Electronic timepiece

An electronic timepiece comprising a step motor composed of an electromagnetic coil excited by two phase alternating driving signals, characterized by comprising means for changing over the electromagnetic coil from a closed circuit condition to an open circuit condition and vice versa, means for detecting shocks, means for discriminating the shock direction, and means for controlling the driving signal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an electronic timepiece which can effect the 
compensation operation with respect to external shock so as to prevent its 
erroneous operation. 
2. Description of the Prior Art 
Many attempts have been made to drive a step motor by a small power output 
under no load or light load and by a large power output under a heavy 
load. In this case, the load mainly consists of a solid resistance load 
such as a wheel train, week date feeding mechanism or the like and of a 
fluid resistance load such as oil or the like. The above mentioned 
attempts can compensate for these loads, but are insufficient in 
compensation action with respect to the external shock load and hence have 
the drawback that, when a step motor is reversely rotated by 1 step due, 
for example, to the reversely rotating shock, the timepiece is delayed by 
2 seconds. As a result, in order to prevent the step motor from rotating 
in a reverse direction, the drag torque between the permanent magnet rotor 
and the stator can not be made too large. As a result, the power input 
required to rotate the rotor by 1 step for the purpose of making the 
potential energy large becomes large. Thus, it is impossible to reduce the 
electric power required for the electronic timepiece to a value smaller 
than a certain limit. 
SUMMARY OF THE INVENTION 
An object of the invention, therefore, is to provide an electronic 
timepiece which can eliminate the above mentioned drawbacks which have 
been encountered with the prior art techniques, which can effect the 
compensation action with respect to the shock load so as to stabilize the 
step operation of the motor, and which can further reduce the electric 
power to be consumed by the motor. 
A feature of the invention is the provision in an electronic timepiece 
comprising a step motor composed of an electromagnetic coil excited by two 
phase alternating driving signals, a permanent magnet rotor and a stator, 
of the improvement comprising means for changing over said electromagnetic 
coil from a closed circuit condition to an open circuit condition and vice 
versa, means for detecting shocks and operative to detect an induced 
voltage to be generated in the electromagnetic coil when said rotor under 
its standstill condition is subjected to external shock, means for 
discriminating the shock direction by the difference between the output 
delivered from said shock detection means and the driving signal, and 
means for controlling the driving signal on the basis of the output 
delivered from said shock direction discriminating means. 
Further objects and features of the invention will be fully understood from 
the following detailed description with reference to the accompanying 
drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows one embodiment of an electronic timepiece as a whole according 
to the invention. In FIG. 1, reference numeral 1 designates a crystal 
oscillation circuit operative to generate a signal to be used as a 
reference signal to the timepiece; 2 a frequency divider circuit composed 
of a multistage flipflop and operative to divide the frequency of the 
signal delivered from the crystal oscillation circuit 1 into 1 second 
signal required for the timepiece; 3 a signal conversion circuit operative 
to combine the outputs delivered from proper output stages of the 
frequency divider circuit 2 so as to generate a normal driving signal 
required under normal condition, a compensation driving signal for 
compensating an erroneous operation of a step motor when it is subjected 
to a reversely rotating shock, a delay driving signal operative, when the 
step motor is subjected to the shock immediately before generation of the 
normal driving signal, to delay the normal driving signal until the shock 
has ceased, a 2 phase high frequency signal operative to open or close an 
electromagnetic coil at a high speed, a signal showing difference in phase 
of the normal driving signal and any other signals required for detecting 
the shock, and 4 a driving circuit operative to be driven by the signal 
conversion circuit 3 and drive a step motor 5. The step motor 5 is 
connected through a transmission mechanism such as a wheel train or the 
like to a display means such as an hour hand, minute hand, second hand or 
the like, not shown in FIG. 1. Reference numeral 6 designates a shock 
detection circuit operative to detect the induced voltage generated in an 
electromagnetic coil 5a when the step motor is subjected to an external 
shock load during the period when the driving signal is supplied from the 
driving circuit 4 to the step motor 5 and throughout total duration except 
several milliseconds after the supply of the driving signal has been 
stopped and supply its output to a control circuit 7. The control circuit 
7 functions to discriminate the direction of the shock on the basis of the 
signal delivered from the shock detection circuit 6 and the phase signal 
of the driving signal delivered from the signal conversion circuit 3 so as 
to generate a control signal which is supplied to the signal conversion 
circuit 3 and delay the driving signal and functions to generate a 
compensation driving signal if the step motor is subjected to the 
reversely rotating shock. 
