JPH11268304A - Ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily solve clogging of a recording head in an ink-jet recording apparatus which discharges ink drops with the utilization of an electrostatic force. SOLUTION: This ink-jet recording apparatus has a purging head 40 in addition to a recording head 10 and a cylindrical opposite electrode 25 opposed to the recording head 10 for holding a recording paper 26. The purging head 40 is arranged adjacent to the opposite electrode 25. The recording head 10 can move along a supporting shaft 16. For purging the recording head 10, the recording head 10 is moved to a position where the recording head faces the purging head 40 and an electric field stronger than required for printing is generated between the recording head 10 and purging head 40. As a result, ink drops are discharged from the recording head 10, so that clogging of the recording head 10 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus using an ink in which a coloring material component is dispersed in a solvent, and flying ink droplets containing the coloring material component onto a recording medium for recording. The present invention relates to an ink jet recording apparatus for performing.

[0002]

2. Description of the Related Art An apparatus for recording an image by forming recording dots by spraying liquid ink into small droplets (hereinafter referred to as "ink droplets") on a recording medium such as recording paper is known. Has been put to practical use as an ink jet printer. Ink jet printers have the advantage that they are less noisy than printers based on other recording methods and do not require processing such as development and fixing, and are becoming widely used as plain paper recording technology.

[0003] Many ink jet printer systems have been proposed to date. In particular, (a) a method in which an ink droplet is caused to fly by the pressure of steam generated by heating using a heating element (for example, Japanese Patent Publication No. 56-9429,
JP-B-61-59911 and the like, or
(B) A method in which an ink droplet is caused to fly by a mechanical pressure pulse using a piezoelectric element (for example, Japanese Patent Publication No. 53-121)
No. 38) is a typical example.

A recording head used in an ink jet printer is mounted on a carriage and is orthogonal to a recording paper transport direction (hereinafter, referred to as a "sub-scanning direction") (hereinafter, referred to as a "main scanning direction"). ), A serial scanning type head that performs recording while moving is used. With this serial scanning head, it is difficult to increase the recording speed. Therefore, a line scanning type printer that has been increased in speed by using a long head in which the length of the recording head is the same as the width of the recording paper has also been proposed.However, to commercialize such a line scanning type head, It is not easy for the following reasons.

[0005] The recording head is provided with a number of individual fine nozzles corresponding to the resolution. However, in principle, local evaporation of the ink tends to occur locally due to evaporation of the solvent, which is a cause of nozzle clogging. It has become. In particular, in the method using the pressure of steam for forming an ink jet, an insoluble substance formed by thermal or chemical reaction of the ink adheres to the inner surface of the nozzle and causes clogging,
Further, in the method using the pressure of the piezoelectric element, a complicated structure such as an ink flow path easily causes clogging.

While a serial scanning type head uses several tens to one hundred and several tens of nozzles, a line scanning type head uses many more nozzles, up to several thousand. For this reason, the line scanning type head has a problem that clogging occurs at a very high frequency with probability and lacks practical reliability.

[0007] Further, in the method using the pressure of steam, a diameter of 20 μm corresponding to a recording dot having a diameter of 50 μm on recording paper is used.
Since it is difficult to generate ink particles with a particle size of μm or less,
It is difficult to manufacture a high-resolution head. Also,
In the method using the pressure of the piezoelectric element, the recording head has a complicated structure, and it is difficult to manufacture a high-resolution head due to a problem in processing technology. For this reason, in any of the conventional inkjet recording methods, there is a limit in improving the resolution in any of the methods.

In order to solve these problems, a plurality of individual electrodes formed of a thin film are arranged on a recording head substrate to form an electrode array, and a voltage is applied to these individual electrodes to reduce electrostatic force. There has been proposed an ink jet recording system in which ink droplets are made to fly from an ink liquid level toward recording paper by utilizing the ink droplets. Specifically, a method of flying ink droplets using electrostatic attraction (for example,
JP-A-62024, JP-A-56-4467, etc.) and a method in which an ink droplet in which a coloring material component is concentrated is made to fly using an ink in which a chargeable coloring material component is dispersed in a solvent ( Japanese Patent Publication No. 7-502218 has been proposed.

In these systems, the configuration of the recording head is
Slit-shaped nozzle structure that does not require a nozzle for each recording dot or nozzleless structure that does not require an ink flow path partition for each recording dot, so it is effective in preventing clogging or recovering from clogging It is. In addition, the latter can stably generate and fly ink droplets having a very small diameter, and thus is suitable for high resolution.

However, in an ink jet recording apparatus using electrostatic force, it is necessary to increase the intensity of the electric field in order to widen the recording gap (the distance from the individual electrode to the recording medium). For that purpose, it is advantageous to make the portion (flying start point) from which the ink droplet is ejected project in a convex shape. Also, in order to realize high definition of images,
Fine recording dots must be formed, and therefore, it is necessary to reduce the width or diameter of the above-mentioned portion. As a result, the flow path of the ink becomes narrow, and even if the ink-jet printer has a nozzleless structure, the ink hardens and clogs easily if the ink is held. Such clogging is a major factor that changes the dimensions of the formed recording dots or causes defects in the recording dots, thereby deteriorating the quality of the formed image.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an ink jet recording apparatus based on a method of discharging ink droplets by utilizing electrostatic force. In clogging of the recording head,
It is to provide a structure that can be quickly removed.

