JP2737727B2 - Ink jet recording head device - Google Patents

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 head device, and more particularly to an ink-jet recording head device using an ink in which charged toner particles are dispersed in an insulating solvent and discharging the toner particles in the solvent by the action of an electric field. The present invention relates to an ink jet recording head device for performing

[0002]

2. Description of the Related Art In a conventional ink jet recording head,
Liquid ink is used as a recording material, and there are roughly two types of ink supply methods. The first supply method is a method in which ink consumed by the discharge of ink is replenished from the ink tank by the action of meniscus force generated in the discharge part without using a pump or the like for supplying ink.
This method is mainly used for a drop-on-demand type ink jet recording apparatus. In this supply method, the ink flows in only one direction from the ink tank to the ink chamber, and ink circulation in the ink chamber is not performed.

A second supply method is a method in which ink is supplied from an ink tank to a head section by a pump or the like. This method is used in a continuous type ink jet recording apparatus disclosed in, for example, JP-A-5-261936 and JP-A-5-185600.
In this supply method, the ink flow is urged in one direction from the ink tank to the ink chamber by a pump or the like, and the ink in the ink chamber is pushed out by the sent ink and returns to the inside of the ink tank, whereby ink circulation is performed. I was

On the other hand, in recent years, an electrostatic ink jet recording apparatus has generally used an ink in which charged toner particles are distributed in an insulating solvent. In an ink jet recording head of this type, an electric field is applied to charged toner particles in a solvent, and the recording is performed by discharging the toner particles from the surface of an ink meniscus. It is. Although the ejection involves a small amount of solvent, most of the flying components are a group of toner particles. on the other hand,
During non-ejection, the solvent is held in the ink chamber by the surface tension of the meniscus formed at the ejection section.

In this type of recording apparatus, the toner in the solvent is consumed in accordance with the ejection operation, so that the density of the toner gradually decreases and the amount of toner concentrated in the ejection section also decreases. The decrease causes problems such as a decrease in print dot diameter and a decrease in print density. Further, if the ejection is continued thereafter, the recording operation by the toner ejection cannot be performed even though the solvent is filled in the ink chamber. Therefore, in this type of printing apparatus, it is necessary to constantly circulate the new ink in the ink tank with the ink in the ink chamber to maintain the toner concentration in the solvent at a predetermined amount.

[0006]

However, in the ink supply method used in the conventional drop-on-demand type recording head, that is, the ink supply method by the action of the meniscus force, the solvent sufficiently filled in the ink chamber is required. There is a disadvantage that the toner consumed during the printing cannot be supplied.

An ink supply method used in a conventional continuous type recording head, that is, an ink supply method in which ink flows in one direction from an ink tank toward an ink chamber by the power of a pump or the like, is a dropping method. It is unsuitable for an on-demand type recording head, and the ink pressure in the ink chamber increases, the ink meniscus of the discharge unit cannot be maintained, and ink leakage from the discharge unit occurs.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to an ink jet recording head apparatus which solves the disadvantages of the prior art, and in particular, provides an ink jet recording head apparatus which performs recording by discharging charged toner in a solvent by a drop-on-demand method. An object of the present invention is to provide an ink jet recording head device that effectively supplies the reduced toner and constantly performs a stable printing operation.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, there is provided an ink chamber for storing ink containing charged toner, and a discharge unit for communicating the ink chamber with the outside. An ejection electrode that is provided adjacent to the ejection unit and ejects toner from the ejection unit, an electrophoresis electrode that is attached to the ink chamber and concentrates the toner in the ink chamber on the ejection unit,
And an ink storage unit interconnected with the ink chamber and storing the ink. Among these, the ink chamber and the ink storage section are connected by an inflow pipe from the ink storage section to the ink chamber and an outflow pipe from the ink chamber to the ink storage section. In addition, both the inflow pipe and the outflow pipe are provided with ink circulation urging means for urging ink circulation between the ink chamber and the ink storage unit, and the ink circulation urging means is provided on the ink chamber side. The apparatus has a fixed amount sending function for making the amount of ink to be sent and the amount of ink sent to the ink storage unit equal and constant.

