BACKGROUND

1. Technical Field

The present invention relates to a movement and a timepiece.

2. Related Art

For example, there is known a timepiece in which a battery is embedded and which performs notification of a time by causing a pointer such as a second hand to rotate using the electrical power of the battery. The movement of the timepiece includes a train wheel unit which drives the pointer and a drive motor. The train wheel unit includes, for example, a first wheel which meshes with a wheel of the drive motor and a second wheel to which the pointer is fixed. A rotational force of the drive motor is transmitted to the second wheel via the first wheel. Accordingly, the pointer rotates.

The first wheel is configured by a resin material which is a comparatively light material in order to suppress a moment of inertia. Meanwhile, since a hand is fixed to the second wheel, the second wheel is configured by a metal material which is a sufficiently strong material. The train wheel unit is configured to hold the positions of the wheels using a main plate and a train wheel bridge which hold the axles of each of the first wheel and the second wheel from both sides.

The first wheel and the second wheel are thin and the distance between the main plate and the train wheel bridge is short. The main plate and the train wheel bridge are configured by a resin material which is a comparatively light material.

In the train wheel unit, in a case in which the first wheel which is configured by a resin material and the second wheel which is configured by a metal material mesh with each other to rotate together, static electricity is generated between the first wheel and the second wheel at times such as when there is friction between the teeth of both wheels and when the teeth which mesh with each other separate from each other. When this phenomenon occurs, due to a charge which is accumulated in the wheels, the main plate and the train wheel bridge which are close to the side surfaces of the wheels polarize easily, and the wheels stick to the train wheel bridge and the frictional resistance greatly rises due to a Coulomb force which is generated between the wheels and the train wheel bridge which has a particularly close distance to the wheels. A problem in that the electric motor module stops occurs depending on the degree of the rise in frictional resistance.

In order to discharge the charge that is accumulated in the wheels, it is important that the electrical resistance of the resin material is low. Therefore, in the related art, there is proposed a technique which is disclosed in JP-A-3-081370, for example, for reducing the electrical resistance of the resin material. In the device which is disclosed in JP-A-3-081370, carbon fibers are mixed into a resin material of a wheel. Pamphlet of International Publication WO 2003/54636 proposes a technique which uses a substrate which is configured by a resin material and a wheel in which carbon fibers and boron are mixed into a resin material.

However, there is a problem in that, since the carbon fibers described in JP-A-3-081370 and Pamphlet of International Publication WO 2003/54636 do not reach the tooth tips of the wheel, sufficient conductivity may not be obtained.

SUMMARY

An advantage of some aspects of the invention is to provide a movement and a timepiece which are capable of securing sufficient conductivity.

A movement according to an aspect of the invention includes an electric motor module which is driven by electrical power of a battery, a first wheel which transmits a drive force of the electric motor module and includes a wheel main body which is configured by a resin material and a metal layer which is configured by a metal material and is provided on a surface of the wheel main body, and a second wheel which transmits the drive force of the electric motor module and is configured by a metal material.

According to this configuration, it is possible to sufficiently secure the conductivity of the first wheel using a metal layer which is configured by a metal material. It is possible to effectively suppress the static electricity caused by the friction which is generated when the first wheel and the second wheel mesh and rotate together. It is possible to discharge the static electricity which is generated by the separating of the first wheel and the second wheel by electrically connecting the first wheel and the second wheel to a structural body having a sufficiently large electrostatic capacity with respect to the static electricity which is generated in the first wheel and the second wheel such as an electrode (the cathode or the anode) of a drive motor electrical power source or the external case, for example.

It is preferable that the movement according to the aspect of the invention further includes a train wheel bridge which supports the first wheel and the second wheel and is conductive.

With this configuration, it is possible to render the train wheel bridge, the first wheel, and the second wheel the same potential. Accordingly, it is possible to prevent the generation of not only the Coulomb force between the first wheel, the second wheel, and the train wheel bridge, but also a Johnson Rahbeck force and a gradient force. As a result, it is possible to more effectively prevent problems such as the electric motor module which drives the first wheel and the second wheel stopping.

It is preferable that the movement according to the aspect of the invention further includes a main plate which supports the first wheel and the second wheel and is conductive.

With this configuration, it is possible to render the main plate, the first wheel, and the second wheel the same potential. Accordingly, it is possible to prevent the generation of not only the Coulomb force between the first wheel, the second wheel, and the main plate, but also a Johnson Rahbeck force and a gradient force. As a result, it is possible to more effectively prevent problems such as the electric motor module which drives the first wheel and the second wheel stopping.

In the movement according to the aspect of the invention, the metal material preferably includes at least a material selected from nickel, tin, and chrome.

With this configuration, the first wheel has excellent abrasion resistance while securing sufficient conductivity.

In the movement according to the aspect of the invention, it is preferable that the first wheel meshes with the second wheel.

In a case in which the first wheel and the second wheel mesh with each other, although static electricity is easily generated in the first wheel, even in this case, the effect of the invention is more effectively exhibited.

In the movement according to the aspect of the invention, it is preferable that the wheel main body includes teeth, and that the metal layer is provided on a tooth surface of the teeth to cover a portion thereof.

With this configuration, the metal layer and the second wheel are capable of contacting each other, for example, it is possible to discharge the static electricity which is generated by the first wheel via the second wheel.

In the movement according to the aspect of the invention, it is preferable that the wheel main body includes a main surface, and that the metal layer is provided on the main surface of the wheel main body.

With this configuration, it is possible to effectively discharge still more static electricity which is generated by the first wheel.

In the movement according to the aspect of the invention, it is preferable that the first wheel meshes with a wheel which is fixed to a rotating axle of the electric motor module.

With this configuration, the first wheel is lightened and it is possible to suppress the moment of inertia of the first wheel.

The movement according to the aspect of the invention may include a plurality of the first wheels which mesh with each other.

In a case in which the train wheel unit includes a plurality of the conductive first wheels, it is possible to discharge the plurality of first wheels by connecting one of the plurality of first wheels to a grounding electrode.

In the movement according to the aspect of the invention, it is preferable that the second wheel is positioned closer to a following side than the first wheel.

According to this configuration, although the second wheel is easily influenced by torque as compared to the first wheel, since the second wheel is configured by a metal material, the strength is high and the resilience is excellent.

In the movement according to the aspect of the invention, it is preferable that a second hand is fixed to the second wheel.

In the train wheel unit which drives the second hand, since a configuration is adopted in which the rotation speeds of the wheels are comparatively fast and static electricity is easily accumulated, the effect of the invention is more effectively exhibited.

A timepiece according to another aspect of the invention includes the movement described above and a casing which stores the movement.

With this configuration, the timepiece which exhibits the effect may be obtained.

