Powertrain and methods for operating a powertrain

Abstract

A powertrain (10) for a hybrid vehicle is provided comprising an internal combustion engine (12) for providing combustion engine-generated mechanical drive power, an electric main drive (14) for providing electric motor-generated electric drive power, an electric auxiliary drive (20) permanently coupled to the internal combustion engine (12) for providing electric motor-generated starting power for starting the internal combustion engine (12), a transmission input shaft (28) that can be coupled to the internal combustion engine (12) and to the main drive (14), and a freewheel (54) for interrupting a power flow generated by the main drive (14) into the internal combustion engine (12).The freewheel (54) allows the function of starting the combustion engine (12) to be transferred to the auxiliary drive (20) permanently coupled to the combustion engine (12), and the drive power provided by the main drive (14) up to maximum power can be used to drive the hybrid vehicle, thus enabling efficient operation of the hybrid vehicle.

Description

[0001] The invention relates to a powertrain and a method for operating such a powertrain, with the aid of which a hybrid vehicle can be powered, and such a hybrid vehicle.

[0002] EP 3 020 588 B1 discloses a drive train for a hybrid vehicle comprising an internal combustion engine which can be coupled via a disconnect clutch to a rotor shaft of an electric machine used as an auxiliary drive which coincides with a transmission input shaft of a manual transmission, and an electric machine used as the main drive which can be coupled to the transmission input shaft via a freewheel, wherein the electric machine used as the main drive can be coupled to an output transmission shaft of the manual transmission via a first gear provided for starting the hybrid vehicle.

[0003] There is a constant need to improve the efficiency of operating a hybrid vehicle.

[0004] The purpose of the invention is to demonstrate measures that enable the efficient operation of a hybrid vehicle.

[0005] The problem is solved according to the invention by a powertrain with the features of claim 1, a method with the features of claim 8, and a hybrid vehicle with the features of claim 11. Preferred embodiments of the invention are specified in the dependent claims and the following description, each of which can individually or in combination represent an aspect of the invention, the scope of protection being determined by the claims.

[0006] One aspect of the invention relates to a drive train for a hybrid vehicle, comprising an internal combustion engine for providing mechanical drive power generated by the internal combustion engine; an electric main drive for providing electric drive power generated by the electric motor; an electric auxiliary drive permanently coupled to the internal combustion engine for providing electric starting power for starting the internal combustion engine; a transmission input shaft that can be coupled to the internal combustion engine and to the main drive; and a freewheel for interrupting a power flow generated by the main drive into the internal combustion engine.

[0007] Since the main drive is permanently coupled to the output shaft, it cannot start the combustion engine unless the car is in motion or being set in motion. Starting the combustion engine, whether stationary or in motion, can instead be accomplished by the electric auxiliary drive permanently coupled to the combustion engine or by a conventional pinion starter. This allows the main drive to be used across its entire power range, both in motor mode to propel the hybrid vehicle and in generator mode to recuperate mechanical power into electrical energy. It is not necessary for the main drive to maintain a torque reserve large enough to initiate a hot and / or cold start of the combustion engine.This allows the main drive to be used up to its maximum output to power the hybrid vehicle, enabling greater utilization of the main drive's electrical capacity and thus, relative to its installed maximum electrical output, more efficient operation of the hybrid vehicle. Since the otherwise available torque reserve can be used to power the hybrid vehicle, it is possible to achieve correspondingly higher acceleration via the main drive without having to start the combustion engine. The freewheel mechanism allows the function of starting the combustion engine to be transferred to the auxiliary drive, which is permanently coupled to the combustion engine. This enables the drive power provided by the main drive up to its maximum output to be used to power the hybrid vehicle, thus ensuring efficient operation.

[0008] The powertrain is designed to propel a hybrid vehicle and can, in particular, provide a purely internal combustion engine drive, a purely electric drive, or a mixed drive in which both mechanical drive power generated by the internal combustion engine and electric drive power generated by the electric motor can be used simultaneously to propel the hybrid vehicle. The drive power can, in particular, be transmitted to the drive wheels via a transmission, with speed and torque conversion. Preferably, two drive wheels can be coupled via a differential. The powertrain can, in particular, enable front-wheel drive, rear-wheel drive, or all-wheel drive for the hybrid vehicle.

[0009] A hybrid vehicle is, in particular, a land vehicle that travels on a road and can be powered by more than one energy source.

[0010] The internal combustion engine, by burning a fuel mixture in at least one combustion cylinder, moves a piston, which, in particular via a connecting rod, sets a crankshaft in motion and thereby transmits the mechanical drive power generated by the combustion engine to the crankshaft. The internal combustion engine can be designed, in particular, as a gasoline engine, diesel engine, or gas engine. The internal combustion engine can, for example, operate on a four-stroke or two-stroke principle. The internal combustion engine can preferably have several combustion cylinders, in particular four, six, eight, or twelve combustion cylinders. The combustion cylinders can, for example, be arranged in a line, in a V-configuration, or in a boxer configuration.

[0011] The main drive and the auxiliary drive are designed as electric machines in which a rotor can rotate relative to a stator, with the rotor interacting electrically and / or magnetically with the stator. For example, the stator has electromagnets that interact electromagnetically with permanent magnets in the rotor. Each rotor can be connected to a rotor shaft, through which torque can be exchanged with at least part of the rest of the drive train. The main drive and / or the auxiliary drive can be electrically connected to a vehicle battery, preferably a rechargeable one, so that the main drive and / or the auxiliary drive can be powered with electrical energy from the vehicle battery and / or electrical energy recuperated from mechanical power can be stored.Mechanical energy recuperation can be achieved, for example, by operating the main drive and / or the auxiliary drive in generator mode during deceleration of the vehicle, coasting, and / or load increase to operate the combustion engine at a fuel-efficient operating point. In particular, the auxiliary drive is dimensioned for a lower maximum power output than the maximum power output of the main drive. For example, the following applies to a ratio V of the maximum power output of the main drive to the maximum power output of the auxiliary drive: 1.0 < V ≤ 10.0, more particularly 1.1 ≤ V ≤ 5.0, preferably 1.2 ≤ V ≤ 2.5, and most preferably 1.5 ≤ V ≤ 2.0.

[0012] The auxiliary drive is permanently coupled to the combustion engine, eliminating the need for a clutch or switching element between the two, thus enabling efficient power transmission. If no power input from the auxiliary drive is desired, and braking by the auxiliary drive operating in generator mode is also not required, the auxiliary drive can be deactivated, for example, by interrupting the circuits for electromagnets. For instance, the auxiliary drive may be used exclusively for starting the combustion engine, thus eliminating the need for a separate pinion starter.

[0013] The transmission input shaft can be part of a transmission, particularly a manual transmission, automatic transmission, dual-clutch transmission, and / or CVT, to introduce drive power that, after conversion of speed and torque, can be output to a transmission output shaft and, in particular, transmitted to drive wheels. The transmission is configured, in particular, as a 5-speed transmission or as a 7-speed transmission with five or seven forward gears, respectively, each with a different gear ratio. A reverse gear can be provided in the transmission. The various gears can be shifted, for example, by means of shift sleeves, preferably synchronizable ones.

[0014] The freewheel can, for example, be designed as a freewheel that locks in one direction of rotation. When driving forward, if the rotational speed applied to the freewheel by the main drive is greater than the rotational speed applied to the freewheel by the internal combustion engine (i.e., the main drive is overtaking), the freewheel can disengage and interrupt torque transmission. Conversely, when driving forward, if the rotational speed applied to the freewheel by the internal combustion engine is greater than the rotational speed applied to the freewheel by the main drive (i.e., the internal combustion engine is overtaking), the freewheel can lock and allow torque transmission. The freewheel is, for example, designed as a pawl freewheel. It is also possible for the freewheel to be switchable between different operating modes.

