JP2606215B2 - Ink jet recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus that ejects ink droplets having different ink weights.

[Conventional technology]

FIG. 9 is a perspective view showing a conventional example of a four-color ink jet head, and FIG. 10 is a conceptual view showing a nozzle orifice arrangement of a conventional example. The nozzle rows N ₁ , N ₂ , N ₃ , and N ₄ correspond to the four colors of ink, respectively, and eject ink droplets having an appropriate weight from the nozzle orifice during the process of moving the ink jet head in the x direction. Record in color on paper. Conventionally, in order to realize gradation expression, a method of changing an input pulse width of a print signal and a method of changing an amplitude of an input pulse have been adopted. However, in the above two methods, it is difficult to change the weight of the ink droplet while keeping the flying speed of the ink droplet constant, and the flying speed of the ink droplet changes and the positional accuracy of the ink droplet attached to the recording paper is inaccurate. There was a problem.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and it is an object of the present invention to provide an ink jet recording apparatus having the same ink droplet flying speed regardless of the magnitude of the ink droplet weight.

[Means for solving the problem]

The ink jet recording apparatus of the present invention includes a nozzle orifice having a plurality of different opening areas for discharging ink droplets having different ink weights, a pressure chamber communicating with the nozzle orifice, and a piezoelectric element for pressurizing the external pressure chamber. Under the same condition that the driving waveforms for driving the piezoelectric elements corresponding to the plurality of nozzle orifices are the same, the piezoelectric elements of the piezoelectric elements are made to have the same flight speed of ink droplets ejected from the nozzle orifices having the different opening areas. The thickness is set.

〔Example〕

FIG. 1 shows an embodiment of the present invention, which is a color inkjet head capable of ejecting ink droplets of two colors. Ink I ₁ in the ink tank T _1, the ink supply tube C, an ink supply preparatory chamber 4, the ink supply path 3, via the pressure chamber 2 a discharge, as an ink droplet from a nozzle orifice 1 of the nozzle orifice array N ₁₁ and N ₁₂ Is done. The ink I ₂ in the ink tank T ₂
Nozzle orifice 1 also nozzle orifice array N ₂₁ and N ₂₂
The ink is ejected as ink droplets. Here, ink droplets speed 7m / s by the nozzle orifice array N ₁₁ and N ₂₁ is for applying a voltage of 100V to 100μsec piezoelectric element, the ink drop weight
It is configured to eject 0.4 μg ink droplets.
On the other hand the nozzle orifice array N ₁₂ and N ₂₂ is a voltage of 100 V 100
The ink droplet speed is 7 by applying to the μsec piezoelectric element.
It is configured to eject ink droplets of m / s and an ink droplet weight of 0.2 μg.

Figure 2 is a perspective view of the components for ejecting ink T ₁ in the embodiment of Figure 1. The flow path is based on the example shown in FIG. Glass channel substrate 7, a flow path ink drop weight to contact the nozzle orifice rows N ₁₁ on one side shows a property that 0.4 [mu] g, also a flow channel communicating with the nozzle orifice rows N ₁₂ on the opposite surface, respectively It is formed by etching. The thickness of the channel substrate 7 preferable in that the distance between the nozzle orifice array N ₁₁ and N ₁₂ is set to be an integer multiple of the desired resolution takes ejection timing of the ink droplets. The components for ejecting ink T ₂ is also exactly the same configuration. However, the viscosity of the ink T ₁ and T _2, the surface tension, it is also possible to change the shape of the ink flow path by differences in temperature characteristics.

FIG. 3 shows the characteristics of a head designed based on the embodiment shown in FIG. Nozzle orifice array N ₁₁ bitter, the nozzle orifice array N ₁₂ correspond respectively. Represents the input pulse to the drive circuit, represents the voltage of the piezoelectric element, and represents the amount of ink ejected from the nozzle orifice 1, respectively. Despite the same voltage and pulse width being applied to both ink channels, there is a difference in the weight of the ejected ink droplets. This is because the shapes of the two ink flow paths are different. In general, in order to reduce the weight of the ink droplet, measures such as reducing the opening area of the nozzle orifice 1, adjusting the width of the ink flow path, and increasing the thickness of the piezoelectric element are taken. The present inventor has prototyped an inkjet head in which the area of the nozzle orifice opening is reduced by 30% and the thickness of the piezoelectric element is increased by 50%. Has been confirmed to be 1/2.

