Capacitive type physical quantity detecting sensor for detecting physical quantity along plural axes

• US 20030070484A1
• Filed: 09/05/2002
• Published: 04/17/2003
• Est. Priority Date: 10/16/2001
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Itakura, Toshikazu
• Granted Patent: US 6,668,614 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A control signal generator transmits a first signal to a movable electrode and a fixed electrode to detect a change in a capacitance formed between the movable electrode and the fixed electrode during a normal physical quantity detection timing interval. Also, the control signal generator transmits a second signal to the movable electrode and the fixed electrode instead of the first signal to move the movable electrode for diagnosing a malfunction of each of a plurality of physical quantity detection portions during a self diagnosis timing interval. The control signal generator transmits the second signal to the movable electrode and the fixed electrode of each physical quantity detection portion during a different timing intervals.

Claims

1. A capacitive type physical quantity detecting sensor comprising:

a plurality of physical quantity detection portions for detecting a physical quantity, the plurality of physical quantity detection portions respectively including;

a movable electrode that moves based on a physical quantity change;

a fixed electrode disposed to face the movable electrode;

a control signal generator for generating control signals;

a C-V converter for outputting a voltage that corresponds to a change of a capacitance formed between the movable electrode and the fixed electrode; and

a signal processing circuit for processing the output voltage from the C-V converter and for outputting a signal corresponding to the physical quantity change;

wherein the control signal generator transmits a first signal to the movable electrode and the fixed electrode to detect the change in the capacitance formed between the movable electrode and the fixed electrode during a normal physical quantity detection timing interval, and transmits a second signal to the movable electrode and the fixed electrode to move the movable electrode for diagnosing a malfunction of each of the physical quantity detection portions in a self diagnosis timing interval,

the control signal generator transmits the second signal to the movable electrode and the fixed electrode of each physical quantity detection portion at different timing intervals.

2. The capacitive type physical quantity detecting sensor according to claim 1, wherein the control signal generator transmits the second signal to the movable electrode and the fixed electrode of a first one of the plurality of physical quantity detection portions, and transmits the second signal to the movable electrode and the fixed electrode of a second one of the physical quantity detection portions after the movable electrode of the first one of the plurality of physical quantity detection portions at least substantially stops.

3. The capacitive type physical quantity detecting sensor according to claim 1, wherein:

in the normal physical quantity detection timing, the movable electrode of each of the physical quantity detection portions is applied for a first voltage via the C-V converter as the first signal, and

during the self diagnosis timing interval, a second voltage different from the first voltage is applied to the movable electrode of each of the plurality of physical quantity detection portions via the C-V converter as the second signal,

wherein the control signal generator applies the second voltage to the movable electrode of each of the plurality of physical quantity detection portions at different timing intervals.

4. A capacitive type physical quantity detecting sensor comprising:

a plurality of physical quantity detection portions for detecting a physical quantity, each of the plurality of physical quantity detection portions respectively including;

a movable electrode that moves based on a physical quantity change;

a fixed electrode disposed to face the movable electrode;

a control signal generator for generating control signals;

a C-V converter for outputting a voltage that corresponds to a change in a capacitance formed between the movable electrode and the fixed electrode; and

a signal processing circuit for processing the output voltage from the C-V converter and for outputting a signal corresponding to the physical quantity change;

wherein the control signal generator transmits a first signal to the movable electrode and the fixed electrode to detect the change in the capacitance formed between the movable electrode and the fixed electrode during a normal physical quantity detection timing interval, and transmits a second signal to the movable electrode and the fixed electrode to move the movable electrode for diagnosing a malfunction of each of the plurality of physical quantity detection portions during a self diagnosis timing interval,

wherein a first frequency of the second signal transmitted to a first one of the plurality of quantity detection portions is different from a second frequency of the second signal transmitted to a second one of the plurality of the physical quantity detection portions.

5. The capacitive type physical quantity detecting sensor according to claim 4, wherein the first frequency of the second signal is different from twice the second frequency of the second signal.

6. The capacitive type physical quantity detecting sensor according to claim 4, wherein a lowest common multiple frequency of the first frequency of the second signal and the second frequency of the second signal is at least four times the first frequency of the second signal and the second frequency of the second signal.

7. The capacitive type physical quantity detecting sensor according to claim 4, wherein:

during the normal physical quantity detection timing interval, a first voltage is applied to the movable electrode of each of the plurality of physical quantity detection portions via the C-V converter as the first signal, and

during the self diagnosis timing interval, a second voltage different from the first voltage is applied to the movable electrode of each of the plurality of physical quantity detection portions via the C-V converter as the second signal,

wherein the control signal generator applies the second voltage at a different frequency than that of the first voltage to the movable electrode of each physical quantity detection portion.