JP2019143762A - Ball screw device and steering device - Google Patents

Abstract

To provide a ball screw device which can impart a necessary preload to a bearing device, and a steering device.SOLUTION: A double-row bearing device 10 comprises: an outer ring 120 having a first outer ring raceway 121 in which a plurality of first rolling bodies 111 belonging to a row near a ball nut part 81 roll, and a second outer ring raceway 122 in which second rolling bodies 112 belonging to a row separated from the ball nut part 81 roll; a first inner ring 130 integrally formed at an external peripheral face of a cylinder part 82, and having a first inner ring raceway 131; and a second inner ring 140 fit to the external peripheral face of the cylinder part 82, and having a second inner ring raceway 141. A ball screw part 5 comprises a preload impartment part 11 for imparting a preload to the double-row bearing device 10 by pressing the first inner ring 130 and the second inner ring 140 to the ball nut part 81 side, and the cylinder part 82 comprises a circular-disc shaped groove part 84 formed at an internal peripheral face of a region in which the first inner ring 130 is formed at an external peripheral face.SELECTED DRAWING: Figure 3

Description

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

  Ball screw shaft member having spiral ball groove on outer peripheral surface, ball nut having spiral ball groove on inner peripheral surface, ball groove formed on ball screw shaft member and ball groove formed on ball nut There is known a ball screw device including a plurality of rolling balls that roll between the two.

  In Patent Document 1, in a ball screw device in which an outer peripheral surface of a ball nut is rotatably supported via a double row bearing device with respect to an inner peripheral surface of a housing, a part of the inner ring of the double row bearing device is a ball nut. There is disclosed a technique in which the outer peripheral surface is integrally provided. The ball screw device described in Patent Document 1 includes a first inner ring in which an inner ring of a double row bearing device is integrally formed with a ball nut (nut), and a second inner ring that is separate from the ball nut. The two inner rings are fixed to the ball nuts with bolts.

US Patent Application Publication No. 2014/0096633

  The technology described in Patent Document 1 is such that the second inner ring is pressed against the first inner ring by a tightening force when the second inner ring is fixed to the ball nut with a bolt, and the double row bearing device is preloaded in the axial direction. Is granted. On the other hand, the first inner ring formed integrally with the ball nut has higher rigidity and is less likely to deform than the second inner ring, which is separate from the ball nut. Is difficult.

  It is an object of the present invention to provide a ball screw device and a steering device that can apply a preload necessary for a bearing device.

  The ball screw device of the present invention includes a housing, a ball screw shaft member having a spiral outer peripheral ball rolling groove formed on the outer peripheral surface, and a ball having a spiral inner peripheral ball rolling groove formed on the inner peripheral surface. A nut having a nut portion and a cylindrical portion adjacent to the ball nut portion in the axial direction, and a plurality of rolling balls arranged between the outer peripheral ball rolling groove and the inner peripheral ball rolling groove And a double row bearing device that rotatably supports the cylindrical portion with respect to the housing.

  The double row bearing device includes two rows of rolling elements arranged in parallel in the axial direction, and a first outer ring on which a plurality of first rolling elements belonging to a row close to the ball nut portion of the two rows of rolling elements are rolled. An outer ring having a raceway and a second outer ring raceway on which a second rolling element belonging to a row away from the ball nut portion of the two rows of rolling elements rolls, and an outer peripheral surface of the cylindrical portion are integrally formed. A first inner ring having a first inner ring raceway on which the plurality of first rolling elements roll at a position facing the first outer ring raceway, and fitted to an outer peripheral surface of the cylindrical portion, and the second outer ring raceway, A second inner ring having a second inner ring raceway on which the plurality of second rolling elements roll at opposing positions. The ball screw device includes a preload applying portion that applies a preload to the double row bearing device by pressing the first inner ring and the second inner ring toward the ball nut portion, and the cylindrical portion is formed on the outer peripheral surface. An annular groove formed on the inner peripheral surface of the portion where the first inner ring is formed is provided.

  The steering device of the present invention includes the above-described ball screw device.

