Method and apparatus for manufacturing a rotationally symmetric permanent magnet

Abstract

This invention provides an efficient method and apparatus for manufacturing rotationally symmetric permanent magnets. [Solution] The apparatus manufactures a rotationally symmetric permanent magnet (30) having a magnetization (38) preferentially oriented radially by flow pressing a rotationally symmetric blank (2) made of magnetic material with a transverse punch (6) perpendicular to the blank axis (17), while reducing the cross-section of the blank (2) and extending the axial length of the blank (2) as the blank (2) flows relative to axial end stoppers (4, 5). The flow pressing is repeated periodically by the transverse punch (6) repeatedly closing and opening, and the blank (2) rotating around the axis of the blank (2) between two consecutive flow pressings. This achieves optimized radial magnetization of the permanent magnet (30) and avoids the blank (2) requiring a specific orientation for magnetization.

Description

Technical Field

[0001] The present invention relates to a method and a pressing apparatus for producing rotationally symmetric, in particular ring-shaped permanent magnets having magnetization preferentially oriented in the radial direction, wherein the method comprises carrying out flow pressing (pressure forming) on a rotationally symmetric blank made of a magnetic material by means of a lateral punch transverse to the blank axis while the blank flows towards an axial end stop, reducing the cross-section of the blank and extending the axial length of the blank. In particular, the present invention relates to the production of ring-shaped permanent magnets for rotors of electric machines, in particular for electric motors.

[0002] The present invention enables responsible consumption and production patterns through the optimization of resource utilization and waste reduction by saving magnetic materials for magnet production. This enables a more sustainable production mode and minimizes the ecological footprint, which is consistent with Sustainable Development Goal 12 (SDG12) of the United Nations. Background Art

[0003] The production of rotationally symmetric, in particular ring-shaped permanent magnets having preferential radial magnetization is extremely important in the fields of manufacturing technology, magnetic materials, and metal powder pressing. These magnets are widely used in various applications, especially in electric motors, generators, and other electromechanical devices.

[0004] Methods and presses of the above type are known from Patent Document 1 (EP 3 822 991 B1) below. Patent Document 1 below discloses the manufacture of a permanent magnet from a blank having a cross-shaped cross section. The blank consists of magnetic powder, so-called powder press members, which are pressed together (compression molded) in the axial direction. The powder press members have radially protruding and block-shaped protrusions in cross section, and a lateral punch is pressed against these protrusions, thereby pushing out the volume of the protrusions in the circumferential direction. The blank thus formed is then magnetized in a magnetic field. To manufacture a ring magnet, the blank can be a hollow body. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] European Patent No. 3822991 [Overview of the project] [Problems that the invention aims to solve]

[0006] The above method, on the one hand, reveals that the special, cross-shaped cross-section of the blank is disadvantageous in the case of a hollow body, because the wall thickness of the hollow body is relatively thin in the intermediate region between two adjacent protrusions. As pressed powder, the compression-molded blank is not extremely stable and is rather deformable by hand, which means that the blank can break in the intermediate region when transported into the press machine. In other words, the brittleness of the powder blank is increased due to the thin-walled areas of its special cross-sectional shape. This leads to substandard products and higher manufacturing costs, and in addition, it imposes difficulties in processing and handling powder blanks.

[0007] Another drawback of the method known from Patent Document 1 is that the pressed blank must have a predetermined orientation in the magnetic field in order to generate preferentially directed magnetization. This orientation must be such that, before forming, the intermediate region located between two adjacent protrusions is positioned between the magnetic poles to be generated for magnetization, i.e., within the magnetic pole gap between the respective north and south poles of a permanent magnet. This is because this intermediate region of the blank, while having the least flow during forming, did not experience as much pressure in the lateral pressing direction as the protrusions. In other words, the volume elements of the protrusions collided with each other during flow. As a result, the Weiss domain was not sufficiently oriented in the intermediate region. In the case of a ring-shaped blank, i.e., a hollow blank, the intermediate region is the region with the least wall thickness. If the blank is twisted relative to this predetermined orientation, the magnetization of the blank will not be optimal, and the performance of the magnet will be impaired.

[0008] Therefore, the need for precise orientation increases the likelihood of manufacturing errors. The total time, cost, and complexity of the manufacturing process are inevitably high. This necessitates a more efficient and effective method for manufacturing rotationally symmetric permanent magnets, particularly ring-shaped ones, that have radially preferred magnetization.

[0009] Therefore, the object of the present invention is to overcome the above-mentioned drawbacks and to provide a method and pressing apparatus that enables easier and more reliable handling of blanks, reduces the amount of inferior products, and allows for non-directional preferential magnetization of pressed blanks. [Means for solving the problem]

[0010] The aforementioned problems are solved by the method having the features of claim 1 and by the press apparatus having the features of claim 13. Further advantageous configurations are described in the dependent claims and are described below.

[0011] The present invention proposes a method for manufacturing a rotationally symmetric, particularly ring-shaped, permanent magnet having a magnetization preferentially oriented radially, by flow pressing a rotationally symmetric blank made of a magnetic material with a transverse punch perpendicular to the blank axis, while reducing the cross-sectional area of ​​the blank and extending the axial length of the blank as the blank flows toward an axial end stopper, wherein the flow pressing is periodically repeated by the transverse punch repeatedly closing and opening, and the blank rotating around the axis of the blank between two consecutive flow pressings.

[0012] Furthermore, a press apparatus has been proposed for manufacturing rotationally symmetric, particularly ring-shaped, permanent magnets having a magnetization preferentially directed radially, by flow pressing a rotationally symmetric blank made of a magnetic material, the press apparatus comprising a transverse punch movable laterally with respect to the blank axis and an axial end stopper for pressing the blank while reducing the cross-section of the blank and extending the axial length of the blank as the blank flows toward an axial end stopper, wherein the press apparatus has means for rotating the blank between two consecutive flow press formings.

[0013] In other words, the blank is fluid-pressed multiple times radially and toward the axis of the blank by a press punch until it reaches the desired final shape, or more precisely, until it reaches a predetermined axial length. In each fluid press, the magnetic material is moved transversally, that is, moved in both the circumferential and axial directions, thereby reducing the outer diameter of the blank somewhat locally, however, the magnetic material can only escape in the axial direction because the volume of material pushed aside in the circumferential direction merges between the transverse punches. Here, "transversal" refers to the direction laterally relative to the forward motion of the transverse punch, that is, the forward motion when the transverse punch moves toward the blank axis. Since the pressing is performed laterally relative to the blank axis, it can be called a transversal pressing method.

[0014] Flow pressing in the circumferential direction aligns the principal crystal axis (c-axis), and therefore the magnetic moment of the material, perpendicular to the flow direction and parallel to the pressing direction. The majority of the magnetic moment or Weiss domain remains radially oriented along the entire axial length of the final shape, thus eliminating the need to cut off magnetic material (bottom and edges of the pan-shaped body) at the axial ends of the flow-pressed blank. This results in less magnetic material being required overall for the manufacture of ring magnets. Furthermore, since the magnetic moment or Weiss domain is radially oriented along the entire circumference of the final shape after flow pressing, a specific orientation of the pressed blank is required during magnetization.

[0015] The rotation of the blank around its axis repeatedly directs different portions of the blank's outer shell towards the lateral punches, each portion being different from the portion pressed in the previous press step. Consequently, portions of the blank that were not pressed in the preceding press and may have overflowed radially are pressed in the next flow press to correspond to the concave inner contour of each press punch, and are also smoothed out accordingly.

