JP2001349902A - Acceleration sensor - Google Patents

Abstract

(57) [Problem] To provide a high-accuracy acceleration sensor. SOLUTION: A fixed part 3a fixed to a moving body, a terminal part 2g on the fixed part 3a, a first beam 2a extending at a right angle from the terminal part 2g, and the first beam Second and third beams 2b and 2c extending in a direction orthogonal to an extending direction axis of the first beam in the same plane; and second and third beams 2
b and 2c, fourth and fifth beams 2d and 2e extending substantially in parallel with the first beam 2a and in the direction of the fixing portion 3a.
A sixth beam 2f connecting end portions of the fourth and fifth beams 2d and 2e, magnets 1a and 1b provided in the middle of the sixth beam 2f, and a magnetic return yoke. 1c
, A non-magnetic base yoke 3b, first, second, third,
Fourth strain resistance elements 11a, 11b, 11c, 11d;
An acceleration sensor electrically connected to the four strain resistance elements and electrically detecting a strain amount generated in the first, fourth, and fifth beams by acceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever type strain gauge type acceleration sensor.

[0002]

2. Description of the Related Art A cantilever type strain gauge type acceleration sensor detects a mechanical strain generated when an acceleration is applied as a change in the resistance value of a strain gauge, and detects the acceleration based on the change in the resistance value. It is to detect. here,
Generally, in order to obtain an electric signal proportional to acceleration, a strain gauge whose resistance value changes due to strain and a comparison gauge for comparison are provided, and these are connected to form a Wheatstone bridge.

It is desirable that the resistance of the comparative gauge does not change at all when an acceleration is applied. In this regard, there is a structure in which a comparative strain gauge is disposed at a place other than the cantilever, but a compensation circuit may be required due to a difference in temperature coefficient from the strain gauge, a difference in atmospheric conditions, and the like. Therefore, there is a case where a semiconductor strain gauge is formed on a cantilever at the same time and close to the same process in the same process. As the arrangement, a comparative strain gauge is formed to be elongated in the direction orthogonal to the strain gauge near the strain gauge formed on the support portion of the cantilever. In this case, the temperature coefficient becomes substantially equal, but since the temperature coefficient is near the supporting portion, the comparative strain gauge is strongly affected by the strain, which causes noise at the time of detection by the strain gauge and lowers the detection accuracy.

Therefore, there is a conventional example in which the noise of the comparative strain gauge is suppressed by contriving the arrangement of the strain resistor as disclosed in Japanese Patent Application Laid-Open No. 4-62477.

The configuration of the conventional example will be described. 11 and 12, one end of a cantilever 2 having a weight 1 attached to the tip is fixed to a support member 3, and the cantilever 2
Are provided with a strain gauge 21 and a comparative strain gauge 22 on the same surface. These are electrically connected to each other by the electrode lead portions 23 to form a bridge. Further, the strain gauge 21 is formed to be elongated in the longitudinal direction of the cantilever 2 at a position close to the support member 3, and the comparative strain gauge 22 is arranged closer to the weight 1 than the strain gauge 21 in the transverse direction of the cantilever 2. Form elongated.

The operation of the acceleration sensor configured as described above will be described below. When the cantilever 2 bends in the direction perpendicular to the paper of FIG. 11 and the direction of the arrow in FIG. 12 by applying acceleration, the strain near the support end is large and the strain is generated in the longitudinal direction. The value changes. On the other hand, the resistance value of the comparative strain gauge 22 that is farther from the support member 3 and has a shorter longitudinal direction that causes strain is hardly changed. Then, by applying the voltage Vs to both ends of the bridge constituted by the strain gauge 21 and the comparative strain gauge 22, an output voltage Vo with little influence of noise is obtained.

[0007]

However, the above conventional acceleration sensor has the following problems.

First, in the conventional example, since the comparative gauge is on the cantilever (cantilever), the effect of the strain does not become zero and the detection accuracy is compared with the case where the comparative strain gauge does not change at all. Drops.