The invention will now be described in detail with reference to FIG. 3 
which concretely shows essential parts of an electronic timepiece 
according to the invention. 
In FIG. 3, reference numeral 21 designates a crystal oscillation circuit; 
22 a frequency divider circuit which functions in the same manner as that 
shown in FIG. 1; 23 a signal conversion circuit composed of a normal 
driving signal generation circuit 23a, compensation driving signal 
generation circuit 23b, delay driving signal generation circuit 23c, 
electromagnetic coil switching signal generation circuit 23d, phase 
discrimination circuit 23e for the normal driving signal, selection gates 
23f, 23g, NOR gates 23h, 23i, AND gates 23j, 23k, 23l, 23m, OR gates 23n, 
23p, and inverters 23q, 23r. Each of these circuits function to generate a 
signal required for its role by means of a combination of the outputs 
delivered from the proper output stages of the frequency divider circuit 
22. These signals can easily be generated, so that means for generating 
these signals are not shown in FIG. 3. 
The normal driving signal generation circuit 23a generates alternately at 
every 1 second alternate pulse signals .phi..sub.1, .phi..sub.2, the 
output terminals for delivering these signals .phi..sub.1, .phi..sub.2 
being properly connected to input terminals of the selection gates 23f, 
23g. 
The compensation driving signal generation circuit 23b generates a signal 
.phi..sub.3 required for the compensation driving operation when the step 
motor is subjected to the reversely rotating shock, the output terminal 
for delivering this signal .phi..sub.3 being connected to input terminals 
of the AND gates 23i, 23k whose respective output terminals are connected 
to respective input terminals of the selection gates 23f, 23g. This 
compensation driving signal .phi..sub.3 is set to be generated after the 
shock has ceased, so that its pulse width may be made equal to the pulse 
width of the normal driving signals .phi..sub.1, .phi..sub.2. 
In the present embodiment, the pulse width of the normal driving signals 
.phi..sub.1, .phi..sub.2 and compensation driving signal .phi..sub.3 is 
set to a pulse width which is shorter than 5.9 m sec. In addition, each of 
these signals may be of a split pulse instead of a continuous pulse. 
The output terminals of the selection gates 23f, 23g are connected to input 
terminals of the NOR gates 23h, 23i whose output terminals are connected 
to the input terminals of the AND gates 23s, 23t and to a driving circuit 
24. 
The delay driving signal generation circuit 23c generates a delayed driving 
signal .phi..sub.4 when the step motor is subjected to the shock 
immediately before the normal driving signal and after the shock has 
ceased. The output terminal of the delay driving signal generation circuit 
23c is connected to input terminals of the AND gates 23l, 23m whose output 
terminals are the input terminals of the NOR gates 23h, 23i. 
The electromagnetic coil switching signal generation circuit 23d generates 
a relatively high frequency continuous signal having a pulse width 
.omega..sub.1 such as signals .phi..sub.5, .phi..sub.6 shown in FIG. 4 and 
.phi..sub.10, .phi..sub.11 shown in FIGS. 10(6) and 11. The output 
terminals for delivering these signals .phi..sub.5, .phi..sub.6 are 
connected through the OR gates 23n, 23p to the AND gates 23s, 23t 
respectively. 
