Gear shifting system

Abstract

A transmission system (300) including a first gear selector assembly (329), the first gear selector assembly (329) including a first selector ring (54) and a second selector ring (56), the first and second selector rings (54, 56) being translatable relative to one another, the first selector ring (54) including a first set of engagement members (45) secured to one another by a first annular member (53), each engagement member (45) of the first set including a first portion (59) located on a first side of the first annular member (53) and a second portion (61) located on a second side of the first annular member (53), each first portion (59) having a first drive surface (67) oriented generally in a first rotational direction and a first non-drive surface (69) oriented generally in a second rotational direction, each second portion (59) having a first drive surface (67) oriented generally in a first rotational direction and a second non-drive surface (69) oriented generally in a second rotational direction. a second selector ring (56) including a second set of engagement members (46) secured to one another by a second annular member (55), each engagement member (46) of the second set including a first portion (63) located on a first side of the second annular member (55) and a second portion (71) located on a second side of the second annular member (55), each first portion (69) having a first drive surface (67) oriented generally in the second rotational direction and a first non-drive surface (69) oriented generally in the first rotational direction, each second portion (71) including a second drive surface (67) oriented generally in the second rotational direction and a second non-drive surface (69) oriented generally in the first rotational direction.

Description

[Technical field]

[0001] The present invention relates to a transmission system. [Background technology]

[0002] In a conventional single-clutch synchromesh transmission system for a vehicle, the transmission must be disengaged from the power source, such as the engine or motor, by operating the clutch before the current gear is deselected and the new gear is engaged. If power is not disengaged when attempting to engage a new gear, the synchromesh device cannot engage the new gear element or must be forced to engage with the risk of damaging the transmission and creating a torque spike in the transmission. This is most often because the engine speed does not match the speed of the new gear. For vehicles such as automobiles with conventional gearboxes and powered by an engine, the selection of a new gear ratio typically takes 0.5 to 1 second to complete. So, when a higher gear is selected, for example, a time delay allows the engine to reduce its speed (by its own inertia) to more closely match the speed of the new gear before the clutch reconnects the engine and the transmission, thereby reducing the possibility of a torque spike when power is applied again.

[0003] Dual Clutch Transmission (DCT) systems have attempted to address this issue by using two clutches to seamlessly transfer torque when shifting between gears, but DCTs have a number of drawbacks, including the need to use two heavy and expensive friction clutches that are complex to control and have parasitic losses, making them less efficient.

[0004] Another type of seamless transmission system is called an instantaneous type transmission system. This group of transmission systems includes at least one selector assembly, which includes first and second sets of engagement elements arranged to selectively engage a drive mechanism with the or each gear element associated therewith. In some instantaneous transmission systems, the first and second sets of engagement elements are arranged to allow a new gear to be selected while a current gear is still engaged, so that a new gear can be selected under the power of some shift type. Typically, at least one selector assembly of an instantaneous transmission system has four modes of operation with the or each rotatably mounted gear element associated therewith: fully engaged in both torque directions; disengaged in both torque directions (neutral); engaged in positive torque direction and disengaged in reverse torque direction; engaged in reverse torque direction and disengaged in positive torque direction.

[0005] It is the last two modes that allow a discrete ratio gearbox to shift ratios up or down instantaneously under load without interruption of torque. Instantaneous gear shifting is described in WO 2004 / 099654, WO 2005 / 005868, WO 2005 / 005869, WO 2005 / 024261 and WO 2005 / 026570, WO 2006 / 095140, WO 2006 / 123128, WO 2006 / 123166, WO 2007 / 132209, WO 2008 / 062192, WO 2008 No. 2008 / 145979, No. 2009 / 068853, No. 2010 / 046654, No. 2010 / 046655, No. 2010 / 046652, No. 2012 / 164237, No. 2020 / 128412, No. 2020 / 183118 and No. 2021 / 156585, the contents of which are incorporated by reference. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2004 / 099654 [Patent Document 2] International Publication No. 2005 / 005868 [Patent Document 3] International Publication No. 2005 / 005869 [Patent Document 4] International Publication No. 2005 / 024261 [Patent Document 5] International Publication No. 2005 / 026570 [Patent Document 6] International Publication No. 2006 / 095140 [Patent Document 7] International Publication No. 2006 / 123128 [Patent Document 8] International Publication No. 2006 / 123166 [Patent Document 9] International Publication No. 2007 / 132209 [Patent Document 10] International Publication No. 2008 / 062192 [Patent Document 11] International Publication No. 2008 / 096140 [Patent Document 12] International Publication No. 2008 / 145979 [Patent Document 13] International Publication No. 2009 / 068853 [Patent Document 14] International Publication No. 2010 / 046654 [Patent Document 15] International Publication No. 2010 / 046655 [Patent Document 16] International Publication No. 2010 / 046652 [Patent Document 17] International Publication No. 2012 / 164237 [Patent Document 18] International Publication No. 2020 / 128412 [Patent Document 19] International Publication No. 2020 / 183118 [Patent Document 20] International Publication No. 2021 / 156585 Summary of the Invention

[0007] In some situations it is desirable to package an instantaneous shifting system in the most efficient manner possible. The inventors have determined that by redesigning the gear selector assembly actuator system, it is possible to improve the packaging of the shifting system and reduce the number of actuator components required.

[0008] Another problem with known instantaneous shifting systems is that in at least one selector assembly, the gear selector rings are opposed and therefore require separate tooling to manufacture the first and second gear selector rings, which is undesirable as it adds additional manufacturing cost and time.

[0009] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to alleviate at least one of the aforementioned problems, or at least to provide a shifting system which is an alternative to existing shifting systems.

[0010] According to a first aspect of the present invention, there is provided a transmission system as set forth in claim 1. The present invention provides an instantaneous type transmission system including a selector assembly, wherein the first and second selector rings may be identical.

[0011] In accordance with another aspect, a transmission system is provided.

[0012] The transmission may include a first gear selector assembly. The first gear selector assembly may include a first selector ring. The first gear selector assembly may include a second selector ring. The first and second selector rings may be translatable relative to one another.

[0013] The first selector ring can include a first set of engagement members secured to one another by a first annular member. Each engagement member of the first set can include a first portion located on a first side of the first annular member and a second portion located on a second side of the first annular member. Each first portion can have a first drive surface oriented generally in the first rotational direction. Each first portion can have a first non-drive surface oriented generally in the second rotational direction. Each second portion can have a second drive surface oriented generally in the first rotational direction. Each second portion can have a second non-drive surface oriented generally in the second rotational direction.

[0014] The second selector ring can include a second set of engagement members secured to one another by the second annular member. Each engagement member of the second set can include a first portion located on a first side of the second annular member. Each engagement member of the second set can include a second portion located on a second side of the second annular member. Each first portion can have a first drive surface oriented generally in the second rotational direction. Each first portion can have a first non-drive surface oriented generally in the first rotational direction. Each second portion can have a second drive surface oriented generally in the second rotational direction. Each second portion can have a second non-drive surface oriented generally in the first rotational direction.

[0015] In general, the first selector ring may be identical to the second selector ring.

[0016] The engagement members in the first set of engagement members can be evenly angularly distributed around the first annular member. For example, the first set of engagement members can include two to four, preferably three, engagement members. In a set of three engagement members, the angle between adjacent engagement members can be approximately 120 degrees.

[0017] The engagement members in the second set of engagement members can be evenly angularly distributed around the second annular member. For example, the first set of engagement members can include two to four, preferably three, engagement members. In a set of three engagement members, the angle between adjacent engagement members can be approximately 120 degrees.

[0018] The first selector ring can include a first set of recesses formed through the first annular member, and each recess in the first set of recesses can be sized, shaped and positioned to receive a respective one of the engagement members in the second set of engagement members. The first set of recesses facilitates relative translational movement between the first selector ring and the second selector ring.

[0019] The second selector ring can include a second set of recesses formed through the second annular member, and each recess in the second set of recesses can be sized, shaped and positioned to receive a respective one of the engagement members in the second set of engagement members. The second set of recesses facilitates relative translational movement between the first and second selector rings.

[0020] The transmission system may include an actuator assembly arranged to control movement of the first and second selector rings.

[0021] The first selector assembly may be mounted on the shaft. The first gear element may be rotatably mounted on the shaft. The second gear element may be rotatably mounted on the shaft. The first selector assembly may be arranged to selectively lock the first and second gear elements for rotation with the first shaft. The shaft may include a first countershaft.

[0022] The first gear selector assembly can be arranged to selectively engage the first gear element in the following operational modes: locking the first gear element for rotation with the shaft in both positive and reverse torque directions; locking the first gear element for rotation with the shaft in the positive torque direction and unlocking it in the reverse torque direction; and locking the first gear element for rotation with the shaft in the reverse torque direction and unlocking it in the positive torque direction.

[0023] With the first gear element engaged by the first and second sets of engaging members and capable of being locked for rotation in positive and reverse torque directions, one of the first and second sets of engaging members may be in a loaded state and the other of the first and second sets of engaging members may be in an unloaded state. The actuator assembly may be arranged to selectively move the unloaded set of engaging members out of engagement with the first gear element, for example to a neutral position.

[0024] The first gear selector assembly can be arranged to selectively engage the second gear element in the following operational modes: locking the second gear element for rotation with the shaft in both positive and reverse torque directions; locking the second gear element for rotation with the shaft in the positive torque direction and unlocking it in the reverse torque direction; and locking the second gear element for rotation with the shaft in the reverse torque direction and unlocking it in the positive torque direction.

[0025] With the second gear element engaged by the first and second sets of engaging members and locked for rotation in positive and reverse torque directions, one of the first and second sets of engaging members may be in a loaded state and the other of the first and second sets of engaging members may be in an unloaded state. The actuator assembly may be arranged to selectively move the unloaded set of engaging members out of engagement with the second gear element, for example to a neutral position.

[0026] The first selector assembly may be mounted to the shaft by a support sleeve, which may include internal splines arranged to lock the support sleeve for rotation with the shaft.

[0027] At least one, and preferably each, of the engagement members in the first set of engagement members can include a linear feature formed on an inwardly facing side that can be arranged to engage a complementary feature on the support sleeve. Typically, the feature comprises a channel and the complementary feature comprises a spline, which provides a rigid connection and allows the engagement member to move axially relative to the shaft.

[0028] At least one, and preferably each, of the engagement members in the second set of engagement members can include a linear feature formed on an inwardly facing side and can be arranged to engage a complementary feature on the support sleeve. Typically, the feature comprises a channel and the complementary feature comprises a spline, which provides a rigid connection and allows the engagement member to move axially relative to the shaft.

[0029] The first gear selector assembly may be arranged to provide torque support during gear shifting to ensure there is no loss of drive during gear shifting.

[0030] The transmission system may include a second gear selector assembly. The actuator assembly may be arranged to control operation of the second gear selector assembly.

[0031] The transmission system may include a third gear selector assembly. The actuator assembly may be arranged to control operation of the third gear selector assembly.

[0032] The actuator assembly may include a shift drum. The shift drum may include a first and a second portion. The second portion may be arranged to rotate relative to the first portion. The second portion may include a first control slot that may be arranged to control operation of the first selector assembly. The second portion may include a second control slot that may be arranged to control operation of the second gear selector assembly. The first portion may include a third control slot that may be arranged to control operation of the third gear selector assembly.

[0033] The actuator assembly can include a first shift fork assembly that can include a first shift fork arranged to control axial movement of the first selector ring and a second shift fork arranged to control axial movement of the second selector ring.

[0034] The actuator assembly may include a first shift collar mounted to the first shift rail. The first shift collar may include a first control member engaging the first control slot. The shift drum may be positioned to adjust a position of the first control member along the first control slot by adjusting a rotational direction of the second portion of the shift drum to thereby control an axial position of the first collar relative to the first shift rail and, therefore, an axial position of at least one of the first and second selector rings.

[0035] The second gear selector assembly can include a third selector ring. The actuator assembly can include a second shift fork assembly, the second shift fork assembly can include a third shift fork arranged to control axial movement of the third selector ring.

[0036] The transmission system may include a first input shaft directly connected to the output of the drive source.The transmission system may include a second input shaft connected to the output of the drive source through a friction clutch.

[0037] A second gear selector assembly may be mounted on the second input shaft. A third gear element may be rotatably mounted on the second input shaft. A fourth gear element may be rotatably mounted on the second input shaft. The second gear selector assembly may be arranged to selectively lock each of the third and fourth gear elements for rotation with the second shaft.

[0038] The odd gears may be grouped together in a first portion of the transmission system. The even gears may be grouped together in a second portion of the transmission system. The second gear selector assembly may be positioned to select between the odd gears and the even gears by selectively forming a torque path to the first and second portions of the transmission system.

[0039] The third gear selector assembly may include a further selector ring. The actuator assembly may include a further shift fork assembly, the further shift fork assembly including a further shift fork arranged to control axial movement of the further selector ring.

[0040] The transmission system may include an output shaft. A third gear selector assembly may be mounted on one of the output shaft, the second countershaft, and a sleeve mounted on the second countershaft. At least one further gear element may be rotatably mounted coaxially with the third gear selector assembly. The third gear selector assembly may be arranged to selectively lock the at least one further gear element for rotation with the shaft on which it is mounted.

[0041] The third gear selector assembly may comprise a preselection selector assembly which may be arranged to preselect a new gear during a gear shift, for example before the first and second gear selector assemblies are operated.

[0042] In accordance with another aspect, a transmission system is provided.

[0043] The transmission may include a first gear selector assembly. The first gear selector assembly may include a first selector ring having a first set of engagement members. The first gear selector assembly may include a second selector ring having a second set of engagement members. The first and second selector rings may be capable of translational movement relative to one another.

[0044] The transmission may include a second gear selector assembly.

[0045] The transmission may include a third gear selector assembly.

[0046] The transmission may include an actuator assembly for controlling operation of the first, second, and third gear selector assemblies. The actuator assembly may include a shift drum having first and second portions. The second portion may be arranged to rotate relative to the first portion. The second portion may include a first control slot arranged to control operation of the first selector assembly. The second portion may include a second control slot arranged to control operation of the second gear selector assembly. The first portion may include a third control slot arranged to control operation of the third gear selector assembly.

[0047] The actuator assembly can include a first motor. The first motor can be positioned to rotate the first portion of the shift drum.

[0048] The actuator assembly can include a second motor. The second motor can be arranged to rotate the second portion of the shift drum. Thus, the first and second portions of the shift drum can rotate independently of one another.

[0049] The first portion of the shift drum may include a shaft having a flange (sometimes referred to as a shoulder) toward one end. The third control slot may be formed in a curved surface of the flange.

[0050] The first portion of the shift drum can include a first sleeve mounted on the shaft. The first sleeve can be mounted on the shaft from the flange toward an opposite end of the shaft. The first sleeve can be fixed for rotation with the shaft.

[0051] At least one additional control slot may be formed in the curved surface of the first sleeve. Typically, the number of control slots in the first portion of the shift drum corresponds to the number of preselection gear assemblies, described below.

[0052] The second portion of the shift drum may include a second sleeve rotatably mounted on the shaft. The first and second control slots may be formed in a curved surface of the second sleeve. Typically, the second sleeve may be disposed between the first sleeve and the flange. In this configuration, the first sleeve may aid in assembly of the shift drum, for example, by rotatably mounting the second sleeve on the shaft.

[0053] The actuator assembly can include a first shift fork assembly. The first shift fork assembly can include a first shift fork arranged to control axial movement of the first selector ring. The actuator assembly can include a second shift fork arranged to control axial movement of the second selector ring.

[0054] The actuator assembly may include a first shift collar mounted to the first shift rail. The first shift collar may include a first control member engaging the first control slot. The shift drum may be positioned to adjust a position of the first control member along the first control slot by adjusting a rotational direction of the second portion of the shift drum, thereby controlling an axial position of the first collar relative to the first shift rail.

[0055] By adjusting the axial position of the first collar on the first shift rail, the axial position of at least one of the first shift fork-first selector ring pair and the second shift fork-second selector ring pair is adjusted relative to the first shift rail.

[0056] The first and second shift forks can be mounted to the second shift rail. An arm can protrude from the shift collar. The arm can be securable to the second shift rail. The arm can be positioned to adjust an axial position of at least one of the first and second shift forks relative to the second shift rail.

[0057] The actuator assembly may include a resilient means arranged to bias the first shift fork to a first axial position. The first axial position may be a neutral operating condition. The actuator assembly may include a resilient means arranged to bias the second shift fork to a second axial position. The second axial position may be a neutral operating condition. The neutral operating condition is a condition in which the respective selector ring is not engaged with any of its associated gear elements.

[0058] The first gear selector assembly may be mounted on the first countershaft. The first gear element may be rotatably mounted on the first countershaft. The second gear element may be rotatably mounted on the first countershaft. The first gear selector assembly may be arranged to selectively lock the first and second gear elements for rotation with the first countershaft. The actuator assembly may be arranged to move the first selector ring into engagement with the first gear element to lock the first gear element for rotation with the first countershaft. The actuator assembly may be arranged to move the first selector ring into engagement with the second gear element to lock the second gear element for rotation with the first countershaft. The actuator assembly may be arranged to move the second selector ring into engagement with the first gear element to lock the first gear element for rotation with the first countershaft. The actuator assembly may be arranged to move the second selector ring into engagement with the first gear element to lock the first gear element for rotation with the first countershaft. The actuator assembly may be arranged to move the second selector ring into engagement with the second gear element to lock the second gear element for rotation with the first countershaft.

[0059] The first gear selector assembly can be arranged to lock the first gear element for rotation with the first countershaft in both positive and reverse torque directions; to lock the first gear element for rotation with the first countershaft in the positive torque direction and unlock it in the reverse torque direction; and to lock the first gear element for rotation with the first countershaft in the reverse torque direction and unlock it in the positive torque direction.

[0060] The first gear selector assembly can be arranged to lock the second gear element for rotation with the first countershaft in both positive and reverse torque directions; to lock the second gear element for rotation with the first countershaft in the positive torque direction and unlock it in the reverse torque direction; and to lock the second gear element for rotation with the first countershaft in the reverse torque direction and unlock it in the positive torque direction.

[0061] The first selector ring can be identical to the second selector ring, which was not the case with previous instantaneous selector assemblies. Using identical selector rings reduces manufacturing costs of the transmission system.

[0062] Each engagement member in the first set of engagement members has a first end and a second end. The first end can include a first drive surface and a first non-drive surface. The second end can include a second drive surface and a second non-drive surface. The first and second drive surfaces are oriented to face the same rotational direction. This differs from conventional instantaneous selector assemblies in which the drive surfaces of any engagement members face opposite rotational directions, making the selector rings incompatible and requiring separate gear selector rings. By orienting the drive surfaces of each engagement member of the selector ring in the same rotational direction, a pair of identical selector rings can be used.

[0063] Each engagement member in the second set of engagement members has a first end and a second end. The first end can include a first drive surface and a first non-drive surface. The second end can include a second drive surface and a second non-drive surface. The first and second drive surfaces are oriented to face the same rotational direction. This differs from conventional instantaneous selector assemblies in which the non-drive surfaces of any engagement members face in opposite rotational directions, making the selector rings incompatible and requiring separate gear selector rings. By orienting the non-drive surfaces of each engagement member of the selector ring in the same rotational direction, a pair of identical selector rings can be used.

[0064] The first selector ring can include a first annular member connecting the first set of engagement members to one another. The first annular member can be recessed to allow the second set of engagement members to pass through the first annular member. This facilitates relative translational movement between the selector rings and allows the annular member to have a relatively large depth, which helps improve the durability of the selector rings.

[0065] The second selector ring can include a second annular member connecting the second set of engagement members to one another. The second annular member can be recessed to allow the first set of engagement members to pass through the first annular member. This facilitates relative translational movement between the selector rings and allows the annular member to have a relatively large depth, which helps improve the durability of the selector rings.

[0066] The first gear selector assembly may be arranged to provide torque support during gear shifting to ensure there is no loss of drive during gear shifting.

[0067] The second gear selector assembly can include a third selector ring. The actuator assembly can include a second shift fork assembly, the second shift fork assembly can include a third shift fork arranged to control axial movement of the third selector ring.

[0068] The actuator assembly may include a second shift collar mounted to the further shift rail, the second shift collar may include a second control member engaging the second control slot, and the shift drum may be arranged to adjust a position of the second control member along the second control slot by adjusting a rotational direction of the second portion of the shift drum, thereby controlling an axial position of the second collar relative to the further shift rail.

[0069] By adjusting the axial position of the second collar on the further shift rail, the axial position of the third shift fork and third selector ring can be adjusted relative to the further shift rail.

[0070] The transmission system includes a first input shaft directly connected to an output of the drive source. The transmission system includes a second input shaft connected to the output of the drive source via a friction clutch. A second gear selector assembly may be mounted on the second input shaft. A third gear element may be rotatably mounted on the second input shaft. A fourth gear element may be rotatably mounted on the second input shaft. The second gear selector assembly may be arranged to selectively lock each of the third and fourth gear elements for rotation with the second shaft. By "directly" it is meant that there is no friction clutch in the drive line between the drive source and the first input shaft. The drive source may be any suitable one, such as a combustion engine or an electric motor. An actuator assembly may be arranged to move the third selector ring into engagement with the third gear element to lock the third gear element for rotation with the second input shaft. An actuator assembly may be arranged to move the third selector ring into engagement with the fourth gear element to lock the fourth gear element for rotation with the second input shaft.

[0071] The odd gears (e.g., 1st gear, 3rd gear, 5th gear) can be grouped together in a first portion of the transmission. The even gears (e.g., 2nd gear, 4th gear, 6th gear) can be grouped together in a second portion of the transmission. The second gear selector assembly can be arranged to select between the odd and even gears by selectively forming torque paths to the first and second portions of the transmission. For example, the odd gears can be drivingly connected to a second countershaft. The even gears can be drivingly connected to a sleeve rotatably mounted on the second countershaft. The second gear selector assembly can be arranged to selectively form a first torque path to the second countershaft. The second gear selector assembly can be arranged to selectively form a second torque path to a sleeve mounted on the second countershaft. The odd side of the transmission can include 1st gear, 3rd gear, and 5th gear. The odd side of the transmission can include further odd gears, such as 7th and 9th gears. The even side of the transmission system can include even gears such as 2nd gear, 4th gear, and 6th gear. The even side of the transmission system can include additional even gears such as 8th gear and 10th gear.

[0072] The third gear selector assembly may include a further selector ring and the actuator assembly may include a further shift fork assembly which may include a further shift fork arranged to control axial movement of the further selector ring.

[0073] The actuator assembly may include a further shift collar mounted on the further shift rail. The further shift collar may include a further control member engaging with the third control slot. The shift drum may be arranged to adjust a position of the further control member along the third control slot by adjusting a rotational direction of the first portion of the shift drum, thereby controlling an axial position of the further collar relative to the further shift rail.

[0074] By adjusting the axial position of the further collar on the further shift rail, the axial position of the further shift fork and the further selector ring can be adjusted relative to the further shift rail.

[0075] The transmission system may include an output shaft. A third gear selector assembly may be mounted on one of the output shaft, the second countershaft, and a sleeve mounted on the second countershaft. At least one further gear element may be rotatably mounted coaxially with the third gear selector assembly. The third gear selector assembly may be arranged to selectively lock the at least one further gear element for rotation with the shaft on which it is mounted. In some embodiments, the third gear selector assembly is arranged to selectively lock the fifth and sixth gear elements to the shaft on which it is mounted.

[0076] The third gear selector assembly may comprise a preselection selector assembly arranged to preselect a new gear before a gear shift takes place. In practice this typically means that a new gear is preselected by the third gear selector assembly before the first gear selector assembly and / or the second gear selector assembly change their operating state during a gear shift, e.g. before selecting a new gear element or before moving to a neutral position.

[0077] The third gear selector assembly may include a further selector ring movable into engagement and disengagement with the further gear element. The further selector ring may be movable into engagement and disengagement with the fifth and sixth gear elements.

[0078] The further selector ring may comprise a gear element arranged to slide axially along the shaft on which it is mounted.

[0079] The transmission system may include at least one additional gear selector assembly, the additional gear selector assembly including a preselection selector assembly configured to preselect a new gear before a gear shift occurs, the additional gear selector assembly including an additional selector ring, the actuator assembly including an additional shift fork assembly, the additional shift fork assembly including an additional shift fork arranged to control axial movement of the additional selector ring, the actuator assembly including an additional shift collar mounted on the additional shift rail, the additional shift collar including an additional control member that engages with a fourth control slot formed in the first portion of the shift drum, the shift drum arranged to adjust a position of the additional control member along the fourth control slot by adjusting a rotational direction of the first portion of the shift drum, thereby controlling an axial position of the additional collar relative to the additional shift rail, and adjusting the axial position of the additional collar on the additional shift rail to adjust the axial position of the further shift fork and the further selector ring relative to the additional shift rail.

[0080] According to another aspect, there is provided a drive train including a drive source, a friction clutch device, and a transmission system according to any of the configurations described herein. The friction clutch device can be a wet friction clutch or a dry friction clutch.

[0081] The present invention has many advantages, including the following: The shifting system is much less complex and easier to control than a DCT type shifting system, and less complex and easier to control than an instantaneous shifting system. Due to the layout of the transmission, the magnitude of the inertia that must be synchronized is relatively small, so the synchronizer capacity is small. In a DCT, the synchronizer capacity is significantly larger. Only one type of synchronizer is required, which reduces manufacturing costs. DCTs often require many different types of synchronizers for different parts of the transmission. The transmission layout and shift strategy employed allows for torque support during at least some gear shifts. The transmission layout is very compact and versatile in the sense that it can be used in front-wheel drive, rear-wheel drive and all-wheel drive vehicles. · Because the layout uses many regular transmission parts, existing production lines can be easily adapted to manufacture this transmission layout. The layout and shift strategy allows the transmission torque to be controlled during gear shifts to eliminate engagement torque spikes, eliminating the need for dampers on any of the gears.

[0082] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which like reference numbers indicate equivalent features and in which: [Brief description of the drawings]

[0083] [Figure 1] 1 is a schematic diagram of a discrete ratio transmission system suitable for use in a vehicle in accordance with an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic isometric front view of two gear selector assemblies used in the transmission of FIG. 1, with associated gear elements shown, and an actuator assembly arranged to operate the gear selector assemblies; [Diagram 3] FIG. 3 is a schematic rear isometric view of the gear selector assembly of FIG. 2, with associated gear elements and actuator assembly shown. [Figure 4] FIG. 3 is a schematic front view of the gear selector assembly of FIG. 2, with associated gear elements shown, and an actuator assembly. [Diagram 5] FIG. 3 is a schematic side view of the gear selector assembly of FIG. 2, with associated gear elements shown, and an actuator assembly. [Figure 6] FIG. 3 is a schematic cross-sectional view of the gear selector assembly of FIG. 2, with associated gear elements and an actuator assembly shown. [Figure 7] FIG. 7 is a schematic enlarged view of a portion of FIG. [Figure 8a] FIG. 3 is an isometric view of first and second gear selector rings from the first gear selector assembly shown in FIG. [Figure 8b] FIG. 8b is an enlarged isometric view of an engagement element from the first gear selector ring of FIG. 8a. [Figure 8c] FIG. 8b is an enlarged isometric view of an engagement element from the second gear selector ring of FIG. 8a. [Figure 9] FIG. 9 is a side view of the pair of selector rings shown in FIG. 8 mounted on the hub and connected to the actuator fork.

[0084] FIG 1 illustrates a drive train including a transmission system 300 according to the present invention, a friction clutch 386, such as a dry friction clutch, and a drive source 380, such as a combustion engine or electric motor. The transmission system is a multi-speed transmission 300. FIG 1 illustrates a six-speed transmission with odd and even gears grouped together. Those skilled in the art will appreciate that the transmission layout can be extended to any number of gears by adding / subtracting gear trains on the odd and / or even sides. The illustrated transmission 300 is particularly suited for vehicles such as motorcycles.

[0085] The transmission system may be arranged as a fully automatic, semi-automatic, or fully manual transmission.

[0086] The transmission system 300 has a first input shaft 301 directly connected to the output of a driving source 380 , and a second input shaft 303 connected to the output of the driving source 380 via a clutch 386 .

[0087] The first input shaft 301 is tubular and is disposed so as to coaxially accommodate a portion of the second input shaft 303 .

[0088] The transmission system includes a countershaft 305. Drive is transferred from a first input shaft 301 to a first countershaft 305 by a gear train comprising a pair of gear elements 302, 304. Gear element 302 is fixed for rotation with the first input shaft. Gear element 304 is fixed for rotation with the first countershaft 305. Gear element 302 meshes with gear element 304.

[0089] The two gear elements 306, 308 are rotatably mounted by bearings on the first countershaft 305. Each gear element 306, 308 is selectively locked for rotation with the first countershaft 305 by a first gear selector assembly 329.

[0090] Gear element 306 meshes with gear element 312, which is rotatably mounted on the second input shaft 303 by a bearing. Gear element 308 meshes with gear element 314, which is rotatably mounted on the second input shaft 303 by a bearing. Gear elements 312, 314 are selectively locked for rotation with the second input shaft 303 by a second gear selector assembly 331. Second selector assembly 331 is a conventional gear selector assembly, such as a synchromesh type selector assembly or a standard selector ring. Each of gear elements 312, 314 includes appropriate engagement mechanisms and / or synchronizing devices.

[0091] The transmission system 300 further includes a countershaft 307 and an output shaft 309. Gear element 312 meshes with gear element 316 which is fixed for rotation with the countershaft 307. Gear element 314 meshes with gear element 318 which is rotatably mounted on the countershaft 307 via a sleeve 330 and a bearing.

[0092] The first through sixth gears are arranged to transfer torque between the countershaft 307 and the output shaft 309. The odd gears are grouped together on a first side of the transmission and the even gears are grouped together on a second side of the transmission. Looking from right to left in FIG. 1, the gears are arranged as follows: 2nd, 6th, 4th, 3rd, 5th, 1st.

[0093] The second gear includes a gear element 332 fixed to rotate with the sleeve 330 and a gear element 334 rotatably mounted on the output shaft 309 via a bearing. The sixth gear includes a gear element 336 rotatably mounted on the sleeve 330 via a bearing and a gear element 338 fixed to rotate with the output shaft 309 and arranged to slide axially along the output shaft 309. The fourth gear includes a gear element 340 fixed to rotate with the sleeve 330 and arranged to slide axially along the sleeve 330 and a gear element 342 rotatably mounted on the output shaft 309 via a bearing.

[0094] Gear element 338 functions as a first preselection device and is arranged to slide into and out of engagement with gear elements 342, 334 to selectively lock gear elements 342 and 334 for rotation with output shaft 309, thereby preselecting fourth gear and second gear, respectively.

[0095] Gear element 340 functions as a second preselection assembly and is positioned to selectively lock gear element 336 for rotation with sleeve 330, thereby preselecting sixth gear.

[0096] The third gear includes a gear element 344 fixed for rotation with the countershaft 307 and a gear element 346 rotatably mounted on the output shaft 309 via a bearing. The gear element 344 is arranged to slide axially along the countershaft 307. The fifth gear includes a gear element 348 rotatably mounted on the countershaft 307 via a bearing and a gear element 350 fixed for rotation with the output shaft 309. The gear element 350 is arranged to slide axially along the output shaft 309. The first gear includes a gear element 352 fixed for rotation with the countershaft 307 and a gear element 354 rotatably mounted on the output shaft 354 via a bearing.

[0097] Gear element 344 functions as a preselection assembly, sliding axially into and out of engagement with gear element 348 to selectively lock gear element 348 for rotation with countershaft 307, thereby preselecting fifth gear. Gear element 350 functions as a preselection assembly, selectively locking gear elements 346, 354 for rotation with output shaft 309, thereby preselecting third and first gears, respectively.

[0098] The pre-selection assemblies 340, 344, 350, 358 are arranged as in a conventional synchromesh type selector device or dog clutch device. The gears selected by the pre-selection assemblies 340, 344, 350, 358 include suitable drive mechanisms that can be engaged by the pre-selection assemblies 340, 344, 350, 358.

[0099] When the second selector assembly 331 is engaged with the gear element 312, a torque path is provided between the second input shaft 303, the countershaft 307, and the odd side of the transmission (i.e., at least one of 1st gear, 3rd gear, and 5th gear). When the second selector assembly 331 is engaged with the gear element 314, a torque path is provided between the second input shaft 303, the sleeve 330, and the even side of the transmission (i.e., at least one of 2nd gear, 4th gear, and 6th gear). Thus, the second selector assembly 331 is positioned to select between the odd and even gears.

[0100] The first selector assembly 329 is configured to engage a first set of drive mechanisms 320 disposed on the gear element 306 and a second set of drive mechanisms 320 disposed on the gear element 308 (see FIG. 1). The drive mechanisms 320 of each gear element 306, 308 each include a group of dogs disposed on a respective side of the gear element 306, 308. Typically, there are three dogs in each group 320. The dogs in a group are evenly distributed circumferentially around the countershaft 305, i.e., the angle between the centers of a pair of dogs is approximately 120 degrees. Three dogs are preferably used because this arrangement provides a relatively large engagement window, i.e., space between the dogs, to receive the engagement members from the first selector assembly 329. Three dogs also provide inherent self-centering and even load distribution. The large engagement window increases the chances that the first selector assembly 329 will fully engage the gear elements 306, 308.

[0101] A first selector assembly 329 is mounted on the countershaft 305 between the drive mechanism 320 which is mounted to the gear elements 306, 308 (see Figures 1 and 4).

[0102] The first gear selector assembly 329 includes first and second sets of engagement members 45, 46 (see Figures 8 and 9). The first set of engagement members 45 includes three members 45a-45c evenly distributed around the countershaft 305. The second set of engagement members 46 includes three members 46a-46c evenly distributed around the countershaft 305.

[0103] The first and second sets of engagement members 45, 46 are mounted on a support 49 which is fixed for rotation with the countershaft 305 (see Figures 7 and 9). The sets of engagement members 45, 46 are arranged to rotate with the countershaft 305 but can slide axially along the support 49, and thus along the countershaft 305, in response to switching movements of the actuator assembly 400. To facilitate this, the support 49 includes six hooks 51 formed in its curved surface, each of which is arranged to engage a channel 52 formed in its respective engagement member 45a-45c, 46a-46c.

[0104] The support 49 includes internal splines 49a arranged to engage external splines formed on the countershaft 305. This provides a very strong connection between the support 49 and the countershaft 305. The spline arrangement locks the support 49, and thus the first and second sets of engagement members 45, 46, for rotation with the countershaft 305.

[0105] The sets of engagement members 45, 46 are arranged such that the members 45a-45c, 46a-46c of each set are alternately arranged on the hooks 51 to allow the member sets 45, 46 to slide along the support 49. The first set of engagement members 45a-45c are rigidly connected to each other by a first annular connector member 53 and move as a unit. Thus, the first set of engagement members 45a-45c and the first annular connector member 53 together form a first gear selector ring 54. The first set of engagement members 45a-45c are evenly distributed around the first annular connector member 53. The second set of engagement members 46a-46c are rigidly connected to each other by a second annular connector member 55 and move as a unit. Thus, the second set of engagement members 46a-46c and the second annular connector member 55 together form a second gear selector ring 56. The second set of engaging members 46a-46c are evenly distributed around the second annular connector member 55. Each set of engaging members 45, 46 are capable of translational movement relative to each other. When there is relative movement between the first and second sets of engaging members 45, 46, the first annular connector member 53 moves on the second set of engaging members 46 and the second annular connector member 55 moves on the first set of engaging members 45.

[0106] The annular connecting members 53, 55 are formed with recesses 60, 62, respectively. The recesses 60 are sized, shaped and positioned to receive the respective second engaging members 46. The recesses 62 are sized, shaped and positioned to receive the respective first engaging members 45. Thus, the number of recesses 60, 62 corresponds to the number of received engaging members 45, 46. The recesses 60, 62 facilitate relative movement of the pairs of engaging members 45, 46.

[0107] The annular connector member 53 can be positioned relative to its engaging members 45 such that the length of each engaging member portion on a first side of the connector member 53 is longer than the length of each engaging member portion on a second side of the connector member. Similarly, the annular connector member 55 can be positioned relative to its engaging members 46 such that the length of each engaging member portion on a first side of the connector member 56 is longer than the length of each engaging member portion on the second side of the connector member. For example, the engaging member portions on the first side of each connecting member 53, 55 can be approximately three to four times the length of the engaging member portions on the second side of each connecting member 53, 55.

[0108] Each of the first set of engagement members 45a-45c has a first end 59 arranged to engage a first group of dogs 320 attached to the gear element 306 and a second end 61 arranged to engage a second group of dogs 320 attached to the gear element 308. The first end 59 of each of the first engagement members 45a-45c is arranged to selectively engage the first group of dogs 320 during deceleration (reverse torque direction) of the gear element 306 and the second end 61 is arranged to selectively engage the second group of dogs 320 during deceleration (reverse torque direction) of the gear element 308. For each of the second set of engagement members 46a-46c, the first end 63 is arranged to engage the second group of dogs 320 during acceleration (positive torque direction) of the gear element 308 and the second end 65 is arranged to engage the first group of dogs 320 during acceleration (positive torque direction) of the gear element 306.

[0109] This arrangement allows the first and second selector rings to be identically positioned relative to one another, as opposed to conventional momentary selector assemblies in which the selector rings are oriented in opposite directions relative to one another. This arrangement reduces manufacturing costs for the first selector assembly 329 since only one type of selector ring 54, 56 is required.

[0110] When both the first and second sets of engagement members 45, 46 are engaged with one of the first and second sets of dogs 320, drive is transmitted in both positive and reverse torque directions between the respective gear elements 306, 308 and the first gear selector assembly 329.

[0111] Each of the first and second ends 59, 61, 63, 65 of the engagement members includes a drive surface 67 for drivingly engaging the respective dog 320, a non-drive surface in the form of a ramp 69, and an end surface 71 (see FIG. 8). The end surface 71 limits axial movement of the engagement members 45a-45c, 46a-46c. In some arrangements, the side surfaces of the dogs 320 may be ramped. In this case, the drive surface 67 may be angled to complement the side surfaces of the dogs 320 to provide face-to-face contact to reduce wear as the engagement members 45a-45c, 46a-46c rotate into engagement. The purpose of the non-drive surface 69 is to prevent locking engagement between the engagement members and the dogs 320. Each non-drive surface 69 is preferably helically shaped and ramped away from the respective end surface 71. The angle of inclination of the non-drive surface 45 may be such that the longitudinal distance between the edge of the non-drive surface furthest from the end surface 71 and the plane of the end surface 71 is greater than the height of the dog 320. This may prevent the transmission from locking up if there is relative rotational motion between the engagement members 45a-45c, 46a-46c and the dog 320 such that the non-drive surface 69 moves towards the respective dog 320. The dog 320 does not strike the side of the engagement members 45a-45c, 46a-46c, but rather engages with the non-drive surface 69. Further relative rotational motion between the dog 320 and the engagement members 45a-45c, 46a-46c causes the dog 320 to slide across the non-drive surface 69 and the inclined surface of the non-drive surface causes the engagement members 45a-45c, 46a-46c to move axially along the countershaft 305 away from the respective dog 320 such that the transmission does not lock up. The non-drive surface 69 thus provides a ratchet effect such that the first gear selector assembly 329 is positioned to slip relative to the gear elements 306, 308, respectively, under certain operating conditions.

[0112] In this manner, the first selector assembly 329 is arranged to selectively engage the gear element 306 in the following operational modes: locking the gear element 306 for rotation with the shaft 305 in both positive and reverse torque directions, locking the gear element 306 for rotation with the shaft 305 in the positive torque direction but not locked in the reverse torque direction, and locking the gear element 306 for rotation with the shaft 305 in the reverse torque direction but not locked in the positive torque direction.

[0113] When the gear element 306 is locked for rotation in the positive and negative torque directions (engaged by the first and second sets of engagement members 45, 46), one of the first and second sets of engagement members 45, 46 is in a loaded state and the other of the first and second sets of engagement members 45, 46 is in an unloaded state. The actuator assembly 400 is arranged to selectively move the unloaded set of engagement members 45, 46 out of engagement with the currently engaged gear element 308, for example to a neutral position.

[0114] The first selector assembly 329 is arranged to selectively engage the gear element 308 in the following operational modes: locking the gear element 308 for rotation with the shaft 305 in both positive and reverse torque directions, locking the gear element 308 for rotation with the shaft 305 in the positive torque direction but not locked in the reverse torque direction, and locking the gear element 308 for rotation with the shaft 305 in the reverse torque direction but not locked in the positive torque direction.

[0115] When the gear element 308 is locked (engaged by the first and second sets of engagement members 45, 46) for rotation in the positive and negative torque directions, one of the first and second sets of engagement members 45, 46 is in a loaded state and the other of the first and second sets of engagement members 45, 46 is in an unloaded state. The actuator assembly 400 is arranged to selectively move the unloaded set of engagement members 45, 46 out of engagement with the currently engaged gear element 306, for example to a neutral position. The first selector assembly 329 can be in a neutral (disengaged) state with respect to the gear elements 306, 308.

[0116] When the first and second sets of members 45, 46 are fully engaged with the gear element 306, the dog 320 is located between each pair of drive faces 67 of the first end 59 of the first set of members 45 and the second end 65 of the second set of members 46. When the first and second sets of members 45, 46 are fully engaged with the gear element 308, the dog 320 is located between the drive faces 67 of the second end 63 of the first set of members 45 and adjacent the drive faces 67 of the first end 61 of the second set of members 46. The dimensions of the dog 320 and the ends 59, 61, 63, 65 of the engagement members ensure that there is little movement of each dog between the drive faces 67 of the acceleration members and the drive faces 67 of the deceleration members as the gear elements 306, 308 move from acceleration to deceleration or vice versa, ensuring that the gears have little or no backlash. Backlash is the lost motion experienced when the dog moves from the driving surface 67 of the acceleration member to the driving surface 67 of the deceleration member, or vice versa, when moving from acceleration to deceleration. Backlash in a conventional dog-type transmission is about 30 degrees. The backlash in a typical automotive transmission according to the present embodiment is less than 5 degrees.

[0117] The transmission system includes a first selector assembly 329, a second selector assembly 331, and an actuator assembly 400 arranged to control operation of at least one pre-selection assembly 340, 344, 350, 358, typically a plurality of pre-selection assemblies 340, 344, 350, 358. In some arrangements, the actuator assembly 400 is arranged to control operation of each of the pre-selection assemblies 340, 344, 350, 358.

[0118] The actuator assembly 400 includes a shift drum 401. The shift drum 401 includes a first portion 403 and a second portion 405. The first portion includes a shaft 407 having a flange 407a located at a first end 411 of the shaft. A sleeve 413 is mounted on the shaft 407 toward a second end 415 of the first shaft 407. The sleeve 413 is fixed for rotation with the shaft 407, for example, by a spline arrangement. The first portion 403 includes a plurality of control slots 409 formed therein. For example, the control slot 409a can be formed in an outer curved surface of the flange 407a. The outer curved surface of the sleeve 413 can include a plurality of control slots 409b-409c formed therein. Typically, the number of control slots 409 formed in the outer curved surface corresponds to the number of pre-selector assemblies 340, 344, 350, 358 (for illustrative purposes, only three control slots 409a-409c are shown in the figures). The second part comprises a sleeve 417 rotatably mounted by bearings on the shaft 407. The sleeve 417 has an outer curved surface which defines a plurality of control slots 419, 421.

[0119] The actuator assembly 400 includes a drive system arranged to selectively rotate the first portion 403 of the shift drum and the second portion 405 of the shift drum, such that the second portion 405 of the shift drum is rotated independently of the first portion 403 of the shift drum. The first portion 403 includes a gear element 423 fixed for rotation with the shaft 407 and the sleeve 413. The second portion 405 includes a gear element 425 fixed for rotation with the sleeve 417. The drive system includes a first electric motor 427 and a first worm gear 429. The first worm gear is in meshing engagement with the gear element 423. The first electric motor is arranged to selectively rotate the first portion 403 (shaft 407 and sleeve 413) by driving the first worm gear 429, which in turn rotates the gear element 423. The drive system includes a second electric motor 431 and a second worm gear 433. The second worm gear 433 is in meshing engagement with the gear element 425. The second electric motor is positioned to selectively rotate the second portion 405 (sleeve 417) by driving the second worm gear 433, which in turn rotates the gear element 425. A control system and / or switching devices (not shown) may be used to control the operation of the first and second electric motors 427, 431.

[0120] The selector assembly 400 includes a first shift fork assembly 433 arranged to control the operation of the first selector assembly 329. The first shift fork assembly 433 includes a shift rail 435, a shift rail 437, a shift collar 439, a first shift fork 441, and a second shift fork 443.

[0121] The shift collar 439 includes a sleeve 445 mounted to the shift rail 435 and arranged to slide axially along the shift rail 435. The shift collar 439 includes a control member 447 protruding radially outward from the sleeve 445. One end of the control member 447 is located within a control slot 419 formed in the sleeve 417. As the sleeve 417 rotates, the control member 447 moves along the control slot 419, and the axial position of the shift collar 439 relative to the shift rail 435 is adjusted due to the serpentine nature of the control slot 419. The shift collar 439 includes an arm 449 protruding radially outward from the sleeve 445 in a direction generally opposite to the direction in which the control member 447 protrudes. The arm 449 has a through hole through which the shift rail 437 passes. The arm 449 is fixed to the shift rail 437, for example the arm can be pinned to the shift rail 437. When the axial position of sleeve 445 is adjusted relative to shift rail 435, the axial position of shift rail 437 is similarly adjusted.

[0122] The first shift fork 441 is positioned to control the movement of the first set of engagement members 45. The first shift fork 441 includes a sleeve 441a and a bifurcated member 441b. The sleeve 441a is mounted on the shift rail 437 between a first stop 451a and an arm 449. A helical spring 453 is mounted between the first stop 451a and the sleeve 441a, and a helical spring 455 is located between the sleeve 441a and the arm 449. The bifurcated member 441b is positioned to engage the first annular connector member 53 and adjust the axial position of the first set of engagement members 45 relative to the first countershaft 305, thereby selectively moving the first set of engagement members 45 into and out of engagement with dogs 320 on the gear elements 306, 308 mounted on the first countershaft 305. The helical springs 453, 455 are positioned to bias the first shift fork 441 to a neutral position, i.e., a position in which the first set of engagement members 45 are not engaged with either of its gear elements 306, 308. The helical springs 453, 455 also damp movement of the first shift fork 441.

[0123] The second shift fork 443 is positioned to control the movement of the second set of engagement members 45. The second shift fork 443 includes a sleeve 443a and a bifurcated member 443b. The sleeve 443a is mounted on the shift rail 437 between the second stop 451b and the arm 449. A helical spring 457 is mounted between the second stop 451b and the sleeve 443a, and a helical spring 459 is located between the sleeve 443a and the arm 449. The bifurcated member 443b is positioned to engage the second annular connector member 55 and adjust the axial position of the second set of engagement members 46 relative to the first countershaft 305, thereby selectively moving the second set of engagement members 46 into and out of engagement with dogs 320 on the gear elements 306, 308 mounted on the first countershaft 305. The helical springs 457, 459 are positioned to bias the second shift fork 443 to a neutral position, i.e., a position in which the second set of engagement members 46 is not engaged with either of its gear elements 306, 308. The helical springs 457, 459 also damp movement of the second shift fork 443.

[0124] The selector assembly 400 includes a second shift fork assembly 461 arranged to control the operation of the second selector assembly 331. The second shift fork assembly 461 includes a shift rail 463, a shift collar 465, and a third shift fork 467.

[0125] The shift collar 465 includes a sleeve 469 mounted to the shift rail 463 and arranged to slide axially along the shift rail 463. The shift collar 465 includes a control member 471 that projects radially outward from the sleeve 469. One end of the control member 471 is located within a control slot 421 formed in the sleeve 417. As the sleeve 417 rotates, the control member 471 moves along the control slot 421 and, due to the serpentine nature of the control slot 421, the axial position of the shift collar 465 is adjusted relative to the shift rail 463. A third shift fork 467 projects radially outward from the sleeve 469 in a direction generally opposite to the direction in which the control member 471 projects.

[0126] The third shift fork 467 is positioned to control the operation of a conventional selector ring 473 that is part of the second selector assembly 331. Axial movement of the sleeve 469 along the shift rail 463 adjusts the axial position of the selector ring 473 relative to the second input shaft 303 to selectively engage and lock the gear elements 312, 314 for rotation therewith. With the selector ring 473 engaged with the gear element 312, a torque path is established between the second input shaft 303 and the odd gears (first, third, fifth gears), with the gear actually selected being determined by the position of the pre-selection assemblies 344, 350. With the selector ring 473 engaged with the gear element 314, a torque path is established between the second input shaft 303 and the even gears (second, fourth, sixth gears), with the gear actually selected being determined by the position of the pre-selection assemblies 338, 340.

[0127] It will therefore be apparent that the direction of rotation of the second portion 405 of the shift drum determines the operative positions of the first, second and third shift forks 441 , 443 , 467 and thus the operative states of the first and second selector assemblies 329 , 331 .

[0128] A plurality of shift forks (not shown) operatively connected to respective ones of the control slots 409a-409c of the first portion 403 of the shift drum are arranged to adjust the axial positions of the preselection assemblies 338, 340, 344, 350. Thus, the direction of rotation of the first portion 403 of the shift drum determines the operative positions of the plurality of shift forks and thus at least some, and preferably each, of the preselection assemblies 338, 340, 344, 350. Thus, in some embodiments, only a single shift drum 401 is required for the entire transmission.

[0129] The transmission provides torque support during power-on upshifts, power-on downshifts, power-off shifts, and power-off downshifts. Thus, there is no loss of drive on the output shaft during gear shifts. The transmission thus provides seamless shifting for all major shift types by preselecting the appropriate gear and then controlling torque using the first and second selector devices 329, 331. By synchronizing the drive source and / or clutch speed with the new gear before making the shift, a substantially shock-free engagement can be provided.

[0130] Some examples of shift sequences and relative positions of the selector assemblies are shown in the table below. In the table below, for the first selector assembly 329, "N" indicates neutral, "E" indicates that gear element 308 is engaged and "O" indicates that gear element 306 is engaged. For the second selector assembly 331, "E" indicates that gear element 314 is engaged and "O" indicates that gear element 312 is engaged. The control slots 409a-409c in the first shift drum part 403 and the control slots 419, 421 in the second shift drum part 405 are positioned to operate the respective selector assemblies accordingly. [Table 1] [Table 2] [Table 3] [Table 4]

[0131] It will be appreciated by those skilled in the art that modifications can be made to the above embodiments that fall within the scope of the present invention, for example, the transmission can include a different number of gears, such as a 7-speed, 8-speed, 9-speed or 10-speed transmission.

[0132] The number of control slots 409 formed in the first portion 403 of the shift drum may vary. The number of control slots 409 formed in the first portion 403 of the shift drum may vary from the number of pre-selector assemblies. If more pre-selection gear selector assemblies are required, additional shift drums may be required.

[0133] The description presents exemplary embodiments and, together with the drawings, serves to explain the principles of the present invention. However, the scope of the present invention is not intended to be limited to the exact details of the embodiments, since variations are obvious to those skilled in the art and are deemed to be encompassed by the claims. The terms of components used in this specification should be given a broad interpretation that includes equivalent functions and features. In some cases, some alternative terms (synonyms) are provided for structural features, but such terms are not intended to be exhaustive.

[0134] Descriptive terms should also be interpreted as broadly as possible: for example, the term "comprising" as used herein means "including" so that each statement in this specification containing the term "comprising" may be interpreted to include features other than the term or the term preceded by it. Related terms such as "comprise" and "comprises" should be interpreted similarly. Terms indicating directions such as "vertical", "horizontal", "up", "down", "upper" and "lower" may be used for convenience of description, usually with reference to the figures, and are not intended to be ultimately limiting, where equivalent functions can be achieved with alternative dimensions and / or orientations.

[0135] Although reference is made herein to embodiments having specific combinations of constituent steps or features, it is envisioned that further combinations and intercombinations of steps or features that are compatible between the embodiments are possible. Indeed, separate features may function as inventions independently of other features and do not necessarily have to be implemented as a complete combination. Any feature of an embodiment may be separated from that embodiment and included in any other embodiment.

Claims

1. 1. A transmission system including a first gear selector assembly, the first gear selector assembly including a first selector ring and a second selector ring, the first and second selector rings being translatable relative to one another, the first selector ring including a first set of engagement members secured to one another by a first annular member, each engagement member of the first set including a first portion located on a first side of the first annular member and a second portion located on a second side of the first annular member, each first portion having a first drive surface oriented generally in a first rotational direction and a first non-drive surface oriented generally in a second rotational direction, each second portion having a first drive surface oriented generally in a first rotational direction and a second non-drive surface oriented generally in a second rotational direction. a second drive surface oriented generally in the second rotational direction and a second non-drive surface oriented generally in the second rotational direction, the second selector ring including a second set of engagement members secured to one another by a second annular member, each engagement member of the second set including a first portion located on a first side of the second annular member and a second portion located on a second side of the second annular member, each first portion having a first drive surface oriented generally in the second rotational direction and a first non-drive surface oriented generally in the first rotational direction, and each second portion including a second drive surface oriented generally in the second rotational direction and a second non-drive surface oriented generally in the first rotational direction.

2. 2. The transmission system of claim 1, wherein said first selector ring is identical to said second selector ring.

3. 3. The transmission system of claim 1 or 2, wherein said engagement members in said first set of engagement members are evenly angularly distributed around said first annular member.

4. 4. A transmission system according to claim 1, 2 or 3, wherein the engagement members in the second set of engagement members are evenly angularly distributed around the second annular member.

5. 5. The transmission system of claim 1, wherein the first selector ring includes a first set of recesses formed through the first annular member, each recess in the first set of recesses sized, shaped and positioned to receive a respective one of the engagement members in the second set of engagement members.

6. 6. The transmission system of claim 1, wherein the second selector ring includes a second set of recesses formed through the second annular member, each recess in the second set of recesses being sized, shaped and positioned to receive a respective one of the engagement members in the second set of engagement members.

7. 7. A transmission system according to claim 1 including an actuator assembly arranged to control movement of the first and second selector rings.

8. 8. A transmission system as claimed in any one of claims 1 to 7, wherein the first selector assembly is mounted on a shaft, a first gear element is rotatably mounted on the shaft, and a second gear element is rotatably mounted on the shaft, the first selector assembly being arranged to selectively lock the first and second gear elements for rotation with the first shaft.

9. The transmission system of claim 8 , wherein said shaft comprises a first countershaft.

10. 10. The transmission system of claim 8 or 9, wherein the first gear selector assembly is arranged to selectively engage the first gear element in the following operational modes: locking the first gear element for rotation with the shaft in positive and reverse torque directions; locking the first gear element for rotation with the shaft in the positive torque direction and unlocking it in the reverse torque direction; locking the first gear element for rotation with the shaft in the reverse torque direction and unlocking it in the positive torque direction.

11. 11. The transmission system of claim 1, wherein with the first gear element engaged by the first and second sets of engaging members and locked for rotation in positive and reverse torque directions, one of the first and second sets of engaging members is in a loaded condition and the other of the first and second sets of engaging members is in an unloaded condition.

12. A transmission system according to claim 11 when dependent on claim 7, wherein the actuator assembly is arranged to selectively move the unloaded set of engagement members out of engagement with the first gear element, such as to a neutral position.

13. 13. A transmission system as claimed in any one of claims 1 to 12, wherein the first gear selector assembly is arranged to selectively engage the second gear element in the following operational modes: locking the second gear element for rotation with the shaft in positive and reverse torque directions; locking the second gear element for rotation with the shaft in the positive torque direction and unlocking it in the reverse torque direction; and locking the second gear element for rotation with the shaft in the reverse torque direction and unlocking it in the positive torque direction.

14. 14. A transmission system as claimed in any one of claims 1 to 13, wherein with the second gear element engaged by the first and second sets of engaging members and locked for rotation in positive and reverse torque directions, one of the first and second sets of engaging members is in a loaded condition and the other of the first and second sets of engaging members is in an unloaded condition.

15. A transmission system according to claim 14 when dependent on claim 7, wherein the actuator assembly is arranged to selectively move the unloaded set of engagement members out of engagement with the second gear element, such as to a neutral position.

16. 16. A transmission system according to any one of claims 8 to 15, wherein the first selector assembly is mounted on the shaft by a support sleeve, the support sleeve including internal splines arranged to lock the support sleeve for rotation with the shaft.

17. 17. The transmission system of claim 16, wherein at least one, and preferably each, of the engagement members in the first set of engagement members includes a linear feature formed on an inwardly facing side and positioned to engage a complementary feature on the support sleeve.

18. 18. A transmission system as claimed in claim 16 or 17, wherein at least one, and preferably each, of the engagement members in the second set of engagement members includes a linear feature formed on an inwardly facing side and arranged to engage a complementary feature on the support sleeve.

19. 19. A transmission system as claimed in any one of the preceding claims, wherein the first gear selector assembly is arranged to provide torque support during gear shifting to ensure there is no loss of drive during the gear shift.

20. 20. A transmission system as claimed in any preceding claim when dependent on claim 7, including a second gear selector assembly and a third gear selector assembly, the actuator assembly being arranged to control operation of the second and third gear selector assemblies.

21. 21. The transmission system of claim 20, wherein the actuator assembly includes a shift drum having a first and second portion, the second portion arranged to rotate relative to the first portion, the second portion including a first control slot arranged to control operation of the first selector assembly and a second control slot arranged to control operation of the second gear selector assembly, and the first portion including a third control slot arranged to control operation of the third gear selector assembly.

22. 22. A transmission system according to any one of claims 1 to 21 when dependent on claim 7, wherein the actuator assembly includes a first shift fork assembly including a first shift fork arranged to control axial movement of the first selector ring and a second shift fork arranged to control axial movement of the second selector ring.

23. 23. A transmission system according to any one of claims 1 to 22 when dependent on claim 7, wherein the actuator assembly includes a first shift collar mounted on a first shift rail, the first shift collar including a first control member engaging the first control slot, and the shift drum arranged to adjust the position of the first control member along the first control slot which controls the axial position of the first collar relative to the first shift rail by adjusting the rotational direction of the second portion of the shift drum.

24. 24. A transmission system according to any one of claims 1 to 23 when dependent on claim 20, wherein the second gear selector assembly includes a third selector ring, and the actuator assembly includes a second shift fork assembly, the second shift fork assembly including a third shift fork arranged to control axial movement of the third selector ring.

25. 25. The transmission system of claim 1, comprising a first input shaft directly connected to the output of a drive source, and a second input shaft connected to the output of the drive source via a friction clutch.

26. 26. A transmission as claimed in claim 25 when dependent on claim 20, wherein the second gear selector assembly is mounted on the second input shaft, a third gear element is rotatably mounted on the second input shaft, and a fourth gear element is rotatably mounted on the second input shaft, the second gear selector assembly being arranged to selectively lock each of the third and fourth gear elements for rotation with the second input shaft.

27. 27. A transmission system as claimed in any one of the preceding claims when dependent on claim 20, wherein odd gears are grouped together in a first portion of the transmission and even gears are grouped together in a second portion of the transmission, and the second gear selector assembly is arranged to select between the odd and even gears by selectively forming a torque path to the first and second portions of the transmission.

28. 28. A transmission system according to any one of claims 1 to 27, wherein the third gear selector assembly includes a further selector ring and the actuator assembly includes a further shift fork assembly, the further shift fork assembly including a further shift fork arranged to control axial movement of the further selector ring.

29. 29. A transmission system according to any one of claims 1 to 28, including an output shaft, the third gear selector assembly being mounted on one of the output shaft, the second counter shaft and a sleeve mounted on the second counter shaft, and at least one further gear element being rotatably mounted coaxially with the third gear selector assembly, the third gear selector assembly being arranged to selectively lock the at least one further gear element for rotation with the shaft on which it is mounted.

30. 30. A transmission system according to any one of claims 1 to 29, wherein the third gear selector assembly comprises a preselection selector assembly arranged to provide a new preselection.

31. A drive train comprising a drive source, a friction clutch device, and a speed change system according to any one of claims 1 to 30.

32. 32. The drive train of claim 31, wherein the friction clutch device is a wet friction clutch or a dry friction clutch.

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