JP2001286163A - Actuator drive method and its equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an actuator to efficiently control a part to be driven. SOLUTION: The actuator is constituted of a fixed part 4, displacement parts 2 and 3, each of which base side is fixed to the fixed part 4 making each tip cross each other, a composition part 5 which is commonly disposed at each tip of the displacement parts 2 and 3, and a pressurizing part which makes the composition part 5 pressure-contact to the part to be driven of the driving object. The drive method of the actuator which transmits its drive force to the part to be driven by making the composition part 5 move elliptically makes change the slope of the composition part 5 against the part to be driven either in the minor axis direction or in the major axis direction of the elliptical orbit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for driving an actuator for driving a driven member such as a rotating disk-shaped rotor or a linearly moving slider.

[0002]

2. Description of the Related Art The above-mentioned actuator is a drive unit comprising a displacement member formed of a piezoelectric element or the like fixed to a fixed portion at a base end thereof and attached to a combining portion at the intersection so as to intersect the front end. Is configured to be brought into pressure contact with a driven member by a pressure unit.

By the way, such an actuator is
A system in which the combining unit is driven so as to form an elliptical locus has been proposed (JP-A-58-148682).

[0004]

However, the elliptical trajectory in which the synthesizing unit moves according to the above proposed method is in a constant state parallel to the normal of the disk-shaped rotor whose major axis rotates. When controlling the rotation speed of
It is necessary to change the voltage output value, so that there is a problem that the efficiency is reduced when the rotor is driven at a high speed.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a method and an apparatus for driving a truss-type actuator capable of efficiently performing drive control on a driven member. And

[0006]

According to the first aspect of the present invention, a fixed portion, a plurality of displacement portions each having a base end fixed to the fixed portion so that each tip side intersects, and a common end to all the displacement portions. The actuator composed of a driving unit composed of a combining unit and a pressurizing unit that presses the combining unit to a driven member to be driven is subjected to an elliptical motion of the combining unit to a driven member. A method of driving an actuator for transmitting a driving force, wherein an inclination of an elliptical locus of the combining section with respect to a driven member in a minor axis direction or a major axis direction is changed.

According to the present invention, the inclination of the elliptical trajectory of the combining section in the minor axis direction or the major axis direction with respect to the driven member changes, so that the output characteristic is set to an arbitrary value from low-speed high torque to high-speed low torque. , So that efficiency can be improved.

According to a second aspect of the present invention, the inclination of the elliptical trajectory of the combining section in the minor axis direction or the major axis direction with respect to the driven member is changed by changing at least the amplitude of the phase difference and the amplitude of the drive signal applied to each displacement section. It is characterized by changing.

According to the present invention, when at least the amplitude of the phase difference and the amplitude of the drive signal applied to each displacement portion is adjusted, the inclination of the elliptical trajectory of the combining portion with respect to the driven member in the short diameter direction or the long diameter direction changes. Will do.

According to a third aspect of the present invention, at least the amplitude of the phase difference and the amplitude is set at a plurality of levels so that the inclination of the elliptical trajectory of the combining section in the minor axis direction or the major axis direction with respect to the driven member is different. Preferably, at least the amplitude level of the phase difference and the amplitude is switched according to the driving speed of the driven member.

In the present invention, at least the amplitude of the phase difference and the amplitude is set at a plurality of levels so as to be an arbitrary value from low-speed high torque to high-speed low torque.
When the level is switched in accordance with the driving speed of the driven member, it is possible to control the speed and the torque to be optimal for the driving speed of the driven member.

According to a fourth aspect of the present invention, there is provided a fixed portion, a plurality of displacement portions each having a base end fixed to the fixed portion so that each tip side intersects, and a composite member commonly disposed at the tip of all the displacement portions. Actuator that moves the combining unit in an elliptical manner to transmit a driving force to a driven member, with respect to an actuator that includes a driving unit that includes a driving unit and a pressing unit that presses the combining unit to a driven member to be driven. In the driving method of (1), in a state where the minor axis direction or major axis direction of the elliptical locus of the combining unit is inclined with respect to the driven member, the driving characteristic of the driven member is changed by changing the minor axis dimension of the elliptical locus. It is characterized by controlling.

According to the present invention, in addition to the change in the inclination of the elliptical trajectory with respect to the driven member, the minor axis dimension of the elliptical trajectory changes, so that the output characteristics can be improved with higher accuracy from low speed and high torque to high speed and low torque. It is possible to adjust the value to an arbitrary value, which can further improve the efficiency.

According to a fifth aspect of the present invention, the minor dimension of the elliptical locus is changed by changing at least the amplitude of the phase difference and the amplitude of the drive signal applied to each displacement portion.

According to a sixth aspect of the present invention, the plurality of displacement portions are
One or more first groups and one or more second groups are distinguished, and the displacement units of both groups are driven.

According to the present invention, when a plurality of displacement parts are composed of more than two, the plurality of displacement parts are divided into two groups, and each group is driven as described above. Control can be performed in the same manner as an actuator having two displacement units.

According to a seventh aspect of the present invention, the plurality of displacement portions are
One or two or more first groups and one or two or more second groups are distinguished, and a displacement unit of one group is driven.

According to the present invention, when the number of the displacement portions is more than two, the plurality of displacement portions are divided into two groups, one of which is a drive side, and the other of which is a drive group. Is driven on the driven side as described above, control can be performed in the same manner as an actuator having two displacement units.

The invention according to claim 8 is a fixing part, a plurality of displacement parts whose base ends are fixed to the fixing part so that the respective tip sides cross each other, and a composite part commonly disposed at the tips of all the displacement parts. Actuator that moves the combining unit in an elliptical manner to transmit a driving force to a driven member, with respect to an actuator that includes a driving unit that includes a driving unit and a pressing unit that presses the combining unit to a driven member to be driven. Wherein the plurality of displacement units are divided into one or more first groups and one or more second groups, and a first group of displacement units and a second group of displacement units are provided. The relationship between the resonance frequency fn ₁ of the in-phase mode in which the displacements of the first group resonates in the same phase and the resonance frequency fn ₂ of the opposite-phase mode in which the displacements of the first group and the second group resonate in opposite phases are as follows: Satisfies formulas A1) and (A2) In this case, one group is driven and controlled.

