JPH0464311B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a liquid jet recording device that performs recording by ejecting liquid to form ejected droplets and attaching the droplets to a recording material such as paper, and in particular, relates to a liquid jet recording device that performs recording by ejecting liquid to form ejected droplets and attaching the droplets to a recording material such as paper. The present invention relates to a liquid jet recording device that forms ejected droplets. [Prior art] The liquid jet recording method (inkjet recording method) is
This is a recording method in which ejected droplets of recording liquid are formed using various methods, and the droplets are attached to a recording material such as paper to perform recording. Among recording devices (printers) that apply such recording methods, a type of liquid that uses heat as energy to form ejected droplets is a device that has a structure suitable for high-density multi-orifice recording heads. Examples include jet recording devices (hereinafter referred to as inkjet printers). Inkjet printers that use heat as the energy for ejecting droplets usually heat the recording liquid to give it a displacement that causes a sudden increase in volume.
A droplet forming means for forming droplets of recording liquid ejected from an orifice (droplet ejection hole) of a nozzle part, and electrothermal energy capable of generating heat and heating the recording liquid by applying an electric signal. It is equipped with a recording head having a conversion element (hereinafter referred to as an ejection heater). On the other hand, the recording liquid used when recording with an inkjet printer has recording characteristics,
Water-based recording liquids are mainly used for safety reasons. This aqueous recording liquid is generally formed of a recording agent such as a pigment or dye, and a solvent component mainly consisting of water or water and a water-soluble organic solvent for dissolving or dispersing the recording agent. . In the above-mentioned printers that use heat as droplet ejection energy and other printers that apply droplet formation methods, the orifice installed at the tip of the nozzle from which recording liquid is ejected is constantly It is often open to the outside air outside the device. For this reason, if recording is not performed for a long period of time, water and volatile organic substances, such as water and volatile organic Solvent components such as solvent evaporate from the orifice into the outside air, and recording agent components and solvent components that are difficult to volatilize remain in the recording liquid, resulting in an increase in the viscosity of the recording liquid retained in this area, and as a result, the recording liquid Immediately after restarting recording, a droplet ejection failure is likely to occur in which droplets are not ejected even though an ejection signal is applied, and recording There was a problem that defects occurred in the initial printed portion of the image. Additionally, some printers cap the ejection surface on which the orifice is installed when the device is not in use, such as when the power is off, but even with such capping, the orifice is not completely isolated from the outside air. Therefore, the above problem also occurs in such printers. On the other hand, in order to obtain a good droplet ejection condition even when the viscosity of the recording liquid increases at low temperatures, the temperature of the recording liquid can always be maintained within a predetermined range.
Japanese Patent Application Laid-Open No. 187364/1987 discloses a recording method in which the recording liquid is heated by constantly applying an electric signal to the ejection heater at a level at which no recording droplets are ejected even when no droplet ejection signal is applied. It is known as However, even in printers using this method, an electric signal is applied to the ejection heater so that the recording liquid is always kept at a high temperature even during a relatively long recording pause or stop period.
The solvent components in the recording liquid evaporate more easily,
There have been cases in which the above-described problem of droplet ejection failure upon resuming recording is more likely to occur. In addition, in this method, the area around the ejection heater is constantly heated, which may impair the durability of the parts surrounding the ejection heater, or cause accumulation of heat around the ejection heater during the recording pause period. The physical properties of the recording liquid itself may change due to heat, causing problems such as discoloration of the recording liquid or precipitation forming in the recording liquid, clogging the orifice and causing droplet ejection failure. It was hot. In addition, immediately after the printer is turned on, the temperature of the ink liquid involved in recording is controlled by environmental conditions such as atmospheric temperature, so starting recording by discharging ink immediately after turning on the power does not ensure a stable printing condition. It's not a desirable thing to get. Therefore, after turning on the power and before starting printing, we perform preliminary heating to keep the ink warm, and then perform preliminary ejection to eject old ink that was at the tip of the nozzle before turning on the power to optimize ejection. It is conceivable to construct an inkjet printer that can be This preliminary heating can be done by applying heat to the ink from the outside by driving a heat insulating means provided in the head unit, or by applying short width pulses and high frequency pulses that do not eject ink to the ejection energy generating element. It is conceivable to supply print output and apply heat to the ink from the inside, so to speak. However, conventionally, print output was performed from a microprocessing unit (MPU) that controlled each part of the printer via a port IC, so high-frequency pulses were used for this preliminary heating, especially internal heating. Add MPU
