Variable-speed drive with trapezoidal power-transfer member
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-06-05
- Publication Date
- 2026-04-15
AI Technical Summary
Existing power transmission systems, such as continuously variable transmissions, face inefficiencies due to high friction between pulleys and belts, limiting torque transmission and efficiency.
A variator with a trapezoidal power transfer member, comprising two rotary reduction mechanisms and a flexible, inextensible power transfer member, where rotating elements are radially movable to maintain constant tension and reduce friction, allowing continuous power transmission between two rotating mechanical elements.
The variator achieves efficient power transmission with reduced friction losses, enabling the transmission of high torques and adjustable reduction ratios through the adaptation of joint spacing and pulley engagement, enhancing the efficiency and torque capacity of power transfer.
Smart Images
Figure EP2024065430_12122024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title: Variator with trapezoidal power transfer device
[0003] The present invention relates to a device for transmitting power from a first rotating mechanical element to a second rotating mechanical element.
[0004] For example, continuously variable transmissions are known. In a vehicle, such a transmission acts like an automatic gearbox with an unlimited number of gears.
[0005] V-belt speed variators are well-known among continuously variable transmissions. The transmission ratio of a conventional pulley-belt system is determined by the diameters of the driving and receiving pulleys. To obtain a continuously variable transmission ratio, a continuously variable diameter of the pulleys, i.e., "tapered" pulleys, is required. Almost all belt variators take advantage of the special geometry of the V-belt, whose trapezoidal section is positioned in the groove of a pulley with tapered walls. A belt speed variator consists of a metal or synthetic belt and two pulleys with variable groove spacing. Depending on the spacing of the pulley walls, the belt penetrates more or less close to the center, which has the effect of changing the gear ratio.
[0006] The respective spacings of the driving and receiving pulleys are inversely proportional: one increases when the other decreases. The driving and receiving pulleys are each formed by a flange embedded on the shaft and another slidingly connected to the same shaft. The user acts on the spacing of the driving pulley by means, for example, of a pressure screw, a flywheel or hydraulic system, a vacuum pump, a rack and pinion assembly, etc. The tension of the belt then causes an inverse variation on the driven pulley. A return spring on the latter minimizes the spacing of the flanges. The pulleys are self-aligned: the center planes of the driving and receiving pulleys coincide at all times with that of the belt, but their position varies according to the translation of the sliding flanges.
[0007] Continuously variable transmissions are also known, which include pulleys with variable center distances. Only the drive is formed by two flanges sliding symmetrically on a hub. The driven, of fixed diameter, is embedded on its shaft. An increase in the center distance (generally by moving the motor positioned on a plate in sliding connection with the frame) results in a reduction in the diameter of the drive pulley and therefore in the transmission ratio (since the diameter of the driven is fixed). This type of system allows for a narrower range of ratios.
[0008] Fixed-center pulley transmissions with a pressure roller are also known. Only the drive pulley is formed by two flanges sliding symmetrically on a hub. The driven pulley, of fixed diameter, is embedded on its shaft and the center distance remains fixed. The use of one or more pressure rollers makes it possible to "artificially reduce" the length of the belt and make it penetrate the drive pulley, resulting in an increase in the spacing of the flanges and a consequent reduction in the diameter of the drive pulley and the transmission ratio. The Mobymatic type transmission is another example of a belt variator.
[0009] The aforementioned transmissions implement the drive of a belt by pulleys and / or rollers, which induces potentially high friction which reduces the efficiency of the transmission and limits the torque which can be transmitted.
[0010] There is a need to provide a novel variator for easily transmitting power, and preferably torque, from a first rotating mechanical element to a second rotating mechanical element.
