JPS61220862A - Ink jet type recorder - Google Patents

Abstract

PURPOSE:To greatly increase the density of recording by moving a thermal head in a rocking manner only by the range of arranging pitch toward the arranging direction of heating elements built in the head. CONSTITUTION:In a ink-jet type recorder in which ink particles coated on a film are jetted toward a recording medium by heat power for recording, a rocking mechanism 19 converts the turning movement of a motor 22 into a rocking movement by an eccentric cam 23 and a crank 24, whereby moving a thermal head 18 in a rocking manner only by the range of arranging pitch of heating elements toward the direction as shown by full-line arrow X. When the motor 22 is turned during the recording period, even each heating element P is moved in a rocking manner within the same range. Recording can thus be made within the pitch 1 similarly to the case with many heating elements P, and thereby the actual density of recording can be raised.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an inkjet recording device.

In particular, the present invention relates to an improvement in an inkjet recording apparatus that performs recording by ejecting ink particles coated on a film toward a recording medium using heat power.

[Technical background of the invention and its problems 3 The recording methods for printing on paper, etc. are classified.

It is classified into impact method and non-impact method.

A recording device that uses a non-impact method.

Essentially, it has advantages such as lower noise and smaller size than those using the impact method.

By the way, recording devices that use the non-impact method are
They are further classified into several types, including recording apparatuses that employ the inkjet recording method. This inkjet recording device is basically...

This method forms dots on a recording medium by ejecting ink particles from a nozzle and causing them to collide with the recording medium, and has the particular advantage of being easy to perform color recording. However, on the other hand, there was a problem in that the nozzles were easily clogged and the recording device lacked stability.

Therefore, recently, an inkjet recording device has been proposed that can significantly alleviate clogging. 11th
The figure schematically shows the main parts of this inkjet recording apparatus. This inkjet recording device has 1
A film 4 is arranged so as to be close to a recording surface 2 of a recording medium 1 such as paper and run in the direction indicated by a solid arrow 3 in the figure. This film 4 is provided with a large number of small recesses or holes 5 having a diameter of several tens of μm at a pitch of several tens of rpm. Then, at a position facing the recording surface 2, ink 6 is filled into each small hole 5 by contacting the surface of the film 4 located on the opposite side to the surface facing the recording surface 2. An ink supply mechanism, for example an ink supply rod 7, is arranged. Further, at a position forward of the ink supply rod 7 with respect to the running direction of the film 4, there is a thermal conductor in contact with a surface of the film 4 located on the opposite side to the surface facing the recording surface 2. A head 8 is arranged.

On the contact surface of the thermal head 8 with the film 4, a large number of heating elements are provided at a predetermined pitch in the width direction of the film 4. The ink supply rod 7 and the thermal head 8 are 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 heat power is applied to the filled ink 6 using a thermal head 8 to form bubbles. The ink particles 9 formed by the bubble formation are made to collide with the recording surface 2. Since a plurality of heating elements are attached to the contact surface of the thermal head 8 with the film 4 in the width direction of the film 4, if a desired heating element among these is energized, the energized heating element is Only the ink 6 filled in the small holes 5 passing through becomes ink particles 9 and collides with the recording surface 2. Therefore, only the ink corresponding to the dot image can be used for recording through the small holes 5 provided in the film 4.

The thermal head 8 used in this recording apparatus performs the same operation as the thermal head in a known thermal transfer type recording apparatus, and the film 4 corresponds to the ink ribbon in the same recording apparatus.

However, even with the inkjet recording apparatus configured as described above, the following problems remain. That is, in principle, the recording density of this recording device also depends on the arrangement pitch of the heating elements incorporated in the thermal head. the current.

In a commonly used thermal head, six to eight heating elements are arranged within a length of one shoe. This is due to limitations such as problems with the constituent materials of the heating elements and nine issues during heat storage in the thermal head, and even if the density of heating elements is increased by some means, the limit is about 20 at most. . Therefore, there was a problem in that the recording density could not be improved.

(Object of the Invention) The present invention was made in view of the above circumstances, and its object is to provide a film having a large number of small holes or a large number of small recesses, and to supply ink to this film. An object of the present invention is to provide an inkjet recording device that combines a mechanism and a thermal head and can significantly improve recording density despite its simple configuration.

[Summary of the invention]

According to the present invention, there is provided an inkjet recording apparatus that includes a head swinging mechanism that swings a thermal head within the range of the arrangement pitch in the arrangement direction of the heating elements incorporated in the thermal head.

