DE102007044442B4 - Apparatus and method for translationally moving non-magnetic articles - Google Patents

Abstract

Device for translationally moving a non-magnetic object which is located on or in a ferrofluid characterized by state parameter, characterized in that it comprises means for generating a locally fixed, periodically temporally alternating, homogeneous magnetic primary field and means for generating a locally fixed in the range of movement of the non-magnetic object , Inhomogeneous magnetic secondary field having in the direction of movement of the non-magnetic article successively arranged portions of alternating opposite polarity, wherein the magnetic primary and the secondary magnetic field are perpendicular to the direction of movement of the non-magnetic object and parallel to each other.

Description

The The invention relates to an apparatus and a method for producing a translatory movement with an electromagnetically driven System for the use in the positioning technology.

It are a variety of transport mechanisms, conveyors and the like translational moving objects known. Disadvantages of this Systems are that they consist of a variety of components and / or lubrication requirements between the moving parts susceptible to wear is present and / or that the miniaturization of such systems impossible or only possible with enormous effort is. These disadvantages can at least in part by the use of colloidal magnetic Overcome liquids become. Colloidal magnetic fluids (hereinafter also Called ferrofluids) undergo a change of shape, position and pressure in the presence of a magnetic field. By using ferrofluids On the one hand, drive media can be - compared to conventional ones Systems - easier Construction of such systems can be realized, on the other hand is at appropriate design no lubrication between each other Parts necessary.

Out The literature has several solutions known in which an electromagnetic field is a change the surface contour a magnetic fluid causes the translational movement (hereinafter also Called locomotion) of one or more on the fluid surface or in the fluid lying non-magnetic object leads.

In the closest prior art, a locally changing electromagnetic field is generated for example by a staggered excitation of cascaded electromagnets, which causes a time-dependent pressure, shape and position change of the ferrofluid at different locations, thereby generating a traveling wave on the ferrofluid surface. For example, in the DE 41 33 307 C2 and in the publication "New Structure of the Magnetic Fluid Linear Pump" (GS Park, SH Park, IEEE Transactions an Magnetics, Vol. 36, No. 5, Year 2000, pages 3709-3711) an actuator or system for moving of an object that works this way.

Further examples where a locally changing electromagnetic field results in the movement of an object are for example DE 102 44 867 B4 . DE 28 32 037 A1 . DE 199 46 820 A1 and JP 56155139 AA known. In these solutions, a locally changing electromagnetic field is generated by moving permanent or electromagnetic functional elements.

Furthermore, several solutions from the literature are known, for example a conveyor system JP 63123719 AA in which the guide between mutually movable parts by means of a standing under the action of a magnetic colloidal magnetic fluid is ensured. The drive, which causes the movement between the moving parts, but based in these solutions not on a time-dependent pressure, shape and position change of the ferrofluid used for leadership.

The mentioned solutions have the disadvantage that generating a locally changing magnetic field, for example, by the use of multiple electromagnets or by moving permanent or electromagnetic functional elements a big Cost and control effort required. Due to the large number of necessary ones Components is the miniaturization of such systems considerably difficult. Furthermore, for these systems are characteristic that the ferrofluid is not fixed in position and accordingly these systems are only in a horizontal position are usable.

task Therefore, it is the object of the present invention to provide a device and to provide a method for translationally moving non-magnetic objects, with which overcome the disadvantages described in a simple and cost-effective manner become.

According to the invention this Task device side by the features of the first claim and procedurally by the features of the ninth claim solved.

preferred Further embodiments of the device according to the invention are in the claims two to eight marked while preferred further embodiments of the method according to the invention in the claims ten to fourteen are specified.

According to the invention Movement of the non-magnetic article through a ferrofluid caused, the surface contour and Pressure (also called state parameter in the following) periodically alternating in the direction of movement in several segments at the same time, repeating locally, changed become.

