JPH0372953B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic timepiece having a plurality of step motors for independently driving a hand that displays a normal time and a hand that displays other times.

FIG. 1 is a plan view showing a well-known step motor consisting of a rotor 1, a stator 2, and a coil block 3 having permanent magnets. The rotation is transmitted to the pointer holding wheel through the dial to display the time. The stator 2 has two narrow parts 2a and 2a' located symmetrically with respect to the center of the rotor 1 between the rotor 1 entry hole and the outer periphery, and two arcuate notches 2b around the rotor 1 entry hole. and 2b'. Let S be the notch area of the notches 2b and 2b', and let θ be the narrow angle connecting the intersection of the circle with the circle at the entrance of the rotor 1 and the center of the rotor 1. In a state where there is no electrical output signal, the rotor 1 generates potential energy in the rotational direction due to the magnetic field of the permanent magnets and the positions and shapes of the stator cutouts 2b and 2b' and the narrow parts 2a and 2a'. A static stable position and a neutral position are created. This static stable position is located at the notches 2b and 2.
It is located approximately 90 degrees rotated relative to b′.

In FIG. 2, the horizontal axis represents the rotor position, and the vertical axis represents potential energy.
Point A is a static stable position, where the rotor 1 is likely to remain at that position when no electrical output signal is applied to the coil, and is likely to remain at this point. The rotational force caused by this is called the pulling torque t, and point B is called the neutral point. The relationship between this pulling torque t, the notch area S of the stator, the narrow angle θ, the magnetic flux φ of the permanent magnet, and the clearance δ between the outer diameter of the permanent magnet and the rotor 1 entry hole of the stator 2 is roughly expressed as t=KSθφ/δ ² (K is the proportionality coefficient). The pulling torque t is the slope of this curve and is determined by the amplitude l, ie the difference in potential energy.

FIG. 3 shows the relationship between the pulling torque t and the maximum value of the output torque T. The larger the pulling torque t, the larger the maximum value of the output torque T. Furthermore, in order to bring the output torque T closer to its maximum value, it is necessary to increase AT (ampere turns), which is the magnetomotive force of the coil 3. Note that the pull torque and the output torque are not uniquely the same. The pull torque is a force that tries to keep the rotor in a fixed position, and in particular, prevents the rotor from rotating due to unbalanced needles in response to external disturbances. As mentioned above, the factors that determine the pulling torque are S, θ, φ, and δ. On the other hand, the output torque is such that the hands can be moved against a load such as a calendar feed torque, and what determines it is the ampere-turn of the coil, the moment of inertia of the rotor, etc. in addition to the factors of the above-mentioned pulling torque.

As mentioned above, in order to maximize the output torque under the condition of the pull torque t, it is necessary to set the optimum values of the above-mentioned ampere-turns, rotor moment of inertia, etc.

In the case of the conventional analog clock using the above-mentioned step motor, even if a disturbance caused an error in the indication, it was impossible to detect it as long as the time accuracy was within the range. However, in watches that use multiple step motors to drive each independently, especially chronograph (hereinafter abbreviated as CG) watches,
It has a CG series and a normal time series, and the CG series is 0.
When the needle is returned to its position, errors caused by disturbances and display errors caused by needle skipping become clear.

That is, if the CG series is a stop watch, it is necessary to return to the 0 position in order to use that function. There are two methods for returning to the zero position. One method uses a cam mechanism to manually return the CG series pointer to the zero position, and the other method drives the CG series step motor to return the CG series pointer to the zero position. It is. With this step motor system, for example, if you start the second CG hand from the 12 o'clock position, advance it to the 4 o'clock position in 20 pulses, and stop the second CG hand at that position, then Reset function allows seconds
When returning the CG pointer to the 12 o'clock position, that is, the 0 position, the CPU of the electronic watch determines that the second CG pointer is at the 4 o'clock position, and drives the step motor for 40 pulses from that position to return the second CG pointer to the 4 o'clock position. Advance to the 12 o'clock position. Here, when the second CG hand is stopped at the 4 o'clock position and the watch is subjected to external disturbances such as a fall impact, rotational force due to the unbalance of the second CG hand acts on the holding wheel, which is applied to the rotor. is transmitted and the rotor rotates. 0 in this state
When returning to position, with the former cam mechanism method,
Second CG regardless of the amount of rotor rotation due to disturbance
Although it is possible to return the pointer to the zero position, in the latter step motor method, the second CG pointer deviates from the zero position by the amount of rotation of the rotor due to disturbance.

Furthermore, it is desirable for the secondary hands (hands held by a holding wheel placed eccentrically from the center of the watch) to have the same shape (with the same level of unbalance) for design reasons, and by standardizing them, processing and This will be advantageous in terms of after-sales service. On the other hand, the reduction ratio from the rotor pinion to the secondary hand holding wheel and the amount of unbalance between the hands held by the holding wheel placed at the center of the watch and the secondary hand differ depending on the time displayed by the secondary hands, so The degree of display error varies. Each motor needs to be optimized depending on the conditions required of the watch, especially the output torque and current consumption.

