JP2538068Y2 - Acceleration detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration detecting device, and more particularly to an acceleration detecting device for detecting an applied force based on a change in capacitance between a pair of electrodes.

[0002]

2. Description of the Related Art In the automobile industry, the machine industry, and the like, the demand for an acceleration detecting device capable of accurately detecting an applied force is increasing. In particular, there is a demand for a small device capable of detecting the acceleration acting on each of the three-dimensional components.

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 based on an externally applied force is converted into an electric signal using a piezoresistance effect. There has been proposed an acceleration detecting device which performs the following. However, such a detection device using a gauge resistor has a problem that the manufacturing cost is high and temperature compensation is required. In view of this, Japanese Patent Application No. 2-274299 proposes a novel acceleration detecting device utilizing a change in capacitance. In this novel acceleration detection device, a capacitance element is formed by a fixed electrode formed on a fixed substrate and a displacement electrode that generates displacement by the action of a force, and based on a change in capacitance of the capacitance element, Each of the three-dimensional components of the applied force can be detected. Further, Japanese Patent Application No. 2-416188 discloses a method of manufacturing the novel acceleration detecting device, and PCT / JP91 / 00428 pertaining to an international application based on the Patent Cooperation Treaty discloses this novel method. An inspection method for an acceleration detection device is disclosed.

[0004]

However, it is difficult to manufacture a new acceleration detecting device utilizing the above-mentioned change in capacitance, which can satisfy both robustness and high sensitivity. There is a problem that there is. In recent years, the demand for the acceleration detection device has been particularly increased in automobiles, and a device capable of detecting acceleration with high sensitivity and having robustness is desired. However, in order to improve the sensitivity of the conventionally proposed acceleration detection device, a structure is required to bend even when a small acceleration is applied, and the robustness is reduced. Become.

Accordingly, an object of the present invention is to provide an acceleration detecting device capable of detecting acceleration with high sensitivity and having robustness.

[0006]

Means for Solving the Problems (1) In a first aspect of the present invention, in an acceleration detecting device, a support substrate having a through hole in a central portion, a first substrate joined to a lower surface of the support substrate, and a first substrate inside the support substrate. A lower housing forming a room, an upper housing joined to an upper surface of the support substrate to form a second room therein, and a diaphragm attached to an upper surface of the support substrate in the second room; A weight body housed in the first room at a predetermined distance from the wall surface of the room and inserted into a through hole of the support substrate, one end of the weight body is joined to the weight body, and the other end is joined to the lower surface of the diaphragm. Provided, and a displacement board joined to the upper surface of the diaphragm, and detects the acceleration acting on the weight as a change in the distance between the displacement board and a predetermined fixed surface in the upper housing. It was made to be able to get.

(2) In the second invention of the present application, in the above-described acceleration detecting device, an auxiliary substrate fixed to an upper housing is further provided between the diaphragm and the displacement substrate, and a through hole formed in the auxiliary substrate is formed. The displacement board is indirectly joined to the diaphragm by a joining member to be inserted, and an external force is detected in consideration of a change in the distance between the displacement board and the auxiliary board.

[0008]

[Operation] In the acceleration detecting device of the present invention, the weight body is the first.
In the room, the connecting member is suspended from the diaphragm. When acceleration acts on the weight, the weight is displaced in the first room due to deformation of the diaphragm. A predetermined interval is provided between the weight and the wall surface of the first room. Therefore, the displacement of the weight body is limited to the predetermined interval. Therefore, even when excessive acceleration acts, the displacement of the weight body does not exceed the limit, and the diaphragm can be protected from damage. Therefore, sufficient robustness can be ensured even in a severe environment such as when mounted on an automobile.

[0009] The displacement of the weight body is transmitted to the displacement substrate joined to the diaphragm. Since the displacement substrate 150 generates displacement only in accordance with the direction and magnitude of the applied acceleration, a change in the distance between a predetermined fixed surface in the upper housing and the displacement substrate is caused by, for example, a change in capacitance. , It is possible to detect the direction and magnitude of the applied acceleration. Since the diaphragm is deformed by the action of a relatively small force, very sensitive detection is possible.

