Vibration type driving device, vibration type actuator control device and device

Abstract

To reduce power consumption when driving a vibration type actuator.SOLUTION: A vibration type drive device 10 comprises a vibration type actuator 200 and a control device 100. The vibration type actuator 200 includes a vibration body 210, which is configured by joining an elastic body 212 and a piezoelectric element 211, and a contact body 220 in contact with the elastic body 212. The control device 100 includes a drive unit 120 including a transformer 1222, which transforms an input signal into an AC voltage to be applied to the piezoelectric element 211, and a control unit 110 which controls a frequency, a phase and a voltage of the input signal. When a frequency in which a primary-side current of the transformer 1222 becomes minimal is defined as f1 and a resonant frequency of unwanted vibration is defined as fu, a relation of 0.79≤f1 / fu≤1.21 is satisfied.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a vibration type driving device, an electronic device and an optical device that include a vibration type driving device, and a control device for a vibration type actuator. [Background technology]

[0002] A vibration actuator is a non-electromagnetically driven actuator (motor) that is configured to bring a contact body into contact with a vibrating body, and extract the vibration energy of high-frequency vibrations generated in the vibrating body as mechanical motion that moves the contact body and the vibrating body relative to each other. The vibrating body is generally configured by joining an electromechanical energy conversion element such as a piezoelectric element to an elastic body. The control device that controls the drive of the vibration actuator has a pulse signal generation circuit that generates a pulse signal and a boost circuit that applies AC voltage amplified by a transformer to the electromechanical energy conversion element.

[0003] A vibration actuator can control the relative movement speed between a contact body and a vibrating body by adjusting the frequency, amplitude, and phase difference of an AC voltage applied to an electromechanical energy conversion element. Therefore, a vibration actuator is used, for example, to drive a focus lens for performing autofocus operations in an imaging device, which is an optical device.

[0004] Autofocusing requires highly accurate positioning control. Generally, a focus lens is controlled to stop at a target position after accelerating, moving at a constant speed, and decelerating using a position sensor or other means, such as position feedback control. In this case, it is desirable to reduce power consumption in the control device and increase the drive efficiency of the focus lens. To achieve this, it is important to design a boost circuit (resonant circuit) that utilizes the electrical resonance of the electromechanical energy conversion element in the drive circuit. When using a boost circuit using a transformer, the circuit constants must be adjusted to match the frequency range used to drive the vibration actuator. Adjusting the circuit constants requires consideration of not only electrical elements such as the transformer, coil, and capacitor, but also the equivalent coil and equivalent capacitor of the mechanical vibration part of the vibrating body. In response to this, for example, Patent Document 1 describes a control device configured so that the parallel resonance frequency generated by the capacitance of the piezoelectric element and the output coil of the boost transformer is between the motor's resonance frequency and the frequency at which the motor's amplitude characteristics first reach their lowest level.

[0005] The drive circuit described in Patent Document 1 can reduce voltage fluctuations in the transformer output in a frequency range slightly higher than the resonant frequency. However, in terms of power consumption, it only manages to keep the reactive current of the vibration actuator low, and a boost circuit that can achieve a greater reduction in power consumption is desired. Note that the reactive current refers to the current that flows through the capacitance of the electromechanical energy conversion element, and is a current component that does not contribute to vibration. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 2879220 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a vibration-type driving device that can reduce power consumption when driving a vibration-type actuator. [Means for solving the problem]

[0008] The vibration type driving device according to the present invention comprises a vibration type actuator having a vibrating body having an elastic body and an electromechanical energy conversion element, and a contact body that comes into contact with the elastic body, wherein the vibrating body and the contact body move relative to each other when the vibrating body vibrates; a control device having a drive unit provided with a transformer that transforms a drive signal generated in response to an input control signal, the drive signal being input to a primary side of the transformer and the secondary side of the transformer being connected to the electromechanical energy conversion element; A vibration type driving device comprising: When the frequency of the drive signal at which the current flowing to the primary side of the transformer becomes minimum is defined as f1, and the resonant frequency of a vibration mode other than the vibration used for the relative movement between the vibrating body and the contact body, which is greater than f1, is defined as fu, At -30°C 0.79≦f1 / fu≦1.21, The above relationship is satisfied. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the power consumption when driving the vibration type actuator. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of a vibration-type driving device according to a first embodiment. [Figure 2] 2A and 2B are diagrams illustrating a schematic configuration and vibration modes of a vibration actuator that constitutes the vibration driving device of FIG. 1. [Figure 3] 1 is a diagram illustrating the admittance-frequency characteristics of a vibrating body that constitutes a vibration type actuator of the present invention. [Figure 4]FIG. 2 is a circuit diagram of a drive circuit that constitutes the vibration-type drive device of FIG. [Figure 5] 5A and 5B are diagrams illustrating variations of the drive circuit of FIG. 4, (a) a third embodiment, and (b) a fourth embodiment. [Figure 6] 5 is a diagram illustrating a pulse signal output from a pulse signal generating circuit of the drive circuit of FIG. 4. [Figure 7] 5 shows the calculation results of the current flowing through the transformer primary coil of the drive circuit of FIG. 4. (a) Example 11, (b) Example 9, and (c) Comparative Example 1 [Figure 8] 10A and 10B are diagrams showing the driving characteristics of the vibration type driving devices of Comparative Example 1 and Comparative Example 2, respectively. [Figure 9] 13A and 13B are diagrams showing the driving characteristics of the vibration type driving devices of Example 9 and Example 10, respectively. [Figure 10] FIG. 2 is a perspective view showing a schematic structure of a lens driving mechanism. [Figure 11] FIG. 10 is a diagram showing another configuration of a vibration type actuator. [Figure 12] FIG. 10 is a diagram showing yet another configuration of the vibration type actuator. [Figure 13] FIG. 1 is a diagram illustrating an example of an apparatus including a vibration-type driving device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, a "vibration-type driving device" includes a "vibration-type actuator" and a "controller," a "vibration-type actuator" includes a "vibrating body" and a "contact body," and a "vibrating body" includes an "elastic body" and an "electromechanical energy conversion element." Furthermore, when a vibration-type actuator is driven, the vibrating body and the contact body move relative to each other, but for the sake of convenience, it is assumed that the vibrating body is fixed in a predetermined position and the contact body is movable relative to the vibrating body.

[0012] The vibration-type driving device according to this embodiment includes a vibrating body having an elastic body and an electromechanical energy conversion element, a contact body that contacts the elastic body, a vibration-type actuator that causes relative movement between the vibrating body and the contact body as the vibrating body vibrates, and a control device that includes a driving unit including a transformer that transforms a drive signal generated in response to an input control signal, the drive signal being input to the primary side of the transformer and the secondary side of the transformer being connected to the electromechanical energy conversion element.

[0013] When the frequency of the drive signal at which the current flowing to the primary side of the transformer is minimized is defined as f1, and the resonant frequency of a vibration mode other than the vibration used for the relative movement between the vibrating body and the contact body, which is greater than f1, is defined as fu, the following relationship is satisfied:

[0014] That is, the relationship 0.79≦f1 / fu≦1.21 is satisfied.

[0015] First Embodiment 1 is a block diagram showing a schematic configuration of a vibration-type driving device 10 according to the first embodiment. The vibration-type driving device 10 includes a vibration-type actuator 200 and a control device 100 that controls the driving of the vibration-type actuator 200. The control device 100 includes a control unit 110 that generates a control signal, a drive unit 120 that receives the control signal and outputs an AC signal to be applied to the vibration-type actuator 200, and a position sensor 130. The control unit 110 includes a command unit 111, a control calculation unit 112, and a relative position detection unit 113. The drive unit 120 includes a pulse signal generation circuit 121 and a boost circuit 122. The vibration-type actuator 200 includes a vibrating body 210 and a contact body 220.

