JP2019203852A - Piezoelectric vibration sensor - Google Patents

Abstract

To provide a piezoelectric vibration sensor with which it is possible to improve sensing sensitivity by devising the junction structure of a substrate with a vibration ring.SOLUTION: A vibration ring 40 is fastened to a substrate 20 by soldering at two limited spots rather than on the entire circumference of the vibration ring 40. With a method by which the entire circumference of the vibration ring 40 is soldered, the movement of the vibration ring 40 is obstructed because of being excessively fastened, but by being provided with a fastened area where the substrate 20 and the vibration ring 40 are firmly fastened and a non-fastened area where they are not fastened, the substrate 20 is significantly bent by vibration propagated to the vibration ring 40, and because of this vibration being further propagated to a piezoelectric element 30, high sensing sensitivity is obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric vibration sensor using a piezoelectric element, for example, to an improvement of a vibration waveform sensor suitable for detecting various vibration waveforms such as a pulse.

  Among sensor devices related to health management by continuous measurement of pulse, a vibration waveform sensor using a piezoelectric element has been devised. An example in which this is wound around a fingertip and used, and the vibration from the arterial blood vessel wall of the fingertip is regarded as a pulse wave and applied to medical practice is disclosed in Patent Document 1 below.

  FIG. 5 shows a basic configuration thereof. FIG. 5A shows a cross section of the piezoelectric vibration sensor 10, FIG. 5B shows an exploded state, and FIG. Shown from the side. In these drawings, the piezoelectric vibration sensor 10 has a structure in which a piezoelectric element 30 is disposed on the main surface of a substrate 20 and this piezoelectric element 30 is covered with a vibration ring 40 that acts as a vibration introducing body. .

  Of the above-described portions, the substrate 20 is for fixing and supporting the piezoelectric element 30, and for extracting the electrodes and amplifying the signals. On the main surface of the substrate 20, a pair of electrode lands 22 and 23 are provided near the center, and a ground conductor 24 is formed around the pair of electrode lands 22 and 23. The electrode lands 22 and 23 are drawn out by through holes 22A and 23A on the back side of the substrate 20. A terminal (not shown) of the piezoelectric element 30 is joined to the electrode lands 22 and 23 with a conductive adhesive or the like. As described above, the piezoelectric element 30 and the amplifier provided on the back surface side of the substrate 20 are connected by the electrode lands 22 and 23 and the through holes 22A and 23A. An insulating resin may be provided so as to cover the electrode lands 22 and 23, and the piezoelectric element 30 may also be covered with the resin.

  Next, the piezoelectric element 30 is provided with a vibration ring 40 so as to surround the piezoelectric element 30, and the vibration ring 40 is electrically joined to the ground conductor 24. The ground conductor 24 is led out to the back side of the substrate 20 through through holes 24A and 24B (only the same drawing (A) is shown). The vibration ring 40 is made of, for example, stainless steel and has conductivity. The vibration ring 40 shares a ground potential with the skin of the human body in contact with the vibration ring 40, introduces microvibration of a living body, for example, the skin, and further has a substrate. It functions as a vibration introducing body that transmits to 20.

  In the piezoelectric vibration sensor 10 as described above, for example, as shown in FIG. 4D, the vibration ring 40 is brought into contact with the skin BD of the human body by a medical fixing tape 12 or the like at an appropriate position such as a human finger. It is attached to. On the other hand, the pulse wave HP, which is a volume change caused by the inflow of blood accompanying the pulsation of the heart, is transmitted to the vibration ring 40 of the piezoelectric vibration sensor 10 as a minute vibration of the skin BD, as shown in FIG. The vibration of the vibrating ring 40 further vibrates the substrate 20 that also functions as a vibrating body or a strain generating body, and the minute vibration transmitted from the vibrating ring 40 is transmitted to the piezoelectric element 30. Thereby, for example, minute vibration of the skin BD is detected as a voltage signal.

International Publication WO 2016/167202

  As described above, in the piezoelectric vibration sensor 10 of the background art, it is necessary to arrange the vibration ring 40 in order to increase the vibration sensing sensitivity. However, the vibration ring 40 may greatly affect the sensor sensitivity depending on the mounting state. Are known. In particular, since minute vibrations from a living body are transmitted as a signal voltage from the vibration ring 40 through the substrate 20 through the piezoelectric element, the bonding structure of the substrate 20 and the vibration ring 40 is sensed as a vibration sensor. Significantly affects sensitivity.

  This invention pays attention to this point, and it is an object of the present invention to provide a piezoelectric vibration sensor capable of improving sensing sensitivity by devising a joint structure between a substrate and a vibration ring.

The present invention includes a circuit board for transmitting vibration, a piezoelectric element provided on the circuit board, and an opening. The circuit board is soldered around the piezoelectric element of the circuit board and comes into contact with an object to vibrate the vibration. A vibration-introducing body that transmits the circuit board to the circuit board, the circuit board and the vibration-introducing body are bonded to each other, and a bonding area that is fixed by solder and a bonding portion that includes a non-fixed area that is not fixed. It is characterized by that.

  According to one of the main forms, a plurality of the fixing regions are provided, and the plurality of fixing regions are arranged at positions symmetrical with respect to the center of the vibration introducing body or a center line passing through the center. It is characterized by being. According to another aspect, the entire range of the fixed region is 120 to 180 degrees as viewed from the center of the vibration introducing body. According to still another embodiment, a center direction passing through the piezoelectric element and its electrode is the non-fixed region. The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

  According to the present invention, since the junction between the circuit board and the vibration introducing body has a fixed region that is fixed and a non-fixed region that is not fixed, the sensing sensitivity can be improved. Can do.

It is a figure which shows Example 1 of this invention. FIGS. (A-1) and (A-2) show a state before the vibration ring is installed, as viewed in the direction of the arrow along the # 1- # 1 line of FIG. (A-2). The figure is (A-1) in the figure. (A), (B) is a figure which shows the plane main part of Example 2 of this invention. (C), (D) is a figure which shows the plane main part of Example 3 of this invention. It is a figure which shows the plane principal part of Example 4 of this invention. It is a figure which shows the plane principal part of Example 4 of this invention. It is a figure which shows an example of the conventional piezoelectric vibration sensor.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

  First, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 shows the basic structure of the piezoelectric vibration sensor of this embodiment. FIGS. (A-1) and (A-2) show a state before the vibration ring is installed. FIG. (A-1) shows a main cross section of the piezoelectric vibration sensor 100, and FIG. -2) indicates a plane. A view in the arrow direction along line # 1- # 1 of FIG. (A-2) is FIG. (A-1). As shown in these drawings, a pair of electrode lands 22 and 23 are provided near the center of the main surface of the substrate 20, and a ground conductor 24 is formed around the pair of electrode lands 22 and 23. The electrode lands 22 and 23 are drawn out by through holes 22A and 23A on the back side of the substrate 20. A terminal (not shown) of the piezoelectric element 30 is joined to the electrode lands 22 and 23 with a conductive adhesive or the like. As described above, the piezoelectric element 30 and the amplifier provided on the back surface side of the substrate 20 are connected by the electrode lands 22 and 23 and the through holes 22A and 23A. The above points are the same as the background art described above.

  As the substrate 20, for example, a resin substrate such as a glass epoxy having a 12 mm square and a thickness of 1 mm is used, but a hard substrate such as ceramic may be used. For example, PZT (lead zirconate titanate) is used as the piezoelectric element 30, but the material is not particularly limited, and a material having appropriate sensitivity (piezoelectric constant, capacitance) is used, and the shape is not limited. For example, “0603 To "3216".

  Next, the attachment (mounting) of the vibration ring 40 to the substrate 20 will be described with reference to FIGS. FIG. 2B-1 is a plan view, and FIG. 2B-2 is a perspective view showing a state when the vibration ring is attached. Solder is generally used to attach the vibration ring 40, but a conductive resin or an adhesive may be used. In short, a means for fixing the substrate 20 and the vibration ring 40 may be used.

  By the way, in the present embodiment, the solders 130 and 132 are provided in two places instead of the entire circumference of the vibration ring 40. As shown in the figure, the soldering position is easy to mount in the central direction passing through the electrode lands 22 and 23 of the piezoelectric element 30 or in the central direction or the central line FQ orthogonal to the central line FP, but is not limited to this. . The intersection of the center lines FP and FQ is the center CP of the piezoelectric element 30, and the center CP is also the center of the vibration ring 40 because the piezoelectric element 30 is located at the center of the vibration ring 40.

  Soldering angles θA and θB (an angle of the fixing region between the substrate 20 and the vibration ring 40) are 20 degrees to 45 degrees in both directions with respect to the center line FQ (total θA + θB = 60 to 90 degrees, soldering) 130 to 132 in total is preferably 120 to 180 degrees). The vibration ring 40 is soldered to the substrate 20 with respect to the two solders 130 and 132 as shown in FIG.