This is extremely difficult due to the slow processing speed. Furthermore, regarding preliminary ejection, it is extremely difficult to precisely control this in the conventional configuration due to software processing time issues, so there is a problem in that optimal preliminary ejection cannot be performed. [Objective] The present invention eliminates such conventional problems, provides a dedicated controller for controlling the ejection of the head unit, and uses the controller to perform preliminary heating processing and preferably preliminary ejection processing when starting up the printer. An object of the present invention is to provide an inkjet printer that can quickly and easily optimize printing conditions. [Structure of the Invention] In order to achieve the above object, the present invention provides a liquid jet recording device that records on a recording material by ejecting droplets, which heats the liquid in accordance with a supplied electric signal. a recording unit having ejection energy generating means including an electrothermal energy conversion element capable of forming flying droplets; and a recording unit that processes input print data and outputs a recording signal for ejecting droplets from the recording unit. and a control means for controlling each part of the liquid jet recording device; independently of this control means, conditions for the electric signal can be set, and the electric signal with the set conditions is supplied to the ejection energy generation means. recording unit control means for performing preliminary heating control, the control means setting an electric signal of a condition in a range in which droplets are not formed to the recording unit control means; The heating control mode is characterized in that the heating control mode includes a heating control mode in which the preliminary heating control is performed. Further, as an embodiment of the present invention, as shown in FIG. 1, a discharge energy generating means 102 includes an electrothermal energy conversion element capable of heating the liquid in response to the supply of an electric signal and forming flying droplets. and a liquid jet recording unit 100 that records on a recording material P by discharging the formed flying droplets;
A recording unit control means 110 that can set an electric signal and supplies an electric signal that causes the ejection energy generation means 102 to form flying droplets in response to the input of the recording signal SA, and a recording unit control means 110 that is provided in the liquid jet recording unit 100 to heating means 120 for heating from the outside
and a heating control means 140 that heats the liquid by the heating means and/or heats the liquid by setting an electric signal to the recording unit control means 110 in a range in which no flying droplets are formed, depending on the environmental conditions.
, an ejection control means 150 for ejecting ejected droplets from the liquid jet recording unit 100 by setting an electric signal for forming ejected droplets in the recording unit control means 110, and a heating control means when the power switch is turned on. 140, and a sequence control means 160 for driving the ejection control means 150. [Example] Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 shows an example of the configuration of a recording section of an inkjet printer to which the present invention can be applied. This example shows the present invention applied to an inkjet printer in which a head unit is mounted on a carriage that moves in a predetermined direction with respect to the recording surface. is applied. 3A and 3B are an enlarged view of the head unit in FIG. 2, and a further enlarged view of its nozzle portion, respectively. In these figures, HU is a liquid ejecting unit mounted on a carriage C, and the number of units can be provided depending on the color of ink used. FC is a flexible cable that collects signal lines etc. that control ink ejection by the liquid jet recording unit HU. The carriage C is fixed to a belt or the like, for example, and is moved in the S direction in the figure by a driving means such as a motor. R
is a guide rail that guides the movement of the carriage C in the S direction. Further, P is a recording material such as paper that is conveyed in the direction f in the figure, and PL is a platen that forms the recording surface of the recording paper P. That is, the carriage C can move in the S direction in the figure along the guide rail R by the drive means and perform recording on the recording surface. ST is a sub-tank installed in carriage C, TB
1 and TB2 are ink supply pipes that communicate with a main tank (not shown) and a sub tank ST, respectively;
and an ink supply pipe unit that communicates the subtank ST with the liquid chamber IR in the head unit HU. Also, CAP is a cap member, and in the S direction,
It is arranged so as to face the liquid jet recording unit HU at the home position H of the cartridge C, and when the cartridge C is at the home position, the cap member
The CAP can be moved toward the liquid jet recording unit HU by a driving means such as a motor and come into contact with the ejection surface thereof. SP is a collection member that comes into contact with the ejection surface of the liquid jet recording unit HU to collect ink, and is made of, for example, a water-absorbing porous material. In Figure 3A, BP is the supply pipe unit TB
2. The liquid chamber IR, nozzle part NZ, flexible cable FC, etc. are arranged, and a base plate is used to support them. BSH is an elastic member to support the periphery of the nozzle part, and FP is a front plate.
TS is a temperature sensor such as a thermistor for temperature detection,
HTR is a heater made of an electrothermal converter such as a positive temperature coefficient thermistor, which is provided in the head unit HU to heat and keep ink from the outside, and TP is a heat conductive plate. In addition, in FIG. 3B, OR is an orifice as an ink ejection hole, and in this example, the orifice is
A predetermined number of ORs were arranged in the nozzle part NZ in the vertical direction.
