JPH06307950A - Strain sensor - Google Patents

Abstract

PURPOSE:To provide a miniature strain sensor in which the connection of operating circuit part is facilitated while preventing the influence of noise. CONSTITUTION:The strain sensor comprises a strain gauge bridge circuit pattern 12 formed at a deforming part on the surface of a beam body 11 subjected to load by thin film process, a wiring pattern 13 formed on the surface of the beam body by thin film process while being separated from the bridge circuit pattern, and an operating circuit part 14 comprising an amplifying circuit, a low-pass filter, an A/D converter, etc., arranged on the wiring pattern 13 while connecting the I/O terminals thereof with the bridge circuit pattern and the wiring pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain sensor using a strain gauge bridge circuit.

[0002]

2. Description of the Related Art Conventionally, as a strain sensor using a strain gauge bridge circuit, for example, JP-A-57-9322 is known.
What is found in Japanese Patent Publication No. 0 is known. As shown in FIG. 6, the strain gauge bridge circuit 2 is directly formed as a pattern on the surface of the beam body 1 by a thin film process as shown in FIG.

In this publication, an amplifier circuit, a low-pass filter, an A / D converter and the like are separately arranged on a printed circuit board, the output terminal of the strain gauge bridge circuit 2 of the beam body 1 and the circuit on the printed circuit board. It was designed so that the output of the strain sensor could be obtained by connecting and with lead wires.

Further, the one found in Japanese Patent Laid-Open No. 58-29441 is known. As shown in FIG. 7, the strain gauge bridge circuit 4 is directly formed as a pattern on the surface of the beam body 3 by a thin film process, the semiconductor chip 5 for the amplifier circuit is arranged, and the electrode lead pattern of the bridge circuit 4 and the amplifier circuit are used. The semiconductor chip 5 is connected by wire bonding, and the output of the amplifier circuit is taken out to the outside.

[0005]

However, in the former case, the strain gauge bridge circuit 2 of the beam body 1 and the circuit on the printed circuit board must be connected by lead wiring, which makes the wiring connection work troublesome. In addition, since a printed circuit board is separately provided, the device becomes large in size, and the signal taken out from the strain gauge bridge circuit 2 by the lead wiring becomes an analog signal, which is susceptible to noise.

In the latter case, since the electrode lead pattern of the bridge circuit 4 and the semiconductor chip 5 for the amplifier circuit are connected by wire bonding, gold is required for the pattern, resulting in high cost and circuits other than the amplifier circuit. Need to be arranged externally, so that the device becomes large in size, and the signal taken out from the amplifier circuit to the outside becomes an analog signal and is susceptible to noise.

Therefore, the present invention can realize miniaturization by arranging an arithmetic circuit section such as an amplifier circuit, a low-pass filter and an A / D converter together with a strain gauge bridge circuit pattern on the beam body, and also an amplifier circuit and a low-pass filter. And the arithmetic circuit unit such as the A / D converter can be easily connected and the cost can be reduced.
Moreover, the present invention intends to provide a strain sensor capable of reliably preventing the influence of noise.

[0008]

The invention according to claim 1 is
The strain gauge bridge circuit pattern formed by the thin film process on the deformed portion of the surface of the beam on which the load acts, and the wiring pattern formed separately on the surface of the beam body by the thin film process from the bridge circuit pattern, and on this wiring pattern The input / output terminals are connected to the bridge circuit pattern and the wiring pattern and arranged, and an arithmetic circuit section including an amplifier circuit, a low-pass filter, an A / D converter, and the like is provided.

According to a second aspect of the present invention, a metal or ceramic elastic body substrate formed by separating the strain gauge bridge circuit pattern and the wiring pattern by a thin film process, and having the same coefficient of thermal expansion as this substrate, are modified. The strain gauge of the bridge circuit is located on the part of the beam body to which the elastic substrate is adhered or joined, and on the wiring pattern, the input and output terminals are arranged to be connected to the bridge circuit output terminal and the wiring pattern. , An amplifier circuit, a low-pass filter, an A / D converter, and the like.

