JPH03234666A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the fidelity to an original picture from decreasing at the time of reproduction recording by providing a device which changes dot density for image in response to the change of image forming speed, and an adjusting device which adjusts a driving signal in response to the said change. CONSTITUTION:Image data (VDATA) which is read by a sensor 111 in an image reader 14 is converted to recording signals (PDATA) in a recording signal formation circuit 21, and they are used as signals to drive a recording bead 9. The recording signals PDATA are converted to driving signals by a head driver 29, and applied from an electric thermal conversion element H0, which is connected to a matrix, to H127. The head driving voltage of the conversion driver 29 is administered by a CPU141, and the driving voltage is controlled in response to a discharge port density to be used. That is, dot- thinning is performed such as at the time of high speed recording, and therefore, when the recording density is low, the driving voltage is made larger, and when the recording density is high such as at the time of normal recording, the driving voltage is controlled to be small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus, and more particularly to an apparatus capable of responding to changes in recording speed by changing recording dot density.

[Prior Art] Conventionally, image forming apparatuses have been proposed that can respond to changes in recording speed by changing recording dot density. This is designed to appropriately thin out dots in order to cope with high-speed recording, thereby increasing the speed of recording (image formation).

[Problems to be Solved by the Invention] However, in such an apparatus, there is a problem in that when recorded data is thinned out while the dot diameter remains constant, the expected image density decreases. This is because in the case of monochrome character printing, the decrease in density due to thinning is often not so noticeable, but for example, in cyan.

When full-color recording is performed using inks (recording agents) of colors corresponding to magenta, yellow, and black, a decrease in density due to thinning and a change in hue due to a change in color balance cannot be ignored. In particular, when reproducing and recording natural images such as photographs, there has been a problem in that the fidelity to the original image is significantly reduced.

[Means for Solving the Problems] The present invention aims to solve such problems, and for this purpose, the present invention provides a recording head that forms an image by recording dots using a recording element, and a recording head that forms an image by recording dots using a recording element, and a drive means for driving the recording element with a drive signal adjusted to modulate the size of the image; a means for changing the dot density of an image to be formed in response to a change in image forming speed; The present invention is characterized by comprising an adjusting means for adjusting the drive signal accordingly.

[Function] According to the present invention, when the dot density is lowered in order to improve the image forming speed, the dot diameter can be increased accordingly and the recording density can be kept constant.

Therefore, even if high-speed recording is performed with a lower resolution, it is possible to form an image with suppressed changes in density and hue.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows, as a preferred embodiment of the image forming apparatus of the present invention, an example of the configuration of a so-called bubble jet (BJ) type color ink jet recording apparatus having an electrothermal converter as the ejection energy generating means.

In FIG. 1, a recording medium 1 such as paper or a plastic sheet is conveyed by conveyance rollers 2 and 3, each consisting of a pair of rollers placed above and below a recording area, and conveyance rollers driven by a sheet feed motor 4. 2, it is transported in the direction of the arrow hole. A guide shaft 5 is provided in front of and parallel to the conveyance rollers 2 and 3. A carriage 6 is reciprocated along this guide shaft 5 in the direction of arrow B by the output of a carriage motor 7 via a wire 8 .

A recording head unit 90, which is a BJ type inkjet head, is mounted on the carriage 6. This recording head unit 90 is for creating a color image, and has four recording head units arranged in the scanning direction corresponding to each color of ink: cyan (C), magenta (M), yellow (Y), and black (BK). recording heads 9, namely 9A, 9
It consists of B, 9C, and 9D. The front surface of each recording head 9, that is, a predetermined distance from the recording medium 1 (for example, 0.8 mm).
) is provided with a recording section in which a plurality of (for example, 128) ink ejection ports are arranged in a vertical line, and an ejection energy generating element ( Electrothermal converter, etc.) 11 is driven (energized) 1~7h width L-Bago L (Kari) 2 minutes, the pressure at this time forms flying ink droplets 12, and onto the recording medium L. Recording is performed while depositing ink dots in a predetermined pattern.

Each recording head 9 is equipped with a circuit board of a drive circuit (driver) 29 for driving as described above.