[0016] The position sensor 130 is, for example, an encoder, and detects the position of the contact body 220. The position sensor 130 may be provided in the vibration actuator 200 as hardware separate from the control unit 110 and the drive unit 120. Here, it is treated as being included in the control device 100 as a component necessary for controlling the vibration actuator 200.

[0017] The command unit 111 generates a position command value for the contact body 220 for each time period and sends it to the control calculation unit 112. The relative position detection unit 113 detects the position of the contact body 220 based on the output signal from the position sensor 130, and sends the detected position signal to the control calculation unit 112. The control calculation unit 112 calculates the position deviation between the position command value input from the command unit 111 and the position signal input from the relative position detection unit 113, converts it into a control signal, and outputs it to the drive unit 120. Note that the control signal is an AC voltage V applied to a piezoelectric element 211 (see FIG. 2) described below that constitutes the vibrating body 210. A ,V B The control parameters are the control parameters of the pulse signal for generating a phase difference, frequency, or pulse width (described later with reference to FIG. 2). These control parameters are the phase difference, frequency, or pulse width, and are generated based on the position deviation. The relative drive speed and drive direction of the contact body 220 and the vibrating body 210 are controlled based on the control amount of each control parameter of the phase difference, frequency, and pulse width output from the control unit 110. In this way, the control unit 110 performs position feedback control, which controls the drive of the vibration actuator 200 based on the deviation between the position command value and the actual position of the contact body 220 at each predetermined time.

[0018] The control calculation unit 112 may be, for example, a PID calculator, but is not limited to this. Here, the configuration is such that position feedback control is performed, but the configuration is not limited to this and may be such that velocity feedback control is performed based on velocity deviation. Furthermore, in consideration of the objective of reducing power consumption when driving the vibration actuator 200, the configuration may be such that open drive control is performed without feedback control.

[0019] The pulse signal generating circuit 121 generates pulse signals with different phases (A-phase pulse signal, A-phase inversion pulse signal, B-phase pulse signal, and B-phase inversion pulse signal (see FIG. 6)) based on control signals (control amounts of phase difference, frequency, and pulse width) and outputs them to the boost circuit 122. The boost circuit 122 boosts the input signal, which is generated by switching a DC power supply with the input pulse signal, to a predetermined voltage using a transformer, thereby generating two-phase AC voltages V with approximately sinusoidal waveforms and different phases. A ,V B Generate.

[0020] AC voltage V A ,V B When vibrations, which will be described later, occur in the vibrating body 210, the contact body 220 moves in a predetermined direction due to the frictional driving force received from the vibrating body 210. The position of the contact body 220 is detected by the position sensor 130, and a detection signal is sent to the relative position detection unit 113. In this way, as described above, position feedback control of the vibration actuator 200 is performed so that the actual position of the contact body 220 follows the position command value for each time period.

[0021] 2A and 2B are diagrams illustrating the schematic configuration of a vibration actuator 200 and the vibration modes excited in a vibrating body 210. Fig. 2A is a perspective view showing the schematic configuration of the vibration actuator 200. The vibrating body 210 constituting the vibration actuator 200 has a substantially rectangular plate-shaped elastic body 212 and a substantially rectangular plate-shaped piezoelectric element 211 bonded to one surface of the elastic body 212 using an adhesive or the like. The other surface of the elastic body 212 (the surface opposite to the surface to which the piezoelectric element 211 is bonded) has protrusions 213 provided in two locations.

[0022] FIG. 2(b) is a diagram showing an electrode pattern provided on the piezoelectric element 211.

[0023] 2(c) and 2(d) are diagrams explaining the first vibration mode and the second vibration mode excited in the vibrating body 210, respectively, and FIG. 2(e) and FIG. 2(f) are diagrams explaining unwanted vibration modes.

[0024] The direction connecting two protrusions 213 in vibrating body 210 is defined as the X direction, the thickness direction of elastic body 212 as the Z direction, and the direction perpendicular to the X and Z directions as the Y direction.

[0025] Two electrode regions, which are divided into approximately two equal parts in the longitudinal direction (X direction), are formed on the surface of piezoelectric element 211 opposite to the surface bonded to elastic body 212, and the polarization direction of the piezoelectric body in each electrode region is the same (+). Although not shown, one electrode (common electrode) is provided over approximately the entire surface of piezoelectric element 211 on the surface bonded to elastic body 212.

[0026] Of the two electrode regions of the piezoelectric element 211 in FIG. 2(b), the left electrode region is supplied with an AC voltage V A is applied to the right electrode area, and an AC voltage V B is applied.

[0027] AC voltage V A ,V B is set to a frequency near the resonant frequency of the vibrating body and in phase, the piezoelectric element 211 expands as a whole at one moment and contracts at another moment. As a result, the vibrating body 210 generates vibrations in a primary out-of-plane bending vibration mode (first vibration mode) in which two nodes appear in the vibrating body 1 approximately parallel to the X direction, as shown in Fig. 2(c).

[0028] Also, AC voltage V A ,V B is set at a frequency near the resonant frequency of the vibrating body and shifted in phase by 180°, one electrode area of ​​the piezoelectric element 211 contracts while the other electrode area expands at a certain moment, and the reverse relationship occurs at another moment. As a result, the vibrating body 210 generates vibrations in a secondary out-of-plane bending vibration mode (second vibration mode) in which three nodes appear in the vibrating body 210 approximately parallel to the Y direction, as shown in Figure 2(d).

[0029] In this way, the electromechanical energy conversion element has a first electrode and a second electrode adjacent to each other, and when the regions where the first electrode and the second electrode are provided are defined as a first region and a second region, respectively, it is configured to generate the following vibrations: a first bending vibration mode in which the first region and the second region both expand or contract, and a second bending vibration mode in which the second region contracts or expands when the first region expands or contracts, respectively.

[0030] On the other hand, AC voltage V A ,V B are configured to have frequencies near the resonance frequency of the unwanted vibration mode, which are higher than the frequencies of the first and second vibration modes, and are shifted in phase by 180°. With this configuration, at a certain moment, one electrode area of ​​the piezoelectric element 211 contracts while the other electrode area expands, and at another moment, the opposite relationship occurs. As a result, the vibrating body 210 generates vibrations in an out-of-plane bending vibration mode (unwanted vibration mode) as shown in FIG. 2(e).

[0031] 2(f), there are two nodal lines X1 and X2 that are approximately parallel to the X direction of the elastic body, and one nodal line Y1 that is approximately parallel to the Y direction. The single approximately parallel nodal line Y1 means that the nodal line Y1 is a continuous curve that intersects with the two long sides of the elastic body 212 and is arranged in parallel with the short sides of the elastic body 212 without intersecting with them.

[0032] The two nodal lines X1 and X2 that are approximately parallel to the X direction of the elastic body 212 mean that the nodal lines X1 and X2 are continuous curves that intersect with the two short sides of the elastic body 212, but do not intersect with each other, and are arranged in parallel with the long sides without intersecting with the long sides.

[0033] In other words, when unwanted high-order bending vibration occurs, the flat surface of elastic body 212 is divided into three in the short direction of elastic body 212 and into two in the long direction of elastic body 212, resulting in a total of six regions. Within each of these regions, there is a maximum amplitude in the out-of-plane vibration of the flat surface of elastic body 212. Furthermore, in adjacent regions of these six regions, the vibrations at the maximum amplitude have opposite phases.

