JP2000258261A - Capacitive load sensor - Google Patents

Abstract

(57) [Problem] To provide a capacitive load sensor having a strong structure capable of withstanding a large load and capable of maintaining highly reliable measurement accuracy for a long period of time. SOLUTION: The structure has a structure in which a spacer 13 is interposed at a peripheral portion between a plurality of metal plates 11 and 12 forming an electrode plate. In particular, a conductive material such as an aluminum alloy, iron, or an iron alloy is used as the spacer. Insulating layers 11b, 12b, 1 that insulate between the metal plates on one or both surfaces of the plate or the spacer
3b is provided as, for example, alumina formed as a chemical conversion film by anodic oxidation treatment, or as a phosphoric oxide film formed by phosphorylation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to, for example, 100 kg
The present invention relates to a capacitance type load sensor having a strong structure capable of withstanding the above large load and having high measurement reliability.

[0002]

2. Related Background Art As shown in FIG. 5, a capacitance type load sensor is basically disposed opposite to each other with a minute gap therebetween to form a pair of electrode plates, and forms a pair of electrode plates. 2 and
The metal plates 1, 2 are interposed at the periphery of the metal plates 1, 2,
An annular spacer 3 insulating between the two.
A structure in which a capacitor is formed by the metal plates 1 and 2 is formed. The metal plates 1 and 2 that bend under load.
It functions so that a change in the distance between them can be grasped as a change in the capacitance through lead wires 4 and 5 connected to the metal plates (electrode plates) 1 and 2, respectively.

The spacer 3 is composed of a spacer body 3a interposed between the metal plates 1 and 2, and a cover body 3b sandwiched between the metal plates 1 and 2 and joined and integrated with the spacer body 3a. 3c. Incidentally, this kind of spacer 3 is usually made of a plastic having a high insulating property, and the spacer body 3a is made of an engineering plastic such as POM (polyoxymethylene), PI (polyisoprene), and PEN (polyethylene naphthalate). The covers 3b and 3c are manufactured by using engineering plastics such as POM and polyacetal. The spacer body 3a and the cover body 3
After sandwiching the metal plates 1 and 2 respectively, b and 3c are joined and integrated by ultrasonic processing or press processing.

[0004]

Recently, various attempts have been made to use the capacitive load sensor having the above-described structure as a seating sensor in a vehicle. For example, by attaching a capacitive load sensor to a leg of a seat in a vehicle, the seat can be reliably detected regardless of the driver's sitting posture. In this case, the load sensor needs to detect a large load of, for example, 100 kg or more, which is the sum of the weight and the weight of the seat.

However, in the load sensor for detecting such a large load, it is necessary to receive the load applied to the metal plates 1 and 2 by the spacer 3, and it is undeniable that a considerable load is applied to the spacer 3. . In addition, in the case of a load sensor incorporated in a vehicle as a seating sensor, a load is often kept applied for a long time, and furthermore, the interior of the vehicle, which is an installation environment, may be considerably heated. is there. For this reason, as described above, the spacer 3 made of plastic is gradually deformed and crushed, which causes a problem that the distance between the metal plates (electrode plates) 1 and 2 tends to change. Such deformation of the spacer 3 is as follows.
This causes a large measurement error of the load measured by the capacitance type load sensor.

Incidentally, the use of a hard material such as glass or ceramic which is not easily deformed as a material of the spacer 3 has been considered. However, since the spacer 3 has a brittle property, it is liable to be damaged when subjected to an impact load. There is a problem to say. The present invention has been made in view of such circumstances, and has as its object to have a strong structure capable of withstanding a large load of, for example, 100 kg or more, and to maintain highly reliable measurement accuracy over a long period of time. It is an object of the present invention to provide a capacitance-type load sensor capable of performing the following.

[0007]

In order to achieve the above-mentioned object, a capacitive load sensor according to the present invention comprises a plurality of metal plates forming an electrode plate, a spacer interposed between the plurality of metal plates. A capacitor is formed by facing metal plates in parallel, and in particular, a conductor such as an aluminum alloy or iron or an iron alloy is used as the spacer, and the surface of one or both of the metal plate and the spacer is provided. The insulating layer for insulating between the metal plates is provided as, for example, alumina formed as a chemical conversion film by anodic oxidation treatment, or as a phosphoric acid film formed by phosphorylation treatment.

