JP2012255512A - Bearing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing structure which is an inner ring-less bearing structure for a steering shaft of a steering apparatus, and with which rattling can be suppressed.SOLUTION: The bearing structure 5 includes a pinion shaft 4, an outer ring 25, a plurality of rolling elements 26, a sleeve 14, and a housing 12 holding the sleeve 14. The pinion shaft 4 has a ring-like first raceway groove 11 which extends in the circumferential direction and is formed on an outer circumferential face of the pinion shaft, and the pinion shaft 4 rotates according to steering. The outer ring 25 is formed ring-like, is fitted externally onto the pinion shaft 4 and has a ring-like second raceway groove 28 which faces the first raceway groove 11 from the radial outside and which is formed on the inner circumferential face of the outer ring. The rolling element 26 is disposed between the pinion shaft 4 and the outer ring 25 and is rollable in the circumferential direction in a state of being fitted in both of the first raceway groove 11 and second raceway groove 28. The sleeve 14 is press-fitted from the radial outside with respect to the outer ring 25, and thus the outer ring 25 is diametrically reduced.

Description

  The present invention relates to a bearing structure used in a steering device.

A steering device for an automobile includes a pinion shaft that rotates as the steering wheel is steered, and a rack that meshes with the pinion of the pinion shaft and steers the wheels while sliding in the vehicle width direction as the pinion shaft rotates. And a housing that holds the pinion shaft and the rack (see Patent Documents 1 and 2).
The pinion shaft is supported by the housing via a bearing. However, Patent Documents 1 and 2 propose an inner ring-less bearing structure in which an inner ring is omitted as a pinion shaft bearing structure.

  In the inner ring-less bearing structure, instead of the inner ring, an annular inner ring raceway extending in the circumferential direction is formed on the outer peripheral surface of the pinion shaft. After a rolling element such as a ball is fitted into the inner ring raceway, the outer ring is fitted onto the pinion shaft, and the rolling element is fitted into the outer ring raceway on the inner peripheral surface of the outer ring to constitute a bearing structure. In the case of the inner ring-less bearing structure, since the inner ring is not necessary, the weight and cost of the steering device can be reduced by reducing the number of parts.

Japanese Utility Model Publication No. 3-123142 Japanese Utility Model Publication No. 62-61771

  When assembling the inner ring-less bearing structure, the rolling element must be fitted into the inner ring raceway of the pinion shaft and the outer ring must be fitted outside the pinion shaft. A positive gap is likely to occur. “A positive gap is generated between the interval and the rolling element” means that the interval is larger than the diameter of the rolling element. Conversely, the fact that the interval is smaller than the diameter of the rolling element is referred to as “a negative gap is generated between the interval and the rolling element”.

When the positive clearance is generated in this way, the outer ring is likely to rattle in the axial direction, and the axial rigidity of the entire bearing structure is reduced. As a result, the pinion shaft is also likely to rattle, and there is a risk that abnormal noise (pinion and rack rattling noise) may occur when the pinion pinion shaft rattling comes into contact with the rack.
The present invention has been made under such a background, and an object thereof is to provide an inner ring-less bearing structure for a steering shaft of a steering device, which can suppress rattling.

  According to the first aspect of the present invention, in the bearing structure (5) used in the steering device (1), an annular first raceway groove (11) extending in the circumferential direction is formed on the outer peripheral surface and rotates in accordance with steering. A steering shaft (4) and a ring-shaped outer ring formed on the inner peripheral surface with a ring-shaped second track groove (28) that is fitted on the steering shaft and faces the first track groove from the outside in the radial direction. 25) and a plurality of rolling elements (26) which are arranged between the steering shaft and the outer ring and are rollable in the circumferential direction while being fitted in both the first raceway groove and the second raceway groove. The bearing structure includes an annular sleeve (14) press-fitted from the radially outer side to the outer ring, and a holding portion (12) for holding the sleeve.

The invention according to claim 2 is characterized in that, in the radial direction, a negative gap is formed in the distance (A) between the first raceway groove and the second raceway groove and the rolling element. The bearing structure according to 1.
A third aspect of the present invention is the bearing structure according to the first or second aspect, wherein the outer ring and the sleeve are made of steel.

