JP3230109B2 - Acceleration sensor unit - 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 sensor unit. For example, the present invention relates to a sensor for detecting acceleration or vibration of an automobile, and an acceleration sensor unit for detecting displacement of a mass portion caused by acceleration or vibration.

[0002]

2. Description of the Related Art FIG. 7 is a schematic sectional view showing a conventional acceleration sensor 50. As shown in FIG. This acceleration sensor 5
0 is a square frame-shaped frame 51 made of a silicon substrate.
A mass portion 52 is provided at the center of the opening portion, and the mass portion 52 is supported by the frame 51 in a cantilever manner by two beams 53. The mass portion 52 is moved in the thickness direction (Y-axis direction in the drawing) of the mass portion 52 by elastic deformation of the beam 53.
The movable electrode 55 is formed on the bottom surface thereof.

A glass substrate 54 is provided on the upper and lower surfaces of a frame 51.
Are overlapped, and the periphery 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 so as to leave 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.

When the mass 52 supported by the beam 53 is displaced by receiving an acceleration in the Y-axis direction, the distance between the movable electrode 55 and the stationary electrode 56 of the mass 52 depends on the displacement of the mass 52. And the capacitance changes. Therefore, acceleration can be detected by outputting the change in the value of the capacitance as an electric signal.

Since the frame 51, the mass 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 technique, and the productivity is improved. Acceleration sensor 5
0 can be produced.

However, according to the electrochemical etching method, it is impossible to uniformly etch from both sides of the silicon substrate, and only one side is etched, so that the beam 53 cannot be formed at the center in the thickness direction of the silicon substrate. . Therefore, when the acceleration sensor 50 is placed horizontally, the center axis Q of the beam 53 and the center of gravity R
Are not located on the same horizontal plane and are susceptible to acceleration in an axis direction other than the detection purpose in the Y-axis direction (for example, the X-axis direction). As shown in FIG. A pedestal 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 intended purpose.

FIG. 9 shows another conventional acceleration sensor 60.
Is to form 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 time control. By employing a structure in which the center of gravity R of 52 is located on the same horizontal plane, the influence of acceleration in the Y-axis direction is reduced.

[0008]

However, in the structure as shown in FIG. 8, a pedestal 57 is attached to each of the acceleration sensors 50 between the glass substrate 54 and the circuit board 58 on the lower surface of the acceleration sensor 50. Need to
As the size of the acceleration sensor 50 is reduced, the workability of attaching the acceleration sensor 50 to the pedestal 57 is significantly reduced. For example, when the acceleration sensor 50 is reduced,
7 itself must be reduced accordingly. For this reason, the angle for tilting the acceleration sensor 50 is
7 becomes difficult, and the angle is also required to have high accuracy. In order to improve the accuracy of the angle, the pedestal 5
7 is large, the mounting area on the circuit board 58 is large. Further, the acceleration sensor 50 is
If it is not accurately mounted, acceleration in the axial direction other than the detection axis will be detected, errors will be easily included, and reliability will be lacking.

Further, the acceleration sensor 60 shown in FIG. 9 is easily affected by the temperature of the etching solution and the concentration of the etching solution because the etching is performed by time control.
It is difficult to control the temperature and concentration, and the etching time varies, so that the productivity of the acceleration sensor 60 is significantly reduced.

The present invention has been made in view of the above-described drawbacks of the conventional example, and has as its object to detect only a detection target axis component using an acceleration sensor having high productivity. It is to provide an acceleration sensor unit that is easy to mount.

[0011]

According to the acceleration sensor unit of the present invention, the mass sensor whose center of gravity is not located at the center axis of the beam is swingably supported by the support by an elastic beam. In an acceleration sensor unit in which the mounting board is mounted on a casing, the mass section of the acceleration sensor mounted on the mounting board swings and detects an acceleration with respect to an axis .
The mass section is set so that the acceleration detection sensitivity of the other axes is minimized.
At the angle where the center of gravity of the beam and the beam are located on the same horizontal plane,
The present invention is characterized in that the mounting substrate is loaded in a casing.