The control circuit (CPU) of the recording device and the RO attached to it
A control unit including M, RAM, etc. is formed on the control board 15, and this control unit receives command signals and data signals (recorded information) from an image reader 14 having, for example, a CCD image sensor, and processes the command signals and data signals (recorded information). Based on this, a driving voltage (
Heat voltage) is applied.

An online/offline switching key 1 is provided on the operation panel 160 attached to the exterior case (not shown) of the recording device.
6A, a line feed key 16B, a form feed key 16c, a recording mode switching key 160, and other key setting sections, as well as a display section including several warning lamps such as an alarm lamp 16E and a power lamp 16F.

FIG. 3 is a block diagram showing an example of the configuration of the control system of the inkjet recording apparatus shown in FIG.

In the image reader 14, 111 is a CCD image sensor for reading a document image related to recording.

102 is a head drive control section, and a head driver 29
In addition, it includes a recording signal generation circuit 121. 12
A variable voltage source 5 generates a voltage for the head driver 29 to drive the recording head 9.

104 is a controller unit that serves as the main control unit of the device;
CPU 141 in the form of a microcomputer. ROMI
43 and RAM 145. CPU141
is a variable voltage source 125. during recording, etc. In addition to the recording signal generation circuit 121, the carriage motor and sheet feed motor 4
A program and other fixed data corresponding to the control means are stored in the ROM 143.

In the recording head 9, 109 is a matrix circuit integrally formed on the substrate constituting the head, and in this example,
The 128 electrothermal conversion elements (HO to H127) are divided into blocks by a predetermined number (m), and the number of blocks is n, mX.
n=128) is used for matrix driving. Note that the recording head 9 is the recording head 9A for each of the above colors.
~9D, and only one is shown in the figure for simplification.

In this configuration, the image data (VDA-A) read by the sensor 111 in the image reader 14 is converted into a recording signal (PDATA) in the recording signal generation circuit 21, and is used as a signal for driving the recording head 9. The recording signal PDATA is converted into a drive signal by the head driver 29, and is applied to the old head 27 from the electrothermal transducer elements (discharge heaters) HO connected in a matrix.

The head drive voltage of the head driver 29 is managed by the CPU 141, and the drive voltage is controlled according to the ejection port density used. That is, control is performed such that dot thinning is performed as in high-speed recording, so that when the recording density is low, the driving voltage is increased, and when the recording density is high as in normal recording, the driving voltage is decreased.

FIG. 3 shows an example of the recording processing procedure according to this example.

First, in step Sl, a predetermined amount of image data VDATA is read from the image reader 14 and inputted to the recording signal generation circuit 121. Next, in step S3, the recording mode set using the switch 160, for example, is determined.

If it is the normal recording mode, the image data vDATA
In response to the CPU 141 (7) instructions, print data PDATA using 128 ejection ports is generated (step S5). Further, the drive voltage is set to a low value (Vl) (step S?).

The generated recording PDATA is input to the head driver 29, where it is converted into a head drive voltage signal for recording using 128 ejection ports according to instructions from the CPU 141. The driving voltage at this time is Vl.

Then, in step S9, the head driver 29 drives the ejection heaters HO to H127 with a drive signal of the drive voltage Vl, and the carriage 6 is scanned at a normal speed to perform recording.

Next, the operation in high-speed recording mode will be explained. In this example, explanation will be given on the assumption that double-speed recording is realized by thinning out the number of ejection ports to be used by half.

The image is read by the image reader l, and the recording signal generation circuit 12
From the image data VDATA input to 1, the CPU 41
According to the instruction, the data corresponding to the 128 outlets are thinned out, and every other 64 outlets (
For example, HO,)12. ..., H126 or old.

H3, . . . , H125) is generated (step 5ll). In addition, the drive voltage has a high value (v
2) is made (step 513).

The generated recording data PDATA is sent to the head driver 2.
9, where it is converted into a head drive voltage signal for performing printing using 64 ejection ports according to instructions from the CPU 41. The driving voltage at this time is 2.

Then, in step S15, the head driver 29 uses the drive signal of the drive voltage v2 to alternately set the ejection heaters HO, H2, . . . H126 and old, H3, . While driving the carriage 6, the carriage 6 is scanned at high speed.

