JPH0441249A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To make a stable recording and obviate complicated mechanism by making an ink supply section of a film nearly contacted and fixed to a thermal head and providing a specific relationship between pitches of pinholes and heat generating elements. CONSTITUTION:Pinholes 30 of a film 22 are always filled with ink 24. The ink in the pinholes on the parts corresponding to heat generating elements 29 is heated by the heat generating elements 29 heated in accordance with a record signal. The heated ink in the pinhole expands and bursts, so that ink particles are ejected on a recording paper 13 so as to record. A relationship between a pitch P of the heat generating element 29 and a pitch p of the pinhole 30 of the film 22 is P=np (n is an integer), and the number of the pinholes on the heat generating elements can be fixed. For example, when P=3p, all the number of the pinholes on the heat generating elements will be 8. The ink is ejected from the pinholes of the same number from the parts corresponding to any heat generating element. Every dots to be formed on the recording paper 13 are constituted of micro dots of the same numbers so that a stable recording will be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inkjet recording apparatus that prints by ejecting ink onto a recording medium such as paper using heat power.

(Prior Art) Recording methods for printing and recording on paper etc. are classified into impact methods and non-impact methods.

A recording device that uses a non-impact method essentially has the following characteristics:
It has the advantage of being lower in noise and smaller in size than those using the impact method.

Recording devices that use this non-impact method are further classified into several types, one of which is one that uses an inkjet method. This inkjet recording device basically forms dots on the recording medium by ejecting ink particles from a nozzle and colliding with the recording medium, and is unique in that it can easily perform color recording. It has many advantages. However, on the other hand, it has drawbacks such as easy clogging of nozzles and lack of stability as a recording device.

Therefore, recently, inkjet recording apparatuses have been proposed that can significantly reduce clogging. FIGS. 13 and 14 are diagrams schematically showing typical examples of the main parts of such an inkjet recording apparatus. In this recording device, a film 4 runs in the direction shown by an arrow 3 in close proximity to a recording surface 2 of a recording medium 1 such as paper.
are placed. This film 4 is provided with a large number of small holes 5 having a diameter of several tens of micrometers and arranged at a pitch of several tens of micrometers. and,
An ink supply rod 7 serving as an ink supply mechanism for filling each small hole 5 with ink 6 is disposed in contact with the surface of the film 4 opposite to the surface facing the recording surface 2 . Further, a film 4 is provided on the downstream side of the ink supply rod 7 in the film running direction.
The thermal head 8 is arranged so as to be in contact with the same surface as the ink supply rod 7 is in contact with. The surface of the thermal head 8 that comes into contact with the film 4 is provided with a film 4.
A plurality of heating elements 8a are provided at a predetermined width in the width direction. Then, the ink supply rod 7 and the thermal head 8
is controlled to move at a speed slower than the running speed of the film 4, for example in the same direction as the running direction of the film 4. That is,
In this recording device, each small hole 5 of the film 4 is filled with ink 6 using an ink supply rod 7, and the filled ink 6 is
A thermal head 8 applies heat power to the ink to form bubbles, and when the bubbles burst, ink particles 9 formed collide with the recording surface 2. In this case, since a plurality of heating elements are provided on the contact surface of the thermal head 8 with the film 4, if a desired heating element among these is made to generate heat, a small Only the ink filled in the holes becomes ink particles 9 and collides with the recording surface 2. Therefore, of the small holes 5 provided in the film 4, only the ink 6 corresponding to the recording signal can be used for recording. In this recording apparatus, the thermal transfer roller 8 performs the same operation as the thermal transfer roller in a known thermal transfer type recording apparatus, and the film 4 corresponds to the ink ribbon in the same apparatus.

However, even such an inkjet recording apparatus has the following problems. That is, in this recording apparatus, as shown in FIG. 14, a plurality of small holes 5 correspond to one heating element 8a of the thermal head 8, and ink 6 is simultaneously applied to the recording surface 2 from the plurality of small holes. Since the principle is that the dots are ejected toward the same direction, dots on the recording surface 2 are formed by an aggregate of a plurality of small dots (microdots). In other words, in this recording method, an aggregate of a plurality of microdots corresponds to one dot in other inkjet recording methods. In this case, the pitch of the heating element is not necessarily synchronized with the pitch of the small holes provided in the film, and since the film is running, the number of small holes on the heating element is always constant. is not limited. Therefore, the aggregate of microdots formed on the recording surface as one recording dot does not necessarily have a constant size, and there is a possibility that stable recording cannot be performed. Furthermore, it is necessary to provide a mechanism for running the film and a mechanism for wiping off excess ink, resulting in a problem that the apparatus becomes complicated.

(Problems to be Solved by the Invention) As described above, in conventional inkjet recording devices, the number of small holes present on the heat generating element is not always constant, and therefore the holes are formed as an aggregate of microdots. There is a risk that the size of the dots printed will not be constant and stable recording will not be possible. Furthermore, a film running mechanism and the like are required, making the apparatus complicated.

