Method for producing permanently magnetized plastic body and rotor for permanent magnet electric machine

Abstract

The invention relates to a method for producing a permanently magnetized plastic body and to a rotor for a permanent magnet electric machine, comprising the following steps: injecting a plastic material having a filler made of a permanently magnetized material into a cavity by injection molding, the plastic material being cured and bonded to form at least one fusion pattern, plastic materials injected through different sprues intersect at the fusion lines, and the mold core forming the radial inner wall of the mold cavity is wrapped by the plastic materials in an injection molding mode; magnetizing the filler in the cured and bonded plastic material such that alternating magnetic poles are formed on the surface of the plastic body or at positions at a distance from the surface of the plastic body, at least one boundary line being formed between the magnetic poles, the magnetic poles extending along the boundary line. According to the invention, the core forms, in the cavity, a recess connected to the gate, in which recess the plastic material is radially offset with respect to the longitudinal axis and / or deflected in the circumferential direction about the longitudinal axis when injected into the cavity.

Description

Field of the Invention

[0001] The present invention relates to a method for manufacturing a plastic body extending along a longitudinal axis and permanently magnetized, and to a rotor for a permanent magnet electric machine, in particular for a permanent magnet motor.

[0002] The rotor for a permanent magnet electric machine to which the present invention particularly relates is made of a plastic material containing a permanently magnetizable filler and is simultaneously injected into a cavity (also called a mold cavity) by means of injection molding through a plurality of gates (feed ports). The plastic material forms a plastic body extending along the longitudinal axis after curing. The longitudinal axis is the rotation axis of the rotor. For example, the above plastic body or plastic material is injection molded against at least substantially a cylindrical core, so that the at least substantially hollow cylindrical plastic body surrounds the core in the circumferential direction along the longitudinal axis. The core thus constitutes the radial inner wall of the cavity. After manufacturing, the plastic body can form the outer periphery of the rotor. Background Art

[0003] After the plastic body is cured, the filler is magnetized in such a way that alternating magnetic poles are formed on the surface of the plastic body. Optionally, the magnetic poles can also be at a certain distance from the surface of the plastic body. At least one boundary line is formed between the magnetic poles, and the magnetic poles extend along this boundary line. Usually, the boundary line is parallel to the longitudinal axis of the plastic body, so that when the rotor in the electric machine runs, the maximum torque generated by the maximized linked magnetic flux can be obtained.

[0004] By axially injecting the plastic material into the axial end region of the cavity, the plastic body is formed step by step along the longitudinal axis in sequence. Then, the plastic material flows axially and sometimes flows to the bottom opposite the cavity. Only in the most unfavorable case will it be distributed circumferentially around the longitudinal axis, so that the plastic materials simultaneously injected into the cavity through different gates flow close to each other in the circumferential direction and cure and bond together, thereby generating weld lines in the confluence region of the mutual flow. For example, when there are three gates distributed around the longitudinal axis, three weld lines will be correspondingly formed, and the weld lines extend parallel to the longitudinal axis respectively.

[0005] The disadvantage of the known method for manufacturing the plastic body described above is that in actual operation, when magnetizing the filler in the cured and bonded plastic material, cracks often occur along the weld lines.

[0006] The above problem can be weakened by the following method. First, in a ring-shaped distribution system outside the cavity, the plastic material is distributed around the cavity, and then it is simultaneously injected into the cavity in the radial direction of the longitudinal axis through a plurality of gates. However, this ring-shaped distribution system requires corresponding installation space outside the radial direction of the cavity and will result in more plastic material consumption because the plastic material remaining in the ring-shaped system will become waste. Summary of the Invention

[0007] The object of the present invention is to provide a method for manufacturing a plastic body that extends along a longitudinal axis and is permanently magnetized, wherein the generation of cracks can be significantly reduced or completely avoided without an external annular feeding system. In addition, a rotor for a permanent magnet motor is provided, which rotor has a plastic body containing a permanently magnetized material, and the plastic body has as few cracks as possible or no cracks at all.

[0008] The above object of the present invention is solved by the method comprising the steps described in Technical Solution 1 and the rotor described in Technical Solution 15. Other technical solutions describe advantageous and particularly suitable embodiments of the present invention.

[0009] The method of the present invention for manufacturing a plastic body that extends along a longitudinal axis and is permanently magnetized comprises the following steps: - injecting a plastic material containing a filler made of a permanently magnetized material into a cavity by injection molding, wherein the plastic material is simultaneously introduced into the cavity through a plurality of gates in such a way that the plastic material flows into the cavity along a predetermined inflow direction respectively, and the plastic material is cured and bonded to form at least one weld line, and the plastic materials injected through different gates meet at the weld line; wherein a cylindrical or hollow cylindrical core that constitutes the radial inner wall of the cavity is injection-molded and coated with the plastic material; - magnetizing the filler in the cured and bonded plastic material in such a way that alternating magnetic poles are formed on the surface of the plastic body or at a position at a certain distance from the surface of the plastic body, and at least one boundary line is formed between the magnetic poles, and the magnetic poles extend along the boundary line.

[0010] According to the present invention, the core forms a groove (German: Tasche) connected to the gate in the cavity, and in the groove, the plastic material is radially offset and / or circumferentially deflected around the longitudinal axis when being injected into the cavity.

[0011] Through this radial and / or circumferential directional deflection relative to the longitudinal axis, the at least one weld line is formed relatively early in the manufacturing process, so that there is more time for firm connection. Thereby, the strength of the weld line is significantly improved. In this process, the deflection (offset) of the plastic material is directly achieved in the core, which constitutes the radial inner wall of the cavity and is especially also made of plastic.

[0012] Preferably, the plastic bodies are successively manufactured along the longitudinal axis. This enables the gates to be arranged in the axial end regions of the cavity.

[0013] Preferably, the gate is located within the axial end region of the cavity. Thus, the injection structure directly located radially outside the cavity can be omitted.

[0014] In particular, the groove is provided within the axial end region of the core, which is axially opposite to the gate along the longitudinal axis direction, and the plastic material is directly injected into the groove through the gate during the injection process. Thereby, it is ensured that the plastic material injected into the cavity through the gate immediately deflects radially and / or circumferentially.

[0015] According to an embodiment of the present invention, the grooves are arranged at intervals in the circumferential direction around the longitudinal axis, and have a radially inner wall extending axially and a bottom connected to the radially inner wall and extending radially with respect to the longitudinal axis. Therefore, in substantially each groove, a right angle is formed between the radially inner wall and the bottom, such that the plastic material particularly generates a particularly large radial deflection.

[0016] According to an alternative embodiment of the present invention, the above-mentioned grooves are arranged at intervals in the circumferential direction around the longitudinal axis, and each groove has a radially inner wall extending axially and a bottom connected to the radially inner wall and extending diagonally with respect to the longitudinal axis. Thereby, when the radially inner wall and the bottom together form an acute angle, compared with the case where the bottom extends radially with respect to the longitudinal axis, the plastic material generates a larger deflection, or when the radially inner wall and the bottom form an obtuse angle with each other, a relatively smaller deflection is achieved.

[0017] Advantageously, when the grooves are respectively bounded by two side walls in the circumferential direction, wherein, according to an embodiment of the present invention, these side walls extend parallel to each other, and according to another embodiment of the present invention, these side walls form an angle with each other (i.e., extend obliquely). It is also conceivable to make these side walls have other shapes and orientations, for example, form curves or have rounded corners (German: Rundungen).

[0018] According to an embodiment of the present invention, the spacing between the side walls of the groove gradually increases in the radial direction with respect to the longitudinal axis. For example, this can be achieved by making the side walls of the groove extend at an angle with each other (i.e., obliquely), or by making the side walls arc-shaped or gradually expand the distance between each other in the form of multiple segments arranged at an angle to each other.

[0019] Particularly preferably, the plastic material is initially injected into the cavity along the direction of the longitudinal axis.

[0020] The plastic body can be manufactured, for example, in the form of a hollow cylinder, which has internal radial protrusions formed by the grooves.

[0021] Advantageously, the plastic material is initially injected into the cavity at a relatively slow flow rate and subsequently at a relatively high flow rate. Thereby, a particularly stable weld line can be achieved, or multiple particularly stable weld lines can be formed.

