JPH0340713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink-on-demand type inkjet (recording) head.

A method that uses the deflection of a piezo element to pressurize ink in a pressure chamber and eject ink droplets from a nozzle.
A so-called ink-on-demand type inkjet recording device has recently attracted particular attention as a non-impact recording device that has a simple mechanism, uses low power, and can print on plain paper.

However, one of the important issues when mass-producing the head of such a recording device is the connection between the piezo element and the lead terminal. In the case of a multi-head with a large number of nozzles in the head, a large number of connections are required, which poses problems in terms of mass production.

1 and 2 show an example of an on-demand multihead. FIG. 1 shows a substrate 1 constituting the head, and FIG. 2 is an assembled view of the head. The pattern inside the substrate 1 shows the shape of grooves that serve as flow paths for ejecting ink. You can see 12 sets of similar grooves, but the names and functions of each part are the same, so to explain one set of grooves in the center, 2 is the groove that will become the pressure chamber, 3 is the groove that will become the pressure chamber.
is a nozzle, 4 is a flow path between pressure chamber 2 and nozzle 3, and 5 is a nozzle.
6 is a supply channel for supplying ink to the pressure chamber, and 6 is a groove that serves as a filter to prevent foreign matter from entering. It is configured. The grooves on both sides are formed so that they are shifted by exactly 1/2 pitch at the nozzle part. This substrate 1 is assembled as an inkjet head as shown in FIG. That is, a member 7 having the same thickness as the substrate and a portion to become the reservoir 8 are placed at a slight distance from each other, and flexible plates 9 and 10 are bonded to both surfaces of the member 7. In this way, the reservoir 8 has openings at both ends, and a series of flow paths from there to the nozzle 3 via the reservoir 8, the filter section 6, the supply path 5, the pressure chamber 2, and the flow path 4 are formed on one side.
It is possible to configure 24 sets on both sides. A total of 24 piezo elements 11 and 12 are connected to the surfaces of the flexible plates 9 and 10 at portions corresponding to the respective pressure chambers on both sides. The basic part of the head is now completed, and in this state, inject ink from the opening in reservoir 8.
Fill the set of flow channels completely with ink, and then remove piezo element 1.
When a voltage pulse is applied to the piezo elements 11 and 12, the piezo elements 11 and 12 close the pressure chamber 2 due to the action of the flexible plates 9 and 10.
bends inward, pressurizes the pressure chamber 2 with ink, and ink droplets are ejected from the nozzle 3. Therefore, dot matrix characters and figures can be recorded by applying voltage pulses to appropriate piezo elements 11 and 12 in accordance with a print command. Since the head has two nozzles, it can print characters in a 24 x 24 dot matrix, and can be used in printers that can record high print quality almost equivalent to type.

However, in order to actually operate such an inkjet head, it is necessary to apply voltage pulses to the front and back electrodes of the piezo elements 11 and 12. Conventionally, as shown in FIG. For example, the surface electrode of the piezo element 11 is connected to the wiring pattern 15 on the head by wire bonding 16 as shown in FIG. 4. For solder connections,
Since the piezo element 11 pinches and vibrates each time ink is ejected, so-called interference between the piezo elements or the pressure chambers does not occur, but the soldering area or the amount of solder directly affects the vibration characteristics of each piezo element. , ink jetting characteristics (jet ink amount,
This results in large variations in printing speed), which causes a major problem in printing quality. Further, in the case of the heads shown in FIGS. 1 and 2, there are many connection points, which requires a large number of man-hours, and there are also concerns about connection strength and long-term durability.
In addition, in the case of a movable head printer, lead wire 1
The other terminal 17 of 3 is connected once to the FPC and then from the FPC to the circuit board, and the fact that there are many connection stages also impairs stability and reliability. Wire bonding (Fig. 4) is also superior in that the area of the piezo 11 connection is very small and stable compared to soldering, but the electrode pattern 15 must be formed on the head. ,
In the head example shown in Figures 1 and 2, wire bonding must be done at multiple locations on both sides, which reduces workability.
It takes a lot of man-hours, and mass production is difficult. In addition, the terminal 19 is connected from the electrode pattern 15 on the head to the FPC via the connector 18, and from the FPC to the circuit board, which again requires a large number of connection stages, which poses a problem in stability and reliability.

