Parallel hybrid powertrain arrangement and a method for starting such a powertrain arrangement

Abstract

Parallel hybrid drive train arrangement (2) for a motor vehicle with an internal combustion engine (4) with a crankshaft, at least one clutch arrangement (10, 14), at least one transmission arrangement (10), at least one electric machine (6), at least one voltage source (16, 18), at least one starting device (22) with a starter torque M SE to overcome a breakaway torque M Vlos of the internal combustion engine (4), wherein the at least one electric machine (6) is provided in series between the internal combustion engine (4) and the transmission arrangement (10), characterized in that the electric machine (6) is designed as a second, additional starting device and that a start control device (24) is provided, which in the case of M SE < M Vlos the electric machine (6) is controlled as a second additional starting device in such a way that the electric machine (6) directly or indirectly preloads the crankshaft in the direction of crankshaft rotation.

Description

[0001] The invention relates to a parallel hybrid drive train arrangement for a motor vehicle with an internal combustion engine having a crankshaft, at least one clutch arrangement, at least one transmission arrangement, at least one electric machine, at least one voltage source, at least one starting device with a starter torque M SE to overcome a breakaway torque M Vlos of the internal combustion engine, wherein the at least one electric motor is provided in series between the internal combustion engine and the transmission arrangement. Furthermore, the invention relates to a method for starting such a drive train arrangement.

[0002] Parallel hybrid drivetrain arrangements are known from the prior art. An example of this can be found in DE 10 2010 036 510 A1 or US 2010 / 0 025 128 A1. A parallel hybrid drivetrain arrangement is characterized by the fact that the electric machine(s) can act on the drivetrain together with the combustion engine. In contrast to the serial hybrid drivetrain arrangement, the combustion engine is therefore directly connected to the drivetrain via machine components. The parallel hybrid drivetrain arrangement disclosed in DE 10 2010 036 510 A1 is designed as a parallel series arrangement, with the at least one electric machine being provided in series between the combustion engine and the transmission arrangement. Such an arrangement is chosen in particular when the electric machine is to be designed essentially to support the combustion engine.The intended starting device with a starter torque M. SE must in any case be designed in such a way that it can withstand the breakaway torque M under all operating conditions, even at particularly cold ambient temperatures. VLos of the internal combustion engine. It should be clear that, under most operating conditions, the starting device is consequently oversized. This is particularly disadvantageous in light of cost optimization and optimal use of installation space. In this context, it is known from the subsequently published DE 10 2015 115 600 A1 to generate a preloading torque on the crankshaft of an internal combustion engine using an electric motor so that the starter device only has to transmit a small amount of torque, which has a positive effect on starting behavior.

[0003] The object of the invention is therefore to avoid the above-mentioned disadvantage in a simple and cost-effective manner.

[0004] This object is achieved according to the invention in that the electric machine is designed as a second, additional starting device and in that a start control device is provided which, in the case of M SE < M Vlos The electric motor is controlled as a second additional starting device, such that the electric motor directly or indirectly preloads the crankshaft in the direction of crankshaft rotation. In this way, the actual starting device can be optimally designed for typical operating conditions, with the electric motor provided in the drive train arrangement being able to be used as an additional starting device if necessary.

[0005] In a particularly advantageous embodiment, a second clutch arrangement is provided between the internal combustion engine and the electric motor. This clutch arrangement can be designed, for example, as a dog clutch. When the clutch arrangement is decoupled, only the electric motor can act on the drivetrain as an electric motor. When the clutch arrangement is engaged, the electric motor can act as an electric motor to increase the torque to be introduced into the drivetrain. However, the electric motor can also be used as a generator in a known manner.

[0006] To minimize torsional vibrations in the drive train, it is advantageous to install a vibration damper, e.g., in the form of a dual-mass flywheel, at the output of the combustion engine. With a dual-mass flywheel, the electric motor can then act on the transmission-side flywheel. By preloading the transmission-side flywheel in the direction of crankshaft rotation, and thus also the crankshaft, the breakaway torque M that must be overcome by the first starting device is reduced. VLos reduced and, on the other hand, the dual-mass flywheel is protected so that a system change can be avoided.

[0007] The task is also solved by a method for starting a parallel hybrid drive train arrangement, wherein firstly the start control device checks how large the starter torque M SE is when M SE > M Vlosis, the combustion engine is then started by the first starting device when M SE < M Vlos is, the electric motor is subsequently controlled as an additional starting device and the crankshaft is preloaded directly or indirectly in the direction of crankshaft rotation.

[0008] The invention is explained in more detail with reference to a drawing, in which the only figure shows a parallel hybrid drive train arrangement according to the invention.

[0009] The single figure shows part of a drivetrain arrangement 2 according to the invention. An internal combustion engine 4 and an electric machine 6 designed as an electric motor form the drive part of the in-line parallel hybrid drivetrain arrangement 2. The electric motor 6 is connected on the output side via a starting element 8, which is designed here as a dual clutch and thus the first clutch arrangement, to a transmission arrangement 10, which distributes the power to a drive axle (not shown in detail). Between the internal combustion engine 4 and the electric motor 6, a vibration damper 12 designed as a dual-mass flywheel and a second clutch arrangement 14 designed as a dog clutch are provided in a known manner.

[0010] Furthermore, a high-voltage source 16 and a low-voltage source 18 are provided in a known manner, which are electrically coupled to one another via a DC-DC converter 20. The high-voltage source 16 is electrically coupled to the electric motor 6, and electrical consumers of the motor vehicle are electrically coupled to the low-voltage source 18 in a known manner. The internal combustion engine 4 is normally started by an external electrical starting device 22. To initiate a starting process, a starting control device 24 is provided, which is schematically shown here as a separate control device. Normally, however, this starting control device 24 is integrated into an engine control device (not shown). If a starting process is to be initiated, the starter torque M is first checked in the starting control device 24 against the background of the existing operating conditions.SE Normally, the torque M that can be generated by the external starting device 22 is SE greater than the breakaway torque M VLos of the internal combustion engine 4. The external starting device 22 can then start the internal combustion engine 4 in a known manner. However, if, for example, in the case of a very low ambient temperature, the starter torque M SE is very low and therefore M SE < as M VLos is, the electric motor 6 is controlled by the control device 24 as an additional starting device, so that a total starter torque (M SE + M EM ) to overcome the breakaway torque M VLos of the combustion engine 4. In order to achieve the necessary total starting torque (M SE + M EM) and to protect the dual-mass flywheel 12 from a system change, the invention provides that, before the actual starting process, a crankshaft (not shown) of the internal combustion engine 4 is preloaded in the crankshaft rotation direction; then, the internal combustion engine 4 is started. After the actual starting process, depending on availability, both the internal combustion engine 4 and the electric motor 6 can further increase their torque to form a pilot torque. This increase can occur digitally, in a ramp-like manner, or asymptotically.

Claims

[1] Parallel hybrid drive train arrangement (2) for a motor vehicle with an internal combustion engine (4) with a crankshaft, at least one clutch arrangement (10, 14), at least one transmission arrangement (10), at least one electric machine (6), at least one voltage source (16, 18), at least one starting device (22) with a starter torque M SE to overcome a breakaway torque M Vlos of the internal combustion engine (4), wherein the at least one electric machine (6) is provided in series between the internal combustion engine (4) and the transmission arrangement (10), characterized by that the electric machine (6) is designed as a second, additional starting device and that a start control device (24) is provided which, in the case of M SE < M Vlos the electric machine (6) is controlled as a second additional starting device in such a way that the electric machine (6) directly or indirectly preloads the crankshaft in the direction of crankshaft rotation. [2] Parallel hybrid drive train arrangement for a motor vehicle according to claim 1, characterized by that a second clutch arrangement (14) is provided between the internal combustion engine (4) and the electric motor (6). [3] Parallel hybrid drive train arrangement for a motor vehicle according to claim 1 or 2, characterized by that a vibration damper (12), e.g. in the form of a dual-mass flywheel, is provided at the output of the internal combustion engine (4). [4] A method for starting a parallel hybrid powertrain arrangement according to any one of the preceding claims, characterized by that first the start control device (24) checks how large the starter torque M SE is when M SE > M Vlos is, the combustion engine (4) is then started by the first starting device (22) when M SE < M Vlosis, the electric machine (6) is subsequently controlled as an additional starting device and the crankshaft is pretensioned directly or indirectly in the direction of crankshaft rotation and then the combustion engine (4) is started.

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