Linear electric machine

Abstract

Linear electrical machine, in particular linear motor, comprising at least one primary part (2) and one secondary part (1), wherein the primary part (2) comprises energizable windings, wherein the secondary part (1) comprises permanent magnets (9) arranged at least in the direction of movement, wherein an air gap is provided between the primary part (2) and the secondary part (1), in which at least one full-surface intermediate layer part (6) is provided where in the intermediate layer part (6) thinned areas, i.e. dilution areas, are provided in such a way, that the intermediate layer part (6) smoothes the magnetic field pattern generated by the permanent magnets (9) in the direction of movement and reduces the force ripple during the movement of the primary part (2) as well as the corresponding effects when moving the superstructures or loads.

Description

The invention relates to a linear electric machine.Synchronous linear motors which consist of a secondary part equipped with permanent magnets and an electromagnetic primary part are generally known. These linear motors are frequently used as highly dynamic servomotors. Improved control technology enables positioning accuracy which results in system-related interference variables having an ever more significant influence.With increasing demands on the motors, undesirable side effects are increasingly becoming more prominent. Like all synchronous motors, the synchronous linear motor also has a certain force ripple. The cause of the ripple is based on the interaction between magnetic pole edges and primary part grooves. This causes a periodic profile over a slot pitch, which is why this profile is also referred to as "slot ripple". Since the total force comprises pole force and slot force, the ripple of the force therefore also comprises the 'slot ripple' and the 'pole ripple'.The ripple of the force leads to a movement imprecision of the conventional synchronous linear motors, which is undesirable particularly when using such motors as precision actuators. For the exact positioning, as required by machine and system manufacturers, the effects of the ripple can be so disturbing that the use of a linear motor is not possible and thus its advantages cannot be utilized.To reduce the force ripple, DE 195 28 043 C1 proposes the provision of beveled surfaces at the angle β on the front and rear end regions of the primary part. However, the manufacture of these beveled surfaces is complicated and expensive. For constructing the laminated core, a number of differently stamped individual sheets corresponding to the width of the core is necessary, which does not allow simple and cost-effective production.EP 1 359 661 A2 discloses a rotary motor in which a soft magnetic cylinder jacket is located between the rotor and the stator, which jacket has slots in the region of the magnets. This structure can lead to severe contamination of the motor due to particles entering through the slots.A linear motor is known from EP 1 322 027 A1.DE 103 18 207 A1 discloses a secondary part of a linear motor.DE 101 57 249 A1 discloses a motor part of an electric linear motor with an air gap-side cover.From GB 1 307 833 A a linear induction motor is known.The invention is based on the object of developing a synchronous linear motor, wherein the movement accuracy is to be improved, a protective effect is to be achieved and the motor is to be produced in a simple and cost-effective manner.According to the invention, the object is achieved in the machine according to the features specified in claim 1.Important features are that the linear electric machine, in particular a linear motor, comprises at least a primary part and a secondary part, wherein the primary part comprises energizable windings, wherein the secondary part comprises permanent magnets arranged at least in the direction of movement, wherein an air gap is provided between the primary part and the secondary part, in which air gap at least one intermediate layer part is provided, wherein thinned regions, i.e. thinned regions, are provided in the intermediate layer part.It is advantageous here that the intermediate layer part lubricates the sections of the magnetic field profile in the direction of movement with a large field gradient. A further advantage is that the whole-area intermediate layer part offers protection of the motor against invading foreign bodies. It is surprising in the invention that the feed force is only slightly reduced, but the force ripple can be greatly reduced.In an advantageous embodiment, the intermediate layer part can be provided on the primary part and / or on the secondary part. It is advantageous here that the type of smearing can be determined by the corresponding position of the intermediate layer part. When the intermediate layer part is fastened to the stationary motor part, the mass on the movable part is advantageously low and the dynamics of the motor are thus increased. When the intermediate layer part is fastened to the movable motor part, the material outlay is advantageously low.In a further advantageous embodiment, the intermediate layer part can be attached to the permanent magnet by magnetic force. It is advantageous here that no additional fastening means are necessary.In a further advantageous embodiment, securing means for fixing the mounting position and / or holding of the intermediate layer part are provided for the intermediate layer part. It is advantageous here that the intermediate layer part can be connected to the machine in a