JP2002096484A - Ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording apparatus capable of obtaining a stable ink discharge property by stirring ink in a pressure generating chamber or a reservoir rather easily and printed matters free from density spots. SOLUTION: The ink-jet recording apparatus is equipped with an ink-jet recording head 20 which discharges an ink drop from nozzle openings 23 by giving a pressure to ink in the pressure generating chamber 22 by driving a pressure generating means 28 installed additionally to the pressure generating chamber 22 communicating with the nozzle opening 23 and the reservoir 27. Precipitation and thickening of pigment ink is prevented by providing a cap 11 which hermetically seals each of the nozzle openings in close contact with the nozzle opening surface and a stirring means 53 which stirs the pigment ink in the pressure generating chamber 22 and the reservoir 27 by driving the pressure generating means 28 under the condition that each of the nozzle openings 23 is hermetically sealed with the sealing cap 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for ejecting ink droplets from a nozzle opening by pressurizing ink supplied to a pressure generating chamber communicating with a nozzle opening for ejecting the ink droplet through a piezoelectric element or a heating element. The present invention relates to an ink jet type recording apparatus having an ink jet type recording head to be operated.

[0002]

2. Description of the Related Art A plurality of pressure generating chambers for generating pressure for ejecting ink droplets by pressure generating means such as a piezoelectric element or a heating element, a common reservoir for supplying ink to each pressure generating chamber, In an ink jet recording apparatus having an ink jet recording head having a nozzle opening communicating with a chamber, a discharge energy is applied to ink in a pressure generating chamber communicating with a nozzle opening corresponding to a print signal of the ink jet recording head. Ink droplets are ejected from the nozzle openings.

[0003] Such an ink jet recording head includes a bubble jet (registered trademark) type in which a resistance wire for generating Joule heat is provided in a pressure generating chamber as a pressure generating means as described above, A part of the generation chamber is composed of a vibration plate, and the vibration plate is roughly classified into two types of a piezoelectric vibration type in which the vibration plate is deformed by a piezoelectric element to discharge ink droplets from nozzle openings. The recording head has a piezoelectric element that extends in the axial direction,
Two types have been put into practical use, one using a piezoelectric element in a contractive longitudinal vibration mode and the other using a piezoelectric element in a flexural vibration mode.

In these ink jet recording heads, ink is supplied from, for example, an ink cartridge or the like filled with ink to a pressure generating chamber of the ink jet recording head through a flow path, and is driven by a driving signal from a driving circuit. When driving energy is applied to the piezoelectric element or the like at a predetermined timing, the ink in the pressure generating chamber is pressurized and discharged from the nozzle opening.

[0005] In such an ink jet recording head, the viscosity of the ink in the pressure generating chamber and the reservoir or the ink in the ink cartridge increases due to the change in the surrounding environmental temperature or the sedimentation of the pigment particles, resulting in poor ink ejection. There is a problem that printing failures such as occur.

Further, when a pigment ink is used as the ink and the stoppage time during which printing is not performed is long, there is a problem that the pigment particles settle, causing density unevenness in subsequent printing.

In order to solve such a problem, for example, there has been proposed an ink jet recording head in which a circulation path for circulating the ink in the pressure generating chamber and the reservoir is provided, and the viscosity of the ink is prevented at a predetermined timing. Have been.

[0008]

However, as described above, if a circulation path for circulating ink is formed in the ink jet recording head, or if an actuator or a pump for circulation is provided, the head becomes large. Further, there is a problem that providing a circulation actuator or a pump increases costs.

In an ink jet recording apparatus using an ink cartridge, it is difficult to circulate the ink including the ink in the ink cartridge.

In the present invention, in view of such circumstances, the ink in the pressure generating chamber or the reservoir can be relatively easily stirred to realize stable ink ejection characteristics and printing quality with less noticeable density unevenness. It is an object to provide an ink jet recording apparatus.

[0011]

According to a first aspect of the present invention, there is provided a pressure generating chamber provided in a pressure generating chamber communicating with a nozzle opening and a reservoir. In an ink jet recording apparatus including an ink jet recording head that applies pressure to ink to eject ink droplets from the nozzle openings, an adhesion cap that is in close contact with the nozzle opening surface and seals each of the nozzle openings, An ink jet recording apparatus comprising: a stirring means for driving the pressure generating means in a state where each nozzle opening is sealed by a close contact cap to stir the ink in the pressure generating chamber and the reservoir.

In the first aspect, the ink in the pressure generating chamber and the reservoir can be easily agitated, the ink ejection characteristics can be maintained well, and even when pigment ink is used, printing in which the density unevenness is inconspicuous. Quality can be realized.

According to a second aspect of the present invention, there is provided an ink jet recording apparatus according to the first aspect, wherein the close contact cap is provided for each nozzle opening corresponding to each ink type.

