JP3132911B2 - Ball screw device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw device having a support bearing mounted outside a ball nut, and more particularly to a structure for applying a preload to a ball screw and a support bearing.

[0002]

2. Description of the Related Art Conventionally, in a power steering mechanism of an automobile, a ball screw device is often used as a device for converting rotation of a motor into sliding motion of a steering rack. This ball screw device has a structure in which a support bearing is attached to the outside of a ball nut, and the ball screw is supported on an automobile frame via the support bearing.

[0003] In the ball screw device equipped with the support bearing as described above, if there is a gap in the fitting portion of the ball screw or the support bearing, there is a problem that rattling of the steering and insufficient rigidity occur. To cope with this problem, Japanese Patent Publication No. 62-25902 proposes a device capable of simultaneously applying a preload to a ball screw and a support bearing.

In this apparatus, as shown in FIG. 2, ball nuts 21 and 22 which are double nuts are connected by a key 23, and the ball 2 is mounted on the outer periphery of the ball nuts 21 and 22.
A pair of outer rings 2 of the bearing 24 for support via the fifth and 26
The preloading member 29 is press-fitted between the outer rings 27 and 28 to urge the outer rings 27 and 28 and the ball nuts 21 and 22 away from each other.

[0005]

However, in the device proposed above, the preload is applied by press-fitting the preload applying member 29 between the outer races 27 and 28.
It is simply determined only by the width dimension of the preload applying member 29. For this reason, there is a disadvantage that only a certain preload can be set, and the preload amount cannot be easily changed or adjusted.

Further, since the outer rings 27 and 28 are separated from each other in the axial direction and the ball nuts 21 and 22 are moved by the movement of the outer rings to apply a preload, the same preload is always applied to the support bearing and the ball screw. Will join. Therefore, there is a problem that the operation of setting the preload amount of the ball screw requiring a large rigidity to be large with respect to the support bearing cannot be performed, and the rigidity of the ball screw shaft tends to be insufficient.

Therefore, according to the present invention, the preload of the ball screw and the support bearing can be simultaneously applied, and the preload can be easily changed. Further, the preload of the ball screw can be arbitrarily set as required. It is an object of the present invention to provide a ball screw device capable of performing the following.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention divides a ball nut fitted on a ball screw shaft in the axial direction, and separates each ball nut into a shaft allowing the axial movement. Connected via a stopping means, an outer ring of a double-row support bearing is provided on the outside of the ball nut so as to be movable in the axial direction, and the inner ring is split axially between the double-row rolling elements, The preload nut for pressing the one of the divided inner rings in the axial direction is attached to the threaded portion provided on the one ball nut.

[0009]

In the above structure, when the outer ring of the support bearing is fixed and the preload nut is moved with respect to the screw portion and one of the inner rings is pressed, the inner ring moves relative to the fixed outer ring. Therefore, a preload is applied to the support bearing. In addition, the movement of the nut for preloading causes the ball nut to move in a direction opposite to the inner ring, that is, a direction in which the divided ball nuts move away from each other, so that a preload is simultaneously applied to the ball screw.

On the other hand, if the preload nut is further rotated in a direction in which the inner rings are joined in a state where the inner rings of the support bearings are joined, only the ball nut moves in a direction in which the inner rings are separated from each other, and the support for the ball screw is reduced. Preload higher than that for bearings can be applied.

[0011]

FIG. 1 shows a ball screw device according to an embodiment. In the figure, reference numeral 1 denotes a ball screw shaft, and two ball nuts 3 and 4 divided in the axial direction via a large number of balls 2 are fitted on the peripheral surface of the ball screw shaft 1.

At the opposite ends of the ball nuts 3 and 4, axial key grooves 5 and 6 are formed, and a key 7 is inserted into both key grooves 5 and 6 so that both keys are inserted. The ball nuts 3 and 4 are connected to each other so as to be prevented from rotating and to be freely approached and separated in the axial direction.

A support bearing 8 composed of double-row angular ball bearings is mounted on the outer diameter surfaces of the ball nuts 3 and 4. The support bearing 8 includes an outer race 10 having a mounting flange 9, two rows of balls 12 and 13 arranged in ball grooves 11 on both sides of the outer race 10, and balls 12 and 13 in each row. A pair of inner rings 14 and 15 are engaged with each other, and each of the inner rings 14 and 15 is fitted on the outer diameter surface of the ball nut 3 or 4 so as to be freely movable in the axial direction.

A thread 16 is formed on the outer diameter surface of one of the ball nuts 4, and a preload nut 17 is screwed into the thread 16, and the end face of the preload nut 17 is formed on the inner race 15. It comes into contact with the outer end face 15a. The outer surface of the other ball nut 3 is provided with an inner ring 1.
A step 18 is formed as a stopper with which the end face of the fourth member 4 contacts.

In the ball screw device of the embodiment having the above-described structure, when the preload nut 17 is rotated on the screw portion 16 with the outer ring 10 of the support bearing 8 being fixed to the fixing member, each ball is rotated. Since the nuts 3 and 4 are prevented from rotating by the key 7, the preload nut 17 is
It moves axially along 6.

As shown in FIG. 1, when the preload nut 17 comes into contact with the outer end surface 15a of the inner race 15 and presses the inner race 15 in the direction of arrow a, the inner race 15 moves axially toward the fixed outer race 10. But the movement is ball nut 3
In order to make the other inner ring 14 stopped by the inner ring 14 approach the outer ring 10, a preload in the contraction direction is applied to each of the balls 12, 13.

The movement of the preload nut 17 is as follows.
Since a load is applied to the ball nut 4 in the direction opposite to that of the inner ring 15 (in the direction of arrow b), the ball nut 4 is axially moved away from the other ball nut 3 by the load, and is applied to each ball 2 of the ball screw. Is applied with a preload in the expanding direction.

By operating the preload nut 17 in this manner, a preload can be simultaneously applied to the ball screw and the support bearing 8, and the balls 2 of the ball screw and the balls 12 and 13 of the support bearing 8 can be applied. The rattling of the fitting portion can be eliminated.

In the above structure, the preload nut 17
When the amount of movement of the preload nut 1 changes, the amount of movement of the inner ring 15 and the ball nut 4 changes in accordance with the change.
The amount of preload applied to the ball screw and the support bearing 8 can be changed or adjusted by adjusting the operation amount of the operation member 7.

On the other hand, the clearance between the inner rings 14 and 15 is set to a size that gives an appropriate preload to the support bearing 8.
After the end faces of the inner rings 14, 15 are joined together, when the preload nut 17 is further tightened toward the inner ring 15, only the ball nut 4 moves in the direction of arrow b and separates from the other ball nut 3. . For this reason, a preload is further applied to each ball 2 of the ball screw,
A large preload equal to or greater than the support bearing 8 can be applied to the ball screw.

In the above embodiment, the preload nut 1
7, the end face of the inner ring 15 is directly pressed.
A spacer may be provided between the nut 17 and the inner ring 15, and the inner ring may be pressed via the spacer.

As the rotation preventing means for the ball nuts 3 and 4, other than the combination of the key and the key groove shown in the figure, a means such as a spline or a serration groove may be used.

[0023]

As described above, according to the present invention, the preload is simultaneously applied to the ball screw and the support bearing since the divided ball nut and the inner ring of the support bearing are relatively moved in the axial direction by screwing the preload nut. can do.

Further, by changing the amount of movement of the preload nut, the amount of movement of the ball nut and the inner ring can be adjusted, so that the amount of preload can be easily changed.

Further, since only the ball nut can be axially moved with the inner ring fixed, the amount of preload of the ball screw can be set arbitrarily larger than that of the support bearing, and the rigidity of the ball screw can be improved. Can be planned.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment.

FIG. 2 is a sectional view showing a conventional example.

[Explanation of symbols]

 1 Ball Screw Shaft 2 Ball 3, 4 Ball Nut 7 Key 8 Support Bearing 10 Outer Ring 12, 13 Ball 14, 15 Inner Ring 16 Thread 17 Preload Nut

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16H 25/20-25/24

Claims (1)

(57) [Claims] 1. A ball nut fitted to a ball screw shaft is divided in an axial direction, and each of the ball nuts is connected via a detent means allowing movement in the axial direction. The inner ring of the row of bearings for support is provided so as to be movable in the axial direction, and the inner ring is axially divided between the rolling elements of the double row, and divided into the threaded portions provided on the one ball nut. A ball screw device equipped with a preload nut that presses one inner ring in the axial direction.