Vibratory actuator and method for manufacturing the same

1. A vibratory actuator comprising:

a vibration member including an elastic member and an electro-mechanical energy transducer fixed to the elastic member, wherein the elastic member has protrusions formed on the elastic member;

a contact member in contact with the elastic member and configured to be moved in a direction relative to the vibration member by a vibration that is generated in the vibration member by an alternating-current (AC) voltage applied to the electro-mechanical energy transducer; and

a pressure member configured to pressurize the vibration member and the contact member,

wherein each of the protrusions includes a first contact surface in contact with the contact member,

wherein the contact member has a second contact surface made of metal sintered material and in contact with the vibration member, and

wherein a ratio of a maximum amount of depression on the second contact surface in a direction of pressurization by the pressure member to a width of the first contact surface in a direction perpendicular to the direction of movement of the contact member relative to the vibration member and the direction of pressurization by the pressure member is 0.05% or less.

2. The vibratory actuator according to claim 1 , wherein the maximum amount of depression is equal to or greater than a film thickness of an oxide layer formed on a surface of the metal sintered material.

3. The vibratory actuator according to claim 1 , wherein a surface pressure acting on the first contact surface by the pressure member is 5 kgf/mm2 or less.

4. The vibratory actuator according to claim 1 ,

wherein each of the protrusions includes a first contact portion having a spherical shape, and

wherein the first contact surface is formed within the spherical shape.

5. The vibratory actuator according to claim 1 , wherein each of the protrusions includes:

a first contact portion where the first contact surface is formed,

a side wall that protrudes from the elastic member to form a hollow structure, and

a connecting portion configured to connect the first contact portion and the side wall and that has flexibility in the direction of pressurization by the pressure member.

6. The vibratory actuator according to claim 1 , wherein the second contact surface of the contact member is impregnated with a resin.

7. A method for manufacturing a vibratory actuator, wherein the vibratory actuator includes:

a vibration member including an elastic member and an electro-mechanical energy transducer fixed to the elastic member, wherein the elastic member has protrusions formed on the elastic member,

a contact member in contact with the elastic member and configured to be moved in a direction relative to the vibration member by a vibration that is generated in the vibration member by a voltage applied to the electro-mechanical energy transducer, and

a pressure member configured to pressurize the vibration member and the contact member,

wherein each of the protrusions has a first contact surface in contact with the contact member, and

wherein the contact member has a second contact surface made of metal sintered material and in contact with the vibration member, the method comprising:

providing a driven member configured to be driven when the contact member is moved relative to the vibration member; and

driving the driven member while increasing an external load applied to the driven member so that a ratio of a maximum amount of depression on the second contact surface in a direction of pressurization by the pressure member to a width of the first contact surface in a direction perpendicular to the direction of movement of the contact member relative to the vibration member and the direction of pressurization by the pressure member is 0.05% or less.

8. The method according to claim 7 , wherein the driven member is driven while stepwisely increasing the external load applied to the driven member.

9. The method according to claim 7 , wherein the driven member is driven while linearly increasing the external load applied to the driven member.

10. The method according to claim 7 , wherein the driven member is driven while nonlinearly increasing the external load applied to the driven member.

11. The method according to claim 7 , wherein the driven member is driven while increasing the external load applied to the driven member from a state of no external load applied to the driven member.

12. The method according to claim 11 , wherein the driven member is driven by an alternating-current (AC) voltage with a frequency determined in accordance with frequency versus speed characteristics in a case of no external load applied to the driven member.

13. The method according to claim 11 , wherein the external load is increased from a state of no external load applied to the driven member at a timing determined in accordance with a speed up rate in a case of no external load applied to the driven member.

14. The method according to claim 13 , wherein the speed up rate is measured at intervals for a predetermined drive time.

15. The method according to claim 13 , wherein the speed up rate is measured at intervals of a predetermined number of reciprocating motions.

16. The method according to claim 11 , wherein a drive time or a number of drives of the driven member in a case where the external load is increased from the state of no external load applied to the driven member is equal to or greater than the drive time or the number of drives of the driven member in the state of no external load applied to the driven member.