The recording speed in the inkjet recording method is greatly influenced by the recovery time of the meniscus at each ejection port. In this example, the amount of ink ejected from one ejection port is large to compensate for the decrease in image density due to thinning, and therefore it takes time for the meniscus to recover, but each ejection port is Since ink is ejected, the meniscus recovery time can be ensured even if the canodge 6 is scanned at high speed.

FIG. 4 shows the ejection openings and print area used in the above two modes. Note that here, it is assumed that square-shaped recording is performed for each ejection port.

In FIG. 4, (a) is a view of the recording head 9 viewed from the ejection port side, and 128 ejection ports are shown. (b
) is the ejection port used during normal recording, and is the same as (a).

(c) is the printing area at a certain scanning position during normal printing. At this time, the recording area A when recording is performed using 128 ejection ports is expressed as A=R''X 12g, where R is the length of one side of a square printed using one ejection port.

(d) shows the ejection ports used during double-speed recording, and even-numbered ejection ports are used. (e) is the recording area at a certain scanning position during double speed recording. Assuming that the length of one side of the square recording area of one ejection port is flR corresponding to the voltage v2, then the recording area B when printing is performed with 64 ejection ports is B. (nR)2x 64=R"x
128 Tona Q, follow A=B.

From the above explanation, it can be seen that when the number of ejection ports used is thinned out, the recording area, that is, the density of the formed image, is maintained unchanged by changing the driving voltage applied to the recording head to increase the recording area.

Note that it goes without saying that the mode of thinning may be changed as appropriate. For example, ink may be ejected from all the ejection ports or from a predetermined ejection port (for example, an even-numbered ejection port) every other dot in the main scanning direction. In addition, ink is not ejected every other dot in the main scanning direction, and
It is also possible to alternately use the even-numbered ejection port groups and the odd-numbered ejection port groups. In this case, one ejection port is driven every three dots in the main scanning direction, so the meniscus This means that even higher speeds can be achieved in relation to the return time.

(Embodiment 2) FIG. 5 shows an example of the configuration of a control system of a recording apparatus according to another embodiment of the present invention, and corresponding parts are given the same reference numerals as in FIG. 2. .

As is clear from the figure, the configuration of this example is almost the same as the configuration shown in the second figure, but in this example, the head driver 129 disposed in the head drive control section 102 is configured to control the pulse width of the ejection heater drive signal. It shall be suitable for modulation. The head drive pulse width of this head driver 129 is managed by the CPU 141, and the drive pulse width is controlled according to the ejection orifice density used in the recording head. That is, when the recording density is low (when dot thinning is performed in response to high-speed recording), the drive pulse width is increased, and when the recording density is high, the drive pulse width is controlled to be decreased.

In this example as well, similar effects can be obtained by using the same processing procedure as in FIG. However, in this example, the pulse width P1 for normal recording is set in step S7, and the pulse width P2 (>P) for high-speed recording is set in step S13.
I) may be set.

Then, when the number of ejection ports to be used is thinned out, the density of the formed image remains unchanged as in FIG. 4 by changing the driving pulse width applied to the print head to increase the print area.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible. For example, changing the driving voltage and changing the pulse width may be performed in combination. Further, for example, the dot diameter may be modulated by disposing a plurality of heaters for one discharge port and selecting them appropriately.

Furthermore, it goes without saying that the present invention can be applied to any image forming apparatus capable of modulating the dot diameter without being limited to the above-mentioned inkjet recording apparatus.

