DE102006014052B3 - Reverse channel for ball screw, has reverse bend that is formed in cross-section such that bend has large section surface so that distance piece does not contact with inner guiding surface when piece guides through bend - Google Patents

Abstract

The channel has a reverse bend (51) and two guiding sections (52, 53) that connect two ends of the bend, a coil groove (21) and a reverse borehole (22). The bend has inner and outer guiding surfaces, where an inner curved line is in contact with the inner surface. A center point of a curved line is provided in a position such that inner and outer lines are not parallel to each other. The bend is formed in a cross-section such that the bend has a large section surface so that a distance piece (4) does not contact with the inner guiding surface when the piece guides through the bend.

Description

The The invention relates to a ball screw, in particular a return channel a ball screw whose inside has a lower curvature and which is non-circular in cross-section, which is a low-friction passing of spacers through the return channel provides.

at usual Ball screws it is common a spacer between each two adjacent rolling balls to provide a low-friction Low noise operation too ensure as well Shocks and wear of the rolling balls to prevent when the rolling balls inside the ball screw move.

When installing the spacer between the rolling balls, it is particularly important how the spacer is dimensioned. If it is dimensioned too small, the spacer located between the two adjacent rolling balls is slightly detached. In the worst case, the spacer may tip over, resulting in seizing of the rolling balls. However, if it is oversized, it often happens that the spacer abuts against the wall of the track, resulting in the interference of normal operation of the trackballs. Therefore, the spacer is usually smaller in size than the diameter of the trackball. From the US 6,742,408 For example, a construction is known in which the maximum outer diameter of the spacer is 0.5 to 0.9 times the outer diameter to solve the above-mentioned problem.

In 1 a conventional ball screw is shown in the construction of an outer circulation system. According to a spiral groove 82 is a return bore 83 in a nut 81 drilled. This is in addition a manifold 84 provided for the return of the rolling balls 7 is available.

Due to the smaller restriction of the contour of the ball screw in the design of the outer circulation system, it is possible that the manifold 84 has a larger curvature. This avoids that the loosening, overturning and interference of the spacer occur whose maximum outer diameter is limited to 0.5 to 0.9 times the outer diameter of the rolling balls, as is usually the case in the aforementioned construction. In addition, a low-friction movement of the rolling balls 7 and spacers 85 in the manifold 84 guaranteed.

The exposed manifold 84 but is slightly exposed to external forces and thereby deformed, which can lead to the interference of the rolling balls and spacers when passing through the manifold 84 be passed. In the worst case, the rolling balls can even be stuck rigidly. In the design of the ball screw the trend towards lightness and compactness, which causes the reduction of the space available for the return of the rolling balls clearance of the ball nut. Therefore, the design of the outer circulation system in the ball screw for the design of the miniaturization is unfavorable. Therefore, the recirculating ball screw provided with the internal circulation structure without additional external circulation system can better meet the demands on the lightness and compactness.

2 turns one off US 6,176,149 known ball screw with an internal circulation system. A spiral groove 92 is in the nut 91 drilled, with the spiral groove 92 at its two ends, each with a return element 93 is provided. Inside the return elements 93 each is a return manifold 931 formed by the rolling balls 7 and spacers 94 be passed.

In the miniaturization of the nut is the radius of curvature of the return manifold 931 of the return element 93 limited due to the reduction in the outer diameter of the nut to a corresponding extent. In this case, the rolling balls 7 though through the return manifold 931 round lead. That between the two adjacent rolling balls 7 provided spacer 94 that does not move in a rolling motion, but from the two rolling balls 7 but pushed inside the return manifold 931 pushed inwards and thus against the inner wall of the return manifold 931 be pressed, causing the rigid sticking of the rolling balls 7 and the spacer 94 inside the return manifold 931 can lead. In this way, the rolling balls 7 not to perform a smooth return operation.

In the sphere of the ball screw, the problem is not yet dealt with that the spacer is pressed against the inner wall of the inside of the return manifold. However, such a solution in the field of linear guide has already been proposed. From the US 6,513,977 results in a linear guide, in which a chamfer is formed at the junction between a curved portion and a straight portion of a return channel. This avoids that interference occurs when the spacer passes from the straight section into the curved section of the return channel.

