JP2007160931A - Ink-jet recording apparatus and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording apparatus which is possible to improve the recording quality, even when the ink temperature is changed during the recording. <P>SOLUTION: The ink-jet recording apparatus detects a temperature of a head when recording of the first sheet of the recording paper immediately after the power supply is turned on, and reads a drive voltage corresponding to the head temperature from a table. The read drive voltage is determined to be a drive voltage V1 to be used in a recording for this time and is started the recording. When the scanning number n of the ink-jet head has reached a value m, a drive voltage V2 to be used for this time is temporarily determined based on the head temperature. When the absolute value of the difference between the drive voltage V1 used previous time and the drive voltage V2 which is intended to be used this time is greater than ΔV, the drive voltage, which is obtained by making a correction, by only ΔV, to the drive voltage V1 of the previous time, is determined to be the drive voltage V2 to be used this time. Therefore, even when the ink temperature is changed during the recording, it is possible to improve the recording quality. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus including an ink jet head that performs recording by ejecting ink onto a recording medium by driving an actuator, and determines the driving voltage of the actuator according to the temperature of the ink, and It relates to the recording method.

Conventionally, as an ink jet recording apparatus of this type, as described in Patent Document 1 (Japanese Patent Publication No. 6-8049), when recording is performed on a plurality of recording sheets, each recording sheet starts recording. A device that determines a driving voltage corresponding to the head temperature is known. FIG. 8 is a graph showing the relationship between the head temperature and the drive voltage when recording is performed at a recording duty of 50% in such an ink jet recording apparatus. For the first sheet of recording paper, the head temperature at the start of recording is 21 ° C., and the drive voltage is set to 24.5V. Recording is performed at the same 24.5 V without changing the drive voltage until the first sheet is recorded. The second and third sheets are recorded with drive voltages of 23.0 V and 22.5 V, respectively.
Japanese Patent Publication No. 6-8049 (Gazette, page 3, right column, lines 14-15)

  By the way, in an ink jet recording apparatus in which a driving IC chip that outputs a driving signal to an actuator is mounted on an ink jet head, when the IC chip or actuator generates heat by a recording operation, the heat is transmitted to ink in the ink jet head, and the temperature of the ink Rises. Further, the heat generation amount of the IC chip and the actuator increases corresponding to the recording density, and the ink temperature increases accordingly. In such a case, it is necessary to lower the driving voltage in order to cope with a decrease in ink viscosity accompanying an increase in ink temperature. However, since the conventional ink jet recording apparatus performs recording at the same driving voltage even if the ink temperature changes in one page, recording corresponding to the ink viscosity cannot be performed, and the recording quality is deteriorated. There is a problem. Especially when recording very high recording density, such as when recording photographic data immediately after the power is turned on, the ink temperature may increase rapidly, resulting in a decrease in recording quality. May become prominent. In addition, today, inkjet printers are used all over the world, and it is necessary to cope with any use environment. In particular, it is necessary to cope with a case where the use environment suddenly changes when the user starts using the printer or during use.

  A first object of the present invention is to realize an ink jet recording apparatus and a recording method capable of maintaining good recording quality even when the ink temperature changes during recording of one page. The second object of the present invention is to provide an ink jet recording apparatus capable of maintaining good recording quality even when the ink temperature changes suddenly according to the driving condition or use environment during recording, and It is to realize a recording method.

Means for Solving the Problems and Effects of the Invention

According to the first aspect of the present invention, there is provided an ink jet recording apparatus having an ink jet head that performs recording by ejecting ink onto a recording medium by driving an actuator, the temperature sensor detecting the temperature of the ink, A driving voltage determining unit that determines a driving voltage for driving the actuator according to the temperature of the ink detected by the temperature sensor, and determines a new driving voltage when the temperature of the ink changes; A drive unit that drives the actuator with the drive voltage determined by the drive voltage determination unit, and the drive voltage determination unit includes the temperature detected at the first time or the drive voltage at the first time determined based on the temperature. The difference between the temperature detected at the second time or the drive voltage set based on the detected temperature With Mel, an ink jet recording apparatus is provided for determining a driving voltage at the second time based on the difference.
According to a second aspect of the present invention, there is provided a recording method using an inkjet head that performs recording by ejecting ink onto a recording medium by driving an actuator, and detecting the temperature of the ink at a first time. Based on the ink temperature at the first time, determining the drive voltage at the first time, detecting the ink temperature at the second time, and based on the ink temperature at the second time. Setting the drive voltage, the temperature of the ink detected at the first time or the drive voltage at the first time determined based on the temperature, and the temperature of the ink detected at the second time or based on the temperature Obtaining a difference from the set drive voltage; determining a drive voltage at the second time based on the difference; Driving the actuator in the driving voltage at the second time when the serial determined, the recording method comprising the method comprising recording by discharging ink onto a recording medium, is provided.

  In these cases, the first time determined based on the difference between the temperature of the ink detected at the first time and the temperature of the ink detected at the second time, or the temperature of the ink detected at the first time. And the drive voltage set based on the temperature of the ink detected at the second time, and the drive voltage at the second time is determined based on the difference. Even when the temperature changes rapidly, the drive voltage does not change rapidly. Therefore, even if the temperature of the ink changes rapidly according to the driving condition or use environment during recording, it is possible to maintain good recording quality. In addition, the time interval between the first time and the second time can be arbitrarily set. By making this time interval shorter than the recording interval of one page, the temperature change of ink during the recording of one page can be achieved. Can be dealt with.