Further, the acceleration sensor mounted on the mounting board may be housed in a package such as a metal package or mounted on a fixed board for mounting on the mounting board, and then mounted on the mounting board.

[0013]

According to the acceleration sensor unit of the present invention, the mass of the acceleration sensor mounted on the mounting board is swung and added.
With respect to the axis for detecting the speed, the acceleration detection sensitivity of the other axis
The center of gravity of the mass section and the beam should be the same so as to minimize
Since the mounting board is loaded in the casing at an angle positioned on the horizontal plane, it is possible to detect acceleration only in the target detection axis direction without being affected by acceleration of other axes. That is, it is not necessary to provide a pedestal, which is difficult to attach, to each acceleration sensor, and the acceleration sensor can easily have a tilt angle by tilting the mounting board on which the acceleration sensor is mounted. For example,
Since the center of gravity of the mass part is not on the center 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 (displacement direction of the mass part) of the acceleration sensor. By providing the mounting substrate with an inclination angle, the center of gravity of the mass portion and the beam can be held in the acceleration sensor unit such that they are substantially on the same horizontal plane.

Further, the inclination angle at which the mounting board is held in the acceleration sensor unit is fixed at a constant angle depending on the shape of the mass of the acceleration sensor. Therefore, by mass-producing the unit main body that can obtain a desired inclination angle, it is possible to easily provide a large number of acceleration sensor units that are not affected by the acceleration in the other axis direction. In addition, even if the tilt angle is different to increase the detection sensitivity by enlarging the mass part, an acceleration sensor unit with good detection sensitivity can be easily provided by manufacturing a unit body with a different tilt angle. can do.

Further, the acceleration sensor need only be mounted horizontally on the mounting board. In addition, since the sensitivity to other axes is reduced by the mounting angle of the mounting board on which the acceleration sensor is mounted, an error with a predetermined inclination angle can be reduced, and the mounting area of the acceleration sensor on the mounting board can be increased. Nor.

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

[0017]

FIG. 1 is a schematic sectional view of an acceleration sensor unit A according to an embodiment of the present invention. 1 is an acceleration sensor for detecting acceleration, and 2 is a circuit board holding the acceleration sensor 1. On the circuit board 2, together with the acceleration sensor 1, the output of the acceleration sensor 1 is detected and amplified as an electric signal. Electronic components 4a and 4b constituting 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 or the like, and a lid. 9.

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

FIG. 2 is a sectional view showing the acceleration sensor 1 provided in the unit main body 6.
Is a capacitance type. In the acceleration sensor 1, a mass portion 12 is disposed at the center of an opening 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. Have been. The mass portion 12 is caused by the elastic deformation of the beam 13 as shown in FIG.
Can be freely displaced minutely in the Y-axis direction.
The frame 11, the beam 13, and the mass portion 12 are formed integrally by using a semiconductor manufacturing process on a crystalline silicon wafer, and the entirety has conductivity, and the mass portion 12 functions as a movable electrode 14. Having. Further, in order to stop the etching of the beam 13 at a predetermined thickness,
A diffusion layer is formed on the crystalline silicon wafer by the thickness of the beam 13 and electrochemically etched with an etching solution such as an aqueous solution of potassium hydroxide to form the frame 11 and the like.

The upper and lower surfaces of the frame 11 are covered with glass covers 16a and 16b, respectively.
The periphery of 6b is adhered to the frame 11 by an adhesive or the like or an anodic bonding method of applying a high voltage at a high temperature to adhere. Depressions 17a and 17b are formed on the inner surfaces of the covers 16a and 16b so that the mass portion 12 can be displaced. Displacements for detecting the displacement of the mass portion 12 are formed on the bottoms of the depressions 17a and 17b of the covers 16a and 16b. The detection electrodes 15a,
15b is provided.

Further, the upper surface side of the movable electrode 14 of the mass portion 12 and the displacement detection 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 15 b 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 change 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 while elastically bending the beam 13 due to inertia force, and stops at a position where the inertia force and the elastic return 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, the mass 1
The gap between the second electrode 2 and the displacement detection electrodes 15a and 15b changes, and the 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 and 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 circuit board 2 is moved together with the acceleration sensor 1 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. The unit body 6 is provided with a fixed angle θ. Thus, 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 receives displacement only in the axial direction (vertical direction), and therefore, acceleration other than in the Y-axis direction is not detected,
The acceleration in only the Y-axis direction is detected. In particular,
No bending moment is generated in the beam 13 depending on 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 acceleration other than in the Y-axis (detection axis) direction (in particular, having 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.
When the acceleration sensor 1 is rotated counterclockwise (counterclockwise) in FIG. 2 around the center, the inclination angle ω (the angle between the central axis of the beam 13 and the horizontal plane) of the acceleration sensor 1 is expressed so as to be negative. 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 in the left direction in FIG. 2) is −50% FSO. As described below, when the acceleration sensor 1 is gradually rotated counterclockwise about the equivalent fulcrum L of the beam 13, the acceleration sensitivity in the X-axis direction becomes larger in both the −X-axis direction and the + X-axis direction. At a tilt angle of −13 °, the acceleration sensitivity in the −X-axis direction becomes 0% FSO. That is, if the circuit board 2 is mounted on the unit main 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 of the beam 13 are substantially on the same horizontal plane. Will be present, minimizing 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 depends on the positional relationship between the center of gravity M and the beam 13 of the mass section 12 and the mass section 12 of the acceleration sensor 1.
Since the acceleration sensor 1 having the same configuration has the same fixed angle θ, the fixed angle θ is determined by the initial measurement as described above, since it is determined by the shape and the weight of each part such as the beam and the beam 13. Therefore, the fixing portion 5a is fixed so as to have a fixed angle θ.
Is provided, and the unit main body 6 is manufactured, the acceleration sensor 1 with good productivity can be manufactured and housed in the unit main body 6, and the acceleration sensor unit A with 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 is possible to easily cope with the acceleration sensor 1 having various shapes such as a mass portion, and the mass portion 12 can be made large to easily improve the detection sensitivity of the acceleration sensor 1. Even if the acceleration sensor 1 is downsized, it is possible to provide the acceleration sensor unit A that can easily detect only the acceleration in the axial direction that is desired to be detected.

FIG. 4 is a sectional view of an acceleration sensor 20 housed in a unit body 6 of an acceleration sensor unit B according to still another embodiment of the present invention. This acceleration sensor 2
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. A piezoresistive element 28 whose resistance value changes according to the amount of strain generated in the piezoresistive element 28 is attached to the upper surface of the beam 23. On the other hand, the frame 21
A glass cover 26 is overlaid on the lower surface of the
6 is adhered to the frame 21 by an anodic bonding method or the like, and a depression 27 is formed on the inner surface of the cover 26 so that the mass 22 can be displaced.

When acceleration or vibration is applied to the acceleration sensor 20, the mass section 2 is moved in accordance with the acceleration or vibration.
2 also oscillates, causing beam 23 to be distorted.
At this time, the resistance value of the piezoresistive element 28 changes in accordance with the amount of distortion generated in the beam 23.
Detected by a detection circuit 3 provided on the circuit board 2,
Since the output is converted into a voltage signal or a current signal corresponding to the magnitude of the acceleration, the acceleration can be known.

In this acceleration sensor 20, as in the case of the acceleration sensor 1 of the first embodiment, the equivalent fulcrum P
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) with respect to. Therefore, only the acceleration in the Y-axis direction is detected by attaching the circuit board 2 to the unit body 6 at a fixed angle θ such 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. be able to.

