JPS6317625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-impact recording device, and more particularly to a device for ejecting liquid by the action of thermal energy.

Non-impact recording methods, especially the so-called inkjet recording methods, produce almost no noise during recording.
Recently, research and development have been actively conducted on this method, as it has great advantages such as being capable of high-speed recording and being able to record on plain paper without the need for special fixing treatment.

The device used in this recording method is usually a recording head that has an ejection orifice for ejecting colored liquid and causing it to fly as droplets, and an inlet for the liquid to flow into. . There are various types of recording heads depending on the method of ejecting liquid from the ejection orifice.

For example, pressurized liquid is supplied from an external liquid supply tank into a nozzle-shaped liquid chamber (pressurized to such an extent that it cannot be discharged from the discharge port by pressure alone), and the liquid in the liquid chamber is A voltage is applied between the electrode installed in front of the discharge orifice,
Liquid is electrostatically discharged from a discharge orifice.

Although this type of recording head has a simple structure, it has the disadvantage that the overall system configuration is complex and requires a high degree of skill and precision in electrically controlling the generation of droplets and the direction of their flight. Another drawback is that it is difficult to create a multi-orifice recording head, which is essential for high-speed recording.

Another type of recording head uses a mechanical vibration method to eject liquid and fly it as droplets. In other words, this type of device periodically changes the volume of the liquid chamber into which liquid is supplied by mechanical vibration of a piezoelectric element, thereby creating a pressure change in the liquid and ejecting it as droplets. . Its specific structure is
USP3747120, IEEE Transactions on Industry
Applications Vol IA-13, No.1, January/
It is disclosed in February 1977 etc.

In such a recording head, the overall system structure is simple. However, since the droplets are generated only by the mechanical vibration of the piezoelectric element, there are problems with responsiveness during high-speed recording, and if a piezoelectric element is used that provides a sufficient volume change to eject droplets, it can be miniaturized. There are some disadvantages such as difficulty in In particular, since miniaturization is difficult, it is not easy to obtain a multi-orifice device in terms of device configuration, and in this sense, it is difficult to achieve high-speed recording.

As described above, conventional recording heads have problems that need to be solved in terms of structure, processing, high-speed recording, multi-orifice design, and overall system configuration. .

The present invention has been made in view of the above points, and
The system aims to provide a simple device.

Another object of the present invention is to provide an apparatus with good ejection response during high-speed recording.

A further object of the present invention is to provide an apparatus that can be easily miniaturized and easily configured to have multiple orifices.

The present invention that achieves these objects includes a plurality of discharge orifices for discharging liquid, a passage provided in communication with each of the discharge orifices, and a state provided in each passage that causes the liquid to be in a state due to heat. A liquid having a thermal energy generating means for generating thermal energy for causing a change, and an electrical/mechanical converter provided upstream of the thermal energy generating means in common with two or more of the thermal energy generating means. It's in the injection device.

In the liquid ejecting device of the present invention, the element provided for each ejection orifice is extremely miniaturized, and high-density multi-orifice structure can be achieved without complicating or enlarging the overall system configuration. . Furthermore, high-speed recording can be easily achieved due to improved ejection efficiency and ejection response, and ease of multi-orifice construction.

This will be explained below with reference to the drawings.

FIG. 1 is a conceptual diagram showing the basic configuration of a liquid ejecting device of the present invention. The liquid is introduced into the head section through the inlet 4 from a supply section 8 consisting of a supply tank, a supply pipe, a filter provided as necessary, or the like.

This head consists of a liquid chamber 1, a heat acting section 2--1 and 2-- which is a space for imparting thermal energy to the liquid.
2 and a heat acting section, respectively. For example, the liquid chamber 1 and the heat acting parts 2-1 and 2-2 are connected to the flow path 3-
1 and 3-2 are connected. In addition, distribution path 3-
1 and 3-2 may be separate or common, or a heat acting section 2-2 may be provided in the liquid chamber 1.
If 1, 2-2 is provided, it is not necessarily necessary.