[0011] The invention relates to a variator with a trapezoidal power transfer member comprising:
[0012] - a first rotary demultiplier mechanism of Zi axis,
[0013] - a second rotary gear mechanism with axis Z2 parallel to axis Zi,
[0014] - a flexible and inextensible power transfer member which drives the first and second gear reduction mechanisms together in rotation around the axes Zi and Z2 respectively, the first gear reduction mechanism comprising a first rotary plate with axis Zi and first rotating elements mounted so as to be able to move in radial translation on the first plate, the second gear reduction mechanism comprising a second rotary plate with axis Z2 and second rotating elements mounted so as to be able to move in radial translation on the second plate, at least three rotating elements of the first gear reduction mechanism and at least three rotating elements of the second gear reduction mechanism being engaged with the power transfer member during a complete revolution of each of the first and second gear reduction mechanisms around the axes Zi and Z2 respectively,and a spacing mechanism for continuously and synchronously moving the first and second rotating members radially relative to the axes Zi and Z2 during rotation of the first and second gear reduction mechanisms about the axes Zi and Z2 respectively, in order to maintain a substantially constant tension in the power transfer member.,
[0015] The variator according to the invention allows continuous transmission of power applied to the first reduction mechanism to the second reduction mechanism and vice versa. Furthermore, since the first and second rotating elements are radially movable, the contact surface between the first and second reduction mechanisms and the power transfer member is limited, and thus the transmission efficiency losses linked to friction between these elements are limited.
[0016] The power transfer member being inextensible, its length is constant. By adapting the joint spacing of the first and second rolling elements with respect to the axes Zi and Z2, a determined reduction ratio can be obtained, by varying the diameter of the power transfer member during its passage in the first plate and in the second plate.
[0017] During a complete revolution of the first, respectively of the second gear mechanism, each of the first, respectively second, rotating elements is engaged with the power transfer member during a part of said revolution then at a distance from said power transfer member in a consecutive part of said revolution before entering into engagement again at the start of a following revolution.
[0018] The first rotating elements are preferably each rotatable about an axis parallel to the Zi axis. The second rotating elements are preferably each rotatable about an axis parallel to the Z2 axis.
[0019] The radial translation of a first rotating element, respectively of a second rotating element, is carried out along a radius of a circle perpendicular to the Zi axis, respectively to the Z2 axis, and whose center is on the Zi axis, respectively the Z2 axis.
[0020] The power transfer member may be selected from a belt, a chain, and a track. The first and second rolling elements may be sprockets or pulleys.
[0021] In particular, the power transfer member is a belt and the first and second rolling elements are pulleys. The pulleys that are engaged with the belt are in contact, preferably non-sliding, with the belt. In this way, the pulleys of the first and second rotary mechanisms and the pulley are mutually driven.
[0022] Preferably, the power transfer member is a chain or a track and the first and second rolling elements are sprockets. The sprockets that are engaged with the power transfer member are meshed with the power member. Advantageously, it is thus possible to transmit high torques that could not be simply transmitted by a frictional connection between a pulley and a belt.
[0023] The first gear reduction mechanism may be rigidly fixed to the first drive shaft and / or the second gear reduction mechanism may be rigidly fixed to the second drive shaft.
[0024] Preferably, the distance between the Zi and Z2 axes is constant.
[0025] The Zi and Z2 axes are parallel, which advantageously allows the power transfer member to be kept perpendicular to the Zi and Z2 axes during power transmission.
[0026] Preferably, the first rolling elements are distributed angularly in a regular manner around the axis Zi and / or the second rolling elements are distributed regularly around the axis Z2. In particular, the first rolling elements may be spaced two by two by an angle 2TI / NI, NI being the number of first rolling elements and / or the second rolling elements may be spaced two by two by an angle 2K / N2, N2 being the number of second rolling elements. Ni may be equal to N2.
[0027] Preferably, the first reduction mechanism comprises at least four first rolling elements and / or the second reduction mechanism comprises at least four second rolling elements.
[0028] Preferably, the first rolling elements are each rotatable about an axis parallel to the axis Zi and the second rolling elements are each rotatable about an axis parallel to the axis Z2. Preferably, in order to ensure radial displacement of the first and second rolling elements relative to the axes Zi and Z2 respectively, the first reduction mechanism comprises first supports, each slidably mounted in a radial groove provided in the first plate and each carrying a corresponding first rolling element and / or the second reduction mechanism comprises second supports, each slidably mounted in a radial groove provided in the second plate and each carrying a corresponding second rolling element.
[0029] The first rolling elements and / or the second rolling elements may be rotatably mounted on the first support, respectively on the second support. For example, each of the first and second supports may comprise a pin, preferably with an axis parallel to the Zi axis or to the Z2 axis respectively, and a corresponding first or second rolling element, respectively, is rotatably mounted on the pin.
[0030] Preferably, the radial grooves formed in the first plate and / or the grooves formed in the second plate are rectilinear.
[0031] The first and second chainrings can be identical, which simplifies the design of the variator.
[0032] Preferably, the spreading mechanism comprises:
[0033] - first and second collars mounted to slide along the axes Zi and Z2 respectively,
[0034] - a first rod comprising first rigid arms each having one end fixed, in particular in an articulated manner, to a corresponding first rolling element and an opposite end fixed in an articulated manner to the first collar,
[0035] - a second rod comprising second rigid arms each having one end fixed, in particular in an articulated manner, to a corresponding second rolling element and an opposite end fixed in an articulated manner to the second collar,
[0036] - at least one spacer fixed in an articulated manner by one of its ends to the first collar and by another of its ends to the second collar, F spacer being pivotally mounted on a spacer axis Z3.
[0037] The spacing mechanism thus makes it possible, by simply rotating the spacer relative to the spacer axis Z3, to move the first collars of the first reduction mechanism apart and to bring the second collars of the second reduction mechanism closer together, and thus to bring the first rolling elements closer to the axis Zi and to move the second rolling elements away from the axis Z2, and vice versa.
[0038] Preferably, the spacer axis Z3 is between the axes Zi and Z2. Preferably, the spacer axis Z3 is at a constant distance from the axes Zi and Z2.
[0039] Preferably, rotation of the spacer about the spacer axis Z3 causes the first collar to move along the axis Zi in a first direction and the second collar to move along the axis Z2 in a second direction opposite to the first direction.
[0040] Preferably, the Z3 axis is in a plane normal to the segment connecting the Zi and Z2 axes.
[0041] The variator with trapezoidal power transfer member may include a control member for controlling the rotation of the spacer around the spacer axis Z3.
[0042] Preferably, to reduce the force applied to the first and second rods, the variator comprises two spacing mechanisms arranged on either side of a median plane of the first and second reduction mechanisms and perpendicular to the axes Zi and Z2 respectively.
[0043] The spacing mechanisms may each comprise a spacer pinion rigidly mounted on the corresponding spacer axis, the spacer pinions of said spacing mechanisms being meshed with each other. Thus, the rotation of one of the spacers about its spacer axis causes the rotation, in an opposite direction, of the other spacer about the spacer axis of the latter.
[0044] The variator may further include a tensioning mechanism to ensure minimal tension in the power transfer member.
[0045] The invention may be better understood by reading the detailed description and the examples which follow, presented for illustrative and non-limiting purposes, and the attached drawing, in which:
[0046] [Fig. 1] is a schematic view from the front (top part) and from above (bottom part) in three different configurations a), b) and c) of a continuous variator with trapezoidal power transfer member according to the invention;
[0047] [Fig. 2] is a schematic front view of a portion of the example continuous variable speed drive with trapezoidal power transfer member illustrated in Figure 1; and
[0048] [Fig. 3] schematically illustrates an example of control of the variator according to the invention. In the figures, the dimensions and scales of the various constituent elements of the accumulator, the variator and the device according to the invention have not always necessarily been respected, for the sake of clarity of the drawing.
[0049] Figures 1 to 3 illustrate an example of a variator with a trapezoidal power transfer member 120 according to the invention.
[0050] It comprises first 121 and second 122 Zi and Z2 axis reduction mechanisms and a power transfer member.
[0051] The first reduction mechanism 121 is for example in rotational cooperation with a first Zi axis control shaft and the second reduction mechanism is for example in rotational cooperation with a second Z2 axis control shaft parallel to the Zi axis.
[0052] The first drive shaft is, for example, the rotation shaft of a crankset of a bicycle and the second drive shaft is, for example, the rotation shaft of a wheel of said bicycle.
[0053] In another example, the first drive shaft is that of an internal combustion engine of a vehicle and the second drive shaft is the rotation shaft of a wheel of a vehicle.
[0054] Preferably, the first gear reduction mechanism 121 may be rigidly attached to the first drive shaft and the second gear reduction mechanism 122 may be rigidly attached to the second drive shaft.
[0055] The power transfer member 85 is flexible and inextensible and drives the first and second gear reduction mechanisms in rotation.
[0056] The first and second gearing mechanisms respectively comprise a first plate 124 with axis Zi and a second plate 125 with axis Z2, both in the form of discs, for example with the same radii.
[0057] They further comprise first rotating elements 126 movable in translation radially relative to the axis Zi on the first plate and second rotating elements 128 movable in translation radially relative to the axis Z2 on the second plate.
[0058] The first and second plates are each provided with grooves 130 extending radially from the center of each of the plates. The grooves are distributed regularly around the axis Zi in the first plate and around the axis Z2 in the second plate.
[0059] First and second supports are slidably mounted in the radial grooves and each respectively carries a first 126 and second 128 rotating element. They are slidably mounted in the grooves and can therefore be moved radially.
[0060] The variator 120 is configured such that during a full revolution of the first support and a full revolution of the second support around the axes Zi and Z2 respectively, at least three of the first rolling elements 126 and at least three of the second rolling elements 128 are engaged with the power transfer member 85. Obviously, during a revolution of the first support, respectively of the second support, at least one of the first, respectively second, rolling elements comes into contact then leaves and comes into contact again with the transfer member.
[0061] Furthermore, the variator with trapezoidal power transfer member 120 comprises two spacing mechanisms 140 for continuously and synchronously moving the first and second rotating elements radially relative to the axes Zi and Z2 respectively, in order to maintain a substantially constant tension in the power transfer member 85. According to an example not illustrated, it may comprise a single spacing mechanism.
[0062] The spacing mechanisms are arranged symmetrically on either side of a median plane PP, perpendicular to the axes Zi and Z2, of the first 124 and second 125 plates.
[0063] Each spacing mechanism comprises first 146 and second 148 collars slidably mounted on the axes Zi and Z2 respectively and first 150 and second 152 rods. The first rods 150, in number equal to the number of first rolling elements 126, the first collar 146, the second rods 152, in number equal to the number of second rolling elements 152 and the second collar 148 of a spacing mechanism are arranged on one side of the median plane.
[0064] Each of the first 150 and second 152 rods has first 154 arms and second 156 arms respectively.
[0065] The first 154 and second 156 arms are rigid. They are each fixed in an articulated manner by one end to a first rolling element 126, respectively to a corresponding second rolling element 128 and by an opposite end to the first collar 146, respectively to the second collar 148, which is on the same side of the median plane as the first rod.
[0066] Furthermore, each spacing mechanism 140 further comprises a spacer 160 which is fixed in an articulated manner by one of its ends to the first collar 146 and by another of its ends to the second collar 148, each spacer 140 being pivotally mounted on a spacer axis Z3 which is perpendicular to the axes Zi and Z2 and arranged equidistant from the axes Zi and Z2.
[0067] By rotating one of the spacers in one direction of rotation around its spacer axis Z3 and the other spacer in an opposite direction of rotation along its spacer axis Z3', the user moves the first collars away from the first plate 124 and brings the second collars closer to the second plate 125, and vice versa when the rotation is F spacer is carried out in an opposite direction of rotation.
[0068] Furthermore, on each spacer 160 is mounted a spacer pinion 162 as illustrated in Figure 3. The spacer pinions 162 of the first and second spacing mechanisms are identical and meshed with each other, such that rotation of one of the spacers in one direction of rotation about its spacer axis causes the other spacer to rotate in the opposite direction, as seen in Figures 3 a) to c).
[0069] The first 150 and second 152 rods being rigid and the first 126 and second 128 rolling elements being mounted radially sliding in the grooves 130 formed in the first 124 and second 125 plates respectively, the distance of the first rods 150 from the first plate brings the first rolling elements 126 closer to the axis ZI and the distance of the second rods 152 from the second plate 125 moves the second rolling elements away from the second plate, as can be seen in Figure 1 a). The approach of the first rods and the distance of the second rods results in an opposite radial displacement of the first and second rolling elements as illustrated in Figure 1 c).
[0070] In this way, the spacing mechanism ensures that the tension in the power transfer member is substantially constant during the rotation of the first and second supports. Furthermore, when the first rolling elements are closer to the Z1 axis than the second rolling elements to the Z2 axis, the radius of curvature of the power transfer member is smaller around the Z1 axis than around the Z2 axis. Thus, the rotational speed of the first plate is higher than the rotational speed of the second plate. This is the opposite when the first rolling elements are further from the Zi axis than the second rolling elements from the Z2 axis, as illustrated in Figure 1 c). Obviously, when the first rolling elements and second rolling elements are equidistant from the Zi and Z2 axes, as illustrated in Figure 1 b), the rotational speed of the first and second plates is identical.The spacing mechanism 140 thus makes it possible to simply adjust and continuously vary the ratio of the rotation speed of the first reduction mechanism to the rotation speed of the second reduction mechanism.
[0071] As will be apparent throughout the present description, the invention provides a variator with a trapezoidal power transfer member which is compact, of simple design and which can be easily arranged within a vehicle transmission kinematic chain.
Claims
Claims 1. Varied with trapezoidal power transfer member (120) comprising: - a first rotary gearing mechanism (121) with axis Zi, - a second rotary gearing mechanism (122) with axis Z2 parallel to axis Zi, - a flexible and inextensible power transfer member (85), which drives together in rotation the first (121) and second (122) reduction mechanisms around the axes Zi and Z2 respectively, the first reduction mechanism comprising a first rotating plate (124) of axis Zi and first rotating elements (126) mounted mobile in radial translation on the first plate, the second reduction mechanism comprising a second rotating plate (125) of axis Z2 and second rotating elements (128) mounted mobile in radial translation on the second plate, at least three rotating elements of the first reduction mechanism and at least three rotating elements of the second reduction mechanism being engaged with the power transfer member (85) during a complete revolution of each of the first and second reduction mechanisms around the axes Zi and Z2 respectively,and a spacing mechanism (140) for continuously and synchronously moving the first (126) and second (128) rotating elements radially relative to the axes Zi and Z2 during rotation of the first and second gear reduction mechanisms about the axes Zi and Z2 respectively, in order to maintain a substantially constant tension in the power transfer member, the spacing mechanism (140) comprising:, - first (146) and second (148) collars mounted to slide along the axes Zi and Z2 respectively, - a first rod (150) comprising first rigid arms (154) each having one end fixed, in particular in an articulated manner, to a corresponding first rolling element (126) and an opposite end fixed in an articulated manner to the first collar, - a second rod (152) comprising second rigid arms (156) each having one end fixed, in particular in an articulated manner, to a corresponding second rolling element and an opposite end fixed in an articulated manner to the second collar, - at least one spacer (160) fixed in an articulated manner by one of its ends to the first collar (146) and by another of its ends to the second collar (148), the spacer being pivotally mounted on a spacer axis Z3.
2. Variator according to claim 1, the power transfer member (85) being a chain or a track and the first (126) and second (128) rolling elements being sprockets.
3. Variator according to any one of claims 1 and 2, the distance between the axes Zi and Z2 being constant.
4. Variator according to any one of the preceding claims, the first reduction mechanism comprising first supports, each slidably mounted in a radial groove (130) provided in the first plate and each carrying a corresponding first rolling element and / or the second reduction mechanism comprising second supports, each slidably mounted in a radial groove (130) provided in the second plate and each carrying a corresponding second rolling element.
5. Variator according to the preceding claim, the radial grooves formed in the first plate and / or the grooves formed in the second plate being rectilinear.
6. Variator according to any one of the preceding claims, the spacer axis Z3 being between the axes Zi and Z2 and / or the spacer axis Z3 being at a constant distance from the axes Zi and Z2.
7. Variator according to any one of the preceding claims, comprising two spacing mechanisms arranged on either side of a median plane (PP) of the first and second reduction mechanisms and perpendicular to the axes Zi and Z2 respectively.
8. Variator according to claim 7, the spacing mechanisms (140) each comprising a spacer pinion (162) rigidly mounted on the corresponding spacer axis, the spacer pinions of said spacing mechanisms being meshed with each other.