JP2007001304A - Ink jet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an ink jet recording apparatus which can improve printing quality at bar outlines of bar-code. <P>SOLUTION: When it is determined to be printing of bar-code (S1: Yes), print data is read (S2). When presence of corresponding dots is determined (S3: Yes), whether there are dots to be printed before/after the corresponding dots is determined (S4). Herein, if there is no dots to be printed before or after the corresponding dots, in other words, when they are determined to be the dots for printing ends of the bar-code in a main scanning direction (S4: No), print data selecting a drive waveform signal B for discharging one ink droplet per one dot is generated (S7). If they are determined not to be the dots for printing the ends of the bar-code in the main scanning direction (S4: Yes), print data selecting a drive waveform signal A for discharging three ink droplets per one dot is generated (S5). Thus, since the end of the bar-code is printed merely by one ink droplet, the amount of blurred ink in the main scanning direction can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs recording by ejecting ink from a nozzle to a printing medium by driving an actuator.

  2. Description of the Related Art Conventionally, as this type of ink jet recording apparatus, there is known an apparatus that controls dot printing in order to prevent so-called blurring in which a dot spreads into a blank portion in a contour portion of a printed image (Patent Documents 1 to 4). . In particular, in the case of printing a barcode (Patent Documents 1 and 3), there is a great demand for preventing erroneous reading of the barcode.

JP 2003-237059 A JP 2002-292848 A JP 2000-103042 A JP 2003-285453 A

However, all of those described in Patent Documents 1 to 3 eject one drop of ink from a nozzle to print one dot on a printing medium. When printing the periphery of an image, other than the periphery. Ink droplets with a volume smaller than that for printing are used, but since the size of one dot depends on one ink droplet, variations in the volume of the ink droplets cause the shape, size and density of the dots, etc. The print quality at the periphery of the image is degraded.
In addition, the image described in Patent Document 4 prints one dot with one drop of ink at the periphery of the image, and prints one dot with two or three ink drops other than the periphery, but has a plurality of pulses. By dividing the common drive waveform by the timing signal, drive pulses for 1 drop, 2 drops and 3 drops are obtained.
However, since the state of residual pressure fluctuation in the ink flow path after ink droplet ejection differs depending on the number of ink droplets ejected continuously, the number of ink droplets ejected continuously can be determined simply by dividing the common drive pulse. Therefore, it is not possible to give the ink the optimum discharge energy according to the ink quality, so that the print quality at the periphery of the image is lowered.
In other words, since it is difficult to accurately control the size of the dots in any of Patent Documents 1 to 4, there is a risk that the dots at the periphery of the image will spread and the print quality will deteriorate.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to realize an ink jet recording apparatus capable of improving the print quality of the image periphery in order to solve the above problems.

  In order to solve the above problem, the invention described in claim 1 includes an ink flow path, a nozzle communicating with the ink flow path, and an actuator that supplies energy for discharging the ink in the ink flow path. And a control circuit for outputting a drive waveform signal for driving the actuator, the print head is moved in the main scanning direction with respect to the print medium, and the drive waveform signal is transferred to the actuator. In the ink jet recording apparatus that discharges the ink in the ink flow path from the nozzle to the print medium, the control circuit changes the number of ink droplets discharged for one dot printing. Storage means for storing a plurality of types of drive waveform signals, and the front and rear of the dots continuously printed in the main scanning direction. Determination means for determining the presence or absence of dots to be printed on, and selection means for selecting a drive waveform signal to be output from the storage means to the actuator based on the determination of the determination means. When it is determined that there are dots to be printed both before and after, the selection unit selects a drive waveform signal for ejecting a plurality of ink droplets from the storage unit and outputs the drive waveform signal to the actuator. When the determination unit determines that there is no dot to be printed before or after the dot, the selection unit prints the dot before or after the dot. A drive waveform signal for ejecting a smaller number of ink droplets than the drive waveform signal selected when it is determined that there is a dot is selected from the storage means and output to the actuator. Using the technical means of.

Here, the “inkjet recording device” includes a type that can complete printing from start to finish without receiving print data from a host device such as a host computer, and a printer connected to a personal computer. , A device that receives print data from a host device and performs printing, and a type that combines a host device. For this reason, in the latter type, at least one of the “control circuit”, “storage means”, “determination means”, and “selection means” may be provided in either the host apparatus or the printing apparatus. Good.
Further, generally, when a single printing pulse is applied to an actuator, a plurality of satellite droplets are ejected together with the main ink droplets. These satellite droplets usually land on almost the same location on the printing medium, and have one dot. Therefore, the main ink droplet and the satellite droplet are combined and counted as one ink droplet.

  According to a second aspect of the present invention, there is provided a print head comprising an ink flow path, a nozzle communicating with the ink flow path, and an actuator for applying energy to the ink in the ink flow path, and the actuator And a control circuit for outputting a drive waveform signal for driving the ink, and by moving the print head in the main scanning direction with respect to the print medium and outputting the drive waveform signal to the actuator, In the ink jet recording apparatus that discharges the ink to the print medium, the control circuit includes a temperature detecting unit that detects an environmental temperature in which the ink jet recording apparatus is placed, and a dot among the dots that are continuously printed in the main scanning direction. Determination means for determining the presence or absence of dots to be printed both before and after the dots, and the determination means When a dot to be printed is determined to be on both sides, a drive waveform signal for discharging a plurality of ink droplets is output to the actuator for the dot, and the determination means When it is determined that there is no dot to be printed, and the temperature detected by the temperature detection means is higher than a predetermined temperature, a drive waveform signal for ejecting a plurality of ink droplets is output to the actuator for the dot. When the determination unit determines that there is no dot to be printed before or after the dot, and the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature, Technical means is used for outputting to the actuator a drive waveform signal for ejecting a smaller number of ink droplets than the drive waveform signal when the temperature is higher than a predetermined temperature.

