Pendulum axle for tricycle type vehicle

Abstract

Vehicle equipped with a driving pendulum axle comprising a shaft (1) placed between two wheels (2) and connected to a mechanism for transmitting a driving torque produced in the vehicle, characterized in that it comprises: at both ends of the shaft (1), a device for transmitting the rotation of the shaft (1) to the wheel (2), said device allowing the inclination of the wheel (2) relative to a point O of the axis of the shaft (1); and a bridge (4) to which the two wheels (2) are rotatably mounted and surrounding the shaft (1), capable of tilting around an axis Y of the direction of movement of the vehicle, said bridge (4) being configured as a pantograph capable of maintaining the parallelism of the wheels (2) when it pivots. Fig. of the abstract: Fig. 2

Description

Title of the invention: Pendulum axle for a tricycle-type vehicle

[0001] The invention relates to the field of mechanical transmissions applied to axles capable of pendulum movements. It relates more particularly to vehicles equipped with a driving pendulum axle. In most cases, for this type of vehicle, the rear axle provides propulsion, which means that it is in mechanical relation with the system generating the propulsive power, for example a pedal assembly for tricycle-type vehicles.

[0002] A pendulum axle refers to a specific mechanical configuration designed to allow it to have a pendulum movement, which means that it can move, depending on the position of the wheels and the mechanical constraints of the terrain applied to it, very flexibly in several directions, for example from front to back or from left to right. The wheels of such an axle must then have a mechanism connecting them to the drive shaft allowing them to rotate around a point of articulation, to provide optimal adaptability to the environment and improve the handling of the vehicle, especially when cornering.

[0003] Tricycles, an example which will be developed more particularly in the text, are in particular much easier and safer to maneuver if they offer increased stability when cornering, which occurs when the rear axle has two wheels and can tilt in the direction of the turn. Such tilting allows the vehicle in particular to maintain better grip on the road. In other words, the pendulum movement of the rear axle, and consequently of the rear wheels, which allows the tricycle to tilt when cornering, offers the possibility of more dynamic driving because it is safer due to better grip.

[0004] Nowadays, however, the majority of two-rear-wheeled tricycles have a rigid rear axle, preventing any comfortable adaptation of the vehicle to the nature of the journey and the environment. There are indeed pendulum axle configurations, but they are provided on two-wheeled front-axle tricycles, vehicles which are, however, known to make steering difficult.

[0005] When the drive comes from the rear, one of the technical difficulties lies in the association of the transmission of the driving energy with a rear axle itself capable of a pendulum movement. The known and used solutions are generally based on cardan joints and grooved slides, by means of which the movement of the pedal assembly is transmitted to the wheels. Such configurations are not only expensive, but also heavy, and consequently operate to the detriment of the vehicle's handling.

[0006] Indeed, in this case, for the wheels to tilt at the same time as the tricycle frame, it is necessary to use for each wheel two cardan-type transmission joints and a sliding connection placed between said joints and allowing an adaptation of the distance which then varies between them. This configuration is shown in [Fig. 1]. It leads to a total per vehicle of four cardan joints and two sliding links, which represents a significant weight in all. The multiplication of these components also reduces the overall reliability of the system.

[0007] The present invention overcomes these drawbacks by proposing a solution which is mechanically much simpler and more robust, leading to increased reliability. The assembly is also based on a small number of basic and lightweight mechanical components, leading to a reduced overall mass, corresponding moreover to a reasonable overall cost. The tricycle of the invention offers, in short, lightness and robustness at a lower cost.

[0008] For these purposes, the vehicle equipped with a driving pendulum axle of the invention, conventionally comprising a shaft placed between two wheels and connected to a mechanism for transmitting an engine torque produced in the vehicle, is such that it comprises:

[0009] - at both ends of the shaft, a device for transmitting the rotation of the shaft to the wheel, said device allowing the inclination of the wheel relative to a point O of the axis of the shaft; and

[0010] - a bridge to which the two wheels are rotatably mounted and surrounding the shaft, capable of tilt around an axis of direction of movement of the vehicle, said bridge being configured as a pantograph capable of maintaining the parallelism of the wheels when it pivots.

