JPS5818909B2 - Inkjet cartridge door - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording device, and particularly to an inkjet recording device that can eject sufficiently large ink droplets with a small driving voltage.

An inkjet recording mechanism that has a device that increases the pressure in an internal ink tank or ink chamber in response to an applied electrical signal, and is one of the parameters of the electrical signal that drives the device. A recording apparatus for controlling the flow rate of ejected ink droplets by varying the flow rate or more and forming an image, mosaic character, or any other image on a recording medium with the ink droplets is disclosed in Japanese Patent Laid-Open No. 48
It is known from the publication No.-9622.

A recording mechanism such as this has a structurally specific mechanical resonance frequency in the range of several tens of kilohertz.

This resonance is caused by, for example, (1) standing waves of sound waves in the ink chamber, (2) natural vibrations of the electric-pressure conversion element or electric-pressure conversion device, (3) natural vibrations of the device itself, (4) of the holding mechanism. Caused by vibration, etc.

If such a resonant frequency exists, when driving the recording mechanism, if any of the frequency components of the drive waveform are close to this mechanical resonance point, parasitic vibrations of the recording mechanism will be induced, and if the resonance Q is high, contributes to the generation of unnecessary ink particles.

The present invention makes active use of such mechanical resonance and controls the vibration amplitude by changing the driving frequency by utilizing the slope of the frequency characteristic of the mechanical vibration amplitude, thereby controlling the ink droplets to be ejected. The present invention provides an inkjet recording device with the following features.

According to the present invention: (1) Since the resonance phenomenon is utilized, the driving voltage level may be small.

(2) Since constant voltage level driving is sufficient, the circuit configuration becomes simple.

(3) An FM modulation circuit is required, but this can be easily realized using known circuit technology.

It has such characteristics.

The principle and embodiments of the present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of a recording mechanism part of an inkjet recording apparatus disclosed in Japanese Patent Application Laid-Open No. 48-9622, in which 1 is a piezo crystal, 2 is a metal diaphragm, and 3 is an ink chamber.

A coupling passage 4 and an outflow passage 5 are connected to the tip of the ink chamber 3.

Reference numeral 6 designates an inflow passage through which ink from the ink supply tube 10 flows into the ink chamber 3, 7 an amplifier, 8.9 a voltage supply lead wire, and 11 a signal input terminal.

When an input signal is applied to the signal input terminal 11, amplified by the amplifier 7, and then the output signal is applied to the piezo crystal 1, the piezo crystal 1 is displaced according to the amplitude of the input signal, and the metal diaphragm 2 Pressure is applied to the ink in the ink chamber 3 through the ink chamber 3.

As a result, the ink in the ink chamber 3 is pushed out as ink droplets through the coupling passage 4 and the outflow passage 5 to the outside.

In an inkjet recording mechanism with such a structure,
As mentioned above, it has a unique resonance frequency in the region of several tens of KHz, and for example, when a sine wave of a constant amplitude is transmitted to a piezo crystal 1.
Looking at the internal stress in the ink chamber 3 when applied to the ink chamber 3, it responds as shown in FIG. 2 to the repetition frequency of the electric signal.

In the figure, 20 indicates a resonance region with a half width of several KHz.

In other words, the pressure within the ink chamber 3 increases at the frequency of the resonance region 20, and the diameter of the ejected ink particles increases.

On the other hand, the relationship between the amplitude of the electric signal applied to the piezo crystal 1 and the diameter of the ejected ink particles is as shown in FIG.

In the figure, a dotted line 30 shows the relationship when driving with an electrical signal whose repetition frequency is outside the resonance region described above, and a solid line 31 shows the relationship when driving with an electrical signal whose repetition frequency is in the resonance region.

32 is a threshold voltage for ejecting ink at a non-resonant frequency.

As shown in FIG. 3, the present invention focuses on the fact that ink ejection and particle size control are possible with a low applied voltage in the resonance region, and utilizes the slope of the resonance region of the mechanical vibration amplitude. The ejected ink droplets are controlled using a small applied voltage.

The frequency width of this slope is from several 100 Hz to several KHz, and the rising side is generally slightly narrower than the falling side.

In the present invention, both the rising and falling slopes can be used, but generally the pressure difference is larger on the rising side, and the ink particle size can be controlled to a greater extent.

In the following embodiment, a case will be described in which the rising side is used.

FIG. 4 shows an embodiment of the present invention.

In the figure, 40 is a frequency modulator, 41 is an input terminal of the frequency modulator 40, 42 is an amplifier, 43 is recording paper, and 44 is an inkjet recording mechanism.

The output frequency of the frequency modulator 40 is configured to vary depending on the level of the control signal applied to the input terminal 41.

That is, the output frequency f.

What is the bacteriostatic signal level■? Hail to you.

g is a function system. The amplifier 42 has a third output level.
The amplifier is determined so that the threshold voltage 32 shown in the figure is achieved.

Now, when the density of the pixel to be recorded changes from black to white, if the recording signal voltage changes from vl to F2 correspondingly, the control voltage ■ applied to the frequency modulator 40 also changes from vl to F2. Varies between F2.

Therefore, the output frequency f when V=V1.

−Fl, output frequency f when ■=■2. −F2, the output frequency f of the frequency modulator 40.

changes between Fl and F2.

Therefore, if F is selected as the resonant frequency of the recording mechanism and F2 is selected as a frequency near the resonant frequency but outside the resonant region, for example, the frequency indicated by 21 in FIG. 2, the control voltage V and frequency f at this time.

, the relationship between the ink particle diameters is as shown in FIG.

Therefore, when a signal V(t) showing a time change as shown in FIG. 50 is applied to the input terminal of the frequency modulator 40, a frequency signal determined by the function system 9(v) is obtained from the frequency modulator 40. .

When this frequency signal is amplified by the amplifier 42 and applied to the recording mechanism 44, the diameter of the ink particles ejected toward the recording paper 43 changes as shown in FIG. 51.

In this case, the ink particle size is controlled not by the voltage of the signal applied to the recording mechanism 44 but by the frequency, and since the resonance region of the recording mechanism 44 is utilized, the driving voltage may be low.

Moreover, the frequency modulator 40 can be easily obtained by known means,
Since the linearity of the amplifier 42 is not a problem, the circuit configuration becomes very simple.

Furthermore, with conventional drive methods, the problem is how to eject ink while avoiding mechanical resonance, which inevitably imposes restrictions on the recording speed, but with the present invention, the resonance phenomenon can be avoided. On the contrary, since it is used in the opposite direction, it is possible to use a high frequency range, and the recording speed can be increased.

[Brief explanation of the drawings] Figure 1 is a cross-sectional view of a conventional inkjet recording mechanism.
FIG. 2 is a diagram showing the frequency characteristics of the pressure inside the ink chamber in the recording mechanism shown in FIG. 1, FIG. FIG. 5 is a diagram illustrating the operation of the embodiment according to the present invention. DESCRIPTION OF SYMBOLS 1... Piezo crystal, 2... Metal diaphragm, 3... Ink chamber, 4... Connection passage, 5... Outflow passage. 7...Amplifier, 10...Ink supply pipe, 20...Resonance area, 40...Frequency transformer, 42...
...Amplifier, 43... Recording paper, 44...
・Recording mechanism.

Claims (1)

[Claims] 1. An inkjet recording mechanism having at least an ink chamber for storing ink to be ejected, a means for increasing the pressure in the ink chamber in accordance with the amplitude of an applied electric signal, and a passage for ejecting the ink in the ink chamber to the outside; an amplifier that supplies an electrical signal; and a frequency modulator that generates an input signal to the amplifier, and the output frequency of the frequency modulator changes the mechanical resonance number of the recording mechanism according to the gray level of the pixel to be recorded. 1 and a non-resonant frequency near the resonant frequency.