Drive control device, drive control method, vibration type drive device and apparatus

Abstract

The present invention provides a drive control device, a drive control method, a vibration-type drive device and an apparatus. The drive control device enables a high output to be stably obtained from a vibration-type actuator over the entire drive frequency range. The vibration-type actuator includes a vibrator and a rotor, the vibrator includes a piezoelectric element, and the drive control device for controlling the vibration-type actuator includes: an amplifier circuit that amplifies a power supply voltage to generate a drive voltage to be applied to the piezoelectric element; and a microcomputer unit that controls the amplifier circuit to generate the drive voltage. The microcomputer unit controls to increase the amplitude of the drive voltage for acceleration from starting the vibration-type actuator to reaching the target speed of the rotor, and when the power supplied to the piezoelectric element exceeds a first power limit P‑Lim1, the frequency of the drive voltage is reduced without changing the amplitude of the drive voltage, and when the power drops below a second power limit P‑Lim2 during the operation of reducing the frequency, the amplitude of the drive voltage is increased.

Description

Technical Field

[0001] The present invention relates to a drive control device and a drive control method that enable stable output to be obtained from a vibration-type actuator, and a vibration-type driving device and apparatus including the vibration-type actuator. Background Art

[0002] As a non-electromagnetic drive actuator, a vibration type actuator is known, which makes a vibrator and a contact body contact each other and excites vibration in the vibrator so that the vibrator and the contact body move relative to each other. The vibrator, for example, has a structure in which an electro-mechanical energy conversion element such as a piezoelectric element is bonded to an elastic body. In the vibration type actuator, an AC voltage is applied to the electro-mechanical energy conversion element to generate high-frequency vibration in the vibrator, and the vibration energy of the high-frequency vibration is output as a mechanical motion in which the vibrator and the contact body move relative to each other.

[0003] Vibration type actuators are applied to various electronic devices and are used, for example, to drive a camera lens in an image pickup device. Generally, a battery is used as a power source in an image pickup device. For example, a technique is known in which a battery voltage is boosted by a DC / DC converter and then further boosted to a predetermined voltage value by an LC resonant circuit. In this case, the electrical resonant frequency of the LC resonant circuit is defined as 1 / {2π×(L×C) 1 / 2}.

[0004] Patent document 1 proposes a technology in which, when a vibration-type actuator is started by increasing a pulse width within a specific frequency range, the increase in the pulse width is stopped when the current value exceeds a predetermined value to prevent the current value from further increasing, thereby effectively utilizing the limited power provided by the battery. In addition, in Patent document 1, when the relative moving speed is equal to or lower than the target speed, control is performed to increase the relative moving speed by shifting the driving frequency toward the low frequency side while fixing the pulse width until the relative moving speed reaches the target speed.

[0005] Reference List

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5791343 Summary of the invention

[0008] Technical issues

[0009] In order to meet the demand of further simplifying the circuit included in the electronic device and reducing the cost, the driving method of the vibration type actuator may include a driving method in which the voltage of the battery is directly increased by an LC resonance circuit without using a DC / DC converter, and the electrical resonance frequency is made close to the mechanical resonance frequency of the vibrator to increase the voltage step-up rate, thereby obtaining a high output. However, in the case of making the electrical resonance frequency close to the mechanical resonance frequency, the output fluctuates greatly within the driving frequency range, which is a new problem.

[0010] Will refer to Fig.10 Describe the problem. Fig.10 : is a diagram showing the relationship between the driving frequency and the driving voltage (the voltage applied to the electro-mechanical energy conversion element) of the vibration-type actuator. The dotted line shows the situation where the mechanical resonant frequency fr' and the electric resonant frequency fe' are far away from each other, and the solid line shows the situation where the mechanical resonant frequency fr and the electric resonant frequency fe are close to each other. In the case where the two resonant frequencies are far away from each other (dashed line), since the voltage variation ΔV' within the driving frequency range is small, the fluctuation of the output and the power is small. However, since the voltage level is low, it is usually necessary to use a mechanism for increasing the voltage such as a DC / DC converter to increase the power supply voltage. On the other hand, in the case where the two resonant frequencies are close to each other (solid line), although the voltage level itself is high, the voltage variation ΔV within the driving frequency range becomes large, so within the driving frequency range, the fluctuation of the output and the power becomes large, which is problematic.

[0011] The present invention provides a simple vibration type driving device in which a stable output can be obtained from a vibration type actuator even when the amount of voltage variation is large within a driving frequency range because the mechanical resonance frequency and the electrical resonance frequency are close to each other.

[0012] Technical solutions to the problem

[0013] A vibration-type driving device according to the present invention comprises: a vibration-type actuator comprising a vibrator and a contact body that move relative to each other; and a drive control device configured to control a drive voltage to be applied to the vibration-type actuator and a frequency of the drive voltage, wherein the drive control device increases the drive voltage to accelerate the drive of the vibration-type actuator from starting the vibration-type actuator to reaching a target speed of relative movement, and when the power supplied to the vibrator exceeds a first power value, the drive control device reduces the frequency of the drive voltage without changing the drive voltage, and when the power drops below a second power value less than the first power value during an operation of reducing the frequency, the drive control device increases the drive voltage.

[0014] Advantageous Effects of the Invention

[0015] According to the present invention, by a simple circuit configuration, a stable output can be obtained from a vibration type actuator even when the amount of voltage variation is large within a driving frequency range because the mechanical resonance frequency and the electrical resonance frequency are close to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view showing a schematic configuration of a vibration-type actuator.

[0017] Figure 2 is a block diagram showing the configuration of a drive control device.

[0018] Figure 3A is a diagram used to describe the drive signal.

[0019] Figure 3B is a diagram for describing the configuration of an amplifier circuit.

[0020] Figure 4 : is a graph showing the relationship between the resonance frequency and the driving voltage of the vibration type actuator.

