FIELD OF THE INVENTION

The present invention relates in general to permanent magnet electric linear motors. In particular, however not exclusively, the present invention concerns flux-switching permanent magnet motors used in elevators.

BACKGROUND

There are known electric linear motors in which the rotor, or the mover, and the stator of the motor are linear. Furthermore, it is known to use permanent magnet electric linear motor in elevators for moving the elevator car instead of a hoisting rope that is coupled to a conventional electric motor.

However, some types of permanent magnet electric linear motors have permanent magnets and coils on same side of airgap of the motor. Thus, there is a limited space for the coils, such as of copper. The limited space for coils limits the efficiency of the motor and, thus, limit the amount of thrust force that can be generated by the motor. There is thus a need to develop electric linear motors.

SUMMARY

An objective of the present invention is to provide a linear rotor for electric linear motor, an electric linear motor, and an elevator. Another objective of the present invention is that the space for the coils in the rotor can be increased which allows incorporation of larger coils.

The objectives of the present invention are reached by a linear rotor for an electric linear motor, an electric linear motor, and an elevator as defined by the respective independent claims.

According to a first aspect, a linear rotor for an electric linear motor is provided. The linear rotor comprises rotor teeth adapted for facing towards a linear stator of the motor. At least one of the rotor teeth comprises two first permanent magnets arranged tilted with respect to each other. In various embodiments, the two first permanent magnets may define a V- shape, wherein a top portion of the V-shape is adapted for facing towards the linear stator.

In various embodiments, the angle between the tilted first permanent magnets may be less than or at most 35 degrees, that is in the range from more than zero to 35 degrees. In a preferable embodiment, the angle between the tilted first permanent magnets may be in the range from five to 15 degrees, or most preferably about ten degrees.

Furthermore, the at least one of the rotor teeth may comprise a first magnetic core portion arranged between said two first permanent magnets with respect to a longitudinal direction of the linear rotor.

Additionally, the at least one of the rotor teeth may comprise further magnetic core portions arranged at sides with respect to a longitudinal direction of the linear rotor other than between said two first permanent magnets. Further, each of the further core portions may be in magnetic coupling with one other rotor tooth.

In some embodiments, the linear rotor may comprise further permanent magnets. Each one of the further permanent magnets may be arranged at an end of one of the first permanent magnets. Additionally, a magnetic field direction of each one of the further permanent magnets may, preferably, be the same as in the respective first permanent magnet.

In an various embodiments, the two first permanent magnets may be arranged next to each other at opposite ends of the first permanent magnets with respect to the ends adapted for facing towards a linear stator of the motor.

Alternatively or in addition, the two first permanent magnets may be arranged in contact with each other at opposite ends of the first permanent magnets with respect to the ends adapted for facing towards a linear stator of the motor.

The opposite ends of said two permanent magnets may be arranged to substantially align with edges of the further core portions.

The linear rotor may comprise coils, wherein each rotor teeth comprises at least one coil arranged around said rotor teeth. In an embodiment, at least part of the coil(s) form a three-phase winding. According to a second aspect, an electric linear motor is provided. The electric linear motor comprises a linear rotor according to the first aspect, or an embodiment thereof. The electric linear motor further comprises a linear stator comprising stator teeth, wherein the linear rotor and the linear stator are configured to be in electromagnetic coupling with each other for moving the linear rotor relative to the linear stator, and to have an air gap between the linear rotor and the linear stator at least during use of the motor.

In various embodiments, the electromagnetic coupling may be arranged to be established by injecting current, that is electrical current, into the coils.

According to a third aspect, an elevator is provided. The elevator comprises an elevator shaft, at least one elevator car and an electric linear motor according to the second aspect, or an embodiment thereof. The elevator further comprises the linear stator arranged to extend in the elevator shaft, and the elevator car coupled to the linear rotor for moving the elevator car in the elevator shaft by the electric linear motor.

The present invention provides a linear rotor for an electric linear motor, an electric linear motor, and an elevator. The present invention provides advantages over known solutions such that the efficiency of the motor can be increased and there is more space for the coils of rotor so that more thrust force can be generated. By having more space for the coils, the average torque can be increased as the volume of permanent magnets is decreased. This will result in higher magnet usage efficiency.

Various other advantages will become clear to a skilled person based on the following detailed description.

The expression "a number of” may herein refer to any positive integer starting from one (1 ), that is being at least one.

The expression "a plurality of” may refer to any positive integer starting from two (2), that is being at least two.

The terms “first”, “second”, “third” and “fourth” are herein used to distinguish one element from other element, and not to specially prioritize or order them, if not otherwise explicitly stated. The exemplary embodiments of the present invention presented herein are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used herein as an open limitation that does not exclude the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.

The novel features which are considered as characteristic of the present invention are set forth in particular in the appended claims. The present invention itself, however, both as to its construction and its method of operation, together with additional objectives and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF FIGURES

Some embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

Figure 1 illustrates schematically an electric linear motor according an embodiment of the present invention.

Figure 2 illustrates schematically a linear rotor according an embodiment of the present invention by a perspective view.

Figures 3A and 3B illustrate schematically an electric linear motor according an embodiment of the present invention.

Figure 4 illustrates schematically an elevator according an embodiment of the present invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Figure 1 illustrates schematically an electric linear motor 100 according an embodiment of the present invention. The electric linear motor 100 may comprise a linear rotor 20 and a linear stator 10 comprising stator teeth 12. The linear rotor 20 and the linear stator 10 are, preferably, configured to be in electromagnetic coupling with each other for moving the linear rotor 20 relative to the linear stator 10. In addition, there is an air gap 15 arranged between the linear rotor 20 and the linear stator 10 at least during use of the motor 100, such as during movement of the rotor 20 and stator 10 relative to each other. The linear stator 10 may comprise a stator core 11 , such as including ferromagnetic material. The stator teeth 12 may, preferably, be integral parts of the stator core 11 or may have been attached thereto separately to form the stator 10. The material of the stator teeth 12 may be the same ferromagnetic material as the rest of the stator core 11 , or at least the portion thereof being of the ferromagnetic material.

Figure 2 schematically a linear rotor 20 according an embodiment of the present invention by a perspective view. The coils 29 have been omitted from Fig. 2 for reasons of better legibility.

The linear rotor 20 may according to various embodiments, such as shown in Figs. 1 and 2, comprise rotor teeth 22 adapted for facing towards a linear stator 10 of the motor 100. At least one of the rotor teeth 22, or several or all of them, comprise(s) two first permanent magnets 23 arranged tilted with respect to each other. As can be seen in Fig. 1 , the first permanent magnets 23 do not extend in parallel with respect to each other relative to their longitudinal direction but rather form an angle therebetween which differs from zero (or 180 degrees). The magnetic field direction of the first permanent magnets 23 are shown with arrows in Fig. 1 .

In various embodiments, the angle between the tilted first permanent magnets 23 may be less than or at most 35 degrees, that is in the range from more than zero to 35 degrees. In a preferable embodiment, the angle between the tilted first permanent magnets 23 may be in the range from five to 15 degrees, or most preferably about ten degrees.

In various embodiments, the linear rotor 20 may comprise coil(s) 29, wherein each rotor teeth 22 comprises at least one coil 29, or several coils, arranged around said rotor teeth 22, such as shown in Fig. 1 with respect to the rightmost one of the rotor teeth 22. In addition, at least part of the coil 29, or the coil(s), may form a three-phase winding. The electromagnetic coupling between the rotor 20 and the stator 10 may, preferably, be arranged to be established by injecting current, that is electrical current, into the coils 29.

As can be seen, the tilting of the first permanent magnets 23 provide more space for the coils 29, or the coils thereof, especially at the end of the rotor tooth 22 in which the first permanent magnets 23 are closer to each other with respect to the other end. Thus, the tilted magnets 23 decrease the amount of ferromagnetic material used. The saved space can be used for the coils 29, such as having coils of copper. This arrangement provides, in some cases, about 30 % more space for the copper and, thus, the thrust force can be made about 30 % higher with same current density relative to the coils 29 in the space in a corresponding rotor having parallel permanent magnets. Alternatively, with the same level of thrust force, the copper losses would be about 23 % less. Or even if the copper area is equal, the machine height could be lowered with respect to the case of parallel permanent magnets.

In an embodiment, the two first permanent magnets 23 define a V-shape, wherein the top portion of the V-shape is adapted for facing towards the linear stator 10, such as illustrated in Fig. 1 .

In addition, the at least one of the rotor teeth 22, or several or all of them, comprise(s) a first magnetic core portion 21 arranged between said two first permanent magnets 23 with respect to a longitudinal direction 5 of the linear rotor 20.

Alternatively or in addition, the at least one of the rotor teeth 22, or several or all of them, comprise(s) further magnetic core portions 25 arranged at sides with respect to a longitudinal direction 5 of the linear rotor 20 other than between said two first permanent magnets 23. Furthermore, each of the further core portions 25 may be in magnetic coupling with one other rotor tooth 22, such as shown in Fig. 1 where the rotor teeth 22 are coupled to each other via the further core portions 25.

In various embodiments, the linear rotor 20 may comprises further permanent magnets 24, wherein each one of the further permanent magnets 24 is arranged at an end, that is at the other end, of one of the first permanent magnets 23. In addition a magnetic field direction of each one of the further permanent magnets 24 may, preferably, be the same as in the respective first permanent magnet 23, as shown in Fig. 1 with the similar kinds of arrows as with respect to the first permanent magnets 23.

In various embodiments, the two first permanent magnets 23 may be arranged next to each other at opposite ends of the first permanent magnets 23 with respect to the ends adapted for facing towards a linear stator 10 of the motor 100 Alternatively or in addition, the two first permanent magnets 23 may be arranged in contact with each other at opposite ends of the first permanent magnets 23 with respect to the ends adapted for facing towards a linear stator 10 of the motor 100.

In an embodiment in which the at least one of the rotor teeth 22 comprises further magnetic core portions 25 arranged at sides with respect to a longitudinal direction 5 of the linear rotor 20 other than between said two first permanent magnets 23, and wherein the two first permanent magnets 23 are arranged next to and/or in contact with each other at opposite ends of the first permanent magnets 23 with respect to the ends adapted for facing towards a linear stator 10 of the motor 100, the opposite ends of said two permanent magnets may be arranged to substantially align with edges of the further core portions 25.

Figures 3A and 3B illustrate schematically an electric linear motor 100 according an embodiment of the present invention. Fig. 3A illustrates the linear rotor 20 at a first position 301 with respect to the linear stator 10. Fig. 3B illustrates the linear rotor 20 at a second position 302 with respect to the linear stator 10. Figs. 3A and 3B further illustrate the magnetic flux flow 51 -54 in the motor 100 at the two positions 301 , 302.

In the first position 301 , the first magnetic flux flow 51 occurs when the rotor tooth 22 on the left in Fig. 3A aligns with one of the stator teeth 12. As can be seen, the first magnetic flux flow 51 has a path which goes via the first magnetic core portion 21 of the rotor tooth 22 in question and returns to the rotor 20 via another stator tooth 12 which is at a corresponding position with one of the further magnetic core portions 25 of another rotor tooth 22. The path then closes through the yoke of the linear rotor 20. In Fig. 3A, the second magnetic flux flow 52 is also shown which goes through the same first magnetic core portion 21 , however, continues along the stator 10 in opposite direction than the first magnetic flux flow 51 .

In the second position 302, the third magnetic flux flow 53 occurs when the rotor tooth 22 on the right in Fig. 3B aligns with one of the stator teeth 12. As can be seen, the third magnetic flux flow 53 has a path which goes via the first magnetic core portion 21 of the rotor tooth 22 in question and returns to the rotor 20 via another stator tooth 12 which is at a corresponding position with one of the further magnetic core portions 25 of another rotor tooth 22. The path then closes through the yoke of the linear rotor 20. In Fig. 3B, the fourth magnetic flux flow 54 is also shown which goes through the same first magnetic core portion 21 , however, continues along the stator 10 in opposite direction than the third magnetic flux flow 53.

The magnetic flux flows 51 -54 shown in Figs. 3A and 3B are only some of the flux flows in the motor 100 and are shown in order to describe the operation of the motor 100. Flowever, a person skilled in the art recognizes that there may also be other flux flows during different operating conditions or positions.

