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AssigneesHitachi, Ltd., Hitachi Automotive Engineering Co., Ltd.
InventorsShigeki Tsuchitani, Seiko Suzuki, Tomoyuki Tanaka, Masayuki Miki, Masahiro Matsumoto, Norio Ichikawa, Hiromichi Ebine, Yukiko Sugisawa, Kanemasa Sato, Sadayasu Ueno, Yasuhiro Asano, Masanori Kubota, Masayoshi Suzuki
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A semiconductor acceleration sensor is formed by a cantilever having a conductive movable electrode of predetermined mass at one end, at least one pair of fixed conductive electrodes which are stationary with respect to the movable electrode located on opposing sides of the movable electrode, and gaps provided between the movable electrode and the fixed electrodes. To prevent the movable electrode becoming fused to the contacted fixed electrode, in a first aspect of this invention, an insulating layer is provided between the movable electrode and fixed electrodes, the layer being either on the movable electrode or on the fixed electrodes and in a second aspect the movable electrode or, preferably, the fixed electrodes, are formed of a high melting point material. In such a second aspect, to improve adhesion between the high melting point material and a substrate to which the fixed electrodes are mounted, a lower melting point material is firstly coated on the substrates. A sensor detector unit processing circuit has the output characteristic of the circuit digitally adjusted by suitable switching of a plurality of resistors, and the sensor chip and the detector unit integrated circuit may be located on a common base and mounted in a hermetically sealed chamber to prevent adverse environmental effects affecting operation of the sensor and detector unit assembly. A gas having a dew point of -40.degree. C. or lower is, advantageously, charged into the hermetically sealed chamber.
A semiconductor acceleration sensor comprising a cantilever having a conductive, movable electrode of predetermined mass at one end thereof, said cantilever being made of a material of silicon type, at least one fixed conductive electrode which is stationary with respect to said movable electrode and located on a side of said movable electrode, said fixed electrode being separated from said movable electrode by a predetermined gap, and insulation means located between the movable electrode and the fixed electrode for preventing a short-circuit therebetween, wherein
A semiconductor acceleration sensor in combination with an acceleration detector unit, said sensor comprising a cantilever having a conductive, movable electrode of predetermined mass at one end thereof, said cantilever being made of a material of silicon type, at least one pair of fixed conductive electrodes which are stationary with respect to said movable electrode and located on opposing sides of said movable electrode, said fixed electrodes being separated from said movable electrode by a predetermined gap, and insulation means located between the movable electrode and the fixed electrode for preventing a short-circuit therebetween, said detector unit comprising a processing circuit for processing signals from the sensor wherein said processing circuit comprises a first capacitor and a first switching means as a feedback element of an operational amplifier, a negative input terminal of said operational amplifier being connected to said movable electrode and a positive input terminal of said operational amplifier being connected to a predetermined reference voltage, a sample hold circuit comprising a second switching means and a second capacitor for detecting electrostatic capacitance difference between the movable electrode and each of the fixed electrodes as a voltage at the terminal of the operational amplifier, an amplification means for amplifying the output of the second switching means and second capacitor, means for generating a waveform train with a period the pulse width of which is modulated by the amplified signal, means for supplying the voltage waveform train to each of the fixed electrodes, means for turning the said first and second switching means ON or OFF for a predetermined period of time in synchronization with the voltage waveform train, means for converting the voltage waveform train to an analogue voltage, and an output adjustment means for adjusting the analogue voltage to a predetermined characteristic, wherein the sensor and detector unit are both located in a hermetically sealed chamber, the detector unit being an integrated circuit and the sensor being an integrated chip device, said integrated circuit and said chip device being both mounted on a base, and a cap is hermetically sealed to said base.
A semiconductor acceleration sensor comprising:
A semiconductor acceleration sensor comprising:
A semiconductor acceleration sensor comprising a cantilever having a conductive, movable electrode of predetermined mass at one end thereof, said cantilever being made of a material of silicon type, at least one fixed conductive electrode which is stationary with respect to said movable electrode and located on a side of said movable electrode, said fixed electrode being separated from said movable electrode by a predetermined gap, and insulation means formed in a defined pattern on at least one of the movable electrode and the fixed electrode for preventing a short circuit therebetween, said insulation means providing a roughened surface on said at least one of said movable electrode and the fixed electrode, wherein
A semiconductor acceleration sensor in combination with an acceleration detector unit, said sensor comprising a cantilever having a conductive, movable electrode of predetermined mass at one end thereof, said cantilever being made of a material of silicon-type, at least one pair of fixed conductive electrodes which are stationary with respect to said movable electrode and located on opposing sides of said movable electrode, said fixed electrodes being separated from said movable electrode by a predetermined gap, insulation means located directly on at least one of said movable electrode and the at least one pair of fixed conductive electrodes, said insulation means being shaped in a defined pattern which does not cover the entire surface of the electrode to which it is applied and said insulation means providing a roughened surface on said electrode to which it is applied, said detector unit comprising a processing circuit for processing signals from the sensor, wherein said processing circuit comprises a first capacitor and a first switching means as a feedback element of an operational amplifier, a negative input terminal of said operational amplifier being connected to said movable electrode and a positive input terminal of said operational amplifier being connected to a predetermined reference voltage, a sample hold circuit comprising a second switching means and a second capacitor for detecting electrostatic capacitance difference between the movable electrode and each of the fixed electrodes as a voltage at the output terminal of the operational amplifier, an amplification means for amplifying the output of the second switching means and second capacitor, means for generating a waveform train with a period the pulsewidth of which is modulated by the amplified signal, means for supplying the voltage waveform train to each of the fixed electrodes, means for turning the said first and second switching means ON or OFF for a predetermined period of time in synchronization with the voltage waveform train, means for converting the voltage waveform train to an analogue voltage, and an output adjustment means for adjusting the analogue voltage to a predetermined characteristic, wherein the sensor and detector unit are both located in a hermetically sealed chamber, the detector unit being an integrated circuit and the sensor being an integrated chip device, said integrated circuit and said chip device being both mounted on a base, a cap hermetically sealed to said base, and an inert gas in said predetermined gap between the movable electrode and said fixed electrodes, whereby said insulation means in said defined pattern prevents said gas from freely moving over said roughened surface and damping of said movable electrode is produced.
Dependencies are inferred from the claim text.