DE102016204314A1 - Linear motion device with flat strain sensor - Google Patents

Abstract

The invention relates to a linear motion device (10) having a rod (12) extending in the direction of a longitudinal axis (11) and a rotor (20) movably connected to at least one row of rolling elements (13) at least in the direction of the longitudinal axis (11) the rod (12) is mounted, wherein each row of rolling elements (13) is associated with a rotor rolling surface (21) on the rotor (20), said rolling bodies (13) at least in a support region (22) of the rotor rolling surface (21) load-transmitting this contact, wherein the rotor (20) with at least one strain sensor (40, 40 ', 40' ') is provided. According to the invention, the at least one strain sensor (40; 40 '; 40 ") has a planar design so that it defines a measuring surface (41), wherein strains, no matter at which point of the measuring surface (41), influence a measuring signal (51 ), wherein the measuring surface (41) extends in the direction of the longitudinal axis (11) over at least 80% of the length of the support region (22).

Description

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

From the EP 1 719 992 B1 a linear motion device in the form of a rail guide is known. The corresponding rotor is provided with a strain sensor in the form of a strain gauge. As a result, the local strain at the location of the strain gauge can be easily detected, whereby the external load of the linear motion device can be determined from this in turn.

An advantage of the present invention is that damage of the linear motion device can be clearly seen from the measurement signal of the strain sensor. This is especially thought of material eruptions in the rotor rolling surfaces, with material eruptions can be seen in the rod rolling surfaces.

According to claim 1, it is proposed that the at least one strain sensor is formed flat, so that it defines a measuring surface, wherein strains, no matter at which point of the measuring surface they occur, influence a measuring signal of the strain sensor, wherein the measuring surface in the direction of the longitudinal axis extends over at least 80% of the length of the support area. The mentioned material outbreaks, which are also referred to as pittings, are very small in the initial stage of a damage, wherein it is not foreseeable at which location of the runner surface they occur. Due to the proposed large-scale strain sensor it does not matter. This strain sensor can easily detect load changes due to material breakouts, no matter where the material broke out.

The measuring surface is preferably formed contiguous. But it is also conceivable that the measuring surface has a plurality of spaced apart measuring surfaces. The corresponding break lines are preferably aligned parallel to the longitudinal direction.

Preferably, the strain sensor extends over the entire length of the support area. Each row of rolling elements is preferably formed endlessly encircling. The linear motion device may be a rail guide, wherein the rod forms the corresponding guide rail and the rotor forms the corresponding guide carriage. Optionally, either the carriage or the guide rail is U-shaped. The linear motion device may also be a rolling element screw, wherein the rod is the corresponding threaded spindle, wherein the rotor is the corresponding nut. It is understood that the mother in addition to the linear movement in the direction of the longitudinal axis can also perform a rotational movement relative to the threaded spindle. It should be noted that the length of the support area is measured in Wälzkörpergewindetrieb along the longitudinal axis and not along the helical rotor rolling surface.

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

It can be provided that the rotor has a main body, which consists of metal, wherein the strain sensor is so firmly connected to the main body in the region of the measuring surface that expansions of the main body can be measured. The main body is that part of the linear motion device which transmits the external load to the rolling elements. Damage to the linear motion device is particularly pronounced at this part. The measuring layer of the strain sensor may be bonded to the main body, wherein it may also be applied directly there in a thin-film process. The main body is preferably made of steel. The length of the main body in the direction of the longitudinal axis usually defines the length of the support area. To the main body, one or more parts may be grown, which are preferably made of plastic. Moreover, it is conceivable that at least one separate Wälzflächenteil is attached to the main body, which consists of hardened steel, wherein said Wälzflächenteil forms at least one rotor rolling surface.

It can be provided that the strain sensor has a measuring layer of piezoelectric material which defines the measuring surface. The piezoelectric material is, for example, the plastic polyvinylidene fluoride (PVDF) or lead zirconium titanate (PZT). In particular, in the first case, the measuring layer can be produced for example in the form of a film, which is glued to the main body. In particular, in the second case, it is conceivable to provide the main body directly with the measuring layer, for example using a thin-film method such as the PVD, the CVD and the sol-gel method. The thickness of the measuring layer is preferably constant, whereby tolerance-related variations of the thickness may be present.

It can be provided that the thickness of the measuring layer is less than 200 microns. If the named layer is formed by a film, the thickness of the measuring layer is for example between 28 μm and 110 μm. Unless the main body is coated directly, the thickness of the measuring layer, for example, 2 microns.

It can be provided that the main body is viewed in cross-section U-shaped with a base and two U-legs, wherein the rod is received between the U-legs.

It can be provided that at least one strain sensor is arranged on the outer side of a U-leg facing away from the rod. As a result, damage to the linear motion device can be detected particularly well.