The present invention has been made with these points in mind, and it is an object of the present invention to provide an inkjet recording device that can perform stable recording and does not require a complicated mechanism.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a film that is provided close to a recording medium and has a large number of small holes, and a film that is provided close to a recording medium and has a large number of small holes. an ink supply mechanism that supplies ink;
The inkjet recording apparatus includes a head unit having a plurality of heating elements that heat the ink supplied to the small holes, and a thermal head that jets the ink onto the recording medium using the heat power of the heating elements. and an inkjet type in which the ink supply portion of the film is fixed in substantially contact with the thermal head, and the pitch p of the small holes and the pitch P of the heat generating elements have a relationship expressed by Pmnp (where n is an integer). Provide a recording device.

(Function) In such a device, there is no need to run the film, and the pitch of the heating elements is an integral multiple of the pitch of the small holes, so the number of small holes on the heating elements can be kept constant. be able to. Therefore, the size of the dots formed by the aggregate of microdots can be made constant,
Stable recording can be performed. Further, complicated mechanisms such as a mechanism for running the film and a mechanism for wiping off excess ink are not required.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing an ink jet recording apparatus according to an embodiment of the present invention. Reference numeral 10 in the figure indicates a frame, and support walls 11a are provided at both ends of the frame 10.
, llb are erected.

These support walls 11a, llb are each provided with bearings (not shown), and the shaft 12 is rotatably supported by these bearings. A rotating drum 14 is installed between the support walls 11a and llb of the shaft 12, and this drum 1
A recording paper 13 is wound around the recording paper 4. This recording paper 1
3 is fixed to the drum 14 by a recording paper holder 15. The shaft 12 is connected to a rotating shaft of a motor 16 supported by the support wall 11a. The motor 16 is driven to rotate in one direction during recording.

Below the rotating drum 14 is a guide shaft 17 parallel to the shaft 12.
A carriage feed screw 18 is provided near the guide shaft 17 and parallel to the guide shaft 17. This carriage feed screw 18 includes a support wall 11a,
It is rotatably supported by a bearing (not shown) attached to the support wall 11a, and one end thereof is connected to the rotating shaft of a carriage feed motor 19 fixed to the support wall 11a.

A carriage 2o is movably mounted on the guide shaft 17 and carriage feed screw 18. This carriage 2
o is moved along the direction of arrow 4o by rotation of feed screw 18 by motor 19. At this time, the guide shaft 17 ensures smooth movement.

The carriage 2o is provided directly below the rotating drum 14, and has four head units 20a.

It is composed of 20b, 20c, and 20d. All of these head units have the same configuration, and each
Y (yellow), M (magenta), C (cyan), BK
(black).

As shown in the plan view and side sectional view of FIGS. 2 and N3, one head unit includes an ink tank 23 disposed with the opening facing upward, and an ink tank 23 stretched over the opening of this tank 23. The thermal head 21 is provided such that it is surrounded by an ink tank 23 and that its tip is in contact with the film 22. At the tip of the thermal head 21 that contacts the film 22, two plural heating elements are provided in the width direction of the film.

The ink tank 23 is filled with ink 24 of each color, and the used amount of ink is constantly supplied to the tank 23 by an ink supply mechanism (not shown). That is,
The tank 23 is always filled with the ink 24, and the film 22 is always in contact with the ink 24.

Note that the thermal head 21 and the bottom of the tank 23 are sealed by seal members 28a and 28b.

On two mutually adjacent sides of the thermal head 21,
Two laminated piezoelectric elements 26a and 26b are provided below the tank 23 as minute displacement mechanisms. These laminated piezoelectric elements 26a and 126b allow the thermal head 21 to be slightly displaced in two mutually orthogonal directions 27a and 27b, thereby changing the recording density as described later.

As shown in FIG. 4, a large number of heating elements 29 of the thermal head 21 are arranged in the width direction of the film 22, as in the conventional one. The heating elements 29 are arranged at a constant pitch P. The heating element 29 has an electrode 31
a, 31b are connected, and these electrodes 31a, 31
Electric power is supplied through b, and heat is generated in response to recording signals.

These heating elements 29 are controlled to generate heat by a head driver (not shown).

A large number of small holes 30 are formed in the film 22,
As described above, since the film 22 is always in contact with the ink 24, the small holes 30 are always filled with the ink 24 in the tank 23.

As shown in FIG. 5, the small holes 30 have a pitch P of heating elements.
They are provided at a constant pitch p that is equal to or smaller than , and the relationship with the pitch P of the heating elements 29 is Pmnp (
However, n is set to be an integer).

During the recording operation, the carriage drive motor 19 is controlled by a control system (not shown) to move the carriage 20 to the right in FIG. 1 every time the rotary drum 14 makes one revolution.

