Electronically controlled mechanical timepiece

Details Electronically controlled mechanical timepiece Electronically controlled mechanical timepiece

2000-09-21

2002-04-16

Roskoski, Bernard (Department: 2859)

Horology: time measuring systems or devices

Power supply details

C368S204000

Reexamination Certificate

active

06373788

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronically controlled mechanical timepiece which is operated by a mechanical energy storing means, such as a mainspring, serving as a drive source, converts a part of mechanical energy into electrical energy by a power generator, and operates a rotation control means by the electrical power so as to control the rotational cycle. More particularly, the present invention relates to an improvement in the peripheral structure of a power generator for converting mechanical energy into electrical energy.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 8-5758 discloses an electronically controlled mechanical timepiece in which mechanical energy generated when a mainspring unwinds is converted into electrical energy by a power generator, the value of current passing through a coil of the power generator, or the like, is controlled by operating a rotation control means by the electrical energy, and a pointer fixed to a gear train is thereby precisely driven so as to indicate the exact time.
FIGS. 17 and 18
are a plan view and a cross-sectional view, respectively, of a timepiece disclosed in the publication.
Referring to the figures, rotational power from a barrel drum
1
with a mainspring built therein is transmitted to a power generator
20
at an increased speed via a gear train consisting of a center wheel and pinion
7
, a third wheel and pinion
8
, a fourth wheel and pinion
9
, a fifth wheel and pinion
10
, and a sixth wheel and pinion
11
supported by a main plate
2
, a train wheel bridge
3
, and a second bridge
113
.
The power generator
20
has a structure similar to that of a step motor for driving a conventional battery-driven electronic timepiece, and comprises a rotor
12
, a stator
150
, and a coil block
160
.
In the rotor
12
, a rotor magnet
12
b
and a rotor inertia disk
12
c
are formed integrally with the shaft of a rotor pinion
12
a
that rotates in connection with the sixth wheel and pinion
11
.
The stator
150
is formed by winding a stator coil
150
b
with 40,000 turns around a stator member
150
a.
The coil block
160
is formed by winding a coil
160
b
with 110,000 turns around a magnetic core
160
a.
The stator coil
150
b
and the coil
160
b
are connected in series so as to output the sum of voltages generated thereby.
In the power generator
20
, electrical power obtained by rotation of the rotor
12
is supplied to an electronic circuit having a quartz oscillator via a capacitor (not shown), and the electronic circuit transmits signals for controlling the rotation of the rotor to the coil in accordance with the detected rotation of the rotor and the reference frequency. As a result, the gear train constantly rotates at a constant rotation speed in accordance with the braking force.
Since pointers are driven by the mainspring serving as a power source in such an electronically controlled mechanical timepiece, a motor for driving the pointers is unnecessary and the number of components is small, which lowers the costs. In addition, only a small amount of electrical energy needs to be generated so as to operate the electronic circuit, and the timepiece can be operated by a small amount of input energy.
In the electronically controlled mechanical timepiece described in the above publication, the rotor
12
must be rotated at a constant speed by the force which is generated by the unwinding of the mainspring, and the rotor inertia disk
12
c
is provided to stabilize the rotation of the rotor
12
.
However, since the main plate
2
and the stator
150
are placed around the rotor inertia disk
12
c
so as to closely face the rotor inertia disk
12
c
in the axial direction, when the gap between the rotor inertia disk
12
c
and the main plate
2
or the stator
150
is too small, air viscosity resistance produced therebetween has an adverse effect on the rotation of the rotor
12
. That is, when the gap between the components is too small, air viscosity resistance increases and a load torque needed to rotate the rotor
12
also increases. As a result, the period of operation of the timepiece is shortened in accordance with the increase.
As the power generator used in the electronically controlled mechanical timepiece, a power generator having a structure similar to that of a brushless motor is sometimes used, besides the power generator including the inertia disk
12
c.
In such a power generator, a pair of disk-like stator members are mounted along the axial direction of the rotor, and are provided with a plurality of magnets arranged in the circumferential direction so that the poles thereof are alternately different. A coil formed on a substrate is interposed between these stator members (between the magnets). Accordingly, since the rotor itself including the disk-like stator members also functions as an inertia disk, the above-described inertia disk
12
c
is unnecessary.
In such a power generator, however, when the gap between the stators, and the main plate or the coil is too small, the above problems are also caused by air viscosity resistance between the components.
OBJECTS OF THE INVENTION
An object of the present invention is to provide an electronically controlled mechanical timepiece in which the period of operation thereof can be extended by reducing the influence of air viscosity resistance.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an electronically controlled mechanical timepiece wherein a mechanical energy transmitting means is driven by a mechanical energy storing means serving as an energy source, electrical power is generated by a power generator rotated by the mechanical energy transmitting means, the rotation cycle of the power generator is controlled by an electronic circuit driven by the electrical power so as to brake the mechanical energy transmitting means and to thereby adjust the speed, characterized in that the power generator has a rotor rotating in connection with the mechanical energy transmitting means, and a constant K is set to be {fraction (1/10)} or less when a gap h between a largest-diameter member in the rotor and a counter component fixed to most closely face the rotor in the axial direction is given by the following formula:
h
=
π
2
⁢
f
⁢
 
⁢
μ
K
⁢
 
⁢
T
rz
⁢
 
⁢
max
⁢
(
r
2
4
-
r
1
4
)
where &pgr; represents the ratio of the circumference of a circle to its diameter, &mgr; represents the air viscosity, f represents the rotational frequency of the rotor, T
rzmax
represents the maximum output torque of the mechanical energy storing means to be transmitted to the rotor, r
1
represents a distance from the center of rotation of the rotor to the inner periphery of a portion where the largest-diameter member in the rotor and the counter component overlap in a plane, and r
2
represents a distance from the center of rotation of the rotor to the outer periphery of the portion where the largest-diameter member in the rotor and the counter component overlap in a plane.
Herein, “counter component” and “largest-diameter member” refer to a component and a member between which viscosity resistance increases as the gap h therebetween decreases, thereby increasing the load torque at the rotor.
Therefore, “counter component” does not include a component, for example, a bridge-shaped or cantilevered supporting member claimed as in the following, which overlaps with the largest-diameter in the rotor in a plane and in which air viscosity resistance between the component and the largest-diameter member does not cause any problem even when the gap h decreases.
Regarding “largest-diameter member”, for example, in a case in which a projection for enhancing inertia is formed at a position on the largest-diameter member, such as a rotor inertia disk, offset outward from the midpoint of the radius of the largest-diameter member so as to protrude toward the counter component, when the area of a portion of the p

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