ELECTRONIC TIMEPIECE

Abstract: Disclosed is an analog electronic timepiece having sweep hands. The timepiece is provided with storage means (102) for storing the rotational energy of an actuator (101) intermittently driven by a time-counting circuit (100) and control means (106) for smoothly driving a display device (104) by controlling the rotational energy through first and second link means (103, 105). In one embodiment of the invention, the control means comprises at least a magnet (41), a power generating yoke (42) and a power generating coil (43) and in another embodiment, it comprises additionally a rectifying circuit (108) which supplies an output current to the time-counting circuit through a power source. (109). The advantages of the present invention are that due to the provision of the control means including a power generating mechanism, no erroneous indication of the display device due to temperature variations takes place and besides the easiness of adjustment of the load torque, a desired hand-operating mode can be easily selected at choice between stepped and sweep hand modes.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an electronic timepiece and more particularly, to control means for an analog electronic timepiece having sweep hands. Prior Art A conventional electronic timepiece, for example, the one disclosed in US-A-3,961,213 has a construction as shown in Fig. 5. The intermittent rotational energy of an actuator is stored by the magnetic attractive forces of a drive magnet 51 engaging a fourth wheel 15 and pinion 15b and a driven magnet 53 immersed in a viscous fluid 54 and the driven magnet 53 is smoothly rotated by the viscous resistance between a bridge 56 and the driven magnet 53. In this case, the driven magnet 53 by its magnetic attractive force is interlocked with a follower magnet 52 which thereby smoothly drives a second hand shaft 15a. Further, the viscous fluid has been sealed by a cap 55. However, in the case of the above mentioned prior art technique, since the viscous resistance of the viscous fluid changes depending on the temperature, the indication of the hand deviates due to the balance between the resistance and the attractive force of the magnet or an erroneous indication of the hand takes place because the viscous resistance becomes too large at low temperatures with respect to the magnetic attractive force. Further, it has been diffcult to completely seal the viscous fluid so that a characteristic change is liable to take place due to a leakage of the fluid. Moreover, as the rotational characteristic (i.e., smoothness) of the hand shaft is determined by the attractive force of the magnet or the viscous resistance of the fluid, not only is there a wide range of quality dispersions among the manufactured products but also it has been extremly difficult to adjust such dispersions. SUMMARY OF THE INVENTION The invention as claimed is intended to remedy these drawbacks. It solves the problem of how to provide an analog electronic timepiece which shows only a slight characteristic change and the rotational characteristic of which can be easily and optionally adjusted. This object is achieved with an electronic timepiece as claimed. The present invention is advantageous in that by the use of the control means including the power generating means, no erroneous indication of the display device nor a failure of keeping correct time due to temperature variations nor any trouble due to a leakage of viscous fluid takes place and further that besides the easiness of adjustment of the load torque, it is easy to select at choice a desired hand-operating mode between stepped and sweep hand modes. Further, the present invention according to claim 2 has significant additional effects in that since the output current from the power generating means is circulated through the power source, the total power consumption decreases thereby extending the life of the power source. BRIEF DESCRIPTION OF THE DRAWINGS The above mentioned objects and mechanisms of the present invention will be more fully understood hereinafter as a result of a detailed description of preferred embodiments when taken in conjunction with the following drawings, wherein: Fig. 1 is a diagramm illustrating a first embodiment of the present invention, Fig. 2 is a diagramm illustrating a second embodiment of the present invention, Fig. 3 is a sectional view of the first embodiment of the present invention, Fig. 4 is a diagramm illustrating a third embodiment of the present invention, and Fig. 5 is a sectional view of a conventional electronic timepiece. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Fig. 1, an actuator 101 is intermittently driven by a time-counting circuit 100 and the resultant intermittent rotational energy of the actuator is stored in storage means 102 so as to drive a display device 104 through first link or speed change means 103. The stored rotational energy is gradually released from the storage means 102 by control means 106 through first link means 103 and second link or speed change means 105, so that the display device 104 is smoothly driven and a sweep motion of the hands is realized. The control means 106 comprises a magnet 41 magnetized to at least more than two poles, a power generating yoke 42 for closing the magnetic flux of the magnet 41 and a power generating coil 43 wound around the yoke 42. When the magnet 41 is driven by the second link means 105, the magnetic flux in the power generating yoke 42 changes so that an induction current flows through the power generating coil 43 whose both ends are shortcircuited. In this case, as the rotary torque applied to the magnet 41 is proportional to the speed of variation of the magnetic flux, i.e., the rotational speed, the control means 106 exerts a load torque proportional to the rotational speed of the magnet 41. In Fig. 3 which is a sectional view of one concrete embodiment of the present invention, a step motor is used as the actuator 101 and a hair spring 10 linking a gear wheel 9 to a pinion 11, both of which are rotatable on the same axis, is used as the storage means 102 so as to store the rotational energy of the actuator 101 as an elastic deformation of the hair spring. By the way, reference numeral 21 designates a main plate, reference numeral 22 designates a wheel train bridge and reference numeral 1 designates a coil adapted to generate a magnetic field for driving a rotor 5 through a stator 4 and a magnetic core 2, elements 1 to 5 forming the spep motor 101. The gear wheel 9, which is linked to the pinion 11 through the hair spring 10 is driven through a sixth pinion 6, a fifth gear wheel 7 and a fifth pinion 8 and turns a fourth wheel 15 carrying a second hand shaft 15a and a hand 16. In the above arrangement, the gear wheel 9, pinion 11, idler 12 and fourth wheel 15 constitute in combination the first link or speed change means 103 for reducing the rotational speed of the step motor. A magnet pinion 40 connected to the magnet 41 is interlocked with the fourth wheel 15 through a step up gear wheel 18b and a step up pinion 18a and thereby magnet 41 is rotated resulting in changes of the magnetic flux through the power generating yoke 42 to allow a current to flow through the short-circuited power generating coil 43 thereby controlling the fourth wheel 15. In this case, the fourth wheel 15, step up pinion 18a and magnetic pinion 40 constitute the second link or speed change means 105 which together with the control means 106 allows the rotational energy storedy by the hair spring 10 to be gradually released such that the hand 16 is driven smoothly. Fig. 2 shows another embodiment of the present invention, wherein a control circuit 107 for controlling the operation of the control means 106 is additionally provided. As shown, the control circuit 107 comprises, for example, a variable resistor 45 and a switch 44 which are inserted in series between both ends of the power generating coil 43. With the above arrangement, it is possible to adjust the load torque by adjusting the current through coil 43. It is further possible to select a stepped motion of the hand by opening switch 44, i.e. turning it to the b-side and thus eliminating the load torque exerted by the control means 106. Moreover, it is even possible to change a complete sweep motion of the hand to a motion substantially equal to a stepped one according to necessesity by optionally adjusting the variable resistor 45 with the switch 44 turned to the a-side. It should be noted that although the present embodiment has been described with respect to a case using a variable resistor as part of the control circuit 107, it is possible to use a capacitor or coil for phase-shifting purposes or for constituting a filter so as to make the load torque dependent on the rotational speed of the magnet. The filter may be a high pass filter. To eliminate speed variations, it may be advantageous to have the load talk exerted by the control means not just in proportion to the rotating speed but to provide additional means for increasing the impedance and decreasing the load talk at low speeds and decreasing the impedance and increasing the load talk in a desired ratio at high speeds. The filter may be used as such means. Moreover, the switch 44 may be of an electronic type using a transistor. Further, an electric current may by applied to the power generating coil to generate a magnetic force and to thereby control the magnet 41. This structure can easily realize a desired hand carrying mode since the characteristics of the control means can be electrically changed. Fig. 4 is a diagrammatical illustration of another embodiment of the present invention, in which the same reference numerals are used for parts which are same or similar to those of Fig. 1. Since those parts have already been described, a further explanation will be omitted. A power source 109 is composed of a primary battery such as a silver battery or a secondary battery such as a capacitor so as to drive the actuator 101 through the time counting circuit 100. Further, an electric current generated by the control means 106 is supplied to the power source 109 thereby reducing the amount of consumption of the electric energy of the power source 