Cvt gearbox for a motor-driven two-wheeled vehicle

Abstract

The invention relates to a CVT gearbox (1) for a motor-driven two-wheeled vehicle, said gearbox comprising a variator (2) having two conical discs (4, 5) that can be displaced with respect to one another and can be adjusted by means of an electromechanical actuator (14), which actuator (14) comprises a two-stage gear assembly (16), the first stage of which is designed as a worm gear (17) and the second stage of which is designed as a rack-and-pinion gear (30), wherein an electric motor (15) acts on a threaded spindle (18) of the worm gear (17), wherein a gearbox element (20) is provided which connects the worm gear (17) to the rack-and-pinion gear (30) and can be rotated about a pivot axis (SW), said gearbox element comprising a shaft (21) which, at the output of the worm gear (17), has a gear segment (19) that meshes with the threaded spindle (18) of the worm gear and, at the input of the rack-and-pinion gear (30), has a gear (22), and wherein the rack-and-pinion gear (30) comprises a sleeve-shaped gear rack (24) which meshes with the gear (22) and surrounds a shaft (31) provided for driving the conical discs (4, 5) that can be displaced relative to one another.

Description

[0001] CVT transmission for a motorized two-wheeler

[0002] The invention relates to a CVT transmission for a motorized two-wheeler, comprising a variator with two conical disks that can be moved relative to one another and adjusted via an actuator.

[0003] A CVT transmission for a motorcycle with adjustment of the conical pulleys of the variator relative to each other using centrifugal weights is described in EP 0 038 316 B1 , column 1, lines 1 - 30.

[0004] An actuator with a two-stage gear arrangement is disclosed in DE 101 05 032 A1, Fig. 1, in conjunction with Chapter

[0001] . In the first gear stage, a worm gear, the worm wheel is driven by an electric motor. A gear meshing with the worm wheel acts directly on a rack via a second gear stage. The latter elements form a second gear stage (rack and pinion gear).

[0005] US 2002 / 0 034 994 A1 discloses a CVT transmission with an adjustment of the conical discs of the variator to each other via a rack and pinion gear.

[0006] Another CVT transmission, generally for a motor vehicle, is known from DE 199 46 336 A1. The transmission comprises a variator with conical pulleys, one of the conical pulleys being axially displaceable and a belt being mounted between the conical pulleys on an adjustable radius. A pressure device ensures frictional engagement between the conical pulleys and the belt drive. The pressure device of this transmission according to DE 199 46 336 A1 comprises positive guide means that cause an axial displacement of the conical pulley depending on the torque to be transmitted and / or an externally adjustable gear ratio. An automatic transmission described in DE 102 22 520 A1 comprises two conical pulley sets, wherein the arrangement of the rotational axes of two conical pulleys of at least one conical pulley set relative to one another is variable. This is intended to counteract the spreading of the conical pulleys.

[0007] Control methods and control systems for CVT transmissions are described in the documents DE 10 2006 044 543 A1 and DE 10 2005 006 157 B4.

[0008] EP 1 743 107 B1 discloses a coaxial electric actuator for a CVT transmission. In this case, an electric actuator comprises an axially movable armature. In this case, too, a belt is provided as the wrapping means.

[0009] EP 1 413 802 B1 describes details of a pulley for a CVT transmission.

[0010] Possible applications include scooters and small cars. Furthermore, EP 1 413 802 B1 points out the fundamental possibility of axially moving the pulleys of a CVT transmission using an electronically controlled actuator.

[0011] Reference is also made to the documents DE 102016 118 877 A1, DE 30 44 286 A1, DE 102021 109 655 A1 and DE 103 14 107 A1.

[0012] The invention is based on the object of creating a CVT transmission specifically for a motorized two-wheeler with improved actuator technology. This should achieve a particularly favorable ratio between equipment complexity and functionality.

[0013] This problem is solved by the novel features of claim 1. Accordingly, the two conical disks of the variator of the CVT transmission are adjustable via an electromechanical actuator. The actuator comprises a two-stage gear arrangement actuated by an electric motor, the first stage of which is designed as a worm gear and the second stage as a rack and pinion gear. A threaded spindle of the worm gear is connected in a rotationally fixed manner to a motor shaft of the electric motor. A gear element connecting the worm gear to the rack and pinion gear and rotatable about a pivot axis is provided. The rack and pinion gear comprises a shaft having a gear segment at the output of the worm gear that meshes with the threaded spindle thereof and a gear at the input of the rack and pinion gear. The rack and pinion gear comprises a sleeve-shaped rack that meshes with the gear and surrounds a shaft provided for driving the mutually displaceable conical disks.Furthermore, a sleeve is provided, which is arranged radially between the shaft and the rack and is rotationally coupled to the rack by means of gear teeth. Finally, a bearing arrangement is provided axially between the rack and the conical disks to provide rotational decoupling between the rack on the one hand and the shaft and the conical disks on the other.

[0014] A motorized two-wheeler is specifically intended to be a scooter.

[0015] The actuator of the CVT transmission is thus formed by a two-stage gear arrangement with a worm gear as the first gear stage and a rack and pinion gear as the second gear stage. By connecting the two gear stages in series, a high overall reduction ratio can be achieved while simultaneously enabling a low-backlash design. A conventional electric motor, such as a brushless DC motor, is suitable for operating the threaded spindle of the worm gear.

[0016] The worm gear is connected to the rack and pinion gear according to the invention via a gear element rotatable about a pivot axis. The latter comprises a shaft having a gear segment meshing with the worm gear's threaded spindle at the output and a gear at the input of the rack and pinion gear. The gear element can generally be constructed in one or more parts.

[0017] According to the invention, the rack of the rack and pinion gear is designed as a sleeve in a particularly space-saving yet robust configuration. It concentrically surrounds a shaft intended to drive the mutually displaceable conical pulleys. Radially between the shaft and the rack, a sleeve exists, which is rotationally coupled to the rack by means of gearing. A bearing arrangement is provided axially between the rack and the conical pulleys to provide rotational decoupling between the rack on the one hand and the shaft and the conical pulleys on the other. The bearing arrangement can, in particular, comprise a rolling bearing, for example in the form of a ball bearing.

[0018] The gear at the input of the rack and pinion gear can also be formed by a gear segment. The pitch circle of this gearing, which is assigned to the second gear stage, is typically smaller, for example, at most half the size of the pitch circle of the gear segment assigned to the worm gear. This allows considerable forces to be introduced into the rack in the longitudinal direction of the rack while maintaining a relatively small displacement path, i.e., the adjustment movements of the pair of conical pulleys.

[0019] The shaft intended to drive the mutually displaceable conical pulleys can be fixedly connected to one of the conical pulleys, while the second conical pulley is displaceable in the axial direction of the shaft in order to vary the effective radius of the conical pulley pair and thus the transmission ratio of the entire gearbox.

[0020] According to a further development of the invention, the gear element can be pivoted by less than one full rotation. For example, the gear element can be pivoted by an angle of at least 60° and no more than 150°.

[0021] Regardless of the geometric relationships between the various gear elements of the two gear stages, an angle sensor can be installed to detect the setting of the rotating gear element assigned to both gear stages. This sensor can be used to measure the distance between the two driven conical pulleys and thus the gear ratio of the continuously variable transmission.

[0022] An embodiment of the invention is explained in more detail with reference to the drawings. They show:

[0023] Fig. 1 Components of a continuously variable transmission for a two-wheeler in exploded view;

[0024] Fig. 2 a variator of the continuously variable transmission in perspective view;

[0025] Fig. 3 the variator and other components of the continuously variable transmission in a partially sectioned view;

[0026] Fig. 4 to 6 show a first variator setting designed for low speeds in different representations;

[0027] Fig. 7 to 9 show a second variator setting designed for high speeds in representations analogous to Fig. 4 to 6;

[0028] Fig. 10 and 11 the continuously variable transmission in the setting according to Figs. 4 to 6 in perspective views;

[0029] Figs. 12 and 13 show the transmission in the configuration shown in Figs. 7 to 9, in views similar to Figs. 10 and 11. A continuously variable transmission, designated overall by reference numeral 1, is intended for use in a motorized two-wheeler, in particular a scooter. The two-wheeler is powered by an internal combustion engine. Alternatively, the two-wheeler may have a hybrid drive, i.e., a combination of internal combustion engine and electric motor drive. Regarding the basic design and function of the continuously variable transmission 1, also generally referred to as a CVT transmission, reference is made to the prior art cited above.

[0030] To vary the gear ratio of the transmission 1, the transmission has a variator 2 comprising a front, actively adjustable pair of conical pulleys 3. A belt acts as a traction mechanism 8 between the conical pulleys 4, 5 of the conical pulley pair 3. The conical pulley 5, located on the outside, in this case on the left side of the vehicle, is provided with external teeth 7. Furthermore, ribs 6 are attached to the conical pulley 5. The common center axis of the conical pulleys 4, 5, i.e., the front conical pulley pair 3, is designated MA and is aligned in the transverse direction of the vehicle.

[0031] In addition to the front conical pulley pair 3, there is a rear conical pulley pair 9 arranged at the level of the rear wheel, which is only passively adjustable and thus adapts to the setting of the front conical pulley pair 3. The rear conical pulley pair 9 is formed from two conical pulleys 10, 11, with a housing 12 located on the side of the outer conical pulley 11, that is to say in this case on the left side of the vehicle, in which a pressure mechanism 13 (not shown in detail) is arranged, which ensures the desired axial force between the conical pulleys 10, 11. The variator 2, together with the pressure mechanism 13, ensures in every operating state of the transmission 1 that the belt 8 runs around the two conical pulley pairs 3, 9 with the required tension.

[0032] The variator 2 includes an electromechanical actuator 14 for adjusting the pair of conical pulleys 3 and thus for setting the effective radius of the conical pulleys 4, 5. Part of the actuator 14 is an electric motor 15, whose longitudinal axis, in this case, is aligned in the longitudinal direction of the vehicle. The electric motor 15 actuates a two-stage gear arrangement, designated overall by 16.

[0033] The first gear stage is a worm gear 17. The input element of the worm gear 17 is a threaded spindle 18, which is rotationally fixedly connected to the motor shaft of the electric motor 15. The output element of the worm gear 17 is in the form of a gear segment 19. The gear segment 19 is part of a gear element, designated overall by 20, which can pivot about a pivot axis SW and simultaneously represents the input element of a rack and pinion gear 30. The pivot axis SW is oriented vertically in the present case, with a rotation of the gear element 20 of no more than 90° being provided between the two extreme settings of the continuously variable transmission 1. The angular position of the gear element 20 can be detected using an angle sensor 23, which is located at the upper end of the gear element 20.

[0034] The pivotable gear element 20 further comprises a shaft 21 and a gear 22 arranged in the lower region of the shaft 21. All parts 19, 21, 22 of the gear element 20 are firmly connected to one another. A bearing for the gear element 20 is not shown for the sake of clarity. The pivoting direction of the gear element 20 is indicated by SR.

[0035] The gear 22 meshes with the teeth of a sleeve-shaped, horizontally movable rack 24. The direction of displacement of the rack 24, parallel to the central axis MA, is indicated by VR. The rack 24 surrounds a shaft 31, which is concentric with the central axis MA and driven by an internal combustion engine. A connecting flange arranged on the end face of the rack 24 facing away from the conical pulley pair 3 is designated by 25. Arranged radially between the shaft 31 and the rack 24 is a sleeve 26, which has teeth 27, 28 for rotationally fixed coupling with the likewise sleeve-shaped rack 24. With the aid of a bearing arrangement 29, the linear movement of the rack 24 can be transmitted to the conical pulley 4, which is driven via the shaft 31. In contrast to the conical pulley 4, the conical pulley 5 is rigidly connected to the shaft 31.

[0036] In the configuration shown in Figures 2 to 6 and 10 and 11, transmission 1 is set to the shortest possible gear ratio. This means that the scooter travels at a low speed while simultaneously exerting a high torque on the rear wheel. The other extreme case, i.e., the longest possible gear ratio, is illustrated in Figures 7 to 9 and 12 and 13. In this case, a higher vehicle speed is achieved, while the torque driving the rear wheel is comparatively low.

[0037] The control of the variator 2 processes signals supplied, in particular, by the angle sensor 23. The angular position of the gear segment 19 is clearly correlated with the distance between the conical pulleys 4, 5 and thus also with the set gear ratio of the transmission 1. Additionally, a sensor can be located on the rear wheel of the scooter, for example in the housing 12, which detects the rotational speed of the rear wheel and is also linked to the control of the variator 2. Furthermore, there are links between the control of the variator 2 and various sensors that detect the engine speed of the internal combustion engine and the throttle valve position of the internal combustion engine. This allows for a fine adjustment of the gear ratio of the continuously variable transmission 1, adapted to the driving situation. List of reference symbols for the continuously variable transmission

[0038] Variator front, actively adjustable conical pulley pair

[0039] Conical disc

[0040] Conical disc

[0041] rib

[0042] external gearing

[0043] Traction device, belt rear, passively adjustable conical pulley pair

[0044] Conical disc

[0045] Conical disc

[0046] Housing

[0047] Contact pressure mechanism

[0048] Actuator

[0049] electric motor

[0050] Gear arrangement

[0051] Worm gear, first gear stage

[0052] threaded spindle

[0053] Gear segment

[0054] Gear element, pivoting

[0055] Wave

[0056] gear

[0057] Angle sensor

[0058] rack

[0059] connecting flange

[0060] sleeve

[0061] Gearing

[0062] Gearing

[0063] Bearing arrangement

[0064] Rack and pinion gear, second gear stage 31 shaft

[0065] MA central axis

[0066] SR swivel direction

[0067] SW swivel axis

[0068] VR shift direction

Claims

Claims CVT transmission (1) for a motorized two-wheeler, comprising a variator (2) with two conical discs (4, 5) that are displaceable relative to each other and adjustable via an electromechanical actuator (14), the actuator (14) comprising a two-stage transmission arrangement (16) actuated by an electric motor (15), the first stage of which is designed as a worm gear (17) and the second stage as a rack and pinion gear (30), wherein a threaded spindle (18) of the worm gear (17) is non-rotatably connected to a motor shaft of the electric motor (15), wherein a transmission element (20) connecting the worm gear (17) to the rack and pinion gear (30) is provided, comprising a shaft (21) which, at the output of the worm gear (17), engages a gear segment (19) meshing with its threaded spindle (18) and, at the input of the rack and pinion drive (30) has a gear (22), wherein the rack and pinion drive (30) has a sleeve-shaped,The rack (24) meshes with the gear (22) and surrounds a shaft (31) for driving the mutually displaceable conical disks (4, 5), wherein a sleeve (26) is provided which is arranged radially between the shaft (31) and the rack (24) and is rotationally fixed to the rack (24) by means of teeth (27, 28), and wherein a bearing arrangement (29) is provided axially between the rack (24) and the conical disks (4, 5) for rotational decoupling between the rack (24) on the one hand and the shaft (31) and the conical disks (4, 5) on the other. CVT transmission (1) according to claim 1, wherein the gear segment (19) of the transmission element (20) is rotatable by an angle of at least 60° to a maximum of 150° about the pivot axis (SW). CVT transmission (1) according to claim 1 or 2, wherein an angle sensor (23) is provided for detecting the setting of the transmission element (20).

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