JPH11142429A - Acceleration sensor - Google Patents

Abstract

(57) [Problem] To provide an acceleration sensor which is hardly affected by external noise, is easy to assemble, and has high reliability in connection of signal lines. SOLUTION: By making a base unit 1 resinous, electrodes of piezoelectric ceramics 5 and 6 are electrically insulated from a base 19, and the piezoelectric ceramics 5 and 6 and a circuit board 11 are entirely covered with a metal case. As a configuration, the influence of external noise is cut off.
Wire 7a as a signal line connection from each electrode to each terminal
7b, 7c, and 7d are connected by ultrasonic waves to improve reliability, improve assemblability, and reduce the size of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for measuring or detecting acceleration of a vehicle running on an internal combustion engine.

[0002]

2. Description of the Related Art FIGS. 9 and 10 show the structure of a conventional acceleration sensor. In the figure, reference numeral 101 denotes a base on which an annular projection 103 having a positioning hole 102 is formed at the center of the surface. Numeral 104 denotes a diaphragm, the center of which is fixed to the annular projection 103 of the base 101 by welding. Reference numeral 105 denotes a piezoelectric ceramic element for sensor output fixed on the upper surface of the diaphragm 104. As shown in FIG. 13, the piezoelectric ceramic element 105 is formed in a donut shape having a circular hole 106 at the center, and the surface is annularly formed with a plus electrode 107 for sensor sensor output and a plus electrode 108 for driving the piezoelectric element. It is divided into two.

The piezoelectric ceramic element 105 is electrically connected to the front surface of the vibration plate 104 in a state where the negative electrode 109 on the entire back surface is fitted with a circular hole 106 on the outer periphery of an annular bead 110 formed at the center of the vibration plate 104. Glued. Numeral 111 denotes a piezoelectric ceramic element for canceling pyroelectricity, which has the same area as the plus electrode 107 of the piezoelectric ceramic element 105 as shown in FIG.
12, a positive electrode 113 on the front surface and a negative electrode 114 on the rear surface. The piezoelectric ceramic element 111 has the positive electrode 113 side of the surface
Is electrically conductively bonded to the rear surface of the substrate with a round hole 112 fitted in the outside of an annular bead 115 formed at the center thereof.

The positive electrode 1 of the piezoelectric ceramic element 105
07 and the negative electrode 114 of the piezoelectric ceramic element 111
Are connected to the lead frames 118 and 119, respectively.
20 and 121, and is connected to a sensor output lead pin 124 via an insulating embedded lead pin 122 and a circuit board 123.

[0005] Reference numeral 125 denotes a lead pin for driving the piezoelectric ceramic element, which is connected to the plus electrode 108 of the piezoelectric ceramic element 105 via a lead frame 126 by solder 127. Reference numeral 128 denotes a power supply lead pin of the circuit board 123, and reference numeral 129 denotes a ground lead pin, which are connected to the circuit board 123, respectively. 13
Reference numerals 0 and 131 denote insulated lead pins for supporting the circuit board 123. The circuit board 123 is provided with an impedance conversion circuit, an output amplification circuit, a filtering circuit, and the like.

The lead pins 122, 124, 125, 12
8, 130 and 131 are sealing glass 132 on the base 101.
, And only the ground lead pin 129 is electrically connected by brazing. 1
Reference numeral 33 denotes a sealing glass for sealing the positioning hole 102 of the base 101. Power is supplied through the power supply lead pin 128 and the ground lead pin 129.

A cap 134 has a peripheral flange 135 fixed to the base 101 by resistance welding over the entire circumference. Thereby, the piezoelectric ceramic element 1
05, 111 and the space 13 containing the circuit board 123
6 is sealed.

A conventional acceleration sensor having such a configuration is mounted on a vehicle body or the like by a bolt 138 and a washer 139 through a mounting hole 137 formed in the base 101.

[0009]

However, in the above-mentioned conventional acceleration sensor, the piezoelectric ceramic elements 105, 1
11 are one of the electrodes 109 and 113 respectively.
Therefore, there is a problem that noise is easily picked up through the base 101 and the cap 134.

When a conventional acceleration sensor is mounted on a vehicle body, there is a problem that noise picked up by the vehicle body itself easily affects the sensor characteristics.

Further, in the assembling work, it is necessary to connect a harness to each of the lead pins 124, 125, 128, 129, so that there is a problem that the assembling work is troublesome and the workability is poor.

Furthermore, since the connection of the signal extraction lead wire from the electrode of the piezoelectric element is soldered, there is a problem that the electrode is peeled off due to the bite of the electrode.

