JPH06265569A - Acceleration sensor unit - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor unit in which the influence of acceleration in the axial directions other than a target axial direction is suppressed. CONSTITUTION:A mass part 12 is disposed in the center of a frame 11 and supported in cantilever by means of two beams 13 with covers 16a, 16b being bonded to the opposite sides of the frame 11. Recesses 17a, 17b for permitting the displacement of the mass part 12 are made in the inner faces of the covers 16a, 16b. Electrodes 15a, 15b for detecting the displacement of the mass part 12 are also provided on the bottom of the recesses 17a, 17b and the surface of the mass part 12 is used as a movable electrode 14 thus manufacturing an acceleration sensor 1. The acceleration sensor 1 is mounted horizontally on a circuit board 2 which is then secured at an angle theta to an insertion groove of an auxiliary fixing member such that the center of gravity M of the mass part 12 and the beam 13 are located on a substantially identical horizontal plane thus completing an acceleration sensor unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor unit. For example, the present invention relates to an acceleration sensor unit that detects acceleration and vibration of an automobile and that detects displacement of a mass portion caused by acceleration and vibration.

[0002]

2. Description of the Related Art FIG. 7 is a schematic sectional view showing a conventional acceleration sensor 50. This acceleration sensor 5
0 is a frame 51 having a rectangular frame shape made of a silicon substrate.
A mass portion 52 is disposed at the center of the opening of the mass portion 52, and the mass portion 52 is cantilevered by the frame 51 by two beams 53. The mass portion 52 has a thickness direction of the mass portion 52 (Y-axis direction in the drawing) due to elastic deformation of the beam 53.
The movable electrode 55 is formed on the bottom surface of the movable electrode 55.

A glass substrate 54 is provided on the upper and lower surfaces of the frame 51.
And the peripheral portion of the glass substrate 54 is joined to the frame 51. A stationary electrode 56 is provided on the inner surface of the glass substrate 54 on the lower surface of the frame 51 with a small gap from the movable electrode 55 of the mass portion 52.
The movable electrode 55 and the stationary electrode 56 form a capacitor.

However, when the mass portion 52 supported by the beam 53 is displaced in response to acceleration in the Y-axis direction, the space between the movable electrode 55 and the stationary electrode 56 of the mass portion 52 is changed according to the displacement amount of the mass portion 52. The gap amount changes and the capacitance changes. Therefore, the acceleration can be detected by outputting the change in the capacitance value as an electric signal.

Further, since the frame 51, the mass portion 52, and the beam 53 are made of a single crystal silicon substrate or the like, the beam 53 and the like can be efficiently formed by using an electrochemical etching method, and the productivity is improved. Acceleration sensor 5
0 can be produced.

However, according to the electrochemical etching method, it is not possible to etch both surfaces of the silicon substrate equally, and only one surface is etched, so that the beam 53 cannot be formed in the center of the silicon substrate in the thickness direction. . Therefore, when the acceleration sensor 50 is placed horizontally, the center axis Q of the beam 53 and the center of gravity R of the mass portion 52
Are not located on the same horizontal plane, and are easily affected by acceleration in the axial direction (for example, the X-axis direction) other than the purpose of detecting the Y-axis direction, and as shown in FIG. Base 57 with an angle that minimizes axial sensitivity
Is provided between the acceleration sensor 50 and the circuit board 58 to suppress the influence of acceleration other than the purpose.

Further, FIG. 9 shows another conventional acceleration sensor 60, which is an acceleration sensor 60.
Forms a beam 53 inside the frame 51 by chemically etching a single crystal silicon substrate from above and below with an etching solution and controlling the etching depth by controlling the time, and the central axis Q of the beam 53 and the mass portion. The influence of acceleration in the Y-axis direction is reduced by adopting a structure in which the center of gravity R of 52 is located on the same horizontal plane.

[0008]

However, in the structure shown in FIG. 8, the pedestal 57 is attached to each acceleration sensor 50 between the glass substrate 54 and the circuit board 58 on the lower surface of the acceleration sensor 50. Because you need
There is a problem that the workability of attaching the acceleration sensor 50 to the pedestal 57 is significantly reduced as the acceleration sensor 50 is downsized. For example, if the acceleration sensor 50 is made smaller, the pedestal 5
7 itself needs to be made smaller accordingly. Therefore, the angle for inclining the acceleration sensor 50 is set to the pedestal 5
It becomes difficult to machine to 7 and the angle also requires high accuracy. Also, in order to improve the angle accuracy, the pedestal 5
If 7 is made large, the mounting area on the circuit board 58 becomes large. Further, the acceleration sensor 50 is attached to the base 57.
If it is not attached correctly, the acceleration in the axial direction other than the detection axis will be detected, and errors will be included easily, resulting in lack of reliability.