[0034] Generally, the vibration of a plate (plate-like body) can be expressed in terms of an (m,n) vibration mode. For example, in the case of a square or rectangular plate, the vibration mode can be expressed as an (m,n) vibration mode depending on the number of nodes in the standing wave of the vibration in the vertical and horizontal directions. A mode with no nodes is expressed as a primary mode, and a mode with one node is expressed as a secondary mode. That is, in the case of a rectangular plate, a vibration mode with m-1 nodes in the vertical direction and n-1 nodes in the horizontal direction is expressed as an (m,n) vibration mode. The vibration mode at each resonant frequency can be identified by exciting the plate at the resonant frequency, measuring the vibration at multiple locations on the plate using a laser Doppler vibrometer, etc., and comprehensively analyzing the obtained vibration data and observing it using animation, etc. In this embodiment, if the unwanted vibration mode is expressed as an (m,n) vibration mode, it can be expressed as a (2,3) vibration mode.

[0035] Here, the two protrusions 213 are disposed near positions that are antinodes of vibration in the first vibration mode and near positions that are nodes of vibration in the second vibration mode. Therefore, they are excited and overlapped so that the vibration phase difference between the first vibration mode and the second vibration mode is approximately ±π / 2. By doing so, the tip of the protrusion 213 performs a pendulum motion with the node of vibration in the second vibration mode as a fulcrum, reciprocating in the X direction, and also reciprocating in the Z direction due to vibration in the first vibration mode. This causes an elliptical motion in the XZ plane on the tip surface of the protrusion 213, applying a frictional driving force to the contact body 220 in contact with the tip surface of the protrusion 213, thereby driving the contact body 220 in the positive or negative direction in the X direction. At this time, the AC voltage V A ,V BBy changing the phase difference or the like, the driving speed of the contact body 220 can be adjusted.

[0036] The unwanted vibration mode is AC voltage V A , V B As the phase difference increases from 0 to π, the amplitude increases, reaching a maximum when the phase difference is 180°. In the unwanted vibration mode, the protrusion 213 vibrates in the Z direction and does not produce elliptical vibration in the XZ plane. Therefore, in the unwanted vibration mode, the contact body does not achieve sufficient speed, but when the unwanted vibration mode is excited, power is consumed. The power consumed by the unwanted vibration is superimposed on the power consumed by the drive vibration.

[0037] That is, AC voltage V A , V B By setting the phase difference between 0° and 180°, the first vibration mode and the second vibration mode are superimposed, and the contact body 220 in contact with the protrusion 213 can be moved in the X direction, but at the same time, an unwanted vibration mode whose resonance frequency is close to the drive vibration is also excited.

[0038] The present invention provides a drive circuit for suppressing the power resulting from this unwanted vibration.

[0039] In this example, a piezoelectric element is used as the electromechanical energy conversion element, and a two-phase AC voltage V A ,V B However, the control device 100 can also be applied to driving and controlling a vibration-type actuator driven by an AC voltage of three or more phases.

[0040] Piezoelectric elements are composed of a piezoelectric material and electrodes. Lead zirconate titanate (Pb(Zr,Ti)O3) is generally used as the piezoelectric material, due to its excellent piezoelectric properties. However, it has been pointed out that lead may leach into the soil and cause harm to ecosystems. Therefore, piezoelectric materials with a lead content of less than 1000 ppm can also be used. A lead content of less than 1000 ppm is preferable, as its impact on the environment is essentially negligible.

[0041] Piezoelectric materials with a lead content of less than 1000 ppm are preferably made of barium titanate-based materials, due to their high piezoelectric constant and ease of manufacture. Here, barium titanate-based materials refer to compositions such as barium titanate (BaTiO3), barium calcium titanate ((Ba,Ca)TiO3), barium zirconate titanate (Ba(Ti,Zr)O3), barium calcium zirconate titanate ((Ba,Ca)(Ti,Zr)O3), sodium niobate-barium titanate (NaNbO3-BaTiO3), sodium bismuth titanate-barium titanate ((Bi,Na)TiO3-BaTiO3), and bismuth potassium titanate-barium titanate ((Bi,K)TiO3-BaTiO3), as well as materials primarily composed of these compositions.

[0042] Among these, barium calcium titanate zirconate ((Ba,Ca)(Ti,Zr)O3, hereafter referred to as BCTZ) is preferred as the main component, from the viewpoint of achieving both the piezoelectric constant and mechanical quality factor of the piezoelectric ceramic. The term "main component" refers to a material whose weight fraction is greater than 50%. Furthermore, Mn and / or Bi may be included as elements other than the main component in order to improve the mechanical quality factor or adjust the phase transition temperature.

[0043] Specifically, BCTZ is a piezoelectric material containing an oxide with a perovskite structure containing Ba, Ca, Ti, and Zr, and Mn. The molar ratio x of Ca to the sum of Ba and Ca is 0.02≦x≦0.30. Furthermore, the molar ratio y of Zr to the sum of Ti and Zr is preferably 0.020≦y≦0.095, and y≦x. The ratio α of the molar amounts of Ba and Ca to the molar amounts of Ti and Zr is preferably 0.9955≦α≦1.01, and the Mn content per 100 parts by weight of oxide is preferably 0.02 parts by weight or more and 1.0 parts by weight or less, calculated as metal. Such a piezoelectric material can be expressed by the following general formula (1): (Ba 1-x Ca x ) α (Ti1-y Zr y )O3 general formula (1) however, 0.986≦α≦1.100, 0.02≦x≦0.30, 0.02≦y≦0.095

[0044] In general formula (1), x, which represents the molar ratio of Ca at the A site, is in the range of 0.02≦x≦0.30. Substituting a portion of the Ba in perovskite-type barium titanate with Ca within this range shifts the phase transition temperature between orthorhombic and tetragonal crystals to a lower temperature, thereby enabling stable piezoelectric vibration within the operating temperature range of the vibration actuator. However, if x is greater than 0.30, the piezoelectric constant of the piezoelectric material may be insufficient, potentially resulting in insufficient performance of the vibration actuator. On the other hand, if x is less than 0.02, the dielectric loss (tan δ) may increase. Increased dielectric loss may increase heat generation when applying voltage to the piezoelectric material to drive the vibration actuator, reducing motor drive efficiency and increasing power consumption.

[0045] In general formula (1), y, which represents the molar ratio of Zr in the B site, is in the range of 0.02≦y≦0.1. If y is greater than 0.1, the depolarization temperature Td becomes low, below 80°C, and the temperature range in which the vibration actuator can be used becomes below 80°C, which is undesirable.

[0046] In this specification, the depolarization temperature Td refers to the lowest temperature at which the piezoelectric constant of a piezoelectric material, when heated from room temperature to Td one week after polarization treatment and then cooled back to room temperature, decreases by more than 10% compared to the piezoelectric constant before heating.

[0047] Furthermore, in general formula (1), α, which represents the ratio of the molar amounts of Ba and Ca at the A site to the molar amounts of Ti and Zr at the B site, is preferably in the range of 0.9955≦α≦1.010. This is because, within this range, abnormal grain growth is less likely to occur and mechanical strength is good. On the other hand, if α is less than 0.9955, abnormal grain growth is more likely to occur in the crystal grains that make up the piezoelectric material, which may reduce the mechanical strength of the piezoelectric material. On the other hand, if α is greater than 1.010, the piezoelectric material may not be densified and may become significantly brittle.

