JPH09257830A - Vibration type acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor being highly accurate and inexpensive. SOLUTION: A parallel beam vibrating body 3 is point-connected between a mass part 1 and a support base 2 through the intermediary of connecting parts 35 and 36. The parallel beam vibrating body 3 is constructed by connecting two beams 38 and 39 by end parts 31 and 32. The parallel beam vibrating body 3 is excited from the end parts 31 and 32 by an exciting means, while the frequency of the parallel beam vibrating body 3 is detected by a detecting means. This frequency changes according to a space between the beams 38 and 39 and the space changes due to displacement of the mass part 1. Accordingly, acceleration can be detected by detection of the change of the frequency by a detecting part. The displacement due to the acceleration can be detected directly and highly accurately as the change of the frequency and, besides, a sensor can be prepared easily by etching an SOI(silicon on insulation) substrate or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting an acceleration acting on an object such as an automobile, and more specifically, it supports a mass portion, a parallel beam vibrating body, and a mass portion and a parallel beam vibrating body. The present invention relates to a vibration type acceleration sensor including a support base and a connecting portion connecting them, and detecting acceleration as a change in frequency due to a change in beam spacing (change in shape rigidity) of a parallel beam vibrating body that resonates and vibrates.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor is generally composed of a mass portion (mass portion) and a plurality of spring elements (beam portions) supporting the mass portion, and detects acceleration as a stress of the spring element.

In the acceleration sensor having such a structure, the mass portion is displaced by the inertial force generated by the action of acceleration. Since the mass portion is supported by the spring element, the stress generated in the spring element by the displacement is displaced until it balances with the inertial force of the mass portion. Therefore, the stress generated in the spring element is proportional to the acceleration. Therefore, the acceleration is detected by measuring the acceleration using a stress detecting means incorporated in the spring element in advance.

Here, as the acceleration detecting means incorporated in the spring element, for example, a type utilizing a semiconductor strain gauge has predominantly been used. In this strain gauge type acceleration sensor, a change in electric resistance when an elastic force acts on the strain gauge is converted into a voltage output, and stress generated in the spring element, that is, acceleration is detected. With respect to this detection method, many improvements have been attempted so far regarding the shape of spring elements, strain gauges, etc., with the aim of improving the conversion efficiency of converting stress into voltage.

On the other hand, in recent years, an acceleration sensor called a vibration type has been studied. This vibration-type acceleration sensor is integrally incorporated in a spring element, and the amount of change in the resonance frequency of the beam-shaped oscillator excited by electrostatic force or the like is transmitted to the beam-shaped oscillator via the spring element. It is based on the fact that it is proportional to the axial stress. Therefore, an electrical (or optical) means is used to measure the change in the frequency of the beam-type vibrator to detect the acceleration. For example, The 8th International Conferenceon Sol
id-State-Sensors and Actuators (Transdusers´795),
The structure is disclosed in DW Burns, pp. 659pp to 662, (1995).

In addition to being able to measure the frequency change very accurately using a frequency counter, this vibration type has a high frequency change (sensitivity) of the oscillator corresponding to the acceleration as compared with the strain gauge method. It has the feature that it can detect acceleration accurately.

FIG. 10 (A) is a schematic diagram of a plane structure of the vibration type acceleration sensor, FIG. 10 (B) is a schematic diagram of a sectional structure for explaining the detection principle, and FIG. 10 (C). Is
An enlarged view of the cross-sectional structure of the spring element (beam portion) is shown.

In FIGS. 10A to 10C, the mass portion 1
1 is connected via a plurality of spring elements 12 to a support portion (frame) 13 that is arranged outside and surrounds the mass portion 11. These are manufactured by etching (boring with an alkaline solution) from both sides of a silicon substrate having a thickness of several hundreds of μm or more. As a result, the mass portion 11 has the spring element 12
While being supported by, it is movable in the Y direction in which the detected acceleration acts.

