JPH0447762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the structure of a strain sensor that converts strain generated in, for example, a structure into an electrical signal and extracts it.

Description of the Prior Art Conventionally, strain gauges have been widely used as means for detecting strain occurring in, for example, structures. FIG. 1 is a schematic cross-sectional view showing an example of the use of a conventional strain gauge. The strain gauge 1 has a structure in which a strain-sensitive resistor 3 made of, for example, metal foil or filament-like thin metal wire is fixed on a plastic substrate 2 made of, for example, polyester. The strain is detected as an electric signal by utilizing the change in the electric resistance of the strain-sensitive resistor 3 such as metal foil. In the structure shown in FIG. 1, the strain gauge 1 is
It is adhered and fixed onto the detection target member 4 with an adhesive 5, and therefore, the strain generated in the detection target 4 is transmitted to the strain sensitive resistor 3 via the adhesive 5 and the plastic substrate 2. When the strain-sensitive resistor 3 is distorted, its electrical resistance value changes, and this is configured to be taken out by the lead wires 6a, 6b.

By the way, as mentioned above, the conventional strain gauge 1 is
Since it is used by being bonded to the object to be detected 4 using adhesive 5, if the object to be detected 4 vibrates frequently, or if external vibrations or shocks are applied, the adhesion may fail. There was a problem in that the strain gauge 1 peeled off from the object to be detected 4 due to the deterioration of the adhesive 5 and the decrease in adhesive strength. Also, 80
When used in a high temperature environment of .degree. C. or higher, the adhesive 5 softens, so that even if distortion occurs in the detection object 4, the distortion cannot be accurately detected.

In addition, since the conventional strain gauge 1 is fixed to the detection target 4 using an adhesive 5, it is necessary to apply the adhesive 5 evenly and evenly in order to perform accurate strain detection. Another problem was that this work required considerable skill.

Purpose of the Invention In view of the above-mentioned problems, the purpose of the present invention is to ensure that the strain-sensitive part does not peel off even when subjected to repeated external vibrations and shocks, and even when used at high temperatures of 80°C or higher. It is an object of the present invention to provide a strain sensor that can be used repeatedly, exhibits a good strain-to-electrical resistance conversion effect, and can perform highly reliable strain detection.

Structure of the Invention A strain sensor according to the present invention includes a strain-receiving structural member, a strain-sensitive resistance layer, and a plurality of electrode layers.
The strain-receiving structural member generates strain in response to applied force. The strain-sensitive resistance layer is directly on the strain-sensitive structural member.
It is formed by vapor deposition, and its electrical resistance changes according to strain. The electrode layer is formed on the strain sensitive resistance layer. The strain sensitive resistance layer includes a first semiconductor layer and a second semiconductor layer. The first semiconductor layer is formed on the strain-receiving structure member side and has a first electrical resistance. The second semiconductor layer is formed on the electrode layer side, has a second electrical resistance lower than the first electrical resistance, and contains the same semiconductor component as the first semiconductor layer. The electrical resistance of at least the path passing through the strain-receiving structural member between the electrode layers is
The electrical resistance is 10 ² times or more the electrical resistance of a path passing only through the second semiconductor layer between the electrode layers.

Other features of the invention will become clear from the following description of the embodiments.

DESCRIPTION OF EMBODIMENTS FIG. 2 is a schematic front sectional view for explaining a first embodiment of the present invention. This example is
Although the strain of the detection object 14 is measured, the detection object 14 itself becomes the strain-receiving structural member here. That is, a direct strain-sensitive resistive thin film layer 17 is closely formed on the detection target 14 as a strain-receiving structural member by vapor deposition methods such as chemical vapor deposition and physical vapor deposition, or other thin film forming means. The strain-sensitive resistive thin film layer 17 includes two silicon thin film resistive layers 18,
On the second silicon thin film resistance layer 19, lead electrodes 21a and 21b are formed for connecting lead wires 16a and 16b. Note that 22 indicates a resin layer for moisture proofing.

The first silicon resistive thin film layer 18 is configured to have a relatively high electrical resistance compared to the second silicon resistive thin film layer 19. That is, the first silicon resistive thin film layer 18 constitutes the first region of the strain sensitive resistive thin film layer 17, while the second silicon resistive thin film layer 19 constitutes the second region.

Further, between the electrodes 21a and 21b, a second
silicon resistive thin film layer 19, first silicon resistive thin film layer 18, detection target member 14 as a strain receiving structural member, first silicon resistive thin film layer 18, and second silicon resistive thin film layer 18.
The electrical resistance of the path sequentially passing through the silicon resistive thin film layer 19 is 10 ² times or more the electrical resistance between the electrodes 21a and 21b via the second silicon resistive thin film layer 19. Therefore, when strain occurs in the strain-receiving structural member 14 that also serves as the object to be detected, the strain-sensitive resistor thin film layer 17 is also distorted, but even if the member 14 to be detected is conductive, the strain-sensitive resistor thin film layer 17 is configured as described above, the strain-sensitive resistive thin film layer 17
The change in electrical resistance due to strain in the second silicon resistive thin film layer 19 can be accurately measured using the lead wires 16a, 1.
6b. This will be explained in more detail with reference to FIG. 3, which shows an equivalent circuit diagram of the embodiment shown in FIG. In addition, in FIG. 3, the resistance of the electrodes 21a, 21b and the detection object 14 is 0.
It is approximated as In Figure 3, A and B
indicate lead wires 16a and 16b, respectively;
_R1 represents the electrical resistance between the electrode 21a-second silicon resistance thin film layer 19-electrode 21b in FIG.
R ₂ is electrode 21a - second silicon resistance thin film layer 1
9 - represents the resistance between the first silicon resistive thin film layer 18 and the detection object 14 as a strain-receiving structural member, R ₃
is electrode 21b - second silicon resistance thin film layer 19 -
First silicon resistive thin film layer 18 - detection target 14
shows the resistance between Since the strain-sensitive resistive thin film layer 17 is configured as described above, the relationship between _the resistance values of R ₁ , R ₂ , _and R ₃ in the circuit diagram of FIG _.
≫R becomes ₁ .

Therefore, the electrodes 21a and 21b of the strain-sensitive resistive thin film layer 17 are connected to each other through the second silicon resistive thin film layer 19.
The electrical resistance between them is reliably insulated from the detection target 14, exhibiting a good strain-to-electrical resistance conversion effect, and making it possible to perform highly reliable strain detection.

According to experiments conducted by the inventors of the present application, in order to fully exhibit the above-mentioned insulating effect, the first
The electrical resistivity of the silicon resistive thin film layer 18 is 1×
It has been found that it is preferable to set the resistance to 10 ⁴ Ωcm or more. In addition, it provides good sensitivity to strain-electrical resistance changes of the strain-sensitive resistive thin film layer 17, and lowers the resistance value when extracting the electrical output signal from the second silicon resistive thin film layer 19 to the outside, thereby reducing the S/N ratio. In order to improve the resistance and perform detection with higher accuracy, it has been found that it is desirable to set the electrical resistivity of the second silicon resistive thin film layer 19 to 1×10 ² Ωcm or less.

As described above, in the embodiment shown in FIG. 2, the strain-receiving structural member also serves as the detection target member 14, and on the detection target member 14, the strain-sensitive resistive thin film layer 17 and the electrodes 21a, It can be seen that since 21b is directly formed, the strain sensor can be constructed without using an adhesive as in the conventional case, and therefore all the various problems caused by the presence of the adhesive layer can be solved. That is, it is possible to effectively eliminate problems such as deterioration in detection accuracy due to peeling of the adhesive layer or softening of the adhesive layer.

In the embodiment shown in FIG. 2, the strain-sensitive resistive thin film layer 17 is composed of two silicon resistive thin film layers 18 and 19, and is therefore formed on the strain-sensitive structural member 14 as the detection target. In this case, films can be continuously formed using the same equipment and materials having the same main components. This is because by changing the concentration of impurities to be mixed, two regions having different electrical resistances can be easily formed. Furthermore, since it is formed using a thin film formation technique, the film quality is uniform, and therefore detection accuracy can be further improved, and furthermore, it greatly contributes to cost reduction.

The material constituting the strain-sensitive resistive thin film layer 17 is as follows:
In addition to the amorphous silicon mentioned above, germanium carbon (diamond), gallium-arsenic,
Various materials such as gallium and phosphorus can be used. Further, it goes without saying that the two regions having different electric resistances constituting the strain-sensitive resistive thin film layer 17 may be formed separately, or may be formed of a multilayer thin film of three or more layers. Further, the detection target 14 as a strain-receiving structural member does not need to be made of a conductive material such as metal, that is, it may be made of an insulating material.

FIG. 4 is a longitudinal sectional view showing a pressure sensor to which the embodiment shown in FIG. 2 is applied. Pressure sensor 31
is the introduction hole 3 into which the fluid whose pressure is to be detected is introduced.
2 and a main body 34 to which the cylindrical member 33 is screwed, and the main body 34 is provided with a strain-receiving structural member 35 that can be distorted by fluid pressure. The above-mentioned first
A silicon resistive thin film layer 18, a second silicon resistive thin film layer 19, and electrodes 21a and 21b are directly formed. A moisture-proof layer 22 made of synthetic resin is formed above the electrodes 21a, 21b, and lead wires 16a, 1 drawn upward from the moisture-proof layer 22 are formed.
6b is a disk 37 fixed to the inner surface of the support 36;
opening 38, resin mold layer 39, cap 40
The pressure sensor 31 is drawn out through the opening 41 of the pressure sensor 31 . Therefore, the lead wires 16a, 16b
Even if an external force is applied to the resin mold layer 39
This external force is received by the resin mold layer 39 and is not transmitted to the strain sensor portion.

