JP3048042B2 - Driving method of inkjet head - Google Patents

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 head, and more particularly to a method for controlling the gradation of recording dots on recording paper by changing the amount of ink droplets ejected from nozzles according to recording information. It relates to a driving method.

[0002]

The driving method of the Prior Art This type of ink jet head, a variety of methods have conventionally been disclosed. For example, the one disclosed in Japanese Patent Application Laid-Open No. 62-25060 is intended to perform recording excellent in frequency response, ejection stability, and variability of the amount of ink droplets.

FIG. 5 shows a driving pulse wave showing an example of a conventional driving method of an ink jet head. This drive pulse changes to V = −V ₁ at t = 0, and at time t =
The voltage is gradually changed to V = −V ₂ by a predetermined time constant until t _{1, the} voltage is rapidly changed to V = + V ₃ at t = t ₁ , and the voltage is maintained until time t = t ₂ , = the time constant from t ₂ t = t ₃ 0 given like becomes [V] is obtained so as to vary the voltage.

Here, an example of a cylindrical piezo used in an ink jet head will be described. In the cylindrical piezo (inkjet head) shown in FIG. 6, the volume of the pressure chamber 11 of the cylindrical piezo 10 decreases when a positive voltage is applied, and the volume of the pressure chamber 11 increases when a negative voltage is applied. Is formed.

Now, when the driving pulse shown in FIG. 5 is applied to the ink jet head in FIG. 6, the voltage suddenly changes in the negative direction at time t = 0, and accordingly the volume of the pressure chamber 11 also increases rapidly. And the position of the meniscus of the ink of the nozzle starts to recede. Next, from t = 0 to t ₁ , the voltage is gradually increased in the positive direction with a predetermined time constant, and the position of the meniscus 13 in the nozzle is changed to a predetermined position by the predetermined time constant. Can be kept.
Next, at time t ₁ , the voltage is rapidly changed in the positive direction to rapidly reduce the volume of the pressure chamber 11, pressurize the ink in the pressure chamber 11, and eject the ink droplet 14 from the nozzle 12.

As described above, by using the driving pulse as shown in FIG.
Since the pressure is applied in a state in which the meniscus 13 is not retracted, the amount of ink droplets to be ejected can be made smaller than when the meniscus 13 is not retracted. Furthermore, by varying the time t ₃ extending from the peak value V ₃ and the peak value V ₃ of the driving pulse to 0 V, the size of the recording dots and the recording paper by changing the amount of ink droplets ejected Can be changed.

[0007]

However, in the above-mentioned prior art, a driving pulse having positive and negative values is required to control the meniscus to eject ink droplets. Also requires two types, positive and negative, which has the disadvantage of complicating the drive circuit and increasing the cost. In addition, since the value of the positive voltage is changed to control the amount of the ink droplet, there is a disadvantage that the driving circuit is further complicated.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the prior art, and to control the amount of ink droplets ejected from an ink jet head in an appropriate amount and in a stable state without increasing the cost of a driving circuit. It is an object of the present invention to provide a method for driving an ink jet head that can be used.

[0009]

According to the first aspect of the present invention, a predetermined electric signal (drive pulse) is applied to a piezoelectric element in accordance with recording information to expand and contract the piezoelectric element. In a method of driving an ink jet head of a type in which a volume change of a pressure chamber is caused and ink droplets are ejected from nozzles communicating with the pressure chamber to form recording dots on recording paper, a driving pulse applied to the piezoelectric element described above. together with the trapezoidal pulse wave, the base
By appropriately adjusting the pulse width of the shaped pulse wave,
Adjust the ink meniscus position in the nozzle
You. The pulse width of the trapezoidal drive pulse is adjusted.
Adjustment for the constant voltage portion of the drive pulse ,
The configuration is adopted.

For this reason, in the invention according to claim 1,
When a voltage is applied to the piezoelectric element, the piezoelectric element expands and contracts accordingly, and as a result, the volume of the pressure chamber changes. Ink droplets are ejected from the nozzles by using the change in the volume of the pressure chamber (the amount of change is indicated by ΔV) due to the properties of the piezoelectric element.
In this case, since a trapezoidal drive pulse was used as the drive pulse for expanding and contracting the piezoelectric element, a single power supply (positive voltage) was used.
As a result, the amount of ink droplets can be controlled, and therefore, gradation recording can be performed without using a complicated circuit and thus without increasing the cost.

Furthermore, in the invention of claim 1 wherein, the ink droplets ejected from the nozzles by adjusting the pulse width of the trapezoidal drive pulses the position of the meniscus of the ink in the Nozzle <br/> Le Adjust the amount, and also this trapezoid
When adjusting the pulse width of the drive pulse of
Discharge from the nozzles
The use of complex circuitry to adjust the volume of ink drops
It is possible to execute with higher accuracy without any .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
4 through FIG. First, in FIG. 1, reference numeral 1 denotes a pressure chamber 1 for ink ejection of an ink jet head.
Is shown. The pressure chamber 1 for discharging ink is provided on a substrate 2 which forms a base of the ink jet head, and has a nozzle 3 on one end side and an ink introduction section (not shown) on the other end side. A piezoelectric element 5 is provided along the longitudinal direction of the pressure chamber 1. Further, a vibration plate 6 for variably controlling the volume in the pressure chamber 1 according to the expansion and contraction operation of the piezoelectric element 5 in the thickness direction is provided in the pressure chamber 1.

[0013] Here, in the present embodiment, the pressure chamber 1
Specifically, the lower side wall in FIG. 1 (the lower side in FIG. 1)
Are constituted by the substrate 2, and the upper side wall (upper surface side) in FIG. Reference numeral 7 denotes a nozzle plate. The nozzle plate 7 is formed with a nozzle 3 which forms a part of the pressure chamber 1 described above.

In the ink jet head shown in FIG. 1, when a voltage is applied to the piezoelectric element 5, the piezoelectric element 5 expands and contracts accordingly, and as a result, the volume of the pressure chamber 1 changes. The ink droplet 13 can be ejected from the nozzle 3 by utilizing the change in the volume of the pressure chamber 1 due to the property of the piezoelectric element 5 (the amount of change is indicated by ΔV).

[0015] Here, an explanation will be made for a driving pulse for driving the piezoelectric element 5 described above. In this embodiment, a trapezoidal pulse wave is used as a drive pulse (voltage pulse) for driving the piezoelectric element 5 as shown in FIG.

[0016] That is, The driving pulses shown in FIG. 2 (a), increasing the voltage with a positive slope V / t ₁ fixed in between "t = 0 to t _10" until time t _1, the time t _{From 1} to (t ₁ + t ₂ ), a constant voltage V [V] is maintained during “t = t _{10 to} t ₂₀ ”, and a constant negative slope V / is maintained during time “t = t _{20 to} t ₃₀ ”. decreasing the voltage with t _3, the time _{"t = t 30 (= t 1} + t 2 + t 3) " in such a 0 [V], a voltage pulse of trapezoidal is used.

Next, the operation of the embodiment will be described with reference to FIGS. 2 to 3. FIG. 3 shows an ejection mechanism of the inkjet head disclosed in FIG. First, time t
3A, the volume ΔV of the pressure chamber 1 gradually increases during the time “t = 0 to t ₁ ” as shown in FIG. 2B. increase in V will continue until "t = t _10".

As the volume of the pressure chamber 1 increases, the meniscus 12 of the ink 11 formed on the nozzle 3
As shown in (b), it is gradually drawn into the nozzle 3.
Thereafter, since the volume ΔV in the pressure chamber 1 is kept constant until “t = t ₂₀ ”, the meniscus 12 once drawn into the nozzle 3 by the capillary action of the ink in the nozzle 3
Returns toward the position of the meniscus 12 in FIG. 3A (FIG. 3C). In this state, the time “t = t
Ink droplets 13 are ejected by returning to the original volume of the pressure chamber 6 at ₂₀ ~t ₃₀ "between.

[0019] A point to be noted here is, time t = t ₂₀ ~
It is that the position of the meniscus is changed between t _30. In other words, by changing the predetermined value region t ₂ of the trapezoidal drive pulses shown in FIG. 2 (a), it is possible to change the position of the meniscus 12 in the nozzle 3 before discharge. As a result, the difference in the position of the meniscus 12 causes the ink drop 1
The amount of 3 can be changed.

FIG . 4 shows the measurement results of the pulse width t ₂ of the driving pulse and the amount of the ink droplet. FIG. 4 shows that the amount of the ink droplet 13 can be changed depending on the magnitude of the pulse width t ₂ . That is, as the pulse width t ₂ is large, it is understood that becomes larger the amount of the resulting ink droplets. However, as is clear from FIG. 4 ^, even if t ₂ is made larger than t ₂ = t ^, the amount of the ink droplet 13 does not increase. This is because the position of the meniscus 12 is completely returned to the position of FIG. 3A at t ₂ = t ^, and does not change any more.

[0021] Thus, in the present embodiment, a driving method for varying the amount of ink droplets 13 for ejecting the ink-jet head is performed depending on the magnitude of the pulse width t of the drive pulses shown in FIG. 2 (a) It turned out to get. Therefore, control of the position of the meniscus and the amount of the ink droplets 13 can be performed by a single power supply that outputs a single voltage value. As a result, it is possible to control the gradation of the recording dots according to the recording information without increasing the cost of the circuit for controlling the inkjet head.

[0022]

Since the present invention is constructed and functions as described above, according to this, the piezoelectric element is expanded and contracted to cause a change in the volume of the pressure chamber to eject ink droplets from the nozzles and to expand and contract the piezoelectric element. Since a trapezoidal driving pulse is used as the driving pulse for the, the amount of ink droplets can be controlled with a single power supply (positive voltage), and therefore, a complicated circuit is not used and thus the cost is increased. Gradation recording without the need for
When adjusting the pulse width, keep the voltage of the drive pulse constant.
Ink droplets ejected from nozzles
Adjust the amount of ink more without using complex circuitry
It is possible to provide an unprecedented and excellent method of driving an ink-jet head that can effectively control the amount of droplets .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a diagram showing the operation of the piezoelectric element disclosed in FIG. 1,
FIG. 2A is a diagram illustrating an example of a trapezoidal driving pulse to be applied, and FIG. 2B is a diagram illustrating a change in volume of a pressure chamber driven by the trapezoidal driving pulse.

3A and 3B are explanatory diagrams showing an ink ejection mechanism of the ink jet head shown in FIG. 1; FIG. 3A is a state diagram showing a state immediately before a drive pulse is applied to a piezoelectric element;
FIG. 3B is a state diagram showing a state when a drive pulse is applied to reach a certain value, and FIG. 3C is a state diagram showing a state when a drive pulse is applied and reaches a certain value and a certain time has elapsed. FIG. 3D is a state diagram showing a state immediately after the time of one drive pulse has elapsed.

FIG. 4 is a diagram showing a correlation between a driving pulse and an amount of an ink droplet in the embodiment in FIG. 1;

FIG. 5 is a diagram showing an example of a conventional method of driving a piezoelectric element of an ink jet (driving pulse).

6 is a schematic explanatory view showing an example of an inkjet head driven by the driving pulse disclosed in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure chamber 2 Substrate 3 Nozzle 5 Piezoelectric element 6 Vibration plate 7 Nozzle plate 11 Ink 12 Meniscus 13 Ink drop

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/205

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein a predetermined electric signal is applied to the piezoelectric element in accordance with the recording information to expand and contract the piezoelectric element to cause a change in the volume of the pressure chamber, thereby discharging ink droplets from a nozzle communicating with the pressure chamber. In a method of driving an ink jet head of a method of forming recording dots on recording paper by using a method, the driving pulse applied to the piezoelectric element is a trapezoidal pulse wave, and the pulse width of the trapezoidal pulse wave is adjusted appropriately.
The ink meniscus in the nozzle can be adjusted
The position of the trapezoidal drive pulse is adjusted by adjusting the pulse width of the drive pulse.
A method for driving an ink-jet head, characterized in that a portion where a pulse voltage is constant is targeted .