

Such a flushing drive signal is usually a periodic signal because of the efficiency of flushing. In particular,
When the unit cycle waveform has a trapezoidal waveform including a continuous first slope, a potential maintaining section, and a second slope, the duration of the trapezoidal waveform, the slope of the first slope, in addition to the frequency of the drive signal. The degree, the magnitude of the potential of the potential maintaining unit, and the degree of inclination of the second inclined part can be controlled as variable parameters.

Specifically, when the frequency of the drive signal is increased (preferably to about 10 kHz), the duration of the trapezoidal waveform, the degree of inclination of the first inclined section, the magnitude of the potential of the potential maintaining section, and the second This is preferable because the setting range allowed for the degree of inclination of the inclined portion becomes large.

In addition, capping means capable of sealing the nozzle opening of the recording head is provided, and the ink droplet ejected from the nozzle opening by the recording head based on the flushing drive signal is received by the capping means. Is preferred.

Alternatively, an opening capable of facing the nozzle opening of the recording head is provided, and an ink absorbing material is disposed on the bottom side of the opening, and the recording head ejects the ink from the nozzle opening based on the flushing drive signal. An ink droplet may be received by the ink absorbing material through the opening.

In the case where the recording head has a plurality of nozzle openings corresponding to a plurality of inks, it is preferable that the flushing drive signal is different for each nozzle opening corresponding to each ink.

In the case where the recording head has a plurality of nozzle openings corresponding to a plurality of inks and a plurality of flushing areas are provided, the recording head controls the recording head based on the flushing drive signal. It is preferable that the ink droplet ejected from the nozzle opening is received in a different flushing area for each ink.

Here, the plurality of inks means inks having different viscosities, inks having different viscosities, inks having different surface tensions, and the like, in addition to inks having different colors.

Further, a fan for preventing a rise in temperature and fan control means for stopping the fan when an ink droplet is ejected from the nozzle opening based on the flushing drive signal by the recording head are provided. Preferably. In this case, the fan control means is configured to stop the fan for at least the time required for the ink droplet ejected from the nozzle opening to land on the opposing landing portion based on the flushing drive signal. Is preferred.

[0044]

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

FIG. 1 shows the structure of the main body of an ink jet recording apparatus to which the present invention is applied. In FIG. 1, reference numeral 1 denotes a carriage. Carriage 1
Are reciprocated by a timing belt (not shown) guided by a carriage shaft 4 horizontally supported and supported by the left and right frames 2 and 3. In the timing belt, an ink jet recording head 5 is mounted below the carriage 1 which is normally driven by a carriage motor (not shown), with the nozzle opening 5k facing downward. The structure of the recording head 5 is the same as the structure described above with reference to FIG.

A black ink cartridge 6 for supplying ink to the recording head 5 and a color ink cartridge 7 are detachably mounted on the upper side of the carriage 1. Below the recording head 5, a paper guide member 8 is arranged corresponding to the scanning direction. On the paper guide member 8, a recording paper 9 as a recording medium is placed. The paper guide member 8 is moved by a paper feeding means (not shown) in a direction perpendicular to the scanning direction of the recording head 5 (a front-back direction on the paper surface of FIG. 1).

In the drawing, reference numeral 10 denotes capping means arranged in a non-printing area (home position). The capping unit 10 is configured to seal the nozzle plate 5m of the recording head 5 when the recording head 5 is directly above the recording head. A suction pump 11 for applying a negative pressure to the internal space of the capping unit 10 is disposed below the capping unit 10.

The capping means 10 functions as a lid for preventing the ink in the nozzle openings 5k of the recording head 5 from drying during the rest period of the recording apparatus. Further, an ink receiver (1st time) during a flushing operation for applying a drive signal irrelevant to printing to the recording head and causing ink droplets to be ejected idle.
Flashing area). Further, it has a function as a means for sucking (cleaning) ink by applying a negative pressure from the suction pump 11 to the recording head 5.

In the vicinity of the capping means 10, there is arranged a wiping member 12 constituted by an elastic plate or the like made of rubber or the like. The wiping member 12 is configured to perform a wiping operation for wiping the nozzle opening surface of the recording head 5 when the carriage 1 reciprocates to the capping unit 10 side.

