JPH04201352A - Image recording device - Google Patents

Abstract

PURPOSE:To obtain an image without concentration change even when a head temperature decreases by a method wherein the temperature of an image recording head and a period of time for interruption are detected when recording is interrupted, and it is corrected in such a manner that the change of recording concentration at the time of resumption of recording is canceled. CONSTITUTION:Image signals which are transferred from a host computer 101 are re-arranged in an interface 103 and input in look-up tables 110 LUT110. For the LUT110, 64 sets of straight lines with different gradients are prepared as tables. When a CPU111 receives a signal which shows a queued condition, the CPU111 detects the temperature T of a recording head 112, and counts a period of time (t) until a signal which shows a normal printing condition is received. When the head temperature right before an interruption is not higher than 25 deg.C, the gradient of the graph by the table of LUT110 stays at 1.0. However, it is decided that the decrease of the head temperature would take place at not lower than 25 deg.C, the gradient of the graph by the table of LUT110 is made larger than 1.0 at the time of resumption of recording to obtain the same image concentration as right before the interruption. Longer the period of time for interruption, more gradually the coefficient is returned to the original after the resumption of printing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording apparatus that can interrupt and resume recording as appropriate when an image is being recorded by driving an image recording head.

(Prior Art) Conventionally, as this type of image recording apparatus, those using digital recording methods such as ink sheet recording and thermal transfer recording are well known.

Particularly, ink sheet recording has the advantage of being easy to produce in color, and is becoming more and more popular for outputting computer graphics.

FIG. 7 is a connection diagram when an inkjet recording apparatus is used for outputting computer graphics, where 101 is a host computer, 102 and 104 are image signals, 103 is an interface, and 105 is an inkjet printer. Image data held by the host computer 1o is sent to the interface 103, and is temporarily stored in a memory (not shown) within the interface. The interface rearranges the image data in memory into a format acceptable to the inkjet printer, and then sends it to the inkjet printer. An inksheet printer performs printing according to the image data sent to it and outputs an image.

Figure 8 is a schematic cross-sectional view of an inksheet printer.
1 is a printer, 2 is a roll paper, 3 and 4 are paper feed rollers, 5 is a cutter, 6 is a carriage, 7 is an inkjet head, 8 is a sub-scanning roller, 9 is a platen, 10.1
1 is a paper guide.

The roll paper 2 is transferred to the platen section 9 by the paper feed roller 3.4.
sent to. In the platen section, a carriage 6 carrying a head performs serial scanning, and a head 7 is driven in response to a signal from an interface to record an image.

The head is equipped with four colors: cyan, magenta, yellow, and fluff, and performs full-color recording.

When the recording for one line is completed, the paper is sub-scanned by the sub-scanning roller 10, and then the recording for one line is repeated again.

When the rear end of the copy reaches the position of the cutter 5, the cutter is rotated to cut the roll paper. The recorded image is discharged through paper guides FI0 and FI11.

The memory that the interface has is usually several MB to several 10M.
However, the traffic data held by the host computer sometimes exceeds this amount. In such a case, it is possible to transfer data equal to the memory capacity of the interface and print it, and after printing is completed, transfer the remaining data to the interface again and print it. This is because, after printing data from the interface, the printer can stop sub-scanning of the roll paper and scanning of the carriage, and wait until the next data is transferred.

In this way, it is possible to record image data no matter how large it is.

[Problem to be solved by the invention]

The conventional image recording apparatus described above has the following problems.

Consider a case where an image as shown in FIG. 9 is to be recorded.

It is assumed that the printing width of the recording head is d, and image recording is performed by scanning in the X direction. It is also assumed that although the images are for 24 scans in total, the memory capacity on the interface is only for 5 scans. In such a case, part A is printed continuously, and then the printer enters a standby state until the image data of part B is transferred. After the transfer is completed, part B is printed continuously, and then the printer goes into a standby state again until the image data of part C is transferred. After the transfer is completed, the portion C is continuously printed, and the image recording is completed.

Generally, the temperature of a recording head increases as printing continues.

When the temperature rises, the viscosity of the ink decreases, the amount of ink ejected increases, and the number of recorded areas rises. However, when the printer enters the standby state, the temperature drops and the recording density decreases. This phenomenon applies to any type of recording head, but it is particularly noticeable in the so-called bubble jet type head proposed by Canon ■, which heats a heater to boil ink and ejects it using the pressure of bubbles.

FIG. 10 shows the change in recording density when the image shown in FIG. 9 is recorded. When printing continuously, the density increases little by little, so the density change is not noticeable, but when E is in between, the density changes suddenly, and the image changes.
It's very noticeable.

It is well known that the head is generally equipped with a temperature detecting means such as a thermistor and a heater to control the temperature in order to keep the head temperature constant.

