Hub motor and drive steering module

Abstract

The invention relates to an electric wheel hub (1) for a vehicle wheel, comprising an electric machine and a disc brake (2). The electric machine comprises a rotor (3) and a stator (4). The disc brake (2) comprises a brake caliper (5) and a brake disc (6), wherein the brake caliper (5) comprises a brake actuator (7) which projects from the brake caliper (5) in the axial direction of the electric machine and is used to actuate the brake caliper (5). It is desirable here to reduce the structural height without significantly reducing the braking torque of the disc brake. According to the invention, the brake disc (6) is arranged outside the stator (4) in the axial direction, and the brake actuator (7) is arranged completely or partially inside the stator (4) in the axial direction. Furthermore, a drive steering module is provided, comprising such an electric wheel hub (1) and a steering device connected thereto, which is designed to provide a steering capability of the wheel over a large angle range.

Description

Technical Field

[0001] This invention relates to a hub motor (also known as a wheel-side motor) for vehicle wheels, comprising a motor and a disc brake. The motor includes a rotor and a stator, and the disc brake includes a caliper and a brake disc. The caliper includes a brake actuator extending axially from the caliper for operating the caliper. The invention also relates to a drive steering module for a vehicle, comprising a hub motor of the type described above. Background Technology

[0002] Such hub motors are known, for example, in WO 2019 / 139545. The brake disc is coaxially arranged inside the rotor and stator. A bearing system is arranged within the brake disc, connecting the axial end of the rotor to the stator plate and to a steering knuckle at the other axial end of the hub motor. The stator plate clamps the brake disc in the section of the brake disc not covered by the axially extending brake calipers and brake actuators.

[0003] Another type of hub motor with a disc brake is known from GB 2479898 A. In this hub motor, the disc brake is not overlapped with the rotor or stator in the axial direction, but is arranged at the axial end of the hub motor. Two brake actuators are used, which are offset 180° in the pole direction and clamp the brake disc from the radial inside.

[0004] Two other types of hub motors with disc brakes are known from DE 10 2012 020 816 A1. In these, the disc brakes are axially offset from the rotor and stator of the motor, respectively. In one variant, the disc brakes are axially positioned inside the rim, while the motor is axially positioned outside the rim; and in another variant, the opposite design is implemented.

[0005] Other hub motors with integrated braking systems are known, for example, in US 9,387,758 B2 and US 2015 / 0137669 A1, in which hydraulic drum brakes are used in particular.

[0006] Other hub motors with integrated wheel brakes are known in DE 10 2019 116 264 A1 and DE 10 2013202 809 A1.

[0007] For example, in-wheel motors are widely used in vehicles such as electric scooters or airplane wheels because of their exceptionally high efficiency and the ability to allow for extremely space-saving designs. For passenger cars or other vehicles, these in-wheel motors with integrated friction brakes, in principle, allow for significant modifications to the vehicle body / body and new control and steering concepts with large steering angles—concepts that would be virtually impossible to achieve in terms of space efficiency using a central motor for two-wheel or four-wheel drive. To fully utilize this concept, further reductions in the axial structural height of the in-wheel motor are also necessary.

[0008] Existing technological solutions either have a large structural height or result in a significant reduction in the braking torque provided by the disc brake due to the reduction in the size of the brake disc. Summary of the Invention

[0009] Therefore, the technical problem to be solved by the present invention is to provide a hub motor of the type described at the beginning, which allows for a compact axial structure height without significantly reducing the braking torque provided by the disc brake.

[0010] According to the present invention, this technical problem is solved by a hub motor having the features of claim 1 and a drive steering module according to claim 17.

[0011] Therefore, a hub motor for a vehicle wheel according to the present invention is provided, comprising a motor and a disc brake, wherein the motor includes a rotor and a stator, and the disc brake includes a brake caliper and a brake disc, the brake caliper including a brake actuator for operating the brake caliper, the brake actuator extending from the brake caliper in the axial direction of the motor, characterized in that the brake disc is arranged axially outside the stator, and the brake actuator is arranged axially, wholly or partially, inside the stator. The rotor includes two coaxially arranged permanent magnet groups, wherein a first permanent magnet group is radially arranged inside the stator, and a second permanent magnet group is radially arranged outside the stator. The brake actuator is arranged overlapping the permanent magnets of the motor in the axial direction.

[0012] This configuration allows for more efficient use of installation space than existing technologies while still providing the greater braking effect of a disc brake. This is possible because the brake disc is arranged axially outside the stator, thus avoiding or at least allowing for a very small reduction in the brake disc radius. Since the brake actuator is located within the hub motor, either fully or partially within the stator, it does not extend axially outward. This reduces the maximum axial extension dimension (structural height) of the hub motor and makes it significantly easier to integrate the hub motor into various bodyworks and steering systems, particularly in conjunction with steering systems with large maximum steering angles.

[0013] Within the framework of this application, when referring to "axial direction" or "axial," this indicates a direction parallel to the drive rotation axis of the hub motor. Correspondingly, "radial direction" or "radial" indicates a direction or distance perpendicular to the drive rotation axis of the hub motor. Finally, "polar direction" or "polar" indicates a tangential circumferential direction around the drive rotation axis. Therefore, these three sets of terms correspond to cylindrical coordinates.

[0014] Preferably, the brake disc does not overlap with either the rotor or the stator in the axial direction, but rather is axially abutted against or fixed to the axial end side of the rotor. This ensures the largest possible radial extension dimension of the brake disc and allows for a relatively large friction surface, thus providing a relatively large maximum braking torque, compared to the solution according to WO 2019 / 139545A1, despite the internal arrangement of the brake calipers. There, the brake calipers are radially positioned outside the brake disc, but this reduces the overall size of the disc brake to allow for its axial arrangement within the rotor and stator.

[0015] Preferably, the brake actuator and the stator winding of the motor are arranged overlapping in the axial direction. As mentioned above, this ensures a smaller structural height because the axial space used by the motor's drive section is also partially utilized by the disc brake.

[0016] Within the framework of this application, the terms rotor and stator should be interpreted narrowly and refer only to elements directly involved in generating the motor's drive torque, such as permanent magnets and stator windings mounted thereon or supporting these elements. Therefore, even if the hub is integrally formed with the stator, it is not entirely considered part of the stator; only the portion directly surrounded by or adjacent to the rotor is considered part of the stator (e.g., in the drive chamber housing). Correspondingly, the rim is not considered part of the rotor; only the rotating element fixed to or supported by the permanent magnet is considered part of the rotor.

[0017] Preferred embodiments and improvements of the present invention can be derived from the dependent claims.

[0018] In a preferred embodiment, the brake caliper clamps the brake disc from the radially inward side. For the same brake disc size, clamping the brake disc from the radially inward side results in a slightly lower maximum braking torque compared to clamping it from the radially outward side, because the friction surface must be reduced for geometric reasons. Surprisingly, the feature combination of the present invention allows this disadvantage to be kept to a minimum, and correspondingly achieves a significant reduction in the maximum axial extension dimension of the hub motor. This is because clamping the brake disc from the radially inward side makes it easier to arrange the brake actuator, which extends axially from the brake caliper, entirely or partially within the rotor and / or entirely or partially within the stator. However, it is also possible to alternatively clamp the brake disc from the radially outward side.

[0019] Preferably, the brake actuator generates the clamping force electromechanically. In this case, the disc brake is an electromechanical disc brake, and therefore not a hydraulic disc brake. The power supply lines of an electromechanical disc brake are mechanically more flexible than the hydraulic high-voltage lines of a hydraulic brake, and therefore easier to bend, for example, to use a hub motor in a drive steering module with a large maximum steering angle.

[0020] According to a preferred embodiment of the invention, the hub motor includes a rim, within which a brake actuator is arranged in both the axial and radial directions. Here, the axial extension of the rim provides a frame within which the brake actuator can be arranged effortlessly without the risk of collision with, for example, elements of a steering device connected to the hub motor that have a large maximum steering angle, or any geometric constraints thereof.

[0021] Preferably, the brake disc is arranged axially within the rim. Accordingly, the axial extension of the rim provides a framework within which the brake disc can be arranged effortlessly without the risk of collision or geometric constraints, for example, with components of the steering mechanism connected to the hub motor and having a large maximum steering angle. Alternatively, the brake disc may extend axially from the rim by less than 5 cm.

[0022] In one embodiment, the entire disc brake extends axially from the rim by less than 10 cm, preferably less than 5 cm, and particularly preferably is completely disposed within the rim in the axial direction. Here, for example, the axial side of the brake caliper or the brake disc may partially extend beyond the axial extension dimension of the rim.