The phase discrimination circuit 23e generates an output signal .phi..sub.7 
corresponding to the normal driving signals .phi..sub.1, .phi..sub.2. The 
output terminal of the phase discrimination circuit 23e is connected to 
the input terminals of the AND gates 23k, 23l and a selection gate 27e of 
a control circuit 27 to be described later. In addition, the output 
terminal of the phase discrimination circuit 23e is connected through the 
inverter 23q to the other input terminals of the AND gates 23j, 23m and 
selection gate 27e whose output terminal is connected to the selection 
gates 23f, 23g and compensation driving signal generation circuit 23b. 
The output terminal of an OR gate 27f of the control circuit 27 is 
connected to the input terminals of the OR gates 23n, 23p and delay 
driving signal generation circuit 23c. 
In FIG. 3, reference numeral 24 designates a driving circuit including two 
P channel MOS transistors 24a, 24b and two N channel MOS transistors 24c, 
24d. Drains of the MOS transistors 24a, 24c are connected with each other, 
while drains of the MOS transistors 24b, 24d are connected with each 
other. Sources of the MOS transistors 24a, 24b are connected in common to 
the plus terminal V.sub.DD of an electrical supply source and sources of 
the MOS transistors 24c, 24d are connected in common to the minus terminal 
V.sub.SS of the electrical supply source. The gates of the four MOS 
transistors 24a, 24b, 24c, 24d are separated one from the other and the 
gate of the MOS transistor 24a is connected to the output terminal of the 
NOR gate 23h provided in the signal conversion circuit 23. The gate of the 
MOS transistor 24b is connected to the output terminal of the NOR gate 23i 
provided in the signal conversion circuit 23, the gate of the MOS 
transistor 24c is connected to the output terminal of the AND gate 23s 
provided in signal conversion circuit 23 and the gate of the MOS 
transistor 24d is connected to the output terminal of the AND gate 23t. 
In FIG. 3, reference numeral 25 designates an electromagnetic coil of the 
step motor having ends connected between common drains a.sub.o, b.sub.o of 
the driving circuit 24. 
Reference numeral 26 shows a shock detection circuit composed of an 
inverter 26a having an input terminal connected to the common drain 
a.sub.o of the driving circuit 24, an inverter 26b having an input 
terminal connected to the output terminal of the inverter 26a, an AND gate 
26e having an input terminal connected to the output terminal of the 
inverter 26b, an inverter 26c having an input terminal connected to the 
common drain b.sub.o of the driving circuit 24, an inverter 26d having an 
input terminal connected to the output terminal of the inverter 26c and an 
AND gate 26f having an input terminal connected to the output terminal of 
the inverter 26d. The output terminals of the AND gates 26e, 26f are 
connected to the input terminals of AND gates 27a, 27b. 
The control circuit 27 is composed of the AND gates 27a, 27b, R-S flipflops 
27c, 27d, the selection gate 27e and the OR gate 27f. The output terminal 
of the AND gate 27a is connected to the set terminal of the R-S flipflop 
27c, the output terminal of the AND gate 27b is connected to the set 
terminal of the R-S flipflop 27d, the output terminal of the R-S flipflop 
27c is connected to the selection gate 27e and to the input terminal of 
the OR gate 27f and the negation output terminal of the R-S flipflop 27c 
is connected to the input terminal of the AND gate 27b. The output 
terminal of the R-S flipflop 27d is connected to the selection gate 27e 
and to the other input terminal of the OR gate 27f and the not output 
terminal of the R-S flipflop 27d is connected to the input terminal of the 
AND gate 27a. 
