Flexural vibrating reed, flexural vibrator, and piezoelectric device
Deterioration of the Q value caused by the thermoelastic effect is suppressed. Since a first depth of a first groove and a second depth of a second groove are smaller than a distance between a surface including a third surface and a surface including a fourth surface, the first and second grooves do not penetrate between the surface including the third surface and the surface including the fourth surface. In addition, the sum of the first depth of the first groove and the second depth of the second groove is greater than the distance between the third and fourth surfaces, a heat transfer path between a first expandable portion (the first surface) and a second expandable portion (the second surface) cannot be formed as a straight line. As such, the heat transfer path between the first expandable portion (the first surface) and a second expandable portion (the second surface) is made to detour to the first and second grooves and and thus be lengthened.
1. A flexural vibrating reed comprising:
a base; and
a vibrating portion extending in an extension direction from the base,
wherein the vibrating portion includes first and second principal surfaces which are mutually opposed, a first groove provided in the first principal surface, and a second groove provided in the second principal surface,
the first and second grooves are spaced apart along a direction orthogonal to the extension direction in a plan view from a normal direction of the first principal surface,
a first depth of the first groove and a second depth of the second groove are smaller than a distance in the normal direction between the first and second principal surfaces, and
the sum of the first and second depths is greater than the distance.
2. The flexural vibrating reed according to claim 1 ,
wherein the vibrating portion has third and fourth principal surfaces which connect the first and second principal surfaces to each other and are mutually opposed, and
the third and fourth principal surfaces have a relationship in which in a case where the third principal surface expands due to flexural vibration of the vibrating portion, the fourth principal surface contracts, and in a case where the third principal surface contracts, the fourth principal surface expands.
3. The flexural vibrating reed according to claim 1 , wherein the first and second grooves are formed from the vibrating portion to the base.
4. The flexural vibrating reed according to claim 1 , wherein, assuming that a flexural vibration frequency of the vibrating portion is f, the Pi is π, a thermal conductivity in the vibrating direction of a material used for the vibrating portion is k, a mass density of the material used for the vibrating portion is ρ, a thermal capacity of the material used for the vibrating portion is C p , and a width in the vibrating direction of the vibrating portion is a, 0.09<f/fm is satisfied when fm=πk/(2 ρC p a 2 ).
5. The flexural vibrating reed according to claim 1 , wherein the first and second grooves are disposed on the base side from a half of the length in the extension direction of the flexural vibrating portion from the base.
6. A flexural vibrator using the flexural vibrating reed according to claim 1 , comprising:
the flexural vibrating reed; and
a package that accommodates the flexural vibrating reed,
wherein the flexural vibrating reed is airtightly sealed in the package.
7. A piezoelectric device using the flexural vibrating reed according to claim 1 , comprising:
the flexural vibrating reed;
an IC chip that drives the flexural vibrator; and
a package that accommodates the flexural vibrating reed and the IC chip, wherein the flexural vibrating reed and the IC chip are airtightly sealed in the package.
8. The flexural vibrating reed according to claim 2 , wherein, assuming that a flexural vibration frequency of the vibrating portion is f, the Pi is π, a thermal conductivity in the vibrating direction of a material used for the vibrating portion is k, a mass density of the material used for the vibrating portion is ρ, a thermal capacity of the material used for the vibrating portion is C p , and a width in the vibrating direction of the vibrating portion is a, 0.09<f/fm is satisfied when fm=πk/(2 ρC p a 2 ).
9. The flexural vibrating reed according to claim 3 , wherein, assuming that a flexural vibration frequency of the vibrating portion is f, the Pi is π, a thermal conductivity in the vibrating direction of a material used for the vibrating portion is k, a mass density of the material used for the vibrating portion is ρ, a thermal capacity of the material used for the vibrating portion is C p , and a width in the vibrating direction of the vibrating portion is a, 0.09<f/fm is satisfied when fm=πk/(2 ρC p a 2 ).
10. The flexural vibrating reed according to claim 2 , wherein the first and second grooves are disposed on the base side from a half of the length in the extension direction of the flexural vibrating portion from the base.
11. The flexural vibrating reed according to claim 3 , wherein the first and second grooves are disposed on the base side from a half of the length in the extension direction of the flexural vibrating portion from the base.