ICH is a liquid flow path that communicates the orifice OR with the liquid chamber IR, and ET is an ejection heater serving as an ejection energy generating element that provides thermal energy for ejection to the ink in the liquid flow path ICH. To record using this device, first connect the main tank to the sub tank via the supply pipe TB1.
Ink is supplied to ST, and then the supply pipe unit
Fill the recording liquid into the liquid chamber IR and the liquid flow path ICH via TB2. Next, an electric signal is applied from a droplet ejection signal generating means, which will be described later, via the flexible cable FC to energize the ejection heater ET. As a result, the ejection heater ET generates heat, and thermal energy is applied to the recording liquid in the liquid flow path ICH near the ejection heater ET, causing an instantaneous increase in the volume of the recording liquid in that area. Bubbles are generated within the recording liquid, and the recording liquid located downstream of the ejection heater ET is ejected from the orifice OR, forming droplets of the recording liquid. Recording is performed by making droplets of the recording liquid adhere to a recording material P such as paper that has been sent in front of the nozzle section. FIG. 4 shows an example of the configuration of a control device for an inkjet printer according to the present invention. For example, this control device receives print data from a host computer, stores one line of print data, and prints it to the head unit.
The print head is controlled by the HU controller to perform printing. First, 1 is a programmable peripheral interface (hereinafter referred to as PPI), which receives print data sent from the host computer of the printer according to this example in parallel and sends the print data to MPU 2. It also controls the console 6 and performs input processing for the home position sensor 7. Reference numeral 2 denotes a microprocessing unit (hereinafter referred to as MPU), which controls various parts within the printer and performs the processing procedures described below. 3 is RAM as a line buffer memory that stores one line of print data received by PPI1, 4 is for font of print output characters.
ROM, 5 is the processing procedure (5th
This is a control ROM that stores the following data (Figs. to 7). Each of these parts 1 to 5 is an address bus AB, a data bus
Connected via DB. 6 is a console having a keyboard switch, a display lamp, etc., and 7 is a home position sensor provided near the home position of the carriage C. 8 is a cap mode switch for detecting the state of the cap member CAP, that is, whether the cap is opened or closed with respect to the head HU, and 9 is a paper sensor for detecting the absence of printing paper. 10 is a controller for the head unit;
Latch the print data and print output time,
Printout starts in response to commands from MPU2.
That is, in this example, the controller 10 is used as a dedicated IC circuit to speed up the processing. As this controller 10, for example,
The material disclosed by the applicant in Japanese Patent Application No. 162802/1988 can be used. Note that once latched print data is output as is if there is no need to change it. Reference numeral 11 represents a driver for driving the head unit HU in accordance with the controller 10, and reference numeral 13 represents a protection circuit for the head unit HU. Reference numeral 14 denotes a driver for driving the ink heating and heat retention heater HTR provided in the head unit HU. 15 is a temperature comparison element of the ink temperature detection element TS provided in the head unit HU. Reference numeral 16 is a switch for instructing switching of the printing font. Reference numeral 17 denotes a signal input switching device for the temperature comparison circuit 15 and the switch 16, which is controlled by the MPU 2. 18 connects the cap member CAP to the head unit HU
This is a driver that drives the motor M3 to move the motor M3. 22 and 24 are respectively
This is a driver that drives the paper feeding motor M1 and the carriage moving motor M2. Also, 2
0 and 21 are head unit HU, respectively.
This is a solenoid for a valve used to bleed air from inside, and its driver. Here, an overview of the processing in the inkjet printer shown in FIGS. 2 to 4 according to this example will be described. In this example, when the printer is powered on and when printing starts, the head unit HU is subjected to preliminary heating processing and preliminary ejection processing to improve the ink ejection state. In addition, in connection with these processes,
Appropriately control capping for the head unit HU. During the preliminary heat treatment, external heat treatment and/or internal heat treatment shall be performed. Here, external heating refers to heating the ink in the head unit HU from the outside by driving the heater HTR, and internal heating refers to applying print output pulses within a range in which no ink is ejected from the head unit HU to the ejection energy generating element. This refers to heating from inside the head by supplying heat to the head. During internal heating, a print output start signal is sent to the head unit controller 10 at each set frequency. When performing preheating, especially internal heating, it is preferable to apply a print output with an appropriate pulse width, frequency and voltage to the head unit HU.
