DE102018107467A1 - Ball screw for a vehicle - Google Patents

Abstract

The invention relates to a ball screw drive (1) for a vehicle, comprising a rotationally driven, axially non-displaceable threaded nut (3) with a threaded spindle (2) axially displaceable along the threaded nut (3), wherein a space exists between the threaded spindle (2) and the threaded nut (3). a plurality of balls (10) are arranged, wherein the threaded spindle (2) by a Verdrehsicherungselement (4) relative to a housing (5) is secured against rotation, wherein the anti-rotation element (4) on the one hand rotatably connected to the housing (5) and on the other hand in at least one of the threaded spindle (2) formed guide groove (6a, 6b) is guided linearly. Furthermore, the invention relates to a use of such a ball screw (1) for an actuator for level adjustment of a vehicle body.

Description

The invention relates to a ball screw for a vehicle, comprising a rotationally driven axially immovable threaded nut with a threaded spindle along the axially displaceable threaded spindle, wherein spatially between the threaded spindle and the threaded nut a plurality of balls are arranged, wherein the threaded spindle is secured against rotation by a Verdrehsicherungselement against a housing , Furthermore, the invention relates to a use of such a ball screw for an actuator for level adjustment of a vehicle body.

Applications in which a screw drive, in particular a ball screw drive is used, are already known from the prior art. In such a ball screw a threaded nut or a threaded spindle must be formed against rotation with respect to other parts of the system. In a device for level control of a vehicle body, the threaded spindle is mounted, for example, damper-proof, wherein the threaded nut is rotated relative to the spindle in order to achieve a linear upward or downward movement. This threaded nut is rotatably mounted in a housing, in addition to a bearing of the threaded nut and a drive unit consisting of a motor and a transmission, is accommodated in the housing. If the load of the vehicle causes a load to be applied to the housing via a spring plate, a system that is not secured against twisting would start to rotate around the threaded spindle and thereby unintentionally move downwards. In order to prevent this, ie to be able to hold the system at the desired height, the housing is secured against rotation with respect to the threaded spindle. In this case, a rotation is provided which prevents the rotation of the threaded spindle to the housing, but allows an axial adjustment of the threaded spindle. Such anti-rotation devices are mounted in the prior art outside the functional range of the ball screw in order not to block and / or hinder this. This anti-rotation can thus be mounted only axially adjacent to the threaded spindle and consist for example of a threaded spindle enclosing sleeve, which are provided with grooves in which certain geometries of the counterparts engage axially displaceable. In other words, the axially adjacent arrangement of the threaded spindle and the rotation lock leads to an additional axial space.

The object of the present invention is to further develop a ball screw for a vehicle, and in particular to reduce an axial space. Preferred embodiments can be found in the dependent claims, the description and the figures.

An inventive ball screw for a vehicle comprises a rotationally driven axially immovable threaded nut with a threaded spindle along the axially displaceable threaded spindle, wherein spatially between the threaded spindle and the threaded nut a plurality of balls are arranged, wherein the threaded spindle is secured against rotation by a Verdrehsicherungselement against a housing, wherein the Anti-rotation element on the one hand rotatably connected to the housing and on the other hand is linearly guided in at least one formed on the threaded spindle guide. The ball screw is intended to perform by the axial displacement of the threaded spindle relative to the threaded nut a lifting movement and thereby to carry the resting on a vehicle axle vehicle weight and lift. As a result, a ride height of the vehicle is changed and the vehicle can be brought into a desired target level position. The ball screw is driven, for example, by means of an electric drive motor which is coupled to the threaded nut, so that a rotary motion produced by the drive motor and thus effected Drehantrieb the threaded nut is converted into a longitudinal displacement of the threaded spindle relative to the threaded nut, wherein depending on the direction of rotation of the threaded nut driving Drive motor, the threaded spindle is moved vertically upwards or downwards. Thus, the nut is fixed stationary. With such a ball screw reliable adjustment movements of the threaded spindle can be performed.