  According to the ball screw device and the steering device of the present invention, the cylindrical portion is formed with an annular groove portion on the inner peripheral surface of the portion where the first inner ring is formed on the outer peripheral surface. Therefore, the double row bearing device can reduce the rigidity of the first inner ring against the pressing force from the preload applying portion. Thus, the ball screw device can apply the necessary preload to the double row bearing device with a small pressing force when applying the preload to the double row bearing device by the pressing force from the preload applying portion.

It is the schematic which shows the steering device in one Embodiment of this invention. It is the expanded sectional view which expanded the site | part in which a steering assistance apparatus and a ball screw apparatus are arrange | positioned among steering apparatuses. It is the figure which expanded further the site | part by which a double row bearing apparatus is arrange | positioned among FIG. It is an expanded sectional view of a ball screw device in the 1st modification, and expands and shows a portion in which a double row bearing device is arranged. It is an expanded sectional view of a ball screw device in the 2nd modification, and expands and shows a portion in which a double row bearing device is arranged. It is an expanded sectional view of a ball screw device in the 3rd modification, and expands and shows a portion in which a double row bearing device is arranged.

  Hereinafter, embodiments to which a ball screw device and a steering device according to the present invention are applied will be described with reference to the drawings. First, a schematic configuration of a steering device 1 using a ball screw device 5 in one embodiment of the present invention will be described with reference to FIG.

(1. Schematic configuration of the steering device 1)
As shown in FIG. 1, the steering device 1 mainly includes a steering shaft member 2, a steered shaft member 3, a steering assist device 4, and a ball screw device 5. The steering shaft member 2 has a steering member 21 that is steered by a driver fixed at one end in the axial direction, and a pinion 22 that forms a rack and pinion mechanism is formed at the other end in the axial direction. The

  The steered shaft member 3 includes a rack 31 that meshes with the pinion 22. The rack 31 and the pinion 22 constitute a rack and pinion mechanism. The rack and pinion mechanism sets the maximum axial force that can be transmitted between the steering shaft member 2 and the steered shaft member 3 based on the application of the steering device 1 or the like. Further, joints 32 are respectively provided at both ends in the axial direction of the steered shaft member 3. Tie rods 33 are connected to both ends of the joints 32, and steered wheels 35 are connected to the tips of the tie rods 33 via knuckle arms 34.

  The steering device 1 converts the steering torque applied to the steering shaft member 2 into a force in the axial direction of the steered shaft member 3 by a rack and pinion mechanism, and imparts it to the steered shaft member 3, thereby turning the steered shaft member. 3 is moved in the axial direction. Then, the steering apparatus 1 steers the steered wheels 35 by moving the steered shaft member 3 in the axial direction.

  The steering assist device 4 applies a steering assist force to the steered shaft member 3. The steering assist device 4 includes a motor 41, a torque sensor 42, a control unit 43, and a driving force transmission unit 44. The motor 41 is a drive source that applies a steering assist force to the steered shaft member 3. The torque sensor 42 detects the steering torque applied to the steering shaft member 2 when the steering member 21 is steered. The control unit 43 determines the steering assist torque to be applied to the steered shaft member 3 based on the output signal of the torque sensor 42 and controls the output of the motor 41.

  As shown in FIG. 2, the driving force transmission unit 44 includes a driving pulley 45, a driven pulley 46, and a toothed belt 47. The driving pulley 45 and the driven pulley 46 are toothed pulleys provided with external teeth of a helical tooth. The toothed belt 47 is an endless rubber belt in which inner teeth of teeth are formed on the inner peripheral surface.

  The drive pulley 45 is a cylindrical member disposed at a position offset with respect to the central axis A of the steered shaft member 3. The drive pulley 45 is provided so as to be rotatable integrally with the output shaft 41a with respect to the output shaft 41a of the motor 41. The driven pulley 46 is a cylindrical member arranged coaxially with the steered shaft member 3. The driven pulley 46 includes a pulley main body 48 in which external teeth are formed, and flanges 49 that are externally fitted to the pulley main body 48 on both sides in the axial direction across the external teeth. The flange portion 49 is an annular member having an outer diameter larger than that of the pulley body 48 and is fixed to the pulley body 48 by press-fitting.

  The toothed belt 47 is stretched over the driving pulley 45 and the driven pulley 46 in a state where the toothed belt 47 meshes with external teeth formed on the driving pulley 45 and the driven pulley 46. Then, the driving force transmission unit 44 transmits the rotational driving force between the driving pulley 45 and the driven pulley 46.

  The ball screw device 5 mainly includes a housing 6, a ball screw shaft member 7, a nut 8, a rolling ball 9, and a double row bearing device 10. The housing 6 is a cylindrical member that houses the steered shaft member 3 and is fixed to the vehicle body. In addition, a case 61 that accommodates the motor 41 and the control unit 43 is fixed to the housing 6. The case 61 communicates with the housing 6, and the output shaft 41 a of the motor 41 is disposed inside the housing 6.

  Boots 62 are provided at both axial ends of the housing 6. The boot 62 is formed in a bellows tube shape that can be expanded and contracted in the axial direction of the steered shaft member 3, and one end of the boot 62 is fixed to the housing 6 and the other end of the boot 62 is fixed to the tie rod 33. The boot 62 covers the connecting portion between the joint 32 and the tie rod 33, and prevents foreign matters from entering the inside of the joint 32 and the housing 6.

  The ball screw shaft member 7 is a shaft member in which a spiral outer peripheral ball rolling groove 71 is formed on the outer peripheral surface. In this embodiment, the steered shaft member 3 also serves as the ball screw shaft member 7, and the outer peripheral ball rolling groove 71 is formed on the outer peripheral surface of the steered shaft member 3 where the rack 31 is not formed. Is formed.

  The nut 8 includes a ball nut portion 81 and a tube portion 82. The ball nut portion 81 is a cylindrical member in which a spiral inner peripheral ball rolling groove 83 is formed on the inner peripheral surface. The inner peripheral ball rolling groove 83 is an outer periphery formed on the ball screw shaft member 7. It is arranged on the outer peripheral side of the ball rolling groove 71. On the other hand, a driven pulley 46 is provided on the outer peripheral surface of the ball nut portion 81 so as to be integrally rotatable. Therefore, the nut 8 is coupled to the motor 41 via the driving force transmission unit 44, and the rotational driving force of the motor 41 is transmitted to the nut 8 via the driving force transmission unit 44. That is, the nut 8 rotates around the central axis A when driven by the motor 41.

  The cylindrical portion 82 is a portion adjacent to the ball nut portion 81 in the axial direction of the nut 8. The outer peripheral surface of the cylindrical portion 82 is supported rotatably with respect to the inner peripheral surface of the housing 6 via the double-row bearing device 10.

  The plurality of rolling balls 9 are arranged so as to roll between the outer peripheral ball rolling groove 71 and the inner peripheral ball rolling groove 83, and the outer peripheral ball rolling groove 71 and the inner peripheral ball rolling groove 83 include a plurality of rolling balls 9. Are screwed through the rolling balls 9. The plurality of rolling balls 9 are infinitely circulated through a pair of deflectors (not shown) provided in the ball nut portion 81 and a passage (not shown) connecting the pair of deflectors.

  Thus, the steering assist device 4 drives the motor 41 in accordance with the steering of the steering member 21, and when the output shaft 41 a rotates by the drive of the motor 41, the rotational force is transmitted via the driving force transmission unit 44 to the nut 8. Is transmitted to. Then, the ball screw device 5 transmits the rotational driving force transmitted to the nut 8 to the steered shaft member 3 as the ball screw shaft member 7 via the plurality of rolling balls 9, and the steered shaft member 3 is Move in the axial direction.

(2. Double-row bearing device 10)
Next, the double row bearing device 10 will be described with reference to FIGS. 2 and 3. As shown in FIG. 2, the double-row bearing device 10 is a double-row angular contact ball bearing, and supports a nut 8 rotatably with respect to the housing 6. The double row bearing device 10 mainly includes two rows of rolling elements 110, an outer ring 120, a first inner ring 130, and a second inner ring 140.

  Two rows of rolling elements 110 are arranged in parallel in the direction of the central axis A of the ball screw device 5. Among the two rows of rolling elements 110, the plurality of first rolling elements 111 belonging to the row close to the ball nut portion 81 (the row on the right side in FIG. 2) are arranged between the outer ring 120 and the first inner ring 130 so as to be able to roll. Is done. In addition, among the two rows of rolling elements 110, the plurality of second rolling elements 112 belonging to the row away from the ball nut portion 81 (the row on the left side in FIG. 2) rolls between the outer ring 120 and the second inner ring 140. Arranged as possible.

  As shown in FIG. 3, the outer ring 120 is a cylindrical member disposed at a position corresponding to the cylindrical portion 82 of the nut 8, and displacement in the axial direction is restricted with respect to the inner peripheral surface of the housing 6. Provided in a state. The outer ring 120 includes a first outer ring raceway 121 and a second outer ring raceway 122. The first outer ring raceway 121 forms a rolling surface on which the plurality of first rolling elements 111 roll, and the second outer ring raceway 122 forms a rolling surface on which the plurality of second rolling elements 112 roll. The first outer ring raceway 121 and the second outer ring raceway 122 face each other in the axial direction.

  Further, the outer ring 120 is formed with an outer ring small-diameter extending portion 123 that connects the first outer ring raceway 121 and the second outer ring raceway 122. The outer ring small-diameter extending portion 123 is a portion that extends along the axial direction of the outer ring 120 and is the portion that has the smallest inner diameter in the outer ring 120. Further, the outer ring 120 includes a first outer large-diameter extending portion 124 that extends from the first outer ring raceway 121 toward one end side in the axial direction (right side in FIG. 2), and the other end side in the axial direction from the second outer ring raceway 122 (left side in FIG. 2). A second outer large-diameter extending portion 125 extending to) is formed. The first outer large diameter extension portion 124 and the second outer large diameter extension portion 125 are portions that extend along the axial direction of the outer ring 120, and are portions that have the largest inner diameter in the outer ring 120.

  The first inner ring 130 is integrally formed on the outer peripheral surface of the cylindrical portion 82 mainly at a position facing the first outer ring raceway 121. The first inner ring 130 includes a first inner ring raceway 131, a first inner ring large-diameter extending portion 132, and a first inner ring small-diameter extending portion 133.

  The first inner ring raceway 131 is a part that forms a rolling surface on which the plurality of first rolling elements 111 roll, and is formed to face the first outer ring raceway 121. The contact point between the first inner ring raceway 131 and the first rolling element 111 is located on one end side in the axial direction from the center of the first rolling element 111 (right side in FIG. 3), and the first outer ring raceway 121 and the first rolling element 111 are in contact with each other. The contact point with the moving body 111 is located on the other end side in the axial direction (left side in FIG. 3) from the center of the first rolling body 111.

  The first inner ring large-diameter extending portion 132 extends from the first inner ring raceway 131 to one end side in the axial direction (right side in FIG. 2), that is, the side where the ball nut portion 81 is formed. The first inner ring large-diameter extending portion 132 is a part extending along the axial direction of the first inner ring 130, and is a part having the largest outer diameter in the first inner ring 130. The first inner ring small-diameter extending portion 133 extends from the first inner ring raceway 131 to the other end side in the axial direction (left side in FIG. 2), that is, the side away from the ball nut portion 81. The first inner ring small-diameter extending portion 133 is a part extending along the axial direction of the first inner ring 130, and is the part having the smallest outer diameter in the first inner ring 130.

  The second inner ring 140 is a cylindrical member formed separately from the nut 8. The second inner ring 140 is press-fitted into the outer peripheral surface of the cylinder portion 82 at a position facing the second outer ring raceway 122. The second inner ring 140 includes a second inner ring raceway 141, a second inner ring large-diameter extending portion 142, and a second inner ring small-diameter extending portion 143.

