JPH0446464B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a pressure-sensitive structure made of a single crystal semiconductor having a plurality of striations of opposite conductivity type whose resistance value changes when a force is applied to a surface layer of one conductivity type. Consisting of two unit cells each having a gauge area, the pressure-sensitive structures of both unit cells are arranged between a common support and a pressure-receiving plate, and the three components of the force applied to the upper surface of the pressure-receiving surface are composed of strain gauges. This invention relates to a pressure sensor that detects the output voltages of three bridges.

[Prior art and its problems]

For example, in a robot hand that handles various objects, its gripping force must be controlled to a value that corresponds to the type of object. To do this, it is necessary to measure the magnitude of the gripping force and its planar distribution.
In order to meet this demand, a small pressure sensor cell as shown in FIG. 1 was developed. This cell is constructed by forming four p-type strain gauge regions 21 and 2 by diffusion on a surface 12 perpendicular to a pressure-receiving surface 11 of a ring-shaped pressure-sensitive structure 1 made of, for example, an n-type silicon single crystal.
2, 23, strain gauges 21, 22,
The three components Fx, Fy, and Fz of the force applied to the pressure-receiving surface 11 of the pressure-sensitive structure 1 supported by the bottom surface 13 on the support body are detected from the output voltages of the three bridge circuits each composed of 23. It is. However, when a load is applied to such a pressure sensor in the y direction, the pressure receiving surface 11 moves toward the support 3 as shown in FIG.
The load may be deformed so that it is no longer parallel to the surface, making it impossible to detect the load in the y direction. Therefore, two unit cells are used, and as shown in FIG. It has been proposed that the upper surface 41 of the pressure receiving plate 4 be used as a pressure receiving surface. However, in such a pressure sensor, two cells are connected to the pressure-sensitive structure 1.
Since the forces applied to A and 1B may be uneven, it is necessary to accurately detect the force from the output voltages obtained from both cells. However, forming the pressure sensitive structures of both cells as shown in FIG. 1 requires twice as many man-hours as compared to the case of a single cell, resulting in an increase in the price of the pressure sensor.

[Purpose of the invention]

In contrast, it is an object of the present invention to enable each pressure-sensitive structure of a pressure-sensitive sensor consisting of two unit cells to be manufactured more easily than in the case of a single cell.

[Key points of the invention]

According to the invention, the pressure-sensitive structures of the two unit cells are each provided with half of the strain gauge area constituting the respective bridge for detecting the three components of force. This is greatly simplified compared to the case where the unit cell includes a full bridge.

[Embodiments of the invention]

FIG. 4 shows the wiring of an embodiment of the present invention, in which the surface 12 of the pressure-sensitive structure 1 of the unit cell includes a strain gauge region 21 for Fz detection, a strain gauge region 22 for Fx detection, and a strain gauge region 22 for Fy detection. Two strain gauge regions 23 are formed in each region. If two such unit cells are used to construct a full bridge for detecting Fx, Fy, and Fz, it is possible to compensate for the non-uniformity of the forces in the two unit cells. The wiring 5 in this pressure-sensitive structure is extremely simple compared to the wiring 5 of the pressure-sensitive structure in FIG. 1 shown in FIG. The number of crossovers has gone from 31 to none, and the number of terminals 6 has been reduced from 8 to 7.

FIG. 6 shows the wiring of another embodiment, in which a half-bridge (figure a) for detecting the Fx component is provided on one side 12 of the pressure-sensitive structure 1, and a half-bridge for detecting Fz and Fy (figure b) on the other side 14. The number of terminals is further reduced compared to the case shown in FIG. To further reduce the number of terminals, if an epitaxial wafer having an epitaxial layer of a conductivity type different from that of the substrate is used, the substrate can be used for ground wiring, and the ground terminals 51 and 52 can be combined into one.

〔Effect of the invention〕

The present invention eliminates the nonuniformity of the force applied to both pressure-sensitive structures by dividing a bridge for detecting three components of the applied force of a pressure-sensitive sensor consisting of two unit cells into two pressure-sensitive structures. In addition, compared to when both pressure-sensitive structures each have a full bridge, the strain gauge area is not only halved, but the wiring density is significantly lower, and there is no crossover, reducing manufacturing man-hours and improving reliability. The performance of the pressure sensor is improved, and an extremely small pressure sensor unit cell can be obtained at a low cost. In addition, due to the reduction in wiring density, there is also room for integrating other elements such as temperature sensors and analog switches into the semiconductor of the pressure-sensitive structure, which greatly increases the effects of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a pressure sensor single cell, FIG. 2 is a front view showing undesirable deformation of the single cell, FIG. 3 is a front view showing deformation of the pressure sensor that is the subject of the present invention, and FIG. The figure is a plan view showing wiring on a pressure-sensitive structure according to an embodiment of the present invention, FIG. 5 is a plan view showing wiring on a pressure-sensitive structure according to a comparative example, and FIGS. FIG. 7 is a plan view showing wiring on both sides of a pressure-sensitive structure according to another example. 1, 1A, 1B...Pressure sensitive structure, 21, 22, 2
3...Strain gauge area, 3...Support body, 4...Pressure receiving plate, 5...Wiring.

Claims (1)

[Claims] 1 A unit cell equipped with a plurality of strain gauges of opposite conductivity type whose resistance value changes when a force is applied to the surface layer of one conductivity type of a pressure-sensitive structure made of a single crystal semiconductor.
The pressure-sensitive structures of both units are arranged between a common support and a pressure-receiving plate, and the three components of the force applied to the upper surface of the pressure-receiving surface are detected from the output voltages of three bridges consisting of strain gauges. 2. A pressure sensor according to claim 1, wherein each of the two unit cell pressure sensitive structures is provided with half of a strain gauge area forming each bridge for detecting three components of force.