The ferrofluid is position-bound by an inhomogeneous, preferably permanent, localized magnetic field (hereinafter also referred to as secondary magnetic field or permanently magnetic bias of the ferrofluid), the field of which is tion is preferably perpendicular to the direction of movement of the non-magnetic article. The secondary magnetic field has successively arranged portions of alternately opposite polarity in the direction of movement.

The change the state parameter is fixed by a local, preferably homogeneous magnetic field with periodically (temporally) alternating changing Amount and / or direction causes the hereinafter also as magnetic primary field or control variable U (t), or whose value is called U.

The Moving the lying on the Ferrofluidoberfläche or in the ferrofluid non-magnetic object is due to the change of state parameters and also achieved by having an asymmetry in geometry of the non-magnetic article and / or over time the tax size within a period exists.

Preferably becomes the magnetic primary field with a single electromagnet and the secondary magnetic field with cascaded permanent magnets alternately with in the direction of movement generated opposite polarization.

The magnetic primary and secondary field are preferably directed parallel to each other. The respective field directions will be in the later also marked with the characters + and -.

The Moving the non-magnetic object is by the time periodically alternating change of the local solid, preferably homogeneous magnetic field, the magnetic primary field or the control variable U (t), reached. Furthermore, in the designation magnetic primary field or Control variable U (t) also its time-dependent Behavior taken into account.

The magnetic primary field or the control variable U (t) is hereinafter referred to as symmetrical, if their temporal Course within a period with the period T for two, consecutively following, opposite field directions, those with + U (t) and -U (t) are equal, and if present, between + U (t) and -U (t) equally long pauses exist. Different functions for the magnetic primary field or the control variable U (t) are called asymmetric.

the one Time within a period while the field direction of the primary magnetic field does not change (no Sign change from U (t)), is called sequence, the change in position of the non-magnetic Object during this time as a movement sequence, called.

Further Details and advantages of the invention are the following description part in which the invention with reference to the accompanying drawings is explained in more detail. It shows:

1 - A perspective view and two sectional views of an embodiment of the device according to the invention

2 - Schematic representation of the dependence of the surface contour of the ferrofluid of the value U of the control variable

3 - Schematic representation of the dependence of the surface contour of the ferrofluid from the sign of the value U of the control variable, surface contour of the ferrofluid for several periods of the magnetic primary field

4 - Three possible embodiments of the non-magnetic object in three views

5 The change in position of the non-magnetic article for a sequence of the control variable

6 Examples of possible time courses of the control variable U (t) for an asymmetric primary magnetic field

First, necessary components of the device according to the invention based on a in 1 described embodiment and the change of the state parameters of the ferrofluid upon change of the control variable U (t) in 2 and 3 considered.

Subsequently, the inventive method for two possible embodiments using the 4 to 6 described as a functional principle with which lying on the ferrofluid surface or in the ferrofluid non-magnetic objects can be moved.

In 1 / A is an embodiment of a uniaxial locomotion shown schematically in perspective. In the illustrated coordinate system, the x-axis denotes the direction of movement, the yz-plane is a plane of symmetry. In the 1 / B and 1 / C are sectional views of the embodiment in the xy and in the yz plane shown.

• – ein Elektromagnet mit der y-Richtung als Feldrichtung, bestehend aus Spule 1, Spulenkörper 6 und Eisenkern 7, mit welchem das periodisch zeitlich alternierend sich ändernde, im Bewegungsbereich bb annähernd homogene magnetische Primärfeld (Bx≈0, Bz≈0) erzeugt wird;
• – das inhomogene magnetische Sekundärfeld bildende dauermagnetische Segmente gleicher Polarisation 2, welche in der Bewegungsrichtung mit der Breite b nacheinander entgegengesetzt, abwechselnd in die positive und negative y-Richtung polarisiert, angeordnet werden;
• – das Ferrofluid 3, dessen Zustandsparameter, bewirkt durch das magnetische Primärfeld, periodisch zeilich alternierend in der Bewegungsrichtung in mehreren Segmenten gleichzeitig, örtlich sich wiederholend, ändern;
• – nichtmagnetischer Gegenstand 4, welcher infolge der periodisch alternierenden Änderung der Zustandsparameter des Ferrofluids im Bewegungsbereich bb fortbewegt wird;
• – Führungselemente 5, die ein seitlich geführtes Fortbewegen des nichtmagnetischen Gegenstands ermöglichen.