Furthermore, it is necessary to prevent ink from entering the piezo element and its wiring section. This is because ink can cause peeling of the adhesive on the piezo element and shorting of the front and back electrodes of the piezo element, so the piezo element part of the head must be sealed with a gasket or holder, but as described above. There was no proposal for a rational method for wiring and sealing.

In addition, as a prior art related to the present invention, Japanese Patent Application Laid-Open No. 1983-1999 regarding inkjet printers
150636, JP-A-52-88026, JP-A-51-147214,
Unexamined Japanese Patent Publications 1977-6308, 118334-1973, 118334-
142120, Unexamined Japanese Patent Publication No. 117334, or Unexamined Japanese Patent Publication No. 1987-
No. 7638, Japanese Patent Publication No. 53-46455, etc., but none of them suggests the above-mentioned problem of the present invention or its solution.

The present invention solves the above-mentioned problems, simplifies the connection structure for supplying print command signals to the piezo element, prevents malfunction of the piezo element due to electrical shoots caused by ink intrusion, and furthermore prevents ink from being ejected from multiple nozzles. An object of the present invention is to provide an on-demand type ink jet head that has uniform ink ejection characteristics.

The on-demand ink jet head of the present invention will be explained below with reference to the drawings. FIG. 5 is a side view of a connection method showing an embodiment of the present invention,
20 is an ink jet head similar to that shown in FIGS. 1 and 2, 21 is a piezo element, and 22 is an ink supply port at both ends of the reservoir. 23 and 24 are FPCs (flexible printed circuit boards), 25 and 26 are flat rubber sheets (rubber elastic bodies) as shown, and 27 and 28 are head covers. As shown in the figure, the head 20 has an FPC 23,
24 and the head covers 27 and 28 from the back side of the FPCs 23 and 24 through the rubber sheets 25 and 26.
Press the FPCs 23 and 24 against the head 20. This completes the connection of the lead terminals of the head 20.
Here, the piezo element 21 is arranged on the surface of the head 20 like the arrangement of the pressure chambers in FIG.
Copper foil wiring is arranged on the head contact surfaces of the FPCs 23 and 24 so as to correspond to the arrangement of the piezo elements 21 within the head 20 surface. Therefore, the piezo element 21
The connection between the FPCs 23 and 24 is made using rubber sheets 25,
26, and the head cover 2
It is a removable connection that can be removed by removing 7 and 28. This point is different from the permanent connection such as the conventional example shown in FIGS. 3 and 4. Therefore, unlike connecting to the 24 piezo elements 21 individually, simply
The head 20 and FPCs 23 and 24 can be connected at once by simply stacking and pressing the FPCs.
By adjusting the position of the head covers 27, 28, etc., connection can be easily achieved under the same conditions without the need for hot kneading.

FIG. 6 is a completed external view after wiring has been completed.
As shown in the figure, attach the head 20 to the head covers 27 and 2.
FPC23 and 24 are coming out from the rear part covered by 8,
The ends 29 and 30 of this FPC are connected to the circuit board. Note that 22 is an ink supply pipe, and 31 is a positioning projection for fixing the head to the printer's carriage. As shown in the figure, the present embodiment has a clean and organized appearance, and the head is not used bare in the conventional examples shown in Figs. 3 and 4, and the piezo element is The connection part should be covered, and in this respect, this embodiment is a reasonable method since it not only covers the connection part, but also the head cover plays a role in the connection. In addition, the connection between the head and the circuit board is only through the FPC, and in this respect as well, it can be summarized in the simplest form. Furthermore, the head covers 27, 2
If 8 is configured to be detachable using screws or a lock mechanism, even an amateur can attach and detach the head 20 and the head 20 separately.
This is advantageous for head maintenance. However, since the inkjet head is a recording head that does not suffer from mechanical fatigue or wear, there is almost no risk of it breaking, so the head covers 27 and 28 can also be made of plastic and permanently fixed together using heat or ultrasonic waves.

