JP2761803B2 - Acceleration sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an acceleration sensor, and more particularly, to a capacitance type acceleration sensor capable of accurately detecting a low acceleration of several G or less in a band of several tens Hz or less. This type of acceleration sensor is mounted on, for example, an automobile or the like and is used for automatic control of a driving mechanism or a braking mechanism.

[Conventional technology]

In general, this type of acceleration sensor includes a pair of fixed electrodes opposed to each other with a predetermined gap therebetween, and a movable electrode forming a capacitive element pair between the pair of fixed electrodes. The movable electrode is displaced in the direction of the fixed electrode in response to the external acceleration, causing a change in the relative capacitance of the capacitive element pair, and detecting the external uniaxial acceleration along the gap direction. Conventionally, a pair of fixed electrodes is formed on each inner surface of a pair of fixed substrates arranged to face each other, and the movable electrode is constituted by a movable piece of a conductive plate member interposed between the fixed electrodes. These components are sequentially mounted on a circuit board having external connection terminals to form a laminated structure. Such a structure is disclosed, for example, in U.S. Pat. No. 4,694,687.

[Problems to be solved by the invention]

The above-described conventional capacitance type acceleration sensor can detect only an external uniaxial acceleration or a linear acceleration applied along a gap between a pair of fixed electrodes, and can detect an external external acceleration applied around a predetermined rotation axis. Angular velocity could not be detected. However, depending on the application of the acceleration sensor, there is a case where it is desired to simultaneously detect the uniaxial acceleration and the angular acceleration. In such a case, conventionally, an angular acceleration sensor must be separately added in addition to the uniaxial acceleration sensor, and there has been a problem that the number of parts increases. Further, since the conventional capacitance type acceleration sensor is limited to detecting uniaxial acceleration, it has no versatility and its use is limited.

[Means for solving the problem]

In view of the above-mentioned problems of the conventional technology, an object of the present invention is to provide a capacitive acceleration sensor capable of detecting angular acceleration in addition to uniaxial acceleration.

In order to achieve this object, an acceleration sensor according to the present invention includes a pair of fixed substrates that are opposed to each other with a predetermined gap along a linear axis direction. One set of fixed electrodes is formed on the inner surface of one fixed substrate. The set of fixed electrodes is divided and arranged along a rotation axis orthogonal to the linear axis. A pair of other fixed electrodes is formed on the inner surface of the other fixed substrate. The other set of fixed electrodes is arranged corresponding to one set of fixed electrodes, and a pair is formed for each fixed electrode facing each other. A movable electrode composed of a conductive plate member is interposed between one set of fixed electrodes and the other set of fixed electrodes. The movable electrode is displaceable in response to uniaxial acceleration along the linear axis direction and angular acceleration about the rotation axis.

Preferably, the conductive plate member has a central portion fixedly supported between the pair of fixed substrates, and a peripheral portion which is flexibly supported by the central portion and forms a movable electrode. This peripheral portion has, for example, a ring shape, while each set of fixed electrodes has a ring shape divided and arranged in the circumferential direction.

[Action]

In the structure of the acceleration sensor according to the present invention described above, a set of capacitive elements is formed between each set of the movable electrode and the fixed electrode. When an external angular acceleration is applied around the rotation axis, the movable electrode is rotationally displaced, and a capacitance difference occurs between the capacitance elements included in the same set. The external angular acceleration is detected according to the polarity and magnitude of the capacitance difference. On the other hand, a pair of capacitive elements is formed between the movable electrode and each pair of fixed electrodes.
When an external uniaxial acceleration is applied along the linear axis, the movable electrode is displaced in parallel, and a capacitance difference occurs between the pair of capacitive elements. External uniaxial acceleration is detected according to the polarity and magnitude of the capacitance difference. In this way, it is possible to detect angular acceleration and uniaxial acceleration simultaneously.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing one embodiment of an acceleration sensor according to the present invention, and shows a cross-sectional shape cut along a linear axis direction. As shown in the figure, the acceleration sensor has a pair of fixed substrates 1 and 2 which are arranged to face each other with a predetermined gap along the direction of the linear axis. One set of fixed electrodes is formed on the inner surface of the upper fixed substrate 1. This set of fixed electrodes is divided and arranged along a rotation axis orthogonal to the linear axis. The other fixed electrode set is also formed on the inner surface of the lower fixed substrate 2. The other fixed electrode set is arranged to face the one fixed electrode set described above, and forms a pair for each fixed electrode facing each other. A conductive plate member 3 is interposed between the fixed substrates 1 and 2. The conductive plate member 3 has a central portion fixedly supported between the pair of fixed substrates 1 and 2, and a peripheral portion which is flexibly supported by the central portion and forms a movable electrode. . The movable electrode can be displaced in response to uniaxial acceleration along a linear axis direction and angular acceleration about a rotation axis.

