JP2003130716A - Strain detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain detector in which water does not reach a strain resistance element and which exhibits an always stable output characteristic. SOLUTION: A first protective layer 20 is installed so as to cover the surface of an insulating board 11 and surfaces of strain resistance elements 17, and a second protective layer 30 is installed so as to cover the surface of the layer 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain detecting device for detecting strain generated by applying a load.

[0002]

2. Description of the Related Art As a conventional strain detecting device of this type, one disclosed in Japanese Patent Laid-Open No. 8-87375 is known.

A conventional strain detecting device will be described below with reference to the drawings.

FIG. 8 is a top view of a conventional strain detecting device, and FIG. 9 is a side sectional view of the strain detecting device.

In FIGS. 8 and 9, reference numeral 1 denotes an insulating substrate made of an elastic material. The insulating substrate 1 is formed by providing an insulating layer 3 on the upper surface of a stick member 2. Reference numeral 4 denotes four strain resistance elements. The strain resistance element 4 is provided on the upper surface of the insulating substrate 1, and the strain resistance element 4 is provided with a pair of power supply electrodes 5, a pair of output electrodes 6 and a pair of G electrodes.
A bridge circuit is configured by being electrically connected to the ND electrode 7. Reference numeral 8 denotes a resin protective layer, and the protective layer 8 is provided so as to cover the upper surface of the strain resistance element 4, the power supply electrode 5, the pair of output electrodes 6, the pair of GND electrodes 7 and other insulating substrates 1. There is.

The operation of the conventional strain detector having the above structure will be described below.

When a shearing load is applied from the upper surface of the insulating substrate 1 at substantially the center, the insulating substrate 1 is subjected to the shearing load.
A bending moment is generated in the four strain resistance elements 4 provided on the upper surface of the insulating substrate 1 by the bending moment.
A bending moment is also generated. When a bending moment is generated in the strain resistance element 4, the resistance value of the strain resistance element 4 changes. Therefore, the change in the resistance value is output to an external computer (not shown) or the like by the pair of output electrodes 6 and the insulating substrate 1
The load applied to is measured.

[0008]

However, in the above conventional structure, the insulating substrate 1, the pair of power supply electrodes 5,
Since only the protective layer 8 made of resin is provided on the upper surfaces of the pair of output electrodes 6 and the pair of GND electrodes 7, the protective layer 8 made of resin absorbs a small amount of water, and high humidity When the strain detecting device is used for a long time in the atmosphere, water reaches the strain resistance element 4 and the resistance value of the strain resistance element 4 varies, so that the output of the strain detecting device becomes unstable. Had challenges.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a strain detecting apparatus having a stable output characteristic without water reaching the strain resistance element. .

[0010]

In order to achieve the above object, the present invention has the following constitution.

According to the first aspect of the present invention, a frame GND electrode electrically connected to the stainless plate is provided on the upper surface of the stainless plate of the substrate, and the frame GND electrode and the GND electrode are electrically connected. The frame GND electrode electrically connected to the stainless plate is provided on the upper surface of the stainless plate, and since the frame GND electrode and the GND electrode are electrically connected, static electricity is applied to the GND electrode. Even so, since the electrostatic charge flows to the GND through the frame GND electrode and the stainless plate, it has an effect of preventing the dielectric breakdown of the insulating layer.

Further, the invention according to claim 2 is one in which a capacitor and an electrostatic discharge resistor are electrically connected in parallel between the frame GND electrode and the GND electrode, and the stainless plate is provided on the upper surface of the stainless plate. Since a frame GND electrode that is electrically connected is provided and a capacitor and a resistance for electrostatic discharge are electrically connected in parallel between the frame GND electrode and the GND electrode, even if static electricity is applied to the GND electrode. The electrostatic charge is absorbed by the capacitor, which keeps the electrostatic voltage low.
It is possible to prevent the dielectric breakdown of the insulating layer, and to discharge the electric charge accumulated in the capacitor by the electrostatic discharge resistance to reduce the potential difference between the GND electrode and the frame GND electrode to zero and separate the stainless plate and the GND electrode. Since the system is used, even if the potential of the stainless plate fluctuates, G
The potential of the ND electrode does not fluctuate, which has the effect of stabilizing the output signals from the pair of output voltages.

