Detection sensor
View Patent ↗It is an object of the present invention to provide a technique that can realize improvement of sensitivity of a vibrator. A platform 50 to which a substance adheres or sticks is provided to be mechanically coupled to a vibrator 20 of a sensor via bridges 51 . Sensitivity of the sensor is improved by causing the mass of a substance adhering or sticking onto the platform 50 as if the substance concentratedly adheres or sticks to places where the platform 50 is connected to the vibrator 20 . It is preferable to connect, via the bridges 51 , the platform 50 to places where the platform 50 vibrates integrally with the vibrator 20 . For this purpose, it is preferable to mechanically couple, via the bridges 51 , the platform 50 to regions where vibration occurs only in one of an r direction or a θ direction in the vibrator 20.
1. A detection sensor comprising:
a disc-like vibrator;
a platform that is mechanically coupled to the vibrator and to which a substance having mass adheres or sticks;
a driving unit that causes the vibrator to vibrate; and
a detection unit that detects the substance by detecting a change in vibration in the vibrator,
wherein an opening is formed in a center of the vibrator, and the platform is arranged on an inner side of the opening and coupled to an inner edge of the opening of the vibrator via bridges.
2. The detection sensor according to claim 1 , wherein the platform is formed such that a resonance frequency thereof is higher than a resonance frequency of the vibrator.
3. A detection sensor comprising:
a disc-like vibrator;
a platform that is mechanically coupled to the vibrator and to which a substance having mass adheres or sticks;
a driving unit that causes the vibrator to vibrate; and
a detection unit that detects the substance by detecting a change in vibration in the vibrator,
wherein the platform is coupled to the vibrator in a position where the platform behaves integrally with the vibrator.
4. The detection sensor according to claim 3 , wherein the platform is coupled to the vibrator in a region where vibration occurs only in one of a Radial direction and a Tangential direction of the vibrator in the vibrator.
5. The detection sensor according to claim 4 , wherein the platform performs, integrally with the vibrator, linear vibration in the Radial direction of the vibrator or rotational vibration in the Tangential direction of the vibrator.
6. The detection sensor according to claim 3 , wherein the platform is coupled to a region where amplitude is the largest or a portion near the region in the vibrator.
7. The detection sensor according to claim 1 , wherein the platform is coupled to the vibrator in positions point-symmetrical or line-symmetrical with respect to the center of the vibrator.
8. The detection sensor according to claim 1 , wherein the vibrator is formed in a ring shape, an outer diameter of which is represented as Ra and an inner diameter of which is represented as Rb because the opening is formed in the center, and
the vibrator is formed with the outer diameter Ra and the inner diameter Rb with which displacement U(r) in a Radial direction and displacement V(r) in a Tangential direction, which are represented by formula (1), in a position r in a position coordinate (r, θ) at the time when the vibrator vibrates substantially satisfy U(r)=0 or V(r)=0 when r is Ra or Rb:
[
Formula
1
]
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
)
Where
h
=
ω
ρ
(
1
-
σ
2
)
E
,
k
=
ω
ρ
(
2
+
2
σ
)
E
,
k
=
h
2
1
-
σ
(
1
)
σ: Poisson's ratio of a vibrator material, E: Young's modulus of the vibrator material, ρ: the density of the vibrator material, ω: angular frequency, n: order of a vibration mode, A 6 , A 7 , A 8 : coefficients uniquely determined according to a peculiar vibration mode defined by an outer diameter and an inner diameter of a vibrator, the Young's modulus, the density, and the Poisson's ratio of the vibrator material, and boundary conditions (in this case, Free-Free conditions) of the vibrator.
9. The detection sensor according to claim 8 , wherein, in the case in which U(r)=0 or V(r)=0 is substantially satisfied when r is Ra in the formula (1), the vibrator is supported in an outer diameter portion thereof.
10. A detection sensor comprising:
a disc-like vibrator;
a platform that is mechanically coupled to the vibrator and to which a substance having mass adheres or sticks;
a driving unit that causes the vibrator to vibrate; and
a detection unit that detects the substance by detecting a change in vibration in the vibrator,
wherein
an opening is formed in a center of the vibrator, and the platform is coupled to an inner edge of the opening of the vibrator via bridges, and
the driving unit drives the vibrator in a (3, 1) mode in which an order m of harmonic vibration is set to 1 and a modal number n of a vibration mode is set to 3.
11. The detection sensor according to claim 10 , wherein, in the vibrator, when an outer diameter is represented as Ra and an inner diameter of the opening is represented as Rb, Rb/Ra is 0.65 to 0.81.
12. The detection sensor according to claim 10 , wherein the vibrator is supported in plural positions where vibration in a Radial direction and a Tangential direction of the vibrator is substantially zero in an outer diameter portion thereof, and supporting positions of the vibrator are at intervals of an angle of 60° with respect to the center of the vibrator or intervals an integer times as large as 60°.
13. The detection sensor according to claim 12 , wherein the vibrator is supported in three places at intervals of 120°.
14. The detection sensor according to claim 10 , wherein the platform is coupled to the opening of the vibrator in two places where the platform behaves integrally with the vibrator and that are symmetrical with respect to the center of the vibrator.
15. The detection sensor according to claim 14 , wherein the platform is coupled to the opening of the vibrator in a position in the vibrator where vibration in a (2, 1) mode in which an order m of harmonic vibration is 1 and a modal number n of a vibration mode is 2 is suppressed.