JPH07125217A - Thermal ink jet head driving method - Google Patents

Abstract

PURPOSE:To change the proper amt. of ink by changing the applied voltage of the drive pulse of a thermal ink jet head and to prevent the deterioration caused by the positional shift of a dot when gradation control is performed. CONSTITUTION:For example, when a voltage V2 is applied to applied voltage V1, timing is delayed only by the difference tS of the flight time of an ink droplet with respect to the timing of a drive pulse at the time of the applied voltage V1 to perform control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal ink jet driving method, and more particularly to changing the volume of a heat bubble generated on a heating resistor by changing the power applied to a driving pulse applied to the heating resistor according to recorded information. The present invention relates to a thermal inkjet driving method for a thermal inkjet recording device that controls gradation by changing the amount of ink droplets ejected from an ink ejection port.

[0002]

2. Description of the Related Art As a recording method for changing the amount of ejected ink droplets in a thermal ink jet recording apparatus, the amount of ink droplets is changed by changing the applied power, particularly the voltage, of a drive pulse applied to a heating resistor of a thermal head. The method has been generally known, for example, Japanese Patent Publication No. 59-3.
1943.

FIG. 3 is a diagram showing the principle of changing the amount of ink droplets in a thermal ink jet recording apparatus. In FIG. 3, only extreme cases of low voltage and high voltage are shown as extreme examples. 3A and 3B show driving pulses applied to the heating resistor 1 of the thermal head, and FIG. 3A shows the case where the voltage is small.
(B) is the case where the voltage is high. Both have the same pulse width. 3C and 3D are respectively shown in FIG.
The states of the thermal bubbles 4 generated on the heating resistor 1 when the drive pulses of (a) and (b) are applied to the heating resistor 1 are shown. Since the heating resistor 1 has a shape in which the width becomes narrower toward the central portion, the resistivity of the narrow portion in the central portion is large, and when a voltage is applied by the drive pulse, the temperature of the central portion is reduced. The temperature distribution is high and the temperature decreases toward the electrodes. Therefore, in the case of FIG. 3C where the voltage is small, only the central portion of the heating resistor 1 has reached the temperature required for vaporization of the ink 5, so that the thermal bubble 4 is generated only in that portion. Therefore, the amount of the ejected ink droplet 6 is as shown in FIG. In the case of a high voltage in FIG. 3D, the temperature of a wider area on the heating resistor 1 reaches the temperature required for vaporization of the ink 5, as compared with the case of a low voltage, and thus when the voltage is low. Larger thermal bubbles 4 are generated on the heating resistor 1. As a result, the voltage is small as shown in FIG.
The amount of the ink droplets 6 is larger than that in the above case, and the amount of the ink droplets 6 ejected can be increased by increasing the voltage.

FIG. 4 is a diagram summarizing the relationship between the above-mentioned applied voltage and the amount of ink droplets, which is a saturation curve as shown in the figure.
The ejection speeds of the ink droplets are also shown because they have the same relationship. When controlling the amount of ink droplets by changing the voltage, it is used in a voltage range in which the amount of ink droplets increases substantially in proportion to the applied voltage, that is, in the range in which the amount of ink droplets shown in FIG. 4 does not saturate. It

[0005]

In the conventional thermal ink jet driving method described above, the applied energy of the drive pulse applied to the heating resistor of the thermal head is changed within a limited range as shown in FIG. It is possible to change the amount of ink droplets, and as a result, it is possible to express the gradation of recording dots. However, at the same time as the amount of ink drops changes, the ejection speed of ink drops also changes. Therefore, when actually printing on the paper surface, in the serial printer, since the ink droplets have a velocity component in the row direction of the recording paper of the inkjet head, the position of the recording dot on the paper surface changes depending on the applied power. However, there is a problem that the print quality deteriorates due to the displacement of the recording dots.

[0006]

According to the thermal ink jet driving method of the present invention, the volume of the thermal bubble generated on the heating resistor is changed by changing the applied power of the driving pulse applied to the heating resistor according to the recorded information. In the thermal ink jet drive method of the thermal ink jet recording apparatus for controlling the gradation of dot ink by changing the amount of ink droplets ejected from the ink ejection port provided on the entire surface of the heating resistor. It is configured by changing the applied power of the drive pulse applied to the heating resistor and by correcting the drive timing of the drive pulse by correcting the difference in the ink flight time from the ink ejection port to the recording paper surface corresponding to the magnitude of the applied power. It

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of the present invention. The drive pulse in FIG. 1 is the time relationship of the drive pulse when performing continuous ejection by changing the applied voltage in any one nozzle. Indicates. In FIG. 1, the applied voltages are V ₁ , V ₂ (V ₁
It shows the case of two stages of <V ₂ ), and the pulse width of the drive pulse is constant in both cases of the applied voltages V ₁ and V ₂ . The relationship between the applied voltage and the ink droplet ejection speed in this case is as shown in FIG. In FIG. 2, the applied voltage V ₁
In this case, the ejection speed of the ink droplet is v ₁ , and the ejection speed of the ink droplet when the applied voltage is V ₂ is v ₂ . Here, the distance from the discharge port to the print surface and is h, the ink droplets in the case of the applied voltage V ₁ is the time to reach the printing surface t _1, the ink droplets in the case of the applied voltage V ₂ is the printing surface Assuming that the time required to reach it is t ₂ , t ₁ = h / v ₁ t ₂ = h / v ₂ , and the ink droplet and the applied voltage V ₂ when the applied voltage is V ₁
In the case of, the time difference t when the ink drops reach the print surface is t
_{Since s} is t _s = t ₁ −t ₂ , as shown in FIG. 1, the drive timing of the drive pulse which is the applied voltage V ₂ is divided by the time difference t _s from the drive cycle t which is the original drive timing. If delayed, the positional deviation of the recording dots is corrected due to the difference in the ejection speed of the ink droplets, and good print quality can be obtained. Although the present embodiment is an example in which the applied voltage has two levels, that is, the gradation has two levels, the applied voltage can be increased in any number of steps. However, as shown in FIG. 4, the range of the applied voltage that can change the amount of the ink droplet is limited, so that there is actually an upper limit.

[0009]

As described above, in the thermal ink jet drive system of the present invention, the amount of ink droplets ejected is changed by changing the applied power of the drive pulse applied to the heating resistor of the thermal head according to the recording information. In such a case, by changing the drive timing of the drive pulse, it is possible to prevent the misalignment of the recording dots caused by the change in the ejection speed that changes at the same time as the change in the ink droplet amount, so that good print quality can be obtained. The effect is that you can do it.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an applied voltage and an ink droplet ejection speed when the applied voltage has two levels.

FIG. 3 is a principle diagram of changing a conventional ink drop amount.

FIG. 4 is a diagram showing a relationship between a conventional applied voltage and the amount of ink droplets.

[Explanation of symbols]

 1 Heating resistor 2, 3 Electrode 4 Hot air bubble 5 Ink 6 Ink drop 7 Discharge port

Claims (1)

[Claims] 1. The ink provided on the front surface of the heating resistor by changing the applied power of the drive pulse applied to the heating resistor according to the recorded information to change the volume of the heat bubble generated on the heating resistor. In the thermal ink jet drive method of the thermal ink jet recording apparatus that controls the gradation of dot ink by changing the amount of ink droplets ejected from the ejection port, the applied power of the drive pulse applied to the heating resistor according to the recording information is set. A thermal ink jet drive method, characterized in that the difference in ink flight time from the ink ejection port to the recording paper surface corresponding to the magnitude of applied power is added to the drive timing of the drive pulse.