JPS61181931A - Pressure sensor - Google Patents

Abstract

PURPOSE:To enable the miniaturization with a larger sensor output, by forming a circular membrane section and a central pressure receiving section surrounded thereby on a silicon plate while two pairs of straingauges are mounted on the surface of the membrane section. CONSTITUTION:A circular groove 11 is formed on a silicon monocrystaline plate 10 so that the bottom part of the groove 11 is made a diaphragm-like flexible membrane part 11A and moreover, a pressure receiving section 12 is set to remain at the center surrounded by the groove 11. Four semiconductor straingauges 14 are formed on the surface (support surface) 10A opposite to the groove-formed surface by a semiconductor process. In addition, a lead 15 is formed by the same semiconductor process to build a bridge circuit between the four straingauges 14. The unit detector 16 for detection of pressure thus obtained is arranged in matrix on the silicon monocrystalline plate 10. As a force is applied to the pressure receiving section 12 in the direction of the arrow, a stress sigma r is generated radially on the side of a support surface 10A with the deformation of the membrane section 11A, causing a tensile (compression) stress at the positions of the strain gauges 14A and 14B.

Description

[Detailed description of the invention]

[Technical field to which the invention pertains 1] The present invention relates to a pressure sensor that is attached to the grip surface of a robot hand and is capable of detecting the magnitude and distribution of a vertical load (hereinafter referred to as pressure) applied to the grip surface. Regarding possible pressure sensors. [Prior Art and Problems 1] As a conventional pressure sensor of this type, for example, as shown in FIG. 7, there is a known one in which a pressure-sensitive conductive rubber material IA is arranged in a matrix on a robot hand 1. . This sensor uses the fact that the resistance between both electrodes of the pressure-sensitive conductive rubber material IA changes when pressure is applied, and detects the resistance change value to detect the force applied to the sensor. This is what I did. Furthermore, there is also one in which a piezoelectric material is used instead of the pressure-sensitive conductive rubber material, as shown in FIG. Although only the structure of the unit sensor is shown here, 2 is a member formed of a piezoelectric material, the piezoelectric member 2 is arranged at the bottom of the hole of the guide plate 3, and the upper part of the member 2 has a flange part 4A. A contact 4 is supported by a spring S. 6 is the upper printed board, 7 is the lower printed board, 6A and ? A is the print surface on print substrates a6 and 7, respectively. Note that the contact 4 and the spring 5 are made of conductive material, and the printed surfaces 6A and 7A are electrically connected via these conductive materials. Therefore, in the case of a pressure sensor configured by arranging such unit sensors in a matrix. The piezoelectric member 2 is compressed by pressing the protrusions of the contacts 4 in the uneven unit sensors, and the electrical resistance value can be changed according to the compressive force. By arranging them in rows and columns, it is possible to detect the resistance change values in the unit sensors arranged at the intersections of these printed surfaces 6A and 7A. However, all such conventional pressure sensors have the following drawbacks. (1) The sensor output is small relative to the applied force. (2) The area where the applied force and sensor output are in a proportional relationship is small. (3) In order to accurately detect the pressure distribution, the unit detector must be made smaller, but it is difficult to make it smaller because the mechanism is complicated. [Objective of the Invention 1 An object of the present invention is to eliminate the above-mentioned drawbacks, provide a pressure sensor that has a large sensor output, and can be miniaturized. [Key Points of the Invention J That is, 1. The present invention includes a silicon plate having an annular membrane portion and a pressure receiving portion formed at the center of the membrane portion, and a silicon plate provided on the surface of the membrane portion of the silicon plate to prevent deflection of the membrane portion. A unit detector is composed of multiple pairs of strain gauges arranged so as to be able to detect the tensile and compressive stress generated by each strain gauge, and a bridge circuit formed between the multiple pairs of strain gauges, and the unit detector is continuously The sensor is arranged in a matrix on a silicon plate, the unit detectors excluding the pressure receiving part and the membrane part are supported by a holding plate, and the pressure receiving part is pressed through the pressure receiving plate. [Embodiment 1 of the Invention] Hereinafter, embodiments of the present invention will be described in detail and specifically based on the drawings. FIGS. 1A and 1B show two unit detectors as an embodiment of the present invention. Here, lO is a silicon single crystal plate, and by forming an annular groove 11 in the silicon single crystal plate 10 by electrolytic discharge machining, etching, etc., the groove l! The bottom portion of the diaphragm-like flexible membrane portion 11A is formed at the bottom, and the pressure receiving portion 12 is left in the central portion surrounded by the groove 11. In addition, in FIG. 1A, such grooves 11 are formed on the back surface side, but the surface opposite to the surface on which the grooves 11 are formed (
