JP2001054948A - Ink-jet recording device and recording head driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always impact an ink droplet on an appropriate position by an appropriate amount, regardless of variation of recording heads in production, or change of the ejection energy or a recording head temperature. SOLUTION: The number of dots ejected simultaneously is counted from image data (DATA) to be recorded. A preset driving pulse width is read out from a memory, corresponding to the number of dots. With fall of an HEin signal as a signal, a counting operation is started. An HE signal is maintained until the count value coincides with the read out driving pulse width so as to drive an ejection opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus and a recording head driving method, and more particularly, to control of a driving pulse width of a recording head.

[0002]

2. Description of the Related Art In recent years, ink jet recording apparatuses which perform recording by discharging ink droplets from discharge ports in a recording head have become widespread and used for various purposes. As a method of discharging ink droplets, a heater is provided in an ink path corresponding to each discharge port of the recording head, bubbles are generated in the ink by the heat energy generated by the heater, and the ink droplets are discharged by the generation pressure of the bubbles. The so-called bubble jet method,
A piezo method in which ink is ejected using pressure generated in ink due to deformation of a piezoelectric element such as a piezo element is exemplified.

[0003] In such an ink jet recording apparatus, a recording speed is increased and a recording result is improved in image quality according to its use.

For example, in order to increase the recording speed, the driving frequency is increased by shortening the interval between the driving pulses of the recording head, or the number of ejection areas is increased by integrating ejection ports. A proposal has been made. Further, in order to realize higher image quality of a recording result, it has been proposed to reduce the amount of ink droplets to be ejected, reduce the diameter of formed dots, and improve the resolution of an image.

[0005]

However, in the above-described conventional ink jet recording apparatus, a slight difference may occur in the ink discharge amount for each nozzle due to manufacturing variations of the recording head. Due to the difference in the ejection amount, the size of the formed dots is not uniform, so that the recording result becomes uneven.

When the number of simultaneously ejecting nozzles is increased in order to increase the recording speed, the current flowing through the recording head increases accordingly, and the voltage decreases by the resistance from the power supply. The ejection energy amount is proportional to the voltage when the driving pulse width is constant, so that the ejection energy amount of each nozzle decreases as the number of nozzles ejected simultaneously increases. Furthermore, when the drive pulse width is short, the amount of ejection energy is small, and thus a change in voltage greatly affects the amount of ejection energy. Similarly, even when the amount of ink droplets to be ejected is small, the amount of ejection energy is small, and similarly, a change in voltage greatly affects the amount of ejection energy.

If the amount of discharge energy is not sufficient to perform the discharge operation, discharge may not be performed properly. For example, in the case of the bubble jet method, if the amount of discharge energy is small, the heater does not generate enough heat, so that the bubble does not grow to the size required for discharge, the ink does not discharge, or the amount of ink is small even if discharged. Or an ejection failure such as an insufficient ejection speed. Due to such an ejection failure, dots of an appropriate size are not formed at an appropriate position, and unevenness and streaks are generated in a completed image, thereby deteriorating the image quality.

In addition, when a recording operation is repeated or an image having a high duty is recorded, the recording head itself may be heated. When the temperature of the recording head rises due to the heat of the recording, the temperature of the ink in the head also rises. When the temperature of the ink is higher than usual, if the heater is heated with the same drive pulse width as usual, bubbles will grow too large. If the bubble is large, the ink droplet may be separated from the ejection port in an inappropriate form, and the ejection direction may be shifted.
If the ejection direction is shifted, the landing position is also shifted, so that the image becomes uneven.

As described above, there is a case where the image quality of the formed image is deteriorated due to the manufacturing variation and the method of use of the recording head.

In view of the above-mentioned conventional problems, the present invention is directed to ink-jet recording in which an appropriate amount of ink droplets are always landed at an appropriate position irrespective of variations in the production of the recording head, changes in the discharge energy and the temperature of the recording head. An apparatus and a recording head driving method are provided.

[0011]

An ink jet recording apparatus according to the present invention uses a recording head having a plurality of discharge ports,
In an ink jet recording apparatus that performs recording by discharging ink droplets from each of the discharge ports, a discharge unit that discharges ink droplets from the discharge ports, and each discharge port is set for each discharge port according to the discharge characteristics of the discharge port. A storage unit for storing the set value, wherein the discharge unit reads a corresponding set value from the storage unit for each discharge port, and sets a pulse width of a drive pulse as the set value.