[0008] Further, the spacer is a plurality of conductor parts interposed on a peripheral portion between the metal plates separated from each other,
These conductive parts are selectively electrically connected to the plurality of metal plates, respectively, to function as electrode leads. That is, the present invention uses a conductor such as nickel or iron having the same rigidity (hardness) as a metal plate as an electrode plate as a spacer, and forms one or both of the metal plate and the spacer on a surface of alumina or phosphoric acid. Forming an insulating layer made of an insulative chemical conversion film such as a passivation film, prevents electrical contact between the metal plates via the conductive spacers, and functions as a capacitor by insulating a plurality of metal plates. The feature is that it is made to be.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A capacitance type load sensor according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is an exploded perspective view showing the structure of the capacitive load sensor according to the first embodiment. In the figure, reference numerals 11 and 12 denote a pair of disk-shaped electrode plates made of a metal plate such as an aluminum alloy, iron or an iron alloy, and reference numeral 13 denotes an annular ring made of a conductive metal plate such as an aluminum alloy, an iron or an iron alloy. (Ring-shaped) spacer.
The pair of electrode plates 11 and 12 are overlapped with each other via a spacer 13, and from above and below the metal rivets 14 inserted into mounting holes 11 a, 12 a and 13 a formed in the periphery thereof. It is fastened and integrally fixed as shown in FIG.

The rivet 14 is overlapped between a nail-shaped shaft portion 14b having a head portion 14a and a spacer 13 between the nail portion 14b and the head portion 14a. And a fixing ring 14c for holding the pair of electrode plates 11 and 12 therebetween. Further, the rivet 14 is used for the electrode plates 11 and 12 as described later.
The tip of the shaft portion 14b that projects through the fixing ring 14c serves as a connection fixing portion with a printed circuit board (not shown) on which a sensor circuit and the like are mounted.

An insulating layer 13b is formed on the surface of the spacer 13 including the inner wall surface of the mounting hole 13a. Incidentally, when the spacer 13 is made of an aluminum alloy, the insulating layer 13b is formed as an alumina chemical conversion film by anodizing the surface. When the spacer 13 is made of iron or an iron alloy, the surface of the spacer 13 is subjected to a phosphorylation treatment so that the insulating layer 13b is formed as a phosphorized film. That is, by performing a surface treatment in accordance with the properties of the material, the insulating layer 13b made of an insulating chemical conversion film is formed on the surface of the material of the spacer 13.

Insulating layers 11b and 12b are also formed on the peripheral edges of the surfaces of the electrode plates 11 and 12 in an annular shape corresponding to the shape of the spacers 13, respectively. These insulating layers 11b and 12b are also provided with the respective mounting holes 11a and 12a.
Is provided including the inner wall surface. However, each electrode plate 11, 1
As for the peripheral surfaces of one of the mounting holes 11a and 12a in FIG. 2 and the inner wall surfaces thereof, the insulating layers 11b and 12b are partially removed in order to realize electrical connection with the rivets 14 used as electrode leads as described above. And the material surface is exposed. The electrode plates 11 and 12 are
As described above, the mounting holes 11a exposing the material surface,
The spacers 12a are positioned so as to be separated from each other, for example, in the diametrical direction, so that they do not overlap each other.

Thus, the insulating layers 11b, 12 as described above
The electrode plates 11 and 12 having b and 13b formed on the surface thereof are superimposed via spacers 13 to form mounting holes 11a and 12b.
According to the electrostatic load sensor having a structure in which the spacer 13 is made of a conductive metal, the insulating layer 1 is formed on the surface of the insulating layer 1 even if the spacer 13 is made of a conductive metal.
Since 3b is formed, insulation between the electrode plates 11 and 12 can be ensured, and the electrode plates 11 and 12 can be insulated from each other so that the electrode plates 11 and 12 can function as a capacitor.

The rivet 14 basically includes the electrode plates 11 and 12 and the spacer 13 and the insulating layers 11 b and 1.
Since the insulation is provided through the electrodes 2b and 13b, the insulation between the electrode plates 11 and 12 is not hindered by the rivets 14. Also, the rivet 14 provided through the mounting hole 11a exposing the material surface of the electrode plate 11 contacts the inner wall surface of the mounting hole 11a exposing the material surface and the surface thereof, and And functions as an electrode lead of the electrode plate 11. The rivet 14 provided through the mounting hole 12a exposing the material surface of the electrode plate 12 is inserted into the inner wall surface of the mounting hole 12a exposing the material surface and the surface of the electrode plate 12 And functions as an electrode lead of the electrode plate 12. Therefore, the pair of electrode plates 11 and 12 can be easily externally connected to a printed circuit board or the like via the rivets 14 and 14.

According to the electrostatic load sensor having the above-described structure, the spacer 13 is made of nickel alloy, iron, or iron alloy equivalent to that of the electrode plates 11 and 12, so that it is very robust. In addition, even when used in an environment where a large load of 100 kg or more is applied for a long period of time, or when exposed to a high-temperature environment, there is almost no possibility of deformation. Moreover, since it is not brittle like glass or ceramic, it can sufficiently withstand unintended impact loads, and the electrode plates 11 and 12 under static pressure can be used.
The distance between them can be maintained stably. As a result, the measurement accuracy can be stably maintained over a long period of time.

