WO2023241798A1

WO2023241798A1 - Switched reluctance machine and method for operating a switched reluctance machine

Info

Publication number: WO2023241798A1
Application number: PCT/EP2022/066417
Authority: WO
Inventors: Sebastian Heinz Pohr
Original assignee: Sebastian Heinz Pohr
Priority date: 2022-06-15
Filing date: 2022-06-15
Publication date: 2023-12-21

Abstract

The invention relates to a switched reluctance machine. The stator (3) and the rotor (2) have a respective plurality of teeth (4, 5), wherein the teeth (5) of the rotor (2) are moved past the teeth (4) of the stator (3) in a movement direction (57) during an operation of the reluctance machine (1), and at least one of the two lateral walls (50-53) of at least one of the teeth (4, 5) which delimits the respective tooth (4, 5) in the movement direction (57) has a bending point (12, 13), by means of which the cross-section (8, 10) of the respective tooth (4, 5) expands on the bending point (12, 13) side facing the air gap (18) in order to form a tooth head (14, 15) of the respective tooth (4, 5). The height (11, 16) of each tooth head (14, 15) is less than a fifth or a sixth of the width (9) of the respective tooth (4, 5), and the height (11, 16) of each tooth head (14, 15) equals the distance from the bending point (12, 13) to the end face (55, 56) which terminates the respective tooth (4, 5) with respect to the air gap (18). The width (9) of each tooth (4, 5) equals the minimum spacing between the two lateral walls (50- 53) outside the tooth head (14, 15), said lateral walls delimiting the respective tooth (4, 5) in the movement direction (57), and the tooth head (14, 15) extends beyond the respective bending point (12, 13) by at least 135% or at least 150% of the height (11, 16) of the respective tooth head (14, 15) in the movement direction (57).

Description

Switched reluctance machine and method for operating a switched one

Reluctance machine

The invention relates to a switched reluctance machine with a stator and a rotor, which are spaced apart from one another by an air gap, the stator and the rotor each having a plurality of teeth, the teeth of the rotor being on the teeth of the stator when the reluctance machine is operated in a direction of movement are guided past, with at least one of the two side walls that delimit the respective tooth in the direction of movement having a kink through which the cross section of the respective tooth widens on the side of the kink facing the air gap in order to form a tooth tip of the respective tooth. In addition, the invention relates to a method for operating a switched reluctance machine.

Reluctance machines are based on the physical principle that systems strive for a state of minimal magnetic resistance.

For example, a rotatable or displaceable yoke will always be arranged with respect to a pair of coils such that the magnetic circuit has a minimum magnetic resistance. In reluctance machines, this is used to exert a torque or force on a rotor by specifying the direction of a magnetic field or by switching magnetic fields sequentially. In synchronous reluctance machines, a rotating magnetic field is used, while in switched reluctance machines, highly pronounced tooth structures on the rotors and stator are used, with a magnetic field of a respective stator pole pair being switched on at a certain point in time at which a relatively small coverage area between the stator teeth of the stator pole pair and the rotor teeth of a pair of rotor teeth is present. Since the magnetic resistance for the stator pole pair decreases when this coverage area increases, this results in a torque in a rotary machine or a driving force in a linear drive. Switched reluctance machines are robust, can be set up with little effort and can typically achieve higher torques than synchronous reluctance machines at low speeds with the same size. Nevertheless, in many applications it would be advantageous to achieve forces or

To further increase torques under otherwise essentially the same boundary conditions.

The invention is therefore based on the object of further increasing the performance of a switched reluctance machine.

The object is achieved according to the invention by a reluctance machine of the type mentioned, with a height of the respective tooth head being less than a fifth or smaller than a sixth of a width of the respective tooth, the height of the respective tooth head being equal to the distance of the bend point from one of the respective ones Tooth is the end surface closing towards the air gap and the width of the respective tooth is equal to the minimum distance between the two side walls delimiting the respective tooth in the direction of movement outside the tooth head, the tooth head being at least 135% or at least 150% of the height of the respective tooth head in the direction of movement extends beyond the respective kink point.

It is already known to use tooth heads on the teeth of the stator and/or the rotor of a reluctance machine in order to shape the force or torque curve, for example in order to reduce torque gaps. Corresponding tooth heads have a relatively large height in the extension direction of the respective tooth, for example at least a third or at least half of the width of the tooth neck, in order to achieve a relatively low reluctance or a relatively high flux density even when the tooth heads are exclusively overlapped without an overlap of the tooth necks achieve, as this initially appears to be advantageous for achieving high forces or torques. In the context of the invention, however, it was recognized that by using tooth heads with a small height or extension perpendicular to the air gap, saturation of the tooth material in a saturation zone that crosses the air gap can be achieved, while in the tooth neck outside the tooth head, for example, a maximum of 70% - 85% of the saturation magnetization of the tooth material can be achieved. By choosing a sufficient width of the tooth head in such a way that it extends in the direction of movement by at least 135% or at least 150% beyond the respective kink point, it is achieved that the field guide cross section in the area of the saturation zone is essentially smaller than during the entire overlap of a pair of teeth is the overlap area and thus the field guide cross section in the area of the tooth end surfaces. This makes it possible to avoid saturation in the area of the tooth end surfaces outside the saturation zone.