FIG. 4 is a block diagram showing a driving circuit for the heads 101 and 102 for ejecting ink droplets of large and small weights. When applied to the embodiment of FIG.
101 nozzle orifice array N _11, the head 102 is considered to be an ink flow path corresponding to the nozzle orifice row N _12.
The ink droplet ejection command is transmitted to the control circuit 401 as a print signal 501 and a gradation signal 601. The control circuit 401 is constituted by logic for selecting both the heads 101 and 102 based on the received gradation signal 601 and outputs the selection result via the signal lines L ₁ and L ₂ . However, it is possible that both the heads 101 and 102 are selected. The signal output from the control circuit 401 is based on the principle that after the ejection timing is adjusted by the delay circuits 201 and 202, the signal reaches the drive circuits 301 and 302 and the ink droplet is ejected from the nozzle orifice 1. The reason for using the delay circuits 201 and 202 is that the nozzle orifice array extends over several rows perpendicular to the printing direction, so that the ink droplet ejection timing is delayed until the relative position between the recording paper and the nozzle orifice 1 becomes an appropriate position. is there.

FIG. 5 is a diagram showing the ink droplet weight with respect to the states of the signal lines L ₁ and L ₂ shown in FIG. At the head
An ejection command is sent to both 101 and 102, and as a result, an ink droplet of 0.6 μg obtained by summing the ejection amounts from both nozzle orifices is obtained. In addition, when only the head 101 is driven, an ink droplet of 0.4 μg is obtained, and when only the head 102 is driven, an ink droplet of 0.2 μg is obtained. Therefore, it can be seen that by appropriately selecting two types of heads that eject ink droplets of different weights, three types of gradation expression can be performed for the same color. Therefore, if three types of heads that eject ink droplets having different weights are appropriately selected, seven types of gradation expression can be performed for the same color. In the embodiment shown in FIG. 1, two colors of ink droplets can be ejected, and three types of gradation expression can be performed for each color, so that a total of 16 types of gradation expression are possible. Here, a color inkjet head capable of ejecting cyan, magenta, and yellow inks as two types of large and small ink droplets, respectively, can represent a total of 64 gradations.

Figure 6 is also an embodiment of the present invention, it is composed of an ink flow path which is based on FIG. 8, two types of ink droplets of the ink I ₁ and I ₂ is a color ink-jet head capable of ejecting. Thus the nozzle orifice array N ₁₁ and N ₁₂ denotes the characteristics of Oyobi respectively, in Figure 3. However, the input pulse to the drive circuit in FIG. 3 is set to have the same voltage and pulse width, but it is not always necessary to make them equal due to differences in ink flow path characteristics and temperature characteristics. . In this embodiment, 16 types of gradation expression are possible as in the embodiment shown in FIG.

〔The invention's effect〕

According to the inkjet recording apparatus of the present invention, since different ink droplets can be recorded on recording paper at the same flight speed, the positional accuracy of the ink droplets adhered on the recording paper becomes accurate, and a desired recorded image is obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a perspective view showing components of the embodiment, FIG. 3 is a waveform diagram showing characteristics of the embodiment, and FIG. FIG. 3 is a block diagram illustrating a driving circuit. FIG. 5 is a waveform diagram showing the states of the signal lines L ₁ and L ₂ in FIG. 4, FIG. 6 is a perspective view of the embodiment of the present invention, and FIGS.
The figure is a sectional view showing the structure of the on-demand type ink jet head. FIG. 9 is a perspective view showing a conventional example. FIG. 10 is a conceptual diagram showing details of a conventional nozzle arrangement. The symbols are described below. 1 ...... nozzle orifice 2 ...... pressure chamber 3 ...... ink supply path 4 ...... ink supply preparatory chamber 5 ...... piezoelectric element 6 ...... diaphragm 7 ...... channel substrate T ₁ through T ₄ ...... ink tank N ₁ NN ₄ , N ₁₁ NN ₂₂ …… Nozzle orifice array C …… Ink supply tube P …… Recording paper

Claims (2)

(57) [Claims] A nozzle orifice having a plurality of different opening areas for ejecting ink droplets having different ink weights;
A pressure chamber that communicates with the nozzle orifice; and a piezoelectric element that pressurizes the pressure chamber. The drive waveforms for driving the piezoelectric elements corresponding to the plurality of nozzle orifices have the different opening areas under the same condition. An ink jet recording apparatus, wherein the thickness of the piezoelectric element is set so as to make the flying speed of ink droplets discharged from a nozzle orifice equal. 2. The pressure chamber in which the opening area of the nozzle orifice is set to be smaller than the other is set thicker than the other piezoelectric elements. The inkjet recording apparatus according to any one of the preceding claims.