〔Effect of the invention〕

According to the present invention, due to the existence of the head swinging mechanism, the thermal head swings in the arrangement direction of the heating elements by the arrangement pitch of the heating elements, so that the heating elements actually incorporated in the thermal head are substantially It is possible to perform recording equivalent to the case where several times to several tens of times as many heating elements are incorporated.

Therefore, despite the simple configuration, the recording density can be significantly improved. Further, since there is no need to increase the number of heating elements actually incorporated into the thermal head, it is possible to facilitate the manufacture of the thermal head.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

The first factor shows the appearance of an inkjet recording apparatus according to an embodiment of the present invention.

In the figure, reference numeral 11 denotes a base formed in the shape of a square plate, and bearings (not shown) are coaxially mounted at positions along one side of the base 11, and these bearings allow the shaft 12 to rotate freely. Supported. A rubber roller 14 for feeding the recording paper 13 is attached to the outer periphery of the shaft 12.

A pinch roller (not shown) is provided below the rubber roller 14 for selectively pressing the recording paper 13 against the rubber roller 14. And the shaft 12 is.

Pulley 15. It is connected via a rubber belt 16 to a paper feed motor 17 fixed on the base 11.

Therefore, at a position facing the circumferential surface of the rubber roller 14,
A thermal head 18 is arranged parallel to the rubber roller 14, and this thermal head 18 is connected to a swing mechanism 19.
Supported by

The thermal head 18 has a structure in which a plurality of heating elements (not shown) are installed on a surface facing the rubber roller 14 at a predetermined pitch in the axial direction of the rubber roller 14 . On the other hand, the swinging mechanism 19 includes a carriage 20 that supports the thermal head 18 and a highly elastic structure that fixes both ends of the carriage 20, that is, both ends of the rubber roller 14 in the axial direction, to the upper surface of the base 11. The pillars 21a and 21b, the motor 22 fixed on the base 11, and the motor 22
The crank 24 is composed of an eccentric cam 23 mounted on a rotating shaft, and a crank 24 whose one end is connected to the eccentric cam 23 and the other end is connected to the carriage 20 via a bearing.
The rotational motion of the motor 22 is converted into a swinging motion by the eccentric cam 23 and the crank 24, and thereby the thermal head 18
is made to swing in the direction indicated by the solid line arrow X in FIG. 1 within a range corresponding to the arrangement pitch of the heating elements.

On the upper surface of the base 11, there is a film guide roller 26 for passing the endless film 25 between the thermal head 18 and the recording paper 14 and for running the film while being in contact with the thermal head 18. 27.2
8.29 is provided, and the film guide roller 28 is connected to the rotating shaft of a motor 3o for driving the film and film.

As the film 25, a strip-shaped film having a large number of small holes is used, similar to the conventional film shown in FIG.

Further, as schematically shown in FIG. 2, the film guide rollers 26 and 27 are arranged at a small angle where the running direction line 32 of the film 25 is with respect to the arrangement direction line 31 of the heating elements P incorporated in the thermal head 18. The film 25 is arranged to be guided so as to be tilted by θ. Furthermore, an ink supply mechanism 33 for supplying ink to the film 25 is arranged on the upper surface of the base 11.

Note that the traveling speed of the film 25 is set higher than the swinging speed of the thermal head 18. Further, the zero paper feed motor 17 is controlled to continuously move the recording paper 13 at a predetermined speed, and each heat generating element of the thermal radar 18 is energized by a head driver (not shown).

With such a configuration, although the recording principle itself is the same as the conventional one, the recording density can be greatly improved even in the case of a thermal head in which the arrangement pitch of one heating element P is relatively wide. Namely.

When the motor 22 starts rotating during recording, the thermal head 18 starts swinging in the direction indicated by the solid line arrow X in FIG. The swinging range is equal to the pitch 1 of the heating elements P incorporated in the thermal head 18. For this reason,
Each heating element P also oscillates in a range equal to pitch 1. Therefore, it is possible to perform recording equivalent to the case where a larger number of heating elements P are provided within the above-mentioned pitch 1, and thereby the actual recording density can be increased, so that the above-mentioned effect can be achieved. will be demonstrated.

In addition, in the case of this embodiment, since the running direction line 32 of the film 25 is inclined by a certain small angle θ with respect to the arrangement direction line 31 of the heat generating elements P incorporated in the thermal head 18, the entire apparatus is The above-mentioned functions can be achieved without increasing the height. That is, the second
As shown in the figure, each heat generating element P is provided at a pitch of 1, and each heat generating element P swings within the above range 1 in the direction indicated by the solid line arrow X in the figure. therefore.

Each heating element P comes into contact only with the track 34 dedicated to each heating element drawn on the film 25, and does not come into contact with other tracks.

