JP2786240B2 - Acceleration sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor that is attached to an object to be detected and detects acceleration applied to the object with high sensitivity.

[Conventional technology]

Conventionally, as a structure generally used for detecting vibration, acceleration, and the like, a thin-walled diaphragm (thin wall) portion on which a semiconductor strain gauge is formed on a semiconductor substrate as a cantilever is formed. There is known a cantilever type semiconductor acceleration sensor that detects a force to be measured in accordance with a change in resistance value of a semiconductor strain gauge by fixing a supporting portion of the semiconductor device and using the other thick portion as a free end.

And in such a semiconductor type acceleration sensor,
Characteristics are almost determined by the shape of the cantilever,
In the resonance frequency range determined by the shape of the cantilever itself, an output several tens times higher than the output in other frequency ranges is output. Therefore, for example, in order to detect the acceleration of an automobile, only a low frequency range (usually about 100 Hz or less) is required. Therefore, in order to cut off a relatively high frequency range including a resonance frequency range, silicon oil or the like is used. The damping liquid is used as a mechanical high-cut filter by using a damping action by viscous resistance by disposing a cantilever in the damping liquid.

In such a semiconductor acceleration sensor, it is desirable to enclose a small amount of air in the package in consideration of expansion and contraction of the damping liquid due to temperature change. However, in such a case, since the damping liquid is not filled in the package, when the semiconductor type acceleration sensor vibrates, the damping liquid undulates, which adversely affects the semiconductor type acceleration sensor as noise. Therefore, in order to prevent the damping liquid from waving, it has been proposed to provide a partition 200 having a communication hole 250 in the damping liquid 700 as shown in FIGS. 15 (a), (b) and (c). (Japanese Patent Application No. 61-236910 (JP-A-63-9077)
No. 4)).

[Problems to be solved by the invention]

However, in the semiconductor acceleration sensor described in Japanese Patent Application No. 61-236910, when mounted on a moving object such as a vehicle to be detected, the arrow direction in the figure is the upward direction, that is, the direction in which gravity acts. Are mounted in the opposite direction, in which case, the partition wall 200 is formed in a direction perpendicular to the arrow direction, that is, parallel to the horizontal direction. When the sensor is turned upside down, some of the gas bubbles 260a of the gas 260 are separated from the gas 260 in a spatially separated state and remain in the chamber on the cantilever 4a side (reproducibility). Is bad). When the moving object vibrates, the vibration causes the bubble 260a to vibrate in the horizontal direction and agitate the damping liquid 700. As a result, the lateral acceleration (the
15 (a), the longitudinal direction of the cantilever 4a) acts on the cantilever 4a, and the characteristics of the sensor deteriorate.

Further, it is conceivable to increase the diameter of the communication hole 250 in order to easily return the remaining gas 260a to the chamber on the gas 260 side in the upward direction. However, according to this sensor configuration, the communication hole 250 is damped by the gas 260. Since the gas 260 also serves as both passages of the liquid 700, the gas 260 can easily pass therethrough, but also the damping liquid 700 can easily flow, and if two or more communication holes 250 are formed as shown in FIG. The damping liquid is circulated through the communication hole 250. As a result, the lateral acceleration is applied to the cantilever 4a in the same manner as described above, thereby deteriorating the characteristics of the sensor.

Therefore, the present invention has been made in view of the above problems, and a main object of the present invention is to provide a sensor in which acceleration detecting means is arranged in a damping liquid without expanding or contracting the damping liquid without deteriorating the characteristics of the sensor. The object of the present invention is to provide a structure capable of absorbing the water.

[Means for solving the problem]

In order to achieve the above object, an acceleration sensor according to the present invention is an acceleration sensor that is attached to an object to be detected and detects an acceleration applied to the object to be detected, the package having at least one chamber; An acceleration detection unit that is installed in the room and receives a part of the acceleration and changes in vibration, and an amount that immerses the entire acceleration detection unit,
And a damping liquid sealed in the package by an amount such that a predetermined amount of gas is present in the package to absorb the thermal expansion, and spatially separated from the gas in a state where the acceleration is not received. The apparatus is characterized in that a means is provided for separating the air bubbles in the state and preventing the air bubbles from staying in the room where the acceleration detecting means is installed.

