GB2352061A

GB2352061A - Timepiece movement

Info

Publication number: GB2352061A
Application number: GB0025548A
Authority: GB
Inventors: Hiroyuki Hashizume; Koji Baba
Original assignee: Seiko Clock Inc
Current assignee: Seiko Time Creation Inc
Priority date: 1996-11-06
Filing date: 1997-11-06
Publication date: 2001-01-17
Anticipated expiration: 2017-11-06
Also published as: GB2352061B; GB0025548D0

Abstract

A timepiece movement comprises a minute wheel 12 and an hour wheel 14, which are rotated by a driving motor S2 (see Fig. 1) via a drive train. Each of the minute wheel 12 and the hour wheel 14 have apertures 12c, 14b formed therein. A luminous element 24 and a light receiving element 23b are arranged to face each other so as to form a light path therebetween. The hour and minute wheels 14, 12 are arranged such that respective apertures can be brought into alignment with the light path. Control means controls the operation of the luminous element 24 and the motor S2 (see Fig. 1) during an initialisation phase and uses a program to determine the position of the hour and minute wheels 14, 12 based upon the angular distance between successive apertures in the hour wheel 14b, 14c (see Fig. 5) detected by the light receiving element 23b.

Description

2352061 TIMZPIECE MOVEMENT The present invention relates to a timepiece

movement, and more particularly to a timepiece movement in which standard positions of a minute wheel and a second wheel, which can be independently rotated, can be detected.

A known timepiece movement is provided with a driving gear train for a second wheel and a driving gear train for a minute wheel having an aperture and a shading portion capable of being moved into the light path between a light emitting diode and an opposing light receiving sensor. This timepiece movement automatically performs an initial position detection by driving the above gear trains when the light emitting diode is operated. The initial position of the second wheel and hour and minute wheels is determined to be a position in which an output of the light" receiving sensor changes from level 0 to level 1.

In the above arrangement, a driving motor for driving the second wheel and a driving motor for driving the minute wheel and the hour wheel are provided and a photo-diode or a photo-transistor is used as the light receiving sensor. The driving motors for the second wheel and the hour and minute wheels are alternately rotated so that the aperture of the second wheel and the aperture of the hour and minute wheels coincide with each other. The light receiving sensor output becomes level 1, and the initial position detection is performed. Since there are a large number of arrangements of the aperture of the second wheel and the aperture of the hour and minute wheels a lot of time is necessary in order to make the apertures coincide with each other. Furthermore, a large proportion of each gear of the gear trains of the second wheel and the hour and minute wheels comprises apertures, thereby increasing the probability that infrared rays of the light emitting diode are transmitted therethrough. However, this construction does not easily enable the position of the hour and minute wheels to be determined so that the time needed for detecting the position increases. Further, since the aperture forms the greater proportion of the gear, the strength of the gear is low.

According to the present invention there is provided a timepiece movement, comprising:

a minute wheel and an hour wheel, which are rotated by a driving motor via a drive train, each of the minute wheel and the hour wheel having apertures formed therein; a luminous element and a light receiving element arranged to face each other so as to form a light path therebetween, the hour and minute wheels being arranged such that respective apertures can be brought into alignment with the light path; and control means for controlling the operation of the luminous element to emit light and the motor to rotate during an initialisation phase and using a program to determine the position of the hour and minute wheel based upon the angular distance between successive apertures in the hour wheel detected by the light receiving element.

Thus, the present invention enables the detection of the position of the second wheel using only a reflection type photo-sensor having a luminous portion and a light receiving portion and without being influenced by the position of hour and minute wheels.

Further, the position of the hour and minute wheels is detected by using only the light receiving portion of the above reflection type photo-sensor and separately having another luminous diode. Since the luminous diode is separately provided, an initial position detection of the hour an6 minute wheels can be performed by a relatively small aperture provided on the hour and minute wheels and by a number of pulses of a driving motor which provides rotation from an aperture to an adjacent aperture. Further, since the apertures provided on the hour and minute wheels are small, the strength of the wheels is sufficient.