You will always be sliding over areas where there is plenty of ink. In this case, even if θ is set to 90 degrees, the above-mentioned function is achieved, but if θ is set small as in this embodiment, the height required to run the film 25 can be suppressed, and the device It is possible to prevent the overall height from increasing.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways. For example, film 2
As shown in FIG.
The ink may be applied to the film 25 by an application roller 44 that rotates in the direction indicated by a solid line arrow 43 in the figure while a part of the application roller 44 contacts the film 25 and contacts the film 25. In this case, if the ink 42 is evenly distributed on the surface of the coating roller 544 by pressing the presser plates 45 and 46 against the surface of the coating roller 44, the film 25
Ink applied to! ! 47 can be made uniform, thereby eliminating variations in print quality.

Further, if ink remains in the small holes of the film 25 after recording, dust may adhere to the film 25.

Otherwise, it may cause the equipment to become contaminated. In order to solve this problem, an ink removing device 51 configured as shown in FIG. 4 may be provided.

That is, electrodes 52 and 53 are placed opposite each other on the upper and lower sides of the film 25, and a voltage is applied between the electrodes 52 and 53 from the power source 54 to form a slope perpendicular to the film surface. An electric field is formed, and the ink B falls from the small holes A of the film 25 by the Coulomb force caused by the electric field. Then, the ink absorbing member 56 catches and stops the fallen ink droplets 55.

It is stored in the collection container 57 using capillary action.

By providing such an ink removal device 51, various adverse effects caused by the ink B remaining on the film 25 can be prevented.

Further, as shown in FIG. 5, the film guide roller 26
Temperature sensors 61 may be provided at a plurality of locations on the outer peripheral surface of the film 25, and the temperature of the film 25 may be controlled based on the outputs of these temperature sensors 61 so as not to exceed a specified value. That is, in general, when a droplet is dropped onto a high-temperature surface, the droplet behaves differently depending on the temperature of the high-temperature surface. FIG. 6 shows the relationship between the temperature of the high-temperature surface and the time required for the droplet to completely evaporate and disappear when the droplet is dropped onto the high-temperature surface. The lifetime of the droplet decreases as the temperature of the nine surfaces increases, but when the concentration exceeds a certain level, the lifetime of the droplet conversely becomes longer, and exhibits a characteristic that it shortens again after passing the peak value. If the temperature of one surface is sufficiently high, the droplets 62 will form as shown in FIG. 7(b).
This is because steam JII 64 is formed between the droplet 62 and the high temperature surface 63, and the amount of heat supplied to the droplet 62 decreases, making it difficult to evaporate. On the other hand, if the temperature of the 9th surface is not high enough, especially.

In the vicinity of point E in Fig. 6, the liquid 16
Air bubbles 65 are formed in the air bubbles 2, which instantaneously evaporate and disappear while explosively generating droplets 66.

The maximum point on the evaporation curve in FIG. 6, ie, point G in FIG. 9, is called the Leidenfrost point, and the surface concentration at this Leidenfrost point is called the Leidenfrost temperature. This Leidenfrost temperature varies depending on the type of droplet.

As can be seen from the above explanation, when recording is performed in the temperature range shown in FIG. Variations are likely to occur.

This is not particularly desirable when printing.

Therefore, in order to perform high-quality recording, it is best to make the ink droplets fly in the state shown in FIG. 7(b). As shown in FIG. 7(b), the droplet 62 is transferred to the vapor film 6.
4, it is necessary to make the high temperature surface 63 higher than the Leidenfrost temperature. That is, in order to perform recording using this recording method, the surface temperature of the heating element incorporated in the thermal head 18 must be made equal to or higher than the Leidenfrost temperature. However, when the surface temperature of the heating element is raised in this way, the heat storage temperature of the film 25 also rises, which causes the ink to fill in the small pores of the film even though no heat is applied by the thermal head. There is a risk that it will start to boil and evaporate. In addition to this, there is a possibility that the surface temperature of the heating element of the thermal head 18 may fluctuate. Therefore, as shown in FIG. 5, a temperature sensor 61 is installed in the film guide roller 26 to monitor the temperature of the film 25, and when the temperature of the film 25 rises excessively, the operation of the apparatus is stopped. Problems that occur when the temperature rises too much can be prevented.

Furthermore, gradation recording may be performed by controlling the surface temperature of a heating element incorporated in the thermal head 18. That is, the boiling phenomenon of a liquid can be roughly divided into two types: nucleate boiling and film boiling. Nucleate boiling occurs when bubbles are generated and separated from the heat transfer surface one after another.