On the other hand, a second flushing area is formed in a non-printing area on the opposite side of the capping means 10 with respect to the central printing area. The second flushing area includes an opening 13 formed in the paper guide member 8 and an absorbing material 14 disposed on the bottom side of the opening 13. This absorbing material 14 absorbs the ink sucked and discharged from the internal space of the capping means 10 by the pump 11 and also absorbs and holds the ink. 15 is stored.

Next, FIG. 2 shows an example of a control circuit mounted on the recording apparatus having the above-described configuration. In FIG. 2, the recording head 5, the ink cartridges 6, 7, the capping means 10, the suction pump 11, and the waste ink tank 15, which have already been described, are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, reference numeral 30 denotes print control means for generating bitmap data based on print data from a host computer (not shown) of the recording apparatus.
This is sent to the head driving means 31. The head drive unit 31 generates a print drive signal based on the bitmap data, and causes the recording head 5 to eject ink. The head driving means 31 sends a flushing drive signal for a flushing operation to the recording head 5 based on a flushing command signal from the flushing control means 32 which is independently generated, in addition to a print drive signal based on the bitmap data. Output. As a result, it is possible to perform idle discharge of ink irrelevant to printing.

Reference numeral 33 denotes cleaning control means.
The pump driving means 34 is operated by a command from the cleaning control means 33, and the driving of the suction pump 11 is controlled. The cleaning control unit 33 includes the print control unit 30.
And / or a command signal from a cleaning command detecting means (CL command detecting means) 35 is supplied. The cleaning command detecting means 35 includes a command switch 3
6 are connected. When this switch 36 is pushed by the user, the command detecting means 35 is operated, and a cleaning operation by a so-called manual operation is executed.

A carriage position control means 37 is connected to the flushing control means 32. At the time of the flushing operation, the flushing control means 32 sends a position control signal to the carriage position control means 37 to drive the carriage motor 38 so that the recording head 5 mounted on the carriage 1 functions as a first flushing area. Control is performed so as to move directly above the capping means 10 or directly above the opening 13 formed in the paper guide member 8 functioning as a second flushing area.

The flushing control means 32 is connected to a fan drive control means 39. At the time of the flushing operation, the flushing control unit 32 sends a control signal to the fan drive control unit 39 to drive the fan motor 40 that drives an exhaust fan (not shown) for suppressing a rise in temperature in the printing apparatus. Control to stop temporarily.

FIG. 3 is a connection diagram showing a control circuit for driving the recording head 5, that is, an example of the configuration of the head driving means 31 shown in FIG. In the figure, reference numeral 50 denotes an input terminal for receiving a timing signal from the printing control means 30 or the flushing control means 32. The timing signal applied to the input terminal is input to the one-shot multivibrator 51. One-shot multivibrator 51 outputs a positive signal and a negative signal from its non-inverted output terminal and inverted output terminal, respectively, in synchronization with the input timing signal.

The one-shot multivibrator 51
Is connected to the base of an NPN transistor 52, and the collector of the NPN transistor 52 is connected to the base of a PNP transistor 53. The emitter of the transistor 53 is connected to the DC power supply VH via the charging resistor 54 and the FET 55, and the collector of the transistor 53 is connected to the other end of the capacitor 56 whose one end is connected to the reference potential point (earth). I have.

Further, the base and the emitter of the transistor 53 are connected to the collector and the base of a PNP transistor 57, respectively.
The emitter 7 is connected to the DC power supply VH.

Thus, when the timing signal is input to the input terminal 50 of the multivibrator 51, the capacitor 56 is charged with the constant current Ir.

The base of an NPN transistor 58 is connected to the inverted output terminal of the one-shot multivibrator 51, and the collector of the NPN transistor 58 is connected to the other end of the capacitor 56.
The emitter of the transistor 58 is connected to the ground via the discharge resistor 59 and the FET 60. Further, the base and the emitter of the transistor 58 are connected to the collector and the base of an NPN transistor 61, respectively, and the emitter of the transistor 61 is connected to the ground.

As a result, when the timing signal supplied to the input terminal 50 of the multivibrator 51 switches, the capacitor 56 is discharged with the constant current If.