According to an embodiment of the invention, a second wheel which is rotated by a first driving motor through a driving gear train for the second wheel and a minute wheel which is rotated by a second driving motor through a driving gear train for the minute wheel are coaxially provided within an upper and lower case in such a manner as to be independently rotatable. The second wheel is provided with an aperture, which can be aligned with the aperture formed on a first high speed transmitting wheel meshed with the second wheel, and with a reflecting portion at a predetermined angular interval from the aperture. A second high speed transmitting wheel meshed with the minute wheel is provided with a plurality of apertures at equal angular intervals. The minute wheel is provided with a plurality of apertures in such a manner as to oppose respective apertures of the second transmitting wheel at equal angular intervals, and the hour wheel, which is coaxially formed with-the minute wheel, is provided with a plurality of apertures which can be aligned with the aperture of the minute wheel and a plurality of light blocking portions having a different angular length to each other. A reflection type sensor comprising a first luminous element and a light receiving element mounted on the upper case, and a second luminous element mounted on the lower case, are respectively provided outside the first transmitting wheel, the second wheel, the second transmitting wheel, the minute wheel and the hour wheel in an opposed manner. A control circuit, for controlling the operation of said first and second driving motors, using an instalied program to perform an initialising action for detecting an initial position of said second, hour and minute wheels. The initializing action is performed by stepwise driving the above second wheel while the first luminous element is emitting light so as to detect a reflecting portion in which an output of the light receiving element is inverted from a level 0 to a level I and the light receiving element and the reflecting portion are opposed to each other. The motor is driven in a stepwise manner such that the second wheel moves through a predetermined angular interval from this position so that the light receiving element and the is aperture of the second wheel are aligned with each other. This position is set as the standard position of the second wheel and the first luminous element is turned off. Next, the minute wheel is stepwise driven while the second luminous element is emitting light so as to detect a position in which the output of the light receiving element changes from level 0 to level 1 and the position is set as a standard position of the hour and minute wheels. Next, the second motor is driven until the output of the light receiving element changes to the level 0, and is driven thereafter for a further time until the output of the light receiving element changes from level 0 to level 1. The number of driving pulses of the second driving motor for the further time is counted and the time is determined by the relation between the time and the counting number stored in the control circuit and the position at which the output of the light receiving element changes is set as a standard position of the hour wheel. It is preferable that the angle between the aperture of the above second wheel and the reflecting portion is 180 degrees.

For a better understanding of the present invention, and to show how it may be brought into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a plan view of the timepiece movement, in which a printed circuit board and an upper case are omitted.

Figure 2 is a cross sectional view along the line A-A in Figure 1.

Figure 3 is another cross sectional view showing a state in which a reflecting portion of a second wheel is positioned in a light path of a reflection type sensor and a second light emitting diode.

Figure 4 is a plan view which shows respective apertures of a fourth wheel for driving a minute hand, a minute wheel and an hour wheel opposed to each other.

Figure 5 is a plan view of the hour wheel.

Figure 6 is a flow chart which shows an initial position detecting operation.

The invention will now be described with reference to the accompanying drawings.

As shown in Figures 1 to 3, an upper case 1 and a lower case 2 are connected opposing each other, and a middle plate 3 is provided between them parallel to the upper case 1 and lower case 2. A first driving motor S1 and a second driving motor S2, which are mentioned below, are provided through pivot portions formed on the upper case 1, the lower case 2 and a supporting hole portion formed in the middle plate 3. The first driving motor S1 and the second driving motor S2 are controlled by a control circuit so as to be independently operated.

The driving motor S1 is provided with a reduction gear train Ri which transmits the rotation of a rotor 4, which is intermittently rotated by the driving motor S1, to a second wheel 7 mentioned below. The driving motor S2 is provided with a reduction gear train R2 which transmits the rotation of a rotor 8, which is intermittently rotated by the driving motor S2, to a minute wheel 12 mentioned below.

The rotor 4 and the driving gear train Ri are rotatably supported by the upper case 1 and the middle plate 3. A driving wheel 5 is meshed with a rotor pinion 4a of the rotor 4, a third gear Ga of a third wheel 6, in an embodiment having a higher speed first transmitting wheel, is meshed with the driving wheel 5 and a second gear 7a of the second wheel 7 is meshed with a third pinion 6b of the third wheel 6.