  In the ink jet recording apparatus and the recording method of the present invention, the drive voltage determination unit may determine the set drive voltage as the drive voltage at the second time when the difference is equal to or less than a predetermined value. When the difference exceeds the predetermined value, the driving is made closer to the set driving voltage from the driving voltage at the first time by a value smaller than the difference voltage between the driving voltage at the first time and the set driving voltage. The voltage may be determined as a driving voltage at the second time. In these cases, even when the temperature of the ink changes between the first time and the second time, recording can be performed using the driving voltage corresponding to the temperature change of the ink. Can be increased. That is, when the temperature change of the ink is large between the first time and the second time, the driving voltage set based on the ink temperature detected at the second time is not used as it is, but the first voltage is not used. Since the drive voltage close to the set drive voltage is used from the drive voltage at the time, it is possible to prevent the drive voltage from changing greatly and to prevent the recording quality from deteriorating. For example, when the driving voltage is lowered, the volume of ink droplets to be ejected becomes small and the ejection speed becomes slow, so that the recording density becomes thin. For this reason, when the driving voltage suddenly drops between the first time and the second time, a gray level difference occurs between the recording area at the first time and the recording area at the second time, and the recording quality deteriorates. However, according to the ink jet recording apparatus and the recording method of the present invention, since the drive voltage does not greatly decrease at the first time and the second time, the recording area of the first time and the second time Since there is no difference in density from the recording area, the recording quality can be improved.

  In the ink jet recording apparatus and the recording method of the present invention, the drive voltage determination unit may determine the drive voltage at the second time every predetermined time from the start of recording, and the predetermined period has elapsed. Thereafter, it may be determined every second time longer than the first time. The ink temperature increases corresponding to the increase in recording time for a predetermined time from the start of recording, and tends to increase gradually after the predetermined time has elapsed. Therefore, instead of determining the drive voltage at the same interval regardless of the elapsed time from the start of recording, the drive voltage is determined every first time from the start of recording, and after the predetermined period has elapsed, the first voltage is determined. By determining the drive voltage every second time longer than the time, it is possible to determine the optimum drive voltage for the change in the ink viscosity accompanying the temperature rise of the ink. In the ink jet recording apparatus and the recording method of the present invention, the interval for determining the drive voltage is set to a short time (first time) during a predetermined period in which the ink temperature rises in response to an increase in the recording time. As a result, the optimum drive voltage corresponding to the ink temperature can be used, and the recording quality can be improved. In addition, when the predetermined period has elapsed and the temperature rise of the ink is gradual, the drive voltage determination interval is set to a long time (second time), thereby reducing unnecessary determination of the drive voltage. it can. For example, as will be described later in the embodiment, when the microcomputer executes the process of determining the drive voltage, the number of processes for determining the drive voltage can be reduced, and accordingly, the load on the microcomputer Can be reduced.

  In the ink jet recording apparatus and the recording method of the present invention, when the difference exceeds a predetermined value, the driving voltage determining unit corrects the driving voltage by an amount corresponding to the predetermined value from the driving voltage at the first time. May be determined as the driving voltage at the second time. For example, the difference (V1−V2 ′) between the driving voltage (V1) at the first time and the driving voltage (V2 ′) set based on the ink temperature detected at the second time is a negative value. When the absolute value exceeds the predetermined value (ΔV), the driving voltage (V1 + ΔV) obtained by adding the predetermined value (ΔV) to the driving voltage (V1) at the first time is the driving voltage (V2) at the second time. You may decide to. Further, when the difference (V1−V2 ′) is a positive value and exceeds the predetermined value (ΔV), a driving voltage obtained by subtracting the predetermined value (ΔV) from the driving voltage (V1) at the first time. (V1−ΔV) may be determined as the drive voltage (V2) at the second time. As described above, when the difference between the drive voltage at the first time and the drive voltage set at the second time exceeds a predetermined value, the drive voltage set at the first time is not used but the set drive voltage is not used. Since the driving voltage corrected by the amount corresponding to the predetermined value can be determined as the driving voltage at the second time from the voltage, there is no possibility that the recording quality is deteriorated due to a large change in the driving voltage.

  The ink jet recording apparatus and the recording method of the present invention may further include a table in which a driving voltage is set for each of a plurality of temperature ranges. If the difference exceeds a predetermined value, the drive voltage between the drive voltage at the first time and the drive voltage set at the second time is read from the table and determined as the drive voltage at the second time. May be. For example, a table that is set so that the drive voltage decreases corresponding to the temperature rise of the ink is provided, and the difference between the drive voltage (V1) at the first time and the drive voltage (V2 ′) set at the second time ( When V1-V2 ′) is a positive value and the absolute value exceeds a predetermined value, the drive voltage (V1) at the first time is closer to the drive voltage (V2 ′) set at the second time. Drive voltage (V2), which is lower than the drive voltage at the first time but higher than the drive voltage (V2 ′) set at the second time, is read from the table. ) May be determined. By doing so, the drive voltage to be determined at the second time can be easily read. In these cases, there is no possibility that the recording quality is deteriorated by a large change in the drive voltage.

  In the ink jet recording apparatus and the recording method of the present invention, the drive voltage determining unit may determine the drive voltage at the second time each time the ink jet head scans the recording medium a predetermined number of times. Good. In these cases, even when a recording area with a low recording density and a recording area with a high recording density coexist in one recording medium, the optimum driving for the ink temperature fluctuated due to a change in the recording density Since the voltage can be used, the recording quality can be improved.

  In the ink jet recording apparatus and the recording method of the present invention, the interval between the first time and the second time may be shorter than the recording time for one recording medium. In this case, even if the ink temperature changes abruptly during recording on one recording medium, the drive voltage does not change abruptly, so that good recording quality can be maintained.