[0012] The recording head driving method according to the present invention is directed to a recording head driving method using an ink jet recording apparatus which performs recording by discharging ink droplets from each discharge port of a recording head having a plurality of discharge ports. A set value set for each ejection port, which is set according to the ejection characteristics of each ejection port, stored in the printer, and the set value is used as a pulse width of a print head drive pulse.

According to the above arrangement, the set value corresponding to the ejection port performing the ejection operation in accordance with the print data is extracted from the storage section, and the drive pulse of the heater of the ejection port is set as the set value.
The heater is driven for a time suitable for each discharge port to generate bubbles sufficient for discharge.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments to which an ink jet recording apparatus and a recording head driving method of the present invention are applied will be described.
This will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view of a printer to which the present invention is applied.

The printer conveys the recording medium 1 by a fixed amount by a pair of conveying rollers 2 and 3 for conveying the recording medium 1 fed to a predetermined position and a sheet feed motor 4 for driving the rollers. A guide shaft 5 is provided in front of and in parallel with the transport rollers 2 and 3. Further, the drive of the carriage motor 7 is transmitted to the carriage 6 via the belt 8, and the carriage 6 is driven by this driving force.
The recording medium 1 is scanned along the guide shaft 5.

A recording head 9 is mounted on the carriage 6. The recording head 9 has a cyan head 9c for discharging cyan ink in the scanning direction of the carriage 6.
A magenta head 9 m for ejecting magenta ink,
Four color heads are provided, a yellow head 9y for discharging yellow ink and a black head 9k for discharging black ink. Each head has 128 ejection ports arranged in a direction perpendicular to the scanning direction of the recording head 9, and prints on the recording medium 1 by ejecting ink droplets from each ejection port when the carriage 6 scans. As described above, an image is formed on the entire recording medium by alternately repeating the recording by the carriage scanning and the paper feeding by the conveying rollers 2 and 3.

A control unit 1 for controlling the driving of each of these parts
Reference numeral 5 includes a CPU, a ROM, a RAM, and the like. The control unit 15 receives a command signal and image data from the host computer 17, activates various drive circuits based on these, and performs recording.

An operation panel 16 provided on an outer case (not shown) of the printer has a key setting section such as a power-on key 16a, an alarm recovery key 16b, and the like.
A display unit including a warning lamp such as a power lamp 16f and an alarm lamp 16e is provided.

FIG. 2 is a longitudinal sectional view showing a part of the ink ejection portion of the recording head.

The recording head 9 has 128 ejection ports 10 arranged for each color in opposition to the recording medium 1. The ink to be ejected is supplied to the common liquid chamber 1 via the ink path 10a.
0b is always supplied. The ink is usually supplied to the common liquid chamber 10
b to the discharge port 10. Ink path 10a
Is equipped with an electrothermal converter (hereinafter referred to as "heater") for each discharge port.
In the recording operation, the heater 11 generates heat to generate a film boiling phenomenon in the ink to generate a bubble 12, and the ink in the ink path 10a is generated by the pressure generated by the bubble. The recording is performed by discharging the droplets 13. Hereinafter, a portion from the discharge port 10 to the common liquid chamber 10b is referred to as a “nozzle”.

FIG. 3 is a block diagram showing the electrical configuration of the recording head.

In the present embodiment, the 128 ejection opening arrays are arranged such that the first 32 are arranged in block 0, the 33rd to 32 are arranged in block 1, the 65th to 32 are arranged in block 2, and the 97th to 32 are arranged in block 3. Divide into four blocks. At the same time, the ejection operation is performed for one block. At the time of recording, the ejection operation is performed in order from block 0. When the ejection operation is performed four times, recording of one row in a predetermined area is completed.

The recording operation is performed as follows.

FIG. 4 is a time chart showing the operation of the recording head.

First, out of DATA, which is image data sent from the control unit, 32 dots from 0 to 31 are transferred with the transfer clock HCLK as a trigger. After the data of 32 dots is transferred, the data is latched by the LAT signal.

The BE signal is a signal for designating a block in which an ejection operation is to be performed. In the case of BE0, the block 0 performs an ejection operation.