This kind of a flux-switching permanent magnet linear motor comprising the first permanent magnets 23 being tilted with respect to each other provides the several of the advantages described in hereinbefore. In the sandwiched flux switching permanent magnet motor according to various embodiments of the present invention, the leakage flux on the top of the permanent magnets 23 is much lower because of the tilted geometry and, thus, the first permanent magnets 23 do not need to come higher level than the ferromagnetic core around them.

Figure 4 illustrates schematically an elevator 200 according to an embodiment of the present invention. The elevator 200 may comprise at least one or a plurality of elevator cars 210 moving in the elevator shaft 213 or the elevator car pathway 213.

In various embodiments, the elevator car(s) 210 may comprise a first electrical drive 212, such as a frequency converter or an inverter, and/or a first energy storage 214 such as a battery or batteries, which are shown with dashed lines indicating the optionality of the feature. The first electrical drive 212 may be utilized for operating a mover arranged to the elevator car 210 for moving the car 210 along the elevator shaft 213. There may also be other electrically operated equipment in the elevator car 210 such as lighting, doors, user interface, emergency rescue equipment, etc. The first electrical drive 212 or a further electrical drive, such as an inverter or a rectifier, may be utilized for operating one or several of said other equipment of the elevator car 210. The first energy storage 214 may, preferably, be electrically coupled to the first electrical drive 212, for example, to the intermediate circuit of the drive, for providing electrical power to the first electrical drive 210 and/or for storing electrical energy provided by the first electrical drive 214 or a further electrical drive or other electrical power source.

There are preferably at least two landing floors, having landing floor doors 219 or openings 219, comprised in the elevator 200. There may also be doors comprised in the elevator car 210. Although shown in Fig. 1 that there are two horizontally separated sets, or “columns”, of vertically aligned landing floors, there could as well be only one column as in conventional elevators or more than two, for example, three.

Regarding the elevator shaft 213, it may be such as defining substantially closed volume in which the elevator car 10 is adapted and configured to be moved. The walls may be, for example, of concrete, metal or at least partly of glass, or any combination thereof. The elevator shaft 213 herein refers basically to any structure or pathway along which the elevator car 210 is configured to be moved.

As can be seen in Fig. 4, the elevator car 210 or cars 210 may be moved along the elevator shaft 213 vertically and/or horizontally depending on the direction of stator beam(s) 216 comprising a linear stator 10 or stators 10. According to embodiments similar to one in Fig. 1 in this respect, the elevator car 10 or cars 10 may be configured to be moved along a number of vertical and/or horizontal stator beams 216, for example, two beams such as in Fig. 3. The stator beams 216 are part of an electric linear motor 100 of the elevator 200 utilized to move the elevator car 210 or cars 210 in the elevator shaft 213. The stator beams 216 may, preferably, be arranged in fixed manner, that is, stationary with respect to the elevator shaft 213, for example, to a wall of the shaft by fastening portions, which may be arranged to rotatable at direction changing positions of the elevator car 210.

The elevator 200 may comprise an elevator control unit 1100 for controlling the operation of the elevator 200. The elevator control unit 1100 may be a separate device or may be comprised in the other components of the elevator 200 such as in or as a part of the electrical drive 212. The elevator control unit 1100 may also be implemented in a distributed manner so that, e.g., one portion of the elevator control unit 1100 may be comprised in the electrical drive 212 and another portion in the elevator car 210. The elevator control unit 1100 may also be arranged in distributed manner at more than two locations or in more than two devices. The elevator control unit 1100 may comprise one or more processors, one or more memories being volatile or non-volatile for storing portions of computer program code and any data values and possibly one or more user interface units. The mentioned elements may be communicatively coupled to each other with e.g. an internal bus.

The processor may be configured to execute at least some portion of computer program code stored in the memory causing the processor, and thus the elevator control unit 1100, to control the operation of the elevator 200. The processor may thus be arranged to access the memory and retrieve and store any information therefrom and thereto. For sake of clarity, the processor herein refers to any unit suitable for processing information and control the operation of the elevator control unit 1100, among other tasks. The operations may also be implemented with a microcontroller solution with embedded software. Similarly, the memory is not limited to a certain type of memory only, but any memory type suitable for storing the described pieces of information may be applied in the context of the present invention.

The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.