1 <fn ₁ / fn ₂ <α + √ (α ² -1) (A1) α = (1-2ζ ² ) / (1-4ζ ² ) (A2) where ζ is the attenuation ratio. In this case, if one group is driven and controlled so as to satisfy the above expressions (A1) and (A2), the same control as the invention of claim 7 becomes possible.

According to a ninth aspect of the present invention, in the method for driving an actuator according to any one of the first, second, fourth, and fifth aspects, the plurality of displacement portions are connected to one or more first groups and one or two or more A driving device for an actuator for driving both groups separately from a second group, comprising two amplifying means for amplifying an oscillating signal such that one lags or advances the other, and outputs the oscillating signal to each group separately. A speed detecting means for detecting the speed of the driven member, and an amplitude control means for controlling an amplitude amount by both or one of the two amplifying means based on a detection result by the speed detecting means,
Phase difference control means for controlling a phase amount of both or one of the signals input to or output from the two amplifying means based on the detection result by the speed detecting means. And

According to the present invention, when at least one of the phase difference and the amplitude of the drive signal applied to each displacement section is adjusted, the inclination of the elliptical trajectory of the combining section in the minor axis direction or the major axis direction with respect to the driven member changes. Will be.

According to a tenth aspect of the present invention, there is provided a method of driving an actuator according to the third aspect, wherein the plurality of displacement portions are classified into one or more first groups and one or more second groups. And two amplifying means for amplifying the oscillating signal so that one lags or advances the other and outputs the signals to each group separately, and both or both of the two amplifying means An amplitude control means for controlling an amplitude amount by one of the signals; a phase difference control means for controlling a phase amount of both or one of the signals input to or output from the two amplification means; A plurality of corresponding drive patterns are stored, and at least one of the amplitude control means and the phase difference control means is stored in a corresponding drive pattern when a predetermined time is reached. Characterized by comprising a control means for controlling.

In the present invention, at least the amplitude of the phase difference and the amplitude is set at a plurality of levels so as to have an arbitrary value from low-speed high torque to high-speed low torque according to the passage of time. When the level is changed over time, for example, it is possible to control the speed and the torque to be optimal for the driving speed of the driven member after the start of driving.

According to an eleventh aspect of the present invention, in the method of driving an actuator according to the third aspect, the plurality of displacement portions are distinguished into one or two or more first groups and one or two or more second groups. And two amplifying means for amplifying the oscillating signal so that one lags or advances the other and outputs the signals to each group separately, and both or both of the two amplifying means Amplitude control means for controlling an amplitude amount by one of the above, phase difference control means for controlling both or one of the phase amounts of signals input to or output from the two amplifying means, and a driven member A plurality of drive patterns corresponding to the speed change are stored, and when the speed of the driven member reaches a predetermined speed, the amplitude control means and Characterized by a control means for controlling at least one of the retardation control means.

According to the present invention, at least the amplitude of the phase difference and the amplitude is set at a plurality of levels so as to have an arbitrary value from low-speed high torque to high-speed low torque in accordance with the speed change of the driven member. If the level is switched in accordance with the change in the speed of the driven member, it is possible to control the speed and the torque to be optimum for the driving speed of the driven member after the start of driving, for example.

[0027]

Embodiments of the present invention will be specifically described below. (First Embodiment) FIG. 1 shows a configuration of a truss-type actuator driven by a driving method according to a first embodiment.

This actuator comprises a driving section 1 for driving a driven member 10 and a pressing section 6 for bringing the driving section 1 into pressure contact with a roller 10. The driving unit 1 includes, for example, two displacement units 2 and 3 intersecting at a 90 ° sandwiching angle.
And a combining unit 5 bonded to the intersection thereof, and a fixing unit 4 bonded to the base ends of the displacement units 2 and 3.

As the displacement units 2 and 3, a laminated piezoelectric element that converts an electric signal into a displacement by a piezoelectric effect is used. For the synthesizing part 5, a metal material such as tungsten which can stably obtain a high friction coefficient and is hard to wear is used.
The fixing portion 4 is made of a metal material such as stainless steel which can be easily manufactured and has high strength. In addition, an epoxy resin adhesive excellent in adhesive strength and strength is used for the bonding. The pressing unit 6 is formed of a coil spring or the like,
Is pressed in the center direction (direction of arrow A) of the disk-shaped rotor 10 as a driven member. The rotor 10 is made of a metal such as aluminum, and its side surface is subjected to a surface treatment such as alumite in order to prevent abrasion due to contact with the composite portion 5.

FIG. 2A shows the structure of a laminated piezoelectric element used as the displacement parts 2 and 3.

The piezoelectric element 2 (or 3) has, for example, P
A piezoelectric material layer 7 formed by thinly extending a material having a piezoelectric effect such as ZT is stacked, and a metal electrode 8 for applying an electric field is sandwiched between the piezoelectric material layers 7. It is configured to be adhered using an agent or the like. Note that the piezoelectric material layers 7 at both ends function as protective layers.

The electrodes 8 are alternately connected to the signal lines 9 in the laminating direction.
a, 9b, and these signal lines 9a, 9b are connected to an external drive power supply 9. When a predetermined voltage is applied to the signal lines 9a and 9b, an alternating electric field is generated in the piezoelectric material layer 7 in the stacking direction. The piezoelectric material layers 7 are stacked so that the directions of polarization are opposite in accordance with the electric field.

When, for example, a DC drive voltage is applied to the piezoelectric element 2 (or 3) from the outside, all the piezoelectric material layers 7 coincide with each other and are displaced in the direction of expansion or contraction. As shown in FIG. 2B, the magnitude and displacement of the externally applied electric field are, as shown in FIG.
It can be regarded as a substantially linear relationship. On the other hand, when an AC voltage is applied to the piezoelectric element 2 (or 3), for example, from the outside, all the piezoelectric material layers 7 repeatedly expand and contract in accordance with the electric field.