According to a third aspect of the present invention, a capacitor is connected between the power supply electrode and the GND electrode and between the pair of output electrodes and the GND electrode, respectively, and the capacitor is connected between the power supply electrode and the GND electrode. , The capacitors are connected between the pair of output electrodes and the GND electrode, respectively. Therefore, even if static electricity is applied to each electrode, the electrostatic charges are absorbed by the respective capacitors, which causes static electricity to be absorbed. Since the voltage can be suppressed to a low level, an excessive current does not flow in the strain resistance element, and as a result, the resistance value of the strain resistance element is stabilized.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A strain detecting apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a top view of a strain detecting device according to an embodiment of the present invention, FIG. 2 is a side sectional view of a position where a strain resistance element is provided in the strain detecting device, and FIG. 3 is each of the strain detecting device. FIG. 4 is a side cross-sectional view of a position where an electrode is provided, and FIG. 4 is a top view showing a state where a conductive adhesive is provided in a slit portion of an insulating substrate in the strain detection device.

1 to 4, reference numeral 11 denotes an insulating substrate made of an elastic material. The insulating substrate 11 is a stainless steel plate 12 containing aluminum, and a protective film 13 made of alumina provided on the upper surface of the stainless steel plate 12. And an insulating layer 13 made of glass provided on the upper surface of the protective film 13.
and a. On the upper surface of the insulating substrate 11, a silver power electrode 14, a pair of output electrodes 15, G
A bridge circuit is configured by providing the ND electrode 16 and the four strain resistance elements 17 so as to be electrically connected by the circuit pattern 18. Further, the insulating substrate 11
At least a pair of temperature characteristic adjusting resistors 19 are provided on the upper surface of the, and one end of the temperature characteristic adjusting resistors 19 is electrically connected to the power supply electrode 14 and the other end is connected via a pair of resistance value measuring electrodes 20. Electrically connected to the strain resistance element 17. Reference numeral 21 is a frame GND electrode, and the frame GND electrode 21 is provided on the upper surface of the stainless plate 12, and the frame GND electrode 21 and the GND are connected to each other.
A capacitor 22 and an electrostatic discharge resistor 23 are electrically connected in parallel with the electrode 16 via a circuit pattern 18. Further, the circuit pattern 18 on the insulating substrate 11 is provided with a slit portion 24 so as to disconnect a part of the circuit pattern 18, and is located in the slit portion 24 and electrically connected to the circuit pattern 18. A pair of silver slit electrodes 25 are provided, and a conductive adhesive 26 is provided so as to electrically connect the pair of slit electrodes 25. A first plating layer 27 made of nickel is provided on the upper surfaces of the power supply electrode 14, the pair of output electrodes 15, and the GND electrode 16, and a second plating layer 27 made of solder is provided on the upper surface of the first plating layer 27. Plating layer 28 is provided. Further, the four strain resistance elements 17 provided on the upper surface of the insulating substrate 11 are separated, and the two narrow pairs of strain resistance elements 17 are located between the strain resistance elements 17 and the narrow portion is formed on the insulating substrate 11. 11
a is provided. Reference numeral 29 denotes a first protective layer made of glass, and the first protective layer 29 includes the insulating substrate 11, at least the strain resistance element 17, and the pair of temperature characteristic adjusting resistors 19.
Is provided so as to cover the upper surface of the. 30 is a second protective layer made of resin, and the second protective layer 30 is the first protective layer 2
It is provided so as to cover the upper surface of 9. In addition, the insulating substrate 1
A capacitor 22 is connected between the power electrode 14 and the GND electrode 16 provided on the upper surface of the capacitor 1, and between the pair of output electrodes 15 and the GND electrode 16, respectively.

With respect to the strain detecting device in the embodiment of the present invention configured as described above, the assembling method thereof will be described below.

First, glass paste (not shown) is formed on the upper surface of the stainless steel plate 12 containing aluminum in advance.
After printing, the insulating substrate 11 is formed by baking at about 850 ° C. for about 10 minutes.

Next, a metal glaze paste (not shown) is printed on the upper surface of the insulating substrate 11 at a position where the strain resistance element 17 and the electrostatic discharge resistance 23 are provided, and then about 1
Dry at 30 ° C. for about 10 minutes.

Next, a thermistor resistance paste (not shown) is applied to the temperature characteristic adjusting resistor 19 on the upper surface of the insulating substrate 11.
After printing at the position where the
By firing at 0 ° C. for about 10 minutes, four strain resistance elements 17, an electrostatic discharge resistance 23 and a temperature adjustment resistance 19 are formed on the insulating substrate 11.