The invention according to claim 4 is the bearing structure according to claim 3, characterized in that the outer ring is made of bearing steel and the sleeve is made of carbon steel.
The invention according to claim 5 is a four-point contact ball bearing structure, which is disposed between the steering shaft and the outer ring, and holds the plurality of rolling elements so as to be arranged at equal intervals in the circumferential direction. A retainer (27) movable in a circumferential direction; and a retaining portion (31) provided on the sleeve for preventing the retainer from coming off between the steering shaft and the outer ring. It is a bearing structure in any one of Claims 1-4 characterized by these.

  In addition, in the above, the numbers in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

  According to the first aspect of the present invention, this bearing structure is an inner ring-less bearing structure. In this bearing structure, since the outer ring is reduced in diameter by a sleeve press-fitted from the radially outer side, the first raceway groove of the steering shaft and the second raceway groove of the outer ring are provided as in the second aspect of the invention. A negative gap is formed in the interval and the rolling elements, and the outer ring is positioned in the radial direction and the axial direction. As a result, in the inner ring-less bearing structure, it is possible to increase the axial rigidity and suppress the rattling of the outer ring.

According to the third aspect of the present invention, since the outer ring and the sleeve are both made of steel, they are thermally expanded and contracted at substantially the same rate. It is possible to suppress the rattling of the outer ring while maintaining the state in which a negative gap is generated by being press-fitted into the outer ring.
According to the fourth aspect of the present invention, the cost of the entire bearing structure can be reduced by using carbon steel that is less expensive than bearing steel for the sleeve.

  According to the invention described in claim 5, since the four-point contact ball bearing structure has high axial rigidity, it is possible to further suppress the rattling of the outer ring. However, if there is a negative gap in the four-point contact ball bearing structure, the rolling elements will slip without rolling, and the rolling elements will move forward or behind in the circumferential direction, causing the cage to become a steering shaft. There is a risk of slipping in the axial direction between the outer ring and the outer ring. Therefore, by positioning the retainer with the retaining portion provided on the sleeve, it is possible to prevent the retainer from coming off between the steering shaft and the outer ring.

FIG. 1 is a cross-sectional view of a steering device 1 according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is an exploded perspective view of the bearing structure 5 provided in the steering device 1. FIG. 4 is a side view of the bearing structure 5 before assembly in the state of FIG. 5 is a cross-sectional view taken along the line AA in FIG.

Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a steering device 1 according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is an exploded perspective view of the bearing structure 5 provided in the steering device 1. FIG. 4 is a side view of the bearing structure 5 before assembly in the state of FIG. 5 is a cross-sectional view taken along the line AA in FIG.

Referring to FIG. 1, this steering device 1 is mainly used in an automobile, and is a device that transmits steering of a steering wheel 2 to a wheel (illustrated) to steer the wheel.
The steering device 1 includes a steering wheel 2, a steering shaft 3 extending from the steering wheel 2, a pinion shaft 4 (steering shaft) that is directly or indirectly connected to the steering shaft 3, and a bearing structure of the pinion shaft 4. 5 and the rack shaft 6 are mainly included.

  The pinion shaft 4 has a predetermined length in the axial direction. A pinion 7 is formed at the end of the pinion shaft 4 opposite to the side connected to the steering shaft 3. Further, the pinion shaft 4 is appropriately formed with a stepped portion 8, a reduced diameter portion 9, etc., but at least the pinion 7 and the first raceway groove 11 described above are formed. The first raceway groove 11 is formed on the outer peripheral surface of the pinion shaft 4 at a position closer to the steering shaft 3 than the pinion 7 and has an annular shape that extends in the circumferential direction while being recessed in an arc shape toward the axial center of the pinion shaft 4. There is no.

The bearing structure 5 includes at least the pinion shaft 4 described above, a housing 12 (holding portion), a bearing unit 13, and a sleeve 14. The bearing structure 5 may further include a pinion plug 15, a rack plug 16, and a yoke 17.
The housing 12 is a hollow body, and in FIG. 1, a round insertion hole 20 for inserting the pinion shaft 4 from the left side is formed on the left side, and a round for screwing the rack plug 16 on the upper side. A screw hole 21 is formed.

The bearing unit 13 includes the first raceway groove 11, the outer ring 25, the rolling element 26, and the cage 27 described above. Here, the member which comprises the bearing unit 13 is formed with the steel material, and especially the outer ring | wheel 25 and the rolling element 26 are formed with bearing steel (SUJ2, SUJ3, SUJ5 etc.).
Referring to FIGS. 3 and 4, the outer ring 25 is an annular body having a diameter slightly larger than that of the pinion shaft 4 in the portion where the first raceway groove 11 is formed. Almost the entire outer peripheral surface of the outer ring 25 is flat along the axial direction. Here, the outer diameter of the outer ring 25 is 42 mm. An annular second raceway groove 28 extending in the circumferential direction while being recessed in a circular arc shape radially outward is formed at the substantially axial center of the inner peripheral surface of the outer ring 25. On the inner peripheral surface of the outer ring 25, almost the entire region where the second raceway groove 28 is not formed is flat along the axial direction.

The rolling elements 26 are spherical bodies, and a plurality (eight in this case) of the rolling elements 26 are provided in one bearing structure 5. The radius of the rolling element 26 and the radius of curvature of the first raceway groove 11 and the second raceway groove 28 described above are substantially the same (see FIG. 2).
The cage 27 has a crown shape. Specifically, the cage 27 is an annular body that is slightly larger in diameter than the pinion shaft 4 and smaller in diameter than the outer ring 25 in the portion where the first raceway groove 11 is formed. The axial dimension of the cage 27 is smaller than the axial dimension of the outer ring 25. At the one end in the axial direction of the retainer 27 (the left end in FIG. 3), an annular flange 29 that extends radially inward over the entire circumference of the inner peripheral surface of the retainer 27 is integrally provided. In addition, the collar part 29 may be interrupted in the circumferential direction. The retainer 27 is formed with a plurality of substantially U-shaped notches 30 that are notched in the radial direction from the other end side in the axial direction (the right end side in FIG. 3) at equal intervals in the circumferential direction. ing. The number of notches 30 is the same as the number of rolling elements 26. In addition, in FIG. 5, illustration of the holder | retainer 27 is abbreviate | omitted.

Next, the procedure for assembling the bearing unit 13 will be described.
First, all the rolling elements 26 are fitted into the first raceway grooves 11 of the pinion shaft 4 from the radially outer side. In each rolling element 26 fitted in the first raceway groove 11, only the end portion on the axial center side of the pinion shaft 4 is fitted in the first raceway groove 11, but the other portions are the first raceway groove. 11 protrudes radially outward (see FIG. 4).

  Next, the retainer 27 is externally fitted to the pinion shaft 4 from the outside in the axial direction (left side in FIGS. 3 and 4). At this time, the retainer 27 is externally fitted to the pinion shaft 4 in order from the notch 30 side. Then, the cage 27 in this state is slid toward the first track groove 11 along the axial direction. When the cage 27 reaches the first raceway groove 11, each rolling element 26 fitted in the first raceway groove 11 is fitted with some play in any notch 30 in the cage 27. (See FIG. 2). Thereby, the holder | retainer 27 will be in the state hold | maintained so that the some rolling element 26 may be located in a line at equal intervals in the circumferential direction. Further, in this state, the retainer 27 is externally fitted with a little play with respect to the pinion shaft 4, so that the retainer 27 can move in the circumferential direction around the pinion shaft 4 while holding the rolling element 26.

  Next, the outer ring 25 is externally fitted to the pinion shaft 4 from the outside in the axial direction (left side in FIGS. 3 and 4), and the outer ring 25 in this state is slid toward the first track groove 11 side along the axial direction. . When the outer ring 25 reaches just before the first raceway groove 11, the portion of each rolling element 26 of the first raceway groove 11 that protrudes from the first raceway groove 11 is one end surface in the axial direction of the outer race 25 (in FIGS. 3 and 4). It hits the inner periphery of the right end surface.

  Therefore, when a certain force is applied to the outer ring 25 in the axial direction so that the inner circumferential surface of the outer ring 25 rides on each rolling element 26, the second raceway groove 28 of the outer ring 25 is formed as shown in FIG. The first track groove 11 is disposed at the same position in the axial direction, and is opposed to the first track groove 11 from the radially outer side over the entire circumference. At this time, in each rolling element 26 fitted in the first raceway groove 11, a portion protruding from the first raceway groove 11 is disposed inside the outer ring 25, and the radial direction with respect to the second raceway groove 28 of the outer ring 25. Fit from inside. As a result, the outer ring 25 is externally fitted to the pinion shaft 4 so as to face the first raceway groove 11 from the radially outer side.