[0010] In addition, by performing detection in consideration of a change in the distance between the displacement substrate and the auxiliary substrate, accurate detection becomes possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. FIG. 1 is a side sectional view of an acceleration detecting device according to an embodiment of the present invention. The support substrate 100 is a flat plate having a through hole 101 at the center, and a screw hole 102 at the end.
Are formed. A screw is inserted into the screw hole 102, and the device is fixed at a predetermined position of an inspection object such as an automobile. A lower housing 110 is provided on the lower surface of the support substrate 100.
Are joined, and a first room R1 is formed inside. Further, on the upper surface of the support substrate 100, the upper housing 12 is provided.
0 are joined, and a second room R2 is formed inside. In the apparatus of this embodiment, each of the support substrate 100, the lower housing 110, and the upper housing 120 is made of metal.

In the second room R2, a bowl-shaped diaphragm 130 is attached so as to face down on the upper surface of the support substrate 100. In this embodiment, the diaphragm 130 is made of phosphor bronze. The diaphragm 130 is
The whole shape is bowl-shaped, and each part has a wavy structure. The use of a bowl-shaped diaphragm having such a waveform is effective in increasing the detection sensitivity. If the sensitivity may be low, a flat diaphragm may be used. The weight 140 is accommodated in the first room R1 so as to keep a predetermined distance from the wall surface of the room. The weight body 140 has a columnar shape in this embodiment, and its side surface and bottom surface are surrounded by the inner wall of the lower housing 110 at a predetermined interval, and the upper surface is located on the lower surface of the support substrate 100. At predetermined intervals. Through hole 10
The weight body 140 is joined to the center of the lower surface of the diaphragm 130 by the joining member 141 through which the weight member 1 is inserted. Therefore, the weight body 140 is suspended from the center of the lower surface of the diaphragm 130 in the air.

When acceleration acts on the weight body 140, the force due to the acceleration is transmitted to the diaphragm 130 via the joining member 141, and as a result, the diaphragm 130 is deformed. After all, the weight body 140 is the first
Exercise based on the acceleration in the room R1. In order to make the movement of the weight body 140 smooth, in the device of the present embodiment, the space portions of the first room R1 and the second room R2 are filled with damping oil. When the oil is completely filled in each room, the oil may leak to the outside when thermally expanded. Therefore, it is actually preferable to partially fill the gas.

The displacement caused by the acceleration acting on the weight body 140 is transmitted from the diaphragm 130 to the displacement board 150 via the joining member 142. Therefore, the displacement substrate 150 generates displacement only in accordance with the direction and magnitude of the applied acceleration. Therefore, if the change in the distance between the predetermined fixed surface in the upper housing 120 and the displacement substrate 150 is detected, the direction and magnitude of the applied acceleration can be detected.

In this device, this change in distance can be detected as a change in capacitance. That is,
Five displacement electrodes 21 to 25 (only three of them are shown in FIG. 1) are formed on the upper surface of the displacement substrate 150, and the inner bottom surface of the upper housing 120 is interposed with an insulating layer 160. 5
The fixed electrodes 11 to 15 (only three of them are shown in FIG. 1) are formed. The reason why the insulating layer 160 is formed is that the upper housing 120 is made of metal as described above. In this embodiment, the displacement substrate 150 is made of an insulator. However, when the displacement substrate 150 is made of a metal, the displacement electrodes 21 to 25 are formed via an insulating layer. As described above, if five pairs of electrodes including the displacement substrate and the fixed substrate are formed, a change in the distance between the electrodes can be detected based on a change in the capacitance of each electrode pair. That is, the acceleration acting on the weight body 140 can be detected. Regarding this detection principle,
It will be described later.

The acceleration detecting device having such a structure has considerable robustness and can detect acceleration with high sensitivity. When acceleration acts on the weight 140, the deformation of the diaphragm 130 causes the weight 140
Are displaced in the first room. A predetermined interval is provided between the weight 140 and the wall surface of the first room R1. Therefore, the displacement of the weight 140 is limited to the predetermined interval. For example, even if the weight body 140 is displaced in the horizontal direction in the drawing beyond a predetermined limit, the lower housing 11
Such an excessive displacement cannot be performed because of the collision with the inner wall of the 0 side surface. Similarly, even if it is displaced upward, it collides with the lower surface of the support substrate 100, and if it is displaced downward, it collides with the inner wall of the bottom surface of the lower housing 110.
Therefore, even when excessive acceleration acts, the displacement of the weight body 140 does not exceed the limit, and the diaphragm 130 can be protected from damage. Therefore, sufficient robustness can be ensured even in a severe environment such as when mounted on an automobile.