The design of the chamfer yes can prevent the spacer abuts against the junction between the curved and the straight portion of the return channel. However, the interference occurs when the spacer comes into contact with the other portion of the return manifold. From the US 6,663,285 For example, another improvement disclosed by the same inventor is known. In the US 6,663,285 the inner edge portion of the return manifold of the linear guide is improved. That is, the radius of curvature of the inner edge portion of the return manifold is reduced such that the inner edge of the return manifold is displaced inwardly, which counteracts the impact of the spacer against the wall of the inner edge of the return manifold.

It should be noted that at the US 6,513,977 and US 6,663,285 is a linear guide. However, the transmission of the structure of the linear guide on the ball screw is very problematic. This is because the return duct of the linear guide provides a larger clearance, whereby the return duct of the linear guide can be configured as a semicircle with a larger radius of curvature such that the semicircular return manifold connects two parallel straight channels. Therefore, the inner edge portion of the return manifold of the linear guide can achieve the reduction of the concentric radius.

In the ball screw, the return manifold is normally provided inside the end cap. How out 4 Obviously, the end cap needs 6 at its two ends of the return manifold 61 each with a straight guide section 62 . 63 Be provided with which a spiral groove 64 a nut and a parallel to the nut extending, extending in the axial direction return bore 65 connect. Therefore, the angle between the two ends of the return manifold is 61 less than 90 °. Will the from the US 6,663,285 known structure in which the reduction of the concentric radius is used, transferred to the end cap of the ball screw, then creates a gap G between the straight guide portion 62 the return manifold 61 and the spiral groove 64 as well as between the guide section 63 the return manifold 61 and the return bore 65 like this in 5 is shown. This may result in a disturbance of the rolling circulation of the rolling balls. In the worst case, however, the rolling balls can be stuck. Therefore it is not possible that at the US 6,663,285 The method of concentric blade replacement used solves the problem that the spacer comes into contact with the wall of the inner edge of the recirculation spindle of the ball screw.

Of the Invention is based on the object, a return channel of a ball screw to create, with which the between two adjacent rolling balls provided spacers low-friction can pass through a return manifold.

These The object is achieved by a ball screw whose end caps each have a return channel to connect the helical groove and the return bore in such a way that a plurality of rolling balls and spacers inside the nut to run back to endless circulation can. The return channel has a return manifold and two straight guide sections on, with the straight guide sections the two ends of the return manifold, the Spiral groove and the return bore connect. The return manifold consists from an inner and an outer guide surface, wherein an inner arc line outside comes into contact with the inner guide surface, while an outer arc line Outside comes into contact with the inner guide surface. The arc length the arc line is smaller than half the circumference. The center of the circle The arc line is at a point next to the center of the circle the outer bow line lies and from the outer arc line is removed, such that the inner and the outer arc line are not parallel to each other, whereby the existing of the inner and the outer guide surface Return manifold in the Cross section not circular is trained. This avoids that the spacer with the inner guide surface comes in contact, when passing through the return manifold.

The spacer does not move in a rolling, but is trapped by two rolling balls and moved. Therefore, the spacer located inside the return manifold is pushed inward and displaced. The inner guide surface of the return manifold must be displaced inward to prevent the inner guide surface from being pushed by the spacer. The inventor has found that the more the spacer approaches the center of the return bend, the smaller the more the inward offset of the spacer Spacer is removed from the center. Therefore, the inward displacement of the arc line need only be adapted to the displacement of the inwardly pushed spacer. Due to the offset of the circle center of the arc line and the increase in the radius of curvature, the curvature of the inner guide surface coming into contact with the arc line is alleviated or reduced. In this way, the spacer is not brought into contact with the inner guide surface, even if it is pushed inwards. As a result, a low-friction passage of the spacer is ensured by the return manifold.