  According to a third aspect of the present invention, in the ink jet recording apparatus according to the second aspect, the control circuit stores a plurality of types of the drive waveform signals that differ in the number of ink droplets ejected for one-dot printing. And a selection means for selecting a drive waveform signal to be output from the storage means to the actuator based on the judgment of the judgment means, and the judgment means prints both before and after the dot. When it is determined that there is a dot, the selection unit selects a drive waveform signal for ejecting a plurality of ink droplets from the storage unit for the dot, and outputs the drive waveform signal to the actuator. When it is determined that there is no dot to be printed either before or after and the temperature detected by the temperature detecting means is higher than a predetermined temperature, the selecting means A drive waveform signal for ejecting a plurality of ink droplets from the storage unit is selected and output to the actuator for the dot, and the determination unit prints a dot to be printed either before or after the dot. And when the temperature detected by the temperature detection means is equal to or lower than a predetermined temperature, the selection means uses the drive waveform signal when the temperature is higher than the predetermined temperature from the storage means for the dot. A technical means for selecting and outputting a drive waveform signal for ejecting a small number of ink droplets to the actuator is used.

  According to a fourth aspect of the present invention, in the inkjet recording apparatus according to any one of the first to third aspects, the determination unit replaces the determination with respect to whether or not there is a dot to be printed before and after the dot. Only the presence / absence of a dot to be printed before a dot is determined, and the selection means selects the drive waveform signal based on the determination by the determination means for the presence / absence of a dot to be printed before the dot. The technical means is used.

  According to a fifth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, the determination means replaces the determination with respect to the presence or absence of dots to be printed before and after the dots. A technique for determining only the presence or absence of a dot to be printed after a dot, and the selection means selects the drive waveform signal based on the determination by the determination means on the presence or absence of a dot to be printed after the dot. Use appropriate means.

  According to a sixth aspect of the present invention, in the ink jet recording apparatus according to the first or third aspect, the storage means outputs a drive waveform signal for ejecting three ink droplets for one dot and one ink droplet for one dot. The technical means of storing the drive waveform signal to be discharged is used.

According to a seventh aspect of the present invention, in the ink jet recording apparatus according to any one of the first to sixth aspects, the control circuit determines whether or not the image to be printed is a bar code. A technical means for performing the above control is used.
The above-mentioned “barcode” is a two-dimensional code formed by arranging a barcode or black region and a white region in a matrix form by arranging a linear or belt-like black region at predetermined intervals across a white region. It means to include.

(Effect of the invention of claim 1)
When there are dots to be printed before and after the dot to be printed, a drive waveform signal for ejecting a plurality of ink droplets is output to the actuator, and there are no dots to be printed before or after the dot Can output a drive waveform signal for ejecting a smaller number of ink droplets than the drive waveform signal to the actuator. That is, at the edge of the image to be printed, by reducing the number of ejected ink droplets, the volume of the ink droplets used for printing one dot can be reduced, so that the volume of one ink droplet itself is reduced. The shape, size, density, and the like of dots printed on the edge of the image can be controlled more accurately than what is to be done.
In addition, since the actuator can be driven by a dedicated drive waveform signal corresponding to the number of ink droplets to be ejected, the shape, size, density, and the like of the printed dots can be accurately controlled.

For example, considering the fact that the state of residual pressure fluctuation in the ink flow path after ink droplet ejection differs depending on the number of ink droplets ejected continuously, a drive waveform signal is created for each number of ink droplets. Is stored in the storage means. Then, the drive waveform signal selected from the storage means is output to the actuator. As a result, the optimum ejection energy corresponding to the number of ink droplets ejected continuously can be given to the ink, so that the shape, size, density, etc. of the dots printed on the edge of the image can be accurately controlled. Can do.
Even if individual differences exist in the characteristics of the inkjet head, such as the flow resistance of the ink flow path, a drive waveform signal corresponding to the individual difference can be created. Can be absorbed.
As described above, according to the first aspect of the present invention, it is possible to realize an ink jet recording apparatus capable of suppressing the spread of dots at the periphery of the image and improving the print quality.

(Effect of the invention described in claim 2)
According to the experiment by the present inventor, when dots are printed in the main scanning direction in a state where the environmental temperature is low and the viscosity of the ink is reduced, the ink that forms the printed dots is the main scanning rather than the sub scanning direction. It was found that there was a tendency to ooze a lot in the direction.
This is because, when the temperature of the ink is lowered, the viscosity of the ink is increased. Therefore, when one dot is printed with a plurality of ink droplets, the landing position of each ink droplet is shifted, and the dots spread in the main scanning direction. It is thought that it is one of.
However, in the invention according to claim 2, when the environmental temperature where the inkjet recording apparatus is placed when printing dots at the edge of an image is lower than a predetermined temperature, the ink droplets discharged for printing one dot Since the number of dots can be reduced, the spread of dots in the main scanning direction can be eliminated, so that the print quality at the edge of the image can be improved.