[0012]

According to the present invention, there is provided an ink jet recording apparatus comprising: a counter electrode having a recording medium held on a surface thereof;
A recording head that is disposed at a position facing the opposing substrate and that discharges ink droplets toward a recording medium by electrostatic force by applying a voltage between the opposing electrode and a recording head that is disposed adjacent to the opposing electrode; A purging head, and a moving means for moving the recording head to a position facing the purging head, by applying a voltage between the purging head and the recording head in a state where the recording head faces the purging head. And ejecting ink droplets toward the purging head by electrostatic force to remove deposits attached to the ink ejection portion of the recording head.

According to the ink jet recording apparatus of the present invention, extraneous matter (particles obtained by condensing the color material components in ink or foreign matter such as flying dust) adheres to the ink ejection portion of the recording head, and the recording head has an eye. When clogging occurs, the recording head can be purged as follows. That is, the recording head is moved from the front surface of the opposing electrode to face the purging head, and in this state, an electric field stronger between the recording head and the purging head is generated as compared with the case of forming recording dots. With this, the ink droplet is ejected toward the purging head with stronger electrostatic force,
The deposit attached to the ink ejection section of the recording head is removed. If the above purging operation is performed periodically, clogging of the recording head can be prevented.

Preferably, the recording head is provided behind a plurality of two-dimensionally arranged control electrodes, and a plurality of control electrodes, each of which has an opening in the vicinity of the center, facing the counter electrode, and is provided behind the control electrode. The ink chamber containing the ink in which the color material components are dispersed, and penetrates the vicinity of the center of the opening, and the tip protrudes from the front surface of the control electrode toward the counter electrode, and extends from the ink chamber along the protruding direction. An ink guide having a slit extending to the leading end is formed, and ink droplets are ejected from the leading end of the ink guide.

Preferably, the purging head comprises an electrode plate facing the recording head and an ink absorbing material, and the ink absorbing material is arranged so as to be in contact with the electrode plate.

Further, preferably, a plurality of through holes are formed in the electrode plate, and the absorbing material is arranged on the back side of the electrode plate.

In this case, if a plurality of grooves intersecting the plurality of through holes are formed on the surface of the electrode plate, the ink sprayed on the surface of the electrode plate is guided to the through holes via the grooves. be able to.

The purging head is provided with an electrode member made of a conductive and ink-absorbing porous material facing the recording head, so that the electrode member itself has the absorbing material. Functions can be combined.

The counter electrode may also have the function of the purging head. In this case, in order to collect ink adhering to the surface of the counter electrode,
It is necessary to provide a cleaning roller.

Further, if a detecting means for detecting the state of the deposit attached to the ink ejection portion of the recording head is provided, the purging operation of the recording head can be automatically performed based on the information from the detecting means. it can. That is, the purging operation can be performed only when necessary.

Alternatively, if instead of the above method, an image recognizing means for monitoring the state of the recording dots formed on the recording medium is provided, the purging operation of the recording head can be performed based on the information from the image recognizing means. It can be done automatically.

[0022]

Next, various examples of an ink jet recording apparatus based on the present invention will be described with reference to the drawings.

(Example 1) FIG. 1 shows an example of an ink jet recording apparatus according to the present invention. This figure is a cross-sectional view of a main part of the ink jet recording apparatus.

This ink jet recording apparatus is used when purging the recording head 10 for discharging ink droplets by using electrostatic force, the cylindrical counter electrode 25 facing the recording head 10, and the recording head 10. And a purging head 40. A recording paper 26 is wound and held around the outer periphery of the counter electrode 25. An ink supply tank 17 is connected to the recording head 10 via an ink supply path 18.

The recording head 10 is supported on a support shaft 16 and moves along the support shaft 16 in a sub-scanning direction (a direction perpendicular to the center axis direction of the counter electrode 25, that is, a horizontal direction in FIG. 1). Can be. The purging head 40 is arranged adjacent to the counter electrode 25 and parallel to the counter electrode 25. During the purging operation of the recording head 10, the recording head 10 is moved from the front of the counter electrode 25 to a position facing the purging head 40.

FIG. 2 is a sectional view of the recording head. FIG.
2 shows a plan view (part) of the front surface (the surface facing the counter electrode) of the recording head.

The recording head 10 is a line scanning type head, and has a large number of control electrodes 20 arranged in the main scanning direction (the horizontal direction in FIG. 2). Each control electrode 20
Opposite to the opposing electrode 25, each opening 21 near the center
Are formed. Behind the control electrode 20, the ink chamber 2
4 are provided. The ink guide 22 is connected to the opening 21.
The slit 2 penetrates near the center of the ink chamber 24 and extends from the inside of the ink chamber 24 to the tip in the axial direction (that is, along the protruding direction).
3 are formed.