Each of the piezoelectric elements 2 and 3 has a unique resonance frequency determined by its structure and electrical characteristics. When the frequency of the drive signal matches the resonance frequency, a resonance phenomenon occurs in which the impedance decreases and the displacement increases. . Since the piezoelectric elements 2 and 3 have a small displacement with respect to the external dimensions, it is preferable to use this resonance phenomenon in order to drive the piezoelectric elements at a low voltage.

In the above-described actuator, when the amplitude and phase of the drive signal for driving the two displacement units 2 and 3 are changed, the trajectory of the synthesis unit 5 is obtained according to the elliptical vibration equation (Lissajous equation).

FIGS. 3A and 3B are diagrams showing the trajectory shapes of the synthesizing unit 5 obtained when the phases of two drive signals for driving the two displacement units 2 and 3 are changed. FIG. (B) when the phase difference between the two drive signals is 90 °, and (c) when the phase difference between the two drive signals is 120 °.
This is the case of ゜.

As can be understood from FIG. 3, in this actuator, when the phase difference between the two drive signals is 90 °, the trajectory of the synthesizing unit 5 is circular, and when the phase difference is smaller than 90 °, the trajectory of the synthesizing unit 5 is When the phase difference is larger than 90 °, the trajectory of the synthesizing unit 5 becomes an elliptical trajectory in which the major axis direction is aligned with the tangential direction B of the driven member.

FIG. 4 is a diagram showing a trajectory obtained when the amplitude of both drive signals is changed in addition to the phase.
(A) is a case where the phase difference is 60 ° and the amplitude of the drive signal of the displacement unit 2 is smaller than the amplitude of the drive signal of the displacement unit 3;
(B) shows a case where the phase difference is 60 ° and the amplitude of the drive signal of the displacement unit 2 is larger than the amplitude of the drive signal of the displacement unit 3;
Is a case where the phase difference is 120 ° and the amplitude of the drive signal of the displacement unit 2 is smaller than the amplitude of the drive signal of the displacement unit 3. (D) is a case where the phase difference is 120 ° and the amplitude of the drive signal of the displacement unit 2 is This is a case where the amplitude of the drive signal of the displacement unit 3 is larger than the amplitude.

As can be understood from FIG. 4, when the amplitude of the drive signal of the displacement unit 2 is smaller than the amplitude of the drive signal of the displacement unit 3 at a phase difference of 60 °, the elliptical locus of the synthesis unit 5 is obtained. When the major axis direction is tilted from the normal direction A of the driven member toward the displacement section 2, and conversely, when the amplitude of the drive signal of the displacement section 3 is made smaller than the amplitude of the drive signal of the displacement section 2, The major axis direction of the elliptical locus is the normal direction A of the driven member.
To the displacement part 3 side.

On the other hand, when the amplitude of the drive signal of the displacement unit 2 is smaller than the amplitude of the drive signal of the displacement unit 3 at a phase difference of 120 °, the elliptical trajectory of the synthesis unit 5 is driven in the minor axis direction. When the amplitude of the drive signal of the displacement unit 3 is made smaller than the amplitude of the drive signal of the displacement unit 2 when the amplitude of the drive signal of the displacement unit 3 is smaller than the amplitude of the drive signal of the displacement unit 2, the elliptical trajectory of the synthesis unit 5 becomes shorter in the minor axis direction. Tilt from the normal direction A of the driven member toward the displacement portion 2.

Therefore, in the present invention, when the amplitude is changed, the elliptical trajectory of the synthesizing unit 5 can be inclined with respect to the normal direction A of the driven member. The major axis direction (or minor axis direction) of the elliptical locus of
Can be changed.

FIG. 5 corresponds to FIG.
FIG. 9 is an explanatory diagram of a driving mode when the amplitude of the drive signal of the displacement unit 2 is made smaller than the amplitude of the drive signal of the displacement unit 3 at a phase difference of 0 °.

In the case of this driving, as described above, the major axis direction of the elliptical locus of the synthesizing unit 5 is inclined by the angle θ with respect to the normal direction A of the driven member. When the actuator is driven in this manner, the synthesizing unit 5 is in pressurized contact with the driven member by the pressing force of the pressurizing unit 6.
The driven member has been deformed by δ. At this time, the force Fr applied by the combining unit 5 to the driven member is expressed by the following equation (1).

Fr = kr × δ (1) where kr is a spring constant determined from the elastic modulus of the driven member. Here, the force Ft along the outer surface of the driven member that drives the driven member is represented by the following equation. 2)

Ft = Fr × sin θ (2) Accordingly, the driving force Ft is a function of θ, and as described above, the angle θ is changed by changing the phase difference and the amplitude of the two driving signals applied to the displacement units 2 and 3. By making the variable, it is possible to control the driving force of the actuator.

FIG. 6 shows a block diagram of a driving device for realizing the driving method of the first embodiment.

This drive device directly receives and amplifies a drive signal from an oscillator 15 and outputs the amplified signal to the displacement unit 2.
And an amplifier 17 that amplifies the drive signal from the oscillator 15 after passing through the delay circuit 14 and outputs the amplified signal to the displacement unit 3, a speed detector 11 that detects the speed of the driven member, and a detection signal of the speed detector 11. Phase control unit 1 for inputting and controlling delay circuit 14
2 and an amplitude control unit 13 that inputs a detection signal of the speed detection unit 11 and controls the amplifiers 16 and 17. In addition,
As the speed detection unit 11, a pulse encoder, an MR sensor, or the like is used.

The speed signal of the driven member detected by the speed detector 11 is input to the phase controller 12 and the amplitude controller 13. The phase control unit 12 compares a command value given from a speed command unit (not shown) with the current speed of the driven member, calculates an optimal phase difference, and inputs the calculated phase difference to the delay circuit 14.
The delay circuit 14 delays the phase by the command value and causes a phase difference between the drive signals applied to the two displacement units 2 and 3. Then, the amplifiers 16 and 17 amplify the drive signals and supply the amplified drive signals to the displacement units 2 and 3, respectively. Further, the amplitude control unit 13 compares a command value given from a speed command unit (not shown) with the current speed of the driven member, calculates an optimum amplitude for each of the displacement units 2 and 3, and The value for each amplifier 1
Input to 6 and 17. The amplifiers 16 and 17 change the amplitude in accordance with the command value from the amplitude control unit 13 and
Supply 3

With this driving device, the driving force of the actuator can be controlled.

