JP2004320846A - Vibration type driving device - Google Patents

Abstract

In a vibration type driving device that generates two bending vibration modes and relatively drives a vibrating body and a driven body, an electrode of an electromechanical energy conversion element can have a simple configuration.
An electro-mechanical energy converter having an elastic body (4) and at least two electrodes, wherein a two-phase drive voltage of the same frequency is applied to the two electrodes to excite vibration in the elastic body. A vibration type driving device comprising: a vibrating body having an element (5); and a driven body (7) in contact with an elastic body, wherein the vibrating body receives two-phase driving voltage inputs having the same phase. The first bending vibration mode and the second bending vibration mode can be formed by receiving the input of the two-phase driving voltage having the opposite phase while receiving the first bending vibration mode. The vibrating body and the driven body are relatively driven by a combination of the two bending vibration modes.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vibration type driving device such as a vibration wave motor that generates vibration in an elastic body and applies a driving force to a driven body by using the vibration energy, and particularly drives the driven body in a linear direction. The present invention relates to a vibration type driving device of the type.
[0002]
[Prior art]
Until now, various proposals have been made for a vibration wave motor that drives a driven body in a linear direction.
[0003]
For example, a plurality of protrusions are provided at predetermined positions on one side surface of an elastic body formed in a square rod shape, and a piezoelectric element is arranged on a surface of the elastic body opposite to the surface on which the protrusions are provided. In a vibrating wave motor, an AC voltage is applied to a piezoelectric element to simultaneously generate a bending resonance vibration and a longitudinal resonance vibration (longitudinal vibration) in an elastic body, thereby causing an elliptical motion in a protrusion. There is a first conventional example (for example, see Patent Document 1).
[0004]
In this configuration, the driven body can be linearly driven by the elliptical motion of the projection by bringing the driven body into pressure contact with the projection.
[0005]
On the other hand, there is a vibration wave motor that excites two different bending vibration modes in an elastic body formed in a rectangular plate shape and generates an elliptic motion at a predetermined mass point (projection or the like) by a combination of the two bending vibration modes. . (Second conventional example, for example, see Patent Document 2).
[0006]
Here, one of the two bending vibration modes (hereinafter, referred to as a first vibration mode) has a cross shape as shown in (a-1) and (a-2) of FIG. The vibration mode has a node. The other bending vibration mode (referred to as a second vibration mode) includes two nodes parallel to a predetermined direction, as shown in (b-1) and (b-2) of FIG. Vibration mode.
[0007]
In order to generate the two bending vibration modes described above, a piezoelectric element having an electrode pattern as shown in FIG. 3 is used. In FIG. 3, 3A is a piezoelectric element for generating the first vibration mode, and 3B is a piezoelectric element for generating the second vibration mode. The symbols “+” and “−” in the figure indicate the polarization direction.
[0008]
In the piezoelectric element 3A, an electrode boundary exists so as to coincide with a cross-shaped node in the first vibration mode, and an AC signal having a frequency near the resonance frequency of the first vibration mode is applied to the four divided electrodes. When Va) is applied, vibration in the first vibration mode occurs. On the other hand, when an AC signal (Vb) having a frequency near the resonance frequency of the second vibration mode is applied to the piezoelectric element 3B, vibration of the second vibration mode occurs in the elastic body.
[0009]
Therefore, two bending vibration modes can be generated on the elastic body by stacking the piezoelectric element 3A and the piezoelectric element 3B and attaching the piezoelectric element 3A and the piezoelectric element 3B to the elastic body. The driven body can be driven by the elliptical motion that occurs in.
[0010]
On the other hand, as shown in FIG. 4, a piezoelectric element formed of a single layer without stacking a plurality of piezoelectric elements can be used as a piezoelectric element that generates two bending vibration modes. In FIG. 4, the electrode connected to the voltage signal Va is a piezoelectric element for generating the first vibration mode, and the electrode connected to the voltage signal Vb is a piezoelectric element for generating the second vibration mode.
[0011]
[Patent Document 1]
Japanese Patent Publication No. 6-106028
[Patent Document 2]
JP-A-6-31765
[0012]
[Problems to be solved by the invention]
However, in the configuration of the vibration wave motor in the first conventional example, since the longitudinal resonance vibration (longitudinal vibration) is used, the resonance frequency becomes too high when the elastic body is reduced in size. Therefore, there is a limit to miniaturization of the vibration wave motor.
[0013]
On the other hand, in the vibration wave motor according to the second conventional example, since two bending vibration modes are combined, the elastic body (vibration wave motor) can be reduced in size as compared with the first conventional example. Further, by changing the ratio of the long side to the short side of the rectangular elastic body, the resonance frequency in each bending vibration mode can be matched, so that the resonance frequency can be easily adjusted as compared with the first conventional example. Thus, it is possible to realize an actuator having good driving efficiency.
[0014]
However, in the second conventional example, in order to excite the vibrating body to a plurality of vibration modes, a piezoelectric element having a dedicated electrode for generating each vibration mode is required. Accordingly, it is necessary to use a piezoelectric element having a complicated electrode pattern or to stack and use the piezoelectric elements, which is not preferable in terms of a manufacturing process, cost, and the like.
[0015]
In addition, since the polarization direction differs for each electrode pattern, not only the polarization process becomes complicated, but also the stiffness of the piezoelectric element changes near the boundary between the electrodes having different polarization directions.
[0016]
[Means for Solving the Problems]
The present invention provides an elastic body, and an electro-mechanical energy conversion element having at least two electrodes, wherein two-phase driving voltages having the same frequency are applied to the two electrodes to excite the elastic body with vibration. A vibration type driving device having a vibrating body provided and a driven body that comes into contact with an elastic body, wherein the vibrating body receives a two-phase driving voltage having the same phase to enter a first bending vibration mode. The second bending vibration mode can be formed by receiving the input of two-phase driving voltages having opposite phases, and the vibration can be formed by a combination of the first bending vibration mode and the second bending vibration mode. The body and the driven body are relatively driven.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
FIG. 5 is an external perspective view of the vibrating body 1 in the vibration wave actuator according to the first embodiment of the present invention. In FIG. 5, reference numeral 4 denotes an elastic body made of a metal material and formed in a rectangular plate shape, 5 denotes a piezoelectric element (electric-mechanical energy conversion element) joined to the back surface of the elastic body 4, and 6 denotes It is a projection provided on the upper surface of the elastic body 4.
[0018]
The protruding portion 6 contacts the driven body at this tip as described later. Here, a contact portion having an excellent coefficient of friction and wear resistance can be provided at the tip of the protrusion 6. Further, the protrusion 6 can be formed integrally with the elastic body 4 by press working or the like, or can be formed separately from the elastic body 4 and then fixed to the elastic body 4.
[0019]
If the projection 6 and the elastic body 4 are formed integrally, the number of assembly steps of the elastic body 1 can be reduced as compared with the case where they are formed separately, and the position of the component (projection 6) is adjusted. Since there is no need, it is possible to prevent variation between components.
[0020]
The vibrating body 1 of the present embodiment can excite two bending vibration modes as described later, and generates an elliptical motion at the tip of the projection 6 by combining the two bending vibration modes.
[0021]
Here, the shape of the vibrating body 1 is formed such that the resonance frequencies of the above two bending vibration modes substantially match. Specifically, the resonance frequency of the two bending vibration modes is matched by appropriately setting the dimension (long side) in the longitudinal direction of the elastic body 4 and the dimension (short side) in the direction orthogonal to the longitudinal direction. Can be.
[0022]
Hereinafter, two bending vibration modes excited by the vibrating body 1 will be described.
[0023]
FIG. 6 is a diagram illustrating two bending vibration modes. The vibration mode shown in FIG. 6A represents one of the two bending vibration modes (referred to as the A mode). The A mode is a secondary bending vibration in the long side direction (arrow X direction) of the rectangular vibrating body 1 (elastic body 4), and has three nodes parallel to the short side direction (arrow Y direction). are doing.
[0024]
Here, the protruding portion 6 is disposed in the vicinity of a position that becomes a node due to the A-mode vibration, and reciprocates in the arrow X direction due to the A-mode vibration. By arranging the protrusions 6 in this way, the protrusions 6 can be displaced most in the direction of the arrow X.
[0025]
The vibration mode shown in FIG. 6B represents the other bending vibration mode (referred to as B mode) of the two bending vibration modes. This B mode is a primary bending vibration of the rectangular vibrating body 1 (elastic body 4) in the short side direction (arrow Y direction) and has two nodes parallel to the long side direction (arrow X direction). are doing.
[0026]
Here, the nodes in the A mode and the nodes in the B mode are substantially orthogonal to each other in the XY plane.
[0027]
Further, the protrusion 6 is arranged near a position that becomes an antinode in the B-mode vibration, and reciprocates in the arrow Z direction by the B-mode vibration. By arranging the protrusions 6 in this manner, the protrusions 6 can be displaced most in the direction of the arrow Z.
[0028]
That is, by making the nodes of the A mode and the nodes of the B mode substantially orthogonal to each other as described above, the positions of the nodes of the A mode can be matched with the positions of the antinodes of the B mode. By arranging, the vibration displacement of the projection 6 can be maximized, and high output can be obtained.
[0029]
As described above, by largely displacing the projection 6 in the X direction and the Z direction, a large driving force can be applied to the driven body that comes into contact with the projection 6.
[0030]
If the two projections 6 are arranged symmetrically with respect to the XZ plane or the YZ plane passing through the center of the elastic body 4, the vibrating body 1 biases the reaction force received from the slider 7 (FIG. 7) at the projections 6. You can receive without. In addition, since the relative positional relationship between the slider 7 and the protrusion 6 is stabilized, the output of the vibrating body 1 can be stabilized without being affected by changes in the environment or load.
[0031]
By generating the vibrations of the A mode and the B mode with a predetermined phase difference, an elliptical motion can be generated at the tip of the protrusion 6. As shown in FIG. 7, a slider 7 as a driven body comes into pressure contact with the tip of the projection 6, and the slider 7 moves in the arrow L direction due to the elliptical motion of the projection 6. Can be.
[0032]
If the electrode pattern of the piezoelectric element is configured in the same manner as in the related art in order to generate the above-described A mode and B mode vibrations in the vibrating body 1, the electrode pattern shown in FIG. 8 is obtained. In FIG. 8, the “+” and “−” symbols indicate the polarization direction.
[0033]
The four electrode regions to which the voltage signal (Va) is connected among the piezoelectric elements shown in FIG. 8 are electrode regions for generating A-mode vibration. When an AC voltage having a frequency near the resonance frequency of the A mode is applied to Va, at a certain moment, two electrode regions (piezoelectric elements) polarized to “+” out of the four electrode regions expand, and “−” The two electrode regions (piezoelectric elements) that have been polarized are shrunk.
[0034]
At another moment, the electrode region (piezoelectric element) polarized to “+” contracts, and the electrode region (piezoelectric element) polarized to “−” expands. As a result, A-mode vibration occurs.
[0035]
On the other hand, one electrode region to which the voltage signal (Vb) is connected among the piezoelectric elements shown in FIG. 8 is an electrode region for generating B-mode vibration. When an AC voltage having a frequency near the B-mode resonance frequency is applied to Vb, the central portion of the piezoelectric element in the short side direction (Y direction) expands and contracts, and the B-mode vibration occurs in the vibrating body.
[0036]
Here, by making the AC voltages of Va and Vb the same frequency (in the present embodiment, frequencies near the resonance frequencies of the A mode and the B mode) with a phase shift of 90 °, the elliptical motion on the protrusion 6 is reduced. appear.
[0037]
FIG. 1 is a diagram showing an electrode pattern of the piezoelectric element according to the present embodiment. As shown in FIG. 1, the piezoelectric element 5 is formed with an electrode region bisected in the longitudinal direction (X direction). In addition, the polarization direction in each electrode region is the same direction (“+”).
[0038]
The AC voltage (V1) is applied to the electrode region located on the right side in FIG. 1 of the two electrode regions of the piezoelectric element 5, and the AC voltage (V2) is applied to the electrode region located on the left side in FIG.
[0039]
In FIG. 1, when V1 and V2 are frequencies near the resonance frequency of the A mode and an AC voltage whose phase is shifted by 180 °, at a certain moment, the piezoelectric element in the right electrode region shrinks and the left electrode region Of the piezoelectric element is extended. At another moment, the relationship is reversed. As a result, the A-mode vibration is generated in the vibrating body 1.
[0040]
Further, if V1 and V2 are AC voltages in the same phase and near the resonance frequency of the B mode, the entire piezoelectric element (two electrode regions) expands at one moment and contracts at another moment. Become. As a result, the B-mode vibration occurs in the vibrating body 1.
[0041]
In addition, the polarization direction in one of the two electrode regions of the piezoelectric element 5 may be set to “+”, and the polarization direction in the other electrode region may be set to “−”.
[0042]
In this case, A-mode vibration is applied to the vibrating body 1 by applying alternating voltages (V1, V2) having a frequency near the resonance frequency of the A mode and the same phase to each of the two electrode regions. Can be generated. Further, by applying alternating voltages (V1, V2) having a frequency near the resonance frequency of the B mode and a phase shift of 180 ° to each of the two electrode regions, the B mode vibration is applied to the vibrating body 1. Can be generated.
[0043]
Here, the relationship between V1 and V2 and the A mode and the B mode will be described with reference to FIG.
[0044]
According to the above description using FIG. 1, the combination of the vectors “V1” and “−V2” becomes the vector indicating the A mode, and the combination of the vectors “V1” and “V2” indicates the vector indicating the B mode. Become. Here, assuming that the amplitudes of V1 and V2 (the magnitudes of the vectors of V1 and V2) are the same and the phase difference is a phase difference θ between 0 ° and 180 ° (0 ° <θ <180 °), FIG. It can be seen that the vectors of (V1 + V2) and (V1-V2) are orthogonal as shown in FIG.
[0045]
This means that the A-mode and B-mode vibrations occur simultaneously and the phase difference of the vibrations is shifted by 90 °. As a result, an elliptical motion can be generated in the protrusion 6 on the elastic body 4, and the slider 7 in contact with the protrusion 6 can be driven.
[0046]
That is, if the voltage amplitudes of V1 and V2 are the same and the phase difference θ between V1 and V2 is other than 0 ° and 180 °, the A mode and the B mode can be generated at the same time, and the phase difference of the vibration must be 90 ° or -90 °. Further, by changing the phase difference θ between V1 and V2, the amplitudes of the A mode and the B mode can be changed.