Next, a silver paste (not shown) is printed on the upper surface of the insulating substrate 11, and the paste is printed at about 600 ° C. for about 1 hour.
After firing for 0 minutes, the power electrode 1 is formed on the upper surface of the insulating substrate 11.
4, a pair of output electrodes 15, GND electrode 16, resistance value measuring electrode 20, circuit pattern 18, frame GND electrode 21
And the slit electrode 25 is formed.

At this time, although the upper surface of the stainless steel plate 12 containing aluminum in the insulating substrate 11 is likely to be oxidized by heat, the protective film 13 made of alumina is formed on the upper surface of the stainless steel plate 12, and this alumina is used. Since the protective film 13 made of is extremely stable against heat, the strain resistance element 1 is formed on the upper surface of the insulating substrate 11.
7, power supply electrode 14, output electrode 15 and GND electrode 16
When the insulating substrate 11 is exposed to a high temperature during firing, the inside of the stainless steel plate 12 is not oxidized, and as a result, the elastic characteristics of the insulating substrate 11 are stabilized, and This has the effect of stabilizing the output of the detection device.

Next, the power supply electrode 14 of the insulating substrate 11,
After printing a paste (not shown) made of glass on the upper surface of the insulating substrate 11 excluding the pair of output electrodes 15, GND electrodes 16, resistance value measuring electrodes 20, and slit electrodes 25,
By firing at about 600 ° C. for about 10 minutes, the first protective layer 29 is formed on the upper surface of the insulating substrate 11.

Next, the power supply electrode 14 is connected to a power supply (not shown) to apply a voltage, and the GND electrode 1
In a state where 6 is grounded, the ambient temperature of the insulating substrate 11 is changed and the pair of temperature characteristic adjusting resistors 19 are trimmed so that the output changes due to the temperature change of the pair of output electrodes 15 become equal to each other.

Next, a resin paste (not shown) is printed on the upper surface of the insulating substrate 11 provided with the first protective layer 29, and the paste is baked at about 200 ° C. for 30 minutes, whereby the insulating substrate 11 is covered. The second protective layer 30 is formed on the upper surface.

Next, the power supply electrode 14 and the pair of output electrodes 15
After the first plating layer 27 made of nickel is formed on the upper surface of the GND electrode 16 and the second plating layer 28 made of solder is formed on the upper surface of the first plating layer 27.

In this case, since the slit portion 24 is provided so as to disconnect a part of the circuit pattern 18 and the conductive adhesive 26 is provided at the slit portion 24,
In the process of assembling the strain detection device, the power supply electrode 14, the pair of output electrodes 15, and the GND electrode 16 are made of nickel and are provided in the vicinity of the slit portion 24 without the conductive adhesive 26. After forming the plating layer 27 and the second plating layer 28 made of solder, the conductive adhesive 26 can be provided at the slit portion 24, whereby the power electrode 14 and the pair of output electrodes 1 are provided.
5. Forming the first plating layer 27 and the second plating layer 28 on the power supply electrode 14, the pair of output electrodes 15 and the GND electrode 16 in a state in which the 5 and GND electrodes 16 and the stainless steel plate 12 are not electrically connected. Because you can
The plating does not adhere to the exposed portion of the stainless steel plate 12, and as a result, the plating can be formed only on each electrode, so that the amount of plating adhered to each electrode is stable. Is.

Next, the conductive adhesive 26 is applied to the upper surface of the slit portion 24 provided on the upper surface of the insulating substrate 11 and the end portion of the circuit pattern 18 located near the slit portion 24.

Next, the capacitor 2 is formed so as to connect between the circuit patterns 18 electrically connected to the power electrode 14 and the GND electrode 16 on the upper surface of the insulating substrate 11.
After mounting 2, the circuit pattern 18 and the capacitor 22 are soldered.

Next, after mounting the capacitor 22 so as to connect between the circuit patterns 18 electrically connected to the pair of output electrodes 15 and the GND electrode 16 on the upper surface of the insulating substrate 11, the circuit pattern 18 is formed. And capacitor 22
Solder and.

Finally, after mounting the capacitor 22 so as to connect between the circuit patterns 18 electrically connected to the frame GND electrode 21 and the GND electrode 16 on the upper surface of the insulating substrate 11, the circuit pattern 18 is formed. Solder the capacitor 22.

Next, the operation of the strain detecting apparatus according to the embodiment of the present invention assembled as described above will be described.

When a shear load is applied to the central portion of the insulating substrate 11, the shear load causes strain on the surface of the insulating substrate 11, and the four strain resistance elements 17 provided on the upper surface of the insulating substrate 11 are distorted. Is also distorted. This strain resistance element 1
When the strain occurs in 7, the resistance value of the strain resistance element 17 changes, and thus the change in the resistance value is output from the pair of output electrodes 15 as an bridge circuit to an external computer (not shown). The load applied to the insulating substrate 11 is measured.

