JP5352050B2 - DRIVE DEVICE AND OPTICAL DISC DEVICE USING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cope with the problem that the shifting speed changes by the temperature of a piezoelectric element and the controllability deteriorates and the problem that there is necessity to prevent the overheat of the piezoelectric element due to drive in high temperature state, since the element deteriorates if the element temperature rises to the temperature determined by the material, in an actuator using a piezoelectric element for its motive power. <P>SOLUTION: In a driver for driving an actuator using a piezoelectric element for its motive power, the ambient temperature or the temperature of the element is measured, and a drive signal to be applied to the piezoelectric element is controlled by the measurement results, and the temperature is controlled into a specified range by the heat generation of the piezoelectric element by the application of the drive signal and the heat radiation while the drive signal is not applied. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

The present invention relates to an optical disc apparatus using a driving device that operates by electrical control using a piezoelectric element as a power source.

  A linear actuator using a contraction of a piezoelectric element as a power source is known. In Patent Document 1 and Patent Document 2, the displacement and contraction displacement of the piezoelectric element are performed at different speeds, the driving member fixed to the piezoelectric element is reciprocated at different speeds, and a moving body frictionally coupled to the driving member is arbitrarily selected. A linear actuator moving in the direction is shown.

  Patent Document 2 discloses a method for correcting the driving frequency of the driving pulse to an optimum value in order to suppress the characteristic change due to the environmental temperature of the driving speed of the actuator described above.

JP 2000-205809 A JP 2006-87217 A

  In a linear actuator using a piezoelectric element as a power source, there is a problem that the moving speed of the moving body changes depending on the environmental temperature or the temperature of the piezoelectric element, and the controllability deteriorates. Further, when the actuator is driven, the piezoelectric element may be overheated due to the heat generated. When the element temperature rises to a temperature determined by the material of the piezoelectric element, there is a problem that the element deteriorates, and there is a problem that overheating of the piezoelectric element must be avoided when the actuator is driven.

  In a drive device for driving an actuator using a piezoelectric element as a power source, the ambient temperature or the temperature of the piezoelectric element is measured, and the drive signal applied to the piezoelectric element is controlled according to the measurement result, and the piezoelectric element during the period in which the drive signal is applied The optical disk device using this drive device is controlled so that the temperature during operation falls within a predetermined range by the heat generation during the above period and the heat radiation during the idle period when no drive signal is applied.

  According to the present invention, it is possible to reduce an influence due to temperature fluctuations of an actuator using a piezoelectric element as a power source, and to obtain an optical disk device that is favorable for a user.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram showing the configuration of an embodiment of a drive device according to the present invention.

  In FIG. 1, 101 is a piezoelectric element that expands and contracts when a voltage is applied, 102 is a moving member, 103 is a drive shaft, 104 is a signal generating means for generating a driving signal for expanding and contracting the piezoelectric element, and 105 is a signal generating means for controlling 104. Control means 106 for controlling the piezoelectric element, and 106 is a measuring means for obtaining the ambient temperature or the temperature of the 101 piezoelectric element. By applying a driving signal to the piezoelectric element 101, the moving body 102 moves along the driving axis 103 and functions as a linear actuator.

  Here, an example of a linear actuator operation composed of 101 to 103 and using a piezoelectric element as a power source will be described with reference to FIG. In FIG. 2, 201a, 201b and 201c are piezoelectric elements, 202a, 202b and 202c are moving members, 203a, 203b and 203c are drive shafts, and 204a, 204b and 204c are fixed members.

  In FIG. 2A, the piezoelectric element 201a has one end fixed to the fixing member 204a and the other end fixed to the drive shaft 203a. The moving member 202a is in contact with the drive shaft 203a and is held by the frictional force of the contact surface. When the piezoelectric element 201a in FIG. 2A is extended at a low speed, the moving member 202a is held and moved by the driving shaft of 203a by the frictional force. FIG. 2B shows a state where the piezoelectric element is extended in this way.

  Next, when the piezoelectric element 201b is rapidly contracted from the state shown in FIG. 2 (b), the moving member 202b stays in place due to the inertial force, so that the friction part between the moving member 202b and the drive shaft 203b As a result, the moving member 202b stays almost in the same position. A state where the piezoelectric element is contracted in this manner is shown in FIG.

  By repeating the expansion of the piezoelectric element at a low speed and the rapid contraction, the moving member can move a long distance along the drive shaft. In addition, the moving member can be driven in the opposite direction by reversing the polarity of the drive signal applied to the piezoelectric element and repeating the contraction at a low speed and the rapid expansion.