The present invention is to solve such a conventional problem, and provides an acceleration sensor which is hardly affected by external noise. It is an object of the present invention to provide a simple acceleration sensor.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a balanced type structure in which both positive and negative electrodes of a piezoelectric ceramic element are electrically insulated from a base. External noise such as electromagnetic waves is shielded by covering the entire circuit board with a metal case.Furthermore, each drive electrode and output electrode of the two piezoelectric ceramics bonded back to back are connected to each terminal. The structure is such that wire bonding connection (ultrasonic connection) is made between them.

As described above, the present invention has the effect of being less susceptible to the influence of external noise, and since the respective electrodes of the piezoelectric element are connected by wire bonding, electrode peeling due to silver erosion of the electrodes at the time of soldering connection can be eliminated. Thus, the quality of the acceleration sensor can be improved, and the workability of the assembly is improved, and the connection work can be automated.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a base unit made of an insulating resin having a projection formed stepwise integrally with a guide cylindrical portion at a central portion on one side, and the base unit is formed of a resin. A base on which the signal lead pins are integrally fixed via a glass sealing portion, a cap hermetically sealed to the base, and a diaphragm having a central portion fixed to the stepped projection, The vibrating plate has two piezoelectric ceramic elements bonded to each other with the positive and negative electrodes back to back, and the output of one piezoelectric ceramic element cancels the pyroelectric phenomenon that occurs in the other piezoelectric ceramic element. At the same time, the other piezoelectric ceramic element is divided into a driving element and an output element, a driving electrode is provided on the driving element, and an output electrode is provided on the output element, and the sensor operates by the output of the output electrode. It is those you can detect the state,
This has the effect that noise due to the pyroelectric phenomenon can be eliminated, and a failure can be checked whether the sensor is operating properly.

According to a second aspect of the present invention, each of the divided drive electrode and output electrode of the two piezoelectric ceramic elements bonded back to back is connected to each terminal by wire bonding ultrasonic bonding. Along with
A printed circuit board having amplification, impedance conversion, filtering, and temperature compensation circuits is hermetically sealed together with piezoelectric ceramic in a cap. The connection between the electrodes and terminals of the piezoelectric element is made by wire bonding ( (Ultrasonic bonding) has the effect of preventing electrode fraying due to silver erosion generated during soldering.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. (Embodiment 1) FIGS. 1 to 4 are views showing the structure of an acceleration sensor according to the present embodiment. 1 is a front sectional view of the acceleration sensor, FIG. 2 is a top sectional view thereof, FIG. 3 is a side sectional view thereof, and FIG. 4 is an enlarged view of a main part of the acceleration sensor.

In the figure, a diaphragm 4 is fixed to a metal projection 1a having a positioning pin 25 formed at the center of one side of a base unit 1 made of an insulating resin by means such as welding at the center. I have. On the upper surface of the vibrating plate 4, the positive electrode on the front surface is divided into a sensor output positive electrode 14 and a positive electrode 15 for driving a piezoelectric element, and the piezoelectric ceramic 5 on which the negative electrode 2 is also formed on the back surface is located at the center of the vibrating plate 4. It is conductively bonded and fixed to the outer periphery of the bead 10a formed in the portion. A pyroelectric canceling piezoelectric ceramic element 6 having a negative electrode 3 having the same area as the positive electrode 14 of the sensor output of the upper piezoelectric ceramic element 5 on the lower surface of the diaphragm 4 on the side opposite to the bonding surface.
Is conductively bonded to the outer periphery of the bead 10b formed on the diaphragm 4.

The sensor output positive electrode 14 and the negative electrode 3 of the pyroelectric canceling element 6 are ultrasonically connected at the connection points 30 and 31 by wires 7a and 7b, respectively. The other ends of the wires 7a and 7b are ultrasonically connected to the front and back of the terminal 9 at connection points 32 and 33, respectively. Therefore, the output signals of the piezoelectric elements 5 and 6 are connected to the output lead pins 12 via the terminals 9, the terminals 34 and the circuit board 11.

This serves to cancel the electric charge generated at the sensor output positive electrode 14 by the pyroelectric phenomenon under the influence of the ambient temperature by the electric charge generated at the negative electrode 3 of the pyroelectric canceling piezoelectric ceramic element. It is. Further, a positive electrode 8 is formed on the bonding surface of the piezoelectric ceramic element 6 and is conductively bonded to the diaphragm 4.

As shown in FIG. 7, the diaphragm 4 is formed with concentric beads 10a and 10b to play a role of improving rigidity and preventing the flow of the adhesive. As shown in FIG. 8, the diaphragm 4 may have a shape in which the outer peripheral portion is drawn to increase the output.

The base unit 1 includes lead pins 12, 1
3 and 16 are insulated and hermetically fixed by a sealing glass 23, and are joined by an adhesive 28 to a base 19 to which only the ground lead pins 17 are conductively joined by means such as brazing. Lead pins 12, 13, 16, 17
Are the lead pins 12a, 13a, 16a, 17 respectively.
a is formed by forming.

The lead pin 13 is a lead pin for driving the element, and is connected to the terminal 19 via the terminal 36. The terminal 19 is connected to the positive electrode 15 for driving the piezoelectric element formed on the piezoelectric ceramic element 5 via the wire 7c.
At 9, ultrasonic connection is made, and ultrasonic connection is made at a connection point 35 to a piezoelectric element driving negative electrode 15 a formed on the piezoelectric element 6 via a wire d. The other ends of the wires 7c and 7d are connected to the connection point 37,
Ultrasonic bonding is performed at 38 places. Therefore, drive signals for the piezoelectric elements 5 and 6 are transmitted to the lead pins 1 for driving the elements.
3 to the positive electrode 15 for driving the piezoelectric element via the circuit board 11, the terminal 36 and the terminal 19.

The lead pins 16 are power supply lead pins of the circuit board 11, and the lead pins 17 are ground lead pins, which are connected to the circuit board 11, respectively.
The lead pin 18 is a lead pin for embedding insulation for supporting the circuit board 11. The circuit board 11
Lead pins 12, 13, 16, 17 and terminal 1
8, 34, 36 are fixed by soldering.

Reference numeral 24 denotes a label attached to identify the acceleration sensors individually. Reference numeral 26 denotes a support terminal for fixing the acceleration sensor to the control board 27. Reference numeral 20 denotes a cap, and the cap 20 is a cap fixing portion 2
At 1, the base 19 is fixed to the base 19 by means such as full circumference resistance welding or full circumference cold pressure welding. Therefore, the space 22 containing the piezoelectric ceramic elements 5 and 6 and the circuit board 11 is sealed.

The circuit section of the circuit board 11 is for the purpose of impedance conversion, output amplification, and filtering.

Next, the acceleration detection path will be described. The acceleration generated in the automobile propagates through the base 19 and the base unit 1 and gives the diaphragm 4 a deflection. The deflection of the vibration plate 4 applies a tensile force and a compressive force to the piezoelectric ceramic element alternately.
An electric charge is generated in 6. This electric charge is converted into a voltage by an impedance conversion circuit provided on the circuit board 11,
With the amplifier circuit, a sensor output with a necessary band and an optimum output level can be obtained.

In addition, a pyroelectric phenomenon occurs in the piezoelectric ceramic in which charge is generated in response to a temperature change. In the present embodiment, since the piezoelectric ceramics 5 and 6 are connected in opposite polarities, the generated charge is canceled. Thus, the influence of the above-described pyroelectric phenomenon is reduced.

Since these acceleration sensors are intended for use in automobiles, high reliability is required. Therefore, the controller is configured to check whether the acceleration sensor is out of order or not. That is, the electrode of the piezoelectric ceramic element 5 is divided, and the positive electrode 15
When a pseudo signal corresponding to the acceleration generated in the vehicle is applied as a drive input, a drive voltage corresponding to the pseudo signal appears on the sensor output positive electrode 14, thereby enabling the failure diagnosis of the sensor.

The circuit section is driven and supplied with power from the power supply lead pins 16 and the ground lead pins 17.

As described above, according to the present embodiment, by making the base unit 1 resinous, the electrodes of the piezoelectric ceramics 5 and 6 are electrically insulated from the base 19, and 6 and the circuit board 11 are entirely covered with a metal case to cut off the influence of external noise, and further, wires 7a, 7b, 7c, 7d are used as signal line connections from each electrode of the piezoelectric ceramics 5 and 6 to each terminal.
By ultrasonic connection, noise due to the pyroelectric phenomenon can be eliminated, failure of the sensor can be checked whether it is operating correctly, and connection between the electrode of the piezoelectric element and the terminal can be done. Since the bonding is performed by wire bonding (ultrasonic bonding), it is possible to prevent electrode peeling due to silver erosion generated at the time of soldering.

Further, according to the present embodiment, the circuit portion is built in, the signal line is taken out through the lead wire which is hermetically implanted on the base, and the cap is fixed by full circumference resistance welding. Since the transducer and the circuit section can be completely sealed, reliability is improved.

By arranging the circuit section above the transducer, the work of connecting the circuit board to the external lead pins becomes easy, and the size of the entire device can be reduced.

By forming concentric beads on the front and back sides of the central portion of the diaphragm, the rigidity of the diaphragm can be improved and the flow of the adhesive during the piezoelectric ceramic bonding can be prevented. In addition, the outer peripheral portion of the diaphragm is subjected to drawing processing to add an additional mass, thereby increasing the sensor output, and increasing the S / S of the sensor characteristics.
N can be improved.

The output and the drive elements are formed concentrically and the drive electrodes are arranged outside and the output electrodes are arranged inside, so that both the sensor output during external excitation and the drive output during electric drive are increased. I can take it.

In the above embodiment, the lead pins 12, 13, 16, and 17 are formed by forming and are perpendicular to the control board 27 (self-standing type). , 16 and 17 may be configured so as to be horizontal (imposition type) with respect to the control substrate 27 without forming.

[0038]

As described above, according to the present invention, the two piezoelectric ceramic elements are bonded to the front and back surfaces of the diaphragm with the positive and negative electrodes back to back, so that the two piezoelectric ceramic elements can be bonded based on the temperature change. Since the generated charges are canceled, there is an effect that noise due to the pyroelectric phenomenon can be eliminated.

Also, by dividing the piezoelectric ceramic element for the sensor into a vibrating electrode and a sensor output electrode, an appropriate drive signal is applied to the drive electrode, and whether the sensor is operating properly depending on the state of the output generated at the sensor output electrode. This has the effect that it can be checked whether or not it is.

Furthermore, since the connection between the electrode and the terminal of the piezoelectric element is performed by wire bonding (ultrasonic bonding), it is possible to prevent the electrode from being peeled off due to silver erosion generated during soldering. Having.

[Brief description of the drawings]

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

FIG. 2 is a top sectional view of the acceleration sensor.

FIG. 3 is a side view of the acceleration sensor.

FIG. 4 is an enlarged view of a main part of the acceleration sensor.

FIG. 5 is a view showing a piezoelectric ceramic element of the acceleration sensor.

FIG. 6 is a view showing a piezoelectric ceramic element of the acceleration sensor.

FIG. 7 is a diagram showing a diaphragm of the acceleration sensor.

FIG. 8 shows a diaphragm of the acceleration sensor.

FIG. 9 is a top view of a conventional acceleration sensor.

FIG. 10 is a front sectional view of a conventional acceleration sensor.

FIG. 11 is an enlarged view of a main part of a conventional acceleration sensor.

FIG. 12 is an enlarged view of a main part of a conventional acceleration sensor.

FIG. 13 is a view showing a piezoelectric ceramic element of a conventional acceleration sensor.

FIG. 14 is a diagram showing a piezoelectric ceramic element of a conventional acceleration sensor.

[Explanation of symbols]

 Reference Signs List 1 base unit 1a protrusion 2 negative electrode of piezoelectric ceramic element 5 3 negative electrode of piezoelectric element 6 for pyroelectric cancellation 4 diaphragm 5 piezoelectric ceramic element 6 piezoelectric element for pyroelectric cancellation 7a, 7b, 7c, 7d wire 10 bead 11 circuit Substrate 12 Output lead pin 13 Element drive lead pin 14 Sensor output positive electrode 15 Piezoelectric element drive positive electrode 16 Power supply lead pin 17 Ground lead pin 19 Base

Claims (2)

[Claims] 1. A base unit made of an insulating resin having a projection integrally formed with a step at a central portion of one surface thereof and a guide cylindrical portion, and a signal lead pin is adhered to the base unit via a glass sealing portion to form a signal lead pin. A base fixed integrally, a cap hermetically sealed to the base, a diaphragm fixed at the center to the stepped protrusion, and positive and negative electrodes bonded to both front and back surfaces of this diaphragm with back Having two piezoelectric ceramic elements, the output of one of the piezoelectric ceramic elements can cancel the pyroelectric phenomenon occurring in the other piezoelectric ceramic element, and the other piezoelectric ceramic element can be used as a drive element and an output element. A driving electrode is provided on the driving element, and an output electrode is provided on the output element, so that the operation state of the sensor can be detected by the output of the output electrode. Degree sensor. 2. A split drive electrode and an output electrode of two piezoelectric ceramic elements bonded back to back are connected to respective terminals by wire bonding ultrasonic bonding, and amplification, impedance conversion, and filtering are performed. An acceleration sensor wherein a printed circuit board having a temperature compensation circuit and the like is hermetically sealed together with piezoelectric ceramic in a cap.