A complementary current amplifier circuit comprising a pair of NPN and PNP transistors 62 and 63 is connected to the other end (charge / discharge terminal) of the capacitor 56. That is, the bases of the transistors 62 and 63 are both connected to the other end of the capacitor 56, and the common emitter of the transistors 62 and 63 forms the output terminal 64. Therefore, the terminal voltage of the capacitor 56 is supplied to the output terminal 64 by current amplification.

Here, the base-emitter voltage of the transistor 57 is set to VBE 57, the charging resistor 54 and the FET
Assuming that the series combined resistance value of Rn 55 is Rr,
The charging current Ir to the transistor becomes: Ir = VBE57 / Rr (1) Further, assuming that the capacitance of the capacitor 56 is CO, the rising time Tr of the charging voltage is Tr = CO × VH / Ir (2).

On the other hand, discharge current If from capacitor 56
Sets the base-emitter voltage of the transistor 61 to VB
If the series combined resistance value of E61, discharge resistor 59 and FET 60 is Rf, If = VBE61 / Rf (3) The fall time Tf of the discharge voltage from the capacitor 56 is as follows: Tf = CO × VH / If (4)

As a result, the terminal voltage of the capacitor 56 becomes
As shown in FIG. 4A, a region (a first slope portion) that rises at a constant gradient α, a saturation region (a potential maintaining portion) that keeps a constant value (V1), and a drop that has a constant gradient β. Area (second
It has a trapezoidal waveform having a duration T1 with a slope. This waveform is current-amplified by the transistors 62 and 63 and is output as a drive signal to each of the piezoelectric elements 5c1, 5c2, 5c3... Of the recording head connected to the output terminal 64.

On the other hand, each of the piezoelectric elements 5c1, 5c2, 5
The other ends of the switches c3 are connected to switching circuits 65 each including a switching element such as a transistor. Then, the switching circuit 65 determines whether each of the piezoelectric elements 5c1, 5c2, 5c3 is based on a signal from the control circuit 66.
The other end of... Can be selectively grounded.

Here, the control circuit 66 includes the print control unit 30.
Alternatively, in response to a command from the flushing control unit 32, a short-time positive pulse signal (FIG. 4) synchronized with the timing signal from the print control unit 30 or the flushing control unit 32.
(C)) is configured to be output. The switching circuit 65 is operated by the positive pulse signal, and the other ends of the piezoelectric elements 5c1, 5c2, 5c3,... Are grounded.

Therefore, the trapezoidal wave voltage (FIG. 4A) from the output terminal 64 causes all the piezoelectric elements 5c1, 5c
2, 5c3 ... are charged. However, when the positive pulse signal shown in FIG. 4C falls during the charging, the switching circuit 65 is turned off. Therefore, the charging of each of the piezoelectric elements 5c1, 5c2, 5c3,... Ends at the voltage (V2) determined by the charging time T3 up to this point.

That is, by controlling the charging time T3, a trapezoidal second drive signal as shown in FIG. 4B can be generated. In this case, the rise of the second drive signal is a re-slope α and a fall slope β, and the duration T2 thereof is almost the same as the first drive signal shown in FIG. 4A.

As described above, each of the piezoelectric elements 5c1, 5c2,
Are supplied with the first drive signal or the second drive signal, so that the piezoelectric elements 5c1, 5c2, 5c
are charged at a substantially constant current and discharged at a substantially constant current. As described above, the piezoelectric element 5c
(5c1, 5c2, 5c3...) Expands and contracts, and each diaphragm 5a is displaced by this action. Therefore, ink is pushed out from the cavity 5f via the communication path 5n, and ink droplets are ejected from the nozzle opening 5k. Then, ink is supplied from the reservoir 5j of the recording head 5 to the cavity 5f.

In the ink jet recording apparatus of this embodiment, the second drive signal having the same rising slope α and falling slope β is used as a driving signal for printing.

On the other hand, the control circuit 66 comprises an FET 55 for determining a charging time constant and an FET 6 for determining a discharging time constant.
It is configured to supply a control voltage to each of the 0 gates. By controlling the voltage value applied to the gates of the respective FETs 55 and 60,
, The substantial impedance (DC resistance value) between the drain and the source can be varied.

For example, an FET 55 for determining a charging time constant
When the DC resistance value between the drain and the source is controlled to be larger, the charging resistor 54 and F
The series combined resistance value Rr due to ET55 becomes large, and the charging current Ir at this time becomes much smaller (see equation (1)). Therefore, as shown in FIG. 5, the rising of the trapezoidal drive signal can reshape the gradient α more gradually as indicated by the broken line α ′.

Similarly, the FET 60 for determining the discharge time constant
When the DC resistance value between the drain and the source is controlled to be larger, the above-described charging resistors 59 and F
The series combined resistance value Rf due to the ET60 also becomes large, and the discharge current If at this time becomes smaller (see Expression (3)). Therefore, although not shown in FIG. 5, the falling slope β of the drive signal can be reduced.

As described above, by adjusting the DC voltage value applied to the FETs 55 and 60, the rising slope α and the falling slope β of the trapezoidal drive signal can be arbitrarily adjusted.

That is, according to the ink jet type recording apparatus configured as described above, the frequency of the drive signal is determined according to the frequency of the timing signal shown in FIG. The level of the drive signal is controlled accordingly. Further, each control signal from the control circuit 66
The rising slope and the falling slope of the drive signal can control the re-slope according to the DC voltage value output to the ETs 55 and 60.

By utilizing such control characteristics, it was possible to set conditions for preventing the recording head from generating the microdroplets S during flushing. Such a condition is achieved by a combination of the frequency of the drive signal, the rising waveform duration time T1, the rise slope α, the drive signal level V1 and the fall slope β, and the characteristics of the combination are completely analyzed. Cannot be explained. However, in the combination of each parameter satisfying such a condition,
When the drive signal applied to the piezoelectric element 5c is displaced more slowly than during normal printing, the cavity 5f serving as a pressure chamber of the recording head 5 is gently pressurized, and the displacement is quickly returned, that is, As shown in FIG.
In many cases, control is performed such that the voltage value V1 is generated at the rising slope of the voltage and the discharge is performed at the sharp falling of β.

Specific numerical values of each parameter are shown below as examples.

The recording head 5 used in the experiment is a head employing a flexural vibrator. That is, the cavity 5
The shape of f is 2.3 (mm) length x 0.22 (m width)
m), the opening diameter of the nozzle opening 5k is φ25 μm, and the diaphragm 5
The thickness of “a” was 10 μm.

Then, a flushing drive signal having a trapezoidal unit period waveform as shown in FIG. 4 is applied between both electrodes of the diaphragm 5a. At this time, the frequency of the drive signal is 1
kHz, the duration T1 of the trapezoidal waveform is 25 μsec, the level V1 of the drive signal is 20 V, and the rising gradient α is 6.6.
7V / μsec, falling slope β is 9.6V / μsec
Met. In this case, no microdroplets were generated. In addition,
The flight speed of the main droplet was 5 m / s or less.

Even under the condition that the microdroplets S are generated, the control conditions are such that the flight speed of each microdroplet S is 4 m / sec or more and the weight of each microdroplet is 10 ng or more. In this case, it was confirmed that the microdrop S had a sufficient momentum so as not to float due to disturbance, and did not lead to generation of mist.

Specific numerical examples of the control conditions in such a case are shown below.

For the recording head 5 similar to the above, the frequency of the drive signal is 1 kHz and the duration T1 of the trapezoidal waveform is 2
5 μsec, drive signal level V1 is 20 V, rising slope α is 10 V / μsec, and falling slope β is 9.6 V
A flashing drive signal having a trapezoidal unit period waveform of / μsec was applied.

In this case, a fine droplet was generated after the main droplet, but the flying speed of the fine droplet was 4 m / sec or more, and the weight of the fine droplet was 10 ng or more. At this time, the flight speed of the main droplet was 7 to 8 m / s.

Further, among the conditions in which a microdroplet is generated,
Under control conditions where the microdroplets merge with the main droplets to be ejected later, the generation of mist can be effectively suppressed even when the momentum of the coalescing microdroplets is less than a predetermined amount. . FIG. 6 schematically shows the principle.

