JPH0524199A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To keep a uniform temperature distribution of a recording head to eliminate density irregularities of a recording image by a method wherein in a plurality of heating elements corresponding to a plurality of ink delivery ports, a drive signal insufficient fat an ink delivery is applied to a heating element out of a use area based on an image forming condition. CONSTITUTION:A recording image signal transmitted from a host device 40, such as an original reading part, is temporarily stored in a recording image signal buffer 31. On the other hand, waveform data of a heater drive pulse is stored in a waveform data ROM 33. A sequence controller 32 individually controls the transmission of the recording image signal from the buffer 31 to a head drive circuit 14 and the transmission of the waveform data from the ROM 33 to the head drive circuit 14, furthermore outputting a latch signal and various types of signals to the head drive circuit 14 at appropriate timings. Based on the outputs of thermistors 15-17 detecting the temperature of a recording head, the controller 32 controls a heater 1 through a temperature control circuit 22 and selectively issues the waveform data at an appropriate timing.

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.

[0002]

2. Description of the Related Art Among known recording apparatuses, a so-called ink-jet type recording apparatus is widely used as a highly reliable apparatus capable of obtaining high quality images at high speed. However, in this recording apparatus, since the viscosity of the recording liquid (ink) changes according to the temperature of the recording head and the recording dot diameter changes, the density of the recorded image may change and the recording quality may deteriorate. There was a problem.

Therefore, in this ink jet recording apparatus, it is general to perform recording by adjusting the temperature of the recording head to a certain temperature.

There are various ink jet recording systems, and one of the ink jet recording systems using heat energy is, for example, Japanese Patent Laid-Open No. 54-5993.
As disclosed in Japanese Patent No. 6 or the like, the recording liquid is rapidly heated, a bubbling phenomenon is caused in the recording liquid by the heating, and the bubbling energy causes the recording liquid to be ejected and ejected from the liquid ejection port. One of its features is that it is easy to integrate. By the way, for example, the discharge port interval 6
It is easy to integrate such as 128 to 256 lines at 3.5 μm. Therefore, it has an advantage that high quality images can be recorded at high speed, which is not found in other ink jet recording systems.

FIG. 3 is a diagram showing the construction of an ink jet recording apparatus of this type. In this figure, the continuous recording paper 313 wound in a roll is indicated by the guide roller 3
After passing through 21, 322, it is conveyed by the rotational frictional force of the sheet feeding roller 323, and is discharged in the direction of arrow 324.

Recording heads 311Y and 311 are provided on the front surface of the recording sheet 313 between the upper and lower guide rollers 321 and 322.
Recording head holder 3 including M, 311C, 311Bk
A carriage 327 carrying 18 is arranged, and this area serves as a recording unit. A guide roller 321,
322 is provided with a guide shaft 325 arranged in parallel,
The carriage 327 reciprocates along the guide shaft 325.

Four recording heads are mounted on the recording head holder 318, and heads 311Y, 311M, 311C, and 311Bk, each of which has 256 nozzles, are supplied with yellow, magenta, cyan, and black ink respectively from ink tanks (not shown). Ink is supplied.

Recording heads 311Y, 311M, 311
C and 311Bk are intermittently fed by the print width of each recording head, and while the recording paper 313 is stopped in the feeding direction, each recording head is scanned in the direction of arrow P and ejects recording ink droplets according to the image signal. To do.

The carriage 327 has a timing belt 32 driven by a carriage motor (pulse motor) 328.
The sheet feeding roller 323 is rotated by a sheet feeding motor 329. Each of these motors is controlled by the control circuit 330.

Image data 33 consisting of R, G, B
5 is converted into Y, M, C, and Bk image information by the image processing circuit 331, and in response to this signal, the control circuit 330 outputs a drive signal to each recording head via the flexible cable 320, and actually outputs each signal. Recording ink droplets are ejected from the recording head.

Here, the recording heads 311Y, 311M,
311C and 311Bk are provided with a plurality of external heaters and temperature detection means for controlling the temperature for the reason described above, and the plurality of external heaters are independently provided according to the temperature of the recording head. , Or at the same time, the head temperature is made uniform, and the recording dot diameter is made uniform, thereby preventing image quality deterioration.

[0012]

However, even in the above-mentioned conventional example, it was difficult to obtain sufficient temperature uniformity of the recording head, that is, uniformity of recording dot diameter.