As described above, since a force that causes excessive displacement is never applied to the diaphragm 130, a delicate diaphragm having a small thickness and exhibiting flexibility even with a small force is used. However, no damage problem occurs. Therefore, by using such a delicate diaphragm, highly sensitive detection becomes possible. The feature of the acceleration detecting device according to the present invention is that it has robustness and can perform highly sensitive detection.

FIG. 2 is a top view of a diaphragm 135 used in an acceleration detecting device according to another embodiment of the present invention.
This diaphragm 135 is formed by forming quadrant-shaped through holes H1 to H4 in the bowl-shaped diaphragm 130 shown in FIG. That is, if the four portions of the diaphragm 130 are cut out in a quadrant, the diaphragm 135 can be obtained. By providing the four through holes H1 to H4, bridge portions B1 to B4 are formed. The central part to which the joining member 142 is joined is the four bridging parts B1 to B4
, The flexibility is further increased, and more sensitive detection becomes possible. The through hole H
Since the openings 1 to H4 are opened, the damping oil in the first room R1 moves to the second room R2 through the through holes H1 to H4 with the displacement of the weight body 140.

The acceleration detecting device shown in FIG. 1 can detect acceleration components in all three-dimensional directions. This detection principle will be described with a simple model shown in FIG. The main components of the model shown in FIG. 3 are a fixed substrate 10, a flexible substrate 20, an operating body 30, and a device housing 40.
It is. FIG. 4 shows a bottom view of the fixed substrate 10. FIG. 3 shows a cross section of the fixed substrate 10 of FIG. 4 cut along the X-axis. The fixed substrate 10 is a disk-shaped substrate as shown, and the periphery thereof is fixed to the device housing 40. On the lower surface, fan-shaped fixed electrodes 11 to 14 and a disk-shaped fixed electrode 15 are formed as shown in the figure. On the other hand, FIG. 5 shows a top view of the flexible substrate 20. FIG. 3 shows a cross section of the flexible substrate 20 of FIG. 5 cut along the X-axis. The flexible substrate 20 is also a disk-shaped substrate as shown, and the periphery thereof is fixed to the device housing 40. On this upper surface, fan-shaped displacement electrodes 21 to 24 and a disk-shaped displacement electrode 25 are formed as shown in the figure. The action body 30 has a columnar shape as shown by a broken line in FIG. The device housing 40 is
It has a cylindrical shape and fixedly supports the periphery of the fixed substrate 10 and the flexible substrate 20. The fixed substrate 10 and the flexible substrate 20 are provided at predetermined intervals at positions parallel to each other. Each of them is a disk-shaped substrate.
Is a substrate having high rigidity and hardly causing bending, whereas the flexible substrate 20 has flexibility and is a substrate which bends when a force is applied. It can be seen that the operation of such a model is equivalent to the operation of the device shown in FIG.