(Effect of the invention according to claim 3)
Even when there is no dot to be printed before or after the dot to be printed, if the environmental temperature is higher than the predetermined temperature, a plurality of ink droplets are ejected to print the dot, and the environmental temperature is lower than the predetermined temperature. Can print the dots by ejecting a smaller number of ink droplets than the ink droplets when the environmental temperature is higher than the predetermined temperature, so that the amount of ink for printing the dots is reduced, and the dots It is possible to reduce the amount of ink that oozes out in the main scanning direction.
In addition, a storage unit that stores a plurality of types of drive waveform signals that differ in the number of ink droplets that are ejected for one-dot printing is provided, and the drive waveform signals can be selected from the storage unit and output to the actuator. .

That is, a dedicated drive waveform signal in which the number of ink droplets ejected for one dot differs depending on the environmental temperature is stored in the storage means for each range of the environmental temperature, and the environmental temperature when printing is performed. Since the corresponding drive waveform signal can be selected from the storage means and output to the actuator, the shape, size, density, etc. of the dots can be accurately controlled in accordance with the environmental temperature.
In addition, even if there are individual differences in the ink jet head, such as flow path resistance of the ink flow path, it is possible to create a drive waveform signal corresponding to the individual difference, and thus variations in ink ejection characteristics due to individual differences Can be absorbed.

(Effect of invention of Claim 4 or 5)
The effect of the ink jet recording apparatus according to any one of claims 1 to 3 is that there is no dot to be printed only before or after the dot to be printed, or the temperature should be printed at a predetermined temperature or lower. When there are no dots to be printed only before or after the dots, by reducing the number of ink droplets to be ejected, the spread of dots at the front or rear edge in the main scanning direction of the image is suppressed and the print quality is improved. It may be.

(Effect of the invention described in claim 6)
According to an experiment conducted by the present inventor, when printing in the main scanning direction from the edge of the image, one dot printed on the edge of the image is printed with one ink droplet, and for the other dots, one dot is printed. It was found that the amount of bleeding in the main scanning direction at the edge of the image can be reduced by printing with three ink droplets.
Therefore, as in the sixth aspect of the invention, a drive waveform signal for ejecting three ink droplets per dot and a drive waveform signal for ejecting one ink droplet per dot are stored in the storage means. When printing the edge of the image, the drive waveform signal for ejecting one ink droplet per dot is selected from the storage means, and when printing the region other than the edge of the image, three ink droplets are printed per dot. By selecting the drive waveform signal to be ejected, it is possible to perform high quality printing with less blurring in the main scanning direction at the edge of the image.

(Effect of the invention described in claim 7)
The control circuit determines whether or not the image to be printed is a bar code. When the image is a bar code, the control circuit performs the above-described control and can form a bar code that does not cause misreading.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings.
[Main configuration of inkjet recording apparatus]
First, the main configuration of the ink jet recording apparatus will be described with reference to FIG. FIG. 1 is an explanatory plan view showing the main configuration of the inkjet recording apparatus.
Two guide shafts 6 and 7 that face each other are provided inside the ink jet recording apparatus 1, and a head holder 9 that also serves as a carriage is attached to the guide shafts 6 and 7. The head holder 9 holds a print head that performs printing by discharging ink onto the printing paper P, that is, an inkjet head 30. The inkjet head 30 includes a head main body provided with nozzles, and an actuator that applies energy for ink ejection to an ink flow path communicating with each nozzle. In this embodiment, a piezoelectric actuator using a piezoelectric element is used as the actuator, and the actuator is disposed so as to constitute a part of the wall surface of the ink flow path.

  In the head body, a black ink nozzle row in which a plurality of nozzles for discharging black ink droplets are arranged, a yellow ink nozzle row in which a plurality of nozzles for discharging yellow ink droplets are arranged, and a plurality of nozzles for discharging cyan ink droplets Are arranged, and a magenta ink nozzle row in which a plurality of nozzles for ejecting magenta ink droplets are arranged. The opening of each nozzle faces the printing surface of the printing paper P fed into the ink jet recording apparatus via a predetermined gap.

The head holder 9 is attached to an endless belt 11 that is rotated by a carriage motor 10, and reciprocates in the main scanning direction along the guide shafts 6 and 7 by driving the carriage motor 10.
The inkjet recording apparatus 1 also includes an ink tank 5a containing yellow ink, an ink tank 5b containing magenta ink, an ink tank 5c containing cyan ink, and an ink tank containing black ink. 5d. Each of the ink tanks 5a to 5d is connected to the inkjet head 30 via flexible tubes 14a, 14b, 14c, and 14d, and a tube joint 20, respectively. The ink stored in each ink tank is supplied to the corresponding ink flow path in the inkjet head 30.

  Further, at the left end in the moving direction of the head holder 9, there is provided an absorbing member 4 that absorbs defective ink ejected from the nozzles during flushing. At the right end of the moving direction of the head holder 9, there is provided a purge device 2 that sucks defective ink inside the inkjet head 30 from the nozzles during purging, and on the left side of the purge device 2 adheres to the nozzle surface. A wiper 3 for wiping off the ink that has been removed is provided.

[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 CPU 57 and a gate array 60. The CPU 57 executes main control necessary for printing such as a printing operation command to the drive circuit 80, printing control described later, output of maintenance commands such as flushing and purging. The gate array 60 receives the print data transmitted from the host computer 71 via the interface (I / F) 41, expands the print data, and controls to store it in the image memory 51. A ROM 43 and a RAM 44 are connected to the CPU 57 and the gate array 60 via an address bus and a data bus.

The ROM 43 includes a storage area 43a in which a drive waveform signal that is a source of a drive signal for the drive circuit 80 to drive the piezoelectric actuator 32 is stored. In this embodiment, in the storage area 43a, a drive waveform signal B for ejecting one ink droplet for one dot printing and three ink droplets for one dot printing are continuously ejected. A drive waveform signal A is stored.
Further, in a storage area other than the storage area 43a, a computer program for the CPU 57 to execute print control described later is stored. The RAM 44 temporarily stores various data received by the gate array 60 from the host computer 71, processing results of the CPU 57, and the like.

  In addition, the CPU 57 includes a medium sensor 58 that detects whether or not the printing paper P is loaded, an origin sensor 46 that detects that the inkjet head 30 is at the home position, and an environment in which the inkjet recording apparatus 1 is placed. A temperature sensor 59 for measuring temperature, a motor driver 48 for driving the carriage motor 10, a motor driver 49 for driving a paper feed motor (LF motor) 50, an operation panel 56 for supplying various signals to the CPU 57, etc. are connected. Has been.

An image memory 51 that temporarily stores print data received from the host computer 71 as image data is connected to the gate array 60.
The gate array 60 includes a determination unit 61 that determines whether or not barcode printing is performed, and a determination unit that determines whether or not there are dots to be printed before and after the dot among the dots that are continuously printed in the main scanning direction. 62 and data generation means 63 are provided. The data generation unit 63 generates print data for executing printing by the drive waveform signal A and print data for executing printing by the drive waveform signal B based on the determination result of the determination unit 62.

  As shown in FIG. 4, the drive waveform signal A is a drive waveform signal for printing one dot by ejecting three ink droplets for one dot of print data, and the drive waveform signal B is 1 This is a drive waveform signal for printing one dot by ejecting one ink droplet for the print data for dots. In this embodiment, the print data for selecting the drive waveform signal A is composed of 2 bits of “01”, and the print data for selecting the drive waveform signal B is composed of 2 bits of “10”. “00” is data indicating non-printing (no dots) (hereinafter referred to as non-printing data).

(Main configuration of drive circuit)
Next, the main configuration of the drive circuit 80 will be described with reference to FIG. In this embodiment, the inkjet head 30 has a total of 64 channels, ch0 to ch63.
The drive circuit 80 includes a serial / parallel conversion circuit 81, a latch circuit 82, a selector 83 disposed for each channel, and a driver 84 disposed for each channel. The serial / parallel conversion circuit 81 is composed of a 64-bit shift register, and receives print data 52 serially transferred in synchronization with the transfer clock 53 from the gate array 60 (FIG. 2). The print data is converted into parallel data according to the rising edge, thereby performing serial / parallel conversion of the print data. That is, the print data 52 generated by the data generation means 63 is set for each channel as 2-bit selection signals sel-0 and sel-1.

  The latch circuit 82 latches each parallel data output from the serial / parallel conversion circuit 81 in accordance with the rising edge of the latch signal 54 transferred from the gate array 60. The 64 selectors 83 provided for each channel each have a plurality of types of drive waveform signals A or drive waveform signals B transferred from the gate array 60 based on the parallel print data output from the latch circuit 82. Select and output.

The drive waveform signals A and B stored in the storage area 43a of the ROM 43 are repeatedly output from the gate array 60 to the selector 83 at a constant cycle, and this is also an injection timing signal. One of the drive waveform signals is selected according to the input of the print data sel-0, sel-1 to the selector 83. In this embodiment, when the print data sel-0 and sel-1 are 0 and 0, non-printing (no dot) is selected, 0 and 1 are the drive waveform signal A, and 1 and 0 are the drive waveform signal B. To do. Thus, by configuring each print data with 2 bits, the drive waveform signal A or the drive waveform signal B can be selected in units of nozzles.
Each of the 64 drivers 84 converts the drive waveform signal output from the selector 83 into a drive waveform signal having a voltage suitable for the inkjet head 30, and outputs the drive waveform signal to the electrodes connected to the piezoelectric actuators of the inkjet head 30.

(Configuration of drive waveform signal)
Next, the configuration of the drive waveform signals A and B will be described with reference to FIG.
The drive waveform signal A cancels the three printing pulses A1 to A3 for ejecting three ink droplets for the printing data for one dot and the residual pressure fluctuation generated in the ink flow path after the ink droplet ejection. For this reason, it is composed of three cancel pulses C1 to C3. The drive waveform signal B is composed of one print pulse B1 for ejecting one ink droplet for one dot of print data.

  The ON (application) time of the first print pulse A1 of the drive waveform signal A is tp1, and after the tw2 hours have elapsed since the first print pulse A1 turned OFF, the first print pulse A1 is applied to the ink flow path. A first cancel pulse C1 for canceling the generated residual pressure fluctuation is applied for tp2 hours. The second print pulse A2 is applied for tp3 hours after elapse of tw3 hours after the first cancel pulse C1 is turned off, and the second print pulse A2 is applied after tw4 hours elapses after the second print pulse A2 is turned off. A second cancel pulse C2 for canceling the residual pressure fluctuation generated in the ink flow path is applied for tp4 hours. The third print pulse A3 is applied for tp5 hours after tw5 hours have elapsed since the second cancel pulse C2 was turned off, and the third print pulse A3 is applied after tw6 hours have elapsed since the third print pulse A3 was turned off. A third cancel pulse C3 for canceling the residual pressure fluctuation generated in the ink flow path is applied for tp6 hours. The tw1 time before the printing pulse A1 is applied is a waiting time between printing timings. The ON (application) time of the print pulse B1 of the drive waveform signal B is tp7.