As shown in FIG. 6, the main droplet M1 is ejected after the main droplet M1 so as to be absorbed (combined) by the main droplet M2 ejected later.
The discharge speeds of 0, M1, and M2 could be controlled. As a result, the previously generated fine droplets merge with the next main droplet M and directly reach the ink absorbing material 14. Therefore, the rate at which the microdroplets S scatter (float) as mist could be suppressed as much as possible.

As shown in FIG. 6, intermediate drops M0 ′, M0 ′, which are discharged immediately after the main drop and have a momentum equal to or more than a predetermined value.
M1 ′ and M2 ′ are also fine droplets in a broad sense, but since these intermediate droplets have a momentum greater than or equal to a predetermined value and do not cause mist generation, they need not be combined with the subsequent main droplet. Of course, they may be combined.

FIG. 7 shows an example of a simulation referred to for performing such control. The horizontal axis in FIG. 7 indicates time (μsec), and the vertical axis indicates distance (mm) from the nozzle. The solid line in the figure indicates the flight characteristics of the previously generated microdroplet, and the two-dot chain line indicates the flight characteristics of the next main drop when the frequency of the drive signal applied to the recording head is 1000 Hz. The dashed-dotted line indicates the flight characteristics of the next main droplet at 3600 Hz, and the short dashed line indicates the 7200 Hz.
Hz, and the long dashed line indicates the case of 28800 Hz.

As can be understood from FIG. 7, the gradient indicating each characteristic indicates the speed. In this simulation, the flight speed of the microdroplets is about 4.5 mmsec, and the flight speed of the main drops is about 8 m / sec. Is set to

For example, when the frequency of the drive signal indicated by the two-dot chain line is 1000 Hz, the period is long, so that the next main droplet M cannot catch up with the previously generated fine droplet in the range shown in FIG. Can not. In such a case, the microdroplets become mist and float.

Further, for example, when the frequency of the drive signal indicated by the short dashed line is 7200 Hz, since the period is short, the main droplet M is generated first within a range of less than 2 mm from the nozzle of the recording head. It will catch up with the minute droplet S.

In particular, the smaller the distance that the succeeding main droplet M catches up with the previously generated microdroplet S, the lower the probability of the existence of the microdroplet S, and the amount of scattered mist can be effectively suppressed. . Preferably, it is preferable that the main droplet M catch up with the previously generated fine droplet S in a range where the distance from the nozzle of the recording head is within 2 mm.

Here, the flight speed of the main droplet is Vm
[M / sec], the flight speed of the microdroplet is Vs [m / s
ec] and the frequency of the drive signal given to the printhead is f [H
z], the distance from the nozzle until the next main drop catches up with the previous microdroplet is L [mm], the time until the next main drop catches up with the previous microdroplet is t [sec], and the next main drop is t [sec]. Considering the conditions under which a droplet catches up with the previous microdrop, the following relational expression holds.

(1 / f + t) × Vs ≦ t × Vm (5) t = L / Vm (6) Then, f ≧ [Vs × Vm by formulas (5) and (6). ] / [(Vm−Vs) × L] (7) can be obtained.

FIG. 8 shows that the flight speed Vm of the main droplet is 8 m / m.
sec, and the distance from the nozzle of the print head is 2 m
Under the control condition that the main droplet M catches up with the previously generated microdroplet S within the range of m or less, the flight speed Vs [m / sec] of the microdroplet and the drive applied to the recording head are calculated based on the equation (7). It considers a combination condition with a signal frequency f [Hz].

As can be understood from FIG. 8, even when the flight speed Vs of the fine droplet is approximately 5 m / sec or more, if the driving signal frequency f is 10 kHz or more, the fine droplet generated following the main ink droplet is used. The droplet S can catch up with the next main ink droplet to be coalesced.

Referring to such simulation results, the flight speed Vm of the main droplet and the flight speed V
s and the frequency f of the drive signal are first set and the duration T1, which is consistent with those parameters, the level V of the drive signal
1. The combination of the rising slope α and the falling slope β is appropriately selected, and the selection of the control conditions for combining the microdroplets S with the subsequent main drops M can be easily realized.

