JPH1144704A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the absorption of the acceleration in a direction vertical to a circuit board, to miniaturize a sensor, and to lower the height thereof by arranging an electronic part or a filling part to be filled in a part or the whole of a clearance between a top surface of a terminal board and a lower surface of a circuit board loaded with an acceleration sensor. SOLUTION: An electronic part of the same height with an electronic part to be arranged under an acceleration sensor 30 is arranged in a lower surface of a circuit board 70 at an appropriate position, and the whole of the circuit board 70 is arranged in parallel with the top surface of the terminal board 60, and deflection of the circuit board 70 due to the acceleration is reduced. Six holes 76 provided in the circuit board 70 are positioned at six lead terminals 62 provided in the terminal board 60, and electrifying by soldering and mechanical fixation are performed. A top surface of the circuit board 70 is loaded with an acceleration sensor 80, three variable resistors 73 and a fixed resistor 74. The acceleration sensor 80 is directly mounted on the circuit board 70, and an electrode provided in the top surface has a connecting electrode in the periphery through a drawing electrode, and electrically connected to the circuit board 70 by a lead wire 77.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor. The acceleration sensor is used for detecting acceleration and vibration of a vehicle, and is used as an operation signal of an active suspension, an airbag, and an ABS antilock brake system. Acceleration sensors for detecting earthquakes have also been developed. The types of the acceleration sensor include a semiconductor type, a piezoelectric element type, and the like. In each case, the acceleration is detected by using the deformation of the detection element due to the acceleration. The present invention relates to an acceleration sensor that is effective for a structure that efficiently transmits signals to a detection element

[0002]

2. Description of the Related Art Acceleration sensors have been developed which are capable of detecting two-axis or three-axis acceleration with a single acceleration sensor from conventional one-axis acceleration detection. At the same time, there is a demand for a small acceleration sensor having good detection sensitivity. Acceleration sensors that can individually measure acceleration in three axial directions with one acceleration sensor have already been developed. For example, International Publication No. WO94 / 23272 describes an acceleration sensor body described below. Please refer to the detection theory of each acceleration sensor.

FIG. 1 is a front sectional view of a capacitive semiconductor acceleration sensor body. FIG. 2 is a top view of the flexible substrate of FIG.
FIG. 3 is a bottom view of the fixed substrate of FIG. 4, 5, and 6 are cross-sectional views of the acceleration sensor when acceleration acts in the + X-axis direction, the -X-axis direction, and the + Z-axis direction. The acceleration sensor body is formed on a flexible substrate 1, a fixed substrate 2, a weight body 3 fixed to the flexible substrate, a sensor housing 4, electrodes F1 to F5 formed on the flexible substrate 1, and a fixed substrate 2. It is composed of electrodes E1 to E5. The outer periphery of the flexible substrate 1 is fixed to the sensor housing 4. In the electrode group formed on the flexible substrate 1 and the electrode group formed on the fixed substrate 2, F1 and E1, F2 and E2, F3 and E3, F4 and E4, and F5 and E5 are arranged to face each other. A capacitance element is formed by a pair of electrodes facing each other. The position of the center of gravity of the weight body 3 is set as the origin O, and an XYZ three-dimensional coordinate system of + X axis in the right direction of the figure, + Z axis in the upward direction, and + Y axis as shown in FIG. 2 is set (the same applies hereinafter). As shown in FIGS. 4, 5 and 6, when the acceleration acts in the + X direction, the −X direction, and the + Z axis direction, the flexible substrate 1 is deformed and the distance from the fixed substrate 1 changes. The capacitances of the two capacitance elements change, and the magnitude of the acceleration in each axial direction can be measured by measuring the change in each capacitance. The weight 3 is for increasing the deformation of the flexible substrate 1 by the action of acceleration, and the weight 3 can increase the sensitivity of the acceleration sensor.

FIG. 7 is a front sectional view of a piezoresistive semiconductor acceleration sensor body, and FIG. 8 is a top view of FIG. 7 showing an arrangement of the piezoresistors. The substrate 11 is formed of semiconductor silicon, and the piezoresistive elements Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 are formed on the upper surface of the substrate 11.
Are formed at positions as shown in FIG. The portion of the substrate 11 where the piezoresistive element is formed is thinly processed, and is easily deformed by the movement of the weight 13 due to acceleration. The magnitude of the acceleration in each axial direction is measured by measuring a change in each resistance value of the piezoresistive element group due to the deformation of the substrate 11.

FIG. 9 is a front sectional view of the piezoelectric acceleration sensor body, and FIG. 10 is a top view of FIG. A piezoelectric element 25 having electrode groups L1 to L16 formed on the upper surface and counter electrode groups M1 to M16 formed on the lower surface is attached to the upper surface of the flexible substrate 21. The outer periphery of the flexible substrate 21 is fixed to the sensor housing 24. When the flexible substrate 21 is deformed by the acceleration, an electric charge is generated in the piezoelectric element 25, and the magnitude of the acceleration in each axial direction can be measured by measuring the potential difference between the upper and lower electrodes that differs depending on the amount of the generated electric charge. .

[0006] Although the three types of acceleration sensor bodies have different measurement (detection) methods, there is no change in measuring the acceleration in each axial direction by deforming the flexible substrate by the acceleration acting on the weight body.

FIG. 11 is a front sectional view of an acceleration sensor in which a piezoelectric acceleration sensor is housed together with a circuit board in a container (indicated by a dashed line), and FIG. 12 is a top view of a main part without the circuit board. Piezoelectric element 33 having detection electrodes S1 to S5, lead electrodes and connection terminal electrodes C1 to C5 formed on the upper surface
Is attached to the upper surface of the flexible substrate 32. Flexible substrate 32
Is fixed to the sensor housing 31. A weight 34 is fixed to the lower surface of the flexible substrate 32 to form a sensor unit. As can be seen from the figure, the detection electrode group is formed eccentrically with respect to the piezoelectric element, but this is because the connection terminal electrode group is formed. The connection terminal electrode is the circuit board 40
(Not shown) and a lead wire 35 respectively. Components necessary for the detection circuit (for example, IC 41, variable resistor 42, resistor 43, etc.) are disposed on both sides of the circuit board 40. The case 30 is firmly fixed to the base 50 of the container, and the whole is covered by the lid 51. Case 3
The reason why 0 is firmly fixed to the base 50 is that, when the acceleration sensor is fixed to the object to be measured, the acceleration applied to the object to be measured is transmitted to the acceleration sensor without attenuating. For the same purpose, the sensor housing 31 is also firmly fixed to the case 30.

[0008]

The three-dimensional axial direction is shown in FIG.
1. When set as shown in FIG. 12, the rigidity of the container must be increased in order to prevent the acceleration in the Z-axis direction from being absorbed by the container or the circuit board. Structure, and the height will be increased. In a structure in which the sensor unit is fixed to the circuit board and solidly attached to the base to reinforce the circuit, the circuit is mounted on one side, which hinders miniaturization.

[0009]

A terminal block having at least a plurality of lead terminals, a circuit board having electronic components mounted on front and back surfaces fixed to the lead terminals, and a circuit board mounted on an upper surface of the circuit board An acceleration sensor body capable of detecting the acceleration in the vertical direction, and a lid member that engages with the terminal block to form a space for accommodating the circuit board and the like. An electronic component or a filling member that fills part or all of the gap is arranged in a gap between the lower surfaces of the circuit boards on which the acceleration sensor body is mounted.

The electrical connection lead between the electrode of the acceleration sensor and the circuit board also serves as a member for fixing the acceleration sensor to the circuit board.

[0011]

FIG. 13 is a front view showing an embodiment of the acceleration sensor according to the present invention. The lid member is indicated by a dashed line. FIG. 14 is a top view of a circuit board on which components are mounted, and shows only main parts. ICs 71 and 72, which are relatively large electronic components, are mounted on the lower surface of the circuit board 70, and at least one of the ICs 71 and 72 is disposed so as to be located on the lower surface of the acceleration sensor body 80, and is located below the acceleration sensor body 80. The gist of the present invention is that the electronic component abuts on the upper surface of the terminal block 60 directly or via an adhesive or the like. When an electronic component having the same height as the electronic component to be arranged at the lower portion of the acceleration sensor body 80 is arranged at a key position on the lower surface of the circuit board 70, the entire circuit board 70 is arranged in parallel with the upper surface of the terminal block 60, and the circuit board is moved by acceleration. 70 can be less distorted. Circuit board 70
The six holes 76 provided on the circuit board 70 are positioned by the six lead terminals 62 provided on the terminal block 60, and electrical conduction and mechanical fixing such as soldering are performed. On the upper surface of the circuit board 70, electronic components such as an acceleration sensor body 80, three variable resistors 73, and fixed resistors 74 are mounted.

The acceleration sensor body 80 is directly mounted on the circuit board 70, and the electrodes provided on the upper surface are provided with connection electrodes (not visible behind the lead wires 77) on the outer periphery through the lead electrodes, and the circuit is connected to the lead wires 77. It is electrically connected to the substrate 70. The acceleration sensor body 80 includes a flexible portion 81, a flexible portion fixing portion 82 (corresponding to a sensor housing), and a weight body 83, and the same applies to any type such as a capacitive type, a piezoresistive type, and a piezoelectric type. Can take a structure. Of course, the same applies to an integral type made of piezoelectric ceramics. It is preferable that a connection portion between the lead wire 77 and the connection electrode is located above the flexible portion fixing portion 82 so that stress is not applied to the flexible portion 81. FIG.
Although the connection structure of the prior art mentioned in the above and the connection by wire bonding are also possible, the present embodiment is more compact,
This is an advantageous structure with fixed strength and the like. If the lower surface of the flexible portion fixing portion 82 and the circuit board 70 are fixed with an adhesive, further fixing strength can be secured.

[0013]

According to the present invention, by disposing electronic components and the like between the lower surface of the circuit board and the upper surface of the terminal block and filling the gap, the acceleration in the direction (Z axis) perpendicular to the circuit board can be prevented from being absorbed. That is, since the acceleration sensor body can be directly mounted on the circuit board, the acceleration sensor can be reduced in size and height.

By using the electrical connection lead wire between the electrode of the acceleration sensor body and the circuit board as a member for fixing the acceleration sensor body to the circuit board, the fixing member for the acceleration sensor body becomes unnecessary, and the number of parts can be reduced. , Miniaturization was achieved.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a capacitive semiconductor acceleration sensor body.

FIG. 2 is a top view of the flexible substrate of FIG. 1;

FIG. 3 is a bottom view of the fixed substrate of FIG. 1;

FIG. 4 is a cross-sectional view when acceleration acts in the + X axis direction.

FIG. 5 is a cross-sectional view when acceleration acts in the −X axis direction.

FIG. 6 is a cross-sectional view when acceleration acts in the + Z axis direction.

FIG. 7 is a front sectional view of a piezoresistive semiconductor acceleration sensor body.

FIG. 8 is a top view of FIG. 7;

FIG. 9 is a front sectional view of a piezoelectric acceleration sensor body.

FIG. 10 is a top view of FIG. 9;

FIG. 11 is a front sectional view of a piezoelectric acceleration sensor.

FIG. 12 is a top view of a main part excluding the circuit board in FIG. 11;

FIG. 13 is a front view of the acceleration sensor of the present invention.

FIG. 14 is a top view of a circuit board on which components are mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flexible board 2 Fixed board 3 Weight 4 Sensor case 11 Substrate 13 Weight 21 Flexible board 24 Sensor case 25 Piezoelectric element 30 Case 31 Sensor case 32 Flexible board 33 Piezoelectric element 34 Weight body 35 Lead wire 40 Circuit board 41 IC 42 Variable resistor 43 Resistance 50 Base 51 Cover 60 Terminal block 62 Lead terminal 70 Circuit board 71 IC 72 IC 73 Variable resistor 74 Fixed resistor 76 Hole 77 Lead wire 80 Acceleration sensor body 81 Flexible part 82 Flexible part fixing part 83 Weight body O Origin E1 to E5 Electrode F1 to F5 Electrode L1 to L16 Electrode Rx1 to Rx4 Piezoresistive element Ry1 to Ry4 Piezoresistive element Rz1 to Rz4 Piezoresistive element S1 to S5 Detection electrodes C1 to C5 Connection Terminal electrode

Claims (2)

[Claims] 1. A terminal block having at least a plurality of lead terminals, a circuit board having electronic components mounted on front and back surfaces fixed to the lead terminals, and a circuit board mounted on an upper surface of the circuit board in a vertical direction of the circuit board. An acceleration sensor comprising an acceleration sensor body capable of detecting acceleration, and a lid member which engages with the terminal block to form a space for accommodating the circuit board and the like. An acceleration sensor, wherein an electronic component or a filling member that fills a part or all of the gap is arranged in a gap between the lower surfaces of the mounted circuit boards. 2. An acceleration sensor, wherein an electrical connection lead wire between an electrode of the acceleration sensor body and the circuit board also functions as a member for fixing the acceleration sensor body to the circuit board.