Murata Manufacturing Co., Ltd.

Murata Mfg. Co., Ltd.

Jun Tabota

Jiro Inoue

Toshihiko Unami

Muneharu Yamashita

Toshihiro Mizuno

Mitsugu Ogiura

Atsushi Mikado

Hiroshi Asano

Keiichi Kami

Yasuharu Matsui

Atsushi Morikawa

Takeshi Eimori

Chikahiro Horiguchi

Masato Koike

Kenji Matsuo

Shinya Oguri

Kosuke Watanabe

Masayuki Ichimaru

Shiro Makino

Tomohiko Kiyohara

An ultrasonic sensor including a case having a bottom portion, and a piezoelectric element that is bonded to an inner surface of the bottom portion and performs bending vibration together with the bottom portion. The piezoelectric element includes a piezoelectric layer having a transmission region and a reception region, a common electrode, a transmission electrode opposing the common electrode with the transmission region interposed therebetween, and a reception electrode opposing the common electrode with the reception region interposed therebetween. The transmission region and the reception region are formed at positions adjacent to each other.

Ultrasonic sensor

A tuning fork-type vibrator includes a tuning fork-type vibrating body including a base and legs. The tuning fork-type vibrating body includes two piezoelectric substrates, an intermediate electrode, surface electrodes and an entire-surface electrode that are laminated together. The surface electrodes are separated by separating portions extending from the base to each of the legs. The widths of the separating portions at a point of connection to the circuit board are wider than those of the separating portions at other points. The separating portions are formed by dividing an electrode provided on the entire surface of a piezoelectric substrate in the vibrating body with a dicer or by laser radiation or etching.

Tuning fork-type vibrator, tuning fork-type vibrator manufacturing method, and angular velocity sensor

An acceleration sensor includes a detection element having a plurality of piezoelectric ceramic layers laminated together and a pair of retaining members that retain an end portion of the detection element in a longitudinal direction thereof at two principal surfaces of the end portion. The detection element includes electrodes between the ceramic layers and on principal surfaces. The detection element obtains a voltage or a charge generated in the detection element in response to an application of acceleration from the principal-surface electrodes and the interlayer electrodes. The piezoelectric ceramic layers are not polarized in areas between the principal-surface electrodes and the interlayer electrodes within a retaining area in which the detection element is retained by the retaining members.

Acceleration sensor

An acceleration sensor outputs a signal in accordance with acceleration. A differentiator outputs a differential signal of the output signal. A comparator inverts the state of an output when the differential signal goes beyond a threshold. A monostable multivibrator maintains the state-inverted signal of the output for a predetermined period of time. An integrator integrates the acceleration detection signal. A comparator inverts the state of an output signal when an integrated signal goes beyond a threshold. A fall determination processor outputs a signal out indicating that a fall has been detected in a situation in which, when the output of the monostable multivibrator is active, the state of the output of the comparator is inverted.

Fall detection device and magnetic disk drive

An acceleration sensor in which a difference in resonance characteristics between two resonators can be easily adjusted even when casing components are already attached to an acceleration-sensor element includes a bimorph acceleration-sensor element having first and second resonators attached to opposite sides of a base plate with respect to a direction in which acceleration is applied. One longitudinal end or both longitudinal ends of the acceleration-sensor element is/are fixed such that the first and second resonators bend in the same direction in response to the acceleration. Changes in frequency or changes in impedance in the first and second resonators caused by the bending of the acceleration-sensor element are differentially detected in order to detect the acceleration. Opposite sides of the acceleration-sensor element with respect to the application direction of acceleration are respectively covered with a pair of casing components. Electrodes disposed on the main surfaces of the respective first and second resonators face one of opposite open planes defined by a combination of the acceleration-sensor element and the casing components with respect to a direction perpendicular to the application direction of acceleration. Accordingly, a trimming process for the electrodes can be readily performed.

A compact, highly sensitive acceleration sensor that is not affected by factors other than acceleration, such as a change in temperature, includes a bimorph acceleration-sensor element including first and second resonators and attached to opposite sides of a base plate with respect to a direction in which acceleration is applied. One longitudinal end or both longitudinal ends of the acceleration-sensor element is/are fixed such that the resonators bend in the same direction in response to the acceleration. Changes in frequency or changes in impedance in the resonators caused by the bending of the acceleration-sensor element are differentially detected in order to detect the acceleration. The acceleration-sensor element is bendable about a central bending plane Nin response to the acceleration, the central bending plane Nbeing positioned at a central portion of the base plate with respect to the application direction of acceleration. Electrodes are disposed on main surfaces of the resonators, the main surfaces being substantially perpendicular to the application direction of acceleration. The height Hof the resonators in a direction that is substantially perpendicular to the application direction of acceleration is smaller than the height Hof the base plate in the direction that is substantially perpendicular to the application direction of acceleration.

Acceleration sensor having resonators with reduced height

A compact, high-sensitivity acceleration sensor that is prevented from being affected by factors other than acceleration, such as a change in temperature, has a bimorph acceleration-sensor element including first and second resonators attached to opposite sides of a base plate with respect to a direction in which acceleration is applied. One longitudinal end of the acceleration-sensor element is fixed such that the first and second resonators bend in the same direction in response to the acceleration. Changes in frequency or changes in impedance in the first and second resonators caused by the bending of the acceleration-sensor element are differentially detected in order to detect the acceleration. The acceleration-sensor element is bendable about a central bending plane in response to the acceleration, the central bending plane being positioned at a central portion of the base plate with respect to the application direction of acceleration. A vibrating section of each of the first and second resonators is disposed close to the fixed end of the acceleration-sensor element.

An acceleration sensor includes a piezoelectric element and a support member for supporting the piezoelectric element at both longitudinal ends thereof. The piezoelectric element includes a laminate having a plurality of piezoelectric layers. An intermediate piezoelectric layer is a dummy layer which generates no charge when acceleration is applied thereto. Each of the two outer piezoelectric layers includes four longitudinally aligned regions separated at two borders and one central border where stress is inverted when the acceleration is applied. The two outer piezoelectric layers are polarized in the direction of thickness of the piezoelectric element such that cells adjacent to each other in the longitudinal direction of the piezoelectric elements have opposite polarization directions and such that cells aligned with each other in the direction of thickness have the same polarization. Electrodes are arranged on the top and bottom major surfaces of the piezoelectric element and between the piezoelectric layers so that two cells on one side of the central border are connected in parallel with the other two cells on the other side of the central border are connected in parallel in each of the two outer piezoelectric layers, and so that the two parallel-connected cells in the one side are serially connected with the other two parallel-connected cells on the other side. At least one of the electrodes on each of the top and bottom major surfaces and between the layers extends to different longitudinal end surfaces of the piezoelectric element.

An acceleration sensor includes a piezoelectric element and a support member for supporting the piezoelectric element at both longitudinal ends thereof. The piezoelectric element includes a laminate of at least two piezoelectric layers. Each of the at least two piezoelectric layers includes three longitudinally aligned regions separated at two borders where stress is inverted in the longitudinal direction of the piezoelectric element when acceleration is applied. Cells, each formed of a respective region, are polarized in the same direction of thickness in each of the two external piezoelectric layers. Electrodes are arranged so that the three cells in the one piezoelectric layer are serially connected, the three cells in the other piezoelectric layer are serially connected, and then the three serially connected cells in the one piezoelectric layer and the three serially connected cells in the other piezoelectric layer are connected in parallel. Electrodes are routed out to the different longitudinal ends of the piezoelectric element.

An acceleration sensor including a bimorph type acceleration detection element including a pair of surface acoustic wave resonators laminated to each other with the back surface of one resonator bonded to the back surface the other resonator. Each resonator includes a piezoelectric substrate and a pair of IDT electrodes which are arranged on the front surface of the piezoelectric substrate. The acceleration detection element is supported at the end thereof so that the acceleration detection element is deflected in the direction of thickness under acceleration. Acceleration is detected by detecting a difference between frequency changes of the two surface acoustic wave resonators or a difference between impedance changes of the two surface acoustic wave resonators, which takes place under acceleration.

An acceleration sensor includes a first resonator and a second resonator which resonate at independent frequencies and each of which includes a piezoelectric body and electrodes arranged on both main surfaces thereof, and a first base plate and a second base plate. A first unimorph type acceleration detection element includes the first resonator bonded to one surface of the first base plate, and a second unimorph type acceleration detection element includes the second resonator bonded to one surface of the second base plate. Each of the first and second unimorph type acceleration detection elements is fixed at one longitudinal end thereof or opposed longitudinal ends thereof such that the first resonator and the second resonator are diametrically opposed to each other or are arranged to face each other to allow the first resonator and the second resonator to independently deflect in response to the application of acceleration. When the two acceleration detection elements are independently deflected in response to the application of acceleration, acceleration is detected by detecting a difference between frequency changes of the first resonator and the second resonator or a difference between impedance changes of the first resonator and the second resonator.

An acceleration sensor includes a sensing element and a pair of supporting members for supporting the sensing element at one end in the longitudinal direction thereof. The sensing element includes four laminated piezoelectric layers, and electrodes are provided at the center in the thickness direction of the sensing element, between a pair of first layers and a pair of second layers, and on the outer surfaces of the pair of second layers. Cells formed by the first and second layers at each side of the center in the thickness direction are electrically connected in parallel. The pair of first layers preferably have substantially the same thickness and the pair of second layers preferably have substantially the same thickness, and the ratio of the thickness T of each first layer to the total thickness T of each first and second layer is about 62% to about 76%.

A piezoelectric type acceleration sensor which is small in size and has a high charge sensitivity and large static capacitance includes a piezoelectric element having a laminate of more than three piezoelectric layers. Electrodes are provided between the piezoelectric layers and the top and bottom surfaces of the laminate. The piezoelectric element is supported at opposed ends. Adjacent ones of the piezoelectric layers are polarized so that charge having the same polarity is accumulated at the electrode interposed the adjacent ones.

An acceleration sensor includes a bimorph type acceleration detection element including a first resonator and a second resonator, each resonator formed of a piezoelectric body and having electrodes arranged on both main surfaces thereof, and an intermediate layer. The acceleration detection element is produced by bonding the first resonator and the second resonator with the intermediate layer interposed therebetween. The acceleration detection element is supported at one longitudinal end or opposed longitudinal ends thereof so that the first and second resonators are integrally deflected under acceleration. The intermediate layer is hard enough to transfer flexural stress in one of the first and second resonator to the other of the first and second resonators and the vibration of the one of the first and second resonators is attenuated when the vibration is transmitted from the one to the other of the first and second resonators. Acceleration is detected by detecting a difference between frequency changes of the first resonator and the second resonator or a difference between impedance changes of the first resonator and the second resonator, which takes place under acceleration.

An acceleration sensor module capable of performing sensitivity adjustment in a minimum arrangement without containing an amplifier includes an acceleration sensor and a trimmable resistor which are mounted on a printed wiring board. At least one terminal of the acceleration sensor and at least one terminal of the trimmable resistor are connected to at least one external connection terminal of the printed circuit board through printed wiring.

Growing community of inventors

Toyama-ken, Japan

Jun Tabota