  In the ink jet recording apparatus and the recording method of the present invention, the temperature sensor may be provided in the ink jet head, and the temperature of the ink may be obtained by detecting the temperature of the ink jet head. Since the temperature of the ink in the ink jet head changes corresponding to the temperature change of the ink jet head, the temperature of the ink jet head detected by the temperature sensor can be regarded as the temperature of the ink.

<First Embodiment>
Next, a first embodiment of the present invention will be described with reference to the drawings.
[Main configuration]
The main configuration of the ink jet recording apparatus according to this embodiment will be described with reference to FIG. The ink jet recording apparatus 1 includes a transport roller 12 that feeds a recording sheet 11 (recording medium) fed from a direction indicated by an arrow F1 in the drawing in a direction indicated by an arrow F2. A carriage shaft 13 is provided on the side of the conveyance roller 12 in parallel with the rotation axis of the conveyance roller 12, and a lower end of a carriage 29 on which the inkjet head 20 is mounted is inserted into the carriage shaft 13. Yes. A carriage motor 14 is provided near one end of the carriage shaft 13, and a pulley 16 is provided near the other end of the carriage shaft 13. A pulley 15 is attached to the rotating shaft of the carriage motor 14, and an endless belt 17 is stretched between the pulley 15 and the pulley 16.

  A carriage 29 is attached to the belt 17, and the carriage 29 reciprocates along the carriage shaft 13 in directions indicated by arrows F 3 and F 4 by driving the carriage motor 14. The inkjet head 20 includes a black ink head 21 that ejects black ink, a yellow ink head 22 that ejects yellow ink, a cyan ink head 23 that ejects cyan ink, and a magenta ink head 24 that ejects magenta ink. Is provided. Each of the heads 21 to 24 includes a pressure chamber that stores ink, an actuator (for example, a piezoelectric element) that applies energy for ink ejection to the pressure chamber, and a nozzle that communicates with the pressure chamber. Each head 21 to 24 is provided with an ink cartridge 25 to 28 for supplying ink corresponding to each head. In FIG. 1, each head 21 to 24 faces the recording paper 11 conveyed by the conveying roller 12, that is, faces downward, and discharges ink downward onto the recording paper 11 to record an image.

  In the vicinity of one end of the conveying roller 12 that is out of the recording range with respect to the recording paper 11, ejection is performed from each of the heads 21 to 24 when performing flushing for ejecting defective ink from the nozzle and restoring the ejection function. An ink absorbing pad 30 made of a porous material that absorbs ink to be used is provided. In the vicinity of the other end of the conveyance roller 12 that is outside the recording range, a purge device 31 that performs purging for recovering the ink discharge function by sucking defective ink or bubbles from the nozzles of the heads 21 to 24 is disposed. ing. The purge device 31 includes a suction cap 32 that covers a nozzle surface on which a plurality of nozzles are arranged, a cam 33 that advances the suction cap 32 in a direction indicated by an arrow F6 in the drawing, and the inside of the suction cap 32 is set to a negative pressure. And a pump 34. Further, adjacent to the outside of the suction cap 32 is a capping device 36 that covers the nozzle surfaces of the heads 21 to 24 of the inkjet head 20 that have returned to the home position (home position) with caps 37 to prevent the nozzles from drying. Is provided. Further, a wiping device 50 for wiping off ink and foreign matters adhering to the nozzle surfaces of the heads 21 to 24 is provided next to the suction cap 32.

[Main configuration of control system]
Next, the main configuration of the control system of the inkjet recording apparatus 1 will be described with reference to FIG. The ink jet recording apparatus 1 includes a microcomputer (drive voltage determining unit) 70, a ROM 74, and a RAM 75. The microcomputer 70 includes an operation panel 81 for a user to give a recording instruction, a motor driver 78 for driving the carriage motor 14, a motor driver 80 for driving the LF motor 79, and the recording paper 11. A paper sensor 76 for detecting the leading edge of the ink jet head, an origin sensor 77 for detecting the origin position of the carriage 29, and a temperature sensor 88 for detecting the temperature of the inkjet head 20 (hereinafter also referred to as head temperature) are connected.

  The temperature sensor 88 is provided inside, on the outer surface, or in the vicinity of the inkjet head 20. The temperature sensor 88 directly detects the temperature of the ink jet head 20, but the temperature of the ink in the ink jet head 20 changes corresponding to the temperature change of the ink jet head 20. The temperature can be regarded as the temperature of the ink. A detection signal detected by the temperature sensor 88 is converted into a digital value by an A / D conversion circuit (not shown) provided in the microcomputer 70, and the microcomputer 70 detects that the ink jet head 20 is based on the digital value. Find the temperature.

  In the ROM 74, a table 74a shown in FIG. The table 74a is a table that is referred to when the microcomputer 70 determines the drive voltage of the inkjet head 20, and a different drive voltage is associated with each head temperature in a plurality of stages. In this embodiment, the range of the head temperature t set in the table 74a is from the lower limit “t <8 ° C.” to the upper limit “46 ° C ≦ t”, and the range is in units of 2 ° C. It is carved. The range of the driving voltage is from the upper limit “28.0 V” to the lower limit “18.0 V”, and the range is engraved in units of 0.5 V, corresponding to each head temperature range. . That is, when the head temperature t increases by 2 ° C., the drive voltage decreases by 0.5V, and conversely when the head temperature decreases by 2 ° C., the drive voltage increases by 0.5V. For example, drive voltages corresponding to head temperatures t of 23 ° C. and 25 ° C. are 24.0V and 23.5V, respectively.

