Vibration wave motor and optical device using vibration wave motor

A vibration wave motor includes a vibrator including a piezoelectric element; a friction member with which the vibrator comes into contact by receiving pressurizing force; and a guide member that holds the vibrator. The guide member includes an input portion on one end portion, the input portion receiving force from outside, and a pressurizing portion on another end portion positioned on an opposite side of the one end portion, the pressurizing portion providing the pressurizing force to the vibrator. A guide portion extending in a direction of relative movement of the vibrator and the friction member is formed between the input portion and the pressurizing portion.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a vibration wave motor and an optical device using the vibration wave motor.

Description of the Related Art

Conventionally, an ultrasonic motor can relatively move a vibrator and a sliding member by applying a high frequency drive voltage to a piezoelectric element to periodically vibrate the vibrator and bringing the vibrator into contact with the sliding member by a pressurizing or pressing force. A linear ultrasonic motor is disclosed in Japanese Patent Application Laid-Open No. 2014-212682, wherein pressurizing force of a spring biases a vibrator toward a contact basic member. Reaction force against the pressurizing force is received by placing rolling members between a movable guide portion of a moving plate attached to a vibrator support member and a cover guide portion of a cover plate.

SUMMARY OF THE INVENTION

However, the rolling members as receiving portions of the reaction force of the vibrator need to be provided in two lines on both sides of the vibrator in a direction of movement in the conventional configuration, and there is a problem that downsizing of the linear ultrasonic motor is difficult.

The present invention provides a vibration wave motor including: a vibrator including a piezoelectric element; a friction member with which the vibrator comes into contact by receiving pressurizing force; and a guide member that holds the vibrator, wherein the guide member includes: an input portion on one end portion, the input portion receiving force from outside; and a pressurizing portion on another end portion positioned on an opposite side of the one end portion, the pressurizing portion providing the pressurizing force to the vibrator, and a first guide portion extending in a direction of relative movement of the vibrator and the friction member is formed between the input portion and the pressurizing portion.

According to the present invention, rolling members as receiving portions of the reaction force of the vibrator need to be arranged only on one side of the vibrator in the direction of the relative movement, and the vibration wave motor can be downsized. In addition, the guide member pressurizes and holds the vibrator. Therefore, the number of members can be reduced, and the vibration wave motor can be downsized.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a cross-sectional view of main parts on a surface orthogonal to a direction A (seeFIG. 2) of relative movement of a vibration wave motor1(ultrasonic motor) illustrating an embodiment of the present invention.FIG. 2is a cross-sectional view on a cross-sectional line II-II ofFIG. 1and is a cross-sectional view in the direction A of the relative movement.FIG. 3is an exploded perspective view illustrating a configuration of members engaged with a pressurizing guide member105. Although an example of a linear vibration wave motor1will be described, the present embodiment can also be applied to a rotary type and other types.

A well-known adhesive or the like is used to fix a piezoelectric element102to a vibration plate101. When a high frequency drive voltage is applied to the piezoelectric element102, vibration at a frequency in an ultrasonic region is generated, and the vibration plate101resonates in a longitudinal direction and a lateral direction. The vibration plate101and the piezoelectric element102form a vibrator100.

When the vibration at the frequency in the ultrasonic region is generated in the piezoelectric element102, a pressure contact portion101aformed on the vibration plate101makes an elliptical motion M as illustrated inFIG. 2. The frequency or the phase of the high frequency drive voltage applied to the piezoelectric element102can be changed to appropriately change the rotation direction or the ellipticity of the elliptical motion M to generate a desirable motion. The pressure contact portion101aof the vibration plate101can be brought into contact by pressure to a friction member103as a counterpart component to thereby generate driving force for relatively moving the vibrator100and the friction member103. The optical axis direction (orthogonal direction inFIG. 1, left and right direction inFIG. 2) can be set as the direction A of the relative movement to drive the vibrator100. A well-known fastening unit, such as a screw, is used to fix the friction member103to a housing104.

As described later, the pressurizing guide member105includes: an input portion105aon one end portion105-1, the input portion105areceiving force (biasing force Fa) from the outside; and a pressurizing portion105bon another end portion105-2positioned on the opposite side of the one end portion105-1(seeFIG. 3), the pressurizing portion105bpressurizing a pressuring plate106. The pressurizing guide member105also has a function of using pressurizing force Fb for pressurizing the pressuring plate106to hold the vibrator100. A plurality of first guide portions105cextending in the direction A of the relative movement of the vibrator100is formed substantially in a line between the input portion105aand the pressurizing portion105b.

Well-known screws or the like are used to fix a cover member107to the housing104. Two second guide portions107aare formed on the cover member107, at positions opposing the two first guide portions105c. Rolling members108are inserted between the first guide portions105cand the corresponding second guide portions107a, and the rolling members108are clamped by clamping force Fc (described later).

A lens holding member112holds an imaging lens (not illustrated), and a guide bar110holds the lens holding member112in the optical axis direction (orthogonal direction to the paper inFIG. 1, left and right direction inFIG. 2) in a manner that the lens holding member112can freely slide. A rack111is held in a manner that the rack111can rotate relative to the lens holding member112, with a central axis B (orthogonal direction to the paper inFIG. 1, left and right direction inFIG. 2) as a rotation center. Rotational biasing force of a torsion spring113provides the rack111with rotation force Fr in the clockwise direction. The input portion105aprovided on the one end portion105-1of the pressurizing guide member105receives the rotation force Fr as force (biasing force Fa) from the outside through an engagement sphere114.

In the described configuration, the vibrator100, the friction member103, the housing104, the pressurizing guide member105, the pressuring plate106, the cover member107and the rolling members108form the vibration wave motor1.

Next, a pressurizing method of the vibrator100and a guide mechanism in the relative movement of the pressurizing guide member105according to the embodiment of the present embodiment will be described in detail. As described in the outline, the torsion spring113provides the rack111attached to the lens holding member112with the rotation force Fr in the clockwise direction as illustrated inFIG. 1. The rotation force Fr acts as the biasing force Fa for biasing the input portion105aprovided on the one end portion105-1of the pressurizing guide member105upward inFIG. 1through the engagement sphere114in the inserted state.

The pressurizing method of the vibrator100will be described first. When the biasing force Fa acts on the input portion105aprovided on the one end portion105-1of the pressurizing guide member105, force for rotation in the counterclockwise direction about spherical centers of the rolling members108is generated in the pressurizing guide member105. Cooperation of the first guide portions105c, the rolling members108and the second guide portions107athat are fixed ends causes the biasing force Fa to act as the pressurizing force Fb on the pressurizing portion105bprovided on the other end portion105-2positioned on the opposite side of the one end portion105-1. The pressurizing force Fb pressurizes the vibrator100against the friction member103through the pressuring plate106and brings the vibrator100and the friction member103into frictional contact. The direction of the pressurizing force Fb can follow a direction in which the vibrator100is perpendicular to the sliding surface of the friction member103.

When the vibrator100is pressurized by the pressurizing force Fb, the biasing force Fa of the input portion105aand reaction force Fb′ of the pressurizing force Fb act on the first guide portions105c, and the force is transmitted to the second guide portions107athrough the rolling members108. The clamping force Fc that is force against the force transmitted to the second guide portions107aacts on the rolling members108, and as a result, the rolling members108are clamped between the first guide portions105cand the second guide portions107a. The clamping force Fc holds the rolling members108between the first guide portions105cand the second guide portions107awithout looseness, in a manner that the rolling members108can roll in the direction A of the relative movement.

As described, the pressurizing guide member105provides the pressurizing force Fb to the vibrator100of the vibration wave motor1of the present invention, and at the same time, the pressurizing guide member105holds the vibrator100. In a conventional configuration, a support member that supports a vibrator, a spring member that pressurizes the vibrator, a spring holding member that holds the spring member and the like need to be provided as separate members. However, one member, i.e. the pressurizing guide member105, pressurizes and holds the vibrator100in the embodiment of the present invention. The configuration allows reducing the number of members and downsizing the apparatus.

Well-known screws or the like are used to fix the friction member103to the housing104, and well-known screws or the like are also used to fix the cover member107including the second guide portions107ato the housing104. A well-known unit, such as a screw, is used to fix the vibration wave motor1to a barrel (not illustrated) that holds the lens holding member112.

With the configuration, a high frequency drive voltage is applied to the piezoelectric element102to generate vibration at a frequency in the ultrasonic region to generate the elliptical motion M on the pressure contact portion101aformed on the vibration plate101as illustrated inFIG. 2. The vibrator100in frictional contact with the friction member103can advance and retreat in the direction A of the relative movement, and the lens holding member112connected to the pressurizing guide member105and the rack111can also advance and retreat in the optical axis direction together with the vibrator100.

Next, the guide mechanism in the relative movement of the pressurizing guide member105will be described. The first guide portions105cincluded in the pressurizing guide member105are V-shaped in cross section as illustrated inFIG. 1and are grooves extending in the direction A of the relative movement as illustrated in FIG.3. The rolling members108are inserted into the first guide portions105cin a manner that the rolling members108can freely roll in the direction A of the relative movement. Like the first guide portions105c, the second guide portions107aV-shaped in cross section and extending in the direction A of the relative movement are formed on the cover member107. Like the first guide portions105c, the rolling members108are inserted into the second guide portions107ain a manner that the rolling members108can roll in the direction A of the relative movement.

FIG. 3is an exploded perspective view illustrating a configuration of members engaged with the pressurizing guide member105of the vibration wave motor1of the present invention. The pressurizing guide member105includes the first guide portions105cat two locations substantially in a line on an extended portion105-3extending in the direction A of the relative movement. The one end portion105-1and the other end portion105-2extend from the extended portion105-3of the pressurizing guide member105in a direction substantially orthogonal to the direction A of the relative movement. Therefore, the one end portion105-1and the other end portion105-2that are parts for pressurizing and holding the vibrator100and the extended portion105-3including the first guide portions105cthat are parts for guiding the vibrator100in the direction A of the relative movement are arranged in a substantially cross shape in plan view.

The two first guide portions105csandwich the one end portion105-1including the input portion105aand the other end portion105-2including the pressurizing portion105b. According to the configuration, the pressurizing guide member105serves as a guide mechanism that guides the vibrator100held by pressurizing, in a manner that the vibrator100can linearly advance and retreat in the optical axis direction.

As illustrated inFIG. 3, a plurality of sphere receiving portions111athat allows fitting the engagement sphere114is formed on the rack111in a direction substantially orthogonal to the direction A of the relative movement. Providing the plurality of sphere receiving portions111aallows changing the position of the engagement sphere114fitted into the sphere receiving portion111a. The engagement sphere114and the sphere receiving portions111aform an input position variable unit115. As illustrated inFIG. 1, the input portion105aincludes grooves that are V-shaped in cross section, in the direction substantially orthogonal to the direction A of the relative movement. This allows the input portion105ato correspond to the position of the engagement sphere114changed by the input position variable unit115. Therefore, the input position variable unit115can change the position of the engagement sphere114to change the magnitude of the force (biasing force Fa) from the outside received by the input portion105aof the pressurizing guide member105to thereby adjust the pressurizing force Fb for pressurizing the vibrator100.

When the vibration wave motor1of the present invention is incorporated into a different optical device, the force of the torsion spring113and the like may be set in advance. However, the input position variable unit115can change the position of the engagement sphere114engaged with the sphere receiving portion111a, and the pressurizing force Fb can be adjusted. Therefore, the input position variable unit115can adjust the pressurizing force Fb without replacing the members, and the compatibility with a different optical device can be increased in the vibration wave motor1.

According to the vibration wave motor1of the present invention, the rolling members108as receiving portions of the reaction force Fb′ of the vibrator100are arranged substantially in a line in the direction A of the relative movement, only on one side of the vibrator100. The configuration eliminates the need to have a space for providing the rolling members108in two lines on both sides of the vibrator100in the direction A of the relative movement (conventional configuration), and the apparatus can be downsized.

As illustrated in a modification inFIG. 4, the friction member103can be tilted and arranged such that the direction of the pressurizing force Fb is perpendicular to a straight line indicated by an alternate long and short dash line C connecting the first guide portion105cand the pressurizing portion105b. In this way, the vibrator100perpendicularly abuts the sliding surface of the friction member103. The driving force can be effectively generated, and the apparatus can be further downsized.

Application Example

FIG. 5is a cross-sectional view of main parts illustrating an application example in which the vibration wave motor1of the present invention is incorporated into, for example, a barrel portion of an optical device. The same constituent members as in the embodiment are provided with the same reference signs.

A first lens holding member11holds a first lens14, and a third lens holding member13holds a third lens16. A peripheral portion of the third lens holding member13includes a cylindrical portion13a, and screws or the like (not illustrated) are used to fasten the cylindrical portion13ato the first lens holding member11at an end portion13bof the cylindrical portion13a. A unit receiving portion13cfor fixing the vibration wave motor1is provided on part of an outer diameter portion of the cylindrical portion13a, and well-known screws or the like are used to removably fix the vibration wave motor1. A second lens holding member12that holds a second lens15is arranged on an inner diameter portion of the cylindrical portion13a.

The second lens15serves as a focusing lens, and the vibration wave motor1of the present invention moves the second lens15in the direction A (optical axis direction) of the relative movement. In this case, the lens holding member12is fitted to a well-known guide bar10through a bearing portion12a, in a manner that the lens holding member12can slide relative to the guide bar10. This allows the second lens15to move in the optical axis direction. The second lens holding member12is connected to the input portion105a(not illustrated) of the pressurizing guide member105through the rack111.

As described, the configuration of providing the rolling members108as receiving portions of the reaction force Fb′ of the vibrator100in two lines on both sides of the vibrator100in the direction A of the relative movement as in the conventional configuration is not necessary in the present invention, and the apparatus can be downsized. Although the application example of the barrel portion of the optical device provided with the vibration wave motor1according to the present invention is described in detail, the present invention is not limited to the application example, and the present invention can be in any form within the scope of the claims.

Downsizing of the vibration wave motor incorporated into the optical device or the like is realized.

This application claims the benefit of Japanese Patent Application No. 2016-120606, filed Jun. 17, 2016, which is hereby incorporated by reference herein in its entirety.