JPH05346356A - Device for detecting physical quantity utilizing change in capacitance - Google Patents

Abstract

PURPOSE:To obtain a durable force detection device with improved temperature characteristics. CONSTITUTION:A displacement body 10 is housed within a fixed body 20 as a device enclosure and is displaced inside when an external force is applied to a point of application P. The displacement body 10 and the fixed body 20 consist of metals. Fixed electrodes B1, B2, and B4 are formed on the inner surface of the fixed body 20 and capacity elements are formed by the fixed electrodes and the opposing surface of the displacement body 10. A force which is applied to the point P is detected based on the change in electrostatic capacity of the capacity elements. The fixed electrode B1 is formed within the fixed body 20 via intermediate layers I1a and I1b. When the intermediate layer I1a is constituted by 42-alloy, the intermediate layer I1b is constituted by glass epoxy resin, and the fixed body 20 is constituted by aluminum, the thermal coefficient of expansion of the entire intermediate layers I1a and I1b becomes equal to that of the fixe body 20, thus preventing the capacitance of the capacity elements from being affected by temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a physical quantity detecting device utilizing a change in electrostatic capacity, and more particularly to a detecting device capable of detecting force / acceleration / magnetism as a change in distance between a pair of electrodes.

[0002]

2. Description of the Related Art In the automobile industry, machine industry and the like, there is an increasing demand for detection devices capable of accurately detecting physical quantities such as force, acceleration and magnetism. In particular, a small device capable of detecting these physical quantities for each of the two-dimensional or three-dimensional components is desired.

In order to meet such demands, a gauge resistor is formed on a semiconductor substrate such as silicon, and mechanical strain generated in the substrate due to an external force is converted into an electric signal by utilizing a piezoresistive effect. A force / acceleration / magnetism detection device has been proposed. However, the detection device using such a gauge resistor has a problem that the manufacturing cost is high and temperature compensation is necessary.

Therefore, in recent years, there has been proposed a detection device for detecting a physical quantity by utilizing a change in electrostatic capacity. For example, Japanese Patent Application No. 2-274299, Japanese Patent Application No. 3-13
8191, Japanese Patent Application No. 3-203875, Japanese Patent Application No. 3-306587, Japanese Patent Application No. 3-89570
Specification, International Publication No. WO91 / under the Patent Cooperation Treaty
Japanese Patent No. 10118 proposes a new detection device that utilizes a change in capacitance. In this novel detection device, a capacitive element is composed of a fixed electrode formed on a fixed substrate and a displacement electrode that is displaced by the action of force, and an action is taken based on a change in the capacitance of the capacitive element. Each of the multidimensional components of the applied force can be detected. Further, Japanese Patent Application No. 2-416188 discloses a method for manufacturing this novel detection device, and PCT / JP91 / 00428 specification relating to an international application based on the Patent Cooperation Treaty discloses this new detection device. A method of inspecting a device is disclosed. Also,
Japanese Patent Application No. 3-203876 discloses a detection device using a piezoelectric element instead of a capacitive element.

[0005]

In the above-mentioned physical quantity detection device, the displacement element is housed in the housing of the apparatus, and the capacitive element is provided by the fixed electrode provided on the inner surface of the housing and the displacement electrode provided on the surface of the displacement object. Is a general structure. Since such a detection device is used by being mounted in an automobile or various industrial robots, it is preferable to use a robust metal for the device housing and the displacement body. On the other hand, since the electrodes must be kept electrically insulated from each other, it is necessary to form the electrodes on the metal surface via the insulating intermediate layer. However, the thermal expansion coefficient is generally different between the metal and the insulating material. Therefore, when the detection device is configured by mixing different materials such as a metal and an insulating material, there occurs a phenomenon that the distance between the displacement electrode and the fixed electrode changes depending on the temperature. That is, the detection result is affected by the temperature, which causes an adverse effect that an accurate detection value cannot be obtained. In particular, in applications for mounting on automobiles and industrial robots, adaptation to a severe temperature environment of −40 to + 100 ° C. is required, and therefore the solution of the problem of improving temperature characteristics is extremely important.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a physical quantity detection device that is robust and that utilizes a change in electrostatic capacitance with good temperature characteristics.

[0007]

[Means for Solving the Problems]

(1) The first invention of the present application has a function as a housing that has a displacement body that is displaced by the action of an external force and a flexible portion that supports the displacement body, and that accommodates at least a part of the displacement body. With a fixed body, a displacement electrode fixed on a partial surface of a portion of the displacement body accommodated in the fixed body, and a displacement electrode facing the displacement electrode and fixed on a partial surface inside the fixed body. A physical quantity that includes a fixed electrode and a detection unit that detects a change in the distance between the displacement electrode and the fixed electrode as a change in the capacitance between the two electrodes, and that detects the external force acting on the displacement body by the detection unit. In the detection device of 1, the fixed body is made of metal, and the fixed electrode is formed on the metal surface via the intermediate layer. The intermediate layer has a thermal expansion coefficient larger than that of the metal constituting the fixed body. A first layer of a first material having a refractive index A second layer made of a second material having a thermal expansion coefficient smaller than that of the metal forming the fixed body, and at least two layers of the first material and the second material. At least one of them is made of an insulating material.