Of the Return manifold, the from the outside with the inner arc line in contact, inner guide surface and the outside with the outer arc line in touch brought, outer guide surface consists, is not circular in cross section formed when the circle center of the inner arc line after Outside shifted and the radius of curvature is enlarged. Since the outer guide surface the passing the rolling balls is used, therefore, the diameter of the outer guide surface is greater than or equal to that of the rolling balls, while those on the inner bow line adapted, inner guide surface in different Form connected to the outer guide surface is. First, the inner guide surface has a U-shaped cross-section and therefore consists of a circular arc section and a straight line section, where the diameter is greater than or equal to that of the rolling balls while the circular arc section with the straight section comes into contact with the outer guide surface in such a way that the return manifold in the Cross-section is elliptical. The other is the inner one Guide surface in cross section circular arc formed, wherein the diameter of the inner guide surface between the diameter the spacers and the rolling balls is such that the inner and the outer guide surface to a non-circular in cross-section trained return manifold are joined together. With the above mentioned Both types is a low-friction passing the spacers through ensures the return manifold.

The Invention has the features specified in claim 1. advantageous Embodiments of the invention are specified in the subclaims.

in the The following describes the objects and mode of operation of the invention the preferred embodiments and the attached Drawings closer explained. Show it:

1 a schematic representation of an outer circulation system of a conventional ball screw;

2 a schematic representation of an internal circulation system of a conventional ball screw;

3 a schematic representation of the internal circulation system of a conventional ball screw, wherein the spacer abuts against the inner edge of the return manifold;

4 a schematic representation of a return manifold in an end cap of a conventional ball screw;

5 a schematic representation of the return manifold whose inner edge is offset by the method of reducing the concentric radius, whereby a gap between the guide portion and the helical groove and between the guide portion and the return hole is formed;

6 a schematic representation of a ball screw according to the invention with sectioned nut;

7 a schematic representation of a return manifold according to the invention;

8th a section through a first embodiment of the return manifold according to the invention; and

9 a section through a second embodiment of the return manifold according to the invention.

As in 6 to 8th shown, a ball screw according to the invention has a spindle 1 and one on the spindle 1 mounted nut 2 on. The spindle 1 and the nut 2 have respective corresponding spiral grooves 11 respectively. 21 in which are numerous rolling balls 3 are located. The nut 2 has a return bore extending in the axial direction 22 on, at both ends of each an end cap 5 is appropriate. Each of the end caps 5 has a return channel to the spiral groove 21 and the return bore 22 connect to. In this way, the numerous rolling balls 3 and several spacers 4 in the nut 2 Make a smooth return to endless circulation.

As in 7 shown, the return channel has a return manifold 51 and two straight guide sections 52 . 53 on, with the straight guide sections 52 . 53 the two ends of the return manifold 51 , the spiral groove 21 and the return bore 22 connect. The return manifold 51 consists of an inner and an outer guide surface 511 . 512 [please refer 8th ]. An inner arc line I comes outside with the inner guide surface 511 in contact while an outer arc line O outside with the inner guide surface 512 comes into contact. The arc length of the arc line I is smaller than half of the circumference. In addition, the circle center of the arc line I is located at a position which is adjacent to the circle center of the outer arc line O and from the outer arc line O is removed. Thus, the inner and the outer arc line are not parallel to each other. In this way, the out of the inner and the outer guide surface 511 . 512 existing return manifold 51 not circular in cross section. This will avoid the spacer 4 with the inner guide surface 511A comes into contact when passing through the return manifold 51 larger cut surface passes.

In the embodiment according to 8th is the outer guide surface 512 Semicircular in cross-section, wherein the diameter of the outer guide surface 512 greater than or equal to the diameter of the rolling balls 3 is. The inner guide surface 511 is provided with a U-shaped cross-section consisting of a semicircle section A and a straight line section B. The diameter of the semicircular section A is greater than or equal to the diameter of the rolling balls 3 , The semicircular section A is above the straight line section B with the outer guide surface 512 connected so that the return manifold 51 is elliptical in cross-section.