[0010]

In the present invention having such a structure, the arithmetic circuit section including the amplifier circuit, the low-pass filter, the A / D converter and the like is arranged on the wiring pattern, and its input and output terminals are formed on the bridge circuit pattern and the wiring pattern. Just connect. The signal extracted from the beam body to the outside is a digital signal by the A / D converter and is not easily affected by noise.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a beam body 11 made of, for example, a duralumin material (A2023 and A2024 material).
The strain gauge bridge circuit pattern 12 is formed such that the strain gauge is located on the deformed portion of the surface of the device by the thin film process. A wiring pattern 13 is formed on the surface of the beam body 11 by a thin film process, separately from the bridge circuit pattern 12.

That is, after forming an insulating layer such as a polyimide resin on the surface of the beam body 11, N is formed by a thin film process.
The strain gauge bridge circuit pattern 12 is formed by the strain gauge pattern formed of the i-Cr-Si thin film layer, the temperature correction pattern formed of the Ti layer, and the lead pattern formed of the Cu layer, and the wiring pattern 13 formed of the Cu layer is simultaneously formed.

Then, as shown in FIG. 3, the bridge circuit pattern 12 is provided with input and output terminals on the wiring pattern 13.
Also, an arithmetic circuit unit 14 including an amplifier circuit, a low-pass filter, an A / D converter, and the like is arranged in connection with the wiring pattern 13. The low-pass filter uses a digital filter, and the A / D converter uses a ΣΔ A / D converter.

The arithmetic circuit section 14 has a configuration as shown in FIG.
In the chip configuration, the input and output terminals of the chip are connected to the lead pattern of the strain gauge bridge circuit pattern 12 and the wiring pattern 13 by cream solder.

The beam body 11 has a Roberval mechanism, two holes 15 and 16 are made to communicate with each other through a communication groove 17 in the side surface, and thin portions 18 and 19 thereof are used as deformation portions.

In the embodiment having such a structure, since the lead pattern and the wiring pattern 13 of the strain gauge bridge circuit pattern 12 are formed of the Cu layer, the arithmetic circuit section 14 uses cream solder and the strain gauge is formed by a solder flow or the like. It can be easily connected to the lead pattern of the bridge circuit pattern 12 and the wiring pattern 13. That is, the connecting work is simpler than that using lead wiring or wire bonding.

Further, in the case of connection using wire bonding, Au must be used as the material of the lead pattern and the wiring pattern, but in this embodiment, the material of the lead pattern and the wiring pattern is Cu, and the cost is reduced. Can be planned.

Further, an amplifier circuit, a low-pass filter, an A / D
Since the arithmetic circuit unit 14 including a converter and the like is arranged on the beam body 11 in a one-chip configuration, it is not necessary to separately provide a circuit board, and the overall size can be reduced.

Further, the processing for amplifying the analog output from the strain gauge bridge circuit pattern 12 and converting it into a digital signal is all performed on the beam body 11.
The signal output from the beam body 11 to the outside is a digital signal resistant to noise. Therefore, the influence of noise can be reliably removed and the accuracy can be improved.

As the arithmetic circuit section 14, an amplifier circuit,
In addition to the low pass filter and the A / D converter, a gate array or a microcomputer may be provided.
In this way, data processing can also be performed on the beam body 11.

When such a strain sensor is incorporated in a scale, the circuit section on the scale main body side and the output terminal of the arithmetic circuit section 14 are connected by a cable. In this case, a connector may be attached to the tip of the cable so that it can be freely connected and disconnected. A flexible cable may be used as the cable.
And the connection with the wiring pattern 13 of the cable is performed by cream solder.

An arithmetic circuit unit 14 for the beam body 11 is also provided.
It is necessary that the arrangement position of (1) and the connection position of the cable with respect to the wiring pattern 13 are on the fixed side of the beam body 11 to the main body of the scale so as not to affect the distortion of the beam body 11 against the load.

Next, another embodiment of the present invention will be described with reference to the drawings. The same parts as those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The one shown in FIG. 4 is one in which the arithmetic circuit section is composed of three chips of an amplifier circuit chip 21, a low-pass filter chip 22 and an A / D converter chip 23. The amplifier circuit chip 21 is a strain gauge bridge circuit pattern 12. Of the lead pattern and the wiring pattern 24 are connected by cream solder, the low-pass filter chip 22 is connected to the wiring pattern 24 and the wiring pattern 25 by cream solder, and the A / D converter chip 23 is connected by the wiring pattern 25 and the wiring pattern. It is connected to 26 with cream solder.