As the ink, an ink is used in which a positively chargeable coloring material component is colloidally dispersed and suspended in an insulating solvent together with a charge control agent and a binder. The ink is supplied from the ink supply tank 17 (FIG. 1) to the ink supply path 1.
8 (FIG. 1) is supplied into the ink chamber 24. The ink 11 in the ink chamber 24 passes through a slit 23 formed at the center of the ink guide 22 and reaches the tip of the ink guide 22 by capillary action.

The control electrode 20 is formed on an insulating substrate 34, and the insulating substrate 34 has a through hole 36 corresponding to the opening 21. The number of these through holes 36 corresponds to the number of recording dots formed at one time. In this example, the insulating substrate 34 is made of polyimide having a thickness of 25 μm, and the control electrode 20 has a thickness of 1 μm.
It is made of 8 μm copper foil. The inner diameter of the opening 21 is set depending on the size of the recording dot to be formed, and is usually 150 to 3.
It is about 00 μm.

The ink guide 22 is a fine projection formed on the surface of the ink guide block 33 made of an insulating member, and has a thickness of about 100 μm, a width of about 150 μm, and a height of about 350 μm. A slit 23 of about 20 to 60 μm is formed, and the tip is machined in a triangular (or trapezoidal) shape. The insulating substrate 34 and the ink guide block 33 are both head block 3
It is fixed on one.

FIG. 4 shows an outline (perspective view) of the purging head.

The purging head 40 includes the recording head 10
The surface facing (FIG. 1) is constituted by an electrode plate 41 (hereinafter, referred to as a “purging electrode”), and a large number of through holes 42 are formed in the purging electrode 41. An absorbing material 43 having ink absorbability is arranged in contact with the back side of the purging electrode 41. Purging electrode 41
Is attached to the front of the casing 44,
Is housed in a casing 44. The purging electrode 41 is connected to the ground.

Next, the operation of the ink jet recording apparatus will be described.

First, the operation for forming recording dots on the recording paper 26 will be described. The formation of recording dots
As shown in FIGS. 1 and 2, the recording head 10 is
5 is performed in a state where the recording paper 26 faces the counter electrode 2.
5 is held on the outer peripheral surface.

The control electrode 20 is always supplied with a bias voltage (for example, DC 1.5 kV) from a bias voltage source 38, while the counter electrode 25 is connected to the ground. When forming recording dots, a pulse-like signal voltage (for example, 500 V) corresponding to an image signal is supplied from the signal voltage source 39 to the control electrode 20, and is superimposed on the bias voltage.

When a signal voltage is supplied to the control electrode 20 in addition to the bias voltage, an electric field formed between the control electrode 20 and the counter electrode 25 is strengthened, and an electrostatic force based on the electric field is applied to the control electrode 20 to cause an ink. The ink droplets 12 are ejected from the tip of the guide 22. The ink droplets 12 fly toward the recording paper 26 and reach the recording paper 26 to form recording dots.

Next, the operation for purging the recording head 10 will be described. Purging of the recording head 10 is performed in a state where the recording head 10 faces the purging head 40. Therefore, first, the recording head 10
Is moved along the support shaft 16 from the state shown in FIG.

In this state, the control electrode 2 of the recording head 10 is
When a pulsed signal voltage is supplied to 0 in addition to the bias voltage, an electric field is formed between the control electrode 20 and the purging electrode 41. The ink droplets 12 are ejected from the tip of the ink guide 22 by receiving the electrostatic force based on the electric field. The ink droplet 12 flies toward the purging electrode 41 and adheres to the surface of the purging electrode 41, and a part thereof is directly trapped in the through hole 42. Purging electrode 41
The ink that has adhered to the surface of the through hole 42 is formed by capillary action.
Through the absorber 43 on the back side.

Thereafter, the recording head 10 returns to the recording operation position shown in FIG. 1, and the purging operation of the recording head 10 ends. The above-described purging operation is automatically performed for each predetermined condition (for example, every predetermined time, after printing a predetermined number of sheets, after a lapse of a certain pause time, or the like), or is performed according to an instruction from an operator.

It is to be noted that in order to remove deposits (particles condensed with color material components in ink or foreign matter such as flying dust) adhering near the tip of the ink guide 22, the ink at the tip of the ink guide 22 must be removed. On the other hand, it is necessary to apply a stronger electric field force than when recording dots are formed. Therefore, in the purging operation, the pulse width of the signal pulse voltage is set longer, the amplitude is set larger, or the distance between the recording head 10 and the purging head 40 is increased as compared with the case of forming the recording dots. Must be set narrow.

As described above, according to the ink jet recording apparatus of the present invention, the purging operation of the recording head can be performed by providing the purging head having the electrode plate (purging electrode). As a result, toner particles and dust adhering to the ink ejection portion of the recording head can be quickly removed, and the quality of the formed image can be maintained in a good state.

(Example 2) FIG. 5 shows another example of a purging head used in an ink jet recording apparatus according to the present invention. This figure is a plan view of the purging head viewed from the front side (purging electrode side).

In this example, the purging head shown in FIG. 4 is partially modified. Purging electrode 41
Has a large number of through-holes 42 and grooves 45 formed on the surface thereof so as to intersect with the respective through-holes 42. The cross-sectional shape of the groove 45 is rectangular so that capillary attraction effectively acts on the attached ink. On the back side of the purging electrode 41, as in the previous example, the absorbent 4
3 (FIG. 4) is disposed, and the purging electrode 41 is connected to the ground.