S:

Außendurchmesser des Abstandsstücks 4

y:

maximale Verschiebung des nach innen geschobenen Abstandsstücks 4

w:

Abstand des Mittelpunkts der Führungsabschnitte 52, 53 des Rücklaufkanals zu ihrer Innenwand

R:

Krümmungsradius der Mittellinie des ursprünglichen Kanals des Rücklaufkrümmers 51

B:

Halbmesser der Rollkugel 3

d:

Dicke des Mittelabschnitts des Abstandsstücks 4 oder der geringste Abstand zwischen beiden benachbarten Rollkugeln 3

x:

maximaler Versatz der Bogenlinie I

r:

Krümmungsradius der ursprünglichen Innenwand des Rücklaufkrümmers 51

m:

Abstand von der Bogenlinie I zum Scheitelpunkt der beiden Innenwand der Führungsabschnitte 52, 53

α:

Winkel, der durch die beiden Führungsabschnitte 52, 53 begrenzt ist.

r2:

Halbmesser der Bogenlinie I nach dem Versatz

The following will be on 7 and 8th Referenced. The spacer 4 does not move in a rolling manner, but is made of two rolling balls 3 trapped and moved. Therefore, this will be inside the return manifold 51 located spacer 4 pushed in and pushed inwards. The inner guide surface 511 the return manifold 51 Must be moved inwards to prevent the inner guide surface 511 from the spacer 4 is encountered. The inventor has found that the inward offset of the spacer 4 the larger, the more the spacer 4 the center of the return manifold 51 approaches, while the smaller the more the spacer 4 away from the center. Therefore, the inward displacement of the arc line I needs only to the displacement of the pushed inward spacer 4 adapt. This means that the maximum offset of the arc line I in dependence on the inwardly made, maximum displacement y of the center of the return manifold 51 located spacer 4 changed. Taking into account the outer diameter S of the spacer 4 and the relevant conditions, the radius r2 of the arc line I and the relevant parameters are defined as follows:

S:

Outer diameter of the spacer 4

y:

maximum displacement of the inwardly pushed spacer 4

w:

Distance of the center of the guide sections 52 . 53 the return channel to its inner wall

R:

Radius of curvature of the center line of the original channel of the return manifold 51

B:

Radius of the trackball 3

d:

Thickness of the central portion of the spacer 4 or the smallest distance between both adjacent rolling balls 3

x:

maximum offset of the arc line I

r:

Radius of curvature of the original inner wall of the return manifold 51

m:

Distance from the arc line I to the vertex of the two inner wall of the guide sections 52 . 53

α:

Angle passing through the two guide sections 52 . 53 is limited.

r2:

Radius of the bow line I after the offset

This results in:

Out the above five Equations can x and r2 are determined. X is the maximum offset of the arc line I denotes, i. x is the distance along the bisector offset arc line I. r2 represents the radius of curvature of the offset Arc line I dar.

Become the sizes of x and r2 detected, then the at the bisector of the Angle α lying Circle center of the arc line I can be determined. Such is the staggered Bow line I available.

Due to the offset of the circle center point of the arc line I and the increase in the radius of curvature r2, the curvature of the inner guide surface coming into contact with the arc line I becomes 511 mitigated or reduced. This will be the spacer 4 with the inner guide surface 511 not brought in contact, even if it is pushed inwards. This is a low-friction passage of the spacer 4 through the return manifold 51 guaranteed. This will avoid the spacer 4 against the return manifold 51 encounters.

It will then open 9 Referenced. Alternatively to the first embodiment, wherein the return manifold 51 is provided with the elliptical cross section, the return manifold 51 an outer guide surface 512A having a circular cross-section [see 9 ]. The diameter of the outer guide surface 512A is greater than or equal to that of the rolling balls to allow easy passage of the rolling balls. In addition, the inner guide surface 511A also circular in cross-section, wherein the diameter of the inner guide surface 511A between the diameter of the spacer 4 and the diameter of the trackball 3 lies. When joining the inner and the outer guide surface 511A . 512A then arises a return manifold 51A with a non-circular cross-section.

In the return manifold is only the spacer 4 pushed inwards. Thus, only the offset portion in the second embodiment is at the cross section of the spacer 4 adapted, allowing for easy passage of the spacer 4 provides. In this way, the effect of the first embodiment can also be achieved.

1

spindle

2

nut

11

spiral groove

21

spiral groove

22

Return bore

3

trackball

4

spacer

5

endcap

51

return path

52

guide section

53

guide section

511

inner guide surface

512

outer guide surface

I

inner bow line

O

outer arc line

A

Semicircle section

B

straight section

S

outer diameter of the spacer

Y

maximum Displacement of the inwardly pushed spacer

W

distance the center of the guide sections of the return channel to her inner wall

R

radius of curvature the centerline of the original one Channel of the return manifold

B

radius the trackball

D

thickness the center portion of the spacer or the smallest distance between both adjacent rolling balls

X

maximum Offset of the arc line

R

radius of curvature the original one Inner wall of the return manifold

M

distance from the arc line to the vertex of the two inner walls of the guide sections

α

Angle, through the two guide sections is limited.

r2

radius the arc line after the offset

51A

return path

511A

inner guide surface

512A

outer guide surface

Claims (3)

Return passage of a ball screw, wherein the ball screw a spindle ( 1 ) and one on the spindle ( 1 ) mounted nut ( 2 ), wherein the spindle ( 1 ) and the nut ( 2 ) corresponding helical grooves ( 11 respectively. 21 ), in which numerous rolling balls ( 3 ) as well as between two adjacent rolling balls ( 3 ) spacers ( 4 ) and wherein the nut ( 2 ) extending in the axial direction return bore ( 22 ), at both ends of which an end cap ( 5 ) and each of the end caps ( 5 ) has a return channel to the helical groove ( 21 ) and the return bore ( 22 ) in such a way that the numerous rolling balls ( 3 ) and several spacers ( 4 ) in the nut ( 2 ) can perform a smooth return to endless circulation, and wherein the return passage is a return manifold ( 51 ) and two straight guide sections ( 52 . 53 ), wherein the straight guide sections ( 52 . 53 ) the two ends of the return manifold ( 51 ), the spiral groove ( 21 ) and the return bore ( 22 ), and wherein the return manifold ( 51 ) of an inner and an outer guide surface ( 511 . 512 ), and wherein an inner arc line (I) on the outside with the inner guide surface ( 511 ), while an outer arc line (O) on the outside with the inner guide surface ( 512 ), and wherein the arc length of the arc line (I) is smaller than half of the circumference, and wherein the circle center of the arc line (I) is located at a location adjacent to the circle center of the outer arc line (O) and the outer arc line (O) is removed, such that the inner and the outer arc line are not parallel to each other, whereby the inner and the outer guide surface ( 511 . 512 ) existing return manifolds ( 51 ) is not circular in cross-section, so that the return manifold ( 51 ) has a larger sectional area, in order to avoid that the spacer ( 4 ) with the inner guide surface ( 511A ) comes into contact when passing through the return manifold ( 51 ). Return passage of a ball screw according to claim 1, characterized in that - the outer guide surface ( 512 ) is formed semicircular in cross-section, wherein the diameter of the outer guide surface ( 512 ) greater than or equal to the diameter of the rolling balls ( 3 ), and - that the inner guide surface ( 511 ) is provided with a U-shaped cross-section consisting of a semicircular section (A) and a straight line section (B), wherein the diameter of the semicircular section (A) is greater than or equal to the diameter of the rolling balls ( 3 ), and wherein the semicircular section (A) over the straight section (B) with the outer guide surface (A) 512 ), so that the return manifold ( 51 ) is elliptical in cross-section. Return passage of a ball screw according to claim 1, characterized in that - the outer guide surface ( 512A ) has a circular cross-section, wherein the diameter of the outer guide surface ( 512A ) is greater than or equal to that of the rolling balls, and wherein the inner guide surface ( 511A ) is also circular in cross-section, wherein the diameter of the inner guide surface ( 511A ) between the diameter of the spacer ( 4 ) and the diameter of the trackball ( 3 ) is such that a return manifold ( 51A ) is non-circular in cross-section, when the inner and outer guide surfaces ( 511A . 512A ) are joined together.