〔Example〕

 Hereinafter, the present invention will be described using embodiments shown in the drawings.

FIG. 1 is a view showing the overall configuration of a first embodiment of the present invention, wherein FIG. 1 (a) is a sectional view taken along a broken frame, and FIG. 1 (b) is a sectional view taken along line BB in FIG. 1 (a). Is shown. In the figure, 10
Reference numeral 0 denotes a stem made of a metal such as Kovar, which forms a part of the package. Then, the welded portion 10 on the outer periphery
Except for 1, a convex portion for mounting the pedestal 6 and the like described later is formed by press working or the like, and there are, for example, four through holes for electrical connection with the outside. Welding 500 leads lead terminal 400
Has been fixed. Reference numeral 401 denotes a hole for mounting the semiconductor acceleration sensor.

Next, the sensor element mounted on the stem 100 and composed of the cantilever 4a and the pedestal 6 will be described with reference to the top view shown in FIG. 2 (a) and the top view shown in FIG. 2 (b). This will be described with reference to a cross-sectional view taken along line A. In the figure, reference numeral 4a denotes a cantilever made of, for example, an N-type silicon single crystal substrate, which has a thin diaphragm portion 7, a free end 1, a guard portion 4b arranged around the free end 1 to protect the free end 1, and a support 4b. 8. The scribing for forming the gap 4c between the free end 1 and the guard portion 4b is performed by etching both surfaces of the cantilever 4a.
The upper surface in FIG. 2B is etched in advance by digging, and etching is performed from the back surface when the diaphragm portion 7 is formed thereafter, so that the formation of the diaphragm portion 7 and the scribe are simultaneously performed.

A base layer 3 formed by plating or evaporating a Ni layer or the like is formed on surfaces of predetermined regions of the support body 8 and the guard portion 4b, and is bonded to a pedestal 6 on which the base layer 3 is formed via a solder layer 5. doing. As shown in FIG. 5, the pedestal 6 has a cantilever 4a which can be displaced in accordance with the acceleration to be measured, and a recess having a predetermined depth in a surface facing the cantilever 4a so as not to be damaged by excessive displacement. 6a is formed.

In the diaphragm portion 7 or on the diaphragm portion 7 (the former is shown), four semiconductors formed by introducing into the diaphragm portion 7 by well-known semiconductor processing technology, for example, thermal diffusion or ion implantation of a P-type impurity such as boron. The semiconductor strain gauges 9 are electrically connected to each other by a wiring layer 11a formed by introducing a P-type impurity at a high concentration and a wiring member 11b made of an Al deposited film or the like. And form a full bridge. The wiring layer 11a
In the event that the diaphragm part 7 is broken at the same time, the wiring is routed from the diaphragm part 7 to the free end part 1 so that the diaphragm part 7 is broken at the same time and an abnormal signal can be output as the output of the semiconductor type acceleration sensor. In the drawing, 10 is a protective film such as a silicon oxide film, 11c is a contact portion between the wiring layer 11a and the wiring member 11b, 11d is a pad portion, and the pad portion 11d and the lead terminal 40 are provided.
0 is electrically connected to the wire 300 by wire bonding.

When acceleration is applied to the free end 1 of the sensor element, the diaphragm 7 is distorted, and the resistance value of the semiconductor strain gauge 9 changes according to the magnitude of the acceleration, and a voltage is applied to the bridge circuit in advance. In this way, an unbalanced voltage is generated as a bridge output, and the detected acceleration is detected according to the voltage value.
The pedestal 6 is fixed to 100 by bonding.