For example, the recording head 311Y shown in FIG.
In the case of a copying machine using 311 Bk to 311 Bk, recording is performed using all 256 nozzles (ink ejection ports) included in the recording head at the time of enlargement copying and equal-magnification copying. The nozzles to be used are controlled by multiplying the image data read by the document reading optical element by a reduction rate of 1/2 so that the number of nozzles used is 128 pixels.

At the time of this reduction, the heat generation state concentrates only on the used portion of the recording head, so that there is a disadvantage that uneven temperature distribution occurs in the recording head and uneven density occurs.

Further, in the ink jet recording apparatus shown in FIG. 3, the recording head is serially scanned for recording, but the length in the sub-scanning direction (that is, the length of the recording paper) corresponds to one scan of the recording head. Since the print width is not an integral multiple of the print width, one scan in the middle is selected, and within the one scan, an image is formed by selecting some of all nozzles as in the case of the reduction. Therefore, also at this time, similarly, there is a drawback that the temperature distribution is unevenly distributed in the recording head, resulting in density unevenness.

Therefore, in view of the above points, the object of the present invention is to
An object of the present invention is to provide an inkjet recording apparatus configured to prevent uneven density in a recorded image by making the temperature distribution in the recording head uniform.

[0017]

In order to achieve the above object, the present invention is an ink jet recording apparatus provided with a recording head having a plurality of ink ejection openings, which is provided for each of the ink ejection openings. Energy that does not result in ink ejection is supplied to a plurality of heating elements, means for designating a usage range of the plurality of heating elements according to image forming conditions, and heating elements outside the designated usage range. And a recording head drive means for applying a drive signal for

[0018]

According to the present invention, by applying a signal (for example, a driving voltage with a minute pulse width) to the extent that ink is not ejected to a heating element (heater) outside the range of use, the temperature distribution It is possible to eliminate the large deviation and suppress the density unevenness of the recorded image.

[0019]

The following is a detailed description of the embodiments of the present invention.

Embodiment 1 FIG. 1 shows an example of a head drive circuit 14 included in an ink jet recording apparatus to which the present invention is applied. In the figure, 1 is a heating element (heater) composed of an electrothermal conversion element provided corresponding to each of the 256 discharge ports,
Bubbles are generated in the ink by the heat generated by the heat generating elements 1, and ink droplets are ejected from the ejection ports by the ink fluctuation caused by the expansion and contraction of the bubbles.

The voltage across each terminal of the heating element 1 is applied to the driving voltage value V via each switching transistor 3.
_It is kept at _H. The bases of the transistors 3 are connected to the outputs of the corresponding AND gates 5.

In FIG. 1, reference numeral 13 is a shift register for storing a waveform data signal serially transferred from the control section of the present ink jet recording apparatus. The heater driving pulse in this embodiment is represented by a 16-step pulse width. Therefore, the continuous 4 bits of the waveform data signal form the waveform data of one heater driving pulse. As a result, the shift register 13 is composed of 256 × 4 bits corresponding to the 256 heating elements 1.

Reference numeral 11 denotes a counter provided for each heating element, and waveform data transferred in parallel from the shift register 13 in accordance with a preset signal from a recording device controller (not shown) is set. .. The counter 11 counts the clock pulses transferred from the control unit based on the set waveform data, that is, in the present embodiment, by a value corresponding to the pulse width of the waveform, and outputs its output during the counting. H ".

In FIG. 1, reference numeral 9 is a shift register for storing a recording image signal which is serially transferred in 1 bit, and is composed of 256 bits corresponding to each heating element 1.

Reference numeral 7 is a data buffer for latching the recording image signal output from the shift register 9 in accordance with the latch signal and outputting this signal. AND gate 5 mentioned above
Each of the two takes the corresponding output of the data buffer 7 and the corresponding output of the counter 11 as two inputs.

FIG. 2 shows the head drive circuit 14 shown in FIG.
FIG. 3 is a block diagram showing in detail a control unit for controlling the head drive circuit 14 by transferring the above various signals to FIG.

In FIG. 2, reference numeral 31 is a recording image signal buffer for temporarily storing a recording image signal transferred from the host device 40 such as a document reading section of a copying machine. The shift between the transfer timing of the print image signal and the drive timing on the print head side using this signal is adjusted.

