Patent Application
20210268890
This application claims priority from German patent application serial no. 10 2020 202 664.5 filed Mar. 2, 2020.
The invention relates to a transmission arrangement for a hybrid drive of a motor vehicle, in particular a utility vehicle, comprising a change-speed transmission, in particular a group transmission with a drive output side, a drive output flange and at least one countershaft.
From DE 10 2016 218 361 A1 a hybridized motor vehicle transmission has become known, which is in the form of a group transmission that has a main group and a range group and which has on its input or drive input side an electric machine that can be coupled to the main group of the group transmission by means of a planetary gearset. The electric machine and the planetary gearset are arranged coaxially with the input shaft of the main group. The main group has two countershafts, each with five fixed wheels which mesh with loose wheels on the input shaft. The range group, arranged on the drive output side, is in the form of a planetary gear system.
Starting from a conventional drive with an internal combustion engine and a multi-gear transmission, a purpose of the present invention is to upgrade the conventional drive to a hybrid drive.
The invention embodies the features specified in the independent claim(s). Advantageous design features emerge from the subordinate claims.
According to the invention it is provided that on a known change-speed transmission, in particular a group transmission for utility vehicles, an add-on transmission with at least one electric machine and at least one gear ratio step is arranged, wherein the at least one electric machine is connected by way of the at least one gear ratio step to the countershaft of the change-speed transmission and can be engaged as an additional electric drive. This gives the advantage that a conventional drive of a motor vehicle with an internal combustion engine can be upgraded to a hybrid drive by the subsequent or optional addition of a hybrid module. The electric machine is preferably designed to operate below the low-voltage limit (48 volts), and is therefore inexpensive. To the existing utility vehicle transmission only a few modifications have to be carried out for the add-on transmission with the electric machine(s), i.e. the hybrid module, to be able to be installed on the change-speed transmission. If necessary, if a hybrid drive is no longer needed, the hybrid module can be taken off again.
According to a preferred embodiment, the hybrid module is arranged on the rear or drive output side of the transmission next to the drive output flange. Advantageously, in its relevant motor/output-flange length the transmission is not made longer by installation parallel to the cardan shaft, or only as little as possible.
According to a further preferred embodiment, in the power flow between the at least one electric machine and the countershaft there is arranged at least one shifting clutch, preferably a claw clutch, by means of which the electrical drive can be connected or decoupled. By way of a gear ratio stage the electric machine drives the countershaft, from which the power flows to the transmission output shaft. Thus, the power of the internal combustion engine and the power of the electric machine are available at the drive output flange. However, it is also possible to switch off the internal combustion engine and drive purely electrically. Furthermore, electrical energy for operating auxiliary aggregates or for storage can be obtained from the kinetic energy of the vehicle or the internal combustion engine.
In a further preferred embodiment two electric machines are fixed on the add-on transmission, wherein on the one hand an axis-parallel arrangement or on the other hand a coaxial arrangement on opposite sides of the add-on transmission are possible. The different arrangements of the electric machines also depend on the incorporation options in the motor vehicle. The larger electrical energy quantity available reduces the fuel consumption more markedly and allows the internal combustion engine to be switched off and re-started while driving.
In a further preferred embodiment an auxiliary transmission with a first or a second planetary gearset, each comprising a sun shaft, a ring gear shaft and a carrier shaft, is associated with the electric machine. This gives the advantage that the drive input and the drive output of the planetary gearset can be arranged coaxially and on the same side, namely the side of the auxiliary transmission adjacent to the add-on transmission. With the gear ratio of the planetary gearset of the auxiliary transmission, the switched-off internal combustion engine can be restarted by an electric machine.
According to a further preferred embodiment the first planetary gearset is shiftable, such that a first gear can be engaged by holding the ring gear shaft still, and a second gear by blocking the sun shaft with the ring gear shaft. Blocking means that the sun shaft and the ring gear shaft are coupled to one another and rotate as a block. This provides on the one hand a gear ratio in the slow range and on the other hand a direct drive (gear ratio 1:1). During block operation the electric machine is operated without additional losses in the planetary transmission in the best efficiency range, while for the very short motor restarting time the additional gear ratio of the planetary transmission is activated.
