JPS629430B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet printing device, and particularly relates to an inkjet printing device that ejects ink only when necessary.
The present invention relates to an on-demand printing device.

An object of the present invention is to provide a downsized printing device.

Another object of the invention is to reduce the energy required for printing.

Still another object of the present invention is to provide a printing device that has a simple structure and is inexpensive.

An example of an ink ejection device of a conventional ink-on-demand printing device is shown in FIG. Using the piezoelectric element 1, an applied electrical signal is converted into a mechanical displacement, and the volume of the pressure chamber 2 is rapidly reduced to eject an ink droplet from the ejection port 3. This method includes
There are disadvantages in that the area of the pressure chamber 2 becomes large and energy efficiency is poor. This is because the amount of displacement of the piezoelectric element can only be obtained less than 1μ, and in order to obtain the required volume change, the area of the pressure chamber must be increased, and from the viewpoint of processing accuracy, the volume of pressure chamber 2 must be reduced. (reducing the height h), most of the added energy is used to compress this large volume of ink, and only a small portion of the energy is used to blow the ink droplets. By not having it. In addition, since the area of the pressure chamber is large, when a large number of ink ejection devices are integrated in a plane, it is necessary to arrange them as shown in Figure 2, which increases the distance d from the pressure chamber to the ejection port and reduces energy efficiency. The problem was that it got even worse.

The present invention eliminates such drawbacks and constructs a compact and energy-efficient inkjet recording device by ejecting ink using discharge energy, and also eliminates the direction of ink ejection that tends to occur when ejecting ink using discharge energy. It is an object of the present invention to provide an inkjet printing device in which irregular bending is made constant and ink ejection is not hindered by gas generated by discharge or gas that is quickly released.

The inkjet printing device of the present invention has a pair of electrodes disposed in an ink pressurizing chamber communicating with an ink reservoir, and discharge from an injection port communicating with an opposite side of the ink reservoir of the pressurizing chamber by a voltage applied between the electrodes. In an inkjet printing device that performs printing by ejecting ink, the distance measured from the end of the pair of electrodes on the injection port side to the injection port is equal to or longer than the diameter of the injection port, and the electrode surface is arranged opposite to the wall surface of the pressurizing chamber so that it is substantially flush with the wall surface of the pressurizing chamber, and the diameter of the pressurizing chamber on the side of the ink reservoir is made thinner, and the diameter of the ink reservoir side of the pressurizing chamber is narrowed, and the diameter extends from the injection port to the pressurizing chamber. It is characterized in that the diameter of the ink flow path is made into a smooth and uniform shape that is the same as the diameter of the pressurizing chamber.

FIG. 3 shows an embodiment of the present invention, where 31 is an ink reservoir that is easily deformed by pressure, and 32 is an ink reservoir 31.
This is a connecting pipe that connects the ink supply port 33 and the ink supply port 33. The ink 34 reaches the ink supply port 33 from the ink reservoir 31 through the connecting pipe 32. 35 is a pressurizing chamber provided with electrodes 36 and 37 above and below. 38 is an ink ejection port. 39 and 40 are lead lines from the electrodes 36 and 37. In the state shown in FIG. 3, the ink 34 is in an equilibrium state at the injection port 38 due to the surface tension and the static pressure of the ink reservoir 31. A control circuit (not shown) controls the driving voltage to the lead wires 39,
40 and is applied to electrodes 36 and 37. The driving voltage is set to be higher than the discharge breakdown voltage determined by the distance between the ink 34 and the electrodes 36 and 37. Therefore, a discharge occurs between the electrodes 36 and 37, and due to the discharge energy at this time, a part of the ink 34 is instantaneously vaporized, and the pressure of the volume expansion causes the injection port 38 to
The ink existing between the pressurizing chamber 35 and the pressurizing chamber 35 is ejected from the ejection port 38 in the form of ink droplets. After injection,
Due to capillary action, the ink 34 is again supplied to the position of the injection port 38 and returns to a steady state.