During the purging operation, of the ink ejected from the recording head 10, the ink directly trapped in the through hole 42 and the ink attached around the through hole 42 are:
It is absorbed in the absorbent 43 (FIG. 4) on the back side. However, depending on the density and arrangement pattern of the through holes 42, a part of the ink attached to the surface of the purging electrode 41 may not flow into the through hole 42 but remain on the surface of the purging electrode 41. This example addresses such a case. That is, the ink that has reached a position distant from the through-hole 42 is guided to the through-hole 42 by the capillary attraction acting through the groove 45 and is absorbed by the absorber 43 (FIG. 4).

Example 3 FIG. 6 shows another example of an ink jet recording apparatus based on the present invention. This figure shows the recording head 10 and the purging head 4 during the purging operation.
FIG. 2 is a cross-sectional view (part) of the main scanning direction 0 (width direction of recording paper).

In this example, the structures of the recording head 10 and the purging head 40 are the same as those in the first example (FIG. 2), but the purging electrode 41 on the purging head 40 side is used.
Is applied in that a pulse voltage is applied and the control electrode 20 on the recording head 10 side is grounded. That is, in the first example, a pulse voltage is applied to the control electrode 20 to eject ink droplets even during the purging operation, as in the case of forming recording dots. Is grounded, and a negative bias voltage and a negative pulse voltage are superimposed and applied to the purging electrode 41 side, thereby forming an electric field between the control electrode 20 and the purging electrode 41.

As described above, by applying a pulse voltage to the purging electrode 41 at the time of the purging operation, the voltage condition at the time of the purging operation can be set independently of the voltage condition at the time of forming the recording dots. Becomes possible. Accordingly, the restriction on the voltage condition on the control electrode 20 side is relaxed, and the configuration of the drive circuit for controlling the formation of the recording dots can be simplified. At the same time, more effective voltage conditions can be set during the purging operation.

(Example 4) FIG. 7 shows another example of a purging head used in an ink jet recording apparatus according to the present invention. This figure is a sectional view of the purging head.

The purging head 40 includes the recording head 10
A purging electrode 41 is disposed on a surface facing (FIG. 1), and a large number of through holes 42 are provided in the purging electrode 41.
Are formed. An absorbing material 43 is arranged in contact with the back side of the purging electrode 41, and an electrode plate 46 (hereinafter, referred to as “ink suction electrode”) is arranged behind the absorbing material 43. That is, the absorbent 43 is sandwiched between the purging electrode 41 and the ink suction electrode 46. The purging electrode 41 is attached to the front surface of the casing 44, and includes the absorbing material 43 and the ink suction electrode 46.
Is housed in a casing 44. The purging electrode 41 is connected to the ground, and the ink suction electrode 46 is connected to a DC voltage source 47. Other configurations are the same as in the first example.

Normally, the purging head 40 is installed downward. In such a case, the suctioned ink tends to accumulate at a lower position in the absorber 43 due to the influence of gravity.
For this reason, the absorption capacity of the absorber 43 in the portion adjacent to the purging electrode 41 is reduced. Also, when toner particles and the like contained in the ink adhere to the absorbent 43,
Absorption capacity decreases. Therefore, by further providing an ink suction electrode 46 inside the purging head 40,
An electric field (arrow in the figure) is formed between the purging electrode 41 and the ink suction electrode 4.
Move to 6 side. In this way, the purging electrode 41
Can enhance the absorbing ability of the absorbing material 43 in the portion adjacent to.

Example 5 FIG. 8 shows another example of a purging head used in an ink jet recording apparatus based on the present invention. This figure is a perspective view of the purging head viewed from the front side (purging electrode side).

In this example, a flat purging electrode 51 is used.
(Electrode plate) is used, and the purging electrode 51 is attached to the lower surface of the casing 54 downward in an inclined posture. The absorbing material 53 is housed in the casing 54 adjacent to the purging electrode 51 and is in contact with one side of the inclined purging electrode 51 on the lower side. Purging electrode 51
In the three surrounding sides excluding one side of the lower side, the casing 5
The edge of 4 protrudes slightly forward from the purging electrode 51, and also serves as a partition frame 55.

Next, the purging operation of the recording head using the purging head will be described. In FIG.
4 shows an arrangement of the purging head 40 with respect to the recording head 10 during a purging operation.

When performing the purging operation, the recording head 1
0 is moved directly below the inclined surface of the purging electrode 51 so that the tip of the ink guide 22 approaches the purging electrode 51. Next, an electric field is formed between the purging electrode 51 and the control electrode 20 on the recording head 10 side to eject ink droplets. After the ejected ink reaches the purging electrode 51, it flows along the inclined surface and is absorbed in the absorbing material 53. That is, by inclining the purging electrode 51, the ink can be guided to the absorbing material 53, so that the ink hardly remains on the surface of the purging electrode 51. The partition frame 55 prevents the ink from escaping around the purging electrode 51.

By disposing the purging electrode 51 and the absorbing material 53 as described above, it is not necessary to provide the purging electrode 51 with a through hole (42; FIG. 4). Therefore, the manufacturing of the purging electrode 51 is facilitated, and
It is not necessary to consider the effect of the through hole on the forming electric field.

