JP3341308B2 - Lens barrel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel having a built-in ultrasonic motor.

[0002]

2. Description of the Related Art Conventionally, this type of lens barrel incorporates an ultrasonic motor, particularly a ring-type ultrasonic motor, and has been used for driving a focusing or zoom optical system or a diaphragm member. The advantages of using an annular ultrasonic motor as an actuator for each part of the lens barrel are as follows.
First, in terms of shape, it is circular and easy to incorporate into the lens barrel.Secondly, in terms of motor performance, it is possible to directly drive the driven ring that operates the focusing optical system etc. with high torque and low rotation. , A gear train and the like that do not require a speed reduction system, good stopping performance, and quiet driving noise.

In other words, since there is no speed reduction system such as a gear train, there is almost no backlash from the motor to the driven ring due to backlash of the gear train, and the stopping accuracy of the ultrasonic motor itself is good. Can be performed very accurately. In addition, since there is no sound generated from the meshing part of the gears and there is almost no driving sound of the ultrasonic motor itself, the operation feeling of the lens is very good, automatic focusing operation in places where silence is required, power zoom operation And so on.

In a conventional lens barrel, when a focusing optical system or the like is driven by using an ultrasonic motor, whether a driving source for rotating a driven ring is an ultrasonic motor or a manually operated ring is used. A switching member for switching is provided, and a structure capable of easily switching between an automatic focusing operation and a manual focusing operation is used (Japanese Patent Laid-Open No. 2-137811).

[0005] Further, the ultrasonic motor pressurizes the stator and the rotor with a predetermined pressing force to drive the rotor by a progressive vibration wave generated in the stator. In general, a large friction loss occurs, so that a pressing force is usually applied by a ball bearing or the like. For example, a thrust bearing for receiving a pressing force of an ultrasonic motor is provided between a member which rotates integrally with the rotor and a fixed lens barrel of the lens (actually disclosed in Japanese Unexamined Patent Application Publication No. Hei.
31929).

[0006]

However, the above-mentioned conventional lens barrel has the following problems. In the former conventional example, since the switching member is provided, the play of the switching portion becomes a play from the motor to the driven ring (cam ring or helicoid ring), which adversely affects the stop accuracy of the rotational drive control of the driven ring. This eliminates the advantage of the direct drive by the ultrasonic motor. It is impossible to reduce the backlash of the switching member to zero, and it is very difficult to manage only the processing accuracy. In addition, this play corresponds to the play of the driven ring itself because the driving method is direct drive, and there is a problem that even if its absolute value is small, it cannot be ignored in control.

On the other hand, when a thrust bearing which receives a pressing force of an ultrasonic motor is provided as in the latter conventional example,
Despite the use of an annular ultrasonic motor that is easy to incorporate into a lens barrel, the outer shape of the lens barrel becomes larger due to the thrust bearing, and its appeal as a product is reduced. Also, in order to guarantee the durability of the bearing part, other than simply increasing the bearing part to increase rigidity, special materials or surface treatment, high-precision processing, etc. are required, but these increase the cost. In addition, there is a problem that the assembly of the bearing portion is complicated. Further, since the bearing portion is a sliding portion to which a load is applied, the driving noise is not small, and the characteristics of the ultrasonic motor are impaired.

A first object of the present invention is to connect a rotor of an ultrasonic motor and a driven ring such as a cam ring or a helicoid ring without play, and to control the driving of the driven ring with high precision. It is to provide a lens barrel. A second object of the present invention is to provide a lens barrel that can be reduced in size and cost by eliminating a thrust bearing that receives a pressing force of an ultrasonic motor.

[0009]

In order to solve the above-mentioned problems, a lens barrel according to the present invention is supported movably with respect to a fixed barrel (1), and includes a focusing or zoom optical system or A driven ring (2) for holding the aperture member movably in the optical axis direction and for moving the focusing or zooming optical system or the aperture member, a stator for generating a progressive vibration wave by exciting the piezoelectric body, and a stator therefor An ultrasonic motor (USM) that is in contact with a stator and applies a driving force to the driven ring by the traveling vibration wave, and has an ultrasonic motor (USM) that moves the driven ring. (2) the rotor (2b) is integrally provided, and is disposed between the driven ring and the fixed lens barrel;
The pressure is applied to the surface within the thickness of
In this configuration, a mechanism for reducing a frictional force generated by the pressurized contact is provided.

In this case, the mechanism for reducing the frictional force has a thrust stopper pin which is implanted in the fixed lens barrel and which fits into a circumferential groove of the cam ring which is the driven ring. be able to. Further, the thrust stopper pin is provided on a shaft (1) which is radially implanted in the fixed lens barrel.
4) and radial bearings (14
a) can be characterized.

On the other hand, the driven ring and the rotor can be characterized by comprising the same member (2, 2b). In addition, the driven ring and the rotor are formed of separate members (2, 20) and are integrally bonded.

[0012]

In the present invention, since the rotor of the ultrasonic motor and the driven ring for driving the focusing optical system and the like are integrally formed, the play from the rotor to the driven ring is zero.
Therefore, the position control of the focusing optical system and the like can be performed with high accuracy by a simple method, and it is possible to dramatically improve the focusing accuracy of automatic focusing.

Further, since the receiving force of the rotor and the stator of the ultrasonic motor is shared by the circumferential groove pins for stopping in the thrust direction of the cam ring which is the driven ring, bearings for the pressure receiving are separately provided. As compared with the case of providing, the cost can be reduced by downsizing and reducing the number of parts.

[0014]

【Example】

(First Embodiment) Hereinafter, an embodiment will be described in more detail with reference to the drawings and the like. FIG. 1 is a view showing a lens barrel having a built-in ultrasonic motor according to a first embodiment of the present invention. The fixed cylinder 1 has a lens chamber 15 for holding the focusing optical system L2 fitted on the inner peripheral side thereof, and a cam ring 2 having a lead groove fitted on the outer peripheral side thereof. The rotation of the focusing optical system L2 and the lens chamber 15 around the optical axis is restricted by the pin 12, and only the straight traveling in the optical axis direction is allowed. On the other hand, the cam ring 2 is restricted from moving straight in the optical axis direction by a plurality of ball bearings 14a and pins 14 provided around the optical axis, and is allowed to rotate only around the optical axis. The pin 13 is provided in the lens chamber 15 so as to protrude in the radial direction. The tip of the pin 13 is fitted in the lead groove 2 a of the cam ring 2. L2 is moved in the optical axis direction to perform a focusing operation.

The rotor 2b of the ultrasonic motor USM projects in the radial direction behind the cam ring 2 and is provided integrally with the cam ring 2. A stator 3 in which a piezoelectric element is bonded to an annular elastic body is disposed behind the rotor 2b. The stator 3 is pressed against the rotor 2b in the optical axis direction by a leaf spring 10. The rotor 2b has a sliding material excellent in wear resistance bonded to a contact surface with the stator 3. The pressing force between the rotor 2b and the stator 3 is set to an optimum value by rotating the pressing force adjusting ring 6 and adjusting the amount of deflection of the leaf spring 10.

The pressure is applied to a bearing 14a for regulating the movement of the cam ring 2 in the direction of the optical axis and a pin 14 serving as the axis thereof.
Can be received at Since the pressure is applied by the bearing 14a, the friction loss accompanying the rotation of the cam ring 2 is very small. Moreover, since there is no need to provide a dedicated bearing for receiving the pressing force of the ultrasonic motor USM, the circumferential groove pin, which is a component of the conventional lens barrel, is used.
It is possible to reduce the number of components and downsize the lens barrel. In this embodiment, since the rotor 2b and the stator 3 are fitted to the same member as compared with the case where the rotor is supported via bearings (conventional example), the center of the rotor 2b and the stator 3 Since the centering of the shaft can be easily and accurately performed, the performance of the ultrasonic motor USM can be improved.

On the other hand, the stator 3 comprises an annular member 8 rotatably fitted on the inner peripheral side of the manual distance operation ring 5 and a protrusion 3.
a and is rotatable about the optical axis integrally with the ring member 8. This annular member 8 is a leaf spring 9
, And is pressed against the manual distance operation ring 5 in the optical axis direction. The friction torque adjusting ring 7 is screwed to a screw provided on the inner peripheral surface of the manual distance operation ring 5, and adjusts the amount of deflection of the leaf spring 9 by rotating the friction torque adjusting ring 7. The sliding friction torque between the manual distance operation ring 5 and the ring member 8 is determined by the rotor 2 when the ultrasonic motor USM is not driven.
b and smaller than the holding torque of the stator 3 and larger than the load torque of the drive unit.

Next, the operation of the first embodiment according to the present invention will be described. At the time of the automatic focusing operation, a predetermined voltage is applied to the piezoelectric element of the stator 3 by an ultrasonic motor drive circuit (not shown) to generate a progressive vibration wave in the stator 3 so that the rotor 2b, that is, the cam ring 2 is moved. It is rotated around the optical axis. As described above, since the annular member 8 integrally engaged with the stator 3 is held with a friction torque larger than the load torque of the drive unit, when the ultrasonic motor USM is driven, the fixed cylinder Rotor 2b for 1
Only the stator 3 rotates, and the stator 3 is held without rotating.
Then, based on a signal from a focus detection device of a camera body (not shown), the ultrasonic motor USM is driven and controlled, and the focusing optical system is stopped at a predetermined position on the optical axis, whereby the automatic focusing operation is performed. Will be At this time, the ultrasonic motor USM
Since there is no backlash between the cam ring 2 and the cam ring 2, the position control of the cam ring 2 can be performed easily and with very high accuracy.

On the other hand, at the time of manual focusing operation, the manual distance operation ring 5 is rotated around the optical axis, so that the annular member 8, the stator 3 and the stator 3 fitted on the inner peripheral side thereof are brought into pressure contact. The cam ring 2 is rotated integrally, and the focusing optical system L2 is moved in the optical axis direction to perform manual focusing. At this time, as described above, the friction torque of the manual distance operation ring 5 and the annular member 8 and the holding torque of the rotor 2b and the stator 3 when the ultrasonic motor USM is not driven are larger than the load torque applied to the cam ring 2. Therefore, only the cam ring 2 rotates with respect to the fixed cylinder 1, and no relative slip occurs between the other rotor 2 b and the stator 3, and between the manual distance operation ring 5 and the ring member 8. When the cam ring 2 comes into contact with the rotation limiting pin 11 and the rotation is restricted, the holding torque of the rotor 2b and the stator 3 is used as described above.
Since the sliding friction torque between the manual distance operation ring 5 and the ring member 8 is set to be small, even if the manual distance operation ring 5 is further turned when the rotation of the cam ring 2 is restricted, the manual distance operation ring 5 will not move. The annular member 8 idles, and the rotor 2b and the stator 3
Are not forcibly rotated at the contact surface of the rotor 2b.
And the sliding surface of the stator 3 is damaged, and the ultrasonic motor US
It does not degrade the performance of M.

In this lens barrel, between the fixed barrel 1 and the lens holding barrel 15, there is a play between the cam pin 13 and the fixed barrel 1, a play between the circumferential shaft 14 and the bearing 14a, and a hole between the bearing 14a and the cam ring 2. And play. However, in this embodiment, the leaf spring 1
Since pressure is applied in one direction by 0, play is relatively close to one side. Therefore, the backlash between the fixed cylinder 1 and the cam ring 2 can be always removed. In the case of increasing the accuracy of AF, when the lens has a large image plane moving coefficient, the above-mentioned play greatly affects the shift on the image plane, and thus such play is extremely useful.

(Second Embodiment) FIG. 2 is a view showing a lens barrel having a built-in ultrasonic motor according to a second embodiment of the present invention. The second embodiment has substantially the same configuration and operation as those of the first embodiment described above, and therefore, portions performing the same functions are denoted by the same reference numerals, and redundant description will be omitted. In the first embodiment, the cam ring 2 and the rotor 2b are formed of the same member. However, in the second embodiment, the cam ring 2 and the rotor 20 are formed as separate members, and these are integrally formed by bonding or the like. ing. The components of the ultrasonic motor USM are required to have high machining accuracy, and in particular, the rotor 20 and the stator 3
The sliding surface requires many steps in order to obtain high surface accuracy. If the rotor 2b and the cam ring 3 are made of the same member as in the first embodiment, large parts must be passed through various processes, which is inefficient and may cause defective parts. There is. By forming the cam ring 2 and the rotor 20 as separate parts as in the second embodiment, the above-mentioned drawbacks can be eliminated, and at the time of assembling and adjusting the cam ring 2, it is possible to perform the operation without losing the rotor portion.

The present invention is not limited to the embodiment described above, and various modifications can be made. For example, as a driven ring of a focusing optical system,
Although the cam ring is described as an example, a helicoid ring may be used. In addition, the description has been given by taking the driving of the focusing optical system as an example, but the present invention can be applied to a driven ring that operates a variable power optical system and a diaphragm member.

[0023]

As described above in detail, according to the present invention, in the lens barrel having the built-in ultrasonic motor, the rotor and the driven ring are integrally formed. As a result, the position of the focusing optical system can be controlled with a very high accuracy by a simple method, and the focusing accuracy of the automatic focusing can be drastically improved. In addition, receiving the pressing force of the rotor and the stator,
Because the circumferential groove pin for stopping the thrust direction of the cam ring, which is the driven ring, is used in common, the size of the lens barrel is reduced and the number of parts is reduced as compared with the case where a bearing for pressure receiving is separately provided. Cost reduction becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed cylinder 2 Cam ring 3 Stator 4 Stator holding member 5 Manual distance operation ring 6 Pressure adjustment ring 7 Friction torque adjustment ring 8 Ring member 9 Leaf spring 10 Leaf spring 11 Rotation limiting pin 12 Straight pin 13 Cam pin 14 Circumferential pin 15 Lens holding cylinder 20 Rotor

Claims (5)

(57) [Claims] 1. A focusing / magnifying optical system or a diaphragm member which is movably supported with respect to a fixed lens barrel and movably holds an focusing or zooming optical system or a diaphragm member in an optical axis direction. A driven ring for moving a member, a stator for generating a progressive vibration wave by excitation of a piezoelectric body, and a rotor which is brought into pressure contact with the stator and gives a driving force to the driven ring by the progressive vibration wave. in the lens barrel having an ultrasonic motor that moves the driven ring, the provided the rotor to the driven ring integrally, wherein disposed between the lens barrel and the drive ring, said driven ring Thickness
Receiving pressure on the surface that is within
A lens barrel provided with a mechanism for reducing a frictional force generated by the pressure contact. 2. The mechanism for reducing a frictional force includes a thrust stopper pin implanted in the fixed lens barrel and fitted into a circumferential groove of a cam ring as the driven ring. 2. The lens barrel according to 1. 3. The lens mirror according to claim 1, wherein the thrust stopper pin comprises a shaft radially implanted in the fixed lens barrel and a radial bearing provided on the shaft. Tube. 4. The lens barrel according to claim 1, wherein the driven ring and the rotor are formed of the same member. 5. The lens barrel according to claim 1, wherein the driven ring and the rotor are formed of separate members and are integrally bonded.