JPH03166949A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To obtain a stabilized reliable printing quality by detecting accurately, in a good responsive manner, temperature of ink in a head by a method wherein a thermistor burying hole is provided to a sub head, and a thermistor element part is held by joining with resin for heat transfer. CONSTITUTION:A thermistor burying hole 7 is provided to a head substrate 5 in forming a mould or by fabrication of boring or the like, and a thermistor 8 is inserted into its inside. Resin for heat transfer 9 of highly viscous silicone resin or high molecular adhesive or the like which is cured with time and is high in thermal conductivity in curing is poured into space between an inner peripheral wall of the thermistor burying hole 7 and the thermistor 8, and is solidified and bonded with time or by a forced means of heating, irradiation of ultraviolet rays, etc. That is, when the resin for heat transfer 9 is cured, the element part of the thermistor 8 is, in an enclosed form with the resin for heat transfer 9, buried inside the thermistor burying hole 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an on-demand inkjet recording device. [Prior Art] Conventionally, the physical properties of ink ejected by an inkjet recording head, such as viscosity, are strongly temperature dependent, and it has always been difficult to maintain the same ink ejection performance over the entire operating temperature range of the inkjet recording head. In order to do this, it was necessary to detect the ink temperature. Therefore, a temperature sensor such as a thermistor has been installed inside the inkjet recording head without being enclosed in a heat transfer layer.

[Problem to be solved by the invention]

However, even when temperature is detected using the above method, there is a large temperature difference between the actual ink temperature and the detected temperature, and the problem is that the detected temperature cannot follow sudden changes in ink temperature. It had Therefore, by solving these conventional problems, the present invention detects the ink temperature inside the head accurately and with good responsiveness, and achieves the same ink ejection performance over the entire operating temperature range of the head. The aim is to ensure stable and reliable printing quality.

[Means to solve the problem]

The inkjet recording head of the present invention is an inkjet recording head comprising a plurality of nozzles lined up at the same pitch and a subhead having a flow path communicating with the nozzles, in which the subhead is provided with a hole for embedding a thermistor, and the thermistor element is inserted into the inkjet recording head. The feature is that the parts are held tightly together by heat transfer resin. [Examples] The present invention will be described below based on Examples. First, FIG. 2 shows a first embodiment of an inkjet recording head according to the present invention. Nozzle 1, pressure chamber 2, filter part 3, ink supply! l
! The sub-head is constructed by a head substrate 5 on which the flow path of the preparation chamber 4 is formed, and a diaphragm 6 bonded to both sides of the head substrate 5. Pressure is applied to the pressure chamber 2 by a piezoelectric element or a heating element. The mechanism is such that the ink droplets are ejected from the nozzle 1 by causing a change. The head substrate 5 and the diaphragm 6 are made of the same material, such as polymer resin, metal material such as stainless steel, ceramic, etc. Further, as shown in FIG. 1, the ink jet/recording head is constructed by arranging the two sub-heads in parallel and positionally fixing them by a member 13 and other parts (not shown in the figure). ．． Incidentally, an inkjet recording head (not shown) formed with one or three or more of the above-mentioned subheads also falls under the scope of the present invention. Here, a thermistor embedding hole 7 is provided in the head substrate 5 during molding or secondary processing such as drilling, and the thermistor 8 is pushed into the inside of the thermistor embedding hole 7. In the space between the peripheral wall and the thermistor 8, a heat transfer resin 9 such as a highly thermally conductive high viscosity silicone resin or a polymer adhesive is injected into the space between the peripheral wall and the thermistor 8, which hardens over time. Alternatively, it is solidified and attached individually by forced means such as heating or ultraviolet irradiation. That is, for the hardening of the heat transfer resin 9, the element part of the thermistor 8 is covered with the heat transfer resin 9 inside the thermistor embedding hole 7 provided in the head substrate 5, as shown in FIGS. It is buried in the form. Next, the setting position of the thermistor installation hole 7 and the direction in which the thermistor 8 is inserted will be explained. Figure 2 (a) (b)
), the thermistor embedding hole 7 is provided outside the flow path area of the head substrate 5 in a direction perpendicular to the flow path forming surface, and the thermistor 8 is similarly perpendicular to the flow path forming surface. It is buried in The structure is such that when manufacturing the head substrate 5 by molding,
The flow path surface of the head substrate 5 and the mold cutting direction of the thermistor embedding hole are the same, which greatly simplifies mold design and mold structure. 3 to 5, a thermistor embedding hole 7 is provided perpendicularly to the end surface of the head substrate 5, and the thermistor 8 is similarly embedded in the direction of the hole. The above structure is very effective for embedding the entire thermistor 8 element portion in the head substrate 5 when the length of the thermistor B element is greater than the thickness of the head substrate 5. Third
．． As shown in Figure 4, the direction of insertion of the thermistor 8 and the end face of the head substrate 5 where the thermistor embedding hole 7 is provided are different, and can be arbitrarily selected depending on the exterior parts of the sub-head and its 42+1 configuration. Further, in the embodiments shown in No. 5rXJ (a) and (b), the thermistor 8 cord part is inserted deep into the head substrate 5 and into the flow 8 region on the flow path forming surface. That is, the eight thermistor elements are fixed inside the head substrate 5 in a state where they are sandwiched between the ink flowing in the flow path. In this structure, when there is a difference in the temperature of the ink flowing through the channels on both sides of the head substrate 5, the thermistor 8 element is located at the center between the channels on both sides, so that the ink temperature in the channels on both sides is averaged. In addition to being able to detect the temperature of the ink, the eight thermistor elements are adjacent to the ink, making it possible to detect the ink temperature with great accuracy and high response. As described above, in the structure of the embodiment shown in FIGS. 2 to 5, the temperature of the ink flowing in the flow path in the subhead is extremely high because the surface area of the flow path is very large, and is almost equal to the temperature of the subhead. That is, the ink temperature is controlled by the temperature of the subhead (head substrate 5). In the present invention, since the thermistor 8 is covered and mounted in the thermistor embedding hole 7 of the head substrate 5 with a heat transfer resin 9 having good thermal conductivity, the temperature of the sub-head, that is, the temperature of the ink, is thermally conductive. It can be detected accurately and quickly using the thermistor 8 with very little loss. Figure 6 shows the temperature-hour characteristics. Curve ■ is the detected temperature characteristic obtained by the present invention, and curve II is that of the prior art. As can be seen from FIG. 6, the detected temperature characteristics obtained by the present invention very quickly follow even sudden changes in the ink temperature within the head. Furthermore, at equilibrium, it is possible to keep the difference between the ink temperature in the head and the ink temperature very small. Also, as in the embodiment shown in FIG. 7, a thermistor embedding hole 7 is arranged in the head substrate 5 near the nozzle 1,
If a temperature difference occurs within the subhead, the ink temperature near the nozzle 1 can be detected, which is very effective. FIG. 8 shows an example of wiring of the thermistor 8,
The wiring of the thermistor 8 can be done by providing a branch on the wiring for the thermistor 8 in the pattern cable 10 such as FPC that connects the piezoelectric element or heating element of the sub-head and the circuit board, and wiring it with the lead wire part of the thermistor 8 by soldering or the like. The number of parts and man-hours above can be reduced. FIGS. 9(a), 9(b), and 9(c) show examples of the attached state of the thermistor 8 according to the present invention. FIG. 9(a) shows the state when the heat transfer resin 9 that hardens over time shown in the first embodiment is used. In FIG. 9(b), a thermistor fixing member 11 made of an insulating material such as a polymer resin is attached to the lead wire portion of the thermistor 8 under pressure, and the thermistor embedding hole 7 is inserted into the thermistor fixing member as shown in the figure. It is press-fitted into the head substrate 5 with the plug attached at 11. A heat transfer resin 9 that cures over time is injected into the space surrounded by the inner circumferential surface of the thermistor embedding hole 7, the outer circumferential surface of the thermistor 8, and the thermistor fixing member 11 without any gaps. In this structure, the lead wire part of the thermistor 8 is fixed by the thermistor fixing part 11, and is also fixed positionally and mechanically to the inner circumferential surface of the thermistor embedding hole 7. This is very effective for the head substrate 5 consisting of , since it can ensure a dark edge with the thermistor 8. In addition, since the thermistor 8 is fixed positionally and mechanically when it is pushed into the thermistor embedding hole 7, the next assembly process can be carried out without securing time for the heat transfer resin 9 to harden, leading to a reduction in assembly man-hours. In FIG. 9(c), instead of the heat transfer resin 9 that hardens over time used in FIG. 9(a), an elastic heat transfer resin 13 made of a tangible silicone resin or rubber is initially used. Eight thermistor elements are enclosed and fixed in the thermistor embedding hole 7. The outer circumferential surface of the elastic heat transfer resin 12 is press-fitted into the inner circumference of the thermistor embedding hole 7, and the inner circumferential surface of the elastic heat transfer resin 12 is press-fitted into the outer circumference of the thermistor 8. In this structure as well, as in the embodiment shown in FIG. 6(b), it is possible to ensure insulation between the thermistor 8 and the head substrate 5 and to reduce the number of assembly steps.

