JPH08132646A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE: To properly control an ink emitting amt. corresponding to the temp. of ink. CONSTITUTION: The heater 6 heating and foaming the ink in the nozzle part 3 of a recording head, the piezoelectric element 7 connected to the diaphragm 8 forming the upper wall part of a common liquid chamber 4 and a fixing frame 10 and a temp. detection part detecting the temp. of the ink in the nozzle part 3 are provided. The change of the ink amt. between the part of the heater 6 and an orifice 1 is controlled by controlling the pressure in the common liquid chamber 4 by controlling the supply of a current to the piezoelectric element 7 immediately before the ink is emitted by the supply of a current to the heater 6 corresponding to the temp. of the ink in the nozzle part 3 and an air bubble is generated by the supply of a current to the heater 6 to emit the ink from the orifice 1 to perform recording.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates bubbles by injecting thermal energy into ink at a predetermined timing and ejects the ink by utilizing a rapid pressure change generated at that time to eject the ink on a recording member. The present invention relates to an inkjet recording apparatus that records by attaching ink to a predetermined place.

[0002]

2. Description of the Related Art Inkjet recording apparatuses mainly use sheets of paper or plastic as recording members,
In particular, compared to other recording methods, it has the advantages of less operating noise, simple and inexpensive basic mechanical structure, and has been adopted in various fields as an output device for computers, word processors and the like. Among them, in an ink jet recording apparatus in which bubbles are generated in the ink by thermal energy and the ink is ejected by utilizing a rapid pressure change caused by the bubbles, the basic parts of nozzles such as heating elements and electrodes are manufactured by a thin film process. Since it is easy to increase the density of nozzles and full multi nozzle, it is becoming the mainstream of ink jet recording apparatus at present.

By the way, in this type of ink jet recording apparatus, gradation recording is carried out by modulating the ink amount between the heating element and the orifice and then ejecting the ink to modulate the ejected ink amount for gradation recording. 60-2
It is disclosed in Japanese Patent No. 7548.

[0004]

However, in the above-mentioned conventional example, when the temperature of the recording head changes due to the environmental temperature change or the history of ink ejection, the viscosity of the ink in the nozzle changes, and the common liquid chamber is changed. When the pressure is reduced at a constant pressure, the amount of ink drawn from the nozzle toward the common liquid chamber changes. Therefore, the amount of ejected ink changes when bubbles are generated after a certain period of time has elapsed since the amount of ink between the heating element and the orifice began to change, and as a result, the modulation characteristic of the ejected ink amount changes and the gradation characteristic of the recorded image changes. However, there was a problem in that the image quality was deteriorated and the image quality was significantly reduced.

The present invention has been made in order to solve the above-mentioned conventional problems, and ejected ink corresponding to a change in the ink amount in the ink flow path before ink ejection depending on the temperature of the ink. It is an object of the present invention to provide an inkjet recording apparatus that performs high-quality image recording by inkjet by appropriately controlling the amount.

[0006]

Therefore, in the ink jet recording apparatus according to the present invention, thermal energy is applied to the ink in the ink flow path by the electrothermal conversion element provided in the recording head to generate bubbles. An ink jet recording apparatus for performing recording by ejecting ink from an orifice by abruptly changing the pressure in the ink flow path and adhering the ink to a predetermined position on a recording member, wherein the ink temperature in the nozzle portion of the recording head The ink temperature detecting means for detecting the ink temperature and the ink amount before the ink is ejected from the electrothermal conversion element part in the ink flow path to the orifice by reducing the pressure in the common liquid chamber that supplies ink to the nozzle part or the nozzle part. Ejection ink amount changing means for changing the discharge ink amount is provided corresponding to the ink temperature detected by the ink temperature detecting means. The configuration, characterized in that changing the pressure reduction amount of the nozzle portion or the common liquid chamber by means, is intended to achieve the above object.

The ejected ink amount changing means has a diaphragm structure part provided in a common liquid chamber for supplying ink to the ink flow path, and a piezoelectric element for pressing the diaphragm structure part. According to a configuration characterized in that the pressure of the common liquid chamber is controlled to change the ink amount before the ink is ejected from the electrothermal conversion element portion in the ink flow path to the orifice, the piezoelectric element is further laminated. Type piezoelectric actuator having a configuration in which expansion / contraction is controlled by controlling energization of the laminated piezoelectric actuator to change pressurization to a common liquid chamber. In order to achieve the above-mentioned object, the configuration is characterized in that the pressure reduction amount inside the nozzle or in the common liquid chamber is changed by changing the change. That.