As a specific example, FIG. 9 shows the results of actual measurement using the drive frequency and the type of ink as parameters for the inside and outside contamination states of the mist due to the mist. ○ in the figure
The mark indicates almost no contamination, the mark .DELTA. Indicates that some contamination was confirmed, the mark X indicates that the degree of contamination was larger, and the mark XX indicates that the degree of contamination was remarkable.

The parameters used in the experiment of FIG.
It is as follows.

For the same recording head 5 as described above, the trapezoidal waveform duration T1 is 25 μsec, the driving signal level V1 is 20 V, the rising gradient α is 10 V / μsec, and the falling gradient β is 1.33 V / μsec. A flushing drive signal having a trapezoidal unit period waveform was applied at each frequency shown in FIG.

The ink used was MJ for Japanese domestic products.
The cartridge used for the 810 cartridge was used.

In detail, taking one of the actual measurement results shown in FIG. 9 as an example, when a black ink is ejected at a driving signal of 4800 Hz, an intermediate droplet and a fine droplet in a narrow sense are generated after the main droplet. Flight speed of the main drop is 7m
/ Sec or more, the weight of the main droplet was 12 ng or more, the flying speed of the microdroplet was 2 m / sec, and the weight of the microdroplet was 3 ng. That is, the microdroplet merged with the subsequent main drop within a range of about 0.6 mm from the nozzle opening.

As can be understood from FIG. 9, the degree of contamination by the cyan and magenta inks tends to be greater than that of the other inks. In other words, the degree of mist generation differs depending on the type of ink, so that if necessary, flushing is performed under different frequency conditions depending on the type of ink to be ejected, so that the degree of contamination is reduced overall. be able to.

However, as can be understood from FIG. 9, when the driving frequency of the flushing is set to 10 kHz or more, the result is that the contamination hardly progresses with any ink.

As described above, since the degree of mist generation differs depending on the type of ink, the first flushing area by the capping means and the position facing the capping means are arranged according to the type of ink. By selectively performing the flushing operation in any of the second flushing regions, the degree of contamination can be reduced overall. For example, in the flushing of cyan and magenta inks, it is preferable to execute the flushing operation using the first flushing area by the capping unit, and in the flushing of black and yellow inks, using the second flushing area.

As described above, at the time of the flushing operation, the fan motor 10 for driving the exhaust fan 101 (see FIG. 1) for suppressing the temperature rise in the recording apparatus.
By temporarily stopping 2, the inconvenience of mist diffusion can be effectively avoided, and the degree of contamination can be further reduced. In this case, the fan drive control means 103
However, control is performed so that the driving of the fan 101 is stopped for a time equal to or longer than the time at which the ink droplets ejected during the flushing operation land on the landing portion, in this embodiment, the capping means 10 or the ink absorbing material 14. It is desirable.

Although the recording head 5 described above is a head employing a so-called flexural vibrator, a head employing a vertical vibrator may be used. However, the cavity (pressure chamber) of the head using the vertical vibrator expands when the piezoelectric element is charged and contracts during the law, so the polarity of the drive signal voltage is opposite to that when the flexural vibrator is used. It should be noted that For example, the signal in FIG. 4A is a signal as shown in FIG.

In the above description, the unit period waveform of the drive signal is a trapezoidal waveform. However, as shown in FIG. 14, for example, a continuous first inclined portion α1 and first potential maintaining portion h
A waveform including the first, second inclined portion α2, second potential maintaining portion h2, third inclined portion β3, third potential maintaining portion h3, and fourth inclined portion β4 may be used as a unit periodic waveform.

In this case, the configuration of the signal generation circuit becomes complicated, but the number of variable control parameters increases, so that more detailed control conditions can be selected.

In addition, various drive signals in the form of inclined steps to which the drive signals shown in FIGS. 4 and 14 are applied can be used, and the mode of using these vibrations is also within the scope of the present invention.

[0111]

According to the present invention, ink droplets ejected from the nozzle openings during flushing are only main ink droplets and no microdroplets are generated, so that contamination due to the generation of microdroplets can be prevented. .

Further, according to the present invention, the momentum of the ink droplet ejected from the nozzle opening at the time of flushing is equal to or more than a predetermined value. It is possible to prevent the contamination due to the scattering of water.