  The microcomputer 70 reads the drive voltage associated with the obtained temperature from the table 74 a and sets it to the drive voltage used by the drive IC (drive unit) 83. The inkjet head 20 is driven by a driving IC 83, and the driving IC 83 is controlled by a gate array (G / A) 73. Each electrode constituting each piezoelectric element provided in the inkjet head 20 is connected to the drive IC 83, and the drive IC 83 generates a drive signal suitable for the inkjet head 20 based on the control of the gate array 73. Apply to each electrode.

  The microcomputer 70, the ROM 74, the RAM 75, and the gate array 73 are connected via an address bus 60 and a data bus 61. The microcomputer 70 generates a recording timing signal TS and a control signal RS according to a program stored in advance in the ROM 74 and transfers the signals TS and RS to the gate array 73. The gate array 73 is based on the recording data stored in the image memory 82 in accordance with the recording timing signal TS and the control signal RS, and transfer data DATA that is recording data for recording the recording data on the recording paper 11; A transfer clock TCK synchronized with the transfer data DATA, a strobe signal STB, and a recording clock ICK are generated, and these signals DATA, TCK, STB, and ICK are transferred to the drive IC 83.

  Further, the gate array 73 stores recording data transferred from an external device such as a host computer (host PC) 71 in the image memory 82. The gate array 73 generates a data reception interrupt signal WS based on the data transferred from the host computer 71 or the like, and transfers the signal WS to the microcomputer 70. The gate array 73 is connected to an encoder sensor 87 that detects the travel position of the carriage 29.

[Determination of drive voltage]
Next, processing performed by the microcomputer 70 to determine the drive voltage will be described with reference to the flowchart of FIG. The microcomputer 70 determines whether or not the power source of the ink jet recording apparatus 1 is turned on (step (hereinafter abbreviated as S) 1). If the microcomputer 70 determines that the power is turned on (S1: Yes), initial setting is performed (S1: Yes). S2). Subsequently, it is determined whether or not recording data to be recorded is stored in the image memory 82 (S3). If it is determined that the recording data is stored (S3: Yes), based on the detection signal from the temperature sensor 88. The head temperature T1 is detected (S4), the table 74a is referenced (S5), the drive voltage associated with the head temperature T1 detected in S4 is read, and the read drive voltage is first The driving voltage V1 used for recording is determined to be (S6).

  Subsequently, printing is started at the drive voltage V1 determined in S6 (S7), and it is determined whether or not printing for one scan is completed (S8). Here, one scanning means that the inkjet head 20 moves from the recording start position to the recording end position in the width direction of the recording paper 11 according to the recording data, and performs the recording operation once. If it is determined that printing for one scan has been completed (S8: Yes), 1 is added to the scan number n, which is the number of scans completed (S9), and the scan number n has reached m. It is determined whether or not (S10). Here, m is an arbitrary integer, for example, 5 or 10.

  If it is not determined that the number of scans n has reached m (S10: No), S7 to S9 are executed, and recording is continued. If it is determined that the scanning number n has reached m (S10: Yes), the head temperature T2 is detected (S11), the table 74a is referred to (S12), and the head temperature T2 detected in S11 is associated. The read drive voltage is read, and the read drive voltage is provisionally determined (set) as the drive voltage V2 used for the current recording (S13). Subsequently, an absolute value (| V1−V2 |) of the difference between the drive voltage V1 determined in the previous S6 and the drive voltage V2 temporarily determined in the current S13 is obtained, and the absolute value of the difference exceeds the predetermined value ΔV. It is determined whether or not there is (S14).

  If it is determined that the absolute value of the difference does not exceed the predetermined value ΔV (S14: No), the drive voltage V2 provisionally determined in S13 is determined as the current drive voltage V2 (S18). That is, the recording contents are such that the head temperature does not rise rapidly during the scanning of m times from the start of recording, and when the fluctuation of the driving voltage is small, the driving voltage is determined with reference to the table 74a. FIG. 5 is a graph showing an example of the relationship between the drive voltage determined by the above processing and the head temperature when recording is performed at a recording duty of 50%. The head temperature is detected a total of four times during the recording of one sheet of recording paper, and the drive voltage is determined for each detection. However, there is no rapid increase in the head temperature at each interval of the head temperature detection timing. At each head temperature detection timing, the drive voltage corresponding to the detected head temperature is read from the table 74a and determined as the drive voltage V2 each time. For example, a drive voltage of 24.5 V corresponding to a head temperature of 21 ° C. is used at the detection timing P1 when starting the recording of the first sheet of recording paper. At the next detection timing P2, a driving voltage of 23.5 V corresponding to a head temperature of 25 ° C. is used.

  In S14, when it is determined that the absolute value of the difference exceeds the predetermined value ΔV (S14: Yes), the previous (first time) drive voltage V1 is greater than the current (second time) drive voltage V2. Is determined to be large (S15), and if it is determined to be large (S15: Yes), a drive voltage obtained by subtracting a predetermined value ΔV from the previously determined drive voltage V1 is determined as the current drive voltage V2 (S16). ). In S15, when it is determined that the previous drive voltage V1 is smaller than the current drive voltage V2 (S15: No), the drive voltage obtained by adding the predetermined value ΔV to the drive voltage V1 determined last time is used as the current drive voltage. V2 is determined (S17). That is, when the absolute value of the difference between the previously determined drive voltage V1 and the currently determined drive voltage V2 exceeds the predetermined value ΔV, the previous value is determined by a predetermined value ΔV that is smaller than the absolute value of the difference. A drive voltage close to the drive voltage V2 determined this time from the drive voltage V1 determined is determined as the drive voltage V2 used this time.

