JP2010190262A - Ball screw device and electric power steering device - Google Patents

Abstract

To provide a ball screw device and an electric power steering device that enable simple and easy mounting of a circulating member.
A ball screw nut 13 is formed with a pair of mounting holes 15a and 15b penetrating the ball screw nut 13 in the radial direction, and extends in the axial direction of the ball screw nut 13 so as to have a shaft thereof. Return holes 17 are formed as through holes that open in the direction end portions 13a and 13b and the mounting holes 15a and 15b. The return hole 17 penetrates the ball screw nut 13 in the axial direction, and the return path L2 is connected to the return hole 17 and the rolling path L1 by the circulation member 16 mounted in each of the mounting holes 15a and 15b. It is formed by doing. When the circulating member 16 is properly attached to the mounting holes 15a and 15b, the opening of the return hole 17 that opens to the axial ends 13a and 13b of the ball screw nut 13 is provided in the circulating member 16. A recess 30 is formed facing the portion 17a.
[Selection] Figure 2

Description

  The present invention relates to a ball screw device and an electric power steering device.

  Conventionally, a rack shaft is inserted and a hollow shaft that is rotated by a motor is provided, and the rotation of the hollow shaft is converted into a reciprocating motion of the rack shaft using a ball screw device as a conversion means, thereby assisting the steering system. There is a so-called rack assist type electric power steering device (EPS) that applies force (see, for example, Patent Document 1).

  Specifically, in such EPS, the ball screw device has a spiral shape formed by facing a screw groove threaded on the outer periphery of the rack shaft and a screw groove threaded on the inner periphery of the ball screw nut. It is formed by arranging a plurality of balls as rolling elements in the rolling path.

  In other words, each ball interposed between the rack shaft and the ball screw nut by being disposed in the rolling path is rotated while receiving the load as the ball screw nut rotates relative to the rack shaft. Roll in the path. Further, the ball screw device has a reflux path that short-circuits between two points set in the rolling path, and the ball that rolls in the rolling path as described above passes through the reflux path. As a result, the two points set in the rolling path are recirculated from the downstream side to the upstream side.

  As described above, the ball screw device converts the rotation of the ball screw nut into the axial movement of the rack shaft by infinite circulation of the balls rolling on the rolling path through the return path. In the EPS described in Patent Document 1, the ball screw nut fixed to the inner periphery of the motor shaft rotates together with the motor shaft, thereby converting the motor torque into an axial assist force to convert the rack shaft into the rack shaft. It is configured to communicate.

  In EPS, there is a strong demand for downsizing of its constituent parts. For this reason, in a ball screw device for EPS, a configuration is generally used in which the circulation path is formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in the radial direction.

  That is, for example, as shown in Patent Document 2, the ball screw nut is formed with a pair of mounting holes corresponding to two points set in the rolling path, and the ball screw nut is disposed in the axial direction. A return hole penetrating through and intersecting each mounting hole is formed. Then, the circulation member mounted in each mounting hole connects the return hole and the rolling path, thereby forming the above-described reflux path.

  However, in the configuration in which the circulation path is formed by the circulation member attached to such an attachment hole, proper attachment of the circulation member is a very important issue. That is, when the attachment position of the circulation member is shifted due to “tilt” or the like at the time of mounting, a step is generated in the connection portion between the circulation member and the through hole in the reflux path. Then, the step difference hinders smooth circulation of the ball in the reflux path, which may cause abnormal noise and vibration.

  In view of this point, in the ball screw device described in Patent Document 2, a localization pin is formed in the circulation member, and a localization hole corresponding to the localization pin is formed on the mounting hole side. The mounting hole is further formed with a locking groove for engaging a C-shaped ring as a locking element. And while ensuring the proper mounting | wearing of a circulating member by engaging a stereotactic pin and a stereotaxic hole, the position after the mounting | wearing is restrained by restraining a circulating member by the C-shaped ring latched by the latching groove | channel. It is the structure which suppresses generation | occurrence | production of deviation | shift.

JP 2006-256414 A JP 2007-78093 A

  However, since the ball screw device used in the EPS is small in itself, the above-described positioning pin, C-shaped ring, and the corresponding positioning hole and locking groove are extremely small. turn into. For this reason, it is difficult to say that it is practical to apply such a configuration to EPS in view of the workability and assemblability, and there is still room for improvement in this respect. It was.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a ball screw device and an electric power steering device in which the circulation member can be appropriately mounted simply and easily. is there.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a screw shaft having a screw groove formed on the outer periphery, a ball screw nut having a screw groove formed on the inner periphery, and the screw shaft. A plurality of balls disposed in a spiral rolling path in which a screw groove and a screw shaft of the ball screw nut are opposed to each other, and the ball screw nut includes a point between two points of the rolling path. A recirculation path that allows infinite circulation of each ball that rolls in the rolling path is formed, and the recirculation path is a mounting hole that penetrates the ball screw nut in the radial direction. In the ball screw device formed by attaching the circulation member to the rolling member, the circulation member connects the through hole and the rolling path that penetrate the ball screw nut in the axial direction and intersect the mounting hole. The circulation path is formed by the circulation member Is formed with a recess facing the opening of the through hole that is opened at the axial end of the ball screw nut in a state where the circulating member is properly attached to the mounting hole. To do.

  According to a second aspect of the present invention, there is provided a screw shaft having a screw groove formed on the outer periphery, a ball screw nut having a screw groove formed on the inner periphery, a screw groove of the screw shaft, and a screw of the ball screw nut. A plurality of balls disposed in a spiral rolling path facing the shaft, and the ball screw nut is short-circuited between two points of the rolling path to Is formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in a radial direction. In the ball screw device, the ball screw nut is formed with a through-hole extending in the axial direction of the ball screw nut and opening in the axial end portion and the mounting hole, and The circulating member is properly installed in the mounting hole Wherein a recess facing the opening of the through hole is formed, and the gist in state.

  According to each of the above configurations, whether or not the circulation member is properly attached to the mounting hole by visually checking the concave portion formed in the circulation member through the opening of the through hole or using a jig. Can be easily determined. In particular, in the first aspect of the present invention, a through hole that originally exists in the ball screw nut as one element constituting the reflux path is used for mounting confirmation using the recess formed in the circulation member. Therefore, it is not necessary to add a new configuration on the ball screw nut side. And the positional relationship between the through-holes is the largest element that defines the proper mounting state of the circulation member. Therefore, by adopting such a configuration, it is possible to perform simple and highly accurate mounting confirmation.

The gist of the invention described in claim 3 is that the outer diameter of the recess is smaller than the inner diameter of the through hole.
The gist of the invention described in claim 4 is that the shape of the recess facing the opening is the same as the cross-sectional shape of the through hole.

  According to each configuration described above, it is easier to determine whether or not the circulation member is properly attached. Specifically, for example, when the mounting state of the circulation member is optimum, the degree of deviation from the optimum state can be easily confirmed by setting the center positions of the through hole and the recess to coincide with each other. Will be able to.

The gist of the invention described in claim 5 is that it comprises a locking means for locking the circulating member by being inserted into the opening of the through hole and engaging with the recess.
In other words, even after proper mounting such as centrifugal force generated by the rotation of the ball screw nut, various forces that deteriorate the mounting state act on the circulating member. However, according to the above configuration, the proper mounting state of the circulation member can be maintained simply and easily.

The gist of the invention described in claim 6 is that caulking balls are used as the locking means.
According to the above configuration, the configuration can be further simplified. In addition, it can be securely fixed by caulking.

  The invention according to claim 7 is a screw shaft in which a screw groove is screwed on the outer periphery, a ball screw nut in which a screw groove is screwed on the inner periphery, a screw groove in the screw shaft, and a screw in the ball screw nut. A plurality of balls disposed in a spiral rolling path facing the shaft, and the ball screw nut is short-circuited between two points of the rolling path to Is formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in a radial direction. In the ball screw device, the circulating member forms the return path by connecting the rolling path and the through hole that passes through the ball screw nut in the axial direction and intersects the mounting hole. And the circulating member includes a ball screw nut. The protrusion which is fitted in the opening of the through hole opened in the direction end portion is formed, and the gist.

  According to an eighth aspect of the present invention, there is provided a screw shaft having a screw groove threaded on the outer periphery, a ball screw nut having a screw groove threaded on the inner periphery, a screw groove of the screw shaft, and a screw of the ball screw nut. A plurality of balls disposed in a spiral rolling path facing the shaft, and the ball screw nut is short-circuited between two points of the rolling path to Is formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in a radial direction. In the ball screw device, the ball screw nut is formed with a through-hole extending in the axial direction of the ball screw nut and opening in the axial end portion and the mounting hole, and The circulating member is properly installed in the mounting hole Wherein the protrusion fits into the opening of the through hole is formed, and the gist in state.

According to each said structure, while being able to carry out structure simple and easily, a circulating member can be appropriately mounted | worn with respect to an attachment hole, and the appropriate mounting state can be maintained.
The gist of the invention described in claim 9 is an electric power steering device including the ball screw device according to any one of claims 1 to 8.

  According to the above configuration, the circulation member can be appropriately mounted easily and simply, and the stable operation of the ball screw device can be ensured. As a result, it is possible to provide an electric power steering apparatus with excellent steering feeling while suppressing generation of sound and vibration.

  According to the present invention, it is possible to provide a ball screw device and an electric power steering device that enable simple and easy mounting of the circulating member with a simple configuration.

Sectional drawing which shows schematic structure of an electric power steering apparatus (EPS). The expanded sectional view near a ball screw device. The perspective view which shows the aspect of the assembly | attachment of the circulation member to a ball screw nut. Sectional drawing of a ball screw nut. (A) (b) The side view of a circulation member, (c) The bottom view of a circulation member. The schematic diagram which shows the shape of the recessed part which faces the opening part of a return hole. Explanatory drawing which shows the aspect of a mounting | wearing confirmation of the circulation member using a jig | tool. Sectional drawing which shows the fixation structure of the circulation member of another example. The side view of the circulation member of another example. The top view of the ball screw nut of another example. Sectional drawing which shows the aspect (and fixing structure) of mounting confirmation of the circulation member of another example. Sectional drawing which shows the fixation structure of the circulation member of another example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the 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 It is accommodated and supported so that it can move 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.

  More specifically, the motor 4 of the present 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. 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.

  Further, the rack shaft 3 of the present embodiment is configured as a screw shaft by screwing a screw groove 11 on the outer periphery thereof. The ball screw device 5 of the present embodiment is formed by screwing a ball screw nut 13 to the rack shaft 3 via a plurality of balls 12.

  Specifically, as shown in FIG. 2, a screw groove 14 corresponding to the screw groove 11 on the rack shaft 3 side is formed on the inner periphery of the ball screw nut 13 formed in a substantially cylindrical shape. The ball screw nut 13 is externally fitted to the rack shaft 3 so that the screw groove 11 faces the screw groove 11 on the rack shaft 3 side. Each ball 12 is disposed in a spiral rolling path L1 formed by the two screw grooves 11 and 14 facing each other.

  Further, the ball screw nut 13 is formed with a reflux path L2 that opens to two locations (connection points P1, P2) in the screw groove 14. 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 12 interposed in the rolling path L1 between the rack shaft 3 and the ball screw nut 13 receives the load by the relative rotation of the ball screw nut 13 with respect to the rack shaft 3, and the rolling path L1. Roll inside. Further, each ball 12 that has rolled in the rolling path L1 further passes through the return path L2 formed in the ball screw nut 13, so that two connection points P1 set in the rolling path L1. , P2 move from the downstream side to the upstream side. Then, the ball screw device 5 converts the rotation of the ball screw nut 13 into the axial movement of the rack shaft 3 as each ball 12 rolling on the rolling path L1 circulates infinitely via the reflux path L2. It is possible.

  Here, in the ball screw device 5 of the present embodiment, the reflux path L2 is formed by attaching the circulation member 16 to a pair of mounting holes 15 (15a, 15b) that penetrate the ball screw nut 13 in the radial direction. (See FIG. 3).

  More specifically, as shown in FIG. 4, the ball screw nut 13 is provided with mounting holes 15a and 15b at positions corresponding to the two connection points P1 and P2, respectively. The ball screw nut 13 is formed with a return hole 17 that passes through the ball screw nut 13 in the axial direction and intersects the mounting holes 15a and 15b. In the ball screw device 5 of the present embodiment, the circulation member 16 attached to each of the mounting holes 15a and 15b connects the return hole 17 and the rolling path L1, thereby forming the above-described reflux path L2. It has become so.

  More specifically, as shown in FIGS. 5A to 5C, the circulating member 16 includes an insertion portion 18 inserted into the mounting hole 15 and an end portion on the opposite side of the insertion portion 18 (see FIG. 5). 5 (a) and (b), and a flange portion 20 that is exposed on the peripheral surface 13s of the ball screw nut 13 by being formed at the upper end portion (see FIG. 3). And each ball 12 which rolled in the said rolling path L1 is set to the edge part (insertion end 18a, lower edge part in Fig.5 (a) (b)) on the opposite side to the flange part 20. As shown in FIG. A scooping portion 21 is formed for scooping up from the rolling path L1.

  As shown in FIG. 5B, in this embodiment, the insertion portion 18 has an opening at the insertion end 18a where the scooping portion 21 is formed, and a flange portion 20 is formed from the insertion end 18a side. A curved groove 22 extending toward the base end side is formed, and a terminal portion 22 a of the curved groove 22 is formed in an arc shape corresponding to the cross-sectional shape of the return hole 17. The circulating member 16 of the present embodiment is such that the position of the end portion 22a of the curved groove 22 and the position of the return hole 17 opening in the mounting hole 15 coincide with each other when the circulating member 16 is mounted in the mounting hole 15. Further, by forming the insertion portion 18, the curved groove 22 functions as a connection path L <b> 3 that connects the rolling path L <b> 1 and the return hole 17.

  In FIG. 5B, a broken line M indicates a reference position of the return hole 17 at the time of mounting (corresponding to a recess 30 described later, see FIG. 5A). Further, in the present embodiment, the peripheral surface 13s of the ball screw nut 13 is formed with a recess 23 corresponding to the flange portion 20 of the circulation member 16 so as to surround the mounting holes 15a and 15b (see FIG. 3 and FIG. 3). (See FIG. 4). And each circulating member 16 is in a state where the exposed surface 20s of the flange portion 20 is flush with the peripheral surface 13s of the ball screw nut 13 by caulking the flange portion 20 disposed in the recess 23. The mounting holes 15a and 15b are mounted.

  As shown in FIG. 2, in this embodiment, the axial end portion 13 a of the ball screw nut 13 is provided with an annular plate-like flange 24 protruding in the radial direction, and the axial direction of the motor shaft 6. An annular plate-like flange 25 corresponding to the flange 24 of the ball screw nut 13 is also provided at the end 6a. In the present embodiment, the flange 25 on the motor shaft 6 side is formed by screwing a flange member 26 formed separately from the motor shaft 6 to the axial end portion 6 a of the motor shaft 6. ing. In the present embodiment, these flanges 24 and 25 are fastened by bolts 27 to connect the ball screw nut 13 constituting the rotation input portion of the ball screw device 5 and the motor shaft 6 as the motor output shaft. The

  That is, in the EPS 1 of the present embodiment, the rotation of the motor 4 that is a drive source is caused by the ball screw nut 13 connected coaxially with the motor shaft 6 to rotate integrally with the motor shaft 6 to the ball screw device 5. Entered. In the ball screw device 5, the EPS 1 converts the rotation of the motor 4 into the axial movement of the rack shaft 3, thereby applying an axial pressing force based on the motor torque as an assist force to the steering system. It has become.

(Confirmation of circulation member mounting and fixing structure)
Next, the mounting confirmation and fixing structure of the circulation member in the present embodiment will be described.
As described above, in a configuration in which the return path is formed by the circulation member attached to the mounting hole of the ball screw nut, proper attachment of the circulation member is extremely important. In particular, in the configuration in which the circulation path 16 is formed by connecting the circulation member 16 between the return hole 17 and the rolling path L1 that intersect the mounting holes 15a and 15b as in the present embodiment, the circulation Due to the displacement of the attachment position of the member 16, a step is generated in the connection portion between the connection path L <b> 3 formed in the circulation member 16 and the return hole 17. And this level | step difference prevents the smooth distribution | circulation of the ball | bowl 12 in the recirculation | reflux path L2, and there exists a possibility that it may become a generation | occurrence | production factor of abnormal noise and a vibration by extension.

  In consideration of this point, when the circulating member 16 is properly attached to the mounting hole 15 (15a, 15b), the end of the ball screw nut 13 in the axial direction ( 13a, 13b) is formed with a recess 30 facing the opening 17a of the return hole 17 as a through hole (see FIGS. 2, 3, and 5A). In the present embodiment, it is possible to confirm whether or not the circulation member 16 is properly mounted, that is, whether or not the mounting position in the mounting hole 15 is correct, by using the recess 30. It has become.

  More specifically, as shown in FIGS. 2 and 3 and FIGS. 5A to 5C, the recess 30 has an insertion portion 18 of the circulation member 16, more specifically, the circulation member 16 has mounting holes 15a and 15b. Is formed on the outer side surface 18b disposed on the outer side in the axial direction of the ball screw nut 13. The “outer surface 18b” is a side surface of the circulating member 16 mounted in the mounting hole 15a and is disposed on the axial end portion 13b side (left side in FIG. 2) of the ball screw nut 13. The circulation member 16 attached to 15b is a side surface disposed on the axial end portion 13a side (left side in FIG. 2) of the ball screw nut 13. And the recessed part 30 respond | corresponds to the terminal part 22a of the curved groove | channel 22 which is formed in the back surface (inner side surface 18c, refer FIG.5 (b)) of the said outer side surface 18b, and functions as the said connection path L3 in this outer side surface 18b. It is formed in the position to do.

  That is, the end portion 22a of the curved groove 22 constituting the connection portion with the return hole 17 in the connection path L3 is located at the position of the return hole when the circulation member 16 is properly mounted in the mounting hole 15. Matches 17. And in this embodiment, the recessed part 30 is formed in the position corresponding to this termination | terminus part 22a, The opening part 17a of the return hole 17 opened to the axial direction edge part (13a, 13b) of the ball screw nut 13 is made. Thus, the position of the concave portion 30 can be confirmed, that is, it can be confirmed whether or not the connection path L3 and the return hole 17 are connected without a step.

  More specifically, as shown in FIG. 6, the recess 30 of the present embodiment has a shape that faces the opening 17 a of the return hole 17 that opens to the axial end 13 b (13 a) of the ball screw nut 13. It is formed in a circular shape so as to have the same shape as the hole 17. Further, the recess 30 is formed so that the outer diameter D1 is smaller than the inner diameter D2 of the return hole 17. The recess 30 is formed so that the circular center O facing the opening 17a coincides with the center O ′ of the return hole 17 when the mounting state of the circulation member 16 is optimal.

  Further, in the present embodiment, confirmation of mounting of the circulation member 16 using the recess 30 is performed by inserting a shaft-shaped jig 31 from the opening 17a of the return hole 17, as shown in FIG.

  Specifically, the jig 31 has an outer diameter D3 that is substantially equal to the inner diameter D2 of the return hole 17 (specifically, slightly smaller), and at its insertion end (right end in the figure), A small-diameter portion 32 that fits into the concave portion 30 formed in the circulation member 16 is formed. Further, a flange 33 is formed at the base end of the jig 31 (the left end portion in the figure). In this embodiment, the protrusion amount h of the jig 31 inserted into the return hole 17 from the opening 17a, that is, the height from the axial end 13b (13a) of the ball screw nut 13 to the flange 33 is set. By measuring, it is determined whether or not the circulation member 16 is properly attached.

  That is, when the mounting state of the circulation member 16 with respect to the attachment hole 15 (15a, 15b) is not appropriate, the concave portion 30 formed in the circulation member 16 is not located at the position facing the opening 17a of the return hole 17. Therefore, in such a case, the protruding amount h of the jig 31 inserted into the return hole 17 from the opening 17a is that the small-diameter portion 32 cannot be fitted into the recess 30, so that the circulating member 16 is properly mounted. Therefore, it is possible to determine that the mounting state of the circulation member 16 is not appropriate.

  Further, in the present embodiment, the ball screw nut 13 that has been determined that the circulating member 16 is properly mounted as a result of the above-described mounting confirmation is provided as a locking means in the return hole 17 from its opening 17a. Is inserted into the recess 30 of the circulation member 16. As the caulking ball 12a, a ball having a larger diameter than the ball 12 as the rolling element is used. The ball 12a engaged with the recess 30 is caulked to lock the circulation member 16 in the mounting hole 15 (15a, 15b) (see FIG. 2).

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The ball screw nut 13 is formed with a pair of mounting holes 15 (15a, 15b) that penetrates the ball screw nut 13 in the radial direction, and passes through the ball screw nut 13 in the axial direction. A return hole 17 intersecting with the mounting holes 15a and 15b is formed. The reflux path L2 is formed by connecting the return hole 17 and the rolling path L1 by the circulation member 16 mounted in each of the mounting holes 15a and 15b. The circulating member 16 is opened to the axial end portions (13a, 13b) of the ball screw nut 13 when the circulating member 16 is properly attached to the mounting holes 15 (15a, 15b). A recess 30 facing the opening 17a of the return hole 17 is formed.

  According to the above configuration, the concave member 30 formed in the circulation member 16 is visually confirmed through the opening 17a of the return hole 17 or by a jig, so that the circulation member 16 is attached to the mounting hole 15 (15a, 15b). It is possible to easily determine whether or not the device is properly mounted.

  (2) The recess 30 is formed in a circular shape so that the shape facing the opening 17 a of the return hole 17 is the same as that of the return hole 17. The outer diameter D1 of the recess 30 is formed to be smaller than the inner diameter D2 of the return hole 17.

  According to the said structure, determination of whether the mounting state of the circulation member 16 is appropriate becomes easier. That is, for example, when the mounting state of the circulation member 16 is optimal, the degree of deviation from the optimal state can be easily confirmed by setting both the centers O and O ′ to coincide with each other. It becomes like this.

  (3) A caulking ball 12 a as a locking means inserted into the return hole 17 from the opening 17 a is engaged with the recess 30. The circulating member 16 is locked in the mounting holes 15 (15a, 15b) by caulking the engaged balls 12a.

  In other words, the circulation member 16 has various forces that deteriorate the mounting state even after it is properly mounted on the mounting hole 15 (15a, 15b), such as a centrifugal force generated by the rotation of the ball screw nut 13. Works. However, according to the above configuration, the proper mounting state of the circulation member 16 can be maintained simply and easily. Moreover, it can be set as a simpler structure by using the ball | bowl 12a, and it can fix reliably by crimping further.

In addition, you may change the said embodiment as follows.
In the above embodiment, the recess 30 is formed in a circular shape so that the shape facing the opening 17a of the return hole 17 is the same as that of the return hole 17, but the recess 30 and the return hole 17 are not necessarily formed. And the shape may not be the same. That is, it is only necessary to determine whether or not the mounting state of the circulation member 16 is appropriate by checking the recess 30 through the opening 17a of the return hole 17.

  -Moreover, although the outer diameter D1 of the recessed part 30 was formed so that it might become smaller than the internal diameter D2 of the return hole 17, it does not necessarily restrict to this. That is, it is only necessary to determine whether or not the mounting state of the circulation member 16 is appropriate by checking the recess 30 through the opening 17a of the return hole 17.

  In the above embodiment, the caulking balls 12 a are used as the locking means for locking the circulation member 16 by being inserted into the opening 17 a of the return hole 17 and engaging with the recess 30. However, the present invention is not limited to this. For example, a member other than the ball 12a, such as a shaft-like body such as the jig 31, may be used as the locking means. Further, “crimping” is not necessarily performed.

  In addition, in the above embodiment, the recessed portion 30 facing the opening 17a of the return hole 17 is formed in the circulating member 16, so that the mounting state of the circulating member 16 can be confirmed via the opening 17a. Instead of 30, a protrusion may be formed.

  That is, as shown in FIG. 8, on the outer surface 18 b of the circulation member 36, the protrusion that fits into the opening 17 a of the return hole 17 when the circulation member 36 is attached to the attachment hole 15 (15 a, 15 b). 37 may be configured. With such a configuration, the circulation member 36 can be properly mounted on the mounting hole 15 (15a, 15b) and the proper mounting state can be maintained simply and easily. In this case, the protrusion 37 may be formed in a flat hemispherical shape. Thereby, the mounting | wearing to the attachment hole 15 (15a, 15b) becomes easy.

  In the above embodiment, the ball screw nut 13 is formed with a return hole 17 that passes through the ball screw nut 13 in the axial direction and intersects each of the mounting holes 15a and 15b, and each of the mounting holes 15a and 15b. Each circulation member 16 attached to the pipe connects the return hole 17 and the rolling path L1 to form a reflux path L2. However, the present invention is not limited to this, and the present invention can also be applied to a ball screw nut in which the return path L2 is formed by one circulation member.

  Specifically, as shown in FIGS. 9 to 11, the circulation member 40 has a base end side (see FIG. 9) between a pair of insertion portions 43 a and 43 b inserted into the mounting holes 42 a and 42 b of the ball screw nut 41. A communication portion 44 that communicates at the middle and upper ends) is provided, and a communication path L4 that extends along the longitudinal direction (left-right direction in FIG. 9) is formed in the communication portion 44. And, by the connecting path L4 formed in the connecting portion 44, the base end from the insertion end (the lower end in FIG. 9, the end on the side where the scooping portion 21 is formed) in each insertion portion 43a, 43b. Each connection path L3 extended to the side is communicated.

  In addition, a communication concave portion 45 corresponding to the communication portion 44 of the circulation member 40 is formed on the peripheral surface 41 s of the ball screw nut 41 so as to communicate between the insertion portions 43 a and 43 b. That is, the circulation member 40 has its insertion portions 43a and 43b inserted into the corresponding mounting holes 42a and 42b, and the communication portion 44 formed between the insertion portions 43a and 43b is attached to the communication recess 45. Thus, the ball screw nut 41 is attached.

  The mounting confirmation and fixing structure disclosed in the above-described embodiments and modifications can also be applied to the ball screw nut 41 having a configuration in which the reflux path L2 is formed by mounting the circulation member 40.

  That is, the ball screw nut 41 includes a through hole 46 that extends in the axial direction of the ball screw nut 41 and opens to the axial end portion 41b of the ball screw nut 41 and the mounting hole 42a. A nut 41 is formed with an axial end 41a and a through hole 47 that opens into the mounting hole 42b. The outer surface 40b of the circulation member 40 faces the opening 46a of the through hole 46 when the circulation member 40 is properly attached to the mounting holes 42a and 42b (and the communication recess 45). A recess 48 and a recess 49 facing the opening 47a of the through hole 47 are formed.

  By configuring in this way, the concave portions 48 and 49 formed in the circulation member 40 (the outer surface 40b thereof) can be visually observed through the openings 46a and 47a of the through holes 46 and 47, as in the above embodiment, or By checking with the jig, it can be easily determined whether or not the circulation member 40 is properly mounted in the mounting holes 42a and 42b (and the communication recess 45). Further, a ball or the like is inserted as a locking means from each through-hole 46, 47 (opening 46a, 47a) and engaged with each recess 48, 49, whereby the circulation member 40 is attached to the mounting holes 42a, 42b (and It is possible to lock the connecting recess 45). As a result, the proper mounting state of the circulation member 40 can be easily maintained with a simple configuration.

  In the case of such a so-called integrated circulation member 40, the through holes 46 and 47 and the recesses 48 and 49 do not necessarily correspond to the position of the communication path L4. In other words, when the circulation member 40 is properly mounted, the recesses 48 and 49 may have any configuration desired for the corresponding through holes 46 and 47 (the opening 46a and the opening 47a). Further, if only mounting confirmation is taken into consideration, a configuration may be provided that includes either a combination of the through hole 46 and the recess 48 or a combination of the through hole 47 and the recess 49.

  Furthermore, as in the circulation member 50 shown in FIG. 12, instead of the recesses 48 and 49 in the circulation member 40, the circulation member 50 is properly attached to the mounting holes 42a and 42b (and the communication recess 45). In this case, the protrusions 51 that fit into the through holes 46 and 47 (the opening 46a and the opening 47a) may be formed. With such a configuration, it is possible to easily ensure proper mounting of the circulation member 50 with a simple configuration, and to maintain the proper mounting state.

  In the above embodiment, the present invention is embodied in the ball screw device 5 for EPS. However, the present invention may be applied to applications used for purposes other than EPS.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 2 ... Housing, 3 ... Rack shaft, 4 ... Motor, 5 ... Ball screw apparatus, 6 ... Motor shaft, 6a ... Axial end part, 11, 14 ... Screw groove, 12, 12a ... Ball, 13, 41 ... Ball screw nut, 13a, 13b, 41a, 41b ... End in axial direction, 13s, 41s ... Peripheral surface, 15 (15a, 15b), 42a, 42b ... Mounting hole, 16, 36, 40, 50 ... circulating member, 17 ... return hole, 17a, 46a, 47a ... opening, 18, 43a, 43b ... insertion part, 18a ... insertion end, 18b, 40b ... outer side, 18c ... inner side, 20 ... flange , 21 ... scooping part, 22 ... curved groove, 22a ... terminal part, 23 ... recess, 24, 25 ... flange, 26 ... flange member, 27 ... bolt, 30, 48, 49 ... recess, 31 ... jig 32 ... Small diameter portion, 33 ... Flange, 37, 51 ... Projection, 44 ... Connection portion, 45 ... Connection recess, 46, 47 ... Through hole, L1 ... Rolling path, L2 ... Return path, L3 ... Connection path, L4 ... communication path, P1, P2 ... connection point, h ... projection amount, D1, D3 ... outer diameter, D2 ... inner diameter, O, O '... center.

Claims (9)

A screw shaft having a screw groove on the outer periphery, a ball screw nut having a screw groove on the inner periphery, and a spiral shape in which the screw groove of the screw shaft and the screw shaft of the ball screw nut are opposed to each other. And a plurality of balls disposed in the rolling path, and the ball screw nut is short-circuited between the two points of the rolling path and infinitely circulates each ball rolling in the rolling path. In the ball screw device formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in the radial direction, the reflux path is formed.
The circulating member forms the return path by connecting the rolling path with a through hole that passes through the ball screw nut in the axial direction and intersects the mounting hole,
The circulation member is formed with a recess facing the opening of the through hole opened at the axial end of the ball screw nut in a state where the circulation member is properly attached to the mounting hole. A ball screw device characterized by the above. A screw shaft having a screw groove on the outer periphery, a ball screw nut having a screw groove on the inner periphery, and a spiral shape in which the screw groove of the screw shaft and the screw shaft of the ball screw nut are opposed to each other. And a plurality of balls disposed in the rolling path, and the ball screw nut is short-circuited between the two points of the rolling path and infinitely circulates each ball rolling in the rolling path. In the ball screw device formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in the radial direction, the reflux path is formed.
The ball screw nut is formed with a through hole extending in the axial direction of the ball screw nut and opening in the axial end and the mounting hole.
The ball screw device, wherein the circulation member is formed with a recess facing the opening of the through hole in a state where the circulation member is properly attached to the mounting hole. In the ball screw device according to claim 1 or 2,
The outer diameter of the recess is smaller than the inner diameter of the through-hole,
A ball screw device characterized by the above. In the ball screw device according to any one of claims 1 to 3,
The concave portion has the same shape as the cross-sectional shape of the through hole as it faces the opening,
A ball screw device characterized by the above. In the ball screw device according to any one of claims 1 to 4,
A ball screw device comprising: a locking means for locking the circulating member by being inserted into the opening of the through hole and engaging with the recess. In the ball screw device according to claim 5,
A ball screw device using a caulking ball as the locking means. A screw shaft having a screw groove on the outer periphery, a ball screw nut having a screw groove on the inner periphery, and a spiral shape in which the screw groove of the screw shaft and the screw shaft of the ball screw nut are opposed to each other. And a plurality of balls disposed in the rolling path, and the ball screw nut is short-circuited between the two points of the rolling path and infinitely circulates each ball rolling in the rolling path. In the ball screw device formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in the radial direction, the reflux path is formed.
The circulating member forms the return path by connecting the rolling path with a through hole that passes through the ball screw nut in the axial direction and intersects the mounting hole,
The ball screw device, wherein the circulation member is formed with a protrusion that fits into an opening of the through hole that is opened at an axial end of the ball screw nut. A screw shaft having a screw groove on the outer periphery, a ball screw nut having a screw groove on the inner periphery, and a spiral shape in which the screw groove of the screw shaft and the screw shaft of the ball screw nut are opposed to each other. And a plurality of balls disposed in the rolling path, and the ball screw nut is short-circuited between the two points of the rolling path and infinitely circulates each ball rolling in the rolling path. In the ball screw device formed by attaching a circulation member to a mounting hole that penetrates the ball screw nut in the radial direction, the reflux path is formed.
The ball screw nut is formed with a through hole extending in the axial direction of the ball screw nut and opening in the axial end and the mounting hole.
The ball screw device, wherein the circulation member is formed with a protrusion that fits into the opening of the through hole in a state in which the circulation member is properly attached to the mounting hole.   An electric power steering apparatus comprising the ball screw device according to any one of claims 1 to 8.