JPH0572228A - Cantilever type acceleration sensor - Google Patents

Abstract

PURPOSE:To attain both improvement of sensitivity and resistance to impact of a cantilever type acceleration sensor. CONSTITUTION:A buffering housing 6 accommodates a gage 2 of an acceleration sensor 1 add a metal base 4 whereon the gage is mounted. The whole of the base 4 is in a state of being hidden inside the housing 6 and the surface B opposite to the surface whereon the gage is mounted faces outside. A fitting stage 9 is fixed on the surface to be fitted to the sensor of a substance P of which the acceleration is to be detected, and the metal base 4 is fixed on the fitting stage 9. A vertical line L from the inner surface of the housing 6 being in contact with the metal base 4 to the fore end of the side edge 6a of the housing and the thickness D of the metal base 4 and the fitting stage 9 are set to be L<D. In another way, the surface B of the metal base 4 being opposite to the surface whereon the gage is mounted is made to project outside of the housing 6 and an elastic body is provided at the side edge 6a of the housing or a groove part with the elastic body is provided on the rear side of the base 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever beam type acceleration sensor in which a mass portion is displaced according to acceleration, and more particularly to a shock resistant structure of the acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Publication No. 1-16767.
As disclosed in Japanese Patent Laid-Open No. 4 (1994), a capacitance type semiconductor acceleration sensor or the like adopts a structure in which a movable electrode (mass part) interposed between fixed electrodes is cantilevered by a beam.
In the case of capacitance type acceleration, when the mass portion is displaced according to the acceleration, the displacement is detected from the change in the capacitance between the fixed electrode and the movable electrode to detect the acceleration.

Other types of cantilever type acceleration sensors include, for example, Japanese Patent Laid-Open Nos. 1-301175 and 1-3.
As disclosed in Japanese Unexamined Patent Publication No. 02169, there are piezoresistive semiconductor acceleration sensors. In these publications, a piezoresistor is formed in order to mitigate the impact when the acceleration sensor is dropped during transportation or mounting. Consideration has been given to encapsulating a cushioning agent (for example, silicon oil) in a package that accommodates the semiconductor cantilever, or to attach a cushioning material to each outer peripheral surface of the package.

This type of acceleration sensor is used in various fields such as vehicle body control and airbag systems.

[0005]

Accelerometers are required to have high responsiveness, especially in the case of an air bag system for ensuring the safety of the driver.

From the above circumstances, further improvement of the sensitivity of the acceleration sensor is desired. The acceleration sensor to be attached to the object to be detected has a higher sensitivity when the encapsulation of the cushioning agent is omitted and the sensor is directly attached rather than being attached via the cushioning material.

However, if there is no buffering means, as described above, the impact when the sensor is dropped during transportation or mounting of the acceleration sensor becomes large, and there is a high possibility that parts of the acceleration sensor will be damaged. In particular, the acceleration that is usually detected by the cantilever type acceleration sensor is about ± 2 G, whereas the drop impact acceleration is 3000 G or more, and depending on the degree of impact, it may exceed 10000 G, and drop impact is extremely tolerable. You will exceed the limit.

The present invention has been made in view of the above points, and it is an object of the present invention to improve the sensitivity of the cantilever beam type acceleration sensor of this type and achieve shock resistance at the same time.

[0009]

In order to achieve the above object, the present invention basically proposes the following cantilever type acceleration sensor. In order to facilitate understanding of the contents, reference will be made to the reference numerals of the drawings (FIGS. 1 and 4 to 6) used for describing the embodiments. In each figure, (a) shows a state before the acceleration sensor is mounted, and (b) shows a state after the mounting.

As shown in FIG. 1, the first invention comprises a metal base 4 on which a gauge 2 of an acceleration sensor is mounted, and a buffering housing 6 for accommodating the gauge 2 and the metal base 4, and the acceleration sensor 1 And the metal base 4 is entirely hidden in the housing 6 and the counter gauge mounting surface B is formed.
Place so that it faces the outside. On the other hand, the mounting base 9 is fixed to the sensor mounting surface of the object P to be detected, and the metal base 4 with the housing 6 is fixed to the mounting base 9 to accelerate the acceleration sensor 1.
Can be installed. A part of the inner surface of the housing 6 abuts on the gauge mounting surface A of the metal base 4, and the distance L of the perpendicular line from the abutting inner surface of the housing to the tip of the housing side edge 6a and the thickness D of the metal base 4 and the mount 9. L <D
Set to.