(2) A second aspect of the invention of the present application is a casing having a displacement body that is displaced by the action of an external force and a flexible portion that supports the displacement body, and that houses at least a part of the displacement body. And a displacement electrode fixed on a partial surface of the displacement body accommodated in the fixed body, and a displacement electrode facing the displacement electrode and fixed on a partial surface inside the fixed body. And a detection unit that detects a change in the distance between the displacement electrode and the fixed electrode as a change in the capacitance between the two electrodes, and detects the external force acting on the displacement body by the detection unit. In the physical quantity detection device, the fixed body and the displacement body are made of metal, and the displacement electrode is formed on the metal surface via the intermediate layer.
First having a coefficient of thermal expansion greater than that of the metal
A first layer made of the above material and a second layer made of a second material having a coefficient of thermal expansion smaller than that of the metal, and a first material At least one of the second material and the second material is made of an insulating material.

(3) The third invention of the present application is such that the displacement body or the fixed body itself is used as the displacement electrode or the fixed electrode in the detection device according to the above-mentioned first or second invention. ..

(4) The fourth invention of the present application is the above-mentioned first to third inventions.
In the detection device according to the invention, the first layer and the second layer forming the intermediate layer are configured so that the change in distance between the displacement electrode and the fixed electrode caused by thermal expansion of each part of the detection device becomes smaller. The thickness ratio of each layer is determined.

(5) The fifth invention of the present application is the above-mentioned first to fourth inventions.
In the detection device according to the invention described above, aluminum is used as the metal constituting the fixed body / displacement body, and 42 is used as the first material.
An alloy and a glass epoxy resin as the second material, respectively.

(6) A sixth aspect of the invention of the present application is a casing having a displacement body that is displaced by the action of an external force and a flexible portion that supports the displacement body, and that houses at least a part of the displacement body. A fixed body having a function as a member, a displacement electrode fixed on a partial surface of a portion of the displacement body accommodated in the fixed body, and a fixed electrode facing the displacement electrode and fixed to the fixed body. , The change in the distance between the displacement electrode and the fixed electrode,
Detection means for detecting as a change in capacitance between both electrodes,
In a physical quantity detecting device for detecting an external force acting on a displacement body by a detection means, the fixed body is made of metal, an opening is provided in a part of a wall surface of the fixed body, and an insulating property is provided on an outer surface of the opening. Attach the middle layer consisting of
A fixed electrode is formed on the inner surface of this intermediate layer.

(7) A seventh invention of the present application is such that, in the detection device according to the sixth invention, the displacement body itself is used as a displacement electrode.

[0014]

[Operation] The displacement body is supported by the flexible portion formed in a part of the fixed body. Therefore, when a force from the outside is applied to the displacement body, the flexible portion is bent, and the position of the displacement body with respect to the fixed body changes. This change in position causes a change in the distance between the displacement substrate provided on the displacement body side and the fixed substrate provided on the fixed body side. This change in the distance includes information on the magnitude and direction of the applied force, and can be detected as a change in the capacitance of the capacitive element formed by the displacement substrate and the fixed substrate.

According to the present invention, the fixed body functioning as the device housing is made of metal. Therefore, the detection device main body has the robustness necessary for application to automobiles and industrial robots. On the other hand, in order to maintain the electrical independence of each electrode, it is necessary to form each electrode via an insulating intermediate layer. Therefore, a plurality of materials having different coefficients of thermal expansion, that is, a metal and an insulating material, coexist, which adversely affects the temperature characteristics.

A feature of the first to fifth inventions of the present application is that the intermediate layer is formed by two layers having different thermal expansion coefficients. By appropriately setting the ratio of the thicknesses of the two layers, the coefficient of thermal expansion of the intermediate layer as a whole can be made equal to the coefficient of thermal expansion of the metal, thus suppressing a change in the distance between the two electrodes due to a temperature change. It will be possible.

A feature of the sixth and seventh inventions of the present application is that the intermediate layers having different thermal expansion coefficients are provided outside the housing. Since the intermediate layer formed on the outside does not expand to the inside of the housing, it does not affect the inter-electrode distance between the two electrodes formed on the inside of the housing.