[0015] In particular, the freewheel allows coupling with an input gear of a first gear intended for starting the hybrid vehicle. The transmission input shaft can have several gear stages, especially those designed as spur gear stages, each providing a driving gear with a specific ratio and which can be selected appropriately. The first gear intended for starting the hybrid vehicle from a standstill can, for example, have a reduction ratio of approximately 1:4, especially from 1:8 to 1:12, which is well suited for both combustion engine starting and electric driving of the hybrid vehicle. The ratio of the main drive for propelling the hybrid vehicle is thus identical to the ratio of the combustion engine for starting the hybrid vehicle from a standstill in first gear.

[0016] Preferably, the main drive is permanently coupled to the input gear of the first gear used to start the hybrid vehicle, with the input transmission shaft being disengageable from the input gear by means of a freewheel. A clutch or other coupling and / or switching element in the torque flow between the main drive and the input gear of the first gear is not required and can be omitted. If the main drive is to be decoupled from the power supply, it is sufficient to disengage it, for example by interrupting the electromagnet circuits, so that the rotor of the main drive's electric machine rotates without electromagnetic interaction with the stator, thus keeping the main drive's drag torques low.

[0017] A maximum output speed of the main drive is particularly advantageous, as it is dimensioned to match the maximum driving speed of the hybrid vehicle. The main drive can remain engaged until the hybrid vehicle reaches its maximum driving speed and does not need to be disengaged. The main drive can be utilized up to its maximum power output.

[0018] In one embodiment, the auxiliary drive is specifically designed as a pinion starter. The auxiliary drive can be comparatively small and cost-effective. In particular, the pinion starter can be positioned for ease of maintenance on the outside of the internal combustion engine and mesh with an external toothing of a flywheel on the internal combustion engine's crankshaft via a pinion driven by the auxiliary drive's electric motor.

[0019] In an alternative embodiment, a separate pinion starter is preferably provided in addition to the auxiliary drive to supply electrically generated starting power for starting the internal combustion engine. A crankshaft of the internal combustion engine forms a rotor shaft of the auxiliary drive, and the auxiliary drive is located at an end of the internal combustion engine pointing away from or towards the transmission input shaft. The rotor shaft of the auxiliary drive can be formed integrally with the crankshaft, which protrudes from the housing of the internal combustion engine on one side or the opposite side. The auxiliary drive can improve acoustics during engine start-up by eliminating a gear tooth.

[0020] Preferably, the internal combustion engine is coupled to the transmission input shaft via a dry friction clutch, in particular a single-disc friction clutch. The auxiliary drive can contribute to driving and / or braking the crankshaft, which improves synchronization of the crankshaft speed with the transmission input shaft speed and allows for a shorter and / or less stressful slip operation of the friction clutch when engaging the crankshaft with the transmission input shaft. This allows a friction clutch designed for lower loads to be used as the disconnecting clutch between the crankshaft and the transmission input shaft, thereby reducing manufacturing costs. In particular, a dry single-disc friction clutch can be used as the disconnecting clutch, which does not require oil cooling.

[0021] Another aspect concerns a method for operating a powertrain, which can be designed and further developed as described above, in which, of the main drive and the auxiliary drive, only the auxiliary drive is used to start the combustion engine, and in particular, only the main drive is used to recuperate mechanical energy into electrical energy. This means that the main drive is not used to start the combustion engine and / or the auxiliary drive is not used for recuperation. Due to the freewheel mechanism, the function of starting the combustion engine can be transferred to the auxiliary drive, which is permanently coupled to the combustion engine, and the drive power provided by the main drive up to its maximum output can be used to power the hybrid vehicle, thus enabling efficient operation of the hybrid vehicle.