In the pressure sensor 31 shown in FIG. 4, the pressure of the fluid is transmitted to the lead wires 16a, 16b as a change in electrical resistance based on the strain transmitted to the second silicon resistance thin film layer 19 via the strain receiving structural member 35. Detected. The embodiment shown in FIG. 2 is thus particularly advantageous when constructed as a dedicated sensor, such as pressure sensor 31. This is because the strain-sensitive resistance thin film layer can be formed on the strain-receiving structure member 35 in advance by a thin film forming means such as vapor deposition.

In the embodiment shown in FIG. 2, two electrodes 21a and 21b are provided as the plurality of electrodes, but the present invention is not limited to this, and three or more arbitrary electrodes may be formed. For example, four electrodes may be formed to form a bridge, as shown in the schematic circuit diagram of FIG. In Figure 5, 61, 62, 6
3 and 64 indicate the second region of the strain-sensitive resistive thin film layer, and E and R indicate the external power source and external resistance.

Effects of the Invention As described above, according to the present invention, the strain-sensitive resistive layer is directly vapor-deposited on the strain-receiving structural member that generates strain. Can be omitted. Therefore, even if external vibrations or shocks are repeatedly applied, the strain-sensitive resistance layer will not peel off from the strain-receiving structural member.
It is possible to obtain a highly reliable strain sensor that can be used repeatedly even at high temperatures of 80°C or higher.

The strain-sensitive resistance layer includes first and second semiconductor layers, and the electrical resistance of the first semiconductor layer formed on the strain-sensitive structure member side is higher than that of the second semiconductor layer formed on the electrode layer side. prices are also getting higher. Therefore, when the strain-receiving structural member exhibits conductivity, even if an insulating layer with extremely high electrical resistivity is not formed between the strain-receiving structural member and the region that becomes the strain-sensitive resistor, a second layer between the electrode layers can be formed. The path passing only through the semiconductor layer can be reliably insulated from the strain-sensitive structure member. As a result, the second semiconductor layer serving as the strain-sensitive resistor exhibits a good strain-to-electrical resistance conversion effect, making it possible to perform highly reliable strain detection.

Furthermore, the two types of semiconductor layers constituting the strain-sensitive resistance layer contain the same semiconductor component. Therefore,
These two types of semiconductor layers can be formed successively in the same equipment using the same main component material. By changing the concentration of impurities to be mixed into the semiconductor layer,
Two types of semiconductor layers having different electrical resistances can be easily formed. Furthermore, since these semiconductor layers are formed by vapor deposition, their film quality is also uniform. Therefore, the detection accuracy of the strain sensor can be further improved, and furthermore, it can greatly contribute to reducing production costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the use of a conventional strain gauge. FIG. 2 is a schematic cross-sectional view showing one embodiment of the present invention. FIG. 3 is an equivalent circuit diagram of the embodiment shown in FIG. 2. Figure 4 shows
FIG. 3 is a vertical cross-sectional view showing a specific structure of a pressure sensor to which the embodiment shown in FIG. 2 is applied. FIG. 5 is an equivalent circuit diagram of still another embodiment of the present invention. In the figure, 14, 35, 51 are strain-receiving structural members, 17 is a strain-sensitive resistive thin film layer, 18 is a first semiconductor resistive thin film layer as a first region, 19, 61, 6
Reference numerals 2, 63, and 64 indicate second semiconductor resistor thin film layers as a second region, and 21a and 21b indicate electrodes.

Claims (1)

[Scope of Claims] 1. A strain-receiving structural member that generates strain in response to applied force; and a strain-receiving structural member formed directly on the strain-receiving structural member by vapor deposition,
and a strain-sensitive resistance layer whose electrical resistance changes in accordance with the strain; and a plurality of electrode layers formed on the strain-sensitive resistance layer, the strain-sensitive resistance layer being connected to the strain-sensitive structural member. a first semiconductor layer formed on the side of the electrode layer and having a first electrical resistance; a second semiconductor layer formed on the electrode layer side and having a second electrical resistance lower than the first electrical resistance; a second semiconductor layer containing the same semiconductor component as the second semiconductor layer, the electrical resistance of a path passing through at least the strain-receiving structural member between the electrode layers is greater than that of a path passing only through the second semiconductor layer between the electrode layers. A strain sensor characterized by having electrical resistance more than ¹⁰ times higher. 2 The electrical resistivity of the first semiconductor layer is 1×
10 ⁴ Ωcm or more, and the electrical resistivity of the second semiconductor layer is 1×10 ² Ωcm or less, the strain sensor according to claim 1 .