JP4630676B2 - Drive device - Google Patents

Description

The present invention relates to a drive device using at least three vibration actuators as drive sources.

  Some conventional drive devices use a plurality of vibration-type motors as drive sources and synthesize drive forces from these vibration-type motors and transmit them to a driven member (see, for example, Patent Document 1). Specifically, the driving force from each vibration type motor is transmitted to one output shaft, and the driven member is driven by the driving force synthesized by this output shaft.

In this drive device, various rotation speeds and output torques can be obtained according to the speed increase / decrease ratio in the power transmission mechanism connected to each vibration type motor and the number of vibration type motors. A desired driving force can be supplied to the driven member.
Japanese Patent Laid-Open No. 06-197564 (paragraph numbers 0008 to 0025, FIG. 1, etc.)

  In the drive device described above, since a plurality of vibration type motors are connected to one output shaft, it is necessary to drive these vibration type motors at substantially the same number of revolutions. However, when there is a large difference in drive characteristics among a plurality of vibration motors, a so-called squealing phenomenon occurs.

  That is, a squealing phenomenon occurs when a vibration type motor having a smaller number of rotations than other vibration type motors is affected by the drive of the other vibration type motor. In the vibration type motor in which the squeal phenomenon occurs, the rotation speed and the output torque are reduced.

One object of the present invention is to provide a drive device that can suppress the occurrence of squeal in each vibration type actuator in a drive device using at least three vibration type actuators as a drive source.

The drive device according to the present invention includes a vibration body that generates vibration by applying a drive signal to the electromechanical energy conversion element , at least three vibration-type actuators including a contact body that contacts the vibration body, and at least three It has a circuit for applying the same drive signal to the vibration type actuator, and a power transmission mechanism for synthesizing drive forces from at least three vibration type actuators and transmitting them to the driven member. Here, when the same drive signal is applied to at least three vibration-type actuators, the number of vibration-type actuators driven at a lower rotation speed than the average rotation speed of these vibration-type actuators is the average of the rotation speeds. More than the number of vibration type actuators driven at a higher rotational speed than the value.

According to the present invention, when at least three vibration actuators are driven, it is possible to suppress the occurrence of a squeal phenomenon in any of the vibration actuators.

  Examples of the present invention will be described below.

  FIG. 1 is a schematic diagram showing the configuration of a drive apparatus that is Embodiment 1 of the present invention.

In FIG. 1, a transmission member (gear) 2 which is a part of the power transmission mechanism is fixed to a rotary shaft 1 which is a part of the power transmission mechanism . The rotating shaft 1 is connected to the driven member 24 through a power transmission mechanism ( not shown ) (mechanism other than the rotating shaft 1 and the transmission member 2) .

  The transmission member 2 meshes with the transmission members (gears) 3 to 8. Each transmission member 3-8 is being fixed to the output shaft of each vibration type motor 9-14. The vibration type motors 9 to 14 are arranged around the rotation shaft 1.

In the above configuration, the driving force of the vibration type motor 9 to 14 is transmitted to the rotating shaft 1 via a respective transmission member 3-8 and the transmitting member 2, the driving force is synthesized in this pathway. And the rotational force of the rotating shaft 1 is transmitted to the driven member 24 via a power transmission mechanism (not shown), and the driven member 24 operates.

  Here, as the driven member 24, for example, a driving unit of an electric head device for turning a mounted TV camera or the like, an electric stage for performing a linear operation in a semiconductor manufacturing apparatus, and a photographing lens in a photographing optical system are used as light. There is a drive unit that moves in the axial direction, and a photosensitive drum in the image forming apparatus.

  Drive signals from the drive circuits 15 to 20 are input to the vibration motors 9 to 14, respectively. An oscillation circuit 21 and a control circuit 22 that supply drive signals are connected to each of the drive circuits 15 to 20. Predetermined power is supplied from the power supply circuit 23 to each circuit described above.

When receiving the control signal from the control circuit 22, the oscillation circuit 21 outputs a signal having a frequency corresponding to the control signal to each of the drive circuits 15-20. Each drive circuit 15-20 outputs a two-phase AC voltage (drive signal) having a phase difference of 90 degrees, and this two-phase AC voltage is applied to each vibration motor 9-14.

  Each vibration type motor 9-14 has the structure shown in FIG. In the vibration type motor, an AC voltage is applied to the piezoelectric element 26 as an electro-mechanical energy conversion element to expand and contract the piezoelectric element 26, and a progressive vibration wave is generated in the elastic body 25 using the expansion and contraction. . Then, the rotating body (contact body) 29 in pressure contact with the elastic body 25 is rotated by the progressive vibration wave.

  A piezoelectric element 26 is bonded to one end surface of the annular elastic body 25, and a synthetic resin friction material 27 is bonded to the other end surface side in contact with the rotating body 29. Thereby, the vibrating body 28 is configured. The rotating body 29 is in pressure contact with the friction material 27 by receiving pressure from a pressure mechanism 32 having a pressure spring 30 and a pressure ring 31.

  When a two-phase AC voltage having a phase difference of 90 degrees is applied to the piezoelectric element 26 of the vibrating body 28, a progressive vibration wave is generated in the vibrating body 28 and rotates due to friction between the friction material 27 and the rotating body 29. The body 29 rotates with respect to the vibrating body 28. A shaft 33 is fixed to the rotating body 29, and the shaft 33 rotates together with the rotating body 29.

  In the present embodiment, the case of using the annular type vibration type motor as shown in FIG. 2 has been described, but other vibration type motors such as a so-called rod type may be used.

  In the configuration of the vibration type motor described above, the vibration amplitude of the vibration body 28 increases as the frequency of the AC voltage applied to the piezoelectric element 26 of the vibration body 28 approaches the resonance frequency of the vibration body 28, and is applied to the vibration body 28. The rotating body 29 in pressure contact can be rotated faster.

  3 and 4 show the relationship between the frequency (drive frequency) of the drive signal applied to the vibration type motor (piezoelectric element) and the rotation speed of the vibration type motor. 3 and 4 show the drive characteristics of the two vibration motors. Fr1 and fr2 in FIG. 3 and fr1 ′ and fr2 ′ in FIG. 4 indicate resonance frequencies of the vibration motors.

  Each vibration type motor has a characteristic that the rotational frequency increases as the drive frequency approaches the resonance frequencies fr1, fr2, fr1 ', fr2' from the high frequency side.

  FIG. 3 shows a case where the difference “| fr1-fr2 |” of the resonance frequencies of the vibrating bodies constituting each vibration type motor is smaller than the case shown in FIG.

  In FIG. 3, when each vibration type motor is driven at the drive frequency f1, the difference in the rotational speed is “N1−N2 (N1> N2)”. Further, when each vibration type motor is driven at the drive frequency f2, the difference in the rotational speed is “N3−N4 (N3> N4)”. Further, when each vibration type motor is driven at the drive frequency f3, the difference in the rotational speed becomes “N5−N6 (N5> N6)”.

  On the other hand, FIG. 4 shows a case where the difference “| fr1′−fr2 ′ |” of the resonance frequencies of the vibrators constituting each vibration type motor is larger than that shown in FIG.

  In FIG. 4, when each vibration type motor is driven at the drive frequency f1, the difference in the rotational speed is “N1′−N2 ′ (N1 ′> N2 ′)”. Further, when each vibration motor is driven at the drive frequency f2, the difference in the rotational speed is “N3′−N4 ′ (N3 ′> N4 ′)”. Further, when each vibration type motor is driven at the drive frequency f3, the difference in the rotational speed becomes “N5′−N6 ′ (N5 ′> N6 ′)”.

  When there is a difference in the resonance frequency of the vibration type motor as described above, when the vibration type motor is driven at the same drive frequency, a difference occurs in the rotation speed, and the difference in the rotation speed increases as the drive frequency approaches the resonance frequency.

  As shown in FIG. 4, in the case where a plurality of vibration type motors having a large difference in resonance frequency are used, the number of vibration type motors on the higher rotation side is larger than the number of vibration type motors on the lower rotation side. In many cases, applying the same drive frequency to each vibration type motor causes the problems described below.

  When the difference in rotational speed of the vibration type motor exceeds a predetermined value, that is, when the drive frequency is smaller than the predetermined frequency and within the range higher than the resonance frequency, the vibration type on the lower rotational speed side A squeaking phenomenon may occur in the motor. That is, the squealing phenomenon occurs because the vibration type motor on the low rotation speed side is affected by the driving of the vibration type motor on the high rotation speed side.

  In the vibration type motor in which the squeal phenomenon has occurred in this way, the rotational speed is further reduced, and the squeal phenomenon is further promoted. And the torque in a drive device will fall by the fall of rotation speed.

  In order to apply the same drive frequency to a plurality of vibration-type motors and rotate the plurality of vibration-type motors at the same rotation speed, the relationship between the drive frequency and the rotation speed shown in FIGS. 3 and 4 is substantially the same. There is a need.

  However, the vibrating body 28 in each of the vibration type motors 9 to 14 includes the elastic body 25, the piezoelectric element 26, and the friction material 27 as described above, and has slight variations. For this reason, in the vibrating body 28 of the vibration type motors 9 to 14, a difference occurs in the resonance frequency, and as a result, the resonance frequencies in the vibration type motors 9 to 14 are different.

  In this way, when the resonance frequencies of the vibration type motors 9 to 14 are different, as described above, a squealing phenomenon occurs in the vibration type motor on the side with a smaller rotation speed.

  Therefore, in this embodiment, the resonance frequency in each of the vibration type motors 9 to 14 is set to be within a range of about 1% or less of the predetermined resonance frequency with respect to the predetermined resonance frequency. The resonance frequency of each of the vibration type motors 9 to 14 can be measured before being incorporated in the driving device, and the measurement result only needs to be within the above-described range.

  In this way, by setting the resonance frequency of each of the vibration type motors 9 to 14 within a range of approximately 1% or less with respect to the predetermined resonance frequency, occurrence of a squealing phenomenon can be suppressed. That is, by setting the resonance frequency of the vibrating body 28 in each of the vibration type motors 9 to 14 to the above-described condition, even if a drive signal having the same frequency is applied to the vibration type motors 9 to 14, the vibration type motor 9. It can suppress that the difference of the rotation speed between ~ 14 becomes larger than predetermined value. Thereby, the squealing phenomenon which arises by the difference in rotation speed beyond a predetermined value can be suppressed.

  For example, when using a plurality of vibration type motors having a resonance frequency of 60 kHz, the resonance frequency of each of the vibration type motors 9 to 14 is within 0.6 kHz (60 kHz × 0.1) with respect to the resonance frequency of 60 kHz. It should be set as follows.

  On the other hand, the rotational speed of each of the vibration type motors 9 to 14 may be set to be within a range of about 15% or less of the predetermined rotational speed with respect to the predetermined rotational speed. Specifically, a drive signal having the same frequency is applied to a plurality of vibration type motors to measure the number of rotations in each vibration type motor in advance, and the number of rotations (drive characteristics indicating the relationship between the drive frequency and the number of rotations). However, a vibration type motor that satisfies the above-described conditions may be incorporated in the drive device.

  In this case as well, the occurrence of the squealing phenomenon can be suppressed as described above.

  For example, when a predetermined drive signal (a drive signal having the same frequency) is applied to rotate the vibration type motors 9 to 14 at 200 r / min, the rotation speed is 30 r / min (with respect to the rotation speed 200 r / min). A vibration type motor within 200r / min × 0.15) may be used.

  Further, in the case of using three or more vibration type motors 9 to 14 as in this embodiment, the average value of the rotation speeds of the plurality of vibration type motors 9 to 14 by applying a predetermined drive signal (the same drive signal). Is a reference value, the number of vibration motors having a lower rotational speed than the reference value may be larger than the number of vibration motors having a higher rotational speed than the reference value. That is, the rotational speed of each of the vibration type motors 9 to 14 can be measured in advance, and based on the measurement result, a vibration type motor that satisfies the above-described conditions may be incorporated in the drive device.

  Even if comprised in this way, generation | occurrence | production of the noise phenomenon at the time of driving a some vibration type motor can be suppressed.

In this embodiment, a gear is used as a power transmission mechanism for transmitting the driving force of each of the vibration type motors 9 to 14 to the rotary shaft 1, but a combination of a pulley and a belt, a combination of a timing pulley and a timing belt, a rotor A power transmission mechanism can also be comprised by the combination of these.

Moreover, although the present Example demonstrated the structure using the six vibration type motors 9-14, this invention can be applied when using three or more vibration type motors. For example, as shown in FIGS. 5 to 7, three or four vibration type motors can be incorporated in the drive device.

Further, when a plurality of vibration type motors are used, as shown in FIGS. 5 and 6, the diameter of the transmission member (gear) fixed to the rotary shaft 1 and the output shaft of each vibration type motor are attached. By changing the diameter of the transmission member (gear), that is, by changing the gear ratio, the torque and the number of rotations of the rotary shaft 1 can be changed. As a result, an appropriate driving force corresponding to the purpose of use can be supplied to the driven member 24. For example, if the reduction ratio is increased by a power transmission mechanism including gears, the number of vibration type motors can be reduced, and an increase in the size of the drive device can be suppressed.

The figure which shows the structure of the drive device which is Example 1 of this invention. Sectional drawing of a vibration type motor. The figure which shows the relationship between the drive frequency and rotation speed of a vibration type motor. The figure which shows the relationship between the drive frequency and rotation speed of a vibration type motor. The figure which shows the structure of the drive device using three vibration type motors. The figure which shows the other structure of the drive device using three vibration type motors. The figure which shows the structure of the drive device using four vibration type motors.

Explanation of symbols

1: Rotating shaft 2: Transmission member (gear)
3-8: Transmission member (gear)
9-14: Vibration type motor 24: Driven member 28: Vibrating body 29: Rotating body 32: Pressurizing mechanism 33: Shaft

Claims (1)

A vibration body that generates vibration by applying a drive signal to the electromechanical energy conversion element; and at least three vibration-type actuators including a contact body that contacts the vibration body;
A circuit for applying the same drive signal to the at least three vibration actuators;
A power transmission mechanism that synthesizes the driving force from the at least three vibration-type actuators and transmits it to the driven member;
When the same drive signal is applied to the at least three vibration actuators, the number of vibration actuators that are driven at a lower rotation speed than the average rotation speed of these vibration actuators is greater than the average rotation speed. The number of vibration type actuators driven at a high rotational speed is larger than the number of vibration type actuators.

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