Further, the mass portion 11 and the spring element 12 are vertically connected via a joint portion 17 for the purpose of protection from the external environment and avoiding damage due to displacement of the mass portion 11 due to excessive acceleration in the Y direction. It is covered with protective caps 15 and 16. The protective caps 15 and 16 are used for the mass portion 1.
1 and the spring elements 12 and the supporting portion 13 are manufactured on the basis of the same silicon substrate in consideration of the balance of thermal expansion coefficient with the silicon material, and are directly bonded without using an adhesive.

A manufacturing process such as etching or bonding based on a silicon substrate is generally called bulk micromachining, and a sensor device manufactured by this method has a size exceeding several mm cubic. To be done.

Further, as shown in FIG. 10C, the spring element 12 has a vibrator 14 as means for detecting acceleration.
Is manufactured in the vacuum chamber 19 using a polycrystalline thin film. The vibrator 14 has a beam shape and resonates and vibrates by an electrostatic force applied by an excitation mechanism (not shown). A vacuum chamber 19 is formed by the sealing member 18.

Here, when acceleration acts on the Y axis, the mass portion 11 is displaced and an axial stress in the X direction is generated in the spring element 12, and the vibrator 14 integrally incorporated in the spring element 12.
The axial stress is transmitted to. As a result, the resonance frequency of the vibrator 14 increases or decreases according to the acceleration, and the acceleration is measured by detecting this frequency. The auxiliary spring element 121 is for assisting the support of the mass portion 11.

According to the technique disclosed in the above-mentioned document, about 10% (about 0.5 per 1G) in the acceleration range 20G specification.
%) Frequency change is obtained. The spring element 12
The manufacturing process in which the vibrator 14 is incorporated into the substrate is a processing target area on the surface of the silicon substrate, and is generally called surface micromachining.

[0014]

However, the acceleration sensor having the above-mentioned structure essentially detects the stress of the spring element. Therefore, there are problems as described in (1) to (5) below.

(1) Since the mass portion is constrained by a plurality of spring elements, thermal stress is generated in the spring elements during the mounting process or the temperature rising / falling process. The above-described conventional acceleration sensor is essentially configured to detect the axial stress generated in the spring element, and as a result, the influence of thermal stress is superimposed on the change in frequency detected by the vibrator, which causes a large difference. There is an error effect. As described above, the conventional acceleration sensor has a drawback that it is easily affected by thermal stress.

(2) The axial stress acting on the beam-shaped oscillator made of a polycrystalline silicon material is transmitted through the spring element that supports the displacement of the mass portion due to the action of acceleration.
As a result, in the process of transmitting the axial stress from the spring element, a transmission loss of the axial stress occurs at the joint with the vibrator,
The axial stress, which is equivalent to the displacement of the mass corresponding to the acceleration, is not accurately transmitted to the vibrator.

(3) The oscillator and the spring element are made of different materials. Therefore, the large axial stress transmitted to the connection portion deteriorates the joint portion, and there is a drawback that the long-term reliability required in transportation means such as an automobile cannot be ensured.

(4) As a manufacturing process of the acceleration sensor, bulk micromachining and surface micromachining are used together. As a result, the whole manufacturing process and steps are complicated and the manufacturing cost is increased.

(5) Further, as a result of utilizing the bulk micromachining process, the sensor structure becomes large and the manufacturing cost increases.

Accelerometers for transportation means such as automobiles and airplanes are required to have high accuracy and low cost. However, the conventional acceleration sensor cannot satisfy these two requirements at the same time.

The present invention has been made to solve the above problems, and provides a highly accurate acceleration sensor that simplifies the manufacturing process and reduces the cost, and that has excellent temperature characteristics and reliability. The purpose is to do.

[0022]

The present invention comprises a support base and
A pair of parallel beams substantially point-connected to the support base via a first connecting portion, a parallel beam vibrating body including end portions respectively connecting the parallel beams at both ends, and the parallel beam vibrating body The mass portion, which is substantially point-connected through the two connecting portions, has a predetermined weight, the exciting means for applying an exciting force to the end portion of the parallel beam vibrating body, and the frequency of the parallel beam vibrating body are detected. And detecting the acceleration based on a change in frequency caused by a change in the distance between the pair of parallel beams in the parallel beam vibrating body.

