JPH08252928A - Ink jet printer and purge method thereof - Google Patents

Abstract

PURPOSE: To provide an ink jet printer reduced in production cost by minimizing the amt. of ink discarded for the purpose of discharging air bubbles and reducing the number of the constitutional parts of an air bubble purge mechanism to the utmost. CONSTITUTION: In an ink jet printer ejecting ink from nozzles to perform printing, a main tank storing ink, a sub-tank recovering purge ink to store the same and the manifold connecting the sub-tank and the main tank to supply ink to the nozzles are arranged to a printing head part 2 and the main tank and the sub-tank are alternately pressurized by a pressure pump 30 to discharge air bubbles in the manifold and the nozzles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer, and more particularly to a bubble purging mechanism and a bubble purging method for an ink jet printer.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a print head of a conventional ink jet printer.

Electromechanical transducer (hereinafter referred to as PZT) 5
The displacement of 4 acts on the ink in the chamber 52 via the diaphragm 53, and the ink particles are ejected from the nozzle 51. At that time, if air bubbles are mixed in the ink in the chamber 52, there is an adverse effect such that ink particles do not fly out. For this reason, air bubbles must not exist in the ink in the manifold 55 of the ink supply path as well as in the chamber 52.

Therefore, a method called pressure purging in which bubbles in the ink are discharged from the nozzles 51 is used.

However, in the case of such pressure purging, it takes a very long time to discharge the bubbles in the ink only from the nozzle 51, and the pressing force is limited. In particular, in the case of a so-called multi-nozzle type inkjet having a plurality of nozzles, it is difficult to remove bubbles only by discharging from the nozzle 51, and it is necessary to apply a higher pressure for a long time.

As a method of solving this problem, a method of installing a check valve composed of a ball 57 and a spring 58 as shown in FIG. 7 has been proposed.

By installing a check valve, the check valve is activated when a high pressure is applied and ink containing air bubbles is discharged from the ejection port 59, and a check is performed when a low pressure is applied. The valve does not operate and the air bubbles are discharged only from the nozzle 51.

Therefore, in the case of actually discharging the bubbles, first, a high pressure is applied in a state where the bubbles are collectively stored in the chamber 52 to open the check valve, and most of the bubbles are discharged from the discharge port 59, Bubbles remaining in the nozzle 51 are discharged from the nozzle 51 at a low pressure.

Various measures have been taken in order to reduce the amount of ink that goes out, that is, the amount of waste ink, by devising the amount of pressurization, the length of pressurization time, the number of pressurizations, and the like.

[0010]

However, even in the above-described conventional bubble purging mechanism, all the ink for bubble discharge is discharged outside the printer, and the ink discharged outside the printer is discarded. That is, there has been a problem that the ink originally used for printing is all discarded because air bubbles generated in the ink flow path are discharged.

The present invention is economical because the amount of ink discarded for discharging bubbles is minimized, and the cost of the product is reduced by minimizing the components of the bubble purging mechanism. The challenge is to provide.

[0012]

In the ink jet printer for ejecting ink from nozzles for printing, the print head section has a main tank for storing ink, and a sub tank for collecting and storing purge ink.
A sub-tank and a main tank are connected to each other, and a manifold for supplying ink to the nozzle is provided, and the main tank and the sub-tank are alternately pressurized by a pressurizing means to remove air bubbles in the manifold and the nozzle. Achieved by the discharging configuration.

According to the present invention, in addition to the above structure, the pressure applied to the main tank is high for a short time and the pressure applied to the sub tank is low for a long time to allow the ink to flow into the sub tank. The present invention is characterized by comprising a control means for setting a pressurizing condition such that the amount and the outflow amount of ink are substantially the same.

Further, in addition to the above construction, the present invention is characterized in that the manifold from the nozzle to the sub-tank is arranged so as to have an elevation angle halfway.