The device consists of the following essential elements:

• - An electromagnet with the y-direction as a field direction, consisting of coil 1 , Bobbin 6 and iron core 7 , with which the magnetic primary field (Bx≈0, Bz≈0), which varies in periodically alternating fashion and is approximately homogeneous in the movement region bb, is generated;
• - The inhomogeneous magnetic secondary field forming permanent magnetic segments of the same polarization 2 which are successively arranged in the direction of movement of width b successively polarized alternately in the positive and negative y-directions;
• - the ferrofluid 3 whose state parameter, caused by the magnetic primary field, periodically alternately in the direction of movement in several segments at the same time, locally repeated, change;
• - non-magnetic object 4 which is propagated as a result of the periodically alternating change of the state parameters of the ferrofluid in the movement region bb;
• - Guide elements 5 which allow lateral movement of the non-magnetic article.

In 2 / A is a possible control variable U (t) shown with the period T. The 2 B to 2 / I represent the surface contour of the ferrofluid 8th the device schematically in the xy plane for different sizes, from the 2 / A selected values U0, U1, U2, U3 - where: U4 = -U1, U5 = -U2, U6 = -U3 -the control variable U (t) within a period for the quasi-static case. The state parameters of the ferrofluid are from Magnetic field B dependent, wherein the pressure is proportional to the magnetic field. The magnetic field in the area of the ferrofluid is composed of the magnetic primary and the secondary magnetic field. The magnetic primary field U (t) causes a change between three states (0, I, II) of the over the permanent magnet 2 lying ferrofluid 3 ,

The in 2 B shown state 0 is the initial position without the presence of the magnetic primary field (U0 = 0). The pressure and the surface contour of the ferrofluid repeats position-independent in the direction of movement with the periodicity of the width b of a permanent-magnetic segment of the same polarization corresponding to the secondary magnetic field.

At the Presence of a magnetic primary field becomes the vertical one Component of the magnetic field By and thus also the magnitude of the magnetic field B over dependent on the permanent magnet segments from its orientation and from the sign of the control variable U (t) alternately stronger or weaker. Both in the magnetic field, as well as in the state parameters of the above Permanent magnet lying ferrofluid occurs in this case, regardless of Sign of the control variable U (t) in the x direction a periodicity the width b2.

The states I in 2 / E and II in 2 / I denote the state parameters of the ferrofluid for the maximum control variables U3 and U6 = -U3 in 2 / A , In the 2 / C and 2 / D is the surface contour of the ferrofluid for the excitations U1, U2, and in the 2 / G and 2 / H for U4 and U5 (s. 2 / A ).

Because of the alternating polarization of the permanent magnet segments with the distance b in the direction of movement, b2 = 2 * b and the offset between the states I and II b3 = b (see enlarged schematic representation of the ferrofluid contour in the xy plane for U = 0, U3 and U6 in 3 / A ). In 3 / B is the periodic alternating change of the surface contour of the ferrofluid for 2 periods of U (t).

• – dass ein symmetrisches Primärfeld hinreichend zur Bewegung des nichtmagnetischen Gegenstandes ist,
• – dass benachbarte Dauermagnetsegmente in der Bewegungsrichtung abwechselnd entgegengesetzt polarisiert angeordnet sind und die gleiche Breite in der Bewegungsrichtung aufweisen,
• – dass eine, in der Bewegungsrichtung geführte, Fortbewegung realisiert wird,
• – dass eine geometrische Asymmetrie des nichtmagnetischen Gegenstands am Kontaktbereich zwischen Ferrofluid und dem nichtmagnetischen Gegenstand zu dessen Fortbewegung zwingend erforderlich ist,
• – dass die Geometrie des bewegten Gegenstands zur konstanten Breite b der Dauermagnetsegmente in Bewegungsrichtung angepasst wird.

