PHYSICAL QUANTITY SENSOR

• US 20150168437A1
• Filed: 05/28/2013
• Published: 06/18/2015
• Est. Priority Date: 05/29/2012
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Jomori, Tomoya, Mochida, Yoichi
• Granted Patent: US 9,476,897 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 1/003 used for damping
• CPC Class Codes: G01P 1/026 for speed measuring devices, e.g. pulse generator
• CPC Class Codes: G01P 3/14 by exciting one or more mechanical resonance systems
• CPC Class Codes: G01P 3/44 for measuring angular speed G01P3/56 takes precedence

Abstract

A physical quantity sensor has a resonance frequency f1 in same-phase mode and a resonance frequency f3 in same-phase absorptive mode greater than the resonance frequency f1. An absolute value Δf3 is a difference between the resonance frequency f3 in the same-phase absorptive mode and a value that is the product of the resonance frequency f1 in the same-phase mode multiplied by n; an avoidance difference D indicates a degree of deviation of the absolute value Δf3 from the resonance frequency f1 in the same-phase mode. A relation (Δf3>f1×D) where the absolute value Δf3 is greater than a value that is the product of the resonance frequency f1 in the same-phase mode multiplied by the avoidance difference D is satisfied, and, simultaneously, the avoidance difference D is provided to be greater than 0%. This can avoid the vibrational excitation by resonance interference from becoming the maximum displacement.

Claims

1. A physical quantity sensor comprising:

a substrate;

a drive weight supported by the substrate via a first spring;

a detection weight supported by the drive weight via a second spring, the detection weight including a detection movable electrode; and

a detection fixed portion including a detection fixed electrode that is arranged to be opposed to the detection movable electrode,

wherein;

an application of a physical quantity, while the drive weight is driven and vibrated, displaces the detection movable electrode and the detection weight

to change an interval between the detection movable electrode and the detection fixed electrode;

the physical quantity is detected based on the changed interval;

f1 is defined as a resonance frequency in same-phase mode where the drive weight moves following the application of the physical quantity in a direction identical to a direction in which the detection weight moves;

f3 is defined as a resonance frequency in same-phase absorptive mode where the drive weight moves following the application of the physical quantity in a direction opposite to a direction in which the detection weight moves;

n is defined as an integer;

the resonance frequency f3 in the same-phase absorptive mode is greater than the resonance frequency f1 in the same-phase mode;

Δ

f3 is defined as an absolute value that is a difference between the resonance frequency f3 in the same-phase absorptive mode and a value that is the product of the resonance frequency f1 in the same-phase mode multiplied by n;

D is defined as an avoidance difference that indicates a degree of deviation of the absolute value Δ

f3 from the resonance frequency f1 in the same-phase mode; and

a relation where the absolute value Δ

f3 is greater than a value that is the product of the resonance frequency f1 in the same-phase mode multiplied by the avoidance difference D is satisfied and, simultaneously, the avoidance difference D is provided to be greater than 0%.

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

the avoidance difference D is provided to be equal to or greater than 5%.

3. The physical quantity sensor according to claim 1, wherein

the avoidance difference D is provided to be equal to or greater than 10%.

4. An oscillatory type angular velocity sensor applying the physical quantity sensor according to claim 1 to angular velocity detection,

the drive weight of the physical quantity sensor being provided as a pair of inner drive weights,

the inner drive weight surrounding the detection weight, the inner drive weight being connected to the detection weight via detection beams corresponding to the second spring,

the oscillatory type angular velocity sensor comprising:

a pair of outer drive weights located at both outer sides that sandwich the pair of inner drive weights; and

a drive fixed portion to generate electrostatic attraction that vibrates the inner drive weight and the outer drive weight in mutually opposite directions,

wherein the inner drive weight is connected to the outer drive weight by drive beams while the outer drive weight and the inner drive weight connected to the detection weight are supported to the substrate by support members that include the first spring,

wherein;

the drive beams are bent based on the electrostatic attraction generated by the drive fixed portion to perform a sensor drive that vibrates the outer drive weight and the inner drive weight;

when an angular velocity is applied as the physical quantity during the sensor drive being performed, the detection beams are bent so that the detection weight is moved in a direction orthogonal to an oscillating direction of the inner drive weight to

change a capacitance between the detection fixed electrode and the detection movable electrode; and

the angular velocity is detected base on the changed capacitance.