EP4616087A1

EP4616087A1 - Continuously variable variator

Info

Publication number: EP4616087A1
Application number: EP24801602.4A
Authority: EP
Inventors: Francesco COLANGELO
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-11-23
Filing date: 2024-11-11
Publication date: 2025-09-17
Also published as: WO2025108747A1; IT202300024879A1

Abstract

A variator (100; 200) comprises: a gear crown (1) comprising gears (10) pivoted to a support frame (11; 211), a conical worm gear (6) disposed in the gear crown (1) in contact with said gear crown (1) and rotating about its own central axis (64), movement means for allowing the sliding of the conical worm gear (6), first coupling means (5) for allowing the coupling of the gears (10) with each other, at least one transmission gear (7; 207) for transmitting motion from the gears (10) to an output shaft (U), second coupling means (8) for allowing the coupling of a gear (10) of the gear crown with said at least one transmission gear (7, 207); the conical worm gear (6) is mounted rotatably idly with respect to a support (65) of the movement means.

Description

CONTINUOUSLY VARIABLE VARIATOR.

Description

The present patent application for an industrial invention relates to a continuously variable variator.

Mechanical transmissions comprising gears are known, which allow the transmission of motion from an input shaft, connected to the shaft of a motor, to an output shaft, varying a ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft, i.e. the rotational speed of the output shaft. Typically, in order to vary this ratio, it is necessary to momentarily interrupt the connection between the input shaft and the output shaft. An example of a well-known mechanical gear transmission is a vehicle gearbox, in which pressing a clutch a driven disc disengages from a driving disc, allowing a driver to engage a desired gear. A gear shift means a change in the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft.

Known mechanical gear transmissions have a drawback due to the fact that it is not possible to continuously vary the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft. Furthermore, in order to vary the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft, it is necessary to interrupt the connection between the input shaft and the output shaft.

Electric variators are known, interposed between an electric generator suitable to produce electrical energy and an electric motor powered by electrical energy produced by the electric generator. The electric variator is suitable to regulate the supply frequency, in order to regulate the rotational speed of the electric motor. These electric variator are used, for example, in hybrid vehicles.

Hydraulic variators are known, comprising a hydraulic pump and a hydraulic motor. Hydraulic variators allow the variation of the speed transmitted to the output shaft by modifying the pressure and flow rate of a fluid, such as oil. These hydraulic variators are used, for example, in large agricultural and industrial machines.

Friction variators are known, that transmit rotation from the input shaft to the output shaft by exploiting friction.

The known variators are inefficient, expensive, not very robust, require maintenance, dissipate a high amount of energy that is transformed into heat and causes high consumption, have high wear and noise.

For these reasons, the known variators are used for specific purposes, only when it is strictly necessary to continuously vary the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft, up to zeroing the rotation of the output shaft. When not strictly necessary, instead of the known variators, it is preferable to use the known mechanical gear transmissions, as they are more reliable than the known variators.

Worm gear transmissions are known for transmitting motion between two perpendicular intersecting shafts. These transmissions comprise a worm gear and a gear wheel with an axis perpendicular to the axis of the worm gear. Teeth of the gear wheel mesh with the threads of the worm gear. The worm gear is always the driver and the gear wheel is always the driven element, meaning that by rotating the worm gear, the rotation is transmitted to the gearwheel. The kinematics of this transmission is irreversible, meaning that attempting to rotate the gear wheel, said gear wheel is blocked by the worm gear. Therefore, it is not possible to transmit motion from the gear wheel to the worm gear. These worm gear transmissions are used in industrial machinery to reduce the high rotational speed of electric motors to a few revolutions per minute, as these worm gear transmissions allow for a significant reduction ratio. A first drawback of these worm gear transmissions is the high abrasion due to the friction between the worm gear and the gear wheel. A second drawback of worm gear transmissions is the fact that the worm gear must make a complete revolution to advance the gear wheel by one tooth, causing friction or slippage between the worm gear and the gear wheel and, consequently, abrasion and energy dissipation. For this reason, worm gear transmissions are not suitable for vehicle transmissions.

RU2763619 discloses a transmission comprising two conical helical gears having helical grooves. The conical helical gears are oriented in opposite directions and are mounted on parallel shafts. Between the conical helical gears, a gear wheel is installed having a rotation axis perpendicular to the rotation axes of the conical helical gears. Teeth of the gear wheel are engaged with the grooves of the conical helical gears.

CN1 16951065 discloses a transmission comprising a gear wheel and a helical worm gear. A thread of the helical worm gear is suitable to mesh with teeth of the gear wheel.

The transmissions disclosed in RU2763619 and CN116951065 are not continuously variable, as they do not allow the modification of the number of revolutions that are transmitted at the output of the transmission.

JAHR A ("ES 1ST KEIN FORMSCHLUESSIGES STUFENLOSES GETRIEBE MOEGLICH", ANTRIEBSTECHNIK, VEREINIGTE FACHVERLAGE, MAINZ, DE, vol. 28, no. 1 , 1 January 1989 (1989-01-01 ), page 45/46, XP001160727, ISSN: 0722-8546) and DANIEL H ("1ST EIN STUFENLOSES ECHT FORMSCHLUESSIGES GETRIEBE MOEGLICH?", ANTRIEBSTECHNIK, VEREINIGTE FACHVERLAGE, MAINZ, DE, vol. 23, no. 5, 1 January 1984 (1984-01-01 ), page 49/50, XP001160734, ISSN: 0722- 8546) consider the realization of a continuously variable variator impossible.

The purpose of the present invention is to provide a variator that allows for continuous variation of the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft, without interrupting the connection between the input shaft and the output shaft, and that is efficient and reliable.

A further purpose is to provide a variator that is, economic, robust, and versatile. These purposes are achieved in accordance with the invention having the features listed in the appended independent claim 1.

Advantageous embodiments appear from the dependent claims.

The variator according to the invention is defined by claim 1 .

The advantages of the variator according to the invention are evident, wherein thanks to the sliding conical worm gear, it is possible to continuously vary the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft, without interrupting the connection between the input shaft and the output shaft. The variator according to the invention is a mechanical type, therefore it is efficient, reliable, economical, robust, and versatile. In fact, the variator according to the invention can be applied to any vehicle and mechanism.

For greater clarity, the description of the variator according to the invention continues with reference to the attached drawings, which have a non-limiting illustrative purpose, wherein:

- Fig. 1 is a front view of the variator according to the invention, partially sectioned by a vertical plane perpendicular to the input shaft axis;

- Fig. 2 is a section of the variator according to the invention, taken along a vertical plane passing through the input shaft axis;

- Fig. 3 is an axonometric view of a first gear of the variator according to the invention;

- Fig. 4 is an axonometric view of a second gear of the variator according to the invention;

- Fig. 5 is an axonometric view of a third gear of the variator according to the invention;

-Fig. 6 is an axonometric view of a conical worm gear of the variator according to the invention;

- Fig. 7 is an axonometric view of a variant of the first gear of the variator according to the invention;

- Fig. 8 is a side view of the conical worm gear and a gear of the variator according to the invention, engaged with each other;

- Fig. 9 is a front view of the conical worm gear and a gear of the variator according to the invention, engaged with each other; - Fig. 10 is a section of a variant of the variator according to the invention, taken along a vertical plane passing through the input shaft axis;

- Fig. 11 is a perspective view of the gear crown, the support frame, and the conical worm gear of the variator of Fig. 10.

With reference to Figs. 1 and 2, a variator according to the invention is described, generally indicated by the reference number 100.

The variator (100) is intended to be connected to an input shaft (I), connected to or coincident with a driveshaft, and to an output shaft (U), in order to transmit a rotary motion from the input shaft (I) to the output shaft (U), varying a rotational speed (i.e. a number of revolutions per unit of time) of the output shaft while maintaining the same rotational speed of the input shaft. Optionally, the output shaft (U) is hollow and the input shaft (I) is disposed inside the output shaft (U), with the input shaft (I) coaxial with the output shaft (U).

The variator (100) comprises a gear crown (1 ) comprising gears (10) radially disposed. The gear crown (1 ) has a central axis (C) intended to coincide with the rotation axis of the input shaft (I). Each gear (10) is rotatably mounted on a support frame (11 ), intended to be rotationally fixed to the input shaft (I). Each gear (10) is pivoted to the support frame (11 ) by means of pins, so as to rotate about said pins. Therefore, the gear crown (1 ) is adapted to rotate together with the support frame (11 ) about the central axis (C) of the gear crown and each gear (10) rotates on itself about its own pins.

The support frame (11 ) is advantageously intended to be made in one piece with the input shaft (I) and to project from one end of the input shaft. The support frame (11 ) comprises a base wall (11a) intended to be connected to the input shaft (I) and a crown (11 b) projecting from the base wall and comprising a plurality of open-fronted and open-sided seats (11d) arranged to form a circle.

The gears (10) comprise:

- first gears (2);

- second gears (3);

- third gears (4). With reference to Fig. 3, each first gear (2) is a toothed wheel and comprises:

- a side wall (20) comprising a plurality of teeth (21 ) projecting outwards;

- a front crown (22);

- a rear wall (23), opposite to the front crown (22).

In this way, the side wall (20), the front crown (22) and the rear wall (23) delimit a cavity (24) accessible through a front opening. The rear wall (23) comprises a first face (25) facing the front opening and a second face, opposite to the first face (25).

With reference to Fig. 4, each second gear (3) is a toothed wheel and comprises:

- a side wall (30) comprising a plurality of teeth (31 ) projecting outwards;

- a rear crown (32);

- a front wall (33), opposite to the rear crown (32).

In this way, the side wall (30), the rear crown (32), and the front wall (33) of each second gear delimit a cavity (34) accessible through a rear opening. The front wall (33) comprises a first face (35) facing the rear opening and a second face, opposite to the first face (35).

With reference to Fig. 5, each third gear (4) is a toothed wheel and comprises:

- a side wall (40) comprising a plurality of teeth (41 ) projecting outwards;

- a central wall (48) comprising a front face (48a) and a rear face;

- a front crown (42) projecting forwardly from the central wall (48);

- a rear crown (43), opposite to the front crown (42) and projecting rearwardly from the central wall (48).

In this way, the side wall (40), the front crown (42), and the front face (48a) of the central wall of each third gear delimit a front cavity (44) accessible through a front opening. The side wall (40), the rear crown (43), and the rear face of the central wall of each third gear delimit a rear cavity, accessible through a rear opening. Each gear (2, 3, 4) comprises:

- a first pin (26, 36, 46) projecting forwardly;

- a second pin (27, 37, 47) projecting rearwardly.

With reference to Figs. 1 and 2, each gear is disposed within one of the seats (11 d) of the support frame (11 ), and the pins (26, 27, 36, 37, 46, 47) of each gear are disposed within two opposite holes (11 e) of a seat. In this way, each gear (2, 3, 4) is rotatably mounted around its respective pins.

With reference to Fig. 7, a variant of the gears of the gear crown according to the invention is shown, comprising a greater number of teeth than the gears of Figs. 3 to 5 and comprising a through central hole suitable to accommodate pins protruding from each seat (11 d) of the support frame (11 ). Each gear is disposed within one of the seats of the support frame (11 ) and the pins protruding from each seat (11 d) of the support frame are disposed in the central hole of each gear. In this way, each gear (2, 3, 4) is rotatably mounted around the pins protruding from each seat (11d) of the support frame.

It should be noted that in Fig. 7 a first gear (2) is shown, however, also the second gears and the third gears can be made with a greater number of teeth than the gears of Figs. 4 and 5 and comprising a through central hole suitable to accommodate pins protruding from each seat of the support frame (11 ).

With reference to Figs. From 1 to 5, the variator (100) comprises first coupling means (5) for allowing the coupling of the gears (10) to each other, so that, by rotating a gear (10) of the gear crown around its respective pins, a rotation is transmitted to the adjacent gears of the gear crown (1 ) around their respective pins. In other words, thanks to the first coupling means (5), by rotating a gear (10) around its respective pins, the other gears will also rotate around their respective pins.

With reference also to Figs. 3 to 5, the first coupling means (5) advantageously comprise:

- pins (50) projecting rearwardly from the gears;

- seats (51 ) projecting forwardly from the gears and housing the pins (50) of the first coupling means of the adjacent gear. More specifically, the pins (50) project from the rear wall (23) of each first gear, from the rear crown (32) of each second gear, and from the rear crown (43) of each third gear. The seats (51 ) of the first coupling means are formed on the front crown (22) of each first gear, on the front wall (33) of each second gear, and on the front crown (42) of each third gear.

When the gears are mounted on the support frame (11 ) to assume the crown shape, the pins (50) of the first coupling means, projecting from one gear, engage with the seats (51 ) of the first coupling means, formed on an adjacent gear, at a portion of the gears proximal to the center of the gear crown.

Although not shown in the figures, the first coupling means may alternatively comprise:

- a first set of teeth projecting forwardly from each gear, and

- a second set of teeth projecting rearwardly from each gear and meshing with the first set of teeth of the adjacent gear.

With reference to Figs. 1 , 2 and 6, the variator (100) comprises a conical worm gear (6) disposed in the gear crown (1 ), perpendicular to the gear crown (1 ) and in contact with said gear crown (1 ), such that a tip (62) of the conical worm gear is proximal to the base wall (11 a) of the support frame and a base (63) of the conical worm gear is distal to the base wall (11a) of the support frame. The conical worm gear (6) is rotatable around itself about its own central axis (64). The central axis (64) of the conical worm gear forms an acute angle (a) with the central axis (C) of the gear crown, such that the portion of the conical worm gear (6) in contact with the gear crown is substantially parallel to the central axis (C), as shown in Fig. 2. The conical worm gear (6) is disposed eccentrically with respect to the gear crown (1 ), such that the conical worm gear (6) is in contact with only a portion of the gear crown (1 ). Advantageously, the conical worm gear (6) is in contact with only an upper portion of the gear crown (1 ) and the portion of the conical worm gear (6) which, during rotation, is disposed superiorly is horizontal. With reference also to Figs. 8 and 9, the conical worm gear (6) comprises a convex side wall (60) and a helical external thread (61 ) shaped to mesh with the teeth (21 , 31 , 41 ) of the side wall of the gears, such that the conical worm gear (6), rotating about its central axis (64), puts at least one gear (10) of the gear crown into rotation.

The conical worm gear (6) is mounted, with respect to the gear crown (1 ), slidably along a horizontal axis parallel to the central axis (C) of the gear crown.

The variator (100) comprises movement means connected to the conical worm gear (6), so as to allow the sliding of the conical worm gear (6) along an axis parallel to the central axis (C) of the gear crown. For example, the movement means can be of a manual type or can comprise a linear actuator. Advantageously, the movement means comprise control means for remotely controlling the sliding of the conical worm gear (6). The movement means comprise a support (65) slidable with respect to a housing of the variator (100), so as to be able to slide but not rotate with respect to the housing. The conical worm gear (6) is slidably fixed to the support (65) and is mounted idly rotatable with respect to said support (65), so that the conical worm gear (6), rubbing against the gear crown (1 ) during the rotation of the input shaft (I) and of the gear crown (1 ), rotates about its own central axis (64).

Thanks to the friction generated between the conical worm gear (6) and the gear crown (1 ) during the rotation of the gear crown (1 ), the conical worm gear (6) is suitable to be rotated around its own central axis (64) by the gear crown (1 ) with a rotational speed dependent on a diameter of a portion of the conical worm gear (6) in contact with the gear crown.

Therefore, the rotation of the conical worm gear (6) around its own central axis (64) is caused by the friction and rubbing between the conical worm gear (6) and the gear crown (1 ), which rotates together with the input shaft (I). It should be noted that the rotation of the conical worm gear (6) around its own central axis (64) is not caused by the engagement between the teeth (21 , 31 , 41 ) of the gears and the external thread (61 ) of the conical worm gear. The engagement between the external thread (61 ) of the conical worm gear and the teeth (21 , 31 , 41 ) of the gears allows the transmission of a rotation from the conical worm gear (6) to at least one of the gears (10) of the gear crown, so that said at least one gear rotates around its own pins. Therefore, the conical worm gear (6) is the driver and said at least one gear (10) is the driven, as occurs in known worm gear transmissions.

As soon as the support frame (11 ) is set in rotation by the input shaft (I), the rubbing between the conical worm gear (6) and the gear crown (1 ) sets the conical worm gear (6) in rotation with a rotational speed dependent on the diameter of a portion of the conical worm gear (6) in contact with the gear crown (1 ). The external thread (61 ) of the conical worm gear engages with the teeth (21 , 31 , 41 ) of the side wall of at least one gear that, rotating together with the support frame (11 ), is positioned in contact with the conical worm gear, setting said at least one gear (10) in rotation around its respective pins with a rotational speed dependent from the rotational speed of the conical worm gear (6).

The conical worm gear (6) is in contact with at least one gear (10) at a time and the conical worm gear (6) and said at least one gear (10) with which it is in contact behave like two gears: the conical worm gear (6) sets in rotation the gear (10) with which it is in contact. In this way, the friction and rubbing generated between the conical worm gear and said at least one gear are minimal, as occurs in a transmission comprising two gears. Consequently, the conical worm gear (6) and the gears (10) of the gear crown are abrasion- resistant, robust and have minimal energy dispersion.

Thanks to the first coupling means, the rotation of the gears (10) around their respective pins is transmitted to all the gears of the gear crown. Therefore, all the gears (10) of the gear crown rotate with the same rotational speed. By moving the conical worm gear (6) closer to the base wall (11 a) of the support frame by means of the movement means, the diameter of the conical worm gear (6) in contact with the gear crown (1 ) increases and, consequently, the rotational speed of the conical worm gear (6) around its central axis (64) decreases. By moving the conical worm gear (6) away from the base wall (11 a) of the support frame by means of the movement means, the diameter of the portion of the conical worm gear (6) in contact with the gear crown (1 ) decreases and, consequently, the rotational speed of the conical worm gear (6) around its central axis (64) increases. Even while moving the conical worm gear (6) between the tip (62) and the base (63), the rotation ratio between the conical worm gear (6) and the gears (10) of the gear crown remains constant.

It should be noted that the gears (10) of the gear crown can rotate around their respective pins only if moved by means of the conical worm gear (6). The conical worm gear (6) acts as a self-locking brake to prevent free rotation of the gears (10) of the gear crown.

Since the friction between the conical worm gear (6) and the gears (10) is minimal, the external thread (61 ) of the worm gear and the teeth of the gears can have any shape that allows them to mesh. For example, the teeth (21 , 31 , 41 ) of the gears can have the same shape as the teeth of the gears in known worm gear transmissions and the external thread (61 ) of the conical worm gear (6) can have the same shape as the thread of the worm gear in known worm gear transmissions.

With reference to Figs. 3, 4, 5, 7, and 9, advantageously, the teeth (21 , 31 , 41 ) of the gears form a circle, in order to couple stably with the external thread (61 ) of the conical worm gear. The teeth (21 , 31 , 41 ) of the gears comprise a concave outer surface with the concavity facing outwards, in order to couple with the convex side wall (60) of the conical worm gear. With reference to Figs. 8 and 9, more precisely, each tooth (21 , 31 , 41 ) of the gears, in longitudinal section (i.e. in the axial section), has a greater height at a front end portion (10a), i.e. at the front wall (33) or the front crown (22, 42), and at a rear end portion (10b), i.e. at the rear wall (23) or the rear crown (32, 43), and a lower height at a central portion (10c) of the teeth (21 , 31 , 41 ), between the front end portion (10a) and the rear end portion (10b). Advantageously, each tooth (21 , 31 , 41 ) of the gears, in transverse section, has a convex curvilinear shape (Fig. 8) or a rectangular shape (Figs. 3 to 5).

With reference to Figs 1 and 2, the variator (100) comprises two opposite transmission gears (7) for transmitting the motion from the gears (10) of the gear crown to the output shaft (U). Each transmission gear (7) is supported by the support frame (11 ) and pivotally mounted with respect of the support frame (11 ) around a pin (73) of the transmission gear comprising an axis (R) perpendicular to the central axis (C) of the support frame (11 ). The pins (73) of both transmission gears (7) have the same axis (R). The support frame (11 ) comprises a support arm (11 c) for each transmission gear (7), pivotally housing the pin (73) of the transmission gear.

Each transmission gear (7) comprises a truncated conical gear (7a) comprising a side wall (70) and a bottom wall (71 ) arranged at a smaller base of the truncated conical gear. The axis (R) of the pin (73) of each transmission gear (7) passes through a central axis of the transmission gear (7). The side wall (70) and the bottom wall (71 ) of the truncated conical gear of each transmission gear delimit a compartment accessible through an opening (72) formed at a larger base of the truncated conical gear (7a). The compartment of each transmission gear (7) houses a portion of the gear crown (1 ). The pin (73) of each transmission gear projects into the compartment of the truncated conical gear (7a) of each transmission gear from the bottom wall (71 ) of said truncated conical gear.

A first gear (2) and a second gear (3) are mounted adjacent to each other and partially within the compartment of the truncated conical gear (7a) of each transmission gear. Said first gear (2) and said second gear (3) are mounted in the support frame (11 ) such that the rear crown (32) of the second gear faces the front crown (22) of the first gear. In this way, the cavity (24) of the first gear is open towards the cavity (34) of the second gear. The other gears (10) of the gear crown are third gears. In other words, since the variator (100) comprises two transmission gears (7), the gear crown (1 ) comprises two first gears (2), two second gears (3) and a plurality of third gears.

The variator (100) comprises second coupling means (8) for allowing the coupling of a gear (10) of the gear crown with one of the transmission gears (7), so that, by rotating a gear (10) of the gear crown about its respective pins, a rotation is transmitted to the transmission gear (7) around the pin (73) of the transmission gear. In other words, thanks to the second coupling means (8), by rotating a gear (10) around its respective pins, the transmission gear (7) rotates around its pin (73).

Advantageously, the second coupling means (8) comprise a gear tooth (80) (Fig. 3) projecting from the first face (25) of the rear wall of each first gear and a gear wheel (74) projecting from the pin (73) of each transmission gear, cooperating with the gear tooth (80) of the second coupling means. The gear wheel (74) of the second coupling means is disposed in the cavity (24) of the first gear and in the cavity (34) of the second gear.

When the first gear (2) rotates at a rotational speed around its respective pins (26, 27), driven by the conical worm gear (6), the gear tooth (80) projecting from the first face (25) of the rear wall of the first gear meshes with the gear wheel projecting from the pin (73) of the transmission gear and drags the transmission gear (7) in rotation around its own rotation axis. Since all the gears (10) of the gear crown rotate around their respective pins with the same rotational speed, the two transmission gears rotate with the same rotational speed.

Advantageously, the variator (100) comprises third coupling means (9) for enabling the coupling of the transmission gears (7) with the output shaft (U), so that, by rotating the transmission gears (7) about the axis (R) of the pins (73) of the transmission gears, a rotation is transmitted to the output shaft (U). Therefore, the rotational speed of the output shaft (U) depends on the rotational speed of the transmission gears (7). In other words, thanks to the third coupling means (9), by rotating the transmission gears (7) around the axis (R) of the pins of the transmission gears, the output shaft (U) rotates around its axis.

Advantageously, the third coupling means (9) comprise an external gear at the larger base of the truncated conical gear (7a) of each transmission gear, suitable to mesh with a gear of the output shaft (U), in order to transmit the rotation to the output shaft (U).

By rotating the input shaft (I) around its own axis, the support frame (11 ) rotates together with the input shaft (I). Consequently, the gear crown (1 ) and the transmission gears (7) rotate together with the support frame (11 ) around the central axis (C) of the gear crown. The gear crown (1 ), rotating around the central axis (C) of the gear crown, rubs against the conical worm gear (6), setting the conical worm gear (6) in rotation around its own central axis (64) with a rotational speed depending on the diameter of the portion of the conical worm gear (6) in contact with the gear crown. The conical worm gear (6), rotating around its own central axis (64), meshes with the teeth (21 , 31 , 41 ) of at least one of the gears of the gear crown and sets at least one gear (10) of the gear crown in rotation about its pins with a rotational speed dependent from the rotational speed of the conical worm gear (6). The gears (10) of the gear crown, thanks to the first coupling means (5), all rotate with the same rotational speed around their respective pins. The first gears (2), thanks to the second coupling means (8), transmit the rotation to the transmission gears (7), which rotate around their own rotation axis (R) with a rotational speed dependent from the rotational speed of the gears (10) around their respective pins. The transmission gears (7), thanks to the third coupling means (9), transmit the rotation to the output shaft (U). The rotational speed of the output shaft (U) depends on the rotational speed of the gears (10) around their respective pins and of the conical worm gear (6), which in turn depends on the diameter of the portion of the conical worm gear (6) in contact with the gear crown (1 ). In other words, the ratio between the number of turns of the input shaft and the number of turns of the output shaft varies according to the diameter of the portion of the conical worm gear in contact with the gear crown. By sliding the conical worm gear (6) using the movement means, maintaining the same rotational speed of the input shaft, the rotational speed of the conical worm gear (6) around its central axis and, consequently, the rotational speed of the gears (10) of the gear crown around its pins increases or decreases, without interrupting the connection between the input shaft and the output shaft.

The advantages of the variator (100) according to the invention are evident, wherein thanks to the sliding conical worm gear (6), it is possible to continuously modify the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft, without interrupting the connection between the input shaft and the output shaft. The variator according to the invention is of a mechanical type, therefore it is efficient, reliable, economical, robust, and versatile. In fact, the variator according to the invention can be applied to any vehicle.

The conical worm gear (6) rotates inside the gear crown (1 ) without slipping on the gear crown (1 ). Therefore, the friction generated between the conical worm gear (6) and the gear crown (1 ) is the minimum required to allow the rotation of the conical worm gear (6). Consequently, the conical worm gear (6) does not wear out nor dissipate energy. Therefore, the efficiency of the variator according to the invention is greater than that of known worm gear transmissions.

Although not shown in the figures, the variator may comprise only one transmission gear. In this case, the gear crown comprises only one first gear, one second gear, and a plurality of third gears.

Although not shown in the figures, the variator may comprise more than two transmission gears. In this case, the gear crown comprises a first gear for each transmission gear, a second gear for each transmission gear, and a plurality of third gears.

Although not shown in the figures, the third gears may be omitted, and the gears may comprise first gears and second gears. In this case, the gear crown comprises a first gear for each transmission gear and a plurality of second gears.

The description continues with reference to Figs. 10 and 11 , which show a second embodiment of the variator according to the invention, indicated overall by reference numeral 200. Identical or corresponding features are indicated by the same reference numbers and their detailed description is omitted. The differences with respect to the first embodiment of the variator according to the invention are described in detail.

The support frame (211 ) is fixed. The gear crown (1 ) has a central axis intended to coincide with the axis of the input shaft (I). Each gear (10) of the gear crown (1 ) is pivotally mounted on the support frame (211 ) so as to rotate about its respective pins.

The support (65) of the movement means is intended to be rotationally fixed to the input shaft (I) and to be slidably mounted relative to the input shaft (I). In other words, the support (65) of the movement means rotates about an axis intended to coincide with the axis of rotation of the input shaft (I) and coincident with the central axis (C) of the gear crown. The input shaft (I) is hollow and the support (65) of the movement means is mounted within the input shaft, so that the conical worm gear (6) can slide relative to the input shaft (I) along an axis coincident or parallel with the central axis (C) of the gear crown. The conical worm gear (6) is slidably and rotationally fixed to the support (65) of the movement means and is mounted idly rotatable around its own central axis (64) on the support (65) of the movement means, such that, when rotating the support (65) of the movement means, said conical worm gear (6) performs a circular trajectory within the gear crown (1 ) and rubs against the gear crown (1 ), thus causing the rotation of the conical worm gear (6) about its own central axis (64).

The support (65) of the movement means comprises:

- a first straight portion (65a) having an axis intended to coincide with the axis of the input shaft (I) and coincident with the central axis (C) of the gear crown;

- a second inclined portion (65b) connected to the first straight portion (65a);

- a third inclined portion (65c) with an inclination coincident with the central axis (64) of the conical worm gear; the third portion (65c) is connected to the second portion (65b) and is at least partially disposed within the conical worm gear (6) and connected with the conical worm gear (6), for example by means of bearings.

In this way, by rotating the support about the axis of the input shaft (I), the conical worm gear (6) engages in turn with all the gears (10) of the gear crown. In fact, thanks to the second inclined portion (65b) of the support, when the support of the movement means rotates together with the input shaft (I), the conical worm gear (6) performs a circular trajectory around the central axis (C) of the gear crown (1 ). Thanks to the friction with the gear crown, the conical worm gear (6) is set into rotation about its own central axis (64) with a rotational speed dependent on the diameter of the portion of the conical worm gear (6) in contact with the gear crown. The external thread (61 ) of the conical worm gear is designed to engage with all the gears (10) of the gear crown in turn, so as to set said gears (10) into rotation about their respective pins with a rotational speed dependent from the rotational speed of the conical worm gear (6).

Thanks to the first coupling means, the rotation of the gears (10) about their respective pins is transmitted to all the gears of the gear crown. Therefore, all the gears (10) of the gear crown rotate at the same rotational speed. By moving the conical worm gear away from the input shaft, the diameter of the portion of the conical worm gear (6) in contact with the gear crown (1 ) increases and, consequently, the rotational speed of the conical worm gear (6) about its central axis (64) decreases. By moving the conical worm gear (6) closer to the input shaft (I), the diameter of the portion of the conical worm gear (6) in contact with the gear crown (1 ) decreases and, consequently, the rotational speed of the conical worm gear (6) about its central axis (64) increases.

The variator (200) comprises a transmission gear (207) comprising a pin (273) supported by the support frame (211 ) and pivotally mounted on itself about the axis (R), so as to transmit the motion from the gears (10) of the gear crown to the output shaft (U). The pin (273) of the transmission gear is pivotally housed in the support arm (211 c) of the support frame. Advantageously, the pin (273) of each transmission gear ends with the gear wheel (74) of the second coupling means.

The transmission gear (207) is made in one piece with the output shaft (U) and the axis (R) of the pin of the transmission gear coincides with the axis of the output shaft (U).

By rotating the input shaft (I) around its own axis, the conical worm gear (6) is rotated, together with the input shaft. Consequently, the conical worm gear (6) rotates with a circular trajectory and the conical worm gear (6) rubs against the gear crown (1 ). In other words, the input shaft (I) sets the support (65) of the movement means and the conical worm gear (6) into rotation. The conical worm gear (6), being free to rotate around the support (65), requires only minimal friction against the gear crown to rotate about its own central axis (64). Therefore, the conical worm gear (6) is subject to little abrasion and tear, thanks to the fact that the friction generated between the conical worm gear (6) and the gear crown (1 ) is minimal.

The conical worm gear (6), rotating, engages with at least one gear (10) at a time, setting said at least one gear (10) of the gear crown into rotation about its respective pins with a rotational speed dependent from the rotational speed of the conical worm gear (6). The gear crown (1 ) comprises a first gear (2), a second gear (3) and a plurality of third gears (4) or a first gear (2) and a plurality of second gears (3). The gears (10) of the gear crown, thanks to the first coupling means (5), all rotate at the same rotational speed about their respective pins. The first gear (2), thanks to the second coupling means (8), transmits the rotation to the transmission gear (207), which rotates about its own axis of rotation (R) with a rotational speed dependent on the rotational speed of the gears (10) about their respective pins. The transmission gear (207), being in one piece with the output shaft (U), transmits the rotation to the output shaft (U). The rotational speed of the output shaft (U) depends on the rotational speed of the transmission gear (207) and of the gears (10) about their respective pins, which in turn depends on the rotational speed of the conical worm gear (6) that depends on the diameter of the portion of the conical worm gear (6) in contact with the gear crown (1 ). In other words, the ratio between the number of revolutions of the input shaft and the number of revolutions of the output shaft varies according to the diameter of the conical worm gear (6) in contact with the gear crown.

The variator (200) does not allow reverse rotation, that is, it is not possible to rotate the output shaft (U) to drive the input shaft (I).

It should be noted that in the description and in the attached figures, details within the scope of a person skilled in the art in the field, such as bearings, counterweights, etc., have been omitted.

Modifications or variations of detail within the scope of a person skilled in the art may be made to the present embodiment of the invention, which, however, fall within the scope of the invention as expressed in the appended claims.

Claims

1. Variator (100; 200) intended to be connected to an input shaft (I) and an output shaft (U); said variator (100; 200) comprising:

- a support frame (11 ; 211 );

- a gear crown (1 ) comprising gears (10) radially disposed and having a central axis (C) intended to coincide with a rotation axis of the input shaft (I); each gear being a toothed wheel and comprising a side wall (20, 30, 40) comprising a plurality of teeth (21 , 31 , 41 ); each gear (10) being pivoted by pins to the support frame (11 ; 211 ), so as to rotate about said pins;

- a conical worm gear (6) disposed in the gear crown (1 ), perpendicular to the gear crown (1 ) and in contact with said gear crown (1 ); said conical worm gear (6) being rotatable about its own central axis (64) and comprising a helical external thread (61 );

- movement means for allowing the conical worm gear (6) to slide along an axis parallel to the central axis (C) of the gear crown; wherein said movement means comprise a sliding support (65) and said conical worm gear (6) is slidably fixed to said support (65); wherein said support frame (11 ; 211 ) or said support (65) of the movement means is intended to be rotationally fixed to the input shaft (I); wherein said conical worm gear (6) is mounted idly rotatable with respect to said support (65), so that the conical worm gear (6), rubbing against said gear crown (1 ) during rotation of the input shaft (I), rotates about its own central axis (64) with a rotational speed dependent on a diameter of a portion of the conical worm gear (6) in contact with the gear crown; wherein the helical external thread (61 ) of the conical worm gear (6) is shaped to mesh with the teeth (21 , 31 , 41 ) of the side wall of the gears, such that the conical worm gear (6), rotating about its own central axis (64), puts at least one gear (10) of the gear crown into rotation; said variator (100; 200) comprising:

- first coupling means (5) for allowing the coupling of the gears (10) to each other, so that, by rotating a gear (10) of the gear crown about its respective pins, a rotation is transmitted to the adjacent gears of the gear crown (1 ) about their respective pins;

- at least one transmission gear (7; 207) pivotally mounted with respect to the support frame (11 ; 211 ), so as to transmit the motion from the gears (10) of the gear crown to the output shaft (U);

- second coupling means (8) for allowing the coupling of a gear (10) of the gear crown with said at least one transmission gear (7, 207), so that, by rotating a gear (10) of the gear crown about its respective pins, a rotation is transmitted to the transmission gear (7; 207).

2. Variator (100; 200) according to claim 1 , wherein the teeth (21 , 31 , 41 ) of the gears comprise a concave outer surface with the concavity facing outwards, so as to engage with a convex side wall (60) of the conical worm gear.

3. Variator (100; 200) according to claim 2, wherein each tooth (21 , 31 , 41 ) of the gears, in longitudinal section, has a greater height at a front end portion (10a) and a rear end portion (10b) and a lesser height at a central portion (10c) of the teeth (21 , 31 , 41 ), between the front end portion (10a) and the rear end portion (10b).

4. Variator (100; 200) according to any one of the preceding claims, wherein the gears (10) comprise:

- at least one first gear (2);

- at least one second gear (3); said at least one first gear (2) comprising:

- a front crown (22);

- a rear wall (23), opposite the front crown (22);

- a cavity (24) delimited by the side wall (20), the front crown (22), and the rear wall (23) and accessible through a front opening; said at least one second gear (3) comprising:

- a rear crown (32);

- a front wall (33), opposite the rear crown (32);

- a cavity (34) delimited by the side wall (30), the rear crown (32), and the front wall (33) of said at least one second gear and accessible through a rear opening; said at least one second gear (3) being mounted adjacent to said at least one first gear (2) with the rear crown (32) of said at least one second gear facing the front crown (22) of said at least one first gear.

5. Variator (100; 200) according to claim 4, wherein the gears (10) comprise third gears comprising:

- a central wall (48) comprising a front face (48a) and a rear face;

- a front crown (42) projecting forwardly from the central wall (48);

- a rear crown (43), opposite the front crown (42) and projecting rearwardly from the central wall (48);

- a front cavity (44) delimited by the side wall (40), the front crown (42), and the front face (48a) of the central wall of each third gear and accessible through a front opening;

- a rear cavity delimited by the side wall (40), the rear crown (43), and the rear face of the central wall of each third gear and accessible through a rear opening.

6. Variator (100; 200) according to claim 4 or 5, wherein the second coupling means (8) comprise a gear tooth (80) projecting from said at least one first gear and a gear wheel (74) projecting from said at least one transmission gear, cooperating with the gear tooth (80) of the second coupling means (8); said gearwheel (74) of the second coupling means being disposed in the cavity (24) of said at least one first gear and in the cavity (34) of said at least one second gear.

7. Variator (100; 200) according to claim 6, wherein said at least one transmission gear (7; 207) is pivotally mounted with respect of the support frame (11 ) around a pin (73; 273) of the transmission gear comprising an axis (R); said gear wheel (74) of the second coupling means projecting from the pin (73; 273) of said at least one transmission gear.

8. Variator (100; 200) according to any one of the preceding claims, wherein the first coupling means (5) comprise:

- pins (50) projecting rearwardly from the gears;

- seats (51 ) projecting forwardly from the gears and housing the pins (50) of the first coupling means of the adjacent gear.

9. Variator (100) according to any one of the preceding claims, wherein the support frame (11 ) is intended to be rotationally fixed to the input shaft (I); said gear crown (1 ) being adapted to rotate together with the support frame (11 ) about the central axis (C) of the gear crown.

10. Variator (100) according to claim 7, wherein said at least one transmission gear (7) comprises a truncated conical gear (7a) comprising:

- a side wall (70);

- a bottom wall (71 ) arranged at a smaller base of the truncated conical gear (7a) of the transmission gear;

- a compartment delimited by said side wall (70) and said bottom wall (71 ) and accessible via an opening (72) formed at a larger base of said truncated conical gear (7a); said axis (R) of the pin (73) of said at least one transmission gear passing through a central axis of said at least one transmission gear; said compartment of said at least one transmission gear (7) housing a portion of the gear crown (1 ).

11. Variator (100) according to claim 10, comprising third coupling means (9) for enabling the coupling of said at least one transmission gear (7) with the output shaft (U), such that, by rotating said at least one transmission gear (7) about the axis (R) of the pin of said at least one transmission gear, a rotation is transmitted to the output shaft (U).

12. Variator (100) according to claim 11 , wherein the third coupling means (9) comprise an external gear at the larger base of the truncated conical gear (7a) of said at least one transmission gear, suitable to mesh with a gear of the output shaft (U), in order to transmit rotation to the output shaft (U).

13. Variator (200) according to any one of claims from 1 to 8, wherein said support frame (211 ) is fixed; said support (65) of the movement means being intended to be rotationally fixed to the input shaft (I) and to be slidably mounted relative to the input shaft (I); said conical worm gear (6) being rotationally fixed to the support (65) of the movement means, such that, when rotating the support (65) of the movement means, said conical worm gear (6) performs a circular trajectory within the gear crown (1 ) and rubs against the gear crown (1 ), thus causing the rotation of the conical worm gear (6) about its own central axis (64).

14. Variator (200) according to claim 13, wherein said support (65) of the movement means comprises:

- a first straight portion (65a) having an axis coincident with the central axis (C) of the gear crown;

- a third inclined portion (65c) with an inclination coincident with the central axis (64) of the conical worm gear; said third portion (65c) being connected to the second portion (65b) and being at least partially disposed within the conical worm gear (6) and connected with the conical worm gear (6).

15. Variator (200) according to claim 13 or 14, wherein said at least one transmission gear (207) is made in one piece with the output shaft (U).