Here, considering the case where water adheres to the upper surface of the strain detecting device, in the strain detecting device according to the embodiment of the present invention, the first protective layer 29 made of glass is used.
Since the second protective layer 30 made of resin is provided so as to cover the upper surface of the above, it is assumed that water has penetrated into the second protective layer 30 by using the strain detection device for a long time in a high humidity atmosphere. Also does not pass through the first protective layer 29 made of glass, and as a result, water does not enter the strain resistance element 17, so there is no fluctuation in the resistance value of the strain resistance element 17 due to water, and it is always stable. This has the effect of being able to provide a strain detection device having the above output characteristics.

Since the second protective layer 30 is made of resin, the firing temperature of the second protective layer 30 is as low as about 200.degree.
As a result, when the second protective layer 30 is fired, the resistance values of the strain resistance element 17 and the temperature characteristic adjustment resistor 19 hardly change.

Further, in the strain detecting apparatus according to the embodiment of the present invention, the temperature characteristic adjusting resistor 19 is provided on the upper surface of the insulating substrate 11. However, as shown in FIG. The thermistor 31 may be provided on the upper surface. In the case of the thermistor 31, the insulating substrate 11 is used.
Since it is possible to measure the temperature of the strain resistance element 17 when the strain detection device is used in an atmosphere where the temperature changes.
Even if the resistance value of the strain resistance element 17 changes, the temperature change of the strain resistance element 17 can be detected by the thermistor 31, so that the change of the resistance value of the strain resistance element 17 can be corrected by the counterpart computer (not shown). In addition, it has an effect that the load applied to the strain detecting device can be accurately detected.

Here, the insulating substrate 11 in the strain detecting device
As shown in FIG. 6, when the stress applied to the insulating substrate 11 is rectangular, the bending stress concentrates on the end portion of the insulating substrate 11, so that the elastic coefficient of the insulating substrate 11 deteriorates. However, in the strain detecting apparatus according to the embodiment of the present invention, the four strain resistance elements 17 are separated into two pairs of strain resistance elements 17, and the separated two pairs of strain resistance elements are separated. Each strain resistance element 17 of the element 17
Since the narrow portion 11a is provided on the insulating substrate 11 located between them, when a load is applied to substantially the center of the strain detection device,
Strain appearing on the surface of the insulating substrate 11 is as shown in FIG.
The insulating substrate 11 is dispersed from the end portion toward the narrow width portion 11a, and as a result, the strain is not concentrated on both ends of the insulating substrate 11, so that the insulating substrate 11 is prevented.
There is a margin at the position where the strain resistance element 17 is provided, and the assembling property is improved.

Further, considering the case where a static electricity of 5 kV or more is applied to the GND electrode 16 by touching the GND electrode 16 on the insulating substrate 11 with a human hand,
In the conventional strain detection device, the insulating layer 13a in the insulating substrate 11 may be destroyed, so it is necessary to have a structure in which static electricity is not applied to the GND electrode.
However, in the strain detecting apparatus according to the embodiment of the present invention, the frame GND electrode 21 electrically connected to the stainless steel plate 12 is provided on the upper surface of the stainless steel plate 12, and the frame GND electrode 21 and the GND electrode 16 are provided. Because it is electrically connected to, static electricity is GND
Even if applied to the electrode 16, the electrostatic charge is frame GND.
Since it flows through the electrode 21 to the GND via the stainless steel plate 12, it has an effect that the dielectric breakdown of the insulating layer 13a can be prevented.

Considering a case where static electricity is applied to the stainless steel plate 12 and the potential of the stainless steel plate 12 fluctuates, the upper surface of the stainless steel plate 12 in the strain detecting apparatus according to the embodiment of the present invention. The frame GND electrode 2 electrically connected to the stainless plate 12
1, the frame GND electrode 21 and the GND electrode 1
6 and the capacitor 22 and the electrostatic discharge resistor 23
Are electrically connected in parallel, even if static electricity is applied to the GND electrode 16, the static electricity charge is absorbed by the capacitor 22, which suppresses the static electricity voltage to a low level, so that the insulation breakdown of the insulating layer 13a is caused. Of the GND electrode 1 by preventing the electric charges stored in the capacitor 22 from being discharged by the electrostatic discharge resistor 23.
6 and the frame GND electrode 21 have a potential difference of zero and the stainless plate 12 and the GND electrode 16 are separate systems, the GND electrode 1 does not change even if the potential of the stainless plate 12 changes.
The potential of 6 does not fluctuate, so that the output signals from the pair of output voltages 15 become stable.

