JP2002257208A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device capable of maximizing movement of a movable ring in a limited space, by solving the problems of a conventional ball non-circulating type ball screw where a distance for a screw shaft and a nut body to relatively move being reduced, and the technical difficulty of forming a holder in a spiral shape, since the holder has a spiral shape twisted by a portion for one lead portion's worth and stepped faces axially protruding, while hitting a stopper pin on its both sides in the width direction. SOLUTION: If a movable ring 92 moves to a prescribed position by rotating, a ball 15c in a pocket 17c at the end part of the holder 17 on its spiral direction side hits a stopper 97b, and balls 15a-15c are regulated so as not to move along spiral grooves 16a, 16b. Since the stopper 97b hits the ball 15c and regulates the movement of the balls 15a-15c, the holder 17 needs to be only easily formed into a simple cylindrical shape, and at least a space for the stepped face which is no longer required can be saved. Therefore, the movement of the movable ring 92 can be maximized in a limited space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball non-circulating ball screw in which a retainer for retaining a ball from scattering is arranged between a screw shaft and a nut body.

[0002]

2. Description of the Related Art Conventional non-circulating ball screws include:
A retainer for holding the ball so that it does not vary is arranged between the screw shaft and the nut body, and the relative movement between the screw shaft and the nut body is, for example, performed by a stopper pin provided on the screw shaft. There is a configuration in which the cage is regulated by hitting the cage.

[0005] As shown in FIG.
Numeral 0 has a spiral shape twisted by one lead, and has stepped surfaces 101 protruding in the axial direction corresponding to stopper pins (not shown) on both sides.

[0004]

In the above-mentioned conventional ball non-circulating ball screw, the retainer 100 has a helical shape twisted by one lead, and has a stepped portion projecting in the axial direction corresponding to the stopper pin. Since the attachment surfaces 101 are provided on both sides in the width direction, the distance by which the screw shaft and the nut body can relatively move is reduced. further,
It was technically difficult to form the retainer 100 in a spiral shape.

[0005]

A ball screw device according to the present invention comprises a spiral groove formed on an outer peripheral surface of a screw shaft and a spiral groove formed on an inner peripheral surface of a nut body externally fitted to the screw shaft. A plurality of balls are provided rotatably between a screw shaft and a nut body with a wall surface as a raceway surface, and a retainer for holding the balls between the screw shaft and the nut body so that the balls do not vary. Are arranged, spirally formed at predetermined intervals in the circumferential direction of the retainer main body, and a screw shaft and a nut body are configured to be relatively movable in the axial direction, and an outer periphery of the screw shaft is provided. At least one of the surface and the inner peripheral surface of the nut body is provided with a regulating member that regulates the movement of the end ball in the helical direction when the screw shaft and the nut body are relatively moved in the axial direction. .

The regulating member is disposed on the outer peripheral surface of the screw shaft and on the inner peripheral surface of the nut body at a position where a predetermined amount of movement is ensured when the screw shaft and the nut body are relatively moved.

Further, the regulating member has a body fixed to the groove wall surface of the spiral groove, a diameter of the body being enlarged with respect to the body and projecting into the spiral groove, and a relative axial direction of the screw shaft and the nut body. A head that hits a ball held in a pocket at the end in the spiral direction during movement.

In the above arrangement, for example, a plurality of balls held by a retainer in which the nut body rotates around the axis moves along the spiral groove, so that the screw shaft moves in the axial direction with respect to the nut body. When the nut body rotates in the opposite direction, the screw shaft moves in the opposite direction with respect to the nut body and contracts.

When the nut body and the screw shaft move relatively in this manner, the preceding ball (the ball held in the pocket at the end in the helical direction) hits the regulating member attached to the helical groove, thereby causing the ball to move. Movement is prevented, and the ball is prevented from detaching from the spiral groove and being separated.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall cross-sectional view in which a ball screw device according to an embodiment of the present invention is used for a continuously variable transmission of a vehicle, FIG. 2 is a cross-sectional view showing the overall configuration of the ball screw device, and FIG. FIG. 4 is a sectional view of the retainer holding the ball.