Further, in the acceleration sensor 60 shown in FIG. 9, since the etching is performed under time control, it is easily affected by the temperature of the etching solution and the concentration of the etching solution.
There is a problem that productivity of the acceleration sensor 60 is remarkably reduced because it is difficult to control the temperature and the concentration and the etching time varies.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object thereof is to detect only a detection target axis component by using an acceleration sensor having high productivity. It is to provide an acceleration sensor unit that can be easily mounted.

[0011]

In the acceleration sensor unit according to the present invention, an acceleration sensor in which a mass portion whose center of gravity is not located on the central axis of the beam is swingably supported by a support by an elastic beam. Is mounted on a mounting board, and the mounting board is mounted in a casing. In an acceleration sensor unit, the acceleration detection sensitivity of another axis is set to the target acceleration detection axis of the acceleration sensor mounted on the mounting board. It is characterized in that the mounting board is loaded in the casing at an angle that minimizes.

The acceleration sensor to be mounted on the mounting board may be housed in a package such as a metal package, or may be mounted on the mounting board after being mounted on a fixed board for mounting on the mounting board.

[0013]

In the acceleration sensor unit of the present invention, the acceleration sensor mounted on the mounting board is mounted on the mounting board at an angle with respect to the target acceleration detection axis that minimizes the acceleration detection sensitivity of other axes. Since the casing is loaded in the casing, it is possible to detect the acceleration only in the target detection axis direction without being affected by the acceleration of other axes. That is, it is not necessary to provide a pedestal that is difficult to attach to each acceleration sensor, and the acceleration sensor can easily have an inclination angle by inclining the mounting substrate on which the acceleration sensor is mounted. For example, since the center of gravity of the mass part is not on the central axis of the beam, the acceleration sensor is mounted even when using an acceleration sensor that is easily affected by directions other than the detection axis direction of the acceleration sensor (displacement direction of the mass part). It is possible to make the mounted substrate have an inclination angle and hold it in the acceleration sensor unit so that the center of gravity of the mass portion and the beam are substantially on the same horizontal plane.

Further, the inclination angle for holding the mounting substrate in the acceleration sensor unit is set to a constant angle depending on the shape of the mass portion of the acceleration sensor and the like. Therefore, by mass-producing a unit body that can obtain a desired tilt angle, it is possible to easily provide a large number of acceleration sensor units that are not affected by acceleration in the other axis direction. Also, in order to increase the detection sensitivity by enlarging the mass part, even if the inclination angle is different, it is easy to provide an acceleration sensor unit with good detection sensitivity by making unit bodies with different inclination angles. can do.

Further, the acceleration sensor need only be mounted horizontally on the mounting board. Also, since the sensitivity of the other axis is reduced depending on the mounting angle of the mounting board on which the acceleration sensor is mounted, it is possible to reduce the error from the predetermined tilt angle and increase the mounting area of the acceleration sensor on the mounting board. Nor.

Further, if the acceleration sensor is previously housed in a package such as a metal package or mounted on a fixed substrate for mounting on the mounting substrate and then mounted on the mounting substrate together with the fixed substrate, the mounting work can be performed. Can be easy.

[0017]

1 is a schematic sectional view of an acceleration sensor unit A according to an embodiment of the present invention. Reference numeral 1 is an acceleration sensor for detecting acceleration, and 2 is a circuit board holding the acceleration sensor 1. On the circuit board 2, the output of the acceleration sensor 1 together with the acceleration sensor 1 is detected as an electric signal and amplified. Electronic components 4a and 4b forming the detection circuit 3 are mounted. The unit body 6 includes a fixing auxiliary member 5 for fixing and holding the circuit board 2 in the acceleration sensor unit A, shield plates 7 and 7 ′ made of a metal plate, a base 8 made of an insulating plastic material, and a lid. It is composed of 9.

After the acceleration sensor 1 is horizontally mounted on the circuit board 2, the acceleration sensor 1 is fixed to the circuit board 2 at a fixed angle .theta.
It is fixed to a.

