JPH0529677A - Controlling method for drive of piezoelectric laminate - Google Patents

Abstract

PURPOSE:To suppress an irregularity in a displacement of a piezoelectric laminate based on a temperature change while preventing thermal deterioration of the laminate. CONSTITUTION:A PTC element 2 is disposed substantially at a center of a piezoelectric laminate 1 in an axial direction. A detected temperature detected by the element 2 is compared with a reference temperature by a controller 8. A power source 4 for heating the PTC is connected to the element 2 based on the result to heat the laminate or to cool it by a cooler 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control method for a piezoelectric laminate.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric laminated body which is displaced by voltage application has been used as an actuator for driving a movable part of various devices. This piezoelectric laminate is generally P
It is configured by stacking a plurality of ZT (PbZrO ₃ .PbTiO ₃ ) elements. By the way, when a voltage is applied to the piezoelectric laminated body, the temperature rises due to self-heating of the piezoelectric laminated body with the passage of time, but the piezoelectric laminated body has a property that the displacement amount changes due to this temperature rise. Therefore, when using the piezoelectric laminate for controlling a controlled device with a small displacement,
The rate of change in displacement of the piezoelectric laminate due to the above temperature cannot be ignored, and the operation as an actuator may not be possible depending on the object. The same inconvenience also occurs when the piezoelectric laminate is used in a place where the environmental temperature changes greatly, such as in the engine room of an automobile.

As a solution to the inconvenience caused by the displacement of the piezoelectric laminate having temperature dependency, Japanese Patent Laid-Open No. 64-10309 discloses a temperature sensor near the piezoelectric laminate and the temperature sensor. There is disclosed a correction device for a piezoelectric laminated body in which a heater is arranged at a position not close to the. This correction device compares the detected temperature detected by the temperature sensor with a reference temperature set to a temperature sufficiently higher than the operating environment temperature of the piezoelectric laminate, and energizes the heater only when the detected temperature is lower than the reference temperature. By heating the piezoelectric laminate, the temperature of the piezoelectric laminate can be maintained at a temperature sufficiently higher than the operating environment temperature, and the variation in displacement of the piezoelectric laminate due to temperature change can be suppressed.

Further, Japanese Patent Application Laid-Open No. 62-10457 discloses a piezoelectric laminate in which a PTC heater is integrally provided between layers or on the outer periphery. In this piezoelectric laminate, a PTC heater having a Curie point near the maximum temperature that rises during driving is used to raise the temperature of the piezoelectric laminate to the vicinity of the maximum temperature during driving and maintain that temperature. By this, the displacement amount of the piezoelectric laminate during driving is kept constant.

[0005]

However, the above-mentioned conventional means for solving the temperature dependence are driven by heating and holding the piezoelectric laminate at a temperature near the maximum temperature during driving or a temperature sufficiently higher than the maximum temperature. By eliminating the temperature change of the piezoelectric laminated body inside, the displacement amount of the piezoelectric laminated body is kept constant. Therefore, there is a problem that the polarization state in the PZT element is deteriorated by heat and the durability of the piezoelectric laminate is impaired. In addition, it is necessary to secure a design value for assembly that allows the displacement in a high temperature state, and if the assembly is performed at room temperature and the temperature is high during use, the variation in displacement is also increased.

The present invention has been made in view of the above circumstances, and a drive control method for a piezoelectric laminate that can suppress variations in displacement of the piezoelectric laminate due to temperature without impairing the durability of the piezoelectric laminate. It is a technical issue to be solved to provide the above.

[0007]

According to the drive control method of a piezoelectric laminate of the present invention, the temperature of the piezoelectric laminate is detected by a PTC element arranged substantially at the center of the piezoelectric laminate in the axial direction, and the detected temperature is detected. It is characterized in that the piezoelectric laminate is heated by the PTC element or cooled by a cooling device based on the result of comparison between the PTC element and a preset reference temperature.