Next, in FIG. 3 which is a perspective view of the whole of the first embodiment of the present invention before hermetic sealing, reference numeral 600 denotes a shell made of a metal such as iron, and a rectangular solid inside the shell together with the stem 100 described above. Make up the package that forms the shape, stem 10
Similarly, a welded portion 601 is provided at a position corresponding to the welded portion 101, and the other portions are formed into a box by forming a concave portion by press working or the like.

As shown in FIG. 1, a partition wall 900, which is a main part of the present invention, is joined in the recess of the shell 600 by, for example, spot welding. The partition wall 900 is made of an elastic material such as a stainless steel plate, for example, and has the shape as shown in FIG. 4, and includes a joint portion 901 with the shell 600, a contact portion 902 with the stem 100, and two communication holes for damping liquid. 903, a gas communication hole 904, and two flat partition walls 905 each having a damping liquid communication hole 903. When the acceleration sensor of the present invention is mounted on a vehicle as an object to be detected, the direction of the center arrow U in FIG. 1 is set to the upward direction of the vehicle (opposite to the direction of gravity), and the direction perpendicular to the paper is set to Attach as the direction of travel. Each of the partition plates 905 has a predetermined angle (for example, 35 °) with respect to the direction perpendicular to the upward direction U, that is, the horizontal direction h, and the gas communication hole 904 is arranged at the top of the partition plate 905. It is formed so that. The communication hole 903 for damping liquid is formed below the communication hole 904 for gas in order to return the damping liquid to the cantilever 4a side. The shell of this partition wall 900
First, the joint 901 is welded to the shell 600, and the width of the partition plate 905 is adjusted to the shell 600 and the stem 100.
By making the distance longer than the interval, the contact portion 902 is pressed against the stem 100 during assembly.

In this way, septum 900 includes shell 600 and stem 10
The interior of the package consisting of 0 is divided into a first chamber A and a second chamber B.

In addition, the above-mentioned predetermined angle is preferably such that the angle formed with the horizontal direction h is large, if the dimensions and the assemblability of the product are ignored. The size of the communication hole 903 for the damping liquid should be as small as possible in order to suppress the flow of the damping liquid 700 easily due to the vibration from the vehicle or the like. For example, when the viscosity of the damping liquid is 50 to 2000 cs, the diameter of the communication hole 903 for the damping liquid may be set to about 0.4 mm.

The smaller the diameter of the gas communication hole 904 is,
This is convenient because it can suppress the ripples and flow of 00, but if it is too small, due to the surface tension of the damping liquid 700, when air bubbles return from the chamber on the cantilever 4a side to the chamber on the gas 800 side, the air bubbles Can not pass through the communication hole 904, in this embodiment, for example, the angle 4 of the partition wall 900
When 0 ° and the viscosity of the damping liquid 700 are 50 cs, the diameter of the gas communication hole 904 may be 1.5 mm.

Further, the shell 600 is provided with a hole 602 for injecting the damping liquid 700 after hermetically sealing the package and a hole 603 for releasing air at that time. Then, by applying an electric current between the shell 600 and the stem 100, the two are welded by electric resistance, and are joined together with good airtightness. Then, after welding, a needle-shaped injector is inserted into the hole 602, and a damping liquid 700 such as a silicone oil is supplied to at least the first chamber A.
Is injected in a predetermined amount so as to substantially satisfy. At that time, the air that flows out of the package through the hole 603, but the air 800 remaining inside the package is
Sealing is performed by filling 602 and 603 with solder.