[0022] A rotor according to the invention for a permanent magnet electric machine (in particular for a permanent magnet motor) has a plastic body manufactured by the method according to the invention. The longitudinal axis preferably corresponds to the axis of rotation of the rotor.

[0023] According to the method of the invention, although the plastic material injected into the cavity flows axially into the cavity, it spreads near the gate due to circumferential deflection around the longitudinal axis and quickly joins to form a ring.

[0024] Preferably, the core and / or the plastic body have radial protrusions and / or radial depressions, by means of which the plastic body and the core are interlocked in a form-fitting manner in the circumferential direction and / or the axial direction of the longitudinal axis.

[0025] According to one embodiment of the invention, the core can be radially deformed during the injection of the plastic material, so that the plastic body is fixed to the core in a form-fitting manner axially. This deformation can be achieved by softening the core material purposefully when injecting the hot plastic material.

[0026] For example, a plurality of mutually alternating magnetic poles can be formed in the plastic body, especially along the circumferential direction around the longitudinal axis. For example, more than four, especially more than eight, for example twelve mutually alternating magnetic poles can be arranged in the circumferential direction.

[0027] The invention will be illustrated below by way of examples and figures. Description of the Drawings

[0028] The drawings show:

[0029] Figure 1 Showing an embodiment of the invention.

[0030] Figure 2 Showing Figure 1 The hollow cylindrical core shown.

[0031] Figure 3 Showing with Figure 2 The deflection of the plastic material when the core shown is present.

[0032] Figure 4 Showing another alternative design of the core;

[0033] Figure 5 Showing with Figure 4The deflection of the plastic material when the core shown is present.

[0034] Figure 6 Shows other embodiments of the core according to the present invention;

[0035] Figure 7 Shows the deflection of the plastic material when the core having other embodiments of the present invention is present. Detailed Description

[0036] Figure 1 An embodiment of the present invention is shown in which the plastic body 2 extends along the longitudinal axis 1 in the form of a hollow cylinder. The plastic body 2 circumferentially surrounds a core 10 around the longitudinal axis 1. The core 10 can also be made of plastic by injection molding, for example. The core 10 forms the radial inner wall of the cavity 5, and the plastic material 3 is injected into the cavity 5.

[0037] In order to inject the plastic material 3 of the plastic body 2, three gates 4.1 - 4.3 are provided at the end of the injection channel 14. The injection channel 14 extends parallel to the longitudinal axis 1. Therefore, the inflow direction of the plastic material 3 through the gates 4.1 - 4.3 is also axial.

[0038] The gates 4.1 - 4.3 are located in the axial end region of the cavity 5, so that when the plastic material 3 is injected through these gates 4.1 - 4.3, the plastic body 2 is sequentially manufactured along the longitudinal axis 1. Due to the alignment of the injection channel 14 and the gates 4.1 - 4.3 as described above, in particular, three weld lines 7 are formed.

[0039] The core 10 circumferentially surrounds a rotor body 15 made of metal, for example. For example, the core 10 can be injection - molded radially outside the rotor body 15. The rotor body 15, together with the core 10 and the plastic body 2, forms the rotor 13 of an electric machine, in particular an electric motor.

[0040] The plastic material 3 of the plastic body 2 contains a filler, and the constituent material of the filler is permanently magnetized after the plastic body 2 is manufactured, so that magnetic poles 8.1, 8.2 are formed on the radially outer surface of the plastic body 2. These magnetic poles are alternately arranged in the circumferential direction around the longitudinal axis 1, and each pair of magnetic poles is differently polarized, so that the directly adjacent magnetic poles 8.1, 8.2 in the circumferential direction have opposite polarities. Only two magnetic poles 8.1, 8.2 are shown in the example. However, these magnetic poles 8.1, 8.2 extend alternately along the entire circumference of the plastic body 2 around the longitudinal axis 1. The magnetization process occurs only after the plastic body 2 is completely manufactured.

[0041] A boundary line 9 is formed between the magnetic poles 8.1, 8.2, and these magnetic poles extend along these boundary lines. The boundary line 9 extends parallel to the longitudinal axis 1.

[0042] In Figures 1 to 7 the illustrated embodiment, the plastic material 3 is first injected into the cavity 5 in the direction of the longitudinal axis 1. Correspondingly, the injection channels 14 and the gates 4.1 - 4.3 are aligned in the longitudinal direction 1. In the illustrated embodiment, three gates 4.1 - 4.3 are arranged at circumferential intervals around the longitudinal axis 1, but other numbers of gates can also be provided. In particular, at least two gates 4.1, 4.2 are provided.

[0043] After the plastic material 3 is injected into the cavity 5 through the gates 4.1 - 4.3, the plastic material 3 in the cavity 5 deviates radially and / or circumferentially from the flow direction parallel to the longitudinal axis 1 with respect to the longitudinal axis 1.

[0044] In all the figures, the same reference numerals denote the corresponding components in different embodiments.

[0045] In Figures 3 to 7 it is shown that grooves 11 formed by the core 10 in the cavity 5 and connected to the gates 4.1 - 4.3, wherein the plastic material 3 deviates radially with respect to the longitudinal axis 1 when being injected into the cavity 5, and part of the plastic material 3 also deflects circumferentially around the longitudinal axis 1. The grooves 11 are respectively located in the region of the axial ends 10.1 of the core 10, and this axial end is opposite to the gates 4.1 - 4.3 in the direction of the longitudinal axis 1, and the plastic material 3 is directly injected into these grooves 11 when being injected through the gates 4.1 - 4.3.

[0046] Corresponding to the gates 4.1 - 4.3, the grooves 11 are arranged at circumferential intervals around the longitudinal axis 1.

[0047] Each groove 11 has: a radially inner wall 11.1 extending axially; a bottom 11.2 connected to the radially inner wall 11.1; and two side walls 11.3, 11.4, and the two side walls 11.3, 11.4 define the scope of the groove 11 on both sides in the circumferential direction around the longitudinal axis 1.

[0048] According to Figure 4 and Figure 5 , the bottom 11.2 of the groove 11 extends radially with respect to the longitudinal axis 1. Thus, the plastic material 3 can be deflected by 90° from the inflow direction 6 parallel to the longitudinal axis 1 when being injected into the cavity 5. According to Figure 2 and Figure 3 , the bottom 11.2 of each groove 11 extends in a diagonal direction with respect to the longitudinal axis 1, wherein the bottom 11.2 forms an obtuse angle with the radially inner wall 11.1. Thus, the plastic material 3 deflects radially by less than 90° from the inflow direction 6 parallel to the longitudinal axis 1 when being injected into the cavity 5.

[0049] According to Figure 7 , the bottom 11.2 of each groove 11 extends in a diagonal direction relative to the longitudinal axis 1 and forms an acute angle with the corresponding inner wall 11.1. Thereby, when the plastic material 3 is injected into the cavity 5, the flow direction 6 parallel to the longitudinal axis 1 is radially deflected by more than 90°.

[0050] According to Figure 2 , the side walls 11.3 and 11.4 of the groove 11 are parallel to each other. Thereby, before the plastic material 3 is circumferentially distributed around the longitudinal axis 1 due to the radially outer wall of the cavity 5, at least the vast majority of it flows out of the groove 11 in the radial direction relative to the longitudinal axis 1.

[0051] According to Figure 4 and Figure 6 , the side walls 11.3 and 11.4 of each groove 11 extend at an angle to each other (i.e., obliquely), Figure 6 the inclination angle in Figure 4 is larger than that in

[0052] For example, as can be seen from Figure 2 , the core 10 may have recessed portions on its radially outer surface, and the plastic material 3 will flow into these recessed portions and solidify and bond therein, thereby achieving anti-torsion locking between the plastic material 3 or the plastic body 2 and the core 10.

[0053] List of reference numerals 1 Longitudinal axis; 2 Plastic body; 3 Plastic material; 4.1 Gate; 4.2 Gate; 4.3 Gate; 5 Cavity; 6 Inflow direction; 7 Weld line; 8.1 Magnetic pole; 8.2 Magnetic pole; 9 Boundary line; 10 Core; 10.1 Axial end; 11 Groove; 11.1 Radial inner wall; 11.2 Bottom; 11.3 Side wall; 11.4 Side wall; 13 Rotor; 14 Injection channel; 15 Rotor body.

Claims

1. A method for producing a plastic body (2), the plastic body (2) extending along a longitudinal axis (1) and being permanently magnetized, the method comprising the following steps: Step 1.1: injecting a plastic material (3) having a filler made of a permanently magnetized material into a mold cavity (5) by injection molding, wherein the plastic material (3) is simultaneously injected into the mold cavity (5) through a plurality of gates (4.1-4.3) in the following manner, i.e., the plastic material (3) flows into the mold cavity (5) along predetermined inflow directions (6), and the plastic material (3) solidifies and bonds, and during this process, at least one weld line (7) is formed, and the plastic materials (3) injected through different gates (4.1-4.3) meet at the weld line (7), wherein: A cylindrical or hollow cylindrical core (10) constituting the radial inner wall of the cavity (5) is injection-molded and coated with the plastic material (3); Step 1.2: Magnetizing the filler in the cured and bonded plastic material (3) in the following manner, that is, forming alternating magnetic poles (8.1, 8.2) on the surface of the plastic body (2) or at a position kept at a certain distance from the surface of the plastic body (2), forming at least one boundary line (9) between the magnetic poles (8.1, 8.2), and the magnetic poles (8.1, 8.2) extending along the boundary line (9); Step 1.3: The core (10) forms a groove (11) connected to the gate (4.1-4.3) in the cavity (5), wherein the plastic material (3) is radially offset relative to the longitudinal axis (1) and / or deflected circumferentially around the longitudinal axis (1) in the groove (11) when being injected into the cavity (5).

2. The method according to claim 1, wherein: The plastic body (2) is manufactured sequentially along the longitudinal axis (1).

3. The method according to claim 1 or 2, wherein: The gates (4.1-4.3) are located in the region of the axial ends of the cavity (5).

4. The method according to any one of claims 1 to 3, wherein: The groove (11) is arranged at an axial end (10.1) of the core (10), which is opposite to the gate (4.1-4.3) along the longitudinal axis (1), and the plastic material (3) directly enters the groove (11) through the gate (4.1-4.3) during the injection process.

5. The method according to any one of claims 1 to 4, wherein: The grooves (11) are arranged at intervals in the circumferential direction around the longitudinal axis (1) and have a radial inner wall (11.1) extending in the axial direction and a bottom (11.2) connected to the radial inner wall (11.1) and extending in the radial direction relative to the longitudinal axis (1).

6. The method according to any one of claims 1 to 4, wherein: The grooves (11) are arranged at intervals in the circumferential direction around the longitudinal axis (1), and have a radial inner wall (11.1) extending in the axial direction and a bottom (11.2) connected to the radial inner wall (11.1) and extending in the diagonal direction relative to the longitudinal axis (1).

7. The method according to claim 6, wherein: The radial inner wall (11.1) and the bottom (11.2) together form an acute angle.

8. The method according to any one of claims 5 to 7, wherein: The groove (11) is limited in the circumferential direction by two side walls (11.3, 11.4).

9. The method according to claim 8, wherein: The side walls (11.3, 11.4) of the groove (11) extend parallel to each other.

10. The method according to claim 8, wherein: The side walls (11.3, 11.4) of the groove (11) extend obliquely to each other.

11. The method according to claim 8 or 10, wherein: The distance between the side walls (11.3, 11.4) of the groove (11) gradually increases in the radial direction relative to the longitudinal axis (1).

12. The method according to any one of claims 1 to 11, wherein: The plastic material (3) is initially injected into the mould cavity (5) in the direction of the longitudinal axis (1).

13. The method according to any one of claims 1 to 12, wherein: The plastic body (2) is manufactured in the form of a hollow cylinder having an inner radial protrusion formed by the groove (11).

14. The method according to any one of claims 1 to 13, wherein: The plastic material (3) is initially injected into the mold cavity (5) at a relatively slow flow rate and then at a relatively high flow rate.

15. A rotor (13) for a permanent magnet motor, in particular a permanent magnet electric motor, characterized in that: A plastic body (2) produced by the method according to any one of claims 1 to 14.

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