The drive control method of the present invention can be applied to both a piezoelectric laminate in which the displacement increases as the temperature rises and a piezoelectric laminate in which the displacement decreases as the temperature rises. The PTC element is arranged substantially at the center of the piezoelectric laminate in the axial direction. It is desirable to set the arrangement of the PTC element depending on the way of heat transfer with the surroundings. Since the center in the axial direction at the time of driving has the highest temperature, the PTC element should be arranged slightly above the center to improve the sensing accuracy. Is preferable, and in order to improve heating efficiency, it is preferable to dispose it slightly below the center.

The PTC element described above has an N content up to the Curie temperature.
As a TC thermistor, the resistance value decreases as the temperature rises. By measuring the resistance value of this PTC element, P
The temperature of the TC element can be calculated and used as the detected temperature of the piezoelectric laminate. The drive control method of the piezoelectric laminate of the present invention is
For example, the following device can be used.

That is, a PTC element disposed substantially at the center of the piezoelectric laminate in the axial direction, resistance measuring means for measuring the resistance of the PTC element, a PTC heating power source for energizing the PTC element, and the PTC element. To the resistance measuring means or the PTC
A changeover switch for selectively connecting a heating power source, a cooling device for cooling the piezoelectric laminate, a temperature of the PTC element calculated from a resistance value measured by the resistance measuring means, and set as a detection temperature of the piezoelectric laminate. A drive control which is configured to switch the changeover switch based on a result of comparison between the detected temperature and a preset reference temperature and to output an operation signal to the PTC heating power source or the cooling device. A device can be employed.

The piezoelectric laminate drive control method of the present invention heats or cools the piezoelectric laminate based on the result of comparison between the detected temperature of the piezoelectric laminate measured by the PTC element and the reference temperature. However, it is preferable to control the drive voltage of the piezoelectric laminate based on the detected temperature in consideration of the fact that it takes time to transfer heat when heating or cooling.
This is because the displacement amount at the detected temperature is calculated from the map showing the relationship between the displacement amount of the piezoelectric laminate and the temperature, and the drive voltage is set so that the difference between this displacement amount and the set displacement amount can be compensated. It can be carried out.

[0012]

In the drive control method for the piezoelectric laminate of the present invention, the PT
When the detected temperature of the piezoelectric laminate detected by the C element is lower than the reference temperature, the PTC element is energized to heat the piezoelectric laminate by the PTC element, and when the detected temperature is higher than the reference temperature, the cooling device is used. Cool the piezoelectric stack. For this reason,
The temperature of the piezoelectric laminate can be maintained at an arbitrary temperature depending on the setting of the reference temperature. Further, since the temperature of the piezoelectric laminated body is measured by the PTC element arranged substantially in the center of the piezoelectric laminated body in the axial direction, the temperature sensing can be accurately performed without being affected by the external environment. Therefore, if the reference temperature is set to, for example, about room temperature, it is possible to reliably prevent thermal deterioration due to high temperature of the piezoelectric laminate, and to suppress variations in displacement of the piezoelectric laminate due to temperature changes as much as possible. Is possible.

[0013]

EXAMPLES Examples of the present invention will be specifically described below.
As shown in the block diagram of FIG. 1, the drive control device used in the drive control method of the piezoelectric laminate of the present embodiment is the piezoelectric laminate 1
PTC element 2 arranged in the axial center of the PTC element 2, a resistance meter 3 for measuring the resistance of the PTC element 2, a PTC heating power source 4 for energizing the PTC element 2, and a resistance meter 3 or PTC heating for the PTC element 2. Changeover switch 5 for selectively connecting the power supply 4 for
A cooling device 6 for cooling the piezoelectric laminate 1, a drive power source 7 for applying a voltage to the piezoelectric laminate 1, a temperature of the PTC element 2 calculated from a resistance value measured by the resistance meter 3, The detected temperature is set, and the changeover switch 5 is switched based on the result of comparison between the detected temperature and a preset reference temperature.
The controller 8 outputs an operation signal to the TC heating power source 4 or the cooling device 6 and outputs a drive voltage signal set based on the detected temperature to the drive power source 7.

The piezoelectric laminate 1 comprises a piezoelectric plate 12 made of PZT having electrodes 11 printed on both front and back surfaces, and a metal electrode plate 1.
3 and 3 are alternately laminated, each piezoelectric plate 12 is held by the lead electrode 14, and the lead electrode 14 is joined to each electrode plate 13. The PTC element 2 is sandwiched in the center of the piezoelectric laminate 1 in the axial direction, and sensing and power supply of the PTC element 2 are performed through the lead electrodes 15. The lead electrodes 14 that energize each electrode plate 13 are insulated from the PTC element 2, and the lead electrodes 15 that energize the PTC element 2 and each electrode plate 13 are insulated. Further, the piezoelectric laminate 1 used in this example has a displacement amount which increases as the temperature rises.

The changeover switch 5 is electrically connected to the controller 8 and operates by receiving a signal from the controller 8. When the changeover switch 5 is connected to the A side in FIG. 1, the PTC element 2 and the resistance meter 3 are connected via the lead electrode 15. When the changeover switch 5 is connected to the B side in FIG. 1, the lead electrode 15
The PTC element 2 and the PTC heating power source 4 are connected via the.

The cooling device 6 includes a cooling pipe 61 arranged on the outer periphery of the piezoelectric laminate 1 via an insulating coating layer (not shown), and an inflow passage 62 for supplying a cooling medium to the cooling pipe 61.
And a discharge passage 63 through which the cooling medium is discharged from the cooling pipe 61.
And a valve 64 provided in the middle of the inflow path 62. The valve 64 is electrically connected to the control unit 8 and receives a signal from the control unit 8 to open and close.

The control unit 8 is a microcomputer in which various information is stored. That is, a map showing the relationship between the temperature of the PTC element 2 and the resistance value, the high temperature side reference temperature D and the low temperature side reference temperature C set according to the temperature characteristics of the piezoelectric laminate 1, and the piezoelectric laminate 1 A map and the like showing the relationship between the displacement amount and the temperature are stored in memory. The drive control method of the piezoelectric laminated body of the present embodiment maintains the temperature of the piezoelectric laminated body 1 within the reference temperature range (C to D) regardless of the environmental temperature, and sets the displacement amount of the piezoelectric laminated body 1 to the set displacement amount. X
The drive is controlled to be constant.

A drive control method of the piezoelectric laminate 1 using the drive control device having the above-mentioned structure will be described with reference to the flowchart of FIG. The changeover switch 5 is connected to the A side by a signal from the control unit 8, and the resistance of the PTC element 2 is measured by the resistance meter 3. This measured resistance value is sent to the control unit 8,
The temperature of the PTC element 2 is calculated according to a map showing the relationship between the resistance value of the PTC element 2 and the temperature, and is set as the detected temperature T of the piezoelectric laminate 1. The detected temperature T is compared with preset reference temperatures C and D (STEP 1).

When the detected temperature T is C ≦ T ≦ D in STEP 1, the control unit 8 sets the drive voltage as follows, and sends this signal to the drive power supply 7 to correct the drive voltage of the piezoelectric laminate 1. To do. This drive voltage setting calculates the displacement amount x at the detected temperature T from the map showing the relationship between the displacement amount of the piezoelectric laminate 1 and the temperature, and calculates the difference ± Δx (between the displacement amount x and the set displacement amount X _0. Δx = x−X ₀ ) is compensated for (see FIGS. 4 and 5). Here, the drive voltage required to set the displacement amount of the piezoelectric laminate 1 at the temperature T ₀ to the set displacement amount X ₀ is set as the target drive voltage Y ₀ . Detection temperature T (T
When the displacement amount x in <T ₀ ) is smaller than the set displacement amount X ₀ , the drive voltage y (Y ₀ <depending on the value of the difference −Δx.
y) is set. Further, when the displacement amount x at the detected temperature T (T ₀ <T) is larger than the set displacement amount X ₀ , the drive voltage y (y <Y ₀ ) is set according to the value of the difference + Δx.

When the detected temperature T is T <C in STEP 1, the control unit 8 switches the changeover switch 5 to the B side, the PTC heating power source 4 is turned on, the PTC element 2 is energized, and the piezoelectric laminate 1 is turned on. To heat. Then, similarly to the above, the control unit 8 sets the drive voltage to correct the drive voltage of the piezoelectric laminate 1. After that, the changeover switch 5 is switched to the A side by the control unit 8 again, and the piezoelectric laminated body 1 is moved in the same manner as above.
The detected temperature T is detected, and the controller 8 compares the detected temperature T with the reference temperature C. Here, if the detected temperature T is equal to or higher than the reference temperature C, the control unit 8 turns off the PTC heating power source 4, the drive voltage is set in the same manner as above, and the drive voltage of the piezoelectric laminate 1 is corrected. On the other hand, if the detected temperature T is lower than the reference temperature C, the control of heating the piezoelectric laminate 1 again is performed.

When the detected temperature T is D <T in STEP 1, the controller 8 opens the valve 62 and the cooling device 6 cools the piezoelectric laminate 1. Then, similarly to the above, the control unit 8
The drive voltage setting is performed in order to correct the drive voltage of the piezoelectric laminate 1. After that, the detected temperature T of the piezoelectric laminate 1 is determined as described above.
Is detected and the controller 8 compares it with the reference temperature D. here,
When the detected temperature T is equal to or lower than the reference temperature D, the control unit 8 closes the valve 63, the drive voltage is set in the same manner as above, and the drive voltage of the piezoelectric laminate 1 is corrected. On the other hand, if the detected temperature T is higher than the reference temperature D, the cooling device 6 causes the piezoelectric laminated body 1 to move.
Cooling continues.

As described above, according to the drive control method of the piezoelectric laminate of the present embodiment, the temperature of the piezoelectric laminate 1 is set to the reference temperature range (C to C).
D) can be maintained. Therefore, the piezoelectric laminate 1
It is possible to reliably prevent deterioration due to heat. Further, it can be applied to the piezoelectric laminated body 1 made of a PZT element having any temperature dependence, and the degree of freedom in element selection and optimum design can be realized. Furthermore, the piezoelectric laminate 1 can be driven at high speed (several hundred Hz or more).
The piezoelectric laminate can be used in a wide range of conditions.

As described above, the temperature of the piezoelectric laminate 1 can be maintained within the reference temperature range, and the driving voltage of the piezoelectric laminate 1 can be corrected according to the detected temperature T. It is possible to suppress variations in displacement due to temperature changes as much as possible.

[0024]

As described above in detail, according to the drive control method for a piezoelectric laminated body of the present invention, the temperature of the piezoelectric laminated body 1 can be maintained within the reference temperature range, so that the deterioration of the piezoelectric laminated body due to heat is surely performed. Therefore, it is possible to suppress variations in displacement of the piezoelectric laminate due to temperature changes as much as possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a drive control device of an embodiment used in a drive control method for a piezoelectric laminate of the present invention.

FIG. 2 is a perspective view of a piezoelectric laminate used in the drive control device.

FIG. 3 is a flowchart when drive control is performed using the drive control device.

FIG. 4 is a diagram showing a relationship between a temperature and a displacement amount of a piezoelectric laminate.

FIG. 5 is a diagram showing a drive voltage value required to obtain a set displacement amount of a piezoelectric laminate.

[Explanation of symbols]

1 is a piezoelectric laminate, 2 is a PTC element, 3 is a resistance meter, 4 is P
TC heating power source, 5 changeover switch, 6 cooling device, 7
Is a drive power source, and 8 is a control unit.

Claims (1)

Claim: What is claimed is: 1. A PTC element disposed substantially at the center of an axial direction of a piezoelectric laminate detects the temperature of the piezoelectric laminate, and compares the detected temperature with a preset reference temperature. A drive control method for a piezoelectric laminate, comprising heating the piezoelectric laminate with the PTC element or cooling it with a cooling device based on the result.