  A method for generating a drive signal for the piezoelectric element described in FIG. 2 will be described. In FIG. 1, the driving signal from the signal generating means 104 is applied to the piezoelectric element 101 by the control means 105 to contract the element. The measuring means 106 acquires the ambient temperature of the apparatus or the temperature of the piezoelectric element, and the control means 105 controls the drive signal according to the temperature information.

FIG. 3 shows an example of the relationship between the application period of the drive signal to the piezoelectric element and the temperature of the piezoelectric element. In FIG. 3, 301 indicates a drive signal applied to the piezoelectric element, and 302 indicates the temperature of the piezoelectric element. When the drive signal is applied to contract the piezoelectric element, the temperature of the piezoelectric element rises by ΔT ₃ during the application period t _d3 .

When the temperature information from the measurement means 106 is lower than the lower limit temperature _Tmin before the movement of the moving member 102, the control means 105 applies the drive signal from the signal generation means 104 to the piezoelectric element 101. The piezoelectric element 101 expands and contracts when a drive signal is applied, and the element temperature rises.

On the other hand, the linear actuator using a piezoelectric element as a power source has a characteristic that the moving speed of the moving member 102 changes depending on the element temperature of the piezoelectric element. When the actuator is driven so that the element temperature is between the lower limit temperature T _min and the upper limit temperature T _max , the drive speed change amount Δv with respect to the drive speed v ₁ at the lower limit temperature and the drive speed v ₂ at the upper limit temperature. (Δv = v ₂ −v ₁ ) can be estimated. When the difference between the upper limit temperature and the lower limit temperature (T _max −T _min ) is reduced, the change in driving speed Δv is also reduced, and the controllability is further improved.

Accordingly, when the temperature is lower than the lower limit temperature _Tmin , a drive signal is applied to the piezoelectric element 101, and the movement of the moving member 102 is controlled after the temperature is increased to _Tmin or more by contraction of the piezoelectric element. , The speed change can be reduced and the controllability of the actuator can be improved.

  Note that the pulse duty, frequency, signal amplitude, signal waveform, and polarity of the drive signal applied to increase the element temperature of the piezoelectric element are not limited to those shown in FIG. 3, and the signal is being applied continuously. It is also conceivable that these change, or that the drive signal is continuously applied, in a plurality of times. Further, it is not always necessary to move the moving member 102 by applying the drive signal, and it is also conceivable to apply a drive signal that does not meet the drive conditions of the actuator to the element.

  The operation of the linear actuator is not limited to that shown in FIG. 2, and the driving method of the present invention can be applied to any actuator that uses a piezoelectric element as a power source.

Further, as shown in FIG. 1, a configuration having 107 display means may be adopted. When the temperature T acquired by the measurement means 106 exceeds the upper limit temperature T _max or the temperature at which the element deteriorates, 107 The warning is displayed by the display means.

  As the measuring means 106, a method of measuring the temperature around the piezoelectric element is conceivable, but other than that, a method of directly measuring the temperature of the piezoelectric element is also conceivable.

  Further, in the optical disk apparatus as shown in FIG. 6, a configuration in which the movable lens in the laser path is driven in the optical axis direction by the linear actuator is also conceivable.

  The structure of 2nd implementation in this invention is shown.

  Similar to the first embodiment, the second embodiment is applied to a driving apparatus having the configuration shown in FIG. When the control unit 105 moves the moving member 102, the maximum drive that the signal generation unit 104 can continuously apply the drive signal to the piezoelectric element 101 with respect to the temperature information from the measurement unit 106 Set the period. After the maximum driving period, a pause period for stopping the driving signal application is set for a certain period of time.

FIG. 4 shows the relationship between the drive signal and the temperature of the piezoelectric element when driving the linear actuator using the piezoelectric element as a power source. FIG. 4A shows that the temperature of the piezoelectric element rises by ΔT _(4a) when the drive signal is continuously applied for the period t _{d (4a)} to contract the piezoelectric element.

On the other hand, in FIG. 4B, the signal application is stopped after applying the signal continuously during the drive period of t _{d (4b)} (t _{d (4b)} <t _{d (4a)} ), and the period t _A rest period in which the piezoelectric element _{s (4b)} is not driven is set. During the idle period, the temperature that has risen during the driving period decreases due to heat dissipation. After the rest period ts _(4b) , the drive signal is applied again to drive the piezoelectric element. After the idle period, a driving amount equivalent to that in FIG. 4A is obtained by driving in the period of (t _{d (4a)} −t _{d (4b)} ).