As the driving device, those having the configuration shown in FIGS. 7 and 8 can be used.

The driving device shown in FIG. 7 uses a controller 20 for inputting signals from a memory 21 and a timer 22 in place of the speed detecting section 11 in the driving device shown in FIG.

In this driving device, the memory 21 stores a plurality of pieces of information. Each piece of information is a drive pattern including phase difference information and amplitude information, and is of various stages from low-speed high-torque to high-speed low-torque.
The timer 22 measures the time from the time of activation, and the controller 20 reads a drive pattern corresponding to the time from the memory 21 every time a predetermined time elapses, and And amplitude control unit 1
Control the appropriate one of the three.

The driving device shown in FIG. 8 uses a memory 21 and a controller 23 for inputting a signal from the speed detecting unit 11 instead of the speed detecting unit 11 in the driving device shown in FIG.

A plurality of pieces of information are stored in the memory 21 of this driving device as before. Each piece of information is a drive pattern including phase difference information and amplitude information, and is of various stages from low-speed high-torque to high-speed low-torque. The speed detector 11 measures the rotation speed of the rotor. When the controller 23 reaches a predetermined speed, the controller 23 reads a drive pattern corresponding to the speed from the memory 21 and reads the drive pattern corresponding to the speed. The corresponding one of the amplitude control units 13 is controlled.

In the case of using these driving devices, it is possible to smoothly start up after the start of driving.

In the first embodiment, the phase difference and the amplitude are changed to adjust the inclination of the elliptical trajectory of the synthesizing unit 5. However, the present invention is not limited to this, and only the amplitude is changed. The degree of inclination of the elliptical locus of the combining unit 5 may be adjusted. However, when the driving torque is also adjusted, it is preferable to change the phase difference.

The driving mode of the two displacement portions 2 and 3 in the first embodiment may be either the resonance mode or the non-resonance mode, but the resonance mode is more efficient and can be driven at a low voltage. There is an advantage. However, when the two displacement units 2 and 3 are driven in the resonance mode, the phase of the voltage and the displacement greatly changes near the resonance frequency.
When the resonance frequency of the piezoelectric element is shifted, for example, the value of the current that is proportional to the displacement is detected, and the phase of the voltage is controlled so that the phase of the current flowing through each displacement section becomes a predetermined value. Is preferred.

In the first embodiment, the laminated piezoelectric element is used for the displacement section. However, the present invention is not limited to this, and a structure including an elastic body in addition to the piezoelectric element may be used. It is also possible to use as.

FIG. 9 is a schematic front view showing a truss-type actuator using a displacement member that includes an elastic body in addition to a piezoelectric element. The displacement parts 2, 3 of this actuator have a configuration in which single-layer piezoelectric elements 2a, 3a and metal elastic bodies 2b, 3b are connected in series.

The use of the actuator having this configuration has the following advantages in addition to the same effects as those obtained by using the laminated piezoelectric element for the displacement portion.
That is, in general, a piezoelectric element is made of a ceramic material, and has a large vibration damping and a small displacement expansion ratio at the time of resonance as compared with a metal or the like. In addition, ceramics are strong in compressive force but weak in tensile force. In particular, multilayer piezoelectric elements have many problems such as the possibility of peeling because of the large number of bonding surfaces. There is an advantage that can be. (Second Embodiment) In the first embodiment, an elliptical trajectory is obtained in the combining unit 5 by providing a drive signal to both the two displacement units 2 and 3 and combining the displacements. On the other hand, in the second embodiment, a desired trajectory is obtained in the combining unit by driving one of the displacement units.

In the second embodiment, this cannot be achieved unless the resonance of the displacement portion is used, but the driving circuit can be simplified since only the displacement portion on one side is driven. Hereinafter, numerical handling and experimental results of the driving method according to the second embodiment will be described. (Modeling of Actuator) The natural vibration modes of the truss-type actuator include, as shown in FIG. 10A, an in-phase mode in which both displacement portions 2 and 3 both made of piezoelectric elements expand and contract in the same phase. There is an anti-phase mode that expands and contracts in the opposite phase as shown in FIG.

Here, as shown in FIG. 11, each mode can be represented by a one-degree-of-freedom viscous damping vibration system including a spring, a weight, and a dashpot. However, the display of the dashpot is omitted.

The in-phase mode is a first vibration system that vibrates in the normal direction A of the driven member, and the anti-phase mode is
Assuming a second vibration system that vibrates in the tangential direction B of the driven member, a vibration model for driving one displacement unit 2 is shown in FIG. The displacement directions of both modes are orthogonal to each other, and the excitation force of the piezoelectric element (displacement portion) 2 is applied in the direction of the axis of symmetry (the direction of the arrow).

In a vibration system having one degree of freedom (spring constant: k, mass of weight: m, viscosity: η), excitation force of sine wave: f (t) =
Displacement when adding F ₀ cosωt: χ (t) is expressed by the following equation (3).

Χ (t) = Xcos (ωt−φ) (3)

[0066]

(Equation 1)

Here, the natural frequency: ωn = √ (k / m),
Damping ratio: ζ = η / 2√ (mk), static displacement: X ₀ = F ₀ /
k, and the resonance frequency is fn = ωn / 2π.

The driving force generated by the piezoelectric element 2 is as follows:
When F ₀ cos ωt is decomposed into two components of a normal direction A and a tangential direction B, the excitation forces f ₁ (t) and f ₂ (t) of the first and second vibration systems, which are the components, are as follows. It is expressed by equation (4).

F ₁ (t) = f ₂ (t) = (F ₀ / √2) cosωt (4) When these are substituted into the above equation (3), the displacement of the first vibration system: χ ₁ (t) Is represented by the following equation (5), and the displacement of the second vibration system: χ ₂ (t) is represented by the following equation (6).

Χ ₁ (t) = X ₁ cos (ωt−φ ₁ ) (5) χ ₂ (t) = X ₂ cos (ωt−φ ₂ ) (6)

[0071]

(Equation 2)

[0072] However, the natural _{frequency: ωn 1 = √ (k 1} / m 1) ωn 2 = √ (k 2 / m 2) damping _{ratio: ζ 1 = η 1 / 2√} (m 1 k 1) ζ 2 = Η ₂ / 2√ (m ₂ k ₂ ) Static displacement: X ₀₁ = F ₀ / (√2 × k ₁ ) X ₀₂ = F ₀ / (√2 × k ₂ ) Resonance frequency: fn _1,2 = ωn _1,2 / 2π.

As described above, when the natural frequency of the first and second vibration systems: ωn _1,2 , the damping ratio: ζ _1,2 , and the static displacement: X _01,02 , the driving frequency: f = The relationship between ω / 2π and the displacement of the first and second vibration systems: χ _1,2 (t) (that is, the trajectory of the synthesis unit) can be obtained. (Condition that the trajectory is circular) Since the first and second vibration systems are orthogonal to each other, the trajectory of the combining unit is circular under the condition that both amplitudes are equal and the phase difference is 90 degrees according to the Lissajous equation. You can see that Then, from the above equations (5) and (6), this condition is expressed by the following equations (7) and (8).

[0074]

(Equation 3)

In order to simplify the above equations (7) and (8), it is assumed that ζ ₁ = ζ ₂ and X ₀₁ = X _02, and the equations (7) and (8) are rearranged and ω is eliminated. Then, the relationship between fn ₁ , fn ₂ and ζ is expressed by the following equation (9).

Ratio of resonance frequencies: fn ₁ / fn ₂ = (α ± √ (α ² -1)... (9) where (1-2ζ ² ) / (1-4ζ ⁴ ) = α When the system damping ratio: 得 is obtained, the ratio of the resonance frequency: fn _1,2 for obtaining a circular locus by one-side driving can be obtained.

The driving frequency: f _{3 at} this time is represented by the following: driving frequency: f ₃ = ω ₃ / 2π (10) ^{_{However, ω 3 2 = [(2ωn}} 1 2 ωn 2 2) / (ω
n ₁ ² + ωn ₂ ² )] (1-2 ² ). (Resonance frequency ratio and trajectory of the combining unit) In the model of FIG. 11, the relationship between the resonance frequency ratio and the trajectory is examined.

FIG. 12 shows a state in which the ratio of the resonance frequencies satisfies the equation (9) and a circular locus is obtained, FIG. 13 shows an example in which the resonance frequencies are apart, and FIG. 14 shows an example in which the resonance frequencies are close. . 12 to 14 show the case where the displacement unit 2 is driven, the attenuation ratio: ζ _1,2 = 0.025, and the value of the resonance frequency is appropriately determined.

In FIG. 12A, assuming that the resonance frequency fn ₁ of the same phase is f ₁ = 64 kHz, the resonance frequency f n ₂ of the opposite phase is f ₂ = 67 from equations (9) and (10).
kHz, and the driving frequency: f ₃ is f ₃ = 65.4 kHz.
Becomes

When the driving frequency f ₃ is equal to 65.4 kHz, the amplitudes of the two vibration systems match as shown in FIG. 12A, and the phase difference becomes 90 degrees as shown in FIG. Therefore, the trajectory of the combining unit is circular as shown in FIG. In a vibration system having the same phase, since the driving frequency is higher than the resonance frequency as shown in FIG. 12A, the amplitude slightly exceeds the peak, and the phase delay is 90 degrees as shown in FIG. 12B. Be larger. On the other hand, in the vibration system of the opposite phase, since the driving frequency is lower than the resonance frequency as shown in FIG. 12A, the amplitude does not reach the peak and becomes slightly smaller, and the phase lag as shown in FIG. Is less than 90 degrees. Further, since the phase delay of the same phase is larger than the phase delay of the opposite phase, the combining part at the intersection rotates counterclockwise.

When the driving frequency is sufficiently lower than the resonance frequency of each vibration system, the amplitude becomes equal and smaller as shown in FIG. 12A, and the phase difference becomes smaller as shown in FIG. Since it approaches 0 degrees, the trajectory of the combining unit has a small elliptical shape extending in the driving direction as shown in FIG. The same applies to the case where the resonance frequency is sufficiently higher than the resonance frequency (see FIG. 12G). When the drive frequency is equal to the resonance frequency, both the amplitude ratio and the phase difference are large, so that FIG.
As shown in 2 (d) and (f), the trajectory of the combining unit is a large ellipse extending in the direction of each vibration system.

As shown in FIG. 13 (a), when the resonance frequencies are separated, the peaks of the displacement hardly overlap.
As shown in FIG. 13B, the phase difference continuously changes between 0 degree and 180 degrees. In this case, when the drive frequency is sufficiently lower or sufficiently higher than the resonance frequency, the trajectory of the combining unit substantially matches the case of FIG. 12 as shown in FIG. 13C or 13G. I do. Also,
When the driving frequency is equal to the resonance frequency, the difference between the amplitudes is sufficiently large. Therefore, as shown in FIGS. 13D and 13F, the trajectory of the synthesizing portion is a large thin elliptical shape extending in the displacement direction of the vibration system. Becomes When the driving frequency is in the middle of the resonance frequency, the amplitude is equal and small, and the phase difference is 1
Since the angle approaches 80 degrees, the trajectory of the combining unit becomes a small and thin ellipse extending in a direction orthogonal to the driving direction as shown in FIG.

When the resonance frequency approaches as shown in FIG. 14 (a), the amplitude and phase curves substantially overlap as shown in FIGS. 14 (a) and 14 (b), and the phase difference becomes a peak-like shape having a low peak. Become. When the driving frequency is sufficiently lower or sufficiently higher than the resonance frequency, the trajectory of the combining unit substantially matches the case of FIG. 12 as shown in FIG. 14 (c) or (g). Also, if the drive frequency is equal to the resonance frequency,
Since the amplitude is almost equal and the phase difference is slightly smaller,
As shown in FIGS. 14D and 14F, the trajectory of the combining unit is a large ellipse extending in the driving direction. When the driving frequency is in the middle of the resonance frequency, the amplitude is equal and large, and the phase difference is slightly small.
As shown in (1), the trajectory of the combining section is a large ellipse extending in the driving direction.

In the above description, the displacement section 2 arranged in the horizontal direction is driven. On the contrary, when the displacement section 3 arranged in the vertical direction is driven, the displacement section 2 is symmetric. Model, and the trajectory of the synthesis unit rotates clockwise.
When the resonance frequency of the same phase is larger than the resonance frequency of the opposite phase, the phase delay of the opposite phase becomes larger than the phase delay of the same phase, and the trajectory of the combining unit also rotates clockwise. (Driving Method of Second Embodiment) As described above, various elliptical trajectories can be obtained by driving only one displacement portion depending on the magnitude of the resonance frequency of the same phase and the opposite phase and the degree of separation between them.

In the second embodiment, the in-phase resonance frequency f
By setting n ₁ to be higher than the resonance frequency fn ₂ of the opposite phase, the trajectory of the combining unit as shown in FIGS. 15 and 16 is obtained. 15 and 16 show an example in which only the displacement unit 3 is driven.

Specifically, in order to form an elliptical trajectory, it is necessary to satisfy the following equation (11) in consideration of the above equation (9), which is a condition that the trajectory of the combining unit is circular.

Fn ₁ / fn ₂ <(α ± √ (α ² -1) (11) In addition, the reverse of the driving direction when the combining unit moves along an elliptical locus and the direction in which the rotor that is the driven member rotates. In order to prevent the phenomenon from occurring, it is necessary to satisfy the following expression (12).

1 <fn ₁ / fn ₂ (12) Therefore, as in the second embodiment, when only one of the two displacement sections is driven to move the combining section along an elliptical locus, the following equation (13) is used. Need to be satisfied.

1 <fn ₁ / fn ₂ <(α ± √ (α ² −1) (13) In more detail, when the above equation (13) is satisfied, the synthesis unit moves along an elliptical locus. Although the driving direction at the time and the direction in which the rotor as the driven member rotates can be matched, the above expression (12) is not satisfied, that is, fn ₁ / fn ₂
If <1, the driving direction when the combining unit moves on an elliptical trajectory is opposite to the direction in which the rotor that is the driven member rotates, and it becomes difficult to drive the rotor.

Also, an elliptical locus inclined obliquely to the normal direction of the rotor 10 can be formed as shown in FIG. As shown in FIG. 16, it is also possible to create an elliptical locus that is not inclined with respect to the normal direction of the rotor 10. In FIGS. 15 and 16, the driven member is driven clockwise. However, if the driven member is to be driven counterclockwise, the driving side displacement section and the driven side displacement section may be exchanged. (Experimental Results) FIG. 17 shows a driving locus and a characteristic diagram of the actuator obtained by the driving method of the first embodiment.

FIGS. 17 (a) and 17 (b) show that the distances from the center of the ellipse in the tangent direction (vertical axis direction) and the normal direction (horizontal axis direction) to the rotor in the elliptical trajectory of the combining section are almost equal. This is the trajectory shape when the elliptical trajectory of the combining unit is changed. The unit of the numbers in the figure is μm.

FIG. 17C is a characteristic diagram in the case where the shape of the trajectory is changed in such a manner. The horizontal axis indicates the driving force (F) of the actuator, and the vertical axis indicates the speed of the rotor. Note that the pressing direction by the pressing unit 6 is the rightward direction of the horizontal axis in FIGS. 17 (a) and 17 (b). FIG.
(D) is a characteristic diagram in the case where the trajectory shape is changed in such a manner, where the horizontal axis represents the driving force (F) of the actuator and the vertical axis represents efficiency. 17 (c) and (d) show the case of the locus shape shown in FIG. 17 (a), and the case of "i" shows the locus shape shown in FIG. 17 (b). It is. Also, A, B, C, D, and E in FIGS. 17A to 17D indicate different driving conditions.

As can be understood from FIG. 17, as shown by the driving conditions B and C in the figure, the rotor was driven so as to have an elliptical locus shape in which the minor axis direction was obliquely inclined with respect to the normal direction of the rotor. It can be confirmed that both the output and the efficiency may be improved as compared with the case where the elliptical trajectory shape has the major axis oriented in the tangential direction of the rotor as in the driving condition A. However, if the minor axis of the elliptical trajectory becomes too small as indicated by the driving condition E in the figure, the combining unit vibrates linearly rather than elliptical driving, and the driving method sticks the driven member. And the output and efficiency characteristics are reduced.

Therefore, at least one of the phase difference and the amplitude is adjusted so that the minor axis of the elliptical locus does not become too small and the elliptical locus has a minor axis obliquely inclined with respect to the normal direction of the rotor. It is preferable to drive with adjustment. This is the same in the case of the second embodiment.

FIG. 18 is a characteristic diagram according to the trajectory shape of the combining unit when one of the two displacement units is driven so that the combining unit has an elliptical trajectory. 18 (a) and 18 (b)
, TS48 and the like indicate the driving conditions, v indicates the speed of the rotor, and η indicates the efficiency.

FIG. 18A shows a state in which the minor axis direction of the elliptical trajectory of the combining unit is inclined with respect to the normal direction of the rotor as shown in FIG. 18B is a characteristic diagram in the case of driving according to the second embodiment, and FIG. 18B satisfies the condition that the trajectory of the combining unit is elliptical as shown in FIG. 16 and the minor axis of the elliptical locus. It is a characteristic diagram in the case of driving in a state where the direction is oriented in the normal direction of the rotor, that is, not inclined.

As apparent from FIG. 18, the output and the efficiency are better when the one-side drive is performed such that the elliptical locus is inclined relative to the normal direction of the rotor as in the second embodiment. Both will improve. Therefore, it is preferable to control the phase difference and the amplitude under such conditions.

In the first and second embodiments described above, the case where the number of the displacement parts is two, that is, the displacement part 2 and the displacement part 3, is shown. However, the present invention is not limited to two displacement parts, but can be applied to three or more displacement parts.

FIG. 19 is a perspective view showing a case where there are four displacement parts. In the case of causing the actuator to vibrate in the x direction, the displacement units a and b are set as a first group, and the displacement units c and d are set as a second group. Can be considered as equivalent to On the other hand, when the vibration in the y direction is performed, similarly, the displacement parts a and d are set as the first group, and the displacement parts a and c are set as the second group. Can be considered as equivalent to

In the above-described embodiment, a circular rotor that rotates as a driven member is described as an example. However, the present invention is not limited to this, and the present invention is not limited to an elliptical rotor or a linear slider. Can be applied to When the driven member is an elliptical rotor or the like, the minor axis direction or major axis direction of the elliptical trajectory of the combining section may be inclined with respect to the normal direction of the rotor. When the slider has a plate shape, the minor axis direction or major axis direction of the elliptical locus of the combining section may be inclined with respect to the thickness direction of the slider. When the surface of the slider in contact with the combining section is a plane, the minor axis direction or the major axis direction of the elliptical locus of the combining section may be inclined with respect to a direction perpendicular to the plane.

In the above-described embodiment, an example is described in which a piezoelectric element is used as the displacement portion. However, the present invention is not limited to this, and a magnetostrictive element or another electromechanical energy conversion element may be used. Can also.

[0102]

As described above in detail, in the case of the present invention, the inclination of the elliptical trajectory of the combining section in the minor axis direction or the major axis direction with respect to the driven member changes, so that the output characteristic changes from low speed and high torque to high speed. It is possible to adjust the value to an arbitrary value up to a low torque, thereby increasing the efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a configuration of a truss-type actuator driven by a driving method according to a first embodiment of the present invention.

FIG. 2A is a front view showing a structure of a laminated piezoelectric element used as a displacement unit constituting a truss-type actuator driven by the driving method according to the first embodiment of the present invention,
(B) is a figure which shows the locus | trajectory of the combination part of a substantially linear relationship.

FIG. 3 is a diagram illustrating a synthesis unit obtained when the phases of two drive signals that respectively drive two displacement units included in a truss-type actuator driven by the drive method according to the first embodiment of the present invention are changed. It is a figure which shows a locus | trajectory shape, (a)
(B) shows the case where the phase difference between both drive signals is 90 °, and (c) shows the case where the phase difference between both drive signals is 120 °.

FIG. 4 shows a trajectory shape obtained when the amplitudes of two drive signals for driving two displacement units constituting a truss-type actuator driven by the drive method according to the first embodiment of the present invention are changed. FIG. 7A is a diagram illustrating a case where the phase difference is 60 ° and the amplitude of the drive signal of one displacement unit is smaller than the amplitude of the drive signal of the other displacement unit, and FIG. In the case where the amplitude of the drive signal of one displacement unit is larger than the amplitude of the drive signal of the other displacement unit, (c)
Is a case where the phase difference is 120 ° and the amplitude of the drive signal of one displacement unit is smaller than the amplitude of the drive signal of the other displacement unit,
(D) is a case where the phase difference is 120 ° and the amplitude of the drive signal of one displacement unit is larger than the amplitude of the drive signal of the other displacement unit.

FIG. 5 corresponds to FIG. 4 (a), and shows a driving mode when the amplitude of the drive signal of one displacement unit is made smaller than the amplitude of the drive signal of the other displacement unit by a phase difference of 60 °. FIG.

FIG. 6 shows a block diagram of a driving device for realizing the driving method of the present invention.

FIG. 7 shows a block diagram of another driving device for realizing the driving method of the present invention.

FIG. 8 shows a block diagram of still another driving device for realizing the driving method of the present invention.

FIG. 9 is a schematic front view showing the configuration of another truss-type actuator driven by the driving method according to the first embodiment of the present invention.

10A and 10B are diagrams showing natural vibration modes of the truss-type actuator, wherein FIG. 10A shows an in-phase mode in which both displacement portions expand and contract in the same phase, and FIG. 10B shows an anti-phase mode in which both displacement portions expand and contract in the opposite phase.

FIG. 11 is a diagram showing a vibration model when driving one displacement unit when the same phase mode is a first vibration system and the opposite phase mode is a second vibration system.

12 is a diagram showing a relationship between the ratio of the resonance frequency and the locus in a state where the ratio of the resonance frequency satisfies the expression (9) and a circular locus is obtained in the vibration model of FIG. 11;

FIG. 13 is a diagram illustrating a relationship between a ratio of a resonance frequency in a state where resonance frequencies are separated and a locus in the vibration model of FIG. 11;

FIG. 14 is a diagram showing a relationship between a ratio of a resonance frequency in a state where the resonance frequency approaches and a locus in the vibration model of FIG. 11;

FIG. 15 is a front view showing a driving state when an elliptical trajectory inclined obliquely to the normal direction of the rotor is formed according to the second embodiment of the present invention.

FIG. 16 is a front view showing a driving state when an elliptical trajectory not inclined with respect to the normal direction of the rotor is formed according to the second embodiment of the present invention.

17A and 17B show a driving locus and a characteristic diagram of an actuator obtained by the driving method according to the second embodiment of the present invention, and FIG. 17A shows that the elliptical locus in the tangential direction and the normal direction to the rotor are almost equal. 7B shows the result of changing the trajectory of the combining unit, and FIG.

18A and 18B are characteristic diagrams according to the trajectory shape of the combining unit when one of the two displacement units is driven such that the combining unit has an elliptical trajectory, and FIG. Figure 1
As shown in FIG. 5, the minor axis direction of the elliptical locus of the combining unit is
FIG. 16B shows a state in which the trajectory of the combining unit is elliptical as shown in FIG. 16, and the minor axis direction of the elliptical trajectory is the normal direction of the rotor. , That is, not tilted.

