JP5321036B2 - Vibration actuator, lens barrel, and optical device - Google Patents

Description

  The present invention relates to a vibration actuator, a lens barrel, and an optical device.

  For example, an ultrasonic motor may be used in an autofocus drive mechanism of a camera. The ultrasonic motor is configured such that an elastic body (stator) provided with a piezoelectric element and a moving element (rotor) are overlapped, and a high frequency voltage having a frequency (driving frequency) in an ultrasonic region is applied to the piezoelectric body. When applied, the elastic body is vibrated to generate a progressive vibration wave. Due to the influence of the progressive vibration wave, the rotor pressurized by the spring is rotationally driven.

  Since the ultrasonic motor is used in a frequency region higher than the resonance frequency, as the driving frequency (f) is lowered, the ultrasonic motor approaches the resonance frequency and the rotation speed increases exponentially. That is, the rotational speed of the rotor of the ultrasonic motor rotates at a high speed when the driving frequency (f) is low, and rotates at a low speed when the driving frequency (f) is high. There was a problem that it was difficult to continue the low-speed rotation stably.

Regarding the control of the rotational speed of the rotor of the ultrasonic motor, there has been proposed a technique for switching the drive voltage from a low voltage to a high voltage when the drive frequency is low (see Patent Document 1). However, in the conventional ultrasonic motor, it is difficult to realize stable rotation of the rotor when the rotor rotates at a low speed.
JP 2002-305484 A

  An object of the present invention is to provide a vibration actuator that can operate stably from a low speed to a high speed, and a lens barrel and an optical device having the actuator.

In order to achieve the above object, a vibration actuator according to the present invention includes:
A vibration member (103) that generates a vibration wave by applying an AC voltage to the electromechanical transducer (104);
A relative movement member (102) that moves relative to the vibration member (103) by the vibration wave;
Voltage applying means (22, 23, 25) for applying the AC voltage to the electromechanical transducer (104);
Control means (20) for changing the amplitude of the alternating voltage according to the relative moving speed between the vibrating member (103) and the relative moving member (102).

  The vibration actuator of the present invention has control means (20) for changing the amplitude of the AC voltage in accordance with the relative movement speed between the vibration member (103) and the relative movement member (102). Therefore, a high voltage can be applied to the actuator when the actuator rotates at a low speed, and the actuator can be stably operated when the actuator rotates at a low speed. In addition, when the actuator rotates at high speed, the relative movement member (102) can operate stably due to the inertial force even when a low voltage is applied, and contributes to energy saving.

  When the moving speed of the relative movement member (102) is smaller than a predetermined value (Ns), the vibration actuator has an amplitude of the alternating voltage with respect to an amplitude of the alternating voltage when the moving speed is larger than the predetermined value (Ns). May be increased. When the rotational speed of the rotor (102) is smaller than a predetermined value, the actuator can be driven stably when the rotor (102) rotates at a low speed by increasing the voltage.

  The vibration actuator may change the amplitude of the AC voltage stepwise. By changing the AC voltage stepwise according to the driving speed of the actuator, the driving speed of the actuator can be changed smoothly.

  The vibration actuator may continuously change the amplitude of the AC voltage. By continuously changing the AC voltage according to the driving speed of the actuator, the driving speed of the actuator can be changed more smoothly.

  The vibration actuator further includes detection means (26) for detecting the movement speed of the relative movement member (102), and performs control according to the movement speed of the relative movement member (102) recognized by the detection means. It may be. Thereby, since the driving speed of the actuator is monitored, feedback control is performed by the control circuit 20, and the actuator can be controlled with high accuracy.

  In the vibration actuator, when it is determined that the moving speed of the relative moving member (102) is equal to or greater than a predetermined time and equal to or less than a predetermined value, the control means (20) You may make it interrupt | block the said alternating voltage applied to the said electromechanical conversion element (102). If the voltage is continuously output when the actuator is not driven for some reason such as a failure, the actuator will overheat, causing a failure. Therefore, failure of the actuator can be prevented by cutting off the AC voltage.

  In the vibration actuator, a resonance circuit (27) may be formed by the voltage application means (25) and the electromechanical transducer (104). It is not necessary to prepare a resonance circuit separately from the voltage applying means, which contributes to the compactness of the device.

