Planetary gear for a force feedback unit of a steering wheel actuator

Abstract

The invention relates to 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, comprising a ring gear (HR) and a sun gear (SO) arranged concentrically with 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 (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 planet gears (PL) has a third helix angle (βPL) that differs from the first helix angle (βHR) and the second helix angle (βSO). The invention further relates to a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.

Description

The invention relates to a planetary transmission for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.The invention further relates to a steering wheel actuator for a steer-by-wire steering system of a motor vehicle.Prior ArtSteer-by-wire steering systems conventionally include a steering wheel actuator. The steering wheel actuator detects the driver's request by means of a precise sensor system and transmits it digitally to the rack actuator. Together, the steering wheel actuator and the rack and pinion actuator form the steering system steer-by-wire.The steering wheel actuator generates the steering feel based on vehicle information such as speed and the rack actuator feedback. The driver thus continuously receives precise information about the driving state.The steering wheel actuator consists of an adjustable steering column and a force feedback unit. The steering column makes it possible to position the steering wheel individually or to store it completely in the cockpit module-for maximum free space during automated driving or at a standstill. The force feedback unit generates and transmits the precise steering feel via a friction-optimized reduction gear, in particular a planetary gear.In practice, however, it is generally not possible to design the planetary gear set completely free of play, which is associated with disadvantageous steering and noise behavior.It is therefore the object of the invention to specify a planetary transmission for a force feedback unit of a steering wheel actuator, which has a play-free design.This object is achieved by the subject matter of claim 1.Disclosure of the InventionThe present invention provides a planetary gear set 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.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 differing from the first helix angle.The present invention furthermore provides a steering wheel actuator for a steer-by-wire steering system of a motor vehicle having an adjustable steering column and a force feedback unit comprising a planetary gear set according to the invention.One concept of the present invention is that the skew angle of the planet / planets deviates from the skew angle of the sun and of the ring gear.This causes a bracing between the sun / planet tooth meshings and between the planetary gear / ring gear, thereby eliminating the tooth play.A further feature is the generation of a two-flank contact between sun / planet and planet / ring gear. Thus, the geometric overpressing can be released with lower resulting stresses in the toothing-by elastic deformation of the entire wheel body-and in particular the geometric changes over the temperature range can be compensated.When the load is increased, the two-flank contact is converted into a better contact pattern in the one-flank contact than is the case with a rigid wheel body.Advantageous embodiments and refinements emerge from the dependent claims and from the description with reference to the figures.According to a preferred development, it is provided that the first skew angle of the toothing of the ring gear and the second skew angle of the toothing of the sun gear have the same amount. This advantageously allows for the components to be unified and, consequently, for a simplification in the production by reducing the components.According to a further preferred development, it is provided that the first skew angle of the toothing of the ring gear and the second skew angle of the toothing of the sun gear are 0°. The ring gear and the sun gear thus effectively have a straight toothing.According to a further preferred development, it is provided that the ring gear, the plurality of planetary gears and the sun gear have a conical toothing, wherein a cone angle of the toothings of the plurality of planetary gears and of the sun gear is oriented counter-conically. This enables a different or opposite mounting direction of the sun wheel and the planetary wheels. Thus, a defined radial compression of the respective wheels can be achieved in an advantageous manner.According to a further preferred development, it is provided that the at least one of the plurality of planetary gears and / or the sun gear can be brought into a defined radial overpression relative to the ring gear by means of at least one setting disk or by the axial press-fit position of a planetary carrier and / or of the sun gear.A defined axial positioning of the respective wheel can thus be made possible, so that the radial overpression of the respective wheel is optimal, and a positioning of the respective wheel can be carried out at this point.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, independently of a component tolerance, is configured 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.By forming the planetary gear from plastic, a freedom of play over the entire tolerance range can thus be advantageously made possible.According to a further preferred development, it is provided that, due to the third skew angle of the toothing of the at least one of the plurality of planetary gears deviating from the first skew angle of the toothing of the ring gear and the second skew angle of the toothing of the sun gear, a prestress is provided between the toothing of the ring gear and the toothing of the at least one of the plurality of planetary gears and a prestress is provided between the toothing of the sun gear and the toothing of the at least one of the plurality of planetary gears.Despite the tolerances of the components, i.e. the planetary gears and the ring gear, a prestress and thus freedom from play between the wheels is nevertheless present.According to a further preferred development, it is provided that in the region of the 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.Not only is the toothing of the planetary gear deformed in this case, but the complete wheel body of the planetary gear is advantageously deformed by the torque acting on it.According to a further preferred development, it is provided that on wherein, in the region of the engagement of the toothing of the at least one of the plurality of planetary gears with the toothing of the sun gear, a second torque acting in the opposite direction to the first torque can be generated about an axis extending radially through the center point of the at least one of the plurality of planetary gears. In total, the two torques cancel each other out, but rotate the wheel body.According to a further preferred development, it is provided that flanks of the toothing of the at least one of the plurality of planetary gears have a crowning and / or a variable profile displacement. The toothing of the planetary gear thus has a spherical contact shape with the ring gear.According to a further preferred development, it is provided that the crowning and / or variable profile displacement is formed at respective axial end sections of the flanks of the toothing. Edge carriers can thus be avoided in an advantageous manner.According to a further preferred development, it is provided that the toothing of the at least one of the plurality of planetary gears has a variable tooth thickness profile. The crowning can also allow a lower Hertzian surface pressure between the planetary gear and the ring gear or sun gear.According to a further preferred development, it is provided that an angle deviation of the first skew angle of the toothing of the ring gear and of the second skew angle of the toothing of the sun gear relative to the third skew angle of the toothing of the at least one of the plurality of planetary gears is between 0.2° and 5°. Thus, an angle deviation over a large angle range can be advantageously made possible.Further possible embodiments, developments and implementations of the invention also include combinations of features of the invention described above or below with respect to the exemplary embodiments, which combinations are not explicitly mentioned.Brief Description of the DrawingsThe accompanying drawings are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention.Other embodiments and many of the advantages mentioned are evident with reference to the drawings. The elements of the drawings shown are not necessarily shown true to scale with respect to one another.The following are shown: FIG. 1 shows a perspective illustration of a planetary gearing 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; FIG. 2 is a longitudinal sectional view A--A of FIG. 1 according to the preferred embodiment of the invention; FIG. 3 is a longitudinal sectional view B--B of FIG. 1 according to the preferred embodiment of the invention; FIG. 4 is a perspective view of a planetary gear of the planetary gear set shown in FIG. 1 according to the preferred embodiment of the invention; FIG. 5 is an enlarged detail view of the longitudinal section A-A in FIG. 1 according to the preferred embodiment of the invention; FIG. 6 is an enlarged detail view of the longitudinal section B-B in FIG. 1 according to the preferred embodiment of the invention; FIG. 7 shows an enlarged detail view of the longitudinal section A-A in FIG. 1 according to a further preferred embodiment of the invention; FIG. 8 shows an enlarged detail view of the longitudinal section B-B in FIG. 1 according to a further preferred embodiment of the invention; and FIG. 9 is a longitudinal sectional view of the planetary gear set 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.In the figures of the drawings, identical reference numerals designate identical or functionally identical elements, components or components, unless indicated to the contrary.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.The planetary gear 10 comprises a ring gear HR and a sun gear SO concentrically arranged with the ring gear HR;Furthermore, the planetary gear 10 comprises a plurality of planetary gears PL meshing with the sun gear SO and the ring gear HR. A toothing of the ring gear HR has a first skew angle β HR and a toothing of the sun gear SO has a second skew angle β SO in this case. A toothing of at least one of the plurality of planetary gears PL further has a third helix angle β PL deviating from the first helix angle β HR and the second helix angle β SO.Due to the elasticity of the ring gear and the entire wheel body of the planetary gear, which is made of plastic, the planetary gear PL is elastically braced. The more elastic the toothed ring, the more geometric tolerance fluctuations and temperature fluctuations can be compensated.FIG. 