Further, the distance between the control electrode 20 and the purging electrode 51 can be adjusted by manipulating the position of the recording head 10 in the moving direction (ie, the position in the horizontal direction). This makes it possible to change the electric field strength formed between the two electrodes, and by simple means,
Optimal purging conditions can be set.

(Example 6) FIG. 10 shows another example of a purging head used in an ink jet recording apparatus according to the present invention. This figure is a perspective view of the purging head viewed from the front side (purging electrode side).

In this example, the purging head shown in FIG. 8 is partially modified. As in the previous example, a flat purging electrode 51 (electrode plate) is used, and the purging electrode 51 is attached to the lower surface of the casing 54 in an inclined posture and downward. In this example,
A plurality of guide plates 56 are attached to the surface of the purging electrode 51 along the inclined direction. The guide plate 56 has a rectangular cross section. Other configurations are the same as in the previous example.

As described above, by attaching the guide plate 56 to the surface of the purging electrode 51, the ink adhering to the surface of the purging electrode 51 is deposited at the corner where the surface of the purging electrode 51 contacts the side surface of the guide plate 56. And then flow along the sides of the guide plate 56. Therefore, the ink can be efficiently guided to the absorbing material 53, and the ink remaining on the purging electrode 51 can be reduced.

(Example 7) FIG. 11 shows another example of a purging head used in an ink jet recording apparatus according to the present invention. This figure is a perspective view of the purging head.

In this example, the purging head 40 is composed of an electrode member 61 made of a porous material that is conductive and has ink absorbency, and a casing 64 that houses the electrode member 61. The casing 64 has an opening 66 on one surface (the surface facing the recording head 10 during the purging operation), and the electrode member 61 is mounted in the opening 66. The electrode member 61 has the functions of the electrode plate and the absorber in each of the above examples. The electrode member 61 is connected to the ground.

During the purging operation, the electrode member 61
An electric field is generated between the recording head and the control electrode (20; FIG. 2) on the recording head side to eject ink droplets from the recording head.
The ink that has reached the electrode member 61 is absorbed by the electrode member 61 as it is. In this way, by configuring the electrode surface from which ink is ejected with a material having an ink absorbing function, ink can be reliably captured with an extremely simple structure.

(Example 8) FIG. 12 shows another example of the ink jet recording apparatus according to the present invention. This figure is a cross-sectional view of a main part of the ink jet recording apparatus. This device has the same structure as that of Example 1 (FIG. 1), and further includes a residual ink absorbing portion 7.
1 and the other configuration is the same as that shown in FIG.

The residual ink absorbing section 71 is disposed at a position facing the purging head 40 with the support shaft 16 interposed therebetween. The residual ink absorbing section 71 is formed by housing an absorbing material 73 (such as a sponge) having a high ink absorbing property in a casing 74.
4, and has a width equal to or greater than the purging head 40 in the main scanning direction (the direction perpendicular to the plane of FIG. 12). On the other hand, purging head 4
0 is movable in the vertical direction as indicated by the arrow in the figure.

In the case of Example 1 described above, the ink ejected to the surface of the purging head 40 is supplied through the through-hole 42 (FIG. 4) to the absorbing material 43 disposed on the back side of the purging electrode 41. However, for example, when the density and size of the arrangement of the through holes 42 are limited, there may be a case where all the ink cannot be absorbed by the absorbing material 43 side. The configuration shown in FIG. 12 is intended to remove the ink that cannot be completely absorbed only by the absorbing material 43 by using the residual ink absorbing section 71.

Next, the function of the residual ink absorbing section 71 will be described.

When the purging operation of the recording head 10 is completed, the recording head 10 is returned to the recording position (the position shown in FIG. 12), and in this state, the purging head 40 is lowered to contact the residual ink absorbing portion 71. As a result, the ink that has adhered to the surface of the purging electrode 41 is absorbed by the ink absorbing material 72 and collected inside the residual ink absorbing unit 71. Thereafter, the purging head 40 rises and returns to a predetermined position, and enters a standby state.

As described above, by separately providing a means for removing the ink remaining on the surface of the purging electrode 41, the surface of the purging electrode 41 can always be kept clean. Therefore, it is possible to solve the problem that the ink solidified on the surface of the purging electrode 41 hinders the flow of the ink at the time of the next purging operation and lowers the absorption efficiency of the absorbing material 43.

The width of the residual ink absorbing portion 71 does not necessarily need to be greater than the width of the purging head 40 as in the above-described example. For example, if the residual ink absorbing portion 71 is configured to be movable in the width direction (main scanning direction) of the purging head 40, the narrower residual ink absorbing portion 71 is provided.
By using the method, the residual ink on the surface of the purging electrode 41 can be removed. Further, if the residual ink absorbing portion 71 is configured to be movable in the sub-scanning direction (the left-right direction in FIG. 12), the residual ink absorbing portion 71 having a smaller depth (dimension in the sub-scanning direction) is used to remove the residual ink. Can be removed. In addition, by moving the residual ink absorbing portion 71 in contact with the surface of the purging electrode 41, the ink absorption efficiency can be improved.

