Planetary gearbox for a force-feedback unit of a steering wheel actuator

Abstract

The invention relates to a planetary gearbox (10) for a force-feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle, the planetary gearbox comprising: a ring gear (HR) and a sun gear (SO) arranged concentrically to the ring gear (HR); a plurality of planetary gears (PL) meshing with the sun gear (SO) and the ring gear (HR), wherein a toothing of the ring gear (HR) has a first helix angle (βHR) and a toothing of the sun gear (SO) has a second helix angle (βSO), and wherein a toothing of at least one of the plurality of planetary gears (PL) has a third helix angle (βPL) which differs from the first helix angle (βHR) and the second helix angle (βSO). The invention also relates to a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.

Description

[0001] Description

[0002] title

[0003] Planetary gear for a force feedback unit of a steering wheel actuator

[0004] The invention relates to a planetary gear for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.

[0005] The invention further relates to a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.

[0006] State of the art

[0007] Steer-by-wire steering systems typically include a steering wheel actuator. The steering wheel actuator uses precise sensors to detect the driver's input and transmits it digitally to the rack and pinion actuator. Together, the steering wheel actuator and rack and pinion actuator form the steer-by-wire steering system.

[0008] The steering wheel actuator generates steering feel based on vehicle information, such as speed and feedback from the rack actuator. This provides the driver with constant, precise information about the driving situation.

[0009] The steering wheel actuator consists of an adjustable steering column and a force feedback unit. The steering column allows the steering wheel to be individually positioned or completely stowed away in the cockpit module – for maximum freedom of movement during automated driving or when stationary. The force feedback unit generates and transmits the precise steering feel via a friction-optimized reduction gear, specifically a planetary gear. In practice, however, it is generally not possible to design the planetary gear completely free of play, which would result in adverse steering and noise characteristics.

[0010] It is therefore the object of the invention to provide a planetary gear for a force feedback unit of a steering wheel actuator, which has a backlash-free design.

[0011] This problem is solved by the subject matter of patent claim 1.

[0012] Disclosure of the invention

[0013] The present invention provides a planetary gear for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle. The planetary gear comprises a ring gear and a sun gear arranged concentrically with the ring gear.

[0014] Furthermore, the planetary gear comprises a plurality of planetary gears meshing with the sun gear and the ring gear, wherein a toothing of the ring gear and a toothing of the sun gear have a first helix angle, and wherein a toothing of at least one of the plurality of planetary gears has a second helix angle deviating from the first helix angle.

[0015] The present invention further provides a steering wheel actuator for a steer-by-wire steering system of a motor vehicle with an adjustable steering column and a force feedback unit comprising a planetary gear according to the invention.

[0016] One idea of ​​the present invention is that the inclination angle of the planet(s) deviates from the inclination angle of the sun and the ring gear.

[0017] This creates tension between the meshing surfaces of the sun / planet and between the planetary gear and the ring gear, eliminating backlash. Another feature is the creation of double-flank contact between the sun / planet and the planet / ring gear. This allows the geometric overpressure to be resolved with lower resulting stresses in the gearing—through elastic deformation of the entire gear body—and, in particular, compensates for geometric changes across the temperature range.

[0018] When the load increases, the double flank contact is converted into a better contact pattern in the single flank contact than is the case with a rigid wheel body.

[0019] Advantageous embodiments and further developments emerge from the subclaims and from the description with reference to the figures.

[0020] According to a preferred embodiment, the first helix angle of the toothing of the ring gear and the second helix angle of the toothing of the sun gear are equal. This advantageously enables standardization of the components and, consequently, simplifies production by reducing the number of components.

[0021] According to a further preferred development, the first helix angle of the toothing of the ring gear and the second helix angle of the toothing of the sun gear are 0°. The ring gear and the sun gear thus effectively have spur gearing.

[0022] According to a further preferred development, it is provided that the ring gear, the plurality of planet gears, and the sun gear have conical toothing, wherein a cone angle of the toothings of the plurality of planet gears and the sun gear is oriented in a counter-conical manner. This enables a different or opposite mounting direction of the sun gear and the planet gears. Thus, a defined radial compression of the respective gears can advantageously be achieved. According to a further preferred development, it is provided that at least one of the plurality of planet gears and / or the sun gear can each be brought into a defined radial over-compression relative to the ring gear by means of at least one adjusting disk or by the axial press-in position of a planet carrier and / or the sun gear.

[0023] This enables a defined axial positioning of the respective wheel so that the radial overpressing of the respective wheel is optimal and positioning of the respective wheel can be carried out at this point.

[0024] According to a further preferred development, it is provided that the at least one of the plurality of planetary gears is formed from plastic, wherein the at least one of the plurality of planetary gears, regardless of a component tolerance, is designed to bring the toothing of the at least one of the plurality of planetary gears into engagement with the toothing of the ring gear and the toothing of the sun gear without play.

[0025] By making the planetary gear out of plastic, it is possible to achieve a zero backlash across the entire tolerance range.

[0026] According to a further preferred development, it is provided that, due to the third helix angle of the toothing of the at least one of the plurality of planetary gears deviating from the first helix angle of the toothing of the ring gear and the second helix angle of the toothing of the sun gear, a preload is provided between the toothing of the ring gear and the toothing of the at least one of the plurality of planetary gears, as well as a preload between the toothing of the sun gear and the toothing of the at least one of the plurality of planetary gears.

[0027] Despite the tolerances of the components, i.e. the planetary gears and the ring gear, there is still a preload and thus freedom from play between the gears.

[0028] According to a further preferred development, it is provided that in

[0029] In the region of engagement of the toothing of the at least one of the plurality of planetary gears with the toothing of the ring gear, a first torque can be generated about an axis extending radially through a center point of the at least one of the plurality of planetary gears.

[0030] Not only the toothing of the planetary gear is deformed, but the entire gear body of the planetary gear is advantageously deformed by the torque acting on it.

[0031] According to a further preferred development, it is provided that, in the region of the engagement of the toothing of at least one of the plurality of planetary gears with the toothing of the sun gear, a second torque acting opposite to the first torque can be generated about an axis extending radially through the center of at least one of the plurality of planetary gears. In sum, the two torques cancel each other out but rotate the gear body.

[0032] According to a further preferred development, the flanks of the toothing of at least one of the plurality of planetary gears have a crowning and / or a variable profile shift. The toothing of the planetary gear thus has a crowned contact shape with the ring gear.

[0033] According to a further preferred development, the crowning and / or variable profile shift is formed at respective axial end sections of the flanks of the toothing. This advantageously prevents edge supports.

[0034] According to a further preferred development, the toothing of at least one of the plurality of planetary gears has a variable tooth thickness profile. The crowning also enables a lower Hertzian surface pressure between the planetary gear and the ring gear or sun gear.

[0035] According to a further preferred development, it is provided that an angular deviation of the first helix angle of the toothing of the ring gear and the second helix angle of the toothing of the sun gear to the third helix angle of the toothing of the at least one of the plurality of planet gears is between 0.2° and 5°. Thus, an angular deviation over a large angular range can be advantageously enabled.

[0036] Further possible embodiments, further developments and implementations of the invention also include combinations of features of the invention described previously or below with regard to the exemplary embodiments that are not explicitly mentioned.

[0037] Short description of the drawings

[0038] The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention.

[0039] Other embodiments and many of the aforementioned advantages will become apparent upon review of the drawings. The elements illustrated in the drawings are not necessarily drawn to scale.

[0040] They show:

[0041] Fig. 1 is a perspective view of a planetary gear for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle according to a preferred embodiment of the invention;

[0042] Fig. 2 is a view of a longitudinal section AA in Fig. 1 according to the preferred embodiment of the invention;

[0043] Fig. 3 is a representation of a longitudinal section BB in Fig. 1 according to the preferred embodiment of the invention;

[0044] Fig. 4 is a perspective view of a planetary gear of the planetary gear shown in Fig. 1 according to the preferred embodiment of the invention; Fig. 5 is an enlarged detailed view of the longitudinal section AA in Fig. 1 according to the preferred embodiment of the invention;

[0045] Fig. 6 is an enlarged detailed view of the longitudinal section BB in Fig. 1 according to the preferred embodiment of the invention;

[0046] Fig. 7 is an enlarged detailed view of the longitudinal section AA in Fig. 1 according to another preferred embodiment of the invention;

[0047] Fig. 8 is an enlarged detailed view of the longitudinal section BB in Fig. 1 according to another preferred embodiment of the invention; and

[0048] Fig.9 is a longitudinal sectional view of the planetary gear for the force feedback unit of the steering wheel actuator for the steer-by-wire steering system of the motor vehicle according to the preferred embodiment of the invention.

[0049] In the figures of the drawings, the same reference symbols designate the same or functionally equivalent elements, parts or components, unless otherwise stated.

[0050] Fig. 1 shows a planetary gear 10 for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.

[0051] The planetary gear 10 comprises a ring gear HR and a sun gear SO arranged concentrically to the ring gear HR;

[0052] Furthermore, the planetary gear 10 comprises a plurality of planet gears PL meshing with the sun gear SO and the ring gear HR. A toothing of the ring gear HR has a first helix angle PHR and a toothing of the sun gear SO has a second helix angle ßso. A toothing of at least one of the plurality of planet gears PL further has a third helix angle PPL which differs from the first helix angle PHR and the second helix angle ßso. Due to the elasticity of the ring gear and the entire wheel body of the planet gear, which is made of plastic, the planet gear PL is resiliently clamped. The more elastic the ring gear, the more geometric tolerance fluctuations and temperature fluctuations can be compensated for.

[0053] Fig. 2 shows a representation of a longitudinal section AA in Fig. 1 according to the preferred embodiment of the invention.

[0054] At least one of the plurality of planetary gears PL is made of plastic. The at least one of the plurality of planetary gears PL is designed, regardless of component tolerance, to engage the toothing of the at least one of the plurality of planetary gears PL with the toothing of the ring gear HR without play.

[0055] A force couple Ai, A2 is applied to the respective contact points of at least one of the plurality of planetary gears PL with the ring gear HR.

[0056] Fig. 3 shows a representation of a longitudinal section BB in Fig. 1 according to the preferred embodiment of the invention.

[0057] The at least one of the plurality of planetary gears PL is designed, regardless of a component tolerance, to engage the toothing of the at least one of the plurality of planetary gears PL with the toothing of the sun gear SO without play.

[0058] A force pair Bi, B2 is applied to the respective contact points of at least one of the plurality of planetary gears PL with the sun gear SO.

[0059] Fig. 4 shows a perspective view of a planetary gear of the planetary gear 10 shown in Fig. 1 according to the preferred embodiment of the invention. In the area of ​​engagement of the toothing of at least one of the plurality of planetary gears PL, a first torque MA can be generated with the toothing of the ring gear HR about an axis A extending radially through a center point of at least one of the plurality of planetary gears PL.

[0060] In the region of the engagement of the toothing of at least one of the plurality of planetary gears PL with the toothing of the sun gear SO, a second torque MB acting in opposition to the first torque MA can be generated about an axis A extending radially through the center of at least one of the plurality of planetary gears PL. Due to the fact that the two torques act in opposite directions, the entire planetary gear is twisted about the axis A.

[0061] Fig. 5 shows an enlarged detailed view of the longitudinal section AA in Fig. 1 according to the preferred embodiment of the invention.

[0062] Due to the third helix angle of the toothing of the at least one of the plurality of planetary gears, which differs from the first helix angle of the toothing of the ring gear and the second helix angle of the toothing of the sun gear, a preload is provided between the toothing of the ring gear and the toothing of the at least one of the plurality of planetary gears, as well as a preload between the toothing of the sun gear and the toothing of the at least one of the plurality of planetary gears.

[0063] An angular deviation of the first helix angle PHR of the toothing of the ring gear HR and the second helix angle ßso of the toothing of the sun gear SO to the third helix angle PPL of the toothing of the at least one of the plurality of planet gears PL is between 0.2° and 5°, in the present embodiment 0.9°.

[0064] The first helix angle PHR of the toothing of the ring gear HR shown in Fig. 5 and the second helix angle ßso of the toothing of the sun gear SO shown in Fig. 6 preferably have the same value. Alternatively, the first helix angle PHR of the toothing of the ring gear HR shown in Fig. 5 and the second helix angle ßso of the toothing of the sun gear SO shown in Fig. 6 can, for example, have different values.

[0065] Fig. 6 shows an enlarged detailed view of the longitudinal section BB in Fig. 1 according to the preferred embodiment of the invention.

[0066] Due to the second helix angle ßpL of the toothing of the at least one of the plurality of planetary gears PL, which deviates from the first helix angle ßso of the toothing of the sun gear SO, a preload is provided between the toothing of the sun gear SO and the toothing of the at least one of the plurality of planetary gears PL.

[0067] An angular deviation of the first helix angle ßhR of the toothing of the ring gear HR and the second helix angle ßso of the toothing of the sun gear SO to the third helix angle ßpL of the toothing of the at least one of the plurality of planet gears PL is between 0.2° and 5°, in the present embodiment 0.9°.

[0068] Fig. 7 shows an enlarged detailed view of the longitudinal section AA in Fig. 1 according to another preferred embodiment of the invention.

[0069] Flanks of the toothing of at least one of the plurality of planetary gears PL have a crowning 12 and / or a variable profile shift.

[0070] The crowning 12 and / or variable profile shift is formed at the respective axial end sections of the flanks of the toothing. The toothing of at least one of the plurality of planetary gears PL has a variable tooth thickness profile 14 due to the crowning 12 and / or variable profile shift. Thus, edge wear at the contact points of the toothing engagement with the ring gear HR can be avoided.

[0071] Fig. 8 shows an enlarged detailed view of the longitudinal section BB in Fig. 1 according to another preferred embodiment of the invention. Flanks of the toothing of at least one of the plurality of planetary gears PL have a crown 12 and / or a variable profile shift.

[0072] The crowning 12 and / or variable profile shift is formed at respective axial end sections of the flanks of the toothing. The toothing of at least one of the plurality of planetary gears PL has a variable tooth thickness profile 14 due to the crowning 12 and / or variable profile shift. Thus, edge supports at the contact points of the toothing engagement with the sun gear SO can be avoided.

[0073] Fig. 9 shows a longitudinal sectional view of the planetary gear for the force feedback unit of the steering wheel actuator for the steer-by-wire steering system of the motor vehicle according to the preferred embodiment of the invention.

[0074] The ring gear HR, the plurality of planetary gears PL, and the sun gear SO have conical toothing. The cone angle of the toothings of the plurality of planetary gears PL and the sun gear SO is oriented in opposite directions.

[0075] The at least one of the plurality of planetary gears PL and / or the sun gear SO can further be brought into a defined radial over-pressing relative to the ring gear HR by means of at least one adjusting disk 16 or by the axial press-in position of a planetary carrier and / or the sun gear SO.

Claims

Claims 1 . Planetary gear (10) for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle, comprising: a ring gear (HR) and a sun gear (SO) arranged concentrically to the ring gear (HR); a plurality of planet gears (PL) meshing with the sun gear (SO) and the ring gear (HR), wherein a toothing of the ring gear (HR) has a first helix angle (PHR) and a toothing of the sun gear (SO) has a second helix angle (ßso), and wherein a toothing of at least one of the plurality of planet gears (PL) has a third helix angle (ßpi_) deviating from the first helix angle (PHR) and the second helix angle (ßso).

2. Planetary gear (10) according to claim 1, wherein the first helix angle (PHR) of the toothing of the ring gear (HR) and the second helix angle (ßso) of the toothing of the sun gear (SO) have an equal amount.

3. Planetary gear according to claim 1 or 2, wherein the first helix angle (PHR) of the toothing of the ring gear (HR) and the second helix angle (ßso) of the toothing of the sun gear (SO) are 0°.

4. Planetary gear (10) according to one of the preceding claims, wherein the ring gear (HR), the plurality of planet gears (PL) and the sun gear (SO) have a conical toothing, wherein a cone angle of the toothings of the plurality of planet gears (PL) and the sun gear (SO) is oriented in a counter-conical manner.

5. Planetary gear (10) according to claim 4, wherein the at least one of the plurality of planet gears (PL) and / or the sun gear (SO) can each be brought into a defined radial over-pressing by means of at least one adjusting disk (16) or by the axial press-in position of a planet carrier and / or the sun gear (SO) relative to the ring gear (HR).

6. Planetary gear (10) according to one of the preceding claims, wherein the at least one of the plurality of planetary gears (PL) is formed from plastic, wherein the at least one of the plurality of planetary gears (PL), regardless of a component tolerance, is designed to bring the toothing of the at least one of the plurality of planetary gears (PL) into engagement with the toothing of the ring gear (HR) and the toothing of the sun gear (SO) without play.

7. Planetary gear (10) according to one of the preceding claims, wherein due to the third helix angle (ß) deviating from the first helix angle (PHR) of the toothing of the ring gear (HR) and the second helix angle (ßso) of the toothing of the sun gear (SO), PL) the toothing of at least one of the plurality of planetary gears (PL), a preload is provided between the toothing of the ring gear (HR) and the toothing of at least one of the plurality of planetary gears (PL) and a preload is provided between the toothing of the sun gear (SO) and the toothing of at least one of the plurality of planetary gears (PL).

8. Planetary gear (10) according to one of the preceding claims, wherein in the region of the engagement of the toothing of the at least one of the plurality of planet gears (PL) with the toothing of the ring gear (HR), a first torque (MA) can be generated about an axis (A) extending radially through a center point of the at least one of the plurality of planet gears (PL).

9. Planetary gear (10) according to claim 8, wherein in the region of the engagement of the toothing of the at least one of the plurality of planet gears (PL) with the toothing of the sun gear (SO), a second torque (MB) acting opposite to the first torque (MA) is increased by a value determined by the Center of the at least one of the plurality of planet gears (PL) radially extending axis (A) can be generated.

10. Planetary gear (10) according to one of the preceding claims, wherein flanks of the toothing of at least one of the plurality of planet gears (PL) have a crowning (12) and / or a variable profile shift.

11. Planetary gear (10) according to claim 10, wherein the crowning (12) and / or variable profile shift is formed on respective axial end portions of the flanks of the toothing.

12. Planetary gear (10) according to one of the preceding claims, wherein the toothing of at least one of the plurality of planet gears (PL) has a variable tooth thickness profile (14).

13. Planetary gear (10) according to one of the preceding claims, wherein an angular deviation of the first helix angle (PHR) of the toothing of the ring gear (HR) and the second helix angle (ßso) of the toothing of the sun gear (SO) to the third helix angle (ßpi_) of the toothing of the at least one of the plurality of planet gears (PL) is between 0.2° and 5°.

14. A steering wheel actuator for a steer-by-wire steering system of a motor vehicle, comprising: an adjustable steering column; and a force feedback unit comprising a planetary gear (10) according to one of claims 1 to 13.

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