109. The control means 106 comprises in addition to the elements 41, 42, 43 explained in connection with Fig. 1 a rectifying circuit 108 including at least one rectifying element 143. When the magnet 41 is driven by the speed change means 105, the magnetic flux in the power generating yoke 42 changes and a voltage proportional to the speed of magnet 41 is induced. Consequently, if the generated current is rectified through the rectifying element 143 and circulated through the power source 109 after smoothing it by a smoothing capacitor 144, it is possible to reduce the amount of current drawn by the time-counting circuit 100 and actuator 101 from the battery forming the power source 109. In this case, to prevent an adverse effect resulting from a reverse flow of the circulating current to the battery, it is effective to add a reverse flow preventing diode to the circuit. On the other hand, when the power source 109 is formed of a secondary battery, the battery may be charged with the circulating current and in that case, the smoothing capacitor 144 can be dispensed with. The electric current generated by the above arrangement has an amplitude proportional to the speed of the magnet and is rectified by the rectifying circuit 108 so that the current flowing to the power source 109 and the resultant rotary torque are porportional to the speed. That is, the higher the rotational speed of the magnet, the larger the amount of power generation and the load torque. Further, when the rotational speed of the magnet decreases, the amount of current flowing to the power source 109 decreases and consequently, the load torque decreases. Accordingly, the variation of the rotational speed of the magnet is hindered by the control means 106 so that the rotational energy of the actuator stored in the storage means 102 through the speed change means 105 and 103 is smoothly released and the display device can be driven continuously. It should be noted that although the present embodiment has been described with respect to a case in which the rectifying circuit 108 is formed of a single rectifying element 143 and the single smoothing capacitor 144 for half-wave rectification, it is not always limited thereto and not problem will arise even if a full-wave rectifying circuit, stabilization circuit or step up-conversion circuit is used. Further, although the load torque pulsates to some extent, since the pulsating cycle is shortened by a speed increase, it is possible to allow the display device to operate with a sufficient degree of smoothness to all appearance. Although in the above-described embodiments, use of a step motor as the actuator has been described, the present invention is not limited thereto and a reciprocating element using a piezoelectric element or an electrostatic motor may of course by used instead. In addition, the storage means has been described as being in the form of a hair spring but any other means, for example, means utilizing the attractive force or repulsive force of a magnet may be used provided it can store rotational energy. It should also be noted that what is intended by the present invention is to gradually release the stored rotational energy by the power generating mechanism and to reduce the amount of consumption of current in the system by circulating the generated current through the power source so that the combination or arrangement of blocks or parts of the timepiece are not limited to the above described embodiments.

Claims: An electronic timepiece comprising a time-counting circuit (100), an actuator (101) intermittently driven by said time-counting circuit (100), storage means (102) for storing the rotational energy from said actuator (101), an analog time display device (104), and control means (106) including a magnet (41) for controlling the release of rotational energy from said storage means (102) to said time display device (104), characterized in that said control means (106) comprises a power generating yoke (42) magnetically coupled with said magnet (41), and a power generating coil (43) on said power generating yoke (42). Timepiece according to claim 1, characterized by a first speed change means (103) connecting said time display device (104) to said storage means (102) and a second speed change means (105) connecting said control means (106) to said time display device (104) and said first speed change means (103). Timepiece according to claim 1 or 2, wherein a current adjusting circuit (107) is connected to said power generating coil (43). Timepiece according to claim 3, characterized in that said current adjusting circuit (107) includes a variable resistor (45) and/or a switch (44) to close or open the the electric circuit to the control means (106). Timepiece according to any of the preceding claims, wherein a rectifying circuit (108) is used for rectifying the current induced in said power generating coil (43), the rectified current being supplied to said time-counting circuit (100) via a power source (109).

Inventors: MIYAZAWA, OSAMU
Applicants: SEIKO EPSON CORPORATION
Application year: 1988
Main classification: G04C3
IPC codes: G04C3