WO2009071502A1

WO2009071502A1 - Linear guide having vibration damper

Info

Publication number: WO2009071502A1
Application number: PCT/EP2008/066505
Authority: WO
Inventors: Peter Lutz; Dietmar Rudy
Original assignee: Schaeffler Kg
Priority date: 2007-12-06
Filing date: 2008-12-01
Publication date: 2009-06-11
Also published as: DE102007059156A1; DE102007059156B4

Abstract

The invention relates to a linear guide having a guide carriage (1) displaceably disposed on a guide rail (2), having a connection (21) for clamping a machine part, for example a toolholder or machine table, and at least one bearing surface disposed at a distance from the connection (21) for supporting the guide carriage (1) on the guide rail (2), wherein the guide carriage (1) comprises an upper carriage segment (9) comprising the connection (21) and a lower carriage segment (10) comprising the at least one bearing surface, and wherein a gap (11) is provided between the upper carriage segment (9) and the lower carriage segment (10), and wherein limited relative displacements between the two carriage segments (9, 10) are provided without relative displacements between the lower carriage segment (10) and the guide rail (2), and having a vibration damper disposed effectively between the two carriage segments (9, 10) for damping vibrations, wherein a lift device (20) for a variable lift of the upper carriage segment (9) relative to the lower carriage segment (10) is provided in the gap (11), wherein the lift device (20) is used as a vibration damper (22).

Description

Linear guide with vibration damper

The present invention relates to linear guides, in which a carriage is arranged longitudinally displaceable on a guide rail.

From DE 42 27 936 A1, for example, a linear guide has become known according to the features of the preamble of claim 1. In this linear guide, the guide carriage has an upper and a lower carriage section, between which a gap is formed. Relative lateral displacements are possible between these two carriage sections in order to be able to compensate for positional tolerances, for example. In addition to this sliding device, a lubricating film damper is formed in a further gap arranged between these two carriage sections. The gap may typically be a few tens of microns in size. A feed channel is connected to this gap, so that, for example, oil can be effortlessly and constantly transported into this gap to form the lubricating film damper.

Linear guides are predominantly used in production machines in the field of metal forming. In the continuous development of such linear guides whose power and dynamic limits are increasingly raised. As a result of this increase, the mass fractions to be moved must be significantly reduced. The omission of mass, however, causes an increased susceptibility to static deformations and, for example, regenerative chatter phenomena, which are due to vibrations that are due to the lighter components.

Accordingly, there is a great need to provide linear guides that are able to vibrate both statically and dynamically on the other hand, for example, to compensate for incorrect positioning by appropriate facilities on the linear guide.

Although in the known written linear guide lateral Relativver- sliding between the two car sections of the carriage are possible, and also a static vibration damping by means of the lubricating film damper used is possible. However, a dynamic vibration damping is not provided. In addition, rolling element sets are arranged between the two carriage sections which are intended to promote relative displacements between the two carriage sections, but such rolling element sets in turn favor the susceptibility of such linear guides to dynamic vibrations.

The described problem is solved with the linear guide according to the invention.

Characterized in that in the gap - which is preferably provided as the only gap for subdivision into the two car sections - a lifting device for a variable stroke of the upper carriage portion opposite the lower carriage portion is provided, wherein the lifting device is used as a vibration damper, the invention offers the advantage in that for an optionally required compensation of incorrect positioning on the one hand and a preferably dynamic vibration damping on the other hand is made possible by the same technical means. The invention thus allows linear guides that are simple in construction, and where vibration damping and stroke adjustment are made possible by the same technical measures.

It has been found that stroke adjustments up to 100 microns are sufficient to compensate for misalignments or clearance tolerances, such as material strain due to temperature changes. In a linear guide according to the invention, the gap may for example be filled with a hydraulic fluid, in which case the gap may be formed as a pressure chamber. Now, when the liquid is pressurized, the pressure in the pressure chamber increases and the corresponding arrangement of the two carriage sections allows a stroke of the upper carriage portion relative to the lower carriage portion, for example by 70 microns. At the same time a targeted vibration compensation can be generated via a suitable power unit with an appropriate control and regulation, so that in the pressure chamber targeted pressure oscillations are built up, which are opposite in an undesirable manner acting dynamic vibrations, so that a compensation is achieved, compared to a smooth running of the carriage allows the guide rail. Consequently, the described combinatorial effect of a stroke adjustment and a dynamic vibration damping can be achieved with simple means-for example hydraulic fluid-in the gap formed as a pressure chamber.

