JPH0715417B2 - Distributed pressure sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distributed pressure sensor, and more specifically, it can be attached to a robot hand or the like to detect the distribution of force applied in a direction perpendicular to the hand. The present invention relates to a distributed pressure sensor.

[Conventional technology]

This kind of distributed pressure sensor has been developed for the purpose of obtaining information such as the strength of the gripping force and the surface pressure distribution by detecting the pressure of the robot hand. FIG. 7 shows a part of such a distributed pressure sensor, and FIG. 8 shows an example of individual pressure sensors constituting the distributed pressure sensor.
The distributed pressure sensor is constructed by adhering a single crystal silicon plate 2 as shown in FIG. 7 on an elastic body 1 which is a substrate made of an elastic material having an appropriate Young's modulus. A load applying section 3 is fixed to the central portion of the crystalline silicon plate 2 by eutectic bonding or bonding with Sn / 10Au, for example, and semiconductor strain gauges 2B and 2C are arranged around the load applying section 3. The individual pressure sensors 4 thus configured are arranged in a matrix. In addition, on the upper surface 2D of the single crystal silicon plate 2, solder pads 2A for signal extraction are formed in addition to the semiconductor strain gauges 2B and 2C and wiring (not shown) for connecting them, and solder for these signals is formed. The solder pad 5B of the flexible printed board 5 having the window 5A formed therein is melt-bonded to the pad 2A so as to overlap each other. Here, the elastic body 1
A groove-shaped groove 1A is formed on the side of the pressure sensor 4 to separate the pressure sensors 4 from each other.

In the above-described structure, when a vertical load is applied to the load applying section 3, the single crystal silicon plate 2 is deformed together with the elastic body 1, so that the semiconductor strain gauge 2B formed on the surface of the single crystal silicon plate 2B. And the resistance value at 2C changes. Therefore, if these changes in resistance value are taken out as a voltage change by the Wheatstone bridge circuit, the magnitude of the vertical load applied to the load applying section 3 can be known, and a plurality of pressure sensors 4 arranged in a matrix are suitable. By scanning the, the distribution of the applied vertical load can be known.

By the way, when the pressure sensor 4 is constructed as shown in FIG. 8 and a vertical load is applied to the load applying portion 3, only compressive strain is generated on the surface of the single crystal silicon plate 2. For this reason, the four semiconductor strain gauges 2B, 2B and 2C, 2C all show positive resistance changes, so when a Wheatstone bridge circuit is configured between these semiconductor strain gauges, the changes in resistance value of the strain gauges are canceled by each other. Since they work together, the resulting output is very small. So the ninth
As the arrangement of the semiconductor strain gauge like the pressure sensor 4A in the figure, the dummy gauge 2E is arranged at a position where distortion does not occur, and the active gauges 2B1 and 2B2 are arranged at a position where distortion occurs.
It is conceivable that the output voltage e _o is obtained by arranging the above and the circuit configuration as shown in FIG. In the pressure sensor 4A of FIG. 9, the shape of the single crystal silicon plate 2 is
Although the method of arranging the solder pad 2A and the shape of the load applying portion 3 are different from the example shown in FIG. 8, the basic configuration and principle are the same as those in FIG.

[Problems to be Solved by the Invention]

However, in the case of the structure shown in FIG. 9 described above, the load applying section 3 deviates from a predetermined position, that is, the accurate center position of the single crystal silicon plate 2 by a certain eccentricity r as shown in FIG. If a horizontal load such as Fx in FIG. 12 is interfered with in this state, there are the following problems.

That is, in the pressure sensor 4A as shown in FIG.
When the Wheatstone bridge circuit is configured as shown in the figure, the output voltage e _o obtained between the output terminals of the circuit is as follows.

e _o = −1 / 4 · K _s (∈ _2b1 + ∈ _2b2 ) e _i … e _i is the power supply voltage, ∈ _2b1 and ∈ _2b2 are active gauges 2B
The longitudinal strains of 1 and 2B2, K _s, are constants called gauge factors. Note that here, since no strain occurs in the dummy gauge 2E, it is assumed that ε _2e = 0.