  A lens barrel according to the present invention includes the vibration actuator according to any one of the above. An optical device according to the present invention includes any of the vibration actuators described above.

  In the above description, in order to explain the present invention in an easy-to-understand manner, the description has been made in association with the reference numerals of the drawings showing the embodiments, but the present invention is not limited to this. The configuration of the embodiment described later may be improved as appropriate, or at least a part of the configuration may be replaced with another component. Further, the configuration requirements that are not particularly limited with respect to the arrangement are not limited to the arrangement disclosed in the embodiment, and can be arranged at a position where the function can be achieved.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a schematic configuration diagram of a camera according to an embodiment of the present invention.
2 is a drive circuit diagram of the AF motor shown in FIG.
FIG. 3 is a side view of an ultrasonic motor used as the AF motor shown in FIG.
FIG. 4 is a flowchart showing an example of control of the drive circuit shown in FIG.
FIG. 5 is a timing chart in the drive circuit shown in FIG.
FIG. 6 is a graph showing the relationship between the drive frequency (f) and the rotational speed (N) in the ultrasonic motor.

  First, the overall configuration of a camera according to an embodiment of the present invention will be described with reference to FIG. In the following description, a single-lens reflex camera in which the lens barrel 100 and the camera body 200 are detachable will be described. As shown in FIG. 1, a lens barrel 100 is detachably attached to the camera body 200.

  As shown in FIG. 1, the camera body 200 includes a battery 1 that is detachably incorporated therein. The negative terminal of the battery 1 is connected to the common ground line 7 of the camera body 200 and to the electrical contact 66. The negative terminal of the battery 1 is also connected to the power circuit 2.

  In a state where the camera body 200 and the lens barrel 100 are connected, the common ground line 7 of the camera body 200 is connected to the common ground line 8 of the lens barrel 100, and conduction is ensured. When the camera body 200 and the lens barrel 100 are coupled, the electrical circuit in the lens barrel 100 and the electrical circuit in the camera body 200 are electrically connected via the electrical contacts 61 to 66. Is done.

  The positive terminal of the battery 1 is connected to a power supply switch 5 controlled by the body CPU 3, and when the power supply switch 5 is turned on, the power supply circuit 11 of the lens barrel 100 and the shake correction motor are connected via the electrical contacts 61. A voltage can be supplied to the (VR motor) 15, the aperture drive circuit 16 and the voltage monitor circuit 18. The positive terminal of the battery 1 is further connected to the power supply circuit 2 in the camera body 200. The power supply circuit 2 is controlled by the body CPU 3.

  The GND terminal of the body CPU 3 is connected to the common ground line 7, and the VDD terminal of the CPU 3 is connected to the positive terminal of the battery 1 and the output terminal of the power supply circuit 2 through respective diodes. For this reason, the body CPU 3 can be activated when the battery is inserted. The operation of the external switch group 4 of the camera body 200 is input to the body CPU 3, and when a predetermined switch input is detected, the body CPU 3 controls the power supply circuit 2 on / off.

  For example, as an operation of the camera, normally, when a shutter button (not shown) is half-pressed, the body CPU 3 controls the power supply circuit 2 on. As a result, the power supply circuit 2 outputs a voltage and supplies power to the lens CPU 9 via the electrical contact 62, so that the lens CPU 9 can operate. Various switches 10 are connected to the lens CPU 9 with the common ground line 8, and various settings and controls of the lens CPU 9 can be changed by operating the various switches 10.

  When the lens CPU 9 becomes operable, the lens CPU 9 communicates with the body CPU 3 via the electrical contacts 63 to 65. As a result, the body CPU 3 switches the power supply switch 5 to the on state, and the lens CPU 9 activates the power supply circuit 11 to supply power to the AF motor driving circuit 12 and the blur correction circuit 13 existing in the lens, thereby performing the operation of each function. Start. Further, since the power supply switch 5 is in the on state, the AF motor 14, the VR motor 15 and the aperture motor 17 in the lens are all operable.

  In the internal circuit of the lens barrel 100, when the AF motor 14 and the VR motor 15 in the lens are in operation, the output of the power supply circuit 11 may go down for some reason. In such a case, the power supply from the power supply circuit 11 to the AF motor driving circuit 12 and the blur correction circuit 13 is stopped, and the loads of the AF motor 14 and the VR motor 15 are supplied via the electrical contacts 61. It is automatically disconnected from one power supply path.

  The AF motor 14 shown in FIG. 1 includes an ultrasonic motor 14a shown in FIG. In this ultrasonic motor 14 a, the rotor 102 is pressed against the stator 103 by the spring 101, the piezoelectric element 104 is bonded to the stator 103, and the substrate 106 is bonded to the piezoelectric element 104. When an AC voltage is applied to the piezoelectric element 104 via the electrode lead wire 105 and the piezoelectric element 104 is excited, a progressive vibration wave is generated in the stator 103 and the rotor 102 is driven to rotate. .

  As shown in FIG. 2, the ultrasonic motor 14a having the piezoelectric element 104 shown in FIG. 3 can be represented by a capacitor component C in the electric circuit, and the secondary of the transformer (transformer) 25 in the AF motor driving circuit 12. The resonance circuit 27 is configured by pairing with the side inductance L2.

  In the AF motor drive circuit 12, a primary side inductance L1 that is paired with a secondary side inductance L2 of a transformer (transformer) 25 is disposed, and a switching element 24 is connected between the primary side inductance L1 and the ground line. The switching element 24 is controlled at the output port OUT of the control circuit 20. The driving frequency (f) of the ultrasonic motor 14a can be changed by changing the frequency of the high-frequency pulse signal output from the output port OUT.

  Only the voltage E1 from the power supply circuits 22 and 23 or the voltage E1 + E2 is applied to the primary inductance L1 of the transformer 25. Switching of only the voltage E1 to the primary inductance L1 or the voltage E1 + E2 is performed by the switching element 21, and the element 21 is controlled by an output signal from the control port CTL of the control circuit 20.

  As shown in FIG. 2, the rotation state of the ultrasonic motor 14a is detected by the rotation detection sensor 26 and input to the monitor port MON of the control circuit 20, so that the rotation state can be always recognized. The control circuit 20 shown in FIG. 2 may be incorporated in the lens CPU 9 shown in FIG. 1 or may be another control circuit. The power supply circuits 22 and 23 shown in FIG. 2 may be incorporated in the power supply circuit 11 shown in FIG. 1 or may be other circuits.

  Next, the control of the ultrasonic motor 14a shown in FIGS. 2 and 3 used as the AF motor 14 shown in FIG. 1 will be described mainly based on FIG.

  When the control starts in step S1 shown in FIG. 4, the switching element 21 is turned on based on the output signal from the control terminal CTL of the control circuit 20 shown in FIG. 2, and in step S2 shown in FIG. Only the voltage E1 from the power supply circuit 22 is applied to the primary inductance L1 of 25. In FIG. 5, the state is shown between time t0 and t1. In this state, no drive signal is output from the output port OUT of the control circuit 20 shown in FIG. Therefore, no vibration traveling wave is generated in the ultrasonic motor 14a, and a signal indicating that the rotation detection of the ultrasonic motor 14a is 0 is input to the monitor port MON of the control circuit 20.

  Next, in step S2, it is determined whether or not the release button is half-pressed based on the input signal to the body CPU 3 shown in FIG. 1, and if not, step S2 and step S3 are repeated, In that case, the operation of step S4 is performed.

  In step S4, as shown at time t1 shown in FIG. 5, a control signal is sent from the control port CTL shown in FIG. 2 to the switching element 21, and the switching element 21 is turned off. As a result, the weighted voltage E1 + E2 from the power supply circuits 22 and 23 is applied as the voltage V1 to the primary inductance L1. In step S4, a relatively high frequency pulse signal is applied to the switching element 24 shown in FIG. 2 from the output port OUT shown in FIG. 2, as shown in FIG. Therefore, a relatively high frequency and high voltage V2 is applied to the secondary inductance L2 and the ultrasonic motor 14a shown in FIG. 2 as shown by the waveform between times t1 and t2 shown in FIG. .

  Next, in step S5 shown in FIG. 4, the control circuit 20 shown in FIG. 2 determines whether or not the rotation speed detected by the rotation detection sensor 26 is 0 for a predetermined time or more. In step S4, if the pulse voltage V2 between the times t1 and t2 shown in FIG. 5 is applied to the ultrasonic motor 14a shown in FIG. The sonic motor 14a should be rotating at a low speed.

  Nevertheless, when the rotation speed detected at the monitor port MON of the control circuit 20 is 0 in step S5 shown in FIG. 4, some failure has occurred or the autofocus control has ended. This is the case. Therefore, in such a case, the process goes to step S7 shown in FIG. 4 to output a control signal from the control circuit 20 shown in FIG. 2 or the lens CPU 9 shown in FIG. The supply of voltage to the motor 14a is cut off.

  In addition, in step S5 shown in FIG. 4, when the detection of the rotational speed detected by the monitor port MON of the control circuit 20 is not 0, it is considered that the autofocus control is continuing in the normal state. In such a case, the process goes to step S6, and the control circuit 20 shown in FIG. 2 determines whether or not the rotational speed of the ultrasonic motor is higher than the predetermined rotational speed Ns shown in FIG.

  When the rotational speed of the ultrasonic motor is lower than the predetermined rotational speed Ns shown in FIG. 6, the process returns to step S4, and steps S4 and S5 are repeated. In order to speed up the autofocus operation, the control circuit 20 lowers the drive frequency from the output terminal OUT shown in FIG. 2, for example, at the timing of time t2 shown in FIG. 5, and increases the rotation speed of the ultrasonic motor 14a.

  As a result, the control circuit 20 shown in FIG. 2 detects that the rotational speed of the ultrasonic motor 14a is higher than the predetermined rotational speed Ns shown in FIG. 6 based on the input signal from the monitor port MON. When a rotational speed higher than the predetermined rotational speed Ns is detected, it can be determined that the rotational speed can continue to rotate stably. In such a case, the process returns to step S2 shown in FIG. 4, and the control circuit 20 shown in FIG. 2 outputs a control signal from the control port CTL as shown by the times t2 to t3 shown in FIG. Turn on 21. Therefore, only the voltage E1 is applied as the voltage V1 to the primary side inductance L1.

  As a result, a voltage V2 having a driving waveform during high-speed rotation from time t2 to time t3 shown in FIG. 5 is applied to the ultrasonic motor 14a shown in FIG. The amplitude of the drive waveform voltage V2 during high-speed rotation is shorter than the drive waveform voltage V2 during low-speed rotation, and is approximately half in this embodiment.

  In order to end the autofocus control, the control circuit 20 shown in FIG. 2 shifts the rotation speed of the ultrasonic motor 14a from the high-speed rotation to the low-speed rotation, for example, at a timing t3 shown in FIG. The drive frequency from the output terminal OUT shown in FIG. 6 is increased, and the rotational speed of the ultrasonic motor 14a is decreased.

  As a result, based on the input signal from the monitor port MON, the control circuit 20 shown in FIG. 2 causes the rotational speed of the ultrasonic motor 14a to be higher than the predetermined rotational speed Ns shown in FIG. 6 in step S6 shown in FIG. Detect low. Therefore, the process returns to step S4 shown in FIG. 4, and the control circuit 20 shown in FIG. 2 outputs a control signal from the control port CTL and turns off the switching element 21 as shown from time t3 to t4 shown in FIG. . Therefore, the voltage E1 + E2 is applied as the voltage V1 to the primary side inductance L1.

  As a result, a voltage V2 having a driving waveform during low-speed rotation from time t3 to time t4 shown in FIG. 5 is applied to the ultrasonic motor 14a shown in FIG. When the control circuit 20 shown in FIG. 2 detects the end of the autofocus operation, the output of the drive pulse signal from the output port OUT is stopped and the drive of the ultrasonic motor 14a is stopped.

  According to the drive circuit 12 including the ultrasonic motor 14a according to the present embodiment and the camera including the lens barrel 100 using the same, a high voltage is applied to increase the drive torque when the ultrasonic motor 14a rotates at a low speed. Thus, the motor 14a can be continuously driven even during low-speed rotation. Further, even when a low voltage is applied during the high-speed rotation of the ultrasonic motor 14a, the rotor 102 can be stably rotated by the inertial force, and contributes to energy saving.

  In FIG. 6, it can be said that the rotation region lower than the predetermined rotation speed Ns is an unstable low-speed rotation region. The unstable low-speed rotation region is based on the characteristics of the ultrasonic motor 14a. As shown in FIG. 6, the drive frequency at which the rotation speed stops when the drive frequency f is moved from higher to lower. This is a region where hysteresis occurs where f1 and the opposite drive frequency f2 are different.

  In such a low-speed rotation region, conventionally, it has been difficult to stably rotate at a low speed, but in the present embodiment, as described above, by increasing the voltage compared to the time of high-speed rotation, the low-speed rotation Even at times, the motor 14a can be driven stably. The predetermined rotational speed Ns shown in FIG. 6 is a value that is 1.2 to 1.3 times or more the maximum rotational speed Nm at which hysteresis occurs, for example.

  In the embodiment described above, as shown in FIG. 5, the frequency of the drive signal output from the output port OUT of the control circuit 20 shown in FIG. 2 changes rapidly at time t2 or t3. However, the present invention is not limited to this, and it may be changed in multiple steps, or may be gradually changed gradually. Similarly, the amplitude of the voltage V2 applied to the ultrasonic motor 14a shown in FIG. 2 also changes abruptly at the time t2 or t3. It may be good or gradually changed gradually.

  Further, in the above-described embodiment, the rotation detection sensor 26 shown in FIG. 2 is used to detect the rotation speed of the ultrasonic motor 14a, and the amplitude of the voltage V2 applied to the ultrasonic motor 14a is changed based on the detection result. I did, but it is not limited to that. For example, without providing the rotation detection sensor 26, the drive frequency signal output from the output port OUT of the control circuit 20 is monitored by the control circuit 20 itself and applied to the ultrasonic motor 14a in accordance with the drive frequency. The amplitude of the voltage V2 may be changed. This is because the driving frequency corresponds to the rotational speed of the ultrasonic motor 14a.

  Furthermore, in the above-described embodiment, an example in which the vibration actuator of the present invention is incorporated in a single-lens reflex camera has been described. It may be incorporated, or may be incorporated into other devices.

FIG. 1 is a schematic configuration diagram of a camera according to an embodiment of the present invention. FIG. 2 is a drive circuit diagram of the AF motor shown in FIG. FIG. 3 is a side view of an ultrasonic motor used as the AF motor shown in FIG. FIG. 4 is a flowchart showing an example of control of the drive circuit shown in FIG. FIG. 5 is a timing chart in the drive circuit shown in FIG. It is a graph which shows the relationship between the drive frequency (f) and rotational speed (N) in an ultrasonic motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 ... AF motor 14a ... Ultrasonic motor 20 ... Control circuit 21, 24 ... Switching element 22 ... Power supply circuit 23 ... Power supply circuit 25 ... Transformer 26 ... Rotation detection sensor 27 ... Resonance circuit 100 ... Lens barrel 102 ... Rotor 103 ... Stator 104 ... Piezoelectric element 200 ... Camera body

Claims (8)

A vibration member that generates a vibration wave by applying an AC voltage to the electromechanical transducer;
A relative movement member that moves relative to the vibration member by the vibration wave;
Voltage application means for applying the alternating voltage to the electromechanical transducer;
Have a control means for changing the amplitude of the AC voltage in accordance with the relative moving speed of the relative movement member and the vibration member,
The control means shuts off the AC voltage applied to the electromechanical transducer from the voltage application means when it is determined that the moving speed of the relative movement member is not less than a predetermined value for a predetermined time or more. A characteristic vibration actuator. The amplitude of the AC voltage is increased when the moving speed of the relative moving member is smaller than a predetermined value with respect to the amplitude of the AC voltage when the relative moving member is larger than the predetermined value. Vibration actuator. The vibration actuator according to claim 1, wherein the amplitude of the AC voltage is changed stepwise. The vibration actuator according to claim 1, wherein the amplitude of the AC voltage is continuously changed. 5. The apparatus according to claim 1, further comprising a detecting unit that detects a moving speed of the relative moving member, wherein control is performed according to the moving speed of the relative moving member recognized by the detecting unit. The vibration actuator described. Vibration actuator according to any one of claims 1 to 5, characterized in that the resonant circuit is formed with the voltage applying means by said electromechanical transducer. A lens barrel having a vibration actuator according to any one of claims 1-6. An optical device having the lens barrel according to claim 7 .

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