  For example, tw1 = 3.067 of the drive waveform signal A (unit: * 0.133 μs, the same applies hereinafter), tp1 = 6.533, tw2 = 9.067, tp2 = 8.533, tw3 = 24.0000, tp3 = 6.533, tw4 = 9.067, tp4 = 8.533, tw5 = 24.000, tp5 = 6.533, tw6 = 9.067, tp6 = 8.533, and tp7 of the drive waveform signal B = 3.067.

[Print control flow]
Next, the flow of printing control by the control system shown in FIG. 2 will be described with reference to FIGS. FIG. 5 is a flowchart showing the flow of printing control. FIG. 7A is an explanatory diagram schematically showing a part of the two-dimensional code, and FIG. 7B is an explanatory diagram schematically showing dots printed at the end of the two-dimensional code.

  When the start of printing is instructed, the discriminating means 61 determines whether the printing is barcode printing or printing of other image data (step (hereinafter abbreviated as S) S1). The determination of the print mode is performed based on an instruction signal included in data received through the interface 41 or an instruction signal from the operation panel 56. Alternatively, even when printing other image data, this determination is unnecessary if dot control is performed around the image as in the case of barcode printing. When printing other image data (S1: No), other print processing similar to the known one is performed (S10), and the process ends. Here, the description is omitted because it is not related to the present invention.

  When barcode printing is performed (S1: Yes), the gate array 60 (FIG. 2) reads print data transmitted from the host computer 71 and stored in the image memory 51 (S2), and prints that should print dots. It is determined whether or not there is data, that is, the dot (S3). Here, when it is determined that the dot is present (S3: Yes), the determination unit 62 prints or prints at a cycle before and after the current print cycle in the main scanning direction and the sub-scanning direction of the inkjet head 30. It is determined whether there is a power dot (that is, a dot to be printed vertically and horizontally with respect to the current dot) (S4). If it is determined that there is no upper, lower, left, or right dot (S4: No), the data generating unit 63 generates print data “10” instructing selection of the drive waveform signal B (S7). If it is determined that there are dots on the top, bottom, left, and right (S4: Yes), print data “01” for instructing selection of the drive waveform signal A is generated (S5). In S3, it is determined that there is no dot. In this case (S3: No), data “00” instructing non-printing is generated (S8).

These generated data are output to the serial / parallel conversion circuit 81, selection signals sel-0 and sel-1 are set for each ink flow path, and each selector 83 is output from the latch circuit 82, respectively. Based on the parallel print data, the drive waveform signals A and B transferred from the gate array 60 or non-printing are selected and output to the driver 84. The ink flow path ejects one or three ink droplets based on the selected drive waveform signal.
In other words, the description will be limited to only the printing in the main scanning direction. When the inkjet head 30 prints the front end portion and the rear end portion of the two-dimensional code in the scanning direction, the drive waveform signal B is selected, and FIG. ), One dot is printed with only one ink droplet, as indicated by D1. When printing from the end of the two-dimensional code and the inner side of both ends, the drive waveform signal A is selected for the second and subsequent dots except for the first dot printed at the beginning of the stroke, and FIG. ), One dot is printed with three ink droplets, as indicated by D2.
However, in the embodiment described here, it is assumed that dots are similarly arranged at the end in the sub-scanning direction.

[Experiment]
Next, an experiment conducted by the present inventor will be described with reference to FIGS. FIG. 8 is a chart showing the experimental results, and FIG. 9 is a graph of the experimental results of FIG.
The inventor of the present application measured the change in the print growth of the two-dimensional code due to the change in the environmental temperature by changing the type of the drive waveform signal. As shown in FIG. 7A, the two-dimensional code is configured by arranging, for example, square black cells G and white cells W formed of 6 dots × 6 dots in a matrix. Here, “Print Growth” means the growth size (the size of bleeding) of the end portion of the black cell G when the two-dimensional code is printed, and the width of one black cell G in FIG. F / E, where E is the height, H is the height, and F is the width of the ink that has grown (bleeded out) from the end of the black cell G in the main scanning direction (X direction). Sought as Print Growth against. Further, J / H, where J is the height of ink that has grown (bleeded out) from the edge of the black cell G in the sub-scanning direction (Y direction), was determined as Print Growth in the Y direction. . That is, the smaller the value of Print Growth, the less ink bleeding at the end of the black cell G.

“P28” in the drive waveform signal of FIG. 8 indicates that all the dots were printed with the same waveform with an ink droplet having a volume of 28 pl. “P28FR” indicates that when there is no dot to be printed before the dot to be printed and there is a dot to be printed after the dot, the waveform is switched and only one ink droplet having a volume of 28 pl is used to obtain one dot. Other than that, printing indicates that one dot is printed by ejecting three ink droplets having a volume of 28 pl in succession.
“P28NR” indicates that if there is a dot to be printed before the dot to be printed and there is no dot to be printed after the dot, the waveform is switched and only one ink droplet having a volume of 28 pl is used to set one dot. Other than that, printing indicates that one dot is printed by ejecting three ink droplets having a volume of 28 pl in succession.

