JP2011051386A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device achieving high reliability and quietness, and excellent steering feeling by reliably fixing a ball screw nut to a hollow shaft without any deformation, and enhancing the work efficiency in manufacturing. <P>SOLUTION: Multiple cutouts 45 are formed in a flange portion 36 formed on an axial end portion 23a of a ball screw nut 23, and (an axial end portion 6a of) a motor shaft 6 has a thin-plate portion 44 extending on the radially outer side of the ball screw nut 23. When the thin-plate portion 44 extending from the motor shaft 6 is caulked into the cutouts 45 serving as engagement recesses having side walls in the circumferential direction, the rotation of the ball screw nut 23 relative to the motor shaft 6 is restricted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus provided with a ball screw device.

  Conventionally, a hollow shaft through which a rack shaft is inserted is provided, and an assist force is applied to the steering system by converting the rotation of the hollow shaft rotated by a motor drive into an axial movement of the rack shaft using a ball screw device. There is a so-called rack assist type electric power steering device (EPS).

  Usually, in such EPS, a ball screw device is formed by interposing a plurality of balls between a ball screw nut fixed to a hollow shaft and a screw portion formed on a rack shaft. That is, a spiral rolling path is formed when a screw portion formed on the inner periphery of the ball screw nut and a screw portion formed on the outer periphery of the rack shaft face each other. And each ball arrange | positioned in the rolling path rolls, receiving the load, and rotation of a ball screw nut is converted into the axial direction movement of a rack shaft.

  Now, as a structure for fixing the ball screw nut to the hollow shaft, for example, as shown in Patent Document 1, a ball screw nut is inserted and inserted from the axial direction into a housing recess formed on the inner periphery of the hollow shaft, and locked. There is a structure in which the ball screw nut is sandwiched between the nuts in the axial direction. By adopting such a configuration, there is an advantage that the axial length can be shortened.

  However, on the other hand, regarding the size in the radial direction, it is inevitable to enlarge the portion where the ball screw nut and the hollow shaft overlap. Further, there is a possibility that the ball screw nut is deformed by tightening with the lock nut, and the rolling path (a screw groove constituting the rolling path) is distorted. Then, this disturbs the smooth rolling of each ball in the rolling path, so that there is a possibility that abnormal noise or vibration is generated, and consequently the steering feeling is deteriorated.

  Therefore, for example, as shown in Patent Document 2, flanges that expand outward in the radial direction are formed at the axial ends of the ball screw nut and the hollow shaft, respectively, and both the flanges are fastened to each other. A connecting structure is conceivable. As a result, the ball screw nut and the hollow shaft can be fixed so as not to rotate relative to each other without deforming the ball screw nut.

  However, the fixing structure by fastening between the flanges also has a problem that it is difficult to improve the productivity because bolt fastening at a plurality of locations is complicated. For this reason, it cannot be said that there is an obvious superiority in comparison with the fixing structure by the clamping pressure using the lock nut.

  Patent Document 3 discloses a structure in which a screw portion is formed on the outer periphery of a ball screw nut, and the ball screw nut is screwed to the inner periphery of the hollow shaft. The stress acting on the ball screw nut can be distributed over the entire outer periphery thereof. Thus, the deformation of the ball screw nut and the accompanying distortion of the rolling path can be suppressed, and at the same time, the workability can be improved.

JP 2006-256414 A JP-A-6-255501 JP 2007-239782 A

However, problems still remain in the structure in which the ball screw nut is fixed to the hollow shaft by screwing.
That is, it is extremely difficult to form a screw portion on the entire outer periphery of a ball screw nut having high strength and rigidity. Further, by arranging the ball screw nut itself in the hollow shaft, it is inevitable to increase the diameter of the portion. Furthermore, in EPS, the motor rotation direction is frequently reversed. Therefore, there is a problem that the reversal of the motor, which is repeatedly performed, acts as a force for generating screw looseness in the ball screw nut screwed to the hollow shaft. However, as described in Patent Document 3, a lock nut is used as a detent means, or a countermeasure such as a set screw that penetrates the hollow shaft and the ball screw nut in the radial direction is used in the rolling path of the ball screw nut. There is a possibility of distortion, and in this respect, there is still room for improvement.

  The present invention has been made to solve the above problems, and its purpose is to securely fix the ball screw nut to the hollow shaft without causing deformation, and to achieve high reliability and quietness. Another object of the present invention is to provide an electric power steering device that realizes the steering feeling and can improve the workability at the time of manufacture.

  In order to solve the above-mentioned problems, the invention according to claim 1 includes a rack shaft provided so as to be capable of reciprocating in an axial direction, a hollow shaft through which the rack shaft is inserted and rotated by a motor drive, A ball screw device that converts the rotation of the hollow shaft into the axial movement of the rack shaft, the ball screw device fixing a ball screw nut to an axial end of the hollow shaft, An electric power steering apparatus formed by arranging a plurality of balls in a spiral rolling path formed by opposing a screw groove threaded on the circumference and a screw groove threaded on the outer periphery of the rack shaft. The ball screw nut is provided with a hollow shaft-like screw shaft at an axial end thereof, and the ball screw nut is engaged with the screw portion formed on the hollow shaft, Axial end of hollow shaft To be those that are screwed, providing the restricting means for restricting the relative rotation between the hollow shaft and the ball screw nut, and the gist.

  That is, by forming a screw shaft at the axial end of the ball screw nut and screwing it onto the axial end of the hollow shaft, the stress acting on the main body portion into which the screw groove is engraved is reduced, and the screw The possibility that the groove is deformed can be greatly reduced. As a result, high quietness and excellent steering feeling can be realized, and workability at the time of manufacturing can be improved. Then, by restricting the relative rotation between the ball screw nut and the hollow shaft by the restricting means, it is possible to suppress the loosening of the ball screw nut and to ensure high reliability.

  According to a second aspect of the present invention, at least one of the ball screw nut and the hollow shaft is provided with a thin plate portion disposed outside an engaging recess formed on the outer periphery of the other side, The gist is that the thin plate portion is caulked in the engaging recess.

  According to a third aspect of the present invention, the engaging recess has a side wall in the circumferential direction and is formed on an outer periphery of the ball screw nut, and the thin plate portion is engaged with the ball screw nut by screwing. The gist of the invention is that the hollow shaft is extended in the axial direction from the axial end of the hollow shaft so as to be arranged on the radially outer side of the joint recess.

According to each of the above configurations, the relative rotation between the hollow shaft and the ball screw nut can be easily and surely controlled with a simple configuration, and the loosening of the screw of the ball screw nut can be suppressed.
The gist of the invention described in claim 4 is that the thin plate portion is formed in an annular shape surrounding the radially outer side of the ball screw nut.

  According to the above configuration, in the ball screw nut screwed to the hollow shaft, the thin plate portion can be easily caulked in the engagement recess regardless of the circumferential position of the engagement recess. Thereby, the workability at the time of manufacture can be further improved.

The gist of the invention described in claim 5 is that the regulating means is formed by engaging an engagement piece formed by the thin plate portion broken by the caulking and a side wall of the engagement recess.
According to the said structure, it becomes difficult to remove | separate an engagement piece from the corresponding engagement recessed part. As a result, the “caulking” can be made stronger in comparison with a case where a part of the thin plate portion is elastically deformed so as to protrude into the engaging recess. Further, the fracture surface engages with the side wall of the engagement recess, so that the engagement piece receives a load generated by relative rotation between the ball screw nut and the hollow shaft in the width direction (circumferential direction of the thin plate portion). It will be. Therefore, the relative rotation between the ball screw nut and the hollow shaft can be more effectively restricted, and as a result, the screw loosening of the ball screw nut can be more reliably suppressed.

  The gist of the invention described in claim 6 is that the thin plate portion is provided on a separate member that is non-rotatably attached to the hollow shaft at least in the screw loosening direction of the ball screw nut.

