DE102020125535A1 - Linear drive with a roller guide - Google Patents

Abstract

Linear drive such as a ball screw drive (1) or the like with a roller guide that has revolving roller bodies (8, 12-17) that are guided between two machine elements (2, 4) in a roller body track (3, 5), with one machine element (4th ) is movable translationally in relation to the other machine element (2) and wherein a sensor (S1, S2, S3, S4) is arranged on a membrane (11) on a machine element (4) in a load-bearing area near the rolling body track (3,5). , which detects the deformation of the membrane (11) by rolling elements (8, 12 to 17) running through the rolling element track and which are under a prestress V, characterized in that at least two sensors (S1, S2, S3, S4) are provided, one winding (18) of the rolling body guide (3,5) and are arranged at such a distance from one another that the sensor signals caused by a rolling body (8, 12 to 17) passing through are phase-shifted in the sensors (S1, S2, S3, S4). detectable i.e.

Description

The invention relates to a linear drive with a rolling body guide according to the preamble of claim 1.

Such linear drives are often used in machine tools in order to move loads linearly quickly or to position them precisely. Such a linear drive is provided with rolling elements such as rollers or balls, which rotate in a rolling element guide. Such a linear drive is given, for example, by a so-called ball screw (KGT), in which the rotational movement of a motor-driven spindle by means of a nut in a linear movement, z. B. a machine table is implemented. The balls are guided in a helical raceway in the nut.

There are nuts that are divided into two in order to achieve preload via an interposed spring assembly or an adjustable thread. In other versions, single nuts are used in which a corresponding oversize of the balls compared to the raceway, z. B. in the order of a few microns, a bias is generated. In such an embodiment, the balls bear against the raceway at four points (4-point contact), forcing them to slide during operation, which leads to a certain amount of wear. This reduces the preload during the service life. The reduced preload can be used in critical machining processes, e.g. B. when using a machine tool, lead to impermissible work results, for example on processing surfaces. This is e.g. This is disadvantageous, for example, when grinding gears, where the accuracy and surface requirements are very high.

Defects such as pitting or chatter marks in spindle operation, which can arise from material fatigue, are also disruptive in high-precision machining processes, as they cause discontinuous feed on the machine tool.

From the DE 102017 205 005 B3 and the DE 10 2013 225 467 B4 is a ball screw (KGT) according to the preamble of claim 1, with which the above disadvantages are to be reduced. Although several sensors are also described there, they are assigned to different windings of the screw thread of the nut. Only one sensor at a time can detect the membrane deformation caused by a ball. This means that in the phase of passage of the contact point between two balls, a sensory detection and thus the corresponding conclusions are not possible. A direction-dependent measurement is also not possible with these KGT.

It is therefore the object of the present invention to eliminate these disadvantages.

Starting from a linear drive according to the preamble of claim 1, this object is achieved by its characterizing features.

Accordingly, a linear drive according to the invention is characterized in that at least two sensors are provided, which are assigned to one turn of the rolling body guide and are arranged at such a distance from one another that the sensor signals caused by the sensors by a rolling body passing through in the at least two sensors are at least partially can be detected simultaneously and out of phase with one another.

As a result of this measure, there is no longer a phase in the passage of a rolling body, such as a ball, in which there is no usable measurement signal. Thus, parameters such as the load, the preload and/or the speed can be recorded and further processed at any time. A direction-dependent measurement, for example of the load and/or the speed, is also possible using a suitable sensor arrangement as claimed.

By detecting the preload, for example with KGT with the above 4-point contact, the wear of the balls can be detected and reacted accordingly. The detection of the load can also be used to control a machining process in order to improve it adaptively and/or to avoid load peaks.

Finally, a cumulative recording of so-called load collectives over a longer period, e.g. B. the operating time, possible.

The membrane is advantageously formed by a flexible wall of a material recess in a wall area of a machine part in the area of the rolling element track. A simple production is thus possible, with the membrane being formed in one piece with the wall area and accordingly being mechanically stable.

A strain gauge and/or a piezoresistive sensor element can be provided as the sensor. These two types of sensors have already proven their worth for the intended purpose, ie for detecting membrane deformation. In principle, however, other types of sensors, e.g. B. capacitive sensors or the like can be used.

If the linear drive according to the invention is designed as a so-called ball screw drive (KGT), with the machine parts being a spindle and a spindle nut, at least two sensors are advantageously arranged in the direction of rotation of the spindle with a distance between the respective axially aligned sensor center lines that is less than half a ball diameter. is in particular smaller than a quarter of the ball diameter. In the case of a ball screw drive, this configuration allows permanent or almost permanent parameter detection in all ball positions, since at least one ball acts on at least one sensor.

If at least two sensors in the axial direction, i. H. arranged in the direction of the spindle axis with an axial offset between the respective sensor center lines aligned along the circumference, which is smaller than a sphere diameter, in particular smaller than a sphere radius, this measure enables good direction-dependent parameter detection. The offset sensors can be arranged on two opposite sides of the middle of the raceway of the rolling element guide to improve the directional dependency of the measurement.