For that portion of the flux density that exceeds the saturation flux density, this saturation zone acts as a type of additional air gap. However, since the saturation zone runs obliquely to the air gap and to the direction of movement, this means that the field lines crossing the air gap in the area of the saturation zone are no longer perpendicular to the direction of movement of the rotor teeth and thus an additional force in the direction of movement or an additional torque due to the attractive force between Rotor and stator can exert on the rotor. In addition, as the overlap of the teeth increases, the length of the saturation zone increases, which corresponds to an increase in the area of a usual air gap, which means that if an approximately constant thickness of the saturation zone is assumed when the overlap changes, this is similar to an extension of the overlap of the tooth end surfaces An additional reluctance force results in the area of the air gap.

The described design of the tooth heads results in a saturation zone crossing the air gap when the reluctance machine is operated with sufficient field strengths, through which additional forces or torques can be provided to drive the rotor. Through geometric considerations it can be estimated that when the same is achieved Flux density in the air gap by using the saturation zone crossing the air gap over a wide range of crossing angles of the saturation zone and thus over a large working stroke, significantly higher torques or driving forces can be achieved than would be achieved without the presence of such a saturation zone. However, it should be noted that when using such a saturation zone to achieve the same flux density in the air gap, due to the necessary saturation of the tooth material and the relatively high resulting flux densities in the area of other bottlenecks, a generally higher magnetization power is typically achieved than in conventional reluctance machines in which such saturation is required avoided is necessary. Therefore, if the switched reluctance machine according to the invention is designed to have the same magnetization power as a conventional switched reluctance machine, higher useful forces or torques can still be achieved than with this, but the increase will be smaller than if the same flux density in the air gap was achieved.

The two side walls of a tooth in the direction of movement are a front and a back side surface in the direction of movement. At the bend point, the angle between the respective side surface and the direction of movement changes. In particular, the angle is reduced at this point, so that the respective side wall on the air gap side of the bend point is guided away from the center of the tooth and thus expands the tooth cross section. The side surface can also run parallel to the direction of movement beyond the bend point, for example to form a rectangular tooth head or something similar. It is even possible for the angle between the side surface and the direction of movement to change its sign, so that the side surface can, for example, run away from the air gap again after reaching the kink, so that a section of the side wall above and below the kink can lie opposite one another.

The direction of extension of the teeth can be essentially perpendicular to the

direction of movement. The direction of movement is for rotary machines the circumferential direction and can also be location-dependent in linear machines, for example if the rotor is guided along a curved stator.

The reluctance machine can be an internal or external rotor or a disk rotor, in which case an approximately cylindrical stator body can be used. Alternatively, the reluctance machine may be a linear machine with a stator that extends along a movement path of the rotor in the direction of movement. The height of the tooth head is measured in particular in the extension direction of the tooth and can therefore be the distance between the bend point and the point of the end surface at which a straight line in the extension direction that intersects the bend point intersects the end surface. Since the kink of a sidewall or surface is an extended structure, the distance along the kink can vary, but remains below the specified limit for the height of the stator tooth.

The side surface and the end surface of the respective tooth can extend essentially parallel to an axial or depth direction of the reluctance machine. The side surfaces are in particular essentially perpendicular to the direction of movement.

To the extent that orientations are described as essentially vertical, essentially parallel or similar, deviations of less than 20°, less than 10° or less than 5° may be permissible, with in particular only tolerance-related deviations being permissible.

The reluctance machine can include a field application device for applying a magnetic field to the teeth, the maximum field strength of the magnetic field and the material of the teeth being selected such that the saturation flux density in at least one area of the respective tooth outside the tooth tip is between 1.15- times and 1.4 times the maximum magnetic flux density achieved in this area during operation of the reluctance machine. The higher the magnetic flux densities permitted outside the tooth tip, the greater the length of the saturation zone that the saturation flux density can be achieved with an otherwise identical design of the reluctance machine. This is relevant because the saturation zone typically engages the kink of a side wall of one of the overlapping teeth on one side and the opposite end or a kink of the opposite side wall of the other of the overlapping teeth on the other side. Thus, the minimum length of the saturation zone is typically achieved with minimal overlap of the tooth necks in the direction of movement and with increasing overlap of the end surfaces of the teeth in the direction of movement, the saturation zone extends until saturation can no longer be maintained due to the limitation of the magnetic flux density outside the tooth head .

The maximum length of the saturation zone and thus the maximum magnetic flux density outside the tooth head thus limit the working stroke of the reluctance machine, via which the additional forces or torques mentioned can be provided. It would therefore initially be advisable to allow the highest possible magnetic flux density outside the tooth tip. At the same time, however, this would mean that in order to achieve the same flux density in the air gap, a significantly higher magnetization power would be required due to the nonlinearity of the magnetization near the saturation limit. However, the flux density in the air gap determines the usable forces or torques that can be achieved, which means that the use of very high magnetic flux densities outside the tooth tip would lead to a reduction in the usable forces or torques for a given magnetization power.

The two effects mentioned above therefore lead to contradictory requirements regarding the magnetic flux density to be used outside the tooth head and thus the field strength with which the teeth are exposed. As part of the development of the invention, it was recognized that the choice of maximum achieved in the area outside the tooth tip magnetic flux density according to the above specification represents a good compromise between the requirements, which at least approximately enables optimal torques or useful forces for a given magnetization power.

The corresponding design of the field application device can be carried out, for example, by appropriate parameterization or design of a control for coils or other field application means or a corresponding programming of a corresponding control device.

The appropriate maximum achieved magnetic flux density and the geometry of the tooth heads, in particular their height h, are mutually dependent if an optimal design of the reluctance machine is to be achieved. The optimal height h of the tooth heads can be given approximately as follows for a given width b, a given ratio of saturation flux density and the maximum magnetic flux density x achieved in the area outside the tooth head and thickness of the air gap d:

The tooth head extends beyond the respective kink point by at least 135% or at least 150% of the height of the respective tooth head in the direction of movement. While, for example, in reluctance machines with a relatively large number of teeth it can be advantageous to use relatively short tooth heads, according to the invention a certain minimum length should be maintained in the reluctance machine explained, which uses a saturation zone crossing the air gap.

This is relevant because the saturation zone penetrates into the tooth tip up to a certain height, which typically depends on the height. However, if the saturation zone extends to the end of the tooth tip, all of the advantages mentioned of extending over an air gap are typically no longer achieved extending saturation zone is reached, since at least in one of the teeth in the area of the end surface on one side of the saturation zone no unsaturated tooth material remains. Ideally, an approximately linear magnetization, i.e. a magnetic flux density below the saturation flux density of the tooth material, is achieved in areas of the tooth heads, particularly in the region of their lateral edges.

The height of the respective tooth head is preferably greater than one twelfth or greater than one tenth of the width of the respective tooth. As will be explained later with reference to FIG. 4 using an example, the magnetic flux guided through the saturation zone must be dissipated either directly via the air gap into the other tooth or indirectly via the lateral region of the tooth tip. If the sum of the area of the interface towards the lateral extension of the tooth tip and the area of the interface towards the air gap is not sufficiently larger than the area of half the length of the saturation zone, then the area of the tooth material lying on the air gap side of the saturation zone would also necessarily be completely saturated and that The same would also apply to the area of the end surface of the opposing tooth. In the case of tooth heads with a very low height, provision of the additional force or additional torque would therefore only be possible via a small working stroke. In order to achieve a large working stroke for the additional forces, it is advisable to adhere to the minimum heights of the tooth head specified above.

As already explained above, the additional forces due to the saturation zone crossing the air gap should be achieved over the largest possible working stroke, i.e. over the largest possible movement length in the direction of movement of the rotor tooth with respect to the stator tooth. A positive force contribution typically results from exceeding the point at which the saturation zone crosses the air gap vertically, which can be the case, for example, if a kink in the front side wall of the rotor tooth in the direction of movement passes the kink in the rear side wall of the stator tooth in the direction of movement. The additional force contribution is present as long as the tooth material of the stator or rotor tooth is completely saturated can be maintained at the kinks mentioned. The movement distance or the rotation angle between the two points mentioned can therefore be viewed as the working stroke.

If it is assumed that the width of the respective tooth represents the maximum constriction of the field guide with sufficient overlap of the end faces of a stator and rotor tooth, then the highest magnetic flux density outside of the tooth neck typically results in the area of width measurement, i.e. in the area of the narrowest point of the tooth neck Tooth tip or outside the saturation range. If, as explained above, the ratio of the saturation flux density to the maximum magnetic flux density achieved in this area during operation of the reluctance machine is denoted by x, it follows that the width b of the tooth should be at least x times the length I of the saturation zone .

If exactly one respective kink point is used on the side walls between which the saturation zone extends and this results in a substantially constant width of the respective tooth, for example on the side of this kink point facing away from the air gap, this can be determined on the basis of geometric considerations which will be referred to later 5 are explained in more detail, it can immediately be seen that the working stroke must necessarily be smaller than the width of the respective tooth, which in this case in particular corresponds to the distance of the kinks on the opposite side walls of the respective tooth or the distance of the kink of a side wall from the opposite side wall can correspond. It may therefore be expedient to modify the geometry of the tooth above the tooth head, which is discussed in more detail below.

At least one of the two side walls of at least one of the teeth can have a further kink that is further away from the air gap than the kink, the cross section of the respective tooth widening in an intermediate region between the further kink and the kink. The saturation zone is in this case, as will be referenced later in an example will be explained on Fig. 17, is not fixedly arranged at the kink, but can, depending on the position of the rotor tooth within the working stroke, slide between the kink and the further kink in order to set a minimum length of the saturation zone. To make this possible, in particular the angle between the direction of movement and the side wall in the intermediate region can be larger than in the tooth head or on the side of the kink facing the air gap, but smaller than on the side of the further kink facing away from the air gap. This results in a multi-stage widening of the tooth towards the air gap.

With essentially the same shape or mirror symmetry of the intermediate regions of opposing teeth of the rotor and stator, a very wide saturation zone can potentially result, since the narrowing of the flux guide cross section, which leads to the saturation zone, can be limited by essentially parallel side walls of the intermediate regions and thus extends along the entire side wall can extend in the intermediate area. This results in a high reluctance and thus typically a reduction in the flux density in the air gap and thus in the useful power or torque provided. Approaches to avoid this are discussed below.

The teeth of the stator or the rotor can have a maximum of one kink per side wall. In other words, in this case, teeth with several kinks in a respective side wall are used only on the rotor side or only on the stator side. The use of only one kink means that the narrow section of the river flow that creates the saturation zone is short, as it only extends directly around the kink, which avoids the problem discussed above.

Alternatively, it is possible that the teeth of the stator and the rotor each have the and the further kink in at least one of their side walls, whereby the cross section of the respective tooth widens in an intermediate region between the kink and the further kink, whereby the Intermediate area of the teeth of the rotor has a shape that differs from the shape of the intermediate area of the teeth of the stator in such a way that the shapes cannot be converted into one another by rotating or mirroring. The different shape of the intermediate areas prevents the constriction of the flow guide cross section, which causes the saturation zone, from being limited by parallel side walls, which means that the problem discussed above can also be avoided.

Preferably, all of the teeth of the rotor and the stator either have at least one kink on exactly one of the side walls to form the tooth head or have at least one kink on both of the side walls to form the tooth head. By using kinks on teeth of the rotor and the stator, in particular in such a way that the kinks are provided on the front side wall of the rotor's tooth in the direction of movement and in the rear side wall of the stator's tooth in the direction of movement, a robust formation of the saturation zone can be achieved sufficient working stroke can be achieved. If, on the other hand, kinks are only provided on one of the opposing teeth, this can result in the saturation zone reaching the air gap, but not completely crossing it, which means that the advantages explained above can only be achieved to a limited extent.

If only one running direction of the reluctance machine is required, it is sufficient if the teeth have a kink on one of the side walls. In this case, the result is a highly asymmetrical tooth head, which in particular only extends in one direction beyond the tooth neck, which can be advantageous for reasons of installation space, especially if a reluctance machine with a relatively large number of stator or rotor teeth is to be used.

If, on the other hand, both running directions are to be used, it is advantageous to provide kinks on both side walls of the respective tooth so that the tooth head extends in both directions beyond the tooth neck to achieve the advantages explained for both directions of rotation and movement of the runner.

The reluctance machine can include the or a field application device, which is set up to apply a magnetic field to the teeth in such a way that in each tooth head, as part of the movement of the rotor with respect to the stator, at least temporarily the magnetic flux density in a section of the tooth head, which is in particular from the Ends of the tooth head are spaced apart in the direction of movement, the saturation flux density of the material of the respective tooth is reached or exceeded. This property of the switched reluctance machine can be checked, for example, by a simulation or, for example, the surface magnetization in the area of the end surfaces facing the air gap can be checked if the saturation zone extends to the end surface. In principle, magnetic saturation of the tooth material can be achieved for any tooth shape with sufficiently large fields, so that, for example, suitable dimensioning and current supply to coils of the reluctance machine is sufficient to implement this feature. Through the geometric design of the teeth explained above, in particular through the limitation of the tooth tip height, it can be achieved that saturated sections of opposing tooth tips form the saturation zone crossing the air gap and thus the additional force or torque contributions explained above can be realized.

The reluctance machine can comprise the or a field application device which is set up to apply a magnetic field to the teeth in such a way that at least during a partial interval of the time interval during which the end surfaces of a respective tooth of the stator and the rotor facing the air gap are at least partially in the direction of movement overlap, resulting in saturation zones overlapping in the direction of movement in these end surfaces, in which the magnetic flux density reaches or exceeds the saturation flux density of the material of the respective tooth. In other words, the reluctance machine can operate be set up in such a way that a saturation zone crossing the air gap results for at least parts of the working stroke of a pair of teeth.

In addition to the switched reluctance machine according to the invention, the invention relates to a method for operating a switched reluctance machine with a stator and a rotor, which are spaced apart from one another by an air gap, the stator and the rotor each having a plurality of teeth, the teeth of the rotor during operation of the Reluctance machine can be guided past the teeth of the stator in a direction of movement, with at least one of the two side walls of at least one of the teeth, which limit the respective tooth in the direction of movement, having a kink through which the cross section of the respective tooth is on the side facing the air gap The kink widens to form a tooth tip of the respective tooth, the teeth being subjected to a magnetic field by a field application device in order to drive the reluctance machine, the

Field application device is operated in such a way that in each tooth head, as part of the movement of the rotor with respect to the stator, the magnetic flux density in a section of the tooth head, which is in particular spaced from the ends of the tooth head in the direction of movement, at least temporarily reaches the saturation flux density of the material of the respective tooth or exceeds.

The method according to the invention can in particular use the reluctance machine according to the invention or the reluctance machine according to the invention can implement the method according to the invention. Regardless of this, the method according to the invention can be further developed with the features explained for the reluctance machine according to the invention with the advantages mentioned there and vice versa.

The tooth material can be saturated by applying sufficiently strong fields to it, for example using suitably dimensioned coils and suitable current supply to the coils during operation the reluctance machine can be used. If the field strength is chosen appropriately, the use of kinks and tooth heads adjoining these leads to the fact that not the entire tooth is saturated, but only a saturation zone, which extends in particular at an angle to the air gap of the reluctance machine, which, as already explained above, creates additional useful forces or .Useful torques of the reluctance machine can be provided.

As explained above, it is advantageous if magnetization occurs outside the saturation zone noticeably below the saturation limit. The field application device can therefore in particular be operated in such a way that the saturation flux density in at least one area of the respective tooth outside the tooth tip is between 1.15 times and 1.4 times the maximum magnetic flux density achieved in this area during operation of the reluctance machine .

Additionally or alternatively, the field application device can preferably be operated in such a way that at least during a partial interval of the time interval during which the end surfaces of a respective tooth of the stator and the rotor facing the air gap at least partially overlap in the direction of movement, saturation zones that overlap in the direction of movement result in these end surfaces, in which the magnetic flux density reaches or exceeds the saturation flux density of the material of the respective tooth.

Further advantages and details of the invention result from the following exemplary embodiments and the associated drawings. Show schematically:

Fig. 1 shows an embodiment of an inventive

Reluctance machine, which is operated according to an exemplary embodiment of the method according to the invention, 2 shows a detailed view of an exemplary embodiment of a reluctance machine according to the invention,

3 shows an exemplary magnetization curve for the material of the teeth of a reluctance machine,

4 - 6 detailed views of exemplary embodiments of the reluctance machine according to the invention,

7 shows an exemplary embodiment of a reluctance machine according to the invention with several stator teeth subjected to a field by a common coil, and

8 - 17 Detailed views of further exemplary embodiments of the reluctance machine according to the invention.