After the semiconductor acceleration sensor configured as described above is assembled to a vehicle, the acceleration sensor is used for detecting the traveling acceleration of the vehicle, detecting a collision (for an airbag), and the like. Even if the sensor 800 is turned upside down or shaken for some reason and the gas 800 enters the first chamber A side, the gas 800 is generated by the buoyancy of the partition plate 905 having an inclination with respect to the horizontal direction h. Along the gas communication hole 904 and immediately returns to the second chamber B. Further, the excess damping liquid 700 returns to the first chamber A through the damping communication hole 903 due to the gravity. Therefore, the air bubbles are separated from the gas 800 in a spatially separated state, and do not stay in the first chamber A.
There is no problem that 0 flows. As a result, only the target acceleration to be detected can be detected without the lateral acceleration that deteriorates the directivity acting on the cantilever 4a of the semiconductor acceleration sensor, and the characteristics thereof can be improved. Although the liquid level of the damping liquid 700 is depressed due to the surface tension at the uppermost portion of the first chamber A, the gas 800 in that portion does not flow due to its buoyancy, deteriorating the characteristics of the sensor at all. Do not let.

According to the present embodiment, the size of the communication hole 903 for the damping liquid can be returned from the second chamber B to the first chamber A by the gravity of the damping liquid 700, but is received from a vehicle or the like. Since the size is set so that it does not flow with vibration, the communication hole 90
The flow of the damping liquid 700 through 3 can be suppressed, and the characteristics of the sensor can be improved accordingly.

Further, since the gas communication hole 904 is formed in only one place, even when the amount of the injection liquid of the damping liquid 700 is large, for example, the gas communication hole 9
The flow through 04 can be minimized.

Furthermore, since the partition wall 900 is formed symmetrically with respect to the cantilever 4a, the stress applied to the damping liquid 700 by the partition wall 900 due to vibration or the like is evenly applied to the cantilever 4a, and the detection accuracy is improved accordingly.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 (a) and 6 (b). Since details other than the partition wall 900 are the same as those in the first embodiment, the same components are denoted by the same reference numerals and description thereof will be omitted. The shape of the partition wall 900 may be a V-shaped cross section as in the present embodiment. In this case, the gas communication holes 904 are formed at the uppermost portions on the left and right ends in FIG. 6 (a).

Next, a third embodiment of the present invention will be described with reference to FIGS. 7 (a) and 7 (b). In this embodiment, details other than the partition wall 900 are the same as those in the first embodiment, and the same components are denoted by the same reference numerals and description thereof will be omitted. The shape of the partition wall 900 may be a flat plate shape as in this embodiment. In the case of the present embodiment, when attached to an object such as a vehicle, it is formed with an inclination with respect to the horizontal direction, a gas communication hole 904 at the upper end thereof, and a damping liquid communication hole 903 near the center of the partition wall 900. Provide.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 8 (a) and 8 (b). In this embodiment, details other than the partition wall 900 are the same as those in the first embodiment, and the same components are denoted by the same reference numerals and description thereof will be omitted. As in this embodiment, the shape of the partition wall 900 may be a curved plate.

Next, a fifth embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In the first to fourth embodiments, the diameters of the gas communication holes 904 and the damping liquid communication holes 903 are not particularly limited, so that the gas 800 is supplied to the first chamber A side for some reason before the sensor is assembled. May enter. Then, the gas 800 that has entered the first chamber A side
As is shown by a circle drawn with a dotted line Medium FIG. 9 (a), may remain in the first chamber A as bubbles 801 in a state of being in contact with the cantilever 4a, the diameter 2r ₁ of the bubble 801 is cantilever 4a If the size is such that it reaches the gap 4c opened in this case, when an impact is applied in this state, a part of the bubble 801 may enter the cantilever 4a as shown in FIG. And if this happens,
Bubbles 801 in cantilever 4a are no longer
Since the sensor cannot be pulled out and the output value of the sensor indicates an abnormal value, and the cantilever 4a may be broken by a relatively small impact, the sensor is treated as a defective product.

This embodiment has been made to address the above-described problem, and minimizes the entry of the gas 800 into the first chamber A even if the sensor is turned upside down or shaken before assembling the sensor. At the same time, even if the gas 800 enters the first chamber A, the air bubbles 801 that may enter the cantilever 4a can quickly return to the second chamber B only by the buoyancy. And to reduce the occurrence rate of defective products of the sensor.