FIG. 2 is a cross-sectional view showing the acceleration sensor 1 provided in the unit main body 6, and the acceleration sensor 1
Is a capacitance type. In this acceleration sensor 1, a mass portion 12 is arranged at the center of an opening portion of a frame 11 having a rectangular frame shape, and the mass portion 12 is supported by the frame 11 in a cantilever manner by two beams 13. Has been done. The mass portion 12 is formed by elastic deformation of the beam 13 as shown in FIG.
It is possible to freely make small displacements in the Y-axis direction.
Further, the frame 11, the beam 13, and the mass portion 12 are integrally formed of a crystalline silicon wafer using a semiconductor manufacturing process, and are entirely conductive, and the mass portion 12 functions as the movable electrode 14. Have. Further, in order to stop the etching of the beam 13 with a predetermined thickness,
A diffusion layer is formed on the crystalline silicon wafer by the thickness of the beam 13 and is electrochemically etched with an etching solution such as an aqueous solution of potassium hydroxide to form the frame 11 and the like.

Glass covers 16a and 16b are stacked on the upper and lower surfaces of the frame 11 to cover the covers 16a and 1b.
The peripheral portion of 6b is adhered to the frame 11 by an adhesive or an anodic bonding method in which a high voltage is applied at a high temperature for adhesion. Indentations 17a and 17b are formed on the inner surfaces of the covers 16a and 16b so that the mass portion 12 can be displaced, and displacements for detecting displacement of the mass portion 12 are formed at the bottoms of the depressions 17a and 17b of the covers 16a and 16b. Detection electrode 15a,
15b is provided.

In addition, the upper surface side of the movable electrode 14 of the mass portion 12 and the displacement detecting electrode 15a, and the movable electrode 1 of the mass portion 12
The capacitor constituted by the lower surface side of 4 and the displacement detection electrode 15b is connected to the detection circuit 3 through the beam 13 and the frame 11. The detection circuit 3 detects a change in the capacitance of the capacitor, converts the change in the capacitance into a change in voltage, and outputs the voltage to a terminal 18 provided in the unit body 6.

When acceleration is applied to the acceleration sensor 1, the mass portion 12 is displaced by the inertial force while elastically bending the beam 13, and the mass portion 12 is stopped at a position where the inertial force and the elastic restoring force of the beam 13 are balanced. . Alternatively, when vibration is applied to the acceleration sensor 1, the mass portion 12 also vibrates according to the vibration. At this time, according to the displacement amount of the mass portion 12, the mass portion 1
The amount of the gap between 2 and the displacement detection electrodes 15a and 15b changes, and the electrostatic capacitance between the movable electrode 14 of the mass portion 12 and the displacement detection electrodes 15a and 15b changes. This change in capacitance is detected by the detection circuit 3, converted into a voltage signal corresponding to the magnitude of the acceleration, and output, so that the acceleration can be known.

After the acceleration sensor 1 is fixed to the circuit board 2, the acceleration sensor 1 and the circuit board 2 are arranged so that the center of gravity M of the mass portion 12 of the acceleration sensor 1 and the beam 13 are substantially on the same horizontal plane. It is attached to the unit body 6 at a fixed angle θ. Then, when acceleration is applied to the acceleration sensor unit A, an inertial force acts on the mass portion 12, but the bending moment about the beam 13 causes Y
The mass portion 12 is displaced only in the axial direction (vertical direction), and thus accelerations other than the Y-axis direction are not detected,
Acceleration only in the Y-axis direction will be detected. In particular,
No bending moment is generated in the beam 13 due to the acceleration in the X-axis direction (horizontal direction), and the acceleration in the X-axis direction is not detected.

As described above, in the acceleration sensor unit A, the acceleration in the Y-axis direction can be accurately measured without being affected by the acceleration other than the Y-axis (detection axis) direction (in particular, it has no sensitivity in the X-axis direction). Can be measured.

FIG. 3 shows a measuring method for determining the fixed angle θ. The vertical axis represents the acceleration sensitivity (% FSO) in the X-axis direction in FIG. 2, and the horizontal axis represents the equivalent fulcrum L of the beam 13.
The inclination angle ω of the acceleration sensor 1 (the angle between the central axis of the beam 13 and the horizontal plane) is expressed so as to be negative when the acceleration sensor 1 is rotated counterclockwise (counterclockwise) in FIG. ing. As shown in FIG. 3, when the inclination angle is 0 °, that is, when the acceleration sensor 1 is held horizontally, the acceleration sensitivity in the −X axis direction (the acceleration sensitivity to the left in FIG. 2) is −50% FSO. As described below, when the acceleration sensor 1 is gradually rotated counterclockwise around the equivalent fulcrum L of the beam 13, the acceleration sensitivity in the X-axis direction is large in both the −X-axis direction and the + X-axis direction. The acceleration sensitivity in the −X axis direction becomes 0% FSO at the inclination angle of −13 °. That is, if the circuit board 2 is mounted on the unit body 6 at a fixed angle θ of, for example, 13 °, the center of gravity M of the mass portion 12 and the equivalent fulcrum L at the base end portion of the beam 13 are substantially on the same horizontal plane. To be present and minimize the acceleration sensitivity in the X-axis direction,
Only the acceleration in the Y-axis direction can be detected.