“PGX” indicates Print Growth in the X direction (main scanning direction), and “PGY” indicates Print Growth in the Y direction (sub-scanning direction).
For example, “P28-PGX” indicates the print growth in the X direction when the entire area of the black cell G is printed by a method of printing one dot by ejecting three ink droplets having a volume of 28 pl continuously. In addition, “P28FR-PGX” and “P28NR-PGX” are printed by only one dot at the front end and the rear end in the X direction of the black cell G, and only by one ink droplet having a volume of 28 pl. The area indicates the print growth in the X direction when printing is performed by a method in which three ink droplets having a volume of 28 pl are continuously ejected to print one dot. The ambient temperature was changed to 10, 15, 20, 25, 30, 35, 38 ° C.

As a result, when the black cell G is printed using the drive waveform signal P28, the print growth in the X direction is 0.145 at the maximum when the environmental temperature is 25 ° C, and the environmental temperatures are 35 ° C and 38 °. For C, the minimum value was 0.136. The print growth in the Y direction was a maximum of 0.1248 when the environmental temperature was 10 ° C., and a minimum of 0.1005 when the environmental temperature was 38 ° C.
Further, when the black cell G is printed using the drive waveform signal P28FR, the print growth in the X direction is 0.115 which is the maximum when the environmental temperature is 10 ° C, and the minimum when the environmental temperature is 35 ° C. Of 0.093. The maximum Y direction print growth was 0.1150 when the ambient temperature was 10 ° C, and 0.099 when the ambient temperature was 38 ° C.

  That is, when printing a black cell G, only one dot at the beginning of printing is printed with one ink droplet, and thereafter, if one dot is printed with three ink droplets, printing is performed with three ink droplets per dot. It was found that the print growth in the X direction and the Y direction can be made smaller than when the entire area of the black cell G is printed by the method. Specifically, it has been found that the print growth in the X direction can be suppressed to 0.115 or less and the print growth in the Y direction can be suppressed to 0.1150 or less.

Further, when the black cell G is printed using the drive waveform signal P28NR, the print growth in the X direction is 0.095 which is the maximum when the environmental temperature is 10 ° C, and the minimum when the environmental temperature is 38 ° C. Of 0.076. The print growth in the Y direction was a maximum of 0.1146 when the environmental temperature was 10 ° C., and a minimum of 0.1003 when the environmental temperature was 38 ° C.
That is, when printing a black cell G, only one dot at the end of printing is printed with one ink droplet, and if one dot is printed with three ink droplets before that, printing is performed with three ink droplets per dot. It was found that Print Growth in the X direction can be made smaller than when the entire area of the black cell G is printed by this method. Specifically, it was found that the print growth in the X direction can be suppressed to 0.095 or less and the print growth in the Y direction can be suppressed to 0.1146 or less.
Based on the experimental results shown in FIG. 8, print growth is calculated when one dot is printed on each of the left and right and upper and lower ends of a black cell with one ink drop. It was shown as “both end adjustment”. Specifically, the value calculated by (“P28FR-PGX” + “P28NR-PGX” − “P29-PGX”) is set as Print Growth in the X direction when both ends are adjusted, and (“P28FR-PGY” + The value calculated by “P28NR−PGY” − “P29−PGY”) is the print growth in the Y direction when both ends are adjusted. From this result, it is expected that the print growth in the X direction can be suppressed to 0.069 or less and the print growth in the Y direction can be suppressed to 0.1131 or less.
Therefore, if each dot at the edge of the black cell is printed with one ink droplet, the size of the black cell can be controlled with higher accuracy, particularly in the main scanning direction. However, as can be seen from the experimental results, a sufficient effect can be obtained on only one side, so that only the front end or only the rear end of the black cell is printed with one ink droplet as described above in the main scanning direction or the sub-scanning direction. You may make it do.

[Effects of Embodiment] (1) As described above, when the inkjet recording apparatus 1 of the above embodiment is used, when printing the black cell G of the two-dimensional code, before or after the dot to be printed or When there are no dots to be printed above or below, that is, when printing black cells G in the main scanning direction, when printing dots at the front and rear ends, and at the top and bottom, one ink droplet is printed per dot. When the ejection drive waveform signal B is output to the piezoelectric actuator 32 and there are dots to be printed on the top, bottom, left, and right of the dot, that is, when printing dots inside both ends (more precisely, the edge), A drive waveform signal A for ejecting three ink droplets for printing can be output to the piezoelectric actuator 32.
In other words, since the number of ink droplets is reduced at the edge of the black cell, the dots printed on the edge of the black cell G corresponding to the start of printing are less than those in which the volume of one ink droplet itself is reduced. The shape, size, density, and the like can be accurately controlled to suppress the spread of dots.

(2) Further, the drive waveform signal A and the drive waveform signal B are stored in the storage area 43a of the ROM 43. The drive waveform signal is selected from the stored drive waveform signals at the edge of the black cell G. When B is used and other dots are printed, the drive waveform signal A can be used. That is, since the piezoelectric actuator 32 can be driven by a dedicated drive waveform signal corresponding to the number of ink droplets to be ejected, the shape, size, density, and the like of the printed dots can be accurately controlled.

