JPH06155732A - Driving method for inkjet recording head - Google Patents

Abstract

(57) [Abstract] [Purpose] The purpose is to improve the print quality by suppressing the fluctuations of the ink speed and the ink weight of the ejected ink droplets due to the ejection cycle and forming ejected ink droplets having a flat frequency characteristic. . Another object is to further improve ink ejection responsiveness by setting a pulse width suitable for each ejection interval time. [Structure] When ink is ejected continuously, the voltage pulse time in the next ink ejection is continuously adjusted to match the return time of the nozzle meniscus according to the time interval from the previous ink ejection to the next ink ejection. And change intermittently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an ink jet recording head, and more particularly to a method for driving an on-demand type ink jet recording head.

[0002]

2. Description of the Related Art A conventional method of driving an ink jet recording head will be described with reference to FIGS.

FIG. 9 shows the main part of the recording head. In FIG. 9, 1 is an ink tank, 2 is an ink supply passage, 3 is an ink pressurizing chamber, 4 is an ink nozzle, and 5 is a vibrating plate. The piezoelectric element 6 is attached on the vibrating plate 5, and is constituted by the vibrating plate 5 and the piezoelectric element 6.

In such a structure, when a pulsed voltage is applied to the piezoelectric element 6, the piezoelectric element 6 expands in the length direction and contracts in the thickness direction as shown by the arrow in the figure. Therefore, the vibrating plate 5 is moved to the ink pressurizing chamber 3 as shown by the dashed line a in the figure.
Bend outside of. As a result, the volume of the ink pressurizing chamber 3 increases. After that, when the voltage of the piezoelectric element 6 is unloaded, the vibration plate 5 is restored again, and the pressure wave generated by the deformation thereof causes the ink in the ink pressurizing chamber 3 to become an ink droplet, and the ink nozzle 4 to draw the ink as shown in FIG. It is discharged in the b direction. In addition,
The recording head has a structure in which the ink pressurizing chamber 3 and the ink nozzle 4 directly communicate with each other, and the ink droplets are ejected in a direction parallel to the pressurizing direction of the ink.

FIG. 10 shows the main part of another recording head, and its basic structure and the principle of ink ejection are the same as those shown in FIG. In this example, however, the ink nozzles 4 are formed in the ink pressurizing chamber 3 side direction, and the ink droplets are ejected in a direction perpendicular to the ink pressurizing direction.

FIG. 11 shows the voltage pulse waveform applied to the piezoelectric element 6 and the ink meniscus position formed on the ink nozzle 4. First, the voltage is applied up to V1 during the voltage application time Tc. Voltage hold time Th
During this period, the state in which the voltage V1 is applied is maintained. next,
The charging voltage V1 is unloaded during the voltage unloading time Td,
At time t3, the electric charge is set to zero.

At the voltage application time Tc, the ink meniscus gradually retreats toward the ink pressurizing chamber 3 as the volume of the ink pressurizing chamber 3 is increased. After that, the nozzle starts returning again and reaches the nozzle surface near the end t2 of the voltage hold. The time after the voltage is applied until the ink meniscus returns to the nozzle surface is hereinafter referred to as the meniscus return time. Then, by unloading the electric charge applied to the piezoelectric element 6 during the voltage unloading time Td, the volume of the ink pressurizing chamber 3 is rapidly reduced, and the ink nozzle 4 is discharged.
More ink is ejected.

The series of steps are repeated n times (n is a natural number) in accordance with the intended print command of the ink jet recording head.

[0009]

Problems that occur when ink is ejected by the method for driving an ink jet recording head according to the above-mentioned conventional method will be described with reference to FIGS.

FIG. 12 shows the damping vibration of the meniscus after the ink ejection and the voltage application timing t0 of the next ink ejection.
Shows the relationship. As shown in the figure, the damping vibration of the meniscus occurs after ink ejection, so the voltage application timing of the next ink ejection may differ due to the difference in the time interval from the previous ink ejection to the next ink ejection (hereinafter, ejection time interval). t0 ',
The meniscus position is different at t0 "(in the figure, two voltage pulse waveforms of the next ink ejection are shown). The meniscus recovery time is different depending on the position and the vibration direction of the meniscus at the voltage application timing t0. , A, when a voltage is applied to the piezoelectric element while vibrating in the direction of returning to the nozzle surface, the ink meniscus formed in the ink nozzle 4 is not drawn into the nozzle so much. When a voltage is applied to the piezoelectric element while vibrating in the direction of returning to the nozzle surface like part b,
The ink meniscus formed on the ink nozzle 4 is largely drawn into the nozzle. Therefore, when driven by the same voltage pulse waveform, as shown in FIG. 13, the ejection time interval and the ink meniscus recovery time generated by applying voltage to the piezoelectric element 6 become shorter as the ejection time interval becomes shorter. The meniscus return time is short, and the longer the ejection time interval is, the slower the meniscus return time is.