fixed position.In a further advantageous embodiment, the securing means can be realized as formed, in particular crimped, edge regions of the intermediate layer part, and / or as an adhesive and / or as screws, rivets, pins or the like, and / or as welded points. It is advantageous here that the fastening can be adapted to the respective linear motor.In a further advantageous embodiment, the dilution regions can be arranged in accordance with the arrangement of the permanent magnets. It is advantageous here that the magnetic field is minimally weakened in the regions of the permanent magnets.In a further advantageous embodiment, the shape of the dilution regions and / or the material of the intermediate layer part can be determined taking into account the properties of the magnetic field between the primary part and the secondary part in such a way that the force undulations can be reduced.In a further advantageous embodiment, the dilution regions can each be realized in a rectangular fashion. It is advantageous here that the intermediate layer part can be produced simply and cost-effectively.In a further advantageous embodiment, the thinning areas can be implemented in such a way that they have no area portions in the direction of movement in front of and behind the magnet surface which appears in plan view and is shown in the same plane of the representation of the thinning areas. Viewed from the primary part to the secondary part, the dilution regions are therefore embodied differently than the shape of the permanent magnets. To reduce the ripple, the dilution regions advantageously also extend in front of and behind the regions of the magnets in the direction of movement. The intermediate layer part is not arranged in the same plane as the magnets, but rather between the magnets and the primary part. It is advantageous in this case that the ripple is reduced in such a way that soft transitions can be achieved.In a further advantageous embodiment, the thinning areas can be implemented in such a way that they have no area portions in the direction of movement in front of and behind the magnet surface which appears in plan view and is shown in the same plane of the representation of the thinning areas. It is advantageous here that the ripple is reduced.In a further advantageous embodiment, the boundary of the dilution regions comprises smooth, continuously differentiable, rectilinear and / or circular boundary line sections in each case. It is advantageous here that the intermediate layer part can be produced simply and cost-effectively.In a further advantageous embodiment, the front and rear surface portions of the dilution region have the same surface area. It is advantageous here that weakening of the magnetic field takes place symmetrically.In a further advantageous embodiment, the dilution regions are each symmetrical to the direction of movement. It is advantageous in this case that a weakening of the magnetic field is effected, which reduces undesired fluctuations in the lateral direction of the motor, in particular thus the jerk perpendicular to the direction of movement.In a further advantageous embodiment, the thinning regions are each bordered by straight and / or circular edge line sections. It is advantageous here that the intermediate layer part can be produced simply and cost-effectively.In a further advantageous embodiment, the surface portions of the dilution regions are bounded in a straight line and / or in a circular manner. It is advantageous here that the intermediate layer part can be produced simply and cost-effectively.In a further advantageous embodiment, the dilution regions have a periodic progression of the dilution in the direction of movement, wherein the period length corresponds to a distance between two magnets, in particular the distance between two adjacent magnets. It is advantageous here that machines of different lengths can be produced according to the same pattern.In a further advantageous embodiment, the surface of the intermediate layer part facing the air gap can be made planar. It is advantageous here that this surface can be easily cleaned and air vortices can be reduced, that is to say the air flow is more laminar or at least less turbulent.In a further advantageous embodiment, the side of the intermediate layer part facing the magnets is uneven, in particular corresponding to the shape of the magnets. It is advantageous here that the space between the magnets can be used for the intermediate layer part.In a further advantageous embodiment, the intermediate layer part is a sheet metal which is planar on both sides, in particular sheet metal made of ferromagnetic material and / or steel sheet, that is to say in particular the dilution region is at a maximum. It is advantageous here that the intermediate layer part can be produced simply and cost-effectively.In a further advantageous embodiment, the intermediate layer part is a plastic casting part which contains magnetizable particles, in particular ferrite particles. It is advantageous that a space-saving design can be produced.In a further advantageous embodiment, the intermediate layer part made of plastic is applied, in particular cast, directly to a machine part, in particular primary part and / or secondary part. It is advantageous here that a composite part can be produced.An important feature in the method for producing and / or retrofitting a linear machine is that an intermediate layer part is installed in an existing linear motor. It is advantageous here that the motor components present can