It can be provided that at least one strain sensor is arranged in a corner region between the base and a U-leg, said corner region facing the rod. As a result, damage to the linear motion device can be detected particularly well. The said corner region is preferably rounded.

It can be provided that at least one strain sensor is arranged on the rod-facing side of the base. As a result, the strain sensor is particularly well protected against environmental influences.

It is also proposed a method for operating a linear motion device according to the invention, wherein from a Meßsginal the at least one strain sensor temporally continuously a spectral analysis is determined, with a damage of the linear motion device is displayed when occur in the spectral analysis broadband shocks. The spectral analysis is preferably calculated by a Fourier transform, most preferably the FFT method is used. Under a shock is to be understood as a signal whose strength increases rapidly over time, and it drops quickly after reaching a maximum value. Such a shock is particularly caused when one of the rolling elements rolls over a damaged area. A broadband signal is preferably understood to be a signal which has a bandwidth of at least 200 Hz in the frequency range between 0 and 1 kHz.

Alternatively, an evaluation of the measurement signal in the time domain is conceivable.

Also proposed is a method for operating a linear motion device according to the invention, wherein a time-variable load of the linear motion device is determined, preferably calculated, from a measurement signal of the at least one strain sensor.

Furthermore, a linear motion device is proposed in which the at least one strain sensor for transmitting a measurement signal is connected to an evaluation device, which comprises a digital computer, wherein the evaluation device is set up to execute at least one of the methods described above.

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.

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

1 a rough schematic side view of a linear motion device according to a first embodiment of the invention;

2 a rough schematic cross section of the linear motion device according to 1 ;

3 a grobschamtischen partial longitudinal section of the linear motion device after 1 in the area of the strain sensor.

4 a rough schematic cross section of a rotor according to a second embodiment of the invention;

5 a rough schematic cross section of a rotor according to a third embodiment of the invention.

1 shows a rough schematic side view of a linear motion device 10 according to a first embodiment of the invention. The linear motion device 10 is presently designed in the form of a rail guide. The pole 12 is formed by a guide rail, which is parallel to a longitudinal axis 11 extends. The pole 12 is made of steel and is preferably in the area of the rod rolling surfaces 14 hardened. The bar rolling surfaces 14 are parallel to the longitudinal axis in the present rail guide 11 aligned at a Wälzkörpergewindetrieb helically with respect to the longitudinal axis 11 are formed.

On the pole 12 is a runner 20 in the form of a guide carriage in the direction of the longitudinal axis 11 movably guided. For a rail guide, this is the only degree of freedom of movement. In a Wälzkörpergewindetrieb the runner leads 20 in addition to the longitudinal movement, a rotation about the longitudinal axis 11 out. The runner 20 includes one main body 30 , which preferably consists of steel. At its two opposite longitudinal ends is in each case an end cap 24 attached, which preferably consists of plastic. Inside the runner 20 For example, run two or four rows of rolling elements (no. 13 in 2 ) endlessly around. The straight sections of the corresponding circulation path are in the main body 30 arranged, wherein the bent portions of the circulation path in the end caps 24 are arranged.

On the outside of the runner 20 , in particular on the outside of the main body 30 , is a strain sensor 40 fastened, with in 1 greatly simplifies only its measuring layer 43 is shown. The measuring layer 43 is preferably made of a piezoelectric material, which is fixed to the main body 30 is connected so that it is subjected to the same material expansions, as the main body 30 , The piezoelectric voltage, which at the measuring layer 43 is present, or the measurement signal 51 , depends on the deformation of the measuring layer 43 which from the main body 30 is effected. Locally occurring deformations, which only affect a small part of the measuring surface, cause this 41 of the strain sensor 40 capture, a usable measurement signal 51 , It does not really matter where on the measuring surface 41 this deformation takes place. The measuring surface 41 is the area over which the measurement layer 43 stuck to the main body 30 connected is. At the measuring layer 43 it may be a film of the plastic polyvinylidene fluoride (PVDF), which with the main body 20 is glued. It is just as possible, a measuring layer 43 made of lead zirconium titanate (PZT) directly on the main body 30 applied. It is also conceivable to apply such layers to a carrier material, for example a plastic film or a metal sheet, which in turn is connected to the main body 30 is glued. In addition to piezoelectric measuring layers 43 also measuring layers can be used, which change their resistance when stretched. The measuring surface 41 is presently rectangular, with the corresponding side of the rectangle parallel or perpendicular to the longitudinal axis 11 run.

The strain sensor 40 is for transmitting the measuring signal 51 to an evaluation device 50 connected. The measuring signal 51 can be directly on the strain sensor 40 be amplified to disturbances in the signal transmission to the evaluation device 50 to minimize. In this case, preferably a charge amplifier is used. The evaluation device 50 may comprise an analog-to-digital converter for digitizing the measurement signal. The evaluation device 50 preferably comprises a digital computer 52 , with which the measuring signal 51 can be processed to cause damage to the linear motion device 10 to recognize. It should be noted that with the present strain sensor 40 also temporally variable loads of the linear motion device 10 are measurable. For measuring static loads of the linear motion device 10 a piezoelectric strain sensor, however, is poorly suited because the measurement signal 51 with static deformations or time-invariant deformations falls to zero over time.

2 shows a rough schematic cross section of the linear motion device 10 to 1 , The strain sensor 40 measured strains are primarily from the rolling elements 13 inside the runner 20 causing, which load transfer on a support area 22 the rotor rolling surfaces 21 at the runner 20 support. The rolling elements 13 are spherical in the present case, with roller or barrel-shaped rolling elements are used. The named support area 22 in the present case extends over the entire length of the main body 30 in the direction of the longitudinal axis 11 so that the length (no. 23 in 1 ) of the support area 22 equal to the length of the main body 30 is. Depending on the design of the inlet slopes at the two opposite longitudinal ends of the rotor rolling surfaces 21 can the carrying area 22 also a bit shorter than the main body 30 be.

The present invention primarily seeks to damage the linear motion device 10 be recognized. Such damage usually occurs first on the rotor rolling surface 21 on, in particular material eruptions on the rotor rolling surface 21 to be observed, which are also referred to as Pittings. Investigations by the applicant have shown that the circulation of such outbreaks by the loaded rolling elements 13 Deformations on the outside of the main body 30 caused, which with a strain sensor 40 are measurable. In the vicinity of said outbreak, locally measurable material strain occurs, with weak deformations on the main body at a greater distance from the damaged area 30 occur. Thus, the location of the maximum deformation depends on the location of the damaged area. The location of the damaged area can not be predicted and can be anywhere along the support area 22 be located. The measuring surface 41 therefore extends in the direction of the longitudinal axis 11 over more than 80% of the length (no. 23 in 1 ) of the support area 22 so that the strain sensor 40 no matter where the causative damage has occurred.

The main body 30 is in cross-section U-shaped with a base 31 and two U-thighs 32 educated. The rotor rolling surfaces 21 are at the stake 12 facing inner sides of the U-legs 32 arranged. Next are two mirror-symmetrical to each other trained strain sensors 40 provided, which in each case on an outer side of an associated U-leg 32 are arranged. This results in a very small distance between the rolling elements 13 and the respective associated strain sensor 40 , so that the measuring signal is particularly strong. In 2 are the strain sensors 40 , in particular the measuring layers 43 , simplified as a solid line. The in 2 shown distance to the main body 30 only serves the clarity of the presentation. In fact, the measuring layer is located 43 corresponding 3 directly on the main body.

3 shows a rough schematic partial longitudinal section of the linear motion device after 1 in the area of the strain sensor 40 , The cutting plane runs parallel to the longitudinal axis. The measuring layer 43 preferably has a substantially constant thickness 44 , which is most preferably less than 200 microns. The measuring layer 43 is immediately fixed to the main body 30 connected. The measuring layer 43 ends with some distance to the longitudinal end of the main body 30 , As a result, the risk of detachment of the edge of the measuring layer 43 from the main body 30 minimized.

4 shows a rough schematic cross section of a runner 20 according to a second embodiment of the invention. The second embodiment is identical to the first embodiment except for the differences described below, so that in this regard to the comments on the 1 to 3 is referenced. Here are in the 1 to 4 the same or corresponding parts with the same reference numerals.

In the second embodiment, the strain sensor is 40 ' no longer on the outside of the U-thighs 32 arranged but in a corner area 33 between the base 31 and a U-thigh 32 , wherein said corner area 33 facing the rod. At the present runner 20 There are two such corner areas, both with a strain sensor 40 ' are provided. The corner areas 33 are rounded, so that the measuring layer 43 can be easily attached there.

Typically occur in said corner areas 33 the highest stresses or strains on the main body 30 on, which are caused by the load on the rolling elements. Accordingly, the rolling over of damaged areas in the rotor rolling surface also has an effect 21 There especially strong. Consequently, a measurement signal is obtained by means of which it is particularly easy to detect damage to the linear movement device.

The measuring layer 43 of the strain sensor 40 ' is in the development considered rectangular, with the corresponding side of the rectangle parallel or perpendicular to the longitudinal axis 11 are aligned. The length of the measuring layer 43 in the direction of the longitudinal axis 11 is identical to the first embodiment.

5 shows a rough schematic cross section of a runner 20 according to a third embodiment of the invention. The third embodiment is identical to the first embodiment except for the differences described below, so that in this regard to the comments on the 1 to 3 is referenced. Here are in the 1 to 3 and 5 the same or corresponding parts with the same reference numerals.

In the third embodiment, the strain sensor is 40 '' no longer on the outside of the U-thighs 32 arranged, but on the rod-facing side of the base 31 , There is the strain sensor 40 '' particularly well protected against environmental influences. The measuring layer 43 of the strain sensor 40 '' is rectangular, with the corresponding sides of the rectangle are aligned parallel or perpendicular to the longitudinal axis. The length of the measuring layer 43 in the direction of the longitudinal axis 11 is identical to the first embodiment.

LIST OF REFERENCE NUMBERS

10

Linear motion device

11

longitudinal axis

12

pole

13

rolling elements

14

Stangenwälzfläche

20

runner

21

Läuferwälzfläche

22

support area

23

Length of the support area

24

endcap

30

main body

31

Base

32

U-leg

33

corner

40

Strain sensor (first embodiment)

40 '

Strain sensor (second embodiment)

40 ''

Strain sensor (third embodiment)

41

measuring surface

42

Length of the measuring surface

43

measuring layer

44

Thickness of the measuring layer

50

evaluation

51

measuring signal

52

digital computer

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 B1 [0002]

Claims (11)

Linear motion device ( 10 ) with one in the direction of a longitudinal axis ( 11 ) extending rod ( 12 ) and a runner ( 20 ' ), which has at least one row of rolling elements ( 13 ) at least in the direction of the longitudinal axis ( 11 ) movable on the pole ( 12 ), each row of rolling elements ( 13 ) a rotor rolling surface ( 21 ) on the runner ( 20 ), wherein said rolling elements ( 13 ) at least in one support area ( 22 ) of the rotor rolling surface ( 21 ) load-bearing abut this, wherein the runner ( 20 ) with at least one strain sensor ( 40 ; 40 '; 40 '' ), characterized in that the at least one strain sensor ( 40 ; 40 '; 40 '' ) is flat, so that it has a measuring surface ( 41 ), whereby strains, at which point of the measuring surface ( 41 ), they influence the measurement signal ( 51 ) of the strain sensor ( 40 ; 40 '; 40 '' ), whereby the measuring surface ( 41 ) in the direction of the longitudinal axis ( 11 ) over at least 80% of the length of the support area ( 22 ). Linear motion device according to claim 1, wherein the rotor ( 20 ) a main body ( 30 ), which consists of metal, wherein the strain sensor ( 40 ; 40 '; 40 '' ) in the region of the measuring surface ( 41 ) so firmly with the main body ( 30 ), that expansions of the main body ( 30 ) are measurable. Linear motion device according to one of the preceding claims, wherein the strain sensor ( 40 ; 40 '; 40 '' ) a measuring layer ( 43 ) of piezoelectric material, which the measuring surface ( 41 ) Are defined. Linear motion device according to claim 3, wherein the thickness ( 44 ) of the measuring layer ( 43 ) is less than 200 microns. Linear motion device according to one of claims 2 to 4, wherein the main body ( 30 ) in cross-section U-shaped with a base ( 31 ) and two U-legs ( 32 ) is formed, wherein the rod ( 12 ) between the U-legs ( 32 ) is recorded. Linear motion device according to claim 5, wherein at least one strain sensor ( 40 ) on the off-the-rack ( 12 ) facing away from the outside of a U-leg ( 32 ) is arranged. Linear motion device according to claim 5 or 6, wherein at least one strain sensor ( 40 ' ) in a corner area ( 33 ) between the base ( 31 ) and a U-leg ( 32 ), said corner region ( 33 ) of the rod ( 12 ) is facing. Linear motion device according to one of claims 5 to 7, wherein at least one strain sensor ( 40 '' ) on the pole ( 12 ) facing side of the base ( 31 ) is arranged. Method for operating a linear motion device according to one of the preceding claims, wherein a measuring signal ( 51 ) of the at least one strain sensor ( 40 ; 40 '; 40 '' ) a temporal spectral analysis is determined, wherein a damage of the linear motion device ( 10 ) is displayed when broadband bursts occur in spectral analysis. Method for operating a linear motion apparatus according to one of claims 1 to 8, wherein a measuring signal ( 51 ) of the at least one strain sensor ( 40 ) a temporally variable loading of the linear motion device ( 10 ), preferably calculated.  Linear movement device according to one of claims 1 to 8, wherein the at least one strain sensor for transmitting a measurement signal to an evaluation device is connected, which comprises a digital computer, wherein the evaluation device for implementing a method according to claim 9 and / or arranged according to claim 10.

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