[0022] In particular, the auxiliary drive and / or the main drive is used to compensate for the temporary loss of drive torque from the combustion engine during gear changes. By increasing the drive power of the main drive and / or the auxiliary drive accordingly, gear changes can be achieved with virtually no interruption in traction. This can be accomplished by utilizing any remaining power reserves in the main drive or in the auxiliary drive.

[0023] Preferably, the auxiliary drive and / or the main drive compensate for changes in the current drive power demand in such a way that the mechanical drive power generated by the internal combustion engine is adjusted more slowly to the currently demanded drive power. Instead of simply adjusting the mechanical power output of the internal combustion engine as quickly as possible to keep pace with a change in the current drive power demand, the currently demanded drive power can be adjusted quickly and efficiently by adjusting the electrical drive power of the main drive and / or auxiliary drive.This allows the adjustment of the mechanical power generated by the combustion engine to be controlled more slowly over time, which facilitates a more energy-efficient operation of the combustion engine as close as possible to the optimal operating point and shifts the energetically unfavorable consequences of short-term fluctuations and / or irregularities in the currently required drive power to an energetically more favorable adjustment of the electrically generated drive power.

[0024] Another aspect concerns a hybrid vehicle with a powertrain that can be configured and further developed as described above, and a control unit for operating the powertrain, wherein the control unit is specifically designed to carry out the procedure that can be configured and further developed as described above. Due to the freewheeling function, the function of starting the combustion engine can be transferred to the auxiliary drive permanently coupled to the combustion engine, and the drive power provided by the main drive up to maximum output can be used to drive the hybrid vehicle, thus enabling efficient operation of the hybrid vehicle.

[0025] The invention is now explained by way of example with reference to the accompanying drawing, using a preferred embodiment as an illustration, wherein the features shown below can represent an aspect of the invention, either individually or in combination, and the scope of protection is defined by the claims. It shows: Fig. 1 A schematic diagram of a powertrain.

[0026] The in Fig.The powertrain shown in Figure 1 can be used to propel a hybrid vehicle, particularly a sports car or racing car. For this purpose, the powertrain 10 includes an internal combustion engine 12, which generates mechanical drive power. It also includes a main electric drive 14, which can generate electrical drive power in motor mode and recuperate mechanical power into electrical energy in generator mode. The internal combustion engine 12 has several combustion cylinders 16, which drive a crankshaft 18. An auxiliary electric drive 20 is permanently coupled to the crankshaft 18, which generates starting power for starting the internal combustion engine 12 in motor mode.In principle, it is possible that a separate pinion starter 22 is provided for cold starting and / or warm starting of the internal combustion engine 12, either in addition to or in the case of the omission of the auxiliary drive 20, but it is also possible to omit the separate pinion starter 22 and replace it completely with the auxiliary drive 20.

[0027] The crankshaft 18 of the internal combustion engine 12, which simultaneously forms a rotor shaft of the auxiliary drive 20, is coupled in the direction of power flow, preferably via a torsional vibration damper 24, for example a dual-mass flywheel, to a disconnecting clutch 26, which is in particular designed as a dry single-disc clutch. Alternatively, the crankshaft 18 can protrude from the rest of the internal combustion engine 12 on the side facing away from the disconnecting clutch 26 in order to connect the auxiliary drive 20 on the side facing away from the disconnecting clutch 26.

[0028] The disconnect clutch 26 can selectively transmit the vibration-damped mechanical drive power of the internal combustion engine to a transmission input shaft 28 of a, preferably automatic, manual transmission 30. For this purpose, the disconnect clutch 26 can interact directly with the transmission input shaft 28. However, it is also possible for the internal combustion engine to be oriented perpendicular to the longitudinal extent of the transmission input shaft 28, and for the disconnect clutch to be coupled to the transmission input shaft 28 via an intermediate bevel gear. The bevel gear can have interlocking bevel gears.

[0029] The transmission 30 can, for example, have a first gear 32, a second gear 34, a third gear 36, a fourth gear 38, and a fifth gear 40, each providing different gear ratios and designed as spur gear pairs. The various gears assigned to the respective gear stages 32, 34, 36, 38, and 40 can be selected by means of a shifting device 42 with shift sleeves. The drive power can be transmitted via gear stages 32, 34, 36, 38, and 40, with the corresponding speed and torque conversion, to a transmission output shaft 44. The transmission output shaft 44 can transmit the drive power converted in the transmission 30, for example, via a coupling 46 and / or a differential 48 to drive axles 50, which in turn can be connected to drive wheels.

[0030] The electric main drive 14 is permanently connected to an input gear 52 of the first gear stage 32, with the first gear stage 32 forming the first driving gear intended for starting the hybrid vehicle from a standstill. The input gear 52 is coupled to the transmission input shaft 28 via a freewheel 54. The freewheel 54 can lock when the transmission input shaft 28 is overrunning and introduce the mechanical drive power generated by the combustion engine into the input gear 52, and can freewheel when the input gear 52 is overrunning, thereby reliably preventing power flow from the main drive 14 to the combustion engine 12. This ensures that a cold start and / or a warm start of the combustion engine 12 is not performed by the main drive 14, but preferably by the auxiliary drive 20. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 020 588 B1

[0002]

Claims

[1] Powertrain (10) for a hybrid vehicle, with an internal combustion engine (12) to provide internal combustion engine-generated mechanical drive power, an electric main drive (14) to provide an electric motor-generated electric drive power, an electric auxiliary drive (20) permanently coupled to the internal combustion engine (12) to provide electrically generated starting power for starting the internal combustion engine (12), a transmission input shaft (28) that can be coupled to the internal combustion engine (12) and to the main drive (14) and a freewheel (54) to interrupt a power flow generated by the main drive (14) into the internal combustion engine (12). [2] Drive train (10) according to claim 1, wherein the freewheel (54) enables coupling with an input gear (52) of a first gear provided for starting the hybrid vehicle. [3] Drive train (10) according to claim 1 or 2, wherein the main drive (14) is permanently coupled to an input gear (52) of a first gear provided for starting the hybrid vehicle, wherein the input transmission shaft (28) can be disengaged from the input gear (52) by means of the freewheel (54). [4] Powertrain (10) according to one of claims 1 to 3, wherein a maximum output speed of the main drive (14) is dimensioned for the maximum driving speed of the hybrid vehicle. [5] Drive train (10) according to one of claims 1 to 4, wherein the auxiliary drive (20) is designed as a pinion starter (22). [6] Drive train (10) according to one of claims 1 to 4, wherein in addition to the auxiliary drive (20) a separate pinion starter (22) is provided to provide an electrically generated starting power for starting the internal combustion engine (12), wherein a crankshaft (18) of the internal combustion engine (12) forms a rotor shaft of the auxiliary drive (20), wherein the auxiliary drive (20) is provided at an end of the internal combustion engine (12) pointing away from the transmission input shaft (18) or at an end pointing towards the transmission input shaft (18). [7] Drive train (10) according to any one of claims 1 to 6, wherein the internal combustion engine (12) is coupled to the transmission input shaft (28) via a dry friction clutch. [8] Method for operating a drive train (10) according to one of claims 1 to 7, wherein of the main drive (14) and the auxiliary drive (20) only the auxiliary drive (20) is used to start the internal combustion engine (12). [9] Method according to claim 8, wherein the auxiliary drive (20) and / or the main drive (14) is used to replenish a drive torque of the internal combustion engine (12) that temporarily drops during a shifting operation between different driving gears. [10] Method according to claim 8 or 9, wherein the auxiliary drive (20) and / or the main drive (14) compensate for a change in the current drive power demanded for the purpose of adjusting the mechanical drive power generated by the internal combustion engine (12) more slowly to the currently demanded drive power. [11] Hybrid vehicle with a powertrain (10) according to any one of claims 1 to 7 and a control device for operating the powertrain (10), wherein the control device is configured to perform the method according to any one of claims 8 to 10.

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