Sufficient processing is possible even with the processing speed of the MPU.
That is, according to this example, the parameters of each print output can be freely changed and set as necessary, so that optimal head heating and software simplification and speeding up can be achieved. Also, when performing preliminary ejection, it is preferable to similarly apply an appropriate print output to the head unit HU using pulse width, frequency, and voltage as parameters. In this example, these parameters and the number of ejections are changed depending on the environmental conditions.
According to this example, such a case can be easily handled using software, and optimal preliminary ejection becomes possible. In addition, in this example, the head controller 10
The print output during preliminary ejection was set to "1" for all dots. Therefore, in this case, there is no need to change the print data each time, so it is possible to simplify the software and speed up the processing. The print state optimization process in this example will be described below. FIGS. 5A and 5B show an example of a printing condition optimization processing procedure according to the present invention. Immediately after turning on the power to the printer, as initial processing, the hardware initializes the PPI 1 and the head unit controller 10, and the software initializes the line buffer memory RAM 3 and checks the operation of the control ROM 5, which are used for processing. Initial setting of each parameter is performed (step S1). After this initial processing is completed, the head cap motor M3 is operated while monitoring the cap mode switch 8 by the MPU 2 to perform head cap opening processing (step S2). Then, while monitoring the home position sensor 7, the carriage motor M2
is operated to move the carriage C to the home position H (step S3). Then, while monitoring the cap mode switch 8,
Operate the cap motor M3 and start the head unit.
A headcap closing process is performed for the HU (step S4), and the motor M1 is further driven to feed the paper by, for example, one line. After these processes, initial processing for the head unit HU is performed. In the initial processing, first, preliminary heating processing (step SH) of the head unit HU is started. FIG. 6 shows an example of a preliminary heating treatment procedure for performing external heating and internal heating. Here, as mentioned above, internal heating refers to applying an output from the controller 10 with a pulse width, voltage, and high frequency within a range that does not eject ink to the head unit HU to generate heat within the head unit HU, and external heating refers to generating heat within the head unit HU. Using the heater HTR installed in the head unit HU as a heating element,
This refers to heating the head unit HU by turning on the driver 14 from the MPU 2. step
At SH1, external heating is started and step SH1 is started.
At step 2, the head unit controller 10 is set to external heating mode. Next, step SH3
The print output is set to "1" for all dots at step SH4, and internal heating is started at step SH4.
During this internal heating, the pulse width, voltage, and frequency of the print output are appropriately set, as will be described later. After preheating the head is started in this way, the temperature of the head unit HU is measured, and if the temperature of the HU is higher than a certain temperature on the high temperature side (step SH5), the preheating is ended. If preheating is started and the high temperature does not exceed a certain temperature even after a certain period of time has passed (step SH6), an internal heating stop command is sent to the controller 10 in step SH7 to prevent thermal damage to the head. Stop heating, then step
The driver 14 is turned off at SH8 to stop external heating. That is, at this time, the preheating is stopped and the process returns to step S6 in FIG. 5A. In addition,
The constant temperature on the high temperature side refers to the upper limit temperature for operation of the head unit 12 (for example, 42° C.). Furthermore, it goes without saying that the external heating and internal heating may be started and stopped in any order. Referring again to FIG. 5, after stopping the preheating, the system waits for a predetermined period of time to average the locally heated temperature distribution within the head unit HU (step S6). After this waiting, preliminary discharge processing (step
SJ). Note that if rapid heating is performed during preheating when the power is turned on, the standby time may be set relatively long. For example here
Can be set to 500ms. FIG. 7 shows an example of a preliminary ejection processing procedure. Here, first, in step SJ1, ejection conditions are set in the head unit controller 10, and then, in step SJ2, the print output for all dots is set to "1". Then, in step SJ3, the print output is applied to the head unit HU to cause ejection, and this is repeated a prescribed number of times by the processing in step SJ4.After completing this process, the process returns to step S10 in FIG. 5, and the print standby state is started. Transition. That is, the initial processing for the head unit HU is completed, and the procedure shifts to a print standby state from the host computer. Note that the parameters of the prescribed number of times of ejection and the ejection conditions can be appropriately set depending on the environmental conditions as described later. When a print signal is supplied from the host computer in the print signal standby state (step S10),
Print data is latched in PPI1 and transferred to RAM3 as a line buffer. Therefore, a signal from the temperature detection element TS provided in the head unit HU is detected by the temperature comparison circuit 15, and it is determined whether the temperature is higher than a certain temperature on the low temperature side, for example, 20° C. or higher (step S11). If the determination is affirmative here, the head cap motor M3 is driven to perform cap opening processing (step S12), and then the controller 10 is set to the normal printing mode to perform preliminary ejection (step SJ; see FIG. 7). on the other hand,
If it is determined that the low temperature is below a certain temperature, the cap is opened (step S13), the preheating process (step SH; see Figure 6) is performed, and the controller 10 waits for a predetermined time (step S15). Preliminary discharge is performed by setting the discharge conditions and the number of discharges (step SJ; see FIG. 7). Note that the standby time in this case can be made shorter than the above-mentioned standby time when rapid heating is not performed such as during startup. Note that the constant temperature on the low-temperature side is referred to as the lower limit operating temperature of the head unit HU. Next, the driver 14 is turned off, external heating is stopped (step S16), and the printing state is entered.