[0018]

EXAMPLES §1 Basic Principle of Detection Apparatus The present invention will be described below based on illustrated examples. First, the basic principle of the physical quantity detection device according to the present invention will be described.
Description will be made based on the basic embodiment shown in FIG. The force detection device according to this embodiment includes a displacement body 10 and a fixed body 20. As shown in the perspective view of FIG. 2, the displacement body 10 has a structure including a disk-shaped flat plate 11 and a square columnar body 12. The columnar body 12 is joined to the lower surface of the flat plate 11. In addition, in the present specification, the displacement body 10 is divided into two components, that is, the flat plate 11 and the columnar body 12 for convenience of the structure description, but in reality, the displacement body 10 can be formed by integral molding. An electrode A1 is formed on the upper surface 11a of the flat plate 11. In addition, the side surfaces 12a, 12b of the columnar body 12,
12c and 12d have electrodes A2, A3, A4, respectively.
A5 is formed. Although only a part of each side surface is shown in FIG. 2, the side surface 12c is a surface located on the opposite side of the side surface 12a and the side surface 12d is a surface located on the opposite side of the side surface 12b. The electrode A4 is formed on the side surface 12c (not shown), and the electrode A5 is formed on the side surface 12d (not shown). Hereinafter, these respective electrodes will be referred to as displacement electrodes A1 to A5, and the surface on which these displacement electrodes are formed will be referred to as a displacement surface.

As shown in FIG. 1, an origin O is defined at one point (for example, the position of the center of gravity) in the displacement body 10, the X axis is on the left side of FIG. When the XYZ three-dimensional coordinate system is defined by defining the Y-axis vertically upwards as shown in FIG.
The axis and the Z axis will be defined. FIG. 1 shows a cross section of the displacement body 10 shown in FIG. 2 on the XZ plane.

On the other hand, the fixed body 20, as shown in FIG.
It is shaped so as to surround the periphery of the displacement body 10. The outer shape of the fixed body 20 is a rectangular parallelepiped, and the flexible portion 21 is provided on the bottom.
Are formed. The flexible portion 21 is formed so as to be deformed by the action of force, and the displacement body 10 is in a state of being supported by the flexible portion 21. That is, the flexible portion 21 is made of a thin flat plate-like member, and in this embodiment, a square window is opened in the central portion thereof, and the columnar body 12 is fixed in the window. Actually, if the columnar body 12 is fixed to the central portion of the flexible portion 21 by a method such as screwing, more reliable fixing can be achieved. Alternatively, a part of the columnar body 12 and a part of the fixed body 20 may be integrally formed, and the remaining part may be fixed by a method such as screwing. As shown in FIG. 1, the displacement body 10 is
It is supported only by this flexible portion 21, and is in a state not in contact with the fixed body 20 except for this supporting portion. The columnar body 12 is surrounded by the enclosing portion 22 from four sides, but a predetermined gap is formed between them. After all, the displacement body 10 is suspended in the space formed inside the fixed body 20. As described above, the flexible portion 21 is deformed by the action of force.
Therefore, when a force is applied to the action point P defined on the bottom surface of the columnar body 12, the flexible portion 21 is bent, and the displacement body 10 is displaced. The displacement state at this time is determined based on the applied force. The basic principle of the present invention is to detect the applied force by detecting this displacement state.

On the inner wall of the fixed body 20, fixed surfaces are formed facing the respective displacement surfaces of the displacement body 10. That is, the fixed surface 20a is a surface facing the displacement surface 11a, and the fixed surfaces 22a, 22b, 22c, 22d are the displacement surfaces 1 respectively.
It is a surface facing 2a, 12b, 12c, 12d. Further, fixed electrodes are formed on the respective fixed surfaces so as to face the displacement electrodes. That is, the fixed electrode B1 is formed on the fixed surface 20a, and the fixed surfaces 22a, 22b, 2
2c and 22d have fixed electrodes B2, B3, B4, respectively.
B5 is formed. FIG. 3 shows the device shown in FIG.
FIG. 4 is a cross-sectional view taken along a plane, in which the positional relationship between each facing surface and each electrode is clearly shown. In order to facilitate the illustration, in the drawings of the present application, the thickness of each electrode is neglected in the perspective view (eg, FIG. 2), and the thickness of each electrode is illustrated in the cross-sectional views (eg, FIG. 1 and FIG. 3). It is emphasized and drawn.

Here, the opposing electrodes A1 and B1 form a capacitive element C1, the opposing electrodes A2 and B2 form a capacitive element C2, and the opposing electrodes A3 and B3.
Form a capacitive element C3, and the opposing electrodes A4 and B4 form a capacitive element C4.
5 and B5 form a capacitive element C5. In general,
The electrostatic capacitance C of the capacitive element is determined by C = εS / d, where S is the electrode area, d is the electrode spacing, and ε is the dielectric constant. Therefore, the capacitance C increases as the distance between the opposing electrodes decreases, and the capacitance C decreases as the distance between the electrodes decreases. Therefore, the distance between the opposing electrodes (that is, the distance between the opposing surfaces) can be obtained based on the change in the capacitance value of each capacitive element. The present detection device utilizes this principle, measures the change in the capacitance between the electrodes, and detects the external force acting on the action point P based on this measurement value.