(Hereinafter, this surface will be referred to as the support surface) Four semiconductor strain gauges 14. That is 14A. 14A, 14B, and 14B are formed by a semiconductor process. Furthermore, conductive wires 15 for configuring a bridge circuit as shown in the figure are formed between these four strain gauges 14 by a similar semiconductor process, and a unit detector 16 for pressure detection constructed in this way is formed. They are arranged in a matrix on a silicon single crystal plate IO. In addition, 17A
and 17B are power supply terminals, and 18A and 18B are output terminals of the unit detector 16. Next, the principle of detecting pressure by the unit detector 16 configured in this way will be explained. FIG. 2 schematically shows the structure of the unit detector 16 in which the diaphragm-like membrane portion 11A of FIG. 1 is formed.
Since the membrane portion 11A is formed in the shape of an annular plate, when a force in the direction of the arrow is applied to the pressure receiving portion 12, the membrane portion 11A deforms as shown in this figure, and this deformation causes the lower surface of the membrane portion 11A to deform. That is, a stress σr as shown in FIG. 3 is generated in the radial direction on the support surface 10A side. That is, tensile stress occurs near the pressure receiving part 12, and compressive stress occurs near the peripheral part of the membrane part. Therefore, when the semiconductor strain gauges 14A and 14B are respectively arranged at the position of the membrane part 11A as shown in FIG. There is a tensile stress at the position,
Further, compressive stress is generated at the position of the strain gauge 14B. Therefore, a bridge circuit is constructed between these four strain gauges 14 as shown in the figure, and terminals +7A and 17
By applying a power supply voltage between the output terminal 18A and
An output voltage can be generated between and 18B. Therefore, since the unit detector 16 having such a configuration can detect the deflection of the circular plate-shaped membrane portion 11A, the difference between the applied force and the generated stress (therefore, the output voltage) can be detected. In addition to being able to achieve linearity over a wide range, semiconductor strain gauges have good sensitivity as is well known, so they have the advantage of providing large and highly accurate output signals. Next, an assembly structure of a pressure sensor configured by arranging the unit detectors 16 configured as described above will be described. Figure 4 shows the cross section of the silicon single crystal plate l.
Strain gauges 14 arranged as shown in FIG. A pressure member 20 is disposed on the base (see figure), and this pressure member 20 is further held by an elastic plate 21. Therefore, as shown in FIG. 5B, the elastic plate 21 is provided with a holding recess 21A at a position corresponding to the pressure member 20, that is, a position corresponding to the pressure receiving part 12 in FIG. 5A.
By fitting the pressure member 20 into the four parts 21A, the pressure member 20 and the elastic plate 21 constitute a pressure receiving plate 22. Further, in FIG. 4, on the lower surface side of the silicon single crystal plate 10 on which the strain gauge 14 is provided, there is a lower holding plate 2 for holding the entire unit detectors arranged in a matrix.
3 is provided, but this holding plate 23 is provided over this range in order to freely hold the pressure receiving part 12 and the membrane part 11A provided on the silicon single crystal plate IO against the pressurizing force applied to the pressure receiving plate 22. As shown in FIG. 5C, the support part 2 has a circular recess 23A and is flat except for this recess 23A.
3B supports the fixed part of each unit detector 16. In the pressure sensor configured in this way, when pressure is applied as shown by the arrow in FIG.
unit detector 1 via the elastic plate 21 and pressure member 20.
Since the unit detector 18 is supported from the bottom by the holding plate 23, the membrane part 11A of the unit detector 18 is
A deflection as shown in FIG. 2 occurs. Therefore, the generated stress is detected for each individual detector 1B by the strain gauge 14 and a bridge circuit configured between them, and thereby the pressurizing force applied to the pressure receiving plate 22 can be detected. . FIG. 6 shows another embodiment of the invention, in which only one of the unit detectors is shown. The shape of the unit detector 26 in this example is the same as that in the previous embodiment, but in this example, four semiconductor strain gauges 14 are formed at positions as shown in the figure. Now, when the membrane portion 11A is deformed by upward pressure from the back side of the page of this figure, the semiconductor strain gauge 1
As described above, tensile stress is generated in the semiconductor strain gauge 4C, so that the semiconductor strain gauge 14G is stretched in the axial direction. on the other hand,
Since the semiconductor strain gauge 140 is formed with its axis perpendicular to the strain gauge 14C, it contracts in the axial direction, so the four semiconductor strain gauges 14 form a bridge circuit as shown in the figure. For example, the pressure applied to the unit detector 26 can be detected as the output voltage from such a bridge circuit. Note that the other configurations when assembled as a pressure sensor are the same as those in the example described above, and their explanation will be omitted.