The HE signal is a pulse signal for driving the nozzle heater. While the pulse of the HE signal is rising, the heater of the block designated by the BE signal generates heat,
The nozzle performs a discharging operation.

However, as described in the subject, each nozzle has its own characteristic due to an error at the time of manufacture, and even if the heater is driven for the same time, ink is discharged from all the discharge ports in the same manner. Not necessarily. Therefore,
In the present embodiment, control for making the pulse width of the HE signal different for each block is performed.

FIG. 5 is a diagram showing the HE signal generation circuit.

First, based on the information detected in the inspection at the time of shipment, a memory is previously prepared in which the excess value of the HE signal for each block from the reference value is stored. The longer the excess value, the longer the time for heating the heater.

An input heat pulse HEin signal, which is a reference signal for driving the nozzle heater, is input from the control unit. This signal has a minimum pulse width necessary for growing bubbles sufficient for ejection.

The HE signal rises simultaneously with the input of the HEin signal.

On the other hand, the falling edge detection circuit
The falling of the in signal is detected and input to the counter.
The counter starts counting from the falling edge of the HEin signal, and adds the count value for each clock signal CLK.

It is assumed that the transfer clock signal HCLK and the clock signal CLK are independently transmitted from the control unit.

The comparator compares the count value with the excess value from the reference value of the corresponding block stored in the memory, and stops the counter when the count value matches the excess value.
While the counter is moving, a pulse is generated from the comparator, and the HE signal is extended by the OR circuit in a manner added to the input heat pulse HEin signal. As mentioned above,
Since the heater generates heat while the HE signal is on, bubbles sufficient for ejection can be generated.

The memory may be one that cuts a pattern set in advance at the time of shipment of the printhead according to the inspection result. With such a method, it is possible to reduce costs.

Also, by mounting a nonvolatile memory and rewriting the memory according to the recording mode, driving environment, etc.,
The control of the drive pulse in this mode is also possible without any control by the control unit of the printer main body.

As described above, by changing the heating time of the heater in accordance with the characteristics of each nozzle due to an error at the time of manufacturing, it is possible to always generate appropriate bubbles, and to form dots at appropriate positions. Can be.

(Embodiment 2) As described in Embodiment 1, in one ejection operation, 32 ejection ports in one block perform the ejection operation. However, depending on the data to be recorded, there are cases where all ejection ports are used and cases where it is not. For example, when a solid image is formed, all 32 ejection openings perform ejection operations.
Only some of the 32 outlets perform a discharging operation. Therefore, the former flows more current than the latter, and the voltage drops during the ejection operation. Therefore, even if the pulse width of the heater drive signal (HE signal) is the same for the former and the latter, the voltage of the former is low.
The discharge energy amount is smaller in the former case. For this reason,
In some cases, it may not be possible to generate enough heat to generate bubbles.

Therefore, in the present embodiment, a description will be given of a case where the number of dots to be ejected is counted in one ejection operation of one block, and the pulse width of the drive signal is changed in accordance with the number of dots.

The configuration of the printer is the same as that of the first embodiment.

FIG. 6 is a diagram showing an HE signal generation circuit according to this embodiment.

When transferring the image data DATA to the recording head, the transfer clock HCLK and DATA are used to
The number of simultaneously driven dots is counted by a counter. When the transfer is completed, the latch signal LAT
, The count value is latched, and a value previously written on the memory is selected by the output of the latch. The counter clears the count value using a one-clock delay signal of the latch signal or a driving pulse before data transfer of the next block is performed, and prepares for the next data transfer.

FIG. 7 is a diagram showing a table stored in the memory.

When the number of simultaneously driven dots is 0 to 7, no voltage drop occurs, so that the reference pulse is sufficient for the drive pulse width. However, if the number of simultaneous drive dots is 8 or more, a voltage drop occurs. Therefore, the drive pulse width is set to the reference pulse + α so that sufficient energy for ejection can be maintained. The value of α is set so as to increase as the number of simultaneously driven dots increases.

The selector reads the upper 3 bits of the count value latched by the latch signal LAT, and reads the upper 3 bits.
If the bit is “000”, it is determined that the number of simultaneous drive dots is any of 0 to 7 dots, and the drive pulse width is used as the reference pulse. Similarly, the top three count values
When the bit is “001”, the reference pulse + 0.5 μ
s, “010”, the reference pulse +1.0 μs,
In the case of “011”, the reference pulse + 1.5 μs, “11”
In the case of “1”, the reference pulse is set to +1.7 μs. Only the amount of α added to the reference pulse having the drive pulse width set in this way is sent to the comparator.

