Murata Manufacturing Co., Ltd.

Yoshihiro Konaka

Shinji Kobayashi

Takahiro Oguchi

Teruhisa Shibahara

Hiroshi Kawai

Yoichi Mochida

Eiichi Takata

Masato Kobayashi

Yasutaka Fujii

Koichi Yoshida

Kazufumi Moriya

Koji Takemura

Toshiya Kawate

Yosuhiro Negoro

A variable capacitance device includes a fixed substrate, a movable portion, driving electrodes, an RF capacitance electrode and an insulating film. The movable portion faces the fixed substrate and can change a gap between the movable portion and the fixed substrate. The driving electrodes are formed on the fixed substrate so as to face the movable portion. The RF capacitance electrode is formed on the fixed substrate so as to face the movable portion and be spaced apart from the driving electrodes. The insulating film is formed between the movable portion and the driving electrodes. The level of a voltage applied to the driving electrodes and the level of a voltage applied to the movable portion are periodically switched and the level of a voltage applied to the RF capacitance electrode and the level of a voltage applied to the movable portion are always the same.

Variable capacitance device

In an acceleration sensor, a first vibrator is arranged on a surface of a substrate such that the vibrator can vibrate in an X-axis direction. An angular-velocity-detecting vibrator is arranged inside the first vibrator such that the vibrator can be displaced in a Y-axis direction. A vibration generating unit and a vibration monitor unit are provided between the substrate and the first vibrator. An angular-velocity-detecting displacement detecting unit is provided between the substrate and the angular-velocity-detecting vibrator. A second vibrator is provided outside the first vibrator such that the vibrator can be displaced in the Y-axis direction. An acceleration-detecting displacement detecting unit is provided between the first and second vibrators. An angular velocity detecting circuit detects angular velocity by performing synchronous detection on a displacement detection signal from the displacement detecting unit using a monitor signal from the vibration monitor unit. On the other hand, an acceleration detecting circuit detects acceleration by performing synchronous detection on a displacement detection signal from the displacement detecting unit using a monitor signal from the vibration monitor unit.

Composite sensor and acceleration sensor

A variable capacitance element includes a movable element provided above a substrate using supporting portions and support beams so as to be displaced from the substrate. An insulating film and a movable electrode are provided on a conductor facing surface of the movable element. A driving electrode is arranged to displace the movable element, between a signal cutoff position and a signal passage position, whereby a high frequency signal transmitted through a transmission line is cut off or allowed to pass. The insulating film uses compressive stress to warp the movable element and the movable electrode in a direction of warping in a convex form toward the transmission line, and maintains this warping direction.

Variable capacitance element

A variable capacitance element includes a coplanar line or signal conduction and a movable body, which are vertically displaced through a supporting bar and which are provided on a substrate. A movable electrode is provided between a first driving electrode and second and third driving electrodes which are movable electrodes. Voltage is applied between the movable electrodes, such that one of the movable electrodes is pressed against the coplanar line through a dielectric film. Thus, high frequency signals conducting through the coplanar line are shut off. When voltage is applied between the other electrodes, the movable electrode and the dielectric film are moved apart from the coplanar line. Thus, high frequency signals are conducted through the coplanar line.

A vibrator includes: a vibrating body; a driving unit for causing the vibrating body to vibrate in a predetermined vibrating direction; and a driving monitoring unit for detecting vibration displacement in a driving direction of the vibrating body. Stabilization of vibration in the driving direction of the vibrating body is achieved by applying positive feedback control to the driving unit based on the state of the vibration displacement in the driving direction of the vibrating body detected by this driving monitoring unit. The driving monitoring unit is constructed and arranged so as to be provided in a barycentric region of the vibrating body to detect the vibration displacement in the driving direction of the barycentric region of the vibrating body.

