JPH08201419A - Acceleration sensor mounting structure - Google Patents

Abstract

PURPOSE: To enable acceleration sensors to detect the total acceleration applied to the sensors in orthogonal three-axis dimensions with nearly equal sensitivity by mounting both acceleration detecting elements so that the directions of their maximum sensitivity can be inclined by a specific angle toward the z-axis from the y- or x-axis. CONSTITUTION: Each acceleration sensor A and B is mounting on a sensor mounting surface 3 by positioning and fixing the external surface of a case lid 8 constituting an insulating case 2 nd the signal electrode 4 of each bimorph element 1 is connected to each wiring pattern formed on the surface 3 by soldering, etc., through an external electrode formed on the case 2. In other words, the directions P of the maximum sensitivity of the elements 1 incorporated in the sensors A and B are inclined upward by 40-50 deg. toward the z-axis from the y- or x-axis. First and second comparator circuits compare the detecting signals of the sensors A and B with preset thresholds and output comparator signals to a logic circuit. The logic circuit outputs the comparator signals to the outside after performing OR logic processing on the signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure for an acceleration sensor used for shock detection.

[0002]

2. Description of the Related Art Among acceleration sensors, there is one in which a bimorph element having fixed ends is used as an acceleration detecting element. As shown in a simplified form in FIG. 4, this acceleration sensor includes a bimorph element 1 and a bimorph element 1. And an insulating case 2 for locating and accommodating the sensor, and then mounting and fixing the sensor on a sensor mounting surface 3 such as a wiring board.

The bimorph element 1 here has a rectangular flat plate shape, and two piezoelectric ceramic plates 6 each having a signal electrode 4 and an intermediate electrode 5 formed on the front and back surfaces are superposed on each other. Each of the piezoelectric ceramic plates 6 that are integrated and face-bonded via the intermediate electrode 5 is polarized along the thickness direction of the piezoelectric ceramic plate 6 in the opposite direction to that of the piezoelectric ceramic plate 6 on the other side. Has been done. The dashed arrows in the figure indicate these polarization directions. Further, at this time, each of the signal electrodes 4 is formed along the longitudinal direction of each of the piezoelectric ceramic plates 6 and is drawn out to different one end portions.

On the other hand, the insulating case 2 is composed of the bimorph element 1.
A pair of sandwiching frames 7 having a U-shape in plan view, which sandwiches only both end portions along the longitudinal direction of the two, and the bimorph element 1 and the sandwiching frames 7 arranged to face each other with the bimorph element 1 interposed therebetween.
A pair of case lids 8 for closing the open surface formed by
It consists of and. Then, each of the signal electrodes 4 of the bimorph element 1 housed in the insulating case 2 is
It is connected to an external electrode (not shown) formed on each different outer end surface of the insulating case 2.

Further, the acceleration sensor is mounted by positioning and fixing the outer surface of either the holding frame 7 or the case lid 8 constituting the insulating case 2 on the sensor mounting surface 3, and the bimorph element 1 Each of the signal electrodes 4 is connected to a wiring pattern (not shown) on the sensor mounting surface 3 after passing through an external electrode formed on the insulating case 2. These wiring patterns are connected to a signal processing circuit (not shown), and the signal processing circuit can process the electrical signal output from the acceleration sensor to detect the acceleration due to the impact. It is supposed to be done.

[0006]

By the way, the bimorph element 1 as an acceleration detecting element has a maximum value when an acceleration in a direction normal to the surface of the piezoelectric ceramic plate 6, that is, a direction along the thickness direction thereof acts. In addition, when the acceleration of 180 degrees reverse direction is applied, the maximum electric signal of opposite positive and negative values and the same absolute value is output. It is the direction in which it occurs, that is, the maximum sensitivity direction P called the main axis of the acceleration sensor. When an acceleration in a direction along the tangential direction of the surface of the piezoelectric ceramics plate 6 is applied, no electric signal is output, that is, the detection sensitivity becomes zero, while either the normal direction or the tangential direction is detected. When the acceleration along the direction acts, the detection sensitivity has a magnitude corresponding to the angle θ formed by the maximum sensitivity direction P and the acting direction of the acceleration, that is, the maximum sensitivity S × cos θ times the detection sensitivity.

Therefore, when the acceleration sensor of the conventional structure is mounted on the sensor mounting surface 3, the maximum sensitivity direction P of the bimorph element 1 is parallel or perpendicular to the sensor mounting surface 3. That is, as shown in FIG. 4, orthogonal two-dimensional coordinate axes (planar coordinate axes) are provided on the sensor mounting surface 3.
x, y are set, orthogonal three-dimensional coordinate axes (spatial coordinate axes) x, y, z with the sensor mounting surface 3 as the xy plane are set, and the insulating case 2 in which the bimorph element 1 is incorporated
When the case cover 8 is attached to the sensor mounting surface 3, the maximum sensitivity direction P of the vertically oriented bimorph element 1 is detected.
Is aligned with the y-axis on the sensor mounting surface 3, x
The acceleration in the direction along the axis and the z axis, that is, the acceleration acting along any direction in the xz plane cannot be detected.

Although not shown, the holding frame 7 of the insulating case 2 is mounted on the sensor mounting surface 3 on which the orthogonal coordinate axes x and y are set, and the maximum sensitivity direction P of the bimorph element 1 is set to the sensor mounting surface 3. When the z-axis is perpendicular to the z-axis, it is impossible to detect the acceleration along any direction in the xy plane constituted by the x-axis and the y-axis. Therefore, coordinate axes x,
In order to detect all of the accelerations that will act along the y and z directions, three acceleration sensors whose maximum sensitivity direction P coincides with each of the x axis, y axis, and z axis are used. The signal must be mounted on the sensor mounting surface 3, which increases the number of accelerometers and the installation space, resulting in high cost, and also a signal for processing the electrical signals output from the three accelerometers. There is an inconvenience that the processing circuit is complicated.

By the way, in order to avoid such inconvenience, the maximum sensitivity direction of the bimorph element is tilted upward from the sensor mounting surface in advance so that the orthogonal coordinate axes x,
There has been proposed an acceleration sensor configured to detect acceleration acting along the three directions of y and z. That is, as an acceleration sensor of this type, although not shown, there is one disclosed in Japanese Patent Application Laid-Open No. 5-133974, in which the maximum sensitivity direction of an acceleration detecting element having a rectangular flat plate shape is set on the sensor mounting surface. There is shown an acceleration sensor characterized in that the acceleration sensor is installed at a tilt angle of 45 degrees (°) and the ridge line of the acceleration detecting element is further tilted at a direction of 45 degrees from the ridge line of the sensor mounting substrate. . And
When the acceleration sensor having such a configuration is adopted, it is true that a single unit has x-axis, y-axis, and z-axis (three directions that match those shown in FIG. 2 according to the present invention: hereinafter, the same. )
The acceleration acting along each direction can be detected.

However, three Cartesian coordinate axes x, y,
The fact that accelerations acting along z can be detected does not mean that accelerations in all directions can be detected, and it is not possible to detect accelerations that act in a plane perpendicular to the maximum sensitivity direction. It will be possible. Furthermore,
It goes without saying that the maximum sensitivity direction in the case of adopting the above configuration is 45 ° with respect to the z axis, but in this case, the x axis and the y axis and the maximum sensitivity direction are substantially 6 degrees.
Since the angle is 0 °, the detection sensitivities in the x-axis, y-axis, and z-axis directions do not become substantially equal.

The present invention was devised in view of these inconveniences, and it is possible to detect acceleration over a wide range while the number is as small as possible, and to operate along any direction of the orthogonal coordinate axes. It is an object of the present invention to provide a mounting structure for an acceleration sensor that has substantially the same detection sensitivity with respect to acceleration.

[0012]

In order to achieve such an object, the structure for mounting an acceleration sensor according to the present invention has a rectangular coordinate axis (x, x, so that the sensor mounting surface is an xy plane).
x, on the sensor mounting surface after setting y, z)
It is equipped with two acceleration sensors that are attached along a direction that coincides with each of the axes y and y, and the maximum sensitivity direction of the acceleration detection element incorporated in one of the acceleration sensors is from the y axis to the z axis. The direction is inclined by 40 to 50 degrees,
Further, it is characterized in that the maximum sensitivity direction of the acceleration detection element incorporated in the other side of the acceleration sensor is a direction inclined by 40 to 50 degrees from the x axis toward the z axis. In addition, the acceleration detecting element in this case is a bimorph element with fixed ends, which is manufactured using piezoelectric ceramics.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially cutaway perspective view showing the structure of the acceleration sensor itself according to this embodiment, FIG. 2 is an explanatory view showing a simplified mounting structure of the acceleration sensor, and FIG. It is a functional block diagram which shows operation | movement when a structure is employ | adopted. Since the configuration of the acceleration sensor itself is basically the same as that of the conventional example, the same components and parts as those in FIG. 4 are denoted by the same reference numerals in FIGS. 1 and 2, and detailed description thereof is omitted here.

As shown in FIG. 1, each of the acceleration sensors A and B according to the present embodiment comprises a bimorph element 1 of both ends fixed type which functions as an acceleration detecting element, and an insulating case 2 which houses this. The acceleration sensors A and B are to be mounted on a sensor mounting surface 3 such as a wiring board. At this time, the bimorph element 1 has the maximum sensitivity direction P
Is tilted with respect to the sensor mounting surface 3 and is positioned and housed in the insulating case 2. The maximum sensitivity direction P has an inclination angle θ from the sensor mounting surface 3 of 40 ° or more and 50 ° or less. , For example, it is set upward at 45 °.

That is, the bimorph element 1 here is
A pair of piezoelectric ceramic plates 6 each having a rectangular flat plate shape and having a signal electrode 4 and an intermediate electrode 5 formed on the front and back surfaces are face-to-face joined, and this is adjusted to the inclination angle θ 45
It has been cut off with °. Each of the piezoelectric ceramic plates 6 joined via the intermediate electrode 5 is polarized along the thickness direction of the piezoelectric ceramic plate 6 in the opposite direction to the other side, and each of the signal electrodes 4 is polarized in each piezoelectric ceramic plate. It is the same as the conventional example in that it is pulled out to different one end portions along the longitudinal direction of 6. Also,
In this case, the insulating case 2 is configured by using the sandwiching frame 7 and the case lid 8 similar to the conventional example, and the signal electrodes 4 of the bimorph element 1 are formed on different outer end surfaces of the insulating case 2. It is connected to an external electrode (not shown).

On the other hand, as shown in FIG. 2, the acceleration sensor mounting structure according to the present embodiment is mounted on the same sensor mounting surface 3 along the directions corresponding to the orthogonal coordinate axes x and y. It also has two acceleration sensors A and B. At this time, as shown in FIG. 3, the first and second comparator circuits 10 and 11 for performing the comparator process of the electric signals V _A and V _B output from the acceleration sensors A and B, respectively. , A logic circuit 12 that performs an OR logic process on the comparator signals V _S1 and V _S2 output from each of the comparator circuits 10 and 11, and each of the comparator circuits 10 and 11 and the logic circuit 12 performs signal processing. It is incorporated in a circuit (not shown).

Each of the acceleration sensors A and B here is mounted on the sensor mounting surface 3 by positioning and fixing the outer surface of the case lid 8 constituting the insulating case 2. Each signal electrode 4 of the bimorph element 1 is soldered to each wiring pattern (not shown) formed on the sensor mounting surface 3 after passing through an external electrode (not shown) formed on the insulating case 2. Connected by etc. That is, the maximum sensitivity direction P of the bimorph element 1 incorporated in the acceleration sensor A at this time is an upward direction inclined by 45 ° from the y axis to the z axis, and the maximum sensitivity direction P of the bimorph element 1 in the acceleration sensor B is set. P is 4 from the x-axis to the z-axis
It is tilted upward by 5 °.

The operation of the acceleration sensors A and B according to this embodiment will be described below with reference to FIGS. In the following description, it is assumed that the maximum sensitivity of the acceleration sensors A and B is S (mV / G: G is gravitational acceleration), and it is detected that an impact with a certain strength or more is applied. The thresholds for this are S ₁ and S ₂ .

First, consider a case where an acceleration of 1 G acts from the positive direction of the Cartesian coordinate axis x on the mounting structure composed of two acceleration sensors A and B arranged according to the positional relationship shown in FIG. While the detection sensitivity of the acceleration sensor A arranged along the direction coinciding with the axis becomes zero, the detection sensitivity of the acceleration sensor B arranged along the direction coinciding with the x axis is cos 45 ° times the maximum sensitivity S. expressed. Therefore, in this case, the electric signal V _A output from the acceleration sensor A is 0 (mV), and the electric signal V _B output from the acceleration sensor _B is S × cos 45 ° × 1 (mV), and the electric signal V _In the second comparator circuit 11 in which only _B is input, comparator processing is performed with S ₂ set as a threshold value, that is, if V _B > S ₂ , comparator signal V _S2 = 1 and V _{2 If B} ≤ S ₂ , the process of setting the comparator signal V _S2 = 0 is executed, and the second comparator circuit 11 to the logic circuit 12 are executed.
A comparator signal V _S2 is output to the.

When an acceleration of 1 G is applied from the positive direction of the Cartesian coordinate axis y, the detection sensitivity of the acceleration sensor A arranged along the direction coinciding with the y axis is co with the maximum sensitivity S.
While being expressed as s45 ° times, the detection sensitivity of the acceleration sensor B arranged along the direction coinciding with the x-axis becomes zero. Therefore, the acceleration sensor A in this case
The electric signal V _A output from S × cos 45 ° × 1 (m
While represented as V), the electric signal V _B output from the acceleration sensor B becomes 0 (mV). As a result, the comparator processing the S ₁ that has been previously set based on the threshold in the first comparator circuit 10 in which only the electric signal V _A from the acceleration sensor A is inputted, i.e., V _A
If> S ₁ , comparator signal V _S1 = 1 and V _A ≦ S
If it is ₁ , after the processing for setting the comparator signal V _S1 = 0 is performed, the first comparator circuit 10 outputs the comparator signal V _S1 to the logic circuit 12.