The balls of the ball screw are for example guided in a cage or connected to a ball strand, wherein the balls extend spatially between the threaded spindle and the nut in a ball channel and are guided for the transmission of radial and axial forces. A ball channel is to be understood as the space radially between the threaded nut and the threaded spindle in which the balls are guided.

By anti-rotation element can be realized a rotation of the threaded spindle. In other words, the anti-rotation element prevents unwanted rotation of the threaded spindle about its own longitudinal axis. In this case, introduced into the threaded spindle torques can be better supported against the housing. Under a rotationally fixed connection of the anti-rotation element with the housing is to be understood that the anti-rotation element is for example integrally connected to the housing and thus is a part of the housing. Alternatively, you can the anti-rotation element be a separate component and be fixed to the housing. In other words, the anti-rotation element is arranged stationary on the housing in order to prevent unwanted rotation of the threaded spindle. The anti-rotation element is formed in particular of a metal. The fact that the anti-rotation element is guided linearly in the at least one guide groove, the ball screw is advantageously formed compact in the axial direction, since the rotation of the threaded spindle is integrated by the anti-rotation in the ball screw. In other words, the ball screw requires no additional axial space.

Preferably, the anti-rotation element has at least one guide segment, which is guided linearly in the associated guide groove on the threaded spindle. The at least one guide segment is provided to support a force acting on the threaded spindle vertical load against the housing. Due to the vertical load, the threaded spindle tends to rotate about its own axis and move downwards. This rotational movement counteracts the at least one guide segment guided in the respective guide groove of the anti-rotation element. For this purpose, the at least one guide segment is preferably formed as an L-shaped angle section, which engages with a short leg at least partially into the respective guide groove. In other words, the threaded spindle is axially displaced relative to the anti-rotation element, wherein an unwanted rotation of the threaded spindle is prevented by the respective at least partially engaging legs in the guide groove. Alternatively, the at least one guide segment may be formed as a pin portion which is linearly guided in the respective guide groove. Of course, further orthogonal to the longitudinal axis of the threaded spindle formed guide segments are used, which engage in a respective guide groove and prevent rotation of the threaded spindle effectively. Furthermore, alternative geometries for the at least one guide segment are conceivable, wherein the at least one guide segment always ensures effective support of the load acting on the threaded spindle relative to the housing.

According to a preferred embodiment, two guide grooves are formed opposite one another on the threaded spindle, wherein the guide grooves are aligned axially parallel to the threaded spindle and at least partially receive a respective guide segment of the anti-rotation element. In other words, the two guide grooves are designed so as to be deflecting from one another on an outer peripheral surface of the threaded spindle in the longitudinal direction, wherein the two guide grooves are arranged parallel to one another and at least partially receive and linearly guide a respective guide segment of the anti-rotation element. This results in a uniform support of the torque against the housing. For large loads, it is conceivable to arrange more than two guide segments on the anti-rotation element in order to realize a uniform force transmission even at high loads.

According to a further preferred embodiment, three guide grooves are formed uniformly distributed to one another on the threaded spindle, wherein the guide grooves are aligned axially parallel to the threaded spindle and at least partially receive a respective guide segment of the anti-rotation element. In other words, the guide grooves are formed distributed at an angle of 120 ° to each other on the circumference of the threaded spindle. Accordingly, the anti-rotation element has a respective guide segment for each guide groove. Alternatively, several guide segments of the anti-rotation element can engage in each guide groove.

Preferably, the threaded spindle has a first track with a first depth and the threaded nut has a second track, wherein the respective guide groove has a second depth, which is smaller than the first depth. The first raceway is formed on the outer peripheral surface of the threaded spindle and the second raceway is formed on an inner peripheral surface of the threaded nut, wherein the first and second raceway are formed and spaced from each other so that a ball can be effectively received spatially between the two raceways. The two raceways are formed in helical shape and corresponding to each other, so that the balls are guided optimally and with low friction losses.

