Patent Application
20100050635
The invention relates to a vehicle drive train, especially for a truck, an automobile, a rail vehicle or some other type of vehicle, which has a hydrodynamic retarder for hydrodynamic braking of the vehicle and an expander for powering the vehicle, in other words for providing tractive force, or for powering a component, especially an ancillary component, of the vehicle or the vehicle drive train.
Drive trains that comprise both a hydrodynamic retarder and a steam-powered expander are described in patent specifications U.S. Pat. No. 5,121,607, U.S. Pat. No. 5,241,817 and U.S. Pat. No. 5,195,881. The hydrodynamic retarder is located inside a transmission (CVT), and its rotation is dependent upon the speed of the vehicle. Secondarily, in other words at a secondary output of the transmission, parallel to the transmission output shaft, an expander is provided, which can be used as a compressor for the purpose of braking the vehicle. In compressor mode, rotation of the expander is also dependent upon the speed of the vehicle. The expander can be activated and deactivated in the transmission by means of a cut out clutch.
Although the described vehicle drive trains have both an expander and a hydrodynamic retarder, these two components operate completely independently of one another, so that each requires its own substantial amount of space inside and outside of the transmission, along with its own heat exchanger for removing heat from the two separate working medium circuits and conducting it to the outside. Thus the structural and energy requirements for the proposed vehicle drive train are so intensive that use of this embodiment in practice has not heretofore been feasible.
The object of the present invention is to further improve upon the described vehicle drive train to make it more cost-effective and more energy friendly to produce and to operate, and to increase the output of the vehicle drive train or its operation beyond what is achieved through a simple combination of two known components. The vehicle drive train of the invention should be as structurally compact as possible.
The object of the invention is achieved with a vehicle drive train having the characterizing features of Claim 1. Advantageous and particularly expedient embodiments of the invention are specified in the dependent claims.
The vehicle drive train of the invention has a hydrodynamic retarder. The retarder is either equipped with a stationary, in other words non-rotating, bladed stator and a rotating, bladed rotor, which together form an especially toroidal working chamber, or is configured as a counter-rotating retarder. In the latter case, the retarder has not just one but at least two bladed rotors, referred to here as rotor and counter-rotating rotor, which in retarder mode rotate in opposite directions, that is, in directions of rotation that are opposite one another. The working chamber for the retarder, which is defined by the rotor and the stator or the rotor and the counter-rotating rotor, is either always filled with working medium or alternatively fillable with working medium. If the working chamber is always filled with working medium, the entire retarder can be disengaged from the vehicle drive train, especially from a transmission in the vehicle drive train, by means of a cut out clutch, or other measures for preventing the exertion of retarding torque are provided, such as the free rotation or free dragging of the stator or counter-rotating rotor. If the working chamber of the retarder can alternatively be filled with and emptied of operating medium, it can be activated and deactivated by filling and emptying the working chamber.
In place of the hydrodynamic retarder, or in addition to the hydrodynamic retarder, another dynamic retarder can also be provided, with which torque is transferred from a rotor to a stator or from a rotor to a counter-rotating rotor. Torque can be transferred via liquid friction from a working medium introduced between rotor and stator or between rotor and counter-rotating rotor, for example, or via shear forces in this working medium. Alternatively, or additionally, torque can be transferred via electrodynamic or magnetic force. Finally, torque may be transferred via mechanical friction. Other transfer possibilities are also conceivable. This dynamic retarder can additionally or alternatively have a working medium, or such working medium can flow through said retarder, for the purpose of removing the heat that is created in the retarder.
Also provided in the drive train is an expander, which is operated by a working medium in the form of fluid or steam, in order to generate mechanical operation or drive power via expansion of the working medium. This mechanical power can be supplied to the drive train to provide tractive force to the vehicle, or the expander can be used to power a component, especially an ancillary component, of the drive train or the vehicle, such as a pump, an electric generator, a compressor, or the like.
The expander, also called an expansion engine, can especially be embodied as a piston engine, a screw-type engine or a turbo engine or turbine. In the embodiment comprising a screw-type engine, two screw-type-type rotors engaged with one another are especially provided, which seal off one or more working chambers or expansion chambers via their mutual engagement with one another, and are placed in rotation by the expansion of the working medium in the expansion chamber or chambers.
According to the invention, the hydrodynamic retarder and the expander are not provided simply side by side in a drive train, but are instead integrated with one another. This integration can involve both a mechanical coupling of the two components and a thermal or heat transfer coupling of the two. Alternatively or additionally, it is possible to provide the working medium for the expander, which is then conducted especially in its own working medium circuit which ordinarily comprises a supply pump, as the control medium for the retarder or for a retarder control system. Thus a control air system which is customarily provided for the retarder can be replaced by the supplementary function of the expander or of the working medium circuit of the expander, wherein the expander, in contrast to the customary control air system, is also capable of providing energy-efficient drive power by utilizing heat sources in the vehicle.
According to a first embodiment of the invention, wherein the embodiments described in what follows can also be combined with one another, the rotor and/or the counter-rotating rotor of the retarder and the expander, especially a drive shaft or drive wheel of the same, are in drive connection with one another, or such connection can optionally be established. In this manner, an existing vehicle drive train with a retarder, especially a primary retarder or secondary retarder, can be upgraded especially easily with an expander, with the expander utilizing the same drive connection, especially the same secondary output of a transmission, which was conventionally provided for the retarder. For example, the expander and the retarder can be arranged on a shared shaft with their housings mounted adjacent to one another, or they can be accommodated within a shared housing.