Here, an overall configuration of a continuously variable transmission using a ball screw device (feed device) 9 will be described with reference to FIG. The illustrated continuously variable transmission includes an input shaft 1 and an output shaft 2 arranged in parallel with each other in a radial direction. The input shaft 1 is rotated at a rotational speed according to an engine output (not shown). Is a dry type continuously variable transmission for transmitting power to wheels (not shown).

A driving side V-groove pulley 3 is provided on the input shaft 1.
A driven V-groove pulley 4 is connected to the output shaft 2, and a composite belt (hereinafter simply referred to as “belt”) 5 is wound between the pulleys 3 and 4. The operation unit 6 is driven to change the width of each of the pulleys 3 and 4 to adjust the winding diameter of the belt 5, so that the engine output is continuously variable and transmitted to the output shaft 2. I have.

The driving side V-groove pulley 3 has a fixed flange 31 fixed to the input shaft 1 and a movable flange 32 disposed coaxially with the input shaft 1 and spline-fitted. The surfaces 31 and 32 have conical surfaces, and a V-groove 33 is formed between the opposing surfaces.

The driven-side V-groove pulley 4 has a fixed flange 41 fixed to the output shaft 2 and a movable flange 42 disposed coaxially with the output shaft 2 and spline-fitted. Both flanges 41 and 42 have conical surfaces facing each other, and a V-groove 43 is formed between the two opposing surfaces. The movable flange 42 is constantly urged toward the fixed flange 41 by a spring member (not shown).

The operation unit 6 performs a stepless speed change operation by sliding the movable flange 32 of the driving side V-groove pulley 3 in the axial direction so as to vary the winding diameter of the belt 5 around the pulleys 3 and 4. And the DC motor 7
, A speed change gear train 8 and a ball screw device (feed device) 9.

The gearshift actuator gear train 8 includes a first gear 81 provided on the motor 7 side, a second gear 82 provided on the driving side V-groove pulley 3 side, a first gear 81 and a second gear 82. And a third gear 83 that meshes with the third gear 83.
The second gear 82 includes a large-diameter gear portion 8 meshed with the third gear 83.
4 and a small-diameter gear portion 85 that is long in the axial direction and is provided at a position away from the large-diameter gear portion 84 in the axial direction.

The ball screw device 9 is of a ball non-circulation type that converts the rotational power given from the second gear 82 of the gearshift actuator gear train 8 into axial driving force, as shown in FIG. In addition, a groove formed on an outer peripheral surface of a fixed ring (corresponding to a screw shaft) 91 to be described later and a groove formed on an inner peripheral surface of a movable ring (corresponding to a nut body) 92 which is externally fitted to the fixed ring 91. A plurality of balls 15a, 15b, and 15c having substantially the same diameter as the spiral grooves 16a and 16b are rotatably provided between the fixed ring 91 and the movable ring 92 by using the groove wall surface of the spiral groove 16b as a raceway surface. The fixed ring 91
Between the ball 15a, 15b, 1
A holder 17 for holding the 5c from scattering is arranged.

The retainer 17 includes balls 15a, 15b,
The pockets 17a, 17b, 17c to which 15c are mounted are formed side by side at predetermined intervals in the circumferential direction of the retainer body 17d, and the fixed ring 91 and the movable ring 92 are relatively movable in the axial direction (in this case, the fixed ring 91 The movable ring 92 is movable in the axial direction.

Then, as shown in FIG.
Is formed in a simple cylindrical shape and has pockets 17a, 17b,
17c are arranged on a spiral of only one lead.

As shown in FIGS. 2 and 3, a movable ring 92 is provided on the outer peripheral surface of the fixed ring 91 and the inner peripheral surface of the movable ring 92.
Pockets 17a, 1 at the end when the body moves in the axial direction.
Stoppers (corresponding to regulating members) 96a, 96b, 97 for regulating the movement of the ball 15c mounted on the 7c in the spiral direction.
a, 97b are arranged, and the respective stoppers 96
a, 96b, 97a, and 97b have a body portion 98 having a fixed ring 91;
Are implanted on the outer circumferential surface of the movable ring 92 and the inner circumferential surface of the movable ring 92.
The head 99 that is expanded in diameter and hits the ball 15c protrudes into the spiral groove 16a and the spiral groove 16b (the portion provided in the movable ring 92 is not shown).

The stoppers 96a, 96b, 97
The positions of “a” and “97b” are arranged at positions where the engine output of the ball screw device 9 can be changed steplessly within a required range.
a, 96a and 96b attached to the spiral groove 16a of the movable ring 92.
97b restricts the movement amount to a predetermined amount in both axial directions.

The fixed ring 91 has a large diameter portion 91a and a small diameter portion 91b, and as shown in FIG.
Is fixedly disposed coaxially with the driving-side V-groove pulley 3 by being mounted between the input shaft 1 and the housing 10 via a rolling bearing 11, and the small-diameter portion 91b is extended in the axial direction and its outer peripheral surface is formed. The helical groove 16a is formed in the groove.

The movable ring 92 is provided on the outer peripheral surface of the body of the movable flange 32 of the driving-side V-groove pulley 3 on the rolling bearing 1.
2, a gear portion (involute spur gear) 95 is formed at an axial end of an outer peripheral portion of the movable ring 92.

The side surface of the movable ring 92 is in contact with the side surface of the movable flange 32, and the rolling bearing 1
2, the movable ring 92 and the movable flange 32 are both configured to be movable in the same axial direction.

The gear portion 95 meshes with the small-diameter gear portion 85 of the second gear 82 to apply rotational power. The gear portion 95 is integrally formed by injecting resin into a radially outwardly extending annular convex portion 92b formed on the outer periphery of the movable ring 92.

A spline (or serration) is formed on the outer peripheral surface of the annular convex portion 92b, and a part of the gear portion 95 made of a resin material bites into the unevenness of the spline so that the spline is prevented from rotating. I have.

In the above configuration, the drive of the engine (not shown) is transmitted to the input shaft 1, and the input shaft 1 and the driving side V-groove pulley 3 rotate around the axis, and the rotational driving force is transmitted via the belt 5 to the driven side. The power is transmitted to the V-groove pulley 4, and the driven V-groove pulley 4 and the output shaft 2 rotate around the axis, the wheels rotate, and the vehicle runs.

When performing a continuously variable transmission operation in a continuously variable transmission, the separation width of the movable flange 32 from the fixed flange 31 of the driving side V-groove pulley 3 is adjusted as necessary to change the winding diameter of the belt 5. It is done by doing.

Here, the operation at the time of the continuously variable transmission will be described. When the DC motor 7 is driven, its rotational power is transmitted to the speed-change actuator gear train 8, which rotates around the axis, and the rotational power is transmitted to the movable ring 92 of the ball screw device 9.
Which rotates around the axis.

In the ball screw device 9, when the movable ring 92 rotates counterclockwise around the axis in the state of FIG. 2, for example, the movable ring 92 moves rightward in the drawing with respect to the fixed ring 91, and the whole is extended. And the movable flange 32
Moves along the axial direction so as to approach the fixed flange 31, the belt 5 rises along the slopes of the movable flange 32 and the fixed flange 31, and the winding diameter of the belt 5 increases, and the rotation of the output shaft 2 The number of revolutions (wheels) increases.

Conversely, when the movable ring 92 rotates clockwise, the movable ring 92 moves to the left in the drawing with respect to the fixed ring 91, and the ball screw device 9 as a whole shrinks, whereby the movable flange 32 is fixed. The belt 5 moves along the axial direction so as to be separated from the flange 31, and the belt 5 descends along the slopes of the movable flange 32 and the fixed flange 31, so that the winding diameter of the belt 5 decreases and the rotation speed of the output shaft 2 decreases. .

The state shown by the solid line in FIG. 2 shows a posture in which the ball screw device 9 as a whole is contracted, and thus the rotation speed of the output shaft 2 is small. In this state, the balls 15a, 15 held in the pocket 17a at the end in the spiral direction are
Of the balls b and 15c, the movement of the ball 15c in the spiral direction is restricted by the stopper 97a. Of the balls 15a, 15b, 15c held in the pocket 17c at another end, the movement of the ball 15c in the spiral direction is restricted by the stopper 96a.

Referring to FIG. 2, the operation for increasing the number of revolutions of the output shaft 2 will be described focusing on the operation of the ball screw device 9.

That is, when the movable ring 92 rotates counterclockwise around the axis in the state shown in FIG. 2, for example, the movable flange 32 moves along the axis so as to approach the fixed flange 31, and the belt 5 moves. It rises along the slopes of the movable flange 32 and the fixed flange 31, the winding diameter of the belt 5 increases, and the number of rotations of the output shaft 2 (wheels) increases. When the ball 15c moves in the direction, the ball 15c separates from the stopper 97a, and the ball 15c held in each of the pockets 17a, 17b, 17c.
a, 15b, 15c are the spiral groove 16a and the spiral groove 16b
Move to the right while rolling along.

The pocket 17c at the end in the spiral direction
The ball 15c of the ball 15c hits the stopper 97b and the stopper 96b holds the ball 15c held in the pocket 17a.
, The spiral grooves 1 of the balls 15a, 15b, 15c
The movement along the groove 6a and the spiral groove 16b is restricted, and the movement is stopped. At this time, the movable ring 92 has reached a position indicated by a virtual line in the figure, for example.

When the rotational speed of the output shaft 2 is reduced again, the movable flange 92 is separated from the fixed flange 31 by rotating the movable ring 92 counterclockwise around the axis in the imaginary line of FIG. The belt 5 moves down along the slopes of the movable flange 32 and the fixed flange 31 so that the winding diameter of the belt 5 is reduced and the number of revolutions of the output shaft 2 is reduced. When the ring 92 rotates and moves to the left in the figure, the ball 15c held in the pocket 17c separates from the stopper 97b and
5a, 15b and 15c are spiral grooves 16a and spiral grooves 16
It moves to the left while rolling along b.

The pocket 17a at the end in the spiral direction
When the ball 15c at a position hits the stopper 97a, the movement of the balls 15a, 15b, 15c along the spiral groove 16a and the spiral groove 16b is restricted, and the ball 15c does not move any further. In some cases, by continuously rotating the movable ring 92, the movable ring 92 further moves to the left.
5a, 15b and 15c rotate only within the spiral grooves 16a and 16b, and the movable ring 92 reaches the position shown by the solid line in the figure.

The stoppers 96a, 96b, 9
7a and 97b are not the ones in which the retainer 17 abuts as in the prior art. , 15c are spiral grooves 16
Since the balls 15a, 15b, and 15c are prevented from moving along the lines a and 16b, the balls 15a, 15b, and 15c can be reliably prevented from falling off.

The retainer 17 is connected to the stoppers 96a, 96
b, 97a, 97b and the balls 15a, 15 at the ends.
Since the movement of b and 15c is not restricted, it is not necessary to form the retainer 17 in a helical shape and form the stepped surfaces protruding in the axial direction on both sides in the width direction as in the related art. The movable ring 92 can be formed in a cylindrical shape, so that it can be easily formed, and the space can be saved because the stepped surface is not required. By maximizing the amount and using it in a continuously variable transmission as described above, the range of continuously variable transmission can be extended.

Further, the ball 15 in the above embodiment is used.
a, 15b and 15c are made of bearing steel,
When carburizing and quenching a, 96b, 97a, 97b,
The balls 15c at the ends are stoppers 96a, 96b, 97
a, 97b are easily pressed when pressed against the spiral groove 16c.
Rolling the groove wall surfaces a and 16b facilitates abrasion of the groove wall surfaces, but the stoppers 96a, 96b, 97a, and 97a are formed by forming the end balls 15c of ceramic.
Even when carburizing and quenching is performed on 97b, since the hardness of the ceramic is higher, it is possible to prevent indentations from occurring on the ball 15c and suppress wear of the groove wall surface.

As in this embodiment, the ball 15c at the end is made of ceramic, so that the ball 15c
c to prevent the formation of indentations on the spiral grooves 16a, 1
The ball 15c having substantially the same diameter as the ball 15c can be used.
The phenomenon of being stuck between the spiral grooves 16a, 16b and the spiral grooves 16a, 16b can be avoided, and the movable ring 92 can be smoothly moved with respect to the fixed ring 91.

When the diameter of the end ball 15c is smaller than the diameter of the ball 15b by, for example, about 15 to 100 μm, the balls 15c are
When the ball 15c is pressed against the b, 97a, 97b, even if an indentation is produced, the ball 15c is unlikely to roll and slide with respect to the groove wall surface. can do.

Further, the inside of the above-mentioned dry type continuously variable transmission is non-lubricated, and is particularly arranged in a power transmission path from the motor 7 to the movable flange 32 of the driving side V-groove pulley 3. Since the second gear 82 and the gear portion 95 of the movable ring 92 are easily worn, the second gear 82 is made of a metal gear, and the gear portion 95 is made of a resin gear. However, the second gear 82 and the movable ring 9
The wear resistance and the aggressiveness of the counterpart of the second gear portion 95 are improved, so that it is possible to greatly contribute to the improvement of the service life and the maintenance-free operation becomes possible.

In the above embodiment, the stoppers 96a, 96b are provided on both the outer peripheral surface of the fixed ring 91 and the spiral grooves 16a, 16b formed on the inner peripheral surface of the movable ring 92 fitted on the fixed ring 91.
The balls 15a, 15b, 15c are provided on one of the outer peripheral surface of the fixed ring 91 and the inner peripheral surface of the movable ring 92, but are not limited thereto. You may comprise so that it may separate.

[0045]

As is apparent from the above description, according to the present invention, a plurality of balls are formed on the screw shaft and the nut body by using the groove wall surfaces of the spiral grooves formed on the outer peripheral surface of the screw shaft and the inner peripheral surface of the nut body as the raceway surfaces. And the ball is held by a retainer so as not to disperse, and the screw shaft and the nut body are configured to be relatively movable in the axial direction. At least one of the peripheral surfaces is provided with a regulating member that regulates the movement of the end ball in the helical direction when the screw shaft and the nut body move relative to each other in the axial direction. When the ball moves relatively, the ball at the end hits the restricting member attached to the spiral groove, thereby preventing the ball from moving and preventing the ball from separating from the spiral groove and being separated.

Further, since the movement of the ball at the end portion is not restricted by applying the retainer to the restricting member, the retainer is formed in a spiral shape as in the conventional case, and the stepped surface protruding in the axial direction is formed to have a width. It is only necessary to form it in a simple cylindrical shape without forming it on both sides in the direction, so that the formation is easy, and the space saving can be achieved by the amount that the stepped surface is unnecessary, so that the limited space can be achieved. The maximum amount of movement of the entire apparatus in the axial direction can be ensured.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a ball screw device according to an embodiment of the present invention used for a continuously variable transmission of a vehicle.

FIG. 2 is a sectional view showing the overall configuration of the ball screw device.

FIG. 3 is an enlarged sectional view of a main part of the ball screw device.

FIG. 4 is a perspective view of the retainer in a state where the ball is also retained.

FIG. 5 is a perspective view of a state in which a ball is held by a retainer of a conventional ball screw device.

[Explanation of symbols]

 Reference Signs List 1 input shaft 2 output shaft 3 driven-side V-groove pulley 4 driven-side V-groove pulley 5 belt 9 ball screw device 15a ball 15c ball 16a spiral groove 16b spiral groove 17 retainer 17a pocket 17c pocket 31 fixed flange 32 movable flange 91 fixed ring 92 Movable ring 96a Stopper 97a Stopper 96b Stopper 97b Stopper

Claims (3)

[Claims] 1. A plurality of balls are formed on a screw shaft by using a groove wall surface of a spiral groove formed on an outer peripheral surface of a screw shaft and a groove wall surface of a spiral groove formed on an inner peripheral surface of a nut body fitted on the screw shaft as a raceway surface. And a nut body, and a retainer is provided between the screw shaft and the nut body for holding the ball so that it does not disperse. In a ball non-circulation type ball screw device formed on a spiral at predetermined intervals in the circumferential direction of the container main body and configured so that the screw shaft and the nut body are relatively movable in the axial direction, the outer peripheral surface of the screw shaft and At least one of the inner peripheral surfaces of the nut body is provided with a regulating member that regulates the movement of the end ball in the helical direction when the screw shaft and the nut body move relative to each other in the axial direction. And ball screw device. 2. The method according to claim 1, wherein the regulating member is disposed on an outer peripheral surface of the screw shaft and on an inner peripheral surface of the nut body at a position where a predetermined amount of movement is secured when the screw shaft and the nut body are relatively moved. The ball screw device according to claim 1, wherein 3. The regulating member has a body fixed to the groove wall surface of the spiral groove, a diameter of the body extending to the body, and a protrusion protruding from the spiral groove. The ball screw device according to claim 1, further comprising a head that hits a ball held in a pocket at an end in a spiral direction during movement.