  For example, it is assumed that a photograph is recorded immediately after the ink jet recording apparatus 1 is turned on. Further, it is assumed that the head temperature at the start of recording is 21 ° C. and the drive voltage V1 is 24.5V. It is assumed that the photo recording is continued even when the head temperature is detected at the next detection timing, and that the detected head temperature has reached 35 ° C. Further, it is assumed that the predetermined value ΔV is set to 2.0V. At this time, since the driving voltage associated with the head temperature of 35 ° C. in the table 4a is 21.0 V, the absolute value of the difference between the previously determined driving voltage V1 and the currently determined driving voltage V2 is 24.V. Since 5V-21.0V = 3.5V and the difference 3.5V> predetermined value 2.0V, 22.5V obtained by subtracting the predetermined value 2.0V from the previous drive voltage V1 of 24.5V is set to 22.5V. The driving voltage V2 is determined.

  That is, the current drive voltage V2 is not determined to be 21.0V suddenly lower than the previous drive voltage V1 of 24.5V, but lower than the previous drive voltage by 21.0V. 22.5V is determined. If the head temperature at the next detection timing is 36 ° C., 20.5 V associated with 36 ° C. in the table 74a is provisionally determined as the current drive voltage V2. Since the previous drive voltage V1 was 22.5V, the absolute value of the difference between the previous time and this time is 22.5V-20.5V = 2.0V, so that it does not exceed the predetermined value of 2.0V. The determined drive voltage V2 of 20.5V is directly determined as the current drive voltage V2.

  As described above, the ink temperature rapidly rises during the execution of the recording between the head temperature detection intervals, and if the drive voltage read from the table 74a is used as it is as the current drive voltage, the fluctuation from the previous drive voltage becomes large. In such a case, a drive voltage obtained by correcting a predetermined value with respect to the drive voltage used last time is used as the current drive voltage to suppress fluctuations in the drive voltage. Accordingly, there is no possibility that the ink discharge characteristics greatly change and the recording quality deteriorates due to a large fluctuation of the drive voltage during the recording. The head temperature is detected every time the number of scans n reaches an arbitrary integer m. By setting m to a value smaller than the number of scans for recording one page, recording during one page is being performed. It is possible to cope with a change in ink temperature.

  For example, in order to cope with a decrease in ink viscosity accompanying an increase in ink temperature, it is necessary to lower the driving voltage. However, if the driving voltage is drastically decreased, a recording area recorded before the driving voltage is changed and a recording area after the driving voltage is changed are recorded. Since the density difference with the recorded area becomes large, the boundary of the recording area becomes conspicuous. However, the inkjet recording apparatus 1 of this embodiment can prevent the drive voltage from fluctuating greatly by correcting the predetermined value with respect to the drive voltage used last time, so that there is no possibility that the boundary of the recording area is noticeable.

  The table 74a is configured such that when the head temperature changes by 2 ° C., the drive voltage changes by 0.5V. Therefore, if the change in the head temperature during the interval for detecting the head temperature exceeds 8 ° C., the drive is performed. The absolute value of the voltage difference exceeds a predetermined value of 2.0V. Therefore, in S14, the change in the head temperature during the interval for detecting the head temperature, that is, the absolute value | T1-T2 | of the difference between the head temperature T1 detected in S4 and the head temperature T2 detected in S11 is obtained. When the temperature exceeds 8 ° C., the current drive voltage V2 may be corrected by executing the above-described S15 to S17. If the absolute value | T1−T2 | of the head temperature difference is 8 ° C. or less, the drive voltage corresponding to the detected head temperature is read from the table 74a and determined as the current drive voltage V2. Good. That is, the difference between the head temperature (ink temperature) detected last time (first time) and the head temperature (ink temperature) detected this time (second time) is obtained, and the current drive voltage is determined based on the difference. May be.

  The stage of the head temperature set in the table 74a is not limited to 2 ° C increments, but may be 0.5 ° C, 1 ° C, 2.5 ° C increments, or increments of 3 ° C or more. The setting can also be made in increments of 0.125 V, 0.25 V, 0.625 V, or increments of 0.75 V or more depending on the head temperature stage. The predetermined value ΔV can also be changed according to the increment of the drive voltage set in the table 74a.

[Effect of the first embodiment]
(1) As described above, when the ink jet recording apparatus 1 of the first embodiment is used, the head temperature is detected each time the ink jet head 20 scans m times to perform recording, and the detected head temperature is set. Since the drive voltage can be switched based on this, recording can be performed using the optimum drive voltage corresponding to the change in ink viscosity accompanying the change in the head temperature, so that the recording quality can be improved. For example, even in a case where a recording area having a low recording density and a recording area having a high recording density are mixed in one recording sheet 11, the driving voltage optimum for the ink temperature fluctuated due to a change in the recording density Recording quality can be improved.