【Effect of the invention】

As explained above, according to the present invention, an annular membrane portion and a central pressure receiving portion surrounded by the membrane portion are formed on a silicon plate, two pairs of strain gauges are attached to the surface of the membrane portion, A bridge circuit is formed between these strain gauges to configure a unit detector, and such unit detectors are arranged in a matrix on the same silicon plate, excluding the pressure receiving part and membrane part of each detector. The pressure receiving part is supported by the support plate, and the pressing force is transmitted from the pressurizing side only to the force receiving part, so that when the pressure receiving part is pressed, the pair of strain gauges is Since tensile stress is generated in the strain gauge and compressive stress is generated in the other pair of strain gauges, an output voltage proportional to the pressing force can be extracted from each unit detector via the bridge circuit. Not only can a large output signal be obtained with high precision against a unidirectional pressing force, but also the unit detector can be made smaller.

[Brief explanation of drawings]

FIG. 1A is a plan view showing an example of the configuration of a unit detector of the pressure sensor of the present invention, FIG. 1B is a sectional view taken along the line A-A, and FIG. FIG. 3 is a stress distribution diagram of tensile and compressive stress generated on the lower surface due to the deflection of the membrane portion as shown in FIG. 2. FIG. FIG. 5A, FIG. 5B, and FIG. 5C are plan views of the silicon single crystal plate, elastic plate, and lower holding plate, respectively, and FIG. 6 is a cross-sectional view showing an example in an assembled state. FIG. 7 and 8 are a perspective view and a sectional view, respectively, showing two examples of the structure of a conventional pressure sensor. 1... Robot hand. IA...Pressure-sensitive conductive rubber material, 2... Piezoelectric member. 3... Guide plate, 4... Contact, 4A... Flange portion, 5... Spring, 6.7... Printed circuit board 10... Silicon single crystal plate, 10A... Support surface , 11...Groove, 11A...Membrane part, 12...Pressure receiving part, 14.14A, 14B, 14C, 140...Strain gauge, 15...Conducting wire, 1e, 2e...Unit detection Vessel, +? A, 17B, 18A, 18B...Terminal, 20.
. . . Pressure member, 21 . . . Elastic plate, 21A . . . Recessed portion, 22 . Figure 5A Figure 5B Figure 5C Figure 26

Claims (1)

[Claims] A silicon plate having an annular membrane portion and a pressure receiving portion formed at the center of the membrane portion, and a silicon plate disposed on the surface of the membrane portion of the silicon plate to prevent tensile and compressive stress caused by deflection of the membrane portion. A unit detector is constituted by a plurality of pairs of strain gauges arranged so that detection is possible, and a bridge circuit formed between the plurality of pairs of strain gauges, and the unit detector is mounted on the continuous silicon plate. A pressure sensor, characterized in that the unit detectors are arranged in a matrix, the unit detectors excluding the pressure receiving part and the membrane part are supported by a holding plate, and the pressure receiving part is pressed through the pressure receiving plate.