[0021] Figure 5 are graphs showing comparison of characteristics in driving sequences according to Example 1 and Comparative Example, respectively.

[0022] Figure 6 is a flowchart of a driving sequence of Example 1 of the vibration-type actuator.

[0023] Fig. 7A It is a graph used to describe the relationship between the pulse width and voltage ratio of the driving signal.

[0024] Figure 7B It is a graph used to describe the pulse width of the drive signal relative to the power supply voltage setting.

[0025] Figure 8 2 are graphs showing comparison of characteristics in driving sequences according to Example 2 and Comparative Example, respectively.

[0026] Fig. 9 is a perspective view showing the appearance of a digital camera including a vibration-type driving device.

[0027] Fig.10 : is a graph showing the relationship between the driving frequency and the driving voltage of the vibration type actuator. DETAILED DESCRIPTION

[0028] 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 driving control device that controls the vibration type actuator.

[0029] <First Embodiment>

[0030] Figure 1 2 is a cross-sectional view showing a schematic configuration of a vibration type actuator 200 included in a vibration type drive device. The vibration type actuator 200 is generally cylindrical in shape. The vibration type actuator 200 includes a first elastic body 201, a second elastic body 202, a piezoelectric element 203, a flexible printed circuit board 204, a lower nut 205 and a shaft 206. The first elastic body 201, the second elastic body 202, the piezoelectric element 203 and the flexible printed circuit board 204 are fastened along the axial direction (thrust direction) of the shaft 206 so that a predetermined holding force is applied by the shaft 206 and the lower nut 205. The first elastic body, the second elastic body 202 and the piezoelectric element 203 form a vibrator 214, and the vibrator 214 is fixed to a predetermined position on the shaft 206.

[0031] The first elastic body 201 is formed of a material having low vibration loss and excellent wear resistance and corrosion resistance. For example, metal or ceramic can be selected for the first elastic body 201, and martensitic stainless steel (for example, a high hardness material such as SUS440C) is particularly preferred. Here, the first elastic body 201 is obtained by cutting a member of SUS440C and then quenching and nitriding the cut SUS440C member to improve wear resistance.

[0032] The piezoelectric element 203 is an electromechanical energy conversion element. Here, a piezoelectric element 203 having a structure in which a plurality of annular piezoelectric bodies having electrodes formed on the front and back sides are stacked in the axial direction of the shaft 206 is used. The piezoelectric element 203 may be formed by alternately stacking a plurality of thin plate-shaped piezoelectric ceramics and electrode layers and sintering the piezoelectric ceramics and the electrode layers at the same time (integrally sintered type), or may be formed by stacking a plurality of single-plate piezoelectric bodies each having electrodes formed on the front and back sides and tightening the stacked piezoelectric bodies in the stacking direction (Langevin type).

[0033] Each electrode layer of the piezoelectric element 203 includes an A-phase electrode, a B-phase electrode, an A'-phase electrode, and a B'-phase electrode. Such a structure of the piezoelectric element 203 is disclosed, for example, in Japanese Patent Publication No. 2013-123335, and therefore its illustration and detailed description will be omitted. Two bending vibrations orthogonal to each other can be excited in the vibrator 214 by applying an alternating current (AC) voltage (hereinafter referred to as "driving voltage") having a predetermined phase difference to the A-phase electrode, the B-phase electrode, the A'-phase electrode, and the B'-phase electrode via the flexible printed circuit board 204. The spatial phase of these two bending vibration modes around the axis is offset by 90 degrees (90°), and the two bending vibrations can have a time phase difference of 90 degrees by changing the phase of the driving voltage. As a result, the bending vibration of the vibrator 214 rotates around the axis 206, and an elliptical motion is generated on the first elastic body 201 (the surface in contact with the contact portion 207a of the rotor 207 described later).

[0034] Due to the bending vibration of the vibrator 214, electric charges are generated in the piezoelectric element 203 by the direct piezoelectric effect. Therefore, the vibration state of the vibrator 214 can be monitored by detecting the electric charges. Therefore, in the piezoelectric element 203, for example, one of the two electrodes formed by dividing one of the plurality of A-phase electrodes is used as a sensor electrode for monitoring the vibration state. In this case, the phase difference between the driving voltage applied to the A-phase electrode and the output signal from the sensor electrode is 90 degrees at the resonant frequency, and gradually increases toward a frequency higher than the resonant frequency. Therefore, the relationship between the frequency of the driving voltage input to the piezoelectric element 203 and the resonant frequency of the vibrator 214 can be monitored by detecting the phase difference between the driving voltage applied to the A-phase electrode and the output signal from the sensor electrode in the state of exciting vibration in the vibrator 214. In addition, the vibration-type actuator 200 can be stably driven by performing the control described later based on the monitoring result.

[0035] The vibration type actuator 200 includes a rotor 207 (contact body), a rotor rubber 208, a compression spring 209, a gear 210 as an output transmission member, a bearing 211, a flange 212, and an upper nut 213. The flange 212 arranged on the upper end side of the shaft 206 is fixed to the shaft 206 by screwing the upper nut 213 onto the shaft 206. The flange 212 is a member for fixing the vibration type actuator 200 at a predetermined position on a device (instrument) on which the vibration type actuator 200 is installed.

[0036] The rotor 207 includes a rotor main ring 207b and a contact portion 207a. The contact portion 207a is fixed to the rotor main ring 207b by an adhesive. The surface of the lower end (the end facing the vibrator 214) of the contact portion 207a contacts the first elastic body 201, and the contact portion 207a is bent so that the diameter of the surface of the lower end is smaller than the diameter of the surface of the upper end. As a result, the contact portion 207a has an appropriate elasticity level. The contact portion 207a is preferably formed by a material having good wear resistance, mechanical strength and corrosion resistance. For example, stainless steel such as SUS420J2 is preferably used. In the vibration type actuator 200, the contact portion 207a is formed by stamping with low production cost and excellent dimensional accuracy and quenching to improve wear resistance. It should be noted that the method of fixing the contact portion 207a to the rotor main ring 207b is not limited to the method using an adhesive, and may include other methods, such as metal brazing (such as soft soldering), welding (such as laser welding or resistance welding), and mechanical joining (such as press fitting or riveting).