That is, the heating process is not performed during the printing operation when the carriage motor M2 is being driven. Further, heat treatment can be performed without increasing power consumption in connection with the printing process in step S20. That is, when the carriage C is in operation and the direction of movement of the carriage is changed at both ends of its movement range, the carriage C stops there, so the heat treatment may be performed at that time. When printing is started and, for example, one line has been printed and the carriage motor M2 is stopped (step S20), it is determined whether the temperature of the head unit HU is higher than a certain temperature on the low temperature side (step S21). If the judgment is affirmative here, the process moves to the next stage, and if the judgment is negative, the process moves to the next stage after turning on the driver 14 and starting external heating (step S22). That is, head unit HU
It is determined whether or not the temperature is higher than a certain temperature on the high temperature side (step S23). Here, if the judgment is positive, it is immediately; if the judgment is negative, it is for a predetermined period of time (for example,
After waiting for 200ms (step S24), external heating is stopped (step S25). Next, as shown in FIG. 5B, the paper feed motor M
1 to feed the paper (step S30),
The process proceeds to the next stage through steps S31 and S32, which are similar to steps S21 and S22, respectively. That is, the MPU 2 turns on the internal timer and determines whether the print data is latched to the PPI 1 within a predetermined time (for example, within 5 seconds) (steps S40 and S41). If the determination is affirmative here, the process moves to step S16 in FIG. 5A. On the other hand, if the determination is negative, the driver 14 is turned off to stop external heating (step S42), the carriage motor M2 is driven to position the carriage C at the home position H (step S43), and the cap motor M3 is then driven to close the cap. After performing the processing (step S44), the process returns to step S10 in FIG. 5A. In this way, in this example, after the preliminary heating process, the preliminary ejection process of ejecting droplets that are not used for recording is performed, so the recording pause or stop period becomes very long, and the evaporation of the solvent component Even if the viscosity of the recording liquid increases significantly due to the above, it is possible to optimize ejection during printing. That is, first, the high viscosity portion of the recording liquid is heated by the preheating process, the temperature thereof is increased, and the viscosity of the recording liquid is lowered to the extent that droplets can be ejected. In this state, by performing the preliminary ejection process next, the recording liquid in this area will be ejected out of the liquid flow path ICH, and the area near the ejection heater ET will be
A recording liquid whose viscosity is within a suitable range for ejection is supplied, and a favorable recording liquid ejection condition can be obtained from then on. In order to confirm the stability of this discharge state, the applicant conducted the following experiment. [Experiment using Example] 24 orifices (orifice diameter 50 x 40 μm)
Using an inkjet printer according to this example, which has a recording head section as shown in FIG. Filled with 25
When resuming recording after a 12-hour recording break in an environment of ℃ 30% RH, voltage 23.5V, pulse width
A signal of 5 μs and a frequency of 10 KHz was applied to the discharge heater ET during preheating. Next, 100 pulses of a signal with a voltage of 23.5 V, a pulse width of 10 μs, and a frequency of 2 KHz are applied to the ejection heater ET to eject droplets not used for recording, and droplets of the recording liquid used for recording are ejected from all 24 orifices. By measuring the number of droplets that failed to be ejected with respect to the recording signal until the printing was stopped, the printing apparatus was evaluated regarding ejection failure after the recording was stopped. The results are shown in Table 1. The composition of the recording liquid used for recording is as follows. CI Direct Black 19 2 parts by weight Diethylene glycol 30 parts by weight Water 70 parts by weight [Experiment using comparative example] It has the same structure as the example, and when recording,
A recording device is used in which only the electrical signal for ejecting the recording droplets used for recording is applied to the ejection heater, and the recording liquid is filled with the above-mentioned recording liquid and heated at 25°C, 30% RH.