Furthermore, in the present invention, in addition to any of the above-mentioned constitutions, the tank pressurizing means is one pressurizing pump common to the main tank and the sub tank, and the valve means provided in the print head portion. It is characterized in that the pressurizing pump is connected to the main tank and the sub-tank by moving the position of the print head.

[0016]

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

FIG. 1 is a perspective view for explaining the mechanism of the printer.

As shown in FIG. 1, the printer 1 includes a print head 2 and the print head 2 having shafts 7a and 7b.
Belt 8 that slides along, motor 1 that drives the belt
0, encoder 6 for knowing the position of print head 2
Consists of

The print head 2 includes an upper lid 3, an ink supply port 5 attached to the upper lid 3, breathing holes 4a and 4b, a nozzle component 20, and air inlets 9a and 9b made of an elastic material such as rubber. Become.

Further, nozzle openings 13a, 13b for sending pressurized air for purging are fixed to the side wall 11,
Nozzle openings 13a, 13b and the air inlets 9a, 9
The b valve constitutes a pressurized air valve.

Reference numerals 12a and 12b are tubes, 15 is a pressurized air branch pipe, 14 is a tube, 30 is a pressure pump, and 31 is a control circuit.

The print head 2 transmits the driving force of the motor 10 to the belt 8 to cause the shafts 7a and 7b to move.
Can be slid on.

FIG. 2 is an exploded perspective view for explaining the print head 2 in more detail.

In FIG. 2, 20a to 20f are nozzles.
Manifold component plate, 19 is nozzle, 21 is PZ
T, 16 is a sub tank, 17 is a main tank, 23a,
Reference numeral 23b is an ink sensor.

Atmospheric pressure acts on the sub tank 16 and the main tank 17.

Further, the main tank 17 and the sub tank 1
Sensors 23a and 23b for detecting the remaining ink amount in 6
The sensor 23a, when the ink remaining amount decreases during printing,
23b senses at about the same time. When the ink is sensed, the ink is inserted by opening the ink supply port 5 provided on the upper lid 3.

FIG. 3 is a conceptual diagram of an ink circuit for explaining the ink circuit of FIG.

In FIG. 3, 18a, 18b, 18c,
18 d is a manifold that connects the main tank 17 and the sub tank 16.

Regarding the concept of the bubble purging operation of the present invention,
A description will be given in combination with FIG.

First, pressurized air is fed under pressure into the main tank 17. Although the pressure loss occurs due to the breathing hole 4b formed in the main tank 17, the size of the breathing hole 4b may be set so that the pressure loss is at most about 10%.
On the other hand, the sub tank 16 side is opened to the atmosphere through the breathing hole 4a (first purging operation).

As a result, the ink in the main tank 17 reaches the manifold 18b via the manifold 18a. Then, although some of the ink is discharged from the nozzle 19, most of the ink is discharged from the manifolds 18c to 18d.
It is collected in the sub tank 16 via. At this time, some of the bubbles existing at arbitrary positions remain in the manifold 18c, but most of the ink is discharged to the sub tank 16.
Regarding the liquid level of ink, the sub tank 16 is the main tank 1
7 is higher than 7, and part of the ink returns from the sub tank 16 to the main tank 17 due to the water head difference, but the amount of return is extremely smaller than the ink supply amount at the previous bubble pressure purging. Therefore, it is necessary to return the ink flowing into the sub tank 16 to the main tank 17.

That is, the side of the main tank 17 is the breathing hole 4b.
To the atmosphere, and the sub-tank 16 side is pressurized by the pump 3
0 is communicated with the sub-tank 16 to supply pressurized air to the inside of the sub-tank 16 to return the ink in the sub-tank 16 to the main tank 17 via the manifold 18 (second purging operation).

During this operation, the pressure loss occurs due to the breathing hole 4a formed in the sub-tank 16, but the size of the breathing hole 4a may be set so that the pressure loss is about 10%.