In a normal driven state of hands, the rotor 4 is rotated a half rotation every second by a driving pulse generated every second from a control circuit, as discussed below. A permanent magnet (not shown) is fixed to the rotor 4.

The rotor 8, the driving gear train R2 and a transmission gear train R3 are rotatably supported by the upper case 1, the middle plate 3 and the lower case 2. A driving wheel 9 is meshed with a rotor pinion 8a of the rotor 8 and a third gear 10a of a third wheel 10 is meshed with the driving wheel 9. A fourth gear 11a of a fourth wheel 11, in an embodiment having a higher speed second transmitting wheel, is meshed with a third pinion 10b of the third wheel 10 and a minute gear 12a of the minute wheel 12 is meshed with a fourth pinion 11b of the fourth wheel 11 for driving the minute hand.

A transmission gear 13a of a transmission wheel 13 is meshed with a minute pinion 12b of the minute wheel 12 and an hour gear 14a of an hour wheel 14 is meshed with a transmission pinion 13b of the transmission wheel 13.

In a normal driven state of hands, the rotor 8 is rotated a half rotation every fifteen seconds by a driving pulse generated from a control circuit. A permanent magnet 8b is fixed to the rotor 8 for driving the minute hand. The second wheel 7 and the minute wheel 12 are coaxially provided in such a manner as to be independently rotated.

As shown in Figure 1, the driving motor S1 for driving the second hand comprises the rotor 4, a coil frame 15, a coil 16 and a stator 17. The driving motor S2 for driving the minute hand comprises a rotor 8, a coil frame 19, a coil 20 and a stator 21. Both of the stators 17 and 21 are positioned and fixed by a plurality of pins 3a, projecting toward the upper case 2, in the middle plate 3, which extend through apertures formed on the stators.

As shown in Figure 3, a printed circuit board 22 is fitted to a guide pin la formed on the outer surface is of the upper case I and an end portion is engaged by an engaging pawl 2a formed on the lower case 2.

A reflection type sensor 23 including both a luminous element (a light emitting diode) 23a having a light emitting function and a light receiving element (a photo-transistor) 23b having a light detecting function is mounted on the upper case 1, and a further luminous element (a light emitting diode) 24 for emitting light to the reflection type sensor 23 is mounted on the lower case 2 opposite the reflection type sensor 23. A pressing plate 25, made of a rectangular thin plate resilient member, is provided in a back surface of the light emitting diode 24. The pressing plate 25 is inserted into a thin groove (not shown) formed on the lower plate 2 and biases and presses the light emitting diode 24 forward. The reflection type sensor 23 and the further light emitting diode 24 are both electrically connected to the printed circuit board 22. Various semiconductor elements (not illustrated) are connected to the printed circuit board 22 so as to form a control circuit. The control circuit controls the operation of the first and second driving motors S1 and S2. A program for performing an initializing action used for detecting an initial position of the second wheel 7 and the hour and minute wheels 14 and 12 is installed in the control circuit. An aperture 3b, which enables the light from the second light emitting diode 24 to reach the reflection type photo-sensor 23, is provided in the middle plate 3.

A timepiece movement of the present embodiment has two driving systems and in order to detect positions of the respective driving systems, two detecting systems are provided in the upper and lower cases 1 and 2.

Initially, a position detecting system for driving the second hand will be explained below.

The third wheel 6 for driving the second hand is provided with a small aperture Gc for detecting an initial position and an aperture 6d for determining the mutual relationship for assembling the gear train. The aperture 6d for determining the mutual relationship is smaller than the aperture Ga, is formed at a position shifted by 180 degrees with respect to the aperture 6a, and is disposed nearer to the center of rotation than the aperture 6c.

The second wheel 7 is provided with a small aperture 7b and a reflecting portion 7c comprising a reflecting plate which transmits light and is arranged such as to reflect the light from the first light emitting diode 23a of the reflection type sensor 23.