Further, according to the present invention, since the fine droplets ejected from the nozzle openings during flushing are combined with the subsequent main ink droplets, contamination due to scattering of the fine droplets can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic front sectional view showing a main body of an embodiment of an ink jet recording apparatus according to the present invention.

FIG. 2 is a block diagram illustrating an example of a control circuit installed in the recording apparatus illustrated in FIG.

FIG. 3 is a connection diagram illustrating a configuration example of a head driving unit in FIG. 2;

4 is a waveform diagram of a drive signal generated by the circuit shown in FIG.

5 is a waveform chart showing a state in which a rise characteristic is controlled in a drive signal generated by the circuit shown in FIG. 3;

FIG. 6 is a schematic diagram illustrating an example of a relationship between a main droplet and a minute droplet of ink during flushing.

FIG. 7 is a characteristic diagram showing an example of flight characteristics of main droplets and minute droplets of ink during flushing.

FIG. 8 is a correlation diagram showing an example of the relationship between the flight speed of the main ink droplet and the minute droplet of ink and the flushing drive frequency.

FIG. 9 is a diagram illustrating an example of an evaluation result obtained by actually measuring a contamination state due to a mist for each type of ink and for each frequency of a drive signal.

FIG. 10 is a cross-sectional view illustrating an example of a recording head used in an ink jet recording apparatus.

FIG. 11 is a schematic diagram illustrating an ink ejection mode when the recording head illustrated in FIG. 10 is flushed.

FIG. 12 is a front view showing a state in which mist is scattered during flushing in a partially sectional state.

FIG. 13 is a waveform chart showing another example of a drive signal.

FIG. 14 is a waveform chart showing another example of a drive signal.

[Explanation of symbols]

 Reference Signs List 1 carriage 4 carriage shaft 5 recording head 5c piezoelectric element 5f cavity (pressure generating chamber) 5m nozzle plate 5k nozzle opening 6 black ink cartridge 7 color ink cartridge 8 paper guide member 9 recording paper (recording medium) 10 capping means (first flushing Area) 11 Suction pump 12 Wiping member 13 Opening hole (second flushing area) 14 Ink absorbent 15 Absorbent storage case (waste ink tank) 30 Print control means 31 Head drive means 32 Flushing control means 33 Cleaning control means 34 Pump drive Means 37 Carriage position control means 38 Carriage motor 39 Fan drive control means 40 Fan motor M Main ink droplet S Micro ink droplet (satellite droplet)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Norihiro Maruyama 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (56) References JP-A-9-174883 (JP, A) Kaihei 4-10941 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/165 B41J 2/175 B41J 2/18 B41J 2/185

Claims (20)