The fixed angle θ at which the circuit board 2 is mounted on the acceleration sensor unit A is determined by the positional relationship between the center of gravity M of the mass portion 12 and the beam 13, and the mass portion 12 of the acceleration sensor 1.
Since the acceleration sensor 1 having the same configuration has the same fixed angle θ because it is determined by the shape and weight of each part such as the beam 13 and the beam 13, the fixed angle θ is obtained by the initial measurement as described above. Therefore, the fixed portion 5a is set to have the fixed angle θ.
If the unit main body 6 is manufactured by providing the above, the acceleration sensor 1 having good productivity can be manufactured and housed in the unit main body 6, and the acceleration sensor unit A having good directivity can be easily manufactured.

If the unit main body 6 provided with the fixing portions 5a having various fixed angles θ is prepared,
It becomes possible to easily deal with the acceleration sensor 1 having various shapes of the mass portion and the like, and the mass portion 12 can be made large to easily improve the detection sensitivity of the acceleration sensor 1. Even when the acceleration sensor 1 is downsized, it is possible to provide the acceleration sensor unit A that can easily detect the acceleration only in the axial direction to be detected.

FIG. 4 shows a sectional view of the acceleration sensor 20 housed in the unit body 6 of the acceleration sensor unit B which is still another embodiment of the present invention. This acceleration sensor 2
Reference numeral 0 denotes a piezoresistive type, which is held horizontally on the circuit board 2 and then attached to the unit body 6 of the acceleration sensor unit B at a fixed angle θ. Further, on the upper surface of the beam 23, a piezoresistive element 28 whose resistance value changes according to the amount of strain generated in the piezoresistive element 28 is attached. On the other hand, the frame 21
A glass cover 26 is placed on the lower surface of the cover 2
A peripheral portion of 6 is adhered to the frame 21 by an anodic bonding method or the like, and a recess 27 is formed on the inner surface of the cover 26 so that the mass portion 22 can be displaced.

However, when acceleration or vibration is applied to the acceleration sensor 20, the mass portion 2 is responsive to the acceleration or vibration.
2 also vibrates, and the beam 23 is distorted.
At this time, the resistance value of the piezoresistive element 28 changes according to the amount of strain generated in the beam 23, and this change in resistance value is
Detected by the detection circuit 3 provided on the circuit board 2,
Since the voltage signal or the current signal corresponding to the magnitude of the acceleration is converted and output, the acceleration can be known.

Even in the acceleration sensor 20, as in the acceleration sensor 1 of the first embodiment, the equivalent fulcrum P of the beam 23 is obtained.
The fixed angle θ can be obtained by initially measuring the inclination angle ω (the angle between the central axis P of the beam 23 and the horizontal plane) centered at. Therefore, by mounting the circuit board 2 on the unit body 6 at a fixed angle θ so that the center of gravity O of the mass portion 22 and the fulcrum P of the beam 23 are substantially on the same horizontal plane, only the acceleration in the Y-axis direction is detected. be able to.

Therefore, even when the piezoresistive acceleration sensor 20 is used, it is possible to provide an acceleration sensor unit which can easily detect the acceleration only in the detection axis direction.

FIG. 5 is a partially broken sectional view of an acceleration sensor unit C which is still another embodiment of the present invention. The acceleration sensor 30 is packaged in a metal package 31 and then mounted on the circuit board 2. After that, it is held and fixed to the unit main body 6 at a fixed angle θ. The capacitor included in the acceleration sensor 30 is connected to the connection terminal 32 of the metal package 31, and is connected to the electronic components 4a, 4c, 4d on the fixed substrate via the connection terminal 32.

FIG. 6 is a partially cutaway sectional view of an acceleration sensor unit D which is another embodiment of the present invention.
The acceleration sensor 40 is fixed on a fixed substrate 41 and then packaged in an insulating plastic case 42.
The capacitor, which is surface-mounted on the circuit board 2 and is configured in the acceleration sensor 40, uses the electronic components 4a, which constitute the detection circuit 3, through the connection terminals (not shown) on the fixed substrate 41.
It is connected to 4c and 4d. Then, in order to minimize the axis sensitivity other than the detection purpose, the circuit board 2 is fixed at the fixed angle θ.
It is held and fixed to the unit body 6.