  That is, it is difficult to integrally form a thin plate portion that is required to be elastically deformed relatively easily and a hollow shaft that is required to have high strength. In this regard, as in the above configuration, by attaching another member provided with the thin plate portion to the hollow portion, the formation of the thin plate portion is facilitated. And the thin plate part formed integrally with the said another member cannot rotate in the screw loosening direction of a ball screw nut. Therefore, according to the said structure, workability | operativity at the time of manufacture can further be improved, suppressing generation | occurrence | production of the screw | thread loosening.

  The invention according to claim 7 is characterized in that the restricting means includes a first engagement portion extending in an axial direction from one of the ball screw nut or the hollow shaft, and the first engagement portion on the other side. It consists of the 2nd engaging part to engage.

According to the above configuration, the relative rotation between the hollow shaft and the ball screw nut can be regulated easily and reliably with a simple configuration, and the screw screw loosening of the ball screw nut can be suppressed.
According to an eighth aspect of the present invention, a flange portion extending radially outward is formed at each axial end portion of the ball screw nut and the hollow shaft facing each other, and the restricting means includes: A shaft-like member that is attached to the flange portion and constitutes the first engagement portion, and the shaft that is provided on the flange portion on the other side opposite to the flange portion on the side to which the shaft-like member is attached. The gist of the present invention is that it is formed of a through-hole that constitutes the second engaging portion by inserting the shaped member.

  That is, when a relative displacement in the circumferential direction occurs between the hollow shaft and the ball screw nut, the shaft member and the through hole engage with each other, thereby restricting relative rotation between the two. Therefore, according to the above configuration, the restricting means can be configured simply and easily assembled, and the screw screw nut can be prevented from loosening.

  According to a ninth aspect of the present invention, the flange portion on the hollow shaft side is formed by coaxially screwing a flange member so that the hollow shaft has a reverse screw relationship with the ball screw nut. In addition, the gist is that the through hole is formed in a long hole shape extending in the circumferential direction.

  According to the above configuration, by screwing the ball screw nut to the hollow shaft, regardless of the circumferential position of the through hole, the other side flange portion can be easily inserted through the through hole. A shaft-like member can be attached. As a result, workability at the time of manufacture can be improved.

  Further, when either one of the hollow shaft and the flange of the ball screw nut is loosened, the other is screwed. Therefore, according to the above configuration, even when the ball screw nut is loosened, the flange member is screwed by the engagement between the shaft-like member provided in each flange and the through hole. Thus, the progress of the loosening of the ball screw nut can be suppressed.

  Furthermore, the occurrence of screw looseness is informed to the driver by using a collision sound generated when the shaft-like member that moves in the through-hole by the relative rotation of the ball screw nut and the hollow shaft contacts the side wall thereof. Can do. The function as the warning means makes it possible to prompt the driver to repair at an early stage where the loosening of the screw does not affect the safety, so that higher reliability can be ensured. Become.

The gist of the invention described in claim 10 is that the shaft-like member is attached to the flange portion by screwing.
According to the said structure, the attachment operation | work of the shaft-shaped member with respect to the flange part becomes easy, and, thereby, the workability | operativity at the time of the manufacture can be improved. Furthermore, the loosening force of the ball screw nut can be more effectively suppressed by generating a frictional force between the opposing flange portions by the fastening force.

  The invention according to claim 11 includes a cylindrical member that is attached to the hollow shaft so as to be axially movable and relatively non-rotatable. The restricting means includes an outer periphery of the ball screw nut and the cylindrical member. The gist is that one nut is screwed into each screw portion formed on the outer periphery of the screw.

  According to the said structure, the relative rotation of a ball screw nut with respect to a hollow shaft can be controlled, and the screw loosening can be suppressed. Then, by adjusting the axial position of the cylindrical member fitted on the hollow shaft, the nut can be easily screwed into the two screw portions juxtaposed in the axial direction. . As a result, it is possible to easily and reliably suppress the loosening of the ball screw nut with a simple configuration.

  According to a twelfth aspect of the present invention, a rolling bearing is interposed between the ball screw nut and the first housing that accommodates the ball screw nut, and is formed at an axial end portion of the first housing. The opening is closed by attachment of the second housing, and a flange portion extending radially outward is formed at the axial end of the ball screw nut on the hollow shaft side, An insertion portion disposed in the first housing is formed in the second housing, and a flange portion of the ball screw nut and an insertion portion of the second housing are in contact with each axial end surface of the rolling bearing. This is the gist.

  According to the said structure, the relative movement of the separation direction in the axial direction of a ball screw nut and a hollow shaft can be controlled. As a result, the ball screw nut can be prevented from being detached and higher reliability can be secured.

  According to a thirteenth aspect of the present invention, the hollow shaft is a motor shaft housed in a motor housing, and a mounting hole for a power feeding connector is formed in the motor housing. The gist is that the means is arranged at a position facing the attachment hole.

  According to the said structure, a control means can be visually recognized through the attachment hole. Thereby, the workability at the time of manufacture can be improved, and as a result, the looseness of the screw of the ball screw nut can be suppressed more easily and reliably.

  According to the present invention, the ball screw nut is securely fixed to the hollow shaft without causing deformation to achieve high reliability, quietness, and excellent steering feeling, and at the same time, workability during manufacturing It is possible to provide an electric power steering device and a method for manufacturing the electric power steering device capable of improving the above.

Sectional drawing which shows schematic structure of an electric power steering apparatus (EPS). The expanded sectional view near the ball screw device in a 1st embodiment. The perspective view of a ball screw nut, a motor shaft, and a flange member in a 1st embodiment. The perspective view of a ball screw nut, a motor shaft, and a flange member in a 1st embodiment. Sectional drawing of the motor shaft in which the flange member of 1st Embodiment was attached (screwing). (A) AA sectional drawing, (b) The front view which shows the state by which the thin-plate part of the flange member was crimped in the notch formed in the flange part of a ball screw nut. Explanatory drawing which shows the operation | work procedure at the time of fixing a ball screw nut (screwing). Explanatory drawing which shows the operation | work procedure at the time of fixing a ball screw nut (screwing). The expanded sectional view near a ball screw nut. The expanded sectional view of the ball screw device vicinity in 2nd Embodiment. The perspective view of the ball screw nut in a 2nd embodiment, a motor shaft, a flange member, and a shaft-like member (bolt). The perspective view of the motor shaft with which the ball screw nut, the flange member, and the volt | bolt were assembled | attached. Explanatory drawing which shows the aspect which a through-hole and a volt | bolt engage. The expanded sectional view of the ball screw apparatus vicinity in 3rd Embodiment. The ball screw nut and motor shaft in a 3rd embodiment, and a perspective view of a cylindrical member and a nut. The perspective view of the motor shaft with which the ball screw nut, the cylindrical member, and the nut were assembled | attached. (A) Side view of motor shaft assembled with ball screw nut, cylindrical member and nut, (b) BB sectional view. The perspective view of the flange member and motor shaft of another example. (A) The side view of the motor shaft in which the flange member of another example was attached, (b) CC sectional drawing. The perspective view of the flange member and motor shaft of another example. (A) The side view of the motor shaft in which the flange member of another example was attached, (b) DD sectional drawing. The schematic diagram which shows the shaft-shaped member as an engaging protrusion as a 2nd engaging part provided in the axial direction edge part of the motor shaft, and a 1st engaging part provided in the ball screw nut. Explanatory drawing which shows the aspect with which the engaging protrusion as a 2nd engaging part and the shaft-shaped member as a 1st engaging part engage. The perspective view of the cylindrical member and motor shaft of another example. (A) The side view of the motor shaft with which the ball screw nut of another example, the cylindrical member, and the nut were assembled | attached, (b) EE sectional drawing.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, in the EPS 1 of the present embodiment, a rack shaft 3 inserted through a substantially cylindrical housing 2 is supported by a rack guide and a sliding bearing (both not shown) so that its axial direction And is supported so as to be movable along. The rack shaft 3 is connected to a steering shaft via a well-known rack and pinion mechanism so as to reciprocate in the axial direction in accordance with a steering operation.

