Valve drive device

1. A valve drive device comprising:

a base including a fluid inlet, a fluid outlet, and a valve seat surface, at least one of the fluid inlet and the fluid outlet being opened at the valve seat surface;

a cover configured to define a valve chamber such that the fluid inlet and the fluid outlet communicate with each other between the valve seat surface and the cover;

a valve element provided at any one of the fluid inlet and the fluid outlet in the valve chamber, configured to open and close the any one of the fluid inlet and the fluid outlet, and comprising a contact surface sliding on the valve seat surface; and

a valve element driver configured to drive and rotate the valve element,

wherein the valve element driver comprises:

a motor comprising a stator comprising at least one core member with a plurality of pole teeth and a drive coil, and a rotor provided with a drive magnet;

a drive gear configured to rotate together with the rotor;

a driven gear configured to rotate the valve element by rotating the drive gear, in a state of meshing with the drive gear; and

a power transmission switching unit configured to switch between a power transmission state where the drive gear and the driven gear mesh with each other and a power non-transmission state where a meshing state between the drive gear and the driven gear is released, the power transmission switching unit comprising: a plurality of convex units formed on the drive gear and protruding toward a radial direction of the drive gear; and a rotation restriction unit provided on the driven gear, and configured to engage with each of the convex units to perform switching from the power non-transmission state to the power transmission state,

wherein the convex units are provided on the drive gear according to an N pole or an S pole of the drive magnet, and

wherein when the stator is excited with an initial excitation pattern in the power non-transmission state, at least one magnetic pole of the drive magnet is located at a position according to the initial excitation pattern, one of the convex units is located at a position corresponding to the rotation restriction unit, and the drive gear and the driven gear do not mesh with each other.

2. The valve drive device according to claim 1 , wherein the number of the at least one magnetic pole of the drive magnet is half of the number of pole teeth provided on the at least one core member.

3. The valve drive device according to claim 1 , wherein the at least one core member comprises four core members, and the stator is formed by laminating the four core members, and

wherein when the number of the at least one magnetic pole of the drive magnet is eight, each of the core members includes four pole teeth.

4. The valve drive device according to claim 1 , wherein the driven gear comprises a meshing unit in which teeth are formed along a circumferential direction of the driven gear, and a non-meshing unit in which the teeth are not formed in the circumferential direction.

5. The valve drive device according to claim 4 , wherein the meshing unit is formed continuously along the circumferential direction, and

wherein meshing between the drive gear and the driven gear is released when switching from the power transmission state to the power non-transmission state is performed.

6. The valve drive device according to claim 4 , wherein the rotation restriction unit is a lever member that is pivotably attached to the non-meshing unit of the driven gear with respect to the driven gear and urged outward in a radial direction of the driven gear, and comprises:

a first contact unit configured to contact each of the convex units when the drive gear is rotated in a first direction; and

a second contact unit configured to contact each of the convex units when the drive gear is rotated in a second direction that is an opposite direction to the first direction,

wherein when a convex unit among the plurality of convex units contacts the first contact unit, the rotation restriction unit is pressed by the convex unit to rotate the driven gear, teeth of the drive gear and teeth of the driven gear mesh with each other, and the power transmission state is obtained, and

wherein when a convex unit among the plurality of convex units contacts the second contact unit, the rotation restriction unit pivots inward in the radial direction against an urging force urging the rotation restriction unit, the drive gear rotates idly without the teeth of the drive gear meshing with the teeth of the driven gear, and the power non-transmission state is maintained.

7. The valve drive device according to claim 6 , further comprising: an urging member configured to urge the rotation restriction unit outward in the radial direction of the driven gear.

8. The valve drive device according to claim 7 , wherein the urging member is a torsion spring held on a shaft of the driven gear,

wherein a holding unit configured to hold one end of the torsion spring is provided on the driven gear, and

wherein the other end of the torsion spring is configured to urge the rotation restriction unit.

9. The valve drive device according to claim 1 , wherein lock avoidance teeth are provided in the drive gear at positions corresponding to the convex units in a circumferential direction, and an addendum circle diameter of the lock avoidance teeth is smaller than an addendum circle diameter of teeth other than the lock avoidance teeth.