DE102017201230A1 - Linear motion device with lifetime monitoring - Google Patents

Abstract

The invention relates to a linear movement device (10, 10 ') having a table (12) and a base (13), the table (12) being guided by at least one linear roller guide (20) on the base (13) in the direction of a longitudinal axis (11). is movably guided, wherein each linear roller guide (20) comprises a base (13) fixed to the guide rail (21) and at least one attached to the table (12) guide carriage (30), each guide carriage (30) the associated guide rail (21) with two legs (31) U-shaped surrounds. According to the invention, at least one displacement sensor (40) is provided, with which a deformation transverse to the longitudinal axis (11) of at least one associated leg (31) of a guide carriage (30) can be measured, wherein the at least one displacement sensor (40) at the table or at the base ( 12, 13) can be fastened or fastened, wherein an evaluation device (41) is provided which is set up so that a change in the preload of at least one associated guide carriage (30) can be determined by using the at least one displacement sensor (40).

Description

The invention relates to a linear motion device according to the preamble of claim 1.

From the EP 1 719 992 B 1 is a linear roller guide is known, which is intended for use in a linear motion device. The carriage is provided with a strain gauge, with which primarily its deformation due to external loads to be measured. It is also disclosed that due to wear, the preload of the guide carriage decreases, whereby the deformation caused thereby with the strain gauge can be measured. It should be noted, however, that the signal of a strain gauge under long lasting static loads subject to a noticeable drift, which is exacerbated by temperature influences.

An advantage of the present invention is that the occurrence of wear on the linear roller guide and therefore the approaching end of the service life can be reliably detected. The corresponding measurements are not influenced by drift phenomena. Furthermore, a small number of sensors are required to monitor all the carriages of a linear motion device.

According to the independent claim it is proposed that at least one displacement sensor is provided with which a deformation transverse to the longitudinal axis of at least one associated leg of a carriage is measurable, wherein the at least one displacement sensor on the table or on the base can be fastened or attached, wherein an evaluation device provided is, which is arranged so that using the at least one displacement sensor, a change in the bias of at least one respective associated guide carriage can be determined.

In a linear roller guide, the rolling elements are preferably installed with an oversize that bend the legs of the carriage elastically, resulting in a bias. This bend, for example, amounts to 35 μm for both legs in total. Due to wear on the rolling elements and / or the Wälzkörperlaufbahnen the bias voltage decreases during the operation of the linear motion device. The resulting deformation of the legs is measured with a displacement sensor. The displacement sensors are attached to the base or the table at least during the measurement, so that their position is essentially unaffected by a change in bias. It should be noted that the base or the table are typically very rigid structures. It should also be noted that the displacement sensor does not have to be permanently connected to the base or the table. It is sufficient if the corresponding firm connection is given during the measurement.

In the dependent claims advantageous refinements and improvements of the invention are given.

It can be provided that both legs of at least one guide carriage are each assigned a separate displacement sensor. Preferably, a separate displacement sensor is assigned to both legs of all guide carriages. Preferably, the linear motion device comprises a plurality of guide carriages. This results in a very stiff leadership of the table relative to the base. This leadership is statically overdetermined. As a result, a tension can result, which affects unevenly on the two legs of a carriage. Also in this case, wear or the end of life can be reliably detected.

It can be provided that the displacement sensor can be fastened or fastened to the base, wherein an auxiliary body is provided, which is fastened in the direction of the longitudinal axis in alignment with at least one associated guide carriage on the table, wherein the auxiliary body with respect to the contour scanned by the respective displacement sensor Transversely to the longitudinal axis has substantially the same dimensions as said guide carriage, wherein the evaluation device is arranged so that by means of the displacement sensor, a path difference between the auxiliary body and an associated leg can be determined. With this measurement arrangement, the influence of the ambient temperature on the measurement result is considerably reduced.

It can be provided that the displacement sensor is a non-contact displacement sensor. This applies in particular if the displacement sensor can be fastened or fastened to the base. The non-contact measurement wear due to a relative movement between carriage and position sensor is avoided.

It can be provided that the at least one displacement sensor is formed by an eddy-current sensor or by a magneto-inductive sensor. These sensor types have the advantage that they are insensitive to the liquids encountered in the field of linear roller guides, such as cooling lubricants. In particular, the measurement result is not corrupted if changing fluids are present. Furthermore, the surface of commercially available linear roller guides can be scanned directly without them being used for this purpose need to be specially processed. In addition, the said displacement sensors are inexpensive.