Alternative lifting devices of the invention provide for the use of piezoelectric materials disposed in the gap. The directed deformation of a piezoelectric material forms microscopic dipoles within the unit cells; There is a shift in the charge centers. The summation over all unit cells of the crystal leads to a macroscopically measurable electrical voltage. Directional deformation means that the applied pressure does not act on all sides of the sample, but only on opposite sides, for example. Conversely, by applying an electrical voltage, for example, a crystal (or the component made of piezoceramic) can be deformed.

Like any other solid, piezoelectric bodies can perform mechanical oscillations. In piezoelectric materials, these vibrations can be electrically excited on the one hand, on the other hand cause again an electrical voltage. The frequency of the oscillation is only from the speed of sound and the dimensions of the piezoelectric body, the sound velocity is a material constant. As a result, piezoelectric components are also suitable for oscillators.

The most important material parameter for the inverse piezo effect and thus for actuators is the piezoelectric charge constant. It describes the functional relationship between the applied electric field strength and the strain generated thereby. The characteristic sizes of a piezoelectric transducer are different for the different directions of action.

In the field of actuators, two main effects are relevant: First, mention must be made of the piezoelectric transverse or transverse effect, with the mechanical force acting transversely to the applied field. The second main effect is the piezoelectric longitudinal or longitudinal effect. The mechanical force acts parallel to the applied field.

The piezoelectric transverse and longitudinal effects result in three different basic elements for piezoelectric actuators: the thickness oscillator, the transverse expansion element, the bimorph. Here, the bimorph is a combination of two transverse expansion elements. An opposite control of the elements causes a bending of the actuator, which is why this receives a separate name

In particular, the above-mentioned thickness vibrator is suitable for the present invention. The deformation when applying a voltage can be used in the thickness vibrator as an actuator, which can also be referred to as a piezo-positioner. According to the invention, a plurality of piezo positioners can also be arranged in the gap and, depending on the type of application, in parallel or series connection. By means of the deformation of one or more piezo elements, piezo positioners allow precise movements which, in the present case, can be used in particular for dynamic vibration damping in linear guides according to the invention. The two car sections are shifted relative to each other in the lifting directions under the action of the active piezoelectric actuator. This shift can then be static, or dynamic.

Of course, other lifting devices are conceivable. For example, in the gap formed between the two carriage sections, an electroactive polymer may be used that can change its shape when an electrical voltage is applied. Depending on the requirements of a dynamic vibration damping suitable vibration dampers can be used, which are also suitable as a lifting device.

In the case of the gap formed as a pressure chamber, this pressure chamber may be variable in volume. It is possible by means of dynamic loading of the pressure chamber to set certain stroke frequencies as well as certain lifting amplitudes of the upper carriage section relative to the lower carriage section. This targeted adjustability can superimpose unwanted vibrations such that a smooth sliding of the carriage is made possible, while ensuring a certain stroke position.

The two carriage sections can be integrally connected to each other. In this case, remaining web portions which connect the two carriage sections to one another are expediently made so thin-walled and flexible that an enlargement of the gap-for example by means of pressurization-is possible. This means that elastically deflectable wall sections can connect the upper carriage section to the lower carriage section in one piece. Preferably, these deflectable wall sections limit the pressure chamber. This means that no separate seals are required to keep the pressure chamber pressure-tight.

In known manner, the carriage is preferably formed in cross-section approximately U-shaped, wherein two legs of the carriage are connected to each other via a floor, wherein the carriage with his two legs, the guide rail engages, and wherein the bottom is provided with the pressure chamber, which is bounded on both its longitudinal sides by a longitudinal direction of the guide carriage longitudinal bore, and wherein between an outer boundary surface of the guide carriage and each of the two longitudinal bores elastically deflectable wall portion is formed. In terms of manufacturing technology, the longitudinal bores can be easily created in the carriage known per se, so that elastically deflectable wall sections are produced in the desired manner, in order to allow an elastic enlargement of the gap.

On the outer contour of the guide carriage, a longitudinal groove parallel to the longitudinal bore and open to the surroundings of the guide carriage can be formed which, together with the longitudinal bore, delimits at least a portion of the elastically deflectable band section. This longitudinal groove is thus positioned so that it provides a suitable elasticity of the wall sections together with the longitudinal bore.

An alternative embodiment of the invention provides that the two car sections are formed by separate car parts, which are interconnected by means of expansion screws. In this case, these two car parts can limit the gap. Since, in this situation, the wall of the pressure chamber has a transition region from the lower carriage part to the upper carriage part, it may be expedient to provide a seal, in particular an O-ring, between the two carriage parts, which seals the pressure chamber to the surroundings of the guide carriage. Thus, the pressure chamber can be pressurized without this pressure undesirably enters the surroundings of the guide carriage.

If the two carriage sections are formed by car parts which are separate from one another, according to a further embodiment according to the invention a guide carriage is provided which, seen in cross-section, is approximately U-shaped. is formed, wherein two legs of the carriage are connected to each other via a floor, wherein the guide carriage engages around the guide rail with its two legs, and wherein the bottom is provided with the pressure chamber, wherein the lower carriage part on its side facing the upper carriage part with a circumferential Is provided, and wherein the upper carriage member is provided with a flange for receiving the expansion bolts and with an engagement portion which engages in the bounded by the circumferential web receiving portion, wherein between the web and the engagement portion is a preferably endless O-ring for sealing the Pressure chamber is arranged opposite the surroundings of the carriage. Now, if the pressure chamber is pressurized, takes place in the limited scope up to about 100 microns, a relative displacement of the two car parts to each other, this relative movement is made possible by an expansion of the expansion screws. The expansion screws also offer the advantage of a high-precision guidance in the direction of the stroke, so that an undesirable tilting or jamming is excluded. The screw axes of the expansion screws are preferably arranged parallel to the stroke direction of the upper carriage part with respect to the lower carriage part to allow the desired relative displacement between the two carriage parts by utilizing a desired elongation of the expansion screws.

The invention will be explained in more detail with reference to three illustrated in a total of seven figures embodiments. Show it:

1 shows a cross section through a carriage of a linear guide according to the invention,

FIG. 2 shows a representation as in FIG. 1, but with a modified carriage,

FIG. 3 shows a representation as in FIGS. 1 and 2, but with a further guide carriage according to the invention, FIGS. 4 to 6 show different representations of a linear guide according to the invention, whose guide carriage is shown schematically in FIG. 1 and FIG

Figure 7 shows a schematic representation of a control circuit of the linear guide according to the invention.

FIGS. 4 to 6 illustrate a linear guide according to the invention with its essential components, while the special features according to the invention are specified in greater detail in FIGS. 1 to 3.

The linear guide according to the invention shown in FIGS. 4 to 6 has a guide carriage 1, which is mounted longitudinally displaceably on a guide rail 2. It can be seen from FIG. 5 that the guide jib 1 is roller-mounted on the guide rail 2 via rollers 3, these rollers 3 circulating in an endless manner in an endless roller channel 4. FIG. 5 shows load sections 5 and return sections 6 of the endless roller channel 4. In the load section 5, the rollers 3 roll on raceways 7, 8 of the guide carriage 1 and the guide rail 2.

Figure 6 shows a perspective view of the carriage 1 without the guide rail.

1 shows a schematic representation of a section through the guide carriage 1 along the line I - I of Figure 4. The figure shows that the carriage 1 has an upper carriage section 9 and a lower carriage section 10, between which a gap 11 is formed is. The gap 11 extends over at least the major part of the supporting structure of the guide carriage 1.

The lower carriage portion 10 is stiff and properly on the Guide rail guided without it may lead to undesirable relative displacements between the lower carriage portion 10 and the guide rail. Likewise, the upper carriage section 9 is also designed to be stiff and is not subject to any appreciable deformations during operation of such a linear guide. The upper carriage section 9 is integrally connected by means of elastically deflectable wall sections 12 with the lower carriage section 10. These elastically deflectable wall sections 12 are bounded on the one hand by the outer contour of the guide carriage 1 and on the other hand by longitudinal bores 13 which are arranged in the longitudinal direction of the guide carriage in the edge region of the guide carriage 1. The upper carriage section 9 is also provided on its longitudinal sides each with an outwardly open groove 14, so that the elastic wall portions 12 are limited by the longitudinal side of the carriage 1, and the groove 14 and further through the longitudinal bore 13. The longitudinal bore 13 limited at the same time the gap 11 at its two longitudinal sides. The gap 11 thus opens into these longitudinal bores 13 a.

The carriage 1 is seen in cross-section approximately U-shaped. Two legs 15 of the guide carriage 1 are connected to one another via a base 16, wherein the guide carriage 1 engages around the guide rail with its two legs 15. The bottom 16 is presently provided with the gap 11 already described.

The gap 11 is formed as a pressure chamber 17, wherein in this pressure chamber 17 hydraulic fluid 18 is filled. About a performance, tax and

Control device 19 - which is merely indicated in the figure 1 - can

Hydraulic fluid 18 are pressurized in the pressure chamber 17.

Under sufficient pressure, the gap 11 widens, so that the upper carriage section 9 performs a lift relative to the lower carriage section 10, but away from the guide rail.

Accordingly, in the gap 11, a lifting device 20 is provided by means of

Strokes are adjustable up to 100 μm. Anyone can do it within the given limits desired stroke can be set as a fixed position of the upper carriage section 9 relative to the lower carriage section 10, wherein only a corresponding pressurization takes place.

Under the pressurization of the pressure chamber 11 with pressure there is a change in the volume of the pressure chamber 11. This enlargement of the pressure chamber 11 is possible because the pressure chamber 11 delimiting wall sections 12 are elastically deflectable. In particular, provided in accordance with the figure 1 angular configuration of the elastic Wandab- section 12 allows flexible elastic deflection.

While the abovementioned mode of operation according to the invention describes an aspect of the invention which is suitable, for example, for compensating misalignments of the upper carriage section 9 with respect to a machine part to be connected to a connection 21 of the guide carriage 1, a further aspect of the present invention can be seen in that FIGS filled with hydraulic fluid 18 pressure chamber 17 forms a damping device 22 which dampens vibrations. This damping device 22 is suitable for substantially suppressing the transmission of vibrations between the upper carriage section 9 and the lower carriage section 10. In addition to a static damping, the linear guide according to the invention described here is particularly suitable for a dynamic vibration damping.

For this purpose, via the power, control and regulation unit 19, for example in the presence of an undesired dynamic oscillation between the upper carriage section 9 and the lower carriage section 10, a targeted pulsating pressurization takes place in a frequency which superimposes the unwanted oscillation such that the upper one Carriage section 9 can run without vibrations. The lifting device 20 forms with the power, control and regulating unit 19 an actuator 23. This actuator allows dynamic vibration damping in this invention Linear guide.

With the actuator 23 a dynamic loading of the pressure chamber 11 with pressure is possible such that certain stroke frequencies and certain stroke amplitudes of the upper carriage section 9 are adjustable.

According to FIG. 2, the carriage 1 can be modified to the effect that approximately in a longitudinal center plane of the carriage 1 a support element

24 is disposed in the gap 11 to allow support of the upper Wagenab- section 9 relative to the lower carriage portion 10, and thus to prevent undesirable bending.

The guide carriage according to the invention shown in FIG. 3 differs from that of FIG. 1 essentially in that the upper carriage section 9 and the lower carriage section 10 are formed by separate carriage parts 24, 25. The associated design measures are explained in more detail below. The under carriage part 25 is provided on its upper carriage part 24 facing side with a circumferential ridge 26. This web 26 is provided with a plurality of threaded holes 27 for receiving expansion screws 28. The inner wall of the web 26 serves as a sealing surface, as will be explained in more detail below.

The upper carriage part 24 is provided with a peripheral flange 29 which has a plurality of bores for receiving the expansion screws 28. The flange 29 rests on the circumferential web 26. Further, the upper carriage member 24 is provided with an engaging portion 30 which in a bounded by the circumferential ridge 26 receiving portion of the lower carriage portion

25 engages. The engagement portion 30 is provided with a circumferential groove 31 into which an O-ring 32 is inserted. When the two carriage parts 24, 25 are connected to each other, the O-ring 32 is applied to sealing surfaces of the circumferential ridge and the groove 31, so that the pressure chamber 17 is properly sealed to the environment of the carriage 1. Upon application of pressure to the pressure chamber 17, the gap 17 increases, the expansion screws 28 being stretched along their screw axes. At low strokes of about 100 μm, the seal described here can be sufficient by means of an O-ring, since this O-ring is predominantly subjected to only static loading. Of course, alternative seals are possible.

Since the O-ring is formed circumferentially, no further seals are required in order to keep the pressure chamber sufficiently resistant to pressure.

Figure 7 shows a schematic illustration of the actuator 23, and in particular the power, control and regulating device 19. On the guide carriage 1, a mass 33 is attached. At this mass 33, a signal generator 34 is arranged, which transmits vibrations occurring at the mass 33 to a controller 35. The controller 35 is connected to a hydraulic unit 36, via which the hydraulic fluid provided in the gap 11 of the guide carriage 1 can be pressurized. The guide carriage 1 itself acts here as a damper, which introduces into the oscillating component-here the mass 33-a "counter-oscillation" phase-shifted by 90.degree .. The oscillation of the mass 33 and the corresponding "counter-oscillation" cancel each other out. This active damping device 22 can - in contrast to the passive dampers - compensate over a wide frequency range, while the known passive damper works optimally only for a specific frequency. The integration of the dynamic damper in the carriage 1 allows a very space-saving design. LIST OF REFERENCE NUMBERS

1 carriage 27 threaded hole

2 guide rail 28 expansion screw

3 roller 29 flange

4 roller channel 30 engaging portion

5 load section 31 groove

6 Return section 32 O-ring

7 track 33 mass

8 track 34 signal generator

9 upper carriage section 35 regulator

10 lower carriage section 36 hydraulic unit

11 gap

12 wall section

13 longitudinal bore

14 groove

15 thighs

16 floor

17 pressure chamber

18 hydraulic fluid

19 Power, control and regulation device

20 lifting device

21 connection

22 damping device

23 actor

24 upper carriage part

25 lower car part

26 surrounding bridge

Claims

claims

1. Linear guide, with a longitudinally displaceable on a guide rail (2) arranged guide carriage (1) having a connection (21) for mounting a machine part, such as tool carrier or machine table, and at least one, spaced from the terminal (21) bearing surfaces for supporting the guide carriage (1) on the guide rail (2), wherein the guide carriage (1) has a connection (21) having the upper carriage portion (9) and the at least one bearing surface having lower

Carriage portion (10), and wherein between the upper carriage portion (9) and the lower carriage portion (10) has a gap (11) is provided, and wherein limited relative displacements between the two car sections (9, 10) without relative shifts between see the lower Carriage section (10) and the guide rail (2) are provided, and with a between the two car sections (9, 10) operatively arranged vibration damper for damping vibrations, characterized in that in the gap (11) a lifting device (20) for a variable lift of the upper Wagenab- section (9) opposite the lower carriage portion (10) is provided, wherein the lifting device (20) is used as a vibration damper (22).

2. Linear guide according to claim 1, wherein the gap (11) as acted upon by pressure, preferably volume variable pressure chamber

(17) is formed.

3. Linear guide according to claim 1, wherein the gap (11) is designed as a pressure chamber (17), wherein by means of dynamic loading of the pressure chamber (17) with pressure certain stroke frequencies and certain Hubamplituden the upper carriage section (9) are adjustable.

4. Linear guide according to claim 1, wherein the upper carriage portion (9) with the lower carriage portion (10) is integrally connected.

5. Linear guide according to claim 4, wherein the upper carriage portion (9) by means of elastically deflectable wall sections (12) is integrally connected to the lower carriage portion (10).

6. Linear guide according to claim 5, wherein the deflectable wall sections (12) delimiting the pressure chamber (17).

7. Linear guide according to claim 1, wherein the upper carriage portion (9) and the lower carriage portion (10) by separate carriage parts (24, 25) are formed, which are preferably connected to each other by means of expansion screws (28).

8. Linear guide according to claims 2 and 7, wherein for sealing the pressure chamber (17) between the two carriage parts (24, 25) a seal, in particular an O-ring (32) is arranged.

9. Linear guide according to claim 2, wherein the guide carriage (1) seen in cross section is formed approximately U-shaped, wherein two legs (15) of the carriage (1) via a bottom (16) are interconnected, wherein the carriage (1 ) with its two legs (15) engages around the guide rail (2), wherein the bottom (16) with the pressure chamber (17) is provided, which in each case at its two longitudinal sides of a longitudinal bore of the guide carriage (1) longitudinal bore (13) is limited, wherein between an outer boundary surface of the guide carriage (1) and each of the two longitudinal bores (13) an elastically deflectable wall portion (12) is formed.

10. Linear guide according to claim 9, wherein one to the longitudinal bore (13) arranged parallel and to the surroundings of the carriage (1) towards open longitudinal groove (14) is formed, which together with the longitudinal bore (13) at least a portion of the elastically deflectable wall portion (12) limited.

11. Linear guide according to claim 2, wherein the guide carriage (1) seen in cross section is formed approximately U-shaped, wherein two legs (15) of the carriage (1) via a bottom (16) are interconnected, wherein the carriage (1) with its two legs (15) engages around the guide rail (2), and wherein the bottom (16) with the pressure chamber (17) is provided, wherein the lower carriage part (10) on its upper carriage part (9) facing side is provided with a circumferential web (26), and wherein the upper carriage part (24) with a flange (29) for receiving the expansion screws (28) and with an engagement portion (30) is provided in the of the circumferential web (26 ) engages limited receiving portion, wherein between the web (26) and the engagement portion, a preferably endless O-ring (32) for sealing the pressure chamber (17) relative to the surroundings of the guide carriage (1) is arranged.

12. Linear guide according to claims 2 and 7, wherein the screw axes of the expansion screws (28) parallel to the stroke direction of the upper carriage part (24) relative to the lower carriage part (25) are arranged.