TRANSMISSION WITH SINGLE RAIL SHIFT MECHANISM BACKGROUND AND SUMMARY

The present invention relates generally to transmissions and, more particularly, to transmissions with a single rail shift mechanism. In transmissions of the type having a single rail shift mechanism, hubs carrying forks are mounted on a rail. A single hub is engaged with the rail at a time and axial movement of the rail causes axial movement of that hub and its associated fork. The fork is disposed in a groove of a sliding jaw clutch splined to a transmission main shaft. When the rail, hub, and fork are axially moved, the fork urges the sliding jaw clutch to slide on the transmission main shaft until it engages a main shaft gear connected to a drive shaft. Power is thus transmitted from the transmission main shaft to the drive shaft through the sliding jaw clutch and the main shaft gear. It is imperative in such structures that only a single hub be axially moved upon axial movement of the rail because of the damage that could result from two or more forks moving two or more sliding jaw clutches against two or more main shaft gears at the same time. It is desirable to provide a simple arrangement for engaging a single hub of a plurality of hubs on a single rail, and for ensuring that disengaged hubs do not move axially upon axial movement of the rail.

According to an aspect of the present invention, a single rail shift mechanism comprises a rail comprising a plurality of depressions disposed at different axial and radial positions along a length of and a circumference of the rail. The mechanism also comprises a plurality of hub assemblies mounted relative to the rail to permit the hub assemblies to move axially relative to the rail, each hub assembly comprising a hub, the hub comprising a wall disposed at least partially around the rail and at least one through hole extending through the wall. The

mechanism also comprises a plurality of spring loaded ball arrangements corresponding to the plurality of depressions in the rail, each spring loaded ball arrangement comprising a ball that is urged toward the rail through the through hole of one of the plurality of hub assemblies. At least one ball of the plurality of spring loaded ball arrangements is urged into a depression of the plurality of depressions when the rail is rotated to one of a plurality of predetermined rotational positions relative to the plurality of spring loaded ball arrangements such that the at least one ball is partially disposed in the depression and partially disposed in the through hole.

According to another aspect of the present invention, a transmission cover comprise a cover body, a plurality of bored members associated with the cover body, each bored member comprising at least one bore, the bored members defining a plurality of supports for shift fork assemblies, each support comprising an opening defined by a partial cylinder extending more than 180° and less than 360° around an axis of the opening, and, in each bore of the plurality of bored members, a spring and a ball arranged so that the spring urges the ball outwardly toward the opening. According to yet another aspect of the present invention, a transmission comprises a rail comprising a plurality of depressions disposed at different axial and radial positions along a length of and a circumference of the rail. The transmission also comprises a plurality of hub assemblies mounted relative to the rail to permit the hub assemblies to move axially relative to the rail, each hub assembly comprising a hub, the hub comprising a wall disposed at least partially around the rail and at least one through hole extending through the wall, and a fork extending from the hub. The transmission also comprises a plurality of spring loaded ball arrangements corresponding to the plurality of depressions in the rail, each spring loaded ball arrangement comprising a ball that is urged toward the rail through the through hole of one of the

plurality of hub assemblies. A plurality of sliding jaw clutches is attached to a transmission main shaft such that the sliding jaw clutches are movable along an axis of the transmission main shaft, each sliding jaw clutch having a groove in which a fork of a corresponding one of the plurality of hub assemblies is disposed. A plurality of main shaft gears is disposed on opposite sides of the plurality of sliding jaw clutches in a direction of the axis of the transmission main shaft. At least one ball of the plurality of spring loaded ball arrangements is urged into a depression of the plurality of depressions when the rail is rotated to one of a plurality of predetermined rotational positions relative to the plurality of spring loaded ball arrangements such that the at least one ball is partially disposed in the depression and partially disposed in the through hole of a hub assembly and axial movement of the rail relative to the spring loaded ball arrangements moves a fork of the hub assembly which moves a sliding jaw clutch against a main shaft gear.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understood by reading the following detailed description in conjunction with the drawings in which like numerals indicate similar elements and in which:

FIG. 1 is a side, partially cross-sectional view of a transmission according to an embodiment of the present invention;

FIGS. 2A, 2B, and 2C are schematic, cross-sectional views at sections A-A, B-B, and C- C of a rail shown schematically in perspective in FIG. 2D according to an embodiment of the present invention;

FIGS. 3 A, 3B, and 3C are schematic, partially cross-sectional views of a transmission according to an embodiment of the present invention in neutral, in a first power transmission mode, and in a second power transmission mode, respectively;

FIGS. 4A-4E are schematic, partially cross-sectional views of portion of a rail and a hub assembly in different positions relative to portions of a support structure according to an embodiment of the present invention;

FIG. 5 is a schematic, partially cross-sectional view of a rail in a support structure according to an embodiment of the present invention; and

FIGS. 6A-6B are schematic, partially cross-sectional views of a portion of a rail and a hub assembly in different positions relative to portions of a support structure according to an embodiment of the present invention, and FIG. 6C is a partially cross-sectional view taken at section 6C-6C of FIG. 6B.

DETAILED DESCRIPTION A transmission 21 according to an embodiment of the present invention is shown in FIG.

1. The transmission 21 may have a variety of uses but it is anticipated that it will ordinarily be used to shift gears in a motor vehicle such as in a heavy duty truck transmission.

The transmission 21 comprises a single rail shift assembly 23. The single rail shift assembly 23 comprises a rail 25. As seen in exaggerated fashion in FIGS. 2A-2D, the rail 25 is ordinarily generally circularly cylindrical. The rail 25 ordinarily comprises a plurality of depressions 27a, 27b, 29a, 29b, 31a, 31b disposed at different predetermined axial and radial positions along a length of and a circumference of the rail, respectively. In FIG. 2D, three sets of depressions are shown at three predetermined axial positions A, B, and C, however, it will be

appreciated that embodiments of the invention may have depressions at fewer or more than three axial positions. In FIG. 2D, a first set of depressions 27a and 27b is disposed at a first axial position A and oriented at 180° to each other around the circumference of the rail, a second set of depressions 29a and 29b is disposed at a second axial position B and oriented at 180° to each other around the circumference of the rail, and a third set of depressions 31a and 31b is disposed at a third axial position C and oriented at 180° to each other around the circumference of the rail.

While embodiments in which two depressions are provided at each predetermined axial position and oriented at 180° to each other are described herein, it will be appreciated that it is possible to have as few as one depression at each predetermined axial position, and there is no theoretical limit to the number of depressions that can be provided at each predetermined axial position. It is also not necessary that two depressions be oriented at 180° to each other. The one or more depressions at each predetermined axial position are oriented at different circumferential positions than the depressions at any other predetermined axial position. As seen in FIGS. 2 A, 2B, and 2C, the three sets of depressions each comprise two depressions oriented at 180° to each other, with each set being radially offset 60° relative to any other set. It will be appreciated that the embodiment of FIG. 2D is merely illustrative and depressions or sets of depressions at different axial positions can be offset at radial angles other than 60°.

A plurality of hub assemblies 33a, 33b, 33c is mounted relative to the rail 25 at positions corresponding to the predetermined axial positions A, B, C. The hub assemblies 33a, 33b, 33c are mounted so as to ordinarily permit the hub assemblies to move axially and rotationally relative to the rail except as otherwise explained. Three hub assemblies 33a, 33b, 33c are shown, however, it will be appreciated that more or fewer hub assemblies may be provided. Each hub assembly 33a, 33b, 33c comprises a hub 35, the hub comprising a wall 37 disposed at least

partially around the rail 25 and at least one through hole 39 extending through the wall, and a fork 41 extending radially from the hub. Ordinarily, there will be as many through holes 39 extending through the wall 37 of each hub 35 as there are depressions at the predetermined axial position to which the hub assembly corresponds, with the holes oriented around the circumference of the hub at the same angle relative to each other as the depressions at the predetermined axial position. For example, if there are two depressions at a predetermined axial position, and they are oriented at 180° to each other, the through holes 39 in the hub 35 of the hub assembly to be disposed at that axial position will also be oriented at 180° to each other.

As seen in FIG. 1, a plurality of spring loaded ball arrangements 43a, 43b, 45a, 45b, 47a, 47b corresponds to the plurality of depressions 27a, 27b, 29a, 29b, 31a, 31b in the rail 25. As seen, for example, with reference to the spring loaded ball arrangements 43 a and 43b associated with the hub assembly 33a in FIGS. 4A-4E, each spring loaded ball arrangement comprises a ball 49 that is urged toward the rail 25 through the through hole 39 of one of the plurality of hub assemblies 33a, 33b, 33c. A spring 51 or other elastic member can be provided to urge the ball toward the rail 25. As seen in FIG. 1, the spring loaded ball arrangements are ordinarily disposed in bores (see bores 53a, 53b in FIGS. 4A-4E) in support structures 53, 55, 57 that can form part of a transmission cover 59. The support structures 53, 55, 57 can, for example, be cast together with the transmission cover 59, or can be otherwise secured to the transmission cover or some other structure in any suitable fashion, such as by bolting, welding, or the like. A plurality of sliding jaw clutches 61, 63, 65 is attached to a transmission main shaft 67 such that the sliding jaw clutches are movable along an axis AT of the transmission main shaft. Each sliding jaw clutch 61, 63, 65 has a groove 71, 73, 75 in which a fork 41 of a corresponding one of the plurality of hub assemblies 33a, 33b, 33c is disposed.

A plurality of main shaft gears is provided, with a pair being disposed on opposite sides of each of the plurality of sliding jaw clutches 61, 63, 65 in a direction of the axis AT of the transmission main shaft. In the embodiment illustrated in FIG. 1, a pair 77 and 79 is disposed on opposite sides of the sliding jaw clutch 61, a pair 81 and 83 is disposed on opposite sides of the sliding jaw clutch 63, and a pair 85 and 87 is disposed on opposite sides of the sliding jaw clutch 65.

A selector lever 89 is typically secured to the rail 25 so that the selector lever is not axially or rotationally movable relative to the rail. The selector lever 89 can be moved by a conventional shift lever arrangement 91 to rotate or axially move the rail 25 relative to the spring loaded ball arrangements in the support structures 53, 55, 57. In the embodiment of FIG. 1, when an operator moves the shift lever arrangement 91, the selector lever 89 and the rail 25 are moved.

When the rail 25 is rotated to a first one of a plurality of predetermined rotational positions relative to the plurality of spring loaded ball arrangements, the balls 49 of two of the plurality of spring loaded ball arrangements 43 a and 43b are urged into depressions 27a and 27b of the plurality of depressions such that the balls are partially disposed in the depressions and partially disposed in the through holes of the hub assembly 33a. Axial movement of the rail 25 relative to the spring loaded ball arrangements 43a, 43b, 45a, 45b, 47a, 47b moves a fork 41 of the hub assembly 33a which moves a sliding jaw clutch 61 against one of the pair of main shaft gears 77 and 79 on opposite sides of the sliding jaw clutch.

When the rail 25 is rotated to a second one of the plurality of predetermined rotational positions relative to the plurality of spring loaded ball arrangements, the balls 49 of another two of the plurality of spring loaded ball arrangements 45 a and 45b are urged into depressions 29a

and 29b of the plurality of depressions such that the balls are partially disposed in the depressions and partially disposed in the through holes of the hub assembly 33b. Axial movement of the rail 25 relative to the spring loaded ball arrangements 43a, 43b, 45a, 45b, 47a, 47b moves a fork 41 of the hub assembly 33b which moves a sliding jaw clutch 63 against one of the pair of main shaft gears 81 and 83 on opposite sides of the sliding jaw clutch.

When the rail 25 is rotated to a third one of the plurality of predetermined rotational positions relative to the plurality of spring loaded ball arrangements, the balls 49 of another two of the plurality of spring loaded ball arrangements 47a and 47b are urged into depressions 31a and 31b of the plurality of depressions such that the balls are partially disposed in the depressions and partially disposed in the through holes of the hub assembly 33c. Axial movement of the rail 25 relative to the spring loaded ball arrangements 43a, 43b, 45a, 45b, 47a, 47b moves a fork 41 of the hub assembly 33c which moves a sliding jaw clutch 65 against one of the pair of main shaft gears 85 and 87 on opposite sides of the sliding jaw clutch.

When a sliding jaw clutch is moved from a neutral position as shown schematically in FIG. 3 A in which it is not in contact with any of the main shaft gears to a position in which it is in contact with a main shaft gear, power is transmitted from the transmission main shaft 67 to the sliding jaw clutches which are ordinarily sp lined to the transmission main shaft, to the one of the main shaft gears in contact with the sliding jaw clutch, and then, ordinarily through other gears G to a drive shaft 93. FIG. 3B shows the hub assembly 33a and its associated fork 41 moved axially forward relative to the support structure 53, which moves the sliding jaw clutch 61 forward against the main shaft gear 77, so that power is transmitted from the transmission main shaft 67 to the drive shaft 93 through the sliding jaw clutch 61 and the main shaft gear 77. FIG. 3 C shows the hub assembly 33a and its associated fork 41 moved axially rearward relative to the

support structure 53, which moves the sliding jaw clutch 61 rearward against the main shaft gear 79, so that power is transmitted from the transmission main shaft 67 to the drive shaft 93 through the sliding jaw clutch 61 and the main shaft gear 79. In similar fashion, power is transmitted from the transmission main shaft 67 to the drive shaft 93: through the sliding jaw clutch 63 and the main shaft gear 81 when the hub assembly 33b and its associated fork 41 are moved axially forward relative to the support structure 55; through the sliding jaw clutch 63 and the main shaft gear 83 when the hub assembly 33b and its associated fork 41 are moved axially rearward relative to the support structure 55; through the sliding jaw clutch 65 and the main shaft gear 85 when the hub assembly 33c and its associated fork 41 are moved axially forward relative to the support structure 57; and through the sliding jaw clutch 65 and the main shaft gear 87 when the hub assembly 33c and its associated fork 41 are moved axially rearward relative to the support structure 57. The particular power transmission mode, i.e., which sliding jaw clutch contacts which main shaft gear, will ordinarily be selected by an operator by moving the shift lever arrangement 91 according to a gearshift pattern. FIGS. 4A-4E demonstrate how an illustrative hub assembly 33a and its associated fork

(FIGS. 1 and 5) can be moved axially by movement of the rail 25. FIG. 5 shows the illustrative hub assembly 33a in the support structure 53, with bores 53a and 53b disposed on opposite sides of the rail 25 and spring loaded ball arrangements 43a and 43b in the bores. The hub assemblies 33a, 33b, and 33c and the support structures 53, 55, and 57 can all appear substantially the same as the hub assembly 33a and the support structure 53 shown in FIG. 5.

FIGS. 4A and 4E show the hub assembly 33a disengaged from the rail 25, as it might appear when in a neutral condition as shown in FIG. 3A or when in a disengaged condition when another one of the hub assemblies 33b or 33c is engaged to the rail. In this condition, the

depressions 27a and 27b can be rotationally offset from through holes 39 in the hub assembly 33a and the spring loaded ball arrangements 43a and 43b in the bores 53a and 53b, as seen in FIG. 4 A, or the depressions can be axially offset from the through holes in the hub assembly and the spring loaded ball arrangements in the bores, as seen in FIG. 4E, or the depressions and through holes can be both radially and axially offset. In the disengaged condition shown in FIGS. 4A and 4E, the balls 49 in the spring loaded ball arrangements 43a and 43b are partially disposed in the through holes 39 in the hub assembly 33a and partially disposed in a bore or annulus 95 of the bores 53a and 53b. As a result, the hub assembly 33a and the support structure 53 are engaged and movement of the rail 25 does not move the hub assembly. When the rail 25 is rotated and axially positioned to align the bores 53a and 53b of the support structure 53 with the depressions 27a and 27b on the rail as seen in FIG. 4B, the springs 51 of the spring loaded ball arrangements 43a and 43b urge the balls 49 into the depressions through the through holes 39 in the hub assembly 33a. Ordinarily, pins 97 are associated with each spring loaded ball arrangement 43 a and 43b and are adapted to urge the balls 49 completely out of the bores 53a and 53b. The radially innermost parts 99 (FIG. 4A) of the pins 97 ordinarily do not extend outside of the bores 53a and 53b so that, when the balls 49 are disposed in the through holes 39 of the hub assembly 33a and the depressions 27a and 27b, the hub assembly and the rail 25 are engaged and the hub assembly and the support structure 53 are disengaged. When the rail 25 is moved axially forward relative to the support structure 53, as seen in FIG. 4C, the hub assembly 33a moves axially forward with the rail, and the fork 41 associated with the hub assembly moves the sliding jaw clutch 61 (FIG. 3B) against the main shaft gear 77 so power is transmitted from the transmission main shaft 67 through the sliding jaw clutch 61 sp lined to the transmission main shaft, through the main shaft gear 77, and to the drive shaft 93.

When the rail 25 is moved axially rearward relative to the support structure 53, as seen in FIG. 4D, the hub assembly 33a moves axially rearward with the rail, and the fork 41 associated with the hub assembly moves the sliding jaw clutch 61 (FIG. 3B) against the main shaft gear 79 so power is transmitted from the transmission main shaft 67 through the sliding jaw clutch 61splined to the transmission main shaft, through the main shaft gear 79, and to the drive shaft 93.

When the rail 25 is moved back to the position shown in FIG. 4B, the rail and the hub assembly 33a can be disengaged by, for example, providing a gradual slope to the depressions 27a and 27b in the circumferential direction so that rotation of the rail urges the balls 49 out of the depressions 27a and 27b against the force of the springs 51. A steeper slope can be provided to the depressions 27a and 27b in the axial direction to avoid unintentional disengagement of the hub assembly 33a and the rail 25 when the rail is only moved axially relative to the support structure 53.

As seen in FIGS. 6A-6C, a single rail shift assembly for use in a transmission according to the present invention can be provided with one or more hub assemblies 133 comprising a bell crank-type arrangement 121 attached to a hub 135 and to a bell crank hub 137 disposed at least partially around the rail 125. The bell crank-type arrangement 121 can be arranged so that axial movement of the hub 135 in a first direction, i.e., in the direction X, causes axial movement of the bell crank hub 137 in a second axial direction Y opposite from the first direction. In the embodiment shown in FIGS. 6A-6C, a pivot point 139 of the bell crank-type arrangement 121 can be attached to a the transmission cover 59 and pins 121a and 121b on ends of the bell crank- type arrangement can slide in slots 141a and 141b of the hub 135 and the bell crank hub 137 so that movement of the hub 135 will be translated into movement in the opposite direction by the

bell crank hub 137. It will be appreciated that other arrangements for translating movement in a first direction into movement in a second direction can be provided, as well. It may be desirable to provide for such movement in a transmission, for example, to simplify or customize a gear shift pattern in a motor vehicle. As seen in FIG. 1, an indicator arrangement 101 can be provided to indicate that the rail

25 is in one of a plurality of predetermined axial positions relative to the plurality of spring loaded ball arrangements and support structures 53, 55, 57. The indicator arrangement 101 can comprise a member such as a ball 103 that is urged by a spring 105 into one of a plurality of recesses 107, 109, 111 arranged at different axial locations on the rail 25. The ball 103 and spring 105 can be disposed in a support structure 113 that may be similar to the support structures 53, 55, and 57 and, like those support structures, may form part of a transmission cover 59. Ordinarily, at least one recess of the plurality of recesses 107, 109, and 111 is a circumferential groove and, ordinarily, all are circumferential grooves. The recesses 107, 109, and 111 can, however, be depressions or recesses that do not extend around the entire circumference of the rail 25. When the rail 25 is in the position shown in, e.g., FIG. 3 A, the ball 103 will be urged into a central recess 109 (FIG. 1) of the plurality of recesses. The force of the spring 105 maintaining engagement of the ball 103 and the central recess 109 will provide some ordinarily relatively easily overcome resistance against movement of the rail 25 axially forward or rearward. When the rail 25 is moved axially forward to the position shown in, e.g., FIG. 3B, by overcoming that resistance, when the ball 103 reaches the axially more forward recess 107, the ball is urged into the recess and axial movement will only be permitted upon again overcoming the resistance provided by the force of the spring 105 causing the ball to engage with the forward recess 107. Likewise, when the rail 25 is moved axially rearward to the position

shown in FIG. 3C, when the ball 103 reaches the axially rearward recess 111, the ball is urged into that recess and axial movement of the rail will only be permitted upon again overcoming the resistance provided by the force of the spring 105 causing the ball to engage with the rearward recess 111. The support structures 53, 55, and 57 will ordinarily include at least one, usually two bores for shift fork assemblies. As seen in FIG. 5, showing the support structure 53 for purposes of illustration, each hub assembly 33a comprises a hub 35 and a fork 41 extending from the hub. The support structure 53 comprises an opening 115 defined by what is referred to here as a partial cylinder extending more than 180° and less than 360° around an axis of the opening. The opening 115 is a partial cylinder in the sense that, in addition to comprising an axially extending component 117 (seen, for example, in FIGS. 4A-4E), it has a radially extending component 119, as well. The axial component 117 of the opening 115 permits hubs 35 to move axially relative to the support structures and the radial component 119 permits the forks 41 to extend radially from the hubs and to move axially with the hubs. The partial cylinder of the opening 115 may have a generally circularly cylindrical component 120 for receiving a circularly cylindrical hub 35. Alternatively, or in addition, to the circularly cylindrical component 120, it may have a non- circularly cylindrical component 122 for receiving a non-circularly cylindrical hub or hub assembly. As seen in FIG. 5, a non-circularly cylindrical component 122 can be in the form of a V-shaped notch in which the fork 41 is slidable and which prevents rotation of the hub assembly 33 a. Instead of or in addition to a V-shaped notch, the portion of the opening 115 in which the hub 35 slides can be circular or non-circular, such as by providing a rib 122' (shown in phantom) on one of the hub and the opening 115 and a rib-receiving opening on the other one of the hub and the opening, or by having the hub be some shape other than generally circular.

In the present application, the use of terms such as "including" is open-ended and is intended to have the same meaning as terms such as "comprising" and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as "can" or "may" is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.

While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.