Drive system for a motor vehicle and corresponding operating method

Abstract

Drive system for a motor vehicle with a) an internal combustion engine (1) for driving the motor vehicle, b) at least one auxiliary unit (10-15), c) an auxiliary unit transmission (16) for mechanically connecting the internal combustion engine (1) to the auxiliary unit (10-15), so that the internal combustion engine (1) drives the at least one auxiliary unit (10-15) via the auxiliary unit transmission (16), d) a first clutch (18) between the internal combustion engine (1) and the auxiliary unit transmission (16), wherein the first clutch (18) selectively connects the internal combustion engine (1) to the auxiliary unit transmission (16) or disconnects it from the auxiliary unit transmission (16), and e) an electric auxiliary motor (17) for alternatively driving the at least one auxiliary unit (10-15) instead of the drive by the internal combustion engine (1), wherein the electric auxiliary motor (17) is mechanically connected to the auxiliary unit transmission (16), f) a second clutch (24) between the electric auxiliary motor (17) and the auxiliary unit transmission (16), the second clutch (24) selectively connecting the electric auxiliary motor (17) to the auxiliary unit transmission (16) or disconnecting it from the auxiliary unit transmission (16), characterized by g) a high-voltage vehicle electrical system (20) with a mains voltage of more than 50 V, wherein the electric auxiliary motor (17) for driving the at least one auxiliary unit (10-15) is fed from the high-voltage vehicle electrical system (20) via an inverter (19), and h) an electric drive motor (21) for electrically driving the motor vehicle instead of the drive by the internal combustion engine (1) or in addition to the drive by the internal combustion engine (1), wherein the electric drive motor (21) is fed from the high-voltage vehicle electrical system (20).

Description

[0001] The invention relates to a drive system for a motor vehicle, in particular for a hybrid vehicle. Furthermore, the invention relates to a corresponding operating method.

[0002] Modern motor vehicles typically have a multitude of auxiliary units (e.g., alternator, injection pump, lubricant pump, cooling water pump, fuel pump, etc.) that require mechanical drive during operation. The auxiliary units can be mechanically driven, for example, by the internal combustion engine (e.g., diesel engine, gasoline engine), which also powers the vehicle. For this purpose, the internal combustion engine can be connected to the auxiliary units via a belt drive or a timing chain. In a hybrid vehicle, however, the internal combustion engine is temporarily shut down, meaning that the internal combustion engine is then unavailable to drive the auxiliary units.

[0003] The problem with a hybrid vehicle in which the auxiliary units are driven by the combustion engine is the fact that the combustion engine is not available to drive the auxiliary units in purely electric driving mode and brakes the belt drive or the timing chain.

[0004] The document US 2009 / 0298646 A1 discloses a device with an engine, a motor / generator and an accessory that is driven by three-phase current. The device can be operated in a first mode in which the engine supplies the rotational power to drive the accessory and the motor / generator. The device can be operated in a second mode for starting the engine and driving the accessory in which the rotational power is delivered by the motor / starter in a first direction of rotation. The device can also be operated in a third mode in which the motor / generator delivers rotational power in a second, opposite direction of rotation to drive the accessory while the engine is not in operation.

[0005] The document DE 10 2011 013 754 A1 relates to a hybrid drive, preferably a serial hybrid drive, for a vehicle, in particular a commercial vehicle, wherein the hybrid drive comprises an internal combustion engine and an electric machine and wherein the internal combustion engine and the electric machine can be connected to one another and / or separated from one another via a clutch and an output is formed between the clutch and the electric machine, via which output energy from the internal combustion engine and / or electrical energy can be supplied to at least one auxiliary unit.

[0006] Document WO 02 / 066293 A1 relates to a starter-generator mechanically connected to an internal combustion engine, comprising a bidirectional AC / DC converter that can be connected to a storage battery via a first switch and to a double-layer capacitor via a second switch. The storage battery is either connected to the double-layer capacitor via a control circuit, or the storage battery and double-layer capacitor are connected to a bidirectional DC / DC converter and a second storage battery via a third switch and a fourth switch.

[0007] For further prior art, reference is made to documents US 2010 / 0 145 573 A1, DE 698 31 049 T2, US 2008 / 0 080 989 A1, US 2012 / 0 055 175 A1, DE 10 2009 016 911 A1, and DE 10 2006 013 502 A1. The invention is therefore based on the object of creating a correspondingly improved drive system for a motor vehicle.

[0008] The drive system according to the invention initially provides, in accordance with the prior art, an internal combustion engine (e.g. diesel engine, gasoline engine) to drive the motor vehicle.

[0009] Furthermore, the drive system according to the invention comprises at least one auxiliary unit, such as an alternator, an injection pump, a lubricant pump, a cooling water pump, a radiator fan, a turbocharger, a brake booster, a fuel pump, or an air conditioning compressor. However, the term "auxiliary unit" used in the context of the invention is not limited to the aforementioned examples of auxiliary units.

[0010] Furthermore, the drive system according to the invention, in accordance with the prior art, comprises an auxiliary unit transmission (e.g. traction transmission, in particular belt transmission or chain transmission) which mechanically connects the internal combustion engine to the at least one auxiliary unit, so that the internal combustion engine can drive the at least one auxiliary unit via the auxiliary unit transmission.

[0011] The invention now additionally provides a first clutch between the internal combustion engine and the auxiliary unit transmission, wherein the first clutch selectively connects the internal combustion engine to the auxiliary unit transmission or disconnects it from the auxiliary unit transmission.

[0012] In a purely electric drive system of the motor vehicle, the first clutch can separate the combustion engine from the auxiliary transmission, so that the combustion engine does not have to run, which would involve mechanical losses.

[0013] When the motor vehicle is driven by the internal combustion engine, the first clutch between the internal combustion engine and the auxiliary unit transmission closes, so that the internal combustion engine then mechanically drives at least one auxiliary unit via the auxiliary unit transmission.

[0014] Furthermore, the drive system according to the invention comprises an electric auxiliary motor that can drive the at least one auxiliary unit instead of the internal combustion engine, wherein the electric auxiliary motor is mechanically connected to the auxiliary unit transmission. The electric auxiliary motor preferably has sufficient drive power to be able to drive all auxiliary units via the auxiliary unit transmission when the internal combustion engine is at a standstill.

[0015] According to the invention, a second clutch is provided between the electric auxiliary motor and the auxiliary unit transmission, which clutch selectively connects the electric auxiliary motor to the auxiliary unit transmission or disconnects it from the auxiliary unit transmission.

[0016] In purely electric driving mode and with the combustion engine at a standstill, this second clutch is preferably closed so that the electric auxiliary motor is connected to the auxiliary unit gearbox and therefore drives the auxiliary units.

[0017] However, when the vehicle is driven by the internal combustion engine, this second clutch can be opened to separate the electric auxiliary motor from the auxiliary unit gearbox, so that the electric auxiliary motor does not have to run, thus reducing losses.

[0018] However, it is also possible for the electric auxiliary motor to run to drive the auxiliary unit transmission when the auxiliary unit transmission is driven by the combustion engine, whereby the electric auxiliary motor then works as a generator and feeds power into the vehicle's electrical system (high-voltage electrical system or low-voltage electrical system).

[0019] In one variant of the invention, the electric auxiliary motor for driving the at least one auxiliary unit is powered by a low-voltage electrical system of the motor vehicle. The term "low-voltage electrical system" used in the context of the invention preferably refers to an electrical system with a voltage of less than 50 V. For example, the voltage of the low-voltage electrical system can be 12 V, 24 V, 42 V, or 48 V DC.

[0020] The electric auxiliary motor, however, is powered by a high-voltage electrical system via an interposed inverter to drive the at least one auxiliary unit. The term "high-voltage electrical system" used in the context of the invention preferably refers to an electrical system with a mains voltage of more than 50 V or more than 60 V.

[0021] Furthermore, the drive system according to the invention also includes an electric drive motor for electrically driving the motor vehicle, wherein the electric drive motor can support or temporarily replace the combustion engine. The electric drive motor is powered by the aforementioned high-voltage electrical system.

