Electric actuator

Abstract

To provide an electric actuator which can inhibit increase in the size of a transmission mechanism.SOLUTION: An electric actuator includes a first shaft, a second shaft, and a transmission mechanism which transmits rotation of the first shaft to the second shaft. The transmission mechanism has: a first gear which may rotate around a first axis; a second gear which may rotate around a second axis and engages with the first gear; a third gear which may rotate around the second axis and is disposed at one side in an axial direction relative to the second gear; a fourth gear which may rotate around the first axis and engages with the third gear; a fifth gear which may rotate around the first axis and is disposed at the one side in the axial direction relative to the fourth gear; and a sixth gear which may rotate around the second axis and engages with the fifth gear. An outer diameter of the second gear is larger than an outer diameter of the first gear. An outer diameter of the fourth gear is larger than an outer diameter of the third gear. An outer diameter of the sixth gear is larger than an outer diameter of the fifth gear. An axial dimension of the second gear is smaller than an axial dimension of the fourth gear, and an axial dimension of the fourth gear is smaller than an axial dimension of the sixth gear.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electric actuator.

Background Art

[0002] An actuator is known in which the rotation of a motor shaft of a motor is decelerated and transmitted to a transmission shaft by a speed reduction mechanism having a plurality of gears (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the actuator as described above, since a plurality of gears of the speed reduction mechanism are arranged side by side along the radial direction centered on the motor shaft, it is difficult to suppress the speed reduction mechanism from increasing in size in the radial direction. Therefore, it is difficult to suppress the actuator from increasing in size in the radial direction.

[0005] In view of the above circumstances, an object of the present invention is to provide an electric actuator capable of suppressing an increase in size of a transmission mechanism.

Means for Solving the Problems

[0006] One aspect of the electric actuator of the present invention includes a motor unit, a first shaft to which the rotation of a rotor of the motor unit is transmitted and which is rotatable about a first axis, a second shaft that is rotatable about a second axis extending in the same direction as the axial direction of the first axis and is arranged radially apart from the first shaft with respect to the first axis, and a transmission mechanism that transmits the rotation of the first shaft to the second shaft. The transmission mechanism includes a first gear that is rotatable about the first axis, a second gear that is rotatable about the second axis and meshes with the first gear, a third gear that is rotatable about the second axis and is arranged on one side of the axial direction with respect to the second gear and is connected to the second gear, a fourth gear that is rotatable about the first axis and meshes with the third gear, a fifth gear that is rotatable about the first axis and is arranged on one side of the axial direction with respect to the fourth gear and is connected to the fourth gear, and a sixth gear that is rotatable about the second axis and meshes with the fifth gear. The outer diameter of the second gear is larger than the outer diameter of the first gear, the outer diameter of the fourth gear is larger than the outer diameter of the third gear, the outer diameter of the sixth gear is larger than the outer diameter of the fifth gear, the axial dimension of the second gear is smaller than the axial dimension of the fourth gear, and the axial dimension of the fourth gear is smaller than the axial dimension of the sixth gear.

Advantages of the Invention

[0007] According to one aspect of the present invention, in an electric actuator, it is possible to suppress an increase in size of the transmission mechanism.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

[0009] In each drawing, the Z-axis direction is the vertical direction with the positive side (+Z side) being the upper side and the negative side (-Z side) being the lower side. In the present embodiment, the upper side corresponds to the other side in the axial direction, and the lower side corresponds to one side in the axial direction. Note that the upper side and the lower side are merely names for explaining the relative positional relationship of each part, and the actual arrangement relationship or the like may be an arrangement relationship or the like other than the arrangement relationship indicated by these names.

[0010] In each drawing, the first direction D1 is a direction orthogonal to the Z-axis direction. In the following description, the side toward which the arrow of the first direction D1 points (+D1 side) is referred to as "one side of the first direction D1", and the side opposite to the side toward which the arrow of the first direction D1 points (-D1 side) is referred to as "the other side of the first direction D1". In each drawing, the second direction D2 is a direction orthogonal to both the Z-axis direction and the first direction D1.

[0011] The direction in which the first axis J1 shown in each drawing extends is parallel to the Z-axis direction. In the present embodiment, the first axis J1 is a virtual axis. The first axis J1 is the central axis of the first shaft 23. In the following description, the direction parallel to the first axis J1 is simply referred to as the "axial direction". The radial direction centered on the first axis J1 is simply referred to as the "radial direction". The circumferential direction centered on the first axis J1 is simply referred to as the "circumferential direction". In each drawing, the circumferential direction is indicated by an arrow θ1.

[0012] The electric actuator 90 of the present embodiment shown in FIG. 1 is attached to a vehicle. More specifically, the electric actuator 90 is mounted on, for example, a park-by-wire type actuator device that is driven based on a shift operation of a driver of the vehicle. As shown in FIG. 2, the electric actuator 90 includes a housing 10, a motor unit 20, a first shaft 23, a substrate holding unit 40, a transmission mechanism 60, a second shaft 70, and a circuit board 80.

[0013] The housing 10 houses therein the motor unit 20, the first shaft 23, the substrate holding portion 40, the transmission mechanism 60, the second shaft 70, and the circuit board 80 respectively. The housing 10 has a case body 11 and a cover member 17.

[0014] The case body 11 is cylindrical and surrounds the first axis J1. The case body 11 has an opening 11b that opens upward. Inside the case body 11, the motor unit 20, the lower portion of the first shaft 23, the substrate holding portion 40, the lower portion of the second shaft 70, and the circuit board 80 are accommodated. The case body 11 has a main body peripheral wall portion 13, a bottom wall portion 14, a connector case 15, and a connector accommodating portion 16.

[0015] The main body peripheral wall portion 13 is substantially cylindrical and extends in the axial direction around the first axis J1. The main body peripheral wall portion 13 surrounds the motor unit 20 from the radially outer side. The main body peripheral wall portion 13 has a first stepped surface 13a and a second stepped surface 13b. Each of the first stepped surface 13a and the second stepped surface 13b is a stepped surface facing upward. Each of the first stepped surface 13a and the second stepped surface 13b is a part of the inner surface of the main body peripheral wall portion 13. When viewed in the axial direction, each of the first stepped surface 13a and the second stepped surface 13b is substantially annular around the first axis J1. The first stepped surface 13a is located below the second stepped surface 13b. In the present embodiment, the outer diameter of the first stepped surface 13a is the same as the inner diameter of the second stepped surface 13b.

[0016] The bottom wall portion 14 is plate-shaped and extends in a direction orthogonal to the axial direction. The bottom wall portion 14 is substantially disk-shaped around the first axis J1. The radially outer end of the bottom wall portion 14 is connected to the lower end of the main body peripheral wall portion 13. A third support portion 14a is provided on the bottom wall portion 14. The third support portion 14a projects upward from the bottom wall portion 14. The third support portion 14a is cylindrical around the first axis J1. The third support portion 14a opens upward. A third bearing 53 is attached to the inner surface of the third support portion 14a.

[0017] The connector case 15 is cylindrical and extends in the axial direction. The connector case 15 is open at the upper side. The connector case 15 is disposed on one side (+D1 side) of the main body peripheral wall portion 13 in the first direction D1. The connector case 15 is connected to the main body peripheral wall portion 13 in the first direction D1. As shown in FIG. 1, the connector case 15 is substantially rectangular when viewed from the axial direction. As shown in FIG. 2, the connector case 15 is provided with a second substrate holding portion 15a and a connector housing portion 16.

[0018] The second substrate holding portion 15a holds the circuit board 80. The second substrate holding portion 15a is substantially cylindrical and protrudes upward from the connector case 15. Although not shown, in the present embodiment, two second substrate holding portions 15a are provided in the connector case 15. Each second substrate holding portion 15a is arranged at an interval in the second direction D2. Each second substrate holding portion 15a has a second shaft portion 15b, a second insertion portion 15c, and a second substrate support portion 15d. The second shaft portion 15b is substantially cylindrical and protrudes upward from the connector case 15. The second insertion portion 15c is substantially cylindrical and protrudes upward from the second shaft portion 15b. The outer diameter of the second insertion portion 15c is smaller than the outer diameter of the second shaft portion 15b. The second substrate support portion 15d protrudes upward from the second insertion portion 15c. The outer diameter of the second substrate support portion 15d is larger than the outer diameter of the second insertion portion 15c.

[0019] The connector housing portion 16 is substantially rectangular tubular and protrudes downward from the connector case 15. The connector housing portion 16 is open at the lower side. The connector housing portion 16 holds a plurality of connector pins 57. Each connector pin 57 extends in the axial direction. The lower end of each connector pin 57 is located inside the connector housing portion 16. The upper end of each connector pin 57 is connected to the circuit board 80.

[0020] The cover member 17 is cylindrical and surrounds the first axis J1. The cover member 17 is open at the lower side. Inside the cover member 17, an upper portion of the first shaft 23, a transmission mechanism 60, and a part of the second shaft 70 are accommodated. The cover member 17 is fixed to the upper end of the case body 11. The cover member 17 closes the opening 11b of the case body 11 from above. As shown in FIG. 1, when viewed from the axial direction, the portion on the other side (-D1 side) in the first direction D1 of the cover member 17 is substantially semicircular with the first axis J1 as the center. When viewed from the axial direction, the portion on one side (+D1 side) in the first direction D1 of the cover member 17 is substantially rectangular and surrounds the second axis J2. As shown in FIG. 2, the cover member 17 has a cover peripheral wall portion 18 and a top wall portion 19.

[0021] In the present embodiment, the second axis J2 is a virtual axis extending in the same direction as the axial direction of the first axis J1. The second axis J2 is located on one side (+D1 side) in the first direction D1 with respect to the first axis J1. In the following description, the radial direction centered on the second axis J2 is simply referred to as the "second radial direction", and the circumferential direction centered on the second axis J2 is simply referred to as the "second circumferential direction". The second circumferential direction is indicated by an arrow θ2 in each figure.

[0022] The cover peripheral wall portion 18 is cylindrical and extends in the axial direction. The cover peripheral wall portion 18 surrounds the transmission mechanism 60 from the outside in the radial direction. The lower end of the cover peripheral wall portion 18 is fixed to each of the upper end of the main body peripheral wall portion 13 and the upper end of the connector case 15. Thereby, the cover member 17 is fixed to the upper end of the case body 11.

[0023] The top wall portion 19 is plate-shaped and extends in a direction orthogonal to the axial direction. The radially outer end of the top wall portion 19 is connected to the upper end of the cover peripheral wall portion 18. The top wall portion 19 is provided with a first support portion 19a and a top wall hole portion 19c. The first support portion 19a projects upward from the top wall portion 19. The first support portion 19a is cylindrical with the first axis J1 as the center. The first support portion 19a is open at the lower side. A first bearing 51 is attached to the inner surface of the first support portion 19a.

[0024] The top wall hole portion 19c is a hole that penetrates the top wall portion 19 in the axial direction. When viewed from the axial direction, the top wall hole portion 19c has a substantially circular shape centered on the second axis J2. A second shaft 70 is passed through the top wall hole portion 19c in the axial direction. As a result, the upper portion of the second shaft 70, that is, the portion on the other side in the axial direction, is located outside the housing 10.

[0025] The motor portion 20 is housed inside the case main body 11. The motor portion 20 has a rotor 21 and a stator 30. In the present embodiment, the rotor 21 is rotatable about the first axis J1. The rotor 21 may be rotatable about a virtual axis that is different from the first axis J1 and the second axis J2 and extends in the axial direction. In the present embodiment, the rotor 21 has an annular shape centered on the first axis J1. Magnets (not shown) are fixed to the rotor 21. A plurality of magnets are arranged at intervals in the circumferential direction.

[0026] The first shaft 23 is rotatable about the first axis J1. The first shaft 23 has a substantially columnar shape that extends in the axial direction about the first axis J1. The first shaft 23 extends in the axial direction across the inside of the case main body 11 and the inside of the cover member 17. In the present embodiment, the first shaft 23 is passed through the inside of the rotor 21 in the axial direction. The outer peripheral surface of the first shaft 23 is fixed to the rotor 21. That is, the first shaft 23 is fixed to the rotor 21. As a result, rotation about the first axis J1 of the rotor 21 is transmitted to the first shaft 23. The lower end of the first shaft 23 is rotatably supported about the first axis J1 by a third bearing 53. The central portion in the axial direction of the first shaft 23 is rotatably supported about the first axis J1 by a second bearing 52. The upper end of the first shaft 23 is located inside the first support portion 19a and is rotatably supported about the first axis J1 by a first bearing 51. When the rotor 21 is rotatable about a virtual axis different from the first axis J1 and the second axis J2, the rotation of the rotor 21 is transmitted to the first shaft 23 via a drive transmission member such as a gear.

[0027] The stator 30 is disposed radially outside the rotor 21. The stator 30 faces the rotor 21 with a gap therebetween in the radial direction. The stator 30 has a stator core 31, an insulator 32, and a coil portion 35.

[0028] The stator core 31 is annular and surrounds the rotor 21 from the radially outer side. The stator core 31 faces the rotor 21 with a gap therebetween in the radial direction. The stator core 31 has a core back portion 31a and a plurality of teeth portions 31b. The core back portion 31a is annular about the first axis J1. The surface facing the lower side of the core back portion 31a is axially supported by the first stepped surface 13a. Thereby, the axial position of the stator core 31 with respect to the case main body 11 is determined. The core back portion 31a is fixed to the inner surface facing the radially inner side of the main body peripheral wall portion 13. Thereby, the stator 30 is fixed to the case main body 11. Each teeth portion 31b protrudes radially inward from the core back portion 31a. Although not shown, the respective teeth portions 31b are arranged at intervals along the circumferential direction. The insulator 32 is attached to the stator core 31. The insulator 32 insulates the stator core 31 and the coil portion 35.

[0029] The coil portion 35 has a plurality of coil main body portions 35a and coil lead-out wires 35b. Each coil main body portion 35a is attached to a different teeth portion 31b via the insulator 32. The coil lead-out wire 35b is drawn upward from the coil main body portion 35a. The upper end of the coil lead-out wire 35b is connected to the circuit board 80. Thereby, the coil portion 35 is electrically connected to the circuit board 80.

[0030] The board holding portion 40 holds the circuit board 80. The board holding portion 40 is housed inside the case main body 11. The board holding portion 40 is disposed above the motor portion 20 and below the circuit board 80. The board holding portion 40 has a cylindrical portion 40a, a first board holding portion 40e, and a second support portion 40j.

[0031] The cylindrical portion 40a is cylindrical and protrudes axially about the first axis J1. The cylindrical portion 40a is open downward. The lower end of the cylindrical portion 40a is axially supported by the second stepped surface 13b. Thereby, the axial position of the substrate holding portion 40 with respect to the case body 11 is determined. The cylindrical portion 40a is provided with a first through hole 40b, a second through hole 40c, and a third through hole 40d. Each of the first through hole 40b, the second through hole 40c, and the third through hole 40d is a hole that penetrates the cylindrical portion 40a axially.

[0032] The first through hole 40b is substantially circular about the first axis J1. The first shaft 23 is passed axially through the first through hole 40b. When viewed axially, the second through hole 40c is substantially circular. Although illustration is omitted, in the present embodiment, three second through holes 40c are provided in the cylindrical portion 40a. Each second through hole 40c is provided at substantially equal intervals along the circumferential direction. The coil lead wire 35b is passed axially through each second through hole 40c. The third through hole 40d is substantially circular about the second axis J2. A fourth bearing 54 is attached to the inner peripheral surface of the third through hole 40d.

[0033] The first substrate holding portion 40e holds the circuit board 80. The first substrate holding portion 40e is substantially columnar and protrudes upward from the cylindrical portion 40a. Although illustration is omitted, in the present embodiment, the substrate holding portion 40 has three first substrate holding portions 40e. Each first substrate holding portion 40e is arranged at intervals along the circumferential direction. Each first substrate holding portion 40e has a first shaft portion 40f, a first insertion portion 40g, and a first substrate support portion 40h. The first shaft portion 40f is substantially columnar and protrudes upward from the cylindrical portion 40a. The first insertion portion 40g is substantially columnar and protrudes upward from the first shaft portion 40f. The outer diameter of the first insertion portion 40g is smaller than the outer diameter of the first shaft portion 40f. The first substrate support portion 40h protrudes upward from the first insertion portion 40g. The outer diameter of the first substrate support portion 40h is larger than the outer diameter of the first insertion portion 40g.

[0034] The second support portion 40j protrudes downward from the cylindrical portion 40a. The second support portion 40j is cylindrical about the first axis J1. The second support portion 40j is open downward. A second bearing 52 is attached to the inner surface of the second support portion 40j.

[0035] The circuit board 80 is plate-shaped and extends in a direction orthogonal to the axial direction. The circuit board 80 is disposed inside the case body 11. The circuit board 80 is disposed above the board holding portion 40 and below the transmission mechanism 60. As described above, a plurality of connector pins 57 are connected to the circuit board 80. When the plurality of connector pins 57 are electrically connected to an external power source (not shown), power is supplied from the external power source to the circuit board 80. Also, as described above, a plurality of coil lead-out wires 35b are connected to the circuit board 80. Thereby, power from the external power source is supplied to the coil portion 35 via the circuit board 80. The circuit board 80 is provided with a first board hole 80a, a second board hole 80b, a third board hole 80c, and a fourth board hole 80d. Each of the first board hole 80a, the second board hole 80b, the third board hole 80c, and the fourth board hole 80d is a hole that penetrates the circuit board 80 in the axial direction.

[0036] When viewed from the axial direction, the first board hole 80a is substantially circular. Although not shown, three first board holes 80a are provided in the circuit board 80. When viewed from the axial direction, each first board hole 80a overlaps a different first board holding portion 40e. A first insertion portion 40g is passed through each first board hole 80a in the axial direction. The surface of the circuit board 80 facing upward is in axial contact with the first board support portion 40h. The surface of the circuit board 80 facing downward is axially supported by the first shaft portion 40f. Thereby, the circuit board 80 is held by the board holding portion 40.

[0037] When viewed from the axial direction, the second substrate hole 80b is substantially circular in shape. Although not shown, two second substrate holes 80b are provided in the circuit board 80. When viewed from the axial direction, each second substrate hole 80b overlaps with a different second substrate holding portion 15a. A second insertion portion 15c is passed through each second substrate hole 80b in the axial direction. The surface of the circuit board 80 facing upward is in axial contact with the second substrate support portion 15d. The surface of the circuit board 80 facing downward is axially supported by the second shaft portion 15b. Thus, the circuit board 80 is held in the housing 10.

[0038] The third substrate hole 80c is substantially circular with the first axis J1 as the center. The first shaft 23 is passed through the third substrate hole 80c in the axial direction. The fourth substrate hole 80d is substantially circular with the second axis J2 as the center. The second shaft 70 is passed through the fourth substrate hole 80d in the axial direction.

[0039] The second shaft 70 outputs the driving force of the electric actuator 90. The second shaft 70 is substantially cylindrical and extends in the axial direction with the second axis J2 as the center. The second shaft 70 is rotatable about the second axis J2. The second shaft 70 is arranged radially apart from the first shaft 23. In the present embodiment, the second shaft 70 is arranged on one side (+D1 side) in the first direction D1 with respect to the first shaft 23. The second shaft 70 passes through the fourth substrate hole 80d and the top wall hole portion 19c in the axial direction. The lower end of the second shaft 70 is located inside the third through hole 40d. The lower end of the second shaft 70 is rotatably supported about the second axis J2 by the fourth bearing 54. The upper portion of the second shaft 70 protrudes outside the housing 10 through the top wall hole portion 19c. The portion of the second shaft 70 protruding outside the housing 10 is connected to a driven member (not shown). Thus, the electric actuator 90 can drive the driven member.

[0040] The first bearing 51 is annular with the first axis J1 as the center. The first bearing 51 is attached to the inner surface of the first support portion 19a. The first bearing 51 rotatably supports the upper end of the first shaft 23 around the first axis J1. In the present embodiment, the first bearing 51 is a sliding bearing. The first bearing 51 may be a ball bearing.

[0041] The second bearing 52 is annular with the first axis J1 as the center. The second bearing 52 is attached to the inner surface of the second support portion 40j. The second bearing 52 rotatably supports the central portion in the axial direction of the first shaft 23 around the first axis J1. In the present embodiment, the second bearing 52 is a ball bearing. The second bearing 52 may be a sliding bearing.

[0042] The third bearing 53 is annular with the first axis J1 as the center. The third bearing 53 is attached to the inner surface of the third support portion 14a. The third bearing 53 rotatably supports the lower end of the first shaft 23 around the first axis J1. In the present embodiment, the third bearing 53 is a ball bearing. The third bearing 53 may be a sliding bearing.

[0043] The fourth bearing 54 is annular with the second axis J2 as the center. The fourth bearing 54 is attached to the inner surface of the third through hole 40d. The fourth bearing 54 rotatably supports the lower end of the second shaft 70 around the second axis J2. In the present embodiment, the fourth bearing 54 is a sliding bearing. The fourth bearing 54 may be a ball bearing.

[0044] The transmission mechanism 60 is disposed above the circuit board 80. The transmission mechanism 60 is housed inside the cover member 17. In the present embodiment, the transmission mechanism 60 is connected to both the first shaft 23 and the second shaft 70. The transmission mechanism 60 transmits the rotation about the first axis J1 of the first shaft 23 to the second shaft 70. Thereby, the second shaft 70 rotates about the second axis J2. In the present embodiment, the transmission mechanism 60 decelerates and transmits the rotation of the first shaft 23 to the second shaft 70. The transmission mechanism 60 may accelerate and transmit the rotation of the first shaft 23 to the second shaft 70, or may transmit the rotation at the same rotational speed as the rotation of the first shaft 23 to the second shaft 70. As shown in FIG. 3, the transmission mechanism 60 includes a first gear 61, a first-stage gear 62, a second-stage gear 65, and a sixth gear 68. The rotation of the first shaft 23 is transmitted in the order of the first gear 61, the first-stage gear 62, the second-stage gear 65, the sixth gear 68, and the second shaft 70.

[0045] The first gear 61 transmits the rotation of the first shaft 23 to the first-stage gear 62. The first gear 61 has an annular plate shape centered on the first axis J1. The first shaft 23 passes axially through the inside of the first gear 61. In the present embodiment, the first gear 61 is fixed to the first shaft 23. Thereby, the first gear 61 can rotate about the first axis J1 together with the first shaft 23. As shown in FIG. 4, a first gear portion 61a is provided on the surface facing the radially outer side of the first gear 61.

[0046] Note that the first gear 61 does not necessarily have to be fixed to the first shaft 23. In this case, the transmission mechanism 60 has a plurality of gears including a fixed gear fixed to the first shaft 23, and the rotation of the first shaft 23 is transmitted to the first gear 61 via such a plurality of gears.

[0047] The gear 62 transmits the rotation of the first gear 61 to the second-stage gear 65. As shown in FIG. 3, the first-stage gear 62 is in the shape of an annular plate centered on the second axis J2. Inside the first-stage gear 62, the second shaft 70 is passed axially. The first-stage gear 62 is rotatably supported about the second axis J2 by the second shaft 70. The first-stage gear 62 has a second gear 63 and a third gear 64. The second gear 63 and the third gear 64 are part of the same single member.

[0048] The second gear 63 is in the shape of an annular plate centered on the second axis J2. The second gear 63 is rotatable about the second axis J2. The second gear 63 faces the first gear 61 in the radial direction. As shown in FIG. 4, on the surface of the second gear 63 facing the second radially outer side, a second gear portion 63a that meshes with the first gear portion 61a is provided. Thereby, the second gear 63 meshes with the first gear 61. The outer diameter of the second gear 63 is larger than the outer diameter of the first gear 61. The number of teeth of the second gear portion 63a is larger than the number of teeth of the first gear portion 61a. Thereby, the rotation of the first shaft 23 and the first gear 61 is decelerated and transmitted to the first-stage gear 62. As shown in FIG. 3, the axial dimension T2 of the second gear 63 is substantially the same as the axial dimension T1 of the first gear 61.

[0049] The third gear 64 is in the shape of an annular plate centered on the second axis J2. The third gear 64 is disposed below the second gear 63, that is, on one side in the axial direction. The third gear 64 is axially connected to the second gear 63. Thereby, the third gear 64 is rotatable about the second axis J2 together with the second gear 63. As shown in FIG. 4, a third gear portion 64a is provided on the surface of the third gear 64 facing the second radially outer side. As shown in FIG. 3, the axial dimension T3 of the third gear 64 is larger than the axial dimension T1 of the first gear 61 and the axial dimension T2 of the second gear 63. Therefore, the axial dimension T1 of the first gear 61 is smaller than the axial dimension T3 of the third gear 64.

[0050] The second-stage gear 65 transmits the rotation of the first-stage gear 62 to the sixth gear 68. The second-stage gear 65 is in the shape of an annular plate centered on the first axis J1. Inside the second-stage gear 65, the first shaft 23 is passed axially. The second-stage gear 65 is rotatably supported about the first axis J1 by the first shaft 23. The second-stage gear 65 has a fourth gear 66 and a fifth gear 67. The fourth gear 66 and the fifth gear 67 are parts of the same single member.

[0051] The fourth gear 66 is in the shape of an annular plate centered on the first axis J1. The fourth gear 66 is rotatable about the first axis J1. The fourth gear 66 faces the third gear 64 in the radial direction. As shown in FIG. 4, on the surface of the fourth gear 66 facing the outside in the radial direction, a fourth gear portion 66a that meshes with the third gear portion 64a is provided. Thereby, the fourth gear 66 meshes with the third gear 64. The outer diameter of the fourth gear 66 is larger than the outer diameter of the third gear 64. The number of teeth of the fourth gear portion 66a is more than the number of teeth of the third gear portion 64a. Thereby, the rotation of the first-stage gear 62 is decelerated and transmitted to the second-stage gear 65. As shown in FIG. 3, the axial dimension T4 of the fourth gear 66 is substantially the same as the axial dimension T3 of the third gear 64. The axial dimension T4 of the fourth gear 66 is larger than the axial dimension T1 of the first gear 61 and the axial dimension T2 of the second gear 63. Therefore, the axial dimension T2 of the second gear 63 is smaller than the axial dimension T4 of the fourth gear 66.

[0052] The fifth gear 67 is in the shape of an annular plate centered on the first axis J1. The fifth gear 67 is arranged below the fourth gear 66, that is, on one side in the axial direction. The fifth gear 67 is axially connected to the fourth gear 66. Thereby, the fifth gear 67 can rotate about the first axis J1 together with the fourth gear 66. As shown in FIG. 4, on the surface of the fifth gear 67 facing the outside in the radial direction, a fifth gear portion 67a is provided. As shown in FIG. 3, the axial dimension T5 of the fifth gear 67 is larger than the axial dimension T3 of the third gear 64 and the axial dimension T4 of the fourth gear 66. Therefore, the axial dimension T3 of the third gear 64 is smaller than the axial dimension T5 of the fifth gear 67.

[0053] The sixth gear 68 transmits the rotation of the second-stage gear 65 to the second shaft 70. The sixth gear 68 is in the shape of an annular plate centered on the second axis J2. The sixth gear 68 faces the fifth gear 67 in the radial direction. Inside the sixth gear 68, the second shaft 70 passes axially. The sixth gear 68 is rotatable about the second axis J2. As shown in FIG. 4, on the surface of the sixth gear 68 facing the second radially outer side, a sixth gear portion 68a that meshes with the fifth gear portion 67a is provided. Thereby, the sixth gear 68 meshes with the fifth gear 67. The outer diameter of the sixth gear 68 is larger than the outer diameter of the fifth gear 67. The number of teeth of the sixth gear portion 68a is more than the number of teeth of the fifth gear portion 67a. Thereby, the rotation of the second-stage gear 65 is decelerated and transmitted to the sixth gear 68. In the present embodiment, the sixth gear 68 is fixed to the second shaft 70. Thereby, the second shaft 70 can rotate about the second axis J2 together with the sixth gear 68. As shown in FIG. 3, the axial dimension T6 of the sixth gear 68 is substantially the same as the axial dimension T5 of the fifth gear 67. The axial dimension T6 of the sixth gear 68 is larger than the axial dimension T3 of the third gear 64 and the axial dimension T4 of the fourth gear 66. Therefore, the axial dimension T4 of the fourth gear 66 is smaller than the axial dimension T6 of the sixth gear 68.

[0054] Note that the sixth gear 68 does not necessarily have to be fixed to the second shaft 70. In this case, the transmission mechanism 60 has a plurality of gears including a fixed gear fixed to the second shaft 70, and the rotation of the sixth gear 68 is transmitted to the second shaft 70 via such a plurality of gears.

[0055] As described above, the rotation of the first gear 61 is decelerated and transmitted to the first-stage gear 62, the rotation of the first-stage gear 62 is decelerated and transmitted to the second-stage gear 65, and the rotation of the second-stage gear 65 is decelerated and transmitted to the sixth gear 68. Therefore, the transmission mechanism 60 decelerates the rotation of the first shaft 23 and transmits it to the second shaft 70. Also, as described above, the rotation of the first gear 61 is decelerated and transmitted to the first-stage gear 62, and the rotation of the first-stage gear 62 is decelerated and transmitted to the second-stage gear 65. Therefore, the rotational torque applied to each of the third gear 64 and the fourth gear 66 is greater than the rotational torque applied to each of the first gear 61 and the second gear 63. Also, as described above, the rotation of the second-stage gear 65 is decelerated and transmitted to the sixth gear 68. Therefore, the rotational torque applied to each of the fifth gear 67 and the sixth gear 68 is greater than the rotational torque applied to each of the third gear 64 and the fourth gear 66.

[0056] According to the present embodiment, the transmission mechanism 60 includes a first gear 61 that is rotatable about a first axis J1, a second gear 63 that is rotatable about a second axis J2 and meshes with the first gear 61, a third gear 64 that is rotatable about the second axis J2 and is disposed below the second gear 63, that is, on one side in the axial direction, and is connected to the second gear 63, a fourth gear 66 that is rotatable about the first axis J1 and meshes with the third gear 64, a fifth gear 67 that is rotatable about the first axis J1 and is disposed below the fourth gear 66 and is connected to the fourth gear 66, and a sixth gear 68 that is rotatable about the second axis J2 and meshes with the fifth gear 67. Therefore, when viewed from the axial direction, the first gear 61, the fourth gear 66, and the fifth gear 67 can be arranged to overlap each other, and when viewed from the axial direction, the second gear 63, the third gear 64, and the sixth gear 68 can be arranged to overlap each other. Therefore, compared with the case where three or more gears included in the transmission mechanism 60 are arranged side by side in the radial direction, it is possible to suppress the transmission mechanism 60 from increasing in size in the radial direction. Therefore, it is possible to suppress the electric actuator 90 from increasing in size in the radial direction.

[0057] According to this embodiment, the axial dimension T2 of the second gear 63 is smaller than the axial dimension T4 of the fourth gear 66, and the axial dimension T4 of the fourth gear 66 is smaller than the axial dimension T6 of the sixth gear 68. Therefore, compared with the case where each of the axial dimension T2 of the second gear 63 and the axial dimension T4 of the fourth gear 66 is equal to or greater than the axial dimension T6 of the sixth gear 68, it is possible to suppress the increase in the size of the transmission mechanism 60 in the axial direction. Accordingly, it is possible to suppress the increase in the size of the electric actuator 90 in the axial direction.

[0058] Also, in this embodiment, compared with the case where each of the axial dimension T2 of the second gear 63 and the axial dimension T4 of the fourth gear 66 is equal to or greater than the axial dimension T6 of the sixth gear 68, it is easier to narrow the contact area between the first gear 61 and the second gear 63 and the contact area between the third gear 64 and the fourth gear 66. Thereby, since the frictional force between the first gear 61 and the second gear 63 and the frictional force between the third gear 64 and the fourth gear 66 can be reduced respectively, the drive transmission efficiency between the meshing gears can be increased. Therefore, the drive transmission efficiency of the transmission mechanism 60 can be increased.

[0059] According to the present embodiment, the outer diameter of the second gear 63 is larger than the outer diameter of the first gear 61, the outer diameter of the fourth gear 66 is larger than the outer diameter of the third gear 64, and the outer diameter of the sixth gear 68 is larger than the outer diameter of the fifth gear 67. Therefore, as described above, the rotational torque applied to the third gear 64 and the fourth gear 66 is larger than the rotational torque applied to the first gear 61 and the second gear 63, and the rotational torque applied to the fifth gear 67 and the sixth gear 68 is larger than the rotational torque applied to the third gear 64 and the fourth gear 66. On the other hand, in the present embodiment, as described above, the axial dimension T4 of the fourth gear 66 is larger than the axial dimension T2 of the second gear 63, and the axial dimension T6 of the sixth gear 68 is larger than the axial dimension T4 of the fourth gear 66. Therefore, the contact area between the third gear 64 and the fourth gear 66 and the contact area between the fifth gear 67 and the sixth gear 68 are each easier to widen as compared with the case where each of the axial dimension T4 of the fourth gear 66 and the axial dimension T6 of the sixth gear 68 is equal to or less than the axial dimension T2 of the second gear 63. Thereby, the stress applied to each of the fourth gear 66 and the sixth gear 68 can be reduced. Therefore, since deterioration of the fourth gear 66 and the sixth gear 68 due to wear or the like can be suppressed, the durability performance of the transmission mechanism 60 can be enhanced.

[0060] According to the present embodiment, the axial dimension T1 of the first gear 61 is smaller than the axial dimension T3 of the third gear 64, and the axial dimension T3 of the third gear 64 is smaller than the axial dimension T5 of the fifth gear 67. Therefore, as compared with the case where each of the axial dimension T1 of the first gear 61 and the axial dimension T3 of the third gear 64 is equal to or larger than the axial dimension T5 of the fifth gear 67, an increase in the size of the transmission mechanism 60 in the axial direction can be more preferably suppressed. Therefore, an increase in the size of the electric actuator 90 in the axial direction can be more preferably suppressed.

[0061] In addition, in the present embodiment, when the axial dimension T1 of the first gear 61 and the axial dimension T3 of the third gear 64 are each greater than or equal to the axial dimension T5 of the fifth gear 67, the contact areas between the first gear 61 and the second gear 63 and between the third gear 64 and the fourth gear 66 can be made more preferably narrower. As a result, the frictional forces between the first gear 61 and the second gear 63 and between the third gear 64 and the fourth gear 66 can be made more preferably smaller. Therefore, the drive transmission efficiency of the transmission mechanism 60 can be more preferably increased.

[0062] In addition, in the present embodiment, as described above, the rotational torque applied to the third gear 64 and the fourth gear 66 is greater than the rotational torque applied to the first gear 61 and the second gear 63, and the rotational torque applied to the fifth gear 67 and the sixth gear 68 is greater than the rotational torque applied to the third gear 64 and the fourth gear 66. In contrast, in the present embodiment, as described above, the axial dimension T3 of the third gear 64 is greater than the axial dimension T1 of the first gear 61, and the axial dimension T5 of the fifth gear 67 is greater than the axial dimension T3 of the third gear 64. Therefore, the stress applied to each of the third gear 64 and the fifth gear 67 can be reduced as compared with the case where the axial dimension T3 of the third gear 64 and the axial dimension T5 of the fifth gear 67 are each less than or equal to the axial dimension T1 of the first gear 61. Therefore, it is possible to suppress the third gear 64 and the fifth gear 67 from deteriorating due to wear or the like, and thus the durability performance of the transmission mechanism 60 can be more preferably enhanced.

[0063] According to the present embodiment, the first gear 61 is fixed to the first shaft 23, and the sixth gear 68 is fixed to the second shaft 70. Therefore, since the transmission mechanism 60 can be configured by six gears, it is possible to suppress the transmission mechanism 60 from becoming larger in size as compared with the case where the transmission mechanism 60 has additional drive transmission members such as separate gears. Therefore, it is possible to suppress the electric actuator 90 from becoming larger in size. In addition, it is possible to suppress an increase in the number of parts of the transmission mechanism 60 as compared with the case where the transmission mechanism 60 has additional drive transmission members such as separate gears. Therefore, it is possible to suppress an increase in the manufacturing cost and manufacturing man-hours of the transmission mechanism 60.

[0064] Further, in the present embodiment, the number of components constituting the transmission mechanism 60 can be reduced as compared with the case where the transmission mechanism 60 further has a separate drive transmission member such as a gear. Therefore, it is possible to suppress a decrease in the drive transmission efficiency of the transmission mechanism 60.

[0065] According to the present embodiment, the rotor 21 is rotatable about the first axis J1, and the first shaft 23 is fixed to the rotor 21. Therefore, since the rotation of the rotor 21 is directly transmitted to the first shaft 23, it is possible to more preferably suppress an increase in the number of components of the electric actuator 90 as compared with the case where the rotation of the rotor 21 is transmitted to the first shaft 23 via a separate drive transmission member such as a gear. Therefore, it is possible to more preferably suppress an increase in the manufacturing cost and manufacturing man-hours of the electric actuator 90.

[0066] According to the present embodiment, the electric actuator 90 includes a housing 10 that houses the first shaft 23, the second shaft 70, and the transmission mechanism 60 therein, and an upper side of the second shaft 70, that is, a portion on the other axial side is located outside the housing 10. Therefore, as described above, the portion of the second shaft 70 that protrudes outside the housing 10 can be directly connected to a driven member (not shown). Thereby, it is possible to more preferably suppress an increase in the number of components of the electric actuator 90 as compared with the case where the second shaft 70 and the driven member are indirectly connected via a separate member. Therefore, it is possible to more preferably suppress an increase in the manufacturing cost and manufacturing man-hours of the electric actuator 90.

[0067] As described above, the embodiments of the present invention have been described. However, each configuration and their combinations in the embodiments are examples, and additions, omissions, substitutions, and other changes of the configuration are possible without departing from the spirit of the present invention. Further, the present invention is not limited by the embodiments.

[0068] The third gear is arranged above the second gear, that is, on the other axial side. The fifth gear may be arranged above the fourth gear. Even in such a configuration, it is possible to suppress the increase in size of the transmission mechanism in both the radial and axial directions.

[0069] Also, at least one of the first bearing and the second bearing may not be provided. When the first bearing is not provided, the upper end of the first shaft is directly supported by the first support portion. When the second bearing is not provided, the central portion in the axial direction of the first shaft is directly supported by the second support portion.

[0070] The configuration of the transmission mechanism is not particularly limited as long as the rotation of the first shaft can be transmitted to the second shaft. For example, the first shaft and the first gear may be part of the same single member, or the second shaft and the sixth gear may be part of the same single member.

[0071] The application of the electric actuator to which the present invention is applied is not particularly limited. The electric actuator may be mounted on a shift-by-wire type actuator device driven based on a driver's shift operation. Also, the electric actuator may be mounted on equipment other than vehicles. In addition, as described above, each configuration described in this specification can be appropriately combined within a range where they do not conflict with each other.

[0072] Note that this technology can take the following configuration. (1) A motor unit, a first shaft to which the rotation of a rotor of the motor unit is transmitted and which is rotatable about a first axis, a second shaft which is rotatable about a second axis extending in the same direction as the axial direction of the first axis and which is arranged radially apart from the first shaft about the first axis, and a transmission mechanism for transmitting the rotation of the first shaft to the second shaft, the transmission mechanism including a first gear rotatable about the first axis, a second gear rotatable about the second axis and meshing with the first gear, a third gear rotatable about the second axis and arranged on one side in the axial direction with respect to the second gear and connected to the second gear, a fourth gear rotatable about the first axis and meshing with the third gear, a fifth gear rotatable about the first axis and arranged on one side in the axial direction with respect to the fourth gear and connected to the fourth gear, and a sixth gear rotatable about the second axis and meshing with the fifth gear, the outer diameter of the second gear being larger than the outer diameter of the first gear, the outer diameter of the fourth gear being larger than the outer diameter of the third gear, the outer diameter of the sixth gear being larger than the outer diameter of the fifth gear, the axial dimension of the second gear being smaller than the axial dimension of the fourth gear, and the axial dimension of the fourth gear being smaller than the axial dimension of the sixth gear, an electric actuator. (2) The axial dimension of the first gear is smaller than the axial dimension of the third gear, and the axial dimension of the third gear is smaller than the axial dimension of the fifth gear, the electric actuator according to (1). (3) The first gear is fixed to the first shaft, and the sixth gear is fixed to the second shaft, the electric actuator according to (1) or (2). (4) The rotor is rotatable about the first axis, and the first shaft is fixed to the rotor, the electric actuator according to any one of (1) to (3). A housing that houses each of the first shaft, the second shaft, and the transmission mechanism therein, and a portion of the second shaft on the other side in the axial direction is located outside the housing. The electric actuator according to any one of (1) to (4).

Explanation of reference numerals

[0073] 10…Housing, 20…Motor unit, 21…Rotor, 23…First shaft, 60…Transmission mechanism, 61…First gear, 63…Second gear, 64…Third gear, 66…Fourth gear, 67…Fifth gear, 68…Sixth gear, 70…Second shaft, 90…Electric actuator, J1…First axis, J2…Second axis

Claims

1. A motor unit, a first shaft to which the rotation of a rotor included in the motor unit is transmitted and which is rotatable about a first axis, a second shaft that is rotatable about a second axis extending in the same direction as the axial direction of the first axis and that is disposed radially apart from the first shaft about the first axis, a transmission mechanism that transmits the rotation of the first shaft to the second shaft, wherein the transmission mechanism includes a first gear that is rotatable about the first axis, a second gear that is rotatable about the second axis and meshes with the first gear, a third gear that is rotatable about the second axis, is disposed on one side of the second gear in the axial direction, and is connected to the second gear, a fourth gear that is rotatable about the first axis and meshes with the third gear, a fifth gear that is rotatable about the first axis, is disposed on one side of the fourth gear in the axial direction, and is connected to the fourth gear, a sixth gear that is rotatable about the second axis and meshes with the fifth gear, wherein an outer diameter of the second gear is larger than an outer diameter of the first gear, an outer diameter of the fourth gear is larger than an outer diameter of the third gear, an outer diameter of the sixth gear is larger than an outer diameter of the fifth gear, an axial dimension of the second gear is smaller than an axial dimension of the fourth gear, and an axial dimension of the fourth gear is smaller than an axial dimension of the sixth gear, the electric actuator.

2. The axial dimension of the first gear is smaller than the axial dimension of the third gear, and the axial dimension of the third gear is smaller than the axial dimension of the fifth gear, the electric actuator according to claim 1.

3. The first gear is fixed to the first shaft, and the sixth gear is fixed to the second shaft, the electric actuator according to claim 1 or 2.

4. The rotor is rotatable about the first axis, and the first shaft is fixed to the rotor, the electric actuator according to claim 1 or 2.

5. A housing that houses each of the first shaft, the second shaft, and the transmission mechanism therein, wherein a portion of the second shaft on the other side in the axial direction is located outside the housing, the electric actuator according to claim 1 or 2. ​ ​

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