JP3139246B2 - Acceleration sensor - 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 used mainly in a vehicle airbag system.

[0002]

2. Description of the Related Art Conventionally, there is an acceleration sensor of this type shown in FIG. The acceleration sensor 50 includes a circuit board 52 on which an acceleration detection element 51 and a signal processing circuit (not shown) for processing an acceleration signal detected by the acceleration detection element 51 are mounted. A plurality of connection terminals 53 (only one pair is shown in the figure) protruding toward the back surface from each of the opposing ends, a metal base plate 54 attached to the back surface of the circuit board 52, and a metal base plate 54. A hermetic case 55 is provided to cover the entire acceleration sensor 50. The connection terminal 53 is provided so as to penetrate the metal base plate 54, and an insulation treatment (not shown) is provided between the connection terminal 53 and the metal base plate 54. In addition,
Reference numeral 56 in the figure denotes an insulating projection provided on the back surface of the metal base plate 54.

[0003]

In the conventional acceleration sensor 50, the connection terminals 53 are inserted through mounting holes (not shown) of the mounting board 60, and the wiring patterns (not shown) between the connecting terminals 53 and the mounting board 60 are provided. (Omitted) is connected and fixed by soldering or the like. Therefore, unnecessary vibration (especially bending) in the mounting board 60.
When a warp occurs due to the occurrence of mechanical distortion, the mechanical distortion is transmitted to the circuit board 52 via the metal base plate 54, and the circuit board 52 may be warped. Such warping of the circuit board 52 affects the acceleration detecting element 51,
This is very inconvenient because it generates an unnecessary output (generates output sensitivity other than the direction in which acceleration is detected, so-called other axis sensitivity, etc.) that causes a malfunction of an in-vehicle airbag system incorporating the acceleration sensor 50 or the like. Met.

In such an acceleration detection sensor,
When the hermetic case 55 is not used, the metal base plate 54 may be omitted. In such a case, the number of members that absorb mechanical strain between the mounting board 60 and the circuit board 52 is reduced by one. In addition, it was easy to generate more unnecessary output.

Accordingly, an object of the present invention is to prevent unnecessary output of the acceleration sensor due to unnecessary vibration.

[0006]

In order to achieve such an object, an acceleration sensor according to the present invention is provided with an insulating projection on a back surface.
Clear the gap between the metal base plate and the surface of the metal base plate.
A circuit board with an acceleration detection element mounted facing away
And projecting to the back side in the thickness direction of the circuit board to the metal base plate
The connection terminal that has been
And a hermetic case that covers the circuit board.
Are arranged in parallel at the opposite end of the circuit board.
The acceleration detection direction of the acceleration detection element to the end of the connection terminal.
Characterized by being orthogonal to the child parallel direction
It is.

[0007]

According to the above construction, when unnecessary vibration (particularly bending) or the like is generated in the mounting board on which the acceleration sensor is mounted via the connection terminal, the mechanical distortion is transmitted to the base plate and warps. Warp the board.

The mechanical distortion due to the warpage of the base plate is not directly transmitted to the circuit board but is transmitted to the circuit board via the connection terminal because a gap is formed between the base plate and the circuit board. However, at this time, since the mechanical strain is absorbed by the elastic deformation (curving) of the connection terminal, it hardly reaches the circuit board.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the present invention, and FIG.
FIG.

The acceleration sensor 1 has a circuit board 3 on which an acceleration detecting element 2 and a signal processing circuit (not shown) for processing an acceleration signal detected by the acceleration detecting element 2 are mounted.
A plurality of connection terminals 4 drawn out of the signal processing circuit and arranged in parallel at each of the opposed ends of the circuit board 3 (five at each of the opposed ends in the figure) and protruding toward the back side; A metal base plate 5 disposed on the back side of the substrate 3. The metal base plate 5 is opposed to the circuit board 3 with a gap A therebetween, and an insulating protrusion 6 is provided on the back surface. The connection terminal 4 penetrates the metal base plate 5 and protrudes to the back side thereof,
Although not shown, an insulation treatment is applied between the connection terminal 4 and the metal base plate 5. A hermetic case 7 is attached to the metal base plate 5, and the entire acceleration sensor 1 is covered by the hermetic case 7.

The acceleration sensor 1 includes a mounting board 10
Implemented in That is, the insulating protrusion 6 is attached to the mounting substrate 1.
By inserting the tip of the connection terminal 4 into a mounting hole (not shown) of the mounting substrate 10 until it comes into contact with the surface of the mounting substrate 10 and soldering the connection terminal 4 to a wiring pattern (not shown) of the mounting substrate 10 in this state, The acceleration sensor 1 is connected and fixed to the mounting board 10.

In the acceleration sensor 1 configured as described above, when unnecessary vibration (especially bending) or the like occurs in the mounting board 10 and warpage occurs, the mechanical strain is transmitted to the metal base plate 5 and the metal base plate 5 Will be warped. However, a gap A is formed between the metal base plate 5 and the circuit board 3, and the mechanical strain due to the warpage of the metal base plate 5 is not directly transmitted to the circuit board 3, but the circuit A is connected via the connection terminal 4. Although transmitted to the substrate 3, such mechanical strain does not reach the circuit board 3 because the connection terminals 4 are absorbed by being elastically deformed and curved. Therefore, no warping occurs in the circuit board 3, and therefore, no unnecessary output (other axis sensitivity or the like) is generated from the acceleration detection element 2 due to the warping of the circuit board 3.

In this acceleration sensor 1, since a plurality of connection terminals 4 are arranged in parallel at each of the opposite ends of the circuit board 3, the metal base plate 5 is placed in the terminal opposite direction B.
When the connection terminal 4 is bent in the direction perpendicular to the terminal facing direction, that is, in the terminal parallel direction C , the connection terminal 4 is not easily bent . Therefore, when the metal base plate 5 is warped in the terminal parallel direction C , the connection terminals 4 hardly bend, and the mechanical distortion of the metal base plate 5 is transmitted to the circuit board 3, and It is conceivable that the substrate 3 is warped.

[0014] To prevent such the inconvenience, terminals of the acceleration detecting direction G the connection terminal 4 of the acceleration detecting element 2
The direction may be orthogonal to the parallel direction C. Then, even if the circuit board 3 is warped due to the warp of the metal base plate 5 along the terminal parallel direction C , the mechanical strain is not picked up by the acceleration detecting element 2 and, therefore, the acceleration sensor Unnecessary output (other-axis sensitivity etc.) hardly occurs from 1.

When the circuit board 3 is lifted and supported in this manner, an element storage space, which has not existed conventionally, is formed on the back surface side. Therefore, if the circuit element D constituting the signal processing circuit is provided in this storage space, the area of the circuit board 3 can be reduced although the overall height is slightly increased.

In the above embodiment, the gap A is left as a space. However, the gap A may be filled by injecting an elastic resin or the like into the gap A.

[0017]

As described above, according to the present invention, even if unnecessary vibration (especially bending) or the like is caused on the mounting board on which the acceleration sensor is mounted via the connection terminal, the base plate is warped. The mechanical strain is transmitted to the circuit board via the connection terminal. However, such mechanical strain is almost absorbed by the elastic deformation (curving) of the connection terminal, so that the circuit board is warped. lost. Moreover, the connection terminals extend in the terminal parallel direction.
If the circuit board warps due to the base board warpage
Also, the acceleration detection direction of the acceleration detection element
By setting the direction perpendicular to the parallel direction, the acceleration detection element
To prevent the detection sensitivity from being affected by the warpage of the circuit board.
When the mechanical strain of the circuit board is
Not backed up.

Therefore, unnecessary output (other-axis sensitivity, etc.) due to the warpage of the circuit board does not occur. Therefore, even if the vehicle-mounted airbag system is configured by incorporating this acceleration sensor, the unnecessary vibration is generated. Almost no malfunction occurred.

If a circuit element or the like mounted on the circuit board is mounted in a gap formed between the circuit board and the base plate, the area of the circuit board is reduced although the height is slightly increased accordingly. There is also an effect that can be done. And on
By providing the gap, various parts can be mounted on both sides of the circuit board.
Since it can be provided, various types of
There is almost no need to provide components. Therefore,
Easily provide edge protrusions at desired positions on the metal base substrate
There is also an effect that can be done. And even metal-based
The following effects can be obtained by providing the substrate. You
That is, this acceleration sensor is attached via the connection terminal.
Even if unnecessary vibrations occur on the member to be
Because it is almost blocked by the base substrate.
Unnecessary vibrations do not cause the circuit board to warp.
Therefore, the effect of preventing unnecessary output is further increased. Ma
Also, the connection terminals are arranged through the metal base substrate.
As a result, the metal base plate is
As a result, the metal base substrate itself warps.
Hard to repel. Even if the metal base substrate is warped
Even the gap formed between the circuit board and the metal base substrate
The warp is absorbed by the circuit board,
Will not occur. Unnecessary output for the above reasons
Prevention effect increases. Also, metal base board and circuit board
Are made of different materials,
Unnecessary vibration is difficult to transmit from the base board to the circuit board.
Therefore, the effect of preventing unnecessary output is further enhanced by that amount. Ma
Also, the connection terminals pass through the metal base plate and project
The connection terminals are easily used as input / output terminals
Can be used for

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an acceleration sensor according to one embodiment of the present invention.

FIG. 2 is an external perspective view of the acceleration sensor according to the embodiment.

FIG. 3 is a cross-sectional view showing the structure of a conventional acceleration sensor.

[Explanation of symbols]

 2 acceleration detecting element 3 circuit board 4 connection terminal 5 metal base plate A gap

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshihiro Mizuno 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Prefecture Murata Manufacturing Co., Ltd. (56) References JP-A-5-40130 (JP, A) JP-A Sho 63-177449 (JP, A) JP-A-5-198701 (JP, A) JP-A-4-56387 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/08 -15/13 G12B 9/08

Claims (1)

(57) [Claims] 1. A metal base having an insulating projection (6) on the back surface.
A gap between the plate (5) and the surface side of the metal base plate (5).
(A), facing each other with an acceleration detection element (2)
The mounted circuit board (3) and the thickness direction of the circuit board (3)
And projecting toward the rear surface side and penetrating through the metal base plate (5).
Connection terminal (4) and attached to the metal base plate (5)
Hermetic case covering the circuit board (3)
(7), wherein the connection terminal (4) is provided at an opposite end of the circuit board (3).
A plurality of the acceleration detecting elements are arranged in parallel with each other.
The direction of acceleration detection (G) of the child (2) is changed to the connection terminal (4).
An acceleration sensor, wherein the direction is orthogonal to the terminal parallel direction .