Like the acceleration sensor units C and D, if the acceleration sensors 30 and 40 are mounted on the metal package 31 or the fixed substrate 41 and then mounted on the circuit board 2, the acceleration sensors 30 and 40 are small. Even if it is made into a simple structure, it can be easily mounted on the circuit board 2, and the capacitor formed in the acceleration sensor 1 is connected to the detection circuit 3, and the piezoresistive element 28 formed on the beam 21 of the acceleration sensor 20.
And the detection circuit 3 are easily connected.

Further, in the above-described embodiment, the capacitors formed on the acceleration sensor 1 and the piezoresistive element 28 formed on the beam 23 of the acceleration sensor 20 are provided through the beams 13 and 23 and the frames 11 and 21. Although it is decided to connect to the detection circuit 3 on the circuit board 2, these detection circuits 3 are connected to the frame 1 of the acceleration sensors 1 and 20.
It may be provided on the units 1 and 21. When the detection circuit 3 is provided on the frames 11 and 21, it is not necessary to provide the detection circuit 3 on the circuit board 2, so that the acceleration sensor units A and B can be further downsized.

[0036]

According to the acceleration sensor unit of the present invention, the acceleration sensor mounted on the mounting board is mounted on the mounting board at an angle with respect to the acceleration detection axis that minimizes the acceleration detection sensitivity of other axes. Since the acceleration sensor unit is tilted and held by the acceleration sensor unit and the acceleration sensor has a tilt angle, it is possible to easily detect the acceleration only in the intended detection axis direction without being affected by the acceleration of other axes. it can.

Further, by mass-producing the unit main body capable of holding the mounting substrate at a desired inclination angle,
It is possible to easily provide an acceleration sensor unit that is not affected by acceleration in the other axis direction, and it is possible to easily provide an acceleration sensor unit with high detection sensitivity by preparing unit main bodies with different inclination angles. it can.

Furthermore, the acceleration sensor need only be mounted horizontally on the mounting board. Also, since the sensitivity of the other axis is reduced depending on the mounting angle of the mounting board on which the acceleration sensor is mounted, it is possible to reduce the error from the predetermined tilt angle and increase the mounting area of the acceleration sensor on the mounting board. Nor.

Further, if the acceleration sensor is previously housed in a package such as a metal package or is mounted on a fixed board for mounting on the mounting board and then mounted on the mounting board together with the fixed board, the mounting work is facilitated. Can be

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an acceleration sensor unit that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an acceleration sensor provided in the above unit body.

3 is a diagram showing the relationship between the inclination angle ω and the acceleration sensitivity in the X-axis direction in FIG. 2 in the above.

FIG. 4 is a cross-sectional view of an acceleration sensor mounted on a unit body of an acceleration sensor unit that is another embodiment of the present invention.

FIG. 5 is a partially cutaway sectional view of an acceleration sensor unit according to still another embodiment of the present invention.

FIG. 6 is a partially cutaway sectional view of an acceleration sensor unit according to still another embodiment of the present invention.

FIG. 7 is a cross-sectional view of a conventional acceleration sensor.

FIG. 8 is a cross-sectional view showing a base provided in the acceleration sensor of the above.

FIG. 9 is a cross-sectional view of an acceleration sensor which is another conventional example.

[Explanation of symbols]

 2 circuit board 3 detection circuit 5 fixing auxiliary member 12 mass part 13 beams 17a, 17b recess 31 metal package

Front Page Continuation (72) Inventor Shiro Fujioka 10 Ouron Co., Ltd.

Claims (3)

[Claims] 1. An acceleration sensor in which a mass portion whose center of gravity is not located on the central axis of the beam is swingably supported by a support by a beam having elasticity is mounted on a mounting board, and the mounting board is loaded in a casing. In the acceleration sensor unit, the mounting board is loaded in the casing at an angle that minimizes the acceleration detection sensitivity of another axis with respect to the intended acceleration detection axis of the acceleration sensor mounted on the mounting board. Acceleration sensor unit. 2. The acceleration sensor unit according to claim 1, wherein the acceleration sensor housed in a package such as a metal package is mounted on the mounting substrate. 3. The mounting unit according to claim 1, wherein the acceleration unit is mounted on a fixed substrate for mounting on the mounting substrate, and the acceleration sensor is mounted on the mounting substrate via the fixed substrate. The described acceleration sensor unit.