For example, in FIG. 1, if a force Fx in the X-axis direction is applied to the point of action P, the left side portion of the flexible portion 21 in the figure contracts, the right side portion extends, and the entire displacement body 10 moves to the left side of the figure. Translate to. That is, the origin O moves in the positive direction on the X axis. For this reason, the electrode interval of the capacitive element C2 formed of the electrode pair A2, B2 becomes small, and the capacitance value increases. On the contrary, the electrode interval of the capacitive element C4 composed of the electrode pair A4, B4 becomes large and the capacitance value decreases. At this time, the distance between the electrode pair A1 and B1, the electrode pair A3 and B3, and the electrode pair A5 and B5 does not change. Further, as shown in FIG. 4, when an external force as indicated by an arrow F in the drawing acts on the point of action P, this external force gives a moment -My about the Y axis to O at the origin. That is, the flexible portion 2
1 causes the displacement body 10 to tilt inside the fixed body 20 as shown in the figure.

In short, the basic principle of this detecting device is to obtain information on the direction of the applied external force by examining the pattern in which the capacitance value of each capacitance element changes, and the change in capacitance value. It is to obtain information about the magnitude of the external force that has been exerted by examining how much the amount is. Moreover, in this embodiment, the displacements are obtained on two different displacement surfaces. Now, the displacement surface 11a on which the electrode A1 is formed is referred to as a first displacement surface, and the electrode A
Displacement surfaces 12a, 12 on which 2, A3, A4, A5 are formed
When b, 12c, and 12d are called the second displacement surfaces, the first displacement surface and the second displacement surface each exhibit a unique displacement mode according to the applied external force. The detection device of this embodiment is
Both the force in each axial direction and the moment around each axis can be detected based on these two types of displacement modes. Note that, in this specification, description of specific detection circuits and the like is omitted. For more detailed detection methods, refer to the above specifications and publications.

§2 Practical Example and Problems to be Solved Next, a more practical example of the above-described detection device and a problem to be solved in this example will be described.
In order to mass-produce such a detection device, it is preferable to simplify the structure as much as possible. One method of simplifying such a structure is to share electrodes. For example, in the basic detection device described in §1,
Two electrodes (displacement electrodes and fixed electrodes) are used to configure one set of capacitive elements, and in the end, ten electrodes (displacement electrodes) are used to configure five sets of capacitive elements C1 to C5. Electrodes A1 to A5 and fixed electrodes B1 to B5) are used. By the way, when detecting the capacitance value of each of the five sets of capacitive elements C1 to C5, it is possible to adopt wiring as shown in FIG. That is, one electrode of each of the capacitive elements C1 to C5 is electrically connected to the same potential, a signal from this is taken out from the common terminal T0, and the other electrode is provided with a separate terminal T1.
The signal is taken out from ~ T5. In other words, the plurality of displacement electrodes are configured by a common single electrode, or
It is possible to configure a plurality of fixed electrodes with one common electrode.

The embodiment shown in FIG. 6 is an embodiment in which the structure is simplified from such a viewpoint. The point that five fixed electrodes B1 to B5 (B3 and B5 are not shown) are formed on the fixed body 20 side is the same as the embodiment of §1, but it should be formed on the displacement body 10 side. Displacement electrodes A1
A5 has been replaced by the common displacement electrode A0, and the displacement body 10 itself is used as the common displacement electrode A0. That is, the displacement body 10 is made of metal, and each part of the surface of this metal block functions as each displacement electrode. For example, the surface portion facing the fixed electrode B1 serves as the displacement electrode A1. By comparing the structure shown in FIG. 6 with the structure shown in FIG. 1, it can be seen how the structure is simplified. To apply the wiring of FIG. 5 to the embodiment of FIG. 6, the displacement body 10 (common displacement electrode A0) is connected to the terminal T0, and the fixed electrodes B1 to B5 are connected to the terminals T1 to T5, respectively. Note that, contrary to the embodiment shown in FIG. 6, the fixed electrode side can be used as the common electrode. In this case, the fixed body 20 is made of metal and is used as a common fixed electrode.
1 to A5 are to be formed.

When such a detecting device is mounted on an automobile or an industrial robot, it is necessary to make the structure as robust as possible. In particular, it is preferable to use a robust metal for the fixed body 20 that functions as a device housing. However, in the structure of the embodiment shown in FIG. 6, the fixed body 20 cannot be made of metal. Because 5 fixed electrodes B1
Since B5 to B5 are directly formed on the inner surface of the fixed body 20, if the fixed body 20 is made of metal, the five fixed electrodes B1 to B5 are brought into conduction. Therefore, when a metal is used as the fixed body 20, as shown in FIG. 7, it is necessary to form five fixed electrodes B1 to B5 via intermediate layers I1 to I5 having insulating properties, respectively ( (B3, B5, I3, I5 are not shown).

