Mitsubishi Denki Kabushiki Kaisha

Nissan Motor Company Limited

Masahiro Tsugai

Nobuaki Konno

Eiji Yoshikawa

Hiroyuki Fujita

Yoshiaki Hirata

Mikio Bessho

Koichi Murakami

Hiroshi Otani

Toru Araki

Hiroshi Toshiyoshi

Yukitsugu Hirota

Makoto Mita

Takashi Sesekura

Yoshio Mita

An inertial detecting device for detecting a change in capacitance of a sensor element caused by inertial force includes a displaceable unit. The displaceable unit includes a movable mass member which is displaceable in the direction of an inertial force and is supported in a space by a pair of beams fixed on the substrate. At least one pair of detection units for detecting the displacement of the displaceable unit are provided on the substrate. The detection unit includes a drive unit and a pair of sensing electrodes which are disposed opposite to the displaceable unit. Any gap can be freely set between the sensing electrode and the movable mass member, thereby changing the sensitivity of the detecting device in a wide range.

Capacitance-type inertial detecting device

An acceleration sensor includes first and second fixed electrodes on a substrate, and a movable electrode located above the first and second fixed electrodes, with respect to the substrate, and facing them. The movable electrode is elastically supported on the substrate by a first elastic supporting body and is movable. A mass, which is elastically supported on the substrate by a second elastic supporting body, moves in response to an acceleration in a direction perpendicular to the substrate. A linking portion links the movable electrode and the mass at a position spaced from an axis of movement of the movable electrode by a distance. Acceleration is measured based on changes in a first capacitance between the first fixed electrode and the movable electrode and a second capacitance between the second fixed electrode and the movable electrode. Thus, a highly impact resistant and highly reliable acceleration sensor is obtained.

Acceleration sensor

A sensitive angular velocity sensor is provided without increasing an inter-electrode gap for inducing a torsional vibration. An angular velocity sensor which employs an electrostatic drive system for inducing drive vibration by using inter-electrode electrostatic attraction includes a pair of inertial mass members which are connected to each other through a connection frame having a length such that the inertial mass members are point-symmetrical with respect to a central point of the connection frame and which are held along a plane direction of a substrate, a pair of elastic beams which are connected to each other at an interval in opposite directions along a longitudinal direction from the central point of the connection frame on opposite sides of the connection frame, a pair of drive plates which are connected to the ends of the elastic beams, which have an electrode constituting an electrostatic attraction generating structure together with a drive electrode on the substrate, and which are supported such that the drive plates can be moved in at least one direction along the plane direction of the substrate to torsionally vibrate the inertial mass members about the central point of the connection frame.

Angular velocity sensor

A conventional angular rate sensor has a problem that the displacement amplitude of a drive gimbal frame is limited due to the Pulled-in phenomenon where the drive gimbal frame is attached to drive electrodes, thereby decreasing its sensor sensitivity. In an angular rate sensor, a drive frame and a driven frame are separately provided. A bending oscillation of the drive frame is transmitted to the driven frame through link beams, causing the rotational oscillation of the driven frame. The displacement amplitude of a rotational oscillation of the driven frame is not limited to provide high sensor sensitivity.

Angular rate sensor

A capacitance detecting circuit which can ensure flexibility in application without restriction imposed by a capacitance arrangement such as a single capacitance, differential capacitance, differential capacitance electrostatic servo and like arrangements, to a great advantage includes an operational amplifier having an inverting input terminal and an output terminal between which a feedback capacitance component is connected, a capacitance sensor having an electrostatic capacitance subjected to change under action of an external force, a switch for electrically charging the capacitance component of the capacitance sensor by connecting a charge/discharge terminal of the capacitance component to a reference voltage at a first clock timing for discharging the feedback capacitance component and switching the charge/discharge terminal to the feedback capacitance component at a second clock timing to transfer electric charge, and a sample-and-hold circuit for converting the transferred electric charge to the sensor output voltage.

Capacitance detecting circuit

A micro-mirror device includes a mirror forming substrate on which a mirror is disposed. A pair of torsion beams are disposed on opposing sides of the mirror forming substrate. An anchor projects from a supporting substrate, supporting the ends of the torsion beams. A driving frame surrounds at least one side of the torsion beams and is connected to the mirror forming substrate through a link beam. A drive force generator drives the driving frame.

Micro-mirror device

A movable electrode structure is formed in a single sensor element, and this movable electrode structure can be displaced along two axes within a plane, and one axis outside the plane. A detecting fixed electrode is provided via a constant space with each of these detecting axes, and a change in capacitances between the movable electrodes and the fixed electrodes is detected. As a result, the acceleration components of the two axes, or the three axes are detected. The dynamic characteristic of the sensor is controlled based on the mass of the variable electrode, the structure and length of the beam for supporting the movable electrode, and also the ratio of the length to the section of this beam.

Multi-axis acceleration sensor and manufacturing method thereof

A pressure switch with improved sealing of an airtight chamber, and improved electrical characteristics reducing chattering, increasing response rate, and minimizing the pressure necessary for activation. The pressure switch includes an upper substrate with a diaphragm readily deformed by an applied stress, a lower substrate overlapped with the upper substrate to form the airtight chamber, a contact electrically switched in response to the deformation of the diaphragm, and a sealing member continuously surrounding the airtight chamber, disposed between the first and second substrate, and hermetically sealing the airtight chamber.

Pressure switch

A vibrating type angular velocity sensor is comprised of: a driving vibrator element 8 supported by a first beam 9 fixed by an anchor portion 3 on a substrate, and driven by a driving comb electrode 12 along an X-axial direction parallel to the substrate; a detecting vibrator element 10 supported by a second beam 11 on the driving vibrator element and being vibratable along a Y-axial direction; and detection electrodes 14 and 15 of an electric capacitance provided with separated from the detecting vibrator element, and the detection electrodes along the X-axial direction, whereby an angular velocity while setting a Z-axial direction perpendicular to the substrate as an axis is detected. Furthermore, the driving vibrator element is fixed on the substrate by way of two sets of the anchor portions arranged at positions symmetrical to each other with respect to the detecting vibrator element. Also, one of the detection electrodes is arranged on the detecting vibrator element, and the other of the detection electrodes is arranged on the driving vibrator element with separated from each other by an equi-interval space.

Vibrating type angular velocity sensor

A semiconductor accelerometer switch having a fixed portion including a first control electrode and a movable portion including a movable body. By applying a voltage between the first control electrode and an electrode on the movable body, electrostatic attraction holds the movable body in an initial position. The movable body is displaced when acceleration having a magnitude in a direction acts on the switch. The threshold of acceleration to be detected and general-purpose properties of the accelerometer switch are easily adjusted.

Semiconductor accelerometer switch

An interface circuit for a capacitive sensor capable of outputting a detection signal with high stability and reliability while suppressing to a minimum the influence of offset and temperature dependency onto the output signal. In a differential capacitance type sensor having a common electrode connected to the ground potential, an electric discharge redistributing method and impedance conversion technique are adopted for obtaining an output voltage which is in proportion to the inter-electrode relative displacement. A switching mechanism is provided for mitigating an offset voltage component contained in the output due to an input offset voltage of the operational amplifier. Further, the sensitivity of the capacitive sensor is increased with the temperature-dependent drift of the sensor output being suppressed by providing additionally a power source change-over switches for allowing the voltages sampled in response to predetermined clocks to be differentially amplified.

Interface circuit for capacitive sensor

A method of micromachining a silicon wafer that simultaneously forms narrow gaps having a width of 10 .mu.m or less and wider gap portions using an anistropic etching solution. The etching solution contains KOH in a concentration of 35% or less and the penetration etching is carried out such that the etching of the opposing walls and the face of the silicon wafer occur at the same rate. A method of manufacturing a capacitance-type acceleration detector in a silicon wafer using the aforementioned etching method.

Method of micromachining a semiconductor

In an interface circuit connected to a capacitance type sensor having two sets of capacitors C1 and C2 whose capacitances are varied, this interface circuit is equipped with an OP amplifier A1 where a feedback/sampling capacitor C3 is connected between its output terminal and its inverting input terminal; and a holding capacitor C4 connected between a non-inverting terminal of the OP-amplifier A1 and a reference voltage source; one ends of the respective capacitors C1, C2, C3 are connected to the inverting input terminal of the OP amplifier A1; at timing .phi.1 of a switching cycle, the other ends of the respective capacitors C1, C2 are connected to a power source and the capacitor C3 is shortcircuited; at timing .phi.2 thereof, the other ends of the capacitors C1, C2 and an output terminal of the OP amplifier A1 are connected to the non-inverting input terminal of the OP amplifier A1; and the switched capacitor type interface interface circuit further includes: a multiplexer for sequentially connecting a plurality of the capacitance type sensors to the capacitance type sensor interface circuit in a second switching cycle having a time period longer than time periods of the switching cycles .phi.1 and .phi.2; and a plurality of sample/hold circuits whose quantity is equal to those of the plural capacitance type sensors, which are sequentially connected to the capacitive type sensor interface circuit in response to the connections of the plural capacitance type sensors in the second switching cycle.

Capacitance type sensor interface circuit

In a switched-capacitor type interface circuit connected to a capacitive sensor having two capacitors (C1, C2) whose value is variable, the interface circuit includes an operational amplifier (A1) with an output terminal and an inverting input terminal between which a feedback/sampling capacitor (C3) is connected, and a holding capacitor (C4) connected between the operational amplifier (A1) and a reference voltage source. The capacitors (C1, C2, C3) have one ends connected to the inverting input terminal of the operational amplifier (A1). The other ends of the capacitors (C1, C2) are connected to a power source and the capacitor (C3) is concurrently short-circuited depending upon predetermined timing, and the other ends of the and capacitors (C1, C2) and the output terminal of the operational amplifier (A1) are respectively connected to a non-inverting input terminal of the operational amplifier (A1) after the elapse of a predetermined time from the predetermined timing.

capacitive sensor interface circuit

A method for compensating an offset voltage temperature drift in a semiconductor strain gage sensor in which a temperature-sensitive power supply is modeled as the one for providing the output voltage V.sub.0 =KV.sub.S (1+.alpha.T), and, under the condition that the resistance of the compensating resistor and the coefficient .alpha. are within practical ranges, respectively, the parameter K is determined so as to minimize the compensating error, thereby both of the primary order term and the secondary order term with respect to the temperature in the offset voltage of the strain gage can be compensated so that the offset temperature drift can be reduced.

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Tokyo, Japan

Masahiro Tsugai