2 is a longitudinal sectional view A-A of FIG. 1 according to the preferred embodiment of the invention.At least one of the plurality of planetary gears PL is formed of plastic. The at least one of the plurality of planetary gears PL is designed, independently of a component tolerance, 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 without play.At the respective contact points of the at least one of the plurality of planetary gears PL with the ring gear HR, a couple of forces A 1, A 2. is applied.FIG. 3 is a longitudinal sectional view B-B of FIG. 1 according to the preferred embodiment of the invention.The at least one of the plurality of planetary gears PL is configured, independently 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.At the respective contact points of the at least one of the plurality of planetary gears PL with the sun gear SO, a couple of forces B 1, B 2. is applied.FIG. 4 is 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 region of the engagement of the toothing of the at least one of the plurality of planetary gears PL, a first torque M A about an axis A extending radially through a center point of the at least one of the plurality of planetary gears PL can be generated with the toothing of the ring gear HR.In the region of the engagement of the toothing of the at least one of the plurality of planetary gears PL with the toothing of the sun gear SO, a second torque M B acting in the opposite direction to the first torque M A can furthermore be generated about an axis A extending radially through the center point of the 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.FIG. 5 shows an enlarged detail view of the longitudinal section A-A in FIG. 1 according to the preferred embodiment of the invention.Due to the third skew angle of the toothing of the at least one of the plurality of planetary gears, which differs from the first skew angle of the toothing of the ring gear and from the second skew angle of the toothing of the sun gear, a prestress is provided between the toothing of the ring gear and the toothing of the at least one of the plurality of planetary gears and a prestress is provided between the toothing of the sun gear and the toothing of the at least one of the plurality of planetary gears.An angular deviation of the first skew angle β HR of the toothing of the ring gear HR and the second skew angle β SO of the toothing of the sun gear SO from the third skew angle β PL of the toothing of the at least one of the plurality of planetary gears PL is between 0.2° and 5°, in the present embodiment 0.9°.The first skew angle β HR of the toothing of the ring gear HR shown in FIG. 5 and the second skew angle β SO of the toothing of the sun gear SO shown in FIG. 6 preferably have the same amount. Alternatively, the first skew angle β HR of the toothing of the ring gear HR shown in FIG. 5 and the second skew angle β SO of the toothing of the sun gear SO shown in FIG. 6 can have different amounts, for example.FIG. 6 shows an enlarged detail view of the longitudinal section B-B in FIG. 1 according to the preferred embodiment of the invention.Due to the second skew angle β PL of the toothing of the at least one of the plurality of planetary gears PL deviating from the first skew angle β SO of the toothing of the sun gear SO, a prestress 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.An angular deviation of the first skew angle β HR of the toothing of the ring gear HR and the second skew angle β SO of the toothing of the sun gear SO from the third skew angle β PL of the toothing of the at least one of the plurality of planetary gears PL is between 0.2° and 5°, in the present embodiment 0.9°.FIG. 7 shows an enlarged detail view of the longitudinal section A-A in FIG. 1 according to a further preferred embodiment of the invention.Flanks of the toothing of the at least one of the plurality of planetary gears PL have a crowning 12 and / or a variable profile displacement.The crowning 12 and / or variable profile displacement is formed at respective axial end sections of the flanks of the toothing. The toothing of the 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 displacement. Edge carriers at the contact points of the tooth engagements with the ring gear HR can thus be avoided.FIG. 8 shows an enlarged detail view of the longitudinal section B-B in FIG. 1 according to a further preferred embodiment of the invention.Flanks of the toothing of the at least one of the plurality of planetary gears PL have a crowning 12 and / or a variable profile displacement.The crowning 12 and / or variable profile displacement is formed at respective axial end sections of the flanks of the toothing. The toothing of the 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 displacement. Edge carriers at the contact points of the toothed engagements with the sun gear SO can thus be avoided.FIG. 9 is a longitudinal sectional view of the planetary gear set 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.The ring gear HR, the plurality of planetary gears PL and the sun gear SO have a conical toothing. A cone angle of the tooth arrangements of the plurality of planetary gears PL and of the sun gear SO is oriented counter-conically.The at least one of the plurality of planetary gears PL and / or the sun gear SO can furthermore each be brought into a defined radial overpression relative to the ring gear HR by means of at least one setting disk 16 or by the axial press-fit position of a planetary carrier and / or of the sun gear SO.

Claims

Planetary gear (10) for a force feedback unit of a steering wheel actuator for a steer-by-wire steering system of a motor vehicle, having: a ring gear (HR) and a sun gear (SO) arranged concentrically with 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 skew angle (β HR) and a toothing of the sun gear (SO) has a second skew angle (β SO) and wherein a toothing of at least one of the plurality of planetary gears (PL) has a third skew angle (β PL) different from the first skew angle (β HR) and the second skew angle (β SO).The planetary gear set (10) according to claim 1, wherein the first skew angle (β HR) of the teeth of the ring gear (HR) and the second skew angle (β SO) of the teeth of the sun gear (SO) have an equal amount.The planetary gear set according to claim 1 or 2, wherein the first skew angle (β HR) of the teeth of the ring gear (HR) and the second skew angle (β SO) of the teeth of the sun gear (SO) are 0°.The planetary gear (10) according to any one of the preceding claims, wherein the ring gear (HR), the plurality of planetary gears (PL) and the sun gear (SO) have a conical toothing, wherein a cone angle of the toothings of the plurality of planetary gears (PL) and the sun gear (SO) is oriented counter-conically.Planetary transmission (10) according to Claim 4, wherein the at least one of the plurality of planetary gears (PL) and / or the sun gear (SO) can be brought into a defined radial compression relative to the ring gear (HR) in each case by means of at least one setting disk (16) or by the axial press-fit position of a planetary carrier and / or of the sun gear (SO).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), independently of a component tolerance, is configured to engage the toothing of the at least one of the plurality of planetary gears (PL) with the toothing of the ring gear (HR) and the toothing of the sun gear (SO) without play.Planetary gear (10) according to one of the preceding claims, wherein, due to the third skew angle (β PL) of the toothing of the at least one of the plurality of planetary gears (PL), which is different from the first skew angle (β HR) of the toothing of the ring gear (HR) and the second skew angle (β SO) of the toothing of the sun gear (SO), a prestress is provided between the toothing of the ring gear (HR) and the toothing of the at least one of the plurality of planetary gears (PL) and a prestress 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).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 planetary gears (PL) with the toothing of the ring gear (HR), a first torque (M A) about an axis (A) radially extending through a center point of the at least one of the plurality of planetary gears (PL) can be generated.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 planetary gears (PL) with the toothing of the sun gear (SO), a second torque (M B) acting in the opposite direction to the first torque (M A) can be generated about an axis (A) extending radially through the centre point of the at least one of the plurality of planetary gears (PL).Planetary gear (10) according to one of the preceding claims, wherein flanks of the toothing of the at least one of the plurality of planetary gears (PL) have a crowning (12) and / or a variable profile displacement.Planetary gear (10) according to claim 10, wherein the crowning (12) and / or variable profile displacement is formed at respective axial end portions of the flanks of the toothing.Planetary gear (10) according to one of the preceding claims, wherein the toothing of the at least one of the plurality of planetary gears (PL) has a variable tooth thickness profile (14).The planetary gear (10) according to any one of the preceding claims, wherein an angular deviation of the first skew angle (β HR) of the toothing of the ring gear (HR) and the second skew angle (β SO) of the toothing of the sun gear (SO) from the third skew angle (β PL) of the toothing of the at least one of the plurality of planetary gears (PL) is between 0.2° and 5°.Steering wheel actuator for a steer-by-wire steering system of a motor vehicle, having: 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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