WO2025209837A1

WO2025209837A1 - A linear vernier machine

Info

Publication number: WO2025209837A1
Application number: PCT/EP2025/057435
Authority: WO
Inventors: Alessandro ACQUAVIVA; Sebastiano Acquaviva; Leonardo MAGGI; Annachiara Tonelli
Original assignee: GEA Mechanical Equipment Italia SpA
Current assignee: GEA Mechanical Equipment Italia SpA
Priority date: 2024-04-04
Filing date: 2025-03-18
Publication date: 2025-10-09
Anticipated expiration: 2026-10-04

Abstract

A linear Vernier machine (1) comprising: − a primary (100) comprising at least two packs (100a, 100b) having a main development parallel to a predefined direction (A-A), each pack (100a, 100b) comprising a plurality of stacked lamination sheets (101a, 101b) having teeth (102) and slots (103) distributed according to an alternating arrangement; − a secondary (110) interposed between the two packs (100a, 100b) of the primary (100) and comprising a plurality of permanent magnets (112); − a winding assembly (120) comprising a plurality of coils (121) which are mutually parallel and aligned along the predefined direction (A-A), the coils (121) being fitted in the slots (103) of the lamination sheets (101a, 101b), the winding assembly (120) surrounding the secondary (110).

Description

DESCRIPTION

A LINEAR VERNIER MACHINE

Technical field

The present invention relates to a linear Vernier machine. In particular, the present invention has a great potential in low-speed applications.

The invention finds application in several sectors, such as automotive, industrial automation, ventilation, pumping, lifting machines, earthmoving, heavy agriculture, gardening, naval sector machines.

A possible application, but not limited to, for the linear version of the Vernier machine described herewith is direct drive linear actuator for high pressure industrial pistons.

In particular, the invention may well be used in the food industry, in particular in the dairy sector, or in the chemical, pharmaceutical or cosmetic industry. The invention can be used in manufacturing areas where homogenization is a step of the production process.

Consider, for example, the production of carbon-based nanostructured materials, such as graphene and carbon nanotubes or cellular breakdown of yeasts, algae, or microorganisms for the production of intracellular material.

Background art

Beyond the numerous variants on the market, electrical machines are essentially divided into two categories, i.e. , the linear and rotary ones.

A linear motor is constituted by a fixed part (the stator, also called “guide” or “track”) and by a movable part (called “mover” or “slider”) that is slidable along the fixed part.

A rotary motor is constituted by a fixed part (the stator) and by a part rotatable around its axis (the rotor).

In accordance with the established terminology, the two parts of an electrical motor may also be identified with the following terms:

- primary, where the windings are located;

- secondary, bearing the permanent magnets. Usually, it is convenient for the primary being fixed (i.e. , being the stator), and for the secondary being movable (i.e., being the mover or rotor).

However, in some solutions the primary is movable (i.e., it is the mover or rotor) and the secondary is fixed (i.e., it is the stator).

Among the electrical machines, Permanent Magnet Vernier Machines (PMVMs) gained a lot of interest over the past couple of decades. This is mainly due to their high torque density enabled by the magnetic gearing effect.

Among scientific literature, reference is made to the following exemplary documents:

- A. Toba and T. A. Lipo, "Generic torque-maximizing design methodology of surface permanent-magnet vernier machine," in IEEE Transactions on Industry Applications, vol. 36, no. 6, pp. 1539-1546, Nov.-Dec. 2000, doi: 10.1109/28.887204;

- C. Shi, R. Qu, Y. Gao, D. Li, L. Jing and Y. Zhou, "Design and Analysis of an Interior Permanent Magnet Linear Vernier Machine," in IEEE Transactions on Magnetics, vol. 54, no. 11 , pp. 1-5, Nov. 2018, Art no. 8106805, doi: 10.1109/TMAG.2018.2840832;

- X. Fan, C. Wang, Z. Zhu, and H. Meng, "Design and Analysis of a High Power Density Permanent Magnet Linear Generator for Direct-Drive Wave Power Generation" in Actuators 2022, 11 (11 ), 327, retrievable at https://doi.Org/10.3390/act11110327 ;

- C. Bode, H. Schillingmann and M. Henke, "A free-piston PM linear generator in vernier topology using quasi-Halbach-excitation," 2014 International Conference on Electrical Machines (ICEM), Berlin, Germany, 2014, pp. 1950-1955, doi: 10.1109/ICELMACH.2014.6960451 ;

- C. Shi, R. Qu, D. Li, X. Ren, Y. Gao and Z. Chen, "Analysis of the Fractional Pole-Pair Linear PM Vernier Machine for Force Ripple Reduction," in IEEE Transactions on Industrial Electronics, vol. 68, no. 6, pp. 4748-4759, June 2021 , doi: 10.1109/TIE.2020.2991932. The state of the art, industry wise, regarding linear motors is mainly related to conventional permanent magnet brushless motors, whereas Vernier machines are still mostly found in academic publications.

The mechanical design and manufacturing can result very complex, in particular for linear motors for considerable sizes, thrust above 10 kN.

Furthermore, these machines suffer from magnetic unbalance between phases, due to the end effects which are not present in rotating machines, which is one of the causes which contributes to thrust ripple and control problems.

One particular challenge related to these machines is to have a reliable mechanical solution keeping the weight of the mover as low as possible to minimize the inertia of the system.

Disclosure of the invention

In this context, the object of the present invention is to provide a linear Vernier machine, which overcomes the outstanding problems of the prior art cited above.