Second, the conventional example has a problem that the frequency band used is narrower than that using an oil damper or the like because it does not have a damper or the like. In other words, the cantilever (cantilever) resonates when it receives acceleration at its resonance frequency or external vibration, so that the resonance frequency of the cantilever (cantilever) can be used only in a much lower frequency range as an acceleration sensor.

According to the present invention, the shape of the cantilever (cantilever) structure is modified so that both compressive and tensile strains are generated on the same surface of the beam, and the strain gauge and the comparative gauge are compressed and tensioned, respectively. By using the comparison gauge not only as a noise source but also as a strain detecting element provided at a place where the opposite distortion occurs, not only the noise reduction but also the efficiency of the distortion detection, that is, the sensor sensitivity is doubled. It is an object of the present invention to provide a high-precision strain gauge type acceleration sensor which has a configuration and incorporates an eddy current damper structure to widen a use frequency band.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an acceleration sensor according to the present invention includes a fixed portion fixed to a moving body, a terminal fixed to the fixed portion, and a right angle from the terminal. An extended first beam, second and third beams extending in a direction orthogonal to an extending direction axis of the first beam in the same plane as the first beam, and , From the third beam to the first
A fourth beam, a fifth beam extending substantially parallel to the first beam and in the direction of the fixed portion, and being line-symmetric with respect to an axis of the first beam in an extending direction; A sixth beam connecting each end portion, a magnetic flux generating means provided in the middle of the sixth beam, and a non-magnetic and conductive material with which the magnetic flux emitted from the magnetic flux generating means is linked. A base yoke, first and second strain-sensitive elements provided on the first beam at positions symmetrical with respect to an axis of the first beam in an extending direction, and the fourth and fifth strain-sensitive elements; A third and a fourth strain-sensitive element provided on the beam at a position orthogonal to the first beam and at a position symmetrical with respect to an axis of the first beam in an extending direction; 2, third,
It is electrically connected to a fourth strain-sensitive element and configured to electrically detect a change in the amount of strain generated in the first, fourth, and fifth beams by acceleration. With this configuration, a highly accurate strain gauge type acceleration sensor can be obtained.

[0012]

According to the first aspect of the present invention, a fixed portion fixed to a moving body, a terminal fixed to the fixed portion, and a right angle extending from the terminal portion. A first beam, second and third beams extending in a direction orthogonal to an extending direction axis of the first beam in the same plane as the first beam, and a second and third beam; Fourth and fifth beams extending from the beam substantially parallel to the first beam and in the direction of the fixed portion, and being line-symmetric with respect to the extending direction axis of the first beam; A sixth beam connecting each end of the fifth beam, a magnetic flux generating means provided in the middle of the sixth beam, and a non-magnetic and conductive magnetic flux generated by the magnetic flux generating means interlinking. A base yoke made of a conductive material, and a first yoke provided on the first beam at a position that is line-symmetric with respect to an axis of the first beam in an extending direction.
A second strain-sensitive element, and the first and second beams on the fourth and fifth beams.
Third and fourth strain-sensitive elements provided on a line orthogonal to the first beam and at a position that is line-symmetric with respect to the axis in the direction of extension of the first beam, and the first, fourth, and Since the first, second, third, and fourth strain-sensitive elements are provided with means for electrically detecting the amount of strain caused by the bending of the fifth beam, the first, fourth, and fifth elements are provided. Compression and tensile strains occur on the same surface of the beam, enabling a full-bridge configuration to increase the strain detection sensitivity. The magnetic flux generating means provided in the middle of the sixth beam and the non-magnetic and conductive An eddy current damper is formed between the base yokes made of a material, and this eddy current damper has an effect of suppressing the vibration amplitude near the resonance frequency of the beam.

According to a second aspect of the present invention, in the first aspect, the second and third beams in the first beam are provided.
A hole is provided in a connection portion with the second beam, and a notch is provided in a connection portion between the fourth and fifth beams with the second and third beams. It has the effect of improving.

According to a third aspect of the present invention, in the first aspect of the invention, since the beam is made of a precipitation-hardened stainless steel sheet having a high proof strength, an excessive force is applied to the beam due to an impact such as a drop. This has the effect that the beam is unlikely to be permanently deformed even if added.