[0048] In general formula (1), the molar ratio of the B-site element to the O element is 1:3, but even if the molar ratio is slightly different, the metal oxide is within the scope of the present invention as long as it has a perovskite structure as the main phase. Whether the metal oxide has a perovskite structure can be determined, for example, by structural analysis using X-ray diffraction or electron beam diffraction.

[0049] The Mn content is preferably 0.02 to 0.40 parts by weight in terms of metal per 100 parts by weight of the metal oxide. A Mn content within this range improves the insulating properties and mechanical quality factor Qm. Here, the mechanical quality factor Qm is a coefficient that represents the elastic loss due to vibration when evaluating a piezoelectric material as a vibrator, and the magnitude of the mechanical quality factor is observed as the sharpness of the resonance curve in impedance measurement. In other words, it is a constant that represents the sharpness of the vibrator's resonance. A larger mechanical quality factor Qm results in a larger amount of strain in the piezoelectric material near the resonance frequency, allowing the piezoelectric material to vibrate more effectively.

[0050] The metal equivalent indicating the Mn content is calculated by converting the elements constituting the metal oxide represented by general formula (1) into oxides from the contents of each of the metals Ba, Ca, Ti, Zr, and Mn, and expressing the relative weight of Mn when the total weight is taken as 100.

[0051] If the Mn content is less than 0.02 parts by weight, the polarization effect required to drive the vibration actuator may be insufficient, while if the Mn content is more than 0.40 parts by weight, the piezoelectric properties of the piezoelectric material may be insufficient or hexagonal crystals without piezoelectric properties may appear.

[0052] Mn is not limited to metallic Mn, and may be contained in the piezoelectric material as a Mn component, regardless of the form of inclusion. For example, Mn may be solid-solved in the B site or contained in the grain boundaries. Alternatively, the Mn component may be contained in the piezoelectric ceramic 1 in the form of metal, ions, oxide, metal salt, complex, or the like. From the viewpoints of insulation properties and ease of sintering, a more preferable form of inclusion is solid-solubilization in the B site.

[0053] Furthermore, the piezoelectric material preferably contains 0.042 to 0.850 parts by weight of Bi, calculated as a metal. The piezoelectric material may contain 0.85 parts by weight or less of Bi, calculated as a metal, per 100 parts by weight of the metal oxide represented by general formula (1). Bi may be present at the grain boundaries of the ceramic piezoelectric material, or may be dissolved in the perovskite structure of (Ba,Ca)(Ti,Zr)O3. The addition of Bi increases the mechanical quality factor and lowers the successive phase transition temperature, thereby reducing the temperature dependence of the piezoelectric constant.

[0054] The piezoelectric material may contain components (hereinafter referred to as minor components) other than the elements contained in the general formula (1) and Mn and Bi, as long as the properties are not affected. The total amount of the minor components is preferably less than 1.2 parts by weight per 100 parts by weight of the metal oxide represented by the general formula (1). If the amount of the minor components exceeds 1.2 parts by weight, the piezoelectric properties and insulating properties of the piezoelectric material may be degraded.

[0055] The method for measuring the composition of a piezoelectric material is not particularly limited. Examples of methods include X-ray fluorescence analysis, ICP atomic emission spectroscopy, and atomic absorption spectroscopy. Any of these methods can be used to calculate the weight ratio and composition ratio of each element contained in the piezoelectric material.

[0056] Figure 3 shows an example of the impedance characteristics of a vibrating body (the vertical axis is admittance). The horizontal axis is frequency, and the vertical axis is admittance excluding the loss component (=ωCd). When measuring admittance, the vibrating body is not in contact with the contact body, and is measured in a state where the vibrating body is able to vibrate freely. The frequency at which the admittance peaks corresponds to the frequency of each vibration mode, and indicates the ease with which current flows, i.e., the magnitude of the vibration mode. This characteristic can be measured using an impedance analyzer or similar device, by applying a small-amplitude AC signal (for example, 50 to 500 mV) to the piezoelectric element and performing a frequency analysis of the response results.

[0057] The first and second vibration modes shown in Figure 2 above are two driving vibrations with peaks at frequencies between 95 and 105 kHz. In order to excite and utilize both the first and second vibration modes at a certain frequency, the frequency difference (Δf) between the first and second vibration modes when the vibrator is not pressurized by the contact body is preferably 1 to 3 kHz. The second vibration mode is located at a higher frequency than the first vibration mode. The resonant frequency varies depending on the shape of the piezoelectric element and elastic body used.

[0058] The unwanted vibration mode shown in Fig. 2 above is a vibration whose peak appears at frequencies of 115 to 125 kHz. The frequency at which this admittance is maximized is the resonant frequency fu of the unwanted vibration. The resonant frequency difference (Δf2) between fu and the second vibration mode is preferably 15 to 25 kHz, and the unwanted vibration mode is located at a higher frequency than the second vibration mode.

[0059] A part of the frequency band between the higher of the resonant frequencies of the first and second vibration modes and the resonant frequency fu of the unwanted vibration mode is the frequency range used to drive the vibration actuator 200.

[0060] Furthermore, by performing an equivalent circuit analysis of the vibrating body using the measurement results, it is possible to determine the equivalent circuit constants of the drive vibration and unwanted vibration, which will be described later. This measurement is performed by changing the temperature of the vibrating body 210 as necessary, and the equivalent circuit constants for each temperature are determined.

[0061] The frequency of each vibration mode varies depending on the density, Young's modulus, and shape of the piezoelectric element and elastic body.

[0062] FIG. 4 is a circuit diagram of the driver 120 constituting the vibration-type driving device of the present invention. The equivalent circuit of the vibrating body 210 is composed of an RLC series circuit corresponding to the mechanical vibration of the vibrating body 210 and the capacitance Cd 214 of the piezoelectric element 211 connected in parallel to the RLC series circuit. In FIG. 4, elements represented by two RLC series circuits corresponding to the drive vibration and the unwanted vibration are shown in parallel with the capacitance 214. The vibration-type actuator of the present invention is driven using the first and second vibration modes described above with reference to FIG. 2. However, when the vibrating body is pressed against a contact body and excited, the frequencies of both vibration modes roughly overlap. Therefore, in the equivalent circuit, the first and second vibration modes are combined and described below as an element responsible for a single drive vibration. In the following description, the frequency at which the admittance is maximized by the first vibration mode is defined as the drive frequency fm.

[0063] (equivalent circuit constants) An RLC series circuit consists of an equivalent coil, an equivalent capacitor, and an equivalent resistor. The capacitance, inductance, and resistance corresponding to the elements responsible for the drive vibration are designated Lm, Cm, and Rm, respectively. The equivalent circuit constants (Lm, Cm, Rm) for the drive vibration can be determined by generating the first vibration mode in the vibrating body, detecting the admittance change at that time, and analyzing the detection results using an equivalent circuit. The first vibration mode has a larger change in admittance than the second vibration mode, so the two can be distinguished.

[0064] The equivalent circuit constants (Lu, Cu, Ru) of the unwanted vibration can be obtained by equivalent circuit analysis of the admittance change due to the unwanted vibration mode.

[0065] The capacitance Cd214 is the capacitance when a signal having a frequency (for example, 1 kHz) sufficiently separated from mechanical vibration is applied to the piezoelectric element.

[0066] (transformer) The step-up transformer 1222 has a magnetically coupled primary coil 1222a and secondary coil 1222b. When a current flows through the primary coil 1222a, a magnetic flux is generated, and a current inductively flows through the secondary coil 1222b, generating a transformed voltage.

