JP2021143722A - Electric actuator - Google Patents

Abstract

To support an axial load generated in a speed reducer, and to suppress the outflow of a lubricant from an engaging portion of the speed reducer.SOLUTION: An electric actuator includes a speed reducer 5 which has an electric motor 4 capable of supplying driving force, an input rotator 2 capable of rotating about a rotation axis X, a planetary rotator 22 capable of rotating and revolving about the rotation axis, and an output rotator 3 capable of rotating about the rotation axis X, and in which the planetary rotator 22 engages with the input rotator 2 and the output rotator 3 to change the rotation phase difference of the output rotator 3 with respect to the input rotator 2. In an axial clearance 35 between the input rotator 2 and the planetary rotator 22, a thrust ball bearing 36 is arranged, which supports the planetary rotator 22 with respect to the input rotator 2 in an axial direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electric actuator.

There is an electric actuator capable of changing the rotational phase difference between an input side in which a driving force is input from the outside and an output side in which the input driving force is output.

As this electric actuator, for example, one used in a variable valve timing device that changes the opening / closing timing of one or both of an intake valve and an exhaust valve of an automobile engine is known.

Generally, this type of electric actuator includes an electric motor and a speed reducer that obtains a driving force by the electric motor to reduce and transmit a rotational force (see, for example, Patent Document 1).

When the speed reducer is not driven by the electric motor, the input side member (for example, sprocket) and the output side member (for example, camshaft) rotate synchronously.

When the speed reducer is driven by the electric motor, the speed reducer changes the rotational phase difference of the output side member with respect to the input side member, thereby adjusting the valve opening / closing timing.

Japanese Unexamined Patent Publication No. 2018-194151

By the way, in the electric actuator described in Patent Document 1, the internal gear arranged between the input rotating body and the output rotating body performs an eccentric rotating motion to obtain a rotational phase difference of the output rotating body with respect to the input rotating body. An eccentric speed reducer that changes is adopted.

The eccentric speed reducer has a meshing structure between an external tooth portion provided on the outer periphery of the input rotating body and the output rotating body and an internal tooth portion provided on the inner circumference of the internal gear.

During the eccentric rotational movement of the internal gear due to the meshing of the external tooth portion and the internal tooth portion, the internal gear tilts with respect to the axial direction, causing skew in the internal gear, and as a result, an axial load is generated in the speed reducer. Due to this axial load, the internal gear is press-fitted in and out, and the efficiency of the reducer is reduced.

In addition, in order to smoothly perform the eccentric rotational movement of the internal gear, a lubricant such as grease is sealed in the housing of the electric actuator. The lubricant easily flows at the meshing part (tooth surface). Therefore, there is a risk that the lubricant will flow out from the meshing portion and be exhausted.

As described above, when the lubricant is depleted at the meshing portion between the external tooth portion and the internal tooth portion, it becomes difficult to maintain the lubricating performance and the sliding resistance at the meshing portion increases. As a result, the efficiency and durability of the reducer are reduced.

Therefore, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to support the axial load generated in the speed reducer and suppress the outflow of the lubricant from the meshing portion of the speed reducer. The purpose is to provide an electric actuator to obtain.

The electric actuator according to the present invention includes an electric motor capable of supplying a driving force, an input rotating body that can rotate around a rotating shaft, a planetary rotating body that can rotate and revolve around a rotating shaft, and a rotating shaft. It has an output rotating body that can rotate around the center, and is equipped with a speed reducer in which the planetary rotating body meshes with each of the input rotating body and the output rotating body to change the rotational phase difference of the output rotating body with respect to the input rotating body. ..

As a technical means for achieving the above-mentioned object, the present invention provides a thrust ball bearing that axially supports the planetary rotating body with respect to the input rotating body in the axial gap between the input rotating body and the planetary rotating body. It is characterized in that it is arranged.

In the present invention, it is possible to prevent the planetary rotating body from being press-fitted in and out by receiving the axial load generated in the planetary rotating body by the thrust ball bearing during the eccentric rotational movement of the planetary rotating body. Further, the thrust ball bearing can suppress the outflow of the lubricant from the meshing portion of the speed reducer, and makes it easier to hold the lubricant at the meshing portion of the speed reducer.

As described above, since the lubricant can be easily held at the meshing portion of the speed reducer, it becomes easy to maintain the lubrication performance, and the sliding resistance at the meshing portion can be reduced.

The thrust ball bearing of the present invention preferably has a structure in which a raceway ring on which a rolling surface of a ball is formed is fitted into an annular concave groove on an end surface of an input rotating body, and the ball is brought into contact with the end surface of a planetary rotating body.

By adopting such a structure, it is possible to easily support the axial load generated by the skew of the planetary rotating body and suppress the outflow of the lubricant from the meshing portion of the speed reducer.

The thrust ball bearing of the present invention preferably has a structure in which the cage for holding the balls at equal intervals in the circumferential direction has a flat disk shape or a disk shape with a flange.

If such a structure is adopted, the outflow of the lubricant from the meshing portion of the speed reducer can be further suppressed by the flat disk-shaped or flanged disk-shaped cage.

According to the present invention, even if the eccentric rotary motion of the planetary rotating body is performed in the speed reducer, the thrust ball bearing receives the axial load generated by the eccentric rotary motion to prevent the planetary rotating body from being press-fitted or removed. This makes it possible to improve the efficiency and reliability of the speed reducer.

Further, by suppressing the outflow of the lubricant from the meshing portion of the speed reducer, it becomes easier to hold the lubricant in the meshing portion. As a result, the lubrication performance can be easily maintained, the sliding resistance at the meshing portion can be reduced, and the efficiency and durability of the speed reducer can be improved.

It is sectional drawing which shows the whole structure of the electric actuator in embodiment of this invention. It is sectional drawing which follows the PP line of FIG. It is sectional drawing which follows the QQ line of FIG. It is an enlarged cross-sectional view of part A which shows the thrust ball bearing of FIG. It is an assembly disassembled perspective view which shows the electric actuator of FIG. FIG. 5 is an enlarged cross-sectional view of a main part showing a thrust ball bearing in another embodiment of the present invention.

An embodiment of the electric actuator according to the present invention will be described in detail with reference to the drawings. In the following embodiments, the electric actuator applied to the variable valve timing device is illustrated, but the electric actuator can be applied to other than the variable valve timing device.

FIG. 1 is a cross-sectional view showing the overall configuration of the electric actuator, FIG. 2 is a cross-sectional view taken along the line PP of FIG. 1, and FIG. 3 is a cross-sectional view taken along the line QQ of FIG. Before explaining the characteristic configuration of this embodiment, the overall configuration of the electric actuator will be described.

As shown in FIGS. 1 to 3, the electric actuator 1 of this embodiment mainly includes an input rotating body 2, an output rotating body 3, an electric motor 4, a speed reducer 5, and a casing 6 accommodating them. It is provided as a component.

The input rotating body 2 is a member that is rotationally driven by inputting a driving force from an external driving source (not shown). The input rotating body 2 integrally has a small diameter portion 11 and a large diameter portion 12 having a diameter larger than that of the small diameter portion 11.

The input rotating body 2 is rotatably supported by a rolling bearing 7 with a seal with respect to the casing 6. The space between the casing 6 and the input rotating body 2 is sealed by the rolling bearing 7 with a seal.

The output rotating body 3 is a member that outputs the driving force input to the input rotating body 2 to the outside. The output rotating body 3 is fastened by bolts 8 so that the shaft 9 as an output shaft rotates integrally. The output rotating body 3 is arranged coaxially with respect to the input rotating body 2 about the rotation axis X and is configured to be relatively rotatable.

A rolling bearing 10 with a seal is arranged on the inner circumference of the large diameter portion 12 of the input rotating body 2. The shaft 9 is rotatably supported by a rolling bearing 10 with a seal with respect to the input rotating body 2. The space between the input rotating body 2 and the shaft 9 is sealed by the rolling bearing 10 with a seal.

The casing 6 is divided into a bottomed cylindrical main body 13 and a lid 14 that closes the main body 13 in order to improve assembleability. The main body portion 13 and the lid portion 14 are integrated by using a fastening means (not shown) such as a bolt.

The lid 14 has a tubular shape for drawing out a power supply line for supplying power to the electric motor 4 and a signal line connected to a rotation number detection sensor (not shown) for detecting the rotation number of the electric motor 4. A protrusion 15 (see FIG. 5) is provided.

The space between the lid portion 14 of the casing 6 and the output rotating body 3 is sealed by a rolling bearing 16 with a seal. The rolling bearing 16 with a seal rotatably supports the output rotating body 3 with respect to the lid portion 14 of the casing 6.

The electric motor 4 is a radial gap type motor having a stator 17 fixed to the main body 13 of the casing 6 and a rotor 18 arranged so as to face each other with a gap inside the stator 17 in the radial direction. The rotor 18 rotates about the rotation axis X with respect to the stator 17 due to the exciting force acting between the stator 17 and the rotor 18.

The main part of the speed reducer 5 rotates integrally with the first external tooth portion 19 formed on the outer periphery of the input rotating body 2, the second external tooth portion 20 formed on the outer periphery of the output rotating body 3, and the rotor 18. A cycloid reducer composed of an eccentric member 21, a planetary rotating body 22 arranged on the inner circumference of the eccentric member 21, and a needle-shaped roller bearing 23 arranged between the eccentric member 21 and the planetary rotating body 22. Is.

The eccentric member 21 integrally includes a small-diameter tubular portion 24 fixed to the inner circumference of the rotor 18 and a large-diameter tubular portion 25 formed to have a larger diameter than the small-diameter tubular portion 24 and projecting axially from the rotor 18. .. The small-diameter tubular portion 24 and the large-diameter tubular portion 25 are rotatably supported by rolling bearings 26 and 27 with respect to the casing 6.

The outer peripheral surface of the eccentric member 21 is formed coaxially with the rotation axis X. The inner peripheral surface of the small diameter tubular portion 24 is arranged so as to be eccentric with respect to each central axis (rotation axis X) of the input rotating body 2 and the output rotating body 3. On the other hand, the inner peripheral surface of the large-diameter tubular portion 25 is arranged coaxially with each central axis (rotation axis X) of the input rotating body 2 and the output rotating body 3.

The planetary rotating body 22 integrally includes a small-diameter tubular portion 28 and a large-diameter tubular portion 29 having a diameter larger than that of the small-diameter tubular portion 28. The first internal tooth portion 30 is formed on the inner circumference of the large-diameter tubular portion 29, and the second internal tooth portion 31 is formed on the inner circumference of the small-diameter tubular portion 28.

Both the first internal tooth portion 30 and the second internal tooth portion 31 are composed of a plurality of teeth having a curved cross section in the radial direction (for example, a trochoidal curve). The pitch circle diameter of the second internal tooth portion 31 is smaller than the pitch circle diameter of the first internal tooth portion 30. Further, the number of teeth of the second internal tooth portion 31 is smaller than the number of teeth of the first internal tooth portion 30.

A first external tooth portion 19 is formed on the outer periphery of the input rotating body 2 so as to mesh with the first internal tooth portion 30 of the planetary rotating body 22. Further, a second external tooth portion 20 is formed on the outer periphery of the output rotating body 3 so as to mesh with the second internal tooth portion 31 of the planetary rotating body 22 so as to face each other.

Both the first external tooth portion 19 and the second external tooth portion 20 are composed of a plurality of teeth having a curved cross section in the radial direction (for example, a trochoidal curve). The pitch circle diameter of the second external tooth portion 20 is smaller than the pitch circle diameter of the first external tooth portion 19. Further, the number of teeth of the second external tooth portion 20 is smaller than the number of teeth of the first external tooth portion 19.

The number of teeth of the first external tooth portion 19 is less than the number of teeth of the first internal tooth portion 30 that mesh with each other, and is preferably one less. Similarly, the number of teeth of the second external tooth portion 20 is also smaller than the number of teeth of the second internal tooth portion 31 that mesh with each other, preferably one less.

In this embodiment, the number of teeth of the first internal tooth portion 30 is 24, the number of teeth of the second internal tooth portion 31 is 20, the number of teeth of the first external tooth portion 19 is 23, and the number of teeth of the second external tooth portion 20 is 20. The number of teeth is 19.

The planetary rotating body 22 is formed between the rolling bearing 32 arranged between the large-diameter tubular portion 29 and the large-diameter tubular portion 25 of the eccentric member 21, and between the small-diameter tubular portion 28 and the small-diameter tubular portion 24 of the eccentric member 21. It is rotatably supported with respect to the eccentric member 21 by the arranged needle roller bearing 23.

In this way, the rolling bearing 32 and the needle roller bearing 23 support the planetary rotating body 22 with respect to the eccentric member 21, thereby reducing the radial runout of the planetary rotating body 22 and reducing the radial runout of the planetary rotating body 22. It suppresses the decrease in power transmission efficiency due to radial runout.

Further, the planetary rotating body 22 is arranged on the inner circumference of the eccentric member 21 via the needle roller bearing 23 and the rolling bearing 32, so that the central axes (rotating shafts) of the input rotating body 2 and the output rotating body 3 are provided. It is arranged eccentrically with respect to X).

Since the planetary rotating body 22 is arranged eccentrically with respect to the rotation axis X, as shown in FIG. 2, the central axis Y of the first internal tooth portion 30 is only a distance E in the radial direction with respect to the rotation axis X. It is eccentric. As a result, the first internal tooth portion 30 and the first external tooth portion 19 are in a state of being meshed with each other in a partial region in the circumferential direction (left side in FIG. 2), and in a region on the opposite side in the radial direction (right side in FIG. 2). It will not mesh.

Further, as shown in FIG. 3, the central axis Y of the second internal tooth portion 31 is also eccentric with respect to the rotation axis X by a distance E in the radial direction. As a result, the second internal tooth portion 31 and the second external tooth portion 20 are in a state of being in mesh with each other in a partial region in the circumferential direction (right side in FIG. 3), and in a region on the opposite side in the radial direction (left side in FIG. 3). It will not mesh.

In addition, in FIGS. 2 and 3, since the directions of arrow viewing are different from each other, the eccentric directions of the first internal tooth portion 30 and the second internal tooth portion 31 are shown in opposite directions in each drawing. However, the first internal tooth portion 30 and the second internal tooth portion 31 are eccentric in the same direction by the same distance E.

An operation example of the electric actuator 1 having the above structure will be described below.

In a state where the electric motor 4 is not energized and the driving force is not supplied from the electric motor 4 to the speed reducer 5, when the input rotating body 2 is rotationally driven by an external driving force, the rotation of the input rotating body 2 is rotated by the planetary rotating body 22. Is transmitted to the output rotating body 3 via. As a result, the output rotating body 3 rotates in synchronization with the input rotating body 2.

That is, the input rotating body 2 and the planetary rotating body 22 rotate integrally while maintaining this meshing state by torque transmission at the meshing portion 33 between the first external tooth portion 19 and the first internal tooth portion 30. Similarly, the planetary rotating body 22 and the output rotating body 3 also rotate integrally while maintaining the meshing positions of the second internal tooth portion 31 and the second external tooth portion 20. Therefore, the input rotating body 2 and the output rotating body 3 rotate while maintaining the same rotation phase.

On the other hand, when the electric motor 4 is energized and the driving force is supplied from the electric motor 4 to the speed reducer 5, the rotor 18 and the eccentric member 21 rotate integrally to cause the planetary rotating body 22 to rotate. An eccentric rotation motion is performed on the input rotating body 2 and the output rotating body 3.

That is, the eccentric member 21 coupled to the rotor 18 is integrally rotated around the rotation axis X by the operation of the electric motor 4. The pressing force associated with the rotation of the eccentric member 21 acts on the planetary rotating body 22 via the needle roller bearing 23 and the rolling bearing 32. Due to this pressing force, a component force in the circumferential direction is generated at the meshing portion 33 between the first internal tooth portion 30 and the first external tooth portion 19, so that the planetary rotating body 22 rotates eccentrically with respect to the input rotating body 2. Exercise.

That is, while the planetary rotating body 22 revolves around the rotation axis X, it rotates around the center Y of the first internal tooth portion 30 and the second internal tooth portion 31. At this time, each time the planetary rotating body 22 revolves once, the meshing position between the first internal tooth portion 30 and the first external tooth portion 19 shifts in the circumferential direction by one tooth, so that the planetary rotating body 22 is decelerated. While rotating (rotating).

Further, due to the eccentric rotational movement of the planetary rotating body 22, each time the planetary rotating body 22 revolves once, the meshing position between the second internal tooth portion 31 and the second external tooth portion 20 is moved in the circumferential direction by one tooth. It shifts. As a result, the output rotating body 3 rotates while being decelerated with respect to the planetary rotating body 22.

By driving the planetary rotating body 22 with the electric motor 4 in this way, the driving force from the electric motor 4 is superimposed on the driving force input from the input rotating body 2, and the rotation of the output rotating body 3 is the rotation of the electric motor 4. It will be in a state affected by the driving force from. Therefore, it is possible to change the relative rotation phase difference of the output rotating body 3 with respect to the input rotating body 2 in the forward and reverse directions.

Here, assuming that the reduction ratio by the speed reducer 5 is I, the rotation speed of the electric motor 4 is Nm, and the rotation speed of the input rotating body 2 is Ns, the phase angle difference of the output rotating body 3 is (Nm-Ns) / I. Become. Further, assuming that the reduction ratio of the first external tooth portion 19 is i1 and the reduction ratio of the second external tooth portion 20 is i2, the reduction ratio I by the reduction gear 5 is obtained by I = i1 × i2 / | i1-i2 |. To be done.

For example, when the reduction ratio (i1) of the first external tooth portion 19 is 24 and the reduction ratio (i2) of the second external tooth portion 20 is 20, the reduction ratio is 120 from the above equation. As described above, in the speed reducer 5 in this embodiment, it is possible to obtain a high torque with a large reduction ratio.

The overall configuration of the electric actuator 1 in this embodiment is as described above, but the characteristic configuration thereof will be described in detail below.

In the electric actuator 1 of this embodiment, the planetary rotating body 22 arranged between the input rotating body 2 and the output rotating body 3 performs an eccentric rotating motion to rotate the output rotating body 3 with respect to the input rotating body 2. An eccentric speed reducer 5 that changes the phase difference is adopted.

The eccentric speed reducer 5 has a meshing structure between the first external tooth portion 19 of the input rotating body 2 and the first internal tooth portion 30 of the planetary rotating body 22, and the second external tooth portion 20 of the output rotating body 3 and the planetary rotation. It has a meshing structure with the second internal tooth portion 31 of the body 22.

During the eccentric rotational movement of the planetary rotating body 22 due to this meshing structure, the planetary rotating body 22 tilts with respect to the axial direction due to the clearance of the rolling bearing 32, causing skew to occur in the planetary rotating body 22, and as a result, the eccentric speed reducer. An axial load is generated at 5.

Further, in order to smoothly perform the eccentric rotational movement of the planetary rotating body 22 due to the meshing structure, a lubricant such as grease (not shown) is put in the housing 6 of the electric actuator 1 and the rolling bearings 7, 10 and 16 with a seal (FIG. 1). See).

In the eccentric rotational movement of the planetary rotating body 22, the meshing portion 33 between the first external tooth portion 19 and the first internal tooth portion 30 and the meshing portion between the second external tooth portion 20 and the second internal tooth portion 31 are caused by the pumping action. The lubricant easily flows in the portion 34.

Therefore, in the electric actuator 1 of this embodiment, measures are taken to support the axial load generated in the eccentric speed reducer 5 and to suppress the outflow of the lubricant from the meshing portions 33 and 34 of the eccentric speed reducer 5. There is.

In this embodiment, as shown in FIGS. 1 and 4, a thrust that axially supports the planetary rotating body 22 with respect to the input rotating body 2 in the axial gap 35 between the input rotating body 2 and the planetary rotating body 22. The ball bearing 36 is arranged.

The thrust ball bearing 36 forms an annular groove 37 on the end surface of the input rotating body 2 facing the planetary rotating body 22, and the raceway ring 39 on which the rolling surface of the ball 38 is formed is press-fitted into the annular groove 37. It has a combined structure.

In the thrust ball bearing 36, since the planetary rotating body 22 performs an eccentric rotating motion, the ball 38 is directly brought into contact with the flat end surface 40 of the planetary rotating body 22 facing the input rotating body 2. As a result, the planetary rotating body 22 can be supported with low friction.

The thrust ball bearing 36 has a flat disk-shaped cage 41. In the cage 41, pockets 44 for accommodating the balls 38 are formed at equal intervals in the circumferential direction. A plurality of (for example, 10 to 12) balls 38 are held at equal intervals in the circumferential direction by a cage 41 arranged between the end face 40 of the planetary rotating body 22 and the orbital ring 39.

During the eccentric rotational movement of the planetary rotating body 22 in the speed reducer 5, the planetary rotating body 22 is tilted with respect to the axial direction due to the clearance of the rolling bearing 32, so that the planetary rotating body 22 is skewed, and as a result, the planetary rotating body 22 is skewed. The axial load generated in the above is supported by the thrust ball bearing 36.

By receiving the axial load by the thrust ball bearing 36 in this way, it is possible to prevent the planetary rotating body 22 from being press-fitted in and out by eliminating the axial gap 35 between the input rotating body 2 and the planetary rotating body 22. As a result, the efficiency and reliability of the speed reducer 5 can be improved.

Further, even if the eccentric rotational movement (pumping action) of the planetary rotating body 22 in the speed reducer 5 is performed by eliminating the axial gap 35 between the input rotating body 2 and the planetary rotating body 22 by the thrust ball bearing 36, It is possible to prevent the lubricant from flowing out from the meshing portions 33 and 34 of the speed reducer 5 to the outside of the speed reducer 5, and it becomes easier for the meshing portions 33 and 34 of the speed reducer 5 to hold the lubricant.

As described above, since it becomes easy to hold the lubricant in the meshing portions 33 and 34 of the speed reducer 5, it becomes easy to maintain the lubrication performance and the sliding resistance in the meshing portions 33 and 34 can be reduced. .. As a result, the efficiency and durability of the speed reducer 5 can be improved.

By fitting the raceway ring 39 into the annular groove 37 of the input rotating body 2 and adopting the thrust ball bearing 36 having a structure in which the ball 38 is brought into contact with the end surface 40 of the planetary rotating body 22, the planetary rotating body 22 It is possible to easily support the axial load generated by the skew and suppress the outflow of the lubricant from the meshing portions 33 and 34 of the speed reducer 5.

In the above embodiment, the case where the cage 41 that holds the balls 38 at equal intervals in the circumferential direction has a flat disk shape is illustrated, but the cage 42 shown in FIG. 6 can also be adopted. In FIG. 6, the same parts as those in FIG. 4 are designated by the same reference numerals, and duplicate description will be omitted.

In the thrust ball bearing 36 of the embodiment shown in FIG. 6, a disk-shaped cage 42 with a flange is illustrated. That is, the cage 42 has a flange portion 43 extending in the axial direction on the outer periphery thereof. The flange portion 43 closes the axial gap 35 between the input rotating body 2 and the planetary rotating body 22.

Even if the eccentric rotational movement (pumping action) of the planetary rotating body 22 in the speed reducer 5 is performed by the flange portion 43, the lubricant flows out from the meshing portions 33 and 34 of the speed reducer 5 to the outside of the speed reducer 5. It becomes easy to hold the lubricant in the meshing portions 33 and 34 of the speed reducer 5.

As described above, since it becomes easy to hold the lubricant in the meshing portions 33 and 34 of the speed reducer 5, it becomes easy to maintain the lubrication performance and the sliding resistance in the meshing portions 33 and 34 can be reduced. .. As a result, the efficiency and durability of the speed reducer 5 can be improved.

The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be carried out in various forms without departing from the gist of the present invention. Indicated by the scope of the claim and further includes the equal meaning described in the claims, and all modifications within the scope.

1 Electric actuator 2 Input rotating body 3 Output rotating body 4 Electric motor 5 Reducer 22 Planetary rotating body 35 Axial gap 36 Thrust ball bearing 37 Annular groove 38 Ball 39 Orbital wheel 40 End face of planetary rotating body 41, 42 Cage 43 Collar X Rotation axis

Claims (4)

An electric motor capable of supplying driving force, an input rotating body that can rotate around a rotating shaft, a planetary rotating body that can rotate and revolve around the rotating shaft, and a rotating body that can rotate around the rotating shaft. It has an output rotating body, and the planetary rotating body is provided with a speed reducer that meshes with each of the input rotating body and the output rotating body to change the rotational phase difference of the output rotating body with respect to the input rotating body.
An electric actuator characterized in that a thrust ball bearing that supports the planetary rotating body in the axial direction is arranged in an axial gap between the input rotating body and the planetary rotating body. The thrust ball bearing has a structure in which a raceway ring on which a rolling surface of a ball is formed is fitted into an annular concave groove on an end surface of the input rotating body, and the ball is brought into contact with the end surface of the planetary rotating body. The electric actuator according to claim 1. The electric actuator according to claim 1 or 2, wherein the thrust ball bearing has a flat disk shape as a cage for holding balls at equal intervals in the circumferential direction. The electric actuator according to claim 1 or 2, wherein the thrust ball bearing has a disc-shaped cage with a flange for holding balls at equal intervals in the circumferential direction.

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