However, when such an insulating intermediate layer is structurally added, a new problem arises. That is, this is an adverse effect on the temperature characteristics. In order to explain this, consider a model as shown in FIG. This model is
In the embodiment shown in FIG. 7, it is shown that the distance between the fixed electrode B1 and the displacement electrode A1 facing the fixed electrode B1 (actually, the upper surface of the displacement body 10 as the common displacement electrode A0) changes with temperature. It is a model. Here, the displacement body 10, the fixed body 20, and the fixed electrode B1 are assumed to be made of the same metal, and only the intermediate layer I1 is made of a different insulating material. Then, consider the vertical extension of the figure that occurs when the temperature of the entire device rises. Here, as shown in FIG. 8, for convenience, six sections D1 to D6 are defined, and the elongations of the device outer side portion M and the device inner side portion N are compared. Section D
With respect to 1, D2 and D6, the outer side portion M of the apparatus and the inner side portion N of the apparatus are made of the same metal, so that the amounts of elongation are the same. Further, in the section D4, since the fixed electrode B1 is made of the same metal as the displacement body 10 and the fixed body 20, the amount of elongation is the same. However, since the length of the section D (that is, the thickness of the fixed electrode B1) is generally about 1 μm, even if a different metal is used as the fixed electrode B1, its influence can be ignored. The sections in question are sections D3 and D5. In the section D3, the outer side portion M of the device extends, whereas the inner side portion N of the device is a void, so there is no extension at all. Also,
Regarding the section D5, although the outer portion M of the device is metal,
Since the device inner portion N is made of an insulating material, the coefficients of thermal expansion are different from each other, and the amount of elongation is different. Since the absolute value of this difference depends on the temperature value, as a result, between the fixed electrode B1 and the displacement electrode A1 that faces the fixed electrode B1 (actually, the upper surface of the displacement body 10 as the common displacement electrode A0). The distance will change with temperature.

Although the above is a problem relating to the extension in the vertical direction of the drawing, the same problem occurs in the left-right direction and the front-back direction (direction perpendicular to the paper surface) of the drawing. In a device that detects the amount of an external force that has acted by measuring the change in the inter-electrode distance, if a phenomenon in which the inter-electrode distance changes due to temperature occurs, the measurement accuracy will be seriously affected. The present invention provides a method for solving such a problem.

§3 First Solution In the model shown in FIG. 8, if the coefficient of thermal expansion of the material used as the intermediate layer I1 becomes equal to the coefficient of thermal expansion of the metal used for the fixed body 20, The above-mentioned problems relating to temperature characteristics are solved. The first solution in the present application is based on this point of view. However, it is a prerequisite that the intermediate layer I1 is an insulating layer, and it is difficult to find an insulating material having the same coefficient of thermal expansion as that of metal. FIG. 9 shows the linear expansion coefficient for some materials. Various insulating materials are shown in the upper row, and various metals are shown in the lower row. In consideration of mass production, aluminum is a representative metal material most suitable for the fixed body 10 as a housing. As shown in FIG. 9, the linear expansion coefficient of this aluminum is 25 (here, the unit is omitted for convenience of description), but the insulating material whose linear expansion coefficient is close to this is shown in the table of FIG. I can't find it.

The basic idea of the inventor of the present application will be that if the intermediate layer is formed by a plurality of layers made of different materials, the linear expansion coefficient of the intermediate layer as a whole can be made equal to that of the metal of the fixed body 10. Is in the idea. A specific example based on this idea is shown in FIG. FIG. 10 shows an extracted portion of the section D5 in the model shown in FIG. In this example, the fixed body 20 and the fixed electrode B1 are
Both are made of aluminum. Also,
The intermediate layer is composed of two layers, a first layer I1a and a second layer I1b. Here, the first layer I1a is made of 42-alloy (42% nickel, 58% iron alloy), and the second layer I1b is made of glass epoxy resin. According to the table of FIG. 9, the linear expansion coefficient of 42-alloy is 4.9, which is smaller than that of aluminum, whereas the linear expansion coefficient of glass epoxy resin is 48, which is larger than that of aluminum. Now, the first layer I1a
Assuming that the ratio of the thickness a of the second layer I1b to the thickness b of the second layer I1b is 1: 1, the linear expansion coefficient of the entire intermediate layer composed of these two layers is obtained by (4.9 + 48) / 2, About 26.5
Becomes In other words, the coefficient of linear expansion of the entire intermediate layer is much closer to that of aluminum. a:
By changing the ratio of b, the linear expansion coefficient of the entire intermediate layer can be set to an arbitrary value of 4.9 to 48. Therefore, if the ratio of a: b is set appropriately, the aluminum linear The expansion coefficient and the linear expansion coefficient of the intermediate layer can be made completely equal.