As can be seen from the above explanation, according to the present invention, the distance from the pressurizing part to the ejection port can be shortened, and energy can be applied to a minute volume of ink comparable to the ejected ink droplet, resulting in good energy efficiency. . Further, since a part of the ink is instantaneously vaporized by the discharge energy, there is less heat escape, which is advantageous in terms of energy. Further, since the structure is simple and an expensive piezoelectric element is not required, an inexpensive ink ejecting device can be provided.

Furthermore, when a pair of electrodes for discharge is provided in the pressurized chamber, the distance measured from the end of the electrode on the injection port side to the injection port is greater than or equal to the diameter of the injection port, as shown in FIG. The discharge electrode surface is arranged to face the pressurizing chamber wall surface so that it is substantially flush with the pressurizing chamber wall surface. Furthermore, the diameter of the ink reservoir side of the pressurizing chamber is made narrower, and the diameter of the ink flow path from the injection port to the pressurizing chamber is made into a smooth, uniform shape that is the same as the diameter of the pressurizing chamber. Therefore, since the discharge electrode is not too close to the injection port, the ink that is pressurized by the discharge energy flies along the inner surface of the nozzle, and there is no variation in the direction of ink flight that occurs when pressure is suddenly applied by the discharge energy, and the ink is constantly sprayed. Ink can be ejected in a fixed direction. In addition, even though the discharge electrode is far from the injection port, the diameter of the pressure chamber on the ink reservoir side is small, and conversely, the area from the pressure chamber to the injection port has a smooth and uniform shape that is the same as the diameter of the pressure chamber. The discharge energy is amplified as it heads toward the ejection port, causing ink to be ejected. At this time, the electrode surface for discharge is placed facing the wall surface of the pressurizing chamber so that it is almost flush with the wall surface of the pressurizing chamber, and the diameter on the ink reservoir side of the pressurizing chamber is narrow, and the pressurizing chamber is connected from the injection port to the pressurizing chamber. Since the diameter of the ink flow path leading to the pressurizing chamber is made to have the same smooth and uniform shape as the diameter of the pressurizing chamber, the gas generated by the discharge is quickly released from the injection port to the outside along with the flying ink. Therefore, the discharge energy is not absorbed due to residual gas, making it impossible to eject ink, and the amount and speed of ink ejection do not vary depending on the amount of residual gas, and dots with a uniform diameter can always be printed. It becomes possible.

Although a single ink ejecting device is shown in the embodiment of FIG. 1, if a large number of ink ejecting devices are integrated to print many dots at the same time, the advantages of small size, low energy consumption, and low cost will be further enhanced. In this case, the desired ink ejecting device can be easily manufactured using ordinary thick film technology.

Although the electrodes were provided above and below the pressurizing chamber, it is also conceivable to arrange them planarly on one surface for ease of manufacturing.

As described above, according to the present invention, it is possible to provide an inkjet printing device that is small in size, has good energy efficiency, has a stable ink ejection direction, and has uniform ink dot diameters.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional ink ejecting device, FIG. 2 is a plan view showing an example of a conventional ink ejecting device, and FIG. 3 is a sectional view showing an embodiment of the present invention. 33 is an ink supply port, 34 is ink, 36,3
7 is an electrode, 35 is a pressurizing chamber, and 38 is an injection port.

Claims (1)

[Scope of Claims] 1. A pair of electrodes are arranged in an ink pressurizing chamber communicating with an ink reservoir, and ink is discharged from an injection port communicating with the opposite side of the pressurizing chamber from the ink reservoir by electric discharge due to a voltage applied between the electrodes. In an inkjet printing device that performs printing by ejecting ink, the distance measured from the end of the pair of electrodes on the ejection port side to the ejection port is equal to or longer than the diameter of the ejection port, and the electrode surface is arranged opposite to the wall surface of the pressurizing chamber so that it is almost flush with the wall surface of the pressurizing chamber, and the diameter of the front pressurizing chamber on the side of the ink reservoir is made thinner, and the diameter of the front pressurizing chamber is made narrower so as to extend from the injection port to the pressurizing chamber. An inkjet printing device characterized in that the diameter of the ink flow path is made into a smooth and uniform shape that is the same as the diameter of the pressurizing chamber.