(Example 9) FIG. 13 shows another example of the ink jet recording apparatus according to the present invention. This figure is a cross-sectional view of a main part of the ink jet recording apparatus. In this example, the purging head includes a pair of rollers 81 and 82.
Other configurations are the same as those shown in FIGS. 2 and 3 in Example 1 above.

In this ink jet recording apparatus, a purging roller 81 (first roller) and a backup roller 82 (second roller) are disposed in parallel with the counter electrode 25 at positions adjacent to the counter electrode 25. I have.
The purging roller 81 and the backup roller 82
Width equal to or greater than counter electrode 25 (dimension in main scanning direction; FIG. 1)
3 has a dimension perpendicular to the paper surface). The purging roller 81 and the backup roller 82 are in contact with each other. The purging roller 81 is made of a conductive member and is connected to a ground (not shown). On the other hand, the backup roller 82 is composed of a shaft and a porous material having a high absorbency for ink wound around the shaft.

Next, the operation of the ink jet recording apparatus when purging the recording head 10 will be described.

The recording head 10 is retracted from the position shown in FIG. 13 in the sub-scanning direction (to the left in FIG. 13), and is moved directly below the first cleaning head 81. Next, while rotating the purging roller 81 and the backup roller 82, a stronger electric field is formed between the recording head 10 and the purging roller 81 as compared to when recording dots are formed,
Ink droplets are ejected from the recording head 10. The ejected ink adheres to the surface of the purging roller 81, and is further carried to a contact position with the backup roller 82 with the rotation of the purging roller 81, and is absorbed by the absorbent constituting the outer peripheral surface of the backup roller 82. You.

The direction of rotation of both rollers 81 and 82 is
The rollers may be in the same direction or in different directions.
Are set so that frictional force acts on the contact portion, the first cleaning 81 to the backup roller 82
The transfer of the ink to the nozzle can be performed efficiently.

As described above, by transferring the ink ejected from the recording head 10 to the backup roller 82 as needed, the ink that has reached the surface of the purging roller 81 is collected, and there is no danger of dripping. Further, the ink ejected from the recording head 10 can be efficiently collected with a simple configuration.

In this example, the movement of the ink from the purging roller 81 to the backup roller 82 is performed only by the contact of the roller. Further, if the operation is performed while an electric field is formed between the two rollers, the efficiency of ink transfer between the two rollers can be improved.

(Example 10) FIG. 14 shows another example of the ink jet recording apparatus according to the present invention. This figure is a cross-sectional view of a main part of the ink jet recording apparatus. In this example, without providing a dedicated purging head, as described below,
The counter electrode 25 also functions as an electrode for purging. The configuration of the recording head 10 is the same as that shown in FIGS. 2 and 3 in Example 1 above.

In this example, a cleaning roller 91 is provided at a position adjacent to the counter electrode 25. The cleaning roller 91 is movable in the sub-scanning direction (the left-right direction in FIG. 14), retreats to the standby position and separates from the counter electrode 25 when forming a recording dot, and advances and moves forward during the purging operation. Contacts the outer peripheral surface of.

Next, the operation when purging the recording head 10 in this ink jet recording apparatus will be described.

At the time of the purging operation, the supply of the recording paper (26; FIG. 1) to the counter electrode 25 is interrupted, and the cleaning roller 91 moves forward, as shown in FIG. Contact Next, a stronger electric field is generated between the recording head 10 and the counter electrode 25 than when recording dots are formed, and ink is ejected from the recording head 10 toward the counter electrode 25. The ink attached to the counter electrode 25 is removed by the cleaning roller 91 as the counter electrode 25 rotates.
The cleaning roller 91 moves to the contact position with the cleaning roller 91. When the purging operation is completed, the cleaning roller 91 moves away from the counter electrode 25 to the standby position, and the state in which the supply of the recording paper is interrupted is released.

As in this example, by making the counter electrode 25 also function as an electrode for purging, the structure of the device can be simplified, and the device can be downsized.

Example 11 FIG. 15 shows another example of the ink jet recording apparatus according to the present invention. This figure is a cross-sectional view of a main part of the ink jet recording apparatus. This apparatus is obtained by adding monitoring mechanisms 101 to 103 for the ink guide 22 of the recording head 10 to the configuration shown in Example 1 (FIG. 1), and the other configuration is the same as that shown in FIG. Is the same as

The monitoring mechanism of the ink guide 22 optically detects clogging at the tip of the ink guide 22, and includes a light emitting unit 101 (detecting unit), a light receiving unit 102 (detecting unit), and a data processing unit 103. (Control device). The light emitting unit 101 and the light receiving unit 102 are arranged so as to sandwich a slit (23; FIG. 2) at the tip of the ink guide 22 therebetween. If clogging occurs due to the adhesion of toner particles to the tip of the ink guide 22, the slit 22
Since the density of the ink increases in the inside, the occurrence of clogging can be detected by monitoring the optical density. The signal from the light receiving unit 102 is subjected to data processing in the data processing unit 103 to determine whether or not clogging has occurred. If clogging at the tip of the ink guide 22 is detected,
The printing operation is interrupted, and the purging operation is automatically performed.

