Reconfigurable power-split drivetrain for a hybrid electric vehicle

Abstract

Drive train (10) comprising: a planetary gear set (14) having an input connected to an internal combustion engine (12), a second input connected to a generator (22), and an output connected to a countershaft (24); a second gear set (26) for driving the generator (22) at overdrive relative to a speed of the internal combustion engine (12); a clutch (30) for releasably connecting the input and the internal combustion engine (12); a second coupling (28) for releasably connecting the second input and the generator (22); and an electric motor (16) connected to the countershaft (24).

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] This invention relates generally to a power-split drivetrain for a hybrid electric vehicle. 2. Description of the state of the art

[0002] The powertrain of a hybrid electric vehicle (HEV) comprises an internal combustion engine, an electric motor / generator, and a traction battery, whereby the internal combustion engine and the electric motor can each drive the wheels alone, the internal combustion engine can charge the traction battery via the electric machine acting as a generator, and kinetic energy of the vehicle can be recovered and regenerated using the wheel brakes to drive the generator and charge the battery.

[0003] In the powertrain of a plug-in hybrid electric vehicle (PHEV), the traction battery has a significantly increased capacity, allowing electrical energy from the power grid to be used to propel the vehicle. As a result, significantly greater use of electric propulsion is expected. The direct connection of the generator to the wheel speed causes the generator shaft to rotate when the vehicle is moving with the internal combustion engine off.This causes several problems, including: (i) as the vehicle speed increases, the generator speed becomes excessively high, causing a durability problem for the bearing, planetary gear set, and generator; (ii) reducing the available torque needed to start the engine; (iii) since the generator is not used, it creates unnecessary rotational loss; and (iv) in reverse with the engine running, the electric motor must respond, reducing the torque available to the wheels.

[0004] JP 2011-240 855 A, US 2004 / 0 112 654 A1 and US 2011 / 0 300 983 A1 disclose generic drive trains. SUMMARY OF THE INVENTION

[0005] The objective technical problem to be solved can be seen as eliminating the disadvantages of the prior art. This problem is solved by independent patent claim 1.

[0006] A drive train comprises: a gear set including a sun gear, a carrier, a ring gear connected to a countershaft, and planetary gears mounted on the carrier and meshing with the sun gear and the ring gear; a second gear set connectable to an internal combustion engine for driving a generator in overdrive; a clutch for releasably connecting the internal combustion engine and the carrier; a second clutch for releasably connecting the sun gear and the generator; and an electric motor connected to a countershaft.

[0007] The powertrain is reconfigurable in that the powertrain operation can be easily switched from powersplit mode to series mode and from series mode to powersplit mode.

[0008] In a charge-sustaining mode, the combustion engine runs either in a series mode or a power-split mode.

[0009] The drivetrain delivers full torque from the traction motor to the wheels, which is an advantage over a single-mode powersplit drivetrain.

[0010] The drivetrain ensures high fuel economy and good drivability of a power split drivetrain, with improved pulling power and starting ability of the vehicle.

[0011] The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims, and drawings. It should be understood that the description and specific examples, while indicating preferred embodiments of the invention, are for illustrative purposes only. Various changes and modifications to the described embodiments and examples will be apparent to those skilled in the art. DESCRIPTION OF THE DRAWINGS

[0012] The invention will be better understood from the following description in conjunction with the accompanying drawings. They show: Fig. 1 a schematic representation of a drive train of a hybrid electric vehicle; Fig. 2 a table showing the engaged and disengaged state of clutches connecting the drive train of Fig. 1 control; Fig. 3 is a schematic diagram of a drive train of a hybrid electric vehicle; Fig. 4 a table showing the engaged and disengaged state of clutches connecting the drive train of Fig. 3 control; Fig. 5 is a schematic diagram of a drive train of a hybrid electric vehicle; Fig. 6 a table showing the engaged and disengaged state of clutches connecting the drive train of Fig. 5 taxes; Fig. 7 is a schematic diagram of a drive train of a hybrid electric vehicle; and Fig. 8 a table showing the engaged and disengaged state of clutches connecting the drive train of Fig. 7 control. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] It will first be Fig. 1, a powertrain 10 includes: a power source, such as an internal combustion engine 12, such as a diesel engine or a gasoline engine; a first planetary gear set 14; an electric motor 16; a countershaft transmission 18; a differential mechanism 20; an electric generator 22; a countershaft 24 drivingly connected to the differential mechanism 20, the output pinion 40, and the electric motor 16; and a second planetary gear set 26. Each electric machine 16, 22 is a motor-generator, although more commonly, the electric machine 16 is referred to as a motor or traction motor and the electric machine 22 is referred to as a generator. The sun gear 27 of the planetary gear set 14 is connected to the generator 22 by a clutch 28. The carrier 32 of the planetary gear set 14 is connected to the internal combustion engine 12 by a clutch 30 via a torsion damper 34 and a shaft 36.The ring gear 39 of the gear set 14 is drivingly connected to the countershaft 24 by an output pinion 40 and a gear 42, which mesh to form a countershaft gear pair 40-42. Planetary gears 43, mounted on the carrier 32, are in constant meshing engagement with the ring gear 39 and the sun gear 27.

[0014] The rotor 44 of the electric motor 16 is connected to the countershaft 24 via the gear pair 46-48.

[0015] The electric motor 16 is electrically connected to a traction battery 50 via an inverter 52 and a high-voltage DC / DC converter 54. Similarly, the generator 22 is connected to the battery 50 via an inverter 56 and the converter 54.

[0016] The countershaft 24 is connected via a pinion 60 and a ring gear 62 of the differential mechanism 20, which transmits power to the vehicle wheels 64, 66 via half shafts or axle shafts 68, 70.

[0017] An oil pump 72 is drivingly connected to the shaft 36 and the output of the internal combustion engine by a pinion 74 and a gear 76.

[0018] The sun gear 80 of the planetary gear set 26 is connected to the generator 22 by a clutch 82. The carrier 86 of the planetary gear set 26 is connected to the internal combustion engine 12 by a clutch 84 via a torsion damper 34 and a shaft 36. The ring gear 88 of the gear set 26 is arranged in a rotationally fixed manner due to its connection to a housing 90. Planetary gears 92, which are mounted on the carrier 86, are in constant meshing engagement with the ring gear 88 and the sun gear 80.

[0019] The powertrain 10 operates in power-split mode when clutches 28, 30 are engaged and clutches 82, 84 are disengaged. The engine 12 is connected to the carrier 32 via clutch 30, and the rotor of the generator 22 is connected to the sun gear 27 via clutch 28. In power-split mode, power generated by the engine 12 and, if the battery 50 is supplying electrical energy to the generator, power generated by the generator 26 is transmitted to the countershaft 24 via gear set 14 and gear pair 40-42, and power generated by the electric motor 16 is transmitted to the countershaft 24 through gear pair 46-48. The axle drive gear pair 60-62 transmits the power from the internal combustion engine 12, the electric motor 16 and the generator 22 to the differential mechanism 20, which transmits power to the vehicle wheels 64, 66 via shafts 68, 70 in a differential-controlled manner.In power-split mode with generator 22 operating as an electric generator, the internal combustion engine 12 supplies power to the generator 22, enabling the battery 50 to be charged. The drivetrain 10 operates in series mode when clutches 28, 30 are disengaged and clutches 82, 84 are engaged. The internal combustion engine 12 is connected to the carrier 86 of the gear set 26 via the clutch 84, the sun gear 80 is overdriven relative to the speed of the internal combustion engine 12, and the clutch 82 connects the overdriven sun gear 80 to the rotor of the generator 22. In series operation, power generated by the internal combustion engine 12 drives the generator 26 at a relatively high speed, thereby charging the battery 50, and power generated by the electric motor 16 is transmitted to the countershaft 24 through the gear pair 46-48.The final drive gear pair 60-62 transmits the power generated by the electric motor 16 to the differential mechanism 20.

[0020] In Fig. 3, the clutch 84 is omitted, whereby the carrier 86 of the gear set 26 is directly and continuously connected to the internal combustion engine 12 via the shaft 36 and the torsion damper 34. The drive train 94 of Fig. 3 operates in power split mode when clutches 28, 30 are engaged and clutch 82 is disengaged. The internal combustion engine 12 is connected to the carrier 32 via clutch 30, and the rotor of generator 22 is connected to the sun gear 27 via clutch 28. In power split mode, power generated by the internal combustion engine 12 and generator 26 is transmitted to the countershaft 24 via gear set 14 and gear pair 40-42, and power generated by the electric motor 16 is transmitted to the countershaft 24 through gear pair 46-48. The final drive gear pair 60-62 transmits the power from the internal combustion engine 12, the electric motor 16 and the generator 22 to the differential mechanism 20. In power split mode with the generator 22 operating as an electric generator, the internal combustion engine 12 supplies power to the generator 22, thereby enabling the battery 50 to be charged.

[0021] The drivetrain 94 from Fig. 3 operates in series mode when clutches 28, 30 are disengaged and clutch 82 is engaged. The engine 12 is directly connected to the carrier 86 of the gear set 26, the sun gear 80 and the generator rotor are overdriven relative to the speed of the engine 12, and the clutch 82 connects the overdriven sun gear 80 to the rotor of the generator 22. In series operation, power generated by the engine 12 drives the generator 26 at a relatively high speed, thereby charging the battery 50, and power generated by the electric motor 16 is transmitted through the gear pair 46-48 to the countershaft 24. The final drive gear pair 60-62 transmits the power generated by the electric motor 16 to the differential mechanism 20.

[0022] In Fig. 5, the clutch 84 is present, but the clutch 82 is omitted, whereby the sun gear 80 of the gear set 26 is directly and continuously connected to the rotor of the generator 22. The drive train 96 of Fig. 5 operates in power split mode when clutches 28, 30 are engaged and clutch 84 is disengaged. The internal combustion engine 12 is connected to the carrier 32 via clutch 30, and the rotor of generator 22 is connected to the sun gear 27 via clutch 28. In power split mode, power generated by the internal combustion engine 12 and generator 26 is transmitted to the countershaft 24 via gear set 14 and gear pair 40-42, and power generated by the electric motor 16 is transmitted to the countershaft 24 via gear pair 46-48. The final drive gear pair 60-62 transmits the power from the internal combustion engine 12, the electric motor 16 and the generator 22 to the differential mechanism 20. In power split mode with the generator 22 operating as an electric generator, the internal combustion engine 12 supplies power to the generator 22, thereby enabling the battery 50 to be charged.

[0023] The drivetrain 96 from Fig. 5 operates in series mode when clutches 28, 30 are disengaged and clutch 84 is engaged. The internal combustion engine 12 is connected to the carrier 86 of the gear set 26 via clutch 84, the sun gear 80 is driven at overspeed relative to the speed of the internal combustion engine 12, and is directly connected to the rotor of the generator 22. In series operation, power generated by the internal combustion engine 12 drives the generator 26 at a relatively high speed, thereby charging the battery 50, and power generated by the electric motor 16 is transmitted through the gear pair 46-48 to the countershaft 24. The final drive gear pair 60-62 transmits the power generated by the electric motor 16 to the differential mechanism 20.

[0024] The drivetrain 98 from Fig.7 comprises: a shaft 102 connected to the rotor of the generator 22; a pinion 100; a gear 104 meshing with the pinion 100; a second countershaft 106 fixedly connected to the gear 104 and to a pinion 108; a gear 110 meshing with the pinion 108; a clutch 112 for opening and closing a drive connection between the shaft 36 and the gear 110; a clutch 114 for opening and closing a drive connection between the shaft 36 and the carrier 32 of the gear set 14; a clutch 116 for opening and closing a drive connection between the sun gear 27 and the shaft 102; and a clutch 118 for opening and closing a drive connection between the shaft 102 and the pinion 100.

[0025] The powertrain 98 operates in power split mode when clutches 114, 116 are engaged and clutches 112, 118 are disengaged. The internal combustion engine 12 is connected to the carrier 32 via clutch 112, and the rotor of the generator 22 is connected to the sun gear 27 via clutch 116. In power split mode, power generated by the internal combustion engine 12 and, if the battery 50 is supplying electrical energy to the generator, power generated by the generator 26 is transmitted to the countershaft 24 via gear set 14 and gear pair 40-42, and power generated by the electric motor 16 is transmitted to the countershaft 24 through gear pair 46-48. The axle drive gear pair 60-62 transmits the power from the internal combustion engine 12, the electric motor 16 and the generator 22 to the differential mechanism 20, which transmits power to the vehicle wheels 64, 66 via shafts 68, 70 in a differential-controlled manner.In power-split mode with generator 22 operating as an electric generator, engine 12 supplies power to generator 22, enabling battery 50 to be charged. Drivetrain 10 operates in series mode when clutches 112, 118 are engaged and clutches 114, 116 are disengaged. Engine 12 is connected via clutch 112, gear 110, pinion 108, countershaft 106, gear 104, pinion 100, and shaft 102 to the rotor of generator 22, which is driven at overdrive relative to the speed of engine 12. In serial operation, power generated by the internal combustion engine 12 drives the generator 26 at a relatively high speed, thereby charging the battery 50, and power generated by the electric motor 16 is transmitted to the countershaft 24 through the gear pair 46-48.The final drive gear pair 60-62 transmits the power generated by the electric motor 16 to the differential mechanism 20. Preferably, the drivetrain 10 includes: a gear set 14 including a sun gear 27, a carrier 32, a ring gear 39 connected to a countershaft 24, and planetary gears 43 supported on the carrier and meshing with the sun gear and ring gear; a second gear set 26 connectable to an internal combustion engine for driving a generator 22 in overdrive; a clutch 30 for releasably connecting the internal combustion engine and the carrier; a second clutch 28 for releasably connecting the sun gear and the generator; and an electric motor 16 connected to a countershaft.

[0026] Furthermore, a differential 20 is provided for transmitting power between the countershaft and vehicle wheels, as well as a first pair of meshing gears 48, 46 connecting the electric motor and the countershaft, a second pair of meshing gears 40, 42 connecting the ring gear and the countershaft, and a third pair of meshing gears 60, 62 connecting the differential and the countershaft.

[0027] Preferably, the second gear set 26 includes a second sun gear 80, a second carrier 86, a second ring gear 88, and second planet gears 92 supported on the second carrier and meshing with the second sun gear and the second ring gear, the drive train further including a third clutch 82 for releasably connecting the second sun gear and the generator. Further preferably, the drive train comprises an electric storage battery; a DC / DC converter electrically connected to the battery; an inverter electrically connected to the electric motor and the converter; and a second inverter electrically connected to the generator and the converter.

[0028] In accordance with the provisions of the Patent Act, the preferred embodiment has been described. However, it should be understood that alternative embodiments may be practiced in a manner other than that specifically illustrated and described herein.

Claims

[1] Drive train (10) comprising: a planetary gear set (14) having an input connected to an internal combustion engine (12), a second input connected to a generator (22), and an output connected to a countershaft (24); a second gear set (26) for driving the generator (22) at overdrive relative to a speed of the internal combustion engine (12); a clutch (30) for releasably connecting the input and the internal combustion engine (12); a second coupling (28) for releasably connecting the second input and the generator (22); and an electric motor (16) connected to the countershaft (24). [2] The driveline (10) of claim 1, further comprising a differential (20) for transmitting power between the countershaft (24) and vehicle wheels (64, 66). [3] The drive train (10) of claim 1, further comprising a first pair of meshing gears (46, 48) connecting the electric motor (16) and the countershaft (24). [4] The driveline (10) of claim 1, further comprising a second pair of meshing gears (40, 42) connecting the output gear and the countershaft (24). [5] The driveline (10) of claim 1, further comprising a third pair of meshing gears (60, 62) connecting the differential (20) and the countershaft (24). [6] The drivetrain (10) of claim 1, wherein the second gear set (26) includes a second sun gear (80), a second carrier (86), a second ring gear (88), and second planetary gears (92) supported on the second carrier (86) and meshing with the second sun gear (80) and the second ring gear (88); wherein the drivetrain (10) further includes a third clutch (82) for releasably connecting the second sun gear (80) and the generator (22). [7] The drivetrain (10) of claim 1, wherein the second gear set (26) includes a second sun gear (80), a second carrier (86), a second ring gear (88), and second planet gears (92) supported on the second carrier (86) and meshing with the second sun gear (80) and the second ring gear (88); wherein the drivetrain (10) further includes a fourth clutch (84) for releasably connecting the internal combustion engine (12) and the second carrier (86). [8] The powertrain (10) of claim 1, further comprising: an electrical storage battery (50); a DC / DC converter (54) electrically connected to the battery (50); an inverter (52) electrically connected to the electric motor (16) and the converter (54); and a second inverter (56) electrically connected to the generator (22) and the converter (54). [9] Drive train (10) according to claim 1, wherein the second gear set comprises: a pinion (100) connected to the generator (22); a second countershaft (106); a gear (104) meshing with the pinion (100) and fixedly connected to the second countershaft (106); a second pinion (108) fixedly connected to the second countershaft (106); a second gear (110) connected to the internal combustion engine (12) and meshing with the second pinion (108). [10] The powertrain (10) of claim 9, further comprising: a third clutch (82) for releasably connecting the internal combustion engine (12) and the second pinion gear (108); and a fourth clutch (84) for releasably connecting the generator (22) and the first pinion gear (100).

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