FIG. 19 is a perspective view showing an actuator to which the present invention can be applied when there are four displacement units.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive part 2, 3 Displacement part 4 Fixed part 5 Synthesizing part 6 Pressurizing part 10 Driven member 11 Speed detection part 12 Phase control part 13 Amplitude control part 14 Delay circuit 15 Oscillator 16, 17 Amplifier 20, 23 Controller 21 Memory 22 timer

Continuation of the front page (72) Inventor Shinya Matsuda 2-3-1, Azuchicho, Chuo-ku, Osaka F-term in Osaka International Building Minolta Co., Ltd. (reference) 5H680 AA04 AA05 AA06 AA08 BB15 CC02 DD01 DD23 DD27 DD37 DD53 DD74 DD95 EE23 FF08 FF21 FF23 FF27 FF30 FF33 GG02 GG20 GG25 GG27

Claims (11)

[Claims] 1. A drive unit comprising: a fixed portion; a plurality of displacement portions each having a base end fixed to the fixed portion such that each tip side intersects; and a synthesizing portion commonly disposed at the tip of all the displacement portions. And a pressurizing unit that presses the combining unit against a driven member to be driven, and a method of driving an actuator that transmits the driving force to the driven member by causing the combining unit to perform elliptical motion. And changing the inclination of the combining section in the minor axis direction or the major axis direction in the elliptical trajectory with respect to the driven member. 2. The method according to claim 1, wherein the inclination of the combining section in the minor axis direction or the major axis direction with respect to the driven member in the elliptical trajectory is changed by changing at least the amplitude of the phase difference and the amplitude of the drive signal applied to each displacement section. The method for driving an actuator according to claim 1, wherein 3. At least a plurality of levels of the phase difference and the amplitude are set at a plurality of levels so that the amount of inclination of the elliptical trajectory of the combining unit with respect to the driven member in the minor axis direction or the major axis direction is different. 3. The method according to claim 1, wherein at least one of the phase difference and the amplitude is switched in accordance with the driving speed. 4. A drive unit comprising: a fixed portion; a plurality of displacement portions each having a base end fixed to the fixed portion such that each tip side intersects; and a synthesizing portion commonly disposed at the tip of all the displacement portions. And a pressurizing unit that presses the combining unit against a driven member to be driven, and a method of driving an actuator that transmits the driving force to the driven member by causing the combining unit to perform elliptical motion. In the state where the minor axis direction or major axis direction of the elliptical locus of the combining unit is inclined with respect to the driven member, the driving characteristics of the driven member are controlled by changing the minor axis dimension of the elliptical locus. Actuator driving method to be used. 5. The method of driving an actuator according to claim 4, wherein the minor axis dimension of the elliptical locus is changed by changing at least the amplitude of the phase difference and the amplitude of the drive signal applied to each displacement portion. . 6. The method according to claim 1, wherein the plurality of displacement units are divided into one or more first groups and one or more second groups, and the displacement units in both groups are driven. Item 6. A method for driving an actuator according to any one of Items 1 to 5. 7. The method according to claim 1, wherein the plurality of displacement units are classified into one or more first groups and one or more second groups, and one of the groups is driven. Item 6. The method for driving an actuator according to item 4 or 5. 8. A drive unit comprising: a fixed portion; a plurality of displacement portions each having a base end fixed to the fixed portion so that each tip side intersects; and a synthesizing portion commonly disposed at the tips of all the displacement portions. And a pressurizing unit that presses the combining unit against a driven member to be driven, and a method of driving an actuator that transmits the driving force to the driven member by causing the combining unit to perform elliptical motion. The plurality of displacement units are divided into one or more first groups and one or more second groups, and the first group displacement units and the second group displacement units resonate in the same phase. and the resonance frequency fn ₁ common mode, the relationship between the resonance frequency fn ₂ reverse-phase mode in which the displacement of the displacement portion and the second group of the first group to resonate in opposite phase, the following (a
A method of driving an actuator, wherein one group is drive-controlled so as to satisfy the expressions (1) and (A2). _{1 <fn 1 / fn 2 <} α + √ (α 2 -1) ... (A1) α = (1-2ζ 2) / (1-4ζ 2) ... (A2) where the ζ damping ratio 9. The actuator driving method according to claim 1, wherein the plurality of displacement portions are divided into one or more first groups and one or more second groups. A driving device for an actuator that drives both groups separately, comprising two amplifying means for amplifying an oscillating signal so that one lags or advances the other and outputs the signals to each group separately, Speed detecting means for detecting a speed; amplitude controlling means for controlling an amplitude amount by both or one of the two amplifying means based on a detection result by the speed detecting means; And phase difference control means for controlling the phase amount of both or one of the signals input to the two amplifying means or output from the two amplifying means. Actuator drive device that. 10. The method of driving an actuator according to claim 3, wherein the plurality of displacement parts are one or two or more first displacement parts.
A drive device for an actuator that drives each of two groups while distinguishing between the group and one or more second groups, wherein the oscillation signal is amplified so that one is delayed or advanced with respect to the other, and each is separately applied to each group. Two amplifying means for outputting; an amplitude controlling means for controlling an amplitude amount by both or one of the two amplifying means; and / or a signal inputted to or outputted from the two amplifying means. A phase difference control means for controlling one phase amount; and a plurality of drive patterns corresponding to a lapse of time are stored. At least one of the amplitude control means and the phase difference control means is stored in a corresponding drive pattern when a predetermined time is reached. And a control means for controlling the driving of the actuator. 11. The method for driving an actuator according to claim 3, wherein the plurality of displacement units are one or more of the first and second displacement units.
A drive device for an actuator that drives each of two groups while distinguishing between the group and one or more second groups, wherein the oscillation signal is amplified so that one is delayed or advanced with respect to the other, and each is separately applied to each group. Two amplifying means for outputting; an amplitude controlling means for controlling an amplitude amount by both or one of the two amplifying means; and / or a signal inputted to or outputted from the two amplifying means. A phase difference control means for controlling one phase amount; a plurality of drive patterns corresponding to a change in speed of the driven member are stored; and when the speed of the driven member reaches a predetermined speed, the amplitude is determined by the stored drive pattern. A driving device for an actuator, comprising: control means for controlling at least one of a control means and a phase difference control means.