JP2557875B2 - Liquid jet recording device - Google Patents

Description

The present invention relates to a liquid jet recording apparatus.

[Conventional technology]

2. Description of the Related Art A liquid jet recording apparatus (inkjet recording apparatus) that ejects a liquid recording material from a recording head to record information such as characters and images is widely known.

The recording material of this kind of device is mainly paper, plastic sheet, etc., and it has the advantages that the operation noise is small compared with other recording methods, the basic mechanical structure is simple and the cost is low, and the computer, word processor, etc. Often used as a recording and output device.

However, in this type of device, since liquid ink (hereinafter, simply referred to as ink) is directly ejected from the nozzles of the recording head to perform recording, in order to always keep the ink in an ejectable state, a recording method of other method is not available. Special consideration not seen is needed.

For example, since the ink remains in the nozzles of the recording head even during non-recording, it is necessary to take measures to prevent the ink in the nozzles from being dried or being deteriorated due to evaporation and the like. For this reason, conventionally, there is known a device in which a so-called capping means is provided which covers the orifice of the recording head with a lid during non-recording to prevent the ink from drying or evaporating.

However, in a low-humidity environment, or in the case of long-term rest, an increase in the viscosity of the ink cannot be avoided only by the above-mentioned drying prevention means, and the air inside the cap that covers the recording head together with the above-mentioned capping means can be avoided. There is also known a recovery mechanism that sucks and applies a negative pressure from the orifice to suck out the ink in the nozzle of the head, or applies a pressure to the inside of the nozzle using a pump or the like to discharge the deteriorated ink from the orifice.

Such a recovery mechanism is automatically driven when the power is turned on, and generally is not driven during recording operation unless there is a significant discharge abnormality. However, there is a problem that the quality of the ink may change due to non-use of the nozzles even during the recording operation.

That is, in an apparatus in which a plurality of nozzles of a print head are provided, there are dots that are hardly printed depending on the statistical properties of print data, and therefore the discharge interval becomes very long, and thus the nozzle ejection drive varies. There is. Therefore, when the number of ejections is small or the ejection interval is long, the ink in the nozzles increases in viscosity due to drying depending on the atmospheric conditions such as humidity and temperature, and the ink ejection from the nozzles becomes unstable or There was a problem that it became impossible.

In order to solve such a problem, there has been proposed a clogging prevention device that causes a recording head to perform an idle discharge operation of discharging a liquid recording material outside a recording area.

[Problems to be solved by the invention]

By the way, the conditions under which non-ejection of the print head strongly depends on the installation atmosphere of the apparatus and the temperature state of the print head, but other than that, for example, a serial scan type in which the print head reciprocates to perform printing. In the recording apparatus, even when the recording paper size changes and the time required for the recording head to reciprocate to perform recording differs, the above-described ejection failure occurrence condition largely depends on this time.
However, in the conventional clogging prevention device, the above-mentioned idle discharge operation is always performed on recording papers of different sizes under the same idle discharge condition, so that the wasteful consumption of the liquid recording material is increased and the running cost is increased. Was the cause of the increase.

The present invention has been made in view of the above points, and an object of the present invention is to perform an optimum idle discharge according to the size of a recording medium, and to perform the idle discharge operation promptly at the same time when the scanning of a predetermined number of scans is completed. It is an object of the present invention to provide a liquid jet recording apparatus which can be changed to the above and which does not waste time.

[Means for solving problems]

In order to achieve the above object, the present invention provides a space for discharging a liquid recording material from a recording head to record information on a recording medium and discharging the recording material from the recording head outside a recording area. In a liquid jet recording apparatus that performs a discharge operation, a scanning unit that causes the recording head to reciprocally scan a region corresponding to the size of the recording medium, and a recording region outside the recording region that is adjacent to a scanning end position of the recording region by the scanning unit. A recording material receiving portion for receiving the recording material ejected by the idle ejection operation at a predetermined position, a judgment means for judging the size of the recording medium, and a scanning means for scanning the recording area a predetermined number of times. Each time the recording head is finished, the recording head is caused to perform a blank discharge a predetermined number of times toward the recording material receiving portion adjacent to the scanning end position of the predetermined number of scans. The control means variably controls at least one of the predetermined number of scans and the predetermined number of discharges according to the size of the recording medium determined by the determination means. When the predetermined number of scans is variably controlled, the predetermined number of scans when the size of the recording medium determined by the determination unit is relatively large is set to the predetermined number of scans when the size of the recording medium is relatively small. When the number of scans is selected to be smaller than the predetermined number of scans and the predetermined number of discharges is variably controlled, the size of the recording medium determined by the determination unit is relatively large. In this case, it is possible to control the predetermined number of ejections by selecting from a plurality of ejection numbers so as to be larger than the predetermined number of ejections when the size of the recording medium is relatively small. And butterflies.

In one aspect of the present invention, the control means detects the temperature of the atmospheric environment in which the liquid jet recording apparatus is installed, the humidity of the atmospheric environment, and the temperature of the recording head. It is possible to variably control at least one of the number of times of scanning and the predetermined number of times of discharging based on the output of.

[Action]

According to the present invention, with the above configuration, it is possible to perform the optimum blank ejection according to the size of the recording medium. Further, since the blank discharge is performed toward the recording material receiving portion adjacent to the scanning end position of the predetermined number of scans, the recording head is positioned adjacent to the recording material receiving portion at the same time as the scanning of the predetermined number of scans is completed. It is possible to quickly shift to the idle discharge operation, and there is no waste.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of the embodiment of the present invention. In the figure, a is a control means for causing the recording head to perform a blank discharge of a predetermined number of discharges toward the recording material receiving portion every time when the scanning of the predetermined number of scans by the scanning means is completed, The size of the print medium is determined, and at least one of the predetermined number of scans and the predetermined number of discharges is variably controlled according to the determined size of the print medium. When the control means a variably controls the predetermined number of scans, the control means a sets a predetermined number of scans when the size of the recording medium is relatively large and a predetermined number of scans when the size of the recording medium is relatively small. When selecting from a plurality of scanning times so as to be smaller than the scanning times and variably controlling the predetermined ejection times, the predetermined ejection times when the judged size of the recording medium is relatively large. Is selected from a plurality of ejection times so as to be larger than the predetermined ejection times when the size of the recording medium is relatively small.

Further, the control means a is based on the output of the detection means b which detects at least one of the temperature, the humidity and the temperature of the recording head of the atmospheric environment in which the liquid jet recording apparatus is installed, and the above-mentioned idle discharge operation is performed. At least one of the number of scans before performing the process and the number of discharges during the idle discharge operation is variably controlled.

FIG. 2 shows a schematic configuration of an embodiment of a liquid jet recording apparatus to which the present invention is applied. In the figure, 1 is a carriage on which a recording head 2 is mounted, and 3 is a guide rail that holds the carriage 1 movably. Both ends of an endless belt 4 are connected to the carriage 1 and are driven by a drive motor 5 to move along a recording surface of a recording paper 6. Reference numeral 7 is a roller for feeding the recording paper 6, 8A and 8B are guide rollers, and 9 is a paper feeding motor.

On the other hand, the recording head 2 is provided with a nozzle 10 for ejecting ink droplets toward the recording paper 6, and the ink 10 is supplied to the nozzle 10 from the ink tank 11 via the supply tube 12 to the nozzle 10. An ink ejection signal is selectively supplied via the flexible cable 12A.

Furthermore, the recording head 2 has a head heating means (hereinafter,
A head heater) 14 and temperature detecting means 15 for detecting the temperature of the head 2 are provided. By inputting a detection signal from the temperature detecting means 15 to a control circuit 28 having a microprocessor, the temperature is detected via a driver 30. The switch 17 connected to the power supply 16 can be turned on / off to control the heating by the head heater 14.

Reference numeral 18 denotes a cap member (cap) which is capped on the orifice surface of the recording head 2 during non-recording, and the carriage 1 is moved in the direction of arrow B during non-recording so that the cap member 18 is pressed against the orifice surface. . Reference numeral 19 is an elastic body attached to the crowning side of the crowning member 18, and the crowning member 18 is equipped with an atmospheric environment temperature detecting means 23 and an atmospheric environment humidity detecting means 20,
The recording environment of the recording head 2 is monitored.

The capping member 18 accommodates the volatile component solution 24 in the ink in the hermetically sealed container-shaped space 25 and also incorporates the liquid holding member 26 into which the solution 24 is impregnated. It is filled with 25 to prevent the volatile component of the ink 13 from evaporating from the tip orifice 10A of the recording head nozzle 10 and prevent the ratio of the volatile component of the ink 13 in the nozzle 10 from changing. As the volatile component solution 24 in the ink used here, the ink 13 itself or a solution containing no dye contained in the ink, or distilled water or the like in the case of a water-based ink is effective and retains the liquid. As the member 26, a sponge-like porous member or a plastic sintered body is effective.

The operation of the liquid jet recording apparatus configured as described above will be described. In FIG. 2, at the time of recording, the carriage 1 is first driven to move in the direction of arrow A from the recording start position in this figure, and each nozzle 10 of the recording head 2 is selectively driven so that ink is ejected from each nozzle 10. A droplet is ejected, and the ink droplet adheres to the recording width portion P of the recording paper 6 facing each nozzle 10 in the sub-scanning direction, which is shaded. As a result, recording is performed in the dot matrix pattern. When printing for one line is completed in this way, the carriage 1 is driven in the direction of arrow B to return to the position shown in the figure, and
The recording paper 6 is fed in the direction of arrow C by the width of the recording width portion P described above, and the above operation is repeated again.

After the above-described recording operation is performed for several lines, the motor driver 22 is driven by the control circuit 28, the carriage 1 is driven in the direction of the arrow B from the position of this drawing, and the recording head 2 is attached to the cap member 18. When moved to a position facing
When the capping member 18 is displaced in the direction of arrow D by a driving means (not shown), the capping member 18 is pressed against the orifice surface of the recording head 2 and capping is performed, the recording head driver 21 is controlled by a control circuit. An idle ejection signal is sent from 28, ink droplets are ejected from the recording head 2, and an idle ejection operation is performed. Next, after this idle discharge operation of the recording head 2 is completed, the crowning member 18 is displaced in the direction of arrow E, the carriage 1 travels again in the direction of arrow A, and the next recording is restarted.

In particular, in the embodiment of the present invention, the above-described blank discharge or blank discharge timing of the blank discharge operation is obtained from the atmospheric temperature detecting means 20, the atmospheric humidity detecting means 23, and the recording head temperature detecting means 15 as described later. The control circuit 28 controls the temperature and humidity information and the size of the recording paper 6.

Next, the principle of the main control operation of the embodiment of the present invention will be described with reference to the characteristic diagrams relating to the recording ink in FIGS. 3 to 6 and FIG.

In general, the ink for inkjet recording has a characteristic curve that varies depending on the concentration of the solvent contained in the ink and the dye contained in the ink, but in any case of water or oil,
The viscosity of the ink changes depending on the ink temperature and the residual rate of volatile components in the ink.

That is, when the temperature of the ink is lowered, or when the residual rate of volatile components in the ink is significantly lowered, the viscosity of the ink is increased, and when the ink viscosity is increased to a certain extent or more, the ink from the inkjet recording head 2 is ejected. Cannot be discharged.

FIGS. 3 and 4 show the outline of the ink temperature change in the case of a water-based ink and the ink viscosity change due to the change in the amount of water evaporation in the ink. The ink temperature T of the recording ink is calculated from the ejection limit ink temperature T _K. Is always high (T> T _K ), and if the water evaporation amount V (90) in the ink is always lower than the ejection limit water evaporation amount K (%) (V <K), the ink ejection limit viscosity Since the ink viscosity is lower than ρ _K, it is possible to prevent the ejection failure of the recording ink.

However, when the ink is ejected from the recording head 2 having a plurality of nozzles 10 as shown in FIG. 2 to perform the print recording, the print is not performed for a long time depending on the nature of the print data and the print data is exposed to the atmosphere. There may be some nozzles that are left standing, and the ink temperature in such nozzles may gradually drop depending on the ink temperature, atmospheric temperature at the nozzle opening, and atmospheric conditions such as humidity. Or
Alternatively, since volatile components in the ink evaporate, the ink viscosity gradually starts to increase, and finally the ink viscosity exceeds the ink ejection limit viscosity ρ _K.

FIG. 5 shows the outline of the temperature drop due to the cooling of the ink in the nozzles 10 of the recording head 2 when the recording head 2 is left in the atmosphere at the temperature T _L (T _L ≦ T _K ). As can be seen from the graph, the temperature T of the recording head 2 is T ₁ , T ₂ , T ₃ (T ₁ <T ₂ <
In the case of T ₃ ), the ink in the nozzle 10 is cooled and the standing time t ₁ , t ₂ , t ₃ for reaching the ink ejection limit temperature T _K at which the ink viscosity ρ becomes the ink ejection limit viscosity ρ _K is t It shows that it changes depending on the temperature of the recording head 2 such that ₁ <t ₂ <t ₃ .

Further, FIG. 6 shows that the recording head 2 having an ink temperature of T ₃ (T ₃ > T _K ) has the atmospheric environment humidity W ₁ , W ₂ , W ₃ , W ₄ , (W ₁ > W ₂ > W ₃ > W ₄ ) Shows an outline of the evaporation of volatile components of the ink in the nozzle 10 of the recording head 2 when left in the environment of (), and there is no problem when the environmental humidity is sufficiently high (W ₁ ) as shown in this figure. However, when the environmental humidity drops to a certain level of W ₂ , W ₃ , W ₄ (W ₂ > W ₃ > W ₄ ), the ink viscosity ρ increases due to evaporation of the ink in the nozzles 10 of the recording head 2, and the ink ink discharge limit water evaporation amount K viscosity [rho is the ink ejection limit viscosity [rho _K
The time t ₂ ′, t ₃ ′, t ₄ ′ when the water evaporates up to (%) is
It can be seen that t ₂ ′ <t ₃ ′ <t ₄ ′ changes depending on the atmospheric environmental humidity.

That is, as shown in FIGS. 5 and 6, the time during which the viscosity of the ink in each nozzle 10 of the recording head 2 changes to the ink ejection limit viscosity ρ _K is the temperature T of the recording head 2.
_A (° C.), atmospheric environment temperature T _B (℃), atmospheric humidity W
Since the carriage 1 having the recording head 2 reciprocates and performs a recording operation for a plurality of lines, the operation interval of the idle ejection operation performed after the ink jet viscosity is the ink ejection limit viscosity ρ _K. The recording head temperature T _A , the atmospheric environment temperature T _B , and the atmospheric environment humidity W described above are used by utilizing the time difference reaching
Change based on.

7 and 8 (A) to (C) show a control model of the operation interval of the idle discharge operation, and the print head temperature T _A
(° C.), atmospheric environment temperature T _B (℃), atmospheric humidity W (%)
Depending on the, the operation interval of the blank discharge operation is every n ₁₁ rows, every n ₁₂ rows,
Every n ₁₃ lines, every n ₁₄ lines, every n ₂₁ lines, ... m every ₁₁ lines, ... l every ₁₁ lines,
The control circuit 28 controls the motor driver 2 and the recording head driver 21 so that the blank discharge operation is switched for each line of the reciprocating movement of the carriage 1.

9 and 10 (A) to 10 (C) show a carriage using a multi-nozzle inkjet recording head 2 for recording with heat energy by an electric / heat converter and the water-based recording ink shown in FIG. 1 shows the actual measurement value of the operation interval of the idle ejection operation according to the ink non-ejection limit time when the longitudinal width of A4 size (about 300 mm) is actually printed back and forth. The conditions that determine
Since it varies depending on the inkjet recording system, the structure of the recording head, the characteristics of the recording ink, and the like, the optimum conditions may be given with reference to experimental values according to each structure.

In addition, in addition, when the liquid jet recording apparatus performs recording on recording sheets of different sizes, the scanning width scanned by the carriage 1 having the recording head 2 for recording depends on the size of the recording sheet. Since this is different, the time required for the carriage to record one line also differs depending on the size of the recording paper, and therefore the number of scans at which the ink viscosity reaches the ink ejection limit ρ _K also differs.

That is, as shown in FIGS. 11A and 11B, when the recording head 2 performs recording at a constant speed v, the width of the recording paper 6 is L ₁ and L ₂ (L ₁ < In the case of L ₂ ), the time t required for one scan is L ₁ / v, L ₂ / v (L ₁ / v <L ₂ / v),
The larger the size of the recording paper 6, the longer the recording head 2 spends for one scan. As described above, the cause of non-ejection of the liquid jet recording head 2 is the evaporation of the volatile components in the ink and the decrease in the ink viscosity due to the decrease in the ink temperature, and in an environment where the temperature and humidity are constant, the recording head 2 Since the time for the ink in the nozzle 10 to reach the ink ejection limit viscosity ρ _K is determined to be constant to some extent, the number of scans when the recording head 2 continues scanning to reach the ink ejection limit viscosity ρ _K depends on the size of the recording paper 6. Come on.

Therefore, in the embodiment of the present invention, FIG.
As shown in (B), the number N of blank discharge pulses in the blank discharge operation,
Alternatively, at least one of the blank ejection intervals M is controlled by the size designation signal PS of the recording paper 6. That is, in the figure (A), after the recording paper size designation signal PS input from a paper cassette (not shown) or a console is input to the blank discharge control circuit 28A in the control circuit 28, The number N of blank discharge pulses is selected according to the size, and the printhead driver
The number of 21 blank ejection pulses is controlled by this selection pulse number N.
As for the number of idle ejection pulses, when the recording paper size is small, the scanning time of the recording head 2 is shorter. Therefore, the decrease in the viscosity of the ink in the nozzles 10 of the recording head 2 is smaller as the recording paper is smaller. The smaller the paper size, the smaller the number of idle discharge pulses.

Further, in this figure (B), the idle discharge interval M is selected according to the recording paper size designation signal PS, and the motor driver 22
Then, the print head driver 21 is controlled to perform the idle discharge operation at the selected idle discharge interval M. As for this idle discharge interval, the viscosity of the ink in the nozzles 10 of the recording head 2 decreases less when the recording paper size is smaller,
The smaller the recording paper size, the wider the scanning interval of the idle discharge operation.

It should be noted that in the above-described embodiment, the liquid jet recording apparatus that performs recording by serial scanning using the multi-nozzle liquid jet recording head has been illustrated, but the present invention is not limited to this and, for example, a liquid that uses a single nozzle recording head. It is obvious that the clogging prevention device of the present invention is also effective for the jet recording device.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform the optimum blank ejection according to the size of the recording medium. Further, since the blank discharge is performed toward the recording material receiving portion adjacent to the scanning end position of the predetermined number of scans, the recording head is positioned adjacent to the recording material receiving portion at the same time as the scanning of the predetermined number of scans is completed. It is possible to rapidly shift to the idle discharge operation, and there is an extraordinary effect that there is no waste of time.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic constitution of the embodiment of the present invention, FIG. 2 is a schematic diagram showing the internal constitution of the embodiment of the present invention, and FIG. 3 is a relation between ink temperature and ink viscosity in the case of water-based ink. FIG. 4 is a characteristic diagram showing the relationship between the water evaporation amount in the ink and the ink viscosity in the case of water-based ink, and FIG. 5 is the temperature decrease of the ink in the nozzle and the water evaporation amount when the recording head is left. FIG. 6 is a characteristic diagram showing the state of continuous change, and FIG. 6 is a characteristic diagram showing the state of continuous change of the water evaporation amount of the ink in the nozzle with respect to the environmental humidity change when the recording head is left unattended. (A) ~ (C) is an explanatory view showing a model example of the control content of the operation interval of the idle discharge operation of the embodiment of the present invention, Fig. 9 and Fig. 10 (A) ~ (C) is the embodiment of the present invention. Irritation when actually measuring with a recording head and moisture ink using thermal energy FIGS. 11 (A) and 11 (B) are explanatory views showing measured values of the operation intervals of the operation, showing that the scanning time of the recording head differs depending on the recording sheet size in the embodiment of the present invention. 12 (A) and 12 (B) are block diagrams showing a configuration example of a control system for performing idle ejection control according to the difference in recording paper size in the embodiment of the present invention. 1 ... Carriage, 2 ... Recording head, 5 ... Drive motor, 6 ... Recording paper, 10 ... Nozzle, 10A ... Orifice, 13 ... Ink, 15 ... Recording head temperature detection means, 18 ... Coupling member, 20 ...... atmospheric temperature detecting means, 21 ... recording head driver, 22 ... motor driver, 23 ... atmospheric humidity detecting means, 25 ... container type space, 26 ... liquid holding member, 28 ... Control circuit, 30 ... driver.

Claims (2)

(57) [Claims] 1. A liquid jet recording in which a liquid recording material is discharged from a recording head to record information on a recording medium, and a blank discharge operation is performed to discharge the recording material from the recording head outside a recording area. In the apparatus, a scanning unit that causes the recording head to reciprocally scan a region corresponding to the size of the recording medium, and the blank discharge at a predetermined position outside the recording region adjacent to a scanning end position of the recording region by the scanning unit. A recording material receiving portion for receiving the recording material ejected by the operation, a judgment means for judging the size of the recording medium, and a predetermined number every time the scanning means scans the recording area a predetermined number of times. The recording head is caused to perform a blank discharge of the number of discharges toward the recording material receiving portion adjacent to the scan end position of the predetermined number of scans. A control means for variably controlling at least one of the predetermined number of scans and the predetermined number of discharges according to the size of the recording medium judged by the means, the control means varying the predetermined number of scans. When controlling, the predetermined number of scans when the size of the recording medium determined by the determination unit is relatively large is greater than the predetermined number of scans when the size of the recording medium is relatively small. When a predetermined number of ejections is variably controlled by selecting from a plurality of scanning times so as to be smaller, the predetermined ejection when the size of the recording medium judged by the judgment means is relatively large. The number of times of ejection is controlled by selecting the number of times of ejection from a plurality of times of ejection so as to be larger than the predetermined number of times of ejection when the size of the recording medium is relatively small. Apparatus. 2. The apparatus according to claim 1, wherein the control means has at least one of a temperature of an atmospheric environment in which the liquid jet recording apparatus is installed, a humidity of the atmospheric environment and a temperature of the recording head. A liquid jet recording apparatus, wherein at least one of the number of scans and the predetermined number of discharges is variably controlled based on an output of a detection unit that detects one of the number of scans.