JP4506458B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that transmits a rotational force of an electric motor used as a generation source of a steering assist force to a steered shaft and moves the steered shaft in the axial length direction to assist steering.

  An electric power steering device for a vehicle has a spiral groove and a steering shaft that moves in the axial length direction according to a steering operation, and a steering wheel that is arranged so that an output shaft intersects the axis of the steering shaft. An auxiliary electric motor, a rotating cylinder that is rotatably arranged around the outer periphery of the spiral groove, and linked to the output shaft via a reduction gear mechanism, and both ends of the rotating cylinder are rotatable in the housing. And a power conversion mechanism that converts the rotational force of the rotating cylinder into a moving force in the axial direction of the steered shaft and transmits it to the steered shaft. (For example, Patent Document 1).

  The power conversion mechanism includes a female screw provided inside the rotary cylinder, a plurality of balls that engage with the female screw and the spiral groove, and an outer peripheral portion of the rotary cylinder. And a circulator for circulating the ball through one circulation hole.

In the housing, first and second insertion holes into which the first and second rolling bearings are inserted, a screw hole connected to one side of the first insertion hole, and an annular shape connected to the other side of the first insertion hole. When the inner ring of the first and second rolling bearings is inserted into the housing and supported in the housing, the outer ring of the first rolling bearing is It is configured to prevent movement of the rotating cylinder in the axial length direction by fixing it between a screw ring screwed into the screw hole and the annular stepped portion.
JP 2002-27497A

  However, in the electric power steering apparatus including the power conversion mechanism as described above, when the steering assist is performed by the electric motor, the reaction force of the steering assist force applied to the steered shaft is applied to the rotating cylinder. Since it is further added to the annular stepped portion and the screw ring, if the step of the annular stepped portion is designed to be small, the reaction step causes a sag in the annular stepped portion, which causes play of the rotating cylinder, and the annular stepped portion If the step is designed to be large, the outer diameter becomes larger than the inner diameter of the housing, and the entire electric power steering apparatus becomes larger, and an improvement measure has been demanded.

  The present invention has been made in view of such circumstances, and prevents the rotating cylinder from rattling in the axial direction due to the reaction force of the steering assist force applied to the steered shaft without designing the housing to have a large diameter. It is an object of the present invention to provide an electric power steering device that can be used.

  An electric power steering apparatus according to a first aspect of the present invention has a spiral groove, and is disposed rotatably on a steered shaft that moves in the axial length direction in response to a steering operation, and an outer periphery of the spiral groove. A rotating cylinder linked to the output shaft, a rolling bearing that rotatably supports the rotating cylinder in the housing, and the rotational force of the rotating cylinder is converted into a moving force in the axial direction of the steered shaft. An electric power steering apparatus including a power conversion mechanism for transmitting to the steered shaft includes first and second screw rings for attaching and holding an outer ring of the rolling bearing, and the housing includes the first and second screw rings. It has a screw hole into which the first and second screw rings are screwed.

  An electric power steering device according to a second aspect of the present invention is provided with a spiral groove, and is disposed rotatably around a turning shaft that moves in the axial length direction in response to a steering operation, and an outer periphery of the spiral groove. A rotating cylinder linked to the output shaft, first and second rolling bearings that rotatably support both ends of the rotating cylinder in the housing, and the axial length of the steered shaft for the rotational force of the rotating cylinder 1st and 2nd screw which attaches and holds the outer ring of the said 1st rolling bearing in the electric power steering device provided with the power conversion mechanism which converts into the moving force to a direction, and transmits to the steering shaft The housing is provided with a screw hole into which the first and second screw rings are screwed and a fitting hole into which the second rolling bearing is fitted.

  An electric power steering apparatus according to a third aspect of the present invention houses a reduction gear mechanism that increases the rotational force of the output shaft and transmits it to the rotating cylinder in the housing, and a plurality of fins are provided outside the housing. Is formed.

  In the electric power steering apparatus according to a fourth aspect of the present invention, the electric motor has a motor case in which a rotor and a stator connected to the output shaft are accommodated, and the output shaft or the rotor is in the motor case. It has the airflow generation part which generates an airflow.

  According to the first invention and the second invention, the first and second screw rings are screwed into the screw holes of the housing, so that the outer ring of the rolling bearing that supports the rotating cylinder on the housing is attached from both sides. Therefore, the reaction force of the steering assist force applied to the steered shaft can be applied to the screwed portions from the rotary cylinder and the rolling bearing to the screw holes of the first and second screw rings, The durability against the reaction force can be increased. In addition, since the annular step portion is not required, it is possible to prevent the rotating cylinder from rattling in the axial length direction due to the reaction force without designing the housing to have a large diameter.

  According to the third invention, when the ambient temperature around the reduction gear mechanism increases due to the heat generated in the meshing portion of the reduction gear mechanism, and the housing temperature increases due to the ambient temperature, the heat dissipation of the housing is enhanced by the fins. Therefore, an increase in the temperature of the housing and the atmosphere can be suppressed, and an increase in the temperature of the reduction gear mechanism can be suppressed. Therefore, when a synthetic resin gear is used for the purpose of reducing the noise of the meshing portion, the durability of the synthetic resin gear can be improved.

  According to the fourth aspect of the invention, when the rotor and the output shaft of the electric motor are rotated to assist the steering, the airflow generator rotates with the rotor and can generate an airflow in the motor case. The temperature rise inside can be suppressed. Therefore, even when an electric motor that generates a relatively large steering assist force is used, it is possible to prevent deterioration of the steering assist performance due to heat and damage of motor components due to heat.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
Embodiment 1
FIG. 1 is a schematic diagram showing the overall configuration of an electric power steering apparatus according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing the configuration of a main part.

  In the electric power steering apparatus shown in FIGS. 1 to 2, one end portion is connected to the steering wheel via the universal joint 1 and the steering shaft 2, and the transmission shaft 3 having the pinion 3a at the other end portion meshes with the pinion 3a. The rack tooth 4a, the rack tooth 4a and the spiral groove 4b at a position spaced apart in the axial length direction thereof, and the steered shaft 4 capable of moving in the axial length direction, and the steered shaft 4 being movable A substantially cylindrical housing 5 for receiving and supporting, an electric motor 6 arranged outside the housing 5 so that the output shaft 6a intersects the axis of the steered shaft 4, and a helical gear linked to the output shaft 6a. The small gear 7, the helical gear 8 meshing with the small gear 7, and the outer periphery of the spiral groove 4 b are arranged coaxially with the steered shaft 4 so that the large gear 8 is externally fitted. The rotating cylinder 9 to be fixed and both ends of the rotating cylinder 9 are The first and second rolling bearings 10 and 11 that are rotatably supported in the ring 5 and the ball 12 as an engaging body that engages with the spiral groove 4b. And a power conversion mechanism A that converts it into a moving force in the axial length direction and transmits it to the steered shaft 4.

  The power conversion mechanism A includes a female screw 9a provided inside the rotary cylinder 9 corresponding to the spiral groove 4b, a plurality of balls 12 engaged with the female screw 9a and the spiral groove 4b, and a female screw 9a of the rotary cylinder 9. Two circulating holes (not shown) penetrating in the radial direction at the facing position, and a circulator 13 for circulating the plurality of balls 12 between the two circulating holes, A circulator 13 is attached to the outer periphery of the rotary cylinder 9 by a holder 14 having a substantially Ω cross section.

  The housing 5 has an electric motor 6 attached thereto, a first cylinder 51 having a first shaft support portion 5a supporting the rack tooth 4a side of the steered shaft 4, and a bolt or the like attached to the first cylinder 51. And a second cylindrical body 52 having a second shaft support portion 5b supporting the spiral groove 4b side of the steered shaft 4.

  The longitudinal direction one side connected to the 2nd cylinder 52 of the 1st cylinder 51 has the accommodating part 5d which accommodates and supports the rotating cylinder 9, and the motor attachment part 5e to which the electric motor 6 is attached, The other side in the longitudinal direction of the first cylindrical body 51 has a first shaft support portion 5a and a first attachment portion 5f attached to the vehicle body.

  A screw hole 5g is provided on one side in the longitudinal direction of the housing portion 5d, and the first and second screw rings 15 and 16 for attaching the outer ring 10a of the first rolling bearing 10 from both sides to the screw hole 5g. Is screwed. Further, an insertion hole 5h into which the second rolling bearing 11 is inserted is provided on the other side in the longitudinal direction of the housing portion 5d.

  The motor mounting portion 5e includes a support hole 5j that penetrates from one side of the housing portion 5d in a direction that intersects the axis of the steered shaft 4, and a screw hole 5k that is formed at a radially outward position of the support hole 5j. The electric motor 6 is attached by a plurality of bolts (not shown) through a bearing cylinder 17 fitted in the support hole 5j.

  The bearing cylinder 17 has a cylindrical portion 17a fitted in the support hole 5j, a flange portion 17b whose diameter is expanded from the cylindrical portion 17a, and a flange portion 17c protruding from the flange portion 17b. A drive shaft 18 having a small gear 7 made of a bevel gear is coupled to the output shaft 6a inside the portion 17a, and is rotatably supported via two rolling bearings 19 and 19. The flange portion 17b is electrically driven. A motor 6 is attached. The flange portion 17c has a through-hole 17d corresponding to the screw hole 5k, and the bearing cylinder 17 is attached to the motor mounting portion 5e by tightening the bolt 20 inserted into the through-hole 17d to the screw hole 5k. Has been.

  An internal thread 9a corresponding to the spiral groove 4b is provided inside the rotary cylinder 9, and first and second rolling bearings 10 and 11 on the outer peripheral portion, a large gear 8 made of a bevel gear, a circulator 13, and , Nuts 21 and 21a are attached.

  On the one side in the axial direction of the rotating cylinder 9, a first fitting portion 9 b on which the first rolling bearing 10 is fitted and an annular shape that restricts movement of the first rolling bearing 10 to the other side in the axial direction. A step portion 9c and a male screw portion 9d are provided, and the inner ring 10b of the first rolling bearing 10 is pressed against the annular step portion 9c by tightening a nut 21 to be screwed to the male screw portion 9d. The inner ring 10 b is fixed between 9 c and the nut 21.

  On the other side in the axial direction of the rotating cylinder 9, a second fitting portion 9e into which the second rolling bearing 11 is press-fitted, a flat mounting portion 9f on which the circulator 13 is mounted and attached, A third fitting portion 9g to which the gear 8 is externally fitted and a male screw portion 9h are provided, and the large gear 8 is pressed and fixed to the annular step portion 9c by screwing a nut 21a to the male screw portion 9h. is doing.

  The first screw ring 15 that is screwed into the screw hole 5g has a male screw on the outer peripheral portion, and a cylindrical portion 15a that is externally fitted to the outer ring 10a of the angular first rolling bearing 10, and the cylindrical portion 15a. And a flange 15b that protrudes radially inward from one end of the ring and abuts on one side of the outer ring 10a. The second screw ring 16 is formed to have the same diameter as the first screw ring 15 and has a contact portion that contacts the other side of the outer ring 10a. By screwing the first and second screw rings 15 and 16 into the screw hole 5g, the outer ring 10a is attached between the flange 15b and the abutting portion, and the frictional resistance of the screwed portion is increased. The axial movement in the axial direction relative to the first cylinder 51, in other words, the axial movement in the axial direction of the rotary cylinder 9 fitted with the first rolling bearing 10 can be prevented. By rotating the first screw ring 15 with the screw ring 16 removed, the axial length positions of the first rolling bearing 10 and the rotary cylinder 9 can be adjusted, and the small gear 7 and the large gear 8 are meshed. The amount of backlash of the part can be adjusted.

  The large gear 8 includes an annular tooth body 81 made of a synthetic resin having teeth on the outer peripheral portion, and a metal annular core body 82 fitted in the annular tooth body 81, and the annular core body A non-rotating convex portion that prohibits relative rotation with the annular toothed body 81 is provided on the outer peripheral portion of 82.

  The second cylinder 52 is formed with a relatively short length, and a sliding bearing as a second shaft support portion 5b is fitted and fixed on the inner side, and the second mounting is attached to the vehicle body on the outer side. A portion 5m is provided.

  In the electric power steering apparatus configured as described above, when the rotating cylinder 9 is supported in the housing 5, the rotating cylinder 9 to which the second rolling bearing 11, the circulator 13, and the large gear 8 are attached is provided. By inserting the outer ring of the second rolling bearing 11 into the second fitting portion 5h from the first rolling bearing 10 side, the other end portion of the rotary cylinder 9 is rotated to the housing 5 It can be supported freely. Thereafter, the first screw ring 15 is screwed into the screw hole 5g, the first rolling bearing 10 is fitted into the first fitting portion 9b, and the second screw ring 16 is screwed into the screw hole 5g. By doing so, the outer ring 10a can be attached between the first and second screw rings 15 and 16, the outer ring 10a can be fixed to the housing 5, and one end portion of the rotary cylinder 9 can be freely rotated to the housing 5. Can be supported. In this configuration, the reaction force of the steering assist force applied from the power conversion mechanism A to the steered shaft 4 is applied to the first and second screw rings 15 and 16 from the rotary cylinder 9 and the first rolling bearing 10. Since the reaction force can be received by the screw surface by being added to the screwed portion to the screw hole 5g, durability against the reaction force can be improved, and the axial direction of the rotary cylinder 9 can be increased over a long period of time. It can prevent rattling. Further, since it is not necessary to provide a step portion having a diameter larger than that of the large gear 8 in the housing 5, it is not necessary to design the housing 5 to have a large diameter.

Embodiment 2
FIG. 3 is a perspective view showing a configuration in which a part of the second embodiment is omitted, and FIG. 4 is an enlarged cross-sectional view showing the configuration of the main part.
In this electric power steering apparatus, a reduction gear mechanism B is constituted by the small gear 7 and the large gear 8 that are accommodated in the first cylindrical body 51, and the outside of the position where the reduction gear mechanism B of the housing 5 is accommodated. A plurality of fins 22 are integrally formed.

  In the second embodiment, the fin 22 protrudes in the horizontal direction when the housing 5 is attached to the vehicle body by the first and second attachment portions 5f and 5m, in other words, parallel to the traveling direction of the vehicle body. It protrudes in the direction to improve heat dissipation. Further, the fins 22 are spaced apart in the vertical direction.

  In the electric power steering apparatus provided with the reduction gear mechanism B, the ambient temperature around the reduction gear mechanism B rises due to the heat generated at the meshing portion of the small gear 7 and the large gear 8, and the temperature of the housing 5 is increased by the ambient temperature. However, since the plurality of fins 22 are provided outside the position where the reduction gear mechanism B of the housing 5 is accommodated, the heat dissipation of the housing 5 can be enhanced by the fins 22. Accordingly, an increase in the housing 5 and the ambient temperature can be suppressed, an increase in the temperature of the small gear 7 and the large gear 8 can be suppressed, and the durability of the large gear 8 having the synthetic resin annular tooth body 81. Can be increased.

The fins 22 may be arranged at a plurality of circumferential positions as shown in the drawing, or may be arranged at a plurality of longitudinal positions of the housing 5.
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof and description of operations and effects are omitted.

Embodiment 3
FIG. 5 is an enlarged cross-sectional view showing a configuration of a main part of the third embodiment.
This electric power steering apparatus includes a rotor 61 connected to the output shaft 6a, a stator 62 disposed around the outer periphery of the rotor 61, and the stator 62 held on the inner periphery thereof. A plurality of fins 23 are provided on an output shaft 6a of an electric motor 6 including a motor case 63 in which a child 62 is accommodated.

  In the second embodiment, the fins 23 are provided at a plurality of circumferential positions of the ring body 24 fitted and fixed to the output shaft 6a, and the fins 23 rotate integrally with the output shaft 6a, so that the motor case The air flow is generated in the air outlet 63.

  The motor case 63 has a bottomed cylindrical portion 63a and a lid portion 63b that closes the opening side of the cylindrical portion 63a. The lid portion 63b is provided with a plurality of ventilation holes 64 communicating with the inside of the bearing cylinder 17. The air in the motor case 63 and the air in the bearing cylinder 17 can be circulated. Further, a plurality of circumferential positions of the stator 62 are provided with through holes 62 a that pass therethrough, so that air flows through the vent holes 62 a and the annular gap 6 b between the rotor 61 and the stator 62. It is configured. Further, a waterproof ring 65 is provided at a connection portion between the motor case 63 and the bearing cylinder 17.

  In the electric power steering apparatus provided with the electric motor 6, the ambient temperature in the motor case 63 increases due to an increase in the amount of current flowing to the drive circuit of the electric motor 6, but it is provided on the output shaft 6a. An airflow can be generated in the motor case 63 by the fins 23, and the air in the motor case 63 and the air in the bearing cylinder 17 can be circulated by the vent holes 64. Since the air in the motor case 63 can be circulated through the air holes 62a and the annular gap 6b of the stator 62 by 62a, the temperature rise in the motor case 63 can be suppressed.

Instead of providing the fins 23 on the output shaft 6 a, a spiral groove may be provided on the outer peripheral portion of the rotor 61, and an air flow may be generated in the annular gap 6 b by the rotation of the rotor 61.
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof and description of operations and effects are omitted.

Embodiment 4
FIG. 6 is an enlarged cross-sectional view showing a configuration of a main part of the fourth embodiment.
The electric power steering apparatus in which the electric motor 6 is disposed outside the housing 5 so that the output shaft 6a intersects the axis of the steered shaft 4 includes a bearing cylinder 17 that rotatably supports the drive shaft 18 in the support hole 5j. The back ring amount of the meshing portion of the small gear 7 and the large gear 8 can be biased in the direction in which the rotation center ring distance of the small gear 7 and the large gear 8 becomes longer or shorter than the motor mounting portion 5e. The first and second contact fitting portions 17e and 17f that are contact-fitted with the support hole 5j are provided at both ends of the cylindrical portion 17a of the bearing cylinder 17, and the small gear 7 and the large gear 8 are provided. In this configuration, the bearing cylinder 17 is prevented from being bent by the meshing reaction force.

  In the fourth embodiment, the first and second contact fitting portions 17e and 17f are eccentric with respect to the central axis of the bearing cylinder 17, and the distance between the rotation centers is obtained by rotating the bearing cylinder 17 in the support hole 5j. And the center portion of the cylindrical portion 17a is formed to have a smaller diameter than the first and second contact fitting portions 17e and 17f. When the bearing cylinder 17 is fitted into the support hole 5j, the first and second contact fitting portions 17e and 17f are in contact with the support hole 5j, and the central portion of the cylindrical portion 17a is not in contact with the support hole 5j. It has become.

  Further, the flange portion 17c protruding from the flange portion 17b of the bearing cylinder 17 is provided with a through hole 17d or a long hole having a diameter larger than that of the screw hole 5k. 20, the bearing cylinder 17 can be biased in a direction in which the distance between the rotation centers becomes longer or shorter.

  In the fourth embodiment, the first and second contact fitting portions 17e and 17f are in contact with the support hole 5j, and the central portion between the first and second contact fitting portions 17e and 17f is in contact. Therefore, the bearing cylinder 17 can be fitted into the support hole 5j with a relatively small contact resistance, and the meshing reaction force can be received by the second contact fitting portion 17f. Deflection of the bearing cylinder 17 due to force can be prevented, and generation of abnormal noise and deterioration of durability due to meshing reaction force can be prevented.

Further, by loosening the bolt 20 and adjusting the position of the bearing cylinder 17 with respect to the motor mounting portion 5e, the small gear 7 can be biased in the direction in which the distance between the rotation centers becomes longer and shorter, and the backlash amount is adjusted. can do.
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof and description of operations and effects are omitted.

Embodiment 5
FIG. 7 is an enlarged cross-sectional view showing a configuration of a main part of the fifth embodiment.
The electric power steering device in which the electric motor 6 is disposed outside the housing 5 so that the output shaft 6a intersects the axis of the steered shaft 4 is made of synthetic resin due to a load applied to the meshing portion of the small gear 7 and the large gear 8. And the drive shaft 18 of the small gear 7 bends, the tooth contact of the meshing portion is deteriorated, and noise of meshing sliding is generated. Therefore, a bearing cylinder that rotatably supports the drive shaft 18 in the support hole 5j. 17 can be biased with respect to the motor mounting portion 5e in a direction in which the rotation center ring distance of the small gear 7 and the large gear 8 becomes longer and shorter. The motor mounting portion 5e is provided with a regulating shaft 25 that makes it possible to adjust the amount of lash and abuts the outer peripheral surface of the cylindrical portion 17a of the bearing cylinder 17 to regulate the deflection of the bearing cylinder 17.

  In the fifth embodiment, the flange portion 17c protruding from the flange portion 17b of the bearing cylinder 17 is provided with a through hole 17d or a long hole having a diameter larger than that of the screw hole 5k, and the motor mounting portion 5e and the screw hole 5k. The bearing cylinder 17 can be biased in a direction in which the distance between the rotation centers becomes longer or shorter than the bolt 20 to be fastened to the bolt.

  Further, the bearing cylinder 17 is fitted in contact with the support hole 5j on the output shaft 6a side and is not in contact with the support hole 5j on the small gear 7 side, and the regulating shaft 25 contacts the outer peripheral surface on the small gear 7 side. It touches.

  The motor mounting portion 5e is formed with a screw hole 5n penetrating in a direction in which the distance between the rotation centers becomes longer and shorter, and a restriction shaft 25 made of a bolt is screwed into the screw hole 5n. It is configured to suppress the bending of the bearing cylinder 17 by rotating the 25.

In the fifth embodiment, the restriction shaft 25 is in contact with the outer peripheral surface of the bearing cylinder 17 and the bending of the bearing cylinder 17 and the small gear 7 in the direction in which the distance between the rotation centers becomes longer or shorter is restricted. Further, it is possible to suppress the bending of the synthetic resin teeth and the drive shaft 18 of the small gear 7 due to the load applied to the meshing portion, and it is possible to maintain an appropriate tooth contact of the meshing portion.
The restriction shaft 25 may be a pin in addition to a bolt.
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof and description of operations and effects are omitted.

  In the above-described embodiment, the ball screw mechanism is used as the power conversion mechanism A that converts the rotational force of the output shaft 6a into the moving force in the axial length direction. A plurality of power transmission rings each including an inner ring member having an engaging annular ring portion on its inner peripheral portion and an outer ring member that rotatably holds the outer peripheral portion of the inner ring member via a plurality of balls. A mechanism that is biased with respect to the axis of the steered shaft 4 and is held in the rotary cylinder 9 may be used.

  In addition, the electric power steering apparatus according to the present invention has a configuration in which the electric motor 6 is disposed at a position intersecting the axis of the steered shaft 4, and the electric motor 6 is disposed in parallel with the steered shaft 4. It may be a configuration. In this case, the small gear 7 and the large gear 8 may be spur gears as well as bevel gears.

1 is a schematic diagram showing an overall configuration of an electric power steering apparatus according to the present invention. It is an expanded sectional view showing the composition of the important section of the electric power steering device concerning the present invention. It is a perspective view which shows the structure which abbreviate | omitted a part of Embodiment 2 of the electric power steering apparatus which concerns on this invention. It is an expanded sectional view which shows the structure of the principal part of Embodiment 2 of the electric power steering apparatus which concerns on this invention. It is an expanded sectional view which shows the structure of the principal part of Embodiment 3 of the electric power steering apparatus which concerns on this invention. It is an expanded sectional view which shows the structure of the principal part of Embodiment 4 of the electric power steering apparatus which concerns on this invention. It is an expanded sectional view which shows the structure of the principal part of Embodiment 5 of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Steering shaft 4b Spiral groove 5 Housing 5g Screw hole 5h Insertion hole 6 Electric motor 6a Output shaft 7 Small gear 8 Large gear 9 Rotary cylinder 10 1st rolling bearing (Rolling bearing)
10a outer ring 11 second rolling bearing 15 first screw ring 16 second screw ring 22 fin 23 fin (air flow generating part)
61 Rotor 62 Stator 63 Motor case A Power conversion mechanism B Reduction gear mechanism

Claims (4)

  A steered shaft that has a spiral groove and moves in the axial length direction in response to a steering operation, a rotating cylinder that is rotatably arranged around the outer periphery of the spiral groove, and is linked to the output shaft of the electric motor; A rolling bearing that rotatably supports the rotating cylinder in a housing, and a power conversion mechanism that converts the rotational force of the rotating cylinder into a moving force in the axial length direction of the steered shaft and transmits it to the steered shaft. The electric power steering apparatus provided includes first and second screw rings for attaching and holding the outer ring of the rolling bearing, and the housing is screwed with the first and second screw rings. An electric power steering device having a screw hole.   A steered shaft that has a spiral groove and moves in the axial length direction in response to a steering operation, a rotating cylinder that is rotatably arranged around the outer periphery of the spiral groove, and is linked to the output shaft of the electric motor; First and second rolling bearings that rotatably support both ends of the rotating cylinder in the housing, and the rotational force of the rotating cylinder is converted into a moving force in the axial length direction of the steered shaft to convert the rolling cylinder. An electric power steering apparatus comprising a power conversion mechanism for transmitting to a rudder shaft, comprising: first and second screw rings for attaching and holding an outer ring of the first rolling bearing; An electric power steering apparatus comprising: a screw hole into which the first and second screw rings are screwed; and an insertion hole into which the second rolling bearing is inserted.   The speed reduction gear mechanism which increases the rotational force of the said output shaft and is transmitted to the said rotation cylinder is accommodated in the said housing, The several fin is shape | molded on the outer side of the said housing. Electric power steering device.   The electric motor includes a motor case in which a rotor and a stator connected to the output shaft are accommodated, and the output shaft or the rotor includes an air flow generation unit that generates an air flow in the motor case. Item 3. The electric power steering device according to Item 1 or 2.

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