WO2005074108A1

WO2005074108A1 - Modular linear motor

Info

Publication number: WO2005074108A1
Application number: PCT/NL2005/000029
Authority: WO
Inventors: Laurentius Gerardus Johannes Wolters; Hendrikus Anthonius Gerhardus Helmink
Original assignee: Mlm Motors B.V.
Priority date: 2004-01-16
Filing date: 2005-01-14
Publication date: 2005-08-11
Also published as: NL1025269C2; EP1706935A1

Abstract

The invention relates to a modular linear motor comprising:, - a number of magnets of alternating polarity placed successively in a plane; - at least two successively placed coil modules, which modules comprise a stack of parallel plates of identical form, each provided with at least three parallel fingers, and electric coils arranged round the fingers; wherein the at least two modules are arranged at a distance from each other.

Description

MODULAR LINEAR MOTOR

The invention relates to a modular linear motor. Such modular linear motors are used for instance to move carriers reciprocally over a limited length. It is possible here to envisage a transport system in a factory or for instance a parking system, wherein pallets with vehicles thereon are displaced in a building. Linear motors are usually constructed in accordance with the power to be produced. The length of the linear motor is determined subject thereto. This means that each linear motor is manufactured as an individual product and that series production is difficult. It is of course possible to manufacture a number of linear motors of different lengths, and therefore different power, but for each length separate dies must be made with which the plates for the lamination stack are stamped. Around this lamination stack are arranged the coils with which the magnetic force is generated, and the driving force thus provided. It is now an object of the invention to provide a linear motor which can be readily adapted to the required power, without specific tools having to be manufactured to enable construction of the linear motor. This object is achieved according to the invention with a modular linear motor comprising: - a number of magnets of alternating polarity placed successively in a plane,- - at least two successively placed coil modules, which modules comprise a stack of parallel plates of identical form, each provided with at least three parallel fingers, and electric coils arranged round the fingers; wherein the at least two modules are arranged at a distance from each other. Three-phase electricity is normally used to energize modular linear motors. With each phase one coil is energized, and because the phases are alternating the three different parallel fingers are thus energized alternately, whereby a propelling force is generated. A linear motor of a desired power can be assembled easily with such coil modules. These coil modules are simply placed successively, whereby a linear motor of a certain length, and therefore of the desired power, is obtained. In a preferred embodiment of the modular linear motor according to the invention, the at least two modules are arranged at a mutual distance. Here the lamination stacks of the different coil modules are thus not in contact, but have a certain distance between them. It has been found that the so-called "cogging" effect of linear motors is hereby reduced. This cogging effect, also referred to as sticking forces, is the result of the electrical asymmetry of the coil modules. When a prior art linear motor with a high number of fingers is examined, a sticking force which causes vibrations is found to occur at the outer ends of the linear motor. It has now been found that these sticking forces are considerably reduced by arranging the modules at a distance from each other. In yet another embodiment of the motor according to the invention, the pitch distance of the at least three parallel fingers and the pitch distance between adjacent fingers of adjacent modules are equal. The modular linear motor can hereby be actuated in the same manner as a linear motor which is constructed integrally. In another preferred embodiment of the modular linear motor according to the invention, the magnets are rotated along the longitudinal axis of the fingers. A second "cogging" effect is hereby reduced. These are the sticking forces which occur when a finger is carried above a magnet and leaves it again. In yet another preferred embodiment of the modular linear motor according to the invention, closing profiles are arranged on either side of the at least two successively placed coil modules. The different coil modules are held together with these closing profiles. Such a closing profile can for instance be an extrusion profile which is sawn off to the desired length during assembly of the linear motor, and thus forms the longitudinal sides of the linear motor. In a preferred embodiment of the modular motor according to the invention, there is arranged in each coil module at least one channel which connects on either side to channels arranged in the closing profiles. Via these channels a cooling agent can be circulated through the coils, whereby it is possible to generate more power with one coil module than with an uncooled coil module. An embodiment of the modular linear motor according to the invention comprises a stationary frame to which the modules are fixed, a guide rail arranged on the frame and a displaceable carriage which supports on the guide rail and on which the magnets are arranged. The guide rail ensures that the distance between the magnets and the coil modules is held constant, whereby a maximum power can be generated. If the distance between the magnets and coil modules becomes too great, too little magnetic force can be generated. In a variant of this modular linear motor, at least two sets of at least two modules are placed back- to-back and the displaceable carriage comprises a U- shaped frame which encases the modules placed back-to- back. A large number of coil modules can hereby be accommodated in a compact embodiment, and a high power can thus be generated. The reaction forces, which are the result of energizing of the modules, are furthermore more or less neutralized they act in opposite directions due to the back-to-back arrangement. Yet another embodiment of the modular linear motor according to the invention comprises a stationary vertical plate on which the magnets of alternating polarity are arranged on either side. A guide rail is further arranged on the plate, on which rail supports a U-shaped carriage, wherein two sets of at least two modules are arranged on the carriage, wherein each set is directed toward a side of the vertical plate which is provided with the magnets. Here also a large number of coil modules is used in a compact embodiment, whereby a high power can once again be generated. The advantage of this embodiment is that the linear motor can have a very large stroke at relatively low cost. Only the vertical plate with the magnets thereon has to be arranged over the whole length of the modular linear motor. The coil modules, which involve the highest costs, can be limited, while a wide range can still be obtained. Such an embodiment is particularly important when loads must be transported over great distances. These and other features of the invention are further elucidated with reference to the accompanying drawings. Fig. 1 shows a perspective view of an embodiment of a linear motor according to the invention. Fig. 2 shows a perspective view of the linear motor of fig. 1 with exploded parts. Fig. 3A and 3B show a second embodiment of a linear motor according to the invention. Fig. 4A and 4B show a third embodiment of a linear motor according to the invention. Fig. 5 shows a cross-sectional view of a fourth embodiment of a linear motor according to the invention. Fig. 1 shows a linear motor 1. This linear motor 1 has a fixed part 2 on which are arranged magnets 3, 4 with an alternating polarity. Linear motor 1 further has two coil modules 5, which are held together on either side by closing profiles 6. A space 7 is provided between coil modules 5. Coil modules 5 are covered at the ends by cover plates 8. In these cover plates 8 are provided recesses for channels 9, 10, with which cooling liquid can be carried through the coil modules . Fig. 2 shows linear motor 1 of fig. 1 with exploded parts. Coil module 5 has a lamination stack 11 which has three fingers 12. A coil 13 is provided around each finger 12. The magnetic force is generated with this coil, and with a correct connection it is possible to ensure that the linear motor produces a propelling force. Pressed through plates 11 are two tubes 14, which ensure on the one hand that plates 11 are held together, and ensure on the other that cooling liquid can flow through the plates. A good heat transfer is achieved by the press fit. Closing profiles 6 are sawn to the correct length and fixed to coil modules 5 via bolts 15 and nuts 16. A channel 9, 10 is provided in closing profiles 6. Tubes 14 of coil modules 5 connect to these channels 9, 10, whereby cooling liquid can be carried through coil modules 5. After assembly of linear motor 1, coils 13 are cast in synthetic resin to prevent damage as a result of vibrations . In fig. 3A and 3B a second embodiment of a linear motor 20 is shown. Parts which correspond to the embodiment according to fig. 1 and 2 are designated with the same reference numerals. Linear motor 20 consists of a stationary part 21 on which a guide rail 22 is arranged. Over this guide rail 22 travels a carriage 23 which is provided with rollers 24, which engage on guide rail 22. Magnets 3, 4 are further arranged on carriage 23. A linear motor as according to fig. 1 and 2 is arranged in stationary part 21. This linear motor again consists of closing profiles 6 and coil modules 5 placed therebetween. Fig. 3B shows clearly that lamination stack 11 is held in place by a tube 14 which debouches on both channels 9, 10 in closing profiles 6. Coils 13 are arranged around the fingers of the lamination stack. It can also be seen in fig. 3B that coils 13 are cast in a synthetic resin 25. Cables 26 which actuate the different coils 13 are laid under coil modules 5. Fig. 4A and 4B show a third embodiment 30 of a linear motor according to the invention. This linear motor 30 has a stationary part 31 and a translating part 32. The translating part 32 has a number of rollers 33 which are guided in the profiled stationary part 31. The translating part 32 is substantially U-shaped and magnets 3 , 4 are arranged alternately on the inside on both legs of the U-shape. The stationary part 31 comprises coil modules 5 which are placed back-to-back and which are held together by means of closing profiles 6. With this back-to-back placement a large number of coil modules can be arranged in a limited space and can develop a correspondingly high power, thereby creating a powerful linear motor. Fig. 5 shows a fourth embodiment 40 of a linear motor according to the invention. This linear motor 40 has a stationary part 41 with a vertical plate 42 on which magnets 3, 4 are arranged alternately on either side. The stationary part 41 is further provided with rollers 43 which form a guide. The translating part 44 once again has coil modules 5, which in this embodiment are directed toward each other so that they can co-act with magnets 3, 4 arranged on vertical plate 42. The coil modules are again held together by closing profiles 6. The translating part 44 further has two frame parts 45 which are provided with rails 46, which co-act with rollers 43. Channels 47 for cooling liquid and cable holes 48 for cables 49 are further provided in frame parts 45. The cables are again provided for actuation of coil modules 5. This embodiment 40 is particularly advantageous for a linear motor which must operate over longer distances. The costs of providing the vertical plate 42 with magnets 3, 4 over a greater length are considerably lower than providing coil modules 5 over this length. This construction can furthermore withstand weather influences well, since the electrical parts are protected from weather influences by the U-shaped construction, while the stationary part 41 comprises no components which are particularly sensitive to weather influences.