  The EPS 1 also includes a motor 4 as a drive source and a ball screw device 5 that converts the rotation of the motor 4 into an axial movement of the rack shaft 3. The EPS 1 of the present embodiment is configured as a so-called rack assist type EPS in which the rack shaft 3, the motor 4, and the ball screw device 5 are integrally accommodated in the housing 2.

  Specifically, the motor 4 of this embodiment has a motor shaft 6 formed in a hollow shaft shape, and the motor shaft 6 is supported by a bearing 7 provided on the inner periphery of the housing 2. Therefore, it is disposed along the axial direction of the housing 2. Further, in the motor 4 of the present embodiment, the motor rotor 9 is formed by fixing the magnet 8 to the peripheral surface of the motor shaft 6. The motor 4 of the present embodiment has a motor stator 10 that surrounds the radially outer side of the motor rotor 9 fixed to the inner periphery of the housing 2, and the rack shaft 3 is inserted into the motor shaft 6. The housing 2 is arranged coaxially with the rack shaft 3.

  Here, in this embodiment, the housing 2 is attached to the cylindrical motor housing 12 having openings 11a and 11b at both ends in the axial direction, and the axial ends 12a and 12b of the motor housing 12. Thus, the side housings 13 and 14 for closing the openings 11a and 11b are assembled.

  Specifically, in the present embodiment, the rack shaft 3 is supported on the side housing 13 attached to the right axial end 12a of the motor housing 12 and the rack shaft 3 is connected to the pinion shaft. The rack guide constituting the rack and pinion mechanism is formed by pressing against (not shown). In the present embodiment, the bearing 7 for supporting the motor shaft 6 is provided in the side housing 13, and the motor housing 6 is attached to the axial end portion 12 a of the motor housing 12. Thus, the motor housing 12 is disposed inside the motor stator 10 formed on the inner periphery of the motor housing 12. The rack shaft 3 and the ball screw device 5 are the remaining one of the openings 11a and 11b formed at both ends of the motor housing 12 in the axial direction, that is, the left axial end of the motor housing 12 in FIG. It becomes the structure assembled | attached from the opening part 11b formed in 12b.

  More specifically, the rack shaft 3 of the present embodiment is configured as a screw shaft by screwing a screw groove 21 on the outer periphery thereof. The ball screw device 5 of the present embodiment is formed by screwing a ball screw nut 23 to the rack shaft 3 via a plurality of balls 22.

  Specifically, as shown in FIG. 2, a screw groove 24 corresponding to the screw groove 21 on the rack shaft 3 side is formed on the inner periphery of the ball screw nut 23 formed in a substantially cylindrical shape. The ball screw nut 23 is fitted on the rack shaft 3 so that the screw groove 24 faces the screw groove 21 on the rack shaft 3 side. Each ball 22 is disposed in a spiral rolling path L1 formed by the two screw grooves 21 and 24 facing each other.

  Further, the ball screw nut 23 is formed with a reflux path L2 that opens to two locations (connection points P1, P2) in the screw groove 24. In this embodiment, the return path L2 is a circulating member having a function of scooping up the balls 22 from the rolling path L1 and a function of re-ejecting to the rolling path L1 with respect to the ball screw nut 23. It is formed by mounting 25. The rolling path L1 is short-circuited between the two connection points P1 and P2 corresponding to the opening position by the return path L2.

  That is, each ball 22 interposed in the rolling path L1 between the rack shaft 3 and the ball screw nut 23 is subjected to the load by the relative rotation of the ball screw nut 23 with respect to the rack shaft 3, and the rolling path L1. Roll inside. Each ball 22 rolled in the rolling path L1 further passes through the return path L2 formed in the ball screw nut 23, so that two connection points P1 set in the rolling path L1. , P2 move from the downstream side to the upstream side. The ball screw device 5 converts the rotation of the ball screw nut 23 into the axial movement of the rack shaft 3 by infinite circulation of the balls 22 rolling on the rolling path L1 through the return path L2. It is possible.

  In the present embodiment, the ball screw nut 23 is connected to the axial end portion 6 a of the motor shaft 6, and the rotation of the motor 4, which is a drive source, causes the ball screw nut 23 to rotate together with the motor shaft 6. Is input to the ball screw device 5. As shown in FIG. 1, in this embodiment, a ball bearing 27 as a rolling bearing is interposed between the ball screw nut 23 and the housing 2 (motor housing 12) that houses the ball screw nut 23. ing. The EPS 1 according to the present embodiment is configured to apply the pressing force of the rack shaft 3 that moves in the axial direction based on the motor torque to the steering system as an assist force for assisting the steering operation.

(Ball screw nut fixing structure)
Next, the fixing structure of the ball screw nut in the EPS of this embodiment will be described.
As shown in FIGS. 2 to 4, in this embodiment, a hollow shaft-like screw extending in the axial direction is provided at the axial end portion 23 a (right end portion in FIG. 2) of the ball screw nut 23. A shaft 30 is formed. A screw portion 32 corresponding to a screw portion 31 formed on the outer periphery of the screw shaft 30 is formed on the inner periphery of the motor shaft 6. In the ball screw nut 23 of the present embodiment, the screw shaft 30 (the screw portion 31) provided at the axial end portion 23a is screwed into the screw portion 32 formed on the inner periphery of the motor shaft 6. Thus, the motor shaft 6 is fixed to the axial end 6a.

  In the present embodiment, a flange member 33 formed to have a larger diameter than the ball screw nut 23 is attached to the outer periphery of the motor shaft 6, specifically, the outer periphery of the axial end portion 6 a. . The rotation of the flange member 33 is restricted, so that the rotation of the ball screw nut 23 and the motor shaft 6 in the same direction when the ball screw nut 23 is screwed can be restricted. Yes.

  That is, when the ball screw nut 23 is screwed from the axial direction to the axial end portion 6a of the motor shaft 6 that is rotatably supported, the gap between the motor shaft 6 and the ball screw nut 23 at the time of the screwing. Therefore, it is necessary to restrict so-called “accompaniment”. In consideration of this point, in the present embodiment, the rotation of the motor shaft 6 can be suppressed by holding the flange member 33 attached to the motor shaft 6 at a predetermined position in the motor housing 12. Yes. Thus, the ball screw nut 23 is configured to ensure easy and reliable screwing.

  More specifically, the flange member 33 of the present embodiment includes a base portion 34 formed in a cylindrical shape and a flange portion (flange portion) 35 that expands radially outward from the outer periphery of the base portion 34. In the present embodiment, the axial end 23a of the ball screw nut 23 is also formed with a flange portion 36 that expands radially outward. And the flange member 33 of this embodiment makes the outer diameter R1 of the flange part 35 larger than the outer diameter R2 of the flange part 36 on the ball screw nut 23 side (see FIG. 2, R1> R2). ), And the outer peripheral edge of the same flange portion 35 is configured to protrude further in the radial direction than the outer peripheral edge of the flange portion 36 on the ball screw nut 23 side.

  In the present embodiment, screw portions 37 and 38 are formed on the inner periphery of the base portion 34 constituting the flange member 33 and the outer periphery of the axial end portion 6a of the motor shaft 6, respectively. The flange member 33 of the present embodiment is screwed onto the outer periphery of the motor shaft 6 (the axial end portion 6a) by screwing the screw portion 37 formed on the base portion 34 with the screw portion 38 on the motor shaft 6 side. It is designed to be screwed.

  Here, in this embodiment, these screw portions 37 and 38 are screwed into the screw portion 31 formed on the screw shaft 30 and the screw portion 32 formed on the inner periphery of the motor shaft 6. It is formed so that it may become the relationship of the reverse screw from which the rotation direction at the time of doing. Specifically, the screw portions 31 and 32 for screwing the ball screw nut 23 are “right screws”, whereas the screw portions 37 and 38 for screwing the flange member 33 are “left screws”. "

  That is, the screw portions 31 and 32 for screwing the ball screw nut 23 and the screw portions 37 and 38 for screwing the flange member 33 are in a reverse screw relationship, so that these ball screw nuts 23. When one of the flange members 33 is loosened by the relative rotation with the motor shaft 6, the other is screwed.