It can be provided that the at least one displacement sensor is attached to the table. This arrangement of the displacement sensor is particularly advantageous for continuous monitoring of the bias voltage. The relative movement between carriage and path sensor is limited to the measured deformation of the legs, so that the use of contact-working displacement sensors is conceivable.

It can be provided that at least one displacement sensor is associated with a lever arm, wherein the displacement sensor is arranged so that it scans a scanning on the lever arm, wherein the lever arm is secured to the associated leg such that when a change in the bias of the scanning transverse to the longitudinal axis A larger way than the leg in question.

Protection is also claimed for a method of operating a linear motion device according to the invention, wherein using the at least one displacement sensor, a change in the bias of at least one respective associated carriage is determined, a life end of the said carriage is displayed when a reduction in the bias voltage in terms of a predetermined limit exceeds. The evaluation device is preferably set up, in particular programmed, to carry out this method and, if desired, the methods described below.

It can be provided that the determination of the bias voltage change is repeated several times in succession, with the linear motion device being in the same position each time. As a result, a falsification of the measurement result is avoided by position-dependent bias voltage fluctuations. The linear motion device preferably performs its intended function between the measurements, for example as a slide of a machine tool.

It can be provided that the determination of the bias voltage change is repeated several times in succession, the linear motion device always having the same load state. Preferably, the external load on the carriage is smaller than the internal load due to the bias in each determination of the bias change. Most preferably, the linear motion device is load-free, with the exception of the bias voltage. As a result, a falsification of the measurement result is avoided by variable external loads. Furthermore, the measuring range to be evaluated is minimized so that more accurate displacement sensors can be used.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

• 1 einen grobschematischen Querschnitt einer vorgespannten Linearwälzführung gemäß einer ersten Ausführungsform;
• 2 einen der 1 entsprechenden Querschnitt, wobei die Vorspannung vermindert ist;
• 3 eine Seitenansicht einer Linearbewegungsvorrichtung gemäß einer ersten Ausführungsform;
• 4 eine der 3 entsprechende Seitenansicht einer Linearbewegungsvorrichtung gemäß einer zweiten Ausführungsform;
• 5 eine Draufsicht der Linearbewegungsvorrichtung nach 3;
• 6 eine Draufsicht der Linearbewegungsvorrichtung nach 4;
• 7 einen grobschematischen Querschnitt einer vorgespannten Linearwälzführung gemäß einer zweiten Ausführungsform; und
• 8 einen grobschematischen Querschnitt einer vorgespannten Linearwälzführung gemäß einer dritten Ausführungsform.

The invention will be explained in more detail below with reference to the accompanying drawings. It shows:

• 1 a rough schematic cross section of a preloaded linear roller guide according to a first embodiment;
• 2 one of the 1 corresponding cross-section, wherein the bias voltage is reduced;
• 3 a side view of a linear motion device according to a first embodiment;
• 4 one of the 3 corresponding side view of a linear motion device according to a second embodiment;
• 5 a top view of the linear motion device according to 3 ;
• 6 a top view of the linear motion device according to 4 ;
• 7 a rough schematic cross section of a preloaded linear roller guide according to a second embodiment; and
• 8th a rough schematic cross section of a preloaded linear roller guide according to a third embodiment.

1 shows a rough schematic cross section of a preloaded linear roller guide 20 according to a first embodiment. The linear roller guide 20 has a guide rail 21 which are of constant cross-sectional shape along a longitudinal axis 11 extending, which is perpendicular to the plane of the 1 is aligned. The guide rail 21 is preferably made of steel and is in the range of the raceways for the rolling elements 22 hardened. The rolling elements 22 are presently designed as balls made of hardened steel, whereby circular cylindrical or barrel-shaped rolling elements are used. The carriage 30 is viewed in cross-section U-shaped. He has a fastening section 32 , of which two legs 31 stand out at right angles. The attachment section 32 is with a table (No. 12 in 2 ) firmly connected. The thigh 31 embrace the guide rail 21 , wherein the rolling elements between the guide rail 21 and thighs 31 are arranged. In the present case are two rows of supporting rolling elements 22 intended, where four or six rows are possible. The rolling elements preferably run endlessly in annular circulation passages. The rolling element raceways on the carriage 30 are preferably made of hardened steel. The diameter of the rolling elements 22 was executed with oversize, so that the thighs 31 bend elastically. As a result, the rolling elements are biased, this bias is then at least partially maintained when an external load on the linear roller guide 20 acts. The result is the linear roller guide 20 also free of play under load. Due to the rolling contact between the rolling elements 22 and the guide rail 21 or the thighs 31 increases the displacement resistance by the bias only slightly.

2 shows one of the 1 corresponding cross-section, wherein the bias voltage is reduced. Such a reduction of the bias voltage, for example, by wear on the Wälzkörperlaufbahnen and / or the rolling elements in the course of operation of the Linearwälzführung 20 arise. Most common are so-called pittings on the rolling element raceways of the carriage 30 to observe. In 2 is purely exemplary of the wear of the rolling elements 22 represented, whose diameter opposite 1 is reduced. The wear-related diameter decrease is shown greatly exaggerated. It can be seen that the bend of the thighs 31 across from 1 is reduced. Thus, wear leads to a decrease in the preload.

The deformation of the legs 31 can by means of in 1 and 2 shown path sensors 40 be measured. The displacement sensor 40 is preferably located where the legs 31 have the largest prestressing deformation, so that the measuring path 43 of the displacement sensor 40 is equal to said deformation. The corresponding measuring direction preferably coincides with the direction of said greatest deformation. At the distance sensor 40 it may be, for example, an eddy current sensor, as it is known for example from the website, on 17.01.2017 under the address http://www.microepsilon.de/displacement-position-sensors/eddy-current-sensor/index. html was available. But it is also a magneto-inductive sensor used, as it is known for example from the website, on 17.01.2017 under the address http://www.micro-epsilon.de/displacement-position-sensors/magneto-inductivesensor /index.html was retrievable. These sensor types have the advantage that they are insensitive to the liquids encountered in the field of linear roller guides, such as cooling lubricants. In particular, the measurement result is not corrupted if changing fluids are present. Furthermore, the surface of commercially available linear roller guideway can be scanned directly, without having to be specially processed for this purpose. In addition, the said displacement sensors are inexpensive.

3 shows a side view of a linear motion device 20 according to a first embodiment. This can with linear roller guides according to the first, the second or the third embodiment (see 1 . 7 and 8th ), where in 3 the first embodiment of a linear roller guide 20 is shown. The corresponding carriage 30 is with a separate table 12 firmly connected and preferably screwed to this. The table 12 typically has a high stiffness. For example, it is formed by the tool carriage of a lathe. But it is also possible that the table supports a (not shown) robot arm stiff.

The guide rail 21 the linear roller guide 20 is at a base 13 fixed, which may be, for example, the machine bed of a lathe or the frame of a press.

In the first embodiment of the linear motion device 10 are the displacement sensors 40 at the base 13 attached. In this embodiment may be thought of the displacement sensors 40 only to install temporarily during the actual measurement. This allows the same displacement sensors 40 to monitor several linear roller guideways. The displacement sensors 40 are each received in a holder, which in turn at the base 13 is attached. The displacement sensors 40 are preferably provided over almost their entire length with an external thread. They are preferably in a customized bore of the holder 44 fitted, using nuts against the holder 44 be tightened, the nuts are screwed onto said external thread.

Preferably, both legs 31 of the carriage 30 each a separate displacement sensor 40 assigned, the two displacement sensors 40 most preferably are mirror images of each other. This arrangement is particularly advantageous when the table 12 statically overdetermined. In this case, in addition to the bias caused by the above-mentioned excess of the rolling elements, an additional bias may be caused, for example, by assembly errors or temperature changes. This additional bias can be uneven on the two legs 31 a carriage 30 impact. By using two displacement sensors 40 Wear can be detected, regardless of which side of the carriage 30 he occurs.

The displacement sensors 40 are to an evaluation device 41 connected, which preferably comprises a programmable digital computer. The method according to the invention is preferably carried out by the evaluation device 41 automated.

4 shows one of the 3 corresponding side view of a linear motion device 20 ' according to a second embodiment. The second embodiment is identical to the first embodiment executed except for the differences described below, so that in this regard to the comments on 3 is referenced. In the 3 and 4 are the same or corresponding parts marked with the same reference numerals.

In contrast to the first embodiment, the displacement sensors 40 at the table 12 the linear motion device 10 ' attached. Preferably, each leg is 31 of each carriage 30 one displacement sensor each 40 assigned, which is most preferably permanently installed. This allows the wear during operation of the linear motion device 10 ' monitor. The actual measurement of the wear is preferably always in the same position and in the same load state of the linear motion device 10 ' performed.

The holders 44 ' for the distance sensors 40 are now at the table 12 the linear motion device 10 ' attached. With regard to the attachment of the displacement sensors 40 on each associated holder 44 ' There are no differences from the first embodiment.

5 shows a plan view of the linear motion device 10 to 3 , The table, the base and the holder are not shown. The linear motion device 10 has two linear roller guides 20 , their guide rails 21 are spaced parallel to each other, wherein they have a longitudinal axis 11 define. Both guide rails 21 are attached to the same base. The guide rails 21 For example, each have a variety of mounting holes 23 bolted to the base. Each linear roller guide 20 has two guide carriages 30 which are in the direction of the longitudinal axis 11 spaced apart from each other. Nevertheless, each is a linear roller guide 20 only two displacement sensors 40 associated, which on opposite sides of the associated guide rail 21 are arranged. This exploits the fact that the various guide carriages move into the measuring range of the displacement sensors by moving the table along the longitudinal axis 40 can be moved so that each carriage is ausmessbar. All four carriages 30 are attached to the same table.

Between the guide carriages 30 and a linear roller guide 20 is a separate auxiliary body 42 arranged, which is also attached to the table. The width of the auxiliary body 42 transverse to the longitudinal axis 11 is preferably equal to the width of an unclamped carriage 30 formed, wherein the auxiliary body 42 in the direction of the longitudinal axis 11 in a flight with the respective guide carriages 30 is arranged. From the measuring signal on the auxiliary body 42 and the measurement signal on a carriage 30 a difference is preferably formed on the basis of which the changes in the bias voltage are determined. The said difference is hardly affected by changes in the ambient temperature, so that the measurement accuracy is high. This is particularly exploited that the measurements on the auxiliary body 42 and on the carriage 30 for a said difference with the same displacement sensor 40 respectively.

6 shows a plan view of the linear motion device 10 ' to 4 , The table, the base and the holder are not shown. The linear motion device 10 ' has two linear roller guides 20 , their guide rails 21 are spaced parallel to each other, wherein they have a longitudinal axis 11 define. Both guide rails 21 are attached to the same base. The guide rails 21 For example, each have a variety of mounting holes 23 bolted to the base. Each linear roller guide 20 has two guide carriages 30 which are in the direction of the longitudinal axis 11 spaced apart from each other. All four carriages 30 are attached to the same table. Every carriage 30 are two displacement sensors 40 assigned, which are transverse to the longitudinal axis 11 on opposite sides of the relevant carriage 40 are arranged. The displacement sensors 40 are, as related to 4 explained, attached to the table.

7 shows a rough schematic cross section of a preloaded linear roller guide 20 ' according to a second embodiment. The second embodiment is identical to the first embodiment except for the differences described below, so that in this regard to the comments on 1 and 2 is referenced. In the 1 . 2 and 7 are the same or corresponding parts marked with the same reference numerals.

The displacement sensor 40 is no longer immediately opposite to an associated leg 31 on the carriage 30 arranged. Rather, the leg 31 in question is with a lever arm 34 firmly connected, which is transverse to the longitudinal axis 11 extends. The displacement sensor 40 scans a scanning area 35 on the lever arm 34 which is at a deformation of the leg in question 31 takes a much larger path than the thigh 31 itself. This allows a greater accuracy of the measurement can be achieved.

The lever arm 34 is presently designed as a straight rod, which on a side surface of the respective leg 31 attached, for example, screwed, is. The displacement sensor 40 is below the guide rail 21 arranged.

If preferred as two displacement sensors 40 per carriage 30 is used for every displacement sensor 40 a separate lever arm 34 intended. The mentioned lever arms 34 are most preferably arranged in mirror image to each other.

The use of a separate lever arm 34 is also advantageous if the cross-sectional shape of the carriage, such as the so-called flange carriage, not for immediate sampling by the displacement sensor 40 suitable is.

8th shows a rough schematic cross section of a preloaded linear roller guide 20 " according to a third embodiment. The third embodiment is identical except for the differences described below to the first or to the second embodiment, so that in this regard to the comments on 1 . 2 and 7 is referenced. In the 1 . 2 . 7 and 8th are the same or corresponding parts marked with the same reference numerals.

In the third embodiment, an L-shaped lever arm 34 ' provided, which with an L-leg on an underside of the associated leg 31 is attached. The other L-leg protrudes upwards over the carriage 30 out. The displacement sensor 40 is accordingly above the carriage 30 arranged.

In the third embodiment, compared to the first and the second embodiment of the linear roller guide results in a direction reversal of the measured path, which is preferably taken into account by the evaluation device.

It should be noted that in addition to the explained lever arms 34 ; 34 ' even more, more complex mechanisms are conceivable with which the path to be measured in the manner of a transmission can be increased.

LIST OF REFERENCE NUMBERS

10

Linear motion device (first embodiment)

10 '

Linear motion device (second embodiment)

11

longitudinal axis

12

table

13

Base

20

Linear roller guide (first embodiment)

20 '

Linear roller guide (second embodiment)

20 "

Linear roller guide (third embodiment)

21

guide rail

22

rolling elements

23

mounting hole

30

carriages

31

leg

32

attachment section

33

rolling body

34

Lever arm (first embodiment)

34 '

Lever arm (second embodiment)

35

scanning

40

displacement sensor

41

evaluation

42

auxiliary body

43

Measuring path

44

Holder (first embodiment)

44 '

Holder (second embodiment)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• EP 1719992 [0002]

Claims (10)

Linear movement device (10, 10 ') with a table (12) and a base (13), wherein the table (12) is movably guided via at least one linear roller guide (20) on the base (13) in the direction of a longitudinal axis (11), wherein each linear roller guide (20) comprises a guide rail (21) fastened to the base (13) and at least one guide carriage (30) fastened to the table (12), each guide carriage (30) comprising the respective associated guide rail (21) with two legs (21). 31) U-shaped surrounds, characterized in that at least one displacement sensor (40) is provided with which a deformation transverse to the longitudinal axis (11) of at least one associated leg (31) of a carriage (30) is measurable, wherein the at least one displacement sensor (40) on the table or on the base (12; 13) is fastened or fixed, wherein an evaluation device (41) is provided which is arranged so that using the at least one displacement sensor (40), a change of the Vor voltage of at least one respective associated guide carriage (30) can be determined. Linear movement device according to Claim 1 , wherein in each case a separate displacement sensor (40) is assigned to both legs (31) of at least one guide carriage (30). Linear motion device according to one of the preceding claims, wherein the displacement sensor (40) is attachable or fixed to the base, wherein an auxiliary body (42) is provided, which in the direction of the longitudinal axis (11) in alignment with at least one associated guide carriage (30) on Table (12) is fixed, wherein the auxiliary body (42) with respect to the scanned by the respective displacement sensor (40) contour transverse to the longitudinal axis (11) has substantially the same dimensions as said guide carriage (30), wherein the evaluation device (41) is arranged so that by means of the displacement sensor (40) a path difference between the auxiliary body (42) and an associated leg (31) can be determined. Linear motion device according to one of the preceding claims, wherein the displacement sensor (40) is a non-contact displacement sensor. Linear movement device according to Claim 4 wherein the at least one displacement sensor (40) is formed by an eddy current sensor or by a magneto-inductive sensor. Linear motion device according to one of Claims 1 . 2 . 4 or 5 wherein the at least one displacement sensor (40) is attached to the table (12). Linear motion device according to one of the preceding claims, wherein at least one displacement sensor (40) is associated with a lever arm (34; 34 '), wherein the displacement sensor (40) is arranged such that it has a scanning region (35) on the lever arm (34; 34'). is scanned, wherein the lever arm (34, 34 ') is fixed to the associated leg (31) such that when a change in the bias of the scanning (35) transverse to the longitudinal axis (11) performs a greater path than the respective leg (31). Method for operating a linear motion device (10, 10 ') according to one of the preceding claims, wherein a change in the preload of at least one associated guide carriage (30) is determined using the at least one displacement sensor (40), a service end of said guide carriage (30 ) is displayed when a reduction in the bias voltage exceeds a predetermined limit in amount. Method according to Claim 8 wherein the determination of the bias change is repeated a plurality of times in succession, with the linear motion device (10; 10 ') being in the same position each time. Method according to Claim 8 or 9 wherein the determination of the bias change is repeated a plurality of times in succession, the linear motion device (10; 10 ') having the same load state each time.

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