As described above, in the vibration type acceleration sensor of the present invention, the beam of the parallel beam vibrating body is deflected by the inertial force of the mass portion generated by the acceleration. As a result, the shape rigidity of the parallel beam oscillator changes, and as a result, the resonance frequency of the parallel beam oscillator changes. This change in resonance frequency is equal to or higher than that of the conventional acceleration sensor of FIG. 10 that detects the stress of the spring element. Therefore, the vibration type acceleration sensor of the present invention can detect acceleration with high accuracy.

Further, in the vibration type acceleration sensor of the present invention, the connection with the package component is performed by the support base. Therefore, the parallel beam oscillator and the mass portion connected to the parallel beam oscillator,
Only the points are connected to the support base, and the other parts are not mechanically restrained. Therefore, even if thermal stress is generated due to the non-uniform thermal expansion coefficient between the support base and the package component, this is not transmitted to the parallel beam vibrating body. Therefore, the vibration type acceleration sensor of the present invention, which detects a change in frequency due to a change in shape of a parallel beam, is essentially not susceptible to thermal stress and has excellent temperature characteristics.

Further, the vibration type acceleration sensor of the present invention is
The displacement of the mass portion due to the action of acceleration is directly detected as a change in shape rigidity of the parallel beam vibrating body, that is, a change in resonance frequency. Therefore, there is no transmission loss as in the conventional vibration type acceleration sensor that converts the axial stress transmitted through the spring element into a change in the frequency of the beam and detects the change, and the connection portion of different materials does not deteriorate. Therefore, the vibration type acceleration sensor of the present invention has higher accuracy and higher reliability.

According to another aspect of the invention, the first supporting base, a pair of parallel beams substantially point-connected to the first supporting base via the first connecting portion, and the parallel beams A first parallel beam vibrating body including end portions respectively connected at both ends, a mass portion substantially point-connected to the first parallel beam vibrating body through a second connecting portion, and a mass portion having a predetermined weight; A pair of parallel beams, which are substantially point-connected to each other through a third connecting portion, and a second parallel beam vibrating body including end portions connecting the parallel beams at both ends, and the second parallel beam vibrating body. A second support base, which is substantially point-connected via a fourth connecting portion, and first and second excitation means for applying an excitation force to the ends of the first and second parallel beam oscillators, respectively. And the frequencies of the first and second parallel beam vibrating bodies are detected. First and second detecting means, and detecting the acceleration based on a difference in change in frequency due to a change in interval between the pair of parallel beams in each of the first and second parallel beam vibrating bodies. Is characterized by.

In the vibration type acceleration sensor of the present invention, the first and second parallel beam vibrating bodies, which are vibrating bodies, are arranged opposite to each other with the mass portion sandwiched therebetween, and differentially detect acceleration. In this way, by arranging the pair as opposed to each other, the rigidity in the direction other than the acceleration axis to be detected is increased,
While maintaining the original sensitivity of acceleration detection, the influence of malfunction on other acceleration components is greatly reduced. Further, the differential detection can cancel out the influence of thermal stress in the direction of the detection axis of acceleration, and is excellent in temperature characteristics.

According to still another aspect of the invention, the mass portion, the parallel beam vibrating body, the supporting base, and the connecting portion are formed on an SOI substrate having a silicon layer on an oxide layer or on a substrate. It is characterized in that the crystalline silicon layer is processed to be integrally formed.

As described above, according to the present invention, the SOI substrate or the polycrystalline silicon layer is etched from the surface, and the mass portion, the parallel beam, the support base, and the connecting portion thereof are hollowed out integrally (surface micromachining). Only). As a result, the sensor structure can be made smaller and lighter, the manufacturing process can be simplified, and the cost can be significantly reduced.

According to still another invention, claim 1
Or the metal layer in which the mass part, the parallel beam vibrating body, the support base, and the first and second connecting parts which constitute the vibration type acceleration sensor are vapor-deposited or plated on the substrate. It is characterized in that it is formed by processing. As a result, similarly to the above, the sensor structure can be made smaller and lighter, the manufacturing process can be simplified, and the cost can be significantly reduced.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

<First Embodiment> A first embodiment of the vibration type acceleration sensor 1000 of the present invention will be described below.