In this way, the problem of thermal expansion in the section D5 of the model of FIG. 8 can be solved. By the way, what about the problem of thermal expansion in section D3? In fact,
The problem in the section D3 can also be solved by the method described above. As described above, the linear expansion coefficient of the intermediate layer can be arbitrarily set by the ratio of a: b. Therefore, the field of view of interest is expanded to the sections D3 to D5, and the electrode spacing in question (the distance between the lower surface of the fixed electrode B1 and the upper surface of the displacement body 10 in the model of FIG. 8) is constant regardless of the temperature. An ideal linear expansion coefficient (a value that is slightly larger than the linear expansion coefficient of aluminum, in other words, a value that can offset the elongation of aluminum in the section D3) is calculated so that the linear expansion coefficient of the intermediate layer I1 is The ratio of a: b may be set so that the coefficient of linear expansion becomes ideal.

A method for calculating the ideal a: b ratio as described above will be described based on a concrete example. Now, in the model of FIG. 8, the lengths of the sections D3, D4 and D5 are represented as L3, L4 and L5 respectively, and L3 + L4 + L
5 = LL. L4 is usually 1μ
Since it is about m, it is ignored here with L4 = 0. Now, let us consider a change in length of each part when a temperature change ΔT occurs. Since the fixed body 20 extends in the outer portion M of the apparatus, the length LL of the sections D3 to D5 changes to the length LL '. Here, if the linear expansion coefficient of aluminum as the material of the fixed body 20 is α, then LL ′ = LL + α · ΔT · LL (1) On the other hand, since the intermediate layer I1 extends in the device inner side portion N, the length L5 of the section D5 changes to the length L5 '. Here, the linear expansion coefficient of the intermediate layer I1 is β (first layer I
L5 ′ = L5 + β · ΔT · L5 (2), where L5 ′ = L5 + β · ΔT · L5 (2) is the apparent linear expansion coefficient determined by the ratio of the thicknesses of 1a and the second layer I1b.

In order for the length L3 of the section D3 to be always constant despite the temperature change ΔT, LL'-L5 '= LL-L5 (3). By rearranging equations (1) to (3), β = α · (LL / L5) (4) is obtained. Now, let's perform a calculation with specific numerical values. Now, L3 = 0.2 mm, L4 = 1 μm (as described above, this value is ignored and L4 = 0), L
If 5 = 2.8 mm, LL = 3.0 mm, and the linear expansion coefficient α of aluminum is 25 × 10 ⁻⁶ , β = about 26.8 × 10 ⁻⁶ can be obtained from the equation (4). Here, as shown in FIG. 10, the intermediate layer I1 is a first layer I1a having a thickness a.
(42-alloy) and the second layer I1b (glass epoxy resin) having the thickness b, the apparent coefficient of linear expansion β is 4.9 × 10 ^{−6 of the} coefficient of linear expansion of 42-alloy.
And the linear expansion coefficient of glass epoxy resin 48 × 10 ⁻⁶ , β = (a · (4.9 × 10 ⁻⁶ ) + b · (48 × 10 ⁻⁶ )) / (a + b) (5) Become. By the way, since a + b = L5 = 2.8 mm and β = about 26.8 × 10 ⁻⁶ , if this is applied to the equation (5), a = 1.378 mm and b = 1.422 mm are obtained. After all, in the case of designing with the above-mentioned specific dimensions, if the intermediate layer I1 is composed of the 42-alloy layer having a thickness of 1.378 mm and the glass epoxy resin layer having a thickness of 1.422 mm, regardless of the temperature change ΔT. , Length of section D3 L
3 is always constant.

A concrete embodiment based on the above principle is shown in FIG. In this embodiment, both the displacement body 10 functioning as a common displacement electrode and the fixed body 20 functioning as a device housing are made of aluminum, and the fixed electrodes B1 to B5 are each made of 42-alloy. The first layer I1a to I5a and the second layer I1b to I5b made of glass epoxy resin are formed on the inner surface of the fixed body 20 through an intermediate layer (some of the components are not shown in FIG.
1 is not shown). The embodiment shown in FIG. 12 is an example in which the fixed electrode side is a common electrode. After all, the displacement body 10
The fixed body 20 is made of aluminum, and the displacement electrodes A1 to A5 are made of 42-alloy first layers J1a to J5a and glass epoxy resin second layers J1b to J5b, respectively. It is formed on the outer surface of the displacement body 10 via an intermediate layer consisting of (part of the components are not shown in FIG. 12). In these examples, since the housing is made of aluminum, it is excellent in robustness, and since the intermediate layer having a linear expansion coefficient close to that of aluminum is used, the temperature characteristic is also good.

Although the intermediate layer is formed of two layers in the above embodiment, it is also possible to form the intermediate layer of three or more layers.

