Hybrid drive for a hybrid vehicle

Abstract

Hybrid drive for a hybrid vehicle, with an internal combustion engine (VM) having a crankshaft (12), and an electric motor (EM1), wherein the electric motor (EM1) is coupled to the crankshaft (12) of the internal combustion engine (VM) via an automatically switching transmission (14, 36), wherein the automatically switching transmission (14, 36) has a planetary gear (22) and / or the automatically switching transmission (14, 36) has switching elements (38) that can be actuated via an actuator (40), and the automatically switching transmission (14, 36) has an output shaft (34) that is coupled to the crankshaft (12) via a gear pair (24).

Description

[0001] The invention relates to a hybrid drive for a hybrid vehicle.

[0002] Hybrid drives are used in modern motor vehicles, where, for example, a combustion engine and an electric motor are combined in the vehicle's drivetrain. The aim is to operate the engines as efficiently as possible.

[0003] DE 10 2006 037 576 A1 and JP 2004 190 497 A each show a drive for a motor vehicle with two electric motors, one of the electric motors being coupled to an internal combustion engine via a switchable planetary gear.

[0004] DE 199 31 963 A1 describes a starter / generator unit for an internal combustion engine which is coupled to a crankshaft of an internal combustion engine via a planetary gear.

[0005] The object of the invention is to provide an improved hybrid drive for a hybrid vehicle.

[0006] The problem is solved by a hybrid drive for a hybrid vehicle having the features of claim 1.

[0007] The self-shifting transmission associated with the electric motor on the combustion engine side features a planetary gear. The planetary gear allows for high gear ratios to be provided in a compact manner.

[0008] Alternatively or additionally, the automatically shifting transmission has shifting elements that can be actuated via an actuator, wherein the actuator can be controlled in particular by a control unit.

[0009] For example, the control unit can control the actuator depending on an operating parameter in the drive train, in particular the speed of the combustion engine or the like, in order to effect a gear change in the automatically shifting transmission.

[0010] In particular, a gear change in the automatic transmission and a switch from engine to generator mode can occur as soon as a predefined engine speed in the control unit is exceeded during the crankshaft drive's acceleration. This functionality preferably runs fully automatically without driver intervention.

[0011] The self-shifting transmission has an output shaft that can be coupled to the crankshaft of the combustion engine, particularly via a gear pair. This allows the electric motor to be compactly integrated into the hybrid drive, with the gear pair providing an additional gear ratio.

[0012] The electric motor, for example, simply provides the starting function for the combustion engine and can also be operated as a generator. This allows the electric motor to assist the acceleration of the crankshaft or crankshaft, ensuring the smoothest, most excitation-free acceleration possible. Above a certain combustion engine speed, the electric motor can be switched to generator mode and, in turn, driven by the combustion engine.

[0013] Preferably, the electric motor is operated in a controlled manner.

[0014] In particular, the electric motor can be designed to meet all starting requirements, in particular low-temperature starts of the combustion engine.

[0015] The electric motor can be used to enable an automatic start-stop system, in which the combustion engine must be switched off and then restarted after a certain period of time. This can be after the vehicle has stopped, for example, at a traffic light, or while coasting, where the vehicle is coasting without the combustion engine. The starting of the combustion engine must meet the highest standards of comfort.

[0016] The hybrid drive can be configured such that a system for compensating for crankshaft speed irregularities, a speed converter, and a multi-speed transmission are connected downstream of the combustion engine to transfer the power of the combustion engine to the driven wheels of a vehicle. This allows for efficient and, as far as possible, excitation-free power transmission to the wheels of the driven vehicle. It is understood that additional components, such as a differential, can be integrated into the drivetrain.

[0017] The vehicle transmission can be either an automatic or a manual transmission. In particular, inexpensive, reliable manual transmissions can be integrated into the hybrid drive and combined with the combustion engine and electric motor in a modular system. This results in cost advantages over existing hybrid solutions, as proven and cost-effective manual transmissions can be used. Alternatively, automatic transmissions, such as those installed in conventional vehicles with combustion engines, can be used.

[0018] Following a further development of the hybrid drive, an additional electric motor is integrated between the characteristic converter and the vehicle transmission. This additional electric motor can be used for electric driving, electric creeping, and braking energy recuperation, or even enable "boosting" when the combustion engine is stopped.

[0019] The additional electric motor can be arranged coaxially or axially parallel to a transmission input shaft of the vehicle transmission, so that the electric motor can be optimally positioned in a vehicle, depending on the available installation space.

[0020] The use of two electric motors in a hybrid drive has the advantage that the hybrid functions on the combustion engine side and the hybrid functions on the drive or vehicle transmission side can be divided into two separate electric motors, so that these motors can each be optimally dimensioned with regard to their intended functionality in the drive train.

[0021] The additional electric motor can be coupled, in particular via a gearbox, to the transmission input shaft of the vehicle transmission in order to operate the electric motor as efficiently as possible.

[0022] According to a further embodiment of the hybrid drive, the planetary gear set has a ring gear associated with a first freewheel and a sun gear associated with a second freewheel. The freewheels serve to enable the electric motor to switch from motor to generator mode, enabling a reversal of the torque flow from the combustion engine to the electric motor.

[0023] In motor operation of the electric motor, drive and output can be achieved via the sun gear and a planet carrier of the planetary gear.

[0024] Input and output can be carried out in generator mode with fixed planets of the planetary gear.

[0025] The gear pairing can be a spur gear stage, whereby known gearings can be used in a cost-effective manner.

[0026] In order to take up as little installation space as possible, the automatically switching transmission can be provided as a transverse transmission.

[0027] According to a further embodiment, the hybrid drive is characterized in that a first gear of the automatically switching transmission has a gear ratio in a range from 1.5 to 2.5, in particular from 1.7 to 2.3, preferably from 1.9 to 2.1, and a second gear of the automatically switching transmission has a gear ratio in a range from 3.5 to 4.5, in particular from 3.7 to 4.3, preferably from 3.9 to 4.1.

[0028] For example, the first gear ratio can be 2 and the second gear ratio can be four.

[0029] In this case, a ratio of four means that an input speed introduced into the automatically shifting transmission by the electric motor is translated into an output speed by the transmission according to the rule i = 4 = input speed / output speed.

[0030] First gear can be used for generator operation, and second gear for engine operation. The lower gear ratio for generator operation ensures that the electric motor is not overloaded even when the combustion engine is revving.

[0031] It is understood that the above-mentioned gear ratios represent the overall gear ratio for the automatic transmission. For example, if a planetary gear is combined with a spur gear stage, where the spur gear stage serves to connect the transmission to the crankshaft, the overall gear ratio results from the gear ratio of the spur gear stage and the gear ratio of the respective gear of the planetary gear.

[0032] In order to achieve a reliable and practical design of the automatically shifting transmission, the ratio of the second gear can be at least 1.5 times, in particular at least twice, the ratio of the first gear.

[0033] The spur gear stage can have a gear ratio in a range from 1.5 to 2.5. In particular, the gear ratio of the spur gear stage can be equal to 2.

[0034] The planetary gear can have a gear ratio of 1 in first gear and a gear ratio in a range from 1.5 to 2.5, in particular from 1.7 to 2.3, preferably from 1.9 to 2.1, in second gear.

[0035] The invention is described in more detail below with reference to a drawing illustrating exemplary embodiments. The drawings schematically show: Fig. 1 a hybrid drive according to the invention, Fig. 2 a representation of an automatically switching transmission of the hybrid drive from Fig. 1, Fig. 3 a further embodiment of an automatically switching transmission of the hybrid drive from Fig. 1.

[0036] In Fig. Figure 1 shows a hybrid drive 10 for a hybrid vehicle. The hybrid drive 10 comprises an internal combustion engine VM, which has a crankshaft 12, and an electric motor EM1. The electric motor EM1 is coupled to the crankshaft 12 of the internal combustion engine VM via an automatically shifting transmission 14.

[0037] The internal combustion engine is followed by a system DU for compensating the speed irregularity of the internal combustion engine VM, a characteristic converter KW, which serves as a starting clutch, and a multi-speed vehicle transmission 16 in order to transfer the power of the internal combustion engine to the driven wheels 18 of the vehicle to be driven.

[0038] The characteristic converter KW can be a hydrodynamic converter or a dry or wet single or multi-disc friction clutch.

[0039] The coupling (or decoupling) of the combustion engine from the drive train can be carried out via the characteristic converter KW or a dry or wet running starting clutch.

[0040] The vehicle transmission 16 may be an automatic transmission or a manually shiftable transmission.

[0041] Another electric motor EM2 is integrated into the drive train between the characteristic converter KW and the vehicle transmission 16. The electric motor EM2 is arranged coaxially with a transmission input shaft 20 of the vehicle transmission.

[0042] Alternatively, the electric motor can also be arranged axially parallel to the transmission input shaft 20, as indicated by the dashed line EM2*.

[0043] The electric motor EM2 or EM2* can be connected to the transmission input shaft 20 via a gearbox 3, 4. The respective gearbox 3, 4 can be single- or multi-speed.

[0044] During engine operation, the electric motor EM1 is used to start and accelerate the combustion engine VM, in particular to implement an automatic start-stop system.

[0045] Furthermore, the EM1 electric motor can be used in generator mode to provide "direct bridged starting." The power generated by the EM1 electric motor is taken directly from the EM2 electric motor and converted into drive power.

[0046] Furthermore, "direct bridged recuperation" can occur in the drivetrain. The EM1 can be operated as a generator or motor up to a certain speed limit with the starting clutch open. In this case, the EM2 takes over recuperation in the force-locking drivetrain.

[0047] Fig. Figure 2 shows the automatically shifting transmission 14, which includes a planetary gear set 22 and a spur gear stage 24. The planetary gear set 22 has a first gear for generator operation and a second gear for motor operation. The first gear has a gear ratio of 1, and the second gear has a gear ratio of 2. The gear ratio of the spur gear stage is 2.