In the present invention, a voltage having the same polarity as that of the toner is applied to the migrating electrode, and the toner is concentrated on the discharge portion under the action of the electric field. Thereafter, a voltage having the same polarity as that of the toner is applied to the ejection electrode, and the toner is ejected from the solvent under the action of the electric field. After the toner is discharged, the amount of toner in the ink chamber decreases. The ink circulation is urged by the ink circulation urging means between the ink storage section and the ink chamber. By this ink circulation, toner is supplied into the ink chamber. On this occasion,
The ink circulation urging means simultaneously urges the ink circulation to both the inflow pipe to the ink chamber and the outflow pipe from the ink chamber, and determines the amount of ink flowing from the inflow pipe to the ink chamber and the ink chamber. Since the amount of ink flowing out from the outlet to the outflow channel is always equal and constant, the ink inside the ink chamber is replaced while the pressure state of the ink in the ejection section is maintained substantially constant.

According to the present invention, the ink circulation urging means is configured as an integral pump for simultaneously energizing the ink inflow operation in the inflow conduit and the ink outflow operation in the outflow conduit. ing. In the present invention, the inflow of ink into the ink chamber and the outflow of ink from the ink chamber are simultaneously energized by a single pump, and even if the performance of the pump changes for some reason, the amount of ink flowing into the ink chamber And the amount of outflow from the ink chamber are always kept equal.

According to the third aspect of the present invention, a configuration is adopted in which a bypass pipe connecting the upstream side and the downstream side of the ink circulation urging means is provided in the inflow pipe.

In the present invention, when the amount of ink in the ink chamber is reduced due to the discharge of toner or some other reason, the ink at the tip of the discharge section is somewhat drawn into the ink chamber. And
A concave meniscus is formed at the tip, and a strong force acts to draw ink into the ink chamber. As a result, an ink flow toward the ink chamber is generated in the bypass pipe where there is almost no ink flow, and the inflow of the inflow pipe is increased. Here, since the outflow from the ink chamber is constant, the reduced amount of ink is replenished to the ink chamber. As a result, the pressure state of the discharge unit is almost returned to the normal state.

On the other hand, when the amount of ink in the ink chamber increases,
The ink at the tip of the ejection part protrudes somewhat outside the ink chamber. Then, a convex meniscus is formed at the front end, and a strong force acts to push the ink from the ink chamber to the ink tank. As a result, an ink flow returning to the ink tank side is generated in the bypass pipe where there is almost no ink flow, and the inflow of the inflow pipe is reduced. Here, since the outflow from the ink chamber is constant, the amount of ink in the ink chamber is reduced. As a result, the pressure state of the discharge unit is almost returned to the normal state.

According to the fourth aspect of the present invention, when the meniscus force of the ink meniscus formed in the discharge section becomes equal to or greater than a predetermined value, the bypass pipe has a flow path resistance that causes an ink flow in the bypass pipe. Is adopted. According to the present invention, when the pressure state of the discharge unit changes and the meniscus force fluctuates by a certain value or more from the normal state, ink flows in the bypass conduit.

With these, the above-mentioned object is to be achieved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIGS.

The ink jet recording head device shown in FIGS. 1 and 2 includes a recording head 4 and an ink tank 1 serving as an ink storage unit that is connected to an ink chamber 7 of the recording head 4 and stores ink 13. ing. The ink chamber 7 and the ink tank 1 are connected by an inflow pipe 18 from the ink tank 1 to the ink chamber 7 and an outflow pipe 17 from the ink chamber 7 to the ink tank 1. Further, both the inflow pipe 18 and the outflow pipe 17 are provided with ink circulation urging means 3 for urging the ink circulation between the ink chamber 7 and the ink tank 1.

