TRANSMISSION FOR A VEHICLE, WITH ELECTRIC GENERATOR AND/OR MOTOR

Abstract

A dual clutch transmission has an electrical machine (25) coupled to the input shafts (15, 16) thereof via one-way clutches (31, 32). The electrical machine acts as a generator, and can be driven at high speed by the input shaft which is not transmitting engine torque. The electrical machine may also act as a motor to start an internal combustion engine via an automatic one-way clutch and reverse speed ratio.

Claims

1-37. (canceled)

38. A dual clutch transmission having drive clutches for driving coaxial input shafts from a motor, and a rotary electrical machine for harvesting and/or transmitting energy from/to said transmission; wherein said electrical machine includes an armature coupled to both said input shafts via respective armature clutches, and wherein at least one of said armature clutches comprises a one-way clutch.

39. A transmission according to claim 38, wherein said armature is coupled to said transmission by one of a gear train, a chain, a toothed belt, and a V belt.

40. A transmission according to claim 38, wherein said input shafts are coupled to said armature at the same end thereof.

41. A transmission according to claim 38, wherein a respective one-way clutch is provided for each said input shaft.

42. A transmission according to claim 41, wherein said one-way clutches are on a rotational axis of said armature.

43. A transmission according to claim 41, wherein said one-way clutches are on a rotational axis of said input shafts, and have a common output member coupled to said electrical machine.

44. A transmission according to claim 41, wherein one of said one-way clutches is lockable to prevent relative rotational movement in either direction.

45. A transmission according to claim 38, wherein a rotational axis of said electrical machine is parallel with said input shafts.

46. A transmission according to claim 38, comprising a casing containing said input shafts, and wherein said armature clutches are within said casing, or said electrical machine is outside said casing, and the armature of the electrical machine passes into said casing via an annular seal.

47. A transmission according to claim 38, wherein said electrical machine is cooled by one of a transmission fluid and a cooling fluid of an internal combustion engine for driving said input shafts.

48. A transmission according to claim 38, wherein said electrical machine is a generator.

49. A transmission according to claim 38, wherein a radially outermost one of the input shafts includes a plurality of axially spaced first gear wheels, and wherein either (i) said armature is connected to the outermost input shaft adjacent an axially endmost of said first gear wheels, or (ii) said plurality of first gear wheels is at the drive clutch side of the connection to said armature or (iii) one of said first gear wheels drives said electrical machine.

50. A transmission according to claim 49, wherein a radially innermost one of the input shafts includes a plurality of axially spaced second gear wheels, and wherein: either (i) said armature is connected to the innermost input shaft adjacent an axially endmost of said second gear wheels, or (ii) said plurality of second gear wheels is at the drive clutch side of the connection to said armature, or (iii) one of said second gear wheels drives said electrical machine.

51. A transmission according to claim 38, wherein an inner one of the input shafts protrudes from an outer one of the input shafts, both the input shafts have gear wheels thereon, and the respective connections to said armature are immediately adjacent and between said gear wheels.

52. A transmission according to claim 38, comprising the co-axial input shafts on an input shaft axis, a layshaft on a layshaft axis parallel to the input shaft axis, a constant mesh forward gear train between one input shaft and said layshaft, a constant mesh reverse gear train between the other input shaft and said layshaft, and a sleeve wherein said sleeve is (i) rotatable about said layshaft for coupling said forward gear train and reverse gear train on demand, or (ii) said sleeve includes a dog clutch.

53. A transmission according to claim 38, comprising two co-axial input shafts on an input shaft axis, a layshaft on a layshaft axis parallel to the input shaft axis, a constant mesh forward gear train for driving between one input shaft and said layshaft, a constant mesh reverse gear train for driving between the other input shaft and said layshaft, and an output shaft in driving connection with said layshaft, wherein said output shaft is disconnectable from said layshaft in use, or wherein said output shaft is on said input shaft axis, a constant mesh gear train connects said layshaft and output shaft, and a dog clutch is provided between said layshaft and said gear train.

54. A method of providing a substantially continual drive connection between a rotary electrical machine and a dual clutch transmission of a motor vehicle, said rotary electrical machine being for harvesting and/or transmitting energy from/to said transmission, and said transmission having co-axial input shafts and drive clutches therefor, the method comprising: connecting an armature of said machine to both said input shafts via respective armature clutches; and driving from said input shafts to said armature through respective one-way clutches.

55. A method of operating a transmission having drive clutches for driving coaxial input shafts from a motor, and a rotary electrical machine for harvesting and/or transmitting energy from/to said transmission; wherein said electrical machine includes an armature coupled to both said input shafts via respective armature clutches, and wherein at least one of said armature clutches comprises a one-way clutch, the method comprising: determining that said electrical machine should harvest energy from said transmission; disconnecting a currently engaged drive clutch; and driving said electrical machine via a selected speed ratio of the transmission.

56. A method according to claim 55, comprising determining that said electrical machine should cease to harvest energy from said transmission; determining that the selected speed ratio is appropriate for driving the vehicle, and if necessary selecting another speed ratio; and engaging the drive clutch associated with the selected speed ratio.

57. A method of starting an internal combustion engine when coupled to a transmission having drive clutches for driving coaxial input shafts from a motor, and a rotary electrical machine for harvesting and/or transmitting energy from/to said transmission; wherein said electrical machine includes an armature coupled to both said input shafts via respective armature clutches, and wherein at least one of said armature clutches comprises a one-way clutch, the method comprising: causing both drive clutches to be disengaged, engaging an armature clutch to permit driving of an input shaft of said transmission by said electrical machine; providing that said input shaft is not connected for drive to an output shaft of said transmission, causing rotation of said input shaft by said electrical machine, engaging a drive clutch associated with said input shaft to start said engine, and disconnecting said drive clutch after starting said engine.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] Other features of the invention will be apparent from the following description of several embodiments illustrated by way of example in the accompanying drawings in which:

[0034] FIG. 1 is a schematic illustration of a dual clutch transmission.

[0035] FIG. 2 illustrates a part of the transmission of FIG. 1, and adapted to the invention.

[0036] FIG. 3 illustrates an alternative to the transmission of FIG. 2.

[0037] FIG. 4 illustrates another alternative to the transmission of FIGS. 1 and 2.

[0038] FIG. 5 illustrates an engine starting arrangement using reverse gear ratio.

[0039] FIG. 6 illustrates an alternative starting arrangement using reverse gear ratio.

DESCRIPTION OF EMBODIMENTS

[0040] With reference to FIG. 1, a driving shaft 11, from a motor such as an internal combustion engine, drives a clutch housing 12 within which two driven plates 13, 14 are separately engageable. The clutch plates are connected to respective transmission input shafts 15, 16 which are co-axial. Each input shaft carries three gear wheels, which mate with respective gear wheels of a layshaft 17. The layshaft is also connected via a gear wheel pair to an output shaft 18 of the transmission, which may be co-axial with the input shafts.

[0041] The transmission provides six speed ratios, indicated by the numbers 1-6, and the odd ratios are associated with one input shaft whilst the even ratios are associated with the other input shaft.

[0042] As is well understood one gear wheel of each ratio pair is loose, and can be engaged with the respective shaft by a mechanism such as a synchromesh cone and dog. These components are omitted to improve clarity. In use one loose gear wheel can be connected to the respective shaft to provide drive from the input shaft to the output shaft.

[0043] In a DCT transmission, the clutches 13, 14 are alternately engaged, so that the speed ratio which is next anticipated can be pre-selected, and the speed ratio change completed by switching drive from one clutch to the other.

[0044] Thus, by way of example, second speed ratio may be selected by coupling the respective loose gear wheel with its shaft, to connect the drive and output shafts 11, 18 via the clutch driven plate 14 and the outer input shaft 16.

[0045] Whilst second speed ratio is driving, third (or first) speed ratio may be also selected by coupling the respective loose gear wheel to its shaft. The respective clutch driven plate 13 is rotated (back driven), but is not engaged by the clutch housing.

[0046] The speed ratio is changed by disengaging driven plate 14 whilst engaging driven plate 13. Second speed ratio is now back driven and may remain engaged, or may be disengaged by de-selecting the respective loose gear from its shaft, for example in favour of fourth speed ratio.

[0047] By this means rapid sequential changes of speed ratio may be performed, with pre-selection of the next anticipated speed ratio. Systems have been developed for predicting and pre-selecting the next speed ratio, and form no part of the present invention. It will be understood that the pre-selected speed ratio may change before being required to take up drive.

[0048] A DCT transmission may have many different arrangements of shafts and gears, but is typically characterised by co-axial input shafts 15, 16. The arrangement illustrated in FIG. 1 is an example only.

[0049] An embodiment of the invention is illustrated schematically in FIG. 2 which shows the region in the centre of the transmission where the inner input shaft 15 protrudes from the outer input shaft 16. The associated adjacent gear wheels 21, 22 associated with speed ratios 2 and 1 of the transmission are illustrated.

[0050] Provided between the gear wheels 21, 22 are respective sprockets 23, 24. In this example the sprockets have the same diameter. An electrical generator 25 is provided radially distant from the axis of the input shafts and has a generator armature 26 having loose sprockets 27, 28 connected to the sprockets 23, 24 by respective chains 29. Each sprocket 27, 28 may be coupled to the generator shaft by a respective one-way (or overrun or sprag) clutch 31, 32. The one-way clutches are arranged in the same sense so as to be automatically engageable to drive the generator shaft in the same direction. One-way clutches are well-known, and need not be further described here.

[0051] In conventional use of a DCT transmission, such as that illustrated in FIG. 1, one input shaft 15, 16 is always in a driven condition from the drive shaft 11, whereas the other input shaft 15, 16 may also be in a driven condition by virtue of pre-selection of the next required speed ratio. In consequence, in accordance with the invention the sprockets 27, 28 are generally both driven, and whichever sprocket is rotating the fastest will cause its associated one-way clutch to be engaged, thus driving the armature of the generator 25.

[0052] The arrangement provides for continual driving of the generator at the highest speed available from one or other of the input shafts 15, 16. It will also be understood that switching from one one-way clutch to the other requires no control mechanism; it is fully automatic.

[0053] The generator 25 may be used, for example, to charge a battery or other energy storage device of a hybrid vehicle.

[0054] The generator 25 also remains coupled to the transmission when the engine is disconnected by releasing the clutch driven plates 13, 14. In such circumstances the engine may be stopped to save fuel, and if the vehicle is coasting both sprockets 27, 28 will be driven from the transmission output shaft 18the faster running sprocket will drive the generator shaft via the associated one-way clutch.

[0055] Whilst coasting, the control system of the transmission may select a speed ratio best suited to driving the generator efficiently, for example a ratio which ensures high speed of one input shaft. Another speed ratio may be pre-selected and matched to vehicle speed so as to provide a torque path from the engine when coasting has ceased. Furthermore, when driving at a low road speed, the control system may cause engagement of a speed ratio to ensure high speed of the back driven input shaft, thereby to provide the highest desirable rotational speed of the electrical machine.

[0056] It will be understood that instead of providing a separate drive component for the generator, such as sprockets 27, 28, a gear wheel of an input shaft may be used to drive the generator via a separate gear train. In this arrangement the input shaft gear wheel fulfils a dual function.

[0057] The arrangement of FIG. 2 provides for connection of the generator to a mid-point of the transmission, and in one embodiment the sprockets and chains are within the transmission casing. The generator is outside the transmission casing, the armature drive shaft passing through a suitable opening and oil seal. In another embodiment, the generator may be within the transmission casing and cooled by the transmission lubricating fluid.

[0058] FIG. 3 illustrates a variant, in which common parts carry the same reference numerals. A sprocket 24a is associated with the inner input shaft 15, and is coupled at the other side of the gear wheels on the inner input shaft. The generator 25a has a through shaft adapted to be driven from either end via respective sprockets 27, 28a and one-way clutches 31, 32a. Operation of this embodiment is identical to that of FIG. 2, but may be more appropriate where the space between the even and odd gear wheels is insufficient to accommodate side-by-side connections to the generator.

[0059] FIG. 4 illustrates a further variant in which common parts carry the same reference numeral. In this embodiment the layshaft 17 is illustrated together with layshaft gears and a reverse gear train R. Selection of each speed ratio is via conventional synchromesh hubs 41-45 by which loose gear wheels can be connected one at a time to the layshaft 17. The output shaft 18 is driven from the layshaft 17 by final drive gear wheels 46, 47 which are in constant mesh.

[0060] In this embodiment, one-way clutches 31, 32 are provided co-axial with the input shaft axis and have a common output which drives via a single chain or belt 29 to the electrical machine 25. The arrangement of FIG. 4 thus has a reduced number of parts as compared with the arrangement of FIG. 2 in which the one-way clutches are co-axial with the generator shaft axis.

[0061] As noted above, one-way clutches are automatic and require no actuation or control device. The embodiments of FIGS. 5 and 6 show arrangements whereby the electrical machine can be used as a starter motor for the vehicle engine, by utilizing reverse gear ratio, thus allowing a conventional engine mounted starter motor to be dispensed with.

[0062] In FIG. 5, a gear wheel arrangement corresponds to FIGS. 1-4, and two one-way clutches are arranged on the axis of the generator shaft, each driven by a respective belt or chain from a respective input shaft.

[0063] However the layshaft 17 can be de-coupled on demand from the output gear wheel 46 via disengagement of a conventional synchromesh hub 47.

[0064] For transmission of torque the synchromesh hub 47 is always engaged, and neutral is obtained by disengagement of the synchromesh hubs associated with the loose layshaft gear wheels.

[0065] Upon disengagement of the synchromesh hub 47, the generator 25 may act as a starter motor in the following manner.

[0066] The generator 25, acting as a motor, may drive the inner input shaft 15 backwardly via the one-way clutch 32; the drive clutch 13 is disengaged. The input shaft 15 drives the layshaft 17 backwardly, by selection of reverse speed ratio. The layshaft 17 drives the outer input shaft 16 forwardly via the 2.sup.nd speed gear wheels. The drive clutch 14 is engaged to rotate the engine forwardly and, if in a condition to start, the engine will start.

[0067] After starting of the engine, the drive clutch 14 may be immediately disengaged, and operation of the generator as starter motor is ceased.

[0068] The arrangement will also work if drive is from the generator via outer input shaft 16, the 2.sup.nd speed gear ratio and reverse speed ratio to the inner input shaft 15 and drive clutch 13.

[0069] It will be appreciated that a different forward ratio may be selected if a higher torque multiplication is required for starting. In this example 4.sup.th speed or 6.sup.th speed gear wheels could be used in place of the 2nd speed gear wheels. Different speed ratios may be used depending on whether the engine is started from a hot or cold condition.

[0070] Flexibility of starting ratio in this embodiment means that the electrical machine design and specification is less constrained than if only one speed ratio was available for engine starting.

[0071] Once the engine is started, and the transmission is in neutral, the layshaft 17 is connected to the output gear wheel 46 for normal transmission operation. Both drive clutches are disengaged, and suitable speed ratios are selected according to the intentions of the vehicle driver. In this condition the transmission operates as a conventional dual clutch transmission.

[0072] In the arrangement of FIG. 6, the disconnectable output gear 46 is not required, and instead a layshaft sleeve 51 is provided to couple the reverse ratio layshaft gear wheel 52 to the loose second speed gear wheel 53. A conventional synchromesh hub is also provided to couple the reverse speed gear wheel 52 to the layshaft 17.

[0073] Operation of the embodiment of FIG. 6 in engine starting mode is identical to that of FIG. 5. The generator 25 drives via one-way clutch 32 to the inner input shaft 15, and then via reverse speed ratio, sleeve 51 and second speed ratio to the outer input shaft 16. In this embodiment the layshaft 17 remains stationary during starting of the engine; however in both the embodiments of FIG. 5 and the embodiment of FIG. 6, the output shaft 18 is disconnected from the input shafts 15, 16.

[0074] Other arrangements are of course possible, provided that drive to the output shaft is obviated, i.e. disengaged or disconnected, during engine starting via the reverse gear train.

[0075] Aspects of the invention will be apparent from the following numbered paragraphs:

[0076] 1. A dual clutch transmission having drive clutches for driving coaxial input shafts from a motor, and a rotary electrical machine for harvesting and/or transmitting energy from/to said transmission; wherein said electrical machine includes an armature coupled to both said input shafts via respective armature clutches.

[0077] 2. A transmission according to paragraph 1 wherein said input shafts are coupled to said armature at the same end thereof.

[0078] 3. A transmission according to paragraph 1 wherein said armature clutches comprise a respective one-way clutch for each said input shaft.

[0079] 4. A transmission according to paragraph 3 wherein said one-way clutches are on the rotational axis of said armature.

[0080] 5. A transmission according to paragraph 3 wherein said one-way clutches are on the rotational axis of said input shafts, and have a common output member coupled to said electrical machine.

[0081] 6. A transmission according to paragraph 3 wherein one of said one-way clutches included is lockable to prevent relative rotational movement in either direction.

[0082] 7. A transmission according to paragraph 1 wherein the rotational axis of said electrical machine is parallel with said input shafts.

[0083] 8. A transmission according to paragraph 1 wherein the radially outermost input shaft has a plurality of axially spaced first gear wheels thereon, and said armature is connected to the outermost input shaft adjacent an axially endmost of said first gear wheels.

[0084] 9. A transmission according to paragraph 8 wherein said plurality of first gear wheels is at the drive clutch side of the connection to said armature.

[0085] 10. A transmission according to paragraph 8 wherein the radially innermost input shaft has a plurality of axially spaced second gear wheels thereon, and said armature is connected to the innermost input shaft adjacent an axially endmost of said second gear wheels.

[0086] 11. A transmission according to paragraph 10 wherein said plurality of second gear wheels is at the drive clutch side of the connection to said armature.

[0087] 12. A transmission according to paragraph 1 wherein the inner input shaft protrudes from the outer input shaft, both the input shafts have gear wheels thereon, and the respective connections to said armature are immediately adjacent and between said gear wheels.

[0088] 13. A transmission according to paragraph 1 and comprising the co-axial input shafts on an input shaft axis, a layshaft on a layshaft axis parallel to the input shaft axis, a constant mesh forward gear train between one input shaft and said layshaft, a constant mesh reverse gear train between the other input shaft and said layshaft, and a sleeve rotatable about said layshaft for coupling said forward gear train and reverse gear train on demand.

[0089] 14. A transmission according to paragraph 1 and comprising two co-axial input shafts on an input shaft axis, a layshaft on a layshaft axis parallel to the input shaft axis, a constant mesh forward gear train for driving between one input shaft and said layshaft, a constant mesh reverse gear train for driving between the other input shaft and said layshaft, and an output shaft in driving connection with said layshaft, wherein said output shaft is disconnectable from said layshaft in use.

[0090] 15. A method of operating a transmission according to paragraph 1, and comprising: [0091] determining that said electrical machine should harvest energy from said transmission, [0092] disconnecting a currently engaged drive clutch; and [0093] driving said electrical machine via the selected speed ratio of the transmission.

[0094] 16. A method according to paragraph 15 and comprising changing said speed ratio within the group of speed ratios associated with the just disconnected drive clutch.

[0095] 17. A method according to paragraph 16 and comprising selecting a speed ratio for obtaining the highest available rotational speed of an input shaft.

[0096] 18. A method according to paragraph 15 and comprising determining that said electrical machine should cease to harvest energy from said transmission; [0097] determining that the selected speed ratio is appropriate for driving the vehicle, and if necessary selecting another speed ratio; and [0098] engaging the drive clutch associated with the selected speed ratio.

[0099] 19. A method of starting an internal combustion engine when coupled to a transmission according to paragraph 1, the method comprising: [0100] causing both drive clutches to be disengaged, [0101] engaging an armature clutch to permit driving of an input shaft of said transmission by said electrical machine; [0102] providing that said input shaft is not connected for drive to an output shaft of said transmission, [0103] causing rotation of said input shaft by said electrical machine, [0104] engaging a drive clutch associated with said input shaft to start said engine, and [0105] disconnecting said drive clutch after starting said engine.

[0106] 20. A method according to paragraph 19, the method comprising causing said electrical machine to rotate said engine via a forward gear train and a reverse gear train coupled in series.