Incidentally, the electrostatic load sensor according to the present invention can also be realized as a structure as shown in FIG. 3, for example. In the second embodiment, the two electrode plates 11 and 12 are realized in the same manner as in the previous embodiment, and the surfaces thereof have the insulating layers 11b and 1 as described above.
2b are provided respectively. On the other hand, the spacer 13
4 is realized as a pair of C-shaped conductor parts 15, 15 arranged apart from each other and along the periphery of the electrode plates 11, 12, as shown in a plan view in FIG. 4. However, the insulating layer 13b as described above is not provided on the surfaces of the conductor parts 15, 15 (spacers 13). These conductive parts 15, 15 and the electrode plates 11, 12
Insulation with the electrode plates 11 and 12 is basically ensured by insulating layers 11b and 12b provided on the surfaces of the respective electrode plates 11 and 12. However, the electrode plate 11 is provided at a mounting hole 11a where the material surface is exposed. The electrode plate 12 is in contact with the surface of one of the conductive parts 15 and is electrically connected thereto.
Is electrically connected to the surface of the battery.

Thus, the above-described pair of conductor parts 15,
The upper and lower surfaces of the electrode plates 11 and 12 superimposed via the spacer 15 are sandwiched between insulating rivets 16 made of engineering plastic and having the mounting holes 11a, 12a and 13a inserted therethrough. Are joined and integrated. Therefore, the electrode plates 11 and 12 are not electrically connected via the rivets 16, and the insulation between them is ensured by the insulating layers 11b and 12b.

Thus, even in the electrostatic load sensor thus configured, the pair of electrode plates 11 and 12 are made of a nickel alloy, iron, or iron alloy equivalent to the electrode plates 11 and 12. Since the structure is superposed via the spacers 13 (conductor parts 15, 15), the spacers 13 (conductor parts 15, 15) are used even in an environment where a large load is applied for a long period of time. The distance between the electrodes 11 and 12 can be kept constant without causing the deformation of (1). Although the rivet 16 for joining and integrating the electrode plates 11, 12 and the spacer 13 is made of an insulating material made of engineering plastic, the rivet 16 is not directly loaded, and the rivet 16 is The rivet 16 is not likely to be deformed since it merely serves to join and integrate the rivet 16. Even if the rivet 16 is deformed, its influence adversely affects the capacitance characteristics between the electrode plates 11 and 12. There is no fear of exerting

The conductor parts 15 and 15 are separated from each other and come into contact with the surfaces of the pair of electrode plates 11 and 12 to function as electrode leads of the respective electrode plates 11 and 12.
Even with this structure, effects such as easy electrical connection with an external circuit can be obtained as in the previous embodiment. Note that the present invention is not limited to the above embodiment. For example, the size (diameter) and the plate thickness of the electrode plates 11 and 12 and the facing distance may be determined according to the magnitude of the load to be measured, the required measurement sensitivity, and the like. In the second embodiment, the conductor component 1
If conductive films 11b and 12b are formed on each of the electrode plates 11 and 12 corresponding to the shapes of the rivets 16 and the rivets 16 are used, a conductive metal may be used. Of course, it is also possible. Further, the present invention can be similarly applied to a case where a capacitor having a multilayer structure in which three or more conductive plates are separated from each other by a predetermined distance is formed. Also, a dielectric can be appropriately interposed between the electrode plates. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0020]

As described above, according to the present invention, the spacer interposed in the peripheral portion between the plurality of metal plates forming the electrode plate and facing each of the metal plates in parallel is equivalent to the electrode plate. It is a structure in which a conductor such as aluminum alloy, iron, or iron alloy is formed as a material, and an insulating layer that insulates between the electrode plates is formed on one or both surfaces of the electrode plate or the spacer. Even when a load is applied, it is possible to realize an electrostatic load sensor having a simple structure that can prevent deformation of the spacer and ensure stable measurement accuracy.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the structure of a capacitive load sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an assembly structure of the capacitive load sensor shown in FIG. 1;

FIG. 3 is a sectional view showing a structure of a capacitance type load sensor according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a planar shape of a spacer (conductive part) in the capacitance type load sensor shown in FIG. 3;

FIG. 5 is a sectional view showing a general structure of a conventional electrostatic load sensor.

[Explanation of symbols]

 Reference Signs List 11 electrode plate (metal plate) 12 electrode plate (metal plate) 13 spacer (metal plate) 14 rivet 15 conductor component (spacer) 16 rivet

Claims (2)

[Claims] 1. A plurality of electrode plates made of a metal plate, a spacer made of a conductor interposed at a peripheral portion between these electrode plates and facing the electrode plates in parallel, and one of the electrode plates or the spacers Or an insulating layer formed on both surfaces thereof to insulate the electrode plates from each other. 2. The method according to claim 1, wherein the spacer is composed of a plurality of conductive parts which are spaced apart from each other and is interposed on a peripheral portion between the electrode plates, and is selectively electrically connected to the plurality of electrode plates. The capacitance type load sensor according to claim 1, wherein: