JPH0626823Y2 - Load sensor by capacitance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a load sensor that forms an electrostatic capacitance between an electrode of a fixed substrate and an electrode of a movable substrate that is deformed by a load, and detects a change in the capacitance due to the load. .

[Conventional technology]

An example of a conventional load sensor that detects a load based on a change in capacitance is a ring-shaped sealing of a fixed substrate 1 made of an insulating material and a movable substrate 2 made of an elastic insulating material as shown in FIGS. 6 and 7. A predetermined gap of 40 to 50 microns is held and opposed to each other with the stopper member 4 interposed therebetween. This fixed substrate 1 and movable substrate 2
Metal electrodes 71 and 72 are provided at the center of the lines, and lead lines 91 and 92 are output from the electrodes 71 and 72 to the outside and are in contact with the terminal portions 11 and 21, and output as a change in capacitance. Further, the sealing member 4 maintains a gap and airtightness, and the fixed substrate 1 is provided with a small hole 5 as a passageway for air to obtain a load sensor as an air condenser.

When a load F is applied to the movable substrate 2 of the load sensor forming the air condenser shown in FIG. 6 as shown by an arrow, the movable substrate 2 is deformed as shown by the dotted line, the electrode gap is changed, and the electrostatic capacitance is changed. Here, if the electrode area is S, the distance between the electrodes is d, and the permittivity of air is ε ₀ , the capacitance C is Can be expressed as D = d ₀ in the initial state of the load F = ₀
Then, when a load is applied, the movable substrate 2 is deformed and d = d ₁ , but since d ₁ <d ₀ , the electrostatic capacitance C changes so as to increase. This capacitance change amount ΔC is extracted and determined as a frequency change Δ by a detection circuit such as a capacitance-frequency converter.

[Problems to be solved by the device]

However, in the conventional load sensor, the movable substrate 2 is usually made of an alumina material or the like, but since it is a ceramic material, it is easily cracked by mechanical or thermal shock, and the temperature characteristic of Young's modulus is not Usually-
Around 100 ppm / ° C also has a great influence on the temperature characteristics of the load sensor. In addition, the Young's modulus of the movable substrate 2 made of ceramic is large, and the deflection amount is usually 1 with respect to the load F.
It is small with a displacement of about 2 micrograms per kilogram. For example, when the change in capacity C with respect to load F is ΔC in a unit load centered on 1 kilogram, the sensitivity ΔC /
In order to set C to about 5%, it is necessary to set the gap length, that is, the thickness of the sealing member 4 to about 50 microns, and it is difficult to process the gap length to an accuracy of 50 microns in manufacturing. There are drawbacks.

[Means for Solving the Problems]

The present invention eliminates the above-mentioned drawbacks of the prior art, and a fixed substrate 1 made of an insulating material having an upper surface with a metal electrode 71 connected to a lead wire conductor printed on the lower surface by a through hole provided in part, and an electrode 71. A ring-shaped sealing member 4, which keeps a gap with a predetermined thickness along the outer edge of the, or a ring-shaped spacer made of a 42% Ni-Fe alloy with a protrusion provided on the outside of the outer periphery is joined. Ring-shaped sealing member 4
It is a load sensor based on capacitance in which a movable substrate 2 formed of a constant elasticity alloy made of a Fe—Ni alloy having a Ni content of 50 to 52% is stacked so as to face the electrode 71 via a capacitor.

[Action]

The electrode 71 on the upper surface of the fixed substrate 1 and the movable substrate 2 made of a constant elastic alloy are movable by forming an air condenser having a gap between the thickness of the sealing member 4 or the thickness of the sealing member 4 and the spacer. When a load is applied to the substrate 2, the substrate 2 is displaced and the capacitance changes, and the load is detected from this change.

〔Example〕

An embodiment of the load sensor based on the capacitance of the present invention is shown in a vertical sectional front view of FIG. 1 and an exploded perspective view of FIG.

As shown in the drawing, a disk-shaped metal electrode 71 is printed on the upper surface of the fixed substrate 1 from an insulating material such as alumina, and a lead is printed on the lower surface through a through hole 8 penetrating a part of the metal electrode 71. It is electrically connected to the line conductor 12. A small hole 5 is provided at the center of the through hole 8 to allow air to flow therethrough. Further, a ring-shaped sealing member 4 having a predetermined thickness made of glass or epoxy adhesive is joined along the outer periphery of the metal electrode 71. The movable substrate 2 made of a constant elastic alloy is stacked on the sealing member 4, and the movable substrate 2 and the metal electrode 71 of the fixed substrate 1 form an air capacitor having a gap of the thickness of the sealing member 4 to form an electrostatic capacitor. Capacity is generated.

Here, the constant elastic alloy used for the movable substrate 2 is Fe, N.
As shown in the characteristic curve diagram of Fig. 5, the temperature characteristics of Young's modulus can be adjusted by the heat treatment temperature of i, Cr, and Ti-based Erinver materials, and the temperature characteristics are almost 0 ppm / ℃. Therefore, the temperature characteristic of Young's modulus is improved as compared with the conventional temperature coefficient of -100 ppm / ° C, and the temperature characteristic with respect to the load is advantageous.

The Young's modulus of the constant modulus alloy is 19000kg / mm ^2, it is about twice the displacement amount is large constantly elastic alloy to the same load since conventional alumina material is 1/2 or less of 40000kg / mm ² of sealing Sensitivity 5% even if the thickness of the stop member 4 is doubled from the conventional one
The degree can be secured. Therefore, the thickness of the sealing member 4 is set to 10
It may be about 0 micro, which facilitates manufacturing.

Further, since the movable substrate 2 is a constant elastic alloy, it is less likely to be cracked by mechanical impact as compared with the conventional alumina material.

Another embodiment of the capacitance-based load sensor of the present invention is shown in the vertical sectional front view of FIG. 3 and the exploded perspective view of FIG.

As shown in the drawing, on the sealing member 4 printed on the insulative fixed substrate 1, Ni 50 to 52% Fe-Ni alloy or Ni 42% Fe-Ni alloy is formed, and it has almost the same shape as the sealing member 4. The metal spacers 3 provided with the protrusions 6 are bonded outward from the outer periphery.

Further, the movable substrate 2 made of a constant elastic alloy and the metal spacer 3 are joined by resistance welding or laser welding, and the protrusion 6 of the spacer 3 is also connected to a welding machine in the case of resistance welding, and the electrode of the movable substrate 2 is also connected. It also serves as a take-out section.

[Effect of device]

As described above, according to the present invention, since the conventional alumina is used for the movable substrate 2 and the constant elastic alloy is used, the load is suitable for mass production, which is strong against mechanical shock and has excellent temperature characteristics. A sensor is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a capacitive load sensor of the present invention, FIG. 2 is an exploded perspective view of FIG. 1, FIG. 3 is a vertical sectional front view of another embodiment of the present invention, and FIG. Fig. 3 is an exploded perspective view, Fig. 5 is a temperature characteristic curve diagram of a constant elastic alloy, Fig. 6 is a vertical sectional front view of a load sensor with a conventional capacitance, and Fig. 7 is an exploded perspective view of Fig. 6. is there. In addition, 1: fixed substrate, 2: movable substrate, 3: spacer, 4: sealing member, 5: small hole, 6: projection, 71, 72: electrode, 8: through hole, 91, 92: lead wire, 11, 21: terminal part, 12: lead wire conductor.

Claims (2)

[Scope of utility model registration request] 1. A fixed substrate 1 made of an insulating material having an upper surface on which a metal electrode 71 connected to a lead wire conductor 12 provided on the lower surface by a through hole 8 provided at a part thereof is attached to an outer edge of the electrode 71. Along the edge of the sealing member 4 or a part of the outer periphery of which a gap is maintained with a predetermined thickness.
A load sensor based on electrostatic capacitance, which is a capacitor formed by stacking movable substrates 2 made of a constant elastic alloy through the sealing member 4 to which a spacer 3 made of a protruding metal material is joined. 2. The movable substrate 2 is a constant elastic alloy, and the spacer 3 is a Fe—Ni alloy containing 50 to 52% Ni or a Fe—Ni containing 42% Ni.
The load sensor according to claim 1, wherein the utility model registration is made of an alloy.