  At this time, each rolling element 26 is placed between the first raceway groove 11 and the second raceway groove 28 while being disposed between the pinion shaft 4 and the outer ring 25 together with the cage 27. . Each rolling element 26 is rotatable in the circumferential direction in a state where the distance between the rolling elements 26 adjacent in the circumferential direction is kept constant by the cage 27. The retainer 27 is movable in the circumferential direction between the pinion shaft 4 and the outer ring 25 in a state where the rolling elements 26 are retained.

  As described above, the bearing unit 13 is completed, and at the same time, the bearing unit 13 is integrated with the pinion shaft 4 to support the pinion shaft 4 rotatably. When the completed bearing unit 13 with the sleeve 14 attached is assembled into the housing 12, the bearing structure 5 is completed. The bearing structure 5 is an inner ring-less bearing structure in which no inner ring exists. The bearing structure 5 has a four-point contact ball bearing structure. For this reason, each rolling element 26 is separated from the respective wall surfaces of the first raceway groove 11 and the second raceway groove 28 in two locations separated in the axial direction (4 in both the first raceway groove 11 and the second raceway groove 28. 2) at point P (see the lower rolling element 26 in FIG. 2).

  However, in the bearing unit 13 (bearing structure 5) at this time, with reference to FIG. 5, the distance A between the first raceway groove 11 and the second raceway groove 28 in the radial direction is larger than the diameter B of the rolling element 26. Is slightly larger (about +2 μm), and a positive gap is generated between the space A and the rolling element 26. In addition, the space | interval A is the part which is in contact with the rolling element 26 in the location which is the innermost radial direction in the part which is contacting the rolling element 26 in the wall surface of the 1st track groove 11, and the wall surface of the 2nd track groove 28. Is the distance in the radial direction from the most radially outer portion.

Therefore, the sleeve 14 is used to make this positive gap a negative gap.
Referring to FIG. 3, the sleeve 14 is an annular body. The sleeve 14 is formed of a steel material (for example, carbon steel equivalent to S10C to S50C) that is less expensive than the bearing steel. Thereby, cost reduction of the whole bearing unit 13 (bearing structure 5) including the sleeve 14 can be achieved.

  Almost all of the outer peripheral surface and inner peripheral surface of the sleeve 14 are flat along the axial direction. Both end surfaces in the axial direction of the sleeve 14 are flat along the radial direction. The inner diameter of the sleeve 14 is smaller than the outer diameter (here 42 mm) of the outer ring 25 before assembly. An annular retaining portion 31 that extends radially inward over the entire circumference of the inner peripheral surface of the sleeve 14 is integrally provided at one end in the axial direction of the sleeve 14 (left end in FIG. 3). The retaining portion 31 may be interrupted in the circumferential direction.

  The sleeve 14 is externally fitted to the pinion shaft 4 from the outside in the axial direction (left side in FIGS. 3 and 4), and the sleeve 14 in this state is slid along the axial direction toward the first track groove 11 side. Referring to FIG. 2, when the sleeve 14 reaches just before the first raceway groove 11, the inner peripheral side of one axial end surface (the right end surface in FIG. 2) of the sleeve 14 is aligned with the axial direction of the outer ring 25 of the bearing unit 13. It hits the end face (left end face in FIG. 2). Therefore, by applying a certain amount of force to the sleeve 14 toward the outer ring 25 side (right side in FIG. 2) in the axial direction, the sleeve 14 is press-fitted into the outer ring 25 from the left side in FIG. The press-fitting is performed until the retaining portion 31 of the sleeve 14 hits one end surface in the axial direction of the outer ring 25 (the left end surface in FIG. 2). As a result of the press-fitting, the outer ring 25 is reduced in diameter and disposed on the radially inner side of the sleeve 14. Thereby, the sleeve 14 and the outer ring 25 are integrated.

  When the outer ring 25 is thus reduced in diameter, the distance A between the first raceway groove 11 and the second raceway groove 28 is slightly smaller than the diameter B of the rolling element 26 (about −10 μm) with reference to FIG. ) And a negative gap is formed between the distance A and the rolling element 26 in the radial direction. Thereby, the outer ring | wheel 25 is positioned in radial direction and an axial direction. As a result, in the inner ring-less bearing structure 5, the axial rigidity can be increased and the rattling of the outer ring 25 can be suppressed.

Further, referring to FIG. 2, since both outer ring 25 and sleeve 14 are formed of steel, they are thermally expanded or contracted at substantially the same rate based on the approximate linear expansion coefficient. . Therefore, under any temperature condition, the sleeve 14 is press-fitted into the outer ring 25 to maintain a state where a negative gap is generated, and rattling of the outer ring 25 can be suppressed.
And since the bearing structure 5 is a 4-point contact ball bearing structure, since the rigidity of an axial direction is high, the rattling of the outer ring | wheel 25 can be suppressed further.

  Since the inner ring-less bearing structure 5 can reduce the cost by reducing the number of parts, according to the present invention, the bearing structure 5 (in other words, the pinion shaft supported by the bearing structure 5 is suppressed by the backlash of the outer ring 25). 4 overall) in the axial direction and high cost can be achieved at the same time. In addition, by improving the rigidity of the pinion shaft 4 in the axial direction, the steering feel of the steering wheel 2 (see FIG. 1) can be improved.

Here, if a negative clearance is generated in the four-point contact ball bearing structure 5, the rolling elements 26 slip without rolling, and the circumferential movement of each rolling element 26 is advanced or delayed. There is a possibility that the device 27 may come off from between the pinion shaft 4 and the outer ring 25 in the axial direction.
Therefore, in a state where the sleeve 14 is externally fitted to the pinion shaft 4, the retaining portion 31 of the sleeve 14 is opposed to the retainer 27 while facing the outer peripheral surface of the pinion shaft 4 from the outside in the radial direction. On the other hand, in the axial direction, the cage 27 is opposed to the pinion shaft 4 from the side (the left side in FIG. 2). At this time, the retaining portion 31 may contact the retainer 27, or a predetermined gap in the axial direction may be ensured between the retaining portion 31 and the retainer 27. In any case, the retainer 27 is positioned so that the retainer 27 is positioned before the retainer 27 is about to come out from between the pinion shaft 4 and the outer ring 25 in the axial direction. 4 and the outer ring 25 can be prevented from coming off.

  Referring to FIG. 1, pinion shaft 4 (bearing structure 5 before completion) in which bearing unit 13 and sleeve 14 are integrated in this way is positioned on the left side in FIG. Is inserted through. At this time, in the pinion shaft 4, the pinion 7 is positioned in the vicinity of the screw hole 21 of the housing 12, and the end of the pinion shaft 4 opposite to the pinion 7 (the left side in FIG. 1) extends from the insertion hole 20. It protrudes to the left side.

At this time, the bearing unit 13 and the sleeve 14 are located slightly inside the housing 12 (on the right side in FIG. 1) than the insertion hole 20.
Here, the inner peripheral surface that divides the hollow portion in the housing 12 has a circumferential surface 12A that extends in the direction away from the insertion hole 20 along the axial direction (right side in FIG. 1) while bordering the insertion hole 20. 12A includes an annular flat surface 12B extending orthogonally from the end farthest from the insertion hole 20 (right end in FIG. 1) in the radial direction. The circumferential surface 12A has a larger diameter than the outer diameter of the sleeve 14, and the inner diameter of the flat surface 12B is smaller than the outer diameter of the sleeve 14 and larger than the inner diameter of the sleeve 14. A spiral thread portion (not shown) is formed on the circumferential surface 12A at least on the insertion hole 20 side. On the inner peripheral surface of the housing 12, a step 12C is formed at a portion where the circumferential surface 12A and the flat surface 12B are connected.

  The bearing unit 13 and the sleeve 14 are disposed inside the circumferential surface 12 </ b> A in the housing 12. At this time, a certain amount of clearance Q is secured in the radial direction between the outer peripheral surface of the sleeve 14 located on the outermost radial direction of the bearing unit 13 and the sleeve 14 and the circumferential surface 12A. Is loosely fitted to the circumferential surface 12A.

  Incidentally, the housing 12 having the circumferential surface 12A is generally formed of aluminum or the like having a linear expansion coefficient greatly different from that of the above-described steel material. Therefore, if this gap Q is not ensured, a difference occurs in the degree of expansion between the housing 12 and the sleeve 14 according to the temperature change, so that the sleeve 14 is pressed into the circumferential surface 12A. The sleeve 14 becomes unstable due to being loosely fitted or loosely fitted. By this gap Q, the difference in the degree of expansion generated between the housing 12 and the sleeve 14 is allowed, and the state of the sleeve 14 can be stabilized.

  A configuration in which the outer ring 25 is reduced in diameter by pressing the circumferential surface 12A into the outer ring 25 instead of the sleeve 14 (strictly speaking, the outer ring 25 is pressed into the circumferential surface 12A) is also conceivable. However, since the degree of expansion between the aluminum housing 12 and the steel outer ring 25 varies depending on the temperature change, the radial gap (see FIG. 5) between the distance A and the rolling element 26 is controlled to be negative. It is difficult to maintain the gap.

  Further, in the sleeve 14, the end surface (the right end surface in FIG. 1) opposite to the retaining portion 31 in the axial direction is in surface contact with the flat surface 12 </ b> B from the left side. In other words, the sleeve 14 is held by the housing 12 by being in surface contact with the flat surface 12B. Accordingly, the sleeve 14 and the bearing unit 13 integrated with the sleeve 14 and the pinion shaft 4 integrated with the sleeve 14 and the bearing unit 13 are prevented from being shifted to the right side in FIG. It is positioned. Note that the pinion plug 15 described below positions the pinion shaft 4 in the axial direction so as not to shift to the left side in FIG. When the pinion shaft 4 is completely positioned in the axial direction, the bearing structure 5 is completed.

  The pinion plug 15 has a cylindrical cap shape. The inner diameter of the pinion plug 15 is larger than the outer diameter of the pinion shaft 4. A spiral thread portion 15 </ b> A is formed on the outer peripheral surface of the pinion plug 15. In a state where the sleeve 14 is in surface contact with the flat surface 12B, the pinion plug 15 is externally fitted to the pinion shaft 4 from the left side in FIG. The pinion plug 15 is assembled to the housing 12 while closing the insertion hole 20 by the screw portion 15A being screwed into a screw portion (not shown) of the circumferential surface 12A. An annular gap in the radial direction between the pinion plug 15 and the pinion shaft 4 is closed with an annular seal 38. Therefore, foreign matter is prevented from entering the housing 12 from the insertion hole 20.

  Further, in FIG. 1, the right end surface of the pinion plug 15 attached to the housing 12 is in surface contact with the retaining portion 31 of the sleeve 14 from the left side (opposite to the flat surface 12B) over the entire circumference. is doing. Thus, the sleeve 14, in other words, the pinion shaft 4 integrated with the sleeve 14 and the bearing unit 13 is positioned in the axial direction so as not to shift to the left side in FIG. 1. Specifically, since the sleeve 14 is sandwiched from both sides in the axial direction by the pinion plug 15 and the flat surface 12B, the entire pinion shaft 4 is not displaced in any direction in the axial direction.

  The pinion shaft 4 is rotatably supported by the housing 12 via the bearing unit 13 with the bearing structure 5 thus completed. In addition, a cylindrical bush 39 is fitted on a portion of the pinion shaft 4 on the tip side (right end side in FIG. 1) from the pinion 7, and the pinion shaft 4 is connected to the pinion shaft 4 via the bush 39. The housing 12 is rotatably supported. Thus, the pinion shaft 4 rotatably supported by the housing 12 rotates according to the steering of the steering wheel 2.

  The rack plug 16 is a circular lid. In relation to the rack plug 16, a circumferential surface 12 </ b> D extending in a direction away from the screw hole 21 (downward in FIG. 1) while rimming the screw hole 21 is formed on the inner peripheral surface of the housing 12. A spiral threaded portion 12E is formed at the end of the circumferential surface 12D on the screwing hole 21 side. The rack plug 16 is externally fitted to a cylindrical main body 41 having an outer diameter substantially the same as the inner diameter of the screw hole 21 and the circumferential surface 12D, and one end in the axial direction of the main body 41 (the upper end in FIG. 1). And an annular lock nut 42. A spiral thread portion 41 </ b> A is formed on the outer peripheral surface of the main body 41.

  The rack plug 16 is attached to the housing 12 such that the main body 41 is fitted into the screw hole 21. As the rack plug 16 is screwed in, the threaded portion between the screw portion 41A of the main body 41 and the screw portion 12E of the circumferential surface 12D increases, and the main body 41 advances into the circumferential surface 12D. By tightening the lock nut 42, the screwed state between the screw portion 41A of the main body 41 and the screw portion 12E of the circumferential surface 12D is maintained.

  The yoke 17 has a cylindrical shape having an outer diameter slightly smaller than the inner diameter of the circumferential surface 12D. The yoke 17 is inserted inside the circumferential surface 12D and can slide along the axial direction of the circumferential surface 12D. A spring 43 is interposed between the rack plug 16 attached to the housing 12 and the yoke 17 in a compressed state. The spring 43 moves the yoke 17 away from the rack plug 16 and into the housing 12. It is energized. The pinion 7 of the pinion shaft 4 is positioned ahead of the yoke 17.

  The rack shaft 6 is long in a direction intersecting (orthogonal in FIG. 1) with the axial direction of the pinion 7 (a direction perpendicular to the paper surface in FIG. 1). The rack shaft 6 is supported by the housing 12 so as to be slidable along the longitudinal direction thereof. The rack shaft 6 in this state is disposed between the yoke 17 and the pinion 7 when viewed from the length direction. A rack 44 is formed on the side surface of the rack shaft 6 facing the pinion 7 along the length direction, and the rack 44 of the rack shaft 6 and the pinion 7 of the pinion shaft 4 are engaged with each other. As described above, the yoke 17 that is biased toward the pinion 7 biases the rack shaft 6 toward the pinion 7, thereby maintaining an appropriate meshing state between the rack 44 and the pinion 7. .

  Both ends of the rack shaft 6 in the length direction protrude from the housing 12, and wheels (not shown) are connected to the both ends via a knuckle arm (not shown). Therefore, when the steering wheel 2 is steered and the pinion shaft 4 is rotated as described above, the rack shaft 6 meshing with the pinion 7 of the pinion shaft 4 moves linearly along the length direction, The wheels on both sides of the rack shaft 6 are steered.

The present invention is not limited to the embodiment described above, and various modifications can be made within the scope of the claims.
For example, the bearing structure 5 supports the pinion shaft 4 in this embodiment, but in addition to the pinion shaft 4, the steering device 1 includes a steering shaft that rotates according to the steering of the steering wheel 2 (described above). A steering shaft 3 and the like, and the bearing structure 5 can be applied to support the steering shaft in general.

  Further, the outer ring 25 is formed of a material having a rigidity lower than that of the sleeve 14 so that the outer ring 25 can be reduced in diameter when the sleeve 14 is press-fitted into the outer ring 25, and the wall thickness (diameter dimension) of the outer ring 25 is reduced. The rigidity of the outer ring 25 may be made lower than that of the sleeve 14 by making it thinner than the sleeve 14.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 4 ... Pinion shaft, 5 ... Bearing structure, 11 ... 1st track groove, 12 ... Housing, 14 ... Sleeve, 25 ... Outer ring, 26 ... Rolling element, 27 ... Cage, 28 ... 2nd track groove , 31 ... retaining part, A ... interval

Claims (5)

In the bearing structure used in the steering device,
An annular first raceway groove extending in the circumferential direction is formed on the outer peripheral surface, and a steering shaft that rotates according to steering;
An annular outer ring formed on an inner peripheral surface of an annular second raceway groove that is externally fitted to the steering shaft and faces the first raceway groove from the radially outer side;
A plurality of rolling elements that are arranged between the steering shaft and the outer ring and are capable of rolling in the circumferential direction in a state of being fitted in both the first track groove and the second track groove;
An annular sleeve press-fitted from the radially outer side to the outer ring;
A holding portion for holding the sleeve;
A bearing structure comprising:   2. The bearing structure according to claim 1, wherein a negative gap is formed in a distance between the first raceway groove and the second raceway groove and the rolling element in the radial direction.   The bearing structure according to claim 1, wherein the outer ring and the sleeve are made of a steel material.   The bearing structure according to claim 3, wherein the outer ring is made of bearing steel, and the sleeve is made of carbon steel. A four-point contact ball bearing structure,
A cage that is disposed between the steering shaft and the outer wheel, and is movable in the circumferential direction while holding the plurality of rolling elements so as to be arranged at equal intervals in the circumferential direction;
A retaining portion provided on the sleeve for preventing the retainer from coming off between the steering shaft and the outer ring;
The bearing structure according to claim 1, comprising:

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