[0023] Preferably, the hub motor includes a central steering knuckle housing in which power and / or coolant and / or signal lines to the hub motor extend. This allows the corresponding lines to extend to the hub motor under protected conditions, particularly in drive steering modules with large maximum steering angles. The coolant lines may be coolant lines. It should be noted that coolant lines are generally different from hydraulic brake lines, as they only transport fluid at low pressure and are therefore mechanically significantly more flexible, thus better able to withstand greater bending.

[0024] In one embodiment, the hub motor includes a central steering knuckle housing, wherein a brake caliper is connected radially outward to the steering knuckle housing. This embodiment allows the brake caliper to be stably fixed together with the brake actuator if the brake caliper clamps the brake disc from the inside. Simultaneously, in the circumferential direction, mounting space is still provided at the same axial position as the brake actuator, which can be used for other purposes (e.g., electronic units) to reduce the structural height.

[0025] In another preferred embodiment, the hub motor includes at least one electronic unit, preferably including an inverter for the motor, which overlaps with the brake actuator in the axial direction but is staggered in the poloidal direction. This allows for particularly efficient use of structural space. Preferably, the electronic unit also includes an electronic component housing, which is preferably connected to the radially outer side of the steering knuckle housing, or is part of the steering knuckle housing.

[0026] Preferably, the electronic unit is offset from the brake actuator in the poloidal direction by at least 90°, more preferably at least 150°, and particularly preferably 180° ± 10°. These angular distances are referenced to the geometric centers of the electronic unit and the brake actuator, respectively. The advantage of this design is that the brake actuator (and brake caliper), as a heat source, is positioned as far away from the electronic unit as possible, as the electronic unit itself is both a heat source and heat-sensitive. This simplifies the cooling of the electronic unit.

[0027] Preferably, the rotor includes a drive cavity housing that forms a drive cavity in which the permanent magnets of the motor are arranged, wherein the stator is surrounded by the drive cavity housing from both sides in the axial direction and from the inside and outside in the radial direction. The drive cavity housing may include a drive cavity outer housing and a drive cavity inner housing, which are preferably connected by a surrounding static sealing element. The drive cavity housing may have an asymmetrical hollow "U"-shaped cross-section in the radial direction, wherein the stator arranged therein also has a corresponding asymmetrical "U"-shaped cross-section in the radial direction. Preferably, the permanent magnets of the motor and the stator windings of the motor are then arranged in the radially outer leg region of the "U" shape of the rotor and stator.

[0028] The rotor comprises two coaxially arranged permanent magnet assemblies. The first permanent magnet assembly is radially arranged inside the stator, and the second permanent magnet assembly is radially arranged outside the stator. Despite the low structural height, this achieves exceptionally high drive torque. For example, the first permanent magnet assembly can be arranged radially outside the drive cavity housing, and the second permanent magnet assembly can be arranged radially inside the drive cavity housing.

[0029] In a preferred embodiment, the brake actuator and / or electronic unit are at the same axial height and located radially inward from the drive cavity (viewed from this position). This design allows the drive cavity (particularly the portion including the permanent magnet and stator winding) to be arranged as radially outward as possible in a space-saving configuration to achieve high drive torque, while effectively utilizing the same axial height but radially inward structural space.

[0030] Preferably, two ball bearings are arranged between the rotor and the stator, each of which is coupled with a sealing strip to provide a dynamic seal. Preferably, the sealing strip provides a seal to the drive cavity (optionally together with a surrounding static sealing element between the drive cavity housing and the drive cavity inner housing), particularly to prevent the ingress of contaminant particles (e.g., from disc brakes). However, alternatively, simple ball bearings without sealing strips can also be used. This tends to provide support with less braking effect, although the prevention of contaminant particle ingress is less effective.

[0031] In one embodiment, two ball bearings are arranged between the rotor and the stator, one ball bearing adjacent to the radially outer side of the stator and the other ball bearing adjacent to the radially inner side of the stator. This design allows for very stable support of the rotor on the stator despite a low structural height.

[0032] Preferably, if at least one double ball bearing is arranged between the rotor and the stator, two double ball bearings are more preferably arranged, wherein the double ball bearing comprises two sub-ball bearings arranged sequentially in the axial direction. Such a double ball bearing can have a smaller radial extension dimension with the same axial extension dimension as a single ball bearing, thereby saving structural space.

[0033] Preferably, the brake disc is fixed to the axial end of the drive chamber housing, which is the axial inner end of the rotor. This allows the brake disc to be designed to be as large as possible in the radial direction, while the disc brake provides a high maximum braking torque. Here, the axial inner end of the rotor refers to the end of the rotor or hub motor facing the vehicle or steering mechanism.

[0034] The technical problem of the present invention is also solved by a drive steering module for a vehicle, comprising a hub motor according to one of the foregoing embodiments and a steering device connected to the hub motor, the steering device being designed to connect the hub motor to the vehicle body and provide independent steering capability of the wheels including the hub motor within an angular range of at least ±60°, preferably at least ±75°, and particularly preferably at least ±90°. The hub motor according to the invention is particularly suitable for use with such a steering device having a large maximum steering angle because the hub motor has a particularly small structural height. In particular, the axial extension of the hub motor is substantially determined by the extension of the wheel rim. According to one embodiment, only the brake caliper or brake disc can extend axially from the wheel rim by less than 10 cm (preferably less than 5 cm). This allows for a stable design of the steering device without collision between the steering device and the hub motor (e.g., disc brakes) at large steering angles. Attached Figure Description

[0035] Further details of the invention can be derived from the description of the described embodiments and the appended claims. In the accompanying drawings: Figure 1 A schematic cross-sectional view of one embodiment of the hub motor according to the present invention is shown. Detailed Implementation

[0036] In the following detailed description of preferred embodiments, the same reference numerals denote components that are substantially the same in these embodiments or in other embodiments. For the purpose of better illustrating the invention, the preferred embodiments shown in the drawings are not necessarily drawn to scale.

[0037] Figure 1 A schematic cross-sectional view of a hub motor 1 for a vehicle wheel according to the present invention is shown, the hub motor including a motor and a disc brake 2. The motor includes a rotor 3 and a stator 4.

[0038] The disc brake 2 includes a brake caliper 5 and a brake disc 6. The brake caliper 5 includes a brake actuator 7 extending from the brake caliper 5 along the axial direction of the motor, which is used to operate the brake caliper 5. The brake actuator 7 is arranged overlapping the rotor 3 and stator 4 in the axial direction. The brake caliper 5 clamps the brake disc 6 from the radially inward side. The brake actuator 7 is arranged inside the hub motor 1 and does not extend outward.

[0039] The brake actuator 7 overlaps axially with the permanent magnets 8 and 9 of the motor and the stator winding 10 of the motor. The rotor 3 includes drive cavity housings 11 and 12, which form a drive cavity 13 in which the permanent magnets 8 and 9 of the motor are arranged. The stator 4 is surrounded axially from both sides and radially from both inside and outside by the drive cavity housings 11 and 12. Here, the drive cavity housings 11 and 12 include an outer drive cavity housing 11 and an inner drive cavity housing 12, which are connected by a surrounding static sealing element 13A. The drive cavity housings 11 and 12 have an asymmetrical hollow "U" shaped cross section in the radial direction. The stator 4 also has an asymmetrical "U" shaped cross section in the radial direction, with its radially outer leg 14 slightly extended relative to the radially inner leg 15. The stator winding 10 of the motor is arranged in the radially outer leg region of the stator 4.

[0040] The permanent magnets 8 and 9 are constructed as two coaxially arranged groups of permanent magnets 8 and 9. The first group of permanent magnets 8 is arranged radially inside the stator 4 and located on the radially outer side of the inner housing 12 of the drive cavity, while the second group of permanent magnets 9 is arranged radially outside the stator 4 and located on the radially inner side of the outer housing 11 of the drive cavity.

[0041] The electronic unit 16 (which includes the motor inverter 17) is partially at the same height as the brake actuator 7 in the axial direction, but is offset in the poloidal direction. This allows for particularly efficient use of structural space. The electronic unit 16 also includes an electronic component housing 18, which is radially connected to or is part of the steering knuckle housing 19.

[0042] The electronic unit 16 is offset by 180° relative to the brake actuator 7. This angular distance refers to the distance between the geometric center of the electronic unit and the geometric center of the brake actuator. The advantage of this design is that the brake actuator 7 and brake caliper 5, as heat sources, are located as far away as possible from the electronic unit 16, which itself is both a heat source and heat-sensitive. This simplifies the cooling of the electronic unit 16. The brake actuator 7 and the electronic unit 16 are partially at the same height along the axial direction and are located radially inward from the drive cavity 13 (viewed from this position).

[0043] Two ball bearings 20 and 21 are arranged between the rotor 3 and the stator 4, each of which is coupled with a sealing strip to provide a dynamic seal. The sealing strip, together with a sealing element 13A between the drive chamber housing 11 and the drive chamber inner housing 12, provides a seal for the drive chamber 13, particularly to prevent the ingress of contaminant particles (e.g., from a disc brake). One ball bearing 21 is adjacent to the radially outer side of the stator 4, and the other ball bearing 20 is adjacent to the radially inner side of the stator 4, particularly the radially inner leg 15. The ball bearings 20 and 21 are designed as double ball bearings, each comprising two sequentially arranged sub-ball bearings 22 and 23 in the axial direction.

[0044] The disc brake 2 is preferably an electromechanical disc brake, and in particular not a hydraulic disc brake. The power supply line of the electromechanical disc brake is mechanically more flexible than the hydraulic high-pressure line of the hydraulic brake, and therefore easier to bend, which is advantageous, for example, for the use of the hub motor 1 in drive steering modules with large maximum steering angles.

[0045] The power supply line 24, coolant line 25, and signal line (not explicitly shown) leading to the hub motor 1 extend within the central steering knuckle housing 19. This allows the corresponding lines to be guided to the hub motor 1 in a protected manner, particularly in drive steering modules with large maximum steering angles.

[0046] The brake caliper 5 is connected to the radially outer side of the steering knuckle housing 19. Because the brake caliper 5 clamps the brake disc 6 from the inside, this embodiment allows the brake caliper 5 to be stably fixed together with the brake actuator 7. However, it is also possible to alternatively have the brake caliper 5 clamp the brake disc 6 from the radially outer side.

[0047] The brake disc 6 is fixed on one axial end of the drive cavity housing 11, 12, which is the inner axial end of the rotor 3.

[0048] The hub motor 1 includes a rim 26 on which a tire 27 is mounted. A brake actuator 7 is arranged within the rim 26 in both the axial and radial directions. The axial extension of the rim 26 thus provides a framework within which the brake actuator 7 can be arranged effortlessly without the risk of collision or geometric constraints, for example, with components of a steering device connected to the hub motor 1 that have a large maximum steering angle. Here, the brake disc 6 is arranged axially within the rim 26. However, the brake disc may also extend axially from the rim 26 by less than 5 cm, for example.

[0049] Here, the disc brake 2 extends slightly beyond the rim 26 in the axial direction, preferably less than 5 cm. Here, the axial side of the brake caliper 5 partially exceeds the axial extension dimension of the rim 26; however, within this small range, it generally does little to restrict the steering device to be connected.

[0050] List of reference numerals

[0051] 1. Hub motor

[0052] 2. Disc brakes

[0053] 3 rotors

[0054] 4. Stator

[0055] 5. Brake calipers

[0056] 6. Brake disc

[0057] 7. Brake Actuator

[0058] 8 permanent magnets

[0059] 9 permanent magnets

[0060] 10 Stator windings

[0061] 11 Drive cavity housing, drive cavity outer shell

[0062] 12 Drive cavity housing, drive cavity inner housing

[0063] 13 Driving cavity

[0064] 13A Sealing Element

[0065] 14 Radial outer leg

[0066] 15. Radial inner leg

[0067] 16 electronic units

[0068] 17 Inverter

[0069] 18 Electronic component housings

[0070] 19 Steering knuckle housing

[0071] 20 ball bearings

[0072] 21 Ball bearing

[0073] 22 ball bearing

[0074] 23 ball bearing

[0075] 24 power supply lines

[0076] 25 Coolant Circuit

[0077] 26 rims

[0078] 27 tires

Claims

1. A hub motor (1) for a vehicle wheel, comprising a motor and a disc brake (2), wherein, The motor includes a rotor (3) and a stator (4), wherein the disc brake (2) includes a brake caliper (5) and a brake disc (6), wherein the brake caliper (5) includes a brake actuator (7) for operating the brake caliper (5), the brake actuator extending from the brake caliper (5) along the axial direction of the motor. The invention is characterized in that the brake disc (6) is arranged axially outside the stator (4), and the brake actuator (7) is arranged axially completely or partially inside the stator (4). The rotor (3) includes two coaxially arranged permanent magnet groups (8, 9), wherein the first permanent magnet group (8) is arranged radially inside the stator (4), and the second permanent magnet group (9) is arranged radially outside the stator (4). The brake actuator (7) and the permanent magnets (8, 9) of the motor are arranged overlapping in the axial direction.

2. The hub motor (1) according to claim 1, characterized in that, The brake caliper (5) clamps the brake disc (6) from the radial inside.

3. The hub motor (1) according to any one of the preceding claims, characterized in that, The brake actuator (7) generates clamping force electromechanically.

4. The hub motor (1) according to any one of the preceding claims, characterized in that, The hub motor (1) includes a rim (26), wherein a brake actuator (7) is arranged in the rim (26) in the axial and radial directions.

5. The hub motor (1) according to claim 4, characterized in that, The brake disc (6) is arranged in the axial direction within the rim (26).

6. The hub motor (1) according to claim 4 or 5, characterized in that, The entire disc brake (2) extends less than 10 cm out of the rim (26) in the axial direction, preferably less than 5 cm out of the rim (26), and particularly preferably is completely arranged inside the rim (26) in the axial direction.

7. The hub motor (1) according to any one of the preceding claims, characterized in that, The hub motor (1) includes a central steering knuckle housing (19) in which power supply lines (24) and / or coolant lines (26) and / or signal lines to the hub motor (1) are arranged.

8. The hub motor (1) according to any one of the preceding claims, characterized in that, The hub motor (1) includes a central steering knuckle housing (19), wherein the brake caliper (5) is connected to the radially outer side of the steering knuckle housing (19).

9. The hub motor (1) according to any one of the preceding claims, characterized in that, The hub motor includes at least one electronic unit (16), which preferably includes an inverter (17) for the motor. The electronic unit overlaps with the brake actuator (7) in the axial direction but is offset in the polar direction.

10. The hub motor (1) according to claim 9, characterized in that, The electronic unit (16) is offset from the brake actuator (7) in the polar direction by at least 90°, preferably at least 150°, and particularly preferably 180° ± 10°.

11. The hub motor (1) according to any one of the preceding claims, characterized in that, The rotor (3) includes a drive cavity housing (11, 12) that forms a drive cavity (13) in which permanent magnets (8, 9) of the motor are arranged. The stator (4) is surrounded by the drive cavity housing (11, 12) from both sides in the axial direction and from the inside and outside in the radial direction.

12. The hub motor (1) according to claim 11, characterized in that, The brake actuator (7) and / or electronic unit (16) are partially at the same height along the axial direction and are located radially inside the drive cavity (13).

13. The hub motor (1) according to any one of the preceding claims, characterized in that, Two ball bearings (20, 21) are arranged between the rotor (3) and the stator (4), wherein each ball bearing (20, 21) is combined with a sealing strip to provide a dynamic seal.

14. The hub motor (1) according to any one of the preceding claims, characterized in that, Two ball bearings (20, 21) are arranged between the rotor (3) and the stator (4), one of which (21) is adjacent to the radial outer side of the stator (4), while the other ball bearing (20) is adjacent to the radial inner side of the stator (4).

15. The hub motor (1) according to any one of the preceding claims, characterized in that, At least one double ball bearing (20, 21) is arranged between the rotor (3) and the stator (4), preferably two double ball bearings (20, 21), wherein the double ball bearing (20, 21) includes two sub-ball bearings (22, 23) arranged sequentially along the axial direction.

16. The hub motor (1) according to any one of claims 11 to 15, characterized in that, The brake disc (6) is fixed on one axial end of the drive chamber housing (11, 12), which corresponds to the axial inner end of the rotor (3).

17. A drive steering module for a vehicle, the drive steering module comprising a hub motor (1) according to any one of the preceding claims and a steering device connected to the hub motor (1), the steering device being designed to connect the hub motor (1) to the vehicle body and to provide independent steering capability of the wheels including the hub motor (1) within an angular range of at least ±60°, preferably at least ±75°, particularly preferably at least ±90°.

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