[0037] The rotor 207 is pressed against the vibrator 214 by the pressing spring 209 via the rotor rubber 208 and contacts the vibrator 214. By generating the above-mentioned elliptical motion in the vibrator 214, a friction driving force can be applied to the rotor 207 to rotate the rotor 207. It should be noted that the rotor rubber 208 has the function of balancing the pressing force and attenuating the vibration transmitted from the rotor 207 to the gear 210.

[0038] In the axial direction of the shaft 206, the gear 210 is arranged between the flange 212 and the first elastic body 201 via the bearing 211. The recessed portion formed on the upper surface of the rotor main ring 207b and the convex portion formed on the gear 210 are matched with each other. The gear 210 receives the force from the pressing spring 209 and rotates integrally with the rotor 207 while sliding relative to the bearing 211 to output the rotational driving force to the outside.

[0039] Figure 2 1 is a block diagram showing a schematic configuration of a drive control device 100 included in a vibration type drive device. The drive control device 100 includes a microcomputer unit 1, an oscillator unit 2, a current detection circuit 3, a speed detection circuit 4, a power supply unit 5, amplifier circuits 11 and 12, and impedance elements 21 and 22.

[0040] The microcomputer unit 1 is a control unit that comprehensively controls the driving of the vibration type actuator 200. In order to excite the above-mentioned vibration in the vibrator 214, the oscillator unit 2 generates four pulse signals (i.e., A phase pulse, A' phase pulse, B phase pulse, and B' phase pulse) in response to the command value from the microcomputer unit 1 as pulse signals serving as driving signals.

[0041] The amplifier circuits 11 and 12 and the impedance elements 21 and 22 are used as drivers in the drive control device 100. The amplifier circuit 11 switches the voltage (power supply voltage) of the power supply unit 5 using the A-phase pulse and the A'-phase pulse, increases the power supply voltage in combination with the impedance element 21, and generates a drive voltage to be applied to the piezoelectric element 203. The amplifier circuit 12 switches the power supply voltage using the B-phase pulse and the B'-phase pulse, increases the power supply voltage in combination with the impedance element 22, and generates a drive voltage to be applied to the piezoelectric element 203. The two drive voltages of different phases generated by the amplifier circuit 11 using the A-phase pulse are applied to the A-phase electrode and the A'-phase electrode of the piezoelectric element 203, which will be referred to later. Figure 3A and Figure 3B A detailed description thereof is provided. In addition, the driving voltage generated by the amplifier circuit 12 using the B-phase pulse is applied to the B-phase electrode and the B′-phase electrode of the piezoelectric element 203 .

[0042] The power supply unit 5 is a power supply such as a battery that supplies a direct current (DC) voltage to the amplifier circuits 11 and 12. The current detection circuit 3 is a current detection unit that detects the current supplied from the power supply unit 5. The product of the current detected by the current detection circuit 3 and the voltage command value given to the amplifier circuits 11 and 12 can be calculated to calculate the consumed power (hereinafter referred to as "power"). The calculated power is input to the microcomputer unit 1 and used as information for performing a driving sequence described later.

[0043] The speed detection circuit 4 detects the speed (rotation speed) and position (rotation angle) of the rotor 207, and transmits information on the detected speed and position of the rotor 207 to the microcomputer unit 1. The microcomputer unit 1 controls the rotation of the rotor 207 by controlling the A-phase pulse and the B-phase pulse for generating the driving voltage to be applied to the piezoelectric element 203 based on the received information on the speed and position of the rotor 207.

[0044] Figure 3A It is a diagram for describing the drive signals (A-phase pulse, B-phase pulse, A′-phase pulse, and B′-phase pulse). Figure 3B is a circuit diagram of amplifier circuits 11 and 12. Figure 3A As shown, the phases of the A-phase pulse and the A'-phase pulse are shifted by 180 degrees, the phases of the B-phase pulse and the B'-phase pulse are shifted by 180 degrees, and the pulse widths (duty ratios) of the respective drive signals are equal. Here, the phases of the A-phase pulse and the B-phase pulse are shifted by 90 degrees.

[0045] FETs 31 to 38 are used as switching elements included in the amplifier circuits 11 and 12. FETs 31 and 34 are switched due to the A-phase pulse, and FETs 32 and 33 are switched due to the A'-phase pulse. The driving voltage generated from the power supply voltage by the switching movement of the FETs 31 to 34 is applied to the A-phase electrode and the A'-phase electrode. FETs 35 and 38 are switched due to the B-phase pulse, and FETs 36 and 37 are switched due to the B'-phase pulse. The driving voltage generated from the power supply voltage by the switching movement of the FETs 35 to 38 is applied to the B-phase electrode and the B'-phase electrode.

[0046] The impedance elements 21 and 22 are used for impedance matching with the vibration type actuator 200, and inductance elements are used here. Figure 2 , Figure 3A and Figure 3B By incorporating the impedance elements 21 and 22 at the predetermined positions shown, the vibration type actuator 200 can be driven with a lower power supply voltage and high efficiency. It should be noted that although not shown, a capacitance element may be provided in parallel with the vibrator 214 for impedance matching.