The small aperture 7b and the reflecting portion 7c are arranged at the same distance from the center and at a predetermined angle to each other i.e. shifted by 180 degrees with respect to each other. The second wheel 7 also is provided with an aperture 7d for determining the mutual relationship for assembling the gear train, and the aperture 7d for determining the mutual relationship is smaller ihan the aperture 7b and is formed nearer to the center of rotation than the aperture 7b.

The third wheel 6 for driving the second hand is.

arranged such that when the aperture 7b or the reflecting portion 7c of the second wheel 7 is disposed in a position opposite to the reflection type sensor 23, the aperture 6c for detecting the initial position is always positioned between the reflection type sensor 23 and the position opposing to the aperture 7b or the reflecting portion 7c.

The surface of the third wheel 6 for driving the second hand is formed as a black surface which does not reflect the light, and the surface of the second wheel 7, except the reflecting portion 7c, is also formed as a black surface which does not reflect the light.

As shown in Figure 4, the fourth wheel 11 in the drive train S2 is provided with three small apertures lic having the same shape and an angular extent of 15 degrees which are formed at the same distance from the center of rotation and at an equal central angular interval of 120 degrees.

The minute wheel 12 is provided with three small apertures 12c having the same shape and an angular extent of 9 degrees which are formed at an equal central angular interval of 120 degrees.

The hour wheel 14 is provided with seven small apertures 14b having the same shape which are formed at a different central angular interval. Accordingly, the seven small apertures 14b of the hour wheel comprise six apertures 14b having an angular extent of 9 degrees and an aperture 14c having an angular extent of 19 degrees. A plurality of light blocking portions 14d having different angular lengths are formed between these apertures.

The apertures for determining the mutual relationship for assembling the gear train (not shown) are formed in each of the fourth wheel 11, the minute wheel 12 and the hour wheel 14. When the gear train is assembled, the aperture 6c of the third wheel, the aperture 7b of the second wheel, the aperture 11c of the fourth wheel, the aperture 12c of the minute wheel and one of the apertures 14b of the hour wheel are aligned along the straight light path between the reflection type sensor 23 and the light emitting diode 24, by means of the aperture for determining the mutual relationship of each of the fourth wheel 11, the minute wheel 12 and the hour wheel 14, the aperture for determining the mutual relationship 6d of the third wheel 6 for driving the second hand and the aperture for determining the mutual relationship 7d of the second wheel 7.

An operation of the position detecting system for driving the second hand and an operation of the position detecting system for driving the hour and minute hands will be explained with reference to Figure 6. while the first light emitting diode 23a of the reflection type sensor 23 is emitting light, the first driving motor S1 is rotated quickly so as to stepwise drive the second wheel 7 so that the reflecting portion 7c of the second wheel 7 is opposite the reflection type sensor 23 and the reflecting portion 7c reflects the light of the first light emitting diode 23. When the reflected light reaches the photo-transistor 23b, the output of the photo-transistor 23b changes from the level 0 to the level 1 and the reflecting portion opposing position is detected. When the output of the photo-transistor 23b changes from the level 0 to the level 1, the first light emitting diode 23a is turned off and the second light emitting diode 24 is turned on.

Next, the first driving motor S1 is again driven fast from the reflecting portion opposing position and -li- the second wheel 7 is stepwise driven to rotate by 180 degrees so that the aperture 7b of the second wheel 7 is aligned with the reflection type sensor 23. This position is determined to be a standard position of the second wheel 7 and the first driving motor Sl is stopped. Accordingly, the position in which the aperture 7b of the second wheel 7 is aligned with the reflection type sensor 23 becomes the standard position of the second wheel 7, whereby the position detection of the second hand is completed. In this state, the aperture 6c of the third wheel for driving the second hand and the aperture 7b of the second wheel are aligned with each other on the straight light path between the reflection type sensor 23 and the second light emitting diode 24 so that the gear train Rl for the second wheel does not affect the light transmission of the second light emitting diode 24 of the hour and minute hands.