According to a fourth aspect of the present invention, in the third aspect of the invention, an alloy thin film resistor is directly formed on an insulating layer formed on a beam and used as a strain gauge. A conventional adhesive or the like does not intervene between the layer and the alloy thin film resistor, and has an effect that high reliability can be ensured particularly in adhesion.

According to a fifth aspect of the present invention, since alumina ceramic is used as the insulating layer in the fourth aspect of the present invention, the linear expansion coefficient of the beam and the insulating layer is substantially similar, Has the effect of realizing high adhesion.

According to a sixth aspect of the present invention, in the fourth aspect, the thin film resistor is composed of 45% by weight of nickel, 45% by weight of chrome, and 10% by weight of aluminum. Has the effect of reducing the rate of change.

According to a seventh aspect of the present invention, in the fourth aspect of the present invention, the terminal electrode portion for extracting a signal from the strain gauge is provided not on the movable portion but on the fixed portion. Does not receive any stress due to the displacement of the beam, and has the effect of ensuring connection reliability.

According to an eighth aspect of the present invention, in the fourth aspect of the present invention, the terminal electrode portion, the circuit board, and the flexible substrate for electrically connecting the terminal electrode portion and the circuit board are provided. An end portion of the flexible substrate connected to the terminal electrode portion is divided into two forks, and each of the crotch portions is provided in two gaps between the first beam and the fourth and fifth beams, respectively. Is disposed so as to be connected to the terminal electrode portion by being inserted from the back side of the flexible substrate, and is configured to be fixed to the fixed body at a portion in front of a portion where the flexible substrate is divided into two branches. The bending motion of the flexible substrate is restricted, and the stress due to the bending of the flexible substrate due to vibration, drop, or the like is hardly transmitted to the terminal electrode portion, and has an effect of improving the connection reliability of the terminal electrode portion.

According to a ninth aspect of the present invention, in the first aspect of the present invention, as a means for generating a magnetic flux, two magnets are polarized in such a manner that the respective magnetizing directions are perpendicular to the surface of the base yoke. Are provided so as to sandwich the sixth beam in a direction opposite to each other, and a return yoke made of a magnetic material that magnetically short-circuits the magnetic poles of the two magnets is provided on the two magnets. This has the function of forming an eddy current damper having a simple structure.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the return yoke is connected to the magnet so that the end face adjacent to the end face of the magnet provided with the return yoke is magnetically short-circuited. Due to the letter shape, the interference of the magnetic flux to the surroundings can be suppressed, and the magnet is not magnetically attracted to the magnetic material outside the sensor, and has the effect of being hardly affected by the external magnetic material.

According to an eleventh aspect of the present invention, since an amplifying circuit for amplifying a signal from the detecting means and a low-pass filter circuit are provided in the first aspect, the signal is amplified to a desired signal. Then, there is an effect that unnecessary frequency components due to beam resonance are removed.

According to a twelfth aspect of the present invention, in the fourth aspect, each of the fourth and fifth beams comprises an upper beam portion and a lower beam portion, and the upper beam portion and the lower beam portion are joined. With this structure, the area of the components involved in the formation of the insulating film and the alloy thin film can be reduced, and this has the effect that more beams can be formed at one time.

According to a thirteenth aspect of the present invention, there is provided an assembling method using a jig or the like in which the fixing portion and the base yoke are connected at one end to form one part. This has the effect that the positional relationship between the magnetic flux generating means and the base yoke can be maintained with a desired accuracy with higher accuracy and with less man-hours, and the damping force of the eddy current damper can be realized with high accuracy.

According to a fourteenth aspect of the present invention, a case fixed to a moving body and at least two sensors are provided.
When a shock is applied due to a configuration including a circuit board mounted so as to have a detection axis, and a rubber damper provided between the case and the circuit board, a shock is applied particularly in the acceleration detection direction. In addition, even if the eddy current damper alone does not have sufficient shock damping force, the rubber damper can absorb the shock, and if it is necessary to detect acceleration in multiple axes simultaneously, it can be played by simply attaching it as a single multi-axis detection unit There is action.

(Embodiment 1) Hereinafter, an acceleration sensor according to Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is a front view of an acceleration sensor according to Embodiment 1 of the present invention, FIG. 2 is a side view, and FIG. 3 is a perspective view of main components including a beam excluding a strain sensitive element. First, an outline of the entire configuration will be described.

In FIG. 1, the beams 2a to 2f and the terminal portion 2g are attached to the fixed portion 3a by screws 4a and 4b. The screws 4a and 4b are preferably made of a non-magnetic material, and here, brass screws are used. As shown in FIG. 2, the fixing portion 3a is integrated with the base yoke 3b so as to be substantially U-shaped. The material is preferably non-magnetic and high in conductivity, and pure copper is used here. A mounting terminal 8 made of brass is fixed to the back surface of the base yoke 3b by welding. The components including the beams 2a to 2f and the terminal portions 2g attached to the fixing portion 3a are fixed to the circuit board 12 by the mounting terminals 8, and the circuit board 12 is fixed to the moving body. I have.

Next, the detailed shapes of the beams 2a to 2f will be described.

In FIGS. 1 and 3, a first beam 2a extending substantially at right angles from a fixing point of a terminal portion 2g fixed to the fixing portion 3a by screws 4a, 4b in the same plane. The second and third beams 2b, 2c extend in a direction substantially perpendicular to the extending direction of the first beam 2a. These second,
The fourth and fifth beams 2d, 2e are substantially parallel to the first beams 2a from the third beams 2b, 2c and in the direction of the fixing portion 3a.
Is extending. A sixth beam 2f is connected to the end of each of the fourth and fifth beams 2d and 2e.

In FIG. 1, FIG. 2 and FIG.
f is samarium cobalt (Sm ₂
Magnets 1a and 1b made of Co ₁₇ ) -based rare earth magnets are provided so as to sandwich the sixth beam 2f so that their polarities are opposite to each other. The magnetization directions of the magnets 1a and 1b are perpendicular to the base yoke 3b. The magnet 1a,
Above 1b, a return yoke 1c made of a ferrite-based magnetic material is provided, and the magnets 1a and 1b are magnetically short-circuited.

In FIG. 2, the magnetic flux from the magnets 1a and 1b is linked to the copper base yoke 3b to form an eddy current damper. The eddy current damper accelerates the sixth beam 2f including the magnets 1a and 1b. , Ie, the movement in the left-right direction is attenuated.

2 and 3, the fixed portion 3a and the base yoke 3b are integrally formed as described above, and the gap between the magnets 1a and 1b and the base yoke 3b is 0.5 m.
The beams 2a to 2f are attached so that the distance becomes m ± 0.2 mm.

In FIGS. 1 and 3, the first beam 2a is provided with a hole 9 at a connection portion with the second and third beams 2b and 2c, and the fourth and fifth beams are provided. In the beams 2d and 2e, notches 10a and 10b are provided at the connection portions with the second and third beams 2b and 2c.

In FIG. 1, the strain-sensitive element has a position on the first beam 2a which is symmetrical with respect to a line orthogonal to the axis of the first beam 2a in the direction of extension of the first beam 2a. First,
The second strain resistance elements 11a and 11b are provided, and the extending direction of the first beam 2a on a line orthogonal to the extending direction axis of the first beam on the fourth and fifth beams 2d and 2e. Third and fourth strain resistance elements 11c and 11d are provided at positions symmetrical with respect to the axis.

The electrical connection between the strain resistance elements 11a to 11d and the circuit board 12 is as follows. The strain resistance elements 11a to 11d are connected to each other by a wiring pattern so as to form a bridge with four elements, and the terminal ends thereof are provided between the screws 4a and 4b by the terminal electrode section 13, and the terminal electrode section 13 and the circuit board 12 are connected. The flexible substrate 5
For electrical connection.

Here, the flexible substrate 5 is connected as follows.

The end of the flexible substrate 5 on the side connected to the terminal electrode section 13 is divided into two forked substrate terminal sections 14a, 1
4b, each of which is inserted into two gaps between the first beam 2a and the fourth and fifth beams 2d and 2e from the back side of the surface on which the terminal electrode portion 13 is provided, and The flexible substrate 5 is fixed to the fixing portion 3a with a resin screw 7 via a resin spacer 6 at a portion before the portion where the flexible substrate 5 is divided into two. The other terminal of the flexible board 5 is connected to the circuit board 12.

Here, the beams 2a to 2f are made of S having a thickness of 0.1 mm.
It is a US631-based precipitation hardening stainless steel sheet. The strain resistance elements 11a to 11d are each formed on an insulating layer directly formed by high-frequency sputtering using alumina (Al ₂ O ₃ ) as a target.
It is formed by high frequency sputtering using an alloy target having a weight composition ratio of aluminum: 10.

A method of manufacturing the strain gauge type acceleration sensor having the above-described structure will be described below.

In FIG. 1, first, the forked substrate terminal portions 14a and 14b on the side connected to the terminal electrode portion 13 are separated by two gaps between the first beam 2a and the fourth and fifth beams 2d and 2e. Then, it is inserted from the back side of the surface on which the terminal electrode portion 13 is provided, and is connected and fixed to the terminal electrode portion 13 by soldering.

Next, the magnets 1a and 1b are arranged so as to sandwich the sixth beam 2f so that the respective magnetizing directions are opposite to each other, and a return yoke 1c is arranged on the magnets 1a and 1b. Fix with an adhesive. In the first embodiment, an epoxy adhesive is used.

In FIG. 2, the beams 2a to 2f assembled as described above are fixed to the fixing portion 3a by screws 4a and 4b. Further, the flexible substrate 5 is fixed to the fixing portion 3a with a resin screw 7 via a resin spacer 6 at a portion in front of a portion where the flexible substrate 5 is divided into two parts.

This acceleration sensor is based on the base yoke 3b.
Is soldered and fixed to the circuit board 12 by mounting terminals 8 which have been welded and fixed to the back surface of the flexible board 5, and then one terminal of the flexible board 5 is soldered and fixed to the circuit board 12 to complete the electrical connection. The circuit board 12 has an amplifier circuit and a filter circuit as means for detecting a change in the amount of distortion generated in the first, fourth, and fifth beams.

The operation of the strain gauge type acceleration sensor constructed and manufactured as described above will be described below with reference to FIGS.
This will be described with reference to FIG.

In FIG. 1, the beams 2a, 2d and 2e bend when acceleration in the direction perpendicular to the plane of the drawing is applied to the acceleration sensor. At this time, since the beam 2a, the beam 2d, and the beam 2e bend and deform in directions opposite to each other, when tensile strain occurs in the strain resistance elements 11a, 11b, compressive strain occurs in the strain resistance elements 11c, 11d, and conversely, strain occurs. When compressive strain occurs in the resistance elements 11a and 11b, tensile strain occurs in the strain resistance elements 11c and 11d. Here, the strain generated in the strain resistance elements 11a and 11b and the strain resistance elements 11c and 11d is proportional to the acceleration and equal in absolute value.
The positions of a and 11b and the strain resistance elements 11c and 11d are determined.

As shown in FIG. 1, the strain resistance elements 11a, 11
Since b is near the hole 9, the strain takes a value close to the maximum value due to stress concentration. Also, since the strain resistance elements 11c and 11d are provided near the base of the simple beam, the strain also takes a value close to the maximum value. By forming a bridge with the distortion resistance elements 11a to 11d, it becomes possible to detect a full bridge in distortion detection. A voltage is applied to this, and the resistance change can be extracted as a voltage change.

In FIGS. 2 and 3, the magnetic flux from the magnets 1a and 1b interlinks with the base yoke 3b made of copper, and
When 1b moves in the left-right direction in FIG. 2 and the arrow direction in FIG. 3, a back electromotive force is generated in the base yoke 3b, and an eddy current flows. Since the eddy current functions to cancel the magnetic flux from the magnets 1a and 1b, the eddy current attempts to prevent the magnets 1a and 1b from moving with respect to the base yoke 3b. Therefore, this eddy current is generated by the sixth beam 2 including the magnets 1a and 1b.
The deflection due to the acceleration of f, that is, the movement in the left-right direction is damped. The generated eddy current is proportional to the relative speed between the magnets 1a and 1b between the base yokes 3b. Therefore, as the relative speed increases, the eddy current increases and the damping force increases. Since the sensor detects the acceleration applied to the cantilever as the displacement of the beam, that is, the strain of the beam, when the frequency of the applied acceleration is high, the speed at which the beam moves is high, the attenuation is large, and the sensor functions as a damper. Even if the resonance frequency of the beams 2a to 2f and the acceleration or external vibration in the vicinity thereof are applied to the beams 2a to 2f, the vibration of the beams 2a to 2f is attenuated by the eddy current damper, and the resonance frequency of the beams 2a to 2f is reduced from a low frequency. Up to a sensor.

An amplifier circuit is provided at the subsequent stage of the bridge to obtain various signal output characteristics, and an unnecessary signal component is removed by a filter circuit. The broken line in FIG. 4 shows the frequency characteristics of the beam having the eddy current damper. With this beam alone, the beam resonates at the frequency fr, so that it can be detected only up to the cutoff frequency fc. However, when this beam is combined with a low-pass filter circuit having the frequency characteristic shown by the broken line in FIG. 4, the final output as a sensor becomes as shown by the thick solid line in FIG. 4, and the upper limit of the frequency that can be detected using the same beam is the cutoff frequency. From fc to the target cutoff frequency fo, the detection frequency range can be expanded.

In order to raise the upper limit of the detection frequency, there is a method of increasing the rigidity of the beam to increase the resonance frequency of the beam.
In this case, the rigidity of the beam is increased, so that the beam is less likely to bend, and the absolute value of the signal due to the bending is reduced. As a result, the ratio (S / N ratio) between the acceleration signal component and the noise component is reduced, and the sensor detection accuracy is reduced.

In the first embodiment, in order to secure the detection sensitivity, a beam having low rigidity and easy bending, that is, a beam having a low resonance frequency, is used in combination with a filter circuit with high accuracy up to a frequency range close to the resonance frequency of the beam. Acceleration can be detected.

Embodiment 2 Hereinafter, an acceleration sensor according to Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 5 is a front view of an acceleration sensor according to Embodiment 2 of the present invention, and FIG. 6 is a side view. Since the configuration is basically the same as that of the first embodiment, the same components are denoted by the same reference numerals and detailed description is omitted. Only different points from the first embodiment will be described.

The second embodiment differs from the first embodiment in the shape of the return yoke 1c in FIG. As shown in FIG. 6, the return yoke 1d has a U-shape so that the end faces adjacent to the end faces of the magnets 1a and 1b are also magnetically short-circuited.

The manufacturing method according to the second embodiment is basically the same as that of the first embodiment, and will not be described. Further, the operation according to the second embodiment is basically the same as the operation relating to the acceleration detection. Therefore, only the operation due to the shape effect of the return yoke 1d different from the first embodiment in the present configuration will be described.

In the first embodiment, the magnets 1a,
1b preferentially generates a magnetic flux on the surface of the base yoke 3b, but also generates a leakage magnetic flux in other directions.
Therefore, when a magnetic body approaches the acceleration sensor from outside, the magnets 1a and 1b are magnetically attracted in the direction of the external magnetic body and the beam is bent, as if acceleration was applied even when no acceleration was applied. It may be output from a sensor. By forming the return yoke 1d as shown in FIG. 6, the side surfaces of the magnets 1a and 1b are also magnetically short-circuited to suppress the generation of leakage magnetic flux. Since the magnetic attraction does not occur, erroneous output of the sensor can be prevented.

Embodiment 3 Hereinafter, an acceleration sensor according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 7 shows a third embodiment of the acceleration sensor according to the present invention.
FIG.

Since the configuration is basically the same as in the first and second embodiments, the same components are denoted by the same reference numerals and detailed description is omitted. Therefore, only different points from the first and second embodiments will be described.

The difference between the first and second embodiments is that the fourth and fifth beams are different from each other in FIG. 7 in that the fourth beam upper portion 2d1, the fourth beam lower portion 2d2, and the fifth beam upper portion 2e1 are different from each other. This is a point separated into the fifth beam lower part 2e2. For this reason, the beams 2a to 2d1, 2e1 are connected to the strain resistance element 11a.
In the third embodiment, the number of beams that can be formed in a single film forming process is increased in the third embodiment compared with the first and second embodiments. FIG. 8 shows a shape diagram of the beam after the formation of the strain resistance element according to the first and second embodiments.
FIG. 9 is a beam shape diagram after forming the strain resistance element in the third embodiment.
Shown in In FIG. 8 showing the first and second embodiments, nine beams are formed in the same frame area, and in FIG. 9 showing the third embodiment, 15 beams are formed in the same frame area.

With regard to the acceleration sensor of the present invention, the cost of joining separately formed beams as in Embodiment 3 to form a detection beam is lower than the cost of forming an integrated beam portion. Therefore, there is an effect that the sensor can be supplied at a lower price as a whole.

Embodiment 4 Hereinafter, an acceleration sensor according to Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 10 is a plan view of an acceleration sensor according to Embodiment 4 of the present invention.

As shown in FIG. 10, a case (not shown) fixed to a moving body and a circuit board 1 in which two acceleration sensors are mounted so as to have two detection axes orthogonal to each other.
2, and rubber dampers 15a, 15b, 15c provided between the case and the circuit board 12.

In FIG. 10, when impact is applied in the vertical and horizontal directions in a plane parallel to the plane of the paper, the rubber dampers 15a, 15b,
Since the shortage of the damping force of the eddy current damper can be compensated for by 15c, damage to the beams 2a to 2f and other sensor components due to impact can be prevented.

Further, when it is necessary to simultaneously detect two-axis accelerations for vehicle control or the like, only one of the two-axis detection units is required to perform the function. In addition, there is an effect that the mounting space can be reduced as compared with a case where two single-axis detection sensors are separately mounted. Further, the output take-out connector and the harness can be reduced as compared with the case where two sensors are attached individually.

Here, the first embodiment is considered from the viewpoint that the acceleration sensors can be arranged close to each other and can be compactly assembled.
Embodiment 2 is more preferable than Embodiment 2.

In the fourth embodiment, two sensors are used.
Although the case where axis detection is performed has been described, for example, there are cases where four sensors are used as a plurality of sensors, and two of them are paired, and two axes are detected in each pair. In that case, the sensor signal becomes redundant within each pair, but this can be used as a fail-safe.

[0067]

As described above, according to the present invention, the shape is devised so that both compressive and tensile strains are generated on the same surface of the beam in spite of the cantilever structure, and the strain gauge and the comparative gauge are generated. By arranging the comparison gauge so that the distortions are equal in magnitude and the directions are opposite, and actively utilizing the comparison gauge as a strain detection element, it not only reduces noise but also doubles the efficiency of distortion detection. And a high-precision strain gauge type acceleration sensor having a wide operating frequency band with a wide operating frequency band by incorporating an eddy current damper structure.

[Brief description of the drawings]

FIG. 1 is a front view of an acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a side view of the acceleration sensor according to the first embodiment of the present invention.

FIG. 3 is a perspective view of main components of the acceleration sensor according to the first embodiment of the present invention.

FIG. 4 is a diagram showing frequency characteristics of beams, circuits, and sensor outputs according to the first embodiment of the present invention.

FIG. 5 is a front view of an acceleration sensor according to Embodiment 2 of the present invention.

FIG. 6 is a side view of the acceleration sensor according to the second embodiment of the present invention.

FIG. 7 is a front view of an acceleration sensor according to Embodiment 3 of the present invention.

FIG. 8 is a beam shape diagram after forming a strain resistance element according to the first and second embodiments of the present invention.

FIG. 9 is a beam shape diagram after forming a strain resistance element according to a third embodiment of the present invention.

FIG. 10 is a plan view of an acceleration sensor according to Embodiment 4 of the present invention.

FIG. 11 is a plan view of a conventional acceleration sensor.

FIG. 12 is a side view of a conventional acceleration sensor.