  (2) In addition, when the difference between the previously determined drive voltage V1 and the currently temporarily determined drive voltage V2 exceeds a predetermined value ΔV, a voltage obtained by correcting the previously determined drive voltage by ΔV is the current drive voltage. It can be used as V2. That is, when the temperature change of the ink between the previous time and the current time is large, the drive voltage V2 provisionally determined based on the ink temperature detected this time is not used as it is, but the drive voltage V1 determined last time is corrected by ΔV. By using the drive voltage, it is possible to avoid a decrease in recording quality due to a large change in the drive voltage.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 6 is a flowchart showing a flow of processing executed by the microcomputer provided in the ink jet recording apparatus of this embodiment to determine the drive voltage, and FIG. 7 is a flowchart showing the continuation of the processing in FIG. . The ink jet recording apparatus of this embodiment is characterized in that the interval for determining the drive voltage is shortened at the time of recording the first sheet and is increased after the second sheet. The ink jet recording apparatus of this embodiment has the same configuration and function as the ink jet recording apparatus 1 of the first embodiment except for a part of the processing executed by the microcomputer, so the description of the same parts is simplified or omitted. For the same configuration, a common code is used.

  When the microcomputer 70 performs the initial setting (S2 in FIG. 6), the microcomputer 70 turns on a recording initial flag indicating that it is the first recording immediately after the power is turned on (S3). Subsequently, it is determined whether there is recording data to be recorded (S4). If it is determined (S4: Yes), the head temperature T1 is detected based on the detection signal from the temperature sensor 88 (S5). ), The table 74a is referred to (S6), the drive voltage associated with the head temperature detected in S5 is read, and the read drive voltage is determined as the drive voltage V1 used for the first recording. (S7).

  Subsequently, printing is started at the drive voltage V1 determined in S7 (S8), and it is determined whether or not printing for one scan is completed (S9). If it is determined that printing for one scan has been completed (S9: Yes), 1 is added to the scan number n, which is the number of scans completed (S10), and the print initial flag is turned on in the previous S3. It is determined whether or not it is performed (S11). That is, it is determined whether the recording to be executed is the first recording immediately after the power is turned on. If it is determined that the recording initial flag is on (S11: Yes), it is determined whether or not the scanning number n has reached m1 (S12). If it is determined that the recording initial flag is not turned on (S11: No), it is determined whether the number of scans n has reached m2 (S13). Here, m1 and m2 are each an arbitrary integer, and m1 <m2. For example, m1 = 5 and m2 = 10.

  Here, when it is determined in S12 that the scanning number n has reached m1 (S12: Yes), or when it is determined in S13 that the scanning number n has reached m2 (S13: Yes), the head temperature T2 is set. Detecting (S14 in FIG. 7), referring to the table (S15), reading the drive voltage associated with the head temperature detected in S14, and using the read drive voltage to perform the current recording. The drive voltage V2 is provisionally determined (S16). In other words, since m1 <m2, the interval for determining the drive voltage (first time) is short during the first recording period immediately after the power is turned on, and the interval after the second sheet (second time) is long. Become. Subsequently, similarly to S15 to S18 (FIG. 4) of the first embodiment, the temporarily determined drive voltage V2 is corrected (S18 to S21).

  Subsequently, it is determined whether or not the first sheet has been recorded (S22). If it is determined that the recording has been completed (S22: Yes), the recording initial flag is turned off (S23). In this way, once the recording initial flag is turned off, in the subsequent cycles, a negative determination is made every time S11 is executed, so it is determined whether or not the number of scans n has reached m2. That is, in the second and subsequent recordings, the interval for determining the drive voltage is longer than in the first recording.

[Effects of Second Embodiment]
(1) As described above, when the ink jet recording apparatus 1 of the second embodiment is used, the head temperature tends to increase corresponding to the increase in the recording time as in the first recording sheet immediately after the power is turned on. In the strong period, the optimum drive voltage corresponding to the ink temperature can be used by shortening the interval for determining the drive voltage, so that the recording quality can be improved. Also, during the period in which the head temperature rises slowly or stagnates, such as after the second sheet of recording paper, the number of processes for determining the drive voltage is increased by increasing the interval for determining the drive voltage. Therefore, the load on the microcomputer 70 can be reduced accordingly.

  (2) The ink jet recording apparatus of the second embodiment is the ink jet recording of the first embodiment except that the interval for determining the drive voltage is changed between the first sheet immediately after power-on and the second and subsequent sheets. Since it has the same configuration and function as the device 1, the effects (1) and (2) of the first embodiment can also be achieved.

<Other embodiments>
(1) In the first and second embodiments, when the absolute value of the difference between the drive voltage V1 used last time and the drive voltage V2 scheduled to be used this time exceeds ΔV, the previous drive voltage V1 is set to ΔV The drive voltage corrected only by this is determined as the drive voltage V2 to be used this time, but a value smaller than ΔV can be set as a correction value separately from ΔV. Also in this case, the same effect as the first and second embodiments can be obtained.

  (2) Since the drive voltage decreases when the head temperature (ink temperature) increases and the drive voltage increases when the head temperature decreases, the absolute difference between the head temperature detected last time and the head temperature detected this time is absolute. The drive voltage V2 used this time can also be determined based on the determination result of whether or not the value exceeds Δ degrees. For example, when the difference is equal to or less than Δ degrees, the drive voltage V2 provisionally determined based on the temperature detected this time is determined as the drive voltage V2 to be used this time, and when the difference exceeds the Δ degree, The drive voltage V1 determined based on the temperature detected last time and the drive voltage V2 temporarily determined based on the temperature detected this time are smaller than the difference between the drive voltage V1 determined last time and the drive voltage V2 temporarily determined this time. The approaching drive voltage is determined as the drive voltage V2 used this time. Also in this case, the same effect as the first and second embodiments can be obtained.

  (3) In the above embodiment, the head temperature detection timing is determined based on the number of scans of the inkjet head 20, but may be determined based on the recording time. For example, the head temperature is detected when it is determined that the recording time has reached a predetermined time. In this case, by setting the predetermined time shorter than the recording time interval for one page, it is possible to cope with a change in ink temperature during printing of one page.