FIG. 1 is a perspective view of the vibration type acceleration sensor 1000 of the first embodiment, FIG. 2 is a plan view of the vibration type acceleration sensor of FIG. 1, and FIG. The configuration of the change detection means is shown. Further, FIG. 4 shows a plan view for explaining the operation principle of the vibration type acceleration sensor 1000 according to the first embodiment.

First, the parallel beam oscillator 3 has a thickness of 1 μm.
m, the depth thickness is 10 μm, and the two beams 38 and 39 each having a length of about 1000 μm are connected by end portions 31 and 32. The distance (distance) between the pair of beams 38 and 39 when there is no deformation was set to 20 μm.

The parallel beam vibrating body 3 is substantially point-connected between the mass portion 1 and the support base 2 via a connecting portion 35 and a connecting portion 36. These connection parts 35,
Reference numeral 36 connects the central portions of the beams 38 and 39 to the mass portion 1 and the support base 2.

The area size of the mass portion 1 is 500 μm.
It is formed in a square, and the support base 2 is 800 μm × 3
It is formed to have a thickness of 00 μm. The depth and thickness are both
10 μm.

Further, as shown in detail in the enlarged view of FIG. 3, the end portions 31 and 32 connecting the two parallel beams 38 and 39 of the parallel beam vibrating body 3 are arranged along the acting direction of acceleration. A comb-shaped groove portion 69 is provided. Then, the parallel beam vibrating body 3 is excited by the exciting force applying means 60 formed so as to mesh with the groove portion 69. That is, the excitation force applying means 60 and the end portions 31 and 32 of the parallel beam vibrating body 3.
During this period, a periodic electrostatic force is applied from the AC power supply 61. Therefore, the parallel beam vibrating body 3 is excited by the periodic electrostatic force.

That is, by applying an electrostatic force, the end portions 31 and 32 of the parallel beam vibrating body 3 are bent in a vibration mode in which the connecting portion 35 and the connecting portion 36 are used as vibration nodes (non-vibration points) in the direction of acceleration. Resonates (frequency 6400 Hz). Therefore, the end portions 31 and 32 are the maximum displacement portions during vibration. The drive in the resonance state is realized by the vibration detection means described later to select the excitation frequency where the amplitude is always the maximum or the excitation frequency where the phase of the drive and the amplitude is shifted by 90 degrees.

Amplitude change detecting means 65 for detecting a change in amplitude due to vibration of the end portions 31 and 32 is provided on the side facing the excitation force applying means 60. A constant voltage is applied to the amplitude change detecting means 65 from a constant voltage source 67 via a resistor 66. Therefore, as the ends 31 and 32 vibrate in the Y direction, the amount of electric charge (current) generated in the region of the groove 69 changes, and the voltage across the resistor 66 changes.
Therefore, by detecting the voltage across the resistor 66 with the voltage detector 68, the vibration of the parallel beam oscillator 3 can be measured as the voltage change of the resistor 66. Therefore, the frequency of the parallel beam oscillator 3 is measured from this measurement result.

In this embodiment, in order to apply the exciting force to the parallel beam vibrating body 3, the groove portion 69 is provided and the electrostatic force is used as the physical quantity of the exciting force.
The shapes of 1 and 32 and the excitation means are not particularly limited to this. For example, there is no problem even if magnetic force or thermal energy is used as the excitation means. In addition, the ends 31, 32
The means for detecting the change in the amplitude and the electrical circuit configuration are not particularly limited to those described above.

Here, the vibration type acceleration sensor 100 of the first embodiment in which the end portions 31 and 32 are excited in the bending vibration mode.
The resonance frequency Fn of the parallel beam oscillator 3 at 0 is expressed by the following equation (1).

[0042]

[Formula 1] Fn = K1√ [EI / Aρ] (1) where Fn is a natural frequency, K1 is a constant determined by the order of the vibration mode, E: Young's modulus, I Is the shape rigidity of the parallel beam oscillator, A is the cross-sectional area of the parallel beam, and ρ is the density.

