Dual clutch transmission and hybrid drive system

Abstract

The invention relates to a dual clutch transmission (4) having a first sub-transmission (5), a second sub-transmission (6), a first intermediate shaft (7) permanently connected in a rotationally fixed manner to a first driven gearwheel (9) and a second intermediate shaft (8) permanently connected in a rotationally fixed manner to a second driven gearwheel (10), wherein a first drive gearwheel (25) belonging to the first sub-transmission (5) and a second drive gearwheel (33) belonging to the second sub-transmission (6) are arranged coaxially to the first intermediate shaft (7) and are connected to one another in a rotationally fixed manner by means of a bridge-type shift element (B). The invention is characterized in that the first sub-transmission (5) comprises exactly three single gearwheel planes (20, 23, 26), namely a first single gearwheel plane (20), a second single gearwheel plane (23) containing the first drive gearwheel (25) and a third single gearwheel plane (26), and the second sub-transmission (6) comprises exactly two single gearwheel planes (29, 30), namely a fourth single gearwheel plane (29) containing the second drive gearwheel (33) and a fifth single gearwheel plane (30), and it is provided that eight transmission gears can be formed with stepped gear ratios.

Description

Technical Field

[0001] The present invention relates to a dual-clutch transmission and a hybrid drive system. Background Art

[0002] A dual-clutch transmission, also suitable for hybrid drive systems, is described in DE 10 2009 002 353 A1. This transmission can shift eight gears and features a shift bridge between the driven gears for third and fourth gear. These two driven gears, which can be connected via the shift bridge, are assigned to different sub-transmissions. A single-stage gear plane for the next lower gear is inserted between them, located on the sub-transmission with the higher gear of the two connected driven gears via the shift bridge. In addition to the eight forward gears, there is also a mechanical reverse gear. In summary, the transmission design is relatively large, particularly in the axial direction, i.e., in the axial direction of the sub-transmission input shafts and the parallel countershafts.

[0003] Dual-clutch transmissions suitable for hybrid drives are also known from the prior art, in particular from DE 10 2010 055 645 A1, DE 10 2013 009 310 A1, DE 10 2007 049 270 A1, DE 10 2012 022 777 A1 and DE 10 2019 004 762 B3. Summary of the Invention

[0004] The object of the present invention is now to specify an improved dual-clutch transmission with eight forward gears, which can be designed to be more compact, in particular in the axial direction of installation.

[0005] According to the invention, this object is achieved by a dual-clutch transmission and a hybrid drive system having the features described below.

[0006] The dual-clutch transmission is based on a first sub-transmission with an associated first clutch and a first sub-transmission input shaft. It also includes a second sub-transmission with an associated second clutch and a second sub-transmission input shaft. The dual-clutch transmission also includes a first countershaft permanently connected to the first driven gear in a rotationally fixed manner, and a second countershaft permanently connected to the second driven gear in a rotationally fixed manner. The first driven gear associated with the first sub-transmission and the second driven gear associated with the second sub-transmission are each arranged coaxially with the first countershaft and can be engaged in a rotationally fixed manner with one another via a shift bridge.

[0007] The dual-clutch transmission according to the present invention comprises in the first sub-transmission exactly three single-stage gear planes: a first single-stage gear plane, a second single-stage gear plane, and a third single-stage gear plane. The second single-stage gear plane comprises a first dynamic gear, which can be engaged with a second dynamic gear via a shift bridge. The second sub-transmission then comprises exactly two single-stage gear planes: a fourth single-stage gear plane and a fifth single-stage gear plane. The fourth single-stage gear plane comprises a second dynamic gear.

[0008] The first clutch and the second clutch together form a dual clutch.

[0009] An element is arranged coaxially with the shaft when the element is arranged coaxially with respect to the axis of rotation of the shaft.

[0010] "A rotationally fixed connection of two rotatably mounted elements means that the two elements are arranged coaxially with respect to one another and are connected to one another in such a way that they rotate at the same angular speed.

[0011] A shift element is a device that allows a driven gear to be connected in a rotationally fixed manner to a shaft arranged coaxially therewith. For the rotationally fixed connection, the shift element has an engaged state. For the rotationally fixed connection, the shift element has a disengaged state. Advantageously, the shift element has a dog tooth row and, if applicable, a synchronization device.

[0012] A single-stage gear plane is a gear plane in which exactly one gear pair consisting of exactly two meshing gears is provided.

[0013] Thus, eight transmission gears designed as forward gears, namely the first through eighth gears, can be realized with gear ratios descending in this numerical order. This design allows for an extremely simple and axially compact design. The elimination of a gear plane with multiple gears and the unified use of three single-stage gear planes in the first sub-transmission and two single-stage gear planes in the second sub-transmission simplify the design accordingly. The disadvantage of not being able to powershift between two non-consecutive gears, since the gears required for this are located on a common sub-transmission and therefore cannot be pre-engaged, can be overcome in exchange for the significant advantage in terms of axial length.

[0014] A dual-clutch transmission with eight transmission gears, all designed as forward gears, can be used, for example, as an 8-speed transmission or as a 6-speed transmission with two crawler gears, also designed as forward gears. Due to its compact overall length, it can be installed, in particular, transversely to the direction of travel, which is a significant advantage in terms of packaging.

[0015] In particular, according to an advantageous development of the dual clutch transmission according to the invention, provision can be made that the first shifting element is designed to connect the first single-stage gear plane to the second countershaft in a torque-transmitting manner to form the first transmission gear and also the second transmission gear.

[0016] The shifting between the two transmission gears can be achieved here by switching the clutches in the double clutch in a power shift manner. By means of a bridge-type shift element, a cascade gear using two sub-transmissions can be achieved here.

[0017] According to another very advantageous embodiment, it can also be provided that a second shifting element is provided, which is designed to connect the second single-stage gear plane to the first countershaft in a torque-transmitting manner to form a sixth transmission gear.

[0018] The third shifting element then serves to connect the third single-stage gear plane to form the third transmission gear and the fourth transmission gear by engaging the second countershaft in a torque-transmitting manner. As with the first and second transmission gears, one of these gears, the fourth, is then designed as a cascade gear. The shift from the third to the fourth transmission gear is performed in a powershift manner by shifting the clutches in the dual clutch.

[0019] According to an advantageous embodiment, a fourth shifting element can be provided in order to connect the fourth single-stage gear plane to the first countershaft in a torque-transmitting manner to form the fifth transmission gear.

[0020] According to a very advantageous embodiment of the dual-clutch transmission, a fifth shifting element is provided for connecting the fifth single-stage gear plane to the second countershaft in a torque-transmitting manner to form the seventh transmission gear and the eighth transmission gear. Here again, a bridge shifting element is used to respectively establish one of these two gears by means of a cascade gear when the fifth shifting element is connected.

[0021] A particularly advantageous development of the dual-clutch transmission according to the invention provides for the first, second, third, fourth, and fifth single-stage gear planes, as well as the first clutch, to be arranged axially one after the other in the stated order. This arrangement, which contributes to a compact design, ultimately results in the first sub-transmission input shaft being designed as a solid shaft and the second sub-transmission input shaft being designed as a hollow shaft, which also contributes to a compact design.

[0022] As described above, a hybrid drive system for a vehicle can include such a dual-clutch transmission according to one of the aforementioned design variants. It then also includes an internal combustion engine and an electric machine. According to the present invention, the hybrid drive system provides that the internal combustion engine is at least indirectly coupled or connectable to the input shaft of the dual-clutch transmission. Indirect coupling means that a mechanism for damping and damping torsional vibrations, such as a dual-mass flywheel or a torsional vibration damper, is provided between the crankshaft of the internal combustion engine and the input shaft of the dual-clutch transmission. The internal combustion engine can also be disconnected and connected via a disconnect clutch, which, together with the dual clutch, can be implemented as a single-piece clutch component.

[0023] According to a particularly advantageous development of the hybrid drive system according to the invention, a separating clutch is provided between the input shaft of the dual-clutch transmission and the dual clutch, the input side of which is connected to the input shaft and the output side of which is connected to the dual clutch, which in turn comprises a first and a second clutch. This results in the aforementioned integral clutch component.

[0024] Another highly advantageous embodiment can therefore provide that the electric motor's rotor is connected to the output side of the disconnect clutch, preferably via a transmission component such as a pinion, chain, belt, or fully shiftable transmission. Particularly preferably, the connection is via a simple pinion, so that when the disconnect clutch is disengaged, the dual-clutch transmission and ultimately its output shaft or its two output gears are driven, as is customary in dual-clutch transmissions. The ability to electrically drive the dual-clutch transmission independently of the internal combustion engine when the disconnect clutch is disengaged, and thus to drive vehicles equipped with a dual-clutch transmission or hybrid drive system purely electrically, also makes it possible to compensate for the need for a mechanical reverse gear, since the electric motor is used for driving in reverse. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further advantageous embodiments of the dual-clutch transmission according to the invention and of the hybrid drive system according to the invention result from the exemplary embodiments explained below with reference to the figures.

[0026] The single FIGURE shows a conceivable embodiment of a hybrid drive system according to the invention, which has a dual-clutch transmission designed according to the invention. DETAILED DESCRIPTION

[0027] The illustration of the single figure shows a hybrid drive system 1 comprising an internal combustion engine 2 and an electric machine 3. Hybrid drive system 1 further comprises a dual-clutch transmission 4, which is divided into a first sub-transmission 5 and a second sub-transmission 6. A driven device (not shown here), for example a gear engaged with the driven shaft or a gear non-rotatably connected to the differential cage, is driven via a first countershaft 7, a second countershaft 8 and driven gears mounted non-rotatably thereon, namely a first driven gear 9 and a second driven gear 10.

[0028] To transmit power from the internal combustion engine 2, a dual-mass flywheel 12 is positioned between the crankshaft of the internal combustion engine 2 and the input shaft 11 of the dual-clutch transmission 4. This serves to damp and attenuate torsional vibrations. Next, a clutch component 13 is provided, which comprises a true dual clutch with a first clutch K1 and a second clutch K2, as well as a separating clutch K0. The input side 14 of the separating clutch K0 is connected to the input shaft 11 of the dual-clutch transmission 4. Furthermore, the output side 15 of the separating clutch K0 is connected via a pinion 16 to the rotor 17 of the electric machine 3. Furthermore, the output side 15 of the separating clutch K0 is connected to the input sides of the two clutches K1 and K2 of the dual clutch, which in turn can connect their output sides 15 to a first sub-transmission input shaft 18 of the first sub-transmission 5 and a second sub-transmission input shaft 19 of the second sub-transmission 6. The first sub-transmission input shaft 18 is designed as a solid shaft, surrounded by the second sub-transmission input shaft 19 as a hollow shaft. The two sub-transmission input shafts 18 and 19 are arranged coaxially with each other.

[0029] Three single-stage gear planes are now assigned to the first sub-transmission 5 and, therefore, the first sub-transmission input shaft 18. The first single-stage gear plane 20 includes a fixed gear 21, which is arranged coaxially with the first sub-transmission input shaft 18 and non-rotatably connected to it, and a third fixed gear 22, which is arranged coaxially with the second countershaft 8 and can be non-rotatably connected thereto via the first shifting element D. Following in the axial direction of the sub-transmission input shafts 18, 19 is a second single-stage gear plane 23, also assigned to the first sub-transmission 5. This second single-stage gear plane 23 has a second fixed gear 24, which is non-rotatably connected to the first sub-transmission input shaft 18 and meshes with a first fixed gear 25, which is arranged coaxially with the first countershaft 7. The second shifting element A is provided to switchably engage the first fixed gear 25 in a non-rotatably connected manner to the first countershaft 7.

[0030] The third single-stage gear plane 26 is also assigned to the first sub-transmission 5. The third fixed gear 27 of the third single-stage gear plane 26 is correspondingly connected to the first sub-transmission input shaft 18 in a rotationally fixed manner. It meshes with a fourth fixed gear 28, which is in turn arranged coaxially with the second countershaft 8. The fourth fixed gear 28 is connected to the second countershaft 8 in a shiftable and rotationally fixed manner via the third shift element E.

[0031] The second sub-transmission 6 is assigned to two further single-stage gear planes: the fourth single-stage gear plane 29 and the fifth single-stage gear plane 30. These two single-stage gear planes each have a fixed gear, a fourth fixed gear 31 and a fifth fixed gear 32, which are non-rotatably connected to the second sub-transmission input shaft 19, which is designed as a hollow shaft. The fourth fixed gear 31 of the fourth single-stage gear plane 29 meshes with a second fixed gear 33, which in turn is non-rotatably connected to the first countershaft 7 via the fourth shifting element C. In the fifth single-stage gear plane 30, its fifth fixed gear 32 meshes with a fifth fixed gear 34, which is also arranged coaxially with the second countershaft 8. The fifth fixed gear 34 can be non-rotatably connected to the second countershaft 8 via the fifth shifting element F, as required.

[0032] In addition to the aforementioned elements, hybrid drive system 1 or its dual-clutch transmission 4 also includes a shift bridge element B, which is arranged axially between first and second fixed gear wheels 25, 33 and, if necessary, connects them to one another in a rotationally fixed manner, without the two fixed gear wheels 25, 33 being simultaneously connected to first countershaft 7 in a rotationally fixed manner. Since first fixed gear wheel 25 is assigned to first sub-transmission 5 and second fixed gear wheel 33 is assigned to second sub-transmission 6, a cascade gear is obtained when shift bridge element B is engaged.

[0033] In the shifting state in which the first movable gear 25 and the second movable gear 33 are connected to each other in a rotationally fixed manner by means of the bridge shift element B, the first movable gear 25 and the second movable gear 33 are always rotatable relative to the first countershaft 7 .

[0034] The first intermediate shaft 7 and the second intermediate shaft 8 are arranged parallel to each other and to the input shaft 11. The rotor 17 is advantageously not arranged coaxially with respect to the input shaft 11, but is also arranged parallel thereto and axially offset. In combination with the wheel set features, this allows the hybrid drive system 1 to be designed as a whole to be very short axially.

[0035] With this design, eight forward gears can now be realized. The transmission ratios and the dimensions or the number of teeth of the individual gears installed in the dual-clutch transmission 4 are then adapted to the respective transmission, so that, for example, eight forward gears with descending transmission ratios are provided, or, for example, six such forward gears and two crawler gears designed as forward gears are provided, depending on the intended application of the hybrid drive system 1.

[0036] The shifting process can now be arranged as can be seen from the gears i_n marked on the individual automatic gears 22, 25, 28, 33, and 34. When the first shift element D is engaged, the first transmission gear is obtained when the bridge shift element B is also engaged and the drive is provided by the second sub-transmission 6, i.e., when the clutch K2 is engaged. The first gear is designed as a cascade gear, which is driven by the first sub-transmission 6 with the clutch K2 engaged and is driven by the second sub-transmission 5 and the second countershaft 8 with its second output gear 10.

[0037] To shift from the first transmission gear to the second, the cascade gear is discontinued by engaging clutches K2 and K1 accordingly. The first two gears can thus be achieved via the first shift element D and the third, driven gear 22. The bridge shift element B can be disengaged during this shift. Shifting between the first and second transmission gears can be accomplished without power interruption.

[0038] To shift into the third transmission gear, if the bridge shift element was previously disengaged, the bridge shift element B is now engaged again, and the third shift element E connects the fourth driven gear 28 to the second countershaft 8. However, the bridge shift element B should preferably remain engaged when shifting from the second transmission gear to the third transmission gear. The third transmission gear is also designed as a cascade gear, so that the clutch K2 is engaged and the clutch K1 is disengaged.

[0039] The clutches are shifted again by disengaging the second clutch K2 and engaging the first clutch K1 , whereby the fourth transmission gear is achieved.

[0040] To shift from the fourth to the fifth transmission gear, the bridge shift element B must first be disengaged, provided it has not already been disengaged. The fifth transmission gear can then be obtained starting from the fourth gear, since the fourth shift element C is engaged and reengaged when shifting into this gear. For the sixth gear, the second shift element A is engaged and reengaged. For the seventh gear, the fifth shift element F corresponds to this. To shift from the seventh to the eighth gear, a cascade gear is again specified, which is engaged by engaging the bridge shift element B and reengaging the clutches K1 and K2 of the dual clutch.

[0041] There is no mechanical reverse gear. Power shifting from second to third gear is also not possible, but these two limitations are acceptable for the sake of an extremely compact axial design. Electric motor 3 enables electric reverse gear and synchronizes the relevant components as needed when shifting from second to third gear.

[0042] An alternative design of hybrid drive system 1, with modified gear dimensions and transmission ratios, provides that, instead of the third and fourth gears being implemented via third single-stage gear plane 26, two crawler gears are implemented via third single-stage gear plane 26 and its associated fourth gear wheel 28. Crawler gears C1 / C2 then replace gears 3 and 4, as shown in the single figure. These crawler gears are shifted as cascade and direct gears, similar to gears 3 and 4 described above. Third gear is implemented via second gear wheel 33 of fourth single-stage gear plane 29, and fourth gear is implemented via first gear wheel 25 of second single-stage gear plane 23. The remaining gears 5 and 6 are then implemented using cascade gears, similar to gears 7 and 8 in the previous exemplary embodiment, via fifth gear wheel 34 of fifth single-stage gear plane 30. This structure can then be realized substantially identical to the above structure except for the selected gear size and number of teeth, wherein two crawler gears C1 / C2 replace gears 3 and 4, gear 3 replaces gear 5, gear 4 replaces gear 6, and gears 5 / 6 replace gears 7 / 8.