When the amplitude comparison with the piezoelectric vibration sensor 10 of the background art mentioned above was performed using the standard pulse wave by the piezoelectric vibration sensor 100 obtained as described above, the following data was obtained. The numerical value is a dimensionless amount by digital output (the original numerical value is obtained by amplifying the voltage output from the piezoelectric vibration sensor with an amplifier). As shown in this table, the conventional technique for soldering the entire circumference is “100”, whereas in the case of the total solder mounting angle of 120 degrees (θA + θB = 60 degrees × 2 places) in this embodiment, “1200”. ”And very high sensing sensitivity is obtained.

  As described above, according to this embodiment, since the vibration ring 40 is fixed to the substrate 20 by soldering not to the entire circumference but to two places, the sensing sensitivity of the piezoelectric vibration sensor 100 is greatly increased. Improvements can be made. In the conventional method of soldering the entire circumference of the vibration ring 40, since it is too firmly fixed, the movement of the vibration ring 40 is obstructed, so that a large sensing sensitivity cannot be obtained. However, according to the present embodiment, the substrate 20 and the vibration ring 40 are firmly fixed to each other and the non-fixed region which is a non-fixed movable part is transmitted to the vibration ring 40. The substrate 20 is greatly bent by the vibration, and the vibration is further transmitted to the piezoelectric element 30, so that high sensing sensitivity can be obtained.

  Next, Embodiment 2 of the present invention will be described with reference to FIGS. 2 (A) and 2 (B). In the piezoelectric vibration sensor 200 of FIG. 6A, the vibration ring 40 is attached at three places, solders 202, 204, and 206, and the angle θ200 is 50 degrees (50 degrees × 3 places). . In this example, it can be considered that the solders 202, 204, and 206 are provided in line symmetry with respect to the central direction FP of the piezoelectric element 30, and viewed from the center of the piezoelectric element 30 (intersection of FP and FQ). Thus, it can be considered that they are provided at point-symmetric positions. The piezoelectric vibration sensor 210 in FIG. 5B is an example in which the angles of the solders 202, 204, and 206 are the same and the positions are shifted by 30 degrees. However, it is a line object with respect to FQ orthogonal to the central direction FP of the piezoelectric element 30, and is point symmetric when viewed from the center of the piezoelectric element 30. In these examples, the amplitude detection sensitivity with the piezoelectric vibration sensor 10 is “500” as shown in Table 1 above, and a higher sensing sensitivity than the conventional technology for the entire circumference is obtained.

  Next, Embodiment 3 of the present invention will be described with reference to FIGS. 2 (C) and 2 (D). In the piezoelectric vibration sensor 300 according to the present embodiment, the vibration ring 40 is attached at four locations of solders 302, 304, 306, and 308, and the angle θ300 is 40 degrees (40 degrees × 4 positions). . It can be considered that the solders 302, 304, 306, and 308 of this embodiment are arranged in either line symmetry or point symmetry with respect to the center of the piezoelectric element 30. In the piezoelectric vibration sensor 310 of FIG. 4D, the angles of the solders 302, 304, 306, and 308 are the same, and the position is shifted by 90 degrees. The amplitude detection sensitivity with the piezoelectric vibration sensor 10 in this example is “300” as shown in Table 1 above, and a higher sensing sensitivity is obtained than the conventional technology for the entire circumference.

  Here, when Examples 1 to 3 described above are compared, the sensing sensitivity decreases as the total angle of solder attachment increases. According to such a result, when the total angle of solder attachment becomes larger than 180 degrees, the movement of the substrate 20 is inhibited, the sensing sensitivity is lowered, and only the sensing sensitivity equivalent to the conventional technology can be obtained. However, if the total angle of solder attachment is reduced from 120 degrees, there is a possibility that the fixing strength of the vibration ring 40 with respect to the substrate 20 may be lowered, and the sensing sensitivity is similarly lowered. Accordingly, the total angle of solder attachment is preferably in the range of 120 degrees to 180 degrees in consideration of mounting strength.

  Next, Embodiment 4 of the present invention will be described with reference to FIGS. FIG. 3 (A) shows the solder mounting position in the above-described first embodiment, but it may be arranged as shown in FIG. 3 (B) by shifting the angle by 90 degrees. From the viewpoint of mounting, FIG. 5A has an advantage that the solder 130 and 132 can be easily worn.