In a further preferred embodiment, for restarting the internal combustion engine the planetary gearset of the auxiliary transmission has a freewheel and only one gear ratio with only one shift position. This reduces the actuation complexity. In this case the sun shaft is driven by the electric machine, while the ring gear shaft drives a gearwheel of the gear ratio step; the carrier shaft is blocked by a freewheel when the electric machine starts the internal combustion engine, so that the electric machine runs in reverse, i.e. in the rotational direction opposite to its direction during hybrid operation.
According to a further preferred embodiment, a refrigerant compressor of an air-conditioning unit on board the motor vehicle is associated with the add-on transmission. In this case the compressor is driven by a further gear ratio step of the add-on transmission. By decoupling the hybrid module from the countershaft, air-conditioning can take place while stationary thanks to the electric machine. While driving, the energy can optionally be drawn from the vehicle or from the internal combustion engine.
In a further preferred embodiment the gear ratio steps of the add-on transmission are in the form of spur gear stages, preferably with the spur gears arranged in one plane. In that way, viewed in an axial direction of the change-speed transmission a narrow add-on transmission is obtained, whose housing serves to support the at least one electric machine, the auxiliary transmission, the compressor and optionally other auxiliary aggregates too.
Example embodiments of the invention are illustrated in the drawing and will be described in greater detail below, so that further features and/or advantages may emerge from the description and/or the drawing, which shows:
The function of the above-described hybrid module, which comprises at least the add-on transmission 3 and an electric machine EM and optionally the auxiliary transmission 5, is to provide an additional electric drive for the conventional drive of a utility vehicle, i.e. an internal combustion engine with the change-speed transmission 1; in other words: the conventional internal combustion engine drive should be upgraded and retrofitted to become a hybrid drive, i.e. hybridized. The power flow from the electric machine EM into the change-speed transmission 1 takes place by way of the intermediate shaft ZW and the first countershaft VW1. During electric additional driving by the electric machine EM (hybrid drive), the first planetary gearset PS1 is blocked, i.e. between the rotor or sun shaft SO1 and the carrier shaft ST1 there is a gear ratio of 1:1. The carrier shaft ST1 drives the second gearwheel Z2, which meshes with the first gearwheel Z1 and forms the first gear ratio step Ü1 (in the slow range). The gear ratio is adapted to the vehicle speed range in which driving most often takes place, so that in this range the electric machine EM can be operated with its best efficiency. During electric driving the shifting clutch 7 in the change-speed transmission 1 is engaged. At the same time, the compressor 4 is driven with the second gear ratio Ü2. Thus, during hybrid operation the sum of the powers of the internal combustion engine and the electric machine EM is delivered to the drive output flange 2.
When not in hybrid operation, i.e. with the internal combustion engine switched off, the electric machine EM can also be used in combination with the auxiliary transmission 5 as the starter motor or starter for the internal combustion engine. For this, the ring gear HR1 of the first planetary gearset PS1 is braked, so that between the sun shaft SO1 driven by the electric machine EM and the driven carrier shaft ST1 a gear ratio in the slow range is obtained. At the input shaft EW of the transmission 1 there is then a sufficiently high torque for restarting the internal combustion engine.
As a further example embodiment of the invention
The function of the above-described arrangement with two electric machines EM1 and EM2 is as follows: during hybrid operation the two electric machines EM1 and EM2 can be switched on together or individually, depending on the power demand: for this, the rotor shafts are coupled via the shifting clutches 27, 28 respectively, to the second gearwheel Z2 or the fourth gearwheel Z4. Both gearwheels Z2 and Z4 mesh with the first gearwheel Z1 and therefore drive the countershaft VW.
When the internal combustion engine has been switched off, the first electric machine EM1 can also be used in combination with the auxiliary transmission 25 for restarting the internal combustion engine. In the restarting case the first electric machine EM1 rotates in the reverse direction and drives via the sun shaft SO2 in the second planetary gearset PS2, wherein the carrier shaft ST2 is blocked by the freewheel 26. Thereby, a gear ratio is obtained between the driven sun shaft SO2 and the driving ring gear shaft HR2 in the slow range. Correspondingly, a sufficiently high torque is available at the countershaft VW to restart the internal combustion engine.
The hybrid strategy and the actuation of the electric machines EM1, EM2 and of the shifting clutches 27, 28 are in the hands of the transmission control unit 6 mentioned earlier (
The electric machines EM, EM1, EM2 are preferably designed for alternating current lower than the low-voltage limit of around 50 volts.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 202 664.5 | Mar 2020 | DE | national |