[0067] In the transformer 1222 of this embodiment, the number of turns of the secondary coil 1222b is several to 22 times that of the primary coil 1222a, and the voltage amplitude on the primary side is amplified according to the ratio of the number of turns.

[0068] The current flowing through the primary coil 1222a of the transformer 1222 is an AC current that flows from the power supply side of the pulse signal generating circuit 121 to the GND side through the coil 1221 and the primary coil 1222a via a selected switching element. Therefore, the power consumption on the primary side of the transformer 1222 varies depending on the on-resistance of the switching element and the resistance components and current values ​​of the coil 1221 and the primary coil 1222a. Due to the turn ratio of the transformer 1222, in this embodiment, the primary current is larger than the secondary current, resulting in larger power consumption. On the other hand, the current flowing on the secondary side of the transformer 1222 is an AC current that flows through at least one of the capacitance Cd214 of the piezoelectric element 211 and the mechanical vibration part (RLC series circuit) via the secondary coil 1222b.

[0069] (electrical resonance frequency) The electrical resonance frequency fe of the vibration type driving device in this embodiment can be adjusted by the transformer 1222, the coil 1221, and the capacitance Cd214 of the piezoelectric element. By adjusting the electrical resonance frequency fe, the voltage V A and V B You can adjust the size of the

[0070] Equation 1 expresses the electrical resonance frequency fe.

[0071]

number

[0072] Here, 'Le' is the inductance of coil 1221, 'L1' is the inductance of transformer primary coil 1222a, 'L2' is the inductance of transformer secondary coil 1222b, and 'M' is the mutual inductance of transformer 1222, which is expressed by the following equation 2. 'Cd' is the electrostatic capacitance of piezoelectric element 214.

[0073]

number

[0074] It is preferable that the electrical resonance frequency fe is higher than the drive frequency by a certain amount. For example, if it is in the range of 1.4 to 1.8 times the center value of the drive frequency range, power consumption due to unwanted vibrations and harmonics can be kept low, which is preferable. If fe is less than 1.4 times, the voltage applied to the unwanted vibration mode increases, increasing the power due to unwanted vibrations. On the other hand, if fe is more than 1.8 times the drive frequency, the harmonics generated by the power supply in addition to the fundamental wave are boosted, increasing the power.

[0075] The electrical resonance frequency fe can also be adjusted by changing the inductance Le of the coil 1221. Alternatively, in order to adjust fe, a capacitor may be connected in parallel to the vibrating body on the secondary side of the transformer 1222. Figure 5(a) shows a circuit 501A in which a capacitor is connected in parallel to the piezoelectric element on the secondary side of the transformer 1222.

[0076] 4 shows a vibration-type driving device having one vibrating body 210 as a representative example, but multiple equivalent vibrating bodies may be prepared to drive one contact body. For example, an equivalent circuit for a composite vibrating body 2103 consisting of three vibrating bodies 210 is shown as circuit 501B in FIG. 5(b).

[0077] In addition, in Figure 4, the AC voltage V A Only the circuit configuration for generating the AC voltage V is shown. BThe circuit configuration for generating the AC voltage V is not shown. B The circuit configuration to generate the AC voltage V A Since the circuit configuration for generating the signal .DELTA..times ...

[0078] Next, the pulse signal generating circuit will be described with reference to FIG.

[0079] (Pulse signal generating circuit) The driving unit 120 is generally composed of a pulse signal generating circuit 121 and a boost circuit 122. The pulse signal generating circuit 121 has an oscillator that generates a pulse signal and a switching circuit (H-bridge circuit) that switches a DC power supply by the pulse signal output from the oscillator, and an AC pulse signal Vi is output from the switching circuit.

[0080] 6(a) is a timing chart of a pulse signal output from an oscillator of pulse signal generating circuit 121. The oscillator outputs an A-phase pulse signal (A+) and an A-phase inverted pulse signal (A-) that is 180 degrees out of phase with the A-phase pulse signal, based on a control signal having information on the phase difference, frequency, and pulse width input from control unit 110. A DC-DC converter circuit (not shown) that supplies DC power is connected to the switching circuit, and the switching element is turned on / off by the pulse signal output from the oscillator to generate an AC pulse signal Vi that is an AC voltage with a rectangular wave and output it to boost circuit 122.

[0081] The pulse signal generating circuit 121 adjusts the pulse width (pulse duty) of the A-phase pulse signal and the A-phase inverted pulse signal by PWM (pulse width modulation) control so as to obtain an AC pulse signal Vi with a desired voltage amplitude. The pulse width is set based on a control signal input from the control unit 110. In addition, although a full-bridge driven switching circuit is used in this embodiment, the present invention is not limited to this, and a half-bridge driven switching circuit or the like may also be used.

[0082] The AC pulse signal Vi generated by the pulse signal generating circuit 121 is input to the boost circuit 122. The boost circuit 122 is composed of a coil 1221 and a transformer 1222 that form a resonant circuit together with the capacitance 214 of the piezoelectric element 211, and generates an AC voltage VA having a substantially sinusoidal waveform by boosting the AC pulse signal Vi to a desired output voltage Vo. Note that the polarity of the transformer 1222 may be either polarity or non-polarity.

[0083] The oscillator of the pulse signal generating circuit 121 outputs a B-phase pulse signal (B+) and a B-phase inverted pulse signal (B-) whose phase is shifted by 180 degrees from the B-phase pulse signal, based on a control signal having information on the phase difference, frequency, and pulse width from the control unit 110 (see FIG. 6(a)). A The AC voltage V is generated in the same way as B is generated.

[0084] 6(b) is a timing chart illustrating the phase difference between the A-phase pulse signal and the B-phase pulse signal. Here, an example is shown in which the A-phase pulse signal and the B-phase pulse signal both have a duty of 50% and a phase difference of +90 degrees. Note that the period from time t0 to t4 is one period of the frequency that drives the vibration actuator 200, and the rising edges of the A-phase pulse signal and the B-phase pulse signal are shifted by 1 / 4 period.

[0085] This embodiment is characterized in that attention is focused on the frequency f1 of the control signal at which the primary current of the transformer constituting the vibration type driving device is minimized, and the circuit constants of the driving unit 120 are set to match the frequency range used to drive the vibration type actuator 200. By making the frequency f1 and the resonant frequency fu of the unwanted vibrations coincide with or approach each other, it is possible to reduce the power consumption of the boost circuit 122 in the driving frequency range.

[0086] That is, in the vibration type driving device of this embodiment, the ratio of the resonant frequency fu of the unwanted vibration to the frequency f1, f1 / fu, is set to satisfy the relationship 0.79≦f1 / fu≦1.21, and by being configured in this manner, power consumption can be reduced.

[0087] FIG. 7 shows the frequency characteristics of the transformer primary current when the vibration-type driving device of this embodiment is driven.

[0088] The vibration type driving devices corresponding to FIGS. 7(a), 7(b), and 7(c) all have the same vibration type actuator, but differ in the coil 1221 and the transformer 1222 in the driving section.

[0089] In this embodiment, the frequency f1 can be calculated using circuit simulation software (collectively called SPICE). When using circuit simulation software, the frequency f1 can be easily calculated even when the vibrating body has multiple RLC series circuits, i.e., multiple mechanical vibration modes.

[0090] The frequency f1 can be calculated simply by using the following equation 3. That is, the inductance Lm215a of the drive vibration equivalent coil, the capacitance Cm216a of the drive vibration equivalent capacitor, the electrostatic capacitance Cd214, and the inductance L2 of the transformer secondary coil 1222B are substituted into the following equation 3.

[0091] According to Equation 3, frequency f1 is a function of parameters related to vibrating body 210 and inductance L2 of secondary coil 1222b of transformer 1222. In other words, frequency f1 can be adjusted by changing inductance L2 without changing vibrating body 210. In the present invention, frequency f1 derived by either of these methods can be used.

[0092]

number

[0093] Referring to FIG. 7, in addition to the reduction in current corresponding to the driving vibration and the unwanted vibration, a reduction in current corresponding to frequency f1 can be seen.

[0094] The vertical axis of the graph in Fig. 7(a) represents the current flowing through the transformer primary coil 1222a in Example 11. f1 is 111.5 kHz (f1 / fu = 0.93) for an unwanted vibration frequency of 120 kHz. In Fig. 7(a), f1 is located between the drive vibration and the unwanted vibration.

[0095] The vertical axis of the graph in Fig. 7(b) represents the current flowing through the transformer primary coil 1222a in Example 9. f1 is 144.9 kHz (f1 / fu = 1.21) for an unwanted vibration frequency of 120 kHz. In Fig. 7(b), f1 is located at a higher frequency than the drive vibration.

[0096] In both Figures 7(a) and 7(b), the relationship 0.79≦f1 / fu≦1.21 is satisfied, and by arranging f1 to coincide with or be close to fu, power consumption due to unwanted vibrations can be suppressed.

[0097] Furthermore, by setting f1 to be equal to or greater than 86.9 kHz and less than 152.1 kHz, it is possible to drive the vibration actuator while more effectively suppressing power consumption.

[0098] (Temperature dependence of electrical resonance) The capacitance Cd214 of the piezoelectric element and the equivalent circuit constants of the mechanical vibration have some temperature dependency, so the frequency f1 changes depending on the temperature at which the vibration actuator is driven. In particular, when the piezoelectric element is made of a piezoelectric material that has a successive phase transition at temperatures lower than room temperature, f1 changes significantly depending on the ambient temperature.

[0099] The vibration actuator of this embodiment is preferably configured so that f1 and the resonance frequency fu of unwanted vibrations satisfy the relationship 0.79≦f1 / fu≦1.21 even at −30° C. Configuring the vibration actuator in this way allows it to be used in low-temperature environments and can be used for general purposes without temperature adjustment.

[0100] When the piezoelectric element 211 is made of the above-mentioned BCTZ, when the temperature of the piezoelectric element is lowered from room temperature to −30° C., the vibration characteristics of the piezoelectric element 211 change compared to those at room temperature.

[0101] Explaining using each element shown in FIG. 4, the capacitance Cd, the inductance corresponding to the equivalent coil of vibration, the capacitance corresponding to the equivalent capacitor, and the resistance value corresponding to the equivalent resistance change. As a result, the frequency f1 at which the current flowing through the primary side of the transformer becomes extremely small in an environment of -30°C shifts to the lower frequency side with respect to f1 at room temperature.

[0102] That is, f1(-30°C) < f1(room temperature).

[0103] The resonance frequency fu of unnecessary vibration also shifts to the lower frequency side at low temperature, but since the shift of f1 is larger, f1 / fu at -30°C becomes smaller than that at room temperature. If 0.91 ≦ f1 / fu ≦ 1.21 at room temperature, it is preferable because the relationship of 0.79 ≦ f1 / fu ≦ 1.21 can be satisfied even at -30°C.

[0104] Furthermore, it is preferable that 1.0 ≦ f1 / fu ≦ 1.21 because the power consumption caused by unnecessary vibration can be further suppressed. When f1 / fu is in the range of 1.0 ≦ f1 / fu ≦ 1.21, the current becomes extremely small on the lower frequency side of the unnecessary vibration (FIG. 7(b)). Therefore, it is preferable because the power caused by unnecessary vibration can be further suppressed in the frequency region close to the driving vibration.

[0105] On the other hand, FIG. 7(c) shows the current flowing through the primary side coil 1222a of the vibration type driving device that does not satisfy the relationship of 0.79 ≦ f1 / fu ≦ 1.21 (Comparative Example 1).

[0106] Specifically, the frequency f1 is 80 kHz with respect to the frequency 120 kHz of unnecessary vibration (f1 / fu = 0.67). In this example, f1 / fu < 0.79, and referring to FIG. 7(c), the frequency f1 is far from the frequency fu on the lower frequency side. Therefore, in the frequency band from the frequency of the driving vibration near 100 kHz to the frequency of the unnecessary vibration of 120 kHz, no decrease in the primary side current value is observed. Thus, it can be seen that the effect of reducing the power consumption caused by unnecessary vibration cannot be obtained.

[0107] <Specific example of boost circuit design> In this embodiment, the boost circuit 122 is designed so that the frequency f1 at which the primary current of the transformer 1222 is minimized and the resonance frequency fu of the unwanted vibration satisfy the relationship 0.79≦f1 / fu≦1.21.

[0108] 8 and 9 are diagrams showing the relationship between the drive speed (movement speed of the contact body 220) and the power consumption when the frequency of the drive voltage is swept from high frequency to low frequency and the vibration actuator is driven.

[0109] In this embodiment, as explained with reference to Fig. 2(b), the phase difference between the drive voltages applied to the two electrodes of the piezoelectric element is set to 90°. Also, as mentioned above, the frequency of the drive voltage at which the admittance becomes maximum in the first vibration mode is set to the drive frequency fm.

[0110] 8 and 9, the frequency at which the velocity profile depicted by the solid line takes on a maximum value roughly corresponds to the drive frequency fm.

[0111] The speed is maximum in the vicinity of the drive frequency fm, and the power shows a local maximum value in the vicinity of the unwanted vibration frequency fu, which is in a frequency range approximately 15 to 25 kHz higher than the drive frequency fm.

[0112] 8(a) and 8(b) correspond to Comparative Examples 1 and 2, respectively. In Comparative Examples 1 and 2, f1 is not near the unwanted vibration frequency fu, and f1 / fu is smaller than 0.79. When the drive voltage frequency exceeds the unwanted vibration frequency fu, the power derived from the unwanted vibration gradually decreases relative to the drive voltage frequency. Therefore, in the drive region between fu and fm where the speed is greater than 0, the powers of both sources are superimposed and increase.

[0113] Furthermore, in this driving region, the power decreases as the driving frequency decreases, reaches a minimum value, and then increases as the driving vibration approaches. In other words, the sign of the power gradient with respect to the driving voltage frequency reverses at the frequency where the power is at a minimum. When the driving voltage frequency is changed by a certain amount, the power increases or decreases depending on the driving frequency region, making it difficult to control the power consumption at the driving voltage frequency.

[0114] Table 1 summarizes the parameters related to the vibrating body 210 and the parameters of the booster circuit 122.

[0115] In a vibration type actuator with good controllability, the power (P 25mm / s ) is the power (P 100mm / s ) is smaller than that of Comparative Examples 1 and 2. 25mm / s P 100mm / s It is larger and less controllable.

[0116] 9(a) and 9(b) correspond to Examples 9 and 10, respectively. Example 10 shows the state in which the vibration type actuator used in Example 9 is cooled to -30°C. In Examples 9 and 10, f1 is in the vicinity of the unwanted vibration frequency fu, and the relationship 0.79≦f1 / fu≦1.21 is satisfied. Therefore, when the drive voltage frequency exceeds the resonance frequency of the unwanted vibration, the power decreases more quickly with respect to the frequency and reaches a minimum value compared to Comparative Examples 1 and 2 (see FIG. 8), in which f1 / fu is outside the range of the present invention. Controllability is good, and P 25mm / s P 100mm / s is smaller than.

[0117] To reduce the power caused by unwanted vibrations, it is sufficient to increase the unwanted vibration frequency fu and move it away from fm. However, if the design of the vibrating body is changed to increase fu - fm, fu - fm increases and at the same time Δf decreases, making it smaller than 1 kHz. If Δf < 1 kHz, the drive characteristics of the vibration actuator will deteriorate significantly, which is not desirable.

[0118] Conversely, if fu-fm is too small, power caused by unwanted vibrations will be superimposed even more in the driving range. Therefore, it is preferable that fu-fm is 18.0 to 23 kHz, that is, the relationship 23≧fu-fm≧18 kHz is satisfied.

[0119] [Table 1]

[0120] In Table 1, the power consumption evaluation rank is expressed as a relative value on a four-level scale, based on the condition that results in the lowest power consumption, '1.0≦f1 / fu≦1.21'. 25mm / s >P 100mm / s Rank 3, Rank 2, Rank 1 25mm / s <P 100mm / s More specifically, in rank 3, P 100mm / s <575mw, P at rank 2 100mm / s <550mw, P at rank 1 100mm / s <500mW. Rank 1 is the lowest power consumption, while rank 4 is the highest.

[0121] As explained above, if the boost circuit is designed so that the frequency f1 of the transformer's primary current and the resonant frequency fu of the unwanted vibration satisfy the relationship 0.79≦f1 / fu≦1.21, the controllability of the vibration actuator can be improved and power consumption can be reduced.

[0122] Second Embodiment In the second embodiment, a configuration will be described in which the vibration-type driving device 10 described as the first embodiment is applied to a lens driving mechanism of an imaging device (optical equipment). Fig. 10 is a perspective view showing a schematic structure of a lens driving mechanism 900 of a lens barrel provided in the imaging device. Note that the control device 100 is not shown. The lens driving mechanism 900 includes a lens holder 902, a vibrating body 901 that drives the lens holder 902, a pressure magnet 905, a first guide bar 903, a second guide bar 904, and a base (not shown).

[0123] The lens holder 902 is a component corresponding to the contact body 2 in FIG. 2. The lens holder 902 has a cylindrical main body 902a, a holding portion 902b that holds the vibrating body 901 and the pressure magnet 905, a first guide portion 902c that forms the first guide portion by fitting with the first guide bar 903, and a drop-off prevention portion 902d. The main body 902a holds a lens 907. The first guide bar 903 and the second guide bar 904 are arranged parallel to each other, and both ends of each of the first guide bar 903 and the second guide bar 904 are fixed to a base (not shown). Here, the lens 907 (optical element) is assumed to be a lens (focus lens) for performing autofocus operation.

[0124] Pressure magnet 905, which constitutes the pressure means, is composed of a permanent magnet and two yokes placed on both ends of the permanent magnet. A magnetic circuit is formed between pressure magnet 905 and second guide bar 904, generating an attractive force between these components. As a result, the tips of the two protrusions provided on vibrating body 901 are held in a state where they are pressed against second guide bar 904 with a predetermined force, forming a second guide section.

[0125] A certain gap is provided between the pressure magnet 905 and the second guide bar 904. Therefore, if the second guide portion is subjected to an external force, there is a risk that the protrusion of the vibrating body 901 and the second guide bar 904 may be separated. However, in this case, the fall-off prevention portion 902d provided on the lens holder 902 abuts against the second guide bar 904, and the holding portion 902b of the lens holder 902 returns to its original position. This causes the protrusion of the vibrating body 901 to return to a state in which it abuts against the second guide bar 904.

[0126] Oscillator 901 has the same structure as oscillator 210 described in the first embodiment, and detailed description of its configuration will be omitted. By applying a two-phase AC voltage to the piezoelectric element of oscillator 901, elliptical vibrations are generated at the two protrusions, generating a frictional driving force between oscillator 901 and second guide bar 904. At this time, because first guide bar 903 and second guide bar 904 are fixed, the generated frictional driving force can move lens holder 902 along the length direction of first guide bar 903 and second guide bar 904. In this way, autofocusing can be performed by adjusting the position of lens 907.

[0127] While the lens driving mechanism 900 uses magnetic force (pressure magnet 905) as the pressure mechanism, this is not limiting and a spring biasing force may also be used. Furthermore, while the lens driving mechanism 900 is configured as a linear vibration-type driving device, this is not limiting and the lens driving mechanism may also be configured as a rotary vibration-type actuator in combination with an annular contact body. That is, the rotational force of the contact body is used to rotate the annular member that holds the lens, and at this time, the amount of rotation of the annular member is converted into a linear movement amount in the optical axis direction using a technique such as engagement between a cam pin and a cam groove. This allows the lens to move in the optical axis direction.

[0128] The vibration type driving device is suitable for driving a focus lens (optical element) in an imaging device, but is not limited to this, and can also drive a zoom lens (optical element) with a similar configuration. The vibration type driving device can also be used as a mechanism for driving a lens (optical element) or an imaging element (optical element) to perform image stabilization.

[0129] Third Embodiment In the third embodiment, a vibration actuator that rotationally drives a contact body using a plurality of vibrating bodies 210 described with reference to Fig. 2 will be described. Fig. 11 is a diagram illustrating the configuration of a vibration actuator 23A in the third embodiment, with a plan view shown on the upper side and a side view shown on the lower side.

[0130] The vibration actuator 23A has vibrating bodies 1A, 1B, and 1C and a contact body 2A. The vibrating bodies 1A, 1B, and 1C are equivalent to the vibrating body 210 described with reference to FIG. 2, and therefore detailed description of their configurations will be omitted. The contact body 2A has a disk shape. The vibrating bodies 1A, 1B, and 1C are held at equal intervals in the circumferential direction on one flat surface of an annular base plate 43 so that a line connecting two protrusions 213 (reference numerals are omitted in FIG. 11) of each vibrating body is a tangent to a circle centered on the rotation center of the contact body 2A. The protrusions 213 of each of the vibrating bodies 1A, 1B, and 1C are in contact with one surface of the contact body 2A, and a rotation shaft 47 is coaxially fixed to the center of the contact body 2A. A disk-shaped scale unit 48 is coaxially fixed to the rotation shaft 47, and the scale unit 48 rotates at the same angular velocity as the contact body 2A. A position sensor 46 is disposed opposite the scale section 48. Based on the result of the position sensor 46 reading the scale (not shown) of the scale section 48, the rotation angle (rotation position) or rotation speed of the contact body 2A can be detected, and feedback control is performed based on the detection result.

[0131] A control device including a drive circuit having a boost circuit 501B shown in Fig. 5(b) is used to drive the vibration actuator 23A. The output voltage Vo output from the boost circuit 105B is supplied as a two-phase AC voltage to the piezoelectric elements 211 of the parallel-connected vibrating bodies 1A, 1B, and 1C via flexible cables 49, and the vibrating bodies 1A, 1B, and 1C are driven simultaneously.

[0132] For example, by generating frictional driving forces in the vibrating bodies 1A, 1B, and 1C in the directions indicated by arrows M1, M2, and M3 in Fig. 11, contact body 2A can be rotated clockwise in the state shown in the upper part of Fig. 11. In this case, by using three vibrating bodies 1A, 1B, and 1C, a large torque can be obtained by combining the torques generated by each vibrating body. As is well known, the rotation speed and direction can be adjusted by adjusting the phase of the two-phase AC voltage.

[0133] <Fourth embodiment> In the fourth embodiment, another example of a vibration actuator that rotationally drives a contact body will be described. Fig. 12(a) is a perspective view showing a schematic configuration of a vibrating body 51 and a contact body 52 that constitute a vibration actuator 23B in the fourth embodiment. Both the vibrating body 51 and the contact body 52 have an annular shape and are arranged coaxially, with the contact body 52 being in contact with the vibrating body 51 while being rotatably supported. Note that Fig. 12(a) shows a portion of the contact body 52 cut away.

[0134] 12(b) is a plan view illustrating the electrodes of the annular piezoelectric element 54 provided on the vibrating body 51. The vibrating body 51 has a structure in which the annular piezoelectric element 54 is bonded to the lower surface (the surface opposite the contact surface with the contact body 52) of a circular elastic body. An electrode pattern is formed on the annular piezoelectric element 54, which is divided into 16 equal parts in the circumferential direction and divided into four phases.

[0135] A control device including a drive circuit having the boost circuit 501A described with reference to Fig. 5(a) is preferably used to drive the vibration actuator 23B. The contact body 52 can be rotationally driven by applying a predetermined AC voltage to the annular piezoelectric element 54 so that the number of waves of progressive vibration in the vibrating body 51 is four waves per rotation. Note that the number of waves of progressive vibration generated in the vibrating body 51 is not limited to four waves. Furthermore, since vibration actuators that operate on such a drive principle are well known, a more detailed description will be omitted.

[0136] 12(c) is a cross-sectional view showing a schematic configuration of a rotational drive device 50 using the vibration actuator 23B. In the rotational drive device 50, a vibrating body 51 is fixed to a housing 53 with screws or the like. The vibrating body 51 is in contact with a friction material provided on a contact body 52. ​​An output shaft 55, which extracts the rotational motion of the contact body 52 to the outside, is rotatably supported on the housing 53 by a ball bearing 56, and a pressure spring 58 urges the contact body 52 to contact the vibrating body 51 and transmits the rotation of the contact body 52 to the output shaft 55.

[0137] A drive unit 60 of various devices that use the rotary drive device 50 as a drive source is connected to the output shaft 55 via a mechanism not shown, and the drive unit 60 operates by receiving the output (rotational drive force) of the output shaft 55.

[0138] Fig. 13(a) is a front view showing the schematic configuration of a pan head device 70 equipped with a rotation drive device 50. The pan head device 70 has a structure that allows a camera (imaging device, rotatable device) fixed to a mounting base 71 (holding member) to be rotated in the pan direction by the rotation drive device 50. Fig. 13(b) is a front view showing the configuration of a transfer drum 81 (rotating drum) of an image forming apparatus or the like that is rotationally driven by the rotation drive device 50. The transfer drum 80 is directly connected to an output shaft 55, and rotates by receiving the rotational drive force of the output shaft 55.

[0139] While the present invention has been described above in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. For example, the object to be driven by a control device including a boost circuit according to this embodiment is not limited to a vibration actuator, and can be used to control, for example, a vibration device using a piezoelectric element, a power generation device, a piezoelectric transducer, etc. Furthermore, while the above embodiment is based on the premise that a movably arranged contact body moves relative to a fixed vibration body, the reverse configuration is also acceptable. [Explanation of symbols]

[0140] 10 Vibration type drive device 100 control device 110 control section 111 Headquarters 112 Control and Calculation Unit 113 Relative position detection unit 120 Drive unit 121 Pulse signal generating circuit 122 Boost circuit 1221 Coil 1222 Trans 1222a transformer primary coil 1222b Transformer secondary coil 130 Position Sensor 200 Vibration Actuator 210 Vibration Body 2103 Complex Vibration Body 220 Contact object 900 Lens drive mechanism 60 Driving parts of various equipment 70 Pan head device 71 Mounting base 71 (holding member) 80 Rotating drums of image forming devices, etc.

Claims

1. a vibration actuator having a vibrating body having an elastic body and an electromechanical energy conversion element, and a contact body that comes into contact with the elastic body, wherein the vibrating body and the contact body move relative to each other when the vibrating body vibrates; a control device having a drive unit provided with a transformer that transforms a drive signal generated in response to an input control signal, the drive signal being input to a primary side of the transformer and the secondary side of the transformer being connected to the electromechanical energy conversion element; A vibration type driving device comprising: When the frequency of the drive signal at which the current flowing to the primary side of the transformer is minimized is defined as f1, and the resonant frequency of a vibration mode other than the vibration used for the relative movement between the vibrating body and the contact body, which is greater than f1, is defined as fu, At -30°C, 0.79≦f1 / fu≦1.21; A vibration type driving device characterized in that the following relationship is satisfied.

2. The vibratory driving device according to claim 1, wherein the electromechanical energy conversion element has a first electrode and a second electrode adjacent to each other, and when the regions where the first electrode and the second electrode are provided are defined as a first region and a second region, the vibratory driving device forms a first bending vibration mode in which the first region and the second region both expand or contract, and a second bending vibration mode in which the second region contracts or expands when the first region expands or contracts, respectively.

3. 3. The vibration type driving device according to claim 1, further comprising a coil connected in series with the transformer on the primary side of the transformer.

4. 4. The vibratory driving device according to claim 1, further comprising a capacitor connected in parallel with the electromechanical energy conversion element on the secondary side of the transformer.

5. The vibration type driving device according to any one of claims 1 to 4, characterized in that, when the resonant frequency of the vibration mode corresponding to the vibration used for the relative movement between the vibrating body and the contact body is fm, the relationship 23 ≧ fu - fm ≧ 18 kHz is satisfied.

6. 6. The vibration type driving device according to claim 1, wherein the electromechanical energy conversion element is a piezoelectric element having a piezoelectric material and an electrode, and the lead content of the piezoelectric material is less than 1000 ppm.

7. 7. The vibratory driving device according to claim 6, wherein the piezoelectric material contains barium calcium zirconate titanate.

8. 8. The vibratory driving device according to claim 1, wherein the frequency f1 is equal to or greater than 86.9 kHz and less than 152.1 kHz.

9. A vibration type driving device according to any one of claims 1 to 8, an optical element driven by a vibration actuator provided in the vibration driving device.

10. A vibration type driving device according to any one of claims 1 to 8, a holding member driven by a vibration actuator provided in the vibration drive device.

11. A vibration type driving device according to any one of claims 1 to 8, a rotating drum driven by a vibration type actuator included in the vibration type driving device.

12. A vibration type driving device according to any one of claims 1 to 8, and a component driven by a vibration actuator provided in the vibration driving device.

13. A control device for a vibration type actuator, comprising: a vibrating body having an elastic body and an electromechanical energy conversion element; and a contact body that comes into contact with the elastic body, wherein the vibrating body and the contact body move relative to each other as the vibrating body vibrates, the control device has a drive unit in which a transformer is disposed that transforms a drive signal generated in response to an input control signal, the drive signal is input to a primary side of the transformer, and a secondary side of the transformer is connected to the electromechanical energy conversion element; When the frequency of the drive signal at which the current flowing to the primary side of the transformer is minimized is defined as f1, and the resonant frequency of a vibration mode other than the vibration used for the relative movement between the vibrating body and the contact body, which is greater than f1, is defined as fu, At -30°C, 0.79≦f1 / fu≦1.21; A control device for a vibration type actuator, characterized in that the following relationship is satisfied.

14. 14. The vibration actuator control device according to claim 13, wherein the frequency f1 is equal to or greater than 86.9 kHz and less than 152.1 kHz.

Images