From this equation, it is understood that the resonance frequency Fn changes depending on the size of the shape rigidity I of the parallel beam vibrating body 3.

Vibration type acceleration sensor 1000 of this embodiment
4, the mass portion 1 is displaced with respect to the support base 2 by the acceleration G, and the parallel beam vibrating body 3 is moved.
The spacing between the beams 38, 39 at is changed.

The shape rigidity I of the parallel beam vibrating body 3
Changes in accordance with the shape change of the parallel beam vibrating body 3, and as shown in FIG. 5, when the acceleration G in the Y direction to be detected acts, the interval H between the beams 38 and 39 becomes narrow. Due to. On the other hand, when the acceleration in the direction opposite to that of FIG. 5 is applied, the interval H between the beams 38 and 39 becomes wider, and the shape rigidity I increases.

That is, the distance H between the beams 38 and 39 of the parallel beam vibrating body 3 is changed by the action of the acceleration G, and the shape rigidity I is changed accordingly. As a result, the resonance frequency F is changed.
n also changes according to the acceleration.

As described above, the present vibration type acceleration sensor directly detects the acceleration as the change in the resonance frequency due to the change in the beam interval (change in the shape rigidity) of the parallel beam vibrating body due to the action of the acceleration. Therefore, unlike the conventional vibration type acceleration sensor described above, no transmission loss occurs when converting and detecting the axial stress transmitted via the spring element.

In the vibration type acceleration sensor of the first embodiment,
As shown in the characteristic diagram of FIG. 6, it has a large frequency change of more than 10% and a good linearity when an acceleration of 1 G is applied. Therefore, the acceleration generated in the transportation means such as a vehicle can be detected with high accuracy and reliability.

Further, the support base 2 is connected to a package component in order to support the inertial force of the mass portion 1 and the parallel beam 3 due to the action of acceleration. However, the mass portion 1 and the parallel beam vibrating body 3 do not have a direct connection portion with a package component, but are simply point-connected to the support base 2 at the connection portion 36.

Generally, the package component is made of a resin material or a ceramic material having different physical properties such as a coefficient of thermal expansion from the silicon material constituting the vibration type acceleration sensor. Therefore, thermal stress is generated in the support base 2 due to the nonuniform thermal expansion coefficient. However, the support base 2
The thermal stress generated in the above is not transmitted to the parallel beam 3 and the mass portion 1 because there is no connecting portion with the package component (it is only point-connected to the supporting base 2 at the connecting portion 36). .

Therefore, the present vibration type acceleration sensor also has a characteristic that it is not easily affected by the thermal stress generated during the temperature rising / falling process and that it has excellent temperature characteristics. The package parts are
It also has the function of protecting the sensor from the surrounding environment. Also, the package component is attached to an object to be measured such as a vehicle.

Further, the vibration type acceleration sensor 1 of this embodiment
000 is an SOI having a thickness of 10 μm as shown in FIG.
(Silicon on Insulator) It is manufactured by etching the substrate. That is, a silicon substrate, silicon oxide (Si
O ₂ ) A bonding layer and an SOI substrate having a three-layer structure of a silicon layer having a thickness of 10 μm are subjected to etching processing to integrally manufacture the mass part 1, the support base 2, the parallel beam vibrating body 3, and the connecting parts 35 and 36. To be done.

From this, the present vibration type acceleration sensor 1000
Can be manufactured in an area size of about 1 mm square (thickness is 10 μm) based on the SOI substrate, and is remarkably downsized in comparison with the conventional acceleration sensor which has been manufactured as several mm cubic or more. And this production can be achieved only by surface micromachining. Therefore, a significant cost reduction is achieved.

The vibration type acceleration sensor 1000 is
The SOI substrate is not necessarily manufactured by etching, but a polycrystalline silicon layer formed on a substrate made of silicon or the like is manufactured by etching or a metal vapor-deposited or plated on a substrate made of silicon or the like is used. You can also make it.

<Second Embodiment> A second embodiment of the vibration type acceleration sensor of the present invention will be described below.