FIG. 4 shows a time chart at respective parts shown in FIG. 3 when the step 
motor is subjected to a reversely rotating shock at a time between the 
normal driving signals. Section I is a condition under which the shock 
load is absent and the outputs .phi..sub.14, .phi..sub.15 delivered from 
the shock detection circuit 26 are LOW (hereinafter will be called as L 
signals), so that the outputs .phi..sub.18, .phi..sub.19 delivered from 
the control circuit 27 are also the L signal. The NOR gate 23h of the 
signal conversion circuit 23 generates a reverse signal .phi..sub.8 of the 
normal driving signal .phi..sub.1, the reverse signal .phi..sub.8 being 
supplied to the gate of the MOS transistor 24a and to one of the input 
terminals of the AND gate 23s. To the other input terminal of the AND gate 
23s is supplied the electromagnetic coil switching signal .phi..sub.5 so 
that the AND gate 23s generates a signal such as .phi..sub.10. Meanwhile, 
the output signal .phi..sub.9 delivered from the NOR gate 23i is a HIGH 
signal (hereinafter will be called as H signal) so that the 
electromagnetic switching signal .phi..sub.6 becomes the output signal 
.phi..sub.11 delivered from the AND gate 23t. If the signal .phi..sub.8 is 
changed over from the H signal to the L signal, the MOS transistors 24a, 
24d shown in FIG. 3 become ON to cause current to flow through the 
electromagnetic coil 25 in a.sub.o .fwdarw.b.sub.o direction, thereby 
rotating the rotor in a given direction. 
FIGS. 8(1) and 8(2) show a step motor for electronic timepieces used in 
general and composed of a stator 101, 102 and 201, 202; a rotor 103 and 
203; and an electromagnetic coil 104 and 204. The pulse width of the 
driving signal .phi..sub.8 is set to t.sub.1 msec and the electromagnetic 
coil switching signal .phi..sub.10 is not generated during t.sub.2 msec 
after the driving pulse .phi..sub.8 has been supplied to the AND gate 23s. 
This is because of the fact that the shock detection circuit 26 does not 
detect the induced voltage due to the free oscillation of the rotor after 
it has been normally driven. If use is made of the duration t.sub.2 msec 
for the purpose of detecting the conventional wheel train load, a signal 
which becomes L signal during t.sub.1 +t.sub.2 msec is supplied to the AND 
gates 26e, 26f instead of their input signals .phi..sub.8, .phi..sub.9 so 
as not to generate during this time the shock detection outputs 
.phi..sub.14, .phi..sub.15. 
FIG. 2 shows another embodiment of an electronic timepiece as a whole 
according to the present invention. The electronic timepiece shown in FIG. 
2 is the same in connection and arrangement as that shown in FIG. 1, but 
further comprises a load detection circuit 15 connected in parallel with 
the shock detection circuit 13 in order to prevent the generation of the 
shock detection outputs .phi..sub.14, .phi..sub.15 during the time t.sub.1 
+t.sub.2 msec. After the lapse of t.sub.2 msec, the electromagnetic coil 
switching signals .phi..sub.5, .phi..sub.6 are generated and supplied to 
respective input terminals of the AND gates 23s, 23t whose outputs 
.phi..sub.10, .phi..sub.11 are supplied to the gates of the MOS 
transistors 24c, 24d. The operation of the driving circuit 24 by means of 
the electromagnetic coil switching signals .phi..sub.5, .phi..sub.6 will 
be described later in detail. 
In section II shown in FIG. 4, NOR gate 23i of the signal conversion 
circuit 23 generates a reverse signal .phi..sub.9 of the normal driving 
signal .phi..sub.2 which is supplied to the gate of the MOS transistor 24b 
and to one of the input terminals of the AND gate 23t. If the signal 
.phi..sub.9 is changed over from an H signal to an L signal, the MOS 
transistors 24b, 24c only shown in FIG. 3 become ON to cause current to 
flow the electromagnetic coil 25 in b.sub.o .fwdarw.a.sub.o direction, 
thereby rotating the rotor in a given direction. From t.sub.2 msec after 
the driving signal has been supplied, the electromagnetic coil switching 
signals .phi..sub.5, .phi..sub.6 are generated from the electromagnetic 
coil switching signal generation circuit 23d and supplied as respective 
outputs .phi..sub.10, .phi..sub.11 delivered from the AND gates 23s, 23t 
to the driving circuit 24. 
FIG. 10 illustrates the operation of the driving circuit 24 by means of the 
electromagnetic coil switching signals .phi..sub.10, .phi..sub.11. The 
driving signals .phi..sub.8, .phi..sub.9 are H signals and the P channel 
MOS transistors 24a, 24b are OFF, so that it is sufficient to consider the 
operation of the N channel MOS transistors 24c, 24d. 