In particular, the object of the present invention is to propose a linear Vernier machine which is easier to manufacture and control with respect to known designs of Vernier machines.

Another object of the present invention is to propose a linear Vernier machine which is versatile, that means it can be used for different types of applications.

Another object of the present invention is to propose a linear Vernier machine which is more compact than known designs.

The stated technical task and specified aims are substantially achieved by a linear Vernier machine comprising:

- a primary comprising at least two packs having a main development parallel to a predefined direction, each pack comprising a plurality of stacked lamination sheets having teeth and slots distributed according to an alternating arrangement;

- a secondary interposed between the two packs of the primary, the secondary comprising a plurality of permanent magnets;

- a winding assembly comprising a plurality of coils which are mutually parallel and aligned along the predefined direction, the coils being fitted in the slots of the lamination sheets of the two packs, the winding assembly surrounding the secondary.

In a preferred embodiment, the primary is a stator, and the secondary is a mover.

In an alternative embodiment, the primary is a mover, and the secondary is a stator.

Preferably, the secondary is distanced from the two packs of the primary. In particular, corresponding air gaps are obtained between each pack of the primary and the secondary.

In a preferred embodiment, the air gaps are of the same thickness in order to have a magnetic and force balance.

In an alternative embodiment, the air gaps are not equal.

In a preferred embodiment, the primary comprises four packs having a main development parallel to the predefined direction. The four packs are arranged in a tubular configuration which surrounds the secondary.

Each of the four packs comprises a plurality of stacked lamination sheets having teeth and slots distributed according to an alternating arrangement. In particular, the lamination sheets of each pack are parallelly aligned and stacked in such a way as to define a plurality of rows of corresponding teeth and a plurality of rows of corresponding slots.

According to one aspect of the invention, the linear Vernier machine comprises a casing having a main development along the predefined direction and delimiting an internal cavity which houses the primary, the secondary and the winding assembly.

Preferably, the casing comprises two elongated shells that are joined together and define a hollow tubular frame, and two side plates for closing the ends of hollow tubular frame. In a preferred embodiment, the linear Vernier machine further comprises means for fixing the primary to the casing in a suspended way within the internal cavity.

For example, the means for fixing comprises one set of parallel rods for each pack of the primary. The rods pass through the lamination sheets of the corresponding pack and protrude with end portions from opposite sides of the pack for being fixed to the casing.

Preferably, the rods of each set of rods are equally distanced and pass through yokes of the corresponding lamination sheets from where the teeth originate.

In an alternative embodiment, the primary is fixed with contact to the casing. For example, the packs are glued to inner walls of the casing.

Each coil of the winding assembly passes through one of the rows of slots of each pack of the primary.

Preferably, each coil of the winding assembly is wound around in order to form flat stacked layers of multiple turns.

According to a preferred embodiment, each coil has an overall rectangular shape. For example, each coil has four straight portions and four connecting portions connecting the straight portions. The straight portions represent the sides of a rectangle, and the connecting portions represent the rounded comers of said rectangle.

Each of the four straight portions are housed in a corresponding row of slots of one of the four packs.

Preferably, the coils are non-overlapping.

The secondary comprises an elongated core having a main development axis which is parallel to the predefined direction. The permanent magnets are fixedly mounted with alternating polarity on outer surfaces of the elongated core.

Preferably, the permanent magnets are equally spaced.

Preferably, the secondary has two shafts passing through the elongated core. In a preferred embodiment, the elongated core comprises a plurality of blocks stacked together along the main development axis. In particular, the blocks are screwed or glued together.

Each block is substantially shaped as a parallelepiped, so that the assembly of all the blocks results in an elongated core that is also shaped as a parallelepiped.

In particular, the permanent magnets consist in plate-like bodies glued on the outer surfaces of the elongated core.

Considering the lamination sheets, each tooth has a tooth width t_w and each slot has a slot width s_w, preferably according to the following condition: tw

0.8 < — < 1.2 sw

The teeth of the lamination sheets are preferably rounded with a rounding radius r_r according to the following condition: 0.5 < < 3

In a preferred embodiment, each lamination sheet has two outer teeth with increased width and with a different connection radius compared to inner teeth.

With regards to the choice of the materials, the elongated core is preferably made of a Soft Magnetic Composite.

The permanent magnets are made of one of the following materials: NdFeB, SmCo, Ferrite.

Each lamination sheet is made of a ferromagnetic material, for example one of the following: iron, nickel, cobalt.

Brief description of drawings

Further characteristics and advantages of the present invention will more fully emerge from the non-limiting description of a preferred but not exclusive embodiment of a linear Vernier machine, as illustrated in the accompanying drawings in which: - figure 1 illustrates a linear Vernier machine, according to the present invention, in a perspective exploded view;

- figure 2 illustrates a part of the linear Vernier machine of figure 1 , where some components have been removed for the sake of comprehension;

- figure 3 illustrates the linear Vernier machine of figure 1 , in a perspective assembled view;

- figure 4 illustrates a side plate of the casing of the linear Vernier machine of figure 1 , in a perspective and partially exploded view;

- figure 5 schematically illustrates the primary, the secondary and the winding assembly of the linear Vernier machine according to the present invention, in a cross-sectional view orthogonal to a predefined direction A-A;

- figures 6(a), 6(b) and 6(c) illustrate different embodiments of lamination sheets forming the packs of the linear Vernier machine according to the present invention, in a planar view;

- figure 7 illustrates parameters of the lamination sheets of figures 6(a), 6(b) and 6(c);

- figure 8 illustrates the winding assembly of the linear Vernier machine according to the present invention, in a perspective view, with a coil exploded for the sake of comprehension;

- figures 9(a) and 9(b) illustrates the secondary of the linear Vernier machine according to the present invention, respectively in a perspective assembled view and in a perspective exploded view;

- figure 10 illustrates the reinforcement bars of the secondary of figure 9(b);

- figure 11 illustrates a block of the elongated core of the secondary of figures 9(a) and 9(b), in a perspective view with partially exploded permanent magnets;

- figure 12 illustrates the structure of the elongated core of the secondary of figures 9(a) and 9(b), in a cross-sectional view according to the main development axis F-F.

Detailed description of preferred embodiments of the invention

With reference to the figures, number 1 indicates a linear Vernier machine comprising a primary 100, a secondary 110 and a winding assembly 120.

The linear Vernier machine 1 comprises a casing 2 housing the primary 100, the secondary 110 and the winding assembly 120.

In particular, the casing 2 has a main development along a predefined direction A-A and delimits an internal cavity 3.

The primary 100, the secondary 110 and the winding assembly 120 are located within the internal cavity 3.

According to one embodiment, the casing 2 comprises two elongated shells 2a, 2b, that are joined together and define a hollow tubular frame. In particular, a lower shell 2a acts as a bottom and an upper shell 2b acts as a cover for the casing 2.

In the illustrated embodiment, the two elongated shells 2a, 2b are not identical, but the lower shell 2a has a larger extension than the upper shell 2b.

In an alternative embodiment, not illustrated, the two elongated shells 2a, 2b are identical.

Both the lower shell 2a and the upper shell 2b have outer fins 4 for allowing heat dissipation. In particular, the outer fins 4 of both elongated shells 2a, 2b are mutually parallel and they are parallel to the predefined direction A-A.

The casing 2 also comprises two opposite side plates 2c, 2d for closing the ends of hollow tubular frame.

The primary 100 comprises at least two components or packs 100a, 100b, having a main development parallel to the predefined direction A-A.

These two packs 100a, 100b are referred here as “first pack 100a” and “second pack 100b”.

The first pack 100a comprises identical lamination sheets 101a which are parallelly arranged and stacked together along a first stacking direction B- B.

Each lamination sheet 101a of the first pack 100a has a plurality of teeth

102 and a plurality of slots 103, which are distributed according to an alternating arrangement, as shown in figures 6(a), (b) and (c).

In this context, the expression “alternating arrangement” means that a slot

103 of the plurality of slots 103 is interposed between a pair of consecutive teeth 102 of the plurality of teeth 102.

Each slot 103 has a slot width s_w, and each tooth 102 has a tooth width t_w, as illustrated in figure 7.

Each lamination sheet 101a of the first pack 100a has also a yoke 104 from which the teeth 102 originate.

The lamination sheets 101a of the first pack 100a are parallelly aligned and stacked in such a way as to define a plurality of rows 105 of corresponding (i.e., matching) teeth 102 and a plurality of rows 106 of corresponding (i.e., matching) slots 103.

In the following description, the rows 105 of corresponding teeth 102 are also shortly referred to as “teeth rows”, whereas the rows 106 of corresponding slots 103 are also shortly referred to as “slots rows”.

The teeth rows 105 are parallel to each other, as well as the slots rows 106 are parallel to each other.

In particular, the teeth rows 105 are distributed according to an alternating arrangement with the slots rows 106. This means that each slots row 106 is interposed between a pair of consecutive teeth rows 105.

The lamination sheets 101a of the first pack 100a are stacked so as to match when they are superimposed along the first stacking direction B-B.

According to one embodiment of the invention, illustrated herewith, the first pack 100a of lamination sheets 101a is arranged in the internal cavity 3 with the first stacking direction B-B which is orthogonal to the predefined direction A-A. This is shown in figure 2.

In particular, the teeth rows 105 and slot rows 106 develop along directions which are parallel to the first stacking direction B-B.

The second pack 100b comprises identical lamination sheets 101b which are parallelly arranged and stacked together along a second stacking direction C-C.

Each lamination sheet 101 b of the second pack 100b has the same structure of the lamination sheets 101a of the first pack 100a. This means that each lamination sheet 101 b of the second pack 100b has teeth 102 alternating to slots 103 and a yoke 104 from which the teeth 102 originate.

The number of teeth 102 and slots 103 of each lamination sheet 101 b of the second pack 100b is preferably the same as the number of teeth 102 and slots 103 of a lamination sheet 101a of the first pack 100a.

The lamination sheets 101 b of the second pack 100b are parallelly aligned and stacked in such a way as to define a plurality of teeth rows 105 and a plurality of slots rows 106, analogously to the lamination sheets 101a of the first pack 100a.

The lamination sheets 101 b of the second pack 100b are stacked so as to match when they are superimposed along the second stacking direction C- C.

According to the illustrated embodiment, the first pack 100a and the second pack 100b of the primary 100 are arranged in the internal cavity 3 with the first stacking direction B-B and the second stacking direction C-C parallel to each other. Both the first stacking direction B-B and the second stacking direction C-C are orthogonal to the predefined direction A-A.

Preferably, the first pack 100a and the second pack 100b are arranged in the internal cavity 3 at two different levels (i.e., at different heights) with respect to the lower shell 2a of the casing 2.

In particular, the first pack 100a is located at a lower level than the second pack 100b with respect to the lower shell 2a.