On the other hand, when an acceleration of 1 G acts from the positive direction of the orthogonal coordinate axis z, the detection sensitivities of the acceleration sensors A and B are both expressed as cos 45 ° times the maximum sensitivity S, and these accelerations The electric signals V _A and V _B output from the sensors A and B are represented as S × cos 45 ° × 1 (mV). Then, the first comparator circuit 10 that only the electrical signal V _A from the acceleration sensor A is input S
_In the second comparator circuit 11 in which the comparator process is executed with ₁ as the threshold value and only the electric signal V _B from the acceleration sensor B is input, the comparator with S ₂ as the threshold value is performed. The first after the process is performed
Also, comparator signals V _S1 and V _S2 are output from the second comparator circuits 10 and 11 to the logic circuit 12, respectively.

Furthermore, the comparator circuits 10 and 11
In the logic circuit 12 to which either one or both of the comparator signals V _S1 and V _S2 are input, OR logic processing based on the comparator signals V _S1 and V _S2 , that is, V _S1 = 1 or V _S2 = 1 Then, the logic circuit signal V _L
After the OR logic processing of = 1 is performed, this logic circuit signal V _L is output to the outside.

That is, as described above, when the mounting structure of the acceleration sensor according to the present embodiment is adopted, the detection sensitivity is substantially equal in any of the orthogonal coordinate axes x, y, z, that is, A detection sensitivity of cos 45 ° times the maximum sensitivity S can be obtained. Further, in the mounting structure according to the present embodiment, the directions in which the sensitivity is not detected are both acceleration sensors A and B.
Since it exists only along one direction orthogonal to the maximum sensitivity direction P, the advantage that acceleration can be detected in a wide range is obtained.

By the way, in the mounting structure of this embodiment, the bimorph element 1 incorporated in each of the acceleration sensors A and B is used.
The maximum sensitivity direction P is inclined at an inclination angle θ of 45 ° from the sensor mounting surface 3, but the maximum sensitivity direction P is not limited to 45 °, and is practically within a range of 40 ° or more and 50 ° or less. Good results have been confirmed by the inventors of the present invention. That is, when the inclination angle θ is 40 °
The ratio of cos 40 ° and cos 45 ° is cos 40 ° / cos 45 °
= 1.083 ..., and the ratio of cos50 ° to cos45 ° when the tilt angle θ is 50 °, cos50 ° / cos45
Therefore, the angle of inclination θ is 4
It is within a range of about ± 10% in the case of 5 °, and it is clear that the detection sensitivity of substantially the same degree can be obtained along any of the orthogonal coordinate axes x, y, and z as in the present embodiment. is there.

[0026]

As described above, according to the mounting structure of the acceleration sensor of the present invention, the accelerations acting in any of the three axial directions orthogonal to each other can be detected by the two acceleration sensors. Sensitivity can be detected, and acceleration can be detected over a wide range. As a result, not only the mounting structure is simplified, but also the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing the configuration of an acceleration sensor itself according to the present embodiment.

FIG. 2 is an explanatory view showing a simplified mounting structure of the acceleration sensor according to the present embodiment.

FIG. 3 is a functional block diagram showing an operation when the mounting structure of the present embodiment is adopted.

FIG. 4 is a partially cutaway perspective view showing a configuration of an acceleration sensor according to a conventional example.

[Explanation of symbols]

 1 Bimorph element (acceleration detection element) 3 Sensor mounting surface A Acceleration sensor B Acceleration sensor P Maximum sensitivity direction x Cartesian coordinate axis y Cartesian coordinate axis θ Tilt angle

Claims (2)

[Claims] 1. The Cartesian coordinate axes (x, y, z) are set so that the sensor mounting surface (3) is an xy plane, and they coincide with the x axis and the y axis on the sensor mounting surface (3). Two acceleration sensors (A,
B), and the maximum sensitivity direction (P) of the acceleration detection element (1) incorporated in one of the acceleration sensors (A, B) is a direction inclined by 40 to 50 degrees from the y axis to the z axis. In addition, the maximum sensitivity direction (P) of the acceleration detection element (1) incorporated in the other of the acceleration sensors (A, B) is a direction inclined by 40 to 50 degrees from the x axis toward the z axis. Accelerometer mounting structure characterized by the following. 2. The mounting structure for an acceleration sensor according to claim 1, wherein the acceleration detecting element (1) is a bimorph element having fixed ends and made of piezoelectric ceramics.