(3) Further, even when there is a variation in ink ejection characteristics due to individual differences in the ink jet head 30 such as flow path resistance of the ink flow path, a drive waveform signal corresponding to the individual difference is stored in the storage area 43a. Therefore, variations in ink ejection characteristics due to individual differences can be absorbed. (4) Further, the discriminating means 61 discriminates whether or not the current printing is a bar code printing, and when it is discriminated that the bar code is printed, the driving waveform signal A or the driving waveform signal B is selected and printed. You can print barcodes without misreading.
As described above, if the inkjet recording apparatus 1 of the above embodiment is used, the print quality of the bar periphery of the barcode can be improved.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to FIG.
The ink jet recording apparatus of this embodiment is characterized in that high quality printing can be performed in consideration of a change in ink viscosity due to environmental temperature. FIG. 6 is a flowchart showing a flow of print control executed by the ink jet recording apparatus. Since the configuration and functions are the same as those of the inkjet recording apparatus of the first embodiment except for part of the print control flow, the description of the same portions is omitted or simplified, and the same reference numerals are used for the same configurations and functions. use.

According to the experiment by the present inventor, as described with reference to FIG. 8, when dots are printed in the main scanning direction in a state where the environmental temperature is low and the viscosity of the ink is increased, a large amount of ink forms the printed dots. I found out there was a tendency to go out.
This is because, when the temperature of the ink is lowered, the viscosity of the ink is increased. Therefore, when one dot is printed with a plurality of ink droplets, the landing position of each ink droplet is shifted, and the dots spread in the main scanning direction. It is thought that it is one of.
Therefore, the inventor of the present application has developed a configuration in which the print quality of the peripheral edge of the black cell G does not deteriorate even when the environmental temperature changes by properly using the drive waveform signal according to the environmental temperature.
In other words, when there is no dot to be printed before the dot to be printed, it is determined whether the environmental temperature is higher than the reference temperature or lower than the reference temperature. The dot is printed. If the temperature is lower than the reference temperature, the dot is printed with one ink droplet.

The temperature sensor 59 (FIG. 2) outputs a signal corresponding to the environmental temperature to the CPU 57, and the CPU 57 calculates the environmental temperature based on the signal fetched from the temperature sensor 59 and stores the calculated environmental temperature in the RAM 44. To do.
If the determination unit 62 determines that there is no dot printed before or after the current print cycle and at any cycle above or below (S4: No), the environmental temperature stored in the RAM 44 is determined. With reference to it, it is determined whether the temperature is higher or lower than a preset reference temperature (for example, 21.3 ° C.) (S6). If it is determined that the environmental temperature is higher than the reference temperature (S6: high), the data generation unit 63 generates print data for selecting the drive waveform signal A (S5). When it is determined that the environmental temperature is lower than the reference temperature (S6: low), the data generation unit 63 generates print data for selecting the drive waveform signal B (S7).
That is, even at the end of the black cell G, when the environmental temperature is higher than the reference temperature, three ink droplets are ejected by the drive waveform signal A to print dots, and when the temperature is lower than the reference temperature, One ink droplet is ejected by the drive waveform signal B to print a dot.

[Effect of Second Embodiment] (1) As described above, when the ink jet recording apparatus of the second embodiment is used, the environmental temperature is lower than the reference temperature when printing the end of the black cell G in the main scanning direction. In this case, by ejecting one ink droplet by the drive waveform signal B, the amount of ink spreading in the main scanning direction at the end of the black cell G can be reduced.
Also, if the ink viscosity is not so low that the amount of ink bleed in the main scanning direction is not a problem and the ambient temperature is not low, printing the edge of the black cell G with only one ink droplet will conversely There is a risk that the print quality at the edge will be reduced due to insufficient amount, but when the ambient temperature exceeds the reference temperature, it is possible to print the edge of the black cell G by ejecting three ink droplets. Therefore, the print quality at the end of the black cell G can be improved.

(2) The ink jet recording apparatus of the second embodiment has the same configuration and functions as those of the ink jet recording apparatus 1 of the first embodiment except for a part of the print control shown in FIG. The effects (2) to (4) of the embodiment can be achieved.

Other Embodiments (1) The number of ink droplets ejected per dot by the drive waveform signal A may be two or four or more. Further, the number of ink droplets ejected per dot by the drive waveform signal B may be less than the number of ink droplets by the drive waveform signal A, and may be two or three or more.

(2) The present invention can also be applied to printing barcodes other than two-dimensional codes or printing images other than barcodes. (3) The present invention can be applied to an ink jet recording apparatus using an actuator using an electrothermal conversion element as a drive source in addition to a piezoelectric actuator using an electromechanical conversion element such as a piezoelectric element. The present invention can also be applied to an ink jet recording apparatus having an ink cartridge on an ink jet head, or an ink jet recording apparatus having a scanner function or a copy function.