First, how to set the diameter of the gas communication hole 904 will be described with reference to FIG. 9 (a). The air bubble 801 that has entered the first chamber A is usually settled down in contact with the wall forming the first chamber A, and therefore, the air bubble 801 is in contact with the wall of the shell 600 forming the first chamber A. Of the partition wall 900, the distance between the portion closest to the gap 4c of the cantilever 4a and the gap 4c
If the 2r _1, the bubble 801 having a diameter of 2r ₁ is to be present in the first chamber A, there is no problem as described above. Therefore, as the diameter 2r ₁ or more bubbles 801 return to the second chamber B side by its buoyancy, it can I set the diameter of the gas communicating hole 904.

Now, the bubble 801 having a diameter of 2r ₁ leaves the slits (gas communicating hole 904) of the diameter of 2r ₂ has to its diameter is 2r ₂ below. Then, when pressure P ₁ for generating a bubble having a diameter of 2r ₂ is obtained, Here, Ts is the surface tension of the damping liquid 700 (20.5 dyn / cm in the case of 50 cs silicon oil).

The pressure P ₂ by buoyancy bubble 801 having a diameter of 2r ₁ is received in the slit of 2r ₂ is It is.

Here, W ₁ is the mass of the damping liquid 700 in an amount corresponding to the volume of the bubble 801, and assuming that the bubble 801 has a spherical shape,
^{_{4 / 3πr 1 3 · ρ (}} ρ is the specific gravity of the damping liquid, silicone oil = 0.96g / cm ^3), G is the weight acceleration.

Then, the diameter of the bubble 801 of 2r ₁ escapes through the slit of 2r ₂ requires the following conditions.

P ₁ <P _{2 From the} above equations (1) and (2), Becomes

For example, when r ₁ = 0.2 cm, setting r ₂ to be larger than 0.41 mm can prevent bubbles 801 from entering cantilever 4a.

As described above, the shell 600 forming the first wall
Wall and out of the partition wall 900, a portion closest to the gap 4c of the cantilever 4a, when the distance between the gap 4c is 2r _1, the diameter 2r ₂ gas communicating hole 904 so as to satisfy the above expression (3) by setting, without the diameter 2r ₁ or more bubbles 801 remain in the first chamber a, it can be suppressed from entering into the cantilever 4a as much as possible. Even if the shape of the gas communication hole 904 is not circular but rectangular as shown in FIG. 1 (b), the bubbles 801 passing through the hole are substantially spherical due to the surface tension of the damping liquid 700. The above equations (1) to (3) can be similarly applied.

Next, how to set the diameter of the damping liquid communication hole 903 will be described with reference to FIGS. 9 (b) and 9 (c).
FIG. 9 (b) shows a state where the sensor is turned upside down, and a state where the largest gas 800 remains under the partition wall 900 on the left side in the figure. FIG. 9 (c) is a view of the partition wall 900 viewed from the side, and the distance D in the figure is the depth of the partition wall 900. The larger the volume of the gas 800 in the liquid, the greater its buoyancy. Therefore, by preventing the maximum volume of the gas 800 that can accumulate below the partition wall 900 from passing through the damping liquid communication hole 903, it is possible to suppress the bubble 801 from entering the first chamber A side. it can.

Thinking in the same way as the idea for setting the diameter of the gas communication hole 904 described above, first, when the pressure P ₃ for generating a bubble having a diameter of 2r ₃ is obtained, Further, when the mass of the amount of damping fluid 700 corresponding to the maximum volume of the gas 800 that may remain on the lower side of the partition wall 900 has a W _2, damping fluid communicating hole diameter of the gas 800 is 2r ₃ 903 The pressure P ₄ due to the buoyancy received at Here, S is the area of the partition wall 900, and in this example, S =
L × D. Then, the gas 800 so as not come off the damping fluid communicating hole 903 of 2r ₃ requires the following conditions.

