JP2577118B2 - Vibration wave drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vibration wave driving device provided with a friction clutch.

[Related Art] In recent years, an ultrasonic motor has been provided which excites a circular or elliptical motion on surface particles of a vibrating elastic body by synthesizing vibrations, and relatively moves a member in frictional contact with the surface and the elastic body. I have.

As an ultrasonic motor, a ring-shaped form and a rod-shaped form have been proposed, but each of these forms a vibration elastic body constituting a stator for generating vibration for driving. The basic driving principle is the same in that a rotational conversion member such as a rotor for converting the driving vibration formed in the vibration elastic body into a rotational force is brought into frictional contact, and the rotational conversion member is rotated by the frictional force.

For example, when an annular ultrasonic motor is used in a lens barrel as a drive source of an autofocus, there is an advantage that the rotation output of the rotor can be directly applied to the focus lens without using a transmission mechanism such as a gear. However, there is a problem that the annular type ultrasonic motor is disadvantageous in terms of manufacturing cost as compared with the rod type ultrasonic motor.

Since a rod-shaped ultrasonic motor cannot be arranged to surround a lens, for example, like an annular ultrasonic motor, the rotational force of a rotor is transmitted to a driven member, such as a focus lens, via a transmission mechanism such as a gear. To be transmitted.

[Problems to be Solved by the Invention] However, when a driven member is driven via a transmission mechanism using a rod-shaped ultrasonic motor as a drive source, a rotation output member such as a gear for transmitting the rotational force of the rotor to the driven member. When a high load is applied to the rotor, the rotation of the rotor becomes unstable, and in the worst case, the rotor stops moving out of the resonance state of the stator vibration. This causes problems such as generation of noise (squeak noise) and abnormal wear between the stator and the rotor.

In order to solve such a problem, Japanese Patent Laid-Open No.
In -97281, the rotor is made to run idle when a high load is applied.However, this method requires a new friction plate between the rotor and the output shaft. It was not effective.

The present invention solves such a conventional problem and provides a simple mechanism that can prevent abnormal wear between the rotor and the stator and generation of abnormal noise even when a high load is externally applied to the drive system. It is an object of the present invention to provide a vibration wave driving device that can be obtained with a structure and that can be downsized.

[Means for Solving the Problems] The configuration of a vibration wave driving device for realizing the object of the present invention is to bring a rotating member into friction contact with a vibrator having an axis extending in a predetermined direction to excite driving vibration on the vibrator. And a hollow rotary output member disposed around the shaft and frictionally coming into contact with the rotary member to take out an output, and a frictional force between the rotary member and the rotary output member. Is set to be smaller than the frictional force between the vibrator and the rotating member.

In this configuration, the frictional force between the rotation member and the rotation output member is provided between the inner peripheral surface of the rotation output member and the shaft, one end of which engages a part of the shaft, and the other end of which rotates the rotation output member. It can be generated by a pressure member which indirectly engages the output member and applies a frictional force to the vibrator and the rotating member.

Further, it has an output gear provided on the outer peripheral surface of the rotation output member and engaging with a load.

[Operation] In the vibration wave driving device configured as described above, when a high load is applied to the rotation output member, the rotation member starts to slide with respect to the rotation output member before the rotation of the rotation member becomes unstable or stops.

Further, a frictional force between the rotating member and the rotation output member is obtained by using a pressure member for applying a frictional force to the vibrator and the rotation member. It can be arranged inside, and the size of the device can be reduced.

Furthermore, the rotation output member and the output gear can be integrated, and the size of the device can be reduced.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 shows an embodiment of a vibration wave driving device according to the present invention, wherein FIG. 1 (a) is a plan view and FIG. 1 (b) is a longitudinal sectional view.

1 is a cylindrical vibration elastic body made of a metal material, 2 is a holding body made of a metal material having the same outer diameter as the vibration elastic body 1, and 3 a to 3 d are the same diameter as the outer diameter of the vibration elastic body 1. Ring-shaped piezoelectric element plates formed on the outer diameter of
Electrode plates 3a to 3d, wherein the electrode plates 4a to 4d and the piezoelectric element plates 3a to 3d are arranged between the vibration elastic body 1 and the pressing body 2, and the bolt 5 is passed through the pressing body 2 These are integrally fixed by screwing them to 1 to form a stator of the vibration wave driving device A.

The vibration wave driving device A applies AC voltages having different phases from a power supply circuit (not shown) to the electrode plates 4a to 4d of the stator, whereby the piezoelectric element plates 3a to 3d form mechanical vibrations on the stator, and these vibrations are generated. In this way, a rope-like movement is excited in the stator, and a rotor 6 described later frictionally contacts the front end of the stator. A rotor 6 has a rear end portion (friction contact portion) 6a in contact with the tapered portion 1a of the vibrating elastic body 1 and obtains an appropriate frictional force by pressing by a pressing spring 10 described later.

Reference numeral 7 denotes a rotational output member made of a friction stabilizing material having a gear 7a, which is frictionally connected between the rear end surface and the end surface of the rotor 6. The gear 7a is for transmitting the rotation of the rotor 6 to the outside.

The frictional force of the frictional connection between the rotor 6 and the rotation output member 7 is generated by the pressure spring 10 so that the force is smaller than the frictional force between the vibrating elastic body 1 and the rotor 6 (the frictional coefficient is reduced). ) Is set.

That is, even when a rotational force is applied to the rotation output member 7 from the outside, the rotor 6 does not rotate because the friction force on the stator is larger than the friction force on the rotation output member 7, and only the rotation output member 7 rotates. Will be.

On the other hand, a bearing 8 is provided on the inner diameter of the rotation output member 7, and the hollow shaft 9 is fitted into the inner diameter of the bearing 8, so that the rotor 6 and the rotation output member 7 can rotate.

The shaft 9 is fitted to the sliding portion 5a of the bolt 5 so as to coincide with the axis of the stator.

Reference numeral 10 denotes a pressure spring, which presses the step 9a of the shaft 9 to press the bearing 8 with the flange 9b, and the pressing force causes the vibration elastic body 1 and the rotor 6, and the rotor 6 and the rotation output member 7 to move. It is configured so that a frictional force is generated between them.

The pressing force of the pressing spring 10 is applied to the hole of the flat holding member 11.
11c is inserted into a pin 5b formed at the tip of the bolt 5 and fixed by a known method such as fixing with an adhesive.

The vibration wave driving device A is fixed by fixing the holding member 11 to a fixing member (not shown) with screws (not shown) through screw holes 11a and 11b.

In supporting the stator of the vibration wave driving device,
It is necessary not to affect the vibration excited by the stator, and the end of the stator becomes the antinode of the vibration, and there is only a displacement in the radial direction, and the displacement is actually very small. , The pin part which is one end of the stator
By fixing at 5b, the vibration of the stator is not affected.

In the vibration wave driving device configured as described above, when a high load is applied to the rotation output member 7, the rotation of the rotor 6 becomes unstable before the rotation of the rotor 6 becomes unstable or stops.
Slides out from the rotary output member 7 and a high load from the rotary output member 7 is not transmitted between the rotor 6 and the stator.

In order to achieve the above operation, selection of the materials of the vibration elastic body 1, the rotor 6, and the rotation output member 7 is problematic. However, a combination of the vibration elastic body 1 made of brass and the rotor 6 made of aluminum is used. When the above operation was performed with the friction coefficient being 0.8 or more, the rotational output member 7 being made of polyacetal, and the friction coefficient with the rotor 6 being 0.2 or less, it was confirmed that the operation was satisfactory. Not only that, if there is a friction coefficient difference of about four times, it was confirmed that the rotor 6 and the rotation output member 7 reliably slipped before the vibration elastic body 1 and the rotor 6 slipped.

As shown in the figure, the vibration elastic body 1, the rotor 6, and the rotation output member 7 are formed to have substantially the same diameter, and the holding member 11 is substantially the same as the vibration elastic body 1, the rotor 6, and the rotation output member 7. It is configured to be larger than the diameter, and it is assembled as a unit to form a unit.

According to the invention according to claim 1, even when a high load is applied to the rotation output member, the rotation member slides out relative to the rotation output member before the rotation of the rotation member becomes unstable or stops. Accordingly, not only the effect of preventing abnormal wear between the vibrator and the rotating member and the occurrence of abnormal sound can be prevented, but also the following effects can be obtained.

That is, since the rotation output member is arranged around the axis, the rotation output member rotates smoothly without blurring, and therefore, the frictional force between the rotation output member and the rotation member is also reduced during rotation. The initial frictional force can be maintained.

For this reason, the possibility that the relationship between the frictional force of the frictional portion between the rotating member and the rotation output member and the frictional force of the two frictional portions of the frictional portion between the vibrator and the rotating member is significantly reduced, and It is possible to further reduce the possibility of occurrence of problems such as abnormal abnormal wear.

According to the second aspect of the present invention, the frictional force between the rotating member and the rotating output member is obtained by using the pressing member for applying the frictional force to the vibrator and the rotating member. Since the member is disposed inside the hollow of the rotary output member, the size of the device can be reduced.

According to the invention according to claim 3, the rotation output member and the output gear can be integrated, and the size of the device can be reduced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a vibration wave driving device according to the present invention, wherein FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional view. A: Ultrasonic motor 1: Elastic vibrator, 2: Holder 3a-3d: Piezoelectric element plate 4a-4d: Electrode plate 5: Bolt, 6: Rotor 7: Rotary output member, 8: Bearing 9: Shaft, 10: Pressure spring 11: holding member.

Claims (3)

(57) [Claims] 1. A rotating member is brought into frictional contact with a vibrator having an axis extending in a predetermined direction to excite driving vibration to the vibrator to drive the rotating member, and is arranged around the axis, and A hollow rotary output member for taking out an output by frictionally contacting the rotary member, wherein a frictional force between the rotary member and the rotary output member is set to be smaller than a frictional force between the vibrator and the rotary member. A vibration wave driving device characterized by the above-mentioned. 2. The rotary power member according to claim 1, wherein the frictional force between the rotary member and the rotary output member is provided between an inner peripheral surface of the rotary output member and the shaft, and one end is engaged with a part of the shaft. A vibration member which is generated by a pressurizing member that applies frictional force to the vibrator and the rotating member, the other end of which is indirectly engaged with the rotation output member. 3. The vibration wave driving device according to claim 1, further comprising an output gear provided on an outer peripheral surface of the rotation output member and engaging with a load.