The present invention eliminates the above-mentioned drawbacks and satisfies each of the desired conditions, and sets the pulling torque according to the unbalance amount of the pointer corresponding to each step motor and the reduction ratio of the wheel train. The present invention is characterized in that the strength against external shocks of each step motor is made similar, and the drive current of each coil is adjusted so that each step motor is driven with a predetermined output torque accordingly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 4 to 8.

10 is a ground plane, 9 is a power supply, 8 is a MOS-IC, and 7 is a circuit board, forming an electrode pattern for transmitting an output signal from the MOS-IC 8 to each motor. 1
1, 21, 31, and 41 are rotors each composed of a rotor magnet, a seat, and a rotor pinion; 13, 22, and 3;
2 and 42 are stators, and 13, 23, 33, and 43 are coil blocks each composed of a magnetic core, a coil lead board, a coil lead board seat, and a coil.
Rotor 11, stator 12 and coil block 1
3. Motors each composed of a rotor 21, a stator 22, and a coil block 23, a rotor 31, a stator 32, and a coil block 33, a rotor 41, a stator 42, and a coil block 43 are used as an hour/minute motor, a second CG motor, and a minute CG motor. Motor, 5/100 seconds
It is called a CG motor.

The rotational motion of the rotor 11 is transmitted from the rotor pinion 11a to the hour wheel 19 via the fifth wheel & pinion 14, the fourth wheel & pinion 15, the third wheel & pinion 16, the second wheel & pinion 17, and the minute wheel & pinion 18. , hour wheel 19 hold a minute hand 50 and an hour hand 51, respectively, and display the minutes and hours of the normal time. On the other hand, the fifth wheel & pinion 14 also meshes with the seconds wheel 20, and the seconds wheel 20 holds the second hand 52 and displays the seconds of the normal time. Further, the reduction ratio of the rotor pinion 11a and the second wheel 20 is set to 1/30, and the hands move in 1 second steps.

The rotational motion of the rotor 21 is transmitted from the rotor pinion 21a via the seconds CG intermediate wheel 24 to the seconds CG wheel 25 holding the seconds CG hand 53, thereby displaying seconds in the CG system. The reduction ratio of the rotor pinion 21a and the second CG wheel 25 is set to 1/30, and the hands move in 1 second steps.

The rotational motion of the rotor 31 is transmitted from the rotor 31a via the minute CG intermediate wheel 34 to the minute CG wheel 35 holding the minute CG hand 54, thereby displaying the minutes of the CG system. The reduction ratio of the rotor pinion 31a and the minute CG wheel 35 is set to 1/15, and the hands move in one-minute steps.

The rotary motion of the rotor 41 is 5/100 seconds CG from the rotor pinion 41a through the intermediate wheel 44.
It is transmitted to the 5/100 second CG wheel 45 holding the hand 55, and displays 5/100 seconds of the CG system. The reduction ratio of the rotor kana 41a and the 5/100 second CG car is set to 1/10 and the hand moves in 5/100 second steps.

The rotors 11, 31, and 41 are common, and the rotor 21 differs from the other rotors only by the rotor pinion 21a. The reduction ratio between each rotor pinion and the gear meshing with the rotor pinion is the same. Stator 32
and 42 are common, and the stators 12 and 22 have notches 12b and 12b' (notch area S ₁ ) and notch 2.
2b and 22b' (notch area S ₁ ) are set to be the same. Notches 32b and 3 of stators 32, 42
The notch area S ₂ of 2b', 42b and 42b' is the notch area
The pull torque t of the motor is set to be approximately twice that of _S1 . Furthermore, the rotor entry hole diameter and stator thickness of the four stators are set to be the same. Since this is implemented using the stator with the least number of component parts in order to change the pulling torque t, it is possible to achieve the lowest cost.

20 second cars, 35 minute CG cars, 45 5/100 second CG cars
is eccentric from the center of the clock, and the seconds CG wheel 25 is located at the center of the clock. In terms of appearance (design), it is desirable that the second hand 52, the minute CG hand 54, and the 5/100 second CG hand 55 have the same shape. ) are approximately the same. When the watch is subjected to a disturbance such as a fall impact, rotational force acts on the holding wheel due to the amount of unbalance of the hands, which is transmitted to the rotor. If this force is greater than the pulling torque,
This impairs the normal movement of the rotor and causes display errors.

Display error can be expressed by a disturbance coefficient, and the larger this value is, the more likely display error is to occur. The relationship between the disturbance coefficient K, needle unbalance amount A, reduction ratio Z, and pulling torque t is expressed as K=A.Z/t. In the embodiment of the present invention, the disturbance coefficient of the second hand 52 is set to 1, and the disturbance coefficient of the auxiliary hand is set to 0.2 to 2, so that it is possible to eliminate display errors caused by disturbances that occur during normal carrying. By the way, set the unbalance amount A of the secondary hand to 2 mgmm or less, and set the unbalance amount of the second CG hand 53 to 4.
It is set below mgmm. The second CG hand 53 has a large amount of unbalance compared to the secondary hand, but when pressed, the second CG hand 53
The pressing force provides a large resistance to disturbances, and the amount of unbalance can be increased accordingly, thereby expanding the variety of designs.Furthermore, the pressing spring 60 is intended to prevent the second CG hand from fluctuating due to buckling.