By providing a mechanism for monitoring clogging at the tip of the ink guide 22 as in this example, the purging operation can be performed only when clogging occurs, thereby increasing the actual operation time of the apparatus. Can be done.
In addition, the self-diagnosis allows the tip of the ink guide 22 to be constantly maintained in a state where there is no attached matter, so that maintenance work by the user is reduced. Further, by switching the electric field condition at the time of the purging operation based on the information from the monitoring mechanism, it is possible to automatically set the optimal purging condition.

The light emitting unit 101 and the light receiving unit 102 may be separately provided for each ink guide 22, or the light emitting unit 1
By scanning the 01 and the light receiving unit 102 in the arrangement direction of the ink guides 22, a plurality of ink guides 22 may be monitored in a pair.

In this example, the light emitting section 101 and the light receiving section 102 are separated from each other, and the clogging is detected by using the transmitted light.
2 can be integrated, and clogging can be detected using reflected light.

Example 12 FIG. 16 shows another example of the ink jet recording apparatus according to the present invention. This figure is a cross-sectional view of a main part of the ink jet recording apparatus. This apparatus is different from the configuration shown in Example 1 (FIG. 1) in that monitoring mechanisms 111 and 112 for monitoring the state of an image formed on the recording paper 26 are further provided.
The other configuration is the same as that shown in FIG.

The monitoring mechanism comprises an image monitor 111 (image recognition means) and a data processor 113 (control device) arranged close to the recording drum 10. The image monitor unit 111 has a light emitting unit and a light receiving unit integrated, and its output signal is sent to the data processing unit 113.

When clogging occurs due to the adhesion of toner particles to the tip of the ink guide 22 of the recording head 10, the size of the recording dots formed on the recording paper 26 is reduced, and sometimes the recording dots are not formed. Therefore, by printing a test pattern on the recording paper 26 and monitoring the test pattern, the state of clogging of the recording head 10 can be determined. As the test pattern, for example, a rectangular solid pattern is suitable.

The test pattern image is displayed on the image monitor 1
11 to the data processing unit 113 for processing. If the density of the test pattern is equal to or less than a predetermined threshold, it is determined that clogging has occurred. If it is determined that the paper is clogged, the printing operation is interrupted, and the purging operation is automatically performed.

The image monitor section 111 may have a light emitting section and a light receiving section separately as in the previous example.
In addition, a line type configuration corresponding to all the ink guides 22,
Alternatively, dots formed by all the ink guides may be monitored in a serial structure. Thus, the recording paper 26
In the case where the purging operation is performed based on the state of the image printed above, the clogging of the recording head can be determined with a high probability, so that the frequency of the purging operation can be appropriately maintained. .

[0092]

According to the ink jet recording apparatus of the present invention, clogging of the recording head can be promptly removed in a type of apparatus which discharges ink droplets by using electrostatic force, so that printing can be performed. Image quality can always be maintained in a good state.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first example of an ink jet recording apparatus according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a recording head portion of the ink jet recording apparatus of FIG.

FIG. 3 is an enlarged plan view of an ink discharge unit of the recording head of FIG. 2;

FIG. 4 is a perspective view of a purging head included in the ink jet recording apparatus of FIG.

FIG. 5 is a front view of a purging head used in a second example of the ink jet recording apparatus according to the present invention.

FIG. 6 is a diagram illustrating a purging operation in a third example of the inkjet recording apparatus according to the present invention.

FIG. 7 is a sectional view of a purging head used in a fourth example of an ink jet recording apparatus according to the present invention.

FIG. 8 is a perspective view of a purging head used in a fifth example of the ink jet recording apparatus according to the present invention.

FIG. 9 is a diagram illustrating a purging operation using the purging head of FIG. 8;

FIG. 10 is a perspective view of a purging head used in a sixth example of the ink jet recording apparatus according to the present invention.

FIG. 11 is a perspective view of a purging head used in a seventh example of the ink jet recording apparatus according to the present invention.

FIG. 12 is a schematic configuration diagram showing an eighth example of the ink jet recording apparatus according to the present invention.

FIG. 13 is a schematic configuration diagram showing a ninth example of an inkjet recording apparatus according to the present invention.

FIG. 14 is a schematic configuration diagram showing a tenth example of an ink jet recording apparatus according to the present invention.

FIG. 15 is a schematic configuration diagram showing an eleventh example of an ink jet recording apparatus according to the present invention.

FIG. 16 is a schematic configuration diagram showing a twelfth example of an ink jet recording apparatus according to the present invention.

