JPH0432775A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To remove irregular stress applied to a movable electrode by fixing the center part of a conductive plate member and forming the peripheral part which is coupled with the center part as the movable electrode. CONSTITUTION:A couple of fixed substrates 1 and 2 are arranged opposite each other across a specific gap, one fixed electrode is formed at the peripheral part of the internal surface of the upper substrate 1, and the other fixed electrode is formed at the peripheral part of the internal surface of the lower substrate 2 correspondingly. The conductive plate member is arranged between the substrates 1 and 2 and this plate member 3 consists of the center part and the peripheral part which is coupled and supported flexibly by the center part. The peripheral part constitutes the movable electrode and is displaced toward the fixed electrode in response to external acceleration to cause relative capacity variation between a couple of capacity elements. The movable electrode is connected electrically to a connecting electrode through the center part of the plate member 3. Then the movable electrode is composed of, for example, an annular piece formed at the peripheral part of the plate member 3 and this annular piece is hardly affected by external stress since it is supported by the center part of the plate member 3 while having a free end.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an acceleration sensor, and particularly to a capacitive acceleration sensor for accurately detecting low accelerations of several G or less in a frequency band of several tens of Hz or less. This type of acceleration sensor is mounted on, for example, an automobile and used for automatic control of a drive mechanism or a braking mechanism.

[Conventional technology]

A capacitance detection type acceleration sensor generally includes a pair of fixed electrodes that are placed opposite to each other with a predetermined gap in between, and a capacitive element pair that is interposed between the pair of fixed electrodes. It consists of a movable electrode that is displaced in the direction of the fixed electrode in response to cause a change in the relative capacitance of the capacitive element pair. In conventional capacitance detection type acceleration sensors, the movable electrode consists of a central part that is flexibly connected and supported around the periphery of a conductive plate member, and the periphery of the conductive plate member is connected to a pair of fixed substrates. It has a structure in which it is supported and fixed between the opposing peripheral parts of.

[Problems to be Solved by the Invention] However, in such a conventional structure, since the conductive plate member is supported and fixed by a pair of substrates at its peripheral portion, the conductive plate member may be damaged due to distortion occurring in the supporting and fixed portion. There is a risk that non-uniform stress will act on the central portion and the neutral point of the movable electrode will become unstable. Therefore, in the conventional structure, in order to prevent non-uniform strain from being applied to the peripheral portion of the conductive plate member, an adhesive was uniformly applied to the peripheral portion to fix the conductive plate member. For this reason, electrical connection to the movable electrode, ie, the central portion of the conductive plate member, has been made via a lead wire. However, since the lead wire itself has a certain weight, there is a problem in that it applies non-uniform stress to the movable electrode, which adversely affects acceleration detection characteristics.

In addition, there were problems in that the assembly of the lead wires was difficult to work with and lacked reliability.

[Means for solving problems]

In view of the above-mentioned problems of the conventional technology, it is an object of the present invention to provide an acceleration sensor having a support structure and a wiring structure that can eliminate as much as possible the non-uniform stress applied to the movable electrode.

In order to achieve this purpose, the capacitance detection type acceleration sensor according to the present invention has as its basic components a pair of fixed electrodes that are arranged opposite to each other with a predetermined gap therebetween, and a fixed electrode located between the pair of fixed electrodes. It has a movable electrode that is interposed to form a capacitive element pair and that is displaced in the direction of the fixed electrode in response to external acceleration to cause a relative capacitance change of the capacitive element pair. In addition, as a characteristic structural feature, the pair of fixed electrodes are formed on the periphery of each inner surface side of a pair of fixed substrates facing each other, and the movable electrode is formed in the center of the conductive plate member. It consists of a peripheral section that is flexibly connected and supported by the section. The center portion of the conductive plate member is supported and fixed between the opposing center portions of a pair of fixed substrates, and the peripheral portion of the conductive plate member, that is, the movable electrode is formed in the center portion of at least one of the fixed substrates. The electrical connection is made through the center of the conductive plate member which is electrically connected to the connecting electrode.

Preferably, the acceleration sensor according to the present invention has a laminated structure including a circuit board on which an external connection circuit button is formed, one fixed substrate, a conductive plate member, and the other fixed substrate, which are stacked in this order. There is.

The fixed electrode and the connection electrode are electrically connected to the circuit button through through-hole buttons formed in each layer.

[For production]

According to the present invention, the movable electrode that is sensitive to external acceleration and is displaced is constituted by, for example, an annular piece formed around the periphery of the conductive plate member, and this annular piece is moved by the central part of the conductive plate member. Since the free end is supported, the structure is not easily affected by external stress. In addition, since electrical conduction to the annular piece is conducted through the center of the conductive plate member, there is no need to use additional parts such as lead wires as in the conventional case. There is no adverse effect on the response linearity to acceleration.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic partially cutaway sectional view showing an embodiment of a capacitance detection type acceleration sensor according to the present invention. As shown in the figure, this acceleration sensor has a pair of fixed substrates 1 and 2 that are placed opposite to each other with a predetermined gap in between. One fixed electrode is formed around the inner surface of the upper fixed substrate 1, and the other fixed electrode is formed correspondingly around the inner surface of the lower fixed substrate 2. A conductive plate member 3 is arranged between the pair of fixed substrates. This plate member 3 is composed of a central portion and a peripheral portion flexibly connected and supported to the central portion. The peripheral part constitutes a movable electrode, which is interposed between a pair of fixed electrodes to constitute a capacitive element pair, and is displaced in the direction of the fixed electrodes in response to external acceleration, causing a relative capacitance change of the capacitive element pair. It has become. The center portion of the conductive plate member 3 is fixed by a support rj between the opposing center portions of a pair of fixed substrates 1 and 2. Further, the peripheral part of the conductive plate member 3, that is, the movable electrode is connected to at least one of the fixed substrates] or the central part of the conductive plate member 3 which is electrically connected to the connecting electrode formed at the center of the inner surface of 2. Electrical connections are to be made.

The present acceleration sensor further includes a circuit board 5 on which an external connection circuit button is formed. On this circuit board 5, a lower fixed board 2, a conductive plate member 3, and an upper fixed board 1 are stacked in order, and together with the circuit board 5, they form a laminated structure. The movable electrode is electrically connected via the central portion of the conductive plate member, which is electrically connected to a connecting electrode formed at the central portion of the inner surface of at least one of the fixed substrates 1 or 2. Further, electrical connections from the fixed electrodes formed on the periphery of the fixed substrate and the connection electrodes formed at the center to the external connection circuit buttons are made via through-hole buttons formed in each layer of the laminated structure. It has become.

A terminal 6 for electrical connection with an external drive circuit is mounted on one end of the circuit board 5. Further, between the circuit board 5 and the lower fixed board 2, there is a through-hole button or a connecting board 7 formed on the front and back sides. Further, the center portion of the conductive plate member 3 is sandwiched and supported and fixed by a pair of conductive spacers 8 and 9. Further, in this embodiment, the fixed electrode formed around the inner surface of the upper fixed substrate 1 is electrically connected to the circuit panel via a conductive member, for example, a pin lOu, which penetrates the above-mentioned laminated structure.

The laminated structure mounted on the circuit board 5 is housed inside the case 11 as it is and is almost completely covered by the cover 12. The laminated structure described above is directly fixed to the case 1 by a screw 13 passing through its center. At this time, a leaf spring 14 and a washer 15 are inserted between the lower surface of the top of the screw 13 and the upper surface of the upper fixed substrate 1, and press each layer of the laminated structure against each other. In addition, in order to maintain parallelism between the pair of fixed substrates and 2, a plurality of parallel pins 16 are inserted around the fixed substrates.

According to the laminated structure described above, all the electrodes are electrically connected to the circuit board 5. The circuit board 5, the connecting board 7, the fixed boards 1 and 2, the spacers 8 and 9, the conductive plate member 3, etc. are electrically connected to each other by pressure contact. Screws 13 and leaf springs 14 are used to relatively fix these layers, and since they are held directly against the case 11, stable pressure is applied to each layer. However, only the fixed electrodes formed around the inner surface of the upper fixed board are directly connected to the circuit board 5 via the pins 10u, simplifying the electric buttons formed on the surfaces of each layer. It has become

In addition, a sensor section for detecting acceleration is mounted on a portion of the circuit board 5 inside the case 11.
A connecting terminal 6 or a connector is mounted on an external portion of the terminal 1. Therefore, even if the connector receives external force, it can be prevented from directly affecting the sensor section.

Next, the main parts used in this acceleration sensor will be individually explained with reference to FIGS. 2 to 7.

First, FIGS. 2A and 2B show the upper fixed substrate], and FIG. 2A is a front view, and FIG. 2B is a back view. Here, the front side refers to the side facing the cover 12 shown in FIG. 1, and the back side refers to the side facing the case 711. This relationship is common to the plate-like members described below. As shown in FIG. 2B, an annular upper fixed electrode 17u is formed on the back surface of the upper fixed substrate around its periphery. Further, a dummy electrode L8u is formed at the center thereof.

A through hole 19u is provided on the button of the upper fixed electrode 17u.
is formed. Further, a through hole 20u is formed on the button of the dummy electrode 18u, into which the pin IOu shown in FIG. 1 is inserted, and a screw hole 21 into which the screw 13 shown in FIG. It is formed. As shown in FIG. 2A, a rectangular metal button 22u is formed on the surface of the substrate 1. This rectangular button 22u is the through hole 1
It is electrically connected to the fixed electrode 17u on the back side via 9u. Therefore, by inserting the pin IOu into the through hole 20u and soldering its top, the pin 10u and the annular fixed electrode 17u are connected to each other.

FIG. 3 is a plan view of the spacer 8. A central opening 23 is formed in the center of the spacer 8 for inserting the screw 13, and a notch 24 is also formed for letting the pin Ou escape. The spacer 8 is made of a conductive material such as gold JiA, and the other spacer 9 (not shown) also has the same shape and configuration.

FIG. 4 is a plan view of the conductive plate member 3. This member 3 is made of an elastic metal material such as beryllium copper or stainless steel, and has an annular peripheral portion 251 and a central portion 26 . The peripheral portion 25m is flexibly supported by the central portion 26 via a plurality of leaf spring pieces 27. Therefore, when the central portion 26 is fixed, the peripheral portion 25m is displaced in the perpendicular direction in response to acceleration applied in the perpendicular direction, and the amount of displacement is proportional to the magnitude of the acceleration. A central opening 2B is formed at the center of the central portion 26, through which the screw 3 is inserted. In addition, an escape hole 29 is also formed to allow the pin lOu to escape. Furthermore, the outer diameter of the central portion 26 is set to approximately correspond to the outer diameter of the spacer 8. This central portion 26 is supported and fixed from both sides using spacers 8 and 9.

5A and 5B show the shape of the lower fixed substrate 2. FIG.

FIG. 5A is a front view, and FIG. 5B is a back view. As shown in FIG. 5A, an annular lower fixed electrode 30.9 is formed on the surface of the substrate 2 at its periphery. A through hole 31g is formed so as to be electrically connected to this lower fixed electrode button. Further, a disk-shaped connection electrode 32m is formed in the center of the substrate 2. This connection electrode 32m is electrically connected to the center portion 26 of the conductive plate member 3 via the spacer 9. A through hole 33m is formed so as to be electrically connected to the button of the connection electrode 32IIl. In addition, there is a screw hole 3 in the center of the board 2 that engages with a screw 13.
4 and a through hole 35 through which the pin 10u is inserted. As shown in FIG. 5B, a metal button 36g is formed on the back surface of the substrate 2, and the through hole 3 described above is formed.
It is electrically connected to the fixed electrode 30.9 via 1g. It also has another metal button 37 mark, and a connection electrode 32+a formed on the surface side through the aforementioned through hole 33m.
It is electrically conductive. In addition to this, a pair of dummy electrodes 38 are also formed.

FIG. 6A is a front view of the connection board 7, and FIG. 6B is a back view. As shown in the figure, a metal button 39N is formed on the surface of the connection board 7, and a through hole 40 is formed.
Contains g. It also has another metal button 41'' and also includes a through hole 42m. At the center of the connecting board 7 is a central opening 43 for passing the screw 13 for assembly.
A notch 44 is formed to allow the conductive pin] O to escape. In addition to this, a pair of dummy buttons 45 are also formed. One metal button 39g is arranged so as to be in surface contact with a metal button 36g formed on the back surface of the lower fixed board 2, and the other metal button 41m is similarly formed on the back surface of the lower fixed board 2. It is arranged so as to be in surface contact with the metal baton 37m. As shown in FIG. 6B, a metal button 46g is formed on the back side of the connection board 7, and is connected to a corresponding metal button 39g on the front side via a through hole 40g. It also has another metal button 47m, which is connected to the corresponding metal button 4J, m on the front side via a through pole 42m.

Finally, FIG. 7 shows the surface shape of the circuit board. As shown in the figure, metal tabs 48II and 49m are formed in the portion of the circuit board 5 that is accommodated in the case 11. One metal button 481) is a metal button 48. formed on the back surface of the connection board 7. &, and the other metal button 4h is arranged so as to make surface contact with a corresponding metal button 47tn also formed on the back surface of the connection board 7. In addition, a pair of dummy electrodes 50 are also formed. Furthermore, a through hole 51 with a metal button is provided.
u, and is adapted to fit into the conduction bottle 10u described above. A screw hole 52 for screwing with the assembly screw 13 is also formed in the center of the circuit board 5. Furthermore, a pair of through holes 53g and 53g' are formed, and the circuit board 5 is fixed to the case 11 via these through holes. A through-hole electrode 54u with a total length of 5 m is provided in the portion of the circuit board 5 that is taken out from the case IJ.
541, 54m, 54g and 54g' are formed. Connecting terminals 6 or connectors shown in FIG. 1 are fixed to these through holes by soldering. Although not shown,
A circuit button for connection is formed on the back side of the circuit board 5, and the metal button 48J), the through hole 54p1, the through hole 51u and the through hole 54υ, the metal button 49■ and the through hole 54D1, and the through hole 5 are connected through this.
3g and through hole 54g and through hole 53g'
and through hole 54g' are electrically connected to each other.

FIG. 8 is a schematic circuit diagram showing the electrical connection of each electrode of the acceleration sensor shown in FIG. 1. The part surrounded by the broken line indicates the acceleration sensor body, and the part outside the range surrounded by the broken line is the external drive circuit. As shown, the upper fixed electrode 1
7u is connected to a lead-out through hole or terminal 54u provided on the circuit board. This connection is made in this order via the through hole 19u, the rectangular metal pattern 22υ, the through hole 20u, the conductive pin IOu, and the through hole 51u. The lower fixed electrode 3011 is an extraction terminal 54g
It is connected to the. This connection is made in order through hole 31.
This is done through the metal button 36p, the metal button 39g, the through hole 4ON, the metal button 46g, and the metal button 48N. The FiJ moving@pole 25rD is connected to the extraction terminal 54e. This connection is made in order by the leaf spring piece 2.
7. Center part 26 of conductive plate member 3, spacer 9, connection electrode 32m1 through-hole 33I111 metal button 37m
1. This is done via a metal button 41m, a through hole 42m, a metal button 47m2, and a metal button 49m. Case 11 and cover 12 have a pair of extraction terminals 54g
and 54g'. This connection is made by fixing the circuit board 5 to the case II with screws through a pair of through holes 53g and 53g'.

Next, the operation of the acceleration sensor according to the present invention will be explained with reference to FIG. As illustrated, the movable electrode 2511 is interposed between the pair of fixed electrodes 17u and 30g to form a capacitive element pair. The movable electrode 25m is displaced toward the fixed electrode in response to external acceleration, causing a relative or differential capacitance change of the capacitive element pair. External acceleration is measured by electrically detecting this change. in general,
The electrode areas of the upper fixed electrode 17u and the lower fixed electrode 30.9 are set to be equal, and the movable electrode 25m is equidistant from both fixed electrodes in a non-accelerated state. Therefore, the capacitances of the capacitive element pair are equal to each other. If the patient is deaf in the form of 20, an external AC power source 55 is connected between the input terminals 54u and 54g to apply a rectangular pulse. Since the capacitance is balanced in the non-acceleration state, a zero level voltage is output to the output terminal 54 connected to the movable electrode 25m. On the other hand, when external acceleration is applied, the movable electrode 25+n is displaced according to the direction and magnitude of the acceleration. As a result, an output voltage appears at the output terminal 54m having a phase corresponding to the direction of acceleration and an amplitude corresponding to the magnitude of the acceleration. The external drive circuit measures the direction and magnitude of external acceleration by electrically processing the phase and amplitude of this output voltage.

The acceleration sensor according to the present invention is intended to accurately detect low accelerations of several G or less in a frequency band of several tens of Hz or less, and is installed in, for example, an automobile. Therefore, they are often treated in the same way as ordinary electronic components, and require a moisture-proof and corrosion-resistant structure.

For this reason, it is preferable to use stainless steel, which has excellent corrosion resistance, as the conductive plate member. Also, it is preferable to apply tin plating to ensure the electrical connection of the conductive pin. It is preferable to apply tin plating or gold plating to the lands of the metal buttons and through holes formed on each substrate. It is preferable to apply alumite treatment to the cover and case.

In addition, after assembling the acceleration sensor, it is preferable to use moisture-proof silicone rubber or the like to fill the gap between the cover, the case, and the board to create a sealed state.

〔Effect of the invention〕

As described above, according to the present invention, the central part of the conductive plate member is fixed, and the peripheral part flexibly connected to this central part is structured as a movable electrode, so that the movable electrode can be freely moved. This has the effect of providing end support and flattening the movable electrode to reduce external stress applied to it. Furthermore, since the plate members are stacked on top of each other and are compressed and fixed to the case by common assembly screws, the assembly workability is extremely excellent. In addition, since the movable electrodes are drawn out through metal buttons and through holes formed on the front and back sides of each board, external stress that occurs when connecting using lead wires as in the past can be eliminated. There is an effect that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic partially cutaway sectional view of the acceleration sensor, FIG. 2A is a front view of the upper fixed board, and FIG. 2B is a back view of the same.
Fig. 3 is a plan view of the spacer, Fig. 4 is a plan view of the conductive plate member, Fig. 5A is a front view of the lower fixed board, Fig. 5B is a back view, and Fig. 6A is the connection. FIG. 6B is a front view of the board, FIG. 6B is a back view, FIG. 7 is a front view of the circuit board, and FIG. 8 is an electric circuit diagram of the acceleration sensor. 1... Upper fixed board 3... Conductive plate member 7... Connection board 9... Spacer 11... Case I3... Assembly screw 25I11... Movable electrode 27... Leaf spring Piece 32rA... Connection electrode 2... Lower fixed board 5... Circuit board 8... Spacer 10u... Conductive pin 12... Cover 17u... Upper fixed electrode 26... Center part 30 , Q...lower fixed electrode Fig. 2 B Fig. 3 Fig. 4 jl! 5TXJA 3m 117 figure

Claims (5)

[Claims] 1. A pair of fixed electrodes are arranged facing each other with a predetermined gap interposed between them, and a capacitive element pair is formed between the pair of fixed electrodes, and the capacitive element pair is displaced in the direction of the fixed electrodes in response to external acceleration. In a capacitance detection type acceleration sensor having a movable electrode that causes a relative capacitance change, the pair of fixed electrodes are formed on each inner surface side away from the center of a pair of fixed substrates arranged to face each other. The movable electrode is composed of a peripheral part that is flexibly connected and supported to the central part of a conductive plate member, and the central part of the conductive plate member is located between the opposing central parts of a pair of fixed substrates. The peripheral part of the conductive plate member is electrically connected to the central part of the conductive plate member, which is electrically connected to the connection electrode formed at the center part of the inner surface of at least one of the fixed substrates. An acceleration sensor characterized by a connection being made. 2. It has a laminated structure including each layer stacked in this order: a circuit board on which a circuit pattern for external connection is formed, one fixed board, a conductive plate member, and the other fixed board, and from the one fixed electrode and the connection electrode. 2. The acceleration sensor according to claim 1, wherein electrical connection to the circuit pattern is made through a through-hole pattern formed in each layer. 3. 3. The acceleration sensor according to claim 2, further comprising a connecting board having a through-hole pattern formed on both sides thereof, interposed between the circuit board and the one fixed board. 4. 3. The acceleration sensor according to claim 2, wherein the other fixed electrode is electrically connected to the circuit pattern via a conductive member penetrating the laminated structure. 5. 2. The acceleration sensor according to claim 1, wherein the central portion of the conductive plate member is supported and fixed by being sandwiched between a pair of conductive spacers.