Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-05-23
2001-08-21
Ponomarenko, Nicholas (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S358000
Reexamination Certificate
active
06278223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a differential type piezoelectric actuator and in particular, to a differential type piezoelectric actuator of a high reliability which can control a very small displacement with a high accuracy and which can easily be mounted.
2. Description on the Prior Art
With a technical innovation nowadays, more and more fine and accurate positioning mechanism is required such as in a magnetic recording apparatus, a scan type tunnel microscope, an interatomic force microscope, and a stepper used in a semiconductor production apparatus. A piezoelectric material has a characteristic to expand and contract when voltage is applied and this displacement amount can be modified by the material, size, and voltage applied. An actuator employing such a piezoelectric material can control a very small displacement with a high accuracy and attracts attention of engineers. Moreover, a piezoelectric actuator has an advantage over an electromagnetic actuator in that no coil is required, the electromagnetic noise is low, and the size can be reduced.
Japanese Patent Publication No. 4-232678 [1] and others disclose a magnetic head positioning mechanism utilizing a differential type piezoelectric element in a magnetic disc apparatus. In this magnetic head positioning mechanism, two piezoelectric elements fixed to a head arm are connected to a support portion, and a pressure generated by expansion and contraction of the piezoelectric elements is transmitted to the support portion, which in turn rotates a tip end of a support spring connected to the support portion. Thus, positioning is controlled.
Moreover, Japanese Patent Publication No. 3-283580 [2] discloses a mechanism to enlarge a displacement generated by two piezoelectric elements, and Japanese Patent No. 2529380 [3] discloses a head positioning mechanism in which two piezoelectric elements are used to move a support spring in a radial direction of a disc.
However, the piezoelectric elements in the mechanism disclosed in document [1] are connected to both ends of movement of the elements. The pressure transmission loss at the connecting points is large. In order to compensate this loss, the piezoelectric element size should be large and the transmission loss generates a displacement hysteresis, which makes it difficult to control positioning with a high accuracy. Moreover, a stress generated by the repeated drive of the piezoelectric elements causes a destruction at the connection boundary, deteriorating reliability. Moreover, since both ends of the two piezoelectric elements are fixed, the size accuracy should be strict and a size adjustment by machining costs a lot.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a differential type actuator of a high reliability which can control a very small displacement with a high accuracy and can easily be assembled and mounted.
The differential type piezoelectric actuator according to the present invention comprises: a drive body having a unitary block of two piezoelectric element blocks and a base block formed from a material constituting the piezoelectric element blocks; and a support spring fixed to free ends in the longitudinal direction of the two piezoelectric element blocks, wherein a differential displacement obtained by expansion and contraction of the two piezoelectric element blocks generates a rotary movement of a tip end of the support spring.
According to another aspect of the invention, a stepped portion is provided at a corner of each free end of the piezoelectric element blocks.
According to still another aspect of the invention, the support spring has two protrusions at its end to be fixed to the free ends of the two piezoelectric element blocks, the two protrusions being fixed to the respective free ends of the two piezoelectric element blocks.
According to yet another aspect of the present invention, an electrode is arranged on both main surfaces of the piezoelectric element blocks in a thickness direction for applying voltage causing expansion and contraction of the piezoelectric element blocks in the length direction.
According to still yet another aspect of the present invention, each of the piezoelectric element blocks is made from conductive layers and piezoelectric material layers which are alternately layered in the thickness direction, and the expansion and contraction of the piezoelectric element blocks is obtained by expansion and contraction in the length direction generated when voltage is applied via the conductive layers.
According to yet another aspect of the present invention, an electrode is provided at the tip end and the bottom in the length direction of the respective piezoelectric element blocks, and the expansion and contraction of the piezoelectric element blocks is obtained by expansion and contraction in the length direction generated when voltage is applied in the length direction via the electrodes.
According to still another aspect of the present invention, each of the piezoelectric element blocks includes conductive layers and piezoelectric material layers which are alternately layered in the length direction, and the expansion and contraction of the piezoelectric element blocks is obtained by expansion and contraction in the length direction generated when voltage is applied in the thickness direction via the conductive layers.
According to still yet another aspect of the present invention, each of the piezoelectric element blocks is provided with electrodes arranged on its both main surfaces in the width direction, and the expansion and contraction of the piezoelectric element blocks is obtained by expansion and contraction in the length direction generated when voltage is applied in the width direction via the electrodes.
According to still another aspect of the present invention, each of the piezoelectric element blocks includes conductive layers and piezoelectric material layers which are alternately layered in the width direction, and the expansion and contraction of the piezoelectric element blocks is obtained by expansion and contraction in the length direction generated when voltage is applied in the width direction via the conductive layers.
REFERENCES:
patent: 4613782 (1986-09-01), Mori
patent: 6066911 (2000-05-01), Lindemann
patent: 3-283580 (1991-12-01), None
patent: 4-232678 (1992-08-01), None
patent: 2529380 (1996-06-01), None
Ochi Atsushi
Sasaki Yasuhiro
Addison Karen B
NEC Corporation
Ponomarenko Nicholas
Young & Thompson
LandOfFree
Differential type piezoelectric actuator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Differential type piezoelectric actuator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Differential type piezoelectric actuator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2503638