Process of making an acceleration detecting element

An angular velocity sensor includes four mass members which are connected by retaining beams, and the retaining beams are fixed to a substrate at node portions which correspond to nodes of the retaining beams when the mass members vibrate such that two adjacent mass members are in opposite phases. The mass members vibrate in an X-axis direction while the overall center of gravity is maintained at an approximately constant position. Two mass members disposed at the central region move in a Y-axis direction in accordance with an angular velocity about a Z axis, and the angular velocity is detected on the basis of the displacements thereof. The mass members vibrate in a stable vibrational state and dimensional errors or other problems, are compensated for by their shapes that are symmetric to each other in the Y-axis direction. Accordingly, the detection accuracy and reliability of the sensor are improved.

Angular velocity sensor

An external-force detecting sensor includes a sensor unit for commonly detecting angular velocity and acceleration; an angular-velocity/acceleration mix signal outputting unit for outputting an angular-velocity/acceleration mix signal comprised of an angular-velocity component in accordance with the magnitude of angular velocity and an acceleration component in accordance with the magnitude of acceleration that are detected by the sensor unit; and a signal separating unit for separating and extracting the angular-velocity component and the acceleration component from the angular velocity/acceleration mix signal to output as an angular-velocity signal and an acceleration signal.

External-force detecting sensor

An RF-MEMS device includes a substrate, a coplanar line arranged on the substrate, a movable element disposed above the coplanar line, and a movable electrode arranged on the movable element so as to face the coplanar line. The movable element includes a high-resistivity semiconductor functioning as an insulator for an RF signal and functioning as an electrode for a low-frequency signal and a DC signal. Electrostatic attraction caused by a DC voltage applied between the movable element functioning as the electrode and a fixed electrode displaces the movable element towards the fixed electrode, thereby varying the capacitance between the movable electrode and the coplanar line. The movable element made of a high-resistivity semiconductor has dielectric loss characteristics in which the dielectric loss decreases as the frequency of a signal increases, thus readily reducing the dielectric loss of an RF signal.

RF microelectromechanical systems device

When a cavity accommodating movable portion of an external force detecting sensor has a narrow structure, the external force detecting sensor is influenced by air damping, and therefore the cavity should have a wide structure. However, when a top surface and bottom surface of the cavity are positioned too high, the range of vertical movement of the movable portion is increased, and when an external impact force is applied to the external force detecting sensor, a movable interdigitated electrode rides on fixed interdigitated electrodes and stays there, thus the external force detecting sensor is rendered inoperable. A height D from the fixed interdigitated electrodes to the top surface and bottom surface of the cavity is set by having, as elements, widths of the movable interdigitated electrode, and fixed interdigitated electrodes set to W , W , and W , the height of the movable interdigitated electrode and fixed interdigitated electrodes set to h, and gaps between the movable interdigitated electrode and fixed interdigitated electrodes set to g and g , and the movable portion is structured so as to securely return to the standstill position due to resiliency of a beam.

External force detecting sensor

An angular velocity sensor includes a support body, a plurality of beams individually supported by the support body, and a coupling part with which a plurality of the beams are commonly coupled, and a vibrating weight formed on the coupling part, wherein each beam comprises a wide beam part and a narrow beam part narrower than the wide beam part.

An angular velocity sensor includes a board, a first vibrator, a second vibrator, a vibration generator, a displacement detector and a frequency adjuster. The first vibrator is supported on the board through first supporting beams and arranged so as to be vibrated in the direction of a first axis. The second vibrator is supported on the first vibrator through second supporting beams and arranged so as to be vibrated in the direction of the first axis and in the direction of a second axis at a right angle to the direction of the first axis. The vibration generator cause the first vibrator to vibrate in the direction of the first axis. The displacement detector detects a displacement of the second vibrator in the direction to the second axis when an angular velocity has been applied around a third axis at right angles with the first and second axes. The frequency adjuster adjusts a vibrating side resonance frequency at the time when the first vibrator is vibrated in the direction of the first axis and adjusts a detecting side resonance frequency at the time when the second vibrator is vibrated in the direction of the second axis by an angular velocity applied around the third axis.

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Sagamihara, Japan

Yoshihiro Konaka