Now, as shown in FIG. 3, an action point P is defined in the action body 30, and an XYZ three-dimensional coordinate system having the action point P as an origin is defined as shown in FIG. That is, the X axis is defined in the right direction in FIG. 3, the Z axis is defined in the upward direction, and the Y axis is defined in the direction perpendicular to the paper surface toward the back side of the paper surface. The central portion of the flexible substrate 20 to which the operating body 30 is joined is an operating portion,
The peripheral portion fixed by the device housing 40 is referred to as a fixed portion, and the portion therebetween is referred to as a flexible portion.
When an external force acts on 0, the flexible portion is bent, and the acting portion is displaced with respect to the fixed portion. In a state where no force acts on the action point P, as shown in FIG. 3, the fixed electrodes 11 to 15 and the displacement electrodes 21 to 25 are kept in parallel at a predetermined interval. Now, fixed electrodes 11 to 15
And the combination of the displacement electrodes 21 to 25 facing each other will be referred to as capacitance elements C1 to C5, respectively. Here, for example, a force Fx in the X-axis direction is applied to the point of action P.
When this acts, this force Fx generates a moment force on the flexible substrate 20, and as shown in FIG.
Will bend. Due to this bending, the distance between the displacement electrode 21 and the fixed electrode 11 increases, but the distance between the displacement electrode 23 and the fixed electrode 13 decreases. Assuming that the force applied to the point of action P is -Fx in the opposite direction, the bending in the opposite relationship to this occurs. Thus, the force Fx
Or when -Fx acts, the capacitance elements C1 and C3
Changes, the force Fx or −Fx can be detected by detecting the change. At this time, the distance between each of the displacement electrodes 22, 24, and 25 and each of the fixed electrodes 12, 14, and 15 may be partially increased or decreased, but may not be changed as a whole. On the other hand, when a force Fy or −Fy in the Y direction acts, the displacement electrode 22 and the fixed electrode 12
And the distance between the displacement electrode 24 and the fixed electrode 14 have the same change. Further, when the force Fz in the Z-axis direction acts, as shown in FIG. 7, the distance between the displacement electrode 25 and the fixed electrode 15 decreases, and when the force −Fz in the opposite direction acts, this distance becomes growing. At this time, the distance between the displacement electrodes 21 to 24 and the fixed electrodes 11 to 14 also becomes smaller or larger, but the change in the distance between the displacement electrode 25 and the fixed electrode 15 is most remarkable. Therefore, the force Fz or -Fz can be detected by detecting a change in the capacitance of the capacitive element C5.

In general, the capacitance C of a capacitive element is determined by C = εS / d, where S is an electrode area, d is an electrode interval, and ε is a dielectric constant. Therefore, the capacitance C increases as the distance between the opposing electrodes decreases, and decreases as the distance increases. This acceleration detecting device utilizes this principle to measure the change in capacitance between the electrodes and detect an external force acting on the point of action P based on the measured value. That is, the acceleration in the X-axis direction is based on the capacitance change between the capacitance elements C1 and C3, and the acceleration in the Y-axis direction is the capacitance elements C2 and C3.
4 based on the capacitance change, the acceleration in the Z-axis direction
5, the detection is performed based on the capacitance change.

Actually, a force component in each axial direction is detected by a detection circuit as shown in FIG. That is, the capacitance values of the capacitance elements C1 to C5 are
The voltage values are converted into voltage values V1 to V5 by 1 to 55. Then, the force in the X-axis direction is calculated by the subtractor 61 as (V1-V
3) is obtained at the terminal Tx as a differential voltage obtained by performing the operation
The force in the Y-axis direction is obtained at the terminal Ty as a difference voltage obtained by performing the operation of (V2−V4) by the subtractor 62, and the force in the Z-axis direction is obtained as it is at the terminal Tz as the voltage V5.

Next, another embodiment will be described. The embodiment shown in FIG. 9 further improves on the embodiment of FIG.
The detection accuracy in the Z-axis direction (vertical direction in the figure) is improved. The diaphragm 130 and the displacement board 150 are connected by a joining member 142, and an auxiliary board 170 is further provided between them. A through-hole is formed at the center of the auxiliary substrate 170, and the through-hole
42 is inserted. Capacitance elements C1 to C5 are configured by displacement electrodes 21 to 25 and fixed electrodes 11 to 15 formed on the upper surface of the displacement substrate 150 in the same manner as in the above-described embodiment. Displacement board 150
The capacitive element C6 is formed by the displacement electrode 26 formed on the lower surface of the auxiliary substrate 170 and the fixed electrode 16
Is configured. In the detection device having such a configuration, the detection value in the Z-axis direction is obtained by the circuit shown in FIG. That is, the capacitance values of the capacitance elements C5 and C6 are set to CV
The conversion circuits 55 and 56 convert the voltage values into V5 and V6, and the subtracter 63 calculates the difference V5-V6, which is used as the detection value in the Z-axis direction. If the difference is used for the detection in the Z-axis direction as described above, the error factor is canceled out, and more accurate detection becomes possible. The reason for this is explained in the international application PCT / JP based on the Patent Cooperation Treaty.
It is described in detail in §4 of the specification of US 91/00428.

