Detection sensor
View Patent ↗There is provided a technique that can increase sensitivity of a resonator. A ratio Rb/Ra between an inner diameter Rb and an outer diameter Ra of the resonator 20 is appropriately selected, and thus there may be a fixed point where an r component (U(Ra) or U(Rb)) of displacement in a radial direction and an r component (V(Ra) or V(Rb)) of displacement in a tangential direction are 0 on an outer diameter portion or an inner diameter portion of the resonator 20 . In this case, the resonator 20 is supported by a holding member 22 constituted by a single-span beam set so that a boundary condition on a side of the resonator 20 is pinned and a boundary condition on a side of an anchor that supports the resonator 20 is clamped at the fixed point, and this prevents vibration energy of the resonator 20 from being lost through the holding member 22 , avoids a state to disturb a vibration mode, and achieves a sensor having high sensitivity.
1. A detection sensor comprising:
a disk-shaped resonator having a vibration characteristic changed by adherence or adsorption of a substance having a mass;
a driving unit that causes vibration of the resonator; and
a detection unit that detects a change in vibration of the resonator to detect the substance,
wherein the resonator having a ring shape with an outer diameter Ra and an inner diameter Rb with an opening formed at the center;
the resonator being formed of the outer diameter Ra and the inner diameter Rb that substantially satisfy U(r)=0 or V(r)=0 when r=Ra or Rb for displacement U(r) in a radial displacement and displacement V(r) in a tangential direction expressed by Expression (19) in a position r on a position coordinate (r, θ) when the resonator vibrates; and
the resonator is supported on an anchor by a single-span beam set so that a boundary condition on a side of the resonator is pinned and a boundary condition on a side of the anchor that supports the resonator is clamped, where Expression 19 is expressed as:
U
(
r
)
=
∂
∂
r
J
n
(
hr
)
+
A
6
n
r
J
n
(
kr
)
+
A
7
∂
∂
r
Y
n
(
hr
)
+
A
8
n
r
Y
n
(
kr
)
V
(
r
)
=
n
r
J
n
(
hr
)
+
A
6
∂
∂
r
J
n
(
kr
)
+
A
7
n
r
Y
n
(
hr
)
+
A
8
∂
∂
r
Y
n
(
kr
)
(
19
)
where
h
=
ω
ρ
(
1
-
σ
2
)
E
,
k
=
ω
ρ
(
2
+
2
σ
)
E
,
k
=
h
2
1
-
σ
,
and
where σ represents Poisson's ratio of a resonator material, E represents Young's modulus of the resonator material, ρ represents a density of the resonator material, ω represents angular frequency, n represents a degree of vibration mode, and A 6 , A 7 and A 8 are constants uniquely determined by natural vibration mode specified by outer diameter and inner diameter of resonator, Young's modulus, density and Poisson's ratio of resonator material, and the boundary condition (in this case, free-free condition) of the resonator,
wherein the single-span beam has a length and a width set so that a vibration frequency thereof is substantially equal to a vibration frequency of the resonator.
2. The detection sensor according to claim 1 , wherein in a case where U(r)=0 or V(r)=0 is substantially satisfied when r=Ra in the Expression (19), the resonator is supported at an outer diameter portion.
3. The detection sensor according to claim 2 , wherein in a case where U(r)=0 is substantially satisfied when r=Ra in the Expression (19), the resonator is supported at a position θ where sin(nθ)=0.
4. The detection sensor according to claim 2 , wherein in a case where V(r)=0 is substantially satisfied when r=Ra in the Expression (19), the resonator is supported at a position θ where cos(nθ)=0.
5. The detection sensor according to claim 1 , wherein the detection unit detects an amount of the substance adhering to the resonator.
6. The detection sensor according to claim 1 , wherein the substance is a particular molecule, or multiple types of molecules having a particular property or characteristic.