Therefore, first, in FIG. 11, the eccentricity r of the load applying unit 3 is
Consider the case of 0. In this case, as shown in Fig. 12, vertical load F _z
Is applied to the load applying section, strains ε _2b1 and ε _2b2 occur in the active gauges 2B1 and 2B2 as shown in FIG. 13A, and the output voltage e _o as shown in FIG. The load is detected. Similarly, when the eccentricity amount r = 0,
Even if a lateral load Fx is applied as shown in Fig. 12, active gauges 2B1 and 2B2 generate ε _2b1 and ε _2b2 of the same size and opposite signs as shown in Fig. 14A.
As shown in Fig. 14B, the output voltage e _o = 0 and the influence of lateral load, that is, the interference does not appear.

Next, if the load applying section 3 is displaced by a certain eccentricity r in the x direction as shown in FIG. 11, when a lateral load Fx is applied, strain ε _2b1 with different magnitudes as shown in FIG. ∈ _2b2
From the equation, the output voltage e _o becomes a very large value as shown in FIG. 15B, and it can be seen that the interference of the lateral load is greatly received.

By the way, eliminating the positional deviation of the load applying section 3, that is, increasing the assembling positioning accuracy leads to a large cost increase and is impractical. Therefore, it is unavoidable that the positional deviation of the load applying section 3 occurs substantially. Therefore, the pressure sensor 4A as shown in FIG. 11, that is, the conventional pressure sensor 4A has a problem that the lateral load interferes and the vertical load cannot be accurately detected.

An object of the present invention is to provide a distributed pressure sensor capable of suppressing the interference of lateral load to a minimum regardless of the accuracy of the mounting position of the load applying section in order to solve the above-mentioned conventional problems. To do.

[Means for Solving the Problems]

In order to achieve the above object, according to the present invention, a plurality of single crystal silicon plates, each having a semiconductor strain gauge and a load applying portion, are arrayed on a substrate made of an elastic material at predetermined intervals. Of the resistance value generated in the semiconductor strain gauge by deforming the single crystal silicon plate together with the elastic material substrate by a vertical load applied to the load applying portion of the single crystal silicon plate. In a distributed pressure sensor that detects the magnitude of the vertical load by a change, a plurality of semiconductor strain gauges are radially provided from the load applying section to a portion near the load applying section where strain is generated by the vertical load. Two sets of active gauges arranged so that the longitudinal direction of the gauges coincide with the radial direction and connected in series by the plurality of semiconductor strain gauges are provided. And disposing two dummy gauges by a semiconductor strain gauge on a portion of the single crystal silicon plate where no strain occurs, thereby forming a Wheatstone bridge between the two sets of active gauges and the two dummy gauges. The vertical load is detected by the output voltage from the Wheatstone bridge.

[Action]

According to the present invention, since the above-mentioned configuration is adopted, the semiconductor strain gauge arranged in the radial direction from the load applying section,
All are equivalent when viewed from the load applying section. As a result, even if the load applying section is displaced from the center in either direction, the respective semiconductor strain gauges complement each other and the interference output in the lateral direction is eliminated or reduced.

As will be described later in the embodiment section, FIG. 5 shows the strain amount and the sensor output generated in each semiconductor strain gauge with respect to the lateral load Fx when the load applying portion of FIG. 1 is displaced in the direction of the active gauge 2B2. The semiconductor strain gauges complement each other to reduce the interference output. Since the semiconductor strain gauges are arranged in the radial direction, this action is similarly exerted when the load applying section is displaced in either direction.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1 shows an embodiment of each pressure sensor 4B constituting the distributed pressure sensor of the present invention. Here, 2B1 to 2B4 are formed on the upper surface 2D of the single crystal silicon plate 2 and are active gauges that are semiconductor strain gauges that detect the load applied to the load applying section 3 as strain, and 2E is a peripheral portion where no strain occurs. It is a dummy gauge that is a semiconductor strain gauge that is formed.On the top surface 2D, in addition to these active gauges 2B1 to 2B4 and the dummy gauge 2E, wiring (not shown) connecting these and solder bumps 2A for signal extraction are formed. Has been done.

Then, the active gauges 2B1 to 2B4 and the dummy gauge 2E are combined into a bridge circuit as shown in FIG.
3 and the output voltage e _o from between the output terminals can be obtained by configuring incorporating the 2B4 as a set, the output voltage e _o in this case is expressed by the following equation.

_{e o = -1 / 8 · K} e (∈ 2b1 + ∈ 2b2 + ∈ 2b3 + ∈ 2b4) e i ... here, e _i is the power supply voltage, ∈ _2b1 ~ _2b4 is active gauge
The longitudinal strain of 2B1 to 2B4, K _e, is a constant called a gauge factor. Since the dummy gauge 2E is not distorted, it is assumed that ε _2e = 0.