However, this type of temperature control has a slow response when the temperature changes rapidly, making it difficult to perform precise temperature control when the temperature changes as shown in D and E in Figure 10. . In particular, when one head is equipped with one thermistor and a heater, and the entire head is to be controlled at a constant temperature, the temperature detected by the thermistor does not reach the specified temperature, and a density difference still remains when printing. It often happens.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and it is possible to obtain a uniform image with no density change on the actual image by correcting the image signal even if the head temperature drops in the atmosphere. The purpose of the present invention is to provide an image recording device that can perform the following functions.

[Means to solve the problem]

The image recording apparatus of the present invention includes a temperature detection means for detecting the temperature of the image recording head when recording by the image recording head is interrupted, an interruption time detection means for detecting the recording interruption time, a temperature detection means and an interruption time detection means. and a correction means for correcting the image signal applied to the image recording head in a direction in which the interruption time does not affect the recording density at the time of restarting recording, preferably by adjusting the correction amount at the time of restarting recording according to the detection result of the recording means. It has a re-correction means that performs re-correction according to the subsequent head history and supplies the re-corrected image signal to the image recording head, or it has means for detecting the environmental temperature and the image signal correction amount when restarting recording is determined based on the environmental temperature. Furthermore, the image recording head ejects ink from the ejection port using thermal energy, and an electrothermal converter is used as a means for generating thermal energy. have.

[For production]

The temperature detection means and the interruption time detection means respectively detect the temperature of the image recording head when recording is interrupted and the time from the interruption to the restart, and cancel the change in recording density at the time of restart based on the detection results. The correction means corrects the image signal and supplies it to the image recording head.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the image recording apparatus of the present invention, FIG. 2 is a graph showing a table stored in the lookup table 110 of the embodiment of FIG. 1, and FIG. 2 is a graph showing data stored in memory 114 of the embodiment of FIG. 1. FIG.

101 is a host computer, 103 is an interface, 110 is a lookup table (LUT), 111
112 is a recording head, 113 is a head temperature detection means such as a thermistor, 114 is a memory, 102 is an image signal from a computer, 104 is an image signal arranged by an interface, 120 is a status instruction signal, 12
1 is the output image signal of the lookup table 110, 12
2 is a look-up table selection signal, and 123 is a head temperature signal.

The 8 image signals transferred from the host computer 101 are temporarily stored in the memory within the interface 103, and then converted to lookup table 1.
10 (hereinafter referred to as LUTllo). LUT
As shown in Figure 2, IIO is from Y=0.69X to Y=
Sixty-four sets of straight lines whose slopes differ by 0.01 up to 1.32x are prepared as tables, and the human signal is converted according to the table selected by the selection signal 122.

The output signal 121 of the LUTIIO is input to the recording head 112. The recording head 112 includes a head drive circuit (not shown), and drives the recording head 112 with a drive pulse according to manually generated image data to eject ink. The amount of ejected ink is configured to be approximately proportional to the magnitude of the drive pulse.

When normal printing starts, the status indicator No. 45 of the interface 103 does not indicate the normal printing status, and the signal is sent to the CPU II.
Send to I. At this time, the CPU 111 selects one with a slope of 1.0 from LUTIIO.

Then, when the image recording for the memory capacity of the interface 103 is completed, the interface 103
Sends a signal indicating a standby state to I11. CPUI 11
Upon receiving this signal, detects the temperature T of the recording head 112 and temporarily stores it in a memory (not shown). Then, the time t until the next signal indicating the normal printing state is received is counted. When the data transfer is completed and the next printing state is entered, the table to be selected from LUTIIO when recording is resumed is determined according to the head temperature T immediately before the interruption and the interruption time t.

FIG. 3 is a graph showing conditions for determining the slope of the graph based on the LUTIIO table that is stored in the memory 114 and is selected when printing is resumed.

When the temperature of the head immediately before the interruption is 25 degrees Celsius or lower, it is determined that the head is at the same temperature as the room temperature and there is no temperature drop due to the interruption. Therefore, the slope of the graph according to the LUTllo table remains 10. be.

However, if the head temperature immediately before the interruption is 25°C or higher,
It was determined that the head temperature would drop due to the interruption, and the slope of the graph based on the LUTIIO table at the time of restart was set to 1.
Make it larger than 0 so that the same image density as immediately before interruption is obtained. The slope of the graph based on the LUTllo table is increased as the interruption time is longer and as the head temperature immediately before the interruption is higher, thereby compensating for density changes during the interruption. Furthermore, after printing is resumed, the coefficients are gradually restored to their original values. For example, on restart, a table corresponding to a graph with a slope of 1.10 is selected from LUTllo,
If the capacity of the interface memory is for 10 scans, 1
The slope is decreased by 0.01 for each scan, and in the 10th scan, an image is recorded based on the LUTIIO table corresponding to the graph with a slope of 101. Then, when recording is restarted after the next standby, correction is similarly performed using the table with a slope of 10 as a reference.

