JP2012217012A - Electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic apparatus that is allowed to be controlled in accordance with internal temperature thereof and that is prevented from increasing in size.SOLUTION: An oscillation device has a diaphragm 10 and a piezoelectric element 20. The piezoelectric element 20 is provided on the diaphragm 10. A capacitance measuring section 52 measures capacitance of the piezoelectric element 20. A temperature calculating section 54 uses conversion data that converts capacitance into temperature, and the capacitance measured by the capacitance measuring section 52, so as to calculate temperature of the piezoelectric element 20. The conversion data is stored in a conversion data storage section 56. A control section 50 controls operation of an electronic apparatus in accordance with the temperature calculated by the temperature calculating section 54.

Description

  The present invention relates to an electronic apparatus having an oscillation device using a piezoelectric element as a vibration source.

  An oscillating device using a piezoelectric element is used as an oscillation source of a speaker or an ultrasonic sensor, for example. This oscillation device has an advantage that it is easy to miniaturize compared to an electrodynamic speaker that vibrates a diaphragm using a magnet.

  Patent Document 1 describes that in an alarm electronic timepiece using a piezoelectric element as a sounding body, temperature is detected based on the oscillation frequency of the piezoelectric body.

  Patent Document 2 and Patent Document 3 describe that the capacitance of a piezoelectric sheet mixed with a piezoelectric ceramic powder during measurement of a polymer is measured, and the measured value is converted into temperature. In Patent Document 2, the piezoelectric sheet has a function of measuring pressure. The converted temperature is used to correct the measured pressure value.

Japanese Utility Model Publication No. 60-191993 JP 2002-16301 A JP 2002-111087 A

  In portable electronic devices, the density of mounted components has increased with the increase in functionality. Along with this, there is a possibility that the inside of the electronic device will be heated. For this reason, this inventor thought that it was necessary to control operation | movement of an electronic device based on the temperature inside an electronic device. However, if a temperature sensor is provided inside the electronic device, the electronic device is increased in size accordingly.

  An object of the present invention is to control an electronic device based on the temperature inside the electronic device and to suppress an increase in size of the electronic device.

According to the present invention, an electronic device comprising:
An oscillation device having a vibration member and a piezoelectric element provided on the vibration member;
A capacitance measuring means for measuring a capacitance of the piezoelectric element;
Temperature conversion means for calculating the temperature of the piezoelectric element using the conversion data for converting the capacitance into temperature and the capacitance measured by the capacitance measurement means;
Control means for controlling the operation of the electronic device based on the calculation result of the temperature calculation means;
An electronic device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, an electronic device can be controlled based on the temperature inside an electronic device, and the enlargement of an electronic device can be suppressed.

It is a figure which shows the structure of the electronic device which concerns on 1st Embodiment. It is a figure for demonstrating an example of the data which the conversion data storage part 56 has memorize | stored. It is a figure which shows the structure of the electronic device which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of an electronic apparatus according to the first embodiment. The electronic apparatus includes an oscillation device, a capacitance measuring unit 52, a temperature calculating unit 54, and a control unit 50. The oscillation device has a diaphragm 10 and a piezoelectric element 20. The piezoelectric element 20 is provided on the diaphragm 10. The capacitance measuring unit 52 measures the capacitance of the piezoelectric element 20. The temperature calculation unit 54 calculates the temperature of the piezoelectric element 20 using the conversion data for converting the capacitance into temperature and the capacitance measured by the capacitance measurement unit 52. In the present embodiment, the conversion data is stored in the conversion data storage unit 56. The control unit 50 controls the operation of the electronic device based on the temperature calculated by the temperature calculation unit 54. An example of the control of the operation performed here is to turn off a certain function of the electronic device. Details will be described below.

  The vibration member 10 has a sheet shape and vibrates due to vibration generated from the piezoelectric element 20. The vibrating member 10 adjusts the basic resonance frequency of the piezoelectric element 20. The fundamental resonance frequency of the mechanical vibrator depends on the load weight and compliance. Since the compliance is the mechanical rigidity of the vibrator, the basic resonance frequency of the piezoelectric element 20 can be controlled by controlling the rigidity of the vibration member 10. The material constituting the vibration member 10 is not particularly limited as long as it is a material having a high elastic modulus with respect to the piezoelectric element 20 which is a brittle material such as metal or resin, but phosphor bronze, stainless steel, etc. from the viewpoint of workability and cost. Is preferred.

  The piezoelectric element 20 is formed of piezoelectric ceramics such as PZT. However, the piezoelectric element 20 may be formed of a polymer material exhibiting piezoelectric characteristics, such as polyvinylidene fluoride.

  The control unit 50 generates a drive signal based on an audio signal input from the outside, and inputs the generated drive signal to the piezoelectric element 20. When the oscillation device is caused to function as a speaker that directly outputs audible sound, the control unit 50 generates a drive signal by amplifying the audio signal. When the oscillation device functions as a parametric speaker, the control unit 50 modulates audio data (original signal) input from the outside to generate modulation data for the parametric speaker, and generates a drive signal based on this data. To do. The frequency of this drive signal is the nth order resonance frequency of the vibrating member 10 and the piezoelectric element 20.

  Further, the control unit 50 shuts down the oscillation device when the temperature calculated by the temperature calculation unit 54 becomes equal to or higher than a reference value while the oscillation device is being driven. This reference value is set to be less than the Curie point of the material constituting the piezoelectric element 20, for example.

  In the present embodiment, the oscillation device has a support member 40. The support member 40 has a cylindrical shape, and is formed of, for example, resin or metal. The cross-sectional shape of the straight cylinder may be a circle or a polygon. The support member 40 holds the edge of the vibration member 10.

  FIG. 2 is a diagram for explaining an example of data stored in the conversion data storage unit 56. In general, the capacitance of a piezoelectric element increases as the temperature increases. For this reason, the correlation between the capacitance and temperature in the piezoelectric element 20 is measured in advance, and an equation for converting the capacitance to temperature is determined based on the measurement result, and this equation is stored in the conversion data storage unit 56. In this case, the temperature calculation unit 54 can easily convert the measurement result of the capacitance measurement unit 52 into the temperature of the piezoelectric element 20.

  Next, the operation and effect of this embodiment will be described. While the piezoelectric element 20 is driven, the piezoelectric element 20 generates heat. When the temperature of the piezoelectric element 20 increases, the oscillation characteristics of the piezoelectric element 20 change. On the other hand, in the present embodiment, the control unit 50 controls the oscillation device based on the calculation result of the temperature calculation unit 54. For this reason, the control unit 50 can drive the piezoelectric element 20 within a range in which the oscillation characteristics of the piezoelectric element 20 do not change.

  In the present embodiment, when the temperature calculated by the temperature calculation unit 54 becomes equal to or higher than the reference value while the oscillation device is being driven, the oscillation device is shut down. When the temperature of the piezoelectric element 20 exceeds the Curie point of the substance constituting the piezoelectric element 20, the polarization of the piezoelectric element 20 is depolarized. On the other hand, when the reference value described above is set to be less than the Curie point of the substance constituting the piezoelectric element 20, it is possible to suppress the depolarization of the piezoelectric element 20.

(Second Embodiment)
FIG. 3 is a diagram illustrating a configuration of the electronic device according to the second embodiment. The electronic device according to the present embodiment has the same configuration as the electronic device according to the first embodiment except for the following points.

  First, the upper end surface of the support member 40 of the oscillation device is attached to the inner wall of the housing 60 of the electronic device. A sound hole 62 is provided in the housing 60. The support member 40 includes a sound hole 62 on the inner side in plan view. For this reason, the sound hole 62 faces the vibration member 10 and the piezoelectric element 20, and the sound wave generated by the vibration member 10 and the piezoelectric element 20 is radiated to the outside of the housing 60 through the sound hole 62.

  A plurality of electronic components 70 are provided in the housing 60. The electronic component 70 is a semiconductor package or a discrete component, and generates heat during operation. The electronic component 70 is provided on, for example, the printed wiring board 72, but may be directly attached on the inner wall of the housing 60.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained. In addition, an electronic component 70 other than the oscillation device is provided in the housing 60. For this reason, even if the oscillation device is not operating, the temperature of the piezoelectric element 20 may increase too much due to heat generated from the electronic component 70.

  On the other hand, in the present embodiment, when the temperature calculated by the temperature calculation unit 54 is equal to or higher than the reference value while the oscillation device is not driven, the input to the electronic component 70 is set to a mode in which the power consumption is low. By controlling, heat generation from the electronic component 70 is suppressed. For this reason, when the reference value described above is set to be less than the Curie point of the substance constituting the piezoelectric element 20, it is possible to suppress the depolarization of the piezoelectric element 20 while the oscillation device is not operating.

  Further, when the reliability of the electronic component 70 decreases at a temperature below the Curie point of the piezoelectric element 20, the reference value described above may be set to a value below the temperature at which the reliability of the electronic component 70 can be ensured. In this case, it is possible to suppress the depolarization of the piezoelectric element 20 and it is possible to suppress the reliability of the other electronic component 70 from being lowered.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

DESCRIPTION OF SYMBOLS 10 Vibration member 20 Piezoelectric element 40 Support member 50 Control part 52 Capacitance measurement part 54 Temperature calculation part 56 Conversion data storage part 60 Case 62 Sound hole 70 Electronic component 72 Printed wiring board

Claims (4)

Electronic equipment,
An oscillation device having a vibration member and a piezoelectric element provided on the vibration member;
A capacitance measuring means for measuring a capacitance of the piezoelectric element;
Temperature conversion means for calculating the temperature of the piezoelectric element using the conversion data for converting the capacitance into temperature and the capacitance measured by the capacitance measurement means;
Control means for controlling the operation of the electronic device based on the calculation result of the temperature calculation means;
Electronic equipment comprising. The electronic device according to claim 1,
The control means is an electronic device that shuts down the oscillation device when the temperature becomes equal to or higher than a reference value. The electronic device according to claim 2,
The electronic device in which the reference value is less than the Curie point of a substance constituting the piezoelectric element. The electronic device according to claim 3,
The oscillation device is disposed in a housing;
An electronic apparatus further comprising an electronic component that is disposed in the housing and generates heat.

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