Injection nozzle for providing a divergently and / or rotationally propagating cooling liquid jet when injecting a cooling liquid onto the winding head of an electric motor, cooling arrangement for cooling a winding head of an electric motor with cooling liquid, and method for cooling a winding head of an electric motor

Abstract

The invention relates to an injection nozzle (10) for providing a divergently and / or rotationally propagating cooling liquid jet (101) when injecting a cooling liquid onto the winding head (2) of an electric motor, wherein the injection nozzle (10) comprises: - a prechamber (20) which opens into an outlet opening (21), which prechamber is surrounded, at least in some portions, by a wall portion (23); and - a guide portion (30) which opens into an inlet portion (22) of the prechamber (20) and is arranged transversely to a longitudinal axis (A) of the prechamber.

Description

[0001] ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0002] Injection nozzle for providing a divergently and / or rotatingly spreading coolant jet when injecting a coolant onto the winding head of an electric motor; cooling arrangement for cooling a

[0003] Winding head of an electric motor with coolant and method for cooling a winding head of an electric motor

[0004] The invention relates to an injection nozzle for providing a divergently and / or rotatingly spreading coolant jet when injecting a coolant onto the winding head of an electric motor, furthermore a cooling arrangement for cooling a winding head of an electric motor with coolant, and furthermore a method for cooling a winding head of an electric motor.

[0005] The invention lies in the technical field of cooling the coils of an electric motor, in particular an electric motor of electrically powered cars or trucks.

[0006] Electric motors typically have a stator in which conductive strands, capable of carrying an electric current, are wound around teeth of the stator to form coils and grouped into electrical phases. By applying an alternating current to the conductive strands, a rotating magnetic field can be generated, which drives a rotor of the electric motor. Some sections of the conductive strands lie within slots of the stator. Other sections of the conductive strands protrude from both ends of the stator and form the so-called winding head.

[0007] During operation of the electric motor, the conductor strands of the coils can heat up. This overall heating, as well as the development of localized heating, for example at the winding heads, can negatively impact the desired efficient continuous operation of the motor. To prevent this, cooling arrangements are known in which a coolant, such as oil, is injected onto the winding heads via injection nozzles. For effective cooling, the coolant should come into contact with as large a portion of the winding head as possible. Due to the necessary injection pressure and limitations imposed by the manufacturing process, the number and size of the injection nozzles cannot simply be increased. Known injection nozzles from the prior art can only inject the coolant directly onto a small area of ​​the winding heads (ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12).This either results in insufficient cooling or requires the use of a large number of such injectors in known cooling arrangements, which in turn is detrimental to the compact design.

[0008] The object of the present invention is to overcome the disadvantages of the prior art by providing an injection nozzle for the improved supply of coolant to the winding head, a compact cooling arrangement, and an improved method for cooling a winding head.

[0009] This problem is solved by the injection nozzle, the cooling arrangement, or the method according to the respective independent claim. Advantageous aspects of the invention are the subject of the dependent claims.

[0010] The invention comprises an injection nozzle for providing a divergently and / or rotatingly spreading coolant jet when injecting a coolant onto the winding head of an electric motor, wherein the injection nozzle comprises: a prechamber opening into an outlet opening, the prechamber being at least partially surrounded by a wall section; and a guide section opening into an inlet section of the prechamber and arranged transversely to a (conceptual) longitudinal axis of the prechamber.

[0011] By arranging the guide section transversely to the (imaginary) longitudinal axis of the pre-chamber, coolant guided through the guide section into the pre-chamber can continue to move with momentum transverse to the longitudinal axis towards the outlet opening. Upon exiting the outlet opening, this causes the resulting coolant jet to spread divergently (i.e., widening outwards from the outlet opening, for example) and / or rotatingly (i.e., rotating around the imaginarily extended longitudinal axis). Such a coolant jet can (directly) supply a particularly large section of the winding head with coolant, so that only a few such injectors are required in a cooling arrangement for cooling the winding head. Preferably, ZF Friedrichshafen AG, File 304972, Friedrichshafen, 2024-08-12

[0012] The guide section has a rectangular or square cross-section with a cross-sectional area in the range of 0.05 mm². 2 up to 5 mm 2 , preferably between 0.1 mm 2 and 3 mm 2 , particularly preferably between 0.2 mm 2 and 2 mm 2 .

[0013] According to an advantageous aspect, the guide section is arranged at an angle between 75° and 105°, preferably substantially or exactly perpendicular to the longitudinal axis of the prechamber. Alternatively or additionally, the guide section is arranged parallel to a tangent to the wall section of the prechamber, offset by a distance greater than or equal to 0 mm. This promotes the movement of coolant with particularly high momentum transverse to the longitudinal axis of the prechamber towards the outlet opening.

[0014] According to a further advantageous aspect, the pre-chamber is partially conical and / or cylindrical and / or thimble-shaped. Preferably, the pre-chamber has a dimension along its (imaginary) longitudinal axis of between 1 mm and 30 mm, more preferably between 2 mm and 20 mm, and particularly preferably between 3 mm and 15 mm. Furthermore, the pre-chamber preferably has a diameter perpendicular to its (imaginary) longitudinal axis of between 1 mm and 30 mm, more preferably between 2 mm and 20 mm, and particularly preferably between 3 mm and 10 mm.

[0015] According to a further advantageous aspect, the guide section has a curved section that is arranged section by section along the wall section of the antechamber. The curved section can be designed to taper or narrow over its course.

[0016] Another advantageous aspect is that the curved section and / or the wall section of the pre-chamber is / are spirally shaped. This spiral shape allows the coolant to be guided into a rotational motion as it passes through the guide section or flows along the wall section.

[0017] According to a further advantageous aspect, the guide section is formed section by section as a (longitudinal, channel-like, or groove-like) recess in the wall section of the pre-chamber. A design as a recess in the wall section, ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12, particularly as a recess with a rectangular or square cross-section, can be produced simply and precisely using injection molding.

[0018] Another advantage is that, when the injector is installed in a cooling arrangement for the winding head with coolant, the inlet opening for the coolant entering the injector via the guide section is smaller than the outlet opening for the coolant exiting the injector. With a constant outlet opening, a smaller inlet opening increases the flow resistance of the coolant. The flow resistance can be adjusted particularly precisely and easily by changing the size of the inlet opening.

[0019] Furthermore, the invention comprises a cooling arrangement for cooling a winding head of an electric motor with coolant, comprising an oil guide ring with at least one injection nozzle arranged circumferentially by the oil guide ring to provide a divergently and / or rotatingly propagating coolant jet. The oil guide ring is arranged around the winding head such that, under pressure, coolant, after passing through the at least one injection nozzle, propagates in a divergent and / or rotating coolant jet towards the winding head. The use of injection nozzles to provide a divergently and / or rotatingly propagating coolant jet reduces the number of injection nozzles required to adequately and uniformly cool the winding head.

[0020] According to a further advantageous aspect, the cooling arrangement comprises a further oil guide ring with at least one injection nozzle arranged circumferentially around the further oil guide ring to provide a divergently and / or rotating coolant jet. The further oil guide ring is arranged around a further winding head such that, under pressure, coolant, after passing through the at least one injection nozzle, spreads in a divergent and / or rotating coolant jet towards the further winding head. One of the oil guide rings is a first oil guide ring arranged on a first winding head, and one of the oil guide rings is a second oil guide ring arranged on a second winding head. ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0021] According to a further advantageous aspect, at least one injector is an injector as described above. Each oil guide ring is clamped against an outer wall in such a way that the inlet section of the prechamber of the at least one injector as described above is fluid-tightly sealed by the outer wall. Because the inlet section of the prechamber is fluid-tightly sealed by the outer wall, coolant can only enter the injector through an inlet opening of the guide chamber. Since the oil guide ring is clamped against the outer wall, the inlet section of the prechamber remains fluid-tightly sealed even under temperature fluctuations.

[0022] According to a further advantageous aspect, at least one injector nozzle, preferably all injectors, is designed to project from an outer wall section of the oil guide ring, pointing away from its central axis. The injectors can each be arranged on the oil guide ring such that the (conceptual) longitudinal axis of the pre-chamber of the respective injector nozzle is directed towards the central axis of the oil guide ring, or it is not directed towards the central axis of the oil guide ring, and in this case, for example, the longitudinal axis of the pre-chamber is skew to the central axis of the oil guide ring.

[0023] Another advantageous aspect is that an outlet opening of at least one injector, preferably outlet openings of all injectors, connects flush to an inner wall section of the oil guide ring. This allows for a particularly compact design.

[0024] The invention further comprises a method for cooling a winding head of an electric motor, comprising the steps of:

[0025] Providing a cooling arrangement as described above; and

[0026] Pressurizing the oil guide ring with coolant such that coolant passes through at least one injector nozzle and, upon exiting the at least one injector nozzle, a divergent and / or rotating jet of coolant is generated, which propagates towards the winding head. ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0027] The diverging and / or rotating coolant jet ensures that a large area of ​​the winding head is supplied with coolant, thus increasing the efficiency of the cooling.

[0028] According to a further advantageous aspect, at least one injector is an injector as described above. The (at least one) divergent and / or rotating coolant jet emerges from the outlet opening of the at least one injector as described above within an opening cone with an opening angle of at least 10°, preferably at least 40°, more preferably at least 70°, and particularly preferably at least 100°. For example, the coolant jet emerges in such a way as to spread out on the conical surface of the opening cone.

[0029] The larger the opening angle, the greater the area of ​​the winding head exposed to the coolant jet, and the better the cooling effect. The opening angle can be controlled via the geometry of the injection nozzle, particularly the guide section and the outlet orifice, and / or by considering operating parameters such as the (temperature-dependent) viscosity of the coolant or the pressure applied to the coolant.

[0030] The invention will now be explained in more detail using exemplary embodiments. These will show:

[0031] Fig. 1 Schematic perspective view of an injection nozzle;

[0032] Fig. 2 Schematic cross-sectional view of the injection nozzle from Fig. 1 in installed state within a cooling arrangement;

[0033] Fig. 3 Schematic side cross-sectional view of an injection nozzle in a further embodiment;

[0034] Fig. 4 Schematic top view of the injection nozzle from Fig. 3;

[0035] Fig. 5 Schematic perspective view of an oil guide ring for a cooling arrangement as in Figs. 6 and 7;

[0036] Fig. 6 Schematic cross-sectional view of an electric motor and a cooling arrangement with injection nozzles from Figs. 1 and 2, shown in a section perpendicular to the axis of rotation of the electric motor; ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0037] Fig. 7 Schematic cross-sectional view of the electric motor and the cooling arrangement from Fig. 6, shown in a section parallel to the axis of rotation of the electric motor; and

[0038] Fig. 8 Detail view of section D from Fig. 7.

[0039] Figures 1 and 2 are described together below. Figure 1 shows a schematic perspective view of an injection nozzle 10, and Figure 2 shows a schematic cross-sectional view of the injection nozzle from Figure 1 in its installed state within a cooling arrangement 100.

[0040] The injection nozzle 10, for providing a divergently and / or rotatingly spreading coolant jet 101 when injecting a coolant onto the winding head 2, has a prechamber 20 with a larger thimble-shaped section and a smaller cylindrical section that opens into an outlet opening 21. The prechamber 20 is partially surrounded by a wall section 23.

[0041] Furthermore, the injection nozzle 10 has a guide section 30 opening into an inlet section 22 of the prechamber 20. This guide section 30 is straight and arranged perpendicular to an imaginary longitudinal axis A of the prechamber 20. The guide section 30 is also arranged parallel to a tangent to the wall section 23 of the prechamber 20, offset by a distance.

[0042] By arranging the guide section 30 perpendicular to the imaginary longitudinal axis A of the pre-chamber, coolant guided through the guide section 30 into the pre-chamber 20 can move with momentum transverse to the imaginary longitudinal axis A towards the outlet opening 21. Upon exiting the outlet opening 21, the resulting coolant jet 101 spreads divergently (widening outwards from the outlet opening 21 in the example shown) and rotates (rotating around the imaginary extended longitudinal axis A in the example shown). This coolant jet 101 can directly wet a particularly large section of the winding head 2 with coolant. ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0043] The guide section 30 is formed as a groove-like recess with a rectangular cross-section in the wall section 23 of the pre-chamber 20. This design can be produced simply and precisely using injection molding. In particular, several guide sections 30 can be arranged at widely spaced intervals.

[0044] In Fig. 2, the injection nozzle 10 is installed in the oil guide ring 3 of a cooling assembly 100 such that the inlet section 22 of the pre-chamber 20 is fluid-tightly covered by an outer wall 4. This allows coolant to enter the injection nozzle 10 only through an inlet opening 32 of the guide chamber 30. The guide section 30 is designed such that, in the installed state, the inlet opening 32 for the coolant entering the injection nozzle 10 via the guide section 30 is smaller than the outlet opening 21 for the coolant exiting the injection nozzle 10. With a constant outlet opening 21, a smaller inlet opening 32 increases the flow resistance for the coolant, and this flow resistance can be adjusted particularly precisely and easily by changing the size of the inlet opening 32.

[0045] A method for cooling the winding head 2 can also be described using Fig. 2. This method comprises the following steps:

[0046] Provision of the cooling arrangement 100; and

[0047] Pressurizing the oil guide ring 3 with coolant such that coolant passes through the injection nozzle 10 and, upon exiting the injection nozzle 10, the divergent and rotating coolant jet 101 is created, which spreads towards the winding head 2.

[0048] In the example shown, the divergent and rotating coolant jet 101 emerges from the outlet opening 21 of the injection nozzle 10 into an opening cone K with an opening angle of 20°. The coolant jet 101 emerges in such a way as to spread out on the conical surface of the opening cone K. In the illustration shown, the coolant jet 101 spreads out spirally on the conical surface of the opening cone K. Alternatively, the coolant jet 101 can spread out flatly on the conical surface of the opening cone K, i.e., without spiraling. ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0049] The opening angle can be controlled via the geometry of the injection nozzle 10, in particular the guide section 30 and the outlet opening 21, taking into account the temperature-dependent viscosity of the coolant or the pressure with which the coolant is subjected.

[0050] Figures 3 and 4 are described together below. Figure 3 shows a schematic side cross-sectional view of an injection nozzle in a further embodiment, and Figure 4 shows a schematic top view of the injection nozzle from Figure 3.

[0051] This injection nozzle 10 is also suitable for providing a divergent and / or rotating coolant jet 101 when injecting a coolant onto the winding head 2 (see Fig. 2). The injection nozzle 10 has a prechamber 20 opening into an outlet opening 21, with a cylindrical section and a conical section opening into the outlet opening 21.

[0052] The wall section 23 is spirally shaped in sections and surrounds the prechamber 20 in sections. Furthermore, the injection nozzle 10 has a guide section 30 with a spirally curved section 31, which opens into an inlet section 22 of the prechamber 20 and is arranged along the wall section 23 of the prechamber 20. An initial part of the guide section 30 is formed as a groove-like recess in the wall section 23.

[0053] Wall section 23 forms an outer band for guide section 30, the course of which guide section 30 follows. Towards the center of the pre-chamber 20, the curved section 31 tapers and narrows along its spiral path. Due to this spiral shape, coolant can be directed into a rotational motion around the imaginary longitudinal axis A as it passes through guide section 30 or flows along wall section 23. Coolant, thus guided through guide section 30 into the pre-chamber 20, then moves with momentum perpendicular to the imaginary longitudinal axis A towards the outlet opening 21. [Reference: ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12]

[0054] The outlet opening 21 causes the resulting coolant jet 101 to spread out divergently and rotatingly (as shown in Fig. 2).

[0055] The curvature section 31 of the guide section 30 shown has a spiral profile that completes a full (360°) revolution. Spiral profiles with smaller or larger revolutions are also possible. In particular, several guide sections 30 arranged at varying circumferences can be provided, each with a curvature section 31 that has a spiral profile.

[0056] Fig. 5 shows a schematic perspective view of an oil guide ring 3 for a cooling arrangement 100 as in Fig. 6 and 7.

[0057] All injectors 10 are designed to project from an outer wall section 5 of the oil guide ring 3 and are directed away from the center point of the oil guide ring 3. In the illustrated embodiment, all injectors 10 are arranged on the oil guide ring 3 such that the (conceptual) longitudinal axis A of the pre-chamber 20 of the respective injector 10 is directed towards the central axis M of the oil guide ring 3.

[0058] Furthermore, the outlet openings 21 of all injection nozzles 10 connect flush to an inner wall section 6 of the oil guide ring 3. This enables a particularly compact design of a cooling arrangement 100, as shown in Figs. 6 and 7.

[0059] From a manufacturing perspective, it may be preferable to design the oil guide ring 3 shown in an alternative embodiment such that the (conceptual) longitudinal axis A of the pre-chamber 20 of the respective injection nozzle 10 is not directed towards the central axis M of the oil guide ring 3. This can be achieved by making the longitudinal axis A of the pre-chamber 20 skew relative to the central axis M of the oil guide ring 3.

[0060] Figures 6 to 8 are described together below. Figure 6 shows a schematic cross-sectional view of an electric motor 1 and a cooling arrangement 100 with injection nozzles 10 from Figures 1 and 2, shown in a section perpendicular to the axis of rotation of the electric motor 1. Figure 7 shows a schematic cross-sectional view of the electric motor and the cooling arrangement from Figure 6, shown in a section parallel to the axis of rotation of the electric motor. Figure 8 shows a detailed view of a section D from Figure 7.

[0061] The cooling arrangement 100 for cooling a winding head 2 of an electric motor 1 with coolant comprises a first oil guide ring 3a and a second oil guide ring 3b, both shown in Fig. 5. Each oil guide ring 3a, 3b has five injection nozzles 10 and two blanking plugs 40. The blanking plugs 40 serve only as circumferential spacers, and injection nozzles 10 could also be arranged there instead.

[0062] The first oil guide ring 3a is arranged around a first winding head 2a, so that, after passing through the injection nozzles 10 of the first oil guide ring 3a, coolant under pressure spreads in a divergent and rotating coolant jet 101 (shown in Fig. 2) towards the first winding head 2a.

[0063] The second oil guide ring 3b is arranged around a second winding head 2b, so that here too, coolant under pressure spreads towards the second winding head 2b after passing through the injection nozzles 10 of the second oil guide ring 3b in a divergent and rotating coolant jet 101 (shown in Fig. 2).

[0064] As shown in Fig. 8, the second oil guide ring 3b (the same applies to the first oil guide ring 3a) is clamped against the outer wall 4 in such a way that the inlet section 22 of the pre-chamber 20 of all injectors 10 is fluid-tightly covered by the outer wall 4. As a result, coolant can only enter the injector 10 through the inlet opening 32 of the guide chamber 30. ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12

[0065] Reference sign

[0066] 1 electric motor

[0067] 2 winding heads

[0068] 2a first winding head

[0069] 2b second winding head

[0070] 3 Oil guide ring

[0071] 3a first oil guide ring

[0072] 3b second oil guide ring

[0073] 4 Exterior wall

[0074] 5 Exterior wall section

[0075] 6 Interior wall section

[0076] 10 Injector nozzle

[0077] 20 Antechamber

[0078] 21 Exit opening

[0079] 22 Entrance section

[0080] 23 Wall section

[0081] 30 Main Section

[0082] 31 Curvature section

[0083] 32 Entrance opening

[0084] 40 blind plugs

[0085] 100 cooling arrangement

[0086] 101 Coolant jet

[0087] A Longitudinal axis

[0088] K opening cone

[0089] M Central axis

[0090] U circumferential direction

Claims

ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12 Patent claims 1. Injection nozzle (10) for providing a divergently and / or rotatably spreading coolant jet (101) when injecting a coolant onto the winding head (2) of an electric motor (1), wherein the injection nozzle (10) comprises: a prechamber (20) opening into an outlet opening (21), the prechamber being at least partially surrounded by a wall section (23); and a guide section (30) opening into an inlet section (22) of the prechamber (20) and arranged transversely to a longitudinal axis (A) of the prechamber.

2. Injection nozzle (10) according to claim 1, wherein the guide section (30) is arranged parallel to the longitudinal axis (A) of the prechamber (20) and / or to a tangent to the wall section (23) of the prechamber (20) at an angle in the range between 75° and 105°, preferably substantially or exactly perpendicular to it, by a distance greater than or equal to 0 mm.

3. Injection nozzle (10) according to one of the preceding claims, wherein the pre-chamber (20) is sectionally conical and / or cylindrical and / or thimble-shaped.

4. Injection nozzle (10) according to one of the preceding claims, wherein the guide section (30) has a curvature section (31) which is arranged section by section along the wall section (23) of the prechamber (20).

5. Injection nozzle (10) according to claim 4, wherein the curvature section (31) and / or the wall section (23) of the prechamber (20) is / are spirally shaped.

6. Injection nozzle (10) according to one of the preceding claims, wherein the guide section (30) is formed section by section as a recess in the wall section (23) of the prechamber (20). ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12 7. Injection nozzle (10) according to one of the preceding claims, wherein, in the installed state of the injection nozzle (10) in a cooling arrangement (100) for cooling the winding head (2) with coolant, an inlet opening (32) for the entry of the coolant via the guide section (30) into the injection nozzle (10) is smaller than the outlet opening (21) for the exit of the coolant from the injection nozzle (10).

8. Cooling arrangement (100) for cooling a winding head (2) of an electric motor (1) with coolant comprising an oil guide ring (3) with at least one injection nozzle (10) arranged in the circumferential direction (U) of the oil guide ring (3) for providing a divergently and / or rotatingly propagating coolant jet (101) , wherein the oil guide ring (3) is arranged around the winding head (2) such that, under pressure, coolant, after passing through the at least one injection nozzle (10), propagates in a divergent and / or rotating coolant jet (101) towards the winding head (2).

9. Cooling arrangement (100) according to claim 8 comprising a further oil guide ring (3) with at least one injection nozzle (10) arranged in the circumferential direction (U) of the further oil guide ring (3) for providing a divergently and / or rotatably propagating coolant jet (101), wherein the further oil guide ring (3) is arranged around a further winding head (2) such that, under pressure, coolant, after passing through the at least one injection nozzle (10), propagates in a divergent and / or rotatable coolant jet (101) towards the further winding head (2), and wherein one of the oil guide rings (3) is a first oil guide ring (3a) arranged on a first winding head (2a) and one of the oil guide rings (3) is a second oil guide ring (3b) arranged on a second winding head (2b).

10. Cooling arrangement according to claim 8 or 9, wherein at least one injector nozzle (10) is an injector nozzle (10) according to one of claims 1 - 7, and wherein each oil guide ring (3) is clamped against an outer wall (4) such that the inlet section (22) of the pre-chamber (20) of the at least one injector nozzle (10) according to one of claims 1 - 7 is fluid-tightly covered by the outer wall (4).

11. Cooling arrangement according to one of claims 8 to 10, wherein at least one injector nozzle (10), preferably all injectors (10), is located from the center point of the oil guide ring (3) ZF Friedrichshafen AG File 304972 Friedrichshafen 2024-08-12 is designed to project away from an outer wall section (5) of the oil guide ring (3).

12. Cooling arrangement according to one of claims 8 to 11, wherein an outlet opening (21) of at least one injection nozzle (10), preferably outlet openings (21) of all injection nozzles (10), connects or connects in a planar manner to an inner wall section (6) of the oil guide ring (3).

13. Method for cooling a winding head (2) of an electric motor (1) , comprising the steps: - Providing a cooling arrangement (100) according to any one of claims 8 to 12; and - Pressurizing the oil guide ring (3) with coolant such that coolant passes through at least one injection nozzle (10) and, upon exiting the at least one injection nozzle (10), a divergent and / or rotating coolant jet (101) is created which spreads towards the winding head (2).

14. Method according to claim 13, wherein at least one injector nozzle (10) is an injector nozzle (10) according to any one of claims 1-7, and wherein the divergent and / or rotating coolant jet (101) exits from the outlet opening (21) of the at least one injector nozzle (10) according to any one of claims 1-7 in an opening cone (K) with an opening angle of at least 10°, preferably at least 40°, more preferably at least 70°, and particularly preferably at least 100°.

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