According to a second embodiment of the invention, a heat exchanger is provided for removing heat from the working medium of the retarder, which also acts as a heat exchanger or condenser for removing heat from the working medium of the expander. According to one embodiment, the working medium circuits of retarder and expander are separate from one another, and channels or flow guides for the two working medium circuits, which are correspondingly sealed off from one another, are provided in the shared heat exchanger. According to an alternative embodiment, the working medium of the retarder can also serve as the working medium for the expander.
According to a third embodiment of the invention, the quantity of heat introduced by the retarder into the working medium of the retarder is converted to mechanical energy in the expander. A heat exchanger which transfers heat from the working medium of the retarder to the working medium of the expander can be provided for this purpose. A heat exchanger of this type can naturally also be integrated into the retarder and/or the expander. Alternatively, the working medium can be used as the working medium for both the retarder and the expander. In either case, a storage reservoir can advantageously be provided, which stores the working medium of the expander in its heated or vaporized state, allowing it to be used at a later time, especially once the retarder has been deactivated, to generate mechanical energy in the expander. Especially advantageously, the reservoir is heated and/or thermally insulated so as to minimize or prevent heat loss.
If retarder and expander are coupled mechanically, a speed reduction mechanism is advantageously provided between these two components—based upon the direction of flow of drive power from the expander to the retarder—so that the retarder rotates at a lower speed than the expander. This is especially advantageous if the expander is embodied as a turbine, for example a steam turbine, or as a screw-type expander. Especially favorably, the rotor of the retarder can form or be equipped with external teeth, or can be non-rotatably connected to a corresponding gear with external teeth, especially forming a single piece. The expander, which in this case has a drive shaft with a pinion gear, for example, can then be arranged, especially axially adjacent to the retarder, such that the pinion gear engages with the external teeth or with the externally toothed gear. Drive power from the expander can then advantageously be introduced into the drive train or the transmission via the rotor of the retarder with a freely rotating stator and counter-rotating rotor, or via the drive shaft of the retarder, usually a secondary output in the transmission, when the working chamber of the retarder has been emptied, to supply tractive force to the vehicle. This secondary output can, in turn, be sped up in relation to a transmission output shaft (in the secondary retarder) or a transmission drive shaft (in the primary retarder), so that the retarder rotor also rotates at a higher speed than the transmission drive shaft or the transmission output shaft.
According to one embodiment, the retarder is embodied as a so-called counter-rotating retarder, wherein in retarder braking mode, the counter-rotating rotor is actively powered by the expander, in order to increase the braking torque of the retarder over that of an embodiment having a rotor and a stator. Advantageously, the absolute values of the two speeds of the rotors differ from one another. According to one embodiment, the speed of the counter-rotating rotor can be adjusted so as to regulate or to control braking torque by regulating the power output of the expander, for example by varying the quantity of working medium flowing through the expander.
In what follows, the invention will be described by way of example in reference to several exemplary embodiments.
On the output side of the transmission 10, in other words opposite the transmission input side, which faces the motor 14 and has a transmission input shaft (not shown) that is driven directly by the motor 14, a retarder 1 is provided in the transmission or—in a variation on this diagram—on the outside of the transmission, which provides hydrodynamic braking of the vehicle. To this end, the rotor (not shown) of the retarder 1 is drive connected to the transmission output shaft 11, which is in turn drive connected to the drive wheels 15.
During the operating mode in which the retarder 1 is activated, in other words during the hydrodynamic braking of the vehicle, heat is generated in the working chamber of the retarder and must be removed via an external cooling circuit 16, usually the vehicle cooling circuit. For this purpose, a heat exchanger 7 is connected to the retarder 1, which conducts the cooling medium for the vehicle cooling circuit and the working medium of the retarder in such a way as to transfer heat from the working medium of the retarder to the cooling medium of the cooling circuit. In this case, the working medium of the retarder can be oil, water, or a water mixture, for example.
In addition to the cooling medium of the cooling circuit and the working medium of the retarder 1, the heat exchanger 7 also conducts the working medium of a working medium circuit 17 of an expander 6. The working medium of the expander 6 is then partially or fully condensed in the heat exchanger 7. Other components of the working medium circuit 17 of the expander 6 include a reservoir 18 for the working medium, a water feed pump 19 and a condenser 20.
As an alternative to the illustrated embodiment, the heat exchanger 7 could also be incorporated into the working medium circuit 17 of the expander 6 so as to allow heat to be transferred from the working medium of the retarder 1 and/or from the cooling medium of the cooling circuit to the working medium of the expander 6. As a rule, the heat exchanger 7 would then be incorporated downstream of the infeed pump 19 and upstream of the steam generator 20 in the direction of flow of the working medium circuit 17 of the expander 6.
Because the working medium of the working medium circuit 17 of the expander 6 has a certain pressure level at least downstream of the water infeed pump 19, for example 6-10 bar, the working medium of the expander 6 could alternatively or additionally act as the control medium for the retarder 1. To enable this, suitable control valves would have to be provided in the working medium circuit 17, to in turn allow control valves of the retarder 1 or in the working medium circuit of the retarder 1 to be activated or controlled or regulated.
The expander 6 shown in
In contrast, in the former embodiment illustrated in
In both embodiments represented in
In both embodiments illustrated in
In the illustrated embodiments, the rotor 2 of the retarder is sped up in relation to the transmission output shaft 11 and is slowed in relation to the expander 6 or the drive shaft 8 of the expander 6.
Of course, it is possible to combine the exemplary embodiments of
| Number | Date | Country | Kind |
|---|---|---|---|
| 200720001285.6 | Jan 2007 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/000776 | 1/31/2008 | WO | 00 | 10/30/2009 |
