JP2734777B2 - Acceleration sensor - Google Patents

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 a running acceleration of an automobile or the like having an internal combustion engine.

[0002]

2. Description of the Related Art FIGS. 7 to 16 show the structure of a conventional acceleration sensor. FIG. 7 is a plan view of a conventional acceleration sensor,
8 is a front sectional view taken along the line VI-VI of FIG. 7, and FIG.
10 is a side sectional view taken along line VII-VII of FIG. 10, FIG. 10 is a plan view of a main part of the conventional example, FIG. 11 is a front sectional view of a main part of the conventional example, and FIG. FIG. 13 is a plan view of a conventional piezoelectric ceramic element for canceling pyroelectricity, FIG. 14 is a plan view of a diaphragm in a conventional example, FIG. 15 is a cross-sectional view of the diaphragm, and FIG. 16 is a circuit diagram of a main part. It is.

In these figures, reference numeral 1 denotes a base, on which an annular projection 3 having a positioning hole 2 is formed at the center of the surface. Reference numeral 4 denotes a diaphragm, the center of which is fixed to the annular projection 3 of the base 1 by means such as welding. Reference numeral 5 denotes a piezoelectric ceramic element for sensor output fixed to the upper surface of the diaphragm 4, and this piezoelectric ceramic element 5 has a structure shown in FIG.
As shown in the figure, the filter is formed in a donut shape having a round hole 6 at the center, and the surface is divided into a plus electrode 7 for sensor output and a plus electrode 8 for driving the piezoelectric ceramic element.

[0004] The piezoelectric ceramic element 5 has a negative electrode 9 on the entire back surface thereof, and a circular hole 6 is fitted on the outer periphery of an annular bead 10 formed at the center of the diaphragm 4. Conductive bonding. Reference numeral 11 denotes a piezoelectric ceramic element for canceling pyroelectricity, as shown in FIG.
It has the same area as the plus electrode 7 of the piezoelectric ceramic element 5, similarly has a round hole 12 at the center, and has a plus electrode 13 on the front surface and a minus electrode 14 on the back surface. The piezoelectric ceramic element 11 has an annular bead 15 formed at the center thereof, with the positive electrode 13 side of the front surface on the back surface of the diaphragm 4.
Are electrically conductively bonded in a state where the round hole 12 is fitted in the outer periphery of the wire.

As shown in FIGS. 12 and 13, the diaphragm 4 has a positioning hole 16 having the same diameter as the positioning hole 2 of the base 1 at the center of the metal disk, and a concentric circular ring around the hole. Beads 10 and 15 are formed on the front surface and the back surface, respectively, in such a manner that the diameters are sequentially increased. Piezoelectric ceramic element 5
The positive electrode 7 and the negative electrode 14 of the piezoelectric ceramic element 11 are
0, 21 and an insulated embedded lead pin 22
And sensor output lead pin 2 via circuit board 23
4 is connected. This is because the piezoelectric ceramic element 5 for sensor output is caused by a pyroelectric phenomenon under the influence of the ambient temperature.
And serves to cancel the electric charge generated in the plus electrode 7 of FIG.

Reference numeral 25 denotes a lead pin for driving the piezoelectric ceramic element, which is connected to the positive electrode 8 of the piezoelectric ceramic element 5 by a solder 27 via a lead frame 26. 28 is a power supply lead pin of the circuit board 23;
Are ground lead pins, each of which is a circuit board 23.
It is connected to the. Reference numerals 30 and 31 denote insulated lead pins for supporting the circuit board 23. Circuit board 23
Is provided with an impedance conversion circuit, an output amplification circuit, a filtering circuit, and the like. 22, 24 of the lead pins,
The reference numerals 25, 28, 30, and 31 are fixed to the base 1 by insulating hermetic means such as sealing glass 32, and only the ground lead pins 29 are conductively connected by means such as brazing. Reference numeral 33 denotes a sealing glass for sealing the positioning hole 2 of the base 1. Power is supplied through a power supply lead pin 28 and a ground lead pin 29. 34 is a cap, and its peripheral flange 35
Are fixed to the base 1 by means such as resistance welding or cold pressure welding over the entire circumference. Thus, the space 3 containing the piezoelectric ceramic elements 5 and 11 and the circuit board 23 is formed.
6 is sealed. The acceleration sensor having such a configuration is used by being attached to a vehicle body or the like of a vehicle with a bolt 38 and a washer 39 through a mounting hole 37 formed in the base 1.

Next, the operation of the above conventional example will be described.
The acceleration generated by the running of the vehicle or the like is transmitted to the diaphragm 4 via the base 1 and gives the diaphragm 4 a bend. The deflection of the diaphragm 4 applies a tensile force and a compressive force to the piezoelectric ceramic elements 5 and 11 alternately, so that electric charges are generated in the piezoelectric ceramic elements 5 and 11. This charge is converted into a voltage by the impedance conversion circuit of the circuit board 23, and is output through a filtering circuit and an amplification circuit so as to have a necessary band and an optimum output level, thereby obtaining a sensor output. In addition, since the piezoelectric ceramic element has a pyroelectric phenomenon that generates electric charges in response to a temperature change, this acceleration sensor connects the piezoelectric ceramic elements 5 and 11 with opposite polarities to each other. The generated charge is cancelled.

In addition, since an acceleration sensor used for an automobile or the like requires particularly high accuracy and quality, the plus electrode of the piezoelectric ceramic element 5 has a sensor so that the controller can check whether or not it operates reliably. The output electrode 7 and the element driving electrode 8 are divided into two parts. By inputting an appropriate signal to the driving electrode from the oscillation circuit on the controller side, the corresponding driving output is output to the sensor output electrode 7. Appears, and the fault diagnosis of the sensor can be performed.

As described above, even the above-described conventional acceleration sensor can measure or detect the acceleration of an automobile or the like.

[0010]

However, in the above-mentioned conventional acceleration sensor, the piezoelectric ceramic elements 5 and 11 adhered to both surfaces of the vibration plate 4 have different dimensions and electrode shapes, so that they are manufactured in separate manufacturing lots. , Due to the difference in characteristics, abnormal charge due to the pyroelectric phenomenon occurs,
It is hard to cancel all of them. Further, since the element driving electrodes 7 are provided only on one side of the piezoelectric ceramic element 5 fixed to the upper surface of the diaphragm 4, when performing a failure diagnosis of the acceleration sensor, the piezoelectric ceramic elements 5, 11 4 has a small driving force for the vibrator unit portion, and therefore the sensor output is small, so that the accuracy of failure diagnosis is low.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an excellent acceleration sensor capable of canceling an abnormal charge due to a pyroelectric phenomenon and having high accuracy of failure diagnosis. .

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a base, a disk-shaped diaphragm having a center fixed to the base, and a diaphragm on each of the front and back surfaces of the diaphragm. Two piezoelectric ceramic elements in which the electrodes on the surface which are conductively bonded with the positive and negative electrodes facing each other are divided into two, lead terminals respectively connected to the respective electrodes of these piezoelectric ceramic elements, and output is performed through the lead terminals. It comprises a circuit board for amplifying and filtering signals, and a metal case for shielding these piezoelectric ceramic elements and the circuit board from the outside.

[0013]

Therefore, according to the present invention, by applying a voltage to the two piezoelectric ceramic elements on the front and back sides of the diaphragm, the vibrator unit composed of the diaphragm and the piezoelectric ceramic elements is driven to take out the sensor output and obtain the acceleration sensor. Since the failure diagnosis is performed, there is an effect that the sensor output increases and the accuracy of the failure diagnosis increases.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the entire acceleration sensor according to the present invention will be described with reference to the drawings only in the points different from the conventional example. FIG.
1A and 1B are a front view and a rear view, respectively, of a piezoelectric ceramic element used for an acceleration sensor according to one embodiment of the present invention. 1 (a) and 1 (b),
Reference numeral 41 denotes a disk-shaped piezoelectric ceramic element.
It is about 0.5 mm thick and has a round hole 41a in the center. Reference numerals 42 and 43 denote positive silver electrodes, and reference numerals 44 and 45 denote negative silver electrodes. The silver electrode 45 is partially cut away to indicate the negative side.