Fig. 1 shows a switched reluctance machine 1 with a stator 3 and a rotor 2. The teeth 4, 5 of the rotor 2 and the stator 3 extend to an air gap 18 which separates the end surfaces 55, 56 of the teeth 4, 5. The reluctance machine 1 includes a field application device 47, which is formed by coils 54 arranged on the teeth 4 of the stator 3.

In the switched reluctance machine, the coils 54 on the opposite teeth 4 of a tooth pair 6 are energized, whereby, due to the reluctance force, a torque is exerted on the rotor 2 in the direction that leads to an increase in the overlap of the end surfaces 56 of the field-actuated tooth pair 6 and the at the time of switching typically already leads with these overlapping end surfaces 55 of a corresponding pair of teeth 5 of the rotor.

In the example, the teeth 4, 5 have a respective kink 12 on both side walls 50, 51 and 52, 53, which limit the respective tooth 4, 5 in the direction of movement 57, i.e. in the circumferential direction in the case of a rotary machine. 13 on. This increases the width 9 of the tooth 4 in the area of the tooth neck and results in an increased width 7 in the area of the tooth head 14, 15, which means that the cross section 8, 10 of the respective tooth, assuming a constant depth of the teeth 4, 5, increases in the direction perpendicular to the image plane, at the respective bend point 12, 13 widens, i.e. lateral expansion areas 58 result.

The use of such tooth heads 14, 15 is known per se and can be used, for example, to achieve a uniform torque curve or to avoid torque gaps. In the switched reluctance machine 1, however, the tooth heads 14, 15 also serve to specifically form a saturation zone that crosses the air gap 18, as will be explained in more detail later. For this purpose, the respective energized coil pair is energized sufficiently strongly by the field application device 47 so that the magnetic flux density in a section of the respective tooth head 14, 15 reaches or exceeds the saturation flux density of the material of the respective tooth 4, 5. The geometry of the tooth heads can ensure that the saturation zone crosses the air gap 18, whereby, as will be explained in more detail later, the available torque of the switched reluctance machine 1 can be increased.

In order to achieve saturation in the tooth head area with not too high magnetization power and at the same time a high flux density in the air gap 18, the height 11 of the respective tooth head 14, 15, which is shown in FIG. 1 only for the teeth 4 of the stator 3, should be smaller than be a fifth or preferably smaller than a sixth of the width 9 of the respective tooth 4, 5. The minimum distance between the two side walls 50, 51 and 52, 53 delimiting the respective tooth 4, 5 in the direction of movement 57 outside the tooth head 14, 15 is considered the width.

The described geometry of the teeth 4, 5 can ensure that the saturation zone is designed to be robust, even if the maximum magnetic flux density in a large part of the tooth 4, 5 outside the tooth head 14, 15 is increased by a factor of 1.15 to 1.4 is smaller than the saturation flux density of the material of the teeth 4, 5. As a result, the magnetization of the tooth 4, 5 can take place outside the saturation zone essentially in the linear region of magnetization, whereby desired flux densities in the air gap 18 can be achieved with acceptable magnetization power.

The formation of the saturation zone 17 crossing the air gap 18 will be explained below with reference to Figures 2 to 5 using the example of a linear machine, since the geometric relationships are easier to understand due to the end faces 55, 56 of the teeth 4, 5 passing one another in a straight line.

In the example, the rotor 2 and thus the only tooth 5 of the rotor shown can be moved in the direction of movement 57, i.e. horizontally in the figure, with respect to the stator 3, of which only one tooth 4 is also shown. Here, in the state shown, a coil (not shown) on the tooth 4 is energized, so that the tooth 5 and thus the stator 2 would be pulled to the right by the reluctance force even without the formation of the saturation zone 17 in order to increase the overlap of the end surfaces 55, 56.

The bend 13 on the front side wall 52 of the tooth 5 and the bend 12 on the rear side wall 51 of the tooth 4 result in a constriction of the field guide through the material, for example sheet metal, of the teeth 4, 5, so that the field guide cross section there is smaller than the cross section 10 in the area of the tooth neck and smaller than the overlap in the area of the tooth end surfaces.

The formation of the saturation zone 17 or the field application used for this is explained below with additional reference to FIG. 3, which shows the magnetization characteristic of the material of the teeth 4, 5, for example electrical sheet metal. Here, the magnetic field strength H is plotted on the x-axis 25 and the magnetic flux density B is plotted on the y-axis 26. Line 27 shows the connection between these variables for the Material of the teeth 4, 5 and the line 28 the corresponding connection for vacuum.

If the field is applied, for example, by a coil running around the tooth 4, the field strength 29 can be adjusted in such a way that a magnetic flux density 30 results outside the tooth head 15 of the tooth 4, in which the magnetization curve 27 increases approximately linearly with the field strength. However, the narrowing of the field guide cross section through the kinks 12, 13 results in magnetization between the kinks 12, 13 at or beyond point 31 and thus beyond the saturation flux density 32. From this point onwards, the flux density varies parallel to the flux density in the vacuum, which is through the line 28 is shown, so that the saturation zone 17 acts approximately as an additional air gap.

Fig. 2 shows schematically the course of the magnetic field lines 19, 20, 21 resulting from the presence of the saturation zone. While the course of the field lines 20, 21 in the area of the air gap 18 essentially corresponds to the course of the corresponding field lines 20, 21 without the presence of the saturation zone 17 corresponds, since the saturation zone there is clearly spaced from the air gap 18, the presence of the saturation zone 17 significantly changes the course of the magnetic field line 19, which crosses the air gap 18 in the area of the saturation zone 17. If the saturation zone 17 were not present, this field line 19 would be essentially perpendicular to the end surfaces 55, 56, so that the magnetic pulling force 22 would run perpendicular to the direction of movement 57 and could therefore not contribute to driving the reluctance machine. The presence of the saturation zone 17, on the other hand, leads to the field line 19 running at an angle to the end surfaces 55, 56, whereby the tensile force 22 is proportional, namely in the example according to a sine function of the angle 46, to the total force 24, which affects the tooth 5 and thus the rotor 2 in Figure 2 pulls to the right, contributes.

A further force contribution results from the fact that the saturation zone 17, as explained, behaves similarly to an air gap, and thus a kind of reluctance force 23 results, which strives to enlarge the interface of the saturation zone 17.

Although this is also angled to the direction of movement 57, it is still included in the total force 24 with a cosine function of the angle 46.

The two additional force contributions mentioned lead to the fact that with the same magnetic flux density in the area of the air gap 18 and the presence of the saturation zone 17, a significantly increased total force 24 or, in the case of a rotary machine, a significantly increased torque typically results than without using the Saturation zone 17 would be provided. However, since the saturation zone 17 increases the overall reluctance of the system, only a slightly smaller but significant gain in force or torque compared to conventional reluctance machines can be expected for the same magnetization power.

As already explained above, a saturation zone 17 results in particular when there is a noticeable restriction of the flow guide cross section through the kinks 12, 13. This results in advantageous dimensions of the tooth heads 15, which will be explained below with additional reference to Figures 4 and 5. 4 already shows a relative position of the teeth 4, 5, which leads to a substantial overlap of the end surfaces 55, 56. 5 shows different positions 41, 42, 43 of the tooth 5 or rotor 2 with respect to the tooth 4 or stator 3, with only the front side wall 51 being shown in dotted or dashed lines for the positions 41, 42.

4, the length 40 of the saturation zone 17 corresponds to the length of the hypotenuse of a triangle, the other side lengths of which are, on the one hand, the distance 39 of the relevant kinks 12, 13 in the direction of movement 57 and, on the other hand, the sum of the heights 11, 16 the tooth heads 14, 15 and the width 33 of the air gap 18.

The ratio of the width 9 of the tooth neck of the tooth 4 to the length 40 of the saturation zone 17 corresponds approximately to the ratio of the saturation flux density of the material of the tooth 4 to the magnetic flux density outside the saturation zone 17, in particular in the tooth necks of the teeth 4, 5. As already explained in the general part, this ratio should be advantageous between 1.15 and 1.4. In order to be able to maintain this ratio over the largest possible displacement path or working stroke of the tooth 5 with respect to the tooth 4, so that the saturation zone 17 can be maintained over this working stroke and thus the additional forces mentioned can result, it is advantageous to have the height 11, 16 of the tooth heads should be kept relatively small, for example smaller than a fifth or smaller than a sixth of the width 9 of the respective tooth 4, 5. The resulting working stroke is further explained below with reference to FIG. 5:

If the tooth 5 is in position 41, the kinks 12, 13 lie vertically one above the other, so that the saturation zone extends vertically through the air gap 18. Since when this position 41 is exceeded, positive additional forces result from the saturation zone, position 41 can be viewed as the beginning of the working stroke 44.

If the tooth 5 is moved further to the right starting from the position 41, the angle 46 between the saturation zone 17 and the air gap 18 is reduced and the length 40, 40 'of the saturation zone 17 increases. Regardless of which magnetic flux densities are permitted outside the tooth heads 14, 15, a theoretical upper limit 45 of the working stroke 44 is reached when the tooth 5 is in position 43, since there the length 40 'of the saturation zone 17 is equal to the width 9 of the teeth 4, 5, which means that in order to achieve the saturation flux density in the saturation zone 17, this would have to be achieved essentially over the entire teeth 4, 5, so that the saturation zone 17 would no longer differ from the other material of the teeth 4, 5 and thus the The additional staff explained would no longer be available.

If a ratio between the saturation flux density and the maximum magnetic flux density to be used in the area of the tooth neck is specified, this ratio also corresponds to the ratio between the width 9 and the length 40 of the saturation zone 17, whereby the position 42 is specified from which the saturation zone 17 can no longer be maintained without it to exceed the maximum magnetic flux density in the neck of the tooth. Additional magnetic forces can therefore only be provided via the working stroke 44 due to the saturation zone 17 used.

To increase the working stroke 44 or the theoretical upper limit 45 of this working stroke 44, it is advantageous to reduce the height 11, 16 of the tooth heads 14, 15, in particular to less than a fifth or less than a sixth of the width 9. However, here it is expedient to avoid an excessive reduction in the heights 11, 16. As shown schematically in Fig. 4, the magnetic flux that is passed through half the length 35 of the saturation zone 17 must either, as shown by the arrow 36, indirectly via the extension region 58 of the tooth 4 or, as shown by the arrow 37 is shown, are dissipated directly via the air gap 18. In order to avoid saturation in the area of the opposite end surface 56 of the tooth 5 or the extension area 58 of the tooth head 15, the areas shown schematically in FIG. 4, which are crossed by the arrows 36, 37, must be larger in total than half the area of the saturation zone 17.

If the teeth 4, 5 are formed essentially perpendicular to the image plane over their entire depth, as shown in Fig. 4, the sum of the lengths of the side surfaces crossed by the arrows 36, 37 in the image plane must be greater than the length 35 of the half saturation zone 17. In order to ensure this also in the area of the maximum working stroke 44, it is expedient if the tooth heads 14, 15 have a certain minimum height, which means that the height 11, 16 should in particular be greater than a twelfth or a tenth of the width 9.