In the inkjet recording apparatus configured in this manner, recording is performed using the same principle as that of conventional apparatuses. That is, while the drum 14 is rotated by the motor 16, the thermal head 2 of each head unit is
1 is operated in response to a recording signal. In this case, the small holes 30 of the film 22 are always filled with ink as described above.
The heating element 29 generates heat in response to a recording signal, and the ink in the small hole corresponding to the element is heated. As a result, the ink in the heated small holes expands and bursts, and ink particles are jetted onto the recording paper 13 and recorded.

In this case, as described above, the pitch P of the heating element 29
and the pitch p of the small holes 30 of the film 22, P=np(
However, n is an integer), and the film 22
Since is fixed, the number of small holes present on the - heating element can be kept constant. For example, as shown in FIG. 6, if the relationship between the pitch P of the two heating elements and the pitch p of the small holes 30 is set to P-3p, the number of small holes on the heating elements will all be 8, and this state When recording is performed, ink is ejected from the same number of small holes from the portion corresponding to any heating element, and every dot formed on the recording paper 13 is composed of the same number of microdots. Therefore, uniform dots are formed on the recording paper without variations in dot size among the heating elements, and stable recording can be performed.

That is, as shown in FIG. 7, if the pitch P of the heating elements 29 or the pitch p of the small holes 30 is not an integral multiple, the number and arrangement of the small holes on each heating element will be constant. When the film is smoothed and run, the variation is further aggravated, but with the structure of the present invention, such problems can be solved.

Furthermore, in this device, the relationship between the pitch P of the heating elements 29 and the pitch p of the small holes 30 remains P=np, and by moving the thermal head in a direction parallel to the surface of the film 22, the recording density is increased. It is possible to change the That is, as described above, the laminated piezoelectric elements 26a, 26b
By slightly displacing the thermal head 21 along the directions 27a and 27b, the number of small holes on each heating element can be changed. For example, if the P-3p relationship holds true, as shown in Figures 8 to 12,
The number of small holes on each heating element can be varied between 4 and 8. As a result, the number of microdots forming the dots formed by ejecting ink changes, and the recording density can be changed. Conventionally, when changing the recording density, it was necessary to change the size of the small holes in the film or change the thickness of the film, which was complicated.
This device is extremely convenient because it can change the recording density by minutely displacing the thermal head. By adjusting the density in this way, it is possible to perform recording at a desired density.

In this case, since the seal members 28a and 28b are provided between the thermal head 21 and the bottom of the tank 23, there is no fear that the ink 24 will leak even if the thermal head 21 is moved.

Although an example has been shown in which the density is changed by moving the thermal head, it is also possible to change the density by keeping the thermal head fixed and slightly displacing the film. Note that although a stacked piezoelectric element was used here as the minute displacement mechanism,
It is not limited to this.

[Effects of the Invention] According to this invention, the pitch p of the small holes in the film and the pitch P of the heating elements of the thermal head are set as P=np (however,
(n is an integer), and since the film is not run, stable recording without dot-to-dot variations can be achieved. Further, a complicated mechanism such as a film running mechanism is not required.

Furthermore, by providing a mechanism for moving the thermal head or film, the number of small holes on the heating element can be changed, and thereby the recording density can be easily changed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an inkjet recording device according to an embodiment of the present invention, FIG. 2 is a plan view showing a head unit of the device shown in FIG. 1, FIG. 3 is a side sectional view thereof, and FIG. is a diagram showing the pitch P of the heating element of the thermal head used in the device of FIG. 1, FIG. 5 is a diagram showing the pitch of the small holes formed in the film used in the device of FIG. 1, and FIG. A diagram showing the positional relationship between the heating element and the small hole in the device according to the present invention, FIG. 7 is a diagram showing the positional relationship between the heating element and the small hole in the conventional device, and FIGS. 8 to 12 show the thermal head. 13 and 34 are perspective views showing the basic configuration of a conventional inkjet printing apparatus. 13; Recording paper (recording medium), 2o; Carriage, 20a
, 20b, 20c, 20d; head unit, 21;
Thermal head, 22; Film, 23; Ink tank, 24: Ink, 29: Heat generating element, 30; Takehiko Suzue, Patent attorney, Patent attorney for the applicant゜Figure

Claims (2)

[Claims] (1) A film provided close to the recording medium and having a large number of small holes, an ink supply mechanism that supplies ink to the small holes of this film, and a plurality of heat generating units that heat the ink supplied to the small holes. an inkjet type recording device, comprising: a head unit having a thermal head that ejects ink onto the recording medium using heat power of the heating element; An ink jet recording apparatus characterized in that the small holes are fixed in contact and the pitch P of the small holes and the pitch P of the heat generating elements have a relationship expressed by P=np (where n is an integer). (2) The inkjet recording apparatus according to claim 1, further comprising a moving mechanism that moves the thermal head or the film in a direction parallel to the film surface.