CN114600340A

CN114600340A - Axial flux machine for an electrical machining device and electrical machining device having an axial flux machine

Info

Publication number: CN114600340A
Application number: CN202080075064.1A
Authority: CN
Inventors: S·拉贝尔; A·弗尔克勒
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-10-31
Filing date: 2020-10-22
Publication date: 2022-06-07
Also published as: WO2021083784A1; EP4052363A1; 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 disk-shaped stator (20), and a disk-shaped rotor (14) arranged adjacent to the stator (20) in an axial direction (A) of the machine shaft (12), wherein the stator (20) is designed as a winding carrier (22) for at least one stator winding (24), and the rotor (14) connected in a rotationally fixed manner to the machine shaft (12) can be set in a rotational motion relative to the stator (20). It is proposed that the stator (20) has 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 one another by laser welding. The invention further relates to an electrical machining device (34) having an axial flux machine (10) according to the invention.

Description

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

Technical Field

The invention relates to an axial flux machine for an electrical machining device, in particular a single-sided axial flux motor, and to an electrical machining device having an axial flux machine, according to the generic type of the independent claims.

Background

Compared to conventional electric motors with a radial flux direction (flussichtung), axial flux machines have the advantage 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 in particular to the larger air gap area with a similar structural volume. Furthermore, due to the smaller iron volume of the rotating parts, a higher efficiency results over a larger rotational speed range.

The construction of the stator of an axial flux machine is relatively expensive due to the required 3D flux guidance. The slots (Nutung) of the lamination stack must usually be punched before the winding process of the stator winding. Furthermore, the individual sheet has the disadvantage that the pole shoes only form tangential projections, which do not allow stator teeth with projecting pole shoes to be wound on the outside, which leads to a small fill factor of the stator winding and to a correspondingly reduced efficiency.

An axial flux machine with a bent and wound lamination stack as a winding carrier is known from DE 102015223766 a 1. The stator of the axial flux machine has a sintered carrier structure made of soft magnetic material and an insert designed as a lamination stack. The insert is attached to the carrier structure by form-locking and/or force-locking and forms at least partially a pole shoe of the axial flux machine. The lamination stack is formed by means of individual layers stacked one on top of the other on a single sheet made of soft iron. The individual sheets are attached to each other in an electrically insulated manner from the respectively adjacent sheets.

Alternatively, the stator of the axial flux machine is also purely made of composite material (Soft Magnetic Composites, SMC). SMC materials consist of a high purity iron powder with a special surface coating on each individual particle. The electrically insulating surface ensures a high electrical resistance even after pressing and heat treatment, which in turn minimizes or avoids eddy current losses. SMC materials are known to those skilled in the art and their composition is therefore not discussed further here.

In order to improve the fill factor of the stator winding in the radial air gap between the stator teeth of the stator, the stator teeth of the winding carrier and the at least one stator yoke acting as a yoke can be produced separately from one another and permanently connected to one another after the stator teeth have been wound by means of a corresponding single-tooth winding of the stator winding. The connection is usually effected here by a joining process, for example by gluing. However, bonding can affect the plane parallelism of the stator teeth with respect to the radial air gap (between the stator teeth) and also requires additional fixation during curing of the bond.

Disclosure of Invention

It is therefore the object of the present invention to provide an axial flux machine with an improved connection between the stator teeth and the stator yoke used as yoke (rackschluss) compared to the prior art.

THE ADVANTAGES OF THE PRESENT INVENTION

The invention relates to an axial flux machine, in particular a single-sided axial flux motor, for an electrical machining device, having a machine shaft (in particular a motor shaft), a disk-shaped stator and a disk-shaped rotor arranged adjacent to the stator in the axial direction of the machine shaft, wherein the stator is designed as a winding carrier for at least one stator winding and the rotor connected in a rotationally fixed manner to the machine shaft can be set in a rotational motion relative to the stator.

To solve the proposed task setup: the stator has a plurality of stator teeth and a first stator yoke, wherein the stator teeth and the first stator yoke are permanently connected to each other by laser welding. This laser welding results in a high plane parallelism of the stator teeth with respect to the radial air gap (between the stator teeth) and at the same time in a simplified and faster production of the stator. Since the adhesion is avoided, an adhesion gap between the stator teeth and the first stator yoke is not generated. Furthermore, there is no need to fix the stator teeth and the first stator yoke during curing of the adhesive.

The invention also relates to an electrical machining device, in particular an electrical machine tool, having an axial flux machine, in particular an axial flux motor, according to the invention.

In the context of the present invention, an electrical processing device is to be understood to mean, in particular, a battery-operated or mains-operated electric power tool for processing a workpiece by means of an electrically driven insertion tool. The electric machining device can be configured not only as a hand-held electric tool, but also as a stationary electric tool. In this context, typical electric power tools are hand-held or vertical drills, screwdrivers, hammer drills, drill hammers, demolition hammers

Planers, angle grinders, vibratory finishing machines, polishers, or the like. However, motor-driven garden appliances, such as lawn mowers, lawn trimmers, branch saws or the like, can also be considered as electrical processing appliances. In addition, the present invention can be applied to an axial flux machine in a home appliance or a kitchen appliance (e.g., a washing machine, a dryer, a cleaner, a blender, etc.).

Herein, the term "axial flux machine" can include not only an axial flux motor, but also an axial flux generator for converting mechanical energy into electrical energy. Likewise, an axial flux machine is also understood to be an axial flux motor as follows: the axial flux motor is at least sometimes used to regenerate electrical energy from mechanical energy, such as may be the case with electrodynamic braking of the axial flux motor.

In a further embodiment of the invention, a bore in the first stator yoke is provided approximately centrally in each case on the surface of the stator tooth lying on the first stator yoke, through which bore the stator tooth can be connected to the first stator yoke by means of laser welding. In this case, the weld seam can extend over the entire circumference of the bore hole or alternatively only point by point over the circumference of the bore hole in order to connect the first stator yoke to the respective stator tooth. Due to the welding in the center of each stator tooth, the guidance of the magnetic flux is only slightly influenced and a high plane parallelism of the stator teeth with respect to the radial air gap (between the stator teeth) can be achieved.

Drawings

The invention is exemplarily explained in the following on the basis of fig. 1 to 10, wherein like reference numerals in the figures denote like components having the same function.

It shows

FIG. 1: a cross section of an axial flux machine according to the invention in the form of a single-sided axial flux motor in a first embodiment,

FIG. 2: a schematic view of another embodiment of a stator of an axial flux machine according to the present invention,

FIG. 3: the stator in figure 2 is an exploded view in a schematic view without stator windings,

FIG. 4: a schematic view of a part of a stator according to the invention in another embodiment,

FIG. 5: a schematic view of another embodiment of a rotor of an axial flux machine according to the present invention,

FIG. 6: a schematic view of a housing of an axial flux machine according to the present invention,

FIG. 7: further schematic view of the empty housing of an axial flux machine according to the present invention in figure 6,

FIG. 8: a schematic view of a cross-section of another embodiment of a cooling air guide in an axial flux machine according to the present invention,

FIG. 9: two embodiments of the delta-parallel circuit of the single-tooth winding of the stator winding of an axial flux machine according to the invention, and

FIG. 10: an electrical machining device, in particular an electrical power tool, in the form of a hammer drill, having an axial flux machine according to the invention.

Detailed Description

In fig. 1 a cross-sectional view of a first embodiment of an axial flux machine 10 according to the present invention is shown. The axial flux machine 10 can likewise be designed as an axial flux motor or as an axial flux generator. The disk-shaped rotor 14 is arranged on the machine shaft 12 of the axial flux machine 10 in a rotationally fixed manner to the machine shaft 12. The rotor 14 is configured as a plate-shaped ring 16 made of soft magnetic iron and carries an alternately magnetized magnetic ring 18, which will also be discussed in more detail with reference to fig. 5. However, since the rotor 14 is generally not exposed to alternating fields and the risk of eddy-current losses is therefore relatively small, the rotor 14 can alternatively also be composed of non-soft magnetic material (e.g. iron) or of soft magnetic steel with a low carbon content. In the axial direction a of the motor shaft 12, a likewise disk-shaped stator 20 is adjacent to the rotor 14 or to the magnet ring 18, which stator is designed as a winding carrier 22 for at least one stator winding 24 (see fig. 2) and has a first stator yoke 26 which serves as a yoke for the magnetic field generated by the stator winding 24 and the magnet ring 18. The rotor 14 can be set in rotational motion relative to the stator 20 or the stator winding 24 by means of the motor shaft 12. For this purpose, the motor shaft 12 is rotatably supported on the one hand by a first bearing 28, which is integrated into the stator yoke 26 and which is configured, for example, as a fixed bearing 30, and on the other hand by a second bearing 36, which is received in a housing 32 (see fig. 10) of an electrical machining device 34 and which is configured, for example, as a floating bearing 38. The first and second bearings 28, 36 are preferably designed as ball bearings. The first bearing 28 is integrated directly into the winding carrier 22 and/or the first stator yoke 26. Thus, the first bearing can be, for example, pressed in or injected. Since, in particular, single-sided axial flux machines have a very high tractive force in the air gap between the rotor 14 and the stator 20 in the axial direction a of the machine shaft 12, this tractive force can be supported by a first bearing 28 in the first stator yoke 26 in the form of a fixed bearing 30 (abdangen). Thus, there is no need to receive axial forces through the housing 32 of the electrical machining apparatus 34 and/or through the housing of the axial magnetic flux machine (see fig. 6 and 7).

For cooling the axial magnetic flux machine 10, a fan wheel 40 is arranged on the machine shaft 12 in a rotationally fixed manner, which fan wheel conveys cooling air through the axial magnetic flux machine 10. For this purpose, the fan wheel 40 preferably sucks in cooling air in the radial direction for subsequently conveying the cooling air in the axial direction through the axial flux machine 10.

Fig. 2 shows a schematic view of another embodiment of a disk-shaped stator 20 of an axial flux machine 10 according to the present invention. The stator 20 basically comprises a first stator yoke 26, a second stator yoke 42, which is arranged adjacent to the first stator yoke in the axial direction a of the machine shaft 12, and a winding carrier 22, which is arranged adjacent to the second stator yoke 42 in the axial direction a of the machine shaft 12. The winding carrier 22 is essentially composed of a plurality of, in particular six, stator teeth 44 which carry the stator windings 24, wherein a single-tooth winding 46 of the stator windings 24 is associated with each stator tooth 44. Referring to fig. 9a, the single-tooth windings 46 are electrically connected to each other in a delta parallel circuit 48.

The stator teeth 44 of the stator 20 and the first stator yoke 26 are formed from a composite material (Soft Magnetic Composites, SMC) and are permanently connected to one another by a joining process, in particular glued. SMC materials consist of a high purity iron powder with a special surface coating on each individual particle. The electrically insulating surface ensures a high electrical resistance even after pressing and heat treatment, which in turn minimizes or avoids eddy current losses. It is particularly advantageous compared to the axial flux machines of the prior art that an axial flux machine or an axial flux motor providing high torque which is extremely resistant to mechanical stresses and at the same time very performance and efficiency can be provided. The engagement of the stator teeth 44 with the first stator yoke 26 enables the external winding of the winding support 22 by applying the stator winding 24 or the single-tooth winding 46 to the stator teeth 44 during the engagement process. In this way, a high fill factor of the stator winding 24 can be achieved.

In contrast to the first stator yoke 26, the second stator yoke 42 of the rotor 20 is made of soft magnetic iron and is designed as a lamination stack 48 (see fig. 3) having a plurality of, in particular six, grooves 50 which are distributed on its outer circumference and serve to receive a composite material. The number of slots 50 corresponds here to the number of stator teeth 44. The second stator yoke 42 thus stabilizes the stator 20 in the event of strong mechanical stresses and ensures improved flux guidance due to its high magnetic permeability. The wire slots of the lamination stack 48 not only promote better reception of the composite material and thus higher stability of the stator 20, but also ensure optimized guidance of the eddy currents substantially caused by the stator windings 24.

According to fig. 3, the second stator yoke 42 for receiving the stator teeth 44 has an annularly arranged, circle segment-shaped recess 52, wherein each groove 50 interrupts 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 circle segment-shaped tooth flange 54, which passes through the circle segment-shaped recess 52 of the second stator yoke 42, and a circle segment-shaped carrier frame 56, which surrounds the tooth flange 54 and has a circumferential U-shaped profile 58 for receiving the stator winding 24 or the single-tooth winding 46. The toothed flange 54 and the carrier frame 56 are permanently connected to one another by a joining process, in particular glued.

Fig. 4 shows a partial schematic view of a stator 20 according to the invention in a further embodiment. In this case, the stator teeth 44 or the tooth flanges 54 (see fig. 3) thereof are guided through the recesses 52 of the second stator yoke 42 and permanently connected to the first stator yoke 26 by laser welding. A bore 60 in the first stator yoke 26, through which the stator teeth 44 can be connected to the first stator yoke 26 by means of laser welding, is arranged approximately centrally on each side of the stator teeth 44 lying on the first stator yoke 26. The weld extends around the entire circumference of bore 60 to permanently connect first stator yoke 26 and the corresponding stator tooth 44. Alternatively, however, it can also be provided that the weld seam extends only point by point over the circumference of the borehole 60. Due to the welding in the center of each stator tooth 44, the guidance of the magnetic flux is only slightly influenced and a high degree of plane parallelism of the stator teeth 44 with the radial air gap located between them can be achieved. Since adhesion is avoided, an adhesion gap between the stator teeth 44 and the first stator yoke 26 can be effectively avoided, and there is no need to fix the stator teeth 44 and the first stator yoke 26 during hardening of the adhesion portion. 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 directly to the stator teeth 44 made of composite material, in particular by means of a bore 60 in the first stator yoke 42, which is designed as a plate-like ring 16 made of soft magnetic iron.

In fig. 5 a cross-sectional schematic view of a rotor 14 of an axial flux machine 10 according to the present invention is shown. The rotor 14 is configured as a plate-like ring 16 made of soft magnetic iron. The rotor 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 rotational motion when the motor is in operation or to induce a voltage into the stator winding 24 when the generator is in operation. The magnet ring 18 is embodied in the form of a circular segment of a magnet, not shown in detail, in such a way that the surface of said magnet coincides to the greatest extent with the circular segment-shaped stator teeth 44 in order to achieve an optimized magnetic flux and at the same time a high torque. Instead of the alternately polarized magnet ring 18, a ring with an embedded single magnet can alternatively also be considered. As mentioned above, the rotor 14 is generally not exposed to the alternating field, so that no or only very little eddy current losses occur here. Thus, the rotor 14 of the axial flux machine 10 can alternatively also be constructed of a non-soft magnetic material.

In a preferred embodiment of the invention, the plate-like ring 16 of the rotor 14 is designed as a rotor yoke 62, which is either permanently connected, in particular glued, to the bidirectional fan 40 by means of a joining process or itself serves as the bidirectional fan 64. In this case,

bidirectional fans

40, 64 have at least one radial air flow direction 66 and one axial air flow direction 68 for cooling axial magnetic flux machine 10, in particular for cooling stator 20 or stator winding 24 and rotor 14. The radial air flow direction 66 is realized here essentially by a plurality of radial air blades 70 arranged circularly in the region of the outer radius of the

bidirectional fan

40, 64, while the axial air flow direction 68 is realized by a plurality of axial openings 72 arranged in the region of the inner radius of the rotor yoke 62.

Thus, referring to fig. 6, the

bi-directional fans

40, 64 cause a radial intake 74 of an air flow 76, accompanied by an axial through-flow 78 of the stator 20 and the rotor 14 of the axial flux machine 10 and a radial escape 80 of the heated air flow 76 from a housing 82 of the axial flux machine 10. The radial intake 74 of the air flow 76 takes place, on the one hand, via the air gap between the stator teeth 44 (see fig. 2) and, on the other hand, in the region of the first stator yoke 26 of the stator 20, in particular on the end face 84 of the first stator yoke 26 that is distal from the rotor 14.

Fig. 7 shows an axial magnetic flux machine 10 with a housing 82 of the axial magnetic flux machine and a cover 86 closing the housing. Fig. 8 shows the housing 82 without the axial flux machine 10 and the cover 86. The housing 82 is open on one side for receiving a cover 86 and has a substantially closed end side 88 (see fig. 8) in opposition. The cover 86 closes the housing 82 and thereby connects the stator 20 and the rotor 14 of the axial flux machine 10 in a force-locking manner. "substantially closed" in this context should be understood to mean that the end face 88 can have a plurality of openings 90, for example for cooling, for cable routing and/or for leadthroughs for the machine shaft 12, but alternatively also that the end face 88 is completely closed. The housing 82 is cylindrical in shape and fixes the stator 20 in such a way that a defined air gap is produced between the rotor 14 or the magnet ring 18 of the rotor and the stator 20 or the winding carrier 22 of the stator. In order to reduce or avoid eddy current losses, the housing 82 is made of a magnetically insulating material, for example plastic (PA66), with a permeability as low as possible. The cover 86 can also be configured accordingly.

The first bearing 28, which is designed as a fixed bearing 30, is fixed in a bearing flange 92 of the cover 86, which first bearing supports the machine shaft 12 in a non-displaceable manner, while the substantially closed end side 86 of the housing 82 has a second bearing 36, which is designed as a floating bearing 38, in a further bearing flange 94 for supporting the machine shaft 12 in a displaceable manner. In this way it is very easy to push the housing 82 open after assembly of the axial flux machine 10 and to remove it again for possible maintenance work.

On the open side of the housing, a plurality of notches 96 and tabs 98 are arranged alternately distributed over the circumference of the housing 82 for receiving and fixing the stator 20. Here, radial projections distributed over the circumference of the first and second stator yokes 26, 42 of the stator 20 (see fig. 2 and 3) fit into corresponding recesses 96 of the housing 82. Correspondingly, the cover 86 also comprises a radial projection configured as a tab 106, which fits into the recess 96 of the housing 82. In this way, high axial forces of the axial flux machine 10 can be conducted in the direction of the cover 86. At least one bore 100 is provided in each web 98 of the housing 82 for fixing the cover 86 and thus also the stator 20 by means of corresponding fastening means 102, in particular screws 104. The fastening means 102 transmits the axial force of the axial flux machine 10 to the housing 82 and is thus subjected to shear forces.

The opening 90 on the substantially closed end side 88 of the housing 82 is designed as a radially and/or axially effective ventilation opening 104, in particular as a ventilation outlet 106, for cooling the axial magnetic flux machine 10 (see also fig. 6). Furthermore, the housing 82 has a plurality of radially active ventilation openings 108, in particular ventilation inlets 110, distributed over the circumference approximately in the middle between the substantially closed end side 88 and the opposite open side in the axial direction a. In addition to the opening 90 for cooling the axial magnetic flux machine 10, a further opening 90 is provided, in particular in the web 98 of the housing 82, which can be used as a lead-through 112 for a sensor line or the like.

In fig. 9a, the circuit diagram of the stator winding 22 is shown as a triangular parallel circuit 48 of six single-tooth windings 46 (see fig. 2) of the stator teeth 44. For each phase, two single-tooth windings 46 are connected in parallel between the connection points U and V, V and W or W and U, respectively. The delta circuit itself causes the entire supply voltage to drop across each single-tooth winding 46. This results in an increase in the number of turns of the single-tooth winding 46 in order to achieve a specific desired rotational speed when the motor is operated or a specific desired energy yield when the generator is operated. By means of the additional parallel circuit, the winding wire diameter can be increased in a particularly advantageous manner and the resulting internal resistance can therefore be reduced. The delta parallel circuit 48 thus enables a reduction of the internal resistance of the axial flux machine 10 compared to a conventional star circuit, which results in a significant increase of the power capability of the axial flux machine 10 compared to previous solutions. Fig. 9b shows an alternative embodiment of a delta parallel circuit 48 for a total of nine single-tooth windings 46 of the stator winding 22.

Fig. 10 shows an exemplary embodiment of an electrical machining device 34 with the axial flux machine 10 according to the invention according to fig. 1. The electric machining tool 34 is designed as an electric power tool 112 in the form of a mains-operated hammer drill with an electric motor-driven hammer impact mechanism 114, which sets a drill chuck 116 for a not shown insertion tool in a rotary and/or percussive motion. The specific configuration of the hammer drill is not discussed in detail here, since this is sufficiently known to the person skilled in the art. An electrical processing device is also understood to mean any other battery-operated or mains-operated electric power tool 112 for processing workpieces by means of an electrically driven insertion tool. The electric machining device can be configured not only as a hand-held electric tool, but also as a stationary electric tool. In this context, typical electric power tools are hand-held or vertical drills, screwdrivers, hammer drills, drill hammers, demolition hammers

The axial flux machine 10 of the electric power tool 112, which operates as an axial flux motor, drives the impact machine 114 via the machine shaft 12 of the axial flux machine in a known manner via a transmission 118. The actuation of the axial flux machine 10 takes place here by means of a main switch 122 arranged in a D-handle 120 of the electric power tool 112, which main switch interacts with electronic means, not shown, for energizing the stator windings 22 connected in the delta parallel circuit 48. The stator 20 of the axial flux machine 10 is directly received in the housing 32 of the electric power tool 112. For this purpose, the stator 20 and the housing 32 are permanently connected to one another by a joining process, in particular by gluing. Alternatively, however, the stator 20 can also be permanently connected to the housing 32 by means of a form-fit connection, in particular by crimping (verpressen). Furthermore, it can be provided that the housing 32 or the transmission housing 122 of the electric power tool 112 receives a second bearing 36, in particular a floating bearing 38, which is connected to the machine shaft 12 of the axial flux machine 10. Instead of the axial flux machine 10 shown in fig. 1, the electric power tool 112 or the electric machining tool 34 can also be equipped with the axial flux machine 10 according to fig. 6 to 8 (without limiting the invention).

Finally, it should be pointed out that the invention is neither limited to the illustrated embodiments according to fig. 1 to 10 nor to the mentioned number of magnets of the stator teeth, of the single-tooth winding and of the magnet ring.

Claims

1. An axial flux machine (10), in particular a single-sided axial flux motor, for an electrical machining appliance (34), the axial magnetic flux machine has a machine shaft (12), in particular a motor shaft, a disk-shaped stator (20), and a disk-shaped rotor (14) arranged adjacent to the stator (20) in an axial direction (A) of the machine shaft (12), wherein the stator (20) is designed as a winding carrier (22) for at least one stator winding (24), and a 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), characterized in that the stator (20) has 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.

2. Axial flux machine (10) according to claim 1, characterized in that a bore hole (60) in the first stator yoke (26) is provided substantially centrally in each face of a stator tooth (44) lying on the first stator yoke (26), through which bore hole the stator tooth (44) can be connected with the first stator yoke (26) by means of laser welding.

3. Axial flux machine (10) according to any of the preceding claims, wherein a weld extends over the entire circumference of the bore hole (60) for connecting the first stator yoke (26) with the respective stator tooth (44).

4. Axial flux machine (10) according to any of the preceding claims 1 or 2, wherein a weld extends only point by point on the circumference of the bore hole (60) for connecting the first stator yoke (26) with the respective stator tooth (44).

5. An electrical machining appliance (34), in particular an electrical machine tool (112), having an axial magnetic flux machine (10) according to one of the preceding claims.