Therefore, in the pressure sensor 4B configured as described above, when the eccentricity amount r of the load applying section 3 is 0, assuming that a vertical load F _z as shown in FIG. 12 is applied to the load applying section 3, the active gauge 2B1 Distortions as shown in Fig. 3A are generated in ~ 2B4, and the output voltage e _o as shown in Fig. 3B is obtained from the equation. Similarly, for the lateral load Fx shown in FIG. 12, the output voltage becomes as shown in FIG. 4A and the output voltage e _o = 0 as shown in FIG. 4B.

Next, when the load applying section 3 is displaced from the center position by the eccentricity amount r in the x direction as described in the prior art, if the lateral load Fx is applied, the strains shown in FIG. It occurs in the active gauges 2B1 to 2B4, and as a result, the output voltage e _o is not zero, but has an extremely small value as shown in FIG. 5B, and it can be seen that the lateral load interference is largely eliminated.

As described above, in the case of the pressure sensor according to the present invention, the strains generated in the four active gauges 2B1 to 2B4 are generated in a mutually complementary manner, and therefore, the lateral force is larger than that in the conventional technique in which the load values are detected by the two active gauges. The load interference can be much smaller.

Needless to say, in the pressure sensor 4B configured as shown in FIG. 1, even if the Wheatstone bridge circuit is configured as shown in FIG. 6, the same effect as in the case of FIG. 2 can be obtained.

〔The invention's effect〕

According to the present invention, as a result of adopting the above configuration, it is possible to eliminate or reduce the interference output due to the lateral load.

[Brief description of drawings]

1 is a block diagram of individual pressure sensors constituting the distributed pressure sensor of the present invention, FIG. 2 is a block diagram of a Wheatstone bridge circuit according to the present invention, FIGS. 3A and 3B to 5A and 5B Up to the figure, an explanatory view showing the relationship between the amount of strain generated in the active gauge and the output voltage of the Wheatstone bridge circuit under different load conditions, FIG. 6 is a configuration diagram of another Wheatstone bridge circuit according to the present invention, and FIG. 8 is a sectional view of a distributed pressure sensor according to the related art, FIGS. 8 and 9 are configuration diagrams of individual pressure sensors according to the related art, FIG. 10 is a configuration diagram of a Wheatstone bridge circuit according to the related art, and FIG. 11 is FIG. FIG. 12 is a plan view showing the eccentricity of the load applying section in the configuration of FIG. 12, FIG. 12 is a cross-sectional view showing the load direction with respect to the pressure sensor, and FIGS. 13A and 13B to 15A and 15B. In an explanatory view showing in different load application states a relationship between the strain amount and the Wheatstone bridge circuit output voltage generated in the active gauge in the conventional sense of pressure sensors. 1 ... Elastic body, 1A ... Groove, 2 ... Single crystal silicon plate, 2A
...... Solder pad, 2B, 2C …… Semiconductor strain gauge, 2
E …… Dummy gauge, 2B1-2B4 …… Active gauge,
3 ... Load application part, 4 , 4A , 4B ... Pressure sensor, 5 ...
Flexible printed circuit board, ∈ _2b1 ~∈ _2b4 ...... strain amount of active gauge.

Claims (1)

[Claims] 1. A plurality of single crystal silicon plates, each having a semiconductor strain gauge and a load applying section, formed on an elastic substrate and arranged in an array at predetermined intervals. The single crystal silicon plate is deformed together with the substrate of the elastic material by a vertical load applied to the load applying portion of the plate, and the magnitude of the vertical load is detected by a change in resistance value generated in the semiconductor strain gauge. In the distributed pressure sensor, a plurality of semiconductor strain gauges are radially provided from the load applying section in a portion where strain is generated by the vertical load in the vicinity of the load applying section, and a longitudinal direction of the semiconductor strain gauge is aligned with the radial direction. So as to form two sets of active gauges connected in series by the plurality of semiconductor strain gauges. Two dummy gauges by a semiconductor strain gauge are arranged in a portion where no strain is generated to form a Wheatstone bridge between the two sets of active gauges and the two dummy gauges, and the output voltage from the Wheatstone bridge is used to A distributed pressure sensor characterized by detecting a vertical load.