Voltage 23.5V, pulse 10μs, frequency 2K when resuming recording after a 12-hour recording pause under
Recording was performed by applying only a Hz droplet ejection electric signal to the heater, and the apparatus was evaluated for ejection failure after recording was stopped in the same manner as in the experiment using the example. The results are shown in Table 1.

[Table] In this way, even when recording is restarted after a particularly long recording pause or stop period, a good and stable droplet ejection condition can always be obtained. Next, the settings of parameters such as the pulse width, frequency, and voltage of print output in the preheating process and the preliminary ejection process will be described. How long the recording pause or stop time causes the viscosity of the recording liquid in the liquid flow path ICH, especially near the orifice OR, to deviate from the preferred range depends on the characteristics of the device used, the physical properties of the recording liquid, and the device. Since each device is different depending on the environmental conditions such as temperature and humidity of the place where the device is installed and used, the parameters of print output during preheating, especially internal heating treatment, should be selected appropriately depending on the individual device and its usage condition. do. In addition, in the preliminary discharge process, the discharge heater ET
The signal supplied to the liquid flow path ejects recording liquid whose viscosity is not within the range suitable for ejecting droplets during recording.
Make sure that it is applied under conditions that allow it to be removed outside the ICH. Furthermore, the number of ejections in the preliminary ejection process is made variable depending on the environmental conditions at that time, so that efficient processing can be performed. FIG. 8 shows the electrical signals applied to the discharge heater ET. Here, v0 is the voltage and wi is the pulse width. During preheating process, the signal is sent to the discharge heater.
Bubbles due to heating when supplied to ET
If this occurs, subsequent ejection of droplets may become unstable, or in some cases, non-ejection may occur. Therefore, during preheating, the discharge heater
The electrical signal applied to the ET must be within a range that does not generate bubbles on the discharge heater ET. On the other hand, these preheating treatments are set when the printer is turned on or when printing begins.
Preheating is used extremely frequently. Therefore, these preliminary heating treatments must not deteriorate the durability of the discharge heater ET. The inventors investigated the durability of the ejection heater ET when the power (W) applied to the ejection heater ET was kept constant and the pulse width wi and the applied voltage v0 were varied during preheating treatment using the ejection heater ET. After examining the performance, it was confirmed that the smaller the pulse width wi and the applied voltage v0, the better the durability of the heater ET. Next, the time required to heat the head unit HU to the desired value is determined by the power (W) applied to the discharge heater ET, but the time required to start printing depends on the performance of the device. In other words, it is desirable that the waiting time be short. However, as mentioned above, the discharge heater
In view of the durability of the heater, it is not desirable to increase the voltage applied to the ET unnecessarily. Furthermore, if bubbles are generated on the ejection heater ET during preheating, this will cause subsequent printing failures or non-ejection, so it is also difficult to increase the pulse width. Therefore, in order to raise the head temperature to the desired temperature in a short period of time without affecting the durability of the heater ET and without causing foaming on the heater, it is necessary to It is effective to increase the frequency of the electrical signal applied to the Figure 9 shows the time (minutes) and the frequency of the preheating signal applied to the discharge heater ET as a parameter.
An example of the relationship with head temperature (°C) is shown. In this case, the applied voltage v0 was 24V, the pulse width wi was 5μs, and the frequencies were 10KHz, 5KHz, and 2KHz. Note that the head temperature is detected by a temperature detection element TS. From this point of view, the applicant conducted experiments as shown in the following two examples by changing the voltage, pulse width, and frequency. (Example 1) 24 orifices (orifice diameter 50 x 40 μm)
Using an inkjet printer according to this example, which has nozzle parts NZ as shown in FIG. was filled and preheated by supplying an electric signal to the discharge heater ET under the conditions shown in Table 2. Then, the surface of the heater was observed using an optical microscope to confirm the presence or absence of bubble generation. The results are shown in Table 2.

[Table] (Example 2) Using an inkjet printer similar to (Example 1), fill the device with a recording liquid having the above composition,
By applying a signal to the discharge heater ET under the conditions shown in Table 3 and repeating the preheating process, the heater
We investigated the durability of ET. The results are shown in Table 3.

[Table] For the above reasons, it is understood that the pulse width of the electric signal supplied to the ejection heater ET in the preheating process should be set to be smaller than the pulse width of the electric signal during recording. According to more detailed experiments by the applicant, the pulse width is preferably in the range of 1 to 1/20 of the pulse width during recording. In addition, during preheating treatment, the discharge heater ET
It can be seen that the electric signal supplied to the recording medium may be set so that the applied voltage is equal to or lower than the applied voltage applied during recording. Furthermore, if the frequency of the electric signal during preheating is set higher than that during recording, the time required for heating can be shortened. The settings of these parameters and the number of pulses are
As described above, this can be done extremely easily by setting this using the controller 10. This allows the preheating conditions to be adjusted to the controller 1.
It is sufficient to set it to 0, and the preheating process can be performed quickly and appropriately without increasing the load on the MPU 2. Further, since the controller 10 outputs the recording signal and the preheating signal based on the settings of the MPU 2, the circuit scale does not increase. Furthermore, since the preliminary ejection process is performed after the preliminary heating process and the standby process, it is possible to make the temperature distribution of the ink uniform, and it is possible to make the printing characteristics uniform. Next, the ejection conditions in the preliminary ejection process will be described. If recording has been paused or stopped for a long time,
The viscosity of the ink that has remained in the orifice OR and its vicinity increases due to the evaporation of water and volatile organic solvents, making it difficult to be ejected.
The viscosity of the stagnant ink can be lowered by the above-mentioned preheating treatment, but the viscosity is higher than that of ink suitable for recording, and the droplet size and speed are different, making it difficult to record. Since this is inappropriate, in this example, preliminary heating is followed by preliminary ejection. During preliminary ejection processing, since ejection may not necessarily occur from the first pulse of the signal applied to the ejection heater ET at that time, the energy of the signal during preliminary ejection is set to be greater than the energy of the signal during printing, and the environment By making the ejection time variable depending on conditions, it is possible to shorten the time required for preliminary ejection and increase efficiency. The reason for increasing the energy of the signal during preliminary ejection is
Specifically, the voltage and/or pulse width may be made larger than during recording. That is, if the voltage and pulse width of the signal applied to the ejection heater ET during printing are 24 V and 10 μs, respectively, the voltage and/or pulse width of the signal may be made larger than those values during preliminary ejection. According to the applicant's experiments, the voltage is 1 to 5 times that of printing, preferably 1 to 2 times, and the pulse width is also 1 to 5 times.
Good results were obtained when the amount was doubled, preferably 1 to 2 times. Further, regarding the setting of the ejection time, the number of ejections, that is, the number of pulses may be set according to the environmental conditions. According to the applicant's experiments, during preliminary ejection after turning on the power and before starting printing (step SJ following step S6 in Fig. 5A), when 100 to 150 pulses were applied to the ejection heater ET, subsequent good Print quality was achieved. After printing starts, the viscosity of ink is high in a low temperature environment, and ejection is less stable than in a high temperature environment, so it is preferable to appropriately set the number of ink ejections. In the applicant's experiments, during preliminary ejection when the low temperature is above a certain temperature (e.g. 20°C) (when an affirmative judgment is made in step S11 in Fig. 5B), 20 to 50 pulses are applied to the ejection heater ET. In addition, it was confirmed that the discharge was stable and the discharge was stabilized when 50 to 100 pulses were applied to the heater ET during preliminary discharge when the temperature was below the constant temperature on the low-temperature side (when a negative determination was made in step S11). Regarding the discharge conditions for these preliminary discharges,
It is sufficient to set the controller 10 at the time of processing, and processing can be performed at high speed and appropriately without increasing the burden on the MPU 2. Further, since the controller 10 outputs the recording signal and the preliminary ejection signal based on the settings of the MPU 2, the circuit scale does not increase. Furthermore, since the viscosity of the ink is lowered by preheating immediately before preliminary ejection, preliminary ejection can be performed reliably. Note that if the area where the printer according to this example is used is limited and clarified in advance, the number of ejections can be changed for each area. For example, in high-temperature, low-humidity areas, where the temperature is constant, ink dries considerably. Therefore, it is possible to stabilize the amount of preliminary ejection on the high temperature side by increasing it than on the low temperature side, and also to change the above-mentioned values for the ejection quantity to obtain stable ink ejection. It is. In the embodiment, an inkjet printer in which a head unit is mounted on a carriage has been described, but the present invention can also be applied to a so-called full multi-type inkjet printer that is equipped with a plurality of head units in the width direction of the recording paper. Of course. In addition, when setting each parameter in the preheating treatment, each parameter in the preliminary discharge treatment, and the number of discharges, it is necessary to set not only the temperature conditions as in the example, but also the environmental conditions such as humidity and pressure. can be taken as a thing. In this example, after preheating is completed, preliminary discharge is performed after a predetermined period of time, but by changing the setting conditions during preheating so that the head unit is heated slowly, the temperature distribution is almost uniform. There is no need to set a standby time if the [Effects] As explained above, according to the present invention, appropriate heating conditions are set in the head controller to perform preheating treatment immediately after the power is turned on, before printing starts, or at the time of printing, so that the control means This has the effect of realizing a liquid jet recording device that can reduce the load on the printer, simplify the software, and quickly and easily optimize the printing condition. Further, according to the present invention, the heating conditions can be easily changed by changing the conditions set during preheating.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is a perspective view showing an example of the configuration of an inkjet printer according to the present invention, and FIGS. 3A and B are enlarged views of the head unit of the printer shown in FIG. FIG. 4 is a block diagram showing an example of the internal circuit configuration of the inkjet printer according to the present invention, and FIGS. 5A and B show print optimization processing. FIGS. 6 and 7 are flowcharts showing an example of a preheating treatment procedure and an example of a preliminary discharge treatment procedure in the process shown in FIG. 5, respectively. FIG. FIG. 9 is a characteristic curve diagram showing the relationship between supply time and temperature using the frequency of the print output signal supplied to the head unit as a parameter. HU...liquid jet recording unit (head unit), C...carriage, R...guide rail, TB
1, TB2...supply pipe, FC...flexible cable, ST...subtank, CAP...cap member, P
...recording material, PL...platen, S...carriage running direction, f...recording material transport direction, H...home position, NZ...nozzle section, FP...front plate, IR...liquid chamber, ICH...ink flow path, OR …Orifice, TS…
Temperature detection element, HTR...external heater, ET...
Discharge heater, M1, M2, M3...Motor, 1...
Programmable peripheral interface (PPI), 2...Microprocessing unit (MPU), 3...Line buffer RAM, 4...ROM for font generation, 5...Control ROM, 6...Console, 7...Home position sensor, 8 ...Cap mode switch, 9...Paper sensor, 10...Head unit controller, 11, 14, 18, 21,
22, 24...driver, 13...protection circuit, 15...
Temperature comparison element, 16... Font changeover switch, 1
7...Input selector.

Claims (1)

[Scope of Claims] 1. In a liquid jet recording device that records on a recording material by ejecting droplets, an electrical device that can heat the liquid in response to a supplied electrical signal and form flying droplets. A recording unit having an ejection energy generating means including a thermal energy conversion element, processing input print data and outputting a recording signal for ejecting droplets from the recording unit, and controlling each part of the liquid jet recording apparatus. a control means for controlling; and the control means is capable of setting conditions for the electric signal independently of the control means, and performs preliminary heating control by supplying the electric signal of the set conditions to the discharge energy generation means. and recording unit control means, the control means setting the recording unit control means with an electric signal of conditions in a range in which no droplets are formed, and causing the recording unit control means to perform the preliminary heating control. A liquid jet recording device characterized by having a control mode. 2. The liquid jet recording apparatus according to claim 1, wherein the control means executes the heating control mode according to environmental conditions. 3. The liquid jet recording apparatus according to claim 1, wherein the control means executes the heating control mode when power is turned on. 4. The heating control mode of the control means is characterized in that an electric signal having a pulse width within a range in which no droplets are formed is set to the recording unit control means to cause the recording unit control means to heat the liquid. A liquid jet recording apparatus according to claim 1. 5. The recording unit includes a heating means for controlling the temperature of the liquid, independent of the ejection energy generating means, and the heating control mode of the control means causes the recording unit control means to heat the liquid. 2. The liquid jet recording apparatus according to claim 1, wherein the liquid is heated by the heating means. 6. The control means sets an electric signal of conditions for forming droplets to the recording unit control means,
2. The liquid jet recording apparatus according to claim 1, further comprising a discharge control mode for preliminary discharge of droplets from said recording unit. 7. The liquid jet recording apparatus according to claim 6, wherein the control means executes the heating control mode when power is turned on, and then executes the ejection control mode. 8. The liquid according to claim 6, wherein the control means executes the heating control mode at the start of recording, then executes the ejection control mode, and then causes recording to be performed using the recording signal. Injection recording device. 9. The liquid jet recording apparatus according to claim 6, wherein the control means executes the heating control mode, waits for a predetermined time, and then executes the ejection control mode.