In particular, the teeth 102 of the lamination sheets 101a of the first pack 100a face the teeth 102 of the lamination sheets 101 b of the second pack 100b, whereas the yokes 104 of the lamination sheets 101a, 101 b of the first pack 100a and of the second pack 100b face internal walls of the casing 2.

In the illustrated embodiment, the yokes 104 of the lamination sheets 101a, 101b of the first pack 100a and of the second pack 100b respectively face the internal walls of the lower shell 2a and of the upper shell 2b.

The secondary 110 is interposed between the first pack 100a and the second pack 100b of the primary 100.

The winding assembly 120 is arranged so as to pass through the packs 100a, 100b of the primary 100 and to surround the secondary 110.

Preferably, the primary 100 comprises more than two components or packs 100a, 100b, 100c, 100d which are arranged in a tubular configuration developing mainly along the predefined direction A-A.

Preferably, the packs 100a, 100b, 100c, 100d are identical, in particular in shape and dimensions.

Alternatively, the packs 100a, 100b, 100c, 100d may differ among each other, as it will be explained later.

The secondary 110 passes through the tubular configuration defined by the packs 100a, 100b, 100c, 100d of the primary 100.

The winding assembly 120 is arranged so as to pass through all the packs 100a, 100b, 100c, 100d of the primary 100 and to surround the secondary 110.

The tubular configuration of the primary 100 (for example of the stator, as it will be explained later) allows to achieve a higher thrust density.

According to one embodiment of the invention, illustrated herewith, the primary 100 comprises four packs 100a, 100b, 100c, 100d, as it will be better described in the following part of description.

Apart from the first pack 100a and the second pack 100b, there will be a third pack 100c and a fourth pack 100d.

The third pack 100c comprises identical lamination sheets 101c which are parallelly arranged and stacked together along a third stacking direction D- D.

Each lamination sheet 101c of the third pack 100c has the same structure of the lamination sheets 101a, 101 b of the first and second packs 100a, 100b. This means that each lamination sheet 101c of the third pack 100c has teeth 102 alternating to slots 103 and a yoke 104 from which the teeth 102 originate.

The number of teeth 102 and slots 103 of each lamination sheet 101c of the third pack 100c is preferably the same as the number of teeth 102 and slots 103 of a lamination sheet 101a, 101 b of the first and second pack 100a, 100b.

The lamination sheets 101c of the third pack 100c are parallelly aligned and stacked in such a way as to define a plurality of teeth rows 105 and a plurality of slots rows 106, analogously to the lamination sheets 101a, 101 b of the first and second packs 100a, 100b.

The lamination sheets 101c of the third pack 100c are stacked so as to match when they are superimposed along the third stacking direction D-D. The fourth pack 100d comprises identical lamination sheets 101d which are parallelly arranged and stacked together along a fourth stacking direction E-E.

Each lamination sheet 101d of the fourth pack 100d has the same structure of the lamination sheets 101a, 101 b, 101c of the other packs 100a, 100b, 100c. This means that each lamination sheet 101 d of the fourth pack 100d has teeth 102 alternating to slots 103 and a yoke 104 from which the teeth 102 originate.

The number of teeth 102 and slots 103 of each lamination sheet 101 d of the fourth pack 100d is preferably the same as the number of teeth 102 and slots 103 of a lamination sheet 101a, 101 b, 101c of the other packs 100a, 100b, 100c.

The lamination sheets 101 d of the fourth pack 100d are parallelly aligned and stacked in such a way as to define a plurality of teeth rows 105 and a plurality of slots rows 106, analogously to the lamination sheets 101a, 101 b, 101c of the other packs 100a, 100b, 100c.

The lamination sheets 101 d of the fourth pack 100d are stacked so as to match when they are superimposed along the fourth stacking direction E- E.

The third pack 100c and the fourth pack 100d of the primary 100 are arranged in the internal cavity 3 with the third stacking direction D-D and the fourth stacking direction E-E parallel to each other. Both the third stacking direction D-D and the fourth stacking direction E-E are orthogonal to the predefined direction A-A.

Preferably, the third pack 100c and the fourth pack 100d are arranged in the internal cavity 3 at a same level (i.e., same height) with respect to the lower shell 2a of the casing 2.

In particular, the teeth 102 of the lamination sheets 101c of the third pack 100c face the teeth 102 of the lamination sheets 101 d of the fourth pack 100d, whereas the yokes 104 of the lamination sheets 101c, 101 d of the third pack 100c and of the fourth pack 100d face internal walls of the casing 2.

As said, the four packs 100a, 100b, 100c, 100d are arranged within the internal cavity 3 according to a tubular configuration.

In this context, the first pack 100a is also referred to as the “bottom pack”, the second pack 100b is also referred to as the “top pack”, and the third and fourth packs 100b, 100c are also referred to as “side packs”.

According to one embodiment of the invention, the lamination sheets 101a, 101 b 101c, 101d of different packs 100a, 100b, 100c, 100d are all identical. In particular, they have the same shape and dimensions. Some embodiments of lamination sheets are illustrated in figures 6(a) to 6(c).

According to another embodiment, the lamination sheets 101a, 101 b, 101c, 101 d of each pack 100a, 100b, 100c, 100d are identical but different in dimension from the lamination sheets 101a, 101b, 101c, 101 d of the other packs 100a, 100b, 100c, 100d.

Preferably, the lamination sheets 101a, 101c, 101c, 101d of different packs 100a, 100b, 100c, 100d are chosen so as to be multiple of a module of lamination sheet. In one example, the module of lamination sheet has seven teeth and six slots.