Under the condition shown in FIG. 10(1), both the electromagnetic coil 
switching signals .phi..sub.10, .phi..sub.11 are H signals so that the 
transistors 24c, 24d become ON. The resistances under conduction 
conditions of the transistors 24c, 24d and the electromagnetic coil 25 
form a closed circuit. Under such condition, if the step motor is 
subjected to shock, the movement of the rotor causes the induced voltage 
to be generated in the coil 25 to make current flow therethrough. 
Under the condition shown in FIG. 10(2), the transistor 24d becomes OFF. 
Immediately before this condition, if current i flows through the 
electromagnetic coil 25, it generates the induced voltage L(di/dt) since 
the input impedance of the shock detection inverter 26c is considerably 
large, and as a result, it is possible to know that the step motor is 
under shock load. 
Under the condition shown in FIG. 10(3), the electromagnetic coil 25 is 
connected in the closed circuit. 
Under the condition shown in FIG. 10(4), the transistor 24c becomes OFF and 
the shock detection inverter 26a is set to be supplied with the induced 
voltage. The shock detection inverters 26c, 26a are alternately operated. 
This is because of the fact that the MOS transistors 24a, 24b, 24c, 24d 
have parasitic diodes 24e, 24f, 24g, 24h, respectively, (see FIG. 10(5)) 
and that lower than -0.3 V of the negatively induced voltage becomes 
clamped so that it is necessary to utilize the positively induced voltage 
only. 
FIG. 11 shows the induced voltage in the electromagnetic coil 25. As shown 
in FIG. 11, the electromagnetic coil 25 generates at its terminal a.sub.o 
a signal .phi..sub.12 and at its terminal b.sub.o a signal .phi..sub.13 
which is reverse with respect to the signal .phi..sub.12. 
FIGS. 9(1), 9(2), 9(3) and 9(4) show envelopes of the waves of the induced 
voltage signal .phi..sub.12 viewed at the terminal a.sub.o of the 
electromagnetic coil 25. FIG. 9(1) shows the signal .phi..sub.12 generated 
when the step motor is subjected to a shock after the driving pulse 
.phi..sub.8 has been supplied to the driving circuit 24 and the step motor 
has rotated by 1 step and then come to a standstill. FIG. 9(2) shows the 
signal .phi..sub.12 generated when the step motor is subjected to a shock 
after the driving pulse .phi..sub.9 has been supplied to the driving 
circuit 24 and the step motor has rotated by 1 step and then came to a 
standstill. FIGS. 9(1) and 9(3) show forwardly rotating shock waves and 
FIGS. 9(2) and 9(4) show reversely rotating shock waves. The wave shown in 
FIG. 9(4) can be detected by the shock detection inverter 26a. The wave 
shown in FIG. 9(2) must be detected by the shock detection inverter 26c. 
In the section II shown in FIG. 4, if the step motor is subjected to a 
reversely rotating shock, in the first place the output .phi..sub.14 is 
delivered from the shock detection circuit 26 and supplied to the input 
terminal of the AND gate 27a of the control circuit 27. In this case, the 
R-S flipflops 27c, 27d together with the outputs .phi..sub.16, 
.phi..sub.17 thereof are set to 0 and the not output .phi..sub.17 is the H 
signal. The signal .phi..sub.14 functions to set through the AND gate 27a 
the R-S flipflop 27c l. As a result, the not output .phi..sub.16 becomes 
the L signal so that the signal .phi..sub.15 can not pass through the AND 
gate 27b. As a result, the output .phi..sub.17 remains as the L signal. 
That is, if the first positive direction voltage of the induced voltage due 
to a shock is detected by the inverter 26a, an not output .phi..sub.16 
becomes the H signal. If the first positive direction voltage of the 
induced voltage due to the shock is detected by the inverter 26c, the 
signal .phi..sub.17 becomes the H signal. 