Next, we will discuss how to seal the head. Fifth
In the figure, the flat area of rubber sheets 25 and 26 is FPC23,
The flat area of the head portion of FPC 24 is slightly larger than that of the rubber sheet 25,
By allowing the portion 26 to protrude a little, a tight seal can be created and ink can be prevented from entering the piezo element 21 portion. However, in order to achieve more reliable sealing, we propose the methods shown in FIGS. 7 and 8. 31 in Figure 7
is a rubber elastic member having a convex portion 35 on the periphery and a slit 33 for inserting the FPC 32;
The FPC 32 is inserted through this slit 33 as shown by an arrow 34. Then, as shown in FIG. 8, the head 20, the rubber elastic member to which the FPC 32 is mounted, and the head holder 36 are laminated from both sides (only one side is shown in the figure) and assembled. By doing this, the convex portion 35 of the rubber elastic member 31 acts as a seal, so that the piezo element 21 and FPC 3 are more securely attached.
It will be appreciated that it is also possible to prevent ink from entering the connection with 2.

Next, we will discuss measures to ensure more reliable contact between the FPC and the piezo element. Figure 9 shows FPC
32 is shown in plan view a and side view b, as shown in the figure, wiring 37 for applying a print signal to the piezo element is provided, and insulation 38 is applied except for the tip portion 39 facing the piezo element. ing. Further, solder 40 is applied to the piezo element facing portion 39. By doing this, as shown in FIG. 8, a rubber member having protrusions around the periphery may be used, or the piezo element facing portion 39 may sink due to the insulating film 38 of the FPC 32, making contact uncertain. can be avoided.

The present invention has been described in detail based on the embodiments above, but the present invention is applicable not only to the ink jet head shown in FIGS. Needless to say, this method is applicable to most of the equipment.

According to the on-demand inkjet head of the present invention described above, a flat rubber elastic member that covers a flexible substrate and has a convex portion protruding toward the flexible plate around the flexible substrate, and a rubber elastic member are provided. By having a head cover that presses the covering rubber elastic member to the flexible plate, the rubber elastic member presses the flexible substrate with uniform pressure,
In addition to making it possible to equalize the jetting characteristics of ink from multiple nozzles, the convex part of the rubber elastic member and the flexible plate form a seal structure, making it possible to reduce the impact on the connection between the flexible plate and the piezo element. There is no ink intrusion, and reliability is improved, especially when using conductive ink. It also ensures electrical conduction between the flexible substrate and the piezo element, increasing the reliability of the inkjet head.

[Brief explanation of the drawing]

1 and 2 are configuration diagrams of an ink jet head, FIGS. 3 and 4 are diagrams showing a conventional lead terminal wiring method, and FIG. 5 is a diagram showing an embodiment of the lead terminal wiring method of the present invention. Figure 6 is the completed external view,
7 and 8 are diagrams showing an embodiment of the head sealing method of the present invention, and FIGS. 9a and 9b are diagrams showing an improved example of the FPC of the present invention. DESCRIPTION OF SYMBOLS 1... Head substrate, 2... Pressure chamber, 3... Nozzle, 9, 10... Flexible plate, 11, 12... Piezo element, 20... Ink jet head, 21...
Piezo element, 23, 24...FPC, 25, 26
...Rubber sheet, 27, 28...Head cover,
31...Rubber elastic member, 32...FPC, 33...
...Slit, 35...Protrusion.

Claims (1)

[Scope of Claims] 1. A plurality of nozzles that eject ink droplets between grooves formed on the surface of the substrate and a flexible plate laminated thereon; an ink flow path that communicates with each of the nozzles; In an on-demand inkjet head, comprising pressure chambers each communicating with a flow path, and having piezo elements mounted on the flexible plate to pressurize the respective pressure chambers via the flexible plate, a flexible substrate that is laminated on the substrate and transmits a printing command signal to the piezo element; and a convex portion that covers the flexible substrate and protrudes toward the flexible plate around the flexible substrate, and that the flexible substrate is inserted into the convex portion. A flat rubber elastic member provided with a slit, and a head cover that covers the rubber elastic member and presses the rubber elastic member to the flexible plate via the piezo element and the flexible substrate. Demand type ink jet head.