Temperature compensation-type balance, timepiece movement, mechanical timepiece and manufacturing method of temperature compensation-type balance
A temperature compensation-type balance includes a balance staff, and a balance wheel having a plurality of bimetal portions disposed in parallel to each other in a circumferential direction around a rotation axis of the balance staff. Connection members connect respective ones of the plurality of bimetal portions and the balance staff. Each bimetal portion is a layered body in which a first member and a second member are radially overlapped, and one end portion in the circumferential direction is a fixed end connected to a respective connection member and the other end portion in the circumferential direction is a free end. The first member is formed of a ceramic material, and the second member is formed of a metal material having a thermal expansion coefficient different from that of the first member.
1. A temperature compensation-type balance comprising:
a balance staff that rotates about a rotation axis; and
a balance wheel that has a plurality of bimetal portions which are disposed in parallel to each other in a circumferential direction around the rotation axis of the balance staff and extended in an arc shape along the circumferential direction of the rotation axis, and connection members which radially connect respective ones of the plurality of bimetal portions to the balance staff, wherein
each bimetal portion is a layered body in which a first member and a second member that is disposed more radially outward than the first member are radially overlapped, one end portion of the bimetal portion in the circumferential direction is a fixed end connected to a respective connection member and the other end portion of the bimetal portion in the circumferential direction is a free end, and the second member has a second V-shaped engagement portion that is engaged with a first V-shaped engagement portion formed in the first member at the free end of the bimetal portion and is bonded to the first member to maintain the engagement therebetween
the first member is formed of a ceramic material, and
the second member is formed of a metal material having a thermal expansion coefficient different from that of the first member.
2. The temperature compensation-type balance according to claim 1 , wherein
the first members and the connection members comprise a one-piece structure made of the ceramic material, and
the second members comprise an electrocast made of the metal material having the thermal expansion coefficient different from that of the first member.
3. The temperature compensation-type balance according to claim 2 , wherein the first member and the second member of each bimetal portion are bonded via an alloy layer.
4. The temperature compensation-type balance according to claim 2 , wherein a weight portion is provided at the free end of each bimetal portion.
5. The temperature compensation-type balance according to claim 2 , wherein the first members and the connection members are formed of any material among Si, SiC, SiO 2 , Al 2 O 3 , ZrO 2 and C.
6. The temperature compensation-type balance according to claim 1 , wherein the second member of each bimetal portion is formed of any material among Au, Cu, Ni, an Ni alloy, Sn and a Sn alloy.
7. The temperature compensation-type balance according to claim 1 , wherein each bimetal portion becomes gradually thinner in thickness along the radial direction from the fixed end side toward the free end side.
8. The temperature compensation-type balance according to claim 7 , wherein in each bimetal portion:
the first member is disposed more radially inward than the second member and is formed of a ceramic material integrated with the connection member, and at least the first member between the first member and the second member becomes gradually thinner in thickness along the radial direction from the fixed end side toward the free end side.
9. The temperature compensation-type balance according to claim 7 , wherein in each bimetal portion, a thickness ratio of the first member to the second member in the radial direction is uniform from the fixed end side to the free end side.
10. The temperature compensation-type balance according to claim 7 , wherein a weight portion is provided at the free end of each bimetal portion.
11. The temperature compensation-type balance according to claim 1 , wherein the first member and the second member of each bimetal portion are bonded via an alloy layer.
12. The temperature compensation-type balance according to claim 1 , wherein a weight portion is provided at the free end of each bimetal portion.
13. The temperature compensation-type balance according to claim 1 , wherein the first member of each bimetal portion and respective connection member are formed of any material among Si, SiC, SiO 2 , Al 2 O 3 , ZrO 2 and C.
14. The temperature compensation-type balance according to claim 1 , wherein the second member of each bimetal portion is formed of any material among Au, Cu, Ni, an Ni alloy, Sn and a Sn alloy.
15. A timepiece movement comprising:
a movement barrel that has a power source;
a train wheel that transfers a rotational force of the movement barrel;
an escapement mechanism that controls rotations of the train wheel; and
the temperature compensation-type balance according to claim 1 for controlling the speed of the escapement mechanism.
16. A mechanical timepiece comprising:
the timepiece movement according to claim 15 .
17. The temperature compensation-type balance according to claim 1 , wherein in each bimetal portion, the second member has a convex engagement portion that is engaged with a concave engagement portion formed in the first member.