JP4261964B2 - Vibration type driving device and control system - Google Patents

Description

[0001]
BACKGROUND 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 using the vibration energy. Is .
[0002]
[Prior art]
Various proposals have been made for vibration wave motors that drive a driven body in a linear direction.
[0003]
For example, a plurality of protrusions are provided at predetermined positions on one side of an elastic body formed in a square bar shape, and a piezoelectric element is disposed on the surface of the elastic body opposite to the surface on which the protrusions are provided. In such a vibration wave motor, an AC voltage is applied to the piezoelectric element, so that a flexural resonance vibration and a longitudinal resonance vibration (longitudinal vibration) are simultaneously generated in the elastic body and an elliptical motion is generated in the 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 protruding portion by bringing the driven body into pressure contact with the protruding portion.
[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 elliptical motion at a predetermined mass point (projection, etc.) by combining the two bending vibration modes. Ru (Refer to the second conventional example, for example, Patent Document 2).
[0006]
Here, one bending vibration mode (referred to as a first vibration mode) of the two bending vibration modes is a cross-like shape as shown in (a-1) and (a-2) of FIG. The vibration mode has nodes. The other bending vibration mode (referred to as the second vibration mode) has two nodes parallel to a predetermined direction as shown in (b-1) and (b-2) of FIG. It has a 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 “+” and “−” symbols in the figure indicate the polarization direction.
[0008]
In the piezoelectric element 3A, the boundary portion of the electrode exists so as to coincide with the cross-shaped node in the first vibration mode, and an alternating-current signal (frequency signal 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 is generated. On the other hand, when an AC signal (Vb) having a frequency near the resonance frequency in the second vibration mode is applied to the piezoelectric element 3B, vibration in the second vibration mode is generated in the elastic body.
[0009]
Therefore, by stacking the piezoelectric element 3A and the piezoelectric element 3B and attaching them to the elastic body, two bending vibration modes can be generated on the elastic body, and a predetermined mass point can be obtained by combining these two bending vibration modes. The driven body can be driven by the elliptical motion generated in the above.
[0010]
On the other hand, as a piezoelectric element that generates two bending vibration modes, as shown in FIG. 4, a piezoelectric element constituted by a single layer without stacking a plurality of piezoelectric elements may be used. In FIG. 4, the electrode connected to the voltage signal Va is a piezoelectric element for generating a first vibration mode, and the electrode connected to the voltage signal Vb is a piezoelectric element for generating a second vibration mode.
[0011]
[Patent Document 1]
Japanese Patent Publication No. 6-106028
[Patent Document 2]
Japanese Patent Laid-Open No. 6-311765
[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 downsized. There is a limit to downsizing a vibration wave motor.
[0013]
On the other hand, since the vibration wave motor in the second conventional example is a combination of two bending vibration modes, the elastic body (vibration wave motor) can be downsized compared to the first conventional example. In addition, since the resonance frequency in each bending vibration mode can be matched by changing the ratio of the long side to the short side of the rectangular elastic body, the resonance frequency can be easily adjusted as compared with the first conventional example. Thus, it is possible to realize an actuator with good driving efficiency.
[0014]
However, in the second conventional example, in order to excite a plurality of vibration modes in the vibrating body, a piezoelectric element having a dedicated electrode for generating each vibration mode is required. As a result, it is necessary to use a piezoelectric element having a complicated electrode pattern, or to stack and use piezoelectric elements, which is not preferable in terms of the manufacturing process and cost.
[0015]
In addition, since the polarization direction is different for each electrode pattern, not only the process of polarization processing becomes complicated, but also there is a problem that the rigidity of the piezoelectric element changes near the boundary of electrodes having different polarization directions.
[0016]
[Means for Solving the Problems]
The present invention is an elastic body. And fixed to the elastic body Electro-mechanical energy conversion element The A provided vibrating body, and a driven body in contact with the elastic body; , A vibration type driving device having The electro-mechanical energy conversion element includes a first electrode for expanding and contracting a first area of the electro-mechanical energy conversion element, and a second electrode adjacent to the first area of the electro-mechanical energy conversion element. A second electrode for expanding and contracting the region of The vibrating body is The first region and the second region expand or contract together First bending vibration mode When , The second region contracts when the first region expands and the second region expands when the first region contracts Second bending vibration mode When, The vibrating body and the driven body are relatively driven by vibration generated by a combination of the first bending vibration mode and the second bending vibration mode.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First 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, 4 is an elastic body made of a metal material and formed in a rectangular plate shape, 5 is a piezoelectric element (electro-mechanical energy conversion element) bonded to the back surface of the elastic body 4, and 6 is It is a protrusion provided on the upper surface of the elastic body 4.
[0018]
The protrusion 6 comes into contact with the driven body at the tip as described later. Here, a contact portion having excellent friction coefficient 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 pressing or the like, or formed separately from the elastic body 4 and then fixed to the elastic body 4.
[0019]
If the protrusion 6 and the elastic body 4 are integrally formed, the number of assembling steps of the elastic body 1 can be reduced as compared with the case where these are separately formed, and the parts (protrusion 6) are aligned. Since it is not necessary, it is possible to prevent variations between parts.
[0020]
The vibrating body 1 of the present embodiment can excite two bending vibration modes as will be described later, and generates elliptical motion at the tip of the protrusion 6 by combining these two bending vibration modes.
[0021]
Here, the shape of the vibrating body 1 is formed so that the resonance frequencies of the two bending vibration modes substantially coincide. 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 do.
[0022]
Hereinafter, two bending vibration modes excited by the vibrating body 1 will be described.
[0023]
FIG. 6 is a diagram showing two bending vibration modes. The vibration mode shown in FIG. 6A represents one bending vibration mode (referred to as A mode) of the two bending vibration modes. This 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). is doing.
[0024]
Here, the protrusion 6 is disposed in the vicinity of a position that becomes a node by the vibration of the A mode, and reciprocates in the arrow X direction by the vibration of the A mode. By arranging the protrusions 6 in this way, the protrusions 6 can be displaced most greatly 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 in the short side direction (arrow Y direction) of the rectangular vibrating body 1 (elastic body 4), and has two nodes parallel to the long side direction (arrow X direction). is doing.
[0026]
Here, the nodes in the A mode and the nodes in the B mode are substantially orthogonal in the XY plane.
[0027]
Further, the protrusion 6 is disposed in the vicinity of a position that becomes an antinode due to the vibration of the B mode, and reciprocates in the arrow Z direction by the vibration of the B mode. By arranging the protrusions 6 in this way, the protrusions 6 can be displaced the most in the direction of the arrow Z.
[0028]
That is, as described above, the position of the A mode node and the position of the antinode of the B mode can be matched by making the node of the A mode and the node of the B mode substantially orthogonal to each other. By disposing, the vibration displacement of the protrusion 6 can be maximized, and a high output can be obtained.
[0029]
As described above, by greatly displacing the protrusion 6 in the X direction and the Z direction, a large driving force can be applied to the driven body that contacts the protrusion 6.
[0030]
If the two protrusions 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 protrusion 6. You can receive without. Further, 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 the environment and load fluctuations.
[0031]
By generating the above-described 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 is brought into pressure contact with the tip of the protrusion 6, and the slider 7 moves in the direction of arrow L due to the elliptical motion of the protrusion 6. Can do.
[0032]
If the electrode pattern of the piezoelectric element is configured in the same way as the prior art in order to cause the vibration body 1 to generate the above-described A mode and B mode vibrations, an electrode pattern as shown in FIG. 8 is obtained. In FIG. 8, the “+” symbol and the “−” symbol indicate the polarization direction.
[0033]
Of the piezoelectric elements shown in FIG. 8, four electrode regions to which the voltage signal (Va) is connected are electrode regions for generating A-mode vibration. When an alternating voltage having a frequency in the vicinity of the resonance frequency of the A mode is applied to Va, two electrode regions (piezoelectric elements) polarized to “+” out of the four electrode regions expand at a certain moment, and “−” Thus, 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 in the piezoelectric element shown in FIG. 8 is an electrode region for generating B-mode vibration. When an AC voltage having a frequency in the vicinity of the B-mode resonance frequency is applied to Vb, the central portion in the short side direction (Y direction) of the piezoelectric element expands and contracts, so that B-mode vibration is generated in the vibrating body.