(57) [Claims] A drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Is a signal such that an ink droplet ejected from the nozzle opening becomes only a main ink droplet. The recording head has a plurality of nozzle openings corresponding to a plurality of inks, and the flushing drive An ink jet recording apparatus, wherein the signal is different for each nozzle opening corresponding to each ink. 2. A flushing drive signal, comprising: a drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Is a signal such that ink droplets ejected from the nozzle openings are only main ink droplets. The recording head has a plurality of nozzle openings corresponding to a plurality of inks, An ink jet recording apparatus, wherein an area is provided, and ink droplets ejected from the nozzle openings by the recording head based on the flushing drive signal are received in different flushing areas for each ink. 3. A printhead for generating a flushing drive signal, a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal, and a device for preventing a temperature rise. A fan, when the recording head ejects ink droplets from the nozzle openings based on the flushing drive signal,
An ink jet recording apparatus, comprising: a fan control unit for stopping the fan; and wherein the flushing drive signal is a signal such that ink droplets ejected from the nozzle openings are only main ink droplets. . 4. A flushing drive signal, comprising: a drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Is a signal such that the momentum of each ejected ink droplet is equal to or more than a predetermined value. The flushing drive signal is a periodic signal, and the unit periodic waveform of the flushing drive signal is a continuous first inclined portion. A trapezoidal waveform comprising a potential maintaining section and a second slope section, the duration of the trapezoidal waveform is 25 μsec, the slope of the first slope section is 10 V / μsec, and the potential maintaining section Wherein the second inclined portion has an inclination of 9.6 V / μsec. 5. A flushing drive signal, comprising: a drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Is a signal such that the momentum of each ejected ink droplet is equal to or greater than a predetermined value. Each ink droplet ejected from the nozzle opening has a weight of 10 ng or more and an ejection speed of 4 m / sec or more. An ink jet recording apparatus, characterized in that: 6. A flushing drive signal, comprising: a drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Is a signal such that the momentum of each ink droplet to be ejected is equal to or greater than a predetermined value. The recording head has a plurality of nozzle openings corresponding to a plurality of inks, and the flushing drive signal is An ink jet recording apparatus characterized in that the ink jet recording apparatus differs for each nozzle opening corresponding to each ink. 7. A flushing drive signal, comprising: a drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. Is a signal such that the momentum of each of the ejected ink droplets is equal to or more than a predetermined value. The recording head has a plurality of nozzle openings corresponding to a plurality of inks, and a plurality of flushing areas are provided. An ink jet recording apparatus provided, wherein ink droplets ejected from the nozzle openings by the recording head based on the flushing drive signal are received in different flushing areas for each ink. 8. A printhead for generating a flushing drive signal, a recording head having a nozzle opening, and ejecting ink droplets from the nozzle opening based on the flushing drive signal, for preventing a rise in temperature. A fan, when ink droplets are ejected from the nozzle openings based on the flushing drive signal by the recording head,
An ink jet recording apparatus, comprising: fan control means for stopping the fan; and wherein the flushing drive signal is a signal such that the momentum of each ejected ink droplet is equal to or greater than a predetermined value. 9. A flushing drive signal, comprising: a drive signal supply unit for generating a flushing drive signal; and a recording head having a nozzle opening and ejecting ink droplets from the nozzle opening based on the flushing drive signal. The ink droplets are ejected intermittently and continuously from the nozzle openings, and the ejected ink droplets have a main ink droplet and a minute droplet ejected after the main ink droplet. An ink jet recording apparatus characterized in that the signal is such that it merges with a subsequent main ink droplet within the range. 10. An ink jet recording apparatus according to claim 1, wherein said flushing drive signal is a periodic signal. 11. A flash memory according to claim 1, wherein the unit period waveform of the flushing drive signal has a trapezoidal waveform composed of a continuous first inclined portion, a potential maintaining portion and a second inclined portion.
0. The ink jet recording apparatus according to 0. 12. The ink jet recording apparatus according to claim 11, wherein the inclination of the first inclined portion is gentle, and the inclination of the second inclined portion is steep. 13. The ink jet recording apparatus according to claim 1, wherein the discharge speed of the ink droplet discharged from the nozzle opening is 5 m / sec or more. 14. An ink jet recording apparatus according to claim 1, wherein said flushing drive signal is generated independently of a print drive signal based on print data. 15. The fan control means according to claim 1, wherein said fan control means stops said fan for at least the time required for ink droplets ejected from said nozzle opening to land on an opposing landing portion based on a flushing drive signal. The ink jet recording apparatus according to claim 3 or 8, wherein: 16. The frequency of the flushing drive signal is
The ink jet recording apparatus according to claim 10, wherein the frequency is 10 kHz or more. 17. A discharge speed of the main ink droplet is 8 m.
/ Sec or more.
17. The ink jet recording apparatus according to any one of claims 16 and 17. 18. The apparatus according to claim 9, wherein said predetermined distance range is a range of 2 mm from the nozzle opening.
And the ink jet recording apparatus according to any one of 16 to 17. 19. A printing apparatus, comprising: capping means capable of sealing a nozzle opening of a recording head, wherein ink droplets ejected from said nozzle opening by said recording head based on said flushing drive signal are received by said capping means. An ink jet recording apparatus according to any one of claims 1 to 18, wherein: 20. An ink jet printer comprising: an opening capable of facing a nozzle opening of a recording head; and an ink absorbing material disposed on a bottom side of the opening, wherein the recording head ejects ink from the nozzle opening based on the flushing drive signal. 20. The ink jet recording apparatus according to claim 1, wherein the droplet is received by the ink absorbing material through the opening.