FIG. 8 is a plan view of the vibration type acceleration sensor 2000 of the second embodiment. In the present vibration type acceleration sensor, parallel beam vibrating bodies (first and second parallel beam vibrating bodies) 3a and 3b are provided as a pair at opposing positions sandwiching the mass portion 1. Supporting bases (first and second supporting bases) 2a at positions opposite to the mass portion 1 with the parallel beam vibrating bodies 3a and 3b sandwiched therebetween.
2b is provided. The parallel beam vibrating body 3a
Is connected to the support base 2a and the mass portion 1 by connecting portions (first and second connecting portions) 35a and 36a,
The parallel beam vibrating body 3b is connected to the mass portion 1 and the support base 2b at connecting portions (third and fourth connecting portions) 35b and 36b.

Then, the present vibration type acceleration sensor 2000
Detects the acceleration in the Y direction in the figure as a differential output of the frequency change of the pair of parallel beam vibrating bodies 3a and 3b.

The sizes and manufacturing methods of the parallel beam vibrating bodies 3a and 3b, the mass portion 1, the support bases 2a and 2b, the excitation means of the parallel beam vibrating bodies 3a and 3b, and the basic principle of detecting acceleration. Is the same as that of the above-described first embodiment, and the description thereof will be omitted.

In the present vibration type acceleration sensor 2000, since the parallel beam vibrating bodies 3a and 3b are provided as a pair at opposing positions with the mass portion 1 sandwiched therebetween, the parallel beam vibrating bodies 3a and 3b when the acceleration acts. The amount of deflection of 3b is
It is given as about 50% of the vibration type acceleration sensor 1000 of the first embodiment in FIG. However, since the deflection has different polarities between the pair of parallel beam vibrating bodies 3a and 3b, the beam interval increases on the one hand and decreases on the other hand. And
The resonance frequencies of the pair of parallel beam vibrating bodies 3a and 3b increase or decrease by the same amount.

As a result, the resonance frequency changes as shown in the characteristic diagram of FIG. By detecting the increase / decrease in the resonance frequency as a differential output, the acceleration can be measured with high accuracy and reliability as in the first embodiment. The differential output can be obtained by calculating the difference in frequency change detected in each of the parallel beam vibrating bodies 3a and 3b in a calculation unit (not shown). The calculation unit may be a calculation unit for analog signals or a calculation unit for digital signals.

Further, in the present vibration type acceleration sensor 2000, since the support bases 2a and 2b are provided as a pair at opposite positions with the mass portion 1 sandwiched therebetween, the vibration type acceleration sensor 2000 accompanying temperature rise and fall. Due to the expansion and contraction of itself, a stress in the Y direction that changes the beam intervals of the parallel beam vibrating bodies 3a and 3b equally is generated. However, in the present vibration type acceleration sensor 2000, since the change in the resonance frequency of the pair of parallel beam vibrating bodies 3a and 3b is detected as a differential output, the influence of the thermal error in the Y direction can be canceled out, and the high frequency is achieved. The accurate acceleration detection function can be maintained.

Further, in the present vibration type acceleration sensor 2000, the parallel beam vibrating bodies 3a and 3b, the support base 2 are provided.
Since a and 2b are provided as a pair at opposing positions sandwiching the mass portion 1, the rigidity other than the Y direction, which is the detection target, is significantly improved and improved. Therefore, X direction and Z
For the directional acceleration, the parallel beam vibrating bodies 3a, 3b
Is more difficult to deform. As a result, it is possible to prevent the frequency change with respect to the acceleration in the X and Z directions, which is generally called a crosstalk component of acceleration. That is, according to the vibration type acceleration sensor 2000, the acceleration component for detection can be measured with high accuracy without being affected by crosstalk with respect to other accelerations.

[0063]

As described above, the vibration-type acceleration sensor of the present invention directly detects acceleration as a change in resonance frequency due to a change in beam interval of the parallel beam vibrating body. Therefore, it is possible to prevent the loss due to transmission and detect the acceleration with high accuracy and reliability.

Further, the parallel beam vibrating body which is an acceleration detecting element and the support base are substantially point-connected. Therefore, it is possible to avoid the influence of thermal stress, which has been a problem in the conventional acceleration sensor, and it is possible to realize good temperature characteristics.