  That is, when the ball screw nut 23 is screwed, the motor shaft 6 tries to rotate in the same direction as the ball screw nut 23, but the accompanying direction is the rotation in the screw tightening direction with respect to the flange member 33. It has become. Therefore, by restricting the rotation of the flange member 33 with a jig or the like, the rotation of the motor shaft 6 accompanying the screwing of the ball screw nut 23 can be suppressed. In this embodiment, when the ball screw nut 23 is screwed, the flange portion 33 of the flange member 33 that protrudes further radially outward than the outer peripheral edge of the ball screw nut 23 is held, thereby It is possible to suppress the accompanying rotation of the motor shaft 6.

  More specifically, as shown in FIGS. 3 and 4, the flange portion 33 of the flange member 33 formed to have a larger diameter than the ball screw nut 23 is engaged with the flange member by engagement with a jig. An engaged portion 39 capable of restricting the rotation of 33 is provided.

  Specifically, in this embodiment, the engaged portion 39 is a peripheral edge of a surface of the flange portion 35 on which the ball screw nut 23 is screwed (a screwing side surface 35a located on the left side in FIG. 5). A plurality of (six in this embodiment) concave portions 40 are formed in the portion. In the present embodiment, the engaged portion 39 has a polygonal cylindrical jig from the axial direction by forming the concave portions 40 at equal intervals in the circumferential direction with respect to the peripheral portion of the screwing side surface 35a. (For example, a hexagonal cylindrical jig) can be engaged (fitted). Then, when the ball screw nut 23 is screwed, a jig is engaged with the engaged portion 39 from the axial direction, thereby suppressing the rotation of the motor shaft 6 and the ball screw from the inside of the jig. By inserting the nut 23, the ball screw nut 23 can be easily and reliably screwed onto the axial end portion 6a of the motor shaft 6.

  Further, in the present embodiment, an engaged portion 41 that can restrict the rotation of the motor shaft 6 by engagement with a jig is formed on the inner periphery of the motor shaft 6. Specifically, the engaged portion 41 has an axial inner side (right side in FIG. 5) inner side than the screw portion 32 for screwing the ball screw nut 23 (see FIG. 6). As shown to a), it forms in the shape which continuously recessedly provided the plural (12 in this embodiment) triangular groove extended in an axial direction at equal intervals in the circumferential direction. When the flange member 33 is screwed, a polygonal shaft (polygonal cylindrical jig) (for example, a hexagonal cylindrical jig) is inserted into the motor shaft 6 and engaged with the engaged portion 41. As a result, the rotation of the motor shaft 6 can be restricted and its rotation can be suppressed.

  In the present embodiment, the flange member 33 has a function as a restricting means for restricting relative rotation between the motor shaft 6 and the ball screw nut 23 screwed to the axial end portion 6a of the motor shaft 6. is doing.

  More specifically, as shown in FIGS. 2 to 5, the flange member 33 attached to the axial end portion 6 a of the motor shaft 6 has a thin plate portion 44 disposed on the radially outer side of the ball screw nut 23. Is formed. The thin plate portion 44 of this embodiment extends from the flange portion 35 (the screwing side surface 35a) of the flange member 33 in the axial direction and toward the screwing side of the ball screw nut 23 (left side in FIGS. 2 and 5). As a result, the ball screw nut 23 is formed in an annular shape so as to surround the flange portion 36 provided on the radially outer side, specifically, the axial end portion thereof. A plurality (four in this embodiment) of notches 45 are formed in the flange portion 36 on the ball screw nut 23 side. In the present embodiment, these notches 45 are formed at equal intervals in the circumferential direction. In this embodiment, the thin plate portion 44 formed on the flange member 33 side is pressed from the outside in the radial direction and caulked into the notches 45, whereby the ball screw nut 23 and the flange member 33, that is, the ball The relative rotation between the screw nut 23 and the motor shaft 6 is restricted.

  Specifically, in this embodiment, when the thin plate portion 44 is folded into each notch 45 by the above-mentioned “caulking”, as shown in FIG. 6B, along the side surface 45a of each notch 45, The thin plate portion 44 is broken. Then, by engaging each engagement piece 46 and each notch 45 formed by breaking the thin plate portion 44, the “caulking” is made stronger, and the ball screw nut 23 and the motor are more reliably connected. The relative rotation with the shaft 6 can be restricted.

Next, an operation procedure for fixing the ball screw nut in the EPS of the present embodiment configured as described above will be described.
As described above, in the present embodiment, the motor shaft 6 is a bearing provided in the side housing 13 that closes one of the openings 11a and 11b formed at both ends of the motor housing 12 in the axial direction. 7, the motor housing 12 is rotatably arranged (see FIG. 1). For this reason, the ball screw nut 23 is inserted together with the rack shaft 3 from the remaining opening 11b of the motor housing 12, and is fixed to the axial end portion 6a of the motor shaft 6 by screwing.

More specifically, as shown in FIG. 7, in the present embodiment, prior to screwing the ball screw nut 23, first, a step of screwing the flange member 33 around the outer periphery of the motor shaft 6 is performed.
Specifically, at this time, the flange member 33 is engaged with a jig 51 having a polygonal cylindrical shape (in this embodiment, a hexagonal cylindrical shape) with respect to the engaged portion 39 formed on the flange portion 35. Combined. In addition, a polygonal shaft-shaped jig 52 (in this embodiment, a hexagonal shaft-shaped jig) is engaged with the engaged portion 41 formed on the inner periphery of the motor shaft 6. The flange member 33 is screwed to the engaged portion on the flange member 33 side while restricting the rotation of the motor shaft 6 by the jig 52 engaged with the engaged portion 41 on the motor shaft 6 side. This is done by rotating the jig 51 engaged with 39.

  When the step of screwing the flange member 33 is completed, the jig 52 is removed from the opening 11b of the motor housing 12. Then, as shown in FIG. 8, after the rack shaft 3 is inserted into the motor shaft 6, a step of screwing a ball screw nut 23 to the axial end portion 6a is performed.

  In this embodiment, at this time, the jig 53 is inserted into the jig 51, and the jig 53 is used to insert the axial end portion 23b of the ball screw nut 23 (the left end in FIG. The ball screw nut 23 can be rotated. Then, the screwing of the ball screw nut 23 restricts the rotation of the flange member 33 by the jig 51 engaged with the engaged portion 39 on the flange member 33 side and suppresses the rotation of the motor shaft 6. While this is done, the jig 53 holding the ball screw nut 23 (the axial end 23b thereof) is rotated.

  When the step of screwing the ball screw nut 23 is completed, the step of caulking the thin plate portion 44 provided on the flange member 33 is then performed. Specifically, each jig 51, 53 used in the step of screwing the ball screw nut 23 is removed from the opening 11b of the motor housing 12, and a tool is inserted from the opening 11b. The ball screw nut 23 is fixed so as not to rotate relative to the motor shaft 6 by “caulking” of the thin plate portion 44.

  Here, as shown in FIG. 1, the motor housing 12 of the present embodiment is formed with an attachment hole 56 for attaching a power supply connector 55 for supplying driving power to the motor 4. The inside can be visually recognized from this attachment hole 56. In the present embodiment, the flange member 33 is arranged at a position facing the attachment hole 56 by being attached to the axial end portion 6 a of the motor shaft 6.

  That is, in this embodiment, in each of the above steps for fixing the ball screw nut 23 to the motor shaft 6, the jig 52 is engaged with the engaged portion 39 of the flange member 33 through the attachment hole 56. It is possible to visually confirm the combined state. Similarly, the “caulking” state of the thin plate portion 44 provided on the flange member 33 can be visually confirmed. In the present embodiment, the ball screw nut 23 can be fixed more easily and reliably.

  In addition, the ball bearing 27 is interposed between the ball screw nut 23 accommodated in the motor housing 12 and the motor housing 12 as described above (see FIG. 1). In the present embodiment, after the step of fixing the ball screw nut 23 to the axial end 6 a of the motor shaft 6 is completed, the ball bearing 27 is opened from the opening 11 b to the motor housing 12, as with the ball screw nut 23. It is inserted inside. The opening 11b of the motor housing 12 used in each of these steps is closed by attaching the side housing 14 as the second housing to the axial end portion 12b of the motor housing 12 as the first housing. It has come to be.

  Here, as shown in FIG. 9, in the present embodiment, the fixed end 14 a of the side housing 14 is formed with an insertion portion 47 disposed in the motor housing 12 by being attached to the motor housing 12. Yes. In the present embodiment, the insertion portion 47 is formed in a substantially cylindrical shape whose outer diameter is substantially equal to the inner diameter of the motor housing 12. The axial end surfaces of the ball bearings 27 are in contact with the insertion portions 47 formed on the side housing 14 and the flange portions 36 formed on the ball screw nut 23, respectively.

  Specifically, the insertion portion 47 of the side housing 14 is brought into contact with the outer ring 27 a of the ball bearing 27, specifically, the axial end surface on the opening 11 b side (left side in the figure), and the ball screw nut 23 The flange portion 36 is in contact with the inner ring 27b of the ball bearing 27, specifically, the axial end surface of the motor shaft 6 side (right side in the figure). In the present embodiment, the axial movement of the ball screw nut 23 toward the opening 11b, that is, the relative movement in the direction away from the motor shaft 6 is restricted, so that the ball screw nut 23 is removed from the motor shaft 6. It is the composition which prevents separation.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The ball screw nut 23 is screwed between a hollow shaft-like screw shaft 30 (the screw portion 31) provided on the axial end portion 23a thereof and a screw portion 32 formed on the inner periphery of the motor shaft 6. Thus, the motor shaft 6 is screwed to the axial end 6a. A plurality of notches 45 are formed in the flange portion 36 provided at the axial end portion 23a of the ball screw nut 23, and the ball screw nut is provided at the motor shaft 6 (the axial end portion 6a thereof). A thin plate portion 44 disposed on the outer side in the radial direction of 23 is formed. The ball screw nut 23 is restrained from rotating relative to the motor shaft 6 by caulking a thin plate portion 44 extending from the motor shaft 6 in each notch 45 as an engagement recess having a side wall in the circumferential direction. Is done.

  According to the above configuration, the relative rotation between the motor shaft 6 and the ball screw nut 23 can be easily and surely restricted with a simple configuration, and the loosening of the ball screw nut 23 can be suppressed.

(2) The thin plate portion 44 is formed in an annular shape surrounding the radially outer side of the ball screw nut 23 (the flange portion 36 thereof) by extending in the axial direction.
According to the above configuration, in the ball screw nut 23 screwed to the motor shaft 6, the notch 45 formed in the flange portion 36 can be easily arranged in any circumferential position. The thin plate portion 44 can be caulked in the notch 45, and thereby the workability at the time of manufacturing can be further improved.

  (3) When folding the thin plate portion 44 into each notch 45 by “caulking”, the thin plate portion 44 is broken along the side surface 45 a serving as the side wall of each notch 45. Then, the engagement pieces 46 and the notches 45 formed by the breakage of the thin plate portion 44 are engaged.

  According to the said structure, it becomes difficult to detach | leave each engagement piece 46 from each notch 45 corresponding. As a result, the “caulking” can be made stronger in comparison with the case where the thin plate portion 44 is simply elastically deformed so as to protrude into the notches 45. Further, the fracture surface engages with the side surface 45 a of each notch 45, so that each engagement piece 46 is formed between the ball screw nut 23 and the motor shaft 6 in the width direction (the circumferential direction of the thin plate portion 44). It receives a load caused by relative rotation. Accordingly, the relative rotation between the ball screw nut 23 and the motor shaft 6 can be more effectively restricted, and as a result, the screw loosening of the ball screw nut 23 can be more reliably suppressed.

  (4) The thin plate portion 44 is formed on the flange member 33 that is attached to the axial end portion 6 a (the outer periphery thereof) of the motor shaft 6. The flange member 33 is screwed coaxially with the motor shaft 6 in a reverse screw relationship with the ball screw nut 23.

  That is, it is difficult to integrally form the thin plate portion 44 that is required to be elastically deformed relatively easily and the motor shaft 6 that is required to have high strength. In this respect, the flange member 33 is not required to be as strong as the motor shaft 6. Accordingly, the thin plate portion 44 can be easily formed by forming the thin plate portion 44 on the flange member 33 as in the above configuration. Further, since the flange member 33 is screwed to the motor shaft 6 in a reverse screw relationship with the ball screw nut 23, the thin plate portion 44 formed integrally with the flange member 33 is a screw of the ball screw nut 23. Cannot rotate in the loose direction. Therefore, according to the above configuration, it is possible to further improve the workability at the time of manufacture while suppressing the looseness of the screw of the ball screw nut 23.

  (5) A ball bearing 27 is interposed between the ball screw nut 23 and the motor housing 12 that houses the ball screw nut 23. The opening 11b of the motor housing 12 is closed when the side housing 14 is attached to the axial end 12b, and the motor housing 12 is attached to the fixed end 14a of the side housing 14 by the attachment. An insertion portion 47 disposed inside is formed. The axial end surfaces of the ball bearings 27 are in contact with the insertion portions 47 formed on the side housing 14 and the flange portions 36 formed on the ball screw nut 23, respectively.

  By setting it as such a structure, the relative movement of the separation direction in the axial direction of the ball screw nut 23 and the motor shaft 6 can be controlled. As a result, the ball screw nut 23 can be prevented from being detached, and higher reliability can be ensured.

  (6) The motor housing 12 is formed with an attachment hole 56 for attaching the power supply connector 55 for supplying driving power to the motor 4. The flange member 33 is attached to the motor shaft 6 and is disposed at a position facing the attachment hole 56.

  According to the above configuration, the flange member 33 can be visually recognized through the attachment hole 56. Thereby, it becomes possible to visually confirm the caulking state of the thin plate portion 44 that forms the restricting means by being provided on the flange member 33. As a result, the looseness of the ball screw nut can be suppressed more easily and reliably.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
For convenience of explanation, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

  As shown in FIGS. 10 to 12, in this embodiment, the flange member is screwed to the axial end portion 6 a (outer periphery) of the motor shaft 6 in a reverse screw relationship with the ball screw nut 23. In FIG. 60, a plurality of screw holes 62 are formed in the flange portion (ridge portion) 61. Further, a plurality of through holes 64 are formed in the flange portion 63 formed at the axial end portion 23a of the ball screw nut 23 so as to face the flange portion 61 on the motor shaft 6 side. In the present embodiment, the two flange portions 61 and 63 provided on the motor shaft 6 side and the ball screw nut 23 side are formed so that their outer diameters are substantially equal. A plurality of bolts 65 inserted through the through holes 64 formed in the flange portion 63 on the ball screw nut 23 side are screwed into the screw holes 62 provided in the flange portion 61 on the motor shaft 6 side. Has been.

  That is, in the present embodiment, the first engagement is extended in the axial direction from the motor shaft 6 by the bolt 65 as a shaft-like member screwed into the flange portion 61 (the screw hole 62) on the motor shaft 6 side. A joint portion is formed, and a second engagement portion that engages with the first engagement portion is constituted by a through hole 64 formed in the flange portion 63 on the ball screw nut 23 side. And when the relative displacement of the circumferential direction arises between the motor shaft 6 and the ball screw nut 23, the bolt 65 as a shaft-shaped member which comprises the 1st engaging part, and the 2nd engaging part By engaging the through-hole 64 (the side wall 64a thereof), the relative rotation between the two is restricted, and as a result, the ball screw nut 23 caused by loosening of the screw is prevented from being detached.

  More specifically, in the present embodiment, the eight screw holes 62 are formed in the flange portion 61 on the motor shaft 6 side at substantially equal intervals along the circumferential direction, and the flange portion on the ball screw nut 23 side is formed. Four through holes 64 are formed in the 63 at substantially equal intervals along the circumferential direction. Specifically, each through hole 64 is formed in a long hole shape extending in the circumferential direction. In this embodiment, the bolts 65 inserted through the corresponding through holes 64 are screwed into the screw holes 62 at positions corresponding to the through holes 64, respectively. .

  That is, by forming the through hole 64 in the shape of a long hole in this way, in the ball screw nut 23 screwed to the motor shaft 6, each through hole 64 formed in the flange portion 63 has any circumferential direction. Regardless of the position, the bolts 65 can be easily screwed into the screw holes 62 formed in the flange portion 61 on the motor shaft 6 side through the through holes 64. And in this embodiment, the improvement of workability | operativity at the time of the manufacture is achieved by this.

  Further, as shown in FIG. 13, when a screw looseness occurs in the ball screw nut 23, a circumferential relative displacement occurs between the ball screw nut 23 and the motor shaft 6 due to the loosening of the screw. Each bolt 65 moves along the circumferential direction in the through-hole 64 formed in the shape of a long hole. The respective bolts 65 abut against and engage with the side walls 64a, thereby restricting relative displacement between the ball screw nut 23 and the motor shaft 6, thereby suppressing further screw loosening of the ball screw nut 23. It is possible.

  Further, it is possible to notify the driver of the occurrence of screw loosening by using a collision sound generated when each bolt 65 moves in the through hole 64 and contacts the side wall 64a. With this function as a warning means, the driver can be urged to repair at an early stage where the loosening of the screw does not affect the safety.

  In this embodiment, each bolt 65 screwed into the screw hole 62 is further screwed, so that the original function as a fastening member, that is, the flange portion 61 on the motor shaft 6 side and the ball screw nut 23 side. A fastening force is generated between the flange portion 63 and the flange portion 63. And it is the structure which suppresses the screw | thread loosening of the ball screw nut 23 using the frictional force which arises by this.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The bolt 65 inserted through the through hole 64 formed in the flange portion 63 on the ball screw nut 23 side is screwed into the screw hole 62 formed in the flange portion 61 on the motor shaft 6 side.

  According to the above configuration, when a relative displacement in the circumferential direction occurs between the motor shaft 6 and the ball screw nut 23, the bolt 65 and the through hole 64 (the side wall 64a) are engaged with each other, The relative rotation between the two is restricted. And thereby, the screw | thread loosening of the ball screw nut 23 can be suppressed.

  Further, by using the bolt 65 as the shaft-like member constituting the first engaging portion, the attaching operation to the flange portion 61 is facilitated, whereby the workability at the time of manufacturing can be improved. Further, the original function as the fastening member, that is, a fastening force can be generated between the flange portion 61 on the motor shaft 6 side and the flange portion 63 on the ball screw nut 23 side. And it becomes possible to suppress the screw loosening of the ball screw nut 23 more effectively by utilizing the frictional force generated thereby.

(2) Each through-hole 64 is formed in the shape of a long hole extending in the circumferential direction.
According to the above configuration, in the ball screw nut 23 screwed to the motor shaft 6, no matter what circumferential position the through holes 64 formed in the flange portion 63 are arranged, the motor shaft 6 side The bolts 65 can be easily screwed to the screw holes 62 formed in the flange portion 61 through the through holes 64. As a result, it is possible to improve workability during the production.

  Further, the bolt 65 moving in the through hole 64 due to the relative rotation of the ball screw nut 23 and the motor shaft 6 makes use of the impact sound generated when the bolt 65 comes into contact with the side wall 64a. I can let you know. The function as the warning means can prompt the driver to repair at an early stage where the loosening of the screw does not affect the safety, and as a result, higher reliability can be ensured.

(3) The flange 61 on the motor shaft 6 side is screwed to the axial end 6 a of the motor shaft 6 so as to have a reverse screw relationship with the ball screw nut 23.
According to the above configuration, when one of the flanges 61 having the respective bolts 65 and the ball screw nut 23 having the respective through holes 64 engaged with the respective bolts 65 is in a loosened state. The other is screwed. Therefore, even when the screw is loosened in the ball screw nut 23, the flange member 61 is screwed by the engagement between the bolts 65 and the through holes 64, so that the ball screw nut 23 The progress of screw loosening can be suppressed.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.
For convenience of explanation, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

  As shown in FIGS. 14 to 17A and 17B, in this embodiment, the outer periphery of the motor shaft 70, specifically, the outer periphery of the axial end portion 70a on the side where the ball screw nut 23 is screwed is provided. A cylindrical member 72 having a screw portion 71 formed on the outer periphery thereof is fitted so as not to be relatively rotatable. Further, on the outer periphery of the ball screw nut 23, specifically, on the outer periphery of the flange portion 73 provided on the axial end 23 a (the right end in FIG. 14, the end on the side screwed to the motor shaft 70), A screw portion 74 corresponding to the screw portion 71 formed on the outer periphery of the motor shaft 70 is formed. In this embodiment, one nut 75 (the screw portion 75a) is provided so as to straddle both the two screw portions 71 and 74 that are juxtaposed in the axial direction by screwing the ball screw nut 23. By screwing, the relative rotation between the motor shaft 70 and the ball screw nut 23 is restricted, and the loosening of the ball screw nut 23 is suppressed.

  More specifically, in this embodiment, an annular fitting recess 76 is formed on the outer periphery of the axial end portion 70 a of the motor shaft 70, and the cylindrical member 72 is formed in the fitting recess 76. On the other hand, it is attached (attached) so as to be axially movable. In the attached state of the cylindrical member 72, the screw portion 71 is an outer periphery of an axial end portion (left axial end portion in FIG. 14) 72a located on the screwing side of the ball screw nut 23. Is formed.

  Here, in the present embodiment, the screw portion 71 formed on the outer periphery of the cylindrical member 72 and the screw portion 74 formed on the outer periphery of the ball screw nut 23 (the flange portion 73) are the ball screws. The outer diameter of the nut 23 when screwed and the height and pitch of the screw thread are set to be substantially equal. Then, by adjusting the axial position of the cylindrical member 72 externally fitted to the motor shaft 70, one nut 75 (the screw portion 75 a) is screwed into the screw portions 71 and 74. It is possible.

  In the present embodiment, a flange portion 77 extending outward in the radial direction is formed on the outer periphery of the cylindrical member 72. The nuts 75 screwed into the screw parts 71 and 74 are screwed in a direction in which they are pressed against the flange parts 77, whereby the screwing positions are fixed.

  Furthermore, the cylindrical member 72 of this embodiment has a plurality of axially extending portions 72b extending in the axial direction from an axial end portion (on the left axial end portion in FIG. 14) 72b located on the antiball screw nut side. An engagement protrusion 78 is provided. A plurality of engagement recesses 79 that engage with the respective engagement protrusions 78 are provided on the outer periphery of the motor shaft 70. Specifically, each engaging recess 79 is formed so as to open on the axial end surface 76 a of the fitting recess 76 formed in the axial end 70 a of the motor shaft 70. That is, each engagement protrusion 78 provided on the cylindrical member 72 (the axial end portion 72b thereof) is connected to the corresponding engagement recess 76 when the cylindrical member 72 is attached to the fitting recess 76. 79 is inserted. In the present embodiment, the relative rotation of the cylindrical member 72 with respect to the motor shaft 70 is restricted by the engagement of each of the engagement protrusions 78 and the engagement recess 79.

  Thus, the cylindrical member 72 attached so as not to rotate relative to the axial end portion 70a of the motor shaft 70, and the two screws formed on the outer periphery of the ball screw nut 23 (the flange portion 73 thereof). By screwing the one nut 75 (the screw portion 75a) across the portions 71 and 74, relative rotation of the ball screw nut 23 with respect to the motor shaft 70 can be restricted, and loosening of the screw can be suppressed. Then, by adjusting the axial position of the cylindrical member 72 externally fitted to the motor shaft 70, the nut 75 can be easily screwed into the two screw portions 71 and 74 juxtaposed in the axial direction. Can be combined. Therefore, according to the above configuration, it is possible to easily and reliably suppress the loosening of the ball screw nut 23 with a simple configuration.

In addition, you may change each said embodiment as follows.
In each of the above embodiments, the present invention is embodied in a coaxial motor type EPS in which the motor 4 and the rack shaft 3 are coaxially arranged. However, the present invention is not limited to this, and a rack assist type EPS having a hollow shaft driven by a motor, in which a ball screw nut is screwed to an axial end portion of the hollow shaft, the motor arrangement is as follows. There is no particular limitation. That is, for example, the present invention may be applied to a so-called parallel type in which the motor and the rack shaft are arranged in parallel, or a rack cross type EPS in which the axis of the motor is arranged obliquely with the rack shaft.

  In the first embodiment, the thin plate portion 44 is formed in an annular shape so as to surround the radially outer side of the ball screw nut 23 (the flange portion 36 thereof). However, the present invention is not limited thereto, and for example, a plurality of thin plate portions formed in a strip shape may be extended in the axial direction from the motor shaft 6 toward the ball screw nut 23 side.

  In the first embodiment, the notch 45 serving as the engagement recess is formed on the ball screw nut 23 side, and the thin plate portion 44 is formed on the motor shaft 6 side. However, the present invention is not limited to this, and a thin plate portion may be formed on the ball screw nut side and an engaging recess may be formed on the motor shaft side. Further, when the shape of the thin plate portion is formed in a strip shape as described above, the thin plate portion and the corresponding engaging recess may be formed on both the ball screw nut side and the motor shaft side. Thereby, it becomes possible to prevent the screws from loosening more reliably.

  In the first embodiment, a plurality of notches 45 are formed in the flange portion 36 provided at the axial end portion 23a of the ball screw nut 23, and the thin plate portions 44 are caulked by the notches 45. The engagement recess was used. However, the present invention is not limited to this, as long as it has a side wall (corresponding to the side surface 45a) that can restrict the relative rotation of the ball screw nut 23 by caulking. A joint recess may be formed.

  Furthermore, in the first embodiment, the thin plate portion 44 is provided on the flange member 33 and is attached to the axial end portion 6a (the outer periphery thereof) of the motor shaft 6 together with the flange member 33. However, the configuration is not limited to this, and a thin plate portion may be formed integrally with the motor shaft.

  -Even if a thin plate portion for caulking is formed on a separate member attached to the motor shaft, the attachment structure is not limited to screwing by a reverse screw such as the flange member 33. Absent. That is, it is only necessary that the ball screw nut 23 is not rotatable in the screw loosening direction with respect to the motor shaft 6. Therefore, the structure which the other member is attached to the motor shaft 6 so that relative rotation is impossible is sufficient.

  Specifically, for example, as shown in FIGS. 18 and 19A and 19B, a flange member 81 is externally fitted on the outer periphery of the motor shaft 80. And it is good also as a structure which controls the relative rotation of the flange member 81 by engaging the engagement protrusion 82 and the engagement recessed part 83 which were provided in these flange member 81 and the motor shaft 80. FIG. Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  In addition, about the structure which fits the flange member 81 on the outer periphery of the motor shaft 80, the fitting recessed part 76 (FIGS. 14-17 (a)) in the axial direction edge part 80a of the motor shaft 80 in the said 3rd Embodiment. A fitting recess 84 similar to that shown in FIG. And also about the engagement protrusion 82 by the side of the flange member 81, and the engagement recessed part 83 by the side of the motor shaft 80, each engagement protrusion 78 in the said 3rd Embodiment and each engagement recessed part 79 (FIG. 14-). What is necessary is just to form like FIG.17 (a) (b)). That is, each engagement protrusion 82 extends in the axial direction from the base 86 of the flange member 81, and each engagement recess 83 is formed in the above-described fitting formed on the axial end 80 a of the motor shaft 80. It is good to form so that it may open to the axial direction end surface 84a of the joint recessed part 84. FIG.

  Furthermore, the configuration of the engaging means for attaching the flange member to the motor shaft so as not to allow relative rotation is not limited to the example shown in FIGS. 18 and 19A and 19B. For example, as shown in FIGS. 20 and 21A and 21B, spline fitting portions (or serrations) are respectively formed on the inner periphery of the base portion 88 of the flange member 87 and the outer periphery of the axial end portion 90a of the motor shaft 90. Fitting portions) 91 and 92 are formed. And it is good also as a structure which controls the relative rotation of the motor shaft 90 and the flange member 87 by making these fit. Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  In the second embodiment, the bolt 65 is used as the shaft-like member constituting the first engaging portion by being attached to the flange portion 61. However, the present invention is not limited to this. For example, a shaft or other member other than a bolt such as a pin may be press-fitted into a hole (hole) formed in the flange portion 61.

  In addition, the through hole 64 through which the bolt 65 as the shaft member is inserted is formed in a long hole shape extending in the circumferential direction. However, the shape is not limited to this, and the shape of the ball screw nut 23 is not limited to this, as long as the relative rotation of the ball screw nut 23 can be restricted by engagement with a shaft-like member (bolt 65 or the like) that constitutes the first engagement portion such as a circular hole. Is not limited to this.

  Furthermore, in the second embodiment, each bolt 65 as a shaft-like member is screwed into the flange portion 61 on the motor shaft 6 side, and each bolt 65 is inserted into the flange portion 63 on the ball screw nut 23 side. A plurality of through holes 64 to be formed are formed. However, the present invention is not limited to this. For example, a shaft-shaped member may be attached to the flange on the ball screw nut side, and a through hole through which the shaft-shaped member is inserted may be provided in the flange portion on the motor shaft side. In addition, a configuration in which a shaft-like member constituting the first engagement portion and a second engagement portion that engages with the first engagement portion are provided on both the flange on the motor shaft side and the ball screw nut side. It may be.

-Moreover, about the 1st engaging part and the 2nd engaging part, it does not necessarily need to be the shaft-shaped member and through-hole which were each provided in the flange part.
Specifically, for example, as shown in FIG. 22, a plurality of (four in this example) second engaging portions projecting outward in the radial direction at the axial end portion 6a of the motor shaft 6. The engaging protrusion 93 is formed. On the other hand, the flange portion 95 on the ball screw nut 23 side is provided with a plurality (four in this example) of shaft-like members 96 as first engaging portions extending in the axial direction toward the motor shaft 6 side.

  In this example, each of the engaging protrusions 93 is an annular plate member in which a protrusion 94a constituting each engaging protrusion 93 is formed on the outer periphery of the motor shaft 6 in the axial direction. It is formed by fixing 94. Further, FIG. 22 shows that the flange 95 on the ball screw nut 23 side indicated by a two-dot chain line (virtual line) and each shaft-like member 96 are axial end portions 6a (plate members 94) of the motor shaft 6 indicated by solid lines. It shows a state of being arranged on the front side of the drawing with respect to (). Accordingly, the “direction extending in the axial direction toward the motor shaft 6 side” of each shaft-like member 96 is a direction from the front side to the back side in FIG.

  Then, as shown in FIG. 23, by the relative rotation of the ball screw nut 23, the shaft-like member 96 as the first engaging portion provided on the ball screw nut 23 side and the motor shaft 6 side are provided. It is good also as a structure which regulates the relative rotation, when each engaging protrusion 93 as a 2nd engaging part contact | abuts and engages. Even with such a configuration, the same effects as those of the second embodiment can be obtained.

  In the third embodiment, the screw portion 74 on the ball screw nut 23 side is formed on the outer periphery of the flange portion 73 provided on the axial end portion 23a. However, the present invention is not limited to this, and a configuration in which the ball screw nut 23 is formed directly on the outer periphery may be employed.

  In the third embodiment, the cylindrical member 72 is attached to the fitting recess 76 formed in the axial end portion 70a of the motor shaft 70. Then, by engaging each engagement projection 78 provided on the cylindrical member 72 with each engagement recess 79 provided on the motor shaft 70, the cylindrical member is movable in the axial direction and is not relatively rotatable. 72 is attached to the motor shaft 70. However, the configuration in which the cylindrical member 72 is attached to the motor shaft 70 so as to be axially movable but not relatively rotatable is not necessarily limited thereto.

  Specifically, for example, as shown in FIGS. 24 and 25 (a) and 25 (b), spline fitting portions are respectively provided on the inner periphery of the cylindrical member 97 and the outer periphery of the axial end portion 98a of the motor shaft 98. (Or serration fitting portions) 99 and 100 may be formed and these may be fitted. Even with such a configuration, the cylindrical member 72 can be attached to the motor shaft 70 so as to be movable in the axial direction and not to be relatively rotatable.

  Although not particularly mentioned in the second and third embodiments, the ball bearing 27 and the side housing 14 interposed between the ball screw nut 23 and the motor housing 12 as shown in FIG. Needless to say, the structure for restricting the axial movement of the ball screw nut 23 using the formed insertion portion 47 may be applied to the configurations of these embodiments.

  In the second embodiment, the flange portions 61 and 63 provided with the elements (bolts 65 and through-holes 64) constituting the restricting means are also located at the positions where the power supply connector 55 formed in the motor housing 12 faces. It is good to set so that it is arranged. Thereby, the workability | operativity at the time of the manufacture can be aimed at. This also applies to the cylindrical member 72 and the flange portion 73 provided with the elements (the screw portions 71 and 74 and the nut 75) constituting the restricting means in the third embodiment.

  In the first embodiment, the flange member 33 provided with the thin plate portion 44 is attached to the axial end 6 a of the motor shaft 6. However, when there is no restriction on assembly, such a flange member 33 may be formed integrally with the motor shaft 6. Similarly, the flange member 60 in the second embodiment may be formed integrally with the motor shaft 6.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Housing, 3 ... Rack shaft, 4 ... Motor, 5 ... Ball screw device, 6, 70, 89, 90, 98 ... Motor shaft, 6a, 70a, 89a, 90a, 98a ... axial end, 7 ... bearing, 11a, 11b ... opening, 12 ... motor housing, 12a, 12b ... axial end, 13, 14 ... side housing, 21 ... screw groove, 22 ... ball, 23 ... Ball screw nut, 23a, 23b ... axial end, 24 ... screw groove, 25 ... circulating member, 27 ... ball bearing, 27a ... outer ring, 27b ... inner ring, 30 ... screw shaft, 31, 32 ... screw part, 33, 60, 81, 87 ... flange member, 34, 86, 88 ... base, 35 ... collar, 36, 63, 73, 95 ... flange, 37, 38 ... screw, 44 ... thin plate, 45 ... notch, 45a ... side 46 ... engagement piece 47 ... insertion part 55 ... feed connector 56 ... mounting hole 61 ... flange part 62 ... screw hole 64 ... through hole 64a ... side wall 65 ... bolt 71 ... screw part , 72, 97 ... cylindrical members, 72a, 72b ... axial ends, 74 ... screw parts, 75 ... nuts, 75a ... screw parts, 76, 84 ... fitting recesses, 78, 82 ... engagement protrusions, 79 , 83 ... engaging recesses, 93 ... engaging protrusions, 96 ... shaft-like members, 91, 92, 99, 100 ... spline fitting parts.

Claims (13)

A rack shaft provided so as to be capable of reciprocating in an axial direction, a hollow shaft through which the rack shaft is inserted and rotated by a motor drive, and a ball screw device that converts rotation of the hollow shaft into axial movement of the rack shaft The ball screw device has a ball screw nut fixed to an axial end portion of the hollow shaft, and is screwed on an outer periphery of the rack shaft and a screw groove screwed on an inner periphery of the ball screw nut. In the electric power steering device formed by arranging a plurality of balls in a spiral rolling path formed opposite to the screw groove,
A hollow shaft-shaped screw shaft is provided at an axial end portion of the ball screw nut, and the ball screw nut is formed by screwing the screw shaft with a screw portion formed on the hollow shaft. Screwed to the axial end of the
Provided with a regulating means for regulating relative rotation between the ball screw nut and the hollow shaft;
An electric power steering device. The electric power steering apparatus according to claim 1, wherein
At least one of the ball screw nut and the hollow shaft is provided with a thin plate portion disposed outside an engagement recess formed on the outer periphery of the other side,
The restricting means is to caulk the thin plate portion in the engaging recess;
An electric power steering device. The electric power steering apparatus according to claim 2,
The engaging recess has a side wall in the circumferential direction and is formed on the outer periphery of the ball screw nut.
The thin plate portion is extended in the axial direction from the axial end portion of the hollow shaft so as to be disposed on the radially outer side of the engagement recess by screwing of the ball screw nut.
An electric power steering device. In the electric power steering device according to claim 3,
The electric power steering device according to claim 1, wherein the thin plate portion is formed in an annular shape surrounding a radially outer side of the ball screw nut. In the electric power steering apparatus according to claim 4,
The electric power steering apparatus, wherein the restricting means is formed by engaging an engagement piece formed by the thin plate portion broken by the caulking and a side wall of the engagement recess. In the electric power steering apparatus according to any one of claims 3 to 5,
The thin plate portion is provided on a separate member that is non-rotatably attached to the hollow shaft at least in the screw loosening direction of the ball screw nut;
An electric power steering device. The electric power steering apparatus according to claim 1, wherein
The restricting means includes a first engagement portion extending in an axial direction from one of the ball screw nut or the hollow shaft, and a second engagement portion that engages with the first engagement portion on the other side. An electric power steering device characterized by comprising: The electric power steering apparatus according to claim 7,
Each axial end of the ball screw nut and the hollow shaft facing each other is formed with a flange portion extending outward in the radial direction,
The restricting means includes a shaft-like member that is attached to the flange portion and constitutes the first engaging portion, and the flange portion on the other side facing the flange portion on the side to which the shaft-like member is attached. Comprising a through hole that is provided and the second engaging portion is formed by inserting the shaft-shaped member;
An electric power steering device. The electric power steering apparatus according to claim 8,
The flange portion on the hollow shaft side is formed by coaxially screwing a flange member so as to be in a reverse screw relationship with the ball screw nut with respect to the hollow shaft. Formed in the shape of a long hole extending in the direction,
An electric power steering device. In the electric power steering apparatus according to claim 8 or 9,
The shaft-like member is attached to the flange portion by screwing;
An electric power steering device. The electric power steering apparatus according to claim 1, wherein
A cylindrical member attached to the hollow shaft so as to be axially movable and relatively non-rotatable;
The restricting means is formed by screwing one nut to each screw portion formed on the outer periphery of the ball screw nut and the outer periphery of the cylindrical member,
An electric power steering device. In the electric power steering device according to any one of claims 1 to 11,
A rolling bearing is interposed between the ball screw nut and the first housing that accommodates the ball screw nut, and an opening formed at an axial end of the first housing is formed on the second housing. It is blocked by attachment,
A flange portion extending radially outward is formed at an axial end of the ball screw nut on the hollow shaft side, and an insertion portion disposed in the first housing is formed in the second housing. ,
The electric power steering device according to claim 1, wherein a flange portion of the ball screw nut and an insertion portion of the second housing are brought into contact with each axial end surface of the rolling bearing. In the electric power steering device according to any one of claims 1 to 12,
The hollow shaft is a motor shaft housed in a motor housing, and the motor housing is formed with a mounting hole for a power feeding connector,
The restricting means is disposed at a position facing the attachment hole;
An electric power steering device.

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