Also in this embodiment, the chips 21 to 23 are arranged on the beam body 11, and the chips 21 to 21 are arranged.
23 with cream solder, the lead pattern and wiring pattern 24 of the strain gauge bridge circuit pattern 12 to
Since it is connected to No. 26, the same effect as the above-mentioned embodiment can be obtained.

In FIG. 5, a strain gauge bridge circuit pattern 12 and a wiring pattern 13 are separately formed on a metal or ceramic elastic substrate 27 by a thin film process, and the same heat as the elastic substrate 27 is used. The deformed portion of the beam body 31 having the expansion coefficient, that is, the thin portion 1
8 and 19 are the strain gauge bridge circuit patterns 1
The elastic substrate 2 so that the strain gauge 2 is positioned
Glue 7.

Then, the arithmetic circuit chip 14 is placed on the wiring pattern 13, and the output terminals are connected to the bridge circuit pattern 12 and the wiring pattern 13 by cream solder and arranged.

For example, the beam body 31 is made of a duralumin material (A
2023 and A2024 material), the elastic substrate 2
7 also uses a duralumin material (A2023 and A2024 material). The elastic substrate 27 is bonded and fixed by using an adhesive such as an epoxy resin. A filler made of fine ceramic powder may be mixed with the adhesive in order to obtain stability after adhesion.

The metallic elastic substrate 27 and the beam body 3 are also provided.
If 1 is a material having heat resistance such as a stainless material, gold may be formed on each surface by plating or the like, and then they may be joined by applying pressure while heating.

A step portion 31a is formed on the upper surface of the beam body 31, and the elastic substrate 27 is positioned by the step portion 31a.

In this way, the strain gauge bridge circuit pattern 12 and the wiring pattern 13 are formed on the metal elastic substrate 27, the arithmetic circuit chip 14 is connected by cream solder, and the metal elastic substrate 27 is placed on the beam member 31. Since it is adhered to the beam body 31, the arithmetic circuit unit chip 14 is arranged on the beam body 31 even in this case, and the same effect as that of the above embodiment can be obtained.

[0033]

As described above, according to the present invention, the amplification circuit together with the strain gauge bridge circuit pattern on the beam body,
By arranging an arithmetic circuit unit such as a low-pass filter and an A / D converter, downsizing can be realized, and a strain gauge bridge circuit pattern and a wiring pattern of the arithmetic circuit unit such as an amplifier circuit, a low-pass filter and an A / D converter can be formed. The connection can be facilitated and the cost can be reduced, and since the signal is output as a digital signal, the influence of noise can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention before mounting an arithmetic circuit unit chip.

FIG. 2 is a diagram showing a shape of an arithmetic circuit unit chip in the embodiment.

FIG. 3 is a perspective view after mounting the arithmetic circuit unit chip of the embodiment.

FIG. 4 is a perspective view showing another embodiment of the present invention.

FIG. 5 is an exploded perspective view showing another embodiment of the present invention.

FIG. 6 is a perspective view showing a conventional example.

FIG. 7 is a perspective view showing a conventional example.

[Explanation of symbols]

 11 ... Beam body 12 ... Strain gauge bridge circuit pattern 13 ... Wiring pattern 14 ... Arithmetic circuit unit

Claims (2)

[Claims] 1. A strain gauge bridge circuit pattern formed by a thin film process on a deformed portion of the surface of a beam body on which a load acts, and a wiring pattern formed on the surface of the beam body by a thin film process separately from the bridge circuit pattern. And an arithmetic circuit section including an amplifier circuit, a low-pass filter, an A / D converter, etc., in which input and output terminals are connected to the bridge circuit pattern and the wiring pattern and arranged on the wiring pattern. Strain sensor to do. 2. A metal or ceramic elastic substrate formed by separating a strain gauge bridge circuit pattern and a wiring pattern by a thin film process, and a strain gauge bridge having the same coefficient of thermal expansion as that of the substrate. A beam body having its elastic substrate bonded or joined so that the strain gauge of the circuit is positioned, and on the wiring pattern, the input and output terminals are arranged by connecting to the bridge circuit pattern and the wiring pattern, and an amplifier circuit, A strain sensor having an arithmetic circuit unit including a low-pass filter and an A / D converter.