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

FIG. 5 is a partially cutaway sectional view of an acceleration sensor unit C according to still another embodiment of the present invention. The acceleration sensor 30 is mounted on a circuit board 2 after being packaged in a metal package 31. Thereafter, it is held and fixed to the unit 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 board via the connection terminal 32.

FIG. 6 is a partially broken sectional view of an acceleration sensor unit D according to still 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 capacitors mounted on the surface of the circuit board 2 and configured in the acceleration sensor 40 are connected to the electronic components 4 a and 4 a constituting the detection circuit 3 through connection terminals (not shown) on the fixed substrate 41.
4c, 4d. Next, in order to minimize the axis sensitivity other than the purpose of detection, the circuit board 2 is fixed at a fixed angle θ.
And is held and fixed to the unit body 6.

If the acceleration sensors 30 and 40 are mounted on the metal package 31 and the fixed substrate 41 and then mounted on the circuit board 2 as in the acceleration sensor units C and D, the acceleration sensors 30 and 40 can be reduced in size. The acceleration sensor 1 can be easily mounted on the circuit board 2, the connection between the capacitor formed in the acceleration sensor 1 and the detection circuit 3, and the piezoresistive element 28 formed on the beam 21
And the detection circuit 3 can be easily connected.

In the above embodiment, the capacitor formed on the acceleration sensor 1 and the piezoresistive element 28 formed on the beam 23 of the acceleration sensor 20 are transmitted through the beams 13 and 23 and the frames 11 and 21. The detection circuits 3 are connected to the detection circuits 3 on the circuit board 2.
It is good also as providing on 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 reduced in size.

[0036]

According to the acceleration sensor unit of the present invention, the acceleration sensor mounted on the mounting board is positioned at an angle with respect to the acceleration detection axis at which the acceleration detection sensitivity of the other axis is minimized. Since the sensor is tilted and held by the acceleration sensor unit and the acceleration sensor is given a tilt angle, it is easy to detect acceleration only in the target detection axis direction without being affected by acceleration of other axes. it can.

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

Further, the acceleration sensor need only be mounted horizontally on the mounting board. Further, since the sensitivity of the other axis is reduced by the mounting angle of the mounting board on which the acceleration sensor is mounted, an error with a predetermined inclination angle can be reduced, and the mounting area of the acceleration sensor on the mounting board can be increased. Nor.

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

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an acceleration sensor unit according to an embodiment of the present invention.

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

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

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

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

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

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

FIG. 8 is a cross-sectional view showing a state where a pedestal is provided in the acceleration sensor according to the first embodiment.

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

[Explanation of symbols]

 Reference Signs List 2 circuit board 3 detection circuit 5 fixing auxiliary member 12 mass 13 beam 17a, 17b depression 31 metal package

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shiro Fujioka 10th Hanazono Todocho, Ukyo-ku, Kyoto-shi, Kyoto Omron Corporation (56) References JP-A-5-78748 (JP, A) JP-A-4- 297875 (JP, A) JP-A-61-97572 (JP, A) JP-A-61-72677 (JP, A) WO 90/10237 (WO, A1) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) G01P 15/00-15/135

Claims (3)

(57) [Claims] An acceleration sensor, which has a center of gravity not located at the center axis of the beam and is swingably supported by a support by a beam having elasticity, is mounted on a mounting board, and the mounting board is mounted on a casing. in the acceleration sensor unit, said Ma of the acceleration sensor mounted to the mounting substrate
The center of gravity of the mass section is positioned such that the acceleration detection sensitivity of the other axis is minimized with respect to the axis for detecting acceleration by swinging of the mass section.
An acceleration sensor unit , wherein the mounting board is loaded in a casing at an angle at which the beams are located on the same horizontal plane . 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 apparatus according to claim 1, wherein the acceleration unit is mounted on a fixed board for mounting on the mounting board, and the acceleration sensor is mounted on the mounting board via the fixed board. The acceleration sensor unit according to the above.