§4 Second Solution Method The second solution method is based on the idea of exposing an intermediate layer having a different coefficient of thermal expansion to the outside of the housing, and an embodiment to which this second solution method is applied. Is shown in FIG. The structure of the displacement body 10 is similar to that of the above-described embodiment, but the structure of the fixed body 30 is slightly different from that of the fixed body 20 of the above-described embodiment.
That is, the displacement portion 10 is supported by the flexible portion 31 and the side surface of the displacement body 10 is surrounded by the surrounding portion 32, which is similar to the above-described embodiment, but the fixed substrates B1 to B5.
It is characterized by how it is formed. An opening O1 is provided in a part of the upper wall surface of the fixed body 30, and an intermediate layer E1 made of an insulating material is attached to the outer side surface of the opening O1 with a screw 33. The fixed electrode B1 is formed on the inner surface of E1. Regarding the fixed electrode B2, an opening O2 is provided in a part of the side wall surface of the surrounding portion 32, and an intermediate layer E2 made of an insulating material is attached to the outer surface of the opening O2 ( Although the cavity 34 in the drawing cannot be said to be outside the housing, in the present specification,
Since the one closer to the displacement body 10 is always called the inner side,
The cavity 34 can be said to be outside with respect to the opening O2), and the fixed electrode B2 is formed on the inner side surface of the intermediate layer E2. The fixed electrodes B3 to B5 are also formed in the same structure.

It will be explained with reference to the model of FIG. 14 that such a structure does not adversely affect the temperature characteristics. This model corresponds to the fixed electrode B1 in the embodiment shown in FIG.
This is a model showing how the distance between the displacement electrode A1 (which is actually the upper surface of the displacement body 10 serving as the common displacement electrode A0) opposed thereto changes with temperature.
Here, the displacement body 10, the fixed body 30, and the fixed electrode B1 are assumed to be made of the same metal, and only the intermediate layer E1 is made of a different insulating material. Then, consider the vertical extension of the figure that occurs when the temperature of the entire device rises. Here, as shown in FIG. 14, for convenience, there are five sections D1 to D.
5 is defined, and the elongations of the apparatus outer side portion M and the apparatus inner side portion N are compared. In the sections D1, D2 and D4, the outer side portion M of the apparatus and the inner side portion N of the apparatus are made of the same metal, so that the amount of elongation is the same. Further, the amount of elongation in the section D5 does not affect the problematic electrode spacing. This is because the intermediate layer E1 is attached to the outside of the fixed body 30, and therefore the expansion is directed only to the outside. In other words, the position of the inner surface of the intermediate layer E1 (indicated by S in the figure) is determined independently of the expansion of the intermediate layer E1. After all, the problem is only in the section D3.

This second solution cannot solve the problem based on the extension of the section D3. However, since the length of the section D3 can be made smaller than the length of the section D5 (thickness of the intermediate layer E1), this is not a big problem. Therefore, the embodiment shown in FIG. 13 can be practically used as a device having sufficient temperature characteristics.

The intermediate layer E1 may extend in the lateral direction due to temperature change. Therefore, as shown in FIG. 13, when the intermediate layer E1 is fixed by the screws 33,
Due to the temperature change, the intermediate layer E1 may warp upward or downward in a convex shape, and the distance between the electrodes may change due to the temperature. To prevent such a phenomenon, the intermediate layer E
It may be fixed so that 1 can move freely in the lateral direction.

The present invention has been described above based on several illustrated embodiments, but the present invention is not limited to these embodiments and can be implemented in various modes other than this. .. For example, the above-described embodiment is an example in which the present invention is applied to a force detection device, but if the displacement body 10 is used as a weight, it can be used as an acceleration detection device, and the displacement body 10 is a magnetic body. If configured, it can also be used as a magnetic detection device.

[0042]

As described above, according to the present invention, an electrode is formed on a metal casing through an insulating intermediate layer in a physical quantity detecting device utilizing a change in electrostatic capacitance, Since this intermediate layer has a two-layer structure and is set to have a thermal expansion coefficient close to that of a metal, it is possible to realize a robust detection device having excellent temperature characteristics. Further, the same effect can be obtained by adopting a structure in which the intermediate layer is attached to the outside of the housing.

[Brief description of drawings]

FIG. 1 is a side sectional view of a force detection device which is the basis of the present invention.

FIG. 2 is a perspective view of a displacement body 10 in the force detection device shown in FIG.

FIG. 3 is a cross-sectional view of the force detection device shown in FIG. 1 taken along the XY plane.

4 is a side sectional view showing a state in which a moment -My about the Y axis is applied to the force detection device shown in FIG.

5 is a circuit diagram showing an example of wiring applied to the force detection device shown in FIG.

6 is a side sectional view of an embodiment in which the structure of the force detection device shown in FIG. 1 is simplified.

FIG. 7 is a side sectional view showing the structure of the force detection device shown in FIG. 6 when the housing is made of metal.

FIG. 8 is a model for explaining the influence of temperature change in the embodiment shown in FIG.

FIG. 9 is a table showing linear expansion coefficients of various materials.

10 is a diagram showing an extracted portion of a section D5 in the model shown in FIG.