〔Effect of the invention〕

As explained above, the inkjet recording head of the present invention detects the ink temperature within the head accurately and with good responsiveness by providing a hole for embedding the thermistor in the subhead and holding the thermistor element part tightly with heat transfer resin. death,
It always ensures the same ink ejection characteristics over the entire operating temperature range of the head, making it possible to obtain stable and reliable print quality.

[Brief explanation of the drawing]

Figure 1 is an exploded structural diagram of the inkjet recording head of the present invention. Figure 2(a). (b) is a side sectional view and a front view of one embodiment of the inkjet recording head of the present invention. FIGS. 3(a) and 3(b) are a rear view and a side sectional view of another embodiment of the inkjet recording head of the present invention. Figure 4 (
a) and (b) are a rear view and a side sectional view of another embodiment of the inkjet recording head of the present invention. Figure 5(a).
(b) is a rear view and a side view of another embodiment of the inkjet recording head of the present invention. Figure 6 is a one-hour characteristic diagram of detected temperature. Figure 7(a). (b) is a side sectional view and a front view of another embodiment of the inkjet recording head of the present invention. Figure 8 (
a) and (b) include the wiring to the head of another example of the inkjet recording head of the present invention (Il side view and front view. Enlarged view of the thermistor installation state of the inkjet recording head according to the present invention. 1... Nozzle 2... Pressure chamber 3... Part of filter 4... Ink supply preparation chamber 5... Head substrate 6... Vibration plate 7...Thermistor embedding hole 8...Thermistor 9...Heat transfer resin 10...Pattern cable 11...Thermistor fixing member 12...Elastic heat transfer resin 13...Sub head Fixed member

Claims (1)

[Claims] In an inkjet recording head composed of a plurality of nozzles lined up at the same pitch and a subhead having a flow path communicating with the nozzles, the subhead is provided with a hole for embedding a thermistor, and the thermistor element is held in close contact with a heat transfer resin. An inkjet recording head characterized by: