JP3047979B2 - Ink jet recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording apparatus that performs recording by discharging ink from a recording head.

[Conventional technology]

2. Description of the Related Art A recording device such as a printer, a copying machine, and a facsimile is configured to record an image formed of a dot pattern on a recording material such as paper or a plastic thin plate based on image information.

The recording device can be classified into an ink jet type, a wire dot type, a thermal type, a laser beam type, and the like according to a recording method. Among them, the ink jet type (ink jet recording device) discharges ink onto a recording material to perform recording. Is performed.

Inkjet recording devices have the advantages of being capable of high-density, high-speed recording, and being of a non-impact type, reducing noise and being able to easily record color images using multicolor inks. Have.

Ink jet recording apparatuses perform recording by forming ink droplets of ink by various methods and attaching the ink droplets to a recording material. A recording apparatus of a method of discharging ink using energy (such as a bubble jet method) can be used.

An ink jet recording apparatus that uses heat as the ink ejection energy usually supplies an electric signal to an electrothermal converter (ejection energy generating element) disposed in a liquid path in the recording head, so that the recording liquid in the liquid path is (Ink) is heated to give the ink a displacement accompanied by a sudden increase in volume,
The liquid droplets are ejected from the ejection ports and recorded.

When printing is performed in such an ink jet printing apparatus, an electrothermal converter that is continuously and frequently driven (heats) and an electrothermal converter that is hardly driven (heats) is used depending on print data. The body will arise.

In such a case, there is a difference in the viscosity of the ink in the ejection portion between the high heat generation duty and the low heat generation duty, and the difference in the volume (size) of the ejected droplets increases. In some cases, the quality of a recorded image is deteriorated, for example, a density difference occurs in the recorded image.

As a method for solving this problem, conventionally, preliminary heating is performed in advance before printing, or printing is interrupted during printing, and a drive signal having a pulse width in a range where ink is not ejected is applied to all heating elements to perform printing. Has been employed to maintain the temperature of the ink to maintain the viscosity of the ink in an appropriate range and to obtain stable ink ejection.

As the preliminary heating method, besides the method of driving the heating means to apply heat to the ink from the outside, an electric signal is supplied to the discharge energy generating element (electrothermal converter) so that the ink is not discharged. In other words, a method of applying heat to the ink from the inside can be considered.

[Technical problem to be solved by the invention]

However, in the conventional ink jet recording apparatus, the control for performing the recording and the control for performing the preliminary heating cannot be performed independently, and wasteful preheating wastes energy and causes excessive temperature rise. There was a technical problem.

The present invention has been made in view of such a conventional technical problem, and an object of the present invention is to correct a temperature difference of ink in each ejection port without interrupting a printing operation, and to perform printing. An ink jet recording apparatus capable of improving the image quality by reducing the density difference of the recorded image without lowering the speed (throughput) and suppressing waste of energy due to unnecessary preheating and excessive temperature rise. To provide.

[Means for solving the problem]

The present invention relates to an ink jet recording apparatus which performs recording by discharging ink from a plurality of discharge ports of an ink jet recording head provided with a plurality of electrothermal converters for generating thermal energy for discharging ink. Control the electric signal to be supplied to the electrothermal transducer corresponding to the predetermined discharge port to discharge ink at the time of recording, the discharge electric signal having a pulse width of a range for discharging ink. Means for applying ink to eject ink and applying a preheating electric signal having a pulse width within a range in which ink is not ejected to the electrothermal transducer corresponding to the ejection port that does not eject ink, thereby heating the ink. And control means capable of controlling whether or not to apply an electric signal for preheating, independently of control of the electric signal for ejection. Accordingly, it is possible to correct the temperature difference of the ink in each ejection port without interrupting the printing operation, to keep the ink viscosity constant irrespective of the printing duty difference, and to reduce the printing speed (throughput). It is an object of the present invention to provide an ink jet recording apparatus capable of improving the image quality by reducing the density difference of a recorded image and suppressing waste of energy due to unnecessary preheating and excessive temperature rise.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 6 is a schematic perspective view showing a main part of an embodiment of the ink jet recording apparatus according to the embodiment of the present invention.

