JPH01242901A - Strain gauge structure for load detection - Google Patents

Abstract

PURPOSE:To increase the gauge rate and to reduce the cost by forming three layers on a conductive substrate by a plasma CVD method and using the deposited hydrogenation amorphous silicon semiconductor as a strain gauge main body. CONSTITUTION:Strain gauges 1 are stuck on strain induction parts 14 and 14 of the aluminum-made strain inducer of the Roberval's parallel motion mechanism of the load cell are stuck and joined on the reverse surfaces of their conductive substrates 2 and when strain is generated as shown by an arrow, interfaces among the p, n, and i layers 4-6 of the hydrogenation amorphous silicon thin film 3 are strained mechanically. Then the strain quantities based on the dependence of currents flowing through the interfaces between the p and n layers 4 and 5 and the interface between the n and i layers 5 and 6 upon the strain are outputted and then converted to generate output signals through electric signal lines 9 and 10. Those signals are detected and amplified by a DC ammeter 11 to detect a load such as the weight of a body to be metered which is put in a hopper, etc., thereby sending a signal for the opening operation of a lid body, etc., to a proper controller.

Description

[Detailed Description of the Invention] <Industrial Application Field> The disclosed technology is applicable to the technical field of strain gauges for load detectors used to measure force such as the weight of an object or applied load. belong to

<Summary of the gist> This invention is attached to the strain generating part of a strain-generating body of an aluminum donkey pal mechanism for detecting a load in a load cell, etc., and electrically controls the amount of strain through an amplifier circuit. The invention relates to an amorphous semiconductor strain gauge structure equipped with electrodes having signal lines connected to the device, and in particular, hydrogenated amorphous strain gauges are formed using a plasma CVD method on a conductive substrate connecting one of the electrodes. P layer and n layer of silicon thin film are 1
An invention relating to a strain gauge structure for load detection, which is formed by depositing three layers of thin films with a layer in between, and the top layer of the thin film is provided with electrodes for connecting signal lines such as those made of gold-antimony alloy. It is.

<Prior art> Generally, a load detector such as a load cell measures the amount of weight change via a strain gauge attached to the strain body based on the amount of deflection within the proportional deformation range of the strain body due to weight change. Widely used in various fields.

In other words, the load detector is a weighing device! It is often used as the center of the a-groove, for example, IFx as the detected object.
The material to be measured is introduced into the weighing hopper by converting the weight change of the hopper into the amount of deflection of the flexure element within a proportional change range, and using the electrical resistance change due to the change in deflection of the strain gauge attached to the flexure element. The load detector occupies an important position in a series of operations such as measuring weight, operating a motor etc. by a control device, and opening a lid etc. of the weighing hopper.

By the way, conventionally, the above-mentioned load detector is made by forming a strain-generating body made of aluminum alloy or the like into a predetermined shape, and pasting strain gauges on both the upper and lower surfaces of the strain-generating body using appropriate adhesive means. Paste 2 sheets each on the top and bottom surfaces.

The structure is such that a Wheatstone bridge circuit is formed by the attached strain gauges.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional load detector, when the strain gauge is attached to the strain-generating body via adhesive means, air bubbles may be mixed in, causing the strain gauge to become distorted. If the strain gauge is not integrated with the strain body and the strain body is bent during measurement, the strain gauge may not be able to accurately follow the strain body, which may lead to a decrease in accuracy.

Furthermore, in addition to requiring considerable skill and complicated processes to bond the strain gauge to the strain-generating body, the resistance value and
Although it is difficult to process for the purpose of improving sensitivity, strain gauges formed by repeatedly meandering a thin metal wire to increase the length are attached to the upper and lower surfaces of the strain generating part of the strain body, and the compression must be measured from both the side and the tension side,
It also had the disadvantage of increased manufacturing costs.

Of course, a highly sensitive strain gauge is required in order to detect the load using a load cell or the like as described above with high precision.