Film boiling is a state in which the entire heat transfer surface is covered with a vapor film and the heat on the heat transfer surface is transferred to the liquid via the vapor film. Roughly speaking, nucleate boiling involves a closed cell region in which bubbles generated on the heat transfer surface separate and separate, and a region in which multiple bubbles generated on the heat transfer surface coalesce into large bubbles that grow and separate. There are two regions: a bubble coalescence region and a bubble coalescence region.

Figure 8 shows the closed cell region, Figure 9 shows the bubble coalescence region, and Figure 10 shows the film boiling region.
) to (e), film 2
5 shows how ink particles are generated from ink B filled in small hole A of No. 5. In the case of the closed cell region shown in FIG. 8, the bubbles 71 generated on the surface of the heating element of the thermal head 18, that is, on the heat transfer surface, separate individually.
The bubble bursts and countless ink particles 72 are scattered.

In this case, each ink droplet 72 is small and the distance it flies is not long, so the number of ink droplets that reach the recording medium is small. Therefore, the dots formed also have a low concentration.

In the case of the bubble coalescence region shown in FIG. 9, the bubbles 71 generated on the heat transfer surface coalesce to form a large air a73. Thereafter, the bubbles 73 grow roughly, and as a result, a liquid 1174 about the diameter of the small hole A is formed. This ruptures to form ink droplets 75 that are somewhat larger than those in the closed cell region shown in FIG. This ink droplet 75 has a longer flight distance than the case shown in FIG. Therefore, the amount reaching the recording medium is large. Therefore, the density of the formed dots is higher than in the case of FIG. Also.

In the case of film boiling shown in FIG. 10, large ink particles 77 are formed because the vapor film 76 formed on the heat transfer surface rapidly expands and pushes up the liquid above. In this case, the flight distance of the ink particles is the longest.

A large amount of ink reaches the recording medium. therefore.

The concentration of the dots formed is the highest (in the case of water, when the heat transfer surface temperature is around 110°C, it becomes a closed cell region;
At 10 to 120℃, it becomes a bubble coalescence region, and also at 2oO
At temperatures above ℃ it becomes a film boiling region. Water-soluble ink has almost the same thermal properties as water. Therefore, Ta-110℃
, vb-ii.

By prescribing three temperatures of ~120°C and Tc-200°C, and selectively setting the temperature of the heating element incorporated in the thermal head 18 to the above temperature, good gradation recording can be achieved. Enables quality records.

Further, the head swinging mechanism may be configured with an electromagnetic drive mechanism. Further, although the above-mentioned embodiment is an example in which the present invention is applied to a line printer type printer, the present invention can also be applied to a serial printer type printer. Other 2 Various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is an external view of an inkjet recording device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the relationship between a thermal head and a film in the recording device, and FIG. 3 is an illustration of an ink supply mechanism. A vertical cross-sectional view showing a modified example, FIG. 4 is an explanatory diagram of the configuration of the ink removing device, FIG. 5 is a diagram for explaining the film temperature detection means, and FIGS. 6 to 7 are reasons for detecting the film temperature. Diagrams for explaining, Figures 8 to 1
FIG. 0 is a diagram for explaining the principle of gradation recording, and FIG. 11 is a schematic diagram showing the basic configuration of an inkjet recording apparatus to which the present invention is directed. DESCRIPTION OF SYMBOLS 11... Frame, 13... Recording paper, 18... Thermal head, 19... Head rocking mechanism, 25...
Film, 26.27.28.29... Film guide roller, 33... Ink supply mechanism, A... Small hole,
B...Ink. Applicant's representative Patent attorney Takehiko Suzue Figure 4 Figure 5 Figure 6 Drawing/1 Invasion L (C) Figure 7 (a) (b) Figure 8 (a) (b) (C) Figure 10yJ

Claims (4)

[Claims] (1) A film having a large number of small holes or a large number of small recesses and provided to run close to a recording medium, and an ink supply mechanism that supplies ink to the small holes or small recesses of this film. , an inkjet recording comprising a thermal head having a plurality of heating elements and a thermal head that contacts a portion of the film where the ink is supplied and uses heat power to eject ink particles on the film toward the recording medium. An inkjet recording apparatus characterized in that the apparatus comprises a head swinging mechanism that swings the thermal head in the arrangement direction of the heating elements within a range of the arrangement pitch of the heating elements. (2) The ink jet recording apparatus according to claim 1, wherein the running direction of the film and the arrangement direction of the heating elements of the thermal head are set to be non-parallel. (3) The inkjet recording apparatus according to claim 1, wherein the head swinging mechanism is mainly composed of a cam crank mechanism. (4) The inkjet recording apparatus according to claim 1, wherein the head swinging mechanism is constituted by an electromagnetic drive mechanism.