Further, the parallel beam vibrating bodies are arranged as a pair at opposite positions sandwiching the mass portion, and the acceleration is differentially detected as a change in resonance frequency based on a change in shape of the pair of parallel beam vibrating bodies. Therefore, there is no detection error for other acceleration components, and good output characteristics and temperature characteristics can be realized.

Furthermore, the vibration-type acceleration of the present invention has an SOI
It can be easily manufactured by etching the substrate or the polycrystalline silicon layer, or by processing the metal layer deposited or plated. Therefore, the manufacturing process is remarkably simplified, the size and weight can be reduced, which has not been achieved by the conventional acceleration sensor, and the cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing a vibration type acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view of the sensor.

FIG. 3 is a diagram showing a configuration of the same sensor excitation and amplitude detection.

FIG. 4 is a plan view showing an acceleration detection principle of the sensor.

FIG. 5 is an explanatory diagram showing the principle of acceleration detection in the sensor.

FIG. 6 is a diagram showing a detection characteristic of the sensor.

FIG. 7 is a diagram illustrating a manufacturing method.

FIG. 8 is a plan view showing a vibration type acceleration sensor according to a second embodiment.

FIG. 9 is a diagram showing a detection characteristic of the sensor.

FIG. 10 is a diagram showing a configuration of a conventional acceleration sensor.

[Explanation of symbols]

1 mass part, 2, 2a, 2b support base, 3, 3a, 3
b parallel beam oscillator, 35, 36, 35a, 35b,
36a, 36b connection part, 1000 Vibration type acceleration sensor of 1st Embodiment, 2000 Vibration type acceleration sensor of 2nd Embodiment.

Claims (5)

[Claims] 1. A parallel beam vibration including a support base, a pair of parallel beams substantially point-connected to the support base via a first connecting portion, and end portions respectively connecting the parallel beams at both ends. A body, a mass portion that is substantially point-connected to the parallel beam vibrating body through a second connecting portion, and has a predetermined weight; and an exciting means that applies an exciting force to the end portion of the parallel beam vibrating body. A detecting means for detecting the frequency of the parallel beam vibrating body, and detecting acceleration based on a change in the frequency resulting from a change in the distance between the pair of parallel beams in the parallel beam vibrating body. Vibration type acceleration sensor. 2. A first support base, a pair of parallel beams substantially point-connected to the first support base via a first connecting portion, and end portions connecting the parallel beams at both ends, respectively. A first parallel beam vibrating body, a mass portion that is substantially point-connected to the first parallel beam vibrating body via a second connecting portion, and has a predetermined weight; and a third connecting portion in the mass portion. A pair of parallel beams substantially point-connected through the second parallel beam vibrating body, and a second parallel beam vibrating body including end portions respectively connecting the parallel beams at both ends, and a second connecting portion substantially connected to the second parallel beam vibrating body. Second support bases that are point-connected to each other, first and second excitation means that apply excitation force to the ends of the first and second parallel beam oscillators, respectively, and the first and second First and second detection for detecting the frequency of two parallel beam oscillators And a means for detecting acceleration based on a difference in frequency change caused by a change in interval between a pair of parallel beams in each of the first and second parallel beam oscillators. Acceleration sensor. 3. The vibration type acceleration sensor according to claim 1, wherein the mass part, the parallel beam vibrating body, the support base and the first and second connecting parts have a silicon layer on the oxide layer. S
A vibration-type acceleration sensor, characterized by being formed by processing an OI substrate. 4. The vibrating acceleration sensor according to claim 1, wherein the mass portion, the parallel beam vibrating body, the support base, and the first and second connecting portions forming the vibrating acceleration sensor are on a substrate. A vibration type acceleration sensor, characterized in that it is formed integrally by processing the polycrystalline silicon layer formed on. 5. The vibration type acceleration sensor according to claim 1, wherein the mass section, the parallel beam vibrating body, the support base, and the first and second connection sections that constitute the vibration type acceleration sensor are provided on a substrate. A vibration-type acceleration sensor, characterized by being formed integrally by processing a metal layer formed by vapor deposition or plating.