As shown in FIG. 4, the second invention is provided with a gauge 2, a metal base 4, and a housing 6 similar to the above, but the metal base 4 has its anti-gauge mounting surface B protruding outside the housing 6. The metal base 4 is arranged and fixed to the sensor mounting surface of the object P to be detected, so that the acceleration sensor 1 can be mounted. In addition, a cushioning elastic body 10 (for example, rubber, sponge, etc.) is provided at the tip of the housing side edge 6a, and this elastic body 10 projects to the outside of the metal base 4 before mounting the acceleration sensor, and mounts the acceleration sensor. In this state, the compression is set until the position is at the same level as the anti-gauge mounting surface B of the metal base 4.

In the third invention, as shown in FIG. 5, the metal base 4 is arranged so that its anti-gauge mounting surface B projects to the outside of the housing 6 as in the second invention. Although the acceleration sensor 1 can be mounted by being fixed to the sensor mounting surface of the object P to be detected, the groove 12 with the elastic body 11 for cushioning is provided on the counter gauge mounting surface B of the metal base 4. The elastic body 11 is projected to the outside of the metal base 4 before the acceleration sensor is attached, and when the acceleration sensor is attached, the elastic body 11 receives the compression force of the attachment and escapes into the groove 12.

In the fourth invention, as shown in FIG. 6, a metal base 4 is used as in the second and third inventions, and an object P to be sensed for acceleration is detected.
Although the acceleration sensor 1 can be mounted by being fixed to the sensor mounting surface of, the housing 6 is covered with a rubber cover 13, and a part 13a of the rubber cover 13 projects outward from the tip of the side edge of the housing 6. The protruding portion 13a of the rubber cover 13 projects to the outside of the metal base 4 before the acceleration sensor is attached, and is positioned at the same level as the anti-gauge mounting surface B of the metal base 4 when the acceleration sensor is attached. It was set to compress until.

[0014]

In the first aspect of the invention, since the rigid metal base 4 is completely hidden in the housing 6 before mounting the acceleration sensor, only the housing 6 directly hits even if it is dropped. As a result, an external impact such as a drop is sufficiently reduced by the housing 6 before being transmitted to the gauge 2. The base 4 is made of metal in order to increase the sensitivity of acceleration detection from the acceleration-detected portion P by increasing the rigidity of the base.

When mounting the acceleration sensor 1, since the metal base 4 is hidden in the housing 6, the mounting base 9 is used and the base 4 is fixed to the mounting base 9. In this case, since the above relationship between L and D is set to L <D, the metal base 4 is in close contact with the surface of the mounting base 9 without floating. Therefore, the acceleration transmitted from the workpiece P is reliably detected with high accuracy.

Unlike the first invention, the second invention to the fourth invention are both in a state in which a part of the metal base (counter gauge mounting side B) projects outside the housing 6. However, before the acceleration sensor 1 is attached, the elastic bodies 10, 11, 13 (13a) are in a state of protruding more than the metal base 4. Therefore, when the acceleration sensor 1 is dropped, the portion directly hit (the hit point) is the housing 6
And any of the elastic bodies 10, 11, 13 (13a). These shock absorbing elements 6, 10, 11, 13 (13
The external impact transmitted to the gauge 2 via a) is sufficiently mitigated.

In the mounted state of the acceleration sensor 1, the elastic bodies 10, 11, 13a are all compressed to the same level as the anti-gauge mounting surface B of the metal base 4, so that the metal base 4 is detected as the object P to be accelerated. It is attached in close contact with and accurately detects the acceleration transmitted from the workpiece P to be processed.

[0018]

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

FIG. 1 is a vertical sectional view showing a first embodiment of the present invention.

In FIG. 1, an acceleration sensor 1 is a hybrid IC board (HI) in which a semiconductor gauge 2 incorporating a cantilever type sensor element and a gauge 2 are mounted via an adhesive 5.
C substrate 3), a HIC substrate 3 with gauge 2 mounted thereon via an adhesive 5, a metal base 4, a housing 6 and the like.

An example of the gauge 2 will be described with reference to FIG. The gauge 2 in FIG. 2 shows a capacitive type of a semiconductor cantilever type of electrostatic servo type, and the detecting portion of the gauge 2 is a silicon plate 21 and two insulating plates (for example, Pyrex glass # 7).
740) 22 and 23 have a laminated structure. A cantilever 24 and a mass portion (movable electrode) 25 are formed on the silicon plate 21 by anisotropic etching.

In the portions of the insulating plates 22 and 23 facing the movable electrode 25, thin metal fixed electrodes 26 and 2 made of a metal conductor are provided.
7 is formed. Movable electrode 25 and upper and lower fixed electrodes 26,
A minute gap (for example, 2 to 3 μm) is ensured between 27. The electrodes 25 and 26 and the electrodes 25 and 27 form a pair of capacitors, respectively.

When vertical acceleration is applied to the gauge 2,
An inertial force acts on the movable electrode 25, the cantilever 4 bends, and the movable electrode 25 is displaced in the direction opposite to the acting direction of acceleration. As a result, the capacitances of the electrodes 25, 26 and the electrodes 25, 27 change according to the changes in the gaps.

Generally, the capacitance can be obtained from a relational expression of C = εS / d (ε: permittivity of air, S: electrode area, d: size of void). The capacitance type acceleration sensor is
The acceleration is detected by the acceleration detection circuit 30 based on the acceleration dependency of the electrostatic capacity. In the present embodiment, since it is of the electrostatic servo type, the acceleration detection circuit 30 operates as follows.

In the electrostatic servo type capacitive sensor, the electrode 2
The detector 31 detects the capacitance difference ΔC between the electrodes 5, 26 and the electrodes 25, 27. The amount of change ΔC is amplified by the amplifier 32, the PWM inverter 33 is controlled so that ΔC becomes zero, the output thereof is converted by the converter 34, and the upper and lower fixed electrodes 2 are converted.
Voltages that invert each other are applied to 6 and 27. By applying an electrostatic force corresponding to the voltage between the electrodes 25, 26 and 25, 27 by applying such a voltage, the movable electrode 2
5 is controlled so that it is always constant. Then, the control signal of the PWM inverter 33 is input to the amplifier 36 via the low pass filter 35, and the acceleration is obtained from the output.

Now, returning to FIG. 1, the structure of the acceleration sensor 1 will be described.

In FIG. 1A, the gauge 2 and the metal base 4 are housed in the housing 6 before the acceleration sensor 1 is attached.

The base 4 is made of metal in order to increase the sensitivity of acceleration transmitted to the gauge 2 via the base 4 by maintaining the rigidity of the base.

The housing 6 is made of synthetic resin in order to have impact resistance, and various shapes are conceivable. The metal base 4 is housed so as to be entirely hidden in the housing 6, and is fixed to the housing 6 with a screw 7 in a state where the counter gauge mounting surface B faces the outside. Gauge mounting surface A of metal base 4
Contacts a part of the inner surface of the housing 6. Since the metal base 4 is hidden in the housing 6 as described above, the thickness of the metal base 4 is set to be smaller than the vertical distance L from the surface of the inner surface of the housing 6 contacting the gauge mounting surface A to the tip of the housing side edge 6a. I made it small.

According to the above construction, when the acceleration sensor 1 is dropped before its attachment, the hit point is the housing 6
Limited to On the other hand, the entire metal base 4 is hidden by the housing 6, so that the metal base 4 is prevented from hitting a fall place such as a floor. As a result, even if a highly rigid element such as the metal base 4 is used, the shock of the housing 6 cushions the drop impact transmitted to the gauge 2 effectively.

In this embodiment, the silicon adhesive 5 between the gauge 2 and the HIC substrate 3 and between the HIC substrate 3 and the metal base 4 has an appropriate thickness (for example, 10 μm to 100 μm).
The adhesive 5 also plays a role of absorbing a drop impact.

Further, the gauge 2 is shown in FIG.
The cantilever 24 that supports the mass portion 25 as described above includes two beam elements 24a and 24b that form a pair.
The lengths, widths, and thicknesses of a and 24b were selected under the condition that both the beam sensitivity and the impact resistance can be achieved. Specifically, FIG.
As shown in the optimum condition data for improving impact resistance in (b), condition 3
To adopt.

When mounting the acceleration sensor 1, the metal base 4 is hidden in the housing 6 so that
The mount 9 is used as shown in FIG. The mount 9 is made of metal and is fixed to the vehicle body (object to be accelerated) P by welding.

The metal base 4 is integrally fixed to the housing 6 with screws 7 on the surface of the mounting base 9, and the acceleration sensor 1 is mounted in this manner. In this case, since the relationship between the above L and the thickness D of the metal base 4 and the mounting base 9 is set to L <D, the metal base 4 adheres to the surface of the mounting base 9 without floating. Therefore, the acceleration transmitted from the workpiece P is reliably detected with high accuracy.

FIG. 4 shows a second embodiment of the present invention. In addition,
In the figure, the same symbols as those in the embodiment of FIG. 1 indicate the same or common elements (the same applies to the drawings after FIG. 4).

In the present embodiment, unlike the first embodiment, a part of the metal base 4 (counter gauge mounting surface B) is the housing 6.
Project outside.