More specifically, in the present embodiment, the recording head 4 includes the ink 13 containing the charged toner.
An ink chamber 7 that stores the ink, an ejection section 5 that communicates the ink chamber 7 with the outside, an ejection electrode 12 that is provided adjacent to the ejection section 5 and that ejects toner from the ejection section 5, and an ink chamber 7.
And an electrophoresis electrode 19 for concentrating the toner in the ink chamber 7 to the ejection section 5. The ink chamber 7
Except for a portion provided on the base and connected to the inflow conduit 18 and the outflow conduit 17 and the discharge part 5 being opened, it is a closed space and is filled with the ink 13. 2, the illustration of the ink chamber 7 is partially omitted, and the ink chamber 7 is closed in the left-right direction of FIG. 2 (not shown).

The ink 13 is a dispersion of fine particles of a thermoplastic resin, a so-called toner, colored together with a charge control agent in a petroleum organic solvent (isoparaffin). The toner is positively charged to a positive polarity by the zeta potential. .

In the discharge section 5, a plurality of discharge electrodes 12 are arranged in parallel with the tip thereof projecting from the discharge section 5 by about 80 μm to 100 μm. Then, an ink meniscus 8 is formed between the adjacent ejection electrodes 12, 12 due to the surface tension of the ink 13. The ejection electrode 12 is formed by forming a conductive material such as Cu or Ni into a band shape by electroforming, and has a width set to about 50 μm. Further, the arrangement width between the adjacent ejection electrodes 12 is arranged at a pitch of 300 dpi, that is, at an interval of 85 [μm].

A flat electrophoretic electrode 19 is integrally fixed around the ink chamber 7 except for the ejection section 5 side. Here, the electrophoresis electrode 19 in the portion fixed in the left-right direction in FIG. 2 is not shown. The migration electrode 19 is formed of a conductive material such as Cu.

When a voltage having the same polarity as that of the toner is applied to the migration electrode 19, the ink 1 in the ink chamber 7 is
The toner in 3 is concentrated on the discharge unit 5, and a voltage having the same polarity as the toner is applied to a predetermined discharge electrode 12 in this state, whereby the toner is discharged from the ink meniscus 8 as a group. In general, a grounded counter electrode (not shown) is provided on an extension of the discharge electrode 12, and an electric field is formed between the discharge electrode 12 and the counter electrode. The toner group flies toward the counter electrode. An image is formed by disposing a recording medium between the ejection electrode 12 and the counter electrode and intermittently ejecting toner groups from a predetermined ejection electrode 12 while conveying the recording medium.

Next, the configuration of the ink circulation system will be described in detail. In the present embodiment, the ink circulation urging means 3 performs the operation of inflow of the ink 13 in the inflow line 18 and the outflow line 1.
7 is an integral pump for simultaneously energizing the outflow operation of the ink 13. Further, the pump 3 as the ink circulation urging means has a fixed amount sending function that always makes the amount of ink sent to the ink chamber 7 side and the amount of ink sent to the ink tank 1 side equal and constant. . Such pumps are generally commercially available. In addition, in the inflow conduit 18,
A bypass line 6 connecting the upstream side and the downstream side of the pump 3
Is attached. The bypass pipe 6 has a predetermined flow path resistance that causes an ink flow in the bypass pipe 6 when the meniscus force 14 of the ink meniscus 8 formed in the ejection unit 5 becomes a certain value or more. .

The inflow line 18 and the outflow line 17 are, for example, tubes, and connect the bypass line 6 to the middle of the inflow line 18 via a branch. The ink tank 1 is a normal water tank, and has a connection port with the inflow pipe 18 and the outflow pipe 17.

As described above, the ink 1 in the ink tank 1
Numeral 3 communicates with the recording head 4 at two places through two pipes 17 and 18 such as pipes or tubes.
7 and 18 pass through the pump 3 on the way. Since the pump 3 is not provided for each of the pipes 17 and 18 but circulates the ink 13 to both the pipes 2 by one, each of the pipes 17 and 18 is provided in the pipes 17 and 18. It is connected to the pump 3 so that the flow directions are reversed.