[0022] Furthermore, the drive system according to the invention preferably also comprises a control device for controlling the first clutch and / or the second clutch. In purely electric driving mode, the control device then opens the first clutch between the internal combustion engine and the auxiliary unit transmission and closes the second clutch between the electric auxiliary motor and the auxiliary unit transmission. In driving mode with the internal combustion engine running, however, the control device closes the first clutch between the internal combustion engine and the auxiliary unit transmission and opens the second clutch between the electric auxiliary motor and the auxiliary unit transmission.

[0023] Furthermore, it should be mentioned that the invention is suitable for various types of hybrid drives, such as serial hybrids, parallel hybrids or mixed hybrids.

[0024] Furthermore, it should be noted that the invention claims protection not only for the above-described drive system according to the invention. Rather, the invention also claims protection for a complete motor vehicle with such a drive system. The motor vehicle according to the invention can, for example, be a hybrid vehicle, particularly in the form of a commercial vehicle (e.g., a truck or bus).

[0025] Finally, the invention also includes a corresponding operating method, as already apparent from the above description, so that a separate description of the operating method can be dispensed with.

[0026] Other advantageous developments of the invention emerge from the dependent claims or are explained in more detail below together with the description of the preferred embodiments with reference to the figures. They show: Fig. 1 a schematic representation of a drive system according to the invention with a clutch between the internal combustion engine and the auxiliary unit transmission and an electric auxiliary motor for driving the auxiliary unit transmission, Fig. 2 a variation of Fig. 1 with an additional clutch between the electric auxiliary motor and the auxiliary gearbox, Fig. 3 a flow chart to illustrate the operating method according to the invention, and Fig. 4 a variation of Fig. 3, wherein the electric auxiliary motor operates as a generator and is driven by the combustion engine via the auxiliary unit transmission.

[0027] Fig. 1 shows an embodiment of a drive system according to the invention for driving a hybrid vehicle, such as a commercial vehicle (e.g. truck, bus).

[0028] The drive system according to the invention initially comprises, in a conventional manner, an internal combustion engine 1, which in this exemplary embodiment is designed as a diesel engine with six cylinders 2. However, with regard to the type of internal combustion engine 1, the invention is not limited to diesel engines, but can also be implemented with other types of internal combustion engines.

[0029] The internal combustion engine 1 is connected to an integrated starter-generator 4 (ISG) via a clutch 3. On the one hand, the integrated starter-generator 4 enables starting of the internal combustion engine 1 in a starter mode. On the other hand, the integrated starter-generator 4 also serves to generate electricity in a generator mode and is driven by the internal combustion engine 1 via the clutch 3.

[0030] Furthermore, the drive system according to the invention comprises an automatic transmission 5, which in this exemplary embodiment is designed as an automated manual transmission (ASG). However, with regard to the design of the automatic transmission 5, the invention is not limited to automated manual transmissions, but can also be implemented with other types of automatic or manual transmissions.

[0031] It should be noted that an alternative option is a so-called serial hybrid drive, in which the combustion engine has no mechanical connection to the drive train, but merely drives a generator to supply the electrical power for the electric drive motor or to charge the drive batteries.

[0032] The automatic transmission 5 is coupled to the combustion engine 2 via a further clutch 6 and has an output shaft 7 in the conventional manner.

[0033] The combustion engine 1 is controlled by a control unit 8 (EDC: Electronic Diesel Control), while the automatic transmission 5 is controlled by another control unit 9 (TCU: Transmission Control Unit).

[0034] In addition, the drive system according to the invention has a plurality of auxiliary units 10-15, which may be, for example, an alternator, an injection pump, a lubricant pump, a cooling water pump, a radiator fan, a brake booster, a fuel pump, a power steering pump or a compressor of an air conditioning system.

[0035] The auxiliary units 10-15 are driven via a belt drive 16 either by the combustion engine 1 or by an electric auxiliary motor 17.

[0036] A clutch 18 is arranged between the internal combustion engine 1 and the belt drive 16, which makes it possible to separate the internal combustion engine 1 from the belt drive 16 when the internal combustion engine 1 is stationary and the belt drive 16 is driven by the electric auxiliary motor 17.

[0037] The electric auxiliary motor 17 is fed from a high-voltage electrical system 20 via an inverter 19, wherein the high-voltage electrical system 20 also feeds an electric drive motor 21, which can drive the motor vehicle purely electrically instead of the combustion engine 1.

[0038] In addition, a conventional low-voltage electrical system 22 is provided, which supplies power to conventional consumers (e.g., radio, lighting, etc.). Optionally, the electric auxiliary motor 17 can be powered not by the high-voltage electrical system 20, but by the low-voltage electrical system 22, as indicated by a dashed line in the drawing.

[0039] Finally, the drive system according to the invention also comprises a control unit 23, which is shown only schematically here and controls the clutch 18 in order to either open or close the clutch 18.

[0040] In operating phases with a conventional drive of the motor vehicle by the internal combustion engine 1, the control unit 23 closes the clutch 18 so that the belt drive 16 and thus the auxiliary units 10-15 are driven by the internal combustion engine 1.

[0041] In purely electric driving mode, however, the control unit 23 controls the clutch 18 in such a way that the clutch 18 separates the internal combustion engine 1 from the belt drive 16, so that the internal combustion engine 1 then stands still and does not generate any losses.

[0042] Fig. 2 shows a modification of the embodiment according to Fig. 1, so that in order to avoid repetition, reference is made to the following description, using the same reference numerals for corresponding details.

[0043] A special feature of this embodiment is that an additional clutch 24 is arranged between the belt drive 16 and the electric auxiliary motor 17, which clutch is also controlled by the control unit 23.

[0044] In purely electric driving mode, the clutch 24 is then closed so that the electric auxiliary motor 17 drives the belt drive 16 and thus the auxiliary units 10-15.

[0045] In a conventional drive by the combustion engine 1, however, the clutch 18 is closed while the clutch 24 is open, so that the electric auxiliary motor 17 does not have to run.

[0046] Fig. 3 shows an example of the operating method according to the invention for the drive system described above in the form of a flow chart.

[0047] In a step S1, the type of drive is continuously checked, whereby a distinction must be made between a pure electric drive and a drive by the combustion engine 1.

[0048] When driven by the internal combustion engine 1, the clutch 18 between the internal combustion engine 1 and the belt drive 16 is closed in a step S2.

[0049] Furthermore, the clutch 24 between the electric auxiliary motor 17 and the belt drive 16 is then opened so that the electric auxiliary motor 17 does not have to run, as this would cause mechanical losses.

[0050] In a purely electric driving mode, however, the clutch 18 between the internal combustion engine 1 and the belt drive 16 is opened in a step S4 so that the internal combustion engine 1 can come to a standstill.

[0051] In addition, in a step S5, the clutch 24 between the electric auxiliary motor 17 and the belt drive 16 is closed so that the electric auxiliary drive 17 can drive the belt drive 16 and thus the auxiliary units 10-15.

[0052] Fig. 4 showed a modification of Fig. 3, so that to avoid repetition, reference is made to the above description.

[0053] A special feature here is that the clutch 24 remains closed even when the combustion engine 1 drives the auxiliary units 10-15 via the auxiliary unit transmission 16. In this operating mode, the auxiliary motor 17 then operates as a generator in a step S6 and feeds electrical current into the low-voltage electrical system 22 and / or the high-voltage electrical system 20.

[0054] The invention is not limited to the preferred embodiments described above. Rather, numerous variants and modifications are possible, which also utilize the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and features of the subclaims, independent of the claims referred to. List of reference symbols: 1 combustion engine 2 cylinders 3 Clutch 4 Integrated starter generator 5 automatic transmissions 6 Clutch 7 Output shaft 8 Control unit for the combustion engine 9 Control unit for the automatic transmission 10-15 auxiliary units 16 Belt drive 17 Electric auxiliary motor 18 Clutch 19 inverters 20 High-voltage electrical system 21 Electric drive motor 22 Low-voltage electrical system 23 Control unit 24 Clutch

Claims

[1] Drive system for a motor vehicle with a) an internal combustion engine (1) for driving the motor vehicle, b) at least one auxiliary unit (10-15), c) an auxiliary unit transmission (16) for mechanically connecting the internal combustion engine (1) to the auxiliary unit (10-15), so that the internal combustion engine (1) drives the at least one auxiliary unit (10-15) via the auxiliary unit transmission (16), d) a first clutch (18) between the internal combustion engine (1) and the auxiliary unit transmission (16), wherein the first clutch (18) selectively connects the internal combustion engine (1) to the auxiliary unit transmission (16) or disconnects it from the auxiliary unit transmission (16), and e) an electric auxiliary motor (17) for alternatively driving the at least one auxiliary unit (10-15) instead of the drive by the internal combustion engine (1), wherein the electric auxiliary motor (17) is mechanically connected to the auxiliary unit transmission (16), f) a second clutch (24) between the electric auxiliary motor (17) and the auxiliary unit transmission (16), the second clutch (24) selectively connecting the electric auxiliary motor (17) to the auxiliary unit transmission (16) or disconnecting it from the auxiliary unit transmission (16), characterized by g) a high-voltage vehicle electrical system (20) with a mains voltage of more than 50 V, wherein the electric auxiliary motor (17) for driving the at least one auxiliary unit (10-15) is fed from the high-voltage vehicle electrical system (20) via an inverter (19), and h) an electric drive motor (21) for electrically driving the motor vehicle instead of the drive by the internal combustion engine (1) or in addition to the drive by the internal combustion engine (1), wherein the electric drive motor (21) is fed from the high-voltage vehicle electrical system (20). [2] Drive system according to claim 1, characterized by , a) that the auxiliary electric motor (17) is an electric machine which operates either as a motor or as a generator, and b) that the electric machine (17) is connected to an on-board electrical system (20, 22) of the motor vehicle and feeds electrical current into the on-board electrical system (20, 22) when the electric machine (17) is driven by the internal combustion engine (1) via the auxiliary unit transmission (16). [3] Drive system according to one of the preceding claims, characterized by that the auxiliary unit transmission (16) is a traction transmission. [4] Drive system according to claim 3, characterized by that the traction drive is a belt drive or a chain drive. [5] Drive system according to one of the preceding claims, characterized bya low-voltage vehicle electrical system (22) with a mains voltage of less than 50 V, wherein the electric auxiliary motor (17) for driving the at least one auxiliary unit (10-15) is fed from the low-voltage vehicle electrical system (22). [6] Drive system according to claim 5, characterized by that the low-voltage vehicle electrical system (22) has a mains voltage of 12 V, 24 V, 42 V or 48 V DC. [7] Drive system according to one of the preceding claims, characterized by a control device (23) for controlling the first clutch (18) and the second clutch (24). [8] Drive system according to one of the preceding claims, characterized by that the drive system drives at least one of the following auxiliary units (10-15): a) alternator, b) injection pump, c) lubricant pump, d) cooling water pump, e) radiator fan, f) turbocharger, g) brake booster, h) fuel pump, i) compressor of an air conditioning system, j) Power steering pump. [9] Motor vehicle with a drive system according to one of the preceding claims. [10] Motor vehicle according to claim 9, characterized by that the motor vehicle is a hybrid vehicle and / or a commercial vehicle. [11] Operating method for a drive system according to one of claims 1-8, comprising the following steps: a) driving the motor vehicle by an internal combustion engine (1), b) driving at least one auxiliary unit (10-15) by the internal combustion engine (1) via an auxiliary unit transmission (16), c) separating the mechanical connection between the internal combustion engine (1) and the auxiliary unit transmission (16) by means of a first clutch (18) between the internal combustion engine (1) and the auxiliary unit transmission (16), d) driving the motor vehicle by an electric drive motor (21) instead of the drive by the internal combustion engine (1), wherein the first clutch (18) between the internal combustion engine (1) and the auxiliary unit transmission (16) is separated when the motor vehicle is driven by the electric drive motor (21), characterized by following step: e) driving the at least one auxiliary unit (10-15) by an electric auxiliary motor (17) which is connected to the auxiliary unit transmission (16) via a second clutch (24). [12] Operating method according to claim 11, characterized by following step: a) Disconnecting the second clutch (24) between the electric auxiliary motor (17) and the auxiliary unit transmission (16) when the motor vehicle is driven by the internal combustion engine (1).

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