FIG. 14 shows the relationship between the ink meniscus position at the time of voltage unloading t2, the ink speed of the ejected ink droplet, and the ink weight. As shown in the figure, as the nozzle meniscus at the time of voltage unloading t2 is drawn into the ink nozzle 4, the ink speed of the ejected ink droplet becomes faster and the ink weight tends to increase. On the contrary, as the height of the ink droplet rises from the nozzle surface, the ink speed of the ejected ink droplet becomes slower and the ink weight decreases.

From the above results, when the discharge is performed with the voltage loading time Tc and the voltage hold time Th being constant irrespective of the discharge time, the position of the nozzle meniscus at the time of voltage unloading t2 is different and Changes in speed and ink weight are likely to occur. For this reason, when the ejected ink droplets adhere to the print medium, the formed dot diameter is different, the print quality is deteriorated, and the shorter the ejection time interval is, the larger the variation amount is. It has a problem that it cannot be raised.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the variation in the ink speed and the ink weight of an ejected ink droplet depending on the ejection time interval, thereby performing printing. It is an object of the present invention to provide a method for driving an inkjet recording head that improves quality and stabilizes ink ejection, and a second object of the present invention is to provide a method for driving an inkjet recording head that achieves high responsiveness. To provide.

[0014]

An ink pressurizing chamber, an ink nozzle communicating with the ink pressurizing chamber, an ink pressurizing chamber disposed outside the ink pressurizing chamber, and deformed by application of a voltage pulse. A method of driving an on-demand type ink jet recording head, comprising: a piezoelectric element that reduces the volume of a chamber; and pressurizing ink in an ink pressurizing chamber by a pressure wave generated when the piezoelectric element is deformed and ejecting the ink from an ink nozzle, The voltage pulse width in the next ink ejection is changed according to the ejection time interval. Further, in the inkjet recording apparatus, a plurality of voltage pulse widths are provided, and one of the plurality of voltage pulse widths is selected according to the ejection time interval in continuous ink ejection. In the ink jet recording head, the voltage pulse width is shortened as the ejection time interval when ink is ejected continuously becomes shorter.

[0015]

EXAMPLES First, examples of the present invention will be described. The basic structure and the basic operation of the main part of the recording head of the present invention are the same as those in FIGS.

The first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows a “previous ink ejection” including a voltage application time Tc, a voltage hold time Th, and a voltage unloading time Td, and a voltage application time T corresponding to an ejection time interval T ′.
“Next ink ejection” including c ′, voltage hold time Th ′, and voltage unloading time Td, and voltage application time Tc ″ according to the ejection time interval T ″, voltage hold time Th ″, and voltage unloading time Td. The voltage pulse waveform which consists of "the next ink discharge" is shown. As described in the conventional example, the ejection time interval and the meniscus recovery time have the relationship of FIG. 13, and the sum of the voltage application time and the voltage hold time for each “next ink ejection” corresponds to the ejection time interval. Match the meniscus return time. As a result, the ink meniscus position of the ink nozzle 4 at the voltage unloading timing t2 can be made constant regardless of the ejection time interval.
It is possible to suppress variations in ink speed and ink weight of ejected ink droplets due to the ejection time interval.

Next, referring to FIG. 2, the relationship between the voltage application time Tc and the voltage hold time Th and the meniscus behavior of the ink nozzle 4 will be described in detail. As shown in the figure, as the voltage is applied, the meniscus of the ink nozzle 4 is once drawn into the nozzle and returns again. When the restored meniscus reaches the edge A of the nozzle surface,
If it is still within the voltage application time Tc, the meniscus is held in the unstable state of the state 1, and when the voltage hold state is entered, the meniscus slowly returns to the stable state of the meniscus of the state 2 from the state 2 to the state 3. Transition. On this occasion,
It takes about 10 μs as the time required to shift from the state 1 to the state 2. Therefore, in the above embodiment, the meniscus position of the ink nozzle 4 at the voltage unloading timing t2 can be made more stable by setting the voltage hold time Th to 10 μs or more.

Further, in the above embodiment, the voltage application time Tc and the voltage hold time Th for the "next ink discharge" are set.
Was added to the meniscus recovery time corresponding to the ejection time interval, and the ink meniscus position at the voltage unloading timing and the ink speed and ink weight of the ejected ink droplet have the relationship shown in FIG. 14, which is necessary. Recording head characteristics (balance between ink speed and ink weight)
It is also possible to set the time corresponding to the ink meniscus position at which Specifically, when the voltage hold time Th is set to 3 μs or less, the ink meniscus position at the voltage unloading timing t2 is in the state 1, and therefore the ink speed becomes faster than the ink ejection in the state 2, Weight is reduced. Further, when the voltage hold time Th is set to 10 to 15 μs, the ink meniscus position at the voltage unloading timing t2 is in the state 3, and therefore the ink speed becomes slower and the ink weight becomes smaller than the ink ejection in the state 2. To increase. As described above, by changing the voltage hold time, it is possible to adjust the balance between the ink speed and the ink weight of the ejected ink droplet of the ink weight, and the meniscus position changes from state 1 to state 3. Therefore, the ink speed can be adjusted to 3 m / s and the ink weight can be adjusted to 0.03 μg / dot.

Next, a second embodiment of the present invention will be described with reference to FIG.
And 4 are shown. As shown in FIG. 3, the ejection interval time T is divided into multiple stages (in the figure, is divided into three), and the sum of the voltage application time Tc and the voltage hold time Th is set according to each time zone. Make changes to. The set amount is shown in FIG.
Based on the relationship between the ejection time interval and the ink meniscus recovery time shown in (2), the meniscus positions are set to be equal in the central time of each ejection interval time zone. When the sum of the voltage application time Tc and the voltage hold time Th is set as described above, as shown in FIG. 4, the ink speeds of the ejected ink droplets in the central time of each ejection time interval band become substantially equal, and the ejection time interval is It is possible to suppress variations in ink speed due to. At this time, regarding the number of divisions of the time zone, the time width, and the division position, the ink speed max.
The setting was made so that the difference between the value and the min value was within 2 m / s.

FIG. 5 shows a flowchart of the drive waveform control in the above embodiment. Further, FIG. 6 shows a timing chart of pulses forming a drive waveform. In FIG. 6, the number of pulse timings equal to the number of divisions of the ejection time interval band is set with reference to the trigger signal (three timings in FIG. 6). Each delayed pulse P
A pulse Pc for applying each voltage to the delay
Rising timing is determined. After that, the pulse Pc falls at the same timing regardless of the delay pulse, and similarly, the pulse Pd for voltage unloading rises and falls at the same timing. A period equal to the voltage hold time is set between the fall of the pulse Pc and the rise of the pulse Pd. The drive waveform shown in FIG. 1 is formed through the drive waveform generation circuit shown in FIG. 8 at the plurality of pulse timings shown in FIG. Here, the drive waveform generation circuit corresponding to each pulse timing is set. After that, the output of the output terminal Vout of the drive waveform generating circuit is sent to the selection SW circuit corresponding to each piezoelectric element, as shown in FIG. The selection SW circuit corresponding to each piezoelectric element outputs a signal from a selection device that selects a driving condition for each piezoelectric element based on a print command signal and a set ejection time interval band, if there are a plurality of drive waveforms. The selected drive waveform is conducted to the piezoelectric element, and the piezoelectric element is driven according to the print command.

[0021]

The present invention described above has the following effects.

(1) It is possible to suppress variations in ink speed and ink weight of ejected ink droplets due to ejection time intervals, and it is possible to form ejected ink droplets having flat frequency characteristics.

(2) Since the pulse width can be set according to the behavior of the nozzle meniscus at each ejection time interval, it is possible to cope with ejection with a narrower ejection interval, which leads to an improvement in responsiveness.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a phenomenon that is a basis of an embodiment of the present invention.

FIG. 3 is a diagram illustrating a second embodiment of the present invention.

FIG. 4 is a diagram for explaining the effect on the characteristics of ejected droplets of the inkjet head according to the second embodiment of the present invention.

FIG. 5 is a diagram showing a flow chart of pulse control for achieving the embodiment of the present invention.

FIG. 6 is a diagram illustrating pulse control for achieving the embodiment of the present invention.

FIG. 7 is a diagram illustrating pulse control for achieving the embodiment of the present invention.

FIG. 8 is a diagram illustrating a typical drive waveform generation circuit for achieving an embodiment of the present invention.

FIG. 9 is a diagram illustrating the basic structure of a conventional inkjet head.

FIG. 10 is a diagram illustrating another basic structure of the conventional inkjet head.

FIG. 11 is a diagram illustrating a voltage pulse waveform and a behavior of a nozzle meniscus in driving an inkjet head of a conventional example.

FIG. 12 is a diagram illustrating a problem in driving an inkjet head of a conventional example.

FIG. 13 is a diagram illustrating a problem in driving an inkjet head of a conventional example.

FIG. 14 is a diagram illustrating a problem in driving an inkjet head of a conventional example.

[Explanation of symbols]

 1, ink tank 2, ink supply path 3, ink pressurizing chamber 4, ink nozzle 5, vibrating plate 6, piezoelectric element

Claims (3)

[Claims] 1. A volume of the ink pressurizing chamber, an ink nozzle communicating with the ink pressurizing chamber, an ink nozzle arranged outside the ink pressurizing chamber, and deformed by application of a voltage pulse. And a piezoelectric element for reducing the pressure of the piezoelectric element, the method for driving an on-demand type inkjet recording head in which ink in the ink pressurizing chamber is pressurized by the pressure wave generated when the piezoelectric element is deformed and ejected from the ink nozzle, A method for driving an ink jet recording head, characterized in that the voltage pulse width in the next ink ejection is changed depending on the time interval from the previous ink ejection to the next ink ejection. 2. The ink jet recording head has a plurality of voltage pulse widths, and selects one of the plurality of voltage pulse widths according to a time interval from a previous ink ejection to a next ink ejection in continuous ink ejection. The method for driving an ink jet recording head according to claim 1, wherein: 3. The ink jet recording head according to claim 1, wherein the voltage pulse width is shortened as the time from the previous ink ejection to the next ink ejection in the continuous ink ejection is shortened. Driving method.