As in the first embodiment, the counter starts counting with the falling edge of the HEin signal as the timing. The comparator generates a pulse until the value of α matches the count value, and generates an HE signal in a form added to the HEin signal by the OR circuit.

The reference pulse may be individually set according to the characteristics of each nozzle.

As described above, by providing the dot count function on the recording head, the printer can be driven under the same conditions regardless of the driving conditions.

(Embodiment 3) In this embodiment, a method of changing the drive pulse width in accordance with a change in the temperature of the recording head will be described.

As described in connection with the problem, when the temperature of the recording head rises, the temperature of the ink in the head also rises. If the heater is driven with the same pulse width as usual, bubbles become too large. Therefore, when the temperature is high, it is preferable to drive the heater with a pulse width shorter than usual.

FIG. 8 shows a circuit for detecting the head temperature.

The temperature of the recording head is detected by a thermistor, and the detection result is converted into a digital output by an A / D conversion circuit.

The selector selects the value of the drive pulse width corresponding to the detected temperature from the memory in which the drive pulse width corresponding to the head temperature is stored. Then, the HE signal is output using this value as the pulse width of the HE signal.

This embodiment may be used in combination with the first and second embodiments.

[0057]

By using the ink jet recording apparatus and the recording head driving method of the present invention, a set value corresponding to a discharge port for performing a discharge operation in accordance with print data is extracted from a storage unit, and the heater of the discharge port is used. By setting the drive pulse to a set value, the heater is driven for a time suitable for each discharge port, and sufficient bubbles can be generated for discharge, and variations in print head manufacturing, discharge energy and changes in print head temperature Regardless, an appropriate amount of ink droplet can always be landed at an appropriate position.

[Brief description of the drawings]

FIG. 1 is a perspective view of a printer to which the present invention is applied.

FIG. 2 is a partial sectional view of a recording head.

FIG. 3 is a diagram illustrating an electrical configuration of a recording head.

FIG. 4 is a time chart illustrating the operation of the recording head.

FIG. 5 is a diagram illustrating an HE signal generation circuit.

FIG. 6 is a diagram illustrating another example of the HE signal generation circuit.

FIG. 7 is a diagram showing a table stored in a memory.

FIG. 8 is a diagram showing a circuit for detecting a head temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording medium 2 Conveying roller 3 Conveying roller 4 Sheet feed motor 5 Guide shaft 6 Carriage 7 Carriage motor 8 Belt 9 Recording head 10 Discharge port 11 Heater 12 Bubbles 13 Ink drop 15 Control part 16 Operation panel 17 Host computer

Claims (22)

[Claims] 1. An ink jet recording apparatus which performs recording by discharging ink droplets from each of said discharge ports using a recording head having a plurality of discharge ports, wherein: a discharge means for discharging ink droplets from said discharge ports; A storage unit for storing a set value set for each discharge port in accordance with a discharge characteristic of each discharge port, wherein the discharge unit reads a corresponding set value from the storage unit for each discharge port, and outputs a drive pulse An ink jet recording apparatus, wherein the pulse width is set to the set value. 2. The ink jet recording apparatus according to claim 1, wherein the ejection characteristics are determined based on a result of a shipping inspection of the recording head. 3. The discharge means counts an elapsed time from a fall of a drive input signal indicating a rise timing of the drive pulse, and determines a pulse width of the drive pulse until the elapsed time matches the set value. 3. The ink jet recording apparatus according to claim 1, wherein 4. The recording head is a recording head that divides the plurality of ejection ports into a plurality of blocks of a predetermined number and performs ejection in a unit of the block. 4. The ink jet recording apparatus according to claim 1, wherein the corresponding set value is read from the control unit. 5. An ink jet recording apparatus which performs recording by ejecting ink droplets from each of said ejection ports using a recording head having a plurality of ejection ports, wherein: an ejection means for ejecting ink droplets from said ejection ports; Dot number counting means for counting the number of simultaneously ejected dots from the image data to be provided; and a storage unit for storing a set value corresponding to the number of simultaneously ejected dots, wherein the ejection means has a setting corresponding to the count value. An ink jet recording apparatus, wherein a value is extracted from a storage unit, and a pulse width of a driving pulse is set as the set value. 6. The ink jet recording apparatus according to claim 5, wherein the set value increases as the count value increases. 7. The discharge unit counts an elapsed time from a fall of a drive input signal indicating a rise timing of the drive pulse, and determines a pulse width of the drive pulse until the elapsed time matches the set value. 7. The ink jet recording apparatus according to claim 5, wherein 8. The recording head is a recording head that divides the plurality of ejection ports into a plurality of blocks of a predetermined number and performs ejection in units of the blocks, and wherein the ejection unit includes the storage unit in units of the blocks. 8. The ink jet recording apparatus according to claim 5, wherein a corresponding set value is read out from. 9. An ink jet recording apparatus which performs recording by ejecting ink droplets from each of the ejection ports using a recording head having a plurality of ejection ports, wherein: an ejection means for ejecting ink droplets from the ejection ports; A recording head temperature measuring unit for measuring a temperature of the recording head; and a storage unit for storing a set value corresponding to each temperature of the recording head, wherein the discharging unit is configured to measure the temperature measured by the recording head temperature measuring unit. An ink jet recording apparatus, wherein a corresponding set value is extracted from a storage unit, and a pulse width of a drive pulse is set as a set value. 10. The ink jet recording apparatus according to claim 9, wherein the set value decreases as the temperature of the recording head increases. 11. The ejection unit counts an elapsed time from a fall of a drive input signal indicating a rise timing of the drive pulse, and determines a pulse width of the drive pulse until the elapsed time matches the set value. 11. The ink jet recording apparatus according to claim 9, wherein 12. The recording head, wherein the recording head divides the plurality of ejection ports into a plurality of blocks each having a predetermined number of units and performs ejection in units of the blocks. The ink jet recording apparatus according to claim 9, wherein a corresponding set value is read from the printer. 13. The recording head according to claim 1, wherein the recording head uses thermal energy to generate bubbles in the ink, and discharges the ink by a pressure at which the bubbles are generated. Ink jet recording device. 14. A method of driving a recording head using an ink jet recording apparatus that performs recording by discharging ink droplets from each discharge port of a recording head having a plurality of discharge ports, wherein each of said plurality of discharge ports is stored in a storage unit. A print head driving method, wherein a set value set for each discharge port is extracted according to the discharge characteristics of the discharge port, and the set value is used as a pulse width of a print head drive pulse. 15. The printhead driving method according to claim 14, wherein the ejection characteristics are determined based on a result of a shipping inspection of the printhead. 16. The method according to claim 1, further comprising counting an elapsed time from a fall of a drive input signal indicating a rise timing of the drive pulse, and extending a pulse width of the drive pulse until the elapsed time matches the set value. The recording head driving method according to claim 14 or 15, wherein: 17. A method of driving a recording head using an ink jet recording apparatus that performs recording by discharging ink droplets from each discharge port of a recording head having a plurality of discharge ports. In addition to counting the number of dots, a set value corresponding to the count value is extracted from each set value corresponding to the number of simultaneously ejected dots stored in the storage unit, and the set value is used as a pulse of a print head drive pulse. A recording head driving method characterized in that the width is a width. 18. The printhead driving method according to claim 17, wherein the set value increases as the count value increases. 19. The method according to claim 19, further comprising counting an elapsed time from a fall of the drive input signal indicating a rise timing of the drive pulse, and extending a pulse width of the drive pulse until the elapsed time matches the set value. 19. The recording head driving method according to claim 17, wherein: 20. A method for driving a recording head using an ink jet recording apparatus which performs recording by discharging ink droplets from each of the discharge ports of a recording head having a plurality of discharge ports, comprising: measuring a temperature of the recording head; Extracting a set value corresponding to the measured temperature from each set value corresponding to each temperature of the print head stored in a storage unit, and using the set value as a pulse width of a print head drive pulse. A method for driving a recording head. 21. The printhead driving method according to claim 20, wherein the set value decreases as the temperature of the printhead increases. 22. A method of counting the elapsed time from the fall of a drive input signal indicating the rise timing of the drive pulse, and extending the pulse width of the drive pulse until the elapsed time matches the set value. 22. The recording head driving method according to claim 20, wherein: