WO2000079288A1

WO2000079288A1 - Acceleration sensor

Info

Publication number: WO2000079288A1
Application number: PCT/JP2000/004012
Authority: WO
Inventors: Hirofumi Fukumoto; Makoto Ishida; Hidekuni Takao
Original assignee: Asahi Kasei Kabushiki Kaisha
Priority date: 1999-06-22
Filing date: 2000-06-20
Publication date: 2000-12-28
Also published as: JP4633982B2; AU5251300A

Abstract

A support (1) is attached fixedly to the center of a glass substrate (5). The support (1) is surrounded at a predetermined distance by a weight (2) in the form of a square frame. The weight (2) is supported movably on the support (1) by thin beams (11-18), which extend along the sides of the support (1). The support (1), the weight (2), and the beams (11-18) are formed of a silicon substrate.

Description

Description Accelerometer Technical field

The present invention relates to an acceleration sensor that includes a weight and a beam that supports the weight movably, and relates to an acceleration sensor that detects acceleration by using the deflection of the beam. In particular, a signal processing circuit is mounted on a structure including a micromachine. Further, the present invention relates to an acceleration sensor capable of detecting acceleration components in multiple axes. Background art

Conventionally, as this type of semiconductor acceleration sensor, for example, a first acceleration sensor as shown in FIG. 15 and a second acceleration sensor described later are known.

As shown in FIG. 15, the first acceleration sensor includes a support 1 made of a silicon substrate fixed to a glass substrate 5, and a rectangular frame-shaped weight made of a silicon substrate disposed around the support 1. Part 2 and four beams 3 made of a thin silicon substrate connecting the support 1 and the weight part 2 and swingably supporting the weight part 2. The stress detecting section 4 is arranged, and the integrated circuit section 6 is formed on the support 1. As shown in FIG. 16, the second acceleration sensor includes a rectangular frame-shaped support 10 fixed to the glass substrate 5, and a weight 9 disposed on the inner periphery of the support 10. It has four thin-walled beams 3 that connect the support 10 and the weight portion 9 and support the weight portion 9 in a swingable manner.

In a conventional dual acceleration sensor configured as described above, each stress detection unit 4 By processing these detection signals in the integrated circuit section 6, acceleration components in the X-axis, Y-axis, and Z-axis directions can be output.

Incidentally, in the conventional dual acceleration sensor, it is necessary to increase the length of each beam 3 in order to increase the detection sensitivity. In order to lengthen each of the beams 3, in a conventional acceleration sensor structure, the size of the support 1 must be reduced, or the entire sensor must be increased.

However, when the support 1 is a silicon substrate, a signal processing circuit such as a CMOS can be mounted (formed) thereon. If the size of the support 1 is reduced, the mounting of the signal processing circuit becomes impossible. The disadvantage that it becomes possible occurs. In addition, increasing the size of the sensor as a whole is preferable in that the detection sensitivity can be increased, but is not necessarily a suitable solution as a whole.

On the other hand, in the conventional second acceleration sensor, since the beam 3 is surrounded by the support 10, the support 10 is moved by the difference in the thermal expansion coefficient of the material while the sensor is packaged in the case 1 OA. When a stress is applied, the stress is applied to each beam 3 in the longitudinal direction, causing inconvenience such as buckling of each beam 3 and shift of an output signal. Further, when the beam 3 is extended inward, the mass of the weight portion 9 is reduced, so that the detection sensitivity is disadvantageously reduced. Therefore, it is desired to improve the detection sensitivity without increasing the size of the entire sensor, and to develop a new acceleration sensor with excellent detection sensitivity even if it is small. In view of the above, a first object of the present invention is to provide a new acceleration sensor that is highly sensitive and can be downsized.

A second object of the present invention is to achieve high sensitivity and downsizing, and furthermore, a stress other than a stress generated by an externally applied acceleration, which is an original function of the acceleration sensor, is transmitted to the detection element. It is an object of the present invention to provide a highly reliable acceleration sensor that does not have any problem. Further, a third object of the present invention is to provide an acceleration sensor including a detection circuit adapted to the first and second objects. Disclosure of the invention

The present invention comprises: a fixed support; a weight disposed so as to surround the support; and a beam for movably supporting the weight on the support, the deflection of the beam due to stress. An acceleration sensor for detecting acceleration by using the support, wherein the support is formed of a square, the weight is formed of a square frame, and the beam has a length direction along each side of the support. In addition, two acceleration sensors are provided on each side, and both ends of each beam are connected to predetermined positions of the support and the overlapping portion, respectively.

According to an embodiment of the acceleration sensor of the present invention, one end of the beam is connected to a side of the support or a central portion of an inner periphery of the weight portion, and the other end of the beam is connected to an inner periphery of the weight portion. The acceleration sensor is connected to a corner of the portion or an end of a side of the support.

According to the acceleration sensor or the embodiment of the present invention having such a configuration, the beam can be made longer than that of the conventional sensor, so that high sensitivity and miniaturization can be achieved.

The present invention also provides a support fixedly having a hollow portion in the center, a weight disposed in the hollow portion of the support, and movably supporting the weight on the support. An acceleration sensor for detecting acceleration by utilizing deflection of the beam due to stress, wherein the support comprises a rectangular frame, the weight portion comprises a square, and the beam comprises Two pieces are arranged on each side of the weight so that the length direction is along each side of the weight, and both ends of each beam are connected to predetermined positions of the support and the weight. An acceleration sensor is provided.

According to an embodiment of the acceleration sensor of the present invention, one end of the beam is connected to an inner periphery of the support or a center of a side of the weight, and the other end of the beam is an inner periphery of the support. The acceleration sensor is connected to the vicinity of a corner of the portion or to an end of a side of the weight portion.

According to this embodiment, even when the weight is in the center and the support surrounds the weight, and the support is integrated with the package, the stress received from the knock cage or the like is not affected by the length of the beam. Since it does not act directly in the vertical direction, the effect on the stress detection element can be suppressed and the reliability of the sensor can be increased. As an embodiment of the acceleration sensor of the present invention, there is an acceleration sensor characterized in that the support, the weight, and each of the beams are formed of a silicon substrate.

According to the acceleration sensor or each embodiment of the present invention having such a configuration, the beam can be made longer than that of a conventional sensor, so that high sensitivity and downsizing can be achieved.

As an embodiment of the acceleration sensor of the present invention, each of the beams includes a piezoresistive element at a stress concentration portion at both ends thereof, and each of the beams includes two beams arranged on each side of the support or each side of the weight portion. A Wheatstone bridge consisting of four piezoresistive elements is configured for each side, and an arithmetic circuit that performs predetermined arithmetic processing on the output signals of these four Wheatstone bridges and obtains acceleration in any direction is provided. There is an acceleration sensor that is characterized by being provided.

As an embodiment of the acceleration sensor of the present invention, each of the beams is provided with a stress detecting element made of a MOSFET at a stress concentration portion at both ends thereof, and is arranged on each side of the support or on each side of the weight portion. A differential amplifier circuit including four MOSFETs arranged on two beams is configured. An acceleration sensor includes an arithmetic circuit for performing predetermined arithmetic processing on a road output signal to obtain acceleration in an arbitrary direction. As an embodiment of the acceleration sensor of the present invention, there is provided an acceleration sensor, wherein the MOSFET is a P-type MOSFET, and the differential amplifier circuit is a CM • S differential amplifier circuit.

As an embodiment of the acceleration sensor of the present invention, the arbitrary directions are three directions of an X axis, a Y axis, and a Z axis, and the X axis direction and the Y axis direction are relative to the length direction of the beam. And the Z-axis direction is the thickness direction of the beam.

According to each embodiment having such a configuration, the arithmetic circuit for performing predetermined arithmetic processing on the output signals of the four sets of circuits to obtain the acceleration in an arbitrary direction is provided. Available. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view showing an appearance structure of a first embodiment of an acceleration sensor of the present invention, a part of which is cut away.

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is a cross-sectional view taken along line aa of FIG.

FIG. 4 is a cross-sectional view taken along line bb of FIG.

FIG. 5 is a perspective view showing the external structure of a second embodiment of the acceleration sensor of the present invention, a part of which is cut away.

FIG. 6 is a plan view of the second embodiment.

FIG. 7 is a sectional view taken along line c-c in FIG.

FIG. 8 is a cross-sectional view taken along line dd of FIG.

FIG. 9 is a diagram illustrating the state of the beam when acceleration is applied.

FIG. 10 is a plan view of a third embodiment of the acceleration sensor of the present invention. FIG. 11 is a diagram illustrating a configuration example of a bridge of the detection unit.

FIG. 12 is a diagram illustrating a configuration example of the acceleration detection circuit.

FIG. 13 is a diagram illustrating a configuration example of a differential amplifier circuit.

FIG. 14 is a diagram illustrating another configuration example of the acceleration detection circuit.

FIG. 15 is a perspective view of a conventional acceleration sensor.

FIG. 16 is a cross-sectional view of another conventional acceleration sensor. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. A first embodiment of the acceleration sensor of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing an appearance structure of the first embodiment, a part of which is cut away. 2 is a plan view, FIG. 3 is a cross-sectional view taken along line aa of FIG. 2, and FIG. 4 is a cross-sectional view taken along line bb of FIG.

The acceleration sensor according to the first embodiment is formed on a glass substrate 5 as shown in FIG. 1 to FIG. Body 1 is fixed. Around the support 1, a weight 2 made of a rectangular frame is arranged at a predetermined interval so as to surround the support 1. The weight portion 2 is movably supported by the support 1 by thin beams 11 to 18, and each of the beams 11 to 18 has a length direction corresponding to each side of the support 1. It is arranged along. The support 1, the weight 2, and the beams 11 to 18 are formed using a silicon substrate.

As shown in the figure, the beams 11 and 12 are arranged so that their length directions are along the upper side of the support 1, and one ends thereof are commonly connected to the center of the upper side of the support 1. Each other end is in contact with the inner corner of the weight 2 Has been continued.

Similarly, beams 13, 14, beams 15, 16, and beams 17, 18 have their lengths on the left, bottom, and right sides of support 1, respectively, as shown. One end of each beam is commonly connected to the center of the corresponding side of the support 1, and the other end is connected to the corresponding corner of the inner periphery of the weight 2 respectively. I have.

Stress detecting elements 21, 22, 23, 24 are arranged at both ends of the beams 11, 12, which are stress concentration portions. Similarly, stress detecting elements 21 to 24 are disposed at both ends of the beams 13 and 14, the beams 15 and 16, and the beams 17 and 18, respectively.

In the example shown, one end of each of the beams 11 and 12 is connected in common to the center of the upper side of the support 1, and the other end is connected to the corner of the inner periphery of the weight 2. Each is connected. However, each of the beams 11 and 12 has one end connected to the center of the inner periphery of the weight 2 and the other end connected to both ends of the upper side of the support 1. Is also good. The same applies to the connection at both ends of beams 13 and 14, beams 15 and 16, and beams 17 and 18.

Next, the operation of the acceleration sensor according to the first embodiment having such a configuration will be described.

Now, when acceleration is applied to the acceleration sensor, the movable weight 2 moves in accordance with the acceleration, and stress is applied to the beams 11 to 18 as the weight 2 moves. At this time, since the stress becomes maximum at both ends of the beam, this stress is detected by the stress detection elements 21 to 24, and the acceleration can be detected based on this detection.

Here, since the magnitude of the stress generated in the beams 11 to 18 when subjected to acceleration is proportional to the length of the beams, the length of the beams 11 to 18 is smaller than that of the conventional configuration. As the length increases, the generated stress increases even at the same acceleration, and the detection sensitivity of the stress detecting elements 21 to 24 improves.

Next, a second embodiment of the acceleration sensor of the present invention will be described with reference to FIGS. FIG. 5 is a perspective view showing an appearance structure of the second embodiment, a part of which is cut away. 6 is a plan view thereof, FIG. 7 is a cross-sectional view taken along line c-c of FIG. 5, and FIG. 8 is a cross-sectional view taken along line d-d of FIG.

The acceleration sensor according to the second embodiment is formed on a glass substrate 5 as shown in FIGS. 5 to 8, and has a truncated square pyramid in the center of the glass substrate 5 and a weight whose upside down is inverted. The part 7 is movably arranged. Around the weight 7, a support 8 composed of a rectangular frame is provided at a predetermined interval so as to surround the weight 7, and the support 8 is fixed to the glass substrate 5. ing. The weight portion 7 is movably supported by the support body 8 by thin beams 31 to 38, and each of the beams 31 to 38 has a length direction corresponding to each side of the weight portion 7. It is arranged along. The support 8, the weight 7, and the beams 31 to 38 are formed using a silicon substrate as a material.

As shown in the figure, the beams 31 and 32 are arranged so that the length direction thereof is along the upper side of the weight portion 7, and one end of each of the beams is commonly connected to the center of the upper side of the weight portion 7. Each other end is connected to a corner of the inner peripheral portion of the support 8.

Similarly, beams 3 3, 3 4, beams 3 5, 3 6, and beams 3 7, 3 8 have their length directions on the left side, bottom side, and right side of weight 7 as shown in the figure. One end of each beam is commonly connected to the center of the corresponding side of the weight 7, and the other end is connected to the vicinity of the corresponding corner of the inner periphery of the support 8. Have been.

Therefore, the four corners of the inner periphery of the support 8 are shown in FIGS. 5 and 6. Such four spaces 39 are formed.

Stress detecting elements 21, 22, 23, 24 are arranged at both ends of the beams 31, 32, which are the stress concentration portions. Similarly, at both ends of the beams 33, 34, the beams 35, 36, and the beams 37, 38, the stress detecting elements 21 to 24 are arranged, respectively.

In the example shown, one end of each of the beams 31 and 32 is commonly connected to the center of the upper side of the weight portion 7, and the other end thereof is connected to a corner of the inner periphery of the support 8. Each is connected. However, each of the beams 31 and 32 has one end connected to the center of the inner periphery of the support 8 and the other end connected to both ends of the upper side of the weight 7. Is also good. The same applies to the connections at both ends of beams 33, 34, beams 35, 36, and beams 37, 38.

Next, an operation of the acceleration sensor according to the second embodiment having such a configuration will be described.

Now, as shown in Fig. 9 (A), when the acceleration in the horizontal direction acts on this acceleration sensor, an inertial force acts on the weight 7 in the direction opposite to the direction of the acceleration, and the beams 35, 36 A compressive stress (1) and a tensile stress (+) are generated at the stress detecting elements 21 to 24 of FIG. Also, as shown in Fig. 9 (B), when a vertical acceleration acts on this acceleration sensor, an inertial force acts on the weight 7 in the direction opposite to the direction of the acceleration, and the beams 35, 3 A compressive stress (-) and a tensile stress (+) are generated at the stress detecting elements 21 to 24 of FIG.

Thus, when acceleration is applied to the acceleration sensor, the movable weight 7 moves according to the acceleration, and the beam 31 to 38 is applied with the movement of the weight 7. At this time, since the stress is maximum at both ends of the beam, this stress is detected by the stress detecting elements 21 to 24, and acceleration is detected based on this detection. Monkey

Here, since the magnitude of the stress generated in the beams 31 to 38 when subjected to acceleration is proportional to the length of the beams, the length of the beams 31 to 38 becomes longer than in the conventional configuration. Accordingly, even at the same acceleration, the generated stress increases, and the detection sensitivity of the stress detecting elements 21 to 24 improves.

Further, the speed sensor according to the second embodiment has a configuration in which the weight 7 is in the center and the support 8 surrounds the weight 7, and the support 8 is integrated with the package. However, the beams 31 to 38 are parallel to each side of the weight portion 7 and the connection of both ends uses the portion excluding the corner of the inner peripheral portion of the support 8 as described above. are doing. For this reason, when stress is applied to the support 8 from the package surrounding the entire acceleration sensor, no direct stress is applied in the longitudinal direction of the beams 31 to 38, and buckling of the beams and output signal No shift occurs.

Next, a third embodiment of the acceleration sensor of the present invention will be described with reference to FIG. FIG. 10 is a plan view of the third embodiment.

The acceleration sensor according to the third embodiment has basically the same configuration as that of the second embodiment, and differs only in the connection structure of each of the beams 31 to 38 to the weight 7. is there.

That is, in the second embodiment, as shown in FIG. 6, one end of each of the beams 31, 32, beams 33, 34, beams 35, 36, and beams 37, 38 is connected to the weight portion. 7 was connected in common to the center of each corresponding side. However, in the third embodiment, as shown in FIG. 10, beams 3 1, 3 2, beams 3 3, 3 4, 3 Each end of 5, 36, and beams 37, 38 is not connected to the center of the corresponding side of the weight 7, but is connected separately at a predetermined interval.

Since the configuration of other parts of the third embodiment is the same as that of the second embodiment shown in FIG. 6, the same components are denoted by the same reference numerals and description thereof will be omitted. I do. Further, the operation of the third embodiment having such a configuration is the same as the operation of the second embodiment, and thus the description thereof will be omitted.

In the second embodiment, the connection between the beams 31 to 38 and the support body 8 uses a portion of the support body 8 excluding the corners of the inner peripheral portion, so that the support body can be moved from the package surrounding the entire acceleration sensor. When stress is applied to 8, the beams 31 to 38 do not act directly in the longitudinal direction of the beams, and the buckling of the beams 31 to 38 and the shift of the output signal are suppressed. did.

On the other hand, in the third embodiment, the connection of the beams 31 to 38 to the support body 8 is the same as that of the second embodiment, and the connection of the beams 31 to 38 to the weight 7 is As shown in FIG. 10, the weights 7 are individually connected to the center of each side at predetermined intervals. Therefore, in the third embodiment, the buckling of the beams 31 to 38 and the shift of the output signal can be more effectively suppressed.

Next, an example of the configuration of an acceleration detection circuit applied to the acceleration sensor according to the first embodiment will be described with reference to FIGS. 1, 2, 11, and 12. FIG.

As shown in FIGS. 1 and 2, when a piezoresistive element is used as each of the stress detection elements 21 to 24 on each side of the support 1, each position of the stress detection elements 21 to 24 is The piezoresistive elements 21a to 24a each formed of a P-type diffusion layer are respectively arranged. These four piezoresistive elements 21a to 24a constitute a Wheatstone bridge as shown in Fig. 11 and the stress detecting elements 21 to 2 of beams 11 and 12 A first wheel bridge 41 shown in FIG. 12 is constituted by the piezoresistive elements 21 a to 24 a arranged at the position 4. Similarly, the resistance elements 2 la to 24 a arranged at the stress detection positions 21 to 24 of the beams 13, 14, beams 15, 16, and beams 17, 18 give As shown in Figure 12, the second, third and Configure the fourth Houston Bridges 42, 43 and 44 respectively. The outputs S 1 to S 4 of the Wheatstone bridge 4 1 to 44 indicate that the stress detecting element 21 and the stress detecting element 23 deform the same with respect to the acceleration in the longitudinal direction of the beam, and the stress detecting element 22 Since the detection element 24 performs the same deformation, no signal is output to its output terminal.

Next, an arithmetic circuit for calculating acceleration signals Xs, Ys, and Zs in the X-axis, Y-axis, and Z-axis directions from the output signals of the Wheatstone bridge 41 to 44 will be described with reference to FIG. I do. The X-axis, Y-axis, and Z-axis are taken as shown in FIG. 2, and the X-axis and the Y-axis are at positions rotated by 45 ° with respect to the longitudinal direction of the beam.

This arithmetic circuit calculates an X-axis acceleration signal Xs by performing an operation of the equation (1) for the output signals S 1 to S 4 of the Wheatstone bridges 41 to 44, and an output signal thereof. With respect to S 1 to S 4, the adder 46 that calculates the acceleration signal Ys in the Y-axis direction by performing the calculation of the expression (2) and the output signal S 1 to S 4 by the calculation of the expression (3) And an adder 47 for obtaining an acceleration signal Zs in the Z-axis direction.

X s = (S 2 + S 3)-(S 1 + S 4) (1)

Y s = (S 3 + S 4) one (S 1 + S 2)… (2)

Z s = S l + S 2 + S 3 + S 4-(3)

Next, the reason why the adders 45 to 47 can obtain the respective acceleration signals Xs, Ys, and Zs using the equations (1) to (3) will be described.

Now, assuming that acceleration is applied in the X-axis direction in Fig. 2, beams 13 and 14 and beams 15 and 16 undergo the same change, and beams 11 and 12 and beams 17 and 18 are the same. And the change is reversed in the former and the latter. Therefore, the output signals S2 and S3 of the Wheatstone bridges 42 and 43 are positive, and the output signals S1 and S4 of the Wheatstone bridges 41 and 44 are negative. So Here, when the outputs S1 to S4 are subjected to the operation of the expression (1) by the adder 45, the acceleration signal Xs in the X-axis direction is obtained.

At this time, the adder 46 performs the operation according to the equation (2), but the output signal S 3 and the output signal S 4 have opposite signs and cancel each other. Similarly, the output signal S 1 and the output signal S 2 have opposite signs. Therefore, the acceleration signal Y s becomes “zero”. At this time, the adder 47 performs the calculation according to the equation (3). Similarly, the acceleration signal Zs becomes “zero”.

Next, assuming that acceleration acts in the Y-axis direction in Fig. 2, beams 15 and 16 and beams 17 and 18 change in the same way, and beams 11 and 12 and beams 13 and 14 The same change is made, and the change is reversed in the former and the latter. Therefore, the output signals S3 and S4 of the Wheatstone bridges 43 and 44 are positive, and the output signals S1 and S2 of the Wheatstone bridges 41 and 42 are negative. Then, when the outputs S1 to S4 are subjected to the calculation of the expression (2) by the adder 46, the acceleration signal Ys in the Y-axis direction is obtained.

At this time, the adder 45 performs the operation according to the equation (1), but the output signal S 2 and the output signal S 3 have opposite signs and cancel each other. Similarly, the output signal S 1 and the output signal S 4 have opposite signs. The acceleration signals X s become “zero” because they cancel each other. At this time, the adder 47 performs the calculation according to the equation (3). Similarly, the acceleration signal Zs becomes “zero”.

Furthermore, if acceleration is applied in the Z-axis direction in Fig. 2, beams 11 and 12, beams 13 and 14, beams 15, 16 and beams 17, 18 change the same. Therefore, the output signals S 1 to S 4 of the Wheatstone bridges 41 to 44 are positive, and when the outputs S 1 to S 4 are subjected to the calculation of the expression (3) by the adder 47, the acceleration in the Z-axis direction is obtained. The signal Z s is obtained.

At this time, the adder 45 performs the calculation according to the formula (1), but the acceleration signal Xs becomes “zero”, and the adder 46 performs the calculation according to the formula (2). The acceleration signal Ys becomes “zero”.

As is clear from the above description, the adders 45 to 47 perform calculations according to the equations (1) to (3), thereby responding to the accelerations in the X-axis, Y-axis, and Z-axis directions. The acceleration signals Xs, Ys, and Zs can be generated simultaneously.

Next, another configuration example of the acceleration detection circuit will be described with reference to FIGS. 1, 2, 13, and 14. FIG.

As shown in FIGS. 1 and 2, this acceleration detection circuit uses a P-type MOS SFET as each of the stress detection elements 21 to 24 on each side of the support 1, and the stress detection elements 21 to 24 P-type MOS FETs 21 b to 24 b are arranged at each position of. These four MOS FETs 2 lb to 24 b constitute a CM 0 S differential amplifier circuit as shown in FIG. 13 as an input transistor.

Then, the first differential amplifier circuit 51 as shown in FIG. 14 is constituted by the MOS FETs 21 b and 24 b arranged at the positions of the stress detecting sections 21 to 24 of the beams 11 and 12. Similarly, the MO SFETs 21 b to 24 b arranged at the positions of the stress detectors 2 of the beams 13, 14, 15, 16, and 17, 18:! , And third and fourth differential amplifier circuits 52 to 54, respectively.

Next, a specific configuration of the differential amplifier circuits 51 to 54 will be described with reference to FIG.

As shown in Fig. 13, this differential amplifier circuit has four P-type MOS FETs 21b to 24b for input arranged in the stress detection units 21 to 24, and a P-type MOSFET 61 as a current source. And two N-type MOSFETs 62 63 constituting a current mirror, and an output signal is outputted from an output terminal 64. The MO SFET 2 lb and the MO SFET 24 b are connected in parallel, the common connected source is connected to the power supply Vdd via the MOS FET 61, and the common connected drain is diode connected. In addition to being connected to the power supply Vss via the M0 SFET 62, a gate bias voltage is applied to both gates.

Similarly, the MOS FET 22b and the MOS FET 23b are connected in parallel, and the commonly connected source is connected to the power supply Vdd via the MOS FET 62 and the commonly connected drain is connected. Is connected to the power supply Vss via the MOSFET 63, and a gate bias voltage is applied to both gates thereof.

The outputs S 1 to S 4 of the differential amplifier circuits 51 to 54 having such a configuration have the same deformation as the MOS FET 51 and the MOS FET 53 for the acceleration in the longitudinal direction of the beam. Since the MOS FET 52 and the MOS FET 54 undergo the same deformation, no signal is output to the output terminal.

Next, refer to FIG. 14 for an arithmetic circuit for calculating acceleration signals Xs, Ys, and Zs in the X-axis, Y-axis, and Z-axis directions from the output signals of the differential amplifier circuits 51 to 54. I will explain. The X-axis, Y-axis, and Z-axis are taken as shown in FIG. 2, and the X-axis and the Y-axis are at positions rotated by 45 ° with respect to the longitudinal direction of the beam.

This arithmetic circuit performs an arithmetic operation of equation (4) on the output signals S5 to S8 of the differential amplifier circuits 51 to 54 to obtain an acceleration signal Xs in the X-axis direction. For the signals S5 to S8, the adder 56 that calculates the acceleration signal Ys in the Y-axis direction by performing the calculation of the expression (5), and for the output signals S5 to S8, performs the calculation of the expression (6) And an adder 57 for obtaining an acceleration signal Zs in the Z-axis direction.

X s = (S 6 + S 7) — (S 5 + S 8)… (4) Ys = (S 7 + S 8)-(S 5 + S 6)… (5)

Z s = S 5 + S 6 + S 7 + S 8 (6)

Next, the reason why the adders 55 to 57 can obtain the acceleration signals Xs, Ys, and Zs using the equations (4) to (6) will be described.

Now, assuming that acceleration is applied in the X-axis direction in Fig. 2, beams 13 and 14 and beams 15 and 16 change in the same way, and beams 11 and 12 and beams 17 and 18 change in the same way. The change is reversed in the former and the latter. Therefore, the output signals S6 and S7 of the differential amplifier circuits 52 and 53 are positive, and the output signals S5 and S8 of the differential amplifier circuits 51 and 54 are negative. Therefore, when the outputs S5 to S8 are subjected to the operation of the expression (4) by the adder 55, the acceleration signal Xs in the X-axis direction is obtained.

At this time, the adder 56 performs the operation according to the expression (5), but the output signal S 7 and the output signal S 8 have opposite signs and cancel each other. Similarly, the output signal S 5 and the output signal S 6 have opposite signs. The acceleration signal Y s becomes “zero” because they cancel each other. At this time, the adder 57 performs the calculation according to the expression (6), but similarly cancels out and the acceleration signal Z s becomes “zero”. Next, assuming that acceleration is applied in the Y-axis direction in Fig. 2, beams 15 and 16 and beams 17 and 18 change in the same way, and beams 11 and 12 and beams 13 and 14 The same change is made, and the change is reversed in the former and the latter. Therefore, the output signals S7 and S8 of the differential amplifier circuits 53 and 54 are positive, and the output signals S5 and S6 of the differential amplifier circuits 51 and 52 are negative. Then, when the outputs S5 to S8 are subjected to the calculation of the expression (5) by the adder 56, the acceleration signal Ys in the Y-axis direction is obtained.

At this time, the adder 55 performs the operation according to the expression (4), but the output signal S 6 and the output signal S 7 have opposite signs and cancel each other. And the output signal S8 have opposite signs and cancel each other, so that the acceleration signal Xs becomes "zero". At this time, the adder 57 performs the calculation according to the equation (6), but similarly cancels out and the acceleration signal Zs becomes “zero”. Furthermore, assuming that acceleration is applied in the Z-axis direction in Fig. 2, beams 11 and 12, beams 13 and 14, beams 15, 16 and beams 17 and 18 all undergo the same change. Therefore, the output signals S5 to S8 of the differential amplifier circuits 51 to 54 are positive, and when the outputs S5 to S8 are calculated by the adder 57 using the expression (6), the Z-axis direction is obtained. Is obtained.

At this time, the adder 55 performs the calculation according to the equation (4), but the acceleration signal Xs becomes “zero”. The adder 56 performs the calculation according to the equation (5), but the acceleration signal Ys is “zero”. It becomes.

As is clear from the above description, the adders 55 to 57 perform the operations as shown in the expressions (4) to (6) to respond to the accelerations in the X-axis, Y-axis, and Z-axis directions. The acceleration signals Xs, Ys, and Zs can be generated simultaneously.

In the above description, the case where two acceleration detection circuits are applied to the first embodiment shown in FIGS. 1 to 4 has been described. However, the two acceleration detection circuits described above can be applied to the second embodiment shown in FIGS. 5 to 8 and the third embodiment shown in FIG. 10 as a matter of course. Omitted. Industrial applicability

As described above, according to the present invention, the beam can be made longer than that of a conventional sensor, so that high sensitivity and miniaturization can be achieved.

According to the present invention, high sensitivity and miniaturization are possible, and further, It is possible to obtain a highly reliable acceleration sensor in which stress other than the stress generated by externally applied acceleration, which is the original function of the speed sensor, is not transmitted to the detection element.

Further, according to the present invention, since an arithmetic circuit for performing predetermined arithmetic processing on output signals of the four sets of circuits to obtain acceleration in an arbitrary direction is provided, it can be used as a three-axis acceleration sensor.

Claims

The scope of the claims

1. A fixed support, a weight disposed so as to surround the support, and a beam for movably supporting the weight on the support, utilizing the deflection of the beam due to stress. An acceleration sensor for detecting acceleration by using the support as a rectangular body, the weight portion as a rectangular frame, and the beam as a longitudinal direction along each side of the support body. An acceleration sensor, wherein two are arranged on each side, and both ends of each beam are connected to predetermined positions of the support and the weight.

2. One end of the beam is connected to the side of the support or the center of the inner periphery of the weight, and the other end of the beam is a corner of the inner periphery of the weight or the side of the support. The acceleration sensor according to claim 1, wherein the acceleration sensor is connected to an end of the acceleration sensor.

3. A support having a hollow portion at the center and fixed, a weight portion disposed in the hollow portion of the support, and a beam for movably supporting the weight portion on the support, and having a stress. Acceleration sensor for detecting acceleration using the deflection of the beam according to

The support is formed of a square frame, the weight is formed of a square, and the beams are arranged two on each side of the beam so that its length direction is along each side of the weight. An acceleration sensor, wherein both ends of a beam are connected to predetermined positions of the support and the weight.

4. One end of the beam is connected to the inner periphery of the support or the center of the side of the weight, and the other end of the beam is near the corner of the inner periphery of the support or the weight. 4. The acceleration sensor according to claim 3, wherein the acceleration sensor is connected to an end of a side of the part.

5. The method according to any one of claims 1 to 4, wherein the support, the weight, and the beams are formed of a silicon substrate. The acceleration sensor according to any one of the preceding claims.

6. Each of the beams is provided with a piezoresistive element at a stress concentration portion at both ends thereof. From four piezoresistive elements arranged on two beams arranged on each side of the support or each side of the weight portion. A plurality of Wheatstone Bridges for each side, and an arithmetic circuit for performing predetermined arithmetic processing on the output signals of the four sets of Wheatstone Bridges to obtain acceleration in an arbitrary direction. The acceleration sensor according to any one of claims 1 to 5, wherein:

7. Each of the beams is provided with a stress detecting element made of a MOSFET at a stress concentration portion at both ends thereof, and is arranged on two beams arranged on each side of the support or on each side of the weight portion. A differential amplifying circuit including two MOSFETs, and an arithmetic circuit for performing predetermined arithmetic processing on output signals of these four sets of differential amplifying circuits to obtain acceleration in an arbitrary direction. 6. The acceleration sensor according to any one of claims 1 to 5, wherein:

8. The acceleration sensor according to claim 7, wherein the MOS FET is a P-type MOS FET, and the differential amplifier circuit is a CMSO differential amplifier circuit.

9. The arbitrary directions are three directions of X-axis, Y-axis, and Z-axis, and the X-axis direction and the Y-axis direction are directions rotated by 45 ° with respect to the length direction of the beam. The acceleration sensor according to claim 6, wherein the Z-axis direction is a thickness direction of the beam.