JPS6222369Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink drop ejecting device that is incorporated into an inkjet printer or the like and ejects minute ink droplets on demand.

The inventors of this invention are Tokko No. 53-12138 and Tokko Sho.
A new device different from the well-known on-demand type ink drop ejecting device disclosed in No. 53-45698 was provided, and a patent application was filed as Japanese Patent Application No. 55-84264 on June 20th. The present invention relates to the improvement of such a novel on-demand type ink droplet ejecting device, and first, the ink droplet ejecting device which is the basis of the present invention described in the above-mentioned patent application specification will be explained.

FIG. 1 is a cross-sectional view showing an ink droplet ejecting device which is the basis of the present invention, in which 1 is a piezoelectric vibration means that vibrates in response to electrical signals such as sinusoidal, rectangular, and sawtooth waves. 2 is a horn-shaped pressure chamber in which the piezoelectric vibrator 1 forms one side wall of the long diameter end and has a small-diameter opening 3 at an opposing location; 4 closes the opening 3 of the horn-shaped pressure chamber 2; A thin plate 5 such as a resin plate, a metal plate, a rubber sheet, or a film is a propagation medium that fills the pressure chamber 2 closed by the thin plate 4 and propagates the vibration of the piezoelectric vibrator 1 to the thin plate 4. The medium 5 is a colloid of powder in a liquid such as water, ink, silicone oil, mercury, etc., a viscoelastic substance such as silicone grease, and a magnetic fluid that has a high vibration propagation rate and has a damping effect against residual vibrations. Those mixed with the above are used as appropriate. Therefore, the thin plate 4 acts as a vibrating part. Reference numeral 6 denotes a front plate which is placed in front of the thin plate 4 with a small space between them and holds an ink layer 7 of a constant thickness therebetween, and 8 is a small hole bored at a location facing the thin plate 4 in the approximate center of the front plate 6. A small diameter orifice 9 is a capillary tube that supplies ink to the ink layer 7 from the outside.

When an electric signal is supplied to the piezoelectric vibrator 1 of the ink droplet ejecting device having such a structure, the piezoelectric vibrator 1 vibrates in a curved manner and when curved toward the pressure chamber 2 side, increases the pressure within the pressure chamber 2 . This pressure increase reaches the small-area thin plate 4 through the propagation medium 5 while being amplified due to the horn-like shape, and rapidly displaces the thin plate 4 toward the ink layer 7 side. Therefore, due to this rapid displacement of the thin plate 4, the ink in the ink layer 7 protrudes from the orifice 8 bored at the opposing location and is ejected as ink droplets. Next, when the piezoelectric vibrator 1 bends in the opposite direction, the pressure in the pressure chamber 2 decreases, the thin plate 4 returns to a flat state, and the ink layer 7 is replenished with ink from the capillary tube 9.

In this way, ink droplets are ejected and ink is replenished by the vibration of the thin plate 4, and it is very important to vibrate the thin plate 4 faithfully in response to electrical signals.

On the other hand, the pressure chamber 2 is filled with the propagation medium 5 by forming a pore 10 communicating with the pressure chamber 2 as shown in FIG. A method is adopted in which the propagation medium 5 is filled and then closed with a screw-type sealing plug 11. According to this method, an elastic packing 12 such as an O-ring is inserted between the seat of the sealing stopper 11 and the detail 10 to close the pore 10 in a watertight manner.

However, if the screwing amount of the sealing plug 11 is increased in order to improve the sealing degree of the sealing plug 11, the pressure of the propagation medium 5 in the pore 10 will increase, pressurizing the propagation medium 5 in the pressure chamber 2, and the As shown in FIG. 2, there is a risk that the thin plate 4 may be bent. When the thin plate 4 is bent in this manner, the thin plate 4 cannot vibrate faithfully even when subjected to pressure changes caused by the piezoelectric vibrator 1, and cannot eject ink droplets on demand.

Furthermore, if the pressure chamber 2 is sealed, there is a risk that the desired ink droplets may not be ejected because the propagation medium 5 filled inside has deteriorated over time.

Therefore, the inventors of the present invention bored a small diameter communication hole 13 in the thin plate 4 as shown in FIG.
We have already proposed a structure that allows communication between the two.

However, in the structure in which the communication hole 13 is bored in the thin plate 4, leakage of the amplified pressure increase within the pressure chamber 2 from the communication hole 13 is inevitable, and for this reason, the communication hole 13
The diameter of the opening must be extremely small.
Moreover, the diameter of this opening can only be formed to the same size as the thickness of the thin plate 4. Furthermore, if the diameter is extremely small, there is a risk of clogging due to foreign matter mixed in the ink.

The present invention has been devised in view of this point, and one embodiment of the present invention will be described in detail below.