By doing this, even if the head temperature decreases during standby, it is possible to obtain a uniform image with no density change on the actual image by correcting the image signal.

In a color image forming apparatus, the above control may be performed independently for each color recording head.

Furthermore, when reducing the slope of the graph based on the table after restarting recording, not only the number of scans but also the recording time, the number of recording pulses, etc. may be counted, and the coefficients may be restored accordingly.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

In this embodiment, an environmental temperature detection means 115 is added to the embodiment shown in FIG. 1, and LUTllo table determination conditions are prepared in the memory 114 for each environmental temperature.

The environmental temperature detection means 115 is composed of a thermistor or the like,
Detects the environmental temperature where the device is placed and sets the environmental temperature No. 13
25 to the CPU 111. The CPU 111 selects a condition determining curve (not shown) according to the environmental temperature, and further determines the slope of the graph based on the LUTIIO table according to the head temperature before interruption and the interruption time. The condition determination curve is stored in the ROM as LUTIIO, and the environmental temperature,
The slope is output using the head temperature before interruption and the interruption time as addresses. The condition determining curve for rough selection by LUTIIO is that when the environmental temperature is low, the head temperature during suspension is large, so a graph with a larger slope is selected, and when the environmental temperature is high, a graph with a smaller slope is selected. Allow the graph to be selected.

By doing so, density changes can be suppressed more accurately.

FIG. 5 is a block diagram showing a third embodiment of the present invention. The same numbers as those in FIG. 1 indicate the same components.

In this embodiment, a binarization circuit 130 is inserted and connected between the LUTIIO of the embodiment shown in FIG. 1 and the recording head 112.

The embodiment shown in Figure 1 uses a recording head that can change the size of the dots according to the size of the input image signal, but this embodiment uses a recording head that cannot change the size of the dots. This is an application of the invention.

The binarization circuit 130 converts the multi-valued image signal into a binary code using a binarization method such as a dither method or an error diffusion method. The recording head prints dots of a fixed size according to the binary code to record an image.

Other operations are the same as in the embodiment of FIG.

With this configuration, even if the temperature drops during standby, when recording resumes, more dots are printed to compensate for the drop in density, making it possible to obtain a uniform image with no change in density on the actual image. .

In the above embodiments, a serial scan type inkjet device has been described, but a full multi-type inkjet device may be used.

In addition to bubble jet type inkjet,
The present invention can be implemented in the same manner as long as the head heats up during driving, such as thermal transfer.

Further, the standby state is not necessarily a time for receiving transferred data, but the present invention is also applicable to cases where the standby state is entered during printing for other purposes, such as performing a head recovery operation during printing.

Furthermore, the present invention brings about excellent effects particularly in the bubble jet type recording head and recording apparatus proposed by Canon (I) among the inksheet recording types.

FIG. 6 is a block diagram showing a bubble jet recording head.

In the recording head IA, in order to eject recording liquid from a plurality of ejection ports 30 provided in a row, an electrothermal transducer 40 that generates thermal energy to which an applied voltage is supplied is arranged for each liquid path. It is set up. By applying a drive signal, the electrothermal transducer 40 generates thermal energy to cause film boiling and form bubbles in the ink liquid path.

The growth of this bubble causes ink droplets to be ejected from the ejection port 30.

For a typical configuration and principle of a recording device using a bubble jet recording head, see, for example, U.S. Pat. No. 47
Preferably, the method is carried out using the basic principle disclosed in Japanese Patent No. 23129 and Japanese Patent No. 4740796. This method can be applied to both the so-called on-demand type and the 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. by applying at least one drive signal to the electrothermal transducer that corresponds to the recorded information and provides a rapid temperature rise exceeding nucleate boiling;
This is effective because it causes the electrothermal transducer to generate thermal energy to cause film boiling on the heat-active surface of the recording head, resulting in the formation of bubbles in the liquid (ink) in one-to-one correspondence with this drive signal. The growth and contraction of the bubbles causes liquid (ink) to be ejected through the ejection openings, thereby forming at least one bubble. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved.

As this pulse-shaped drive signal, US Pat. No. 446
The ones described in the specification of No. 3359 and the publication of No. 4345262 are used. Incidentally, US Pat. No. 4,313,124 of the invention regarding the temperature increase rate of the heat acting surface
If the conditions described in the specification are adopted, even better recording can be made.