[Explanation of symbols]

10: recording head, 11: ink, 12 ...
Ink droplets, 11: support shaft, 17: ink supply tank, 18: ink supply path, 20: control electrode,
21 ... opening, 22 ... ink guide, 23 ...
・ Slit, 24 ・ ・ ・ Ink chamber, 25 ・ ・ ・ Counter electrode, 26 ・ ・ ・ Recording paper, 31 ・ ・ ・ Head block, 3
3 ... ink guide block, 34 ... insulating substrate, 36 ... through hole, 38 ... bias voltage source, 3
9 ... signal voltage source, 40 ... purging head, 4
DESCRIPTION OF SYMBOLS 1 ... Purging electrode (electrode plate), 42 ... Through-hole, 43 ... Absorbent, 45 ... Groove, 46 ... Ink suction electrode, 47 ... DC voltage source, 51 ... -Purging electrode (electrode plate), 53 ... absorber, 54 ... casing, 55 ... partition, 56 ... guide plate, 61
... Electrode member (ink-absorbing porous body), 64
· Casing, 71 ··· Residual ink absorbing part, 73 ···
· Absorber, 74 ··· Casing, 81 ··· Purging roller (first roller), 82 ··· Backup roller (second roller), 91 ··· Cleaning roller, 101 ··· Light emitting unit ( Detecting unit), 102: light receiving unit (detecting unit), 103: data processing unit (control device), 111: image monitoring unit (image recognizing unit), 1
13 Data processing unit (control device)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Hosaka 1st location, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture. (72) Inventor Kazushi Nagato Toshiba Komukai, Sai-ku, Kawasaki-shi, Kanagawa. No. 1 Town Toshiba R & D Center (72) Inventor Kazuhiko Higuchi No. 1 Komukai Toshiba Town, Sachi-ku, Kawasaki City, Kanagawa Prefecture Toshiba R & D Center (72) Inventor Hideyuki Nakao, Kawasaki City, Kanagawa Prefecture 1, Komukai Toshiba-cho, Ward Inside Toshiba R & D Center

Claims (11)

[Claims] An ink droplet is directed toward a recording medium by electrostatic force by applying a voltage between a counter electrode which is provided on a surface thereof and holding a recording medium and a counter substrate and facing the counter electrode. A recording head that discharges the recording head, a purging head disposed at a position adjacent to the counter electrode, and a moving unit that moves the recording head to a position facing the purging head. In this state, by applying a voltage between the purging head and the purging head, the ink droplets are ejected toward the purging head by electrostatic force, thereby removing the deposits adhering to the ink ejection portion of the recording head. Characteristic inkjet recording device. 2. The recording head, comprising: a plurality of two-dimensionally arranged control electrodes opposed to the counter electrode, each having an opening near the center, two-dimensionally arranged; An ink chamber containing an ink in which a color material component is dispersed, and penetrating the vicinity of the center of the opening, and a front end portion protrudes from the front surface of the control electrode toward the counter electrode, and extends from the ink chamber along the protruding direction. The ink jet recording apparatus according to claim 1, further comprising: an ink guide having a slit extending to a tip end, wherein the ink droplet is ejected from the tip end of the ink guide. 3. The purging head according to claim 1, further comprising: an electrode plate facing the recording head; and an ink absorbing material disposed so as to contact the electrode plate. Item 3. An ink jet recording apparatus according to Item 2. 4. The ink jet recording apparatus according to claim 3, wherein a plurality of through holes are formed in the electrode plate, and the ink absorbing material is disposed on a back side of the electrode plate. 5. The ink jet recording apparatus according to claim 4, wherein a plurality of grooves intersecting with the plurality of through holes are formed on a surface of the electrode plate. 6. The ink jet printer according to claim 1, wherein the purging head includes an electrode member made of a porous material that is conductive and has ink absorbability, facing the recording head. 3. The ink jet recording apparatus according to claim 1. 7. The purging head is opposed to the recording head, is in contact with a cylindrical first roller made of a conductive member, and is in contact with the outer periphery of the first roller. The inkjet recording apparatus according to claim 1, further comprising: a second cylindrical roller formed of a porous material provided with the second roller. 8. A detecting means for detecting a state of a substance adhering to an ink ejection portion of the recording head, and moving the recording head to a position facing the purging head based on information from the detecting means. The ink jet recording apparatus according to claim 1, further comprising: a control device configured to discharge ink droplets from the recording head toward the purging head. 9. A detecting means for detecting a state of an adhering substance attached to a tip portion of the ink guide; and moving the recording head to a position facing the purging head based on information from the detecting means. The ink jet recording apparatus according to claim 2, further comprising: a control device configured to discharge ink droplets from the tip of the ink guide toward the purging head. 10. An image recognizing means for monitoring a state of a recording dot formed on the recording medium, and moving the recording head to a position facing the purging head based on information from the image recognizing means. 3. A control device for ejecting ink droplets from the recording head toward the purging head, further comprising:
3. The ink jet recording apparatus according to claim 1. 11. A method in which a voltage is applied between a counter electrode having a surface on which a recording medium is held and a counter substrate, and a voltage is applied between the counter electrode and the counter electrode, whereby an ink droplet is directed toward the recording medium by electrostatic force. A cleaning head, which is movably disposed at a position adjacent to the counter electrode and whose outer peripheral portion is formed of a porous material having ink absorbency, and a cleaning roller which moves the cleaning roller to form the counter electrode. A driving mechanism for contacting the surface of the counter electrode, and generating a stronger electric field between the recording head and the counter electrode in a state where the cleaning roller is in contact with the surface of the counter electrode as compared to when recording an image. By
The ink droplets are ejected toward the counter electrode by electrostatic force, and the ink adhered to the surface of the counter electrode is collected by the cleaning roller, thereby removing the deposit attached to the ink ejection portion of the recording head. An inkjet recording apparatus.