According to the second aspect, it is possible to prevent color mixture due to ink attached to the close contact cap.

According to a third aspect of the present invention, there is provided the ink jet recording apparatus according to the first or second aspect, wherein the stirring means stirs the ink for each ink type.

In the third aspect, the ink can be stirred for each ink type in accordance with the frequency of use of the ink, so that the ink can be stirred efficiently.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the agitating means is provided with a function of the pressure generating means at the time of agitation according to a length of a stop time of the pressure generating means. An ink jet recording apparatus characterized in that control is changed.

In the fourth aspect, optimal stirring can be performed according to the amount of sedimentation and thickening of the ink.

According to a fifth aspect of the present invention, there is provided the ink jet recording apparatus according to the fourth aspect, wherein the stirring means changes the time for driving the pressure generating means.

In the fifth aspect, optimal stirring is performed by changing the time for driving the pressure generating means and adjusting the stirring time.

According to a sixth aspect of the present invention, there is provided an ink jet recording apparatus according to the fourth or fifth aspect, wherein the stirring means changes the driving voltage of the pressure generating means.

In the sixth aspect, optimal stirring is performed by changing the driving voltage of the pressure generating means and adjusting the stirring force.

A seventh aspect of the present invention is the ink jet recording apparatus according to any one of the fourth to sixth aspects, wherein the stirring means changes the number of times the pressure generating means is driven.

In the seventh aspect, the number of times of agitation is adjusted by changing the number of times of driving the pressure generating means,
Optimal agitation is performed.

An eighth aspect of the present invention is the piezoelectric element according to any one of the first to seventh aspects, wherein the pressure generating means is provided on a diaphragm provided on one surface of the pressure generating chamber. An ink jet recording apparatus is characterized in that:

In the eighth aspect, by driving the piezoelectric element, the ink in the pressure generating chamber and the ink in the reservoir can be easily stirred.

[0027]

(Embodiment 1) FIG. 1 is a schematic view showing an example of an ink jet recording apparatus according to Embodiment 1.

As shown in FIG. 1, in the ink jet recording apparatus according to the present embodiment, the recording head units 1A and 1B having the ink jet recording heads (hereinafter referred to as recording heads) are provided with cartridges 2A and 2B constituting ink supply means. The carriage 3 on which the recording head units 1A and 1B are mounted is provided on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. The recording head units 1A and 1B
Each of them ejects a black ink composition and a color ink composition.

The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears (not shown) and the timing belt 7, so that the carriage 3 on which the recording head units 1A and 1B are mounted moves along the carriage shaft 5. Moved. On the other hand, the apparatus main body 4 has a paper discharge roller 8 near a platen provided along the carriage 3, and can be rotated by the driving force of a paper feed motor (not shown). A recording sheet S, which is a recording medium such as a fed paper, is conveyed.

In such an ink jet recording apparatus, the carriage 3 is moved along the carriage shaft 5, and the recording head ejects ink to print on the recording sheet S.

A cap 9 for sealing the nozzle opening surface of the recording head is provided at one end of the carriage 3 in the moving direction.
The cap 9 has a suction pump 1
0 is connected, and a so-called recovery operation such as cleaning is performed.

Further, in this embodiment, the cap 9
Is provided with a close contact cap 11 which is in close contact with the nozzle opening surface of the recording head and seals each of the nozzle openings. As will be described later in detail, in a state where the nozzle openings of the recording head are sealed by the close contact cap 11, the stirring means stirs the ink, thereby causing ejection instability due to the thickened ink and causing the ink to settle. Prevent density unevenness of printed matter.

Here, an ink jet recording head mounted on the above ink jet recording apparatus will be described. FIG. 2 is a sectional view showing an example of the ink jet recording head according to the first embodiment of the present invention.

The recording head 20 of the present embodiment is of a type having a longitudinal vibration type piezoelectric element.
A plurality of pressure generating chambers 22 are provided in parallel, and both sides of the spacer 21 are sealed by a nozzle plate 24 having a nozzle opening 23 corresponding to each pressure generating chamber 22 and a diaphragm 25. Further, the spacer 21 is formed with a reservoir 27 that communicates with each of the pressure generating chambers 22 via an ink supply path 26 and serves as a common ink chamber for the plurality of pressure generating chambers 22. , An unillustrated ink cartridge is connected.

On the other hand, on the side opposite to the pressure generating chambers 22 of the vibration plate 25, the tips of the piezoelectric elements 28 are in contact with the regions corresponding to the respective pressure generating chambers 22, respectively. These piezoelectric elements 28 include a piezoelectric material 29 and electrode forming materials 30 and 31.
And an inactive region that does not contribute to vibration is fixed to the fixed substrate 32. The fixed substrate 32, the diaphragm 25, the spacer 21
And the nozzle plate 24 are integrally fixed via a base 33.