[0047]
As described above, according to the present embodiment, the piezoelectric element 5 having a simple configuration in which the electrode pattern is bisected in the longitudinal direction of the vibrator 1 and having the same polarization direction in each electrode region is used. Even the vibrating body 1 can generate an elliptical motion on the protrusion 6 of the vibrating body 1.
[0048]
By making the electrode pattern a simple structure in this way, the wiring connected to each electrode region can be made a simple structure. In addition, by making the polarization direction the same direction over the entire area of the piezoelectric element, the polarization process can be easily performed as compared with a piezoelectric element having a different polarization direction, and the rigidity of the piezoelectric element near the boundary of the electrode region becomes uniform. , An ideal vibration can be generated.
[0049]
In addition, by driving the driven body using the two bending vibration modes, compared to a vibration wave actuator that drives the driven body by a combination of bending vibration and longitudinal vibration, the rise of the natural frequency can be suppressed. The size of the actuator can be reduced.
[0050]
In the vibration type driving device of the present embodiment, the driven body is driven by a combination of the secondary bending vibration mode (A mode) and the primary bending vibration mode (B mode). However, the present invention is not limited to this.
[0051]
That is, elliptical motion can be generated by a combination of a mode generated when an AC voltage having a phase difference of 0 ° is applied to V1 and V2 and a mode generated when an AC voltage having a phase difference of 180 ° is applied to V1 and V2. If so, any bending vibration mode (a bending vibration mode having a different order) may be used.
[0052]
In the present embodiment, as shown in FIGS. 5 and 7, a description has been given of a vibrating body in which two protrusions 6 are provided on the upper surface of the elastic body 4. However, the position and number of the protrusions 6 are appropriately set. be able to.
[0053]
For example, one projection 6 can be provided at the center of the elastic body 4 as shown in FIG. 18, or four projections 6 can be provided on the elastic body 4 as shown in FIG.
[0054]
In the vibrating body 1 'shown in FIG. 18, the protrusion 6 reciprocates in the X direction as shown in FIG. 19A due to A-mode vibration, and as shown in FIG. 19B due to B-mode vibration. Reciprocates in the Z direction. Then, due to the combination of the A mode and the B mode, an elliptical motion is generated at the tip of the protrusion 6, and the slider 7 moves in the arrow L direction.
[0055]
Here, since the protrusion 6 is arranged near the node in the A mode and near the antinode in the B mode, the displacement in the X direction and the Z direction becomes large, and the slider 7 has a large driving force. Can give power.
[0056]
In the vibrating body 1 ″ shown in FIG. 20, the protrusion 6 reciprocates in the X direction as shown in FIG. 21A due to the A-mode vibration, and also as shown in FIG. 21B due to the B-mode vibration. As shown, the reciprocating motion occurs in the Z direction, and the combination of the A mode and the B mode causes an elliptical motion at the tip of the protrusion 6, thereby driving a driven body (not shown) in contact with the protrusion 6.
[0057]
Here, since the four protrusions 6 are arranged near the nodes in the A mode and near the antinodes in the B mode, the displacements in the X direction and the Z direction are large.
[0058]
Further, in the present embodiment, the case where the driven body (slider 7) formed in a rod shape is brought into contact with the protrusion 6 as shown in FIG. 7 has been described, but the present invention is not limited to this.
[0059]
Specifically, as shown in FIG. 22 (a), a driven body 7 'formed in a disk shape is brought into contact with the projection 6, and the driven body 7' is driven in the direction shown by the arrow. It can be a vibration wave actuator. Also, as shown in FIG. 22 (b), a vibrating wave actuator having a configuration in which a driven body 7 ″ formed in an annular shape is brought into contact with the projection 6 and the driven body 7 ″ is driven in a direction indicated by an arrow. It can be.
[0060]
(2nd Embodiment)
In the above-described first embodiment, in the vibrating body having the rectangular elastic body and the piezoelectric element, the phase difference of the AC voltage (V1, V2) applied to the piezoelectric element having the electrode having the simple two-part structure is 0 ° and It has been described that by setting the phase difference to a value other than 180 °, it is possible to generate an elliptical motion in the protrusion of the vibrator.
[0061]
In the second embodiment of the present invention, a method of controlling the vibration wave actuator described in the first embodiment will be described. The structure of the vibration wave actuator is the same as that of the above-described first embodiment, and a description thereof will be omitted.
[0062]
In the present embodiment, the vibration wave actuator of the first embodiment is used as a drive source in a lens unit of a video camera. FIG. 10 shows a cross-sectional view (a cross-sectional view in a direction orthogonal to the optical axis) of the lens unit.
[0063]
In FIG. 10, reference numeral 8 denotes a lens barrel. Reference numeral 9 denotes a lens (photographing lens), which is held by a frame 10. Reference numeral 11 denotes a shaft, which is used as a guide when the lens 9 moves in the optical axis direction (a direction perpendicular to the plane of FIG. 10). Here, the focal length of the photographing optical system can be changed by moving the lens 9 in the optical axis direction.