(Others) In addition to the above-described recording apparatus, the present invention can be applied to any apparatus capable of modulating the dot diameter, such as a thermal recording method. This method brings about excellent effects in recording heads and recording devices based on this method. This is because such a system can achieve higher recording density and higher definition.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. The electrothermal converter that is
Generating thermal energy in the electrothermal transducer and producing film boiling on the thermally active surface of the recording head by applying at least one drive signal that corresponds to recorded information and provides a rapid temperature rise above nucleate boiling. As a result, bubbles in the liquid (ink) can be formed in a one-to-one correspondence with this drive signal, which is effective. The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection opening to form at least one droplet. If this drive signal is in the form of a pulse, bubble growth and contraction will occur immediately and appropriately.
Particularly responsive liquid (ink) ejection can be achieved,
More preferred. This pulse-shaped drive signal is described in U.S. Pat. Nos. 4,463,359 and 4,345,262.
Those described in the specification are suitable. In addition, regarding the temperature increase rate of the above-mentioned heat-acting surface, the August visit @
Even better recording can be achieved by adopting the conditions listed in the 2pm IE4313 + 24th book day, Kasubo Rikogon P. The configuration of the recording head is as disclosed in the above-mentioned specifications. US Pat. No. 4,558,333 discloses a combination configuration of an outlet, a liquid path, and an electrothermal converter (straight liquid flow path or right-angled liquid flow path), as well as a configuration in which a heat acting part is arranged in a bending region. , US Pat. No. 4,459,600 is also included in the present invention. In addition, Japanese Patent Application Laid-Open No. 1989-5 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 9-123670 and Japanese Patent Application Laid-Open No. 59/1989 which discloses a configuration in which a discharge portion is made to correspond to an opening that absorbs pressure waves of thermal energy.
The effects of the present invention are also effective even when the configuration is based on Japanese Patent No. -138461. In other words, regardless of the form of the recording head, recording can be performed reliably and efficiently.

Furthermore, a full line type with a length corresponding to the maximum width of the recording medium that can be recorded by the recording device is described.
K L ★ Pass 1 -r-t, ★ Meiyo Hibi 1 + 1
This type of recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head. In addition, in serial type devices like the one shown above, there is a replaceable chip-type recording head that, when attached to the device body, enables electrical connection to the device body and ink supply from the device body. ,
Alternatively, the present invention is also effective when using a cartridge type recording head in which an ink tank is integrally provided in the recording head itself.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Furthermore, the type and number of recording heads mounted are not limited to the upper side; for example, in addition to one installed for single-color ink, for multiple inks of different recording colors and densities, A plurality of corresponding numbers may be provided.

In addition, the inkjet recording apparatus of the present invention may take the form of an image output terminal for information processing equipment such as a computer, a copying apparatus combined with a reader, etc., or a facsimile apparatus having a transmitting/receiving function. It may be something.

[Effects of the Invention] As explained above, according to the present invention, in an image forming apparatus that has a function of increasing the recording speed by thinning out recorded data, a decrease in density can be compensated for by modulating the dot diameter. It turns out. Therefore, even in an image forming apparatus that performs full-color recording, for example, a decrease in density due to thinning and a change in hue due to a change in color balance are not noticeable, and a decrease in fidelity to the original image can be prevented.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a schematic configuration of a color inkjet recording apparatus as an example of a suitable apparatus to which the present invention is applied. FIG. 2 is a block diagram showing an example of its control system. FIG. 4 is a flowchart showing an example of the control procedure, FIG. 4 is an explanatory diagram for explaining the effects of this example, and FIG. 5 is a block diagram showing another embodiment of the present invention. l... Recording medium, 4.7... Motor, 6... Carriage, 9.9A to 9D... Recording spatula 14... Image league, do, 102... Head drive control section, 104 ... Controller, 109 ... Matrix circuit, 121 ... Recording signal generation circuit, 29, 129 ... Head driver, 141 ... CPU. (a) NosuruinJL (0) (1) (2) (3) (4) (
126) (12'7) R-

Claims (1)

[Claims] 1) A recording head that records dots using a recording element to form an image, and a recording head that drives the recording element with a drive signal that is adjusted to modulate the size of the recorded dots. An image forming apparatus comprising: a driving means; a means for changing the dot density of an image to be formed in response to a change in image forming speed; and an adjusting means for adjusting the driving signal in accordance with the change. Device. 2) Claim 1, wherein the adjusting means adjusts at least one of the pulse width or the voltage of the drive signal.
The image forming apparatus described in . 3) The recording head has the form of an inkjet recording head that forms an image by discharging ink, and the inkjet recording head generates film boiling in the ink as energy used to discharge the ink. 3. The image forming apparatus according to claim 1, further comprising an electrothermal conversion element that generates thermal energy as the recording element. 4) The recording head according to any one of claims 1 to 3, wherein a plurality of recording heads are arranged corresponding to a plurality of types of recording materials having different colors, and color recording is performed using the plurality of recording heads. The image forming apparatus described in .