Electricity: motive power systems – Reciprocating or oscillating motor – Energizing winding circuit control
Reexamination Certificate
1999-07-28
2001-01-30
Ramirez, Nestor (Department: 2834)
Electricity: motive power systems
Reciprocating or oscillating motor
Energizing winding circuit control
C318S127000, C318S126000, C318S686000, C310S050000
Reexamination Certificate
active
06181090
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application HEI 10-213306, filed Jul. 28, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for driving of a linear oscillating motor during reciprocating oscillation, and a linear oscillating motor.
2. Discussion of Background Information
A linear oscillating motor includes a fixed magnet (e.g., an electromagnet). A movable member, which includes a magnet (e.g., an electromagnet or a permanent magnet), is supported relative to the fixed magnet to freely oscillate. A detector detects various oscillation parameters (e.g., amplitude, velocity, acceleration, etc.) of the movable member. In response to the output of the detector, a controller applies current to a coil of the fixed magnet to control oscillation of the movable member.
As the movable member oscillates, it generates a generally sinusoidal induced voltage within a magnetic detection coil adjacent the movable member. The period of full oscillation is separated into two half-periods (defined by the points at which the induced voltage is zero) over which drive control occurs.
When the oscillation frequency is relatively high, a high performance controller must be used to control the drive current since control must be based on a period shorter than the half-period. Such high performance controllers are expensive, and increase the overall cost of the device.
SUMMARY OF THE INVENTION
The present invention provides a method for driving a linear oscillating motor with high frequency oscillation without requiring the use of a high performance controller. The linear oscillating motor includes a fixed magnet (e.g., an electromagnet or a permanent magnet). A movable member is supported so as to freely oscillate relative to the fixed magnet, and is provided with an electromagnet or a permanent magnet. A detector detects displacement of the movable member relative to the fixed magnet. A controller generates a control current to control oscillation of the movable member, in response to the output of the detector. The controller provides a variable drive current (based upon the output of the detector) to oscillate the movable member during only one (a first half-period) of the two half-periods (making up the oscillation period of the movable member). During the other half-period (a second half-period), the controller oscillates the movable member according to a fixed drive current (waveform) which has a predetermined constant energy.
Based upon the output of the detector, the controller may optionally not apply the fixed drive current waveform during the other half-period (which may be considered as applying a zero current waveform). A variable drive current control region, defined as the region over the portion of the full period over which the controller applies variable drive current, may be expanded into the second half-period. Furthermore, when the fixed drive current is not applied, the variable drive current control region may be adjusted based upon output of the detector. This can reduce fluctuation in amplitude of drive current within a full oscillation period.
The detector can detect displacement of the movable member during either or both of the half-periods.
According to an embodiment of the invention, a method for driving a linear oscillating motor is provided. The motor includes a fixed magnetic member, a movable member having a magnet and being supported to oscillate relative to the fixed magnetic member, a detector that detects displacement of the movable member, and a controller that oscillates the movable member by sending drive current to a coil of the fixed magnetic member. The method includes controlling, during a first half-period that occurs within a full amplitude period of the movable member, the drive current based upon the output of the detector. The method also includes controlling, during a second half-period that occurs within a full amplitude period of the movable member, the drive current based on a fixed drive current waveform.
A feature of the above embodiment provides for monitoring an output of the detector, and suppressing the fixed drive current waveform during the second half-period, such that no drive current is applied to the coil during the second half-period. The suppression of the drive current control can be adjusted based upon the output of the detector.
Detection of displacement of the movable member can occur during either or both of the first and second half-periods.
According to another embodiment of the invention, a method for driving a linear oscillating motor is provided. The motor includes a fixed magnetic member, a movable member having a magnet and being supported to oscillate relative to the fixed magnetic member, a detector that detects displacement of the movable member, and a control that controls oscillation of the movable member. The method includes detecting an oscillation parameter of the movable member; triggering variable control of oscillation of the movable member, where the variable control is based upon the oscillation parameter; terminating variable control triggering, fixed control of oscillation of the movable member, where the fixed control is independent of the oscillation parameter; and terminating fixed control.
According to features of the above embodiment, the magnet is a permanent magnet or an electromagnet.
According to another feature, after terminating fixed control, the method repeats from one of the detecting and the triggering variable control.
The above noted motor preferably includes a coil, and the further control applies a predetermined current waveform to the coil. The predetermined current waveform is zero current, or at least a portion of the predetermined current waveform is a non-zero current.
In another feature of the above embodiment, the movable member oscillates to define a period consisting of two half-periods, variable control occurs over one of the two half-periods, and fixed control occurs over the other of the two half-periods.
According to another embodiment of the invention, a linear motor is provided. A fixed magnet is provided. A movable magnet is supported by movable member. The movable member is supported to oscillate over a full-period relative to the fixed magnet. At least one of the fixed and movable magnets has a coil. The full-period includes first and second half-periods. A detector, mounted adjacent to the movable member, generates an output voltage based upon movement of the movable member. A control unit outputs a drive control current to the first coil over at least a portion of the first and second half-periods. The drive control current is based upon the output voltage during the first half-period, and is independent of the output voltage during the second half- period.
According to a feature of the above embodiment, the drive control is based on a predetermined drive current waveform during the second half-period. The predetermined current waveform is zero, or at least a portion of the predetermined drive current waveform is not zero.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.
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Amaya Hidetoshi
Ibuki Yasuo
Okamoto Toyokatsu
Greenblum & Bernstein P.L.C.
Jones Judson H.
Matsushita Electric & Works Ltd.
Ramirez Nestor
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