Considering the case where static electricity enters from the outside by touching the power supply electrode 14 or the pair of output electrodes 15 on the insulating substrate 11 with a finger, for example, one embodiment of the present invention. In the strain detecting apparatus in 1), the capacitor 2 is provided between the power supply electrode 14 and the GND electrode 16 and between the pair of output electrodes 15 and the GND electrode 16.
Since the two are connected to each other, even if static electricity is applied to the power supply electrode 14 or the pair of output electrodes 15, the static electricity charges are absorbed by the respective capacitors 22, thereby suppressing the static electricity voltage to be low. Therefore, an excessive current does not flow through the strain resistance element 17, and as a result, the resistance value of the strain resistance element 17 becomes stable.

Here, further considering the case where the power supply electrode 14, the GND electrode 16, and the pair of output electrodes 15 on the insulating substrate 11 are connected to the mating terminals (not shown),
In the strain detection device in one embodiment of the present invention,
A first plating layer 27 made of nickel is provided on the upper surfaces of the power supply electrode 14, the GND electrode 16, and the pair of output electrodes 15, and a second plating layer 28 made of solder is provided on the upper surface of the first plating layer 27. Power source electrode 1
4, the GND electrode 16 and the pair of output electrodes 15 do not transfer silver to the second plating layer 28 made of solder, and as a result, the power supply electrode 14, the GND electrode 16,
This has the effect of improving the reliability of the electrical connection of the pair of output electrodes 15 to the counterpart terminals (not shown).

[0042]

As described above, according to the present invention, since the second protective layer is provided so as to cover the upper surface of the first protective layer, the strain detecting device can be used for a long time in a high humidity atmosphere. However, even if water penetrates into the second protective layer, it does not pass through the first protective layer, and as a result, fluctuations in the resistance value of the strain resistance element due to water are also eliminated, so that strain that always has stable output characteristics is obtained. It has an effect that a detection device can be provided.

[Brief description of drawings]

FIG. 1 is a top view of a strain detection device according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a position where a strain resistance element is provided in the strain detection device.

FIG. 3 is a side sectional view of a position where each electrode is provided in the strain detection device.

FIG. 4 is a top view showing a state in which a conductive adhesive is provided in a slit portion of an insulating substrate in the strain detection device.

FIG. 5 is a top view of a strain detection device according to another embodiment of the present invention.

FIG. 6 is a diagram showing a stress state generated in the insulating substrate when the insulating substrate has a rectangular shape according to an embodiment of the present invention.

FIG. 7 is a diagram showing a stress state generated in the insulating substrate in the state where the narrow portion is provided in the insulating substrate of the strain detecting device according to the embodiment of the present invention.

FIG. 8 is a top view of a conventional strain detection device.

FIG. 9 is a side sectional view of the strain detector.

[Explanation of symbols]

11 Insulating substrate 11a narrow part 12 stainless steel plate 13 Protective film 13a insulating layer 14 power electrode 15 Output electrode 16 GND electrode 17 Strain resistance element 18 circuit patterns 19 Temperature characteristic adjustment resistor 20 Resistance measurement electrode 21 frame GND electrode 22 Capacitor 23 Resistance for electrostatic discharge 24 slit part 26 Conductive adhesive 27 First plating layer 28 Second plating layer 29 First protective layer 30 Second protective layer

Continued front page    (72) Inventor Yukio Mizukami             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 2F049 CA07 CA11 DA02

Claims (3)

[Claims] 1. A substrate, four strain resistance elements forming a bridge circuit electrically connected to a power supply electrode, a pair of output electrodes and a GND electrode provided on the upper surface of the substrate, and at least the strain resistance element is covered. The substrate includes a plurality of protective layers, the substrate is composed of a stainless plate, a protective film provided on the upper surface of the stainless plate, and an insulating layer provided on the upper surface of the protective film. A frame GND electrode for connection is provided, and this frame GND is
A strain detection device in which an electrode and a GND electrode are electrically connected. 2. The strain detecting apparatus according to claim 1, wherein a capacitor and an electrostatic discharge resistor are electrically connected in parallel between the frame GND electrode and the GND electrode. 3. The strain detecting apparatus according to claim 1, wherein capacitors are electrically connected between the power supply electrode and the GND electrode, and between the pair of output electrodes and the GND electrode, respectively.