Next, in order to perform the position detection of the hour and minute hands, while the second light emitting diode 24 is switched on, the second driving motor S2 is rotated quickly so as to stepwise drive the minute wheel 12. In a short time, the second light emitting diode 24, the aperture l4b of the hour wheel, the aperture 12c of the minute wheel, the aperture llc of the fourth wheel for driving the minute hand and the reflection type sensor 23 are aligned and the light of the second light emitting diode 24 reaches the photo transistor 23b, thereby detecting the position in which the output of the photo-transistor 23b changes from the level 0 to the level i. This position is set as a standard position of the.hour and minute wheels 14 and 12. If the second driving motor S2 is driven from this position, the output of the photo-transistor 23b changes to the level 0, and by determining, on the basis of the times previously stored in the control circuit, the time corresponding to the number of driving pulses of the second driving motor S2 until the output of the photo-transistor 23b is further inverted from the level 0 to the level 1, this inverted position is set as the standard position of the hour wheel.

Accordingly, when the second driving motor S2 is driven from the standard position of the hour and minute wheels 14 and 12, the fourth wheel 11 for driving the minute hand is rotated at a degree of 15 degrees for a first pulse so as to invert the output of the photo transistor 23b to the level 0.

The fourth wheel 11 for driving the minute hand is structured such that the minute wheel 12 rotates an angle of 10.5 degrees, which is not less than the angle is of 9 degrees of the aperture 12c, every 7 pulses while the next aperture 11c comes to the position opposing to the second light emitting diode 24 at 8 pulses, the output of the photo-transistor 23b is inverted to the level 0 and the number of the driving pulse of the second driving motor S2 is counted until the output of the photo-transistor 23b is further inverted from the level 0 to the level 1 thereafter is set to an integral multiple of 80. In the present embodiment, the timing of the level 1 is set to twelve o'clock, twenty minutes past two o'clock, three o'clock, five o'clock, six o'clock, forty minutes past seven o'clock, nine o'clock, and forty minutes past eleven o'clock. In order to show what time the level 1 corresponds to, the time is set to twelve o'clock when the number of driving pulses from the level 0 to the level 1 is 80 pulses; to twenty minutes past two o'clock when 560 pulses are counted; to three o'clock when 160 pulses are counted; to five o'clock when 480 pulses are counted; to six o'clock when 240 pulses are counted; to forty minutes past seven o'clock when 400 pulses are counted; to nine o'clock when 320 pulses are counted; and to forty minutes past eleven o'clock when 640 pulses are counted. When the time corresponding to the number of the driving pulses taken for the output to change from the level 0 to the level 1 is determined, the second light emitting diode 24 is turned off.

Accordingly, after completing the initial position detection, the initial position detecting time is automatically corrected to the present time informed by the standard frequency second time signal by means of the control circuit and then used.

In the present embodiment, while detecting the standard position of the second wheel, the first light emitting diode 23a is turned off when the output of the photo-transistor 23b is inverted from the level 0 to the level 1. However, the invention is not limited to this structure and the first light emitting diode 23a may be turned off any time before the minute wheel is stepwise driven during operation of the position detecting system for driving the hour and minute hands.

As mentioned above, since the timepiece movement in accordance with the present invention uses a reflection type photo-sensor and the driving gear train for driving the second hand is independently provided as a single detecting system, the operation for detecting the position of the second hand can be performed using only the driving gear train for driving the second hand, so that the initial position detecting operation can be quickly performed.

Since the detect-ion of the position of the hour and minute hands can be performed be detecting the number of pulses between the apertures, the detection of their position can be performed without rotating the hour wheel for a complete revolution and the initial position detection can be performed quickly.

Since the detection of the hour and minute hands are performed using smali apertures, the strength of the gear can be increased. if the angle between the aperture of the second wheel and the reflecting portion is 180 degrees, the aperture and the reflecting portion can be easily set.

Claims

1. A timepiece movement, comprising:

2. The timepiece movement as claimed in claim 1, further comprising a second wheel having an aperture formed therein wherein during the initialisation phase the second wheel is controlled so that the aperture of the second wheel is aligned with the light path.

3. The timepiece movement as claimed in claim 1 or 2, wherein the hour wheel has a plurality of apertures formed therein, and the angular distances between successive pairs are different.

4. The timepiece movement as claimed in any one of the preceding claims, wherein the hour wheel has a plurality of light blocking portions of different angular lengths formed thereon.