In the recording head 20 configured as described above, ink is supplied to the reservoir 27 via the ink flow path communicated with the ink cartridge, and the ink is supplied to the ink supply path 26.
Are distributed to the respective pressure generating chambers 22 through the pressure generating chambers. In practice, the piezoelectric element 28 is contracted by applying a voltage to the piezoelectric element 28. Thereby, the vibration plate 25 is deformed together with the piezoelectric element 28 (pulled up in the drawing), the volume of the pressure generating chamber 22 is expanded, and the ink is drawn into the pressure generating chamber 22. Then, after the inside is filled with ink up to the nozzle opening 23, when the voltage applied to the electrode forming materials 30 and 31 of the piezoelectric element 28 is released in accordance with a recording signal from the drive circuit, the piezoelectric element 28 is expanded. To return to the original state. As a result, the vibration plate 25 is also displaced and returns to the original state, so that the pressure generating chamber 22 contracts, the internal pressure increases, and ink droplets are ejected from the nozzle openings 23.

FIG. 3 is a block diagram showing a configuration for controlling ink ejection by such an ink jet recording head.

As shown in FIG. 3, the ink jet recording apparatus according to the present embodiment includes a recording head 20 which is a mechanism for actually performing printing and a control unit 50 for controlling the operation of the recording head 20.

The printing control means 51 of the control unit 50 controls the printing operation of the recording head 20 and, for example, causes the recording head 20 to execute printing via a recording head driving circuit 52 in response to the input of a print signal.

The agitating means 53 causes the recording head 20 to close the cap 11 when the suspension time of the recording head 20, specifically, the suspension time of the piezoelectric element 28 exceeds a predetermined time.
, The nozzle cap 23 is sealed with the close contact cap 11, and the piezoelectric element 28 of the recording head 20 via the recording head driving circuit 52.
To perform a stirring operation for stirring the ink in the pressure generating chamber 22 and the reservoir 27. The piezoelectric element 28
Specifically, the stop time is a period in which the power is turned on but the print signal is not input, the piezoelectric element 28 is in the standby state, and a period in which the power is turned off.

The driving voltage of the piezoelectric element 28 during the stirring operation is not particularly limited. For example, if the driving voltage is about half that during the flushing, the ink can be surely stirred.

Further, the stirring means 53 changes the control of the piezoelectric element 28 during the stirring operation according to the length of the stop time of the piezoelectric element 28. For example, in the present embodiment, the stirring means 53
Changes the drive time of the piezoelectric element 28 according to the length of the stop time of the piezoelectric element 28. That is, the longer the stop time of the piezoelectric element 28 is, the longer the stirring time is.

The piezoelectric element 2 changed by the stirring means 53
The control of 8 is not limited to the driving time of the piezoelectric element 28. For example, the driving voltage of the piezoelectric element 28 or the number of times of driving may be changed, or, of course, these may be combined.

The time counting means 54 measures the stop time of the piezoelectric element 28, and the stirring means 53 determines whether or not to execute the stirring operation based on the measurement result of the time counting means 54. .

As described above, in the present embodiment, the piezoelectric element 2
When the stop time of No. 8 is equal to or longer than a predetermined time, that is, when the nozzle 8 has been left for a long time, the stirring means 53 seals the nozzle opening 23 with the close contact cap 11 and drives the piezoelectric element 28. The ink in the pressure generating chamber 22 and the reservoir 27 is stirred. This can prevent the ink in the pressure generation chamber 22 and the reservoir 27 from thickening due to sedimentation, thereby causing unstable ejection due to the thickened ink, and the occurrence of density unevenness in the printed matter due to the sedimented pigment ink. Can be prevented.

Hereinafter, based on the flowchart of FIG.
An ink ejection operation of the ink jet recording apparatus according to the embodiment will be described.

As shown in FIG. 4, when the power is turned on in step S1, the stirring unit 53 stops the piezoelectric element 28 for a predetermined time or more based on the measurement result of the timer 54 in step S2. It is determined whether or not. If the stop time is equal to or longer than the predetermined time (step S2: Y
es), in step S3, the stirring means 53 executes the stirring operation. That is, the recording head 20 is attached to the contact cap 11.
The nozzle opening 23 is sealed by the close contact cap 11, and the piezoelectric element 28 is driven via the recording head driving circuit 52 to move the pressure generating chamber 22.
The pressure in the pressure generating chamber 22 and the ink in the reservoir 27 are agitated by applying pressure to the ink in the inside. Thereafter, if there is a print signal in step S4 (step S4: Yes), the print control unit 51 determines in step S5 that the printhead driving circuit 5
Printing is performed by driving the piezoelectric element 28 via the second element 2, and when printing is completed, the process returns to step S2.

If the stop time of the piezoelectric element 28 is not equal to or longer than the predetermined time in step S2, the process proceeds to step S5 without performing the ink stirring operation. In this case, since the stop time of the piezoelectric element 28 is short, there is almost no sedimentation of the ink in the pressure generating chamber 22 and the reservoir 27, and there is no need to stir the ink. Of course, when the power is turned on,
The ink stirring operation may be performed without fail.

As described above, in the present embodiment, by performing such an ink discharge operation, good ink discharge characteristics are always maintained, and printing in which density unevenness is not conspicuous even when pigment ink is used. Can be realized.

In this embodiment, the inks in the pressure generating chambers 22 and the reservoirs 27 corresponding to all the nozzle openings 23 are simultaneously agitated. However, the present invention is not limited to this. The stirring operation may be performed every time. Further, when the stirring operation is performed for each ink type, the interval at which the stirring operation is performed or the control of the piezoelectric element during the stirring operation may be changed according to the characteristics of each ink type. Good. This makes it possible to efficiently execute the optimal stirring operation according to the frequency of use for each ink type.

In the present embodiment, the ink stirring operation is performed before printing is performed. However, the present invention is not limited to this. For example, the ink stirring operation is periodically performed during printing. You may do so. Alternatively, the stirring operation of the ink may be performed every time the ink of the volume of the reservoir 27 is discharged from the nozzle opening 23. In this case, even if the ink has settled in the ink cartridge,
Since the ink is agitated each time the ink is supplied to the reservoir 27, the viscosity of the ink can be reliably prevented, and the occurrence of ejection instability due to the thickened ink and the occurrence of density unevenness of the printed matter due to the settled pigment ink can be ensured. Can be prevented.

(Other Embodiments) The ink jet recording apparatus of the present invention has been described above, but the present invention is not limited to these.

For example, in the above-described embodiment, all the nozzle openings 23 are sealed by one contact cap 11, but the present invention is not limited to this. For example, the nozzle openings corresponding to each ink type are sealed. A plurality of close caps may be provided. Thereby, it is possible to prevent color mixture due to the ink attached to the contact cap.

For example, in the above-described embodiment, the close contact cap 11 is used to seal the nozzle opening 23 when performing the ink agitation operation. However, printing is waited for a predetermined time or more. The head end surface of the recording head 20 is capped with the close contact cap 11,
Drying of the nozzle may be prevented.

In the above-described embodiment, a piezoelectric vibration type ink jet recording head has been described as an example of the ink jet recording head (recording head). However, the present invention is not limited to this. It is needless to say that the present invention can be applied to ink jet recording heads having various structures such as a recording head.

[0056]

As described above, according to the present invention, the stirring means drives the pressure generating means to stir the pigment ink in the pressure generating chamber and the reservoir in a state where each nozzle opening is sealed with the close contact cap. Therefore, it is possible to prevent viscosity increase due to sedimentation of the pigment ink, and it is possible to prevent occurrence of unstable ejection due to the thickened pigment ink and occurrence of density unevenness of the printed matter due to the sedimented pigment ink.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an ink jet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing an ink jet recording head according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram illustrating a control configuration of the ink jet recording apparatus according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating an example of an ink ejection operation according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Adhesion cap 20 Ink jet recording head 22 Pressure generating chamber 23 Nozzle opening 27 Reservoir 28 Piezoelectric element

Claims (8)

[Claims] An ink jet type in which pressure is applied to ink in the pressure generating chamber by driving pressure generating means provided in a pressure generating chamber communicating with a nozzle opening and a reservoir to discharge ink droplets from the nozzle opening. In an ink jet recording apparatus having a recording head, a contact cap which is in close contact with the nozzle opening surface and seals each of the nozzle openings, and the pressure generating means is driven in a state where each nozzle opening is sealed by the contact cap. And an agitating means for agitating the pigment ink in the pressure generating chamber and the reservoir. 2. The ink jet recording apparatus according to claim 1, wherein the contact cap is provided for each nozzle opening corresponding to each ink type. 3. An ink jet recording apparatus according to claim 1, wherein said stirring means stirs the ink for each ink type. 4. The stirrer according to claim 1, wherein the stirrer changes control of the pressure generator at the time of stirring according to a length of a stop time of the pressure generator. Inkjet recording device. 5. An ink jet recording apparatus according to claim 4, wherein said stirring means changes the time for driving said pressure generating means. 6. An ink jet recording apparatus according to claim 4, wherein said stirring means changes a driving voltage of said pressure generating means. 7. An ink jet recording apparatus according to claim 4, wherein said stirring means changes the number of times of driving of said pressure generating means. 8. An ink jet printer according to claim 1, wherein said pressure generating means is a piezoelectric element disposed on a vibration plate provided on one surface of said pressure generating chamber. Expression recording device.