  The second inner ring raceway 141 is a portion that forms a rolling surface on which the plurality of second rolling elements 112 roll, and is formed to face the second outer ring raceway 122. The contact point between the second inner ring raceway 141 and the second rolling element 112 is located on the other end side in the axial direction (left side in FIG. 3) from the center of the second rolling element 112, and the second outer ring raceway 122 and the second rolling element 112. The contact point with the rolling element 112 is located on one end side in the axial direction (right side in FIG. 3) from the center of the second rolling element 112.

  The second inner ring large-diameter extending portion 142 extends from the second inner ring raceway 141 to the other end side in the axial direction (left side in FIG. 2), that is, the side away from the ball nut portion 81 and the first inner ring 130. The second inner ring large-diameter extending portion 142 is a part extending along the axial direction of the second inner ring 140, and is a part having the largest outer diameter in the second inner ring 140. The second inner ring small-diameter extending portion 143 extends from the second inner ring raceway 141 to one axial end side (the right side in FIG. 2), that is, the ball nut portion 81 side and the first inner ring 130 side. The second inner ring small diameter extending portion 143 is a part extending along the axial direction of the second inner ring 140, and is a part having the smallest outer diameter in the second inner ring 140.

  Here, the ball screw device 5 further includes a preload applying portion 11. In the present embodiment, the preload imparting portion 11 is a lock nut in which a female screw that engages with a male screw formed on the outer peripheral surface of the cylindrical portion 82 is formed on the inner peripheral surface. The ball screw device 5 applies a preload to the double row bearing device 10 by pressing the first inner ring 130 and the second inner ring 140 toward the ball nut portion 81 while screwing the preload applying portion 11 into the cylindrical portion 82.

  And the nut 8 forms the annular groove part 84 in the internal peripheral surface of the site | part in which the 1st inner ring | wheel 130 is formed in an outer peripheral surface on the internal peripheral surface of the cylinder part 82, and the rigidity of the 1st inner ring | wheel 130 is made. It is low. In this regard, the first inner ring 130 is formed integrally with the nut 8, while the second inner ring 140 is formed separately from the nut 8. Therefore, when the groove portion 84 is not provided in the nut 8, the rigidity of the first inner ring 130 is higher than that of the second inner ring 140 and is not easily deformed. Therefore, in this case, in order to apply the necessary preload to the double row bearing device 10, the preload applying portion 11 that is a lock nut is strongly tightened against the cylindrical portion 82, and the first inner ring 130 and the second inner ring are pressed with a large pressing force. It is necessary to press 140 toward the ball nut portion 81 side.

  However, if the preload imparting portion 11 is strongly tightened with respect to the cylindrical portion 82, the tensile stress applied to the other end side in the axial direction applied to the cylindrical portion 82 (the opposite side to the ball nut portion 81) increases. Deformation may occur.

  In this regard, since the cylindrical portion 82 reduces the rigidity of the first inner ring 130, when the pressing force in the axial direction is applied from the preload applying portion 11, the first inner ring 130 is moved to the ball nut portion 81 side. Can be easily deformed. Thereby, the ball screw device 5 can apply the necessary preload to the double row bearing device 10 while reducing the pressing force by the preload applying portion 11.

  As a result, the ball screw device 5 can prevent the ball nut portion 81 from being deformed due to the tight tightening of the lock nut as the preload applying portion 11. Therefore, the ball screw device 5 can smoothly roll the plurality of rolling balls 9 between the outer peripheral ball rolling groove 71 and the inner peripheral ball rolling groove 83. Further, the double row bearing device 10 can set the internal clearance between the rolling element 110 and the first outer ring raceway 121, the second outer ring raceway 122, the first inner ring raceway 131 and the second inner ring raceway 141 to appropriate dimensions. Generation of sound (rattle sound) can also be prevented. Since the steering device 1 can smoothly transmit power from the motor 41 to the steered shaft member 3, the steering feeling can be improved.

(3. About groove part 84)
Here, in the present embodiment, the inner diameter D1 of the groove portion 84 is formed to be larger than the outer diameter D2 of the portion where the second inner ring 140 is fitted to the outer peripheral surface of the cylindrical portion 82. Therefore, the double row bearing device 10 can easily deform the first inner ring 130 when the pressing force from the preload applying portion 11 is applied to the first inner ring 130 via the second inner ring 140.

  Further, the groove portion 84 is formed on the first inner ring raceway 131 side with respect to the boundary B1 between the first inner ring raceway 131 and the first inner ring large diameter extending portion 132. That is, the groove portion 84 is formed at a position farther from the ball nut portion 81 than the first inner ring large-diameter extending portion 132 in the axial direction. In this case, the first inner ring 130 can suppress deformation of the portion where the first inner ring large-diameter extending portion 132 is formed when the pressing force from the preload applying portion 11 is applied.

  Thereby, the double row bearing device 10 can prevent the first inner ring large-diameter extending portion 132 from being deformed so as to fall down toward the ball nut portion 81 due to the pressing force from the preload applying portion 11. The required preload can be reliably applied to 10. Moreover, since the double row bearing device 10 can reliably receive the thrust load applied to the first inner ring 130 from the first rolling element 111, the function as the bearing device can be sufficiently exhibited.

  On the other hand, the groove portion 84 is formed so as to straddle the boundary B <b> 2 between the first inner ring raceway 131 and the first inner ring small diameter extending portion 133. A part of the groove 84 is formed at a position overlapping the first inner ring raceway 131 and the first inner ring small-diameter extending part 133 in the axial direction. Thereby, the 1st inner ring | wheel 130 can make low the rigidity of the site | part in which the 1st inner ring track | line 131 and the 1st inner ring | wheel small diameter extension part 133 are formed in an axial direction. That is, since the double row bearing device 10 can easily deform the first inner ring 130, the necessary preload can be applied to the double row bearing device 10 while reducing the pressing force from the preload applying portion 11. it can.

  Further, since the ball screw device 5 uses a lock nut as the preload applying portion 11, for example, the double row bearing device 10 is obtained by caulking the end portion on the other axial end side (left side in FIG. 3) of the cylindrical portion 82. Compared with the case where a preload is applied to the cylinder portion 82, the radial deformation of the cylindrical portion 82 can be suppressed. Therefore, the ball screw device 5 can apply the necessary preload to the double row bearing device 10 while suppressing deformation of the first inner ring raceway 131 and the like.

  As described above, in the ball screw device 5, the nut 8 has an annular groove portion 84 on the inner peripheral surface of the inner peripheral surface of the cylindrical portion 82 where the first inner ring 130 is formed on the outer peripheral surface. Is formed. Therefore, the double row bearing device 10 can reduce the rigidity of the first inner ring 130 with respect to the pressing force from the preload applying portion 11. Thereby, the ball screw device 5 can apply the necessary preload to the double row bearing device 10 with a small pressing force when the preload is applied to the double row bearing device 10 by the pressing force from the preload applying portion 11.

(4. Modification of groove)
Subsequently, a modification of the groove will be described with reference to FIGS. 4 to 6. That is, in the above-described embodiment, the groove portion 84 is located farther from the ball nut portion 81 than the first inner ring large-diameter extension portion 132 in the axial direction, and the first inner ring raceway 131 and the first inner ring small-diameter extension portion. The case where it is formed at a position overlapping with 133 has been described. However, the present invention is not limited to this, and the groove portion may be provided in a manner as shown in the following first to third modifications.

  First, a first modification will be described with reference to FIG. The groove part 284 formed in the cylinder part 282 in the first modification is formed closer to the first inner ring small-diameter extending part 133 than the boundary B2. That is, the groove portion 284 is formed at a position farther from the ball nut portion 81 than the first inner ring raceway 131. Moreover, the groove part 284 is formed in the position which overlaps with the 1st inner ring | wheel small diameter extension part 133 in an axial direction.

  In this case, the rigidity of the first inner ring 130 can be reduced at a portion where the first inner ring small-diameter extending portion 133 is formed. Thereby, the double row bearing device 10 can easily deform the first inner ring 130. Therefore, the ball screw device 205 can apply the necessary preload to the double row bearing device 10 while reducing the pressing force from the preload applying portion 11.

  Moreover, since the groove part 284 is not formed in the site | part in which the 1st inner ring track 131 is formed in the axial direction, the 1st inner ring 130 can suppress that the rigidity of the site | part in which the 1st inner ring track 131 is formed falls. . Thereby, since the double row bearing device 10 can suppress the deformation of the first inner ring raceway 131 when the preload is applied, the first rolling element 111 can be smoothly rolled.

  Furthermore, since the groove part 284 is not formed in the site | part in which the 1st inner ring | wheel large diameter extension part 132 is formed in the axial direction, the 1st inner ring | wheel 130 of the site | part in which the 1st inner ring | wheel large diameter extension part 132 is formed. It can suppress that rigidity falls. Accordingly, the ball screw device 205 can prevent the first inner ring large-diameter extending portion 132 from being deformed so as to fall down toward the ball nut portion 81 due to the pressing force from the preload applying portion 11. In contrast, the necessary preload can be applied. Moreover, since the double row bearing device 10 can reliably receive the thrust load applied to the first inner ring 130 from the first rolling element 111, the function as the bearing device can be sufficiently exhibited.

  Next, a second modification will be described with reference to FIG. The groove part 384 formed in the cylinder part 382 in the second modification is formed at a position straddling the boundary B1. That is, a part of the groove 384 is formed at a position overlapping the first inner ring raceway 131 and the first inner ring large-diameter extending part 132 in the axial direction. On the other hand, the groove portion 384 is formed closer to the first inner ring raceway 131 than the boundary B2. That is, the groove portion 384 is formed at a position closer to the ball nut portion 81 than the first inner ring small diameter extending portion 133.

  In this case, in the ball screw device 305, the groove portion 384 is formed in a portion of the first inner ring 130 having a large thickness dimension in the radial direction. Therefore, when the preload is applied from the preload applying portion 11, the double row bearing device 10 suppresses deformation of the first inner ring small-diameter extending portion 133 and the first inner ring raceway 131 where the thickness dimension is small. it can. Therefore, the double row bearing device 10 can smoothly roll the first rolling element 111.

  Next, a third modification will be described with reference to FIG. The groove portion 484 formed in the cylindrical portion 482 in the third modification includes a groove side surface 484c that connects the groove bottom 484a and the groove opening edge 484b opposite to the ball nut portion 81. The groove side surface 484c is formed such that the inner diameter decreases from the groove bottom 484a toward the groove opening edge 484b.

  In this case, the ball screw device 405 moves to the other end in the axial direction (on the opposite side to the ball nut portion 81) applied to the tube portion 82 when the lock nut as the preload applying portion 11 is tightened to the tube portion 82. The rigidity of the first inner ring 130 against the tensile stress can be reduced. As a result, the double-row bearing device 10 can easily deform the first inner ring 130 at a portion where the groove portion 484 is formed when a preload is applied. Therefore, the ball screw device 405 can apply a necessary preload to the double row bearing device 10.

(5. Other)
The present invention has been described based on the above embodiment, but the present invention is not limited to the above embodiment, and various modifications can be easily made without departing from the spirit of the present invention. Can be inferred. For example, in the above-described embodiment, an example in which the present invention is applied when the double-row bearing device 10 is a double-row angular ball bearing has been described. The present invention can also be applied to a row bearing device such as a double row tapered roller bearing.

  In the above embodiment, the case where a lock nut is used as the preload applying portion 11 has been described, but the present invention is not limited to this. For example, the ball screw devices 5, 205, 305, and 405 may use a snap ring or the like as the preload applying unit 11. Further, the ball screw devices 5, 205, 305, and 405 can apply preload to the double row bearing device 10 by caulking the ends of the cylindrical portions 82, 282, 382, and 482 on the other end side in the axial direction. Good. In this case, the diameter-enlarged portion formed at the other end in the axial direction of the cylindrical portions 82, 282, 382, and 482 by caulking corresponds to the preload applying portion.

  1: Steering device, 5, 205, 305, 405: Device, 6: Housing, 7: Ball screw shaft member, 8: Nut, 9: Rolling ball, 10: Double row bearing device, 11: Preload application unit, 71 : Outer peripheral ball rolling groove, 81: ball nut portion, 82, 282, 382, 482: tube portion, 83: inner peripheral ball rolling groove, 84, 284, 384, 484: groove portion, 110: rolling element, 111: First rolling element, 112: Second rolling element, 120: Outer ring, 121: First outer ring raceway, 122: Second outer ring raceway, 130: First inner ring, 131: First inner ring raceway, 132: First inner ring large diameter Extended portion, 133: first inner ring small diameter extended portion, 140: second inner ring, 141: second inner ring raceway, 484a: groove bottom, 484b: groove opening edge, 484c: groove side surface

Claims (7)

A housing;
A ball screw shaft member in which a spiral outer peripheral ball rolling groove is formed on the outer peripheral surface;
A nut having a ball nut portion having a spiral inner peripheral ball rolling groove formed on the inner peripheral surface, and a cylindrical portion adjacent to the ball nut portion in the axial direction;
A plurality of rolling balls arranged between the outer peripheral ball rolling groove and the inner peripheral ball rolling groove;
A double row bearing device for rotatably supporting the cylindrical portion with respect to the housing;
A ball screw device comprising:
The double row bearing device comprises:
Two rows of rolling elements parallel in the axial direction;
Of the two rows of rolling elements, a first outer ring raceway on which a plurality of first rolling elements belonging to a row close to the ball nut portion rolls, and of the two rows of rolling elements, a row away from the ball nut portion An outer ring having a second outer ring raceway on which a second rolling element belonging to
A first inner ring integrally formed on the outer peripheral surface of the cylindrical portion, and having a first inner ring raceway in which the plurality of first rolling elements roll at a position facing the first outer ring raceway;
A second inner ring having a second inner ring raceway, which is fitted to the outer peripheral surface of the cylindrical portion, and in which the plurality of second rolling elements roll at a position facing the second outer ring raceway,
With
The ball screw device includes a preload applying portion that applies a preload to the double row bearing device by pressing the first inner ring and the second inner ring toward the ball nut portion.
The said cylinder part is a ball screw apparatus provided with the annular groove part formed in the internal peripheral surface of the site | part in which said 1st inner ring | wheel is formed in an outer peripheral surface.   2. The ball screw device according to claim 1, wherein an inner diameter of the groove portion is formed to be larger than an outer diameter of a portion where the second inner ring is fitted to an outer peripheral surface of the cylindrical portion. The first inner ring is
The first inner ring raceway;
A first inner ring large-diameter extending portion extending from the first inner ring raceway to the side where the ball nut portion is formed;
With
The groove portion is formed at a position away from the ball nut portion from the first inner ring large-diameter extending portion in the axial direction,
The ball screw device according to claim 1 or 2, wherein at least a part of the groove is formed at a position of the first inner ring raceway in the axial direction. The first inner ring is
The first inner ring raceway;
A first inner ring small-diameter extending portion extending from the first inner ring raceway to the side away from the ball nut portion;
With
The groove portion is formed at a position away from the ball nut portion from the first inner ring raceway in the axial direction.
The ball screw device according to claim 1 or 2, wherein at least a part of the groove is formed at a position of the first inner ring small-diameter extending portion in the axial direction. The first inner ring is
The first inner ring raceway;
A first inner ring large-diameter extending portion extending from the first inner ring raceway to the side where the ball nut portion is formed;
With
The ball screw device according to claim 1 or 2, wherein at least a part of the groove portion is formed at a position of the first inner ring large-diameter extending portion in the axial direction. The groove portion includes a groove side surface that connects a groove bottom and a groove opening edge on the opposite side of the ball nut portion;
With
The ball screw device according to any one of claims 1 to 5, wherein the groove side surface is formed so that an inner diameter decreases from the groove bottom toward the groove opening edge.   A steering apparatus comprising the ball screw device according to any one of claims 1-6.

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