FIG. 6 shows an ink jet recording apparatus provided with a plurality (four in the illustrated example) of full line type ink jet recording heads capable of recording in the full width in the transport direction of a recording material capable of performing full color recording.

In FIG. 6, reference numerals 31 and 32 denote a pair of rollers for sandwiching a recording material 33 such as a sheet of paper or a thin plastic plate and transporting the recording material 33 in the sub-scanning direction (conveying direction) indicated by an arrow F.

35Bk, 35Y, 35M, and 35C are full multi-type ink jet recording heads 35 in which discharge ports are arranged over substantially the entire width of the recording material 33.

In the case of full-color printing, for example, black, yellow, magenta, and cyan are used as ink colors ejected from the four print heads 35.
The plurality of inkjet recording heads 35 are arranged in this order from the upstream side (from the bottom) in the recording material transport direction.

Numeral 36 denotes a recovery system, which faces each of the recording heads 35 in place of the recording material 33 in the ejection recovery processing.

Further, each of the ink jet recording heads 35 is mounted on the head mounting portion 37 with its mutual positional relationship being regulated.

The ink jet recording head 35 is a recording head that discharges ink using thermal energy, and includes an electrothermal converter for generating thermal energy.

In addition, the ink jet recording head 35 performs recording by discharging ink from a discharge port by growth of bubbles due to film boiling generated by thermal energy applied by the electrothermal transducer.

As described above, the ink jet recording apparatus according to the embodiment of the present invention, that is, the head mounting portion 37 for mounting the ink jet recording head 35 according to the embodiment of the present invention, and the ink jet recording head 35 mounted on the head mounting portion 37 An ink jet recording apparatus having transport means 31 and 32 for transporting the recording material 33 to a recording position is configured.

FIG. 7 is a partially cutaway perspective view illustrating the detailed structure of the recording head 35.

In FIG. 7, the recording head 35 includes a substrate 102 of an ejection energy generating means, an electrothermal transducer 306, an electrode 103, and a liquid path wall 1.
04, top plate 105, etc.

The electrothermal transducer 306 and the electrode 103 are formed by a method of forming a film on the substrate 102 through a semiconductor manufacturing process such as etching, vapor deposition, or sputtering.

The ink 106 is supplied from an ink tank (not shown) to a common liquid chamber 108 of the recording head 35 through an ink supply pipe 107.

Reference numeral 109 in FIG. 7 denotes a supply port to which the ink supply pipe 107 is connected.

The ink 106 supplied into the common liquid chamber 108 is supplied into each liquid path 110 by capillary force, and is maintained in a stable state by forming a meniscus at the discharge port 111 at the tip end thereof.

When electricity is supplied to the electrothermal transducer 306, the liquid on the surface of the electrothermal transducer is heated to cause a bubbling phenomenon, and the energy of the bubbling causes ink droplets to be ejected from the ejection openings 111.

Reference numeral 112 denotes a discharge port surface on which a plurality of discharge ports 111 are arranged.

With the above configuration, for example, the discharge port density 400 dpi
A multi-type inkjet recording head can be configured with a high-density ejection port arrangement (16 nozzles / mm).

FIG. 1 is a block diagram showing a basic configuration of an ink jet recording apparatus according to an embodiment of the present invention.

In FIG. 1, a recording head 35 includes a discharge energy generating means 102 including a discharge energy generating element 306 composed of a heating resistor or the like capable of heating ink in response to supply of an electric signal and forming a flying ink droplet. Is provided.

The recording head 35 includes the ejection energy generating element 30
In accordance with the drive of 6, the ink is ejected from the ejection port to form an image on the recording material 33 such as paper or a thin plastic plate.

Reference numeral 204 denotes a printhead control unit. The printhead control unit 204 is configured to be able to switch the pulse width of an electric signal, and according to the input of the print signal 210, to the ejection energy generation unit 102 ( 306) is supplied so as to supply an electric signal for ejection having a pulse width in a range in which a flying ink droplet is formed.

The recording head control means 204 includes a heating control means 2.
03 is connected, and the heating control means 203 supplies an electric signal for preheating of a pulse width in a range where a flying ink droplet is not formed, thereby simultaneously performing a recording operation and an ejection port which does not eject ink. It is configured to heat a portion of the ink.

FIG. 2 is a block diagram showing a configuration of a control system of an ink jet printing apparatus according to a related technique considered in forming the present invention.

In FIG. 2, reference numeral 206 denotes a group of signal lines connected to a microprocessor unit for controlling the entire recording apparatus. Data to be recorded is transferred via the group of signal lines, and the recording data is temporarily stored. The data is written to a buffer RAM (read-only temporary storage device) 201 for storing.

The data read control circuit 202 synchronizes the generation of the discharge electric signal with the discharge command signal 209 for being controlled by the control means 204, and reads the written data from the buffer RAM 201 via the read signal group 207. The print data is read out, a print signal 210 is generated based on the print data, and this is transferred to the print head control circuit 204.

On the other hand, the heating control circuit 203 generates a shift register shift clock 211, a shift data latch signal 212, a preliminary heating control signal 213, and a heating element (ejection energy generating element) heating signal 214 in synchronization with the ejection command signal 209. Are sent to the recording head control circuit 204.

The printhead control circuit 204 applies a voltage to the ejection energy generating element (electrothermal converter) in the printhead 35 based on each of the above-described signals, heats the ink in the liquid path, and discharges ink droplets from the ejection ports. Is discharged.

Reference numeral 208 denotes a driving power supply for the ejection energy generating element, that is, a heating element driving power supply.

FIG. 3 is a circuit diagram showing details of the recording head 35 and the recording head control circuit 204.

In FIG. 3, the recording signal 210 sent from the data read control circuit 202 is taken into the shift register 301 by the shift register shift clock 211 sent from the heating control circuit 203, and then the shift data latch signal 212
Is latched by the latch circuit 302.

Then, a logical product of the heating element heating signal 214 having a pulse width for discharging a flying ink droplet and the recording signal 210 is output from the AND gate 303.

Then, the OR gate 304 outputs a logical sum of the logical product from the AND gate 303 and the preheating control signal 213.

The drive transistor 305 of the discharge heating element (discharge energy generating element) 306 is turned on by the output (logical sum) from the OR gate 304.

That is, all of the ejection heating elements 306 arranged for each ejection port in the recording head 35 are heated by either the heating element heating signal 214 or the preliminary heating control signal 213 in accordance with the recording signal 210. It is configured as follows.

 FIG. 4 is a timing chart of the above signals.

In the driving means of the recording head 35 described above with reference to FIGS. 2 and 3, by providing the preliminary heating control signal 213 in addition to the heating element heating signal 214, the normal recording signal 210
Is turned on, a signal of a pulse width at which a flying ink droplet is formed is turned on.
A pulse width signal that does not form a flying ink droplet is applied to the ejection heating element 306 whose 210 is not turned on.

FIG. 5 is a block diagram showing the configuration of the ink jet recording apparatus according to the present invention.

In this embodiment, in addition to the configuration of the related art shown in FIG. 2, a preheating start signal 215 can be input from the microprocessor unit to the heating control circuit 203, and the preheating start signal 215 The heating control signal 213 is configured to be able to be turned on / off independently of a discharge command signal 209 for controlling a discharge electric signal.

According to the present embodiment, an ink jet recording apparatus can be obtained in which the heating (preliminary heating) of the ink at the ejection ports that do not perform ink ejection can be appropriately controlled on / off by the microprocessor unit of the recording apparatus.

As described above, in the ink jet recording apparatus according to the embodiment of the present invention, that is, in the ink jet recording apparatus which performs recording by discharging ink from the recording head 35, the pulse width of the electric signal supplied to the discharge energy generating means 306 (or 102) is changed. At the time of recording, an electric signal having a pulse width within a range in which no ink is ejected is applied to the ejection energy generating means 306 (or 102) of an ejection port that does not eject ink at the same time that ink is ejected from a predetermined ejection port during recording. And heating the ink in the discharge port.

According to the embodiment described above, the recording head control circuit 20
By adding a preheating control circuit 203 to 4, simultaneously with the recording heat generation, the preheating electric signal 213 having a pulse width in a range where no flying ink droplets are formed on the heating element 306 of the ejection port having no recording signal 210 is applied. By doing so, the temperature difference between the ink at the recording (ejection) ejection port and the ink at the non-recording ejection port is corrected, and the density difference of the image formed on the recording material 33 is reduced. An ink jet recording apparatus capable of recording a better image was obtained.

In the present invention, in particular, since the control of the electric signal for ejection and the electric signal for preheating can be controlled independently, if the ink in each ejection port does not have a large temperature difference, Recording can be performed by stopping the electric signal for heating.

For this reason, it is possible to suppress energy waste and excessive temperature rise due to unnecessary preheating.

In addition, since the preheating can be performed without interrupting the recording operation, the recording speed is not reduced and the throughput can be improved.

Furthermore, since a complicated sequence is not required, an effect that software can be simplified can be obtained.

In the above embodiment, the case where the present invention is applied to an inkjet recording apparatus having a plurality of line-type recording heads has been described as an example.However, the present invention relates to a case where one recording head is used. Alternatively, in the case of a serial scan type ink jet recording apparatus in which a recording head is mounted on a carriage, the present invention can be carried out regardless of the number of recording heads or a difference in a scanning method at the time of recording. What you get.

The present invention provides an excellent effect particularly in an ink jet recording head of a bubble jet method using film boiling among ink jet recording methods and an ink jet recording apparatus using the recording head.

The representative configuration and principle are preferably performed using the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796.

This method can be applied to any of the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged on a sheet or a liquid path holding a liquid (ink). By applying at least one drive signal to the electrothermal transducer, which corresponds to the recorded information and provides a rapid temperature rise exceeding nucleate boiling,
This is effective because thermal energy is generated in the electrothermal transducer, and the film is boiled on the heat-acting surface of the recording head. As a result, bubbles in the liquid (ink) can be formed in one-to-one correspondence with the drive signal.

By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed.

When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,434,262 are suitable.

Further, if the conditions described in US Pat. No. 4,313,124 relating to the invention relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As a configuration of the recording head, in addition to the combination configuration (a linear liquid flow path or a right-angled liquid flow path) of a discharge port, a liquid path, and an electrothermal converter as disclosed in each of the above-mentioned specifications, a heat acting section A configuration using U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose a configuration in which the is bent, is also included in the present invention.

In addition, JP-A-59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing pressure waves of thermal energy. The present invention is also effective as a configuration based on JP-A-59-138461, which discloses a configuration in which is adapted to a discharge unit.

Further, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be reduced by a combination of a plurality of recording heads as disclosed in the above specification. Either a configuration that satisfies the above or a configuration as a single recording head that is integrally formed may be used, but the present invention can more effectively exert the above-described effects.

In addition, a replaceable chip-type recording head that can be electrically connected to the apparatus main body and supplied with ink from the apparatus main body by being attached to the apparatus main body, or provided integrally with the recording head itself The present invention is also effective when a cartridge type recording head is used.

It is preferable to add recovery means for the printhead, preliminary auxiliary means, and the like, which are provided as components of the printing apparatus of the present invention, since the effects of the present invention can be further stabilized.

If these are specifically mentioned, for the recording head,
Capping means, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof, and performing a predischarge mode in which discharge is performed separately from recording. Is also effective for performing stable recording.

Further, the printing mode of the printing apparatus is not limited to the printing mode of only the mainstream color such as black, but may be a printing head integrally formed or a combination of a plurality of printing heads. The present invention is extremely effective for an apparatus having at least one of the full colors.

In the embodiments of the present invention described above, the ink is described as a liquid, but the ink is solidified at room temperature or below, and is softened or liquid at room temperature, or the ink itself is 30 ° C. In general, the temperature is adjusted within a range of not more than ° C. and the temperature is controlled so that the viscosity of the ink is in a stable ejection range. Therefore, it is sufficient that the ink is in a liquid state when the use recording signal is applied.

In addition, positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or use ink that solidifies in a standing state to prevent evaporation of the ink. Or use
In any case, heat is first applied by heat energy, such as one in which the ink is liquefied and ejected as an ink liquid by application in accordance with the recording signal of the heat energy, or one which starts to solidify when it reaches the recording material. Use of an ink having a liquefying property is also applicable to the present invention.

In such a case, as in JP-A-54-56847, the ink is opposed to the electrothermal converter while being held as a liquid or a solid in the concave portions or through holes of the porous sheet. It is good also as a form.

In the present invention, the most effective one for the above-mentioned ink is the one that executes the above-mentioned film boiling method, and the above-mentioned electrothermal conversion in which a heating signal is supplied in a range where the recording signal is not applied and the ejection is not performed. The heating signal to the body is preferably in a range where film boiling does not occur, and preferably in a range where nucleate boiling does not occur.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, printing is performed by discharging ink from a plurality of discharge ports of an inkjet print head including a plurality of electrothermal transducers that generate thermal energy for discharging ink. In the ink jet recording apparatus, an electric signal supplied to the electrothermal converter is controlled, and at the time of recording, the range of the ink to be discharged to the electrothermal converter corresponding to the predetermined discharge port from which ink is to be discharged. An electric signal for discharge having a pulse width is applied to cause ink to be ejected, and a preheating electricity having a pulse width in a range where ink is not ejected is applied to the electrothermal transducer corresponding to the ejection port which does not eject ink. A means for applying a signal to heat the ink, and whether or not to apply an electric signal for preheating can be controlled independently of the control of the electric signal for ejection. Control means, the ink temperature difference between each ejection port can be reduced without interrupting the printing operation, and the ink viscosity is kept constant regardless of the printing duty difference. The image quality can be improved by reducing the density difference of the recorded image without lowering the speed (throughput).

In the present invention, in particular, since the control of the electric signal for ejection and the electric signal for preheating can be controlled independently, if the ink in each ejection port does not have a large temperature difference, Recording can be performed while the electric signal for heating is stopped, and energy waste and excessive temperature rise due to unnecessary preheating can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an ink jet recording apparatus according to the present invention, FIG. 2 is a block diagram showing a control system of the ink jet recording apparatus according to the related art,
FIG. 3 is a circuit diagram showing the configuration of the recording head and the recording head control circuit in FIG. 2, FIG. 4 is a timing chart of each signal in FIGS. 2 and 3, and FIG. FIG. 6 is a block diagram showing a control system of the recording apparatus, FIG. 6 is a perspective view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention, and FIG. 7 is a partially cutaway perspective view showing a detailed configuration of the recording head. . In the following, reference numerals indicating major components in the drawings are listed. 33: recording material, 35: recording head, 102: discharge energy generating means, 203: heating control circuit, 204: recording head control circuit, 210: recording signal, 213: preliminary heating control signal, 214 ... heating element heating signal, 306 ... electrothermal converter (ejection energy generating element).

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-127361 (JP, A) JP-A-1-95056 (JP, A)

Claims (3)

(57) [Claims] 1. An ink jet recording apparatus which performs recording by discharging ink from a plurality of discharge ports of an ink jet recording head provided with a plurality of electrothermal transducers for generating thermal energy for discharging ink. The electric signal supplied to the body is controlled, and at the time of recording, an electric signal for ejection having a pulse width within a range for ejecting ink is applied to the electrothermal transducer corresponding to the predetermined ejection port to eject ink. Is applied to eject ink, and an electric signal for preheating having a pulse width in a range where ink is not ejected is applied to the electrothermal transducer corresponding to the ejection port that does not eject ink, thereby heating the ink. Means, and control means capable of controlling whether or not to apply an electric signal for preheating independently of control of the electric signal for ejection. An ink jet recording apparatus. 2. The method according to claim 1, wherein the electrothermal transducer generates bubbles by film boiling in the ink by generating the thermal energy, and causes the ink to be ejected from the ejection port by growth of the bubbles. Item 2. An ink jet recording apparatus according to item 1. 3. The ink jet recording apparatus according to claim 1, wherein the recording head is a full line type head having a plurality of the ejection ports over the entire width of a recordable recording material.