Thus, bubble purging can be performed by performing the first purging operation and the second purging operation.
At this time, as shown in FIG. 6A, the pressure P ₁ when pressurizing the main tank 17 (first purge operation) and the pressure P ₂ when pressurizing the sub tank 16 (second purge operation)
And the pressurizing time is set to t ₁ on the main tank 17 side and t ₂ on the sub tank 16 side so that the ink inflow amount and the ink outflow amount to the sub tank 16 are substantially the same.
(Of course t ₁ <t ₂ ) is set.

That is, since the first purging operation is intended to remove bubbles, the pressure is higher than the surface tension acting on the bubbles remaining in the print head 2 (the ink flow velocity that overcomes the surface tension of the bubbles). Is applied to the ink to move the bubbles to the sub tank 16. On the contrary, since the second purging operation is intended only for the movement of the ink, a pressure lower than the surface tension acting on the bubbles is applied to the ink, and only the ink is transferred from the sub tank 16 to the main tank 17 without backflowing the bubbles. Move to. By this series of operations,
Manifold 18 positively when pressurizing main tank 17
The bubbles inside can be moved, and only the ink can be moved when the sub tank 16 is pressurized. Moreover, only one of the ink tanks will not be filled with ink, and the bubbles can be discharged in a short time.

In order to more effectively discharge the air bubbles remaining in the nozzle 19, the third purging operation is performed as follows.
It is advisable to apply the same pressure to the main tank 17 and the sub tank 16 for purging.

That is, as shown in FIG. 6 (b), the main tank 17 and the sub-tank 1 have an internal pressure P ₃ and a purge time t _3.
By pressurizing 6 at the same time, the bubbles in the nozzle 19 can be effectively discharged. Of course, the pressure applied at this time must be higher than the surface tension acting on the bubble.

On the other hand, in the conceptual diagram of the ink circuit shown in FIG. 3, in order to enhance the bubble purging effect, the manifolds 18a, 18 communicating from the main tank 17 to the nozzle 19 are provided.
It suffices to reduce the cross-sectional area of b. As a result, the flow velocity of the ink in the manifold at the time of pressurizing the ink is increased and the bubbles are easily moved.

However, in practice, it is required to increase the cross-sectional area of the manifolds 18a and 18b in order to make the ink supply during printing smooth.

Therefore, in the present invention, since the bubbles are moved by the first purging operation in which the pressure is increased from the main tank 17 side toward the sub tank 16 side, the manifold 18 communicating with the sub tank 16 from the nozzle 19 is previously prepared.
The c is arranged so as to have an elevation angle θ so that bubbles can easily move to the sub tank 16. With this configuration, the bubbles tend to move to the right end portion of the manifold 18c even when the purging operation is not performed.

Further, during the first purging operation, the ink and the air bubbles can be expelled at a stretch to the sub tank 16 side.

Further, during the second purging operation, air bubbles must move down the manifold 18 and because the purging pressure is low, the air bubbles stay at the upper portion of the manifold 18c and are discharged during the first purging operation to be performed next. Will be done.

The first purge operation and the second purge operation of the present invention
The structure that enables the purging operation is also useful when ink is supplied.

Usually, it takes several minutes, and in some cases, tens of minutes, from when the ink is supplied to the ink supply port 5 until the liquid level in the main tank 17 and the liquid level in the sub tank 16 are balanced. Especially in the case of hot-melt ink, it takes time from the insertion of solid ink to the dissolution,
It takes a very long time from the ink supply to the printing operation.

On the other hand, in this configuration, approximately half the amount of the replenished ink is positively moved to the sub-tank 16 side using the pressurizing operation (first purging operation) of only the main tank 17. The additional effect of being able to be set can be obtained.

Next, a specific structure for performing the first to third purge operations will be described.

In order to perform the purging operation, the print head 2 is moved leftward (on the side wall 11 side) in FIG. 1 so that the nozzle openings 13a and 13b face the positions inserted into the insertion openings 9a and 9b, respectively. If the valve open / close state is selected and the pressurizing pump 30 is driven, bubble purging is possible.

FIG. 4 is a cross-sectional view showing the opened / closed state of the valve structure of the print head 2.