[0016] The manufacturing method according to the present invention is similar to known rotary aging, i.e., similar to a chipless forming method directed toward a reduction in the cross-section or wall thickness of a workpiece, but this forming method uses a press device in which a transverse punch rotates around the workpiece and vibrates continuously in the radial direction at high speed, thereby striking the workpiece at a speed typically faster than 1,000 strokes per minute. Furthermore, in rotary aging, the workpiece is a long bar or tube, and these bars or tubes are continuously moved axially by the press tool so as to pass over the vibrating transverse punch, or a tapering of the cross-section is generated in a limited axial portion of these bars or tubes. In the latter case, the radial vibration of the transverse punch is superimposed with a radial feed motion by a wedge-shaped outer tappet, which further increases the complexity of the press tool.

[0017] Surprisingly, it has been shown that the orientation of the Weiss domain can be achieved by periodically and repeatedly flow-pressing a rotationally symmetric blank made of magnetic material, and that this orientation enables the manufacture of permanent magnets that are preferentially oriented radially. For this effect, the present invention utilizes the fact that the magnetic material flows or is pressed against an axial end stopper during flow-pressing. Known rotary aging does not have this effect because there is no axial end stop for the workpiece. However, since the magnetic material requires a certain pressing force for the orientation of the Weiss domain, the end stopper is important for magnetic reasons in the method according to the present invention. If the material can always escape and flow, as in conventional rotary aging, the optimal orientation of the magnetic moment cannot be achieved.

[0018] The present invention solves the problems described at the beginning of this specification, namely the increased brittleness of powder blanks, the specific orientation of pressed blanks for magnetization, and the increased susceptibility and complexity of the manufacturing process. The blanks used in the method according to the present invention are more stable, and the pressing method is more reliable and simpler.

[0019] The permanent magnet to be manufactured is rotationally symmetrical, having a circular cross-section. Viewed in the axial direction, the permanent magnet to be manufactured may be cylindrical, that is, it may have a constant cross-section along its axis. The method according to the present invention also enables the manufacture of permanent magnets whose diameter changes along the axis. That is, for example, it is also possible to manufacture conical permanent magnets, particularly conical ring magnets. The conical outer contour serves to fix the permanent magnet in place, for example, in an outer rotor application where the ring-shaped permanent magnet is part of a rotor that rotates around an internally located stator. In other words, the conical outer contour allows the permanent magnet to be fixed within the support ring.

[0020] Advantageously, the final shape of the pressed blank directly corresponds to the shape of the permanent magnet to be manufactured, thereby eliminating the need for further forming steps. In this case, the lateral punch directly defines the final shape or outer contour of the permanent magnet to be manufactured.

[0021] The outer contour of the blank can be cylindrical or conical in its axial longitudinal section. The radial cross-section is preferably circular, but may optionally be polygonal.

[0022] In one implementation variation, the blank is a solid workpiece, particularly a solid cylindrical body. This is used to manufacture rotationally symmetric permanent magnets having a solid cross-section, such as solid cylindrical or solid conical permanent magnets.

[0023] In another preferred embodiment, the blank constitutes a hollow body, particularly a hollow cylindrical body. Preferably, the hollow space extends coaxially with the blank axis passing through the blank, thereby eliminating the need to remove material from the interior to manufacture a ring magnet. Therefore, the hollow blank is used to manufacture rotationally symmetric permanent magnets having a hollow cross-section, i.e., tubular or ring-shaped permanent magnets. To achieve the final shape, only the cross-section or wall thickness of the blank needs to be reduced.

[0024] Preferably, the cross section of the hollow space is also circular. Alternatively, however, the cross section may be polygonal. However, the cross section of the hollow space and the cross section on the outside of the blank should be dimensioned such that there are no partially thin-walled portions smaller than 2 mm along the circumference, because such thin-walled portions increase the risk of breakage of the blank. Therefore, a blank having a circular outer diameter and a circular hollow space has improved structural integrity. Preferably, the wall thickness of the blank is not less than 2 mm. Ideally, the wall thickness is between 10 mm and 20 mm.

[0025] The inner contour of the blank can be selected independently of the outer contour, but from the viewpoint of process technology, it is advantageous if both contours are cylindrical, that is, the blank as a whole forms a cylindrical or tubular member.

[0026] Furthermore, a hollow cylindrical blank has the advantage that a rotatable center pin protrudes through the blank and can be used to rotate the blank by rotating the center pin. For this purpose, a force fit (friction fit) and / or a form fit can already be provided between the center pin and the blank before the first flow pressing. Such a force fit (friction fit) and / or form fit is obtained, for example, when the blank is first pressed (compression molded) in the axial direction in a press device before flow pressing. Alternatively, play can be provided between the blank and the center pin before flow pressing, whereby no force fit (friction fit) or form fit is yet obtained. In this case, the force fit (friction fit) or form fit is obtained in the first flow pressing, because the magnetic material is pressed against the center pin.

[0027] In order to achieve form-fitting coupling in the circumferential direction between the center pin and the blank, the center pin can have an outer contour different from a circular shape, and the center pin does not rely on force coupling (friction coupling), which enables the rotational motion of the center pin to be transmitted to the blank. Therefore, form-fitting coupling is particularly advantageous for the following reason: that is, after the pressed blank reaches its final shape, it must be pushed off from the center pin, and for this reason, the blank should not adhere too fixedly to the center pin. To prevent the magnetic material from welding to high-temperature tool components, a release agent can be applied to the blank and / or the center pin. However, when there is no form-fitting coupling, the release agent carries the risk of relative rotational motion between the center pin and the blank. To avoid this when force coupling (friction coupling) is insufficient for rotational interlocking of the blank, an additional form-fitting coupling between the center pin and the blank is meaningful. For example, the center pin can thereby have a substantially angular cross-section, in particular a rectangular cross-section, with rounded outer edges.

[0028] In the method according to the present invention, it can be assumed that the blank is rotated a total of 6 to 24 times. This results in uniform flow of the magnetic material and the absence of dead zones having unflowed regions when viewed in the circumferential direction.

[0029] Meaningfully, it should be avoided that the rotation angle of the blank of 360° is divided by the number n of lateral punches or is a multiple of this angle, for the reason that in this case, the circumferential portion of the blank pressed by the first lateral punch in the last flow pressing is only completely rotated in the circumferential direction to the position in front of the second lateral punch adjacent to the first lateral punch, which causes the same circumferential portion to be pressed again in the next flow pressing. Accordingly, the intermediate portions between the pressed circumferential portions, which have not been pressed in the last flow pressing, remain unpressed further.

[0030] The number of horizontal punches can take values ​​between 4 and 8, for example, 4, 5, 6, or 8.

[0031] Therefore, when 4, 5, 6, or 8 lateral punches are arranged or used, it is ideal for the blank to be rotated at an angle between 25° and 45°, preferably between 30° and 35°. This rotation is minimal on the one hand, but sufficient on the other hand to press the blank along its entire circumference.

[0032] It is even more advantageous if the rotation angle when repeatedly rotating the blank is numerically different from the rotation angle of the previous rotation. That is, the rotation angle in the first rotation could be, for example, 25°, and in the second rotation it could be 35°. In one implementation variation, it can even be assumed that a numerically different rotation angle is used for each rotation of the blank. This ensures that the same circumferential portion of the blank is not pressed alternately.

[0033] In one implementation variation, the blank can be rotated back and forth instead of always rotating in the same direction. In this case, the blank performs an oscillating rotational motion or a reciprocating rotational motion. This makes it possible to manufacture a ring magnet with four poles having a smaller radius when viewed circumferentially toward the ends, for example, for use in the rotor of an electric motor, thereby forming a gap expansion that generates a sine-shaped inductive action within the stator of the electric motor.

[0034] Fluid pressing can be performed, for example, 6 to 12 times per minute. In other words, a new fluid pressing operation is performed every 5 to 10 seconds. Preferably, the fluid pressing is performed without abrupt movements, using continuous force introduction maintained for several seconds, for example, 5 to 10 seconds, and the force introduction is brought about by a forward motion that advances a lateral punch with a predetermined stroke length. Thus, the method according to the present invention is fundamentally different from known rotary aging, which typically involves approximately 1000 punches per second, i.e., acting on the workpiece with abrupt movements. The method according to the present invention is far quieter, with fluid pressing operations performed at a relatively small number of times per minute. Furthermore, the method according to the present invention takes into account the material and properties of the blank. That is, magnetic materials are brittle and can easily break under the force of abrupt movements. Furthermore, the blank may be a powder pressing member, which is relatively soft, plastic and easily deformable, at least at the start of the method. In this case, punching will cause breakage within the blank.

[0035] As a result of repeated flow pressing, the blank is formed into its final shape through a gradual process. In this process, the press travel distance performed each time by the lateral punch increases by the stroke length of the lateral punch with each iteration of the flow pressing, and can take a value between 0.25 mm and 1.0 mm. Preferably, the press travel distance is larger at the start of the method and decreases with each flow pressing. In this process, the blank forming speed also changes.

[0036] More preferably, in the method according to the present invention, the blank may be heated to a processing temperature before fluid pressing, and then fluid pressed in this heated state. This promotes the fluidity and deformability of the magnetic material, thereby promoting the orientation of the Weiss domains. This heating can be performed using a heating device within the press apparatus. The processing temperature can be located between 750°C and 900°C. Thus, the fluid press according to the present invention may be referred to as a warm fluid press or a hot fluid press.

[0037] As previously described, the blank is often a powder press member, which is made by axially pressing magnetic material powder within a press die of a press device using an upper punch and a lower punch. The upper and lower punches move relative to each other in the axial direction while the powder press member is positioned between them, and the press die has an internal space that defines the outer contour of the blank. In this case, the powder press member is made of compacted powdered magnetic material and is also called a green member. Compaction reduces the hollow space within the magnetic powder, thereby reducing the volume of a given mass of magnetic powder. However, within the powder press member, the powder particles are not bonded to each other, and therefore the powder press member can be pulverized again with little force. Nevertheless, the powder press member facilitates portioning of the amount of magnetic powder.

[0038] This press apparatus can be the same as the press apparatus that performs the flow pressing according to the present invention. In other words, the press apparatus according to the present invention includes not only a lateral punch and an optionally provided center pin, but also a press die and an upper and lower punch guided within the press die, wherein the upper and lower punches are axially movable relative to each other in order to create a blank from the powder press member by axial pressing within the press die. This has the advantage that the upper and lower punches can constitute end stoppers for the blank during flow pressing. To this end, the blank and the upper and / or lower punches are appropriately positioned relative to each other before flow pressing so that the upper and / or lower punches constitute axial end stoppers for the flowing magnetic material during flow pressing of the blank. A further advantage of performing axial pressing of the powder press member and flow pressing of the blank on the same apparatus is that energy is saved because additional heating of the workpiece is not required between both of these pressing steps. Furthermore, the risk of stress cracking during cooling is avoided. Oxidation is also reduced because there is no need to transport the hot blank from one press apparatus to the other.

[0039] Before the first flow press, gaps may form between the blank and the upper punch, or between the blank and the lower punch, or between the blank and the upper punch and the blank and the lower punch, and these gaps continuously decrease as a result of the flow press. However, it is also possible for the upper and / or lower punches to be in contact with the blank without any gaps, to be spring-biased to press against the blank, and to be able to flex during the flow press. In this case, the upper and / or lower punches are pushed back against the corresponding spring force during the flow press of the magnetic material. This has the advantage that, even at the first flow press, or more precisely at any point, free flow of the magnetic material does not occur at the axial end of the blank, but rather a reaction force exists due to the spring force that promotes the orientation of the Weiss domains.

[0040] As previously described, the means for rotating the blank can be the aforementioned center pin protruding through the blank, on which the blank is positioned so as to be unable to rotate relative to the center pin as a result of force coupling (friction coupling) and / or shape coupling. In this case, the center pin is rotatable or rotatable. Alternatively, the means for rotating the blank can be a rotary table on which the blank is positioned and which is rotatable or rotatable. Further alternative, the means for rotating the blank can be a lower punch on which the blank is mounted and which is rotatable or rotatable. This means can be rotated or swiveled, for example, using a servo motor.

[0041] In one implementation variation, the flow press can be performed radially with respect to the blank axis. This means that the direction of motion of the lateral punch is linear and the force direction is always directed toward the blank axis. In this case, the lateral punch has a symmetrical pressing surface. This simplifies the structure of the press and ensures that the pressing surface is evenly loaded. However, it is also possible for the direction of motion of the lateral punch to be secant with respect to the blank axis, or to extend along a curved trajectory that curves in an arc toward the blank axis. Secant means that the main direction of motion of the lateral punch is parallel to the radius, that is, directed in a direction that passes by the blank axis. This allows for influence on the material flow in the circumferential direction.

[0042] For the magnetic material used in powder press components, a ferromagnetic material containing rare earth elements, such as an alloy made of neodymium-iron-boron (NdFeB), can be used.

[0043] Further advantages and features of the present invention will be described below based on examples and accompanying drawings.

[0044] Within the framework of this specification, it should be noted that the concepts of "having," "containing," or "having the content of" do not in any way preclude the existence of other characteristics. Furthermore, the use of an indefinite article with respect to a single object does not preclude the plural form of that object.

[0045] The reference numerals used in the figures have the same meaning and identify elements that function identically or similarly from one figure to the next. [Brief explanation of the drawing]

[0046] [Figure 1] This figure shows a flowchart of the method according to the present invention. [Figure 2] This figure shows a flowchart for step S3 of the method shown in Figure 1. [Figure 3] This figure shows the axial pressing of a powder press member for blanking. [Figure 4] This figure shows a radial cross-section of a ring magnet with a preferred radial orientation. [Figure 5] Figure 2 shows the molding process of a blank during fluid press. [Figure 6] This is a diagram illustrating the steps of the method according to the present invention. [Figure 7] This diagram shows a press machine in a perspective view. [Figure 8] This diagram shows the start and end states of a press machine during a fluid press, superimposed on a radial cross-section at the height of a lateral punch. [Figure 9] This figure shows the axial cross-section of the press machine along the EE cutting line in Figure 8. [Figure 10] This is a diagram showing the punch itself. [Figure 11] This figure shows a punch body having an edge projection at its circumferential end. [Figure 11a] This figure shows an enlarged view of the punch body shown in Figure 11, which includes a pressing surface. [Figure 12]This figure shows a punch body having a stepped projection at its axial end. [Modes for carrying out the invention]

[0047] Figure 1 illustrates the overall procedure of the method according to the present invention, which consists of the steps described below.

[0048] In the first step S1, the powder press member 1, which is made of fine-particle powdered magnetic material, is manufactured by compression molding this powder. The magnetic material may be, for example, rare earth element-iron-cobalt-boron or neodymium-iron-boron (NdFeB). The powder press member 1 is a hollow body having an arbitrary ring shape. The hollow space 14 is cylindrical and may be circular or polygonal in cross-section.

[0049] In the second step S2, the powder press member 1 is compacted to form a blank 2. At this time, the powder press member 1 is introduced into a hot press and pressed axially with a force F at a temperature between 750°C and 850°C. Figure 3 illustrates this process. During this process, the height of the powder press member 1 is reduced, thereby achieving maximum density.

[0050] In the third step S3, a lateral punch 6 is used to press laterally with respect to the blank axis 17, and the blank 2 is formed by radial flow pressing (press molding), causing the material volume of the blank 2 to flow in the axial direction. This molding is repeated n times, and the blank 2 is rotated after each press. Figure 2 shows a detailed view of the third step S3.

[0051] The forming in step S3 is carried out while the blank is heated, more precisely at a processing temperature of 750-850°C. The blank is then further heated, or reheated if the second step S2 was performed outside the press equipment that performed the radial pressing in step S3 (step S31).

[0052] Once the processing temperature is reached, the first flow press is initiated. This is illustrated in the program technically in Figure 2, where first the control variable i is initialized to a value of 1 (see step S32). Next, the first flow press is performed (step S33). This flow press is performed using a force of approximately 15-20 kN in the lateral direction, i.e., radially, relative to the blank axis 17. This press step S33 is performed for a number of times n, ranging from 6 to 24, to achieve uniform deformation of the blank 2.

[0053] After the first flow press and after each subsequent flow press, a question is asked as to whether the planned number of press formings n has already been performed (see step S34). If not, the counter variable i is incremented by 1 (step S35), and the flow press in step S33 is repeated. However, before that, the blank 2 is rotated around the blank axis 17, that is, rotated at an angle between 25° and 45° (step S36). This rotation yields a more stable permanent magnet 30 in the shape of a circular ring. In this case, the tool does not rotate around the workpiece, that is, the lateral punch 6 does not rotate around the blank 2, but the workpiece (blank) rotates around itself, and the tool (lateral punch 6) is fixed. Once the planned number of press formings n has been performed, the third step S3 is completed, and step S4 is executed.

[0054] In each flow press in step S33, the lateral punch 6 moves to close and open. More precisely, the lateral punch 6 first moves radially in the direction of the blank axis 17 (this corresponds to a closing motion), thereby moving a portion of the material volume of the blank 2 to close. Subsequently, the lateral punch 6 moves to open again in order to release the blank 2, by retracting radially from the blank axis 17 (this corresponds to an opening motion). In each closing motion, or each second or third closing motion, the lateral punch moves slightly further forward, until at the end of the last, i.e., nth flow press, they are flush with each other in the circumferential direction.

[0055] Figure 5 shows the forming process of blank 2 during the fluid press in step S3 from three visual perspectives: a side view (top), a top view (middle), and an oblique view (bottom). Each figure is shown at four different time points A through D. In this case, the same time point is arranged vertically. Therefore, Figure 5 shows 12 individual figures of blank 2, and chronologically, blank 2 is formed from left to right.

[0056] Before the first flow press, i.e., at time A, the blank 2 is provided as the shape shown on the far left. This shape represents the state of the blank 2 after axial pressing of the powder press member 1, and is the initial shape 2a for the flow press. In the initial shape 2a, the blank 2 has an outer diameter of approximately 29-31 mm and an axial length (height) of 12-14 mm. The final shape 2b of the blank 2 is shown on the far right. The blank 2 is a hollow body having a cylindrical outer contour 13 with a circular cross-section and a concentric hollow space 14 with a cylindrical inner contour 16 with a circular cross-section. The blank axis is indicated by reference numeral 17.

[0057] Time point B shows the blank 2 after the first flow press in step S33. The lateral punch 6 is moved here to close and then open again, as visualized by the bidirectional arrows, and in its resting position it is spaced apart from the blank 2. The lateral punch 6 deforms the blank 2 using its pressing surface 43 (see Figures 10-13), thereby shifting the pressed surface 15 of the outer shell of the blank 2 in the direction of the blank axis 17 relative to the original outer diameter 11, which is characterized by the dashed circle.

[0058] The lateral punches 6 define the outer contour of the final shape 2b of the blank 2 only when they are closed and in contact with each other (see time point D in Figure 5 for this). Therefore, at the start of the flow press, there are intermediate regions 18 between two adjacent pressed surfaces 15 that are not pressed by the lateral punches 6. Within these intermediate regions 18, protrusions 21 are formed that project radially from the blank 2 as a result of the flow press. These protrusions 21 are elongated and extend parallel to the blank axis 17, as shown in the side view (upper) and perspective view (lower) at time point B. At this time, some of the magnetic material of the blank 2 is ejected radially from the intermediate regions 18 during the flow press, allowing the protrusions 21 to extend radially beyond the outer diameter 11 of the initial shape 2a.

[0059] The blank 2 is lengthened in the axial direction by the flow press, which can be seen based on the side view (top) and the perspective view (bottom). At times B, C, and D, the center pin 7 protrudes through the hollow space 14. The center pin 7 has a square cross-section, and this cross-section has rounded side edges such that its diagonal from one side edge to the opposite side edge is substantially corresponding to the inner diameter 12 of the hollow space 14 of the initial shape body 2a, or several times smaller by a tenth of a millimeter, in order to insert the center pin 7 into the hollow space 14. As a result, there is free space between the side portion of the center pin 7 and the inner contour portion 16 of the hollow space 14. The inner diameter 12 is illustrated by a circle similarly shown as a dashed line in Figure 5. As can be seen from the top view (middle panel) at time B in Figure 5, based on the previous inner diameter 12 and the new inner contour 19 of the hollow space 14, the first flow press moves a portion of the material volume of the blank 2 toward the center pin 7 and pushes it into the free space. Furthermore, the material volume of the blank 2 surrounds the center pin 7 at its side edges in a shape-coupled and force-coupled (friction-coupled) manner.

[0060] At time point C, the blank 2 has been fluid-pressed for the second time, but with a relative orientation to the lateral punch 6 that is rotated by an angle 20° counterclockwise compared to the orientation at time point B. This rotated orientation is still present at time point C, as shown in Figure 5. The rotation at angle 20 occurred before the second fluid press and has the following result: the protrusion 21 that existed at time point B has been rotated in front of the lateral punch 6 and was part of the pressed surface 15 during the second fluid press, i.e., it was pressed in the same way. This can be seen by the fact that the protrusion 21 is now substantially flattened and therefore no longer protrudes radially from the blank 2 as a protrusion 21. Instead, a new protrusion 22 has formed within the intermediate region 18. The magnetic material of the blank 2 has also been further pushed toward the center pin 7 and is now in contact with the center pin 7 almost all the way around, so that the new inner contour 19 corresponds almost to the outer contour of the center pin 7. Furthermore, the side view (top) and perspective view (bottom) at time point C show that, compared to time point B, blank 2 has become longer in the axial direction due to the new flow press.

[0061] The rotation of the blank 2 at a rotation angle 20 around the rotation axis 17 of the blank 2, and the subsequent flow pressing, are performed several more times after time C in Figure 5 until the final shape 2b at time D in Figure 5 is achieved. In this process, the rotation angle and direction may be the same or different between the two press formings. The previous protrusions 21 are no longer visible in the final shape 2b due to the repeated rotation and pressing of the blank 2. The cylindrical outer contour 24 of the final shape 2b is smooth, or smooth except for slight irregularities 23, which cannot be removed by further radial pressing.

[0062] In the final shape 2b, the blank 2 has reached its desired length, which is determined by the distance between the upper punch 4 and the lower punch 5 of the press device 50 that performs the flow press. The axial end faces of the upper punch 4 and the lower punch 5, facing the blank 2, constitute axial end stoppers during the axial flow of the blank 2 during pressing. In the final shape 2b, the blank 2 has an outer diameter of approximately 23 mm and an axial length (height) of approximately 30 mm. Thus, compared to the initial shape 2a, the blank 2 has been reduced in diameter by approximately 7 mm, or in wall thickness by approximately 3.5 mm, and its axial length has been increased by approximately 17 mm. The final shape 2b constitutes a hollow cylindrical body (circular cylinder) corresponding to the ring-shaped permanent magnet 30 to be manufactured.

[0063] It should be noted that the drawing in Figure 5 is used solely to illustrate the basic concept of the method according to the present invention. In particular, the dimensions of the projections 21 and 22 have been selected here so that the projections 21 and 22 can be clearly seen in the detailed view in Figure 5. In practice, the stroke length of the lateral punch 6 may be so small that the projections 21 and 22 are almost indistinguishable, or at best still identifiable in the first press forming.

[0064] To reduce the blank 2 (in outer diameter) from 31 mm to 23 mm, or approximately 8 mm, each lateral punch 6 must move a maximum stroke length of 4 mm. This can be done, for example, in n=10 fluid press forming processes using a press travel distance of 0.4 mm each. In other words, in the first fluid press, the lateral punch 6 moves along a stroke length of 0.4 mm relative to the blank 2, and this stroke length is the same as the press travel distance mentioned above. In the second fluid press, the lateral punch 6 moves with a stroke length of 0.8 mm, in the third fluid press with a stroke length of 1.2 mm, and so on, until in the tenth fluid press the total stroke length is 4 mm, while the blank 2 is pressed only by a press travel distance of 0.4 mm in each fluid press. The total stroke of the lateral punch 6, i.e., the total length of the movement of the lateral punch 6, is understood to have an offset added that corresponds to the distance between the lateral punch 6 and the blank 2 before the fluid press.

[0065] Now, returning to Figure 1, in the fourth step S4 following step S3, the pressed blank 2 is cooled to room temperature. Cooling occurs at a rate of approximately 10°C per minute.

[0066] In the fifth step S5, the pressed blank 2 undergoes final mechanical processing, during which the blank 2 is brought to the desired shape and size.

[0067] In the sixth step S6, the formed and final processed blank 2 is magnetized. This magnetization can be performed with the blank mounted inside the rotor of the electric motor, thereby magnetizing the rotor. In other words, the blank 2 is mounted in a non-magnetic state and is magnetized only after the rotor is completed. The result is a ring-shaped permanent magnet 30 having radially preferred magnetization 38.

[0068] The manufactured permanent magnet 30 has a circular cross-section that provides high mechanical stability. This permanent magnet 30 is not easily damaged, thus ensuring reliable integration. Furthermore, the permanent magnet 30 also possesses an optimal radial magnetic preference direction 38, eliminating the need for precise orientation during magnetization. The radial magnetic preference direction 38 of the permanent magnet 30 is shown in Figure 4. Therefore, this method is generally error-resistant, reliable, and stable.

[0069] In Figure 5, a blank 2 is formed in the initial shape 2a, having a circular inner contour 16 of a hollow space 14 in cross-section. This inner contour 16 gradually conforms to the outer contour of the center pin 7 during the flow press, whereas in another embodiment variation, the inner contour 16 of the hollow space 14 of the initial shape 2a can directly correspond to the cross-section of the center pin 7 when viewed in cross-section. This is true, for example, when the axial press in the second step S2 is performed by the same press device 50 that performs the radial flow press; more precisely, when the center pin 7 shown in Figure 5 has already protruded through the powder press member 1 during the axial press in step S2. This applies to the press device 50 described below based on Figures 6 to 9.

[0070] Figure 6 shows the main components of the press apparatus 50 according to the present invention, as well as the progress of the method according to the present invention performed in the press apparatus 50. The press apparatus 50 according to the present invention is used to manufacture a ring-shaped permanent magnet 30 by forming a blank 2 from its initial shape to a final shape 2b. The press apparatus 50 includes an upper punch 4, a lower punch 5 with a center pin 7, a press die having an upper part 8 and a lower part 9, and a lateral punch 6. A cover plate 91 covers the press dies 8 and 9, which are heatable to heat the blank 2 to a processing temperature. Furthermore, a spacer plate 52 is positioned between the cover plate 91 and the press die or upper part 8.

[0071] The lower punch 5 is configured as a hollow shaft, and a center pin 7 is coaxially movably guided within the lower punch 5. The center pin 7 can be moved and rotated linearly relative to the lower punch 5 and upper punch 4, independently of them. Press dies 8 and 9 are used to guide the upper punch 4 and lower punch 5 in the axial direction. For this purpose, press dies 8 and 9 have axial longitudinal holes, and their cross-sections substantially correspond to the outer cross-sections of the lower punch 5 and upper punch 4. The upper punch 4 and lower punch 5 similarly have the same cross-section. The upper punch 4 and lower punch are also movable relative to each other within the longitudinal holes. Press dies 8 and 9 further have lateral holes, within which a lateral punch 6 is linearly guided along the lateral press axis 39 in the direction lateral to the longitudinal press axis 10.

[0072] The first part of Figure 6, Figure A, shows the insertion position of the powder press member 1 into the press device 50 according to the present invention. For this purpose, the upper punch 4 is moved to a distance from the press molds 8 and 9 in order to position the powder press member 1 on the lower punch 5. In addition, the lower punch 5 is fed out from the press molds 8 and 9 such that the axial end of the lower punch 5 protrudes slightly in front of the cover plate 91. To achieve axial centering of the powder press member 1, the center pin 7 protrudes slightly from the lower punch 5 in the axial direction, thereby allowing the powder press member 1 to be placed on the lower punch 5 such that the center pin 7 is located in the hollow space 14.

[0073] The lower punch 5 continues to move within the press molds 8 and 9 until the powder press member 1 is completely positioned within the lower part of the press mold 9, that is, below the lateral punch 6. This is shown in part B of Figure 6, at which point the powder press member 1 is positioned at a first axial height H1. The upper punch 4 follows the lower punch 5, and is first positioned so that its axial end facing the powder press member 1 is in contact with the powder press member 1 (see part B). The center pin 7 is positioned so that it completely fills the hollow space 14 of the powder press member 1, and in particular so that it protrudes into the blind hole 51 of the upper punch 4. This state is the initial state at the start of the axial press in the second step S2, and the press molds 8 and 9 continue to be heated for the axial press.

[0074] The lower punch 5 then presses the powder press member 1 against the upper punch 4 in the axial direction, moving toward the upper punch 4 as a result of the resulting volume reduction of the powder press member 1. The center pin 7 moves along with this movement, and as a result, the center pin 7 is inserted deeper into the blind hole 51 at the end of the axial press. Partial figure C of Figure 6 shows the final state of the axial press. At this point, a blank 2 is formed from the powder press member 1, in which the magnetic material is compacted, and in terms of shape and size, it differs from the powder press member 1 only in its axial length.

[0075] The manufactured blank 2 is then moved to a second axial height H2 where the lateral press axis 39 of the lateral punch 6 is located. This transport is performed by a center pin 7 to which the blank 2 is force-coupled (friction-coupled) based on the axial press. As shown in the partial diagram D of Figure 5, the blank 2 is then positioned in the center with respect to the axial height of the lateral punch 6, either in front of or between the lateral punch 6. The height of the lateral punch 6 is dimensionally determined so that the height of the lateral punch 6 is greater than the axial length of the blank 2 in the initial shape 2a of the blank 2, in order to allow the blank 2 to flow axially in a controlled manner during forming. The pressing and flow orient the crystal axes within the magnetic material that generate magnetic dipoles radially.

[0076] To prevent the movement of the lateral punch 6 from being obstructed, the upper punch 4 and lower punch 5 are set back from the alignment of the lateral punch 6. However, the upper punch 4 and lower punch 5 are positioned so that they constitute axial end stoppers for the axially flowing blank 2. As shown in the partial diagram D of Figure 5, the upper punch 4 is aligned with the upper guide portion of the lateral punch 6, or the upper guide portion of the lateral hole in the press die 8, 9, and the lower punch 5 is aligned with the lower guide portion of the lateral punch 6, or the lower guide portion of the lateral hole in the press die 8, 9. Since the size of the lateral punch 6 along the longitudinal press axis 10 is greater than the axial length of the blank 2, the positioning of the upper punch 4 and lower punch 5 provides a gap to the blank 2 such that an upper hollow ring space 58 is formed between the upper punch 4 and the blank 2, and a lower hollow ring space 59 is formed between the blank 2 and the lower punch 5. The ring spaces 58 and 59 form empty relief volumes for the material to be formed in the blank 2. Furthermore, the axial end faces of the upper punch 4 and lower punch 5 constitute axial end stoppers for the blank 2 to be formed, as these end faces define the ring spaces 58 and 59.

[0077] Part D of Figure 5 shows the initial state of the fluid press according to the present invention following step S3, in the direction laterally to the longitudinal press axis 10 or laterally to the blank axis 17. At this time, the lateral punch 6 is moved to close laterally to the blank axis 17 or radially toward the blank axis 17 (closing motion) under the application of a press force F illustrated by the thick arrow in Part D, and the blank 2 is pressed thereafter. Since the blank 2 already has maximum density due to the axial press, the radial press causes the volume elements of the blank 2 to move (i.e., flow). This occurs in the axial direction because the blank 2 can only escape into the ring spaces 58, 59. Thus the blank 2 flows in the axial direction, and the length of the blank 2 increases (see the detailed view in Figure 5, upper panel, from time A to time B).

[0078] This radial flow press is performed repeatedly according to the present invention. This causes the lateral punch 6 to be pulled back again radially away from the blank axis 17 (opening motion), thereby releasing the blank 2. The stroke length of the lateral punch 6 is short in the first flow press so that the blank 2 does not reach the end stopper, i.e., the upper punch 4 and lower punch 5. It is only after multiple flow presses that the blank 2 reaches them.

[0079] After the first radial flow press (step S33 in Figure 2), the blank 2 is rotated 25 around its axis 17, which is the same as the longitudinal press axis 10 (step S36 in Figure 2). This rotation 25 is performed from 25° to 45°, for example, at a rotation angle 20 in Figure 5, i.e., 30°. The rotation of the blank 2 is brought about by the rotation of the center pin 7. The lower punch 5 is hollow to accommodate the center pin 7. The lower punch 5 has a hollow space that extends along its entire axial length and has a cylindrical diameter, thereby allowing the center pin 7 to rotate relative to the lower punch 5. However, a shape coupling between the center pin 7 and the lower punch 5 is also possible, allowing the lower punch 5 to rotate in order to rotate the blank 2.

[0080] After rotation, the lateral punch 6 performs a further closing motion, and the blank 2 is pressed again. At this time, the stroke length of the lateral punch 6 is greater than that of the previous flow press, but not yet at its maximum. The volume elements of the blank 2 are moved again, and the blank 2 flows slightly further in the axial direction. Subsequently, the lateral punch 6 performs a new opening motion, followed by further rotation 25 of the blank 2 by the center pin 7 and further closing motion of the lateral punch 6. This is repeated from n=6 to n=24 times. After the nth flow press, the blank 2 is finally flowed against the upper punch 4 and lower punch 5, and is therefore completely pressed. The final shape 2b thus produced is then discharged from the press device 50.

[0081] Partial diagram E of Figure 5 shows the extrusion position of the final shape 2b that constitutes the molded blank 2. For extrusion, the upper punch 4 is first moved out of the press die and positioned apart from the cover plate 91. The lower punch 5 is similarly moved slightly forward from the cover plate 91. The center pin 7 is pulled back within the lower punch 5 and exits the pressed blank 2. The final shape 2b can then be removed from the press device 50.

[0082] Figures 7, 8, and 9 show the press apparatus 50 as a perspective view (Figure 7), a radial cross-section (Figure 8), and an axial cross-section (Figure 9).

[0083] The press device 50 has a turntable 54 including a lower plate 55 and an upper plate 56, in which the upper plate 56 has been removed in Figure 7 to make the lateral punch 6 and press space visible. The stroke pistons 61 of each hydraulic cylinder 53 are connected to the turntable 54 on opposite sides. A joint eye 62 fixed to the end of the stroke piston 61 engages with a bolt 63 that extends between both plates 55 and 56 of the turntable 54 and is fixedly connected to these plates 55 and 56. The stroke piston 61 is linearly movable, and the motion of the stroke piston 61 is directed tangentially to the turntable 54, so that the turntable 54 is rotated by an angle α by the motion of the stroke piston 61 (see Figure 8).

[0084] Each of the lateral punches 6 is connected to a knee lever 64 via a knee joint (hinge joint) 66 at its radially outer end. The knee lever 64 engages with a joint bolt 67 and is pivotable (rotatable) around the axis of the joint bolt 67. The joint bolt 67 is fixedly connected at both ends to both plates 55, 56 of the turntable 54. To save material, the plates 55, 56 of the turntable 54 have extensions 77, and one of the joint bolts 67 of the knee lever 64 is located in the area of ​​these extensions 77. This reduces the outer diameter of the upper plate 55 and the lower plate 56 between two adjacent extensions 77 in the circumferential direction. Two of each of the extensions 77 on one side are simultaneously used as points of action for one of each of the stroke pistons 61, and in this case, both of these extensions 77 are configured to be wider in the circumferential direction than both of the other extensions 77 in order to provide sufficient space for the points of action.

[0085] Each knee lever 64 has a fork-shaped receiving portion directed toward the corresponding lateral punch 6, which includes an upper projection 68 and a lower projection 69 spaced apart from and opposite to the upper projection 68. The knee joint 66 is composed of a joint pin which extends through both projections 68, 69 and is fixed beyond these projections 68, 69. A pivot 90 is disposed between the projections 68, 69 of the fork-shaped receiving portion, and the pivot 90 constitutes the outer radial end of the lateral punch 6. The pivot 90 has a hole through which the joint pin similarly extends.

[0086] Each lateral punch 6 is guided within a guide element 65, which is fixed to a flat portion 74 of the outer wall of the heating box 71. The heating box 71 surrounds a heating chamber 72, and within the heating chamber 72, a heater 57 consisting of heating wires 78 is arranged to surround the press die (see Figures 8 and 9). The lateral punch 6 extends into the interior of the heating chamber 72 through an opening 75 in the heating box 71 (see Figure 7 in particular). In Figure 7, the upper part 8 of the press die has been removed, so that the lower part 9 of the press die, which is equipped with the lateral punch 6, is visible.

[0087] As shown in Figures 8 and 9, the lateral punch 6 consists of a punch support 70 and elongated punch bodies 40, 41, and 42, respectively. Figures 10 to 12 show various implementation variations of the punch bodies 40, 41, and 42. The punch bodies 40, 41, and 42 are detachably fixed to the punch support 70. This fixing is done at one radially inward end of the punch support 70, while the other radially outward end has a pivot 90, which is used to connect the punch support 70 to a knee lever 64 via a knee joint 66. Only the punch support 70 is guided within the guide element 65, and its radially inward end is located inside the heating chamber 72 to allow for easy removal of the punch bodies 40, 41, and 42.

[0088] Figure 7 shows the press device 50 with the lateral punch 6 pressed in. In this state, as can be seen in the partial diagram D of Figure 6, the center pin 7 protrudes beyond the lateral punch 6 in the axial direction.

[0089] Figure 8 shows the start and end positions of the rotational movement of the press device 50 as an overlay. A ring-shaped blank 2 can be seen in the center of the press device 50. The lateral punch 6 is open here. The rotation of the turntable 54 results in the axis of the joint bolt 67 moving along a circular orbit. This causes the knee lever 64 to rotate around the joint bolt 67, in which case, depending on the direction of motion, the lateral punch 6 is either pulled out of or pushed into the guide element 65. For radial flow pressing, the stroke piston 61 moves out of the stroke cylinder 53 (arrow P), causing the turntable 54 to rotate clockwise from the start position by an angle α to the end position. This rotation angle α is then converted into a linear stroke of length H. During the rotational movement, the lateral punch 6 moves along the lateral press axis 39, increasingly toward the blank axis 17, in which case the blank 2 is deformed so that it flows in the axial direction. At the end position, the lateral punches 6 are fully pressed in, and the pressing surfaces 43 of the lateral presses 6 are adjacent to and in contact with each other so that they completely form the outer contour of the final shape 2b (see Figure 7).

[0090] However, according to the present invention, the rotation of the turntable 54 from the starting position to the ending position is not performed immediately. Instead, the turntable 53 is first rotated by an allocated rotation angle α / n, then rotated back to the starting position, and then rotated again towards the ending position, gradually increasing the rotation angle. In this case, each new rotation is performed by twice the allocated rotation angle, 2α / n. This forward and backward rotation is performed n times, and in this process, the rotation angle is increased by an allocated rotation angle α / n with each new rotation until the total rotation angle n·α / n = α in the nth rotation. As a result, with each rotation of the turntable 54, the stroke length of the lateral punch 6 increases, and the blank 2 is pressed more. At the starting position of the turntable 53, which is reached again each time, the blank 2 is rotated by an additional angle of 20 (Figure 5), and only then is the rotational movement of the turntable using the gradually increasing rotation angle repeated.

[0091] Figure 9 shows an axial cross-section of the press apparatus 50. In this figure, the turntable 54 also includes the upper plate 56, the upper part 8 of the press dies 8 and 9, the spacer plate 52, and the cover plate 91, as illustrated in Figure 6. The upper punch 4 extends into the press dies 8 and 9 through a hole 92 in the cover plate 91. Furthermore, in Figure 9, it can be seen that the turntable 54 has a guide groove 82 on the underside of the lower plate 55 of the turntable 54, and that the slide shoe 81 is located within the guide groove 82. The slide shoe 81 constitutes a support for the turntable 54 and is made of bronze. The guide groove 82 is either a single circular track or forms a single circular guide groove. The press dies 8 and 9 are placed on an upright ring 83 supported on a support plate 80. The slide shoe 81 and the heating box 71 are also supported on this support plate 80. The support plate 80 has a central hole 84 through which the lower punch 5 passes and extends. The axial end of the lower punch 5 opposite to the upper punch 4 is received in the lower punch holder 85, in which case a projection of the holder 85 engages in a shape-coupled manner with a recess 37 (ring groove) of the lower punch 5. A swivel drive unit 26, not shown in detail in Figure 9, is operationally connected to the center pin 7 for rotating the center pin 7 (arrow 25) and thereby causing the blank 2 to rotate. The swivel drive unit 26 includes, for example, a servo motor and a shaft 27 driven by the servo motor, on which a worm gear device is fixed, and this worm gear device engages with a gear of the type of worm gear that is mounted on the center pin 7 in a relative-non-rotatable manner. Below the support plate 80 is a cooling plate 87 with cooling passages for cooling the press device 50 after the pressing process (see step S4 in Figure 1). Furthermore, Figure 9 shows that the press device 50 is attached to the press table 88.

[0092] Three different configurations of the punch bodies 40, 41, and 42 are illustrated in Figures 10 to 12. These differ only in the configuration of the press surface 43 used to press the outer shell surface 15 of the blank 2. The punch bodies 40, 41, and 42 have, for example, a rectangular cross-section, particularly a square cross-section, and an overall elongated basic shape, in which the press surface 43 is formed at one axial end of the punch bodies 40, 41, and 42. At the other axial end, the punch bodies 40, 41, and 42 have a mushroom shape. This mushroom shape is formed by an extension 45 with a circular cross-section that is recessed from the outer contour of the punch bodies 40, 41, and 42, i.e., has smaller dimensions. The extension 45 is stepped and spaced apart relative to the punch bodies 40, 41, and 42 such that the extension 45 has a mushroom head-shaped expansion 46. The extension 46 is also circular in cross-section and does not extend radially beyond the outer surface of the punch bodies 40, 41, and 42. The punch bodies 40, 41, and 42 are integral with the extension 45 and the mushroom-shaped extension 46, although the extension 45 can also be screwed into the punch bodies 40, 41, and 42. This configuration at the ends of the punch bodies 40, 41, and 42 opposite the press die is used for quick and easy replacement of the lateral punch 6, by providing the extension 45 and the extension 46 to be shape-coupled into a pocket 73 of the punch support 70 (see Figure 9). Such a pocket 73 is formed at the end of the punch support 70 facing the press die. In this case, the pocket 73 is open toward the press die so that the extension 45 can extend radially outward from the pocket 73. Furthermore, the pocket 73 is opened axially toward the cover plate 91 in order to allow the punch bodies 40, 41, and 42 to be inserted into the pocket 73 parallel to the vertical press axis 10 by axial fitting.

[0093] In the implementation variation shown in Figure 10, the press surface portion 43 corresponds to a portion of the cylindrical outer shell in terms of its overall axial height. In each circumferential direction, the press surface portion 43 is defined by flat side portions 44, which are positioned at a 45° angle with respect to the longitudinal axis of the punch body 40. When the lateral punches 6 are mounted and facing each other, the side portions 44 of adjacent lateral punches 6 come into contact with each other when the lateral punches 6 are pressed, thereby forming a closed ring, as can be seen in the middle right of Figure 5.

[0094] During deformation of the blank 2, magnetic material may reach between the opposing side portions 44 of adjacent lateral punches 6, resulting in burrs (steps) on the one hand and incomplete pressing of the lateral punches 6 on the other. To avoid such burrs, the implementation variation of the punch body 41 shown in Figure 11 shows an extension of the side portion 44 such that edge projections 47 extend along the edges that define the press surface portion 43 in the circumferential direction. As shown in the enlarged view of the axial end of the punch body 41 in Figure 11a, both edge projections 47 are nose-shaped, in other words, approximately triangular in cross-section. These edge projections 47 cause the volume portion located on the outside to change direction radially inward at the end of the lateral flow press, thereby moving the magnetic material of the blank 2 away from the side portions 44. A longitudinal groove is then formed in the final shape 2b as a result of the edge projections 47.

[0095] A third implementation variation of the punch body 42 is shown in Figure 12. In this implementation variation, the press surface 43 has stepped radial projections 48 at its upper and lower axial ends, respectively, and the radial projections 48 constitute axial flow restrictors 49 for the blank 2 to be formed. The flow restrictors 49 prevent the material of the blank 2 from reaching between the upper punch 4 and the upper part of the press die 8, and between the lower punch 5 and the lower part of the press die 9, which could result in burrs on the one hand, and wear of the punches 4, 5 and the press die as a result of the punching motion on the other hand.

[0096] In detail, the present invention achieves the following advantages:

[0097] 1. Improved Flow Pressing Method: The present invention provides an improved flow pressing method by further rotating the blank around its axis during processing. In other words, the proposed method involves additional rotation of the blank around its axis during processing. This rotation contributes to the creation of a circular, mechanically more stable permanent magnet or magnetic ring. The pressing process is performed in multiple successive passes, preferably 6 to 24 times. This results in a better magnet that is easier to reuse and does not require special orientation during magnetization. Before each pressing pass, the magnet is rotated 25° to 45° around its axis.

[0098] 2. Improved Mechanical Stability: The circular cross-section of the circular hollow blank improves the structural integrity of the blank and makes the blank less prone to breakage compared to the cross-sectional shape with a partially thin wall portion of, for example, 1 mm, as provided in the blank shape described in Patent Document 1. This improvement not only reduces waste and manufacturing costs but also facilitates the handling and further processing of the magnet.

[0099] 3. Optimized Magnetic Orientation: The present invention solves the problem of suboptimal magnetic orientation, particularly in the thin-walled portions of blanks that are fluid-pressed according to Patent Document 1. The repeated pressing process and the additional rotation between the two pressing processes result in a better and more uniform radial preference orientation in the magnet, thereby eliminating the need for precise orientation during magnetization. The improved magnetic orientation enhances the performance of the magnet and the entire electromechanical device.

[0100] 4. Improved Method Reliability and Efficiency: Improved blank stability makes the entire manufacturing process, including axial pressing and blank handling, more reliable. In addition, the elimination of the need for precise orientation of mounting for magnetization saves time, reduces manufacturing costs, and thereby improves the overall efficiency of the manufacturing process.

[0101] 5. Wide Range of Applications: Using the novel method according to the present invention, a ring magnet having radially preferred magnetization can be manufactured from a blank made of magnetic material. However, this method is also applicable to the manufacture of other rotationally symmetric permanent magnets. This versatility expands the applicability of the method and makes it a useful supplement to the existing repertoire of manufacturing techniques for permanent magnets. This method is applicable to a wide range of magnetic materials and magnetic products.

[0102] In summary, the proposed method offers a significant improvement over the current state of technology in the manufacture of rotationally symmetric ring-shaped permanent magnets with radially preferred magnetization. This method addresses the limitations of the existing technology described in Patent Document 1 and, compared to Patent Document 1, results in a magnet with improved structural integrity because the aforementioned intermediate region where the magnetic material is less fluid is absent. Optimized magnetic orientation of the magnet and improved reliability and efficiency are achieved. Furthermore, this method has a wide range of applications.

[0103] It should be noted that the above description is provided solely as an example for the purpose of specific explanation and does not limit the scope of protection of the present invention. Furthermore, features of the present invention described with “can,” “for example,” “preferably,” “optionally,” “ideally,” “advantageously,” “in some cases,” or “suitable” should be taken purely as optional and, likewise, do not limit the scope of protection as defined solely by the claims. Where the above description mentions elements, components, method steps, values, or information having known, conceivable, or predictable equivalents, these equivalents are also included in the present invention. Similarly, the present invention includes any changes, developments, or modifications of embodiments that involve replacement, addition, modification, or omission of elements, components, method steps, values, or information relating to the subject matter, as long as the fundamental idea of ​​the present invention is maintained, regardless of whether the changes, developments, or modifications result in an improvement or deterioration of the embodiments.

[0104] Although the above description of the present invention describes numerous features relating to one or more specific embodiments, including material, non-material, and methodological features, these features can also be used independently of the specific embodiments, as long as they do not necessitate the presence of further features. Conversely, these features described in relation to one or more specific embodiments can be combined with each other as they do not exclude each other or result in technical incompatibility, and can also be combined with other disclosed or undisclosed features of illustrated or undisclosed embodiments. [Explanation of symbols]

[0105] 1 Powder Press Member 2 Blank 2a Blank Initial Shape 2b Blank Final Shape 4. Upper punch 5. Lower punch 6. Sideways punch 7 Center pin 8 Top 9 Lower part 10. Vertical press axis 11. Outer diameter of the initial shape 12. Inner diameter of the initial shape 13 Outer contour 14 Hollow space 15 Pressed surface 16 Inner contour 17 Blank axis 18 Intermediate region between pressed surfaces 19 New inner contour 20 rotation angle 21 Protrusion 22 New protrusion 23 Unevenness 24 Outer contour of the final shape 25 rotations 26 Swivel drive unit 27 Drive shaft 30 permanent magnets 37 Recess 38 Magnetization 39 Lateral press axis 40 Punch body 41 Punch body 42 Punch body 43 Press surface 44 Side part 45 Extension 46. ​​Expanded portion, mushroom head shape in the radial direction. 47 Edge protrusion 48. Radial stepped projection 49 Axial flow limiting section 50 Pressing device 51 Blind Hole 52 Spacer Plate 53 Hydraulic cylinder, stroke cylinder 54 Rotating platform 55 Lower plate of the rotating platform 56. Top plate of the rotating stand 57 Heater 58 Upper hollow ring space (empty escape volume) 59. Lower hollow ring space (empty escape volume) 61-stroke piston 62 Joint Eye 63 volts 64 Knee Lever 65 Guidance Elements 66 Knee joint 67 Joint bolts 68 Upper protrusion (fork-shaped receiving part) 69 Lower protrusion (fork-shaped receiving part) 70 Punch Support 71 Heating box 72 Heating chamber 73 pockets 74 Flat area 75 Opening 77 Expansion section 78 Heating wire 80 Support Plate 81. Slide shoe, bronze, forming a support for the turntable. 82 Guide groove section 83 Vertical Ring 84 Hole 85 Lower punch holder 87 Cooling Plate 88 Pressing table 90 Pivot 91 Cover Plate 92 Hole

Claims

1. A method for manufacturing a rotationally symmetric, particularly ring-shaped, permanent magnet (30) having magnetization preferentially oriented in the radial direction, by flow pressing a rotationally symmetric blank (2) made of a magnetic material with a transverse punch (6) perpendicular to the blank axis (27) while the blank (2) flows relative to an axial end stopper (4), thereby reducing the cross-sectional area of ​​the blank (2) and extending the axial length of the blank (2), The fluid press is performed in a periodic manner by the lateral punch (6) repeatedly closing and opening, and the blank (2) rotating around its axis between two consecutive fluid press forming cycles. A method characterized by the following.

2. The blank (2) constitutes a hollow body. The method according to claim 1, characterized by the above.

3. A rotatable center pin (7) protrudes through the blank (2) and is rotated in order to rotate the blank (2). The method according to at least claim 2, characterized by the above.

4. The blank (2) is rotated a total of 6 to 24 times. The method according to claim 1 or 2, characterized by the above.

5. The rotation of the blank (2) shall be performed at an angle between 25° and 45°, preferably between 30° and 35°, when using four, five, six, or eight lateral punches. A method according to any one of claims 1 to 4, characterized by the above.

6. The rotation angle when the blank (2) is repeatedly rotated is changed in value compared to the rotation angle of the previous rotation. A method according to any one of claims 1 to 5, characterized by the above.

7. The blank (2) is rotated back and forth. A method according to any one of claims 1 to 6, characterized by the above.

8. The aforementioned fluid press is performed 6 to 12 times per minute. A method according to any one of claims 1 to 7, characterized by the above.

9. The aforementioned fluid press is performed using continuous force application maintained for multiple seconds, without any sudden movements. A method according to any one of claims 1 to 8, characterized by the above.

10. The blank (2) is heated to a deformation temperature before the fluid press, and is then fluid pressed in this heated state. A method according to any one of claims 1 to 9, characterized by the above.

11. The blank (2) is a powder press member (1), which is made by axially pressing a powder of a magnetic material within the press molds (8, 9) of a press device (50) using an upper punch (4) and a lower punch (5), the upper punch (4) and the lower punch (5) move relative to each other in the axial direction while the powder press member (1) is positioned between them, and the press molds (8, 9) have an internal space that defines the outer contour of the blank (2). A method according to any one of claims 1 to 10, characterized by the above.

12. The blank (2) and the upper punch (4) and / or the lower punch (5) are positioned relative to each other before the flow press such that the upper punch (4) and / or the lower punch (5) constitute axial end stoppers for the magnetic material flowing during the flow press of the blank (2). The method according to claim 11, characterized by the above.

13. A press apparatus (50) for manufacturing a rotationally symmetric, particularly ring-shaped, permanent magnet (30) having a magnetization preferentially directed in the radial direction, by flow pressing a rotationally symmetric blank (2) made of a magnetic material, wherein the press apparatus (50) includes a lateral punch (6) that is movable laterally with respect to the blank axis (27) and axial end stoppers (4, 5) in order to press the blank (2) while reducing the cross-sectional area of ​​the blank (2) and extending the axial length of the blank (2) as the blank (2) flows toward axial end stoppers (4, 5), Means are provided for rotating the blank (2) between two consecutive flow press molding operations. A press device (50) characterized by the following.

14. The number of the aforementioned lateral punches (6) shall be a value between 4 and 8. The press apparatus (50) according to claim 13, characterized by the above.

15. A press die (8, 9) and an upper punch (4) and a lower punch (5) guided within the press die (8, 9) are provided, and the upper punch (4) and the lower punch (5) are relatively movable in the axial direction in order to create the blank (2) from the powder press member by axial pressing within the press die (8, 9). A press apparatus (50) according to claim 13 or 14, characterized by the above.

16. The means for rotating the blank (2) includes a rotary table on which the blank (2) is mounted without support, or a center pin (7) protruding through the blank (2) on which the blank (2) is mounted so as not to rotate relative to the blank (2), wherein the rotary table or the center pin (7) is rotatable or rotatable. A press apparatus (50) according to claim 13, 14, or 15, characterized by the above.

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