As described above, the maximum value of the temperature rise becomes ΔT _(4b) (ΔT _(4b) <ΔT _(4a) ) during the suspension period, and the temperature rise can be suppressed.

  In addition, since the change in the element temperature is suppressed, the amount of change Δv in the driving speed of the actuator becomes small, and the controllability can be improved.

In order to make the change in the driving speed of the actuator within a predetermined range (lower limit temperature T _min , upper limit temperature T _max ), the drive signal application period and rest period performed by the control means 105 will be described.

If the temperature T ₀ of the pre-driver is a T ₀ <T _max, so as not to exceed the upper limit temperature by the temperature rise △ T _{d (4b)} in the driving period t _d to apply a continuous drive signal _{(4b) (△} T _{d (4b)} ≦ (T _max −T ₀ )).

Also, when driving again actuator immediately after the rest period is not lower than the lower limit temperature by decreases in heat dissipation rest period t _{s (4b)} temperature _{△ T s (4b) (△} T s (4b) ≦ ((ΔT _{d (4b)} + T ₀ ) −T _min )). If the above conditions are satisfied, the length of the driving period and the rest period may be variable depending on the pre-driving temperature T ₀ , even if the lengths are not constant.

  By controlling the driving period and the rest period described above and driving the actuator within a predetermined temperature range, overheating of the piezoelectric element can be prevented and element deterioration can be avoided. This is particularly effective when the ambient temperature of the apparatus is high.

  The structure of 3rd implementation in this invention is shown.

  As in the first embodiment, the third embodiment is applied to a driving apparatus having the configuration shown in FIG. The control means 105 controls the signal generation means 104, and periodically repeats the drive period in which the drive signal is applied to the piezoelectric element 101 and the pause period in which the drive signal is not applied to step the moving member 102. The driving device is moved to the above-mentioned position, and the driving period and the rest period are controlled by the temperature from 106 measuring means.

FIG. 5 shows an example of a temperature change of the piezoelectric element when a driving signal that periodically repeats a driving period and a rest period is used when driving a linear actuator using a piezoelectric element as a power source. Figure 5 (a), the piezoelectric element contracts by repeatedly driving period t _d at a constant period t _{p (5a) (5a)} a rest period t _{s (5a),} the moving member constituting the linear actuator Move. Since the temperature of the piezoelectric element rises during the driving period and is cooled by heat dissipation during the idle period, the piezoelectric element operates in a temperature range of ΔT _(5a) with _respect to the temperature T ₀ before driving.

When the pre-drive temperature T ₀ is high, there is a concern that the piezoelectric element deteriorates and the controllability of the 102 moving member is impaired. Therefore, using the lower limit T _min and the upper limit T _max of the linear actuator driving temperature, the lengths of the previous driving period and the rest period are controlled so that the temperature T from 107 measuring means is in the range of T _min <T <T _max. . Temperature T ₀ and the temperature difference between the upper limit temperature before the piezoelectric element driving if (T _max -T ₀₎ is small, the driving period t _d a _(5a) as short as time t _a, rest period t _{s (5a)} By increasing the time t _a , the temperature rise ΔT _(5a) is suppressed. A case where the length of t _a is proportional to the temperature T ₀ is also conceivable.

A description will be given of a suppression method different from the temperature increase suppression method by adjusting the ratio of the driving period and the rest period per cycle described above. In FIG. 5 (b), the driving period t _{d (5b)} (t _{d (5b)) is} shorter than that in FIG. 5 (a) by a shorter period t _{p (5b)} (t _{p (5b)} <t _{p (5a) ).} The piezoelectric element is driven by repeating <t _{d (5a)} ) and the rest period ts _(5b) . The ratio t _{d (5b)} / t _{s (5b)} of the driving period t _{d (5b) to} the rest period t _{s (5b ) is made} equal to or less than the ratio t _{d (5a)} / t _{s (5a)} in FIG. Therefore, the temperature rise can be reduced (ΔT _(5b) <ΔT _(5a) ).

When the temperature T ₀ before driving the piezoelectric element is sufficiently low and the temperature difference (T _max −T ₀ ) from the upper limit temperature is large, the control as shown in FIG. 5C is used. In FIG. 5 (c), the drive period t _{d (5c)} and the rest period t _{s (} ) are obtained with a longer period t _{p (5c)} (t _{p (5c)} > t _{p (5a)} ) than in FIG. 5 (a). _5c) is repeated to drive the piezoelectric element. Temperature rise in the driving period _{t d (5c) △ T (} 5c) is greater than the temperature rise △ T _(5a) in FIG. _{5 (a) (△ T (} 5c)> △ T (5a)) is, △ T _(5c) ≦ (T _max −T ₀ ) may be satisfied.

  In the driving method of FIG. 5 (c), the number of activations from the stop state of the moving member decreases with a long cycle, so that the influence of the acceleration time for each activation can be reduced.

  Therefore, in an apparatus that drives a piezoelectric element by periodically repeating a driving period and a rest period, element deterioration is prevented by short-period driving at a high temperature, and a driving speed is obtained by long-period driving at a low temperature.

  According to the present invention, since a linear actuator using a piezoelectric element as a power source is small, it is used to drive a small lens such as a camera or an optical disk device. In these devices, the operation stability under various temperature environments can be improved by using the control method for reducing the influence of the temperature change of the present invention.

The block diagram of the linear actuator which uses a piezoelectric element as a motive power source, and its drive means. It is a figure which shows an example of a structure and drive operation | movement of a linear actuator which uses a piezoelectric element as a motive power source. Explanatory drawing which shows an example of the application of the drive signal to a piezoelectric element, and a temperature change. FIG. 6 is an explanatory diagram illustrating an example of a method for controlling a drive signal applied to a piezoelectric element and a temperature change of the piezoelectric element in Example 2. FIG. 6 is an explanatory diagram illustrating an example of a method for controlling a drive signal applied to a piezoelectric element and a temperature change of the piezoelectric element in Example 3. The block diagram of the optical disk apparatus which uses the linear actuator which uses a piezoelectric element as a power source for the displacement of a lens.

Explanation of symbols

101, 601 ... piezoelectric element, 102,602 ... moving member, 103,603 ... drive shaft,
104, 604 ... Signal generating means, 105, 605 ... Control means, 106, 606 ... Measuring means,
107, 607 ... display means, 201a, 201b, 201c ... piezoelectric element, 202a, 202b, 202c ... moving member,
203a, 203b, 203c ... drive shaft, 204a, 204b, 204c ... fixing member,
608 ... optical disc, 609 ... laser, 610 ... movable lens, 611 ... objective lens,
612 ... Rotary motor.

Claims (6)

A piezoelectric element that expands and contracts when a voltage is applied;
Signal generating means for generating a drive signal for the piezoelectric element;
Control means for controlling the signal generating means and controlling application of a drive signal to the piezoelectric element;
Measuring means for measuring the ambient temperature or the temperature of the piezoelectric element;
The control means controls the application period of the drive signal according to the measurement result,
The ambient temperature or the temperature of the piezoelectric element during driving is controlled to be within the range of the lower limit temperature T _min to the upper limit temperature T _max (T _min <T _max ),
For the temperature T before driving obtained from the measuring means,
The relationship between the temperature rise ΔT ₁ due to continuous driving signal application during the driving period t ₁ and the upper limit temperature T _max in the driving device is
((T + Δ ≦ T ₁ ) ≦ T _max )
Adjusting the continuous drive period t ₁ of the drive signal;
After the drive period t _1, the temperature change amount △ T ₂ Not applying a driving signal rest period t _2,
A driving device characterized by having a rest period t ₂ having a relationship of (T + ΔT ₁ ) −ΔT ₂ ≧ T _min . The drive device according to claim 1,
When the temperature T measured by the measuring means before the moving member is driven by the piezoelectric element satisfies the relationship of the lower limit temperature T _min > T,
The control means generates a drive signal for a fixed drive period t _h ,
A drive device characterized in that the temperature is raised to a lower limit temperature T _min or more. The drive device according to claim 1,
A display means for indicating an abnormality of the apparatus;
A temperature T measured by the measuring means;
When the deterioration temperature T _{c of the} piezoelectric element has a relationship of (T> T _c ),
An apparatus for displaying an abnormality of the apparatus on the display means. The drive device according to claim 1,
The control means controls the signal generating means to apply a drive signal to the piezoelectric element; and
The piezoelectric element is driven by periodically repeating a pause period in which a drive signal is not applied,
When the measurement temperature by the measurement means is high,
A driving apparatus characterized in that driving is performed by repetition of a fast cycle while maintaining a ratio between a driving period and a rest period. The drive device according to claim 1,
The control means controls the signal generating means to apply a drive signal to the piezoelectric element; and
The piezoelectric element is driven by periodically repeating a pause period in which a drive signal is not applied,
When the measurement temperature by the measurement means is low,
A driving device that is driven by repeating a slow cycle while maintaining a ratio between a driving period and a rest period. The drive device according to claim 1 to claim 5,
An optical disk device used for displacement of an optical lens.

Images