[0048] The planetary gear set comprises a sun gear 26, a ring gear 28, and a planet carrier 30 that supports the planets 32. A freewheel FI2 is associated with the sun gear 26, and a freewheel FI1 is associated with the ring gear 28.

[0049] During engine operation, the planet carrier 30 and thus the shaft 34 are driven via the planets 32 and the sun gear 26.

[0050] In generator mode of the electric motor EM1, the drive is via the planet carrier 30, with the planets 32 at a standstill.

[0051] The freewheels FI1 and FI2 enable torque reversal for generator operation.

[0052] In Fig. 3 shows a further embodiment of an automatically switching transmission 36. Alternatively or in addition to the embodiments described with reference to Fig. 2 for the automatically shifting transmission 14, the automatically shifting transmission 36 has shifting elements 38 which can be actuated via an actuator 40, wherein the actuator 40 can be controlled in particular by a control unit (not shown).

[0053] Depending on a signal from the control unit, a switching process can be triggered in which the switching elements 38 are moved by the actuator 40 from a first switching position 1 to a second switching position 2.

[0054] The ratio of the planetary gear in the first switching position 2 can be greater than one, while in the second switching position 2 the planetary gear is “blocked”, which is accompanied by a ratio i = 1.

[0055] The switching from the first switching position 1 to the second switching position 2 preferably takes place fully automatically, in particular depending on an operating parameter of the drive train predefined in the control unit, such as a speed of the combustion engine VM.

[0056] Thus, a switching operation from the first to the second switching position and a switching from motor to generator operation of the EM1 can take place as soon as a speed of the combustion engine VM predefined in the control unit is exceeded when the crank mechanism 12 is started up.

Claims

[1] Hybrid drive for a hybrid vehicle, with an internal combustion engine (VM) having a crankshaft (12), and an electric motor (EM1), wherein the electric motor (EM1) is coupled to the crankshaft (12) of the internal combustion engine (VM) via an automatically switching transmission (14, 36), wherein the automatically switching transmission (14, 36) has a planetary gear (22) and / or the automatically switching transmission (14, 36) has switching elements (38) which can be actuated via an actuator (40), and the automatically switching transmission (14, 36) has an output shaft (34) which is coupled to the crankshaft (12) via a gear pair (24). [2] Hybrid drive according to claim 1, characterized bythat a system (DU) for compensating the speed irregularity of the crankshaft (12), a characteristic converter (KW) and a multi-speed vehicle transmission (16) are connected downstream of the internal combustion engine (VM) in order to transmit the power of the internal combustion engine (VM) to driven wheels (18) of a vehicle. [3] Hybrid drive according to claim 2, characterized by that the vehicle transmission (16) is an automatic transmission or a manually shiftable transmission. [4] Hybrid drive according to claim 2 or claim 3, characterized by that a further electric motor (EM2, EM2*) is integrated between the characteristic converter (KW) and the vehicle transmission (16). [5] Hybrid drive according to claim 4, characterized bythat the further electric motor (EM2, EM2*) is arranged coaxially or axially parallel to a transmission input shaft (20) of the vehicle transmission (16), wherein the electric motor (EM2, EM2*) can be coupled to the transmission input shaft (20) in particular via a transmission (3, 4). [6] Hybrid drive according to one of the preceding claims, characterized by that the planetary gear (22) has a ring gear (28) to which a first freewheel (FI1) is assigned, and a sun gear (26) to which a second freewheel (FI2) is assigned. [7] Hybrid drive according to one of the preceding claims, characterized by that the gear pair (24) is a spur gear stage. [8] Hybrid drive according to one of the preceding claims, characterized by that the automatically switching transmission (14, 36) is a transverse transmission. [9] Hybrid drive according to one of the preceding claims, characterized bythat a first gear of the automatically switching transmission (14, 36) has a gear ratio in a range from 1.5 to 2.5, in particular from 1.7 to 2.3, preferably from 1.9 to 2.1, and a second gear of the automatically switching transmission has a gear ratio in a range from 3.5 to 4.5, in particular from 3.7 to 4.3, preferably from 3.9 to 4.

1. [10] Hybrid drive according to claim 9, characterized by that the ratio of the second gear corresponds to at least 1.5 times, in particular at least twice, the ratio of the first gear. [11] Hybrid drive according to one of claims 9 or 10, characterized by that the first gear is intended for engine operation and the second gear for generator operation of the electric motor (EM1). [12] Hybrid drive according to one of the preceding claims, characterized by that the gear pair (24) has a gear ratio in a range from 1.5 to 2.

5. [13] Hybrid drive according to claim 9, characterized by that the planetary gear (22) has a gear ratio of 1 in the first gear and a gear ratio in a range from 1.5 to 2.5, in particular from 1.7 to 2.3, preferably from 1.9 to 2.1, in the second gear.

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