Here, reference numeral 15 indicates the resistance of the flow in each of the pipes 17 and 18, reference numeral 16 indicates the resistance of the flow in the bypass pipe 6, and reference numeral 14 indicates the meniscus force of the discharge section 5. Is shown. The connection position between the ink tank 1 and each of the conduits 17 and 18 is set in accordance with the ink pressure generated in the ink chamber 7, and the pressure of the inflow conduit 18 on the ink tank 1 side and the pressure on the ink chamber 7 side are set. Need to be adjusted so that Further, the connecting portion between the ink chamber 7 and each of the conduits 17 and 18 may be provided in a direction perpendicular to the ink discharging direction, instead of in FIG. Further, the ink tank 1 may be provided with a stirring means for preventing the sedimentation of the toner in the tank.

When the pump 3 is set to the operating state, ink circulation is urged to the inflow pipe 18 and the outflow pipe 17. The ink feeding directions of the inflow pipe 18 and the outflow pipe 17 are opposite to each other, and the inflow flow 10 into the ink chamber 7 is different.
And an outflow 9 to the ink tank 1 respectively.
Here, the two pipe lines 17 and 18 connecting the ink tank 1 and the ink chamber 7 are connected to a single pump 3.
For this reason, even if the performance of the pump 3 changes for some reason, the amount of ink 13 sent to the inflow line 18 and the amount of ink sent to the outflow line 17 are maintained at the same level.
Therefore, under the condition that the ink circulation system is closed with respect to disturbance, the amount of the ink 13 in the ink chamber 7 and the pressure state in the ejection unit 5 are constant, and the ink 13 in the ink chamber 7 is fixed.
Is held by the ink meniscus 8 formed in the ejection unit 5.

On the other hand, during the printing operation, the amount of the ink 13 in the ink chamber 7 is reduced as long as the toner is discharged, even if the same amount of the ink 13 always flows into and out of the ink chamber 7. . Further, even during printing standby, the amount of the ink 13 decreases due to drying or the like. Further, it is practically difficult to always completely match the inflow amount and the outflow amount of the ink 13.

Therefore, in order to always keep the amount and pressure of the ink 13 in the ink chamber 7 constant, as described above,
A bypass pipe 6 that avoids the pump 3 is provided in the inflow pipe 18. The flow path resistance of the bypass pipe 6 is set so high that almost no ink flow occurs in the bypass pipe 6 when the discharge unit 5 is in a normal pressure state.

Then, the amount of the ink 13 in the ink chamber 7 changes due to the ejection of the toner or some other cause.
Is changed and the meniscus force 14 fluctuates by a certain value or more, an ink flow occurs in the bypass pipe 6 and the amount of ink flowing from the inflow pipe 18 into the ink chamber 7 is adjusted.

FIG. 3 shows the state of the ink flow generated in the bypass pipe 6 as the ink 13 in the ink chamber 7 increases or decreases.
5 to FIG. First, in the normal state shown in FIG. 3, almost no ink flow occurs in the bypass pipe 6.

Next, when the amount of the ink 13 in the ink chamber 7 decreases, as shown in FIG. 4, the ink 13 at the tip of the discharge unit 5 is somewhat drawn into the ink chamber 7. Then, a concave meniscus 8 is formed at the front end, and a strong force for drawing the ink 13 into the ink chamber 7 acts. As a result, an ink flow toward the ink chamber 7 is generated in the bypass pipe 6 where there is almost no ink flow, and the inflow 10 of the inflow pipe 18 is increased. Here, since the outflow flow 9 from the ink chamber 7 is constant, the reduced amount of the ink 13 is refilled into the ink chamber 7. As a result, the pressure state of the discharge unit 5 is almost returned to the normal state.

On the other hand, when the ink 13 in the ink chamber 7 increases, as shown in FIG. Then, a convex meniscus 8 is formed at the tip, and a strong force acts to push the ink 13 from the ink chamber 7 to the ink tank 1. As a result, the bypass line 6 with almost no ink flow
Causes an ink flow returning to the ink tank 1 side,
The inflow 10 of the inflow line 18 is reduced. Here, since the outflow flow 9 from the ink chamber 7 is constant, the amount of the ink 13 in the ink chamber 7 is reduced. As a result, the pressure state of the discharge unit 5 is almost returned to the normal state.