The phase discrimination circuit 23e of the signal conversion circuit 23 is 
set so as to deliver an L signal output by means of the ordinary driving 
signal .phi..sub.8 and deliver an H signal output by means of the 
reversing signal .phi..sub.9. In this case, the reversing signal 
.phi..sub.9 causes the phase discrimination circuit 23e to deliver an H 
signal, so that the control circuit output .phi..sub.19 is generated, 
thereby showing that the step motor is subjected to an reversely rotating 
shock. The control circuit output .phi..sub.18 becomes an H signal during 
t.sub.5 m sec to cause the compensation driving signal generation circuit 
23b to generate its output .phi..sub.3 which becomes the compensation 
driving signal which is in phase with the reversing signal .phi..sub.9. 
This compensation driving signal functions to correct the erroneous 
operation when the step motor becomes reversely rotated by the shock. 
When the step motor is not reversely rotated, this compensation driving 
signal does not operate the rotor, so that there is no inconvenience. 
After a shock has been detected, the electromagnetic switch signal can be 
stopped. In the present embodiment, in order to improve the stability of 
the electronic timepiece circuit, the OR gate output .phi..sub.19 of the 
control circuit 27 is set such that it becomes an H signal irrespective of 
the direction of shock after the shock has been detected and that the 
electromagnetic switching signal is prohibited during a given time. 
FIG. 5 shows a time chart at respective parts shown in FIG. 3 when the step 
motor is subjected to a forwardly rotating shock at a time between the 
normal driving signals in a similar manner as that shown in FIG. 4. 
Contrary to the case shown in FIG. 4, the signal .phi..sub.15 becomes the 
first detection output and the signal .phi..sub.17 becomes an H signal. 
The output signal .phi..sub.18 delivered from the control circuit 27 
remains as an L signal, and as a result, the compensation driving signal 
.phi..sub.3 is not generated. The output signal .phi..sub.19 becomes an H 
signal and the electromagnetic coil switching signal is prohibited for a 
given time. 
If the step motor is subjected to a forwardly rotating shock, even when the 
rotor is forwardly rotated by 1 step, the rotor is not operated by the 
normal driving signal and the erroneous operation is compensated. As a 
result, it is not necessary to generate the compensation driving signal. 
FIG. 6 shows a time chart at respective parts shown in FIG. 3 when the step 
motor is subjected to the reversely rotating shock immediately before the 
step motor is subjected to the normal driving signal .phi..sub.9. As shown 
in FIG. 6, in the first place, the output signal .phi..sub.15 is generated 
to make the output signal .phi..sub.17 of the R-S flipflop 27d an H 
signal. Since the not signal .phi..sub.7 of the output signal .phi..sub.7 
delivered from the phase discrimination circuit 23e is also an H signal, 
the output signal .phi..sub.18 delivered from the control circuit 27 
becomes an H signal. As a result, a compensation pulse is generated after 
the shock has ceased and the normal driving pulse .phi..sub.9 is delayed 
and then supplied to the driving circuit 24. As a result, it is possible 
to correct the erroneous operation of the step motor even when it is 
rotated in the reverse direction by the shock. 
FIG. 7 shows a time chart at respective parts shown in FIG. 3 when the step 
motor is subjected to the forwardly rotating direction immediately before 
the step motor is subjected to the normal driving pulse .phi..sub.9. As 
shown in FIG. 7, the normal driving pulse .phi..sub.9 is delayed and 
supplied to the driving circuit after the shock has ceased. 
As stated hereinbefore, the electronic timepiece according to the invention 
is capable of correcting the erroneous operation of the step motor by 
means of a compensation signal if the step motor is subjected to an 
external shock load in such direction that the shock tends to reversely 
rotate the step motor, of delaying the normal driving signal if the step 
motor is subjected to an external shock load immediately before the normal 
driving signal and hence preventing the erroneous operation of the step 
motor, thereby significantly improving the stability of the electronic 
timepiece, and decreasing the drag torque produced between the rotor and 
the stator of the step motor and hence decreasing the power input required 
for rotating the rotor by 1 step, thereby considerably reducing the 
consumed electric power.