  The piezoelectric vibration sensor 400 of FIG. 3C is an example in which five solders 402 to 410 are arranged at equal intervals and symmetrical with respect to the central direction FP of the piezoelectric element 30. The piezoelectric vibration sensor 500 shown in FIGS. 4D and 4E is an example in which six solders 502 to 512 are arranged at equal intervals, and the arrangement shown in FIG. 4D is shifted by 30 degrees. It is.

  In the piezoelectric vibration sensor 600 of FIG. 4A, the four solders 602 to 608 are not equally spaced as in the example shown in FIGS. 2C and 2D, but the solders 602 and 604 and the solders 606 and 608 are not provided. The interval is narrow, and the intervals between the solders 604 and 606 and the solders 602 and 608 are wide. The piezoelectric vibration sensor 610 in FIG. 4B is an example in which the vibration ring is not a cylinder but an ellipse, and two solders 612 and 614 are provided. Of course, in this example, as described above, a larger number of solders may be provided. The piezoelectric vibration sensor 620 in FIG. 6C is an example in which the vibration ring is not a cylinder but a rectangle, and four solders 622 to 628 are provided. Of course, also in this example, as described above, the number of solders may be increased or decreased.

  The piezoelectric vibration sensor 630 in FIG. 4D is an example in which the opposing solders 632 and 636 among the four solders 632 to 638 are set short, and the solders 634 and 638 are set long, and the four solders 632 to 638 are set. Is not a line object with respect to the center lines FP and FQ, but is symmetrical with respect to the center CP. In the piezoelectric vibration sensor 640 of FIG. 5E, the solders 642 and 644 are short and the solder 646 is long. This example is not point-symmetric with respect to the center CP but is line-symmetric with respect to the center line FP.

In addition, this invention is not limited to the Example mentioned above, A various change can be added in the range which does not deviate from the summary of this invention. For example, the following are also included.
(1) The solder or fixing region shown in the above embodiment is an example, and can be appropriately changed within the scope of the present invention.
(2) The vibration ring shown in the above embodiment is also an example, and may have various shapes and structures. For example, since it may be affected by environmental electromagnetic noise such as hum noise, it may be structured to be electromagnetically shielded in order to improve it (see International Publication WO 2017/187710). Alternatively, an electromagnetic shield structure with a cap as filed as Japanese Patent Application No. 2018-58943 may be used.

  According to the present invention, since the junction between the circuit board and the vibration introducing body has a fixed region that is fixed and a non-fixed region that is not fixed, the sensing sensitivity can be improved. It is suitable as a sensor such as a pulse wave.

10: Piezoelectric vibration sensor 12: Fixed tape 20: Substrate 22, 23: Electrode land 22A, 23A: Through hole 24: Ground conductor 24A, 24B: Through hole 30: Piezoelectric element 40: Vibration ring 100: Piezoelectric vibration sensors 130, 132 : Solder 200: Piezoelectric vibration sensors 202, 204, 206: Solder 210: Piezoelectric vibration sensor 300: Piezoelectric vibration sensors 302, 304, 306, 308: Solder 310, 400: Piezoelectric vibration sensors 402 to 410: Solder 500: Piezoelectric vibration sensor 502 to 512: Solder 600: Piezoelectric vibration sensor 602 to 608: Solder 610: Piezoelectric vibration sensor 612, 614: Solder 620: Piezoelectric vibration sensor 622 to 628: Solder 630: Piezoelectric vibration sensor 632 to 638: Solder 640: Piezoelectric vibration sensor 642, 644, 646 Solder BD: Skin CP: central FP, FQ: central direction through the center line HP: pulse

Claims (4)

A circuit board for transmitting vibrations;
A piezoelectric element provided on the circuit board;
A vibration introducing body that includes an opening, is soldered around the piezoelectric element of the circuit board, and contacts the object to transmit the vibration to the circuit board;
Bonding the circuit board and the vibration introducing body, a bonding region that is fixed by solder, and a bonding portion where there is a non-fixed region that is not fixed,
A piezoelectric vibration sensor characterized by comprising:   The plurality of fixing regions are provided, and the plurality of fixing regions are arranged at positions that are symmetrical with respect to the center of the vibration introducing body or a center line passing through the center. Piezoelectric vibration sensor.   3. The piezoelectric vibration sensor according to claim 2, wherein the entire range of the fixed region is 120 to 180 degrees as viewed from the center of the vibration introducing body.   The piezoelectric vibration sensor according to claim 1, wherein a center direction passing through the piezoelectric element and its electrode is the non-fixed region.

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