A waveform data ROM 33 stores waveform data of the heater driving pulse. In this embodiment, the look-up table method is controlled, and the nozzle to be used is selected according to the reduction ratio (signal 34) designated by the document reading unit, and ink is ejected to the nozzle to be used. A pulse width capable of dot formation is given to a non-used nozzle to such an extent that ink is not ejected.

Reference numeral 32 denotes a sequence controller including a CPU, etc., which transfers the recording image signal from the recording image signal buffer 31 to the head drive circuit 14 and the waveform data R.
Similarly, the transfer of the waveform data from the OM 33 to the head drive circuit 14 is controlled, and at the same time, the latch signal, the clock signal and the preset signal are transferred to the head drive circuit 14.

The sequence controller 32 controls the heater 1 via the temperature control circuit 22 in accordance with the outputs of the thermistors 15, 16 and 17 which are temperature detecting means arranged in the recording head (not shown). Then, the temperature of the recording head is appropriately maintained, and the waveform data stored in the waveform data ROM 33 is appropriately selected and sent to the recording head at an appropriate timing.

In the present embodiment, the number of used nozzles is selected according to the reduction ratio (for example, the number of used nozzles is 128 when the reduction ratio is 50%), and 10 μs (driving voltage value) is selected for the selected used nozzles. 25V), 3 for unused nozzles
By applying a pulse waveform of μs, a uniform reduced image without density unevenness could be recorded.

Embodiment 2 In the second embodiment, a case will be described in which the number of used nozzles changes while recording is performed while repeating scanning.
Such a case occurs when the length of the recording paper (length in the sub-scanning direction) is not an integral multiple of the recording width of one scan.

In the second embodiment, the waveform data when all nozzles are used is selected by the signal from the sequence controller 32 during normal recording, and the waveform corresponding to the recording paper size is selected for only one scan in the middle. By selecting the data, the image on the entire surface of the recording paper can be recorded without density unevenness.

Embodiment 3 In each of the above-mentioned embodiments, the present invention is applied to the recording head having 256 nozzles, but it is applicable to an apparatus using a full multi-head having nozzles for the print width of the recording paper used. On the other hand, it is particularly effective. For example, when using a head with nozzles for A4 length (297 mm),
Since the number of nozzles used by the head changes when using paper of A4 size or smaller, the present invention can be applied. Further, even when the size is reduced, the number of nozzles used is changed as in the first embodiment, so that the present invention can be applied.

(Others) The present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, particularly in the ink jet recording system. The present invention provides excellent effects in a recording head and a recording apparatus of the type in which the thermal energy causes a change in ink state. This is because such a system can achieve high density recording and high definition recording.

Regarding the typical structure and principle thereof, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal as a result
This is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection openings to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

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

Further, the present invention can be effectively applied to a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

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

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add the ejection recovery means of the recording head, the preliminary auxiliary means and the like because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping means, a cleaning means, a pressure or suction means for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but may be either integrally formed of the recording heads or a combination of a plurality of them. The present invention is also very effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet method, it is common to adjust the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. At times, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy for changing the state of the ink from the solid state to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in a standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP 54-56847 A or JP 60-7.
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as the form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and further a facsimile apparatus having a transmitting / receiving function It may be a form or the like.

[0044]

As described above, according to the present invention, since the heating elements in the non-use range are supplied with energy that does not result in ink ejection, the temperature distribution of the recording head is made as uniform as possible. A uniform image without spots can be obtained.

The practice of the present invention does not have any adverse effect on the life of the recording head or the like.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a head drive circuit included in an inkjet recording apparatus to which the present invention is applied.

FIG. 2 is a block diagram showing a control unit of the head drive circuit 14 shown in FIG.

FIG. 3 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 1 heating element (heater) 3 switching transistor 5 AND gate 7 data buffer 9 shift register 11 counter 13 shift register 14 head drive circuit 15 to 17 thermistor 313 recording paper 321 and 322 guide roller 311 recording head 325 guide shaft 327 carriage

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 9012-2C B41J 3/04 103 X

Claims (1)

Claim: What is claimed is: 1. An ink jet recording apparatus comprising a recording head having a plurality of ink ejection openings, wherein a plurality of heating elements are provided for each of the ink ejection openings and image forming conditions. A unit for designating a range of use of the plurality of heating elements according to the above, and a recording head for applying a drive signal for supplying energy that does not result in ink ejection to the heating elements outside the designated range of use. An inkjet recording apparatus comprising: a driving unit.