The valve has a two-valve structure, one valve communicating with the sub-tank 16 and the other valve communicating with the main tank 17. 31a, 31b are air holes, 33a, 33
b is a pin, 34a and 34b are balls, 35a and 35b are springs, and 36 is a stopper. The pin 33a is slightly shorter than the pin 33b.

FIG. 4A shows the first purge operation. The valve on the sub-tank 16 side is "closed" because the ball 34a closes the air passage, and the valve on the main tank 17 side is "valve: closed" with the pin 33b pushing the ball 34b to the left. It is "open".

FIG. 4B shows the third purge operation. When the print head 2 is moved to the left from the state of FIG. 4 (a) to the state of FIG. 4 (b), the pin 33a pushes the ball 34a in the valve on the sub-tank 16 side, so "valve: open". Becomes At this time, the valve on the main tank side is also open.

FIG. 4C shows the second purge operation. When the print head 2 is further moved to the left from the state of FIG. 4B to the state of FIG. 4C, the main tank 1
In the valve of No. 7, the tip of the nozzle port 13b comes into contact with the plug 36 to close the air passage, so that the valve is closed. On the other hand, the sub-tank 16 side is "valve: open".

Therefore, the purging procedure shown in FIG.
That is, the removal of air bubbles in the manifold 18 is performed by the first purge operation shown in FIG. 4A and the second purge operation shown in FIG.
This is achieved by alternately carrying out (c). In addition, FIG.
(B) of the purging procedure, that is, the removal of bubbles in the nozzle 19 is achieved by setting the state of FIG. 4B which is the third purging operation.

FIG. 5 shows a summary of these operations.
It is a flowchart of FIG.

When a command for the purging operation is issued from the control means 31, the print head 2 is moved to the first purging operation position (see FIG. 4).
After moving to (a)), the first purge operation is performed at the purge pressure P ₁ and the purge time t ₁ set by the control means 31.

Next, the print head 2 moves to the second purge operation position (FIG. 4 (c)) and performs the second purge operation at the purge pressure P ₂ and the purge time t ₂ set by the control means 31. .

Then, this series of operations is repeated a predetermined number of times, preferably 3 to 5 times.

Further, the print head 2 is moved to the third purge operation position (FIG. 4B), and the third purge operation is performed at the purge pressure P ₃ and the purge time t ₃ set by the control means 31.

This series of operations is repeated a predetermined number of times, preferably 3 times.
Repeat 5 times to complete the purging operation.

As described above, by using one pressurizing pump, the valve provided in the print head portion, and the position movement of the print head, a complicated bubble purging operation can be achieved at a low cost with very few components. Then, only by moving the position of the print head 2, pressurization of only the main tank 17, pressurization of only the sub-tank 16, and simultaneous pressurization of the main tank 17 and the sub-tank 16 can be selected.

[0061]

According to the present invention, by alternately pressurizing the main tank and the sub-tank to discharge the air bubbles in the manifold and the nozzle, the ink discharged to the outside of the printer for air bubble discharge as in the conventional case. It is possible to discharge the air bubbles in the manifold and the nozzle by reducing the amount of ink to be discarded as much as possible without discarding all.

Further, by simultaneously pressurizing the main tank and the sub tank to discharge the bubbles from the nozzle, the bubbles in the nozzle can be effectively discharged.

Further, when the main tank and the sub tank are alternately pressurized, the pressure applied on the main tank side is high pressure for a short time.
When the main tank 17 is pressurized, the pressurizing pressure on the sub-tank side is set to a low pressure for a long time and the pressurizing condition is set so that the ink inflow amount and the ink outflow amount to the sub-tank side are substantially the same. Bubbles in the manifold 18 can be positively moved, and on the other hand, when the sub-tank 16 is pressurized, the flow velocity in the manifold 18 does not become too high, so that only ink can be moved, and only one ink tank can be moved. Since the main tank 17 and the sub tank 16 can be repeatedly and alternately pressurized because the ink does not fill up, bubbles can be discharged in a short time.

Further, the tank pressurizing means is constituted by one pressurizing pump common to the main tank and the sub tank, and valve means provided in the print head section, and the pressurizing pump, the main tank and the sub tank are provided. Since the connection with is made by moving the position of the print head, it is possible to reduce the component cost of the bubble purging mechanism as much as possible and reduce the product cost.

[Brief description of drawings]

FIG. 1 is a perspective view of an inkjet printer that is an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the print head shown by reference numeral 2 in FIG.

FIG. 3 is a conceptual diagram of an ink flow path of the print head 2.

FIG. 4 is a cross-sectional view for explaining opening and closing of a valve of the print head 2.

FIG. 5 is a flowchart for explaining a bubble purging operation of the print head 2.

FIG. 6 is an explanatory diagram showing a relationship between a bubble purge pressure of the print head 2 and time.

FIG. 7 is a cross-sectional view of a printhead of a conventional inkjet printer.

[Explanation of symbols]

2 ... Print head, 9 ... Air insertion port, 13 ... Nozzle port, 20 ... Nozzle components that form manifold
0 ... Pressurizing pump, 33 ... Pin, 34 ... Ball, 35 ... Spring, 36 ... Plug.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazunobu Hayashi 1060 Takeda, Hitachinaka City, Ibaraki Prefecture Hitachi Koki Engineering Co., Ltd.

Claims (7)

[Claims] 1. An ink jet printer for ejecting ink from nozzles for printing, wherein a print head section connects a main tank for storing ink, a sub tank for collecting and storing purge ink, and a sub tank and a main tank, An ink jet printer characterized in that a manifold for supplying ink to a nozzle is provided, and the main tank and the sub tank are alternately pressurized by a pressurizing means to discharge air bubbles in the manifold and the nozzle. . 2. An ink jet printer that ejects ink from nozzles to print, wherein a print head unit connects a main tank for storing ink, a sub tank for collecting and storing purge ink, and a sub tank and a main tank, A manifold for supplying ink to the nozzle is provided, the main tank and the sub tank are simultaneously pressurized by a pressurizing means to discharge air bubbles from the nozzle, and the main tank and the sub tank are alternately pressurized. An ink jet printer characterized in that bubbles are discharged from the manifold and the nozzle. 3. The alternating pressure of the main tank and the sub tank according to claim 1 or 2, wherein the pressure applied on the main tank side is high pressure for a short time, and the pressure applied on the sub tank side is low pressure for a long time. An ink jet printer characterized by comprising control means for setting a pressurizing condition such that the ink inflow amount and the ink outflow amount to the sub tank side are substantially the same. 4. The method according to claim 1, wherein
An ink jet printer characterized in that a manifold extending from a nozzle to a sub tank is arranged so as to have an elevation angle halfway. 5. The method according to any one of claims 1 to 4,
The tank pressurizing means is composed of one pressurizing pump common to the main tank and the sub tank, and a valve means provided in the print head section. The pressurizing pump is connected to the main tank and the sub tank by a print. An ink jet printer characterized in that it is configured to perform by moving the position of a head. 6. A nozzle in a print head portion, which is provided with a main tank for storing ink, a sub tank for collecting and storing purge ink, and a manifold for connecting the sub tank and the main tank and supplying ink to the nozzle. A method for purging bubbles from an ink jet printer that ejects ink from a main unit to apply a pressure greater than the surface tension of bubbles remaining in the manifold to the main tank side to move the ink and bubbles from the main tank to the sub tank. The purge operation of No. 1 and the second purge operation of moving only the ink from the sub tank to the main tank by alternately applying a pressure force smaller than the surface tension of the bubbles to the sub tank side. Method. 7. The purging method according to claim 6, further comprising: applying a pressing force larger than the surface tension of the bubbles remaining in the manifold to the main tank and the sub-tank to discharge the ink and the bubbles from the nozzles. A method for purging an inkjet printer, which is characterized by being carried out.