P ₃ > P _{4 From the} above equations (4) and (5), Becomes

For example, if W ₂ = 0.15 g, D = 0.35 cm, L = 1.3 cm, and the amount of gas 800 present in the package is 11%, then r ₃ is
If it is smaller than 0.32 mm, it is possible to prevent the bubbles 801 from entering the first chamber A.

As described above, if Motomare maximum volume of the gas 800 that may remain on the lower side of the partition wall 900 can be designed to diameter 2r ₃ of the damping fluid communicating hole 903 so as to satisfy the equation (6), the bubble 801 can be prevented from entering the first chamber A, and thus the air bubbles 801 can be prevented from entering the cantilever 4a.

Although the first to fifth embodiments have been described above, in those embodiments, the communication hole formed in the partition wall 900 may be only the gas communication hole 904, and the communication hole 903 for the damping liquid may not be formed. . In this case, the damping liquid 700 that has entered the second chamber B will travel along the interface of the partition wall 900 and return to the first chamber A, and it will take a long time before an appropriate amount returns. However, instead, the communication hole for the damping liquid
Since there is no 903, the effect that there is no problem such that the bubble 801 enters the first chamber A when reversed, or there is no problem that the damping liquid 700 flows through the communication hole 903 for the damping liquid. is there. In each embodiment,
When attaching the partition wall 900 to the shell 600 as shown in FIG. 11, a gap may be generated between the partition wall 900 and the shell 600 due to processing limitations, but this gap is used as the communication hole 903 for the damping liquid. You may use it positively.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. 12 (a) and 12 (b). Since the details after the partition wall 900 are the same as those in the first embodiment, the same components are denoted by the same reference numerals and description thereof will be omitted. Partition wall 900 of this embodiment
Are formed in parallel with the horizontal direction, and do not have the effect of guiding air bubbles that have entered the first chamber A to the second chamber B, but instead have a function for damping liquid opened in the partition wall 900. The diameter of the communication hole 903 is set so that only the damping liquid 700 can pass and the bubbles 800 in the damping liquid 700 cannot pass through.

Therefore, air bubbles do not enter the second chamber B from the first chamber A side, and the diameter of the communication hole 903 for the damping liquid is sufficiently small.
Flow of 0 can be suppressed as much as possible, and the characteristics of the sensor can be improved. Note that, specifically, the diameter of the communication hole 903 for the damping liquid is the diameter 2r ₃ set by the above equation (6).
Smaller in diameter.

Next, a seventh embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In this embodiment, there is no partition in the package, and
Attach it to the object to be detected with the corner 604 of 600 facing upward. In the present embodiment, the upper walls 605 and 606 of the shell 600 have a tilt component with respect to the horizontal direction, and the gas 800 moves upward along these walls 605 and 606 due to its buoyancy, and the upper corner 604 Then, the movement is suppressed. Therefore, also in the present embodiment, it is possible to suppress the gas 800 from swaying in the horizontal direction, and it is possible to improve the characteristics of the sensor. Needless to say, a partition may be provided to suppress the flow of the damping liquid 700.

Next, an eighth embodiment of the present invention will be described with reference to FIG.

In this embodiment, the partition is removed, and the air bag 850 made of vinyl or the like is fixed by the solid member 905. The air bag 850 may be bonded to the shell 600 or the stem 100 using an adhesive instead of the fixing member 905. In this case, the position of the air bag 850 may be anywhere as long as it does not come into contact with the sensor element 4c including the cantilever (detailed illustration is omitted). With this configuration, the flow of the damping liquid 700 in the package is suppressed, and the gas does not move, so that a high-sensitivity acceleration sensor with excellent reproducibility can be provided.

The present invention is not limited to the above-described embodiment, but can be variously modified as shown below, for example, without departing from the gist thereof.

(1) The acceleration detecting means referred to in the present invention may be any means that detects acceleration by receiving an acceleration and a part of which vibrates, thereby detecting the acceleration. In addition to a semiconductor type cantilever, a piezoelectric type or metal It may be of a distortion type or the like. Further, a double-supported beam may be used instead of a cantilever (a cantilever).