According to one embodiment, the lamination sheets 101a, 101 b, 101c, 101d of each pack 100a, 100b, 100c, 100d have teeth 102 with increased width at opposite ends in order to balance the flux linkage and align the back EMFs among and within different packs. These teeth 102, which are referred here as “end teeth” or “outer teeth” preferably have a different connection radius compared to the inner teeth 102. This is shown in figures 6(a), (b) and (c).

In other embodiments (not illustrated) the primary 100 comprise further packs arranged so as to prolong the tubular configuration in the predefined direction A-A. The further packs have an analogous structure of the packs 100a, 100b, 100c, 100d already described, with lamination sheets being multiple of the module of lamination sheet.

Therefore, as said, the packs can be identical or can differ, but in general they are obtained as multiple of the module with six slots.

According to one embodiment, the linear Vernier machine 1 further comprises means for fixing 140 the primary 100 to the casing 2 in a suspended way within the internal cavity 3.

In particular, the means for fixing 140 the primary 100 to the casing 2 comprises a plurality of rods, for example made of steel.

For each pack 100a, 100b, 100c, 100d of the primary 100, a corresponding set of parallel rods 140 comprises rods passing through the corresponding lamination sheets 101a, 101 b, 101c, 101d and protruding with their end portions from opposite sides of the pack 100a, 100b, 100c, 100d.

Preferably, for each pack 100a, 100b, 100c, 100d of the primary 100 the rods 140 are equally distanced and pass through the yokes 104 of the corresponding lamination sheets 101a, 101 b, 101c, 101 d.

In particular, in the yoke 104 of each lamination sheet 101a, 101 b, 101c, 101 d is obtained a plurality of through holes 107 equally distanced for allowing the passage of the rods 140.

The number of through holes 107 of each lamination sheet 101a, 101 b, 101c, 101 d corresponds to the number of rods 140 of the set.

In the embodiment illustrated herewith, the rods 140 are grouped as follows:

- a first set of mutually parallel rods 140 pass through the lamination sheets 101a of the first pack 100a, the rods of the first set being parallel to the first stacking direction B-B;

- a second set of mutually parallel rods 140 pass through the lamination sheets 101 b of the second pack 100b, the rods of the second set being parallel to the second stacking direction C-C;

- a third set of mutually parallel rods 140 pass through the lamination sheets 101c of the third pack 100c, the rods of the third set being parallel to the third stacking direction D-D;

- a fourth set of mutually parallel rods 140 pass through the lamination sheets 101 d of the fourth pack 100d, the rods of the fourth set being parallel to the fourth stacking direction E-E.

The casing 2 has four groups of holes 14, each group being configured to receive the end portions of the rods 140 of the sets of rods.

The holes 14 are preferably blind holes. The holes 14 are dimensioned so as to receive the end portions of the rods 140 protruding from the packs 100a, 100b, 100c, 100d.

Therefore, the primary 100 is arranged in a suspended way in the internal cavity 3, meaning that the primary 100 does not contact the casing 2.

In another embodiment, the primary 100 is fixed with contact to the casing 2 in order to ensure proper mechanical robustness.

In particular, each pack 100a, 100b, 100c, 100d of the primary 100 is glued to one of the inner surfaces of the casing 2.

For example, the first pack 100a, the third pack 100c and the fourth pack 100d are glued to the lower shell 2a of the casing 2, whereas the second pack 100b is glued to the upper shell 2b of the casing 2.

The side plates 2c, 2d of the casing 2 host bearings and cooling fans 5 with protecting grids 6.

In one embodiment, the fans 5 are mounted on one of the side plates (for example 2d) so that air flows within the whole linear Vernier machine 1 and cools the losses generated within the winding assembly 120 and the primary 100 and flows out on the other side plate (for example 2c) which might not have fans but only the protecting grids 6.

The winding assembly 120 comprises a plurality of identical coils 121 . Preferably, the winding assembly 120 is a multi-phase winding.

More preferably, the winding assembly 120 is a three-phase winding.

Each coil 121 is made of a wire of an electrically insulated conductor, preferably copper or aluminum. Each coil 121 can be either impregnated with varnish or potted with epoxy resin to improve mechanical stiffness of the winding and thermal conductivity.

Each coil 121 has a number of turns that is chosen in order to reach the desired voltage.

Preferably, each coil 121 is wound around in order to form flat stacked layers of multiple turns. For example, in figure 8 each coil 121 shows two flat stacked layers of 16 turns each, for a total of 32 turns.

According to one embodiment, each coil 121 has an overall rectangular shape with rounded comers.

The coils 121 may be easily wound with an automated process and inserted in the primary 100 during the assembly.

The coils 121 of the winding assembly 120 are mutually parallel and aligned along the predefined direction A-A.

In particular, the coils 121 are non-overlapping.

According to one aspect of the invention, the winding assembly 120 is arranged with the coils 121 housed in the slots 103 of the packs 100a, 100b, 100c, 100d of the primary 100.

In other words, the slots 103 accommodate the coils 121. In particular, each coil 121 pass through all the packs 100a, 100b, 100c, 100d of the primary 100.

Each coil 121 is partially housed in a slots row 106 of each pack 100a, 100b, 100c, 100d of the primary 100.

In particular, each coil 121 is wound around in order to form stacked layers of multiple turns along the slot width s_w, referring to each pack 100a, 100b,

100c, 100d.

