Seamless gearbox

Abstract

The present invention relates to a seamless gearbox, in particular for a motorcycle that is mechanically operated, for example by the rider's feet. The input shaft of the seamless gearbox of the invention is divided into two elements, each connected to the "next" or "previous" gear, which are connected to the torque input (e.g. a clutch) through a system. The system according to a preferred embodiment of the invention allows, based on the relative speed between the two elements, to select only the appropriate one of the two elements to transmit torque, and avoids (for safety reasons) the simultaneous transmission of torque to both elements.

Description

Technical Field

[0001] The present invention relates to a seamless transmission system, in particular to a seamless transmission system for a motorcycle. Background Art

[0002] Conventional motorcycle transmissions operate shifts in a manner that places the transmission in a "neutral" position between one gear and another, resulting in a torque interruption (zero traction) during the time the transmission is in this neutral position; this results in insufficient acceleration and discontinuous (instability) forces acting on the vehicle.

[0003] To avoid this problem, several attempts have been made in motor vehicles to create seamless gearbox changes. In the specific field of motorcycles, the size constraints of the engine (the engine needs to be kept in a relatively small space compared to cars) make the solution more difficult to achieve. Seamless gearbox operation, where the gearbox does not need to be in neutral between gears and therefore no torque interruption occurs during the gearshift (both up and down); vehicle stability is improved and, in motorcycle racing, this has a positive impact on lap times.

[0004] The most recently known solution is based on a dual clutch transmission (DCT) mechanism that provides two different clutches and two independent shafts, one for odd speeds (e.g. 1, 3, 5) and one for even speeds (e.g. 2, 4, 6). It can be described as two independent transmission mechanisms (one for odd speeds and one for even speeds), whose respective clutches and shafts are contained in one housing and work as a unit. They are controlled by an electronic central unit. Perfect management of the two clutches by the electronic central unit is extremely important to avoid "conflicts" between the two shaft mechanisms. In addition, the drive mechanism of the DCT is usually an electro-hydraulic system including a pressure pump, control valves and an oil reservoir. This results in a very complex device that significantly increases the overall weight, cost and complexity of manufacturing and service of the motorcycle. All the above-mentioned disadvantages are unacceptable for high-performance motorcycles, making it inconvenient to use DCT transmission.

[0005] Other recently known solutions for seamless gearbox systems work based on a very complex and precise combination of mechanical systems, without using any electronic control. This complexity and precision require very high production costs and frequent maintenance by highly skilled operators. For these reasons, these solutions are not currently used in mass production motorcycles, their use being limited to racing applications.

[0006] It is an object of the present invention to alleviate at least some of the disadvantages of currently available prior art systems. Summary of the invention

[0007] According to the present invention, a motorcycle seamless transmission system for selecting gears is provided, comprising: a first input shaft for odd-numbered gears, the first input shaft being associated with a first plurality of sprockets; a second input shaft for even-numbered gears parallel to the first input shaft, the second input shaft being associated with a second plurality of sprockets; an output shaft having a plurality of output sprockets, each of the plurality of output sprockets corresponding to a sprocket on the first input shaft or on the second input shaft; a torque management system adapted to transmit torque alternately and exclusively to one of the first input shaft and the second input shaft. The torque management system comprises a first second lockable roller bearing and a second lockable roller bearing and an input hub. The torque management system receives torque from the main clutch through the input hub, and transmits the torque exclusively and selectively to only one of the two input shafts. The first input shaft of the odd-numbered gear receives torque from the first lockable roller bearing when the first lockable roller bearing is locked; the second input shaft of the even-numbered gear receives torque from the second lockable roller bearing when the second lockable roller bearing is locked, and the first and second roller bearings are selectively and exclusively locked according to the relative rotation speed of the two input shafts. In a preferred embodiment of the present invention, the first and second input shafts are coaxially arranged, wherein the first input shaft is preferably arranged inside the second input shaft.

[0008] In a possible embodiment of the present invention, the first input shaft can engage the 1st gear sprocket, the 3rd gear sprocket and the 5th gear sprocket, and the second input shaft can engage the 2nd gear sprocket, the 4th gear sprocket and the 6th gear sprocket, each sprocket in the first and second input shafts is associated with a corresponding sprocket in the output shaft.

[0009] In the above-mentioned motorcycle gearbox system, gear selection is mechanically controlled by, for example, a selection barrel and a plurality of shift forks. More specifically, gear selection is preferably mechanically controlled by a system of levers and gear rings.

[0010] In alternative embodiments of the invention, the lockable bearings of the torque management system may be different kinds of bearings, such as ball bearings: the basic characteristics of bearings are that they can roll (i.e., are "rolling") and can be locked (i.e., they are lockable).

[0011] According to another aspect of the present invention, there is provided a motorcycle comprising a seamless transmission system as described above.

[0012] By means of the present invention it is possible to achieve a seamless gearbox mechanism integrated into a conventional gearbox, suitable for mass production and motorcycle racing. The system according to a preferred embodiment of the present invention is fully mechanical (does not require any electronic control) and is based on a pre-selection system: the "next" gear is engaged while the "previous" gear is still engaged and torque is still transmitted by the "previous" gear. When the "next" gear is overspeed, the torque management system switches the torque connection from the "previous" gear to the "next" gear, and then the "previous" gear is disengaged. The system according to a preferred embodiment of the present invention works on all gear changes, both upshifts and downshifts.

[0013] The layout of the system according to the preferred embodiment of the invention mainly corresponds to the layout of a conventional motorcycle gearbox, including an input clutch, an output shaft and an output chain sprocket, a selection cylinder and a shift fork for shifting gears. The characteristic is that the input shaft is divided into two elements, each of which is connected to the "next" or "previous" gear linked to the input (clutch) through the system. The system according to the preferred embodiment of the invention allows to select only the appropriate one of the two elements to transmit torque, based on the relative speed between the two elements, by mechanical functions only, and to avoid simultaneous torque transmission to both elements at the same time.

[0014] One of the advantages of the solution provided by the present invention is that the gearshift mechanism remains conceptually unchanged from a conventional motorcycle, so that the gearshift is driven by a mechanical mechanism actuated by the rider's foot and sequential speed changes are obtained by tooth-to-tooth engagement.

[0015] Although the present description is directed to motorcycles, those skilled in the art will readily appreciate that the same invention may be applied to transmissions for any other type of motor vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and other advantages, objects and features of the present invention will be better understood by those skilled in the art through the following description and with the aid of the accompanying drawings, which illustrate examples of embodiments which should not be construed as limiting the scope of the present disclosure as defined by the appended claims.

[0017] In short, the accompanying drawings show:

[0018] - Figure 1 A gearbox assembly according to a preferred embodiment of the present invention is characterized, showing two input shafts and an output shaft.

[0019] - Figure 2 Characterized by Figure 1 The transmission assembly according to the preferred embodiment of the present invention is shown, wherein a main clutch assembly is added to transmit torque to the input shaft through a torque management system;

[0020] - Figure 3 Yes Figure 2 A three-dimensional view of the gearbox assembly is shown with the shift drum and ratchet mechanism added;

[0021] - Figure 4 Yes Figure 3 A view of the gearbox assembly shown;

[0022] - Figure 5 and 6 It shows that Figure 4 Some components of the gearbox assembly shown, separated from each other;

[0023] - Figure 7 is a pictorial representation of two lockable roller bearings that exclusively and selectively transmit torque to one input shaft in accordance with a preferred embodiment of the present invention;

[0024] - Figure 8 is a pictorial representation of a cross section of two lockable roller bearings showing the components of the lockable roller bearings and how they operate during the driving and coasting phases;

[0025] - Figure 9a-12b It shows how the transmission according to the preferred embodiment of the present invention works during the gear shifting in the driving phase and the coasting phase; specifically, the diagram represents the upshift from the 5th gear to the 6th gear and the downshift from the 6th gear to the 5th gear.

[0026] Specific implementation of the preferred embodiment

[0027] Figure 1A preferred embodiment of the invention is shown. Torque is transmitted from the engine through a main gear (not shown), a main clutch (not shown) to the gearbox system 100 shown. The gearbox system comprises two input shafts, one for odd gears 101 and the other for even gears 103. In the present embodiment, the odd shaft 101 is placed coaxially with the even shaft and inside the even shaft, but different arrangements are possible (e.g. the even shaft is placed inside or the two shafts are not coaxially placed). Each input shaft is associated with a dedicated lockable roller bearing: in the present embodiment, the odd shaft 101 is associated with a lockable roller bearing 105 and the even shaft 103 is associated with a lockable roller bearing 107. The torque management system receives torque from the main clutch through the input hub 109 and transmits the torque exclusively and selectively to only one of the two input shafts 101 and 103. The first input shaft 101 of the odd-numbered gear receives torque from the first lockable roller bearing 105 when the first lockable roller bearing 105 is locked; the second input shaft 103 of the even-numbered gear receives torque from the second lockable roller bearing 107 when the second lockable roller bearing 107 is locked, and the first and second roller bearings are selectively and exclusively locked according to the relative rotation speed of the two input shafts. In a preferred embodiment of the present invention, the first and second input shafts are coaxially arranged, wherein the first input shaft 101 is preferably arranged inside the second input shaft 103. Although the traction torque flow (i.e., transmitted from the engine to the wheels) is described in this description, it will be readily understood by those skilled in the art that in coasting, torque is transmitted in the opposite direction. In a preferred embodiment, the odd-numbered input shaft 101 can engage the 1st gear sprocket 111, the 3rd gear sprocket 113, and the 5th gear sprocket 115, while the even-numbered input shaft 103 can engage the 2nd gear sprocket 112, the 4th gear sprocket 114, and the 6th gear sprocket 116. Each sprocket in the input shaft is associated with a corresponding sprocket in the output shaft 117: 111b for 1st gear, 113b for 3rd gear, 115b for 5th gear, 112b for 2nd gear, 114b for 4th gear, 116b for 6th gear. In the present invention we refer to the case of a gearbox with 6 speeds, but other arrangements are possible: the skilled person will understand that appropriate modifications of the gearbox system are necessary. In the present embodiment, the lockable bearings of the torque management system are described as roller bearings, however any kind of rolling bearings such as ball bearings may be used instead, as long as they are lockable.

[0028] As with conventional motorcycle gearboxes, gear selection is done by the selector cylinder ( Figure 1The shifting operation is mechanically controlled by a plurality of sprockets (not shown) and a shift fork (not shown). In a conventional gearbox, no more than one pair of sprockets (e.g., 111 and 111b) can be engaged on the associated shaft at any given time, while in the system according to the present invention, two pairs of sprockets (e.g., 111 and 111b, and 112 and 112b) can be engaged simultaneously. Specifically, during a shifting operation, one gear associated with an odd-numbered input shaft and one gear associated with an even-numbered input shaft will be engaged simultaneously: in a preferred embodiment, the two pairs of sprockets that are engaged simultaneously correspond to two consecutive gears (e.g., 1st and 2nd, 2nd and 3rd, etc.). The same double engagement occurs in both upshift and downshift operations.

[0029] Figure 2 A gearbox system 100 is shown with the addition of a main clutch (essentially corresponding to a conventional motorcycle clutch and comprising an outer basket 201 , a plate 203 , an inner drum 205 ) connected to a main range sprocket 207 (engaged to the engine crankshaft, not shown) and an input hub 109 .

[0030] Figure 3 A perspective view of a gearbox system according to a preferred embodiment of the present invention is shown, showing a selector barrel 301, a shift fork 303 and a ratchet mechanism 305. In a conventional 6-speed motorcycle gearbox, there are usually 3 shift forks operating different gear sprockets, but in the preferred embodiment of the present invention, because the 3rd and 4th gear sprockets are associated with two different input shafts, additional shift forks are required.

[0031] Figure 4 A rendering of the above-described gearbox assembly is shown (like reference numerals are used to illustrate components). Figure 5 and Figure 6 Shows Figure 4 A rendering of some of the components of the transmission assembly shown, with the components separated from each other.

[0032] Figure 7 A preferred embodiment of a double lockable roller bearing system is shown, wherein a lockable roller bearing 107 is connected to the even input shaft 103 and a lockable roller bearing 105 is connected to the odd input shaft 101. Each lockable roller bearing 107 and 105 consists of several rollers 701, which are held in place by roller cages 707 and 705, respectively. The two roller cages 707 and 705 are engaged together with a tooth-to-tooth system that allows a defined angular clearance. In a preferred embodiment of the invention, the angular clearance is between 10° and 25°.

[0033] Figure 8A portion of two lockable roller bearings is shown which has the direction of torque when it is transmitted from the engine through the input hub 109, rollers 701 and either the even axle 103 or the odd axle 101 to the wheels.

[0034] In the following, an example of how a gearbox assembly according to a preferred embodiment of the present invention works is shown. Specifically, we show the gearbox system starting from the 5th gear engaged in the drive mode and then upshifting to the 6th gear. The downshift operation operates in the opposite direction.

[0035] exist Figure 9a-9b In the embodiment, 5th gear is engaged and the engine drives the wheels through the input shaft, which receives torque from the lockable roller bearings (in this case the odd-numbered lockable roller bearings) and transmits the torque to the output shaft 117, and as Figure 9a As shown, a pair of sprockets (an input sprocket and an output sprocket) engage with each other. Figure 9b The behavior of two lockable roller bearings is shown, with the rollers of the odd-numbered lockable roller bearing in contact and transmitting torque, while the even-numbered shaft idles.

[0036] exist Figure 10a-10b In the figure, ω represents the angular velocity, and T is the transmission ratio: ω in ,ω out ,ω odd ,ω even Represent the rotation speeds of the input hub, output shaft, and first and second input shafts respectively. Fig.10a It shows how torque transfer is transferred from the pair of sprockets corresponding to 5th gear to the pair of sprockets corresponding to 6th gear. Fig.10b The behavior of two lockable roller bearings is shown: the even-numbered shaft is slower, so the torque is transferred to the even-numbered rollers and the input is slowed down to the even-numbered shaft speed (6th gear ratio). Fig.11a As shown, the odd-numbered axle overruns and drags the cage and rollers. The even-numbered cars are locked in place by the rollers, preventing the odd-numbered cars from rotating back onto the ramp. Fig.11b Shown is the cage alignment when upshifting from 5th to 6th gear.

[0037] Engage and drive in a manner similar to 5th gear ( Figure 9a and 9b ), Fig.12a Torque transfer from an input shaft (in this case the even-numbered input shaft) to an output shaft is shown through engagement of a pair of sprockets (one on the input shaft and one on the output shaft) corresponding to 6th gear. Figure 12b The behavior of a lockable roller bearing is shown, where the rollers are in contact with the even-numbered shaft and transmit torque, while the odd-numbered shaft is idle and will slow down to the even-numbered shaft speed.

Claims

1. A motorcycle seamless transmission system for selecting gears, comprising: - a first input shaft (101) for odd-numbered gears, associated with a first plurality of sprockets; - a second input shaft (103) for even-numbered gears, coaxial with the first input shaft, the second shaft being associated with a second plurality of sprockets; - an output shaft (117) having a plurality of output sprockets, each of the plurality of output sprockets corresponding to a sprocket on the first input shaft or on the second input shaft; - A torque management system adapted to transmit torque alternately and exclusively to one of a first and a second input shaft, wherein the torque management system comprises first (105) and second (107) lockable roller bearings and an input hub (109), wherein the first input shaft (101) for odd-numbered gears receives torque from the first lockable roller bearing (105) when the first lockable roller bearing is locked, and the second input shaft (103) for even-numbered gears receives torque from the second lockable roller bearing (107) when the second lockable roller bearing is locked, the first and second roller bearings being selectively and exclusively locked according to the relative rotational speed of the two input shafts.

2. The motorcycle transmission system of claim 1, wherein the torque management system receives torque from a master clutch via an input hub (109).

3. The motorcycle transmission system of claim 1, wherein the first and second input shafts are coaxially disposed.

4. The motorcycle transmission system according to claim 3, wherein the first input shaft (101) is located inside the second input shaft (103).

5. A motorcycle gearbox system according to any preceding claim, wherein: The first input shaft (101) may engage the odd-numbered gear sprockets, while the second input shaft (103) may engage the even-numbered gear sprockets, each sprocket in the first and second input shafts being associated with a corresponding sprocket in the output shaft.

6. The motorcycle transmission system according to claim 5, wherein: The first input shaft (101) is capable of engaging a 1st gear sprocket (111), a 3rd gear sprocket (113) and a 5th gear sprocket (115), while the second input shaft (103) is capable of engaging a 2nd gear sprocket (112), a 4th gear sprocket (114) and a 6th gear sprocket (116), each sprocket in the first and second input shafts being associated with a corresponding sprocket in the output shaft (117): (111b) for the 1st gear, (113b) for the 3rd gear, (115b) for the 5th gear, (112b) for the 2nd gear, (114b) for the 4th gear and (116b) for the 6th gear.

7. A motorcycle gearbox system according to any preceding claim, wherein the selection of gear is mechanically controlled by a selector cylinder and a plurality of shift forks.

8. A motorcycle gearbox system according to any preceding claim, wherein selection of gear is mechanically controlled by a lever and ring gear system.

9. A motorcycle seamless transmission system for selecting gears, comprising: - a first input shaft (101) for odd-numbered gears, associated with a first plurality of sprockets; - a second input shaft (103) for even-numbered gears, coaxial with the first input shaft, the second shaft being associated with a second plurality of sprockets; - an output shaft (117) having a plurality of output sprockets, each of the plurality of output sprockets corresponding to a sprocket on the first input shaft or on the second input shaft; - A torque management system adapted to transmit torque alternately and exclusively to one of a first and a second input shaft, wherein the torque management system comprises first (105) and second (107) lockable roller bearings and an input hub (109), wherein the first input shaft (101) for odd-numbered gears receives torque from the first lockable roller bearing (105) when the first lockable roller bearing (105) is locked, and the second input shaft (103) for even-numbered gears receives torque from the second lockable roller bearing (107) when the second lockable roller bearing (107) is locked, the first and second roller bearings being selectively and exclusively locked according to the relative rotational speed of the two input shafts.

10. A motorcycle comprising a motorcycle gearbox system according to any preceding claim.

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