Here, in order for the bypass line 6 to function as described above, the flow resistance 15 of the inflow line 18 and the outflow line 17 must be equal to the magnitude Pc1 of the flow resistance 16 and the flow resistance 16 of the bypass line 6. The relationship between the magnitude Pc2 and the magnitude Pmn of the ink meniscus force 14 of the ejection unit 5 may be set as follows.

First, the ink 13 normally sent by the power of the pump 3 does not flow backward through the bypass line 6.
It is assumed that Pc1 <Pc2. When the amount of the ink 13 changes by a certain amount or more, Pc2 <Pm so that the ink 13 flows into the bypass pipe 6 under the action of the meniscus force 14.
n. That is, it may be set as follows.

Pc1 <Pc2 <Pmn Equation (1)

As described above, according to the present embodiment, the ink circulation urging means 3 is provided in both the inflow pipe 18 and the outflow pipe 17, and the inflow of the ink 13 from the inflow pipe 18 into the ink chamber 7 is performed. Amount and ink 1 from the ink chamber 7 to the outlet line 17
3 is always kept equal and constant, so that the pressure state of the ink 13 of the ejection unit 5 is maintained almost constant.
The ink 13 in the ink chamber 7 can be replaced, and the toner reduced in the ink solvent can be replenished while keeping the state of the ink meniscus 8 formed in the discharge unit 5 stable. Sufficient toner can be concentrated, and a decrease in toner density can be prevented, thereby improving print quality.

Further, since the ink inflow operation in the inflow line 18 and the outflow operation in the outflow line 17 are simultaneously urged by the integral pump 3, the size of the apparatus can be reduced as compared with the case where a plurality of pumps are mounted. Not only can you plan,
Even if the performance of the pump 3 changes for some reason, the ink flow rate in the inflow pipe 18 and the ink flow rate in the outflow pipe 17 can be constantly maintained at the same level.

Further, since the bypass pipe 6 connecting the upstream side and the downstream side of the ink circulation urging means 3 is provided in the inflow pipe 18, the ink 13 in the discharge section 5 decreases or increases for some reason. Even if the shape of the meniscus 8 is undesirably deformed, the amount of the ink 13 flowing into the ink chamber 7 can be increased or decreased according to the meniscus force 14 generated by the deformation of the meniscus 8, and the toner discharge and drying can be performed. Alternatively, the shape of the meniscus 8 can be always kept stable even when the amount of ink increases or decreases due to an excessive inflow or the like.

In addition, the flow path resistance of the bypass pipe 6 is set so that an ink flow is generated in the bypass pipe 6 when the meniscus force 14 fluctuates by a certain value or more. The amount of ink in 7 is increased or decreased,
It is possible to prevent inconvenience such as giving vibration to the ink meniscus 8 which has been stable, and it is possible to maintain a stable state of the meniscus 8.

In particular, by adjusting the flow path resistance of each of the conduits 17 and 18 as described above, the ink amount is reduced by the ejection, the ink amount is reduced by the drying during non-ejection, or the ink amount is affected by other disturbances. Is changed, the ink amount in the ink chamber 7 and the pressure state of the ejection unit 5 are adjusted to be constant. Thus, even when there is some disturbance, the pressure balance in the ink chamber 7 is maintained, and stable printing can always be performed.

[0043]

Since the present invention is constructed and functions as described above, according to the present invention, both the inflow pipe and the outflow pipe are provided with ink circulation urging means, so that the ink is supplied from the inflow pipe to the ink chamber. Since the inflow amount of the ink and the outflow amount of the ink from the ink chamber to the outflow conduit are always kept equal and constant, the ink state in the ink chamber is maintained while the pressure state of the ink in the ejection section is kept almost constant. It is possible to replenish the reduced toner in the ink solvent while keeping the state of the ink meniscus formed in the ejection section stable, so that sufficient toner can be always concentrated on the ejection section, The print quality can be improved by preventing the density from decreasing.

