Transmission and active roll stabilizer with such a transmission

Abstract

Gearbox, comprising an input shaft (1) which is in a first screw engagement (4) with a pusher part (3) designed as a hollow shaft (2) and the input shaft (1) engages in the pusher part (3), and with an output shaft (5) which is in a second screw engagement (6) with the pusher part (3) and the output shaft (5) engages in the pusher part (3), wherein the pusher part (3) is arranged to be axially displaceable relative to the input shaft (1) and to the output shaft (5), characterized in that the two screw engagements are formed on the inner circumference of the pusher part (3).

Description

[0001] The present invention relates to a transmission and an active roll stabilizer with such a transmission.

[0002] In automotive applications, chassis actuators often require high reduction gears if high torques are to be provided on the output side.

[0003] DE 10 2014 205 262 A1 discloses an active roll stabilizer with a gear system designed as a multi-stage planetary gear, which is housed in a housing of the roll stabilizer. A first torsion bar is connected in a rotationally fixed manner to the housing. A second torsion bar is connected in a rotationally fixed manner to an output shaft of the gear system. An electric motor is arranged in the housing, the motor shaft of which is connected in a rotationally fixed manner to an input shaft of the gear system. The three-stage planetary gear system significantly reduces the motor shaft speed and enables pivoting movements of the output shaft with sufficiently high torques, which in the case of active roll stabilizers can exceed 1000 Nm. Particularly in automotive applications, the gear systems in actuators must be low-noise. Due to the large number of meshing interactions between sun gears, ring gears, and planetary gears, undesirable rattling noises can occur, particularly during load changes.

[0004] DE 10 2018 125 973 A1 discloses an actuator device for an electromechanical steering assembly, the rotationally driven threaded spindle of which is connected to a non-rotatable threaded nut and a hollow shaft-shaped sliding element. The threaded spindle is in screw engagement with the inner circumference of the sliding element. The output element is in screw engagement with the outer circumference of the sliding element.

[0005] The object of the invention was to provide an alternative transmission and an active roll stabilizer with this transmission, which has a slim radial transmission design.

[0006] According to the invention, this object was achieved by the transmission according to claim 1 and by the active roll stabilizer according to claim 10. Expedient further developments are specified in the dependent claims.

[0007] The transmission according to the invention is provided with an input shaft suitable for rotationally fixed connection to a motor shaft of a motor. This input shaft is in a first threaded engagement with a thrust part of the transmission. The threaded engagement, like a screw / nut connection, converts a relative rotational movement of the input shaft relative to the thrust part into an axial displacement of the thrust part relative to the input shaft.

[0008] The transmission further comprises an output shaft that is in second threaded engagement with the thrust member. The threaded engagement converts the axial displacement of the thrust member into a relative rotational movement of the output shaft. The thrust member can be cylindrical or hollow-cylindrical in a simple and cost-effective manner.

[0009] The thrust member of this transmission according to the invention is arranged so as to be axially displaceable relative to both the input shaft and the output shaft. The thrust member, whose axial thrust is generated by the first screw engagement, drives the output shaft on the output side via the second screw engagement and generates a rotary or pivoting movement of the output shaft relative to the thrust member.

[0010] The first screw engagement therefore means a first gear stage and the second screw engagement means a further gear stage, which together ensure a sufficiently large reduction ratio.

[0011] For the initial screw engagement, conventional screw drives with screw threads can be used. The pitch of the screw drive determines the axial advance of the thrust part by actuating the input shaft, which is preferably connected in a rotationally fixed manner to the motor shaft of an electric motor.

[0012] The second screw engagement can be advantageously implemented using helical gearing. In this case, a multitude of teeth on the thrust part, wound helically around the longitudinal axis of the thrust part, mesh with a multitude of teeth on the output side, wound helically around the longitudinal axis of the output shaft. As the thrust part advances axially, the output shaft pivots around its longitudinal axis. This creates a second pitch that determines the angle of rotation of the output shaft depending on the axial advance of the thrust part.

[0013] The first and second screw engagement can be designed as a recirculating ball, which is known from ball screws.

[0014] The transmission according to the invention has few moving parts and contributes to a reduction of unwanted rattling noises, particularly during load changes in the transmission.

[0015] If necessary, the interacting components can be spring-loaded to prevent backlash between the input shaft and the thrust member, as well as between the thrust member and the output shaft. It is thus conceivable to hold the thrust member under axial spring preload. The machine parts that engage with each other in screw engagement—that is, the thrust member, the input shaft, and the output shaft—can be held in play-free contact by this axial preload. This axial preload can be achieved, for example, by a spring element.

[0016] If the gearbox includes a housing, the thrust part can be guided so as to be longitudinally displaceable along a guideway of the housing during operation of the gearbox; consequently, the thrust part is secured against rotation relative to the housing in this case. The spring element can therefore be supported on the housing on the one hand and axially spring-loaded against the thrust part on the other. If only pivoting movements of the output shaft are required - as is the case with active roll stabilizers, for example - the axial travel of the thrust part is determined by the desired angle of rotation of the driven torsion bar. The axial travel and the design of the spring are coordinated so that a sufficiently large spring preload can be maintained over the entire axial travel of the thrust part.

[0017] The first screw engagement can have a first pitch, and the second screw engagement can have a second pitch. The ratio of the two pitches to each other significantly influences the speed ratio of the output shaft to the input shaft. If the first pitch is very small, an axial thrust of the thrust part can be provided under a large axial thrust force. The second pitch determines the pivoting movement of the output shaft relative to the thrust part under its axial thrust. With a very large pitch in the second screw engagement, a correspondingly large torque can be generated on the output shaft.

[0018] Preferably, the input shaft and the thrust member and the output shaft have a common transmission axis, wherein the input shaft and the output shaft rotate or pivot about this transmission axis, and wherein the thrust member is displaceable along the transmission axis.

[0019] The thrust member is arranged in a rotationally fixed manner relative to the input shaft and the output shaft. It can be supported circumferentially on a guideway of a gearbox housing.

[0020] The input shaft and output shaft can be rotatably mounted in the housing. The thrust member, which is also housed in the housing, can be mounted in a rotationally fixed and axially displaceable manner. The housing can, for example, have a guide groove in which the thrust member is mounted for longitudinal displacement.

[0021] Preferably, the thrust part has a smaller-diameter thrust section and a larger-diameter thrust section, with the smaller thrust section being in threaded engagement with the input shaft and the larger thrust section being in threaded engagement with the output shaft. This refinement with two threaded engagements arranged at different diameters represents an additional gear stage. Such transmissions can be used in automotive applications where the provision of high torques is required.

[0022] The output shaft can accordingly be provided on its side facing the thrust section with a larger output-side shaft section, whose diameter matches the larger thrust section, and to which a smaller-diameter output-side shaft section connects. This shaft section can, for example, be connected in a rotationally fixed manner to a torsion bar of an active roll stabilizer.

[0023] The thrust part can be designed as a hollow shaft, into which the input shaft for the first screw engagement engages on one side and the output shaft for the second screw engagement engages on the other. This hollow shaft can be stepped, allowing the screw engagements described above to be achieved at different diameters. The cylindrical or cylindrically stepped hollow shaft can be manufactured from steel in a tube by forming, with the two screw engagements being effective on the inner circumference of the hollow shaft.

[0024] For slim and lightweight gears, hollow shafts can be advantageously used as thrust components. In this case, the teeth or threads for the first and second screw engagement can be formed on the inner circumference of the hollow shaft.

[0025] The first screw engagement may comprise an input-side thread wound helically around the longitudinal axis of the input shaft, which is in operative engagement with a first thrust-side thread wound around the longitudinal axis of the thrust part

[0026] The second screw engagement can be designed as a helical gear with a second pitch. A plurality of teeth on the thrust part, wound helically around the longitudinal axis of the thrust part, mesh with a plurality of teeth on the output side, wound around the longitudinal axis of the output shaft. As a result, the axial advance of the thrust part causes a pivoting movement of the output shaft around the longitudinal axis.

[0027] The longitudinal axes of the input shaft, the output shaft and the thrust part can coincide and form a common transmission axis.

[0028] Alternatively, the thread can be designed as a ball groove wound helically around the longitudinal axis, with intermeshing ball grooves forming ball channels in which balls are arranged, rolling along the intermeshing ball grooves. According to this refinement, known ball screws are designed as screw engagements. The balls transmit the forces between the input shaft and the thrust member.

[0029] For the second screw engagement, in the case of helical gearing, adjacent circumferential teeth wound helically around the longitudinal axis can similarly form ball grooves in which balls are arranged. The balls transmit the forces between the thrust part and the output shaft.

[0030] A preferred application of the transmission according to the invention is an active roll stabilizer of a motor vehicle equipped with the described transmission. This roll stabilizer comprises a housing accommodating the transmission, a first torsion bar connected in a rotationally fixed manner to the housing, and a second torsion bar connected in a rotationally fixed manner to the output shaft of the transmission. An electric motor is housed in the housing, the motor shaft of which is connected in a rotationally fixed manner to the input shaft of the transmission. The thrust member can be guided longitudinally displaceably in a guide groove of the housing.

[0031] The invention is explained in more detail below with reference to three exemplary embodiments illustrated in a total of seven figures. They show: Fig. 1 a first embodiment of a transmission in a schematic representation in a first operating position, Fig. 2 the gearbox Fig. 1 in a second operating position, Fig. 3 a longitudinal section through a trapezoidal thread for use in the gearbox, Fig. 4 a second embodiment of a transmission in schematic representation, Fig. 5 a longitudinal section through a ball screw drive for use in the gearbox according to Fig. 3, Fig. 6 a third embodiment of a transmission in schematic representation, and Fig. 7 a view of an active roll stabilizer for a motor vehicle.

[0032] The Fig. 1 and Fig. 2 show a schematic representation of a transmission in two different operating positions. An input shaft 1 is rotationally fixedly connected to a motor shaft of an electric motor (not shown here). The input shaft 1 engages with a thrust part 3 designed as a hollow shaft 2. A first screw engagement 4 is established between the input shaft 1 and the hollow shaft 2. Furthermore, an output shaft 5 is arranged coaxially to the input shaft 1 and the hollow shaft 3, which is in a second screw engagement 6 with the hollow shaft 2. These shafts are arranged coaxially on a common transmission axis 7.

[0033] When the gearbox is actuated, the hollow shaft 2 is displaced relative to the input shaft 1 and the output shaft 5 in the axial direction. Fig. 1 the hollow shaft is in a first operating position, in Fig. 2, the hollow shaft 2 is displaced to the right. When the electric motor is actuated, the input shaft 1 rotates, and the first screw engagement 4 causes an axial displacement of the hollow shaft 2. Under the axial displacement of the hollow shaft 2 relative to the output shaft 3, the second screw engagement 6 causes a pivoting movement of the hollow shaft 2. The hollow shaft 2 is secured against rotation with respect to the input shaft 1 and the output shaft 5.

[0034] The hollow shaft 2 has a hollow cylindrical thrust section 8 with a smaller diameter and a hollow cylindrical thrust section 9 with a larger diameter, wherein the smaller thrust section 8 is in the first screw engagement 4 with the input shaft 1 and the larger thrust section 9 is in the second screw engagement 6 with the output shaft 5.

[0035] The first screw engagement 4 is formed by a screw drive 31 with a screw thread, which has an input-side thread 10 wound helically around the longitudinal axis of the input shaft 1, which is in operative engagement with a first thrust-part-side thread 11 wound around the longitudinal axis of the hollow shaft 2 and formed on its inner circumference.

[0036] The second screw engagement 6 is formed by a helical gearing 30, which has teeth 12 on the inner circumference of the hollow shaft 2, which are wound helically around the longitudinal axis of the hollow shaft 2 and mesh with output-side teeth 13 formed on the outer circumference of the output shaft 5, which are wound helically around the longitudinal axis. A plurality of circumferentially adjacent teeth 12, 13 mesh with one another.

[0037] The transmission has a housing 19 (only indicated here), in which the input shaft 1 is rotatably mounted, and in which the hollow shaft 2 is secured against rotation and axially displaceable. To secure the hollow shaft 2 against rotation, for example, a guide groove (not shown) can be provided in the housing 19, into which a spring (not shown) attached to the hollow shaft 2 engages. The guide groove extends parallel to the transmission axis 7.

[0038] Fig. 3 shows a possible technical implementation for the first screw engagement 4 of the first embodiment using a trapezoidal thread engagement 14. In the first embodiment, a trapezoidal external thread 15 forms the input-side thread 10 formed on the outer circumference of the input shaft 1. In the first embodiment, a trapezoidal internal thread 16 forms the first thread 11 formed on the inner circumference of the hollow shaft 2 on the smaller thrust section 8.

[0039] Fig. Figure 1 also shows a preloading device 18 formed by a spring element 17, the purpose of which is to keep the screw-engaged components in contact with each other under axial spring load to further prevent possible noise generation. The spring element 17 is axially supported on the housing 19 on one side and axially spring-loaded against the hollow shaft 2 on the other.

[0040] The first screw engagement 4 has a first pitch, and the second screw engagement 6 has a second pitch. The first pitch can be smaller than the second pitch. The smaller the first pitch, the higher the number of revolutions of the input shaft to achieve a desired axial thrust of the hollow shaft 2. The larger the second pitch, the smaller the angle of rotation of the output shaft 5 relative to the housing 19, and the greater the torque that can be transmitted to the output shaft 5.

[0041] The diameter jump between the first screw engagement 4 and the second screw engagement 6 acts as a further gear stage in the sense of a desired reduction of the gear.

[0042] The embodiment according to the Fig. 4 and Fig. 5 differs from the first embodiment essentially by a different design of the two screw engagements 4 and 6.

[0043] In the case of the first screw engagement 4, the input-side thread 10 and the first thrust-side thread 11 are each formed by a helically wound ball groove 20, 21. These ball grooves 20, 21 form a ball channel 22 in which balls 23 are arranged. The balls 23 transmit the drive force from the input shaft 1 to the hollow shaft 2.

[0044] In the case of the second screw engagement, circumferentially adjacent teeth 12, 13 similarly form ball grooves in which these balls 23 are arranged and transmit the thrust force of the hollow shaft 2 to the output shaft 5.

[0045] The Fig. The embodiment shown in Figure 6 differs from the first embodiment only in that the output shaft 5 is designed as a hollow cylinder 24, thus not having a diameter step as an additional gear reduction. This design can be used for slim gear designs.

[0046] Fig.Figure 7 shows a known active roll stabilizer of a motor vehicle equipped with the transmission described above. The figure shows an actuator housing 25, which simultaneously forms the housing 19 described above. The actuator housing 25 houses the transmission and the electric motor, whose motor shaft is non-rotatably connected to the input shaft 1 of the transmission. A first torsion bar 26 is non-rotatably connected to the actuator housing 25. A second torsion bar 27 is non-rotatably connected to the output shaft 5 of the transmission. Reference symbol 1 input shaft 2 hollow shaft 3 drawer 4 first screw engagement 5 Output shaft 6 second screw engagement 7 Gear axle 8 smaller thrust section 9 larger thrust section 10 input thread 11 first thread on the thrust part side 12 teeth on the thrust part side 13 exit teeth. 14 Trapezoidal thread engagement 15 trapezoidal external thread 16 trapezoidal internal threads 17 Spring element 18 Pre-tensioning device 19 housings 20 ball groove 21 ball groove 22 ball channel 23 ball 24 hollow cylinders 25 actuator housing 26 first torsion bar 27 second torsion bar 28 ------ 29 ------- 30 helical gears 31 screw drive

Claims

[1] Gearbox, with an input shaft (1) which is in a first screw engagement (4) with a thrust part (3) designed as a hollow shaft (2) and the input shaft (1) engages in the thrust part (3), and with an output shaft (5) which is in a second screw engagement (6) with the thrust part (3) and the output shaft (5) engages in the thrust part (3), wherein the thrust part (3) is arranged so as to be relatively displaceable in the axial direction relative to the input shaft (1) and relative to the output shaft (5), characterized by that the two screw engagements are formed on the inner circumference of the thrust part (3). [2] Gearbox according to claim 1, the first screw engagement (4) of which comprises a screw drive (31) with a first pitch, and the second screw engagement (6) of which is formed by helical gearing. [3] Transmission according to claim 1 or 2, wherein the input shaft (1) and the thrust part (3) and the output shaft (5) have a common transmission axis (7), wherein the input shaft (1) and the output shaft (5) rotate and / or pivot about this transmission axis (7), and wherein the thrust part (3) is displaceable along the transmission axis (7). [4] Transmission according to claim 3, with a housing (19) in which the input shaft (1) is rotatably mounted, and in which the thrust part (3) is mounted in a rotationally secured and axially displaceable manner. [5] Transmission according to one of claims 1 to 4, the thrust part (3) of which has a smaller diameter cylindrical or hollow cylindrical thrust section (8) and a larger diameter cylindrical or hollow cylindrical thrust section (9), wherein the smaller thrust section (8) is in screw engagement with the input shaft (1) and the larger thrust section (9) is in screw engagement with the output shaft (5). [6] Transmission according to one of claims 1 to 5, the first screw engagement (4) of which has an input-side thread (10) wound helically around the longitudinal axis of the input shaft (1), which is in operative engagement with a thrust-side thread (11) wound around the longitudinal axis of the thrust part (3). [7] Gearbox according to one of claims 1 to 6, the second screw engagement (6) of which is formed by a helical toothing (30) with a plurality of teeth (12) on the thrust part side wound helically around the longitudinal axis of the thrust part (3) and which are in operative engagement with a plurality of teeth (13) on the output side wound around the longitudinal axis of the output shaft (5). [8] Gearbox according to claim 6, the input-side thread (10) and the thrust-part-side thread (11) are designed as ball grooves (20, 21) wound helically around the longitudinal axis, the ball grooves (20, 21) forming ball channels (22) in which balls (23) are arranged which roll on the ball grooves (20, 21). [9] Gearbox according to claim 7, the teeth (12) of which on the thrust part side define ball grooves wound around the longitudinal axis, and the teeth (13) of which on the output side define ball grooves wound around the longitudinal axis, these ball grooves defining ball channels in which balls (23) are arranged. [10] Active roll stabilizer of a motor vehicle, with the transmission according to one of claims 1 to 9, and with an actuator housing (25) receiving the transmission, and with a first torsion bar (26) which is connected in a rotationally fixed manner to the actuator housing (25), and with a second torsion bar (27) which is connected in a rotationally fixed manner to the output shaft (5) of the transmission, and with an electric motor arranged in the actuator housing (25), the motor shaft of which is connected in a rotationally fixed manner to the input shaft (1) of the transmission, wherein the thrust part (3) is guided in a guide groove of the actuator housing (25) so as to be longitudinally displaceable.

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