Among electrical resistance strain gauges, conventional metal foil strain gauges have a low strain sensitivity of about 2 in terms of gauge factor, whereas recently developed hydrogenated amorphous silicon thin films such as NLL and P In the case of a strain gauge made of a single layered thin film, the strain sensitivity of the gauge factor is about four layers at most, and therefore it cannot be said to be highly sensitive.

<Object of the Invention> The object of the invention is to provide a strain gauge which is attached to the strain generating part of the strain body of a load detection device such as a load cell based on the above-mentioned prior art and which converts the amount of strain into an electrical signal and outputs it to an amplifier circuit. The problem is considered a technical problem to be solved, and the sensitivity of the gauge factor is significantly increased, manufacturing is easy and low cost, and durability is improved. The present invention aims to provide a strain gauge structure for load detection.

<Means/effects for solving the problems> In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims, is based on the above-mentioned purpose. The silane gas is decomposed through glow discharge using the CVD method, and the 0-layer thin film is formed by doping by introducing diborane gas, the i-layer is formed only by silane gas, and the 0-layer thin film is formed by doping by introducing phosphine gas. Three layers of hydrogenated amorphous silicon thin films are stacked, electrodes are formed between the top thin film and the conductive substrate, and electrical signal lines made of copper-nickel alloy are connected to determine the gauge factor. Distortion sensitivity is 100-12
This technique employs technical means to selectively use forward bias and reverse bias characteristics to perform various measurements without having a sensitivity as high as 0.

<Embodiment - Configuration> Next, one embodiment of the present invention will be described below with reference to the drawings.

In the embodiment shown in FIG. 1, reference numeral 1 denotes a strain gauge for load detection, which is the central point of the invention, and is used, for example, in a load cell for weight measurement, and is attached to the top surface of a conductive substrate 2 made of stainless steel and rA. As will be explained in detail, three layers of hydrogenated amorphous silicon IIH3 are formed by stacking and depositing them by plasma CVD. N layers are formed and laminated to predetermined thicknesses of 0.05 micrometers, 0.8 micrometers, and 0.057198 meters, respectively, and an upper layer of gold-andimony alloy is formed on top of the top layer 6. An electrode 7 is formed in the form of a thin film of 0.15 micrometers, etc., and an electric signal line is connected to the upper electrode 7 and the conductive substrate 2 via a well-known appropriate conductive adhesive 8.8. 9.10 is connected to the DC voltage power source 12 in a forward bias state via a DC ammeter 11 for output display, and the strain gauge 1 is connected to the donkey pal mechanism of the load cell as shown in FIG. The back surface of the conductive substrate 2 is integrally bonded to the strain-generating portions 14, 14, etc. of the strain-generating body 13 made of aluminum or the like via an epoxy adhesive or the like.

In addition, in the embodiment shown in FIG. 8, four strain generating parts 14, 14,
Four strain gauges 1.1.1.1 are attached to the surface of ..., but in this invention, as mentioned above, since the gauge factor is extremely high with a maximum of 100 to 120, - It is sufficiently practical to attach two strain gauges 1.1 only to the surface of the 5th side.

Regarding the strain sensitivity characteristics of the three-layer hydrogenated amorphous silicon 3 formed by the plasma CVD method, see Section 9.1.
As shown in figure 0, the applied voltage is 0.1 volt, O:O
12 volts, M: 0.3 volts, ■: 0.4 volts, B: 0.6 volts, bias on the horizontal axis, current change as sensitivity/initial current (current change rate, i.e. sensitivity) % on the vertical axis, it can be seen that the strain sensitivity changes depending on the power supply voltage in the forward bias state shown in Figure 9, where the p layer is at a positive potential and the n layer is at a negative potential. It has been found that the desired strain sensitivity can be obtained by manipulating , and conversely, in a reverse bias state where the p-layer side is set to a negative potential and the n-layer side is set to a positive potential, as shown in Figure 10, Since the distortion sensitivity is a constant characteristic that does not depend on the power supply voltage, stable measurements can be obtained even under poor conditions where the power supply voltage fluctuates, and therefore forward bias and reverse bias characteristics can be obtained. By selectively using these, measurements for various purposes can be performed.

Therefore, the load detection strain gauge 1 shown in FIG.
The manufacturing process will be briefly explained with reference to FIGS. 2 to 7. First, as shown in FIG. It is set in a predetermined position on the electrode 16, 5iHa (silane) gas is introduced into the vacuum vessel 15, and a glow discharge is caused inside the vacuum vessel 15 via the electrodes 16 and 16' by a power source to decompose the silane gas.

Then, the well-known plasma CVD process is applied to the upper surface of the conductive substrate 2.
In forming a hydrogenated amorphous silicon thin film by the method, as shown in Fig. 3, 82H6 (diporan) is first mixed with P<5iHa (silane) gas to form the p layer.
In the p layer formed by introducing gas and doping treatment, B (boron) atoms are incorporated into Si (silicon) atoms, resulting in a hydrogenated amorphous silicon with a thickness of 0.05 mm.
A thin film semiconductor 4 with a pH of micrometers is formed.

Next, as shown in FIG. 4, glow discharge is performed with only 5it-(a (silane) gas introduced) to form the i-layer into a predetermined thin film with a thickness of 0.8 micrometers without any doping treatment. 5, and then, as shown in FIG.
Doping treatment is performed by introducing iH4 (silane) gas and PH3 (phosphine) gas together, and P (phosphorus) atoms are incorporated into Si (silicon) atoms, resulting in a thickness of 2k0.
A predetermined thin layer 6 of 0.05 micrometers is formed.

In addition, each S! introduced into the vacuum container 15! H4 (silane) gas, B2H6 (diborane) gas, PH3 (phosphine)
Regarding the gas, the valves are switched as appropriate without breaking the vacuum state, and the p layer-1 layer-n layer is formed on the conductive substrate 2.
The layers are deposited in sequence.

Incidentally, when forming such a hydrogenated amorphous semiconductor 3, a three-layer junction structure of p layer-1 layer-n layer is used, that is, a structure in which one layer is interposed between the p layer and the n layer. There is a need.

In this way, when the thin film 3 of hydrogenated amorphous silicon semiconductor is formed to a predetermined thickness on the top of the conductive substrate 2, the vacuum condition in the vacuum container 15 is released and a sample of the laminate is taken out. As shown in Figure 6, Sen's vacuum lid @ device 1
6, and a gold-antimony alloy containing 1% antimony is bonded to the top of the 0 layer 6 of the hydrogenated amorphous silicon semiconductor 3 by integral vapor deposition to a predetermined thickness using a well-known vacuum evaporation method. accumulate.

After that, the seventh
As shown in the figure, a conductive adhesive 8.8 such as silver paste is applied to the upper surface of the upper electrode 7 made of gold-antimony alloy and the upper surface of a predetermined portion of the conductive substrate 2, so that the copper-nickel alloy wire is electrically connected. Signal lines 9 and 10 are connected and extended to form a load detection strain gauge 1.

In this way, the vacuum container 15 is
Three layers of amorphous semiconductor thin film 3 are deposited on a conductive substrate 2 in the following manner: 0 layers, 4 layers, 1 layers, 5 layers, and 6 layers.

Note that in the above embodiment, p is first placed on the conductive substrate 2.
In this example, we deposited a layer, then an i layer, and then an n layer, but it is also possible to stack the n layer first, then the i layer, and finally the p layer, but the p layer Since there is a problem with the combination of stainless steel and the n-layer making electrical ohmic contact with the gold-antimony alloy, when stacking the n-layer-1@-p layer with IIFt, It is preferable to carry out this process after investigating whether stainless steel and gold-antimony alloy are an appropriate material combination for the lower electrode and the upper electrode, that is, whether ohmic contact will occur.

If it is not suitable, it is necessary to use another suitable chemical compound material.