According to the second aspect of the present invention, the inflow operation of the ink in the inflow line and the outflow operation of the outflow line are simultaneously urged by the integral pump. In addition to downsizing, even if the performance of the pump changes for some reason, the ink flow rate in the inflow pipe and the ink flow rate in the outflow pipe can be constantly maintained at the same level.

According to the third aspect of the invention, since the bypass pipe connecting the upstream side and the downstream side of the ink circulation urging means is provided in the inflow pipe, the ink in the discharge section is reduced or increased for some reason. However, even if the shape of the meniscus is undesirably deformed, the amount of ink flowing into the ink chamber can be increased or decreased according to the meniscus force generated by the deformation of the meniscus. The shape of the meniscus can always be kept stable even when the amount of ink increases or decreases due to the above.

According to the fourth aspect of the present invention, since the flow path resistance of the bypass pipe is determined so as to generate an ink flow in the bypass pipe when the meniscus force fluctuates by a certain value or more, the ink is carelessly printed. The amount of ink in the room is increased or decreased,
It is possible to provide an unprecedented excellent ink jet recording head device capable of preventing inconvenience such as giving vibration to a stable ink meniscus and maintaining a stable state of the meniscus.

[Brief description of the drawings]

FIG. 1 is a connection block diagram showing one embodiment of the present invention.

FIG. 2 is an enlarged schematic view of the embodiment shown in FIG.

FIG. 3 is an explanatory diagram showing ink flow in a bypass pipe when ink pressure of a discharge unit is in a normal state;
3A shows the state of the meniscus and the meniscus force, and FIG. 3B shows the ink flow generated in the bypass conduit.

FIG. 4 is an explanatory diagram showing an ink flow in a bypass conduit when the ink pressure of a discharge unit is lower than normal;
4A shows the state of the meniscus and the meniscus force, and FIG. 4B shows the ink flow generated in the bypass conduit.

FIG. 5 is an explanatory diagram showing an ink flow in a bypass conduit when the ink pressure of a discharge unit is higher than normal;
5A shows the state of the meniscus and the meniscus force, and FIG. 5B shows the ink flow generated in the bypass conduit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink tank (ink storage part) 3 Pump (ink circulation urging means) 4 Recording head 5 Discharge part 6 Bypass line 7 Ink chamber 12 Discharge electrode 17 Outflow line from ink chamber 18 Inflow line to ink chamber 19 Electrophoresis electrode

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hitoshi Minemoto 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Kazuo Shima 5-7-1 Shiba, Minato-ku, Tokyo Japan Electric Co., Ltd.

Claims (4)

(57) [Claims] 1. An ink chamber for storing ink containing charged toner, an ejection section communicating the ink chamber with the outside, an ejection electrode provided adjacent to the ejection section and ejecting the toner from the ejection section, An electrophoresis electrode provided adjacent to the ink chamber for concentrating toner in the ink chamber to the ejection section; and an ink storage section interconnected with the ink chamber and storing the ink, wherein the ink chamber and the ink storage section Are connected by an inflow pipe from the ink storage section to the ink chamber and an outflow pipe from the ink chamber to the ink storage section, wherein both the inflow pipe and the outflow pipe have An ink circulation urging unit for urging the ink circulation between the ink chamber and the ink storage unit is provided, and the ink circulation urging unit sends the ink to the ink chamber. An ink jet recording head apparatus characterized in that it comprises a rate feed capability to the equivalent amount and a certain amount of the amount of ink delivered ink amount and the ink reservoir side. 2. The ink pump according to claim 1, wherein the ink circulation urging means is an integral pump for simultaneously energizing the ink inflow operation in the inflow conduit and the ink outflow operation in the outflow conduit. 2. The ink jet recording head device according to 1. 3. The ink jet recording head device according to claim 1, wherein a bypass pipe connecting the upstream side and the downstream side of the ink circulation urging means is provided in the inflow pipe. 4. The bypass pipe has a flow path resistance that causes an ink flow in the bypass pipe when a meniscus force of an ink meniscus formed in the discharge section becomes a predetermined value or more. The inkjet recording head device according to claim 3, wherein: