EP4052363A1

EP4052363A1 - Axial flux machine for an electrical processing device and electrical processing device with an axial flux machine

Info

Publication number: EP4052363A1
Application number: EP20796783.7A
Authority: EP
Inventors: Sebastian Laber; Andreas Voelkle
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-10-31
Filing date: 2020-10-22
Publication date: 2022-09-07
Also published as: CN114600340A; WO2021083784A1; DE102019216861A1

Abstract

The invention relates to an axial flux machine (10), in particular a single-sided axial flux motor, for an electrical machining device (34), having a machine shaft (12), in particular a motor shaft, a disc-shaped stator (20) and a disc-shaped rotor (14) arranged adjacent to the stator (20) in the axial direction (A) of the machine shaft (12), wherein the stator (20) is formed as a winding carrier (22) for at least one stator winding (24) and the rotor (14), which is connected to the machine shaft (12) in a rotationally fixed manner, can be set in a rotational movement relative to the stator (20). According to the invention, the stator (20) comprises a plurality of stator teeth (44) and a first stator yoke (26), wherein the stator teeth (44) and the first stator yoke (26) are permanently connected to each other by laser welding. The invention also relates to an electrical processing device (34) with an axial flux machine (10).

Description

title

Axial flux machine for an electrical machining device and electrical machining device with an axial flux machine

description

The invention relates to an axial flux machine, in particular a one-sided axial flux motor, for an electrical machining device and an electrical machining device with an axial flux machine according to the preamble of the independent claims.

State of the art

Axial flux machines have the advantage over conventional electric machines with radial flow direction that they are very efficient and have a significantly reduced overall length. In addition, a higher torque or power density can be achieved with the same outer diameter. These improvements are due, among other things, to a larger air gap area with a comparable construction volume. Thanks to the lower iron volume of the rotating components, there is also a higher degree of efficiency over a larger speed range.

The construction of a stator of an axial flux machine is relatively complex due to the required 3-D magnetic flux guidance. The grooves in the laminated core usually have to be punched out before the stator winding is wound. In addition, the individual sheets result in disadvantages such that the pole pieces only protrude tangentially and that the stator teeth with the pronounced pole pieces cannot be wound externally, which results in a low fill factor of the stator winding and a correspondingly reduced efficiency. From DE 102015 223 766 A1 an axial flow machine with bent and wound laminated cores as winding supports is known. The stator of the axial flow machine has a sintered support structure made of soft magnetic material and an insert designed as a laminated core. The insert is connected to the support structure via a form fit and / or force fit and at least partially forms a pole piece of the axial flow machine. The laminated core is formed by means of individual, stacked layers of single metal sheets, which consist of a soft iron. The individual sheets are electrically connected to one another in an insulated manner with respect to the respectively adjacent sheet.

Alternatively, the stators of axial flux machines are also built purely from composite materials (Soft Magnetic Composites - SMC). S MC materials consist of high-purity iron powder with a special surface coating on each individual particle. This electrically insulating surface ensures a high electrical resistance even after pressing and heat treatment, which in turn minimizes or prevents eddy current losses. SMC materials are known to the person skilled in the art, so that their composition will not be discussed further here.

To improve the fill factor of the stator winding in the radial air gaps between the stator teeth of the stator, the stator teeth of the winding carrier and at least one stator yoke serving as a magnetic yoke can be manufactured separately and, after the stator teeth have been wound with the respective individual tooth windings of the stator winding, they can be permanently connected to one another. The connection is usually made via a joining process, for example by gluing. Gluing can, however, affect the planparality of the stator teeth to the radial air gap between them and also requires additional fixation during the hardening of the glue.

It is therefore the object of the invention to provide an axial flux machine with a connection between the stator teeth and the stator yoke serving as a return path, which is improved compared to the prior art. Advantages of the invention

The invention relates to an axial flux machine, in particular a one-sided axial flux motor, for an electrical processing device, with a machine shaft, in particular a motor shaft, a disk-shaped stator and a disk-shaped rotor arranged in the axial direction of the machine shaft adjacent to the stator, the stator as a winding carrier for at least one Stator winding is formed and the rotatably connected to the machine shaft dene rotor relative to the stator can be set in a rotary motion.

To achieve the object, it is provided that the stator has a plurality of stator teeth and a first stator yoke, the stator teeth and the first stator yoke being permanently connected to one another by laser welding. The laser welding results in a high level of parallelism between the stator teeth and the radial air gaps between them in connection with a simplified and faster production of the stator. By avoiding adhesive bonding, there is no adhesive gap between the stator teeth and the first stator yoke. In addition, it is not necessary to fix the stator teeth and the first stator yoke while the bond is hardening.

The invention also relates to an electrical processing device, in particular an electric machine tool, with an axial flux machine according to the invention, in particular an axial flux motor according to the invention.

In the context of the invention, the electric machining device is to be understood to mean, among other things, battery-powered or mains-operated electric machine tools for machining workpieces by means of an electrically driven insert tool. The electrical processing device can be designed both as a handheld electrical tool and as a stationary electrical machine tool. Typical power tools in this context are hand or standing drills, screwdrivers, impact drills, rotary hammers, demolition hammers, planes, angle grinders, orbital grinders, polishing machines or the like. Motor-driven garden tools such as lawnmowers, lawn trimmers, pruning saws or the like are also suitable as electrical processing devices. Furthermore, the invention is applicable to axial flow machines in household and Kitchen appliances such as washing machines, dryers, vacuum cleaners, mixers, etc. can be used.

The term axial flux machine can include both an axial flux motor and an axial flux generator for converting mechanical into electrical energy. An axial flux machine is also to be understood as an axial flux motor that is used at least temporarily for recuperation from mechanical to electrical energy, as can be the case, for example, with electrodynamic braking of an axial flux motor.

In a further development of the invention it is provided that in each case approximately in the middle of each surface of a stator tooth resting on the first stator yoke a drilling is provided in the first stator yoke, through which the stator tooth can be connected to the first stator yoke by means of laser welding. A weld seam for connecting the first stator yoke and the respective stator tooth can extend over the entire circumference or, alternatively, only selectively over the circumference of the bore. By welding in the middle of each stator tooth, the guidance of the magnetic flux is only slightly influenced and a high level of plane parallelism between the stator teeth and the radial air gap between them can be achieved.

Embodiments

drawing

The invention is explained below by way of example with reference to FIGS. 1 to 10, the same reference symbols in the figures indicating the same components with the same mode of operation.

Show it

1: a section through an axial flux machine according to the invention in the form of a one-sided axial flux motor in a first exemplary embodiment, 2: a schematic view of a further exemplary embodiment of a stator of the axial flux machine according to the invention,

3: an exploded view of the stator from FIG. 2 in a schematic view without the stator winding,

4: a schematic view of a section of the stator according to the invention in a further exemplary embodiment,

Fig. 5: a schematic sectional view of a rotor of the fiction, contemporary axial flow machine,

6: a schematic view of a housing of the axial flow machine according to the invention,

FIG. 7: a further schematic view of the empty housing of the axial flow machine according to the invention from FIG. 6,

8: a schematic view of a further exemplary embodiment of the cooling air duct within the axial flow machine according to the invention in a section,

FIG. 9: two exemplary embodiments of triangular parallel connections in FIG

Single tooth windings of a stator winding of the axial flux machine according to the invention and

10: an electrical processing device, in particular an electric machine tool in the form of a hammer drill, with an axial flow machine according to the invention.

Description of the exemplary embodiments

In Figure 1, a first embodiment of an axial flow machine 10 according to the invention is shown in a section. The axial flux machine 10 can equally be designed as an axial flux motor or as an axial flux generator. On a machine shaft 12 of the axial flow machine 10 is rotatably fixed with the Maschi nenwelle 12, a disc-shaped rotor 14 is arranged. The rotor 14 is designed as a laminated ring 16 made of soft magnetic iron and carries an alternately magnetized magnetic ring 18, which will be discussed in greater detail with reference to FIG. However, since the rotor 14 is usually not exposed to an alternating field and thus the risk of eddy current losses is relatively low, the rotor 14 can alternatively consist of non-soft magnetic materials such as iron or of a soft magnetic steel with a low carbon content. In the axial direction A of the motor shaft 12, adjacent to the rotor 14 or to the magnet ring 18, there is also a disk-shaped stator 20, which is designed as a winding carrier 22 for at least one stator winding 24 (see FIG. 2) and which has a first stator yoke 26 which serves as a magnetic return path of the magnetic field resulting from the stator winding 24 and the magnetic ring 18. Relative to the stator 20 or the stator winding 24, the rotor 14 can be set in a rotary movement via the motor shaft 12. For this purpose, the motor shaft 12 is on the one hand via a first bearing 28 integrated in the stator yoke 26, which is designed, for example, as a fixed bearing 30, and on the other hand via a second bearing 36 accommodated in a housing 32 of an electrical machining device 34 (see FIG. 10), the example is designed as a floating bearing 38, rotatably mounted. The first and second bearings 28, 36 are preferably designed as ball bearings. The first bearing 28 is integrated directly into the winding support 22 and / or into the first stator yoke 26. For example, it can be pressed in or injected. Since, in particular, one-sided axial flux machines have a very high tensile force in the axial direction A of the machine shaft 12 in the air gap between the rotor 14 and the stator 20, this can be intercepted by the first bearing 28, designed as a fixed bearing 30, in the first stator yoke 26. It is therefore not necessary to absorb the axial force through the housing 32 of the electrical machining device 34 and / or through a housing of the axial flow machine (cf. FIGS. 6 and 7).

To cool the axial flow machine 10, a fan wheel 40 is arranged on the machine shaft 12 in a rotationally fixed manner and transports the cooling air through the axial flow machine 10. For this purpose, the fan wheel 40 preferably sucks in the cooling air radially in order to then convey it axially through the axial flow machine 10. FIG. 2 shows a schematic view of a further exemplary embodiment of the disk-shaped stator 20 of the axial flux machine 10 according to the invention. The stator 20 essentially comprises the first stator yoke 26, a second stator yoke 42 arranged adjacent to it in the axial direction A of the machine shaft 12, and the second stator yoke 42 42 in the axial direction A of the machine shaft 12 arranged adjacent winding carrier 22. The winding carrier 22 consists essentially of a plurality of, in particular six, stator teeth 44 carrying the stator winding 24, each stator tooth 44 being assigned a single tooth winding 46 of the stator winding 24. With reference to FIG. 9 a, the individual tooth windings 46 are electrically connected to one another in a triangular parallel circuit 48.

The stator teeth 44 and the first stator yoke 26 of the stator 20 are made of composite materials (Soft Magnetic Composites - SMC) and are permanently connected to one another, in particular glued, by means of a joining process. SMC materials consist of high-purity iron powder with a special surface coating on each individual particle. This electrically insulating surface ensures a high electrical resistance even after pressing and heat treatment, which in turn minimizes or prevents eddy current losses. With a particular advantage over prior art axial flux machines, an axial flux machine that is extremely resistant to mechanical loads and at the same time very powerful and efficient, or a high-torque axial flux motor, can be provided. The joining of the stator teeth 44 with the first stator yoke 26 enables the winding carrier 22 to be wound externally by applying the stator winding 24 or the individual tooth windings 46 to the stator teeth 44 during the joining process. In this way, a high fill factor of the stator winding 24 can be achieved.

The second stator yoke 42 of the rotor 20, in contrast to the first stator yoke 26, is made of soft magnetic iron and is designed as a laminated core 48 (see FIG. 3) with a plurality, in particular six, grooves 50 distributed over its outer circumference for receiving the composite materials. The number of slots 50 corresponds to the number of stator teeth 44. The second Stator yoke 42 thus stabilizes the stator 20 in the event of strong mechanical stress and ensures improved magnetic flux guidance due to its high permeability. The grooving of the laminated core 48 not only results in better absorption of the composite materials and thus the greater stability of the stator 20, but also ensures an optimized guidance of the eddy currents caused by the stator winding 24 essentially.

According to FIG. 3, the second stator yoke 42 has ring-shaped, circular segment-shaped recesses 52 for receiving the stator teeth 44, each groove 50 interrupting the outer circumference of the second stator yoke 42 up to the respective radially inner recess 52. Each stator tooth 44 is formed by a circular segment-shaped tooth flange 54, which engages through the circular segment-shaped recess 52 of the second stator yoke 42, and a circular segment-shaped support frame 56 encompassing the tooth flange 54 with a circumferential U-profile 58 for receiving the stator winding 24 or the individual tooth windings 46 . Tooth flange 54 and support frame 56 are permanently connected to one another, in particular glued, by means of a joining process.

FIG. 4 shows a schematic view of a section of the stator 20 according to the invention in a further exemplary embodiment. The stator teeth 44 or their tooth flanges 54 (see FIG. 3) are passed through the recesses 52 of the second stator yoke 42 and permanently connected to the first stator yoke 26 by laser welding. In each case approximately in the center of each surface of a stator tooth 44 resting on the first stator yoke 26, a bore 60 is provided in the first stator yoke 26, through which the stator tooth 44 can be connected to the first stator yoke 26 by means of laser welding. For the permanent connection of the first stator yoke 26 and the respective stator tooth 44, a weld seam extends over the entire circumference of the bore 60. Alternatively, however, it can also be provided that the weld seam extends only selectively over the circumference of the bore 60. By welding in the middle of each stator tooth 44, the guidance of the magnetic flow is only slightly influenced and a high level of plane parallelism of the stator teeth 44 to the radial air gap between them can be achieved. By avoiding a bond, an adhesive gap between the stator tooth 44 and first stator yoke 26 are avoided and there is no fixation of stator tooth 44 and first stator yoke 26 during the curing of the bond neces sary. With reference to FIG. 1, it is alternatively also conceivable to dispense with the second stator yoke 42 and instead to connect the first stator yoke 26, designed as a laminated ring 16 made of soft magnetic iron, directly to the stator teeth 44 made of composite materials, in particular by means of the bore 60 in the first To weld stator yoke 42.

In Figure 5, a schematic view of the rotor 14 of the axial flow machine 10 according to the invention is shown in section. The rotor 14 is designed as a laminated ring 16 made of soft magnetic iron. It also carries an alternately polarized magnet ring 18, which interacts with the stator winding 24 of the stator 20 in order to set the rotor 14 in rotation during motor operation or to induce a voltage in the stator winding 24 in generator operation. The magnets of the magnet ring 18, not shown in detail, are designed in the shape of a segment of a circle that their surfaces largely overlap with the segment of a circle stator teeth 44 in order to achieve an optimal magnetic flux in conjunction with a high torque. Instead of an alternately polarized magnetic ring 18, a ring with embedded individual magnets is alternatively also conceivable. As already mentioned, the rotor 14 is generally not exposed to an alternating field, so that no or only very low eddy current losses occur here. Therefore, the rotor 14 of the axial flow machine 10 can alternatively also consist of a non-soft magnetic material.

In a preferred embodiment of the invention, the laminated ring 16 of the rotor 14 is designed as a rotor yoke 62 which is either permanently connected to a bidirectional fan 40 by a joining process, in particular glued, or which itself serves as a bidirectional fan 64. The bidirectional fan 40, 64 has at least one radial air flow direction 66 and one axial air flow direction 68 for cooling the axial flow machine 10, in particular for cooling the stator 20 or the stator winding 24 and the rotor 14. The radial air flow direction 66 is essentially defined by a plurality of radial air blades 70 arranged in a circle in the outer radius area of the bidirectional fan 40, 64 and the axial air flow direction 68 by a plurality in the inner radius area of the rotor yoke 62 arranged axial openings 72 achieved.

Thus, with reference to FIG. 6, the bidirectional fan 40, 64 causes a radial suction 74 of an air flow 76 with an axial flow 78 through the stator 20 and the rotor 14 of the axial flow machine 10 and a radial outlet 80 of the heated air flow 76 from a housing 82 of the Axial flux machine 10. The radial suction 74 of the air flow 76 takes place on the one hand through the air gap between the stator teeth 44 (see FIG. 2) and on the other hand in the area of the first stator yoke 26 of the stator 20, in particular on a distal end face viewed from the rotor 14 84 of the first stator yoke 26.

In FIG. 7, the axial flow machine 10 is shown with its housing 82 together with a cover 86 that closes it. FIG. 8 shows the housing 82 without axial flow machine 10 and cover 86. The housing 82 is open on one side to accommodate the cover 86 and, opposite, has an essentially closed end face 88 (cf. FIG. 8). The cover 86 closes the housing 82 and thus frictionally connects the stator 20 and the rotor 14 of the axial flow machine 10. In this context, “essentially closed” should be understood to mean that the end face 88 has a plurality of openings 90, for example for cooling , as cable passages and / or as a lead-through for the machine shaft 12, but alternatively also that the end face 88 is completely closed. The housing 82 is cylindrical and fixes the stator 20 in such a way that a defined air gap is created between the rotor 14 or its magnetic ring 18 and the stator 20 or its winding carrier 22. To reduce or avoid Wirbelstromverlusten the housing 82 is made of a magnetically insulating mate rial with the lowest possible permeability such as plastic (PA66) ago. The cover 86 can also be designed accordingly.

While the first bearing 28 formed as a fixed bearing 30 is fixed in a bearing flange 92 of the cover 86 and supports the machine shaft 12 immovably, the essentially closed end face 86 of the housing 82 has the second bearing designed as a floating bearing 38 in a further bearing flange 94 36 for the displaceable mounting of the machine shaft 12. In this way the housing 82 can be pushed on very easily after the assembly of the axial flow machine 10 and removed again for any service work.

On its open side, a plurality of recesses 96 and tabs 98 for receiving and fixing the stator 20 are arranged alternately over the circumference of the housing 82. Radial projections (see FIGS. 2 and 3) distributed over the circumference of the first and second stator yokes 26, 42 of the stator 20 engage in the respective recesses 96 of the housing 82. Accordingly, the cover 86 also contains radial projections formed as tabs 106 which engage in the recesses 96 of the housing 82. In this way, the high axial forces of the axial flow machine 10 can be dissipated in the direction of the cover 86. In each tab 98 of the housing 82 there is at least one bore 100 for fixing the cover 86 and consequently also the stator 20 by means of corresponding fastening means 102, in particular screws 104. The fastening means 102 transmit the axial force of the axial flow machine 10 to the housing 82 and are thus subject to shear stress.

The openings 90 on the essentially closed end 88 of the housing 82 are designed as radially and / or axially acting ventilation openings 104, in particular as ventilation outlet openings 106, for cooling the axial flow machine 10 (see also FIG. 6). In addition, the housing 82 has a plurality of radially acting ventilation openings 108 distributed over the circumference, in particular ventilation inlet openings 110, approximately centrally between the essentially closed end face 88 and the open side opposite in the axial direction A. In addition to the openings 90 for cooling the axial flow machine 10, further openings 90 are provided, in particular in the tabs 98 of the housing 82, which can serve as feedthroughs 112 for sensor lines or the like.

FIG. 9a shows a circuit diagram of the stator winding 22 as a triangular parallel circuit 48 of the six individual tooth windings 46 of the stator teeth 44 (see FIG. 2). Two individual tooth windings 46 are connected in parallel between the connection points U and V, V and W or W and U per phase. The delta connection as such has the effect that on each individual tooth winding 46 the entire Supply voltage drops. This requires an increase in the number of turns of the individual tooth windings 46 in order to achieve a specifically required speed in motor operation or a specifically required energy yield in generator operation. Due to the additional parallel connection, the winding wire diameter can be increased in a particularly advantageous manner and thus the resulting internal resistance can be reduced. The triangular parallel connection 48 thus enables the internal resistance of the axial flux machine 10 to be reduced compared to a conventional star connection, which leads to a significant increase in the performance of the axial flux machine 10 compared to previous solutions. FIG. 9 b shows an alternative embodiment of the triangular parallel circuit 48 for a total of nine individual tooth windings 46 of the stator winding 22.

In FIG. 10, an exemplary embodiment of an electrical machining device 34 with the axial flow machine 10 according to the invention according to FIG. 1 is shown. The electrical processing device 34 is designed as an electric machine tool 112 in the form of a mains-operated hammer drill with an electric motor driven percussion mechanism 114, which sets a drill chuck 116 for a tool (not shown) in a rotary and / or percussive movement. The exact design of the hammer drill will not be discussed in detail here, since this is well known to the person skilled in the art. Any other battery-powered or mains-operated power tool 112 for machining workpieces by means of an electrically driven insert tool can also be understood as an electrical machining device. The electrical Bear processing device can be designed both as an electrical hand tool and as a stationary electrical machine tool. Typical electric machine tools in this context are hand or standing drills, screwdrivers, impact drills, rotary hammers, demolition hammers, planes, angle grinders, orbital grinders, polishing machines or the like. Motor-driven gardening tools such as lawn mowers, lawn trimmers, pruning saws or the like can also be used as electrical processing equipment. Furthermore, the invention is applicable to axial flow machines in household and kitchen appliances, such as washing machines, dryers, vacuum cleaners, mixers, etc.

The axial flux machine 10 of the power tool machine 112, which operates as an axial flux motor, drives by means of its machine shaft 12 in a known manner the hammer mechanism 114 via a gear 118. The axial flux machine 10 is controlled via a main switch 122 arranged in a D handle 120 of the electric power tool 112, which interacts with electronics not shown to energize the stator winding 22 connected in a triangular parallel circuit 48. The stator 20 of the axial flux machine 10 is received directly in the housing 32 of the electric machine tool 112. For this purpose, the stator 20 and the housing 32 are permanently connected to one another, in particular glued, by a joining process. Alternatively, however, the stator 20 can also be permanently connected to the housing 32, in particular pressed, by a form fit. Furthermore, it can be provided that the housing 32 or a gear housing 122 of the electric machine tool 112 receives the second bearing 36 connected to the machine shaft 12 of the axial flow machine 10, in particular as a floating bearing 38. Instead of the axial flow machine 10 shown according to FIG. 1, the electric machine tool 112 or the electric machining device 34 can also be equipped with a

Axial flux machine 10 according to Figures 6 to 8 be equipped.

Finally, it should be pointed out that the invention is not limited to the exemplary embodiments shown according to FIGS. 1 to 10 or to the number of stator teeth, individual tooth windings and magnets of the magnetic ring mentioned.

Claims

Expectations

1. Axial flux machine (10), in particular one-sided axial flux motor, for an electrical processing device (34), with a machine shaft (12), in particular a special motor shaft, a disk-shaped stator (20) and an axial direction (A) of the machine shaft (12) adjacent to the stator (20) on an ordered disc-shaped rotor (14), the stator (20) being designed as a winding carrier (22) for at least one stator winding (24) and the rotor (14), which is non-rotatably connected to the machine shaft (12), is relatively the stator (20) can be set in a rotary movement, characterized in that the stator (20) has a plurality of stator teeth (44) and a first stator yoke (26), the stator teeth (44) and the first stator yoke (26) are permanently connected to each other by laser welding.

2. Axial flux machine (10) according to claim 1, characterized in that in each case approximately in the middle of each surface of a stator tooth (44) resting on the first stator yoke (26) has a bore (60) in the first stator yoke (26) is seen through which the stator tooth (44) can be connected to the first stator yoke (26) by means of laser welding.

3. Axial flux machine (10) according to one of the preceding claims, characterized in that a weld seam for connecting the first stator yoke (26) and the respective stator tooth (44) extends over the full circumference of the bore (60).

4. Axial flux machine (10) according to one of the preceding claims 1 or 2, characterized in that a weld seam for connecting the first stator yoke (26) and the respective stator tooth (44) extends only punk tuell over the circumference of the bore (60).

5. Electrical processing device (34), in particular Elektrowerkzeugma machine (112), with an axial flux machine (10) according to eggs of the preceding claims.