[0047] The rate of voltage boosting by the driver including the amplifier circuits 11 and 12 and the impedance elements 21 and 22 has a maximum value at the electrical resonance frequency fe which is the resonance frequency of the driver. fe=1 / {2π×(L×C) 1 / 2}, wherein the inductance of the impedance elements 21 and 22 is L, and the capacitance of the piezoelectric element 203 is C. In the drive control device 100, the range of the drive frequency (the frequency of the drive signal) is made close to the electrical resonance frequency fe to increase the drive voltage to be applied to the piezoelectric element 203, thereby realizing the following circuit configuration, in which a DC / DC converter as a boost unit is not used. It should be noted that increasing the drive voltage means increasing the voltage value of the effective drive voltage. Methods for changing the voltage value of the effective drive voltage include methods for changing the amplitude or pulse width of the drive voltage.

[0048] In addition, in the vibration type actuator 200, the vibration amplitude can be increased by using the mechanical resonance phenomenon of the vibrator 214, thereby driving the rotor 207 at a high speed. Therefore, making the driving frequency range close to the electrical resonance frequency fe is equivalent to making the mechanical resonance frequency fr close to the electrical resonance frequency fe. However, as mentioned above with reference to Fig.10 As described above, when the mechanical resonance frequency fr is too close to the electric resonance frequency fe, the output of the vibration type actuator becomes unstable. On the other hand, when the mechanical resonance frequency fr is far from the electric resonance frequency fe, when there is no boost unit such as a DC / DC converter, the output becomes insufficient. Considering the balance of these issues, it is expected that the difference (fe-fr) between the mechanical resonance frequency fr and the electric resonance frequency fe is 8kHz to 30kHz.

[0049] Next, a drive control method for the vibration type actuator 200 performed by the drive control device 100 will be described. Figure 4 and Figure 5 An overview of control of the vibration-type actuator 200 is described. Figure 4 : is a graph showing the relationship between various resonance frequencies and driving voltages of the vibration-type actuator 200 . Figure 5 1 and 2 are graphs showing comparison of characteristics in driving sequences of the vibration-type actuators 200 according to Example 1 and Comparative Example, respectively. Figure 5 The upper part shows the relationship between driving frequency and power, Figure 5 The middle part shows the relationship between the driving frequency and the pulse width, and Figure 5 The lower part shows the relationship between the driving frequency and the speed.

[0050] The microcomputer unit 1 gradually increases the pulse width (duty ratio) of the drive signal (A phase pulse, A' phase pulse, B phase pulse and B' phase pulse) at a frequency fs (starting frequency) to start the vibration type actuator 200. When the pulse width increases, the effective drive voltage increases. As a result, the power also increases. Figure 5 As shown in the upper part of , when the predetermined first power limit P-Lim1 (first power value) is reached, the pulse width is fixed. Figure 4 and Figure 5 As shown in the middle of FIG. 2 , when the pulse width reaches a duty ratio of 22%, the pulse width is fixed. When the driving frequency is reduced (shifted to the low frequency side) in this state, since the driving frequency is made close to the mechanical resonance frequency fr of the vibrator 214, the amplitude of the vibration excited in the vibrator 214 increases, so that the speed of the rotor 207 increases, as shown in FIG. Figure 5 as shown in the lower part of .

[0051] In the comparative example as a conventional driving method, since the driving frequency is reduced while the pulse width is fixed at 22%, Figure 4 As shown in FIG. 1 , when the mechanical resonance frequency fr and the electrical resonance frequency fe are close to each other, the driving voltage is reduced, and a voltage reduction ΔV' occurs between the frequency fs and the frequency fx. It should be noted that the frequency fx is any frequency lower than the frequency fs, in other words, the frequency fx is a frequency at which a voltage reduction ΔV occurs from the driving voltage at the frequency fs. As a result, as Figure 5 As shown in the upper part of Figure 5As shown in the lower part of , the rated speed is not reached even when the driving frequency is reduced to the mechanical resonance frequency fr. It should be noted that the rated power P-Lim0 is the rated power of the vibration type actuator 200. By driving the vibration type actuator 200 with a high output that does not exceed the rated power, the components driven by the output of the gear 210 can be stably driven.

[0052] On the other hand, in Example 1, since the pulse width is increased when the power drops below the predetermined second power limit P-Lim2 (second power value) during the operation of reducing the driving frequency, voltage shortage can be prevented even in the case where the mechanical resonance frequency fr and the electrical resonance frequency fe are close to each other. However, in Example 1, the maximum value of the pulse width is set to a duty ratio of 50%, and the reason for this will be described later. As a result, as Figure 5 As shown in the lower part of FIG. , the rotor 207 can be driven at a speed significantly exceeding the rated speed, so that it can be driven with spare power. Figure 6 The shown flowchart describes such a driving sequence according to Example 1.

[0053] Figure 6 1 is a flowchart for describing a driving sequence of the vibration type actuator 200 according to Example 1 performed by the drive control device 100. The microcomputer unit 1 executes a predetermined program to control the operation of each component included in the drive control device 100, thereby realizing Figure 6 Each process (step) indicated by S and a number in the flowchart of . It should be noted that Figure 6 The flowchart shows the control from starting the rotation of the rotor 207 to starting the stop operation.

[0054] In S1, the microcomputer unit 1 turns on the drive signal at the frequency fs and sets the pulse width of the drive signal (in Figure 6 The speed command value (referred to as "PW") in the figure gradually increases from zero (0). The rate of increase may be consistent with respect to time, or may be based on a predetermined speed command value. In S2, the microcomputer unit 1 determines whether the speed of the rotor 207 has reached the target speed. In the case where the microcomputer unit 1 determines that the speed of the rotor 207 has reached the target speed ("Yes" in S2), the process proceeds to S3, and in the case where the microcomputer unit 1 determines that the speed of the rotor 207 has not yet reached the target speed ("No" in S2), the process proceeds to S7.