Due to the smaller second depth of the respective guide groove, the respective guide groove does not interfere with the guidance of the balls on the first track with the first depth. Thus, the balls are always safely guided in the ball channel, wherein the balls transmitted during operation of the ball screw radial and axial forces between the threaded spindle and the threaded nut. Further, despite the guide groove formed substantially transversely to the first raceway, falling out of the balls from the ball channel is prevented. Thus, the space formed by the ball channel is limited radially by the first and second tracks.

Since the respective guide groove has a smaller second depth than the first depth of the first raceway of the threaded spindle, the guide groove is thus divided in the longitudinal direction of the threaded spindle into a plurality of Führungsnutabschnitten whose number depends on the slope of Thread of the ball screw and the diameter of the balls. In other words, the first raceway and the respective guide groove intersect several times along the longitudinal axis of the threaded spindle. Accordingly, the respective guide segment of the anti-rotation element is preferably designed such that the guide segment extends over a plurality of guide groove sections of the respective guide groove in order to realize a secure and error-free linear guidance of the threaded spindle relative to the anti-rotation element. Furthermore, this ensures a sufficiently large contact surface of the respective guide segment on the side walls of the respective guide groove sections in order to be able to absorb the surface pressures acting on the torque. Thus, the length of the respective guide segment engaged Führungsnutabschnitte is large enough to transfer the acting surface pressures can. In this case, the respective guide segment of the anti-rotation element is arranged axially adjacent to the ball strand in order not to hinder the rolling of the balls or to block.

The invention includes the technical teaching that the respective guide groove has a width which is smaller than the diameter of the balls. As a result, no balls can tilt in the ball channel or fall out of this. Thus, the ball screw is characterized safer.

Preferably, a respective loading section and a respective unloading section are formed on the first track in an intersection region of the first track with the respective guide groove. During operation of the ball screw, the balls are loaded substantially uniformly and thus transmit radial and axial forces between the threaded spindle and the threaded nut. Consequently, the balls roll along the raceways and are thus guided laterally. In the crossing region of the first track with the respective guide groove, however, a relieving of the respective ball, which passes through the crossing area, since the lateral guidance of the balls by the first track crossing guide groove is partially omitted. Consequently, there is an intersection between the first track and the guide groove in the crossing area.

Thus, the balls are not suddenly relieved when entering the intersection and then loaded again abruptly, the track immediately before the intersection by the guide groove on the ramp-shaped relief section. The relief section is thus in the rolling direction of the balls in front of the respective guide groove. In other words, the first raceway in the relief section is designed such that the balls entering the relief section are guided out of a load zone and thus are no longer under load in the intersection area. A load zone is that region of the ball channel in which the balls are laterally supported during operation of the ball screw and thereby experience the maximum load. Thus, the balls emerge from a load zone in the respective crossing region and are then reintroduced into a second load zone following the first load zone. In other words, the balls in the load zone bearing balls and the balls in the crossing region are non-supporting or only partially bearing balls of the ball screw, wherein the balls are guided alternately from a load zone in an intersection region and then again in a load zone.

In the crossing region, the respective ball is continuously continued by the still moving ball strand and thus moved through the intersection of the respective guide groove load-free. As a result, an unwanted canting of the respective ball is prevented at the respective guide in the crossing area. Despite the unloaded state of the ball in the crossing area, the guidance of the ball due to the less deeply formed guide grooves is sufficiently ensured even in the crossing area. After the crossing, the respective ball in the ramp-shaped loading section, which lies in the rolling direction of the balls behind the respective guide groove, guided in the next load zone, whereby the load of the balls increases again to a maximum.

Depending on the direction of rotation of the rotationally driven threaded nut and the rolling direction of the balls in the ball channel changes. Thus, the position of the unloading and loading section of the respective crossing section is dependent on the direction of rotation of the threaded nut.

Further preferably, the loading section and the unloading section have a ramp-shaped course. The ramp-shaped course of the relief section or of the loading section is to be understood as meaning that the first raceway widens laterally in the relief section in order to steadily reduce the lateral guidance of the respective ball and thus to continuously relieve the ball entering the relief section. In the loading section, the first track tapers sideways steadily up to the starting shape, so that the respective ball experiences a continuously increasing load up to the load within the load zone. Controlling and smoothing this transition into the load-free intersection area and out of the intersection area can prevent or negatively affect the service life be reduced at least and thus in particular the acoustics of the ball screw can be improved.

The ball screw according to the invention is particularly suitable for use in an actuator for level adjustment of a vehicle body. Alternatively, such a ball screw can be used in any actuator, such as a clutch plate, a brake actuator or a steering actuator.

• 1 eine vereinfachte schematische Schnittdarstellung eines erfindungsgemäßen Kugelgewindetriebs in einer ersten axialen Endposition,
• 2 eine vereinfachte schematische Schnittdarstellung des Kugelgewindetriebs gemäß 1 in einer zweiten axialen Endposition,
• 3a eine vereinfachte schematische Ansicht einer Gewindespindel des Kugelgewindetriebs gemäß den 1 und 2,
• 3b eine vereinfachte schematische Seitenansicht der Gewindespindel gemäß 3a,
• 3c eine vereinfachte schematische Querschnittansicht der Gewindespindel gemäß den 3a und 3b, und
• 4 eine vereinfachte schematische Ansicht eines exemplarischen Kreuzungsbereichs an der Gewindespindel.

Further measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to FIGS. It shows

• 1 2 is a simplified schematic sectional view of a ball screw according to the invention in a first axial end position,
• 2 a simplified schematic sectional view of the ball screw according to 1 in a second axial end position,
• 3a a simplified schematic view of a threaded spindle of the ball screw according to the 1 and 2 .
• 3b a simplified schematic side view of the threaded spindle according to 3a .
• 3c a simplified schematic cross-sectional view of the threaded spindle according to the 3a and 3b , and
• 4 a simplified schematic view of an exemplary crossing region on the threaded spindle.

According to the 1 and 2 comprises a - shown here very simplified - ball screw 1 for a - not shown - vehicle a rotationally driven axially immovable threaded nut 3 with one along the threaded nut 3 axially displaceable threaded spindle 2 , The threaded nut 3 is for example driven by a - not shown here - drive unit and can have a - here also not shown - external thread. Spatially between the threaded spindle 2 and the nut 3 which are arranged coaxially with each other are a plurality of balls 10 arranged closer in 3a are shown and explained.

By means of the balls 10 becomes the threaded spindle 2 by a rotation of the threaded nut 3 shifted axially. The present is the threaded spindle 2 vertically arranged and along a longitudinal axis 17 axially displaceable. Furthermore, the threaded spindle 2 by an anti-rotation element 4 opposite a housing 5 secured against rotation, wherein the anti-rotation element 4 rotatably with the housing 5 connected is. In other words, the anti-rotation element 4 stationary in the housing 5 arranged.

The anti-rotation element 4 here has two guide segments 7a . 7b partly in an associated guide groove 6a . 6b the threaded spindle 2 recorded and linearly guided. Alternatively, the anti-rotation element may also have three guide segments, wherein each guide segment is partially received in a corresponding guide groove of the threaded spindle and guided linearly.

The guide grooves 6a . 6b are on an outer circumferential surface of the threaded spindle 2 arranged and axially parallel to the longitudinal axis 17 the threaded spindle 2 aligned. The respective leadership segment 7a . 7b has a present hook-shaped geometry, wherein a leg 18a . 18b of the guide segment 7a . 7b orthogonal to the longitudinal axis 17 is formed and partially in the associated guide groove 6a . 6b is introduced. This allows a rotation of the threaded spindle 2 realize that so at an unwanted rotation about the longitudinal axis 17 is prevented due to an acting load. For example, vertical loads can be imposed on the threaded spindle by a vehicle body 2 act, which would cause a rotation and thus an axial downward movement. The resulting torque of the threaded spindle 2 is through the guide segments 7a . 7b in the case 5 directed. In other words, the torque of the threaded spindle is supported 2 on the housing 5 from. Thus, the threaded spindle 2 during operation of the threaded nut 3 only axially guided and can not around the longitudinal axis 17 twist.

In 1 is the threaded spindle 2 shown at an axial starting point, wherein the threaded spindle 2 in this case is shut down vertically maximum. By the operation of the threaded nut 3 and the associated rotation becomes the threaded spindle 2 axially displaced, that is displaced vertically upward in the axial direction. The axial end point of the axial displacement is in 2 shown. In other words, the threaded spindle 2 axially displaceable between the starting point and the end point. It can be seen that the threaded spindle 2 through the in the guide grooves 6a . 6b engaging guide segments 7a . 7b is always secured against rotation. Furthermore encloses the anti-rotation element 4 the threaded nut 3 from the outside and the guide segments 7a . 7b are immediately axially adjacent to the threaded nut 3 arranged so that a space-saving design of the ball screw 1 present and the rotation in the ball screw 1 is integrated.

The 3a . 3b and 3c show a detailed view of the ball screw 1 according to the 1 and 2 from different perspectives. In 3a is the anti-rotation element 4 not shown here for the sake of simplicity. The threaded spindle 2 has a first career 8a with a first depth 9a and the nut 3 a second career 8b on. The respective guide groove 6a . 6b has a second depth 9b which is smaller than the first depth 9a the first career 8a , Furthermore, the respective guide groove 6a . 6b a width 12 on, which is smaller than the diameter 11 the balls 10 , This will make the balls 10 safely in a space between the two tracks 8a . 8b radially formed ball channel 21 led and tilting or falling out of the balls 10 from the ball channel 21 will be prevented.

According to 3b extend the guide segments 7a . 7b over several guide sections 16 the associated guide grooves 6a . 6b , whereby the threaded spindle is particularly safe along the guide segments 7a . 7b to be led. Furthermore, it is achieved that a sufficiently large contact surface of the respective guide segment 7a . 7b laterally to the respective Führungsnutabschnitte 16 is formed to accommodate the acting surface pressures can. This is especially the case 3c out. Thus, the length of the respective guide segment 7a . 7b engaged Führungsnutabschnitte 16 big enough to transfer the effective surface pressures.

4 shows an example of an intersection area 15 between the first career 8a and the first guide groove 6a , At the circumference of the threaded spindle 2 are a variety of crossing areas 15 formed, with the number of crossing areas 15 Depends on the thread pitch of the threaded spindle 2 and the nut 3 , Analogous to this are also crossing areas 15 between the first career 8a and the second guide groove 6b educated.

The crossing area shown here 15 extends along the first track 8a in a rolling direction 19 the balls 10 and is presently designed such that the ball 10 in the crossing area 15 is not or only slightly burdened. Under a slight load only is to be understood that the ball 10 when passing through the crossing area 15 not tilted. When turning the threaded nut 3 and the resulting longitudinal displacement of the threaded spindle 2 go through the ball 10 a variety of crossing areas 15 the first career 8a , wherein the respective unwinding direction 19 Depends on the direction of rotation of the rotary-driven threaded nut 3 , In unwinding direction 19 rolls the ball 10 from a first load zone 22a first in a ramp-shaped relief section 14 of the crossing area 15 , wherein the discharge section 14 in unwinding direction 19 in front of a crossroads 20 between the first career 8a and the guide groove 6a lies. In the relief section 14 becomes the respective ball 10 from the beginning of the discharge section 14 until the intersection 20 continuously relieved. Thus, the career widens 8a starting from a semi-circular initial shape on the side so that the ball 10 no forces of the threaded spindle 2 picks up and thus load-free in the first career 8a to be led. Due to the ramp-shaped course of the relief section 14 becomes the ball 10 thus evenly relieved and through the intersection 20 passed.

After crossing the intersection 20 becomes the ball 10 back in one on the crossing area 15 following load zone 22b guided. The ball will do that 10 in a ramped loading section 13 guided, the present in the unwinding direction 19 behind the crossroads 20 the career 8a with the guide groove 6a lies. The first career 8a tapered continuously to the semicircular initial shape, hence the ball 10 is continuously loaded again until it reaches the second load zone 22b reached and from the crossing area 15 exit. In other words, the ball lies 10 at the beginning of the load section 13 load-free and points at the end of the load section 13 in the operation of the ball screw 1 occurring load on. Due to the ramp-shaped course of the loading section 13 becomes the ball 10 thus evenly loaded and out of the crossing area 15 led out. A risk for canting the ball 10 is due to such a configuration of the crossing area 15 minimized.

LIST OF REFERENCE NUMBERS

1

Ball Screw

2

screw

3

threaded nut

4

anti-rotation

5

casing

6a, 6b

guide

7a, 7b

guide segment

8a, 8b

career

9a, 9b

depth

10

Bullet

11

diameter

12

width

13

load section

14

relief section

15

crossing area

16

guide groove

17

longitudinal axis

18a, 18b

leg

19

unrolling

20

crossing

21

ball channel

22a, 22b

load zone

Claims (9)

A ball screw (1) for a vehicle, comprising a rotationally driven axially immovable threaded nut (3) with an axially displaceable along the threaded nut (3) threaded spindle (2), wherein spatially between the threaded spindle (2) and the threaded nut (3) a plurality of balls (10) are arranged, wherein the threaded spindle (2) by a Verdrehsicherungselement (4) relative to a housing (5) is secured against rotation, characterized in that the anti-rotation element (4) on the one hand rotatably connected to the housing (5) and on the other hand in at least one on the threaded spindle (2) formed guide groove (6a) is linearly guided. Ball screw (1) to Claim 1 , characterized in that the anti-rotation element (4) has at least one guide segment (7a) which is linearly guided in the associated guide groove (6a) on the threaded spindle (2). Ball screw (1) according to one of the preceding claims, characterized in that on the threaded spindle (2) two guide grooves (6a, 6b) are formed opposite to each other, wherein the guide grooves (6a, 6b) are aligned axially parallel to the threaded spindle (2) and a receive respective guide segment (7a, 7b) of the anti-rotation element (4) at least partially. Ball screw (1) according to one of Claims 1 or 2 , characterized in that on the threaded spindle (2) three guide grooves (6a, 6b) are evenly distributed to each other, wherein the guide grooves (6a, 6b) are aligned axially parallel to the threaded spindle (2) and a respective guide segment (7a, 7b) of the At least partially accommodate anti-rotation element (4). Ball screw drive (1) according to one of the preceding claims, characterized in that the threaded spindle (2) has a first track (8a) with a first depth (9a) and the threaded nut (3) has a second track (8b), wherein the respective guide groove (6a, 6b) has a second depth (9b) which is smaller than the first depth (9a). Ball screw drive (1) according to one of the preceding claims, characterized in that the respective guide groove (6a, 6b) has a width (12) which is smaller than the diameter (11) of the balls (10). Ball screw drive (1) according to one of the preceding claims, characterized in that on the first track (8a) in an intersection region (15) of the first track (8a) with the respective guide groove (6a, 6b) a respective load section (13) and a respective relief portion (14) are formed. Ball screw (1) to Claim 7 , characterized in that the loading portion (13) and the discharge portion (14) have a ramp-shaped course. Use of the ball screw (1) after one of Claims 1 to 8th in an actuator for level adjustment of a vehicle body.

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