  (4) In the above-described embodiment, the table 74a in which different driving voltages are associated with each head temperature is provided. However, the present invention is not limited to this. For example, the correction indicating the correction value of the drive voltage corresponding to the difference in ink temperature between the first time and the second time, or the difference between the drive voltage at the first time and the drive voltage provisionally determined at the second time. You may further provide the correction voltage table which preset the voltage. As shown in the correction voltage table 74b of FIG. 9, when the absolute value of the ink temperature difference exceeds a predetermined value (| T1-T2 |> 8), or as shown in the correction voltage table 74c of FIG. When the absolute value of the drive voltage difference exceeds a predetermined value (| V1−V2 |> 2), the correction voltage may be set to a constant value (ΔV = 2.0). Next, the flow of processing executed by the microcomputer provided in the ink jet recording apparatus of this embodiment to determine the drive voltage at the second time will be briefly described with reference to the flowchart shown in FIG. In FIG. 11, each step from the start to S13 is the same as each step from the start to S13 in FIG. In FIG. 11, after the drive voltage V2 is provisionally determined in S13, the absolute value of the difference between the ink temperature at the first time and the ink temperature at the second time, or the drive voltage at the first time and the second time is provisionally determined. The absolute value of the difference from the drive voltage is calculated (S14). Next, the correction voltage table 74b or 74c is referred to (S15), and ΔV corresponding to the difference calculated in S14 is determined as a correction voltage (S16). Next, it is determined whether or not the drive voltage V1 determined in S6 is greater than the drive voltage V2 provisionally determined in S13 (S17). If it is determined that the drive voltage V1 is greater (S17: Yes), the drive determined in S6 is determined. A drive voltage obtained by subtracting the correction voltage ΔV determined in S16 from the voltage V1 is determined as the drive voltage V2 at the second time (S18). When it is determined that the drive voltage V1 determined in S6 is equal to or lower than the drive voltage V2 provisionally determined in S13 (S17: No), the correction voltage ΔV determined in S16 is set to the drive voltage V1 determined in S6. The added drive voltage is determined as the drive voltage V2 at the second time (S19). As described above, when the drive voltage at the second time is determined, the correction voltage ΔV corresponding to the absolute value of the ink temperature difference or the absolute value of the drive voltage difference is determined from the correction voltage table 74b or 74c. It may be determined by reading and correcting the driving voltage at the first time by ΔV. By determining the drive voltage at the second time in this manner, the drive voltage does not change abruptly even when the ink temperature changes abruptly, as in the above-described embodiment, and good recording is achieved. Quality can be maintained. Note that S14 to S20 in the flow of the present embodiment can be applied to the second embodiment by replacing S17 to S21 in the second embodiment.

  (5) In the above embodiment, the microcomputer 70 sets the drive voltage corresponding to the temperature detected by the temperature sensor 88 with reference to the table 74a, but is not limited thereto. For example, the microcomputer 70 may store in advance a calculation formula for obtaining the drive voltage from the temperature detected by the temperature sensor 88. The microcomputer 70 may calculate and set the drive voltage from the temperature detected by the temperature sensor 88 based on the calculation formula every time the temperature sensor 88 detects the temperature. By doing so, it is not necessary to prepare the table 74a in advance, and the ROM 74 can be used effectively.

  (6) In the above embodiment, the temperature of the ink jet head detected by the temperature sensor 88 is regarded as the temperature of the ink. For example, the inside of the ink cartridges 25 to 28, the ink flow paths of the ink heads 21 to 24, or the ink A temperature sensor 88 may be provided inside the flow path from the cartridge to the inkjet head, and the temperature of the ink in each ink cartridge or the ink in each ink flow path may be directly measured. In this case, in order to measure the ink temperature as close as possible to the ink temperature at the time of actual ejection, it is desirable that the temperature sensor 88 be provided near the nozzles in each ink flow path.

  (7) In the embodiment, the absolute value | T1-T2 | of the difference T2 between the temperature T1 of the ink detected at the first time and the temperature of the ink detected at the second time, or the first time. The difference between the drive voltage V1 at the first time determined based on the ink temperature T1 detected in step 1 and the drive voltage V2 provisionally determined (set) based on the ink temperature detected at the second time When the absolute value | V1−V2 | is equal to or less than a predetermined value, the provisionally determined drive voltage V2 is determined as the drive voltage at the second time, but is not limited thereto. For example, in S14 of FIG. 4, when | T1-T2 | is equal to or smaller than a predetermined value ΔT, or when | V1-V2 | is equal to or smaller than a predetermined value ΔV, in S18, instead of the set drive voltage V2, the first The driving voltage V1 at the time may be determined as the driving voltage at the second time as it is. At this time, when | T1-T2 | or | V1-V2 | exceeds the predetermined value, the driving voltage at the second time may be determined in the same manner as in the embodiment. According to this embodiment, when the difference is equal to or smaller than the predetermined value, that is, while the temperature change of the ink is within the predetermined range, the drive voltage is kept constant. Further, only when the difference exceeds a predetermined value, that is, when the temperature of the ink changes suddenly, the driving voltage is corrected by an amount corresponding to the predetermined value from the driving voltage kept constant. Therefore, it is not necessary to change the drive voltage while the temperature change of the ink is small, and the drive voltage can be easily controlled. Further, even when the ink temperature changes suddenly, the drive voltage does not change suddenly, and good recording quality can be maintained.