In particular, each coil 121 has a first straight portion 121a housed in a slots row 106 of the first pack 100a, a second straight portion 121 b housed in a slots row 106 of the second pack 100b, a third straight portion 121c housed in a slots row 106 of the third pack 100c, and a fourth straight portion 121 d housed in a slots row 106 of the fourth pack 100d. Each coil 121 also has connecting portions 121 e, 121f, 121g, 121 h which connect the straight portions 121a, 121b, 121c, 121 d.

Preferably, each coil 121 has an overall rectangular shape with rounded corners where the straight portions 121a, 121 b, 121c, 121 d represent the sides of the rectangle and the connecting portions 121 e, 121f, 121g, 121 h represent the rounded comers or vertexes of the rectangle.

Stacking layers of multiple turns allows to completely fill the slots 103 of the primary 100 with electrically conductive material and to improve the efficiency by reducing the stator winding resistance.

Assuming a module of lamination sheet with seven teeth and six slots, there are six coils fitted in the slots.

The secondary 110 comprises an elongated core 111 having a main development axis F-F and bearing a plurality of permanent magnets 112.

In particular, each permanent magnet 112 consists in a block of parallelepiped shape. For example, each permanent magnet 112 is a plate-like body.

Preferably, the permanent magnets 112 are fixedly mounted with alternating polarity on outer surfaces of the elongated core 111.

According to one embodiment of the invention, the permanent magnets 112 are glued on the outer surfaces of the elongated core 111.

In the illustrated embodiment, the elongated core 111 is substantially shaped as a parallelepiped and the permanent magnets 112 are fixedly mounted (for example glued) on the outer faces of the parallelepiped.

Preferably, the elongated core 111 comprises a plurality of blocks 113 stacked together along the main development axis F-F.

According to the embodiment illustrated herewith, the blocks 113 are kept together by connecting means, such as for example screws 114.

In the illustrated embodiment, each block 113 is substantially shaped as a parallelepiped, so that the assembly of all the blocks 113 results in an elongated core 111 that is also shaped as a parallelepiped.

Preferably, the permanent magnets 112 cover all the faces of each block 113.

Each block 113 can be either with a single magnetic pole or multiple poles according to the main development axis F-F. The permanent magnets 112 are preferably equally spaced.

Preferably, each block 113 is segmented (which means laminated) in order to reduce eddy currents losses within the permanent magnets 112.

According to the illustrated embodiment, the secondary 110 has two shafts 115 passing through the elongated core 111. This configuration serves to minimize the secondary’s weight to outer surface ratio, ensuring a low inertia, and at the same time show enough space to host the two shafts 115 and secondary’s yoke for flux closure.

In alternative embodiment, the shafts 115 can be more than two.

The blocks 113 have through-holes 116 for fitting the shafts 115 as a mechanical support able to transfer the thrust in a distributed manner to the external load and to be guided in the moving direction, which is the main development axis F-F.

Additional steel reinforcement bars 117, shown in figure 10, can be added to provide additional rigidity to the secondary 110.

For example, these bars 117 are made of two steel parts that can be screwed together to lock in the blocks 113.

Additionally, the blocks 113 can be glued together and fixed to the shafts 115 by either glue, fixed by interference or fixed by other means such as tolerance rings or a ring locking mechanism.

It is extremely important that the secondary 110 is supported properly to guarantee mechanical reliability and enough stiffness to prevent the secondary 110 from bending. The placement of the secondary 110 (which is usually the mover) in the center of the tubular configuration of the primary 100 (which is usually the stator) is extremely important as the magnetic force unbalance due to eccentricity can be critical.

In an alternative embodiment (not illustrated), the elongated core 111 is substantially shaped as a cylinder and the permanent magnets 112 are fixedly mounted (for example glued) on the outer surface of the cylinder.

Preferably, the secondary 110 is coaxially arranged inside the primary 100 and the winding assembly 120.

In particular, the secondary 110 is arranged within the internal cavity 3 with its main development axis F-F that is parallel to the predefined direction A- A, as shown in figure 1 .

The secondary 110 passes through the tubular cavity defined by the coils 121 of the winding assembly 120 and is partially surrounded by the four packs 100a, 100b, 100c, 100d of the primary 100. This is shown in figure 5.

The secondary 110 is distanced from the primary 100, so that the permanent magnets 112 do not contact the primary 100.

In particular, a first air gap 130a is obtained between the secondary 110 and the first pack 100a, a second air gap 130b is obtained between the secondary 110 and the second pack 100b, a third air gap 130c is obtained between the secondary 110 and the third pack 100c, and a fourth air gap 130d is obtained between the secondary 110 and the fourth pack 100d.

The air gaps 130a, 130b, 130c, 130d are preferably of the same thickness in order to have a magnetic and force balance. In an alternative variant, it is possible to have unequal gaps, a controlled eccentricity, and use the magnetic unbalance to compensate for the weight of the secondary 110.

The number of teeth s of each lamination sheet 101a, 101 b, 101c, 101d is chosen in combination with the pole pair number p of the corresponding winding assembly 120 and the number of pairs m of permanent magnets 112 in the secondary 110, according to the condition:

Hl — S = — p

Each lamination sheet 101a, 101 b, 101c, 101d of the primary 100 is made of a ferromagnetic material in order to carry the magnetic flux through the teeth 102 and the yoke 104.

In particular, each lamination sheet 101a, 101b, 101c, 101d is made of one of the following materials: iron, nickel, cobalt.