FIGS. 2A and 2B are a plan view and a side sectional view, respectively, of a metal diaphragm. In FIG.
Is a disk-shaped metal diaphragm having a convex portion 4 at the center.
6a and a round hole 46b are provided. FIGS. 3A and 3B are a plan view and a front sectional view, respectively, showing a transducer unit. 3A and 3B, the projection 46a of the diaphragm 46 is welded and fixed to the annular projection 47 such that the projection 46a is positioned downward in the drawing. Hereinafter, the side to which the diaphragm 46 is fixed by welding is referred to as a lower surface, and the opposite side is referred to as an upper surface. The annular projection 47 is similar to the annular projection 3 shown in FIG. The silver electrodes 44 and 45 (minus side) of the piezoelectric ceramic element 41 are vibrated on the upper surface of the vibrating plate 46, and the silver electrodes 42 and 43 (positive side) of the piezoelectric ceramic element 41 are vibrated on the lower surface of the vibrating plate 46. Conductive bonding is performed so as to face the plate 46. That is, the electrodes are conductively bonded to the vibration plate 46 such that the opposite silver electrodes of the two piezoelectric ceramic elements 41 have opposite polarities. 48,
Reference numeral 49 denotes a lead terminal. The lead terminal 48 electrically connects the silver electrode 42 of the piezoelectric ceramic element 41 on the upper surface and the silver electrode 44 of the piezoelectric ceramic element 41 on the lower surface. The lead terminal 49 is a piezoelectric ceramic on the upper surface. Silver electrode 4 of element 41
3 and the silver electrode 45 of the piezoelectric ceramic element 41 on the lower surface side are electrically connected. 50 and 51 are leads, and lead 5
Numeral 0 is a drive input pin which is connected to the lead terminal 48 by solder or the like and performs a failure diagnosis of the sensor. This is the same as the lead pin 25 shown in the conventional example. The lead 51 is connected to the lead terminal 49 by soldering or the like, and is also connected to the substrate 52. And outputs the acceleration as an electric signal.

Next, the operation of the above embodiment will be described.
The operation of outputting an electric signal by applying an acceleration is the same as that of the conventional example, but differs greatly in the failure diagnosis of the acceleration sensor. FIG. 4 shows a circuit diagram of a main part of the acceleration sensor of the present invention. When an electric input such as a sine wave or a rectangular wave is applied to the lead 50 from the outside, the two piezoelectric ceramic elements 41 on the upper surface side and the lower surface side operate as actuators like a general piezoelectric buzzer. That is, the silver electrodes 42, 4
The portion 4 expands and contracts mechanically, and the polarity is reversed, so that when one expands, the other contracts. By this operation, the entire two piezoelectric ceramic elements 41 are moved, and as a result, the piezoelectric ceramic element 41 including the vibration plate 46 is flexed and vibrated. Then, since the silver electrodes 43 and 45 are sensor output electrodes, the silver electrodes 43 and 45 output charges generated by bending to the substrate 52. That is, a failure diagnosis of the acceleration sensor itself is performed by applying an electric input to the piezoelectric ceramic element 41 and confirming an output that appears when the vibrator unit section including the vibration plate 46 and the piezoelectric ceramic element 41 vibrates.

As described above, according to this embodiment, the silver electrodes on both surfaces of the two piezoelectric ceramic elements 41 are both concentrically divided into two, and electrodes for driving the piezoelectric ceramic elements 41 are provided on both surfaces. By adhering to both surfaces of the vibration plate 46, the driving force of the vibration unit is increased, and a large sensor output for failure diagnosis is obtained, so that the accuracy of failure diagnosis can be improved. Have.

Further, since the piezoelectric ceramic elements 41 adhered to both sides of the vibration plate 46 are the same as those on both sides, the piezoelectric ceramic elements 41 can be produced in the same production lot, and the production efficiency can be improved, and the piezoelectric ceramic elements having uniform characteristics can be obtained. Can be used, so that there is also an effect that abnormal output due to temperature change (pyroelectricity) can be reduced.

Further, when changing the polarity of the output of the acceleration sensor, it is only necessary to reverse the front and back directions of bonding the piezoelectric ceramic element 41 to the diaphragm, and it is not necessary to change the electric circuit.

FIGS. 5A, 5B, and 6 are a plan view, a front sectional view, and a circuit diagram, respectively, showing a main part of another embodiment. Reference numeral 53 denotes a lead terminal, which is connected to a cut-and-raised portion 54a provided at the center of a vibration plate 54 with the piezoelectric ceramic elements 41 adhered to both surfaces thereof by soldering or the like, and is connected to a substrate 56 by a lead 57. . On the substrate 56, the output of the piezoelectric ceramic element 41 is subjected to impedance conversion, filtering,
Add amplification and temperature characteristic correction. This embodiment shows a case where the annular protrusion 55 is electrically insulated from a case (not shown) of the acceleration sensor main body.

[0021]

According to the present invention, as is apparent from the above embodiment, the electrodes on both sides of the two piezoelectric ceramic elements are both concentrically divided into two, and electrodes for driving the piezoelectric ceramic elements are provided on both sides. As a result, the driving force for driving the vibration unit increases, and a large sensor output for failure diagnosis can be obtained. This has the effect of improving the accuracy of failure diagnosis.

Further, since the piezoelectric ceramic elements adhered to both sides of the diaphragm are the same on both sides, they can be produced in the same production lot, thereby improving the production efficiency and using piezoelectric ceramic elements having uniform characteristics. Therefore, there is also an effect that abnormal output due to temperature change (pyroelectricity) can be reduced.

Further, when changing the polarity of the output of the acceleration sensor, it is only necessary to reverse the direction of the front and back sides of bonding the piezoelectric ceramic element to the diaphragm, and it is not necessary to change the electric circuit.

[Brief description of the drawings]

FIG. 1A is a front view of a piezoelectric ceramic element used for an acceleration sensor according to an embodiment of the present invention. FIG. 1B is a rear view of the piezoelectric ceramic element.

2A is a plan view of the diaphragm of the embodiment. FIG. 2B is a side sectional view of the diaphragm.

FIG. 3A is a plan view showing the vibrator unit of the embodiment. FIG. 3B is a front sectional view showing the vibrator unit.

FIG. 4 is a circuit diagram showing a main part of the embodiment.

5A is a plan view showing a main part of another embodiment. FIG. 5B is a front sectional view showing a main part of another embodiment.

FIG. 6 is a circuit diagram showing a main part of another embodiment.

FIG. 7 is a plan view of a conventional acceleration sensor.

8 is a front sectional view taken along the line VI-VI in FIG. 7;

9 is a side sectional view taken along the line VII-VII in FIG. 7;

FIG. 10 is a plan view of a main part in a conventional example.

FIG. 11 is a front sectional view of a main part of a conventional example.

FIG. 12 is a plan view of a piezoelectric ceramic element for sensor output in a conventional example.

FIG. 13 is a plan view of a pyroelectric canceling piezoelectric ceramic element in a conventional example.

FIG. 14 is a plan view of a diaphragm in a conventional example.

FIG. 15 is a sectional view of a diaphragm in a conventional example.

FIG. 16 is a circuit diagram of a main part of a conventional example.

[Explanation of symbols]

 41 piezoelectric ceramic element 42, 43, 44, 45 silver electrode 46 diaphragm 47 annular projection 48, 49 lead terminal 50, 51 lead

Continuation of the front page (56) References JP-A-63-289460 (JP, A) JP-A-62-24154 (JP, A) JP-A-3-269363 (JP, A) JP-A-3-142365 (JP) JP-A-61-270665 (JP, A) JP-A-3-142366 (JP, A) JP-A 64-5115 (JP, U) JP-A-4-1456 (JP, U) JP 4-3360 (JP, U) Table 2-503952 (JP, A) US Patent 4,331,935 (US, A)

Claims (2)

(57) [Claims] 1. A base, a disk-shaped diaphragm having a center fixed to the base, and positive and negative electrodes on the front and back surfaces of which are electrically conductively bonded to each other on both front and back surfaces of the diaphragm. Two piezoelectric ceramic elements divided into two concentric circles, lead terminals respectively connected to the respective electrodes of the piezoelectric ceramic elements, a circuit board for amplifying and filtering a signal output through the lead terminals, and An acceleration sensor comprising a piezoelectric ceramic element and a metal case for shielding the circuit board from the outside. 2. The acceleration sensor according to claim 1, wherein the two piezoelectric ceramic elements have the same material, size, and divided shape of the front and rear electrodes.