be easily expanded by one component for reducing the groove ripple.In a further advantageous method, the air gap between the primary and secondary parts is adjustable to two fixed quantities, a first air gap being adjusted when no intermediate layer part is used, a second air gap being adjusted when an intermediate layer part is inserted. It is advantageous that both modes of use, namely with and without an intermediate layer part, can be taken into account in the construction of the machine.In a further advantageous method, machines can be produced in at least two variants from a modular unit, wherein the modular unit comprises at least a primary part, a secondary part, an intermediate layer part and a first and second chassis, wherein the chassis is provided between the primary part and secondary part and enables a rail-guided relative movement between the primary part and secondary part, wherein the first variant is produced from the primary part, the secondary part, and the first chassis, such that a first air gap is provided between the primary part and secondary part, wherein the second variant is produced from the primary part, the secondary part, the intermediate layer part and the second chassis, such that a second air gap is provided between the primary part and secondary part, wherein the intermediate layer part is arranged in the second air gap.It is advantageous here that numerous variants can be produced from standardized individual components.In a further advantageous embodiment, the optimum shape of the recesses can be determined by an inverse simulation of the electromagnetic properties of the secondary part. It is advantageous here that the design of the recesses can be adapted to the geometry of the motor components and the electromagnetic interactions between the components. The recess can be determined in such a way that a strong or even maximum reduction of the ripple can be achieved with a still large or even maximum feed force of the motor.In a further advantageous embodiment, the material suitable for the motor type for producing the intermediate layer part is determined by an inverse simulation of the electromagnetic properties of the secondary part. The material properties can thus also be additionally taken into account. In particular, the intermediate layer part can be produced from cost-effective soft magnetic material, for example sheet metal.In a further advantageous embodiment, the intermediate layer part can be retrofitted into an existing linear motor with little effort. It is advantageous in this case that the existing motor can be retained and that the ripple can nevertheless be reduced in a cost-effective manner.In a further advantageous embodiment, the recesses in the intermediate layer part are designed as dilution regions, wherein the intermediate layer part can be produced both from homogeneous magnetizable material of variable thickness and from variably magnetizable material of homogeneous thickness.Further advantages are evident from the dependent claims.The invention will now be explained in more detail with reference to the drawings:FIG. 1 shows a linear motor according to the invention in a sectional view.FIG. 2 shows differently pronounced recesses 10 ato 10 efor a respective linear motor according to the invention in plan view.The linear motor in FIG. 1 consists of a primary part 2, which comprises the stator, which comprises a laminated core and associated windings which are interconnected with one another and are not shown.The primary part 2 is held by a mounting plate 3.The mounting plate 3 also serves for dissipating at least the heat of the motor which is produced by ohmic losses in the windings. In addition, grooves are provided on the side of the mounting plate 3 facing away from the secondary part 1, in which grooves loads can be applied by means of slot nuts, which loads the linear motor is intended to move.The secondary part 1 is mounted on a base plate 5. On the base plate 5 are mounted the guide rails 4 on which guide carriages 8 are movably arranged. The guide carriages 8 are connected to the primary part 2.The stator is cast with a casting compound in order to improve the heat flux. The larger the surface of the mounting plate 3 is designed, for example by introducing cooling ribs, the better the heat dissipation to the environment can be effected. In addition, the dissipation of the heat from the stator to the mounting plate 3 is improved by enlarging the flange surface 7, that is to say the contact surface between the primary part 2 and the mounting plate 3.In a further exemplary embodiment according to the invention, the guide carriages 8 are connected to the primary part 2 in such a way that this connection of the guide carriages 8 on the primary part 2 is designed as a movable bearing for compensating thermal expansion. Thus, the accuracy of movement can be improved.In the exemplary embodiment according to FIG. 1, the secondary part 1 comprises permanent magnets arranged in series, which are arranged in alternating magnetization direction.Between the secondary part 1 according to FIG. 1 and the primary part 2 there is an air gap into which the intermediate layer part 6 according to the invention is introduced.Since the secondary part 1 is provided with permanent magnets, no additional fastening means is necessary for fastening the intermediate layer part 6 on the secondary part 1, since it is pulled towards the permanent magnets by the magnetic forces of the latter. The intermediate layer part 6 is additionally secured against