Accelerated speed sensor

Abstract

An accelerated speed sensor (1A) having a high voltage sensitivity and capable of preventing reduction of polarization due to pyroelectric effect, comprises a piezoelectric element (2) and support members (10, 11) for supporting the piezoelectric element at both longitudinal ends thereof, the piezoelectric element is laminated with three piezoelectric layers (2a, 2b, 2c), each of the two outer piezoelectric layers (2a, 2c) are longitudinally divided into four units (1)-(4), (5)-(8), respectively, when being applied accelerated speeds. Interlayer electrodes (3, 4) and main surface electrodes (5a, 5b, 6a, 6b) are provided on the piezoelectric element (2) so that two cells (1, 2, 5, 6) on one side of the piezoelectric element and two cells (3, 4, 7, 8) on the other side are connected respectively, and the parallel-connected two sets of cells on the two sides are connected in series. The electrodes (5a, 6a), (5b, 6b) induced to different ends of the piezoelectric element (2) are connected with each other.

Description

technical field [0001] The present invention relates to an acceleration sensor using a piezoelectric element. Background technique [0002] Conventionally, as acceleration sensors using piezoelectric ceramics, such as Figure 11 As shown in (a), the piezoelectric element 20 having a bimorph structure in which two self-piezoelectric ceramic layers 21 and 22 are placed in close contact with each other and connected in series is held by one side. 23 and 24 are main surface electrodes, 25 is an interlayer electrode, 26 is a supporting portion, and 27 and 28 are extraction electrodes. Figure 11 (b) is a circuit diagram. In this case, the polarization directions P of the layers 21 and 22 are reversed in the thickness direction so that the voltages generated when the acceleration G is applied can be added. [0003] In the acceleration sensor having such a structure, when the temperature changes, a voltage is generated on each layer 21, 22 due to the pyroelectric effect. [0004]...

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Problems solved by technology

However, if there is concern about the decrease in insulation resistance as described above, the thickness of each layer cannot be made thin, so it is difficult to improve the sensitivity.

[0007] As mentioned above, when the layers are connected in series, the advantage is that the voltage sensitivity is high, but there is also a problem that the polarization is lowered due to the pyroelectric effect voltage.

In the case of connecting the layers in parallel, the advantage is that it can prevent the polarization drop due to the pyroelectric effect voltage, but the thickness cannot be made thin because of the fear of voltage sensitivity drop and insulation resistance drop, so the sensitivity cannot be improved.

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