A means 6 for mechanically generating a pressure change in the liquid in the liquid chamber 1 is provided on the inside or outside wall of the liquid chamber 1 . This means 6 may be one that causes a pressure change by changing the volume of the liquid chamber 1, or may be one that causes a pressure change in the liquid by vibrating the liquid chamber in the liquid discharge direction. .

On the other hand, the heat acting sections 2-1 and 2-2 are provided with thermal energy generating means 7-1 and 7-2 for applying thermal energy to the liquid inside.

The mechanical pressure change generating means 6 includes, for example, an electromechanical transducer such as a piezoelectric element or one that vibrates a metal plate integrated with a coil by electromagnetic induction, while the thermal energy generating means 7-1 and 7
-2, an electrothermal converter such as a thermal head is used, and these are very precise elements (1
(having a density of 10 or more lines per mm) and is preferably used in the present invention. In addition, high-energy radiation such as laser light can also be used as a thermal energy generation source, and in this case, 7-1 and 7-2
As a result, thermal energy is selectively transferred to the heat acting part 2-
An appropriate optical system having a deflector such as an electro-optic element or an acousto-optic element is used to provide a high-density multi-orifice.

Further, the liquid injection device of the present invention includes the above-described pressure change generating means 6 and thermal energy generating means 7-1, 7.
A control section 9 is provided to synchronize and operate the two.

The control section includes, for example, a power amplification circuit, a timing circuit, etc., and is capable of selecting the thermal energy generating means to be activated in response to the image signal, and controlling the pressure change generating means to generate thermal energy at an appropriate timing. It has the functions of activating the means, applying appropriate signal voltage values to the elements, and, as the case may be, setting conditions so that the droplets are generated in the best possible manner.

Although FIG. 1 shows an example in which two heat acting parts and discharge orifices are provided for one liquid chamber, generally more heat acting parts and discharge orifices are provided.

To briefly describe the operating principle of the above-mentioned device,
For example, as the recording signal S, the ejection orifice 5-1
When a signal to discharge liquid is input from
The control unit 9 selects the mechanical pressure change generating means 6 and the thermal energy generating means 7-1 and operates them in synchronization. At this time, if only one of the means operates, no liquid is discharged, but by operating both of them, the pressure of the liquid changes due to the change in the volume of the liquid chamber 1, and the heat acting part 2-1 Pressure changes due to changes in the state of the liquid (volume expansion due to thermal energy, generation of bubbles, etc.) act almost simultaneously to cause the liquid to be discharged. Note that "synchronization" here does not necessarily mean that the pressure change generating means 6 and the thermal energy generating means 7-1 (or 7-2) operate completely simultaneously, but also that the pressure change of the liquid by these means It includes all methods in which the change is transmitted substantially simultaneously to the liquid in the vicinity of the discharge orifice, causing the liquid to be discharged. Generally, it takes a finite amount of time for the pressure change caused by the volume changing means to be transmitted toward the discharge orifice, so the thermal energy generating means 7-1 is activated after a predetermined time. For example, as shown in FIG. 2a, in response to the applied signal A to the pressure change generating means 6, the thermal energy generating means 7-1 (or 7-2)
In some cases, the timing of application of the application signal B to the two terminals may be applied almost simultaneously, or in other cases, as shown in FIG. The time difference at which these elements should be operated depends on, for example, the physical properties of the liquid (viscosity, surface tension, coefficient of thermal expansion, specific heat, etc.), the liquid chamber 1 according to means 6, etc.
the amount of change in volume, the amount of thermal energy generated by the means 7-1, 7-2, the amount of energy (voltage value, time) of the signal for operating the means 6, 7-1 or 7-2,
It is set according to many parameters such as the waveform of the signal and the diameter of the flow path or discharge orifice. Although FIG. 2 shows the case where the waveforms of the signals A and B are rectangular waves, they may also be selected from trapezoidal, sawtooth, or sine waveforms.

Means 6 for mechanically generating a pressure change in liquid and thermal energy generating means 7-1 in the present invention,
7-2 can be operated by operating these means only when discharging the liquid, as shown in Figure 2 a and b, or by operating the means in A when the device is activated, as shown in Figure 2 c. By a signal (by generating a pressure change that does not cause liquid to be discharged by itself)
The pressure change generating means 6 is operated continuously,
The thermal energy generating means 7-1 (or 7-2) may be activated by the signal B only when the liquid is to be discharged, and the pressure changes caused by these means may be matched to cause the liquid to be discharged.

The liquid ejecting device of the present invention is extremely preferable in terms of high-density multi-orifice or high-speed recording.

In conventional devices of this kind, for example, devices that eject liquid using only piezoelectric elements, it was difficult to miniaturize the element to generate sufficient ejection energy, and it was difficult to create multiple orifices. . Generally, it is quite difficult to provide even one discharge orifice every few mm. However, in the device of the present invention, the elements (electrothermal converters, etc.) provided for each discharge orifice are extremely small and precise, and the number of discharge orifices per 1 mm is extremely small and precise.
High-density multi-orifice configuration of 10 or more can be easily achieved, and the density of recorded images can be improved.

In addition to the above advantages, the energy required for discharging the liquid is generated by the volume changing means of the liquid chamber and the thermal energy generating means of the heat acting section, so this method is better than the method of discharging the liquid using only thermal energy. For example, the amount of heat generated and temperature can be kept low,
The responsiveness during high-speed recording is improved, and the amount of energy applied to each element can be reduced by appropriately setting the operating timing of the pressure change generating means and the thermal energy generating means. The lifespan of the device and the lifespan of the device can be extended, and by setting the conditions, the pressure change generating means itself performs a pumping action for pumping the liquid into the heat-acting part, so that a pump for supplying the liquid is not necessarily required. Effects such as the simplification of the structure of the liquid supply section are recognized.

Furthermore, by providing an electrical/mechanical converter in common with two or more of the thermal energy generating means on the upstream side of the thermal energy generating means (on the supply source side of the supplied liquid), the electrical/mechanical converter is difficult to miniaturize. Even if it is, it can be placed without any problem. Of course, since the thermal energy generating means provided for each passage can be easily increased in density, the requirement for high-density multi-orifice structure can be fully achieved.

Alternatively, as shown in FIG. 3, if a plurality of heads shown in FIG. 1 are installed as a unit, a multi-orifice array that covers the entire span of the recording medium can be obtained relatively accurately and easily, and the apparatus can be Favorable results can be obtained in terms of configuration, high-speed recording, maintenance of the device, and the like. Here, 10-1, 10-2 and 10-3 in FIG. 3 are the head units shown in FIG. 1, and the other numbers represent the same numbers as shown in FIG. 1.

In FIG. 3, the mechanical pressure change generating means, thermal energy generating means, control section, etc. of the liquid chamber 1 are omitted.

When such a large number of elements are installed, it is desirable to drive them by a matrix.

In the liquid ejecting device of the present invention, the shape and material of the liquid chamber, the type, shape, and installation position of the mechanical pressure change generating means and thermal energy generating means can be varied in various ways. For example, the electro-mechanical converter is part of the wall of the liquid chamber facing the discharge orifice, and a heat acting part is provided between the liquid chamber and the discharge orifice, and the electro-mechanical converter is placed on the outer periphery of the cylindrical liquid chamber. (for example, as a cylindrical piezo vibrator), and a plurality of heat acting parts may be provided in the liquid chamber.

FIG. 4 shows a cross-sectional perspective view of one discharge orifice in an example in which a piezoelectric element is installed inside the liquid chamber as a mechanical pressure change generating means so as to change the volume of the liquid chamber. This device has a structure in which a lid-like plate having many thin grooves is integrated with a substrate on which thermal energy generating means and the like are provided. Liquid is introduced into the liquid chamber 1 from a liquid supply section 8 such as a tank through the inlet 4.
A piezoelectric element 6' (not shown in the figure, but usually has a structure in which a piezo element and a diaphragm are laminated) is installed in the liquid chamber 1 and is operated by the control section 9. . Between the liquid chamber and each heat acting part,
A flow path 3 is provided.