Claims

1. Modular linear motor comprising: - a number of magnets of alternating polarity placed successively in a plane; - at least two successively placed coil modules, which modules comprise a stack of parallel plates of identical form, each provided with at least three parallel fingers, and electric coils arranged round the fingers; wherein the at least two modules are arranged at a distance from each other.

2. Modular linear motor as claimed in claim 1, wherein the pitch distance of the at least three parallel fingers and the pitch distance between adjacent fingers of adjacent modules are equal.

3. Modular linear motor as claimed in claim 1 or 2, wherein the magnets are rotated along the longitudinal axis of the fingers .

4. Modular linear motor as claimed in any of the foregoing claims, wherein closing profiles are arranged on either side of the at least two successively placed coil modules.

5. Modular motor as claimed in claim 4, wherein at least one channel is arranged in each coil module, which channel connects on either side to channels arranged in the closing profiles.

6. Modular linear motor as claimed in any of the foregoing claims, comprising a stationary frame to which the modules are fixed, a guide rail arranged on the frame and a displaceable carriage which supports on the guide rail and on which the magnets are arranged.

7. Modular linear motor as claimed in claim 6, wherein at least two sets of at least two modules are placed back-to-back and wherein the displaceable carriage comprises a U-shaped frame which encases the modules placed back-to-back.

8. Modular motor as claimed in any of the claims 1-5, comprising a stationary vertical plate on which the magnets of alternating polarity are arranged on either side, a guide rail arranged on the plate, a U- shaped carriage supporting on the guide rail, wherein two sets of at least two modules are arranged on the carriage, wherein each set is directed toward a side of the vertical plate which is provided with the magnets.