The output torque of the hour/minute motor and second CG motor is
Each calendar load (not shown), pressing spring 60
In order to increase the safety factor of stopping due to the load, a constant torque is required, and the minute CG motor and 5/100
Since the CG motor has a large disturbance coefficient K, it is necessary to increase the pulling torque.In order to satisfy these requirements, reduce power consumption, and extend the service life, coil blocks 13, 23, 33, and 43 are used.
Change AT (coil blocks 13, 23, 33
and 43 are common), and the output signals from MOS-IC8 (pulse widths of 5.4 msec and 6.8 msec, respectively) are set differently.

As described above, in this embodiment, the reduction ratio of the wheel train of the long hand-shaped first pointer whose rotation axis is at the center of the watch is made larger than the reduction ratio of the wheel train of the second pointer whose rotation axis is eccentric from the center of the watch. As a result, the pulling force between the rotor and stator of the first step motor that moves the first pointer is set to be smaller than the pulling force of the second step motor. The first pointer, which has the axis of rotation at the center of the watch, inevitably has a large pointer length, has a small step angle, and is used frequently.
By making the step motor's pulling torque smaller than the others, significant power consumption can be achieved.

In addition, in this embodiment, the pulling torque of the second step motor having a small reduction ratio of the wheel train is increased, and the pulling torque of the first step motor that drives the long hand-shaped first pointer is increased. The strength against external shocks of each step motor can be made similar to each other by reducing the speed reduction ratio in the row by increasing the pull torque of the second step motor that drives the second pointer having a small speed reduction ratio. . In other words, with this configuration, when an external impact is applied, all the step motors will operate normally until the impact value reaches a certain level, and if the impact value exceeds this, the needle skipping phenomenon will occur in all the step motors. This solves the conventional problem of only specific step motors being extremely vulnerable to external disturbances.

In this example, in order to obtain appropriate pulling torque for each motor, the notch area of the stator is changed. A similar effect can be obtained by changing the stator thickness, etc. Furthermore, although the description has been made using a chronograph, the present invention may be applied to a clock using two or more step motors such as an analog alarm, or may be applied to a two-piece step motor or the like.

Furthermore, in this embodiment, the four step motors have two types of pull torque t (notch area S ₁ and S ₂ ), but by setting the pull torque of each step motor separately, lower power consumption can be achieved. It is also possible to

As described above, according to the present invention, the pulling torque is set according to the unbalance amount of the pointer corresponding to each step motor and the reduction ratio of the wheel train, and the strength against external shocks of each step motor is approximated. By adjusting the drive current of each coil so that each step motor is driven with a predetermined output torque accordingly, when an external impact occurs, only a specific step motor will respond to the external impact. In addition to solving the problem of being extremely weak against shock, if the shock value exceeds the limit value, needle skipping occurs in all step motors. This has the effect of making it possible to detect indication errors within accuracy.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a step motor.
FIG. 2 is a diagram showing the relationship between the rotational position of the rotor and potential energy, and FIG. 3 is a diagram showing the pulling torque and output torque. FIG. 4 is an assembled plan view showing one embodiment of the present invention. 5 to 8 are assembled sectional views showing one embodiment of the present invention. 1, 11, 21, 31, 41...rotor, 2, 1
2, 22, 32, 42...stator, 2b, 2b',
12b, 12b', 22b, 22b', 32b, 32
b', 42b, 42b'...notch, 3, 13, 23,
33, 43...Coil block, 14...Fifth wheel, 2
0...second car, 24...second CG intermediate car, 25...second CG car,
34...minute CG intermediate car, 35...minute CG car, 44...5/
100 seconds CG intermediate car, 45...5/100 seconds CG car, 52...
Second hand, 53...Second CG hand, 54...Minute CG hand, 55...
5/100 second CG hand.

Claims (1)

[Claims] 1. Unbalance amount A having a rotating shaft at the center of the clock
The watch consists of a first pointer in the shape of a long hand with a large diameter, a second pointer in the shape of a short hand with a small unbalance amount A that has a rotation axis eccentric from the center of the watch, and a rotor, stator, and coil with permanent magnets, each of which has a different shape. first and second step motors driven by a predetermined output torque T; a first wheel train with a large reduction ratio Z that transmits the rotation of the first step motor to the first pointer; and the second step motor. In an electronic watch equipped with a second wheel train having a small reduction ratio Z that transmits the rotation of Set the torque t to make each step motor similar in strength against external shock, and adjust the drive current of each coil so that the first and second step motors are driven with the predetermined output torque T. An electronic watch that is characterized by: K=A・Z/t