[0008]

With the above structure, an ink jet recording apparatus which modulates the ejected ink amount by ejecting ink after changing the ink amount from the heating element to the orifice by depressurizing the inside of the nozzle or the common liquid chamber That is, by changing the pressure reduction amount inside the nozzle or the common liquid chamber when changing the ink amount between the heating element and the orifice according to the temperature of the recording head,
Even when the temperature of the recording head changes, it is possible to stably maintain a predetermined amount of ink ejection for the image data, and as a result, a predetermined ejection ink amount modulation characteristic is always maintained and high quality is maintained. It is possible to maintain stable image recording.

[0009]

1 is a sectional view of a recording head included in an embodiment of the present invention. 2 is a timing chart of the ink ejection process, FIG. 3 is a data diagram showing the temperature dependence of ink viscosity, and FIG. 4 shows the end surface of ink (hereinafter referred to as meniscus) when the common liquid chamber is depressurized at a constant pressure. FIG. 5 is a data diagram showing the temperature dependence of the time variation characteristic of the amount drawn into the nozzle (hereinafter referred to as the meniscus receding amount). FIG. 5 is the temperature dependence of the relationship between the amount of ejected ink and the time from the start of receding of the meniscus until bubble formation. Data chart showing sex
FIG. 7 is a data diagram of the voltage applied to the piezoelectric element necessary to realize the time-varying characteristic of the predetermined meniscus receding amount at each ink temperature. FIG. 7 is a perspective view showing the appearance of the recording head included in the embodiment of the present invention. is there.

First, the recording head of this embodiment will be described with reference to FIG. Reference numeral 1 denotes an orifice for ejecting ink, and one or a plurality of orifices are juxtaposed on the end surface of the recording head, behind which nozzle portions 3 are respectively connected, and they are all connected to a common liquid chamber 4. Ink is constantly supplied to the common liquid chamber 4 by an ink supply pipe (not shown). Reference numeral 2 denotes a substrate, which is not shown in the drawing, but in addition to an insulating film, an anti-cavitation film, etc., a heater, an electrode, etc. are formed in a thin film structure corresponding to the nozzle portion 3. A support member 5 is made of aluminum or the like and supports the substrate 2.

Next, description will be made with reference to FIG. Figure 1
8 is a cross-sectional view from the orifice 1 to the common liquid chamber 4 when the recording head shown in FIG. 7 is cut in a plane parallel to the nozzle portion 3 and perpendicular to the substrate 2, and a heater 6 in the nozzle portion 3 is formed.
A mechanism for appropriately changing the ink amount between the nozzle and the orifice 1 is also shown.

Reference numeral 6 denotes a heater, from which thermal energy is introduced into the ink to generate bubbles, and the ink is ejected from the orifice 1 due to the abrupt pressure change generated at this time. Reference numeral 8 denotes a diaphragm which forms the upper surface of the common liquid chamber 4 and is supported by the other side surface of the common liquid chamber 4 via an elastic body 9. Reference numeral 7 denotes a piezoelectric element, one end of which is supported by a diaphragm 8 and the other end of which is fixed to a fixed frame 10. The support member 5 is fixed to the fixed frame 10. An appropriate voltage is applied to the piezoelectric element 7 by a power supply device (not shown), and the piezoelectric element 7 expands and contracts in the direction of the arrow in the figure. 20
Is ink and is shown by the shaded area. Although not shown on the substrate 2, a temperature detecting portion is formed in a thin film structure together with a heater and electrodes, and its output is connected to a controller (not shown). This controller changes the voltage applied to the piezoelectric element 7 in accordance with the temperature detected by the temperature detector.

Next, the ink ejection process will be described with reference to FIG. (A), (B), (C) shown in FIG.
The five graphs (D) and (E) are synchronized timing charts, and the abscissas are all times of the same unit in synchronization. Graph (A) is the pixel clock, graph (B) is the voltage applied to the piezoelectric element, and graph (C) is the meniscus receding amount. The meniscus is positive when the meniscus is inside the nozzle, and the meniscus goes out of the orifice. The case is omitted. Graph (D) shows the voltage applied to the heater 6 to generate bubbles (hereinafter referred to as heat pulse), and graph (E) shows the volume change of bubbles generated by the heat pulse.