[0064]
Reference numeral 12 denotes a vibrating body of the vibration wave actuator described in the first embodiment, which is configured such that the protrusion 6 comes into contact with the slider 7 provided on the frame 10.
[0065]
Reference numerals 13 and 14 are known encoders for detecting the position of the lens 9 in the optical axis direction. The encoder scale 13 is irradiated with light by the light emitting / receiving element 14, and the reflected light from the encoder scale 13 is read by the light emitting / receiving element 14 to detect the position information of the lens 9.
[0066]
Next, a method for controlling the above-described vibration wave actuator will be described. FIG. 11 is a block diagram illustrating a control device according to the present embodiment.
[0067]
In FIG. 11, reference numeral 15 denotes a vibration wave actuator. Position information of the lens 9 driven by the vibration wave actuator 15 is measured by an encoder 16 (13 and 14 in FIG. 10) and a position counter 17. The position information of the lens 9 measured by the position counter 17 is compared with a position command input from the outside in the position comparing unit 18. This comparison result is input to the phase difference selection unit 19 and the frequency determination unit 20.
[0068]
As described in the first embodiment, the amplitudes of the two-phase AC voltages (V1, V2) applied to the two electrodes of the vibration wave actuator 15 (piezoelectric element) are the same, and the phase difference θ of the AC voltage is 0. By setting the angle to other than 180 ° and 180 °, vibrations of the A mode and the B mode having a phase shift of 90 ° occur in the vibrating body 12.
[0069]
Here, when the phase difference θ of V2 with respect to V1 is an arbitrary value (0 ° to 180 °), the magnitudes of the A-mode amplitude (Aa) and the B-mode amplitude (Ab) are given by the following equation (1). It is determined by (2).
[0070]
Aa = | 2 × cos ((π−θ) / 2) | (1)
Ab = | 2 × cos (θ / 2) | (2)
FIG. 12 shows the relationship between the vibration amplitude of the A mode and the B mode obtained by the above equations (1) and (2) and the phase difference θ between V1 and V2. In FIG. 12, the horizontal axis represents the phase difference θ, and the vertical axis represents the magnitude of the amplitude in the vibration mode (A mode and B mode). Further, the phase difference of the vibration in the B mode with respect to the A mode is switched between 90 ° and −90 ° at the boundary of 180 ° between V1 and V2. That is, the drive direction of the driven body (slider 7) is reversed on both sides (+ direction and-direction in the figure) of the phase difference 180 ° between V1 and V2.
[0071]
Here, the position comparing unit 18 compares the position information of the lens 9 obtained from the position counter 17 with the target position (stop position) of the lens 9 commanded from the outside, thereby driving the slider 7 by the vibration wave actuator. The direction is determined. Then, the phase difference θ between V1 and V2 is selected by the phase difference selection unit 19 according to the determined driving direction. That is, the phase difference selection unit 19 sets the phase difference θ of V2 with respect to V1 to 90 ° when the driving direction of the slider 7 is to be the + direction, and 270 ° when the driving direction of the slider 7 is to be the − direction.
[0072]
Note that the lens 9 can be driven even if the phase difference θ is other than 90 ° and 270 °, but in the present embodiment, the phase difference θ when the amplitudes of the A mode and the B mode are uniformly generated. Certain 90 ° and 270 ° are selected.
[0073]
Next, control of the driving frequency will be described. The relationship between the frequency of the AC voltage (V1, V2) applied to the vibration wave actuator 15 and the driving speed is the same as that of a general vibration wave motor utilizing resonance, and as shown in FIG. 13, the resonance frequency (fr) Is the peak of the speed, and the characteristic is such that the driving speed gradually decreases on the higher frequency side than fr and decreases rapidly on the lower frequency side.
[0074]
When controlling the driving speed with this characteristic, the driving control is performed at a frequency in a frequency region higher than the resonance frequency (fr).
[0075]
The position comparator 18 measures a deviation between the current position of the lens 9 based on the output of the position counter 17 and a target position input from outside. When the above-mentioned deviation is large, the frequency deciding section 20 makes the driving frequency close to the resonance frequency (fr), thereby increasing the driving speed. When the above deviation is small, the driving frequency is made slower by moving the driving frequency away from the resonance frequency (fr) to a higher frequency side.
[0076]
When the deviation of the position of the lens 9 falls within a predetermined range, the AC voltage (V1, V2) may not be applied to the vibration wave actuator.
[0077]
The drive signal generation circuit 21 generates a two-phase signal (corresponding to V1 and V2) with the phase difference θ selected by the phase difference selection unit 19 and the frequency determined by the frequency determination unit 20. I have. The two-phase signal is boosted by the booster circuit 22 to a voltage at which the vibration wave actuator can operate.
[0078]
The boosted AC voltages (V1, V2) are applied to the vibration wave actuator 15 (piezoelectric element). This makes it possible to configure a lens unit in which the lens 9 moves quickly to the target position.
[0079]
(Third embodiment)
In the second embodiment, the driving speed is changed by changing the frequency of the AC voltage (V1, V2) applied to the vibration wave actuator according to the difference between the current position of the lens 9 and the target position. In addition, the phase difference θ between the applied voltages V1 and V2 is selected from either 90 ° or 270 ° according to the driving direction of the driven body (slider 7).
[0080]
In this case, as shown in FIG. 14, the elliptical motion generated at the protrusion (6 in FIG. 5) of the vibrating body changes the amplitude ratio between the A mode, which is the horizontal amplitude of the elliptic motion, and the B mode, which is the vertical amplitude. Instead, the driving state is such that the amplitudes are different.
[0081]
When it is desired to drive the lens 9 at a lower speed, since the B-mode amplitude is too small in the driving method as in the above-described second embodiment (FIG. 14B), the protrusion 6 is moved downward of the elliptical motion. That is, the slider 7 may come into contact with the slider 7 even when the slider 7 moves in the direction opposite to the feed direction, and a situation may occur in which stable low-speed driving cannot be performed.
[0082]
The third embodiment of the present invention is a further improvement of the above-described second embodiment, and is intended to stably realize low-speed driving. Hereinafter, the control method will be described.
[0083]
Note that, in the present embodiment, the configuration of the vibration wave actuator is the same as the configuration of the vibration wave actuator described in the first embodiment, and a case where this vibration wave actuator is mounted on the lens unit described in the second embodiment will be described. I do.
[0084]
In order to drive the vibration wave actuator stably at low speed, it is necessary to increase the amplitude of the B mode, which is the vibration in the direction in which the slider 7 is pushed up, and to reduce the amplitude of the A mode, which is the vibration of the slider 7 in the feed direction. Conceivable.
[0085]
For example, as shown in FIG. 15, when the amplitude of the B mode is kept constant during the high-speed driving and the low-speed driving, and the driving speed of the slider 7 is controlled by changing the amplitude of the A mode, the high-speed driving can be performed. It is possible to drive the slider 7 stably in a wide range from to low-speed driving.
[0086]
FIG. 16 is a block diagram illustrating a control device according to the present embodiment. The difference from the control device (the block diagram in FIG. 11) described in the second embodiment is that a phase difference determination unit 23 and an amplitude determination unit 24 are provided. Other configurations are the same as in the second embodiment.
[0087]
In this embodiment, the driving speed is controlled by fixing the frequencies of the AC voltages V1 and V2 applied to the vibration wave actuator to a predetermined frequency near the resonance frequency (fr), and manipulating the phase difference θ and the amplitude of V1 and V2. Control.
[0088]
As described in the second embodiment, the relationship between the phase difference θ of the voltages (V1, V2) applied to the electrodes of the piezoelectric element in the vibration wave actuator and the amplitudes of the A mode and the B mode with respect to the relationship shown in FIG. However, this is the case where the voltage amplitudes of V1 and V2 are constant within the range of the phase difference θ of 0 ° to 180 °.
[0089]
In this case, the B-mode vibration changes due to the phase difference θ as shown by the broken line in FIG. Therefore, in the present embodiment, the amplitude of the B mode is made constant by changing the amplitude of the applied voltage (V1, V2) according to the phase difference θ.
[0090]
FIG. 17 shows a state of the vibration amplitude when the amplitude of the applied voltage (V1, V2) is changed according to the phase difference θ between V1 and V2 so that the amplitude of the B mode becomes constant. The voltage amplitude on the line connecting the circle marks in FIG. 17 is a value proportional to the reciprocal of the B-mode amplitude shown in FIG. 12, and corrects the change in the B-mode amplitude. That is, the voltage amplitude of V1 and V2 is obtained by multiplying the coefficient (K) obtained by the following equation (3) according to the phase difference θ.
[0091]
K = | 1 / (2 × cos (θ / 2)) | (3)
The voltage amplitude obtained by using the above equation (3) has a relationship as shown by a circle mark in FIG. By applying voltages of this amplitude (V1 and V2) to the two electrodes of the piezoelectric element, the amplitude of the B mode becomes constant as shown by the dotted line in the figure.
[0092]
At this time, the amplitude of the A mode has such a characteristic that the phase difference θ increases from 0 ° to 180 ° and decreases from 180 ° to 360 ° as shown by the solid line in FIG. As in FIG. 12, the driving directions are opposite on the right side (−direction) and the left side (+ direction) in FIG. 17 with the phase difference of 180 ° as a boundary.
[0093]
In the present embodiment, the following drive control is performed using the characteristics described above.
[0094]
First, the position comparison unit 18 compares the current position of the lens 9 with the target position. The phase difference determining unit 23 determines the driving direction based on the comparison result of the position comparing unit 18, and sets the phase difference θ between V1 and V2 to a value in an area smaller than 180 ° (an area in the + direction in FIG. 17). Or a value in a region larger than 180 ° (a region in the minus direction in FIG. 17).
[0095]
Further, the phase difference determination unit 23 determines the phase difference θ so as to have a speed corresponding to the distance between the current position of the lens 9 and the target position.
[0096]
For example, in the case where the lens 9 (slider 7) is driven in the + direction and the driving speed is set to be high, the phase difference θ is set to a large value in a region where the phase difference θ is smaller than 180 °. Determined to be. When the driving speed is set to be low, the phase difference θ is determined to be a small value in a region where the phase difference is smaller than 180 °. In the region where the phase difference θ is smaller than 180 °, the amplitude of the B mode is constant, and the amplitude of the A mode increases as the phase difference θ approaches 180 ° from 0 °. Can be performed stably.
[0097]
When the lens 9 (slider 7) is driven in the negative direction and the driving speed is high, the phase difference θ is set to a small value in a region where the phase difference θ is larger than 180 °. Determined to be. When the driving speed is set to be low, the phase difference θ is determined to be a large value in a region where the phase difference is larger than 180 °. In the region where the phase difference θ is larger than 180 °, the amplitude of the B mode is constant, and the amplitude of the A mode increases as the phase difference θ approaches 360 ° to 180 °. Can be performed stably.
[0098]
After the phase difference determination unit 23 determines the phase difference θ, the amplitude determination unit 24 determines the voltage amplitude (the value on the line connecting the circle marks in FIG. 17) corresponding to the determined phase difference θ. When determining the voltage amplitude, the voltage amplitude may be obtained from the phase difference θ by the above-described arithmetic expression (3), or may be obtained by storing a plurality of relationships between the phase difference θ and the voltage amplitude in a storage circuit in advance. Good.
[0099]
When the value of the phase difference θ is determined by the phase difference determination unit 23 and the voltage amplitude is determined by the amplitude determination unit 24, these data are input to the drive signal generation circuit 21 and a signal corresponding to the input is generated. You. Then, the voltages (V1, V2) boosted by the boosting circuit 22 are applied to the piezoelectric element of the vibration wave actuator.
[0100]
As a result of the above-described drive control, among the vibrations of the vibration wave actuator, the vibration amplitude of the B mode, which is the vibration in the push-up direction with respect to the slider 7, can be kept constant, and the vibration amplitude of the A mode can be changed. Can be operated stably in a wide range from a high speed to a low speed.
[0101]
Each embodiment described above is also an example of the case where each of the following inventions is implemented, and each of the following inventions is implemented by adding various changes and improvements to each of the above embodiments.
[0102]
[Invention 1] An electro-mechanical energy conversion element having an elastic body and at least two electrodes, wherein a two-phase driving voltage having the same frequency is applied to the two electrodes to excite vibration in the elastic body. A vibrating body with
A vibration-type driving device having a driven body that contacts the elastic body,
The vibrating body forms the first bending vibration mode by receiving the input of the two-phase driving voltages having the same phase, and forms the second bending vibration by receiving the input of the two-phase driving voltages having the opposite phase. It is possible to form a vibration mode,
A vibratory driving device, wherein the vibrating body and the driven body are relatively driven by a combination of the first bending vibration mode and the second bending vibration mode.
[0103]
In the vibration type driving device according to the first aspect, the first bending vibration mode formed by inputting the two-phase driving voltages having the same phase to the two electrodes and the two-phase driving voltage having the opposite phase are set to two. By combining with the second bending vibration mode formed by inputting to one of the electrodes, the vibrating body and the driven body can be relatively driven. That is, by setting the phase difference between the two-phase drive voltages to a value between the same phase and the opposite phase, a bending vibration mode combining the first bending vibration mode and the second bending vibration mode is generated in the vibrating body. By this bending vibration mode, an elliptical motion is generated at a predetermined mass point of the elastic body, so that the vibrating body and the driven body can be relatively driven.
[0104]
According to the configuration of the vibration type driving device described above, the electrode pattern of the electro-mechanical energy conversion element can have a simple configuration as compared with the related art. In addition, since a single piezoelectric element can be used, the configuration can be simpler than that of a laminated piezoelectric element.
[0105]
[Invention 2] The vibration type driving device according to Invention 1, wherein the two electrodes are polarized so that the polarization directions are the same.
[0106]
According to the second aspect, by setting the polarization directions of the two electrodes to be the same, the polarization processing of each electrode can be easily performed. In addition, since the rigidity of the electro-mechanical energy conversion element between the two electrodes does not change (unevenness in rigidity), ideal vibration can be generated.
[0107]
[Invention 3] The elastic body is formed in a rectangular shape,
The first bending vibration mode is a primary vibration mode in a direction orthogonal to the longitudinal direction of the vibrator, and the second bending vibration mode is a secondary vibration mode in a longitudinal direction of the vibrator. The vibration-type driving device according to the invention 1 or 2, wherein:
[0108]
[Invention 4] A control system including the vibration-type driving device according to any one of Inventions 1 to 3, and a control device that controls driving of the vibration-type driving device,
The control device changes the relative driving direction of the vibrating body and the driven body by changing a phase difference between the two-phase driving voltages, and in a region on a higher frequency side than a resonance frequency, A control system, wherein a relative driving speed of the vibrating body and the driven body is changed by changing a frequency of the driving voltage.
[0109]
[Invention 5] A control system including the vibration-type driving device according to any one of Inventions 1 to 3, and a control device that controls driving of the vibration-type driving device,
A control system, wherein the control device controls a relative driving speed of the vibrating body and the driven body based on a phase difference and an amplitude of the two-phase driving voltages.
[0110]
[Invention 6] A control system including the vibration-type driving device according to any one of Inventions 1 to 3, and a control device that controls driving of the vibration-type driving device,
The control device is configured such that, with respect to a change in the phase difference between the two-phase drive voltages, the vibration amplitude in one of the first bending vibration mode and the second bending vibration mode becomes constant. The amplitude of the driving voltage can be set so that the vibration amplitude in the other bending vibration mode changes, and by changing the phase difference between the two-phase driving voltages, the relative vibration between the vibrating body and the driven body is changed. A control system characterized by changing a driving speed or a driving direction.
[0111]
According to the sixth aspect, for example, by changing the phase difference between the two-phase drive voltages, the vibration amplitude in the pushing-up direction of the driven body is made constant, and the vibration in the driving direction (feeding direction) of the driven body. Since the amplitude can be changed, the driven body can be driven stably in a wide range from high-speed driving to low-speed driving.
[0112]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the electrode of an electromechanical energy conversion element can be made into a simple structure in the vibration type drive device which produces | generates two bending vibration modes and drives a vibrating body and a driven body relatively. .
[Brief description of the drawings]
FIG. 1 is a view showing an electrode pattern of a piezoelectric element according to an embodiment.
FIG. 2 is a diagram showing a vibration mode in a vibrating body of the related art.
FIG. 3 is a diagram showing an electrode pattern of a piezoelectric element according to the related art.
FIG. 4 is a diagram showing an electrode pattern of a piezoelectric element according to the related art.
FIG. 5 is an external perspective view of a vibrating body according to the embodiment.
FIG. 6 is a view showing a vibration mode in the vibrating body of the embodiment.
FIG. 7 is an external perspective view of the vibration wave actuator according to the embodiment.
FIG. 8 is a view showing an electrode pattern of a piezoelectric element according to a conventional concept.
FIG. 9 is a diagram showing a relationship between a voltage applied to a piezoelectric element and a vibration mode by a vector.
FIG. 10 is a diagram illustrating a mechanism of a lens unit according to a second embodiment.
FIG. 11 is a control block diagram according to a second embodiment.
FIG. 12 is a diagram illustrating a relationship between a phase difference of an applied voltage and a vibration amplitude.
FIG. 13 is a diagram showing a relationship between a driving frequency and a driving speed of the vibration wave actuator.
FIG. 14 is a diagram illustrating an elliptical motion of a protrusion in the vibration wave actuator.
FIG. 15 is a diagram illustrating an elliptical motion of a protrusion in the vibration wave actuator.
FIG. 16 is a control block diagram according to a third embodiment of the present invention.
FIG. 17 is a diagram showing a relationship between a phase difference of an applied voltage and a vibration amplitude.
FIG. 18 is an external perspective view of a vibration wave actuator that is a modification of the first embodiment.
FIG. 19 is a diagram showing a vibration mode of a vibrating body.
FIG. 20 is an external perspective view of a vibration wave actuator that is a modification of the first embodiment.
FIG. 21 is a diagram showing a vibration mode of a vibrating body.
FIG. 22 is an external perspective view of a vibration wave actuator that is a modification of the first embodiment.
[Explanation of symbols]
4: elastic body, 5: piezoelectric element, 6: protrusion, 7, 7 ', 7 ": slider
8: lens barrel, 9: lens, 10: frame, 11: shaft
12, 15: vibration wave actuator, 13: encoder scale
14: light emitting and receiving element, 16: encoder
17: position counter, 18: position comparator, 19: phase difference selector
20: frequency determination unit, 21: drive signal generation circuit, 22: booster circuit
23: phase difference determination unit, 24: amplitude determination unit

Claims (1)

A vibration comprising: an elastic body; and an electro-mechanical energy conversion element having at least two electrodes, wherein two-phase driving voltages having the same frequency are applied to the two electrodes to excite the elastic body with vibration. Body and
A vibration-type driving device having a driven body that contacts the elastic body,
The vibrating body forms the first bending vibration mode by receiving the input of the two-phase driving voltages having the same phase, and forms the second bending vibration by receiving the input of the two-phase driving voltages having the opposite phase. It is possible to form a vibration mode,
A vibratory driving device, wherein the vibrating body and the driven body are relatively driven by a combination of the first bending vibration mode and the second bending vibration mode.

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