[Correspondence between each claim and embodiment]
The piezoelectric actuator 32 corresponds to the actuator of claim 1, and the ink jet head 30 corresponds to the print head. The CPU 57, the image memory 51, the ROM 43, the RAM 44, the gate array 60, and the drive circuit 80 correspond to the control circuit of claim 1, the printing paper P corresponds to the print medium, and the storage area 43a corresponds to the storage means. S4 functions as the determining means of claim 1, and S5 and S7 function as the selecting means. The temperature sensor 59 corresponds to the temperature detection means of claim 2.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory plan view showing a main configuration of an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing a main configuration of a control system of the inkjet recording apparatus 1 in blocks. 4 is an explanatory diagram showing the main configuration of a drive circuit 80 in blocks. FIG. It is explanatory drawing which shows the structure of the drive waveform signal A and B. FIG. 6 is a flowchart illustrating a flow of printing control. 10 is a flowchart illustrating a flow of print control in the second embodiment. FIG. 7A is an explanatory diagram schematically showing a part of the two-dimensional code, and FIG. 7B is an explanatory diagram schematically showing dots printed at the end of the two-dimensional code. It is a chart which shows an experimental result. FIG. 9 is a graph of experimental results in the X direction in FIG. 8. FIG. 9 is a graph of experimental results in the Y direction in FIG. 8.

Explanation of symbols

1 Inkjet recording device 30 Inkjet head (printing head)
32 Piezoelectric actuator
43a Storage area (storage means)
59 Temperature sensor (temperature detection means)
60 Gate array (control circuit)
P Printing paper (medium to be printed)

Claims (7)

A print head including an ink flow path, a nozzle communicating with the ink flow path, an actuator for applying energy to the ink in the ink flow path, and a drive waveform signal for driving the actuator. A control circuit that outputs the ink, and moves the print head in the main scanning direction with respect to the print medium and outputs the drive waveform signal to the actuator, thereby causing ink in the ink flow path to flow through the nozzles. In an inkjet recording apparatus that discharges from the medium to be printed,
The control circuit stores a plurality of types of drive waveform signals that differ in the number of ink droplets to be ejected for printing one dot, and a front of the dot among dots that are continuously printed in the main scanning direction. Determination means for determining the presence or absence of dots to be printed both on and after, and selection means for selecting a drive waveform signal to be output from the storage means to the actuator based on the determination of the determination means,
When the determination unit determines that there are dots to be printed both before and after the dot, the selection unit outputs a drive waveform signal for ejecting a plurality of ink droplets to the dot. Select from and output to the actuator,
When the determination unit determines that there is no dot to be printed before or after the dot, the selection unit has a dot printed before or after the dot with respect to the dot. An inkjet recording apparatus, wherein a drive waveform signal for ejecting a smaller number of ink droplets than a drive waveform signal selected when it is determined to be present is selected from the storage means and output to the actuator. A print head including an ink flow path, a nozzle communicating with the ink flow path, an actuator for applying energy to the ink in the ink flow path, and a drive waveform signal for driving the actuator. And a control circuit for outputting the ink jet recording, wherein the print head is moved in the main scanning direction with respect to the print medium, and the drive waveform signal is output to the actuator, thereby discharging ink to the print medium. In the device
The control circuit includes temperature detection means for detecting an environmental temperature in which the inkjet recording apparatus is placed, and dots that are printed both before and after the dots among dots that are continuously printed in the main scanning direction. Determination means for determining the presence or absence of
When the determination unit determines that there are dots to be printed both before and after the dot, a drive waveform signal for ejecting a plurality of ink droplets to the dot is output to the actuator.
When the determination unit determines that there is no dot to be printed before or after the dot, and the temperature detected by the temperature detection unit is higher than a predetermined temperature, a plurality of the dots are determined. A drive waveform signal for ejecting ink droplets is output to the actuator,
When the determination unit determines that there is no dot to be printed before or after the dot, and the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature, the temperature is An inkjet recording apparatus, wherein a drive waveform signal for ejecting a smaller number of ink droplets than a drive waveform signal when the temperature is higher than a predetermined temperature is output to the actuator. The control circuit stores a plurality of types of the drive waveform signals that differ in the number of ink droplets ejected for one-dot printing, and outputs the drive waveform signal from the storage unit to the actuator based on the determination of the determination unit Selecting means for selecting a drive waveform signal;
When the determination unit determines that there are dots to be printed both before and after the dot, the selection unit ejects a plurality of ink droplets from the storage unit to the dot. To output to the actuator,
When the determination unit determines that there is no dot to be printed before or after the dot, and the temperature detected by the temperature detection unit is higher than a predetermined temperature, the selection unit sets the dot to the dot. On the other hand, a drive waveform signal for ejecting a plurality of ink droplets from the storage means is selected and output to the actuator,
When the determination unit determines that there is no dot to be printed before or after the dot, and the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature, the selection unit The drive waveform signal for ejecting a smaller number of ink droplets than the drive waveform signal when the temperature is higher than a predetermined temperature is selected from the storage means and output to the actuator. The ink jet recording apparatus described. The determination means determines only the presence or absence of dots to be printed before the dots instead of determining the presence or absence of dots to be printed before and after the dots,
The inkjet recording according to any one of claims 1 to 3, wherein the selection unit selects the drive waveform signal based on the determination by the determination unit whether or not there is a dot to be printed before the dot. apparatus. The determination means determines only the presence or absence of dots to be printed after the dots instead of determining the presence or absence of dots to be printed before and after the dots,
4. The ink jet recording apparatus according to claim 1, wherein the selection unit selects the drive waveform signal based on the determination unit that determines whether or not there is a dot to be printed after the dot. .   The storage unit stores a drive waveform signal for ejecting three ink droplets per dot and a drive waveform signal for ejecting one ink droplet per dot. Inkjet recording device. 7. The ink jet recording apparatus according to claim 1, wherein the control circuit determines whether an image to be printed is a bar code, and performs the control when the image is a bar code.

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