JPS6117313B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for driving a step-type synchronous motor for a timepiece, and more particularly, to a method for reducing noise (impact noise) of a step-type synchronous motor for a timepiece.

The general operating principle of a step-type synchronous motor 10 for a watch is shown in FIG. Although the diagram here shows a case where the permanent magnet rotor 100 has two poles, the same applies to a case where the permanent magnet rotor 100 has multiple poles.

A typical step-type synchronous motor 10 for watches has a permanent magnet rotor 100 magnetized symmetrically with N and S.
and a stator 102 whose magnetic poles are alternately excited by an excitation coil 103.
The left and right sides are asymmetrical, and a misalignment is created between the stator 102 and the permanent magnet rotor 100, so that even in a statically stable state, the magnetic pole position of the permanent magnet rotor 100 remains at X as shown in Figure 1a. A phase is generated by θ0 with respect to the axis.

When electrical input pulses are alternately applied from the drive unit 104 to the excitation coil 103 in this state, the permanent magnet rotor 100 rotates stepwise by a constant angle each time the excitation direction changes.

The drive waveform of the step-type synchronous motor for watches is the second waveform.
In the figure, the length from the rising pulse a to the rising pulse b of the next reverse pulse is determined by how many seconds the hands move.
τ indicates excitation time. Here, the width of the excitation time τ is narrow because the coil is excited and the permanent magnet rotor 100 is
This is because once the rotation of the pulse ends, the excitation is useless until the next pulse.

To explain the operation of the step type synchronous motor 10 in more detail, the permanent magnet rotor 100 is stable at a position of θ0 before voltage is applied, and when voltage is applied, it rotates at the rising edge of the pulse waveform. , as shown in Figure 1b, it temporarily stabilizes at the θ position while making damped oscillations, and then moves from θ to θ0 at the falling edge of the pulse waveform while also making damped oscillations, resulting in a total of 1 step, and the same operation follows. do.

When the permanent magnet rotor 100 rotates and takes one step while continuing the damping motion, the bearing and shaft of the permanent magnet rotor 100, the permanent magnet rotor 100
The next gear transmitted and the teeth of the permanent magnet rotor 100〓〓〓〓〓
Since there is a clearance between the mating parts, impact noise is generated when these parts collide with each other. This was causing motor noise.

In recent years, with the shift from mechanical watches to crystal watches, the noise of watches has been decreasing, and the noise of step-type synchronous motors for watches has become a major problem.

By the way, one method of reducing this impact noise is to reduce the angular velocity of the permanent magnet rotor 100. For this reason, conventionally, as shown in FIG.
A method has been proposed in which the angular velocity of the permanent magnet rotor 100 is reduced by chopping the latter half of the drive pulse (the part shown in the figure) into fine pulses, thereby reducing the noise. However, the sound pressure distribution state of the impact sound within the drive pulse is as shown in FIG. As can be seen from Figure 4, the part where the sound pressure is large, that is, the part that generates a large impact sound, is the first half of the applied driving pulse (part A in Figures 3 and 4). . Therefore, even if the second half of the drive pulse is stopped to reduce the impact noise generated in the second half of the drive pulse as in the conventional method, the step type synchronous motor for a watch 10
This was insufficient to reduce noise, causing problems.

SUMMARY OF THE INVENTION The present invention has been made in view of the conventional drawbacks, and an object of the present invention is to provide a more effective noise reduction mechanism for a step-type synchronous motor for a timepiece.

In order to achieve the above object, the present invention detects the front part of a step hand movement pulse output from a waveform shaping circuit, and modulates the step hand movement pulse with a frequency signal having a cycle shorter than the pulse width of the pulse during the detection period. It is characterized by:

FIG. 5 is a circuit diagram showing a motor drive section in an embodiment of the present invention, and FIG. 6 is a time chart. This embodiment uses a reference signal generator 2, a frequency dividing circuit 4 that divides the frequency signal of the reference signal generator 2 to 0.5Hz, a waveform shaping circuit 6 according to the present invention, a drive circuit 8, and a step type synchronous motor 10 for a watch. configured. The waveform shaping circuit 6 includes an AND gate 12,
14, 16, 18, 20, 22, inverter 2
4, 26, 28, 30, exclusive or gates 32, 34.

Next, the operation of this circuit will be explained.

Output lines 40, 42, 44, 46 of frequency dividing circuit 4,
48 has 8Hz, 4PH, 2Hz, 1Hz, 0.5 respectively.
Hz signal is generated. These signals are applied to AND gate 12. And 8Hz of output line 40,
4Hz of output line 42, 2Hz of output line 44, output line 4
The 1 Hz signal on output line 48 and the 0.5 Hz signal on output line 48 are applied to AND gate 14 via inverter 24 . As a result, the output line 5 of the AND gate 12
0 has a pulse width of 2 seconds as shown in Figure 6.
A signal outputting a 62.5 mS pulse is obtained, and the same signal as the signal on the output line 50 with a 1 second phase shift is obtained on the output line 52 of the AND gate 14. The signal on this output line 50 is applied to one of the AND gates 18. The AND gate 18 has an inverter 2
A 16Hz signal 54 from the frequency divider circuit 4 via the inverter 6 and a 32Hz signal 56 from the frequency divider circuit 4 via the inverter 28 are applied. On the other hand, the signal on output line 52 is applied to one input of AND gate 16. AND gate 16 also has 16Hz signal 52 and 32Hz signal 54
is applied. This allows AND gate 18
On the output line 58 of the AND gate 18, a signal that outputs a pulse with a pulse width of 15.625 mS with a period of 2 seconds is obtained as shown in FIG.
The same signal as the signal on the output line 58 with a second phase shift is obtained. The signal on this output line 58 is the AND gate 2
The signal on output line 60 is applied to one input of AND gate 20. The other input of the AND gates 20 and 22 receives a 512Hz signal 6 from the frequency divider circuit 4 via the inverter 30.
2 is applied. For this reason, and gate 22
The signal of the output line 58 modulated with the 512 Hz signal 62 is obtained on the output line 64 of. Further, on the output line 66 of the AND gate 20, a signal of the output line 60 modulated with a 512 Hz signal is obtained. The signal on output line 64 is applied to one input of exclusive OR gate 32, and the signal on output line 66 is applied to one input of exclusive OR gate 34. The signal on the output line 50 of the AND gate 12 is applied to the other input of the exclusive OR gate 32, and the signal on the output line 52 of the AND gate 14 is applied to the other input of the exclusive OR gate 34. As a result, the output line 68 of the exclusive OR gate 32 receives a pulse that is in phase with the signal obtained on the output line 50 and that is in phase with the signal obtained on the output line 50.
A signal is obtained in which the front part of the bus is modulated with a 512Hz signal. Further, the output line 70 of the exclusive OR gate 34 has the same phase as the signal obtained on the output line 52 and the front part of the pulse obtained on the output line 52.
The signal will be modulated with a 512Hz signal. The step hand motion pulses on the output lines 68 and 70 are applied to the timepiece step type synchronous motor 10 via the drive circuit 8.

The drive pulse obtained in this way is shown in the front part of the drive pulse (the part B in the figure) as shown in Figure 7.
is being tuned with a 512Hz signal. Therefore, when the front part of the drive pulse is applied to the step-type synchronous motor 10 for a timepiece, the angular velocity of the permanent magnet rotor 100 of the step-type synchronous motor 10 for a timepiece is small, so that the impact noise becomes small. Therefore, as mentioned above, most of the impact noise caused by the step-type synchronous motor 10 for watches is generated when the front part of the drive pulse is applied, so it is necessary to eliminate most of the noise caused by the step-type synchronous motor 10 for watches. I can do it.

In this embodiment, a 512 Hz signal is used as a signal for chopping the step hand movement pulse, and the chopping time is set to 15.625 mS, but these values are not limited.

As described above, according to the present invention, by stepping the front part of the step hand movement pulse,
By reducing the angular velocity of the permanent magnet rotor of the motor, a watch motor with less noise can be provided, which is highly effective.

[Brief explanation of the drawing]

Figures 1a and 1b are diagrams showing the operating principle of a step-type synchronous motor for a watch, and Figure 2 shows drive waveforms of the step-type synchronous motor for a watch. FIG. 3 is a diagram showing drive pulses of a conventional step-type synchronous motor for a timepiece. Figure 4 shows the sound pressure distribution state of the impact sound within the drive pulse. FIG. 5 is a partial block circuit diagram showing an embodiment of the present invention. Figure 6 is the time chart. FIG. 7 is a diagram showing drive pulses in the present invention. 4... Frequency dividing circuit, 6... Waveform shaping circuit, 8...
Drive circuit, 10... step type synchronous motor for clock, 100... permanent magnet rotor. 〓〓〓〓〓

Claims (1)

[Claims] 1. A reference signal generator that generates a constant periodic signal with a relatively high frequency, a frequency dividing circuit that divides the constant periodic signal to a predetermined frequency, and a step movement using a plurality of frequency signals from the frequency dividing circuit. a waveform shaping circuit that outputs pulses, a drive circuit that converts the step hand movement pulses into drive pulses for driving a motor, and a motor that is driven by the drive pulses and moves an indicator hand via a timepiece wheel train; In the electronic timepiece, the waveform shaping circuit includes detection means for detecting the front part of the step hand movement pulse, and detecting the front part of the step hand movement pulse detected by the detection means with a period shorter than the pulse width of the step hand movement pulse. A noise reduction mechanism for a watch, characterized in that a modulation means for modulating with a frequency signal is added.