<Embodiment - Effect> In the above configuration, as shown in FIG. 8, the strain generating portion 14 of the aluminum strain body 13 of the donkey pal mechanism of the load cell.
14 (...), the strain gauge 1 is attached to the back side of the conductive substrate 2 using epoxy adhesive, and if a strain as shown in the first solid arrow occurs, the hydrogen List of amorphous silicon thin films 3 II! Mechanical strain will be applied to the interface of 0 layer 4.5.6.
Due to the dependence of the current flowing through the interface between layer 1 5 and interface between layer i 5 and layer 0 6 on strain, the amount of strain is output, converted, and output via electrical signal line 9.10. A signal is generated.

Then, the output signal is detected by the DC ammeter 11, and similarly to the conventional method, it is detected by, for example, a Wheatstone bridge, and the output is amplified. A load such as weight is detected, and a signal for opening the lid can be sent to an appropriate control device.

It goes without saying that the embodiments of the present invention are not limited to the above-mentioned embodiments. For example, when a strain gauge is attached to the strain-generating portion of the strain-generating body without forming a donkey-pal mechanism, the strain-generating body When the strain gauge itself is used as the lower electrode, parts other than the strain gauge are masked and formed in the order of p layer - 1ll - n layer (upper electrode), or when the strain body is not used as the lower electrode, the strain gauge If the body is made of a metal such as dielarmine, it is coated with an insulating film in advance, and then the parts other than the strain gauge are masked and stacked in the order of p layer (lower electrode) - layer 1 - layer n (upper electrode). Or, if the strain body is made of a non-metal such as glass, an n-layer (
Various embodiments can be adopted, such as forming the layer in the order of (lower electrode) - 1 layer=n layer (upper electrode).

Furthermore, although there are various modes of applying strain to the strain gauge, the mode of the above-mentioned embodiment is considered to be the simplest, stable, and highly reproducible.

<Effects of the Invention> As described above, according to the present invention, plasma CV
By using a hydrogenated amorphous silicon semiconductor strain gauge body in which the p-layer and n-layer are laminated in a thin film form via the i-layer using the D method, the strain sensitivity of the gauge factor can be increased to 1.
00 to 120, the sensitivity is extremely high, and an excellent effect is achieved in that load detection can be performed with extremely high accuracy.

Therefore, by selectively adopting the forward bias and reverse bias states as shown in Figure 9.10, by manipulating the power supply voltage, and by controlling the power supply voltage to fluctuate. By selectively using electrical forward and reverse characteristics that enable stable measurements even under adverse conditions, it is possible to flexibly select measurement applications.

By forming a thin film of hydrogenated amorphous silicon semiconductor on the strain gauge body by plasma CVD, the manufacturing cost can be lowered and it is easier to manufacture than conventional crystalline semiconductor strain gauges. It has the effect of being durable.

Further, since a design can be adopted in which the electrode and the strain body can be used in common, the effect that the electric signal line can be easily taken out is achieved.

Furthermore, since the strain sensitivity is extremely high, it is easy to control the strain sensitivity, and therefore, there is also a flexible effect in that strain measurement can be selected depending on the application.

[Brief explanation of the drawing]

The drawings are explanatory diagrams of one embodiment of the present invention, in which Fig. 1 is a schematic perspective view of the overall structure, Figs. The figure is a schematic perspective view of how a strain gauge is attached to a strain-generating body, and Figures 9 and 10 are characteristic graphs of current change rate with respect to strain due to forward bias and reverse bias. 13... Strain body, 14... Strain generation part, 9.10.
...Signal line, 3...p-1-n junction, 1...strain gauge,
4.5.6...Hydrogenated amorphous silicon thin film, 4
...0 layer, 6...n layer, 5...1@, 7
... Electrode, 2... Conductive substrate Fig. 2 Fig. 4 1516゛ Fig. 6 Fig. 3 Fig. 5 Fig. 7 Prisoner ■ Clan

Claims (1)

[Claims] (1) In an amorphous semiconductor strain gauge structure that has an electrode attached to the strain generating part of a strain-generating body for load detection and that connects a signal line, a hydrogenated amorphous silicon thin film is formed on a conductive substrate that has an electrode. A strain gauge structure for load detection, characterized in that a layer and an n layer are laminated into three thin film layers via an i layer, and an electrode for connecting a signal line is provided on the top layer of the thin film. .