CAPACITANCE TYPE PHYSICAL QUANTITY SENSOR

• US 20150143906A1
• Filed: 06/06/2013
• Published: 05/28/2015
• Est. Priority Date: 06/13/2012
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ogawa, Akira
• Granted Patent: US 9,964,562 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/13 by measuring the force required to restore a proofmass subjected to inertial forces to a null position
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0882 for providing damping of vibrations

Abstract

A capacitance type physical quantity sensor including a movable electrode formed in a weight part, and a fixed electrode facing the movable electrode is provided. A first movable sensing electrode and a first fixed sensing electrode face each other in a first y direction. A second movable sensing electrode and a second fixed sensing electrode face each other in a second y direction. A first movable damping electrode is located in the middle between two first fixed damping electrodes, faces one of the first fixed damping electrodes in the first y direction and faces the other of the first fixed damping electrodes in the second y direction. A plurality of the first movable damping electrodes are located point-symmetrically with respect to the center of the weight part or line-symmetrically with respect to a center line passing the center in the y direction.

Claims

1. A capacitive physical quantity sensor comprising:

a substrate having one surface along a x-y plane, which is defined by a x direction and a y direction perpendicular to each other;

an anchor fixed to the one surface of the substrate;

a detection beam connected to the substrate through the anchor;

a weight connected to the detection beam;

a movable electrode formed in the weight; and

a fixed electrode opposed to the movable electrode on the x-y plane, wherein

the detection beam has flexibility in the y direction;

the movable electrode includes a first movable detection electrode, a second movable detection electrode and a first movable damping electrode;

the fixed electrode includes a first fixed detection electrode, a second fixed detection electrode and a first fixed damping electrode;

the first fixed detection electrode is located separately from the first movable detection electrode in a first y direction and is opposed to the first movable detection electrode in the first y direction, the first y direction being one direction in the y direction;

the second fixed detection electrode is located separately from the second movable detection electrode in a second y direction and is opposed to the second movable detection electrode in the second y direction, the second y direction and the first y direction are opposite directions;

the first movable damping electrode is located at a center between corresponding two of the first fixed damping electrodes and is opposed to one of the corresponding two of the first fixed damping electrodes in the first y direction and is opposed to the other of the corresponding two of the first fixed damping electrodes in the second y direction; and

a plurality of the first movable damping electrodes are located point-symmetrically with respect to the center of the weight, or line-symmetrically with respect to a center line, which passes through the center of the weight in the y direction.

2. The capacitive physical quantity sensor according to claim 1, wherein:

the weight has a frame shape in which ends of two first stick portions extending along the y direction are connected to ends of two second stick portions extending along the x direction; and

the first movable damping electrodes are formed in the first stick portions.

3. The capacitive physical quantity sensor according to claim 2, wherein:

the movable electrode includes a second movable damping electrode;

the fixed electrode includes a second fixed damping electrode;

the second movable damping electrode is formed in the second stick portions;

the second movable damping electrode is located at a center between two of the second fixed damping electrodes and is opposed to one of the two of the second fixed damping electrodes in a first x direction being one direction in the x direction and is opposed to the other of the two of the second fixed damping electrodes in a second x direction opposite to the first x direction; and

a plurality of the second movable damping electrodes are located point-symmetrically with respect to the center of the weight, or line-symmetrically with respect to the center line, which passes through the center of the weight in the y direction.

4. The capacitive physical quantity sensor according to claim 1, wherein:

the first movable damping electrodes have a geometrically similar relation with the first fixed damping electrodes; and

the first movable damping electrodes and the first fixed damping electrodes have a constant interval therebetween.

5. The capacitive physical quantity sensor according to claim 1, wherein:

a first fixed detection pad for taking out a capacitance formed between the first movable detection electrode and the first fixed detection electrode is formed in the first fixed detection electrode-;

a second fixed detection pad for taking out a capacitance formed between the second movable detection electrode and the second fixed detection electrode is formed in the second fixed detection electrode;

a movable detection pad for applying a constant voltage is formed in the weight;

a damping pad for applying a diagnostic voltage different in polarity from the voltage applied to the first movable detection pad is formed in the first fixed damping electrode;

the voltages having different polarities are applied to the first fixed detection pad and the second fixed detection pad for a predetermined time period, respectively; and

immediately after application of the voltages, the diagnostic voltage is applied to the damping pad and the capacitance of the first detection capacitor at a time of the voltage application is taken out from the first fixed detection pad and the capacitance of the second detection capacitor is taken out from the second fixed detection pad.

6. A capacitive physical quantity sensor comprising:

a substrate having one surface along a x-y plane defined by a x direction and a y direction perpendicular to each other;

an anchor fixed to the one surface of the substrate;

a detection beam connected to the substrate through the anchor;

a weight connected to the detection beam;

a movable electrode formed in the weight; and

a fixed electrode opposed to the movable electrode in a z-direction, which is perpendicular to the x-y plane,

wherein;

the detection beam has flexibility in the z-direction;

the movable electrode includes a first movable detection electrode, a second movable detection electrode and a first movable damping electrode;

the fixed electrode includes a first fixed detection electrode, a second fixed detection electrode and a first fixed damping electrode;

the first fixed detection electrode is located apart from the first movable detection electrode in a first z-direction being one direction in the z-direction and is opposed to the first movable detection electrode in the first z-direction;

the second fixed detection electrode is located apart from the second movable detection electrode in a second z-direction being opposite to the first z-direction and is opposed to the second movable detection electrode in the second z-direction;

each of a plurality of the first movable damping electrodes is located at a center between corresponding two of the first fixed damping electrodes, is opposed to one of the corresponding two of the first fixed damping electrodes in the first z direction, and is opposed to the other of the corresponding two of the first fixed damping electrodes in the second z direction; and

the plurality of the first movable damping electrodes are located point-symmetrically with respect to a center of the weight, or line-symmetrically with respect to a center line, which pass through the center of the weight in the z-direction.