FIG. 4 is a cross-sectional view showing the device of the present invention, with 1
〜12 is a piezoelectric vibrator as in FIGS. 1 to 3〜
The difference is that the elastic packing is made of a communication hole 13 of the device shown in FIG.
The communication passage 14 has an aperture diameter larger than the aperture diameter of
It is located where it was formed. That is, the pressure chamber 2 is constantly in communication with the ink layer 7 via the communication passage 14. In addition, the communication passage 14 has pores 1 for degassing.
0 is connected. Since the pressure chamber 2 and the ink layer 7 are in communication, ink is used as the propagation medium 5' filled in the pressure chamber 2.

In this way, the pressure chamber 2 of the ink droplet ejecting device having the communication passage 14 in the pressure chamber 2 is filled with the propagation medium 5' made of ink by passing the pressure chamber 2 through the communication passage 14 and the pores 10. The pressure chamber 2 is immersed in the ink in an open state to perform vacuum degassing, and the air in the pressure chamber 2 is replaced with the propagation medium 5' through the pores 10. At the same time, the air in the ink layer 7 is also evacuated through the same pores 10 and filled with the same quality ink of the propagation medium 5'. Then, a sealing plug 11 having an elastic packing 12 inserted therein is screwed into the pore 10 which is connected to the pressure chamber 2 and the ink layer 7. Furthermore, when the amount of screwing of the sealing plug 11 is increased in order to seal the pore 10 watertightly, the pressure of the ink within the pore 10 increases, and the propagation medium 5' attempts to pressurize the pressure chamber 2. However, this pressure increase leaks from the communication passage 14 to the ink layer 7 side, and the propagation medium 5' is not pressurized. That is, the pressure increase generated by watertightly closing the pores 10 leaks to the ink layer 7 side without pressurizing the propagation medium 5' and without bending the thin plate 4. layer 7
The inside pressure is the same, and the thin plate 4 is held in a flat state when no injection is performed.

When an electric signal is supplied to the ink droplet ejecting device in which the thin plate 4 is in a flat state when not ejecting by providing the communication passage 14 in this way, the pressure inside the pressure chamber 2 increases and the propagation medium 5' is The thin plate 4 is pressurized while being amplified by the horn shape of the chamber 2. At this time, in the case where the communication hole 13 shown in FIG. Pressure chamber 2 from near the long diameter end
Since the thin plate 4 is in communication with the communication passage 14, the thin plate 4 vibrates efficiently with almost no pressure increase leaking from the communication passage 14. Further, as mentioned above, since almost no pressure rise leaks from the communication passage 14, there is no need to make the diameter of the opening of the communication passage 14 extremely small. If the thickness of the thin plate 4 is 10 to 30 μm, it can be made to a large diameter of 200 to 500 μm, which is easier to process than the 10 to 70 μm for the communication hole 13, and the accuracy is less of a problem. No. Furthermore, since the opening diameter becomes larger, the occurrence rate of clogging is also dramatically reduced.

As is clear from the above description, the ink droplet ejecting device of the present invention forms a communication passage in a pressure chamber whose pressure changes by means of a pressure change means, and constantly communicates the pressure chamber with an ink layer holding ink. However, despite the structure in which the abnormal pressure increase that occurs when filling the pressure chamber with ink leaks to the ink layer side, and the ink pressure in the pressure chamber and the ink layer are the same when not ejecting, The aperture diameter of the communication passage can be made larger than that of conventional devices, which eliminates various concerns that have arisen due to the need for a minute diameter, and also reduces leakage due to pressure rise during injection. It can be made smaller. Therefore, the vibrating section can efficiently and faithfully respond to pressure changes of the pressure changing means, and can eject ink droplets on-demand stably over time.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing a conventional ink droplet ejecting device, and FIG. 4 is a cross-sectional view showing the device of the present invention, in which 1 is a piezoelectric vibrator, 2 is a pressure chamber, 7 is an ink layer, and 8 is a sectional view showing a device according to the present invention. In the orifice, 10 indicates a pore, 13 indicates a communication hole, and 14 indicates a communication passage.

Claims (1)

[Scope of utility model registration request] A pressure change means is associated with a pressure chamber filled with ink, and the pressure change caused by the pressure change means is applied to a thin plate that closes a small opening provided at a location opposite the pressure change means in the pressure chamber. In the ink drop ejecting device, the ink is applied intensively to the pressure chamber, and the ink in the ink layer held on the front surface of the thin plate is ejected as ink droplets from an orifice provided at a location facing the thin plate. A communication passage having an opening diameter that does not affect the vibration of the thin plate is formed to communicate this pressure chamber with the ink layer, and a pore connected to this communication passage for degassing is formed in a sealing member. An ink droplet ejecting device characterized in that the ink droplet ejecting device is characterized in that the ink pressure in the pressure chamber and the ink layer is the same when the pressure chamber is not ejected.