The acceleration sensor further includes a circuit board 5 on which an external connection circuit pattern is formed. The circuit board 5 has the external connection terminals 6 mounted thereon, and the circuit board has the lower fixed substrate 2, the conductive plate member 3, and the upper fixed substrate 1 stacked thereon in this order. Make up the structure. In this embodiment, a connection board 7 is additionally inserted between the lower fixed board 2 and the circuit board 5. External connection terminals 6 from some fixed electrodes and movable electrodes
Electrical connection is made via interlayer contact of metal patterns formed on the front and back surfaces of each layer and conducted by through holes.

The central portion of the conductive plate member 3 is fixed between the fixed substrates 1 and 2 via a pair of conductive spacers 8 and 9. In this embodiment, in order to simplify the shape of the metal pattern formed on each layer, a set of fixed electrodes formed on the inner surface of the upper fixed substrate 1 is connected to the circuit board 5 via the conductive pins 10ux and 10uy. The structure is directly connected. The portion of the circuit board 5 on which the laminated structure is mounted is housed inside the case 11, and the terminals 6 are arranged outside the case 11.
The laminated structure is almost completely covered by the cover 12.
Further, the laminated structure is directly fixed to the bottom of the case 11 by an assembling screw 13 penetrating the central part. Assembly screw
The axis of 13 coincides with the aforementioned linear axis. A leaf spring 14 and a washer 15 are inserted between the top lower surface of the screw 13 and the upper surface of the upper fixed substrate 1 to press each layer. or,
The relative parallelism between the pair of fixed substrates 1 and 2 is maintained by a plurality of parallel pins 16 inserted in the thickness direction.

Next, the main components of the acceleration sensor will be described in detail with reference to FIGS. 2A and 2B show plan shapes of the upper fixed substrate 1. FIG. FIG. 2A is a front view of the fixed substrate 1, and FIG. 2B is a back view of the same. Here, the front surface refers to the side facing the cover 12 shown in FIG. Hereinafter, this front-back relationship is used in common for all plate members. Second
As shown in FIG. B, a ring-shaped set of fixed electrodes is formed around the rear surface of the upper fixed substrate 1. This set is composed of fixed electrodes 17ux and 17uy which are vertically arranged separately along a rotation axis orthogonal to a linear axis perpendicular to the paper surface. Further, a dummy electrode 18u is formed at the center of the back surface of the upper fixed substrate 1. A through hole 19ux is formed on one fixed electrode 17ux, and a through hole 19ux is formed on the other fixed electrode 17uy.
19uy is formed. In addition, the dummy electrode 18u has a through hole 20ux that engages with the conductive pin 10ux and a through hole 20uy that engages with the conductive pin 10uy. At the center of the substrate 1 is formed a screw hole 21 to be screwed with the assembling screw 13. Further, four through holes are formed at four corners of the substrate 1 to engage with the parallel pins 16.

As shown in FIG. 2A, a pair of rectangular metal patterns 22ux and 22uy are formed on the surface of the substrate 1.
The fixed electrode 17ux is electrically connected to one rectangular metal pattern 22ux via the through hole 19ux. On the other hand, through hole 19uy
The fixed electrode 17uy is electrically connected to the other rectangular metal pattern 22uy via. One conductive pin 10 inserted into through hole 20ux
ux is soldered to the rectangular metal pattern 22ux while the through hole
The other conductive pin 10uy inserted through 20uy is a rectangular metal pattern.
Soldered to 22uy.

FIG. 3 shows a plan view of the spacer 8. As shown in the figure, the spacer 8 has a central opening 23 at the center thereof, and a notch at the periphery to allow the conduction pins 10ux and 10uy to escape.
24x and 24y are respectively formed.

FIG. 4 shows a planar shape of the conductive plate member 3. As shown, the conductive plate member 3 has a peripheral portion having a ring shape and a central portion 26 surrounded by the peripheral portion. Peripheral part is movable electrode 25
m, and a central portion 26 is formed by a plurality of leaf spring members 27.
Are supported flexibly. It is a so-called free end support, and the movable electrode 25m can be displaced in a direction perpendicular to the plane of the conductive member, that is, in a linear axis direction, and can be rotated or tilted about a rotation axis orthogonal to the linear axis. The central portion 26 has an outer diameter substantially the same as that of the conductive spacer 8, and is brought into electrical contact with the movable electrode 25 m via the leaf spring piece 27 when it comes into surface contact therewith. That is, the central part 26
Is fixedly held in a gap between both fixed substrates via a pair of conductive spacers 8 and 9. In the center of the central part 26, an opening 28
Are formed on the upper and lower sides thereof, and through holes 29y and 29x for allowing the conduction pins 10uy and 10ux to escape therefrom are formed.

FIG. 5A shows the front surface shape of the lower fixed substrate 2, and FIG. 5B shows the back surface shape. As shown in the figure, a set of ring-shaped fixed electrodes is formed on the surface of the lower fixed substrate 2. This set includes two fixed electrodes 30lx and 30ly which are vertically divided along the rotation axis direction. One fixed electrode
30lx has a through hole 31lx, and the other fixed electrode 30ly also has a through hole 31ly. One fixed electrode 30lx formed on the surface of the lower fixed substrate 2
Are arranged in opposition to the corresponding fixed electrodes 17ux formed on the back surface side of the upper fixed substrate 1 so as to form a pair. Similarly, the lower fixed electrode 30ly is the corresponding upper fixed electrode.
17uy is aligned oppositely to form a pair.

At the center of the surface of the substrate 2, a connection electrode 32m is formed. The connection electrode 32m is in surface contact with the lower spacer 9, and conducts to the movable electrode 25m. On the upper surface of the connection electrode 32m, a through hole 33m, a center screw hole 34 to be screwed with the assembling screw 13, and an opening 35x for allowing one conductive pin 10ux to escape.
And an opening 35y for allowing the other conduction pin 10uy to escape. Further, four through holes for locking the parallel pins 16 are formed at four corners of the substrate 2. The through holes correspond to the through holes formed in the upper fixed substrate 1 and
The parallelism of the pair of fixed substrates 1 and 2 is maintained by using the parallel pins 16.

As shown in FIG. 5B, a first metal pattern 36lx, a second metal pattern 36ly, a third metal pattern 37m, and a fourth dummy metal pattern 38 are provided on the back surface of the substrate 2 at the center opening 34. Are arranged along the perimeter. These four metal patterns all have a uniform film thickness and a dummy metal pattern 38.
Is for achieving an even contact balance when making surface contact with another layer. The first metal pattern 36lx is connected to the fixed electrode 30 formed on the surface of the substrate 2 through the through hole 31lx.
Conducted to lx. In addition, the second metal pattern 36ly is electrically connected to the other fixed electrode 30ly via the through hole 31ly. Further, the third metal pattern 37m is electrically connected to the connection electrode 32m formed on the surface of the substrate 2 via the through hole 33m.

FIG. 6A shows the front surface shape of the connecting substrate 7, and FIG. 6B shows the same back surface shape. As shown in the figure, a first fan-shaped metal pattern 39lx is formed on the front side of the connection board 7, and is electrically connected to the back side through the through hole 40lx. Also, the second
The fan-shaped metal pattern 39ly is formed through holes
Conducting to the back side through 40ly. Furthermore, a third fan-shaped metal pattern 41m is provided, and a through-hole 42m
Through to the back side. Further, a fourth fan-shaped dummy metal pattern 45 is provided. These four fan-shaped metal patterns correspond to the four fan-shaped metal patterns formed on the back surface of the lower fixed substrate 2 and are in surface contact with each other. That is, the first metal pattern 39lx of the connection substrate 7 comes into surface contact with the first metal pattern 36lx of the lower substrate 2. Similarly, the second metal pattern 39ly is in surface contact with the corresponding second metal pattern 36ly, and the third metal pattern 41m is in contact with the corresponding third metal pattern 3ly.
At 7 m, the dummy metal pattern 45 comes into surface contact with the corresponding dummy metal pattern 38. A central opening 43 for inserting the assembling screw 13 is formed at the center of the connection board 7, and a notch 44x for diametrically separating the conductive pins 10ux and 10uy around the center opening 43 is provided. 44y are each formed.

As shown in FIG. 6B, four fan-shaped metal patterns are also formed on the back surface of the connection substrate 7. Of these, metal patterns
46lx is electrically connected to the first metal pattern 39lx on the front side through the through hole 40lx, and the metal pattern 46ly is a through hole.
The second metal pattern 39ly on the front side is electrically connected to the third metal pattern 41m on the front side through the through hole 42m. The remaining fan-shaped metal patterns are dummy.

FIG. 7 shows the surface shape of the circuit board 5. The circuit board 5 has a part housed in the case 11 and a part arranged outside the case 11. Four rectangular metal patterns are arranged at the center of the portion accommodated in the case. Of these, the first rectangular metal pattern 48lx is connected to the terminal pattern 54ux via a pattern (not shown) arranged on the back surface. Similarly, the second rectangular metal pattern 48ly is connected to the terminal pattern 54uy via a wiring (not shown).
The rectangular metal pattern 49m is also connected to the terminal pattern 54m. The remaining fourth rectangular metal pattern 50 is a dummy electrode for ensuring uniform surface contact. The circuit board 5 also has through holes 51ux, 51uy, 53g and 53g 'provided with land patterns.
Having. The through-hole 51ux provided with the land pattern is connected to the terminal pattern 54ux via a wiring on the back side (not shown), similarly, 51uy is connected to 54uy, 53g is connected to 54g, and 53g 'is the corresponding 54g. ′. In addition,
A central opening 52 for inserting the assembling screw 13 is formed at the center of the portion of the circuit board 5 housed in the case.

First rectangular metal pattern formed on the surface of circuit board 5
49 m is in surface contact with a metal pattern 47 m formed on the back surface of the connection substrate 7. In addition, the second rectangular metal pattern 48lx is
Surface contact with the fan-shaped metal pattern 46lx formed on the back surface of the.
Similarly, the third rectangular metal pattern 48ly comes into surface contact with the sector-shaped metal pattern 46ly formed on the back surface of the connection substrate 7. The through hole 51ux provided with the land pattern is adapted to engage with the end of the conductive pin 10ux, and electrical conduction is obtained by soldering. The other through-hole 51uy provided with the metal pattern is adapted to engage with the end of the conductive pin 10uy, so that electrical conduction is obtained by soldering. The circuit board 5 is fixed to the case 11 by screws via a pair of through holes 53g and 53g '. The through holes 53g and 53g 'provided with these metal patterns are for grounding the case 11 and the cover 12 to the outside.

Finally, the operation of the acceleration sensor will be described in detail with reference to FIGS. FIG. 8 is a schematic diagram showing a relative positional relationship between a fixed electrode and a movable electrode. The electrodes actually have a ring shape or a ring shape, but are schematically shown in a rectangular shape for easy understanding in the drawings. One upper fixed electrode 17ux is arranged to face the movable electrode 25m, and forms a capacitive element UX. The other upper fixed electrode 17uy is also arranged to face the movable electrode 25m, and constitutes the capacitive element UY.
These two capacitive elements UX and UY form an upper set.
One lower fixed electrode 30lx is arranged to face the movable electrode 25m, and forms a capacitive element LX. The other lower fixed electrode 30ly
Are also arranged opposite to the movable electrode 25m, and constitute the capacitive element LY. These capacitive elements LX and LY form a lower set. Also, the capacitive element UX and the capacitive element LX share a common movable electrode 25m.
Are aligned with each other via a pair. Similarly,
The capacitive element UY and the capacitive element LY also form a pair. When the acceleration sensor having such a structure receives an acceleration along a linear axis as indicated by an arrow, the movable electrode 25m is displaced in parallel, and a difference in capacitance is generated between the pair of capacitance elements. By detecting this difference, the uniaxial acceleration along the linear axis can be measured. on the other hand,
When the acceleration sensor receives angular acceleration about the rotation axis as indicated by the arrow, the movable electrode 25m is rotationally displaced. As a result, a difference in capacitance occurs between the capacitive elements of the same set.
The angular acceleration can be measured by detecting this difference. For example, when the movable electrode 25m rotates clockwise about the rotation axis, the movable electrode 25m approaches one upper fixed electrode 17ux, and the capacitance of the capacitive element UX increases. The movable electrode 25m is the other upper fixed electrode 17u
The capacitance of the capacitive element UY moves away from y, and the capacitance decreases. In this manner, the balance of the capacitance between the capacitive elements of the same set is broken, and the angular acceleration can be detected. A capacitance imbalance also occurs between the lower capacitive elements LX and LY. The upper set and the lower set are in a complementary relationship.

FIG. 9 is a schematic circuit diagram showing the connection relationship among the four capacitive elements UX, UY, LX and LY described above. The four capacitive elements are connected in parallel, and a movable electrode 25m serving as a common electrode is connected to an external extraction pattern 54m. Individual fixed electrode 17ux,
17uy, 30lx and 30ly are connected to the corresponding external connection terminal patterns 54ux, 54uy, 54lx and 54ly, respectively. Conduction from one upper fixed electrode 17ux to the corresponding terminal 54ux is performed via a through hole 19ux, a rectangular metal pattern 22ux, a through hole 20ux, a conduction pin 10ux, and a through hole 51ux. The conduction from the other upper fixed electrode 17uy to the corresponding terminal 54uy is:
19uy through hole, 22uy rectangular metal pattern, 20uy through hole,
This is performed via the conduction pin 10uy and the through hole 51uy. The conduction from one lower fixed electrode 30lx to the corresponding terminal 54lx is through hole 31lx, sector metal pattern 36lx, sector metal pattern 39lx, through hole 40lx, sector metal pattern 46lx,
And a rectangular metal pattern 48lx. The conduction from the other lower fixed electrode 30ly to the corresponding terminal 54ly is through hole 31ly, sector metal pattern 36ly, sector metal pattern 39.
ly, through holes 40ly, fan-shaped metal patterns 46ly, and rectangular metal patterns 48ly. The conduction from the movable electrode 25m to the corresponding input terminal 54m is performed by the central portion 26 of the conductive plate member 3, the lower spacer 9, the connection electrode 32m, and the through hole 3.
3m, fan-shaped metal pattern 37m, fan-shaped metal pattern 41m, through hole 42m, fan-shaped metal pattern 47m, and rectangular metal pattern 49m
Is performed via

FIG. 10 is a circuit block diagram showing a configuration of a detection circuit connected to the acceleration sensor main body. The block surrounded by the dashed line on the left side shows the acceleration sensor main body, and the portion surrounded by the dashed line on the right side shows the detection circuit. Both blocks are first
It is connected via a terminal 6 shown in the figure. The detection circuit 101
One oscillation circuit 102 and four buffers 103 to 106
And two comparators 107 and 108. As shown, the pulse signal of the oscillation circuit 102 is supplied to the input terminal 54m of the acceleration sensor main body. As a result, a pulse signal having a pulse height according to the capacitance value of the corresponding capacitance element is output to the output terminals 54lx, 54ly, 54ux, and 54uy of the acceleration sensor main body. The output signal supplied from the output terminal 54ux connected to one upper capacitive element UX is applied to the positive input terminal of the comparator 107 via the buffer 105. The output signal supplied from the output terminal 54uy connected to the other upper capacitive element UY is also supplied to the positive input terminal of the comparator 107 via the buffer 106. The output signal supplied from the output terminal 54lx connected to one lower capacitive element LX is buffered.
The signal is applied to the negative input terminal of the comparator 107 via the signal 103. Similarly, the output terminal connected to the other lower capacitive element LY
The output signal supplied from 54ly is also applied to the negative input terminal of the comparator 107 via the buffer 104. Comparator 107 outputs an electric signal representing uniaxial acceleration α according to the difference between the amplitude values of the signals applied to both input terminals.

The output signals supplied from the output terminals 54lx and 54uy of the acceleration sensor main body are applied to the positive input terminal of the other comparator 108. The output signals supplied from the output terminals 54uy and 54ux of the acceleration sensor body are applied to the negative input terminal of the comparator 108. Therefore, an electrical signal representing the angular acceleration is output to the output terminal of the comparator 108.

In the above-described embodiment, the fixed electrode is divided into two along one rotation axis, but the present invention is not limited to this. For example, by dividing the fixed electrode into four along two rotation axes orthogonal to each other, an angular acceleration component for each rotation axis can be detected.

〔The invention's effect〕

As described above, according to the present invention, there is an effect that angular acceleration in addition to uniaxial acceleration can be detected at the same time.

[Brief description of the drawings]

1 is a schematic cross-sectional view of an acceleration sensor, FIG. 2A is a front view of an upper fixed substrate, FIG. 2B is a back view thereof, FIG. 3 is a plan view of a spacer, and FIG. 4 is a conductive plate member. 5A is a front view of the lower fixed substrate, FIG. 5B is a rear view thereof, FIG. 6A is a front view of the connecting substrate, FIG. 6B is a rear view thereof, and FIG. FIG. 8 is a schematic view showing the arrangement of fixed electrodes and movable electrodes, FIG. 9 is a schematic circuit block diagram showing the connection of a plurality of capacitive elements, and FIG.
FIG. 10 is a circuit diagram showing an electrical configuration of a detection circuit connected to the acceleration sensor main body. DESCRIPTION OF SYMBOLS 1 ... Upper fixed board 2 ... Lower fixed board 3 ... Conductive plate member 5 ... Circuit board 6 ... Terminal 7 ... Connection board 8 ... Spacer, 9 ... Spacer 10ux and 10uy ... Conduction pin, 11 ... Case 12 ... Cover 17ux and 17uy ... Top fixed electrode 25m ... Movable electrode, 26 ... Central part 27 ... Leaf spring piece 30lx and 30ly ... Bottom fixed electrode 101 ... Detection circuit

Continuation of the front page (56) References JP-A-4-20865 (JP, A) JP-A-3-202777 (JP, A) JP-A-3-61814 (JP, A) JP-A-1-299467 (JP) JP-A-60-147654 (JP, A) JP-A-3-183963 (JP, A) JP-A-4-32776 (JP, A) JP-A-61-63167 (JP, U) U.S. Pat. (US, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01P 15/125

Claims (4)

(57) [Claims] 1. A pair of fixed substrates disposed to face each other with a predetermined gap along a linear axis direction, and a pair of fixed substrates formed on an inner surface of one of the fixed substrates and along a rotation axis orthogonal to the linear axis. One fixed electrode set divided on the other side and the other fixed electrode formed on the inner surface of the other fixed substrate and opposed to the one fixed electrode set and forming a pair. And a conductive plate member interposed between the set of one fixed electrode and the set of the other fixed electrodes. The set corresponds to uniaxial acceleration along the linear axis direction and angular acceleration around the rotation axis. An acceleration sensor of a capacitance detection type comprising a movable electrode capable of being displaced. 2. The conductive plate member has a central portion fixedly supported between a pair of fixed substrates, and a peripheral portion flexibly supported by the central portion to form a movable electrode. Item 2. The acceleration sensor according to item 1. 3. The acceleration sensor according to claim 1, wherein the peripheral portion has a ring shape, and the set of fixed electrodes has a ring shape divided and arranged in the circumferential direction. 4. Detecting an angular acceleration according to a capacitance difference generated in a pair of capacitive elements formed between the movable electrode and the fixed electrode pair, and detecting an angular acceleration between the movable electrode and the fixed electrode pair. 2. The acceleration sensor according to claim 1, further comprising a detection circuit for detecting a uniaxial acceleration according to a capacitance difference generated between a pair of the configured capacitance elements.