An evaluation unit is preferably provided for determining the load, in particular the direction-dependent load, and/or the preload and/or the speed of the rolling bodies using the various sensor signals. Since the sensors initially only supply the data on the deformation of the membrane, such an evaluation unit makes sense in order to determine the desired parameters from these sensor data directly in the linear drive and to supply them for further processing.

The evaluation unit can determine the load, in particular the direction-dependent load, and/or the prestress, for example by adding and/or averaging the various sensor signals. In line with the times, this is preferably carried out mathematically and digitally.

The evaluation unit can be designed for the cumulative detection of loads and/or speeds. For this purpose, an associated data memory is provided, for example, in order to store the recorded sensor data and/or evaluated parameters over a desired period of time.

In the case of cumulative data acquisition, in particular, the evaluation unit can be designed to determine and possibly also to report a maintenance and/or repair case.

Furthermore, the evaluation unit can be provided with a control unit for controlling a load and/or a speed depending on the evaluation of the sensor signals. In this way, overloading can be avoided and, under certain circumstances, the accuracy of the positioning can also be improved. For this purpose, the evaluation unit and/or the control unit are designed, for example, to regulate back load peaks on the basis of the sensor signals.

In addition, the evaluation unit and/or the control unit can be designed for adaptive control of a machining process based on the sensor signals. By intelligently adapting the machining process, taking into account the data recorded by sensors and the evaluated parameters, not only can peak loads be avoided, but the entire workflow can also be optimized.

An embodiment of the invention is shown in the drawing and is explained in more detail below with reference to the figures.

• 1 eine perspektivische Darstellung eines Kugelgewindetriebs nach dem Stand der Technik,
• 2 eine perspektivische Darstellung einer Spindelmutter gemäß der Erfindung in der Seitenansicht,
• 3 eine perspektivische Darstellung eines Ausschnittes eines Längsschnittes durch die Spindel und Spindelmutter nach 2,
• 4 eine schematische Zeichnung eines Teils einer längs geschnittenen Spindelmutter mit Laufbahn und Kugel,
• 5 eine schematische Zeichnung eines Teils einer quer geschnittenen Spindelmutter mit Laufbahn und aufeinanderfolgenden Kugeln,
• 6 ein Lastdiagramm mit Kraft aus einer Richtung +X,
• 7 ein Lastdiagramm mit Kraft aus der entgegengesetzten Richtung -X und
• 8 ein Diagramm zur Vorspannungsermittlung.

show in detail

• 1 a perspective view of a ball screw according to the prior art,
• 2 a perspective view of a spindle nut according to the invention in side view,
• 3 a perspective view of a section of a longitudinal section through the spindle and spindle nut 2 ,
• 4 a schematic drawing of a part of a longitudinally sectioned spindle nut with raceway and ball,
• 5 a schematic drawing of a part of a cross-sectioned spindle nut with raceway and successive balls,
• 6 a load diagram with force from one direction +X,
• 7 a load diagram with force from the opposite direction -X and
• 8th a diagram for determining the preload.

In 1 a conventional ball screw (KGT) 1 is shown without a motor. On a spindle 2 are a spindle-side, thread-shaped Ball track 3 as a rolling element guide and a spindle nut 4 attached. The spindle nut is shown partially cut open so that the course of the ball raceway 5 on the nut side can be seen, which has a threaded section 6 corresponding to the raceway on the spindle side and a return section 7 for returning rotating balls 8 . The reference numbers of the components mentioned are retained below in the description of the exemplary embodiment according to the invention.

In 2 it can be seen that a recess 9 in the wall 10 of the spindle nut 4 forms a deformable membrane 11 at the base of the recess 9 . Four sensors S1 to S4 are attached to the membrane 11, for example in the form of strain gauges. The sensors are offset in pairs with an axial offset A relative to the sensor center line SMA in the axial direction. The sensors are also arranged along the circumference of the ball track (3.5) at a distance U relative to the associated sensor center line SMU.

A thread of the two ball tracks 3, 4, ie the spindle-side ball track 3 and the opposite nut-side ball track 4 runs approximately centrally under the arranged with an axial offset A sensors S1, S2 and S3, S4. Each passing ball 8 has a ball diameter K and thus causes successive deformations of the membrane 11 in the area of each sensor S1 to S4. The sensors only measure one winding 18 (cf. 3 ).

In 4 two different load directions -X and +X are shown, ie directions in which a load acting on the spindle nut when the KGT is actuated acts on the ball guide.

The representation after 5 1 is shown without the curvature of the spindle and ball raceways 3,5 for the sake of simplicity to illustrate the sequence of passage of the balls 12-17 under the sensors S1-S4.

This process is reflected in oscillating sensor signals from sensors S1 to S4 6 and 7 low. In 6 is with the arrow P the position of the ball 13 from 5 illustrated below sensor S1. In the diagram shown there is a load from the +X direction, as shown in 4 is also marked with L+, which is superimposed with the effect of the prestress. In the position P, the membrane 11 is therefore in the area of the sensor S1 under maximum deformation and therefore generates a maximum M1 in the diagram according to FIG 6 , while the area under sensor S2 is minimally deformed, which corresponds to minimum M2.

As in 6 can be seen, the mean value (signal out) can be assigned to the F+ exerted by a load in the +X direction. This value can be detected at any time depending on the direction of the sensor arrangement and membrane design, both in motion and at a standstill.

In 7 the deformations occurring from the -X direction due to the ball 14 located in position P under the sensor S3 can be seen in the sensor signals S3 and S4, which remain despite the load from the prestress acting in the opposite direction. Accordingly, however, the signals from sensors S3 and S4 are significantly smaller in this case. Here, too, the resultant force F- in direction x- can be assigned to the mean value (signal out). This value can also be recorded at any time depending on the direction thanks to the specified sensor arrangement and membrane design, both in motion and at a standstill.

In 8th shows the evaluation of the added signals S1+2 and S3+4, ie the sum signals formed on the one hand from the sensors S1 and S2 and on the other hand from the sensors S3 and S4. Since both sum signals are symmetrical to each other, there is no directional load here, so that the bias voltage V can be derived directly from the mean value.

The function and the advantages of the invention are clearly recognizable on the basis of the illustrated and described exemplary embodiment. However, a person skilled in the art can also implement this in other ways by means of modifications within the scope of the claims.

Reference List

1

Ball screw drive (KGT)

2

spindle

3

ball raceway on the spindle side

4

spindle nut

5

nut-side ball track

6

threaded section

7

return section

8th

balls

9

recess

10

wall

11

membrane

12

bullet

13

bullet

14

bullet

15

bullet

16

bullet

17

bullet

18

coil

S1

sensor

S2

sensor

S3

sensor

S4

sensor

A

axial offset

SMA

sensor centerline

u

Circumferential distance

SMU

sensor centerline

K

ball diameter

-X

load direction

+X

load direction

F+

power

f

power

M+

maximum

M-

minimum

P

position

V

preload

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102017205005 B3 [0005]
• DE 102013225467 B4 [0005]

Claims (12)

Linear drive such as a ball screw drive (1) or the like with a roller guide that has revolving roller bodies (8, 12-17) that are guided between two machine elements (2, 4) in a roller body track (3, 5), with one machine element (4th ) is movable translationally in relation to the other machine element (2) and wherein a sensor (S1, S2, S3, S4) is arranged on a membrane (11) on a machine element (4) in a load-bearing area close to the rolling element track (3,5). , which detects the deformation of the membrane (11) by rolling elements (8, 12 to 17) running through the rolling element track and which are under a prestress V, characterized in that at least two sensors (S1, S2, S3, S4) are provided, which are assigned to one turn (18) of the rolling body guide (3,5) and are arranged at such a distance from one another that the sensor signals caused in the sensors (S1, S2, S3, S4) by a rolling body (8, 12 to 17) passing through phase-shifted detectable are. linear drive after claim 1 , characterized in that the membrane (11) is formed by a flexible wall of a material recess (9) in a wall (10) of a machine part (4) in the region of the rolling element track (3.5). Linear drive according to one of the preceding claims, characterized in that a strain gauge and/or a piezoresistive sensor element is provided as the sensor (S1, S2, S3, S4). Linear drive according to one of the preceding claims, characterized in that the linear drive is a ball screw drive (1) and the machine parts are a spindle (2) and a spindle nut (4), with two sensors (S1, S2, S3, S4) in the direction of rotation of the spindle (2) are arranged with a distance (U) between the respective axially aligned sensor center lines SMU which is less than half a sphere diameter (K), in particular less than a quarter of a sphere diameter (K). linear drive after claim 4 , characterized in that two sensors (S1, S2, S3, S4) are arranged in the axial direction, ie in the direction of the spindle axis, with an axial offset (A) between the respective sensor center lines SMA aligned along the circumference, which is smaller than a ball diameter (K ), In particular smaller than half a sphere diameter (K). Linear drive according to one of the preceding claims, characterized in that an evaluation unit is provided for determining the load, in particular the direction-dependent load (L+, L-), and/or the preload (V) and/or the speed of the rolling bodies using the various sensor signals . Linear drive according to one of the preceding claims, characterized in that the evaluation unit is designed to determine the load, in particular the directional load (L+,L-) and/or the prestress (V) by adding and/or averaging the various sensor signals. Linear drive according to one of the preceding claims, characterized in that the evaluation unit is designed for the cumulative determination of loads and/or speeds. Linear drive according to one of the preceding claims, characterized in that the evaluation unit is designed to report maintenance and/or repairs. Linear drive according to one of the preceding claims, characterized in that the evaluation unit is designed with a control unit for controlling a load and/or a speed depending on the evaluation of the sensor signals. Linear drive according to one of the preceding claims, characterized in that the evaluation unit and/or the control unit is designed to control load peaks using the sensor signals. Linear drive according to one of the preceding claims, characterized in that the evaluation unit and/or the control unit is designed for adaptive control of a machining process using the sensor signals.

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