[0011] The shaft transmitting the rotation from the vehicle's motor means, for example a pedal assembly whose pedals are actuated by the user, has a rectilinear geometry, often parallel to the ground surface and perpendicular to the instantaneous direction of movement of the cycle. The structure mentioned above represents a major mechanical simplification compared to the shaft portions connected by cardan joints or sliding connections, which, it is recalled, leads to an overall geometry broken up into several sections with orientations changing from one section to another and connected by intermediate mechanical components.

[0012] The device for transmitting rotation from the shaft to the wheel of the invention of course allows inclinations of the wheel in all directions, it has a circular functional symmetry.

[0013] More precisely, according to a first possible variant, the device for transmitting the rotation of the shaft to the wheel may comprise:

[0014] - N spherical connecting tips fixed radially to the end of the shaft, the centers of the spherical bonds being located in a plane perpendicular to the axis of the tree that it cuts at a point O, and located on the perimeter of a circle of diameter r where they are separated by an angle of 360° / N;

[0015] - N spherical connecting tips integral with the wheel, directed towards its axis of rotation, the centers of the spherical connections being located in a plane perpendicular to the axis of rotation of the wheel and passing through O, and located on the periphery of a circle of diameter R > r where they are separated by an angle of 360° / N;

[0016] - N connecting rods whose ends are equipped with spherical connecting elements capable to cooperate with the spherical connecting tips of the shaft and the wheel respectively, connecting said tips and having an identical length.

[0017] Preferably, N is equal to 3, and the separation angle is equal to 120°. The resulting distribution of the forces transmitted to the wheel by the shaft allows a good mechanical connection while limiting the number of components - and consequently the weight and cost - of the mechanism described.

[0018] Furthermore, according to one possibility, the connecting rods have a length greater than (R - r) between the centers of the spherical connections and have, from the axis of rotation towards the periphery of the wheel, an inclination in the direction of rotation of the wheel with a view to the advancement of the vehicle. As a result, and maximally if the wheel is perpendicular to the shaft, the end pieces secured to the wheel and those which are fixed to the shaft have an angular offset which favors the driving of the wheel by the shaft, since the connecting rods are inclined, in the plane of the wheel, in the direction of the advancement of the vehicle. This length greater than (R - r) also makes it possible to better absorb the relative movements of the wheel and the shaft when said wheel is stressed in planes not perpendicular to the axis of the shaft. Finally, this configuration makes it possible to limit the volume of the central space allocated, in the wheel, to the mechanism of connection with the shaft.The inclination of the connecting rods is designed such that a cylindrical volume of reduced diameter is sufficient, which incidentally allows, if necessary, to limit the diameter of the wheel.

[0019] With the configuration explained above applied to the two wheels, the position of the shaft is well controlled, because it requires a positioning of the shaft parallel to the ground as soon as possible, or at the very least parallel to the line connecting the contact zones of the wheels to the ground. In this configuration, the shaft however has a degree of freedom in the axial direction, because the connections made by the connecting rods do not allow this movement to be blocked. This axial translational movement is however not desired and, to block it, according to a possibility specific to the invention, on the one hand each end of the shaft can have a spherical surface with center O, and on the other hand the wheel then comprises, opposite the spherical end of the shaft, a part interposed between the spherical end of the shaft and a flat wall of the wheel parallel to a plane perpendicular to the axis of the wheel, said part being free to move in contact with said flat wall and comprising a spherical recess with center O and radius making the spherical recess suitable for fitting the end of the shaft when they are in contact.

[0020] This part constitutes a stop for the end of the shaft in the event of axial movement in the direction of the wheel, and the wall can, if necessary, limit the amplitude of the movements of the wheel relative to the shaft according to the other degrees of freedom. This solution on the two opposite wheels of the axle makes it possible to correctly block the shaft when it moves axially, that is to say in the direction of the X axis, the blocking remaining effective even in the event of inclination of the wheels.

[0021] According to a second variant, the device for transmitting the rotation of the shaft to the wheel may be a tripod ball joint fitted to the end of the shaft, the radial journals carrying the balls of which are integral with the shaft and converge at O, the balls providing spherical connections with the wheel in cooperation with cylindrical slides integral with the wheel oriented parallel to the axis of rotation of the wheel. In this case, the axial locking that must be implemented is similar to that implemented in the first variant, with adaptations linked to the use of the tripod ball joint. Thus, the end of the shaft has a spherical surface with center O, the wheel comprising, opposite the spherical end of the shaft, a part interposed between the spherical end of the shaft and a flat wall of the wheel perpendicular to the axis of the wheel.This part is free to move in contact with said flat wall and has a spherical recess with center O and radius making the spherical recess suitable for fitting the end of the shaft when they are in contact.

[0022] According to a third variant, the device for transmitting the rotation of the shaft to the wheel may be a cardan joint whose geometric center is located at O.

[0023] Preferably, the shaft is equipped with a differential connected to the engine torque transmission mechanism. The differential is interposed between the drive element, generally a pinion or a pulley for a tricycle, and the two outer parts of the shaft or half-shafts. The movement is then transmitted to each wheel at speeds adapted to the location of the latter when taking a turn, and to any friction / constraints individually encountered.

[0024] In the configuration of the invention, the transmission shaft is associated with a tilting bridge connecting the two wheels, in this case a rear bridge, and which comprises:

[0025] - a crosspiece each end of which is provided with a wheel support assembled to the wheel via a bearing allowing the rotation of the wheel relative to said support, each support being rotatably mounted on the crosspiece along a pivot axis parallel to the tilting axis of the bridge;

[0026] - a bar whose ends are rotatably connected to the wheel supports, according to a axis parallel to the pivot axis of said supports.

[0027] The bar is separate from the cross member, and its articulation to the wheel support is separate from the articulation of the cross member to said supports. The assembly therefore constitutes an articulated parallelogram structure, in a pantograph, ensuring the parallelism of the movements of the bar relative to the cross member, and consequently relative to the transmission shaft of the axle.

[0028] The vehicle of the invention may for example consist of a tricycle comprising a frame provided with a rear axle according to the description above, which is such that the bridge of the rear axle is mounted tilting on the frame, said frame comprising stops limiting the rotation of the bridge in both directions. The pivoting amplitude of the bridge is therefore not unlimited, it covers an angular sector compatible with the normal use made of such a vehicle.

[0029] According to a possibility particularly suited to a tricycle, the engine torque of the vehicle is transmitted to the axle shaft by a chain or a belt capable of deforming in the event of the shaft tilting. This is typically the case in a pedal system, which equips most tricycles, the forces applied by the user on the pedals being transmitted to a chain or a belt which retransmits them to a pulley or a rear sprocket, linked in this case to the differential equipping the rear axle shaft.

[0030] This vehicle may also include means for locking the inclination of the bridge, allowing, if necessary, the vehicle to be stabilized in a given location. These locking means may, for example, consist of a disc brake controlled by a handle located at the level of a handlebar of the vehicle. In a tricycle, the control handle of the cable controlling the disc brake may then be placed near the brake handles controlling the brakes of the front and rear wheels.

[0031] Other aims and advantages of the present invention will become apparent during the description which follows, which presents a preferred embodiment of the invention. This is however given only as an indicative and non-limiting example, applied to a tricycle.

[0032] Understanding of this description will be facilitated by referring to the attached drawings in which:

[0033] [Fig.l] shows a rear axle according to the prior art, with universal joints and slides;

[0034] [Fig.2] represents a schematic perspective view of the device for transmitting the rotation of the shaft to the wheel of the invention;

[0035] [Fig.3] shows a sectional view of the system for locking the axial translational movement of the shaft relative to the wheel;

[0036] [Fig.4] represents a schematic view of the shaft equipped with a differential;

[0037] [Fig.5] illustrates in perspective view the hub of a wheel equipped with the device of transmission of rotation from the shaft to the wheel;

[0038] [Fig.6] shows in perspective view the rear axle of the tricycle; and

[0039] [Fig.7] represents a tricycle equipped with a rear axle according to the invention.

[0040] With reference to [Fig.2], the schematic view of the device for transmitting the rotation of the shaft to the wheel is represented in a reference frame (O; X; Y; Z), conventional with an origin consisting of the point O already mentioned and three perpendicular directions respectively X corresponding to the axis of the shaft 1 of the axle (sometimes horizontal), Y marking the direction of movement of the tricycle and Z being the perpendicular to the last two (often vertical). The wheel 2 is mechanically connected to the shaft 1 in such a way that the latter can essentially transmit its rotation to it. For this purpose, the shaft 1 comprises three spherical connecting ends 11, 12, 13, in this case each comprising a ball joint, extending from the shaft 1 radially at 120° from each other.Similarly, a circular strip 24 delimiting a central hollow cylindrical volume 20 of the wheel 2 (also visible in figures 3 and 5) comprises three spherical connecting end pieces 21, 22, 23, each also comprising a ball joint, and extending from the wall 24 radially at 120° from each other in the direction of the central axis of rotation of the wheel 2. Connecting rods 31, 32, 33 connect the end pieces 11, 12, 13 of the shaft 1 to the end pieces 21, 22, 23 of the wheel 2. Their ends are provided to cooperate with the ball joints of the end pieces 11 to 13 and 21 to 23, which means in particular that these ends, when they are engaged with those of said end pieces, share the center of rotation. In the schematic representation of [Fig.2], the ends of the spherical connections of the connecting rods 31, 32, 33 are female while the ends of the spherical connections of the end pieces secured to the shaft 1 or the wheel 2 are male and fitted with ball joints, but this can of course be reversed, on one or the other or both ends of the connecting rods 31, 32, 33.

[0041] The centers of the spherical connections from the shaft 1 are located in a plane perpendicular to the axis X of the shaft 1, on a circle of radius r and center O defining this plane. As regards the wheel 2, the centers of the spherical connections are located on a circle of radius R (> r), said circle being located in a plane perpendicular to the axis of rotation of the wheel 2 which also passes through the point O. This point O is itself located on the axis of the shaft 1, in the vicinity of its end, and it appears as the point of articulation around which the wheel 2 moves according to degrees of freedom in rotation with respect to the three axes. Whatever the inclination taken by the wheel 2 with respect to the shaft 1, the rotational movement of the shaft 1 can be transmitted, via such a device, to the wheel 2.

[0042] The connecting rods 31, 32, 33 are in reality, and this appears in figures 2 and 5, of such length that they are inclined, from the axis of rotation X towards the periphery of the wheel 2, in the direction F of rotation of the wheel 2 with a view to the advancement of the vehicle. in the Y direction. This inclined character, which results in particular from a length between the centers of the spherical connections at the ends of the rod greater than (R - r), allows the exercise on the wheel 2 of a force with a more marked driving tangential component, and is consequently sought. [Fig.5] shows that due to the proximity of the virtual circles of diameter r and R, the rods 31, 32, 33 are in practice very inclined between the spherical connecting ends 11, 12, 13 secured to the shaft 1 and the spherical connecting ends 21, 22, 23 of the wheel 2. [Fig.5] also clearly shows the cylindrical hollow volume 20 in which this particular device takes place.

[0043] The mechanical connection between the shaft 1 and the wheel 2 as described does not block translational movements along the X axis, along which the shaft 1 can move, which is not desired. This is the reason why the wheel 2 comprises a part 26 designed to block the shaft in this direction. This part 26 is placed in the center of the central hollow cylindrical volume 20 of the wheel 2, on a flat bottom wall 25 (see in particular [Fig. 3]) perpendicular to the axis of rotation of the wheel 2, on which it is free to move plane on plane. The part 26 has a spherical recess which cooperates with the end of the shaft 1, which is made up of a portion of a sphere with center O and radius Rs, without obstructing the movements of the wheel relative to the Y and Z axes.

[0044] The radius of this spherical recess of the part 26 is in reality Rs + ô. The two spherical shapes, convex of the end of the shaft 1 and concave of the recess of the part 26, consequently fit closely together, providing spherical guidance of one (the shaft 1) in the other (the recess). It should be noted that the axial locking effected remains effective even in the event of inclination of the wheel 2.

[0045] In general, on a tricycle, the transmission to the shaft 1 of the driving power generated at the pedal assembly is carried out via a chain 16 (see [Fig.4]), or more rarely by a belt. This is what is shown in [Fig.4], which also shows the differential 15 equipping the shaft 1, therefore consisting of two half-shafts separated by said differential 15, which comprises a pinion for connection with the chain 16, or a pulley for connection with a belt. The speed Q at this pinion is regulated by the differential at each wheel 2 of the axle, depending on the nature of the movement which may require a different speed Q2 at each wheel 2, as shown in [Fig.4], for example and typically when taking a turn.

[0046] In the event of transmission of the engine movement by chain or belt, the pendulum movements which occur at the rear axle are easily compensated by the torsion capacity of the chain or belt. Conventional chains, which are designed to move on a set of sprockets of quite different sizes, in fact have sufficient flexibility to allow them to transverse flexion. This flexibility allows the transmission of movement from the bottom bracket axis, which is perpendicular to the median plane of the frame, to the transmission axis, the orientation of which varies depending on the ground on which the tricycle is rolling.

[0047] The rear axle is not only composed of the shaft 1 and the wheels 2, but it also comprises a rear bridge 4 also connecting the two wheels 2, and which appears in figures 6 and 7. This bridge 4, articulated to the frame C of the tricycle T along the axis 49, surrounds the shaft 1, and comprises several articulated elements which allow it to operate in a deformable parallelogram in the manner of a pantograph. Thus, it first comprises a reticulated crosspiece 40, each end of which is provided with a cylindrical wheel support 41. The crosspiece 40 is assembled to the wheel 2 via a bearing 42 allowing the rotation of the wheel 2 relative to said support 41, and the bearing surface of which is fixed on the collar 26 delimiting the outlet of the recess 20 to ensure this rotary connection between wheel 2 and crosspiece 40. Each support 41 is mounted to rotate at two points on the crosspiece 40 along a pivot axis Y1 parallel to the tilting axis 49 of the bridge 40.This axis of rotation 49 of the bridge 4 is placed centrally in the crosspiece 40 and it is visible in figures 6 and 7. The crosspiece 40 also surrounds a differential with which the shaft 1 is provided, which is not visible in the figures.

[0048] The bridge 4 also has a bar 45 whose ends are connected to rotate with the supports 41 of the wheel 2, along an axis Y2 parallel to the pivot axis of said supports 41, and which terminates the structure of the deformable parallelogram / pantograph constituting the bridge 4. The rotary connection along the axis Y1 between the cross member 40 and the wheel support 41 is made in two diametrically opposite locations on the support 41, in a direction which is parallel to the direction of the vehicle, materialized by the axis Y. The rotary connection along the axis Y2 between the cross member 40 and the support 41 is made between the two aforementioned locations, in the middle, that is to say in this case at the top of the cylindrical support 41, so that the deformable parallelogram of the rear axle of the tricycle T is well balanced.

[0049] [Fig.7] shows a complete tricycle T, with its frame C equipped with a pedal assembly P and to which the rear axle is mounted. It illustrates the way in which the pendulum axle easily adapts to the configuration of the location, for example one wheel in contact with a tarred rolling surface while the other is raised because it is placed on the edge of this surface. In this case, the right wheel, the highest, is positioned at least 10 cm above the left wheel, and the axle has a configuration with two vertical wheels 2 connected by an inclined bridge 4. In the event of a bend, the bridge 4 is on the contrary parallel to the ground while the two wheels 2 are inclined and parallel in appearance. A possibility of locking the inclination of the bridge has been mentioned, which allows stabilization of the vehicle whatever the lateral slope, and which can, if necessary, be implemented with the other brakes to stabilize the vehicle whatever the either its position. It should be noted that the vehicle's tilting capacity is managed by the frame, which provides a stop limiting the tilting, in both directions, of bridge 4.

[0050] The design methods illustrated by the figures are of course not exhaustive of the invention, which on the contrary includes variants of form for example for the device for transmitting rotation from the shaft to the wheel, for the reticulated structure of the cross member 40, or even for the means for blocking the inclination of the rear axle, and / or for other components of the pendulum axle of the invention.

Claims

Claims

1. Vehicle equipped with a driving pendulum axle comprising a shaft (1) placed between two wheels (2) and connected to a mechanism for transmitting an engine torque produced in the vehicle, characterized in that it comprises: - at both ends of the shaft (1), a device for transmitting the rotation of the shaft (1) to the wheel (2), said device allowing the inclination of the wheel (2) relative to a point O of the axis of the shaft (1); and - a bridge (4) to which the two wheels (2) are rotatably mounted and surrounding the shaft (1), capable of tilting around an axis Y of the direction of movement of the vehicle, said bridge (4) being configured as a pantograph capable of maintaining the parallelism of the wheels (2) when it pivots.

2. Vehicle according to the preceding claim, characterized in that the device for transmitting the rotation of the shaft (1) to the wheel (2) comprises: - N spherical connecting tips (11, 12, 13) fixed radially to the end of the shaft (1), the centers of the spherical connections being located in a plane perpendicular to the axis X of the shaft (1) which it intersects at a point O, and located on the periphery of a circle of diameter r where they are separated by an angle of 3607N; - N spherical connecting tips (21, 22, 23) integral with the wheel (2), directed towards its axis of rotation, the centers of the spherical connections being located in a plane perpendicular to the axis of rotation of the wheel (2) and passing through O, and located on the periphery of a circle of diameter R > r where they are separated by an angle of 3607N; - N connecting rods (31, 32, 33) whose ends are equipped with spherical connecting elements capable of cooperating with the spherical connecting end pieces (11, 12, 13; 21, 22, 23) respectively of the shaft (1) and of the wheel (2), connecting said end pieces (11, 12, 13; 21, 22, 23) and having an identical length.

3. Vehicle according to the preceding claim, characterized in that N is equal to 3, and the separation angle is equal to 120°.

4. Vehicle according to one of claims 2 and 3, characterized in that the connecting rods (31, 32, 33) have a length greater than (R - r) between the centers of the spherical connections and have, from the axis of rotation towards the periphery of the wheel (2), an inclination in the direction of rotation of the wheel (2) with a view to the advancement of the vehicle.

5. Vehicle according to one of claims 2 to 4, characterized in that each end of the shaft (1) has a spherical surface with center 0, the wheel (2) comprising, opposite the spherical end of the shaft (1), a part (26) interposed between the spherical end of the shaft and a flat wall (25) of the wheel (2) perpendicular to the axis of the wheel (2), said part (26) being free to move in contact with said flat wall (25) and comprising a spherical recess with center 0 and radius making the spherical recess capable of matching the end of the shaft (1) when they are in contact.

6. Vehicle according to claim 1, characterized in that the device for transmitting the rotation of the shaft (1) to the wheel (2) is a tripod ball joint fitted to the end of the shaft (1), the radial journals carrying the balls of which are integral with the shaft (1) and converge at 0, the balls ensuring spherical connections with the wheel (2) in cooperation with cylindrical slides integral with the wheel (2) oriented parallel to the axis of rotation of the wheel (2), said end of the shaft (1) having a spherical surface with center 0, the wheel (2) comprising, opposite the spherical end of the shaft (1), a part (26) interposed between the spherical end of the shaft and a flat wall (25) of the wheel (2) perpendicular to the axis of the wheel (2),said part (26) being free to move in contact with the wall (25) and comprising a spherical recess with center 0 and radius making the spherical recess capable of fitting the end of the shaft (1) when they are in contact.,

7. Vehicle according to claim 1, characterized in that the device for transmitting the rotation of the shaft (1) to the wheel (2) is a cardan joint whose geometric center is located at 0.

8. Vehicle according to one of the preceding claims, characterized in that the shaft (1) is equipped with a differential (15) connected to the mechanism (16) for transmitting the engine torque.

9. Vehicle according to one of the preceding claims, characterized in that the tilting bridge (4) connecting the two wheels (2) comprises: - a cross member (40) each end of which is provided with a wheel support (41) assembled to the wheel (2) via a bearing (42) allowing the rotation of the wheel (2) relative to said support (41), each support (41) being rotatably mounted on the cross member (40) along a pivot axis Y1 parallel to the tilting axis (49) of the bridge (4); - a bar (45) the ends of which are connected for rotation to the wheel supports (41), along an axis Y2 parallel to the pivot axis Y1 of said supports (41).

10. Vehicle according to the preceding claims, characterized in that it consists of a tricycle (T) comprising a frame (C) provided with a rear axle whose bridge (4) is mounted tilting on the frame (C), said frame (C) comprising stops limiting the rotation of the bridge (4) in both directions.

11. Vehicle according to the preceding claim, characterized in that the engine torque of the vehicle is transmitted to the shaft (1) of the axle by a chain or a belt (16) capable of deforming in the event of tilting of the shaft (1).

12. Vehicle according to one of claims 8 and 9, characterized in that it comprises means for blocking the inclination of the bridge (4).

13. Vehicle according to the preceding claim, characterized in that the locking means consist of a disc brake managed by a handle located at the level of a handlebar of the vehicle.

Images