[0055] In S3, the microcomputer unit 1 controls the pulse width by frequency control or pulse width control (in Figure 6The speed of the rotor 207 is controlled by the drive signal (referred to as "F / PW control" in the flowchart). In the speed control here, when the speed of the rotor 207 is lower than the target speed, the pulse width of the drive signal is increased to increase the speed, and when the speed of the rotor 207 is higher than the target speed, the pulse width of the drive signal is reduced to reduce the speed. It should be noted that due to an increase in the external load during driving, etc., the speed of the rotor 207 may decrease, and the pulse width may reach the maximum pulse width PW-max (specifically, 50%, i.e., the initial value). In this case, although not described in the flowchart, speed control can be performed by reducing the drive frequency to increase the speed and then adjusting the drive frequency as needed.

[0056] In S4, the microcomputer unit 1 determines whether the rotation angle of the rotor 207 has reached the stop operation start position. It should be noted that the stop operation start position is determined in consideration of the position at which the rotor 207 finally stops and the current speed of the rotor 207. In the case where the microcomputer unit 1 determines that the stop operation start position has been reached ("Yes" in S4), the microcomputer unit 1 ends the processing and starts the stop operation, and in the case where the microcomputer unit 1 determines that the stop operation start position has not been reached ("No" in S4), the processing proceeds to S5. In S5, the microcomputer unit 1 determines whether the power is equal to or higher than the first power limit P-Lim1. In the case where the microcomputer unit 1 determines that the power is lower than the first power limit P-Lim1 ("No" in S5), the processing returns to S3, and in the case where the microcomputer unit 1 determines that the power is equal to or higher than the first power limit P-Lim1 ("Yes" in S5), the processing proceeds to S6.

[0057] In S6, the microcomputer unit 1 changes the maximum pulse width PW-max to a pulse width obtained by subtracting a certain value from the pulse width immediately before the power exceeds the first power limit P-Lim1 or at the moment when the power exceeds the first power limit P-Lim1. It should be noted that the initial value of the maximum pulse width PW-max is PW-max0. Here, even in the case of power overshoot due to interference or the like, the first power limit P-Lim1 is set to a value at which the power does not exceed the rated power P-Lim0, and the first power limit P-Lim1 is preferably set to a value corresponding to 80% to 95% of the rated power P-Lim0. On the other hand, the second power limit P-Lim2 is set to a value lower than the first power limit P-Lim1 and at which sufficient output can be obtained within the rated power, and the second power limit P-Lim2 is preferably set to a value corresponding to 70% to 90% of the rated power P-Lim0. In the microcomputer unit 1, after the processing in S6, the processing enters S12.

[0058] Meanwhile, in the case where the microcomputer unit 1 determines in S2 that the speed of the rotor 207 has not reached the target speed ("No" in S2), the process proceeds to S7. In S7, the microcomputer unit 1 determines whether the power is equal to or higher than the first power limit P-Lim1. In the case where the microcomputer unit 1 determines that the power is equal to or higher than the first power limit P-Lim1 ("Yes" in S7), the process proceeds to S9, and in the case where the microcomputer unit 1 determines that the power is lower than the first power limit P-Lim1 ("No" in S7), the process proceeds to S8.

[0059] In S8, the microcomputer unit 1 determines whether the pulse width of the drive signal is less than PW-max0. In the case where the microcomputer unit 1 determines that the pulse width is less than PW-max0 ("Yes" in S8), the process returns to S1, and in the case where the microcomputer unit 1 determines that the pulse width is equal to or greater than PW-max0 ("No" in S8), the process proceeds to S10.

[0060] It should be noted that PW-max0, which is the initial value of the maximum pulse width, is a fixed value set according to the power supply voltage. Generally, a battery has the highest voltage when it is fully charged (100%), and the battery has the lowest voltage just before it runs out of power. Since the drive control device 100 does not use a DC / DC converter, in this state, the drive voltage is reduced, and the output is also reduced accordingly.

[0061] Here, we will refer to Fig. 7A and Figure 7B A method for setting the initial value PW-max0 of the maximum pulse width is described. Fig. 7A is a graph showing the relationship between the pulse width and the voltage ratio of the drive signal. When the pulse width is 50%, the voltage ratio of the fundamental component is set to 1. The fundamental component referred to here is a voltage component with the same frequency as the drive signal. The voltage of the square wave is composed of a combination of different sine waves (fundamental wave and its harmonics), and its component ratio varies according to the pulse width. In other words, the voltage of the fundamental component can be controlled by changing the pulse width. Figure 7B is a graph for describing the pulse width of the driving signal set relative to the power supply voltage. As described above, since the power supply voltage fluctuates according to the state of the battery, the voltage of the fundamental wave component can be kept constant by determining the pulse width of the driving signal according to the value of the power supply voltage. In the driving sequence according to Example 1, as Figure 7B As shown, for the lowest power supply voltage, the initial value PW-max0 of the maximum pulse width of the drive signal is set to 50%. Then, the maximum pulse width PW-max is changed to make the voltage of the fundamental wave component the same, thereby preventing the fluctuation of the drive voltage.

[0062] Will describe again Figure 6 Flowchart of. In S9 following the case of "Yes" in S7, the microcomputer unit 1 changes the maximum pulse width PW-max to a value obtained by subtracting a certain value from the pulse width immediately before the power exceeds the first power limit P-Lim1 or at the moment the power exceeds the first power limit P-Lim1. It should be noted that the initial value of the maximum pulse width is set to PW-max0. As a result, the power can be prevented from exceeding the rated power P-Lim0. So far, the control in S1, S2, and S7 to S9 corresponds to the control until the power exceeds Figure 5 The control is performed until the frequency fs in reaches the first power limit P-Lim1.

[0063] In S10, the microcomputer unit 1 increases the speed of the rotor 207 by reducing the drive frequency while maintaining the pulse width of the drive signal. The processing in S10 may be performed by open drive, or may be performed according to the speed command value. In the case of accelerating the rotor 207 to the target speed by open drive, it is sufficient to monotonically reduce the drive frequency. On the other hand, in the case of following the speed command value, the drive frequency is basically reduced. However, since the actual speed of the rotor 207 may exceed the speed command value, it may be necessary to increase and decrease the drive frequency.

[0064] In S11, the microcomputer unit 1 determines whether the speed of the rotor 207 has reached the target speed. In the case where the microcomputer unit 1 determines that the speed of the rotor 207 has reached the target speed ("Yes" in S11), the process proceeds to S12, and in the case where the microcomputer unit 1 determines that the speed of the rotor 207 has not yet reached the target speed ("No" in S11), the process proceeds to S15. In S12, the microcomputer unit 1 performs speed control on the rotor 207 by frequency control or pulse width control. In the speed control here, when the speed of the rotor 207 has not yet reached the target speed, the driving frequency is reduced to increase the speed, and when the speed of the rotor 207 exceeds the target speed, the driving frequency is increased (shifted to the high frequency side) to reduce the speed.

[0065] It should be noted that, although not shown, in the case where the speed of the rotor 207 increases due to a decrease in the external load during driving and thus the driving frequency reaches the frequency fs, speed control is performed by adjusting the pulse width. In this way, speed control is performed by changing (adjusting) the driving frequency at a frequency lower than the frequency fs, and speed control is performed by increasing / decreasing (adjusting) the pulse width at the frequency fs.

[0066] In S13, the microcomputer unit 1 determines whether the stop operation start position is reached. The processing in S13 is equivalent to the processing in S4. In the case where the microcomputer unit 1 determines that the stop operation start position is reached ("Yes" in S13), the microcomputer unit 1 ends the processing and starts the stop operation, and in the case where the microcomputer unit 1 determines that the stop operation start position has not been reached ("No" in S13), the processing enters S14. In S14, the microcomputer unit 1 determines whether the power is equal to or higher than the rated power P-Lim0. In the case where the microcomputer unit 1 determines that the power is lower than the rated power P-Lim0 ("No" in S14), the processing returns to S12, and in the case where the microcomputer unit 1 determines that the power is equal to or higher than the rated power P-Lim0 ("Yes" in S14), the processing enters S19.

[0067] In processing S15 after determining in S11 that the speed of the rotor 207 has not reached the target speed, the microcomputer unit 1 determines whether the power is equal to or higher than the rated power P-Lim0. In the case where the microcomputer unit 1 determines that the power is lower than the rated power P-Lim0 ("No" in S15), the processing proceeds to S16, and in the case where the microcomputer unit 1 determines that the power is equal to or higher than the rated power P-Lim0 ("Yes" in S15), the processing proceeds to S19.

[0068] The processing in S16 to S18 is a characteristic processing in the driving sequence according to Example 1. In S16, the microcomputer unit 1 determines whether the power is equal to or lower than the second power limit P-Lim2. In the case where the microcomputer unit 1 determines that the power is equal to or lower than the second power limit P-Lim2 ("Yes" in S16), the processing proceeds to S17, and in the case where the microcomputer unit 1 determines that the power exceeds the second power limit P-Lim2 ("No" in S16), the processing returns to S10. In S17, the microcomputer unit 1 determines whether the maximum pulse width of the drive signal is less than PW-max0. In the case where the microcomputer unit 1 determines that the pulse width is less than PW-max0 ("Yes" in S17), the processing proceeds to S18, and in the case where the microcomputer unit 1 determines that the pulse width is equal to or greater than PW-max0 ("No" in S17), the processing returns to S10. In S18, the microcomputer unit 1 increases the pulse width of the drive signal, and then the processing returns to S10.

[0069] This routine of S10, S11, and S15 to S18 corresponds to the following control, in which when the power reaches Figure 5 After the first power limit P-Lim1 in the drive frequency is reduced from the frequency fs to the frequency fx. It should be noted that, as mentioned above with reference to Fig. 7A and Figure 7BAs described, in the drive sequence according to Example 1, the maximum value of the pulse width of the drive signal is set to a duty cycle of 50% in consideration of the power supply voltage. Therefore, after the pulse width is fixed to 50%, even when the power drops below the second power limit P-Lim2, the pulse width does not increase, but the speed of the rotor 207 can be increased by reducing the drive frequency.

[0070] When the above-mentioned cycles of S10, S11 and S15 to S18 are performed, the pulse width increases between the frequency fs and the frequency fx, and the power is substantially constant, as shown in FIG. Figure 5 As shown in Example 1 in the middle and upper parts of . In other words, in the comparative example, the power decreases and the speed is insufficient due to the decrease in the driving voltage, but in Example 1, the decrease in the driving voltage is prevented by increasing the pulse width, and as a result, the power is substantially constant and the speed is sufficient. It should be noted that for stable driving, it is desirable that the power change in the interval where the power is constant (the interval where the power is maintained at the second power limit P-Lim2) is 10% or less of the value of the second power limit P-Lim2.

[0071] In the case where the microcomputer unit 1 determines in S14 that the power is equal to or higher than the rated power P-Lim0 ("Yes" in S14), or in the case where the microcomputer unit 1 determines in S15 that the power is equal to or higher than the rated power P-Lim0 ("Yes" in S15), the process proceeds to S19. In S19, the microcomputer unit 1 reduces the power by increasing the driving frequency or reducing the pulse width, and then the process returns to S13. The driving sequence according to Example 1 is as described above.

[0072] It should be noted that Figure 6 In the flowchart of , various determinations are made based on the value of the electric power, but the current detected by the current detection circuit 3 can also be used as a determination reference. Figure 6 The individual processes of the stop operation are not described in the flowchart of , but the control of the stop operation basically follows the opposite path to that at the start in terms of power, pulse width and speed. That is, when the stop operation start position is reached, the speed starts to be reduced by increasing the drive frequency. In addition, when the power is equal to or higher than the first power limit P-Lim1, the power is reduced by reducing the pulse width. When the drive frequency reaches the frequency fs by repeating these steps, the pulse width is reduced regardless of the power, and the rotor 207 stops at the stop position.

[0073] As described above, even in the case where the voltage change amount ΔV is large within the driving frequency range because the mechanical resonance frequency fr and the electrical resonance frequency fe are close to each other, the voltage change amount ΔV can be increased by Figure 6The driving sequence is applied to the drive control device 100 having a simple circuit configuration to drive the vibration-type actuator 200 with a stable output over the entire driving frequency range.

[0074] <Second Embodiment>

[0075] In the second embodiment, a driving sequence will be described in which the second power limit P-Lim2 and the first power limit P-Lim1 have the same value. The first and second embodiments differ from each other only in the control performed by the microcomputer unit 1, and only this difference will be described below.

[0076] Figure 8 2 are graphs showing comparison of characteristics in driving sequences of the vibration-type actuator 200 according to Example 2 and the comparative example, respectively. Figure 8 The upper part of shows the relationship between the driving frequency and the power (upper part), Figure 8 The middle part shows the relationship between the driving frequency and the pulse width, and Figure 8 The lower part of shows the relationship between the driving frequency and the speed. As in Example 1, in Example 2, the vibration type actuator 200 is started by gradually increasing the pulse width of the driving signal at the frequency fs. As the pulse width increases, the speed of the rotor 207 gradually increases, and the power also increases. When the power reaches the first power limit P-Lim1, the pulse width is fixed (at Figure 8 The middle of the group is 22%).

[0077] When the driving frequency is reduced from here, the driving frequency approaches the mechanical resonance frequency fr of the vibrator 214, and therefore, the vibration amplitude of the vibrator 214 increases, and the speed of the rotor 207 increases. In this case, in the conventional driving method according to the comparative example, since the driving frequency is reduced while the pulse width of the driving signal is fixed to 22%, Figure 4 As shown in FIG. 1 , the voltage decreases, and a voltage decrease ΔV' occurs between the frequency fs and the frequency fx. As a result, in the comparative example, the power does not exceed Figure 8 The rated power P-Lim0 shown in the upper part of FIG. 1 is 0. However, even when the frequency of the drive signal is reduced to the mechanical resonance frequency fr (as shown in FIG. Figure 8 ), the speed of the rotor 207 will not exceed the rated speed.

[0078] On the other hand, in Example 2, when the power is equal to or lower than the first power limit P-Lim1, the pulse width of the drive signal is increased to prevent the voltage from becoming insufficient. As a result, the speed of the rotor 207 greatly exceeds the rated speed, so that it can be driven with a surplus. In addition, since the first power limit P-Lim1 is set to a value that does not exceed the rated power P-Lim0 even in the case of power overshoot due to interference, etc., although the power consumption increases, the drive voltage also increases. Therefore, a higher and more stable output can be obtained without exceeding the rated power.

[0079] <Third Embodiment>

[0080] In the third embodiment, a digital camera (imaging apparatus) will be described as an example of an apparatus including a vibration-type drive device. Fig. 9 3 is a perspective view showing the appearance of a digital camera 300. The digital camera 300 includes a camera body 301 and a lens barrel 302 arranged on the front surface of the camera body 301. A plurality of lens groups (not shown) including a focusing lens that can move in the optical axis direction of the lens barrel 302 are arranged in the lens barrel 302. In addition, in the lens barrel 302, the gear 210 of the vibration-type actuator 200 is meshed with a gear (rotation transmission member) for moving the focusing lens arranged in the lens barrel 302 in the optical axis direction.

[0081] The vibration type actuator 200 is driven by the drive control method according to Example 1 or Example 2, and since the focus lens moves stably and quickly in the optical axis direction, smooth focusing on the subject can be achieved. In addition, since the drive control device 100 has a simple circuit configuration, the size of the camera body 301 is hardly increased even if the drive control device 100 is mounted on the camera body 301. It should be noted that the vibration type actuator 200 can also be used to drive the zoom lens included in the lens barrel 302 in the optical axis direction.

[0082] Although the present invention has been described in detail above based on the preferred embodiments of the present invention, the respective embodiments are merely embodiments of the present invention, and the respective embodiments may be appropriately combined with each other.

[0083] For example, in the above implementation, as the structure of the vibration type actuator controlled by the drive control device 100, the following structure is described, wherein the relative movement between the vibrator and the contact body is expressed as a rotational motion. However, the construction of the vibration type actuator is not limited to this. For example, the drive control method of Example 1 and Example 2 can also be applied to the drive of a linear drive type vibration type actuator, wherein the relative movement between the vibrator and the contact body is expressed as a linear motion.

[0084] In addition, in the third embodiment, the digital camera using the vibration type drive device has been described. However, the specific application example of the vibration type drive device is not limited to this. The vibration type drive device can be widely applied to devices (instruments) including components that need to be positioned by driving the vibration type actuator 200.

[0085] <Other embodiments>

[0086] The present invention can also be implemented by the following process, in which a program that implements one or more functions of the above-mentioned embodiment is provided to a system or device via a network or storage medium, and one or more processors in a computer of the system or device read and execute the program. In addition, the present invention can also be implemented by a circuit (e.g., ASIC) that implements one or more functions.

[0087] The present invention is not limited to the above-described embodiments, and various changes and modifications may be made without departing from the spirit and scope of the present invention. Therefore, the claims are attached to disclose the scope of the present invention.

[0088] This application claims the benefit of Japanese Patent Application No. 2018-194399, filed October 15, 2018, which is hereby incorporated by reference herein in its entirety.

[0089] Reference numerals list

[0090] 1 microcomputer unit;

[0091] 2 Oscillator units;

[0092] 5. Power supply unit;

[0093] 11, 12 amplifier circuit;

[0094] 100 drive control equipment;

[0095] 200 Vibration type actuator;

[0096] 203 Piezoelectric element;

[0097] 207 rotor;

[0098] 214 vibrator;

[0099] 300 digital camera.

Claims

1. A vibration type driving device, comprising: a vibration type actuator including a vibrator and a contact body that move relative to each other; as well as a drive control device configured to control a drive voltage to be applied to the vibration-type actuator and a frequency of the drive voltage, wherein, from starting the vibration-type actuator to reaching a target speed of relative movement, the drive control device increases the drive voltage to accelerate the drive of the vibration-type actuator, when the power supplied to the vibrator exceeds a first power value, the drive control device reduces the frequency of the drive voltage without changing the drive voltage, and when the power drops below a second power value less than the first power value during an operation of reducing the frequency, the drive control device increases the drive voltage, and Among them, the drive control device also includes an oscillation unit that generates a pulse signal. The drive control device generates the drive voltage by utilizing the pulse signal to switch the DC power supply voltage, changes the drive voltage by changing the pulse width of the pulse signal, and changes the frequency of the drive voltage by changing the frequency of the pulse signal.

2. The vibration type driving device according to claim 1, wherein: The maximum value of the pulse width is set according to the voltage value of the power supply voltage, and When the pulse width reaches the maximum value, the drive control device does not increase the pulse width even if the power drops below the second power value.

3. The vibration type driving device according to claim 2, wherein: The drive control device changes the pulse width and frequency of the pulse signal so that after the power drops below the second power value which is less than the first power value, and until the pulse width reaches the maximum value in the operation of increasing the drive voltage by increasing the pulse width, the change in power is equal to or less than 10% of the second power value.

4. A vibration-type driving device, comprising: a vibration type actuator including a vibrator and a contact body that move relative to each other; as well as a drive control device configured to control a drive voltage to be applied to the vibration-type actuator and a frequency of the drive voltage, Wherein, from starting the vibration-type actuator to reaching the target speed of relative movement, the drive control device increases the drive voltage to accelerate the drive of the vibration-type actuator, and when the power supplied to the vibrator exceeds a predetermined power value, the drive control device reduces the frequency of the drive voltage and increases the drive voltage.

5. The vibration type driving device according to claim 4, wherein: The drive control device also includes an oscillation unit that generates a pulse signal. The drive control device generates the drive voltage by switching a DC power supply voltage using the pulse signal, changes the drive voltage by changing the pulse width of the pulse signal, and changes the frequency of the drive voltage by changing the frequency of the pulse signal.

6. The vibration type driving device according to claim 5, wherein: The maximum value of the pulse width is set according to the voltage value of the power supply voltage, and When the pulse width reaches the maximum value, the drive control device does not increase the pulse width even if the power drops below the predetermined power value.

7. The vibration type driving device according to claim 6, wherein: The drive control device changes the pulse width and frequency of the pulse signal so that after the power drops below the predetermined power value and until the pulse width reaches the maximum value in the operation of increasing the drive voltage by increasing the pulse width, the change in power is equal to or less than 10% of the predetermined power value.

8. The vibration type driving device according to any one of claims 1 to 7, wherein: The drive control device monotonically decreases the frequency of the drive voltage in the operation of decreasing the frequency of the drive voltage.

9. The vibration type driving device according to claim 1 or 4, wherein: The drive control device controls the frequency of the drive voltage based on a predetermined speed command value in an operation of reducing the frequency of the drive voltage.

10. The vibration type driving device according to claim 1 or 4, wherein: A difference between a resonance frequency of the drive control device and a resonance frequency of the vibrator is in a range of 8 KHz to 30 KHz.

11. An apparatus comprising: The vibration type driving device according to claim 1 or 4; as well as A member configured to be positioned by driving the vibration-type actuator controlled by the drive control device of the vibration-type drive device.

12. A drive control device for a vibration-type actuator, the vibration-type actuator comprising a vibrator and a contact body that move relative to each other, the drive control device comprising: an amplifying unit configured to amplify a power supply voltage to generate a driving voltage to be applied to the vibrator; as well as a control unit configured to control generation of the drive voltage by the amplification unit, Wherein, from starting the vibration-type actuator to reaching the target speed of relative movement, the drive control device increases the drive voltage to accelerate the drive of the vibration-type actuator, when the power supplied to the vibrator exceeds a first power value, the drive control device reduces the frequency of the drive voltage without changing the drive voltage, and when the power drops to below a second power value less than the first power value during the operation of reducing the frequency, the drive control device increases the drive voltage.

13. A drive control device for a vibration type actuator, the vibration type actuator comprising a vibrator and a contact body that move relative to each other, the drive control device comprising: an amplifying unit configured to amplify a power supply voltage to generate an AC driving voltage to be applied to the vibrator; as well as a control unit configured to control generation of the drive voltage by the amplification unit, Wherein, from starting the vibration-type actuator to reaching the target speed of relative movement, the drive control device increases the drive voltage to accelerate the drive of the vibration-type actuator, and when the power supplied to the vibrator exceeds a predetermined power value, the drive control device reduces the frequency of the drive voltage and increases the drive voltage.

14. A drive control method for a vibration type actuator, the vibration type actuator comprising a vibrator and a contact body that move relative to each other, the drive control method comprising the following steps: From starting the vibration-type actuator to reaching a target speed of relative movement, increasing a driving voltage to accelerate the driving of the vibration-type actuator; When the power supplied to the vibrator exceeds a first power value, reducing the frequency of the driving voltage without changing the driving voltage; and When the power drops below a second power value that is smaller than the first power value during the operation of reducing the frequency, the driving voltage is increased.

15. A drive control method for a vibration type actuator, the vibration type actuator comprising a vibrator and a contact body that move relative to each other, the drive control method comprising the following steps: From starting the vibration-type actuator to reaching a target speed of relative movement, increasing a driving voltage to accelerate the driving of the vibration-type actuator; and When the power supplied to the vibrator exceeds a predetermined power value, the frequency of the driving voltage is reduced and the driving voltage is increased.

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