Preferably, the lamination sheets 101a, 101 b, 101c, 101 d are iron based to improve manufacturability and to enhance performance.

The elongated core 111 of the secondary 110 is also made of a ferromagnetic material, in particular a soft ferromagnetic material.

Preferably, the elongated core 111 is made of a Soft Magnetic Composite.

Soft Magnetic Composites (shortly SMC) are made of ferromagnetic powder particles (for example iron powder particles) coated with an insulating layer.

The permanent magnets 112 are made of one of the following: NdFeB, SmCo, Ferrite. Alternatively, any other hard magnetic material that allows permanent magnetization can be used.

The embodiment illustrated herewith has a three-phase distributed winding assembly 120 with p=1 placed in six slots 102 and the secondary has ten magnets which means m=5.

The example is a base case, meaning that, depending on the performance needs, multiple of this base case can be aligned in a modular way. The tooth width t_w to slot width ratio s_w is found to be optimal with the following condition: t z

0.8 < — < 1.2 sw

This ratio allows to maximize thrust and to minimize thrust ripple.

For the end teeth 102 on the two sides of each lamination sheets 101a, 101 b, 101c, 101d, the optimal thickness is found with the following condition:

The teeth 102 are preferably rounded on the edge facing the airgaps 130a, 130b, 130c, 130d in order to reduce the cogging thrust and to reduce the harmonic content of the back EMF. The teeth rounding radius r_r is found to be optimal with the following condition: 0.5 < < 3

According to a preferred embodiment, the primary 100 is a stator and the secondary 110 is a mover.

In particular, the packs 100a, 100b, 100c, 100d are stator components. Therefore, the stator is a multi-stator.

The stator components or packs 100a, 100b, 100c, 100d are fixed parts, whereas the mover 110 is movable with respect to the stator components 100a, 100b, 100c, 100d.

The mover 110 is slidable along the main development axis F-F with respect to the stator components 100a, 100b, 100c, 100d, which surround the mover 110.

In this embodiment, the mover 110 bearing the permanent magnets 112 linearly moves within the ferromagnetic stator components 100a, 100b, 100c, 100d, thus inducing the magnetic flux therein.

The airgaps 130a, 130b, 130c, 130d separate the mover 110 from the stator components 100a, 100b, 100c, 100d. According to an alternative embodiment, the primary 100 is a mover and the secondary 110 is a stator.

In particular, the packs 100a, 100b, 100c, 100d are mover components.

The stator 110 is the fixed part, whereas the mover components or packs 100a, 100b, 100c, 100d are movable with respect to the stator 110.

The mover components 100a, 100b, 100c, 100d are slidable with respect to the stator 110 along directions which are parallel to the predefined direction A-A.

The characteristics of the linear Vernier machine proposed herewith emerge clearly from the above description, as do the advantages.

The proposed linear Vernier machine presents a high torque/thrust density and is particularly attractive for low-speed direct drive applications.

The main advantages compared to existing solution are given from a combination of multiple-stator tubular configuration and modular mover assembly.

In particular, by adjusting the number of modules which are aligned in the main development direction, the linear Vernier machine can be tailored to meet specific thrust requirements

In addition, the construction of the stator windings is simplified with respect to known solutions, improving reliability, cost, and efficiency of the machine.

The non-overlapping stator winding assembly is intrinsically well isolated and has shorter end windings reducing the non-active conductor material. The manufacturing and assembly of the stator winding is also greatly improved.

In addition, the mechanical stiffness of the mover is significantly improved. Furthermore, the thrust is transferred in a distributed manner and the machine achieves overall mechanical robustness.

Claims

1 . A linear Vernier machine (1 ) comprising:

- a primary (100) comprising at least two packs (100a, 100b) having a main development parallel to a predefined direction (A-A), each pack (100a, 100b) comprising a plurality of stacked lamination sheets (101a, 101 b) having teeth (102) and slots (103) distributed according to an alternating arrangement;

- a secondary (110) interposed between the at least two packs (100a, 100b) of the primary (100), the secondary (110) comprising a plurality of permanent magnets (112);

- a winding assembly (120) comprising a plurality of coils (121 ) which are mutually parallel and aligned along the predefined direction (A-A), said coils (121 ) being fitted in the slots (103) of the lamination sheets (101a, 101 b) of the at least two packs (100a, 100b), the winding assembly (120) surrounding the secondary (110), characterized in that each tooth (102) of the lamination sheets (101a, 101 b) has a tooth width t_lv and each slot (103) of the lamination sheets

(101 a, 101 b) has a slot width s_w according to the following condition: t'W

0.8 < — < 1.2 sw

2. The linear Vernier machine (1 ) according to claim 1 , wherein the secondary (110) is distanced from the at least two packs (100a, 100b) of the primary (100), corresponding air gaps (130a, 130b) being obtained between each pack (100a, 100b) and the secondary (110).

3. The linear Vernier machine (1 ) according to claim 2, wherein the air gaps (130a, 130b) are of the same thickness in order to have a magnetic and force balance.

4. The linear Vernier machine (1 ) according to claim 2, wherein the air gaps (130a, 130b) are not equal.

5. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein the teeth (102) are rounded with a rounding radius n according to the following condition: 0.5 < < 3

6. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein the lamination sheets (101a, 101 b) of each pack (100a, 100b) have two outer teeth (102) with increased width and with a different connection radius compared to inner teeth (102).

7. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein the primary (100) comprises four packs (100a, 100b, 100c, 100d) having a main development parallel to the predefined direction (A-A), said packs (100a, 100b, 100c, 100d) being arranged in a tubular configuration which surrounds the secondary (110), each pack (100a, 100b, 100c, 100d) comprising a plurality of stacked lamination sheets (101a, 101 b, 101c, 101d) having teeth (102) and slots (103) distributed according to an alternating arrangement.

8. The linear Vernier machine (1 ) according to claim 7, wherein the lamination sheets (101a, 101 b, 101c, 101d) of each pack (100a, 100b, 100c, 100d) are parallelly aligned and stacked in such a way as to define a plurality of rows (105) of corresponding teeth (102) and a plurality of rows (106) of corresponding slots (103), each coil (121 ) of the winding assembly (120) passing through one of the rows (106) of slots (103) of each pack (100a, 100b, 100c, 100d) of the primary (100).

9. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein each coil (121 ) of the winding assembly (120) is wound around in order to form flat stacked layers of multiple turns.

10. The linear Vernier machine (1 ) according to claim 8 or 9, wherein each coil (121 ) of the winding assembly (120) has an overall rectangular shape.

11. The linear Vernier machine (1 ) according to claim 10, wherein each coil (121 ) of the winding assembly (120) has four straight portions (121 a, 121 b, 121 c, 121 d) and four connecting portions (121 e, 121f, 121 g, 121 h), each of the four straight portions (121 a, 121 b, 121 c, 121 d) being housed in a corresponding row (106) of slots (103) of one of the four packs (100a, 100b, 100c, 100d), said connecting portions (121 e, 121f, 121 g, 121 h) connecting the straight portions (121a, 121 b, 121 c, 121 d), said straight portions (121a, 121 b, 121 c, 121 d) representing the sides of a rectangle and said connecting portions (121e, 121f, 121 g, 121 h) representing the rounded corners of said rectangle.

12. The linear Vernier machine (1 ) according to any one of claims 8 to 11 , wherein said coils (121 ) are non-overlapping.

13. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein the secondary (110) comprises an elongated core (111 ) having a main development axis (F-F) which is parallel to said predefined direction (A-A), the permanent magnets (112) being fixedly mounted with alternating polarity on outer surfaces of the elongated core (111 ).

14. The linear Vernier machine (1 ) according to claim 13, wherein the elongated core (111 ) is made of a Soft Magnetic Composite.

15. The linear Vernier machine (1 ) according to claim 13 or 14, wherein the permanent magnets (112) consist in plate-like bodies glued on the outer surfaces of the elongated core (111 ).

16. The linear Vernier machine (1 ) according to any one of claims 13 to 15, wherein the elongated core (111 ) comprises a plurality of blocks (113) stacked together along the main development axis (F-F).

17. The linear Vernier machine (1 ) according to claim 16, wherein each block (113) is substantially shaped as a parallelepiped, so that the assembly of all the blocks (113) results in an elongated core (111) that is also shaped as a parallelepiped.

18. The linear Vernier machine (1 ) according to claim 16 or 17, wherein the blocks (113) are screwed or glued together.

19. The linear Vernier machine (1 ) according to any one of claims 13 to

18, wherein the permanent magnets (112) are equally spaced.

20. The linear Vernier machine (1 ) according to any one of claims 13 to

19, wherein the secondary (110) has two shafts (115) passing through the elongated core (111 ).

21. The linear Vernier machine (1 ) according to any one of the preceding claims, further comprising a casing (2) having a main development along said predefined direction (A-A) and delimiting an internal cavity (3), the casing (2) comprising two elongated shells (2a, 2b) that are joined together and define a hollow tubular frame and two side plates (2c, 2d) for closing the ends of hollow tubular frame, said internal cavity (3) housing the primary (100), the secondary (110) and the winding assembly (120).

22. The linear Vernier machine (1 ) according to claim 21 , further comprising means for fixing (140) the primary (100) to the casing (2) in a suspended way within the internal cavity (3).

23. The linear Vernier machine (1 ) according to claim 22, wherein said means for fixing (140) comprises one set of parallel rods for each of the at least two packs (100a, 100b) of the primary (100), said rods (140) passing through the lamination sheets (101a, 101 b) of the corresponding pack (100a, 100b) and protruding with end portions from opposite sides of the pack (100a, 100b) for being fixed to the casing (2).

24. The linear Vernier machine (1 ) according to claim 23, wherein the rods (140) of each set of rods are equally distanced and pass through yokes (104) of the corresponding lamination sheets (101a, 101 b) from where the teeth (102) originate.

25. The linear Vernier machine (1 ) according to claim 21 , wherein the primary (100) is fixed with contact to the casing (2).

26. The linear Vernier machine (1 ) according to claim 25, wherein the at least two packs (100a, 100b) are glued to inner walls of the casing (2).

27. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein each lamination sheet (101a, 101 b) of the at least two packs (100a, 100b) is made of a ferromagnetic material.

28. The linear Vernier machine (1 ) according to claim 27, wherein each lamination sheet (101a, 101b) of the at least two packs (100a, 100b) is made of one of the following materials: iron, nickel, cobalt.

29. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein said permanent magnets (112) are made of one of the following materials: NdFeB, SmCo, Ferrite.

30. The linear Vernier machine (1 ) according to any one of the preceding claims, wherein said primary (100) is a stator and said secondary (110) is a mover.

31. The linear Vernier machine (1 ) according to any one of the claims 1 to 29, wherein said primary (100) is a mover and said secondary (110) is a stator.