The configuration of the recording head includes, in addition to the combination configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in each of the above-mentioned specifications. U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600 disclose an arrangement in which a portion is bent.
The structure described in each specification may be used. In addition, JP-A No. 123 of 1982 discloses a configuration in which a slit common to a plurality of electrothermal converters is used as a discharge part of the electrothermal converters.
No. 670 and Japanese Unexamined Patent Publication No. 13 of 1982, which discloses a configuration in which the discharge part does not have holes for absorbing pressure waves of thermal energy.
The present invention is also effective with a configuration based on the No. 8461 publication.

Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by a recording device, the length can be increased by combining multiple recording heads as disclosed in the above-mentioned specification. Either a configuration satisfying the above requirements or a configuration as a single recording head integrally formed may be used, but the present invention can more effectively exhibit the above-mentioned effects.

In addition, there are also replaceable chip-type recording heads that are installed in the main body of the device to enable electrical connection to the main body of the device and supply of ink from the main body of the device, or those that are installed integrally with the print head itself. The present invention is also effective when using a cartridge type recording head.

Further, it is preferable to add recovery means, preliminary auxiliary means, etc. to the recording head provided as a configuration of the recording apparatus of the present invention, since the effects of the present invention can be further predetermined. Specifically, these include a caving means for the recording head, a cleaning means, a pressurizing or suction means, an electrothermal transducer or a separate scale element, and a preliminary ejection for ejecting these. Mode is also effective for stable recording.

Furthermore, the recording mode of the recording device is not limited to a recording mode in which only the mainstream color such as black is used; the recording head may be configured integrally or in combination with a plurality of recording heads; The present invention is also extremely effective for devices equipped with at least one full color image.

In the embodiments of the present invention described above, the ink is explained as a liquid, but the ink solidifies at room temperature or lower, and becomes soft or liquid at room temperature, or
It may be one that softens or becomes liquid in a temperature range of 30° C. or higher and 70° C. or lower, which is the temperature range generally used for temperature adjustment in ink jets. That is, it is sufficient if the ink is in a liquid state when the recording signal is applied. In addition, it is possible to prevent the temperature rise caused by heat energy by actively using it as energy to transform the ink from a solid state to a liquid state, or to use ink that solidifies when left in order to prevent ink evaporation. Iruka,
In any case, ink may be liquefied by application of thermal energy in response to a recording signal and ejected as liquid ink, or it may have already begun to solidify by the time it reaches the recording medium. The use of ink is also applicable to the present invention. In such a case, the ink is held in a liquid or solid state in the recesses or through holes of the porous sheet, as described in JP-A-54-56847 or JP-A-60-71260. It may also be in a form that faces the electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

(Effects of the Invention) As explained above, the present invention provides an image signal to be applied to the image recording head when resuming recording based on the temperature of the image recording head when recording is interrupted and the time from the interruption until resuming recording. By correcting this, it is possible to compensate for changes in image density due to interruptions and obtain a uniform image without any changes in density.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the image recording apparatus of the present invention, FIG. 2 is a graph showing a table stored in the lookup table 110 of the embodiment of FIG. 1, and FIG. FIG. 1 is a graph showing data stored in the memory 114 of the embodiment, FIGS. 4 and 5 are block diagrams showing the second and third embodiments of the present invention, and FIG. 6 is a valve jet. FIG. 7 is a block diagram showing a conventional inkjet printer, FIG. 8 is a block diagram showing the conventional inkjet printer of FIG. 7, and FIG. 9 is a block diagram showing a conventional inkjet printer. FIG. 10 is a diagram for explaining the operation of the conventional example. 101------Host computer, 103---
-Interface, 110-----LUT, 111-----CPU, 112--Recording head, 113--Head temperature detection means, 114-----
Memory, 115---Environmental temperature detection means, 130---Binarization circuit. Patent applicant Canon Co., Ltd.

Claims (1)

[Scope of Claims] 1. In an image recording apparatus capable of interrupting and resuming recording as appropriate while driving an image recording head to record an image, the temperature of the image recording head at the time of interrupting recording is detected. a temperature detection means for detecting a recording interruption time; an interruption time detection means for detecting a recording interruption time; An image recording apparatus comprising: a correction means for correcting a given image signal. 2. An image according to claim 1, further comprising re-correction means for re-correcting the correction amount at the time of resuming recording according to the head history after resuming recording, and supplying the re-corrected image signal to the image recording head. Recording device. 3. The image recording apparatus according to claim 1, further comprising: means for detecting the environmental temperature; and an environmental temperature correction means for determining the image signal correction amount at the time of restarting recording, also taking into account the environmental temperature. . 4. Any one of claims 1 to 3, wherein the image recording head uses thermal energy to eject ink from the ejection ports, and has an electrothermal converter as a means for generating thermal energy. The image recording device described in section. 5. Any one of claims 1 to 3, wherein the recording head is a full-line type recording head having a plurality of ink ejection ports over the entire recording width of the recording material. The image recording device according to item 1.