[0036]
Here, when the alternating voltages of Va and Vb are set to the same frequency with a phase difference of 90 ° (in this embodiment, a frequency near the resonance frequency of the A mode and the B mode), the elliptical motion is generated on the protrusion 6. appear.
[0037]
FIG. 1 is a diagram showing an electrode pattern of a piezoelectric element according to this embodiment. As shown in FIG. 1, the piezoelectric element 5 is formed with an electrode region that is divided into two equal parts in the longitudinal direction (X direction). In addition, the polarization direction in each electrode region is the same direction (“+”).
[0038]
Of the two electrode regions of the piezoelectric element 5, an AC voltage (V1) is applied to the electrode region located on the right side in FIG. 1, and an AC voltage (V2) is applied to the electrode region located on the left side.
[0039]
In FIG. 1, when V1 and V2 are alternating voltages having a frequency near the resonance frequency of the A mode and the phase is shifted by 180 °, at a certain moment, the piezoelectric element in the right electrode region contracts and the left electrode region The piezoelectric element extends. At the other moment, the relationship is reversed. As a result, vibration of the A mode is generated in the vibrator 1.
[0040]
Further, if V1 and V2 are AC voltages having a frequency in the vicinity of the resonance frequency of the B mode and the same phase, the entire piezoelectric element (two electrode regions) expands at a certain moment and contracts at another moment. Become. As a result, B-mode vibration is generated in the vibrator 1.
[0041]
The polarization direction in one of the two electrode regions in the piezoelectric element 5 may be “+”, and the polarization direction in the other electrode region may be “−”.
[0042]
In this case, the A-mode vibration is applied to the vibrating body 1 by applying AC voltages (V1, V2) having the same phase and the same phase to the two electrode regions as described above. Can be generated. Further, by applying AC voltages (V1, V2) having a frequency near the B-mode resonance frequency and having a phase shifted by 180 ° to each of the two electrode regions, vibration of the B mode is applied to the vibrator 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 description using FIG. 1 described above, the combination of the vectors “V1” and “−V2” is a vector indicating the A mode, and the combination of the vectors “V1” and “V2” is 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 indicates that the vibrations in the A mode and the B mode are generated at the same time, and the phase difference between 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 brought into 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 simultaneously, and the vibration phase difference is always 90. It will be either ° or -90 °. Moreover, the amplitude of A mode and B mode can be changed by changing phase difference (theta) of V1 and V2.
[0047]
As described above, according to this embodiment, the piezoelectric element 5 having a simple configuration in which the electrode pattern is divided into two equal parts in the longitudinal direction of the vibrating body 1 and the polarization directions of the electrode regions are the same direction is used. Even in the case of the vibrating body 1, elliptical motion can be generated in the protrusion 6 of the vibrating body 1.
[0048]
In this way, by making the electrode pattern simple, the wiring connected to each electrode region can be made simple. In addition, since the polarization direction is the same over the entire piezoelectric element, the polarization process can be performed more easily than the piezoelectric elements with different polarization directions, and the rigidity of the piezoelectric element near the boundary of the electrode region becomes uniform. Can generate ideal vibration.
[0049]
In addition, by driving the driven body using two bending vibration modes, the vibration wave is suppressed with an increase in the natural frequency compared to the vibration wave actuator that drives the driven body by a combination of bending vibration and longitudinal vibration. The actuator can be downsized.
[0050]
Note that the vibration type driving apparatus of the present embodiment is configured to drive the driven body 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, an 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. Any bending vibration mode (bending vibration modes having different orders) may be used.
[0052]
In the present embodiment, as shown in FIG. 5 and FIG. 7, the vibration body in which the two protrusions 6 are provided on the upper surface of the elastic body 4 has been described. However, the position and number of the protrusions 6 are appropriately set. be able to.
[0053]
For example, one protrusion 6 can be provided at the center of the elastic body 4 as shown in FIG. 18, or four protrusions 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. Reciprocate 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, thereby moving the slider 7 in the arrow L direction.