When the recording sequence is started, a voltage is applied to the piezoelectric element 7 prior to the pixel clock, as shown in graphs (A) and (B). Then, the piezoelectric element 7 extends in the direction of the arrow shown in FIG. 1, but since the upper end portion of the piezoelectric element 7 is fixed to the support member 5 by the fixing frame 10, eventually the diaphragm 8 contracts due to the contraction of the elastic body 9. It will move in the direction of the support member 5. At this time, the volume of the inside of the common liquid chamber 4 is rapidly reduced, and as a result, the pressure is rapidly increased. Then, due to this pressure, the ink with which the nozzle portion 3 is filled is changed to the orifice 1.
Is extruded from. However, in the orifice portion 1, the ink is held by the surface tension without being ejected or flowing out to the entire end face, and as the pressure inside the common liquid chamber 4 is relaxed after a certain time, the nozzle portion 3
Return to inside. Thereafter, at time t0, the piezoelectric element 7 is synchronized with the pixel clock as shown in the graph (B).
When the voltage applied to is set to a zero potential or a reverse polarity potential, the piezoelectric element 7 contracts and the diaphragm 8 moves again in the direction away from the support member 5.

Then, the volume of the inside of the common liquid chamber 4 suddenly increases, and as a result, the pressure sharply decreases. Then, the ink in the nozzle portion 3 is drawn toward the common liquid chamber 4, and the meniscus receding amount changes as shown in the graph (C). When a heat pulse is applied to the heater 6 at the timing shown in the graph (D) when the meniscus receding amount reaches a predetermined amount, bubbles are generated and grow as shown in the graph (E) with a delay of several μs. . At this time, if the meniscus receding amount is large, that is, if the ink amount existing between the heating element and the orifice at the time of bubble generation is small, the ejected ink amount is small, and conversely, if the ink amount is large, the ejected ink amount also becomes large. . Therefore, the amount of ejected ink can be changed by appropriately changing the time from when the piezoelectric element 7 starts contracting until the heat pulse is applied to the heater 6.

When the temperature of the recording head changes,
The ink temperature in the nozzle also changes, and the ink viscosity changes accordingly, as shown in FIG. Therefore, the time-varying characteristic of the meniscus receding amount when the common liquid chamber is depressurized at a constant pressure changes, as shown in FIG.

The horizontal axis of FIG. 4 is the elapsed time after the pressure reduction of the common liquid chamber 4 is started by the mechanism shown in FIG. 1, the vertical axis is the meniscus receding amount, T1 and T2 are ink temperatures, and T1 is
<T2, and the temporal change of the meniscus receding amount after the depressurization of the common liquid chamber 4 is started changes like a graph of a circular plot when the ink temperature is T1, and the ink temperature is T
When it is 2, it changes like the graph of a square plot.

At this time, the ejection ink amount modulation characteristic changes as shown by the circle plot graph in FIG. 5 when the ink temperature is T1, and as shown by the square plot graph when the ink temperature is T2. Changes to. The horizontal axis of FIG. 5 is exactly the same as that of FIG. 4, both are synchronized, and the vertical axis is the ejected ink amount when bubbles are generated at each time.

Therefore, when the temperature of the recording head fluctuates, the amount of ejected ink changes when bubbles are generated after a certain period of time from when the amount of ink between the heating element and the orifice starts to change, and the modulation characteristic of the predetermined amount of ejected ink is changed. Will not be obtained.

On the other hand, in the present embodiment, the voltage applied to the piezoelectric element, which gives a predetermined time-dependent characteristic of meniscus receding amount as shown in FIG. 6, is supplied corresponding to each ink temperature. Is stored in the controller as data, and the controller determines a predetermined value from the voltage data applied to the piezoelectric element 7 according to the temperature data of the recording head sent from the temperature detection unit formed on the substrate 2 to the controller (not shown). Select and set the voltage that gives the time change characteristic of the meniscus receding amount of.

