Iron-core linear motor comprising printed circuit board windings

Abstract

The invention relates to a primary part (2), constructed on a printed circuit board (4), of a linear motor (3). In order to enable a high force density in the most cost-effective and space-saving manner possible, the printed circuit board (4) comprises openings between the conductors of the winding (1), with iron teeth (6) passing through said openings, wherein the winding (1) is designed as a distributed winding (1).

Description

[0001] Ironcore linear motor with printed circuit board windings

[0002] The invention relates to a primary part of a linear motor mounted on a circuit board, as well as to a linear motor with such a primary part. Such motors are used in many industrial applications, for example, in particular for multi-axis machine tools or production systems where linear travel paths are performed with high precision and dynamics.

[0003] A linear motor generally comprises at least a primary part with electromagnetic coils and a secondary part, usually equipped with permanent magnets whose magnetic fields interact with the coils of the primary part via an air gap, allowing translational force transmission between the two elements. In a printed circuit board (PCB) motor, the coils of the primary part are implemented on a printed circuit board (PCB), thus achieving a particularly compact and lightweight design. Printed circuit board motors are also characterized by comparatively low manufacturing costs and an excellent force-to-mass ratio.

[0004] DE 10 2017 102 344 B4 discloses a printed circuit board for a linear motor comprising a coil formed from at least one conductor track running spirally within a layer of the printed circuit board. In order to meet higher force requirements for electric motors with such a printed circuit board, it further comprises a coil core made of a ferromagnetic or ferrimagnetic material, which extends in a direction perpendicular to the layer.

[0005] US Pat. No. 6,160,327 B1 discloses a primary part for a linear motor with an air-core coil. The use of a distributed winding reduces cogging and harmonic components in the air gap torque compared to a motor with a concentrated winding.

[0006] Furthermore, linear motors are known, for example from US 2011 0219 989 A1, in which a primary part is arranged between two secondary parts equipped with permanent magnets. The interaction of the primary part with the two secondary parts allows for high efficiency and high power density.

[0007] The invention is based on the object of enabling a high force density in a linear motor in the most cost-effective and space-saving manner possible.

[0008] This object is achieved by a primary part of a linear motor having the features of claim 1. Furthermore, the object is achieved by a method having the features of claim 9. Advantageous embodiments of the invention can be found in the dependent claims.

[0009] The primary part is implemented on a printed circuit board. This means that the individual coil windings are implemented on a printed circuit board. In an advantageous embodiment of the invention, the printed circuit board is a multilayer board. The distributed winding has windings in various layers of the multilayer board. In this embodiment, the superimposed windings are connected to one another via vias between the layers, so-called electrical vias.

[0010] In many industrial systems, for example multi-axis machine tools, only very limited installation space is available for translational drives. For cost reasons, ironless linear drives are often used today to control the machine axes, as the production of iron cores is very complex. A disadvantage of ironless motors, however, is their significantly lower force density, which is only around 10% of that of an iron-core linear motor, meaning that the above-mentioned installation space requirements cannot always be met. One option for increasing the efficiency of an ironless linear motor is a design with two secondaries and a primary part mounted between them. However, due to the doubling of the number of permanent magnets in this type of design, the costs also increase considerably.

[0011] The application area of ​​printed circuit board motors, also known as PCB (Printed Circuit

[0012] The range of motors known as "board" motors can be significantly expanded with iron-core primary components. However, to avoid eddy current losses in today's linear motors, the iron cores must be laminated, which, depending on the application, increases manufacturing complexity and thus costs to unacceptable levels.

[0013] The invention is based on the finding that the costs for an iron-core linear motor in the form of a printed circuit board motor can be significantly reduced compared to the prior art if the winding is designed as a distributed winding. This is because a distributed winding design results in a significantly higher number of iron teeth compared to an iron-core printed circuit board motor with a concentrated winding, as is known from the prior art. What initially appears to be a disadvantage in terms of manufacturing and costs is, on closer inspection, a considerable advantage, particularly in the inventive design of the linear motor as a printed circuit board motor. This is because the significantly higher number of iron teeth in a printed circuit board motor with a distributed winding means that each individual iron tooth can be made considerably thinner while maintaining the same overall iron content in the motor.For example, if the number of iron teeth in a PCB motor with distributed winding is doubled compared to a PCB motor with concentrated winding, the tooth thickness of each iron tooth in the distributed winding can be halved compared to the tooth thickness of each iron tooth in the concentrated winding. Therefore, the cost of lamination of the iron teeth in the distributed winding can be significantly reduced compared to the cost of lamination in the concentrated winding.

[0014] The manufacturing effort for a linear motor with a primary part of the type described here can be considerably reduced in a particularly advantageous embodiment of the invention if the iron teeth are implemented by at least one folded motor lamination. A metal sheet with a silicon alloy is generally used as the motor lamination in order to reduce the conductance of the sheet and thus eddy current losses. For this purpose, a thin motor lamination, for example 0.2 - 1 mm thick, can be folded so that it forms both the magnetic return path of the primary part and its iron teeth. Due to the often low PCB thickness of a maximum of 4 mm required for manufacturing purposes and the large number of teeth in a distributed winding, the usual motor lamination thickness of 0.2 mm to 1 mm is sufficient for the flux concentration in the primary part.Instead of the usual lamination of the iron teeth in the form of laminated or punched individual sheets, in this design each tooth consists of only two sheet sections folded over each other.

[0015] Two adjacent iron teeth can be formed as the legs of a sheet metal section bent into an LI shape. The laterally aligned teeth can be bent from a single motor sheet metal, into which the U-shaped legs are folded at a distance equal to the pitch of the primary part. The sheet metal is folded from opening to opening to create the adjacent teeth. Alternatively, two adjacent teeth can be formed from a single sheet metal bent into a U shape, allowing a multitude of individual sheets to be inserted into the openings of the PCB.

[0016] In any case, an additional return plate can be provided which is magnetically coupled to the motor plate or plates and further reduces the magnetic resistance in the primary part.

[0017] Another possibility is to fill the openings with a ferromagnetic screen printing material.

[0018] The primary part according to the invention comprises a distributed winding. In addition to the advantages already mentioned, this significantly reduces cogging compared to a linear motor with a concentrated winding in the primary part, thus improving the motor's synchronous operation. Distributed windings are also characterized by a reduced harmonic content in the magnetic air gap field.

[0019] The combination of the distributed winding with iron teeth, which penetrate the openings in the circuit board between the conductor tracks, contributes significantly to increasing the force-to-mass ratio while simultaneously achieving good synchronization behavior similar to an ironless motor. The distributed winding can be implemented using a wave winding design. With this topology, PCB motors can combine the cost advantages in the production of the primary components with optimal efficiency in use. Alternatively, the distributed winding can also be designed as a lap winding.

[0020] The method according to the invention for producing a primary part for a linear motor is characterized by the following process steps:

[0021] • Applying a distributed winding to a printed circuit board,

[0022] • Introduction of openings in the circuit board between adjacent conductors of the distributed winding and

[0023] • Filling the openings with a magnetically conductive material to form iron teeth.

[0024] In this process, a motor lamination can be bent into at least a U-shape. The legs of the resulting U-shaped lamination section can be inserted into the cutouts of the circuit board to form the iron teeth. The additional effort required to integrate the motor lamination during the production of the primary part can be reduced if a single 0.2 to 1 mm thick lamination is folded and inserted from cutout to cutout.

[0025] The invention is explained in more detail below using the embodiments illustrated in the figures. Functionally identical elements are referenced by the same reference numerals, even if the elements may have different designs.

[0026] They show:

[0027] FIG 1 is a plan view of a distributed winding for a primary part of a linear motor, which is implemented on a printed circuit board,

[0028] FIG 2 shows a cross-sectional view of a linear motor with a primary part implemented as a printed circuit board with distributed winding and a secondary part,

[0029] FIG 3 shows a section of a folded motor sheet for a primary part according to an embodiment of the invention and FIG 4 shows a schematic representation of a linear motor according to an embodiment of the invention.

[0030] FIG 1 shows a plan view of a distributed winding 1 for a primary part 2 of a linear motor 3, which is implemented on a printed circuit board 4. The printed circuit board 4 is a multilayer printed circuit board. The distributed winding 1 is realized in the form of a wave winding with three phases. Each phase contains two parallel-connected conductor tracks 5, which are arranged directly adjacent to one another in each layer and meander in a wave-like manner across the layer. By way of example, two of these parallel-connected conductor tracks are identified in FIG 1 with the reference numeral 5. The wave-shaped conductor tracks 5 of one phase are connected to the wave-shaped conductor tracks of the vertically adjacent layers of the multilayer printed circuit board via electrical vias 11.

[0031] An iron tooth 6 extends vertically between each two conductor tracks 5, which, due to its high magnetic conductivity, significantly increases the motor's power density. One of these iron teeth 6 is designated by reference numeral 6 as an example.

[0032] The iron teeth 6 are made from a folded motor lamination. For this purpose, a motor lamination approximately 0.2 to 1 mm thick, as is commonly used for the manufacture of stator or rotor lamination stacks, is folded in such a way that the iron teeth 6 rise vertically. This creates a series of U-shaped lamination sections, the legs of which form the iron teeth 6. These penetrate openings within the circuit board 4.

[0033] FIG 2 shows a cross-sectional view of a linear motor 3 with a primary part 2 implemented as a printed circuit board 4 with distributed winding 1 and a secondary part 10. The secondary part 10 is equipped with permanent magnets 12. In terms of construction, this primary part 2 corresponds to that shown in FIG 1. Clearly visible in the cross-section is the folded motor sheet, which is used to form the legs of the U-shapes, which also represent the iron teeth 6 of the primary part 2. On the other hand, the same motor sheet also functions as a magnetic return between the individual teeth by means of sheet metal bridges 7, which each connect two legs of an II-shape and thus two iron teeth 6.

[0034] The circuit board 4, which is equipped with the motor sheet, is coated on its top and bottom sides with a dielectric cover layer 8. This cover layer 8 meets the requirements for basic insulation of the primary part 2 and thus ensures the necessary contact protection. The dielectric cover layer 8 on both sides allows the lateral insulation between the iron teeth 6 and the circuit board 4 to be reduced to the level necessary for functional insulation, which enables a higher force density of the linear motor 3 based on the concept presented. In addition to the magnetic return path created by the metal bridges 7 of the motor sheet, a ferromagnetic return plate 9 is provided on the bottom of the primary part 2 to further increase the magnetic conductance of the primary part. The ferromagnetic return plate 9 is arranged on a screw-on side of the primary part 2, which can be connected, for example, to a machine tool.

[0035] FIG. 3 shows a section of a folded motor lamination for a primary part 2 according to one embodiment of the invention. All iron teeth 6 of the primary part, two of which are shown here as an example, are folded from a single motor lamination, which allows for very cost-effective production. The magnetic return path between the iron teeth is also realized by the single motor lamination in the form of the illustrated metal bridges.

[0036] FIG. 4 schematically shows a linear motor 3 according to an embodiment of the invention, comprising a primary part 2 according to one of the previously described embodiments and a secondary part 10. The secondary part 10 comprises a plurality of permanent magnets (not shown here) of alternating polarization. Through the interaction of the magnetic field of the permanent magnets with the three-phase wave winding of the primary part 2, a force is generated in a horizontal direction in an air gap of the linear motor 3. List of reference symbols

[0037] Distributed winding

[0038] Primary part

[0039] linear motor

[0040] circuit board

[0041] Conductor tracks

[0042] Irontooth

[0043] Sheet metal bridges dielectric cover layer ferromagnetic return plate

[0044] Secondary part electrical vias

[0045] Permanent magnets

Claims

Patent claims 1 . Primary part (2) for a linear motor (3) with a printed circuit board (4) and a winding (1 ) realized on the printed circuit board (4), wherein the printed circuit board (4) has openings between the conductors of the winding (1 ) which are penetrated by iron teeth (6), characterized in that the winding (1 ) is designed as a distributed winding (1 ).

2. Primary part according to claim 1, wherein the iron teeth (6) are realized by at least one folded motor sheet.

3. Primary part according to claim 2, wherein two adjacent iron teeth (6) are formed as legs of a sheet metal section bent into a U-shape.

4. Primary part according to one of claims 2 or 3 with a ferromagnetic return plate (9) which is magnetically coupled to the motor plate.

5. Primary part according to claim 1, wherein the openings are filled with a ferromagnetic screen printing material.

6. Primary part according to one of the preceding claims, wherein the distributed winding (1) is designed as a wave winding.

7. Primary part according to one of the preceding claims, wherein the printed circuit board (4) is designed as a multilayer board and the distributed winding (1) comprises turns in different layers of the multilayer board.

8. Linear motor (3) with a primary part (2) according to one of the preceding claims.

9. Method for producing a primary part (2) for a linear motor (3) with the following method steps: • Applying a distributed winding (1) to a printed circuit board (4), • Making openings in the printed circuit board (4) between adjacent conductors of the distributed winding (1 ) and • Filling the openings with a magnetically conductive material to form iron teeth (6).

10. The method according to claim 9, wherein at least one U-shape is folded into a motor sheet and the legs of the resulting U-shaped sheet section (7) are introduced into the openings of the circuit board (4) to form the iron teeth (6).

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