On the other hand, an electrothermal converter 7' which is selectively operated by a control section 9 is installed in each of the plurality of heat acting sections 2' which are divided from the liquid chamber 1. The electrothermal converter 7' has two layers: a high thermal conductivity layer 13 (for example, alumina, metal, etc.) and a low thermal conductivity layer 14 (for example, an oxide such as SiO ₂ , polyimide, etc.) to improve thermal response. On the substrate of the structure, a resistive layer 15
The selective electrode 16 and the common electrode 16' for energization are etched into a predetermined shape (the selective electrode 16 and the electrothermal converter 7' are provided for each discharge orifice).

For example, the recording signal S input to the control section 9 is converted into a pulse signal and applied to the piezoelectric element 6' through the lead _R1 , causing a pulse-like pressure change in the liquid in the liquid chamber 1.

On the other hand, the signals passing through leads R ₂ and R ₃ are based on the liquid physical properties.
It is applied to the electrothermal transducer 7' at a predetermined position corresponding to the recording signal with appropriate timing set according to various parameters such as the volume of the liquid chamber.
In the heat acting section 2' where the selected electrothermal converter 7' is provided, the liquid undergoes a state change and a pressure change.

As a result, the pressure change generated by the piezoelectric element matches the pressure change generated by the selected electrothermal transducer, and droplets 11 are ejected from the ejection orifice 5' in accordance with the recording signal. The droplets adhere to the recording medium 12 to form a recorded image.

Further, FIG. 5a shows an example in which a cylindrical piezoelectric element is used as a mechanical pressure change generating means. In this device, a cylindrical piezoelectric element 6'' installed around a tubular liquid chamber 1 and an electrothermal transducer 7' installed on a substrate 18 are operated in synchronization, and liquid is discharged from a discharge orifice. The method of installing the electrothermal converter 7', the common electrode 16', the selection electrode 16, the substrate 18, etc. is the same as that of the device shown in FIG. 4, and the device shown in FIG. The cylindrical piezoelectric element 6'' and the electrothermal transducer 7' are actuated by signals applied from the control section through leads _R1 ' and _R2 , _R3, respectively. Ru. However, the method of synchronizing these elements is the same as the apparatus shown in FIG. 4, and other numbers in the figure represent the same things as in FIG.

Further, FIG. 5b shows a schematic plan view of a multi-orifice head in which the head shown in FIG. 5a is used as a unit and a plurality of such units are provided.
That is, around the liquid chamber 1-1 having the inlet 4-1, one cylindrical piezoelectric element 6''-1 or the liquid chamber 1-1
A plurality of electrothermal converters 7'-1 to 7'-3
and heat acting sections 2-1 to 2-3 are provided.
Note that a common chamber Q1 and flow passages 3-1 to 3-3 are provided between the heat acting parts _2-1 to 2-3 and the liquid chamber 1-1.

As described above, the liquid ejecting device of the present invention has various embodiments, and all of these exhibit excellent characteristics in improving recording performance.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the basic configuration of the device of the present invention, FIG. 2 a, b, and c are explanatory diagrams showing the timing of signal application to the elements, and FIG. The conceptual diagram in the case of providing the device, FIG. 4, and FIG. 5 a and b are schematic diagrams showing embodiments of the present invention. In the figure, 1...liquid chamber, 2-1, 2-2...thermal action section, 3-1, 3-2...flow passage, 4...inlet, 5
-1,5-2...Discharge orifice, 6...Mechanical pressure change generating means, 7-1,7-2...Thermal energy generating means, 8...Supply section, 9...Control section, 10-1,1
0-2, 10-3...Head unit, 11...Droplet, 12...Recorded object.

Claims (1)

[Claims] 1. A plurality of discharge orifices for discharging liquid, a passage provided in communication with each discharge orifice, and generating thermal energy for causing a state change due to heat in the liquid provided for each passage. a thermal energy generating means; and two of the thermal energy generating means on the upstream side of the thermal energy generating means.
A liquid ejecting device characterized by having an electrical/mechanical converter provided in common with the above.