[0055]
Here, since the protrusion 6 is disposed in the vicinity of the node of the A mode and in the vicinity of the antinode of the B mode, the displacement in the X direction and the Z direction is increased, and the slider 7 is driven greatly. Can give power.
[0056]
Further, in the vibrating body 1 ″ shown in FIG. 20, the protrusion 6 reciprocates in the X direction as shown in FIG. 21 (a) by the A mode vibration, and in FIG. 21 (b) by the B mode vibration. As shown in the figure, it reciprocates in the Z direction, and the combination of the A mode and the B mode causes an elliptical motion at the tip of the projection 6, thereby driving a driven body (not shown) in contact with the projection 6.
[0057]
Here, the four protrusions 6 are arranged in the vicinity of the A-mode node and in the vicinity of the B-mode antinode, so that the displacement in the X direction and the Z direction becomes large.
[0058]
Moreover, although this embodiment demonstrated the case where the to-be-driven body (slider 7) formed in the rod shape was made to contact the projection part 6 as shown in FIG. 7, this invention is not limited to this.
[0059]
Specifically, as shown in FIG. 22 (a), the driven body 7 ′ formed in a disk shape is brought into contact with the protrusion 6, and the driven body 7 ′ is driven in the direction indicated by the arrow. It can be a vibration wave actuator. Further, as shown in FIG. 22 (b), a driven wave 7 ″ formed in an annular shape is brought into contact with the protrusion 6, and the driven wave 7 ″ is driven in the direction indicated by the arrow. It can be.
[0060]
(Second Embodiment)
In the first embodiment described above, the phase difference of the AC voltage (V1, V2) applied to the piezoelectric element having a simple two-divided structure electrode in the vibrating body having the rectangular elastic body and the piezoelectric element is 0 ° and It has been explained that elliptical motion can be generated in the protrusions of the vibrating body by setting the phase difference to other than 180 °.
[0061]
In the second embodiment of the present invention, a control method of the vibration wave actuator described in the first embodiment will be described. Since the structure of the vibration wave actuator is the same as that of the first embodiment described above, description thereof is omitted.
[0062]
In this 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 sectional view of the lens unit (a sectional view in a direction perpendicular to the optical axis).
[0063]
In FIG. 10, 8 is 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 (direction orthogonal to the paper surface 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 vibration body of the vibration wave actuator described in the first embodiment, and is configured such that the protrusion 6 contacts 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 position information of the lens 9 is detected by irradiating the encoder scale 13 with light by the light projecting / receiving element 14 and reading the reflected light from the encoder scale 13 by the light projecting / receiving element 14.
[0066]
Next, a method for controlling the vibration wave actuator described above will be described. FIG. 11 is a block diagram for explaining a control device in the present embodiment.
[0067]
In FIG. 11, 15 is 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 comparison unit 18. This comparison result is input to the phase difference selector 19 and the frequency determiner 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 making the angle other than 0 ° and 180 °, vibrations in the A mode and the B mode, which are 90 ° out of phase, are generated in the vibrating body 12.
[0069]
Here, the magnitude of the amplitude (Aa) of the A mode and the amplitude (Ab) of the B mode when the phase difference θ of V2 with respect to V1 is an arbitrary value (0 ° to 180 °) is expressed by the following equation (1): It is calculated | required by (2).
[0070]
Aa = | 2 × cos ((π−θ) / 2) | (1)
Ab = | 2 × cos (θ / 2) | (2)
FIG. 12 shows the relationship between the vibration amplitudes of the A mode and 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 amplitude of the vibration mode (A mode and B mode). Further, the phase difference between the vibrations in the B mode with respect to the A mode is switched between 90 ° and −90 ° with the phase difference 180 ° between V1 and V2 as a boundary. That is, the drive direction of the driven body (slider 7) is reversed on both sides (+ direction and-direction in the figure) with the phase difference 180 ° between V1 and V2 as a boundary.
[0071]
Here, the position comparison 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 outside, thereby driving the slider 7 by the vibration wave actuator. The direction is determined. Then, the phase difference selection unit 19 selects the phase difference θ between V1 and V2 according to the determined driving direction. That is, in the phase difference selector 19, the phase difference θ of V2 with respect to V1 is set to 90 ° when the driving direction of the slider 7 is set to the + direction, and the phase difference θ is set to 270 ° when the driving direction is set to the − direction.
[0072]
Although it is possible to drive the lens 9 even with a phase difference θ other than 90 ° and 270 °, in the present embodiment, the phase difference θ when the amplitudes of the A mode and the B mode are generated uniformly is used. Some 90 ° and 270 ° are selected.
[0073]
Next, control of the drive frequency will be described. The relationship between the frequency of the alternating voltage (V1, V2) applied to the vibration wave actuator 15 and the driving speed is the same as that of a vibration wave motor using general resonance, and as shown in FIG. 13, the resonance frequency (fr) Is the speed peak, and the driving speed gently decreases on the higher frequency side than fr, and the driving speed rapidly decreases on the lower frequency side.
[0074]
When the drive speed is controlled in this characteristic, the drive control is performed at a frequency in a frequency region higher than the resonance frequency (fr).
[0075]
The position comparison unit 18 measures the deviation between the current position of the lens 9 based on the output of the position counter 17 and the target position input from the outside. In the frequency determination unit 20, when the deviation is large, the drive frequency is made close to the resonance frequency (fr) so as to increase the drive speed. Further, when the deviation is small, the drive frequency is set to be low by moving the drive frequency away from the resonance frequency (fr) to the high frequency side.
[0076]
In addition, when the deviation of the position of the lens 9 is within a predetermined range, an 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) that has the phase difference θ selected by the phase difference selector 19 and the frequency determined by the frequency determiner 20. Yes. 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). Thereby, a lens unit in which the lens 9 moves quickly to the target position can be configured.
[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. Further, the phase difference θ between the applied voltages V1 and V2 is selected to be 90 ° or 270 ° depending on the driving direction of the driven body (slider 7).
[0080]
In this case, the elliptical motion generated in the protrusion (6 in FIG. 5) of the vibrating body changes in the amplitude ratio between the A mode which is the horizontal amplitude of the elliptical motion and the B mode which is the vertical amplitude as shown in FIG. Without such a drive state, the amplitude is 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 second embodiment described above (FIG. 14B), the protrusion 6 is below the elliptical motion. In other words, there may be a case where the slider 7 is in contact with the slider 7 even when moving in the direction opposite to the feeding direction, and a stable low-speed drive cannot be performed.
[0082]
The third embodiment of the present invention is a further improvement of the above-described second embodiment, and is for stably realizing low-speed driving. Hereinafter, the control method will be described.
[0083]
In this embodiment, the configuration of the vibration wave actuator is the same as that of the vibration wave actuator described in the first embodiment, and the case where this vibration wave actuator is mounted on the lens unit described in the second embodiment will be described. To do.
[0084]
In order to stably drive the vibration wave actuator at a 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 decrease the amplitude of the A mode, which is the vibration in the feed direction of the slider 7. Conceivable.
[0085]
For example, as shown in FIG. 15, when the drive speed of the slider 7 is controlled by changing the amplitude of the A mode by keeping the B mode amplitude constant during the high speed drive and the low speed drive, the high speed drive is achieved. Thus, the slider 7 can be stably driven in a wide area from low speed to low speed driving.
[0086]
FIG. 16 is a block diagram for explaining a control device in the present embodiment. The difference from the control device (block diagram of 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 those in the second embodiment.
[0087]
In this embodiment, the frequency of the AC voltages V1 and V2 applied to the vibration wave actuator is fixed to a predetermined frequency near the resonance frequency (fr), and the driving speed is adjusted by manipulating the phase difference θ and the amplitude of V1 and V2. To control.
[0088]
As described in the second embodiment, the relationship between the amplitudes of the A mode and the B mode with respect to the phase difference θ of the voltages (V1, V2) applied to the electrodes of the piezoelectric element in the vibration wave actuator is as shown in FIG. However, this is a case where the voltage amplitudes of V1 and V2 are constant within a phase difference θ of 0 ° to 180 °.
[0089]
In this case, as shown by the broken line in FIG. 12, the B-mode vibration changes due to the phase difference θ. 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 the state of the vibration amplitude when the amplitude of the applied voltage (V1, V2) is changed in accordance with the phase difference θ between V1 and V2 so that the amplitude of the B mode is 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 (V1 and V2) of this amplitude to the two electrodes of the piezoelectric element, the amplitude of the B mode becomes a constant amplitude as shown by the dotted line in the figure.
[0092]
At this time, the amplitude of the A mode has such characteristics 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 direction is reversed on the right side (− direction) and the left side (+ direction) in FIG. 17 with a 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 determination unit 23 determines the drive direction based on the comparison result in the position comparison unit 18, and sets the phase difference θ between V1 and V2 to a value in a region smaller than 180 ° (region in the + direction in FIG. 17). Or to determine the value in a region larger than 180 ° (region in the negative direction in FIG. 17).
[0095]
Further, the phase difference determination unit 23 determines the phase difference θ so that the speed is in accordance with the distance between the current position of the lens 9 and the target position.
[0096]
For example, when the lens 9 (slider 7) is driven in the + direction and the driving speed is high, the phase difference θ is a large value in a region where the phase difference θ is smaller than 180 °. Decide to be. When the driving speed is set to a low speed, 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 from 0 ° to 180 °. Can be performed stably.
[0097]
When the lens 9 (slider 7) is driven in the-direction and the driving speed is high, the phase difference θ is a small value in a region where the phase difference θ is larger than 180 °. Decide to be. When the driving speed is set to a low speed, 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 180 ° from 360 °. Can be performed stably.
[0098]
After the phase difference θ is determined by the phase difference determination unit 23, the amplitude determination unit 24 determines the voltage amplitude corresponding to the determined phase difference θ (the value on the line connecting the circle marks in FIG. 17). When determining the voltage amplitude, it may be obtained from the phase difference θ by the above equation (3), or may be obtained by storing in advance a relationship between a plurality of phase differences θ and the voltage amplitude in the storage circuit. Good.
[0099]
When the value of the phase difference θ is determined by the phase difference determining unit 23 and the voltage amplitude is determined by the amplitude determining unit 24, these data are input to the drive signal generation circuit 21, and a signal corresponding to this input is generated. The Then, the voltages (V1, V2) boosted by the booster circuit 22 are applied to the piezoelectric element of the vibration wave actuator.
[0100]
As a result of the drive control described above, 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 made constant and the vibration amplitude of the A mode can be changed. Can be operated stably from a high speed to a low speed.
[0103]
In the vibration type driving device of the present invention, The first and second regions in the electro-mechanical energy conversion element both expand or contract A first bending vibration mode; The second region contracts when the first region expands and the second region expands when the first region contracts By combining with the second bending vibration mode, the vibrating body and the driven body can be relatively driven. Ie , Shake Generating a bending vibration mode in which a first bending vibration mode and a second bending vibration mode are combined in a moving body; so In this bending vibration mode, the vibrating body and the driven body can be driven relatively by causing an elliptical motion at a predetermined mass point of the elastic body.
[0104]
According to the configuration of the vibration-type driving device described above, the electrode pattern of the electro-mechanical energy conversion element can be simplified as compared with the conventional technology. In addition, since a single piezoelectric element can be used, a simple configuration can be obtained as compared with a laminated piezoelectric element.
[0106]
Book invention like By making the polarization directions of the two electrodes the same direction, the polarization treatment at each electrode can be easily performed. Moreover, since the rigidity of the electromechanical energy conversion element between the two electrodes does not change (stiffness unevenness), ideal vibration can be generated.
[0111]
Book invention In For example, by changing the phase difference between the two-phase drive voltages, the vibration amplitude in the driven-up direction of the driven body can be made constant and the vibration amplitude in the drive direction (feeding direction) of the driven body can be changed. Therefore, the driven body can be stably driven in a wide range from high speed driving to low speed driving.
[0112]
【The invention's effect】
According to the present invention, in the vibration type driving device that generates two bending vibration modes and relatively drives the vibrating body and the driven body, the electrode of the electro-mechanical energy conversion element can have a simple configuration. .
[Brief description of the drawings]
FIG. 1 is a diagram showing an electrode pattern of a piezoelectric element according to an embodiment.
FIG. 2 is a diagram illustrating a vibration mode in a vibration body according to a conventional technique.
FIG. 3 is a diagram showing an electrode pattern of a piezoelectric element in the prior art.
FIG. 4 is a diagram showing an electrode pattern of a piezoelectric element in the prior art.
FIG. 5 is an external perspective view of a vibrating body according to the present embodiment.
FIG. 6 is a diagram illustrating a vibration mode in the vibrating body according to the embodiment.
FIG. 7 is an external perspective view of a vibration wave actuator according to the present embodiment.
FIG. 8 is a diagram 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 as 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 the second embodiment.
FIG. 12 is a diagram showing a relationship between a phase difference of applied voltage and vibration amplitude.
FIG. 13 is a diagram illustrating a relationship between a driving frequency and a driving speed of a vibration wave actuator.
FIG. 14 is a diagram for explaining an elliptical motion of a protrusion in a vibration wave actuator.
FIG. 15 is a diagram for explaining the elliptical motion of the protrusion in the vibration wave actuator.
FIG. 16 is a control block diagram according to the third embodiment of the present invention.
FIG. 17 is a diagram showing a relationship between a phase difference of applied voltage and 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 illustrating a vibration mode of a vibrating body.
20 is an external perspective view of a vibration wave actuator that is a modification of the first embodiment. FIG.
FIG. 21 is a diagram illustrating a vibration mode of a vibrating body.
22 is an external perspective view of a vibration wave actuator that is a modification of the first embodiment. FIG.
[Explanation of symbols]
4: Elastic body, 5: Piezoelectric element, 6: Projection, 7, 7 ′, 7 ″: Slider
8: Lens barrel, 9: Lens, 10: Frame, 11: Shaft
12, 15: Vibration wave actuator, 13: Encoder scale
14: Light emitting / receiving element, 16: Encoder
17: Position counter, 18: Position comparison unit, 19: Phase difference selection unit
20: Frequency determination unit, 21: Drive signal generation circuit, 22: Booster circuit
23: Phase difference determination unit, 24: Amplitude determination unit

Claims (5)

Elastic body and an electric secured to elastic body - a vibrating body provided with a mechanical energy conversion element,
A driven body in contact with the elastic member, a vibration type driving apparatus having,
The electro-mechanical energy conversion element is adjacent to the first electrode for expanding and contracting the first area of the electro-mechanical energy conversion element, and the first area of the electro-mechanical energy conversion element. A second electrode for expanding and contracting the second region,
The vibrating body includes a first bending vibration mode in which both the first region and the second region expand or contract, and the second region contracts when the first region extends, A second bending vibration mode in which the second region expands when the first region contracts ,
A vibration type driving apparatus, wherein the vibration body and the driven body are driven relatively by vibration generated by a combination of the first bending vibration mode and the second bending vibration mode. 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 vibrating body, and the second bending vibration mode is a secondary vibration mode in the longitudinal direction of the vibrating body. The vibration-type drive device according to claim 1 . A vibration type driving apparatus according to claim 1 or 2, a control system and a control device for controlling the driving of the vibration type driving apparatus,
The control device changes a relative driving direction of the vibrating body and the driven body by changing a phase difference between two-phase driving voltages applied to the first electrode and the second electrode. A control system characterized by A vibration type driving apparatus according to claim 1 or 2, a control system and a control device for controlling the driving of the vibration type driving apparatus,
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 two-phase driving voltages applied to the first electrode and the second electrode. A control system characterized by A vibration type driving apparatus according to claim 1 or 2, a control system and a control device for controlling the driving of the vibration type driving apparatus,
The controller controls the first bending vibration mode and the second bending vibration mode with respect to a change in phase difference between two-phase driving voltages applied to the first electrode and the second electrode. The amplitude of the drive voltage can be set so that the vibration amplitude in one bending vibration mode becomes constant and the vibration amplitude in the other bending vibration mode changes, and the first electrode and the second electrode A control system, wherein a relative driving speed or a driving direction of the vibrating body and the driven body is changed by changing a phase difference between two-phase driving voltages applied to the electrodes .

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