WO2016009785A1

WO2016009785A1 - Rotary drive device and articulated robot equipped with the same

Info

Publication number: WO2016009785A1
Application number: PCT/JP2015/067810
Authority: WO
Inventors: Masanori Takahashi; Yuki Oda
Original assignee: Canon Kabushiki Kaisha
Priority date: 2014-07-16
Filing date: 2015-06-15
Publication date: 2016-01-21
Also published as: JP2016025670A; JP6448239B2

Abstract

A rotary drive device that is capable of cooling a built-in vibration-type actuator without dispersing worn powder generated in the vibration-type actuator to a working atmosphere. A vibration-type actuator includes a vibration body and a driven body that are in pressure contact with and rotate relatively, and an electro-mechanical energy conversion element that is attached to the vibration body and excites vibration on the vibration body for relatively rotating the vibration body and the driven body when drive voltage is applied. A casing in which the vibration-type actuator is arranged has an inlet, and a vent to which negative pressure is supplied and that is disposed so that air guided through the inlet into the casing flows toward a pressurized contact part of the vibration body and a pressurized contact part of the driven body. An output member transmits rotational force of the vibration-type actuator to outside of the casing.

Description

DESCRIPTION

Title of Invention

ROTARY DRIVE DEVICE AND

ARTICULATED ROBOT EQUIPPED WITH THE SAME

Technical Field

[0001] The present invention relates to a rotary drive device equipped with a vibration-type actuator, and an articulated robot equipped with the rotary drive device.

Background Art

[0002] An articulated manipulator and an articul robot that have a plurality of arms are provided with build-in motors that give necessary driving force at joints that rotate and bend the arms . Since a motor generates heat due to a drive loss, a cooling mechanism for preventing the motor itself and an arm from becoming an elevated temperature is needed.

[0003] There is a known structure in which an air hose is arranged through a cavity of an arm and a branch opening is formed on the air hose near a motor so as to cool the motor by spraying a cooling wind to the motor (see PTL 1) . Moreover, there is a known structure in which a ventilation flue for cooling is formed in an arm, and a motor and the arm are cooled by ventilating cooling air to an end effector side of a robot arm from a base side of a robot and by exhausting from a front end of the robot arm (see PTL 2) .

[0004] On the other hand, an articulated robot using a vibration-type actuator that drives a driven body by a vibration body needs structure of preventing worn powder generated in the vibration-type actuator from dispersing outside in addition to a cooling structure for the vibration-type actuator . Accordingly, there is a proposed structure in which a vent is formed on a case that contains a vibration-type actuator at a position that does not face to outer peripheries of a stator (vibrator) and a rotor (driven body) (see PTL 3) .

[0005] If the cooling methods described in the above-mentioned PTL 1 and PTL 2 are applied to an articulated robot using a vibration-type actuator as a motor, the following problems occur. That is, the cooling structure of PTL1 has a problem in that the cooling wind sprayed from the hose flies up the worn powder generated at a friction point between the vibrator and the driven body of the vibration-type actuator, and that the worn powder dispersed inside the arm disperses to a working atmosphere through a gap between arms. Moreover, the cooling structure of PTL 2 also has a problem in that the worn powder is included in the exhaust steam from the front end of the robot arm, and that the worn powder is dispersed to a work object and a working atmosphere. The cooling and dustproof structure of PTL 3 has a problem in that the worn powder must pass through the vent, and that the dispersion of the worn powder to a work object and a working atmosphere cannot be prevented.

Citation List

Patent Literature

[0006]

PTL 1: Japanese Laid-Open Patent Publication (Kokai) No. 7-246587 (JP 7-246587A)

PTL 2: Japanese Examined Utility Model Publication (Kokoku) No. 59-36390 (JU 59-36390B)

PTL 3: Japanese Laid-Open Patent Publication (Kokai) No. 6-205590 (JP 6-205590A)

Summary of Invention

Technical Problem

[0007] The present invention has an object to provide a technique for cooling a vibration-type actuator in a rotary drive device without dispersing worn powder generated in the vibration-type actuator to an atmosphere where various apparatuses are installed.

Solution to Problem

[0008] Accordingly, a first aspect of the present invention provides a rotary drive device including a vibration-type actuator including a vibration body and a driven body configured to be in pressure contact with and to rotate relatively each other, and an electro-mechanical energy conversion element configured to be attached to the vibration body and to excite vibration on the vibration body for relatively rotating the vibration body and the driven body when drive voltage is applied, a casing in which the vibration-type actuator is arranged, the casing having at least one inlet, and at least one vent to which negative pressure is supplied and that is disposed so that air guided through the at least one inlet into the casing flows toward a pressurized contact part of the vibration body and a pressurized contact part of the driven body, and an output member configured to transmit rotational force of the vibration-type actuator to outside of the casing.

[0009} Accordingly, a second aspect of the present invention provides an articulated robot equipped with the rotary drive device of the first aspect.

[0010] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings .

Advantageous Effects of Invention

[0011] According to the present invention, the vibration-type actuator in the rotary drive device is cooled without dispersing worn powder generated in the vibration-type actuator to an atmosphere where various apparatuses are installed.

Brief Description, of Drawings

[0012] [FIG. 1] FIG. 1 is a view showing an outline structure of an example of an articulated robot equipped with a rotary drive device.

[FIG. 2] FIG. 2 is a sectional view schematically showing a structural example of the rotary drive device (tip arm) with which the articulated robot in FIG. 1 is provided .

[FIG. 3] FIG. 3 is a sectional view schematically showing a structural example of a rotary drive device (tip arm) .

[FIG. 4A] FIG. 4 A is a plan view showing a structural example of a vibrator that constitutes a vibration-type actuator with which the tip arm in FIG. 3 is provided.

[FIG. 4B] FIG. 4B is a cross sectional view taken along the A-A line in FIG. 4A.

[FIG. 5] FIG. 5 is a sectional view schematically showing a structural example of a rotary drive device (tip arm) .

[FIG. 6] FIG. 6 is a sectional view schematically showing a structural example of a rotary drive device (tip arm) .

[FIG. 7] FIG. 7 is a partial perspective view showing structure of a modified example of a ring shape projection formed on a casing that constitutes the tip arm in FIG. 6.

Description of Embodiments β

[0013] Hereafter, embodiments according to the present invention will be described in detail with reference to the attached drawings. In the embodiments, an arm of an end effector side (hereinafter referred to as a "tip arm") of an articulated robot that has a plurality of joints will be taken up as a rotary drive device according to the present invention. However, the present invention is not limited to this.

[0014] FIG. 1 is a view showing an outline structure of an example of an articulated robot 100 equipped with a tip arm 10 that is a rotary drive device according to a first embodiment of the present invention. The articulated robot 100 is a 6-axis articulated robot that has six axes from a first axis to a sixth axis as rotation axes. Rotation directions around the axes are illustrated. Since movements around the axes do not directly relate to the present invention, detailed descriptions about the movements are omitted.

[0015] In the articulated robot 100, a vibration-type actuator is built in the tip arm 10, which is the sixth axis unit, as a rotary motor. Moreover, a hose 20 is arranged along the arms from a mount side of the articulated robot 100, and is attached to the tip arm 10. The inside of the hose 20 keeps a negative pressure state that is lower than air pressure of a working atmosphere of the articulated robot 100 as mentioned later. Then, an inlet 24 (see FIG. 2) is formed at an end effector side of the tip arm 10. [0016] FIG. 2 is a sectional view schematically showing a structural example of the tip arm 10. The tip arm 10 has a cylindrical casing 21 as an exterior member and a vibration-type actuator 50 arranged inside the casing 21 in summary. The vibration-type actuator 50 is formed in a circle around an output shaft 40 as a rotation shaft, and is provided with a vibration body 51, a piezoelectric element 52, a rotational moving body 61, and an energizing member 62. A vibrator 53 has the vibration body 51 and the piezoelectric element 52, and is fixed to the casing 21 in its center.

[0017] The piezoelectric element 52 that is an electro-mechanical energy conversion element is attached to the vibration body 51. A polar zone 71 of a predetermined pattern is formed on the piezoelectric element 52. When drive voltage of a predetermined frequency is applied to the polar zone 71 through a wiring 72, a progressive vibratory wave (drive vibration) occurs in the vibration body 51. The vibration body 51 is made from metal, such as stainless steel, for example, and nitriding treatment etc. for improving antiwear quality is applied to a portion that contacts the rotational moving body 61 of the vibration body 51. The energizing member 62 is attached to the rotational moving body 61 in a state to be combined with the output shaft 40, and makes the rotational moving body 61 as a driven body contact the vibration body 51 while giving pressure thereto. The rotational moving body 61 is made from metal, such as stainless steel, for example, and nitriding treatment etc. for improving antiwear quality is applied to a portion that contacts the vibration body 51. The output shaft 40, which transmits the rotational force of the vibration-type actuator 50 to the outside of the casing 21, is supported by the casing 21 via bearings 44 arranged at both ends of the casing 21 in an axial direction. Thus, the drive vibration excited in the vibration body 51 gives the rotational moving body 61 rotational driving force (friction drive force) , which rotates a rotation output member 41 connected with the output shaft 40, rotating the output shaft 40.

[0018] The inlet 24 is formed through an end face (face that intersects perpendicularly with the rotation axis) at the side of the rotation output member 41 of the casing 21. Moreover, a through hole 22 is formed through an end face opposing to the end face through which the inlet 24 is formed. A hose 20 is inserted into the through hole 22 so as to open in the casing 21. That is, the opening part in the casing 21 of the hose 20 functions as a vent. It should be noted that a gap between the through hole 22 and the hose 20 is filled up with sealant 25 holding the hose 20 and blockading the through hole 22.

[0019] Negative pressure is supplied to the hose 20. This keeps negative pressure state in the casing 21 as compared with air pressure outside the casing 21. Air in the casing 21 is exhausted through the hose 20. Any methods can be employed to supply the negative pressure. For example, the negative pressure is supplied by attaching an exhaust fan or an exhaust pump to a tank (not shown) to which the hose 20 is connected, or by connecting the hose 20 to an exhaust pipe that is branched from an exhaust duct etc. Alternatively, an exhaust path may be formed between the tip arm 10 and the arm of the fifth axis unit to which the tip arm 10 is connected. In such a case, the air in the casing 21 is exhausted through the; arm of the fifth axis unit by supplying the negative pressure to the arm of the fifth axis unit.

[0020] The exhausting with the hose 20 forms an air stream in the casing 21 so that the air that flows into the casing 21 through the inlet 24 is exhausted to the hose 20 as shown by the broken-line arrow. The air stream cools the vibration-type actuator 50. Since the air stream is formed near a pressurized contact part of the vibration body 51 and a pressurized contact part of the rotational moving body 61 in this embodiment, this pressurized contact parts are cooled efficiently, and the temperature rises of the vibrator 53 and the rotational moving body 61 due to frictional heat of the pressurized contact parts are reduced effectively.

[0021] Since the vibration-type actuator 50 obtains the driving force using the frictional force by the pressurized contact between the vibration body 51 and the rotational moving body 61, worn powder is generated at the pressurized contact part of the vibration body 51 and the pressurized contact part of the rotational moving body 61. The worn powder generated in this way rides on the air stream formed in the casing 21, and is discharged to the outside of the tip arm 10 through the hose 20. The air in the casing 21 flows in a direction to keep away from the side of an end effector that will be attached to the rotation output member 41, which prevents the worn powder from discharging through the inlet 24. Accordingly, when the articulated robot 100 handles a part or a work object that should avoid dust, dispersion of the worn powder to the work object side is prevented.

[0022] It should be noted that the inlet 24 is formed so that the pressurized contact part of the vibration body 51 and the pressurized contact part of the rotational moving body 61 are located in the course of the air stream formed in the casing 21. And therefore, the inlet 24 may be formed at a position other than the end face at the side of the rotation output member 41 (end effector side) of the casing 21. For example, the inlet 24 may be formed through a cylindrical side face of the casing 21. In this case, if the hose 20 is attached to the face opposite to the end face of the side of the rotation output member 41 of the casing 21, the inlet 24 should be formed at a position on the cylindrical, side face of the casing 21 between the end face at the side of the rotation output member 41 and the pressurized contact parts of the vibration body 51 and the rotational moving body 61. Moreover, the arranged position of the hose 20 may be changed according to the formed position of the inlet 24 so that the pressurized contact part of the vibration body 51 and the pressurized contact part of the rotational moving body 61 is located in the course of the air stream formed in the casing 21.

[0023] The number and size of the inlet 24 can be changed (designed) as long as the air stream reduces the temperature rises of the vibrator 53 and the rotational moving body 61. Moreover, a filter that catches dust may be disposed in the air flow path from the inlet 24 to the opening of the hose 20.

[0024] FIG. 3 is a sectional view schematically showing a structural example of a tip arm 10A that is a rotary drive device according to a second embodiment of the present invention. Members of the tip arm 10A in FIG. 3 that are identical to the members of the tip arm 10 in FIG. 2 are represented by the same reference signs, and their duplicated descriptions are omitted. Members of the tip arm 10A that are not identical but correspond to the members of the tip arm 10 are represented by the corresponding signs to which "A" is added at the ends.

[0025] The tip arm 10A has a cylindrical casing 21A as an exterior member and a vibration-type actuator 50A arranged inside the casing 21A in summary. The

vibration-type actuator 50A is provided with a vibration body 51A, the piezoelectric element 52, a rotational moving body 61A, and an energizing member 62A. The vibration body 51A and the piezoelectric element 52 constitute a vibrator 53A. The vibrator 53A is fixed to the casing 21A in the center. The rotational moving body 61A is attached to the energizing member 62A, and the energizing member 62A is attached to a rotation output member 41A. Moreover, the rotation output member 41A is connected with an inner ring of a cross roller bearing 44A, and an outer ring of the cross roller bearing 44A is attached to the casing 21A.

[0026] FIG. 4A is a plan view showing a structure of an example of the vibrator 53A in the vibration-type actuator 50A. FIG. 4B is a cross sectional view taken along the A-A line in FIG. 4A. The vibrator 53A has the vibration body 51A, and the piezoelectric element 52 attached to the vibration body 51A. The vibration body 51A is a disk, and is formed so that a thickness of the outer periphery is larger than a thickness of the center. Slits 54A are provided on the upper surface of the outer periphery in a circumferential direction with intervals in the circumferential direction. An upper face of a convex part 54B is in pressure contact with the rotational moving body 61A. The convex part 54B is between adjacent slits 54A. The vibration body 51A has a plurality of holes 55A for fixing the vibration body 51A to the casing 21A with screws .

[0027] Inlets 24 are formed through an end face of the casing 21A at the side of the rotation output member 41A. A hose 20A is inserted into a through hole 22A formed through an end face opposing to the end face through which the inlets 24 are formed. Negative pressure is supplied to the hose 20A. The vibration-type actuator 50A uses the slits 54A formed on the vibration body 51A as a part of an air flow path inside the casing 21. Namely, the air that flows into the casing 21A through the inlets 24 passes through the slits 54A formed on the vibration body 51A first, and flows into the inside of the vibration-type actuator 50A (a space surrounded by the vibration body 51A, the rotational moving body 61A, and the energizing member 62A) as shown by the broken-line arrows. Then, the air flowed into the inside of the vibration-type actuator 50A is exhausted through the hose 20A.

[0028] Since the tip arm 10A is configured so that the air flows just near the pressurized contact parts of the vibration body 51A and rotational moving body 61A in this way, the temperature rises of the vibrator 53A and the rotational moving body 61A due to the frictional heat at the pressurized contact part is more effectively reduced. Moreover, the air in the casing 21A flows in a direction to keep away from the side of the rotation output member 41A in the tip arm 10A as with the tip arm 10, which prevents the worn powder from discharging through the inlets 24A.

[0029] It should be noted that holes may be formed through the energizing member 62A of the vibration-type actuator 50A in the direction parallel to the rotation axis in order to give suitable spring property and to reduce the weight. In such a case, the holes are preferably- blockaded with members such as a film or rubber in order to keep the flow velocity of the air that flows into the inside of the vibration-type actuator 50A through the slits

54A.

[0030] On the other hand, if the holes formed through the energizing member 62A are not blockaded, it is preferable to form the through hole 22 in the same position as the tip arm 10 in FIG. 2 and to insert the hose 20 without forming the through hole 22A. In addition, it is preferable to make the gap between the surface of the inner circumference of the casing 21A and the pressurized contact parts of the vibration body 51A and rotational moving body 61A as narrow as possible. Accordingly, the flow path is formed so that the air taken from the inlets 24A is guided to the inside space of the vibration-type actuator 50A through the holes, and is exhausted to the hose 20 through the slits 54A. That is, it is preferable to form the air flow path so that the air taken from the inlets 24A flows into the inside space of the vibration-type actuator 50A, flows just near the pressurized contact parts of the vibration body 51A and rotational moving body 61A, and is exhausted in the direction to keep away from the working area of the articulated robot 100. The inlets 24A may be formed at positions other than the end face at the side of the rotation output member 41 of the casing 21A as with the case of the tip arm 10 in FIG. 2. [0031] FIG. 5 is a sectional view schematically showing a structural example of a tip arm 10B that is a rotary drive device according to a third embodiment of the present invention. The tip arm 10B is provided with a detected body 81, a detecting element 82, and a detection wiring 83 in addition to the tip arm 10A in FIG. 3. Accordingly, members of the tip arm 10B that are identical to the members of the tip arm 10A are represented by the same reference signs, and their duplicated descriptions are omitted.

[0032] The detected body 81 of the tip arm 10B is a code wheel having a predetermined reflection pattern, is attached to the rotation output member 41A, and rotates together with the rotation output member 41A. The detecting element 82 is a reflection-optical rotary encoder that detects the rotary position of the rotation output member 41A according to the detected rotary position of the detected body 81, and is fixed to the casing 21A. The detection wiring 83 is used to supply operating power to the detecting element 82 and to take out an output of the detecting element 82.

[0033] Since the air stream in the casing 21A of the tip arm 10B is the same as the air stream in the casing 21A of the tip arm 10A in FIG. 3, the description is omitted. In the tip arm 10B, the gap between the detected body 81 and the detecting element 82 is located at the upper stream side of the air stream than the pressurized contact parts of the vibration body 51A and rotational moving body 61A in the casing 21A. Accordingly, the worn powder generated at the pressurized contact part does not easily disperse to the vicinity of the detecting element 82, which reduces erroneous detection due to the worn powder adhering to the detecting element 82.

[0034] FIG. 6 is a sectional view schematically showing a structural example of a tip arm IOC that is a rotary drive device according to a fourth embodiment ofthe present invention. The tip arm IOC improves the air stream in the casing 21 in the tip arm 10 in FIG. 2, and structure of a casing 21C of the tip arm IOC is the largest feature. Accordingly, the structure of the casing 21C will be described in detail below. Members of the tip arm IOC that are identical to the members of the tip arm 10 are represented by the same reference signs, and their duplicated descriptions are omitted.

[0035] Two inlets 24 are formed through an end face at the side of the rotation output member 41 in the casing 21 at two points that are symmetrical about the rotation axis. Moreover, two through holes 22 are formed through an end face of the casing 21C opposing to the end face through which the inlets 24 are formed so that the through holes 22 respectively oppose to the inlets 24. Hoses 22C are inserted into the through holes 22 so as to open in the casing 21C.

[0036] A ring shape projection 91 projected toward the rotation axis is formed on the inner circumference of the cylindrical side face of the casing 21C at the position opposing to the pressurized contact parts of the vibration body 51 and rotational moving body 61. Thus, in the tip arm IOC, cross section of the air flow path between the ring shape projection 91 and the pressurized contact parts of the vibration body 51 and rotational moving body 61 becomes small. Accordingly, the flow velocity of the air flowed into the casing 21C through the inlets 24 becomes large when the air passes through the gap between the ring shape projection 91 and the pressurized contact parts of the vibration body 51 and rotational moving body 61. Since a heat transfer coefficient of air increases as the flow velocity increases, the air flowing near the pressurized contact part takes heat from the pressurized contact part more efficiently. Thus, the temperature rises of the vibrator 53 and the rotational moving body 61 due to the frictional heat generated at the pressurized contact part is reduced more effectively.

[0037] FIG. 7 is a partial perspective view showing a structural example of a ring shape projection 92 that is a modified example of the ring shape projection 91. Spiral grooves 92A are formed on the ring shape projection 92 in the circumferential direction at nearly regular intervals so as to have a predetermined angle to the axial direction of the rotation axis. When the ring shape projection 92 has such structure, a spiral airflow is generated so as to surround the outer circumference of the rotational moving body 61. When the vibrator 53 is driven, depressions are generated in the circumferential direction on the pressurized contact parts of the vibration body 51 and rotational moving body 61. The spiral airflow formed with the spiral grooves 92A flow into the depressions generated on the pressurized contact part efficiently. Accordingly, the temperature rises of the vibrator 53 and the rotational moving body 61 due to the frictional heat generated at the pressurized contact part is reduced more effectively.

[0038] When the rotational moving body 61 rotates mainly in a specific direction particularly, the spiral grooves 92A are formed so that a spiral airflow is generated in the direction contrary to the rotation direction of the rotational moving body 61. This increases the relative velocity between the surface of the rotational moving body 61 and the spiral airflow, which cools the pressurized contact part of the vibration body 51 and the pressurized contact part of the rotational moving body 61 more effectively. It should be noted that the number of the inlets 24 is not limited to two. Similarly, the numbers of the through holes 22 and the hoses 20 are not limited to two. The numbers or sizes of them are arbitrarily determined as long as the object that reduces the temperature rises in the vibrator 53 and in the rotational moving body 61 is achieved. [0039] Although the embodiments of the invention have been described, the present invention is not limited to the above-mentioned embodiments, the present invention includes various modifications as long as the concept of the invention is not deviated. The embodiments mentioned above show examples of the present invention, and it is possible to combine the embodiments suitably.

[0040] Although the structure in which the rotational moving body 61 as the driven body rotates with respect to the fixed vibrator 53 is taken up in the above-mentioned embodiments, the present invention is not limited to such structure. For example, a rotary drive device that reciprocates within a certain angle may have structure in which a vibrator rotates with respect to a fixed driven body. That is, the vibration-type actuator must have structure in which the vibrator and the driven body are relatively rotated.

[0041] Each of the above-mentioned embodiments described the example that builds the vibration-type actuator as the rotary motor in the tip arm 10 that is the sixth axis unit of the articulated robot 100. However, the present invention is not limited to such structure. The above-mentioned structure is applicable to the other axis units and to a rotary drive unit built in an end effector unit (not shown) . Moreover, the cooling and

dust-discharging structure for the tip arm 10 is applicable to not only the articulated robot 100 but also various rotary drive devices such as a photoconductive drum in an image forming apparatus.

Reference Signs List

[0042]

10, 10A, 10B, IOC

50 50A Vibration-type actuator

20, 20A, 20C Hose

21, 21A, 21C Casing

40 Output shaft

41 Rotation output member

51 Vibration body

52 Piezoelectric element

53 Vibrator

61, 61A Rotational moving body

62, 62A Energizing member

91, 92 Ring shape projection

92A Groove

Claims

1. A rotary drive device comprising:

a vibration-type actuator comprising:

a vibration body and a driven body configured to be in pressure contact with and to rotate relatively each other; and

an electro-mechanical energy conversion element configured to be attached to said vibration body and to excite vibration on said vibration body for relatively rotating said vibration body and said driven body when drive voltage is applied;

a casing in which said vibration-type actuator is arranged, said casing having:

at least one inlet; and

at least one vent to which negative pressure is supplied and that is disposed so that air guided through said at least one inlet into said casing flows toward a pressurized contact part of said vibration body and a pressurized contact part of said driven body; and

an output member configured to transmit rotational force of said vibration-type actuator to outside of said casing.

2. The rotary drive device according to claim 1, wherein said vibration body is fixed inside said casing and said driven body rotates with respect to said vibration body, wherein said output member is rotatably supported by said casing, and

wherein rotational force of said driven body is transferred to said output member.

3. The rotary drive device according to claim 1 or 2, wherein said vibration body is a disk.

4. The rotary drive device according to claim 1 or 2, wherein a thickness of an outer periphery of the vibration body is larger than a thickness of a center of the vibration body.

5. The rotary drive device according to claim 4 , wherein the vibration body has slits provided on an upper surface of the outer periphery in a circumferential direction with intervals in the circumferential direction.

6. The rotary drive device according to claim 5, wherein an upper face of convex part of the vibration body is in pressure contact with the driven body, and wherein the convex part is between adjacent slits.

7. The rotary drive device according to claim 5,

wherein the slits become a part of an air flow path in said casing.

8. The rotary drive device according to any one of claims

1 to 7, further comprising an encoder configured to detect rotation position of said driven body,

wherein said encoder is located at an upper stream side in an air flow path in said casing than the pressurized contact part of the vibration body and the pressurized contact part of said driven body.

9. The rotary drive device according to any one of claims 1 to 8, wherein the casing includes a projection on an inner circumference of said casing at a position opposing to at least one of the pressurized contact part of the vibration body and the pressurized contact part of the driven body.

10. The rotary drive device according to claim 9, wherein spiral grooves are formed on an inner circumference of the proj ection .

11. The rotary drive device according to claim 9, wherein said driven body is rotated in a direction, and the spiral grooves are formed so that a spiral airflow is generated in the direction contrary to the rotation direction of said driven body.

12. An articulated robot equipped with the rotary drive device according to one of claims 1 to 11.