JP2858791B2 - Excitation method of piezoelectric actuator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation method for a piezoelectric actuator, and more particularly to an excitation method for a piezoelectric actuator used as a drive source for a print head of a dot matrix type impact printing apparatus.

[Conventional technology]

FIG. 4 and FIG. 5 are a block diagram of an example of a conventional excitation method of a piezoelectric actuator and a timing chart for explaining the operation.

The piezoelectric body 7 is a piezoelectric actuator connected to the mechanism 8, one of the electrodes is grounded and the other electrode is a coil L.
Is connected to the switch circuit 5 via a switch D6, and further connected to the switch circuit 6 via a reverse current preventing diode D6. The switch circuit 5 is turned on only when a drive signal is applied. At this time, when the switch 6 is turned off, an excitation voltage is applied to the piezoelectric body 7 via the coil L when the switch circuit 5 is turned on. You. The switch circuit 6 is in a conductive state during the application time of the braking signal, like the switch circuit 5, is in the cut-off state during the time when the braking signal is not applied, and the switch circuits 5 and 6 are not simultaneously in the conductive state. I have to.

Since the coil L is connected in series to the piezoelectric body 7, the current I2 flowing through the piezoelectric body 7 via the coil L when the switch circuit 5 is turned on has a sinusoidal current waveform. The charging process is performed until the terminal voltage V2 of the piezoelectric body 7 gradually increases and the terminal voltage V2 of the piezoelectric body 7 reaches a peak from 0 volt.

On the other hand, in the discharging process, the current is discharged to the excitation power supply side through the diode D5 until the terminal voltage V2 of the piezoelectric body 7 becomes equal to the excitation voltage. At this time, the switch circuit 6 is in the cut-off state, but when the switch circuit 6 is turned on by the braking signal, one end of the reverse current preventing diode D6 is grounded, and is composed of the piezoelectric body 7, the coil L, and the reverse current preventing diode D6. A series closed circuit is formed, and the electric charge accumulated in the piezoelectric body 7 is discharged through the closed circuit. The voltage applied to the piezoelectric body 7 by this excitation method ranges from 0 volt to a positive peak voltage.

[Problems to be solved by the invention]

In the conventional piezoelectric actuator excitation method described above, the fifth
As shown in the time chart of the figure, the voltage applied to the piezoelectric body generates dimensional distortion by a positive voltage with reference to 0 volt, but the magnitude of the dimensional distortion obtained by this method is limited. Exists.

It has also been found that when the actuator element is operated at a high speed, the amount of enlarged displacement of the dimensional distortion of the piezoelectric body obtained by the mechanism 8 tends to be small.

Therefore, it is difficult to realize a printer capable of high-speed printing.

[Means for solving the problem]

In the excitation method of the piezoelectric actuator of the present invention, a series circuit is formed by a coil and a piezoelectric body in a charging process, and an excitation voltage is applied by a first switch circuit operated by a drive signal. When the voltage applied between the electrodes of the piezoelectric body in the circuit having the second switch means for discharging the voltage via the coil is a negative electrode, and the voltage of the negative electrode during which the piezoelectric actuator is contracting is applied to the electrode of the piezoelectric body. There is a means for applying a bias.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 and 2 are a block diagram and a timing chart showing one embodiment of the present invention.

The piezoelectric body 3 is a piezoelectric actuator connected to the mechanism 4, one of the electrodes is grounded and the other electrode is a coil L.
Is connected to the switch circuit 1 through the switch circuit 2, and further connected to the switch circuit 2 through the reverse current prevention diode D2. The switch circuit 1 is turned on only when the drive signal is at the level "1". At this time, the switch circuit 2 is turned off. When the switch circuit 1 is turned on, the excitation voltage is applied via the coil L to the piezoelectric element. 3 is applied. Similarly to the switch circuit 1, the switch circuit 2 is in the conductive state during the time when the braking signal is at the level "1", is in the cut-off state during the time when the brake signal is at the level "0", and the switch circuits 1 and 2 are simultaneously in the conductive state. I try not to be.

Since the coil L is connected to the piezoelectric body 3 in series, the current I1 flowing through the piezoelectric body 3 through the coil L when the switch circuit 1 is turned on has a sine wave current waveform. In addition, the terminal voltage V1 of the piezoelectric body 3 gradually increases, and after the switch circuit 1 becomes conductive, the terminal voltage V1 of the piezoelectric body 3 becomes larger.
The charging process is performed until V1 reaches a peak.

On the other hand, in the discharging process, the current is discharged to the excitation power supply side through the diode D1 until the terminal voltage V1 of the piezoelectric body 3 becomes equal to the excitation voltage. At this time, the switch circuit 2 is in the cut-off state, but when the switch circuit 2 is turned on by the braking signal, one end of the reverse current preventing diode D2 is grounded, and the electric body 3, the coil L and the reverse current preventing diode are grounded.
A series closed circuit composed of D2 is formed, and the electric charge accumulated in the piezoelectric body 3 is discharged through this closed circuit.

By the way, in the excitation method of the present embodiment, a circuit in which a diode D3 and a constant voltage diode D4 are connected in series is connected in parallel between the electrodes of the piezoelectric body 3, and the voltage value set by the constant voltage diode D4 has a negative polarity. The voltage is applied to the piezoelectric body. Diode D3 is a constant voltage diode when charging
It prevents it from flowing into D4. It is necessary that the voltage value of the negative polarity does not exceed a value that degrades the dimensional distortion characteristics of the piezoelectric body. A mechanism for setting a negative voltage applied to the piezoelectric body 3 by the constant voltage diode D4 and expanding a displacement of dimensional distortion generated in the piezoelectric body 3 is attached.

〔The invention's effect〕

As described above, according to the present invention, by energizing the electrodes of the piezoelectric actuator in a voltage range from negative polarity to positive polarity, it is possible to obtain a larger displacement and a higher printing pressure than in the conventional method. Therefore, it is possible to realize an impact printer capable of printing at a higher speed than the impact printer according to the conventional method.

[Brief description of the drawings]

1 and 2 are a block diagram and a timing diagram, respectively, showing an embodiment of the present invention. FIG. 3 is a diagram showing a relationship between a voltage applied to a piezoelectric body and a dimensional distortion of the piezoelectric body caused by each. FIG. 4 and FIG. 5 are a block diagram and a timing diagram showing an excitation method of a conventional piezoelectric actuator. 1,2,5,6… Switch circuit, 3,7… Piezoelectric, 4,8… Mechanism, L… Coil, D1-D3, D5-D7… Diode, D4
.... Constant voltage diode.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kei Kitayama 3-20-4 Nishishinbashi, Minato-ku, Tokyo Japan Electric Engineering Co., Ltd. (72) Inventor Masaki Yukino 3- 20-4 Nishishinbashi, Minato-ku, Tokyo No. Japan Electric Engineering Co., Ltd. (56) References JP-A-2-194575 (JP, A) JP-A-63-177481 (JP, A) JP-A-63-50080 (JP, A) 287283 (JP, A) JP-A-50-125696 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02P 2/00 H01L 41/08

Claims (1)

(57) [Claims] 1. A piezoelectric actuator for generating a dimensional distortion according to an excitation voltage applied to an electrode to drive a mechanical mechanism, a coil of the piezoelectric actuator connected in series to the electrode, and an application timing of the excitation voltage. First switch means for applying the excitation voltage to the piezoelectric actuator via the coil in response to a drive signal; and charging the piezoelectric actuator in response to a braking signal indicating braking timing of the dimensional distortion. And a second switch means for discharging through the piezoelectric actuator, an excitation voltage in a voltage range from negative polarity to positive polarity within a range in which the dimensional distortion does not change from contraction to expansion, is applied to the electrodes of the piezoelectric actuator. An excitation method for a piezoelectric actuator, characterized by applying a voltage.