Electricity: motive power systems – Positional servo systems – With stabilizing features
Patent
1998-04-13
1999-10-26
Ip, Paul
Electricity: motive power systems
Positional servo systems
With stabilizing features
318254, 318701, 318685, H02P 800
Patent
active
059734698
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FILED
The present invention relates to a motor driving apparatus for enabling high-speed rotation under phase detection control.
BACKGROUND ART
To rotate a motor at a high speed with a large torque is one of the most important factors in terms of an improvement in basic performance of the motor, and has been studied and developed for many years. For example, an electronic timepiece as one of products using motors has been advanced to have many functions in recent years. Timepieces having various functions such as stopwatch function, an alarm function, and a dual time function, in addition to normal time display have been developed and commercially available. These multifunctional timepieces always perform the fast forwarding operation of pointing hands when the system is initialized in an initial state, e.g., in loading the battery, or when the mode is shifted or the hand position is zeroed in normal use. For this reason, high-speed rotation of the motor is very important in terms of an improvement in operability, and the like.
A large-torque motor is indispensable when a flat weight is attached to a motor to use a timepiece as a vibration alarm for informing the time using vibrations generated upon rotation of the motor, or when a disk is attached instead of a pointing hand to a timepiece motor to perform display other than display of the time.
When the motor is rotated at a high speed, even if output of a driving pulse is stopped, the motor may not immediately stop due to the inertia of the motor or parts (e.g., a reduction ring train and a pointing hand in the timepiece) connected to the motor. Normally, to obtain a predetermined number of rotation, a corresponding number of pulses are output. In this case, however, the number of output pulses is not equal to the number of rotation of the motor.
In, e.g., a timepiece pointing hand, this is a fatal defect and leads to a time display error and the like. In addition, the magnetic pole generated at the stator by a driving pulse output in driving the motor next may shift from the pole position of the rotor depending on the pole position of the rotor upon stopping the motor, and the motor may not normally rotate. Therefore, in a system for driving the motor at a high speed, and accurately controlling the rotation speed of the motor to a desired value, it is important that the motor must be stopped at a predetermined position.
A conventional motor driving apparatus will be described below by exemplifying the stepping motor of an electronic timepiece.
FIG. 1 is a view of the arrangement of a motor driving apparatus constituted by a conventional bipolar stepping motor, and FIGS. 2 to 7 are plan views, respectively, showing the positional relationship between the magnetic poles of a stator and a rotor. As a means for converting an electrical signal into a mechanical rotating motion, the bipolar stepping motor is constituted by a driving coil 101, a flat stator 102, and a rotor 103, as shown in FIG. 1. The flat stator 102 has a step 102a, as shown in FIG. 2.
Motor drivers 104a and 104b are arranged to cause a current to flow through the driving coil 101 by changing the potential across the two terminals of the driving coil 101, thereby exciting the flat stator 102. In the bipolar motor shown in FIG. 1, when no current flows through the driving coil 101, the pole position of the rotor 103 with respect to the flat stator 102 is at a statically stable point 110 shown in FIG. 2; when a current flows through the driving coil 101 to excite the flat stator 102, it is at an electromagnetically stable point 111 shown in FIG. 3.
Normally, in the electronic timepiece, a driving pulse signal for changing the potential across the two terminals of the driving coil 101 is output from the motor driver 104a or 104b for 4 to 5 mS to cause a pulse current to flow through the driving coil 101, thereby rotating the rotor 103. When the rotor 103 rotates during the supply of the current to the driving coil 101, and comes to nearly a pole position shown in FIG. 4 with respe
REFERENCES:
patent: 4158800 (1979-06-01), Jahelka et al.
patent: 5627444 (1997-05-01), Fulks
patent: 5734241 (1998-03-01), Okada et al.
patent: 5886486 (1999-03-01), Jeong et al.
Higuchi Haruhiko
Ichikawa Masakazu
Kihara Hiroyuki
Murakami Tomomi
Tsuchiya Hidetaka
Citizen Watch Co. Ltd.
Ip Paul
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