It is explanatory drawing which shows the main structures of the inkjet recording device which concerns on 1st Embodiment. FIG. 2 is a block diagram illustrating a main configuration of a control system of the inkjet recording apparatus 1 illustrated in FIG. 1. It is explanatory drawing of the table 74a. It is a flowchart which shows the flow of the process which the microcomputer 70 performs in order to determine a drive voltage. It is a graph which shows an example of the relationship between a drive voltage and head temperature. It is a flowchart which shows the flow of the process which the microcomputer 70 performs in order to determine a drive voltage in 2nd Embodiment. It is a flowchart which shows the continuation of the process of FIG. It is a graph which shows the relationship between the head temperature and drive voltage in the conventional inkjet recording device. It is explanatory drawing of the correction voltage table 74b. It is explanatory drawing of explanatory drawing 74c of a correction voltage table. It is a flowchart which shows the flow of the process which the microcomputer 70 performs in order to determine a drive voltage in other embodiment.

Explanation of symbols

1 Inkjet recording apparatus 11 Recording paper (recording medium)
20 Inkjet head 74a Table

Claims (18)

An inkjet recording apparatus having an inkjet head that performs recording by ejecting ink onto a recording medium by driving an actuator,
A temperature sensor for detecting the temperature of the ink;
A driving voltage determining unit that determines a driving voltage for driving the actuator according to the temperature of the ink detected by the temperature sensor, and determines a new driving voltage when the temperature of the ink changes;
A drive unit that drives the actuator with the drive voltage determined by the drive voltage determination unit,
The driving voltage determining unit obtains a difference between the temperature detected at the first time or the driving voltage determined at the first time and the temperature detected at the second time or the driving voltage set based on the temperature. An inkjet recording apparatus that determines a driving voltage at the second time based on the difference.   The drive voltage determination unit determines the set drive voltage as the drive voltage at the second time when the difference is equal to or less than a predetermined value, and the first time when the difference exceeds the predetermined value. A drive voltage that is close to the set drive voltage from the drive voltage at the first time by a value smaller than a difference voltage between the drive voltage at and the set drive voltage is determined as the drive voltage at the second time. Item 10. The ink jet recording apparatus according to Item 1.   The drive voltage determination unit determines the drive voltage at the second time every first time for a predetermined period from the start of recording, and every second time longer than the first time after the predetermined period elapses. The inkjet recording apparatus according to claim 1, which is determined as follows.   When the difference exceeds a predetermined value, the driving voltage determination unit determines a driving voltage corrected by an amount corresponding to the predetermined value from the driving voltage at the first time as the driving voltage at the second time. The ink jet recording apparatus according to claim 1.   The inkjet recording apparatus according to claim 1, further comprising a table in which a driving voltage is set for each of a plurality of temperature ranges.   When the difference exceeds a predetermined value, the drive voltage determination unit reads a drive voltage between the drive voltage at the first time and the set drive voltage from the table, and drives the drive voltage at the second time The inkjet recording apparatus according to claim 5, which is determined as follows.   2. The ink jet recording apparatus according to claim 1, wherein the drive voltage determination unit determines the drive voltage at the second time each time scanning of the ink jet head with respect to the recording medium is performed a predetermined number of times.   The inkjet recording apparatus according to claim 1, wherein an interval between the first time and the second time is shorter than a recording time for one recording medium.   The inkjet recording apparatus according to claim 1, wherein the temperature sensor is provided in the inkjet head, and the temperature of the ink is obtained by detecting the temperature of the inkjet head. A recording method using an inkjet head that performs recording by discharging ink onto a recording medium by driving an actuator,
Detecting the temperature of the ink at the first time;
Determining the drive voltage at the first time based on the temperature of the ink at the first time;
Detecting the temperature of the ink at the second time;
Setting a drive voltage based on the temperature of the ink at the second time;
The difference between the temperature of the ink detected at the first time or the driving voltage at the first time determined based on the temperature and the temperature of the ink detected at the second time or the driving voltage set based on the temperature. Seeking and
Determining a driving voltage at the second time based on the difference;
Driving the actuator with the determined driving voltage at the second time, and discharging and recording ink on the recording medium;
Recording method.   When the difference is less than or equal to a predetermined value, the set driving voltage is determined as the driving voltage at the second time, and when the difference exceeds the predetermined value, the driving voltage at the first time and the setting The drive voltage at the second time is determined as a drive voltage at which the drive voltage at the first time is close to the set drive voltage by a value smaller than a difference voltage with respect to the set drive voltage. Recording method.   The drive voltage at the second time is determined every first time for a predetermined period from the start of recording, and the drive voltage at the second time is every second time longer than the first time after the predetermined period has elapsed. The recording method according to claim 10, wherein:   11. The recording according to claim 10, wherein when the difference exceeds a predetermined value, a driving voltage corrected by an amount corresponding to the predetermined value from the driving voltage at the first time is determined as the driving voltage at the second time. Method.   The recording method according to claim 10, wherein the driving voltage at the second time is determined with reference to a table in which the driving voltage is set for each of the temperature ranges divided into a plurality.   The drive voltage between the drive voltage at the first time and the set drive voltage is read from the table and determined as the drive voltage at the second time when the difference exceeds a predetermined value. The recording method described in 1.   The recording method according to claim 10, wherein the driving voltage at the second time is determined every time scanning of the inkjet head with respect to the recording medium is performed a predetermined number of times.   The recording method according to claim 10, wherein an interval between the first time and the second time is shorter than a recording time for one recording medium.   The recording method according to claim 10, wherein the temperature of the ink is a temperature of the ink in the inkjet head, and the temperature of the ink is obtained by detecting the temperature of the inkjet head.

Images