Multilayer piezoelectric element, injection apparatus, and fuel injection system

Abstract

Provided is a multilayer piezoelectric element which achieves a high response speed and an increase in the displacement amount, ensures sufficient mechanical strength, and can suppress degradation of characteristics. A multilayer piezoelectric element (1) includes a layered body (7) in which a piezoelectric layer (3) and an internal electrode layer (5) are alternately layered. In the multilayer piezoelectric element (1), a polarization domain (12) lying astride a plurality of crystal grains (11) is formed in the piezoelectric layer (3). Since the polarization domain (12) lying astride the crystal grains (11) is formed in the piezoelectric layer (3), in the multilayer piezoelectric element (1), the response speed and the displacement amount can be increased, high mechanical strength is ensured, and degradation of characteristics can be suppressed.

Description

technical field [0001] The present invention relates to a laminated piezoelectric element, an injection device using the laminated piezoelectric element, and a fuel injection system. The multilayer piezoelectric element of the present invention is used, for example, as a driving element (piezoelectric actuator), a sensor element, and a circuit element. As the driving element, for example, a fuel injection device of a motor vehicle engine, a liquid injection device such as an inkjet head, a precision positioning device such as an optical device, and an anti-vibration device are exemplified. As the sensor element, for example, a combustion pressure sensor, a knock sensor, an acceleration sensor, a load sensor, an ultrasonic sensor, a pressure sensitive sensor, and a yaw rate sensor are exemplified. Moreover, as a circuit element, a piezoelectric gyroscope, a piezoelectric switch, a piezoelectric transformer, and a piezoelectric circuit breaker are mentioned, for example. Back...

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Problems solved by technology

[0004] In the above-mentioned multi-layer piezoelectric element, there is a problem that the movement of the domain wall is restricted by the grain boundary of the piezoelectric layer, and the response speed is slowed down.

Furthermore, since the movement of the domain walls is constrained by the grain boundaries of the piezoelectric layer, there is a problem that the amount of displacement of the multi-layer piezoelectric element is reduced.

In addition, in order to reduce the grain boundaries of the piezoelectric body layer, although the crystal grains can be enlarged, when the crystal grains of the piezoelectric body layer are large, the mechanical strength of the piezoelectric ceramics decreases, so there is a problem in the structure of the stack due to continuous driving. Cracks occur in the piezoelectric ceramics, that is, the piezoelectric layer of the piezoelectric element, and the displacement gradually decreases.

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