US3711754A

US3711754A - Circuit for driving a moving element

Info

Publication number: US3711754A
Application number: US00022804A
Authority: US
Inventors: K Nemoto
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-03-28
Filing date: 1970-03-26
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16
Also published as: DE2014512A1; ES377741A1; DE2014512B2; FR2037277A1; BR7017375D0; DE2014512C3; CH555062A; SE373962B; CH457870A4; GB1274126A

Abstract

An electric circuit is disclosed for starting an output member in vibratory motion and maintaining the vibrations at a constant amplitude. A coil is electromagnetically coupled to the output member and performs both the driving and pick-up functions. The circuit includes two oppositely polarized transistors cooperating with a coupling capacitor to deliver current pulses of a relatively large pulse width to the coil to start the output member in vibratory motion. The pulse width is progressively decreased until the output member is vibrationally maintained at a constant amplitude and frequency.

Description

United States Patent 91 Nemoto Jan. 16, I973 [54] CIRCUIT FOR DRIVING A MOVING 3,597,634 8/1971 Flaig ..318/128 x ELEMENT 3,229,225 1/1966 Schimpf ..3|s 132 x [76] Inventor: Kouji Nemoto, Ninomiya-l082, OTHER PUBLICATIONS Akita-machi, Nishitoma-gun, 3

H TokyoJapan Transistor Manual 1964 General Electric Company,

pages 106-107 [22] I Filed: March 26,1970 Elementary Circuit Properties of Transistors, Vol. 3, [21] Appl.No.: 22,804 1966, John Wiley & Sons, Inc. New York, pages [30] ForeignApplicafion Prim-"y Dam Primary Examiner-Richard B. Wilkinson March 28, 1969 Japan ..44/23160 Assistant Weldon Attorney-Robert E. Burns and Emmanuel J. Lobato [52] U.S. CL... ..3l8/l26, 58/23 [51] Int. Cl. ..H02k 33/00 [57] ABSTRACT [58] 27 5:15: g g g% g An electric circuit is disclosed for starting an output member in vibratory motion and maintaining the vibrations at a constant amplitude. A coil is electromagnetically coupled to the output member and [56] Reerences cued performs both the driving and pick-up functions. The UNITED STATES PATENTS circuit includes two oppositely polarized transistors cooperating with a coupling capacitor to deliver current pulses of a relatively large pulse width to the coil 530,662 9/1970 318/127 X to start the output member in vibratory motion. The 3,553,955 1/1971 Keeper et aL 3|3/]27 x pulse width is progressively decreased until the output 3,306,030 2/1967 Niley ..58/23 member is vibrationally maintained at a constant am- 3,403,312 9/1968 Sparing 318/130 plitude and frequency. 3,407,344 10/1968 Bansho ..58/23 3,365,635 1/1968 Shelley ..3I8/128 1 Claim, 8 Drawing Figures CIRCUIT FOR DRIVING A MOVING ELEMENT This invention relates to a driving circuit for driving a moving element and more specifically relates to a mechanical vibrator or motor rotor for use as a reference vibrator or oscillator for timepieces.

A variety of driving circuits are known for driving mechanical vibrators, for example, tuning forks and balance wheels, as reference vibrators for timepieces. One such known circuit comprises an astable multioscillator, a coil coupled as a load to the astable multioscillator which combines pick-up and driving functions, and a vibrator having attached thereto a magnet. In such a circuit, the coil coacts with the magnet to serve as a transducer and the astable multioscillator is triggered by an electric signal induced in the coil by the vibratory motion of the vibrator to drive the vibrator. In the conventional driving circuit above described, the pulse width of the driving pulse is kept constant and consequently the vibrator cannot be supplied with a sufficient pulse for its starting. Therefore, the vibrator is incapable of self-starting and must initially be driven by an external force. The same drawback applies to the type of ordinary driving circuit wherein a motor is used instead ofa mechanical vibrator; here again, the motor cannot start by itself.

The present invention eliminates the foregoing disadvantages of the existing vibrator driving circuits and provides a new, improved driving circuit.

According to one aspect of the present invention, a driving circuit for a moving element is provided which comprises first and second transistors having opposite polarities connected such that the collector of the first transistor is serially coupled to the base of the second transistor and a biasing resistor is connected between the base of the first transistor and a power source. Another resistor is connected to the emitter of the first transistor and the emitters of both transistors are capacitively coupled to each other. A coil is electromagnetically coupled to a moving element and combines the function of driving the moving element with the function of picking up the motion of the moving element. The coil is connected to the emitter of the second transistor and a d-c voltage source is connected to constitute a series circuit with the resistors, capacitor and coil. Thus, the pulse of driving current that is supplied by the coil to the moving element has a sufficiently large pulse width at the time of starting to effect self-starting of the moving element.