Although the present invention has been described based on the illustrated embodiments, the present invention is not limited to these embodiments, but can be implemented in various other modes. The shape of each part in the acceleration detecting device shown in FIG. 1 can be freely changed in design. For example, the weight 140 can be formed into a sphere or an ellipsoid. Also,
The number and arrangement of the electrodes are not limited to the above embodiment. In the above-described embodiment, five sets of capacitance elements are formed by five fixed electrodes and five displacement electrodes. However, one set of electrodes is used as one common electrode to form five sets of capacitance elements. It doesn't matter. The capacitance element is not necessarily 5
Neither is it necessary. It is also possible to perform three-dimensional acceleration detection by using four sets of capacitive elements. If two-dimensional or one-dimensional acceleration detection is performed, two or one set of capacitive elements is sufficient. Further, a method for detecting the displacement state of the displacement substrate 150 is not limited to a method for detecting a change in capacitance due to a capacitance element. For example, in the device shown in FIG.
When a piezoelectric element is inserted between the piezoelectric element and the displacement electrodes 21 to 25, the distance between the electrodes can be detected by the electromotive force of the piezoelectric element.

[0025]

As described above, in the acceleration detecting device according to the present invention, the displacement of the weight body is limited to the first room, the weight body is suspended by the diaphragm, and the acceleration acting on the weight body is reduced. Is detected, acceleration detection with high sensitivity is possible, and sufficient robustness can be ensured.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an acceleration detection device according to an embodiment of the present invention.

FIG. 2 is a top view of a diaphragm used in another embodiment of the present invention.

FIG. 3 is a side sectional view of a simple model for explaining the operation of the acceleration detection device shown in FIG. 1;

4 is a bottom view of the fixed substrate 10 in the model shown in FIG.

FIG. 5 is a top view of a flexible substrate 20 in the model shown in FIG.

FIG. 6 is a side sectional view showing a state where a force Fx in the X-axis direction is applied to the model shown in FIG. 3;

7 is a side sectional view showing a state where a force Fz in the Z-axis direction is applied to the model shown in FIG. 3;

8 is a circuit diagram showing a signal processing circuit used in the acceleration detection device shown in FIG.

FIG. 9 is a side sectional view of an acceleration detecting apparatus according to another embodiment of the present invention.

10 is a circuit diagram of a signal processing circuit used in the detection device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Fixed board 11-16 ... Fixed electrode 20 ... Flexible board 21-26 ... Displacement electrode 30 ... Working body 40 ... Device housing 51-56 ... CV conversion circuit 61-63 ... Subtractor 100 ... Support board 101 ... Penetration Hole 102: Screw hole 110: Lower housing 120: Upper housing 130, 135 ... Diaphragm 140: Weight body 141, 142 ... Joining member 150: Displacement board 160 ... Insulating layer 170 ... Auxiliary board B1-B4 ... Bridge section H1 to H4: through hole R1: first room R2: second room

Claims (2)

(57) [Scope of request for utility model registration] 1. A support substrate having a through hole in a central portion, a lower housing joined to a lower surface of the support substrate to form a first room therein, and a lower housing joined to an upper surface of the support substrate, An upper housing forming a second room, a diaphragm attached to an upper surface of the support substrate in the second room, and a predetermined distance from a wall surface of the room in the first room. The weight member accommodated therein, inserted through the through hole, one end is joined to the weight body, the other end is joined to the lower surface of the diaphragm, and directly or indirectly to the upper surface of the diaphragm And a bonded displacement board,
An acceleration detecting device, wherein an acceleration acting on the weight body can be detected as a change in a distance between the displacement board and a predetermined fixed surface in the upper housing. 2. The acceleration detecting device according to claim 1, further comprising: an auxiliary substrate fixed to the upper housing between the diaphragm and the displacement substrate, and a joining member inserted through a through hole formed in the auxiliary substrate. Acceleration detection, wherein the displacement board is indirectly joined to the diaphragm by means of a diaphragm, and an external force is detected in consideration of a change in the distance between the displacement board and the auxiliary board. apparatus.