GEARBOX ASSEMBLIES AND DEVICE

Description

[0001] This invention relates to gearing assemblies and apparatus.

[0002] Gearing assemblies and apparatus of the present kind may be found useful in a variety of vehicular applications or in other machinery where a simple robust and compact gearbox is useful. Gearing assemblies are used commonly on vehicles where it is desired to drive a wheel or axle at a different rotational speed to the revolutions of an engine or motor. Assemblies of the present kind may find a particular application in a gearing system for an electrical hub drive and applications of the present systems are discussed herein in that context by way of example, although it should be noted that the invention is not limited to such applications.

[0003] Electric hub drive or hub mounted electric drive (HMED) units are finding increasing use in vehicles where it is advantageous for the wheels to be driven independently. Applications include, for example large vehicles and vehicles adapted for use on difficult, for example steep and uneven, terrain. HMED units are finding increasing use on hybrid vehicles. HMED units are finding increasing use on military vehicles particularly for use on difficult terrain.

[0004] In such a system each wheel is provided with a hub mounted electric drive assembly, typically comprising a housing containing an electric motor and a drive train including a drive shaft arranged inside a suitable hub mounted housing. An output shaft of the hub drive drives the wheel. The hub drive assembly can fit at least partly within space available inside the diameter and the overall width of the wheel rim and tyre assembly, in at least some cases.

[0005] The use of individual hub mounted electric drive units can eliminate the need for conventional transmission and drive shafts and can offer enhanced vehicle capabilities through improvements in vehicle performance, fuel economy, design configuration, increased stealth capability and reduced whole of life costs.

[0006] Generally, an electric hub drive will be such that it needs to have a large torque range and a large speed range as well as desirably being compact. A multispeed gear change mechanism is desirable to facilitate this. Higher gear ratios can be used to provide higher torques at lower speeds and lower gear ratios can be used to allow for higher speeds (with low available output torque).

[0007] In providing gearing assemblies and apparatus for, amongst other things, use in such units, it is desirable if a compact design can be achieved and if there is flexibility in terms of the positioning of various parts of the gearing assembly and / or apparatus necessary to provide the different gear changes and where appropriate, flexibility for positioning controls operable by a user for controlling those gear changes.

[0008] In some previous designs of gearing assemblies or apparatus, two separate shift forks have been provided for making gear changes. One for operating a corresponding clutch on a first side of a driving motor of the system, and one for operating two separate clutches provided on a second side of the motor.

[0009] One example of such a gearing assembly is shown in WO2016 / 146628. In that device, three different gears are provided. Two of the gears are selectable by use of a first shift fork provided on one side of the motor using first and second dog clutches. In that arrangement, the dog clutches operate using mutually engageable axially extending teeth such that in order to engage the clutch, a dog hub carrying axially extending teeth is moved axially into engagement with corresponding teeth on the remainder of the clutch and in order to disengage the clutch, the dog hub is moved in the axially opposite direction. As such, axial movement of the dog hub to its maximum extent in one direction engages a first dog clutch whereas axial movement of the dog hub in the opposite axial direction to the maximum extent engages a second dog clutch. With the arrangement of WO2016 / 146628, in order to provide the third gear, a third dog clutch and a second shift fork for operating the third clutch are provided on the other side of the motor. Another example of a gearing assembly can be found on US2004007084A1.

[0010] It would be desirable to provide gearing assemblies and apparatus which provide more flexibility in design and, for example can allow the provision of a more compact design and / or allow a choice of position for a shift fork associated with a respective clutch.

[0011] According to a first aspect of the present invention there is provided a gearing apparatus comprising the combination of features of claim 1, the dependent claims show further advantageous embodiments of the invention.