slipping. This can be carried out by flanging the edge regions of the part or else by additional fastening means, such as rivets, screws or pins, and / or by adhesive bonding.In a further exemplary embodiment according to the invention, the permanent magnets are arranged at regular distances from one another.The permanent magnets are covered by the intermediate layer part 6. This intermediate layer part 6 smoothes the magnetic field profile generated by the permanent magnets in the direction of movement. Thus, the force ripple during the movement of the primary part 2 is reduced and the corresponding effects during the movement of the superstructures or loads are also reduced.In various further exemplary embodiments according to the invention, the intermediate layer part 6 has differently pronounced recesses. For the purpose of illustration, FIG. 2 shows various kinds of recesses 10 ato 10 ein a plan view, which can then be used for the various exemplary embodiments.For a better understanding, a secondary part 1 is also added in FIG. 2. The relative position of the respective recesses ( 10 ato 10 e) to the magnets can thus also be represented.The permanent magnets 9 are shown in dashed lines.Such recesses ( 10 a, 10 b, 10 c, 10 d, 10 e) have the effect that the magnetic field is, on the one hand, smoothed, but the respective peak value of the magnetic field profile is not reduced or is only insignificantly reduced in the direction of movement. The achievable feed force is therefore only slightly reduced and nevertheless a more uniform movement is achievable.In an advantageous embodiment, the recesses are, as shown in FIG. 10a, rectangular and placed parallel over the permanent magnet 9. This very simply smoothes the magnetic field profile between two permanent magnets 9.In further advantageous exemplary embodiments, the recesses ( 10 bto 10 e) are designed in such a way that they have surface portions in front of and behind the magnet surface, which appears in plan view and is represented in the same plane of the representation of the recesses.In a further advantageous exemplary embodiment, the recesses can be formed as parallelograms, as shown in FIG. 10 b. The oblique arrangement ensures a smearing of the ripple effect over the travel path of the secondary part 1 and thus an improved movement accuracy. It is essential in this arrangement that the surface portions mentioned and even the recess 10b itself are bounded in a straight line. Thus, the manufacture is simple and cost-effective. Instead of a parallelogram, rectangles or other polygons can also be used in further exemplary embodiments.In a further advantageous embodiment, the boundary of the recesses can be formed, as shown in FIG. 10c, in the shape of an arrow, i.e. also in a straight line, wherein this recess 10c is arranged symmetrically to the direction of movement.In a further advantageous exemplary embodiment, the boundary of the recesses is formed with circular portions, as shown in FIG. 10 d, wherein this recess 10 dis arranged symmetrically with respect to the direction of movement.In a further advantageous exemplary embodiment, the boundary of the recesses is, as shown in FIG. 10 e, formed with arbitrary smooth portions, wherein smooth, continuously differentiable function profiles are used.In a further advantageous embodiment, the arrangement of the permanent magnets 9 on the secondary part 1 can be carried out obliquely, i.e. at an angle different from 90°, with respect to the direction of movement, wherein the optimum shape of the recesses ( 10 ato 10 e) is oriented at the position of the permanent magnets 9.In a further advantageous embodiment, the arrangement of the recesses ( 10 ato 10 e) is such that, in a common projection plane of the permanent magnets 9 and of the recesses ( 10 ato 10 e) in plan view, the surface portions of the recesses ( 10 ato 10 e) which project beyond the projection surfaces of the permanent magnets 9 are of the same size in the direction of movement in front of and behind the permanent magnets 9. It is advantageous here that the symmetry brings about a uniform improvement in the force ripple during the forward and rearward movement of the machine.In a further advantageous embodiment, the shape of the recesses ( 10 ato 10 e) is determined by inverse simulation of the magnetic field in the machine. For optimization, the parameters force development, ripple and air gap height are varied.In a further advantageous embodiment, the magnetic properties of the primary part 2 are included for optimizing the intermediate layer part 6.In another exemplary embodiment according to the invention, the intermediate layer part 6 can be fastened to the primary part 2 instead of to the secondary part 1. In a further development, such a part can also be fastened to the secondary part 1.In another exemplary embodiment according to the invention, the reduction of the force ripple can also be carried out via a corresponding thickness profile of the intermediate layer part 6 in the direction of movement instead of by means of the recesses ( 10 ato 10 e).In another exemplary embodiment according to the invention, the reduction of the force ripple is also provided via thinned regions, i.e. thinning regions, instead of by means of the recesses ( 10 ato 10 e). The dilution can be carried out by the composition of materials of different magnetizable qualities. It is advantageous here that the intermediate layer part can be made with constant thickness and width.List of reference characters1 Secondary part 2 Primary part 3 Mounting plate 4 Guide rail 5 Base plate 6 Intermediate layer part 7 Flange surface 8 Guide carriage 9 Permanent magnets 10 a- e Recesses

Claims

Linear electric machine, in particular a linear motor, comprising at least one primary part (2) and a secondary part (1), wherein the primary part (2) comprises windings which can be supplied with current, wherein the secondary part (1) comprises permanent magnets (9) arranged at least in the direction of movement, wherein an air gap is provided between the primary part (2) and the secondary part (1), in which air gap at least one fully-over intermediate layer part (6) is provided, wherein thinned regions, that is to say thinning regions, are provided in the intermediate layer part (6) in such a way that the intermediate layer part (6) brings about smoothing of the magnetic field profile generated by the permanent magnets (9) in the direction of movement and reduces the force ripple during the movement of the primary part (2) and the corresponding effects during the movement of the superstructures or loads.Linear electric machine according to Claim 1, characterized in that the intermediate layer part (6) is provided on the primary part (2).Linear electric machine according to Claim 1, characterized in that the intermediate layer part (6) is provided on the secondary part (1).Linear electric machine according to Claim 3, characterized in that the intermediate layer part (6) is held on the secondary part (1) by the magnetic force of the permanent magnets (9).Linear electric machine according to one of the preceding claims, characterized in that securing means are provided for fixing the mounting position and / or holding the intermediate layer part (6).Linear electric machine according to Claim 5, characterized in that the securing means are - designed as shaped, in particular crimped, edge regions of the intermediate layer part (6), - and / or as an adhesive - and / or as screws, rivets, pins or the like, - and / or as welded points.Linear electric machine according to one of the preceding claims, characterized in that the dilution regions are arranged in accordance with the arrangement of the permanent magnets (9).Linear electric machine according to one of the preceding claims, characterized in that the shape of the dilution regions and / or the material of the intermediate layer part (6) are determined in such a way that the force undulations are reduced, taking into account the properties of the magnetic field between the primary part (2) and the secondary part (1).Linear electric machine according to one of the preceding claims, characterized in that the dilution regions are each of rectangular design.Linear electric machine according to one of the preceding claims, characterized in that the dilution regions are designed in such a way that they have no area fractions in the direction of movement upstream and downstream of the magnet surface which appears in plan view and is represented in the same plane of the representation of the dilution regions.Linear electric machine according to one of Claims 1 to 9, characterized in that the dilution regions are designed in such a way that they have area fractions in the direction of movement upstream and downstream of the magnet surface which appears in plan view and is represented in the same plane of the representation of the dilution regions.Linear electric machine according to one of the preceding claims, characterized in that the boundary of the dilution regions comprises smooth, continuously differentiable, rectilinear and / or circular boundary line sections in each case.Linear electric machine according to one of Claims 10 to 12, characterized in that the front and rear area fractions of the dilution regions have the same area value.Linear electric machine according to one of the preceding claims, characterized in that the dilution regions are in each case symmetrical with respect to the direction of movement.Linear electric machine according to one of the preceding claims, characterized in that the dilution regions are each bordered by rectilinear and / or circular edge line sections.Linear electric machine according to one of Claims 10 to 15, characterized in that the surface portions are bounded in a straight line and / or in a circular manner.Linear electric machine according to one of the preceding claims, characterized in that the dilution regions have a periodic progression of the dilution in the direction of movement, wherein the period length corresponds to a distance between two permanent magnets (9), in particular the distance between two adjacent permanent magnets (9).Linear electric machine according to one of the preceding claims, characterized in that the surface of the intermediate layer part (6) facing the air gap is of planar design.Linear electric machine according to one of the preceding claims, characterized in that the side of the intermediate layer part (6) facing the permanent magnets (9) is uneven, in particular runs in a manner corresponding to the shape of the permanent magnets (9).Linear electric machine according to one of the preceding claims, characterized in that the intermediate layer part (6) is a sheet metal which is planar on both sides, in particular sheet metal made of ferromagnetic material and / or steel sheet.Linear electric machine according to one of the preceding claims, characterized in that the intermediate layer part (6) is a plastic casting which contains magnetizable particles, in particular ferrite particles.

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