A rubber 10 is attached to the tip of the side edge 6a of the housing so as to surround the metal base 4. The rubbers 10 are arranged in a continuous shape or at appropriate intervals. As shown in FIG. 4 (a), the rubber 10 projects outside the metal base 4 and the screw 7 before the acceleration sensor is attached, and in the state where the acceleration sensor is attached, the rubber 10 is as shown in FIG. 4 (b). It is set so that it is compressed to a position on the same level as the anti-gauge mounting surface B of 4.

Therefore, even if the acceleration sensor 1 is dropped before the acceleration sensor 1 is mounted during the transportation or the mounting work thereof, the hitting point is the housing 6 or the rubber 10.
The shock transmitted to the gauge 2 is mitigated by these elements 6 and 10.

When the acceleration sensor 1 is attached, the housing 6 and the metal base 4 are integrally fixed to the object P to be detected by a screw 7. By this attachment force, the rubber 10 is compressed to the same level as the anti-gauge mounting surface B of the metal base 4, and the metal base 4 is attached in close contact with the surface of the object P to be sensed and the acceleration detection sensitivity is improved. Can keep good.

FIG. 5 is a vertical sectional view showing a third embodiment of the present invention. Also in this embodiment, as in the second embodiment, the metal base 4 is
The anti-gauge mounting surface B is arranged so as to project to the outside of the housing 6, and the metal base 4 is fixed to the sensor mounting surface of the object P to be detected, so that the acceleration sensor 1 can be mounted.

On the anti-gauge mounting surface B of the metal base 4, grooves 12 are provided along the four sides of the base, and a cushioning rubber 11 is mounted in the groove 12. This rubber 11 projects outside the metal base 4 and the screw 7 as shown in FIG. 5A before the acceleration sensor is attached. The mounting of the acceleration sensor 1 is carried out in the same manner as in the second embodiment, and as shown in FIG.
It is set to escape to within 2.

With this configuration, when the acceleration sensor 1 is dropped before the acceleration sensor 1 is attached, the hit location is limited to the housing 6 or the rubber 11, and these elements 6, 1
By 1, the shock transmitted to the gauge 2 is alleviated.

After the acceleration sensor 1 is attached, the rubber 11 is at the same level as the anti-gauge mounting surface B of the metal base 4, so that the metal base 4 can be attached in close contact with the surface of the object P to be detected. Accurate acceleration detection sensitivity can be maintained.

FIG. 6 is a vertical sectional view showing a fourth embodiment of the present invention. In this embodiment as well, the acceleration sensor 1 is the object P to be detected.
It is mounted in the same manner as in the second and third embodiments. Housing 6
Is covered by a rubber cover 13. Rubber cover 13
Part 13a of the housing 6 protrudes outward from the tip of the side edge of the housing 6. In the state before the acceleration sensor is attached, the protruding portion 13a of the rubber cover 13 protrudes outside the metal base 4 and the screw 7 as shown in FIG.
In the attached state, as shown in FIG. 6 (b), the compression was set to the same level as the anti-gauge mounting surface B of the metal base 4.

In this embodiment, if the sensor is dropped before the acceleration sensor 1 is attached, the impact is relieved because the contact area is limited to the rubber cover 13. Further, good detection sensitivity can be obtained as in each of the above-mentioned embodiments.

[0046]

As described above, according to the present invention, by devising the attachment and protection of the metal base for mounting and supporting the cantilever type gauge, it is possible to sufficiently withstand a drop impact of 10,000 G or more. In addition, the effect of maintaining good acceleration detection sensitivity is achieved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a state before and after attachment of an acceleration sensor according to a first embodiment of the invention.

FIG. 2 is a circuit configuration diagram of the acceleration sensor according to the above embodiment.

FIG. 3 is an explanatory view showing a part of the acceleration sensor according to the above embodiment and data of optimum conditions for improving impact resistance thereof.

FIG. 4 is a longitudinal sectional view showing a state before and after attachment of the acceleration sensor according to the second embodiment of the invention.

FIG. 5 is a vertical cross-sectional view showing a state before and after attachment of an acceleration sensor according to a third embodiment of the invention.

FIG. 6 is a vertical cross-sectional view showing a state before and after attachment of an acceleration sensor according to a fourth embodiment of the invention.

[Explanation of symbols]

1 ... Acceleration sensor, 2 ... Gauge, 4 ... Metal base, 5 ...
Adhesive, 6 ... Housing, 6a ... Housing side edge, 7 ...
Screw, 9 ... Mounting base, 10, 11, 13 ... Elastic body, 12 ...
Grooves, 22, 23 ... Fixed electrode, 24 ... Cantilever, 25 ... Mass part (movable electrode), A ... Gauge mounting surface, B ... Anti-gauge mounting surface, P ... Accelerated object to be detected.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadane Ueno 2520 Takaba, Katsuta-shi, Ibaraki Pref., Sawa Plant, Hitachi, Ltd. (72) Kinmasa Sato 2477 Kashima Yatsu, Katsuta-shi, Ibaraki Katsuta-shi, Ibaraki 3 Hitachi Automotive Engineering Co., Ltd. (72) Inventor Yasuhiro Asano 2477 Kashima Yatsu Kashima, Katsuta City, Ibaraki Prefecture 3 Hitachi Automotive Engineering Co., Ltd.

Claims (8)

[Claims] 1. A cantilever type acceleration sensor having a mass portion that displaces in response to acceleration, comprising a metal base on which a gauge of the acceleration sensor is mounted, and a buffering housing which accommodates the gauge and the metal base. The metal base is arranged so that the entire surface of the metal base is hidden inside the housing so that the counter gauge mounting surface faces the outside.On the other hand, the mounting base is fixed to the sensor mounting surface of the object to be detected. , A metal base with a housing is fixed to the mounting base to enable the mounting of the acceleration sensor, and a part of the inner surface of the housing abuts on a gauge mounting surface of the metal base, and from the abutting inner surface of the housing to the housing side. A cantilever type acceleration sensor characterized in that a distance L of a vertical line to a tip of an edge and a thickness D of the metal base / mounting base are set to L <D. 2. A cantilever type acceleration sensor having a mass portion that displaces in response to acceleration, comprising a metal base on which a gauge of the acceleration sensor is mounted, and a buffering housing which accommodates the gauge and the metal base. To form an acceleration sensor, the metal base is arranged such that its anti-gauge mounting surface protrudes out of the housing, and the metal base is fixed to the sensor mounting surface of the object to be detected to enable the acceleration sensor to be mounted. Further, an elastic body for cushioning is provided at the tip of the side edge of the housing, and this elastic body projects to the outside of the metal base before the acceleration sensor is attached, and in the state where the acceleration sensor is attached,
A cantilever type acceleration sensor, characterized in that it is set so as to be compressed to a position on the same level as the anti-gauge mounting surface of the metal base. 3. A cantilever type acceleration sensor having a mass portion that is displaced according to acceleration, comprising a metal base on which a gauge of the acceleration sensor is mounted, and a buffering housing which accommodates the gauge and the metal base. To form an acceleration sensor, the metal base is arranged such that its anti-gauge mounting surface protrudes out of the housing, and the metal base is fixed to the sensor mounting surface of the object to be detected to enable the acceleration sensor to be mounted. In addition, a groove with an elastic body for cushioning is provided on the anti-gauge mounting surface of the metal base, and this elastic body protrudes outside the metal base before the acceleration sensor is mounted, and the acceleration sensor is mounted. In a state, a cantilever type acceleration sensor is set such that it receives a compressive force due to mounting and escapes into the groove. 4. A cantilever type acceleration sensor having a mass portion that displaces in response to acceleration, comprising a metal base on which a gauge of the acceleration sensor is mounted, and a buffering housing which accommodates the gauge and the metal base. To form an acceleration sensor, the metal base is arranged such that its anti-gauge mounting surface protrudes out of the housing, and the metal base is fixed to the sensor mounting surface of the object to be detected to enable the acceleration sensor to be mounted. In addition, the housing is covered with a rubber cover, and a part of the rubber cover is projected to the outside of the tip of the side edge of the housing. Also protrudes to the outside, and with the acceleration sensor attached, until it reaches the same level as the anti-gauge mounting surface of the metal base. Cantilever type acceleration sensor, characterized in that set to condensation. 5. The cantilever type acceleration sensor according to claim 1, wherein the elastic body is made of rubber or sponge. 6. The cantilever acceleration sensor according to claim 1, wherein the acceleration sensor includes a capacitance gauge or a piezo effect gauge. 7. The cantilever beam for supporting the mass portion according to claim 1, wherein the cantilever beam comprises two beam elements that form a pair, and the length, width, and A cantilever type acceleration sensor characterized in that the thickness is selected under the condition that both beam sensitivity and shock resistance can be achieved. 8. The gauge according to any one of claims 1 to 7, wherein the gauge is fixed to the metal base directly or by interposing other elements with an adhesive, and the adhesive itself includes the adhesive itself. A cantilever type acceleration sensor characterized by having a thickness enough to absorb a shock.