For example, when the ink temperature is T1 in FIG. 6, it is set to V1 and when the ink temperature is T2, it is set to V2 so that a predetermined time change characteristic of the meniscus receding amount is always realized, and then the image data is set. Accordingly, by generating bubbles at a predetermined time interval after the contraction of the piezoelectric element 7 is started, a stable discharge of a predetermined amount of ink is always maintained. In FIG. 6, the horizontal axis represents the ink temperature, and the vertical axis represents the voltage applied to the piezoelectric element that realizes the piezoelectric element contraction process in which a predetermined time change characteristic of the meniscus receding amount is obtained for each ink. When the temperature is low, the ink viscosity increases, so a larger pressure is required to draw the ink toward the common liquid chamber.Therefore, a large voltage is applied to the piezoelectric element in order to maintain the time-varying characteristic of the predetermined meniscus receding amount. Need to be applied.

As described above, according to this embodiment,
Even if the printhead temperature fluctuates, a predetermined ejection ink amount modulation characteristic can always be stably maintained, and high-quality image recording can be stably maintained.

[0023]

As described above, according to the present invention, ink is discharged after the ink amount between the heating element and the orifice is changed by reducing the pressure inside the nozzle or the common liquid chamber. An ink jet recording apparatus that modulates the amount of ejected ink by changing the amount of depressurized ink inside the nozzle or in the common liquid chamber when changing the amount of ink from the heating element to the orifice according to the temperature of the recording head. As a result, even when the temperature of the recording head changes, it is possible to maintain a stable discharge of a predetermined amount of image data, and as a result, a predetermined discharge ink amount modulation characteristic is always maintained. It becomes possible to stably maintain high-quality image recording.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a recording head included in an embodiment.

FIG. 2 is a time chart of an ink ejection process of an example.

FIG. 3 is a data diagram showing temperature dependence of ink viscosity.

FIG. 4 is a data diagram showing the temperature dependence of the time change characteristic of the meniscus receding amount when the common liquid chamber is depressurized at a constant pressure.

FIG. 5 is a data diagram showing the temperature dependence of the ejected ink amount with respect to the time from the start of meniscus retreat to the generation of bubbles.

FIG. 6 is a data diagram of printing voltage for a piezoelectric element necessary to realize a time-varying characteristic of a predetermined meniscus receding amount at each ink temperature.

FIG. 7 is a perspective view of a recording head included in one embodiment.

[Explanation of symbols]

 1 Orifice 2 Substrate 3 Nozzle Part 4 Common Liquid Chamber 5 Support Member 6 Heater 7 Piezoelectric Element 8 Diaphragm 9 Elastic Body 10 Fixing Frame 20 Ink

Claims (4)

[Claims] 1. An electrothermal conversion element provided in a recording head applies thermal energy to ink in an ink flow path to generate bubbles, thereby rapidly changing the pressure in the ink flow path to cause the ink to flow from an orifice. An ink jet recording apparatus for ejecting and recording ink by adhering ink to a predetermined portion of a recording member, comprising ink temperature detecting means for detecting ink temperature in a nozzle portion of the recording head, and ink for the nozzle portion or the nozzle portion. Is provided with a discharge ink amount changing means for changing the ink amount before the ink is discharged from the electrothermal converting element portion in the ink flow path to the orifice by depressurizing the common liquid chamber. It is possible to change the depressurized amount in the nozzle section or the common liquid chamber by the ejected ink amount changing means in accordance with the detected ink temperature. An ink jet recording apparatus according to symptoms. 2. The ejected ink amount changing means has a diaphragm structure portion provided in a common liquid chamber for supplying ink to an ink flow path, and a piezoelectric element for pressing the diaphragm structure portion. 2. The ink jet recording apparatus according to claim 1, wherein the pressure of the common liquid chamber is controlled to change the amount of ink before the ink is ejected from the electrothermal converting element portion in the ink flow path to the orifice. 3. The piezoelectric element is a laminated piezoelectric actuator, and is configured to expand and contract by controlling energization of the laminated piezoelectric actuator to change the pressure applied to the common liquid chamber. The inkjet recording device described. 4. The ink jet recording apparatus according to claim 2, wherein the piezoelectric element changes the amount of pressure reduction in the nozzle or in the common liquid chamber by changing the applied voltage.