[Explanation of symbols]

 1a, 1b Magnet 1c Return Yoke 2a First Beam 2b Second Beam 2c Third Beam 2d Fourth Beam 2e Fifth Beam 2f Sixth Beam 2g Terminal 3a Fixed Part 3b Base Yoke 4a, 4b Screw Reference Signs List 5 flexible substrate 9 hole 10a, 10b notch 11a first distortion resistance element 11b second distortion resistance element 11c third distortion resistance element 11d fourth distortion resistance element 12 circuit board 13 terminal electrode section 14a, 14b Board terminal 15a, 15b, 15c Rubber damper

Claims (14)

[Claims] 1. A fixed part fixed to a moving body, a terminal part fixed to the fixed part, a first beam extending at a right angle from the terminal part, and the same plane as the first beam. Within the first
Second and third extending in the direction perpendicular to the extending direction axis of the beam
A fourth beam extending from the second and third beams substantially parallel to the first beam and in the direction of the fixed portion, and being line-symmetric with respect to the axis of the first beam in the extending direction. A fifth beam, a sixth beam connecting end portions of the fourth and fifth beams, a magnetic flux generating means provided in the middle of the sixth beam, and the magnetic flux generating means. A base yoke made of a non-magnetic and conductive material with which the generated magnetic flux interlinks, and a first yoke provided on the first beam at a position symmetrical with respect to an axis of the first beam in a direction in which the first beam extends. And the second strain-sensitive element, and are provided on the fourth and fifth beams on a line orthogonal to the first beam and at a position which is line-symmetric with the axis of the first beam in the extending direction. 3rd, 4th
And the first, second, third, and fourth strain-sensitive elements are electrically connected to the first, fourth, and fourth strain-sensitive elements by acceleration.
Means for electrically detecting a change in the amount of strain generated in the fifth beam. 2. A hole is provided in a connection portion between the first beam and the second and third beams, and the second and third beams are provided in the fourth and fifth beams.
The acceleration sensor according to claim 1, wherein a cutout portion is provided in a connection portion with the third beam. 3. The acceleration sensor according to claim 1, wherein the beam is made of a precipitation-hardened stainless steel sheet. 4. The acceleration sensor according to claim 3, wherein the strain-sensitive element comprises a thin-film resistor formed directly on an insulating layer formed on the beam. 5. The acceleration sensor according to claim 4, wherein the insulating layer is made of alumina ceramic. 6. The acceleration sensor according to claim 4, wherein the thin-film resistor is composed of 45% by weight of nickel, 45% by weight of chromium, and 10% by weight of aluminum. 7. The acceleration sensor according to claim 4, wherein a terminal electrode portion for extracting a signal from the strain resistance element is provided between two fixed points. 8. A terminal electrode part, a circuit board, and a flexible board for electrically connecting the terminal electrode part and the circuit board, wherein the end of the flexible board connected to the terminal electrode part is forked. Separately, each crotch is inserted into two gaps between the first beam and the fourth and fifth beams from the back side of the surface on which the terminal electrode portion is provided so as to be connected to the terminal electrode portion. 5. The acceleration sensor according to claim 4, wherein the acceleration sensor is provided and fixed to a fixed body at a portion before a portion of the flexible substrate that is split into two. 9. As means for generating a magnetic flux, two magnets are arranged so that the respective magnetizing directions are perpendicular to the surface of the base yoke, the polarities thereof are opposite to each other, and the sixth beam is sandwiched therebetween.
2. A return yoke made of a magnetic material for magnetically short-circuiting a magnetic pole on a side not facing the base yoke.
2. The acceleration sensor according to 1. 10. The acceleration sensor according to claim 9, wherein the return yoke is substantially U-shaped so that an end face adjacent to an end face of the magnet provided with the return yoke is magnetically short-circuited. 11. The acceleration sensor according to claim 1, further comprising an amplification circuit for amplifying a signal from the detection means and a filter circuit. 12. The acceleration sensor according to claim 4, wherein each of the fourth and fifth beams comprises an upper beam portion and a lower beam portion, and the upper beam portion and the lower beam portion are joined. 13. The acceleration sensor according to claim 1, wherein the fixed portion and the base yoke are connected at an end to form one part. 14. A case fixed to a moving body, a circuit board on which a plurality of sensors are mounted so as to have at least two detection axes, and a rubber damper provided between the case and the circuit board. The acceleration sensor according to claim 1, further comprising: