JP2010096317A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device, reducing leakage of a lubricant without any increase in the outside diameter of a nut. <P>SOLUTION: This ball screw device includes: a screw shaft 20; a nut 30; a housing 10; a plurality of rolling bearings 50 in which inner rings 51 fixed to the nut 30 are rotatable to outer rings 52 fixed to the housing 10 through rolling elements 53; and an annular member 60 arranged axially side by side with the rolling bearings 50. The annular member 60 is provided with an annular member inner ring 61 fixed to the nut 30 and a pair of contact seals 63, 63 forming an oil passage C together with an annular member outer ring 62 fixed to the housing 10. The oil passage C communicates with a first greasing groove 61c formed in the annular member inner ring 61 and a second greasing groove 62c formed in the annular member outer ring 62. The first greasing groove 61c communicates with a first greasing hole 31 and the second greasing groove 62c communicates with a second greasing hole 74. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a feed screw device such as a ball screw device and a roller screw device, and more particularly to a ball screw device that rotates a nut.

Conventionally, in a feed screw device such as a ball screw device or a roller screw device that is used by rotating a nut, the structure for supplying grease or the like to the inside thereof includes a structure for supplying grease from the nut side and a screw shaft side. Are roughly divided into two structures for supplying grease.
Among these, a ball screw device having a structure for supplying grease from the nut side for the purpose of reducing the manufacturing cost required by the structure for supplying grease from the screw shaft side and ensuring reliable supply of grease to the inside of the nut is disclosed. (For example, Patent Document 1).

FIG. 8 is a cross-sectional view showing the configuration of the ball screw device described in Patent Document 1. As shown in FIG. As shown in FIG. 8, the ball screw device 100 described in Patent Document 1 is a screw mechanism that converts the rotation operation of the nut 110b into the reciprocation operation of the screw shaft 110a.
The end plate 104 is provided with a bearing mechanism 102 that rotatably supports the screw mechanism. The bearing mechanism 102 includes a bearing case 114, a cover member 115, and a cylindrical sleeve 116.

  The bearing case 114 is fixed to the end plate 104 with bolts 121b, and a cover member 115 is fixed to the cross head (not shown) side of the bearing case 114 with bolts 121a. Two bearings 117 and 117 are incorporated in the bearing case 114, and the sleeve 116 is rotatably supported by these bearings 117 and 117. A nut 110 b is accommodated in the sleeve 116.

  A nut flange 110c is provided on the rear end surface of the nut 110b. The nut flange 110c, the sleeve 116, and the pulley 113 provided on the rear end face side of the nut flange 110c are integrated by being connected by a bolt 121c. That is, the pulley 113, the sleeve 116, and the nut 110b are integrated. A timing belt is wound around the pulley 113, and the sleeve 116 and the nut 110b rotate when the pulley 113 is driven to rotate by a driving force of a servo motor (not shown).

Next, the greasing structure of the bearing mechanism will be described.
An annular oil groove 120 b is formed on the inner peripheral surface 116 b of the sleeve 116. An annular oil groove 120 a is also formed on the front end surface 116 a (end surface on the cover member 115 side) of the sleeve 116. Further, the sleeve 116 is formed with a grease supply hole 119b as a grease flow path so as to communicate the oil groove 120a and the oil groove 120b.

  Further, the nut 110b is provided with a plurality of grease supply holes 119c that similarly serve as grease flow paths so as to penetrate from the outer peripheral surface 110b1 to the internal ball circulation path. The greasing hole 119c is provided substantially at the center of the nut 110b, the position of the greasing hole 119c, the oil groove 120b provided on the inner peripheral surface 116b of the sleeve 116, and the greasing hole connected to the oil groove 120b. The position of 119b matches.

The rotation operation of the nut 110b and the sleeve 116 is supported by the bearings 117 and 117 as described above, but the lubricating oil sealed in the bearings 117 and 117 leaks to the outside (downward in the figure). A seal member 118c is disposed on the outer periphery of the sleeve 116 so as not to be ejected.
A minute gap is formed between the cover member 115 that fixes and holds the bearings 117 and 117 and the front end surface 116a of the sleeve 116 in which the oil groove 120a is formed. The cover member 115 is provided with a greasing hole 119a serving as a grease passage. The greasing hole 119a is provided so as to coincide with the position of the oil groove 120a provided on the front end surface 116a of the sleeve 116 and the greasing hole 119b connected to the oil groove 120a. Further, connecting parts (not shown) such as a grease tube and a grease nipple for supplying grease to the greasing hole 119a are provided at the end of the greasing hole 119a opposite to the sleeve 116.

Seal members 118 a and 118 b are disposed on the surface of the cover member 115 on the sleeve 116 side and the outer peripheral surface of the sleeve 116, respectively. The seal member 118a is provided on the inner peripheral side of the oil groove 120a. The seal member 118b is provided on the outer peripheral side of the oil groove 120a and at a position between the oil groove 120a and the bearing 117. The seal members 118a and 118b are for preventing leakage of grease supplied from the grease supply hole 119a. That is, the seal member 118a prevents leakage from the minute gap between the cover member 115 and the end surface of the sleeve 116 provided with the oil groove 120a toward the screw shaft 110a, thereby saving the amount of grease. Cost reduction and easy control of the amount of lubrication can be achieved. On the other hand, the seal member 118b prevents leakage toward the outer peripheral bearing 117, and thereby has an effect that there is no confusion with lubricating oil such as grease used for the bearings 117 and 117.
JP 2007-170425 A

However, in the ball screw device described in Patent Document 1, since the sleeve having the greasing hole is provided integrally with the nut, the cost is increased due to an increase in the number of parts, and the outer diameter is increased by the thickness of the sleeve. There is a problem such as.
Further, in the ball screw device described in Patent Document 1, the seal member is positioned only by the groove that accommodates the seal member. And it has sealing properties by pressing the seal member, but the O-ring or the like generally used as the seal member has a small cross-sectional area and presses by deforming the entire cross-sectional shape. It is necessary to increase (the size of the pressure against deformation). For this reason, if the amount of deformation when the seal member is pressed is large, the resistance of the sealed portion increases due to the rotation of the sleeve relative to the cover member. On the other hand, if the amount of deformation when the seal member is pressed is small, there is a problem that the lubricant (grease) is likely to leak to the outside when the seal is worn.

  Therefore, the present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide a ball screw device in which leakage of the lubricant is reduced without increasing the outer diameter of the nut.

A ball screw device according to claim 1 of the present invention for solving the above problems includes a screw shaft, a nut screwed to the screw shaft via a rolling element, and
A housing formed in a cylindrical shape with an inner diameter larger than the outer diameter of the screw shaft;
A ball screw device comprising: a plurality of rolling bearings housed in the housing, the inner ring fixed to the nut being rotatable with respect to the outer ring fixed to the housing via a rolling element,
An annular member inner ring arranged in the axial direction together with the inner ring and fixed to the nut; an annular member outer ring spaced apart from the outer ring of the annular member and arranged in the axial direction together with the outer ring and fixed to the housing; An annular member having a pair of annular contact seals that seals between the annular member inner ring and the annular member outer ring in the axial direction and forms an oil passage is provided in parallel with the rolling bearing in the axial direction. ,
The annular member inner ring has a first greasing groove that communicates the oil passage with a first greasing hole formed in the nut, and the annular member outer ring has a second grease supply that communicates with the outside. A second greasing groove that communicates the oil hole with the oil passage is formed.

Moreover, the ball screw device according to claim 2 of the present invention for solving the above-described problem is characterized in that the pair of contact seals forming the oil passage are pressed from the inside toward the outside. .
Further, in a ball screw device according to a third aspect of the present invention for solving the above-mentioned problem, an annular shape in which the first greasing groove and the first greasing hole are communicated with the annular member inner ring. The oil groove is formed.

Further, in a ball screw device according to a fourth aspect of the present invention for solving the above-mentioned problems, the second greasing hole is formed in a housing or a cover member provided in an axial direction to prevent entry of foreign matter. It is characterized by that.
Further, in a ball screw device according to claim 5 of the present invention for solving the above-described problem, a circle that communicates the second greasing groove and the second greasing hole to the annular member outer ring. An annular oil groove is formed.

According to the ball screw device of the present invention, since the annular member having the annular member inner ring, the annular member outer ring, and the pair of contact seals forming the oil passage is provided, lubrication can be performed without increasing the outer diameter of the nut. The leakage of the agent can be reduced.
Further, by positioning an annular oil groove between the first greasing groove and the first greasing hole, the nut and the annular member can be easily aligned without worrying about the phase difference. Can do. Further, by positioning an annular oil groove between the second greasing groove and the second greasing hole, the housing or the cover member and the annular member can be easily positioned without worrying about the phase difference. Can be combined.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view along the axial direction showing the configuration of the ball screw device according to the first embodiment of the present invention. 2A and 2B are cross-sectional views showing the configuration of the annular member in the first embodiment of the ball screw device according to the present invention, in which FIG. 2A is a cross-sectional view along the axial direction, and FIG. It is sectional drawing which follows the IIb line. 3A and 3B are diagrams showing the configuration of the cover member in the first embodiment of the ball screw device according to the present invention, wherein FIG. 3A is a side view and FIG. 3B is a front view. FIG. 4 is a cross-sectional view along the axial direction showing the configuration of the contact seal provided in the annular member in the ball screw device according to the first embodiment of the present invention.

  As shown in FIG. 1, the ball screw device 1 includes a housing 10, a screw shaft 20, a nut 30, a rolling bearing 50, an annular member 60, and a cover member 70. The screw shaft 20 and the nut 30 are screwed together via a plurality of rolling elements 40. The nut 30 is formed in a cylindrical shape with an inner diameter larger than the outer diameter of the screw shaft 20. A screw groove 30 a is formed on the inner peripheral surface of the nut 30 so as to face the screw groove 20 a formed in a spiral shape on the outer peripheral surface of the screw shaft 20. The rolling element 40 can roll in a rolling path formed by the thread groove 20a and the thread groove 30a.

Further, the nut 30 is formed with a greasing hole 31 as a first greasing hole that penetrates the thread groove 30a and the outer peripheral surface 30b.
A through hole 11 having an inner diameter larger than the outer diameter of the nut 30 is formed in the housing 10 in the axial direction. A nut 30 to which the screw shaft 20 is screwed is accommodated in the inner peripheral surface 11 a of the through hole 11 via the rolling bearing 50 and the annular member 60.

  The rolling bearing 50 accommodated in the through hole 11 of the housing 10 includes two or more rolling bearings 50, 50, 50,... (In the present embodiment and the drawings, the number of the rolling bearings 50 is four). Are arranged side by side so that these axial directions coincide with the axial direction of the screw shaft 20 (hereinafter, the axial direction of the screw shaft 20 is simply referred to as “axial direction”).

  The rolling bearings 50, 50, 50,... Are inner rings 51a, 51b, 51c,..., Outer rings 52a, 52b, 52c,..., Inner rings 51a, 51b, 51c,. 52a, 52b, 52c, and so on, and rolling elements 53a, 53b, 53c,. Are fixed to the outer peripheral surface 30 b of the nut 30, and the outer rings 52 a, 52 b, 52 c,... Are fixed to the inner peripheral surface 11 a of the through hole 11. A preload is applied to the rolling bearings 50, 50, 50,..., The relative positions of the inner ring 51 and the outer ring 52 of the rolling bearing 50 are fixed, and when a load is applied to the nut 30 from the outside. The inner ring 51 and the outer ring 52 relatively move in the axial direction within the range of elastic deformation. Since the annular member inner ring 61 and the annular member outer ring 62 of the annular member 60 are pressed against the inner ring 51 and the outer ring 52 of the rolling bearing 50, the positional deviation between the annular member inner ring 61 and the annular member outer ring 62 is rolling. This is the range of elastic deformation of the bearing 50. In addition, the sealing performance of grease can be maintained by setting the deformation amount when the contact seal 63 described later is pressed to be equal to or greater than the elastic deformation range of the rolling bearing 50.

In the ball screw device 1 having such a configuration, the screw shaft 20 and the nut 30 move relative to each other in the axial direction when the nut 30 rotatably engaged with the screw shaft 20 rotates with respect to the housing 10. It has become.
Moreover, the annular member 60 accommodated in the through-hole 11 similarly to the rolling bearings 50, 50, 50,... Includes an annular member inner ring 61 and an annular member outer ring 62. The annular member inner ring 61 abuts on the inner ring 51a and is fixed in the axial direction, and the annular member outer ring 62 abuts on the outer ring 52a and is fixed in the axial direction.

An outer ring 52a, 52b, 52c,... And an annular member outer ring 62 arranged in parallel with each other in the axial direction, and an end surface 12a of the annular step portion 12 formed on the inner peripheral surface 11a of the through hole 11, It is fixed in the axial direction so as to be sandwiched between the cover member 70 and contact the inner peripheral surface 11 a of the through hole 11.
On the other hand, the inner rings 51a, 51b, 51c,... And the annular member inner ring 61 that are arranged in parallel with each other in the axial direction include an end surface 32a of the annular step portion 32 formed on the outer peripheral surface 30b of the nut 30; It is fixed in the axial direction by being sandwiched between a lock nut 83 fixed to the outer peripheral surface 30b of the nut 30 via a spacer 81 and a pulley 82.

  The pulley 82 has an annular shape having an inner peripheral surface 82 a that fits to the outer peripheral surface 30 b of the nut 30, and is fixed in contact with the outer peripheral surface 30 b of the nut 30 by the axial biasing force of the lock nut 83. Yes. The nut 30 can be rotated by suspending the pulley 82 and a drive motor (not shown) with a drive belt or the like and driving the drive motor. Here, as a mechanism for rotating the nut 30, another rotational power transmission mechanism such as a gear may be used instead of the pulley 82, and a positioning key is used so that the pulley 82 and the nut 30 do not shift in the rotation direction. You may restrain using.

<Annular member>
As shown in FIG. 1, the annular member inner ring 61 is fixed by being sandwiched between the end surface 32a of the annular step 32 and the inner ring 51a. The annular member outer ring 62 is fixed by being sandwiched between the cover member 70 and the outer ring 52a.
Here, as shown in FIG. 2, the annular member 60 includes an annular member inner ring 61, an annular member outer ring 62, and a contact seal 63. Both the annular member inner ring 61 and the annular member outer ring 62 have an annular shape, and the outer diameter of the annular member inner ring 61 is set smaller than the inner diameter of the annular member outer ring 62 by a predetermined dimension.
The annular member inner ring 61 and the annular member outer ring 62 are provided with one or more greasing grooves or greasing holes as a path for grease or the like from the inner circumferential surfaces 61a and 62a to the outer circumferential surfaces 61b and 62b.

  Specifically, the annular member inner ring 61 has two pairs of grease feed grooves 61c in a direction opposite to each other on the surface along the line IIb-IIb as a first greasing groove that communicates the inner circumferential surface 61a and the outer circumferential surface 61b. Is formed. The annular member inner ring 61 is formed with an annular oil groove 61d along the inner peripheral surface 61a. The oil groove 61d communicates with the greasing groove 61c. That is, an annular member 60 that connects the greasing hole 32 and the greasing groove 61c to the ball screw device 1 regardless of the direction of the greasing hole 32 formed in the rotating nut 30 by the annular oil groove 61d. Assembled.

  On the other hand, the annular member outer ring 62 is formed with a greasing groove 62c as a second greasing groove that communicates the inner peripheral surface 62a and the outer peripheral surface 62b. One end of the greasing groove 62 c is formed at a position facing the outer peripheral surface 61 b of the annular member inner ring 61 and the inner peripheral surface 62 a of the annular member outer ring 62. The other end portion of the greasing groove 62c is bent in the annular member outer ring 62, and forms a groove portion that faces the outer circumferential surface 62b in the direction in which the cover member 70 is installed along the axial direction.

<Oil channel C>
A predetermined interval is secured between the outer peripheral surface 61 b of the annular member inner ring 61 and the inner peripheral surface 62 a of the annular member outer ring 62. A pair of contact seals 63, 63 that seal the gap in the axial direction are attached to the inner peripheral surface 62 a of the outer ring 62.
Thus, the oil passage C is formed by the greasing groove 61c and the oil groove 61d formed in the annular member inner ring 61, the resin groove 62c formed in the annular member outer ring 62, and the pair of contact seals 63, 63. Is formed.

<Cover member>
As shown in FIG. 3, the cover member 70 includes an annular main body 71 and a flange 72 formed on the outer peripheral surface of the main body 71. An annular oil groove 73 is formed on the outer peripheral edge of the main body 71.
The cover member 70 has a greasing hole 74 as a second greasing hole that passes through the main body 71 and the flange 72 and is formed in the vicinity of the outer edge of the main body 71. The greasing hole 74 is formed so as to communicate with the oil groove 73.

The cover member 70 makes the main body 71 on the side where the flange portion 72 is not formed abut on the annular member outer ring 62, and the flange portion 72 is in the axial end surface 10 a on the side where the annular member outer ring 62 of the housing 10 is provided. It is installed in the ball screw device 1 in contact with the
Thus, by forming the oil groove 73 in the main body 71, the oil can be assembled to the ball screw device 1 without worrying about the phase difference from the resin groove 62c formed in the annular member outer ring 62.

<Contact seal>
As shown in FIG. 4, as the contact seal 63, an annular contact seal used for a general rolling bearing or the like is used. The contact seal 63 has sealing properties by being installed so as to press in the axial direction. Specifically, one of the contact seals 63, 63 is fixed to the inner peripheral surface 62 a of the annular member outer ring 62, and the other of the contact seals 63 is in contact with the outer peripheral surface 61 a of the annular member inner ring 61. By using such a contact seal 63 as a seal member, the sliding resistance can be reduced even if the amount of deformation when pressing the contact seals 63 and 63 is large, since the elasticity is smaller than that of the O-ring. In addition, by using such a contact seal 63 as a seal member, even if the contact seal 63 is somewhat worn, the sealing performance can be maintained if the wear amount is equal to or less than the deformation amount. In addition, since the contact seal 63 has low elasticity, even if it is displaced in the axial direction as much as the elastic deformation of the rolling bearing 50 used by the annular member inner ring 61 and the annular member outer ring 62, the change in the pressure is small and an almost constant pressure is obtained. be able to.

Further, the pressing direction of the two contact seals 63 is set from the inner side (oil passage C) to the outer side (through hole 11) (see the arrow direction in FIG. 4). Therefore, it is possible to prevent the grease from flowing out from the inside to the outside. When a similar contact seal is used as a contact seal 63 for a rolling bearing or the like, it is pressed from the outside to the inside to prevent the entry of foreign matter from the outside.
Further, by arranging the annular member 60 formed with the oil passage C communicating with the greasing hole 31 for supplying grease to the screw shaft 20 in parallel with the rolling bearing 50 in the axial direction, the outer diameter of the nut 30 can be changed to a sleeve or the like. It will not be bigger than providing.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The ball screw device according to this embodiment is different from the first embodiment described above only in the formation position of the annular member outer ring and the greasing hole communicating with the greasing groove formed in the annular member outer ring. The description of the same components having the same reference numerals as those of the first embodiment will be omitted. FIG. 5 is a cross-sectional view along the axial direction showing the configuration of the ball screw device according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view showing the configuration of the annular member in the second embodiment of the ball screw device according to the present invention, where (a) is a cross-sectional view along the axial direction, and (b) is VIb- of (a). It is sectional drawing which follows a VIb line. FIG. 7 is a cross-sectional view taken along the axial direction for explaining an O-ring installation location in the second embodiment of the ball screw device according to the present invention.

As shown in FIG. 5, the ball screw device 1 according to this embodiment includes a greasing hole 13 that penetrates the outer peripheral surface (not shown) and the inner peripheral surface (the inner peripheral surface 11 a of the through hole 11) of the housing 10. (Second greasing hole) is formed in the housing 10. The annular member outer ring 62 is formed with an oil groove 62d that connects the greasing hole 13 and the greasing groove 62c.
The oil groove 62d is formed along the outer peripheral surface 62b of the annular member outer ring 62 as shown in FIGS. 6 (a) and 6 (b). As described above, the oil groove 62d is formed on the outer peripheral surface 62b of the annular member outer ring 62, so that the annular member 60 can be formed without worrying about the phase difference at the position where the greasing hole 13 and the greasing groove 62c communicate with each other. The ball screw device 1 can be assembled.

Note that the oil groove 61d formed in the annular member inner ring 61 and the oil groove 74 provided in the cover member 70 do not need to form the annular oil grooves 61d and 74 if the phases of the oil groove 61d are aligned with a positioning pin or the like. An oil passage can be formed.
Further, in preparation for a case where a slight amount of grease leaks from the fitting gap of the annular member inner ring 61, the annular member outer ring 62, the cover member 70, etc., an O-ring or the like is appropriately installed at a position indicated by an arrow in FIG. The sealing property may be further improved.

Further, when the housing 10 is thick, it is difficult to make the grease hole 13 that is long in the radial direction as in the second embodiment. On the other hand, if the greasing hole 74 is formed in the cover member 70 as in the first embodiment, the greasing route may be formed in the axial direction, and the processing is easy.
As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change and improvement can be performed. For example, the positional relationship between the rolling bearing 50 and the annular member 60 can be appropriately changed depending on the position of the greasing hole 31 formed in the nut 30. For example, a plurality of annular members 60 may be installed between the rolling bearings 50 provided. When a plurality of the greasing holes 31 are formed in the nut 30, two or more sets of the annular members 60 may be provided.

It is sectional drawing which follows the axial direction which shows the structure in 1st Embodiment of the ball screw apparatus which concerns on this invention. It is sectional drawing which shows the structure of the annular member in 1st Embodiment of the ball screw apparatus which concerns on this invention, (a) is sectional drawing which follows an axial direction, (b) is along the IIb-IIb line | wire of (a). It is sectional drawing. It is a figure which shows the structure of the cover member in 1st Embodiment of the ball screw apparatus which concerns on this invention, (a) is a side view, (b) is a front view. It is sectional drawing which follows the axial direction which shows the structure of the contact seal with which the annular member in 1st Embodiment of the ball screw apparatus which concerns on this invention was equipped. It is sectional drawing which follows the axial direction which shows the structure in 2nd Embodiment of the ball screw apparatus which concerns on this invention. It is sectional drawing which shows the structure of the annular member in 2nd Embodiment of the ball screw apparatus which concerns on this invention, (a) is sectional drawing which follows an axial direction, (b) is along the VIb-VIb line | wire of (a). It is sectional drawing. It is sectional drawing which follows the axial direction explaining the installation location of an O-ring in 2nd Embodiment of the ball screw apparatus which concerns on this invention. It is a figure which shows the structure of the conventional ball screw apparatus.

Explanation of symbols

1 Ball screw device 10 Housing 13 Greasing hole (second greasing hole)
20 Screw shaft 30 Nut 31 Greasing hole (first greasing hole)
40 Rolling elements 50 Rolling bearings 51 Inner ring 52 Outer ring 53 Rolling elements 60 Annular member 61 Annular member inner ring 61c Grease groove (first grease groove)
61d Oil groove 62 Ring member outer ring 62c Greasing groove (second greasing groove)
62d Oil groove 63 Contact seal 70 Cover member 73 Oil groove 74 Greasing hole (second greasing hole)
C oil passage

Claims (5)

A screw shaft, and a nut screwed onto the screw shaft via a rolling element,
A housing formed in a cylindrical shape with an inner diameter larger than the outer diameter of the screw shaft;
A ball screw device comprising: a plurality of rolling bearings housed in the housing, the inner ring fixed to the nut being rotatable with respect to the outer ring fixed to the housing via a rolling element,
An annular member inner ring arranged in the axial direction together with the inner ring and fixed to the nut; an annular member outer ring spaced apart from the outer ring of the annular member and arranged in the axial direction together with the outer ring and fixed to the housing; An annular member having a pair of annular contact seals that seals between the annular member inner ring and the annular member outer ring in the axial direction and forms an oil passage is provided in parallel with the rolling bearing in the axial direction. ,
The annular member inner ring has a first greasing groove that communicates the oil passage with a first greasing hole formed in the nut, and the annular member outer ring has a second grease supply that communicates with the outside. A ball screw device, characterized in that a second greasing groove that communicates the oil hole with the oil passage is formed.   The ball screw device according to claim 1, wherein the pair of contact seals forming the oil passage are pressed from the inside toward the outside.   3. The ball screw according to claim 1, wherein the annular member inner ring is formed with an annular oil groove that communicates the first greasing groove with the first greasing hole. apparatus.   The ball screw device according to any one of claims 1 to 3, wherein the second greasing hole is formed in a housing or a cover member provided in an axial direction to prevent intrusion of foreign matter.   The annular member outer ring is formed with an annular oil groove that communicates the second greasing groove and the second greasing hole. The ball screw device described.

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