Claims

1. A dual-clutch transmission (4), comprising: - a first sub-transmission (5) to which a first clutch (K1) and a first sub-transmission input shaft (18) are assigned; - a second sub-transmission (6) to which a second clutch (K2) and a second sub-transmission input shaft (19) are assigned; - a first intermediate shaft (7) permanently connected to the first driven gear (9) in a rotationally fixed manner, and a second intermediate shaft (8) permanently connected to the second driven gear (10) in a rotationally fixed manner, in, The first driven gear (25) assigned to the first sub-transmission (5) and the second driven gear (33) assigned to the second sub-transmission (6) are respectively arranged coaxially with the first intermediate shaft (7) and can be connected to each other in a rotationally fixed manner by means of a bridge shift element (B). The first sub-transmission (5) comprises exactly three single-stage gear planes, each of which is provided with exactly one gear pair consisting of exactly two mutually meshing gears, namely a first single-stage gear plane (20), a second single-stage gear plane (23) including the first driven gear (25), and a third single-stage gear plane (26), and The second sub-transmission (6) comprises exactly two single-stage gear planes, each provided with exactly one gear pair consisting of exactly two meshing gears, namely a fourth single-stage gear plane (29) and a fifth single-stage gear plane (30) containing the second driven gear (33), and is configured such that the first transmission gear, the second transmission gear, the third transmission gear, the fourth transmission gear, the fifth transmission gear, the sixth transmission gear, the seventh transmission gear and the eighth transmission gear can be configured with gear ratios that decrease in the order mentioned. A first shifting element (D) is provided, which is designed to connect the third driven gear (22) of the first single-stage gear plane (20) arranged coaxially with the second intermediate shaft (8) to the second intermediate shaft (8) in a rotationally fixed manner to form the first transmission gear and the second transmission gear, A second shift element (A) is provided, which is designed to connect the first driven gear (25) of the second single-stage gear plane (23) arranged coaxially with the first intermediate shaft (7) to the first intermediate shaft (7) in a rotationally fixed manner to form the sixth transmission gear, A third shift element (E) is provided, which is designed to connect the fourth driven gear (28) of the third single-stage gear plane (26) arranged coaxially with the second intermediate shaft (8) to the second intermediate shaft (8) in a rotationally fixed manner to form the third transmission gear and to form the fourth transmission gear, A fourth shift element (C) is provided, which is designed to connect the second driven gear (33) of the fourth single-stage gear plane (29) to the first intermediate shaft (7) in a rotationally fixed manner to form the fifth transmission gear, A fifth shift element (F) is provided which is designed to connect the fifth driven gear (34) of the fifth single-stage gear plane (30) to the second intermediate shaft (8) in a rotationally fixed manner to form the seventh transmission gear and to form the eighth transmission gear.

2. The dual clutch transmission according to claim 1, wherein: The first single-stage gear plane (20), the second single-stage gear plane (23), the third single-stage gear plane (26), the fourth single-stage gear plane (29), the fifth single-stage gear plane (30), and the clutch member (13) including the first clutch (K1) and the second clutch (K2) are arranged axially one after another in the mentioned order.

3. A hybrid drive system (1) comprising an internal combustion engine (2), an electric motor (3) and a dual clutch transmission (4) according to one of the preceding claims, characterized in that: The internal combustion engine (2) is at least indirectly coupled or coupleable to an input shaft (11) of the dual-clutch transmission (4).

4. The hybrid drive system according to claim 3, wherein A separating clutch (K0) is provided between the input shaft (11) and the dual clutch (K1 / K2), the input side (14) of the separating clutch being engaged to the input shaft (11) and the output side (15) of the separating clutch being engaged to the dual clutch (K1 / K2) comprising a first clutch (K1) and a second clutch (K2).

5. The hybrid drive system according to claim 4, characterized in that: The rotor (17) of the motor (3) is connected to the output side (15) of the separation clutch (K0).

6. The hybrid drive system according to claim 5, characterized in that: The rotor (17) of the electric motor (3) is connected to the output side (15) of the separation clutch (K0) via a transmission component (16).

Images