Once the moving element has started its motion, the coil picks up the motion and the electric signal thereby induced is superposed on the base-to-emitter voltage to trigger the transistors. As the moving element approaches a steady motion, a driving current with a progressively decreasing pulse width is automatically developed and applied. This results in small power consumption during the steady motion. Also, a driving force synchronized with the motion of the moving element is obtained.

It is an object of the present invention to provide a driving circuit capable of self-starting the motion of the moving element and minimizing the power consumption during the steady motion of the moving element.

Another object of the present invention is to provide a driving circuit which is simplified in construction, inexpensive to manufacture, and adapted for mass production.

Other features, advantages, and objects of this invention will become apparent from the following detailed description taken in conjunction with the accompany ing drawings, in which:

FIG. 1 is a diagram of a driving circuit according to the present invention;

FIG. 2 is a diagrammatic plan view, on an enlarged scale, of the transducer shown in FIG. 1;

FIG. 3A is a wave form explanatory of the condenser voltage;

FIG. 3B is a wave form explanatory of the base-toemitter voltage of the transistor;

FIG. 3C is a wave form explanatory of the current that flows through the coil;

FIG. 4 is a diagram of another embodiment of driving circuit embodying the present invention;

FIG. 5 is a diagram of still another form of driving circuit embodying the present invention; and

FIG. 6 is a diagram of yet another form of driving circuit embodying the present invention.

Referring specifically to FIG. 1, there is shown a driving circuit employing a balance wheel 1 as the output or moving element. The balance wheel together with a coil L, which is electromagnetically coupled with the balance wheel 1, comprise a transducer which combines the pick-up and driving functions. The balance wheel 1, as better shown in FIG. 2, consists of a rotatably mounted center shaft 2, a disk 3 supported by the shaft, a permanent magnet 4 fixed to the upper surface of the disk 3, and a mass 5 functioning as a counterbalance. The ring-shaped coil L is secured in position so that when the disk 3 rotates, the magnet 4 passes thereunder. The coil L converts an electric signal applied thereto into a mechanical motion of the balance wheel 1 and, at the same time, picks up the mechanical motion of the balance wheel 1 and converts the same into an electric signal. In other words, it combines both functions of driving and pickup coils. The collector of an NPN transistor Tr, and the base of a PNP transistor Tr are serially coupled and a resistor R is connected between the base of the transistor Tr, and the positive terminal of a power source E to bias the transistor Tr, in the forward direction. To the emitter of the transistor Tr, is connected a resistor R Between the emitters of the two transistors Tr, and Tr a condenser C is connected for capacitive coupling of the two emitters. The combined pick-up and driving coil L is connected to the emitter of the transistor Tr The positive terminal of the power source E, coil L, condenser C, resistor R,, a switch S, and the negative terminal of the power source E are connected together in a series circuit. The collector of the transistor Tr is connected to the switch S. Thus, four component circuits are formed: i.e., a charge loop consisting of the power source E, coil L, condenser C, resistor R and switch S; a discharge loop consisting of the condenser C, emitter and base of the transistor Tr and collector and emitter of the transistor Tr a branched discharge loop consisting of the condenser C, emitter and collector of the transistor Tr and resistor R and an oscillating circuit consisting of the power source E, coil L, emitter and collector of the transistor Tr and the switch S.

The operation of this driving circuit will now be explained with reference to the graphs of FIG. 3. When the switch S is closed, the base and emitter of the transistor Tr, are biased in the forward direction, but the transistor Tr, remains in the OFF position because the condenser C is charged by the charge loop.

FIG. 3A gives time t on the axis of abscissa and the voltage V in the condenser C on the axis of ordinate. By the charge loop, the condenser voltage as represented by a wave form a, is increased up to a certain level A,. In FIG. 3B,-time t is plotted on the axis of abscissa against the base-to-emitter voltage V of the transistor Tr, on the axis of ordinate. While the condenser C is being charged, the voltage as represented by a wave form b rises to the level 8,. The transistor Tr, is switched ON when its base-to-emitter voltage reaches the level 8,. Accordingly, the charge on the condenser C begins to be discharged by the discharge loop, through the circuit composed of the emitter and base of the transistor Tr,, collector and emitter of the transistor Tr,, and condenser C. At the same time, the transistor Tr, is instantaneously switched ON, whereupon a large current flows from the power source E through the coil L and the emitter and collector of transistor Tr On the other hand, the discharge current from the condenser C is also branched through the loop composed of the emitter and collector of the transistor Tr,, resistor R, and condenser C. Thereupon, the condenser voltage drops as represented by a wave form a, in FIG. 3A and the base-to-emitter voltage of the transistor Tr, is increased and maintained by the branched discharge to a level B in FIG. 3B. The charge on the condenser C is discharged by a time constant which is governed by the capacity of the condenser C, the resistance value of the resistor R, and the resistance components of the transistors Tr, and Tr,. When the voltage of the condenser C drops to A the transistor Tr, is switched OFF and the transistor Tr, is immediately turned OFF, too. FIG. 3C, in which time t is plotted on the axis of abscissa against the current I, that flows through the coil L on the axis of ordinate, shows a driving pulse current e flowing through the coil L. As the transistor Tr, is switched OFF, the condenser C is charged again, and the cycle of operation above described is repeated to carry out astable oscillation.

