JPS6246267A - Oscillation sensor - Google Patents

Abstract

PURPOSE:To reduce the size of an oscillation sensor by integrating the bending oscillator of an oscillation detector and an electric circuit for processing signals in one laminated piezoelectric element. CONSTITUTION:Disk-shaped piezoelectric elements 1a and 1b having polarizing axes in the direction of thickness constitute a laminated piezoelectric element 1, which is formed with slits 2 and a portion surrounded by the slits 2 forms a bending oscillation mode oscillator 3. The upper, lower and adhered surfaces of the oscillator 3 are provided with electrodes thereon and, when the elements 1a and 1b are so sticked together that the direction of the polarizing axes of the elements 1a and 1b are reverse to each other, the electrodes on the upper and lower surfaces of the oscillator 3 form electrodes for taking out an output. A fixing member 5 with a groove 6 formed in an area against which the oscillator 3 abuts is fixedly mounted to the element 1 by adhesion or the like so that the member 5 is conducted with the lower surface electrode of the oscillator 3 and the surroundings of the oscillator 3 are fixed. Further, an electrode 4 capable of constituting an electric circuit is provided on the upper surface of the element 1 except the oscillator 3 and the upper surface electrode of the oscillator 3 and the input electrode of the electric circuit are common, constituting a signal-processing circuit for impedance transformation and the like, said signal-processing circuit having the member 5 earthed to the electric circuit. Thus, the size of an oscillation sensor can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vibration sensor suitable for detecting elastic vibrations in a vibrating body, particularly a resonant vibration sensor with excellent detection sensitivity at a predetermined frequency, and a non-resonant vibration sensor suitable for detecting elastic vibrations in a vibrating body. This relates to acceleration sensors used in

Conventional technology Conventionally, piezoelectric sensors that detect elastic vibrations in a vibrating object have been either resonant type sensors that match the resonance frequency to the natural frequency of the vibrating object and detect only specific frequency components, or non-resonant sensors that detect vibration components in a predetermined frequency range. A rectangular bonded piezoelectric vibrator, which has a cantilever structure in a bending vibration mode, is widely known, and is designed to improve sensitivity, especially at low frequencies.

In the case of a vibration sensor with a cantilever structure, it is difficult to achieve the fixing condition of fixing the vibrator at one end, but
A bending surface vibrator with a cantilever structure, which is a vibration detection portion as shown in Publication No. 0923, is fabricated by cutting a groove in a disk-shaped bonded piezoelectric element, and the bending vibrator is attached to one end of the disk-shaped bonded piezoelectric element. In some cases, the bonded piezoelectric element is integrated with a disk and has a structure in which the peripheral portion of the disk is fixedly supported, thereby stabilizing the fixing conditions. The signal of such a piezoelectric vibration sensor is outputted as a predetermined output signal through a separately prepared charge amplifier or voltage amplifier.

Problems to be Solved by the Invention In such conventional vibration sensors, the lower the frequency, the higher the output impedance of the sensor becomes, making it easier for ambient noise to enter. In addition, noise countermeasures for the circuit must be taken into consideration, making it expensive. Or, if the signal processing circuit part is built into the sensor and the signal is output at low impedance to reduce the influence of noise,
There was a problem in that the circuit part hindered miniaturization of the sensor.

Accordingly, the present invention integrates the vibration detection portion and the signal processing circuit to reduce the influence of noise and to achieve miniaturization at low cost.

Means to Solve the Problem A flexural vibration mode vibrator was created by providing a cutout in a bonded piezoelectric element, which has a structure in which two plate-shaped piezoelectric elements having polarization axes in the thickness direction whose periphery is fixed are bonded together. In addition, an electric circuit for processing the output signal of the bending vibrator is configured on the upper surface of the bonded piezoelectric element excluding the bending vibrator section.

By integrating the bending vibrator part that detects operational vibration and the signal processing circuit, there is no need for a connecting cable between the signal of the vibration detection section and the processing circuit, and if the signal processing circuit is voltage amplification, the cable capacity is reduced. Uniform sensor sensitivity can be obtained. In addition, converting the high impedance output of the vibration detection section to low impedance using a signal processing circuit has the great advantage of being less susceptible to external noise and allowing cables to be connected to the outside using regular electric wires, making it cheaper and more compact. This makes it possible to mass-produce the product.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view showing an embodiment of a vibration sensor according to the present invention. The disk-shaped piezoelectric elements 1a and 1b having polarization axes in the thickness direction are laminated together.A "U"-shaped slit (cutout) 2 is formed in the laminated piezoelectric element 1 by laser processing or the like. The portion surrounded by the slit 2 becomes a flexural vibration mode vibrator 3 having a cantilever structure. The bending vibrator 3 has electrodes on the upper and lower surfaces and the bonding surface,
When the piezoelectric elements 1a and 1b are pasted together so that their polarization axes directions are opposite to each other, the upper and lower surface electrodes of the bending sensor 3 serve as output extraction electrodes. A fixing member 5 made of a conductive material such as metal and having a groove 6 in the part where the bending vibrator 3 contacts is bonded to the piezoelectric element 1 so as to be electrically connected to the lower electrode of the bending vibrator 3. and the periphery of the bending vibrator 3 is used. The top surface of the bonded piezoelectric element, excluding the bending vibrator 3, has an electrode 4 that can form an electric circuit. As a result, a signal processing circuit such as impedance conversion is configured. The laminated piezoelectric element 1 excluding the bending vibrator 3 is necessary to stabilize the fixing condition of fixing one end of the cantilever structure, but a signal processing circuit is configured in this part regardless of vibration detection. This allows for miniaturization, and the signal processing circuit converts the output signal to low impedance, making it resistant to external noise. It also eliminates the need for printed circuit boards and special cables, making it inexpensive and easy to mass-produce. It becomes something.

FIG. 2 shows an example of the case assembled as a photographic sensor, in which the fixing member 6 is made of a resin-based copper clad plate such as epoxy, and the laminated piezoelectric element and signal processing circuit part 7 are made of metal. After forming a shield with a polyurethane resin or the like, it is molded with a polyurethane resin or the like. By using a copper clad plate as the fixing member, input and output to the signal processing circuit can be performed using the copper foil of the fixing member 5, and the groove 6 in the part where the bending vibrator hits can be easily made by etching the copper foil. This makes it easy to assemble and highly suitable for mass production.

Effects of the Invention According to the present invention, by integrating the bending vibrator of the vibration detection section and the signal processing electric circuit into the same bonded piezoelectric element, the sensor can be made smaller and more resistant to external noise. This eliminates the need for printed circuit boards, special cables, etc., making it inexpensive and highly suitable for mass production.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a vibration sensor according to an embodiment of the present invention, and FIG. 2 is a perspective view of the same embodiment after assembly. 1... Bonded piezoelectric element, 2... Slit, 3... Bending mode vibrator, 6...
・Fixed member. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) A bonded piezoelectric element having a structure in which two plate-shaped piezoelectric elements having polarization axes in the thickness direction are bonded together, a fixing member that fixes the periphery of the bonded piezoelectric element, and a cutout in the bonded piezoelectric element. a rectangular bending vibration mode vibrator formed by providing a rectangular bending vibration mode vibrator, electrodes provided on the upper and lower surfaces of the rectangular bending vibrator and a bonding surface, and a bonded piezoelectric element excluding the rectangular bending vibrator portion. A vibration sensor comprising: an electrode constituting an electric circuit on an upper surface; and an electric circuit configured on the upper surface of the bonded piezoelectric element. (2) The vibration sensor according to claim 1, wherein the fixing member fixing the periphery of the bonded piezoelectric element is made of a conductive material. (3) The vibration sensor according to claim 1, wherein the fixing member for fixing the periphery of the bonded piezoelectric element is made of a resin-based copper clad plate.