FIG. 11 is a side sectional view of a force detection device according to a specific embodiment of the present invention.

FIG. 12 is a side sectional view of a force detection device according to another specific embodiment of the present invention.

FIG. 13 is a side sectional view of a force detection device according to still another specific example of the present invention.

FIG. 14 is a model for explaining the influence of temperature change in the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Displacement body 11 ... Disc-shaped flat plate 11a ... 1st displacement surface 12 ... Square columnar columnar body 12a-12d ... 2nd displacement surface 20 ... Fixed body 20a ... 1st fixed surface 21 ... Flexible part 22 ... Enclosing part 22a-22d ... 2nd fixed surface 30 ... Fixed body 31 ... Flexible part 32 ... Enclosing part 33 ... Screw 34 ... Cavity A1-A5 ... Displacement electrode B1-B5 ... Fixed electrode C1-C5 ... Capacitance element D1 -D6 ... Section E1, E2, E4 ... Intermediate layer I1, I2, I4 ... Intermediate layer I1a, I2a, I4a ... 1st layer I1b, I2b, I4b ... 2nd layer J1a, J2a, J4a ... 1st layer J1b, J2b, J4b ... second layer M ... device outer part N ... device inner part O ... origin O1, O2 ... opening P ... point of action T0-T5 ... output terminal

Claims (7)

[Claims] 1. A fixed body having a displacement body that is displaced by the action of an external force, and a flexible portion that supports the displacement body, and has a function as a housing that houses at least a part of the displacement body. A displacement electrode fixed on a partial surface of the displacement body accommodated in the fixed body, and a fixed electrode facing the displacement electrode and fixed on a partial inner surface of the fixed body. And a detection means for detecting a change in the distance between the displacement electrode and the fixed electrode as a change in the electrostatic capacitance between the two electrodes, and the external force acting on the displacement body is detected by the detection means. In the detection device, the fixed body is made of metal, and the fixed electrode is formed on the metal surface via an intermediate layer, and the intermediate layer has a coefficient of thermal expansion larger than that of the metal. From the first material with A first layer and a second layer made of a second material having a thermal expansion coefficient smaller than that of the metal, and the first material and the second material A physical quantity detection device utilizing a change in capacitance, characterized in that at least one of the second materials is made of an insulating material. 2. A fixed body having a displacement body that is displaced by the action of an external force, and a flexible portion that supports the displacement body, and has a function as a housing that houses at least a part of the displacement body. A displacement electrode fixed on a partial surface of the displacement body accommodated in the fixed body, and a fixed electrode facing the displacement electrode and fixed on a partial inner surface of the fixed body. And a detection means for detecting a change in the distance between the displacement electrode and the fixed electrode as a change in the electrostatic capacitance between the two electrodes, and the external force acting on the displacement body is detected by the detection means. In the detection device, the fixed body and the displacement body are made of metal so that the displacement electrode is formed on the metal surface via an intermediate layer, and the intermediate layer has a coefficient of thermal expansion higher than that of the metal. Has a large coefficient of thermal expansion At least two layers of a first layer made of a first material and a second layer made of a second material having a coefficient of thermal expansion smaller than that of the metal; and At least one of the first material and the second material is made of an insulating material. A physical quantity detection device utilizing a change in electrostatic capacity. 3. The detection device according to claim 1 or 2, wherein the displacement body or the fixed body itself is used as a displacement electrode or a fixed electrode, and a physical quantity detection device utilizing a change in capacitance is used. .. 4. The detection device according to claim 1, wherein the change in the distance between the displacement electrode and the fixed electrode caused by thermal expansion of each part of the detection device is smaller than the intermediate value. A physical quantity detection device utilizing a change in capacitance, characterized in that a thickness ratio of each of a first layer and a second layer constituting the layer is determined. 5. The detection device according to claim 1, wherein the metal is aluminum and the first material is 42.
An alloy and a glass epoxy resin as the second material are used, respectively, to detect a physical quantity utilizing a change in capacitance. 6. A fixed body having a displacement body that is displaced by the action of an external force and a flexible portion that supports the displacement body, and has a function as a housing that houses at least a part of the displacement body. A displacement electrode fixed on a partial surface of the displacement body accommodated in the fixed body, a fixed electrode facing the displacement electrode and fixed to the fixed body, and the displacement electrode A detection device that detects a change in the distance between the fixed electrode and the fixed electrode as a change in capacitance between the electrodes; and a detection device that detects an external force acting on the displacement body by the detection device. The fixed body is made of metal, an opening is provided in a part of the wall surface of the fixed body, an intermediate layer made of an insulating material is attached to the outer surface of the opening, and a fixed electrode is formed on the inner surface of the intermediate layer. Capacitance characterized by A physical quantity detection device that utilizes changes in the temperature. 7. The detection device according to claim 6, wherein the displacement body itself is used as a displacement electrode, and the physical quantity detection device utilizes a change in capacitance.