The saturation zone 17, although it is only shown as a line in Figures 4, 5, extends over a certain width, so that it enters a certain extent into the expansion area 58 of the tooth head, which extends beyond the width 9. It should be avoided that the saturation zone 17 extends to the end of the tooth tip 15, as this would result in the advantages of the saturation zone 17 crossing the air gap being partially lost. It is therefore expedient if the tooth head 15 extends over a length 34 respective kink point 12, 13 extends in the direction of movement, which is at least 135% or at least 150% of the height 11, 16 of the corresponding tooth head 14, 15.

The above explanations can be transferred essentially unchanged to the internal rotor machine shown in FIG. 1, other internal and external rotors or disc rotors. For clarification, the course of the field lines 19 to 21, as shown in FIG. 2 for a linear machine, is shown for a rotary machine in FIG. In the area of the air gap 18, a similar course results as already discussed with reference to FIG. 2 and thus also the additional forces. For better understanding, various geometric dimensions are also shown again in FIG. 6, in particular the height 11, 16 of the tooth heads 14, 15 and the length 34 by which they extend beyond the respective tooth neck. The corresponding variables and their influence on the formation of the saturation zone 17 or the provision of the additional torque or the additional force have already been explained with reference to FIGS. 4 and 5.

Fig. 7 shows a further example of a reluctance machine 1, with a significantly larger number of teeth 4, 5 of the rotor 2 and the stator 3 being used compared to the embodiment according to Fig. 1. In order to reduce the number of coils 57 required and thus the weight and costs of the reluctance machine 1, in the embodiment shown in FIG 48 are subjected to field. Through this configuration, torque gaps can be avoided as well as in configurations in which separate magnetic poles of the same number as the number of teeth 4 used in FIG. 7 would be used, without the need for correspondingly complex wiring and control.

In such a configuration, however, one of the teeth 5 of the rotor 2 should simultaneously overlap with several teeth 4 of the same energized magnetic pole 48 can be avoided, so that the permissible expansion of the teeth 4, 5 in the circumferential direction is limited. Therefore, in the exemplary embodiment shown, tooth heads 14, 15 are used which only extend in one direction away from the respective tooth neck in the circumferential direction beyond it. The formation of the saturation zone 17 can therefore only provide additional forces when the rotor 2 rotates clockwise. The machine shown is therefore optimized for operation with only one specified direction of rotation, which is, however, sufficient for many applications. However, a design with tooth heads in both circumferential directions is possible.

Another special feature of the reluctance machine 1 shown in FIG. 7 is that different teeth 4 of the stator 3 have different widths 9, 9 '. The dimensions of the tooth heads are preferably tailored to the respective width 9, 9 'of the respective tooth 4. Alternatively, shapes of the tooth heads 14, 15 can be used that lie within the intervals discussed for all widths 9, 9 'used.

In the previous exemplary embodiments, it was assumed that the extension region 58 of the respective tooth head 14, 15 that widens the tooth neck is essentially rectangular or that the respective side wall 50 to 53 bends at right angles at the respective bend point 12, 13. For the formation of the saturation zone 17, however, it is sufficient if the kinks 12, 13 clearly define a narrow point for the magnetic flux, so that the specific angle at which the respective side wall 50 to 53 bends at the respective kink 12, 13 and the shape of the extension area 58 beyond the kink 12, 13 only has an indirect influence on this and can thus be varied, for example, to optimize other properties.

Purely by way of example, Figures 8 to 13 show various possible shapes of the extension area 58, which differ on the one hand with regard to the bend angle at the bend point 12, on the other hand with regard to the further course of the side wall after the bend point 12 and thirdly with regard to the curvature of the side wall 51 differ beyond the bend point 12, so that, for example, there is a concave, a convex or no curvature.

14 to 17, on the other hand, show configurations in which on the side of the kink 12 facing away from the air gap, the side wall 51 has a further kink 49, at which the tooth 4 already widens in front of the tooth head. This can be advantageous because this causes the saturation zone 17, 17 'to move between the kink points 12 when the tooth 4 is displaced, as is shown by way of example for the positions 42, 43 in FIG. 17, depending on the current stroke 59 relative to the position 41. 49 can move, whereby the theoretical upper limit 45 of the working stroke can be greater than the width 9 of the teeth 4, 5.

In the intermediate region 60, the side wall can, for example, be straight, convex or concave, as shown in FIGS. 14 to 16.

In the example shown in Fig. 17, only the teeth 4 of the stator 3 have side walls 50, 51 with several kinks 12, 49, while on the rotor side there is only exactly one kink 13 per side wall 52, 53. Alternatively, it would also be possible, for example, to use side walls 52, 53 with several kinks exclusively on the rotor side.

In principle, it is also possible to use side walls 50 to 53 with several kinks 12, 13, 49 on both the rotor and stator sides for the teeth 4, 5. However, the intermediate region 60 between the kinks 12, 49 and 13, 49 should be shaped differently for the rotor-side teeth 5 and for the stator-side teeth 4, so that it can be avoided that the latter is very wide due to parallel side wall sections delimiting the saturation zone 17 .

Claims

Patent claims

1 . Switched reluctance machine with a stator (3) and a rotor (2), which are spaced apart from one another by an air gap (18), the stator (3) and the rotor (2) each having a plurality of teeth (4, 5), the Teeth (5) of the rotor (2) are guided past the teeth (4) of the stator (3) in a direction of movement (57) during operation of the reluctance machine (1), with at least one of the two side walls (50-53) being at least one of the teeth (4, 5), which limit the respective tooth (4, 5) in the direction of movement (57), has a bend (12, 13) through which the cross section (8, 10) of the respective tooth (4, 5 ) on the side of the kink (12, 13) facing the air gap (18) in order to form a tooth head (14, 15) of the respective tooth (4, 5), characterized in that a height (11, 16) of the respective Tooth head (14, 15) is smaller than a fifth or smaller than a sixth of a width (9) of the respective tooth (4, 5), the height (11, 16) of the respective tooth head (14, 15) being equal to the distance between the The bend point (12, 13) is from an end surface (55, 56) that closes the respective tooth (4, 5) towards the air gap (18) and the width (9) of the respective tooth (4, 5) is equal to the minimum distance between the two the side walls (50-53) delimiting the respective tooth (4, 5) in the direction of movement (57) are outside the tooth head (14, 15), the tooth head (14, 15) being at least 135% or at least 150% of the height ( 11, 16) of the respective tooth head (14, 15) extends in the direction of movement (57) beyond the respective kink point (12, 13).

2. Switched reluctance machine according to claim 1, characterized in that it comprises a field application device (47) for applying a magnetic field to the teeth (4, 5), the maximum field strength (29) of the magnetic field and the material of the teeth (4 , 5) are selected so that the saturation flux density (32) in at least one area of the respective tooth (4, 5) outside the tooth head (14, 15) is between 1.15 times and 1.4 times the maximum in this one Area reached during operation of the reluctance machine (1) magnetic flux density (30). Switched reluctance machine according to claim 1 or 2, characterized in that the height (11, 16) of the respective tooth head (14, 15) is greater than a twelfth or greater than a tenth of the width (9) of the respective tooth (4, 5). . Switched reluctance machine according to one of the preceding claims, characterized in that at least one of the two side walls (50-53) of at least one of the teeth (4, 5) has a further kink (49) which is further away from the air gap (18) than the kink (12, 13), the cross section (8, 10) of the respective tooth (4, 5) widening in an intermediate region (60) between the further kink (12, 13) and the kink (49). Switched reluctance machine according to claim 4, characterized in that the teeth (4, 5) of the stator (3) or the rotor (2) have a maximum of one kink (12, 13) per side wall (50-53). Switched reluctance machine according to claim 4, characterized in that the teeth (4, 5) of the stator (3) and the rotor (2) each have the and the further kink point (12, 13, 49) in at least one of their side walls (50-53). ), whereby the cross section (8, 10) of the respective tooth (4, 5) widens in an intermediate region (60) between the kink point (12, 13) and the further kink point (49), the intermediate region (60) being the Teeth (4, 5) of the rotor (2) have a shape that differs from the shape of the intermediate region (60) of the teeth (4, 5) of the stator (3) in such a way that the shapes are not converted into one another by rotating or mirroring can be. Switched reluctance machine according to one of the preceding claims, characterized in that all teeth (4, 5) of the rotor (2) and the Stator (3) either has at least one kink (12, 13, 49) on exactly one of the side walls (50-53) to form the tooth head (14, 15) or at least one kink (12, 13, 49) on both of the side walls (50-53). 12, 13, 49) to form the tooth head (14, 15). Switched reluctance machine according to one of the preceding claims, characterized in that it comprises the or a field application device (47) which is set up to apply a magnetic field to the teeth (4, 5) in such a way that in each tooth head (14, 15). As part of the movement of the rotor (2) with respect to the stator (3), at least temporarily the magnetic flux density (30) in a section of the tooth head (14, 15), in particular from the ends of the tooth head (14, 15) in the direction of movement (57). is spaced apart, the saturation flux density (32) of the material of the respective tooth (4, 5) is reached or exceeded. Switched reluctance machine according to one of the preceding claims, characterized in that it comprises the or a field application device (47) which is set up to apply a magnetic field to the teeth (4, 5) in such a way that at least during a sub-interval of that time interval during which the end surfaces (55, 56) of a respective tooth (4, 5) of the stator (3) and the rotor (2) facing the air gap (18) at least partially overlap in the direction of movement (57), in these end surfaces (55, 56) This results in saturation zones (17) overlapping in the direction of movement (57), in which the magnetic flux density (30) reaches or exceeds the saturation flux density (32) of the material of the respective tooth (4, 5). Method for operating a switched reluctance machine with a stator (3) and a rotor (2), which are spaced apart from one another by an air gap (18), the stator (3) and the rotor (2) each having several teeth (4, 5) have, wherein the teeth (5) of the rotor (2) during operation of the reluctance machine (1) in a direction of movement (57) on the Teeth (4) of the stator (3) are guided past, with at least one of the two side walls (50-53) at least one of the teeth (4, 5) which delimit the respective tooth (4, 5) in the direction of movement (57). Has a kink (12, 13), through which the cross section (8, 10) of the respective tooth (4, 5) on the side of the kink (12, 13) facing the air gap (18) widens to form a tooth head (14, 15) of the respective tooth (4, 5), the teeth (4, 5) being subjected to a magnetic field by a field application device (47) in order to drive the reluctance machine (1), characterized in that the field application device (47) is operated in such a way that in each tooth head (4, 5) as part of the movement of the rotor (2) with respect to the stator (3), the magnetic flux density (30) is at least temporarily in a section of the tooth head (14, 15), which is in particular from the ends of the tooth head are spaced apart in the direction of movement, the saturation flux density (32) of the material of the respective tooth (4, 5) is reached or exceeded.