(2) In the above-described first to fifth and seventh embodiments, the portion having a tilt component with respect to the horizontal direction may be formed by a stepped wall, in which case, the entire portion is tilted with respect to the horizontal direction. I just want to.

〔The invention's effect〕

As described above, according to the present invention, in the damping liquid sealed in the room in which the acceleration detecting means is installed, the air bubbles which deteriorate the characteristics of the sensor do not remain, so that the flow of the damping liquid is prevented. As much as possible,
As a result, the effect of the lateral acceleration can be reduced, so that there is an effect that the characteristics of the sensor can be improved.

[Brief description of the drawings]

FIG. 1A is a sectional view of a broken frame according to a first embodiment of the present invention.
FIG. 2B is a cross-sectional view taken along the line BB in FIG. 2A, FIG. 2A is a top view of the sensor element in FIG. 1, and FIG. A section view, line 3
FIG. 4 is a perspective view of the whole of the first embodiment of the present invention before hermetic sealing, FIG. 4 (a) is a front view of the partition wall of the first embodiment of the present invention, and FIG. a) bottom view, FIG. 4 (c)
FIG. 5A is a cross-sectional view taken along the line CC of FIG. 5A, FIG. 5 is a perspective view of the base, FIG. 6A is a cross-sectional view of a broken frame of the second embodiment of the present invention,
FIG. 6 (b) is a sectional view taken along the line BB in FIG. 6 (a), FIG. 7 (a) is a sectional view of a broken frame of the third embodiment of the present invention, and FIG. FIG. 8A is a cross-sectional view taken along the line BB, FIG. 8A is a cross-sectional view of a main part of the frame according to the fourth embodiment of the present invention, and FIG. 8B is a cross-sectional view taken along the line BB in FIG. FIGS. 9 (a) and 9 (b) are schematic cross-sectional views for explaining a fifth embodiment of the present invention, and FIG. 9 (c) is a view of the partition seen from right beside, and FIG.
FIG. 11 is a cross-sectional view showing a state in which air bubbles have entered the cantilever. FIG. 11 is a cross-sectional view of a broken frame showing an example in which a gap is used as a communication hole for damping liquid. FIG. 12 (a) is a sixth embodiment of the present invention. 12 (b) is a cross-sectional view taken along the line BB in FIG. 12 (a), FIG. 13 is a cross-sectional view of the seventh embodiment of the present invention, and FIG. Sectional view of the broken frame of the eighth embodiment,
15A is a cross-sectional view of a conventional semiconductor acceleration sensor taken along a broken frame, FIG. 15B is a cross-sectional view taken along line BB in FIG. 15A, and FIG. 15C is FIG. It is CC sectional view taken on the line in FIG. 1 free end, 4a cantilever, 6 pedestal, 8 base, 100 support, 600 stem, 600 shell, 700 damping liquid, 800 gas, 900 partition wall, 903 … Communication hole for damping liquid, 904… Communication hole for gas.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masato Imai 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Corporation (72) Inventor Hirohito Shioya 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Nihon Denso Co., Ltd. (72) Inventor Haruyuki Ikeo 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Electric Equipment Co., Ltd. Kibun 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-63-90774 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01P 15 / 08 G01P 15/12

Claims (1)

(57) [Claims] 1. An acceleration sensor attached to an object to be detected to detect an acceleration applied to the object, comprising: a package having at least one room; An acceleration detecting means, a part of which changes in vibration, and an amount such that the entirety of the acceleration detecting means is immersed and a predetermined amount of gas is present in the package to absorb the thermal expansion. When the acceleration is not received, the air bubbles separate from the damping liquid sealed in the package and are spatially separated from the gas, and the air bubbles remain in the room where the acceleration detection unit is installed. An acceleration sensor, comprising: means for preventing the acceleration sensor.