According to a first embodiment of the method according to the invention, the movement of the non-magnetic object is defined by its non-symmetrical geometric shape and by the preferably symmetrical primary magnetic field of the ferrofluid under permanent magnetic bias. The features of the principle of operation according to this method are:

• That a symmetrical primary field is sufficient for the movement of the non-magnetic object,
• - That adjacent permanent magnet segments are arranged alternately polarized in the direction of movement and have the same width in the direction of movement,
• That a, guided in the direction of movement, locomotion is realized,
• That a geometrical asymmetry of the non-magnetic object is absolutely necessary at the contact area between the ferrofluid and the non-magnetic object for its movement,
• - That the geometry of the moving object is adapted to the constant width b of the permanent magnet segments in the direction of movement.

In 4 three possible embodiments of the geometry of the non-magnetic article for movement according to this first embodiment of the method according to the invention are shown. The contact area between the moving non-magnetic object and the ferrofluid is with 10 designated. In the example in 4 / A is the necessary geometric asymmetry through obliquely arranged bristles 9 with the angle a, in the example in 4 / B by non-symmetrical material removal, where a2> a, on the side of the ferrofluid, in the example in 4 / C ensured by bristles with a variable angle of attack a, where a by a schematically illustrated actuator 11 be varied can.

Due to the existing geometric asymmetry of the embodiments according to 4 / A and 4 / B is a movement in a br direction possible, which is defined by the angle a. The variant in 4 / C allows a translational movement in two opposite directions, the direction with the angle of attack a through the actuator 11 is set. When a <90 °, a movement in the positive x-direction, at a> 90 ° in the negative x-direction is realized.

Following from the principle of operation according to this first embodiment of the method according to the invention are the contact areas 10 of the moving nonmagnetic article with the ferrofluid in the direction of movement br, preferably at twice the spacing or its multiple (n is an even number), as the width b of a permanent magnet segment having the same polarization in the direction of movement (br = n · b). This ensures that the resultant of the ferrofluid pressure resulting force at all contact areas with and without electromagnetic excitation of the ferrofluid in their size and direction is the same. On the other hand, if this geometric condition is not fulfilled, it affects the individual contact areas 10 in their size and direction different resulting forces that can cancel out in their effect, and thus cause no movement of lying on the Ferrofluidoberfläche or in the ferrofluid non-magnetic object. With the number and the design, such as the angle of attack a, the contact areas 10 between ferrofluid and non-magnetic article, the magnitude of the resulting force exerted by the ferrofluid on this article can be determined.

To explain the translational motion of a non-magnetic article according to this first embodiment of the method according to the invention is a periodic rectangular bipolar electromagnetic excitation U (t) with the period T, as in 5 / A represented, considered. U (t) is symmetrical, ie it is equal in magnitude for both field directions. Duration of arousal per polarity and period is T / 2. The symmetry in the function of U (t) as well as the arrangement of the permanent magnets in the device allow the movement to be described by means of only one sequence of duration T / 2, with a constant primary magnetic field. The movement behavior of the non-magnetic object is independent of the field direction of the magnetic primary field.

In terms of locomotion, three phases (I, II and III) can be distinguished. To describe the translational movement of the non-magnetic object are out 5 / A picked out five times t0 to t4 and for this the positions of this object in the 5 / C to 5 / G shown schematically in the xy plane. In 5 / B the function u (t) for the displacement of the non-magnetic object in the direction of movement is shown.

A sign change of the control variable U (t) or the reversal of the field direction of the magnetic primary field between t0 and t1 causes a change in the magnetic field in the region of the ferrofluid. There is a redistribution and change of pressure in the ferrofluid, which also results in the change of the surface contour of the ferrofluid. If the nonsymmetrical parts of the article, such as obliquely arranged bristles, lie over such permanent magnetic segments in the ferrofluid in which the reversal of the field direction U (t) causes a pressure increase in the ferrofluid, ferrofluid causes such a resultant force on the bristles and thus exercised the object, according to which in phase I, a displacement of the non-magnetic object from the in 5 / C shown starting position predominantly in the positive y-direction, as in 5 / D shown at t1. Subsequently, in phase II, a displacement of the object in the negative y-direction and also in the direction of movement, the positive x-direction, as in 5 / E and 5 / F shown for t2 and t3. At the end of this phase, the displacement of the object u (t4) is equal to the width b of a permanent magnetic segment of the same polarization.

At this position includes the magnetic field and the pressure in the ferrofluid local minimum, so that is the ferrofluid on the object exercised resulting Force at this position smallest. After this phase takes place therefore in phase III with magnetic constant remaining primary field no further movement of the non-magnetic object. He remains even after setting the magnetic primary field in the same position, because the magnetic field, the ferrofluid pressure and thus also the ferrofluid exerted on the article resulting Force at this position even without electromagnetic excitation a local Minimum. A locomotion of the non-magnetic object from this position in the same horizontal direction can with a Sign change of the control variable U (t), according to the same scheme as described above. For the translational movement of the non-magnetic object is a reversal in the field direction after each motion sequence of the magnetic primary field necessary.

The most important interacting factors from the perspective of locomotion are: type and quantity of ferrofluid, width b of one Permanent magnetic segment of the same polarization in the direction of movement, geometry and mass of the moving object, friction between the moving object and lateral guide elements, homogeneity of the magnetic primary field, time course of the control variable U (t), size of the magnetic secondary field, ratio between the primary magnetic and the secondary magnetic field. By these factors, the locomotion, or the average speed of locomotion of the non-magnetic object can be influenced.

To a second embodiment the method according to the invention is the movement of the non-magnetic object by a on the acting under permanent magnet biasing ferrofluid asymmetric magnetic primary field Are defined.

in the Difference to the first embodiment of the inventive method is in this embodiment the asymmetric primary magnetic field for advancing the non-magnetic article imperative and the contact area between non-magnetic Object and ferrofluid preferably geometrically symmetric, For example, a flat surface. The permanent magnet segments of different polarization are at this embodiment arranged inclined to each other.

The change of position of the non-magnetic article per excitation period is attached this embodiment not directly related to the width b of the permanent magnet segments, so that an unguided movement in the direction of movement is realized.

resultant from the asymmetric primary magnetic field and from each other inclined arrangement of the permanent magnet segments is that of ferrofluid practiced resulting force on the moving non-magnetic object in the dynamic case for both field directions vary in size. This difference in power causes the moving of the non-magnetic object when the asymmetric magnetic primary field, the time-dependent behavior of the ferrofluid as well as the inertia this object be coordinated with each other. The speed of movement of the non-magnetic object can be influenced by the frequency of the primary magnetic field.

For this embodiment the method according to the invention one can distinguish between two variants. At a first Variant becomes the locomotion of the non-magnetic object through an asymmetric primary field realized that has two opposite field directions. In This case may be a change of direction in the translational movement of the non-magnetic object solely by a corresponding change of the magnetic primary field will be realized. Preferably, in this case, the mass distribution of the non-magnetic article should be uniform over the contact area.

The second variant of the second embodiment the method according to the invention represents a special case in which the magnetic primary field only has a field direction.

6 shows selected examples of an asymmetric primary field U (t) and thus for the asymmetry in the periodically changing in strength and polarity magnetic field for the second embodiment of the method according to the invention.

in this connection indicate Umax or -Umax each the maximum sizes of magnetic primary field for the respective field directions, t denotes the time.

In 6. / A is the asymmetry due to different courses for both field directions with the same maximum amplitude, in 6 / B by qualitatively equal courses for both field directions with different sized maximum amplitude, in 6 / C by qualitatively identical courses with the same maximum amplitude, but with different times (t1 ≠ t2) of both field directions and in 6 / D shown by pauses t3 between periods.

In the 6 / E and 6 / F two possible examples of the asymmetric magnetic primary field U (t) for the second variant of the second embodiment of the method according to the invention are shown. In 6 / E is the asymmetric primary field by pauses between the periods of a field direction and in 6 / F generated by the difference between ascending and descending in the course of U (t).

1

Kitchen sink

2

Permanent magnet segment same polarization

3

ferrofluid

4

nonmagnetic object

5

guide element

6

bobbins

7

iron core

8th

surface contour of the ferrofluid

9

bristles

10

contact area between ferrofluid and moving non-magnetic object

11

actuator

a

tilt angle

a2

tilt angle

b

width a permanent magnet segment of the same polarization in the direction of movement

b2

width a ferrofluidic segment in the presence of the primary field

bb

range of motion

br

direction the movement of the object

t

Time

T

period

u

shift of the non-magnetic object in the direction of movement (x direction)

U

value the tax quantity

U (t)

function the tax size over the Time

Claims (14)

Apparatus for translating a non-magnetic article which is located on or in a characterized by state parameters ferrofluid characterized in that it comprises a locally fixed in the movement area of the non-magnetic object means for generating a locally fixed, periodically temporally alternating homogeneous primary magnetic field and means for generating , Inhomogeneous magnetic secondary field having in the direction of movement of the non-magnetic article successively arranged portions of alternating opposite polarity, wherein the magnetic primary and the secondary magnetic field are perpendicular to the direction of movement of the non-magnetic object and parallel to each other. Device according to claim 1, characterized that the non-magnetic article is in contact with the ferrofluid Bristle-like formations having a fixed or variable angle of attack and the temporal Course of the magnetic primary field is symmetric or asymmetric within a period. Device according to claim 1, characterized that the non-magnetic object is asymmetrical in the direction of movement Has mass distribution and the time course of the magnetic Primary field within a period is symmetric or asymmetric. Device according to one of claims 1 to 4, characterized that the means of generating a locally fixed, periodically in time alternating, magnetic primary magnetic field with an electromagnet Iron core is. Device according to one of claims 1 to 4, characterized that the means of generating a locally fixed, periodically in time alternating, homogeneous primary magnetic field is a Helmholtz coil pair. Device according to one of claims 1 to 6, characterized that the means of generating a locally solid, inhomogeneous secondary magnetic field cascaded permanent magnets with in the direction of movement of the non-magnetic object alternately opposite polarity are. Device according to one of claims 1 to 6, characterized that the means of generating a locally solid, inhomogeneous secondary magnetic field cascaded electromagnets in the direction of movement of the non-magnetic object alternately opposite polarity are. Device according to one of claims 1 to 8, characterized that they have means for laterally guided having translational movement of the non-magnetic article. Method for translationally moving a non-magnetic Object based on or in one by state parameter characterized ferrofluid is located, with a device according to a the claims 1 to 9, characterized in that the translational movement of the non-magnetic object through the periodically temporally alternating change the state parameter of the ferrofluid is realized, the change of the State parameters of the ferrofluid through the periodically timed alternating, in several segments within the range of motion simultaneous, local in accordance with the secondary magnetic field sections repeating change of magnetic primary field he follows. Method according to claim 10, characterized that the state parameters of ferrofluid its surface contour and the pressure is. Method according to one of claims 10 or 11, characterized that the inhomogeneous magnetic secondary field is permanently present. Method according to one of claims 10 or 11, characterized that the inhomogeneous magnetic secondary field during the translational Moving the non-magnetic object is present. Method according to one of claims 10 to 13, characterized that the periodically alternating, homogeneous magnetic primary field has a field direction. Method according to one of claims 10 to 13, characterized that the periodically alternating, homogeneous magnetic primary field has two opposite field directions.