' The period of the astable oscillation is set at a frequency greater than the natural frequency of the moving element, and the driving pulse current e,, is set at a value that can give a sufficient driving force to effect starting of the moving element.

The balance wheel 1 is started by the driving pulse current e,,, and an inducedvoltage is produced in the coil L. Thus, the base-to-emitter voltage of the transistor Tr, is applied with a wave form 17,, or the wave form b shown in FIG. 3B superposed with the in-- duced voltage. With the attainment of the voltage 3,, the transistor Tr, is triggered. At this time the condenser'C is charged as with the wave form a, to a voltage A;,. The transistor Tr, is switched ON with the baseto-emitter voltage 8,, while, in the manner already described, the transistor Tr 'is switched ON by the discharge current which is dictated by the time constant of the condenser C, with the result that the condenser C discharges as represented by the wave form a, and the driving pulse current e, flows through the coil L, .thereby driving the balance wheel 1. As the procedure above described is repeated and the amplitude of the balance wheel 1v is gradually increased,

the induced voltage also rises and is applied as such to the base-to-emitter voltage, thus increasing the frequency at which the transistor Tr, is triggered. Accordingly, the charging and discharging intervals of the condenser C are shortened by degrees. The pulse width of the driving pulse current that flows through the coil L while the transistor Tr is ON is steadily decreased. When the balance wheel 1 has attained a state of steady vibration with a constant amplitude and frequency, the pulse current also becomes a stable and steady driving pulse current e having a predetermined pulse width.

Hence, the balance wheel 1 sustains its steady vibration.

Since the driving pulse current e,, that acts on the vibrator while the vibrator is kept still in the manner above described is much larger than the driving pulse current e that acts when the vibrator has attained the state of steady vibration, the vibrator can start by itself without the necessity of an external force being applied thereto. When the vibrator attains its steady vibration, the vibrator is driven by a driving pulse current e having a much narrower pulse width than the starting pulse widths and, accordingly, the power loss is reduced to a minimum. Another feature is that the vibrator is driven with a pulse current that is produced at a frequency synchronized with the natural frequency of the vibrator.

By relocating the two transistors and coupling the power source with the terminals reversed, it is possible to obtain another embodiment of the invention. The operation of the resulting driving circuit is entirely the same as that of the circuit illustrated in FIG. 1.

Another embodiment of the present invention will now be explained with reference to FIG. 4. In this embodiment, a driving circuit having a transducer equipped with a tuning bar 16 instead of the balance wheel 1 is used. The tuning bar 16 of the transducer is fixed at one end and is provided at its free end with a magnet bar 17 attached to one side and with a mass 18 attached to the other side effective to counterbalance the weight of the magnet bar. A ring-shaped coil L,,,' is secured in place such that the magnet bar 17 is slidable with respect thereto. In the driving circuit shown, a thermistor Rth is connected between the collector of the transistor Tr,, and the emitter of the transistor Tr,,. In the figure, reference symbols E,,,, S,,,, R,,, C,,, and R denote parts similar to their counterparts in FIG. 1. In this embodiment, the temperature characteristics of the transistors Tr,, and Tr,, can be improved.

FIG. 5'shows another embodiment of a driving circuit having atransducer in which the moving element is a rotor 29 of a motor. The rotor 29 is a ferrite disk mounted on a journalled shaft 30 and has two pairs of magnetic poles N and S. A ring-shaped coil L combining the pick-up and'driving functions is fixed in spaced and the positive terminal of a power source E In the diagram, symbols Tr C L S C Tr and R indicate parts which are substantially equivalent to their counterparts in FIG. I. In this embodiment, the driving pulse current can be advantageously shaped as desired.

What I claim and desire to Secure By Letters Patent I. A circuit for driving a moving element comprising: a movably mounted output element, two transistors of opposite polarities, means serially connecting the collector of one of said transistors to the base of the other transistor, 21 d-c power source, a biasing resistor connected between the base of said one transistor and said

Claims

1. A circuit for driving a moving element comprising: a movably mounted output element, two transistors of opposite polarities, means serially connecting the collector of one of said transistors to the base of the other transistor, a d-c power source, a biasing resistor connected between the base of said one transistor and said power source, another resistor connected between the emitter of said one transistor and said power source, means capacitively coupling together the emitters of said transistors, a coil electromagnetically coupled to said output element and electrically connected to the emitter of said other transistor effective to both vibrationally drive said output element and pick-up the movement of the vibrating output element, means connecting the collector of said other transistor to said power source, and means electrically connecting said power source, said other resistor, said capacitor and coil in series.