[0012] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a drive system in the form of a hub drive system and including gearing apparatus; Figure 2 schematically shows in more detail part of the gearing apparatus of the drive system shown in Figure 1; Figure 3A and Figure 3B show a dog hub and dog ring of the gearing apparatus shown in Figure 2, with the dog hub and dog ring shown separately in Figure 3A and shown in an engaged position in Figure 3B; Figure 4A and Figure 4B show respectively in more detail the teeth provided on the dog hub (Figure 4A) and the dog ring (Figure 4B) of Figures 3A and 3B; Figure 5A shows in more detail part of a shift arrangement of the gearing apparatus of Figure 2 in position on a shaft of the gearing apparatus; Figure 5B shows part of the shift arrangement in isolation when not mounted on the shaft; Figure 5C shows the shaft in isolation without the shift arrangement in position; Figure 6 schematically shows an alternative gearing apparatus which is similar to that shown in Figure 2; Figure 7 shows yet another gearing apparatus which has some similarities with that shown in Figures 2 but has a different arrangement of dog clutches; and Figure 8 shows the engaging components of dog clutches of the type which may be used in some of the dog clutches of the gearing apparatus shown in Figure 7.

[0013] Figure 1 schematically shows a drive system in the form of an electric hub drive. The hub drive comprises an electric motor 1 for driving a wheel 2 and as can be seen schematically in Figure 1, the majority of the hub drive may be housed in the hub 2a of the wheel 2. The motor 1 comprises a stator 1a and a rotor 1b which is mounted for rotation via bearings 1c about an output shaft 3. The output shaft 3 is arranged for rotatingly driving the wheel 2 via a gear reduction stage 31. Further a braking system 32 is provided for breaking rotation of the output shaft 3 and hence rotation of the wheel 2. The structure and operation of the gear reduction stage 31 and braking system 32 are not particularly pertinent to the present invention and detailed description thereof is omitted. Indeed in some implementations the gear reduction stage and braking system might be omitted.

[0014] The hub drive system further comprises gearing apparatus 4 which in turn comprises a gearing assembly 5 and a shift arrangement 6 for acting on the gearing assembly 5 and changing between gears. The gearing assembly 5 includes the shaft 3 as a rotary output member.

[0015] Considering now Figure 2 as well as Figure 1, the gearing assembly 5 comprises a dog hub 51 which is mounted for axial movement relative to the output shaft 3 but with rotational movement between the dog hub 51 and shaft 3 resisted. In the present embodiment, this mounting is achieved via the provision of mutually engaging splines on the outer curved surface of the shaft 3 and in the bore of the dog hub 51.

[0016] The gearing assembly 5 also comprises a gearing arrangement 52 which comprises a plurality of planetary gear stages. Each planetary gear stage comprises a sun gear 521a, 521b, 521c and planetary gears 522 carried on a respective planet carrier 523. A common fixed ring gear 524 is provided within which the planetary gears 522 can run. Each planet carrier 523 is borne on the sun gear 521b, 521c of the subsequent planetary gear stage.

[0017] A first of the sun gears 521a in the series is carried by the motor rotor 1b so as to rotate therewith. Each of the planetary gear stages act as a reduction gear. These gear stages preferably use planet gears which are small in comparison with the sun gear to give a relatively low reduction ratio of say in the order of 2.7:1 per stage.

[0018] In the present embodiment there are two gear stages of approximately 2.7:1 which therefore gives a mechanical ratio spread of approximately 7:1 and combined with a traction motor, this can give a range of approximately 20:1. This ratio spread is typical of that required for a high performance military vehicle, either a wheel driven vehicle with a hub drive or a tracked vehicle. For a vehicle with a lower power to weight ratio, a third planetary gear stage could be added to give an overall spread of approximately 50:1.

[0019] Where a planetary gear reduction is used with a ratio of approximately 2.7:1 and this has small planet gears, this will lead to relatively large sun gears. This is advantageous as it provides space inside the sun gears which can be used.

[0020] Each sun gear 521a, 521b, 521c comprises a dog ring 53 which is arranged for cooperation with the dog hub 51 so as to act as a dog clutch. Each dog ring 53 correspondingly acts as an output of the gearing arrangement 52.

[0021] Figures 3A and 3B show the dog hub 51 and one of the dog rings 53 in isolation. In Figure 3A these parts are shown separately from one another whereas in Figure 3B they are shown engaged with one another. Incidentally, in Figure 3B, the dog ring 53 is shown carrying planetary gears 522 whereas in Figure 3A there are no planetary gears. Thus this corresponds to the dog ring 53 carried by the first sun gear 521a which does not act as a planet carrier.

[0022] As can be seen most clearly in Figures 3A and 3B, the dog hub 51 carries a hub set of dog teeth 51a and the dog ring 53 carries a ring set of dog teeth 53a. These sets of teeth are radially extending and arranged to mutually engage with one another as shown in Figure 3B. That is to say the dog hub 51 is arranged to engage with the dog ring 53 when appropriately axially aligned with one another. Thus the dog hub 51 may be moved axially between positions where it engages with the dog ring 53 of the first sun gear 521a or the dog ring 53 of the second sun gear 521b or the dog ring 53 of the third sun gear 521c. It will be appreciated that the dog hub 51 may also be moved to intermediate positions where there is no engagement such that "neutral" positions can be adopted between gears. Furthermore the dog hub 51 may be moved between all of these positions by use of the shift arrangement 6 as will be described in more detail further below.

[0023] The teeth in the hub set of teeth 51a are provided on a curved circumferential surface of the dog hub 51. Teeth in the ring set of teeth 53a are provided on a curved (inner) circumferential surface of the dog ring 53. Each tooth has a root at the respective curved surface and projects radially therefrom.

[0024] The hub set of teeth 51a and ring sets of teeth 53a (a portion of which are shown in more detail in Figures 4A and 4B) are arranged to allow rotational drive to be transferred from the respective sun gear 521a, 521b, 521c to the output shaft 3 via the dog hub 51 when there is appropriate alignment. Further the teeth 51a, 53a are arranged to allow engagement to be achieved by movement of the hub 51 axially into alignment with the respective dog ring 53 and to allow disengagement by axial movement away from that aligned position when not under rotational load.

[0025] Furthermore the sets of teeth 51a, 53a are arranged so that the set of hub teeth 51a may pass through the set of ring teeth 53a when there is appropriate register between the sets of teeth. As will be appreciated, when engagement has been achieved as shown in Figure 3B, the sets of teeth 51a, 53a are in register and thus disengagement of the teeth by movement of the hub 51 in either axial direction away from the engaging position is possible.

[0026] Thus the dog hub 51 may be moved from a first position in which it is engaged with the dog ring 53 of the second sun gear 521b to a first disengaged position which is axially to one side of its engaged position and to a second disengaged position which is axially to the other side of its first engaged position. Furthermore from the disengaged positons the dog hub 51 may be moved to second and third engaged positions, that is respectively into engagement with the dog ring 53 of the first sun gear 521a or the dog ring 53 of third sun gear 521c.

[0027] With the dog hub 51 axially positioned so that its teeth 51a are engaged with the dog ring 53 of the first sun gear 521a, drive is provided directly from the motor rotor 1b to the output shaft 3 via the dog ring 53 of the first sun gear 521a and the dog hub 51. Here the dog ring 53 of the first sun gear 521a and the dog hub 51 are acting as a first dog clutch.

[0028] When the dog hub 51 is axially aligned with the dog ring 53 of the second sun gear 521b, then rotational drive from the motor rotor 1b occurs via the first planetary gear stage with the dog ring 53 of the second sun gear 521b and the dog hub 51 acting as a second dog clutch. Here there is a speed reduction so the output shaft 3 rotates more slowly than the motor rotor 1b.

[0029] Similarly when the dog hub 51 is aligned with the dog ring 53 of the third sun gear 521c then drive from the motor rotor 1b is provided to the shaft 3 via two planetary gear stages with the dog ring 53 of the third sun gear 521c and dog hub 51 acting as a third dog clutch.

[0030] It will be appreciated that if a further planetary gear stage is provided then this may be engaged using the same mechanism. That is to say a fourth dog clutch arrangement may be provided with an appropriate dog ring carried on a fourth sun gear.

[0031] Thus one "common" dog hub 51 and appropriate shift arrangement can be used to provide any number of gears desired. The hub set of teeth 51a and the ring set of teeth 53a are profiled to help with operation of the system. First facing edges of the teeth which will contact with the respective other set of teeth during engagement are radiused to reduce contact stress and help to guide the teeth into engagement with one another. These radiused portions can be seen for example in Figures 4A and 4B. On the hub set of teeth 51a, radiused surfaces 51b are provided at outer edges of the teeth and side walls of the teeth. On the ring set of teeth 53a radiused surfaces 53b are provided at the tips of the teeth, in troughs between the teeth and on sidewalls of the teeth.

[0032] It will be noted that during engagement of the sets of teeth 51a, 53a there will tend to be relative rotation between the dog hub 51 and the dog ring 53. These radiused surfaces 51b, 53b are chosen with the aim of guiding the teeth into mutual engagement with one another.

[0033] Furthermore the respective sets of teeth 51a, 53a are profiled to encourage engagement and alignment of the teeth to be maintained when under rotational load when the respective dog clutch is transferring load. In particular the mating surfaces of the teeth which transfer such load comprise complementary concave and convex portions which can rest in one another during rotational drive. In the present embodiment, the dog hub teeth 51a have a groove 51c provided in a side wall surface which is arranged to accept a corresponding convex portion 53c in the dog ring teeth 53a to help maintain alignment between the respective sets of teeth under rotational load. As will be appreciated, under rotational load, the convex portions 53c will tend to nestle into the concave groove portions 53c so resisting axial movement of the dog hub 51 out of engagement with the dog ring 53.

[0034] It will be appreciated that with the above-described gearing assembly a shift fork might be provided for directly acting on the dog hub 51 for shifting its axial position to select the desired gears.

[0035] However, in the present arrangement a different form of shifting arrangement 6 is provided. As schematically illustrated in Figure 1 the shift arrangement 6 comprises a shift fork 61 for accepting inputs from a user and at least one shift stick 62 for transmitting inputs from the shift fork 61 to the dog hub 51. The arrangement allows axial movement of the shift fork 61 to cause a corresponding axial movement of the dog hub 51.

[0036] In this case, whilst the dog hub 51 and gearing assembly 5 as a whole is provided on one side of the motor 1, the shift fork 61 is provided on the opposite side of the motor 1. This again allows more flexibility in the arrangement of the system and for example allows the provision of the shift fork 61 to be on an inboard side of the motor whereas the gearing arrangement is on the outboard side of the motor. This can help from an overall system design point of view. In addition this can help to lead to a more compact arrangement where, as can be seen for example by consideration of Figure 2, part of the axial extent of the dog hub 51 may be accommodated at least partly within the axial extent of the motor rotor 1b. In the present case this is true at least when the dog hub 51 is in position which corresponds to it being retracted to its maximum extent towards the location of the motor 1.

[0037] More detail of the shift arrangement can be seen by consideration of Figures 5A, 5B and 5C as well as Figure 2. The shift arrangement 6 comprises a shift ring 63 to which are connected three shift sticks 62 with the remote end of the shift sticks 62 being connected to the dog hub 51. Each of the shift sticks 62 is located in a respective axial slot 33 provided in the outer curved surface of the shaft 3. These slots 33 and hence the shift sticks 62 may be equally spaced around the circumference of the shaft 3. In the current embodiment the shift sticks 62 are spaced in this way and thus are spaced 120° from each other. The slots for the shift sticks may be machined into the outer curved surface of the shaft 3. As can be seen by consideration of, for example Figure 5A and Figure 2, the shift sticks 62 pass through the interior of the bearing 1c and hence through the rotor 1b.

[0038] The shift ring 63 is arranged to be acted on via the shift fork 61 so the axial movement of the shift fork 61 will cause axial movement of the dog hub 51 via the shift ring 63 and the shift sticks 62.

[0039] It should be noted that in alternatives, different numbers of shift sticks 62 might be provided. Further if it is desired to provide independent control of more than one dog hub, independent shift sticks or sets of shift sticks might be provided with each stick or set for controlling a respective dog hub. Then each dog hub may have its own respective associated set of shift sticks 62 and respective shift ring 63 for control by a respective shift fork.

[0040] Figure 6 shows an alternative gearing apparatus which is similar to that shown in Figure 2. Detailed description of most of Figure 6 is omitted for the sake of brevity with it being understood that those features not described are the same as those of the gearing apparatus shown in Figure 2. The difference between the gearing arrangement shown in Figure 6 and that shown in Figure 2 is that an additional reduction gear stage 54 is provided between the motor rotor 1b and the remainder of the gearing arrangement 52. Thus the output of this first reduction gear 54 acts as the input to the first sun gear 521a such that the highest gear available is via this reduction gear 54 and all the other gears are reduced. With an arrangement such as this, the reduction gear arrangement 31 of Figure 1 between the output shaft 3 and the wheel 2 to be driven might be omitted.

[0041] Figure 7 schematically shows yet another gearing apparatus. Again this is similar to that described above in relation to Figures 2 and a detailed description of those parts in common is omitted with it to be understood that those parts not described are the same as in the apparatus of Figure 2. Here a different form of gearing assembly 5 is provided where different forms of dog clutch are provided but otherwise the gearing assembly is as described in relation to Figures 2 to 5.

[0042] In this arrangement, the dog hub 51 carries separate sets of dog teeth 51a, 51a' and 51a". Further the sun gears of the gearing arrangement 52 carry different types of dog ring 53, 53' and 53".

[0043] The first set of dog teeth 51a is arranged for engagement with the dog ring 53 carried by the second sun gear 521b. This set of dog teeth 51a and dog ring 53 are of the type described above and shown, for example in Figures 3A and 3B. That is to say the respective dog teeth 51a, 53a are radially extending and arranged so that when aligned and engaged, rotational drive may be transmitted via the sets of dog teeth 51a, 53a and also so that the teeth may be moved out of axial alignment with each other in either direction away from the aligned position.

[0044] On the other hand the second and third sets of dog teeth 51a', 51a" provided on the dog hub 51 are of the more conventional axial extending type and are arranged for mutual engagement with corresponding axial sets of teeth 53', 53" provided on the first sun gear 521a and the third sun gear 521c. In this case these sets of teeth extend from axial faces on the dog hub 51, and sun gears 521a, 521c. Figure 8 shows the type of dog teeth arrangements which may be used for these dog clutches.

[0045] Thus whilst the first dog clutch 53, 51a is one of the type where the two sets of dog teeth may pass through one another, the second 53', 51a' and third 53", 51a" dog clutches are ones where engagement is provided by axial movement in a first direction and disengagement can only be achieved by axial movement in the reverse direction.

[0046] Thus engagement of the second set of hub teeth 51a' with the corresponding dog ring 53' may be achieved with the dog hub 51 at one axial extent of its movement whilst engagement of the third set of hub teeth 51a" may be achieved with the corresponding dog ring 53" with the hub 51 at its opposite axial extent of travel. On the other hand engagement of the first dog clutch via the first set of dog teeth 51a and the appropriate dog ring 53 may be provided at an intermediate axial position of the dog hub 51.

[0047] In this way, again three different gears may be selectively engaged using axial travel of a common dog hub 51 to select each.

[0048] Further it will be appreciated that further dog rings 53 of the type shown in Figure 3A and 3B might be provided at other intermediate positions for engagement via the first set of dog teeth 51a (or indeed other sets of appropriate dog teeth) if it were desired to provide more gears.

[0049] Further note that what is relevant is the relative axial position of the dog hub at which a gear is engaged not the axial positions of the respective clutches. Thus while axially extending teeth type "one way" clutches need to be used at an end of axial travel of a common dog hub (if at all), they need not be provided at the axially outermost location. A "pass through" type clutch at the end of a line of clutches can still be engaged with the dog hub in an intermediate location - this being down to the location of the respective sets of teeth on the hub. Further in other cases multiple independent dog hubs might be used rather than a common dog hub.

[0050] Note that the arrangement shown in Figure 7 might be advantageous in some circumstances in that whilst the first dog clutch 53, 51a provides the capability of having more than two gears with the provision of a single axially moveable dog hub, the use of the more conventional dog clutches 53', 51a', 53", 51a" at either end of the dog hub 51 can facilitate the provision of different torque transfer capabilities of the dog clutches and / or the provision of different diameters of dog clutch which may be useful, bearing in mind available space requirements. Thus for example a larger diameter dog clutch may be used where greater torque transfer capabilities are required and / or where greater internal space within the dog clutch might be useful. Correspondingly a smaller diameter dog clutch might be used where lower torque transfer capabilities are required and / or where space outside of the dog clutch might be useful / required for some other purpose.

Claims

1. A gearing apparatus (4) comprising a gearing assembly (5) comprising a rotary input member, a rotary output member and a gearing arrangement (52) between the input member and the output member selectively engageable to effect a driving engagement between the input member and the output member through at least a first torque connection having a first gear ratio and a second torque connection having a second gear ratio, the gearing apparatus (4) further comprising a shift arrangement (6) for shifting the gearing arrangement (52) between a first state in which there is driving engagement between the input member and the output member through the first torque connection and a second state in which the gearing arrangement (52) does not provide driving engagement between the input member and the output member through the first torque connection, the shift arrangement (6) comprising at least one shift stick (62) for acting on the gearing assembly (5) for shifting the gearing arrangement (52) between at least the first state and the second state, wherein one of the rotary input member and the rotary output member comprises a first shaft (3) and the at least one shift stick (62) is arranged for axial movement therewithin relative to the shaft (3) for acting on the gearing assembly (5) in shifting the gearing arrangement (52) between the first state and the second state, characterized in that the at least one shift stick (62) is carried in a slot (33) extending axially in the outer surface of the first shaft (3).

2. Gearing apparatus (4) according to claim 1 in which the gearing arrangement (52) has a third state in which there is driving engagement between the input member and the output member through the second torque connection and the at least one shift stick (62) is arranged for acting on the gearing assembly (5) for shifting the gearing arrangement (52) between at least the first state, the second state and the third state.

3. Gearing apparatus (4) according to claim 1 or 2 in which the shift arrangement (6) comprises a plurality of shift sticks (62) which are angularly spaced from one another around the first shaft (3) and disposed in respective slots (33) extending axially in the outer surface of the first shaft (3).

4. Gearing apparatus (4) according to claim 3 in which the plurality of shift sticks (62) are arranged in respective sets, with the or each shift stick (62) in a respective set arranged to act in parallel with any other members of the set, whilst acting independently of the or each shift stick (62) in any other set or sets.

5. Gearing apparatus (4) according to claim 4 wherein the shift arrangement (6) comprises at least one pair of shift sticks which are arranged to act in parallel on the gearing assembly (5).

6. Gearing apparatus (4) according to claim 5 wherein the shift sticks (62) comprising the at least one pair of shift sticks are disposed in respective slots (33) which are diametrically opposed around the first shaft (3).

7. Gearing apparatus (4) according to claim 4 wherein the shift arrangement (6) comprises at least three shift sticks (62) which are arranged to act in parallel on the gearing assembly (5).

8. Gearing apparatus (4) according to claim 7 wherein the at least three shift sticks are disposed in respective slots (33) which are equally spaced around the first shaft (3).

9. Gearing apparatus (4) according to any one of the preceding claims wherein the shift arrangement (6) comprises a shift ring (63) arranged to transfer actuation from a shift fork (61) to the at least one shift stick (62) so as to move the at least one shift stick (62) axially relative to the first shaft (3) for shifting the gearing arrangement (52).

10. Gearing apparatus (4) according to any one of the preceding claims which comprises at least one clutch for use in shifting the gearing arrangement (52) between states, the clutch comprising at least one clutch hub (51) which is mounted on the first shaft (3) so as to allow axial movement of the clutch hub (51) relative to the first shaft (3) with rotation of the clutch hub (51) relative to the first shaft (3) being resisted, wherein the at least one shift stick (62) is arranged for acting on the at least one clutch hub (51) for causing axial movement thereof.

11. Gearing apparatus (4) according to claim 10 when dependent on any one of claims 4 - 9 in which each set of shift sticks (62) is arranged for acting on a respective clutch hub (51).

12. A drive system comprising a gearing apparatus (4) according to any one of the preceding claims and a motor (1) comprising a rotor (1b) and a stator (1a).

13. A drive system according to claim 12 in which the gearing arrangement is provided at a location spaced axially in a first direction from the motor rotor and a shift fork for operating the shift mechanism is provided at a location spaced axially in a second, opposite, direction from the motor rotor.

14. A drive system according to claim 12 or 13 wherein the at least one shift stick (62) passes within the axially extending slot (33) provided in the first shaft (3) from one side of the motor rotor (1b), through a bearing (1c) supporting the motor rotor (1b), to the other side of the motor rotor (1b).

15. A vehicle comprising a gearing apparatus (4) according to any one of claims 1 - 11 or a drive system according to any one of claims 12 - 14.